JP6080567B2 - Operation control method for coal gasification combined cycle plant and coal gasification combined cycle plant - Google Patents

Description

  The present invention relates to an operation control method for a coal gasification combined power plant and a coal gasification combined power plant.

  In a coal-fired power plant, particularly a coal-fired boiler plant that burns coal to obtain steam for steam turbines, the ash in the combustion gas adheres to the surface of the heat transfer tube in the boiler and the heat transfer performance decreases. In order to solve this problem, there is a technique for installing a soot blower in a boiler, intermittently removing ash on the surface of the heat transfer tube, and preventing a decrease in heat transfer performance. Similarly to a coal-fired boiler, in a combined coal gasification combined power plant that gasifies coal to obtain gas turbine fuel, ash generated by gasification adheres to a downstream heat recovery boiler. Therefore, the soot blower prevents a decrease in heat transfer performance. As for the operation of such a soot blower, there is one disclosed in Patent Document 1, for example.

  Patent Document 1 relates to a coal-fired boiler plant, and the reheater outlet steam temperature rapidly rises due to the soot blower of the reheater. In order to avoid this, reheat provided in the rear heat transfer section of the boiler furnace before the soot blower is performed. Is added as a preceding signal to adjust the flow rate of the flue gas to the heater and superheater with the gas distribution damper, the amount of passing gas on the reheater side is reduced to reduce the amount of heat absorption, and the reheater outlet steam temperature is reduced. By performing the control to decrease in advance, the reheater outlet steam temperature is prevented from rapidly increasing.

JP 2004-264002 JP

  However, the gas distribution damper control in Patent Document 1 is specific to the shape of the coal-fired boiler and the heat transfer surface arrangement, and cannot be applied to the combined coal gasification combined power plant. In particular, in a coal gasification combined power plant, gas after passing through a heat recovery boiler is used as fuel for a gas turbine. Therefore, when the amount of gas passing through the heat exchanger is controlled, the output fluctuation of the gas turbine or the pressure fluctuation in the gas system is caused.

  An object of the present invention is to provide an operation control method for a coal gasification combined power plant and a coal gasification combined power plant that can stably control the steam generated by a heat recovery boiler by reducing the influence of soot blower operation.

  In order to achieve the above object, the present invention is characterized in that the fluctuation of the evaporation amount of the heat recovery boiler is suppressed by controlling the evaporator circulation flow rate in the heat recovery boiler.

  According to the present invention, it is possible to stably control boiler-generated steam by reducing the influence of soot blower operation.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

The principal part schematic of the coal gasification combined cycle power plant by the 1st example of the present invention. The schematic diagram which shows the evaporation amount at the time of injections, such as a soot blower concerning embodiment of this invention, and a circulating water flow rate. The principal part schematic of the coal gasification combined cycle power plant by the 2nd example of the present invention. Schematic of an example of a coal gasification combined power plant to which the present invention is applied.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, an example of a combined coal gasification combined power plant to which the embodiment of the present invention is applied will be described with reference to FIG. The coal gasification combined power plant is composed of a gasification part that gasifies fuel, a gas purification part that purifies the obtained gas, a power generation part that extracts power from the purified gas and the obtained steam.

  The gasification part includes a gasification furnace 1 and a heat recovery boiler (syngas cooler) 3. In the gasification furnace 1, the fuel transported by the fuel transport pipe 9 is gasified. The gasified fuel (high-temperature fuel gas) is introduced into the heat recovery boiler 3 through the communication pipe 2 and cooled by heat exchange with the economizer 5 and the evaporator 6 in the heat recovery boiler 3. Moreover, in the heat recovery boiler 3, steam is obtained by heat exchange with the fuel gas. The water supply to the economizer 5 is supplied from the exhaust heat recovery boiler 16 (the low pressure economizer of the exhaust heat recovery boiler). Circulating water to the evaporator 6 is forcedly circulated from the steam drum 4 by the circulation pump 7. Steam generated in the heat recovery boiler 3 is recovered by the steam drum 4. Although not shown in FIG. 4, as will be described later, a soot blower is provided to remove fuel ash accumulated on the surface of the heat transfer tubes of the heat saving boiler 3 and the evaporator 6 of the heat recovery boiler 3. Yes.

