U.S. patent application number 09/799285 was filed with the patent office on 2001-11-01 for process for the inhibition of scale.
Invention is credited to Duggirala, Prasad Yogendra, Morris, John David, Reed, Peter Edward, Severtson, Steven John.
Application Number | 20010035271 09/799285 |
Document ID | / |
Family ID | 22507277 |
Filed Date | 2001-11-01 |
United States Patent
Application |
20010035271 |
Kind Code |
A1 |
Duggirala, Prasad Yogendra ;
et al. |
November 1, 2001 |
Process for the inhibition of scale
Abstract
The present invention is directed to an improved process for
inhibiting calcium carbonate scaling in aqueous systems such as
that employed in the kraft process for the production of wood pulp.
Such an improved process is achieved by the addition to the system
of at least one antiscalant comprising at least one monomer unit
derived from the group consisting of 1,2-dihydroxy-3-butene,
N-(hydroxymethyl) acrylamide, and N-(sulfomethyl) acrylamide, and
at least one monomer unit derived from the group consisting of
maleic acid, acrylic acid, acrylamide, methacrylic acid, itaconic
acid, vinyl sulfonic acid, styrene sulfonic acid,
N-tertbutylacrylamide, butoxymethylacrylamide,
N,N-dimethylacrylamide, sodium acrylamidomethyl propane sulfonic
acid, and salts thereof. The present invention further provides a
novel class of polymer antiscalants which are polymers comprising a
1,2-dihydroxy-3-butene monomer unit and at least one monomer unit
derived from the groups consisting of maleic acid, acrylic acid,
acrylamide, methacrylic acid, itaconic acid, vinyl sulfonic acid,
styrene sulfonic acid, N-tertbutylacrylamide,
butoxymethylacrylamide, N,N-dimethylacrylamide, sodium
acrylamidomethyl propane sulfonic acid, and salts thereof, with the
proviso that said polymers do not contain the monomer unit
--(CH.sub.2--CH.dbd.CH--CH.sub.2--O)--.
Inventors: |
Duggirala, Prasad Yogendra;
(Naperville, IL) ; Morris, John David;
(Plainfield, IL) ; Reed, Peter Edward;
(Plainfield, IL) ; Severtson, Steven John;
(Shoreview, MN) |
Correspondence
Address: |
Nalco Chemical Company
Patent & Licensing Department
One Nalco Center
Naperville
IL
60563-1198
US
|
Family ID: |
22507277 |
Appl. No.: |
09/799285 |
Filed: |
March 5, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09799285 |
Mar 5, 2001 |
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09436016 |
Nov 9, 1999 |
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6235152 |
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09436016 |
Nov 9, 1999 |
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09144145 |
Aug 31, 1998 |
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6146495 |
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Current U.S.
Class: |
162/48 ; 162/72;
162/82 |
Current CPC
Class: |
C02F 5/10 20130101; D21C
9/008 20130101; D21C 3/226 20130101; D21C 11/106 20130101 |
Class at
Publication: |
162/48 ; 162/72;
162/82 |
International
Class: |
D21C 003/20 |
Claims
We claim:
1. A process for treating an aqueous liquid having scale forming
salts of calcium therein which comprises adding to said aqueous
liquid a scale inhibiting amount of a polymeric antiscalant
comprising: (A) 1,2-dihydroxy-3-butene monomer units, and, (B) at
least one monomer unit derived from the group consisting of maleic
acid, acrylic acid, acrylamide, methacrylic acid, itaconic acid,
vinyl sulfonic acid, styrene sulfonic acid, N-tertbutylacrylamide,
butoxymethylacrylamide, N,N-dimethylacrylamide, sodium
acrylamidomethyl propane sulfonic acid, and salts thereof, with the
proviso that said polymeric additive does not include the monomer
unit --(CH.sub.2--CH.dbd.CH--CH.sub.2--O)--.
2. The process of claim 1 wherein said aqueous system is at a
temperature in the range of from about 100.degree. C. to about
200.degree. C. and a pH in the range of from about 10 to about
14.
3. The process of claim 1 wherein said polymeric antiscalant has a
weight average molecular weight in the range of from about 1,000 to
about 100,000.
4. The process of claim 3 wherein said polymeric antiscalant is
added to said aqueous system in an amount such there is provided
from about 1 ppm to about 200 ppm of additive in the resulting
treated aqueous system.
