Gas temperature control strategy for supercritical carbon dioxide boiler

Abstract

A gas temperature control strategy for a supercritical carbon dioxide boiler, comprising: during the low-load and rapid variable-load operation of a supercritical carbon dioxide boiler, by adjusting a coal quantity, the overall heat load of the boiler is adjusted, so as to control the average value of a main gas temperature and a reheat gas temperature, by adjusting the opening degree of a flue gas damper at the tail of the boiler, the heat absorption quantity distribution of main gas and reheat gas is changed, so as to control the difference between the main gas temperature and the reheat gas temperature, and at the same time, a unit load instruction-based coal quantity feed-forward instruction and a flue gas damper opening degree feed-forward instruction are introduced. The technical effect is that the present invention is applicable to an arrangement solution of a heating surface of a supercritical carbon dioxide boiler in which main gas and reheat gas radiation heat transfer quantity and convection heat transfer quantity are close to each other, and can improve the accuracy of gas temperature control during variable-load operation of the boiler, thereby improving the peak regulation capability of the supercritical carbon dioxide boiler.

Description

Supercritical carbon dioxide boiler gas temperature control strategy TECHNICAL FIELD

[0001] The present application belongs to the technical field of power plant thermal control, and particularly relates to a supercritical carbon dioxide boiler gas temperature control strategy. BACKGROUND

[0002] The supercritical carbon dioxide cycle has advantages of high cycle thermal efficiency, compact system and equipment, and flexible operation, and can help coal-fired generating units to transform and upgrade to basic support and system regulation power sources. The supercritical carbon dioxide boiler, as a heat source equipment of the supercritical carbon dioxide power cycle, its deep peak shaving capacity and rapid load changing capacity are the key to realize flexible and efficient operation of the supercritical carbon dioxide coal-fired generating unit. Since there is a large thermal inertia in the process of heat transfer from the flue gas to the working medium through the pipe wall, the gas temperature will be over-temperature or not up to standard during the load changing operation, the gas temperature not up to standard will cause the power generation efficiency of the unit to be reduced and the coal consumption to be increased, and the gas temperature over-temperature will cause the pipe wall temperature of the boiler to be too high, and even cause the unit to be shut down, and long-term frequent over-temperature of the pipe wall of the boiler will affect the service life of the boiler equipment. Therefore, the supercritical carbon dioxide boiler gas temperature control must be carried out.

[0003] The steam temperature control strategy of the traditional supercritical water steam boiler is to take water-coal ratio as the core, adjust the separator outlet steam temperature through water-coal ratio, combine with water injection desuperheating technology, and then control the main steam temperature, and the reheat steam temperature is generally controlled through boiler tail flue gas damper, flue gas recirculation and water injection desuperheating technology, and some scholars propose high-pressure heater steam throttling control of reheat steam temperature and water-coal ratio participation in reheat steam temperature control. Compared with the traditional supercritical water steam boiler, the supercritical carbon dioxide boiler has the characteristics of high boiler inlet working medium temperature, working medium far away from the large specific heat region, and high reheat gas heat absorption proportion, the working medium heat absorption process is in the superheated region and the temperature rise is small, the reheater increases the furnace radiation heating surface, and the whole boiler heat transfer mechanism changes significantly, so the steam temperature control strategy of the traditional supercritical water boiler cannot be directly applied to the supercritical carbon dioxide boiler, and therefore, it is necessary to develop an effective gas temperature control strategy in combination with the supercritical carbon dioxide boiler heating surface arrangement scheme.

[0004] SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art, and provides a new technical solution of a supercritical carbon dioxide boiler gas temperature control strategy.

[0006] According to one aspect of the present application, a supercritical carbon dioxide boiler gas temperature control strategy is provided, comprising:

[0007] In the process of supercritical carbon dioxide boiler low load and rapid load change operation, the boiler overall thermal load is adjusted by adjusting the coal quantity, the average value of the main gas temperature and the reheated gas temperature is controlled, the heat absorption distribution of the main gas and the reheated gas is changed by adjusting the opening of the boiler tail flue damper, the difference value of the main gas temperature and the reheated gas temperature is controlled, and meanwhile, the coal quantity feedforward instruction and the flue damper opening feedforward instruction based on the unit load instruction are introduced.

[0008] Optionally, the control logic of the average value of the main gas temperature and the reheated gas temperature is as follows:

[0009] Firstly, the load instruction from the unit coordinated control system CCS is subjected to function f1(x) to generate the average value instruction of the main gas temperature and the reheated gas temperature, and the load instruction from the unit coordinated control system CCS is subjected to function f2(x) to generate the coal quantity instruction feedforward.