  The fuel gas that has finished heat exchange in the heat recovery boiler 3 is introduced into the gas purification section. The gas purification part is constituted by a dust collector 11 that collects unburned components from the fuel gas, and a gas purification facility 12 that removes unnecessary substances to produce purified gas. The purified gas is supplied to the gas turbine 15 through the fuel pipe 13. A fuel control valve 14 is installed in the fuel pipe 13, and the flow rate of purified gas supplied to the combustor of the gas turbine 15 is controlled by the fuel control valve 14.

  The power generation portion includes a gas turbine 15, an exhaust heat recovery boiler 16, and a steam turbine 19. In the gas turbine 15, purified gas is burned to obtain power (the generator is not shown). The exhaust heat recovery boiler 16 introduces exhaust gas from the gas turbine 15 and generates steam by heat exchange between the feed water from the feed water pump 10 and the gas turbine exhaust gas. The steam is recovered by the exhaust heat recovery boiler drum 17. Steam from the steam drum 4 of the heat recovery boiler joins the exhaust heat recovery boiler drum 17. The steam of the exhaust heat recovery boiler drum 17 is superheated by the superheater of the exhaust heat recovery boiler 16 and supplied to the steam turbine 19 through the main steam pipe 18 to obtain power by the steam turbine 19 (the generator is not shown). doing.).

  In this embodiment, the steam turbine 19 is composed of a high-pressure turbine and a low-pressure turbine, and the exhaust steam of the high-pressure turbine is superheated by the superheater of the exhaust heat recovery boiler 16 and introduced into the low-pressure turbine via the main steam pipe 18. It has come to be. The exhaust steam from the low-pressure turbine is condensed by the condenser 20 and supplied again to the low-pressure economizer of the exhaust heat recovery boiler 16 by the feed water pump 10. In the exhaust heat recovery boiler shown in FIG. 4, illustration of a low-pressure drum and the like is omitted.

  Next, the first embodiment of the present invention will be described in detail with reference to FIG.

  A large number of soot blowers are attached to the economizer 5 and the evaporator 6 of the heat recovery boiler for removing the ash content of fuel accumulated on the surface. The soot blower gas is supplied from a soot blower holder 8 held at a high pressure. The flow rate, operation time, and operation interval of the soot blower are determined by the soot blower amount determining means 31 and controlled by the economizer soot blower flow control valve 24 and the evaporator soot blower flow control valve 25. As these, conventional ones can be used, and detailed description is omitted.

  In the present invention, the evaporator circulation flow rate is controlled in order to stably control the evaporation amount of the heat recovery boiler. That is, a predetermined heat transfer amount from the fuel gas to the steam is obtained in the heat recovery boiler without being affected by the above-described soot blower operation.

  The amount of heat transfer from the fuel gas to the steam is determined by the amount of temperature drop of the fuel gas when heat loss outside the system is ignored. Therefore, by controlling the temperature difference between the gas temperature at the evaporator outlet (gas side outlet) and the circulating water temperature at the evaporator inlet (circulated water side inlet), the amount of heat transfer from the fuel gas to the steam is substantially controlled. (In other words, controlling the temperature difference between the gas temperature at the evaporator outlet and the circulating water temperature at the evaporator inlet is synonymous with controlling the amount of heat transfer from the fuel gas to the steam).

  Therefore, in this embodiment, the evaporator circulation flow rate is controlled so that the temperature difference between the gas temperature at the evaporator outlet in the heat recovery boiler and the circulating water temperature at the evaporator inlet is close to the temperature difference set value. Specifically, the evaporator outlet gas temperature is measured by the fuel gas temperature measuring device 21, the evaporator inlet circulating water temperature is measured by the circulating water temperature measuring device 22, and the evaporator circulating flow rate control means 33 evaporates. The opening degree of the evaporator circulation flow control valve 23 is adjusted using PID control so that the temperature difference between the evaporator outlet gas temperature and the evaporator inlet circulating water temperature is close to a predetermined value (temperature difference set value).