5. The process of claim 4 wherein said polymeric antiscalant is
derived from a mixture of 1,2-dihydroxy-3-butene and either maleic
acid, acrylic acid or a combination of maleic acid and acrylic
acid.
6. The process of claim 5 wherein said 1,2-dihydroxy-3-butene
monomer units are present in an amount in the range of from about 1
mole percent to about 50 mole percent.
7. The process of claim 5 wherein said polymeric antiscalant is a
terpolymer of 1,2-dihydroxy-3-butene, maleic acid and acrylic
acid.
8. The process of claim 5 wherein said polymeric antiscalant is a
copolymer of 1,2-dihydroxy-3-butene and maleic acid.
9. In a kraft process for the production of wood pulp which
comprises the steps of digesting wood chips in a digesting zone,
bleaching the resulting wood pulp in a bleaching zone, and
concentrating the separated liquor from the digesting zone in an
evaporation zone, the improvement which comprises adding to at
least one of said digesting zone, bleaching zone and evaporation
zone a polymeric antiscalant in an amount sufficient to inhibit the
scale formation therein, said polymeric antiscalant comprising: (A)
at least one monomer unit derived from the group consisting of
1,2-dihydroxy-3-butene, N-(hydroxymethyl) acrylamide and
N-(sulfomethyl) acrylamide and, (B) at least one monomer unit
derived from the group consisting of maleic acid, acrylic acid,
acrylamide, methacrylic acid, itaconic acid, vinyl sulfonic acid,
styrene sulfonic acid, N-tertbutylacrylamide,
butoxymethylacrylamide, N,N-dimethylacrylamide, sodium
acrylamidomethyl propane sulfonic acid, and salts thereof.
10. The process of claim 9 wherein said polymeric antiscalant is
added to the digesting zone.
11. The process of claim 9 wherein said polymeric antiscalant is
added to the bleaching zone.
12. The process of claim 9 wherein said polymeric antiscalant is
added to the evaporation zone.
13. The process of claim 9 wherein said polymeric antiscalant has a
weight average molecular weight in the range of from about 1,000 to
about 100,000.
14. The process of claim 13 wherein said polymeric antiscalant is
added in an amount in the range of from about 1 ppm to about 200
ppm.
15. The process of claim 14 wherein said polymeric antiscalant is
derived from a mixture of N-(sulfomethyl) acrylamide and either
maleic acid, acrylic acid or a combination of maleic acid and
acrylic acid.
16. The process of claim 15 wherein said N-(sulfomethyl) acrylamide
is present in an amount in the range of from about 1 mole percent
to about 20 mole percent.
17. The process of claim 14 wherein said polymeric antiscalant is
derived from a mixture of N-(hydroxymethyl) acrylamide and either
maleic acid, acrylic acid or a combination of maleic acid and
acrylic acid.
18. The process of claim 17 wherein said N-(hydroxymethyl)
acrylamide is present in an amount in the range of from about 1
mole percent to about 50 mole percent.
19. The process of claim 14 wherein said polymeric antiscalant is
derived from a mixture of 1,2-dihydroxy-3-butene and either maleic
acid or a combination of maleic acid and acrylic acid.
20. The process of claim 19 wherein said 1,2-dihydroxy-3-butene
monomer units are present in an amount in the range of from about 1
mole percent to about 50 mole percent.
21. The process of claim 19 wherein said polymeric antiscalant is a
terpolymer of 1,2-dihydroxy-3-butene, maleic acid and acrylic
acid.
22. The process of claim 19 wherein said polymeric antiscalant is a
copolymer of 1,2-dihydroxy-3-butene and maleic acid.
23. The process of claim 21 wherein said terpolymer is 33.3 mole
percent 1,2-dihydroxy-3-butene, 33.3 mole percent maleic acid and
33.3 mole percent acrylic acid.
24. The process of claim 22 wherein said copolymer is 50 mole
percent 1,2-dihydroxy-3-butene and 50 mole percent maleic acid.
