JP7316993B2 - Method for producing ashless coal - Google Patents

Description

The present invention relates to a method for producing ashless coal.

High-strength coke is used as iron-making coke such as blast furnace coke. In the case of obtaining high-strength coke, so-called high-coking coal, which is conventionally highly caking, is used as raw material coal. However, since hard-coking coal is relatively expensive, techniques for reducing the amount of hard-coking coal used are being studied today.

Attempts have been made to use ashless coal as coking coal capable of obtaining high-strength coke while suppressing the amount of hard-coking coal used. For example, Patent Literature 1 proposes a method of using ashless coal as a caking additive and using mixed coal obtained by mixing this ashless coal with thermal coal as a coke raw material.

JP 2015-193740 A

In Patent Document 1, coal and a solvent are mixed to prepare a slurry, a solution containing a solvent-soluble coal component is separated from the slurry, and the solvent is evaporated from the solution to obtain ashless coal. It is stated that the production of

However, as a result of intensive studies by the present inventors, the method for producing ashless coal described in the above publication has room for further improvement from the viewpoint of improving the extraction rate of solvent-soluble components of coal. I found out.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for producing ashless coal that can improve the extraction rate of solvent-soluble components of coal.

A method for producing ashless coal according to one aspect of the present invention includes a slurry preparation step of preparing a slurry by mixing coal, a solvent and formic acid, and raising the temperature of the slurry prepared in the slurry preparation step to add the above An elution step of eluting solvent-soluble components of coal, a separation step of separating a solution in which the solvent-soluble components are eluted in the solvent from the slurry, and evaporating the solvent from the solution separated in the separation step. and an evaporation step.

In the method for producing ashless coal, coal, solvent and formic acid are mixed in the slurry preparation step, and the slurry is heated in the elution step to improve the extraction rate of solvent-soluble components of coal. can do. More specifically, coal generates radicals (coal radicals) when its temperature is raised to 300° C. or higher. Insufficient extraction of soluble components. On the other hand, the method for producing ashless coal can stabilize coal radicals by heating the slurry after mixing coal and formic acid. As a result, polycondensation of coal caused by coal radicals can be suppressed, and the extractability of solvent-soluble components of coal can be improved.

The temperature for mixing the coal and the formic acid in the slurry preparation step is preferably 80° C. or lower. Thus, by setting the mixing temperature of the coal and the formic acid in the slurry preparation step to be equal to or lower than the upper limit, it is possible to easily and reliably improve the extraction rate of the solvent-soluble components of the coal.

The content of the formic acid in the slurry prepared in the slurry preparation step is preferably 6% by mass or less with respect to the total content of the coal and the formic acid. Thus, when content of the said formic acid is below the said upper limit, it is low-cost and ash-free coal can be manufactured efficiently.

As described above, the method for producing ashless coal according to one aspect of the present invention can improve the extraction rate of the solvent-soluble components of coal.

FIG. 1 is a flowchart showing a method for producing ashless coal according to one embodiment of the present invention. FIG. 2 : is a schematic diagram which shows the manufacturing apparatus of the ash-free coal which can implement the manufacturing method of the ash-free coal of FIG. FIG. 1 to No. 9 is a graph showing the relationship between the content of formic acid in the slurry using bituminous coal No. 9 and the extraction rate of solvent-soluble components of the coal. FIG. 10 to No. 1 is a graph showing the relationship between the content of formic acid in slurries using 12 bituminous coals and the extraction rate of solvent-soluble components of coal.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. For the numerical values described in this specification, it is possible to arbitrarily combine the described upper limit values and lower limit values. In this specification, all numerical ranges from the upper limit to the lower limit that can be combined are described as suitable ranges.

[Method for producing ashless coal]
The method for producing ashless coal in FIG. 1 (hereinafter also referred to as "the production method") includes a slurry preparation step S1 of preparing a slurry by mixing coal, a solvent and formic acid, and a slurry prepared in the slurry preparation step S1 Elution step S2 for eluting the solvent-soluble components of the coal into the solvent by raising the temperature, Separation step S3 for separating the solution in which the solvent-soluble components are eluted in the solvent from the slurry, and separation step S3 and an evaporation step S4 for evaporating the solvent from the separated solution. In the evaporation step S4, the solvent-soluble component is precipitated by evaporating the solvent. This precipitated solvent-soluble component constitutes the ashless coal produced by the production method. In the present invention, "increase the temperature of the slurry prepared in the slurry preparation step" means that after mixing coal and formic acid, the temperature of the mixture of coal and formic acid is increased. It does not limit the temperature rising time of.

