AU2011241630A1 - Coal gasification system and coal gasification method - Google Patents

Abstract

Disclosed are a coal gasification system and a coal gasification method, comprising a drying apparatus which turns subbituminous coal or brown coal into moisture-regulated coal by drying until same contain a specified moisture content; and a coal gasification reaction furnace which produces at least hydrogen gas and carbon monoxide gas by burning the moisture-regulated coal. The specified moisture content is set to a quantity such that when the moisture vapour emitted from the moisture-regulated coal and tar are chemically reacted, the tar does not stick inside through holes.

Description

DESCRIPTION COAL GASIFICATION SYSTEM AND COAL GASIFICATION METHOD 5 TECHNICAL FIELD [0001] The present invention relates to a coal gasification system and a coal gasification process for producing products such as methane from coal as a raw material. The present application claims priority on Japanese Patent Application No. 10 2010-095497 filed on April 16, 2010, the content of which is incorporated herein by reference. BACKGROUND ART [0002] 15 In order to gasify coal to produce a combustible gas efficiently, there has been considered a coal gasification system which includes a coal gasification reaction furnace having various constitutions such as a fixed bed, a fluid bed and an air jet bed (entrained bed). As one example thereof, for example, a coal gasification system is known which 20 has been disclosed in Patent Document 1. This coal gasification system includes: a thermal decomposition gasification reaction furnace (upper reaction vessel) for thermally decomposing coal; a heat exchanger for recovering sensible heat from a gas and the like which are generated from the thermal decomposition gasification reaction furnace; a cyclone for separating char (coal residue not yet gasified or thermally decomposed 25 residue) from the gas and the like; and a desulphurization apparatus for removing sulfur 2 content from the gas from which the char has been separated so as to purify the gas. [0003] A lower portion of the thermal decomposition gasification reaction furnace is communicatively connected to a high-temperature gasification furnace (lower reaction 5 vessel). Coal, an oxygen-containing gas such as oxygen, oxygen-enriched air or the like, and steam are supplied to the high-temperature gasification furnace. The high-temperature gasification furnace generates a high-temperature gas which mainly includes hydrogen gas and carbon monoxide gas. The thermal decomposition gasification reaction furnace includes: a coal feeding 10 nozzle for feeding coal into the thermal decomposition gasification reaction furnace; and a steam nozzle for adding steam into the thermal decomposition gasification reaction furnace. Char, a volatile gas, and the like are generated by thermal decomposition reactions of the coal supplied via the coal feeding nozzle into the thermal decomposition gasification reaction furnace. Here, the generated char is decomposed into various gases 15 by the following chemical equations. [0004] C (char)+ H 2 0 -+ CO + H 2 ''' (1) C (char) + CO 2 - 2CO ... (2) [0005] 20 Patent Document I describes that, among the above chemical equations, a reaction rate of the chemical equation (1) is several times greater than that of the chemical equation (2); and therefore, steam is supplied from the steam nozzle to give a steam-enriched atmosphere inside the thermal decomposition gasification reaction furnace, which is extremely effective in decomposing char. 25 On the other hand, in general, coal tar mainly including carbon is generated by 3 thermal decomposition of coal, and the coal tar adheres inside the thermal decomposition gasification reaction furnace. With an increase in the quantity of adhered coal tar, the coal tar will finally clog at a portion of the thermal decomposition gasification reaction furnace, and there is a fear that the thermal decomposition gasification reaction furnace 5 may not be operated normally. However, this coal tar is also gasified by the chemical reactions shown in the above chemical equations (1) and (2). In this instance, adhesion of coal tar includes adhesion of carbonaceous materials derived from the coal tar. PRIOR ART DOCUMENT 10 Patent Document [0006] Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2002-155289 15 DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention [0007] However, with an increase in the quantity of steam supplied into the thermal decomposition gasification reaction furnace, a temperature inside the thermal 20 decomposition gasification reaction furnace is lowered; and thereby, the reaction rates of the above chemical reactions are decreased. Furthermore, in order to supply steam into the thermal decomposition gasification reaction furnace, certain apparatuses such as a steam nozzle, a steam supplying pump, and the like are required. This poses a problem that a coal gasification system is increased in dimension. 25 [0008] 4 The present invention has been made in view of the above problems, an object thereof is to provide a coal gasification system and a coal gasification process which eliminate a need for installing an apparatus for supplying steam into an upper reaction vessel and are capable of adjusting (regulating) a quantity of steam inside the upper 5 reaction vessel. Means for Solving the Problems [0009] In order to attain the above-described object, a coal gasification system according 10 to one aspect of the present invention includes: a dryer which dries coal to obtain moisture-adjusted coal having a predetermined moisture content; and a coal gasification reaction furnace which burns the moisture-adjusted coal to generate hydrogen gas and carbon monoxide gas. The coal gasification reaction furnace includes: a lower reaction vessel; an upper reaction vessel which is installed above the lower reaction vessel and is 15 communicatively connected to the lower reaction vessel; a burner unit which supplies the moisture-adjusted coal and an oxygen-containing gas into the lower reaction vessel to bum the moisture-adjusted coal; and a nozzle unit which supplies the moisture-adjusted coal into the upper reaction vessel. [0010] 20 According to the above-described coal gasification system, coal is dried by the dryer so as to contain a predetermined moisture content; and thereby, moisture-adjusted coal is obtained. This moisture-adjusted coal is supplied together with an oxygen-containing gas into the lower reaction vessel and is burned by the burner unit; and thereby, a high-temperature gas mainly including carbon monoxide gas is generated inside 25 the lower reaction vessel. The high-temperature gas generated inside the lower reaction 5 vessel flows into the upper reaction vessel. Furthermore, apart from the moisture-adjusted coal supplied into the lower reaction vessel, the moisture-adjusted coal is supplied from the nozzle unit into the upper reaction vessel and is heated by the high-temperature gas which flows into the upper reaction vessel. When the 5 moisture-adjusted coal is heated by the high-temperature gas, thermal decomposition takes place to generate coal tar and char which mainly include carbon. The coal tar and the char chemically react with a predetermined quantity of moisture which is intentionally allowed to remain in the moisture-adjusted coal and are gasified (refer to the chemical equation (I)). 10 In general, coal such as sub-bituminous coal and brown coal contains moisture of as much as 30% to 60% (percent by weight). Therefore, in drying procedures, conditions are controlled so that a predetermined content of moisture is intentionally allowed to remain, and the remaining moisture is utilized to generate steam; and thereby, gasification of coal tar is accelerated. Thus, unlike conventional procedures, it is 15 possible to prevent adhesion of coal tar inside a gasification reaction furnace, while supplying no steam into the upper and lower reaction vessels. As a result, it is possible to suppress a decrease in temperature inside the furnace with an increase in the quantity of steam supplied into the gasification reaction furnace, and it is also possible to suppress a delay in a reaction rate of chemical reactions resulting from the decrease in temperature. 20 Furthermore, since the need for installing an apparatus for supplying steam into the gasification reaction furnace is eliminated, the coal gasification system can be downsized. [0011] The above-described coal gasification system may further include: a pressure measurement unit which measures a difference between a furnace pressure at a portion 25 below the nozzle unit and a furnace pressure at an upper portion of the upper reaction 6 vessel; and a control unit which controls the dryer on the basis of the difference in pressure measured by the pressure measurement unit, thereby, the moisture content contained in the coal is adjusted. [0012] 5 Coal tar tends to adhere in a concentrated manner on an inner face of the upper reaction vessel above the nozzle unit. Therefore, according to the coal gasification system of the present invention, a difference between a furnace pressure at a portion below the nozzle unit and a furnace pressure at an upper portion of the upper reaction vessel is measured by using the pressure measurement unit. Then, in the case where a difference 10 in pressure at which coal tar adheres is detected, the dryer is controlled to increase the moisture content of coal. When moisture-adjusted coal of which the moisture content is increased is heated by a high-temperature gas, coal tar and char mainly includingcarbon are generated by thermal decomposition. At the same taime , moisture is evaporated and turned into steam. Coal tar and char chemically react with a part of the generated steam 15 and are gasified. Furthermore, coal tar which adheres on the inner face of the reaction vessel reacts chemically with remaining steam and is gasified. Thereby, it is possible to suppress adhesion of coal tar on the inner face of the upper reaction vessel. [0013] Furthermore, a coal gasification system according to one aspect of the present 20 invention includes: a dryer which dries sub-bituminous coal or brown coal having a moisture of 20% or more by mass ratio so as to contain a predetermined moisture content, thereby obtaining moisture-adjusted coal; and a coal gasification reaction furnace which burns the moisture-adjusted coal to produce at least hydrogen gas and carbon monoxide gas. The coal gasification reaction furnace includes: a lower reaction vessel which has 25 an accommodation space in an interior thereof; and an upper reaction vessel which is 7 installed above the lower reaction vessel. The lower reaction vessel includes a burner unit which supplies the moisture-adjusted coal and an oxygen-containing gas at a predetermined ratio into the lower reaction vessel and which supplies no steam, thereby burning the moisture-adjusted coal. The upper reaction vessel includes: a through hole 5 which is communicatively connected to the accommodation space of the lower reaction vessel via a diameter reducing portion and which extends vertically; and a nozzle unit which supplies only the moisture-adjusted coal into the upper reaction vessel and which supplies no steam. The above-described predetermined moisture content is set to a quantity at which no coal tar will adhere inside the through hole by chemical reactions 10 between steam and coal tar which is generated from the moisture-adjusted coal. [0014] Sub-bituminous coal and brown coal contain moisture of as much as 30% to 60% (percent by weight). According to the present invention, at first, sub-bituminous coal or brown coal is dried by the dryer to obtain moisture-adjusted coal, and the 15 moisture-adjusted coal is treated (regulated) so as to contain moisture in a quantity greater than a remained moisture content of coal in a conventional coal gasification system. More specifically, the moisture content of the moisture-adjusted coal is adjusted so that no coal tar will adhere inside the through hole by chemical reactions taking place between a predetermined moisture content of the moisture-adjusted coal and coal tar generated from 20 the moisture-adjusted coal in the upper reaction vessel. Then, the moisture-adjusted coal and an oxygen-containing gas are supplied at a predetermined ratio from the burner unit into the accommodation space inside the lower reaction vessel, while supplying no steam; and thereby, the moisture-adjusted coal is burned. And only the moisture-adjusted coal is supplied from the nozzle unit to the 25 through hole inside the upper reaction vessel, while supplying no steam.

