Abstract:
A slag crusher ( 20 ) is provided in a combustor of a gasifier ( 10 ) for gasifying a carbonaceous feedstock, and discharges falling slag generated in the combustor from the gasifier ( 10 ). The slag crusher ( 20 ) is provided with: a screen ( 22 ) provided so as to intersect with the direction in which the slag falls, the screen ( 22 ) having a plurality of openings ( 30 ) and passing slag having a diameter smaller than that of the openings ( 30 ); a spreader ( 24 ) for moving over the top surface of the screen ( 22 ) and crushing slag deposited on the top surface of the screen ( 22 ); and a nozzle ( 26 ) for spraying high-pressure water onto the slag deposited on the screen ( 22 ). The slag deposited on the top surface of the screen ( 22 ) thereby more easily passes from the openings ( 30 ) in the screen ( 22 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a slag discharge apparatus and a slag discharge method. 
       BACKGROUND ART 
       [0002]    An ash hopper, in which slag (molten slag) produced in and falling from a combustor is collected, is provided in a lower portion of a gasifier which gasifies a carbonaceous feedstock such as coal (PTLs 1 and 2). 
         [0003]    A slag crusher which includes a screen and a spreader is provided in the ash hopper. The slag falling from the combustor is rapidly cooled by water so as to be solidified, and falls on a top face of the screen included in the slag crusher. 
         [0004]    The screen is provided transversely with respect to the fall direction of the slag and includes a plurality of openings. Accordingly, slag which is smaller than diameters of the openings passes through the screen, and falls to the lower portion of the ash hopper. 
         [0005]    Meanwhile, slag which is larger than the diameters of the openings, or a slag lump which is an accumulation of the slag which is smaller than the diameters of the openings is accumulated on the top face of the screen. In the slag lump, slag is combined by a friction force in particle layers or cross-linking due to powder pressure. 
         [0006]    Accordingly, for example, the spreader provided on the top face of the screen is moved along the top face of the screen by a hydraulic cylinder, and the spreader crushes the slag by applying a force to the slag accumulated on the top face of the screen so as to allow the slag to pass through the screen. 
         [0007]    The slag, which falls from the openings of the screen to the lower portion of the ash hopper and is accumulated, is discharged from the gasifier out of a system via a lock hopper. 
       CITATION LIST 
     Patent Literature 
       [0008]    [PTL 1] Japanese Unexamined Patent Application Publication No. H7-247484 
         [0009]    [PTL 2] Japanese Unexamined Patent Application Publication No. H9-38510 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0010]    However, even when the spreader is operated, the accumulated slag may be not crushed, and the slag may not pass through the screen by only collecting the slag in the operating direction of the slag crusher. 
         [0011]    In addition, an accumulation amount of the slag on the top face of the screen increases, the slag may not be discharged from the gasifier, and the inner portion of the ash hopper may be filled with the slag. In this case, the operation of the gasifier cannot be continued, and the gasifier is stopped. 
         [0012]    The present invention is made in consideration of the above-described circumstances, and an object thereof is to provide a slag discharge apparatus and a slag discharge method capable of allowing the slag accumulated on the top face of the screen more easily to pass through the openings of the screen. 
       Solution to Problem 
       [0013]    In order to solve the above-described problems, a slag discharge apparatus and a slag discharge method of the present invention adopt the following means. 
         [0014]    According a first aspect of the present invention, there is provided a slag discharge apparatus which is provided on a combustor of a gasifier gasifying a carbonaceous feedstock and discharges slag produced in and falling from the combustor out of the gasifier, comprising: a screen which is provided transversely with respect to the fall direction of the slag and has a plurality of openings to allow slag which is smaller than diameters of the openings to pass through the screen; crushing means for moving along a top face of the screen to crush the slag accumulated on the top face of the screen; and water flow generating means for allowing liquid to flow onto the slag accumulated on the screen to generate a water flow. 
         [0015]    The slag discharge apparatus according to the present configuration is provided on a combustor of a gasifier gasifying the carbonaceous feedstock and discharges slag produced in and falling from the combustor out of the gasifier. 
         [0016]    In addition, the slag discharge apparatus includes the screen which is provided transversely with respect to the fall direction of the slag and has the plurality of openings. The slag, which is smaller than the diameters of the openings of the screen, passes through the openings so as to fall. Meanwhile, the slag, which does not pass through the openings and is accumulated on the top face of the screen, is crushed by the crushing means moving along the top face of the screen. 
         [0017]    Here, the slag which is accumulated on the top face of the screen includes a slag lump in which slag smaller than the diameters of the openings is combined by a friction force or cross-linking due to powder pressure. 
         [0018]    In order to remove the accumulated slag, liquid flows from the water flow generating means onto the slag accumulated on the top face of the screen to generate a water flow. The combination due to the cross-linking is cut by spouting the pressurized liquid onto particles of the slag which are combined by the cross-linking. Accordingly, the slag is gently fluidized from a stationary state. In addition, for example, the liquid spouted onto the slag is water. 