First, with reference to FIG. 2, an example of an ashless coal manufacturing apparatus (hereinafter also referred to as "the manufacturing apparatus") capable of implementing the manufacturing method will be described.

[Ash-free coal manufacturing equipment]
The manufacturing apparatus includes a slurry preparation unit 1 for mixing coal X, solvent Y and formic acid F, and increasing the temperature of slurry S prepared in the slurry preparation unit 1 to elute solvent-soluble components of coal X into solvent Y. An elution part 2, a separation part 3 for separating the solution L in which the solvent-soluble component is eluted into the solvent Y from the slurry S, and an _evaporating part (first and an evaporator 4). The separation section 3 solid-liquid separates the slurry S into a solution L and a solid content concentrate M containing solvent-insoluble components. The first evaporator 4 deposits the solvent-soluble components by evaporating the solvent _YR1 . This precipitated solvent-soluble component constitutes the ashless coal HPC produced by the production apparatus. In addition, the manufacturing apparatus includes a first recovery line 5 for recovering the solvent _YR1 evaporated in the first evaporator 4, and a solid content concentrated liquid M separated in the separation section 3. a second recovery line 6 for recovering the solvent _YR2 that is in and

<Slurry Preparation Department>
The slurry preparation unit 1 includes a coal supply unit 11 capable of supplying coal X, a formic acid supply unit 12 capable of supplying formic acid F, a mixing tank 13 in which coal X and formic acid F are mixed, and a solvent Y are stored. a solvent tank 14, a pump 15 for pressure-feeding the solvent Y stored in the solvent tank 14, a preheater 16 for heating the solvent Y pressure-fed by the pump 15, coal X and formic acid F sent from the mixing tank 13 and a mixing pipe 17 for mixing the solvent Y sent from the solvent tank 14 . The coal supply unit 11 and the mixing tank 13, the formic acid supply unit 12 and the mixing tank 13, the mixing tank 13 and the mixing pipe 17, and the solvent tank 14 and the mixing pipe 17 are connected by pipes.

(Coal supply department)
As the coal supply unit 11, a known hopper such as a normal pressure hopper or a pressurized hopper can be used.

〔coal〕
The type of coal X is not particularly limited, and includes bituminous coal, inferior coal that is cheaper than bituminous coal (for example, sub-bituminous coal or lignite), and the like. Among them, by using bituminous coal as coal X, the production efficiency of ashless coal HPC can be further enhanced. The particle size of the coal X is not particularly limited, but finely pulverized coal, for example, one having a particle size of 1 mm or less is preferably used. Moreover, as the coal X, lump coal can also be used. Lump coal has a large particle size, so the efficiency of separation in the separation unit 3 can be improved. In addition, "lump coal" means coal in which the mass ratio of coal having a particle size of 5 mm or more to the mass of the entire coal is 50% or more. The term "particle size (particle diameter)" means a value measured according to the general rules for sieving tests of JIS-Z8815 (1994). For sieving coal, for example, a metal mesh sieve specified in JIS-Z8801-1 (2019) can be used.

As the coal X, it is also preferable to use low-fluidity coal with a maximum fluidity of less than 1000ddpm. By using the low-fluidity coal as the coal X, the production cost of the ashless coal can be reduced while maintaining the production efficiency of the ashless coal.

(Formic acid supply unit)
As the formic acid supply unit 12, for example, a known pressure vessel can be used. The formic acid F is supplied from the formic acid supply unit 12 so as to stabilize the coal radicals generated by the temperature rise of the coal X. Formic acid F may be supplied from the formic acid supply unit 12 in the form of an aqueous formic acid solution or a formic acid compound.

(Mixing tank)
The mixing tank 13 is configured to mix the coal X supplied from the coal supply unit 11 and the formic acid F supplied from the formic acid supply unit 12 . In the mixing tank 13, coal X and liquid formic acid F are mixed. The upper limit of the mixing temperature of coal X and formic acid F is preferably 80°C, more preferably 60°C. If the mixing temperature exceeds the upper limit, the volatilization amount of the formic acid F increases, and it may become difficult to sufficiently elute the solvent-soluble components of the coal X into the solvent Y in the elution tank 18 described later. On the other hand, the lower limit of the mixing temperature is preferably 20°C, more preferably 25°C. If the mixing temperature is less than the above lower limit, the viscosity of the formic acid F increases, which may reduce the handleability.

