Waste heat recovery boilers, steam turbine equipment and gasification equipment

Abstract

To provide an exhaust heat recovery boiler, steam turbine equipment, and gasification equipment capable of taking out auxiliary steam at a constant pressure regardless of a load of a gas turbine, and operating a steam turbine under optimum conditions regardless of a pressure of the requested auxiliary steam.SOLUTION: An exhaust heat recovery boiler 20 generating steam using an exhaust gas guided from a gas turbine and circulated in a flow channel 82 includes: a first super-heater 92a for super-heating a steam at a prescribed pressure; steam piping PS1 connected to a steam outlet of the first super-heater 92a; a pressure regulation valve 100 disposed in the steam piping PS1; auxiliary steam piping PS2 connected to the steam piping PS1 at an upstream side with respect to the pressure regulation valve 100 in a steam flowing direction; and a pressure gauge 102 disposed on the steam piping PS1 at the upstream side with respect to the pressure regulation valve 100 in the steam flowing direction and measuring a pressure of the steam circulated in the steam piping PS1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a heat recovery steam generator, a steam turbine facility, and a gasification facility. [Background technology]

[0002] Integrated coal gasification combined cycle (IGCC) is known as a plant that supplies carbon-containing solid fuel such as coal into a gasification furnace, partially combusts the carbon-containing solid fuel, gasifies it, and performs combined power generation (for example, Patent Document 1).

[0003] Patent Document 1 discloses a heat recovery boiler equipped with a high-pressure superheater, a high-pressure evaporator, and a low-pressure economizer, and describes that a steam turbine is driven by steam supplied from the high-pressure superheater. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-206643 Summary of the Invention [Problem to be solved by the invention]

[0005] A part of the steam generated by the heat recovery boiler is supplied as auxiliary steam to various equipment (for example, a gasifier, a gas purification facility, etc.).

[0006] Such auxiliary steam may be supplied from the outlet of the high-pressure turbine, but in the configuration disclosed in Patent Document 1, the pressure at the outlet of the high-pressure turbine may be designed based on the pressure required for the auxiliary steam. In this case, the steam turbine must be designed taking into account the pressure required for the auxiliary steam, which limits the degree of freedom in designing the steam turbine and may result in a situation where the steam turbine is not operated under optimal conditions.

[0007] Furthermore, depending on the load of the gas turbine, the temperature of the exhaust gas introduced into the heat recovery steam generator may fluctuate (for example, during partial load). In this case, it may be impossible to extract auxiliary steam at a constant pressure from the same extraction point. For this reason, to enable extraction of auxiliary steam at a constant pressure when the temperature of the exhaust gas fluctuates, other extraction points may be provided at positions with higher temperatures and pressures than the extraction point at rated load, and these extraction points may be configured to be switchable. However, configuring the extraction point to be switchable increases equipment costs and may result in a decrease in economic efficiency. In addition, in consideration of partial load of the gas turbine, the extraction point may be located on the high-temperature, high-pressure side of the extraction point at rated load. However, in this configuration, auxiliary steam is extracted from an extraction point with sufficient capacity at rated load, which is one cause of reduced efficiency.

[0008] The present invention has been made in view of the above circumstances, and has as its object to provide a heat recovery boiler, steam turbine equipment, and gasification equipment that can extract auxiliary steam at a constant pressure regardless of the load on the gas turbine, and that can operate the steam turbine under optimal conditions regardless of the required pressure of the auxiliary steam. [Means for solving the problem]

[0009] In order to solve the above problems, the heat recovery steam generator, steam turbine facility, and gasification facility according to the present invention employ the following measures. That is, a heat recovery boiler according to one embodiment of the present invention is a heat recovery boiler that generates steam using exhaust gas guided from a gas turbine and flowing through a flow path, and is equipped with a first superheater that superheats steam at a predetermined pressure, a steam pipe connected to the steam outlet of the first superheater, a pressure regulating valve provided on the steam pipe, an auxiliary steam pipe connected to the steam pipe upstream of the pressure regulating valve in the steam flow direction, and a pressure gauge provided on the steam pipe upstream of the pressure regulating valve in the steam flow direction and that measures the pressure of steam flowing through the steam pipe.

