Gasification system and method for operating gasification furnace

Abstract

To provide a gasification system and an operational method of a gasification furnace, that can suitably control a gasification reaction.SOLUTION: A gasification system comprises: a gasification furnace 1 that heats a gas raw material (wood chips) M as a carbon source together with a gasifying agent (air A, steam V) to generate a gasified gas G; combustion equipment (generator 2, tar combustion device 15) that burns fuel (gasified gas G, tar T) to generate an exhaust gas E; and an exhaust gas supply flow channel 25 that collects an exhaust gas E generated from the combustion equipment 2, 15 and supplies the exhaust gas to the gasification furnace 1, wherein the gasification system is configured to be able to control an amount of oxygen supplied to the gasification furnace 1 by supplying the exhaust gas E generated from the combustion equipment 2, 15 to the gasification furnace 1 as the gasifying agent.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a technology for producing gasification gas from a carbon source such as woody biomass, and more particularly to a system for controlling a gasification reaction in a gasification furnace and a method for operating such a gasification furnace. [Background technology]

[0002] Fig. 4 shows an example of a conventional general gasification system. In this example, a biomass power generation system is assumed in which wood chips are used as a gas raw material M, which is a carbon source for gasification gas, and the wood chips M are heated together with a gasifying agent in a gasification furnace 1 to obtain gasification gas G by pyrolysis, and the gasification gas G is combusted in an engine generator 2 (hereinafter simply referred to as "generator 2") to generate power.

[0003] Wood chips M are thrown from above a hopper 4 by a chip crane 3 , transported to the gasification furnace 1 by a conveyor 5 connected to the outlet of the hopper 4 , and thrown into the gasification furnace 1 .

[0004] Here, an upflow type gasifier is assumed as the gasifier 1. Wood chips M as gas raw material are fed into the gasifier 1 through a raw material inlet 1a provided at the top, while air A and steam V as gasifying agents are fed into the gasifier 1 through a gasifying agent supply inlet 1b provided at the bottom.

[0005] Air A as a gasifying agent is sent to the gasifier 1 through the gasifying agent supply path 1c by the blower 6. The gasifying agent supply path 1c, which runs from the blower 6 to the gasifying agent supply port 1b, branches into two paths along the way, one of which is provided with a humidifier 7. In the humidifier 7, steam V as a gasifying agent is added to the air A. In this way, the air A sent out from the blower 6 is supplied to the gasifier 1 with an appropriate amount of steam V mixed in it.

[0006] Of the gases (air A and steam V as gasifying agents) supplied to the gasifying agent supply port 1b, the oxygen reacts with a part of the wood chips M in the lower layer of the furnace, causing them to burn. The heat generated by the combustion causes some of the components of the wood chips M to pyrolyze, generating gasification gases that include carbon monoxide, gaseous hydrogen, methane, etc.

[0007] The generated gasification gas G is extracted from a gas outlet 1d provided at the top of the gasification furnace 1 and sent to a cooler 8 provided at the rear of the gasification furnace 1. As the gasification gas G is cooled, the water vapor and tar contained in the gasification gas G are condensed and removed from the gasification gas G. The gasification gas G from which the water vapor and tar have been removed is then sent to a dust collector 9, where liquid droplets and particles remaining in the gasification gas G are removed.

[0008] The tar T condensed in the cooler 8 and the tar T collected in the dust collector 9 are sent to a tar separator 10. The treatment of the tar T after being sent to the tar separator 10 will be described later.

[0009] The gasification gas G from which tar T and particles have been removed by the cooler 8 and dust collector 9 is sent by a fan 11 to a generator (engine generator) 2 serving as a combustion facility. The generator 2 combusts the gasification gas G to generate electricity, and the generated exhaust gas E flows into an exhaust passage 12 and is discharged from an exhaust stack 13 provided on the outlet side of the exhaust passage 12. A heat exchanger 14 for recovering exhaust heat from the exhaust gas E is provided midway through the exhaust passage 12, and the role of this heat exchanger 14 will be described later.

