JP2008050458A - Method and apparatus for producing solid fuel and solid fuel produced by the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a solid fuel with simplified work process and suppressing the generation of odor in the solid fuel production process as far as possible and provide a solid fuel produced by the method. <P>SOLUTION: The method for producing a solid fuel by drying sewage sludge or animal feces comprises a block forming step to form the sewage sludge or animal feces to a block of a prescribed size, a surface-forming step to increase the surface density of the block formed by the block forming step to be higher than the density of the inner part, and a crust-forming step to form a crust on the surface of the block by the heat-treatment of the surface-formed block. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for producing a solid fuel using sewage sludge or livestock dung as a raw material, and a solid fuel produced by the method.

As a method for producing a solid fuel using sewage sludge as a raw material, for example, the following is proposed.
A carbonization step of carbonizing sewage sludge dried to a water content of 0 to 50% at about 520K to 770K, and at least one of waste oil and waste oil residue with respect to the sludge carbide obtained by the carbonization. And a mixing granulation step of mixing and granulating the mixture (see Patent Document 1).

As another solid fuel production method, there is a sludge treatment method characterized by mixing a sewage dewatered cake, a waste plastic pulverized product and / or a waste paper crushed product, and drying after molding (see Patent Document 2).
JP 2006-152097 A JP 2006-15174 A

In other general solid fuel production methods including Patent Documents 1 and 2, measures against strong odor generated in each step of the solid fuel production method are not sufficient.
In particular, in the method of Patent Document 1, a mixed granulation process is performed in which at least one of waste oil and waste oil residue is mixed and granulated after the carbonization process, but the sludge after the carbonization process is powdered. Therefore, there is a problem that the processing environment is very bad and the work in the granulation process is complicated.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. A solid fuel manufacturing method and manufacturing apparatus capable of suppressing the generation of odors in the solid fuel manufacturing process as much as possible and simplifying the work process, and the manufacturing method. The purpose is to obtain a solid fuel.

  In order to solve the above-mentioned problems, the inventor conducted the measurement of the particle size change in the drying process of the sludge particles containing the solid content, the observation of the internal structure, and the influence of the heat treatment temperature on the odor.

1) Measurement of change in particle diameter during drying process Particles having an initial particle diameter d ₀ = 7 mm were heat-treated with an air flow at a predetermined temperature, and the change in particle diameter during the drying process was measured.
In addition, the particle | grains for drying experiment of a sewage sludge were created as follows. First, sewage sludge is torn into a lump of a certain size, and then the lump of lump is rolled on the plate surface so that the density of the surface of the lump is higher than the internal density. , Molded into a spherical shape or similar shape. During this molding, if the squeezing is performed so as to apply a little pressure, a lump having a smooth surface with few uneven surfaces is obtained.

  FIG. 2 shows the change of the particle diameter d (mm) with respect to the dimensionless time t when the heat treatment temperature Ta = 473K and 343K, together with the history of the water content ratio C (%). Here, the water content ratio C (%) means the ratio of the amount of moisture contained in the particles to the dry mass excluding moisture.

  As can be seen from FIG. 2, the particle size is smaller when Ta = 343K than when Ta = 473K. When Ta = 343K, the initial particle size is 84%, and when Ta = 473K, the initial particle size. The particle diameter was 90% of the diameter. Assuming that the temperature distribution in the particle radial direction is larger as the heat treatment temperature Ta is higher, in the case of Ta = 473K, the surface is heated faster than the inside and dried, and volume shrinkage occurs to form a shell that becomes a hard solid wall. It is thought that it becomes difficult to occur. On the other hand, in the case of Ta = 343K, not only the exterior but the entire drying progresses, so that the moisture in the interior evaporates before the surface becomes completely hard, and it seems that shrinkage occurs.

