Process Technology Operation Standards for Electrostatic Tar Collector Posts

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Operating Standards for the Electrostatic Tar Collector Process 1. Working principle of the electrostatic tar collector: The gas coming from the cross-tube primary cooler contains very fine suspended tar droplets in an amount of about 10 g/Nm3. After passing through the electrostatic tar collector, the tar content in the gas is reduced to 20 mg/Nm3, meeting the requirements of subsequent production processes. Coke oven gas containing tar droplets enters the regular hexagonal honeycomb tubes from the bottom of the electrostatic tar collector and exits from the top of the device. The honeycomb tube is set up as a high-voltage non-uniform electric field; the honeycomb tube serves as the positive electrode (also known as the precipitation electrode), while a wire (stainless steel wire) located at the center of the honeycomb tube functions as the negative electrode (also known as the corona electrode). Under the influence of the high-voltage electric field, gas molecules become ionized and collide violently around the corona electrode, generating a large number of positive and negative ions. Outside the corona electrode, only negative ions exist; as a result, in most of the interior space of the tar catcher, the tar droplets turn into negatively charged particles that move toward the precipitation electrode. Since the tube walls and the equipment casing are grounded, these negatively charged tar particles discharge when they reach the tube walls, deposit there, and then accumulate at the bottom of the collector, thereby achieving the removal of tar droplets from the gas. 2. Main technical parameters of the electrostatic tar catcher: 2.1 Electrostatic tar catcher DN5200, H=14544 ； Resistance: 500Pa ； Ground resistance < 4Ω ； Rated operating voltage: 65kV ； Rated operating current: 1500mA ； 2.2 Precipitation electrode type: honeycomb ； Material: OCr18Ni9 ； Shape and dimensions: regular hexagon, distance between opposite sides 250 mm, length: 5.5 m ； Number of holes: 276 ； 2.3 Corona wire Diameter: Φ2.3mm (stainless steel) ； Quantity: 276 pieces ； Effective length 5.5×276=1518m ； After installation, deviation of ±5mm from the central value is allowed ； 2.4 Processing medium: coke oven gas ； Processing capacity: 35,200 Nm3/h; gas temperature: 22–40°C; gas pressure: -5 kPa ； 2.5 Tar content in gas entering the furnace: ≤10g/Nm3 ； Gas tar content in the outlet gas: ≤20mg/Nm3 ； Tar removal rate: ≥99.8% ； 2.6 Steam heating for the insulating box of porcelain insulators: The temperature of the jacket surrounding the insulating box for porcelain insulators should be between 110~120°C, with a minimum of 90°C; the steam pressure should be ≥0.4 MPa ； 2.7 Flow rate of circulating ammonia water for top cleaning: 22 m3/h ； Pressure: 0.03~0.05MPa ； 2.8 Nitrogen filling volume for the insulation box of the electrostatic tar catcher: 50~80 m3/h per unit ； Nitrogen purity greater than 99.5% ； 2.9 The oxygen content in the gas inside the electrostatic tar catcher should be less than 1.5% (ensure this) ； 2.10 The verticality of the lead in the electrostatic tar catcher shall not exceed 5 mm ； 3. Scope of the electric tar catcher unit: electric tar catcher, nitrogen heater, porcelain insulating box and steam heating system, water seal tank, pipes and valves within the system, as well as auxiliary facilities such as instruments and lighting. 4. Operating procedures for the electric tar catcher: 4.1 Requirements for normal operation: 4.1.1 Check whether the tar discharge pipeline at the bottom of the electric tar catcher is unobstructed, as well as whether the exhaust pipe of the water seal tank is unobstructed ； 4.1.2 Strictly follow the technical operating procedures for this position, make careful adjustments to ensure that control parameters such as temperature, pressure, flow rate, and resistance in all relevant areas remain within normal ranges ； 4.1.3 Regularly inspect the equipment, pipelines, valves, etc. within the system; any oil or steam leaks or other abnormalities should be reported promptly and addressed immediately ； 4.1.4 Keep a good track of the equipment’s operating conditions; record all control parameter values once per hour ； 4.2 Startup operations of the electrostatic precipitator: 4.2.1 Nitrogen purging and removal of the gas isolation valve: 4.2.1.1 Open the valves for the vent pipe at the top of the electrostatic precipitator as well as the DN80 connection pipe inside it; close the valve for the tar discharge pipe at the bottom of the electrostatic precipitator ； 4.2.1.2 Feed nitrogen into the vessel and the coal gas pipeline at the vessel’s outlet; expel the air inside the vessel and in the coal gas pipeline at the