DESCRIPTION TITLE OF THE INVENTION: COAL DRY DISTILLATION DEVICE TECHNICAL FIELD [0001] The present invention relates to a coal pyrolysis device for pyrolysis of dried coal and is beneficial particularly for refining low-rank coal (low-quality coal) that is porous and contains a large amount of moisture such as brown coal and subbituminous coal. BACKGROUND ART [0002] Low-rank coal (low-quality coal) containing a large amount of moisture such as brown coal and subbituminous coal is low in the amount of heat generation per unit mass. Thus, they undergo heat treatment to be dried. In this way, the amount of heat generation per unit mass is increased. [0003] As a coal refinement device for refining such a low-rank coal, there has been an external heating rotary kiln which is an indirect heating pyrolysis device configured to perform pyrolysis by indirectly heating low-rank coal with heating gas, for example. The low-rank coal undergoes heat treatment at a stage before the rotary kiln to become dried coal, and this dried coal is fed into an inner tube. The dried coal undergoes pyrolysis by the indirect heating to become pyrolysis coal, and this pyrolysis coal is discharged from the inner tube. PRIOR ART DOCUMENT PATENT DOCUMENT [0004] Patent Document 1: Japanese Patent Application Publication No.
2003-176985 SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION [0005] Meanwhile, the above pyrolysis not only produces pyrolysis gases (pyrolysis gases) such as carbon monoxide, water vapor, methanol, tar from the dried coal (low-rank coal) but also produces gases of its minor components such as mercury. The rotary kiln has a structure in which a heating part for heating the dried coal and a discharge part for discharging the pyrolysis coal are distant from each other. Thus, the pyrolysis coal gets cooled as it is moved toward the discharge part. The cooled pyrolysis coal adsorbs the mercury in the pyrolysis gas. As a result, the concentration of mercury in the pyrolysis coal per unit mass increases. [0006] In view of the above, the present invention has been made to solve the above-mentioned problem, and an object thereof is to provide a coal pyrolysis device capable of manufacturing pyrolysis coal with a low mercury content. MEANS FOR SOLVING THE PROBLEM [0007] A coal pyrolysis device according to a first aspect of the invention for solving the above-mentioned problem is a coal pyrolysis device including a pyrolysis device main unit including an inner tube to which dried coal is fed and an outer tube which covers the inner tube, and configured to produce pyrolysis coal and pyrolysis gas by indirectly heating the dried coal in the inner tube with heating gas fed into the outer tube, characterized in that the coal pyrolysis device comprises low-mercury-content pyrolysis coal producing means for reducing adsorption of mercury contained in the pyrolysis gas to the pyrolysis coal, or removing the pyrolysis coal to which the mercury has adsorbed, to produce the pyrolysis coal containing a small amount of the mercury. [0008] A coal pyrolysis device according to a second aspect of the invention for solving the above-mentioned problem is the coal pyrolysis device according to the first aspect of the invention according to the above-described invention, characterized in that the low-mercury-content pyrolysis coal producing means is a discharge pipe through which to discharge the gas in the inner tube, and a gas inlet port of the discharge pipe is located in the inner tube between a substantially center portion in a longitudinal direction and an exit of a coal heating portion in which the coal is heated by the heating gas. [0009] A coal pyrolysis device according to a third aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the second aspect of the invention, characterized in that the coal pyrolysis device further comprises: pyrolysis coal discharging means for discharging the pyrolysis coal; and carrier gas feeding means for feeding carrier gas to the pyrolysis coal discharging means. [0010] A coal pyrolysis device according to a fourth aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the third aspect of the invention, characterized in that the coal pyrolysis device further comprises heating gas delivering means for delivering the heating gas discharged from the outer tube to the inert gas feeding means. [0011] A coal pyrolysis device according to a fifth aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the fourth aspect of the invention, characterized in that the heating gas delivering means includes: cooling means for cooling the heating gas; purifyingmeans for purifying the cooledgas cooled by the cooling means; and a purified gas delivery pipe through which to deliver the purified gas purified by the purifying means to the inert gas feeding means. [0012] A coal pyrolysis device according to a sixth aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the first aspect of the invention, characterized in that the low-mercury-content pyrolysis coal producing means is preheating drying means, provided at a stage before the pyrolysis device main unit, for producing preheated dried coal by indirectly heating the dried coal before being fed into the inner tube with preheating gas. [0013] A coal pyrolysis device according to a seventh aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the sixth aspect of the invention, characterized in that the dried coal is heated by the preheating gas to between 280 and 350 0 C. [00141 A coal pyrolysis device according to an eighth aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the first aspect of the invention, characterized in that the coal pyrolysis device further comprises pyrolysis coal discharging means for discharging the pyrolysis coal, and the low-mercury-content pyrolysis coal producing means includes: a classification device configured to classify the pyrolysis coal discharged from the pyrolysis coal discharging means into coarse pyrolysis coal with a predetermined particle size or larger and fine pyrolysis coal with a particle size smaller than the predetermined particle size; and fine pyrolysis coal discharging means for discharging the fine pyrolysis coal classified by the classification device. [0015] A coal pyrolysis device according to a ninth aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the eighth aspect of the invention, characterized in that the classification device includes a classification plate through which the pyrolysis coal is classified, and a through-hole in the classification plate measures 0.42 mm to 2 mm. [0016] A coal pyrolysis device according to a tenth aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the first aspect of the invention, characterized in that the coal pyrolysis device further comprises pyrolysis coal discharging means for discharging the pyrolysis coal, and the low-mercury-content pyrolysis coal producing means includes: a classification device located between the inner tube and the pyrolysis coal discharging means and configured to classify the pyrolysis coal discharged from the inner tube into coarse pyrolysis coal with a predetermined particle size or larger and fine pyrolysis n coal with a particle size smaller than the predetermined particle size; and fine pyrolysis coal discharging means for discharging the fine pyrolysis coal classified by the classification device. [0017] A coal pyrolysis device according to an eleventh third aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the first aspect of the invention, characterized in that the coal pyrolysis device further comprises pyrolysis coal discharging means for discharging the pyrolysis coal, and the low-mercury-content pyrolysis coal producing means is a pyrolysis coal transport acceleration device configured to quickly transport the pyrolysis coal in the inner tube toward the pyrolysis coal discharging means. [0018] A coal pyrolysis device according to a twelfth aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the eleventh aspect of the invention, characterized in that a tip portion of the pyrolysis coal transport acceleration device is located in the vicinity of a furnace wall of the outer tube on a pyrolysis coal discharge port side. [0019] A coal pyrolysis device according to a thirteenth aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the first aspect of the invention, characterized in that the coal pyrolysis