2) Observation of internal structure (observation of particle cross section during drying)
In order to clarify the internal state in the drying process when the sludge particles were dried, a cross section of the particles being dried was photographed and observed. The cases of Ta = 473K and Ta = 343K are shown in FIGS. 3 (a) to 3 (c) and FIGS. 4 (a) to 4 (c), respectively.
(A) of each figure shows the particle | grain cross section of an initial state. In this case, it can be seen that the solid content including the white fibrous substance is completely dissolved in moisture. Regarding the drying process, when Ta = 473K, the surface is first dried to form an outer shell, and then a crack is formed inside, which develops and grows into a void. On the other hand, in the case of Ta = 343K, the shell as in the case of Ta = 473K cannot be clearly confirmed, and the whole is dried. At the stage where the moisture content C is 43% ((b) in each figure), the difference due to the heat treatment temperature is obvious, and when Ta = 473K, the inside is still wet, but when Ta = 343K, the inside is slightly It can be seen that a white fibrous substance is deposited after drying.

From the above measurement of the particle size change during the drying process and observation of the internal structure, it is considered that the following differences occur in the drying characteristics of the sludge particles depending on the heat treatment temperature.
In the case of high-temperature drying, the surface is first dried to form an outer shell immediately before the volume shrinks. The interior is dried through its outer shell, but the outer shell is hard and prevents volume shrinkage.

  It is considered that shell formation in the sludge particles occurs due to a balance between the evaporation rate of moisture from the particle surface and the diffusion rate of moisture inside. That is, when the heat treatment temperature is high, the evaporation rate is large, and the temperature gradient and moisture content gradient near the particle surface become steep, so that the surface dries and forms a shell even before the volume shrinks while the internal moisture content is high. . The change in particle size is smaller than that during low temperature drying because the shell is hard and prevents volume shrinkage. Also, the solid content that is a solute in the drying process diffuses from the inside to the surface like moisture, but in the case of high-temperature drying, the vicinity of the surface dries quickly and hardens, and the internal solid content becomes difficult to diffuse, so the whole It is thought that it becomes a sparse porous particle (see FIG. 3C).

On the other hand, in the case of low-temperature drying, the surface dries quickly, but no shell is formed, and the whole is dried, resulting in significant volume shrinkage, and volatilization of the solid content easily occurs.
When the heat treatment temperature is low, the temperature gradient and moisture content gradient in the particles are small, so the solids move to the surface, hard shells do not form, and it is thought that significant volume shrinkage occurs as drying progresses (See FIG. 4 (c)). Under the condition of 343K, the shell is not formed until it is completely dried, and during the heat treatment, moisture and volatile matter are released to the outside from the surface having a low pressure resistance, so that the surface becomes uneven.

Note that the particles having initial particle diameters d ₀ = 5 mm and 3 mm show almost the same characteristics as in the case of d ₀ = 7 mm for all conditions, but the same as the case where the thickness of the shell and the outer skin is d ₀ = 7 mm. Met.

From the above experiment, it was found that there is a significant difference between the case where the heat treatment conditions of the sludge particles are high temperature (473 K) and the case where the temperature is low temperature (343 K). The experiment was conducted and the following results were obtained.
When the surface of the sludge mass is formed smoothly and then heat-treated in a high temperature field of 443K to 513K, for example, when heat-treated while applying a high-temperature air current, a hard shell is formed, and the surface of the shell is smooth and fibrous. Are arranged regularly. This phenomenon was the same when the sludge particles were heat-treated while rolling the externally heated high temperature rolling surface inner wall.

On the other hand, when the heat treatment temperature is lower than 443 K, the surface after the heat treatment becomes uneven even when a sludge mass that is smooth by eliminating irregularities from the surface of the mass and the density of the surface of the mass is higher than the inside is used. More specifically, under the conditions of 373K and 343K, even if a spherical sludge lump having a well-shaped shape is used, the surface becomes uneven after the heat treatment, and the surface is cracked. On the other hand, under the condition of 343K, as described above, the mass of the mass is greatly contracted, and a hard shell is not formed until it is completely dried.
When the heat treatment temperature was low, the particle surface after the heat treatment was rough, and it was confirmed that the fibrous substance was entangled randomly. This is considered to be because moisture or volatile components are released from the surface with low pressure resistance to the outside during the heat treatment process, and the smooth surface is destroyed.