[0010] In the tar separator 10, the tar T collected in the cooler 8 and the dust collector 9 is separated based on the specific gravity of the components. Among the separated components of the tar T, components with a high specific gravity are sent to the tar combustion device 15. The tar combustion device 15 is a combustion facility that burns the tar T as fuel.

[0011] Among the components of the tar T separated in the tar separator 10, components with a low specific gravity are sent to the light tar concentrator 16, where they are concentrated by evaporation and then sent to the tar combustion device 15 for combustion. Flash steam F generated during the concentration is heated by a steam heater 17 and then sent to the tar combustion device 15.

[0012] The above-mentioned steam heater 17 is installed in the exhaust flow path 18 through which the exhaust gas E generated in the tar combustion device 15 flows, and here the flash steam F is heated by the exhaust heat of the exhaust gas E. In addition, a combustion air heater 19 is installed downstream of the steam heater 17. Air for burning the tar T (combustion air A1) is sent to the combustion air heater 19 by operation of a fan 20, and the combustion air A1 is heated here by the exhaust heat of the exhaust gas E before being supplied to the tar combustion device 15.

[0013] A heat exchanger 21 is provided downstream of the combustion air heater 19 in the exhaust passage 18. The heat exchanger 14 provided in the exhaust passage 12 of the generator 2 and the heat exchanger 21 provided in the exhaust passage 18 of the tar combustion device 15 are connected by a heat medium passage 22, and a heat medium H such as water circulates in the heat medium passage 22 to recover exhaust heat from the exhaust gas E. The heat medium passage 22 is further connected to the light tar concentrating device 16, and the exhaust heat recovered by the heat medium H in the heat exchangers 14, 21 is used to concentrate the tar T in the light tar concentrating device 16.

[0014] A fan 23 is installed downstream of the heat exchanger 21 in the exhaust flow path 18, and the operation of the fan 23 drives the flow of exhaust gas E in the exhaust flow path 18. The exhaust gas E is discharged from an exhaust stack 24 provided on the outlet side of the exhaust flow path 18.

[0015] Incidentally, examples of prior art documents relating to the generation of gasification gas by such a gasification furnace include Patent Document 1 listed below. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] JP 2005-273456 A Summary of the Invention [Problem to be solved by the invention]

[0017] In the gasification system described above, the properties of the wood chips M used as the gas raw material, i.e., the composition of organic matter that constitutes the wood chips M and the moisture content, vary depending on the plant species, growth conditions, storage conditions, etc. In particular, the moisture content has a significant effect on the amount of heat and oxygen required in the gasification process. In other words, the higher the moisture content, the greater the amount of heat required to dry the wood chips M, and the greater the amount of oxygen required to cover that amount of heat. For this reason, from the perspective of supplying the oxygen required for gasification, the required supply amount of air A as a gasification agent varies depending on the moisture content of the wood chips M.

[0018] On the other hand, at the gas outlet 1d of the gasifier 1, it is desirable to keep the pressure of the gasification gas G slightly lower than atmospheric pressure. This is to minimize the possibility of outside air flowing into the flow path of the gasification gas G and to smoothly supply the gasification gas G to the downstream generator 2. Since it is necessary to keep the pressure constant in this way, the supply amount of air A as a gasification agent cannot be changed significantly. As a result, even when the moisture content of the wood chips M is low and the amount of oxygen required for gasification is relatively small, it is necessary to supply air A in excess of the amount of oxygen required for gasification, and the components of the wood chips M are burned by the surplus oxygen (i.e., the carbon content becomes carbon dioxide instead of methane or carbon monoxide), which is one of the factors that hinders improvement of the efficiency of gasification.