25. Polymers comprising: (A) 1,2-dihydroxy-3-butene monomer units
and (B) at least one monomer unit derived from the groups
consisting of maleic acid, acrylic acid, acrylamide, methacrylic
acid, itaconic acid, vinyl sulfonic acid, styrene sulfonic acid,
N-tertbutylacrylamide, butoxymethylacrylamide,
N,N-dimethylacrylamide, sodium acrylamidomethyl propane sulfonic
acid, and salts thereof, with the proviso that said polymers do not
contain the monomer unit--(CH.sub.2--CH.dbd.CH--CH.sub.2--
-O)--.
26. Polymers of claim 25 having a weight average molecular weight
in the range of from about 1,000 to about 100,000.
27. Polymers of claim 25 having a weight average molecular weight
in the range of from about 1,000 to about 50,000.
28. Polymers of claim 25 wherein the mole percent of (A) is in the
range of from about 1 to 50 percent of the total mole percent in
the polymer.
29. Polymers of claim 25 wherein (B) is derived from maleic
acid.
30. Polymers of claim 25 wherein (B) is a mixture of maleic acid
and acrylic acid.
31. A polymer of claim 30 wherein the mole ratio of the terpolymer
is 33.3:33.3:33.3.
32. A polymer of claim 29 wherein the mole ratio of the copolymer
is 50:50.
Description
[0001] This invention relates to a process for the inhibition of
scale formation in aqueous systems which are generally maintained
under harsh conditions. The invention more particularly relates to
an improved kraft process wherein calcium carbonate scale in
inhibited. In one specific aspect of this invention, there is
provided novel polymeric antiscalants which are useful in the
preclusion of calcium carbonate scaling in industrial aqueous
systems.
BACKGROUND OF THE INVENTION
[0002] Scale forms when the concentration of a dissolved mineral
exceeds its solubility limit and the mineral precipitates. Scale is
and can be a problem in equipment used in many types of industrial
operations utilizing an aqueous system.
[0003] As used herein the term "aqueous system" is meant to include
any system containing water, including but not limited to cooling
water, boiler water, desalination, gas scrubbers, blast furnaces,
sewage sludge thermal conditioning equipment, reverse osmosis
evaporators, paper processing, mining circuits and the like wherein
such systems are operated under harsh conditions of temperature and
pH.
[0004] The term "harsh conditions" as used herein is intended to be
definitive of an aqueous system wherein the temperature is in the
range of from about 100.degree. C. to about 200.degree. C. and the
pH is in the range of from about 10 to about 14.
[0005] Typical equipment used in industrial aqueous operations that
require scale inhibition includes, but is not limited to, boilers,
evaporators, heat exchangers, other heat transfer equipment, pipes
and any other equipment that comes into contact with the aqueous
system.
[0006] For purposes of this application, such industrial operations
are illustrated by the kraft process for the production of wood
pulp.
[0007] Wood pulp is the basic raw material used in the manufacture
of almost all grades of paper and various types of packing products
such as drums and cartons.
[0008] In order to produce pulp from wood, it is necessary to
separate the cellulose fibers from the various organic compounds,
mainly lignin, which bind them together. Various mechanical and
chemical methods are used to effect this separation, but the most
widely used technique is known as the kraft or sulphate process,
since it produces pulp which gives high strength and good aging
properties to paper products.
[0009] In the kraft process, a cooking liquor (white liquor) of
sodium hydroxide and sodium sulphide is used to extract the lignin
from wood. The process of extraction is carried out in digesters,
either batch or continuous. The pH in the digester is generally
between about 11 and about 14.
[0010] The liquor temperature is maintained between about
150.degree. to about 175.degree. C. A period of from about 2 to
about 3 hours is usually required for complete digestion. The pulp
is then washed before being sent for further treatment such as
bleaching prior to its further use.
[0011] The economics of the kraft process depend on the recovery of
the cooking liquor. In this recovery process, the digestion
chemicals contained in the used cooking liquor (black liquor) are
recovered via evaporators, furnaces and a causticizer for reuse in
preparing new cooking liquor. Before the black liquor can be used
as a feed it is necessary that the black liquor be concentrated,
usually to 45% by weight or higher. This concentration is carried
out in a multiple-effect evaporator, where live steam is introduced
to the first unit (where the liquor is at its highest solids
concentration) and flows to the final unit. Such evaporators can be
described as one long heat transfer surface where the purpose is to
boil off water by providing significant contact between the black
liquor and steam heated surfaces. However, a common problem which
is experienced in such evaporators is the formation of substantial
amounts of deposits which tend to stick to the interior walls or
tubes of the evaporator. The primary source of liquor scaling in
the evaporator system is insoluble calcium carbonate.
