Safety operation protection method for bag dust collectors of industrial furnace flue gas

Abstract

The present invention discloses a safety operation protection method for a bag filter of industrial furnace flue gas. The inlet flue (2) is connected to the inlet of the bag filter (1); a spark control system (3) and an alkali ash injection system (4) are sequentially installed on the inlet flue (2) along the flue gas flow direction; a hopper material level combined monitoring system (5) and a nitrogen filling protection system (6) are installed on the hopper of the bag filter (1); an overpressure protection device (7) is installed on the shell of the bag filter (1); the monitoring and automatic control system (8) is connected and controlled with the spark control system (3), the alkali ash injection system (4), the hopper material level combined monitoring system (5), and the nitrogen filling protection system (6) through wires or cables. The present invention proposes a series of safety prevention technical measures to eliminate potential safety hazards, prevent safety accidents, and effectively ensure the safe, stable, and efficient operation of the bag filter system for industrial furnace flue gas.

Description

Technical Field

[0001] The present invention relates to the technical field of dust removal and environmental protection, and specifically to a method for the safe operation protection of a bag-type dust collector for industrial furnace flue gas. Background Art

[0002] Bag dust removal technology is widely used in the treatment of industrial furnace flue gas pollution due to its advantages such as high efficiency, stability, extremely low emissions, and remarkable pollution reduction and carbon emission reduction effects.

[0003] However, the characteristics of large fluctuations in industrial furnace flue gas temperature, complex flue gas components, and large changes in dust physical properties pose increasingly severe tests on bag-type dust collectors; in addition, dust collector accidents have occurred frequently in recent years, posing higher requirements for the safe, stable, and efficient operation of bag-type dust collectors.

[0004] During the operation of a bag-type dust collector, abnormally high flue gas temperature or incandescent sparks are likely to burn and scald the filter bags, causing damage to the filter bags, exceeding the dust emission standard, and even causing large-scale combustion of the filter bags, thereby triggering safety accidents such as fires and equipment collapses.

[0005] On the other hand, during the start-up and shutdown stages of the kiln or in case of production abnormalities, the flue gas temperature is relatively low, often lower than the acid dew point, and the flue gas is prone to condensation, which is extremely likely to cause the filter bags to be clogged and caked, and the resistance of the dust collector and the system to rise sharply, thus seriously affecting production.

[0006] In addition, a lot of combustible and flammable components are contained in the dust of furnace flue gas. When the dust is intercepted and collected by the filter bags, the dust particles settle and accumulate inside the ash hopper. The combustible and flammable components in the dust accumulate heat during the accumulation process and may undergo smoldering spontaneous combustion.

[0007] On the one hand, the smoldering of the dust will cause the fine dust particles to agglomerate, resulting in poor ash discharge and excessive accumulation of dust in the ash hopper, which may crush the ash hopper.

[0008] On the other hand, the flame generated by the spontaneous combustion of the dust may burn the filter bags, thereby leading to exceeding the emission standard and triggering a fire.

[0009] Looking at the frequent dust collector collapses or ash hopper drop accidents in recent years, one of the main reasons is the malfunction or inaccuracy of the high-level alarm signal of the ash hopper, resulting in untimely ash discharge, excessive ash accumulation in the ash hopper, crushing of the equipment, and causing safety accidents and losses of personnel and property.

[0010] Furthermore, the negative pressure of the flue gas system of some industrial furnaces can be as high as 20000 Pa (such as the sintering machine head / pelletizing process), which is much greater than the equipment pressure resistance of a conventional bag-type dust collector. Therefore, for a high-negative-pressure dust removal system, strengthening the equipment structure strength, adding safety protection devices, preventing the equipment shell from being sucked in, and ensuring the safe operation of the equipment are all key issues that must be considered and guarded against for bag-type dust collectors. Summary of the Invention

[0011] In view of the problems that the flue gas of existing industrial furnaces and kilns contains sparks, abnormal high temperature, low-temperature condensation, etc., which may cause the failure of the filter bags of bag-type dust collectors, as well as potential safety hazards or accident risks such as spontaneous combustion of accumulated ash in the ash hoppers of bag-type dust collectors, overloading and collapse, and overpressure deformation of the shell, the present invention proposes a technical method for the safe operation protection of bag-type dust collectors for industrial furnace and kiln flue gas.

[0012] The technical solution of the present invention is: a method for the safe operation protection of bag-type dust collectors for industrial furnace and kiln flue gas, including a bag-type dust collector, an inlet flue, a spark control system, an alkali ash injection system, a combined ash hopper level monitoring system, a nitrogen filling protection system, an overpressure protection device, and a monitoring and automatic control system; the bag-type dust collector includes an ash hopper, a shell, a dust cleaning device, and a filtering element; the inlet flue is connected to the inlet of the bag-type dust collector; the spark control system and the alkali ash injection system are sequentially installed on the inlet flue along the flue gas flow direction; the combined ash hopper level monitoring system and the nitrogen filling protection system are installed on the ash hopper of the bag-type dust collector; the overpressure protection device is installed on the shell of the bag-type dust collector; the monitoring and automatic control system is connected and controlled with the spark control system, the alkali ash injection system, the combined ash hopper level monitoring system, and the nitrogen filling protection system through wires or cables;

[0013] For the bag-type dust collector for sintering machine head pellet flue gas, an inlet flue, a spark control system, an alkali ash injection system, a combined ash hopper level monitoring system, a nitrogen filling protection system, an overpressure protection device, and a monitoring and automatic control system are configured; for the bag-type dust collector for high-concentration pulverized coal collection, a combined ash hopper level monitoring system, a nitrogen filling protection system, an overpressure protection device, and a monitoring and automatic control system are configured;

