U.S. patent application number 10/628336 was filed with the patent office on 2004-03-25 for treatment of solid containing material derived from effluent.
Invention is credited to Phipps, Jonathan.
Application Number | 20040055715 10/628336 |
Document ID | / |
Family ID | 31998968 |
Filed Date | 2004-03-25 |
United States Patent
Application |
20040055715 |
Kind Code |
A1 |
Phipps, Jonathan |
March 25, 2004 |
Treatment of solid containing material derived from effluent
Abstract
A method of treating solid containing material derived from
effluent or sludge from a plant for de-inking paper, the material
containing calcium in the form of one or more insoluble calcium
compounds, the method including the steps of treating the material
with an acid to cause dissolution of the calcium thereby forming a
calcium ion-containing solution in which insoluble solids are
suspended, separating the solution from the insoluble solids and
incinerating the separated solids. The solution containing calcium
ions may be treated by adding one or more reagents to form a
calcium compound precipitate, e.g., calcium carbonate. The
particulate solids produced following the incineration step and
following the precipitate formation may be employed as pigments or
fillers in paper making or paper coating.
Inventors: |
Phipps, Jonathan;
(Cambridge, GB) |
Correspondence
Address: |
Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
1300 I Street, N.W.
Washington
DC
20005-3315
US
|
Family ID: |
31998968 |
Appl. No.: |
10/628336 |
Filed: |
July 29, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10628336 |
Jul 29, 2003 |
|
|
|
10300913 |
Nov 21, 2002 |
|
|
|
10300913 |
Nov 21, 2002 |
|
|
|
09996931 |
Nov 30, 2001 |
|
|
|
09996931 |
Nov 30, 2001 |
|
|
|
09148685 |
Sep 4, 1998 |
|
|
|
6425973 |
|
|
|
|
Current U.S.
Class: |
162/4 ; 162/7;
162/8 |
Current CPC
Class: |
D21H 17/01 20130101;
D21H 17/67 20130101; D21C 11/0007 20130101 |
Class at
Publication: |
162/004 ;
162/007; 162/008 |
International
Class: |
D21B 001/08; D21B
001/32; D21C 005/02 |
Claims
What is claimed is:
1. A method for treating waste material produced by an industrial
plant for treating paper, wherein said waste material contains
calcium in the form of one or more insoluble calcium compounds,
said method comprising: (A) treating said waste material with an
acid to cause dissolution of the calcium, thereby forming a calcium
ion-containing solution in which insoluble solids are suspended;
(B) separating the suspended insoluble solids from the calcium
ion-containing solution in (A); and (C) incinerating the insoluble
solids obtained in (B), and wherein fibrous material in said waste
material derived from effluent or sludge is not subjected to
combustion or ignition prior to (A).
2. A method for treating waste material produced by an industrial
plant for treating paper, wherein said waste material contains (a)
calcium in the form of one or more insoluble calcium compounds, and
(b) fibrous material, said method comprising: (A) treating said
waste material containing (a) calcium in the form of one or more
insoluble calcium compounds and (b) fibrous material with an acid
to cause dissolution of the calcium, thereby forming a calcium
ion-containing solution in which insoluble solids are suspended;
(B) separating the suspended insoluble solids from the calcium
ion-containing solution in (A); and (C) incinerating the insoluble
solids obtained in (B).
3. A method for treating waste material produced by an industrial
plant for treating paper, wherein said waste material contains
calcium in the form of one or more insoluble calcium compounds,
said method comprising: (A) treating said waste material with an
acid to cause dissolution of the calcium, thereby forming a calcium
ion-containing solution in which insoluble solids are suspended;
(B) separating the suspended insoluble solids from the calcium
ion-containing solution in (A); and (C) incinerating the insoluble
solids obtained in (B).
4. A method for treating waste material waste produced by an
industrial plant for treating paper, said waste material containing
(a) calcium in the form of one or more insoluble calcium compounds
and (b) fibrous material, the method including the steps of
treating the material containing (a) calcium in the form of one or
more insoluble calcium compounds and (b) fibrous material with an
acid to cause dissolution of the calcium thereby forming a calcium
ion-containing solution in which insoluble solids are suspended,
separating the solution from the insoluble solids and incinerating
the insoluble solids.
