JP2017020435A - Coal gasification complex power-generating plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coal gasification complex power-generating plant capable of operating without the excess of the reference value of the gasification furnace pressure even at 5%/min from a minimum load to a maximum load.SOLUTION: A coal gasification complex power-generating plant that comprises: a coal fuel supply part; a fuel gasification part; a gas purification part; a power generation part by gas and steam; and a control part that controls the gas quantity supplying to the power generation part and the coal amount to the fuel supply part, in which the control part includes: a gas amount control part which determines the gas amount from the gas purification part in accordance with a power generation output command 14 when increasing the output; and a coal amount control part which determines the coal amount by a cooperation command signal obtained corresponding to a power generation output command 14 and a gas control signal controlling a gas pressure 18 in the gasification part to a target value 19, in which the target value 19 of the gas pressure is set to be higher than a normal target value during a period from a first time point before the output increase start time of the power generation output command which increases when the output changes up to a second time point after the output increase completion point.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a coal gasification combined power plant, and more particularly to a coal gasification combined power plant that can operate stably when a load changes.

  In recent years, in order to realize a low-carbon society, it is required to reduce the environmental load by introducing renewable energy and building a highly efficient power plant. Under such circumstances, it is an urgent task to reduce the environmental burden and increase the efficiency of thermal power generation, which plays a central role in the supply and demand of electricity, both domestically and overseas.

  One method for reducing the environmental burden in thermal power generation is to select a low-carbon fuel. In general, compared to the case of using coal, power generation using low-carbon fuel oil and natural gas has a greater effect on power generation efficiency and the environment.

  However, the reserves of low-carbon fuel are limited, and it is necessary to make effective use of coal with abundant reserves from the viewpoint of the best mix of power sources.

  Therefore, a coal gasification compound is a method that can generate coal with a large impact on the environment compared to the case where power is generated using oil and natural gas, while generating electricity with high efficiency and greatly reduced impact on the environment. Electric power generation (IGCC) plants have attracted attention.

  Patent Document 1 is known as a specific configuration example and control method of a typical coal gasification combined power plant.

Japanese Patent Laid-Open No. 11-22485

  Compared to a combined cycle (C / C) power generation that generates power using oil and natural gas, the rate of change in load is 5% / min. Therefore, it is difficult to follow the load with respect to the load command, and the load change rate is about 3% / min. For this reason, even in the case of a coal gasification combined power plant, it is desired to realize a load change rate of 5% / min, which is equivalent to combined cycle (C / C) power generation using oil or natural gas. .

  In addition, the oxygen-blown coal gasification combined power plant must be operated (1) load followability from the viewpoint of the steam system (2) pressure controlled from the coal supply system and gasifier relationship (3) There are three difficulties of operation restrictions due to the specifications of the main device. As a conventional method, the method of cooperative control based on the gas turbine GT lead base of Patent Document 1 has been studied. However, when the load change command value increases, there is a problem that the reference value of the gasifier pressure is exceeded and the plant trips. is there.

  From the above, the object of the present invention is to operate a coal gasification combined power plant without exceeding the standard value of the gasifier pressure even at 5% / min from the minimum load to the maximum load equivalent to the natural gas combined power plant. It is possible to provide a combined coal gasification combined power plant that can be applied not only from the lowest load to the maximum load but also in an intermediate load zone.

From the above, in the present invention, a fuel supply unit that supplies coal, a gasification unit that gasifies the supplied fuel, a gas purification unit that purifies the obtained gas, a purified gas, and an obtained gas A power generation unit that extracts power from the generated steam, a control unit that controls at least the amount of gas supplied to the power generation unit, and the amount of coal supplied to the fuel supply unit, and the control unit generates power output that increases with time when the output increases Gas amount control unit that determines the amount of gas from the gas purification unit to be given to the power generation unit according to the command, cooperative command signal obtained according to the power generation output command, and gas that controls the gas pressure in the gasification unit to the target value A coal gasification combined power plant comprising a coal amount control unit that determines a coal amount by the sum of control signals,
The target value of the gas pressure is a normal target value in a period from the first time before the output increase start time of the power generation output command that increases with time when the output changes to the second time after the output increase completion time. It is a coal gasification combined power plant characterized by being set higher.

