High-voltage control method for electrostatic precipitators based on different stages of manufacturing processes

Abstract

This invention addresses the lack of existing electrostatic precipitator (ESP) control methods for multiple process stages, highlighting the need for further energy consumption reduction in ESP systems with multiple process stages. It proposes a high-voltage control method for ESPs based on different manufacturing process stages, belonging to the field of ESP technology. By monitoring the flue gas emission velocity at each manufacturing process stage, the flue gas emissions are divided into three stages. Control schemes for each high-voltage electric field within the ESP are formulated according to the emission characteristics of each stage. This invention provides precise time-segmented control of the high-voltage electric fields across multiple process stages, utilizing the capacitive characteristics of the high-voltage electric fields for intermittent power supply. While meeting emission requirements, this further reduces the energy consumption of the ESP system.

Description

Technical Field

[0001] This invention belongs to the field of electrostatic precipitator technology, specifically relating to a high-voltage control method for electrostatic precipitators based on different stages of production processes. Background Technology

[0002] In the field of air pollution control, electrostatic precipitators (ESPs) are widely used for controlling particulate matter pollution. In industries such as steelmaking and cement manufacturing, the particulate matter content in flue gas flues fluctuates dramatically depending on the different stages of product production. Meeting new and stricter national emission standards presents a new challenge for ESP technology. Simultaneously, users have both a need to reduce emissions and further lower pollutant levels, as well as a need to simultaneously reduce operating power consumption and lower operating costs while meeting national emission standards. Typical optimized control methods for electrostatic precipitators (ESPs), such as those in patent applications CN202111061474.3 ("A Multi-Signal Optimized Energy-Saving ESP Control Method") and CN202210952460.9 ("An Optimized Control Method and System for Electrostatic Precipitators in Power Plants"), involve installing a turbidity meter at the ESP outlet to monitor changes in emissions. Based on these emissions, control parameters such as voltage and current of the high-voltage power supply at each stage of the ESP are adjusted to increase or decrease the output power, thereby achieving optimized control that reduces emissions and operational energy consumption. This method is highly effective for relatively stable operating conditions, such as particulate matter control in coal-fired power plants. However, its effectiveness is less than ideal for pollution control in process-stage manufacturing industries like steelmaking. For example, the entire steelmaking process typically takes only a few tens of minutes. Within this short cycle, it involves several stages: steelmaking preparation, ferroalloying, blowing preparation, blowing, temperature measurement and sampling, supplementary blowing, tapping, slag splashing for furnace protection, and slag removal. During these different stages, the flue gas flow rate, velocity, temperature, particulate matter, and oxygen content all vary significantly. Furthermore, the time it takes for the particulate-laden flue gas to reach the turbidity meter at the electrostatic precipitator outlet after passing through the flue and precipitator can be several seconds to tens of seconds. This results in a significant lag in turbidity feedback. By the time the high-voltage power supply to the electrostatic precipitator is adjusted based on the current turbidity value, changes may have already occurred in the upstream process stages, leading to large fluctuations and poor optimization results. Summary of the Invention

[0003] This invention addresses the problem that existing technologies lack a control method for electrostatic precipitators (ESPs) across multiple process stages, and that the energy consumption of ESP systems across multiple process stages needs further reduction. It proposes a high-voltage control method for ESPs based on different process stages in manufacturing.

[0004] The objective of this invention is achieved through the following technical solution: a high-voltage control method for electrostatic precipitators based on different stages of manufacturing processes, comprising the following steps:

[0005] Step 1: By monitoring the flue gas emission velocity at each stage of the production process, the flue gas emissions at each stage of the production process are divided into three stages: the initial stage, the stable stage, and the transition stage.

[0006] Step 2: Develop control schemes for each high-voltage electric field within the dust collector based on the characteristics of flue gas emissions at each stage;

[0007] Step 3: Install turbidity monitoring equipment at the flue gas emission outlet of the dust collector. The high-voltage electric field controller dynamically adjusts the output power of each high-voltage electric field according to the flue gas turbidity feedback value. It also calculates the time for the flue gas to reach the high-voltage electric field at each process stage based on the flue gas emission velocity. Each high-voltage electric field dynamically adjusts its power output time according to the flue gas velocity.

[0008] The control scheme in step two is divided into a high-power output scheme and an energy-saving output scheme; the high-power output scheme is used in the initial stage of flue gas emission, the energy-saving output scheme is used in the stable stage, and the transition stage is adjusted from the energy-saving output scheme to the high-power output scheme.

