Circulating fluidized bed combined combustion peak shaving control system

Abstract

The application discloses a circulating fluidized bed composite combustion peak regulation control system and relates to the technical field of coal combustion control. The circulating fluidized bed composite combustion peak regulation control system comprises a load control system, a main steam pressure control system and a bed temperature change rate control system. In the main steam pressure control system, a PC coal control subsystem is used for adjusting PC coal quantity D PC to control main steam pressure p0, and a main steam control valve control subsystem is used for adjusting main steam control valve opening degree μ to control main steam pressure p0. The bed temperature change rate control system is used for controlling ash quantity according to the difference between a given bed temperature change rate υ Tb0 and a measured bed temperature change rate υ Tb . The application can automatically increase or decrease the load of a circulating fluidized bed unit according to a set load change rate, the load increase rate is increased from the current 1% Pe / min to more than 3% Pe / min, and the load decrease rate is greater than 2%.

Description

Technical Field

[0001] The present invention relates to the technical field of coal combustion control, in particular to a circulating fluidized bed composite combustion peak regulation control system. Background Art

[0002] Circulating fluidized bed (CFB) low-calorific-value coal-fired power generation units are rapidly developing based on the comprehensive utilization of my country's coal resources. Compared to pulverized coal units, CFB boilers possess high thermal inertia and strong coupling. The presence of large amounts of bed material and castables results in high heat storage and thermal inertia in CFB boilers. Research on CFB power generation units reveals that the load response rate of most units rarely exceeds 1%Pe / min. Slow load response is an inherent characteristic of CFB units.

[0003] Chinese patent publication number CN118328379A discloses a pulverized coal delivery system and circulating fluidized bed boiler. An air compressor delivers compressed air to an air-powder mixer. A pulverized coal silo stores pulverized coal and delivers it to the air-powder mixer via a pulverized coal feeder. The air-powder mixer mixes the compressed air and coal and outputs the mixture. The outlet of the air-powder mixer is connected to a main pulverized coal delivery pipe, which is connected to the inlets of each pulverized coal delivery pipe via a distributor. The pulverized coal delivery pipes are connected to secondary air ducts on the front, rear, and side walls of the circulating fluidized bed boiler via a sleeve-type connection. The air-powder delivery pipes deliver the mixture to the furnace of the circulating fluidized bed boiler. The patent describes a composite combustion rapid peak-shaving system, but does not address how to automatically and rapidly increase or decrease the load of the circulating fluidized bed unit. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a circulating fluidized bed composite combustion peak-shaving control system, which at least achieves the purpose of automatic combustion control during the process of load increase and decrease.

[0005] In order to solve the above technical problems, the present invention provides a circulating fluidized bed composite combustion peak-shaving control system, which includes a load control system, a main steam pressure control system and a bed temperature change rate control system;

[0006] The load control system is used to respectively perform load increase coordinated control and load decrease coordinated control through high selection and low selection according to the difference between the load command Pg and the measured load signal P, and control the step increase or step decrease of CFB coal, primary air volume, and secondary air volume according to the set load increase rate set value or load decrease rate set value respectively; at the same time, the initial value of the step increase of the dynamic adjustment amount PC coal and circulating ash or fly ash is given in the load increase coordinated control, and the initial value of the step decrease of the dynamic adjustment amount circulating ash is given in the load decrease coordinated control;

[0007] The main steam pressure control system includes a PC coal control subsystem and a main steam regulating valve control subsystem; according to the main steam pressure deviation given value |△p00 The difference between | and the absolute value of the measured main steam pressure deviation value |△p0| enters the PC coal control subsystem and the main steam regulating valve control subsystem through high selection and low selection respectively;

[0008] The bed temperature change rate control system is used to set a value υ according to the bed temperature change rate. Tb0 and the measured bed temperature change rate υ Tb The difference controls the gray amount.

