JP2018030951A - Method for producing solid fuel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a solid fuel in which a solid fuel having relatively high strength can be produced from a powder fuel.SOLUTION: The method for producing a solid fuel according to the present invention is a method for producing a solid fuel by compression-molding a coal powder fuel and includes the steps of: mixing, to the coal powder fuel, a pulverized fuel having an average particle size larger than that of the coal powder fuel; compression-molding the mixture produced in the mixing step; and pulverizing a part of the solid fuel produced in the compression molding step, and in which, characterized, as the pulverized fuel used in the mixing step, the solid fuel pulverized in the pulverizing step is used. The mixing ratio of the pulverized fuel based on the mixture in the mixing step is preferably 5 mass% or more and 50 mass% or less. It is preferable to further mix a powdery coal with binding property having a greater binding property than the coal powder fuel. The mixing ratio of the powdery coal with binding property based on the mixture in the mixing step is preferably 5 mass% or more and 30 mass% or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a solid fuel.

  Powdered fuel has a relatively small bulk density and is likely to disappear due to scattering, so that the handling cost is likely to increase and there is a risk of causing dust pollution. For this reason, powdered fuel is compressed and molded into granular (briquette) for easy handling.

  For example, modified coal obtained by heating and dehydrating low-grade coal such as lignite in oil is usually powdered, so it is desirable to compress and granulate it. However, in order to mold reformed coal obtained from low-grade coal with a low degree of carbonization, it is necessary to perform compression molding at a considerably high pressure, which not only increases the manufacturing cost but also causes insufficient pressure to convey There is a risk of causing powdery troubles along the way.

  On the other hand, the technique which improves the intensity | strength of the solid fuel obtained by humidifying reformed coal and pressure-molding is proposed (refer Unexamined-Japanese-Patent No. 2010-116544). However, even in the method described in the above publication, pulverization may occur depending on the use of solid fuel and the manner of handling.

JP 2010-116544 A

  In view of the above inconveniences, an object of the present invention is to provide a method for producing a solid fuel in which a solid fuel having a relatively high strength can be obtained from a powder fuel.

  The invention made in order to solve the above-mentioned problems is a method for producing a solid fuel by compression-molding a coal-based powdered fuel, wherein a pulverized fuel having an average particle size larger than that of the coal-based powdered fuel is added to the coal-based powdered fuel. As a pulverized fuel used in the mixing step, comprising a step of mixing, a step of compression molding the mixture obtained in the mixing step, and a step of pulverizing a part of the solid fuel obtained in the compression molding step. A solid fuel production method using the solid fuel pulverized in the pulverization step.

  The production method of the solid fuel can compress the raw material relatively reliably at the time of compression molding by mixing the pulverized fuel with the coal-based powdered fuel, and can prevent the solid fuel from being insufficient in strength due to poor compression. . Therefore, the solid fuel manufacturing method can manufacture a solid fuel having a relatively high strength.

  The mixing ratio of the pulverized fuel based on the mixture in the mixing step is preferably 5% by mass or more and 50% by mass or less. Thus, by setting the mixing ratio of the pulverized fuel based on the mixture in the mixing step within the above range, the strength of the solid fuel obtained can be improved more reliably while suppressing an increase in manufacturing cost. can do.

  In the mixing step, binding powder coal having a binding property larger than that of the coal-based powder fuel may be further mixed. Thus, solid fuel with higher strength can be obtained by mixing the binding powdered coal with the coal-based powdered fuel.

  The mixing ratio of the binding coal powder based on the mixture in the mixing step is preferably 5% by mass or more and 30% by mass or less. Thus, by setting the mixing ratio of the binding coal powder based on the mixture in the mixing step within the above range, the strength of the obtained solid fuel can be improved more reliably and the quality can be reduced. Can be suppressed.

