JP2020066722A - Method of producing coke - Google Patents

Abstract

To provide a method of producing coke that enables the production of high strength coke at a low cost through increase of fluidity of blended coal for coke.SOLUTION: A method of producing coal, comprising a step of mixing a first coal with an ashless coal, a step of heating the blended coal obtained in the mixing step, a step of adding a second coal to the blended coal resulting from the heating step, and a step of dry-distilling the blended coal for coke obtained by the step of addition of the second coal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing coke.

  Coke used for iron making in a blast furnace functions as a reducing agent for iron ore (iron oxide), as a heat source (fuel), and withstands the load between the coke itself and the iron ore, and has air permeability in the furnace. Three major functions are expected as the function of the filler to secure the above. In order to fulfill these functions, the coke is required to have a certain strength and reactivity (reducing property and combustibility).

  Generally, coke is produced by forming coal and then steaming it at a high temperature of 1000 ° C. or higher (hereinafter, sometimes referred to as “dry distillation”). When coking coal, which is a highly cohesive coal, is used as the coal, strong coke can be easily obtained, but such coking coal is relatively expensive. Therefore, it is desirable to use inexpensive inferior coal for the purpose of reducing the production cost of coke. However, when the poor quality coal is used, the strength of the coke is reduced due to its low caking property, so that the amount of the poor quality coal that can be blended is limited.

  On the other hand, in order to obtain coke while suppressing the amount of coking coal having a high degree of caking, a method has been proposed in which mixed coal obtained by mixing steam coal and ashless coal is used as a coke raw material (JP (See JP-A-2015-193740). In this method, ashless coal is used as a caking filler (binder), and the mixed coal is made to have the same properties as the coking coal by controlling the Gieseler flow and the average maximum reflectance. It curbs the amount of charcoal used and reduces the cost of coke raw materials.

  In the method of producing coke using such a caking filler, if the flowability of steam coal, which is the blended coal for coke, is insufficient, the strength of coke may not be sufficiently increased. Therefore, in the method for producing coke using the caking filler, it is required to improve the fluidity of the mixed coal for coke during production.

JP, 2005-193740, A

  The present invention has been made based on the above circumstances, and an object of the present invention is to provide a method for producing coke that can inexpensively produce high-strength coke by increasing the fluidity of the coking coal blend. And

  The present inventors improved the fluidity of the coal blending coal by preheating the mixed coal obtained by mixing a part of the coal blending coal for coke used as a coke raw material and ashless coal. The present invention has been completed and the present invention has been completed. It is not clear why this heat treatment improves the fluidity of the coal blending coal for coke, but the present inventors have found that the ashless coal, which was present as granules before the heat treatment, was heated inside the coal particles by the heat treatment. It is believed that this is because it was impregnated into the coal and changed into a form that facilitates fluidization of coal.

  That is, the method for producing a coke of the invention made to solve the above-mentioned problems is a step of mixing the first coal and the ashless coal, a step of heating the mixed coal obtained in the mixing step, and the heating step. It is provided with a step of adding the second coal to the subsequent mixed coal, and a step of dry-distilling the mixed coal for coke obtained in the additional step.

  In the coke manufacturing method, since ashless coal is used as the caking filler, the coke manufacturing cost can be reduced. Moreover, in the coke manufacturing method, in the heating step, the mixed coal obtained by mixing the first coal, which is a part of the coal of the coal blend for coke, and the ashless coal is preheated. In the method for producing the coke, the heat treatment can improve the fluidity of the coal blend for coke. Therefore, the strength of the obtained coke can be increased by using the method for producing the coke. From the above, by using the coke manufacturing method, it is possible to manufacture coke having high strength at low cost.

  Before the additional step, a step of cooling the mixed coal after the heating step may be further provided. By further providing the cooling step in this way, it is not necessary to continuously operate the heating step and the dry distillation step, and thus operation management becomes easier. Further, the mixed coal after the cooling step can be used as one of the coke raw materials in the same manner as steam coal or the like. Therefore, since the coke production method includes the cooling step, the additional step and the dry distillation step can be performed in the existing equipment, so that new equipment investment can be eliminated and the production cost can be reduced.

  The heating temperature in the heating step is preferably 250 ° C. or higher and 500 ° C. or lower. By setting the heating temperature in the heating step within the above range, the effect of improving the fluidity of the mixed coal for coke can be enhanced while suppressing the progress of dry distillation of the mixed coal.

  The content of ashless coal in the mixed coal is preferably 5% by mass or more and 30% by mass or less. By setting the blending amount of the ashless coal in the mixed coal within the above range, the fluidity improving effect of the coking blended coal can be enhanced while suppressing the decrease in the strength of the coke.

