Pre-de-naphthalene anti-blocking VOCs recovery system and process

Abstract

The application discloses a front naphthalene removal anti-blocking VOCs recovery system and process, and belongs to the technical field of VOCs waste gas recovery and purification in the coking industry. The system comprises a Fisher pressure regulator, a nitrogen heater, a separation tank and a hot ammonia water spraying pipeline. High-pressure nitrogen is decompressed by the Fisher pressure regulator and heated by the nitrogen heater, and then is sent into a VOCs main pipe to be mixed with waste gas. A temperature measuring point interlocks a steam regulating valve to maintain constant temperature to inhibit naphthalene crystallization. A pressure measuring point interlocks a nitrogen sealing regulating valve and a pressure control valve to maintain a slight positive pressure to prevent air from penetrating. The waste gas is sent into the separation tank to be reversely contacted with hot ammonia water containing ammonia, so that coal dust and coke dust are physically intercepted and naphthalene vapor is removed through similar solubility. The purified waste gas is front-connected to a coal gas pipeline before a washing tower or before a primary cooler. The application avoids impurities from entering downstream equipment from the source, and improves the safety and stability of system operation.

Description

Technical Field

[0001] This invention relates to the field of VOCs waste gas recovery and purification technology in the coking industry, specifically to a pre-treatment naphthalene removal and anti-clogging VOCs recovery system and process. Background Technology

[0002] In the coking production process, various raw material storage tanks and intermediate product storage tanks continuously release VOCs (volatile organic compounds) into the exhaust gas. Besides volatile organic compounds, the exhaust gas also contains naphthalene vapor and solid impurities such as coal powder and coke powder. Naphthalene is sensitive to temperature fluctuations and easily crystallizes after cooling. Naphthalene crystals, combined with coal powder, coke powder, and other impurities, easily adhere to and clog pipelines and equipment. Existing technologies, such as the coking VOCs exhaust gas clean recovery and treatment system disclosed in Chinese invention patent application CN109621621A, mostly employ a process route of nitrogen protection collection, condensation, and oil washing to remove naphthalene. However, existing VOCs recovery processes in the coking industry still have the following shortcomings: 1. Inappropriate process access location: Existing conventional VOCs recovery processes often connect the waste gas to the front end of the blower. The waste gas is not pretreated, and impurities such as naphthalene vapor, coal powder, and coke powder enter the downstream desulfurization tower, benzene washing tower and other core equipment with the airflow, causing blockage and wear of pipelines and packing, resulting in reduced purification effect, high equipment maintenance frequency and poor system operation continuity.

[0003] 2. Unsafe pressure condition selection: Most similar devices operate with a slightly negative pressure pipeline, where the internal pressure of the equipment pipeline is lower than the external atmospheric pressure, making it easy for air to be drawn in due to the negative pressure; coking VOCs and coke oven gas are both flammable and explosive media, and the mixing of air poses a safety hazard.

[0004] 3. Unstable nitrogen pressure regulation method: The plant's public high-pressure nitrogen is directly connected to the exhaust gas main for pressure regulation and replenishment. There is no dedicated stage pressure reducing component. It relies on valves for direct throttling and pressure regulation, resulting in large pipeline pressure loss, uncontrollable pressure drop, and violent pressure fluctuations, making it difficult to maintain stable pipeline operating conditions.

[0005] 4. Lack of anti-crystallization and naphthalene removal structure: Conventional equipment only collects and transports waste gas, without nitrogen constant temperature mixed gas temperature control, making it difficult to control naphthalene crystallization; at the same time, no ammonia water spray naphthalene removal unit is set up specifically, so it is impossible to remove coal powder, coke powder impurities and gas phase naphthalene components in advance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a pre-treatment naphthalene removal and anti-clogging VOCs recovery system and process. This system pre-purifies VOCs waste gas before it is incorporated into the gas pipeline, removing impurities such as coal powder, coke powder, and naphthalene. Simultaneously, it maintains a slightly positive pressure in the pipeline for safe operation and constant temperature to prevent crystallization, thus preventing impurities from entering downstream equipment and causing blockage and wear.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A pre-treatment naphthalene removal and anti-clogging VOCs recovery system includes a Fisher pressure regulator, a nitrogen heater, a nitrogen sealing regulating valve, a pressure control valve, a VOCs main pipe, tank vent gas channels, a separator, a hot ammonia spray pipe, pressure measuring points, temperature measuring points, and a steam regulating valve. The nitrogen inlet pipe is connected to the Fisher pressure regulator, and the outlet of the Fisher pressure regulator is connected to the nitrogen heater. The steam regulating valve is installed on the steam supply pipe of the nitrogen heater, and the outlet pipe of the nitrogen heater is connected to the VOCs main pipe through the nitrogen sealing regulating valve. The heated nitrogen mixes with the exhaust gas to maintain the pipe temperature and inhibit naphthalene crystallization. Multiple tank vent gas channels are connected in parallel. The VOCs system is then connected to the VOCs main pipe, which is equipped with pressure measuring points, temperature measuring points, and a pressure control valve. The pressure measuring points are interlocked with the pressure control valve to maintain a slight positive pressure in the VOCs main pipe, and the temperature measuring points are interlocked with the steam regulating valve to maintain the pipeline temperature and inhibit naphthalene crystallization. The end pipe of the VOCs main pipe is connected to the upper air inlet of the separator. The hot ammonia water spraying pipe is installed inside the separator chamber. The spraying medium is ammonia-containing hot ammonia water, which comes into countercurrent contact with the waste gas to remove coal dust, coke dust, and naphthalene vapor. The gas phase outlet of the separator can be connected to the gas pipeline before the scrubbing tower or the gas pipeline before the primary cooler. A liquid phase discharge port is set at the bottom of the separator.