[0010] The heat recovery boiler according to this embodiment generates steam using exhaust gas guided from a gas turbine and flowing through a flow path, and includes a first superheater that superheats steam at a predetermined pressure, a steam pipe connected to the steam outlet of the first superheater, a pressure regulating valve provided in the steam pipe, an auxiliary steam pipe connected to the steam pipe upstream of the pressure regulating valve in the steam flow direction, and a pressure gauge provided in the steam pipe upstream of the pressure regulating valve in the steam flow direction, for measuring the pressure of steam flowing through the steam pipe. This makes it possible to control the front pressure of the auxiliary steam pipe using the pressure regulating valve and pressure gauge (controlling the pressure upstream of the pressure regulating valve using the pressure regulating valve), and steam at a constant pressure can be extracted as auxiliary steam from the first superheater through the auxiliary steam pipe regardless of the load on the gas turbine. The "pressure upstream of the pressure regulating valve" referred to here refers to, for example, the steam pressure of the first superheater, the steam pressure in the steam pipe, and the steam pressure in the auxiliary steam pipe. Furthermore, when a first evaporator that supplies steam at a predetermined pressure to the first superheater is installed, the pressure in the first evaporator can be adjusted by a pressure regulating valve through front pressure control. Furthermore, if a second superheater that superheats steam at a pressure higher than a predetermined pressure is installed upstream of the first superheater in the exhaust gas flow direction, and the steam supplied from the second superheater or the steam discharged from the steam turbine driven by that steam is extracted as auxiliary steam, the steam turbine may not be able to operate under optimal conditions depending on the required pressure of the auxiliary steam, which could result in a decrease in performance of the entire facility. However, by using the steam extracted from the first superheater as auxiliary steam as in this embodiment, the steam turbine can be operated under optimal conditions regardless of the required pressure of the auxiliary steam. This is because the first superheater, which serves as the auxiliary steam supply source, and the second superheater, which serves as the steam supply source for driving the steam turbine, are independent superheaters. The auxiliary steam is used, for example, as a heating source for fuel gas supplied to a gas turbine.

[0011] Moreover, the heat recovery steam generator according to one aspect of the present invention includes a control unit that determines the opening degree of the pressure regulating valve based on information from the pressure gauge.

[0012] The heat recovery steam generator according to this aspect includes a control unit that determines the opening degree of the pressure regulating valve based on information from the pressure gauge, thereby enabling front pressure control.

[0013] Furthermore, a heat recovery boiler according to one aspect of the present invention includes a first evaporator that generates steam at the predetermined pressure and supplies the steam at the predetermined pressure to the first superheater, and an extraction pipe that extracts exhaust gas from the flow path downstream of the first evaporator in the gas flow direction.

[0014] The heat recovery boiler according to this embodiment includes a first evaporator that generates steam at a predetermined pressure and supplies the steam at the predetermined pressure to a first superheater, and an extraction pipe that extracts exhaust gas from a flow path downstream of the first evaporator in the gas flow direction. As a result, by maintaining the pressure of the first evaporator constant using the pressure regulating valve, the temperature of the first evaporator can be maintained constant. Therefore, the temperature of the exhaust gas in the flow path downstream of the first evaporator in the flow direction of the exhaust gas (particularly, at a position close to the first evaporator) can be maintained constant. Then, by extracting exhaust gas from the flow path downstream of the first evaporator in the flow direction of the exhaust gas, exhaust gas at a constant temperature can be extracted regardless of the load on the gas turbine. The extracted exhaust gas is used, for example, to dry carbon-containing solid fuel. In addition, compared to when exhaust gas is extracted from upstream of the first superheater in the flow direction of the exhaust gas, the amount of heat exchanged between the steam and the exhaust gas in the first superheater and the first evaporator can be increased. The first evaporator may be configured to supply steam to the first superheater connected to the steam pipe, and the pressure (for example, low pressure, medium pressure, high pressure, etc.) is not limited.

[0015] In addition, in a heat recovery steam generator according to one embodiment of the present invention, the predetermined pressure is set to a pressure higher than a first pressure, and a second evaporator is provided that generates steam at the first pressure, and the extraction pipe extracts exhaust gas from the flow path between the first evaporator and the second evaporator.

[0016] In the heat recovery boiler of this embodiment, the predetermined pressure is set to a pressure higher than the first pressure, and the system is equipped with a second evaporator that generates steam at the first pressure, and the extraction piping extracts exhaust gas from the flow path between the first evaporator and the second evaporator. By maintaining the pressure of the first evaporator constant using the pressure regulating valve, the temperature of the first evaporator can be maintained constant. Therefore, the temperature of the exhaust gas in the flow path between the first evaporator and the second evaporator (particularly, the position close to the first evaporator) can be maintained constant. Then, by extracting the exhaust gas from between the first evaporator and the second evaporator, it is possible to extract exhaust gas at a constant temperature regardless of the load on the gas turbine. The extracted exhaust gas is used, for example, to dry carbon-containing solid fuel. In addition, compared to when exhaust gas is extracted from upstream of the first superheater in the flow direction of the exhaust gas, the amount of heat exchanged between the steam and the exhaust gas in the first superheater and the second evaporator can be increased.

[0017] Furthermore, a steam turbine facility according to one embodiment of the present invention includes the above-mentioned heat recovery boiler provided with a second superheater that superheats steam at a second pressure higher than the predetermined pressure, and a steam turbine driven by steam supplied from the second superheater.

