JP2014163634A - Combustion method of byproduct coal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce cost and power required for pulverization of byproduct coal.SOLUTION: A combustion method of byproduct coal preliminarily sets a reference value of a particle diameter on the basis of particle diameter distribution of byproduct coal; determines whether a large particle having a particle diameter larger than the reference value is included in byproduct coal (step S2); when the large particle having the particle diameter larger than the reference value is included, classifies byproduct coal (step 3); combusts byproduct coal comprising particles having a particle diameter equal to or smaller than the reference value (step S6); and combusts only byproduct coal comprising particles having a particle diameter equal to or larger than the reference value, after pulverization (step 5).

Description

  The present invention relates to a method for combusting by-product coal produced as a by-product when obtaining ashless coal from which ash is removed from coal.

  In the production of steel using a blast furnace, coke obtained by heating and carbonizing raw coal is used as a reducing agent. In recent years, however, the price of coking coal has tended to increase due to the expansion of steel production in emerging countries and the oligopoly on the raw material supply side. Therefore, reducing the cost of coke has become an issue.

  In order to solve the above problems, a method of using ashless coal (hypercoal) as a coking binder has been devised. Ashless coal is a slurry prepared by mixing coal raw material mixed with caking coal in general coal and a solvent, and heating the resulting slurry to extract a coal component soluble in the solvent. By separating the solution containing coal components soluble in the solvent and the solid concentrate containing coal components insoluble in the solvent from the extracted slurry by gravity sedimentation, and separating the solvent from the separated solution. can get.

  Further, as disclosed in Patent Document 1, as a method for burning coal, a method (pulverized coal combustion method) in which coal is pulverized into fine particles and burned is employed. In this method, there is a tendency that the combustibility is improved if the particle size is reduced, and the maximum particle size is set to 150 μm or less. However, the pulverized coal obtained by pulverizing a lump of coal also contains particles having a large particle size with poor combustibility, and the weight passing through a 200 mesh (mesh 74 μm) sieve as an index indicating the degree. Percentage is used. A general pulverized coal combustion boiler is often operated at a weight ratio of about 80%.

JP-A-2-183703

  By the way, in the manufacturing process of ashless coal, by-product coal is manufactured as a by-product other than the ashless coal which is a final product.

  By-product coal is undissolved coal remaining after extracting soluble components from coal (coal remaining after extraction of components soluble in a solvent). And there is a possibility that such byproduct charcoal will be used as fuel for boilers and the like. However, as a result of the ashless coal manufacturing process, the by-product coal has a higher ash differentiation and smaller particle size than the original coal. Therefore, when using by-product coal as fuel, it is necessary to fully consider its properties.

  For example, when general coal is used for pulverized coal combustion, it is necessary to pulverize it into fine particles in order to improve combustibility, and a dedicated device (pulverizer) and a power source for operating the device are necessary. become. However, a test result has been obtained that by-product coal exhibits high combustibility even when the particle size is larger than that of general coal. Therefore, when by-product coal is used for pulverized coal combustion, it is desirable that the by-product coal is not pulverized as much as possible in order to reduce the cost and power involved in pulverization.

  The objective of this invention is providing the combustion method of the byproduct coal which can reduce the cost and power concerning grinding | pulverization of a byproduct coal.

  The combustion method of by-product coal in the present invention is to evaporate and separate the solvent from the solid concentrate remaining when the solution containing coal components soluble in the solvent is separated from the slurry obtained by mixing and heating the coal and the solvent. A by-product coal combustion method, wherein a reference value of a particle size is set in advance based on a particle size distribution of the by-product coal, and particles having a particle size larger than the reference value are added to the by-product coal. A judgment step for judging whether or not it is included, and a combustion step for burning the by-product coal composed of particles having a particle diameter equal to or smaller than the reference value.

  According to the by-product coal combustion method of the present invention, the cost and power associated with the pulverization of the by-product coal can be reduced.

