JP2573136B2 - Method for producing deashed high concentration coal water slurry - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a high-concentration degasser which can be easily handled as a fluid fuel, such as heavy oil, etc., such as pumping, loading and storage, and which can be burned by a boiler burner. The present invention relates to a method for producing ash coal-water slurry.

[0002]

2. Description of the Related Art It has been conventionally practiced to pulverize coal into a coal-water slurry, but there is a problem in treating ash in the coal. Coal is usually present underground and contains some non-combustible components (ash) such as Al ₂ O ₃ , SiO ₂ or Fe ₂ O ₃ . This ash not only wears the boiler walls during combustion and lowers combustion efficiency, but also makes transportation costs uneconomical. Therefore, when using raw coal having a high ash content in the production of a high-concentration coal-water slurry, the coal is selected with a relatively coarse particle size,
There is also a method of producing a slurry by pulverizing only low-ash coal as a raw material for a slurry. However,
In this method, coal other than low ash content is not used as a raw material for slurry, and there is a problem that the utilization efficiency of coal is reduced.

[0003] In the case of using raw coal having a relatively high ash content, there is also a method of pulverizing the coal to reduce the ash content, and then subjecting the entire coal to a deashing treatment. There is a problem that not only the deashing treatment equipment is increased in size and the processing cost is accordingly increased, but also the loss of coal in the deashing process is increased.

In order to solve the above problems, Japanese Patent Laid-Open No.
No. 9-215391 discloses that raw coal that has been crushed in advance is classified into fine coal and coarse coal by a sieve, and the coarse coal is sent to a coarse-grain separator, and low-ash coal, medium-ash coal, and high-ash coal are separated. After being separated into specific gravity and charcoal (hard), this medium-ash coal is finely pulverized together with fine-grained charcoal by a pulverizer to form a coal-water slurry, and then guided to a flotation machine to perform demineralization treatment to remove the deashed slurry. (Floss), and this floss is introduced into a dehydrator to form a relatively high-concentration demineralized slurry. On the other hand, the low-ash coal is pulverized and mixed with the demineralized slurry from the dehydrator by a pulverizer. A process for producing a deashed, highly concentrated slurry having a solids concentration above 60% by weight is described.

Japanese Patent Application Laid-Open No. Sho 61-123699 discloses that a coal-water slurry is obtained by separating coarse coal into low ash coal, medium ash coal, and high ash coal, and finely pulverizing the medium ash coal. , After being separated by floating separation, dehydrated to obtain a solid concentration of 40 to 60 wt%.
This coal-water slurry and the coarse-grained low-ash coal are finely pulverized, and based on the set value of the solid concentration of the high-concentration slurry of the final product, the coarse-grained coal and the coal-
A method of producing a deashed coal-water slurry in which a part of low ash coal obtained by specific gravity separation is mixed with medium ash coal in order to adjust the mixing ratio with the amount of coal in the water slurry. Is described.

JP-B-3-21596 discloses a compound of the general formula CH ₂ ＣC (R) COO- (XO) ₁ -Y (wherein R is a hydrogen or methyl group, and X is C 2
Alkylene group of ₁ to 4, ₁ is a number of 1 to 100 on average, and Y is hydrogen, an alkyl group of 1 to 5 carbon atoms, a phenyl group or an alkyl group of 1 to 9 carbon atoms as 1 to 3 substituents. Shows an alkylphenyl group having With a polyalkylene glycol mono (meth) acrylate monomer (I) represented by the following general formula: CH ₂ ＣC (R) COOZSO ₃ M (wherein, R is a hydrogen or methyl group, and Z is 1 carbon atom)
To 4 alkylene groups, M represents hydrogen, an alkali metal, an alkaline earth metal, an ammonium group or an amine base. A) a sulfoalkyl (meth) acrylate-based monomer (II) represented by the formula (I):
And the molar ratio of the monomer (II) to 1: 5 to 1: 500
And the monomer (I) and the monomer (II)
Of a water-soluble copolymer obtained from a raw material monomer having a total of 50 mol% or more of all monomers, and a dispersion selected from a polystyrene sulfonate or a styrene-styrene sulfonate copolymer. It is described that the agent is added to the coal-water slurry.