[0019] In view of the above circumstances, the present invention aims to provide a gasification system and a method for operating a gasification furnace that can suitably control the gasification reaction. [Means for solving the problem]

[0020] The present invention relates to a gasification furnace that heats wood biomass, a gas raw material as a carbon source, together with a gasifying agent to generate gasification gas; A facility for burning the gasification gas generated in the gasification furnace; a tar combustion device that combusts tar recovered from the gasification gas generated in the gasification furnace; an exhaust gas supply passage that recovers exhaust gas generated from a facility that combusts the gasification gas and exhaust gas generated from the tar combustion device and supplies the exhaust gas to the gasification furnace; The exhaust gas from the exhaust supply passage is supplied to the gasification furnace as a gasifying agent. Enable , The moisture content of the gas feedstock is determined through the temperature distribution inside the gasification furnace. The moisture content is then determined, and the level is judged. increasing the supply of exhaust gas to the gasification furnace when the moisture content is determined to be low; If the moisture content is determined to be high, the supply of exhaust gas to the gasification furnace is reduced, The amount of oxygen supplied to the gasification furnace is controlled. The present invention relates to a gasification system characterized by the above.

[0027] The present invention also provides a gasification furnace for heating a gas raw material, wood biomass, as a carbon source, together with a gasifying agent to generate a gasification gas; A facility for burning the gasification gas generated in the gasification furnace; and a tar combustion device that combusts tar recovered from the gasification gas generated in the gasification furnace, The exhaust gas generated from the facility for burning the gasification gas and the exhaust gas generated from the tar combustion device are collected, providing an exhaust gas supply passage for supplying the exhaust gas to the gasification furnace; The exhaust gas from the exhaust supply passage is supplied to the gasification furnace as a gasifying agent. Enable , The moisture content of the gas feedstock is determined through the temperature distribution inside the gasification furnace. The moisture content is then determined, and the level is judged. If the moisture content is determined to be low, the supply of exhaust gas to the gasification furnace is increased; If the moisture content is determined to be high, the supply of exhaust gas to the gasification furnace is reduced, Controlling the amount of oxygen supplied to the gasification furnace. The present invention relates to a method for operating a gasification furnace, characterized by the above. Effect of the Invention

[0030] According to the gasification system and the gasification furnace operation method of the present invention, it is possible to obtain the excellent effect of suitably controlling the gasification reaction. [Brief description of the drawings]

[0031] [Figure 1] 1 is a block diagram illustrating an example of a gasification system according to an embodiment of the present invention. [Diagram 2] 1 is a graph showing an example of the relationship between the moisture content of a gas raw material and the consumption amount in a conventional example. [Diagram 3] 2 is a flowchart showing an example of the procedure of a method for operating a gasification furnace according to an embodiment of the present invention. [Figure 4] FIG. 1 is a block diagram showing an example of a general gasification system using wood biomass as a gas feedstock. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0033] Fig. 1 shows an example of a gasification system according to the present invention, in which parts with the same reference numerals as in Fig. 4 represent the same items. The basic configuration is similar to the conventional example shown in Fig. 4, and includes a gasification furnace 1 that reacts wood chips M to obtain gasification gas G, and a generator (engine generator) 2 as a combustion facility that burns the gasification gas G produced in the gasification furnace 1 as fuel.

[0034] Wood chips M fed into a hopper 4 by a chip crane 3 are transported by a conveyor 5 and fed into the raw material feed opening 1a of the gasifier 1. Air A and steam V as gasifying agents are supplied from a gasifying agent supply opening 1b provided below the gasifier 1. Air A as a gasifying agent is sent from the gasifying agent supply opening 1b through a gasifying agent supply path 1c by a blower 6. Steam V as a gasifying agent is added to air A as necessary by a humidifier 7 provided midway through the gasifying agent supply path 1c.

[0035] A portion of the oxygen contained in air A as a gasifying agent burns a portion of the wood chips M in the lower part of the furnace, and some of the components of the wood chips M are heated together with the gasifying agent by the combustion heat generated at that time, and are pyrolyzed to generate gasified gas G. The gasified gas G is extracted from a gas outlet 1d provided at the top of the gasification furnace 1 and sent to a cooler 8 in the subsequent stage, where tar T is removed. The gasified gas G from which tar T has been removed is then sent to a dust collector 9, where remaining tar T and particles are removed. The tar T condensed in the cooler 8 and the tar T collected in the dust collector 9 are sent to a tar separator 10.

