Supercritical carbon dioxide boiler gas temperature control strategy

Abstract

The application provides a supercritical carbon dioxide boiler gas temperature control strategy, comprising: in the process of low load and rapid variable load operation of the supercritical carbon dioxide boiler, adjusting the coal quantity to regulate the overall thermal load of the boiler, controlling the average value of the main gas temperature and the reheated gas temperature, adjusting the opening of the boiler tail flue damper to change the heat absorption distribution of the main gas and the reheated gas, controlling the difference value of the main gas temperature and the reheated gas temperature, and introducing the coal quantity feedforward instruction and the flue damper opening feedforward instruction based on the unit load instruction. One technical effect of the application is that the application is suitable for the supercritical carbon dioxide boiler heating surface arrangement scheme with close radiation heat transfer and convection heat transfer of the main gas and the reheated gas, can improve the gas temperature control precision in the process of variable load operation of the boiler, and improves the peak shaving capacity of the supercritical carbon dioxide boiler.

Description

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 the flexible and efficient operation of the supercritical carbon dioxide coal-fired generating unit. Due to the 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, and the gas temperature not up to standard will cause the power generation efficiency of the unit to decrease and the coal consumption to increase, 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 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 at the same time, scholars propose high-pressure heater steam throttling control reheat steam temperature, and water-coal ratio participates in the control of the reheat steam temperature. 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 superheating 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. SUMMARY

[0004] The present application aims to at least solve one of the technical problems existing in the prior art, and provide a new technical solution of a supercritical carbon dioxide boiler gas temperature control strategy.

[0005] According to one aspect of the present application, a supercritical carbon dioxide boiler gas temperature control strategy is provided, comprising:

[0006] 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.

[0007] Optionally, the control logic of the average value of the main gas temperature and the reheated gas temperature is as follows:

[0008] 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.

[0009] 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.

[0010] 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.

[0011] Optionally, the control logic of the difference value of the main gas temperature and the reheated gas temperature is as follows:

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] Optionally, the value of the proportional link K in the control logic is -1.

[0017] Optionally, the value of the proportional link K in the control logic is adjusted according to the field device condition.

[0018] 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℃.

[0019] One technical effect of the present application is that:

[0020] In the embodiments 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 reheater increasing the radiation heating surface, improves the gas temperature control precision in the boiler operation, and improves the peak shaving capacity of the boiler. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a supercritical carbon dioxide boiler heating surface arrangement schematic diagram;

[0022] Figure 2 It 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

[0023] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. Note that the relative arrangement, numerical expressions, and numerical 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.

[0024] 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 explanation only, and are not to be understood as limiting the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0025] Figure 1The supercritical carbon dioxide boiler is arranged with a schematic diagram of heating surface, a gas cooling wall in a lower furnace, a reheated gas cooling wall in an upper furnace, a high-temperature superheater and a high-temperature reheater in a horizontal flue, a low-temperature superheater and a parallel split-flow economizer on one side of a vertical flue, a low-temperature reheater and a parallel split-flow economizer on the other side of the vertical flue, a flue gas adjusting baffle at an outlet of the split-flow economizer, a combined flue after the flue gas adjusting baffle, and an air preheater and an air preheater arranged with environmental protection facilities.

[0026] During the peak-shaving operation of the supercritical carbon dioxide boiler, the coal quantity and the 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 the 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, and therefore, 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 with a small temperature rise, and the reheater has increased radiation heating surface, and the flue gas passes through the split-flow economizer arranged in the vertical flue, and the heat transfer characteristics of the supercritical carbon dioxide boiler change significantly, and the steam temperature control strategy of the conventional water boiler cannot be directly applied.

[0027] According to the above characteristics of the supercritical carbon dioxide boiler, according to one aspect of the present application, referring to Figure 1 and Figure 2 , a gas temperature control strategy of a supercritical carbon dioxide boiler is provided, which comprises:

[0028] 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 gas baffle, 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 gas baffle 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.

[0029] In the embodiments of the present application, the gas temperature control strategy of the supercritical carbon dioxide boiler is suitable for 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 with a small temperature rise, and the reheater has increased radiation heating surface, the average values of the main gas temperature and the reheated gas temperature are controlled by the coal quantity, the deviation between the main gas temperature and the reheated gas temperature is controlled by the flue gas baffle, the coal quantity instruction feedforward based on the unit load instruction and the flue gas baffle opening degree instruction feedforward are introduced, the characteristics of the supercritical carbon dioxide boiler that the working medium is far away from the large specific heat region, the heat absorption process is in the superheating region with a small temperature rise, and the reheater has increased radiation heating surface can be effectively adapted, the gas temperature control accuracy during the operation of the boiler is improved, and the peak-shaving capacity of the boiler is improved.