[0009] In a preferred embodiment, the load control system includes a first adder, a load increase coordination control loop, and a load decrease coordination control loop;

[0010] The first adder is used to calculate the difference between the load command Pg and the measured load signal P;

[0011] The load increase coordination control loop is connected to the output end of the first adder via a high selector, and the load increase coordination control loop is used to control the step increments of CFB coal, primary air volume, and secondary air volume and provide the initial value of the step increment of the dynamic adjustment amount PC coal, circulating ash or fly ash according to the set load increase rate given value;

[0012] The load reduction coordination control loop is connected to the output end of the first adder through a low selection. The load reduction control loop is used to control the step reduction of CFB coal, primary air volume, secondary air volume and give the initial value of the step reduction of circulating ash according to the set load reduction rate given value.

[0013] In a preferred embodiment, the main steam pressure control system includes a second adder, which is used to calculate the main steam pressure deviation given value |△p 00 The difference between the absolute value of the measured main steam pressure deviation △p0 enters the PC coal control subsystem and the main steam valve control subsystem according to the high and low values ​​of the difference. The PC coal control subsystem is used to adjust the PC coal quantity G PC To control the main steam pressure p0, the main steam regulating valve control subsystem is used to adjust the main steam regulating valve opening μ to control the main steam pressure p0.

[0014] In a preferred embodiment, the PC coal control subsystem includes a PC coal controller, a first limiter, a first transfer function module and a third adder connected in sequence; the third adder is used to calculate the main steam pressure p0 and the main steam pressure set value p 00 The difference △p0, △p0= p0- p 00 , p0 and p 00 The allowable deviation value is △p;

[0015] When the second adder outputs a difference greater than 0, the PC coal controller is connected to the output end of the second adder through a high selector, and the PC coal controller adjusts the PC coal amount D according to the difference △p0pc , PC coal quantity D pc After passing through the first limiter, the pressure is transmitted to the first transfer function module, the first transfer function module outputs the main steam pressure p0, and the main steam pressure p0 is input to the third adder;

[0016] When △p0>△p, the PC coal controller reduces the PC coal amount D pc , thereby reducing the main steam pressure p0 and making △p0≤△p; when -△p0>△p, the PC coal controller increases the PC coal amount D pc , so that the main steam pressure p0 increases, making -△p0≤△p, PC coal quantity D pc The adjustment is limited;

[0017] The main steam regulating valve control subsystem includes a main steam regulating valve controller and a second transfer function module; when the second adder outputs a difference value less than 0, the main steam regulating valve controller is connected to the output end of the second adder through a low selection, and the main steam regulating valve controller adjusts the main steam regulating valve opening μ according to Δp0. The second transfer function module receives the main steam regulating valve opening μ signal and outputs the main steam pressure p0 to the third adder;

[0018] When △p0>△p, the main steam regulating valve controller increases the main steam regulating valve opening μ, thereby reducing the main steam pressure p0 and making △p0≤△p; when -△p0>△p, the main steam regulating valve controller closes the main steam regulating valve opening μ, thereby increasing the main steam pressure p0 and making -△p0≤△p.

[0019] In a preferred embodiment, the bed temperature change rate control system includes a fourth adder, an ash content controller, a second limiter, a third transfer function module and a differentiator connected in sequence;

[0020] The fourth adder is used to calculate the bed temperature change rate given value υ Tb0 and the measured bed temperature change rate υ Tb The gray amount controller is connected to the output of the fourth adder, the gray amount controller controls the gray amount adjustment mechanism to reduce or increase the gray amount G h The second limiter receives the gray volume G output by the gray volume controller h The signal is transmitted to the third transfer function module, and the third transfer function module outputs the bed temperature T b , bed temperature T b After being processed by the differentiator, it becomes the bed temperature change rate υ Tb signal; the output of the differentiator is connected to the input of the fourth adder, and the bed temperature change rate υ Tb The signal is transmitted to the fourth adder.