  The raw material for the ashless coal may be steam coal. By using steam coal as the raw material for the ashless coal in this manner, the manufacturing cost can be reduced while ensuring the fluidity of the blended coal for coke.

  Here, ashless coal (Hypercoal, HPC) is a type of reformed coal obtained by reforming coal, and is a reformed coal obtained by removing ash and insoluble components from coal using a solvent as much as possible. Is. However, the ashless coal may contain ash as long as the fluidity and expandability of the ashless coal are not significantly impaired. Generally, coal contains 7% by mass or more and 20% by mass or less of ash, but ashless coal may contain about 2% by mass, and in some cases about 5% by mass. In addition, "ash content" means the value measured based on JIS-M8812: 2004.

  Further, the “general coal” is a coal having a calorific value (anhydrous ashless standard) (kcal / kg) of 5800 or more and less than 8400, and examples thereof include bituminous coal, subbituminous coal, and brown coal.

  As described above, by using the method for producing the coke, the coke having high strength can be produced at a low cost by increasing the fluidity of the coal blend for coke.

It is a flowchart which shows the manufacturing method of the coke which concerns on one Embodiment of this invention. It is a flowchart which shows the detail of the ashless coal manufacturing process of FIG. It is a schematic diagram which shows the manufacturing apparatus of the ashless coal used in the ashless coal manufacturing process of FIG. 5 is a graph showing the amount of Hm component in Example 1 and Comparative Example 1. 5 is a graph showing the amounts of Hm components in Example 2 and Comparative Example 2. 9 is a graph showing the amounts of Hm components in Example 3 and Comparative Example 3. 9 is a graph showing the amounts of Hm components in Example 4 and Comparative Example 4.

  Hereinafter, a coke manufacturing method according to an embodiment of the present invention will be described.

  As shown in FIG. 1, a coke manufacturing method according to an embodiment of the present invention includes an ashless coal manufacturing step S1, a mixing step S2, a heating step S3, a cooling step S4, an additional step S5, and a dry distillation. And step S6.

[Ashless coal manufacturing process]
In the ashless coal manufacturing step S1, ashless coal is manufactured. In the method for producing coke, as the ashless coal production step S1, as shown in FIG. 2, a slurry preparation step S11, a solid-liquid separation step S12, and a solvent evaporation step S13 are provided. This ashless coal manufacturing step S1 can be performed using, for example, an ashless coal manufacturing apparatus as shown in FIG. First, the ashless coal manufacturing apparatus will be described.

<Ashless coal production equipment>
The ashless coal manufacturing apparatus shown in FIG. 3 includes a coal supply unit 1, a solvent supply unit 2, a mixing unit 3, a pump 4, a heating unit 5, an elution unit 6, a solid-liquid separation unit 7, The 1st solvent evaporation part 8 and the 2nd solvent evaporation part 9 are mainly provided.

(Coal supply department)
The coal supply unit 1 supplies coal to the mixing unit 3. As the coal supply unit 1, a known coal hopper such as a normal pressure hopper used under a normal pressure condition and a pressure hopper used under a normal pressure condition and a pressurized condition can be used.

  The coal supplied from the coal supply unit 1 is a raw material for ashless coal. As the coal, various quality coals can be used. Above all, it is preferable that the raw material of the ashless coal is steam coal. By using steam coal as the raw material for the ashless coal in this manner, it is possible to reduce the production cost of coke while ensuring the fluidity of the blended coal for coke. As the steam coal, bituminous coal having a high extraction rate may be used, or less expensive poor quality coal (subbituminous coal, brown coal) may be used.

  When coal is classified by particle size, finely pulverized coal is preferably used. Here, "finely pulverized coal" means, for example, coal in which the mass ratio of coal having a particle size of less than 1 mm is 80% or more with respect to the mass of the entire coal. Further, lump coal can be used as the coal supplied from the coal supply unit 1. Here, “lump coal” means, for example, 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. In the agglomerated coal, the particle size of the undissolved solid content coal is kept larger than that of the finely pulverized coal, so that the separation in the solid-liquid separation unit 7 described later can be made efficient. Here, the “particle size (particle size)” refers to a value measured according to the general rule of sieving test of JIS-Z8815: 1994. In addition, for sorting by the particle size of coal, for example, a metal net sieve defined in JIS-Z8801-1: 2006 can be used.

