A control method for excessive particulate matter emissions during abnormal speed reduction of a continuous annealing furnace

Abstract

The present invention belongs to the technical field of continuous annealing furnace production, and specifically relates to a control method for excessive particulate matter emissions under abnormal speed reduction of a continuous annealing furnace, in which the strip temperature control forms a closed-loop linkage with the environmental protection mode and the production mode. During normal production, the production mode is entered. When an abnormal speed reduction occurs during the production process of the production line, the environmental protection mode is entered. After the problem is solved, the production mode is entered again. Through the closed-loop feedback control of the burner when the production line has an abnormal speed reduction, and the closed-loop feedback control of the environmental protection mode, the switch mode, the proportional mode and the standby mode, small flow combustion is always guaranteed, each partition switches combustion, and the oxygen content does not fluctuate much, so that the oxygen content can be controlled below 10%, and the actual measured value of sulfur dioxide is less than 35%, thereby avoiding exceeding the environmental protection emission index. Keep the regional burner ignited, and the gas volume is reduced in steps to ensure that the oxygen content in the exhaust gas pipe is at a certain value, the total conversion value is stable, and the stability of the production line is improved with significant results.

Description

Technical Field

[0001] The invention belongs to the technical field of continuous annealing furnace production, and particularly relates to a method for controlling excessive particle emission under abnormal speed reduction of a continuous annealing furnace. Background Art

[0002] During the cold rolling annealing furnace production process, when an abnormality occurred on the production line, the burner combustion was in automatic control mode, reducing the production line speed, but the heating temperature in the annealing furnace remained high. During this process, the actual temperature in the annealing furnace exceeded the set value, and the automatic control sequence of the heating zone was stopped. This caused the heating burner to abnormally shut down, resulting in the burner control unit (BCU) no longer igniting and heating. The gas flow in each heating zone pipeline dropped significantly, eventually reaching zero flow, generating a large amount of exhaust gas. The oxygen content in the combustion exhaust gas rose rapidly, increasing pollutants such as sulfur dioxide. This caused environmental emissions to exceed the standard according to the environmental conversion value (ECV = (measured pollutants * 13) / (21 - measured oxygen content). Limited by human reaction ability and operator experience, the temperature difference between the actual and set values of the annealing furnace's secondary data during the production line abnormality made it difficult for personnel to quickly adjust the burner control mode. This easily resulted in a decrease in gas flow and an increase in oxygen content. During the ECV calculation process, the environmental index remained high. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for controlling excessive particulate matter emissions under abnormal speed reduction of a continuous annealing furnace, thereby keeping the regional burners ignited and reducing the gas volume in steps to ensure a certain oxygen content in the exhaust gas pipeline and a stable total conversion value.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a method for controlling excessive particulate matter emissions under abnormal speed reduction of a continuous annealing furnace, comprising the following steps:

[0005] 1) During normal production, the strip temperature is controlled according to the process PLC and furnace zone PLC, the air-fuel ratio is cross-controlled, and PID closed-loop control is completed through air flow control and gas flow control to ensure the appropriate ratio of gas flow to combustion-supporting fan flow, and normal production mode is completed through burner control;

[0006] 2) The power limit of the heating zone is set by load limit to form a closed loop interlock with the strip temperature control and burner control;

[0007] 3) If the production line experiences an abnormal slowdown, it enters environmental mode and adjusts the burner control unit. Once the problem is resolved, it re-enters production mode. The burner environmental mode closed-loop feedback control during an abnormal slowdown analyzes the oxygen content in a single zone to determine the number of burners required to ignite, thereby controlling the gas flow in each zone to maintain a low flow rate and avoid zero flow.

[0008] Furthermore, the process PLC is used to receive the production line speed, and the furnace area PLC is used to receive the steel coil information.

[0009] Furthermore, the cross-control air-fuel ratio adjusts the combustion fan flow and pressure through air flow control, and realizes gas flow and pressure control through gas flow control. The air flow control and gas flow control complete PID closed-loop control, wherein the oxygen content of the combustion fan is adjustable, the single burner inlet is controlled at 3%, and the gas calorific value is controlled at 17MJ / NM 3 , ensure the appropriate ratio of gas flow to combustion fan flow, so that the nitrogen oxide emission value is 150mg / NM 3 the following.

