Dust removal equipment

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I. Operating instructions for bag filters
The long-bag low-pressure pulse bag filter features innovations in blowback technology, filter structure, and microcomputer control. It has the advantages of high air handling capacity, small footprint, low steel consumption, relatively low equipment cost, low operating energy consumption, and easy operation and maintenance. Its technical specifications have reached the level of similar advanced foreign products introduced in recent years; it also boasts unique features in terms of control technology. 1. Preparations before starting the dust collector: If the filter bags are being used for the first time, pre-spraying the bags is necessary to prevent them from becoming clogged. If the filter bag is already in use and has not had its dust removed, there will still be residual dust on it; in such a case, pre-spraying is not necessary ； Special note: For boilers without a pre-spraying device, it is important to keep the bypass valve open during boiler drying and ignition. (Purpose: To prevent sparks generated during these processes from burning the filter bags, as well as to avoid oil and gas from adhering to the filter bags and causing dust accumulation.) ； Only after the boiler is burning properly can the dust-containing flue gas from the boiler be directed to the filtration chamber of the dust collector. Check whether the doors of all flue gas pipelines are closed ； Check whether the equipment pipes and connections are leaking ； Adjust the injection pressure, pulse frequency, and pulse width ； Check whether the air supply conditions for the lift valve are met and unobstructed ； Activate the ash conveying system and ensure its proper operation at all times ； Check whether the air inlet control valve for each filtration chamber is open. 2. Startup of the dust collector (1) Before starting the dust collector, it is necessary to check whether the air supply is turned on; the dust collector can only be started and operated once the air supply is active. (2) Check whether the manual control valve for the air inlet of each compartment is open ； (3) To start the exhaust fan, at least four (five) chambers must be online to ensure sufficient flue gas flow ； (4) Carefully inspect the lift valves, pulse valves, etc., in each chamber to ensure that these devices are functioning properly. (5) During the initial startup phase, the pressure drop across the dust collector is relatively low due to the small volume of air flow and dust. As a result, the automatic cleaning mode is postponed; no cleaning can be performed until stable operation is achieved. In this situation, differential pressure control is the preferred cleaning method. The thickness of the dust layer can be determined by an increase in the differential pressure (optional). Only then can the dust collector commence the cleaning process. (For those without a pressure difference control device, it is controlled by the PLC.) (6) At the initial start-up of the dust collector, no complete layer of powder covers the surface of the filter bags; a small amount of escaping fine dust may form plume-like smoke at the chimney outlet. 3. After the dust collector is started, a layer of powder will form on the surface of the filter bags, and the dust collector will then carry out a dust cleaning procedure in offline mode. Generally, the best indicator of the performance of a dust collector is the pressure value of the dust removal system (the absence of a pressure display is controlled automatically by the control cabinet). In particular, the pressure value in each individual filtration chamber of the dust collector serves as an excellent indicator of the condition of the filter bags. A sudden increase or decrease in this pressure value indicates that the filter bags may be clogged, leaking, the valves may not be functioning properly, the cleaning system may be malfunctioning, or there may be too much ash accumulated in the ash hopper. To protect the filter bags, the pressure level in each filtration chamber must not exceed 2000 Pa. (1) Dust cleaning of filter bags: Remote control: Select the “Remote” position using the switch; once the system meets the requirements for remote control, dust cleaning can be carried out remotely. Local control: Select the switch to set it to the “local” position; once the system meets the conditions for local control, the dust removal process can be carried out locally. (2) Shutting down the dust collector: The dust collector is shut down using the PLC, and its lift valve will close as well; subsequently, the inlet control valve should be closed manually (Note: The ash conveying system must not be stopped during the cleaning of the filter bags or when there is still ash remaining in the ash hopper). The closing of the filtration chamber is controlled by the PLC. A single filtration chamber should only be taken offline when it is absolutely necessary, and it should be brought back online as soon as possible, because its offline status increases the frequency at which the dust collector needs to be cleaned. The filtration chamber can be completely taken offline by shutting off the lift valve via PLC or manually, and by fully closing the manual control valve for the air inlet. Labels are hung on and limits are set for the inlet and outlet valves of the offline filtration chamber to prevent them from being suddenly opened while people are inside. Note: Since the flue gas contains a large amount of water vapor, other condensable gases, and acidic components, when the dust collector is shut down for more than 4 hours, please follow the steps below (to prevent rapid corrosion): Continue to remove the flue gas from the filter chamber of the dust collector after shutting down the main equipment. Clean the filter bags 3-5 times before shutting down the dust collector. Empty the dust in the ash hopper completely. Stop the ash transfer system from operating. Start the induced draft fan and clean the dust collector over a period of about an hour. Turn off the induced draft fan. Before entering the filtration chamber, use a exhaust fan to ventilate the area; after the inspection is complete, close the inspection doors promptly. 