  From the above results, when the sludge mass is heat-treated at 443K to 513K, preferably 453K or more, the particle size reduction of the mass is small and the shape before the heat treatment is kept, and after the heat treatment, the surface is smooth and hard shell The knowledge that it will be formed.

Next, the effect of the surface state of the sludge mass on the mass during the drying process was also confirmed. As a result, it was found that when the sludge of a smooth lump having few uneven surfaces is heat-treated at 443K to 513K, a harder shell tends to be formed than lump sludge having uneven surfaces.
Eliminating irregularities on the surface reduces the amount of heat transferred from the high-temperature airflow into the sludge, and the temperature gradient on the particle surface is larger than irregularities, resulting in a shorter volume. A shell forms on the surface soon after shrinking. If the shell can be formed while the internal temperature is low and the amount of moisture and volatile components generated from the inside is small, a very dense and hard shell is formed over the entire surface of the lump.

Next, the thickness of the sludge block was considered.
Depending on the time of exposure to the hot air stream, the thickness of the shell also changes. The longer the time, the thicker the shell. For example, the shell thickness was 0.1 mm to ₁ mm under the conditions of 453K to 493K using sludge particles having an initial particle diameter d ₀ = 7 mm. It was found that the thickness of the shell needs to be 0.1 mm or more in order to maintain the hardness of the sludge mass after drying so as not to break into powder.
Moreover, as the initial particle diameter increases, the thickness required to prevent the sludge mass after drying from breaking into a powder is required to be large. The initial particle diameter is about 0.2 mm at 20 mm, and is 0. The knowledge that about 25 mm is required was obtained. Under the conditions of 453K to 493K using sludge particles having an initial particle diameter of 30 mm, the shell thickness was measured after complete drying, and the maximum thickness was 3.2 mm.

  When the heating method was considered, the following knowledge was obtained. When the sludge of a smooth lump with few uneven surfaces is heat-treated at 443K to 513K while rolling the inner wall of a hot rolling surface heated externally, a dense shell is obtained in a shorter time than in the case of heat treatment using a high-temperature air flow. I found out that In the case of the method of rolling an externally heated high-temperature inner surface of the rolling surface, heat is transmitted by contact between solids, and therefore, it is considered that an action of pressing and hardening the lump body surface works in the heat treatment step.

In addition, although the sewage sludge was mentioned as an example in the above, the same experiment was performed also about livestock dung and the same result was obtained.
In addition, depending on the quality of sewage sludge and livestock excrement, it was confirmed that a hard shell with luster might be formed.

3) Effect of heat treatment temperature on odor Next, an odor experiment was conducted to clarify the relationship between the heat treatment temperature and the odor coefficient. Table 1 shows the experimental conditions at this time.

The experimental results are shown in the graph of FIG. In the graph of FIG. 5, the vertical axis indicates the odor coefficient, and the horizontal axis indicates the heat treatment temperature (° C.).
The “odor coefficient” is uniquely defined in this experiment, and is obtained by performing an odor test by a human olfaction method as shown below. Hereinafter, this odor experiment will be outlined.

  This test was conducted by a pair of tester and subject. First, dry particle samples prepared using the drying temperature as a parameter are divided into numbered containers. The examiner chooses a sample at random, and gives it to the subject without giving the number. The subject confirms the odor of the sample by olfaction, and tells the tester that 1 if any odor is felt, 0 if no odor is felt at all. This operation was performed for all samples, and this was regarded as a single odor test. This test was repeated, an average value was obtained for each condition, and the value was defined as “odor coefficient”. In order to obtain a highly reproducible result, it was performed until the value of the odor coefficient in each condition was stabilized. When the number of tests was 30 times or more, the value of the odor coefficient was stable even under the conditions.

  From FIG. 5, the odor coefficient decreases rapidly when the heat treatment temperature is 443K or more, and becomes almost zero when the heat treatment temperature is 473K. From this, it was confirmed that the odor of the sludge dry particles depends on the heat treatment temperature, and that the odor of the dry particles can be greatly reduced by drying at a heat treatment temperature of 473K.

