A main steam system pressure control method based on main pipe control

Abstract

The present invention relates to a pressure control method, in particular to a pressure control method for a main steam system based on a mother pipe, which is used for a mother pipe steam supply system in a thermal power plant, an industrial park or a chemical park. During the simultaneous operation of multiple boilers, a unified main steam mother pipe pressure controller is used to generate a boiler control command under a mother pipe mode to act on each boiler through unified scheduling and coordination. At the same time, each boiler has its own outlet pressure regulating system. The two systems can achieve disturbance-free switching, and the final command of each boiler acts on a fuel controller to control the increase or decrease of fuel, match the pressure of boiler combustion and steam production, and more accurately and effectively control the main steam mother pipe pressure. It avoids the instability of heating load users caused by changes in the main steam mother pipe pressure, meets the heating needs of heat users, and has high safety, good reliability and simple structure.

Description

Technical Field

[0001] The present invention relates to a pressure control method, in particular to a main steam system pressure control method based on a main pipe, which is used for a main pipe steam supply system in a thermal power plant and an industrial park or a chemical park. Background Art

[0002] The steam outlets of multiple boilers are connected through the mother pipe, and the steam flows through the mother pipe to supply steam to the steam turbine or heat users. The rated steam pressure of the boiler outlet is 9.8MPa, the rated steam temperature is 540℃, and the rated evaporation capacity of the boiler is 480t / h. Since the steam mother pipe is responsible for supplying steam to heat users, the steam pressure of the steam mother pipe is required to remain stable to avoid unnecessary frequent fluctuations. Each boiler has its own adjustment system, and the combustion conditions of each boiler are different, and the steam pressure at the outlet is also different. The change in outlet pressure has a great impact on the pressure of the steam mother pipe. If the pressure of the steam mother pipe fluctuates too much, it will inevitably affect the stable operation of the steam turbine and the operation safety of the heat load users. When multiple boilers are running at the same time, the stability of the mother pipe pressure affects the safety, economic and technical indicators of the entire steam supply system. Therefore, under the condition that multiple boilers are running at the same time, the control mode and method of the main steam pressure of the mother pipe is of great significance. Summary of the invention

[0003] The present invention mainly solves the deficiencies in the prior art and provides a main steam pipe-controlled steam system pressure control method which can monitor the main steam pipe pressure and the outlet steam pressure of multiple boilers, set the main steam pipe pressure target value according to the demand of the steam supply system for the main steam pipe pressure, and generate a positive main steam pipe pressure control instruction after comparing it with the actual main steam pipe pressure to act on multiple boilers, so that the multiple boilers can synchronously and coordinately adjust their respective outlet pressures to match the main steam pipe pressure, maintain the safe and stable operation of the steam heating system, and has high safety and reliability.

[0004] The above technical problems of the present invention are mainly solved by the following technical solutions:

[0005] A main steam system pressure control method based on a main pipe is performed in the following steps:

[0006] (I) Composition of the main steam pressure control system of the main pipe:

[0007] Includes multiple boilers, controllers, main steam headers, steam turbines, control valves and heating users;

[0008] The controller is used to control the amount of coal fed into the coal feeder to adjust the steam pressure of the boiler;

[0009] (II) Control methods:

[0010] Coal feeder No. 1 (C1) adjusts the amount of fuel entering boiler No. 1, and the superheated steam at the outlet of boiler No. 1 (G1) flows through pipeline No. 1 (L1) and enters the main steam main pipe L4 through valve No. 1 (V1). Coal feeder No. 2 (C2) adjusts the amount of fuel entering boiler No. 1, and the superheated steam at the outlet of boiler No. 2 (G2) flows through pipeline No. 2 (L2) and enters the main steam main pipe L4 through valve No. 2 (V2). Coal feeder No. 3 (C3) adjusts the amount of fuel entering boiler No. 3, and the superheated steam at the outlet of boiler No. 3 (G3) flows through pipeline No. 3 (L3) and enters the main steam main pipe L4 through valve No. 3 (V3).