  The method further comprises the step of measuring the strength of the solid fuel obtained in the compression molding step, and adjusting the mixing ratio of the binding powdery coal in the mixing step according to the measured value. When the lower limit is not reached, the binding ratio of the binding coal powder is increased, and when the strength of the solid fuel exceeds a predetermined upper limit, the mixing ratio of the binding coal powder is preferably decreased. In this way, the quality of the solid fuel can be stabilized by adjusting the mixing ratio of the binding coal powder according to the strength of the solid fuel.

  It is preferable to further include a step of measuring the production amount of the solid fuel obtained in the compression molding step and adjusting the mixing ratio of the pulverized fuel in the mixing step according to the measured value. Thus, by measuring the production amount of the solid fuel obtained in the compression molding step and further adjusting the mixing ratio of the pulverized fuel in the mixing step according to the measured value, the compression molding speed is set appropriately. And the quality of the obtained solid fuel can be stabilized.

  It is good to supply each raw material to a mixer with a conveyor scale at the said mixing process. Thus, by supplying each raw material to a mixer with a conveyor scale at the said mixing process, coal-type powder fuel, a grinding | pulverization fuel, and a binding powder coal can be continuously measured and supplied comparatively accurately.

  A modified coal obtained by heating and dehydrating low-grade coal in oil may be used as the coal-based powder fuel, and a low-grade coal powder may be used as the binding powder coal. Thus, by using the modified coal obtained by heating and dehydrating low-grade coal in oil as the coal-based powder fuel, and using the low-grade coal powder as the binding powder coal, it is relatively inexpensive and expensive. A quality solid fuel can be provided.

  The “average particle diameter” means a sieve opening with a mass integrated value of 50% in a particle size distribution obtained by a sieving test based on JIS-Z8815 (1994). Further, “high binding property” means that “crushing strength” measured in accordance with JIS-Z8841 (1993) when compression molding under the same conditions is high.

  As described above, the method for producing a solid fuel can produce a solid fuel having a relatively high strength from a powder fuel.

It is a schematic diagram which shows the structure of the manufacturing apparatus used for the manufacturing method of the solid fuel of one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[Solid fuel production equipment]
FIG. 1 shows a schematic configuration of a solid fuel production apparatus used in a solid fuel production method according to an embodiment of the present invention.

  The solid fuel production apparatus in FIG. 1 is an apparatus for obtaining a granular solid fuel by compression molding coal-based powdered fuel.

  The solid fuel production apparatus of FIG. 1 includes a first silo 1 that stores coal-based powdered fuel, a second silo 2 that stores pulverized fuel having an average particle size larger than that of the coal-based powdered fuel, and a coal-based powdered fuel. And a third silo 3 for storing binding coal powder having a high binding property.

  In addition, the solid fuel production apparatus of FIG. 1 has a first conveyor scale 4 that discharges coal-based powdered fuel from the first silo 1 at an arbitrary speed (mass per hour), and binder powdered coal from the second silo 2. A second conveyor scale 5 that discharges at an arbitrary speed and a third conveyor scale 6 that discharges pulverized fuel from the third silo 3 at an arbitrary speed are provided.

  1 is supplied with coal-based powdered fuel from the first conveyor scale 4, supplied with binding powdered coal from the second conveyor scale 5, and supplied with pulverized fuel from the third conveyor scale 6. And a mixer 7 for mixing these three kinds of raw materials and a mixed raw material silo 8 for storing a mixture of coal-based powdered fuel, binding powdered coal and pulverized fuel discharged from the mixer 7.

  In addition, the solid fuel production apparatus of FIG. 1 pulverizes a molding machine 9 which compresses and molds the mixture supplied from the mixed raw material silo 8 to a target solid fuel, and a part of the solid fuel formed by the molding machine 9. And a crusher 10 to perform. The solid fuel pulverized by the pulverizer 10 is supplied to the third silo 3 as the pulverized fuel. The conveyance of the granular materials (coal-based powdered fuel, binding powdered coal, pulverized fuel, and solid fuel) between components can be performed by a known technique such as a chute, a belt conveyor, a bucket conveyor, or a pneumatic conveyor. .

