U.S. patent application number 09/984606 was filed with the patent office on 2002-07-18 for method of preventing scaling involving inorganic compositions, and compositions therefor.
This patent application is currently assigned to HERCULES INCORPORATED. Invention is credited to Fader, Mitzi K., Ling, Tien-Feng, Nguyen, Duy T., Wang, Xiang Huai, Zhang, Fushan.
Application Number | 20020094299 09/984606 |
Document ID | / |
Family ID | 23304681 |
Filed Date | 2002-07-18 |
United States Patent
Application |
20020094299 |
Kind Code |
A1 |
Nguyen, Duy T. ; et
al. |
July 18, 2002 |
Method of preventing scaling involving inorganic compositions, and
compositions therefor
Abstract
A composition including at least one of polyvalent metal
silicate and polyvalent metal carbonate and at least one protein. A
weight ratio of the at least one polyvalent metal silicate and
polyvalent metal carbonate to the at least one protein is from
about 50:1 to 1:1.
Inventors: |
Nguyen, Duy T.;
(Jacksonville, FL) ; Fader, Mitzi K.;
(Jacksonville, FL) ; Wang, Xiang Huai;
(Alpharetta, GA) ; Zhang, Fushan; (Jacksonville,
FL) ; Ling, Tien-Feng; (Alpharetta, GA) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1941 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
HERCULES INCORPORATED
Wilmington
DE
|
Family ID: |
23304681 |
Appl. No.: |
09/984606 |
Filed: |
October 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09984606 |
Oct 30, 2001 |
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09523663 |
Mar 10, 2000 |
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09523663 |
Mar 10, 2000 |
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09333891 |
Jun 16, 1999 |
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Current U.S.
Class: |
422/13 |
Current CPC
Class: |
C02F 5/105 20130101;
C02F 2209/06 20130101; C02F 5/00 20130101 |
Class at
Publication: |
422/13 |
International
Class: |
C23F 011/06 |
Claims
What is claimed is:
1. A composition comprising: at least one of polyvalent metal
silicate and polyvalent metal carbonate; at least one protein; and
wherein a weight ratio of the at least one polyvalent metal
silicate and polyvalent metal carbonate to the at least one protein
is from about 50:1 to 1:1.
2. The composition of claim 1, wherein the at least one protein
comprises soy protein.
3. The composition of claim 1, further comprising: water; and wood
pulp.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a divisional application of U.S.
application Ser. No. 09/523,663, filed Mar. 10, 2000, which is a
continuation-in-part application of U.S. application Ser. No.
09/333,891, filed Jun. 16, 1999, the disclosures of which are
expressly incorporated by reference herein in their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to methods and inorganic
compositions, such as polyvalent metal silicates and polyvalent
metal carbonates, for inhibiting the formation, deposition, and/or
adherence of scale deposits on substrate surfaces in contact with a
scale-forming aqueous system. The scale deposits may be alkaline
earth metal scale deposits, such as alkaline earth metal carbonate
scale deposits, especially calcium carbonate scale deposits, or
alkaline earth metal oxalate deposits. The present invention may be
advantageously used to prevent scale in a variety of processes such
as kraft pulping processes.
[0004] 2. Discussion of Background
[0005] Scale build-up is a serious problem in many industrial water
systems, such as cooling towers, heat exchangers, evaporators,
pulping digesters, washers, and in the production and processing of
crude oil-water mixtures, etc. The build-up of scale deposits
reduces the efficiency of heat transfer systems, interferes with
fluid flow, facilitates corrosive processes and harbors bacteria.
Calcium carbonate, generated in various processes, is one of the
most commonly observed scale formers in industrial water systems.
This scale is an expensive problem in many industries, which causes
delays and shutdowns for cleaning and removal.
[0006] In particular, most industrial waters contain metal ions,
such as calcium, barium, magnesium, aluminium, strontium, iron,
etc. and several anions such as bicarbonate, carbonate, sulfate,
oxalate, phosphate, silicate, fluoride, etc. When combinations of
these anions and cations are present in concentrations which exceed
the solubility of their reaction products, precipitates form until
product solubility concentrations are no longer exceeded. For
example, when the concentrations of calcium ion and carbonate ion
exceed the solubility of the calcium carbonate reaction products, a
solid phase of calcium carbonate will form.
[0007] Solubility product concentrations are exceeded for various
reasons, such as partial evaporation of the water phase, change in
pH, temperature or pressure, and the introduction of additional
ions which form insoluble compounds with the ions already present
in the solution. As these reaction products precipitate on the
surfaces of the water carrying system, they form scale or
deposits.
[0008] For boiler systems and similar heat exchange systems, the
mechanism of scale formation is apparently one of crystallization
of scale-forming salts from a solution which is locally
supersaturated in the region adjacent the heating surface of the
system. The thin viscous film of water in this region tends to
become more concentrated than the remainder of the solution outside
this region. As a result, the solubility of the scale-forming salt
reaction product is first exceeded in this thin film, and
crystallization of scale results directly on the heating surface.
In addition to this, a common source of scale in boiler systems is
the breakdown of calcium bicarbonate to form calcium carbonate
water and carbon dioxide under the influence of heat.
[0009] For open recirculating cooling water systems, in which a
cooling tower, spray pond, evaporative condenser, and the like
serve to dissipate heat by evaporation of water, the chief factor
which promotes scale formation is concentration of solids dissolved
in the water by repeated evaporation of portions of the water
phase. Thus, even a water which is not scale forming on a
once-through basis usually will become scale forming when
concentrated a multiple number of times.
[0010] Also as disclosed in U.S. Pat. No. 3,518,204 to HANSEN et
al., the disclosure of which is herein incorporated by reference in
its entirety, water supplies employed as cooling media frequently
contain silts such as bentonitic or kaolinitic minerals. During use
of such silt containing waters in these systems, the silts react or
associate with other impurities which are present in the water such
as calcium and magnesium which are commonly referred to as
"hardness". As a consequence of such reaction or association, a
precipitate is formed and precipitated upon the surfaces of the
system containing the water. Such depositions may build up to the
extent that flow through the system is reduced or halted, and the
system must be shut down for costly cleaning. In addition, when
such deposition occurs on heat transfer surfaces, heat exchange is
reduced with a corresponding loss in process efficiency.
[0011] Scaling in kraft pulping processes occurs by a different
mechanism as a result of the presence of organic ligands. Black
liquor generated in the kraft pulping digester contains a very high
content of organics such as lignin, fatty/rosin soaps,
hemicelluloses, etc. Lignin fragments formed during pulping,
specifically those containing adjacent hydroxyl groups on an
aromatic ring, have a high tendency to interact with calcium
(originally from tree) to greatly increase its solubility in black
liquor. As the temperature increases (e.g., the temperature found
near the tube wall of an evaporator or cooking heater), the pH has
a tendency to decrease, especially if the residual active alkali is
low. As a consequence, calcium ions can be displaced from the
lignin by hydrogen ions, and react with carbonate ions thus
producing calcium carbonate scale. In addition to lignin, there are
many different organic species that complex calcium in the black
liquor. Any of these organic species, whose ability to complex with
calcium depends on the pH being in the normal pH range of black
liquor, will contribute to calcium carbonate scaling by releasing
ionic calcium as the temperature increases. Therefore, as long as
some of the aforementioned organic compounds are present and
sufficient calcium is available, a liquor will have the capacity to
deposit calcium carbonate scale. In addition to calcium and
carbonate, black liquor normally contains a number of other ions
such as sodium and sulfate which can precipitate and form
scale.
[0012] In the paper industry, alkalinity from alkali digesting
solution and from dissolved solids from the wood chips, results in
an increased alkalinity of the black liquor, often reaching pH's of
12-13 and even higher. Under high pH conditions, the precipitation
of calcium carbonate is especially difficult to control. Acid is
often added to lower the pH to prevent calcium carbonate
scaling.
[0013] In the papermaking process, calcium oxalate scale often
forms on process equipment during the bleaching/delignification of
pulp by chlorine, caustic soda, chlorine dioxide, hypochlorite and
peroxide. Usual areas of scale build-up are on washer drum face
wires; in washer vats; in stock lines and pumps; in filtrate tanks,
lines, and pumps; on extraction screens; and in treatment towers.
The formation of calcium oxalate scale provides an economic
hardship on mills principally because of lost production due to
decreased bleaching/delignification efficiency and equipment
downtime associated with the removal of scale.
[0014] In the oil industry, the formation of insoluble calcium
salts is also a problem in the secondary recovery of oil from
subterranean formations by processes in which water is introduced
into injection wells and forced through the underground formations
to cause oil to be produced in a producing well. This type of
process is usually referred to as a waterflood system.
[0015] In view of the above, scale formation and deposition are
generated by the mechanisms of nucleation, crystal growth, and
aggregation of scale-forming particles. Various approaches to
reducing scale development include inhibition of nuclei/crystal
formation, modification of crystal growth, and dispersion of the
scale-forming particles.
[0016] Chelating or sequestering agents have been commonly used to
prevent deposition, precipitation and crystallization of calcium
carbonate in water-carrying systems. Other types of chemicals which
have been actively explored as calcium carbonate scale inhibiting
agents are threshold inhibitors.
[0017] Threshold inhibitors include water soluble polymers,
phosphonates, and polyphosphates (e.g., U.S. Pat. No. 5,182,028 to
BOFFARDI et al., the disclosure of which is herein incorporated by
reference in its entirety, discloses sodium hexametaphosphate and
monofluorophosphate). Such chemicals are effective as scale
inhibitors in amounts considerably less than that
stoichiometrically required.
[0018] Water soluble polymers, including groups derived from
acrylamide, maleic acid, vinyl acetate, vinyl alcohol, and acrylic
acid have been used to control calcium carbonate deposition. For
instance, such polymers are disclosed in U.S. Pat. No. 5,282,976 to
YEUNG; U.S. Pat. No. 5,496,914 to WOOD et al.; U.S. Pat. No.
4,008,164 to WATSON et al.; U.S. Pat. No. 3,518,204 to HANSEN et
al.; U.S. Pat. Nos. 3,928,196 and 4,936,987 to PERSINSKI et al.;
U.S. Pat. No. 3,965,027 to BOFFARDI et al.; U.S. Pat. No. 5,441,602
to HARRIS et al.; U.S. Pat. No. 5,580,462 to GILL; and U.S. Pat.
No. 5,409,571 to TOGO et al., the disclosures of which are herein
incorporated by reference in their entireties.
[0019] Polyallylamines having phosphonic, carboxylic, or sulfonic
groups are also used as scale control agents as disclosed in U.S.
Pat. No.5,629,385 to KUO and U.S. Pat. No. 5,124,046 to SHERWOOD et
al., the disclosures of which are herein incorporated by reference
in their entireties.
[0020] Additionally, a number of anionic polyelectrolytes, such as
polyacrylates, polymaleic anhydrides, copolymers of acrylates and
sulfonates, and polymers of sulfonate styrenes, have been employed.
Examples of polyelectrolytes are disclosed in U.S. Pat. No.
4,640,793 to PERSINSKI et al.; U.S. Pat. No. 4,650,591 to BOOTHE et
al.; U.S. Pat. No. 4,457,847 to LORENC et al.; U.S. Pat.
No.5,407,583 to GILL et al.; and U.S. Pat. No. 4,671,888 to YORKE,
the disclosures of which are herein incorporated by reference in
their entireties.
[0021] Polyepoxysuccinic acid for inhibiting the formation and
deposition of scale in aqueous systems is disclosed in U.S. Pat.
Nos. 5,062,962 and 5,147,555 to BROWN et al., the disclosures of
which are herein incorporated by reference in their entireties.
[0022] Phosphonate based compounds are extensively used as calcium
carbonate scale control agents. Examples include ether
diphosphonate (U.S. Pat. No. 5,772,893 to REED et al., and U.S.
Pat. No. 5,647,995 to KNELLER et al., the disclosures of which are
herein incorporated by reference in their entireties),
hydroxyethylidene-1,1-diphosphonic acid, amino tri(methylene
phosphonic acid), aminomethylene phosphonates (U.S. Pat. No.
4,931,189 to DHAWAN et al., the disclosure of which is herein
incorporated by reference in its entirety),
N,N-bis(phosphonomethyl)-2-am- ino-1-propanol (U.S. Pat.
No.5,259,974 to CHEN et al., the disclosure of which is herein
incorporated by reference in its entirety), methylene phosphonates
of amino-terminated oxyalkylates (U.S. Pat. No. 4,080,375 to
QUINLAN, the disclosure of which is herein incorporated by
reference in its entirety), polyether polyamino methylene
phosphonates (EP 0 516 382 B1, the disclosure of which is herein
incorporated by reference in its entirety), and ethanolamine
N,N-dimethylene phosphonic acid (U.S. Pat. Nos. 2,917,528 and
2,964,549 to RAMSEY et al., the disclosures of which are herein
incorporated by reference in their entireties).
[0023] Additionally, it is known that certain inorganic
polyphosphonates would prevent precipitation when added in amounts
less than the concentrations needed for sequestering or chelating,
as disclosed in U.S. Pat. No. 2,358,222 to FINK et al. and U.S.
Pat. No. 2,539,305 to HATCH, the disclosures of which are herein
incorporated by reference in their entireties.
[0024] U.S. Pat. No. 3,960,576 to CARTER et al., the disclosure of
which is herein incorporated by reference in its entirety,
discloses that inorganic-silicate-based compositions also comprised
of an organic phosphonate and carboxy methyl cellulose are useful
for inhibiting corrosion of metal surfaces.
[0025] MANAHAN, Environmental Chemistry, pp. 183-213 (1991), the
disclosure of which is herein incorporated by reference in its
entirety, with particular attention directed to pp. 193-195,
discloses use in environmental chemistry of sodium aluminum
silicate minerals or zeolites as water softeners. The softening of
water by aluminum silicate minerals and zeolites is based on
ion-exchanging properties of the minerals. The divalent cations,
which are responsible for water hardness, are replaced by sodium
ions contained in the aluminum silicates, and then removed by
filtration. An example of a micaceous mineral which has been used
commercially in water softening is glauconite,
K.sub.2(MgFe).sub.2Al.sub.- 6(Si.sub.4O.sub.10).sub.3OH.sub.12.