[0007]

Problems to be Solved by the Invention
Considering the process described in No. 91 in terms of coal pulverization, a pulverized coal slurry having a relatively low concentration is obtained, and this and a coarsely pulverized low ash content are charged into a wet pulverizer to obtain a desired high concentration pulverized coal. A method for producing a slurry, that is, a two-stage pulverization method is used. This method makes it possible to widen the particle size composition of the pulverized coal and increase the solid concentration of the coal-water slurry. Therefore, the concentration of the pulverized coal slurry to be fed into the wet pulverizer is 40 to 40%. A range of 60% by weight is desirable. Therefore, even in the production of a deashed high-concentration slurry by a two-stage pulverization method combining coarse-grain separation and pulverized coal flotation, it is possible to produce a high-concentration slurry having a solid concentration of about 70% by weight, and flotation and dewatering. The slurry concentration obtained from the process is substantially limited to a specific range, 40-60% by weight.

When a high-concentration slurry is produced, the slurry concentration, which is an important factor, is usually set. After this concentration is set, if the slurry concentration obtained in the above-mentioned flotation / dewatering step is limited, the final pulverization step (pulverizer)
The mixing ratio between the amount of low ash coal to be sent to and the amount of coal in the slurry from the flotation / dewatering process must be within a certain range. However, in JP-A-59-215391, the mixing ratio is uniquely determined by the properties of the coal, the coal particle size of the coarse particle sorting, and the coarse particle sorting conditions. Is not always satisfied.

The method described in JP-A-61-123699 requires a dewatering step, a slurry concentration adjusting step, and the like after the flotation step, so that the steps are complicated and the consumption of the dehydrator is greatly increased. In addition, there is a problem that the scale-up is limited.

In the above-mentioned conventional publication, flotation is carried out after washing with acidic water, or washing is carried out with acidic water after flotation, so that the eluted components and ash in coal are simultaneously removed. At the same time, a method of mixing deashed coal (floss) obtained by flotation treatment with low-ash coal obtained by specific gravity separation to form a deashed high-concentration coal water slurry, and at that time, a polystyrene-based dispersant and Nothing is disclosed about a method using an additive blended with a poly (meth) acrylic acid-based dispersant.

In producing a high-concentration coal-water slurry,
As described above, previously performing decalcification such as specific gravity selection, flotation, and underwater granulation has been studied, and some of them have been put to practical use. However, when producing a high-concentration coal water slurry of low-grade coal, multivalent cations of elements such as calcium, magnesium and iron are eluted from the coal, and these eluted ions produce a high-concentration coal-water slurry. In this case, the dispersing action of the anionic dispersing agent added is hindered and the amount of the dispersing agent added is increased, and the eluted ions increase the cohesiveness of the slurry, causing blockage and storage during pipe flow. It causes coagulation and sedimentation in the tank.

In order to solve the above problems, it is necessary to remove alkaline earth elements and the like from coal in advance to reduce the amount of polyvalent cations eluted. The specific gravity sorting method, the flotation method, and the underwater granulation method, which have been conventionally studied, have a small effect of removing alkaline earth elements and the like. In addition, in order to produce a stable deashed coal high-concentration coal water slurry that has excellent stability and hardly causes sedimentation separation, it is necessary to adjust the rheology to an appropriate rheology according to the properties of the raw coal and the degree of deashing. However, it was difficult to adjust rheology only by adding a conventional polystyrene-based dispersant or poly (meth) acrylic acid-based dispersant.