8 [0015] Both of carbon and moisture to be supplied into the upper reaction vessel are contained in moisture-adjusted coal. The moisture-adjusted coal is thermally decomposed to generate coal tar and char which mainly include carbon. The moisture of 5 the moisture-adjusted coal is heated inside the upper reaction vessel and turned into steam. Coal tar, char and steam immediately after being generated from the moisture-adjusted coal are in a mixed state. In the case where these coal tar, char and steam are supplied individually from different nozzles, the coal tar, the char and the steam are spaced away from each other; and therefore, no reaction may take place. However, according to the 10 above aspect, since the coal tar, the char and the steam are in a mixed state, it is possible to prevent a failure of the occurrence of the reactions. At this time, the moisture content in the moisture-adjusted coal which is supplied into the upper reaction vessel is adjusted by the dryer to a quantity at which no coal tar will adhere inside the through hole by chemical reactions between coal tar and steam 15 generated by thermal decomposition of the moisture-adjusted coal. Therefore, there is no chance that the through hole is clogged by an increasing quantity of coal tar adhered inside the through hole. As described above, steam, coal tar and char which are in a mixed state inside the upper reaction vessel are allowed to react more reliably. Therefore, it is possible to decrease steam or eliminate a need for steam which is supplied into the upper 20 reaction vessel for preventing adhesion of coal tar inside the upper reaction vessel. [0016] In the above-described coal gasification system, the predetermined moisture content may be set to be in a range of 15% or more to 40% or less by mass ratio as a content in the moisture-adjusted coal. 25 In this instance, the moisture content of the moisture-adjusted coal is set to be in a 9 range of 15% or more by mass ratio; and thereby, reactions between coal tar and steam inside the upper reaction vessel is accelerated so that no coal tar will adhere inside the through hole. [0017] 5 In the above-described coal gasification system, the coal gasification reaction furnace may include a pressure measurement unit which measures a difference in pressure between either of an internal pressure at a portion below the nozzle unit in the through hole of the upper reaction vessel or an internal pressure in the accommodation space of the lower reaction vessel and an internal pressure at an upper end portion of the through hole. 10 In this instance, the coal gasification system may include a control unit which controls the dryer on the basis of the difference in pressure measured by the pressure measurement unit, and thereby, the moisture content of the coal is adjusted.. In this instance, even in the case where coal tar generated by thermal decomposition of coal adheres inside the upper reaction vessel, the coal tar will adhere in 15 a concentrated manner at a portion inside the through hole of the upper reaction vessel which is above the nozzle unit in a perpendicular direction. Therefore, one position at which the difference in pressure is measured is given as a portion of the through hole of the upper reaction vessel which is below the nozzle unit in the perpendicular direction or the accommodation space of the lower reaction vessel, and the other position is given as 20 an upper end portion of the through hole. Thereby, a portion at which the difference in pressure is measured can be prevented from being clogged by coal tar, and the difference in pressure can also be reliably measured. Furthermore, in the case where coal tar adheres inside the through hole, a difference in pressure measured by the pressure measurement unit is increased. At this 25 time, the control unit increases the moisture content of the moisture-adjusted coal; and 10 thereby, chemical reactions between coal tar and steam are accelerated. As a result, it is possible to gasify the coal tar adhered inside the through hole of the upper reaction vessel. [0018] In a coal gasification process according to one aspect of the present invention, any 5 one of the coal gasification systems described above is used to carry out the following steps: a drying step of drying the sub-bituminous coal or the brown coal so as to contain a predetermined moisture content, thereby obtaining the moisture-adjusted coal; and a chemical reaction step of supplying the moisture-adjusted coal and an 10 oxygen-containing gas into the lower reaction vessel while supplying no steam from the burner unit, thereby burning the moisture-adjusted coal, and supplying only the moisture-adjusted coal into the upper reaction vessel from the nozzle unit, thereby subjecting the moisture-adjusted coal to chemical reaction.. [0019] 15 In the above-described coal gasification process, in the chemical reaction step, coal tar generated from the moisture-adjusted coal may be allowed to react chemically with steam generated by heating moisture contained in the moisture-adjusted coal, thereby at least carbon monoxide gas and hydrogen gas may be produced. [0020] 20 A coal gasification process according to one aspect of the present invention includes: drying coal to obtain moisture-adjusted coal which contains a predetermined moisture content; supplying the moisture-adjusted coal and an oxygen-containing gas into a lower reaction vessel of a coal gasification reaction furnace; burning the moisture-adjusted coal to generate a high-temperature gas; supplying the 25 moisture-adjusted coal into an upper reaction vessel which is communicatively connected ll to the lower reaction vessel of the coal gasification reaction furnace; and heating the moisture-adjusted coal supplied into the upper reaction vessel by the high-temperature gas which flows from the lower reaction vessel to the upper reaction vessel. [0021] 5 When the moisture-adjusted coal supplied into the upper reaction vessel is heated by the high-temperature gas, coal tar and char mainly including carbon are generated by thermal decomposition. The coal tar and the char react chemically with a predetermined quantity of moisture which is intentionally allowed to remain in the moisture-adjusted coal and are gasified. Thereby, unlike conventional procedures, it is possible to prevent 10 adhesion of coal tar inside the gasification reaction furnace without supplying steam to the upper reaction vessel and the lower reaction vessel. As a result, it is possible to suppress a decrease in temperature inside the furnace with an increase in the quantity of steam supplied to the gasification reaction furnace, and it is also possible to suppress a delay in a reaction rate of chemical reactions resulting from the decrease in temperature. 15 Furthermore, since the need for installing an apparatus for supplying steam into the gasification reaction furnace is eliminated, the coal gasification system can be downsized. Effects of the Invention [0022] 20 According to the coal gasification system and the coal gasification process of the present invention, the need for installing an apparatus for supplying steam into the upper reaction vessel is eliminated and it is possible to adjust (regulate) a quantity of steam inside the upper reaction vessel. 25 BRIEF DESCRIPTION OF THE DRAWINGS 12 [0023] Fig. I is a block diagram which shows a coal gasification system according to a first embodiment of the present invention. Fig. 2 is a partial cutaway view which shows major parts of the coal gasification 5 system. Fig. 3 is a sectional view which shows a dryer of the coal gasification system. Fig. 4 is a graph which shows a change in moisture content of moisture-adjusted coal with respect to an outlet temperature at a grinding unit of the coal gasification system. Fig. 5 is a graph which shows a relationship of an increasing rate of coal tar 10 adhered inside a through hole with the moisture content of the moisture-adjusted coal in the coal gasification system. Fig. 6 is a partial cutaway view which shows major parts of a coal gasification system according to a second embodiment of the present invention. Fig. 7 is a graph which shows a relationship of a difference in pressure measured 15 by a pressure measurement apparatus of the coal gasification system with the moisture content of the moisture-adjusted coal necessary for returning the difference in pressure to a normal value. BEST MODE FOR CARRYING OUT THE INVENTION 20 [0024] (First Embodiment) Hereinafter, an explanation will be made for the coal gasification system according to the first embodiment of the present invention while referring to Fig. I to Fig. 5. As shown in Fig. 1, a coal gasification system I is a plant in which a synthesis gas 25 mainly including hydrogen gas and carbon monoxide gas is synthesized from a raw 13 material of coal and final products such as methane, methanol, ammonia, and the like are produced from the synthesis gas. Examples of coal used in the coal gasification system I of the present embodiment include sub-bituminous coal and brown coal which contain moisture of 20% or more by weight ratio. 5 The coal gasification system I includes a coal drying and grinding equipment (dryer) 2, a coal supplying equipment 3, a coal gasification reaction furnace 4, a heat recovery equipment 5, a char recovery equipment 6, a shift reaction equipment 7, a gas purification equipment 8, a chemical synthesis equipment 9, and an air separation equipment 10. 10 [0025] As shown in Fig. 2, the coal drying and grinding equipment 2 includes a drying unit 13 for heating coal and a grinding unit 14 for grinding the coal into particles having a predetermined particle diameter (outer diameter). In general, coal is not uniform in particle diameter, and sub-bituminous coal and 15 brown coal contain a large quantity of moisture, for example, approximately 30% to 60% by mass ratio. Thus, sub-bituminous coal or brown coal heated by the drying unit 13 is ground into particles, so that the particle diameter thereof becomes, for example, in a range of 10 gm or more to 100 .tm or less by using the grinding unit 14. Thereby, the sub-bituminous coal or the brown coal is treated (regulated) so as to have a predetermined 20 moisture content. As described above, moisture-adjusted coal having a predetermined moisture content is produced from coal having a moisture content of approximately 30% to 60% by mass ratio. Since moisture is evaporated from the coal by grinding the heated coal, the moisture content of the moisture-adjusted coal is determined when the moisture-adjusted coal is fed out from the grinding unit 14. Therefore, both of the drying 25 unit 13 and the grinding unit 14 function as a dryer for drying coal.

