JPS61145322A - Control device in combined cycle plant for producing coal gas - Google Patents

Abstract

PURPOSE:To aim at enhancing the efficiency of a combined cycle plant upon low load operation, by providing a turbine speed and load control system for regulating the amount of fuel fed to a burner, and a gasifying furnace pressure control system for regulating the amounts of coal and air fed into a gas furnace. CONSTITUTION:A slurry-like coal steam mixed with water is gasified to produce coarse gas in a gasifying furnace 2, and is introduced into a burner 7 through a desulfurizer 4 and a gas turnbine 6. A fuel flow regulating valve 20 regulates the amount of fuel in accordance with a set load value, an actual output power and actual rotational speed of a turbine 9. Further, a coal stream regulating valve 21 and an air flow regulating valve 22 regulate the amount of coal and the amount of air in accordance with the deviation between the pressure which is set in accordance with the set load value and the internal pressure of the gasifying furnace 2. With this arrangement, the efficiency of the combined cycle plant may be enhanced even upon low load operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a control device for a coal gasification combined cycle plant, and more particularly to a control device for a plant suitable for operating the plant with a system pressure of variable pressure.

[Technical background of the invention and one point in between]

Coal gasification combined cycle system converts coal into gas,
The gas is used as fuel gas to run the gas tank.
It is a highly efficient power generation system that generates electricity.

This system has attracted attention in recent years due to its superiority in environmental measures, such as the effective use of coal and the ease of desulfurization).

An example of a coal gasification combined cycle power generation system is shown in FIG. 5, and the device and load control method will be explained below using this figure.

The fuel coal is mixed with water in a slurry generator 1 to form a slurry-like coal flow, and a gasification reaction is caused in a gasifier 2 using air as an oxidizing agent to generate crude gas. Since this crude gas has a high temperature, the temperature is lowered by the gas cooler 3 to a temperature that can be desulfurized, and the crude gas flows into the desulfurization device 4 . At this time, heat is exchanged with water to generate steam, which is stored in the gas cooler drum 5. The gas purified by the desulfurization device 4 is heated by a gas heater 6, mixed with compressed air provided by a compressor 8 in a combustor 7, combusted, and sent to a gas turbine 9, which rotates the gas turbine to generate electricity. The exhaust gas from this gas turbine 9 is led to an exhaust heat recovery boiler 10,
The heat is exchanged sequentially with the super heater 11, evaporator 12, and economizer 13, and then released into the atmosphere. Steam generated by the evaporator 12 is stored in a steam drum 14, superheated by a superheater 11 together with steam from the gas cooler drum 5, flows into a steam turbine 15, and generates electricity using the generated torque. steam turbine 1
The steam that has done work in step 5 becomes water in the converter 16 and is led to the exhaust heat recovery boiler 10 through the feed water heater 17 and the deaerator 18. The water heated by the economizer 13 of the exhaust heat recovery boiler IO is subjected to a gas cooler drum 5 on one side and a steam drum 14 on the other side.

On the other hand, the air to be fed into the gasification furnace 2 is extracted from the combiner f8, further compressed by a booster air compressor al19, and then allowed to flow into the gasifier 2.

When such a plant is operated under load, a control signal corresponding to the load deviation is output from the control device to operate the fuel flow regulating valve 20 that adjusts the flow of fuel flowing into the gas turbine 9, and the gasifier 2 is operated. Coal slurry t, which is the fuel flowing into
This is done by operating the coal (slurry) flow rate adjustment valve 21 that adjusts the flow rate of the coal (slurry) and the air flow rate adjustment valve 22 that adjusts the air that is the oxidizing agent.

Since the steam turbine output is determined by the energy of the gas turbine exhaust gas, the load of combined power generation is determined by the gas turbine (
: Determined by the inflowing fuel flow.

In the coal gasification combined cycle plant configured as described above, load control has conventionally been performed by controlling the opening and closing of the fuel flow rate regulating valve 20 while keeping the internal pressure of the gasifier 2 constant. . That is, when the load was high, the opening of the fuel flow control valve was kept large, and when the load was low, the opening was made small, and in this way, the amount of fuel flowing into the combustor 7 was controlled by adjusting the valve opening. .

However, if the internal pressure of the gasifier is kept constant ζ2 regardless of the load C2 as described above, in the case of low load (= gas flow rate decreases, the gas flow rate slows down, Gasification C: The necessary fluidized bed height and desulfurization equipment: Both the required fluidized bed heights cannot be secured, and the efficiency of the gasification reaction and desulfurization reaction decreases.In addition, the gasification furnace has a gas A part of the turbine compressor discharge rush is boosted and guided by the step-up compressor, but when the turbine load decreases, the compressor discharge pressure also decreases, so as described above. In order to maintain the internal pressure of the gasifier at the same level as under high load, the work of the boost compressor must increase as the load decreases, requiring extra power. In order to achieve this, if the opening degree of the fuel flow rate adjustment valve is reduced, there are various problems with the system that maintains the load inside the gasifier (constant regardless of the load), such as an increase in throttling loss when the valve is removed.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and an object of the present invention is to provide a control device for a coal gasification combined nitrite plant that can operate the plant while maintaining high efficiency even under low load. shall be.

