1. Use of a hydrosoluble copolymer consisted of: - methacrylic acid monomers and/or any one of its salts, - optionally, acrylic acid monomers and/or any one of its salts, - monomers with formula (I): R – X – R’ (I) wherein: R represents a polymerizable unsaturated function, in particular acrylate, methacrylate, methacryl-urethane, vinyl or allyl, R’ designates hydrogen or an alkyl group having from 1 to 4 carbon atoms, X represents a structure including n unit(s) of ethylene oxide EO and m unit(s) of propylene oxide PO, positioned randomly or regularly, m and n are two non-zero integers and comprised between 1 and 150, to prepare an aqueous suspension of calcium hydroxide from powdered calcium hydroxide.

2. An aqueous suspension of calcium hydroxide, comprising at least one copolymer consisted of: - methacrylic acid monomers and/or any one of its salts, - optionally, acrylic acid monomers and/or any one of its salts, - monomers with formula (I): R – X – R’ (I) wherein: R represents a polymerizable unsaturated function, in particular acrylate, methacrylate, methacryl-urethane, vinyl or allyl, R’ designates hydrogen or an alkyl group having from 1 to 4 carbon atoms, X represents a structure including n unit(s) of ethylene oxide EO and m unit(s) of propylene oxide PO, positioned randomly or regularly, 32 m and n are two non-zero integers and comprised between 1 and 150.

3. Use according to claim 1 or the suspension according to claim 2, wherein said suspension has a dry content of at least 40 wt.%.

4. Use or suspension according to any one of the preceding claims, wherein the viscosity of said aqueous suspension measured by a Brookfield DVIII viscosimeter at 10 rpm is comprised between 25 and 1,000 mPa.s at 20°C.

5. Use or suspension according to any one of the preceding claims, wherein the copolymer has a molecular mass comprised between 30,000 and 200,000 g/mol as determined by Steric Exclusion Chromatography (SEC).

6. Use or suspension according to any one of the preceding claims, wherein said monomer with formula (I) is such that n and m are two non-zero integers and n + m > 17.

7. Use or suspension according to any one of the preceding claims, wherein the function R of said monomer with formula (I) represents the methacrylate function.

8. Use or suspension according to any one of the preceding claims, wherein the function R’ of said monomer with formula (I) represents H or CH3.

9. Use or suspension according to any one of the preceding claims, wherein said monomer with formula (I) is consisted of, expressed in percentage by weight of each of its components: - 5 to 30 wt.% of methacrylic acid monomers and/or any one of its salts, - 0 to 10 wt.% of acrylic acid monomers and/or any one of its salts, - 70 to 95 wt.% of monomers with formula (I).

10. Use of the aqueous suspension of calcium hydroxide according to any one of claims 1, 3 to 9, to treat industrial fumes, in particular for desulfurization of the fumes, or to treat household wastewater, in particular potable water, or industrial water. 33

11. A method for preparing an aqueous suspension of calcium hydroxide according to any one of claims 2 to 9, comprising a step consisting of subjecting the suspension to a homogenous shearing.

12. A method according to claim 11, wherein a homogenous shearing is applied with a degree of shearing greater than 50,000 s-1.

13. A method according to claim 11 or 12, wherein a mixer of the rotor-stator type is used to perform said homogenous shearing.

14. A method according to any one of claims 11 to 13, wherein the device used to perform said homogenous shearing is equipped with a recirculation loop.

15. A method according to any one of claims 11 to 14, wherein a device configured for a power expenditure of at least 1,000 W/m3 is used to perform said homogenous shearing. Dated this 3rd day of June, 2015 HIRAL CHANDRAKANT JOSHI AGENT FOR COATEX 34 ABSTRACT Title: USE OF A WATER-SOLUBLE COPOLYMER FOR PREPARING AN AQUEOUS LIME SUSPENSION The present invention relates to a lime-based suspension comprising a water-soluble copolymer as an additive, as well as a method for preparing such a suspension. Such suspensions are in particular used as chemical neutralizing agents in industrial or household methods.