[0014] For the bag-type dust collectors for industrial flue gas of coal-fired boilers, cement and non-ferrous rotary kilns, and glass furnaces, an inlet flue, an alkali ash injection system, a combined ash hopper level monitoring system, and a monitoring and automatic control system are configured;

[0015] The spark control system includes a spark induction device and a spark extinguishing device. Along the air flow direction on the inlet flue, the spark induction device is installed in front and the spark extinguishing device is installed behind; the alkali ash injection system includes an alkali ash storage tank and an alkali ash injection device, and the injection point is set on the inlet flue; the combined ash hopper level monitoring system includes a level gauge and a thermometer. A set of level gauges and thermometers are respectively and simultaneously set at the same height on different sides of the upper and lower parts of the ash hopper for combined high and low level monitoring. A set of level gauges includes a lower level gauge and an upper level gauge; a set of thermometers includes an upper level thermometer and a lower level thermometer;

[0016] The alkali ash injection system includes an alkali ash storage tank and an alkali ash injection device, and the injection point is set on the inlet flue;

[0017] The ash hopper level combination monitoring system includes a level gauge and a thermometer. A set of level gauges and thermometers are simultaneously arranged at the same height on different sides of the upper and lower parts of the ash hopper for high and low level combination monitoring. A set of level gauges includes a lower level gauge and an upper level gauge; a set of thermometers includes an upper level thermometer and a lower level thermometer.

[0018] The nitrogen filling protection system includes a nitrogen gas supply device, a nitrogen filling port, and a control device; the nitrogen filling port is arranged in the area below the lower level gauge of the ash hopper, and one control device is set for each ash hopper or group of ash hoppers;

[0019] The overpressure protection device includes a rupture disc and a self - reset valve, and the overpressure protection device is installed on the shell; the monitoring and automatic control system includes a monitoring system and an automatic control system, and the monitoring system includes primary detection elements for temperature, pressure, and level.

[0020] According to the embodiment of the present invention, the protection method of the spark control system is to detect sparks in the flue gas in real time through infrared, light - sensing or temperature detection methods. When sparks are detected, the monitoring and automatic control system immediately interlocks and starts the spark extinguishing device, and sprays water, or inert gas to extinguish the sparks; when no sparks are detected or the flue gas temperature is within the normal range, the spark extinguishing device stops working.

[0021] According to the embodiment of the present invention, the protection method of the soda ash injection system is as follows: when the filter element is a new filter bag, pre - spray the new filter bag to make the new filter bag fully pre - dust - loaded and attach a dust layer with a thickness ≥ 2mm on the surface of the filter bag; during the normal operation of the bag - type dust collector, the inlet flue gas temperature of the bag - type dust collector is monitored in real time. When the monitored temperature is lower than the acid dew point temperature, the monitoring and automatic control system immediately interlocks and starts the soda ash injection system, and timely injects alkaline powder into the inlet flue duct. Through the entrainment and adsorption of the alkaline powder with the acidic components and humid gas in the flue gas, it helps to reduce the acid dew point and inhibit or delay acid condensation; when the inlet flue gas temperature is higher than the acid dew point temperature, stop injecting soda ash.

[0022] According to the embodiment of the present invention, the protection method of the ash hopper level combination monitoring system is: during the normal operation of the bag - type dust collector, the monitoring and automatic control system monitors the high, low levels and temperature combination of the ash hopper in real time. When the level gauge is abnormal or fails, using the change rule that the temperature gradually decreases before and after the thermometer is covered by dust, by monitoring the temperatures of the upper and lower thermometers of the ash hopper in real time and comparing them with the historical temperature values ≥ 3 minutes ago respectively, when the temperature monitored in real time shows a continuous downward trend and the temperature difference exceeds the set value, it is determined that the thermometer has been covered by dust, and thus the position of the ash hopper level is judged.

[0023] According to the embodiments of the present invention, the protection method of the nitrogen filling protection system is to monitor the temperature change of the ash temperature of the lower discharging level of the ash hopper in real time. When the ash temperature in the ash hopper exceeds the set upper limit value, the monitoring and automatic control system immediately interlocks and starts the control device to implement nitrogen filling protection for the corresponding ash hopper. When the ash temperature drops below the set lower limit value, the nitrogen filling stops.

[0024] According to the embodiments of the present invention, the overpressure protection device sets the bursting pressure of the rupture disc and the opening pressure of the self-resetting valve according to the maximum working pressure of the dust removal system, the designed pressure resistance and explosion protection requirements of the bag filter. When the working pressure of the bag filter exceeds the preset pressure value, the rupture disc bursts instantaneously, and at the same time the self-resetting valve opens instantaneously to relieve pressure, and automatically resets and closes under the pressure lower than the set value. The bag filter continues to work and waits for an opportunity to stop the machine to replace the rupture disc.

[0025] According to the embodiments of the present invention, the bag filter includes pulse jet type, mechanical vibration type, reverse air blowing type, compartment bag filter, direct-through bag filter, pre-charged bag filter, electrostatic bag composite filter, top vertical air inlet bag filter; the filtration methods include internal filtration and external filtration; the dust cleaning methods adopted by the dust cleaning device include pulse jet, mechanical vibration, reverse blowing or reverse suction and acoustic dust cleaning types; the filter elements include filter bags and filter cartridges, and their cross-sectional shapes can adopt circular, rectangular, corrugated, folded or other special-shaped structures; the materials adopted by the filter elements are non-metallic and metallic.