It is a schematic diagram of an ashless coal manufacturing facility. It is a schematic diagram of a byproduct coal combustion facility. It is a flowchart which shows the combustion method of byproduct charcoal. It is a figure which shows the particle diameter distribution of byproduct charcoal. It is a graph which shows the evaluation result of an unburned rate. It is a graph which shows the evaluation result of an unburned rate. It is a figure which shows the SEM image of the particle | grains in the middle of combustion.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(Method for producing ashless coal)
First, the manufacturing method of ashless coal is demonstrated. As shown in FIG. 1, the ashless coal production facility 100 used in the method for producing ashless coal includes a coal hopper 1, a solvent tank 2, and a slurry preparation tank 3 in order from the upstream side of the ashless coal (HPC) production process. , Transfer pump 4, preheater 5, extraction tank 6, gravity sedimentation tank 7, filter unit 8, and solvent separators 9 and 10.

  The manufacturing method of ashless coal has a slurry adjustment process, an extraction process, a separation process, an ashless coal acquisition process, and a byproduct coal acquisition process. Hereinafter, each step will be described. In addition, there is no restriction | limiting in particular in the coal used as a raw material in this manufacturing method, A bituminous coal with a high extraction rate may be used, and cheaper inferior quality coal (subbituminous coal, lignite) may be used. The ashless coal means ash content of 5% by weight or less, preferably 3% by weight or less.

(Slurry preparation process)
The slurry preparation step is a step of preparing a slurry by mixing coal and a solvent. This slurry preparation process is implemented in the slurry preparation tank 3 in FIG. Coal as a raw material is charged into the slurry preparation tank 3 from the coal hopper 1, and a solvent is charged into the slurry preparation tank 3 from the solvent tank 2. The coal and solvent charged into the slurry preparation tank 3 are mixed by the stirrer 3a to become a slurry composed of coal and solvent.

  The mixing ratio of coal with respect to the solvent is, for example, 10 to 50% by weight on the basis of dry coal, and more preferably 20 to 35% by weight.

(Extraction process)
The extraction step is a step of heating the slurry obtained in the slurry preparation step to extract a coal component soluble in the solvent (dissolve in the solvent). This extraction step is performed in the preheater 5 and the extraction tank 6 in FIG. The slurry prepared in the slurry preparation tank 3 is supplied to the preheater 5 by the transfer pump 4 and heated to a predetermined temperature, then supplied to the extraction tank 6, and held at the predetermined temperature while being stirred by the stirrer 6a. Extraction is performed.

  When extracting coal components that are soluble in the solvent by heating the slurry obtained by mixing coal and solvent, a solvent with a large dissolving power for coal, often an aromatic solvent (hydrogen donating property) Or a non-hydrogen-donating solvent) and coal are mixed and heated to extract organic components in the coal.

  The non-hydrogen donating solvent is a coal derivative which is a solvent mainly composed of a bicyclic aromatic and purified mainly from a coal carbonization product. This non-hydrogen-donating solvent is stable even in a heated state and has excellent affinity with coal. Therefore, the proportion of soluble components (herein, coal components) extracted into the solvent (hereinafter also referred to as extraction rate) In addition, it is a solvent that can be easily recovered by a method such as distillation. Main components of the non-hydrogen donating solvent include bicyclic aromatic naphthalene, methyl naphthalene, dimethyl naphthalene, trimethyl naphthalene and the like, and other non-hydrogen donating solvent components have aliphatic side chains. Naphthalenes, anthracenes, fluorenes, and these include biphenyl and alkylbenzenes having long aliphatic side chains.

  In the above description, the case where a non-hydrogen-donating compound is used as a solvent has been described, but it is needless to say that a hydrogen-donating compound (including coal liquefied oil) typified by tetralin may be used as a solvent. . When a hydrogen donating solvent is used, the yield of ashless coal is improved.

  Further, the boiling point of the solvent is not particularly limited. From the viewpoints of pressure reduction in the extraction step and separation step, extraction rate in the extraction step, solvent recovery rate in the ashless coal acquisition step, etc., for example, a solvent having a boiling point of 180 to 300 ° C., particularly 240 to 280 ° C. Preferably used.

  The heating temperature of the slurry in the extraction step is not particularly limited as long as the solvent-soluble component can be dissolved, and is, for example, 300 to 420 ° C. from the viewpoint of sufficient dissolution of the solvent-soluble component and improvement of the extraction rate. More preferably, it is 360-400 degreeC.