The upper limit of the content of formic acid F after mixing in the mixing tank 13 (content relative to the total content of coal X and formic acid F) is preferably 6% by mass, more preferably 3% by mass. If the content of formic acid F exceeds the above upper limit, the production cost of ashless coal HPC may increase. On the other hand, the lower limit of the content of formic acid F is not particularly limited, but from the viewpoint of sufficiently increasing the extraction rate of the solvent-soluble components of coal X, for example, 0.2% by mass is preferable, and 0.5% by mass is preferable. more preferred.

(solvent tank)
A solvent Y is stored in the solvent tank 14 . The solvent tank 14 may be constructed so that the solvent _YR sent from the reuse line 7 described later is circulated. According to this configuration, it is easy to increase the extraction rate of the solvent-soluble component of the coal X and improve the production efficiency of the ashless coal HPC.

〔solvent〕
The solvent Y is not particularly limited as long as it can elute solvent-soluble components of the coal X, but for example, a coal-derived bicyclic aromatic compound is preferably used. Since this bicyclic aromatic compound has a basic structure similar to that of the structural molecule of coal, it has a high affinity with coal, and a relatively high elution rate can be obtained. Examples of the coal-derived bicyclic aromatic compound include methylnaphthalene oil, naphthalene oil, and the like, which are distillates of by-product oil in producing coke by carbonizing coal.

Although the boiling point of the solvent Y is not particularly limited, for example, the lower limit of the boiling point of the solvent Y is preferably 180°C, more preferably 230°C. On the other hand, the upper limit of the boiling point of the solvent Y is preferably 300°C, more preferably 280°C. If the boiling point of the solvent Y is less than the above lower limit, the solvent Y tends to volatilize, which may make it difficult to adjust and maintain the mixing ratio of each component in the slurry S. Conversely, if the boiling point of the solvent Y exceeds the above upper limit, it may become difficult to separate the solvent-soluble component of the coal X and the solvent Y in the first evaporator 4 .

(pump)
The pump 15 is arranged in a pipe connecting the solvent tank 14 and the mixing pipe 17 . The type of the pump 15 is not particularly limited as long as it can pump the solvent Y stored in the solvent tank 14, and examples thereof include positive displacement pumps and non-positive displacement pumps. Examples of positive displacement pumps include diaphragm pumps and tube diaphragm pumps. Examples of the non-displacement pump include a centrifugal pump.

(preheater)
The specific configuration of the preheater 16 is not particularly limited as long as the solvent Y can be heated. The preheater 16 includes, for example, a resistance heater and an induction heating coil. Moreover, as the preheater 16, it is also possible to use the thing which heats using a heat medium.

The lower limit of the temperature of the solvent Y after heating (after preheating) by the preheater 16 is preferably 300°C, more preferably 350°C. On the other hand, the upper limit of the temperature of the solvent Y is preferably 480°C, more preferably 450°C. If the temperature of the solvent Y is less than the above lower limit, the bonds between the molecules constituting the coal X cannot be sufficiently weakened, and the extractability of the solvent-soluble components of the coal X may become insufficient. Conversely, when the temperature of the solvent Y exceeds the above upper limit, the amount of heat required to maintain the temperature of the solvent Y becomes unnecessarily large, which may increase the production cost of the ashless coal HPC.

(mixing tube)
The mixing pipe 17 prepares the slurry S by mixing the coal X and the formic acid F sent from the mixing tank 13 and the solvent Y sent from the solvent tank 14 .

The lower limit of the coal concentration in the slurry S based on anhydrous coal is preferably 5% by mass, more preferably 10% by mass. On the other hand, the upper limit of the coal concentration is preferably 40% by mass, more preferably 30% by mass. If the coal concentration is less than the lower limit, the elution amount of the solvent-soluble component of the coal X in the elution tank 18, which will be described later, is less than the processing amount of the slurry S, so the production efficiency of the ashless coal HPC is reduced. There is a risk. Conversely, if the coal concentration exceeds the upper limit, the solvent-soluble components of the coal X are saturated in the solvent Y, and the elution rate of the solvent-soluble components may decrease.

<Elution part>
The elution section 2 includes a mixing tube 17 and an elution tank 18 connected downstream of the mixing tube 17 .