device further comprises pyrolysis coal discharging means for discharging the pyrolysis coal in the inner tube, the low-mercury-content pyrolysis coal producing means is a plate body fixed to the pyrolysis coal discharging means and extending in a longitudinal direction of the inner tube, and the plate body is located in contact with an upper portion of the pyrolysis coal. [0020] A coal pyrolysis device according to a fourteenth aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the thirteenth aspect of the invention, characterized in that the coal pyrolysis device further comprises inert gas feeding means for feeding inert gas into the pyrolysis coal discharging means. [0021] A coal pyrolysis device according to a fifteenth aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the first aspect of the invention, characterized in that the coal pyrolysis device further comprises pyrolysis coal discharging means for discharging the pyrolysis coal, and the low-mercury-content pyrolysis coal producing means is aheating device provided in the pyrolysis coal discharging means and configured to heat the pyrolysis coal in the vicinity of the pyrolysis coal discharging means. [0022] A coal pyrolysis n device according to a sixteenth aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the fifteenth aspect of the invention, characterized in that the heating device is a burner. [0023] A coal pyrolysis device according to a seventeenth aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the fifteenth aspect of the invention, characterized in that the heating device is a heat exchange tube which is provided rotatably and in which heating gas is capable of flowing. [0024] A coal pyrolysis device according to an eighteenth aspect of the invention for solving the above-mentioned problem is the above-described coal pyrolysis device according to the first aspect of the invention, characterized in that the coal pyrolysis device further comprises pyrolysis coal discharging means for discharging the pyrolysis coal, and the low-mercury-content pyrolysis coal producing means is an oxidant feed device configured to feed oxidant to the pyrolysis coal in the vicinity of the pyrolysis coal discharging means. EFFECT OF THE INVENTION [0025] According to the coal pyrolysis devices according to the present invention, they include the low-mercury-content pyrolysis coal producing means. In this way, the adsorption of mercury to the pyrolysis coal can be reduced, or the pyrolysis coal having a large amount of adsorbed mercury is removed. Accordingly, pyrolysis coal with a low mercury content can be manufactured. BRIEF DESCRIPTION OF THE DRAWINGS [0026] [Fig. 1] Fig. 1 is a schematic configuration diagram showing a first embodiment of a coal pyrolysis device according to the present invention. [Fig. 2] Fig. 2 is a schematic conf iguration diagram showing a second embodiment of the coal pyrolysis device according to the present invention. [Fig. 3] Fig. 3 is a schematic conf iguration diagram showing a third embodiment of a pyrolysis coal manufacturing facility according to the present invention. [Fig. 4] Fig. 4 is a schematic configuration diagram showing a fourth embodiment of the coal pyrolysis device according to the present invention. [Fig. 5] Fig. 54 is a schematic configuration diagram showing a fifth embodiment of the coal pyrolysis device according to the present invention. [Fig. 6] Fig. 6 is a graph showing the relation between the particle size of pyrolysis coal and the amount of mercury adsorption. [Fig. 7] Fig. 7 is a schematic configuration diagram showing a sixth embodiment of the coal pyrolysis device according to the present invention. [Fig. 8] Fig. 8 is a schematic configuration diagram showing a seventh embodiment of the coal pyrolysis device according to the present invention. [Fig. 9] Fig. 9 is a schematic configuration diagram showing an eighth embodiment of the coal pyrolysis device according to the present invention. [Fig. 10] Fig. 10 is a schematic configuration diagram showing a ninth embodiment of the coal pyrolysis device according to the present invention. [Fig. 11] Fig. 11 is a schematic configuration diagram showing a tenth embodiment of the coal pyrolysis device according to the present invention. [Fig. 121 Fig. 12 is a schematic configuration diagram showing an eleventh embodiment of the coal pyrolysis device according to the present invention. [Fig. 13] Fig. 13 is a schematic configuration diagram showing a twelfth embodiment of the coal pyrolysis device according to the present invention. MODES FOR CARRYING OUT THE INVENTION [0027] Modes for carrying out a coal pyrolysis device according to the present invention will be described through embodiments . EMBODIMENT 1 [0028] A coal pyrolysis device according to a first embodiment of the present invention will be described with reference to Fig. 1. [0029] The coal pyrolysis device according to this embodiment is a rotary kiln and includes an indirect-heating pyrolysis device main unit 111 as shown in Fig. 1. The pyrolysis device main unit Ill includes an inner tube 112, an outer tube 113 provided in such a way as to cover the inner tube 112, and a support 114 on which the inner tube 112 is rotatably supported. The outer tube 113 has a gas receive port (not shown) through which to receive heating gas 1 and a gas discharge port (not shown) through which to discharge heating gas 2 having heated the inner tube 112. The section of the inner tube 112 surrounded by the outer tube 113 is a coal heating portion. The pyrolysis device main unit 111 includes a feeder 115 configured to feed dried coal 11 into the inner tube 112, a separation tank 116 provided at an opening end portion of the inner tube 112, and a hopper 117 provided to the separation tank 116. [0030] The pyrolysis n device main unit ill further includes a discharge pipe 101 through which to discharge gas inside the inner tube 112 such for example as pyrolysis gas 21 to be described later. The discharge pipe 101 is located along the axis of the inner tube 112. A gas inlet port (tip portion) 101a of the discharge pipe 101 is located in a section D1 between a substantially center portion 112a of the inner tube 112 in the longitudinal direction (a substantially center portion of the outer tube 113 in the longitudinal direction) where the temperature of the dried coal 11 reaches 400 0 C, and a coal heating portion exit 112c of the inner tube 112 defined by a wall portion 113a of the outer tube 113. This is because if the gas inlet port 101a of the discharge pipe 101 is located at the feeder 115 side of the substantially center portion 112a of the inner tube 112 (closer to a coal heating portion entrance 112b of the inner tube 112 defined by a wall portion 113b of the outer tube 113) , the pyrolysis gas 21 will contact the dried coal 11 of which the temperature is low (the temperature is yet to be raised), causing condensation of the tar, and this tar will impair emission of mercury from the dried coal 11. On the other hand, if the gas inlet port 101a is located at the hopper 117 side of the wall portion 113a of the outer tube 113 at the coal discharge side, the pyrolysis coal 12 will adsorb the mercury in the pyrolysis gas 21 when the pyrolysis coal 12 gets cooled and the pyrolysis gas 21 contacts the cooled pyrolysis coal 12. In sum, by positioning the gas inlet port 101a of the discharge pipe 101 within the section D1, it is possible to more reliably prevent contact of the gas in the inner tube 112 with the cooled pyrolysis coal 12. [0031] Note that a suction blower (not shown) or the like is coupled to a base end portion of the discharge pipe 101. Thus, by sucking the gas in the inner tube 112, in particular the pyrolysis gas 21, at a predetermined suction speed, e.g. a speed higher than the speed at which the coal (dried coal 11, pyrolysis coal 12) is moved inside the inner tube 112, it is possible to prevent the gas in the inner tube 112 from flowing toward the separation tank 116 from the coal heating portion exit 112c of the inner tube 112 and discharge the gas in the inner tube 112 to the outside of the system. In other words, it is possible to prevent the gas in the inner tube from contacting the cooled pyrolysis coal 12 and discharge the gas to the outside of the system through the discharge pipe 101. The diameter of the discharge pipe 101 is set to such a size that the gas in the inner