JP2009263498A - Coal-gasification power generation system and method for eliminating mercury in coal-gasification power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coal-gasification power generation system which can curtail as much as possible the mercury discharging into the atmosphere, by recovering the mercury contained in the coal-gasification gas. <P>SOLUTION: The coal-gasification power generation system, provided with a gasification furnace 2 for producing the coal-gasification gas by the gasification of coal, a dust collection apparatus 5, which is arranged at the downstream side of the gasification furnace 2 and recovers the coal char in the coal-gasification gas, a gas turbine 10 of power generation facilities which is arranged at the downstream side of the dust collection apparatus 5 and burns the coal-gasification gas as a fuel, and a chimney 15 for discharging an exhausted gas from the gas turbine 10 into the atmosphere, is characterized in that the system is also provided at the downstream side of the gas turbine 10 before the chimney 15 with a bag filter 16, and the coal char recovered in the dust collection apparatus 5 is fed into the above exhausted gas at the upstream side of the bag filter 16, and recovered by the bag filter 16. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coal gasification power generation system and a method for removing mercury in the coal gasification power generation system, and is particularly useful when applied to the removal of mercury, which is a trace element contained in coal gasification gas.

  Coal exists in a large area of the world, has a large recoverable reserve and is stable in price, so it has high supply stability and low price per calorific value. For this reason, coal-fired power generation plays an important role in securing energy and stabilizing energy prices.

  One of the power generation methods using coal as fuel is IGCC (Integrated Coal Gasification Combined Cycle). In coal gasification combined cycle power generation, coal is gasified by a coal gasification power generation system, and the resulting coal gasification gas is purified and burned in a combustor, so that the gas turbine is rotationally driven by the combustion gas from the combustor. To generate electricity. At the same time, in addition to the power generation by the gas turbine, the steam turbine is rotationally driven by the steam obtained by recovering the heat of the exhaust gas of the gas turbine to generate power.

  A coal gasification power generation system in such a coal gasification combined power generation includes a gasification furnace that gasifies without completely burning coal, and a gas purification facility that performs desulfurization of the coal gasification gas generated in the gasification furnace. The refined coal gasification gas is supplied to a gas turbine or the like of a power generation facility to perform a predetermined work. The exhaust gas discharged from the gas turbine or the like after being combusted by the gas turbine or the like and discharged from the gas turbine or the like is discharged into the atmosphere through the chimney.

  Here, the coal gasification gas contains trace amounts of various harmful elements. Mercury is one of such trace elements, but conventionally, its emission into the atmosphere via exhaust gas has not been particularly regulated. However, it is desirable to reduce mercury in exhaust gas as much as possible from the viewpoint of environmental conservation.

  There exists patent document 1 as a well-known technique which discloses the purification system including the process of removing the volatile trace element in coal gasification gas. This discloses a technique of using coal ash discharged from the gasification furnace as a scavenger in order to remove volatile trace gas contained in the coal gasification gas generated in the gasification furnace. It is not intended to collect mercury. Moreover, since patent document 1 aims at adsorption | suction of the element in the volatile trace gas in coal gasification gas with much sulfur content from a gasification furnace to a desulfurization process, it cannot remove mercury in this atmosphere.

  On the other hand, Patent Document 2 can be cited as a publicly known document for recovering mercury in exhaust gas. This is a technology that adsorbs and recovers mercury with particulate ash containing unburned carbon, but it is a technology that recovers mercury in the exhaust gas from a waste incineration facility and is not related to a coal gasification power generation system.

JP 2000-38589 A Japanese Examined Patent Publication No. 7-38935

  In view of the above-described conventional technology, the present invention provides a coal gasification power generation system and a coal gasification power generation system capable of recovering mercury contained in coal gasification gas and reducing mercury discharged into the atmosphere as much as possible. An object is to provide a method for removing mercury.