The present invention relates to the technical field of the preparation of aqueous suspensions
of calcium dihydroxide. More specifically, the present invention relates to the use of a
hydrosoluble copolymer to prepare a lime-based suspension, as well as aqueous suspensions
of lime comprising such a polymer. Such suspensions are in particular used as a chemical
neutralizing agent in industrial or household methods.
Calcium dihydroxide Ca(OH)2, also called slaked lime or hydrated lime, is obtained by
hydrating calcium oxide CaO, also called quicklime, according to the following exothermic
reaction: CaO + H2O �� Ca(OH)2.
In the context of the present invention, the terms "calcium hydroxide" or "calcium
dihydroxide" are used equivalently to designate particles of Ca(OH)2.
Calcium hydroxide-based products assume various forms: powdered (dry, powdery form
product), plastic pastes, or aqueous suspensions dispersions (milk of lime).
The present invention more particularly relates to a calcium hydroxide-based product found
in the form of an aqueous suspension. Such aqueous slaked lime suspensions may be used as
chemical neutralizing agents in many industrial methods. Examples include industrial
effluent treatment, for example gaseous effluents such as acid fumes. Examples also include
the treatment of potable water, wastewater or industrial water.
Aqueous suspensions of slaked lime are in particular characterized by their dry matter content
(wt.%). The person skilled in the art traditionally seeks to increase the dry matter content in
aqueous suspensions of slaked lime, primarily for economic reasons: by increasing the dry
matter content of the aqueous suspensions of slaked lime, transport and handling costs are
reduced per ton of product. Furthermore, the annoyances due to the manipulation of powders
(hygiene, handling) are reduced and implementation is made easier.
To increase the dry matter content of aqueous suspensions of slaked lime, it is in particular
possible to use a dispersing agent.
The expression "dispersing agent" refers to an agent that has the ability to improve the
dispersion state of the particles of Ca(OH)2 within the aqueous suspension. Concretely, when
3
these agents are used in aqueous suspensions of a mineral material, they cause a decrease in
viscosity. Thus, an aqueous suspension of a mineral material including a dispersing agent will
have a viscosity lower than that of the same aqueous suspension of mineral material not
containing said dispersing agent.
A certain number of prior art documents describes the use of dispersing agents. Document EP
0 061 354 (Blue Circle) describes the use of anionic oligomeric polyelectrolytes, for example
methacrylic acid homopolymers, carboxymethylcellulose or sulfonate, to manufacture
aqueous dispersions of slaked lime.
Document FR 2 677 351 (Italcementi) describes a concentrated aqueous suspension of
calcium hydrate, which contains at least 40% of solid hydrated lime obtained from powdered
hydrated lime, slaked lime or quicklime, and a hydrosoluble polymer that may be an alkali or
alkaline earth metal polyacrylate.
Document EP 0 594 332 (Rohm & Haas) describes the use of polymeric anionic dispersing
agents to obtain dispersions of aqueous quicklime or slaked lime. These dispersing agents are
chosen from among homopolymers, copolymers and terpolymers having carboxylic acid,
sulfonic acid or phosphoric acid functionalities. The monomers that impart such an acid
functionality, for example acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic
anhydride, itaconic acid, mesaconic acid, fumaric acid, citraconic acid, vinylacetic acid,
acryloxypropionic acid, vinylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-
methylpropanesulfonic acid, allyl sulfonic acid, allyl phosphonic acid, vinylphosphonic acid,
and vinylsulfonic acid.
Document US 2008/0011201 (Ultimate Nominees) describes the combined use of a
polycarboxylate dispersant and a carbohydrate dispersant to prepare a milk of lime for
applications in the food and potable water field. In particular, according to this document, the
carbohydrate dispersant is a sugar, in particular chosen from among aldoses, saccharides,
disaccharides and polysaccharides. Also, examples of a polycarboxylate dispersant are in
particular the salts of maleic styrene anhydride copolymers or polycarboxylate polyether
salts. This document in particular describes the combined use of a comb-type copolymer, in
4
particular Ethacryl® G (polycarboxylate dispersant by the company Coatex) and a glucose
syrup (carbohydrate dispersant) to prepare a 50% hydrated lime suspension/dispersion.
Document EP 0 848 647 (Chemical Lime Company) describes the use of a dispersing agent
of the anionic polyelectrolyte type, combined with an alkali metal hydroxide, to prepare a
lime suspension that may be quicklime or slaked lime. The anionic polyelectrolyte is chosen
from among polyacrylic acid, polycarboxylic acid and polyphosphoric acid, copolymers of
polyacrylic acid, polycarboxylic acid and polyphosphoric acid and their alkali metal salts.
Document FR 6 687 396 (Lhoist) describes a method for slaking calcium oxide or
magnesium oxide in the presence of SO3
-, SO4
2- or Cl- ions and in that during or at the end of
the reaction, a polymer or copolymer is added comprising monomers chosen from among
acrylic acid and its salts, methacrylic acid and its salts, vinylbenzyl sulfonic acid and its salts,
acrylamido-2-methylpropanesulfonic acid and its salts,
2-sulfoethyl methacrylate and its salts.
Document JP 09 122471 (Nippon Shokubai) describes the use of copolymers consisted of a
carboxylic monomer and a monomer of the polyalkylene glycol methacrylate type as
dispersing agent making it possible to obtain aqueous dispersions of slaked lime with a low
viscosity. This document illustrates the use, to that end, of copolymers having a molecular
weight of less than 20,000 g/mol.
Document WO 2010/106111 (Lhoist) relates to compositions comprising slaked lime and/or
quicklime and an organic polymer incorporated into the solid phase of the slaked lime. The
polymers described in this document may be non-ionic, anionic, cationic or amphoteric and
of quite varied natures. They may be obtained from monomers chosen from among anionic
monomers having a carboxylic function or a sulfonic acid function, non-ionic monomers
(acrylamide, methacrylamide, N-vinyl pyrrolidone, vinyl acetate, vinyl alcohol, acrylate
esters, allyl alcohol, N-vinyl acetamide, N-vinylformamide), cationic monomers (quaternized
or salified ADAME or MADAME, DADMAC, APTAC, MAPTAC), optionally combined
with one or more hydrophobic monomer(s) preferably chosen from the group comprising the
esters of alkyl chain, arylalkyl and/or ethoxylated methacrylic acid, the derivatives of alkyl
chain, arylalkyl or dialkyl methacrylamide, the allyl cationic derivatives, the derivatives of
5
anionic or cationic hydrophobic methacryloyl, or the anionic and/or cationic monomers
derived from methacrylamide bearing a hydrophobic chain.
In using the polymers of the prior art, the inventors nevertheless observed a problem of
sedimentation when the suspensions are kept without agitation for a period exceeding
3 days, in particular during transport thereof. A paste then forms in the bottom of the vats
containing the suspensions, which makes it difficult, if not impossible, to pump them.
The inventors further noted that this sedimentation problem was due to a poorly adapted
rheology of the suspensions currently available and poor de-agglomeration of the lime
particles.
The dispersing agents that are currently available do not make it possible to obtain fully
satisfactory aqueous lime suspensions, in particular in terms of sedimentation and rheological
properties.
An object of the present invention is to avoid the problem of sedimentation when the lime
suspensions are kept without agitation.
Another object of the present invention is to propose aqueous suspensions of lime that are as
concentrated as possible and have a rheology suitable for their uses in industrial methods.
Surprisingly, the inventors have shown that by using a polymer with a particular structure, it