(Coal powder fuel)
Examples of coal-based powder fuel that is the main raw material of solid fuel include modified coal (Upgraded Brown Coal, etc.) obtained by heating and dehydrating small coal, such as pulverized coal and low-grade coal (subbituminous coal and lignite), in oil. Etc. can be used. Especially, the manufacturing method of the said solid fuel can manufacture a granular solid fuel by using as a main raw material the reformed coal which was not easy to granulate conventionally.

(Binding pulverized coal)
As the binding coal powder, pulverized coal having a binding property larger than that of the coal-based powder fuel may be used. In order to suppress an increase in cost, a relatively inexpensive low-grade coal (preferably adhesive coal) is used. It is preferable to use it.

  In addition, the binding property in compression molding of coal-based powdered fuel is greatly influenced by the moisture content of the raw material. The lower limit of the moisture content of the binding coal powder is preferably 20% by mass, and more preferably 25% by mass. On the other hand, the upper limit of the moisture content of the binding coal powder is preferably 60% by mass, and more preferably 55% by mass. When the water content of the binding coal powder is less than the above lower limit, the strength of the obtained solid fuel may not be sufficiently improved. On the other hand, when the water content of the binding powdered coal exceeds the above upper limit, the blending amount of the binding powdered coal may not be easily adjusted.

  The lower limit of the 20% particle diameter D20 of the binding coal powder is preferably 0.005 mm, and more preferably 0.010 mm. When the 20% particle diameter D20 of the binding powdered coal is less than the above lower limit, handling of the binding powdered coal may be difficult due to dusting or the like. On the other hand, the upper limit of the 90% particle diameter D90 of the binding coal powder is preferably 3 mm, and more preferably 1 mm. When the 90% particle diameter D90 of the binding coal powder exceeds the above upper limit, the strength of the solid fuel obtained by insufficient mixing with the coal-based powder fuel may vary. In addition, “20% particle diameter D20” and “90% particle diameter D90” mean that, in a sieving test based on JIS-Z8815 (1994), the cumulative mass under the screen became 20% of the mass of all particles. It means the size of the mesh of the screen when it is 90% and the size of the screen when it is 90%.

(Pulverized fuel)
As the pulverized fuel, a pulverized solid fuel finally obtained by the solid fuel manufacturing method is used.

  The lower limit of the 20% particle diameter D20 of the pulverized fuel is preferably 0.5 mm, and more preferably 1 mm. When the 20% particle diameter D20 of the pulverized fuel is less than the lower limit, the compression moldability of the mixture with the coal-based powder fuel may not be sufficiently improved. On the other hand, the upper limit of the 90% particle diameter D90 of the pulverized fuel is preferably 10 mm, and more preferably 7 mm. When the 90% particle diameter D90 of the pulverized fuel exceeds the above upper limit, the miscibility with the coal-based powder fuel becomes insufficient, and the strength of the obtained solid fuel may vary.

(silo)
As silos 1, 2, 3, and 8, any coal-based powdered fuel, pulverized fuel, and binding pulverized coal may be stored and discharged as necessary.

Among them, the first silo 1 for storing coal-based powdered fuel, the third silo 3 for storing pulverized fuel, and the mixed raw material silo 8 for storing raw material mixture are configured to be able to have a nitrogen atmosphere inside. Is preferred. More specifically, inside the first case silo 1, third silos 3 and mixed material silo 8, a measuring mechanism for measuring the internal carbon dioxide (CO ₂₎ concentration, the CO ₂ concentration measuring mechanism was measured rose And a gas supply mechanism for introducing nitrogen gas (N ₂ ) into the substrate.