[0011] The main steam flows through the No. 5 pipeline (L5) and the No. 5 valve (V5) into the No. 1 steam turbine (T1), maintaining the normal operation of the steam turbine T1; the main steam flows through the No. 6 pipeline (L6) and the No. 6 valve (V6) into the No. 2 steam turbine (T2), maintaining the normal operation of the steam turbine T2;

[0012] The main steam flows through the main steam main pipe L4, and is delivered to the heating users E1, E2, and E3 through valve No. 4 (V4); the control ends of the boilers G1, G2, G3, and the coal feeders C1, C2, and C3 are respectively connected to the controller; by adjusting the coal feed amount, the steam pressure at the outlet of each boiler is controlled to ensure that the steam pressure of the steam main pipe meets the requirements of the heating users.

[0013] Preferably, the control ends of boiler No. 1, coal feeder No. 1, boiler No. 2, coal feeder No. 2, boiler No. 3 and coal feeder No. 3 are respectively connected to the controller.

[0014] As a preference, more than three boilers are designed with a unified control system, the control object is the steam supply main pipe pressure, and the set pressure is the pressure value required by the steam supply user; the steam main pipe pressure set value is calculated by the fourth-order inertia link and the control object pressure deviation through the PID controller to generate the boiler steam supply main pipe control instruction, which is used as the load instruction of the unit boiler under the main pipe pressure control mode:

[0015] The formation of steam main pipe pressure deviation is as described in formula (1):

[0016] DV=SP * (1-e -t / 5 )*(1-e -t / 10 )(1-e -t / 15 )(1-e -t / 20 )-PV (1)

[0017] In the formula, DV is the main pipe steam pressure deviation, SP is the main pipe pressure set value, PV is the main pipe pressure actual value, and t is time;

[0018] The main pipe pressure control command is as described in formula (2):

[0019] BM=DV*(K p +K i +K d ) (2)

[0020] BM is the output command of the main pipe steam pressure controller acting uniformly on each boiler in the main pipe pressure control mode, K P \K I \K D They are proportional, integral and differential control respectively.

[0021] The control method also includes taking the average value of the steam flow of three (or more) operating boilers as the feedforward signal output of the mother pipe pressure controller.

[0022] The feedforward signal FF has the following relationship with the average steam flow rate Q0 of the boiler: Average steam flow rate, boiler load, feedforward output value relationship table

[0023] Boiler load L(%) <![CDATA[Average steam flow rate Q0 (t / h)]]> Feedforward output value (%) 30 5.8 3 40 7.5 3.8 50 9.43 5.1 60 11.18 6.2 70 12.52 6.9 80 13.56 7.6 90 16.8 8.5 95 17.64 9.1 100 18.73 9.5

[0024] Preferably, the control method further comprises a pressure control system for each boiler, the control object is the steam pressure at the outlet of the superheater of each boiler, the set pressure is manually set, and the deviation between the two is generated by PID calculation to generate a boiler master control instruction, which is called a unit boiler control instruction;

[0025] This instruction and the load instruction in the mother pipe pressure control mode perform disturbance-free switching between the mother pipe mode and the unit mode through pressure control load bias;

[0026] The main steam deviation of a single boiler is formed as described in formula (3):

[0027] DV n =SP n *(1-e -t / 5 )*(1-e -t / 10 )(1-e -t / 15 )(1-e -t / 20 )-PV n (3)

[0028] DV in the formula n is the main steam pressure deviation of the boiler outlet of the nth boiler, SP n is the set value of the outlet steam pressure of the nth boiler, PV n is the actual value of the steam pressure at the outlet of the nth boiler, and t is the time;

[0029] The steam outlet pressure control command of the nth boiler unit is as described in formula (4):

[0030] BP n =DV n *(K p +Ki +K d ) (4)

[0031] BP n is the output command of the boiler pressure controller of the nth boiler in the unit control mode, K P \K I \K D They are proportional, integral and differential control functions respectively;

[0032] Under different control modes, the final control command of the nth boiler master and the boiler output command under the mother pipe mode and unit mode have the following relationship:

[0033] B n =BP n -BM (5)

[0034] When MODE=1, BD n =BM+B n (6)

[0035] When MODE=0, BD n =BP n (7)

[0036] When MODE=1, it is the boiler unit control mode; when MODE=1, it is the main pipe pressure control mode; BD n B is the final command output of the nth boiler master control; n is the load bias of the main steam pipe pressure control of the nth boiler. In the non-main pipe pressure mode, B n Track the deviation between the control command of the nth boiler unit mode and the control command of the main pipe mode; in the main pipe mode, Bn can be set manually, BP n Tracking BM and B n of and;

[0037] The above method can realize the disturbance-free switching between the unit mode and the mother tube mode.