14 The moisture content of the moisture-adjusted coal produced in a granular form by the coal drying and grinding equipment 2 is set to be in a range of 15% or more to 40% or less by mass ratio which is lower than the moisture content of the coal before being dried. 5 An infrared moisture meter, for example, can be used to measure the moisture content of the coal before being dried and that of the moisture-adjusted coal after being dried and ground. For example, a heating temperature and a heating time of the drying unit 13 or a particle diameter of coal after being ground by the grinding unit 14 is controlled; and thereby, it is possible to adjust (regulate) the moisture content of the 10 moisture-adjusted coal. [0026] As shown in Fig. 3, the drying unit 13 is constituted with a double cylinder structure including an internal cylinder 15 and an external cylinder 16 which are arranged coaxially. The internal cylinder 15 and the external cylinder 16 are arranged so that each 15 of the leading ends is inclined downward at a certain angle with respect to a horizontal plane. A hopper 17 which supplies coal B into the internal cylinder 15 is connected to the base end (the diagonally upward side in a perpendicular direction) of the internal cylinder 1 5. A feeding mechanism 18 which feeds the coal B to the leading end side (the diagonally downward side in the perpendicular direction) is arranged inside the internal 20 cylinder 15. A flow adjusting valve 19 which supplies steam having a constant temperature at a adjusted flow rate is connected to the leading end portion of the external cylinder 16 between the external cylinder 16 and the internal cylinder 15. The steam supplied between the internal cylinder 15 and the external cylinder 16 flows in a direction opposite 25 to the direction at which the coal B is fed, and the steam is discharged from a discharge 15 pipe 20 connected to the external cylinder 16. A temperature sensor which measures an outlet temperature of the grinding unit 14 is installed at an outlet of the grinding unit 14 shown in Fig. 2. [0027] 5 While the drying unit 13 having the above-described structure measures a temperature by the temperature sensor of the grinding unit 14, the drying unit 13 operates the flow adjusting valve 19 so as to adjust (regulate) a quantity of steam flowing between the internal cylinder 15 and the external cylinder 16. Then, while feeding the coal B to the leading end thereof through the inside of the internal cylinder 15, the drying unit 13 10 heats the coal B by steam; and thereby, the moisture content of the coal B is adjusted. A process of drying coal by the drying unit is not restricted in particular, as long as it is capable of adjusting the moisture content of the coal. It may be, for example, a process of heating coal by steam as described in the present embodiment and a process of heating coal by using a heater and the like. In the case where the drying unit 13 of the 15 present embodiment shown in Fig. 3 is used, it is possible to grind and dry coal at the same time by using a single apparatus; and therefore, it is possible to downsize equipment and reduce the cost. [0028] Fig. 4 shows one example of results in which the coal drying and grinding 20 equipment 2 was used to dry the coal B. In Fig. 4, the coal B was subjected to primary drying and then the coal B was supplied to the drying unit 13 in a state in which the moisture content of the coal B was reduced to 25%. The horizontal axis in Fig. 4 shows an outlet temperature of the grinding unit 14 measured by the temperature sensor, while the longitudinal axis shows the moisture content of the moisture-adjusted coal after the 25 grinding unit 14. According to the test result, when the outlet temperature of the 16 grinding unit 14 is 75*C, the moisture content of the moisture-adjusted coal is 5%. In addition, when the outlet temperature of the grinding unit 14 is 50*C, the moisture content of the moisture-adjusted coal is 18%. The outlet temperature of the grinding unit 14 is increased with an increase in a 5 flow rate of steam flowing between the internal cylinder 15 and the external cylinder 16. And, it is found that when the outlet temperature of the grinding unit 14 is increased, the coal B is heated up to a higher temperature inside the internal cylinder 15; and thereby, the moisture content of the moisture-adjusted coal is reduced which is discharged from an outlet of the grinding unit 14. 10 [00291 As shown in Fig. 2, the moisture-adjusted coal ground by the grinding unit 14 is mixed with a carrier gas inside the coal supplying equipment 3 so that it can be supplied into the coal gasification reaction furnace 4. The carrier gas which contains the moisture-adjusted coal is pressurized up to a predetermined pressure and supplied into the 15 coal gasification reaction furnace 4. The moisture-adjusted coal in which a certain amount of moisture is evaporated after flowing out from the drying unit 13 moves inside a space where dried nitrogen is filled so that the moisture content will not change. The air separation equipment 10 shown in Fig. I liquefies air by compression and separates dried oxygen gas, nitrogen gas, and the like due to a difference in boiling point 20 from the liquefied air. The oxygen gas separated by the air separation equipment 10 is supplied to the coal gasification reaction furnace 4. [0030] As shown in Fig. 2, the coal gasification reaction furnace 4 is an apparatus which burns moisture-adjusted coal in the interior thereof so as to produce at least hydrogen gas 25 and carbon monoxide gas. The coal gasification reaction furnace 4 includes a partial 17 oxidation unit (lower reaction vessel) 26 and a thermal decomposition unit (upper reaction vessel) 28 installed at Dl above the partial oxidation unit 26 in the perpendicular direction. An accommodation space 26a is formed inside the partial oxidation unit 26. The thermal decomposition unit 28 includes a through hole (tubular portion) 27 which is 5 communicatively connected to the accommodation space 26a of the partial oxidation unit 26 via a diameter reducing portion 28a and extends in a vertical direction D. The coal gasification reaction furnace 4 is made with heat-resistant bricks and the like. The diameter reducing portion 28a is installed between the through hole 27 and the accommodation space 26a; and thereby, the partial oxidation unit 26 and the thermal 10 decomposition unit 28 can be operated under mutually independent reaction conditions. A slag cooling water tank 29 is installed at D2 below the partial oxidation unit 26. The partial oxidation unit 26 is communicatively connected to the slag cooling water tank 29 in the vertical direction (perpendicular direction) D. A diameter-reduced minor diameter portion is formed at a portion where the partial oxidation unit 26 is connected to 15 the slag cooling water tank 29. [00311 The partial oxidation unit 26 is formed into a substantially cylindrical shape extending in the vertical direction D. On an inner circumferential surface of the partial oxidation unit 26, a plurality of gasification burners (burner units) 30 are installed which 20 are formed into a cylindrical shape extending along an axis line Cl. Each of the gasification burners 30 is connected to the coal supplying equipment 3 and the air separation equipment 10 and is capable of supplying moisture-adjusted coal and an oxygen-containing gas (hereinafter referred to as moisture-adjusted coal and the like) at a predetermined ratio into the partial oxidation unit 26. The gasification burner 30 is 25 arranged in such a manner that the leading end thereof faces obliquely downward with 18 respect to a horizontal plane and the axis line Cl thereof is positioned to be tilted with respect to a center axis line C2 of the partial oxidation unit 26. Thereby, the gasification burners 30 are arranged in such a manner that an ejecting gas flows to form a swirl flow which swirls around the center axis line C2 of the partial oxidation unit 26. 5 Furthermore, a cooling device (not illustrated) is installed on an outer circumferential surface of the partial oxidation unit 26 and is capable of cooling the partial oxidation unit 26 which is heated by burning of the moisture-adjusted coal. [0032] The thermal decomposition unit 28 is formed into a tubular shape or a cylindrical 10 shape extending in the vertical direction D. An inner diameter of the through hole 27 is smaller than that of the accommodation space 26a of the partial oxidation unit 26. At an intermediate portion of the thermal decomposition unit 28 in the vertical direction D, a plurality of nozzle units 31 are installed which supply only moisture-adjusted coal into the thermal decomposition unit 28. Each of the nozzle units 15 31 is connected to the coal supplying equipment 3. It is noted that, unlike a conventional thermal decomposition unit, the thermal decomposition unit 28 does not include a steam nozzle for supplying steam to the thermal decomposition unit. Furthermore, the number of the gasification burners 30 and that of the nozzle units 31 are not restricted and any number is acceptable. 20 An end portion 27a of the D l above the through hole 27 of the thermal decomposition unit 28 is connected to the heat recovery equipment 5. [00331 Furthermore, in the present embodiment, the coal gasification system I includes a pressure measurement apparatus (pressure measurement unit) 33 which measures a 25 difference in pressure inside the through hole 27 of the thermal decomposition unit 28.