[0026] Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed.,
vol. 24, pp.367-384 (1984), the disclosure of which is herein
incorporated by reference in its entirety, discloses that deposits
are usually controlled with dispersants and scale inhibitors in
cooling and process water. Among the dispersants mentioned are
polymers and copolymers, for example, poly(acrylic acid) and its
salts, acrylamideacrylic acid copolymers and poly(maleic acid).
[0027] "Deactivation of Calcium Scaling Liquors", The Members of
the Paper Institute of Paper Chemistry, Project 3234, Report Three,
pp. 88-119 (November 1977), the disclosure of which is herein
incorporated by reference in its entirety, discloses adding reagent
grade calcium carbonate at 1% loading in most experiments and at 5%
and 20% in a few other experiments, to function as a seed in the
liquor as a deposition surface for calcium carbonate.
[0028] ADAMS, "Low-Cost Evaporator Upgrades Boost Performance,
Reduce Scaling", Pulp & Paper, pp. 83-89 (February 1999),
discloses a salting method which involves adding sodium sulfate to
control scaling.
[0029] CA 2,229,973 discloses a method of inhibiting black liquor
in evaporators, wherein the liquor is heat-treated to precipitate
calcium carbonate. This document discloses that no calcium
carbonate needs to be added to the liquor to be heat-treated.
[0030] EP 0 916 622 discloses a process for preventing scale
formation in a paper-making process, wherein calcium sulfate or
calcium oxalate are added as a seed to prevent formation of calcium
sulfate scale or calcium oxalate scale, respectively.
[0031] Further, it is known to use clays such as talc and bentonite
in paper making for fillers, pitch control, and retention and
drainage control. In filler applications, talc or bentonite may be
added in an amount which is typically relatively high.
[0032] In pitch control applications, talc or bentonite may be
added before the washer and after the digester. At this position,
the temperature of the aqueous system is relatively low. The use of
talc and bentonite for pitch control is discussed in BOARDMAN, "The
Use of Organophilic Mineral Particulates in the Control of Anionic
Trash Like Pitch", TAPPI Proceedings (1996), the disclosure of
which is herein incorporated by reference in its entirety. In
particular, this article discloses using two pounds per ton of
montmorillonite. It is known that pitch deposits may sometimes
include calcium carbonate.
[0033] In retention and drainage control, it is believed that
bentonite and a high molecular weight cationic polymer (e.g.,
molecular weight of about 1.times.10.sup.6 to 10.times.10.sup.6)
may be added just before the headbox. For instance, it is believed
that 3-10 lb of bentonite/ton of oven dried fibers may be added
near the headbox which would result in about 15-50 ppm of bentonite
in the aqueous system for a 1 wt % aqueous paper furnish. It is
believed that the aqueous system just before the headbox typically
has a pH of about 5 to 8.5 and a temperature of about 40.degree. C.
to 60.degree. C. As an example, U.S. Pat. No.4,753,710 to LANGLEY
et al. teaches that the bentonite particle size after swelling is
preferably at least 90% below 2 microns.
SUMMARY OF THE INVENTION
[0034] The present invention is directed to preventing scale
formation and/or deposition, such as alkaline earth metal scale
deposition, especially calcium carbonate scale deposition, or
alkaline earth metal oxalate scale deposition.
[0035] The present invention is also directed to providing
inorganic compounds, such as polyvalent metal silicates and
polyvalent metal carbonates, that can effectively prevent scale
formation and/or deposition.
[0036] The present invention is further directed to providing a
family of compounds that can effectively prevent scale formation
and/or deposition on surfaces, such as metallic and plastic
surfaces, in contact with a scale-forming aqueous system.
[0037] In accordance with one aspect, the present invention is
directed to a method for inhibiting scale deposits in an aqueous
system, comprising: at least one of adding and forming anti-scalant
in the aqueous system such that an amount of anti-scalant in the
aqueous system is up to about 1000 ppm, wherein the anti-scalant
comprises at least one of polyvalent metal silicate and polyvalent
metal carbonate, wherein the aqueous system has a pH of at least
about 9, and wherein a mean particle size of the anti-scalant is
less than about 3 microns.
[0038] In accordance with another aspect, the present invention is
directed to a method for inhibiting scale deposits in an aqueous
system, comprising: at least one of adding and forming anti-scalant
in the aqueous system such that an amount of anti-scalant in the
aqueous system is up to about 1000 ppm, wherein the anti-scalant
comprises at least one of polyvalent metal silicate and polyvalent
metal carbonate, and wherein the aqueous system has a pH of at
least about 9; and adding dispersant to the aqueous system.
[0039] In accordance with still another aspect, the present
invention is directed to a method for inhibiting scale deposits in
an aqueous system, comprising: forming anti-scalant in the aqueous
system such that an amount of anti-scalant in the aqueous system is
up to about 1000 ppm, wherein the anti-scalant comprises at least
one of polyvalent metal silicate and polyvalent metal carbonate,
wherein a mean particle size of the anti-scalant is less than about
3 microns.
[0040] In accordance with yet another aspect, the present invention
is directed to a method for inhibiting scale deposits in an aqueous
system, comprising: forming anti-scalant in the aqueous system such
that an amount of anti-scalant in the aqueous system is up to about
1000 ppm, wherein the anti-scalant comprises at least one of
polyvalent metal silicate and polyvalent metal carbonate; and
adding dispersant to the aqueous system.
[0041] In accordance with another aspect, the present invention is
directed to a method for inhibiting scale deposits in an aqueous
system of a pulping mill, comprising: at least one of adding and
forming anti-scalant in the aqueous system at at least one of
before a pulping digester and at a pulping digester, wherein the
anti-scalant comprises at least one of polyvalent metal silicate
and polyvalent metal carbonate.
[0042] In accordance with still another aspect, the present
invention is directed to a method for inhibiting scale deposits in
an aqueous system of a pulping mill, comprising: at least one of
adding and forming anti-scalant in the aqueous system at at least
one of immediately before a bleach plant stage and at a bleach
plant stage, wherein the anti-scalant comprises at least one of
polyvalent metal silicate and polyvalent metal carbonate.
[0043] In accordance with yet another aspect, the present invention
is directed to a method for inhibiting scale deposits in an aqueous
system, comprising: at least one of adding and forming anti-scalant
in the aqueous system such that an amount of anti-scalant in the
aqueous system is up to about 1000 ppm, wherein the anti-scalant
comprises at least one of magnesium aluminum silicate, hydrated
magnesium aluminum silicate, calcium bentonite, saponite,
sepiolite, magnesium carbonate, ferrous carbonate, manganese
carbonate, dolomite, hectorite, amorphous magnesium silicate, and
zinc carbonate.
[0044] In accordance with a further aspect, the present invention
is directed to a method for inhibiting scale deposits in an aqueous
system, comprising: at least one of adding and forming anti-scalant
in the aqueous system such that an amount of anti-scalant in the
aqueous system is up to about 1000 ppm, wherein the anti-scalant
comprises polyvalent metal carbonate, wherein a mean particle size
of the anti-scalant is less than about 3 microns.
[0045] In accordance with another aspect, the present invention is
directed to a method for inhibiting scale deposits in an aqueous
system, comprising: at least one of adding and forming anti-scalant
in the aqueous system such that an amount of anti-scalant in the
aqueous system is up to about 1000 ppm, wherein the anti-scalant
comprises polyvalent metal carbonate; and adding dispersant to the
aqueous system.
[0046] In accordance with yet another aspect, the present invention
is directed to a method for inhibiting scale deposits in an aqueous
system, comprising: at least one of adding and forming anti-scalant
in the aqueous system, wherein the anti-scalant comprises at least
one of polyvalent metal silicate and polyvalent metal carbonate;
and adding at least one protein to the aqueous system.
[0047] In accordance with still another aspect, the present
invention is directed to a composition comprising: at least one of
polyvalent metal silicate and polyvalent metal carbonate; at least
one protein; and wherein a weight ratio of the at least one
polyvalent metal silicate and polyvalent metal carbonate to the at
least one protein is from about 50:1 to 1:1.
[0048] In one aspect, the anti-scalant comprises polyvalent metal
silicate and comprises at least one of sodium montmorillonite,
magnesium aluminum silicate, talc, hydrated magnesium aluminum
silicate, calcium bentonite, saponite, sepiolite, sodium
aluminosilicate, hectorite, and amorphous magnesium silicate.
[0049] In another aspect, the anti-scalant comprises polyvalent
metal carbonate and comprises at least one of calcium carbonate,
magnesium carbonate, ferrous carbonate, manganese carbonate,
dolomite, and zinc carbonate. For example, the anti-scalant may
comprise ground calcium carbonate. As another example, the
anti-scalant comprises ground calcium carbonate and sodium
montmorillonite.
[0050] In still another aspect, the anti-scalant has a specific
surface area of about 10 to 1000 m.sup.2/g.
[0051] In another aspect, the scale comprises alkaline earth metal
scale. In this regard, the scale may comprise at least one of
calcium carbonate and calcium oxalate.
[0052] In yet another aspect, the aqueous system may have a
concentration of Ca.sup.+2 of about 10 to 500 ppm and a
concentration of CO.sub.3.sup.-2 of about 100 to 30,000 ppm prior
to addition of the anti-scalant. As another example, the aqueous
system may have a concentration of Ca.sup.+2 of about 10 to 500 ppm
and a concentration of oxalate of about 0.1 to 10,000 ppm prior to
addition of the anti-scalant.
[0053] In another aspect, the aqueous system has a temperature of
about 25.degree. C. to 500.degree. C.
[0054] In still another aspect, the aqueous system is at a pressure
of about 80 to 1500 psi.
[0055] In a further aspect, the anti-scalant is at least one of
added and formed one of before and in at least one of a cooling
tower, heat exchanger, evaporator, pulping digester, pulp washer,
and pulp bleaching equipment.
[0056] In yet another aspect, the aqueous system involves one of
papermaking, mining, textile making, auto making, food processing,
steel making, water treatment, and petroleum processing.
[0057] In still another aspect, at least one additional
anti-scalant is added to the aqueous system.
[0058] In another aspect, at least one protein is added to the
aqueous system.
[0059] In a further aspect, the scale comprises calcium carbonate,
the anti-scalant has a specific surface area of about 10 to 1000
m.sup.2/g, the aqueous system has a pH of about 9 to 14, the
aqueous system has a concentration of Ca.sup.-2 of about 10 to 500
ppm and a concentration CO.sub.3.sup.-2 of about 100 to 30,000 ppm
prior to addition of the anti-scalant, and the aqueous system has a
temperature of about 25.degree. C. to 500.degree. C.
[0060] In another aspect, up to about 10 ppm of coagulant is added
to the aqueous system.
[0061] In still another aspect, the anti-scalant is removed from
the aqueous system by using at least one of a clarifier, flotation
cell, settling tank, filter, centrifuge, and osmosis device.
[0062] In some aspects, the aqueous system has a pH of about 2 to
12. As another example, the aqueous system has a pH of about 2 to
14.
[0063] In another aspect, the aqueous system is oxidative.
[0064] In yet another aspect, the scale comprises at least one of
calcium oxalate and calcium carbonate, the anti-scalant has a
specific surface area of about 10 to 1000 m.sup.2/g, the aqueous
system has a pH of about 2 to 12, the aqueous system has a
concentration of Ca.sup.+2 of about 10 to 500 ppm prior to addition
of the anti-scalant, also prior to addition of the anti-scalant the
aqueous system has at least one of a concentration of oxalate of
about 0.1 to 10,000 ppm and a concentration of CO.sub.3.sup.-2 of
about 100 to 30,000 ppm, and the aqueous system has a temperature
of about 25.degree. C. to 500.degree. C.
[0065] In some aspects, the anti-scalant has a mean particle size
less than about 100 microns.
[0066] In another aspect, the at least one protein comprises soy
protein.
[0067] In yet another aspect, the composition also includes water
and wood pulp.
DETAILED DESCRIPTION OF THE INVENTION
[0068] The particulars shown herein are by way of example and for
purposes of illustrative discussion of the various embodiments of
the present invention only and are presented in the cause of
providing what is believed to be the most useful and readily
understood description of the principles and conceptual aspects of
the invention. In this regard, no attempt is made to show details
of the invention in more detail than is necessary for a fundamental
understanding of the invention, the description making apparent to
those skilled in the art how the several forms of the invention may
be embodied in practice.
[0069] All percent measurements in this application, unless
otherwise stated, are measured by weight based upon 100% of a given
sample weight. Thus, for example, 30% represents 30 weight parts
out of every 100 weight parts of the sample.
[0070] Unless otherwise stated, a reference to a compound or
component, includes the compound or component by itself, as well as
in combination with other compounds or components, such as mixtures
of compounds.
[0071] Before further discussion, a definition of the following
terms will aid in the understanding of the present invention.
[0072] "Nucleation initiator/promoter": substance which initiates
and promotes nucleation and precipitation of polyvalent metal
silicate or polyvalent metal carbonate in the solution phase.
[0073] "Water hardness": amount of magnesium and calcium ions in an
aqueous solution.
[0074] As an overview, the present invention relates to methods and
inorganic compositions for inhibiting the formation, deposition,
and adherence of scale deposits on substrate surfaces in contact
with a scale-forming aqueous system. The scale deposits may be
alkaline earth metal scale deposits, such as alkaline earth metal
carbonate scale deposits, especially calcium carbonate scale
deposits, or alkaline earth metal oxalate scale.
[0075] The preferred anti-scalants of the present invention include
polyvalent metal silicates and polyvalent metal carbonates. The
polyvalent metal silicate or polyvalent metal carbonate may be
crystalline or amorphous. The polyvalent metal silicates and
polyvalent metal carbonates may have functional groups such as
carboxylic, sulfonate, sulfate, and phosphate. For example, the
functional groups may be obtained by treating a polyvalent metal
silicate or polyvalent metal carbonate with an organic or inorganic
compound having a functional group such as carboxylic, sulfonate,
sulfate, and phosphate. Examples of these compounds include
polymers such as polyacrylate and polyacrylic acid, and surfactants
such as alkylbenzene sulfonate, alkylbenzene sulfate, and
alkylbenzene phosphate ester.
[0076] Polyvalent metal silicates include clays. Clays are
naturally occurring hydrous aluminosilicates with a 2- or 3-layer
crystal structure which has ion substitution for aluminium,
examples of such ion substitutes include magnesium, iron, and
sodium. Alkali and alkaline earth elements may also be constituents
of clays. Hydrogen is usually present as hydroxyl in the structure
and as water both within the structure and absorbed on the surface.