[0010] Furthermore, the closed-loop feedback control of the burner environmental protection mode when the production line experiences an abnormal speed reduction is as follows: Based on the steel grade information received at the second level and the actual furnace temperature and exhaust fan speed calculated by the pyrometer and the single-zone oxygen content of the flue gas analysis, the number of burners required to be ignited is calculated to control the stability of the gas flow rate. Based on the fact that the actual furnace temperature is greater than the set value, the burner is delayed and closed, and the burner heating load power of zone 1 is set to 20%, maintaining low-flow combustion. After the gas volume stabilizes for 1-2 minutes, 4-5 burners are ignited, and the heating area is selected as the burner of the bottom 1-2 layers in zones 1-2. At this time, the set 20% power of zone 1 is canceled, and the ignited burners are switched every 2 minutes to ensure that the oxygen content in the exhaust gas pipe continues to decrease, and the gas volume in each zone always maintains low-flow combustion, and there is no zero flow state.

[0011] The present invention has the following beneficial effects: The present invention ensures low-flow combustion all the time through the burner closed-loop feedback control when the production line slows down abnormally, as well as the closed-loop feedback control of the environmental protection mode, switch mode, proportional mode and standby mode. Each partition switches combustion, and the oxygen content fluctuates slightly. The burner combustion mode can be changed quickly according to process requirements. When the production line slows down abnormally, it automatically enters the newly developed environmental protection mode, which can control the oxygen content below 10%, and the actual measured value of sulfur dioxide is less than 35%, ensuring the stability of the conversion value and avoiding exceeding the environmental protection emission index. Keep the regional burners ignited, and reduce the gas volume in steps to ensure a certain value of oxygen content in the exhaust gas pipe, and the total conversion value is stable, thereby improving the stability of the production line production, with significant results. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a flow chart of the control method of the present invention.

[0013] Figure 2 It is a schematic diagram of the burner cyclic ignition of the present invention. DETAILED DESCRIPTION

[0014] The following are specific embodiments of the present invention to further describe the technical solution of the present invention, but the scope of protection of the present invention is not limited to these embodiments. Any changes or equivalent substitutions that do not deviate from the concept of the present invention are included in the scope of protection of the present invention.

[0015] like Figure 1 As shown, the process PLC receives production line speed information, while the furnace PLC receives coil information. Strip temperature control forms a closed-loop linkage with the environmental and production modes. During normal production, strip temperature is controlled based on the process and furnace PLCs. The air-fuel ratio is cross-controlled, and PID closed-loop control is implemented through air and gas flow control to ensure an appropriate ratio of gas flow to the combustion-supporting fan. Burner control ensures normal production.

[0016] The cross-control air-fuel ratio adjusts the combustion fan flow and pressure through air flow control, and realizes gas flow and pressure control through gas flow control. The air flow control and gas flow control complete PID closed-loop control. The oxygen content of the combustion fan can be adjusted, the inlet volume of a single burner is controlled at 3%, and the calorific value of the gas is controlled at 17MJ / NM. 3 , ensure the appropriate ratio of gas flow to combustion fan flow, so that the nitrogen oxide emission value is 150mg / NM 3 the following.

[0017] Heating zone power limitation is implemented through load limit settings, forming a closed-loop interlock with strip temperature control and burner control. If an abnormal speed reduction occurs during production, the line enters environmental mode, adjusts the burner control unit, and resumes production mode after the problem is resolved.

[0018] When the production line experiences an abnormal speed reduction, the burner environmental protection mode closed-loop feedback control analyzes the number of burners required to ignite based on the oxygen content in a single zone, thereby controlling the gas volume in each zone to always maintain low-flow combustion and avoid a zero-flow state. First, based on the steel grade information received at the secondary level, the actual furnace temperature and exhaust fan speed measured by the pyrometer, and the oxygen content in a single zone analyzed by the flue gas, the number of burners required to be ignited is calculated to control the stability of the gas flow rate. If the actual furnace temperature is greater than the set value, the ignition of 20% of the total number of burners in a single zone is delayed to ensure that the oxygen content in the exhaust gas pipe continues to decrease. The gas volume in each zone always maintains low-flow combustion and does not experience a zero-flow state.