19 The pressure measurement apparatus 33 includes a first piping 34, a second piping 35, and a main body 36. The first piping 34 is connected to the accommodation space 26a of the partial oxidation unit 26, while the second piping 35 is connected to the end portion 27a of the through hole 27. The main body 36 measures a difference in pressure between the 5 internal pressure of the first piping 34 and that of the second piping 35. A predetermined quantity of water W is accommodated in the slag cooling water tank 29 and cools slag which flows down from the partial oxidation unit 26, as will be described below. [0034] 10 When the coal gasification reaction furnace 4 having the above-described structure is operated, a chemical reaction step is carried out as described in the following. First, moisture-adjusted coal and the like are supplied at a predetermined flow rate from the gasification burners 30 into the partial oxidation unit 26. As described above, each of the gasification burners 30 is arranged so that an ejecting gas flows to form a swirl 15 flow. Therefore, the moisture-adjusted coal and the like ejected from the gasification burners 30 move to the D2 downward and the flow thereof forms a swirl flow turning around the center axis line C2 of the partial oxidation unit 26. At this time, the inside of the partial oxidation unit 26 is high in temperature and pressure (for example, the temperature is in a range of 1300*C or higher to 1700'C or less and the pressure is in a 20 range of 2 MPa or more to 3 MPa or less). Under such a condition, the temperature of the moisture-adjusted coal is increased, and the moisture-adjusted coal is thermally decomposed. In these procedures, char and a volatile gas which contains coal tar, steam, and the like are generated separately. Furthermore, the moisture-adjusted coal is burned to generate high-temperature carbon monoxide gas, carbon dioxide gas, and hydrogen gas 25 as shown in chemical equations (3) to (5) described below as well as slag (ash).