These substitutions create a wide diversity in chemical composition
within the broad general class of phyllosilicates or layer
silicates. It is well known that relatively small differences in
the chemical composition of clays can greatly influence their
chemical and physical properties.
[0077] All phyllosilicates contain silicate or aluminosilicate
layers in which sheets of tetrahedrally coordinated cations, Z,
such as ions of magnesium, aluminum, and iron, of composition
Z.sub.2O.sub.5 are linked through shared oxygens to sheets of
cations, which are octahedrally coordinated to oxygens and
hydroxyls. When one octahedral sheet is linked to one tetrahedral
sheet, a 1:1 layer is formed as in kaolinite; when one octahedral
sheet is linked to two tetrahedral sheets, one on each side, a 2:1
layer is produced as in talc and pyrophyllite. Structural units
that may be found between aluminosilicate layers are sheets of
cations octahedrally coordinated with hydroxyls, as in chlorites,
and individual cations which may or may not be hydrated, as in
smectites, bentonites, vermiculites, and micas. Some 2:1 layer
silicates swell in water, ethylene glycol, and a wide range of
similar compounds by intercalation of molecules between 2:1
layers.
[0078] Polyvalent metal carbonates include various combinations of
polyvalent metals and carbonates. Preferred examples of the
polyvalent metal include calcium, magnesium, iron, manganese, and
zinc. For instance, alkaline earth metal carbonates include calcium
carbonate mixed with magnesium carbonate.
[0079] The polyvalent metal silicates and polyvalent metal
carbonates may be synthetic or naturally occurring. Examples of
synthetic polyvalent metal silicates and polyvalent metal
carbonates include precipitated calcium carbonate and
silica-derived products such as magnesium silicate,
aluminosilicate, magnesium aluminum silicate, etc. As discussed in
more detail below, various particle sizes, surface areas, pore size
diameters, and ion exchange capacities of synthetic polyvalent
metal silicates and polyvalent metal carbonates can be made
commercially.
[0080] Preferred examples of the anti-scalants of the present
invention are listed in the following non-limiting list which is
not intended to be an exhaustive list:
NATURAL POLYVALENT METAL SILICATES AND METAL CARBONATES
Polyvalent Metal Silicates
[0081] sodium montmorillonite (bentonite)
[0082] magnesium aluminum silicate
[0083] smectite clay
[0084] colloidal attapulgite clay
[0085] talc (hydrous magnesium silicate)
[0086] hydrated magnesium aluminum silicate (e.g., smectite
clay)
[0087] calcium bentonite
[0088] saponite (magnesium bentonite)
[0089] sepiolite
Polyvalent Metal Carbonates
[0090] calcium carbonate
[0091] ground calcium carbonate
[0092] magnesium carbonate
[0093] ferrous carbonate
[0094] manganese carbonate
[0095] dolomite
SYNTHETIC POLYVALENT METAL SILICATES AND METAL CARBONATES
Polyvalent Metal Silicates
[0096] sodium aluminosilicate
[0097] hydrated Na-A type zeolite
[0098] mordenite zeolite
[0099] synthetic amorphous precipitated silicate
[0100] magnesium aluminum silicate
[0101] synthetic hectorite (synthetic magnesium silicate)
[0102] amorphous magnesium silicate
Polyvalent Metal Carbonates
[0103] calcium carbonate
[0104] precipitated calcium carbonate
[0105] magnesium carbonate
[0106] zinc carbonate
[0107] ferrous carbonate
[0108] manganese carbonate
[0109] In selecting other anti-scalants which may be useful in the
present invention, compounds with an aluminosilicate backbone tend
to function as anti-scalants.
[0110] Further, the selection of other anti-scalants may be based
upon how the anti-scalants of the present invention are
hypothesized to function. While not wishing to be bound by theory,
the present invention may involve one or more of the following
mechanisms, depending upon the type of anti-scalant.
[0111] For some anti-scalants, the mechanism of the present
invention may involve ion exchange similar to the ion exchange
involved in water softening. For instance, sodium ions could be
exchanged for calcium ions, so as to reduce the concentration of
calcium ions in the aqueous system to reduce precipitation of
calcium compounds. It is believed that reducing the calcium
concentration also slows the growth rate of calcium based crystals,
such that the crystals which are formed tend to be smaller and more
uniform. Smaller crystals are more stable in the aqueous phase and
are less likely to precipitate on the equipment.
[0112] According to another hypothesized mechanism, the
anti-scalant of the present invention may function as a nucleation
initiator/promoter. Thus, the anti-scalant of the present invention
may function as a seed. For instance, the scaling compound may
precipitate on the anti-scalant instead of precipitating on the
equipment. The nucleation initiator/promoter may be inorganic.
Although other compounds may function as nucleation
initiator/promoters, it is particularly believed that ground
calcium carbonate functions as a nucleation promoter/initiator.
[0113] According to still another hypothesized mechanism, the
anti-scalant of the present invention may function through surface
adsorption. Although surface adsorption may be involved in the ion
exchange and nucleation mechanisms described above, surface
adsorption may be an independent mechanism. For instance, in
surface adsorption it is not necessary for a separate solid phase
to be formed on the surface of the anti-scalant.
[0114] In view of the above, it is hypothesized that the
anti-scalant of the present invention may function as at least one
of an ion exchanger, a nucleation promoter/initiator, and a surface
adsorber, depending upon the anti-scalant.
[0115] The above listed anti-scalants may also be used in
combination with each other. It was surprisingly found that some
combinations of the above-listed anti-scalants resulted in
synergism. In particular, combinations of sodium montmorillonite
with either ground calcium carbonate or magnesium aluminum silicate
yield unexpected results.
[0116] Regarding the combination of calcium carbonate and sodium
montmorillonite, the weight ratio of calcium carbonate to sodium
montmorillonite is preferably about 0.1:1 to 20:1, more preferably
about 0.5:1 to 7:1, and most preferably about 1:1 to 4:1. Thus, the
amount of calcium carbonate in the combination of calcium carbonate
and sodium montmorillonite, with respect to a total amount of
anti-scalant, is preferably about 10 wt % to 95 wt %, more
preferably about 30 wt % to 90 wt %, and most preferably about 50
wt % to 80 wt %. Accordingly, the amount of sodium montmorillonite
in the combination of calcium carbonate and sodium montmorillonite,
with respect to a total amount of anti-scalant, is preferably about
5 wt % to 90 wt %, more preferably about 10 wt % to 70 wt %, and
most preferably about 20 wt % to 50 wt %.
[0117] Concerning the combination of magnesium aluminum silicate
and sodium montmorillonite, the weight ratio of magnesium aluminum
silicate to sodium montmorillonite is preferably about 0.1:1 to
20:1, more preferably about 0.5:1 to 7:1, and most preferably about
1:1 to 4:1. Thus, the amount of magnesium aluminum silicate in the
combination of magnesium aluminum silicate and sodium
montmorillonite, with respect to a total amount of anti-scalant, is
preferably about 10 wt % to 95 wt %, more preferably about 30 wt %
to 90 wt %, and most preferably about 50 wt % to 80 wt %.
Accordingly, the amount of sodium montmorillonite in the
combination of magnesium aluminum silicate and sodium
montmorillonite, with respect to a total amount of anti-scalant, is
preferably about 5 wt % to 90 wt %, more preferably about IO wt %
to 70 wt %, and most preferably about 20 wt % to 50 wt %.
[0118] The particle size of the anti-scalant is preferably small.
More specifically, depending upon the anti-scalant, the mean
particle size of the anti-scalant is preferably less than about 100
microns, more preferably less than about 10 microns, most
preferably less than about 3 microns, with ranges of preferably
about 0.01 to 10 microns, more preferably about 0.1 to 5 microns,
and most preferably about 0.1 to 3 microns. When calcium carbonate
is formed in situ, as described below, the particle size is
preferably about 0.01 to 10 microns, more preferably about 0.01 to
5 microns. Further, for alkaline earth metal carbonates, including
ground calcium carbonate, the mean particle size is preferably less
than about 2 microns, more preferably less than about 1 micron, and
most preferably less than about 0.5 micron, with a range of about
0.1 to 2 microns. In this application, particle size is measured by
dynamic light scattering at 25.degree. C. in aqueous solution.
[0119] One reason that the particle size of the anti-scalant should
be small is to increase the specific surface area. Depending upon
the anti-scalant, the specific surface area of the anti-scalant is
preferably about 10 to 1500 m.sup.2/g, more preferably about 50 to
1000 m.sup.2/g. For example, zeolites available from Zeolyst
International, Delfziji, the Netherlands can be synthesized with a
specific surface area in the range of about 400 to 950 m.sup.2/g.
In this application, surface area is measured by measuring a low
temperature (77K) nitrogen isotherm, from which the surface area is
calculated using BET equations.
[0120] In this regard, the particle size and surface area of the
anti-scalants of the present invention may be adjusted by milling,
grinding, or by adjusting temperature, pH, pressure, or other
chemical/physical parameters of the environment in which it is
made. With regard to calcium carbonate, depending on the milling
process and dispersants added to the limestone starting material,
different particle sizes and specific surface areas of ground
calcium carbonate particles can be generated. Dispersants are used
to control the viscosity, particle size, and stabilize the ground
calcium carbonate slurry, which is typically about 75 wt % of
solids. In this regard, dispersants stabilize particles from coming
together so that particle size distribution is lowered. The
following dispersants can be used but are not limited to: anionic
polymers (e.g., polyacrylates, polysulfonates, polymaleates,
lignosulfonates), nonionic polymers (e.g., polyvinyl alcohols,
polyvinyl acetates, ethoxylate/propoxylate (EO/PO) block
copolymers), cationic polymers (e.g., polyethylene imines,
polyamines), anionic surfactants (e.g., dialkyl sulfosuccinates,
alkyl phosphates, alkyl ether sulfates), cationic surfactants
(e.g., fatty amine salts, alkyl quaternary amines), nonionic
surfactants (e.g., sorbitan alkanoate, ethoxylated sorbitan
alkanoate, alkyl phenol ethoxylate, fatty alcohol ethoxylate).
[0121] The scale inhibition effect of the anti-scalants of the
present invention may also be enhanced by the presence of
dispersants such as those noted above. Although the dispersants may
be pre-mixed with the anti-scalant, such as during the milling
process, the dispersant may also be added to the aqueous system
separate from the anti-scalant of the present invention, either
before or after the anti-scalant of the present invention. As an
example, when calcium carbonate is formed in situ, as discussed in
more detail below, it is preferred that a dispersant, such as those
discussed above, e.g., polyacrylate, is also added. When a
dispersant is used with the in situ formed calcium carbonate, a
synergistic effect often results. For example, depending upon the
pH, temperature, calcium concentration, and carbonate
concentration, blends of precipitated calcium carbonate to
dispersant at weight ratios of preferably about 50:1 to 1:1, more
preferably about 20:1 to 1:1, and most preferably about 10:1 to
1:1, are often several times more effective than the individual
components.
[0122] The scale inhibition effect of the anti-scalants of the
present invention may also be enhanced by the presence of at least
one protein. Although the protein may be pre-mixed with the
anti-scalant, the protein may also be added to the aqueous system
separate from the anti-scalant of the present invention, either
before or after the anti-scalant of the present invention. Examples
of proteins which may be used in combination with the present
invention include soy protein such as "Soyprotein 3230" protein and
"Soyprotein 4950" protein, both available from Central Soya, Fort
Wayne, Ind. It has been found that "Soyprotein 4950#1097-1"
protein, which is "Soyprotein 4950" protein that has been treated
with enzyme for 30 minutes, and which is available as available
from Central Soya, Fort Wayne, Ind., may improve the scale
inhibition effect of the anti-scalants of the present
invention.
[0123] When a protein is used with the anti-scalant of the present
invention, an unexpected and surprising synergistic effect may
result. For example, blends of anti-scalant of the present
invention and protein at weight ratios of anti-scalant to protein
of preferably about 50:1 to 1:1, more preferably about 20:1 to 1:1,
and most preferably about 10:1 to 1:1, are often several times more
effective than the individual components. For instance, mixtures of
ground calcium carbonate and either "Soyprotein 3230" protein or
"Soyprotein 4950 #1097-1" protein are often several times more
effective than the individual components.
[0124] Depending upon the type of anti-scalant, the ion exchange
capacity of the anti-scalant may be an important variable. For
anti-scalants which may involve ion exchange for preventing
scaling, such as zeolites, the ion exchange capacity is preferably
at least about 0.1 meq/g, more preferably at least about 0.5 meq/g,
and most preferably about 1.0 meq/g, with ranges typically of about
0.1 to 10 meq/g, more typically about 0.5 to 8.0 meq/g, and most
typically about 1.0 to 8.0 meq/g. In contrast to some of the
anti-scalants of the present invention, the ion exchange capacity
of ground calcium carbonate is not important when the ground
calcium carbonate is used to seed out calcium carbonate.
[0125] When calcium carbonate is used as the anti-scalant, it is
preferred that ground calcium carbonate is used. Ground calcium
carbonate can be produced by either dry or wet grinding of a feed
rock in which the calcium carbonate species are usually divided
into chalk, limestone, and marble. In the dry method, after
screening to remove large particles, the feed rock may be dried
such as in a rotary dryer and milled such as in a ball, roller, or
hammer mill. The finest particles are typically air classified from
the bulk material, with the coarse particles returned to the mill
for further milling. This method is used for chalk fillers that are
easily crumbled and typically produce coarse particles of 5 to 10
microns. Wet grinding, after crushing and ball milling, is more
typical for the production of ground calcium carbonates from
limestones and marbles. Flotation is used in this process to remove
the contaminants, resulting in a high brightness of the finished
product. Products having a median particle size less than 2 microns
are usually wet ground in media or sand mills. Dispersants, such as
those discussed above, are usually added during the grounding
process to form a high solids slurry of the ground calcium
carbonate. The level of impurities in the ground calcium carbonate
is typically at least about 0.5 wt %, more typically at least about
0.8 wt %, and most typically at least about 1 wt %, with a range of
typically about 1 to 2 wt %.