4. Maintenance Instructions (1) Fault-free operation: All maintenance related to the filter bags can be carried out in the clean air chamber. The portable access cover at the top of the dust collector is used for inspecting and replacing the filter bags, nozzles, etc. The dust collector is equipped with a maintenance platform for inspecting and servicing the dust removal system, electrical control equipment, and valves. As part of the maintenance procedures, periodic inspections are required to ensure \"fault-free operation\": during each shift, routine checks are carried out on the pressure drop in various chambers, valves, cylinders, air inlet and outlet valves, as well as the operation of the compressed air supply or (air tank drainage), with records to be kept at least once every four hours ； Weekly: Observe the entire dust removal cycle system to ensure that the dust removal cycle, the operation of the inlet and outlet valves, and PLC operations are functioning properly. Check the door seal ； Monthly: Conduct a detailed inspection of all air inlet and outlet valve controllers, solenoids, limit switches, motors, and equipment based on their operational functions ； Annually: One to two filter bags are randomly selected from each filtration chamber to analyze and predict their service life and the need for replacement ； Whenever possible, or at least once a year, inspect the possible dust accumulation on the filter plates in the clean gas section of each filter chamber of the dust collector, the condition of the filter bags, the dust accumulation in the ash hoppers, the performance of electrical components, and any sealing leaks in the valves. (2) Maintenance of various components: Filter bags: Regularly inspect the clean air chamber and filter bags; abnormal fluctuations in the differential pressure across various chambers can also be used to check for the presence of dust accumulation, moisture, rust, or smoke coming from the chimneys. Once any of the above situations occur, it indicates that there is a damaged filter bag, air leakage, or incorrect operating conditions. Electronic control components: Like other parts of the dust collector, electronic control components do not require regular maintenance; however, we should check them during the regular maintenance intervals. The inspection of assembled components such as solenoid valves can be carried out by replacement; defective components are sent to the manufacturer for repair or replacement. Electromagnetic pulse valve: Failures of diaphragm valves can be caused by continuous stimulation, accumulation of internal impurities, excessive wear of the diaphragm, or a worn spark plug blocking the shell and tube. A failure to open in a diaphragm valve can be detected by an excessive pressure drop in the compressed air supply line or by a continuous hissing sound from the valve. After identifying the cause of the problem, first relieve the system pressure, then remove the valve cover to check whether there are any debris at the seal of the diaphragm, whether the diaphragm is damaged, and whether the spring has failed. Do not attempt to disassemble the diaphragm valve when system pressure has not been relieved. The reason for the shutdown fault could be an insufficient excitation signal, a coil failure, the accumulation of internal impurities, or excessive piston wear. The detection of a closing failure in diaphragm valves can be carried out by checking for an excessively weak pulse sound when activating the solenoid valve. If the solenoid valve does not operate, or if the electromagnetic part functions but the valve does not operate, it indicates a problem with the electromagnetic actuation or controller, which needs to be replaced. The inspection of solenoid valves includes checking whether all connections are secure when the power is disconnected, and whether the valve operates properly. Dust collector condition: The water vapor deposits inside the dust collector chamber, in the form of small puddles or rust spots, are caused by the condensation of water vapor or acids present in the hot flue gases, or by leaks from the outside. The water vapor problem is caused by insufficient insulation at the operating temperature and high moisture content in the flue gas, which leads to the condensation of hot flue gas; it can also be caused by the filter chamber being closed for too long with too high a temperature of the flue gas inside. This issue can be resolved by improving insulation or adjusting the operating procedures. If the water vapor is caused by a leak, the best way to seal it is to clean the area first and then apply epoxy or silicone sealant. Sealing welding can also be