JP2000120403A - Integrated gas combined power generating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an integrated gas combined power generating system capable of appropriately supplying steam to high-pressure gasifying furnace for power generation. SOLUTION: In gasifying processes, coarse gas obtained by gasifying carbonaceous fuel is supplied as fuel gas to a gas turbine 13 in a combined power generating process 48, and exhaust gas from the gas turbine 13 is recovered by waste heat recovery boiler 46 to generate steam, thereby driving a steam turbine 20. A comprehensive load controller 31 controls the fuel gas supplied from a gasifying process 47 to the combined power generating process 48. A steam turbine controller 25 controls steam supplied from the waste heat recovery boiler 46 to the steam turbine 20. High-pressure steam required in a gasifying furnace 5 of the gasifying process 47 is obtained from a high-pressure steam header of the waste heat recovery boiler 46.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gasification combined cycle system including a gasification process for gasifying carbonaceous fuel to obtain a fuel gas, and a combined cycle process including a gas turbine and a steam turbine.

[0002]

2. Description of the Related Art With the demand for effective use, diversification, and higher efficiency of energy resources, a combined gasification combined cycle system (I) that generates electricity using a carbonaceous fuel such as coal or petroleum residual oil.
GCC (Integrated Gasifcation Combind Cycle) is attracting attention. This gasification combined cycle system is a combination of a gasification plant and a combined cycle plant, and its high power generation efficiency, environmental suitability, and economy are attracting attention.

The characteristics of an integrated gasification combined cycle system are its environmental compatibility and compatibility with a wide range of coal types and various fuels. It has been developed and is expected as the most promising power generation system for thermal power generation in the future. The gasification combined cycle system is a large-scale and complex system including a combined gasification furnace, gas purification equipment and a gas turbine, a heat recovery steam generator (HRSG), and a steam turbine.

[0004] Among the constituent equipment of the integrated gasification combined cycle system, the gasification furnace has been used for heat utilization of coal gas, production of synthesis gas, and the like since a relatively long time. In the 1940's, coal gasification technology was developed and commercialized for city gas production. There are a fixed-bed furnace type Rurugi furnace, a fluidized bed type winkle furnace, and a spouted bed type Kobbers Tozek furnace.
These were first-generation atmospheric pressure furnaces (atmospheric pressure furnaces), and had a small coal throughput of about 10 tons / day. After that, coal resources were reviewed again due to the oil crisis in the 1970s, and the development of a coal gasification power generation plant combined with a combined cycle plant together with a large-capacity coal-fired power plant began.

[0005] The gas pressure of the gasification furnace is required to be 30 K to 40 K instead of the conventional normal pressure. This is because the fuel gas obtained in the gasifier process is burned in the combustor as fuel for the gas turbine. As a gasifier type, a spouted bed type which has a good response and is capable of complete gasification is mainly used.

[0006] For the gasification of coal, partial oxidation using oxygen, water or air is applied. The main reactions are a dry distillation reaction in which coal decomposes into char (C), hydrogen (H), and hydrocarbon (CmHm), and a gasification reaction of char (see (1) to (1) below).
(3)) and a combustion reaction ((4) and (5) below).

C + H ₂ O → CO + H ₂ −A kcal (1) (water gasification reaction) C + CO ₂ → 2CO−B kcal (2) C + 2H ₂ → CH ₄ + C kcal (3) C + O ₂ → CO ₂ + D kcal… (4) 2C + O ₂ → 2CO ₂ + E kcal… (5)

The center of the gasification reaction is a water gasification reaction. CO generated here, H ₂ to form a high calorific value coal gas burning in a gas turbine. The integrated gasification combined cycle system is based on the type of gasification furnace used and the type of gas purification system consisting of a dust removal device and a desulfurization device.
Although various systems are conceivable, a gasification fuel supply method using coal slurry will be described below, and a gasification furnace that performs medium-calorie gasification using oxygen as a gasifying agent will be described.

FIG. 4 is a configuration diagram of such an integrated gasification combined cycle system. The integrated gasification combined cycle system includes a gasification process 47 for supplying a crude gas obtained by gasifying a carbonaceous fuel as a fuel gas, and burning the fuel gas from the gasification process 47 to drive the gas turbine 13 to reduce the exhaust gas. A combined power generation process 48 for recovering the waste heat from the exhaust heat recovery boiler 46 to generate steam to drive the steam turbine 20; a general load control unit 31 for controlling fuel gas supplied from the gasification process 47 to the combined power generation process 48; Heat recovery boiler 46
And a steam turbine control device 25 for controlling steam supplied to the steam turbine 20 from the steam turbine.