[0012] The cooking liquor (white liquor) produced from this process
contains sodium hydroxide, sodium sulphide and sodium carbonate due
to incomplete reaction in the causticizer, as well as soluble
calcium and precipitated calcium carbonate.
[0013] In the kraft process, calcium is extracted from the wood,
and because of the high pH, temperature and presence of carbonate
in the cooking liquor this calcium precipitates as calcium
carbonate. The most visible form of the scale is in the cooking
liquor heaters which maintain desired digester process conditions
and often have to be cleaned about every 2-4 weeks.
[0014] Scale formation can also occur on the liquor separator
screens which in turn leads to a restriction of liquor flow which
reduces plant production and eventually necessitates plant shutdown
for cleaning.
[0015] Because of the tendency for calcium carbonate scaling in the
aqueous systems of the kraft process due to the conditions
experienced therein, there becomes a real need for the addition of
antiscalants to various locations within the process.
[0016] In addition to the scaling problem experienced in the
digester, scaling is also a problem in the equipment used for
carrying out the bleaching of the wood pulp. Pulp produced by the
kraft process is normally bleached in a multistage sequence to
obtain the desired brightness and strength. Different bleaching
agents are used for this purpose. Chlorine or chlorine dioxide is
the most reactive bleaching agent to the lignin remaining in the
pulp. Although conditions in the bleach plant are less severe than
those found in a kraft digester, the driving force for scale
formation is significant. For example, calcium concentrations can
climb to over 100 ppm, the pH of the stream entering the bleaching
stages is greater than about 11 and the temperatures are still
elevated.
[0017] From the foregoing, it can be seen that while conditions
vary in severity with various stages of the kraft process i.e. the
digester, bleach plant and evaporator, such aqueous systems as are
contained within the various stages are all under harsh conditions
of temperature and pH and as such experience the problem of scale
formation during operation.
[0018] Thus, it becomes readily apparent that there is a real need
in the kraft process for the production of wood pulp which
comprises the steps of digesting wood chips in a digesting zone,
bleaching of the resulting wood pulp in a bleaching zone and the
concentrating of the separated liquor from the digesting zone in an
evaporation zone for the providing of an improvement thereto which
comprises the addition of a polymeric antiscalant which will
inhibit the formation of scale.
[0019] Accordingly, it is an object of the present invention to
provide a novel process for the inhibition of calcium carbonate
scale in aqueous systems which otherwise experience such scale
formation due the harsh conditions occurring in the system.
[0020] Another object of the present invention is to provide a
process for improving the kraft process for the production of wood
pulp wherein the formation of calcium carbonate scale is inhibited
during plant operations.
[0021] A still further object of this invention is to provide novel
polymeric antiscalants for use in the treatment of industrial
aqueous systems.
[0022] Other aspects, objects and the several advantages of this
invention will become apparent in light of the following
specification and appended claims.
SUMMARY OF THE INVENTION
[0023] In accordance with one embodiment of the present invention,
we have discovered a process for treating an aqueous liquid having
scale forming salts of calcium therein which comprises adding to
said aqueous liquid a scale inhibiting amount of a polymeric
antiscalant comprising:
[0024] (A) 1,2-dihydroxy-3-butene monomer units and,
[0025] (B) at least one monomer unit derived from the group
consisting of maleic acid, acrylic acid, acrylamide, methacrylic
acid, itaconic acid, vinyl sulfonic acid, styrene sulfonic acid,
N-tertbutylacrylamide, butoxymethylacrylamide,
N,N-dimethylacrylamide, sodium acrylamidomethyl propane sulfonic
acid, and salts thereof, with the proviso that said polymers does
not include the monomer unit --(CH.sub.2--CH.dbd.CH--CH.sub-
.2--O)--.
[0026] In another embodiment of the present invention, there is
provided an improved kraft process for the production of wood pulp
using novel polymer antiscalants.
