CA1231032A - Coal-water dispersion - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A coal-water dispersion comprising coal particles dis-persed in water and a dispersing agent comprising polymerized fatty acids, polymerized rosin acids and/or polymerized fatty or rosin acid derivatives which have been partially esterified with a polyalkylene glycol or monoester or monoether thereof, having a residual acid value higher than 3.

Description

The present invention relates to a dispersing agent for solid hydrophobic coal particles dispersed in water, and more specifically use thereof for dispersing coal particles in water.

Crude tall oil is obtained as a by-product in the raft or sulfate pulping process. The black liquor separated from the pulp contains sulfate soap. By separation of this soap and splitting thereof by acidification crude tall oil is formed. The splitting normally is effected with sulfuric acid. There are, however, other reactions than splitting of sodium soaps of fatty and rosin acids taking place e.g. esterification and sulphonation. This is apparent from the fact that tall oil split with sulfuric acid will have other characteristics than tall oil being split with weaker acids. The expression crude tall oil in this connection also comprises the extractive material produced in the sulfite pulping process.

Crude tall oil consists of fatty colds, rosin colds and neutral substances. The fatty acids are a mixture of oleic acid and linoleic acid comprising smaller amounts of other saturated and polyunsaturated acids, The rosin acids are diterpenes with a cyclic, rigid, hydrophobic part. The neutral part of the crude tall oil mainly consists of polycyclic hydrocarbons, strolls and other high molecular alcohols such a a-sitosterol, battalion and long chain fatty alcohols. The amount of neutral part depends on the wood furnish, pine giving about 10~ neutral substance and birch just below 30% neutral substance of the extractive material.

The main part of the crude tall oil being produced is .,",~
., I,.

2 ~23~32 further refined by fractionated distillation, tall oil head, tall oil fatty acid/ tall oil rosin acid and pitch being obtained as different fractions. The economy of this process depends on the composition of the tall oil. Thus in turn depends on the composition of the wood furnish to the sulfite pulping industry. Some crude tall oils have a composition that makes them economically unfeasible for distillation. The increased proportion of birch and the decreased proportion of pine during the last years have resulted in that tall oil of the kind not being distillable has become more common. The producers have difficulties in selling this crude tall oil and it is in some cases burnt.

The composition of distillable crude tall oil normally is within the following limits:

Acid value: 120 - 170 Fatty acid content: 32 - 55%
Rosin content: 11 - 50%
Unsaponifiable: 5 - 24%
.

A typical Scandinavian crude tall oil has the following values:
Acid value: 143 Rosin content: 30%
Unsaponifiable: 15%

Variations in the tall oil depend on which trees are used in the pulp process as well as where they have been growing. A pulp digested on birch alone give about 70%
fatty acids and 30% unsaponifiable. Rosin acids do only exist in coniferous trees.
Uncharged particles of a colloidal size, that is smaller

3 ~23~L~33;~
than about 0.1 em, as well as larger particles, so-called coarse disperse particles, have a tendency to agglomerate in solution forming particle aggregates This can be pro-vented-in accordance with known principles, Ida. by -starkly or electrostatically stabilization of the par tides. In starkly stabilization by means of polymers the polymer molecule is absorbed to the particle surface.
It is known since long that the best polymers for this purpose should have one part having a high affinity to the dispel-soon medium and another part being attracted to the particulate is also known that the addition of substances having ionic groups, such as polyelectrolytes, increases the stability of the dispersion. For larger particles, which settle under the influence of gravity, a stabilization against sedimentation is in also required In US-A-4 358 293 there is thus disclosed a dispersion of coal particles in water, wherein as dispersing agent is used a non-ionic surfactant polyalkylene oxide compound having a hydrophobic portion and a hydrophilic portion, and wherein the hydrophilic portion comprises at least 100 units of ethylene oxide It also known from the SE-patent application 8104645-0 to disperse coal particles in water by means of several different additives, such as a tensile which is absorbed to the particle surface causing repulsion between the particles, and interacting hydrophilic polymers which are supposed to provide starkly hindrance.
SE-patent application 8301502-4 finally, describes a dispersing agent for coal particles in water being obtained by esterification of tall oil pitch with polyalkylene glycol.
Tall oil fatty acids and tall oil rosin acids as well, can be reacted with for instance polyethylene glycol to form products having dispersing characteristics. A partial ~31~)3~
esterification of crude tall oil with polyethylene glycol or polyethylene glycol derivatives during heating will give a disk pursing agent for solid hydrophobic particles in water. This substance has substantially better characteristics compared to a tall oil fatty acid esterified with polyethylene glycol during the same conditions as to the ability to produce a particle disk pension having a high solid proportion and a liquid flow.