The present invention that achieves the above object is based on the findings of the following experiment. Generally, in a coal gasification power generation system, coal char which is coal fine particles contained in coal gasification gas generated in a gasification furnace is collected by a dust collecting means on the downstream side of the gasification furnace. This is because the coal char containing unburned content is returned to the gasifier as part of the raw material. Accordingly, the present inventors have come up with the idea of using the recovered coal char not only as a raw material but also as a mercury adsorbent, and conducted an experiment to investigate the adsorption characteristics of mercury by the coal char. The experimental conditions are as shown in Table 1. That is, a change in mercury concentration with time by bringing a gas having a predetermined gas composition containing mercury (Hg) having a concentration of 9.4 to 9.6 μg / m ³ at the reactor inlet into contact with a predetermined amount of coal char. Was measured. In addition, the gas composition in this case simulated the exhaust gas of the power generation equipment in the coal gasification power generation system to the gas composition shown in Table 1, and the coal char was also the amount shown in Table 1.

  Here, the leftmost column condition in Table 1 corresponds to the characteristic of FIG. 1, the middle column condition corresponds to the characteristic of FIG. 2, and the leftmost column condition corresponds to the characteristic of FIG. FIG. 1 is a characteristic diagram when contact between a gas containing hydrogen chloride (HCl) and coal char is started at timing A, and FIG. 2 is a timing of contact between a gas not containing hydrogen chloride (HCl) and coal char. FIG. 3 is a characteristic diagram when starting at B, and FIG. 3 starts contact of a gas not containing hydrogen chloride (HCl) with coal char at timing C and at timings D, E, and F for 2 sec, 10 sec, and 30 sec, respectively. It is a characteristic view at the time of inject | pouring hydrogen chloride. In the experiment shown in FIG. 3, the chlorine gas is supplied in a spike shape by changing the supply time so that the evaluation when chlorine gas is injected can be performed at the same time.

  Referring to FIG. 1, it can be seen that in a gas containing hydrogen chloride, mercury can be almost completely removed by contact with coal char. Referring to FIG. 2, although not as much as in the case shown in FIG. 1, it can be seen that about 50% of mercury can be removed even without hydrogen chloride. Referring to FIG. 3, it can be seen that a larger amount of coal char can remove more mercury than the case shown in FIG. It can also be seen that the mercury removal effect is remarkably improved at the timings D, E, and F at which hydrogen chloride is intermittently injected, and that the longer the injection time, the more effective.

  The experimental results shown in FIGS. 1 to 3 indicate that mercury in the exhaust gas can be adsorbed if a part of the coal char returned to the gasification furnace is extracted and supplied to the exhaust gas of the power generation facility. . And it has shown that the case where chlorine gas is contained in exhaust gas can adsorb mercury more effectively, and the amount of coal char can adsorb mercury more effectively.

Based on this finding, the first aspect of the present invention is:
A gasification furnace for gasifying coal to generate coal gasification gas; a first dust collecting means for recovering coal char in the coal gasification gas on the downstream side of the gasification furnace; A power generation facility for generating power using the coal gasification gas as fuel downstream of the dust means; and a discharge means for discharging the exhaust gas of the coal gasification gas used for power generation in the power generation facility to the atmosphere. A coal gasification power generation system,
A second dust collecting means is provided downstream of the power generation facility and the discharging means, while the coal char recovered by the first dust collecting means is disposed on the upstream side of the second dust collecting means. The coal gasification power generation system is characterized in that it is supplied to the inside and recovered by the second dust collecting means.

  According to this aspect, the coal char in the coal gasification gas recovered by the first dust collecting means on the downstream side of the gasification furnace is supplied into the exhaust gas after being supplied to the power generation facility, and the coal The char can be captured and recovered downstream by the second dust collecting means.

The second aspect of the present invention is:
In the coal gasification power generation system described in the first aspect,
In the coal gasification power generation system, halogenated gas is supplied to the second dust collecting means.

  According to this aspect, the mercury adsorption by the coal char can be further promoted by supplying the halogenated gas.

The third aspect of the present invention is:
In the coal gasification power generation system described in the second aspect,
In the coal gasification power generation system, the halogenated gas is mixed with a backwash gas for backwashing the second dust collecting means.

  According to this aspect, the halogenated gas can be supplied most rationally.

The fourth aspect of the present invention is:
In the coal gasification power generation system described in the second aspect or the third aspect,
In the coal gasification power generation system, the halogenated gas is hydrogen chloride gas.

  According to this aspect, the most economical halogenated gas can be supplied.

According to a fifth aspect of the present invention,
In the coal gasification power generation system according to any one of the first to fourth aspects,
The first dust collecting means has a cyclone and a filter connected in series in order from the upstream side, and the coal char of a large particle size recovered by the cyclone occupying the coal char supplied into the exhaust gas. The coal gasification power generation system is characterized in that the ratio between the amount and the amount of coal char with a small particle size recovered by the filter can be adjusted.