[0126] The inhibition of scaling by ground calcium carbonate
relative to precipitated calcium carbonate was unexpected and
surprising. While not wishing to be bound by theory, it is
hypothesized that the non-porous structure of ground calcium
carbonate is more effective than the porous structure of
precipitated calcium carbonate. It is believed that the pores of
the precipitated calcium carbonate slow the diffusion of aqueous
calcium carbonate to the surface of the calcium carbonate, such
that precipitation of aqueous calcium carbonate on precipitated
calcium carbonate is slow relative to the ground calcium
carbonate.
[0127] Many of the above-described anti-scalants are commercially
available. Additionally, it is possible to form some of the
above-described anti-scalants in situ. For example, calcium
carbonate, magnesium carbonate, amorphous aluminum silicate, and
ferric carbonate may be made in situ.
[0128] There are several ways to make calcium carbonate in situ
which may function as an anti-scalant in accordance with the
present invention. For example, one can purge C0.sub.2 into an
aqueous solution which contains calcium ions, e.g., cooking liquor
or bleach plant filtrate. As another example, calcium ions, e.g.,
from calcium salt, can also be added to an aqueous solution
containing carbonate ions, e.g., cooking liquor or bleach plant
filtrate. In yet another example, calcium carbonate can be produced
via the reaction of CaO with carbonate ions, e.g., calcium
carbonate may be made by the causticizing reaction in the Kraft
mill recovery system in which slaked lime (CaO) reacts with
carbonate ions (via sodium carbonate) to form NaOH and calcium
carbonate.
[0129] When the anti-scalant of the present invention is formed in
situ, it was surprisingly found that some combinations of known
anti-scalants with the in situ formed anti-scalants resulted in
synergism. In particular, synergistic results occur when
precipitated calcium carbonate, i.e., calcium carbonate that was
formed in situ, is combined with known anti-scalants such as
polyacrylic acid, polymaleic acid, copolymers of acrylic acid and
2-acrylamido-2-methylpropanesulfonic acid, and copolymers of
acrylic acid and 2-hydroxy-3-allyloxypropanesulfonic acid, and
phosphorous compounds such as nitrilotrimethylenephosphonic acid,
hydroxy-ethylidenephosphonic acid, phosphonobutanetricarboxylic
acid, and sodium hexametaphosphate. To avoid degrading the
effectiveness of the anti-scalant of the present invention, the pH
of the known anti-scalant is preferably above about 8, more
preferably above about 9, and most preferably above about 10, prior
to adding the anti-scalant of the present invention. In this
regard, polyvalent metal carbonates, such as calcium carbonate,
typically start to dissolve at pH less than 7, and polyvalent metal
silicates become ineffective at low pH due to protonation of
hydrogen ions. To maximize effectiveness, the weight ratio of
precipitated calcium carbonate to conventional anti-scalant is
preferably about 10:1 to 100:1, more preferably about 4:1 to 8:1,
most preferably about 6:1.
[0130] The amount of anti-scalant added to the aqueous system
depends upon such variables as the temperature, the pH, and the
presence of other compounds. Regarding temperature, higher
temperatures usually require higher amounts of anti-scalant. The
effect of changes in pH on the amount of anti-scalant required
depends upon the type of anti-scalant. Similarly, the effect of the
presence of other compounds on the amount of anti-scalant depends
on the other compound. For instance, compounds containing magnesium
and iron may act as poisons such that more anti-scalant would be
necessary. In contrast, compounds such as lignin function as
enhancers such that less anti-scalant is necessary.
[0131] In view of the above, the anti-scalant is added to the
aqueous system at a concentration of preferably about 1 ppb to 10
ppm, more preferably about 1 ppb to 7 ppm, and most preferably
about 1 ppb to 5 ppm, per ppm of water hardness. Thus, the
anti-scalant is added to the system at a concentration of up to
about 50 ppm, more preferably up to about 75 ppm, even more
preferably up to about 95 ppm, even more preferably up to about 200
ppm, even more preferably up to about 500 ppm, and most preferably
up to about 1000 ppm, with ranges of preferably about 1 to 1000
ppm, more preferably about 1 to 500 ppm, and most preferably about
1 to 200 ppm.
[0132] The aqueous system to which the anti-scalant is added may
contain metal ions, such as ions of calcium, barium, magnesium,
aluminum, strontium, iron, etc. and anions such as bicarbonate,
carbonate, oxalate, sulfate, phosphate, silicate, fluoride,
etc.
[0133] The scale which is intended to be prevented by the present
invention may be formed by any combination of the above-noted ions.
For example, the scale may involve a combination of calcium
carbonate and calcium oxalate. The scale typically comprises at
least about 90 wt % of inorganic material, more typically at least
about 95 wt % of inorganic material, and most typically at least
about 99 wt % of inorganic material.
[0134] In aqueous systems having calcium ions and carbonate ions to
which the anti-scalant may be added, prior to the addition of the
anti-scalant, the [Ca.sup.+2] is usually present at about 10 to 500
ppm, more usually about 20 to 300 ppm, and most usually about 50 to
200 ppm. Moreover, prior to addition of the anti-scalant, the
[CO.sub.3.sup.-2] in such systems is usually present at about 100
to 30,000 ppm, more usually about 500 to 25,000 ppm, and most
usually about 1000 to 20,000 ppm.
[0135] In aqueous systems having calcium ions and oxalate ions to
which the anti-scalant may be added, prior to the addition of the
anti-scalant, the [Ca.sup.+2] is usually present at about 5 to 600
ppm, more usually about 10 to 500 ppm, even more usually about 20
to 500 ppm, and most usually about 30 to 400 ppm. Moreover, prior
to addition of the anti-scalant, the [oxalate] in such systems is
usually present at about 0.1 to 10,000 ppm, more usually about 1 to
5000 ppm, and most usually about 5 to 1000 ppm.
[0136] The aqueous system may also include other additives and
compounds. For instance, the polyvalent metal anti-scalants of the
present invention may be used with other anti-scalants such as
those discussed in the Background of the present application, such
as phosphates, acrylates, phosphonates, epoxysuccinic anhydrides,
sulfonates, and maleates. The amount of other anti-scalant to be
combined with the anti-scalant of the present invention depends
upon the system conditions as well as the types of anti-scalants.
The weight ratio of other anti-scalant to the anti-scalant of the
present invention is preferably from about 1:100 to 100:1, more
preferably about 1:30 to 30:1, and most preferably about 1:10 to
10:1. Although the anti-scalants may be added separately to the
aqueous system, with the anti-scalant of the present invention
added before or after the other anti-scalant, it is preferred that
the anti-scalants are pre-mixed prior to addition to the aqueous
system. The procedures for using the anti-scalants together should
preserve the physical/chemical properties of the blends when
mixing, e.g., the pH of the other anti-scalant is preferably above
about 8, more preferably above about 9, and most preferably above
about 10, for the reasons discussed above.
[0137] Other examples of additives include surfactants (e.g.,
ethoxylate/propoxylate (EO/PO) block copolymers, alkyl phenol
ethoxylates, dialkyl sulfosuccinates, alkyl phosphates, alkyl ether
sulfates, ethoxylated sorbitan alkanoates, fatty amine salts, fatty
alcohol ethoxylate, and silicon based surfactants), dispersants
such as those discussed above, pulping aids (e.g., AQ
(anthraquinone), polysulfide, and the surfactants mentioned above),
bleaching agents (e.g., enzymes, hydrogen peroxide, chlorine
dioxide, hypochlorite, oxygen, ozone, and chelating agents such as
EDTA (ethylenediamine tetraacetic acid), as well as flocculation,
coagulation, and clarification polymers in system purge programs,
as discussed in more detail below, e.g., effluent treatments,
recovery boilers, clarifiers, filters, flotation cells, cleaners,
and screens.
[0138] The aqueous system to which the anti-scalant is added may be
at an elevated temperature. For instance, the temperature of the
system may typically be about 25.degree. C. to 500.degree. C., more
typically about 70.degree. C. to 500.degree. C., even more
typically about 80.degree. C. to 200.degree. C. When the
anti-scalant is added to a digester, the temperature of the aqueous
system is usually about 150.degree. C. to 175.degree. C. When the
anti-scalant is added at a chip chute pump prior to the digester,
the temperature of the aqueous system is usually about 80.degree.
C. to 110.degree. C.
[0139] The anti-scalants of the present invention work under
various pH conditions. In particular, the anti-scalants of the
present invention preferably work at a pH from about 2 to 14, more
preferably about 3 to 14, and most preferably about 4 to 14, such
as 10 to 14. As noted above, changes in pH may cause scaling.
[0140] In this regard, the anti-scalants of the present invention
work under acidic conditions against some forms of scale, such as
oxalate scales. For oxalate scaling, the aqueous system to which
the anti-scalant is added often has a pH less than about 7, such as
about 2 to 7, even more usually about 3 to 7. For instance, the pH
in a typical bleach plant stage is usually about 2 to 12, more
usually about 2 to 7, and even more usually about 2.5 to 5.
[0141] For carbonate scaling, the aqueous system to which the
anti-scalant is added often has a basic pH, more usually a pH of at
least about 9, with ranges of usually about 5 to 14, more usually
about 9 to 14, even more usually about 10 to 13. In this regard,
bleaching sequences in paper production generally occur at high pH,
such as typically about 9 to 14, more typically about 10 to 12.
[0142] The aqueous system to which the anti-scalant is added may be
under oxidative conditions. The ability of the anti-scalants of the
present invention to function under oxidative conditions is
important because bleaching conditions are often oxidative.
Furthermore, oxidative conditions often degrade known
anti-scalants. The oxidative conditions may be a result of hydrogen
peroxide or chlorine dioxide. The hydrogen peroxide may be present
at a level of about 100 to 10,000 ppm, more typically about 200 to
2000 ppm, even more preferably about 240 to 750 ppm. The chlorine
dioxide may be present at a level of about 200 to 10,000 ppm, more
typically about 500 to 3000 ppm, even more typically about 600 to
1100 ppm.
[0143] The aqueous system to which the anti-scalant is added may be
under atmospheric conditions or under pressure. For instance, the
pressure is typically about 14 to 1500 psi, more typically about 80
to 1500 psi. When the aqueous system comprises a digester of a
paper mill, the pressure at the digester is typically about 125 to
150 psi. When the aqueous system comprises a boiler, the pressure
at the boiler is typically up to about 1500 psi.
[0144] When the anti-scalant is not formed in situ, to ensure that
the anti-scalant is adequately dispersed in the aqueous system, the
anti-scalant is preferably added in the form of a water-based
slurry. Depending upon the anti-scalant, the water-based slurry may
comprise less than about 5 wt % of anti-scalant, less than about 2
wt % of anti-scalant, at least about 40 wt % of anti-scalant, at
least about 50 wt % of anti-scalant, at least about 60 wt % of
anti-scalant, or at least about 75 wt % of anti-scalant. For
example, for ground calcium carbonate, if the amount of calcium
carbonate is less than about 75 wt %, it may precipitate out of the
slurry. As another example, for bentonite, if the amount of
bentonite is greater than about 5 wt %, it is difficult to
pump.
[0145] Examples of the systems to which the anti-scalant may be
added include industrial water systems preferably having water
throughputs of at least about 10 gpm, more preferably at least
about 20 gpm, and even more preferably at least about 1000 gpm.
Examples of industrial water systems of the present invention
include cooling towers, heat exchangers, evaporators, pulping
digesters, pulp washers, and pulp bleaching equipment. The
industrial water systems may be involved in mining (e.g., ore
washing under alkaline conditions), textiles (e.g., cooling towers,
heat exchangers, washing processes), automotive (e.g., cooling
towers, heat exchangers), food processing (e.g., processing
equipment, clarification, aeration, sterilization, and breweries),
steel making (e.g., cooling towers, heat exchangers), water
treatment (e.g., water purification), and petroleum (e.g., in the
production and processing of crude oil-water mixtures).
[0146] In particular, scale deposition in a digester in kraft pulp
manufacturing can be controlled in accordance with the present
invention. It follows that the run length of the digester can be
extended to achieve improvements in productivity, uniform quality
of pulp, and a reduction in energy loss. Further, troubles arising
from scale deposit are greatly diminished, which makes a valuable
contribution to improvement of operating efficiency.
[0147] The addition point of the anti-scalant may be at or before
where scale may be formed. For example, the anti-scalant may be
added before a pulping digester or at the pulping digester. As
another example, the anti-scalant may be added immediately before
or in bleaching plant equipment. When the anti-scalant is added
before the pulping digester, it is often added after or during
mechanical treatment of the wood chips. For instance, the
anti-scalant may be added after a chip bin, at a wood chip chute
pump, at a cooking liquor heater pump, or at an in-line drainer.
When the anti-scalant is added directly to the digester or other
systems, the addition point may be targeted to where the
anti-scaling is needed most. For instance, the anti-scalant may be
added in the cooking zone of the digester.
[0148] The anti-scalants of the present invention perform better
than known anti-scaling polymers under many conditions. In addition
to adequate or improved performance, the raw material cost of the
polyvalent metal silicates and polyvalent metal carbonates is
significantly lower than that of the known anti-scalants.
Therefore, an advantage of the present invention is
cost-effectiveness.
[0149] Once the anti-scalant has been used, e.g., after the pulp
leaves the digester or after the bleaching process is completed, it
may be preferred that the anti-scalant be removed from the system,
e.g., the cooking liquor or the bleaching liquid. The removal of
the anti-scalant depends upon the system and may involve mechanical
and/or chemical separation techniques.
[0150] The mechanical separation may be by devices such as
clarifiers, flotation cells, settling tanks, filters (pre-coat and
cloth covered), centrifuges, and osmosis devices.
[0151] The chemical separation may involve use of clarifying aids,
which may involve combining or reacting organic or inorganic
chemicals with solids to form large masses that tend to separate
rapidly. High molecular weight organic water soluble polymers are
widely used as coagulants. Coagulant polymers may be cationic
(e.g., polydiallyldimethylammonium chloride (polyDADMAC),
polyamines), anionic (e.g., polyacrylamides, polyamides,
polyacrylic acids), and nonionic (e.g., polyethylene oxide,
polyvinyl alcohol). The amount of coagulant polymer is preferably
up to about 10 ppm, more usually up to about 5 ppm, and most
usually up to about 0.5 ppm. The coagulant polymers may have a
molecular weight greater than about 1.times.10.sup.6, with a usual
range of about 1.times.10.sup.6 to 10.times.10.sup.6. Inorganic
compounds such as alum hydroxide and iron hydroxide can also be
used as coagulants.
