WO2018037809A1

WO2018037809A1 - Solid fuel production method

Info

Publication number: WO2018037809A1
Application number: PCT/JP2017/026685
Authority: WO
Inventors: 高橋　洋一; 知和中川
Original assignee: 株式会社神戸製鋼所
Priority date: 2016-08-24
Filing date: 2017-07-24
Publication date: 2018-03-01
Also published as: JP6640679B2; JP2018030950A

Abstract

The present invention addresses the issue of providing a production method for solid fuel, whereby a solid fuel having relatively high strength can be obtained. This production method for solid fuel compresses and molds coal-based powdered fuel and comprises: a step in which a binding coal powder having greater binding properties than the coal-based powdered fuel is mixed into the coal-based powdered fuel; a step in which a feeding hopper having a feed screw is used to supply the mixture obtained in the mixing step to a compression and molding machine; and a step in which the mixture is compressed and molded by the compression and molding machine. The loose bulk density of the mixture relative to the consolidated bulk density thereof is no more than 0.8 and the ratio between the spatial density of one lap of the lower end of the execution part of the feed screw in the feeding hopper and the spatial density of one lap of the upper end of the execution part of the feed screw is 0.3-0.6.

Description

Method for producing solid fuel

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, reformed coal obtained by heating and dehydrating low-grade coal such as lignite in oil is usually in the form of powder, so it is desired to granulate by compression molding. 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, a technique for improving the strength of the obtained solid fuel by humidifying the reformed coal and press-molding has been proposed (see JP 2010-116544 A). 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 from which a solid fuel having a relatively high strength can be obtained.

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, and is bound to the coal-based powdered fuel with a higher binding property than the coal-based powdered fuel. A step of mixing the pulverized coal, a step of supplying the mixture obtained in the mixing step to the compression molding machine using a supply hopper having a supply screw, and a step of compression molding the mixture by the compression molding machine. The ratio of the loose bulk density to the hard bulk density of the mixture is 0.8 or less, and the space corresponding to the lower part of the execution part of the supply screw with respect to the spatial volume of the upper part of the supply part of the supply screw of the supply hopper This is a method for producing a solid fuel having a volume ratio of 0.3 to 0.6.

The method for producing the solid fuel has a ratio of the loose bulk density to the solid bulk density of the mixture within the above range, and an execution part of the supply screw with respect to a space volume corresponding to one upper end of the execution part of the supply screw of the supply hopper. By setting the ratio of the space volume for one round of the lower end within the above range, the mixture of raw materials can be supplied to the compression molding machine at a relatively high density. For this reason, since the solid fuel manufacturing method can compress and mold the mixture of raw materials by applying sufficient pressure with a compression molding machine, it is possible to manufacture a solid fuel with relatively high strength.

The ratio of the space volume of one lower end of the execution part of the supply screw to the space volume of the upper end of the supply part of the supply screw of the supply hopper is 0. The ratio of the loose bulk density to the solid bulk density of the mixture. 6 times or more and 0.9 times or less are preferable. Thus, the ratio of the space volume of the lower part of the execution part of the supply screw to the space volume of the upper part of the execution part of the supply screw of the supply hopper is within the above range, thereby compressing the mixture of raw materials. The amount supplied to the molding machine can be made more appropriate, and the strength of the obtained solid fuel can be increased.

In the mixing step, it is preferable to further mix a part of the solid fuel obtained in the compression molding step. In this way, in the mixing step, by further mixing the pulverized part of the solid fuel obtained in the compression molding step, the ratio of the loose bulk density to the hard bulk density of the mixture can be made relatively easy. Within the above range.

The average particle diameter of the pulverized solid fuel mixed in the mixing step is preferably 1 mm or more and 8 mm or less. Thus, when the average particle diameter of the pulverized solid fuel mixed in the mixing step is within the above range, the pressure in the compression molding machine can be increased more reliably.

As the coal-based powder fuel, modified coal obtained by heating and dehydrating low-grade coal in oil may be used, and 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.

Note that “high binding property” means that “crushing strength” measured in accordance with JIS-Z8841 (1993) when compression molding under the same conditions is high. Also. “Loose bulk density” means the apparent specific gravity of a granular material containing a large amount of air that has been dropped by an injection method (a method of dropping powder through a funnel-shaped member) and received in a container. The “hard bulk density” means the apparent specific gravity of a powder obtained by tapping 180 times of a powder containing a large amount of air obtained by an injection method. The “loose bulk density” and the “hard bulk density” can be measured using, for example, “Powder Tester PT-S type” manufactured by Hosokawa Micron. 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 according to JIS-Z8815 (1994).