[0038] 5. A main steam system pressure control method based on main pipe control according to claim 3, characterized in that: the control method also includes the unit boiler instruction and the load instruction under the main pipe pressure control mode acting on the fuel control module after the mode is selected, and the fuel amount required for a single boiler is converted through the function corresponding to the boiler load and the fuel.

[0039] The nth boiler outputs the final instruction BD n The corresponding fuel quantity TF n There are the following relationships:

[0040]

[0041]

[0042] The comparison deviation between the above fuel setting value and the measured fuel is input into the fuel main control PID control module for calculation. The output instruction directly controls the coal intake of the boiler, controls the boiler combustion to correspond to the set steam pressure, and maintains safe and stable operation of the unit.

[0043] The present invention can achieve the following effects:

[0044] During the simultaneous operation of multiple boilers, the present invention uses a unified main steam main pipe pressure controller to generate boiler control instructions under the main pipe mode to act on each boiler through unified scheduling and coordination. At the same time, each boiler has its own outlet pressure regulation system. The two systems can achieve disturbance-free switching, and the final instructions of each boiler act on the fuel controller to control the increase and decrease of fuel, match the pressure of boiler combustion and steam production, and control the main steam main pipe pressure more accurately and effectively. Avoid the instability of heating load users caused by changes in the main steam main pipe pressure, meet the heating needs of heat users, and have high safety, good reliability and simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the connection structure of the present invention;

[0046] Figure 2 It is a logic flow diagram of boiler load instruction generation in the mother tube control mode of the present invention;

[0047] Figure 3 It is a logic flow diagram of boiler control instruction generation in boiler unit mode of the present invention;

[0048] Figure 4 It is a schematic diagram of switching between boiler control instructions in boiler unit mode and load instructions in main pipe mode in the present invention;

[0049] Figure 5 The present invention Figure 1-Figure 4 Descriptive diagram of the meaning of the symbols in the text;

[0050] Figure 6 It is a schematic block diagram of the circuit principle connection structure of the present invention.

[0051] The technical solution of the present invention is further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0052] Example 1: As shown in the figure, a method for controlling the pressure of a main steam system based on a main pipe is performed in the following steps:

[0053] (I) Composition of the main steam pressure control system of the main pipe:

[0054] Includes multiple boilers, controllers, main steam headers, steam turbines, control valves and heating users;

[0055] The controller is used to control the amount of coal fed into the coal feeder to adjust the steam pressure of the boiler;

[0056] (II) Control methods:

[0057] Coal feeder No. 1 (C1) adjusts the amount of fuel entering boiler No. 1, and the superheated steam at the outlet of boiler No. 1 (G1) flows through pipeline No. 1 (L1) and enters the main steam main pipe L4 through valve No. 1 (V1). Coal feeder No. 2 (C2) adjusts the amount of fuel entering boiler No. 1, and the superheated steam at the outlet of boiler No. 2 (G2) flows through pipeline No. 2 (L2) and enters the main steam main pipe L4 through valve No. 2 (V2). Coal feeder No. 3 (C3) adjusts the amount of fuel entering boiler No. 3, and the superheated steam at the outlet of boiler No. 3 (G3) flows through pipeline No. 3 (L3) and enters the main steam main pipe L4 through valve No. 3 (V3).

[0058] The main steam flows through the No. 5 pipeline (L5) and the No. 5 valve (V5) into the No. 1 steam turbine (T1), maintaining the normal operation of the steam turbine T1; the main steam flows through the No. 6 pipeline (L6) and the No. 6 valve (V6) into the No. 2 steam turbine (T2), maintaining the normal operation of the steam turbine T2;

[0059] The main steam flows through the main steam main pipe L4, and is delivered to the heating users E1, E2, and E3 through valve No. 4 (V4); the control ends of the boilers G1, G2, G3, and the coal feeders C1, C2, and C3 are respectively connected to the controller; by adjusting the coal feed amount, the steam pressure at the outlet of each boiler is controlled to ensure that the steam pressure of the steam main pipe meets the requirements of the heating users.

[0060] The control ends of boiler No. 1, coal feeder No. 1, boiler No. 2, coal feeder No. 2, boiler No. 3 and coal feeder No. 3 are connected to the controller respectively.