20 [0035] 2C + 02 - 2CO -.. (3) C + 0 2 -+ C0 2 (4)

C+H

2 0-CO +H 2 -- (5) 5 [0036] The temperature of gases, slag, and the like generated inside the partial oxidation unit 26 is increased and the gases, the slag, and the like are swollen. Thereby, the gases, the slag, and the like receive a buoyancy force toward the DI upward and they ascend inside the partial oxidation unit 26 while swirling. 10 Slag occurring inside the partial oxidation unit 26 is in a melted state. Some portion of the slag is partially cooled by the above-described cooling device on an inner circumferential surface of the partial oxidation unit 26 and adheres on the inner circumferential surface. The other portion of the slag drops down into the water W inside the slag cooling water tank 29 installed below the partial oxidation unit 26 to be I 5 cooled and is recovered. [0037] A gas such as steam, coal tar, char, and the like generated inside the partial oxidation unit 26 are fed out from the partial oxidation unit 26 and ascend inside the through hole 27 of the thermal decomposition unit 28. With regard to the inside of the 20 partial oxidation unit 26, the temperature is adjusted to be in a range of I 000*C or more and the pressure is adjusted to be in a range of I MPa or more. Moisture-adjusted coal is supplied into the through hole 27 by the nozzle unit 31. The moisture-adjusted coal is dried by the coal drying and grinding equipment 2 so as to have the above-described predetermined moisture content. 25 The moisture-adjusted coal supplied from the nozzle unit 3 1 produces coal tar by 21 thermal decomposition. Furthermore, the predetermined amount of moisture in the moisture-adjusted coal is heated and turned into steam. Coal tar and steam which are generated from the moisture-adjusted coal supplied from the nozzle units 31 are mixed with coal tar and steam coming up (ascending) inside the partial oxidation unit 26. Then, 5 these are decomposed into carbon monoxide gas and hydrogen gas as shown in the chemical equation (6) described below. A portion of carbon in the moisture-adjusted coal supplied into the thermal decomposition unit 28 reacts with carbon dioxide gas inside the thermal decomposition unit 28 and turns into carbon monoxide gas as shown in the chemical equation (7) 10 described below. [0038] C (coal tar) + H 2 0 -> CO +H 2 - (6) C + CO 2 - 2CO --- (7) [0039] 15 Here, Fig. 5 shows a relationship between an increasing rate of coal tar adhered inside the through hole 27 and a moisture content of moisture-adjusted coal. The horizontal axis of Fig. 5 shows the moisture content of the moisture-adjusted coal, and the longitudinal axis shows an increasing rate of adhered coal tar. The greater the moisture content of the moisture-adjusted coal is, the more the 20 reaction between coal tar and steam is accelerated; and thereby, the increasing rate of adhered coal tar decreases. More specifically, in the case where the moisture content of the moisture-adjusted coal is lower than 15%, a quantity of adhered coal tar is increased and the coal tar adheres inside the through hole 27. On the other hand, in the case where the moisture content of the moisture-adjusted coal is greater than 15%, no coal tar adheres 25 inside the through hole 27. And, even when coal tar adheres inside the through hole 27 22 due to some reasons, the coal tar is decomposed into a gas and disappears with the lapse of time. Even if coal having a moisture content of approximately 60% is not heated by the drying unit 13 and is ground as it is by the grinding unit 14, the moisture content of the 5 moisture-adjusted coal does not exceed 40% because moisture evaporates from the ground coal. As described above, the moisture content of the moisture-adjusted coal becomes in a range of 40% or less by mass ratio; and thereby, it is possible to prevent the above-described chemical reactions from being delayed by steam generated from the moisture-adjusted coal. 10 The chemical reaction step is completed in accordance with the above procedures. [0040] Then, as shown in Fig. 1, a high-temperature synthesis gas mainly including hydrogen gas and carbon monoxide gas is delivered together with char from the thermal decomposition unit 28 and they are supplied to the heat recovery equipment 5. 15 In the heat recovery equipment 5, heat is exchanged between the synthesis gas delivered from the thermal decomposition unit 28 and external steam to raise a temperature of the steam. The steam is supplied to the above-described drying unit 13 and the like for the purpose of drying coal and the like. The synthesis gas cooled by the heat recovery equipment 5 is supplied from the 20 heat recovery equipment 5 to the char recovery equipment 6, and char contained in the synthesis gas is recovered by the char recovery equipment 6. The synthesis gas which has passed through the char recovery equipment 6 is supplied to the shift reaction equipment 7. Then, steam is supplied into the shift reaction equipment 7 in order to raise a ratio of hydrogen gas to carbon monoxide gas in the 25 synthesis gas to a certain value. In the shift reaction equipment 7, carbon dioxide gas 23 and hydrogen gas are generated from carbon monoxide gas in the synthesis gas and steam by a shift reaction as shown by the chemical equation (8) described below. [0041] CO + H 2 0 - C0 2 + H 2 - (8) 5 [0042] The components of the synthesis gas have been formulated (adjusted) in the shift reaction equipment 7, and then the synthesis gas is supplied to the gas purification equipment 8, and carbon dioxide gas as well as gases and the like which contain sulfur as a component are recovered from the synthesis gas. 10 The synthesis gas purified in the gas purification equipment 8 is supplied to the chemical synthesis equipment 9 to produce products such as methane, methanol, and the like. [0043] Next, an explanation will be made for an operation method in the case where coal 15 tar adheres inside the through hole 27 due to some reasons in the coal gasification system I having the above-described structure, with an emphasis given to the drying unit 13 and the coal gasification reaction furnace 4. As shown in Fig. 4, moisture content of the obtained moisture-adjusted coal is assumed to be XO when a temperature of a temperature sensor of the grinding unit 14 is 20 TO. An explanation will be made for the case where this moisture-adjusted coal is supplied from the nozzle units 31 of the coal gasification reaction furnace 4 to operate the coal gasification reaction furnace 4, and no coal tar adheres inside the through hole 27. It is assumed that coal tar adheres inside the through hole 27 and a difference in pressure measured by the pressure measurement apparatus 33 becomes greater than a set 25 value. At this time, an operator uses the flow adjusting valve 19 of the drying unit 13 to 24 decrease a flow rate of steam flowing through the drying unit 13 by a predetermined rate. Thereby, a temperature of the temperature sensor is lowered to be TI, and the moisture content of the moisture-adjusted coal obtained by the drying unit 13 is increased from XO to be X 1. 5 The moisture-adjusted coal in which the moisture content is increased to X l is supplied from the nozzle units 3 1 into the through hole 27; and thereby, a greater quantity of steam is produced from the moisture-adjusted coal. Then, as shown in the chemical equation (6), reactions between coal tar adhered inside the through hole 27 and steam are accelerated, and the adhered coal tar is gasified and disappears. 10 [0044] When the difference in pressure is decreased to a difference in pressure of the normal operation, the flow adjusting valve 19 may be used to increase a flow rate of steam flowing through the drying unit 13 in order to keep a reaction rate inside the thermal decomposition unit 28 at a predetermined value or higher. Thereby, a temperature of the 15 temperature sensor may be raised to TO or T2, for example, and the moisture content of the moisture-adjusted coal may be lowered to XO or X2. (0045] As described above, according to the coal gasification system I of the present embodiment, at first, the coal drying and grinding equipment 2 is used to dry 20 sub-bituminous coal or brown coal which contains moisture of 20% or more by weight ratio. Thereby, moisture-adjusted coal is produced which has a predetermined moisture content that is greater than a remaining moisture content of coal in a conventional coal gasification system. More specifically, the moisture content of the coal is adjusted so that no coal tar will adhere inside the through hole 27 by chemical reactions between a 25 predetermined moisture content of the moisture-adjusted coal and coal tar generated from 25 the moisture-adjusted coal in the thermal decomposition unit 28. Then, the moisture-adjusted coal and an oxygen-containing gas are supplied at a predetermined ratio from the gasification burners 30 to the accommodation space 26a inside the partial oxidation unit 26, while supplying no steam; and thereby, the 5 moisture-adjusted coal is burned. At the same time, only the moisture-adjusted coal is supplied from the gasification burners 30 to the through hole 27 inside the thermal decomposition unit 28, while supplying no steam. Here, the oxygen-containing gas indicates a gas which contains oxygen and is not restricted to oxygen gas but examples thereof include air and oxygen-enriched air. However, in order to suppress the lowering 10 of a heat generation rate of the synthesis gas generated by the thermal decomposition unit 28, highly-concentrated oxygen gas having an oxygen content of 85% or more is preferably used as the oxygen-containing gas. [0046] Both of carbon and moisture to be supplied into the thermal decomposition unit 15 28 are ontained in the moisture-adjusted coal. And, coal tar and char mainly including carbon are produced by thermal decomposition from the moisture-adjusted coal. Furthermore, the moisture of the moisture-adjusted coal is heated inside the thermal decomposition unit 28 and is turned into steam. Coal tar, char, and steam immediately after being produced from the moisture-adjusted coal are in a mixed state. Therefore, no 20 case will take place in which steam is supplied to a position away from coal tar and char to result in a failure of their reactions, as found in the case where they are supplied from different nozzles. At this time, the moisture content of the moisture-adjusted coal supplied into the thermal decomposition unit 28 is adjusted by the coal drying and grinding equipment 2 to 25 a quantity at which no coal tar will adhere inside the through hole 27 by chemical 26 reactions between coal tar and steam. Therefore, there is no chance that a quantity of coal tar adhered inside the through hole 27 is increased to clog the through hole 27. Then, steam, coal tar and char which are in a mixed state inside the thermal decomposition unit 28 are allowed to react more reliably. Thereby, it is possible to decrease an amount 5 of steam as compared with conventional procedures or eliminate a need for steam which is supplied from outside into the thermal decomposition unit 28 for preventing adhesion of coal tar. As a result, it is possible to accelerate chemical reactions inside the thermal decomposition unit 28. [0047] 10 Furthermore, moisture is supplied to the thermal decomposition unit 28 in a state of being contained in the moisture-adjusted coal. Therefore, the need for installing an apparatus such as a steam nozzle or the like which supplies steam to the thermal decomposition unit 28 is eliminated. Therefore, it is possible to reduce costs of manufacturing the coal gasification system 1. 