  Also, the heating time (extraction time) is not particularly limited, but is, for example, 10 to 60 minutes from the viewpoint of sufficient dissolution and improvement of the extraction rate. The heating time is the total heating time in the preheater 5 and the extraction tank 6 in FIG.

  The extraction process is performed in the presence of an inert gas such as nitrogen. The pressure in the extraction tank 6 is preferably 1.0 to 2.0 MPa, although it depends on the temperature at the time of extraction and the vapor pressure of the solvent used. When the pressure in the extraction tank 6 is lower than the vapor pressure of the solvent, the solvent volatilizes and is not confined in the liquid phase, so that extraction cannot be performed. In order to confine the solvent in the liquid phase, a pressure higher than the vapor pressure of the solvent is required. On the other hand, if the pressure is too high, the cost of the equipment and the operating cost increase, which is not economical.

(Separation process)
In the separation step, the slurry obtained in the extraction step is concentrated by a gravity sedimentation method in which a solution containing a coal component that is soluble in a solvent and a coal component that is insoluble in a solvent (a solvent insoluble component such as ash) is concentrated. It is a process of separating into liquid (solvent insoluble component concentrate). This separation step is performed in the gravity settling tank 7 in FIG. The slurry obtained in the extraction step is separated into a supernatant liquid as a solution and a solid content concentrated liquid by gravity in the gravity settling tank 7. The supernatant liquid in the upper part of the gravity settling tank 7 is discharged to the solvent separator 9 through the filter unit 8 as necessary, and the solid concentrate settled in the lower part of the gravity settling tank 7 is sent to the solvent separator 10. Discharged.

  The gravitational sedimentation method is a method in which a slurry is retained in a tank to settle and separate solvent-insoluble components using gravity. A solvent-insoluble component (for example, ash) having a specific gravity greater than that of a solution containing a coal component that is soluble in the solvent is settled by gravity in the lower part of the gravity settling tank 7. A continuous separation process is possible by continuously discharging the supernatant from the top and the solid concentrate from the bottom while continuously supplying the slurry into the tank.

  The gravity sedimentation tank 7 is preferably kept warm (or heated) or pressurized in order to prevent reprecipitation of solvent-soluble components eluted from coal. The heat retention (heating) temperature is, for example, 300 to 380 ° C., and the tank internal pressure is, for example, 1.0 to 3.0 MPa.

  As a method for separating the solution containing the coal component dissolved in the solvent from the slurry obtained in the extraction step, there are a filtration method, a centrifugal separation method, and the like in addition to the gravity sedimentation method.

(Ashless coal acquisition process)
The ashless coal acquisition step is a step of obtaining ashless coal (HPC) by evaporating and separating the solvent from the solution (supernatant liquid) separated in the separation step. This ashless charcoal acquisition process is performed by the solvent separator 9 in FIG. The solution separated in the gravity settling tank 7 is filtered by the filter unit 8 and then supplied to the solvent separator 9, and the solvent is evaporated and separated from the supernatant in the solvent separator 9. Here, it is preferable that the solvent is separated from the solution in the presence of an inert gas such as nitrogen. In this embodiment, the solvent is evaporated and separated from the solution in nitrogen gas introduced into the solvent separator 9.

  As a method for separating the solvent from the solution (supernatant liquid), a general distillation method, evaporation method or the like can be used. The solvent separated by the solvent separator 9 is returned to the solvent tank 2 and circulated and used repeatedly. In addition, although it is preferable to circulate and use a solvent, it is not indispensable (the same is true in the by-product charcoal acquisition step described later). By separating the solvent from the supernatant, ashless charcoal (HPC) substantially free of ash can be obtained. Ashless coal contains almost no ash, has no moisture, and exhibits a higher calorific value than raw coal. Furthermore, softening meltability (fluidity), which is a particularly important quality as a raw material for coke for iron making, has been greatly improved, and the obtained ashless coal (HPC) is good even if the raw coal does not have softening meltability Soft meltability. Therefore, ashless coal can be used, for example, as a blended coal for coke raw materials. In addition, ashless coal containing almost no ash content has high combustion efficiency and can reduce the generation of coal ash. Therefore, the use of ashless coal as a gas turbine direct injection fuel in a high-efficiency combined power generation system based on gas turbine combustion has attracted attention.

