METHOD AND APPARATUS FOR MANUFACTURING SOLID FUEL FROM RAW MATERIAL COAL

Abstract

A raw material slurry in which a coal is mixed with a mixed oil containing a heavy oil and a solvent oil is subjected to a water vaporization treatment with a vaporizer, and is subjected to solid-liquid separation with a mechanical solid-liquid separator. A separated solid is heated with a dryer while a carrier gas is flown, so as to vaporize the oil and produce a solid fuel. The carrier gas is fed to a cooler through a pipe, and the above-described vaporization oil is condensed and recovered. In a method and an apparatus for manufacturing a solid fuel, an occurrence of blocking in a pipe between the above-described dryer and the cooler can be prevented. An oil is flown on an inner wall surface of the pipe in the neighborhood of a cooler inlet portion with respect to the pipe between the dryer and the cooler.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technical field of a method and an apparatus for manufacturing a solid fuel from a raw material coal.

2. Description of the Related Art

Examples of known technologies for manufacturing solid fuels from raw material coals include a method for manufacturing a solid fuel described in Japanese Unexamined Patent Application Publication No. 7-233383. In the method for manufacturing a solid fuel described in this patent document, a mixed oil containing a heavy oil and a solvent oil is mixed with a porous coal to prepare a raw material slurry, the resulting slurry is heated to facilitate dehydration of the porous coal and, in addition, the mixed oil containing the heavy oil and the solvent oil is allowed to be contained in pores of the porous coal. Thereafter, the resulting slurry is subjected to solid-liquid separation.

According to the method for manufacturing a solid fuel disclosed in the above-described patent document, the coal is dehydrated and, in addition, a high-calorie solid fuel having a poor spontaneous combustion property, excellent transportability, and an excellent storage property can be produced.

Such a method is particularly useful for a low-rank coal generally containing a high content of moisture and having a low calorie. Since the porous coal contains large amounts of water, the transportation of the porous coal is tantamount to transporting water and, therefore, the transportation cost is relatively high. From this point of view, the transportability is poor, and the calorie is decreased correspondingly to the high content of moisture. Consequently, it is desired that the porous coal is dehydrated. However, if this dehydration is performed by a drying vaporization type dehydration method in which a tubular dryer or the like is used, there is a danger that spontaneous combustion accident may occur due to adsorption of oxygen to active sites present in pores of the dehydrated porous coal and an oxidation reaction.

On the other hand, in the method for manufacturing a solid fuel, disclosed in the above-described patent document, water in pores of the porous coal is gasified and vaporized by heating the raw material slurry (the mixture of the mixed oil containing the heavy oil and the solvent oil and the porous coal) and, in addition, the inside of the pore is covered with the mixed oil containing the heavy oil, and eventually, this mixed oil, in particular the heavy oil of higher priority, fills in the pore. Therefore, the above-described adsorption of oxygen to active sites present in pores and the oxidation reaction are suppressed and, thereby, the spontaneous combustion is suppressed. Furthermore, dehydration occurs by the above-described heating, and the calorie is increased due to the dehydration and the pores being filled in with oil, as described above. Consequently, dehydration is performed and, in addition, a high-calorie solid fuel having a poor spontaneous combustion property, excellent transportability, and an excellent storage property can be produced.

With respect to an apparatus for manufacturing the above-described solid fuel, the above-described patent document (Japanese Unexamined Patent Application Publication No. 7-233383) discloses an apparatus for manufacturing a solid fuel, the apparatus including a mixing tank in which a mixed oil containing a heavy oil and a solvent oil is mixed with a porous coal to prepare a raw material slurry, a vaporizer for heating the raw material slurry so as to remove steam, and a solid-liquid separator for subjecting the heated and treated slurry to solid-liquid separation. Here, the porous coal corresponds to a low-rank coal. This apparatus for manufacturing a solid fuel is a basic apparatus to produce the above-described solid fuel.