[0061] More than 3 boilers are designed with a unified control system. The control object is the steam supply main pipe pressure, and the set pressure is the pressure value required by the steam supply user. The steam main pipe pressure set value is calculated by the fourth-order inertia link and the pressure deviation of the control object through the PID controller to generate the boiler steam supply main pipe control instruction. This instruction is used as the load instruction of the unit boiler in the main pipe pressure control mode:

[0062] The formation of steam main pipe pressure deviation is as described in formula (1):

[0063] DV=SP*(1-e -t / 5 )*(1-e -t / 10 )(1-e -t / 15 )(1-e -t / 20 )-PV (1)

[0064] In the formula, DV is the main pipe steam pressure deviation, SP is the main pipe pressure set value, PV is the main pipe pressure actual value, and t is time;

[0065] The main pipe pressure control command is as described in formula (2):

[0066] BM=DV*(K p +K i +K d ) (2)

[0067] BM is the output command of the main pipe steam pressure controller acting uniformly on each boiler in the main pipe pressure control mode, K P \K I \K D They are proportional, integral and differential control respectively.

[0068] The control method also includes a pressure control system for each boiler. The control object is the steam pressure at the outlet of the superheater of each boiler. The set pressure is manually set. The deviation between the two is calculated by PID to generate the boiler master control instruction, which is called the unit boiler control instruction.

[0069] This instruction and the load instruction in the mother pipe pressure control mode perform disturbance-free switching between the mother pipe mode and the unit mode through pressure control load bias;

[0070] The main steam deviation of a single boiler is formed as described in formula (3):

[0071] DV n =SP n *(1-e -t / 5 )*(1-e -t / 10 )(1-e -t / 15 )(1-e -t / 20 )-PV n (3)

[0072] DV in the formula n is the main steam pressure deviation of the boiler outlet of the nth boiler, SP n is the set value of the outlet steam pressure of the nth boiler, PV n is the actual value of the steam pressure at the outlet of the nth boiler, and t is the time;

[0073] The steam outlet pressure control command of the nth boiler unit is as described in formula (4):

[0074] BP n =DV n *(K p +K i +K d ) (4)

[0075] BPn is the output command of the boiler pressure controller of the nth boiler in the unit control mode, K P \K I \K D They are proportional, integral and differential control functions respectively;

[0076] Under different control modes, the final control command of the nth boiler master and the boiler output command under the mother pipe mode and unit mode have the following relationship:

[0077] B n =BP n -BM (5)

[0078] When MODE=1, BD n =BM+B n (6)

[0079] When MODE=0, BD n =BP n (7)

[0080] When MODE=1, it is the boiler unit control mode; when MODE=1, it is the main pipe pressure control mode; BD n B is the final command output of the nth boiler master control; n is the load bias of the main steam pipe pressure control of the nth boiler. In the non-main pipe pressure mode, B n Track the deviation between the control command of the nth boiler unit mode and the control command of the main pipe mode; in the main pipe mode, Bn can be set manually, BP n Tracking BM and B n of and;

[0081] The above method can realize the disturbance-free switching between the unit mode and the mother tube mode.

[0082] The control method also includes that the unit boiler instruction and the load instruction under the mother pipe pressure control mode act on the fuel control module after the mode is selected, and the fuel amount required for a single boiler is converted through the function corresponding to the boiler load and the fuel.