(By-product coal acquisition process)
The byproduct charcoal acquisition step is a step of obtaining byproduct charcoal by evaporating and separating the solvent from the solid concentrate separated in the separation step. This byproduct charcoal acquisition step is performed by the solvent separator 10 in FIG. The solid content concentrate separated in the gravity sedimentation tank 7 is supplied to the solvent separator 10, and the solvent is evaporated and separated from the solid content concentrate in the solvent separator 10. Here, it is preferable to carry out the evaporation and separation of the solvent from the solid concentrate in the presence of an inert gas such as nitrogen. In the present embodiment, the solvent is evaporated and separated from the solid concentrate in the nitrogen gas introduced into the solvent separator 10.

  As a method for separating the solvent from the solid concentrate, a general distillation method or evaporation method can be used as in the above-described ashless coal acquisition step. The solvent separated by the solvent separator 10 is returned to the solvent tank 2 and circulated and used repeatedly. By separating the solvent, by-product charcoal (also referred to as RC or residual charcoal) in which solvent-insoluble components including ash and the like are concentrated can be obtained from the solid concentrate. By-product charcoal contains ash, but has no water and has a sufficient calorific value. By-product coal does not exhibit softening and melting properties, but the oxygen-containing functional groups are eliminated, so that when used as a blended coal, it inhibits the softening and melting properties of other coals contained in this blended coal. It is not a thing. Therefore, this by-product coal can be used as a part of the blended coal of the coke raw material, as in the case of ordinary non-slightly caking coal, and is used for various fuels without using the coke raw coal. It is also possible.

(By-product coal combustion method)
Next, a method for combusting by-product coal will be described. As shown in FIG. 2, the by-product coal combustion facility 20 used in the by-product coal combustion method includes an upstream by-product coal hopper 21, a classifier 22, and a pulverizer in order from the upstream side of the by-product coal combustion process. 23, a downstream by-product coal hopper 24, and a pulverized coal combustion boiler 25 are provided.

  The upstream by-product coal hopper 21 stores by-product coal by-produced in the ashless coal production process. In addition, without using the upstream side by-product coal hopper 21, the by-product coal may be stored in a pile. The classifier 22 classifies the by-product coal supplied from the upstream side by-product coal hopper 21 into particles having a particle size equal to or smaller than a reference value and particles having a particle size larger than the reference value. Here, the reference value is a value of the particle diameter set in advance based on the particle diameter distribution of the byproduct coal, and is 500 μm in the present embodiment. The pulverizer 23 pulverizes particles having a particle size larger than a reference value to obtain particles having a particle size equal to or less than the reference value. The downstream by-product coal hopper 24 stores by-product coal composed of particles having a particle size of a reference value or less. The pulverized coal combustion boiler 25 burns by-product coal supplied from the downstream by-product coal hopper 24.

  The combustion method of by-product coal of this embodiment has a measurement process, a judgment process, a classification process, a crushing process, and a combustion process. Hereinafter, each process is demonstrated, referring the flowchart of FIG.

(Measurement process)
First, a part of the by-product coal stored in the upstream side by-product coal hopper 21 is taken out as a sample, and the particle size distribution of the by-product coal is measured (step S1, hereinafter, simply referred to as S1, the same applies to others). For measuring the particle size distribution, a sieve or a laser diffraction / scattering method is used. Here, the laser diffraction scattering method utilizes the fact that the intensity distribution of the light diffracted and scattered by the laser irradiated to the particles of by-product coal dissolved in water differs for each particle diameter. In the present embodiment, the particle size distribution of the sample taken out from the upstream side by-product coal hopper 21 is measured. However, the particle size distribution of the total amount of by-product coal stored in the upstream side by-product coal hopper 21 is measured. May be measured.