In the method for manufacturing a solid fuel, disclosed in the above-described patent document, the solid-liquid separation of the slurry after being subjected to the dehydration treatment (water vaporization treatment) is performed as described below, for example. The dehydrated slurry is subjected to solid-liquid separation with a mechanical solid-liquid separator, e.g., a centrifugal separator, and the solid (in a wet state) thereby separated is heated in a dryer while a carrier gas is flown, so as to vaporize oil. The resulting vaporized oil (hereafter may be referred to as vaporization oil) is fed to a cooler together with the carrier gas, and is condensed (the gaseous oil is converted to a liquid oil), so as to be recovered (refer to the paragraph [0040] in the above-described patent document).

When the oil is vaporized in the above-described dryer, the solid fuel is produced and, in addition, a fine powder solid fuel, that is, a fine powder of solid fuel (coal) is generated (hereafter may be referred to as a fine coal powder). This fine powder solid fuel is fine particles and, therefore, is entrained in the carrier gas from the dryer, so as to be transported to the cooler.

Although this fine powder solid fuel can be removed by disposing a dust collector between the dryer and the cooler, the fine powder cannot be removed completely. Therefore, the fine powder is adhered and accumulated inside the pipe, and problems occur in that, for example, the pipe is blocked.

That is, with respect to the pipe between the dust collector and the cooler, the temperatures are low in the neighborhood of the cooler inlet portion, and there are places at which the temperatures are lower than or equal to the dew-point temperature of the vaporized oil, the oil condensates at these places, so that the fine powder is adhered. The fine powder is accumulated and, eventually, the inside of the pipe is blocked.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the above-described circumstances.

The inventors of the present invention conducted intensive research to overcome the above-described problems, and as a result, the present invention has been completed. According to the present invention, the above-described problems may be overcome.

The present invention relates to a method and an apparatus for manufacturing a solid fuel from a low-rank coal serving as a raw material, and has the following configuration.

A method for manufacturing a solid fuel from a raw material coal according to a first aspect of the present invention includes the steps of mixing the coal into a mixed oil containing a heavy oil and a solvent oil to prepare a raw material slurry; heating the raw material slurry in a vaporizer to vaporize water; subjecting the resulting raw material slurry to solid-liquid separation with a mechanical solid-liquid separator to obtain a separated solid (cake); heating the separated solid in a dryer while a carrier gas is flown, so as to vaporize the oil and produce a solid fuel; and cooling the carrier gas from the dryer in a cooler to recover oil in the carrier gas, wherein an oil is flown in the neighborhood of a cooler inlet portion of a pipe for introducing the carrier gas into the cooler.

According to a second aspect, in the method for manufacturing a solid fuel of the first aspect, at least one type of the oil condensed in the above-described cooler; the oil separated by the solid-liquid separation with the above-described mechanical solid-liquid separator; and the oil condensed and recovered with the above-described cooler is used as the oil to be flown into the pipe for introducing the carrier gas into the cooler.

According to a third aspect, in the method for manufacturing a solid fuel of the first or second aspect, the oil recovered with the above-described cooler is introduced from an upper portion of the above-described cooler and is brought into contact with the carrier gas.

According to a fourth aspect, in the method for manufacturing a solid fuel of any one of the first aspect to the third aspect, the oil recovered with the above-described cooler is used as a part of the oil to be mixed with the coal in the preparation of the above-described raw material slurry.

According to a fifth aspect of the present invention, an apparatus for manufacturing a solid fuel includes a vaporizer for heating a raw material slurry prepared by mixing a coal into a mixed oil containing a heavy oil and a solvent oil to vaporize water; a mechanical solid-liquid separator for subjecting the raw material slurry to obtain a separated solid, from which water has been vaporized, to mechanical solid-liquid separation; a dryer for heating the separated solid while a carrier gas is flown, so as to vaporize the oil; and a cooler for cooling the carrier gas from the dryer, so as to recover oil in the carrier gas, wherein a device for flowing an oil in the neighborhood of a cooler inlet portion of a pipe for introducing the carrier gas into the cooler is included.