[0009] The initial output power of the energy-saving output scheme is 50% of that of the high-power output scheme. During the stable phase, if both the average and peak emissions of flue gas turbidity exceed the emission limits, the output power of the energy-saving output scheme in the stable phase of the current process segment in the next cycle of this production process stage will be higher than the initial output power. If neither the average nor peak emissions of flue gas turbidity exceed the emission limits, the output power of the energy-saving output scheme in the stable phase of the current process segment in the next cycle of this production process stage will be lower than the initial output power. The average emissions, peak emissions, energy consumption, and main flue gas flow parameters corresponding to the control scheme of the high-voltage electric field in the current process stage will be stored in a database to evaluate the control scheme of the high-voltage electric field, accumulate data, and automatically match the optimal control scheme of the high-voltage electric field during operation.

[0010] Preferably, the three stages of flue gas emission are determined according to the flue gas emission flow rate, and are divided into the initial stage where the flue gas flow fluctuates greatly, the stable stage where the flue gas flow is relatively stable, and the transition stage where the current process section ends and the next process section begins.

[0011] Preferably, the high-power output scheme is that the high-voltage electric field outputs power according to the rated power.

[0012] Preferably, in the control scheme of the high-voltage electric field, the power supply cycle of the high-voltage electric field is uniformly decomposed into multiple microscopic equal time periods, and the power supply is intermittently supplied by utilizing the capacitance characteristics of the high-voltage electric field.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The present invention can precisely control the high voltage electric field in multiple process stages according to different processes in different time periods, and use the capacitive characteristics of the high voltage electric field to supply power intermittently, thereby further reducing the energy consumption of the electrostatic precipitator system while meeting emission requirements. Attached Figure Description

[0014] Figure 1 This is a flowchart of the steelmaking process.

[0015] Figure 2 This is a flowchart of the flue gas control process of the present invention;

[0016] Figure 3 This is a flowchart of the control method of the present invention;

[0017] Figure 4 Voltage waveform diagram of the high-voltage electric field for implementing the present invention. Detailed Implementation

[0018] The present invention will be further described below with reference to the embodiments illustrated in the accompanying drawings:

[0019] A method for high-voltage control of electrostatic precipitators based on different stages of manufacturing processes includes the following steps:

[0020] Step 1: By monitoring the flue gas emission velocity at each stage of the production process, the flue gas emissions at each stage of the production process are divided into three stages: the initial stage, the stable stage, and the transition stage.

[0021] Step 2: Develop control schemes for each high-voltage electric field within the dust collector based on the characteristics of flue gas emissions at each stage;

[0022] Step 3: Install turbidity monitoring equipment at the flue gas emission outlet of the dust collector. The high-voltage electric field controller dynamically adjusts the output power of each high-voltage electric field according to the flue gas turbidity feedback value. It also calculates the time for the flue gas to reach the high-voltage electric field at each process stage based on the flue gas emission velocity. Each high-voltage electric field dynamically adjusts its power output time according to the flue gas velocity.

[0023] The control scheme in step two is divided into a high-power output scheme and an energy-saving output scheme. The high-power output scheme is used in the initial stage of flue gas emission, that is, the high-voltage electric field outputs at the rated power. The energy-saving output scheme is used in the stable stage. The transition stage is adjusted from the energy-saving output scheme to the high-power output scheme.

[0024] This embodiment uses the steelmaking process as an example for illustration, such as... Figure 1As shown, the complete steelmaking process includes: steelmaking preparation stage G1, ferrous metal charging stage G2, blowing preparation stage G3, blowing stage G4, temperature measurement and sampling stage G5, supplementary blowing stage G6, tapping stage G7, slag splashing and furnace protection stage G8, slag removal stage G9, and circulating waiting stage G10. Each stage requires a certain amount of time to complete. Steelmaking preparation stage G1 requires T1 time, ferrous metal charging stage G2 requires T2 time, blowing preparation stage G3 requires T3 time, blowing stage G4 requires T4 time, temperature measurement and sampling stage G5 requires T5 time, supplementary blowing stage G6 requires T6 time, tapping stage G7 requires T7 time, slag splashing and furnace protection stage G8 requires T8 time, slag removal stage G9 requires T9 time, and circulating waiting stage G10 requires T10 time. The entire steelmaking process cycle is generally only a few tens of minutes, with one cycle ending immediately followed by the next, repeating continuously. Within a short cycle, the process involves several stages: steelmaking preparation, ferroalloying, blowing preparation, blowing, temperature measurement and sampling, supplementary blowing, tapping, slag splashing for furnace protection, and slag removal. During these different stages, the flue gas flow rate, velocity, temperature, particulate matter, and oxygen content all vary significantly. Furthermore, the time it takes for the particulate-laden flue gas to reach the turbidity meter at the electrostatic precipitator outlet after passing through the flue and precipitator typically ranges from a few seconds to over ten seconds. This results in a significant lag in turbidity feedback. By the time the high-voltage power supply to the electrostatic precipitator is adjusted based on the current turbidity value, changes may have already occurred in the preceding process stages, leading to large optimization fluctuations, poor performance, and high energy consumption.