5. A method for obtaining kaolin from a waste material produced by
an industrial plant for treating paper, comprising: obtaining a
composition comprising kaolin and combustible organic compounds,
wherein said composition has been obtained by treating a waste
material, produced by an industrial plant for treating paper, to
remove calcium; and subjecting said composition to at least one
heat treatment process effective to incinerate said combustible
organic compounds and calcine remaining particulate material,
wherein said remaining particulate material comprises kaolin.
6. The method according to claim 5, wherein said calcium has been
removed from said waste material with a composition comprising at
least one acid.
7. The method according to claim 6, wherein said at least one acid
is a dilute acid.
8. The method according to claim 6, wherein said at least one acid
is a mineral acid.
9. The method according to claim 8, wherein said mineral acid is
chosen from hydrochloric acid and sulfuric acid.
10. The method according to claim 5, wherein the composition is
subjected to at least one drying process prior to being subjected
to at least one heat treatment process.
11. The method according to claim 5, wherein the composition is
subjected to at least one washing process prior to being subjected
to at least one heat treatment process.
12. The method according to claim 5, wherein said at least one heat
treatment process is performed in an incineration device.
13. The method according to claim 12, wherein said incineration
device is a fluidized bed furnace.
14. The method according to claim 5, wherein said at least one heat
treatment process is performed at a temperature ranging from
800.degree. C. to 1200.degree. C.
15. The method according to claim 14, wherein said at least one
heat treatment process is performed at a temperature ranging from
950.degree. C. to 1050.degree. C.
16. The method according to claim 15, wherein said at least one
heat treatment process is performed at a temperature of
1000.degree. C.
17. The method according to claim 5, wherein following said at
least one heat treatment process, said particulate material is
subjected to at least one additional treatment.
18. The method according to claim 17, wherein said particulate
material subjected to at least one additional treatment is provided
in a form chosen from a dry form and an aqueous suspension.
19. The method according to claim 17, wherein said at least one
additional treatment is chosen from communition, particle size
classification, washing, and the addition of at least one chemical
agent.
20. The method according to claim 19, wherein said communition is
performed by at least one of attrition grinding and media
grinding.
21. The method according to claim 19, wherein said at least one
chemical agent is chosen from optical brightening agents and
coagulants.
22. The method according to claim 5, wherein the particulate
material is provided to a paper mill.
23. The method according to claim 22, wherein the particulate
material is delivered to a paper mill in a form chosen from a dry
form and an aqueous slurry form.
24. A filler comprising a product obtained by the process of claim
5.
25. A paper composition comprising a filler according to claim
24.
26. The filler according to claim 24, wherein said filler is a
paper-making filler.
27. The filler according to claim 24, further comprising at least
one additional filler.
28. The filler according to claim 27, wherein said at least one
additional filler is chosen from silicates, talc, calcium
carbonate, calcium sulfate, and titanium dioxide.
29. The filler according to claim 24, wherein said filler is in the
form of a dilute slurry.
30. A polymer composition comprising a product obtained according
to the method of claim 5.
31. A coating composition comprising a product obtained according
to the method of claim 5.
32. A paint composition comprising a product obtained according to
the method of claim 5.
33. The method according to claim 1, wherein said insoluble calcium
compounds comprise at least one compound chosen from calcium
carbonate, calcium sulphate, calcium phosphate, and calcium
silicate.
34. The method according to claim 1, wherein said calcium compound
is calcium carbonate.
35. The method according to claim 1, wherein said calcium
ion-containing solution is treated to form a precipitate.
36. The method according to claim 35, wherein said precipitate
comprises an insoluble calcium compound.
37. The method according to claim 36, wherein said precipitate is a
calcium carbonate precipitate.
38. The method according to claim 35, wherein said precipitate is
formed by combining the calcium ion-containing solution with at
least one substance chosen from an alkali metal salt, an alkali
metal hydroxide, and carbon dioxide.
39. The method according to claim 38, wherein said alkali metal
salt is chosen from sodium salts.
40. The method according to claim 38, wherein said alkali metal
salt is sodium carbonate.
41. The method according to claim 38, wherein said alkali metal
hydroxide is sodium hydroxide.