[0027] Thus, in the kraft process for the production of wood pulp
which comprises the steps of digesting wood chips in a digesting
zone, bleaching the resulting wood pulp in a bleaching zone, and
concentrating the separated liquor from the digesting zone in an
evaporation zone, there is provided the improvement which comprises
adding to at least one of said digesting zone, bleaching zone and
evaporation zone a polymeric antiscalant in an amount sufficient to
inhibit the scale formation therein, said antiscalant
comprising:
[0028] (A) at least one monomer unit derived from the group
consisting of 1,2-dihydroxy-3-butene, N-(hydroxymethyl) acrylamide
and N-(sulfomethyl) acrylamide and,
[0029] (B) at least one monomer unit derived from the group
consisting of maleic acid, acrylic acid, acrylamide, methacrylic
acid, itaconic acid, vinyl sulfonic acid, styrene sulfonic acid,
N-tertbutylacrylamide, butoxymethylacrylamide,
N,N-dimethylacrylamide, sodium acrylamidomethyl propane sulfonic
acid, and salts thereof.
[0030] In a still further embodiment of the present invention,
there are provided novel polymers comprising:
[0031] (A) 1,2-dihydroxy-3-butene monomer units and
[0032] (B) at least one monomer unit derived from the groups
consisting of maleic acid, acrylic acid, acrylamide, methacrylic
acid, itaconic acid, vinyl sulfonic acid, styrene sulfonic acid,
N-tertbutylacrylamide, butoxymethylacrylamide,
N,N-dimethylacrylamide, sodium acrylamidomethyl propane sulfonic
acid, and salts thereof, with the proviso that said polymers do not
include the monomer unit --(CH.sub.2--CH.dbd.CH--CH.sub.2-
--O)--.
DETAILED DESCRIPTION OF THE INVENTION
[0033] The present invention is based upon our discovery that
calcium carbonate scale in aqueous systems which experience harsh
conditions of temperature and pH can be inhibited by the addition
to such systems a scale inhibiting amount of a polymeric
antiscalant comprising:
[0034] (A) at least one monomer unit derived from the group
consisting of 1,2-dihydroxy-3-butene, N-(hydroxymethyl) acrylamide
and N-(sulfomethyl) acrylamide and,
[0035] (B) at least one monomer unit derived from the group
consisting of maleic acid, acrylic acid, acrylamide, methacrylic
acid, itaconic acid, vinyl sulfonic acid, styrene sulfonic acid,
N-tertbutylacrylamide, butoxymethylacrylamide,
N,N-dimethylacrylamide, sodium acrylamidomethyl propane sulfonic
acid, and salts thereof.
[0036] Such polymeric antiscalants have a weight average molecular
weight (Mw) in the range of from about 1,000 to about 100,000,
preferably from about 1,000 to about 50,000. For purposes of this
application, all weight average molecular weights are measured by
aqueous gel permeation chromatography (GPC) relative to either a
polyethylene glycol standard or a polystyrene sulfonate
standard.
[0037] The amount of polymeric antiscalant which is employed in the
practice of this invention is dependent on the nature of the system
being treated. In carrying out the process of scale inhibition in
accordance with the present invention, the selected polymeric
antiscalant is added to the aqueous system to be treated in an
amount sufficient to preclude scale formation, deposition on or
adherence to the metallic surfaces of the system being treated. In
general, effective amounts of the selected polymeric antiscalant
are in the range of from about 1 ppm to about 200 ppm.
[0038] The polymeric antiscalants, as employed in the process of
this invention, can be used alone or in combination with other
known scale inhibitors and dispersing agents which are stable under
the conditions prevailing in the system being treated. However,
such additional scale inhibitors are not required in obtaining
satisfactory results when carrying out the process of the present
invention using the polymeric antiscalants as described herein.
[0039] The particular dosage of polymeric antiscalant will be
dependent upon the conditions which are normally experienced in the
system being treated. Thus, in the kraft process, the highest
dosage levels of polymeric antiscalant will be to the digester with
lesser amounts being required for the bleach plant and
evaporator.