  The lower limit of the carbon content of the steam coal is preferably 70% by mass. On the other hand, the upper limit of the carbon content of the steam coal is preferably 85% by mass, more preferably 82% by mass. If the carbon content of the steam coal is less than the lower limit, the elution rate of the solvent-soluble component may decrease. On the contrary, if the carbon content of the steam coal exceeds the upper limit, the cost of the supplied coal may increase.

(Solvent supply section)
The solvent supply unit 2 supplies the solvent to the mixing unit 3. The solvent supply unit 2 has a solvent tank for storing the solvent, and supplies the solvent from the solvent tank to the mixing unit 3. The solvent supplied from the solvent supply unit 2 is mixed with the coal supplied from the coal supply unit 1 in the mixing unit 3.

  The solvent supplied from the solvent supply unit 2 is not particularly limited as long as it dissolves coal. For example, a bicyclic aromatic compound derived from coal is preferably used. Since the basic structure of this two-ring aromatic compound is similar to the structural molecule of coal, it has a high affinity with coal and a relatively high extraction rate can be obtained. Examples of the bicyclic aromatic compound derived from coal include methylnaphthalene oil and naphthalene oil, which are distilled oils as by-product oils when carbon is dry-distilled to produce coke.

(Mixing section)
The mixing unit 3 mixes the coal supplied from the coal supply unit 1 and the solvent supplied from the solvent supply unit 2.

  As the mixing section 3, a preparation tank 31 can be used. The solvent and coal are supplied to the preparation tank 31 via a supply pipe. In the preparation tank 31, the supplied solvent and coal are mixed to prepare a slurry. Further, the preparation tank 31 has a stirrer 31a, and maintains the mixed state of the slurry by holding the mixed slurry while stirring with the stirrer 31a.

  As a minimum of coal concentration on the anhydrous carbon basis in slurry in preparation tank 31, 10 mass% is preferred and 13 mass% is more preferred. On the other hand, the upper limit of the coal concentration is preferably 25% by mass, more preferably 20% by mass. If the coal concentration is less than the lower limit, the amount of the solvent-soluble components eluted in the heating unit 5 described later is smaller than the amount of the slurry processed, which may reduce the production efficiency of ashless coal. . On the other hand, when the coal concentration exceeds the upper limit, the solvent-soluble component is likely to be saturated in the solvent, so that the elution rate of the solvent-soluble component may be reduced.

  The slurry prepared in the preparation tank 31 of the mixing section 3 is sent to the heating section 5 via a supply pipe.

(pump)
The pump 4 is arranged in a supply pipe that supplies the slurry from the mixing unit 3 to the heating unit 5, and pumps the slurry stored in the preparation tank 31 to the heating unit 5.

  The type of the pump 4 is not particularly limited as long as the slurry can be pressure-fed to the heating unit 5 via the supply pipe, but for example, a positive displacement pump or a non-positive displacement pump can be used. Examples of the positive displacement pump include a diaphragm pump and a tube diaphragm pump, and examples of the non-positive displacement pump include a centrifugal pump.

(Heating part)
The heating unit 5 heats the slurry obtained in the mixing unit 3.

  A heating furnace 51 can be used as the heating unit 5. The heating furnace 51 is not particularly limited as long as it can heat the slurry passing through it, and examples thereof include a resistance heating type heater and an induction heating coil. Further, the heating furnace 51 may be configured to perform heating by using a heating medium, and has, for example, a heating pipe arranged around the flow path of the slurry passing through the inside, and the heating pipe has steam. The slurry may be heated by supplying a heat medium such as oil.

  The lower limit of the temperature of the slurry after being heated by the heating furnace 51 is preferably 300 ° C, and more preferably 360 ° C. On the other hand, the upper limit of the temperature of the slurry is preferably 420 ° C, more preferably 400 ° C. If the temperature of the slurry is lower than the lower limit, the bond between molecules forming coal cannot be sufficiently weakened, and the elution rate may decrease. On the contrary, when the temperature of the slurry exceeds the upper limit, the amount of heat for maintaining the temperature of the slurry unnecessarily increases, which may increase the manufacturing cost.

(Elution part)
The elution section 6 elutes the coal component soluble in the solvent from the coal in the slurry obtained by the mixing section 3 and heated by the heating section 5.

  As the elution section 6, an extraction tank 61 can be used, and the heated slurry is supplied to the extraction tank 61. In the extraction tank 61, the solvent-soluble coal component is eluted from the coal while maintaining the temperature of the slurry. Moreover, the extraction tank 61 has a stirrer 61a. The elution can be promoted by stirring the slurry with the stirrer 61a.

  The elution time in the elution section 6 is not particularly limited, but is preferably 10 minutes or more and 70 minutes or less from the viewpoint of the extraction amount of the solvent-soluble component and the extraction efficiency.