According to a sixth aspect, in the apparatus for manufacturing a solid fuel of the fifth aspect, the device for flowing the oil on the inner wall of the above-described pipe includes an oil inflow pipe connected to an upper side wall of the pipe; and a device for supplying the oil to the oil inflow pipe.

According to a seventh aspect, in the apparatus for manufacturing a solid fuel of the sixth aspect, the device for supplying the oil to the above-described oil inflow pipe is an oil supply device for supplying the oil condensed in the above-described cooler to the above-described oil inflow pipe.

According to an eighth aspect, in the apparatus for manufacturing a solid fuel of the sixth aspect, the device for supplying the oil to the above-described oil inflow pipe is connected to the above-described oil inflow pipe and an upper portion of the cooler.

In the method for manufacturing a solid fuel according to an aspect of the present invention, water in the raw material slurry prepared by mixing the coal and a mixed oil containing the heavy oil and the solvent oil is vaporized with a vaporizer, and the resulting raw material slurry is subjected to solid-liquid separation with the mechanical solid-liquid separator. Subsequently, the separated solid is heated in the dryer while the carrier gas is flown, so as to vaporize the oil and produce the solid fuel. The oil (vaporization oil) vaporized in the dryer is fed to the cooler together with the carrier gas, and the above-described vaporization oil is condensed and recovered. At this time, an occurrence of blocking in the pipe may be prevented by flowing the oil in the neighborhood of the cooler inlet portion of the pipe for introducing the carrier gas into the cooler.

The apparatus for manufacturing a solid fuel according to an aspect of the present invention may perform the above-described method for manufacturing a solid fuel according to an aspect of the present invention and, by extension, the above-described operational effect may be exerted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram showing a process for manufacturing a solid fuel according to Example 1 and Comparative example 1 of the present invention.

FIG. 2 is a schematic diagram showing the detail of a final drying section in the process for manufacturing a solid fuel according to Comparative example 1.

FIG. 3 is a schematic diagram showing the detail of a final drying section in the process for manufacturing a solid fuel according to Example 1 of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The blocking of the pipe for introducing the carrier gas into the cooler can be suppressed by keeping the temperature of the pipe with a heater or the like. However, it is difficult to keep the temperature in the neighborhood of the cooler inlet portion of the pipe, and condensation of the vaporization oil occurs. A fine powder solid fuel contained in the carrier gas is adhered and accumulated on this condensation portion and, thereby, blocking of the pipe occurs. In the present invention, the oil is flown on the inner wall surface of the pipe in the neighborhood of the cooler inlet portion with respect to the pipe between the dryer and the cooler and, thereby, the fine powder is washed away before adhering to the pipe inner wall, so that no fine powder is accumulated in the pipe, nor occurs blocking. When a dust collector is disposed in the piping between the dryer and the cooler, the amount of fine powder in the carrier gas may be decreased, and blocking may be suppressed. However, it is economically difficult to completely remove the fine powder. Therefore, the present invention is also useful in the case where the dust collector is disposed.

In the method for manufacturing a solid fuel according to an aspect of the present invention, as described above, the oil is flown on the inner wall surface of the pipe in the neighborhood of the cooler inlet portion with respect to the pipe between the dryer and the cooler, as described above. The frequency and the speed of flowing of the oil on the inner wall surface of the pipe are not specifically limited. However, it is desirable to flow the oil continuously in order to more reliably prevent the occurrence of blocking in the pipe. Furthermore, it is desirable that the speed of flowing of the oil (amount of oil inflow) is larger. Even when the oil flown on the inner wall surface of the pipe is flown on the vaporizer side, this oil is heated and vaporized again so as to become vaporization oil, and eventually, enters the cooler. Therefore, there is no problem in that the oil is flown on the vaporizer side. However, it is desirable that the oil flown on the inner wall surface of the pipe is flown on the cooler side and enters the cooler, in order to prevent consumption of energy required for vaporizing the oil.

