Valve control method for flue gas collecting system of gas collecting hood of electrolytic cell

Abstract

The invention discloses a valve control method for a flue gas collecting system of a gas collecting hood of an electrolytic cell, and belongs to the technical field of energy conservation and emission reduction of electrolytic aluminum. According to the method, an initial pressure set value and an initial valve opening set value of each electrolytic cell exhaust branch pipe are set, a PID algorithm is adopted to calculate a valve opening control value, and a PID controller regulates and controls the opening of the corresponding valve. Then disturbance is conducted upwards by 1% of the amplitude according to the initial pressure, and the control steps are repeated till the power consumption of the smoke exhaust system is minimum. The total deviation is calculated by combining the pressure and the valve opening deviation, the dead zone limit value is introduced to avoid frequent action of the valve, the pressure consistency of all branch pipes is ensured through the PID control rule, and the system stability is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of energy conservation and emission reduction of electrolytic aluminum, and relates to a valve control method of a fume collection system of a gas collecting hood of an electrolytic cell. Background Art

[0002] The fume hood flue gas collection system is an important production auxiliary system of the electrolytic cell, which is mainly used to discharge the flue gas generated by the electrolytic cell during the reaction process. The regulation of this system has a great influence on the consumption of electric energy. By adjusting the pressure balance of the flue gas system through valve control, substantial energy saving can be achieved. Under normal circumstances, the pressure balance of each cell in the fume hood of the electrolytic cell is poor due to the differences in the operating conditions, position in the system, flue size, etc. of each electrolytic cell, but the branch pipe regulating valves are not adjusted differently. In order to ensure the discharge of flue gas, the power of the flue gas emission device can only be increased, resulting in an increase in overall energy consumption. Therefore, it is necessary to achieve pressure balance through individual adjustment of each valve in the fume hood fume collection system, so as to provide a new solution for reducing the energy consumption of the fume hood fume collection system of the electrolytic cell. Summary of the Invention

[0003] The purpose of the present invention is to provide a valve control method for a fume collection system of an electrolytic cell gas collecting hood, which has the characteristic of adjusting different valves individually.

[0004] The technical solution adopted by the present invention is a valve control method for the flue gas collection system of the electrolytic cell gas collecting hood, which is specifically carried out according to the following steps: Follow these steps: Step 1: Set the initial pressure setting value for each electrolyzer exhaust branch pipe in the flue gas collection system and the initial opening setting value of each electrolyzer exhaust branch valve ; Step 2: Based on the initial pressure, use The algorithm calculates the opening control value of each exhaust branch valve ; Step 3: The controller controls the opening value of each valve Control the opening of the corresponding valve; Step 4: The initial pressure is disturbed upward by 1%, and steps 2 to 3 are repeated. The cycle is stopped when the power consumption of the smoke exhaust system is the minimum.

[0005] The present invention is also characterized in that: In step 1, the initial pressure setting value is set for each electrolyzer exhaust branch is the pressure value of the exhaust main pipe of the electrolyzer, and the initial opening setting value of the valve of each electrolyzer exhaust branch pipe Set to the middle position of the valve's normal operating range.

[0006] Opening control value in step 2 The calculation is performed according to the following steps: Step 2.1: According to the pressure setting value and opening setting value The input deviation is calculated based on the current actual branch pressure and valve opening. ; Step 2.2: Based on The control law of the controller is combined with the input deviation Calculate the opening control value .

[0007] Total deviation in step 2.2 Calculated as follows: Step 2.1.1: Calculate the pressure deviation separately and valve opening deviation , the specific calculation method is as follows:

[0008]

[0009] in is the actual pressure of the current branch pipe, is the actual opening of the current branch valve; Step 2.1.2: Based on pressure deviation and valve opening deviation Calculating the total deviation , the specific calculation method is as follows:

[0010] in, The adjustment coefficient of valve opening to pressure is set in the range of 0.02-0.1. Step 2.1.3: Convert the total deviation , combined with the input deviation of the deviation dead zone judgment time , the dead zone can be expressed as follows using the nonlinear link expression:

[0011] in, is the set dead zone limit, when When it is zero, the corresponding valve opening remains unchanged in this round.