         [0019]    In addition, the slag which is easily fluidized is made to flow by the liquid from the water flow generating means. Accordingly, the slag falls along with the liquid from the openings of the screen without moving the crush means. In addition, the slag easily falls from the openings by moving the crushing means. 
         [0020]    As described above, in the present configuration, the slag accumulated on the top face of the screen can easily be passed through the openings of the screen. 
         [0021]    In the first aspect, preferably, the water flow generating means is provided on a side wall of the screen which is erected in parallel with respect to an operating direction of the crushing means. 
         [0022]    According to the present configuration, it is possible to easily and uniformly spout the pressurized liquid onto the accumulated slag. 
         [0023]    In the first aspect, preferably, the water flow generating means is provided in the crushing means. 
         [0024]    According to the present configuration, since the pressurized liquid is more reliably spouted onto the slag crushed by the crushing means, the combination due to the cross-linking of the accumulated slag is cut, and the slag easily passes through the screen. 
         [0025]    In the first aspect, preferably, the crushing means includes an inclined surface which is inclined forward with respect to a crushing direction of the slag. 
         [0026]    According to the present configuration, since a downward force is applied to the accumulated slag, the combination due to the cross-linking of the accumulated slag is cut, and the slag easily passes through the screen. 
         [0027]    In the first aspect, preferably, the water flow generating means is provided on the inclined surface, and spouts the liquid in the direction of the screen. 
         [0028]    According to the present configuration, since the downward force is also added to the slag, which is crushed by the crushing means, due to the spouted liquid, it is possible to more reliably crush the accumulated slag. 
         [0029]    In the first aspect, preferably, the water flow generating means is provided in the screen. 
         [0030]    According to the present configuration, it is possible to prevent the slag from being accumulated on the top face of the screen, and it is possible to easily and uniformly spout the pressurized liquid onto the accumulated slag. 
         [0031]    In the first aspect, preferably, the water flow generating means spouts gas instead of the liquid. 
         [0032]    In the first aspect, preferably, the slag discharge apparatus further includes a guide which limits the movement direction of the crushing means. 
         [0033]    According to the present configuration, it is possible to stably move the crushing means such as a case where it is possible to prevent the crushing means from floating when the crushing means moves. 
         [0034]    In the first aspect, preferably, a plurality of crushing means adjacent to each other are provided on the top face of the screen, the screen is partitioned between the adjacent crushing means by partition means so as to be divided, and the water flow generating means is provided below each divided region. 
         [0035]    According to the present configuration, since the slag on the screen is made to flow by the water flow generated by the water flow generating means, it is possible to prevent the slag from remaining on the screen. 
         [0036]    In the first aspect, preferably, before a predetermined crushing means is operated, the water flow from the water flow generating means provided below the region corresponding to the predetermined crushing means moves the slag to the regions corresponding to adjacent other crushing means. 
         [0037]    According to the present configuration, relatively small slag is made to flow to the regions corresponding to other crushing means by the water flow from the water flow generating means, and falls from the screen. In addition, since the operating crushing means crushes relatively large slag which has not been made to flow by the water flow, it is possible to prevent large slag from remaining on the screen. 
         [0038]    In the first aspect, preferably, the lower end portion of the crushing means comes into surface-contact with a surface, which faces crushing means when the crushing means moves, in a width direction. 
         [0039]    According to the present configuration, since the lower end portion of the crushing means comes into surface-contact with the surface, which faces crushing means when the crushing means moves, in the width direction, a gap between the lower end portion of the crushing means and the surface facing the crushing means does not occur. Therefore, according to the present configuration, since it is possible to more reliably crush the slag on the screen, it is possible to prevent large slag from remaining on the screen. 
         [0040]    According to the present configuration, since gas is spouted from the top face of the screen in a state where the top face of the screen is filled with water, combination due to cross-linking of the slag is cut by rising of air bubbles. Accordingly, since the slag is fluidized, the slag accumulated on the top face of the screen more easily passes through the openings of the screen. 
         [0041]    According to a second aspect of the present invention, there is provided a slag discharge method of using a slag discharge apparatus which is provided on a combustor of a gasifier gasifying a carbonaceous feedstock and discharges slag produced in and falling from the combustor out of the gasifier, comprising: a first step of allowing liquid from water flow generating means to flow onto slag accumulated on a top face of a screen, which is provided transversely with respect to the fall direction of the slag and has a plurality of openings, to generate a water flow; and a second step of moving crushing means for crushing the slag accumulated on the top face of the screen along the top face of the screen. 
       Advantageous Effects of Invention 
       [0042]    According to the present invention, excellent effects are obtained in which slag accumulated on a top face of a screen can easily pass through openings of the screen. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0043]      FIG. 1  is a longitudinal section view of a gasifier according to a first embodiment of the present invention. 
           [0044]      FIG. 2  is a longitudinal section view of a slag crusher according to the first embodiment of the present invention. 
