Ashless coal manufacturing method and ashless coal manufacturing device

Abstract

To provide a method of manufacturing an ashless coal and an apparatus for manufacturing an ashless coal, capable of suppressing an ashless coal in a solvent to be evaporated and separated.SOLUTION: A method of manufacturing an ashless coal includes: a preparation step of mixing a coal and a solvent to prepare a slurry; an elution step of eluting a solvent soluble component of the coal in the solvent of the slurry; a separation step of separating from the slurry a solution in which the solvent soluble component is eluted in the solvent at the elution step; and an evaporation step of evaporating the solvent from the solution separated at the separation step. The evaporation step is carried out under a gas atmosphere including carbon dioxide.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for producing ashless coal and an apparatus for producing ashless coal. [Background technology]

[0002] High-strength coke is used as coke for steelmaking, such as blast furnace coke. To obtain high-strength coke, so-called strong coking coal, which has high caking properties, has traditionally been used as the raw coal. However, because strong coking coal is relatively expensive, techniques for reducing the amount of strong coking coal used are currently being considered.

[0003] Attempts have been made to use ashless coal as raw coal from which high-strength coke can be obtained while reducing the amount of heavily coking coal used. For example, Patent Document 1 proposes a method for producing this ashless coal, in which pre-pasted coal is mixed with a solvent to obtain a slurry, the slurry is separated into a solution in which solvent-soluble components of the coal are dissolved in the solvent, and a solids-concentrated liquid containing solvent-insoluble components of the coal, and the solvent in the solution is evaporated and separated to obtain ashless coal (Japanese Patent Laid-Open Publication No. 2016-056282). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-056282 Summary of the Invention [Problem to be solved by the invention]

[0005] In the manufacturing method of Patent Document 1, the solvent in the solution is evaporated and separated to precipitate the solvent-soluble components, thereby obtaining ashless coal. According to this manufacturing method, some of the solvent-soluble components may evaporate together with the solvent before being precipitated as ashless coal. In order to more efficiently manufacture ashless coal, it is desirable to prevent the solvent-soluble components from being included in the solvent that is evaporated and separated.

[0006] In view of these circumstances, the present invention aims to provide a method for producing ashless coal and an apparatus for producing ashless coal that can prevent solvent-soluble components of coal from being included in the solvent that is evaporated and separated. [Means for solving the problem]

[0007] A method for producing ashless coal according to one embodiment of the present invention that solves the above-mentioned problems includes a preparation process of mixing coal and a solvent to prepare a slurry, an elution process of eluting solvent-soluble components of the coal into the solvent of the slurry, a separation process of separating from the slurry a solution in which the solvent-soluble components have been eluted into the solvent in the elution process, and an evaporation process of evaporating the solvent from the solution separated in the separation process, wherein the evaporation process is carried out in an atmosphere of a gas containing carbon dioxide.

[0008] Another aspect of the present invention that solves the above-mentioned problem provides an ashless coal manufacturing apparatus that includes a preparation unit that mixes coal and a solvent to prepare a slurry, an elution unit that dissolves solvent-soluble components of the coal into the solvent of the slurry, a separation unit that separates a solution in which the solvent-soluble components have been dissolved in the solvent from the slurry, and an evaporation unit that evaporates the solvent from the separated solution, and the evaporation unit has an evaporator that evaporates the solvent to obtain ashless coal, and a gas supplier that supplies a gas containing carbon dioxide to the evaporator. [Effects of the Invention]

[0009] The ashless coal production method and ashless coal production apparatus of the present invention can prevent solvent-soluble components of coal from being included in the solvent that is evaporated and separated. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a conceptual diagram showing an apparatus for producing ashless coal according to one embodiment of the present invention. [Figure 2] FIG. 2 is a flow diagram showing a method for producing ashless coal according to another embodiment of the present invention using the production apparatus of FIG. [Figure 3] FIG. 3 is a graph comparing the volatile content of ashless coal obtained by performing the evaporation step of FIG. 2 under different conditions. [Figure 4] FIG. 4 is a distribution diagram showing the elemental composition distribution of the ashless coal of FIG. [Figure 5] FIG. 5 is a graph comparing the soluble and insoluble components in tetrahydrofuran for Samples 1 to 4 in FIG. [Figure 6] FIG. 6 is a graph comparing the thermoplasticity of Sample 1 in FIG. 3, Sample 6 in which Sample 3 is added to Sample 1 in FIG. 3, and Sample 7 in which Sample 4 is added to Sample 1 in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] A method for producing ashless coal according to one embodiment of the present invention includes a preparation process for mixing coal and a solvent to prepare a slurry, an elution process for eluting solvent-soluble components of the coal into the solvent of the slurry, a separation process for separating from the slurry a solution in which the solvent-soluble components have been eluted into the solvent in the elution process, and an evaporation process for evaporating the solvent from the solution separated in the separation process, wherein the evaporation process is carried out under an atmosphere of gas containing carbon dioxide.