(Judgment process)
Next, based on the measured particle size distribution, it is determined whether or not by-product coal contains particles having a particle size larger than the reference value (S2). Here, the reference value is set to 500 μm based on the particle size distribution of normal by-product coal based on the maximum particle size being 500 μm or less. And the byproduct charcoal which consists of particle | grains whose particle diameter is 500 micrometers or less shows high combustibility, even if it does not grind | pulverize. When it is determined that particles having a particle size larger than the reference value are not included in the by-product coal (S2: NO), all of the by-product coal stored in the upstream side by-product coal hopper 21 has a particle size. Is made up of particles below the reference value, and the by-product coal in the upstream by-product coal hopper 21 is sent to the downstream by-product coal hopper 24. The byproduct coal in the downstream byproduct coal hopper 24 is burned in the pulverized coal combustion boiler 25 (S6).

  In this way, when the by-product coal is composed of particles having a particle size of the reference value or less, the by-product coal is burned as it is without being pulverized. Thereby, since the opportunity of a grinding | pulverization can be reduced, the cost and power which concern on the grinding | pulverization of byproduct charcoal can be reduced.

(Classification process)
On the other hand, when it is determined that particles having a particle diameter larger than the reference value are included in the by-product coal (S2: YES), the by-product coal in the upstream by-product coal hopper 21 is sent to the classifier 22. The classifier 22 classifies the by-product coal into particles having a particle size equal to or smaller than a reference value and particles having a particle size larger than the reference value (S3). A sieve is preferably used for classification.

  And it is judged whether a particle diameter is a particle | grain below a reference value (S4). When it is determined that the particle size is a particle having a reference value or less (S4: YES), the particle is sent to the downstream side by-product coal hopper 24. The byproduct coal in the downstream byproduct coal hopper 24 is burned in the pulverized coal combustion boiler 25 (S6). On the other hand, when it is determined that the particle diameter is larger than the reference value (S4: NO), the particle is sent to the pulverizer 23.

(Crushing process)
The pulverizer 23 pulverizes the particles having a particle diameter larger than the reference value sent from the classifier 22 to obtain particles having a particle diameter equal to or smaller than the reference value (S5). Then, the particles are sent to the downstream side by-product coal hopper 24. The byproduct coal in the downstream byproduct coal hopper 24 is burned in the pulverized coal combustion boiler 25 (S6).

  Thus, by pulverizing only the particles having a particle size larger than the reference value, the cost and power associated with the pulverization of by-product coal can be suitably reduced.

(Combustion process)
The byproduct coal sent to the downstream side byproduct coal hopper 24 is supplied to the pulverized coal combustion boiler 25. The pulverized coal combustion boiler 25 burns by-product coal that is supplied from the downstream by-product coal hopper 24 and has particles having a particle size equal to or smaller than a reference value (S6). By-product coal burned in the pulverized coal combustion boiler 25 is not mixed with any other types of coal or ashless coal. That is, by-product coal having a purity of 100% is burned in the pulverized coal combustion boiler 25.

  In addition, when there are a plurality of by-product coal lots produced under the same production conditions such as raw coal, weather, and each production process, the particle size distribution is estimated to be the same for each lot. Therefore, when there are a plurality of by-product coal lots manufactured under the same manufacturing conditions, the measurement process and the determination process are performed for one lot, and the lots for which the measurement process and the determination process are performed for the other lots. Assuming that the particle size distribution is the same, the measurement step and the determination step may be omitted.

(Flammability evaluation)
Next, the combustibility of the by-product coal was evaluated under the condition that the by-product coal was not pulverized. Table 1 shows the composition analysis results of the coal samples used in this test. By-product coal used was by-product coal produced from Australian bituminous coal. This by-product coal is characterized by low volatile content and high ash content compared to raw bituminous Australian bituminous coal. Here, the fuel ratio is a value obtained by dividing fixed carbon by volatile matter. Industrial analysis values and elemental analysis values are anhydrous base (% -DB), total calorific value is kcal / kg-AD (air-dry), and moisture is air-dry base (% -AD).

  The particle size distribution of the byproduct coal used in this test is shown in FIG. From the particle size distribution shown in FIG. 4, it can be seen that about 50% of particles having a size of 75 μm or less and about 30% of particles having a size of 150 μm or more and 500 μm or less are included. Moreover, the particle diameters of the byproduct coal used in this test are all 500 μm or less.

