CA1107958A - Slurry of coal-water-anionic organic surfactant - Google Patents

Abstract

SLURRY OF COAL-WATER-ANIONIC ORGANIC
SURFACTANT

ABSTRACT OF THE INVENTION
This invention relates to a method for making and utilizing a novel partially de-ashed, pseudoplastic coal-water slurry for pumpline conveyance to coal-water slurry combustion and gasification processes. The novel coal-water slurry is deflocculated while retaining pseudoplastic rheology by adding to pulverized coal particles dispersed in water a deflocculating amount of an anionic organic surfactant, preferably in the presence of alkali.

Description

SLURRY ()1~` ~`OAL-WI~T~.R-I~N:LONIC ORG/~NIC
SURF~CTAN'r U~C~GROU~I) 0~ T~IE INVENI'ION

Tllis inverltion r~lates to a me~:hod for preparing and utilizin~ a partially de-~she(l coal-wa~r slurry for generation of heat energy in a furn~ce provicle~ witI~ slurry conveying means and a coal-slurry atomizer-burner.

More particularly, this i.nvention relates to an improved partially de-ashed coal-water slurry having pseudoplastic rheological properties.

Processes for preparing aIld ut~ ,ing p~ Lly de-ashed solid-luel-water slurries and conveyin~ the sLu~ry by various conveying means, such as pumps, are known. O. Schwartz and H. Merten, ~rennstoff l~aerme Kraft 18 (10), 474-~ (1966) (Ger) describe a pilot plant in which coal t~as pulverized - dry or wet in ball mills an~ disk grinders t.o provide parti.cles up to 77% -iner than 0.06 mm.

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Coal-water slurries containing :Erom 40 to 60% by weight of coal were so prepared. Piston, centrifugal and screw pumps were used to pump the slurry. Settling was avoided by using flow rates in the turbulent range. A rotation atomizer was found better tl~an a pressure atomizer for burning the slurry.

U.K. Patent #711,105 teaches wetting pulverized coal particles with aromatic or aliphatic oil wetting agents, to cause separation of clay and other waste particles from ` the oil-wetted coal particles in a water flotation process using impact plate mills to obtain the necessary dispersion of the particles. The pH of the pulp of coal and debris particles is taught to be carefully maintained -to obtain economic recovery of the coal particles. The operation can be carried out underground and the pulp or recovered coal-water slurry pumped to an above-ground station for separation of the water from the coal particles.

French Patent ~1,581,112 teaches preparing and - burning aqueous slurries containing about 60 wgt% coal by mixing coal dust filtered from washing water already - containing ultrafine coal par~icles, to prevent buildup of suspended and dissolved material.

U.S. 3,423,313 teaches separation of a high solids content underflow from the liquid phase of a low-solids con~ent slurry in a mechanic21-type thickener utilizing flocculant materials. The thickeners may be used for water clarification in the coal mining industry and for recovering coal fines.

-2-U.S. 3,996,026 teaches preparation of a finely-divided solid fuel-water mixture having a total water content between 35 and 55% by weight and containing sufficient organic liquid of a type selected to improve pumpability of the slurry, such as, naphtha. The slurry is then heated to maintain the water under pressure and in the liquid phase. The organic liquid is removed rom the slurry prior to injecting the remaining mixture into a solid fuel gasification zone. The process relates to the gasification of coal to provide gaseous fuel or synthesis gas.
U.S. 3,682,114 teaches a method for atomizing a coal liquid suspension consisting of pulverized coal - and water in approximately 60 to 40 weight ratio. Other liquids, such as methanol, which are low-boiling also are taught to be used in the slurry. The coal is maintained in suspension by mechanical means such as an agitator, prior to being pumped to an atomizer attached to the furnace of a steam boiler~

U.S. 3j950,147 teaches a process for converting coal or the like particles into gas, heat, or gas and heat~ within a pressurized processing chamber in which particles of the coal are maintained during processing in an agitated cond~ion and wherein the coal is finely pulverized and separated from larger particles, and e~entually rom the liquid, and fed in dry form to the processing chamber.