  According to this aspect, each of the coal char having a large particle diameter that is less likely to cause clogging of the second dust collecting means and the coal char having a small surface area that has a large surface area per unit weight and excellent mercury adsorption ability are provided. It can be used properly considering its features.

The sixth aspect of the present invention is:
In the coal gasification power generation system according to any one of the first to fifth aspects,
In the coal gasification power generation system, the coal char recovered by the second dust collecting means is configured to be supplied and circulated again into the exhaust gas upstream of the second dust collecting means. is there.

  According to this aspect, the coal char adsorbed with the mercury collected by the second dust collecting means can be sent to final disposal in a state where the mercury concentration is increased to some extent.

The seventh aspect of the present invention is
In the coal gasification power generation system according to any one of the first to sixth aspects,
A coal gasification power generation system characterized in that coal char is also supplied from the first dust collecting means to the coal gasification gas in a flue gas treatment facility that performs flue gas treatment of coal gasification gas after desulfurization. is there.

  According to this aspect, mercury can be recovered even in the flue gas treatment facility, and accordingly, the amount of mercury discharged from the coal gasification power generation system into the atmosphere can be reduced.

The eighth aspect of the present invention is
The coal char in the coal gasification gas is recovered by the first dust collecting means on the downstream side of the gasification furnace that gasifies the coal to generate the coal gasification gas, and supplied to the power generation facility for power generation. The coal char recovered by the first dust collecting means is supplied into the exhaust gas of the coal gasification gas later, and the mercury in the exhaust gas is adsorbed to the coal char and recovered by the second dust collecting means. The present invention resides in a method for removing mercury in a coal gasification power generation system.

  According to this aspect, by supplying the coal char into the exhaust gas after being subjected to power generation by the power generation facility, the mercury in the exhaust gas can be adsorbed and removed by the coal char.

  According to the present invention, the coal char in the coal gasification gas recovered by the first dust collecting means on the downstream side of the gasification furnace is supplied into the exhaust gas after being subjected to power generation by the power generation facility, and the coal The char can be captured and recovered downstream by the second dust collecting means. As a result, mercury in the exhaust gas can be satisfactorily removed while adsorbed on the coal char, and leakage of mercury into the atmosphere can be prevented beforehand.

  Hereinafter, the best mode for carrying out the present invention will be described. In addition, description of this embodiment is an illustration and this invention is not limited to the following forms.

  FIG. 4 is a block diagram showing a coal gasification power generation system according to an embodiment of the present invention. As shown in the figure, in the coal gasification power generation system, coal pulverized by the pulverizer 1 is transferred to the gasification furnace 2 for gasification. At this time, air is separated into oxygen gas and nitrogen gas by an air separation device (ASU) 3, and oxygen and nitrogen gas are supplied to the gasifier 2. Nitrogen gas functions as a carrier gas for coal. The gas purification equipment cools the gas with a gasification gas cooler (syngas cooler) 4, removes the dust with a dust collector 5, passes through a gas gas heater 6, and is contained in the gasification gas (syngas, reducing gas) with a water washing tower 7. After the hydrogen sulfide gas is removed by washing with water, it is desulfurized by the desulfurization tower 8 and cooled by the gas gas heater 6. The gas purified by the gas purification equipment is combusted in the combustor 9, and the gas turbine 10 is driven by the combustion gas. As a result, the generator 11 generates power. At this time, combustion air compressed by the compressor 12 is supplied to the combustor 9. The exhaust gas that has finished its work in the gas turbine 10 is recovered by the waste heat recovery boiler 14 and then discharged into the atmosphere via the chimney 15 as a discharge means. The steam generated in the waste heat recovery boiler 14 as a result of heat exchange with the exhaust gas is supplied to the steam turbine 13 to rotate it. That is, the generator 11 is rotationally driven using the gas turbine 10 and the steam turbine 13 as prime movers.