was possible to obtain concentrated aqueous suspensions that are stable over time.
More specifically, a first object of the present invention relates to the use of a hydrosoluble
copolymer consisted of:
- monomers of methacrylic acid and/or any one of its salts,
- optionally, monomers of acrylic acid and/or any one of its salts,
- monomers with formula (I):
R – X – R’
(I)
6
wherein:
R represents a polymerizable unsaturated function, in particular acrylate, methacrylate,
methacryl-urethane, vinyl or allyl,
R’ designates hydrogen or an alkyl group having from 1 to 4 carbon atoms,
X represents a structure comprising n unit(s) of ethylene oxide EO and m unit(s) of propylene
oxide PO, positioned randomly or regularly and
m and n are two non-zero integers and comprised between 1 and 150,
to prepare an aqueous suspension of calcium hydroxide from powdered calcium hydroxide.
The present invention also relates to an aqueous suspension of calcium hydroxide,
comprising at least one copolymer consisted of:
- monomers of methacrylic acid and/or any one of its salts,
- optionally, monomers of acrylic acid and/or any one of its salts,
- monomers with formula (I):
R – X – R’
(I)
wherein:
R represents a polymerizable unsaturated function, in particular acrylate, methacrylate,
methacryl-urethane, vinyl or allyl,
R’ designates hydrogen or an alkyl group having from 1 to 4 carbon atoms,
X represents a structure comprising n unit(s) of ethylene oxide EO and m unit(s) of propylene
oxide PO, positioned randomly or regularly,
m and n are two non-zero integers and comprised between 1 and 150.
The inventors in fact realized that for aqueous suspensions to have the expected properties
relative to stability over time and concentration, it was necessary to disperse the calcium
hydroxide particles in the presence of a hydrosoluble comb copolymer of having a backbone
of methacrylic acid and poly(alkylene glycol) side chains with a particular structure.
The expression "powdered calcium hydroxide" refers to slaked lime particles. Slaked lime is
a lime consisted of a set of solid particles, primarily calcium dihydroxide Ca(OH)2, which is
the result of the reaction of quicklime particles with water, that reaction being called
hydration or slaking. Slaked lime is also called hydrated lime. In general, the slaked lime may
7
contain impurities, which primarily result from the quicklime, for example magnesia,
magnesium oxide, Al2O3, Fe2O3, MgO, S, SiO2, Mn3O4, silicates, etc. Slaked lime may
assume a powdery form or take the form of an aqueous suspension, called milk of lime.
In the context of the present invention, the slaked lime is dispersed in powdered form in an
aqueous solution so as to obtain a concentrated milk of lime that is stable over time. The
starting mineral material may for example be a powdered slaked lime that is commercially
available. Examples include the slaked lime sold under the names Supercalco® 97,
Supercalco® 97/20, Sorbacal® SP, Standard Hydrated Lime, MicroCal® HF.
The particular methacrylic copolymer according to the invention is a hydrosoluble comb
copolymer having a backbone of methacrylic acid, and optionally acrylic acid, and
poly(alkylene glycol) side chains.
The expression "poly(alkylene glycol)" refers to a polymer of the glycol alkylene derived
from an olefinic acid.
The poly(alkylene glycol) chains of the copolymer according to the present invention contain
a proportion of ethylene-oxy groups and a proportion of propylene-oxy groups. The
poly(alkylene glycol) chains according to the present invention may for example comprise a
dominant proportion of ethylene-oxy groups associated with a secondary proportion of
propylene-oxy groups. Specific examples of glycol alkylene polymers comprise:
poly(alkylene glycols) having an average molecular weight of 1,000, 4,000, 6,000, 10,000
and 20,000 g/mol, polyethylene-polypropylene glycols having an ethylene oxide percentage
comprised between 20 and 80 wt.% and a propylene oxide percentage comprised between 20
and 80 wt.%.
It should be noted that the ethylene-oxy groups and the propylene-oxy groups of the side
chains of the copolymer may be positioned randomly, regularly or in a block.
More specifically, the polymer according to the present invention is consisted of:
- monomers of methacrylic acid and/or any one of its salts,
- optionally, monomers of acrylic acid and/or any one of its salts,
- monomers with formula (I):
8
R – X – R’
(I)
wherein:
R represents a polymerizable unsaturated function, in particular acrylate, methacrylate,
methacryl-urethane, vinyl or allyl,
R’ designates hydrogen or an alkyl group having from 1 to 4 carbon atoms,
X represents a structure including n unit(s) of ethylene oxide EO and m unit(s) of propylene
oxide PO, positioned randomly or regularly,
m and n are two non-zero integers and comprised between 1 and 150.
Thus, the copolymer according to the invention has a backbone consisted of methacrylic acid
monomers, and optionally acrylic acid monomers. The inventors in fact realized that the
presence of methacrylic acid monomers in the backbone of the copolymer according to the
invention was essential to resolve the technical problem at the origin of the present invention.
According to one embodiment of the invention, the copolymer has a backbone consisted
exclusively of methacrylic acid monomers.
According to another embodiment of the invention, the copolymer has a backbone consisted
of methacrylic acid monomers and acrylic acid monomers.
Thus, in the context of the present invention, it is not possible to use a copolymer having a
backbone consisted exclusively of acrylic acid monomers.
The inventors further noted that the use, in the context of the present invention, of the combtype
copolymer marketed under the name Ethacryl® G (polycarboxylate dispersant by the
company Coatex, which does not contain methacrylic acid monomers) is not suitable to
resolve the technical problem at the origin of the present invention.
Said copolymer is obtained using the known conventional free radical copolymerization
methods in solution, bulk, direct or inverse emulsion, in suspension, or by precipitation in
appropriate solvents, in the presence of catalytic systems and known transfer agents, or using
controlled radical polymerization methods such as Reversible Addition Fragmentation
9
Transfer (RAFT), Atom Transfer Radical Polymerization (ATRP), Nitroxide Mediated
Polymerization (NMP) or cobaloxime mediated radical polymerization.
It is obtained in an acid form and optionally distilled. It may also be partially or completely
neutralized by one or more neutralizing agents chosen from among sodium, calcium,
magnesium and potassium hydroxide and mixtures thereof, or chosen from among the
amines.
According to one embodiment of the present invention, said copolymer is 100% neutralized
with sodium hydroxide.
According to another embodiment of the present invention, said copolymer is partially
neutralized with sodium hydroxide.
According to one embodiment, said aqueous suspension of calcium hydroxide contains a
hydrosoluble copolymer concentration that varies between 0.01 and 10 wt.%, based on the
total weight of calcium hydroxide particles in the suspension.
According to another embodiment, said aqueous suspension of calcium hydroxide contains a
hydrosoluble copolymer concentration that varies between 0.05 and 5 wt.%, based on the
total weight of calcium hydroxide particles in the suspension.
According to still another embodiment, said aqueous suspension of calcium hydroxide
contains a hydrosoluble copolymer concentration that varies between 0.1 and 3.0 wt.%, based
on the total weight of calcium hydroxide particles in the suspension.
According to another embodiment, said aqueous suspension of calcium hydroxide contains a
hydrosoluble copolymer concentration that varies between 0.2 and 2.0 wt.%, based on the
total weight of calcium hydroxide particles in the suspension.
According to another embodiment, the aqueous suspension according to the present invention
is composed of an aqueous solution, for example water, optionally additivated, calcium
hydroxide particles and a copolymer according to the present invention.
10