(Conveyor scale)
The conveyor scales 4, 5, and 6 are a combination of a weigher (for example, a load cell) and a belt conveyor as defined in JIS-B7606 (1997). The conveyor scales 4, 5 and 6 measure the weight of coal-based powdered fuel, pulverized fuel or binding powdered coal present on the belt conveyor in real time, and adjust the conveyor speed of the belt conveyor, The fuel, pulverized fuel, or binding pulverized coal discharge amount per hour can be arbitrarily set.

(Mixer)
The mixer 7 only needs to be able to uniformly mix coal-based powdered fuel, pulverized fuel, and binding pulverized coal. For example, a mixer that rotates a container, a mixer having stirring blades, or the like can be used. It may be a continuous type or a continuous type. As a mixer which rotates a container, things, such as a V type and a double cone type, are mentioned, for example. On the other hand, examples of the mixer having a stirring blade include a paddle mixer and a ribbon mixer. Moreover, you may use the static mixer which mixes the granular material which falls by gravity without using power, for example using a fixed stirring blade etc. as the mixer 7. FIG.

(Molding machine)
Examples of the molding machine 9 include a double roll molding machine and a tableting molding machine. Among them, a double roll molding machine having a relatively large processing capability is preferably used. The double roll molding machine has a structure in which a pair of cylindrical rolls are horizontally adjacent to each other, and the roll rotates in a direction from the upper side toward an adjacent point. A large number of cavities are provided on the outer peripheral surface of the pair of rolls so as to face each other and rotate synchronously. Thereby, a double roll molding machine can compress a granular material between opposing cavities, and can shape | mold into a granule.

  The molding machine 9 preferably includes a supply hopper having a supply screw so that a mixture of coal-based powdered fuel, pulverized fuel, and binding powdered coal can be stably supplied to the cavity.

  In particular, when a double roll molding machine is used as the molding machine 9, not only the compression-molded granular material but also the raw material mixture can be discharged through the gap between the pair of rolls without being molded. Further, for some reason, the supply of the raw material mixture to the cavity becomes insufficient, and it may be pulverized without being sufficiently compressed. For this reason, you may provide the sieve which isolate | separates the raw material mixture discharged without shape | molding immediately after the molding machine 9. FIG. The raw material mixture separated from the molded solid fuel may be supplied again to the mixed raw material silo 8.

(Crusher)
The pulverizer 10 is not particularly limited, and a known rotary cutter, hammer mill, or the like can be used.

  Although depending on the type of the pulverizer 10, when pulverized fuel that has not been sufficiently reduced in diameter can be discharged from the pulverizer 10, the pulverized fuel discharged from the pulverizer 10 in order to prevent troubles in the molding machine 9. A sieve that separates the large-diameter particles therein may be provided, and the separated large-diameter particles may be re-supplied to the pulverizer 10.

  The solid fuel production method that can be performed using the solid fuel production apparatus as described above includes a step of mixing a pulverized fuel and a binding coal powder with a coal-based powder fuel <mixing step>, and this mixing step. Compression molding process <compression molding process>, part of the solid fuel obtained in this compression molding process <grinding process>, and the strength of the solid fuel obtained in the compression molding process Measure and adjust production ratio of solid fuel obtained in compression molding process <strength adjustment process> to adjust the mixing ratio of binding coal powder in the mixing process according to the measured value, and mix according to the measured value And a step of adjusting the mixing ratio of the pulverized fuel in the step.

<Mixing process>
In the mixing step, the coal-based powder fuel, the pulverized fuel, and the binding powder coal are supplied from the silos 1, 2, and 3 to the mixer 7 using the conveyor scales 4, 5, and 6, and the coal-based powder fuel is mixed by the mixer 7. Then, the pulverized fuel and the binding coal powder are mixed to obtain a mixture.