The gasification furnace 5 of the gasification process 47 is an oxygen-blown system supplied with coal slurry, and the water for the water-based gasification reaction is in the form of a coal-water slurry in which coal dust and water are mixed. It is supplied to the gasification furnace 5. The gasification furnace 5 is a facility that generates coal gas (referred to as crude gas with respect to refined gas).

To the gasification furnace 5, coal / water slurry produced by the slurry production apparatus 1 is supplied as a gasification fuel by a slurry pump 2, and a gasification fuel control valve 3 (a variable speed fuel charge pump is also used). However, for the sake of simplicity, the pressure is adjusted by a control valve (described below) and supplied to the gasification furnace 5.

An oxygen gas as a gasifying agent is supplied to a gasification furnace 5 through an oxygen flow control valve 4, and a water gasification reaction in the gasification furnace 5 causes CO and H _{2 as} flammable gases.
A high temperature crude gas (about 1000 ° C.) containing The crude gas produced in the gasification furnace 5 enters a dust removing device 6 composed of a scrubber or the like, where fine particles such as ash contained in the gas are removed. Here, the gasification fuel control valve 3
And the oxygen flow control valve 4 are provided with an overall load control unit 31 described later.
Is controlled by

Next, the gas is cooled to the allowable temperature at the inlet of the desulfurizer 8 by the gas cooler 7 and is sent to the desulfurizer 8.
The gasified fuel contains at most about several% (% by weight) of sulfur, and the sulfur content in the crude gas is desulfurized by the desulfurization device 8. The gasified gas after desulfurization is sent to the gas turbine 13 of the combined power generation process 48 under the control of the fuel flow control valve 10 as a clean and refined gas (refined gas). The pressure of the fuel gas obtained through the desulfurization device 8 is detected by the gas pressure detector 9 and input to the general pressure controller 34 of the general load control unit 31. And it is used for control of the gasification fuel control valve 3 and the oxygen flow rate control valve 4 by the centralized load control unit 31. The fuel flow control valve 10 is also controlled by the overall load control unit 31.

The fuel gas that has passed through the fuel flow control valve 10 is sent to the combustor 11 of the gas turbine 13 of the combined cycle power plant 48, where it is burned by the compressor 12 of the gas turbine 13 with air pressurized from the atmosphere. This combustion gas is sent to the gas turbine 13, and is driven by the gas turbine 13 to generate power using the generator 21 a of the gas turbine 13. The output of the generator 21a is detected by the output detector 29a and input to the general load controller 32 of the general load control unit 31.

The combustion gas after driving the gas turbine 13 is:
Because of the high temperature (about 600 ° C), the exhaust heat recovery boiler (HR
SG) 46, where the heat is recovered to steam and discharged from the chimney 17 to the atmosphere as low-temperature exhaust gas (about 100 ° C.). In the exhaust heat recovery boiler 46, a water or steam heat exchanger called a superheater 14, an evaporator 15, and an economizer 16 are sequentially arranged in accordance with the flow of the exhaust gas, and heat of the exhaust gas energy of the gas turbine 13 is recovered.

The steam generated by the heat recovery of the evaporator 15 is turned into superheated steam (in a dry steam state) from the steam drum 18 via the superheater 14 and sent to the steam turbine 20. The dry steam enters the steam turbine 20 via the control valve 19 of the steam turbine, drives the steam turbine, and generates power using the generator 21 b of the steam turbine 20. The output of the generator 21b is detected by an output detector 29b and is controlled by a general load controller 32 of the general load controller 31.
Is input to The rotation speed of the steam turbine is detected by the rotation speed detector 30 and input to the steam turbine control device 25.

On the other hand, the low-pressure wet steam that has worked in the steam turbine 20 becomes water in the condenser 22,
Is sent to the above-described economizer 16 via the deaerator 24, and the cycle of turning into steam again is repeated.

In the integrated gasification combined cycle system as described above, power is generated by the generator 21a of the gas turbine 13 and the generator 21b of the steam turbine 20, and the power generation output is adjusted by the fuel flow control valve 10 of the gas turbine 13. And the control valve 19 of the steam turbine of the steam turbine 20. On the other hand, the gas pressure is controlled by adjusting the gas generation amount by adjusting the gasification fuel control valve 3 (and the oxygen flow rate control valve 4) of the gasification furnace.

Of the two operating terminals for controlling the power generation output, the steam turbine control valve 19 of the steam turbine 20
Since the thermal efficiency is better when the variable pressure operation is fully opened, the operation is performed with the steam turbine control valve 19 kept constant.