In order to reduce the amount of additive (dispersant) added when producing a high-concentration coal-water slurry, improve the ultimate concentration, reduce the cohesiveness of the produced slurry, and increase the melting point of combustion ash. Contains calcium contained in the raw coal,
It is effective to remove elements such as magnesium, iron, sodium, and potassium.In order to selectively remove these alkali and alkaline earth elements, flotation treatment is performed after washing with acidic water, or The present inventors have found that a method of performing flotation treatment and then washing with acidic water is effective. Also, in addition to acid washing, when producing a high-concentration slurry of demineralized charcoal obtained, the use of a polystyrene-based dispersant and polymethacrylic acid-based dispersant is used to ensure proper rheological stability. The present inventors have found that it is possible to produce a high-density slurry of deashed charcoal having a good quality.

The present invention has been made based on these findings, and solves the above-mentioned problems, can reduce the amount of a dispersant to be added, is excellent in stability, and can easily adjust the rheology. It is an object of the present invention to provide a method capable of producing a concentrated coal water slurry.

[0015]

In order to achieve the above-mentioned object, a method for producing a deashed high-concentration coal water slurry according to the present invention is characterized in that a medium-ash coal obtained by specific gravity separation is treated with acidic water to a pH of 5 or more.
After dewatering by flotation after washing in the range of ~ 1 or by dewatering coal by flotation, the coal is washed in the pH range of 5 to 1 and then added with the low ash coal obtained by specific gravity separation. A method of producing a deashed high-concentration coal water slurry by mixing with a dispersing agent (dispersant) and water and wet-grinding the mixture. A polystyrene sulfonic acid-based dispersant and a poly (meth) acrylic acid-based dispersant are added as additives. It is characterized by using.

Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 shows one embodiment of the method of the present invention. 1
0 is a specific gravity sorter, 12 is a first wet mill, 14 is an acid washing tank, 16 is a flotation machine, and 18 is a second wet mill. As a wet mill, a ball mill, a rod mill, or the like is used. The method for producing a deashed high-concentration coal water slurry in FIG. 1 includes the following steps (a) to (d). (A) a specific gravity sorting step of specific gravity sorting raw coal into low ash coal, medium ash coal and high ash coal, (b) a first wet grinding step of wet crushing the specific ash sorted medium ash coal into a water slurry, (C) a flotation step of adding a collector and a foaming agent to the slurry from the first wet pulverization step and blowing gas to flotate and demineralize, (d) demineralized coal from the flotation step and The low-ash coal from the specific gravity separation step is composed of a water-soluble copolymer containing a polyalkylene glycol mono (meth) acrylate monomer and a sulfoalkyl (meth) acrylate monomer as essential raw material monomers. A dispersant (A), a dispersant (B) selected from a polystyrene sulfonate and a styrene-styrene sulfonate copolymer as a main component, and water are added, and wet pulverization is performed. Density 6
A second wet grinding step to obtain a deashed coal-water slurry in excess of 0% by weight;

In FIG. 1, an acid or acidic water is added to and mixed with the slurry from the first wet grinding step, and
After adjusting to pH 5 to 1 and washing with stirring, this slurry is introduced into a flotation step. The method in this case includes the following steps (a) to (e). (A) a specific gravity sorting step of specific gravity sorting raw coal into low ash coal, medium ash coal and high ash coal, (b) a first wet grinding step of wet crushing the specific ash sorted medium ash coal into a water slurry, (C) an acid washing step in which an acid or acidic water is added to and mixed with the slurry from the first wet step, and the slurry is adjusted to a pH of 5 to 1 and stirred and washed; (d) a slurry collected from the acid washing step Flotation step of adding a foaming agent and a foaming agent and blowing gas to flotate to demineralize, (e) deashed coal from the flotation step and low-ash coal from the specific gravity separation step,
A dispersant (A) comprising a water-soluble copolymer containing a polyalkylene glycol mono (meth) acrylate monomer and a sulfoalkyl (meth) acrylate monomer as essential raw materials, and a polystyrene sulfonate And styrene-
A dispersing agent having a dispersing agent (B) selected from a styrene sulfonate copolymer as a main component, and water are added and wet pulverized to obtain a deashed coal-water slurry having a solid concentration exceeding 60% by weight. Second wet grinding step, In the above method, if the pH of the coal slurry to be acid-washed is less than 1, the acid concentration becomes too high to wash sufficiently, and the material selection of the apparatus becomes extremely difficult. Become. On the other hand, when the pH exceeds 5, the acid concentration becomes too low to wash sufficiently.