[0018] The steam turbine equipment according to this aspect includes the above-mentioned heat recovery boiler provided with a second superheater that superheats steam at a second pressure higher than the predetermined pressure, and a steam turbine driven by steam supplied from the second superheater. This allows the first superheater, which serves as a supply source of auxiliary steam, and the second superheater, which serves as a supply source of steam for driving the steam turbine, to be independent superheaters, allowing the steam turbine to be operated under optimal conditions regardless of the required pressure of auxiliary steam.

[0019] Furthermore, a gasification facility according to one aspect of the present invention includes the above-mentioned exhaust heat recovery boiler, a gasification furnace that gasifies a carbon-containing solid fuel, a gas purification facility that purifies the generated gas gasified in the gasification furnace, and a gas turbine driven by the fuel gas purified by the gas purification facility, and the steam extracted by the auxiliary steam piping heats the fuel gas supplied to the gas turbine.

[0020] The gasification equipment according to this embodiment includes the above-mentioned exhaust heat recovery boiler, a gasification furnace that gasifies the carbon-containing solid fuel, a gas purification facility that purifies the product gas gasified in the gasification furnace, and a gas turbine driven by the fuel gas purified by the gas purification facility, and the steam extracted by the auxiliary steam piping heats the fuel gas supplied to the gas turbine. This allows fuel gas with the highest possible temperature to be supplied to the gas turbine, thereby improving the combustion efficiency in the gas turbine.

[0021] Furthermore, a gasification facility according to one aspect of the present invention includes the above-described exhaust heat recovery boiler and a gasification furnace that gasifies a carbon-containing solid fuel, and the exhaust gas extracted by the extraction piping dries the carbon-containing solid fuel that is supplied to the gasification furnace.

[0022] The gasification facility according to this aspect includes the above-mentioned exhaust heat recovery boiler and a gasification furnace that gasifies the carbon-containing solid fuel, and the exhaust gas extracted by the extraction pipe dries the carbon-containing solid fuel that is supplied to the gasification furnace. This allows the carbon-containing solid fuel to be dried using exhaust gas at a constant temperature regardless of the load on the gas turbine, thereby avoiding a shortage of drying heat. [Effects of the Invention]

[0023] The heat recovery steam generator, steam turbine equipment, and gasification equipment according to the present invention can extract auxiliary steam at a constant pressure regardless of the load on the gas turbine, and can operate the steam turbine under optimal conditions regardless of the required pressure of the auxiliary steam. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic configuration diagram showing an integrated coal gasification combined cycle power generation facility according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the arrangement of heat exchangers and piping of a heat recovery boiler. [Figure 3] FIG. 10 is a diagram showing the relationship between the load of the gas turbine and the outlet gas temperature and saturation temperature of the intermediate-pressure evaporator. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, a heat recovery steam generator, a steam turbine facility, and a gasification facility according to an embodiment of the present invention will be described with reference to the drawings.

[0026] [Overall configuration of integrated coal gasification combined cycle power generation facility] FIG. 1 shows a schematic configuration of an integrated coal gasification combined cycle power generation facility according to this embodiment. An integrated coal gasification combined cycle (IGCC) power plant 1 is equipped with a gasifier 3. The gasifier 3 uses air as an oxidant and employs an air combustion system that produces combustible gas (produced gas) from carbon-containing solid fuels such as coal. The integrated coal gasification combined cycle power plant 1 refines the produced gas produced in the gasifier 3 in a gas refinement system 5 to produce fuel gas, which is then supplied to a gas turbine unit 7 to generate power. In other words, the integrated coal gasification combined cycle power plant 1 is an air combustion (air-blown) power plant. Although the present embodiment will be described as air-blown, oxygen-blown may also be used. As the carbon-containing solid fuel supplied to the gasification furnace facility 3, for example, coal is used.

[0027] The integrated coal gasification combined cycle power generation system 1 includes a coal supply system 9, a gasification furnace system 3, a char recovery system 11, a gas purification system 5, a gas turbine system 7, a steam turbine system 18, a generator 19, and a heat recovery steam generator (HRSG) 20.

[0028] The coal supply facility 9 receives coal, a carbon-containing solid fuel, as raw coal from a coal supply bunker and pulverizes the coal in a coal mill 13 to produce pulverized coal pulverized into fine particles. The pulverized coal produced in the coal mill 13 travels from each pulverized coal hopper 14 through a coal supply line 15, is pressurized with nitrogen gas as an inert gas for transportation supplied from an air separation facility 42, and is supplied to the gasification facility 3. The inert gas is an inert gas with an oxygen content of approximately 5% by volume or less, and typical examples include nitrogen gas, carbon dioxide gas, and argon gas, but is not necessarily limited to approximately 5% or less.

[0029] When the coal contains a large amount of moisture, the coal may be dried using exhaust gas extracted from the heat recovery boiler 20. Details of the extracted gas will be described later.