The overall load control is performed by the fuel flow control valve 10 of the gas turbine 13 and the gasification fuel control valve 3 of the gasifier.
One is performed as a main operation terminal. The oxygen flow control valve 4 is automatically controlled in response to a command to the gasification fuel control valve 3.

Generally, the quality of the load operation of the whole plant depends on how fast and stable the load response is and whether the load can be stably followed even during a large load change. In the course of this load change, it is important to change the load while keeping the plant parameters within an appropriate range so as not to limit the equipment.

That is, the load change of the whole plant is controlled by using the fuel flow control valve 10 of the gas turbine 13 and the gasification fuel control valve 3 of the gasification furnace 5 as operating terminals. The control targets are generated power and gas pressure. Gas pressure stability means
It is to suppress the increase or decrease in pressure that occurs when the amount of gas generated from the gasifier and the amount of gas consumed in the gas turbine equipment become unbalanced, that is, to control the gas pressure to be constant. . As described above, in the control of the integrated gasification combined cycle system, the fuel flow rate of the gas turbine 13 or the gas generation amount of the gasification furnace 5, that is, the gas pressure (the pressure detected by the gas pressure detector 9) is changed based on the load command. It is important to control while keeping the value within an allowable range.

In the case of a general thermal power plant, the generated power and the steam pressure are controlled as main controlled variables, and feedback control is applied to the control valve 19 of the steam turbine 20 and the fuel input to the boiler. The turbine follow,
There is a turbine lead system. Also in the case of the integrated gasification combined cycle system, the power generation output and the gas pressure, which are the controlled variables, are controlled by the gasification fuel flow rate to the gasification furnace 5 (the oxygen flow rate is controlled along with the gasification fuel), A similar basic control method has been proposed depending on how to feed back the fuel flow to the turbine 13.

Among them, what is generally considered as a normal load control system is a so-called cooperative control system in which advanced control is added to the gas turbine reed system. This cooperative control system is a gas turbine reed system corresponding to a general steam turbine reed system for thermal power (the fuel consumption of the gas turbine is adjusted by controlling the power generation output by the fuel flow control valve 10 of the gas turbine, and the gas pressure is controlled. Control is gasifier 5
Method by adjusting the supply command value of the gasification fuel flow rate to the fuel)
In this embodiment, a preceding control element for improving the response of the gasification furnace 5 is added.

FIG. 5 shows the mechanism of the cooperative control system. In this cooperative control system, in addition to the gas turbine reed system, a preceding command signal created based on the load target value is given to the gasifier control to speed up the response of the gasification furnace 5, thereby achieving the gas turbine reed system. This is an improvement in the poor pressure responsiveness which is a disadvantage of the above.

This method is also introduced in a paper written by the Institute of Electrical Engineers of Japan (Goshima, Nagata et al .: Examination of Load Followability of Integrated Coal Gasification Combined Cycle Power Plant B, Vol. 110, No. 10, 1990). This cooperative control method is expected to be used as the most excellent load control method of the combined gasification power generation system at present, and as the control method during normal operation in the future combined gasification power generation system.

In response to the MW command, which is a load target value given as a plant, in the overall load control unit 31 of FIG. 4, the overall load control unit 31 controls the output of the combined power generation system (while maintaining the gas pressure at a set value). Control. The power output of the generator 21a of the gas turbine 13 and the power output of the generator 21b of the steam turbine 20 are respectively detected by an output detector 29.
a, 29b, and feeds back to the overall load controller 32 of the overall load controller 31 {(1) in the figure,
(2)｝.

The overall load controller 32 calculates a deviation between the load target value (MW command) and the generator output, and operates so as to eliminate the deviation. That is, a command value to the fuel flow control valve 10 of the gas turbine 13 is calculated so that the deviation is eliminated, and the fuel flow control valve 10 of the gas turbine 13 is adjusted by the command to adjust the output of the gas turbine 13. Is done. The output of the steam turbine 20 also changes according to the output of the gas turbine 13, and this control operation is performed until the outputs of the gas turbine 13 and the steam turbine 20 match the MW command. A method of controlling the output of the steam turbine 20 will be described later.

The general load controller 31 controls the gas pressure together with the MW command (load target value). In the preceding command function means 33, a preceding command for improving the response of the gas pressure control is created by the MW command, and is given to the pressure control side in advance. The gas pressure of the plant is the desulfurizer 8
The signal of the gas pressure detector 9 installed at the outlet of the controller is fed back and calculated by the general pressure controller 34 so as to eliminate the deviation from the pressure setting. Is added to the preceding command value.