[0012] Dead band limit It is equal to the algebraic sum of the per-unit value of the pressure deviation to the gas collecting main pressure and the per-unit value of the valve opening deviation to the maximum valve opening.

[0013] In step 2.2 The control law of the controller is shown as follows:

[0014] Where, is the opening control value , 、 、 are the proportional, integral, and differential gains respectively.

[0015] The differential term in the controller's control law is calculated using the following formula:

[0016] in, is the output of the differential channel, is the filtering constant, substitute the above formula into The control law of the controller can be obtained:

[0017] in, is the sampling period, is the input deviation during the last adjustment process, is the input deviation during this adjustment.

[0018] The actual opening control value of the valve during the control process The selection is as follows:

[0019] in, It is the lower limit of the valve opening during normal operation.

[0020] The beneficial effects of the present invention are: 1. The present invention is The control law is used to control the valve opening of each valve in the fume collection system of the fume hood. According to the actual operating conditions of different valves, the corresponding valve opening control parameters are given for each valve to ensure that the system has good control stability.

[0021] 2. The present invention uses the total deviation of pressure deviation and valve opening deviation to calculate the valve opening control parameter, quantifying the relationship between valve opening and pressure change, and ensuring that the pressure of each flue gas branch is consistent after the valve opening is adjusted. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural diagram of the fume collection system of the fume hood.

[0023] In the figure: 1. Flue gas main pipe; 2. Flue gas branch pipe; 3. Flue gas discharge device; 4. Branch pipe regulating valve; 5. Pressure sensor; 6. Electrolyzer. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Example 1: The valve control method of the flue gas collection system of the electrolytic cell gas collection hood is specifically carried out in the following steps: Follow these steps: Step 1: Set the initial pressure setting value for each electrolyzer exhaust branch pipe in the flue gas collection system and the initial opening setting value of each electrolyzer exhaust branch valve ; Step 2: Based on the initial pressure, use The algorithm calculates the opening control value of each exhaust branch valve ; Step 3: The controller controls the opening value of each valve Control the opening of the corresponding valve; Step 4: The initial pressure is disturbed upward by 1%, and steps 2 to 3 are repeated. The cycle is stopped when the power consumption of the smoke exhaust system is the minimum.

[0026] This application obtains the opening control coefficient of each exhaust branch valve based on the initial pressure and valve opening, and controls different exhaust branch valves separately to ensure that the system has good control stability.

[0027] Example 2: Based on Example 1: In step 1, the initial pressure setting value is set for each electrolyzer exhaust branch is the pressure value of the exhaust main pipe of the electrolyzer, and the initial opening setting value of the valve of each electrolyzer exhaust branch pipe Set to the middle position of the valve's normal operating range.

[0028] Initial pressure setting value in the first round of calculation Equal to mains pressure , initial valve opening setting value Equal to the middle position of the valve's normal operating range. In subsequent rounds of calculations, the pressure setting value The pressure setting value of the previous round Obtained by perturbing the signal by 1% upwards. Example 3: Based on Example 1: Opening control value in step 2 The calculation is performed according to the following steps: Step 2.1: According to the pressure setting value and opening setting value The input deviation is calculated based on the current actual branch pressure and valve opening. ; Step 2.2: Based on The control law of the controller is combined with the input deviation Calculate the opening control value .

[0029] Control relies solely on the error signal to adjust the device, eliminating the need for a complex mathematical model of the controlled object, making it suitable for black-box systems. It also exhibits a high tolerance for system parameter changes, external disturbances such as load fluctuations, and environmental noise. The integral phase, in particular, eliminates steady-state errors, ensuring good control stability.

[0030] Example 4: Based on Example 3: Total deviation in step 2.2 Calculated as follows: Step 2.1.1: Calculate the pressure deviation separately and valve opening deviation , the specific calculation method is as follows:

[0031]

[0032] in is the actual pressure of the current branch pipe, is the actual opening of the current branch valve; Step 2.1.2: Based on pressure deviation and valve opening deviation Calculate the raw total deviation , the specific calculation method is as follows:

[0033] in, The adjustment coefficient of valve opening to pressure is set in the range of 0.02-0.1. The total deviation is used to participate in subsequent control to quantify the relationship between valve opening and pressure change, ensuring that the pressure of each branch is consistent after the valve is adjusted.