  ADVANTAGE OF THE INVENTION According to this invention, it can be set as the control system which can adapt to any load change zone | band equivalent to natural gas (5% / min, the minimum load to the maximum load) in a coal gasification combined power plant.

The figure which shows the load follow-up control circuit part which is the main components of the control part E of FIG. The figure which shows the typical apparatus structural example of the coal gasification combined power plant which concerns on the Example of this invention. The figure which shows the furnace pressure fluctuation | variation of the gasification furnace after a cooperative control gain and a load change start. The figure which shows the furnace pressure overshoot of the gasification furnace after completion | finish of a cooperative control gain and load change. The figure which showed the fluctuation | variation of the gasifier pressure when a load change was carried out by making a cooperation command gain into 1 with time progress. The figure which showed the signal of each part of the control system of FIG. 1 at the time of load change. The figure which shows the relationship between the assumed load change time tx and the bias period ty before and behind a load change in a table | surface form. The figure which shows the relationship between the assumed load change time tx and the bias period ty before and behind a load change in a graph format. The figure which shows the response result when changing load by the assumed case.

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

  FIG. 2 shows a typical apparatus configuration example of a combined coal gasification combined power plant according to an embodiment of the present invention.

  The coal gasification combined power plant shown in FIG. 2 is roughly classified into its functions. A fuel supply part A for supplying coal as pulverized coal, a gasification part B for gasifying fuel, and refining the obtained gas A gas purification part C, a power generation part D for extracting power from the purified gas and the obtained steam, and a control part E thereof.

  Among these, the fuel supply part A supplies pulverized coal and oxygen to the gasification part B. In the coal supply system 1 including a mill, the coal is pulverized under the nitrogen environment provided by the air separator 31. . In addition, pulverized coal is supplied to the gasification part B together with oxygen provided by the air separator 31.

  The gasification part B includes a gasification furnace 2 and a syngas cooler 3. The gasification furnace 2 gasifies the fuel (coal) transported by the fuel transport pipe 32, and the syngas cooler 3 cools the fuel gas by heat exchange with the feed water in the syngas cooler economizer or syngas cooler evaporator. To do. The water supply to the syngas cooler economizer is supplied from an exhaust heat recovery boiler HRSG, which will be described later, and the steam generated in the syngas cooler 3 is recovered to the exhaust heat recovery boiler HRSG by the syngas cooler drum.

  The gas refining portion C removes solids and the like contained in the fuel gas cooled by the syngas cooler 3 with the dust removing device 33 and then guides it to the gas generating device 5 through the heating device 34 to generate gas. The generated gas is input to the gas turbine combustor 6 of the power generation part D via the heating device 34, but a part of the surplus gas is discharged from the ground flare 11.

  The power generation portion D is roughly composed of a gas turbine GT, an exhaust heat recovery boiler HRSG, and a steam turbine ST. The gas turbine GT includes a compressor 7 that compresses air, a combustor 6 that combusts a generated gas using the compressed air, and a gas turbine unit 34. The generator 10 is driven by the obtained mechanical power. Get generated power. In the example of FIG. 1, the gas turbine shaft, the steam turbine shaft, and the generator shaft are arranged on the same axis to drive the generator 10.