           [0045]      FIG. 3  is a front view of a spreader according to the first embodiment of the present invention. 
           [0046]      FIG. 4  is a longitudinal sectional view when a spreader according to a second embodiment of the present invention is viewed from a side. 
           [0047]      FIG. 5  is a longitudinal sectional view when the spreader according to the second embodiment of the present invention is viewed from a front side. 
           [0048]      FIG. 6  is a longitudinal section view of a screen according to a third embodiment of the present invention. 
           [0049]      FIG. 7  is a longitudinal section view of a screen according to a modification example of the third embodiment of the present invention. 
           [0050]      FIG. 8  is a longitudinal section view of a screen according to a fourth embodiment of the present invention. 
           [0051]      FIG. 9  is a longitudinal section view of a screen according to a modification example of the fourth embodiment of the present invention. 
           [0052]      FIG. 10  is a top view of a slag crusher according to a fifth embodiment of the present invention. 
           [0053]      FIG. 11  is a longitudinal section view of a screen and a side wall according to the fifth embodiment of the present invention. 
           [0054]      FIG. 12  is a longitudinal section view for explaining floating of a spreader. 
           [0055]      FIG. 13  is a top view of a slag crusher according to a sixth embodiment of the present invention. 
           [0056]      FIG. 14  is a longitudinal section view when the slag crusher according to the sixth embodiment of the present invention is viewed from the side. 
           [0057]      FIG. 15  is a longitudinal section view when the slag crusher according to the sixth embodiment of the present invention is viewed from the front side. 
           [0058]      FIG. 16  is a longitudinal section view when viewed from the side to explain a remaining state of slag. 
           [0059]      FIGS. 17A and 17B  are longitudinal section views when a slag crusher according to a seventh embodiment of the present invention is viewed from the side. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0060]    Hereinafter, embodiments of a slag discharge apparatus and a slag discharge method according to the present invention will be described with reference to the drawings. 
       First Embodiment 
       [0061]    Hereinafter, a first embodiment of the present invention will be described. 
         [0062]      FIG. 1  is a longitudinal section view of a gasifier  10  according to the first embodiment. 
         [0063]    As carbonaceous feedstocks applied to the gasifier according to the first embodiment, there are wastes such as waste tires or plastics in addition to heavy fuels such as coal, petroleum coke, coal coke, asphalt, pitch, or oil shale. In the following embodiments, a case in which the gasified carbonaceous feedstock is coal will be described. 
         [0064]    In the following embodiments, a case in which the gasified carbonaceous feedstock is coal will be described. 
         [0065]    In the gasifier  10 , pulverized coal which is supplied from a coal supply device (not shown) and char which is recovered by dedusting device (not shown) react with an oxygen containing gas in a combustor  12  under a high temperature atmosphere of approximately 1500° C. to 1800° C. which is an ash melting point or more. Accordingly, when the pulverized coal is combusted at a high temperature in the combustor  12 , coal gas which is combustible gas is generated, and slag  14  in which ash in the pulverized coal is melted is generated. 
         [0066]    In addition, the high-temperature coal gas obtained by the high temperature combustion in the combustor  12  flows into a reductor  16  which is provided on the upper stage of the combustor  12 . The pulverized coal and the char are also supplied to the reductor  16 , the supplied pulverized coal and char are further gasified, and coal gas which is combustible gas is generated. In addition, the combustor  12  according to the first embodiment is an entrained bed type combustor. However, the combustor  12  is not limited to this, and may be a fluidized bed type combustor or a fixed bed type combustor. 
         [0067]    An ash hopper  18 , which collects the slag  14  produced in and falling from the combustor  12 , is provided in the lower portion of the gasifier  10 . 
         [0068]    The ash hopper  18  is provided with a slag crusher  20  which crushes the slag  14  and discharges the slag out of the gasifier  10 . In addition, a region of the lower portion of the gasifier  10  which is provided with the slag crusher  20  is filled with water. 
         [0069]      FIG. 2  is a longitudinal section view showing a configuration of the slag crusher  20  according to the first embodiment. 
         [0070]    The slag crusher  20  is provided with a screen  22  (also referred to as a crusher mesh), a spreader  24 , and a nozzle  26 . 
         [0071]    The slag  14  falling from the combustor  12  is rapidly cooled by water (hereinafter, referred to as “ash hopper water”) which is spouted from an ash hopper water-supply pipe  28  so as to be solidified, and the solidified slag falls to the top face of the screen  22  provided in the slag crusher  20 . 
         [0072]    The screen  22  with a plurality of openings  30  is provided transversely with respect to the fall direction of the slag  14 , and slag  14  which is smaller than diameters of the openings  30  passes through the screen. For example, the screen  22  is a plate-shaped member which includes the openings  30 . In addition, the shape of each of the openings  30  is not particularly limited, and for example, has a circular shape, a polygonal shape, or the like. 