  The lower limit of the mixing ratio of the binding pulverized coal based on the mixture (ratio to the whole coal-based powdered fuel, binding pulverized coal and pulverized fuel) is preferably 5% by mass, and more preferably 8% by mass. On the other hand, the upper limit of the mixing ratio of the binding coal powder based on the mixture is preferably 30% by mass, and more preferably 25% by mass. When the mixing ratio of the binding coal powder based on the mixture is less than the lower limit, the strength of the solid fuel may not be sufficiently improved. On the contrary, when the mixing ratio of the binding coal powder based on the mixture exceeds the upper limit, the price of the solid fuel may be unnecessarily increased.

  The lower limit of the mixing ratio of the pulverized fuel based on the mixture (the ratio of the coal-based powder fuel, the pulverized fuel and the pulverized fuel to the whole) is preferably 5% by mass, and more preferably 8% by mass. On the other hand, the upper limit of the mixing ratio of the pulverized fuel based on the mixture is preferably 50% by mass, and more preferably 40% by mass. When the mixing ratio of the pulverized fuel based on the mixture is less than the lower limit, the production amount of the solid fuel may not be sufficiently improved. Conversely, if the mixing ratio of the pulverized fuel based on the mixture exceeds the above upper limit, the production efficiency of the final solid fuel excluding the amount used as the pulverized fuel may be unnecessarily lowered, or the particles of the pulverized fuel There is a possibility that the strength of a part of the solid fuel obtained by forming a gap between them becomes insufficient (the variation in strength becomes large).

  The mixing time (residence time) of the raw material by the mixer 7 is generally preferably 30 minutes or less when the mixer 7 is a paddle mixer as an example, but is not limited to this. Mixing is required. The degree of mixing of raw materials can be evaluated by, for example, collecting samples after mixing in small amounts and observing the variation in moisture. If the moisture value varies widely, mixing is insufficient, so it can be determined that the mixing time by the mixer 7 needs to be increased.

<Compression molding process>
In the compression molding process, a coal-based powder fuel, a pulverized fuel, and a mixture of the pulverized fuel are compression-molded by a molding machine 9 to obtain a target granular solid fuel.

<Crushing process>
In the pulverization step, a part of the solid fuel obtained in the compression molding step is pulverized by the pulverizer 10 to obtain the above pulverized fuel.

  By mixing the pulverized fuel obtained in this pulverization step with the coal-based powder fuel, the apparent specific gravity of the mixture subjected to compression molding can be made larger than that of the coal-based powder fuel. Thereby, in the compression molding process, it becomes possible to fill the cavity of the molding machine with sufficient raw material granules, and the strength of the solid fuel obtained by relatively increasing the pressure during molding can be improved.

<Strength adjustment process>
In the strength adjustment step, first, the strength of the solid fuel obtained in the compression molding step is measured. As a measurement method for measuring the strength of the solid fuel, for example, a compression fracture test, a tensile test, an impact test, a drop test, or the like can be employed.

  Further, in this strength adjustment step, when the measured solid fuel strength is less than a predetermined lower limit, the mixing ratio of the binding coal powder is increased, and when the solid fuel strength exceeds a predetermined upper limit. Reduce the mixing ratio of binding coal powder. Thus, the solid fuel of the stable quality can be obtained by adjusting the intensity | strength of solid fuel with the mixing ratio of binding powdered coal.

<Production adjustment process>
In the production volume adjustment process, the production volume of the solid fuel obtained in the compression molding process is measured, and when the measured production volume of the solid fuel is less than the desired lower limit, the mixing ratio of the pulverized fuel is increased. When the production amount exceeds a predetermined upper limit, the mixing ratio of the pulverized fuel is decreased.

  In this way, the production amount can be adjusted to a desired value by the mixing ratio of the pulverized fuel, and by optimizing the operation speed of the molding machine 9, it is possible to suppress the variation in the strength of the obtained solid fuel and improve the quality. Can be further stabilized.