[0036] The gasification gas G from which tar T and particles have been removed by the cooler 8 and dust collector 9 is sent by a fan 11 to a generator 2 serving as a combustion facility and combusted. The generated exhaust gas E flows into an exhaust passage 12 and is discharged from an exhaust stack 13 provided on the outlet side of the exhaust passage 12.

[0037] In the tar separator 10, the tar T recovered from the gasification gas G in the cooler 8 and dust collector 9 is separated according to the specific gravity of the components, and the components with a high specific gravity are sent to the tar combustion device 15 as a combustion facility and combusted. The components with a low specific gravity are sent to the light tar concentrating device 16, concentrated, and then sent to the tar combustion device 15 and combusted. Flash steam F generated during concentration is heated in a steam heater 17 and sent to the tar combustion device 15.

[0038] A steam heater 17 is installed in the exhaust flow path 18 through which exhaust gas E generated in the tar combustion device 15 flows, and here, flash steam F is heated by the exhaust heat of the exhaust gas E. A combustion air heater 19 is installed downstream of the steam heater 17, and combustion air A1 is sent here by operation of a fan 20, heated by the exhaust heat of the exhaust gas E, and then supplied to the tar combustion device 15.

[0039] Heat exchangers 14, 21 are provided in the exhaust passage 12 and at a position downstream of the combustion air heater 19 in the exhaust passage 18, respectively. The heat exchanger 14 and the heat exchanger 21 are connected by a heat medium passage 22, and a heat medium H such as water circulates within the heat medium passage 22. The heat medium passage 22 is further connected to the light tar concentrating device 16, and the exhaust heat recovered by the heat medium H in the heat exchangers 14, 21 is used for concentrating the tar T in the light tar concentrating device 16.

[0040] A fan 23 is installed downstream of the heat exchanger 21 in the exhaust flow path 18, and the operation of the fan 23 drives the flow of exhaust gas E in the exhaust flow path 18. The exhaust gas E is discharged from an exhaust stack 24 provided on the outlet side of the exhaust flow path 18.

[0041] The above configuration is common to the conventional example shown in Figure 4, but the present embodiment shown in Figure 1 is characterized in that an exhaust supply passage 25 is connected to the exhaust passages 12, 18, and exhaust gas E is recovered from this exhaust supply passage 25 and supplied to the gasification furnace 1 as a gasifying agent.

[0042] The inlet of the exhaust supply passage 25 is connected to a position between the heat exchanger 14 and the exhaust stack 13 in the exhaust passage 12, and is connected to a position between the fan 23 and the exhaust stack 24 in the exhaust passage 18, and each exhaust supply passage 25 merges with each other on the downstream side. The outlet of the exhaust supply passage 25 is connected to the gasifying agent supply passage 1c. An opening / closing valve 26 is provided in the exhaust supply passage 25 so that the exhaust supply passage 25 can be opened and closed. In this way, exhaust gas E can be introduced into the air A flowing through the gasifying agent supply passage 1c as necessary.

[0043] The connection position of the exhaust gas supply passage 25 to the gasifying agent supply passage 1c may be on the upstream side (indicated by a solid line in the figure) or the downstream side (indicated by a dashed line in the figure) of the blower 6. When the exhaust gas supply passage 25 is connected to the downstream side of the blower 6, it is preferable to provide a fan 27 midway so that the exhaust gas E is pressurized and sent to the gasifying agent supply passage 1c.

[0044] In this way, for example, when the moisture content of the wood chips M is high, only air A (or air A and steam V) is supplied to the gasifier 1 as a gasifying agent, and when the moisture content of the wood chips M is low, air A as a gasifying agent is mixed with exhaust gas E containing little oxygen and supplied. By such an operation, it is possible to control the amount of oxygen supplied to the gasifier 1. The oxygen concentration in the air A is generally about 21%, but the oxygen concentration in the exhaust gas E discharged from the generator 2 is, for example, about 10%, and the oxygen concentration in the exhaust gas E discharged from the tar combustion device 15 is, for example, about 4 to 5%. By recovering the exhaust gas E with a low oxygen concentration in this way and supplying it to the gasifier 1 as a gasifying agent, the amount of oxygen supplied can be adjusted without greatly changing the total volume and pressure of the gasifying agent supplied, and therefore without greatly changing the pressure inside the gasifier 1.

