Technical specifications for wet electrostatic precipitators

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I. General Overview of the Equipment: After coal is gasified, the resulting raw gas contains many impurities such as tar, dust, moisture, and hydrogen sulfide. The presence of these impurities has a severe impact on the pressurization, transportation, desulfurization, and purification of the gas, as well as on the quality of products that use coal as a raw material or fuel. Therefore, gas purification is an essential part of the coal gasification process. The purification of gas can be roughly divided into rough purification, semi-precise purification, and precise purification. For rough purification, vertical tubes are commonly used as primary cooling and dust removal devices; the efficiency of water-based dust removal in this case is generally 70–80%, while the efficiency of removing coke particles is only 20–30%. Semi-precise purification often makes use of cyclone dust collectors. For gas with a high purity level, where the dust content is below 0.1–2 g/Nm3, precise purification is necessary. Wet electrostatic precipitators are one of the effective devices for removing coke particles and dust. Wet electrostatic precipitators utilize the principle of high-voltage electrostatics to charge the dust and tar mist in the gas, causing them to move in a directed manner toward the collection electrode, thereby achieving the purpose of removing tar and dust. It features a compact structure, easy maintenance, small footprint, suitability for integration into existing systems, low power consumption (0.5 kWh per 1000 standard m3), and high desulfurization efficiency (over 99.6%). It can be widely used for the precise purification of producer gas, coking gas, water gas, and semi-water gas, making it an ideal device for gas dust and desulfurization in industries such as chemicals, ceramics, and gas stations. Product Overview: This product is a tower-type device, which consists of a cylinder, an air flow distribution system, sedimentation electrodes and corona electrodes, an explosion-proof valve, an insulating box, and other components. 1. The upper part of the cylinder is equipped with a gas outlet, manhole, and explosion-proof hole, and it contains a fixing frame for the corona wire as well as suspension rods. The top cover is equipped with an intermittent flushing device to regularly remove dust and tar adhering to the corona wires, thereby maintaining the proper operating condition of the equipment. 2. The lower part of the cylinder is mainly equipped with a corona wire fixing frame and two layers of air flow distribution plates. The two-layer air distribution plate ensures even gas distribution to improve dust removal efficiency. 3. The precipitation electrode is the main working area of a wet electrostatic precipitator; it consists of multiple rows of electrodes, and strict tolerance requirements apply to the spacing, straightness, parallelism, and perpendicularity of these electrodes. 4. The corona wire is positioned through the center of each electrode using upper and lower fixing frames; high-voltage direct current is applied to the corona wire and the collector electrode, thereby creating an electric field for dust removal as well as a gas passage. 5. At the top of the cylinder, there are four insulated enclosures placed on the equipment’s roof; one of these enclosures is equipped with accessories for high-voltage use. The insulated enclosures are heated and kept warm using a steam heating system, thereby preventing water vapor in the gas from condensing and contaminating the insulators, thus ensuring their insulation properties. The insulated enclosures also have temperature monitoring ports, vent ports, and other features. 6. The corona electrode wire is precision-machined from SUS316L stainless steel, while the cylinder and other components are made of carbon steel. 7. The cylinder is fabricated from 10mm thick steel plates, and the top cover is equipped with three insulating boxes; each of these boxes contains a porcelain insulator used to suspend the corona electrode. 8. The precipitation electrode is made of ∮325×8mm steel pipes (Q235-A) or ∮273×5mm steel pipes (Q235-A). ∮273×2mm stainless steel coil tube. Evenly distributed in the middle of the cylinder, to collect dust from the gas. 9. The corona electrode is made of nickel-chromium wire with a diameter of 2.5 mm. Production technical requirements: 1. The material of the raw materials must meet the specifications outlined in the drawings, and their chemical composition and mechanical properties must comply with the requirements of relevant standards. 2. The material certification documents must be complete, and they should be issued by the manufacturer or the distributor. 