At least one type of the oil condensed in the cooler, the oil separated by the solid-liquid separation with the above-described mechanical solid-liquid separator, and the oil condensed and recovered with the above-described cooler may be used as the oil to be flown on the inner wall surface of this pipe. Consequently, it is not required to prepare separately the oil to be flown in the pipe.

In the method for manufacturing a solid fuel according to an aspect of the present invention, the oil condensed in the cooler may be introduced from the upper portion of the above-described cooler and be brought into contact with the carrier gas. When the oil is introduced (circulated) from the upper portion of the cooler, the condensation of the vaporization oil in the cooler may be facilitated. Since the fine powder entered in the cooler together with the carrier gas is washed away with the oil, the fine powder may be separated (removed) from the carrier gas efficiently.

In the method for manufacturing a solid fuel according to an aspect of the present invention, the oil condensed in the cooler may be used as a part of the oil to be mixed with the coal in the preparation of the raw material slurry. When the oil condensed in the cooler is used (circulated) as a part of the mixed oil in the preparation of the raw material slurry, as described above, economies are achieved because the amount of addition of oil is decreased in the case where the present invention is put into execution continuously.

Furthermore, when the oil condensed in the cooler is used (circulated) as a part of the oil in the preparation of the raw material slurry, as described above, the fine powder contained in this oil may eventually be recovered as a solid fuel.

The apparatus for manufacturing a solid fuel according to an aspect of the present invention includes the vaporizer for heating the raw material slurry prepared by mixing the coal into the mixture containing the heavy oil and the solvent oil to vaporize water; the mechanical solid-liquid separator for subjecting the raw material slurry to obtain a separated solid, from which water has been vaporized, to mechanical solid-liquid separation; the dryer for heating the separated solid while the carrier gas is flown, so as to vaporize the oil; and the cooler for cooling the carrier gas from the dryer, so as to recover the oil in the carrier gas, wherein the device for flowing the oil in the neighborhood of the cooler inlet portion of the pipe for introducing the carrier gas into the cooler is included.

According to the apparatus for manufacturing a solid fuel of an aspect of the present invention, the above-described method for manufacturing a solid fuel according to an aspect of the present invention can be performed and, by extension, the operational effect similar to those in the method for manufacturing a solid fuel according to the aspects of the present invention may be exerted. That is, since the above-described vaporizer, the mechanical solid-liquid separator, the dryer, and the cooler are disposed, the water vaporization treatment, the solid-liquid separation with the mechanical solid-liquid separator, the vaporization of the oil with the dryer, and the condensation and the recovery of the vaporization oil with the cooler of the method for manufacturing a solid fuel according to the aspects of the present invention may be performed. In addition, the device for flowing the oil on the inner wall surface of the pipe in the vicinity of the cooler (in the neighborhood of the cooler inlet portion) is disposed with respect to the pipe between the dryer and the cooler. Consequently, no fine powder may be adhered and accumulated in the pipe, and blocking in the pipe may be prevented.

In the apparatus for manufacturing a solid fuel according to an aspect of the present invention, the oil inflow pipe, in which a hole is disposed in an upper side wall of the pipe portion and a tube is connected for allowing the oil to flow into the pipe, and a device for supplying the oil to the oil inflow pipe may be used as the device for flowing the oil on the inner wall surface of the pipe in the vicinity of the cooler with respect to the pipe between the dryer and the cooler.

The device for supplying the oil to the above-described oil inflow pipe may supply the oil condensed in the cooler to the above-described oil inflow pipe. Alternatively, the device for supplying the oil may supply the oil condensed in the cooler to the above-described oil inflow pipe and an upper portion of the cooler.

In the present invention, the carrier gas is not specifically limited, and for example, an inert gas, e.g., argon or nitrogen, may be used. The carrier gas has an operational effect of facilitating the drying in the dryer.