tube 112 can be discharged and the discharge pipe 101 does not contact the dried coal 11 in the inner tube 112. [0032] In this embodiment described above, the discharge pipe 101, the suction blower, and the like serve as low-mercury-content pyrolysis coal producing means. [0033] The operation of the coal pyrolysis device configured as above will be described below. [0034] First, raw coal, e.g. a low-rank coal (not shown) such as brown coal or bituminous coal is subjected to drying treatment with a drying device (not shown) to be dried coal 11, and the dried coal 11 is fed to the feeder 115. The feeder 115 feeds the dried coal 11 into the inner tube 112 by predetermined increments. [0035] On the other hand, heating gas 1 produced in a combustion furnace (not shown) or the like is fed into the outer tube 113. The heating gas 1 heats the inner tube 112, thereby indirectly heating the dried coal 11 in the inner tube 112. As a result, pyrolysis coal 12 is produced, and pyrolysis gas 21 is produced. Note that the heating gas 1 is adjusted such that the temperature of the coal (dried coal 11, pyrolysis coal 12) in the inner tube 112 reaches 400 to 4500C at the coal heating portion exit 112c. The pyrolysis coal 12 is gradually moved inside the inner tube 112 to the separation tank 116 and is discharged from the separation tank 116 to the hopper 117. The pyrolysis gas 21 is discharged through the discharge pipe 101 to the outside of the system. Since the gas inlet port 101a of the discharge pipe 101 is located within the section D1, i.e. a position where the temperature of the coal (dried coal 11, pyrolysis coal 12) is high, the pyrolysis gas 21 having a high concentration of mercury is discharged to the outside of the system without flowing to the vicinity of the coal heating portion exit 112c. Thus, the pyrolysis gas 21 can be prevented from contacting the cooled coal (dried coal 11, pyrolysis coal 12) . Also, in the coal heating portion exit 112c side (separation tank 116 side) of the inner tube 112, the direction of flow of the pyrolysis gas 21 is the opposite to the direction of movement of the coal, and the pyrolysis gas 21 having a low concentration of mercury flows there. Thus, adsorption of mercury to the coal can be prevented. Accordingly, the pyrolysis coal 12 discharged to the hopper 117 is low in mercury content. [0036] Subsequently, the above-described operations are repeated. As a result, the pyrolysis coal 12 with a low mercury content can be manufactured continuously. [0037] Thus, according to the coal pyrolysis device according to this embodiment, it includes the discharge pipe 101 with its gas inlet port 101a located in the inner tube 112, and therefore the pyrolysis gas 21 can be discharged without contacting the cooled pyrolysis coal 12. Hence, it is possible to prevent adsorption of the mercury in the pyrolysis gas 21 due to contact with the cooled pyrolysis coal 12, and thereby manufacture pyrolysis coal 12 with a low mercury content. EMBODIMENT 2 [0038] A coal pyrolysis device according to a second embodiment of the present invention will be described with reference to Fig. 2. This embodiment involves a configuration obtained by adding a carrier gas feed device to the coal pyrolysis device according to the first embodiment described above. In this embodiment, the same components as those in the coal pyrolysis device according to the first embodiment described above are denoted by the same reference numerals. [0039] As shown in Fig. 2, the coal pyrolysis device according to this embodiment further includes a carrier gas feed device 121 serving as carrier gas feeding means. The carrier gas feed device 121 includes: a carrier gas feed device main unit 122 configured to feed carrier gas 31 which is an inert gas (such for example as nitrogen or combustion exhaust gas subjected to exhaust gas treatment such as mercury removal) ; and a carrier gas delivery pipe 123 communicating with a gas delivery port of the carrier gas feed device main unit 122 and also communicating with the hopper 117. [0040] The carrier gas 31 is adjusted to the temperature of the pyrolysis coal to be discharged (e.g. 400 0 C to 450*C) . This is because if lower than 400"C, the carrier gas 31 will cool the inner tube 112 and deteriorate the energy efficiency. On the other hand, if higher than 450 0 C, the carrier gas 31 will supply thermal energy to the pyrolysis coal 12 and accelerate the pyrolysis of the dried coal 11. This in turn reduces the weight of the pyrolysis coal and concentrates the mercury, thereby reducing its volatile portion. As a result, pyrolysis coal with poor ignitability is obtained. For this reason, the carrier gas 31 within the above-mentioned predetermined temperature range is fed. In this way, it is possible to prevent the pyrolysis coal 12 from being cooled in the vicinity of the coal heating portion exit 112c inside the inner tube 112, lower the concentration of mercury in the gas, and reduce the adsorption of the mercury to the pyrolysis coal 12. [0041] The amount of the carrier gas 31 to be fed by the carrier gas feed device 121 is adjusted according to the amount of the gas to be sucked by the above-mentioned suction blower coupled to the discharge pipe 101. This is because if the amount of the carrier gas 31 to be fed is smaller than the difference between the amount of the gas to be sucked by the suction blower and the amount of the pyrolysis gas to be produced, the carrier gas 31 cannot bring about an effect of preventing contact between the cooled pyrolysis coal 12 and the pyrolysis gas 21. On the other hand, if the amount of the carrier gas 31 to be fed is larger than the difference between the amount of the gas to be sucked by the suction blower and the amount of the pyrolysis gas to be produced, the amount of the carrier gas 31 inside the inner tube 112 will be so large that the production of the pyrolysis coal 12 may possibly be impaired. [0042] In this embodiment described above, the discharge pipe 101, the carrier gas feed device 121, and the like serve as the low-mercury-content pyrolysis coal producing means. [0043] The operation of the coal pyrolysis device configured as above will be described below. Note that in this embodiment, like the coal pyrolysis device according to the first embodiment described above, the feeder 115 feeds dried coal 11 into the inner tube 112 by predetermined increments, and the heating gas 1 fed into the outer tube 113 indirectly heats the dried coal 11 in the inner tube 112 to produce pyrolysis coal 12. [0044] As the pyrolysis coal 12 is produced as described above, pyrolysis gas 21 is produced. In this step, the carrier gas feed device 121 is controlled to feed the carrier gas 31 into the hopper 117, while the suction blower is controlled according to the amount of the pyrolysis gas 21 produced and the amount of the carrier gas 31 fed to discharge the gases inside the inner tube 112 such as the pyrolysis gas 21 and the carrier gas 31 to the outside of the system through the discharge pipe 101. Here, the carrier gas 31 contacts the pyrolysis coal 12 and flows into the discharge pipe 101. Hence, the pyrolysis gas 21 can -be prevented from contacting the pyrolysis coal 12 in the vicinity of the coal heating portion exit 112c of the inner tube 112. The pyrolysis gas 21 can be prevented from flowing into the separation tank 116. Thus, it is possible to prevent adsorption of the mercury in the pyrolysis gas 21 to the pyrolysis coal 12. Accordingly, the pyrolysis coal 12 discharged to the hopper 117 is low in mercury content. [0045] Subsequently, the above-described operations are repeated. As a result, the pyrolysis coal 12 with a low mercury content can be manufactured continuously. [0046] Thus, according to the coal pyrolysis device according to this embodiment, it includes the carrier gas feed device 121 configured to feed the carrier gas 31 into the hopper 117, and the pyrolysis gas 21 can be prevented from flowing into the separation tank 116 by feeding the carrier gas 31 into the hopper 117. As a result, it is possible to prevent adsorption of the mercury in the pyrolysis gas 21 due to contact with the cooled pyrolysis coal 12, and thereby more reliably manufacture pyrolysis coal 12 with a low mercury content. EMBODIMENT 3 [0047] A pyrolysis coal manufacturing facility according to a third embodiment of the present invention will be described