[0012] In the method for producing ashless coal, the evaporation step is carried out in an atmosphere of a gas containing carbon dioxide, and as a result, the solvent-soluble components of the coal in the solution are slightly oxidized, and are prevented from being contained in the solvent that is evaporated and separated.

[0013] The gas is preferably carbon dioxide, which promotes oxidation of the solvent-soluble components and further prevents them from being contained in the solvent.

[0014] In at least one of the preparation step and the leaching step, it is preferable to raise the temperature of the coal after mixing with the solvent, which makes it easier to leach the solvent-soluble components of the coal in the leaching step.

[0015] Another aspect of the present invention relates to an apparatus for producing ashless coal, and the apparatus includes a preparation unit that mixes coal and a solvent to prepare a slurry, an elution unit that dissolves solvent-soluble components of the coal into the solvent of the slurry, a separation unit that separates the solution in which the solvent-soluble components have been dissolved into the solvent from the slurry, and an evaporation unit that evaporates the solvent from the separated solution, and the evaporation unit has an evaporator that evaporates the solvent to obtain ashless coal, and a gas supplier that supplies a gas containing carbon dioxide to the evaporator.

[0016] The ashless coal production apparatus includes a gas supplier that supplies a gas containing carbon dioxide to an evaporator that evaporates and separates the solvent. Therefore, the evaporation and separation of the solvent can be performed in an atmosphere of the gas containing carbon dioxide, and the solvent-soluble components can be prevented from being contained in the solvent that is evaporated and separated.

[0017] [Details of the Mode for Carrying Out the Invention] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that with regard to 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, it is assumed that all numerical ranges from the upper limit values ​​to the lower limit values ​​that can be combined are described as suitable ranges. Furthermore, the diagrams showing the ashless coal production apparatus conceptually or schematically show each component (each component), and the shape, scale, etc. of the actual components are different.

[0018] [First embodiment] <Ashless coal manufacturing equipment> As shown in FIG. 1 , an ashless coal production apparatus 1 (hereinafter also referred to as “production apparatus 1”) according to one embodiment of the present invention is R and a solvent T to prepare a slurry Y; and a preparation unit 2 for mixing the solvent T in the slurry Y. R The apparatus mainly includes an elution section 3 for eluting the solvent-soluble components of the slurry Y, a separation section 4 for separating a solution L in which the solvent-soluble components have been eluted into the solvent T from the slurry Y, and an evaporation section 5 for evaporating the solvent T from the separated solution L. The evaporation section 5 evaporates the solvent T to obtain ashless coal C. Hand a gas supply unit 53 that supplies a gas G containing carbon dioxide to the first evaporator 51. In this embodiment, the evaporation unit 5 S It has a second evaporation section 52 for obtaining

[0019] 〔coal〕 Coal C R The type of coal is not particularly limited, and examples thereof include bituminous coal and inferior coals (such as subbituminous coal or lignite) that are cheaper than bituminous coal. R By using bituminous coal as H Coal C can be produced more efficiently. R The particle size of the coal is not particularly limited, but finely ground coal, for example, coal with a particle size of 1 mm or less, is preferably used. R Lump coal can also be used as the sieve. Lump coal has a large particle size, which allows for more efficient separation in the separation section 4 described below. Note that "lump coal" refers to coal in which the mass ratio of coal with a particle size of 5 mm or more to the total mass of coal is 50% or more. Furthermore, "particle size (particle size)" refers to a value measured in accordance with the general rules for sieving tests in JIS-Z8815 (1994). For example, a metal mesh sieve specified in JIS-Z8801-1 (2019) can be used to sieve coal.