It has now been found that an improved dispersing agent for coal particles in water is obtained if the viscosity of the crude oil is increased, that is a molecular enlargement is achieved before the esterification. A polymerization of the different components of crude tall oil, such as fatty acids, rosin acids and fatty or rosin acid derivatives, also gives products with enlarged molecules, which can be used to prepare improved dispersing agents.

The fatty acid could be saturated or unsaturated and should have at least 10 carbon atoms, preferably at least 16 car-bun atoms. As examples of fatty acids can mentioned palmiticacid, Starkey acid, oleic acid, linoleic acid, linolenic acid, pinolenic acid.

According to the present invention there is provided a coal-water dispersion comprising coal particles dispersed in water and a dispersing agent in an amount of 0.01-5% by weight of the dispersion, wherein the dispersing agent is a partial ester of dim Eric, trim Eric or oligomeric fatty acid-containing compost-lion selected from the group consisting of: (a) a crude tall oil having been polymerized so that its viscosity at 50C has been at least doubled; (b) a polymerized fatty acid compound; and (c) residue obtained in distilling fatty acids from fats or oil, which composition has been partially esterified with a polyalky-tone glycol compound having an average molecular weight of at least 4,000 and mainly being composed of ethylene oxide units, said dispersing agent having a residual acid value higher than 3.

~l~31~3~:

The dispersing agent of the invention is a partial ester of a dim Eric, trim Eric or oligomeric fatty acid-containing composition selected from the group consisting of: (a) a crude tall oil having been polymerized so that its viscosity at 50C
has been at least doubled; (b) a polymerized fatty acid compound;
and (c) a residue obtained in distilling fatty acids from fats or oil, which composition has been partially este~ified with a polyalkylene glycol compound having an average molecular weight of at least 4,000 and mainly being composed of ethylene oxide units, said dispersing agent having a residual acid value higher than 3.

Polymerized fatty acid refers to a diver, triter or oligomer product obtained by polymerizing one or several differ-en fatty acids. The diver fatty acid will produce a well per-forming dispersing agent.

The polymerized fatty acid compound comprises for example a fatty acid polymerized with a \ - pa -:1~3~32 rosin acid or any other compound and a polymerized mixture of different fatty acids, rosin acids and/or higher alcohols or other neutral substances.

A preferred dispersing agent of the invention is crude tall oil, which has been polymerized so that its viscosity at 50C has been at least doubled, and partially esterifi- -Ed with a polyalkylene glycol or monster or monoether thereof, having a residual acid value higher than 3.

An increase of the average molecular weight of the crude tall oil or the compononents thereof effect the properties as dispersing agents after the partial esterification with the polyethylene glycol. The reason for this is that a just large enough hydrophobic unit to which different types of hydrophilic groups as acid and hydroxyl are linked is desirable. To the carboxylic acid groups polyethylene glycol chains are added. The molecule so formed is to have adequate characteristics as to the interaction with water to be able to serve as a dispersing agent, that is a nominally water insoluble part adsorbing to the hydra-phobic surface and a nominally water soluble Hart strongly interacting with water. The molecule so adsorbed on the particle will thus give a starkly protection by means of the polyethylene-glycol chains as well as an electrostat-teal one by means of the groups being charged in neutral phi These two protective mechanisms counteract a particle aggregation due to the attractive forces (Van de Weals) between the parties. The size of the hydrophobic as well as of the hydrophilic part is of importance for the extent of well performance of a dispersing agent. It is known form the literature that the ability of a polyethylene oxide chain to give starkly protection depends on its length. The size and the type of hydrophobic part also effect the adsorption of the dispersing agent from the water solution to to particle surface.