The signal after this addition is sent to the gasification furnace 5 as a request command to the gasification furnace 5, which is an operation terminal of the gasification furnace.
And the oxygen flow control valve 4 are supplied from a gasifier fuel controller 36 and an oxygen flow controller 35, respectively. As a result, the gasified fuel that has become the coal / water slurry and the oxygen gas that is the gasifying agent are introduced into the gasification furnace 5, and the water gasification reaction in the gasification furnace 5 causes CO, which is a combustible gas, to be discharged. A high temperature crude gas (about 1000 ° C.) containing H ₂ is generated to regulate gas generation.

On the other hand, in the steam turbine control device 25, the pressure control is employed for the output control in order to improve the efficiency. A rotation speed detector 30 is provided to the steam turbine controller 25.
Speed signal and speed setting value 26 (50 Hz or 6
0 Hz), which is fed back to a proportional controller 27 (generally called a governor controller) which operates with a deviation from the frequency, and corresponds to control at the time of frequency change and at the time of overspeed.
Normally, the frequency is stable because it is synchronized with the system frequency, and the output of the proportional controller 27 hardly changes. Therefore, the control valve 19 of the steam turbine by the signal of the fully open command value 28 supplies the steam generated from the exhaust heat recovery boiler 46 when fully opened to the steam turbine 20 without any loss so that the steam turbine 20 can be operated efficiently. Is considered.

[0032]

In such a conventional integrated gasification combined cycle system, water (H ₂ O) for the water gasification reaction, which is the center of the gasification reaction, is gasified in the form of a water slurry. Gasification furnaces that have been introduced into the furnace 5, but have recently been pulverized coal directly into the furnace, and gasification of fuel that does not contain moisture such as heavy oil or residual oil obtained by extracting heavy oil from crude oil. It is gasified in furnaces and is increasingly used for power generation. In this case, it is necessary to supply high-pressure steam to the gasification furnace 5.

The pressure of the gasification furnace 5 rises from a normal pressure to about several tens of K for syngas production, and after power generation, overcomes the pressure of the gas turbine combustor 11 and refines the coal in the combustor 11. 30K-40 to introduce gas
The pressure has risen to K. The current pressure of the gasifier 5 is at this level, and the pressure of the gasifier 5 will be increased in the future. That is, it is suitable for the gasification furnace 5 of the gasification combined cycle power generation system for power generation which has a large capacity and excellent operability with a compact size and improved reaction speed.

The operating pressure of the gasification furnace 5 is considered to be about 80K, which is about twice that of the conventional case. In this case, even if the same amount of gas is handled, the pressure becomes twice and the volume becomes half. The volume of various gasification containers is also reduced to half, making the equipment compact.

Further, a quench-type gasifier, which does not include a syngas cooler of the gasifier 5 which is costly from the viewpoint of economy, has recently been used. In this case, the crude gas generated by the gasifier is gaseous. Once the quench at the bottom of
After passing through, it enters the carbon scrubber. In this case, the higher the gas pressure, the higher the temperature of the quench water, and thus the higher the gas temperature, which is advantageous for energy recovery by heat exchange with the gas using steam.

The conventional steam supply to the gasification furnace 5 at 30K to 40K is not problematic if the steam is supplied from a medium-pressure steam header, but if steam is supplied to the gasification furnace at 80K as well, It is necessary to supply high-pressure steam, which is close to the maximum pressure of the steam generated in the exhaust heat recovery boiler 46, stably and responsively. That is, an effective method for supplying high-pressure steam to the gasification furnace 5 is required due to an increase in the operating pressure of the gasification furnace 5. Further, even in a low load zone in which the generated steam pressure of the exhaust heat recovery boiler 46 is reduced, it is necessary to stably supply high-pressure steam at a high pressure (80 K or more) required by the gasification furnace 5.

The fuel supply to the gasification furnace 5 is a necessary condition that an optimum amount of steam is supplied at the same time, and when the supply of the steam is hindered, the supply of the gasification fuel to the gasification furnace 5 is limited. Since a failure occurs and becomes a hindrance to the load control response, the supply of steam requires a high-speed control response in cooperation with the load control.

An object of the present invention is to provide a combined gasification power generation system that can appropriately supply steam to a high-pressure gasification furnace for power generation.