[0045] Fig. 2 shows the relationship between the moisture content of the wood chips M and the consumption of the wood chips M in the conventional example shown in Fig. 4. The solid line in the figure shows the theoretical value when gasification is performed by adding the amount of oxygen required for gasification according to the moisture content of the wood chips M when generating electricity at rated output. When considering the consumption of wood chips M to generate the required amount of electricity in the generator 2, it is theoretically thought that the higher the moisture content of the wood chips M, the greater the weight of wood chips M consumed per day (because carbon needs to be burned to evaporate the moisture), and the lower the moisture content, the smaller the weight consumed per day.

[0046] In contrast, the dashed line in the figure shows the relationship between moisture content and consumption of wood chips M when power is generated at rated output in an actual facility. Compared to the theoretical value shown by the solid line, the consumption of wood chips M is higher in areas with low moisture content. This means that even though the required amount of gasification gas G should be able to be generated with a small amount of wood chips M if only the amount of oxygen required for gasification is supplied, as explained above, an excess amount of air A is supplied to maintain pressure, and as a result, carbon that should theoretically be usable as gasification gas is burned by the oxygen contained in the excess air A and turns into carbon dioxide.

[0047] Therefore, by using exhaust gas E with a low oxygen content as the gasification gas as in the present embodiment shown in Figure 1, the total amount of gasifying agent supplied to the gasification furnace 1 can be prevented from fluctuating significantly, and the amount of oxygen supplied can be brought close to an appropriate value while maintaining the pressure at the gas outlet 1d of the gasification furnace 1 close to atmospheric pressure, thereby improving the gasification efficiency when the moisture content of the wood chips M is low.

[0048] In order to carry out the above-mentioned operation, it is desirable to somehow grasp the moisture content of the wood chips M. Several examples of specific methods for this will be described below.

[0049] For example, as shown by the reference numeral 28 in the figure, a temperature sensor is provided in the gasifier 1 as a moisture content monitor, and the moisture content of the wood chips M can be grasped through the temperature inside the furnace. Here, a case where a plurality of temperature sensors 28 are attached at different heights inside the furnace is illustrated. In the case of the upflow type gasifier 1, a gasifying agent containing oxygen is supplied from below, and combustion by oxygen occurs in the lower layer of the wood chips M, so that the temperature inside the furnace is highest at the bottom and decreases from there toward the top. Here, when the moisture content of the wood chips M is high, the heat generated by combustion at the bottom is quickly taken away by the evaporation of moisture as it is transferred upward, so that the temperature drops significantly in the area slightly above the bottom. On the other hand, when the moisture content of the wood chips M is low, the amount of heat used for drying is small, and the high temperature area continues widely up to a relatively high position. Due to such differences in temperature distribution, the moisture content of the wood chips M can be grasped to some extent. Incidentally, instead of such a temperature distribution, the moisture content of the wood chips M may be grasped from the temperature at a certain point or the average value of temperatures measured at a plurality of positions.

[0050] Alternatively, the moisture content of the wood chips M can be determined by measuring the composition of the gasification gas G generated from the wood chips M. When gas is used as fuel in facilities such as power plants, it is common to sample a portion of the fuel gas and analyze its composition for the purpose of determining the amount of heat generated by combustion. FIG. 1 illustrates a sampling unit 29 for analyzing the gasification gas G as a moisture content monitoring unit. In the sampling unit 29, a portion of the gasification gas G from which tar T and particles have been removed by the dust collector 9 is extracted as a sampling gas S, and the composition is analyzed using various methods (for example, a non-dispersive infrared absorption method or a method using a magnetic oxygen concentration meter). The moisture content of the wood chips M can be determined based on the results of the composition analysis of the sampling gas S.