         [0073]    The slag  14  passing through the openings  30  falls to the lower portion of the ash hopper  18  along with the ash hopper water. As shown in  FIG. 1 , a lock hopper  34  is connected to the lower portion of the ash hopper  18 , and the slag  14  falling to the lower portion of the ash hopper  18  is discharged out of the system via the lock hopper  34 . 
         [0074]    In addition, as an example, the gasifier  10  of  FIG. 1  adopts a gravity falling method in which the slag  14  is discharged out of the system by making the slag  14  fall to the lock hopper  34 . However, the present invention is not limited to this, and a horizontal suction method may be adopted in which the slag  14  is extracted so as to be reused without causing the slag  14  to fall to the lock hopper  34 . 
         [0075]    The spreader  24  is moved along the top face of the screen  22  by the hydraulic cylinder  36  and guide rods  37 , and crushes the slag  14  accumulated on the top face of the screen  22 . In addition, the position of the spreader  24  shown in  FIG. 2  is a standby position before the spreader moves along the top face of the screen  22 . 
         [0076]    A receiving plate  38  is provided on a side opposite to the standby position of the spreader  24 . That is, the spreader  24  moves from the standby position to the receiving plate  38 , and the slag  14  accumulated on the top face of the screen  22  is collected. In addition, the slag  14  is interposed between the spreader  24  and the receiving plate  38 , and the accumulated slag  14  is crushed. In addition, protrusion portions  40  are provided on a front surface of the spreader  24  so as to easily crush the slag  14 . In addition, as an example, each of the protrusion portions  40  shown in  FIG. 2  has a conical shape. However, the shape of the protrusion portion  40  is not limited to this and may have a truncated cone shape, a polygonal pyramid shape, a polygonal frustum of pyramid shape, or the like. 
         [0077]    In addition, the spreader  24  according to the first embodiment is provided with an inclined surface  24 A which is inclined forward with respect to the crushing direction of the slag  14 . The inclined surface  24 A is provided on the lower portion of the spreader  24 . The spreader  24  collects the accumulated slag  14  mainly by the inclined surface  24 A. The portion above the inclined surface  24 A becomes a perpendicular surface  24 B perpendicular to the screen  22 . 
         [0078]    In addition, the nozzle  26  is water flow generating means which causes liquid to flow onto the slag  14  accumulated on the screen  22  to generate a water flow, and as a specific example, the nozzle  26  is a spouting hole which spouts pressurized liquid. The nozzle  26  according to the first embodiment is provided on the inclined surface  24 A of the spreader  24 . As shown in a front view of the spreader  24  of  FIG. 3 , for example, the plurality of nozzles  26  are horizontally provided on the inclined surface  24 A. 
         [0079]    For example, the pressurized liquid which is spouted from the nozzle  26  is water. However, the present invention is not limited to this, and the pressurized liquid may be liquid which can cut cross-linking of the slag  14  as described below. In addition, in descriptions below, the pressurized water is referred to as high pressure water. For example, the pressure of the high pressure water is 3 MPa to 5 MPa. 
         [0080]    A water supply pipe  42 , through which the high pressure water is supplied to the ash hopper water-supply pipe  28 , is branched and connected to the nozzle  26 . More specifically, the branched water supply pipe  42  is connected to a high pressure hose  44 . The high pressure hose  44  has flexibility so as to correspond to the movement of the spreader  24 , and is supported by a high pressure hose receiver  46 . 
         [0081]    The high pressure hose  44  is connected to a high pressure water header  48 . The high pressure water header supplies the plurality of nozzles  26  with the high pressure water. 
         [0082]    Next, an operation of the slag crusher  20  according to the first embodiment will be described. 
         [0083]    The slag  14  generated in the combustor  12  falls on the top face of the screen  22 . 
         [0084]    In the slag  14  which falls on the top face of the screen  22 , the slag  14  which is smaller than the diameters of the openings  30  of the screen  22  passes through the openings  30 , and falls to the lower portion of the ash hopper  18 , that is, the lower portion of the gasifier  10 . 
         [0085]    Meanwhile, the slag  14  which is larger than the diameters of the openings  30 , or slag lumps which are accumulations of the slag  14  which is smaller than the diameters of the openings  30  cannot pass through the openings  30 , and are accumulated on the top face of the screen  22 . 
         [0086]    Accordingly, the spreader  24  moves from the standby position to the receiving plate  38  along the top face of the screen  22  every fixed time interval. Accordingly, the spreader  24  crushes the accumulated slag  14  such that the slag  14  easily passes through the openings  30 . 
         [0087]    In addition, since the spreader  24  according to the first embodiment applies a downward force to the accumulated slag  14  using the inclined surface  24 A, the accumulated slag  14  can be more reliably crushed. 
         [0088]    However, the slag lumps, in which small slag  14  is combined by cross-linking, are not crushed by the spreader  24 , do not pass through the openings  30 , and may be collected in the movement direction of the spreader  24 . 