[0030] The gasification furnace facility 3 is supplied with pulverized coal produced in the coal supply facility 9, and also receives char (unreacted coal and ash) recovered in the char recovery facility 11, which is returned and supplied so that it can be reused.

[0031] A compressed air supply line 41 extending from a gas turbine unit 7 (compressor 61) is connected to the gasification furnace facility 3, and a portion of the compressed air compressed by the gas turbine unit 7 is boosted to a predetermined pressure by a booster 68 so that it can be supplied to the gasification furnace (gasification section) 16. The air separation facility 42 separates and generates nitrogen and oxygen from atmospheric air, and the air separation facility 42 and the gasification furnace facility 3 are connected by a first nitrogen supply line 43. A coal feed line 15 extending from a coal feed facility 9 is connected to this first nitrogen supply line 43. A second nitrogen supply line 45 branching off from the first nitrogen supply line 43 is also connected to the gasification furnace facility 3, and a char return line 46 extending from a char recovery facility 11 is connected to this second nitrogen supply line 45. Furthermore, the air separation facility 42 is connected to the compressed air supply line 41 by an oxygen supply line 47. The nitrogen separated by the air separation equipment 42 is used as a carrier gas for coal and char by flowing through a first nitrogen supply line 43 and a second nitrogen supply line 45. The oxygen separated by the air separation equipment 42 is used as an oxidizing agent in the gasification furnace equipment 3 by flowing through an oxygen supply line 47 and a compressed air supply line 41.

[0032] The gasification furnace facility 3 includes, for example, a two-stage entrained flow type gasification furnace 16. The gasification furnace facility 3 gasifies coal (pulverized coal) and char supplied therein by partially burning them with an oxidizing agent (air, oxygen) to produce a generated gas. The interior of the gasification furnace 16 is pressurized, for example, to 3 to 4 MPa (gauge pressure). Burners 30 and 31 are provided in two stages, one above the other. A combustor section 32 is provided at a position corresponding to the lower burner 30, and supplies heat for gasification by burning a portion of the pulverized coal. A reductor section 33 is provided at a position corresponding to the upper burner 31, and gasifies the pulverized coal. A syngas cooler 35 (produced gas cooler) is provided downstream of the reductor section 33, and cools the produced gas to a predetermined temperature before supplying it to the char recovery facility 11. Steam is generated in the syngas cooler 35, and the generated steam is guided to the heat recovery steam generator (HRSG) 20.

[0033] A produced gas line 49 that supplies produced gas to the char recovery facility 11 is connected to the gasification furnace facility 3, and the produced gas containing char can be discharged.

[0034] The char recovery facility 11 includes a dust collection facility 51 and a supply hopper 52. In this case, the dust collection facility 51 is composed of one or more cyclones or porous filters, and is capable of separating char contained in the product gas generated in the gasification furnace facility 3. The product gas from which the char has been separated is sent to the gas purification facility 5 through a gas discharge line 53. The supply hopper 52 stores the char separated from the product gas in the dust collection facility 51. A char bin 54 is disposed between the dust collection facility 51 and the supply hopper 52. A plurality of supply hoppers 52 are connected to the char bin 54. A char return line 46 from the supply hopper 52 is connected to the second nitrogen supply line 45.

[0035] The gas purification equipment 5 purifies the product gas from which the char has been separated by the char recovery equipment 11 by removing impurities such as sulfur compounds and nitrogen compounds. The gas purification facility 5 purifies the produced gas to produce fuel gas, which is then supplied to the gas turbine unit 7. Since the produced gas from which the char has been separated still contains sulfur components (such as H2S), the gas purification facility 5 removes and recovers the sulfur components using an amine absorbent or the like for effective use.

[0036] Specifically, after passing through a COS converter 21, a scrubber 22, and a cooling and scrubbing tower 23, the gas is introduced into an H2S absorption tower 24, where H2S is absorbed. The absorbing solution that has absorbed H2S in the H2S absorption tower 24 is regenerated in an absorbing solution regeneration tower 25 and returned to the H2S absorption tower 24. The H2S gas separated from the absorbing solution in the H2S absorption tower 24 is incinerated in an off-gas combustion furnace 26, and then introduced into a flue gas desulfurization system 27.

[0037] The gas turbine device 7 includes a compressor 61, a combustor 62, and a gas turbine 63, and the compressor 61 and the gas turbine 63 are connected by a rotary shaft 64. A compressed air supply line 65 from the compressor 61 is connected to the combustor 62, and a fuel gas supply line 66 from the gas purification facility 5 is also connected to the combustor 62.

[0038] A combustion gas supply line 67 is connected between the combustor 62 and the gas turbine 63. The gas turbine device 7 is provided with a compressed air supply line 41 extending from the compressor 61 to the gasifier facility 3, and a booster 68 is provided in the middle of the line. Therefore, in the combustor 62, a part of the compressed air supplied from the compressor 61 is mixed with at least a part of the fuel gas supplied from the gas purification facility 5 and combusted to generate combustion gas, and the generated combustion gas is supplied to the gas turbine 63. Then, the gas turbine 63 rotates a rotary shaft 64 with the supplied combustion gas, thereby rotating the generator 19.