[0152] The present invention will be further illustrated by way of
the following Examples. These examples are non-limiting and do not
restrict the scope of the invention.
[0153] Unless stated otherwise, all percentages, parts, etc.
presented in the examples are by weight.
EXAMPLES 1-39 AND COMPARATIVE EXAMPLES 1 AND 2
[0154] A bottle test was conducted to determine the effect of
polyvalent metal silicates and polyvalent metal carbonates on
calcium carbonate scale inhibition and to compare their performance
to known scale inhibitors. As discussed in more detail below, the
test conditions were 70.degree. C., pH 12.4, and a one-hour
incubation time with mild agitation.
[0155] An aqueous hardness solution of 2.205 wt % calcium chloride
was prepared. An aqueous alkaline solution of 0.18 wt % sodium
carbonate and 0.2125 wt % sodium hydroxide was prepared. Both
solutions were simultaneously added to 100 ml glass bottles
followed by anti-scalants, as listed in Table 1, in proportions to
achieve 100 g of final solution having the compositions listed in
Tables 2 and 3, below. The solution pH was adjusted to 12.4 by
adding sodium hydroxide. As shown in Tables 2 and 3, the final
solution involved either a "mild" scaling condition of 60 ppm
Ca.sup.+2 (150 ppm as CaCO.sub.3) and 1000 ppm CO.sub.3.sup.-2, or
a "harsh" scaling condition of 100 ppm Ca.sup.+2 (250 ppm as
CaCO.sub.3) and 10,000 ppm CO.sub.3.sup.-2.
[0156] After being agitated for 1 hour at 70.degree. C., the
solution was removed from the test bottle and subjected to vacuum
filtration using a #4 Whatman filter (pore size<20-25 .mu.m).
Concerning the pore size of the filter, for these Examples and
Comparative Examples, it is approximated that CaCO.sub.3 crystals
having a particle size less than about 20-25 microns have less
tendency to precipitate on a substrate, and that crystals having a
particle size greater than about 20-25 microns would be more likely
to precipitate on a substrate and, therefore, would likely
precipitate as scale. For instance, the relationship between
particle size, crystallization rate, and precipitation is discussed
in column 3 of U.S. Pat. No. 3,518,204 to HANSEN et al., the
disclosure of which is herein incorporated by reference in its
entirety. The filtrate sample was added to 2 grams of 30 wt %
hydrochloric acid to prevent further crystal formation/growth.
[0157] After removal of the test solution from the test bottle, an
"adherent" sample was generated for each test bottle, which
involved rinsing the glass bottle with 50 grams of 14 wt % nitric
acid. The adherent sample indicates the amount of calcium carbonate
that deposits onto the bottle surface during the test period.
[0158] All liquid samples were analyzed by Inductively Coupled
Plasma (ICP) for calcium ion concentrations. ICP was conducted by
using an "IRIS-AP Duo" inductively coupled plasma spectrometer
available from Thermo Jarrell Ash Corporation, Franklin, Mass. The
operating conditions of the "IRIS-AP Duo" inductively coupled
plasma spectrometer were as follows. The exhaust was turned on and
the pressure gauge indicated a pressure drop of 0.8 to 1.2 psi. The
CID (charge injection device) temperature was below -70.degree. C.
and the FPA (Focal Plane Array) temperature was above 5.degree. C.
The purge time was set to 90 seconds. The ignition parameters were:
RF (Radio Frequency) Power: 1150 watts, Auxiliary Flow: medium,
Nebulizer Flow: 0.55 L/min, and Pump Rate 110 rpm. The purge gas
valves for tank and main were set to 4 L/min and 6 L/min,
respectively. The camera valve setting was 2 L/min. After the
spectrometer was set as discussed above, the spectrometer was
allowed to warm up for at least 15 minutes before running the
auto-sampler.
[0159] As noted above, Table 1 lists the anti-scalants which were
used in the Examples and Comparative Examples of the present
application.
1TABLE 1 Anti- Trade Physical/Chemical Scalant Chemical Name Name
Mfg. Properties A sodium Valfor 100 The PQ Corp., Silica-to-alumina
molar ratio = 2:1 aluminosilicate Valley Forge, median particle
size 3 to 6 .mu.m (hydrated Na-A PA normal pore size diameter = 4.2
Angstroms type zeolite) pH of 1 wt % dispersion = 10 to 11 ion
exchange capacity = 5.6 Meq/g hydrated zeolite calcium exchange
capacity = 270-300 mg CaCO.sub.3/g anhydrous zeolite Na.sub.2O(17
wt %), Al.sub.2O.sub.3(28 wt %), SiO.sub.2(33 wt %), H.sub.2O(22 wt
%) B sodium Valfor CBV The PQ Corp., SiO.sub.2/Al.sub.2O.sub.3 mole
ratio = 20 aluminosilicate 20A Valley Forge, Surface Area = 500
m.sup.2/g (mordenite type PA zeolite) C magnesium Min-U-Gel
Floridin, median particle size 3.22 .mu.m aluminum silicate 400
Tallahassee, FL (range 3.02 to 3.47 .mu.m) (colloidal pH = 9.7 sp.
gr. = 2.4 attapulgite clay) Al.sub.2O.sub.3(10.37 wt %),
SiO.sub.2(58.66 wt %), MgO(8.59 wt %), Fe.sub.2O.sub.3(3.56 wt %),
CaO(2.59 wt %), H.sub.2O(11.4 wt %) D ground calcium Hydrocarb
OMYA, Inc., mean particle diameter = 1.9 .mu.m carbonate 60
Proctor, VT specific surface area = 6 m.sup.2/g pH slurry = 8.5 sp.
gr. = 2.71 E ground calcium Hydrocarb OMYA, Inc., mean particle
diameter = 0.7 .mu.m carbonate 65 Proctor, VT specific surface area
= 14 m.sup.2/g pH slurry = 8.5 sp. gr. = 2.71 F ground calcium
Hydrocarb OMYA, Inc., mean particle diameter = 0.3 .mu.m carbonate
HG Proctor, VT pH slurry = 8.5 sp. gr. = 2.71 G sodium Bentolite
Southern Clay particle size range = 0.1 to 5 microns
montmorillonite HS Products, Inc., pH = 10.3 moisture = 6 wt %
(bentonite) Gonzales, TX H synthetic hectorite Laponite Southern
Clay surface area = 370 m2/g (synthetic RD Products, Inc., pH of 2
wt % suspension = 9.8 magnesium Gonzales, TX SiO.sub.2(59.5 wt %),
MgO(27.5 wt %), silicate) Na.sub.2O(2.8 wt %), Li.sub.2O(0.8 wt %),
ignition loss (8.2 wt %) I talc Vantalc R.T. Vanderbilt mean
particle diameter = 2.8 .mu.m (hydrous F2003 Co., Norwalk, specific
surface area = 10 m.sup.2/g magnesium CT pH slurry = 9.5 sp. gr. =
2.75 silicate) SiO.sub.2(59.5 wt %), MgO(30.4 wt %),
Al.sub.2O.sub.3(0.4 wt %), Fe.sub.2O.sub.3(3.2 wt %), CaO(0.3 wt
%), ignition loss (6.3 wt %) J magnesium Veegum R.T. Vanderbilt
SiO.sub.2(63 wt %), MgO(10.5 wt %), aluminum silicate Co., Norwalk,
Al.sub.2O.sub.3(10.5 wt %), Fe.sub.2O.sub.3(0.9 wt %), (smectite
clay) CT CaO(2.3 wt %), Na.sub.2O(2.4 wt %), K.sub.2O(1.3 wt %),
ignition loss (7.5 wt %) sp. gr. = 2.6 pH slurry = 9.5 K hydrated
Veegum HV R.T. Vanderbilt SiO.sub.2(62 wt %), MgO (11.9 wt %),
magnesium Co., Norwalk, Al.sub.2O.sub.3(10.7 wt %),
Fe.sub.2O.sub.3(0.7 wt %), aluminum silicate CT CaO (2.4 wt %),
Na.sub.2O(2.6 wt %), (smectite clay) K.sub.2O(1.7 wt %), ignition
loss (9 wt %) L sodium Zeolex 23A Kraft Chemical avg. particle size
= 6 .mu.m aluminosilicate Co., Melrose pH of 20 wt % dispersion =
10.2 (synthetic Park, IL surface area = 75 m.sup.2/g amorphous
precipitated silicate) M amorphous DAC III Delta Chem., sp. gr. =
2.5 magnesium silicate Inc., Searsport, ME N a blend of magnesium
GEL IMV Nevada, 97% minimum <200 mesh bentonite and calcium
Armdosa SiO.sub.2(47.2 wt %), Al.sub.2O.sub.3(14.1 wt %), bentonite
Valley, NV MgO(12.4 wt %), Fe.sub.2O.sub.3(2 wt %), CaO(4.2 wt %) O
sepiolite Thermogel IMV Nevada, finely-ground powder Armdosa
SiO.sub.2(56 wt %), Al.sub.2O.sub.3(4 wt %), MgO(20 Valley, NV wt
%), Fe.sub.2O.sub.3(1 wt %), CaO(0.5 wt %) P hydrated Veegum F R.T.
Vanderbilt 2 to 4 wt % cristobalite magnesium Co., Norwalk,
aluminum silicate CT Q hydrated VanGel B R.T. Vanderbilt 4 to 6 wt
% cristobalite magnesium Co., Norwalk, aluminum silicate CT R
sepiolite Sepiogel F IMV Nevada, 90% minimum <325 mesh Armdosa
moisture = 14 wt % Valley, NV S calcium bentonite IGB IMV Nevada,
98% minimum <200 mesh Armdosa moisture = 13 wt % Valley, NV
SiO.sub.2(50.9 wt %), Al.sub.2O.sub.3(20.8 wt %),
Fe.sub.2O.sub.3(1.5 wt %), MgO(2.4 wt %), CaO(4 wt %) T saponite
Imvite 1016 IMV Nevada, finely-ground powder moisture = 10 wt %
(magnesium Armdosa SiO.sub.2(44.6 wt %), Al.sub.2O.sub.3(7.8 wt %),
bentonite) Valley, NV Fe.sub.2O.sub.3(2.5 wt %), MgO(22.8 wt %),
CaO(4.5 wt %) U magnesium Magnabrite American soft white flakes
aluminum silicate T Colloid Co., sp. gr. = 2.6 Arlington Heights,
IL V precipitated Multifex MM Whittaker, Clark particle size of
0.07 microns calcium Ultrafine & Daniels, Inc., with untreated
surface carbonate Particle 5961 South Plainfield, NJ W reagent
grade ACS reagent Sigma particle size >2 microns precipitated
[471-34-1] Chemical chelometric standard calcium carbonate
Corporation, St. Louis, MO
[0160] The conditions and results of these tests are shown in
Tables 2 and 3 below. For Table 2 the test conditions were at a
temperature of 70.degree. C., pH of 12.5, [Ca.sup.+2]=60 ppm, and
[CO.sub.3.sup.-2]=1000 ppm. In Table 2, "% inhibition" is a
relative measure of how much scale formation is prevented, such
that higher values reflect better prevention of scale formation.
Percent inhibition is calculated as follows: 1 % inhibition = ( Ca
conc . of treated sample ) - ( Ca conc . of untreated sample ) ( Ca
conc . total ) - ( Ca conc . of untreated sample )
[0161] Taking into consideration that the Ca concentration (as
CaCO.sub.3) of the untreated sample is the Ca concentration (as
CaCO.sub.3) of Comparative Example 1 which is 5.9 ppm, and taking
into consideration that the Ca concentration (as CaCO.sub.3) total
is 150 ppm, the percent inhibition for Example 1 is
11%=(21-5.9)/(150-5.9). Although higher % inhibitions are
preferred, the % inhibition is preferably at least about 85%. Also,
in Table 2, "% deposition" is the weight percent of Ca (as
CaCO.sub.3) which deposited on the surface.
2 TABLE 2 Soluble Calcium Conc. (CaCO.sub.3 Scale Deposition
crystal size <20 micron) on Surface Ca Conc. Ca Conc. Conc. (as
CaCO.sub.3) (as CaCO.sub.3) Example Anti-scalant (ppm) (ppm) %
Inhibition (ppm) % deposition Comp. 1 None -- 5.9 -- 22 15% 1 A 50
21 11% 2.8 2% 2 A 100 96 63% 7.6 5% 3 B 25 17 8% 13 9% 4 B 50 16 7%
9 6% 5 B 100 19 9% 9.7 7% 6 C 25 54 33% 2.8 2% 7 C 50 63 40% 2.3 2%
8 C 100 76 49% 1.8 1% 9 G 25 56 35% 2.8 2% 10 G 50 54 33% 1.6 1% 11
G 100 139 92% 1.1 1% 12 H 100 96 62% 7 5% 13 I 25 38 22% 2.1 1% 14
I 50 41 25% 2.1 1% 15 I 100 33 19% 1.9 1% 16 L 100 23 12% 17 11% 17
M 100 55 34% 7.4 5% 18 N 50 128 85% 1.8 1% 19 N 100 138 92% 2.7 2%
20 0 50 88 57% 2.7 2% 21 0 100 96 63% 2.7 2% 22 P 50 102 67% 1.4 1%
23 P 100 92 60% 2.4 2% 24 Q 50 73 47% 2.5 2% 25 Q 100 93 60% 5.1 3%
26 R 50 108 71% 1.5 1% 27 R 100 110 72% 1.8 1% 28 S 50 97 63% 2.2
2% 29 S 100 117 77% 2.9 2% 30 T 50 127 84% 1.9 1% 31 T 100 127 84%
2.1 1% 32 U 50 118 78% 1.5 1% 33 U 100 122 81% 1.2 1%
[0162] Table 2 shows that under the "mild" scaling condition (i.e.,
60 ppm Ca.sup.+2 and 1000 ppm CO.sub.3.sup.-2), all tested
anti-scalants, except anti-scalants B and L, were effective at
either inhibiting crystal formation or reducing scale deposition on
surface. The percent scale deposition was significantly reduced
when calcium carbonate was treated with these polyvalent metal
silicates and polyvalent metal carbonates, especially anti-scalants
C, G, I, and N-U.