[Summary of the invention]

The present invention relates to a gasifier that oxidizes coal with air and gasifies it, a combustor that burns the gas obtained in the gasifier together with air supplied from a compressor, and a combustion gas of the combustor. A gas turbine driven by C2, the exhaust gas of the gas turbine and the gas obtained from the gasification furnace are used as heat sources (two heat recovery boilers that generate steam, and the steam obtained from the waste heat recovery boiler). A control device for a coal gasification combined cycle plant that has a driven steam turbine and a Shimoda compressor that pressurizes a part of the air obtained from the compressor and supplies it to the gasifier, and its configuration is roughly divided into two parts: one is a turbine speed load control system that adjusts the amount of fuel flowing into the combustor based on the load setting value and the actual output and rotation speed of the turbine; The other one is to adjust the amount of coal t and air flowing into the gasification furnace based on the deviation between the pressure variably set according to the load setting value and the pressure inside the gasification furnace, and also to adjust the amount of air and the amount of coal flowing into the gasification furnace. It is a gasifier variable pressure control system that controls the rotation speed.
The invention consists of these two parts. Here, the pressure that is variably set according to the load setting value is set by a function generator or the like so as to be suitable for the plant. Therefore, the pressure inside the gasifier changes according to the load setting value, and the plant can be operated with high efficiency even when the turbine is under low load.

[Embodiments of the invention]

The present invention will be more clearly understood from the following examples.

11& is a system diagram of the control device of the coal gasification condenser (India cycle plant) shown in FIG. The load setting value 31 is applied to the output detector and the obtained turbine design value 1 is applied to the output detector.
37, and the deviation is input to the comparison calculator 39 after being integrated by the proportional integrator (2) and the actual turbine rotation obtained by the rotation speed detection (4). It is compared with the numerical signal 41, and the adjustment rate 42 is added to the deviation to control the opening/closing of the flow mM!iI valve 20.

In addition, in the gasifier function generator 34, a pressure setting value is output according to the load setting value 31, and this pressure setting is used in comparison 4. ・1 direct signal is the pressure at which the pressure inside the gasifier 2 is detected. It is compared with the gasifier internal pressure signal 46 obtained by the detector 45, and its deviation is integrated by the proportional integrator 47, thereby controlling the opening and closing of the rush current regulating valve 22.

On the other hand, in the adder 35, the output signal of the proportional integrator 47 is added to the load setting value 31, and the addition result is branched and sent to the comparison calculator 48 and the coal flow rate function generator 4, respectively.
9 is input. In comparison operation 4, the above addition result is compared with the boost compressor rotation speed signal 51 obtained by the boost compressor rotation speed detector 50, and the deviation is input to the proportional controller 52, and its output is used to control the boost compressor drive motor. 53 is rotational speed controlled. In addition, the coal flow rate function generator 49 outputs a coal flow rate set value 54 corresponding to the above addition result, and this coal flow rate set value 54 is determined by the comparison calculator 55 (secondly, the coal flow rate obtained by the coal flow rate detector 56). It is compared with a signal 57, and its deviation is integrated by a proportional integrator 58, thereby controlling the opening and closing of the coal flow rate regulating valve 21.

2 and 3 are diagrams showing the relationship between the input and output of the gasifier king function generator 34 and the coal flow rate function generator 49, respectively, with the horizontal axis (the input value On the other hand, the pressure setting value or the coal dispersion setting value that satisfies a certain relationship is output. The value is output proportional to the load setting value (2).

Next): The operation of the above configuration will be explained in the case where the load setting value decreases.

When the load setting value 31 decreases, the turbine speed load control system I operates to apply the fuel adjustment valve in the closing direction. At this time, the set pressure decreases due to the action of the gasifier field function generator, causing a deviation from the gasifier internal pressure 46, and accordingly, the air flow rate regulating valve 22 also operates in the closing direction. When the air flow rate decreases in this way, the gasification reaction within the gasifier 2 becomes slower and the gas pressure decreases. At the same time, the output signal of the adder 35 also becomes smaller, the rotational speed of the FEE compressor drive motor 53 decreases, and the amount of air supplied decreases. On the other hand, the adder 3
5, the output of the coal flow function generator 49 decreases, so the coal flow rate regulating valve 21 operates in the closing direction and the amount of coal (slurry) supplied also decreases.

As mentioned above, when the pressure inside the gasifier 2 decreases due to the action of the gasifier variable pressure control system, the action of the turbine speed load control system l (=therefore, the fuel flow regulating valve operated in the closing direction). 20 increases the opening degree again, and control is performed so that the output of the turbine satisfies the load setting value.