Examples of usable dryers include dryers of heating type, reduced pressure type, and heating and reduced pressure type. That is, the water vaporization treatment with the vaporizer may be performed by the system in which water is vaporized through by heating, the system in which water is vaporized through a reduced pressure, the system in which water is vaporized through heating and a reduced pressure, or the like.

The type of mechanical solid-liquid separator is not specifically limited, and various types may be used. For example, a centrifugal separator, a compressor, a sedimentation tank, and a filter may be used. However, in general, the centrifugal separator is used.

In the present invention, the coal used as a raw material for the solid fuel is not specifically limited. However, the present invention is significantly useful for a low-rank coal containing a high content of water. The low-rank coal refers to a coal having a water content of 20% or more and being desired to be dehydrated. Examples of low-rank coals include brown coal, lignite, and subbituminous coal. Examples of brown coal include a Victorian coal, a North Dakota coal, and a Beluga coal. Examples of subbituminous coals include a West Banko coal, a Binungan coal, and a Samarangau coal. The low-rank coal is not limited to the above-described examples, and the low-rank coal in the present invention includes every coal having a large water content and being desired to be dehydrated.

The heavy oil refers to a heavy fraction, such as a vacuum residue oil, which does not substantially exhibit a vapor pressure even at, for example, 400° C., or an oil containing the heavy fraction.

The water vaporization treatment of the raw material slurry refers to a treatment in which the low-rank coal in the raw material slurry is dehydrated. That is, it refers to a treatment in which water contained in a coal is vaporized and steam thereby generated is removed.

EXAMPLES

The example and the comparative example of the present invention will be described below. The present invention is not limited to this example, and appropriate modifications within the spirit or scope of the invention can be made and they are included in the scope of the present invention.

Comparative Example 1

FIG. 1 shows a flow of a process for manufacturing a solid fuel (a process from a raw material coal up to production of a solid fuel) according to Comparative example 1. FIG. 2 shows the detail of a final drying section (vaporization separation) in this manufacturing process. FIG. 1 also shows a process for manufacturing a solid fuel according to Example 1. FIG. 2 is related to Comparative example 1 and, therefore, the section shown in FIG. 2 is different from that related to Example 1.

As shown in FIG. 1, after a raw material coal (low-rank coal) was pulverized in a pulverization section, the pulverized coal was mixed with a mixed oil containing a heavy oil and a solvent oil in a mixing section, so that a raw material slurry was produced. At this time, an Indonesian Samarangau coal having a water content of 35 percent by mass (percent by weight) was used as the raw material low-rank coal. For the mixed oil containing the heavy oil and the solvent oil to be mixed with the low-rank coal, a mixed oil of asphalt and kerosene was used in early stage of the operation. Thereafter, the oils produced from the solid-liquid separation section and the final drying section, which are described below, were circulated as a circulating oil toward the mixing section, the heavy oil and the solvent oil were added to the circulating oil, and the resulting oil was used as the mixed oil. The kerosene belongs to the solvent oil, and the asphalt belongs to the heavy oil. The amount of asphalt in the mixed oil was specified to be 0.5 percent by weight (percent by mass).

After the above-described raw material slurry was preheated in a preheating section, a water vaporization treatment was performed in a vaporization section (vaporizer). The slurry subjected to the water vaporization treatment was fed into the solid-liquid separation section (mechanical separation), and was subjected to solid-liquid separation with a mechanical solid-liquid separator. At this time, a heating type vaporizer was used. A centrifugal separator was used as the mechanical solid-liquid separator.

The liquid (oil) separated with the above-described mechanical solid-liquid separator was circulated as a circulating oil toward the mixing section. On the other hand, the solid (cake) separated with the above-described mechanical solid-liquid separator was fed into the final drying section (vaporization separation), and was heated with a dryer while a carrier gas was flown, so that oil was vaporized and a solid fuel was produced. That is, as shown in FIG. 2, the above-described solid (cake) was put into the dryer, heating was performed while the carrier gas was flown, so that the oil was vaporized and, thereby, the solid fuel was produced. As shown in FIGS. 1 and 2, the resulting solid fuel was fed from the dryer to a cooling section, and was cooled so as to become a powder solid fuel. Alternatively, the resulting solid fuel was cooled in the cooling section and, thereafter, was molded in a molding section so as to become a molded solid fuel, or was fed directly to the molding section without being fed to the cooling section, so as to be molded into a molded solid fuel. A nitrogen gas was used as the above-described carrier gas.