[0026] According to the embodiments of the present invention, the combined monitoring system for the ash hopper material level uses a combination of a level gauge and a thermometer to monitor the material level height in the ash hopper. An upper level gauge and an upper level thermometer are installed at the same height in the upper part of each ash hopper; a lower level gauge and a lower level thermometer are installed at the same height in the lower part of each ash hopper; the level gauges and thermometers at different heights are installed on different wall plates of the ash hopper, and the level gauges and thermometers at the same height are installed on the same wall plate of the ash hopper; the temperature of each thermometer on the ash hopper and the comparison temperature difference change signal of itself form a double monitoring signal that cooperates with each other and is fed back to the monitoring and automatic control system in real time, and interlocks to control the start and stop of the ash unloading and conveying device.

[0027] According to the embodiments of the present invention, the nitrogen filling port is arranged in the area below the lower discharging level of each ash hopper, 300-1000 mm away from the ash hopper outlet; the control device adopts types such as solenoid valves or pneumatic valves, and one is configured for each ash hopper, or one can be configured for a group of multiple ash hoppers; the monitoring system monitors the temperature change of the thermometer at the lower discharging level of the ash hopper in real time, feeds it back to the automatic control system in real time and interlocks to control the start and stop of the nitrogen filling control device as needed.

[0028] According to the embodiments of the present invention, the explosion relief diaphragm is used in combination with the self - resetting valve or used alone. The explosion relief diaphragm is made of aluminum or other metal materials, and the self - resetting valve adopts a spring or counterweight method. The explosion relief pressure of the explosion relief diaphragm and the opening pressure of the self - resetting valve in the same over - pressure protection device are equal, and are set as required according to the maximum working pressure of the dust removal system, the designed pressure resistance of the bag filter, and the explosion - proof requirements.

[0029] The beneficial effects of the present invention are as follows: Aiming at the problems that the flue gas of industrial furnaces contains sparks, abnormal high temperature, low - temperature condensation, etc., which may cause the failure of the filter bags of the bag filter, as well as potential safety hazards or accident risks such as spontaneous combustion of the ash accumulated in the ash hopper of the bag filter, overloading and collapse, and over - pressure deformation of the shell, a series of safety prevention and control technical measures are proposed, forming a complete set of technical methods for the safe operation protection of the bag filter, eliminating potential safety hazards, preventing safety accidents, and effectively ensuring the safe, stable, and efficient operation of the bag filter system for industrial furnace flue gas. Brief Description of the Drawings

[0030] Figure 1 is the flow chart of the safety operation protection method for the bag filter of industrial furnace flue gas.

[0031] Figure 2 is the schematic diagram of the external shape of the bag filter equipment.

[0032] Figure 3 is the schematic diagram of the layout of the ash hopper, level gauge, thermometer, and nitrogen filling port.

[0033] In the figure: 1 bag filter, 11 ash hopper, 12 shell, 13 dust cleaning device, 14 filter element; 2 inlet flue; 3 spark control system, 31 spark induction device, 32 spark extinguishing device; 4 soda ash injection system, 41 soda ash storage tank, 42 soda ash injection device; 5 combined ash hopper level monitoring system, 51 level gauge, 511 upper level gauge, 512 lower level gauge, 52 thermometer, 521 upper level thermometer, 522 lower level thermometer; 6 nitrogen filling protection system, 61 nitrogen gas supply device, 62 nitrogen filling port, 63 control device; 7 over - pressure protection device; 8 monitoring and automatic control system. Detailed Embodiments

[0034] The following further elaborates the detailed embodiments of the present invention in conjunction with the drawings. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the protection scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the application.

[0035] Technical method for the safe operation and protection of a bag filter for industrial furnace flue gas, including a bag filter 1, an inlet flue 2, a spark control system 3, an alkali ash injection system 4, a combined ash hopper level monitoring system 5, a nitrogen filling protection system 6, an overpressure protection device 7, and a monitoring and automatic control system 8, etc.

[0036] The bag filter 1 described above mainly consists of an ash hopper 11, a housing 12, a dust cleaning device 13, and a filter element 14, etc.; the inlet flue 2 is connected to the inlet of the bag filter 1; the spark control system 3 includes a spark induction device 31 and an extinguishing device 32, which are installed at intervals in the inlet flue 2 in the front-rear order; the alkali ash injection system 4 includes an alkali ash storage tank 41 and an injection device 42, and the injection point is set on the inlet flue 2; the combined ash hopper level monitoring system 5 mainly includes a level gauge 51 and a thermometer 52, which are installed on different wall plates and at different heights of the ash hopper 11 of the bag filter; the nitrogen filling protection system 6 for the ash hopper mainly includes a nitrogen gas supply device 61, a nitrogen filling port 62, and a control device 63, and the nitrogen filling port 62 is set in the area below the lower level gauge 512 of each ash hopper 11; the overpressure protection device 7 mainly includes a rupture disk and a self-resetting valve, which are installed on the housing 12 of the bag filter; the monitoring and automatic control system 8 mainly includes a monitoring system and an automatic control system, which are connected to the above-mentioned protection systems through wires (cables) to monitor the operation data in real time and implement overlimit alarm and automatic interlock control.

[0037] The bag filter 1 mentioned above refers to various types of filter dust collectors used for industrial flue gas dust removal, including pulse jet type, mechanical vibration type, reverse blowing type, multi-compartment bag filter, straight-through bag filter, pre-charged bag filter, electrostatic bag composite dust collector, top vertical inlet bag filter, etc. The filtration methods include internal filtration and external filtration.