[0034] Step 2.1.3: Convert the original total deviation , combined with the deviation dead zone to obtain the total deviation involved in the regulation , the dead zone can be expressed as follows using the nonlinear link expression:

[0035] in, is the set dead zone limit, when When it is zero, the corresponding valve opening remains unchanged in this round.

[0036] Dead band limit It is equal to the algebraic sum of the per-unit value of the pressure deviation to the gas collecting main pressure and the per-unit value of the valve opening deviation to the maximum valve opening.

[0037] In the actual valve opening adjustment process, input deviation may be encountered In the case of a smaller value, the calculated valve opening has a smaller change range than the existing opening value. In order to avoid excessive valve control action during the actual valve opening adjustment process, the input deviation of the valve opening value calculation needs to be calculated before the valve opening value calculation is performed. Set the deadband to ignore small deviations and avoid excessive valve actuation.

[0038] Embodiment 5: Based on Example 3: In step 2.2 The control law of the controller is shown as follows:

[0039] Where, is the opening control value , 、 、 are the proportional, integral, and differential gains respectively.

[0040] The differential term in the controller's control law is calculated using the following formula:

[0041] in, is the output of the differential channel, is the filtering constant, substitute the above formula into The control law of the controller can be obtained:

[0042] in, is the sampling period, is the input deviation during the last adjustment process, is the input deviation during this adjustment.

[0043] when When it is increased, the response speed of the valve will be accelerated, but the adjustment amount of the valve opening will increase; when it is reduced It will slow down the response speed of the valve, but the steady-state error during the adjustment process will increase.

[0044] reduce The adjustment amount of valve opening can be reduced, but the steady-state error increases; increasing This eliminates steady-state errors but may cause oscillations.

[0045] Increase It can reduce the adjustment amount of the valve opening and speed up the valve response speed, but too large May introduce high-frequency noise.

[0046] In the actual control process, the control law needs to be mapped to the specific valve, and the valve opening is adjusted according to the actual situation of each valve. 、 、 Each value must be determined independently, and the specific method of determining the value is determined according to conventional techniques, such as the critical proportional gain method or the open-loop step response method. The following is the value determination process of the critical proportional gain method: First, let the system run in closed loop and set 、 , As the adjustment variable, gradually increase it until the system output shows a constant amplitude continuous oscillation and then record the time when the oscillation occurs. and the period of the oscillation waveform , finally based on Parameter table calculation 、 、 .

[0047] Example 6: Based on Example 1 The actual opening control value of the valve during the control process The selection is as follows:

[0048] in, It is the lower limit of the valve opening during normal operation.

[0049] The opening control value is When the valve is fully opened, In the actual control process, in order to prevent the problem of smoke being unable to be discharged due to the closure of all valves, the minimum opening of each valve is set. At the same time, due to the mechanical structure of the valve, the maximum opening of the valve is fixed. The controller controls the valve opening and ensures that the valve is open by adopting nonlinear control with high and low limits. The controlled valve opening can quickly exit saturation at the upper limit of the calculated value, and can ensure the necessary pressure and flow of the flue gas at the lower limit. When the calculated valve opening control value is greater than or equal to 1, the control is performed according to the valve opening value of 1. When the calculated valve opening control value is less than or equal to When the valve opening value is Control is performed, when the calculated top valve opening value is greater than And when it is less than 1, control is performed according to the calculated opening value.

[0050] Workflow: Conventional fume hood collection systems such as Figure 1 As shown, the present application's adjustment method for such a system is as follows: Step 1: Set the initial pressure setting value for each electrolyzer exhaust branch pipe in the flue gas collection system and the initial opening setting value of each electrolyzer exhaust branch valve , where the initial pressure setting value is is the pressure value of the electrolyzer exhaust main pipe and the initial valve opening setting value Set to the middle position of the valve's normal operating range; Step 2: Calculate the pressure deviation separately and valve opening deviation , the specific calculation method is as follows:

[0051]

[0052] in is the actual pressure of the current branch pipe, is the actual opening of the current branch valve; Then the pressure deviation and valve opening deviation Calculating the total deviation , the specific calculation method is as follows:

[0053] in, The adjustment coefficient of valve opening to pressure is set in the range of 0.02-0.1. Step 3: Convert the original total deviation , combined with the deviation dead zone to obtain the total deviation involved in the regulation , the dead zone can be expressed as follows using the nonlinear link expression:

[0054] in, is the set dead zone limit, when When it is zero, the corresponding valve opening remains unchanged in this round.