(Elution tank)
The elution tank 18 has a stirrer 18a and a heater (not shown). The slurry S mixed in the mixing pipe 17 is sent to the elution tank 18 . More specifically, the slurry S containing the solvent Y heated by the preheater 16 and the coal X and formic acid F rapidly heated by mixing with the solvent Y is sent to the elution tank 18 . Note that “rapid temperature rise” means heating at a heating rate of, for example, approximately 10° C./second or more and 500° C./second or less. The temperature of the slurry S after this rapid temperature rise is, for example, about 350° C. or more and 420° C. or less.

The elution tank 18 stirs the slurry S with a stirrer 18a while maintaining the temperature of the slurry S sent from the mixing pipe 17 with a heater. Thereby, the elution tank 18 makes the solvent Y dissolve the solvent-soluble component of the coal X. As shown in FIG.

In the manufacturing apparatus, after the coal X and the liquid formic acid F are mixed, the mixture of the coal X and the formic acid F is mixed with the solvent Y to raise the temperature. Coal X is mixed with solvent Y and heated to 300° C. or higher to generate coal radicals, but the presence of formic acid F during the temperature rise stabilizes the coal radicals. As a result, the polycondensation of the coal X caused by the coal radicals can be suppressed, and the extraction rate of the solvent-soluble components of the coal X can be improved.

The lower limit of the internal pressure of the elution tank 18 is preferably 1.1 MPa, more preferably 1.5 MPa. On the other hand, the upper limit of the internal pressure of the elution tank 18 is preferably 5 MPa, more preferably 4 MPa. If the internal pressure of the elution tank 18 is less than the above lower limit, the solvent Y may decrease due to evaporation, and the elution amount of the solvent-soluble component of the coal X may become insufficient. Conversely, if the internal pressure exceeds the upper limit, the effect of increasing the elution amount of the solvent-soluble component may not be sufficiently obtained with respect to the increase in cost for maintaining the pressure.

The stirring time in the elution tank 18 is not particularly limited, but can be 10 minutes or more and 70 minutes or less from the viewpoint of the elution efficiency of the solvent-soluble components.

<Separation part>
The separation section 3 is connected to the elution tank 18 by a pipe. Separation unit 3 separates slurry S sent from elution tank 18 using centrifugal separation method or gravity sedimentation method, etc., and contains solution L in which the solvent-soluble component is eluted into solvent Y, solvent-insoluble component, and solvent Y. Solid-liquid separation is performed with a solid content concentrated liquid M.

As a solid-liquid separation method in the separation unit 3, a gravity sedimentation method is preferable because it can increase the sedimentation velocity and improve the separation efficiency. Moreover, the gravity sedimentation method is also preferable from the viewpoint that the slurry S can be treated continuously. When the slurry S is separated by the gravity sedimentation method, the solution L containing the solvent-soluble components accumulates in the upper part of the separation section 3 . This solution L is discharged to the first evaporator 4 after being filtered using a filter unit as necessary. On the other hand, the solid content concentrate M containing the solvent-insoluble components accumulates in the lower portion of the separating section 3 and is discharged to the second evaporating section 19, which will be described later.

The interior of the separation section 3 is preferably heated and pressurized. As a lower limit of the heating temperature in the separation part 3, 300 degreeC is preferable and 350 degreeC is more preferable. On the other hand, the upper limit of the heating temperature in the separation section 3 is preferably 420°C, more preferably 400°C. If the heating temperature is less than the lower limit, the solvent-soluble component may reprecipitate, resulting in a decrease in separation efficiency. Conversely, if the heating temperature exceeds the upper limit, the operating cost for heating may increase.

The lower limit of the internal pressure of the separation section 3 is preferably 1 MPa, more preferably 1.4 MPa. On the other hand, the upper limit of the internal pressure is preferably 3 MPa, more preferably 2 MPa. If the internal pressure is less than the lower limit, the solvent-soluble component may reprecipitate, resulting in a decrease in separation efficiency. Conversely, if the internal pressure exceeds the upper limit, the operating cost for pressurization may increase.

<First evaporator>
The first evaporator 4 evaporates the solvent _YR1 from the solution L separated by the separator 3 . The first evaporator 4 deposits the solvent-soluble component as ashless coal HPC by evaporating the solvent _YR1 . The ashless coal HPC deposited in the first evaporator 4 exhibits a higher calorific value than, for example, coke raw coal. Furthermore, this ashless coal HPC has significantly improved softening meltability, which is a particularly important quality as a raw material for coke for ironmaking, and exhibits far superior fluidity to, for example, raw coal. Therefore, this ashless coal HPC is suitably used as coking coal to be mixed with coke raw material.