[0051] Alternatively, the moisture content of the wood chips M can also be determined from the consumption of the wood chips M, which are the gas raw material. For example, as shown by the theoretical value indicated by the solid line in FIG. 2, the amount of gas raw material (wood chips M) required to provide a certain amount of heat with the gasification gas G increases as the moisture content increases. Therefore, for example, the chip crane 3 shown in FIG. 1 monitors the consumption of the wood chips M, which are the gas raw material (in this case, the chip crane 3 serves as a raw material consumption monitoring unit). The chip crane 3 can determine the amount of wood chips M fed into the hopper 4 during a certain time period as the consumption. If the consumption of wood chips M is high relative to the amount of power generated by the generator 2 in the downstream stage, it can be determined that the moisture content of the wood chips M is high.

[0052] Of course, a more direct method is to periodically sample the wood chips M, dry them, and determine the moisture content from the difference in weight before and after drying by manual analysis.

[0053] In addition, various other methods are possible for determining the moisture content of the wood chips M. As the principle for determining the moisture content and the configuration of the moisture content monitoring unit, any appropriate principle or configuration can be adopted as long as the moisture content can be determined. In addition, multiple types of devices and equipment may be used in combination as the moisture content monitoring unit.

[0054] Based on the moisture content thus determined, the introduction of the exhaust gas E as a gasification agent can be controlled based on, for example, human judgment. 3,28,29 Depending on the moisture content of the wood chips M determined by this, a person decides whether or not to reduce the amount of oxygen supplied to the gasification furnace 1; if the moisture content is high, the on-off valve 26 is closed and only air A, or air A and water vapor V, are supplied to the gasification furnace 1 as a gasification agent; on the other hand, if the moisture content is low, the on-off valve 26 is opened (and fan 27 is operated) and exhaust gas E is introduced into the gasification furnace 1 as a gasification agent.

[0055] Such an operation may be performed, for example, by setting a certain threshold value for the moisture content, closing the on-off valve 26 if the determined moisture content is equal to or higher than the threshold value, and opening the on-off valve 26 if the moisture content is below the threshold value, or by adjusting the opening degree of the on-off valve 26 depending on the magnitude of the moisture content. In this way, by changing the supply or non-supply of the exhaust gas E as a gasifying agent or the supply amount depending on the moisture content of the gas raw material M, it is possible to optimize the gasification reaction depending on the moisture content.

[0056] In addition, the moisture content of the wood chips M may be automatically linked to the opening and closing of the on-off valve 26. For example, as shown in FIG. 3,28,29 The moisture content obtained by the above process can be input to the control device 31, and the control device 31 can be configured to open / close and control the opening degree of the on-off valve 26 in accordance with the input moisture content.

[0057] The method of operating the gasification furnace in the gasification system as described above can be summarized in a flowchart as shown in FIG.

[0058] First, the moisture content of the wood chips M, which are the gas raw material, is determined (step S1). As described above, the moisture content can be determined by at least one of the moisture content monitoring units 3, 28, 29, or by manual analysis, etc. Next, the system operator or the control device 31 judges whether the determined moisture content is high or not (step S2). Here, the judgment may be made based on whether the moisture content of the wood chips M determined by a certain moisture content monitoring unit, or some numerical value reflecting the moisture content (such as the temperature in the gasification furnace 1, the moisture ratio in the sampled gas S, or the consumption amount of the wood chips M) exceeds a certain threshold value, or, as described above, the moisture content can be determined based on the temperature distribution in the gasification furnace 1.

[0059] If it is determined that the moisture content of the wood chips M is low, the on-off valve 26 is opened and the exhaust gas E is supplied as a gasifying agent to the gasification furnace 1 from the exhaust supply passage 25 (step S3). Here, the supply amount of the exhaust gas E may be further adjusted depending on the moisture content.