FIG. 2 shows another embodiment of the method of the present invention. In this example, the low ash coal from the specific gravity sorting process is
Low ash coal wet pulverizer 20 such as ball mill and rod mill
And a low-ash coal-wet pulverization step of introducing the mixture to a second wet-pulverization step after wet pulverization in advance.

FIG. 3 shows another embodiment of the method of the present invention. The method of the present embodiment is such that the acid washing step and the flotation step in FIG. 1 are interchanged, and acid or acidic water is added to and mixed with the demineralized coal from the flotation step, and the demineralized coal is adjusted to pH 5-1. After adjusting to the range and washing with stirring, this deashed charcoal is introduced into the second wet grinding step. The method in this case includes the following steps (a) to (e). (A) a specific gravity sorting step of specific gravity sorting raw coal into low ash coal, medium ash coal and high ash coal, (b) a first wet grinding step of wet crushing the specific ash sorted medium ash coal into a water slurry, (C) a flotation step of adding a collector and a foaming agent to the slurry from the first wet pulverization step and blowing a gas to flotate and demineralize; An acid washing step in which acid or acidic water is added and mixed, and the deashed coal is adjusted to pH 5 to 1 and stirred and washed; (e) deashed coal from the acid washing step and low ash coal from the specific gravity separation step To
A dispersant (A) comprising a water-soluble copolymer containing a polyalkylene glycol mono (meth) acrylate monomer and a sulfoalkyl (meth) acrylate monomer as essential raw materials, and a polystyrene sulfonate And styrene-
A dispersing agent having a dispersing agent (B) selected from a styrene sulfonate copolymer as a main component, and water are added and wet pulverized to obtain a deashed coal-water slurry having a solid concentration exceeding 60% by weight. Second wet grinding step, As the acid used in the present invention, hydrochloric acid, nitric acid, acetic acid, sulfuric acid and the like are used.

FIG. 4 shows yet another embodiment of the method of the present invention. In the present embodiment, the low ash coal from the specific gravity separation step is introduced into a low ash coal wet pulverizer 20 such as a ball mill and a rod mill and wet-pulverized in advance, and then introduced into the second wet pulverization step. It is provided with a pulverizing step.

In the above method of the present invention, the ratio of the dispersant (A) to the dispersant (B) is adjusted so that A / B = 1/2.
It is preferred to be in the range of 0 to 10/1. A / B is 1 /
If the ratio is less than 20 or the ratio A / B exceeds 10/1, a satisfactory effect cannot be obtained.

[0022]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following Examples, and appropriate modifications may be made without departing from the scope of the invention. It can be implemented by Example 1 With respect to Chinese coal having the properties shown in Table 1, raw coal was subjected to demineralization treatment by a conventional flotation method (Comparative Example 2), and acidic water having a pH of 4.0 (hydrochloric acid water) according to the present invention. ), And the properties of the demineralized coal and the raw coal (Comparative Example 1) subjected to flotation treatment were compared. The test Chinese coal has a high Ca content, and when producing a high-concentration coal water slurry, the action of the dispersant is inhibited by the dissolved Ca ²⁺ ions, and the dispersant addition rate is 0.9 wt. %, Which is a factor that reduces economic efficiency.