42. The method according to claim 35, wherein calcium carbonate is
separated from said calcium ion-containg solution.
43. The method according to claim 42, wherein said separation is
performed with at least one method chosen from filtration,
evaporation, separation via a hydrocyclone, and separation via a
centrifuge.
44. A filler comprising a product obtained by the method of claim
1.
Description
BACKGROUND OF THE INVENTION
[0001] This is a continuation-in-part application of U.S.
application Ser. No. 10/300,913, filed Nov. 21, 2002, which is a
continuation of U.S. application Ser. No. 09/996,931, filed Nov.
30, 2001 (Now Abandoned), which is a continuation of U.S.
application Ser. No. 09/148,685, filed Nov. 22, 2000 (Now U.S. Pat.
No. 6,425,973).
[0002] 1. Field of the Invention
[0003] The present invention relates to the treatment of solid
containing material derived from effluent, especially to recover
useful materials therefrom.
[0004] In particular, this invention is concerned with a method for
recovering useful materials from what has hitherto been regarded as
the waste material produced by an industrial plant for treating
paper, especially for de-inking waste paper.
[0005] Paper and paperboard products are generally made by
preparing a dilute aqueous suspension containing cellulosic fibres
derived from wood or from some other suitable fibrous material, and
de-watering the suspension on a moving wire mesh belt to form a
sheet material. The suspension may also contain a proportion of a
mineral filler material which improves the brightness and opacity
of the finished paper or board. Natural cellulosic fibrous
materials are generally expensive, and the trees or other plants
from which they are obtained must be replaced if the balance of the
environment is not to be disturbed. It is therefore desirable to
incorporate in the aqueous suspension from which the sheet material
is made a substantial proportion of cellulosic fibrous material
which has been recovered from waste paper. Most waste paper which
is recycled has been printed on at least one of its surfaces, and
it is necessary to separate the printing ink residue from the
cellulosic fibres if the recovered material is to be suitable for
use as a starting material in a paper making process. If the ink is
not separated, the fibrous material will generally be unacceptably
dark in colour. Generally, printing ink contains elemental carbon
(carbon black) and other dark material which causes the dark
coloration.
[0006] Commercially operated processes for de-inking waste paper
generally comprise a pulping stage in which the waste paper is
subjected to mechanical agitation in water which also contains
sodium hydroxide which causes the fibres to swell, and which breaks
down most ink vehicles by saponification or hydrolysis, sodium
silicate which acts as a pH buffer and agglomerates detached ink
particles to a convenient size, and a surfactant which wets the ink
particles and helps to keep them in suspension. The suspension
formed in the pulper is passed through a primary screening system
in which heavy foreign bodies, such as staples, paper clips and
pieces of grit are removed. The suspension passing through the
screens is then fed to a treatment plant comprising one or more
froth flotation cells, or one or more washing units, or a
combination of washing units and flotation cells. The froth
flotation cells are each provided near the bottom with a rotating
impeller and means for admitting air under pressure in the form of
fine bubbles in the region of the impeller. It may also be
advantageous to add to the suspension, before it enters the
flotation cell, a reagent known as a collector which attaches
itself preferentially to the ink particles and increases their
affinity with air relative to that with water. As a result, the ink
particles are preferentially lifted by the air bubbles to the
surface of the suspension in the flotation cell, where they are
discharged in a froth product.
[0007] In the washing units the pulp is subjected to agitation in
fresh or recycled water, optionally containing a dispersing agent,
and the washed pulp is then drained on a screen of aperture size
such as to retain the relatively long cellulosic fibres, while
allowing to pass the mineral and organic particles and the fine
fibre fragments.
[0008] The suspension which is discharged from the bottom of the
flotation cell, and/or the suspension which passes the screens of
the washing steps, is de-watered and the de-watered material, which
consists of substantially de-inked cellulosic fibre material, may
be subjected to further purification steps before being finally
de-watered and dried for re-use in a sheet forming process.