  In the exhaust heat recovery boiler HRSG, combustion exhaust gas WG from the gas turbine GT is introduced, and steam is generated by heat exchange between the feed water W from the feed water pump 4 and the gas turbine combustion exhaust gas WG. More specifically, the feed water W from the condenser 35 is pressurized by the feed water pump 4 and introduced into the exhaust heat recovery boiler HRSG. In the exhaust heat recovery boiler HRSG, a economizer 36, an evaporator 37, and a superheater 38 are sequentially arranged from the downstream side of the exhaust gas WG, and the feed water is converted into superheated steam by heat exchange between the heat exchanger and the exhaust gas WG. The main steam pipe 40 is guided to the high pressure turbine 9 of the steam turbine ST to drive it.

  The steam that has worked in the high-pressure turbine 9 is guided again to the exhaust heat recovery boiler HRSG, is reheated in the reheater 39 to become reheated steam, and the reheat turbine of the steam turbine ST is reheated via the reheat steam pipe 41. It is guided to 8 to drive it. In addition, the water supply and steam in each part of the exhaust heat recovery boiler HRSG are appropriately extracted from the steam piping part and used for other purposes. As a typical example, in the syngas cooler economizer or the syngas cooler evaporator in the gasification furnace 2, a system for cooling the fuel gas by exchanging heat with feed water is shown, and the steam after cooling is an exhaust heat recovery boiler. Collected on drum. Note that steam from the syngas cooler drum joins the exhaust heat recovery boiler drum via a syngas cooler steam flow control valve.

  As described above, the combined coal gasification combined power plant of FIG. 2 includes the fuel transport pipe 32 that transports the fuel, the gasification furnace 2 that gasifies the fuel to generate the fuel gas, and the syngas cooler fuel saving from the fuel gas. A syngas cooler 3 that generates heat by recovering heat with a gas generator and a syngas cooler evaporator, a gas purification facility 5 that is connected to a dust removing device 33 to remove unnecessary substances in the fuel gas to obtain purified gas, and purification Gas turbine GT that uses gas as a power source, exhaust heat recovery boiler HRSG that obtains steam from exhaust gas WG of gas turbine GT, feed water pump 4 that supplies water to exhaust heat recovery boiler HRSG, exhaust heat recovery boiler HRSG, and syngas cooler drum The basic components are an exhaust heat recovery boiler drum that recovers steam obtained from the steam, and a steam turbine ST that uses steam obtained from the exhaust heat recovery boiler drum as a power source. Is shall.

  The control part E appropriately controls each of the fuel supply part A, the gasification part B, the gas purification part C, and the power generation part D. The amount of each plant required to obtain a desired power generation output at an appropriate timing is appropriately controlled.

  FIG. 1 is a diagram showing a load following control circuit portion that is a main component of the control portion E. One of the main functions of the load following control circuit part is to appropriately control the amount of gas given to the gas turbine GT in response to the power generation output command, and the other main function is the input amount of coal (supply) The amount is controlled to an appropriate amount. In short, this control is for chronologically balancing the total energy amount given to the coal gasification combined power plant and the total energy amount taken out from the coal gasification combined power plant.

  Among these controls, the former control obtains the deviation between the power generation output command 14 of FIG. 1 and the actual power generation output 12 by the subtractor 42, and the gas turbine control valve GCV at the gas turbine combustor inlet via the proportional integration controller 43. This is realized by giving as the opening command 13. The power generation output 12 is the total amount of the output of the gas turbine GT and the output of the steam turbine ST.

  On the other hand, in the latter coal input amount control, the control amount C1 determined corresponding to the power generation output command 14 and the gasification pressure are appropriately controlled to the target value to keep the gasification pressure in any state. The control reflects the control amount C2.

  Among these, in the control part C1, the cooperation command 15 is created from the power generation output command 14, and the cooperation control added to the coal supply command 20 is performed. Further, in the control portion C2, the deviation between the gasifier pressure 18 and the gasifier pressure target 19 is obtained by the subtractor 44, and the coal supply command 20 is determined by the proportional integral control by the regulator 45.

  The load follow-up control circuit in FIG. 1 is for the purpose of emphasizing and controlling the gas generation side (coal supply) and the gas usage side (GCV opening degree). The side also performs coordinated control to increase or decrease to the extent appropriate for the amount of gas used. The cooperative command function generator 15 sets the ratio of how much the coal amount should be changed when the power generation output command 14 changes by a unit amount.