used to fix the leak, but it is essential to remove the filter bag or cover it before welding in order to prevent damage from the welding sparks, as such damage can be fatal to the filter bag. Leaks in the access door are usually caused by improper tightening of the door or problems with the gasket. Properly tighten the inspection door and replace worn or deformed gaskets to resolve leaks in the inspection door. Pressure drop of the dust collector: The pressure drop of the system is the best indicator of the dust collector’s performance and condition. Based on the operation logs, any abnormal pressure drop model indications must be checked immediately! An excessively low pressure drop indicates a leak in the system; check whether the chimney is smoking and whether there is dust accumulation on the flue deck. There are many reasons for an excessively high pressure drop: clogged filter media, malfunctioning dust cleaning systems, faulty air inlet and outlet valves, excessive ash accumulation in the ash hopper, and blocked pipelines of the pressure differential gauge. Filter bag damage: In the event of filter bag damage occurring during the warranty period, there must be a record of the replacement, indicating the chamber and location of the filter bag that was replaced as well as the date of replacement; the damaged filter bag should also be submitted to the supplier for analysis. II. Electrostatic Precipitator 1. Inspections before operation: (i.e., acceptance inspections) (1) Check whether all welds are firm and reliable, and whether there are any missed or incorrect welds. Check whether the shell, ash hopper, inlet and outlet reducers, etc., have good airtightness and whether the air leakage rate meets the requirements. (2) Check whether the bolts of the cathode, anode, distribution plate, and transverse dust collection plates (including all rapping systems and hanging devices) are tightened and securely welded. (3) Remove sharp corners, burrs, and weld slag from all areas of the anode and cathode. (4) Check whether the cathode, anode, distribution pole rapping device, and ash discharge device rotate smoothly. (5) Check whether all reducers, ash discharge valves, fans, etc. rotate smoothly, as well as the oiling condition of the rotating parts. (6) Check whether the contact of each porcelain insulator post (or quartz tube used as a support) is stable and whether the stress is evenly distributed. (7) Check for equal and unequal pole distances: When the height of the anode plate is 8m or less, the allowable deviation for equal and unequal pole distances is ±5mm; when the height of the anode plate is greater than 8m, the allowable deviation for equal and unequal pole distances is ±8mm. Inspection area: Each channel is inspected at both the front and rear ends of the electric field, with 5–9 inspection points arranged in the vertical direction. That is, a point below the suspension beam, a point in the middle section, and a point above the impact rod need to be checked; 1-2 points should be inspected between the suspension beam and the middle part. At 1-2 points (evenly spaced) between the impact rod and the middle section, any areas that fail the inspection need to be readjusted and repaired. The areas in the middle that do not meet the requirements are adjusted based on the results of inspections at both the front and back ends of each channel, so that they meet the specified standards. The results of the inspection and adjustments shall be recorded, with the inspector, the construction party, and the construction representative from the manufacturer signing on the record. (8) Inspect the interior of the dust collector to check for any tools or other items used for installation or repair, as well as for any foreign objects stuck to the anode and cathode. Also, check whether there are any foreign objects inside the ash discharge valve at the bottom of the ash hopper. All foreign objects must be removed completely. (9) Check whether the airtightness of all manhole covers and maintenance doors is satisfactory. (10) The grounding resistance of the measuring unit should be less than 4 ohms. (11) Use a 2500-volt megohmmeter to check that the insulation resistance of the electric field and high-voltage power supply system is not less than 1000 megohms. (12) Use a 1000-volt megohmmeter to check the insulation of the shaking motor, the ash discharge motor, and their cables; the insulation resistance for all other components should be no less than 0.5 megohms. (13) The grounding cables for the dust collector housing and the high-voltage rectifier transformer should be in good condition and properly secured. (14) The operating mechanism of the high-voltage disconnector is flexible and its positioning is accurate. (15) Check whether the wiring of high- and low-voltage power supply equipment is correct. (16) Check whether the silicon rectifier transformer is installed firmly and whether the quality of the insulating oil meets the requirements. (17) Check whether all display devices, alarm devices, and safety interlock devices are sensitive and reliable. (18) Check against the drawings to ensure there are no incorrectly installed or missing components. 