[0038] The dust cleaning methods adopted by the dust cleaning device 13 include pulse jet, mechanical vibration, reverse blowing (suction) air, and acoustic wave dust cleaning, etc.; the filter element 14 includes filter bags and filter cartridges, and its cross-sectional shape can adopt circular, rectangular, corrugated, folded or other special-shaped structures; the materials adopted by the filter element 14 include non-metallic and metallic, etc.

[0039] The spark induction device 31 in the spark control system 3 is installed upstream (front) of the inlet flue 2 along the gas flow direction, and the spark extinguishing device 32 is installed downstream (rear) of the inlet flue 2. The two are installed at intervals, and the spark extinguishing device 32 is spaced from the bag filter 1.

[0040] The induction methods of the spark induction device 31 include infrared, light sensing, and temperature, etc.; the extinguishing methods of the spark extinguishing device 32 include spraying (liquids such as water) or injecting inert gases (nitrogen, argon, etc.), etc.

[0041] The Mars detection device 31 detects Mars in real time and feeds back to the automatic control system 8, and interlocks to control the start and stop of the Mars extinguishing device 32 as needed.

[0042] The Mars control system 3 can effectively prevent Mars from threatening the filter bags and ensure the safe operation of the bag filter 1.

[0043] For the described alkali ash injection system 4, the injection points are set on the inlet flue 2, and appropriate positions are selected according to the adopted Mars extinguishing method; the alkali ash storage tank 41 can be a fixed storage bin or a tank truck; the power used by the injection device 42 is high-pressure gas such as compressed air; the alkaline ash can be slaked lime, quicklime, fly ash or other alkaline powders. The monitoring system monitors the temperature of the flue gas at the inlet of the bag filter 1 in real time and feeds back to the automatic control system 8 in real time, and interlocks to control the alkali ash injection device 42 as needed to inject the alkaline ash in the alkali ash storage tank 41 into the inlet flue 2.

[0044] The alkali ash injection system 4 can effectively protect the filter bags from the threats of condensation corrosion and caking, extend the service life of the filter bags, and ensure normal production.

[0045] For the described hopper level combined monitoring system 5, a level gauge 51 and a thermometer 52 are used to jointly monitor the level height in the hopper 11.

[0046] At the same height in the upper part of each hopper 11, an upper level gauge 511 and an upper level thermometer 521 are installed simultaneously; at the same height in the lower part of each hopper 11, a lower level gauge 512 and a lower level thermometer 522 are installed simultaneously; a middle level gauge or a middle level thermometer can also be installed at the same height in the middle of each hopper 11 as needed; the level gauges 51 and thermometers 52 at different heights should be installed on different wall plates of the hopper 11, and the level gauges 51 and thermometers 52 at the same height should be installed on the same wall plate of the hopper 11.

[0047] The temperature of each thermometer 52 on the hopper 11 and the comparison temperature difference change signal of itself form a dual monitoring signal that cooperates with each other with the signal of the level gauge 51, and feeds back to the monitoring and automatic control system 8 in real time, and interlocks to control the start and stop of the ash unloading and conveying device as needed.

[0048] The hopper level combined monitoring system 5 can effectively prevent safety risks caused by the failure of the level gauge and the out-of-control of the level, and ensure the safe operation of the dust collector.

[0049] For the described nitrogen filling protection system 6, the nitrogen filling port 62 is set in the area below the lower level of each hopper 11, 300 - 1000 mm away from the outlet of the hopper 11; the control device 63 can be in the form of an electromagnetic valve or a pneumatic valve, etc., and the number can be 1 for each hopper 11, or 1 for a group of multiple hoppers 11.

[0050] The nitrogen filling protection system 6 can effectively prevent and control the occurrence of spontaneous combustion and fire accidents in the ash hopper, and ensure the safe operation of the dust collector.

[0051] The monitoring system tracks and monitors the temperature change of the lower material level thermometer 522 of the ash hopper 11 in real time, feeds back to the automatic control system 8 in real time, and interlocks and controls the start and stop of the nitrogen filling control device 63 as needed.

[0052] The explosion-relief diaphragm and the self-resetting valve of the overpressure protection device 7 can be used in combination or separately. The explosion-relief diaphragm can be made of aluminum or other metal materials, and the self-resetting valve can be made of springs or counterweights as needed. The explosion-relief pressure of the explosion-relief diaphragm in the same overpressure protection device 7 is equal to the opening pressure of the self-resetting valve, and both are set as needed based on the maximum working pressure of the dust removal system and the design pressure resistance and explosion-proof requirements of the bag dust collector 1. The specifications and installation quantity of the overpressure protection device 7 are selected according to the design needs.

[0053] Monitoring and automatic control system 8, wherein the monitoring system mainly monitors the temperature, pressure and material level of the above-mentioned protection systems in real time; the automatic control system can be controlled by PLC or DCS, and according to the real-time feedback signal of the monitoring system, the start and stop of the corresponding protection system can be controlled through the automatic control system interlock.

[0054] The monitoring and automatic control system 8 monitors the operating parameters in real time through the primary instrument in the monitoring system, and feeds back to the automatic control system in real time. When any over-limit signal is detected, the automatic control system will promptly trigger the relevant protection system to start implementing safety protection, and at the same time send out an alarm signal to remind the operator and production process to promptly investigate the cause, adjust or implement relevant safety protection operations. When the monitored data returns to normal and the over-limit alarm signal is lifted, the automatic control system sends a command to stop the above-mentioned safety protection systems from working and is in standby status.