[0039] The steam turbine unit 18, which is included in any steam turbine facility, includes a steam turbine 69 connected to the rotary shaft 64 of the gas turbine unit 7. A condenser 72 is connected downstream of the steam turbine 69. The generator 19 is connected to the base end of the rotary shaft 64. The generator 19 may be disposed between the steam turbine 69 and the gas turbine 63. The heat recovery steam generator 20 is connected to an exhaust gas line 70 from the gas turbine 63, and generates steam by exchanging heat between feedwater guided from the condenser 72 and the exhaust gas of the gas turbine 63. A steam supply line 71 is provided between the heat recovery steam generator 20 and the steam turbine unit 18. The steam generated in the heat recovery steam generator 20 includes steam generated by heat exchange with the generated gas in a syngas cooler (SGC) 35 of the gasifier 16. Therefore, in the steam turbine device 18, the steam turbine 69 is rotationally driven by the steam supplied from the heat recovery boiler 20, and the rotation shaft 64 is rotated, thereby rotating the generator 19.

[0040] A chimney 75 is connected to the outlet of the heat recovery boiler 20, and the combustion gas is released into the atmosphere. Note that a gas purification facility may be provided at the outlet of the heat recovery boiler 20.

[0041] [Operation of coal gasification combined cycle power generation facility] Next, the operation of the integrated coal gasification combined cycle power generation facility 1 according to this embodiment will be described. In the integrated coal gasification combined cycle power generation plant 1, when raw coal (coal) is supplied to the coal mill 13 of the coal supply facility 9, the coal is pulverized into fine particles in the coal mill 13 to become pulverized coal. At this time, if the coal contains a large amount of moisture, the coal is dried by the exhaust gas extracted from the heat recovery boiler 20.

[0042] Pulverized coal produced in the coal feeding facility 9 is supplied to the gasifier facility 3 through a first nitrogen supply line 43 by nitrogen supplied from an air separation facility 42. In addition, char recovered in a char recovery facility 11 (described later) is supplied to the gasifier facility 3 through a second nitrogen supply line 45 by nitrogen supplied from the air separation facility 42. Furthermore, compressed air extracted from a gas turbine unit 7 (described later) is pressurized by a booster 68, and then supplied to the gasifier facility 3 through a compressed air supply line 41 together with oxygen supplied from the air separation facility 42. In the gasifier 3, the supplied pulverized coal and char are combusted with compressed air (oxygen) and gasified to generate generated gas. This generated gas is then discharged from the gasifier 3 through a generated gas line 49 and sent to the char recovery facility 11.

[0043] In this char recovery facility 11, the produced gas is first supplied to a dust collection facility 51, where fine char particles contained in the produced gas are separated. The produced gas from which the char has been separated is then sent to the gas purification facility 5 through a gas discharge line 53. Meanwhile, the fine char particles separated from the produced gas are deposited in a supply hopper 52 and returned to the gasification furnace facility 3 through a char return line 46 for recycling.

[0044] The product gas from which char has been separated in the char recovery system 11 is purified in the gas purification system 5 to remove impurities such as sulfur compounds and nitrogen compounds, and a fuel gas is produced. The purified fuel gas is heated by the heater 105 using auxiliary steam extracted from the heat recovery boiler 20 as a heat source. At this time, the fuel gas is heated to a predetermined temperature range (for example, about 200°C). Note that the fuel gas before heating is at about 120°C to 130°C.

[0045] The fuel gas heated by the heater 105 may be further heated by a fuel gas heater 80 provided at an intermediate position in the fuel gas supply line 66. In this case, the fuel gas is heated to approximately 300°C to 600°C. The fuel gas heater 80 uses auxiliary steam extracted from the heat recovery steam generator 20 as a heat source.

[0046] The compressor 61 generates compressed air and supplies it to the combustor 62. The combustor 62 mixes the compressed air supplied from the compressor 61 with fuel gas heated by the fuel gas heater 80 and burns the mixture to generate combustion gas. The combustion gas rotates a gas turbine 63, which rotates the compressor 61 and the generator 19 via a rotary shaft 64. In this way, the gas turbine device 7 can generate electricity.

[0047] The heat recovery boiler 20 generates steam by exchanging heat between the exhaust gas discharged from the gas turbine 63 and the feed water supplied from the condenser 72, and supplies this generated steam to the steam turbine device 18. The steam turbine device 18 is rotationally driven by the steam supplied from the heat recovery boiler 20, thereby rotationally driving the generator 19 via the rotary shaft 64, thereby generating electricity. The gas turbine unit 7 and the steam turbine unit 18 do not have to rotate and drive one generator 19 on the same shaft, but may rotate and drive a plurality of generators on different shafts.