[0055] Step 4: Adoption The control law of the controller is used to control the opening value The control law used in this method is as follows:

[0056] in, is the sampling period, is the input deviation during the last adjustment process, is the input deviation during this adjustment, 、 、 are the proportional, integral, and differential gains respectively.

Claims

1. A valve control method for a fume collection system of an electrolytic cell gas collecting hood, characterized in that: Follow these steps: Step 1: Set the initial pressure setting value for each electrolyzer exhaust branch pipe in the flue gas collection system and the initial opening setting value of each electrolyzer exhaust branch valve ; Step 2: Based on the initial pressure, use The algorithm calculates the opening control value of each exhaust branch valve ; Step 3: The controller controls the opening value of each valve Control the opening of the corresponding valve; Step 4: Initial Pressure Setting Perform disturbance with an amplitude of 1% upward, repeat steps 2 and 3, and stop the cycle when the power consumption of the smoke exhaust system is the minimum.

2. The valve control method for the fume collection system of the electrolytic cell gas collecting hood according to claim 1 is characterized in that: In step 1, each electrolyzer exhaust branch pipe is set to an initial pressure setting value is the pressure value of the exhaust main pipe of the electrolyzer, and the initial opening setting value of the valve of each electrolyzer exhaust branch pipe is Set to the middle position of the valve's normal operating range.

3. The valve control method for the fume collection system of the electrolytic cell gas collecting hood according to claim 1 is characterized in that: The opening control value in step 2 The calculation is performed according to the following steps: Step 2.1: According to the pressure setting value and initial opening setting The input deviation is calculated based on the current actual branch pressure and valve opening. ; Step 2.2: Based on The control law of the controller is combined with the input deviation Calculate the opening control value .

4. The valve control method for the fume collection system of the electrolytic cell gas collecting hood according to claim 3 is characterized in that: The total deviation in step 2.2 Calculated as follows: Step 2.1.1: Calculate the pressure deviation separately and valve opening deviation , the specific calculation method is as follows: in is the actual pressure of the current branch pipe, is the actual opening of the current branch valve; Step 2.1.2: Based on pressure deviation and valve opening deviation Calculating the total deviation , the specific calculation method is as follows: in, The adjustment coefficient of valve opening to pressure is set in the range of 0.02-0.

1. Step 2.1.3: Convert the total deviation , combined with the input deviation of the deviation dead zone judgment time , the dead zone can be expressed as follows using the nonlinear link expression: in, is the set dead zone limit, when When it is zero, the corresponding valve opening remains unchanged in this round.

5. The valve control method for the fume collection system of the electrolytic cell gas collecting hood according to claim 4 is characterized in that: The deadband limit It is equal to the algebraic sum of the per-unit value of the pressure deviation to the gas collecting main pressure and the per-unit value of the valve opening deviation to the maximum valve opening.

6. The valve control method for the fume collection system of the electrolytic cell gas collecting hood according to claim 3 is characterized in that: In step 2.2 The control law of the controller is shown as follows: Where, is the opening control value , 、 、 are the proportional, integral, and differential gains respectively.

7. The valve control method for the fume collection system of the electrolytic cell gas collecting hood according to claim 6 is characterized in that: described The differential term in the controller's control law is calculated using the following formula: in, is the output of the differential channel, is the filtering constant, substitute the above formula into The control law of the controller can be obtained: in, is the sampling period, is the input deviation during the last adjustment process, is the input deviation during this adjustment.

8. The valve control method for the fume collection system of the electrolytic cell gas collecting hood according to claim 1 is characterized in that: The actual opening control value of the valve during the control process The selection is as follows: in, It is the lower limit of the valve opening during normal operation.

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