[0025] Therefore, such as Figure 3 As shown, this invention divides the time of each process stage into three stages:

[0026] The initial stage—corresponding to the time from the start of operation to the stable working state of the current process stage. Before reaching a steady state, the flue gas containing dust particles fluctuates greatly, and the electrostatic precipitator needs to output high power during this stage.

[0027] Stable stage—The current process stage has entered a stable working state, with small fluctuations in the flue gas containing dust particles and a relatively small amount of dust particles. During this stage, based on the characteristics of the flue gas generated by the current process state, the energy-saving power output of the electrostatic precipitator can be selected while meeting emission requirements.

[0028] Transition Phase – Ensure that dust emissions do not exceed standards when changing from one process stage to another. For example, if the current process stage selects an energy-saving output scheme for the electrostatic precipitator, and the flue gas volume and dust concentration increase when transitioning to a new process stage, the high-voltage control strategy should be changed in advance, and the operating power of the high-voltage power supply should be increased. This allows the electrostatic precipitator's electric field to be prepared in advance to adapt to the requirements of the next process stage, ensuring that the emission values ​​do not exceed standards. This involves switching to a high-power output scheme for the electrostatic precipitator.

[0029] The initial output power of the above energy-saving output scheme is 50% of that of the high-power output scheme. During the stable phase, if the average and peak emissions of flue gas turbidity exceed the emission limits, the output power of the energy-saving output scheme in the stable phase of the next process stage will be higher than the initial value. If the average and peak emissions of flue gas turbidity do not exceed the emission limits, the output power of the energy-saving output scheme in the stable phase of the next process stage will be lower than the initial value. The average emissions, peak emissions, energy consumption, and main flue gas flow parameters corresponding to the control scheme of the high-voltage electric field in the current process stage will be stored to establish a database. The control scheme of the high-voltage electric field will be evaluated, data will be accumulated, and the optimal control scheme of the high-voltage electric field will be automatically matched during operation.

[0030] like Figure 2 As shown, in order to better save energy, the multiple high-voltage electric fields in the electrostatic precipitator are arranged according to the order of flue gas flow. The time it takes for the flue gas to pass through a high-voltage electric field is calculated by dividing the length of the high-voltage electric field by the flow velocity of the flue gas. Each high-voltage electric field starts its power output and changes its power output according to this time difference.

[0031] Furthermore, the high-voltage electric field exhibits capacitive characteristics, providing high-voltage energy storage. The capacitive characteristics of the electric field are related to its mechanical structure. After each electrostatic precipitator is constructed, the electric field has a stable capacitance parameter, typically ranging from tens to hundreds of nanofarads depending on the field size, which can be measured using a capacitance meter. The voltage decay time of the high-voltage electric field when there is no power supply is related to the magnitude of the electric field capacitance, the distance between the electric field plates and the electrodes, the shape of the electrodes, and also to the characteristics of the flue gas at the current process stage. When a single high-voltage electric field is operating at high power or energy-saving power, the power supply cycle can be evenly decomposed into multiple microscopic equal time intervals for intermittent power supply.

[0032] The high-voltage power supply control time is divided into X high-voltage power supply cycles. Assuming the residence time of flue gas in a single high-voltage electric field is 5 seconds, and X is 1000, then the high-voltage power supply cycle is 5ms. Within the high-voltage power supply cycle, the cycle is further divided into two time periods: power supply time Tgx and energy-saving time Tjx, which are output cyclically.

[0033] The energy-saving time Tjx is generally calculated as the time it takes for the electric field voltage value to decay to the corona initiation voltage (the voltage value corresponding to zero current when the load is zero, generally 25KV) after the high-voltage power supply voltage peak reaches the rated value and the power supply output is completely stopped. In order to reduce the fluctuation of the outlet emission value, the energy-saving time Tjx can be calculated as the time it takes for the electric field voltage value to decay to 1.5 times the corona initiation voltage (the voltage value corresponding to zero current when the load is zero, generally 25KV, at which time the voltage is about 37.5KV) after the high-voltage power supply voltage peak reaches the rated value and the power supply output is completely stopped.