  The operation of the present embodiment will be described. The heat transfer performance between the fuel gas and the heat transfer tube is always changed by repeating the accumulation of ash on the heat transfer tank and the removal of the ash by the operation of the soot blower in the economizer 5 and the evaporator 6 of the heat recovery boiler. If the heat transfer performance between the fuel gas and the heat transfer tube is reduced due to the accumulation of ash, increasing the circulating water flow rate in the evaporator 6 will increase the circulating water flow rate and increase the temperature difference between the heat transfer tube and the circulating water. And promote heat transfer. That is, assuming that the evaporator circulation flow rate is constant, if the heat transfer performance between the fuel gas and the heat transfer pipe is reduced, the temperature difference between the evaporator outlet gas temperature and the evaporator inlet circulating water temperature is larger than the temperature difference set value. Become. In this embodiment, the circulating water flow rate is increased to promote heat transfer between the heat transfer pipe and the circulating water so that the temperature difference between the evaporator outlet gas temperature and the evaporator inlet circulating water temperature is close to the temperature difference set value. ing. In addition, when the heat transfer performance between the fuel gas and the heat transfer tube is restored by the soot blower, the circulating water flow rate of the evaporator 6 is decreased to reduce the circulating water flow rate and the temperature difference between the heat transfer tube and the circulating water. And suppresses heat transfer. That is, when the heat transfer performance between the fuel gas and the heat transfer pipe is restored, the temperature difference between the evaporator outlet gas temperature and the evaporator inlet circulating water temperature is higher than the temperature difference setting value while the circulating water flow rate is increased. Get smaller. The temperature difference between the evaporator outlet gas temperature and the evaporator inlet circulating water temperature is made close to the temperature difference set value by reducing the circulating water flow rate and suppressing the heat transfer between the heat transfer tube and the circulating water. In other words, in this example, the change in the heat transfer performance between the fuel gas and the heat transfer tube is compensated by adjusting the heat transfer performance between the heat transfer tube and the circulating water, and the overall heat transfer performance from the fuel gas to the circulating water varies. It can be said that they do not.

  FIG. 2 illustrates the above-described operation in terms of the relationship between the heat recovery boiler evaporation amount and the evaporator circulation flow rate. The soot blower flow rate, the heat recovery boiler evaporation amount, and the evaporator circulation in the coal gasification combined power plant of this embodiment. The flow rate is illustrated.

  If the evaporator circulation flow rate is constant, the amount of heat recovery boiler evaporation varies as shown by the dotted line in FIG. 2B due to the influence of the heat transfer performance between the fuel gas and the heat transfer tube. That is, the heat transfer performance between the fuel gas and the heat transfer tube gradually decreases due to the accumulation of ash, and the heat transfer performance of the fuel gas and the heat transfer tube recovers rapidly due to the soot blower operation. Gradually decreases and repeats the fluctuation that the amount of evaporation of the heat recovery boiler is rapidly recovered by the operation of the soot blower. On the other hand, in this embodiment, the evaporator circulation flow rate is controlled so that the temperature difference between the evaporator outlet gas temperature and the evaporator inlet circulating water temperature is close to the temperature difference set value. The evaporator circulation flow rate is controlled as shown by the solid line. Thereby, the fluctuation of the heat transfer performance between the fuel gas and the heat transfer tube is compensated by adjusting the heat transfer performance between the heat transfer tube and the circulating water, and the amount of heat recovery boiler evaporation as shown by the solid line in FIG. Stable control is possible.

  Therefore, according to the present embodiment, it is possible to obtain a predetermined heat transfer amount from the fuel gas to the steam in the heat recovery boiler without being affected by the soot blower operation, and to stably control the evaporation amount of the heat recovery boiler. it can.