  According to the knowledge of the present inventors, the facts of FIGS. 3, 4, and 5 are known. First, FIG. 3 shows the coordinated control gain on the horizontal axis, and the furnace pressure fluctuation (kpa) of the gasifier after the start of load change on the vertical axis. The fluctuation range is suppressed.

  FIG. 4 shows the coordinated control gain on the horizontal axis and the furnace pressure overshoot (kpa) of the gasification furnace after the end of load change on the vertical axis. FIG. 4 shows that when the cooperative control gain is made larger than 0.7, overshoot over a long period of the furnace pressure occurs after the load change.

  3 and 4 show that the cooperative gain should be high for good control during the load change period, but if it is too high, the effect of excessive coal input will appear after the end of the load change control period. Overshoot occurs. Therefore, it is preferable to adopt an optimum value of the cooperative control gain, which is 0.7, in which there is no overshoot and the gasifier pressure fluctuation is minimized.

  Incidentally, FIG. 5 shows the change in the gasifier pressure when the load is actually changed with the cooperative command gain being 1, with the passage of time. First, it is assumed that the load change starts at time t1 and the load change ends at time t2. Where the gasifier pressure should be 3.470 (MpaA), it rises due to overshoot immediately after the load change, then decreases by 2 (kpa) at the load change end character time t2, and then increases toward time t3, The gasifier pressure after the end of the load change is 3.472 (MpaA), indicating that overshoot has occurred. And the overshoot after this completion | finish has shown continuing over a long period of time.

  In the present invention, the gasification furnace pressure control in which the following predictive control concept is introduced to the control component C2 that holds the gasification pressure at the same time while giving consideration to the cooperative control gain for the control component C1. Run. Since this consideration requires a great time delay from the fuel supply portion A in FIG. 2 to the gas turbine combustor of the power generation portion D via the gasification portion B and the gas purification portion C, this delay is preceded. It is to be solved by predictive control.

  Therefore, in the present invention, as shown in FIG. 1, the gasifier pressure target 19 is created from the power generation schedule 16 via the prediction function 17, and the gasifier pressure target 19 is changed to change the gasifier pressure 18. To control.

  FIG. 6 is a diagram showing signals of each part of the control system of FIG. 1 when the load changes. In this figure, the horizontal axis is time, and the vertical axis items are power generation schedule (MW) 16, power generation output command (MW) 14, gasifier pressure target value (MPa) 19, gasifier pressure (MPa) 18, The coal supply amount 20 is shown.

  In this figure, the power generation schedule 16 is, for example, a planned value of daily power generation output at the power plant, and has a planned value of increasing the power generation output from Gmin to Gmax at time t10. On the other hand, in order to achieve the power generation output Gmax at time t10, the power generation output command (MW) 14 issues a time change command that starts increasing from t9, which is tx time before t10, and becomes power generation output Gmax at time t10. . In this case, the rate of change is set to 5% / min, which is equivalent to a combined cycle (C / C) power generation that generates power using oil or natural gas.

  Here, the power generation output command (MW) 14 is given on the one hand as the opening command 13 of the gas turbine control valve GCV at the gas turbine combustor inlet, and the gas amount at the gas turbine control valve GCV inlet is sufficiently secured. It is assumed that

  For this reason, on the other hand, an operation for securing the presupposed gas amount is necessary, and this viewpoint is reflected in the setting of the gasification pressure target value 19. In setting the gasification pressure target value 19, since it is necessary to determine the coal supply amount that is upstream of the process amount in the coal gasification combined power plant, the starting point is t9, which is tx time before the target output achievement t10. Furthermore, measures for gasification pressure control are required from t8 before ty time. Moreover, in order to cope with the problem of the furnace pressure overshoot of the gasification furnace after the end of the load change described with reference to FIG. 4, it is necessary to continue to implement the gasification pressure control measure until t11 after ty time from the target output achievement t10. There is.