outlet through the vent pipe at the top of the vessel. Once a large amount of nitrogen begins to emerge from the vent pipe, reduce the valve opening of that vent pipe ； 4.2.1.3 With the nitrogen pressure inside the vessel maintained at 500 Pa, install blind flanges on the gas inlet and outlet valves, then close the vent pipe valve; the vessel is kept under a positive pressure of 500 Pa using nitrogen ； 4.2.2 Supplying gas: 4.2.2.1 Before the gas is fed into the device, it must be checked to ensure that its oxygen content is less than 1.5% ； 4.2.2.2 Slowly open the gas inlet valve, and open the gas outlet valve ； 4.2.2.3 After the gas inlet and outlet valves are opened, close the DN80 connecting pipe valve (also close the nitrogen valve and plug it with a blind flange), then slowly close the gas supply pipe of the electrostatic tar catcher, and observe the resistance in the gas system ； 4.2.3 Confirmation of the temperature in the insulating box for porcelain insulators: 4.2.3.1 Steam is used for indirect heating in the middle part of the insulating box for porcelain insulators; heating is carried out in stages before operation, with the amount of steam gradually increased. After 2–4 hours of steam heating, gas can be introduced, and the temperature inside the jacket of the insulating box must be maintained between 110–120°C, with a minimum of 90°C ； 4.2.3.2 The nitrogen fed into the lower part of the porcelain insulator box is heated to a temperature of 90–100°C using a steam jacket, with the flow rate controlled at 50–80 m3/h per unit ； 4.2.4 Connecting the high-voltage power supply: 4.2.4.1 Ensure the following conditions are met before powering on: 4.2.4.1.1 The grounding resistance of the electrostatic tar collector and the protective shielding shall not exceed 4Ω ； 4.2.4.1.2 The insulation resistance of porcelain insulators and corona electrode systems, measured using a 2500V megohmmeter, shall be not less than 100 MΩ ； 4.2.4.1.3 The insulation resistance of primary low-voltage circuits and devices, measured using a 500V megohmmeter, shall be not less than 0.5 MΩ. 4.2.4.2 Then gradually increase from the lowest voltage to the selected operating voltage ； 4.2.5 Operation of the electrostatic tar catcher: 4.2.5.1 Open the tar discharge valve at the bottom of the electrostatic tar catcher; the tar flows naturally to the underground drainage tank via the water seal groove (once the drainage tank is full, it is pumped to the lower condensate tank using an submersible pump) ； 4.2.5.2 Adjust the DC output voltage and current of the rectifier to the selected operating voltage and current values ； 4.2.5.3 The following items shall be checked once per hour: 4.2.5.3.1 Rectifier output voltage and current ； 4.2.5.3.2 Temperature, pressure, flow rate of gas, oxygen content in the gas, and tar content in the gas after the device ； 4.2.5.3.3 Temperature of the porcelain insulator box, flow rate, pressure, and temperature of the nitrogen used to protect the insulator box ； 4.2.5.3.4 Tar discharge status (check whether the water seal tank and vent pipe are unobstructed) ； 4.2.5.4 Flushing: 4.2.5.4.1 When the tar discharge volume decreases significantly, use steam from the bottom to clean the tar discharge pipe ； 4.2.5.4.2 When the voltage drops to its lowest value, the high-voltage power should be turned off ； Then, the hot ammonia water from the circulating ammonia water pump is sprayed through the top spray pipes ； 4.3 Shutdown of the electrostatic tar catcher: 4.3.1 Cut off the high-voltage power supply to ground the output terminal of the rectifier and the corona electrodes of the electrostatic tar catcher ； 4.3.2 Close the gas inlet and outlet valves (decide whether to open the valve of the electric tar catcher’s gas connection pipe or activate another electric tar catcher based on the system resistance) ； 4.3.3 Nitrogen replacement of gas: 4.3.3.1 Open the nitrogen valve to introduce nitrogen into the device and the gas pipes at the outlet ； 4.3.3.2 After the nitrogen pressure inside the vessel becomes positive, open the vent pipe valve at the top of the vessel and the DN80 connection pipe valve ； 4.3.3.3 Take a gas sample for analysis in front of the vent pipe valve to confirm that the gas inside the equipment has been replaced by nitrogen, after which close the vent pipe valve at the top of the device as well as the nitrogen valve ； 4.3.3.4 Stop supplying nitrogen to the porcelain insulator box, and at the same time stop supplying heated steam to it ； 4.3.4 Steam displacement of nitrogen: 4.3.4.1 Open the steam valve, as well as the DN80 connection pipe valve and the top vent valve of the vessel ； Steam is introduced to drive away the nitrogen from inside the device and the gas outlet pipe ； 4.3.4.2 At a steam pressure of 500 Pa, plug the blind flanges