~:3~L~)32 An increase of the average molecular weight is reflected in an increased viscosity there is, however, no linear connection.

It has been found that a viscosity of the crude tall oil at 50C above 1000 mPa.s,determined on an Emil rotation viscosimeter (Respirator A/S, Denmark gives an improved dispersing ability. -.

It is also of importance that the residual acid value of the product obtained is higher than 3, that is that there are a sufficient number of free acid groups left after the reaction, as these groups contribute to the electrostatic repulsion between the particles to be disk pursed. Products having a residual acid value lower than and about 3 have clearly inferior proper its compared to corresponding products having a higher residual acid value. A residual acid value within the range 5 - 12 seems to be adequate.

Crude tall oil can be polymerized in accordance with several known processes. In heating crude tall oil, optionally in the presence of catalysts, reactions take place which among other things bring about an increase of the viscosity. An example of the chemical reactions taking place-is esterifica~ion, that is the reaction of the acid groups with alcohols, which are both present in the crude tall oil. This reaction is catalyzed by strong acids such as sulfuric acid, residues of which are present in the crude tall oil from the splitting step. Crude tall oil has a hydroxyl value of about 25 due to the free alcohols, and these hydroxyl groups are in principle removed by reaction during the polymerization.

Diets- Alder reactions between molecule shaving isolated an conjugated double bonds also take place. The proper-lion of conjugated double bonds is of critical importance for the amount of product being formed by the Diels-Alder reaction. The conjugation of isolated double bonds is catalyzed by anthraquinone, which is present in the crude tall oil when this chemical has been added to the digester in the sulfite pulping industry. According to an embody-mint of the invention the dispersing agent it based on fatty or rosin acid derivatives, which are derived prom fatty or rosin acids containing conjugated double bonds which have been reacted according to Diels-Alder in order to increase the number of caboxylic acid groups.
Oxidative polymerization also takes place in crude tall oil. This refers to such reactions between oxygen and olefines resulting in the formation of a high concentra-lion of free radicals. This type of polymerization ox crude tall oil is consequently facilitated by supplying air.
! Boron trifluoride is a strong Lewis acid. From literature BF3 is a known polymerization reagent for compounds come prosing double bonds, for instance vegetable and animal oils. Terrapins too, as I- and pinion, dipentine, skyline can be polymerized with BF3. The reaction between Patty and rosin acids respectively and BF3 is known from literature. Reactions with alcohols can also be accomplish-Ed by means of BF3.
. .
The viscosity of crude tall oil can also be increased by adding multi functional alcohol and acid during heating.
Jo According to another embodiment of the invention the disk pursing agent is based on fatty Reagan acid derivatives derived from fatty ooze Lo acids which have been reacted with a multi functional alcohol and/or carboxylic acid.
Suitable polybasic acids are chiefly malefic android, phthalic android- isophthalic android, trimellitic acid.

~23103~

Suitable polyhydric alcohols are principally ethylene glycol, diethylene glycol, glycerol, trimethylol propane, ditrimethylol propane, monopentaerythritole, dipentaexythritol, neopentyl glycol. In addition substances with hydroxylic groups as well as carboxylic groups can be used, such as dimethylol prop ionic acid.

A traditional way to increase the molecular weight is standoff boiling. Treatment with boric acid also polymerizes crude tall oil. Boric acid is known from the literature to give prone rings when reacted with fatty acid.

An improved dispersing agent of the invention is obtained if the amount of large molecules is increased by distillation of the polymerized crude tall oil before the partial ester-ligation.

A residue obtained in distilling fatty acids from fats or oils of animal or vegetable origin can also be partially eastward with a polyalkylene glycol or a monster or monoether thereof to produce a dispersing agent with imp proved properties.
Pi dispersing agent of the invention is obtained by reacting polymerized crude tall oil and polyalkylene-glycol or a monster or monoether thereof. The polyp alkaline glycol is mainly composed by ethylene oxide units, as it is essential that it has a hydrophilic character.
As examples of monstrous thereof can be mentioned esters of carboxylic acids of the type R-COOH, wherein R is a hydrocarbon residue of 1 - 19 carbon atoms, preferably 1 - 4 carbon atoms, such as acetic acid, prop ionic acid, butyric acid. Menorahs of polyalkylene glycol are alkyd ethers, wherein the alkyd group can have 1-20 carbon atoms, preferably 1-5 carbon atoms. As examples can be mentioned monoethers of polyethylene glycol of the formula R-O-(CH2CH2O)n-CH2 SHEA, wherein R is alkyd with 1-5 carbon atoms and n is a number ~12. For economical reasons polyethylene glycol is, however, preferred.