[0020] Also, Coal C R It is also preferable to use low fluidity coal with a maximum fluidity of less than 1000 ddpm as the coal C. R By using the low fluidity coal, ashless coal C H While maintaining the production efficiency of ashless coal C H The manufacturing cost can be reduced.

[0021] 〔solvent〕 As solvent T, coal C RThe solvent is not particularly limited as long as it can elute the solvent-soluble components of the above, but for example, a bicyclic aromatic compound derived from coal is preferably used. This bicyclic aromatic compound has a high affinity with coal because its basic structure is similar to the structural molecules of coal, and a relatively high elution rate can be obtained. Examples of the coal-derived bicyclic aromatic compound include methylnaphthalene oil and naphthalene oil, which are distilled oils obtained as by-products when carbonizing coal to produce coke.

[0022] The boiling point of the solvent T is not particularly limited, but for example, the lower limit of the boiling point of the solvent T is preferably 180°C, more preferably 230°C. On the other hand, the upper limit of the boiling point of the solvent T is preferably 300°C, more preferably 280°C. If the boiling point of the solvent T is lower than the lower limit, the solvent T is likely to volatilize, and the coal C in the slurry Y is likely to be volatilized. R On the other hand, if the boiling point of the solvent T exceeds the upper limit, the coal C in the evaporation section 5 may become difficult to adjust and maintain the mixing ratio. R There is a risk that the solvent-soluble components of (I) and solvent T cannot be easily separated.

[0023] [Preparation Department] The preparation unit 2 includes a solvent storage tank 21 for storing the solvent T and a coal storage tank 22 for storing the coal C. R and a coal storage tank 22 for storing the coal.

[0024] The preparation section 2 also has a solvent supplier 23 for pumping the solvent T stored in the solvent storage tank 21, and a preheater 24 for heating the solvent T pumped by the solvent supplier 23.

[0025] (Coal storage tank) The coal storage tank 22 stores coal C R and supplying coal C to the mixing tube 25 described later through a coal supply line P2. R The coal storage tank 22 is not particularly limited, and examples thereof include a known atmospheric pressure hopper or a pressure hopper.

[0026] (Solvent storage tank) The solvent storage tank 21 is a tank for storing the solvent T. The solvent storage tank 21 is not particularly limited, and examples thereof include known liquid tanks. As will be described later, the solvent storage tank 21 may be configured to be supplied with the solvent discharged in the evaporation section 5. In this way, ashless coal C can be produced at a lower cost. H can be manufactured.

[0027] (Solvent supplier) The solvent supplier 23 is disposed in a solvent supply line P1 that connects the solvent reservoir tank 21 with a mixing pipe 25 (described later). The solvent supplier 23 is not particularly limited, and examples thereof include known positive displacement pumps and non-positive displacement pumps. Examples of the non-positive displacement pump include a centrifugal pump.

[0028] (preheater) The preheater 24 is disposed in the solvent supply line P1 downstream of the solvent supplyer 23. The preheater 24 is not particularly limited, and examples thereof include a known resistance heater or induction heating coil. Alternatively, the preheater 24 may be one that uses a heat medium for heating.

[0029] The lower limit of the temperature of the solvent T after heating (preheating) by the preheater 24 is preferably 300°C, more preferably 350°C. On the other hand, the upper limit of the temperature of the solvent T is preferably 480°C, more preferably 450°C. If the temperature of the solvent T is lower than the above lower limit, the coal C R The bonds between the molecules that make up coal C R On the other hand, if the temperature of the solvent T exceeds the upper limit, the amount of heat required to maintain the temperature of the solvent T becomes unnecessarily large, and the ashless coal C may not be sufficiently eluted. H This may increase the manufacturing cost.

[0030] [Mixing tube] The preparation unit 2 receives the solvent T sent from the solvent storage tank 21 and the coal C sent from the coal storage tank 22. RThe mixing tube 25 supplies the slurry Y to the elution section 3, which will be described later.

[0031] In the mixing tube 25, coal C R The heated solvent T is mixed with the coal C. R In other words, coal C after mixing with solvent T is heated. R The temperature of the solvent T and the coal C heated in the preheater 24 is increased in the adjusting section 2. R By mixing these, a slurry Y is generated whose temperature is raised to 300°C or higher.

[0032] The mixing tube 25 may have a heater (not shown) capable of maintaining the temperature of the slurry Y or heating the slurry Y.