[0040] In the practice of a presently preferred embodiment of this
invention, whereby there is achieved an improvement in the kraft
process for production of wood pulp through the addition to the
digester, bleach plant or evaporator of polymeric antiscalants as
herein defined, such addition of the selected antiscalant can be
carried out by any means known in the art for addition of
antiscalants to a harsh environment. For example, a solution of the
selected antiscalant can be continuously introduced into the
digester in amounts sufficient to achieve the desired concentration
level. Not only does addition at this stage serve to preclude
scaling in the digester, it permits antiscalant to be carried over
to the washers from which the pulp is screened and cleaned. In
addition to the addition of the antiscalants to the digester, such
antiscalants can also be introduced into one or more of the
bleaching towers, washers or caustic extraction towers which are
normally provided in multiple stages to permit the desired
chlorination and extraction so as to achieve delignification and
ultimate brightening of the pulp. Likewise, since efficient
recovery of chemicals from the digestor liquor and reconstitution
of the chemicals to form fresh while liquor for use in the digester
is desired, addition of one or more of the polymeric antiscalants
of this invention to the evaporators serving to concentrate such
liquor from the digestor for further use in the process will serve
to reduce or preclude undesirable scaling in such equipment.
[0041] Thus, by treating one or more of the kraft process zones
wherein undesired calcium carbonate scaling is otherwise
experienced, there is achieved by the process of the present
invention an overall improvement in the efficiency of the kraft
process due to the inhibition of scale formation which in turn
permits longer operating periods.
[0042] A further embodiment of the present invention are a novel
group of polymeric antiscalants which exhibit antiscalant
properties when employed in aqueous systems having scale forming
salts of calcium.
[0043] Such novel antiscalants are those polymers comprising
1,2-dihydroxy-3-butene monomer units and at least one monomer unit
derived from the group consisting of maleic acid, acrylic acid,
acrylamide, methacrylic acid, itaconic acid, vinyl sulfonic acid,
styrene sulfonic acid, N-tertbutylacrylamide,
butoxymethylacrylamide, N,N-dimethylacrylamide, sodium
acrylamidomethyl propane sulfonic acid, and salts thereof, with the
proviso that said novel polymers do not include the monomer unit
--(CH.sub.2--CH.dbd.CH--CH.sub.2--O)--.
[0044] The novel antiscalant polymers can have a mole content of
1,2-dihydroxy-3-butene from about 1 to about 50 percent of the
total mole percent in the polymer.
[0045] In one presently preferred embodiment of the present
invention, the novel antiscalant compositions are a 50 mole
percent:50 mole percent copolymer of 1,2-dihydroxy-3-butene and
maleic acid having a molecular weight of approximately about 4,000;
and a 33.3 mole percent:33.3 mole percent:33.3 mole percent
terpolymer of 1,2-dihydroxy-3-butene, maleic acid and acrylic acid
having a molecular weight of approximately 10,000.
[0046] Such novel polymeric antiscalants can be prepared by
conventional free radical polymerization in an aqueous media. Such
processes are well known to those skilled in the art. In general, a
typical conventional free radical polymerization process includes
adding one or more monomers to a reaction vessel followed by
neutralization with a suitable base. Polymerization catalysts may
also be added to the vessel up-front or fed in gradually during the
course of the reaction. Water soluble initiators such as any free
radical or redox initiator or combination thereof are added along
with any other optional monomer to the reaction mixture in separate
feeds over the same amount of time, usually 4 to 6 hours. The
reaction temperature is maintained from about 90.degree. to about
100.degree. C. Additional initiator may be used after addition is
complete to reduce residual monomer level. At the end of the
reaction, a suitable base is added to adjust pH.
[0047] 1,2-dihydroxy-3-butene can be obtained from Eastman Chemical
Company, Fine Chemicals, P.O. Box 431, Kingsport, Tenn. 37662,
(telephone number is 1-800-327-8626) or it can be made
synthetically by hydrolyzing epoxy butene.
EXAMPLES
[0048] The following examples are intended to be illustrative of
the present invention and to teach one of ordinary skill how to
make and use the invention. These examples are not intended to
limit the invention in any way.
Example I
Autoclave Testing of Antiscalant Procedure for the Control of
Calcium Carbonate in Kraft Digesters and Bleach Plants
[0049] In carrying out the tests of the various polymeric
antiscalants, a concentrated synthetic black liquor was prepared as
follows.
[0050] In a 1000 mL beaker, 4 grams (g) of Na.sub.2CO.sub.3, 2 g of
indulin AT(precipitated lignin) and 16 mL of 500 g/l NaOH were
diluted to a volume of 1000 mL using distilled water. The beaker
was mixed on a stir plate until no precipitated lignin and sodium
carbonate were detected. The dissolved liquor was filtered with a
0.45 .mu.m filter and transferred to a 2000 mL graduated cylinder.