According to another embodiment, the aqueous suspension according to the present invention
is composed of water, particles of calcium hydroxide and a copolymer according to the
present invention. According to this embodiment, the aqueous suspension does not comprise
any additive other than the copolymer described in the present application, i.e., it does not,
for example, comprise another polymer or dispersant.
According to one embodiment, the aqueous suspension is an aqueous suspension containing a
dry content of at least 40 wt.%, based on the total weight of the aqueous suspension.
According to another embodiment, the aqueous suspension according to the present invention
has a calcium hydroxide particle content comprised between 40 to 60 wt%, based on the total
weight of the aqueous suspension.
The viscosity of said aqueous suspension measured by a Brookfield DVIII viscosimeter at 10
rpm being comprised between 25 and 1,000 mPa.s at 20°C, said suspension being obtained
using the method according to the present invention.
According to another embodiment, the aqueous suspension according to the present invention
has a calcium hydroxide particle content comprised between 45 to 55 wt.%, based on the total
weight of the aqueous suspension.
According to one embodiment of the present invention, said copolymer has a molecular mass
comprised between 30,000 and 200,000 g/mol as determined by steric exclusion
chromatography (SEC).
According to another embodiment of the present invention, the copolymer has a molecular
mass comprised between 30,000 and 160,000 g/mol as determined by steric exclusion
chromatography (SEC).
According to one embodiment of the present invention, in said hydrosoluble copolymer, said
monomer of formula (I) is such that n and m are two non-zero integers and n + m > 17.
According to one embodiment of the present invention, in said hydrosoluble copolymer, the
function R of said monomer with formula (I) represents the methacrylate function.
11
According to one embodiment of the present invention, in said copolymer, the function R’ of
said monomer with formula (I) represents H or CH3.
According to one embodiment of the present invention, in said copolymer, said monomer
with formula (I) is consisted of, expressed in percentage by weight of each of its components:
- 5 to 30 wt.% monomers of methacrylic acid and/or any one of its salts,
- 0 to 10 wt.% monomers of acrylic acid and/or any one of its salts,
- 70 to 95 wt.% monomers with formula (I).
According to one embodiment of the present invention, in said copolymer, said monomer of
formula (I) is consisted of, expressed in percentage by weight of each of its components:
- 7 to 22 wt.% monomers of methacrylic acid and/or any one of its salts,
- 0 to 5 wt.% monomers of acrylic acid and/or any one of its salts,
- 78 to 93 wt.% monomers with formula (I).
A third object of the present invention also relates to the use of the aqueous suspension of
slaked lime according to the invention in the following applications.
The suspensions may be used in the treatment of power plant fumes for plants using fuels (in
particular coal) for example containing sulfur and other impurities that generate acid
molecules (sulfur dioxide, sulfur trioxide, sulfuric acid, hydrochloric acid, hydrofluoric acid,
etc.) or pollutants (mercury, heavy metals, etc.).
They may also be used in household or industrial waste incineration plants that generate the
same types of pollutants, additionally with dioxins. Using lime in a concentrated aqueous
suspension, sprayed into the fumes, makes it possible to trap the pollutants, which are then
eliminated in the solid residues produced by the reaction with the lime and the partial or total
drying of said reaction products.
The suspensions may be used as neutralizing agents for acid reaction products, allowing their
elimination and solid and/or neutralized form or their use in the form of calcium salt (for
example as neutralized sulfonates and phenates as additives for lubricant products). Nonexhaustively,
examples include the neutralization of acid sludge resulting from the
12
manufacture of titanium dioxide, and the neutralization of acid solutions produced during
methods for manufacturing chemical products.
The aqueous suspension of the present invention may be used as neutralizing agents for
mining effluents, with the aim of neutralizing the acidity and/or separating the heavy metals
in solution before discharging the fluids into the natural environment or lagoon.
The suspensions may be used in water decarbonatation methods, these methods making it
possible to reduce the temporary hardness of the water (partial or complete elimination of
hydrogencarbonates of the alkaline earth metals). The waters thus treated are intended to be
used as potable or industrial water, optionally after readjusting the pH using carbon dioxide
or any other acid suitable for the final application.
The purification treatments for potable water, wastewater or industrial water create residues
called sludge. These sludge are first separated from the purified water, then treated so as to
stabilize and concentrate them. The method for treating these sludge is generally called
conditioning and uses organic and/or mineral additives.
The present invention also relates to the use of the aqueous suspension of slaked lime
according to the invention to condition the sludge from wastewater treatment plants. The lime
in suspension is used first to favor the flocculation of the sludge, and secondly to sterilize
said sludge using the pH by keeping said sludge at a pH of 12 or more for 24 to 72 hours or
more.
The suspensions may be used in the treatment of aggregates used during the production of
bituminous coatings. The adhesion of the bituminous emulsions on the aggregates is greatly
improved when these aggregates are treated beforehand using lime. This better adhesion
leads to bituminous coatings that are more resistant to wear and deformation, and which have
a prolonged physical integrity.
The aqueous suspensions of the present invention may be used to produce construction
materials such as cellular concrete. The lime is mixed with cement, sand and aluminum
powder. The high pH of the mixture causes a gaseous release of hydrogen by etching of the
13
aluminum, and the aerated paste thus produced is molded, then autoclaved to create parts
made from cellular concrete.
The aqueous suspensions of the present invention may be used in the treatment of
contaminated soils so as to neutralize the acidity of the soils, immobilize the pollutants by
neutralization or flocculation, and thereby prevent the pollutants from reaching the
groundwater.
The aqueous suspensions of the present invention may be used in the treatment of agricultural
soils so as to correct the pH of those soils, enrich said soils by contributing a calcium or
calcium magnesium source in the case of dolomitic limes, and make those soils less
impermeable by flocculation of the clays that they contain.
The aqueous suspensions of the present invention may be used in the treatment of surface
water, lakes, ponds and rivers for the purpose of adjusting the pH of the water to reduce the
impact of the acidification of said water, acidification of pluvial or animal origin in the case
of fish farming.
The aqueous suspensions of the present invention may be used to produce food for cattle or
poultry, and inter alia, as a source of calcium or of calcium and magnesium.
The aqueous suspensions of the present invention may be used in the paper industry, for
example as a component of paper pulp.
They may also be used for sugar refining.
They may also be used to produce precipitated calcium carbonate (PCC).
The present invention also relates to the use of the aqueous suspension of calcium hydroxide
according to the invention to treat industrial fumes, in particular for desulfurization of the
fumes, or to treat household wastewater, in particular potable water, or industrial water.
14
The present invention also relates to a method for treating gases or fumes comprising a step
consisting of injecting/spraying an aqueous suspension of slaked lime according to the
invention into the gases or fumes to be treated so as to eliminate the acid compounds, sulfur
