CA2012197A1 - High concentration coal aqueous slurry and process for producing same - Google Patents
High concentration coal aqueous slurry and process for producing sameInfo
- Publication number
- CA2012197A1 CA2012197A1 CA002012197A CA2012197A CA2012197A1 CA 2012197 A1 CA2012197 A1 CA 2012197A1 CA 002012197 A CA002012197 A CA 002012197A CA 2012197 A CA2012197 A CA 2012197A CA 2012197 A1 CA2012197 A1 CA 2012197A1
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- Prior art keywords
- coal
- coal particles
- size
- moiety
- slurry
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Classifications
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L1/00—Liquid carbonaceous fuels
- C10L1/32—Liquid carbonaceous fuels consisting of coal-oil suspensions or aqueous emulsions or oil emulsions
Abstract
ABSTRACT OF THE DISCLOSURE
A coal aqueous slurry having a high concentration and a high dispersion stability, and thus utilizable for industrial use, comprises coal particles having a size of 500 µm or less and dispersed in an aqueous medium containing a dispersing additive at a particle size distribution in which a variation coefficient in size of the coal particles is 0.3 or more, determined in accordance with the equation C = .sigma./M, M = .SIGMA.(log10Si) x Vi and .sigma. = (.SIGMA.((log10Si - M) x Vi)2)0.5 wherein C: the variation coefficient in size of the coal particles, M: an average general logarithmic size of the coal particles, Si: an average size in µm of a portion of the coal particles in fraction No. i which is one of a plurality of fractions provided by dividing the entire amount of the coal particles in accordance with the order of the particle size, each fraction consisting of coal particles having a size in a predetermined range, Vi: a ratio in weight or volume of the portion of the coal particles in the fraction No. i to the entire amount of the coal particles, and .sigma.: a standard deviation of the size of the coal particle.
A coal aqueous slurry having a high concentration and a high dispersion stability, and thus utilizable for industrial use, comprises coal particles having a size of 500 µm or less and dispersed in an aqueous medium containing a dispersing additive at a particle size distribution in which a variation coefficient in size of the coal particles is 0.3 or more, determined in accordance with the equation C = .sigma./M, M = .SIGMA.(log10Si) x Vi and .sigma. = (.SIGMA.((log10Si - M) x Vi)2)0.5 wherein C: the variation coefficient in size of the coal particles, M: an average general logarithmic size of the coal particles, Si: an average size in µm of a portion of the coal particles in fraction No. i which is one of a plurality of fractions provided by dividing the entire amount of the coal particles in accordance with the order of the particle size, each fraction consisting of coal particles having a size in a predetermined range, Vi: a ratio in weight or volume of the portion of the coal particles in the fraction No. i to the entire amount of the coal particles, and .sigma.: a standard deviation of the size of the coal particle.
Description
- l 2012197 HIGH CONCENTRATION COAL AOUEOUS SLURRY AND
PROCESS FOR PRODUCING SAME
BACKGROUND OF THE INVENTION
1) Field of the Invention The present invention relates to a high concentration coal aqueous slurry and a process for producing same. More particularly, the present invention relates to a high concentration coal aqueous slurry having an excellent stability during storage and transportation, and a process for producing same.
PROCESS FOR PRODUCING SAME
BACKGROUND OF THE INVENTION
1) Field of the Invention The present invention relates to a high concentration coal aqueous slurry and a process for producing same. More particularly, the present invention relates to a high concentration coal aqueous slurry having an excellent stability during storage and transportation, and a process for producing same.
2) Description of the Related Arts Recently, the importance of coal as an energy ~ource ha~ been rediscovered, but coal is disadvanta-geous in that it is a solid material and thus is diffi-cult to transport, store and handle, in comparison with oil.
Accordingly, many attempts have been made to eliminate the above-mentioned disadvantages by finely pulverizing a coal material, dispersing the resultant fine coal particle~ in an aqueous medium to provide a coal aqueous slurry which can be stored, transported and handled as a liquid material, and supplying the coal aqueous slurry as a fuel for boilers for power plants and other industrial uses. For example, such attempts are disclosed in Japanese Unexamined Patent Publication (Kokai) Nos. 58-38791, 60-18585, 61-57689 and 62-116691.
For the coal aqueous slurry, it is necessary to increase the concentration of coal particles and to enhance the stability in transportation and storage. A
high concentration coal aqueous slurry should comprise 60% to 75% by weight of finely pulverized coal particles and 25% to 40% of an aqueous medium containing a small amount of an additive, for example, a dispersing agent, and this high concentration of coal particles can be obtained by adjusting the size of the coal particles in - 2 ~ 2197 the aqueous slurry to a suitable level and distribution thereof, and by adding an appropriate additive to the aqueous slurry.
Therefore, attempts have been made to provide a method of controlling the distribution of the size of the coal particles in the aqueous slurry in accordance with an optimum particle size distribution formula.
Those attempts, however, are not always satisfactory.
Also, the conventional methods are disadvantageous in that the high concentration of coal particles in the aqueous slurry can be realized only by adding a certain amount of a dispersing agent to the aqueous medium.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a high concentration coal aqueous slurry having an excel-lent stability during transportation and storage, and a process for producing same.
The above-mentioned object can be attained by the high concentration coal aqueous slurry of the present invention comprising coal particles having a size of 500 ~m or less and dispersed in an aqueous medium containing a dispersing additive at a particle size distribution in which a coefficient of variation in size of the coal particles is 0.3 or more determined in accordance with the equation (I):
C = ~/M (I) wherein C represents the coefficient of variation in the size of the coal particles, M represents an average general logarithmic size of the coal particles calculated in accordance with the equation (II):
E( gl0S ) S (II) in which M is as defined above, Si represents an average size in ~m of the coal particles in fraction No. i which is one of a plurality of fractions provided by dividing the entire amount of the coal particles in accordance with the order of the particle size, each fraction consisting of coal particles having a size in a 2~2197 predetermined range, and Vi represents a ratio of the amount in weight or volume of the portion of the coal particles in fraction No. i to the entire amount of the coal particles, and o represents a standard deviation of the size of the coal particles calculated in accordance with the equation (III):
o = (~((loglOSi-M~ x Vi) )0-5 (III) in which Si, M and Vi are as defined above.
~he above-mentioned high concentration coal aqueous slurry can be produced by the process of the present invention comprising the steps of:
preparing dehydrated coal cakes comprising 60%
by weight or more of coal particles having a size of 500 ~m or less, by pulverizing a coal material in a wet pulverizing manner and dehydrating the resultant coal particle aqueous slurry;
mixing the dehydrated coal cakes with water and a dispersing additive in a kneader to provide a coal aqueous slurry (A) containing 60% to 80% by weight of the coal particles;
subjecting a portion (B) of the coal aqueous slurry (A) to a further fine pulverizing procedure to further finely pulverize the coal particles in the portion (B); and mixing the resultant further finely pulverized portion (B) with the remaining portion (D) of the coal aqueous B lurry (A).