[0030] Optionally, referring to Figure 2 , the control logic of the average value of the main gas temperature and the reheated gas temperature is as follows:

[0031] Firstly, the load instruction from the unit coordination control system CCS generates the main gas temperature and reheated gas temperature average value instruction through function f1(x), and the load instruction from the unit coordination control system CCS generates the coal quantity instruction feedforward through function f2(x);

[0032] Then, the main gas temperature and reheated gas temperature average value instruction is subtracted by the average value of the real-time value 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;

[0033] Finally, the deviation of the main gas temperature and the reheated gas temperature average value is subjected to PID operation to obtain the coal quantity increment, and the coal quantity increment is added to the coal quantity instruction feedforward to form the coal quantity instruction.

[0034] 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.

[0035] Optionally, referring to Figure 2 , the control logic of the difference value of the main gas temperature and the reheated gas temperature is as follows:

[0036] Firstly, the real-time value of the main gas temperature is subtracted by the real-time value of the reheated gas temperature to obtain the difference value of the main gas temperature and the reheated gas temperature;

[0037] Then, the load instruction from the unit coordination control system CCS generates the superheated side flue damper opening degree instruction feedforward through function f3(x), and the load instruction from the unit coordination control system CCS generates the reheated side flue damper opening degree instruction feedforward through function f4(x);

[0038] Finally, the difference value of the main gas temperature and the reheated gas temperature is subjected to dead zone function and PID operation to obtain the superheated side flue damper opening degree increment, and the superheated side flue damper opening degree increment is added to the damper opening degree instruction feedforward and subjected to M / A hand automatic operation station and MFT switching function to form the superheated side flue damper opening degree instruction; at the same time, the superheated side flue damper opening degree increment is superimposed on the reheated side flue damper opening degree instruction feedforward after passing through the proportional link K, and subjected to M / A hand automatic operation station and MFT switching function to form the reheated side flue damper opening degree instruction.

[0039] In the above embodiment, the control logic of the difference value of 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.

[0040] 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 simple and accurate.

[0041] Optionally, the value of the proportional link K in the control logic is -1. This helps to simply and quickly obtain the increment of the superheating side flue gas damper opening degree.

[0042] 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 increment of the superheating side flue gas damper opening degree according to the field device condition.

[0043] Optionally, the dead zone range of the deviation between the main gas temperature and the real-time value of the reheating gas temperature in the control logic is set to -2-2℃. This helps to accurately obtain the increment of the superheating side flue gas damper opening degree.

[0044] 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. The control logic comprises: The average value of the main gas temperature and the reheated gas temperature is controlled by adjusting the coal quantity to regulate the overall thermal load of the boiler, controlling the average value of the main gas temperature and the reheated gas temperature, adjusting the opening degree of the tail flue damper of the boiler to change the heat absorption distribution of the main gas and the reheated gas, controlling the difference value of the main gas temperature and the reheated gas temperature, introducing a coal quantity feedforward instruction based on the unit load instruction and a flue damper opening degree feedforward instruction. 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) is subjected to a function f1(x) to generate a main gas temperature and reheated gas temperature average value instruction, and the load instruction from the unit coordinated control system (CCS) is subjected to a function f2(x) to generate a coal quantity instruction feedforward; Then, the average value of the main gas temperature and the 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 a 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. 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) is subjected to a function f3(x) to generate a superheated side flue damper opening degree instruction feedforward, and the load instruction from the unit coordinated control system (CCS) is subjected to a function f4(x) to generate a reheated side flue damper opening degree instruction feedforward; 2. The supercritical carbon dioxide boiler gas temperature control strategy of claim 1, wherein, Finally, the difference value of the main gas temperature and the reheated gas temperature is subjected to a dead zone function and a 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 the M / A hand automatic operation station and the 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 the proportional link K, and the reheated side flue damper opening degree instruction is formed through the M / A hand automatic operation station and the MFT switching function.

3. The supercritical carbon dioxide boiler gas temperature control strategy of claim 2, wherein, The functions f1(x), f2(x), f3(x) and f4(x) in the control logic can be linearly interpolated according to the supercritical carbon dioxide boiler thermal calculation or performance calculation results.

4. The supercritical carbon dioxide boiler gas temperature control strategy of claim 2, 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 3, wherein, The value of the proportional link K in the control logic is adjusted according to the field device condition. The dead zone range of the real-time value deviation of the main gas temperature and the reheated gas temperature in the control logic is set to -2-2 DEG C.

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