JP3977890B2 - Gasification power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compound gasification/generation system which is highly safe and has good tolerance of operation. SOLUTION: A composite coal gasification/generation system B is provided with a gasifier 1, a formed gas condenser 2, a deduster 5 composed of a cyclone 3 and a porous filter 4, a desulfurizer 6 and a gas turbine 7 which are arranged in the given order from the upstream side. The turbine 7 is provided with an air extraction system 111 through which the waste gas produced from the turbine 7 is fed into the gasifier 1. The system B is provided with also an air separator 13 to which an air compressor is connected. The nitrogen separated with the separator 13 is fed into the gasifier 1 and the inside of the system, while the oxygen is mixed with the air in the extraction system 111.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gasification power generation system that operates a gas turbine with gasification gas generated from fossil fuel.
[0002]
[Prior art]
Gasification of fossil fuels such as coal to generate flammable gas, and this flammable gas is burned by a gas turbine to generate electricity, and steam generated by the heat exchanger and exhaust heat recovery boiler of this power generation system is also generated. A gasification combined power generation system that is led to a steam turbine and used for power generation is known.
FIG. 8 shows an example of a conventional air-blown coal gasification combined power generation system. The configuration of the main part of the coal gasification combined system A is composed of a gasification furnace 1, a generated gas cooler 2, a cyclone 3 and a porous filter 4 disposed in the annulus portion 1 a in order from the upstream side, The desulfurization device 6 and the gas turbine 7 are arranged in this order.
[0003]
In the gasifier 1, raw coal is introduced from the pulverized coal supply line 101 to the pulverized coal supply device 8, and is supplied to the gasifier 1 through the pulverized coal conveyance line 102. The gasifier 1 brings the raw coal finely pulverized by the pulverized coal supply device 8 into contact with a gasifying agent 9 such as oxygen. Then, the raw coal is combusted and gasified at a high temperature of 1500 to 2000 ° C. to generate a combustible gas, which is discharged to the product gas cooler 2. At this time, the slag generated in the gasification furnace 1 is discharged from the slag discharge line 116 from the lower part of the gasification furnace 1.
In the produced gas cooler 2, the introduced combustible gas including carbon monoxide, hydrogen gas, methane gas and the like is cooled to recover heat, and is discharged to the dust removing device 5 on the downstream side. In the dedusting device 5, coarse particles of solid unreacted char contained in the combustible gas are dedusted by the cyclone 3, and fine particles that could not be dedusted by the cyclone 3 are dedusted by the porous filter 4. Here, the char separated from the combustible gas is collected in the gasification furnace 1 through the char supply line 103 and reused, and the combustible gas dedusted by the dedusting device 5 is sent to the desulfurization device 6. Discharged.
[0004]
In the desulfurization device 6, sulfur contained in the combustible gas is separated, and the combustible gas is discharged to the gas turbine 7 through the combustible gas supply line 104 and the combustion unit 7 b. The gas turbine 7 generates electricity by rotating the turbine using combustible gas as fuel. The exhaust heat recovery boiler 11 disposed on the downstream side of the gas turbine 7 introduces a combustible gas exhaust gas combusted in the gas turbine 7, generates steam with the heat, and discharges the steam to the line 124. . And it discharges | emits to the steam turbine 12 with the vapor | steam which generate | occur | produced in the above-mentioned generated gas cooler 2, makes this operate, and uses it for electric power generation. The steam is cooled by the cooler 12b and is sent to the product gas cooler 2 by the condensate pump 12c.
The compressed air generated by the gas turbine air compressor 7a is also partially introduced into the extraction air system 111, compressed by the extraction air compressor 21 through the regenerative heat exchanger 9 on the upstream side, and then downstream. It passes through the regenerative heat exchanger 10 and is introduced into the gasification furnace 1 through the gasification gas supply line 114.
[0005]
[Problems to be solved by the invention]
The gasification complex system provided with the above extraction air system is used because it has an extraction air booster, and there is no increase in in-house power by the oxygen production apparatus, and power transmission end efficiency is good. Since this extracted air is used when supplying unreacted char to the pressurized gasification furnace, there is a risk that the temperature of oxidation is increased, and there is a drawback that safety is lacking.
On the other hand, because the gasifying agent is air, the furnace is kept at a high temperature in order to melt ash and discharge it stably as slag, and the calorific value of the combustible gas necessary for stable combustion of the gas turbine is constant. In order to satisfy the requirement of ensuring the above level at the same time, the ratio of the amount of fossil fuel and the amount of gasifying agent (in this case, air) should be within the range from the lower limit satisfying the former and the upper limit satisfying the latter. There was a drawback that it was necessary to drive and the driving margin was small. In particular, in the partial load, since the heat loss of the furnace is relatively larger than the rated load, the operation margin tends to be further reduced.