with reference to Fig. 3. This embodiment is an example of a pyrolysis coal manufacturing facility employing the coal pyrolysis device according to the second embodiment described above. In this embodiment, the same components as those in the coal pyrolysis device according to the second embodiment described above are denoted by the same reference numerals. [0048] As shown in Fig. 3, the pyrolysis coal manufacturing facility according to this embodiment includes the above-described pyrolysis device main unit (inner tube 112, outer tube 113), the above-described discharge pipe 101, and the above-described carrier gas feed device 121, and further includes an indirect-heating drying device 311, a combustion furnace 321, a cooling device 331, a granulation device 341, a heating gas delivery device, and the like. Note that pyrolysis coal 12 produced in the pyrolysis device main unit 111 is delivered to the cooling device 331. The cooling device 331 cools the pyrolysis coal 12 to a predetermined temperature or below to obtain cooled coal 13, and delivers the cooled coal 13 to the granulation device 341. The granulation device 341 granulates the cooled coal 13 to a predetermined size to obtain a product 14 and discharges the product 14. [0049] The indirect-heating drying device 311 includes an inner tube 312 to which raw coal 10 is fed and an outer tube 313 provided in such a way as to cover the inner tube 312. As heating gas 61 obtained in a later-described heat exchanger 323 is fed into the outer tube 313, the heating gas 61 indirectly heats the raw coal 10 in the inner tube 312. As a result, dried coal 11 is produced, and gas 51 is produced by the drying. A gas discharge port of the inner tube 312 communicates with a gas receive port of the later-described combustion furnace 321 through a blower 314, and the gas 51 produced by the drying is delivered to the combustion furnace 321 by the blower 314. A coal discharge port of the inner tube 312 communicates with a coal feed port of the inner tube 112 of the above-described pyrolysis device main unit, and the dried coal 11 is delivered into the inner tube 112 of the pyrolysis device main unit. Note that heating gas 62 used for heating the inner tube 312 is discharged to the outside of the system. [0050] The combustion furnace 321 includes a burner 322 and the heat exchanger 323. A gas receive port of the burner 322 communicates with a gas discharge port of the discharge pipe 101 of the pyrolysis device main unit, and the pyrolysis gas 21 and the carrier gas 31 are delivered to the burner 322. A gas discharge port of the heat exchanger 323 communicates with a gas receive port of the outer tube 313 of the drying device 311, and the heating gas 61 produced in the heat exchanger 323 is delivered to the outer tube 313 of the drying device 311. A gas discharge port of the combustion furnace 321 communicates with the gas receive port of the outer tube 113 of the pyrolysis device main unit, and combustion exhaust gas produced in the combustion furnace 321 is delivered as the heating gas 1 to the outer tube 113 of the pyrolysis device main unit. [0051] The gas discharge port of the outer tube 113 of the pyrolysis device main unit communicates with a gas receive port of a vapor generator 351 serving as cooling means through a gas delivery pipe 361, and the heating gas 2 used for heating the inner tube 112 is delivered to the vapor generator 351. The heating gas 2 is cooled by the vapor generator 351 to a predetermined temperature or below to become primary cooled gas 3. A gas discharge port of the vapor generator 351 communicates with a gas suction port of a blower 352 through a communication pipe 362. A gas discharge port of the blower 352 communicates with a gas receive port of an exhaust gas purification device 353 through a delivery pipe 363. In other words, the primary cooled gas 3 is delivered through the blower 352 to the exhaust gas purification device 353 serving as purifying means. The exhaust gas purification device 353 purifies the primary cooled gas 3 by removing NOx, Sox, mercury, particulate matters (PMs) therefrom to thereby produce purified gas 4. [0052] A gas discharge port of the exhaust gas purification device 353 communicates with a funnel (not shown) through a purified gas discharge pipe 364. A flow rate adjustment valve (three-way valve) 354 is provided at a given point along the purified gas discharge pipe 364, and the flow rate adjustment valve 354 communicates with a purified gas delivery pipe 365. The purified gas delivery pipe 365 communicates with the carrier gas delivery pipe 123. In other words, part of the purified gas 4 is discharged to the outside of the system through the funnel. The rest of the purified gas 4 is delivered to the carrier gas delivery pipe 123 through the flow rate adjustment valve 354 and the purified gas delivery pipe 365. Thus, the carrier gas 31 and the purified gas 4 are fed into the inner tube 112 of the pyrolysis device main unit as carrier gas. [0053] In this embodiment described above, the gas delivery pipe 361, the vapor generator 351, the communication pipe 362, the blower 352, the delivery pipe 363, the exhaust gas purification device 353, the purified gas discharge pipe 364, the flow rate adjustment valve 354, the purified gas delivery pipe 365, the carrier gas delivery pipe 123, and the like serve as a heating gas delivery device which is heating gas delivering means. [0054] Thus, according to the pyrolysis coal manufacturing facility according to this embodiment, the purified gas 4 obtained by the heat exchange with and the purifying treatment of the heating gas 2 is fed into the inner tube 112 of the pyrolysis device main unit together with the carrier gas 31. Accordingly, the energy can be saved as compared to a case where only new carrier gas is fed. EMBODIMENT 4 [0055] A coal pyrolysis device according to a fourth embodiment of the present invention will be described with reference to Fig. 4. This embodiment involves a configuration obtained by adding a preheating drying device at a stage before the coal pyrolysis device according to the first embodiment described above in place of the discharge pipe provided thereto. In this embodiment, the same components as those in the coal pyrolysis device according to the first embodiment described above are denoted by the same reference numerals. [0056] As shown in Fig. 4, the coal pyrolysis device according to this embodiment includes the pyrolysis device main unit 111 and further includes a preheating drying device 131 serving as preheating drying means provided at a stage before the pyrolysis device main unit 111. [0057] The preheating drying device 131 is a rotary kiln and includes an inner tube 132, an outer tube 133 provided in such a way as to cover the inner tube 132, and a support 134 on which the inner tube 132 is rotatably supported. The outer tube 133 has a gas receive port (not shown) through which to receive preheating gas 6 and a gas discharge port (not shown) through which to discharge preheating gas 7 having heated the inner tube 132. The section of the inner tube 132 surrounded by the outer tube 133 is a coal heating portion. The preheating drying device 131 includes a feeder 135 configured to feed dried coal 11 into the inner tube 132, a separation tank 136 provided at an opening end portion of the inner tube 132, and a hopper 137 provided to the separation tank 136. A gas discharge port 138 is provided at an upper portion of the separation tank 136. A gas discharge pipe 139 communicates with the gas discharge port 138. [0058] The pyrolysis device main unit 111 includes the above-mentioned inner tube 112, the above-mentioned outer tube 113, the above-mentioned support 114, the above-mentioned feeder 115, the above-mentioned separation tank 116, and the above-mentioned hopper 117. The separation tank 116 communicates with a gas discharge pipe 119 through a gas discharge port 118 provided at an upper portion of the separation tank 116. The feeder 115 of the pyrolysis device main unit 111 communicates with a coal discharge port of the hopper 137 of the preheating drying device 131, and preheated dried coal 15 is fed to the feeder 115 of the pyrolysis device main unit 111. [0059] In this embodiment described above, the preheating drying device 131 and the like serve as the low-mercury-content pyrolysis coal producing means. [0060] The