oxides, hydrochloric acids, etc. therefrom.
Another object of the present invention relates to a method for preparing an aqueous
suspension of calcium hydroxide according to the invention.
More specifically, the present invention relates to a method for preparing an aqueous
suspension of calcium hydroxide, comprising the following steps:
a) preparing an aqueous solution containing a copolymer according to the invention,
and
b) mixing calcium hydroxide in powdered form with said aqueous solution of step a).
According to one embodiment, said method further comprises the step consisting of
subjecting the suspension to homogenous shearing.
In the context of the present invention, and according to this embodiment, homogenous
shearing results in applying the same minimal mechanical strains for all of the parts of the
aqueous suspension mistreated.
According to another embodiment, said method further comprises the step consisting of
subjecting the suspension to homogenous shearing with a degree of shearing greater than
50,000 s-1.
Such a degree of shearing makes it possible to obtain a suspension having a high slaked lime
content, which does not settle and is stable over time. Applying such a degree of shearing to
the suspensions of slaked lime, combined with the use of a hydrosoluble copolymer with a
particular chemical structure, therefore makes it possible to achieve these aims. The
rheological properties of the resultant dispersion over time are thereby significantly
optimized.
According to one embodiment, a homogenous shearing with a degree of shearing greater than
60,000 s-1, in particular greater than 70,000 s-1, is applied.
15
The homogenous shearing required according to this embodiment of the present invention
may be obtained according to several alternatives.
According to a first alternative, it is possible to consider subjecting the suspension to a
constant shearing rate.
For example, the invention is not limited to this particular embodiment.
However, at a given moment, the shearing rate may be different for two points of the
suspension. Thus, by varying the geometry of the device used to generate the shearing forces,
it is possible to modulate the shearing rate applied to said dispersion in time and/or space.
Because the dispersion is fluid when it undergoes the shearing, each part thereof may thus
experience a shearing rate that varies over time. The shearing is said to be homogenous when,
irrespective of the variation of the shearing rate over time, it passes through a minimum value
that is the same for all parts of the dispersion, at a given moment that may differ from one
location of the dispersion to another.
It is possible to consider introducing the suspension of aqueous lime into the shearing device
in the form of a whole aqueous suspension (the entire suspension is introduced into the
device) or in the form of a primary aqueous suspension (only part of the suspension is
introduced into the device).
The shearing device may have varied configurations. The exact configuration is not essential
according to the invention in as much as at the output of that device, the entire dispersion has
undergone the same minimal shearing.
As an illustration, but non-limitingly, devices that may be implemented according to the
invention to apply homogenous shearing in particular include the IKA® Magic Lab mixer
and the Dispax Reactor® DR2000.
According to one embodiment of the present invention, a mixer of the rotor-stator type is
used to perform said homogenous shearing, for example with a degree of shearing greater
than 50,000 s-1.
16
According to another embodiment, a mixer is used consisted of several rotor-stator pairs in
direct series.
According to one embodiment of the present invention, a mixer is used consisted of
cylindrical parts that have a tangential speed greater than 40 m/sec.
A mixer of the rotor-stator type is generally consisted of two concentric discs delimiting an
enclosure in which the primary dispersion circulates. One of the discs is stationary (stator),
and the other is driven by a uniform rotating movement around its axis (rotor). Such a device
comprises a supply line for providing product (in this case, lime suspension) through which
the upper disc passes to emerge in the central part of the enclosure. The suspension passes
through the air gap formed between the stator and the rotor. The rotor (part of the device
driven by a motor) and the stator (stationary part) are respectively consisted, on their outer
ring, of slits that allow the circulation of the lime suspension to be sheared. Such a device
also comprises an output duct connected to a reservoir intended to receive the suspension thus
sheared.
The shearing device may comprise a recirculation loop that makes it possible to multiply the
passages into the shearing device.
Thus, according to one embodiment, the device used to perform said homogenous shearing is
equipped with a recirculation loop.
According to one embodiment, a configured device for a power expenditure of at least 1000
W/m3 is used to perform said homogenous shearing.
EXAMPLES
In all of the tests that follow, the suspensions are evaluated using the parameters described
below.
The viscosity (expressed in mPa.s) of each suspension is measured at 20°C with a Brookfield
DVIII-type viscosimeter. The viscosity values indicated are measured before agitation or
after agitation, at a speed of 10 rpm and 100 rpm, and at different storage times. The viscosity
17
values after 1 month of storage and after agitation of the suspension (using equipment of the
Rayneri type, for example) are particularly relevant to evaluate characteristics of the
invention (influence of the polymer, influence of the equipment, influence of the minimum
degree of shearing) in light of the use of the suspensions in industrial methods.
The sedimentation of each suspension is evaluated by measuring the height of the deposition
in the container. The sedimentation values are expressed in %, i.e., as the ratio of a deposition
height to the total height of the suspension in the container, multiplied by 100.
EXAMPLE 1
This example illustrates the use of different polymers (prior art, invention, outside invention)
in a method for preparing an aqueous suspension of calcium hydroxide (slaked lime)
according to the invention.
Several aqueous suspensions of calcium hydroxide, each having a solid content of
48 ± 1%, are prepared in this example. 503 g of water, as well as a quantity of the polymer
corresponding to 1.41 wt.% dry (based on the total weight of the solids in the suspension), are
placed in a container, said polymer being a polymer of the prior art or a polymer according to
the present invention. Then, 485 g of slaked lime
(Supercalco® 97, Carmeuse) are placed in the container with agitation.
An IKA® Magic Lab-type mixer adjusted so as to produce shearing of 82,000 s-1 is next
supplied with the mixture obtained in the preceding step. A recirculation loop allows several
passages in the air gap formed by the rotor and the stator of the IKA mixer.
Once sheared, the suspension is stored so that these viscosity, sedimentation and
1-month stability parameters can be evaluated.
The polymers used in example 1 have the following characteristics:
Test 1-1:
This test illustrates the use, in a method according to the invention, of a homopolymer outside
the invention, commercially available under the name Rheosperse® 3010, Coatex, France
18
and consisted of monomers of acrylic acid, 100% neutralized with sodium hydroxide
(molecular weight: 4,000 g/mol).
Test 1-2:
This test illustrates the use, in a method according to the invention, of a copolymer outside
the invention, commercially available and consisted of monomers of acrylic acid and
macromonomers with vinyl-PEG2000 structure, i.e., monomers including 46 units of ethylene
oxide.
Thus, this comb polymer does not include monomers of methacrylic acid on the one hand,
and units of propylene oxide on the other hand, on its macromonomers.
Test 1-3:
This test illustrates the use, in a method according to the invention, of a copolymer outside
the invention, commercially available and consisted of 15 wt.% of acrylic acid monomers and