Alternatively, the above-mentioned high concentra-tion coal aqueous slurry can be produced by another process of the present invention comprising the steps of:
pulverizing a coal material at a high concen-tration of 60% to 80% by weight in an aqueous medium containing a dispersing additive, to provide a moiety slurry (E) consisting of a high concentration coal aqueous slurry containing coal particles having a size of lO0 ~m or less; and 2~1 2197 separately providing a moiety cake (F) consisting of dehydrated coal cakes containing coal particles having a size of 500 ~m or less by pulverizing a coal material in a low concentration in an aqueous medium free from the dispersing additive and dehydrating the resultant low concentration coal aqueous slurry; and mixing the moiety slurry (E) with the moiety cake (F), B~IEF DESCRIPTION OF THE DRAWINGS
Figure l shows a relationship between the coeffi-cient C of variation in the size of coal particles and the concentration of the coal particles in a coal aqueous slurry of the present invention, having a viscosity of l000 cp;
Fig. 2 shows a relationship between the coeffi-cient C of variation in the size of coal particles and the precipitation percentage of the coal particles in the coal aqueous slurry when the coal aqueous slurry is subjected to a dispersion stability test by a centrifugal acceleration tester;
Fig. 3 shows a relationship between the coeffi-cient C of variation in the size of the coal particles in the coal aqueous slurry and the ratio of the minimum amount of a dispersing agent necessary to ad~ust the viscosity of the coal aqueous slurry to a predetermined level at a predetermined concentration of the coal particles to the entire amount of the coal particles;
Fig. 4 shows the relationships between the average general logarithmic size in ~m of the coal particles in 3G three different types of coal aqueous slurries ~, ~
and ~ shown in Figs. l to 3 and the cumulative weight percent of the coal particles having a respective size or less;
Fig. 5 is a flow sheet showing the process for producing the high concentration coal aqueous slurry of the present invention; and, Fig. 6 is a flow sheet showing another process for 2~2197 producing the high concentration coal aqueous slurry of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The inventors of the present invention made various attempts to eliminate the disadvantages of the conven-tional coal aqueous slurries, and during those attempts, the inventors carried out research into the relationship between the distribution of sizes of the coal particles in the coal aqueous slurry and the stability of the coal particles dispersed in the slurry, and discovered that the stability of a coal aqueous slurry having a wide distribution of size of coal particles and containing very fine coal particles in a large enough amount is higher than that of another coal aqueous slurry having a narrow distribution of size of coal particles having one single peak.
Namely, a coal powder consisting essentially of three types of fine coal particles, each type having a different size, and having particle size distribution peaks at sizes of about 10 ~, about 20 ~, and about 40 ~m, was mixed with another coal powder consisting essentially of three types of coarse coal particles, each type having a different size, and having particle size distribution peaks at sizes of about 80 ~m, about 160 um, and about 300 ~, at a mixing ratio of 10:90 to 90:10 by weight, and each mixture was dispersed and kneaded in an aqueous medium containing an anionic surface active agent, by a kneader. From research into the physical properties of the resultant coal aqueous slurries, it was concluded that a coal aqueous slurry having a coefficient C of variation in size of the coal particles dispersed therein, of 0.3 or more, determined from the equation (I):
C = o/M (I) r exhibits a satisfactory concentration and stability during storage and transportation over a long period.
In the equation (I), C represents the coefficient 2~ 2197 of variation in the size of the coal particles, M
represents an average general logarithmic size of the coal particles calculated from the equation (II):
M = ~(lglOSi) x Vi (II) in which M is as defined above, Si represents an average size in ~m of a portion of the coal particles in fraction No. i which is one of a plurality of fractions provided by dividing the entire amount of the coal particles in accordance with the order of the particle size, each fraction consisting of coal particles having a size in a predetermined range, and Vi represent a ratio of the amount in weight or volume of the portion of the coal particles in fraction No. i to the entire amount of the coal particles, and ~ in the equation (I) represents a standard deviation of the size of the coal particles calculated from the equation (III):
~ ((loglOSi - M) x Vi)2)0 5 (III) in which Si, M and Vi are as defined above.
As stated above, the variation coefficient C in the size of the coal particles should be 0.3 or more, and preferably as large as possible. Usually, the variation coefficient C of the coal particle size is preferably 0.5 or more, and practically, upto 0.7 or 0.8.
When the variation coefficient C of the coal particle size is less than 0.3, the resultant coal aqueous slurry has an unsatisfactorily low concentration and exhibits a poor stability.
In the coal aqueous slurry of the present inven-tion, the coal particles must have a size of 500 ~m or less, preferably 300 ~m or less, more preferably 200 ~m or less.
When the maximum size of the coal particles is more than 500 ~m, the resultant coal aqueous slurry has a disadvantage in that, when the coal aqueous slurry is subjected to combustion, the amount of unburnt carbon becomes undesirably large.
Figure l indicates a relationship between the 2~ 2~ ~7 variation coefficient C in size of coal particles in a coal aqueous slurry and the concentration of coal particles in a coal aqueous slurry having a viscosity of 1000 cp.
The distribution of the coal particle size can be determined by an apparatus for the measurement of particle size distribution available under the trademark of Microtrac Model SRA 7995-10, from Leeds &
Northrup Co.
The concentration of coal particles in an aqueous slurry thereof can be determined in accordance with the heat-drying method of Japanese Industrial Standard (JIS) M 8812.
In view of Fig. 1, it is understood that where the variation coefficient C of coal particle sizes is in the range of from 0.3 to about 0.5, the concentration of the coal particles in the coal aqueous slurry having a viscosity of 1000 cp is in the range of from about 65%
to about 72% and increases with the increase in the variation coefficient C of the coal particle sizes, and where the variation coefficient C of the coal particle sizes is more than 0.5, the concentration of the coal particles in the coal aqueous slurry having a viscosity of 1000 cp becomes substantially constant at a level of about 71% to about 73~.
Figure 2 shows the relationship between the variation coefficient C of the coal particle sizes in a coal aqueous slurry and the precipitation percentage of the coal particles when a dispersion stability test is applied to the coal aqueous slurry in the following manner.
In the dispersion stability test, a coal aqueous slurry is subjected to a 20G centrifugal acceleration test for 8 hours, and the percentage of the precipitated portion of the coal particles based on the entire weight of the coal particles in the coal aqueous slurry is calculated.
~ ~ 4~ 9 7 Figure 2 indicates that the precipitation percentage of the coal particles at a satisfactory level of about 60~ or less can be obtained at a variation coefficient of the coal particle sizes of the coal aqueous slurry of 0.3 or more. In particular, where the variation coefficient C of the coal particle sizes is about 0.5 or more, the precipitation percentage of the coal particles is substantially constant at a level of 10% or less.
Figure 3 shows the relationship between the variation coefficient C of the coal particle sizes of a coal aqueous slurry and the ratio (~) of the minimum amount of a dispersing agent needed to adjust the viscosity of the coal aqueous slurry to a standard level of lO00 cp. at the concentration as indicated in Fig. l, to the entire amount of the coal particles.