[0006]
Further, conventionally, a part of the combustible gas is branched and pressurized before entering the gas turbine for purging or sealing the equipment in the system or for transporting coal or unreacted char. It was. In order to use this combustible gas, it is necessary to install a cooler in order to reduce in-house power before boosting, as well as a booster compressor, which has the disadvantage that the equipment becomes complicated. In addition, flammable gases generally contain hydrogen sulfide (H ₂ S) derived from sulfur contained in fossil fuels such as coal, moisture, etc., are prone to corrosion, and require strict management of operating temperature, etc. There was a drawback of being.
In addition, the gasification complex system can be supplied with nitrogen as an inert gas used to improve safety, and the operating margin (particularly partial load, where partial load is the rated power output of the generator) By improving the oxygen concentration of the gasifying agent (that is, by increasing the oxygen concentration) in order to improve the required power generation amount (for example, 20-30%) relative to (100%) There is a system equipped with an air separation device (ASU) capable of simultaneously supplying oxygen, which can increase the gas temperature in the furnace and increase the calorific value of the combustible gas.
[0007]
However, a large-capacity air separation device generally used in a gasification power generation system adopts a cryogenic separation method, and cools to an extremely low temperature of the boiling points of oxygen and nitrogen, so that it is difficult to change the load, In addition, there is a drawback that it takes time to start.
The present invention has been made in view of the above problems, and has an air separation device having the advantages of ensuring safety and improving operating margin while maintaining the characteristics of the extraction air system in the power generation system, and An object of the present invention is to provide a gasification power generation system in which the drawbacks associated with an air separation device are eliminated.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a gasification power generation system according to the present invention comprises a gasification furnace for bringing a fossil fuel and a gasifying agent into contact with each other and generating a combustible gas by combustion and gasification, and combustion of the combustible gas. A gasification power generation system comprising: a gas turbine that generates electricity by rotating a turbine; and an extraction air system line that supplies air partially extracted from the gas turbine air compressor as a gasifying agent to the gasification furnace. Provided with an air separation device connected to a raw material air compressor for introducing the atmosphere, a part of the nitrogen separated by the air separation device is introduced into the gasification furnace, and the remaining nitrogen is supplied to the gasification furnace. There is a nitrogen supply line that is introduced into the system between the gas turbines, and an oxygen-enriched air supply line that mixes the separated oxygen into the extraction air system line.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to drawing to the same structure as a prior art example, and the detailed description is abbreviate | omitted.
FIG. 1 shows a gasification combined power generation system B according to the present invention. This differs from the air-blown coal gasification combined system A described in the conventional example of FIG. 8 in that an air separation device 13, a control device 19, and facilities attached thereto are provided. Hereinafter, these apparatuses will be described.
[0010]
An air separation device 13 shown in FIG. 1 is a device that separates nitrogen and oxygen contained in air, and is provided with a raw material air compressor 22 for sucking air from the atmosphere outside the power generation system to suck air. Yes. Of the air separated by the air separation device 13, nitrogen gas is discharged to the nitrogen supply line 113, and oxygen is discharged to the oxygen-enriched air supply line 112.
In the nitrogen supply line 113, the nitrogen gas is compressed by the nitrogen compressor 23 and discharged to the downstream side, and then branches in two directions. That is, a part of the nitrogen gas is used as a pressurized medium or a conveying medium when supplying the pulverized coal supply device 8 and the char to the gasification furnace via the nitrogen control valve 31 or 32, and the remaining nitrogen gas The gas is sent to the downstream side of the product gas cooler 2 in the system via the nitrogen control valve 35, and an amount of nitrogen is flowed through the system so that the oxygen concentration to the gasification furnace is optimal. .
In the oxygen-enriched air supply line 112, the oxygen gas is compressed by the oxygen compressor 24 and discharged to the downstream side, and then mixed with the gas in the extraction air system line 111 through the oxygen control valve 38. In this case, mixing may be performed in the middle of the extraction air system line 111 or the burner tip of the gasification furnace 1.
[0011]
The control device 19 shown in FIG. 2 is for controlling the flow rate of each gas in the extraction air system line 111, the nitrogen supply line 113, and the oxygen-enriched air supply line 112. The flow rate of each gas of the extraction air control valve 27 provided in the air system line 111 is controlled. Flow lines 41 to 50 for detecting the flow rates of the respective gases flowing through the pipe lines are provided in the pipe lines of the respective lines where these control valves are disposed. The control device 19 is connected to the generators 7c and 12a, the pulverized coal supply device 8, the compressors 21 to 26, and the control panels 21a and 26a for controlling them. The char supply line 103 is also provided with a flow meter 51 and a control valve 30 for detecting the char flow rate, and is connected to the control device 19 to control the char flow rate.