The liquor was diluted to a final volume of 2 liters.
[0051] 5000 ppm actives based samples of the antiscalant
chemistries and calcium solutions were made. All the glassware and
autoclaves were acid cleaned using a 10% solution of
H.sub.2SO.sub.4, 16 B.U.N. tubes were filled with 20 mL of double
distilled water and placed in a test tube rack filling a matrix or
8 columns and 2 rows. The autoclave digester was preheated to a
temperature of 50.degree. C. (approximately 30 minutes). 25 mL of
double distilled water and enough antiscalant solution to produce
the desired actives concentrations in 100 mL were added to eight
100 mL volumetric flasks. 50 mL of the concentrated black liquor
and 2 mL of 5000 ppm calcium solution were added to each flask and
the flasks were brought up to 2 mL below the fill line. The flasks
were hand mixed to redissolve any precipitate which formed upon
addition of calcium. The contents (100 mL) of the flask were
transferred to the autoclaves (Lorentzen & Wettre autoclaves).
2 mL of the sample were transferred to the B.U.N. tubes for the
estimation of initial calcium concentration. The autoclaves were
sealed with a wrench and the autoclave heater was set as per the
desired temperatures. The autoclaves were rotated and heating was
begun and the samples were lowered into the hot oil bath. Effect on
inhibition of calcium carbonate precipitation in the kraft digester
was evaluated at 170.degree. C. for 30 minutes. For the bleach
plant screening, the samples were allowed to reach 100.degree. C.
and run for 30 minutes at that temperature. The heating was turned
off and the samples were raised out of the oil bath. The autoclaves
were cooled for 10 minutes in a tub of cold water immediately after
removal. The autoclaves were opened and 2 mL of this liquor was
filtered through a 0.45 .mu.m syringe filter and transferred to the
B.U.N. test tubes for the estimation of final calcium. The B.U.N.
tubes were all brought up to the 25 mL line using double distilled
water and parafilm was placed over the top. The samples were hand
mixed. The calcium levels were measured using atomic absorption
using calibrated standards. The percent scale inhibition is
expressed as below:
% Inhibition=filtered calcium/initial calcium* 100
[0052] The following results were obtained.
[0053] It is understood that for each test run, the results given
for BLANK (no antiscalant) are not an example of the invention, but
rather they are comparative examples.
1 In the kraft Digester % Inhibition at Various Additive
Concentrations Blank (no antiscalant) 4.4 4.4 Polymer (antiscalant)
50 ppm 100 ppm 50:50 copolymer of 8.4 16 1,2-dihydroxy-3-butene,
maleic acid Sulfomethylated 6.3 10 poly(maleic acid, acrylic
acid)
[0054]
2 In the Bleach Plant % Inhibition at Various Additive
Concentrations Blank (no antiscalant) 10 10 Polymer (antiscalant)
50 ppm 100 ppm 33.3:33.3:33.3 25 62 terpolymer of
1,2-dihydroxy-3-butene, maleic acid, acrylic acid 50:50 copolymer
of 52 60 1,2-dihydroxy-3-butene, maleic acid Sulfomethylated 34 67
poly(maleic acid, acrylic acid) 45:45:10 terpolymer of 40 62 maleic
acid, acrylic acid, N-hydroxymethyl acrylamide
Example II
Evaluation of Antiscalant Chemistries for Controlling Scale in
Black Liquor Evaporators
[0055] A 12" long Teflon.RTM. reactor with an inside diameter of
1.5" and an outside diameter of 2" was used in these screening
experiments. A 0.25" cartridge heater (600 W) was inserted into the
reactor bottom via a bored 0.5" threaded reducing bushing that was
screwed into the bottom Teflon.RTM. endcap. A stainless steel
adapter attached to the top endcap was used to seat the {fraction
(24/40)} ground-glass joint of a reflux condenser, with a
Teflon.RTM. sleeve inserted to facilitate sealing of the ground
glass-stainless connection. The cooking was carried at 100.degree.
C. for 60 minutes. The remaining experimental procedure was
followed in accordance with the directions outlined in the kraft
digesters and bleach plants screening test procedure of Example
I.
[0056] The following results were obtained.