For the steno hindrance effect to be pronounced it is necessary that the polyalkylene glycol has a sufficiently high molecular weight, 600 at the lowest. Conveniently the molecular weight is between 4,000 and 10,000, but also higher values can be applicable For the preparation of a dispersing agent of the invention polymerized tall oil and polyalkylene glycol or a monster or monoether thereof, are reacted in a ratio of 10:90 to 90:10, preferably 30:70 to 70:30, by mixing and heating during a period of time being sufficient for the acid value to be reduced with at least 2 units. A larger amount of tall oil will give a less expensive product and a larger amount of polyelkylene glycol will give a more efficient product.

If the polyethylene glycol and crude tall oil are used as reactants the reaction can be proceeded at 200 to 300C for 1-12 h at atmospheric pressure, preferably 230-280C, depending on the molecular weight and the residual acid value desired.

The dispersing agent of the invention is used for dispersing coal particles in water for the preparation of a so-called coal-water slurry. Many ways to prepare and stabilize coal-water slurries have been suggested. The reason for this is that slurries of a high coal content make possible transport and combustion of coal in liquid form. By this a less risky and more environmentally adapted handling is achieved compared to the handling of dry, solid coal or oil. To make the coal-water slurry fluid at the concentration ranges in question chemicals have to be added. The dispersing agents previously used make the preparation of a dispersion of pulverized coal in water which can be pumped more expensive and thereby the use of the new technique more difficult. By means of the dispersing agent of the invention having varying amounts of ionic groups, such a chemical can be produced at a low price, which is of great importance for a commercial utilization of coal-water slurries.

' When the dispersing agent of the invention is used to disperse coal particles in water it is convenient to use the dispersing agent in an amount of 0.01-5~, preferably 0.05-2, and preferably 0.3-1%, based on the total weight. The particle size of the coal normally is mainly within the range 1-20 m.

The invention is described in a more detailed way in the following Examples, in which the stated percentages and proportions are based on the weight.

The dispersing characteristics of the reaction products prepared in Examples 1-4 have been determined in the same way as the oil value for pigment ISIS 17 61 05); the stated value, however, defines the amount of coal particles which can be dispersed into a free flowing product. The following procedure is used; l g bituminous coal having a particle size distribution that more than 40% is within the range 60-90/~m, is weighed on a blasted glass plate. Water comprising I dispersing agent is added. The amount of aqueous phase which has to be added to make the coal-slurry free flowing in working the pulverized coal with a spatula is noted. The accuracy is +0.5%.

The flow properties and the stability of the coal-water mixture (CAM), which are critical for the pump ability and storage durability thereof, are inter aria dependent on the way in which the mixture has been prepared. To obtain reproducible CWM-tests the following procedure has been used in Examples 4-8.

, 31~)32 The dispersing agent is swelled in water of 80C and then homogenized in an Ultraturra~x mixer. Alkali is then added if desired. This liquid is added in portions to the pulverize coal, which consists of sieved particles which have passed through a mesh opening of 250 em. The premixed CAM sample is disintegrated in a dissolver at 2000 ruin for 20 minutes.

The viscosity of these CAM samples was measured in a Brook field viscosimeter, type LVF, Noah at 30 r/min. BY this the apparent viscosity is obtained. The storage stability was measured by means of the following penetration test which discloses tendencies for aggregation and/or sedimentation in the CAM sample. A glass rod I g, 1.7 mm) is allowed to fall to the bottom in a CAM sample of a volume of 100 ml and a height of 173 mm and the time required is measured.
Example 1 Heating of crude tall oil and partial esterification with polyethylene glycol.