[0039]

According to the first aspect of the present invention, there is provided an integrated gasification combined cycle system comprising: a gasification process for supplying a crude gas obtained by gasifying carbonaceous fuel as a fuel gas; and a fuel from the gasification process. A combined power generation process that drives the gas turbine by burning the gas, collects the exhaust gas from the exhaust heat recovery boiler and generates steam to drive the steam turbine, and a fuel gas supplied from the gasification process to the combined power generation process. An overall load control unit for controlling the steam turbine control device for controlling steam supplied from the exhaust heat recovery boiler to the steam turbine; and a high pressure steam required for a gasification furnace in the gasification process. Characterized by being obtained from a high-pressure steam header.

In the integrated gasification combined cycle system according to the first aspect of the present invention, the high-pressure steam required in the gasification furnace in the gasification process is supplied from the high-pressure steam header of the exhaust heat recovery boiler.

According to a second aspect of the present invention, in the integrated gasification combined cycle system according to the first aspect, the high-pressure steam header is provided between a superheater inlet of the exhaust heat recovery boiler and a control valve of the steam turbine. It is a high-pressure steam line.

In the integrated gasification combined cycle system according to the second aspect of the present invention, in addition to the function of the first aspect, the high-pressure steam required in the gasification furnace of the gasification process is supplied to the superheater inlet of the exhaust heat recovery boiler and the steam. It is supplied from a high pressure steam line between the turbine and a control valve.

In the combined gasification combined cycle system according to a third aspect of the present invention, in the second aspect of the present invention, a steam pressure detector for detecting a pressure of the high-pressure steam header is provided, and the steam turbine control device includes the steam turbine controller. The combined gasification combined cycle system according to claim 2, wherein steam pressure control is performed based on a pressure signal detected by the pressure detector.

In the integrated gasification combined cycle system according to the third aspect of the present invention, in addition to the operation of the second aspect, the steam turbine control device performs steam pressure control based on a pressure signal of a high-pressure steam header.

According to a fourth aspect of the present invention, in the gasification combined cycle system according to the third aspect of the present invention, the steam turbine controller includes a steam turbine speed adjusting means and a pressure detected by the steam pressure detector. Pressure control means based on a signal.

In the integrated gasification combined cycle system according to the fourth aspect of the present invention, in addition to the operation of the third aspect of the present invention, the steam turbine control device achieves a governor function by the speed adjusting means and controls the steam pressure by the pressure control means. To achieve.

According to a fifth aspect of the present invention, in the gasification combined cycle system according to the fourth aspect, the pressure control means of the steam turbine control device calculates a pressure deviation between a steam pressure set value and a steam pressure signal. A comparator, a steam pressure controller that calculates a pressure control signal based on the pressure deviation, and a throttle operation of the steam turbine control valve with the pressure control signal prior to the fully open command value of the steam turbine control valve. And a low value priority unit for

In the combined gasification combined cycle system according to the fifth aspect of the invention, in addition to the effect of the fourth aspect, the pressure deviation between the steam pressure set value and the steam pressure signal is obtained by a comparator, and based on the pressure deviation. Then, the pressure control signal is calculated by the steam pressure controller, and the control valve of the steam turbine is throttled by the pressure control signal prior to the fully open command value of the control valve of the steam turbine by the low value priority unit.

According to a sixth aspect of the present invention, in the integrated gasification combined cycle system according to the fifth aspect of the present invention, a high value priority device is provided after the low value priority device of the pressure control means, and an output of the low value priority device is provided. A larger one of the signal and the minimum steam flow command value is selected to operate the control valve of the steam turbine.

In the integrated gasification combined cycle system according to the invention of claim 6, in addition to the effect of the invention of claim 5, the high-priority unit allows the minimum steam flow command value to be selected at least, and maintains the pressure in order to maintain the pressure. It is possible to prevent the steam turbine control valve from being fully closed for a long time, so that the minimum steam flow rate of the steam turbine cannot be secured.

A gasification combined cycle system according to a seventh aspect of the present invention is the gasification combined cycle system according to the third aspect of the present invention, wherein the steam supplied to the gasification passage is replaced with a steam pressure detector for detecting the pressure of the high-pressure steam header. A steam pressure control device is provided in the vicinity of a steam flow control valve for adjusting pressure, and steam pressure control is performed based on a pressure signal detected by the steam pressure sensor.

In the combined gasification combined cycle system according to a seventh aspect of the present invention, instead of the operation of the third aspect of the present invention, the steam turbine control device comprises a steam flow control valve for adjusting the steam supplied to the gasification path. The steam pressure is controlled based on the pressure signal detected by the supply steam pressure detector provided in the vicinity of.

According to an eighth aspect of the present invention, in the integrated gasification combined cycle system according to the fifth aspect of the present invention, the steam turbine control device incorporates a load target value as a preceding control command, and uses the load target value as an incomplete differentiator. And is added to the steam pressure set value as a load change signal at the time of load change.