[0010] Then, the average value of the main gas temperature and the reheated gas temperature is obtained by subtracting the average value of the real-time values of the main gas temperature and the reheated gas temperature from the average value instruction of the main gas temperature and the reheated gas temperature.

[0011] Finally, the coal quantity increment is obtained by subjecting the average value deviation of the main gas temperature and the reheated gas temperature to PID operation, and the coal quantity instruction is formed by adding the coal quantity instruction feedforward to the coal quantity increment.

[0012] Optionally, the control logic of the difference value of the main gas temperature and the reheated gas temperature is as follows:

[0013] Firstly, the difference value of the main gas temperature and the reheated gas temperature is obtained by subtracting the real-time value of the reheated gas temperature from the real-time value of the main gas temperature.

[0014] Then, the load instruction from the unit coordinated control system CCS is subjected to function f3(x) to generate the superheated side flue damper opening instruction feedforward, and the load instruction from the unit coordinated control system CCS is subjected to function f4(x) to generate the reheated side flue damper opening instruction feedforward.

[0015] Finally, the superheated side flue damper opening increment is obtained by subjecting the difference value of the main gas temperature and the reheated gas temperature to the dead zone function and PID operation, the superheated side flue damper opening instruction is formed by adding the damper opening instruction feedforward to the superheated side flue damper opening increment and passing through the M / A hand automatic operation station and the MFT switching function, and meanwhile, the reheated side flue damper opening instruction is formed by adding the reheated side flue damper opening instruction feedforward to the superheated side flue damper opening increment after passing through the proportional link K and passing through the M / A hand automatic operation station and the MFT switching function.

[0016] Optionally, the functions f1(x), f2(x), f3(x) and f4(x) in the control logic can be obtained by linear interpolation according to the supercritical carbon dioxide boiler thermal calculation or performance calculation results.

[0017] Optionally, the value of the proportional link K in the control logic is -1.

[0018] Optionally, the value of the proportional link K in the control logic is adjusted according to the field device condition.

[0019] Optionally, the dead zone range of the deviation between the real-time values of the main gas temperature and the reheated gas temperature in the control logic is set to -2-2℃.

[0020] One technical effect of the present application is that:

[0021] In the embodiment of the present application, the supercritical carbon dioxide boiler gas temperature control strategy adopts the strategy of controlling the average value of the main gas temperature and the reheated gas temperature by the coal amount, controlling the deviation of the main gas temperature and the reheated gas temperature by the flue gas damper, simultaneously introducing the coal amount instruction feedforward based on the unit load instruction and the flue gas damper opening degree instruction feedforward, which can effectively adapt to the characteristics of the supercritical carbon dioxide boiler working medium far away from the large specific heat region, the heat absorption process in the superheating region and small temperature rise, and the increase of the radiation heating surface of the reheater, improves the gas temperature control precision in the boiler operation, and improves the peak shaving capacity of the boiler. BRIEF DESCRIPTION OF DRAWINGS

[0022] Fig. 1 is a schematic diagram of the supercritical carbon dioxide boiler heating surface arrangement;

[0023] Fig. 2 is a gas temperature control logic diagram of a supercritical carbon dioxide boiler gas temperature control strategy according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement, numerical expressions, and values of the components and steps set forth in these embodiments are not limiting to the scope of the present application unless otherwise specifically stated.

[0025] The embodiments of the present application will be described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the accompanying drawings are exemplary and are for the purpose of explaining the present application only, and cannot be understood as limiting the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present application.

[0026] Fig. 1 is a schematic diagram of the supercritical carbon dioxide boiler heating surface arrangement, the lower furnace is arranged with the gas cooling wall, the upper furnace is arranged with the reheated gas cooling wall, the horizontal flue is arranged with the high-temperature superheater and the high-temperature reheater, the vertical flue is divided into two sides, one side is arranged with the low-temperature superheater and the parallel split-flow economizer, the other side is arranged with the low-temperature reheater and the parallel split-flow economizer, the flue at the outlet of the split-flow economizer is provided with a flue gas adjusting damper, the flues behind the flue gas adjusting damper are combined, and the environmental protection facilities and the air preheater are arranged.

[0027] During the peak-shaving operation of the supercritical carbon dioxide boiler, the coal quantity and working medium flow will change, and the thermal load of the boiler will also change. Considering that the process of heat transfer from flue gas to working medium through the boiler tube wall has thermal inertia, the changes of the main gas temperature and the reheated gas temperature will be delayed with the load adjustment, that is, the load following property of the boiler gas temperature is not good, so the gas temperature control is needed to avoid the over-temperature or under-temperature of the boiler during the peak-shaving operation. However, the supercritical carbon dioxide boiler has the characteristics that the working medium is far away from the large specific heat region, the heat absorption process is in the superheating region and the temperature rise is small, and the reheated gas has a high proportion of heat absorption. Therefore, the furnace radiation heating surface needs to increase the reheated gas cold wall, the vertical flue arrangement needs to split the economizer and other heating surface arrangement features. The heat transfer characteristics of the supercritical carbon dioxide boiler change significantly, and the steam temperature control strategy of the conventional water boiler is difficult to be directly applied.