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U. S. 3,9~1,552 teaches a process wherein pulverized coal is slurried with water then with oil, or if desired, oil and pulverized alkalies. Preferably lime or limestone is added, and the mixture is subjected to sonic vibrations to produce a li~uid suspension of the coal. Lime is used optionally to reduce the sulfur dioxide in burning where the coal contains sulfur.
The resulting dispersion is utilized and burned in a furnace.
The above processes all relate to coal-water slurries in which mechanical agitation or sonic vibration are used or - 10 oil, or other liquid, is added to the slurry to maintain the coal particles in suspension in the water phase prior to feeding - it to a burner or gasifier unit. In contrast to these prior art processes, the process of the present invention utilizes an -~ anionic organic surfactant as a deflocculating agent to convert a high solids coal-water slurry to a pseudoplastic mass which can be pumped in a pipeline.
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DESCRIPTION OF THE DRAWING
The features and benefits of ihe present invention will become more apparent from the following description with reference being made to the accompanying drawing, the preferred embodiments, and the specific Example. In the drawing, Figs. 1 and 2 are shear diagrams. Figs. 3, 4 and 5 are deflocculation curves of pseudoplastic coal-water-anionic organic surfactant slurries made according to the invention. Fig. 6 is a flow diagram for an integrated process for preparing and utilizing a pseudoplastic coal-water-anionic organic surfactant slurry to generate heat. Fig. 7 is a cross-section of a typical atomizer for combustion of the coal-water-anionic organic surfactant slurry of this invention.

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SUMMARY OF THE INVENTION
. _ The present i~vention relates to a novel deflocculated coal-water slurry which has pseudoplastic properties to enhance pumpability of the slurry. In the slurry, pulverized coal is maintained in deflocculated condition in the water. The slurry is deflocculated and simultaneously rendered pseudoplastic by the presence in the slurry of an effective amount of an anionic surfactant deflocculating agent.
In one aspect the invention comprehends a pumpable, pseudoplastic coal-water-anionic surfactant slurry comprised of at least about 55 percent by weight of coal, at least about 20 percent by weight of water, and at least about 0.2 percent by weight of dry coal of an anionic organic surfactant and less than 5 weight percent of ash. Preferably, the deflocculating agent is in the presence of a deflocculating enhancing amount of an alkali metal carbonate, hydroxide or silicate.
Also disclosed is a method for preparing the novel deflocculated pseudoplastic coal-water-anionic organic surfactant slurry. The invention also relates to utilizing the slurry as a fuel for generation of heat energy in a suitable atomizer of a burner of a furnace, and for other uses, to all of which uses the slurry is delivered by pipeline and conveying means for the slurry, such as pumps.

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A pseudoplastic fluid is one whose apparent Viscosity or consistency decreases with increasing rate of shear. In a shear stress vs shear rate diagram, as shown in Fig. 1 of the drawing, the curve for a pseudoplastic fluid shows a non- -linearly decreasing shear stress w;`th a linearly increasing rate of shear. In a pure pseudoplastic system no yield stress is observed so that the curve passes through the origin. However, most real systems do exhibit a yield stress indicating some plasticity. The lower the yield stress and the more pseudoplas-tic, the more pumpable such a fluid would be.
In general the flow curve is a straight line on a logarithmic plot and can be defined by T = K fdu~ n where N ~1, u is velocity and r is distance.
~dr~
The apparent viscosity of the fluid is given by ua = K (du) n-l. ;

- In a plot of logarithm of viscosity versus logarithm o shear rate, as shown in Fig. 2, the pseudoplastic line is seen to lie below that of a Newtonian fluid. Coal-water-anionic organic surfactant slurries of the present invention provide viscosity-shear rate diagrams which approximate the pseudoplas-tic li~e in Fig. 2. Procedures for determining viscosities and shear rates are well-known and need not be described herein in detail.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The novel coal-water-anionic organic surfactant slurry to which the invention relates comprises finely-divided particles of coal such as those used in most known coal-water slurries which can be conveyed by known pumping means, such as piston or screw pumps. The coal used in the slurry can be any coal suitable for pulverizing to a particle size of 50 ~m or finer. However, particles of coal of greater or lesser initial size can be used to obtain the benefits of the invention.