[0033] Coal C on a dry coal basis in slurry Y R The lower limit of the concentration of coal C is preferably 5 mass %, more preferably 10 mass %. R The upper limit of the concentration of coal C is preferably 40 mass %, more preferably 30 mass %. R If the concentration is less than the above lower limit, the coal C R The amount of eluted solvent-soluble components of the ashless coal C is small compared to the amount of slurry Y treated. H On the other hand, the production efficiency of Coal C may decrease. R When the concentration of exceeds the upper limit, coal C in solvent T R When the solvent-soluble components are saturated, the elution rate of the solvent-soluble components may decrease.

[0034] [Elution part] The elution section 3 is a section of the slurry Y containing coal C in a solvent T. R The elution unit 3 has a elution tank 31 connected downstream of the mixing pipe 25. The elution tank 31 is a tank for storing the slurry Y, and includes an agitator 311 and a heater (not shown) for maintaining the temperature of the slurry Y or for heating the slurry Y. The slurry Y produced in the mixing pipe 25 is sent to the elution tank 31.

[0035] (Elution tank) In the leaching tank 31, the temperature of the slurry Y sent from the mixing tube 25 is maintained or increased by the heater, and the slurry Y is stirred by the stirrer 311. By stirring the slurry Y at a predetermined temperature, the coal C R The solvent-soluble components of the above can be efficiently dissolved into solvent T.

[0036] The lower limit of the internal pressure of the leaching tank 31 is preferably 1.1 MPa, more preferably 1.5 MPa. On the other hand, the upper limit of the internal pressure of the leaching tank 31 is preferably 5 MPa, more preferably 4 MPa. If the internal pressure of the leaching tank 31 is below the lower limit, the solvent T will be reduced by evaporation, resulting in the coal C R On the other hand, if the internal pressure exceeds the upper limit, the cost of maintaining the pressure increases, and the ashless coal C may not be able to sufficiently elute the solvent-soluble components. H This may increase the manufacturing cost.

[0037] The stirring time in the elution tank 31 is not particularly limited, but can be set to 10 minutes or more and 70 minutes or less from the viewpoint of the elution efficiency of the solvent-soluble components.

[0038] The slurry Y stirred in the elution tank 31 is supplied to the separation section 4 via a slurry supply line P3.

[0039] [Separation part] The separation unit 4 separates a solution L in which the solvent-soluble components have been dissolved in the solvent T from the slurry Y. The separation unit 4 includes a solid-liquid separator 41 that performs solid-liquid separation using a centrifugal separation method, a gravity settling method, or the like. The separation unit 4 separates the slurry Y sent from the elution tank 31 into a solution L in which the solvent-soluble components have been dissolved in the solvent T, and a solids concentrated liquid M containing the solvent-insoluble components and the solvent T. The separation unit 4 supplies the solution L to a first evaporator 51 via a solution supply line P4, and supplies the solids concentrated liquid M to a second evaporator 52 via a concentrated liquid supply line P5.

[0040] (Solid-liquid separator) The solid-liquid separator 41 in the separation section 4 is preferably an apparatus using gravity settling, which can increase the settling rate and improve separation efficiency. Gravity settling is also preferable from the viewpoint of enabling continuous processing of the slurry Y. When separating the slurry Y by gravity settling, the solution L containing the solvent-soluble components accumulates in the upper part of the separation section 4. This solution L is filtered using a filter unit as necessary and then supplied to the first evaporator 51. On the other hand, the solids concentrated liquid M containing the solvent-insoluble components accumulates in the lower part of the separation section 4 and is supplied to the second evaporator 52.

[0041] The inside of the solid-liquid separator 41 is preferably heated and pressurized. The lower limit of the heating temperature in the solid-liquid separator 41 is preferably 300°C, more preferably 350°C. On the other hand, the upper limit of the heating temperature in the solid-liquid separator 41 is preferably 420°C, more preferably 400°C. If the heating temperature is below the lower limit, the solvent-soluble components may be reprecipitated in the slurry Y, resulting in a decrease in separation efficiency. On the other hand, if the heating temperature exceeds the upper limit, the cost of heating may increase.