[0048] [Configuration of waste heat recovery boiler] Next, the configuration of the heat recovery steam generator 20 according to this embodiment will be described. 2 shows a heat recovery steam generator 20 in which multiple heat exchangers are provided in a flow path 82. Exhaust gas (GT exhaust gas) guided from a gas turbine 63 flows from bottom to top in the figure. The heat recovery steam generator 20 has a three-pressure configuration having, in order from the bottom (upstream side of the GT exhaust gas), high-pressure (second pressure), medium-pressure (predetermined pressure), and low-pressure (first pressure) heat exchangers. The arrangement of the heat exchangers may be changed as appropriate depending on the specifications of the facility, and the order of the heat exchangers may be reversed or multiple heat exchangers may be installed in parallel.

[0049] In the portion of the flow path 82 located upstream of the GT exhaust gas, a high-pressure superheater (second superheater) 93a, a high-pressure evaporator 93b, and a high-pressure economizer 93c are provided, in that order from the upstream side of the GT exhaust gas. In addition, a reheater 94 is provided between the high-pressure superheater 93a and the high-pressure evaporator 93b in the flow direction of the GT exhaust gas. Furthermore, a denitration device 90 is provided between the high-pressure evaporator 93b and the high-pressure economizer 93c. A steam supply line 71 is connected to the steam outlet of the high-pressure superheater 93 a, and is configured to supply steam to the steam turbine 69 .

[0050] In a portion of the flow path 82 located midstream of the GT exhaust gas, an intermediate-pressure superheater (first superheater) 92a and an intermediate-pressure evaporator (first evaporator) 92b are provided, in that order from the upstream side of the GT exhaust gas. A steam pipe PS1 is provided between the intermediate-pressure superheater 92a and the reheater 94, connecting the steam outlet of the intermediate-pressure superheater 92a to the steam inlet of the reheater 94. A pipe through which steam discharged from the steam turbine 69 is conducted may be connected to the steam pipe PS1. A pressure regulating valve 100 is provided in the steam pipe PS1 upstream of this connection in the steam flow direction. Further, an auxiliary steam pipe PS2 branches off from the steam pipe PS1 upstream of the pressure regulating valve 100. Furthermore, the steam pipe PS1 upstream of the branch point of the auxiliary steam pipe PS2 is provided with a pressure gauge 102 capable of measuring the pressure of the steam. The installation location of the pressure gauge 102 is not limited to the location shown in the figure, and it may be provided in, for example, the medium-pressure evaporator 92b (drum).

[0051] In a portion of the flow path 82 located downstream of the GT exhaust gas, a low-pressure evaporator (second evaporator) 91b and a low-pressure economizer 91c are provided in this order from the upstream side of the GT exhaust gas.

[0052] A high-temperature extraction pipe PG1 is provided between the intermediate-pressure evaporator 92b and the low-pressure evaporator 91b, and is configured to extract the GT exhaust gas flowing through the flow path 82 between the intermediate-pressure evaporator 92b and the low-pressure evaporator 91b. The extraction position by the high-temperature extraction pipe PG1 is preferably close to the intermediate-pressure evaporator 92b.

[0053] A low-temperature extraction pipe PG2 is provided downstream of the low-pressure economizer 91c, and is configured to extract the exhaust gas flowing through the flow path 82 downstream of the low-pressure economizer 91c.

[0054] The high-temperature extraction pipe PG1 and the low-temperature extraction pipe PG2 are joined together and are configured to be led to the coal mill 13 as a single piping system.

[0055] [Operation of the heat recovery boiler, steam pipes, and auxiliary steam pipes] Next, the operation of the heat recovery steam generator 20 according to this embodiment will be described. High-temperature GT exhaust gas guided from the gas turbine 63 flows from bottom to top through a flow path 82. Each heat exchanger (superheater, evaporator, economizer, reheater, etc.) exchanges heat between the GT exhaust gas and water (including steam) to heat feedwater, generate steam at a predetermined pressure, superheat the steam, etc. In addition, a denitrification device 90 neutralizes harmful substances contained in the GT exhaust gas flowing through the flow path 82.

[0056] The low-pressure economizer 91c heats the feedwater supplied from the condenser 72. The low-pressure evaporator 91b generates low-pressure (first pressure) steam using the water heated by the low-pressure economizer 91c.

[0057] The intermediate-pressure evaporator 92b generates intermediate-pressure steam using water heated in an intermediate-pressure economizer (not shown). The steam generated in the intermediate-pressure evaporator 92b is superheated by the intermediate-pressure superheater 92a. The degree of superheating by the intermediate pressure superheater 92a can be, for example, as follows: That is, the degree of superheating is set to a degree (for example, 10°C or more and 15°C or less) that prevents the auxiliary steam from becoming wet steam due to pressure loss in the pressure regulating valve 100 or due to temperature reduction while the auxiliary steam is being supplied to the destination of use.