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Particles of coal of 10 ~m or less in average diameter are more advantageous than particles of larger sizes. Coal having average diameter paxticles of 1 ~m or less are especially preferred for practice of the invention, in order to enhance de-ashing of the coal by flocculation-flotation process steps and to enhance deflocculation while retaining pseudoplastic rheology of the coal-water slurry product of the invention.
The kind of coal used for practice of the invention is not critical. Coals found in the United States, particularly low volatile bituminous coals, from West ~irginia or Montana fields, have been used and are preferred. However, anthracite, semi~anthracite, medium and high-volatile bituminous, sub-bit-uminous and lignite coals all may advantageously be used to practice the invention.
The coal used to prepare the coal-water slurry can be obtained in finely-divided form by cleaning and pulverizing larger sized coal to the desired particle sizes. Preferably, the coal content of the pulverized coal is enriched by known clay and mineral separation processes to obtain a coal of low ash content, e.g. under 5 %. However, the ash content of the coal may be higher or lower than 5 %, e.g. from 0.5 %
to 10 % while permitting the benefits of the invention to be obtained.
The coal for use in the process can be obtained in a dry or wet form and mixed with water to form a coal-water slurry. Preferably the coal is wet milled in known ways to prevent dust and explosion hazards. The wet milled coal can be mixed with sufficient additional water to make a mixture which, when it is made pseudoplastic according to the invention, will be readily pumpable in a pipeline. Usually, the water content of the coal-water slurry product will be in the range C~

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of about 20% to 55~ ~y weiqht o$ slurry. Preferably, the water content will be from 22% to 45~ by weight.
The coal-water-anionic organic surfactant slurry hereof is prepared by adding to a coal~water slurry consisting of coal and water an amount of an anionic surfactant e*fective to deflocculate the pulverized coal particles to a pseudoplastic rheological state at high solids content and to maintain the particles in dispersed, or deflocculated, form in the water phase of the slurry during storage and pumping to an atomizer of a coal-water slurry burner or other use means.
The anionic organic surfactant which is used to prepare the pseudoplastic coal-water-anionic organic slurry may be any anionic organic surfactant which is effective to produce a high-solids content coal-water slurry with the necessary pseu-doplastic rheological properties. Economics of coal-water slurry preparation, storage, conveying and atomization dictate that as high a solids content coal as is practical be utilized. Accord-ingly, those anionic organic surfactants which provide a coal-water slurry with coal content of at least 55~ are preferably used.
The surfactant to be used can be selected by experi-me~tal tests to determine those most suitable of those available at a particular time and place where the invention is to be practiced. In making a selection of a suitable surfactant, one can use a coal-water slurry containing about 55 to 80 weight percent of coal. A viscometer, such as a Brookfield LVT visco-meter, is used to measure the viscosity of the slurry versus spindle speed in centipoise (cps). The viscosities at a con-stant revolutions per minute (rpm) are measured for different amounts of surfactant in a constant amount of coal slurry until an optimum decrease in viscosity is obtained. Suitable surfac-tants will produce a sharp reduction in viscosity. The viscosi-ties are then plotted to make deflocculation curves, such as those shown in Figs. 3, 4, and 5 C~

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Examples of anionic orc3anic suxfactants which pro-vide desired pseudoplastic rheological properties in coal-water slurries containing about 55 to 80 weight ~ of coal are shown in Table 1. In some cases, mixtures of the surfactants can be beneficially used.

Anionic Organic S`urfactant Trademark Form % conc.
2-ethylhexyl polyphosphoric Strodex ester acid anhydrideMO-100 Liquid 100 10 Potassium Salt of Strodex MO-100 MOK-70 Paste 70 Complex organic polyphos- Strodex phoric ester acid anhydride MR-100Liquid 100 " " Strodex SE-100 Liquid 100 " " Strodex P-100 Liquid 100 " " Strodex PK-90 Liquid 90 20 Potassium salt of complex Strodex organic polyacid anhydride MRK-98Liquid 98 " " Strodex SEK-50 Liquid 50 " Strodex PSK-58 Liquid 58 " " Strodex V-8 Liquid 85 Sodium salt of a condensed Lomar DPowder 86-mono n~phthalene sulfonic Lomar NCO 90 30 acid Lomar PW
Sodium salt of a condensed mono napthalene sulfonic Lomar LSPowder 95 acid Ammonia salt of a condensed mono napthalene sulfonicLomar OWA Powder 89 acid Solution of sodium salt of a condensed mono napthalene Lomar PL Liquid 45 sulfonic acid 40 (Unknown)Hydrodyne-Aquadyne Strodex is a trademark of Dexter Chemical Corporation.
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Lomar is a trademark of Diamond Shamrock Process ~hemicals, Inc.
Hydrodyne-Aquadyne is a trademark of Aquadyne Company. The anionic character o~ this surfactant is confirmed by its infrared spectra, which closely resembles those of Strodex PK90 and Strodex V-8.
Other suitable anionic organic surfactants can be selected from those listed in McCutcheonls, ~etergents &
Emulsifiers North American, 1976 annual edition, McCutcheon Division, MC Publishing Co., Ridgewood, N. J. 07451 and in Encyclopedia of Surface-Active Agents, J-P. Sisley, Chemical Publishing Company, Inc., New York, New York (1964, Vol II).
In contrast to the anionic organic surfactants useful in the practice of the invention, the following organic compounds were tested and found unsuitable as effective defloccu-lants for forming a pseudop~astic coal-water slurry: benzene, kerosene, sodium acetate, stearic acid, oxalic acid, oleic acid, tannic acid, n-butyl alcohol, isobutyl alcohol, Nalco 334, (only slightly anionic), Nalco 321 (cationic amine), Nalco 345 (polyol ester, nonionic), Nalco 393 (Zn with inorganic dispersant), Nalco 918 ~inorganic polyphosphate).
Nalco is a trademark of National Aluminate Company.
The following inorganic compounds also were found unsuitable as effective deflocculants: KF, Li2CO3 Mg(NO3)2 NaNO3 Na2SO4 and Calgon (trademark for sodium hexametaphosphate).
The following alkali inorganic compounds were found effective to enhance the deflocculant activity of the anionic organic surfactant: K2CO3 NaOH, and Na2SiO3 9H20. When used, the alkali material preferably is added before the anionic organic surfactant is added to the slurry but this order is not essential. Mixtures of the alkali materials also can be used.