[0042] The lower limit of the internal pressure of the solid-liquid separator 41 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 below the lower limit, the solvent-soluble components may be reprecipitated in the slurry Y, resulting in a decrease in separation efficiency. On the other hand, if the internal pressure exceeds the upper limit, the cost of pressurization may increase.

[0043] [Evaporation section] The evaporation section 5 has a first evaporator 51 that evaporates the solvent T from the solution L separated in the separation section 4, and a gas supplier 53 that supplies a gas containing carbon dioxide via a gas supply line P8. The first evaporator 51 evaporates the solvent T in the solution L to precipitate the solvent-soluble components. The precipitated solvent-soluble components are used to produce ashless coal C produced by the production apparatus. HThe evaporation section 5 has a second evaporator 52 that evaporates the solvent T from the solids-concentrated liquid M separated in the separation section 4. The second evaporator 52 evaporates the solvent T in the solids-concentrated liquid M to produce by-product coal C. S is precipitated.

[0044] The evaporation section 5 is equipped with a first discharge line P6 for discharging the solvent T evaporated in the first evaporator 51, a second discharge line P7 for discharging the solvent T evaporated in the second evaporator 52, and a reuse line 54 for reusing the solvent T in the first discharge line P6 and the second discharge line P7 in the preparation section 2.

[0045] (First evaporator) The first evaporator 51 evaporates the solvent T in the solution L to convert the solvent-soluble components into ashless coal C. H The ashless coal C precipitated in the first evaporator 51 H For example, ashless coal C has a higher calorific value than raw coal. H The thermoplasticity, which is an especially important quality for a raw material for coke in steelmaking, has been significantly improved, and for example, it exhibits fluidity far superior to that of raw coal. H is suitably used as raw coal to be blended with coke raw materials.

[0046] The first evaporator 51 may be configured to evaporate the solvent T by a general distillation method using, for example, an evaporation separation method, or may be configured to evaporate the solvent T by an evaporation method such as a spray drying method.

[0047] (gas supply) The gas supplier 53 supplies the gas G containing carbon dioxide via the gas supply line P8 to the first evaporator 51. Therefore, in the first evaporator 51, evaporation and separation of the solvent T is carried out in an atmosphere of the gas G containing carbon dioxide.

[0048] By performing evaporation and separation of the solvent T under an atmosphere of gas G containing carbon dioxide, the above-mentioned solvent-soluble components (ashless coal C) present in the solution L are separated. H) is slightly oxidized. Therefore, the amount of the solvent-soluble components remaining in the evaporated solvent T can be reduced, and the amount of the precipitated ashless coal C H The amount of can be increased.

[0049] There are no particular limitations on the gas supplier 53, and for example, a known high-pressure gas tank can be used. In this case, it is preferable that the gas supply line P8 has an on-off valve (not shown) that can arbitrarily start and stop the supply of gas.

[0050] The carbon dioxide-containing gas G is not particularly limited, and for example, exhaust gas emitted from a factory or the like may be used. The concentration of carbon dioxide in the gas G is not particularly limited, and for example, the lower limit may be 5%, 10%, 15%, 20%, or 25%. The concentration of carbon dioxide in the gas G is preferably high, and it is more preferable that the gas G consists of carbon dioxide. When the gas G consists of carbon dioxide, the oxidation of the solvent-soluble components in the solution L can be promoted.

[0051] (Second evaporator) The second evaporator 52 evaporates the solvent T from the concentrated solids solution M to produce by-product coal C S The second evaporator 52 may be configured to evaporate the solvent T by an evaporation method such as an evaporation separation method or a spray drying method, similar to the first evaporator 51.

[0052] By-product coal C precipitated in the second evaporator 52 S Although by-product coal C does not exhibit thermoplasticity, since the oxygen-containing functional groups have been eliminated, when it is used as a coal blend, it does not inhibit the thermoplasticity of other coals contained in the coal blend. Therefore, this coal blend can also be used as part of a coal blend for coke raw materials. S may be disposed of without recovery.

[0053] (First discharge line) The first discharge line P6 supplies the solvent T evaporated and discharged in the first evaporator 51 to the recycle line 54. The first discharge line P6 may have a heat exchanger (not shown) for liquefying the discharged solvent T.

[0054] (Second discharge line) The second discharge line P7 supplies the solvent T evaporated and discharged in the second evaporator 52 to the recycle line 54. The second discharge line P7 may have a heat exchanger (not shown) for liquefying the discharged solvent T.