In the combined gasification combined cycle system according to the eighth aspect of the present invention, in addition to the operation of the fifth aspect, a change in the load target value is added to the steam pressure set value as a load change signal at the time of load change. Improve the steam pressure responsiveness when changing.

[0055]

Embodiments of the present invention will be described below. FIG. 1 is a configuration diagram of an integrated gasification combined cycle system according to an embodiment of the present invention. This embodiment is different from the conventional example shown in FIG. 4 in that a steam line 49 for obtaining high-pressure steam required in a gasification furnace of a gasification process from a high-pressure steam header of an exhaust heat recovery boiler is provided. A steam pressure detector 39 for detecting the pressure of the header is provided,
A supply steam pressure detector 40 is provided near a steam flow control valve 38 for adjusting the steam supplied to the gasification passage 5, and the steam pressure detected by the steam pressure detector 39 or the supply steam pressure detector 40, and further, The load target value (MW setting) is input to the steam turbine control device 25 and used for controlling the control valve 19.

Further, the general load control unit 31 is additionally provided with a gasification furnace steam controller 37 for controlling a steam flow control valve 38 for controlling steam supplied to the gasification passage 5. The other configuration is the same as that of the conventional example shown in FIG. 4, and therefore, the same elements are denoted by the same reference numerals, and overlapping description will be omitted.

In FIG. 1, the high pressure steam required in the gasification furnace of the gasification process is supplied from a high pressure steam line between the inlet of the superheater 14 of the exhaust heat recovery boiler 46 and the control valve 19 of the steam turbine 20. Is configured.

On the other hand, the pressure at the preceding stage of the steam turbine control valve 19 is detected by the steam pressure detector 39 and fed back to the steam turbine control device 25. This allows
The steam turbine control device 25 includes a steam turbine control valve 19.
Is controlled to meet the steam pressure requirement on the gasification furnace 5 side.

The inlet pressure of the steam flow control valve 38 of the gasification furnace 5 is detected by a gasification furnace supply steam pressure detector 40 and fed back to the steam turbine controller 25. As a result, a decrease in steam pressure is detected at an early stage so that the response of the steam pressure is accelerated, and the gasifier 5 is supplied with an optimal oxygen flow rate corresponding to the gasification fuel flow rate with respect to the gasifier command value. The steam flow will be injected without delay.

FIG. 2 is a configuration diagram of the steam turbine control device 25 according to the embodiment of the present invention. The rotation speed signal from the rotation speed detector 30 and the speed setting value 26 (50 Hz or 60 Hz) are added to the adder 5 by the steam turbine controller 25.
0a, and the speed deviation obtained by the adder 50a is input to the proportional controller 27 (governor controller). The proportional controller 27 corresponds to the control at the time of frequency change and overspeed, and the output of the proportional controller 27 hardly changes at normal times because the frequency is stable because it is synchronized with the system frequency. do not do. Therefore, the output signal of the adder 50b becomes a control signal from the high-priority unit 41, and the control valve 19 of the steam turbine 20 is controlled by the control signal from the high-priority unit 41.

On the other hand, the MW command (load target value) is input to the adder 50c via the imperfect differentiator 45, and is added to the steam pressure set value P0 so as to speed up the response of the steam pressure. Thereby, when the load increases, the steam pressure set value is apparently increased temporarily (differentially), the steam turbine control valve 19 is closed momentarily, and the pre-stage pressure of the steam turbine control valve 19 is reduced. To quickly supply steam to the gasification furnace 5.

The pressure at the preceding stage of the steam turbine control valve 19 detected by the steam pressure detector 39 and the inlet pressure of the steam flow control valve 38 of the gasification furnace 5 detected by the gasification furnace supply steam pressure detector 40 are: , The adder 50 via the switch 51
c. FIG. 2 shows a case in which the switch 51 selects the pressure at the preceding stage of the steam turbine control valve 19 detected by the steam pressure detector 39 and inputs the selected pressure to the adder 50c.

In the adder 50c, a pressure deviation between the pressure of the previous stage of the steam turbine control valve 19 detected by the steam pressure detector 39 and the steam pressure set value P0 is calculated. The load change from is taken into account.

The output signal of the adder 50c is input to the steam pressure controller 44, and outputs a control signal such that the pressure at the preceding stage of the steam turbine control valve 19 matches the steam pressure requirement on the gasification furnace 5 side. The control signal from the steam pressure controller 44 is input to a low value priority unit (LVG) 43, and a low value of the fully open command value 28 is selected. The output signal of the low value priority device (LVG) 43 is further output to the high value priority device (HV).
G) 41, and the larger one of the minimum steam flow rate command value 42 is selected and input to the adder 50b. Thereby, the minimum flow rate of the steam turbine 20 is secured.