Figure 3 shows that, at the variation coefficient C
of the coal particle sizes of 0.3 or more, the necessary minimum amount of the dispersing agent is at a satisfactory level of 0.8% or less. In particular, where the variation coefficience is about 0.4 or more, the necessary minimum amount of the dispersing agent is reduced to a low level of 0.4~ or less.
~he coal particle size distributions of the coal aqueous slurries ~, ~ and ~ indicated in Figs. l to 3 are indicated in Fig. 4.
From the coal particle size distribution curves, the variation coefficient C was calculated as follows.
Coal aqueous slurry ~: C = 0.722 " ~: C = 0.473 ~ ~: C = 0.344 The processes of the present invention for producing the above-mentioned high concentration coal aqueous slurry will be explained in detail below.
In one process of the present invention, a coal material consists of a mixture of two types of portions PC and PF each having a different particle size 2~2~97 g of the coal particles therein.
The coal particles in portion FC preferably have a size of from l00 ~m to 500 ~m and are in a content of 30% by weight or more.
Also, the coal particles in portion PF pr~ferably have a size of l00 ~m or less, and a content of coal particles having a size of l0 ~m or less is 40% by weight or more.
Preferably, the mixing ratio in weight of the portion PF to the portion PC is in the range of 8:3 to 5:5.
Also, in the above-mentioned process, the aqueous medium preferably contains a dispersing additive consisting of, for example, at least one dispersing agent for preventing the agglomeration of the coal particles, in an amount needed to ad~ust the viscosity of the resultant coal aqueous slurry to a standard level of l000 cp or less. The amount of the additive is preferably in the range of from 0.3~ to 0.8~ based on the entire weight of the coal particles in the coal aqueous slurry.
The dispersing agent preferably comprises at least one member selected from non-ion and anion ~urface active agents usually employed for the conventional coal aqueous slurry.
Optionally, a stabilizer for preventing the deposition of the coal particles is added to the coal particle aqueous slurry. The stabilizer preferably comprises at least one member selected from cellulose compounds, for example, alkali metal salts of carboxymethyl cellulose and xanthan gum materials, usually utilized for the conventional coal aqueous slurry.
In this process of the present invention, a coal material is pulverized in a wet pulverizing manner and the resultant coal particles in an aqueous medium (water) are dehydrated to provide dehydrated coal cakes comprising 60% by weight or more of coal particles having a size of 500 ~m or less; the resultant de-hydrated coal cakes are mixed with an aqueous medium containing a dispersing additive in a kneader to provide a coal aqueous slurry (A) containing 60~ to 80% by weight of the coal particles; a portion (B) of the coal aqueous slurry (A) is subjected to a further fine pulverizing procedure to further finely pulverize the coal particles in the portion (B); and the resultant further finely pulverized portion (B) is mixed with the remaining portion (D) of the coal aqueous slurry (A), to provide a high concentration coal aqueous slurry having a coal particle size variation coefficient C of 0.3 or more.
In the above-mentioned process, preferably the portion (B) of the coal aqueous slurry (A) is in an amount of 50% to 80~, based on the entire weight of the coal aqueous slurry (A). Also, the fine pulverizing procedure is preferably carried out to an extent such that the resultant further finely pulverized coal particles having a size of 5 ~m or less in the portion (B) are in a content of 15% by weight or more.
The above-mentioned process will be further explained with reference to Fig. 5.
In Fig. S, a pulverizer or mill 1 is charged with a coal material and an aqueous medium through an inlet 2, and the coal material is pulverized at a low concentration of 50% by weight or less. The resultant coal aqueous slurry is fed into a classifying device 4 through a conduit 3, and a classified portion of the coal aqueous slurry containing coal particles having a particle size of 500 ~ or less, preferably 200 ~m or less, is fed into a dehydrating device 5 and dehydrated to provide dehydrated coal particle cakes. The remaining portion of the coal aqueous slurry containing coarse coal particles is returned to the pulverizer 1 through the inlet 2 and re-pulverized.
i 9 7 The coal particle cakes formed in the dehydrating device S are introduced into a kneader 6 and mixed in the kneader 6 with an aqueous medium in an amount necessary to adjust the concentration of the coal particles to a level of 60% to 80%, and preferably, containing an additive in an amount of 0.3% to 0.8%
based on the entire weight of the coal particles in the cakes.
The resultant coal aqueous slurry (A) is withdrawn from the kneader 6 through a conduit 7. A portion (B) of the coal aqueous slurry (A), preferably in an amount of about 50% to about 80% by weight, is fed into a pulverizer 9 to further finely pulverize the coal particles in the portion (B) and the resultant portion (B) containing the further finely pulverized coal particles is fed into a kneader 10 and mixed therein with the remaining portion (D) of the coal aqueous slurry (A) in an amount of from 20% to 50% by weight, which is directly introduced from the kneader 6 into the kneader 10 through a conduit 8.
The further fine pulverizing procedure is carried out preferably to an extent such that, after the portion (B) is mixed with the remaining portion (D), the resultant coal aqueous slurry contains coal particles having a size of 5 ~ or less in a content of 15~ by weight or more, more preferably 20% by weight or more, based on the total weight of the coal particles in the resultant high concentration coal aqueous slurry, and the resultant high concentration coal aqueous slurry is recovered from the kneader 10 through a conduit 11.
In another process for producing the high concen-tration coal aqueous slurry of the present invention, a coal material is pulverized in a high concentration of 60% to 80~ by weight in an aqueous medium containing a dispersing additive to provide a moiety slurry (E) consisting of a high concentration coal aqueous slurry containing coal particles having a size of 100 ~n or 2 ~ 7 less; separately, a moiety cake (F) consisting of dehydrated coal cakes containing coal particles having a size of 500 ~ or less, preferably 100 ~m or more, is prepared by pulverizing a coal material in a low concentration of, for example, 30 to 50% by weight, in an aqueous medium free from the additive and by dehydrating the resultant low concentration coal aqueous slurry; and the moiety slurry (E) is mixed with the moiety cake (F).
Before the step of mixing the moiety slurry (E) with the moiety cake (F) in the above-mentioned process, the moiety cake (F) may be mixed and kneaded with one or both of an aqueous medium and a portion of the final high concentration coal aqueous slurry prepared in the foregoing procedure, to provide a moiety slurry (G) consisting of an aqueous slurry of coal particles in a concentration of 60% to 80~ by weight, and the resultant moiety slurry (G) then mixed with the moiety slurry (E).
In the above-mentioned process, the moiety cake (F) may be further mixed with a dispersing additive in an amount of 0.3 to 0.8~ based on the weight of the coal in the moiety slurry (G).
In the moiety slurry (E), the coal particles contained preferably have a size of from 100 ~ to 500 ~m and are in a content of 30% by weight or more.