[0009] The de-inking treatment plant reject consists of an aqueous
effluent or sludge which is produced in large volumes. The reject
from some plants is discarded and transferred to a waste disposal
site, e.g., a landfill site. The reject from other plants is
incinerated and this beneficially reduces the volume of the reject
and generates useful heat energy from the combustion of organic
components. The ash from the incineration is subsequently disposed
of. However, in both cases, there is an undesirable cost and
environmental impact associated with disposal. Also, potentially
useful materials are wasted by the disposal process. The de-inking
treatment plant reject generally contains, in addition to the ink
particles and various additives employed in paper, a substantial
proportion of the inorganic filler particles which were originally
present in the waste paper. These filler particles usually consist
predominantly of a mixture of kaolin clay and calcium carbonate in
various proportions, although other inorganic filler particles such
as silicates, talc, calcium sulphate or titanium dioxide may also
be present in minor proportions.
[0010] 2. Related Prior Art
[0011] In the prior art, various patent specifications have been
published which describe processes for incinerating waste solids
from de-inking sludge. In some of these processes the ash produced
following incineration is further treated to render the particulate
material contained in the ash suitable for re-use in a paper making
process. Examples of specifications describing such processes
include WO96/32354. Where the sludge solids treated include calcium
carbonate this can react with kaolin present to produce a glassy
composite phase which causes the particulate product to be
abrasive. As described in EP798268-A1, the incineration temperature
may be controlled so as to minimise formation of the glassy phase,
but this procedure can be relatively complicated and expensive to
operate and may cause the resulting particulate product to have
inferior optical properties, e.g., a reduced brightness.
SUMMARY OF THE INVENTION
[0012] The present invention allows treatment of calcium
compound-containing solids obtained from a waste paper de-inking
sludge to be carried out in a manner which does not suffer from the
problems of the prior published processes referred to earlier and
allows improved products suitable for re-use as pigments and
fillers, e.g., for addition to papermaking compositions, to be
obtained in a simpler and cheaper manner.
[0013] According to the present invention there is provided a
method of treating solid containing material derived from effluent
or sludge from a plant for de-inking paper, the material containing
calcium in the form of one or more insoluble calcium compounds, the
method including the steps of treating the material to cause
dissolution of the calcium thereby forming a calcium ion-containing
solution in which insoluble solids are suspended, separating the
solution from the insoluble solids and incinerating the insoluble
solids. The method according to the present invention is considered
to comprise any one of those steps, and is alternatively considered
to comprise at least two of those steps in combination.
[0014] The treated solid containing material may comprise the said
effluent or sludge, optionally after diluting with water, and may
comprise the particulate materials described hereinbefore. The said
calcium compound may comprise calcium carbonate and/or calcium
sulfate and/or calcium silicate, and/or calcium phosphate.
[0015] The method of the invention may surprisingly and
beneficially be operated in a less costly manner than that
described in EP798268-A1, because it does not require use of the
close temperature control (which requires use of expensive
automation equipment), multiple calcination steps and recarbonation
(following aqueous dispersion) of the resulting ash all as required
in the process of EP798268-A1. As illustrated later, the product of
the method of the invention, even though produced by a less
complicated and less costly process, shows properties relevant to
re-use, e.g., in a paper making process, comparable with those
obtained for the product of the process of EP798268-A1.
DESCRIPTION OF THE INVENTION
[0016] The said treatment to cause dissolution of the calcium
comprises addition of an acid which may be a dilute acid. The
dilute acid used may comprise any one or more of the dilute acids
known to form soluble calcium salts. Mineral acids such as
hydrochloric acid are preferred. Some dilute acids, e.g., sulfuric
acid, which may be employed will cause the calcium ions released to
form a partially soluble salt, e.g., calcium sulfate. In this case,
the partially soluble salt will remain in the subsequently
separated and calcined solids.
[0017] In the method according to the present invention the calcium
dissolution step may be carried out with the assistance of heating
and other suitable agents, e.g., mechanical agitation or
stirring.
[0018] After calcium has been dissolved over a sufficient period of
time, which will depend upon the amount of calcium to be dissolved,
the calcium ion-containing solution will generally have suspended
therein particulate solid material whose content will depend on the
composition of the original de-inking effluent or sludge and any
treatment which has been applied to it. The solid particulate
material may be separated from the calcium ion-containing solution
by one or more suitable known separation techniques, e.g.,
filtration, evaporation or by use of a hydrocyclone or a
centrifuge, applied in one or more stages.