In this embodiment, in the heat recovery boiler, the amount of heat transfer from the fuel gas to the steam corresponding to the gasifier load is obtained. Specifically, in this embodiment, the temperature difference set value is determined using the evaporator outlet temperature difference determining means 32. That is, the gasifier load command is input to the evaporator outlet temperature difference determining means 32, and the temperature difference set value ΔT _Demand between the evaporator outlet gas temperature and the evaporator inlet circulating water temperature is determined. In this embodiment, the temperature difference set value ΔT _Demand is defined as a function of the gasifier load so as to coincide with the plant heat balance. However, the function may be adjusted with reference to actual machine operation data. Then, based on the temperature difference set value ΔT _Demand obtained by the evaporator outlet temperature difference determining means 32, the temperature difference between the measured evaporator outlet gas temperature and the evaporator inlet circulating water temperature in the evaporator circulation flow control means 33. The evaporator circulation flow control valve 23 is adjusted using PID control so that the actual measurement value ΔT is close to the temperature difference set value ΔT _Demand .

  In addition, as can be seen from FIG. 2, when the soot blower is operated, the evaporator circulation flow rate is set in order to prevent the heat recovery boiler evaporation from fluctuating rapidly due to a sudden change in the heat transfer performance between the fuel gas and the heat transfer tube. It is desirable to change it quickly. Therefore, in the present embodiment, the soot blower operation command is also transmitted from the soot blower amount determination means 31 to the evaporator circulation flow rate control means 33. That is, in the control device of this embodiment, the soot blower operation command is detected, and the soot blower operation time and the preceding command (reduction bias) corresponding to the operation position are added to the evaporator circulation flow control valve opening command. . Thereby, at the time of a soot blower operation | movement, an evaporator circulation flow rate can be changed rapidly and the influence of the heat-transfer performance change by a soot blower can be suppressed in advance.

  A second embodiment will be described with reference to FIG. This embodiment is applied to the coal gasification complex plant shown in FIG. 4 as in the first embodiment, and includes a gasification furnace 1, a connecting pipe 2, a heat recovery boiler 3, a economizer 5, and an evaporator 6. The steam drum 4, the circulation pump 7, the soot blower holder 8, the soot blower amount determining means 31, the economizer soot blower flow control valve 24, and the evaporator soot blower flow control valve 25. These are the same as in the first embodiment, and detailed description thereof is omitted. Further, in this embodiment, a steam flow measuring device 26 and an evaporator outlet flow rate determining means 34 are provided at the steam piping outlet of the steam drum 4.

  In this embodiment, instead of controlling the temperature difference between the gas temperature at the evaporator outlet and the circulating water temperature at the evaporator inlet, the evaporator outlet flow rate (steam flow rate at the steam piping outlet of the steam drum 4) is a predetermined value (outlet flow rate setting). Value)).

In this embodiment, in order to obtain a heat transfer amount from the fuel gas to the steam corresponding to the gasifier load, a gasifier load command is input to the evaporator outlet flow rate determining means 34, and the evaporator outlet flow rate is determined. A set value F _Demand is determined, and control is performed with the evaporator outlet flow rate set value F _Demand as a target value. The evaporator outlet flow rate set value F _Demand is defined as a function of the gasifier load so as to coincide with the plant heat balance, as in the first embodiment. However, the function may be adjusted with reference to actual machine operation data. Then, the evaporator circulation flow rate control valve 23 is adjusted using PID control so that the actual flow rate F measured by the steam flow rate measuring device 26 is close to the evaporator outlet flow rate setting value F _Demand .

  According to the present embodiment, the desired steam flow rate is taken out from the steam drum 4 with respect to the gasifier load regardless of the change in the heat transfer performance between the fuel gas and the heat transfer tube due to the soot blower operation and the change in the fuel gas flow rate. Can do.

  Furthermore, in this embodiment, the plant load command is input to the evaporator circulation flow rate control means 33, and the preceding command is added to the evaporator circulation flow rate control valve opening degree command with respect to the plant load change command. When the plant load command is a load increase command, the preceding command is a command to add an increasing bias to the evaporator circulation flow control valve opening command, and when the plant load command is a load decrease command, the preceding command is This is a command for adding a debiasing to the evaporator circulation flow control valve opening command. By controlling the steam flow rate of the steam drum 4 in advance, the heat transfer performance between the heat transfer pipe and the circulating water is changed, and the effect of compensating for the delay in heat transfer from the fuel gas to the steam is obtained. As a result, the load following performance of the plant can be improved.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment. For example, the advance control based on the plant load command in the second embodiment can be applied to the first embodiment.