[0055] (Recycling line) The reuse line 54 supplies the solvent T1, which is a mixture of the solvent T supplied from the first discharge line P6 and the solvent T supplied from the second discharge line P7, to the solvent storage tank 21. That is, in the manufacturing apparatus 1, the solvent T is recycled by refluxing.

[0056] <Manufacturing method of ashless coal> As shown in Fig. 2, the method for producing ashless coal (hereinafter also referred to as "the production method") includes a preparation step S1 of preparing a slurry by mixing coal and a solvent, an elution step S2 of eluting solvent-soluble components of the coal into the solvent in the slurry prepared in the preparation step S1, a separation step S3 of separating from the slurry a solution in which the solvent-soluble components have been eluted into the solvent, and an evaporation step S4 of evaporating the solvent from the solution separated in the separation step S3. In the production method, the evaporation step S4 is carried out in an atmosphere of a gas containing carbon dioxide.

[0057] In the evaporation step S4, the solvent is evaporated to precipitate the solvent-soluble component. The precipitated solvent-soluble component is the ashless coal produced by the production method.

[0058] Below, each step of the manufacturing method will be described in detail using the manufacturing apparatus 1 of FIG. 1 as an example.

[0059] [Preparation process] The preparation step S1 is performed in the preparation unit 2. In the preparation step S1, coal C supplied from the coal storage tank 22 is R The solvent T supplied from the solvent reservoir 21 and heated by the preheater 24 is mixed in the mixing tube 25 .

[0060] In the preparation step S1, the solvent T is heated by the preheater 24 to prepare the coal C R By mixing with Coal C R In the preparation step S1, heated solvent T and coal C are mixed. R By mixing the above, a heated slurry Y is produced.

[0061] [Elution process] The leaching step S2 is performed in the leaching unit 3. In the leaching step S2, the slurry Y produced in the preparation unit 2 is supplied to the leaching tank 31, and the slurry Y is stirred in the leaching tank 31 while maintaining or increasing the temperature of the slurry Y. In the leaching step S2, the heated slurry Y is stirred to dissolve the coal C in the solvent T. R The temperature of the slurry Y in the elution step S2 is 300°C or higher, and preferably 350°C or higher and 420°C or lower.

[0062] [Separation process] The separation step S3 is carried out in the separation section 4. In the separation step S3, the slurry Y treated in the elution step S2 is subjected to solid-liquid separation using a method such as centrifugation or gravity settling into a solution L in which the solvent-soluble components are eluted into the solvent T and a concentrated solids solution M containing the solvent-insoluble components and the solvent T.

[0063] [Evaporation process] The evaporation step S4 is carried out in each of the first evaporator 51 and the second evaporator 52. In the evaporation step S4, the first evaporator 51 evaporates the solvent T in the solution L separated in the separation step S3, and the solvent-soluble components are dissolved in the ashless coal C. H Ashless coal C obtained by evaporation step S4 H The second evaporator 52 evaporates the solvent T in the solids concentrated liquid M separated in the separation step S3, and produces by-product coal C. S is precipitated.

[0064] In the evaporation step S4, the solvent T is evaporated and separated in a first evaporator 51 under an atmosphere of a gas G containing carbon dioxide. By evaporating and separating the solvent T under an atmosphere of a gas G containing carbon dioxide, the solvent-soluble components (ashless coal C) present in the solution L are removed. H ) is slightly oxidized. Therefore, the amount of the solvent-soluble components remaining in the evaporated solvent T can be reduced, and the amount of the precipitated ashless coal C H can be increased.

[0065] In addition to the above-mentioned steps, the production method also includes a first solvent recovery step of discharging and recovering the solvent T evaporated in the first evaporation section 51 in the evaporation step S4, a second solvent recovery step of discharging and recovering the solvent T evaporated in the second evaporation section 52 in the evaporation step S4, and a recycling step of reusing the solvent T recovered in the first solvent recovery step and the second solvent recovery step in the preparation step S1. Hereinafter, an example of specific procedures for the first solvent recovery step, the second solvent recovery step, and the recycling step will be described.