[0023]

[Table 1]

The method and conditions for the washing with acidic water and the treatment by the flotation method in the present embodiment are as follows. (1) After coarsely pulverizing the raw material coal, it was separated into three stages in a specific gravity range of 1.20 to 1.50 using a mixed specific gravity liquid of carbon tetrachloride and benzene. Separated specific gravity 1.20 to 1.30
Coal of low ash coal, coal of specific gravity 1.30-1.40 was medium ash coal, and coal of specific gravity 1.40-1.50 was high ash coal. (2) Water was mixed with 2 kg of a 50% by weight coal water slurry obtained by pulverizing a medium ash coal to 50% by weight or less to prepare a 10% by weight slurry. (3) While stirring the slurry in the stirring layer, hydrochloric acid was added to adjust the pH to 4. (4) After stirring for 20 minutes after the addition of hydrochloric acid, the mixture was transferred to a flotation machine, to which 10 g of kerosene as a collecting agent and 1 g of MIBC (methyl isobutyl carbinol) as a foaming agent were added, and air was added thereto. After stirring and mixing for 10 minutes without blowing air, bubbles were generated while blowing air, and flotation was performed for 10 minutes to collect overflowing decalcified coal (floss). (5) The recovered deashed coal is mixed with the low ash coal separated in (1), water is added to the slurry to a predetermined slurry concentration, and a sodium polystyrene sulfonate-based dispersant and poly (meth) acrylic An additive (dispersant) obtained by mixing an acid-based dispersant in a weight ratio of 1/1 was added at 0.6% by weight based on the solid content based on the active ingredient, and this was wet-pulverized with a wet ball mill, and 200 mesh pass ( 82% by weight)
A coal water slurry having a solid content of 65% by weight was prepared. Table 2 shows the properties of the slurry at this time.

[0025]

[Table 2]

Comparative Example 1 0.9 wt% of a dispersant (sodium polystyrene sulfonate) was added to raw coal, water was added and wet pulverization was carried out, 200 mesh pass 80%, solid content concentration 61 wt%. Was prepared. Table 2 shows the properties of the slurry at this time.

Comparative Example 2 A slurry of flotation-treated coal was prepared by the following treatment method and treatment conditions. (1) Water was mixed with 2 kg of a 50% by weight coal water slurry obtained by wet milling raw coal to 200% or less to 50% by weight to prepare a 10% by weight slurry. (2) Next, 1 g of MIBC (methyl isobutyl carbinol) as a foaming agent and 10 g of kerosene as a collecting agent
After adding and stirring and mixing for 10 minutes without blowing air,
Blow air for 10 minutes to generate air bubbles,
A water slurry (floss) of the overflowing coal was recovered. (3) Next, air was introduced into the flotation machine, and flotation was performed for 10 minutes. (4) The floss collected during the flotation treatment is filtered under pressure,
The treated charcoal was obtained. (5) A dispersant (sodium polystyrene sulfonate) was added to the recovered treated coal at 0.7% by weight based on the coal,
Wet pulverization was performed to prepare a coal water slurry having a 200 mesh pass of 81 wt% and a solid content of 62 wt%.

The raw coal water slurry (Comparative Example 1), the conventional water slurry of flotation-treated coal (Comparative Example 2) and the treated coal water slurry after flotation treatment after washing with acidic water according to the present invention (Comparative Example 2) The analysis results of Example 1) are shown in Table 2 in comparison. For conventional flotation processing charcoal, Ca ²⁺ eluted, Mg ²⁺ ion content has been reduced compared to raw coal, processing coal washing after flotation treatment with acid water of the present invention was done, Ca ² Alkaline earth elements such as ⁺ and Mg ²⁺ were further reduced significantly. Further, since the viscosity of the slurry is almost the same level, the coal water slurry according to the method of the present invention can be most concentrated, and the stability is improved because the amount of coagulated sediment is reduced. Was confirmed.

Example 2 A high-concentration coal water slurry was prepared using the treated coal subjected to the flotation treatment after the washing treatment with the acidic water obtained in Example 1, and the conventional flotation treated coal and raw coal. , Ultimate concentration (25 ° C, 1
0 concentration) and the required addition rate of the dispersant. The preparation method was as follows.