The first evaporator 4 may be configured to evaporate the _{solvent YR1, for example, by a general distillation method using an evaporation separator, or may be configured to evaporate the solvent YR1 by} an evaporation method such as a spray drying method. may

<First collection line>
The first recovery line 5 recovers the solvent _YR1 evaporated in the first evaporator 4 and sends it to the reuse line 7 . The first recovery line 5 may have a heat exchanger (not shown) for liquefying the solvent _YR1 evaporated in the first evaporation section 4 .

<Second collection line>
The second recovery line 6 includes a second evaporator 19 to which the solid content concentrate M separated in the separation unit 3 is supplied, and a solvent discharge pipe 20 that connects the second evaporator 19 and the reuse line 7. . The second evaporator 19 evaporates the solvent _YR2 from the solid content concentrated liquid M to obtain residue coal RC. The second evaporator 19 may be configured to evaporate the solvent _YR2 by a general distillation method using an evaporator, for example, and is configured to evaporate the solvent _YR2 by an evaporation method such as a spray drying method. may The solvent discharge pipe 20 recovers the solvent _YR2 evaporated in the second evaporator 19 and sends it to the reuse line 7. A heat exchanger (not shown) for liquefying the solvent _YR2 evaporated in the second evaporation section 19 may be arranged in the solvent discharge pipe 20 .

<Reuse line>
The reuse line 7 returns the solvent _YR1 sent from the first recovery line 5 and the solvent _YR2 sent from the second recovery line 6 to the solvent tank 14 . The reuse line 7 may be configured to return only one of the solvent _YR1 sent from the first recovery line 5 and the solvent _YR2 sent from the second recovery line 6 to the solvent tank 14. good. In the recycling line 7, both or one of the solvent _YR1 sent from the first recovery line 5 and the solvent _YR2 sent from the second recovery line 6 are subjected to fractional distillation, and then fractionated. It may be configured such that the solvent after distillation is refluxed to the solvent tank 14 .

The manufacturing apparatus mixes coal X, solvent Y, and formic acid F in a slurry preparation unit 1, and then raises the temperature of this slurry S in an elution unit 2, thereby improving the extraction rate of solvent-soluble components of coal X. can do.

Next, each step of the manufacturing method will be described in detail, taking the case of using the manufacturing apparatus of FIG. 2 as an example.

<Slurry preparation process>
The slurry preparation step S1 is performed in the slurry preparation section 1 . In the slurry preparation step S<b>1 , first, the coal X supplied from the coal supply unit 11 and the formic acid F supplied from the formic acid supply unit 12 are mixed in the mixing tank 13 .

The upper limit of the mixing temperature of the coal X and the formic acid F in the slurry preparation step S1 is preferably 80°C, more preferably 60°C. If the mixing temperature exceeds the upper limit, the volatilization amount of the formic acid F increases, and the coal radicals generated by the temperature rise of the coal X may not be sufficiently stabilized. On the other hand, the lower limit of the mixing temperature is preferably 20°C, more preferably 25°C. If the mixing temperature is less than the above lower limit, the viscosity of the formic acid F increases, which may reduce the handleability.

Subsequently, in the slurry preparation step S1, the coal X and formic acid F mixed in the mixing tank 13 are mixed with the solvent Y supplied from the solvent tank 14 and heated by the preheater 16. That is, in the slurry preparation step S1, the slurry S is prepared by two-stage mixing of coal X and formic acid F and mixing of this mixture and solvent Y.

The upper limit of the content of formic acid F in slurry S prepared in slurry preparation step S1 is preferably 6% by mass, more preferably 3% by mass, relative to the total content of coal X and formic acid F. If the content of formic acid F exceeds the above upper limit, the production cost of ashless coal HPC may increase. On the other hand, the lower limit of the content of formic acid F is not particularly limited, but from the viewpoint of sufficiently increasing the extraction rate of the solvent-soluble components of coal X, for example, 0.2% by mass is preferable, and 0.5% by mass is preferable. more preferred.