[0021] The present invention provides a composite combustion peak-shaving control system for a circulating fluidized bed boiler peak-shaving system, which can automatically increase or decrease the load of the circulating fluidized bed unit according to the set load change rate. The load increase rate is increased from the current 1%Pe / min to more than 3%Pe / min, and the load reduction rate is greater than 2%. The main steam pressure change range and the bed temperature change rate are kept within the allowable limits, thereby realizing automatic, safe and rapid load increase or decrease of the circulating fluidized bed unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the control principle of the load control system of the present invention;

[0023] Figure 2 This is a schematic diagram of the control principle of the main steam pressure control system of the present invention;

[0024] Figure 3 It is a schematic diagram of the control principle of the bed temperature change rate control system of the present invention.

[0025] In the figure, 1-first adder, 3-load increase coordination control loop, 5-load decrease coordination control loop, 6-second adder, 8-PC coal controller, 9-first limiter, 10-first transfer function module, 11-third adder, 12-absolute value calculation module, 14-main steam regulating valve controller, 15-second transfer function module, 16-fourth adder, 17-ash amount controller, 18-second limiter, 19-third transfer function module, 20-differentiator;

[0026] 2 is the high selection in the load control system, 4 is the low selection in the load control system, 7 is the high selection in the main steam pressure control system, and 13 is the low selection in the main steam pressure control system. DETAILED DESCRIPTION

[0027] In response to the circulating fluidized bed boiler composite combustion rapid peak-shaving system provided by the invention patent with publication number CN118328379A, this embodiment provides a control system and strategy for the circulating fluidized bed composite combustion during load increase and load decrease, thereby realizing automatic combustion control during load increase and decrease.

[0028] The concept of the present invention is to design a new load control system containing a step feed of CFB coal air volume and a dynamic adjustment amount, a main steam pressure control system containing a PC coal control subsystem and a main steam regulating valve control subsystem, and a bed temperature change rate control system, which can enable the circulating fluidized bed unit to automatically increase or decrease the load according to the set load change rate, and keep the main steam pressure change range and bed temperature change rate within the allowable limits.

[0029] The circulating fluidized bed composite combustion peak shaving control system provided in this embodiment includes a load control system, a main steam pressure control system and a bed temperature change rate control system, and the circulating fluidized bed composite combustion peak shaving control is performed based on the above systems.

[0030] The load control system is used to implement load control. Based on the difference between the load command Pg and the measured load signal P, it performs load-up coordinated control and load-down coordinated control via high and low selection, respectively. It controls the step increments or step decrements of the CFB coal, primary air volume, and secondary air volume, respectively, according to the set load-up rate setpoint or load-down rate setpoint. Simultaneously, initial step increment values ​​for the dynamic adjustment variables PC coal and recycled ash or fly ash are specified during load-up coordinated control, while initial step decrements for the dynamic adjustment variable recycled ash are specified during load-down coordinated control.

[0031] like Figure 1 As shown, the load control system includes a first adder 1 , a load increase control loop 3 and a load decrease control loop 5 .

[0032] The first adder 1 is used to calculate the difference between the load command Pg and the measured load signal P. When the difference is positive, the load control system enters the load increase coordination control loop 3 through the high selection 2. When the difference is negative, the load control system enters the load decrease coordination control loop 5 through the low selection 4.

[0033] Specifically, the load increase coordination control loop 3 is connected to the output end of the first adder 1 through the high selection 2 in the load control system. The load increase coordination control loop 3 controls the step increments of C FB coal, primary air volume, and secondary air volume according to the set load increase rate given value, and gives the initial value of the step increment of the dynamic adjustment amount PC coal and circulating ash or fly ash.

[0034] Specifically, the load reduction coordination control loop 5 is connected to the output end of the first adder 1 through the low selection 4 in the load control system. The load reduction coordination control loop 5 controls the step reduction of CFB coal, primary air volume, and secondary air volume according to the set load reduction rate given value, and gives the initial value of the step reduction of the dynamic adjustment amount circulating ash.

[0035] Main steam pressure control system is used to perform main steam pressure control, such as Figure 2 As shown, it includes a PC coal control subsystem, a main steam regulating valve control subsystem and a second adder 6.