         [0089]    Accordingly, the high pressure water is spouted from the nozzles  26 , which are provided on the inclined surface  24 A of the spreader  24 , toward the slag  14 . Since the high pressure water is spouted to the particles of the slag  14  combined by cross-linking, the combination by cross-linking is cut. Accordingly, the slag  14  is gently fluidized from a stationary state. 
         [0090]    In addition, since the nozzles  26  are provided on the inclined surface  24 A, the high pressure water is more reliably spouted to the slag  14  which is crushed by the spreader  24 . Accordingly, it is possible more reliably crush the accumulated slag  14 . 
         [0091]    Moreover, a time interval of the emission of the high pressure water from the nozzles  26  may be the same as a time interval of the movement of the spreader  24 , or the emission of the high pressure water may be intermittently or continuously performed regardless of the time interval of the movement of the spreader  24 . 
         [0092]    In addition, the slag  14 , which is easily fluidized, is made to flow by the high pressure water spouted from the nozzles  26 . Accordingly, the slag  14  falls from the openings  30  of the screen  22  along with the high pressure water without moving the spreader  24 . In addition, the slag  14  easily falls from the openings  30  even by moving spreader  24 . 
         [0093]    As described above, the slag crusher  20  according to the first embodiment is provided with the screen  22  which is provided transversely with respect to the fall direction of the slag  14  and has the plurality of openings  30  to allow the slag  14  which is smaller than diameters of the openings  30  to pass through the screen, the spreader  24  which moves along the top face of the screen  22  to crush the slag  14  accumulated on the top face of the screen  22 , and the nozzles  26  which spouts the high pressure water onto the slag  14  accumulated on the screen  22 . 
         [0094]    Accordingly, the slag crusher  20  causes the slag  14  accumulated on the top face of the screen  22  to more easily pass through the openings  30  of the screen  22 . Therefore, even when the slag  14  is accumulated on the top face of the screen  22 , it is possible to more reliably discharge the slag  14  by the slag crusher  20 . As a result, it is possible to prevent the operation of the gasifier  10  from being stopped due to accumulation of the slag  14 , and a continuous operation of the gasifier  10  can be performed. 
         [0095]    Moreover, in the slag crusher  20  according to the first embodiment, the nozzles  26  are provided on the inclined surface  24 A of the spreader  24 . However, the present invention is not limited to this, and the nozzles  26  may be provided on the perpendicular surface  24 B of the spreader  24 . 
       Second Embodiment 
       [0096]    Hereinafter, a second embodiment of the present invention will be described. 
         [0097]    Since the configuration of the gasifier  10  according to the second embodiment is the same as the configuration of the gasifier  10  according to the first embodiment shown in  FIG. 1 , descriptions thereof are omitted. 
         [0098]      FIG. 4  is a longitudinal section view when the spreader  24  according to the second embodiment is viewed from a side.  FIG. 5  is a longitudinal section view when the spreader  24  according to the second embodiment is viewed from a front side, and is a section view taken along A-A in  FIG. 4 . In addition, in  FIGS. 4 and 5 , the same reference numerals as those of  FIGS. 2 and 3  are assigned to the same configuration portions as those of  FIGS. 2 and 3 , and descriptions thereof are omitted. 
         [0099]    The nozzles  26  according to the second embodiment are provided on the inclined surface  24 A, and spouts high pressure water in the direction of the screen  22 . 
         [0100]    For example, a header  50  is provided in the inner portion of the spreader  24 . The plurality of nozzles  26  facing downward are connected to the header  50 , and the high pressure water is spouted from the nozzles  26  to the top face of the screen  22 . Moreover, the time interval of the emission of the high pressure water from the nozzles  26  may be the same as the time interval of the movement of the spreader  24 , or the emission of the high pressure water may be intermittently or continuously performed regardless of the time interval of the movement of the spreader  24 . In addition, when the high pressure water header  48  is provided in the slag crusher  20 , the header  50  may not be provided. 
         [0101]    Accordingly, in the slag crusher  20  according to the second embodiment, since the downward force is applied to the slag  14 , which is crushed by the spreader  24 , by the high pressure water, it is possible to more reliably crush the accumulated slag  14 . 
       Third Embodiment 
       [0102]    Hereinafter, a third embodiment of the present invention will be described. 
         [0103]    Since the configuration of the gasifier  10  according to the third embodiment is the same as the configuration of the gasifier  10  according to the first embodiment shown in  FIG. 1 , descriptions thereof are omitted. 
         [0104]    In the slag crusher  20  according to the third embodiment, nozzles  60  which spouts high pressure water are provided in the screen  22 . 
         [0105]      FIG. 6  is an example of a longitudinal section view of the screen  22  according to the third embodiment of the present invention. 
         [0106]    In the example of  FIG. 6 , the nozzles  60 , to which the high pressure water is supplied via headers  62 , are provided on the side surface of the openings  30  of the screen  22 . The water supply pipe  42 , through which the high pressure water is supplied to the ash hopper water-supply pipe  28 , is branched, and is connected to the header  62 . 