Also, in the moiety cake ( F ) or the moiety slurry (G), the coal particles preferably have a size of 100 or less, and contain particles having a size of 10 um or less in a content of 40~ by weight or more.
Preferably, the moiety slurry (E) is mixed with the moiety cake (F) or the moiety slurry (G) in a mixing ratio such that the ratio in weight of the coal particles in the moiety slurry (E) to the coal particles in the moiety cake (F) or the moiety slurry (G) is in the range of from 8:2 to 5:5.
After mixing the moiety slurry (E) with the moiety cake ( F ) or the moiety slurry (G) in the above-mentioned ~ 7 process, the resultant high concentration coal aqueous slurry preferably contains coal particles having a size of 5 ~ or less and in a content of 15% by weight or more, more preferably 20% by weight or more, based on the total weight of the coal particles in the resultant high concentration coal aqueous slurry.
Referring to Fig. 6, a coal material and an aqueous medium free from an additive are charged into a pulverizer or mill la through an inlet 2a, to provide a low concentration coal aqueous slurry. The resultant low concentration coal aqueous slurry is introduced into a classifying device 4 through a conduit 3a and a classified moiety slurry consisting of a portion of the pulverized coal aqueous slurry and containing coal particles having a size of 500 un or less, preferably 200 um or less r is introduced into a dehydrating device 5. The remaining portion of the coal aqueous slurry containing coarse coal particles is recycled to the pulverizer la through the inlet 2a and re-pulverized.
The moiety cake (F) is introduced from the dehydrating device 5 into a kneader 6 and mixed and kneaded with at least one member selected from an aqueous medium which contains an additive, for example, a dispersing agent, in an amount of 0.3% to 0.8% based on the weight of the coal particles, and a portion of the final high concentration coal aqueous slurry prepared in a foregoing procedure and supplied through a conduit 11, to convert the moiety cake (F) to a moiety slurry moiety (G) consisting of an aqueous slurry of coal particles in a concentration of 60% to 80% by weight.
The moiety slurry (G) is fed from the kneader 6 into a kneader 10 through a conduit 7.
Separately, a coal material, an aqueous medium, and a dispersing additive are fed into a pulverizer lb through an inlet 2b and the coal material is pulverized 2~-~2i~7 therein at a high concentration to provide a moiety slurry (E) consisting of a high concentration coal aqueous slurry containing pulverized coal particles having a size of 100 ~ or less.
In the pulverizer lb, the dispersing additive is preferably in an amount of from 0.3% to 0.8% based on the weight of the coal particles.
The moiety slurry (E) is introduced from the pulverizer lb into the kneader 10 through a conduit 3b and mixed with the moiety slurry (G) therein.
The moiety cake (F) may be directly introduced into the kneader 10 together with an additional amount of an aqueous medium and an additive.
In an example, a high concentration coal aqueous slurry was prepared by the process as indicated in Fig. 6.
A moiety slurry (E) was prepared from a coal material, water, and an anionic surface active agent in an amount of 0.4% based on the weight of the coal material in the pulverizer lb. The resultant moiety slurry (E) contained pulverized coal particles at a coal particle concentration of about 68% by weight. The pulverized coal particles had a size of 100 ~ or less and contained particles having a size of 10 ~ or less in a content of 40~, based on the entire weight of the coal particles. The moiety slurry (E) was fed into the kneader 10.
A moiety cake (F) was prepared from a coal material and an aqueous medium free from the dispersing additive by using the pulverizer la, the classifying device 4, and the dehydrating device 5, and then fed together with an aqueous medium into the kneader 6 to provide a moiety slurry (G) containing coal particles having a size of 200 ~ or less and in a concentration of about 75~ by weight.
The mixing ratio of the moiety slurry (E) to the moiety slurry (G) corresponded to a mixing ratio in .
2 ~ 9 7 weight of the coal particles in the moiety slurry (E) to those in the moiety slurry (G), of 70:30.
The resultant high concentration coal aqueous slurry contained pulverized coal particles having a size of 200 ~ or less and in a concentration of about 70%, and had a variation coefficient C of the size of the coal particles of 0.495.
In accordance with the present invention, a coal aqueous slurry having a high concentration and a high dispersion stability of coal particles during storage and transportation, and thus utilizable for industrial use, can be obtained by controlling only the largest size of the coal particles and the variation coef-ficient C of size of coal particle to specific levels, respectively.
Also, the present invention effectively reduces the amounts of the dispersing agent and/or stabilizer needed to stabilize the coal particles dispersion.
Accordingly, many attempts have been made to eliminate the above-mentioned disadvantages by finely pulverizing a coal material, dispersing the resultant fine coal particle~ in an aqueous medium to provide a coal aqueous slurry which can be stored, transported and handled as a liquid material, and supplying the coal aqueous slurry as a fuel for boilers for power plants and other industrial uses. For example, such attempts are disclosed in Japanese Unexamined Patent Publication (Kokai) Nos. 58-38791, 60-18585, 61-57689 and 62-116691.
For the coal aqueous slurry, it is necessary to increase the concentration of coal particles and to enhance the stability in transportation and storage. A
high concentration coal aqueous slurry should comprise 60% to 75% by weight of finely pulverized coal particles and 25% to 40% of an aqueous medium containing a small amount of an additive, for example, a dispersing agent, and this high concentration of coal particles can be obtained by adjusting the size of the coal particles in - 2 ~ 2197 the aqueous slurry to a suitable level and distribution thereof, and by adding an appropriate additive to the aqueous slurry.
Therefore, attempts have been made to provide a method of controlling the distribution of the size of the coal particles in the aqueous slurry in accordance with an optimum particle size distribution formula.
Those attempts, however, are not always satisfactory.
Also, the conventional methods are disadvantageous in that the high concentration of coal particles in the aqueous slurry can be realized only by adding a certain amount of a dispersing agent to the aqueous medium.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a high concentration coal aqueous slurry having an excel-lent stability during transportation and storage, and a process for producing same.
The above-mentioned object can be attained by the high concentration coal aqueous slurry of the present invention comprising coal particles having a size of 500 ~m or less and dispersed in an aqueous medium containing a dispersing additive at a particle size distribution in which a coefficient of variation in size of the coal particles is 0.3 or more determined in accordance with the equation (I):
C = ~/M (I) wherein C represents the coefficient of variation in the size of the coal particles, M represents an average general logarithmic size of the coal particles calculated in accordance with the equation (II):
E( gl0S ) S (II) in which M is as defined above, Si represents an average size in ~m of the coal particles in fraction No. i which is one of a plurality of fractions provided by dividing the entire amount of the coal particles in accordance with the order of the particle size, each fraction consisting of coal particles having a size in a 2~2197 predetermined range, and Vi represents a ratio of the amount in weight or volume of the portion of the coal particles in fraction No. i to the entire amount of the coal particles, and o represents a standard deviation of the size of the coal particles calculated in accordance with the equation (III):
o = (~((loglOSi-M~ x Vi) )0-5 (III) in which Si, M and Vi are as defined above.