  In this embodiment, a bag filter 16 as a second dust collecting means is arranged between the waste heat recovery boiler 14 and the chimney 15 on the downstream side, and the dust collector 5 as the first dust collecting means. A part of the coal char recovered in step 1 is supplied into the exhaust gas upstream of the bag filter 16 as the second dust collecting means. As a result, the mercury in the exhaust gas can be adsorbed on the coal char, and the coal char in this state can be recovered by the bag filter 16. The dust collector 5 in this embodiment is composed of a cyclone 5A and a filter 5B connected in series in order from the upstream side, and returns the coal char recovered in each to the gasification furnace 2, and a part of each in the exhaust gas. To supply. Here, in the cyclone 5A, coal char having a relatively large particle size is recovered, while in the filter 5B, coal char having a relatively small particle size is recovered. When coal char with a large particle size is supplied to the exhaust gas, the possibility of clogging in the downstream bag filter 16 is less than for coal char with a small particle size. On the other hand, since coal char with a small particle size has a large surface area per unit weight, it is considered that the mercury adsorption capacity is superior to that of coal char with a large particle size when supplied into exhaust gas. Here, the coal char discharged from the filter 5B is supplied to the upstream side of the bag filter 16 or returned to the gasification furnace 2, and the coal char discharged from the cyclone 5A is mainly used as the bag filter. 16 is adjusted to supply to the upstream side. Thus, the mercury concentration in the exhaust gas is monitored, and when the mercury concentration is low, the coal char is supplied into the exhaust gas only from the cyclone 5A and the filter 5B or the cyclone 5A. The operation is such that the amount of coal char is increased and supplied into the exhaust gas. However, it is not limited to this driving method.

  Further, the bag filter 16 may be configured to supply hydrogen chloride gas. This is because the mercury adsorption performance by the coal char is remarkably improved when hydrogen chloride gas is injected, as is clear by comparing the experimental results shown in FIG. 1 and the experimental results shown in FIG. Here, it is desirable to keep the hydrogen chloride gas to be injected as small as possible. This is to prevent unreacted chlorine gas from being discharged into the atmosphere through the chimney 15.

  Here, the bag filter 16 is regularly backwashed to prevent clogging. Backwashing restores the removal performance as a filter by flowing cleaning gas from the opposite side of the normal gas flow and blowing away dust such as coal char accumulated in the filter over time, reducing pressure loss. Work for. Air or nitrogen gas is widely used as the backwash gas. Therefore, it is considered optimal that hydrogen chloride gas is mixed into the backwash gas and injected into the bag filter 16 during backwashing. In this case, the injection amount is more preferably controlled according to the detected mercury concentration in the exhaust gas.

  Note that the coal char recovered by the bag filter 16 may be supplied again into the exhaust gas and circulated on the upstream side of the bag filter 16. As a result, final disposal by collecting coal char can be performed in a state where mercury concentrated to some extent is adsorbed.

  Furthermore, wet desulfurization is performed in the gas purification equipment in this embodiment. That is, the coal gasification gas is first washed with the water washing tower 7, and then the washed coal gasification gas is desulfurized with the desulfurization tower 8. In such wet desulfurization, desulfurized coal gasification gas exiting the regeneration tower 17 is discharged into the atmosphere through a filter 18 constituting a smoke exhausting facility. Therefore, by supplying coal char to the upstream side of the filter 18, mercury of the coal gasification gas exhausted from the filter 18 can be adsorbed and recovered. That is, such a configuration can also remove secondary mercury, which can contribute to an improvement in overall mercury removal efficiency.

  As described above, according to the present embodiment, the coal char in the coal gasification gas recovered by the dust collector 5 on the downstream side of the gasification furnace 2 is supplied into the exhaust gas after being subjected to power generation by the power generation facility, This coal char can be captured and recovered by the bag filter 16 downstream. As a result, mercury in the exhaust gas can be satisfactorily removed while adsorbed on the coal char, and leakage into the atmosphere can be prevented beforehand. Here, since coal char is supplied in the exhaust gas which hardly contains the sulfur content which burned coal gasification gas after desulfurization, mercury adsorption by coal char is performed favorably.

  FIG. 4 shows a coal gasification power generation system when wet desulfurization is performed, but the coal gasification power generation system according to the present invention may be a coal gasification power generation system adopting a dry desulfurization method. This is shown in FIG. As shown in FIG. 5, the coal gasification power generation system has many components that are the same except that a dry desulfurization method is adopted. Therefore, the same parts as those in FIG. A duplicate description is omitted. In the coal gasification power generation system, there is no coal gasification gas that is sent from the dry-type desulfurization device 19 to the flue gas treatment, so a part of the coal char is supplied from the dust collector 5 only downstream of the waste heat recovery boiler 14. Then, the bag filter 16 is configured to collect.