[0058] The high-pressure evaporator 93b generates high-pressure (second pressure) steam using water heated in the high-pressure economizer 93c. Furthermore, the steam generated in the high-pressure evaporator 93b is superheated by the high-pressure superheater 93a and then supplied to the steam turbine 69 via the steam supply line 71. Note that if the steam turbine 69 is a two-pressure type or a three-pressure type, the steam superheated by the high-pressure superheater 93a will be supplied to the high-pressure steam turbine.

[0059] Next, the operation of the steam pipe PS1 and the auxiliary steam pipe PS2 will be described. A portion of the steam superheated by the intermediate-pressure superheater 92a is extracted as high-temperature, intermediate-pressure auxiliary steam via the steam pipe PS1 and the auxiliary steam pipe PS2. The auxiliary steam is supplied to a wide range of destinations, but as one example, it is supplied to the fuel gas heater 80 and used to heat the fuel gas. This allows the fuel gas cooled in the gas purification equipment 5, which is provided in the gasification equipment, to be supplied to the gas turbine 63 at a temperature close to the combustion temperature in the gas turbine 63, thereby enabling the operation of the gas turbine 63 to be made more efficient. The gas turbine 63 is provided in, for example, a gasification facility in which the gas purification facility 5 is provided.

[0060] At this time, the pressure of the auxiliary steam supplied through the auxiliary steam pipe PS2 is controlled by so-called front pressure control using the pressure regulating valve 100. This makes it possible to maintain the pressure of the auxiliary steam constant regardless of the temperature and pressure of the GT exhaust gas, which fluctuate depending on the load on the gas turbine 63, for example. In addition, by controlling the front pressure using the pressure regulating valve 100, the steam pressure of the intermediate pressure superheater 92a, the steam pressure of the intermediate pressure evaporator 92b, the steam pressure in the steam pipe PS1, etc. are kept constant regardless of the load on the gas turbine 63. Furthermore, when the pressure of the intermediate-pressure evaporator 92b is kept constant by the front-pressure control, the saturation temperature in the intermediate-pressure evaporator 92b is kept constant. Therefore, the temperature downstream of the intermediate-pressure evaporator 92b (the outlet temperature of the intermediate-pressure evaporator 92b) is also kept constant. As a result, the temperature of the GT exhaust gas heat-exchanged by the intermediate-pressure evaporator 92b is kept constant regardless of the load on the gas turbine 63.

[0061] The GT exhaust gas extracted from near the outlet of the medium-pressure evaporator 92b by the high-temperature extraction pipe PG1 is mixed with the GT exhaust gas extracted by the low-temperature extraction pipe PG2, and after the temperature is adjusted to, for example, 180°C or higher and 270°C or lower, the gas is supplied to the coal mill 13 as gas for drying coal.

[0062] Here, the opening degree of the pressure regulating valve 100 is determined by the control unit 104 based on information related to pressure acquired from the pressure gauge 102. In other words, the pressure gauge 102 and the control unit 104 are configured to monitor the steam pressure upstream of the pressure regulating valve 100, and the control unit 104 is configured to appropriately determine the opening degree of the pressure regulating valve 100.

[0063] The control unit 104 is composed of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program, and the CPU reads this program into RAM or the like and executes information processing and arithmetic operations to realize various functions. The program may be pre-installed in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Examples of computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0064] This embodiment has the following advantages. The pressure regulating valve 100 enables control of the front pressure for the auxiliary steam pipe PS2, and auxiliary steam at a constant pressure can be extracted from the intermediate pressure superheater 92a via the steam pipe PS1 and the auxiliary steam pipe PS2 regardless of the load on the gas turbine 63. Furthermore, if the steam supplied from the high-pressure superheater 93a or the steam discharged from the steam turbine 69 driven by that steam were extracted as auxiliary steam, the auxiliary steam would be highly superheated and would therefore need to be cooled using spray water. This cooling is undesirable as it leads to heat loss throughout the facility. However, the auxiliary steam extracted from the intermediate-pressure superheater 92a is at a lower temperature than the steam supplied from the high-pressure superheater 93a, etc. This makes it possible to avoid losses due to cooling the auxiliary steam using spray water.