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. It is a typical detailed sectional view of the supply hopper of FIG.

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.

1 is an apparatus for obtaining granular solid fuel by compressing and 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 binding powdered coal having a higher binding property than coal-based powdered fuel, and a coal-based powdered fuel. And a third silo 3 for storing pulverized fuel having an average particle size larger than that.

The solid fuel production apparatus of FIG. 1 includes a mixer 4 that mixes coal-based powdered fuel, binding powdered coal, and pulverized fuel supplied from silos 1, 2, and 3, and a raw material discharged from the mixer 4. And an intermediate silo 5 for storing the mixture.

In addition, the solid fuel production apparatus of FIG. 1 has a raw material supply hopper 6 that temporarily holds the raw material mixture discharged from the intermediate silo 5, and the raw material mixture is supplied from the raw material supply hopper 6. And a compression molding machine 7 for compressing and molding the desired solid fuel.

1 further includes a pulverizer 8 for pulverizing a part of the solid fuel formed by the compression molding machine 7. The solid fuel pulverized by the pulverizer 8 is supplied to the third silo 3 as the pulverized fuel. In addition, the conveyance of the granular material (coal-based powdered fuel, binding powdered coal, pulverized fuel, and solid fuel) between components should be performed by a known technique such as a chute, a belt conveyor, a bucket conveyor, or a pneumatic conveyor. Can do.

The method for producing the solid fuel that can be performed using the solid fuel production apparatus as described above includes a step of mixing the binding powdered coal and the pulverized fuel with the coal-based powder fuel by the mixer 4 <mixing step> The process of supplying the raw material mixture to the compression molding machine 7 using the supply hopper 6 <supply process>, the process of compressing the raw material mixture using the compression molding machine 7 <compression molding process>, and the compression molding process. And crushing a part of the solid fuel to be pulverized.

<Mixing process>
In the mixing step, coal-based powdered fuel, binding powdered coal and pulverized fuel are supplied from the silos 1, 2 and 3 to the mixer 4, and the mixer 4 mixes these coal-based powdered fuel, binding powdered coal and pulverized fuel. Thus, a raw material mixture is obtained. The raw material mixture obtained in this way is transferred to the intermediate silo 5 and stored in the intermediate silo 5.

(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 pulverized coal, pulverized coal having a higher binding property than that of the coal-based pulverized fuel may be used, but in order to suppress an increase in cost, it is preferable to use a relatively low-grade pulverized coal.

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. Note that “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 sieve was 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 production method is used.

The lower limit of the average particle size of the pulverized fuel is preferably 1 mm, and more preferably 2 mm. On the other hand, the upper limit of the average particle diameter of the pulverized fuel is preferably 8 mm, and more preferably 6 mm. If the average particle size of the pulverized fuel is less than the lower limit, the compression moldability of the raw material mixture may not be sufficiently improved. On the other hand, when the average particle size 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.

Further, 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 raw material mixture 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.

(Raw material mixture)
The lower limit of the bulk density of the raw material mixture obtained by mixing coal-based powdered fuel, binding powdered coal and pulverized fuel is preferably 0.5 g / cc, more preferably 0.6 g / cc. On the other hand, the upper limit of the bulk density of the raw material mixture is preferably 1.0 g / cc, more preferably 0.9 g / cc. If the bulk density of the raw material mixture is less than the above lower limit, the raw material mixture may not be sufficiently filled into the cavity of the compression molding machine 7 to be described later, and the raw material mixture may not be compression-molded. There is a possibility that the strength of is insufficient. On the other hand, when the solid bulk density of the raw material mixture exceeds the above upper limit, the filling of the raw material mixture into the cavity of the compression molding machine 7 may be excessive, which may cause an overload of the compression molding machine 7.

The lower limit of the ratio of the loose bulk density to the solid bulk density of the raw material mixture (hereinafter sometimes referred to as bulk density ratio) is preferably 0.5, and more preferably 0.55. On the other hand, the upper limit of the bulk density ratio is 0.8, preferably 0.75. If the bulk density ratio is less than the above lower limit, the raw material mixture may not be sufficiently filled into the cavity of the compression molding machine 7 and the raw material mixture may not be compression molded, and the strength of the solid fuel obtained is insufficient There is a risk of becoming. On the other hand, when the bulk density ratio exceeds the upper limit, filling of the raw material mixture into the cavity of the compression molding machine 7 may be excessive and cause overloading of the compression molding machine 7.