[0036] The second adder 6 is used to calculate the main steam pressure deviation given value |△p 00 The difference between the absolute value of the measured main steam pressure deviation △p0 enters the PC coal control subsystem and the main steam valve control subsystem according to the high and low values ​​of the difference. The PC coal control subsystem is used to adjust the PC coal quantity D PCTo control the main steam pressure p0, the main steam regulating valve control subsystem is used to adjust the main steam regulating valve opening μ to control the main steam pressure p0.

[0037] The PC coal control subsystem includes a PC coal controller 8, a first limiter 9, a first transfer function module 10, and a third adder 11 connected in sequence. The PC coal controller 8 is connected to the output end of the second adder 6 through the high select 7 in the main steam pressure control system. The PC coal controller 8 calculates the value of |△p output by the second adder 6. 00 The difference between | and |△p0| adjusts the PC coal quantity D pc , PC coal quantity D pc After passing through the first limiter 9, it is transmitted to the first transfer function module 10; the first transfer function module 10 outputs the main steam pressure p0, and the main steam pressure p0 signal is input to the third adder 11, and the third adder 11 calculates the main steam pressure value p0 and the main steam pressure set value p 00 The difference △p0, △p0= p0- p 00 , p0 and p 00 The allowable deviation value is △p. The first limiter 9 is used to set the PC coal quantity D pc The first transfer function is PC coal quantity D pc The relationship between it and the main steam pressure p0 is a characteristic of the boiler control object and is generally obtained through experiments.

[0038] The main steam valve control subsystem includes a main steam valve controller 14 and a second transfer function module 15. The main steam valve controller 14 is connected to the output end of the second adder 6 through the low selector 13 in the main steam pressure control system. The main steam valve controller 14 is connected to the output end of the second adder 6 according to |△p 00 The difference between | and |Δp0| regulates the main steam regulating valve opening μ. Second transfer function module 15 receives the main steam regulating valve opening μ signal and outputs the measured main steam pressure value p0 to third adder 11. The second transfer function represents the relationship between the main steam regulating valve opening μ and the main steam pressure p0. This is a characteristic of the controlled object and is clearly defined in the unit operating procedures.

[0039] When the difference value output by the second adder 6 is greater than 0, the main steam pressure control system enters the PC coal control subsystem through the high selection 7, and the PC coal controller 8 determines the difference between the main steam pressure p0 and the main steam pressure set value p 00 The difference △p0= p0- p 00 , adjust PC coal quantity D PC , PC coal quantity D PC The signal is input to the first transfer function module 10 through the first limiter 9. The first transfer function module 10 outputs the main steam pressure p0. The main steam pressure p0 signal is input to the third adder 11. At the same time, the main steam pressure set value p 00The negative value of is input to the third adder 11, and the third adder 11 outputs the measured main steam pressure deviation △p0. When △p0>△p, the PC coal controller reduces the PC coal amount D pc , thereby reducing the main steam pressure p0 and making △p0≤△p; when -△p0>△p, the PC coal controller increases the PC coal amount D pc , thereby increasing the main steam pressure p0 and making -△p0≤△p.

[0040] When the difference value output by the second adder 6 is less than 0, the main steam valve control subsystem is entered through the low selection 13 in the main steam pressure control system. The main steam valve controller 14 calculates the difference value according to the main steam pressure p0 and the main steam pressure set value p 00 The difference △p0= p0-p 00 The throttle valve opening μ is adjusted, and the throttle valve opening μ signal is input to the second transfer function module 15. The second transfer function module 15 outputs the main steam pressure p0. The main steam pressure p0 signal is input to the third adder 11. The third adder 11 outputs the measured main steam pressure deviation △p0. When △p0>△p, the main steam throttle valve controller increases the main steam throttle valve opening μ, thereby reducing the main steam pressure p0, so that △p0≤△p; when -△p0>△p, the main steam throttle valve controller closes the main steam throttle valve opening μ, thereby increasing the main steam pressure p0, so that -△p0≤△p.