[0055] The monitoring and automatic control system 8 can automatically interlock and control various safety protection systems and devices, effectively prevent various safety risks, and ensure the safe operation of the bag dust collector.

[0056] Embodiment 1: For the complex operating conditions such as the sintering machine head (pellet) flue gas containing sparks, large temperature fluctuation range (80-250°C in normal operation), high moisture content, high corrosiveness, high negative pressure (up to 20,000 Pa) and frequent start-up and shutdown, it is a severe test for the bag filter, and various operation protection measures must be fully implemented. The technical method for safe operation protection of the sintering machine head (pellet) flue gas bag filter 1 is as follows: configure the air inlet flue 2, the spark control system 3, the alkali ash injection system 4, the ash hopper level combination monitoring system 5, the nitrogen filling protection system 6, the overpressure protection device 7 and the monitoring and automatic control system 8, etc.

[0057] The structural types of the bag filter 1 include: pulse jet type, mechanical vibration type, reverse air blowing type, precharged bag filter, electric bag composite type, top vertical air inlet type, etc. Its main structure is composed of a hopper 11, a housing 12, a dust cleaning device 13, a filter element 14, etc. Among them, the dust cleaning methods adopted by the dust cleaning device 13 include pulse jet, mechanical vibration, reverse (suction) air blowing, etc.; the filter element 14 includes filter bags and filter cartridges, and its cross-sectional shape can be circular, rectangular, corrugated, folded or other special-shaped structures; the materials adopted by the filter element 14 are non-metallic, metallic, etc.

[0058] The described inlet flue 2 is connected to the air inlet of the bag filter 1.

[0059] The described spark control system 3 mainly includes two parts: a spark sensing device 31 and an extinguishing device 32. The main devices are installed on the inlet flue 2 of the bag filter, installed at intervals along the air flow direction. The spark sensing device 31 is installed in the front (upstream), and the spark extinguishing device 32 is installed in the back (downstream).

[0060] During normal operation, the spark sensing device 31 detects the sparks in the flue gas in the inlet flue 2 in real time through infrared, light sensing or temperature, etc. When sparks are detected, the monitoring and automatic control system 8 immediately interlocks and starts the spark extinguishing device 32, and timely extinguishes the sparks by spraying (liquids such as water) or injecting inert gases (nitrogen, argon, etc.); when no sparks are detected or the flue gas temperature T1 is within the normal range (preferably T1 = 120 - 160 °C), the spark extinguishing device 32 stops working and is in a real-time standby state.

[0061] The described soda ash injection system 4 mainly includes two parts: a soda ash storage tank 41 (which can adopt a fixed storage bin or a tank truck) and a soda ash injection device 42. The soda ash injection point is set on the inlet flue 2, and a suitable position is selected according to the adopted spark extinguishing method.

[0062] The implementation methods are as follows: Method for pre-coating ash on newly installed filter elements 14 such as filter bags of the bag filter 1: First, the tanker injection method is preferred. Prepare the tanker 41 and alkaline ash in advance, connect the tanker interface and check the injection pipeline, start the alkaline ash injection device 42 to start pre-coating ash, and stop pre-coating ash when the thickness of the dust attached to the filter bag surface reaches more than 2 mm. Method for protecting against sudden low flue gas temperature during the operation of the bag filter 1: First, a fixed alkaline ash storage bin is preferred. Prepare alkaline ash in the alkaline ash storage tank 41 in advance, connect and check the conveying and gas source pipelines in the alkaline ash injection device 42. The monitoring system monitors the inlet flue gas temperature of the bag filter 1 in real time. When it is monitored that the temperature is lower than the acid dew point temperature T2 (set by the system after determination or calculation, generally preferably between T2 = 100 - 120 °C), the automatic control system immediately interlocks and starts the alkaline ash injection device 42, and uses the injected alkaline powder to entrap and adsorb the acidic components and humid gas in the flue gas, assisting in reducing the acid dew point and effectively inhibiting or delaying acid condensation; when the monitoring system monitors that the inlet flue gas temperature is higher than the acid dew point temperature T2, the automatic control system interlocks to stop the alkaline ash injection and is in a real-time standby state. It effectively protects the filter bag from the threat of condensation corrosion and caking, extends the service life of the filter bag, and ensures normal production.

[0063] The ash hopper level combination monitoring system 5 mainly includes a level gauge 51 and a thermometer 52, and is installed on different wall plates and at different heights of each ash hopper 11 of the bag filter, that is, an upper level gauge 511 and an upper level thermometer 521 are installed at the same height (2 / 3 of the ash hopper height) on the upper part of each ash hopper 11, and a lower level gauge 512 and a lower level thermometer 522 are installed at the same height (about 1.0 - 1.5 m) on the lower part of each ash hopper 11. A middle level gauge and a middle level thermometer can also be set in the middle of the ash hopper 11 as needed.

[0064] During normal operation, the monitoring and automatic control system 8 monitors the high and low levels and temperature combination of the ash hopper 11 in real time. When the level gauge appears abnormal or fails, using the changing rule that the temperature gradually decreases before and after the thermometer is covered by dust, by monitoring the temperatures of the upper level thermometer 521 and the lower level thermometer 522 of the ash hopper 11 in real time, and comparing them with the historical temperatures of the same measuring point 3 - 5 minutes ago for level judgment.