  Even in this case, mercury in the exhaust gas is recovered just like the case shown in FIG. 4, and mercury discharged into the atmosphere through the chimney 15 can be removed as much as possible.

  In addition, although the power generation equipment in the said embodiment has a gas turbine, of course, it does not restrict to this. This can be applied in the same way to power generation equipment that uses a gas engine as a prime mover and power generation equipment that has a fuel cell.

  Further, in the above embodiment, hydrogen chloride gas is supplementarily injected, but it is not always necessary to inject it when the hydrogen concentration is low. This is because a sufficient hydrogen removal effect may be obtained even without implantation. Furthermore, the halogen gas is not limited to hydrogen chloride. For example, hydrogen bromide and hydrogen fluoride can be applied.

  It can be effectively used in the industrial field where power is supplied using coal gasification equipment.

It is a characteristic view which shows the mercury removal characteristic at the time of making the gas containing hydrogen chloride (HCl) and coal char contact. It is a characteristic view which shows the mercury removal characteristic at the time of making the gas which does not contain hydrogen chloride (HCl), and coal char contact. It is a characteristic view which shows the mercury removal characteristic at the time of making the gas which does not contain hydrogen chloride (HCl), and coal char contact. It is a block diagram which shows the coal gasification gas power generation system which concerns on embodiment of this invention. It is a block diagram which shows the coal gasification gas power generation system which concerns on other embodiment of this invention.

Explanation of symbols

2 Gasifier 5 Dust collector (first dust collector)
5A cyclone 5B filter 10 gas turbine 11 generator 15 chimney (discharge means)
16 Filter (second dust collecting means)
18 Filter (smoke treatment facility)

Claims (8)

A gasification furnace for gasifying coal to generate coal gasification gas; a first dust collecting means for recovering coal char in the coal gasification gas on the downstream side of the gasification furnace; A power generation facility for generating power using the coal gasification gas as fuel downstream of the dust means; and a discharge means for discharging the exhaust gas of the coal gasification gas used for power generation in the power generation facility to the atmosphere. A coal gasification power generation system,
A second dust collecting means is provided downstream of the power generation facility and the discharging means, while the coal char recovered by the first dust collecting means is disposed on the upstream side of the second dust collecting means. A coal gasification power generation system characterized by being supplied to the inside and recovered by the second dust collecting means. In the coal gasification power generation system according to claim 1,
A coal gasification power generation system characterized in that a halogenated gas is supplied to the second dust collecting means. In the coal gasification power generation system according to claim 2,
The coal gasification power generation system characterized in that the halogenated gas is mixed with a backwash gas for backwashing the second dust collecting means. In the coal gasification power generation system according to claim 2 or claim 3,
The coal gasification power generation system, wherein the halogenated gas is hydrogen chloride gas. In the coal gasification power generation system according to any one of claims 1 to 4,
The first dust collecting means has a cyclone and a filter connected in series in order from the upstream side, and a coal char having a large particle size recovered by the cyclone occupying in the coal char supplied into the exhaust gas. A coal gasification power generation system characterized in that the ratio between the amount and the amount of coal char with a small particle size recovered by the filter can be adjusted. In the coal gasification power generation system according to any one of claims 1 to 5,
The coal gasification power generation system is configured such that the coal char recovered by the second dust collecting means is supplied and circulated again into the exhaust gas upstream of the second dust collecting means. In the coal gasification power generation system according to any one of claims 1 to 6,
A coal gasification power generation system, characterized in that coal char is also supplied from the first dust collecting means to the coal gasification gas in a flue gas treatment facility that performs flue gas treatment of coal gasification gas after desulfurization. The coal char in the coal gasification gas is recovered by the first dust collecting means on the downstream side of the gasification furnace that gasifies the coal to generate the coal gasification gas, and supplied to the power generation facility for power generation. The coal char recovered by the first dust collecting means is supplied into the exhaust gas of the coal gasification gas later, and the mercury in the exhaust gas is adsorbed to the coal char and recovered by the second dust collecting means. A method for removing mercury in a coal gasification power generation system characterized by the above.

Images