The lower limit of the mixing ratio of the binding coal powder in the raw material mixture (ratio to the entire raw material mixture) 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 is preferably 30% by mass, and more preferably 25% by mass. When the mixing ratio of the binding coal powder is less than the above lower limit, the strength of the solid fuel may not be sufficiently improved. Conversely, if the mixing ratio of the binding coal powder exceeds the above upper limit, the price of the solid fuel may increase unnecessarily.

The lower limit of the mixing ratio of the pulverized fuel in the raw material mixture 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 is preferably 50% by mass, and more preferably 40% by mass. When the mixing ratio of the pulverized fuel is less than the lower limit, the strength of the solid fuel may not be sufficiently improved. Conversely, if the mixing ratio of the pulverized fuel exceeds the above upper limit, the production efficiency of the solid fuel may be unnecessarily lowered, and the strength of the solid fuel obtained by forming gaps between the particles of the pulverized fuel becomes insufficient. There is a fear.

(silo)
As silos 1, 2, 3, and 5, coal-based powdered fuel, binding powdered coal, pulverized fuel, and a raw material mixture obtained by mixing these may be respectively 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 intermediate silo 5 for storing raw material mixture can be configured to be able to have a nitrogen atmosphere inside. preferable. More specifically, the first silo 1, the third silo 3 and the intermediate silo 5 are provided with a measurement mechanism for measuring the carbon dioxide (CO ₂ ) concentration inside, and when the CO ₂ concentration measured by the measurement mechanism increases. It is preferable to include a gas supply mechanism for introducing nitrogen gas (N ₂ ).

(Mixer)
The mixer 4 only needs to be able to uniformly mix coal-based powdered fuel, binding powdered coal, and pulverized fuel. 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 4. FIG.

The mixing time (residence time) of the raw material by the mixer 4 is generally preferably 30 minutes or less when the mixer 4 is a paddle mixer, for example. 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. When the moisture value varies widely, mixing is insufficient, so it can be determined that the mixing time by the mixer 4 needs to be increased.

<Supply process>
In the supply step, the raw material mixture is discharged from the intermediate silo 5 and supplied to the compression molding machine 7 while compressing the raw material mixture using the supply hopper 6.

(Supply hopper)
As shown in FIG. 2, the supply hopper 6 includes a supply hopper body 10 and a supply screw 11 that rotates within the supply hopper body 10. The supply hopper 6 is connected to the raw material charging port of the compression molding machine 7 and supplies the raw material mixture to the compression molding machine 7 while compressing the raw material mixture by the supply screw 11.

The supply hopper main body 10 has at least an execution portion (a portion where the raw material mixture is compressed by the supply screw 11) formed in a cylindrical shape or a conical shape.

The supply screw 11 has a rotary shaft 12 concentric with the execution unit of the supply hopper main body 10 and screw fins 13 arranged in a spiral shape on the outer periphery of the rotary shaft 12.

The supply hopper 6 has a space volume corresponding to one rotation of the supply screw 11 (from the internal volume of the supply hopper main body 10 to the supply screw 11) by the diameter reduction of the supply hopper main body 10 and the change in the pitch of the screw fins 13 of the supply screw 11. The volume obtained by subtracting the volume of is configured to gradually decrease.

As a lower limit of the ratio of the space volume of one execution portion lower end of the supply screw 11 to the space volume of one execution portion upper end of the supply screw 11 of the supply hopper 6 (hereinafter referred to as screw space volume ratio), 0.3 And 0.35 is preferable. On the other hand, the upper limit of the screw space volume ratio is 0.6, preferably 0.55. When the screw space volume ratio is less than the lower limit, the supply of the raw material mixture to the compression molding machine 7 becomes excessive, and the compression molding machine 7 may be overloaded. Conversely, when the screw space volume ratio exceeds the upper limit, a sufficient amount of the raw material mixture cannot be supplied to the cavity of the compression molding machine 7 to be described later, and the strength of the solid fuel may be insufficient. In addition, when the screw fin 13 of the supply screw 11 is less than two rounds, the space volume for one round of the execution unit upper end and the space volume for one round of the execution unit lower end are partly calculated. .

The lower limit of the ratio of the screw space volume ratio of the feed hopper 6 to the bulk density ratio of the raw material mixture is preferably 0.6, and more preferably 0.65. On the other hand, the upper limit of the ratio of the screw space volume ratio of the supply hopper 6 to the bulk density ratio of the raw material mixture is preferably 0.9, more preferably 0.85. When the ratio of the screw space volume ratio of the supply hopper 6 to the bulk density ratio of the raw material mixture is less than the lower limit, the compression molding machine 7 is overloaded by excessive supply of the raw material mixture to the compression molding machine 7. There is a risk of becoming. Conversely, when the ratio of the screw space volume ratio of the supply hopper 6 to the bulk density ratio of the raw material mixture exceeds the above upper limit, the supply of the raw material mixture to the compression molding machine 7 becomes insufficient, so that the strength of the solid fuel May be insufficient.