(Solid-liquid separation part)
The solid-liquid separation unit 7 separates the slurry, which has been eluted by the elution unit 6, into a liquid component containing a solvent-soluble component and a solid component containing a solvent-insoluble component. The solvent-insoluble component is an extraction residue that mainly contains ash and insoluble coal that are insoluble in the extraction solvent, and that further contains the extraction solvent.

  The separation in the solid-liquid separation unit 7 can be performed by, for example, the gravity sedimentation method. Here, the gravity sedimentation method is a separation method in which solid content is sedimented by utilizing gravity in a sedimentation tank to perform solid-liquid separation. When the separation is performed by the gravity settling method, the liquid component containing the solvent-soluble component is collected in the upper part of the settling tank. This liquid component is filtered using a filter unit as needed, and then discharged to the first solvent evaporation unit 8. On the other hand, the solid content containing the solvent-insoluble component is collected in the lower part of the solid-liquid separation section 7 and discharged to the second solvent evaporation section 9.

  Further, when performing the separation by the gravity settling method, it is possible to discharge the liquid component containing the solvent-soluble component and the solid component containing the solvent-insoluble component from the sedimentation tank while continuously supplying the slurry into the solid-liquid separation unit 7. it can. This allows continuous solid-liquid separation processing.

  The time for maintaining the slurry in the solid-liquid separation unit 7 is not particularly limited, but can be, for example, 30 minutes or more and 120 minutes or less, and the sedimentation separation in the solid-liquid separation unit 7 is performed within this time. When the agglomerate coal is used as the coal, the sedimentation separation is made efficient, so that the time for maintaining the slurry in the solid-liquid separation unit 7 can be shortened.

  It is preferable to heat and pressurize the inside of the solid-liquid separation section 7. As a lower limit of the heating temperature in the solid-liquid separation section 7, 300 ° C is preferable, and 350 ° C is more preferable. On the other hand, the upper limit of the heating temperature in the solid-liquid separation section 7 is preferably 420 ° C, more preferably 400 ° C. If the heating temperature is lower than the lower limit, the solvent-soluble component may be re-precipitated and the separation efficiency may be reduced. On the contrary, if the heating temperature exceeds the upper limit, the operating cost for heating may increase.

  The lower limit of the pressure in the solid-liquid separation unit 7 is preferably 1 MPa, more preferably 1.4 MPa. On the other hand, the upper limit of the pressure is preferably 3 MPa, more preferably 2 MPa. If the pressure is less than the lower limit, solvent-soluble components may be re-precipitated and the separation efficiency may be reduced. On the contrary, if the pressure exceeds the upper limit, the operating cost for pressurization may increase.

  In addition to the gravity sedimentation method, for example, a filtration method or a centrifugal separation method may be used as a method for separating the liquid content and the solid content. When a filtration method or a centrifugal separation method is used as the solid-liquid separation method, a filter, a centrifugal separator or the like is used as the solid-liquid separation unit 7.

(First solvent evaporation section)
The first solvent evaporation unit 8 evaporates and recovers the solvent from the liquid component separated by the solid-liquid separation unit 7. Ashless coal HPC is obtained by evaporative recovery of this solvent.

  As the method for evaporating and separating the solvent, a separation method including a general distillation method using an evaporative separator and an evaporation method (a spray dry method or the like) can be used.

(Second solvent evaporation section)
The second solvent evaporation unit 9 evaporates and separates the solvent from the solid content separated by the solid-liquid separation unit 7 to obtain byproduct coal RC. The second solvent evaporation unit 9 can be configured similarly to the first solvent evaporation unit 8.

  Although the by-product charcoal RC does not exhibit softening and melting properties, the oxygen-containing functional group is eliminated. Therefore, the by-product coal RC does not impair the softening and melting properties of other coals contained in this coal blend when used as the coal blend. Therefore, this coal blend can be used as a part of the coal blend of the coke raw material. Further, the by-product coal RC may be used as a fuel similarly to general coal.

  Next, each step of the ashless coal manufacturing step S1 will be described.

<Slurry preparation process>
In the slurry preparation step S11, a slurry containing coal and a solvent is prepared.

  In the slurry preparation step S11, first, the coal supplied from the coal supply unit 1 and the solvent supplied from the solvent supply unit 2 are mixed by the preparation tank 31 of the mixing unit 3 to form a slurry.

  Next, the obtained slurry is heated. Specifically, the prepared slurry is supplied to the heating furnace 51 of the heating unit 5 by the pump 4 and heated to a desired temperature.