As described above, the reason why the odor is reduced is that, as described above, according to drying at 473K, a hard shell is formed on the surface of the sludge particles, and the odor is adsorbed on the formed shell. It is believed that there is.
That is, when the surface of the sludge particles is heat-treated at 443 K or more, not only the water evaporates from the surface but also the property of the solid content on the surface changes and becomes a substance that easily adsorbs odor components. Although the component of this shell has not been specified, it is considered that it has a function similar to the adsorption action of activated carbon with respect to the adsorption action of odor.
The function of suppressing this odor improves as the heat treatment temperature is increased up to a heat treatment temperature of 513K.

  If it exceeds 513K, the effect of adsorbing the odor generated at the time of drying is obtained, but another odor such as a protein burnt is newly generated. The heat treatment at this temperature brings about the properties of a shell different from the shell formed at 513 K or less, and generates another type of malodor even after the temperature decreases after drying. Therefore, it is not preferable to perform heat treatment at a temperature higher than 513 K from the viewpoint of suppressing a strong odor generated from the sludge dried product.

  The heat treatment temperature of about 443K corresponds to the boiling point of substances such as fatty acids and organic acids, but when dried at 473K, volatile fatty acid and organic acid substances such as butyric acid, valeric acid, and their structures. Substances with similar formulas are broken down into substances with no odor or weak odor.

  From the above results, when targeting sewage sludge and livestock dung, the heat treatment temperature needs to be 443K to 513K, preferably 453K to obtain a sufficiently stable odor reduction effect by drying. 493K.

In addition, the sludge particle | grains which acquired the odor reduction effect in said experiment use the smooth lump which has few uneven surfaces. Particles with uneven or torn cut surfaces or cracks on the surface release malodorous components from it during heat treatment, so even if it is in the temperature range where shell formation is possible, the odor reduction effect is Hard to get. Therefore, in order to obtain the effect of reducing odor, it is necessary to make the surface smooth by increasing the density of the surface of the massive body than the internal density.
When heat-treated at 443K to 513K, a dense hard shell in which fibrous substances are regularly arranged on the particle surface has an effect of suppressing odor, but this shell has a smooth lump with few uneven surfaces. It is more reliably formed by heat-treating the sludge subjected to the surface molding process. When heat-treating a “smooth lump with few uneven surfaces” formed so as to be in a “mud dumpling” state where the surface is smooth and uniformly pressed, at 443K to 513K, preferably 453K to 493K, It has the effect of most suppressing bad odors that occur during sludge drying.

  The present invention has been made based on the knowledge based on the above-described experiment, and specifically has the following configuration.

(1) The method for producing a solid fuel according to the present invention is a method for producing a solid fuel by drying sewage sludge or animal dung, and a lump forming step for converting the sewage sludge or animal dung into a lump of a predetermined size. And a surface molding step in which the density of the surface of the block formed in the block forming step is higher than the internal density, and a shell is formed on the surface of the block by heat-treating the surface formed block. It includes a shell forming step.

(2) A method for producing solid fuel by drying sewage sludge or livestock dung,
A lump forming step for turning sewage sludge or livestock dung into a lump of a predetermined size, and surface forming for smoothly shaping the lump's surface by rolling the lump formed in the lump forming step in a container And a shell forming step of forming a shell on the surface of the lump by heat-treating the lump formed on the surface.
In addition, it is preferable that a surface shaping | molding process is an aspect which makes a crack of the surface of a molded object.

(3) Also, a method for producing solid fuel by drying sewage sludge or livestock dung,
A lump forming step for forming sewage sludge or livestock dung into a lump of a predetermined size, and a surface forming step for smoothly shaping the surface of the lump by pressing the surface of the lump formed in the lump forming step And a shell forming step of forming a shell on the surface of the massive body by heat-treating the surface-molded massive body.

(4) Moreover, in the thing as described in said (1)-(3), the heat processing of a shell formation process is an aspect which applies hot air to a lump or rolls a lump on a heating body. It is what.