[0019] The solid material remaining after the acid dissolution step
may be treated, optionally after a drying step, by one or more heat
treatment steps which provide incineration of the combustible
organic compounds present and calcining of the remaining
particulate material which is likely to comprise principally
kaolin.
[0020] The heating step applied to calcine the kaolin-containing
particulate material may be carried out at a temperature higher
than that employed in the examples described in EP798268-A1. For
example, a single incineration and calcination step may be applied
in a known incineration device, e.g., a fluidised bed furnace, at a
temperature of between 900.degree. C. and 1200.degree. C.,
desirably from 950.degree. C. to 1050.degree. C. Carbon present
from the ink contained in the de-inking sludge is oxidised quickly
at this temperature.
[0021] The resulting particulate material following incineration
and calcination may be further treated, either in a dry form or in
the form of an aqueous suspension, to improve the properties of the
particulate material, e.g., by comminution such as attrition or
media grinding in a known manner, particle size classification (if
not previously applied), washing, addition of chemical agents,
e.g., optical brightening agents, coagulants etc. The resulting
particulate product may be delivered in dry or aqueous slurry form
to a paper mill for use in a paper making or paper coating process
in a known manner optionally together with other known pigments,
e.g., kaolin, calcined kaolin, calcium carbonate, talc, titanium
dioxide, talc or calcium sulfate.
[0022] Where the recovered product is recycled for reuse in a paper
mill, the paper mill may be associated with the de-inking plant
from which the treated sludge has been obtained.
[0023] Where the recovered product is recycled for reuse in a paper
mill it may be used as a paper making filler in the mill in a known
manner. This filler, optionally mixed with other fillers as
described earlier, may be employed as a dilute slurry by mixture
with a dilute cellulose fiber slurry to produce a paper making
furnish. The solids of the furnish composition may for example
constitute from 0.2% to 2%, e.g., from about 0.5% to 1% by weight
of an aqueous suspension.
[0024] After the solid material has been separated the calcium
ion-containing solution may be treated to form a precipitate of
useful insoluble calcium compound. An alkali metal salt, e.g., a
sodium salt, may be added to the solution to provide the required
anion. For example, sodium carbonate may be added to the calcium
ion-containing solution to produce a calcium carbonate precipitate.
Where the calcium ion-containing solution comprises calcium
chloride, sodium chloride is left in solution.
[0025] Alternatively, an alkali metal hydroxide, e.g., sodium
hydroxide, may be added to release calcium hydroxide.
[0026] Where the calcium ion-containing solution contains calcium
hydroxide, formed for example by addition of an alkali metal
hydroxide to a calcium salt solution, carbon dioxide may
conveniently be added to the calcium hydroxide solution to form a
calcium carbonate precipitate. Formation of precipitated calcium
carbonate by addition of carbon dioxide to calcium hydroxide is, of
course, well known in the pigment producing art.
[0027] The insoluble calcium compound product thereby formed, e.g.,
calcium carbonate, may be separated from the aqueous medium in
which it is formed by a suitable separation process, e.g.,
filtration, evaporation or by use of a hydrocyclone or a
centrifuge. The product may be stored and thereafter supplied for
use in one of the applications described hereinafter, especially as
a particulate filler in the manufacture or coating of paper. Where
the solution contains little dissolved material after formation of
the calcium compound precipitate, e.g., after calcium hydroxide has
been converted to calcium carbonate using carbon dioxide, the
suspension or slurry containing the precipitate may itself be used
optionally with partial dewatering.
[0028] For example, the suspension may be delivered to a paper mill
for use of the suspension as a particulate filler supply for use in
paper manufacture or one of the other pigment or filler
applications described for the calcined kaolin-containing material
described earlier. The method of use may be as for that
material.
[0029] If the solution in which the insoluble calcium precipitate
is produced contains dissolved species these may optionally be
recovered and re-used. For example, where the dissolved species
comprises sodium chloride solution this may be electrolysed in a
known way to produce sodium hydroxide plus hydrogen and chlorine
gases. The gases may be recombined to produce hydrogen chloride
from which hydrochloric acid can be recovered which can be
re-cycled for re-use in the acid dissolution step. The sodium
hydroxide can be recycled for re-use as the alkali metal hydroxide
for addition to the calcium ion-containing solution. In addition,
carbon dioxide is produced in the dissolution step this may be
re-cycled for re-use in the precipitation step. In this way, the
need to purchase chemical reagents and to dispose of by-products
can be minimised or avoided.