Crude tall oil having the analysis data below two called not distillable crude tall oil) is charged into a reactor provided with a mechanical stirrer and protective atmosphere.
To the reactor was connected a short column to collect reaction water in the receiver belonging to it.
Analysis data:

Acid value = 134 Rosin content = 14%
Unsaponifiable = 23 Viscosity (20C Emil) = 505 maps The temperature ox the crude tall oil was increased to 280C and retained for 2 hours, thereafter the viscosity was 1 400 maps icky Emil) and the acid value had de-dined 32- units to 102.

To this heated crude tall oil (105 g) polyethylene glycol of a molecular weight of 8000 ~245 g) us charged. The -12 ~3~032 temperature of the mixture was maintained at 280C for 2 hours. A 3% water solution of the reaction mixture can maximally disperse 68~ coal.

Heating of crude tall oil and partial esterification with polyethyleneglycol can also be performed in one step. This will, however, give a somewhat inferior disk pursing agent, maximum 67% coal in the slurry.

Heating of crude tall oil from the sulfite pulping process and partial esterification with polyethylene-glycol.

The extractive material of the trees can be recovered also in producing pulp by the sulfite process This so called sulfite anthraquinone process is reported in literature to give a tall oil of good quality. By ultrafiltration and evaporation a stream rich on extractive material (dry matter content 40%) can be obtained from the sulfite pulping process. This emulsion of water and extractive material from the wood can be broken by the addition of diluted acid and heating. The lipid phase which is separated then has an acid value of 63.
By reaction thereof with polyethyleneglycol (molecular weight 8000) at 280C to an acid value of 8 a substance is obtained which when added to water (1% of the total mixture) makes it possible to disperse 69~ coal and obtain a parboil slurry.

Heating of crude tall oil in the presence of BF3 and partial esterification with polyethylene glycol.
Dehydrated crude tall oil (1660 g) having an acid value of 140, a rosin content of 29% and a viscosity of 115 maps (50C) are charged into a reactor provided with a mechanical 13 1~31~32 stirrer with protective atmosphere. The temperature of the crude tell owl is raised to 125C and BF3-solution (20 g) is added. The mixture is kept at this temperature for 4 Horace and then the temperature is increased to 250C and the reaction mixture blown with water steam for 1 hour. 120 ml oil is taken away together with the steam The reaction product so obtained has an acid value of 120 and a viscosity at 50C of 2 100 maps The boron-trifluoride solution has a content of 47% in deathly--ether.

The reaction can also be interrupted by addition of water without steam blowing. During these conditions the reaction mixture will, however, contain BF3 residues. Fatty acids and rosin acids can also be treated in this way.
The table below shows the properties of different dispersing agents as to their ability to produce a coal-water slurry having a high coal content. ill dispersing agents have been prepared by partial esterification with polyethylene glycol (molecular weight 4000) at 280C.

Lipid part Maximum coal content in the coal-water slurry (~) BF3-treated fatty acid 66 25 BF3- " rosin acid 68 BF3- " crude tall oil 67 Crude tall oil 66.

As a comparison it can be mentioned that distilled water can disperse about 50% coal in a flowing slurry. The addition of crude tall oil to the water in an amount of I (pi = 7) has no positive effect on this. The effect of the length of the chain of the polyethylene glycol chain is also of importance for the function of the dispersing agent. Polymerized rosin acid has a capacity for dispersing maximum 68% when being reacted with polyethylene glycolof a molecular weight of 4000 while 70% coal in water can be dispersed if the polyethylene glycolchain is prolonged (molecular weight 8000).

Pure rosin acid being esterified with polyethylene glycol can disperse 69% coal and pure tall oil fatty acid esterified with polyethyleneglycol (molecular weight 8000) can disperse 61~ coal in water at the most Pure fatty acid and polymerized fatty acid being ester-fled with polyethyleneglycol both give coal-water slurries of a short consistency, all other dispersing agents give a slurry of a smoother consistency.