3. Purchased components must be accompanied by a product certification issued by the manufacturer, and all technical specifications must meet the requirements specified in the drawings and relevant standards; in the case of insulating porcelain capacitors, such certification must bear the signatures of both the manufacturer and our own company. 4. Key power supply components are Siemens electrical components. 5. The diameter deviation of the cylinder body is ±5mm. 6. The ellipticity of the cylinder body is ±3mm. 7. The verticality of the outer surface of the cylinder is ±5mm. 8. The surfaces of the welds and heat-affected zones must be free from defects such as cracks, pores, arc pits, and inclusions. 9. All welds of the cylinder shall undergo an oil immersion test, and the insulation box’s thermal insulation jacket shall be subjected to a pressure test at 0.4 MPa. VII. Precipitation electrodes The precipitation electrodes are the core of electrostatic tar capturers; there are strict technical requirements regarding the spacing between the electrodes as well as their vertical alignment. 1. The manufacturing tolerance for the sedimentation tube itself is an ellipticity of 2 millimeters, with a length tolerance of 5 millimeters. 2. The inside of the precipitation tube must not be painted. 3. Settlement pole: After installation, the verticality deviation of the settlement pole should be ≤4mm. 4. To ensure that the deviation does not exceed limits, adjustments are made using a rubber ring and a water cap installed at the upper part of the sedimentation electrode, as well as a fixing frame at the lower part of the sedimentation electrode, followed by acceptance testing. 5. All water caps in each tank must be at the same level. 　VIII. Design and manufacturing standards: JB88001.3 “Technical specifications for electrostatic precipitators”; JB88002.3 “Testing of dust removal efficiency of precipitators”; JB/T6409–92 “Wet tubular electrostatic precipitators for gas treatment”; ZB J88001.4 “Testing of air flow distribution in electrostatic precipitators”; ZB J88001.5 “Testing of pressure drop in electrostatic precipitators”; ZB J88001.7 “Method for testing electrostatic precipitators under no-load conditions with voltage applied”; ZB K46008.1 “Rectifier equipment for high-voltage electrostatic precipitation in industrial applications”; ZB K46008.2 “Testing methods for rectifier equipment used in high-voltage electrostatic dust removal”. Associated electrical components: JB/T9688–1999 “Power supply standards”. IX. Installation technical requirements: 1. Due to transportation constraints, the outer shell is manufactured at the site of the user’s facility, while all other components and structural parts are produced in our factory. 2. For all workpieces, we will manufacture them in accordance with the technical specifications provided in the drawings, applying rust-proof coatings. Appropriate distances will be left for those parts that need to be installed and welded on site, and serial numbers will be marked. 　 3. For all components that require testing, after conducting the tests, we will provide you with a test report and a certificate of conformity. 　 4. The vertical deviation of the overall height of the equipment is ±5 mm. 　5. The corona wire should be adjusted to the center of the precipitation electrode, with a deviation of ±3 mm. 　6. The joint between the bell-shaped porcelain vase and the flange should be securely bonded, with no leakage. 　7. The equipment cylinder shall be welded to a separately installed ground wire, with a grounding resistance not exceeding 4Ω. 　8. The insulation of the corona electrode from ground (porcelain insulator) shall be not less than 100 MΩ. 　9. After the manufacturing and installation are completed, a comprehensive airtightness test should be conducted. The test is carried out at 35 KPa (gauge pressure) in accordance with JB888001.3 \"Technical Requirements for Electrostatic Dust Removal\". X. Technical requirements for debugging: 1. Close all access holes, open the explosion-proof valve covers, and carry out load testing. Each jacket should be able to be heated to 75–110°C using steam; the air inside the container should be replaced with steam or nitrogen, ensuring that the oxygen content in the gas is less than 0.6%. After that, coal gas can be introduced. 　 2. Set the adjustment switch to position “0”, turn on the power supply for the rectifier control box, and adjust the voltage regulation switch so that the voltage rises gradually. The increase can be faster below 15 KV; once the voltage reaches 20 KV, the increase per step should be slower, at 1 KV per step, with the voltage held at that level for 1 minute until the required operating voltage is achieved. 　 3. Conduct gas composition analysis in accordance with normal operating procedures to ensure that the oxygen content is below 0.6%. XI. Equipment Maintenance 　1. Three to six months after the equipment has been in operation, clean the porcelain insulators of the bell cover and check the condition of the adhesions. 　 