~he above-mentioned high concentration coal aqueous slurry can be produced by the process of the present invention comprising the steps of:
preparing dehydrated coal cakes comprising 60%
by weight or more of coal particles having a size of 500 ~m or less, by pulverizing a coal material in a wet pulverizing manner and dehydrating the resultant coal particle aqueous slurry;
mixing the dehydrated coal cakes with water and a dispersing additive in a kneader to provide a coal aqueous slurry (A) containing 60% to 80% by weight of the coal particles;
subjecting a portion (B) of the coal aqueous slurry (A) to a further fine pulverizing procedure to further finely pulverize the coal particles in the portion (B); and mixing the resultant further finely pulverized portion (B) with the remaining portion (D) of the coal aqueous B lurry (A).
Alternatively, the above-mentioned high concentra-tion coal aqueous slurry can be produced by another process of the present invention comprising the steps of:
pulverizing a coal material at a high concen-tration of 60% to 80% by weight in an aqueous medium containing a dispersing additive, to provide a moiety slurry (E) consisting of a high concentration coal aqueous slurry containing coal particles having a size of lO0 ~m or less; and 2~1 2197 separately providing a moiety cake (F) consisting of dehydrated coal cakes containing coal particles having a size of 500 ~m or less by pulverizing a coal material in a low concentration in an aqueous medium free from the dispersing additive and dehydrating the resultant low concentration coal aqueous slurry; and mixing the moiety slurry (E) with the moiety cake (F), B~IEF DESCRIPTION OF THE DRAWINGS
Figure l shows a relationship between the coeffi-cient C of variation in the size of coal particles and the concentration of the coal particles in a coal aqueous slurry of the present invention, having a viscosity of l000 cp;
Fig. 2 shows a relationship between the coeffi-cient C of variation in the size of coal particles and the precipitation percentage of the coal particles in the coal aqueous slurry when the coal aqueous slurry is subjected to a dispersion stability test by a centrifugal acceleration tester;
Fig. 3 shows a relationship between the coeffi-cient C of variation in the size of the coal particles in the coal aqueous slurry and the ratio of the minimum amount of a dispersing agent necessary to ad~ust the viscosity of the coal aqueous slurry to a predetermined level at a predetermined concentration of the coal particles to the entire amount of the coal particles;
Fig. 4 shows the relationships between the average general logarithmic size in ~m of the coal particles in 3G three different types of coal aqueous slurries ~, ~
and ~ shown in Figs. l to 3 and the cumulative weight percent of the coal particles having a respective size or less;
Fig. 5 is a flow sheet showing the process for producing the high concentration coal aqueous slurry of the present invention; and, Fig. 6 is a flow sheet showing another process for 2~2197 producing the high concentration coal aqueous slurry of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The inventors of the present invention made various attempts to eliminate the disadvantages of the conven-tional coal aqueous slurries, and during those attempts, the inventors carried out research into the relationship between the distribution of sizes of the coal particles in the coal aqueous slurry and the stability of the coal particles dispersed in the slurry, and discovered that the stability of a coal aqueous slurry having a wide distribution of size of coal particles and containing very fine coal particles in a large enough amount is higher than that of another coal aqueous slurry having a narrow distribution of size of coal particles having one single peak.
Namely, a coal powder consisting essentially of three types of fine coal particles, each type having a different size, and having particle size distribution peaks at sizes of about 10 ~, about 20 ~, and about 40 ~m, was mixed with another coal powder consisting essentially of three types of coarse coal particles, each type having a different size, and having particle size distribution peaks at sizes of about 80 ~m, about 160 um, and about 300 ~, at a mixing ratio of 10:90 to 90:10 by weight, and each mixture was dispersed and kneaded in an aqueous medium containing an anionic surface active agent, by a kneader. From research into the physical properties of the resultant coal aqueous slurries, it was concluded that a coal aqueous slurry having a coefficient C of variation in size of the coal particles dispersed therein, of 0.3 or more, determined from the equation (I):
C = o/M (I) r exhibits a satisfactory concentration and stability during storage and transportation over a long period.
In the equation (I), C represents the coefficient 2~ 2197 of variation in the size of the coal particles, M
represents an average general logarithmic size of the coal particles calculated from the equation (II):
M = ~(lglOSi) x Vi (II) in which M is as defined above, Si represents an average size in ~m of a portion of the coal particles in fraction No. i which is one of a plurality of fractions provided by dividing the entire amount of the coal particles in accordance with the order of the particle size, each fraction consisting of coal particles having a size in a predetermined range, and Vi represent a ratio of the amount in weight or volume of the portion of the coal particles in fraction No. i to the entire amount of the coal particles, and ~ in the equation (I) represents a standard deviation of the size of the coal particles calculated from the equation (III):
~ ((loglOSi - M) x Vi)2)0 5 (III) in which Si, M and Vi are as defined above.
As stated above, the variation coefficient C in the size of the coal particles should be 0.3 or more, and preferably as large as possible. Usually, the variation coefficient C of the coal particle size is preferably 0.5 or more, and practically, upto 0.7 or 0.8.
When the variation coefficient C of the coal particle size is less than 0.3, the resultant coal aqueous slurry has an unsatisfactorily low concentration and exhibits a poor stability.
In the coal aqueous slurry of the present inven-tion, the coal particles must have a size of 500 ~m or less, preferably 300 ~m or less, more preferably 200 ~m or less.
When the maximum size of the coal particles is more than 500 ~m, the resultant coal aqueous slurry has a disadvantage in that, when the coal aqueous slurry is subjected to combustion, the amount of unburnt carbon becomes undesirably large.
Figure l indicates a relationship between the 2~ 2~ ~7 variation coefficient C in size of coal particles in a coal aqueous slurry and the concentration of coal particles in a coal aqueous slurry having a viscosity of 1000 cp.
The distribution of the coal particle size can be determined by an apparatus for the measurement of particle size distribution available under the trademark of Microtrac Model SRA 7995-10, from Leeds &
Northrup Co.
The concentration of coal particles in an aqueous slurry thereof can be determined in accordance with the heat-drying method of Japanese Industrial Standard (JIS) M 8812.
In view of Fig. 1, it is understood that where the variation coefficient C of coal particle sizes is in the range of from 0.3 to about 0.5, the concentration of the coal particles in the coal aqueous slurry having a viscosity of 1000 cp is in the range of from about 65%
to about 72% and increases with the increase in the variation coefficient C of the coal particle sizes, and where the variation coefficient C of the coal particle sizes is more than 0.5, the concentration of the coal particles in the coal aqueous slurry having a viscosity of 1000 cp becomes substantially constant at a level of about 71% to about 73~.
Figure 2 shows the relationship between the variation coefficient C of the coal particle sizes in a coal aqueous slurry and the precipitation percentage of the coal particles when a dispersion stability test is applied to the coal aqueous slurry in the following manner.