Treatment of crude tall oil with multi functional alcohol and acid and partial esterification with polyethylene~qlycol By adding multi functional alcohol and acid to crude tall oil a viscosity increase is obtained. Tall oil having the analysis data according to example 1 (548 g) is charged I, in a reactor equipped as in example 1 together with Audrey f Of - Polyol POX product consisting of polyhydric alcohols having a functionality between 2 and 4, produced by Perstorp ABE (91 g) and malefic Andy; The mixture is kept at 230C until the acid value has declined to - 34, the viscosity then being 5000 maps (Emil 50C).
To 105 g of the reaction mixture is added 245 g polyp ethylene glycol (molecular weight 8000~ and the temperature is raised to 280C. After 2 h the acid value of the mixture is 9 and a 3% water solution can disperse 70% coal.

An addition of amine to the dispersing agent also increases the amount of coal in the coal-water slurry. By adding 0.5~ diethylene thiamine to the dispersing agent which has been prepared above and maintaining the mixture for 1.5,h at 160C the coal-water slurry can disperse another 1%.

In the same way other multi functional acids and alcohols can also be reacted with tall oil. Some examples follow below.

1~:3~03~

A common photo in all cases is that a polymerization has taken place and that the product after reaction at 280C with polyethylene glyc~l molecular weight 8000) has a residual acid value.

Additive to the Viscosity of Residual acid Mum amount crude I oil the polymerized value of the of coal in free crude tall oil polyethylene- flawing coal ~20 (50C),MPa-s glycolester --slurry with 1% dispersing agent Trimethylol propane 1 200 6 71 Trimellitic acid Monopentaerythritol 4 700 7 69 Malefic android 15 Trimethylol propane 1 600 7 70 Malefic android Dipentaerythritol40 000 6 71 Malefic android The viscosity of a 70% C CAM prepared from 0.5% of the reaction of tall oil and trimethylol propane and trimellitiC
acid stated above is 270 maps and the time for penetration, as defined above, is 14 s. after one week of storage.

Standoff boiling is a traditional way to increase the molecular weight. An ester of tall oil fatty acid and dipentaerythritol with a residual acid value of 9 - 11 having a viscosity (20C, EIoppler) off - 500 maps after standoff boiling has a viscosity of 3500 - 6500 maps (20C). The viscosity of the reaction product of crude tall oil, trimethylol propane and malefic android prepared above can in 2 h be increased from 1600 ma s to 14 500 ma s (50C) by standoff boiling at 272C
under protective atmosphere. By air blowing the sample the same increase of viscosity can be accomplished but at a lower temperature, about 250C.

16 ~23~03~

Heating of crude tall oil in the presence of boric acid and partial esterification with polyethylene glycol.

Crude tall oil (800 g) having an acid value of 134, a rosin content of 14% is charged into a reactor provided with a stirrer and receiver for collecting water. The crude tall oil is dehydrated by raising the temperature to 185C and then cooled to 50 C and 24 g boric acid is added. The mixture was heated to 270C and maintained at this temperature for 9 h r the viscosity of the oil having been increased from 80 maps (50C) to 2250 maps During the heating of the crude oil tall a substantial molecular enlargement has taken place.

90 g of the product obtained and 210 g polyethylene glycol (molecular weight 8000) are charged into a reactor and heated. After 1 h at 280C the acid value of the mixture has decreased 3 units. Addition of 0.5% of this product to a 70% C CAM gives a slurry having a viscosity of 340 maps and not forming a hard sediment after storing for 18 days.

Polymerizing crude tall oil in the presence of a cobalt catalyst and distillation of the product obtained followed by partial esterification with polyethylene glycol.

Dry crude tall oil (800 g) having an acid value of 141 and a rosin content of 30% as well as 0.1% cobalt catalyst (Co napthenate) are charged into a reactor and the mixture is kept at 270C for approximately 8 h. The viscosity then is 5500 maps at 20C. From this product 30% of the most volatile components are removed by distillation. After reaction with polyethylene glycol (molecular weight 8000) in the ratio 3:7 at 240C an additive for dispersing coal in water is obtained.

17 ~3~)3;~

Reaction time Acid value Viscosity of Penetration time h 70%C CAM after Ed 0.5% additive s maps 0.75 32 3415 ~60 1.0 29 240 10 2.0 28 215 12 -An additive prepared as above but from crude tall oil not being polymerized or distilled, gives a CAM which after 7 days has formed a sediment.