[0034] Continuing with the example of a 5ms high-voltage power supply cycle, the power supply time Tgx is 2ms, and the energy-saving time Tjx is the time difference between the voltage decay of the high-voltage electric field and the time when the voltage drops to 1.5 times the corona voltage of the electric field, which is 3ms. Because the electric field exhibits capacitive characteristics and has a high-voltage energy storage effect, the flue gas residence time is 5 seconds. Compared to the energy-saving time Tjx of 3ms, the dust removal efficiency is almost unaffected, but the power supply output can be greatly reduced, thereby saving energy.

[0035] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for controlling high voltage for electrostatic precipitation based on different stages of production manufacturing processes, characterized by, It comprises the following steps: Step one: divide the flue gas emission of each production process into three stages of starting stage, stable stage and transition stage by monitoring the flue gas emission flow rate of each production process stage; Step two: develop a control scheme for each high-voltage electric field in the dust collector according to the flue gas emission characteristics of each stage; Step three: set a turbidity monitoring device at the flue gas emission outlet of the dust collector, and the high-voltage electric field controller controls the output power of each high-voltage electric field to be dynamically adjusted according to the flue gas turbidity feedback value, and calculates the time for the flue gas of each process stage to reach the high-voltage electric field according to the flue gas emission flow rate, and each high-voltage electric field dynamically adjusts the power output time according to the flue gas flow rate; The control scheme in step two is divided into a high-power output scheme and an energy-saving output scheme; the starting stage of flue gas emission adopts the high-power output scheme, the stable stage adopts the energy-saving output scheme, and the transition stage adjusts from the energy-saving output scheme to the high-power output scheme; The output power initial value of the energy-saving output scheme is 50% of the high-power output scheme. In the stable stage, if the average and peak values of flue gas turbidity emission at this time exceed the emission limit value, the output power of the energy-saving output scheme of the stable stage in the current process section in the next cycle period of this production process stage is higher than the output power initial value, and if the average and peak values of flue gas turbidity emission do not exceed the emission limit value, the output power of the energy-saving output scheme of the stable stage in the current process section in the next cycle period of this production process stage is lower than the output power initial value; A database is established by storing the average, peak, energy consumption value and main parameters of flue gas flow of the control scheme of the high-voltage electric field in the current process stage, and the control scheme of the high-voltage electric field is evaluated, data is accumulated, and the best control scheme of the high-voltage electric field is automatically matched in operation.

2. The method of claim 1, wherein the method is based on different process stages of production manufacturing of an electrical precipitation high voltage control. The three stages of flue gas emission are determined according to the flue gas emission flow rate, and are divided into a starting stage with large flue gas flow fluctuation, a stable stage with relatively stable flue gas emission, and a transition stage from the end of the current process section to the next process section.

3. The method of claim 1, wherein the method is based on different process stages of production manufacturing of an electrical dust precipitation high voltage control. The high-power output scheme is that the high-voltage electric field outputs at rated power.

4. The method of claim 1, wherein the method is based on the different process stages of production manufacturing of the electrostatic precipitator high voltage control. In the control scheme of the high-voltage electric field, the power supply period of the high-voltage electric field is evenly divided into multiple micro equal time periods, and the high-voltage electric field is intermittently powered by using the capacitance characteristics of the high-voltage electric field.

5. The method of claim 4, wherein the method is based on different process stages of production manufacturing of an electrical dust precipitation high voltage control. The method of intermittent power supply is to divide the high-voltage power supply control time into X high-voltage power supply periods, divide the high-voltage power supply period into two times: power supply time Tgx and energy-saving time Tjx, and output cyclically.

6. The method of claim 5, wherein the method is based on different process stages of production manufacturing of an electrical dust precipitation high voltage control. The energy-saving time Tjx is the time required for the voltage of the high-voltage electric field to decay to 1.5 times the corona starting voltage after the high-voltage electric field stops power supply output.

7. The method of claim 5, wherein the method is based on different process stages of production manufacturing of electrostatic precipitators high voltage control. The energy-saving time Tjx is the time required for the voltage of the high-voltage electric field to decay to 1.5 times the corona starting voltage after the high-voltage electric field stops power supply output.

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