[0060] If it is determined in step S2 that the moisture content is high, the on-off valve 26 is closed, and only gases other than the exhaust gas E (air A and water vapor V) are supplied as a gasifying agent (step S4). By operating the gasifier 1 while repeating this process, it is possible to supply an appropriate amount of oxygen for gasifying the wood chips M without causing large fluctuations in the pressure inside the gasifier 1.

[0061] In the embodiment, the case where wood chips are used as the gas feedstock is described, but the present invention is not limited thereto. As long as the gasification furnace is capable of using materials with different moisture contents as the gas feedstock, the present invention can be applied to various gasification systems. In other words, the gas feedstock may be a material containing biomass other than wood chips (e.g., garbage, etc.) or a material other than biomass, such as coal.

[0062] In addition, the combustion equipment is illustrated here as having the generator 2, which is an engine generator that burns the gasification gas G, and the tar combustion device 15 that burns the tar T, but the combustion equipment is not limited to these. Any device or equipment that generates exhaust gas that can be used as a gasifying agent, that is, exhaust gas with a lower oxygen content than air, can be used in the practice of the present invention, regardless of its type or configuration. However, if the above-mentioned combustion equipment (the generator 2 and the tar combustion device 15) that burns the gasification gas G or tar T generated in the gasification furnace 1 as fuel is used as a supply source of exhaust gas, the gasification furnace 1 as a supply destination of the exhaust gas E as a gasifying agent also functions as a supply source of fuel (gasification gas G or tar T) to the combustion equipment, so that the overall configuration of the gasification system can be made compact. In this embodiment, the generator 2 and the tar combustion device 15 are used as the combustion equipment that is the supply source of the exhaust gas E, but only the exhaust gas E generated from one of them may be supplied to the gasification furnace 1 as a gasifying agent.

[0063] In addition, although an upflow type gasifier 1 has been exemplified as the gasifier, the present invention can also be applied to a downdraft type gasifier. However, in a downdraft type gasifier, the gas feedstock is generally dried to a certain degree before being fed into the gasifier, so that the fluctuation in the moisture content of the gas feedstock is not as large as in an upflow type gasifier. The effects of the present invention can be more prominently exhibited when applied to an upflow type gasifier in which the moisture content of the gas feedstock fluctuates greatly, as in the above-described embodiment.

[0064] As described above, the gasification system of the present embodiment comprises a gasification furnace 1 that heats a gas raw material (wood chips) M as a carbon source together with a gasifying agent (air A, steam V) to generate gasification gas G, a combustion equipment (generator 2, tar combustion device 15) that burns a fuel (gasification gas G, tar T) to generate exhaust gas E, and an exhaust supply passage 25 that recovers the exhaust gas E generated from the combustion equipment 2, 15 and supplies it to the gasification furnace 1, and is configured to be able to control the amount of oxygen supplied to the gasification furnace 1 by supplying the exhaust gas E generated from the combustion equipment 2, 15 to the gasification furnace 1 as a gasifying agent.

[0065] In addition, in the operating method of the gasification furnace of the above embodiment, the gasification furnace 1 heats the gas raw material M as a carbon source together with gasifying agents A and V to generate gasification gas G, and recovers exhaust gas E generated from combustion equipment 2, 15 that combusts fuels G and T and supplies it as a gasifying agent to control the amount of oxygen supplied to the gasification furnace 1.

[0066] In this way, the amount of oxygen supplied to the gasification furnace 1 can be adjusted without causing large fluctuations in the pressure inside the gasification furnace 1.

[0067] In addition, the gasification system of this embodiment is equipped with at least one of the following combustion equipment (generator 2) for combusting the gasification gas G generated in the gasification furnace 1, or a tar combustion device 15 for combusting the tar T recovered from the gasification gas G generated in the gasification furnace 1 (both in this embodiment).

[0068] Furthermore, in the operating method of the gasification furnace in this embodiment, the combustion equipment is at least one of equipment (generator 2) that combusts the gasification gas G generated in the gasification furnace 1, and a tar combustion device 15 that combusts the tar T recovered from the gasification gas G generated in the gasification furnace 1 (both in this embodiment).