  The gasifier pressure target value (MPa) 19 in FIG. 6 sets the period from time t8 to t11 as the gasifier pressure control target period from the above viewpoint. In the prediction function 17 in FIG. 1, this period is determined from the power generation schedule (MW) 16 and the target pressure in this period is determined. FIG. 6 shows an example in which the pressure target value during this period is given a larger value of PH than the PL during normal operation. The pressure target value during this period can be arbitrarily determined using an appropriate index.

  By the high-pressure gasifier pressure control in the gasifier pressure control target period, the actual gasifier pressure shows a furnace pressure overshoot tendency during the load change period shown in FIG. The regulator 45 determines the control signal C2 by proportional-integral control from the gasifier pressure target and the measured value.

  On the other hand, a signal for setting the cooperative command gain to about 0.7 is given as the control signal C1. The coal supply amount 20 in FIG. 6 is a target signal obtained by combining the control signals C1 and C2, and the coal supply amount is determined from the time t8 preceding the start of control of the gas turbine control valve GCV by the control signal C1. By increasing the amount, the gas amount at the gas turbine control valve GCV inlet is sufficiently secured. Further, the control is continued until time t12 after the time t11 after the end of the load change, thereby addressing the problem of the furnace pressure overshoot of the gasifier after the end of the load change.

  By setting the cooperative command gain to about 0.7, the response during the load change period can be maintained relatively high, and the furnace pressure overshoot of the gasifier after the load change can be suppressed. Yes.

  Next, the result of simulating the effect of the present invention will be described. 7 and 8 assume the relationship between the load change time tx and the bias period ty before and after the load change. 7 shows a table format, and FIG. 8 shows a graph format.

  On the vertical axis side of the table of FIG. 7, there are six cases from A to F. On the horizontal axis side, the load change and the bias period ty before and after the load change are illustrated by numerical values. As the load change, the change amount and the load change time tx are adopted and numerically displayed. As shown in the graph of FIG. 8, the case has a straight line relationship with the change width in 1/6 units so that the six cases from A to F can also correspond to the intermediate load band.

  FIG. 9 is a diagram illustrating a response result when the load is changed according to an assumed case. In FIG. 9, the load change time tx is adopted on the horizontal axis and the gasifier pressure fluctuation range (kPa) is adopted on the vertical axis, the response at the time of control by the GT lead, the cooperative control by the GT lead (the control described in Patent Document 1) The response at the time of method) and the response at the time of predictive cooperative control by GT lead according to the present invention are shown. However, the load change time tx is set to a load change rate of 5% / min, which is about the combined cycle (C / C) power generation using oil or natural gas. Moreover, the bias value in each case is set to a half value in the sense that the gasifier pressure drop peak value at the time of the GT lead-based cooperative control is dispersed vertically.

  According to the simulation result, the response at the time of control by the GT lead deviates from the allowable fluctuation range of the gasifier pressure fluctuation range at the level of case C, that is, at the stage of about 4/6 load. Even in the case of the response at the time of cooperative control by the GT lead, the allowable fluctuation range has been deviated before the 6/6 load is reached. In the response at the time of predictive cooperative control by the GT lead of the present invention, the allowable fluctuation range can be greatly reduced.

  From the result of FIG. 9, it was confirmed that the gasifier pressure was within the allowable value by simulation in cases B to F as described above. From the above, it has been found that the present invention can be applied not only to the change from the minimum load to the maximum load but also to an intermediate load. In addition, at the time of load reduction, the increase in the gasifier pressure can be suppressed by burning the gas with the ground flare 11. In case A, the change from the maximum load to the minimum load is 5% / min. Therefore, the load change time cannot be further increased in plant operation.