In the dispersion stability test, a coal aqueous slurry is subjected to a 20G centrifugal acceleration test for 8 hours, and the percentage of the precipitated portion of the coal particles based on the entire weight of the coal particles in the coal aqueous slurry is calculated.
~ ~ 4~ 9 7 Figure 2 indicates that the precipitation percentage of the coal particles at a satisfactory level of about 60~ or less can be obtained at a variation coefficient of the coal particle sizes of the coal aqueous slurry of 0.3 or more. In particular, where the variation coefficient C of the coal particle sizes is about 0.5 or more, the precipitation percentage of the coal particles is substantially constant at a level of 10% or less.
Figure 3 shows the relationship between the variation coefficient C of the coal particle sizes of a coal aqueous slurry and the ratio (~) of the minimum amount of a dispersing agent needed to adjust the viscosity of the coal aqueous slurry to a standard level of lO00 cp. at the concentration as indicated in Fig. l, to the entire amount of the coal particles.
Figure 3 shows that, at the variation coefficient C
of the coal particle sizes of 0.3 or more, the necessary minimum amount of the dispersing agent is at a satisfactory level of 0.8% or less. In particular, where the variation coefficience is about 0.4 or more, the necessary minimum amount of the dispersing agent is reduced to a low level of 0.4~ or less.
~he coal particle size distributions of the coal aqueous slurries ~, ~ and ~ indicated in Figs. l to 3 are indicated in Fig. 4.
From the coal particle size distribution curves, the variation coefficient C was calculated as follows.
Coal aqueous slurry ~: C = 0.722 " ~: C = 0.473 ~ ~: C = 0.344 The processes of the present invention for producing the above-mentioned high concentration coal aqueous slurry will be explained in detail below.
In one process of the present invention, a coal material consists of a mixture of two types of portions PC and PF each having a different particle size 2~2~97 g of the coal particles therein.
The coal particles in portion FC preferably have a size of from l00 ~m to 500 ~m and are in a content of 30% by weight or more.
Also, the coal particles in portion PF pr~ferably have a size of l00 ~m or less, and a content of coal particles having a size of l0 ~m or less is 40% by weight or more.
Preferably, the mixing ratio in weight of the portion PF to the portion PC is in the range of 8:3 to 5:5.
Also, in the above-mentioned process, the aqueous medium preferably contains a dispersing additive consisting of, for example, at least one dispersing agent for preventing the agglomeration of the coal particles, in an amount needed to ad~ust the viscosity of the resultant coal aqueous slurry to a standard level of l000 cp or less. The amount of the additive is preferably in the range of from 0.3~ to 0.8~ based on the entire weight of the coal particles in the coal aqueous slurry.
The dispersing agent preferably comprises at least one member selected from non-ion and anion ~urface active agents usually employed for the conventional coal aqueous slurry.
Optionally, a stabilizer for preventing the deposition of the coal particles is added to the coal particle aqueous slurry. The stabilizer preferably comprises at least one member selected from cellulose compounds, for example, alkali metal salts of carboxymethyl cellulose and xanthan gum materials, usually utilized for the conventional coal aqueous slurry.
In this process of the present invention, a coal material is pulverized in a wet pulverizing manner and the resultant coal particles in an aqueous medium (water) are dehydrated to provide dehydrated coal cakes comprising 60% by weight or more of coal particles having a size of 500 ~m or less; the resultant de-hydrated coal cakes are mixed with an aqueous medium containing a dispersing additive in a kneader to provide a coal aqueous slurry (A) containing 60~ to 80% by weight of the coal particles; a portion (B) of the coal aqueous slurry (A) is subjected to a further fine pulverizing procedure to further finely pulverize the coal particles in the portion (B); and the resultant further finely pulverized portion (B) is mixed with the remaining portion (D) of the coal aqueous slurry (A), to provide a high concentration coal aqueous slurry having a coal particle size variation coefficient C of 0.3 or more.
In the above-mentioned process, preferably the portion (B) of the coal aqueous slurry (A) is in an amount of 50% to 80~, based on the entire weight of the coal aqueous slurry (A). Also, the fine pulverizing procedure is preferably carried out to an extent such that the resultant further finely pulverized coal particles having a size of 5 ~m or less in the portion (B) are in a content of 15% by weight or more.
The above-mentioned process will be further explained with reference to Fig. 5.
In Fig. S, a pulverizer or mill 1 is charged with a coal material and an aqueous medium through an inlet 2, and the coal material is pulverized at a low concentration of 50% by weight or less. The resultant coal aqueous slurry is fed into a classifying device 4 through a conduit 3, and a classified portion of the coal aqueous slurry containing coal particles having a particle size of 500 ~ or less, preferably 200 ~m or less, is fed into a dehydrating device 5 and dehydrated to provide dehydrated coal particle cakes. The remaining portion of the coal aqueous slurry containing coarse coal particles is returned to the pulverizer 1 through the inlet 2 and re-pulverized.
i 9 7 The coal particle cakes formed in the dehydrating device S are introduced into a kneader 6 and mixed in the kneader 6 with an aqueous medium in an amount necessary to adjust the concentration of the coal particles to a level of 60% to 80%, and preferably, containing an additive in an amount of 0.3% to 0.8%
based on the entire weight of the coal particles in the cakes.
The resultant coal aqueous slurry (A) is withdrawn from the kneader 6 through a conduit 7. A portion (B) of the coal aqueous slurry (A), preferably in an amount of about 50% to about 80% by weight, is fed into a pulverizer 9 to further finely pulverize the coal particles in the portion (B) and the resultant portion (B) containing the further finely pulverized coal particles is fed into a kneader 10 and mixed therein with the remaining portion (D) of the coal aqueous slurry (A) in an amount of from 20% to 50% by weight, which is directly introduced from the kneader 6 into the kneader 10 through a conduit 8.
The further fine pulverizing procedure is carried out preferably to an extent such that, after the portion (B) is mixed with the remaining portion (D), the resultant coal aqueous slurry contains coal particles having a size of 5 ~ or less in a content of 15~ by weight or more, more preferably 20% by weight or more, based on the total weight of the coal particles in the resultant high concentration coal aqueous slurry, and the resultant high concentration coal aqueous slurry is recovered from the kneader 10 through a conduit 11.
In another process for producing the high concen-tration coal aqueous slurry of the present invention, a coal material is pulverized in a high concentration of 60% to 80~ by weight in an aqueous medium containing a dispersing additive to provide a moiety slurry (E) consisting of a high concentration coal aqueous slurry containing coal particles having a size of 100 ~n or 2 ~ 7 less; separately, a moiety cake (F) consisting of dehydrated coal cakes containing coal particles having a size of 500 ~ or less, preferably 100 ~m or more, is prepared by pulverizing a coal material in a low concentration of, for example, 30 to 50% by weight, in an aqueous medium free from the additive and by dehydrating the resultant low concentration coal aqueous slurry; and the moiety slurry (E) is mixed with the moiety cake (F).