The operation of the embodiment of the present invention will be described with reference to FIG. The preceding command from the MW command (load target value) to the gasifier 5 is calculated by the preceding command function means 33 and added to the control signal of the general pressure controller 34 by the adder 50. That is, the advance signal from the MW command (load target value) to the gasification furnace 5 is added to the control signal of the general pressure controller 34, and the oxygen flow controller 35 issues a command signal to the oxygen flow control valve 4, the gasification furnace Fuel controller 36
Then, a command signal to the gasification fuel control valve 3 and a command signal to the gasification furnace steam flow control valve 38 by the gasification furnace steam controller 37 are generated.

The steam flow command is given from the gasification furnace steam controller 37 to the steam flow control valve 38 to adjust the opening degree. This steam is supplied to the steam turbine control valve 19.
From the high-pressure steam header between the steam generator and the super heater 14 to the steam flow control valve 38 of the gasification furnace 5.

In the operation region where the fuel flow rate of the gas turbine 13 is large, that is, when the combined power generation process 48 is operated in a high load zone, the high-pressure steam pressure of the exhaust heat recovery boiler 46 is relatively high, but when the partial load is reached. , This pressure gradually decreases. If the steam turbine control valve 19 is operated with the valve fully open as in the conventional case, the steam pressure decreases as shown by the characteristic curve B in FIG. 3, which hinders the supply of high-pressure steam to the gasification furnace 5. I will.

Therefore, in the steam turbine control device 25 of this embodiment, the minimum set value C of the steam supply pressure required by the gasifier 5 is set as a target value.
This command value and the pressure of the outlet of the exhaust heat recovery boiler 46, that is, the pressure in front of the steam turbine control valve 19 (steam pressure detector 39
From the steam pressure controller 4
In step 4, a relevance command for the steam turbine control valve 19 is calculated and output. This signal is compared with a fully open command value 28 by a low value priority unit (LVG) 43 for selecting a low value, and a command is issued to the steam turbine control valve 19 so that the steam pressure in the low load zone becomes a predetermined steam pressure setting. Give a value.

This situation is shown by a characteristic curve A in FIG. The output of the low-priority unit (LVG) 43 is output from the high-priority unit (H
VG) 41 is compared with the minimum steam flow rate command value 42 to output one of the high values. This is because the steam turbine control valve 19 is almost fully closed due to the steam pressure control. This is for ensuring the minimum steam flow rate for preventing the minimum flow rate to the steam turbine 20 from being unable to be ensured.

Here, a fuel containing no moisture, such as a gasification furnace 5 for directly charging collected coal into a furnace or heavy oil or a residual oil obtained by extracting heavy oil or the like from crude oil, is used in the gasification furnace 5. When gasification is used for power generation, high-pressure steam must be supplied to the gasification furnace. The gasifier 5 is in the direction of higher pressure in the future, and it is necessary to effectively supply high-pressure steam to the gasifier by increasing the operating pressure of the gasifier.

Further, even in a low load zone where the generated steam pressure of the exhaust heat recovery boiler 46 is reduced, it is necessary to stably supply high pressure steam at a high pressure (80 K or more) required by the gasification furnace 5. Have been.

In the embodiment of the present invention, steam is supplied to the high-pressure gasification furnace 5 for power generation from the outlet of the superheater 14 of the exhaust heat recovery boiler 46, and the amount of fuel supplied to the gasification furnace 5 is reduced. A matched optimal amount of steam is supplied simultaneously. Therefore, it is possible to achieve a smooth supply of gasified fuel to the gasification furnace 5 and to realize a stable load control response of the entire integrated gasification combined cycle system.

Further, in the embodiment of the present invention, the control response of the steam pressure in cooperation with the load control is obtained. In other words, it is necessary to supply the gasifier 5 with the optimum oxygen flow rate and the steam flow rate corresponding to the gasification fuel flow rate without delay with respect to the gasification furnace command value. In order to speed up the response, the inlet pressure of the steam flow control valve 38 of the gasifier 5 is changed to the gasifier supply steam pressure detector 4.
0, and this signal is fed back to the steam turbine controller 25 as a feedback signal for pressure control. Thereby, the pressure drop can be detected at an early stage, and the control response of the pressure is improved.