  Further, the coal component soluble in the solvent is eluted from the coal in the obtained slurry. Specifically, the heated slurry is supplied to the extraction tank 61, and is stirred at a stirrer 61a and held at a desired temperature for elution.

<Solid-liquid separation process>
In the solid-liquid separation step S12, the slurry in which the solvent-soluble component of coal is eluted in the slurry preparation step S11 is subjected to solid-liquid separation into a liquid component containing the solvent-soluble component and a solid component containing the solvent-insoluble component.

  Specifically, the slurry discharged from the extraction tank 61 is supplied to the solid-liquid separation unit 7, and the slurry supplied into the solid-liquid separation unit 7 is separated into the liquid component and the solid component by, for example, a gravity sedimentation method. .

<Solvent evaporation process>
In the solvent evaporation step S13, the solvent is evaporated from the liquid component separated in the solid-liquid separation step S12. This gives ashless charcoal HPC.

  Specifically, the liquid component separated by the solid-liquid separation unit 7 is supplied to the first solvent evaporation unit 8, the solvent is evaporated by the first solvent evaporation unit 8, and the liquid component is mixed with the solvent and ashless coal HPC. To separate.

  In the solvent evaporation step S13, the solvent may be evaporated from the solid content that has been separated in the solid-liquid separation step S12. Specifically, the solid content separated by the solid-liquid separation unit 7 is supplied to the second solvent evaporation unit 9, and the solvent is evaporated by the second solvent evaporation unit 9. As a result, by-product charcoal RC can be obtained from the solid content.

[Mixing process]
In the mixing step S2, the first coal and the ashless coal are mixed.

  The first coal is a coal raw material for coke. The above-mentioned first coal is not particularly limited, and a proper proportion that makes it possible to fuse the whole coal by carbonization of raw coal such as strong caking coal, weak caking coal or the like and inferior coal which is a non-caking coal. Can be used in combination. Above all, it is preferable to include inferior coal and strongly coking coal as the first coal. Inferior coal is cheaper than strong coking coal, so the coke production cost can be further reduced by including poor coking coal while maintaining the strength of coke by including strong coking coal in the coal.

  The first coal is preferably in the form of finely pulverized granules. When the first coal is made granular, the lower limit of the 20% particle diameter D20 of the first coal depends on the device for crushing the first coal and the first coal handling device, 0.1 mm is preferable and 0.2 mm is more preferable. If the 20% particle diameter D20 of the first coal is less than the above lower limit, an unnecessarily large crushing power may be required, or dust or the like may make it difficult to handle the first coal. On the other hand, the upper limit of the 90% particle diameter D90 of the first coal is preferably 3 mm, more preferably 1 mm. If the 90% particle size D90 of the first coal exceeds the above upper limit, the mixability in the mixing step may be insufficient, or the strength of the coke obtained by the increase in the particle gap may be insufficient. is there. In addition, "20% particle diameter D20" and "90% particle diameter D90" mean that all particles are sieved in order from a mesh with a metal mesh sieve specified in JIS-Z8801-1 (2006) in order from the largest mesh. Means the size of the sieve mesh when the cumulative mass under the sieve is 20% of the mass of all particles and the mesh size of the sieve when it is 90%.

  As with the first coal, it is preferable that the ashless coal is also finely crushed into particles. When making the ashless coal granular, the lower limit of the 20% particle size D20 and the upper limit of the 90% particle size D90 of the ashless coal are the lower limit of the 20% particle size D20 and the upper limit of the 90% particle size D90 of the first coal. The same can be done with.

  Further, the mixing method is not particularly limited, but may be performed using, for example, a known mixer. This mixing step may also serve as a step of crushing the first coal and the ashless coal into the above-described particle diameters.

  The lower limit of the blending amount of ashless coal in the mixed coal after the mixing step S2 is preferably 5% by mass, and more preferably 10% by mass. On the other hand, the upper limit of the amount of the ashless coal blended is preferably 30% by mass, more preferably 20% by mass. If the blending amount of the ashless coal is less than the above lower limit, the first coal cannot be sufficiently coated with the ashless coal, and the fluidity improving effect of the blended coal for coke may be insufficient. Further, since the ratio of the ashless coal functioning as a caking filler to the entire coke becomes too low, the strength of the coke produced may decrease. On the contrary, when the amount of the ashless coal blended exceeds the upper limit, the average thickness of the ashless coal coating the first coal becomes large, and the effect of improving the fluidity of the coke blended coal may not be sufficiently exhibited. There is.

[Heating process]
In the heating step S3, the mixed carbon obtained in the mixing step S2 is heated.