[0065] When it is detected in real time that the temperature T3 of the upper material level thermometer 521 gradually decreases and the temperature difference reaches ΔT (e.g., ΔT≥10°C, adjustable), it indicates that the thermometer has been covered by dust. Thus, it is judged that the ash level has exceeded the high material level, and the automatic control system immediately gives an alarm and interlocks to start the ash unloading and conveying system; conversely, when it is detected in real time that the temperature T4 of the lower material level thermometer 522 gradually increases and the temperature difference reaches ΔT (e.g., ΔT≥10°C, adjustable), it is judged that the ash level is lower than the low material level, and the automatic control system interlocks to stop the ash unloading and conveying system. This effectively prevents the failure of the level gauge 51 from causing out-of-control material level and safety risks, and ensures the safe operation of the dust collector.

[0066] The ash hopper nitrogen filling protection system 6 mainly includes a nitrogen gas supply device 61, a nitrogen filling port 62, and a control device 63, and its implementation method is as follows: A nitrogen filling port 62 is arranged in the area below the lower material level gauge 512 of each ash hopper 11, and the control device 63 is arranged in groups of 1 - 4 ash hoppers 11.

[0067] During normal operation, by monitoring the temperature T4 of the lower material level thermometer 522 of each ash hopper 11 in real time, when the ash temperature T4 of a certain ash hopper 11 or a group of ash hoppers 11 exceeds the set upper limit value Tmax (Tmax≥240°C, adjustable), the automatic control system immediately interlocks to start the control device 63 to implement nitrogen filling protection for the corresponding ash hopper 11. When the ash temperature T4 drops to the set lower limit value Tmin (Tmin≤200°C, adjustable), the automatic control system stops nitrogen filling. This effectively prevents and controls the occurrence of ash accumulation spontaneous combustion and fire accidents, and ensures the safe operation of the dust collector.

[0068] The overpressure protection device 7 mainly includes a bursting disc and a self - reset valve. Its implementation method is: According to the maximum working pressure of the dust removal system and the maximum pressure resistance of the dust collector, set the bursting pressure of the bursting disc and the opening pressure P1 of the self - reset valve (generally P1≥ - 15KPa), and manufacture the overpressure protection device 7 accordingly. The overpressure protection device 7 is installed on the bag - type dust collector housing 12, and the quantity (≥2) is selected as required. When the system working pressure P2 is greater than the pressure P1 preset by the overpressure protection device 7, the bursting disc bursts instantly, and at the same time, the self - reset valve opens instantly to relieve pressure. When the system pressure is lower than the set pressure P1 of the self - reset valve, it resets and closes automatically, and the dust collector can continue to work. Wait for the process equipment to be repaired or stop the machine opportunistically to replace the bursting disc, effectively ensuring the structural safety of the bag - type dust collector.

[0069] The monitoring and automatic control system 8 mainly includes two parts: a monitoring system and an automatic control system.

[0070] The monitoring system mainly includes primary detection elements such as temperature, pressure, and material level; the automatic control system uses a PLC or DCS system.

[0071] During normal operation, the primary instrument in the monitoring system monitors the operating parameters in real time and provides real-time feedback to the automatic control system. When any over-limit signal is detected, the automatic control system will promptly trigger and start the corresponding protection system to implement safety protection, and at the same time send out an alarm signal to remind operators and production processes to promptly investigate the causes and adjust or implement relevant safety protection operations. When the monitored data returns to normal and the over-limit alarm signal is lifted, the automatic control system sends a command to stop the above-mentioned safety protection systems and is in standby status.

[0072] Embodiment 2: For a bag filter for collecting high-concentration coal powder, the ash accumulated in the ash hopper is very likely to spontaneously combust and cause fire and explosion risks. In principle, the ash hopper 11 does not store ash.

[0073] The safe operation protection method for the bag filter 1 for collecting high-concentration coal powder is as follows: configure the ash hopper 11 with a material level combination monitoring system 5, a nitrogen filling protection system 6, an overpressure protection device 7 and a monitoring and automatic control system 8, etc.

[0074] The ash hopper material level combined monitoring system 5 mainly includes a level meter 51 and a thermometer 52, and is installed at different heights of each ash hopper 11 of the bag filter 1, that is, an upper level meter 511 and an upper level thermometer 521 are installed at the same height (about 2 / 3 of the ash hopper height) on the upper part of each ash hopper 11, and a lower level meter 512 and a lower level thermometer 522 are installed at the same height (about 500mm) on the lower part of each ash hopper 11.

[0075] During normal operation, the monitoring system performs real-time combined monitoring of material level and temperature. When the material level meter is abnormal or malfunctions, the temperature of the upper material level thermometer 521 and the lower material level thermometer 522 of the ash hopper 11 are monitored in real time, and compared with the historical temperature of the same measuring point 3 to 5 minutes ago, and the material level is judged. For example, when the temperature T5 of the lower material level thermometer 522 is gradually decreased and the temperature difference reaches ΔT (ΔT ≥ 10°C, adjustable), it means that the ash in the ash hopper 11 is above the low material level, and the monitoring and automatic control system 8 issues a The alarm signal notifies the operator to manually start the ash unloading device, or to start the ash unloading device through the automatic control system interlock, to avoid the risk of spontaneous combustion of accumulated ash; when the temperature T6 of the upper material level thermometer 521 is gradually decreasing and the temperature difference reaches ΔT (ΔT ≥ 10°C, adjustable), it means that the ash stored in the ash hopper 11 has reached the high material level. The automatic control system immediately interlocks to start the ash unloading device or implements emergency manual ash discharge, and sends an alarm signal at the same time; when the ash stored in the ash hopper 11 is lower than the low material level and the alarm signal is released, the automatic control system interlocks to stop ash unloading. The double safety risks of overload and spontaneous combustion of ash hopper 11 caused by failure of the material level meter 51 can be reliably avoided.