A dispersing agent was prepared from pitch obtained during distillation of fatty acids, mainly C-18 unsaturated. These fatty acids originate from a mixture of edible oils.

30% pitch (acid value = 27) was reacted with 70% polyethylene glycol (MY = 8000) at 280C for -I h. From this product a 70% C
CAM containing 0.5% additive was prepared. This CAM has an apparent viscosity of 390 maps and the time for penetration amounts to 8 seconds after 9 days.

Dimerizing ox fatty acids improves the dispersing properties in the corresponding polyethylene glycol ester, compared to the monomer acid. Tall oil fatty acid (acid value 192) and dimerized fatty acid (acid value 193) respectively were reacted with polyethylene glycol (molecular weight 8000) by heating at 220 - 250C in a ratio of 3:7. The reaction was followed by reduction in acid number and the ability of the reaction minutes (0.5& w/w) to disperse 70% w/w coal in water as well as the stability of the slurry against sedimentation was examined. This example also shows that a polyethylene glycol with a diver fatty acid in both chain ends has very good dispersing properties for coal in water.

~23~)3~:
Tall oil fatty acid and polyethylene glycol (My 8000) Acid value Viscosity of slurry Penetration time reduction maps s of reaction ' -mixture 2.6 970 >60

4.4 130 >60 6.6 250 >60 9.4 540 >60 1 1 *

*Impossible to disperse in water.

Dimerized fatty acid and polyethylene glycol (My 8000) Acid value seduction Viscosity of slurry Penetration time of reaction maps s mixture 2.7 200 >60

5.5 200 28 7.5 210 16 9.3 220 6

Claims (11)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A coal-water dispersion comprising coal particles dispersed in water and dispersing agent in an amount of 0.01-5%
by weight of the dispersion, wherein the dispersing agent is a partial ester of a dimeric, trimeric or oligomeric fatty acid-containing composition selected from the group consisting of: (a) a crude tall oil having been polymerized so that its viscosity at 50°C has been at least doubled; (b) a polymerized fatty acid compound; and (c) a residue obtained in distilling fatty acids from fats or oil, which composition has been partially esterified with a polyalkylene glycol compound having an average molecular weight of at least 4,000 and mainly being composed of ethylene oxide units, said dispersing agent having a residual acid value higher than 3.

2. A coal-water dispersion according to claim 1, wherein the fatty acid-containing composition comprises fatty acid derivatives derived from fatty acids which have been reacted with a multifunctional alcohol and/or carboxylic acid.

3. A coal-water dispersion according to claim 1 com-prising a partial ester of a polymerized crude tall oil as dis-persing agent, wherein said dispersing agent has been obtained by heating the polyalkylene glycol compound with crude tall oil at a temperature of up to 280°C for a sufficient period of time for the acid value to be reduced by at least 2 units.

4. A coal-water dispersion according to claim 3, wherein the most volatile components in the polymerized crude tall oil have been removed by distillation before the partial esterification.

5. A coal-water dispersion according to claim 1 com-prising a partial ester of a polymerized fatty acid compound as dispersing agent, wherein the polymerized fatty acid compound is a dimeric, trimeric and/or oligomeric product obtained by poly-merizing fatty acids.

6. A coal-water dispersion according to claim 5, wherein the fatty acid is a tall oil fatty acid.

7. A coal-water dispersion according to claim 1, wherein the polyalkylene glycol compound is an alkyl monoether of a polyalkylene glycol, the alkyl group having 1-5 carbon atoms.

8. A coal-water dispersion according to claim 1, wherein the polyalkylene glycol compound is a monoester of a polyalkylene glycol and a carboxylic acid R-COOH, wherein R is a hydrocarbon radical having 1-4 carbon atoms.

9. A coal-water dispersion according to claim 1, wherein the polyalkylene glycol compound has an average molecular weight of from 4,000 to 10,000.

10. A coal-water dispersion according to claim 1, wherein the polyalkylene glycol compound is polyethylene glycol.

11. A coal-water dispersion according to claim 1, wherein the dispersing agent content is from 0.3 to 1% by weight of the dispersion.