[0163] In Table 3 below, the test conditions were at a temperature
of 70.degree. C., pH 12.5, [Ca.sup.+2]=100 ppm, and
[CO.sub.3.sup.-2]=10,000 ppm.
3 TABLE 3 Soluble Calcium Conc. (CaCO.sub.3 Scale Deposition
crystal size <20 micron) on Surface Ca Conc. Ca Conc. Conc. (as
(as Example Anti-scalant (ppm) CaCO.sub.3) % Inhibition CaCO.sub.3)
% deposition Comp. 2 None -- 15 -- 27.0 11% 34 G 50 54 17% 4.5 2%
35 N 50 161 62% 3.7 2% 36 0 50 87 31% 4.5 2% 37 R 50 95 34% 4.2 2%
38 T 50 181 71% 3.1 1% 39 U 50 154 59% 2.9 1%
[0164] Table 3 indicates that anti-scalants G, N, O, R, T, and U
were also effective at reducing scale formation and deposition
under the "harsh" condition (i.e., 100 ppm Ca.sup.+2 and 10,000 ppm
CO.sub.3.sup.-2).
[0165] In looking at the data of Tables 2 and 3, it should be noted
that polyvalent metal silicates and polyvalent metal carbonates,
such as magnesium aluminum silicate, magnesium silicate, magnesium
bentonite, calcium bentonite, and sepiolite, are not normally used
as water softeners, due to the lack of ion-exchanging properties.
However, these polyvalent metal silicates and polyvalent metal
carbonates perform effectively for CaCO.sub.3 scale control.
Surprisingly, sodium aluminosilicates (e.g., anti-scalant B and L),
which supposedly function as water softeners, do not perform as
well in terms of inhibiting CaCO.sub.3 crystal formation and
reducing scale deposition.
EXAMPLES 40-43 AND COMPARATIVE EXAMPLES 3-7
[0166] A "Parr.RTM." bomb test was conducted to compare the
performance of sodium montmorillonite (bentonite), i.e.,
anti-scalant G, with a known anti-scaling polymer. The experiments
were conducted at a temperature which simulates the temperature of
kraft pulping processes.
[0167] The test conditions were 170.degree. C., pH 12.4, 60 ppm
Ca.sup.+2, 1000 ppm CO.sub.3.sup.-2, and a one-hour incubation time
without agitation. The carbonate solution was preheated to
70.degree. C. before mixing to obtain solutions having the
concentrations listed in Tables 4 and 5, using the procedure
described in Examples 1-39 and Comparative Examples 1 and 2.
[0168] After adding the solution to a Parr.RTM. bomb, Model 4751
available from Parr Instrument Company, Moline, Ill., having a
capacity of 125 ml, the bombs were placed in an oven at 170.degree.
C. for one hour at a typical pressure of between 120 and 150 psi.
After treatment, the bombs were removed from the oven and allowed
to cool for one hour. The resulting fluids were removed from the
bombs and subjected to a vacuum filtration as described in Examples
1-39 and Comparative Examples 1 and 2. After the fluid was removed
from the bomb, an "adherent" sample was also generated from each
Parr.RTM. bomb by dissolving the deposited calcium carbonate on the
substrate surface with 50 grams of 14 wt % nitric acid. All fluid
samples were analyzed by Inductively Coupled Plasma (ICP) for
calcium ion concentrations using the procedure described in
Examples 1-39 and Comparative Examples 1 and 2.
[0169] In Table 4 below, the test conditions were at a temperature
of 170.degree. C., pH 12.5, [Ca.sup.+2]=60 ppm, and
[CO.sub.3.sup.-2]=1000 ppm. Comparative Examples 4 and 5 involve
"DRAWFAX342" copolymer of maleic acid and acrylic acid (2:1 molar
ratio) having a molecular weight of about 2700, available from Draw
Chemical Company.
4 TABLE 4 Soluble Calcium Conc. Scale Deposition (crystal size
<20 micron) on Surface Ca Conc. Ca Conc. Conc. (as (as % Example
Anti-scalant (ppm) CaCO.sub.3) % Inhibition CaCO.sub.3) Deposition
Comp. 3 None -- 11 -- 77 51% 40 G 25 44 24% 62 41% 41 G 50 56 32%
43 29% 42 G 100 128 84% 21 14% Comp. 4 DF342 20 34 16% 58 39% Comp.
5 DF342 30 22 7% 47 31%
[0170] Table 4 shows that anti-scalant G, i.e., sodium
montmorillonite, is more effective than the known polymer, i.e.,
"DRAWFAX342" copolymer of maleic acid and acrylic acid, with
respect to the inhibition of crystal growth and reduction in scale
deposition.
[0171] In Table 5 below, the test conditions were at a temperature
of 170.degree. C., pH 12.5, [Ca.sup.+2]=100 ppm, and
[CO.sub.3.sup.-2]=10,00- 0 ppm.
5 TABLE 5 Soluble Calcium Conc. Scale Deposition (crystal size
<20 micron) on Surface Ca Conc. Ca Conc. Conc. (as (as % Example
Anti-scalant (ppm) CaCO.sub.3) % Inhibition CaCO.sub.3) Deposition
Comp. 6 None -- 7.4 -- 88 35% 43 G 100 125 48% 8 3% Comp. 7 DF342
100 106 41% 98 39%
[0172] Table 5 shows that anti-scalant G, i.e., sodium
montmorillonite, performed even better when subjected to the
"harsh" condition.
EXAMPLES 44-66 AND COMPARATIVE EXAMPLES 8-18
[0173] These Examples and Comparative Examples involve using a
dynamic tube blocking test to study the effectiveness of various
scale inhibitors. A basic solution containing carbonate and
anti-scalant was mixed with a calcium solution in a capillary to
test the effectiveness of the anti-scalants in preventing scaling
as measured by pressure build-up in the capillary.
[0174] In view of the above, except for Examples 54 and 55 which
involved 73.78 g/l Na.sub.2CO.sub.3, the basic solution
included:
[0175] 37.09 g/l Na.sub.2CO.sub.3;
[0176] 6 g/l NaOH (50 wt %); and
[0177] anti-scalant in an amount to obtain the concentrations of
Tables 6 and 7.
[0178] The basic solution was fed through a first capillary at a
flow rate of 12.5 ml/min. The calcium solution involved 0.74 g/l
CaCl.sub.2.2H.sub.2O and was fed at a rate of 12.5 ml/min through a
second capillary which joined the first capillary to form a 2
meter-long capillary tube (internal diameter 0.127 cm).
[0179] As a result, the basic solution and calcium solution were
mixed to form a supersaturated solution. The composition of the
supersaturated aqueous solution was as follows, except for Examples
54 and 55 which involved 20,000 ppm of carbonate:
6 Calcium ions 96 ppm Carbonate ions 10,054 ppm NaOH 0.15 wt % (pH
= 12.5) Temperature 170.degree. C.
[0180] The supersaturated solution was pumped through the 2
meter-long capillary at a flow rate of 25 ml/min at a temperature
of 170.degree. C. and pressure of 55 psi.
[0181] Calcium carbonate crystals formed and precipitated as soon
as the two solutions were mixed in the capillary tube. The degree
of precipitation was dependent on the effectiveness and
concentration of the scale inhibitor, and was indicated by the back
pressure across the capillary, which was measured by a pressure
transducer. A low differential pressure was indicative of an
effective treatment. The test was run for 30 minutes or until an
increase of 1 psi was obtained. The longer the time (i.e., induced
time) elapsed to reach 1 psi, the more effective the chemical
treatment.
[0182] As listed in Tables 6 and 7, a number of polyvalent metal
silicates and polyvalent metal carbonates were tested using the
dynamic tube blocking test and the results were compared to the
performance of known anti-scalants, such as PESA (polyepoxysuccinic
acid), AMP (amino tri-(methylene phosphonic acid)), PBTC
(2-phosphonobutane-1,2,4-tricarbox- ylic acid), "DRAWFAX342"
copolymer (described above), and "SB 37105" polyacrylic acid having
a molecular weight of 3300, available from Performance Process
Incorporated, Mundelein, Ill.
7TABLE 6 Conc. Induction Time to 1 psi Example Anti-scalant (ppm)
[CO.sub.3.sup.-2] (minutes) Comp. 8 None -- 10,054 2 Comp. 9 PESA
25 10,054 2 Comp. 10 PESA 50 10,054 2 Comp. 11 DF342 50 10,054 11
Comp. 12 DF342 70 10,054 14 Comp. 13 DF342 150 10,054 20 Comp. 14
SB 37105 45 10,054 6 Comp. 15 SB 37105 150 10,054 26 Comp. 16 AMP
60 10,054 24 Comp. 17 PBTC 50 10,054 14 44 E 30 10,054 29 45 F 10
10,054 29 46 F 15 10,054 >30 (0.7 psi @ 30 min) 47 F 30 10,054
26 48 G 15 10,054 10 49 G 30 10,054 31 (0.9 psi @ 30 min) 50 G 50
10,054 >30 (0.8 psi @ 30 min) 51 G 70 10,054 >30 (0.3 psi @
30 min) 52 G 150 10,054 >30 (0.3 psi @ 30 min) 53 K 150 10,054
20 54 K 500 20,000 4 55 G 200 20,000 >30 (0.5 psi @ 30 min)
[0183] The results in Table 6 indicate that PESA and maleic acid
copolymer were not effective at inhibiting crystal growth and
reducing scale deposition on the tube surface, as reflected by the
very short induction time (2-6 minutes) to reach a differential
pressure of 1 psi. In comparison, the untreated calcium carbonate
solution reached this differential pressure in approximately 2
minutes.
[0184] Table 6 also indicates that the performance of anti-scalants
E, F, and G was superior to the known anti-scalants. For instance,
the performance of anti-scalant G at 30 ppm was more efficient than
that of AMP at 60 ppm. It was expected that sodium aluminosilicate
zeolite (i.e., anti-scalant A) would not perform well under the
conditions of 96 ppm calcium and 20,000 ppm carbonate
concentration, while Example 55 shows that under these conditions
anti-scalant G still effectively controlled CaCO.sub.3 scale
formation and deposition.
[0185] Table 7 involves scale inhibition of sodium montmorillonite
blended with either another polyvalent metal silicate or a
polyvalent metal carbonate.
8TABLE 7 Anti- Conc. Induction Time to 1 psi Ex. Scalant (ppm)
(minutes) Comp. 18 None 2 56 G 30 ppm 31 (0.9 psi @ 30 min) 57 G 50
ppm >30 (0.8 psi @ 30 min) 58 G 70 ppm >30 (0.3 psi @ 30 min)
59 G/J (1:1) 40 ppm >30 (0.4 psi @ 30 min) 60 J 70 ppm 6 61 J
150 ppm 20 62 G/E (1:1) 30 ppm >30 (0.9 psi @ 30 min) 63 G/E
(1:3) 30 ppm 26 (0.6 psi @ 30 min) 64 G/F (2:1) 10 ppm >30 (0.3
psi @ 30 min) 65 G/F (2:1) 20 ppm >30 (0.3 psi @ 30 min) 66 G/F
(2:1) 200 ppm >30 (0.2 psi @ 30 min)
[0186] Table 7 shows that a strong synergism was observed when
anti-scalant F was blended with anti-scalant G at a weight ratio of
1:2 before addition to the aqueous system. For instance, at 30
minutes the blend still exhibited a very low differential pressure
(0.3 psi), at a very low dosage of 10 ppm. In comparison, a
differential pressure of 1 psi was reached for anti-scalant G (15
ppm) at 10 minutes and 29 minutes for anti-scalant F (10 ppm) at
the same pressure. Table 7 also shows that a blend of anti-scalant
J and anti-scalant G appeared to show a synergy.
EXAMPLES 67-71 AND COMPARATIVE EXAMPLES 19-26
[0187] A bottle test was conducted to compare the effect of calcium
carbonate and known anti-scalants on calcium carbonate and calcium
oxalate scale inhibition at different pH's. As discussed in more
detail below, the test conditions were 70.degree. C. and a one-hour
incubation time wiuth mild agitation.
[0188] Final solutions were generally prepared in accordance with
the procedure of Examples 1-39 and Comparative Examples 1 and 2. In
this regard, although the amount of solution used in each bottle
test was 100 g, the amount of final solution prepared was sometimes
greater than 100 g. In each case, however, the final solution had
60 ppm calcium, 500 ppm carbonate, and 100 ppm oxalate. The source
for calcium and carbonate was the same as Examples 1-39 and
Comparative Examples 1 and 2, and the source for oxalate was sodium
oxalate. The solution pH was adjusted to the pH listed in Table 8,
below, by adding sodium hydroxide.
[0189] After being agitated for 1 hour at 70.degree. C., the
solution was removed from the test bottle and subjected to vacuum
filtration using a #114 Whatman filter (pore size 20 .mu.m). As
noted above, it is approximated that CaCO.sub.3 and calcium oxalate
crystals having a particle size less than about 20 microns have
less tendency to precipitate on a substrate, and that crystals
having a particle size greater than about 20 microns would be more
likely to precipitate on a substrate and, therefore, would likely
precipitate as scale. The filtrate sample was added to 2 grams of
30 wt % hydrochloric acid to prevent further crystal
formation/growth.
[0190] After removal of the test solution from the test bottle, an
"adherent" sample was generated from each test bottle in the same
manner as Examples 1-39 and Comparative Examples 1 and 2. All
liquid samples were analyzed by Inductively Coupled Plasma (ICP)
for calcium ion concentrations in the same manner as Examples 1-39
and Comparative Examples 1 and 2.
[0191] The conditions and results of these tests are shown in Table
8 below. For Table 8 the test conditions were at a temperature of
70.degree. C., [NaCl]=0.3 wt %, [Ca.sup.+2]=100 ppm,
[CO.sub.3.sup.-2]=500 ppm, and [oxalate]=100 ppm. In Table 8, SL
4560 and SL 4600 are "SL 4560" anti-scalant and "SL 4600"
anti-scalant, respectively, both available from Hercules
Incorporated, Wilmington, Del. "SL 4560" and "SL 4600"
anti-scalants are proprietary blends of polycarboxylate and
phosphate.