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The amount of anionic organic surfactant defloccu-lant used can be determined e~perimentally as described above for a particular coal-water slurry to convert it to a pseudo-plastic mass. The amount will ~ary depending upon such factors as the concentration of the coal, the particle size and particle size distribution, the amount of ash, i.e. clays and other minerals present, the temperature of the mass, the pH, and the anionic organic surfactant and its concentration. Specifically, in determining the amount of anionic organic surfactant needed, a series of measurements are made of viscosities versus shear rates as described above for a series of coal-water slurries containing a range of amounts of surfactant for a constant amount of coal-water slurry. The data can be plotted on a -~ logarithmic chart as shown in Fig. 2 and used as a guide to the optimum quantities of surfactant to use.
Fig. 3 shows semi-logarithmic plots of deflocculation cu~ves obtained with varying amounts of sodium salt of condensed mono naphthalene sulfonic acid (Lomar PWA and Lomar PW) and of the ammonia salt of said sulfonic acid (Lomar D) dispersed in water in parts of surfactant per 100 parts of coal (dry basis) in a coal-water-anionic organic surfactant slurry containing 55 wgt. ~ of West Virginia coal. Pseudoplasticity is retained at full deflocculation when about 0.4 to 0.7 gm of the anionic surfactant is present per 100 gms of dry coal in a deflocculated coal slurry containing 55 weight % of coal.
Fig. 4 similarly shows semi-logarithmic plots of deflocculation curves obtained with varying amounts of potassium salt of complex organic polyphosphate ester acid anhydride (Strodex V8 and Strodex PK-90) and of Hydrodyne-Aquadyne dis-persed in water in ml. of surfactant per 100 parts of coal (dry basis) in a coal-water-anionic organic surfactant slurry containing 55 wgt. ~ of West Virginia coal slurry. It is seen '3~

that pseudoplasticity is retained when about 1 to 2 mls of liquid anionic surfactant are present per 100 gms of dry coal in a deflocculated coal slurry containing 55 weight ~ of coal.
Quantities of other anionic organic surfactants to use can be determined similarly. In general, the flow behavior of the slurry is controlled below the solids content or the deflocculant addition level at which dilatency begins to occur i.e. below the level at which viscosity increases as shear rate increases. Pumpability of the coal-water-anionic organic sur~
factant slurry is optimum under pseudoplastic rheological con-ditions and decreases rapidly as dilatency is approached.
As discussed above r certain alkali inorganic com-pounds can be added to the slurry to enhance the pseudoplasticity of the slurry in the presence of the anionic organic surfactant.
The effects of the addition of NaOH to a 55% coal-water slurry containing varying amounts of an anionic organic surfactant, Lomar D, a~e shown in Table 2.