[0065] Furthermore, the pressure of the intermediate-pressure evaporator 92b can be maintained constant by the pressure regulating valve 100. This allows the saturation temperature of the intermediate-pressure evaporator 92b to be maintained constant, as shown in FIG. 3. Therefore, the temperature of the GT exhaust gas in the flow path 82 between the low-pressure evaporator 91b and the intermediate-pressure evaporator 92b (particularly at a position close to the intermediate-pressure evaporator 92b) can be maintained constant (a temperature equal to or higher than the temperature required for drying coal (T1 in FIG. 3)). By extracting the GT exhaust gas from between the low-pressure evaporator 91b and the intermediate-pressure evaporator 92b, it is possible to extract GT exhaust gas at a constant temperature regardless of the load on the gas turbine 63. By using the extracted GT exhaust gas to dry coal, it is possible to stably dry coal using the GT exhaust gas at a constant temperature. Note that if the pressure of the intermediate-pressure evaporator 92b is not controlled, for example, the temperature of the extracted GT exhaust gas may decrease as the load on the gas turbine 63 decreases. In addition, compared to when GT exhaust gas is extracted from upstream of the medium-pressure superheater 92a, the amount of heat exchanged between the steam and exhaust gas in the medium-pressure superheater 92a and the medium-pressure evaporator 92b can be increased.

[0066] In addition, by extracting the steam from the intermediate-pressure superheater 92a as auxiliary steam and using the steam from the high-pressure superheater 93a as the driving source for the steam turbine 69, the steam turbine 69 can be operated under optimal conditions regardless of the required pressure of the auxiliary steam.

[0067] In the above embodiment, the configuration of the heat recovery steam generator 20 has been described as an example of a three-pressure configuration, but it may also be a two-pressure configuration of high pressure and medium pressure, for example. [Explanation of symbols]

[0068] 1. Coal gasification combined cycle power generation facility (gasification facility) 5 Gas purification facilities 16 Gasifier 18 Steam turbine equipment 20 Waste heat recovery boiler 63 Gas Turbine 69 Steam Turbine 82 Flow path 91b Low-pressure evaporator (second evaporator) 92a Medium pressure superheater (first superheater) 92b Medium pressure evaporator (first evaporator) 93a High pressure superheater (second superheater) 100 Pressure Regulating Valve 102 Pressure gauge 104 Control Unit PG1 High temperature bleed piping (bleed piping) PS1 Steam Pipe PS2 Auxiliary steam piping

Claims

1. A heat recovery boiler that generates steam using exhaust gas guided from a gas turbine and flowing through a flow path, a first superheater for superheating steam at a predetermined pressure; a steam pipe connected to a steam outlet of the first superheater; a pressure regulating valve provided in the steam pipe; an auxiliary steam pipe connected to the steam pipe upstream of the pressure regulating valve in the steam flow direction; a pressure gauge that is provided in the steam pipe upstream of the pressure regulating valve in a steam flow direction and that measures the pressure of steam flowing through the steam pipe; a first evaporator that generates steam at the predetermined pressure and supplies the steam at the predetermined pressure to the first superheater; an extraction pipe that extracts exhaust gas from the flow path downstream of the first evaporator in a gas flow direction; Equipped with The predetermined pressure is higher than the first pressure, a second evaporator for generating steam at the first pressure; The exhaust gas extraction pipe extracts exhaust gas from the flow path between the first evaporator and the second evaporator.

2. a control unit that determines the opening degree of the pressure regulating valve based on information from the pressure gauge; The heat recovery steam generator according to claim 1, comprising:

3. A heat recovery boiler that generates steam from exhaust gas guided from a gas turbine and flowing through a flow path, the heat recovery boiler comprising: a first superheater that superheats steam at a predetermined pressure; a steam pipe connected to the steam outlet of the first superheater; a pressure regulating valve provided on the steam pipe; an auxiliary steam pipe connected to the steam pipe upstream of the pressure regulating valve in the steam flow direction; a pressure gauge that is provided on the steam pipe upstream of the pressure regulating valve in the steam flow direction and measures the pressure of steam flowing through the steam pipe; and a second superheater that superheats steam at a second pressure higher than the predetermined pressure. a steam turbine driven by steam supplied from the second superheater; Steam turbine installations equipped with:

4. A heat recovery boiler that generates steam from exhaust gas guided from a gas turbine and flowing through a flow path, the heat recovery boiler comprising: a first superheater that superheats steam at a predetermined pressure; a steam pipe connected to the steam outlet of the first superheater; a pressure regulating valve provided on the steam pipe; an auxiliary steam pipe connected to the steam pipe upstream of the pressure regulating valve in the steam flow direction; and a pressure gauge provided on the steam pipe upstream of the pressure regulating valve in the steam flow direction, for measuring the pressure of steam flowing through the steam pipe; a gasifier for gasifying the carbon-containing solid fuel; a gas purification facility that purifies the generated gas gasified in the gasification furnace; the gas turbine driven by the fuel gas purified by the gas purification facility; Equipped with The steam extracted by the auxiliary steam pipe heats the fuel gas supplied to the gas turbine.

5. The heat recovery steam generator according to claim 1 or 2; a gasifier for gasifying a carbon-containing solid fuel; Equipped with The exhaust gas extracted by the extraction pipe is supplied to the gasification furnace, and the carbon-containing solid fuel is dried in the gasification facility.

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