operation of the coal pyrolysis device configured as above will be described below. [0061] First, raw coal, e.g. a low-rank coal (not shown) such as brown coal or bituminous coal is subjected to drying treatment with a drying device (not shown) to be dried coal 11, and the dried coal 11 is fed to the feeder 135 of the preheating drying device 131. The feeder 135 feeds the dried coal 11 into the inner tube 132 of the preheating drying device 131 by predetermined increments. [0062] On the other hand, preheating gas 6 produced in a combustion furnace (not shown) or the like is fed into the outer tube 133 of the preheating drying device 131. The preheating gas 6 heats the inner tube 132, thereby indirectly heating the dried coal 11 in the inner tube 132. The preheating gas 6 is adjusted such that the dried coal 11 at a coal heating portion exit 132c will be at 280 to 350 C. As a result, preheated dried coal 15 is produced and gas 22 is produced by the preheating. Here, when the dried coal 11 is heated to 350 0 C, about 80% of the mercury in the coal is emitted. Thus, the gas 22 produced by the preheating is a gas with a high concentration of mercury. This gas 22 produced by the preheating is discharged to the outside of the system through the separation tank 136, the gas discharge port 138, and the gas discharge pipe 139. The preheated dried coal 15 is gradually moved inside the inner tube 132 to the separation tank 136 and is discharged to the hopper 137. [0063] Subsequently, the preheated dried coal 15 in the hopper 137 is delivered to the feeder 115 of the pyrolysis device main unit 111. [0064] The feeder115 of the pyrolysis device main unit 111 feeds the preheated dried coal 15 into the inner tube 112 of the pyrolysis device main unit 111 by predetermined increments. On the other hand, heating gas 1 produced in a combustion furnace (not shown) or the like is fed into the outer tube 113 of the pyrolysis device main unit 111. The heating gas 1 heats the inner tube 112, thereby indirectly heating the preheated dried coal 15 in the inner tube 112. The heating gas I is adjusted such that the preheated dried coal 15 at the coal heating portion exit 112c will be at 400 to 450 0 C. As a result, pyrolysis coal 16 is produced, and pyrolysis gas 23 is produced. The pyrolysis coal 16 is gradually moved inside the inner tube 112 to the separation tank 116 and is discharged from the separation tank 116 to the hopper 117. The pyrolysis gas 23 is discharged to the outside of the system through the gas discharge port 118 of the separation tank 116 and the gas discharge pipe 119. [0065] The above-described preheated dried coal 15 is a coal from which the gas 22 produced by the preheating and containing a high concentration of mercury is emitted by the preheating drying device 131. Thus, the pyrolysis gas 23 is a gas with a lower concentration of mercury than the gas 22 produced by the preheating. For this reason, even if the coal in the inner tube 112 of the pyrolysis device main unit ill contacts the pyrolysis gas 23 and adsorbs the mercury in the pyrolysis gas 23 as the coal is moved toward the hopper 117, the pyrolysis coal 16 discharged to the hopper 117 of the pyrolysis device main unit 111 is low in mercury content because the concentration of mercury in the pyrolysis gas 23 is low. [0066] Subsequently, the above-described operations are repeated. As a result, the pyrolysis coal 16 with a low mercury content can be manufactured continuously. [0067] Thus, according to the coal pyrolysis device according to this embodiment, it includes the pyrolysis device main unit 111 and the preheating drying device 131 provided at a stage before the pyrolysis device main unit 111. Also, the preheating drying device 131 heats the dried coal 11 to such a temperature (280 to 350 0 C) that the percentage of mercury emitted therefrom will be about 80%, to thereby let the dried coal 11 emit its mercury and obtain the preheated dried coal 15. The pyrolysis device main unit 111 indirectly heats the preheated dried coal 15 to obtain the pyrolysis coal 16. In this way, the temperature of the preheated dried coal 15 in the preheating drying device 131 decreases to a smaller extent than conventional cases where pyrolysis coal is manufactured using one rotary kiln, and therefore the adsorption of mercury to the coal can be reduced. Accordingly, pyrolysis coal 16 with a low mercury content can be obtained.
EMBODIMENT 5 [0068] A coal pyrolysis device according to a fifth embodiment of the present invention will be described with reference to Figs. 5 and 6. This embodiment involves a configuration obtained by adding a classification device in place of the discharge pipe provided to the coal pyrolysis device according to the first embodiment described above. In this embodiment, the same components as those in the coal pyrolysis device according to the first embodiment described above are denoted by the same reference numerals. [0069] As shown in Fig. 5, the coal pyrolysis device according to this embodiment includes the above-described pyrolysis device main unit 111 and further includes a classification device 141 serving as classifying means for classifying later-described pyrolysis coal 12a discharged from the hopper 117. [0070] The classification device 141 includes a classification tank 142 and a perforated plate (classification plate) 143 provided inside the classification tank 142. The classification tank 142 is partitioned into a main classification chamber 142a and a sub classification chamber 142b by the perforated plate 143. The perforated plate 143 is located under a pyrolysis coal receive port of the classification tank 142. The perforated plate 143 is located in such a way as to incline toward a coarse pyrolysis coal discharge port. The perforated plate 143 has multiple through-holes. The diameter of each through-hole is set to a predetermined size, e.g. 0.42 mm to 2.0 mm. [0071] The above-described classification device 141 further includes a fine pyrolysis coal discharge pipe 144, a gas delivery blower 145, and a gas delivery pipe 146. The fine pyrolysis coal discharge pipe 144 communicates with a fine pyrolysis coal discharge port at the bottom of the sub classification chamber 142b of the classification tank 142 and also communicates with the gas delivery pipe 146. The gas delivery pipe 146 communicates with a gas delivery port of the gas delivery blower 145 and also communicates with a gas discharge pipe 119. [0072] In this embodiment described above, the classification device 141 and the like serve as the low-mercury-content pyrolysis coal producing means. The fine pyrolysis coal discharge pipe 144, the gas delivery blower 145, the gas delivery pipe 146, and the like serve as fine pyrolysis coal discharging means. [0 073] The operation of the coal pyrolysis device configured as above will be described below. Note that in this embodiment, like the coal pyrolysis device according to the first embodiment described above, the feeder 115 feeds dried coal 11 into the inner tube 112 by predetermined increments. [0074] The heating gas 1 is fed into the outer tube 113. As a result, dried coal 11 inside the inner tube 112 is indirectly heated, producing pyrolysis coal 12 and producing pyrolysis gas 21. The pyrolysis coal 12 is gradually moved inside the inner tube 112 to the separation tank 116. The pyrolysis gas 21 is gradually moved inside the inner tube 112 to the separation tank 116 while contacting the pyrolysis coal 12. The pyrolysis coal 12 gets after passing the coal heating portion exit 112c of the inner tube 112 until reaching the separation tank 116. Hence, the pyrolysis coal 12 accordingly adsorbs part of the mercury in the pyrolysis gas 21 and becomes mercury-adsorbed pyrolysis coal 12a. The mercury-adsorbed pyrolysis coal 12a is discharged to the hopper 117. Since the mercury in the pyrolysis gas 21 adsorbs to the pyrolysis coal 12, this gas 21 becomes low-mercury-content pyrolysis gas 21a. The low-mercury-content pyrolysis gas 21a flows into the gas discharge pipe 119 through the gas discharge port 118. [0075] Here, the amount of mercury adsorption to the pyrolysis coal will be described with reference to Fig. 6 showing the relation between the particle size of the coal (pyrolysis coal) and the mercury content (mg/kg). As shown in Fig. 6, it is confirmed that the mercury content is 0.028 mg/kg when the particle