(1) Method of the Present Invention (Example 2) In the case of a treated coal obtained by washing medium-ash coal with acidic water (hydrochloric acid water) and then performing a flotation treatment, the method was obtained by the method shown in Example 1. An additive obtained by adding 30% by weight of low-ash coal to the treated coal, and further adding a 2/1 (weight ratio) sodium polystyrene sulfonate-based dispersant and a poly (meth) acrylic acid-based dispersant and water Was added in a predetermined amount, and the mixture was wet-pulverized with a ball mill, and the slurry taken out of the mill was stirred at 3000 rpm for 10 minutes with a homomixer at high speed to produce a high-concentration coal-water slurry. (2) In the case of conventional flotation coal Coal deashed coal obtained by treating medium ash coal by the conventional flotation method is 3
After adding 0% by weight of low ash coal and further adding a predetermined ratio of polystyrene-based dispersant and water, wet-milling with a ball mill, high-speed stirring at 3000 rpm for 10 minutes with a homomixer to produce a high-concentration coal-water slurry. did. (3) In the case of raw coal After coarsely pulverizing coal into 3 mm or less in advance, adding a predetermined ratio of water and a polystyrene-based dispersant, and wet-pulverizing with a ball mill, the slurry is mixed with a homomixer for 30 minutes.
The mixture was stirred at a high speed of 00 rpm for 10 minutes to produce a high-concentration coal water slurry.

Table 3 shows the productivity of the high-concentration coal-water slurry of the coal treated by the method of the present invention (Example 2) produced by the above method, the conventional coal subjected to flotation treatment, and the raw coal. 5 and 6 show the relationship between the coal concentration and the viscosity and the relationship between the dispersant addition rate and the viscosity. FIG. 5 shows a comparison regarding the improvement of the slurry concentration-enhancing property by each cleaning treatment. The coals shown in Table 1 were used as test coals, and the particle size was 78 to 82% of 200 mesh pass. Line (1)
Is a polystyrene sulfonic acid-based dispersant and poly (meth)
An acrylic acid-based dispersant and a weight ratio (w / w) of 2: 1 were added in a total amount of 0.6 wt% according to the method of the present invention. Is a comparative example in which only 0.7 wt% of the dispersant was added.
The comparative example which added wt% is shown.

FIG. 6 shows the dispersant reducing effect of each cleaning treatment. Coal shown in Table 1 was used as the test coal, the coal concentration was 61 to 65 wt%, and the particle size was 78 to 82% of a 200-mesh pass. Line (1) shows that a polystyrene sulfonic acid-based dispersant and a poly (meth) acrylic acid-based dispersant are added at a weight ratio (w / w) of 2: 1 and the slurry concentration is 65 wt%. According to the method of the present invention. Line (2) is a comparative example in which only a polystyrenesulfonic acid-based dispersant was added, and the slurry concentration was 63 wt%. Line (3) is a comparative example in which only a polystyrenesulfonic acid-based dispersant was added, and the slurry concentration was 61 wt%. In the method according to the present invention, the ultimate concentration is 4% by weight as compared with the raw coal, the calorific value per unit weight of the slurry is improved by about 11%, and the required dispersant addition rate is 5%.
0% reduction and the stability of the product slurry could be improved.

[0033]

[Table 3]

[0034]

As described above, the present invention has the following effects. (1) The rheology of the product coal water slurry can be controlled in an appropriate range, and a deashed coal coal water slurry having excellent stability can be produced. (2) When an acid washing step is provided, use Ca, Mg, F
Since elements such as e, Na, and K can be selectively removed, the amount of the dispersant added can be reduced, and the ultimate concentration of the product slurry can be increased.

[Brief description of the drawings]

FIG. 1 is a process explanatory diagram showing one embodiment of a method for producing a deashed high-concentration coal water slurry of the present invention.

FIG. 2 is a process explanatory view showing another embodiment of the method of the present invention.