3 Summary of Screening Result for the Control of Calcium Carbonate
Scaling in the Black Liquor Evaporators % Inhibition at Various
Polymer Concentrations Blank (no antiscalant) 10 10 Polymer
(antiscalant) 100 ppm 200 ppm 45:45:10 maleic acid, 38 99 acrylic
acid, N-hydroxymethyl acrylamide 33.3:33.3:33.3 terpolymer 69 95
maleic acid, acrylic acid, dihydroxy-3-butane 50:50 copolymer
maleic 37 72 acid, 1,2-dehydroxy-3-butane Sulfomethylated poly 63
100 (maleic acid, acrylic acid)
Example III
Preparation of a 33.3 Mole Percent Acrylic Acid/33.3 Mole Percent
Maleic Acid/33.3 Mole Percent 1,2 Dihydroxy-3-ButeneTerpolymer
[0057] To a 5-neck, 100 mL resin flask equipped with a mechanical
stirrer, reflux condenser, and syringe pumps for continuous
addition of monomers and initiators were charged 10.7 g of
distilled water, 12.74 g of maleic anhydride, 20 g of a 57 weight
percent solution of 1,2-dihydroxy-3-butene, and 12.48 g of 50
weight percent aqueous solution of sodium hydroxide using cooling
to control any exotherm. The mixture was then heated to
approximately 98.degree. C. At temperature, 0.67 g of a 0.15
percent solution of iron sulfate heptahydrate dissolved in
distilled water was added to the reaction mixture. Next, 1.87 g of
acrylic acid were added to the reactor followed by 0.34 g of an
initiator solution consisting of 0.145 g sodium persulfate, 1.06 g
of a 30 weight percent hydrogen peroxide solution, and 4 g of
distilled water. The remaining initiator solution and a solution of
7.5 g of acrylic acid and 2.22 g of distilled water, were then fed
separately into the flask at a constant rate over a period of
approximately 4.5 hours while the reaction temperature was held
between 90.degree. C. and 100.degree. C. After monomer and
initiator feeding was complete, the reaction was held at
temperature for an additional 30 minutes. An additional initiator
solution consisting of 9.86 g of a 30 weight percent hydrogen
peroxide solution, 1.31 g of sodium persulfate, and 5 g of
distilled water was then fed into the reactor over a period of 3
hours, and again held after addition for 30 minutes. The reaction
was cooled to 80.degree. C., and a solution of 1.02 g of sodium
metabisulfite and 3.63 g of distilled water was added over a half
hour period. The reaction mixture was held at temperature for an
additional 30 minutes and then cooled to room temperature.
.sup.13CNMR confirmed product formation. The product had a weight
average molecular weight of approximately 10,000, as measured by
gel permeation chromatography (GPC) using polyethylene glycol (PEG)
MW standards.
Example IV
Preparation of a 50 Mole Percent Maleic Acid/50 Mole Percent
1,2-Dihydroxy-3-Butene Copolymer
[0058] To the reactor described in Example III were charged 15 g of
distilled water, 15.39 g of maleic anhydride, 24.24 g of a 57
weight percent solution of 1,2-dihydroxy-3-butene, and 13.80 g of a
50 weight percent aqueous solution of sodium hydroxide using
cooling to control any exotherm. The mixture was then heated to
approximately 98.degree. C. At temperature, an initiator solution
consisting of 2.57 g of sodium persulfate, 18.86 g of a 30 weight
percent hydrogen peroxide solution, and 5.49 g of distilled water
was then fed into the flask at a constant rate over a period of
approximately 4.5 hours while the reaction temperature was held
between 90.degree. C. and 100.degree. C. After monomer and
initiator feeding was complete, the reaction was held at
temperature for an additional 30 minutes. The reaction was then
cooled to 80.degree. C., and a solution of 1.02 g of sodium
metabisulfite and 3.63 g of distilled water was added over a half
hour period. The reaction mixture was held at temperature for an
additional 30 minutes and then cooled to room temperature.
.sup.13CNMR confirmed product formation. The product had a weight
average molecular weight of approximately 4,000, as measured by gel
permeation chromatography (GPC) using polyethylene glycol (PEG) MW
standards.
[0059] The specific examples herein disclosed are to be considered
as being primarily illustrative. Various changes beyond those
described, will, no doubt, occur to those skilled in the art; and
such changes are to be understood as forming a part of this
invention insofar as they fall within the spirit and scope of the
appended claims.
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