(5) Further, in the above (1) to (4), the heat treatment temperature in the shell forming step is set to 443K to 513K.

(6) Moreover, in the thing as described in said (1)-(5), including the moisture content adjustment process of adjusting the moisture content of a sewage sludge or livestock dung to 60%-80% before a lump formation process. It is a feature.

(7) The solid fuel production apparatus according to the present invention is an apparatus for producing solid fuel by drying sewage sludge or livestock dung, and a lump forming apparatus for converting the sewage sludge or livestock dung into a lump of a predetermined size. And a surface molding device that makes the density of the surface of the block formed by the block forming device higher than the internal density, and heat-treating the surface-formed block to form a shell on the surface of the block It is characterized by including a heating device.

(8) Moreover, the lump forming apparatus according to the above (7) includes a perforated plate, a pushing device that pushes sewage sludge or animal dung into the perforated plate, and a predetermined length of sewage sludge or animal dung that has passed through the perforated plate. And a cutting mechanism for cutting.

(9) Moreover, the surface shaping | molding apparatus as described in said (7) or (8) is equipped with the container which accommodates a lump, and the rotating plate which rotates in this container, The lump was accommodated in the container. The lump is rolled in the container by rotating the rotating plate in the state.

(10) Further, the surface molding apparatus according to the above (7) or (8) includes a container for storing the lump and a rotating mechanism for rotating the container, and the lump is stored in the container. The lump is rolled in the container by rotating the container.

(11) Moreover, the surface molding apparatus as described in said (7) or (8) is provided with the roll which opposes, and it was made to pressurize the surface of the said lump by letting a lump pass between this roll It is characterized by.

(12) The solid fuel according to the present invention is manufactured by any one of the methods (1) to (6).

In the present invention, the sewage sludge or livestock excrement is made into a lump of a predetermined size, the density of the lump surface is made higher than the internal density, and a shell is formed around the lump by heat treatment. Therefore, odor can be suppressed throughout the manufacturing process.
Moreover, since it shape | molds before a drying process, a granulation process becomes unnecessary after drying and a process can be simplified.
Further, since there is no step of granulating after the drying step, there is no problem of deterioration of the processing environment due to the powdered product being dried and floating.

[Embodiment 1]
FIG. 1 is an explanatory view schematically showing a method for producing a solid fuel according to an embodiment of the present invention.
The solid fuel manufacturing method according to the present embodiment includes a lump forming step (FIG. 1A) for converting sewage sludge to a lump having a predetermined size, and a surface of the lump formed in the lump forming step. The surface forming step (FIG. 1B) for increasing the density of the material to be higher than the internal density, and the shell forming step for forming a shell on the surface of the lump by heat-treating the surface-formed lump (FIG. 1 ( c)). When the shell forming step is completed, the solid fuel is obtained through a drying step.
Hereafter, each process and what is related to each process will be described in detail.

<Raw material>
The raw material used in the present embodiment is sewage sludge.
It is assumed that the water content of the sewage sludge as a raw material is 60% to 80%. Therefore, when the moisture content of the sewage sludge is larger than 80%, it is not possible to form a lump by adhering around the container when the lump is formed.
In addition, it is preferable that a moisture content is 68%-73%. When the moisture content is within this range, the surface molding process for increasing the surface density of the mass from the inside smoothly proceeds.

  In order to increase the operation rate of the surface molding process, when the moisture content of the lump sludge before entering the process is higher than 80%, a pre-drying process step by blowing dry air or room temperature airflow or drying under reduced pressure is added. There is a case. At this time, it is desirable to dry the lumps while maintaining the state of 318K or less, preferably 308K or less. This is because if the pre-drying temperature of the mass is increased to 318 K or higher, malodor is generated in this pre-drying step.

In addition, when the water content of the sewage sludge is lower than 60%, a lump can be formed, but since each lump is hard, it is difficult to form a smooth surface with few uneven surfaces. In this case, if the pressing force is increased in order to eliminate unevenness, the lump is cracked or broken.
Therefore, it is preferable to carry out preliminary drying or addition before the lump forming step or after the lump forming step to bring the water content into the above range.