15 Drying of coal by the coal drying and grinding equipment 2 requires certain energy for heating the coal. In the present embodiment, moisture-rich coal is supplied to the thermal decomposition unit 28 without being dried to a remaining moisture content of coal in a conventional coal gasification system. Then, the moisture of the moisture-adjusted coal is allowed to efficiently react in the thermal decomposition unit 28; 20 and thereby, it is possible to reduce some of energy needed for drying coal by conventional procedures. [0048] Furthermore, the moisture content of the moisture-adjusted coal is set to be in a range of 15% or more; and thereby, reactions between coal tar and steam in the thermal 25 decomposition unit 28 is accelerated. As a result, it is possible to prevent adhesion of 27 coal tar inside the through hole 27. [0049] There is a case where coal tar generated by thermal decomposition of the moisture-adjusted coal may adhere, depending on conditions. The inventors have found 5 from test results that in such a case, coal tar adheres in a concentrated manner at a predetermined position of D l above the nozzle unit 31 (for example, at a position of D I several hundred millimeters above the nozzle unit 3 1) in the through hole 27 of the thermal decomposition unit 28. That is, the first piping 34 of the pressure measurement apparatus 33 is connected to the accommodation space 26a of the partial oxidation unit 26, 10 and the second piping 35 is connected to the end portion 27a of the Dl above the through hole 27. The pressure measurement apparatus 33 is constituted as described above; and thereby, it is possible to prevent each of the piping 34 and the piping 35 from being clogged by coal tar and a difference in pressure can be reliably measured. It has been found that coal tar is less likely to adhere at a portion of D2 below the 15 nozzle unit 31 in the through hole 27 of the thermal decomposition unit 28. Thus, the first piping 34 may be connected to this portion. [0050] Furthermore, in the present embodiment, the pressure measurement apparatus 33 may not be installed, in the case where a quantity of coal tar adhered inside the through 20 hole 27 of the coal gasification reaction furnace 4 can be measured by using other devices such as an endoscope for industrial use or the like. Moisture content of moisture-adjusted coal to be supplied into the partial oxidation unit 26 is not necessarily equal to moisture content of moisture-adjusted coal to be supplied into the thermal decomposition unit 28. For example, equipment for drying, 25 grinding and supplying coal is made ready in two systems; and thereby, it is possible to 28 supply moisture-adjusted coal into the partial oxidation unit 26 and supply other moisture-adjusted coal into the thermal decomposition unit 28, and moisture content of the other moisture-adjusted coal is different from that of the moisture-adjusted coal. It is preferable that the moisture content of the moisture-adjusted coal to be supplied into the 5 partial oxidation unit 26 is decreased because excessively high moisture content results in a lower efficiency. It is also preferable that the moisture content of the moisture-adjusted coal to be supplied into the thermal decomposition unit 28 is increased because the moisture content thereof contributes to prevention of adhesion. [0051] 10 (Second Embodiment) Next, an explanation will be made for the second embodiment of the present invention. The same symbols will be given to the same parts as those of the first embodiment described above, and an explanation thereof will be omitted here. Only points different from those of the first embodiment will be explained. 15 As shown in Fig. 6, a coal gasification system 41 of the present embodiment includes a control unit 42 for adjusting moisture content of moisture-adjusted coal on the basis of a difference in pressure measured by a pressure measurement apparatus 33, in addition to individual constituents of the coal gasification system I of the first embodiment. 20 [0052] The control unit 42 includes a memory and a calculation unit which are not illustrated. The control unit 42 is electrically connected to a pressure measurement apparatus 33, a drying unit 13 and a temperature sensor of a grinding unit 14. The memory stores a relational expression which covers a temperature of the temperature 25 sensor of the grinding unit 14 and moisture content of moisture-adjusted coal after coming 29 out from coal drying and grinding equipment 2 as shown in Fig. 4, and a relational expression which covers a difference in pressure measured by the pressure measurement apparatus 33 and moisture content of moisture-adjusted coal necessary for returning the difference in pressure to a normal value as shown in Fig. 7. 5 Furthermore, the calculation unit is capable of receiving a signal from the pressure measurement apparatus 33 and also capable of controlling the drying unit 13 on the basis of the above-described relational expressions stored in the memory. [0053] Next, an explanation will be made for a method for operating the 10 above-constituted coal gasification system 41 in the case where coal tar adheres inside the through hole 27 due to some reasons, with an emphasis given to the drying unit 13, the coal gasification reaction furnace 4 and the control unit 42. As is the case with the operation method described in the first embodiment, the moisture content of the obtained moisture-adjusted coal is assumed to be XO when a 15 temperature of the temperature sensor of the grinding unit 14 indicates TO. An explanation will be made for the case where by supplying this moisture-adjusted coal from the nozzle units 31, a difference in pressure measured by the pressure measurement apparatus 33 becomes PO (refer to Fig. 7) and the coal gasification reaction furnace 4 is operated with no coal tar adhered inside the through hole. 20 It is assumed that coal tar adheres inside the through hole 27 and a difference in pressure measured by the pressure measurement apparatus 33 is increased to P1 from PO shown in Fig. 7. At this time, the calculation unit of the control unit 42 receives a signal from the pressure measurement apparatus 33; and thereby, an increased difference in pressure is detected. Then, the calculation unit calculates X l which is the moisture 25 content corresponding to P1 of the difference in pressure by referring to the relational 30 expression stored in the memory which covers a difference in pressure measured by the pressure measurement apparatus 33 and a moisture content of moisture-adjusted coal as shown in Fig. 7. The calculation unit also calculates TI which is the temperature of the temperature sensor corresponding to X l of the moisture content by referring to the 5 relational expression stored in the memory which covers a temperature of the temperature sensor and moisture content of moisture-adjusted coal as shown in Fig. 4. Then, the calculation unit controls the drying unit 13 such that temperature measured by the temperature sensor becomes TI. By this control, the moisture-adjusted coal in which the moisture content has been increased to XI is supplied from the nozzle 10 units 31 of the coal gasification reaction furnace 4 into the thermal decomposition unit 28. Thereby, reactions between coal tar adhered inside the through hole 27 and steam are accelerated to gasify the adhered coal tar and the coal tar will disappear. In the case where a difference in pressure measured by the pressure measurement apparatus 33 is excessively large, the time required for gasifying and eliminating the 15 adhered coal tar becomes long. Thus, it is preferable that the control unit 42 starts to carry out the above-described control when a difference in pressure measured by the pressure measurement apparatus 33 is increased by 10% to 30% as compared with the difference during normal operation. [0054] 20 It is assumed that a difference in pressure measured by the pressure measurement apparatus 33 is decreased to the difference in pressure during normal operation, that is, to PO or P2 (refer to Fig. 7). At this time, in order to keep the reaction rate at a predetermined value or higher, it is acceptable that the calculation unit is used to calculate the temperatures TO, T2 corresponding to the differences in pressure PO, P2 by referring to 25 the both relational expressions, and the temperature of the temperature sensor is adjusted 31 to TO or T2 and the moisture content of the moisture-adjusted coal is decreased to XO or X2. [0055] As described above, the coal gasification system 41 of the present embodiment 5 eliminates a need for installing an apparatus for supplying steam into the thermal decomposition unit 28 and is capable of adjusting the moisture content of coal supplied into the thermal decomposition unit 28. Furthermore, in the case where coal tar adheres inside the through hole 27, a difference in pressure measured by the pressure measurement apparatus 33 is increased. 10 At this time, the calculation unit increases the moisture content of the moisture-adjusted coal by using the coal drying and grinding equipment 2. Thereby, chemical reactions between coal tar and steam are further accelerated; and as a result, it is possible to gasify the coal tar adhered inside the through hole 27 of the thermal decomposition unit 28. [0056] 15 An explanation has been made above in detail for the embodiments of the present invention by referring to the drawings. A specific constitution shall not be restricted to these embodiments and the present invention includes modifications of constitutions and the like within a scope not departing from the features of the present invention. For example, in the first embodiment and second embodiment described above, 20 there may be a case where, depending on operation conditions of the coal gasification reaction furnace 4, the moisture content of the moisture-adjusted coal supplied into the partial oxidation unit 26 is greater than a quantity of steam necessary for the partial oxidation unit 26. In this case, two coal types are produced in the coal drying and grinding equipment 2. One (first coal type) of the two coal types is coal having a 25 suitable moisture content to be supplied into the thermal decomposition unit 28, and the 32 other (second coal type) is coal having a moisture content lower than that of the former coal (first coal type) and used for the partial oxidation unit 26. Then, these two coal types may be supplied respectively to the partial oxidation unit 26 and the thermal decomposition unit 28. 5 (Example 1) [00571 The above-described coal gasification system I was used, and a temperature inside the partial oxidation unit 26 was set to 1300'C, and a flow rate of moisture-adjusted 10 coal having a moisture content of 18% and a flow rate of an oxygen-containing gas (oxygen gas in this example) were set to 650 (kg/h) and 345 (Nm 3 /h), respectively which were supplied from the gasification burners 30 into the partial oxidation unit 26. No steam was supplied into the partial oxidation unit 26. An apparatus also acting as a grinder shown in Fig. 3 was used as a dryer; and 15 thereby, coal was dried and ground into particles having sizes of 10 pam or more to 100 pam or less. Under the above-described conditions, the moisture-adjusted coal having a moisture content of 18% was supplied from the nozzle units 31 into the thermal decomposition unit 28 at a quantity of 150 (kg/h), while supplying no steam. In this case, 20 it has been found that no coal tar adhered inside the through hole 27. As described above, according to the coal gasification system I which is an example of the present invention, adhesion of coal tar was prevented without installing an apparatus such as a steam nozzle or a steam supplying pump, and the system could be operated stably. Therefore, it is possible to design a compact constitution as a whole 25 system.