[0028] In view of the above characteristics of the supercritical carbon dioxide boiler, according to one aspect of the present application, referring to FIGS. 1 and 2, a supercritical carbon dioxide boiler gas temperature control strategy is provided, comprising:

[0029] During the low load and rapid load change operation of the supercritical carbon dioxide boiler, the overall thermal load of the boiler is adjusted by adjusting the coal quantity, the average values of the main gas temperature and the reheated gas temperature are controlled, the heat absorption distribution of the main gas and the reheated gas is changed by adjusting the opening degree of the boiler tail flue damper, the difference between the main gas temperature and the reheated gas temperature is controlled, and at the same time, the coal quantity feedforward instruction based on the unit load instruction and the flue damper opening degree feedforward instruction are introduced, so as to improve the gas temperature control accuracy during the load change operation of the supercritical carbon dioxide boiler, and further improve the peak-shaving capacity of the boiler.

[0030] In the embodiment of the present application, the supercritical carbon dioxide boiler gas temperature control strategy is aimed at the characteristics that the working medium of the supercritical carbon dioxide boiler is far away from the large specific heat region, the heat absorption process is in the superheating section and the reheated gas has a small temperature rise, and the reheated gas increases the radiation heating surface. It uses the strategy of controlling the average values of the main gas temperature and the reheated gas temperature by the coal quantity, and controlling the deviation of the main gas temperature and the reheated gas temperature by the flue damper, and at the same time, introduces the coal quantity instruction feedforward based on the unit load instruction and the flue damper opening degree instruction feedforward, which can effectively adapt to the characteristics that the working medium of the supercritical carbon dioxide boiler is far away from the large specific heat region, the heat absorption process is in the superheating region and the reheated gas has a small temperature rise, and the reheated gas increases the radiation heating surface, improves the gas temperature control accuracy during the operation of the boiler, and improves the peak-shaving capacity of the boiler.

[0031] Optionally, referring to FIG. 2, the control logic of the average values of the main gas temperature and the reheated gas temperature is as follows:

[0032] Firstly, the load instruction from the unit coordinated control system CCS generates the average value instruction of the main gas temperature and the reheated gas temperature through the function f1(x), and the load instruction from the unit coordinated control system CCS generates the coal quantity instruction feedforward through the function f2(x);

[0033] Then, the average value of the main gas temperature and the reheated gas temperature is subtracted from the average value of the real-time value of the main gas temperature and the reheated gas temperature to obtain a deviation of the average value of the main gas temperature and the reheated gas temperature.

[0034] Finally, the deviation of the average value of the main gas temperature and the reheated gas temperature is subjected to PID operation to obtain a coal quantity increment, and the coal quantity increment is added to the coal quantity instruction to form a coal quantity instruction.

[0035] In the above embodiment, the control logic of the average value of the main gas temperature and the reheated gas temperature is reasonable, which helps to accurately obtain the coal quantity instruction.

[0036] Optionally, referring to FIG. 2, the control logic of the difference between the main gas temperature and the reheated gas temperature is as follows:

[0037] First, the real-time value of the main gas temperature is subtracted from the real-time value of the reheated gas temperature to obtain a difference between the main gas temperature and the reheated gas temperature.

[0038] Then, the load instruction from the unit coordination control system CCS is subjected to function f3(x) to generate a superheated side flue damper opening degree instruction feedforward, and the load instruction from the unit coordination control system CCS is subjected to function f4(x) to generate a reheated side flue damper opening degree instruction feedforward.

[0039] Finally, the difference between the main gas temperature and the reheated gas temperature is subjected to a dead zone function and PID operation to obtain a superheated side flue damper opening degree increment, the superheated side flue damper opening degree increment is added to the damper opening degree instruction feedforward, and is subjected to M / A hand automatic operation station and MFT switching function to form a superheated side flue damper opening degree instruction; at the same time, the superheated side flue damper opening degree increment is subjected to a proportional link K and is superimposed on the reheated side flue damper opening degree instruction feedforward, and is subjected to M / A hand automatic operation station and MFT switching function to form a reheated side flue damper opening degree instruction.

[0040] In the above embodiment, the control logic of the difference between the main gas temperature and the reheated gas temperature is reasonable, which helps to accurately obtain the superheated side flue damper opening degree instruction and the reheated side flue damper opening degree instruction.