[0069] In this way, the gasification furnace 1, which is the supply destination of exhaust gas E as a gasifying agent, also functions as a source of fuel (gasification gas G and tar T) to the combustion equipment, making it possible to make the overall configuration of the gasification system compact.

[0070] Moreover, the gasification system of this embodiment is configured to be able to switch the supply of the exhaust gas E to the gasification furnace 1 depending on the moisture content of the gas material M.

[0071] In addition, in the method of operating the gasification furnace of this embodiment, the supply of the exhaust gas E to the gasification furnace 1 is switched depending on the moisture content of the gas raw material M.

[0072] In this way, the supply amount of the exhaust gas E as a gasifying agent can be changed according to the moisture content of the gas raw material M, and the gasification reaction can be optimized according to the moisture content of the gas raw material M.

[0073] Moreover, the gasification system of this embodiment can be configured so that the moisture content of the gas material M can be grasped from the temperature inside the gasification furnace 1.

[0074] Moreover, the gasification system of this embodiment can also be configured so that the moisture content of the gas material M can be grasped through the composition of the gasification gas G generated in the gasification furnace 1.

[0075] Furthermore, the gasification system of this embodiment can also be configured so that the moisture content of the gas raw material M can be grasped through the consumption amount of the gas raw material M.

[0076] In addition, in the gasification system of this embodiment, a raw material selected from biomass, garbage, and coal (in this embodiment, wood chips) is used as the gas raw material M. In this way, in the gasification system using biomass as the gas raw material M, the above-mentioned action and effect can be achieved.

[0077] Therefore, according to the present embodiment, the gasification reaction can be suitably controlled.

[0078] Incidentally, the gasification system and the method of operating the gasification furnace of the present invention are not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention. [Explanation of symbols]

[0079] 1 Gasifier 2 Combustion equipment (generator) 15 Combustion equipment (tar combustion equipment) 25 Exhaust supply passage A Gasification agent (air) G Gasification gas T Tar M Gas raw material (wood chips) V Gasification agent (steam)

Claims

1. a gasification furnace for heating a gas raw material, wood biomass, as a carbon source, together with a gasifying agent to generate a gasified gas; A facility for burning the gasification gas generated in the gasification furnace; a tar combustion device that combusts tar recovered from the gasification gas generated in the gasification furnace; an exhaust gas supply passage that recovers exhaust gas generated from a facility that combusts the gasification gas and exhaust gas generated from the tar combustion device and supplies the exhaust gas to the gasification furnace; The exhaust gas from the exhaust supply passage can be supplied to the gasification furnace as a gasifying agent; The moisture content of the gas raw material is grasped through the temperature distribution in the gasification furnace, and the level of the grasped moisture content is determined; If the moisture content is determined to be low, the supply of exhaust gas to the gasification furnace is increased; If the moisture content is determined to be high, the supply of exhaust gas to the gasification furnace is reduced, The amount of oxygen supplied to the gasification furnace is controlled. A gasification system comprising:

2. a gasification furnace for heating a gas raw material, wood biomass, as a carbon source, together with a gasifying agent to generate a gasified gas; A facility for burning the gasification gas generated in the gasification furnace; and a tar combustion device that combusts tar recovered from the gasification gas generated in the gasification furnace, providing an exhaust gas supply passage for recovering exhaust gas generated from a facility for combusting the gasification gas and exhaust gas generated from the tar combustion device and supplying the exhaust gas to the gasification furnace; The exhaust gas from the exhaust supply passage can be supplied to the gasification furnace as a gasifying agent; The moisture content of the gas raw material is grasped through the temperature distribution in the gasification furnace, and the level of the grasped moisture content is determined; If the moisture content is determined to be low, the supply of exhaust gas to the gasification furnace is increased; If the moisture content is determined to be high, the supply of exhaust gas to the gasification furnace is reduced, Controlling the amount of oxygen supplied to the gasification furnace. A method for operating a gasification furnace comprising the steps of:

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