2. Pre-operational trial run: (1) Before putting the electrostatic precipitator into operation, conduct a trial run of each component to identify any issues individually and rectify them in a timely manner. (2) The dielectric strength test of high-voltage cable joints (referring to indoor types) is carried out in accordance with their respective test procedures. (3) Adjustment of the incubator temperature control system: Adjust the temperature relay to keep the incubator temperature 30°C above the flue gas dew point temperature. (4) Heating test of the electric heater inside the incubator: Turn on the electric heater of the incubator and check whether the temperature relay control system is sensitive and accurate. (5) Test run of the ash unloading system: Start the feeder, check whether the sound is normal and whether it opens/closes smoothly; run it for 60 minutes. (6) Trial operation of the anode and cathode rapping mechanisms. (7) Trial operation of the air flow distribution plate rapping mechanism. It refers to equipment equipped with an air flow distribution plate that is vibrated separately; the trial operation of its vibration mechanism is the same as that of the anode and cathode vibrations, lasting for 60 minutes. (8) Level detection device; check and adjust it after it is put into operation. (9) No-load operation of high-voltage power equipment: 3. After the startup and commissioning procedures have been checked and found to be satisfactory during the trial run, operation can then be initiated. (1) 6 hours before the equipment is put into operation, power should be supplied to the heater in the insulation box (also known as the insulator chamber), and the temperature relay and monitoring device should be activated to enable automatic control of electric heating. (2) Start the rapping devices for the anode, cathode, and gas distribution plate. (3) Start the ash discharge device and ash conveying device; simultaneously, start the level monitoring and control device. (4) The ash hopper heating device must be activated 6 hours before the equipment is put into operation. (5) The equipment itself must be preheated with flue gas before operation; the preheating time can be determined based on the temperature within the electric field, as long as the temperature in that field is above 20°C at the dew point. (6) Start the fan, and gradually increase the fan control valve from a small opening to the desired value. (7) Power supply is not possible when fuel is being used; power can only be supplied during combustion. (If a bypass flue is available, smoke can pass through it when fuel is being used.) (8) Once the requirements are met, the power supply equipment can be put into operation. (9) Inspections after the equipment is put into operation: 4. Operation: (1) After passing the acceptance tests, it can be brought into full operation. (2) During operation, the operator should monitor the various high-voltage rectifier control cabinets, central control panels, as well as the instruments and indicator lights on the consoles for any abnormalities. (3) Operators must pay close attention to changes in voltage and current, especially secondary voltage and secondary current, in order to determine any changes in the performance of the electrostatic precipitator, identify any faults in the equipment’s structure, and detect any changes in the properties of the flue gas. Thus, corresponding measures can be taken. Record the primary voltage and current values, as well as the secondary voltage and current values and the number of flashovers at the occurrence of arcing and flashovers. (4) An electrostatic precipitator must operate under high voltage to achieve the best dust removal effect. During operation, the operator must be aware of the discharge conditions of the electric field. This ensures that the spark discharge does not occur too frequently; it is advisable to keep it within the range of 50–60 times per minute. Adjustments can be made if necessary to achieve automatic tracking. (5) Adjust the rapping cycle appropriately based on operational conditions; try to make it as long as possible so as to keep the electrodes clean while minimizing secondary dust dispersion. When making adjustments, ensure that the rapping occurs across all electric fields. (6) During operation, the temperature inside the insulation box must be maintained above the flue gas dew point temperature of 20°C to prevent water vapor, acid mist, and dust in the flue gas from condensing on the surfaces of porcelain poles and porcelain bushings (or quartz tubes), thereby causing creepage breakdown. 5. Shutdown procedure: (1) First, reduce the speed of the fan until it stops running. (2) Turn the voltage adjustment knob to the “decrease” position; once the high voltage has dropped to near zero, press the “stop” button. (3) Turn off the air switch and high-voltage circuit breaker, and move the power key on the control panel to the “OFF” position. Turn the high-voltage isolating switch to the “grounded” position. (4) Anode, cathode rapping and distribution plate rapping systems. After turning off the high-voltage power supply for the electric field, it continued to operate for 2 hours. In the event of a prolonged shutdown, the ash discharge and conveying systems should remove all the ash. (5) The manhole and access doors can be opened only after the equipment itself has been shut down for 8 hours. If required for internal temporary inspections, the manhole or access door can be opened after 4 hours of shutdown to allow cooling. (6) During the shutdown period, remove the fuses from the control panel and the power panel, and hang warning signs stating “Do not close” on the control panel and the high-voltage disconnect switch handles.