  In addition to sewage sludge, water-containing organic sludge such as livestock manure, human waste sludge, food processing residue sludge, and papermaking sludge can be used as a raw material for the solid fuel.

<Block formation process>
The lump forming step is a step of turning the sewage sludge into a lump having a predetermined size.
As shown in FIG. 1 (a), a specific method for making sewage sludge into a mass is to press and push the sewage sludge 1 into a perforated plate (die) 3 with a screw pump or a Mono pump, etc. 1 is a linear body 5, and this is cut into a fixed length by a cutting mechanism 7, thereby forming a cylindrical block 9.
But the method of making it into the lump 9 is not limited to said method.

<Surface molding process>
The surface molding step is a step of making the density of the surface of the block 9 formed in the block formation step higher than the internal density (FIG. 1 (b)).
As a specific aspect of the surface forming step, a method as shown in FIG. In the example shown in FIGS. 1B and 1I, a rotating disk 13 is provided at the bottom of a cylindrical container 11, and the lump 9 is placed in the container and the disk 13 is rotated to rotate the lump 9. Is rolled on a disk so that the density of the surface of the massive body is made higher than the internal density, and the surface of the massive body is made smooth without cracks.

  Further, in the example shown in FIGS. 1B and 1I, the cylindrical body 15 that is inclined is rotated around the cylindrical axis, and the bulk body 9 is inserted into the cylindrical body 15 from above, thereby forming the bulk body. As the body 9 rolls in the cylinder, the density of the surface of the massive body 9 is made higher than the internal density as in the case of FIGS. 1B and 1I, and the surface of the massive body is smooth without cracks. It is to make a state.

  In addition, the example shown in FIGS. 1B and iii is to pressurize the surface of the mass 9 so that the density of the surface of the mass 9 is higher than the internal density. Specifically, as shown in FIGS. 1B and iii, the mass 9 is passed between a pair of opposed rolls 17 so that the density of the surface of the mass 9 is reduced to the internal density. The surface of the mass 9 is made smooth without cracks. In general, in addition to the function of pressurizing the surface, the roll is provided with a depression on the surface so as to be spherical or a mass close to a sphere.

<Shell formation process>
The shell forming step is a step of forming a shell on the surface of the block 18 by heat-treating the surface-molded block 18.
As a specific aspect of the shell forming step, there is a method shown in FIG. For example, as shown in FIG. 1 (c) (i), an inclined cylindrical body 19 is rotated around a cylindrical axis, and a high temperature gas 21 is passed through it, and the cylindrical body 19 is surface-molded. By inserting the lump 18, a shell 22 is formed on the surface of the lump 18. Further, as shown in FIGS. 1 (c) (ii), the cylindrical body 23 having the heated inner surface is rotated around the cylindrical axis, and the massive body 18 formed by surface molding is passed through the cylindrical body 23. Then, a shell 22 is formed on the surface of the lump 18.

  The heat treatment temperature is preferably 443K to 513K. If it is less than 443K, the formation of the shell becomes insufficient. On the other hand, when it exceeds 513K, a bad smell is produced from the sludge or livestock dung during the heat treatment. Further, when the temperature is further increased, hydrocarbons or hydrogen are liable to volatilize from sludge or livestock dung, and the carbonization of the lump after drying is reduced due to a structure that facilitates carbonization.

<Drying process>
A drying process is a process of drying the lump body in which the shell shape was formed into solid fuel.
The temperature in the drying process is not particularly limited. The temperature at the shell forming step may be, for example, around 473K, or it may be dried at room temperature under reduced pressure. Since the shell is formed at any temperature, it is possible to suppress the odor from being emitted from the outside air in the drying process. However, if the temperature in the drying step is too high, carbonization causes a problem that the calories of the solid fuel are reduced. Therefore, the temperature is preferably lower than the temperature in the shell formation step.
In addition, as a dryer used for a drying process, the thing of the aspect which consists of a warm air drying chamber provided with the belt conveyor which conveys a block, for example may be sufficient.