As described above, according to this embodiment, in response to a change in the load setting value, the turbine speed load control system first operates the fuel flow control valve to follow the load, while the gasifier variable pressure control system operates the fuel flow control valve to follow the load. The pressure setting value decreases as the load setting value changes, and the air flow rate regulating valve operates in the closing direction depending on the deviation between the above setting value and the actual pressure in the furnace. At the same time, the rotational speed of the booster compressor is controlled to reduce the air condensation supplied, and the coal (slurry) It is also adjusted in accordance with the output of the coal quantity function generator. In this way, the amount of coal and air flowing into the gasifier are controlled by the coal flow rate control valve and booster compressor rotation speed sea based on the load setting value and pressure setting value, and each wax settles to the final setting value. Transient fluctuations up to the fuel flow control valve,
Since it is controlled by an air flow rate adjustment valve, stable load control can be achieved. Note that the internal pressure of the gasifier does not necessarily have to be the pressure at the gasifier 2, but may be the pressure at the upstream point of the fuel flow rate regulating valve 20.

FIG. 4 shows another embodiment. In this embodiment, the turbine speed load control system and the gasifier transformer pressure control system are connected to each other via a bias device, and the gasifier pressure deviation and turbine load are controlled respectively. This allows advance control by providing a deviation. In the following, when the same parts as those shown in the It figure (Sansui) are shown, the same reference numerals are attached and explained.

In Fig. 4C2, the turbine speed load control system (■) is under negative closed control, but the above load deviation includes the difference between the pressure setting value 43, which is the output of the gasifier function generator, and the gasifier internal power signal 46. is added as a feedforward signal by an adder 61 via a bias device 60. Also,
Conversely, the load deviation is added to the difference between the pressure setting value 43 and the gasifier internal pressure signal 46 by an adder 63 via a biaser 62 as a feedforward signal.

However, the addition result of the lever is the air flow rate function generator 64, the boost compressor rotation speed function generator 65, and the coal flow rate function generator 66.
: Two people input the input signal (two corresponding set values are output from each function generator, and these set values, the narrow air flow fine signal 68 obtained by the air flow rate detector 67, and the boost compressor rotation speed signal) 51 and the coal flow rate signal 57 are respectively sent to the comparison calculator 485.
2.66 and based on the deviation, the airflow fine adjustment valve 22. The boost compressor drive motor 53 and the coal fine adjustment valve 21 are controlled.

As described above, the pressure setting value is determined according to the change in the load setting value, and the air flow rate adjustment valve, the Nobuta compressor drive motor, and the coal The fine adjustment valve is operated to perform variable pressure operation of the gasifier to obtain a gasifier pressure suitable for the load. Furthermore, since this gasifier variable pressure control m system incorporates the load deviation bias as a feedforward signal, it is possible to detect pressure fluctuations due to load fluctuations in advance and perform more reliable and stable counterpressure control. I can do it. On the other hand, in the turbine speed load control system C2, load fluctuations due to soil force fluctuations can be detected in advance and good load control can be achieved by adding a pressure deviation bias to the load deviation and operating the fuel flow regulating valve C2. can be realized.

〔Effect of the invention〕

As described above, since the present invention has a configuration in which the gasifier pressure is reversed depending on the load setting, the present invention (according to the present invention (2) enables plant operation up to a low load of about 25% of the rated value. It is possible to realize a coal gasification combined plant that can sustain operation with extremely high efficiency even under low load conditions.

[Brief explanation of the drawing]

IF diagram is a control system diagram of a control device for a coal gasification combined cycle plant according to an embodiment of the present invention, FIGS. 2 and 3 are diagrams explaining the action of the function generator, and FIG. A control system diagram showing another example of the fifth factor is a system diagram of a coal gasification compiler'F Nikle plant. 2...Gasifier 7...Combustor 8...Compression aI 9...Gas turbine 10...
Exhaust heat recovery boiler 15...Steam turbine 19...
Boost compressor 20...Fuel flow fine adjustment valve 21...
・Coal circulation welfare adjustment valve 22... Coal circulation welfare adjustment valve...
・Control device 31...Load setting value 34...
Gasification furnace soil function generator 37... Turbine actual output signal 41... Turbine actual rotation speed signal 53... Boosting compressor drive motor agent Patent attorney Noriyuki Chika (one idiot) Figure 2 Shell Translation A 11j- Part 3 Illustrated P1 I Through

Claims (1)

[Claims] A gasifier that oxidizes coal with air and gasifies it; a combustor that burns the gas obtained in the gasifier together with air supplied from a compressor; and a combustor that is driven by the combustion gas of the combustor. a gas turbine, an exhaust heat recovery boiler that generates steam using the exhaust gas of the gas turbine and the gas obtained in the gasifier as a heat source, and a steam turbine driven by the steam obtained by the exhaust heat recovery boiler; A control device for a coal gasification combined cycle plant having a booster compressor that pressurizes a part of the air obtained from the compressor and supplies it to the gasifier, which controls the load setting value, the actual output of the turbine, and the actual output of the turbine. a turbine speed load control system that adjusts the amount of fuel flowing into the combustor based on the rotational speed; and a turbine speed load control system that adjusts the amount of fuel flowing into the combustor based on the rotation speed; A control device for a coal gasification combined cycle plant comprising a gasifier variable pressure control system that adjusts the amount of coal and air flowing into the gasifier and controls the rotation speed of the boost compressor.