33 As a comparative example, 561 (kg/h) of coal (moisture content of 5%), 345 (Nm 3 /h) of an oxygen-containing gas (oxygen gas in the comparative example), and 89 (kg/h) of steam were supplied into the partial oxidation unit 26. Furthermore, 130 (kg/h) of coal having a moisture content of 5% and 22 (kg/h) of steam were supplied from the 5 nozzle units 31 into the thermal decomposition unit 28. In this case, it has been found that no coal tar adhered inside the through hole 27. However, an apparatus such as a steam nozzle, a steam supplying pump, or the like was required; and therefore, the size of equipment as a whole was increased, and the cost of equipments was also increased, as compared with Example 1. 10 (Example 2) [0058] The above-described coal gasification system I was used, and a difference in pressure between the inside of the partial oxidation unit 26 and the thermal decomposition 15 unit 28 was measured by using the first piping 34 and the second piping 35. Then, 606 (kg/h) of coal having a moisture content of 10% and 330 (Nm 3 /h) of oxygen-containing gas (oxygen gas in this example) were supplied into the partial oxidation unit 26. Furthermore, moisture-adjusted coal having a moisture content of 12% was supplied at a quantity of 136 (kg/h) from the nozzle units 31 into the thermal decomposition unit 28. 20 Thereby, operation was carried out. An apparatus also acting as the grinder described in Fig. 3 was used as a dryer; and thereby, the coal was dried and ground into particles having sizes of 10 pm or more to 100 pm or less. As a result, approximately 20 hours after the start of operation, a difference in pressure between the inside of the partial oxidation unit 26 and the thermal decomposition 25 unit 28 began to increase. At a time point when the difference in pressure was increased 34 by approximately 20% before the increase, an outlet gas temperature at the grinding unit 14 was lowered from 65*C to 45*C. Consequently, the moisture content of the moisture-adjusted coal became 18% by mass ratio. Then, it was confirmed that after the start of feeding the moisture-adjusted coal into the reaction furnace, a difference in 5 pressure between the inside of the partial oxidation unit 26 and the thermal decomposition unit 28 began to decrease and returned nearly to the level before the increase in difference in pressure. [0059] An explanation has been made above for preferred embodiments of the present 10 invention; however, the present invention shall not be restricted thereto. The present invention may be subjected to addition of the constitution, omission, replacement and other modifications within a scope not departing from the features of the present invention. The present invention shall not be restricted to the above description but will be restricted only by the scope of the attached claims. 15 INDUSTRIAL APPLICABILITY [0060] The coal gasification system and the coal gasification process eliminate a need for installing an apparatus for supplying steam to an upper reaction vessel and are capable of 20 adjusting a quantity of steam inside the upper reaction vessel. Description of Symbols [0061] 1, 41: Coal gasification system 25 2: Coal drying and grinding equipment (dryer) 35 4: Coal gasification reaction furnace 26: Partial oxidation unit (lower reaction vessel) 26a: Accommodation space 27: Through hole 5 28: Thermal decomposition unit (upper reaction vessel) 28a: Diameter reducing portion 30: Gasification burner (burner unit) 33: Pressure measurement apparatus (pressure measurement unit) 42: Control unit 10 D: Vertical direction