[0012]
With such a configuration, the combined gasification power generation system B cools the air exhausted from the gas turbine 7 with the regenerative heat exchanger 9 and compresses it with the extraction air compressor 21, and then passes through the regenerative heat exchanger 10 again. Discharge to the gasifier 1 side. At this time, oxygen separated by the air separation device 13 is mixed with the air in the extraction air system line 111 through the oxygen-enriched air supply line 112. At this time, the flow meter 48 arranged in the oxygen-enriched air supply line 112 detects the flow rate of oxygen gas, and the flow meter 49 arranged in the extraction air system line 111 detects the extraction air gas flow rate. Then, the control device 19 adjusts the throttle amounts of the control valves 38 and 39 and introduces a gas containing oxygen and nitrogen into the gasification furnace 1 at a preferable mixing ratio as the gasifying agent 9. Thereby, combustible gas is efficiently generated.
On the other hand, in the nitrogen supply line 113, the control device 19 similarly detects the flow rate of nitrogen gas by the flow meters 41, 42, 45, adjusts the throttle amount of the control valves 31, 32, 35, and controls the control valves 31, 32. Is adjusted to an appropriate throttle amount for the pulverized coal and char pressurization line 115 or the conveying line 117, and the control valve 35 is adjusted so that all these nitrogen and oxygen mixing ratios are suitable. The aperture amount is adjusted and returned to the line 121.
[0013]
In this embodiment, since the air-blown gasification combined power generation system is employed, the power required for supplying oxygen is small and efficient. Similarly, the power generation system of the present invention equipped with an extraction air system supplies an inert gas used for ensuring safety and improves the acidity concentration of the gasifying agent in order to improve the operating margin. An air separation device is provided. Therefore, the power generation system of the present invention has the advantages of both a power generation system including a bleed air system and a power generation system including an air separation device.
[0014]
Further, the extraction air system is provided with an extraction air compressor that is efficient and has a high load change rate, and a separate air compressor is used for the air separation device that has a low load change rate. Therefore, during partial load, the air separator is operated at a constant load or a gradual load change, so that the oxygen concentration is increased from that at the rated load, and the temperature in the furnace is raised or maintained to stabilize the ash flow. Can be made possible. Further, by returning the remaining nitrogen to the system, it is possible to improve the load change rate while making the calorific value of the combustible gas at the gas turbine inlet almost constant. A conceptual diagram is shown in A and B of FIG.
[0015]
Furthermore, by installing a separate raw material air compressor and nitrogen or oxygen bleed or circulation line in an air separation device with a long start-up time, only the air separation device is started on its own schedule. It is possible to minimize the startup time of the system and minimize startup utilities such as power. That is, it is not necessary to start the gas turbine and the gasifier in accordance with the long start-up time of the air separation device.
[0016]
[Example 1]
FIG. 4 shows one embodiment to which the present invention is applied. In the combined power generation system B shown in FIG. 1, shut-off valves 31 and 32 and flow meters 41 and 42 are installed in the nitrogen line 113 in the pulverized coal supply device 8 and the conduit for the pressurized conveyance of the char. In the present embodiment, in addition to this, a shut-off valve 36 and a flow meter 46 are installed in the backwash line of the char collection filter 4, and the shut-off valve 34 and the flow meter 44 are installed in the annulus line 119 of the gasifier 1. The shut-off valve 37 and the flow meter 47 are installed in the pipe line 123 for the return line to the gas turbine inlet.
As a result, in addition to the safe pressurized conveyance of pulverized coal and char, the filter can be backwashed safely, and the annulus of the gasification furnace 1 is sealed with nitrogen to prevent intrusion of product gas. However, by preventing the accumulation of char, corrosion of the structure in the annulus can be prevented, and the inspection environment can be improved. In the figure, the line connecting the annulus portion 1 a to the downstream side line of the gasifier 1 is a pressure equalizing line 120.
[0017]
[Example 2]
FIG. 5 shows one embodiment to which the present invention is applied. In the present embodiment, the shutoff valve 33 and the flow rate in the quench line 118 for the molten ash particles in the product gas of the gasification furnace 1 are provided in the nitrogen line 113 in addition to the shutoff valves 31 and 32 for pressurized pulverized coal and char. A total of 43 are installed.
As a result, when the outlet temperature of the gasification furnace 1 (for example, the melting point of ash) is high and char adheres to the bank of the downstream product gas cooler 2 and sinter solidifies, it is used as a quench (quenching) gas. Nitrogen is introduced into and mixed in the gasification furnace 1, and it is possible to efficiently reduce the molten particles of ash in the gas together with the gas temperature at the outlet of the gasification furnace 1.