methacrylic acid monomers, as well as 85 wt.% of macromonomers of MPEG5000 (i.e.,
methoxy(EO)113 units).
Thus, this comb polymer does not include propylene oxide units on its macromonomers.
Tests 1-4 to 1-8: copolymers with a particular structure, according to the invention or outside
the invention.
These tests illustrate the use of hydrosoluble copolymers, according to the invention or
outside the invention, having:
- a negatively charged backbone consisted of monomers of acrylic acid and/or methacrylic
acid, randomly polymerized, and
- non-charged side chains consisted of poly(alkylene glycol) units.
Test 1-4: outside invention
The copolymer has the following composition (in wt.% relative to the total weight of the
copolymer):
- 12.8% of acrylic acid monomers,
19
- 87.2% of monomers with formula (I): R – X – R’, wherein R represents a methacrylate
function, R’ designates hydrogen, X represents a structure including 46 units of ethylene
oxide EO and 15 units of propylene oxide PO, positioned randomly.
Molecular mass: 38,000 – 52,000 g/mol.
Partial NaOH neutralization; pH: 3-4.5.
This copolymer, which does not include methacrylic acid monomers, is a copolymer outside
the invention.
Test 1-5: according to the invention
The copolymer has the following composition (in wt.% relative to the total weight of the
copolymer):
- 7.44% of methacrylic acid monomers,
- 92.56% of monomers with formula (I): R – X – R’, wherein R represents a methacrylate
function, R’ designates hydrogen, X represents a structure including
46 units of ethylene oxide EO and 15 units of propylene oxide PO, positioned randomly.
Molecular mass: 110,000 – 150,000 g/mol.
Partial NaOH neutralization; pH: 3-4.5.
Test 1-6: according to the invention
The copolymer has the following composition (in wt.% relative to the total weight of the
copolymer):
- 19.8% of methacrylic acid monomers,
- 3% of acrylic acid monomers, and
- 77.2% of monomers with formula (I): R – X – R’, where R represents a methacrylate
function, R’ designates hydrogen, X represents a structure including 46 units of ethylene
oxide EO and 15 units of propylene oxide PO, positioned randomly.
Molecular mass: 34,000 – 44,000 g/mol.
Total NaOH neutralization; pH: 7.7.
Test 1-7: according to the invention
The copolymer has the following composition (in wt.% relative to the total weight of the
copolymer):
- 12.5% of methacrylic acid monomers,
20
- 87.5% of monomers with formula (I): R – X – R’, wherein R represents a methacrylate
function, R’ designates hydrogen, X represents a structure including 46 units of ethylene
oxide EO and 15 units of propylene oxide PO, positioned randomly.
Molecular mass: 60,000 – 95,000 g/mol.
Total NaOH neutralization; pH: 6.7-7.7.
Test 1-8: outside the invention
The copolymer has the following composition (in wt.% relative to the total weight of the
copolymer):
- 24% of methacrylic acid monomers,
- 4.3% of acrylic acid monomers, and
- 71.7% of monomers with formula (I): R – X – R’, wherein R represents a methacrylate
function, R’ designates H, X represents a structure including 46 units of ethylene oxide
EO.
Neutralization: 100% NaOH.
Molecular mass: 17,900 g/mol.
This copolymer, whereof the monomers with formula (I) do not include propylene oxide
units, is a copolymer outside the invention.
The sedimentation results and various viscosity measurements are shown in Table 1 below:
Tests Sedimentation
T0
viscosity
Afag
T0
10 rpm
viscosity
Afag
T0
100 rpm
viscosity
Befag
T0+1m
10 rpm
viscosity
Befag
T0+1m
100 rpm
viscosity
Afag
T0+1m
10 rpm
viscosity
Afag
T0+1m
100 rpm
1-1 PA 15% 10 58 1,000 124 2,770 382
1-2 PA 0 9,840 1,140 21,000 4,550 11,020 1,146
1-3 PA 0 1,940 386 17,800 3,820 7,220 1,000
1-4 OINV 0 290 170 19,000 3,310 16,460 1,900
1-5 INV 0 300 159 4,620 890 590 230
1-6 INV 0 250 152 1,320 478 730 234
1-7 INV 0 170 114 1,260 462 330 170
1-8 OINV 30% 30 40 1,900 802 470 202
Table 1
PA: Prior Art
OINV: Outside INVention
INV: INVention
Afag: After agitation
Befag: Before agitation
21
First, it is possible to see that the polymers of tests 1-1 (homopolymers of acrylic acid) and 1-
8 (copolymers not including propylene oxide and its side chains) do not make it possible to
avoid sedimentation. The use of these polymers therefore does not make it possible to resolve
the technical problem at the origin of the present invention.
The measurement of the viscosity 10 rpm after agitation and at T0 shows that the polymers of
tests 1-2 and 1-3 do not make it possible to obtain suspensions of slaked lime having
rheological characteristics allowing them to be used in industrial methods, in particular
rheological characteristics suitable for pumping of the suspensions. The suspension obtained
in test 1-2 using the prior art polymer in fact has a viscosity of 9,840 mPa.s at T0 after
agitation. The suspension obtained in test 1-3 using another prior art polymer in turn has a
viscosity of 1,940 mPa.s at T0 after agitation. These values, which are outside the range of
claimed viscosities (between 25 and 1,000 mPa.s at 20°C), are incompatible with the
expected use of the suspensions.
The measurement of the viscosity 10 rpm after agitation at T0 + 1 month shows that the
polymer of test 1-4 does not make it possible to obtain a concentrated suspension of lime that
has a suitable viscosity. In fact, this viscosity is 16,460 s-1.
The rheological profiles of the lime suspensions of tests 1-5, 1-6 and 1-7 (use of a copolymer
according to the invention) are suitable for the use of suspensions in industrial methods.
EXAMPLE 2
This example illustrates the use of shearing equipments, which may be identical or different,
optionally adjusted to different degrees of shearing to prepare an aqueous suspension of
calcium hydroxide (slaked lime) containing a copolymer according to the invention.
A first series of three aqueous suspensions of calcium hydroxide (tests 2-1 to 2-3), each
having a solid content of 48 ± 1%, are prepared by placing 503 g of water and a quantity of a
polymer corresponding to 1.41 wt.% dry (based on the total weight of the solids in the
suspension) in a container. Said polymer is that of test 1-5. Then, 485 g of slaked lime
(Supercalco® 97, Carmeuse) are placed in the container with agitation.
22
A second series of three aqueous suspensions of calcium hydroxide (tests 2-4 to 2-6), each
having a solid content of 48 ± 1%, are prepared by placing 503 g of water and a quantity
corresponding to 1.41 wt.% dry of a polymer (based on the total weight of the solids in the
suspension) in a container, said polymer being that of test 1-6. Then, 485 g of slaked lime
(Supercalco® 97, Carmeuse) are placed in the container with agitation.
Tests 2-1 and 2-4
A mixer of the Ultraturax® type (rotor-stator type), adjusted so as to produce a shearing of
approximately 40,000 s-1 and which procures a homogenous shearing according to the
definition of the present invention, is supplied with the mixture obtained in the preceding
step.
A recirculation loop allows several passages in the mixer. The recirculation time is set at 15
minutes.
Tests 2-2 and 2-5
A mixer of the Rayneri® type, adjusted so as to produce a shearing of approximately 3,000 s-
1 (which does not procure a homogenous shearing according to the definition of the present
invention), is supplied with the mixture obtained in the preceding step.
A recirculation loop allows several passages in the mixer. The recirculation time is set at 15
minutes.
Tests 2-3 and 2-6
A mixer of the IKA® Magic Lab type, adjusted so as to produce a shearing of 82,000 s-1 and
which procures a homogenous shearing according to the definition of the present invention, is
then supplied with the mixture obtained in the preceding step.
A recirculation loop allows several passages in the air gap formed by the rotor and stator of
the IKA mixer. The recirculation time is set at 15 minutes.
Once sheared, the suspensions are stored for evaluation of the viscosity, sedimentation, and 1
month stability parameters.
23
The results for sedimentation and various viscosity measurements are shown in Table 2
below:
Tests Sedimentation
T0
viscosity
Afag
T0
10 rpm
viscosity
Afag
T0
100 rpm
viscosity
Befag
T0+1m
10 rpm
viscosity