Claims (9)

1. A coal gasification system including: a dryer which dries coal to obtain moisture-adjusted coal having a predetermined 5 moisture content; and a coal gasification reaction furnace which burns the moisture-adjusted coal to generate hydrogen gas and carbon monoxide gas, wherein the coal gasification reaction furnace includes: a lower reaction vessel; 10 an upper reaction vessel which is installed above the lower reaction vessel and is communicatively connected to the lower reaction vessel; a burner unit which supplies the moisture-adjusted coal and an oxygen-containing gas into the lower reaction vessel to burn the moisture-adjusted coal; and a nozzle unit which supplies the moisture-adjusted coal into the upper reaction 15 vessel.

2. The coal gasification system according to Claim 1, wherein the coal gasification system further includes: a pressure measurement unit which measures a difference between a furnace 20 pressure at a portion below the nozzle unit and a furnace pressure at an upper portion of the upper reaction vessel; and a control unit which controls the dryer on the basis of the difference in pressure measured by the pressure measurement unit, thereby, the moisture content of the coal is adjusted. 25 37

3. A coal gasification system including: a dryer which dries sub-bituminous coal or brown coal having a moisture of 20% or more by mass ratio so as to contain a predetermined moisture content, thereby obtaining moisture-adjusted coal; and 5 a coal gasification reaction furnace which burns the moisture-adjusted coal to produce at least hydrogen gas and carbon monoxide gas, wherein the coal gasification reaction furnace includes: a lower reaction vessel which has an accommodation space in an interior thereof; and 10 an upper reaction vessel which is installed above the lower reaction vessel, wherein the lower reaction vessel includes: a burner unit which supplies the moisture-adjusted coal and an oxygen-containing gas at a predetermined ratio into the lower reaction vessel and which supplies no steam, thereby burning the moisture-adjusted coal, 15 wherein the upper reaction vessel includes: a through hole which is communicatively connected to the accommodation space of the lower reaction vessel via a diameter reducing portion and which extends vertically; and a nozzle unit which supplies only the moisture-adjusted coal into the upper 20 reaction vessel and which supplies no steam, and wherein the predetermined moisture content is set to a quantity at which no coal tar will adhere inside the through hole by chemical reactions between steam and coal tar which are generated from the moisture-adjusted coal. 25

4. The coal gasification system according to Claim 3, 38 wherein the predetermined moisture content is in a range of 15% or more to 40% or less by mass ratio with respect to the moisture-adjusted coal.

5. The coal gasification system according to Claim 3 or Claim 4, 5 wherein the coal gasification reaction furnace includes: a pressure measurement unit which measures a difference in pressure between either of an internal pressure at a portion below the nozzle unit in the through hole of the upper reaction vessel or an internal pressure in the accommodation space of the lower reaction vessel and an internal pressure at an upper end portion of the through hole; and 10 a control unit which controls the dryer on the basis of the difference in pressure measured by the pressure measurement unit, thereby, the moisture content of the coal is adjusted.

6. A coal gasification process which uses the coal gasification system according to any 15 one of Claim 3 to Claim 5, the coal gasification process including: a drying step of drying the sub-bituminous coal or the brown coal so as to contain a predetermined moisture content, thereby obtaining the moisture-adjusted coal; and a chemical reaction step of supplying the moisture-adjusted coal and an 20 oxygen-containing gas into the lower reaction vessel while supplying no steam from the burner unit, thereby burning the moisture-adjusted coal, and supplying only the moisture-adjusted coal into the upper reaction vessel from the nozzle unit, thereby subjecting the moisture-adjusted coal to chemical reaction. 25

7. The coal gasification process according to Claim 6, 39 wherein in the chemical reaction step, coal tar generated from the moisture-adjusted coal is allowed to react chemically with steam generated by heating moisture contained in the moisture-adjusted coal, thereby at least carbon monoxide gas and hydrogen gas are produced. 5

8. A coal gasification process including: drying coal so as to contain a predetermined moisture content, thereby obtaining moisture-adjusted coal which contains the predetermined moisture content; supplying the moisture-adjusted coal and an oxygen-containing gas into a lower 10 reaction vessel of a coal gasification reaction furnace; burning the moisture-adjusted coal inside the lower reaction vessel to generate a high-temperature gas; supplying the moisture-adjusted coal into an upper reaction vessel which is communicatively connected to the lower reaction vessel of the coal gasification reaction 15 furnace; and heating the moisture-adjusted coal supplied into the upper reaction vessel by the high-temperature gas which flows from the lower reaction vessel to the upper reaction vessel. 20

9. The coal gasification process according to Claim 8, wherein at least one of sub-bituminous coal and brown coal is used as the coal.