<Advantages>
In the method for producing solid fuel, since the pulverized fuel obtained by pulverizing a part of the solid fuel obtained in the compression molding process is mixed with the coal-based powder fuel, the bulk density of the raw material mixture becomes relatively large. Thereby, in the manufacturing method of the said solid fuel, it becomes possible to enlarge a molding pressure in a compression molding process, and can improve the intensity | strength of the obtained solid fuel.

  Moreover, since the solid fuel manufacturing method mixes the binding powdered coal with the coal-based powder fuel, the binding property of the raw material mixture is improved, and the strength of the obtained solid fuel can be further improved. Thus, the manufacturing method of the said solid fuel can manufacture the solid fuel with comparatively big intensity | strength from powdered fuel.

[Other Embodiments]
The said embodiment does not limit the structure of this invention. Therefore, in the above-described embodiment, the components of each part of the above-described embodiment can be omitted, replaced, or added based on the description and common general knowledge of the present specification, and they are all interpreted as belonging to the scope of the present invention. Should.

  In the manufacturing method of the solid fuel, when the binding property of the coal-based powdered fuel is sufficient, mixing of the binding powdered coal may be omitted.

  In the method for producing solid fuel, the adjustment step can be omitted when conditions such as the properties of the raw material are stable. In addition, in the adjustment process, the binding powder coal is discharged not with the strength of the solid fuel, but with the solid fuel discharged from the compression molding machine and separated by a sieve or separated at the time of the transfer of the conveyor. The mixing ratio may be adjusted. Further, in the adjusting step, the strength of the obtained solid fuel can be adjusted by adjusting the operating speed of the molding machine instead of the mixing ratio of the binding coal powder.

  EXAMPLES Hereinafter, although this invention is explained in full detail based on an Example, this invention is not interpreted limitedly based on description of this Example.

Example 1
First, a modified coal powder obtained by heating and dehydrating lignite coal in oil is used as the coal-based powder fuel, and a pulverized coal powder pulverized and passed through a sieve having a mesh opening of 3 mm is used as the binding powder coal. Then, a mixture of coal-based powdered fuel and binding powdered coal at a mass ratio of 85:10 was compression molded by a double roll molding machine to obtain a granular solid fuel. At this time, the rotation speed of the double roll molding machine was adjusted so that the crushing strength of the obtained solid fuel was 0.7 MPa, which is a value required for a briquette of general coal-based fuel. The bulk density of the coal-based powdered fuel was measured and found to be 0.52 g / cc. Moreover, as a double roll molding machine, “K205” manufactured by Furukawa Industries Systems Co., Ltd. was used, and a roll having a cavity having a major axis of 38 mm, a minor axis of 38 mm, and a volume of 22 cc was mounted.

  The solid fuel thus obtained is pulverized and passed through a sieve having an opening of 10 mm as the pulverized fuel. The coal-based powdered fuel, the binding powdered coal and the pulverized fuel are mixed at a mass ratio of 85: 10: 5. The raw material mixture was obtained by mixing. This raw material mixture was compression molded by a double roll molding machine, and the rotational speed of the double roll molding machine was adjusted so that the crushing strength of the obtained solid fuel was 0.7 MPa.

  The solid fuel obtained by compression molding the raw material mixture containing the pulverized fuel was further pulverized and passed through a sieve having an opening of 10 mm as a new pulverized fuel. And the cycle which compression-molds with the double roll molding machine the raw material mixture which mixed coal-based powdered fuel, binder powdered coal, and the new pulverized fuel by the ratio of 85: 10: 5 was repeated.

  When the operation was stabilized by repeating this cycle, the bulk density of the raw material mixture was measured and found to be 0.56 g / cc. The “bulk density” was measured as a loose apparent specific gravity using “Powder Tester PT-S type” manufactured by Hosokawa Micron Corporation. In addition, the rotational speed of the double roll molding machine when the operation was stabilized was 0.83 times the standard rotational speed when compression-molding bituminous coal pulverized coal to produce coal-based fuel briquettes.