  In addition, the flow of water and steam, heat exchange, and the like are those that are considered necessary for explanation, and not all the flow of water and steam, heat exchange, etc. are necessarily shown on the plant. Actually, various devices such as water and steam flow and heat exchange have been made in order to improve the thermal efficiency of the plant.

1 ... Gasification furnace
2 ... Connecting pipe
3 ... Heat recovery boiler
4 ... Steam drum
5 ... economizer
6 ... Evaporator
7 ... Circulation pump
8 ... Soot blower holder
9… Fuel transfer pipe
10 ... Water supply pump
11 ... Dust collector
12… Gas purification equipment
13… Fuel piping
14 ... Fuel control valve
15 ... Gas turbine
16… Waste heat recovery boiler
17… Waste heat recovery boiler drum
18 ... Main steam piping
19… Steam turbine
20 ... Condenser
21… Fuel gas temperature measuring device
22… Circulating water temperature measuring device
23… Evaporator circulation flow control valve
24… economizer soot blower flow control valve
25… Evaporator soot blower flow control valve
26… Steam flow measuring device
31 ... Soot blower amount determining means
32… Evaporator outlet temperature difference determining means
33 ... Evaporator circulation flow rate control means
34 ... Evaporator outlet flow rate determination means

Claims (5)

An operation control method for a coal gasification combined power plant that controls the evaporation amount of a heat recovery boiler that recovers heat from the fuel gas of the coal gasification combined power plant,
The gas temperature at the evaporator gas side outlet of the heat recovery boiler is measured, the circulating water temperature at the evaporator circulating water side inlet of the heat recovery boiler is measured, and the actual temperature difference between the gas temperature and the circulating water temperature is the temperature. The evaporator circulation flow rate of the heat recovery boiler is controlled so as to be close to the difference set value,
Operation control of a coal gasification combined power plant characterized in that the evaporator circulation flow rate of the heat recovery boiler is controlled in advance based on a soot blower operation command for removing the ash content of fuel accumulated on the surface of the heat transfer tube of the heat recovery boiler. Method.   The operation control method for a coal gasification combined cycle plant according to claim 1, wherein the temperature difference set value is determined based on a gasification furnace load command of the coal gasification combined cycle plant. A gasification furnace that gasifies fuel to generate fuel gas; a heat recovery boiler that recovers heat from the fuel gas by a economizer and an evaporator to generate steam; and the gasification furnace and the heat recovery boiler A connecting pipe to be connected, a steam drum that recovers steam obtained from the heat recovery boiler, a circulation pump that circulates can water of the steam drum, a gas turbine that uses the fuel gas as fuel, and an exhaust gas of the gas turbine An exhaust heat recovery boiler that collects heat from the steam to obtain steam, a steam turbine that uses steam obtained from the exhaust heat recovery boiler and the steam drum as a power source, and deposited on the surface of the economizer and the evaporator A soot blower for removing fuel ash, a circulation flow rate control valve for controlling the circulating water flow rate of the evaporator, and a control device for the circulation flow rate control valve;
The said control apparatus controls the said circulation flow control valve so that the fluctuation | variation of the evaporation amount of the said heat recovery boiler accompanying the operation | movement of the said soot blower may be controlled, The coal gasification combined power plant characterized by the above-mentioned. The gas temperature measuring device provided at the evaporator gas side outlet of the heat recovery boiler according to claim 3 , and the circulating water temperature measuring device provided at the evaporator circulating water side inlet of the heat recovery boiler , The control device is configured such that the temperature difference between the gas temperature measured by the gas temperature measuring device and the circulating water temperature measured by the circulating water temperature measuring device is close to the temperature difference set value determined based on the gasifier load command. The coal gasification combined power plant characterized by controlling said circulation flow control valve so that it may become. The steam flow measuring device provided at the steam pipe outlet of the steam drum according to claim 3 , wherein the control device determines an actual flow rate measured by the steam flow measuring device based on a gasifier load command. And controlling the circulating flow rate control valve so as to be close to the evaporator outlet flow rate set value.

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