<Compression molding process>
In the compression molding process, a granular solid fuel is obtained by compression molding the raw material mixture using the compression molding machine 7.

(Compression molding machine)
Examples of the compression molding machine 7 used in the compression molding process 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 rolls rotate in a direction from above to 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.

In particular, when a double roll molding machine is used as the compression molding machine 7, 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 compression molding machine 7. FIG. The raw material mixture separated from the molded solid fuel may be supplied again to the intermediate silo 5.

<Crushing process>
In the pulverization step, a part of the solid fuel obtained in the compression molding step is pulverized by the pulverizer 8 to obtain the above pulverized fuel. The pulverized fuel thus obtained is transferred to the third silo 3 and stored.

By mixing the pulverized fuel obtained in this pulverization step with the coal-based powder fuel, the bulk density of the raw material mixture to be 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.

(Crusher)
The pulverizer 8 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 8, when pulverized fuel that has not been sufficiently reduced in diameter can be discharged from the pulverizer 8, the pulverization discharged from the pulverizer 8 in order to prevent troubles in the compression molding machine 7. A sieve for separating large-diameter particles in the fuel may be provided, and the separated large-diameter particles may be re-supplied to the pulverizer 8.

<Advantages>
In the method for producing the solid fuel, the ratio of the loose bulk density to the bulk density of the mixture is within the above range, and the supply screw 11 is executed with respect to the space volume corresponding to one round of the upper end of the supply screw 11 of the supply hopper 6. The raw material mixture can be supplied to the compression molding machine 7 at a relatively high density by setting the ratio of the space volume for one round at the lower end of the part within the above range. For this reason, since the raw material mixture can be compression-molded by applying a sufficient pressure by the compression molding machine 7 in the method for producing the solid fuel, a solid fuel having a relatively high strength can be produced.

[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 method for producing solid fuel, the pulverized fuel may not be mixed in the mixing step. That is, the raw material mixture supplied from the supply hopper to the compression molding machine may not include the pulverized fuel.

Further, in the method for producing solid fuel, the strength of the solid fuel obtained in the compression molding process is measured, and the mixing ratio of the binding coal powder, the operation speed of the compression molding machine, etc. are determined according to the strength of the solid fuel. You may adjust. In addition, as a measuring method of 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.

Hereinafter, the present invention will be described in detail based on examples, but the present invention is not construed as being limited based on the description of the examples.

(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. The raw material mixture was obtained by mixing coal-based powdered fuel and binding powdered coal at a mass ratio of 90:10. The loose bulk density and the hard bulk density of this raw material mixture were measured using, for example, “Powder Tester PT-S type” manufactured by Hosokawa Micron Corporation. The loose bulk density was 0.50 g / cc, and the solid bulk density was 0.72 g / cc. cc.

The raw material mixture was supplied to a compression molding machine using a supply hopper having a screw space volume ratio of 0.52. As a compression molding machine, a double roll molding machine “K-4020” manufactured by Furukawa Industries Systems Co., Ltd. was used, and a roll with a diameter of 1 m having a cavity having a major axis of 42 mm, a minor axis of 24 mm, and a volume of 15 cc was mounted. The raw material mixture was compression molded by this compression molding machine to obtain a granular solid fuel. At this time, the compression molding machine could be stably operated at a speed at which the production amount was 10 ton / h. Further, the crushing strength of the obtained solid fuel was measured according to JIS-Z8841 (1993) and found to be 100 kgf.

(Example 2)
A mixture of coal-based powdered fuel similar to that in Example 1 and binder powdered coal at a mass ratio of 80:10 is the same as that in Example 1 using a supply hopper having a screw space volume ratio of 0.47. The granular solid fuel obtained by supplying to the compression molding machine was pulverized and passed through a sieve having an opening of 10 mm as a pulverized fuel. Coal-based powdered fuel, binding powdered coal, and pulverized fuel were mixed at a mass ratio of 80:10:10 to obtain a raw material mixture. A cycle in which this raw material mixture was compression molded with a compression molding machine and the obtained solid fuel was pulverized to obtain a new pulverized fuel was repeated until the operating conditions were stabilized. In this stable state, the loose bulk density of the raw material mixture was 0.55 g / cc, and the solid bulk density was 0.88 g / cc. Moreover, the production amount at this time was 11 ton / h, and the crushing strength of the obtained solid fuel was 105 kgf.