; ~ Lomar D Viscosity, cps at 60 rpm 20 0.4 1.15 450 1.2 0.75 175 2.0 0.80 450 Table 2 shows a ratio of NaOH to Lomar D of 1.2:0.75 to provide an optimum low viscosity of 176 cps at 60 rpm, while retaining pseudoplasticity.
Fig. 5 shows deflocculation curves obtained using West Virginia bituminous coal-water slurry, 67.4 wgt. ~ solids, deflocculated with from about 0.75 to 1.05 gms of Lomar D per `
100 parts of coal (dry basis) and varying amounts of NaOH and K2CO3. The alkali materials were prepared as 10N solutions in water and added in various amounts by volume to the slurry. In Fig. 5, 0 = Oml; lN = 1 ml of 10N-NaOH; 3N = 3 ml 10N-NaOH;

Cl ~7~8 5N = 5ml 10N-NaOH; lK = 1 ml 10N-K2CQ3. It is seen from the deflocculation curves that the use of 3 ml of 10N-NaOH pro-vides optimum low viscosity at about 0.75 gm of Lomar D per 100 gms of coal in this coal-water-anionic organic surfactant slurry.
EXAMPLE
The practice of the invention in an integrated process will now be described with reference to Figs. 6 and 7 of the drawing.
Bituminous coal from West Virginia, containing about 21% ash as mined or washed is introduced into a crusher 1 wherein it is crushed to about 2" size or less. The term "ash" is used herein to define non-combustible content of the coal, such as clay and various minerals. The crushed coal is charged into a mill 2, preferably a ball mill, where it is re-duced to a particle size of 95% ~ 30~m. The particles of finely pulverized coal are then charged to a slurry tank 3 containing water sufficient to maintain a solids content of about 10% by weight. The pH of the mass in tank 3 is maintained at a pH of 10 or higher by addition of a solution of NaOH to cause defloc-culation and separation of ash materials. Tank 3 is provided with a high intensity agitator 4 to effect dispersion of all particles. After about 20 minutes agitation, the slurry is continuously pumped by pump 3a through line 7 through the hydro-cyclone 5 and hence back to tank 3. The hydrocyclone 5 removes the higher specific gravity minerals, preferably flocculated, and delivers them to scrap or reprocessing. After a suitable time of cycling the slurry through the hydrocyclone to maximize ash removal, the valve 3B is closed and ~alve 3C opened to filter press 6 to filter the batch from tank 3. Filtrate from filter press 6 is recycled to tank 3. The pH of the water is adjusted b~ addition of a solution of caustic soda (NaOH).
The partially ash-free coal thus obtained contains from about 0.5 to 10 wgt. ~ of ash. Treatment of the coal in tank 3 is, C~.

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however, beneficial to remove at least gross amounts of the ash content of the coal, thereby increasing the net btu value of the coal-water slurry. The filter cake from filter 6 containing the coal and about 25 wgt. ~ water is discharged to a second slurry tank 8 where the cake is agitated by means of a low speed agitator 9 operated as in tank 3. The filter cake is dispersed in tank 8 with sufficient excess dry coal if necessary to pro-vide a slurry containing about 20wgt. % of the coal. Aqueous treatment of the coal for ash removal, deflocculation, and concentration also provides a suitable vehicle for sulfur removal.
Anionic organic surfactant, preferably Lomar D, and a solution of 10 normal (lON) NaOH are added to tank 8.
Addition of the surfactant and NaOH solution cause defloccula-tion of the coal in the water. The Lomar D is added at a rate of about 1.25 parts and the NaOH at a rate of about 0.75 parts ; 10N NaOH based on 100 parts of dry coal by weight. A stable, deflocculated pseudoplastic coal-water-anionic organic surfac-tant slurry is formed. The slurry contains about 75 wgt. ~ of 20 partially ash-free coal, 1.25 wgt. ~ of Lomar D, 0.30 wgt. %
NaOH, the remainder being water.
The pseudoplastic coal-water-anionic organic surfactant slurry is discharged from tank 8 to a storage tank 10. Successive charges of the coal-water-anionic organic surfactant slurry are blended continuously in tank 10, preferably by pumping it continuously through a recycle pipeline 11 leading from the bottom of tank 10 to the top of tank 10. Uniformity of the coal-water-anionic organic surfactant slurry is thus main-tained and provides slurry of a substantially uniform btu content.
Also, the recycling aids to minimize unwanted settling of the coal in the slurry should inadequate amounts of anionic organic sur-~l .