[0008] Furthermore, the temperature measuring point can realize high and low temperature alarms, and the measuring point signal is interlocked with the steam regulating valve. By adjusting the steam supply, the temperature of the nitrogen and waste gas mixture is stabilized in a temperature range that can suppress the formation of naphthalene crystals, preferably 75-80℃.

[0009] Furthermore, the pressure measuring point can realize high and low pressure alarms. The measuring point signal is interlocked with the nitrogen sealing regulating valve and the pressure control valve to maintain the internal pressure of the VOCs main pipe in the set slightly positive pressure range, preferably 0.8-0.9 kPa. Under normal operating conditions, the pressure control valve is the main regulator, and when the pressure drops, the nitrogen sealing regulating valve opens to assist in nitrogen replenishment.

[0010] Furthermore, the hot ammonia water spraying pipe sprays ammonia-containing hot ammonia water into the separation tank, and the waste gas comes into countercurrent contact with the ammonia-containing hot ammonia water. The hot ammonia water physically intercepts coal powder and coke powder and absorbs naphthalene vapor through the similarity of free ammonia and naphthalene.

[0011] Furthermore, when the gas phase outlet of the separator is connected to the gas pipeline before the scrubbing tower, the purified waste gas flows through the scrubbing tower, primary cooler, and electrostatic precipitator for further purification along with the gas.

[0012] This invention also provides a pre-naphthalene removal and anti-clogging VOCs recovery process, which uses the above-mentioned pre-naphthalene removal and anti-clogging VOCs recovery system and includes the following operating steps: S1. Collection and stabilization of exhaust gas from coking tanks: The VOCs exhaust gas generated by each coking tank is collected into the VOCs main pipe through its corresponding tank exhaust gas channel. Nitrogen is continuously introduced through the nitrogen sealing regulating valve and, in conjunction with the pressure control valve, a slight positive pressure is maintained in the gas phase inside the VOCs main pipe. S2. Nitrogen pressure regulation and heating and mixing with exhaust gas: High-pressure nitrogen is introduced into the Fisher pressure regulator to complete the pressure reduction, and low-pressure nitrogen enters the nitrogen heater for heat exchange and heating. Temperature measurement points collect pipeline temperature in real time and interlock the steam regulating valve to dynamically adjust the steam supply. The temperature-regulated nitrogen is sent into the VOCs main pipe to mix fully with the exhaust gas to maintain the pipeline temperature and inhibit naphthalene crystal precipitation. S3, VOCs main pipe pressure stabilization and control: The pressure measuring point monitors the internal pressure of the VOCs main pipe in real time. When the pressure deviates from the set range, an alarm is triggered and the pressure control valve is interlocked to adjust the opening to maintain a slight positive pressure inside the VOCs main pipe. Under normal operating conditions, the pressure control valve is the main regulator. When the pressure drops, the nitrogen sealing regulating valve opens to assist in nitrogen replenishment. S4. Hot ammonia water washing to remove coal powder and naphthalene: VOCs waste gas after constant temperature and pressure regulation is sent into the separator. Hot ammonia water spray pipe continuously sprays ammonia-containing hot ammonia water. The waste gas and hot ammonia water come into counter-current contact to remove coal powder, coke powder and naphthalene vapor from the waste gas. The liquid medium containing impurities is discharged from the bottom of the separator. S5. Purified waste gas transportation: The waste gas that has completed the removal of impurities and naphthalene is transported through the selected transportation path according to the equipment configuration of the plant. When the plant is equipped with a scrubbing tower, it is sent to the gas pipeline in front of the scrubbing tower. When the plant is not equipped with a scrubbing tower, it is sent to the gas pipeline in front of the primary cooler and finally connected to the coke oven gas negative pressure pipeline for unified treatment.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. Pre-treatment purification: The exhaust gas is pre-treated for naphthalene removal and dust removal before entering the scrubbing tower and primary cooler, which prevents impurities from being carried into downstream gas equipment from the source, effectively alleviating equipment blockage problems and reducing maintenance frequency. 2. Staged pressure reduction and constant temperature protection: Fisher pressure regulator achieves stable pressure reduction of high-pressure nitrogen, reducing pressure loss caused by direct throttling; temperature measuring point interlock steam regulating valve stabilizes the temperature of the mixed gas, inhibits naphthalene crystallization during the delivery stage, and prevents pipeline blockage; 3. Dual-valve interlocking micro-positive pressure stabilization: The pressure measuring point is simultaneously interlocked with the nitrogen sealing regulating valve and the pressure control valve, and nitrogen is replenished in stages to stabilize the pressure. The entire process operates under micro-positive pressure to avoid the safety hazards caused by the intake of air due to negative pressure. 4. Reverse spray dual-effect purification: The ammonia-containing hot ammonia water in the separation tank comes into reverse contact with the waste gas, physically intercepts solid dust and dissolves naphthalene through similar-like dissolution, and completes the removal of solid and gaseous impurities in one step, with high purification efficiency; 5. Strong adaptability of dual output channels: It can be flexibly connected to the gas pipeline before the scrubbing tower or the primary cooler to adapt to different coking plant renovation conditions; it operates with automated interlocking, requires little manual intervention, and relies on the plant's own produced hot ammonia water as the scrubbing medium, resulting in low operation and maintenance costs and ensuring long-term stable operation of the gas purification device. Attached Figure Description