(Example 3)
A solid fuel was produced under the same conditions as in Example 1 except that a feed hopper having a screw space volume ratio of 0.40 was used. The production amount at this time was 7.5 ton / h, and the crushing strength of the obtained solid fuel was 120 kgf.

Example 4
A solid fuel was produced under the same conditions as in Example 2 except that a feed hopper having a screw space volume ratio of 0.58 was used. The production amount at this time was 12 ton / h, and the crushing strength of the obtained solid fuel was 68 kgf.

(Comparative Example 1)
A mixture of coal-based powdered fuel similar to that in Example 1 and binding powdered coal at a mass ratio of 20:20 is used in the same manner as in Example 1 using a supply hopper having a screw space volume ratio of 0.60. The granular solid fuel obtained by supplying to the compression molding machine was pulverized and passed through a sieve having an opening of 10 mm as a pulverized fuel. Coal-based powdered fuel, binding powdered coal, and pulverized fuel were mixed at a mass ratio of 20:20:60 to obtain a raw material mixture. An attempt was made to compress this raw material mixture with a compression molding machine, but the compression molding machine stopped due to overload, and solid fuel could not be obtained. At this time, the loose bulk density of the raw material mixture was 0.82 g / cc, and the solid bulk density was 0.88 g / cc.

(Comparative Example 2)
A raw material mixture was obtained under the same conditions as in Example 1 except that a feed hopper with a screw space volume ratio of 0.15 was used, and this raw material mixture was compression molded with a compression molding machine. The machine stopped due to overload and solid fuel could not be obtained.

(Comparative Example 3)
A solid fuel was produced under the same conditions as in Example 1 except that a feed hopper having a screw space volume ratio of 0.80 was used. The production amount at this time was 12 ton / h, and the crushing strength of the obtained solid fuel was 15 kgf. Moreover, the obtained solid fuel was not formed sufficiently densely, and the shape was incomplete.

Table 1 below summarizes the results of Examples 1 to 4 and Comparative Examples 1 to 3. The table also shows the ratio of the loose bulk density to the bulk density of the raw material mixture (bulk density ratio) and the ratio of the screw space volume ratio to the bulk density ratio.

As in Examples 1 to 4 shown in this table, it was confirmed that a solid fuel having a relatively high strength can be produced by setting the bulk density ratio and screw space volume ratio in appropriate ranges. In particular, Example 1 in which the ratio of the screw space volume ratio to the bulk density ratio was within a preferable range was higher in productivity than Example 3 in which the ratio of the screw space volume ratio to the bulk density ratio was slightly smaller. Further, in Example 2 in which the ratio of the screw space volume ratio to the bulk density ratio is within a preferable range, the strength of the solid fuel obtained is higher than that in Example 4 in which the ratio of the screw space volume ratio to the bulk density ratio is slightly larger. It was. On the other hand, in Comparative Example 1 where the bulk density ratio is too large and Comparative Example 2 where the screw space volume ratio is too small, the compression molding machine is overloaded, and in Comparative Example 3 where the screw space volume ratio is too large, the strength of the obtained solid fuel is low. It was enough.

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 inferior compression moldability as a raw material.

1, 2, 3, 5 Silo 4 Mixer 6 Supply hopper 7 Compression molding machine 8 Crusher 10 Supply hopper body 11 Supply screw 12 Rotating shaft 13 Screw fin

Claims

A method for producing a solid fuel by compression molding a coal-based powdered fuel,
Mixing the coal-based powdered fuel with binding coal powder having a binding property larger than that of the coal-based powdered fuel;
Supplying the mixture obtained in the mixing step to a compression molding machine using a supply hopper having a supply screw;
A step of compression-molding the mixture with a compression molding machine,
The ratio of the loose bulk density to the hard bulk density of the mixture is 0.8 or less,
A method for producing a solid fuel, wherein a ratio of a space volume of one lower end of the execution part of the supply screw to a space volume of one upper end of the execution part of the supply screw of the supply hopper is 0.3 or more and 0.6 or less.
The ratio of the space volume of the supply screw at the lower end of the supply screw to the space volume of the supply screw at the upper end of the supply portion of the supply hopper is 0.6, which is the ratio of the loose bulk density to the solid bulk density of the mixture. 2. The method for producing a solid fuel according to claim 1, wherein the method is not less than twice and not more than 0.9 times.
The method for producing a solid fuel according to claim 1, wherein in the mixing step, a part of the solid fuel obtained in the compression molding step is pulverized and further mixed.
The method for producing a solid fuel according to claim 3, wherein an average particle diameter of the pulverized solid fuel mixed in the mixing step is 1 mm or more and 8 mm or less.
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. Solid fuel production method.