         [0107]      FIG. 7  is a longitudinal section view of the screen according to a modification example of the third embodiment. 
         [0108]    In the example of  FIG. 7 , the nozzles  60 , to which the high pressure water is supplied via the headers  62 , are provided on the top face of the screen  22 . 
         [0109]    In addition, the time interval of the emission of the high pressure water from the nozzles  60  may be the same as the time interval of the movement of the spreader  24 , or the emission of the high pressure water may be intermittently or continuously performed regardless of the time interval of the movement of the spreader  24 . 
         [0110]    In the slag crusher  20  according to the third embodiment, since the high pressure water is spouted to particles of the slag  14  combined by cross-linking, the combination by the cross-linking is cut. Accordingly, the accumulated slag  14  is easily fluidized. 
         [0111]    Moreover, since the pressure water is spouted from the lower portion of the screen  22  toward the upper portion, it is possible to prevent the slag  14  from being accumulated on the top face of the screen  22 , and it is possible to easily and uniformly spout the pressurized liquid to the accumulated slag  14 . 
       Fourth Embodiment 
       [0112]    Hereinafter, a fourth embodiment of the present invention will be described. 
         [0113]    Since the configuration of the gasifier  10  according to the fourth embodiment is the same as the configuration of the gasifier  10  according to the first embodiment shown in  FIG. 1 , descriptions thereof are omitted. 
         [0114]      FIGS. 8 and 9  are longitudinal section views of the screen  22  according to the fourth embodiment. In addition, in  FIGS. 8 and 9 , the same reference numerals as those of  FIGS. 6 and 7  are assigned to the same configuration portions as those of  FIGS. 6 and 7 , and descriptions thereof are omitted. 
         [0115]    In this screen  22  according to the fourth embodiment, high pressure gas (hereinafter, referred to as “high pressure gas”) instead of the high pressure water is spouted from the nozzles  60 . Accordingly, the headers  62  are connected to the high pressure gas supply pipe  42  through which the high pressure gas is supplied. 
         [0116]    Moreover, the time interval of the emission of the high pressure gas from the nozzles  60  may be the same as the time interval of the movement of the spreader  24 , or the emission of the high pressure gas may be intermittently or continuously performed regardless of the time interval of the movement of the spreader  24 . 
         [0117]    Due to the high pressure water spouted from the nozzles  60  provided in the spreader  24  or the water from the ash hopper water-supply pipe  28 , the top face of the screen  22  is filled with water. 
         [0118]    In addition, in the slag crusher  20  according to the fourth embodiment, since the gas is spouted from the top face of the screen  22  in the state where the top face of the screen  22  is filled with water, air bubbles of the high pressure gas rise from the top face of the screen  22 . The combination of the slag  14  by cross-linking is cut by the rising of the air bubbles. Accordingly, since the slag  14  is fluidized, the slag  14  accumulated on the top face of the screen  22  more easily passes through the openings  30  of the screen  22 . 
       Fifth Embodiment 
       [0119]    Hereinafter, a fifth embodiment of the present invention will be described. 
         [0120]    Since the configuration of the gasifier  10  according to the fifth embodiment is the same as the configuration of the gasifier  10  according to the first embodiment shown in  FIG. 1 , descriptions thereof are omitted. 
         [0121]      FIG. 10  is a top view of the slag crusher  20  according to the fifth embodiment. 
         [0122]      FIG. 11  is a longitudinal section view of the screen  22  and side walls  70  according to the fifth embodiment, and is a sectional view taken along A-A in  FIG. 10 . In addition, in  FIGS. 10 and 11 , the same reference numerals as those of  FIGS. 2 and 3  are assigned to the same configuration portions as those of  FIGS. 2 and 3 , and descriptions thereof are omitted. 
         [0123]    The slag crusher  20  according to the fifth embodiment includes nozzles  72  which spout high pressure water at the side walls  70  of the screen  22  which are erected in parallel with respect to the operating direction of the spreader  24 . 
         [0124]    As shown in  FIG. 11 , for example, the nozzles  72  are provided in the lower portions of the side walls  70 . 
         [0125]    In the slag crusher  20  according to the fifth embodiment, it is possible to easily and uniformly spout the high pressure water to the accumulated slag  14 . In addition, since the nozzles  72  are provided on the side walls  70 , it is possible to easily install the nozzles  72  on the slag crusher  20 . 
         [0126]    In addition, the high pressure water spouted from the nozzles  72  may be also used as the ash hopper water. 
       Sixth Embodiment 
       [0127]    Hereinafter, a sixth embodiment of the present invention will be described. 
         [0128]    Since the configuration of the gasifier  10  according to the sixth embodiment is the same as the configuration of the gasifier  10  according to the first embodiment shown in  FIG. 1 , descriptions thereof are omitted. 
         [0129]    Here, as shown in  FIG. 12 , when the spreader  24  crushes the slag  14 , since the slag  14  is crushed at the lower portion of the spreader  24 , the spreader  24  is plunged forward, a load is generated in the guide rods  37  or the like, and the guide rods  37  are likely to be damaged. 