Befag
T0+1m
100 rpm
viscosity
Afag
T0+1m
10 rpm
viscosity
Afag
T0+1m
100 rpm
2-1 OINV 30% 70 107 3,300 560 430 168
2-2 OINV 20% 50 98 2,400 236 790 220
2-3 INV 0 300 159 4,620 890 590 230
2-4 OINV 30% 650 162 1,600 580 1,890 380
2-5 OINV 30% 260 107 19,300 1,800 1,000 240
2-6 INV 0 250 152 1,320 478 730 234
Table 2
OINV: Outside INVention
INV: INVention
Afag: After agitation
Befag: Before agitation
One can first see that the degree of shearing used in tests 2-1 and 2-4 (Ultraturax® adjusted
to 40,000 s-1) and tests 2-2 and 2-5 (mixer 3,000 s-1) does not make it possible to avoid
sedimentation.
However, the degree of shearing of tests 2-3 and 2-6 (IKA adjusted to 82,000 s-1), combined
with the use of the polymer with a particular structure, makes it possible not only to avoid the
problem of sedimentation, but also to obtain suspensions whereof the rheological profile is
suitable for the expected use.
EXAMPLE 3
This example illustrates the use of two polymers according to the invention in a method for
preparing an aqueous suspension of calcium hydroxide (slaked lime) with a high content of
dry matter (> 50 wt.%).
Two aqueous suspensions of calcium hydroxide, each having a solid content of 50 to 51%,
are prepared in this example. 478 g of water, as well as a quantity corresponding to 1.41 wt.%
dry of a polymer, based on the total weight of the solids in the suspension, are placed in a
24
container. Then, 505 g of slaked lime (Supercalco® 97, Carmeuse) are placed in the container
with agitation.
A mixer of the IKA® Magic Lab type, adjusted so as to produce a shearing of
82,000 s-1, is then supplied with the mixture obtained in the preceding step. A recirculation
loop allows several passages in the air gap formed by the rotor and the stator of the IKA
mixer.
Once sheared, the suspension is stored for evaluation of its viscosity, sedimentation, and 1-
month stability parameters.
The polymers used in this example have the following characteristics:
Test 3-1: according to the invention
The copolymer has the following composition (in wt.% relative to the total weight of the
copolymer):
- 7.44% of methacrylic acid monomers,
- 92.56% of monomers with formula (I): R – X – R’, wherein R represents a methacrylate
function, R’ designates hydrogen, X represents a structure including
46 units of ethylene oxide EO and 15 units of propylene oxide PO, positioned randomly.
Molecular mass: 110,000 - 150,000 /gmol.
Partial NaOH neutralization; pH: 3-4.5.
Test 3-2: according to the invention
The copolymer has the following composition (in wt% relative to the total weight of the
copolymer):
- 19.8% of methacrylic acid monomers,
- 3% of acrylic acid monomers and
- 77.2% monomers with formula (I): R – X – R’, wherein R represents a methacrylate
function, R’ designates hydrogen, X represents a structure including 46 units of ethylene
oxide EO and 15 units of propylene oxide PO, positioned randomly.
Molecular mass: 34,000 – 44,000 g/mol.
Total NaOH neutralization; pH: 7.7.
The results for sedimentation and various viscosity measurements are shown in Table 3
below:
25
Tests Sedimentation
T0
viscosity
Afag
T0
10 rpm
viscosity
Afag
T0
100 rpm
viscosity
Befag
T0+1m
10 rpm
viscosity
Befag
T0+1m
100 rpm
viscosity
Afag
T0+1m
10 rpm
viscosity
Afag
T0+1m
100 rpm
3-1 50.4%
lime 0% 980 393 4,900 1,980 1,930 687
3-2 50.56%
lime
0% 530 261 13,600 3,048 3,300 839
Table 3
Afag: After agitation
Befag: Before agitation
The results demonstrate that it is possible, according to the method of the present invention,
and using hydrosoluble copolymers with a particular structure, to prepare suspensions of
slaked lime with a high concentration that remain stable over time.
EXAMPLE 4
This example illustrates the use of two polymers according to the invention in a method for
preparing an aqueous suspension of calcium hydroxide from two different types of starting
slaked lime, i.e., a lime having an average particle diameter between 4 and 5 μm
(Supercalco® 97, Carmeuse) and a lime having an average particle diameter between
2 and 3 μm (Supercalco® 97/20, Carmeuse).
Several aqueous suspensions of calcium hydroxide, each having a solid content of
48 ± 1%, are prepared in this example. 503 g of water, as well as a quantity corresponding to
1.41 wt.% dry of a polymer (based on the total weight of the solids in the suspension), are
placed in a container. Then, 485 g of slaked lime, specifically Supercalco® 97 (Carmeuse) in
tests 4-1 and 4-3, or Supercalco® 97/20 (Carmeuse) in tests 4-2 and 4-4, are placed in the
container with agitation.
A mixer of the IKA® Magic Lab type, adjusted so as to produce a shearing of
82,000 s-1, is then supplied with the mixture obtained in the preceding step.
A recirculation loop allows several passages in the air gap formed by the rotor and the stator
of the IKA mixer.
26
Once sheared, the suspension is stored for evaluation of these viscosity, sedimentation, and 1-
month stability parameters.
The polymers used in this example have the following characteristics:
Tests 4-1 and 4-2: according to the invention
The copolymer has the following composition (in wt.% relative to the total weight of the
copolymer):
- 7.44% of methacrylic acid monomers,
- 92.56% of monomers with formula (I): R – X – R’, wherein R represents a methacrylate
function, R’ designates hydrogen, X represents a structure including
46 units of ethylene oxide EO and 15 units of propylene oxide PO, positioned randomly.
Molecular mass: 110,000 – 150,000 g/mol.
Partial NaOH neutralization; pH: 3-4.5.
Tests 4-3 and 4-4: according to the invention
The copolymer has the following composition (in wt.% relative to the total weight of the
copolymer):
- 19.8% of methacrylic acid monomers,
- 3% of acrylic acid monomers and
- 77.2% of monomers with formula (I): R – X – R’ wherein R represents a methacrylate
function, R’ designates hydrogen, X represents a structure including 46 units of ethylene
oxide EO and 15 units of propylene oxide PO, positioned randomly.
Molecular mass: 34,000 – 44,000 g/mol.
Total NaOH neutralization; pH: 7.7.
The results for sedimentation and different viscosity measurements are shown in Table 4
below:
Tests Sedimentation T0 viscosity Afag T0
10 rpm
Viscosity Afag T0
100 rpm
4-1 INV 0% 300 159
4-2 INV 0% 280 203
4-3 INV 0 250 152
4-4 INV 0% 190 126
Table 4
27
Afag: After agitation
Befag: Before agitation
The results demonstrate that it is possible, according to the method of the present invention,
using hydrosoluble copolymers with a particular structure, to prepare suspensions of slaked
lime with a high concentration remaining stable over time, irrespective of the initial particle
size of the slaked lime.
EXAMPLE 5
The purpose of this example is to illustrate the total organic carbon (TOC) levels present in
the aqueous phase of the lime suspensions dispersed with the polymers of the prior art or with
the polymers of the invention, and thereby to determine the free polymer concentrations in
the aqueous phase.
This example also makes it possible to illustrate the soluble Ca2+ ions content present in the
aqueous phase of the lime suspensions dispersed with the polymers of the prior art or with the
polymers of the invention.
Method for preparing the suspensions
Several aqueous suspensions of calcium hydroxide, each having a solid content of
48 ± 1%, are prepared in this example. 503 g of water, as well as a quantity corresponding to
1.41 wt.% dry of a polymer (based on the total weight of the solids in the suspension), are
placed in a container, said polymer being according to the prior art or the present invention.
Then, 485 g of slaked lime (Supercalco® 97, Carmeuse) are placed in the container with
agitation.
A mixer of the IKA® Magic Lab type, adjusted so as to produce a shearing of
82,000 s-1, is then supplied with the mixture obtained in the preceding step. A recirculation
loop allows several passages in the air gap formed by the rotor and the stator of the IKA
mixer.
28
Test 5-1
The copolymer has the following composition (in wt.% relative to the total weight of the
copolymer):
- 7.44% of methacrylic acid monomers,
- 92.56% of monomers with formula (I): R – X – R’, wherein R represents a methacrylate