When the oil was vaporized in the above-described dryer, the solid fuel was generated and, in addition, a fine coal powder (floating fine powder solid fuel, that is, fine powder of coal) was generated. As shown in FIG. 2, the resulting fine coal powder and the oil (vaporization oil) vaporized in the dryer were fed from the dryer through a heated pipe to a dust collector together with the carrier gas, and were subjected to a treatment for removing the fine coal powder in the dust collector. The resulting gas was fed to the cooler (gas cooler) through a heated pipe, and the vaporization oil was condensed and recovered with this cooler. The carrier gas exited from the cooler was introduced (circulated) into the dryer through a pipe. The heating temperature of the pipe between the above-described dryer and the dust collector was 160° C., and the temperature of the inner wall surface thereof was higher than the dew-point temperature (120° C.) of the vaporization oil. The heating temperature of the pipe between the above-described dust collector and the cooler was 150° C. to 170° C. at substantially every portion, and the temperature of the inner wall surface thereof was higher than the dew-point temperature of the vaporization oil. However, the temperature of the inner wall surface of a pipe portion (the pipe portion in the region indicated by “low temperature portion of pipe is blocked” in FIG. 2) in the vicinity of the cooler was lower than or equal to the dew-point temperature of the vaporization oil.

The oil condensed in the above-described cooler was taken out of the lower portion of the cooler, was introduced (circulated) from the upper portion of the above-described cooler by a pump through a pipe and, in addition, was circulated as a circulating oil toward the mixing section through a pipe branched from this pipe, so as to be used as a part of the oil in the preparation of the raw material slurry.

The above-described process for manufacturing a solid fuel was performed continuously.

As a result, at that point in time when 8 hours had elapsed after the start of the operation of the process, the inside of the pipe between the dust collector and the cooler was blocked, it became impossible to feed the vaporization oil and the carrier gas to the cooler, and the carrier gas was not able to be circulated at all. The place at which this blocking occurred was a pipe in the vicinity of the cooler (pipe at the place in the neighborhood of the cooler inlet portion, where heating was inadequate, and the temperature of the inner wall surface of the pipe was lower than or equal to the dew-point temperature of the vaporization oil) with respect to the pipe between the dust collector and the cooler, that is, in the inside of the pipe in the region indicated by “low temperature portion of pipe is blocked” in FIG. 2. In this pipe, the fine coal powder in the state of being wet with the oil was adhered and accumulated on the pipe inner wall surface so as to cause blocking.

Example 1

FIG. 1 shows a flow of a process for manufacturing a solid fuel (a process from a raw material coal up to production of a solid fuel) according to Example 1. FIG. 3 shows the detail of a final drying section (vaporization separation) in this manufacturing process.

An apparatus for manufacturing a solid fuel according to Example 1 is different from the apparatus for manufacturing a solid fuel according to Comparative example 1 only in the final drying section. That is, the final drying section in the apparatus for manufacturing a solid fuel according to Example 1 includes an oil inflow pipe (flow path) for flowing the oil condensed in the cooler into the pipe in the vicinity of the cooler (pipe in the neighborhood of the cooler inlet portion, where heating was inadequate, and the temperature of the inner wall surface of the pipe was lower than or equal to the dew-point temperature of the vaporization oil) with respect to the pipe between the dust collector and the cooler, and is different from that in the apparatus for manufacturing a solid fuel according to Comparative example 1 only in this point. This oil inflow pipe (flow path) is configured by being branched from the pipe for introducing (circulating) the oil condensed in the cooler from the upper portion of the above-described cooler and being pipe-connected in such a way that the oil can be flown into the pipe in the vicinity of the above-described cooler.