Before the step of mixing the moiety slurry (E) with the moiety cake (F) in the above-mentioned process, the moiety cake (F) may be mixed and kneaded with one or both of an aqueous medium and a portion of the final high concentration coal aqueous slurry prepared in the foregoing procedure, to provide a moiety slurry (G) consisting of an aqueous slurry of coal particles in a concentration of 60% to 80~ by weight, and the resultant moiety slurry (G) then mixed with the moiety slurry (E).
In the above-mentioned process, the moiety cake (F) may be further mixed with a dispersing additive in an amount of 0.3 to 0.8~ based on the weight of the coal in the moiety slurry (G).
In the moiety slurry (E), the coal particles contained preferably have a size of from 100 ~ to 500 ~m and are in a content of 30% by weight or more.
Also, in the moiety cake ( F ) or the moiety slurry (G), the coal particles preferably have a size of 100 or less, and contain particles having a size of 10 um or less in a content of 40~ by weight or more.
Preferably, the moiety slurry (E) is mixed with the moiety cake (F) or the moiety slurry (G) in a mixing ratio such that the ratio in weight of the coal particles in the moiety slurry (E) to the coal particles in the moiety cake (F) or the moiety slurry (G) is in the range of from 8:2 to 5:5.
After mixing the moiety slurry (E) with the moiety cake ( F ) or the moiety slurry (G) in the above-mentioned ~ 7 process, the resultant high concentration coal aqueous slurry preferably contains coal particles having a size of 5 ~ or less and in a content of 15% by weight or more, more preferably 20% by weight or more, based on the total weight of the coal particles in the resultant high concentration coal aqueous slurry.
Referring to Fig. 6, a coal material and an aqueous medium free from an additive are charged into a pulverizer or mill la through an inlet 2a, to provide a low concentration coal aqueous slurry. The resultant low concentration coal aqueous slurry is introduced into a classifying device 4 through a conduit 3a and a classified moiety slurry consisting of a portion of the pulverized coal aqueous slurry and containing coal particles having a size of 500 un or less, preferably 200 um or less r is introduced into a dehydrating device 5. The remaining portion of the coal aqueous slurry containing coarse coal particles is recycled to the pulverizer la through the inlet 2a and re-pulverized.
The moiety cake (F) is introduced from the dehydrating device 5 into a kneader 6 and mixed and kneaded with at least one member selected from an aqueous medium which contains an additive, for example, a dispersing agent, in an amount of 0.3% to 0.8% based on the weight of the coal particles, and a portion of the final high concentration coal aqueous slurry prepared in a foregoing procedure and supplied through a conduit 11, to convert the moiety cake (F) to a moiety slurry moiety (G) consisting of an aqueous slurry of coal particles in a concentration of 60% to 80% by weight.
The moiety slurry (G) is fed from the kneader 6 into a kneader 10 through a conduit 7.
Separately, a coal material, an aqueous medium, and a dispersing additive are fed into a pulverizer lb through an inlet 2b and the coal material is pulverized 2~-~2i~7 therein at a high concentration to provide a moiety slurry (E) consisting of a high concentration coal aqueous slurry containing pulverized coal particles having a size of 100 ~ or less.
In the pulverizer lb, the dispersing additive is preferably in an amount of from 0.3% to 0.8% based on the weight of the coal particles.
The moiety slurry (E) is introduced from the pulverizer lb into the kneader 10 through a conduit 3b and mixed with the moiety slurry (G) therein.
The moiety cake (F) may be directly introduced into the kneader 10 together with an additional amount of an aqueous medium and an additive.
In an example, a high concentration coal aqueous slurry was prepared by the process as indicated in Fig. 6.
A moiety slurry (E) was prepared from a coal material, water, and an anionic surface active agent in an amount of 0.4% based on the weight of the coal material in the pulverizer lb. The resultant moiety slurry (E) contained pulverized coal particles at a coal particle concentration of about 68% by weight. The pulverized coal particles had a size of 100 ~ or less and contained particles having a size of 10 ~ or less in a content of 40~, based on the entire weight of the coal particles. The moiety slurry (E) was fed into the kneader 10.
A moiety cake (F) was prepared from a coal material and an aqueous medium free from the dispersing additive by using the pulverizer la, the classifying device 4, and the dehydrating device 5, and then fed together with an aqueous medium into the kneader 6 to provide a moiety slurry (G) containing coal particles having a size of 200 ~ or less and in a concentration of about 75~ by weight.
The mixing ratio of the moiety slurry (E) to the moiety slurry (G) corresponded to a mixing ratio in .
2 ~ 9 7 weight of the coal particles in the moiety slurry (E) to those in the moiety slurry (G), of 70:30.
The resultant high concentration coal aqueous slurry contained pulverized coal particles having a size of 200 ~ or less and in a concentration of about 70%, and had a variation coefficient C of the size of the coal particles of 0.495.
In accordance with the present invention, a coal aqueous slurry having a high concentration and a high dispersion stability of coal particles during storage and transportation, and thus utilizable for industrial use, can be obtained by controlling only the largest size of the coal particles and the variation coef-ficient C of size of coal particle to specific levels, respectively.
Also, the present invention effectively reduces the amounts of the dispersing agent and/or stabilizer needed to stabilize the coal particles dispersion.
Claims (8)
1. A high concentration coal aqueous slurry comprising coal particles having a particle size of 500 µm or less and dispersed in an aqueous medium containing a dispersing additive, at a particle size distribution in which a coefficient of variation in size of the coal particles is 0.3 or more determined in accordance with the equation (I):
C = .sigma./M (I) wherein C represents the coefficient of variation in the size of the coal particles, M represents an average general logarithmic size of the coal particles calculated in accordance with the equation (II):
M = .SIGMA.(log10Si) x Vi (II) in which M is as defined above, Si represents an average size in µm of the coal particles in fraction No. i which is one of a plurality of fractions provided by dividing the entire amount of the coal particles in accordance with the order of the particle size, each fraction consisting of coal particles having a size in a predetermined range, and Vi represents a ratio of the amount in weight or volume of the portion of the coal particles in fraction No. i to the entire amount of the coal particles, and o represents a standard deviation of the size of the coal particles calculated in accordance with the equation (III):
.sigma. = (.SIGMA.((log10Si - M) x Vi)2)0.5 (III) in which Si, M and Vi are as defined above.
C = .sigma./M (I) wherein C represents the coefficient of variation in the size of the coal particles, M represents an average general logarithmic size of the coal particles calculated in accordance with the equation (II):
M = .SIGMA.(log10Si) x Vi (II) in which M is as defined above, Si represents an average size in µm of the coal particles in fraction No. i which is one of a plurality of fractions provided by dividing the entire amount of the coal particles in accordance with the order of the particle size, each fraction consisting of coal particles having a size in a predetermined range, and Vi represents a ratio of the amount in weight or volume of the portion of the coal particles in fraction No. i to the entire amount of the coal particles, and o represents a standard deviation of the size of the coal particles calculated in accordance with the equation (III):
.sigma. = (.SIGMA.((log10Si - M) x Vi)2)0.5 (III) in which Si, M and Vi are as defined above.