[0018]
[Example 3]
FIG. 6 shows one embodiment to which the present invention is applied. In this embodiment, the nitrogen supply line 113 is provided with a pipe line 125 for a nitrogen bleed line, and the shut-off valve 40 and the flow meter 50 are installed therein. By bleeding part of the nitrogen from this line, it is possible to improve the oxygen enrichment effect.
For example, when the operating state in the furnace is the same as before the bleed, the nitrogen amount is reduced using the bleed line when returning the nitrogen to the gas turbine inlet (pipe having the shut-off valve 37) by the balance amount. As a result, the calorific value of the product gas at the gas turbine inlet can be increased. That is, when using a coal type that has a remarkably high melting point of ash, the heat generated from the generated gas is necessary for stable combustion of the gas turbine in order to maintain a high temperature in the furnace under normal and balanced operating conditions. It becomes lower than the limit value (the amount of input oxygen and the amount of input coal are high). In such a case, stable operation is possible by using the bleed line.
FIG. 7 shows a combined gasification combined power generation system that incorporates all of the first to third embodiments described above.
[0019]
【The invention's effect】
As described above, according to the present invention, the air separation device has the advantages of maintaining safety and improving the operating margin while maintaining the characteristics of the extraction air system in the power generation system, and the air separation device. It is possible to obtain a gasification power generation system that eliminates the above drawbacks. Specifically, by operating the air separation device at a constant load or a gradual load change at the partial load, the oxygen concentration is increased from that at the rated load, and the temperature in the furnace is increased or maintained to maintain the ash The flow rate of the combustible gas at the inlet of the gas turbine can be made substantially constant and the load change rate can be improved by returning the remaining nitrogen into the system.
[Brief description of the drawings]
FIG. 1 is a schematic view of a combined gasification power generation system according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of a control device of a combined gasification power generation system.
FIG. 3A is a diagram showing the relationship between the flow rate of bleed air and oxygen and the load of the combined gasification combined power generation system according to the embodiment of the present invention, and FIG. It is a diagram which shows the relationship between oxygen concentration, load, etc. of this.
FIG. 4 is a schematic view of a combined gasification combined power generation system according to Embodiment 1 of the present invention.
FIG. 5 is a schematic diagram of a combined gasification combined power generation system according to Embodiment 2 of the present invention.
FIG. 6 is a schematic view of a combined gasification combined power generation system according to Embodiment 3 of the present invention.
FIG. 7 is a schematic view of a combined gasification combined power generation system incorporating all of Examples 1 to 3.
FIG. 8 is a schematic view of a conventional combined gasification combined power generation system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Gasification furnace 2 Product gas cooler 3 Cyclone 4 Porous filter 5 Dedusting device 6 Desulfurization device 7 Gas turbine 8 Coal coal 8a Pulverized coal supply device 9, 10 Regenerative heat exchanger 11 Waste heat recovery boiler 12 Steam turbine 13 Air separation Device 19 Control device 21 Extraction air compressor 22 Raw material air compressor 23 Nitrogen compressor 24 Oxygen compressor 31-40 Control valve 41-50 Flow meter 111 Extraction air system 113 Nitrogen supply line B Gasification combined power generation system

Claims (2)

A gasification furnace for producing a combustible gas by contacting a fossil fuel with a gasifying agent;
A gas turbine that generates electricity by rotating the turbine by burning combustible gas; and
In a gasification power generation system provided with a bleed air system line for supplying air partially extracted from a gas turbine air compressor as a gasifying agent to the gasification furnace,
An air separation device connected to the raw material air compressor for introducing the atmosphere is provided.
A nitrogen supply line for introducing a part of nitrogen separated by the air separation device into the gasification furnace and introducing the remaining nitrogen into a system system between the gasification furnace and the gas turbine , A nitrogen supply line for introducing a part of nitrogen into the gasifier introduces an annulus line for introducing the nitrogen into the annulus portion of the gasifier and a pulverized coal supply device in the preceding stage of the gasifier. A nitrogen supply line including a pressure line and a transfer line for introducing the nitrogen and transferring the char to the gasification furnace;
A gasification power generation system comprising an oxygen-enriched air supply line for mixing separated oxygen into the extraction air system line.   A gas flow meter for detecting the nitrogen and oxygen amounts in the nitrogen supply line, the oxygen-enriched air supply line and the extraction air system line is provided. The gasification power generation system according to claim 1, further comprising a control device for controlling the outflow amount and the outflow amount of air in the extraction air system line.

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