  As described above, in the present embodiment, sludge is formed into a lump, and further, the surface of the lump is formed and a shell is formed on the surface of the lump that has been surface-molded. Odor emission can be suppressed as much as possible throughout the manufacturing process. Moreover, since there is no granulation process after the drying process, the process can be simplified and the production efficiency is improved.

It is explanatory drawing of the manufacturing method of the solid fuel which concerns on one embodiment of this invention. It is a graph which shows the measurement result of the particle size change in the drying process of the sludge particle | grains containing solid content. It is a photograph of the cross section of the drying process of the sludge particle | grains containing solid content. It is a photograph of the cross section of the drying process of the sludge particle | grains containing solid content. It is a graph which shows the relationship between heat processing temperature and an odor coefficient.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sewage sludge 3 Perforated plate 7 Cutting mechanism 9 Lump 11 Container 13 Disk 15 Cylinder 17 Roll 18 Surface-formed lump 19 Cylinder 21 Hot gas 22 Shell 23 Cylinder

Claims (12)

A method of producing solid fuel by drying sewage sludge or livestock dung,
A lump forming step for converting sewage sludge or livestock dung into a lump of a predetermined size, a surface forming step for making the surface density of the lump formed in the lump forming step higher than the internal density, and surface forming. A method for producing a solid fuel, comprising: a shell forming step of forming a shell on the surface of the lump by heat-treating the lump. A method of producing solid fuel by drying sewage sludge or livestock dung,
A lump forming step for turning sewage sludge or livestock dung into a lump of a predetermined size, and surface forming for smoothly shaping the lump's surface by rolling the lump formed in the lump forming step in a container And a shell forming step of forming a shell on the surface of the lump by heat-treating the lump formed on the surface. A method of producing solid fuel by drying sewage sludge or livestock dung,
A lump forming step for forming sewage sludge or livestock dung into a lump of a predetermined size, and a surface forming step for smoothly shaping the surface of the lump by pressing the surface of the lump formed in the lump forming step A method for producing a solid fuel, comprising: a shell forming step of forming a shell on the surface of the lump by heat-treating the lump formed on the surface. The heat treatment in the shell forming step is a mode in which hot air is applied to the lump or the lump is rolled on the heating element. The solid fuel production according to any one of claims 1 to 3, Method. The method for producing a solid fuel according to any one of claims 1 to 4, wherein a heat treatment temperature in the shell forming step is set to 443K to 513K. The solid fuel according to any one of claims 1 to 5, further comprising a moisture content adjusting step of adjusting the moisture content of sewage sludge or livestock dung to 60% to 80% before the lump forming step. Production method. An apparatus for producing solid fuel by drying sewage sludge or livestock dung,
A lump forming apparatus that converts sewage sludge or livestock excrement into a lump of a predetermined size, a surface forming apparatus that makes the density of the surface of the lump formed by the lump forming apparatus higher than the internal density, and surface forming. An apparatus for producing a solid fuel, comprising: a heating device that forms a shell on the surface of the lump by heat-treating the lump. The lump forming apparatus includes a perforated plate, a pushing device that pushes sewage sludge or livestock dung into the perforated plate, and a cutting mechanism that cuts the sewage sludge or livestock dung that has passed through the perforated plate into a predetermined length. An apparatus for producing a solid fuel according to claim 7. The surface molding apparatus includes a container for storing a lump and a rotating plate that rotates in the container, and the lump is rolled in the container by rotating the rotating plate while the lump is received in the container. The solid fuel production apparatus according to claim 7 or 8, wherein the solid fuel production apparatus according to claim 7 or 8 is used. The surface molding apparatus includes a container for storing the lump and a rotating mechanism for rotating the container, and rotates the lump in the container by rotating the container while the lump is accommodated in the container. The solid fuel manufacturing apparatus according to claim 7 or 8, wherein 9. The production of a solid fuel according to claim 7 or 8, wherein the surface molding apparatus includes opposing rolls, and presses the surface of the lump by passing the lump between the rolls. apparatus. A solid fuel produced by the method according to claim 1.