  The heating step S3 can be performed using a known heater. It is considered that this heat treatment liquefies the ashless coal and impregnates the first coal contained in the mixed coal with the ashless coal.

  The lower limit of the heating temperature in the heating step S3 is preferably 250 ° C, more preferably 300 ° C. On the other hand, the upper limit of the heating temperature is preferably 500 ° C, more preferably 400 ° C. If the heating temperature is less than the lower limit, the viscosity of the ashless coal is too high, and it may be difficult to coat the surface of the first coal. On the other hand, if the heating temperature exceeds the upper limit, carbonization of the mixed coal may occur, and coke having high strength may not be manufactured in the carbonization step S6 described below.

  The heating rate in the heating step S3 is not particularly limited, but can be 1 ° C./minute or more and 10 ° C./minute or less. If the heating rate is less than the lower limit, it takes a long time to raise the temperature, which may reduce the production efficiency of coke. On the other hand, if the heating rate exceeds the upper limit, the manufacturing equipment required for raising the temperature becomes expensive, and the equipment investment may increase.

  As a minimum of heating time in heating process S3, 30 minutes are preferred and 60 minutes are more preferred. If the heating time is less than the lower limit, impregnation of the ashless coal into the first coal may be insufficient. On the other hand, the upper limit of the heating time is not particularly limited, but may be 120 minutes, for example. If the heating time exceeds the upper limit, the heating time becomes unnecessarily long, and thus the production efficiency of coke may decrease.

[Cooling process]
The cooling step S4 cools the mixed coal after the heating step S3 before the additional step S5 described later.

  By cooling the mixed coal in the cooling step S4, the mixed coal can be stably stored in a state where the surface of the first coal is coated with ashless coal. That is, since the coke manufacturing method includes the cooling step S4, it is not necessary to continuously operate the heating step S3 and the carbonization step S6, and thus operation management is facilitated. The mixed coal after the cooling step S4 can be used as one of the coke raw materials in the same manner as, for example, steam coal. Therefore, since the coke manufacturing method includes the cooling step S4, the additional step S5 and the dry distillation step S6 can be performed in the existing equipment, so that new equipment investment can be eliminated and the manufacturing cost can be reduced.

  The cooling method is not particularly limited, and for example, natural cooling at room temperature (10 ° C. or higher and 40 ° C. or lower), air cooling in which air is blown by a fan or the like can be used.

  The cooling rate in the cooling step S4 is not particularly limited, but can be 1 ° C./minute or more and 10 ° C./minute or less. If the cooling rate is less than the lower limit, it takes a long time to cool, and thus the production efficiency of coke may decrease. On the other hand, if the cooling rate exceeds the upper limit, the manufacturing equipment required for cooling becomes expensive, and the equipment investment may increase.

  The upper limit of the temperature of the mixed coal after the cooling step S4 is preferably 80 ° C, more preferably 50 ° C. If the temperature of the mixed coal exceeds the upper limit, handling and storage of the mixed coal may be difficult. On the other hand, the lower limit of the temperature of the mixed coal is not particularly limited, and may be room temperature, for example. If the temperature of the mixed coal is less than the lower limit, refrigeration equipment is required to keep the temperature of the mixed coal at room temperature or lower, which may increase capital investment.

  The cooling time in the cooling step S4 is determined by the time required for the mixed coal to reach the desired temperature or lower. On the other hand, the cooling time may be within the time until the mixed coal after the cooling step S4 is used in the additional step S5, and a cooling method is appropriately selected as necessary.

[Additional process]
In the additional step S5, the second coal is added to the mixed coal after the mixing step S3 and the cooling step S4.

  The second coal is a coke raw material. The second coal may be one type of coal, but is usually a blended coal in which several types of coal are mixed. In this way, it is possible to control the quality of coke produced by mixing several types of coal and adjusting the blending ratio. When the second coal is the blended coal, the second coal may include the same type of coal as the first coal, but may be different types of coal.

  The second coal is preferably in the form of finely pulverized granules. When making the second coal granular, the lower limit of the 20% particle size D20 and the upper limit of the 90% particle size D90 of the second coal are the lower limit of the 20% particle size D20 and the 90% particle size D90 of the first coal. The same as the upper limit of.

  After adding the second coal, it is preferable to mix the mixed coal and the second coal using, for example, a known mixer. By mixing the mixed coal and the second coal in this way, the quality of the obtained coke can be controlled.