9TABLE 8 % Scale Example Anti-scalant Dosage, ppm as actives pH
Inhibition 67 F 0.5 9.4 84 68 F 0.5 10.0 90 69 F 0.5 10.5 83 70 F
0.5 11.0 80 71 F 0.5 11.5 95 Comp. 19 SL 4560 2.5 9.4 94 Comp. 20
SL 4560 2.5 10.0 91 Comp. 21 SL 4560 2.5 11.0 67 Comp. 22 SL 4560
2.5 11.0 39 Comp. 23 SL 4560 2.5 11.5 28 Comp. 24 SL 4600 5.0 9.4
87 Comp. 25 SL 4600 5.0 10.0 40 Comp. 26 SL 4600 5.0 10.5 41
[0192] Table 8 shows that anti-scalant F, i.e., calcium carbonate,
which is in accordance with the present invention, performs well
relative to known anti-scalants. In particular, lower dosages of
the anti-scalant of the present invention generally performed at
least as well as higher dosages of the known anti-scalants.
Furthermore, lower dosages of the anti-scalant of the present
invention outperformed higher dosages of the known anti-scalants at
higher pH.
EXAMPLES 72-74 AND COMPARATIVE EXAMPLES 27-35
[0193] A bottle test was conducted to compare the effect of calcium
carbonate and known anti-scalants on calcium carbonate and calcium
oxalate scale inhibition at higher concentrations of at least one
of calcium, carbonate, and oxalate, relative to Examples 67-71 and
Comparative Examples 19-26. The procedures were the same as in
Examples 67-71 and Comparative Examples 19-26, except that the
concentration of at least one of calcium, carbonate, and oxalate
was increased as shown in Tables 9-11, below.
[0194] The conditions and results of a first set of tests are shown
in Table 9 below. For Table 9 the test conditions were at a
temperature of 70.degree. C., 1 hour incubation time, pH=11.0,
[NaCl]=0.3 wt %, [Ca.sup.+2]=100 ppm, [CO.sub.3.sup.-2]=500 ppm,
and [oxalate]=100 ppm. In Table 9, as well as in Tables 10 and 11,
SL 4560 and SL 4600 refer to "SL 4560" anti-scalant and "SL 4600"
anti-scalant, respectively, both available from Hercules
Incorporated, Wilmington, Del., and AR970A refers to "AR970A"
polyacrylate anti-scalant available from ALCO Chemical,
Chattanooga, Tenn. For Table 9, the % inhibition is based on 20 ppm
of calcium carbonate recovered in an untreated sample, and the
dashes "-" indicate not tested.
10 TABLE 9 % Inhibition, at indicated dosage of actives (ppm)
Example Anti-scalant 0.1 0.5 1.0 2.5 5.0 10.0 50.0 Comp. 27 SL 4560
-- 3 8 29 32 92 -- Comp. 28 SL 4600 -- 2 3 8 17 43 -- 72 F 0 29 86
-- 89 -- 92 Comp. 29 AR 970A -- -- -- -- 9 13 --
[0195] Table 9 shows that the calcium carbonate of the present
invention inhibited scaling more effectively than the known
anti-scalants under the conditions described.
[0196] The conditions and results of a second set of tests are
shown in Table 10 below. For Table 10 the test conditions were at a
temperature of 70.degree. C., 1 hour incubation time, pH =11.0,
[NaCl]=0.3 wt %, [Ca.sup.+2]=100 ppm, [CO.sub.3.sup.-2]=1000 ppm,
and [oxalate]=100 ppm. For Table 10, the % inhibition is based on
24 ppm of calcium carbonate recovered in an untreated sample.
11 TABLE 10 % Inhibition, at indicated dosage of actives (ppm)
Example Anti-scalant 0.1 0.5 1.0 2.5 5.0 10.0 50.0 Comp. 30 SL 4560
-- 0 1 11 17 18 -- Comp. 31 SL 4600 -- 0 0 0 2 5 -- 73 F 0 12 92 --
93 -- 97 Comp. 32 AR 970A -- -- -- -- 5 3 --
[0197] Table 10 shows that the calcium carbonate of the present
invention inhibited scale more effectively than the known
anti-scalants under the conditions described.
[0198] The conditions and results of a third set of tests are shown
in Table 11 below. For Table 11 the test conditions were at a
temperature of 70.degree. C., 1 hour incubation time, pH=11.0,
[NaCl]=0.3 wt %, [Ca+.sup.+2]=100 ppm, [CO.sub.3.sup.-2]=1000 ppm,
and [oxalate]=300 ppm. For Table 11, the % inhibition is based on
30 ppm of calcium carbonate recovered in an untreated sample.
12 TABLE 11 % Inhibition, at indicated dosage of actives (ppm)
Example Anti-scalant 0.1 0.5 1.0 2.5 5.0 10.0 50.0 Comp. 33 SL 4560
-- 0 1 8 10 22 -- Comp. 34 SL 4600 -- 0 0 0 3 9 -- 74 F 0 24 90 --
93 -- 97 Comp. 35 AR 970A -- -- -- -- 2 4 --
[0199] Table 11 shows that the calcium carbonate of the present
invention inhibited scale more effectively than the known
anti-scalants undeer the conditions described.
EXAMPLES 75-82 AND COMPARATIVE EXAMPLES 36-47
[0200] A bottle test was conducted to compare the effect of calcium
carbonate and known anti-scalants on calcium carbonate scale
inhibition under oxidative conditions and at higher concentrations
of calcium, relative to Examples 1-39 and Comparative Examples 1
and 2. The procedures were the same as in Examples 1-39 and
Comparative Examples 1 and 2, except as specified below, e.g., the
concentration of calcium was higher, the pH was lower, and some of
the examples were under oxidative conditions from hydrogen
peroxide.
[0201] Final solutions were generally prepared in accordance with
the procedure of Examples 1-39 and Comparative Examples 1 and 2. In
this regard, although the amount of solution used in each bottle
test was 100 g, the amount of final solution prepared was sometimes
greater than 100 g. In each case, however, the final solution had
100 ppm calcium and 1000 ppm carbonate. The solution pH was
adjusted to 11.0 by adding sodium hydroxide.
[0202] In those Examples involving hydrogen peroxide, the hydrogen
peroxide was as follows: 1 g of 5000 ppm of hydrogen peroxide was
added to 1 g of the anti-scalant and the solution was incubated for
10 minutes at 70.degree. C. After the incubation, the hydrogen
peroxide solution was added to 98 g of solution containing calcium
carbonate or oxalate.
[0203] After being agitated for 1 hour at 70.degree. C., the
solution was removed from the test bottle and subjected to vacuum
filtration using a #114 Whatman filter (pore size 20 .mu.m). After
removal of the test solution from the test bottle, an "adherent"
sample was generated from each test bottle in the same manner as
Examples 1-39 and Comparative Examples 1 and 2. All liquid samples
were analyzed by Inductively Coupled Plasma (ICP) for calcium ion
concentrations in the same manner as Examples 1-39 and Comparative
Examples 1 and 2.
[0204] Conditions and results are shown in Table 12 below. For
Table 12 the test conditions were at a temperature of 70.degree.
C., 1 hour incubation time, pH=11.0, [Ca.sup.+2]=150 ppm, and
[CO.sub.3.sup.-2]=1000 ppm.
13TABLE 12 Dosage, ppm Example Anti-scalant as actives
[H.sub.2O.sub.2] (ppm) % Inhibition 75 F 0.5 0 56 76 F 1 0 89 77 F
5 0 96 78 F 50 0 92 Comp. 36 SL 4560 5 0 8 Comp. 37 SL 4560 10 0 8
Comp. 38 SL 4560 25 0 98 Comp. 39 SL 4560 50 0 99 Comp. 40 SL 4600
5 0 0 Comp. 41 SL 4600 50 0 13 79 F 0.5 50 15 80 F 1 50 89 81 F 5
50 95 82 F 50 50 98 Comp. 42 SL 4560 5 50 1 Comp. 43 SL 4560 10 50
5 Comp. 44 SL 4560 25 50 99 Comp. 45 SL 4560 50 50 100 Comp. 46 SL
4600 5 50 0 Comp. 47 SL 4600 50 50 14
[0205] Table 12 shows that anti-scalant F of the present invention
inhibits calcium carbonate scale more effectively than the known
anti-scalants at lower dosages. Table 12 also shows that the
anti-scalant of the present invention inhibits calcium carbonate
scale more effectively than the known anti-scalants under oxidative
conditions at lower dosages.
EXAMPLES 83-88 AND COMPARATIVE EXAMPLES 48-59
[0206] A bottle test was conducted to compare the effect of calcium
carbonate and known anti-scalants on calcium carbonate and calcium
oxalate scale inhibition under oxidative conditions and at higher
concentrations of oxalate. The procedures were the same as in
Examples 75-82 and Comparative Examples 36-47, except as specified
below, e.g., the concentration of calcium was lower and oxalate was
present.
[0207] Conditions and results are shown in Table 13 below. For
Table 13 the test conditions were at a temperature of 70.degree.
C., 1 hour incubation time, pH=11.0, [NaCl]=0.3 wt %,
[Ca.sup.+2]=100 ppm, [CO.sub.3.sup.-2]=1000 ppm, and [oxalate]=300
ppm.
14TABLE 13 Dosage, ppm Examples Anti-scalant as actives
H.sub.2O.sub.2 [ppm] % Inhibition 83 F 0.5 0 24 84 F 1.0 0 90 Comp.
48 SL 4560 5 0 10 Comp. 49 SL 4560 10 0 25 Comp. 50 SL 4600 5 0 3
Comp. 51 SL 4600 10 0 9 85 F 0.5 50 53 86 F 1.0 50 89 87 F 25.0 50
100 88 F 50 50 97 Comp. 52 SL 4560 5 50 11 Comp. 53 SL 4560 10 50
13 Comp. 54 SL 4560 25 50 98 Comp. 55 SL 4560 50 50 98 Comp. 56 SL
4600 5 50 0 Comp. 57 SL 4600 10 50 7 Comp. 58 SL 4600 25 50 8 Comp.
59 SL 4600 50 50 30
[0208] Table 13 shows that the anti-scalant of the present
invention inhibits calcium carbonate and calcium oxalate scale
better than known anti-scalants at low concentrations under
non-oxidizing conditions. Table 13 also shows that the anti-scalant
of the present invention inhibits calcium carbonate and calcium
oxalate scale better than known anti-scalants at low concentrations
under oxidizing conditions, and the anti-scalant of the present
invention inhibits the scale at least comparable to the known
anti-scalants at higher concentrations under oxidizing
conditions.
EXAMPLES 89-96 AND COMPARATIVE EXAMPLES 60-74
[0209] These Examples and Comparative Examples involve using a
dynamic tube blocking test to study the effectiveness of various
scale inhibitors against calcium carbonate scale. The procedures
for these Examples and Comparative Examples were the same as in
Examples 44-66 and Comparative Examples 8-18, except as noted
below.
[0210] In each of these Examples and Comparative Examples, a basic
solution included:
[0211] Na.sub.2CO.sub.3 and, optionally, sodium oxalate in an
amount to obtain the concentrations of Table 14;
[0212] 3 g/l NaOH; and
[0213] anti-scalant in an amount to determine the threshold
concentration.
[0214] The threshold concentration was the minimum concentration
required to maintain the capillary pressure below 1 psi for 35
minutes run time.
[0215] The basic solution was fed through a first capillary at a
flow rate of 12.5 ml/min. The calcium solution involved
CaCl.sub.2.2H.sub.2O was fed at a rate of 12.5 ml/min through a
second capillary which joined the first capillary to form a 2
meter-long capillary tube (internal diameter 0.127 cm). The
CaCl.sub.2.2H.sub.2O of the calcium solution was at a concentration
to obtain the concentrations of Table 14. Accordingly, the basic
solution and calcium solution were mixed to form a supersaturated
solution having the concentrations shown in Table 14.
[0216] In Table 14, SL 4324 refers to "SL 4324" polyacrylate
anti-scalant available from Hercules Incorporated, Wilmington, Del.
In Table 14, the test conditions were at 80.degree. C. and a pH of
11.
15TABLE 14 Threshold [Ca] [CO.sub.3.sup.-2] [oxalate]
[H.sub.2O.sub.2] Concentration, Examples Anti-Scalant (ppm) (ppm)
(ppm) (ppm) ppm as actives Comp. 60 SL 4324 100 1000 0 0 >32
Comp. 61 SL 4600 100 1000 0 0 >15 Comp. 62 SL 4560 100 1000 0 0
11 89 F 100 1000 0 0 1.1 Comp. 63 SL 4324 200 1000 0 0 >24 Comp.
64 SL 4600 200 1000 0 0 >15 Comp. 65 SL 4560 200 1000 0 0 15.6
90 F 200 1000 0 0 1.1 Comp. 66 SL 4560 100 2500 0 0 11 91 F 100
2500 0 0 0.75 Comp. 67 SL 4560 100 5000 0 0 >11 92 F 100 5000 0
0 0.75 Comp. 68 SL 4560 100 500 100 0 13.5 93 F 100 500 100 0 1.1
Comp. 69 SL 4600 100 500 100 0 >13.5 Comp. 70 SL 4560 100 1000
100 0 8 94 F 100 1000 100 0 0.75 Comp. 71 SL 4600 100 1000 100 0
>15 Comp. 72 SL 4560 100 1000 300 0 11 95 F 100 1000 300 0 0.9
Comp. 73 SL 4600 100 1000 300 0 >15 Comp. 74 SL 4560 100 1000
300 25 11 96 F 100 1000 300 25 1.1
[0217] Table 14 shows that the minimum threshold concentration of
the anti-scalant of the present invention is lower than the minimum
threshold concentration of the known anti-scalants under all of the
conditions tested.
EXAMPLES 97-116 AND COMPARATIVE EXAMPLES 75-78
[0218] A bottle test was conducted to compare the effect of calcium
carbonate anti-scalant of the present invention and known
anti-scalants on calcium oxalate scale inhibition under acidic
conditions, with the exception of Example 116 which was under basic
conditions. The procedures were the same as in Examples 1-39 and
Comparative Examples 1 and 2, except as specified below.
[0219] Final solutions having the concentrations listed in Table 15
were generally prepared in accordance with the procedure of
Examples 1-39 and Comparative Examples 1 and 2. In this regard,
although the amount of solution used in each bottle test was 100 g,
the amount of final solution prepared was sometimes greater than
100 g. The solution pH was adjusted to the pH listed in Table 15 by
adding hydrochloric acid, or sodium hydroxide in the case of
Example 116.