[0066] [First solvent recovery step] The first solvent recovery step is performed in a first discharge line P6 that connects the first evaporation section 51 and the reuse line 54. In the first solvent recovery step, the solvent T evaporated in the first evaporation section 51 is discharged into the first discharge line P6, and the discharged solvent T is sent to the reuse line 54. In the first solvent recovery step, the discharged solvent T may be liquefied and then sent to the reuse line 54.

[0067] [Second solvent recovery step] The second solvent recovery step is performed in a second discharge line P7 that connects the second evaporation section 52 and the recycle line 54. In the second solvent recovery step, the solvent T evaporated in the second evaporation section 52 is discharged into the second discharge line P7, and the discharged solvent T is sent to the recycle line 54. In the second solvent recovery step, the discharged solvent T may be liquefied and then sent to the recycle line 54.

[0068] [Reuse process] The recycling step is carried out in a recycling line 54. In the recycling step, the solvent T recovered in the first solvent recovery step and the solvent T recovered in the second solvent recovery step are supplied to a solvent storage tank 21. The solvent T supplied to the solvent storage tank 21 is reused as part of the solvent T in the preparation step S1.

[0069] <Advantages> The manufacturing apparatus 1 and the manufacturing method perform evaporation and separation of the solvent T under an atmosphere of a gas containing carbon dioxide, thereby separating the solvent-soluble component (ashless coal C) present in the solution L. H ) is slightly oxidized. Therefore, the amount of the solvent-soluble components remaining in the evaporated solvent T can be reduced, and the amount of the precipitated ashless coal C H Therefore, according to the manufacturing apparatus 1 and the manufacturing method, the ashless coal C H can be efficiently produced.

[0070] [Other embodiments] The above-described embodiments do not limit the configuration of the present invention. Therefore, the above-described embodiments may include omissions, substitutions, or additions of components based on the description in this specification and common general technical knowledge, and all of these should be construed as falling within the scope of the present invention.

[0071] The preheater 24 of the preparation section 2 in the production apparatus 1 is not an essential component, and may be used to heat the produced slurry Y. For example, a heater may be provided in the mixing tube 25 to heat the slurry Y to 300°C or higher, or the slurry Y may be heated by a heater provided in the elution tank 31.

[0072] Instead of reusing the solvent T discharged to both the first discharge line P6 and the second discharge line P7 in the preparation unit 2, only one of the discharged solvents may be recovered and reused. In addition, the reuse line 54 may be configured to perform a fractional distillation process on both or either of the solvent T discharged to the first discharge line P6 and the solvent T discharged to the second discharge line P7, and then supply the distilled solvent to the solvent storage tank 21.

[0073] The manufacturing method does not necessarily have to include the first solvent recovery step, the second solvent recovery step, and the recycling step. In this case, the manufacturing apparatus does not necessarily have to include the first discharge line P6, the second discharge line P7, and the recycling line 54. Furthermore, when the manufacturing method includes only one of the first solvent recovery step and the second solvent recovery step, the manufacturing apparatus only needs to include either the first discharge line P6 corresponding to the first solvent recovery step or the second discharge line P7 corresponding to the second solvent recovery step. [Example]

[0074] The present invention will be described in detail below based on examples, but the present invention should not be construed as being limited by the descriptions in these examples.

[0075] Untreated ashless coal was prepared as sample 1. The sample coal was mixed with a solvent to prepare a slurry, and this slurry was subjected to the leaching process, separation process, and evaporation process to obtain ashless coal samples 2 to 5. The evaporation process for samples 2 to 5 was carried out by placing 1 g of the solution separated in the separation process on a boat inside a quartz tube under the conditions shown in Table 1. The inside of the quartz tube was heated in an electric furnace at a rate of 10°C / min, and after treatment, the quartz tube was cooled by blowing air through it. 1-methylnaphthalene, an industrial bicyclic aromatic compound, was used as the solvent.

[0076] [Table 1]

[0077] The ratio of carbon dioxide in the atmosphere of Sample 5 was 97% (H2O was 3%).

[0078] [Comparison of weight reduction ratios] Figure 3 shows the weight loss ratios measured by thermogravimetry for samples 1 to 5 as the temperature rose to 900°C at 10°C / min in a nitrogen stream. The mass change for sample 1 after the test was 0.574, and the volatile content of the ashless coal in sample 1 was 42.6%. Sample 4, which was tested in a carbon dioxide atmosphere, had a mass change of 0.658, and the volatile content was 34.2%. This shows that evaporating the solvent in a carbon dioxide atmosphere reduced the volatile content by 8.4%. Sample 5, in which the solvent was evaporated in an atmosphere containing carbon dioxide and water vapor, also had a volatile content close to that of sample 4. Sample 3, in which the evaporation process was carried out in a nitrogen atmosphere, did not achieve a significant reduction in volatile content.