[0041] Optionally, the functions f1(x), f2(x), f3(x) and f4(x) in the control logic can be obtained by linear interpolation according to the supercritical carbon dioxide boiler thermal calculation or performance calculation results. This makes the obtaining method of each function in the control logic relatively simple and accurate.

[0042] Optionally, the value of the proportional link K in the control logic is -1. This helps to simply and quickly obtain the superheated side flue damper opening degree increment.

[0043] Optionally, the value of the proportional link K in the control logic is adjusted according to the field device condition. This helps to accurately obtain the superheated side flue damper opening degree increment according to the field device condition.

[0044] Optionally, the dead zone range of the deviation between the real-time value of the main gas temperature and the reheat gas temperature in the control logic is set to -2-2℃. This helps to accurately obtain the increment of the flue gas damper opening degree on the superheating side.

[0045] It can be understood that the above embodiments are only exemplary embodiments for illustrating the principles of the present application, and the present application is not limited thereto. Various modifications and improvements can be made by those of ordinary skill in the art without departing from the spirit and essence of the present application, and these modifications and improvements are also considered to be within the protection scope of the present application.

Claims

1. A supercritical carbon dioxide boiler gas temperature control strategy, characterized by, The application relates to a control logic for a supercritical carbon dioxide boiler. During low load and rapid load change operation of the supercritical carbon dioxide boiler, the overall thermal load of the boiler is adjusted by adjusting the coal quantity, the average value of the main gas temperature and the reheated gas temperature is controlled, the heat absorption distribution of the main gas and the reheated gas is changed by adjusting the opening degree of the tail flue damper of the boiler, the difference value of the main gas temperature and the reheated gas temperature is controlled, meanwhile, a coal quantity feedforward instruction based on the unit load instruction and a flue damper opening degree feedforward instruction are introduced.

2. The supercritical carbon dioxide boiler gas temperature control strategy of claim 1, wherein, The control logic of the average value of the main gas temperature and the reheated gas temperature is as follows: Firstly, the load instruction from the unit coordinated control system (CCS) generates a main gas temperature and reheated gas temperature average value instruction through a function f1(x), and the load instruction from the unit coordinated control system (CCS) generates a coal quantity instruction feedforward through a function f2(x); Then, the main gas temperature and reheated gas temperature average value instruction is subtracted from the average value of the real-time values of the main gas temperature and the reheated gas temperature to obtain the deviation of the main gas temperature and the reheated gas temperature average value; Finally, the deviation of the main gas temperature and the reheated gas temperature average value is subjected to PID operation to obtain a coal quantity increment, and the coal quantity increment is added to the coal quantity instruction feedforward to form a coal quantity instruction.

3. The supercritical carbon dioxide boiler gas temperature control strategy of claim 2, wherein, The control logic of the difference value of the main gas temperature and the reheated gas temperature is as follows: Firstly, the real-time value of the main gas temperature is subtracted from the real-time value of the reheated gas temperature to obtain the difference value of the main gas temperature and the reheated gas temperature; Then, the load instruction from the unit coordinated control system (CCS) generates a superheated side flue damper opening degree instruction feedforward through a function f3(x), and the load instruction from the unit coordinated control system (CCS) generates a reheated side flue damper opening degree instruction feedforward through a function f4(x); Finally, the difference value of the main gas temperature and the reheated gas temperature is subjected to a dead zone function and PID operation to obtain a superheated side flue damper opening degree increment, the superheated side flue damper opening degree increment is added to the damper opening degree instruction feedforward, and the superheated side flue damper opening degree instruction is formed through M / A hand automatic operation station and MFT switching function; meanwhile, the superheated side flue damper opening degree increment is added to the reheated side flue damper opening degree instruction feedforward after being subjected to a proportional link K, and the reheated side flue damper opening degree instruction is formed through M / A hand automatic operation station and MFT switching function. The functions f1(x), f2(x), f3(x) and f4(x) in the control logic can be obtained through linear interpolation according to the results of thermal calculation or performance calculation of the supercritical carbon dioxide boiler.

4. The supercritical carbon dioxide boiler gas temperature control strategy of claim 3, wherein, The value of the proportional link K in the control logic is -1.

5. The supercritical carbon dioxide boiler gas temperature control strategy of claim 4, wherein, The value of the proportional link K in the control logic is adjusted according to the field device condition.

6. The supercritical carbon dioxide boiler gas temperature control strategy of claim 4, wherein, The dead zone range of the deviation of the real-time values of the main gas temperature and the reheated gas temperature in the control logic is set to -2-2 DEG C.

7. The supercritical carbon dioxide boiler gas temperature control strategy of claim 5, wherein, ​

Images