[0041] Bed temperature change rate control system is used to perform bed temperature change rate control, according to the bed temperature change rate given value υ Tb0 and the measured bed temperature change rate υ Tb The difference controls the gray amount.

[0042] like Figure 3 As shown, the bed temperature change rate control system includes a fourth adder 16, an ash quantity controller 17, a second limiter 18, a third transfer function module 19 and a differentiator 20 which are connected in sequence.

[0043] The fourth adder 16 is used to calculate the bed temperature change rate given value υ Tb0 and the measured bed temperature change rate υ Tb The difference.

[0044] The ash amount controller 17 is connected to the output end of the fourth adder 16, and the ash amount controller 17 controls the ash amount adjustment mechanism to reduce or increase the ash amount D h The second limiter 18 receives the gray amount D output by the gray amount controller h The signal is transmitted to the third transfer function module 19, and the third transfer function module 19 outputs the bed temperature T b , bed temperature T b After being processed by the differentiator 20, it becomes the bed temperature change rate υ TbThe output of the differentiator 20 is connected to the input of the fourth adder 16, the bed temperature change rate υ Tb The signal is transmitted to the fourth adder 16, and the fourth adder 16 calculates the bed temperature change rate given value υ Tb0 and the measured bed temperature change rate υ Tb The difference between Tb0 -υ Tb )>0, the ash amount controller 17 controls the ash amount adjustment mechanism to reduce the ash amount D h , so that the bed temperature increases; when (υ Tb0 -υ Tb )<0, the ash amount controller 17 controls the ash amount adjustment mechanism to increase the ash amount D h , so that the bed temperature is lowered.

[0045] The second limiter 18 is used to set the gray amount D h The third transfer function is the gray amount D h and bed temperature T b The relationship between them belongs to the characteristics of the boiler control object and is obtained through experiments.

[0046] Taking a 350MW fluidized bed unit as an example, the system provided in this embodiment is used to implement the control strategy during the load increase and load decrease of a circulating fluidized bed composite combustion unit. The load increases from 150MW to 190MW, and the coordinated control is set to a load increase rate of 14MW / min, a CFB coal step increment of 41t / h, and a primary air step increment of 7.4×10 4 Nm 3 / h, secondary air step increment 10.3×10 4 Nm 3 / h, the initial value of the PC coal step increment is 9.8t / h, the initial value of the fly ash step increment is 10t / h, the measured load increase rate is 3.82%Pe / min, the average bed temperature change rate is 2℃ / min, and the main steam pressure deviation does not exceed 0.5MPa.

Claims

1. A circulating fluidized bed composite combustion peak-shaving control system, characterized in that: Including load control system, main steam pressure control system and bed temperature change rate control system; The load control system is used to respectively perform load increase coordinated control and load decrease coordinated control through high selection and low selection according to the difference between the load command Pg and the measured load signal P, and control the step increase or step decrease of CFB coal, primary air volume, and secondary air volume according to the set load increase rate set value or load decrease rate set value respectively; at the same time, the initial value of the step increase of the dynamic adjustment amount PC coal and circulating ash or fly ash is given in the load increase coordinated control, and the initial value of the step decrease of the dynamic adjustment amount circulating ash is given in the load decrease coordinated control; The main steam pressure control system includes a PC coal control subsystem and a main steam regulating valve control subsystem; according to the main steam pressure deviation given value |△p 00 The difference between | and the absolute value of the measured main steam pressure deviation value |△p0| enters the PC coal control subsystem and the main steam regulating valve control subsystem through high selection and low selection respectively; The bed temperature change rate control system is used to set a value υ according to the bed temperature change rate. Tb0 and the measured bed temperature change rate υ Tb The difference controls the gray amount.