size of the coal is 0.42 mm or smaller, the mercury content is 0.024 mg/kg when the particle size of the coal is 0.42 mm to 2.0 mm, and the mercury content is 0.008 mg/kg when the particle size of the coal is 2. O mm to 3. O mm. In other words, it is confirmed that the mercury in the pyrolysis gas adsorbs preferentially to fine coal with a small particle size and a large specific surface area. [0076] Subsequently, the mercury-adsorbed pyrolysis coal 12a (fine pyrolysis coal 12aa, coarse pyrolysis coal 12ab) in the hopper 117 is transferred into the classification tank 142 of the classification device 141 and fed onto the perforated plate 143. The gas delivery blower 145 delivers inert gas 32 to the gas delivery pipe 146 at a gas flow rate that allows classification of the mercury-adsorbed pyrolysis coal 12a. As a result, negative pressure is generated in the sub classification chamber 142b of the classification tank 142, so that the pyrolysis coal 12a is classified through the perforated plate 143. Specifically, the fine pyrolysis coal 12aa smaller than the through-holes of the perforated plate 143 drops into the sub classification chamber 142b while the coarse pyrolysis coal 12ab larger than the through-holes of the perforated plate 143 remains in the main classification chamber 142a. Thus, by setting the diameter of each through-hole of the perforated plate 143 to 0.42 mm, coal with a particle size of 0.42 mm or smaller and a large amount of adsorbed mercury can be dropped as the fine pyrolysis coal 12aa into the sub classification chamber 142b. The diameter of each through-hole of the perforated plate 143 is preferably set to 2.0 mm. In this way, coal with a particle size of 2. 0 mm or smaller and a large amount of adsorbed mercury can be dropped as the fine pyrolysis coal 12aa into the sub classification chamber 142b. Note that the inert gas 32 is a gas with no reactivity with the fine pyrolysis coal 12aa, and nitrogen and the like are available, for example. [0077] The fine pyrolysis coal l2aa in the sub classification chamber 142b is delivered to the gas discharge pipe 119 together with the inert gas 32 through the fine pyrolysis coal discharge pipe 144 and the gas delivery pipe 146. The fine pyrolysis coal 12aa is then discharged to the outside of the system together with the inert gas 32 and the low-mercury-content pyrolysis gas 21a. [0078] On the other hand, the coarse pyrolysis coal 12ab in the main classification chamber 142a is discharged to the outside of the system through a coarse pyrolysis coal discharge port at the bottom of the main classification chamber 142a. [0079] Thus, according to the coal pyrolysis device according to this embodiment, it includes the pyrolysis device main unit 111 and the classification device 141. Hence, by transferring the pyrolysis coal 12a obtained in the pyrolysis device main unit 111 into the classification device 141, the fine pyrolysis coal 12aa with a large amount of adsorbed mercury can be classifiedand removed from the mercury-adsorbed pyrolysis coal 12a in the classification device 141. Accordingly, the coarse pyrolysis coal l2ab with a small amount of adsorbed mercury can be obtained as pyrolysis coal with a low mercury content. EMBODIMENT 6 [0080] A coal pyrolysis device according to a sixth embodiment of the present invention will be described with reference to Fig. 7. This embodiment involves a configuration obtained by changing the arrangement of the classification device provided to the coal pyrolysis device according to the fifth embodiment described above. In this embodiment, the same components as those in the coal pyrolysis device according to the fifth embodiment described above are denoted by the same reference numerals. [0081] As shown in Fig. 7, the coal pyrolysis device according to this embodiment includes the above-described pyrolysis device main unit 111 and further includes a classification device 151 serving as classifying means located between the inner tube 112 and the hopper 117. [0082] The classification device 151 includes a classification tank 152 and a perforated plate 153 provided inside the classification tank 152. The classification tank 152 is partitioned into a main classification chamber 152a and a sub classification chamber 152b by the perforated plate 153. The perforated plate 153 is located under a pyrolysis coal receive port of the classification tank 152 (the opening end portion of the inner tube 112) . The perforated plate 153 is located in such a way as to incline from the pyrolysis coal receive port toward a coarse pyrolysis coal discharge port through which to discharge later-described coarse pyrolysis coal 12ad in the classification tank 152. The perforated plate 153 has multiple through-holes. The diameter of each through-hole is set to a predetermined size, e.g. 2.0 mm. [0083] The above-described classification device 151 further includes a gas delivery pipe 154, a gas delivery blower 155, and a gas discharge pipe 157 communicating with a gas discharge port 156 of the classification tank 152. The gas delivery pipe 154 communicates with an inert gas receive port at the bottom of the sub classification chamber 152b of the classification tank 152 and also communicates with a gas delivery port of the gas delivery blower 155. [0084] In this embodiment described above, the classification device 151 and the like serve as the low-mercury-content pyrolysis coal producing means. The gas delivery blower 155, the gas delivery pipe 154, the perforated plate 153, the gas discharge port 156, the gas discharge pipe 157, and the like serve as the fine pyrolysis coal discharging means. [0085] The operation of the coal pyrolysis device configured as above will be described below. Note that in this embodiment, like the coal pyrolysis device according to the fifth embodiment described above, the feeder 115 feeds dried coal 11 into the inner tube 112 by predetermined increments. {0086] The heating gas 1 is fed into the outer tube 113. As a result, dried coal 11 inside the inner tube 112 is indirectly heated, producing pyrolysis coal 12 and producing pyrolysis gas 21. The pyrolysis coal 12 is gradually moved inside the inner tube 112 to the classification tank 152. The pyrolysis gas 21 is gradually moved inside the inner tube 112 to the classification tank 152 while contacting the pyrolysis coal 12. The pyrolysis coal 12 is cooled after passing the coal heating portion exit 112c of the inner tube 112 until reaching the classification tank 152. Hence, the pyrolysis coal 12 accordingly adsorbs part of the mercury in the pyrolysis gas 21 and becomes mercury-adsorbed pyrolysis coal 12a. The mercury-adsorbed pyrolysis coal 12a is transferred onto the perforated plate 153 in the classification tank 152. Since the mercury in the pyrolysis gas 21 adsorbs to the pyrolysis coal 12, this gas 21 becomes low-mercury-content pyrolysis gas 21a. The low-mercury-content pyrolysis gas 21a flows into the gas discharge pipe 157 through the gas discharge port 156. [0087] Here, as described in Embodiment 5 above, the amount of mercury adsorption to the pyrolysis coal is dependent on the particle size of the pyrolysis coal, and the mercury in the pyrolysis gas mostly adsorbs to fine pyrolysis coal 12ac with a particle size of 2.0 mm or smaller. Note that the amount of mercury adsorption to the coarse pyrolysis coal 12ad with a particle size larger than 2.0 mm is smaller than that of the fine pyrolysis coal 12ac. [0088] Subsequently, the gas delivery blower 155 delivers inert gas 33 at approximately 400 0 C into the classification tank 152 through the gas delivery pipe 154 at a gas flow rate that allows classification of the mercury-adsorbed pyrolysis coal 12a. As a result, only the fine pyrolysis coal 12ac in the mercury-adsorbed pyrolysis coal 12a floats. For example, the gas flow rate of the inert gas 33 delivered by the gas delivery blower 155 is adjusted to 7 m/s. In this case, coal with a particle size of 2. 