[0076] The described hopper nitrogen filling protection system 6 mainly includes a nitrogen gas supply device 61, a nitrogen filling port 62, and a control device 63, and its implementation method is as follows: A nitrogen filling port 62 is arranged in the area below the lower material level gauge 512 of each hopper 11, and a control device 63 is configured.

[0077] During normal operation, by real-time monitoring the temperature T5 of the lower material level temperature gauge 522 of each hopper 11, when the ash temperature of a certain hopper or a group of hoppers 11 exceeds the set upper limit value Tmax (Tmax≥140°C, adjustable), the automatic control system immediately interlocks and starts the control device 63 to implement nitrogen filling protection for the corresponding hopper 11. When the ash temperature T5 drops to the set lower limit value Tmin (Tmin≤120°C, adjustable), the automatic control system stops nitrogen filling. It can effectively prevent and control the occurrence of ash accumulation spontaneous combustion and fire accidents, and ensure the safe operation of the dust collector.

[0078] The described overpressure protection device 7 mainly includes a rupture disc and a self-resetting valve. Its implementation method is: According to the maximum working pressure, design pressure resistance, and explosion protection requirements of the dust collector, set the bursting pressure of the rupture disc and the opening pressure P3 of the self-resetting valve (generally P3 = +1000Pa), and manufacture the overpressure protection device 7 accordingly. Install the overpressure protection device 7 on the bag type dust collector housing 12, and the quantity (≥2) is selected as needed. When the system working pressure P4 is greater than the pressure P3 preset by the overpressure protection device 7, the rupture disc bursts instantly, and at the same time the self-resetting valve opens instantly to relieve pressure. When the system pressure is below the set pressure P3 of the self-resetting valve, it resets and closes automatically. The dust collector can continue to work, and stop the machine as soon as possible to replace the rupture disc and related maintenance, effectively ensuring the structural safety of the bag type dust collector.

[0079] The described monitoring and automatic control system 8 has the same composition, function, and safety protection implementation method as in Embodiment 1.

[0080] Embodiment 3: For industrial flue gas bag type dust collectors such as coal-fired boilers, cement and non-ferrous rotary kilns, and glass furnaces, because the flue gas has a high moisture content and sulfur content, and it is easy to carry unburned oil mist during the startup process. To prevent the filter bags from being blocked and caked, and to ensure the long-term safe and reliable operation of the bag type dust collector 1, such bag type dust collectors 1 should adopt operation protection measures. The specific safety operation protection technical methods are as follows: Configure an inlet flue 2, an alkali ash injection system 4, a hopper material level combined monitoring system 5, and a monitoring and automatic control system 8, etc.

[0081] The described alkali ash injection system 4 has the same composition, function, and safety protection implementation method as in Embodiment 1.

[0082] The described hopper material level combined monitoring system 5 has the same composition, function, and safety protection implementation method as in Embodiment 1.

[0083] The described monitoring and automatic control system 8 has the same composition, functions and safety protection implementation method as in Embodiment 1.

Claims

1. A safety operation protection method for a bag filter of industrial furnace flue gas. The adopted operation system includes a bag filter (1), an inlet flue (2), a spark control system (3), an alkali ash injection system (4), a combined ash hopper level monitoring system (5), a nitrogen filling protection system (6), an overpressure protection device (7), and a monitoring and automatic control system (8). The bag filter (1) includes an ash hopper (11), a housing (12), a dust cleaning device (13), and a filter element (14). The inlet flue (2) is connected to the inlet of the bag filter (1). The spark control system (3) and the alkali ash injection system (4) are sequentially installed on the inlet flue (2) along the flue gas flow direction. The combined ash hopper level monitoring system (5) and the nitrogen filling protection system (6) are installed on the ash hopper (11) of the bag filter. The overpressure protection device (7) is installed on the housing (12) of the bag filter. The monitoring and automatic control system (8) is connected and controlled with the spark control system (3), the alkali ash injection system (4), the combined ash hopper level monitoring system (5), and the nitrogen filling protection system (6) through wires or cables. The combined ash hopper level monitoring system (5) includes a level gauge (51) and a thermometer (52). A set of level gauges (51) and thermometers (52) are respectively and simultaneously arranged at the same height on different sides of the upper and lower parts of the ash hopper (11). A set of level gauges (51) includes an upper level gauge (511) and a lower level gauge (512). A set of thermometers (52) includes an upper level thermometer (521) and a lower level thermometer (522). The nitrogen filling protection system (6) includes a nitrogen gas supply device (61), a nitrogen filling port (62), and a control device (63). The nitrogen filling port (62) is arranged in the area below the lower level gauge (512) of the ash hopper (11). One control device (63) is set for each ash hopper (11) or group of ash hoppers. The overpressure protection device (7) includes a rupture diaphragm and a self - reset valve. The overpressure protection device (7) is installed on the housing (12). The monitoring and automatic control system (8) includes a monitoring system and an automatic control system. The monitoring system includes primary detection elements for temperature, pressure, and level. Characterized in that: The protection method of the alkali ash injection system (4) is as follows: When the filter element (14) is a new filter bag, pre - spray the new filter bag to make the new filter bag fully pre - dust - loaded and attach a dust layer with a thickness ≥ 2 mm on the surface of the filter bag. When the bag filter (1) is operating normally, monitor the inlet flue gas temperature of the bag filter (1) in real time. When it is monitored that the temperature is lower than the acid dew point temperature, the monitoring and automatic control system (8) immediately interlocks and starts the alkali ash injection system (4), and timely injects alkaline powder into the inlet flue (2). Through the entrainment and adsorption of the alkaline powder with the acidic components and humid gas in the flue gas, it helps to reduce the acid dew point and inhibit or delay acid condensation. When the inlet flue gas temperature is higher than the acid dew point temperature, stop the alkali ash injection.