2. Check for dust accumulation on the corona electrode and precipitation electrode; in particular, excessive accumulation on the corona electrode can reduce the dust removal efficiency. 　 3. Check whether the corona electrode is located at the center of the precipitation electrode, and look for any signs of breakage, damage, misalignment, or movement. 　 4. Check the inner surface of the precipitation tube for any protrusions or areas that could lead to breakdown. 5. Inspect the tar buildup on the air flow distribution plate and clean it with steam. Operation procedures for electrostatic precipitators 1. Preparations before startup (1) Adjust the continuous water flushing valve so that the water film on the inner wall of the collection electrode is uniform, with no water columns present, and ensure that the water flow rate remains within the specified range. (2) Adjust the intermittent flushing valve, and check whether each nozzle distributes water evenly and is free of blockages. (3) Check whether all explosion-proof valves and explosion-proof membranes are reliable. (4) Inform the instrument technician that the electrician will check whether the electrical appliances, instruments, and signals are functioning properly. (5) Open the steam heating valve of the insulation box to maintain the temperature inside it at 70–90. (6) Open the electric precipitator vent valve, purge with steam, or displace with gas. (7) Notify the laboratory technician to conduct a test; when the oxygen content is <0.4%, close the vent valve, open the outlet valve, and inform the conveyor to prepare for gas delivery. (8) Once the replacement work and preparations for electrical equipment and instruments are completed, the machine can be started. 2. Driving and normal operation (1) Apply high voltage in accordance with the technical operating procedures for electrical equipment. (2) Check whether the working pressure and current are within the specified range. (3) Pay attention to the gas pressure and temperature; adjust the operating voltage and current of the electrostatic precipitator promptly according to these changes. (4) The electrostatic precipitator is intermittently flushed every 8 hours. (5) Pay attention to changes in the gas oxygen content in front of the inlet; when the oxygen content exceeds 0.6%, the high-voltage power supply to the electrostatic precipitator should be stopped immediately. 3. Intermittent flushing operation (1) Before intermittent flushing, cut off the high-voltage power. (2) Open the intermittent flushing valve and flush for 15–30 minutes. (3) After closing the intermittent flushing valve for 3–5 minutes, high-voltage power is applied. 4. Shutdown procedures (1) Temporary shutdown during production: Upon receiving a shutdown order, first contact the personnel in charge of the blowers and conveyors. Disconnect the high voltage in accordance with the regulations for electrical equipment. Close the outlet valve of the electrostatic precipitator. Adjust the inlet valve of the electrostatic precipitator to maintain positive pressure in the gas. (2) When stopping the equipment for long-term parking or maintenance, upon receiving the stop order, contact the gas delivery team. In accordance with electrical equipment regulations, cut off the high-voltage power supply to shut down the unit. Close the inlet valve of the electrostatic precipitator, and fill the water seal at the outlet of the electrostatic precipitator with water to ensure normal overflow. Close the steam valve of the insulation box to stop heating, and close the continuous flushing valve. After turning on the intermittent flushing valve and flushing for 15 to 30 minutes, turn off the intermittent flushing valve and inform the gas station to install a blind flange at the gas outlet. Blow the electrostatic precipitator with steam and perform replacement. Contact the analysis engineer for sampling and analysis; stop the replacement once it is approved. Open the upper and lower manholes for natural ventilation; maintenance can be carried out only when the oxygen content inside the dust collector is >20.8%. 5. Emergency shutdown (1) In the event of the following situations during production, an emergency shutdown should be initiated: short circuits in the electrical system or severe discharge phenomena; breakdown or damage to cable connections or electrical components; excessive temperature rise in the transformer or very high temperatures; occurrence of electric shock incidents; oxygen concentration exceeding 0.4%. This also applies in the event of an emergency shutdown of the furnace. (2) Steps for emergency shutdown: Immediately cut off the power supply in accordance with the technical operating procedures for electrical equipment. Notify the furnace operator. Seal the drum. Handle it at the conveyor operator station.