  The lower limit of the blending amount of coal (the total amount of the first coal and the second coal) in the blended coal for coke obtained in the additional step S5 is preferably 80% by mass, more preferably 90% by mass. On the other hand, the upper limit of the amount of coal blended is preferably 98% by mass, more preferably 95% by mass. When the amount of coal is less than the above lower limit, the proportion of ashless coal is relatively high, so the effect of reducing manufacturing costs by using coal that is cheaper than ashless coal may be insufficient. is there. On the other hand, when the amount of the coal blended exceeds the upper limit, the proportion of the ashless coal that functions as a caking filler is relatively low, which may reduce the strength of the coke produced.

[Dry distillation process]
In the carbonization step S6, the coking coal blend obtained in the additional step S5 is carbonized.

  In the carbonization step S6, for example, a shaft furnace, a coke furnace or the like is used to fill the above-mentioned coal blend for coke and carbonization is carried out under the conditions described below to obtain coke.

As a lower limit of the packing density of the above coal blending coal for the coke in the furnace, 700 kg / m ³ is preferable on an anhydrous basis, and 720 kg / m ³ is more preferable. On the other hand, the upper limit of the packing density of the coal blended coal for coke in the furnace is not particularly limited, but it is considered that the limit is 900 kg / m ^{3 on a} dry basis in consideration of the specific gravity of coal. When the packing density of the above coal blend for coke is less than the above lower limit, the strength of the coke obtained may be insufficient.

  As a lower limit of the dry distillation temperature (maximum reached temperature), 950 ° C is preferable, and 1000 ° C is more preferable. On the other hand, the upper limit of the dry distillation temperature is preferably 1200 ° C, more preferably 1100 ° C. The lower limit of the dry distillation time (dry distillation temperature holding time) depends on the size of the furnace, but in the case of a coke oven with 30 tons per gate, 8 hours are preferable, and 10 hours are more preferable. On the other hand, the upper limit of the dry distillation time is preferably 24 hours, more preferably 20 hours, from the viewpoint of production efficiency.

  The lower limit of the temperature rising rate of the coking coal blend in the carbonization step S6 is preferably 1 ° C / min, more preferably 2 ° C / min. On the other hand, the upper limit of the temperature rising rate is preferably 5 ° C./min, more preferably 4 ° C./min. If the heating rate is less than the lower limit, the coke production efficiency may be insufficient. On the contrary, when the temperature rising rate exceeds the upper limit, the strength of the coke obtained may be insufficient.

〔advantage〕
In the coke manufacturing method, since ashless coal is used as the caking filler, the coke manufacturing cost can be reduced. Further, in the coke manufacturing method, in the heating step S3, the mixed coal obtained by mixing the first coal, which is a part of the coal of the coke blending coal, and the ashless coal is preheated. In the method for producing the coke, the heat treatment can improve the fluidity of the coal blend for coke. Therefore, the strength of the obtained coke can be increased by using the method for producing the coke. From the above, by using the coke manufacturing method, it is possible to manufacture coke having high strength at low cost.

[Other Embodiments]
The coke manufacturing method of the present invention is not limited to the above embodiment.

  In the above-described embodiment, the case where the coke manufacturing method includes the cooling step has been described, but a coke manufacturing method that does not include the cooling step is also intended by the present invention. That is, in the additional step, the second coal may be added to the mixed coal after the heating step while maintaining the heating temperature. By adding the second coal to the coal blend while maintaining the heating temperature in this way, the fluidity of the coal blend for coke can be more easily secured than in the case of passing through the cooling step. It is possible to further reduce the occurrence of insufficient strength due to.

  In the above-described embodiment, the case where the ashless coal manufacturing process is provided is described as the coke manufacturing method, but a coke manufacturing method that does not include the ashless coal manufacturing process is also intended by the present invention. For example, the ashless coal prepared in advance may be used to start the mixing process.

  Further, the ashless coal production process is not limited to that of the above-described embodiment including a slurry preparation process, a solid-liquid separation process, and a solvent evaporation process. As a method for producing ashless coal, for example, a method of producing by mixing and heating coal and a hydrogen donating solvent can be used.

  Moreover, each process of the said ashless coal manufacturing process is not limited to the above-mentioned method. For example, in the slurry preparation step, a slurry may be prepared by mixing a preheated solvent with pasted coal in a carrier pipe and rapidly raising the temperature.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[Example 1]
Poor quality coal A was prepared as a raw material coal. The inferior coal A and the ashless coal were uniformly mixed in a mass ratio of 9: 1. The obtained mixed coal was heated to 340 ° C. at 3 ° C./minute, and after reaching 340 ° C., the temperature was kept constant and heat treatment was performed for 100 minutes. Then, it was cooled to room temperature at a rate of 3 ° C./min. Thus, as Example 1, mixed carbon after the heating step was obtained.