Claims

1. A method for controlling the pressure of a steam system based on a main pipe, characterized in that Follow these steps: (I) Composition of the main steam pressure control system of the main pipe: Includes multiple boilers, controllers, main steam headers, steam turbines, control valves and heating users; The controller is used to control the amount of coal fed into the coal feeder to adjust the steam pressure of the boiler; (II) Control methods: Coal feeder No. 1 (C1) adjusts the amount of fuel entering boiler No. 1, and the superheated steam at the outlet of boiler No. 1 (G1) flows through pipeline No. 1 (L1) and enters the main steam main pipe L4 through valve No. 1 (V1). Coal feeder No. 2 (C2) adjusts the amount of fuel entering boiler No. 2, and the superheated steam at the outlet of boiler No. 2 (G2) flows through pipeline No. 2 (L2) and enters the main steam main pipe L4 through valve No. 2 (V2). Coal feeder No. 3 (C3) adjusts the amount of fuel entering boiler No. 3, and the superheated steam at the outlet of boiler No. 3 (G3) flows through pipeline No. 3 (L3) and enters the main steam main pipe L4 through valve No. 3 (V3). The main steam flows through the No. 5 pipeline (L5) and the No. 5 valve (V5) into the No. 1 steam turbine (T1), maintaining the normal operation of the steam turbine T1; the main steam flows through the No. 6 pipeline (L6) and the No. 6 valve (V6) into the No. 2 steam turbine (T2), maintaining the normal operation of the steam turbine T2; The main steam flows through the main steam main pipe L4, and is delivered to the heating users E1, E2, and E3 through valve No. 4 (V4); the control ends of the boilers G1, G2, and G3, and the coal feeders C1, C2, and C3 are connected to the controller respectively; by adjusting the coal feed amount, the steam pressure at the outlet of each boiler is controlled to ensure that the steam pressure at the steam main pipe meets the requirements of the heating users; More than 3 boilers are designed with a unified control system. The control object is the steam supply main pipe pressure, and the set pressure is the pressure value required by the steam supply user. The steam main pipe pressure set value is calculated by the fourth-order inertia link and the pressure deviation of the control object through the PID controller to generate the boiler steam supply main pipe control instruction. This instruction is used as the load instruction of the unit boiler in the main pipe pressure control mode: The formation of steam main pipe pressure deviation is as described in formula (1): DV=SP*(1st -t / 5 )*(1st -t / 10 )(1st -t / 15 )(1st -t / 20 )-PV(1) In the formula, DV is the main pipe steam pressure deviation, SP is the main pipe pressure set value, PV is the main pipe pressure actual value, and t is time; The main pipe pressure control command is as described in formula (2): BM=DV*(K p +K i +K d )(2) BM is the output command of the main pipe steam pressure controller acting uniformly on each boiler in the main pipe pressure control mode, K P \K I \K D They are proportional, integral and differential control functions respectively; The control method also includes a pressure control system for each boiler. The control object is the steam pressure at the outlet of the superheater of each boiler. The set pressure is manually set. The deviation between the two is calculated by PID to generate the boiler master control instruction, which is called the unit boiler control instruction. This instruction and the load instruction in the mother pipe pressure control mode perform disturbance-free switching between the mother pipe mode and the unit mode through pressure control load bias; The main steam deviation of a single boiler is formed as described in formula (3): DV n =SP n *(1st -t / 5 )*(1st -t / 10 )(1st -t / 15 )(1st -t / 20 )-PV n (3) DV in the formula n is the main steam pressure deviation of the boiler outlet of the nth boiler, SP n is the set value of the outlet steam pressure of the nth boiler, PV n is the actual value of the steam pressure at the outlet of the nth boiler, and t is the time; The steam outlet pressure control command of the nth boiler unit is as described in formula (4): BP n =DV n *(K p +K i +K d )(4) BP n is the output command of the boiler pressure controller of the nth boiler in the unit control mode, K P \K I \K D They are proportional, integral and differential control functions respectively; Under different control modes, the final control command of the nth boiler master and the boiler output command under the mother pipe mode and unit mode have the following relationship: B n =BP n -BM(5) When MODE=1, BD n =BM+B n (6) When MODE=0, BD n =BP n (7) When MODE=1, it is the boiler unit control mode; when MODE=1, it is the main pipe pressure control mode; BD n B is the final command output of the nth boiler master control; n is the load bias of the main steam pipe pressure control of the nth boiler. In the non-main pipe pressure mode, B n Track the deviation between the control command of the nth boiler unit mode and the control command of the main pipe mode; in the main pipe mode, Bn is manually set, BP n Tracking BM and B n of and; The above method can realize the disturbance-free switching between the unit mode and the mother tube mode.

2. The method for controlling the pressure of a steam system based on a main pipe according to claim 1, characterized in that: The control ends of boiler No. 1, coal feeder No. 1, boiler No. 2, coal feeder No. 2, boiler No. 3 and coal feeder No. 3 are connected to the controller respectively.

3. The method for controlling the pressure of a steam system based on a main pipe according to claim 1, characterized in that: The control method also includes that the unit boiler instruction and the load instruction under the mother pipe pressure control mode act on the fuel control module after the mode is selected, and the fuel amount required for a single boiler is converted through the function corresponding to the boiler load and the fuel.

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