[0220] After being agitated for 1 hour at the temperature listed in
Table 15, the solution was removed from the test bottle and
subjected to vacuum filtration using a #114 Whatman filter (pore
size 20 .mu.m). After removal of the test solution from the test
bottle, an "adherent" sample was generated from each test bottle in
the same manner as Examples 1-39 and Comparative Examples 1 and 2.
All liquid samples were analyzed by Inductively Coupled Plasma
(ICP) for calcium ion concentrations in the same manner as Examples
1-39 and Comparative Examples 1 and 2.
[0221] Conditions and results are shown in Table 15 below.
16TABLE 15 Dosage, Anti- ppm as [Ca] [oxalate] Temp. % Examples
Scalant actives (ppm) (ppm) pH (.degree. C.) Inhibition 97 F 1 200
100 5 80 2.8 98 F 5 200 100 5 80 4.3 99 F 10 200 100 5 80 0 100 F
50 200 100 5 80 0 101 F 100 200 100 5 80 2.2 102 F 200 200 100 5 80
41.8 103 V 50 200 100 5 80 16.3 104 V 100 200 100 5 80 41.1 105 V
200 200 100 5 80 84.4 106 G 50 200 100 5 80 0 107 G 200 200 100 5
80 0 Comp. 75 SL 4600 1 200 100 5 80 31.9 Comp. 76 SL 4600 5 200
100 5 80 91.5 Comp. 77 SL 4600 10 200 100 5 80 91.5 Comp. 78 SL
4600 50 200 100 5 80 100 108 F 50 100 200 3.5 80 11.0 109 F 100 100
200 3.5 80 0 110 F 200 100 200 3.5 80 58.1 111 F 10 100 200 3.5 60
7.4 112 F 50 100 200 3.5 60 44.3 113 F 100 100 200 3.5 60 91.5 114
F 100 100 200 6.0 60 0 115 F 200 100 200 6.0 60 9.3 116 F 200 100
200 6.0 60 0
[0222] Table 15 shows that higher dosages of the anti-scalant of
the present invention were required to inhibit scale as well as the
known anti-scalant under acidic conditions.
[0223] Table 15 also shows that the anti-scalant of the present
invention at the dosages listed in Table 15 did not effectively
inhibit scale when the temperature was above 60.degree. C. and the
pH was 6 or higher. Thus, while not wishing to be bound by theory,
it is believed that calcium oxalate scale forms more quickly at
lower temperature and higher pH.
EXAMPLES 117-130 AND COMPARATIVE EXAMPLES 79-82
[0224] These Examples and Comparative Examples involve using a
dynamic tube blocking test to study the effectiveness of various
scale inhibitors, including precipitated calcium carbonate to
inhibit in situ formation of calcium carbonate and calcium oxalate
scale. The procedures for these Examples and Comparative Examples
were the same as in Examples 89-96 and Comparative Examples 60-74,
except as noted below.
[0225] A basic solution included:
[0226] 3.50 g/l Na.sub.2CO.sub.3;
[0227] 0.3 g/l sodium oxalate;
[0228] 3 g/l NaOH; and
[0229] anti-scalant in an amount to obtain the concentrations of
Table 16.
[0230] The basic solution was fed through a first capillary at a
flow rate of 12.5 ml/min. The calcium solution involved 0.74 g/l
CaCl.sub.2.2H.sub.2O and was fed at a rate of 12.5 ml/min through a
second capillary which joined the first capillary to form a 2
meter-long capillary tube (internal diameter 0.127 cm).
[0231] As a result, the basic solution and calcium solution were
mixed to form a supersaturated solution. The composition and
conditions of the supersaturated aqueous solution were as
follows:
17 Calcium ions 100 ppm Carbonate ions 1000 ppm Oxalate ions 100
ppm NaOH 0.15 wt % (pH = 11) Temperature 80.degree. C.
[0232] The supersaturated solution was pumped through the 2
meter-long capillary at a flow rate of 25 ml/min at a temperature
of 80.degree. C. and pressure of 55 psi.
[0233] In Table 16, AR 808 refers to "AR 808" polyacrylate
available from ALCO Chemical, Chattanooga, Tenn. The pressure in
the capillary was measured at different isted in Table 16.
18 TABLE 16 Weight Ratio Capillary Pressure Concentration, of PCC
to Measurement Examples Anti-Scalant as ppm actives Polymer Time
(min) P (psi) Comp. 79 None 12 3 Comp. 80 AR 808 12 <10 2.5
Comp. 81 AR 808 24 14 3.5 Comp. 82 AR 808 32 23 3 117 V 5 <10
1.5 118 V 30 18 1.5 119 V 50 35 0.3 120 V:AR 808 5 4:1 35 0.15 121
V:AR 808 5 6:1 35 0.25 122 V:AR 808 2.5 4:1 32 1.2 123 V:AR 808 2.5
6:1 35 0.4 124 V:AR 808 2.5 8:1 33 1.1 125 V:AR 808 1.5 4:1 30 1.5
126 V:AR 808 1.5 6:1 35 1.2 127 V:AR 808 1.5 8:1 23 1.2 128 F 0.4
<10 1.5 129 F 0.6 30 1.6 130 F 0.75 35 0.7
[0234] Table 16 shows that precipitated calcium carbonate, which is
similar to what would be formed in situ, inhibits scale more
effectively than a known polymer in calcium carbonate and calcium
oxalate forming systems. Table 16 also shows a synergistic effect
when the precipitated calcium carbonate and the known polymer are
pre-mixed before being added to the aqueous system.
EXAMPLES 131-141 AND COMPARATIVE EXAMPLES 83-85
[0235] A bottle test was conducted to compare the effect of calcium
carbonate anti-scalant of the present invention and known
anti-scalants on calcium oxalate scale inhibition. The procedures
were the same as in Examples 97-116 and Comparative Examples 75-78,
except as specified below.
[0236] The solution pH was adjusted to 11 by adding sodium
hydroxide. In each case listed in Table 17, the concentration of
calcium ions was 100 ppm, the concentration of oxalate ions was 200
ppm, and the temperature was 80.degree. C.
19TABLE 17 Concentration, Weight Ratio of % Examples Anti-Scalant
as ppm actives PCC to Polymer Inhibition 131 V 20 0 132 V 100 0
Comp. 83 SL 4600 5 96.4 Comp. 84 SL 4600 10 96.8 Comp. 85 SL 4600
20 97.8 133 V:SL 4600 5 4:1 49.0 134 V:SL 4600 10 4:1 69.8 135 V:SL
4600 20 4:1 96.7 136 V:SL 4600 5 1:4 93.3 137 V:SL 4600 10 1:4 90.8
138 V:SL 4600 20 1:4 99.8 139 V:SL 4600 5 1:1 83.5 140 V:SL 4600 10
1:1 94.2 141 V:SL 4600 20 1:1 100.0
[0237] Table 17 shows that precipitated calcium carbonate does not
inhibit calcium oxalate scale more effectively than a known
polymer. Table 17 also shows that precipitated calcium carbonate
and the known polymer can be pre-mixed before being added to the
aqueous system to inhibit calcium oxalate scale.
EXAMPLES 142-143
[0238] These Examples and Comparative Examples involve using a
dynamic tube blocking test to compare the effectiveness of ground
calcium carbonate with reagent grade calcium carbonate. The
procedures for these Examples and Comparative Examples were the
same as in Examples 89-96 and Comparative Examples 60-74, except as
noted below.
[0239] In Table 18, the test conditions were at 170.degree. C., 2.6
wt % NaOH, 35 ppm calcium, and 6500 ppm carbonate. The threshold
concentration was the minimum concentration required to maintain
the capillary pressure below 1 psi for 35 minutes run time.
20TABLE 18 Example Anti-Scalant Threshold Concentration, ppm as
actives 142 F 9 143 W >200
[0240] Table 18 shows that ground calcium carbonate inhibits
scaling better than reagent grade calcium carbonate.
EXAMPLES 144-149 AND COMPARATIVE EXAMPLES 86-88
[0241] These Examples and Comparative Examples involve using a
dynamic tube blocking test to study the effectiveness of reagent
grade precipitated calcium carbonate and ground calcium carbonate
in inhibiting calcium carbonate scale. The procedures for these
Examples and Comparative Examples were the same as in Examples
117-130 and Comparative Examples 79-82, except where noted
below.
[0242] The pressure in the capillary was measured at different
times as listed in Table 19. In Table 19, each Example and
Comparative Example was conducted at a pH of about 13 with 2.6 wt %
of NaOH being added, except for Comparative Example 88 and Examples
148 and 149 which were conducted at a pH of 11.
21 TABLE 19 Capillary Pressure Concen- Measure- tration, ment Anti-
as ppm [Ca] [CO.sub.3.sup.-2] Temp. Time P Examples Scalant actives
(ppm) (ppm) (.degree. C.) (min) (psi) Comp. 86 None 35 6500 170 5
3.8 144 W 200 35 6500 170 4 3.5 145 F 12 35 6500 170 35 0.7 Comp.
87 None 90 10,000 170 3 3.3 146 W 50 90 10,000 170 17 2.7 147 F 15
90 10,000 170 35 0.25 Comp. 88 None 100 1000 80 10 2.2 148 W 30 100
1000 80 18 1.5 149 F 0.75 100 1000 80 35 0.5
[0243] Table 19 shows that ground calcium carbonate inhibited
calcium carbonate scale better than precipitated calcium
carbonate.
EXAMPLES 150-170 AND COMPARATIVE EXAMPLES 89-102
[0244] These Examples and Comparative Examples involve using a
dynamic tube blocking test to study the effectiveness of various
scale inhibitors, including precipitated calcium carbonate to
inhibit in situ formation of calcium carbonate scale. The
procedures for these Examples and Comparative Examples were the
same as in Examples 89-96 and Comparative Examples 60-74, except as
noted below.
[0245] In Table 20, SP 3230 refers to "Soyprotein 3230" protein and
SP 4950 refers to "Soyprotein 4950" protein, both available from
Central Soya, Fort Wayne, Ind. The SP 4950-1 refers to "SP 4950
#1097-1" protein also available from Central Soya, which involves
"Soyprotein 4950" protein which was treated with enzyme for 30
minutes prior to use. S12-29 refers to "S12-29" anionic protein and
S12-21 refers to "S12-21" anionic protein, both available from
Donlar Corporation, Bedford Park, Ill.
[0246] In Table 20, the conditions were 90 ppm of calcium, 10,000
ppm of carbonate, 2.6 wt % of NaOH, and a temperature of
170.degree. C. The pressure in the capillary was measured at
different times as listed in Table 20.
22 TABLE 20 Capillary Pressure Weight Ratio Measurement
Concentration, of GCC to Time P Examples Anti-Scalant as ppm
actives Protein (min) (psi) Comp. 89 None 4 4.5 150 F/SP 3230 1.5
4:1 5 1.5 151 F/SP 3230 3 4:1 24 1.5 152 F/SP 3230 4 4:1 31 1.5 153
F/SP 3230 5 4:1 35 0.5 154 F/SP 3230 5 2:1 35 0.5 155 F/SP 3230 5
1:2 33 2 156 F/S 12-29 5 1:1 14 1.8 157 F/S 12-29 7 1:1 16 1.8 158
F/S 12-21 5 1:1 13 1.8 Comp. 90 SP 4950 5 1:1 34 1.2 159 F/SP
4950-1 5 1:1 35 1.4 160 F/SP 4950-1 7 1:1 35 0.3 Comp. 91 SP 3230
20 4 3.5 161 F 11.25 35 0.4 162 F 7.5 30 2 Comp. 92 SP 4950 20 4 2
Comp. 93 SP 4950-1 20 4 3
[0247] Table 20 shows that ground calcium carbonate, i.e.,
anti-scalant F, inhibits scale when used in combination with
proteins. For instance, ground calcium carbonate shows synergistic
results when used in combination with SP 3230.
[0248] In Table 21, SP 4950-2 refers to "SP 4950 #1097-2" protein
available from Central Soya, Fort Wayne, Ind., which involves
"Soyprotein 4950" protein which was treated with enzyme for 2 hours
prior to use. Calpro 75 refers to "Calpro 75" whey protein
available from Calpro ingredients, Corona, Calif. HC 200 refers to
"Casein HC 200" casein protein available from National Casein Co.,
Chicago, Ill.
[0249] In Table 21, the conditions were 35 ppm of calcium, 6500 ppm
of carbonate, 2.6 wt % of NaOH, and a temperature of 170.degree. C.
The pressure in the capillary was measured at different times as
listed in Table 21.
23 TABLE 21 Capillary Weight Pressure Ratio Measurement
Concentration, of GCC to Time P Examples Anti-Scalant as ppm
actives Protein (min) (psi) Comp. 94 None 4 4.5 163 F/SP 4950-1 8
1:1 35 0.5 164 F/SP 4950-1 5 1:1 24 1.9 165 F/SP 4950-1 5 2:1 10 2
166 F/SP 4950-1 5 1:2 14 1.8 167 F/SP 4950-2 5 1:1 21 2 Comp. 95
F/HC 200 5 1:1 10 2.4 Comp. 96 F/Calpro 75 10 1:1 35 2 Comp. 97
F/Calpro 75 10 2:1 33 1.5 Comp. 98 F/Calpro 75 10 4:1 29 1.6 Comp.
99 F/Calpro 75 10 1:2 12 1.6 Comp. 100 SP 4950-1 10 8 1.7 Comp. 101
SP 4950-2 10 8 2 168 F 9 35 0.6 169 F 7.5 27 2.5 170 V 40 17 1.5
Comp. 102 HC 200 10 5 1.7
[0250] Table 21 also shows that ground calcium carbonate, i.e.,
anti-scalant F, inhibits scale when used in combination with
proteins. For instance, ground calcium carbonate shows synergistic
results when used in combination with SP 4950-1 when used at a
weight ratio of 1:1.
[0251] While the invention has been described in connection with
certain preferred embodiments so that aspects thereof may be more
fully understood and appreciated, it is not intended to limit the
invention to these particular embodiments. On the contrary, it is
intended to cover all alternatives, modifications and equivalents
as may be included within the scope of the invention as defined by
the appended claims.
* * * * *