[0030] The method according to the present invention beneficially
allows minimization of the amount of solid waste from a de-inking
plant thereby reducing or eliminating the cost and environmental
impact of disposal of such waste. Furthermore, the method allows
one or more useful products to be recovered in a manner which is
simpler and cheaper than the relevant prior art.
[0031] The useful product recovered includes a calcined
kaolin-containing particulate material which does not suffer
substantially from the abrasiveness normally caused by incinerating
kaolin and calcium carbonate together. In this case, the calcined
kaolin composition may be used in various pigment employing
applications, e.g., paper making as described earlier or in paper
coating, filling of polymers, paints and the like. Such a product
may show improved optical properties, e.g., brightness, compared
with products produced by incineration of solids from de-inking
sludge by prior published methods without discoloration from ink
coloring materials, e.g., carbon, and in a cheaper manner.
[0032] A further product, for example calcium carbonate, may also
be recovered without the dark coloration normally associated with
de-inking reject and is suitable for use in the various
applications in which precipitated calcium compounds, e.g., calcium
carbonate, are known to be useful, e.g., as a particulate filler or
extender material in paper, polymers, paints and the like or as a
coating pigment or colour ingredient for coating of paper, paper
board, plastic papers and the like.
[0033] Other particulate materials, e.g., silicate and
aluminosilicate material contained in the de-inking reject may, as
described hereinbefore, be converted after calcination into useful
products, e.g., pozzolans, and the reagents used in the method
according to the present invention may be recycled thereby
minimizing reagent costs and waste disposal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIGS. 1 and 2 are schematic flow diagrams of alternative
methods embodying the invention.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0035] Embodiments of the present invention will now be described
by way of example with reference to the accompanying drawings.
[0036] As shown in FIG. 1, in a first example of a method embodying
the invention, input solid-containing material 1, preferably in the
form of an aqueous suspension, comprises, reject sludge from a 10
paper de-inking plant (not shown).
[0037] The material 1 is subject to an acid dissolution step in a
vessel 3 in which calcium present in the input material is
dissolved as a soluble salt, e.g., calcium chloride, by use of
dilute hydrochloric acid. The suspension formed by the acid
dissolution step is subject to a solid/liquid separation step in a
separator 5. Solids obtained by the separation step in the
separator 5 is delivered to an incinerator 9, e.g., operated at a
temperature of 800.degree. C. to 1200.degree. C. as appropriate,
which oxidises the combustible organic material and carbon present
in the solids and produces an inorganic product 11 comprising
predominantly calcined kaolin (metakaolin). The product 11
optionally with further treatment, e.g., comminution, particle size
classification and washing, may be delivered in dry or slurry form
for use as a filler in paper making in the manner described
earlier.
[0038] The solution separated by the liquid/solid separation step
in the separator 5 may be delivered to a vessel 12 in which sodium
carbonate is added in a quantity calculated to give a required
amount of precipitated calcium carbonate according to the amount of
calcium present. The solution entering the vessel 12 may be
monitored on-line by a monitor 13 to determine its calcium ion
concentration and hence the required concentration of sodium
carbonate in the vessel 12. The solution separated by the
liquid/solid separation in the separator 5 may alternatively be
delivered to a vessel 15 via a line also monitored by a monitor 13
in which sodium hydroxide solution is added to the solution to form
calcium hydroxide which will dissolve in the water present up to
its limiting solubility. Carbon dioxide is added in a reactor 17
(which may be the same as the vessel 15 or a separate reactor). The
required amount of carbon dioxide to be added may, as an
indication, be calculated from the amount of calcium hydroxide
present which in turn can be determined from the concentration of
calcium ions monitored by the monitor 13. It is not essential to
calculate the required amount of carbon dioxide since after all
calcium hydroxide has been consumed the pH of the solution will
drop indicating that the reaction has terminated.