2. A process for producing the high concentration coal aqueous slurry as claimed in claim 1, comprising the steps of:
preparing dehydrated coal cakes comprising 60% by weight or more of coal particles having a size of 500 µm or less, by pulverizing a coal material in a wet pulverizing manner and dehydrating the resultant coal particles;
mixing the dehydrated coal cakes with water and a dispersing additive in a kneader to provide a coal aqueous slurry (A) containing 60% to 80% by weight of the coal particles:
subjecting a portion (B) of the coal aqueous slurry (A) to a further fine pulverizing procedure to further finely pulverize the coal particles in the portion (B); and mixing the resultant further finely pulverized portion (B) with the remaining portion (D) of the coal aqueous slurry (A).
preparing dehydrated coal cakes comprising 60% by weight or more of coal particles having a size of 500 µm or less, by pulverizing a coal material in a wet pulverizing manner and dehydrating the resultant coal particles;
mixing the dehydrated coal cakes with water and a dispersing additive in a kneader to provide a coal aqueous slurry (A) containing 60% to 80% by weight of the coal particles:
subjecting a portion (B) of the coal aqueous slurry (A) to a further fine pulverizing procedure to further finely pulverize the coal particles in the portion (B); and mixing the resultant further finely pulverized portion (B) with the remaining portion (D) of the coal aqueous slurry (A).
3. The process as claimed in claim 2, wherein the portion (B) of the coal aqueous slurry (A) is in an amount of 50% to 80% based on the entire weight of the coal aqueous slurry (A), and the fine pulverizing procedure is carried out to an extent such that, after the portion (B) is mixed with the remaining portion (D), the resultant coal aqueous slurry contains coal particles having a size of 5 µm or less in a content of 15% by weight or more.
4. A process for producing a high concentration coal aqueous slurry as claimed in claim 1, comprising the steps of:
pulverizing a coal material at a high concentration of 60% to 80% by weight in an aqueous medium containing a dispersing additive, to provide a moiety slurry (E) consisting of a high concentration coal aqueous slurry containing coal particles having a size of 100 µm or less; and separately providing a moiety cake (F) consisting of dehydrated coal cakes containing coal particles having a size of 500 µm or less, by pulverizing a coal material in a low concentration in an aqueous medium free from the dispersing additive and dehydrating the resultant low concentration coal aqueous slurry; and mixing the moiety slurry (E) with the moiety cakes (F).
pulverizing a coal material at a high concentration of 60% to 80% by weight in an aqueous medium containing a dispersing additive, to provide a moiety slurry (E) consisting of a high concentration coal aqueous slurry containing coal particles having a size of 100 µm or less; and separately providing a moiety cake (F) consisting of dehydrated coal cakes containing coal particles having a size of 500 µm or less, by pulverizing a coal material in a low concentration in an aqueous medium free from the dispersing additive and dehydrating the resultant low concentration coal aqueous slurry; and mixing the moiety slurry (E) with the moiety cakes (F).
5. The process as claimed in claim 4, wherein before mixing with the moiety slurry (E) the moiety cake (F) is mixed and kneaded with one or both of an aqueous medium and a portion of the final high concentration coal aqueous slurry prepared in a foregoing procedure, to provide a moiety (G) consisting of an aqueous slurry of coal particles in a concentration of 60% to 80% by weight, and the resultant moiety slurry (G) is then mixed with the moiety slurry (E).
6. The process as claimed in claim 5, wherein the moiety cake (F) is further mixed with a dispersing additive in an amount of 0.3 to 0.8% based on the weight of the coal in the moiety slurry (G).
7. The process as claimed in claim 4, 5 or 6, wherein the moiety slurry (E) is mixed with one of the moiety cake (F) and the moiety slurry (G) in a mixing ratio such that the ratio in weight of the coal particles in the moiety slurry (E) to those in the moiety cake (F) or the moiety slurry (G) is in the range of from 8:2 to 5:5.
8. The process as claimed in any of claims 4 to 7, wherein the resultant coal aqueous slurry contains coal particles having a size of 5 µm or less in a content of 15% by weight or more.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1063576A JP2603127B2 (en) | 1989-03-17 | 1989-03-17 | Method for producing high concentration coal / water slurry |
| JP1-63576 | 1989-03-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2012197A1 true CA2012197A1 (en) | 1990-09-17 |
Family
ID=13233223
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002012197A Abandoned CA2012197A1 (en) | 1989-03-17 | 1990-03-14 | High concentration coal aqueous slurry and process for producing same |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JP2603127B2 (en) |
| KR (1) | KR0138512B1 (en) |
| CN (1) | CN1028242C (en) |
| CA (1) | CA2012197A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10287522B2 (en) | 2013-01-31 | 2019-05-14 | General Electric Company | System and method for preparing coal water slurry |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102732341A (en) * | 2011-04-07 | 2012-10-17 | 通用电气公司 | Coal water slurry and preparation method thereof |
| CN105038878B (en) * | 2015-07-08 | 2017-03-01 | 中煤科工清洁能源股份有限公司 | A kind of method preparing water-coal-slurry |
| KR101992622B1 (en) | 2017-04-21 | 2019-09-30 | 한국에너지기술연구원 | A viscosity measurement apparatus for high temperature coal slurry and method for testing stability of high temperature coal slurry using thereof |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59157184A (en) * | 1983-02-28 | 1984-09-06 | Babcock Hitachi Kk | Preparation of coal-water slurry |
| JPS60156796A (en) * | 1984-01-25 | 1985-08-16 | Mitsubishi Heavy Ind Ltd | Manufacture of highly concentrated coal-water slurry |
| JPS62265392A (en) * | 1986-05-12 | 1987-11-18 | Kubota Ltd | Coal/water slurry |
-
1989
- 1989-03-17 JP JP1063576A patent/JP2603127B2/en not_active Expired - Lifetime
-
1990
- 1990-03-14 CA CA002012197A patent/CA2012197A1/en not_active Abandoned
- 1990-03-17 CN CN90102130A patent/CN1028242C/en not_active Expired - Lifetime
- 1990-03-17 KR KR1019900003605A patent/KR0138512B1/en not_active IP Right Cessation
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10287522B2 (en) | 2013-01-31 | 2019-05-14 | General Electric Company | System and method for preparing coal water slurry |
Also Published As
| Publication number | Publication date |
|---|---|
| KR0138512B1 (en) | 1998-04-27 |
| CN1046179A (en) | 1990-10-17 |
| AU628490B2 (en) | 1992-09-17 |
| JP2603127B2 (en) | 1997-04-23 |
| AU5133590A (en) | 1990-09-20 |
| KR900014567A (en) | 1990-10-24 |
| JPH02245095A (en) | 1990-09-28 |
| CN1028242C (en) | 1995-04-19 |
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