0 mm or smaller and a large amount of adsorbed mercury floats as the fine pyrolysis coal 12ac. The fine pyrolysis coal 12ac is then discharged to the outside of the system together with the pyrolysis gas 21a and the inert gas 33 from the gas discharge port 156 through the gas discharge pipe 157. [0089] On the other hand, the coarse pyrolysis coal 12ad on the perforated plate 153 is transferred to the hopper 117 and discharged to the outside of the system. [0090] Thus, according to the coal pyrolysis device according to this embodiment, the classification device 151 is provided between the inner tube 112 and the hopper 117. Hence, by transferring the pyrolysis coal 12a obtained in the pyrolysis device main unit 111 into the classification device 151, the fine pyrolysis coal l2ac with a large amount of adsorbed mercury can be classified and removed from the mercury-adsorbed pyrolysis coal 12a in the classification device 151. Accordingly, the coarse pyrolysis coal 12ad with a small amount of adsorbed mercury can be obtained as pyrolysis coal with a low mercury content. EMBODIMENT 7 [0091] A coal pyrolysis device according to a seventh embodiment of the present invention will be described with reference to Fig. 8. This embodiment involves a configuration obtained by adding a pyrolysis coal discharge acceleration device in place of the discharge pipe provided to the coal pyrolysis device according to the first embodiment described above. In this embodiment, the same components as those in the coal pyrolysis device according to the first embodiment described above are denoted by the same reference numerals. [0092] As shown in Fig. 8, the coal pyrolysis device according to this embodiment includes the above-described pyrolysis device main unit 111 and further includes a pyrolysis coal transport acceleration device 181. Note that the hopper 117 serves as pyrolysis coal discharging means. [0093] The pyrolysis coal transport acceleration device 181 is a device configured to quickly transport the pyrolysis coal 12 in the inner tube 112 to the hopper 117 and is a screw feeder or the like, for example. A tip portion 181a of the device 181 is positioned at the coal heating portion exit 112c of the inner tube 112. Thus, the pyrolysis coal transport acceleration device 181 can shorten the period of time the pyrolysis coal 12 stays in the section that is not heated by the heating gas 1. This can reduce the cooling of the pyrolysis coal 12 and also shorten the period of time the pyrolysis coal 12 and the pyrolysis gas 21 contact each other As a result, it is possible to reduce the adsorption of the mercury in the pyrolysis gas 21 to the pyrolysis coal 12 to be discharged from the separation tank 116 to the hopper 117. [0094] In this embodiment described above, the pyrolysis coal transport acceleration device 181 and the like serve as the low-mercury-content pyrolysis coal producing means. [0095] Thus, according to the coal pyrolysis device according to this embodiment, it includes the pyrolysis device main unit 111 and the pyrolysis coal transport acceleration device 181, and the pyrolysis coal 12 can be quickly transported from the coal heating portion exit 112c of the inner tube 112 to the separation tank 116 and discharged to the hopper 117. In this way, the adsorption of mercury to the pyrolysis coal due to the cooling of the pyrolysis coal can be reduced. Accordingly, pyrolysis coal 12 with a low mercury content can be obtained. EMBODIMENT 8 [0096] A coal pyrolysis device according to an eighth embodiment of the present invention will be described with reference to Figs. 9A and 9B. This embodiment involves a configuration obtained by adding a pyrolysis gas contact prevention plate body in place of the discharge pipe provided to the coal pyrolysis device according to the first embodiment described above. In this embodiment, the same components as those in the coal pyrolysis device according to the first embodiment described above are denoted by the same reference numerals. [0097] As shown in Figs. 9A and 9B, the coal pyrolysis device according to this embodiment includes the above-described pyrolysis device main unit 111 and further includes a pyrolysis gas contact prevention plate body 191. [0098] The pyrolysis gas contact prevention plate body 191 has its base end portion fixed to a sidewall portion of the separation tank 116 and extends in the extending direction of the inner tube 112. A tip portion 191a of the plate body 191 has a shape extending in suchawayas to incline obliquelyupward. The plate body 191 is located in such a way as to contact an upper surface portion 12c of a pyrolysis coal layer formed by laying layers of pyrolysis coal 12 produced in the inner tube 112. Thus, the pyrolysis coal 12 passes through the portion where the coal is heated by the heating gas 1, and gets cooled until discharged to the separation tank 116 and the hopper 117, but its contact with the pyrolysis gas 21 is prevented by the plate body 191. The pyrolysis coal 12 is discharged from the separation tank 116 to the hopper 117.
[0099] In this embodiment described above, the pyrolysis gas contact prevention plate body 191 and the like serve as the low-mercury-content pyrolysis coal producing means. [0100] Thus, according to the coal pyrolysis device according to this embodiment, it includes the pyrolysis device main unit 111 and the pyrolysis gas contact prevention plate body 191, and the plate body 191 prevents the contact between the pyrolysis gas 21 and the pyrolysis coal 12 that is being cooled. In this way, adsorption of the mercury in the pyrolysis gas 21 due to contact with the cooled pyrolysis coal 12 can be prevented. Accordingly, pyrolysis coal 12 with a low mercury content can be obtained. EMBODIMENT 9 [0101] A coal pyrolysis device according to a ninth embodiment of the present invention will be described with reference to Figs. 10A and 10B. This embodiment involves a configuration obtained by adding an inert gas feed device to the coal pyrolysis device according to the eighth embodiment described above. In this embodiment, the same components as those in the coal pyrolysis device according to the eighth embodiment described above are denoted by the same reference numerals. [0102] As shown in Figs. 10A and 10B, the coal pyrolysis device according to this embodiment includes the above-described pyrolysis device main unit 111 and the above-described pyrolysis gas contact prevention plate body 191 and further includes an inert gas feed device 201. [0103] The inert gas feed device 201 is provided in communication with a gas delivery port of the hopper 117. The inert gas feed device 201 is a device configured to feed inert gas 34 at approximately 400 0 C into the hopper 117. The inert gas 34 is a gas with no reactivity with the pyrolysis coal 12, and nitrogen and the like are available, for example. As the inert gas 34 is fed into the hopper 117, the inert gas 34 flows between the plate body 191 and the inner tube 112 toward the feeder 115. In this way, the pyrolysis gas 21 can be prevented from entering the space between the inner tube 112 and the plate body 191. The pyrolysis coal 12 is discharged from the separation tank 116 to the hopper 117. Note that the inert gas 34 is discharged to the outside of the system together with the pyrolysis gas 21 through the gas discharge port 118 and the gas discharge pipe 119. [0104] In this embodiment described above, the pyrolysis gas contact prevention plate body 191, the inert gas feed device 201, and the like serve as the low-mercury-content pyrolysis coal producing means. [0105] Thus, according to the coal pyrolysis device according to this embodiment, it includes the pyrolysis device main unit 111, the pyrolysis gas contact prevention plate body 191, and the inert gas feed device 201, and the inert gas 34 is fed to the hopper 117 and the inert gas 34 flows between the plate body 191 and the inner tube 112. Tn this way, a similar advantageous effect to that by the coal pyrolysis device according to the eighth embodiment described above can be achieved. In addition, while the pyrolysis gas 21 is prevented from flowing into the space between the plate body 191 and the inner tube 112, the pyrolysis gas 21, if present between the plate body 191 and the inner tube 112, can be discharged toward the feeder 115 by the inert gas 34. Accordingly, pyrolysis coal 12 with a low mercury content can be obtained more reliably. EMBODIMENT 10 [0106] A coal pyrolysis device according to a tenth embodiment of the present invention will be described with reference to Fig. 11. This embodiment involves a configuration obtained by adding a heating device in place of the discharge pipe provided to the coal pyrolysis device according to the first embodiment described above. In this embodiment, the same components as