  As described above in detail, in the GT lead-based cooperative control, since the cooperative command is input simultaneously with the power generation command, it is considered that the coal supply amount change cannot follow the load change and the gasifier pressure fluctuation increases. Therefore, in the present invention, paying attention to the power generation schedule implemented at a normal power plant, it was examined whether followability could be improved by giving a prediction command before the load increase from the schedule. Usually, since the power plant operates on a schedule determined in advance, the timing when the load increases and decreases is known. For this reason, a logic has been considered in which a gas function corresponding to the GT inlet is already entered at the timing when the load starts to rise by inputting a schedule function as a gasifier pressure command in advance. Therefore, in addition to GT lead-based cooperative control, a method for suppressing fluctuations in gasifier pressure by applying a bias for a certain period of time as a prediction command to the pressure setting value of the gasifier before power generation command change was invented. It is.

  More specifically, in the oxygen-blown coal gasification combined cycle power generation, there is a limit to the gasifier pressure suppression in the cooperative command to the gasifier simultaneously with the start of load change. Therefore, a control system was invented by applying a prediction command determined based on the power generation schedule in advance to the gasifier, thereby suppressing fluctuations in the gasifier pressure within an allowable value and not leading to a plant trip. is there.

  In addition, a function having a load change time tx and a load change time range ty as a prediction function is linear from the optimum value of ty when changing from the minimum load to the maximum load at 5% / min. Assumed to be a function. As a result, it has been found that a coal gasification combined power plant can be realized to cope with any load change.

A: Fuel supply part B: Gasification part C: Gas purification part D: Power generation part E: Control part 1: Coal supply system 2: Gasification furnace 3: Syngas cooler 4: Feed water pump HRSG: Waste heat recovery boiler 5: Gas Refiner 6: Combustor 7: Compressor GT: Gas turbine 8: Reheat turbine 9: High pressure turbine 10: Generator 11: Ground flare 12: Power generation output 13: GCV opening command 14: Power generation output command 15: Cooperation command Function generator 16: Power generation schedule 17: Prediction function 18: Gasifier pressure 19: Gasifier pressure target 20: Coal supply command 31: Air separator 32: Fuel transfer pipe 33: Dedusting device 34: Gas turbine section 35 : Condenser 36: economizer 37: evaporator 38: superheater 39: reheater 40: main steam pipe 41: reheat steam pipe 42, 44: subtractor 43, 45: regulator

Claims (3)

A fuel supply unit that supplies coal, a gasification unit that gasifies the supplied fuel, a gas purification unit that purifies the obtained gas, and a power generation unit that extracts power from the purified gas and the obtained steam And a control unit that controls at least the amount of gas supplied to the power generation unit and the amount of coal supplied to the fuel supply unit, and the control unit generates the power generation according to a power generation output command that increases with time when the output increases. A gas amount control unit for determining a gas amount from the gas purification unit to be supplied to a unit, a cooperative command signal obtained according to the power generation output command, and a gas control signal for controlling a gas pressure in the gasification unit to a target value A coal gasification combined power plant comprising a coal amount control unit that determines the amount of coal according to the sum of:
The target value of the gas pressure is a normal value in a period from a first time before the output increase start time of the power generation output command that increases with time when the output changes to a second time after the output increase completion time. Coal gasification combined power plant characterized by being set higher than the target value. A coal gasification combined cycle plant according to claim 1,
Regarding the target value of the gas pressure, when the output change time is tx, and the time between the output change start time and the first time is ty, the relationship between tx and ty is linear and specified from the lowest load to the maximum load. Coal gasification combined power plant characterized by being able to change at a rate of change and to be able to handle intermediate load zones. The coal gasification combined cycle plant according to claim 1 or 2,
The cooperative command signal obtained according to the power generation output command is obtained by multiplying a coefficient of a magnitude that suppresses fluctuations in gas pressure during output increase and suppresses overshoot of gas pressure after completion of output increase. A coal gasification combined cycle power plant.

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