Further, by adding the MW command (load target value) to the steam pressure set value P0 by the incomplete differentiator 45, when the load is increased, the steam pressure set value P0 is temporarily changed (differentiated). ) To instantaneously raise the steam turbine control valve 19.
Is closed, and the pre-stage pressure of the steam turbine control valve 19 is increased, so that the steam can be quickly supplied to the gasification furnace 5.

[0075]

As described above, according to the present invention, in order to stably supply high-pressure steam to the gasifier, the high-pressure steam from the steam turbine is supplied to the steam flow control valve of the gasifier. A steam supply route will be installed to control the pressure in front of the steam turbine control valve to meet the steam pressure requirements of the gasifier.
Therefore, the supply of the high-pressure steam to the gasification furnace can be stably performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an integrated gasification combined cycle system according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a steam turbine control device according to the embodiment of the present invention.

FIG. 3 is a characteristic diagram of a pressure control function of the steam turbine control device according to the embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional integrated gasification combined cycle system.

FIG. 5 is an explanatory diagram of a cooperative control method in a generalized load control unit of a conventional integrated gasification combined cycle system.

[Explanation of symbols]

 3 Gasification Fuel Control Valve 4 Oxygen Flow Control Valve 5 Gasification Furnace 9 Gas Pressure Detector 10 Fuel Flow Control Valve 13 Gas Turbine 19 Steam Turbine Control Valve 20 Steam Turbine 25 Steam Turbine Controller 31 General Load Control Unit 38 Steam Flow Control Valve 39 Steam pressure detector 40 Supply steam pressure detector 46 Waste heat recovery boiler 47 Gasification process 48 Combined cycle power plant 49 Steam line

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02C 6/18 F02C 6/18 A F22B 1/18 F22B 1/18 C (72) Inventor Masakazu Shirakawa Kanagawa 2-4, Suehirocho, Tsurumi-ku, Yokohama-shi F-term in Toshiba Keihin Works Co., Ltd. 3G081 BA02 BA13 BB00 BC07 BD00 DA04 DA22 3L021 AA08 BA03 CA10 DA04 EA04 FA12 FA28

Claims (8)

[Claims] 1. A gasification process in which a crude gas obtained by gasifying carbonaceous fuel is supplied as a fuel gas, a fuel gas from the gasification process is burned to drive a gas turbine, and the exhaust gas is discharged by a waste heat recovery boiler. A combined power generation process for recovering and generating steam to drive the steam turbine, a general load control unit for controlling fuel gas supplied from the gasification process to the combined power generation process, and the steam turbine from the exhaust heat recovery boiler. A steam turbine control device for controlling the supplied steam, and a gasification combined, wherein high pressure steam required in a gasification furnace of the gasification process is obtained from a high pressure steam header of the exhaust heat recovery boiler. Power generation system. 2. The gasification complex according to claim 1, wherein the high-pressure steam header is a high-pressure steam line between a superheater inlet of the heat recovery steam generator and a control valve of the steam turbine. Power generation system. 3. A steam pressure detector for detecting a pressure of the high-pressure steam header, wherein the steam turbine control device comprises:
The combined gasification combined cycle system according to claim 2, wherein steam pressure control is performed based on a pressure signal detected by the steam pressure detector. 4. The steam turbine control device according to claim 3, wherein the steam turbine control device has a speed adjusting means for the steam turbine and a pressure control means based on a pressure signal detected by the steam pressure detector. Gasification combined cycle system. 5. A pressure control means of the steam turbine control device, comprising: a comparator for calculating a pressure deviation between a steam pressure set value and a steam pressure signal; and a steam pressure controller for calculating a pressure control signal based on the pressure deviation. And a low-priority device for narrowing down the control valve of the steam turbine with the pressure control signal in preference to the fully open command value of the control valve of the steam turbine. An integrated gasification combined cycle system as described in the above. 6. A high-priority unit provided downstream of the low-priority unit of the pressure control means, and a larger one of an output signal of the low-priority unit and a minimum steam flow command value is selected to select the larger one. The combined gasification combined cycle system according to claim 5, wherein the control valve is operated. 7. A supply steam pressure detector is provided in the vicinity of a steam flow control valve for controlling steam supplied to the gasification passage, instead of the steam pressure detector for detecting the pressure of the high-pressure steam header. The combined gasification power generation system according to claim 3, wherein steam pressure control is performed based on a pressure signal detected by the supply steam pressure detector. 8. The steam turbine control device takes in a load target value as a preceding control command, processes the load target value by an incomplete differentiator, and adds the load target value to the steam pressure set value as a load change signal at the time of load change. The integrated gasification combined cycle system according to claim 5, wherein