[0019] The details are as follows: Based on the steel type information received at the second level and the actual furnace temperature and exhaust fan speed calculated by the pyrometer and the oxygen content in a single zone of the flue gas analysis, the number of burners required to be ignited is calculated to control the stability of the gas flow rate. Based on the fact that the actual furnace temperature is greater than the set value, the burner is delayed closed and the burner heating load power of zone 1 is set to 20%. Maintain low flow combustion. After the gas volume stabilizes for 1-2 minutes, ignite 4-5 burners and select the burners of the bottom 1-2 layers in zones 1-2 for heating. At this time, the 20% power setting for zone 1 is canceled and the ignited burners are switched every 2 minutes to ensure that the oxygen content in the exhaust gas pipe continues to decrease. The gas volume in each zone always maintains low flow combustion and there is no zero flow state. Figure 2 As shown, the required zone load = Ton / Tc. The zone load is the number of burners used for ignition divided by the total number of burners. Each zone and each layer of burners ignites in a cycle. Ton is the ignition operating time of a single burner, Tc is the burner cycle time, and TopOn is the delay time for the next burner to ignite.

[0020] The present invention is not limited to the above-mentioned embodiments. Anyone should be aware that any structural changes made under the guidance of the present invention, and any technical solutions that are the same or similar to those of the present invention, fall within the scope of protection of the present invention.

[0021] The technology, shape, and structure not described in detail in the present invention are all well-known technologies.

Claims

1. A method for controlling excessive particulate matter emissions during abnormal speed reduction in a continuous annealing furnace, characterized in that: The following steps are involved: 1) During normal production, the strip temperature is controlled according to the process PLC and furnace zone PLC, the air-fuel ratio is cross-controlled, and PID closed-loop control is completed through air flow control and gas flow control to ensure the appropriate ratio of gas flow to combustion-supporting fan flow, and normal production mode is completed through burner control; 2) The power limit of the heating zone is set by load limit to form a closed loop interlock with the strip temperature control and burner control; 3) When an abnormal speed reduction occurs during the production line, the production line will enter the environmental protection mode, adjust the burner control unit, and enter the production mode after the problem is solved; The environmental protection mode is controlled as follows: according to the steel grade information received at the second level and the actual furnace temperature and exhaust fan speed calculated by the pyrometer and the oxygen content in a single zone of the flue gas analysis, the number of burners required to be ignited is calculated to control the stability of the gas flow rate. According to the actual value of the furnace temperature being greater than the set value, the burner is guaranteed to be closed with a delay, and the burner heating load power of zone 1 is set to 20%, and the combustion is maintained at a small flow rate. After the gas volume stabilizes for 1-2 minutes, 4-5 burners are ignited, and the heating area is selected as the burners of the bottom 1-2 layers in zones 1-2. At this time, the set 20% power of zone 1 is canceled, and the ignited burners are switched every 2 minutes.

2. The method for controlling excessive particulate matter emissions during abnormal speed reduction of a continuous annealing furnace according to claim 1, characterized in that: The process PLC is used to receive the production line speed, and the furnace area PLC is used to receive the steel coil information.

3. The method for controlling excessive particulate matter emissions during abnormal speed reduction of a continuous annealing furnace according to claim 1, characterized in that: The cross-control air-fuel ratio adjusts the combustion fan flow and pressure through air flow control, and realizes gas flow and pressure control through gas flow control. The air flow control and gas flow control complete PID closed-loop control, wherein the oxygen content of the combustion fan is adjustable, the single burner inlet is controlled at 3%, and the gas calorific value is controlled at 17MJ / Nm 3 , ensure the appropriate ratio of gas flow to combustion fan flow, so that the nitrogen oxide emission value is 150mg / Nm 3 the following.

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