function, R’ designates hydrogen, X represents a structure including
46 units of ethylene oxide EO and 15 units of propylene oxide PO, positioned randomly.
Molecular mass: 110,000 – 150,000 g/mol.
Partial NaOH neutralization; pH: 3-4.5.
Test 5-2
The copolymer has the following composition (in wt.% relative to the total weight of the
copolymer):
- 12.8% of acrylic acid monomers,
- 87.2% of monomers with formula (I): R – X – R’, wherein R represents a methacrylate
function, R’ designates hydrogen, X represents a structure including 46 units of ethylene
oxide EO and 15 units of propylene oxide PO, positioned randomly.
Molecular mass: 38,000 – 52,000 g/mol.
Partial NaOH neutralization; pH: 3-4.5.
This copolymer, which does not include methacrylic acid monomers, is a copolymer outside
the invention.
Test 5-3
The polymer used is a homopolymer outside the invention, commercially available under the
name Rheosperse® 3010, Coatex, France and consisted of acrylic acid monomers, 100%
neutralized with sodium hydroxide (molecular weight: 4,000 g/mol).
The obtained suspensions are filtered.
A sample of the filtrate is withdrawn and analyzed according to the methods described below.
TOC measurement:
The TOC (Total Organic Carbon) is measured using a Shimadzu TOC-V CSH, using a
method based on a catalytic oxidation method by combustion at 680°C.
29
The carbon atoms of the samples are oxidized in CO2. The eluent gas pushes the CO2 into a
system allowing the elimination of the H2O molecules and halogenated compounds. An IR
(infrared) detector measures the CO2 concentration. A calibration curve makes it possible to
determine the carbon concentration in the sample.
Ions assaying:
The ion content is evaluated using ionic chromatography by using Metrohm 761 Compact ICtype
equipment. The separation of the ions and the polar molecules is based on their charge.
The results of the TOC and free Ca2+ ion content measurements are shown in Table 5 below:
Tests Ca2+ ppm TOC ppm polymer concentration ppm
5-1 INV 1064 1640 396
5-2 OINV 995 3900 856
5-3 PA 291 100 17
Table 5
OINV: Outside INVention
INV: INVention
PA: Prior Art
First, it is possible to see that the free Ca2+ ion content vary significantly based on the nature
of the polymer used. This free Ca2+ ion content in a lime suspension dispersed with an acrylic
acid homopolymer (test 5-3) is low compared to that of an aqueous lime suspension dispersed
with a copolymer having a (meth)acrylic acid backbone and poly(alkylene glycol) side chains
(tests 5-1 and 5-2).
Furthermore, although the quantities of starting polymer (1.41 wt.% dry) are identical for
each of the suspensions, it is noted that the polymer concentrations in the filtrate of each
suspension vary significantly based on the polymer used. When the polymer used is an
acrylic acid homopolymer, the concentration of soluble polymer in the aqueous phase is
practically nonexistent.
Furthermore, less free copolymer remains in the filtrate of the lime suspension when a
copolymer according to the invention is used. Without being bound by any theory, one may
30
think that the particular structure of the copolymer according to the invention is suited to the
chemical nature of the lime, which improves the chemical interactions between the
copolymer and the Ca(OH)2 particles.
There are fewer free copolymers in the lime suspensions prepared according to the method of
the invention by using a copolymer with a particular structure, since a larger quantity thereof
is adsorbed to the surface of the slaked lime particles.
It is thus demonstrated that subjecting a concentrated aqueous suspension of lime to a
shearing operation under specific conditions in the presence of a copolymer according to the
invention makes it possible to obtain a concentrated, stable lime suspension that is novel
relative to the lime suspensions of the prior art, due to the particular chemical interactions
between the copolymers and the lime particles.
31
WE CLAIM:
1. Use of a hydrosoluble copolymer consisted of:
- methacrylic acid monomers and/or any one of its salts,
- optionally, acrylic acid monomers and/or any one of its salts,
- monomers with formula (I):
R – X – R’
(I)
wherein:
R represents a polymerizable unsaturated function, in particular acrylate,
methacrylate, methacryl-urethane, vinyl or allyl,
R’ designates hydrogen or an alkyl group having from 1 to 4 carbon atoms,
X represents a structure including n unit(s) of ethylene oxide EO and m unit(s) of
propylene oxide PO, positioned randomly or regularly,
m and n are two non-zero integers and comprised between 1 and 150,
to prepare an aqueous suspension of calcium hydroxide from powdered calcium
hydroxide.
2. An aqueous suspension of calcium hydroxide, comprising at least one copolymer
consisted of:
- methacrylic acid monomers and/or any one of its salts,
- optionally, acrylic acid monomers and/or any one of its salts,
- monomers with formula (I):
R – X – R’
(I)
wherein:
R represents a polymerizable unsaturated function, in particular acrylate,
methacrylate, methacryl-urethane, vinyl or allyl,
R’ designates hydrogen or an alkyl group having from 1 to 4 carbon atoms,
X represents a structure including n unit(s) of ethylene oxide EO and m unit(s) of
propylene oxide PO, positioned randomly or regularly,
32
m and n are two non-zero integers and comprised between 1 and 150.
3. Use according to claim 1 or the suspension according to claim 2, wherein said
suspension has a dry content of at least 40 wt.%.
4. Use or suspension according to any one of the preceding claims, wherein the viscosity
of said aqueous suspension measured by a Brookfield DVIII viscosimeter at 10 rpm is
comprised between 25 and 1,000 mPa.s at 20°C.
5. Use or suspension according to any one of the preceding claims, wherein the
copolymer has a molecular mass comprised between 30,000 and 200,000 g/mol as
determined by Steric Exclusion Chromatography (SEC).
6. Use or suspension according to any one of the preceding claims, wherein said
monomer with formula (I) is such that n and m are two non-zero integers and
n + m > 17.
7. Use or suspension according to any one of the preceding claims, wherein the function
R of said monomer with formula (I) represents the methacrylate function.
8. Use or suspension according to any one of the preceding claims, wherein the function
R’ of said monomer with formula (I) represents H or CH3.
9. Use or suspension according to any one of the preceding claims, wherein said
monomer with formula (I) is consisted of, expressed in percentage by weight of each
of its components:
- 5 to 30 wt.% of methacrylic acid monomers and/or any one of its salts,
- 0 to 10 wt.% of acrylic acid monomers and/or any one of its salts,
- 70 to 95 wt.% of monomers with formula (I).
10. Use of the aqueous suspension of calcium hydroxide according to any one of claims 1,
3 to 9, to treat industrial fumes, in particular for desulfurization of the fumes, or to
treat household wastewater, in particular potable water, or industrial water.
33
11. A method for preparing an aqueous suspension of calcium hydroxide according to any
one of claims 2 to 9, comprising a step consisting of subjecting the suspension to a
homogenous shearing.
12. A method according to claim 11, wherein a homogenous shearing is applied with a
degree of shearing greater than 50,000 s-1.
13. A method according to claim 11 or 12, wherein a mixer of the rotor-stator type is used
to perform said homogenous shearing.
14. A method according to any one of claims 11 to 13, wherein the device used to
perform said homogenous shearing is equipped with a recirculation loop.
15. A method according to any one of claims 11 to 14, wherein a device configured for a
power expenditure of at least 1,000 W/m3 is used to perform said homogenous
shearing.
Dated this 3rd day of June, 2015
HIRAL CHANDRAKANT JOSHI
AGENT FOR
COATEX
34
ABSTRACT
Title: USE OF A WATER-SOLUBLE COPOLYMER FOR PREPARING AN AQUEOUS
LIME SUSPENSION
The present invention relates to a lime-based suspension comprising a water-soluble
copolymer as an additive, as well as a method for preparing such a suspension. Such
suspensions are in particular used as chemical neutralizing agents in industrial or household
methods.