         [0130]    Accordingly, as shown in  FIGS. 13 to 15 , the slag crusher  20  according to the sixth embodiment is provided with guides  80  which limit the movement direction of the spreader  24 . That is, the guides  80  are provided along the movement direction of the spreader  24 . 
         [0131]    In addition,  FIGS. 13, 14, and 15  respectively are a top view of the slag crusher  20  according to the sixth embodiment, a longitudinal section view when viewed from the side, and a longitudinal section view when viewed from the front side. 
         [0132]    In addition, in the slag crusher  20  according to the sixth embodiment, a pair of two spreaders  24  which face each other is provided, and the pair of spreaders  24  moves on the top face of the screen  22  to crush the slag  14 . 
         [0133]    In addition, in the slag crusher  20  according to the sixth embodiment, for example, two sets of pairs of spreaders  24  are provided on the top face of the screen  22  to be adjacent to each other, and the screen  22  is partitioned between the adjacent spreaders  24  so as to be divided by the partition portion  81 . In addition, a purge nozzle  83  is provided below each of the divided regions (hereinafter, referred to as a “first chamber  82 _ 1 ” and a “second chamber  82 _ 2 ”). As shown in  FIG. 13 , the spreader  24  of a first system and the spreader  24  of a third system are paired with each other, and the spreader  24  of a second system and the spreader  24  of a fourth system are paired with each other. 
         [0134]    In addition, the slag crusher  20  may include three sets or more of pairs of spreaders  24 . In this case, the screen  22  is divided into three or more regions by two or more partition portions  81 . 
         [0135]    As shown in  FIGS. 14 and 15 , the guide  80  is formed of side plates  80 A provided on both side surfaces of the spreaders  24  and an upper plate  80 B provided on the spreaders  24 . 
         [0136]    The upper plate  80 B covers a portion of a movement range of the upper portion of the spreader  24 . In addition, since the partition portion  81  is provided on the side surface of the spreader  24 , the partition portion  81  partitions the screen  22  and has a function of the guide  80 . In addition, the side plates  80 A may be integrated with the side walls  70  of the screen  22 . 
         [0137]    Since the guides  80  are provided, the movement of the spreader  24  is more stabilized. Particularly, since floating of the spreader  24  is prevented by the upper plate  80 B, it is possible to prevent the spreader  24  from being plunged forward. 
         [0138]    The purge nozzle  83  is provided below the screen  22  in the vicinity of approximately the center of each of the first chamber  82 _ 1  and the second chamber  82 _ 2 , and allows liquid (for example, water, and hereinafter, referred to as a “purge water”) to flow onto the slag  14  from below the screen  22  to generate a water flow. Among slag  14  positioned on the screen  22 , relatively small slag  14  (light slag  14 ) floats from the screen  22  by the purge water. 
         [0139]    Next, an operation method of the slag crusher  20  according to the sixth embodiment will be described. 
         [0140]    In the slag crusher  20  according to the sixth embodiment, the pair of spreader  24  is alternately operated. That is, the slag crusher  20  of the second system and the fourth system are not operated during the operations of the slag crushers  20  of the first system and the third system. Meanwhile, the slag crushers  20  of the first system and the third system are not operated during the operations of the slag crushers  20  of the second system and the fourth system. 
         [0141]    Moreover, in the slag crusher  20 , before a predetermined spreader  24  is operated, the slag  14  is moved to the regions corresponding to adjacent other spreaders  24  by the water flow from the purge nozzle  83  provided below the region corresponding to the predetermined spreader  24 . 
         [0142]    It will be specifically described with reference to  FIG. 15 . 
         [0143]    Before the spreaders  24  of the first and third systems are operated, the purge water flows from the purge nozzle  83  which is provided below the first chamber  82 _ 1 . The slag  14  on the screen  22  of the first chamber  82 _ 1  is floated by the water flow, and since both sides of the slag crusher  20  are inner walls of the gasifier  10 , the floated slag  14  moves to the second chamber  82 _ 2 . In this case, since the slag  14  which moves to the second chamber  82 _ 2  is relatively small (light) slag  14 , relatively large (heavy) slag  14  remains in the first chamber  82 _ 1 . 
         [0144]    The slag  14  which moves to the second chamber  82 _ 2  falls from the openings  30  of the screen  22  of the second chamber  82 _ 2 . 
         [0145]    Meanwhile, the slag  14  which remains in the first chamber  82 _ 1  is crushed by the operations of the spreaders of the first and third systems and falls from the openings  30  of the screen  22  of the first chamber  82 _ 1 . 
         [0146]    In addition, after the slag crusher  20  operates the spreaders  24  of the first and third systems, the slag crusher  20  operates the spreaders  24  of the second and fourth systems. In this case, before the spreaders  24  of the second and fourth systems are operated, the purge water flows from the purge nozzle  83  provided below the second chamber  82 _ 2 , the slag  14  on the screen  22  of the second chamber  82 _ 2  moves to the first chamber  82 _ 1 , and thereafter, the spreaders  24  of the second and fourth systems are operated. 