on the gas inlet and outlet pipes, and also plug the nitrogen blind flange ； 4.3.5 Opening the manhole for inspection: 4.3.5.1 Open the manhole in sequence from top to bottom ； 4.3.5.2 Conduct component analysis of the gases inside the equipment to ensure safety and prevent poisoning ； 4.5.3 Entering the equipment to conduct an inspection ； 4.3.6 Steam is used to clean the tar removal pipes to keep them unobstructed ； 5. Startup procedures for the electrostatic precipitator after maintenance: After maintenance on the electrostatic precipitator, the following steps must be followed before it is put back into operation: 5.1 Air-tightness test of the electrostatic precipitator: 5.1.1 Conduct an air-tightness test after the electrostatic precipitator has been properly manufactured and installed (with a vertical deviation of lead not exceeding 5 mm) ； 5.1.2 Air or nitrogen shall be introduced into the electrostatic tar catcher, and a comprehensive airtightness test shall be conducted using air or nitrogen at a gauge pressure of 35 kPa. The pressure should be increased gradually during the test; once the target pressure is reached, the supply of gas shall be stopped. The pressure shall be maintained for 2 hours, with an allowable average leakage rate of 1% per hour ； 5.1.3 During the testing process, strictly check the tightness at the sealing ring of the porcelain insulator; any leakage is not allowed ； 5.1.4 After the airtightness test is passed, welding shall not be performed on the hull; if welding is necessary, the airtightness test must be conducted again ； 5.2 Air load testing of the electrostatic tar catcher: 5.2.1 Initial condition of the equipment: 5.2.1.1 The gas inlet and outlet valves are fully closed, and blind flanges are installed ； 5.2.1.2 The top vent valve, the bottom tar-ammonia discharge valve, the connection pipe valves, and the manholes should all be opened, while all other valves should remain closed ； 5.2.1.3 The output side of the rectifier and the corona electrode should be grounded ； The grounding resistance of equipment and protective shields is less than 4Ω ； 5.2.1.4 Fill the water seal tank with water ； 5.2.2 Internal inspection: 5.2.2.1 There are no foreign objects such as metal pieces, wood, or fabric inside the equipment ； 5.2.2.2 No contact on the corona electrode and precipitation electrode sides ； 5.2.2.3 No abnormalities on the insulator surface ； 5.2.3 Preparatory work before testing: 5.2.3.1 Fill the porcelain insulating box with 25# transformer oil, up to a level 100 mm away from the end flange ； 5.2.3.2 Open the manhole on the insulating box of the porcelain insulator, wipe the high-voltage porcelain insulator with a clean cloth, and seal the manhole after cleaning it ； 5.2.3.3 Before conducting a voltage test, the middle part of the porcelain insulator box is heated indirectly using steam; heating is carried out in stages prior to commissioning, with the amount of steam gradually increased. It takes 2–4 hours of steam heating before a voltage test can be performed ； And maintain the jacket temperature of the porcelain insulator box at 110~120°C, with a minimum of not lower than 90°C℃ ； 5.2.3.3 Insulation resistance test: 5.2.3.3.1 An insulation test shall be conducted before energizing the high-voltage circuit; the insulation resistance of porcelain insulators and corona electrode systems shall be measured using a 2500V megohmmeter and must be greater than 100MΩ ； 5.2.3.3.2 The resistance value of primary low-voltage circuits and devices is measured using a 500V megohmmeter; it should be 0.5 MΩ to confirm there are no abnormalities ； 5.2.4 Air load voltage testing: 5.2.4.1 Open the upper and lower manholes, fill the equipment with clean air, and apply high-voltage power for insulation strength testing ； 5.2.4.2 Start by increasing the voltage gradually from the lowest level; maintain each voltage level for 10–15 minutes. Once the secondary current reaches full load or the secondary voltage reaches 50 kV or more, keep that level stable for 20 minutes. The parameters obtained from these air testing procedures serve as the basis for putting this electric precipitator into operation ； 5.2.4.3 During the testing process, if internal arcing is detected, the power supply should be turned off, the corona electrode should be grounded, and the interior of the electrostatic tar catcher should be inspected; in particular, it is necessary to ensure that the deviation of the corona wire from its center is not greater than ±5mm ； 5.2.4.4 After the test, disconnect the high-voltage power supply and ground the output side of the rectifier as well as the corona electrode ； 5.2.4.5 Open the vent pipe, and close the manhole and valve ； 6. Long-term shutdown of the electrostatic tar catcher: In the event of a long-term