  Furthermore, as an index of the effective production amount excluding those obtained from pulverized solid fuel among the obtained solid fuel, the ratio of the above-mentioned rotational speed ratio of coal-based powdered fuel and binding powdered coal It was 0.79 when the effective production ratio which multiplied the total mass ratio was calculated.

(Example 2)
First, a mixture of coal-based powdered fuel similar to Example 1 and binder powdered coal at a mass ratio of 70:10 is compression-molded with a double roll molding machine, and the resulting solid fuel has a crushing strength of 0. The rotational speed of the double roll molding machine was adjusted to 7 MPa.

  The solid fuel thus obtained is pulverized and passed through a sieve having a mesh opening of 10 mm. The pulverized fuel is used as a pulverized fuel. The mass ratio of coal-based powdered fuel, binding powdered coal and pulverized fuel is 70:10:20. The raw material mixture was obtained by mixing. This raw material mixture was compression molded by a double roll molding machine, and the rotational speed of the double roll molding machine was adjusted so that the crushing strength of the obtained solid fuel was 0.7 MPa.

  The solid fuel obtained by compression molding the raw material mixture containing the pulverized fuel was further pulverized and passed through a sieve having an opening of 10 mm as a new pulverized fuel. When the operation is stabilized by repeating a cycle in which a raw material mixture obtained by mixing coal-based powdered fuel, binding powdered coal and new pulverized fuel in a mass ratio of 70:10:20 is compressed by a double roll molding machine, The bulk density of the raw material mixture was 0.58 g / cc, the rotational speed of the double roll molding machine was 0.97 times the standard rotational speed, and the effective production ratio was 0.77.

(Example 3)
First, a mixture of coal-based powdered fuel similar to Example 1 and binder powdered coal at a mass ratio of 60:20 is compression-molded by a double roll molding machine, and the resulting solid fuel has a crushing strength of 0. The rotational speed of the double roll molding machine was adjusted to 7 MPa.

  The solid fuel thus obtained is pulverized and passed through a sieve having an opening of 10 mm as the pulverized fuel. The coal-based powdered fuel, the binding powdered coal and the pulverized fuel are mixed at a mass ratio of 60:20:20. The raw material mixture was obtained by mixing. This raw material mixture was compression molded by a double roll molding machine, and the rotational speed of the double roll molding machine was adjusted so that the crushing strength of the obtained solid fuel was 0.7 MPa.

  The solid fuel obtained by compression molding the raw material mixture containing the pulverized fuel was further pulverized and passed through a sieve having an opening of 10 mm as a new pulverized fuel. When the operation is stabilized by repeating a cycle in which a raw material mixture obtained by mixing coal-based powdered fuel, binding powdered coal and new pulverized fuel in a mass ratio of 60:20:20 is compressed by a double roll molding machine, The bulk density of the raw material mixture was 0.59 g / cc, the rotational speed of the double roll molding machine was 1.07 times the standard rotational speed, and the effective production ratio was 0.86.

Example 4
First, a mixture of coal-based powdered fuel similar to Example 1 and binder powdered coal at a mass ratio of 40:20 is compression-molded by a double roll molding machine, and the resulting solid fuel has a crushing strength of 0. The rotational speed of the double roll molding machine was adjusted to 7 MPa.

  The solid fuel thus obtained is pulverized and passed through a sieve having an aperture of 10 mm as the pulverized fuel. The coal-based powdered fuel, the binding powdered coal and the pulverized fuel are mixed at a mass ratio of 40:20:40. The raw material mixture was obtained by mixing. This raw material mixture was compression molded by a double roll molding machine, and the rotational speed of the double roll molding machine was adjusted so that the crushing strength of the obtained solid fuel was 0.7 MPa.