In the process for manufacturing a solid fuel according to Example 1, by the above-described oil inflow pipe (flow path), the oil (oil condensed in the cooler) was flown into the pipe in the vicinity of the cooler with respect to the pipe between the dust collector and the cooler, and the oil was flown on the inner wall surface of this pipe. Except for this point, the process for manufacturing a solid fuel was continuously performed in a manner similar to that in the case of Comparative example 1. The flowing of the oil into the pipe in the vicinity of the above-described cooler was performed continuously, and the inflow rate (the amount of inflow of the oil) was specified to be 1 liter/minute.

As a result, even at that point in time when 5 days had elapsed after the start of the operation of the process, no blocking occurred in the inside of the pipe between the dust collector and the cooler, the vaporization oil and the carrier gas were able to be fed to the cooler as in an initial stage of the operation, and the carrier gas was able to be circulated. The operation was terminated at this time, and the state of the inside of the pipe between the dust collector and the cooler was examined. No fine coal powder was accumulated in this pipe, nor was even adhesion of the fine coal powder observed.

The present invention may be suitable for use in conversion of a low-rank coal to a reformed coal by dehydration and reduction of the spontaneous combustion property and, therefore, is useful.

Claims

1. A method for manufacturing a solid fuel from a raw material coal, the method comprising the steps of:

mixing the coal into a mixed oil containing a heavy oil and a solvent oil to prepare a raw material slurry;

heating the raw material slurry to vaporize water;

subjecting the resulting raw material slurry in a vaporizer to solid-liquid separation with a mechanical solid-liquid separator to obtain a separated solid;

heating the separated solid in a dryer while a carrier gas is flown, so as to vaporize the oil and produce a solid fuel; and

cooling the carrier gas from the dryer in a cooler to recover oil in the carrier gas,

wherein an oil is flown in the neighborhood of a cooler inlet portion of a pipe for introducing the carrier gas into the cooler.

2. The method for manufacturing a solid fuel according to claim 1, wherein at least one type of:

the oil condensed in the cooler;

the oil separated by the solid-liquid separation with the mechanical solid-liquid separator; and

the oil condensed and recovered with the cooler is used as the oil to be flown into the pipe for introducing the carrier gas into the cooler.

3. The method for manufacturing a solid fuel according to claim 1 or claim 2, wherein the oil recovered with the cooler is introduced from an upper portion of the cooler, so as to be brought into contact with the carrier gas.

4. The method for manufacturing a solid fuel according to any one of claims 1 to 3, wherein the oil recovered with the cooler is used as a part of the oil to be mixed with the coal in the preparation of the raw material slurry.

5. An apparatus for manufacturing a solid fuel, the apparatus comprising:

a vaporizer for heating a raw material slurry prepared by mixing a coal into a mixture containing a heavy oil and a solvent oil to vaporize water;

a mechanical solid-liquid separator for subjecting the raw material slurry to obtain a separated solid, from which water has been vaporized, to mechanical solid-liquid separation;

a dryer for heating the separated solid while a carrier gas is flown, so as to vaporize the oil; and

a cooler for cooling the carrier gas from the dryer, so as to recover oil in the carrier gas,

wherein a device for flowing an oil in the neighborhood of a cooler inlet portion of a pipe for introducing the carrier gas into the cooler is included.

6. The apparatus for manufacturing a solid fuel according to claim 5, wherein the device for flowing the oil into the pipe comprises:

an oil inflow pipe connected to an upper side wall of the pipe; and

a device for supplying the oil to the oil inflow pipe.

7. The apparatus for manufacturing a solid fuel according to claim 6, wherein the device for supplying the oil to the oil inflow pipe supplies the oil condensed in the cooler to the oil inflow pipe.

8. The apparatus for manufacturing a solid fuel according to claim 6, wherein the device for supplying the oil to the oil inflow pipe is connected to the oil inflow pipe and an upper portion of the cooler.