shutdown, all valves and manholes on the equipment should be closed to reduce corrosion inside the equipment; nitrogen should be used for protection, with the nitrogen pressure inside kept at 500 Pa ； 7. Maintenance of electrostatic tar collectors: 7.1 To ensure the proper operation of electrostatic tar collectors, it is necessary to strengthen management, establish operational rules and procedures, assign dedicated personnel to carry out regular inspections and repairs, and keep proper records of operations ； 7.2 After each shutdown and subsequent gas displacement, the interior of the vessel must be purged with steam. The valves for the steam pipelines in the upper and lower sections of the vessel, as well as the tar discharge valve, should be opened until the interior is completely purged. Afterwards, the upper and lower manholes should be opened to allow natural ventilation and drying, and any tar mixtures present inside the vessel should be removed ； 7.3 Regularly inspect the high-voltage insulators. Before starting up the equipment, wipe the surface of these insulators with a clean cloth. The insulation resistance of both the insulators and the corona electrode system should be greater than 100 MΩ, as measured using a 2500V megohmmeter ； 7.4 During maintenance, check whether all components and fasteners inside the detector body are secure and reliable, and meet the requirements of the technical specifications. In particular, inspect the corrosion status of the electrode wires; if the corrosion is severe, the wires must be replaced ； 7.5 During operation, the temperature of the jacket surrounding the porcelain insulator box should be maintained at 110–120°C, with a minimum of 90°C℃ ； Ensure that the pressure gauge functions properly, valves open smoothly, steam traps are unobstructed, and there are no leaks in the valves and pipes ； 7.6 Regularly inspect the protective plate at the top of the electrostatic tar catcher (the protective plate is made of aluminum with a thickness of 1 mm), and promptly clean away the dust and water accumulated on its surface ； 7.7 Regularly inspect the transformer oil in the insulating box of porcelain insulators; conduct a dielectric strength test on the transformer oil every year to check whether its quality meets the specified standards, and replace it promptly if it does not meet those standards ； 7.8 Regularly service and calibrate the oxygen analyzer to ensure accurate data ； 7.9 When the resistance of the electrostatic tar catcher exceeds the specified value, cut off the high-voltage power and clean it using hot ammonia water or steam ； When put into operation, it shall be done in accordance with the relevant regulations ； 7.10 When switching blowers or installing/removing blind flanges on coal gas pipelines, the electrostatic tar collector should have its high-voltage power turned off ； 7.11 The grounding resistance of the high-voltage generator and the tower should be measured once each in winter and summer; the grounding resistance should be less than 4Ω ； 7.12 Keep the control cabinet clean; the dashboard should be wiped regularly, and it is necessary to check that all switches, buttons, indicator lights, and instruments are functioning properly and free of any defects ； 7.13 In winter, it is necessary to prevent the steam inlets and outlets of steam pipes and heating pipes in porcelain insulator boxes from freezing ； When stopping the steam supply, the condensate in the pipes should be drained to ensure proper operation of the steam traps ； 8. Common faults of electric tar collectors and troubleshooting methods: Sequence Number, Fault Condition, Cause Analysis, Solution. 1. Continuous tripping while there is no problem with the entire wiring system: Contamination or tar on the surface of the insulating porcelain bottles; clean them with a clean cotton cloth. The insulating porcelain insulator is damaged and needs to be replaced. Dew forms on the surface of the insulating porcelain insulators; ensure that the temperature of the insulation box is between 110–120°C. Corona electrode wire broken; replace the electrode wire. The tar layer attached to the precipitation electrode and the corona electrode is too thick; it is cleaned by spraying with circulating ammonia water to cause the tar to flow off. The corona wire is not centered; adjust the position of the hook and the adjusting hook so that the electrode wire is within ±5mm of the center position. The suspension column is not centered; adjust its position so that it is within ±5mm of the centered value. 2. The temperature inside the insulated box is below 90°C; the steam heating temperature is insufficient. Increase the steam flow to raise the temperature. 3 Tar discharge stopped: The tar discharge pipe is blocked; clean it with steam until tar flows out.