2. The circulating fluidized bed composite combustion peak shaving control system according to claim 1, characterized in that: The load control system includes a first adder, a load increase coordination control loop and a load decrease coordination control loop; The first adder is used to calculate the difference between the load command Pg and the measured load signal P; The load increase coordination control loop is connected to the output end of the first adder via a high selector, and the load increase coordination control loop is used to control the step increments of CFB coal, primary air volume, and secondary air volume and provide the initial value of the step increment of the dynamic adjustment amount PC coal, circulating ash or fly ash according to the set load increase rate given value; The load reduction coordination control loop is connected to the output end of the first adder through a low selection. The load reduction control loop is used to control the step reduction of CFB coal, primary air volume, and secondary air volume and provide the initial value of the step reduction of the cycle grayscale according to the set load reduction rate given value.

3. The circulating fluidized bed composite combustion peak shaving control system according to claim 1 or 2, characterized in that: The main steam pressure control system includes a second adder, which is used to calculate the main steam pressure deviation given value |△p 00 The difference between the absolute value of the measured main steam pressure deviation △p0 enters the PC coal control subsystem and the main steam valve control subsystem according to the high and low values ​​of the difference. The PC coal control subsystem is used to adjust the PC coal quantity D PC To control the main steam pressure p0, the main steam regulating valve control subsystem is used to adjust the main steam regulating valve opening μ to control the main steam pressure p0.

4. The circulating fluidized bed composite combustion peak shaving control system according to claim 3, characterized in that: The PC coal control subsystem includes a PC coal controller, a first limiter, a first transfer function module and a third adder connected in sequence; the third adder is used to calculate the main steam pressure p0 and the main steam pressure set value p 00 The difference △p0, △p0=p0- p 00 , p0 and p 00 The allowable deviation value is △p; When the second adder outputs a difference greater than 0, the PC coal controller is connected to the output end of the second adder through a high selector, and the PC coal controller adjusts the PC coal amount D according to the difference △p0 pc , PC coal quantity D pc After passing through the first limiter, the pressure is transmitted to the first transfer function module, the first transfer function module outputs the main steam pressure p0, and the main steam pressure p0 is input to the third adder; When △p0>△p, the PC coal controller reduces the PC coal amount D pc , thereby reducing the main steam pressure p0 and making △p0≤△p; When -△p0>△p, the PC coal controller increases the PC coal amount D pc , so that the main steam pressure p0 increases, making -△p0≤△p, PC coal quantity D pc The adjustment is limited; The main steam regulating valve control subsystem includes a main steam regulating valve controller and a second transfer function module; when the second adder outputs a difference value less than 0, the main steam regulating valve controller is connected to the output end of the second adder through a low selection, and the main steam regulating valve controller adjusts the main steam regulating valve opening μ according to Δp0. The second transfer function module receives the main steam regulating valve opening μ signal and outputs the main steam pressure p0 to the third adder; When △p0>△p, the main steam regulating valve controller increases the main steam regulating valve opening μ, thereby reducing the main steam pressure p0, making △p0≤△p; When -△p0>△p, the main steam regulating valve controller closes the main steam regulating valve opening μ, thereby increasing the main steam pressure p0 and making -△p0≤△p.

5. The circulating fluidized bed composite combustion peak shaving control system according to claim 1 or 4, characterized in that: The bed temperature change rate control system includes a fourth adder, an ash quantity controller, a second limiter, a third transfer function module and a differentiator connected in sequence; The fourth adder is used to calculate the bed temperature change rate given value υ Tb0 and the measured bed temperature change rate υ Tb The gray amount controller is connected to the output of the fourth adder, the gray amount controller controls the gray amount adjustment mechanism to reduce or increase the gray amount D h The second limiter receives the gray amount D output by the gray amount controller h The signal is transmitted to the third transfer function module, and the third transfer function module outputs the bed temperature T b , bed temperature T b After being processed by the differentiator, it becomes the bed temperature change rate υ Tb signal; the output of the differentiator is connected to the input of the fourth adder, and the bed temperature change rate υ Tb The signal is transmitted to the fourth adder.

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