  The solid fuel obtained by compression molding the raw material mixture containing the pulverized fuel was further pulverized and passed through a sieve having an opening of 10 mm as a new pulverized fuel. When the operation is stabilized by repeating a cycle in which a raw material mixture obtained by mixing coal-based powdered fuel, binding powdered coal and new pulverized fuel in a mass ratio of 40:20:40 is compressed by a double roll molding machine, The bulk density of the raw material mixture was 0.64 g / cc, the rotational speed of the double roll molding machine was 1.25 times the standard rotational speed, and the effective production ratio was 0.77.

(Comparative Example 1)
First, only the same coal-based powdered fuel as in Example 1 was compression molded by a double roll molding machine, and the rotational speed of the double roll molding machine was adjusted so that the crushing strength of the obtained solid fuel was 0.7 MPa. The rotational speed of the double roll molding machine after the adjustment was 0.34 times the reference rotational speed.

(Comparative Example 2)
First, a mixture of coal-based powdered fuel similar to Example 1 and binder powdered coal at a mass ratio of 85:15 is compression-molded with a double roll molding machine, and the resulting solid fuel has a crushing strength of 0. The rotational speed of the double roll molding machine was adjusted to 7 MPa. The rotational speed of the double roll molding machine after the adjustment was 0.41 times the reference rotational speed.

  Table 1 below collectively shows the results of Examples 1 to 4 and Comparative Examples 1 and 2.

  As shown in this table, the rotational speed of the double roll molding machine could be made relatively large by crushing the solid fuel and mixing the pulverized fuel with the raw material. In other words, assuming that the rotational speed of the double roll molding machine is constant, it was confirmed that a solid fuel having a relatively high strength can be produced by mixing the pulverized fuel with the raw material.

  The method for producing a solid fuel according to the present invention can be suitably used for producing a granular solid fuel using a coal-based powder fuel having poor compression moldability as a raw material.

1, 2, 3, 8 Silo 4, 5, 6 Conveyor scale 7 Mixer 9 Molding machine 10 Crusher

Claims (8)

A method for producing a solid fuel by compression molding a coal-based powdered fuel,
Mixing the pulverized fuel having an average particle size larger than that of the coal-based powder fuel with the coal-based powder fuel;
A step of compression molding the mixture obtained in the mixing step;
Crushing a part of the solid fuel obtained in the compression molding process,
A method for producing a solid fuel, wherein the solid fuel pulverized in the pulverization step is used as the pulverized fuel used in the mixing step.   The method for producing a solid fuel according to claim 1, wherein a mixing ratio of the pulverized fuel based on the mixture in the mixing step is 5% by mass or more and 50% by mass or less.   The method for producing a solid fuel according to claim 1 or 2, wherein the binding pulverized coal having a higher binding property than the coal-based powdered fuel is further mixed in the mixing step.   The method for producing a solid fuel according to claim 3, wherein a mixing ratio of the binding powdered coal based on the mixture in the mixing step is 5% by mass or more and 30% by mass or less. A step of measuring the strength of the solid fuel obtained in the compression molding step and adjusting the mixing ratio of the binding coal powder in the mixing step according to the measured value;
In the above adjustment step, the mixing ratio of the binding coal is increased when the strength of the solid fuel is less than the predetermined lower limit, and when the strength of the solid fuel exceeds the predetermined upper limit, The method for producing a solid fuel according to claim 3 or 4, wherein the mixing ratio is decreased.   6. The method according to claim 1, further comprising a step of measuring a production amount of the solid fuel obtained in the compression molding step and adjusting a mixing ratio of the pulverized fuel in the mixing step according to the measured value. The manufacturing method of the solid fuel of description.   The method for producing a solid fuel according to any one of claims 1 to 6, wherein each raw material is supplied to the mixer by a conveyor scale in the mixing step.   8. The reformed coal obtained by heating and dehydrating low-grade coal in oil as the coal-based powder fuel, and using low-grade coal powder as the binding powder coal. The manufacturing method of the solid fuel as described in 2.

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