those in the coal pyrolysis device according to the first embodiment described above are denoted by the same reference numerals. [0107] As shown in Fig. 11, the coal pyrolysis device according to this embodiment includes the above-described pyrolysis device main unit 111 and further includes a heating device 211. [0108] The heating device 211 is a device capable of directly heating the pyrolysis coal 12 and the inner tube 112 in the vicinity of the coal heating portion exit 112c and includes a burner 212. The temperature of the burner 212 is 1200 to 1300 C, and the pyrolysis coal 12 is heated to and maintained at about 400 to 4500C. The pyrolysis coal 12 is discharged from the separation tank 116 to the hopper 117. [0109] In this embodiment described above, the heating device 211 and the like serve as the low-mercury-content pyrolysis coal producing means. [0110] Thus, according to the coal pyrolysis device according to this embodiment, it includes the pyrolysis device main unit 111 and the heating device 211, and the burner 212 provided to the heating device 211 heats the pyrolysis coal 12 and the inner tube 112 in the vicinity of the separation tank 116. In this way, the pyrolysis coal 12 does not get cooled before it is discharged to the separation tank 116, and adsorption of the mercury in the pyrolysis gas due to contact with cooled pyrolysis coal can be prevented. Accordingly, pyrolysis coal 12 with a low mercury content can be obtained. EMBODIMENT 11 [0111] A coal pyrolysis device according to an eleventh embodiment of the present invention will be described with reference to Figs. 12A and 12B. This embodiment involves a configuration obtained by changing the arrangement of the heating device provided to the coal pyrolysis device according to the tenth embodiment described above. In this embodiment, the same components as those in the coal pyrolysis device according to the tenth embodiment described above are denoted by the same reference numerals. [0112] As shown in Figs. 12A and 12B, the coal pyrolysis device according to this embodiment includes the above-described pyrolysis device main unit Ill and further includes a heating device 221. [0113] The heating device 221 is a device capable of directly heating the pyrolysis coal 12 in the vicinity of the coal heating portion exit 112c of the inner tube 112 and is formed of a rotary indirect heat exchange tube 222, for example. There are multiple heat exchange tubes 222 located inside the inner tube 112 and provided in such a way as to be rotatable about the axis of the inner tube 112 in the circumferential direction thereof. A tip portion 222a of each of the heat exchange tubes 222 is located at the separation tank 116 side of the coal heating portion exit 112c. The heat exchange tubes 222 are fed with heating gas 8 such for example as combustion exhaust gas or exhaust gas as gas having heated a pyrolysis furnace, adjusted to a predetermined temperature. Thus, by feeding the heating gas 8 into the heat exchange tubes 222 and rotating the heat exchange tubes 222, the pyrolysis coal 12 in the inner tube 112 in the vicinity of the separation tank 116 contacts the heat exchange tubes 222 which are being heated by the heating gas 8, so that the pyrolysis coal 12 contacting the heat exchange tubes 222 are directly heated. Accordingly, the pyrolysis coal 12 is maintained at about 400 to 450 0 C. The pyrolysis coal 12 is discharged from the separation tank 116 to the hopper 117. Note that heating gas 9 after heating the heat exchange tubes 222 is discharged to the outside of the system. [0114] In this embodiment described above, the heating device 221 and the like serve as the low-mercury-content pyrolysis coal producing means. [0115] Thus, according to the coal pyrolysis device according to this embodiment, it includes the pyrolysis device main unit 111 and the heating device 221, and the heat exchange tubes 222 provided to the heating device 221 heat the pyrolysis coal 12 in the vicinity of the separation tank 116. In this way, like the coal pyrolysis device according to the tenth embodiment described above, the pyrolysis coal 12 does not get cooled before it is discharged to the separation tank 116, and adsorption of the mercury in the pyrolysis gas due to contact with cooled pyrolysis coal can be prevented. Accordingly, pyrolysis coal 12 with a low mercury content can be obtained. EMBODIMENT 12 [0116] A coal pyrolysis device according to a twelfth embodiment of the present invention will be described with reference to Fig. 13. This embodiment involves a configuration obtained by adding an oxidant feed device in place of the heating device provided to the coal pyrolysis device according to the eleventh embodiment described above. In this embodiment, the same components as those in the coal pyrolysis device according to the eleventh embodiment described above are denoted by the same reference numerals. [0117] As shown in Fig. 13, the coal pyrolysis device according to this embodiment includes the above-described pyrolysis device mainunit 111 and further includes an oxidant feed device 231.
[0118] The oxidant feed device 231 is a device configured to feed oxidant 42 to the pyrolysis coal 12 in the vicinity of the coal heating portion exit 112c of the inner tube 112. The oxidant feed device 231 includes a device main unit 232 serving as an oxidant feed source and an oxidant feed pipe 233. The oxidant feed pipe 233 communicates with an oxidant discharge port of the device main unit 232. The oxidant feed pipe 233 is located along the axis of the inner tube 112. Multiple oxidant injection nozzles 234 are provided in the vicinity of a tip portion of the oxidant feed pipe 233 along the longitudinal direction thereof. The oxidant is an oxygen-containing gas (oxygen concentration: 5% or lower) such for example as combustion exhaust gas or mixed gas (air, nitrogen gas). The oxidant is adjusted to such a temperature, e.g. about 400 to 450 0 C, that it does not cool the pyrolysis coal 12 and is capable of reacting with the pyrolysis coal 12. Thus, when the oxidant feed device 231 feeds the oxidant 42 to the pyrolysis coal 12 in the inner tube 112 in the vicinity of the coal heating portion exit 112c through the oxidant feed pipe 233 and the oxidant injection nozzles 234, part of the pyrolysis coal 12 and its volatile component such as tar produced therefrom combust and generate heat, thereby heating the pyrolysis coal 12 in the vicinity of the coal heating portion exit 112c. Pyrolysis coal 12b thus heated is discharged from the separation tank 116 to the hopper 117. [0119] In this embodiment described above, the oxidant feed device 231 and the like serve as the low-mercury-content pyrolysis coal producing means.
[0120] Thus, according to the coal pyrolysis device according to this embodiment, it includes the pyrolysis device main unit 111 and the oxidant feed device 231, and the oxidant 42 is fed to the pyrolysis coal 12 in the vicinity of the coal heating portion exit 112c. In this way, the pyrolysis coal 12b heated by the combustion and heat generation in the above area does not get cooled before it is discharged to the separation tank 116, and adsorption of the mercury in the pyrolysis gas due to contact with cooled pyrolysis coal can be prevented. Accordingly, pyrolysis coal 12b with a low mercury content can be obtained. [0121] [OTHER EMBODIMENTS] The coal pyrolysis devices including the discharge pipe 101 are described in the above first and second embodiments. Note, however, that coal pyrolysis devices may include a discharge pipe with multiple holes provided in the peripheral surface in the vicinity of a tip portion thereof. INDUSTRIAL APPLICABILITY [0122] The coal pyrolysis devices according to the present invention can manufacture pyrolysis coal with a low mercury content and can therefore be utilized significantly beneficially in various industries. EXPLANATION OF REFERENCE NUMERALS [0123] 1 heating gas 6 preheating gas 11 dried coal 12 pyrolysis coal 15 preheated dried coal 16 pyrolysis coal 21 pyrolysis gas 31 to 34 carrier gas 42 oxidant 101 discharge pipe 111 pyrolysis device main unit 121 carrier gas feed device 131 preheating drying device 141, 151 classification device 181 pyrolysis coal transport acceleration device 191 pyrolysis gas contact prevention plate body 201 inert gas feed device 211, 221 heating device 231 oxidant feed device