  In this test, in order to evaluate the combustibility of the by-product coal under conditions where the by-product coal is not crushed, (1) by-product coal comprising particles having a particle diameter of 45 to 75 μm (HPC-RC 45-75 μm) And (2) by-product coal (HPC-RC 75-150 μm) composed of particles having a particle size of 75 to 150 μm, and (3) by-product coal composed of particles having a particle size of 150 to 425 μm (HPC-RC 150-). 425 μm), (4) unclassified by-product coal (HPC-RC Total) composed of particles having a particle size distribution shown in FIG. 4, and (5) particle size used in an actual boiler. Was compared with Australian bituminous coal consisting of particles of 45-75 μm (Australian bituminous coal 45-75 μm).

  Here, the combustion conditions in this test were determined in consideration of the air ratio of the actual pulverized coal furnace and the furnace temperature (about 1200 ° C.). Specifically, the air ratio was 1.2, and the test temperatures were 1000 ° C and 1200 ° C. Here, the air ratio is obtained by dividing the supply air amount by the theoretical air amount.

In this test, evaluation was performed using the unburned rate as an indicator of burnout. The unburned rate (Uc ^* ) can be determined from the carbon content in the combustion ash (unburned carbon in ash, Uc) and the ash content (Ash), as shown below. The unburned rate means that the smaller the value, the better the combustibility. The reason why the ash content is taken into account is that the ash content varies depending on the coal brand. In this test, combustion ash was collected from several locations in the furnace, and the unburned rate was calculated from the unburned carbon contained in the combustion ash.

  5 and 6 show the evaluation results of the unburned rate. FIG. 5 shows the unburned rate when the test temperature is 1000 ° C., and FIG. 6 shows the unburned rate when the test temperature is 1200 ° C. The particle size of by-product charcoal is (1) (HPC-RC 45-75 μm), (2) (HPC-RC 75-150 μm), (3) (HPC-RC 150-425 μm), (4) (HPC- RC Total), and the particle size of Australian bituminous coal was one condition of (5) (Australian bituminous coal 45-75 μm). Here, “45-75 μm” means a sample on a sieve of 45 μm or more and 75 μm or less. “Total” is a sample that contains about 50% of particles of 75 μm or less and about 30% of particles of 150 μm or more and 500 μm or less, in which the particle diameter is not classified as shown in FIG.

  When paying attention to the particle size of the by-product coal, the lowest unburned rate is (1) (HPC-RC 45-75 μm), and it was confirmed that the unburned rate increases as the particle size increases. This is because the completion time of the char surface reaction increases as the particle diameter increases. On the other hand, the unburned rate of (4) (HPC-RC Total) was higher than (2) (HPC-RC 75-150 μm) and lower than (3) (HPC-RC 150-425 μm). From this, it is considered that particles of 150 μm or more and 500 μm or less included in about 30% of (4) (HPC-RC Total) are the cause of increasing the unburned rate. This result confirmed that the test temperature had the same tendency at 1000 ° C. and 1200 ° C.

  In general coal, it is known that the unburnt rate increases as the fuel ratio increases. However, the by-product coal produced as a by-product of the ashless coal production process has a low unburned rate despite a high fuel ratio. This reversal phenomenon will be considered using an SEM image of particles in the middle of combustion shown in FIG. These SEM images are test results at a test temperature of 1000 ° C. The difference in shape is noticeable in the particles of Australian bituminous coal and by-product coal during combustion. That is, Australian bituminous coal has a balloon structure that is considered to have low reactivity as described above, while by-product coal has a skeleton structure that is porous like pumice and has a rough surface shape. As a cause of the by-product coal having such a structure, it is conceivable that a component having soft melting property was removed by solvent extraction in the production process of ashless coal. And it is estimated that such a structure is the reason which improved the combustibility of byproduct charcoal.

  From the results of the unburned rate in this test, it is understood that the by-product coals (1) to (4) have good combustion characteristics similar to the Australian bituminous coals (5). It can also be seen that the unburned rate of by-product coal is approximately the same as that of Australian bituminous coal if the particle size is 150 μm or less.