FIG. 3 is a process explanatory view showing another embodiment of the method of the present invention.

FIG. 4 is a process explanatory view showing still another embodiment of the method of the present invention.

FIG. 5 is a graph showing the relationship between coal concentration and viscosity in Example 2.

FIG. 6 is a graph showing the relationship between the dispersant addition rate and the viscosity in Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Specific gravity sorter 12 1st wet grinder 14 Acid washing tank 16 Flotation machine 18 2nd wet grinder 20 Low ash coal wet grinder

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshitaka Imori 1-1, Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries, Ltd.

Claims (5)

(57) [Claims] 1. The following steps (a) to (d): (a) a specific gravity sorting step in which raw coal is classified into low ash coal, medium ash coal and high ash coal, and (b) specific gravity sorting. (C) adding a collector and a foaming agent to the slurry from the first wet pulverization step and blowing a gas to flotate the slurry. (D) a dealkylated coal from the flotation step and a low ash coal from the specific gravity separation step, a polyalkylene glycol mono (meth) acrylate monomer and a sulfoalkyl (meth) acrylate Dispersant (A) comprising a water-soluble copolymer containing a monomer as an essential raw material monomer
And a dispersant having a dispersant (B) selected from a polystyrene sulfonate and a styrene-styrene sulfonate copolymer as a main component, and water, and wet-pulverized to obtain a solid concentration of 60% by weight. A second wet pulverization step of obtaining a demineralized coal-water slurry exceeding the above. 2. The following steps (a) to (e): (a) a specific gravity separation step of separating raw coal into low ash coal, medium ash coal and high ash coal, and (b) specific gravity separation. (C) adding or mixing acid or acidic water to the slurry from the first wet process to adjust the slurry to a pH of 5 to 1; An acid washing step of stirring and washing, (d) a flotation step of adding a collector and a foaming agent to the slurry from the acid washing step and blowing gas to flotate to demineralize, and (e) flotation step Water-soluble using polyalkylene glycol mono (meth) acrylate-based monomer and sulfoalkyl (meth) acrylate-based monomer as essential raw materials for deashed coal and low-ash coal from the above specific gravity separation process A dispersant (A) comprising a copolymer and polystyrene A dispersant containing a sulfonate and a dispersant (B) selected from styrene-styrene sulfonate copolymer as a main component, and water are added and wet-pulverized to remove demineralization exceeding a solid concentration of 60% by weight. A second wet pulverizing step of obtaining a coal-water slurry. 3. The following steps (a) to (e): (a) a specific gravity separation step of separating raw coal into low ash coal, medium ash coal and high ash coal, and (b) specific gravity separation. (C) adding a collector and a foaming agent to the slurry from the first wet pulverization step and blowing a gas to flotate the slurry. (D) an acid washing step in which acid or acidic water is added to and mixed with the demineralized coal from the flotation step, and the demineralized carbon is adjusted to pH 5-1 to stir and wash; ) A polyalkylene glycol mono (meth) acrylate monomer and a sulfoalkyl (meth) acrylate monomer are used as an essential raw material in the deashed coal from the acid washing step and the low ash coal from the specific gravity selection step. Dispersant (A) composed of a water-soluble copolymer to be used as a polymer, and polystyrene A dispersant containing a sulfonate and a dispersant (B) selected from styrene-styrene sulfonate copolymer as a main component, and water are added and wet-pulverized to remove demineralization exceeding a solid concentration of 60% by weight. A second wet pulverizing step of obtaining a coal-water slurry. 4. The low ash coal wet pulverizing step of wet-pulverizing the low ash coal from the specific gravity sorting step and then introducing the low ash coal into the second wet pulverizing step. A method for producing a deashed high-concentration coal water slurry. 5. The method according to claim 1, wherein the ratio of the dispersant (A) to the dispersant (B) is in the range of A / B = 1/20 to 10/1. 4. The method for producing a deashed high-concentration coal water slurry according to 4.