[Comparative Example 1]
Poor quality coal A was prepared as a raw material coal. The inferior coal A and the ashless coal were uniformly mixed in a mass ratio of 9: 1. In this way, as Comparative Example 1, a mixed coal that had not been heat-treated was obtained.

[Evaluation]
The fluidity of the obtained Example 1 and Comparative Example 1 was evaluated.

The high temperature in-situ ¹ H-NMR relaxation time measurement method was used for the evaluation of fluidity. For the relaxation time measurement, an Apollo NMR spectrometer manufactured by Tecmag equipped with a high temperature probe manufactured by CSIRO was used. Specifically, the sample is put into a quartz sample tube having an outer diameter of 9.5 mm, dried in a nitrogen stream in the above-mentioned high temperature probe at 125 ° C. for 1 hour, and then heated at a temperature rising rate of 3 ° C./min. Then, the measurement was performed. For the measurement of the spin-spin relaxation time T2, a solid echo method was used in order to avoid the influence of the oversaturation of the amplifier, which occurs after the RF pulse irradiation, on the signal.

  From the solid echo signal obtained by the above measurement, the voltage corresponding to the fluid molecular weight (hereinafter, also referred to as “Hm component amount”) was measured based on the difference in attenuation behavior, that is, magnetic relaxation behavior. The results are shown in Fig. 4. The Hm component amount can be determined to have higher fluidity, especially when the numerical value at the peak is larger.

[Example 2 and Comparative Example 2]
Mixed coal of Example 2 and Comparative Example 2 was obtained in the same manner as in Example 1 and Comparative Example 1 except that the inferior coal B having a different production site from the inferior coal A was prepared as the raw material coal. For Example 2 and Comparative Example 2, the results of measuring the amount of Hm component by the high temperature in-situ ¹ H-NMR relaxation time measurement method in the same manner as in Example 1 and Comparative Example 1 are shown in FIG.

[Example 3 and Comparative Example 3]
Mixed coal of Example 3 and Comparative Example 3 was obtained in the same manner as in Example 1 and Comparative Example 1 except that strong coking coal C was prepared as the raw material coal. FIG. 6 shows the results of measuring the amount of Hm component in Example 3 and Comparative Example 3 by the high temperature in-situ ¹ H-NMR relaxation time measurement method in the same manner as in Example 1 and Comparative Example 1.

[Example 4 and Comparative Example 4]
The mixed coals of Example 4 and Comparative Example 4 were obtained in the same manner as in Example 1 and Comparative Example 1 except that, as the raw material coal, the strong coking coal D having a different production site from the strong coking coal C was prepared. . For Example 4 and Comparative Example 4, the results of measuring the amount of Hm component by the high temperature in-situ ¹ H-NMR relaxation time measurement method in the same manner as in Example 1 and Comparative Example 1 are shown in FIG. 7.

  From FIG. 4 to FIG. 7, in Examples 1 to 4 in which the heating step was performed regardless of the raw coal, the amount of Hm component in the peak was increased more than in Comparative Examples 1 to 4 in which the heating step was not performed. I understand that. That is, it can be said that the fluidity of the mixed coal for coke can be improved by preheating the mixed coal obtained by mixing a part of the coal of the mixed coal for coke and the ashless coal.

  As described above, by using the method for producing the coke, the coke having high strength can be produced at a low cost by increasing the fluidity of the coal blend for coke.

DESCRIPTION OF SYMBOLS 1 Coal supply part 2 Solvent supply part 3 Mixing part 31 Preparation tank 31a Stirrer 4 Pump 5 Heating part 51 Heating furnace 6 Elution part 61 Extraction tank 61a Stirrer 7 Solid-liquid separation part 8 1st solvent evaporation part 9 2nd solvent evaporation part

Claims (5)

Mixing the first coal and ashless coal,
A step of heating the mixed carbon obtained in the mixing step,
A step of adding a second coal to the mixed coal after the heating step,
And a step of dry-distilling the mixed coal for coke obtained in the above-mentioned additional step.   The method for producing coke according to claim 1, further comprising a step of cooling the mixed coal after the heating step before the additional step.   The method for producing coke according to claim 1 or 2, wherein the heating temperature in the heating step is 250 ° C or higher and 500 ° C or lower.   The method for producing coke according to claim 1, claim 2 or claim 3, wherein an amount of ashless coal in the mixed coal is 5% by mass or more and 30% by mass or less.   The method for producing coke according to claim 1, wherein the raw material of the ashless coal is steam coal.

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