<Elution process>
The elution step S2 is performed in the elution section 2 . In the elution step S2, after the slurry S is heated in the mixing tube 17, the slurry S is stirred in the elution tank 18 while maintaining the temperature thereof. In the elution step S2, the temperature of the slurry S is increased and the solvent soluble components of the coal X are eluted into the solvent Y by stirring. The temperature of the slurry S after the temperature rise in the elution step S2 can be about 350° C. or higher and 420° C. or lower.

In the production method, after the coal X and the liquid formic acid F are mixed in the slurry preparation step S1, the slurry S is heated to 300° C. or higher in the elution step S2. Coal X generates coal radicals when heated to 300° C. or higher, and the presence of formic acid F at the time of temperature elevation stabilizes the coal radicals. Specifically, the coal radicals can be stabilized by supplying hydrogen and electrons to the coal X by the reaction represented by the following formula 1. As a result, the polycondensation of the coal X caused by the coal radicals can be suppressed, and the extraction rate of the solvent-soluble components of the coal X can be improved.
HCOOH→CO ₂ +2H ⁺ +2e ⁻・・・1

The internal pressure and stirring time of the elution tank 18 in the elution step S2 can be as described for the elution tank 18 of the manufacturing apparatus.

<Separation process>
The separation step S3 is performed in the separation section 3 . In the separation step S3, the slurry S processed in the elution step S2 is separated into a solution L in which the solvent-soluble components are eluted into the solvent Y, and solids containing the solvent-insoluble components and the solvent Y using a centrifugal separation method, a gravity sedimentation method, or the like. Solid-liquid separation is performed with the concentrated liquid M.

The heating temperature in the separation section 3 and the internal pressure of the separation section 3 in the separation step S3 can be as described for the separation section 3 of the manufacturing apparatus.

<Evaporation process>
The evaporation step S<b>4 is performed in the first evaporation section 4 . In the evaporation step S4, the solvent _YR1 is evaporated from the solution L separated in the separation step S3, and the solvent-soluble components are precipitated as ashless coal HPC. The ashless coal HPC obtained in the evaporation step S4 is suitably used as coking coal to be blended with the coke raw material.

In addition to the above steps, the production method includes a first recovery step of recovering the solvent _YR1 evaporated in the evaporation step S4, and a solid content concentrate M separated in the separation step S3. A second recovery step of recovering the solvent _YR2 contained in M, and a reuse step of reusing the solvent recovered in one or both of the first recovery step and the second recovery step in the slurry preparation step S1 and An example of specific procedures of the first recovery step, the second recovery step, and the recycling step will be described below.

<First recovery step>
The first recovery step is performed in the first recovery line 5 . In the first recovery step, the solvent _YR1 evaporated in the evaporation step S4 is recovered and sent to the reuse line 7. In the first recovery step, the solvent _YR1 may be liquefied and sent to the recycling line 7 .

<Second recovery step>
The second recovery step is performed in the second recovery line 6 . In the second recovery step, the solvent YR2 is evaporated from the solid content concentrate M separated in the separation step _S3 to obtain after-product coal RC. In the second recovery step, the solvent _YR2 separated from the residue coal RC by evaporation is recovered and sent to the recycling line 7 . In the second recovery step, the solvent _YR2 may be liquefied and sent to the recycling line 7 .

<Reuse process>
The recycling process is performed in the recycling line 7 . In the recycling step, the solvent _YR1 recovered in the first recovery step and the solvent _YR2 recovered in the second recovery step are returned to the solvent tank 14 . The solvent _YR returned to the solvent tank 14 is reused as part of the solvent Y in the slurry preparation step S1. In the reuse step, only one of the solvent _YR1 recovered in the first recovery step and the solvent _YR2 recovered in the second recovery step may be returned to the solvent tank 14. Further, in the recycling step, both or one of the solvent _YR1 recovered in the first recovery step and the solvent _YR2 recovered in the second recovery step is subjected to fractional distillation, and then fractionated. The solvent _YR after distillation may be refluxed to the solvent tank 14 .

<Advantages>
In the production method, coal X, solvent Y, and formic acid F are mixed in the slurry preparation step S1, and the temperature of the slurry S is raised in the elution step S2, thereby improving the extraction rate of the solvent-soluble components of the coal X. can do. Therefore, according to the said manufacturing method, the manufacturing efficiency of ash-free coal HPC can be improved.

[Other embodiments]
The above embodiments do not limit the configuration of the present invention. Therefore, in the above embodiment, the components of each part of the above embodiment can be omitted, replaced, or added based on the description of the present specification and common general technical knowledge, and all of them are interpreted as belonging to the scope of the present invention. should.