         [0147]    In this way, in the slag crusher  20  according to the sixth embodiment, small slag  14  is made to flow to the regions corresponding to other spreaders  24  by the water flow from the purge nozzle  83  and falls from the screen  22 . In addition, since the operating spreader  24  crushes relatively large slag  14  which has not been made to flow by the water flow, it is possible to prevent large slag  14  from remaining on the screen  22 . 
       Seventh Embodiment 
       [0148]    Hereinafter, a seventh embodiment of the present invention will be described. 
         [0149]    Since the configuration of the gasifier  10  according to the seventh embodiment is the same as the configuration of the gasifier  10  according to the first embodiment shown in  FIG. 1 , descriptions thereof are omitted. In addition, in the slag crusher  20  according to the seventh embodiment, a pair of two spreaders which face to each other is provided, and the spreaders  24  move on the top faces of the pair of the screens  22  to crush the slag  14 . 
         [0150]    Here,  FIG. 16  is a longitudinal section view for explaining a remaining state of the slag  14 . 
         [0151]    As shown in  FIG. 16 , if a gap between the lowest protrusion portion  40  and the screen  22  is generated even when the spreaders  24  move, the slag  14  may remain in the gap. 
         [0152]    Accordingly, as shown in  FIGS. 17A and 17B , the lower end portion of each of the spreaders  24  according to the seventh embodiment includes a protrusion  90  which is formed to come into surface-contact with a surface, which faces the spreader  24  when the spreader  24  moves, in the width direction. For example, the protrusion  90  is formed in a rectangular parallelepiped shape which extends in the width direction of the spreader  24 . 
         [0153]    In addition,  FIGS. 17A and 17B  are longitudinal section views when the slag crusher  20  according to the seventh embodiment is viewed from the side,  FIG. 17A  shows a state before the spreaders  24  move, and  FIG. 17B  shows a state after the spreaders  24  move. 
         [0154]    In addition, as shown in  FIG. 17B , if the spreaders  24  move, since the surfaces of the protrusions  90  of the spreaders  24  which face each other come into surface-contact with each other in the width direction, there is no gap between the spreaders  24  facing each other. 
         [0155]    Accordingly, in the slag crusher  20  according to the seventh embodiment, since it is possible to more reliably crush the slag  14  on the screen  22 , it is possible to prevent large slag  14  from remaining on the screen  22 . 
         [0156]    Hereinbefore, the present invention is described using the embodiments. However, the technical scope of the present invention is not limited to the scope described in the embodiments. Various modifications or improvements are added to the embodiments within a scope which does not depart from the gist of the present invention, and aspects to which modifications or improvements are added are also included in the technical scope of the present invention. In addition, the plurality of embodiments may be combined. 
         [0157]    For example, in the first to fifth embodiments, the aspect is described, in which the spreader  24  and the receiving plate  38  face each other and the spreader  24  moves toward the receiving plate  38 . However, the present invention is not limited to this, and an aspect may be adopted in which the spreader  24  is provided instead of the receiving plate  38  and a pair of spreaders  24  moves on the top face of the screen  22  to crush the slag  14 . 
         [0158]    Moreover, in the sixth and seventh embodiments, the aspect is described, in which the spreaders  24  face each other and the pair of spreaders  24  moves on the top face of the screen  22  to crush the slag  14 . However, the present invention is not limited to this, and an aspect may be adopted in which the spreader  24  and the receiving plate  38  face each other and the spreader  24  moves toward the receiving plate  38 . 
         [0159]    Moreover, in the sixth and seventh embodiments, the slag crusher  20  may include the nozzles  26 ,  60 , and  72  described in the first to fifth embodiments, and the nozzles  26 ,  60 , and  72  may appropriately spout high pressure water or high pressure gas. For example, in a case where the spreader  24  is not operated, the nozzles  26 ,  60 , and  72  spout high pressure water or high pressure gas. 
         [0160]    Moreover, in the above-described embodiments, the aspect in which water or gas flows through the nozzles  26 ,  60 , and  72  and the purge nozzle  83  is described. However, purity of water is not particularly limited, and an aqueous solution, a solution, or the like may be adopted so as to easily discharge the slag  14 . In addition, for example, the gas is air or an inert gas (nitrogen gas, argon gas, or the like). However, the gas is not particularly limited. 
       REFERENCE SIGNS LIST 
       [0000]    
       
         
           
               10 : gasifier 
               12 : combustor 
               14 : slag 
               20 : slag crusher 
               22 : screen 
               24 : spreader 
               24 A: inclined surface 
               26 : nozzle 
               30 : opening 
               60 : nozzle 
               70 : side wall 
               72 : nozzle 
               80 : guide 
               81 : partition portion 
               83 : purge nozzle