  Further, if the by-product coal is composed of particles having a particle size of 500 μm or less, the by-product coal of (4) containing particles having a particle size of 150 μm or more and 500 μm or less in a proportion of 30% by weight or less is pulverized. It can be seen that it can be burned without. Therefore, the opportunity of grinding | pulverization can be reduced by burning such byproduct charcoal, without grind | pulverizing.

(effect)
As described above, according to the by-product coal combustion method according to the present embodiment, a reference value of the particle size is set in advance based on the particle size distribution of the by-product coal, and the particle size is larger than the reference value. Is determined to be included in the by-product coal, and the by-product coal composed of particles having a particle diameter equal to or smaller than a reference value is burned. Here, when combusting general coal, it is necessary to grind into fine particles in order to improve combustibility. However, a test result has been obtained that by-product coal exhibits high combustibility even when the particle size is larger than that of general coal. Therefore, when the by-product coal is composed of particles having a particle size of a reference value or less, the by-product coal is burned as it is without being pulverized. Thereby, since the opportunity of a grinding | pulverization can be reduced, the cost and power which concern on the grinding | pulverization of byproduct charcoal can be reduced.

  For by-product charcoal containing particles having a particle size larger than the reference value, by-product charcoal is obtained by pulverizing particles having a particle size larger than the reference value to obtain particles having a particle size equal to or smaller than the reference value. After all the particle size of the coal is less than the standard value, the by-product coal is burned. Thus, by pulverizing only the particles having a particle size larger than the reference value, the cost and power associated with the pulverization of by-product coal can be suitably reduced.

  In addition, by-product coal comprising particles having a particle size of 500 μm or less and containing particles having a particle size of 150 μm or more and 500 μm or less in a proportion of 30% by weight or less is burned as it is without being pulverized. Generally, in pulverized coal combustion of coal, the maximum particle size is required to be 150 μm or less. However, if the by-product charcoal is composed of particles having a particle size of 500 μm or less, even if it contains particles having a particle size of 150 μm or more and 500 μm or less in a proportion of 30% by weight or less, it has high combustibility without pulverization. Show. Therefore, the opportunity for pulverization can be reduced by burning such by-product coal without pulverization.

(Modification of this embodiment)
The embodiment of the present invention has been described above, but only specific examples are illustrated, and the present invention is not particularly limited, and the specific configuration and the like can be appropriately changed in design. Further, the actions and effects described in the embodiments of the invention only list the most preferable actions and effects resulting from the present invention, and the actions and effects according to the present invention are described in the embodiments of the present invention. It is not limited to what was done.

DESCRIPTION OF SYMBOLS 1 Coal hopper 2 Solvent tank 3 Slurry preparation tank 3a Stirrer 4 Transfer pump 5 Preheater 6 Extraction tank 6a Stirrer 7 Gravity settling tank 8 Filter unit 9,10 Solvent separator 20 Byproduct coal combustion equipment 21 Upstream side byproduct coal hopper 22 Classifier 23 Crusher 24 Downstream side byproduct coal hopper 25 Pulverized coal combustion boiler 100 Ashless coal production facility

Claims (3)

This is a by-product coal combustion method obtained by evaporating and separating the solvent from the solid concentrate remaining when the solution containing coal components soluble in the solvent is separated from the slurry obtained by mixing and heating the coal and the solvent. And
A determination step of setting a reference value of the particle diameter in advance based on the particle size distribution of the byproduct charcoal, and determining whether particles having a particle diameter larger than the reference value are included in the byproduct charcoal,
A combustion step of burning the by-product coal consisting of particles having a particle size of the reference value or less;
A by-product charcoal combustion method characterized by comprising: When the by-product coal contains particles having a particle size larger than the reference value, a classification step of classifying the particles into particles having a particle size equal to or smaller than the reference value and particles having a particle size larger than the reference value;
Pulverizing particles having a particle size larger than the reference value to make particles having a particle size equal to or less than the reference value; and
The by-product coal combustion method according to claim 1, further comprising: The by-product charcoal comprising particles having a particle diameter of 500 μm or less and containing particles having a particle diameter of 150 μm or more and 500 μm or less in a proportion of 30% by weight or less is burned. By-product coal combustion method.