[0039] The precipitate-containing slurry formed either in the
vessel 11 or in the reactor 17 is subjected to dewatering, e.g., by
evaporation, in a concentrator 19. Output material 21 in slurry or
dry powder form, as appropriate, from the concentrator 19 is
delivered to a storage tank 23 for onward supply to a user plant,
e.g., a paper making mill or plant in which the material 21 is to
be used as a paper filler material in the manner described FINNEGAN
HENDERSON FARABOW earlier.
[0040] Liquid 22 separated by the concentrator 19 may be discharged
as effluent or may be treated to recover reagents therefrom. For
example, where the liquid 22 comprises predominantly sodium
chloride solution, this may be electrolysed to produce hydrogen and
chlorine and to leave sodium hydroxide. The hydrogen and chlorine
may be combined to produce HCl for re-use in the acid dissolution
step in the vessel 3 leaving, from the electrolysis, sodium
hydroxide in the vessel 15 which may be re-used.
[0041] An alternative method embodying the present invention is
illustrated in FIG. 2. In this case, input material 25 comprises
de-inking plant effluent sludge preferably diluted with clean
water. This material 25 is delivered to an acid tolerant vessel 27
in which dilute hydrochloric acid is added. The suspension
remaining in the vessel 27 is subjected to liquid/solid separation
in a separator 29. The solid separated may be washed in a washer
unit 31 and thereafter dried in a dryer 26 and incinerated in a
fluid bed incinerator 28 operating at a temperature of about
1000.degree. C. Heat energy 36 is generated by the combustion of
organic material in the incinerator 28. Carbon is oxidized in the
incinerator. The solids output or ash from the incinerator 28
indicated by output 34 comprises predominantly calcined clay
(metakaolin). This product may be used as a pigment or filler as
described earlier, e.g., by re-use in paper making.
[0042] The solution indicated as 30 separated by the separator 29
and/or by the washer unit 31 is delivered to a concentrator 33.
Extracted water 32 may be re-used in the washing unit 31. The
solution concentrated by the concentrator 33 comprising mainly
calcium chloride is delivered to an electrolytic cell 35. Hydrogen
37 and chlorine 39 are produced by the cell 35 and are delivered to
a reactor 41 in which they are reacted to form hydrogen chloride
gas 42. The HCl gas 42 may be recycled after dilution as dilute
hydrochloric acid for addition in the vessel 27.
[0043] A calcium hydroxide-containing slurry formed by electrolysis
of calcium chloride in the cell 35 is delivered to a reactor 43, in
a metered amount, and an appropriate amount of carbon dioxide 45
which may be obtained as a by-product from the acid dissolution in
the vessel 27 is supplied to the reactor 43 to provide conversion
of the calcium hydroxide present to precipitated calcium carbonate.
The product slurry formed may be concentrated by dewatering in a
concentrator 46 and delivered to a storage tank 47 for onward
delivery as a product, e.g., as a particulate filler in paper
manufacture. Alternatively, the product slurry formed in the
reactor 43 may be delivered via the storage tank 47 for use without
dewatering. Water 46 obtained from the dewatering process in the
concentrator 46 may be recycled for dilution of the HCl output
42.
EXAMPLE
[0044] A deinking sludge having a calcium carbonate content of
about 5% by weight and a kaolin content of about 40% by weight,
based on the dry solids weight of the sludge, was treated in the
manner described with reference to FIG. 1 by addition of dilute
hydrochloric acid to dissolve the calcium carbonate present
followed by incineration and calcination in a furnace at a
temperature of about 1000.degree. C. for several hours overnight.
The product obtained was redispersed in water and milled by
sandgrinding and then subjected to the tests described later in
this Example. The Product is there referred to as `Product 2`. For
comparison purposes, a further product, Product 1, was made without
acid dissolution by the more complicated and costly method
described in EP798268 using carefully controlled incineration and
calcination at a temperature of 750.degree. C.
[0045] Products 1 and 2 were tested as follows:
[0046] The ISO brightness was measured and the particle size
distribution was measured using a SEDIGRAPH 5100 machine. The
results which were obtained are as shown in Table 1 as follows.