~7~8 factant be use~ in a tank 8 to deflocculate the coal particles.
This is a contingency plan and should not be necessaxy. As discussed abo~e, the amount of anionic organic sur~actant which must be used to obtain the benefits and advantages of the invention must be sufficient to form a pseudoplastic mass.
If an excess amount is used the mass may be dilatent and exces-sively viscous and even unpumpable. If an inadequate amount is used the system will be still pseudoplastic but with a high viscosity and attendant pumping difficulties.
The blended deflocculated pseudoplastic coal-water slurry can be pumped directly from the bottom of tank 10 to an atomizer burner 12 of a furnace 13 used to generate heat energy to heat water in a steam boiler or pumped to storage tanks. Details of a typical atomizer burner for burning a coal-water-anionic organic surfactant are shown in Fig. 7.
Net heat content of coal-water-anionic organic surfactant slurry of the above composition of the E~ample was determined to be about 105,000 btu/gallon of slurry when burned in the atomizer of a gas supported burner, compared to fuel oil which provides about 130,000 btu/gallon. In the fur-nace, the slurry burned cleanly and efficiently with no detect-able smoke, sparks, or odor.
The flame produced by the burning of the coal slurry can be radiation stabilized, although it may be possible for self-stabilization to occur at about 75~ solids content in a properly designed burner.
Cost calculations which have been made show that deflocculated coal-water-anionic organic surfactant slurry of the invention can be produced in large quantities to make the slurry competitive with oil on an equivalent heating value basis.

~i~7'~5i3 Although the invention has been described in relation to use of the deflocculated coal-water-anionic organic surfactant sluxry for heat generation by direct combustion, it is also intended that the slurry of th~ invention be used in coal gasi~ication or liquifaction processes to provide fuel gases and other coal byproducts. Besides being useful in con-ventional heat generating systems, this coal-water-anionic organic surfactant slurry may provide unique properties for MHD generators (magneto-hydro-dynamic) in as much as said alkali ions are already present.
While the inventors hereof do not intend to be bound by any theory as to the reasons for the advantages obtain-ed by use of an anionic organic surfactant for deflocculating the pulveriæed coal particles in water, they believe that like ionic charges on the coal particles may in some way be involved and that repellencies of the particles are enhanced by the presence in the slurry of the anionic organic surfactant, especially in the presence of certain alkali materials.
It is to be understood that the foregoing description and Example are illustrative only and that changes can be made in the ingredients and their proportions and in the sequence and combinations of process steps discussed without departing from the scope of the invention as defined in the following claims.

Claims (11)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A pumpable, pseudoplastic coal-water-anionic sur-factant slurry comprised of at least about 55 percent by weight of coal, at least about 20 percent by weight of water, and at least about 0.2 percent by weight of dry coal of an anionic or-ganic surfactant and less than 5 weight percent of ash.

2. A coal-water-anionic organic surfactant slurry as in Claim 1 wherein said coal is present in said slurry at from about 55 to 80 weight percent based on weight of slurry.

3. A coal-water-anionic organic surfactant slurry as in Claim 1 wherein said surfactant is present in said slurry at from 0.2 to 0.7 parts per 100 parts of dry coal in a deflocculated coal slurry containing about 55 weight percent of coal.

4. A coal-water-anionic surfactant slurry as in Claim 1 wherein said coal is bituminous, semi-bituminous, an-thracite, semi-anthracite, or lignite coal.

5. A coal-water-anionic surfactant slurry as in Claim 1 wherein said slurry contains an alkali selected from carbonate, hydroxide or silicate of sodium or potassium or mixtures thereof to enhance the deflocculating activity of said anionic organic surfactant.

6. A coal-water-anionic organic surfactant slurry as in Claim 5 wherein said alkali is present in said slurry at about 0.4 to 2 parts per 100 parts of dry coal.

7. A coal-water-anionic organic surfactant slurry as in Claim 1 wherein said anionic organic surfactant is selected from:
(i) 2-ethylhexyl polyphosphoric ester acid anhydride and its potassium salt,

Claim 7 - cont'd ...
(ii) complex organic polyphosphoric ester acid anhydride and its potassium salt, (iii) condensed mononaphthaline sulfonic acid and its sodium and ammonium salts, (iv) Hydrodyne-Aquadyne, and (v) mixtures thereof.

8. A coal-water-anionic organic surfactant slurry as in Claim 6 wherein said alkali is NaOH, K2CO3, or Na2SiO3.9 H2O.

9. A coal-water-anionic organic surfactant slurry as in Claim 1 wherein the coal is a partially de-ashed coal.

10. A coal-water-anionic organic surfactant slurry as in Claim 9 wherein the coal is a substantially low sulfur coal.

11. A coal-water-anionic organic surfactant according to Claim 1 wherein said surfactant is sodium salt of a condensed mononaphthalene sulfonic acid.