For example, the manufacturing method may not include the above-described first recovery step, second recovery step, and recycling step. In this case, the manufacturing apparatus may not include the above-described first recovery line, second recovery line, and recycling line. Further, when the manufacturing method includes only one of the first recovery process and the second recovery process, the manufacturing apparatus corresponds to the first recovery line and the second recovery process corresponding to the first recovery process. Any one of the second recovery lines may be provided.

In the slurry preparation step, coal, solvent and formic acid may be mixed at the same time. In this case, for example, the slurry may be heated after the coal, solvent and formic acid are mixed.

EXAMPLES The present invention will be described in detail below based on examples, but the present invention is not limitedly interpreted based on the description of these examples.

No. 1.0 mm or less in particle diameter passed through a sieve with an opening of 1.0 mm. 1 to No. 12 bituminous coals were used as the coal, and 1-methylnaphthalene, which is an industrial bicyclic aromatic compound, was used as the solvent, and 240 g of the solvent was mixed with 40 g of the coal. Next, this mixture was mixed with formic acid at room temperature to prepare a slurry. The slurry prepared by the above procedure was put into an autoclave with a capacity of 500 cc having a stainless filter, and heated to 380° C. under a pressure condition of 2.0 MPa. Furthermore, while maintaining the temperature at 380° C., the mixture was stirred at a rotation speed of 600 rpm for 40 minutes to elute out the solvent-soluble components of the coal into the solvent. After this stirring, the solution in which the solvent-soluble component was eluted into the solvent was separated from the slurry by rapid filtration at the same temperature. The solid content concentrate remaining after separation of the solution was washed with acetone and dried, and the weight of the residue (solvent-insoluble component) was measured. Using the weight of the coal before preparation of the slurry and the weight of the residue, the extractability of the solvent-soluble components of the coal was calculated. No. 1 to No. Fig. 3 shows the relationship between the formic acid content [% by mass] (content of formic acid relative to the total content of coal and formic acid) in the slurry using bituminous coal in No. 9 and the extraction rate [% by mass] of solvent-soluble components. , No. 10 to No. Fig. 4 shows the relationship between the formic acid content [% by mass] (content of formic acid relative to the total content of coal and formic acid) in the slurry using No. 12 bituminous coal and the extraction rate [% by mass] of solvent-soluble components. show.

As shown in FIGS. 1 to No. In any of No. 12, the extraction rate of solvent-soluble components is increased by including formic acid in the slurry. Also, No. 1 to No. 12, by increasing the formic acid content between 0% and 6% by mass, the extraction rate of the solvent-soluble components is generally increased corresponding to the increase in the formic acid content. there is From this, it can be seen that the extractability of solvent-soluble components can be improved by preparing a slurry by mixing formic acid with coal and then raising the temperature of this slurry.

As described above, the method for producing ashless coal according to one aspect of the present invention can increase the extraction rate of solvent-soluble components of coal, so it is suitable for efficiently producing ashless coal. there is

1 slurry preparation unit 2 elution unit 3 separation unit 4 first evaporation unit 5 first recovery line 6 second recovery line 7 reuse line 11 coal supply unit 12 formic acid supply unit 13 mixing tank 14 solvent tank 15 pump 16 preheater 17 mixing Pipe 18 Elution tank 18a Stirrer 19 Second evaporator 20 Solvent discharge pipe F Formic acid L Solution M Solid content concentrate S Slurry X Coal Y, _YR , _YR1 , _YR2 solvent HPC Ash-free coal RC Residual coal

Claims (3)

A slurry preparation step of preparing a slurry by mixing coal, a solvent and formic acid;
An elution step of eluting solvent-soluble components of the coal into the solvent by raising the temperature of the slurry prepared in the slurry preparation step;
A separation step of separating a solution in which the solvent-soluble component is eluted into the solvent from the slurry;
A method for producing ashless coal, comprising: an evaporation step of evaporating the solvent from the solution separated in the separation step. The method for producing ashless coal according to claim 1, wherein the temperature of mixing the coal and the formic acid in the slurry preparation step is 80°C or less. The production of ashless coal according to claim 1 or 2, wherein the content of the formic acid in the slurry prepared in the slurry preparation step is 6% by mass or less with respect to the total content of the coal and the formic acid. Method.

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