1TABLE 1 PHYSICAL PROPERTIES Product 1 (comparative) Product 2
Brightness, ISO 82.2 83.4 PSD 100 100 % < 10 microns % < 5
microns 100 100 % < 2 microns 97 99 % < 1 micron 88 92 % <
0.5 micron 53 64 % < 0.25 micron 12 24
[0047] These results show that a better brightness and finer
particle size distribution are obtainable using a method embodying
the invention which is simpler and cheaper to run than that
described in EP798268-A1.
[0048] Products 1 and 2 were evaluated in 48gsm newsprint to
compare their performance as fillers.
[0049] Handsheets were made on a TAPPI sheet mold and dried on a
Noble & Wood drum dryer. The sheets were then conditioned
before testing. Experimental conditions for the handsheet study are
given in Table 2 below.
[0050] The handsheets were tested for brightness, opacity, caliper,
Gurley porosity, burst and % ash. Scattering and absorption
coefficients along with bulk were calculated. The handsheets were
then calendered, conditioned again and tested.
[0051] Handsheet properties are given in Table 3 below. Sheet
properties were interpolated at 5% filler to give a comparison of
the pigments. The results obtained are shown in Table 4 below.
2TABLE 2 EXPERIMENTAL CONDITIONS OF SHEET FORMATION The following
handsheet preparation conditions were employed to make handsheets
in accordance with TAPPI standard T205.om-88 ("Forming handsheets
for physical tests of pulp"). Pulp: 90% TMP 10% Kraft Final
consistency 0.3% solids in aqueous suspension Grammage 48 gsm PH
4.8 Sheet Mold Tappi Calendering conditions Machine calender at
38.degree. C. 1 nip @ 150 psi 1 nip @ 250 psi 1 nip @ 250 psi
[0052] For calendering preparation, the handsheets were placed in
the desiccator for 10 minutes with water to allow the moisture
content of the sheets to increase to .about.8%. Between each nip
the sheets were placed back in the desiccator for 5 minutes and
then only one set was removed at a time.
3TABLE 3 UNCALENDERED HANDSHEET PROPERTIES % ISO Grammage
Brightness Pigment Tappi Hunter Optest Gurley Burst gsm Ash %
Scatter Opacity L a b Formation Porosity Index Product 1 Sample 1
47.0 2.8 59.3 2652 88.2 87.0 -1.3 14.0 90.4 13.6 1.73 Sample 2 46.4
6.0 61.6 3164 90.3 87.9 -1.3 13.2 84.1 15.5 1.75 Sample 3 45.7 8.3
61.6 2485 90.6 87.6 -1.3 12.9 76.1 8.4 1.81 Product 2 Sample 1 46.6
2.9 59.4 1995 87.5 87.1 -1.3 14.0 94.1 12.8 1.82 Sample 2 46.8 6.0
61.6 2414 89.0 88.0 -1.3 13.4 88.1 12.1 1.53 Sample 3 45.7 8.7 62.7
2236 89.6 88.4 -1.3 12.0 83.9 11.5 1.49
[0053]
4TABLE 4 CALENDERED HANDSHEET PROPERTIES % ISO DATA Grammage
Brightness Pigment Tappi Hunter Gurley Filler gsm Ash % Scatter
Opacity L a b Porosity Product 1 Sample 1 47.0 2.8 58.9 2402 88.3
86.5 -1.2 13.7 37.1 Sample 2 46.4 6.0 61.6 2731 90.9 87.4 -1.1 13.0
35.4 Sample 3 45.7 8.3 61.6 2400 90.7 87.2 -1.1 12.6 29.4 Product 2
Sample 1 46.6 2.9 59.3 1822 87.6 86.8 -1.1 13.8 42.2 Sample 2 46.8
6.0 61.3 2014 88.6 87.6 -1.1 13.2 27.9 Sample 3 45.7 8.7 62.3 2202
89.9 88.0 -1.1 12.7 26.5
[0054] The results shown in Tables 3 and 4 illustrate that the
product obtained by the method embodying the invention gives
similar properties (which are superior in some cases) to those
obtained for the product of the process described in EP798268-A1
but, as described earlier, the product of the method embodying the
invention may be obtained by a less expensive de-inking sludge
treatment process.
* * * * *