[0079] [Comparison of elemental composition distribution] The elemental composition distributions of samples 2 to 5 are shown in Figure 4. For ashless coal subjected to solvent recovery in a carbon dioxide atmosphere, the oxygen content, i.e., O / C, tends to increase, indicating slight oxidation.

[0080] [Comparison of solvent-soluble components] The results of tetrahydrofuran elution for each sample after measuring the volatile content are shown in Figure 5. In Figure 5, "soluble" represents the ratio of soluble components in tetrahydrofuran, and "residue" represents the ratio of insoluble components in tetrahydrofuran. Figure 5 shows that sample 4, which was treated in a carbon dioxide atmosphere, had a higher residue yield and residue ratio than sample 3, which was treated in a nitrogen atmosphere. This indicates that the conversion to heavier components clearly progressed during treatment in a carbon dioxide atmosphere.

[0081] [Comparison of softening and melting properties] The thermoplasticity and melting properties of bituminous coal (Sample 8), a sample (Sample 6) in which 10% by mass of Sample 3 was added to 90% by mass of Sample 8, and a sample (Sample 7) in which 10% by mass of Sample 4 was added to 90% by mass of Sample 8 were compared using a Gieseler plastometer. The results are shown in FIG. 6. Sample 7 has lower melting properties than Sample 6. In other words, it can be seen that Sample 7, in which ashless coal in which the solvent was evaporated in a carbon dioxide atmosphere was added, has lower melting properties than Sample 6, in which ashless coal in which the solvent was evaporated in a nitrogen atmosphere was added. When ashless coal is used as a caking additive, if its melting properties are too high, it can reduce the strength of the coke. The ashless coal obtained by the present invention has suppressed melting properties rather than excessive melting properties, making it suitable as a caking additive. [Industrial Applicability]

[0082] The ashless coal manufacturing method and ashless coal manufacturing apparatus of the present invention are suitable for the efficient production of ashless coal because they can suppress the ashless coal in the solvent that is evaporated and separated. [Explanation of symbols]

[0083] 1. Ashless coal production equipment 2 Preparation section 21 Solvent storage tank 22 Coal storage tank 23 Solvent supply 24 Preheater 25 Mixing tube 3 Elution part 31 Elution tank 311 Stirrer 4 Separation part 41 Solid-liquid separator 5 Evaporation section 51 First evaporator 52 Second evaporator 53 Gas supply 54 Recycle Line C R coal C H Ashless coal C S By-product charcoal G Gas L solution M solids concentrate P1 Solvent supply line P2 Coal Supply Line P3 Slurry supply line P4 Solution supply line P5 Concentrate supply line P6 First discharge line P7 Second discharge line P8 Gas supply line T Solvent Y Slurry

Claims

1. a preparation step of mixing coal and a solvent to prepare a slurry; a leaching step of leaching a solvent-soluble component of the coal into the solvent of the slurry; a separation step of separating a solution in which the solvent-soluble components have been dissolved into the solvent in the elution step from the slurry; an evaporation step of evaporating the solvent from the solution separated in the separation step; Equipped with A method for producing ashless coal, in which the evaporation step is carried out in an atmosphere of gas having a carbon dioxide ratio of 97% or more.

2. The method for producing ashless coal according to claim 1, wherein the gas comprises carbon dioxide.

3. The method for producing ashless coal according to claim 1 or 2, wherein the temperature of the coal after mixing with the solvent is increased in at least one of the preparation step and the leaching step.

4. a preparation unit that mixes coal and a solvent to prepare a slurry; an elution section that elutes a solvent-soluble component of the coal into the solvent of the slurry; a separation unit that separates a solution in which the solvent-soluble component is dissolved in the solvent from the slurry; an evaporation section for evaporating the solvent from the separated solution; Equipped with The evaporator comprises an evaporator for evaporating the solvent to obtain ashless coal, and a gas supplier for supplying gas having a carbon dioxide ratio of 97% or more to the evaporator.

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