2. The safety operation protection method of the bag filter for industrial furnace flue gas according to claim 1, characterized in that: The protection method of the described Mars control system (3) is to detect Mars in the flue gas in real time through infrared, light sensing or temperature detection methods. When Mars is detected, the monitoring and automatic control system (8) immediately interlocks and starts the Mars extinguishing device (32), and sprays water or inert gas to extinguish the Mars; when no Mars is detected or the flue gas temperature is within the normal range, the Mars extinguishing device (32) stops working.

3. The safety operation protection method of the bag filter for industrial furnace flue gas according to claim 2, wherein: For the described ash hopper level combination monitoring system (5), when the bag filter (1) is operating normally, the monitoring and automatic control system (8) monitors the high, low level and temperature of the ash hopper in real time. When the level gauge malfunctions or fails, using the changing rule that the temperature gradually decreases before and after the thermometer (52) is covered by dust, by monitoring the temperatures of the upper and lower thermometers (52) of the ash hopper (11) in real time and comparing them with the historical temperature values ≥3 minutes ago respectively, when the temperature monitored in real time shows a continuous downward trend and the temperature difference exceeds the set value, it is determined that the thermometer has been covered by dust, and thus the ash hopper (11) level position is judged.

4. The safety operation protection method of the bag filter for industrial furnace flue gas according to claim 3, characterized in that: The protection method of the described nitrogen filling protection system (6) is to monitor the ash temperature change of the lower level thermometer (522) of the ash hopper (11) in real time. When the ash temperature in the ash hopper (11) exceeds the set upper limit value, the monitoring and automatic control system (8) immediately interlocks and starts the control device (63) to implement nitrogen filling protection for the corresponding ash hopper (11). When the ash temperature drops below the set lower limit value, the nitrogen filling stops.

5. The safety operation protection method of the bag filter for industrial furnace flue gas according to claim 4, characterized in that: The described overpressure protection device (7) sets the bursting pressure of the rupture disc and the opening pressure of the self - reset valve according to the maximum working pressure of the dust removal system, the designed pressure resistance and explosion protection requirements of the bag filter (1). When the working pressure of the bag filter (1) exceeds the preset pressure value, the rupture disc bursts instantly, and at the same time the self - reset valve opens instantly to relieve pressure and self - resets and closes when the pressure is lower than the set value. The bag filter (1) continues to work and waits for an opportunity to stop the machine to replace the rupture disc.

6. The method for protecting the safe operation of a bag filter for industrial furnace flue gas according to claim 5, characterized in that: The described bag filter (1) includes pulse jet type, mechanical vibration type, reverse blowing type, sectional chamber bag filter, straight - through bag filter, pre - charged bag filter, electrostatic - bag composite filter or top vertical air - inlet bag filter; the filtration methods include internal filtration and external filtration; the cleaning methods adopted by the cleaning device (13) include pulse jet, mechanical vibration, reverse blowing or reverse suction and acoustic cleaning types; the filter elements (14) include filter bags or filter cartridges, and their cross - sectional shapes adopt circular, rectangular, corrugated, folded or other special - shaped structures; the materials adopted by the filter elements (14) include non - metals and metals.

7. The method for protecting the safe operation of a bag filter for industrial furnace flue gas according to claim 6, characterized in that: The ash hopper level combined monitoring system (5) uses a level gauge (51) and a thermometer (52) to jointly monitor the level height in the ash hopper (11). An upper level gauge (511) and an upper level thermometer (521) are installed simultaneously at the same height in the upper part of each ash hopper (11); a lower level gauge (512) and a lower level thermometer (522) are installed simultaneously at the same height in the lower part of each ash hopper (11); the level gauges (51) and thermometers (52) at different heights are installed on different wall panels of the ash hopper (11), and the level gauges (51) and thermometers (52) at the same height are installed on the same wall panel of the ash hopper (11); the temperature of each thermometer (52) on the ash hopper (11) and the comparison temperature difference change signal of itself form a dual monitoring signal that cooperates with each other with the signal of the level gauge (51), and is fed back to the monitoring and automatic control system (8) in real time, and the start and stop of the ash unloading and conveying device are controlled in a linked manner.

8. The method for protecting the safe operation of a bag filter for industrial furnace flue gas according to claim 7, characterized in that: The nitrogen filling port (62) is arranged in the area below the lower level of each ash hopper (11), 300 - 1000 mm away from the outlet of the ash hopper (11); the control device (63) uses a solenoid valve or a pneumatic valve, and one is configured for each ash hopper (11), or one is configured for a group of multiple ash hoppers (11); the monitoring system tracks and monitors the temperature change of the lower level thermometer (522) of the ash hopper (11) in real time, feeds it back to the automatic control system (8) in real time, and controls the start and stop of the nitrogen filling control device (63) in a linked manner as needed.

9. The method for protecting the safe operation of the bag filter for industrial furnace flue gas according to claim 8, characterized in that: The rupture disc is used in combination with a self - reset valve, or used alone. The rupture disc is made of aluminum or other metal materials, and the self - reset valve uses a spring or a counterweight method; the rupture pressure of the rupture disc and the opening pressure of the self - reset valve in the same over - pressure protection device (7) are equal, and are set as needed according to the maximum working pressure of the dust removal system, the designed pressure resistance and explosion - proof requirements of the bag - type dust collector (1).

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