[0014] Figure 1 is a process flow diagram of the present invention; In the diagram: 1. Fisher pressure regulator, 2. Nitrogen heater, 3. Nitrogen sealing regulating valve, 4. Pressure control valve, 5. VOCs main pipe, 6. Tank venting channel, 7. Separator, 8. Hot ammonia spray pipe, 9. Pressure measuring point, 10. Temperature measuring point, 11. Steam regulating valve. Detailed Implementation

[0015] The following is in conjunction with the appendix Figure 1 The specific embodiments of the present invention will be further described in detail below. In the figure, PRCA is a pressure recording and control alarm instrument, TRCA is a temperature recording and control alarm instrument, BG is tank vent gas, and PV is a pressure regulating valve.

[0016] like Figure 1 As shown, in the pre-treatment naphthalene removal and anti-clogging VOCs recovery system of the present invention, the common high-pressure nitrogen gas in the plant first enters the Fisher pressure regulator 1, and after staged pressure reduction, it is reduced to a low-pressure range suitable for VOCs transportation conditions; the reduced-pressure low-pressure nitrogen gas enters the nitrogen heater 2, and exchanges heat with steam to raise the temperature. The steam regulating valve 11 is installed on the steam supply pipeline of the nitrogen heater 2 to regulate the amount of heating steam. The condensate after heat exchange is discharged from the condensate outlet of the nitrogen heater 2; the heated nitrogen gas is sent to the VOCs main pipe 5 through the nitrogen sealing regulating valve 3, and fully mixes with the VOCs waste gas, relying on the stable temperature environment to inhibit the crystallization and precipitation of naphthalene.

[0017] VOCs emissions from the raw material and intermediate product storage tanks in the coking plant are collected in parallel through their respective tank venting channels 6 and then fed into the VOCs main pipe 5. The VOCs main pipe 5 is equipped with a temperature measuring point 10, a pressure measuring point 9, and a pressure control valve 4. The temperature measuring point 10 collects the mixed gas temperature in real time, providing high and low temperature alarms, and is interlocked with the steam regulating valve 11. By dynamically adjusting the steam supply, the mixed gas temperature is stabilized at 75-80℃, higher than the naphthalene crystallization temperature, ensuring no naphthalene precipitation during transport. The pressure measuring point 9 monitors the main pipe pressure in real time, providing high and low pressure alarms, and is interlocked with the nitrogen blanketing regulating valve 3 and the pressure control valve 4. Under normal operating conditions, the nitrogen blanketing regulating valve 3 maintains a small opening for continuous nitrogen replenishment, with the pressure control valve 4 performing the main pressure regulation. When the pressure drops too quickly and the pressure control valve 4 is fully closed but still cannot stabilize the pressure, the nitrogen blanketing regulating valve 3 is gradually opened to assist in nitrogen replenishment, maintaining VOCs levels throughout the process. The internal pressure of main pipe 5 is in a slightly positive pressure range of 0.8-0.9 kPa to prevent outside air from seeping in due to negative pressure.

[0018] After being regulated by constant temperature and pressure, the VOCs waste gas is sent to the upper inlet of the separator 7 through the end of the VOCs main pipe 5. The waste gas flows from bottom to top in the separator 7. The hot ammonia water spray pipe 8 is installed at the upper part of the separator 7 cavity, continuously spraying hot ammonia water containing ammonia downwards. The waste gas and the hot ammonia water are in full contact in the opposite direction. The hot ammonia water removes the coal powder and coke powder solid particles carried in the waste gas through physical flushing and interception. At the same time, relying on the principle of similar solubility of naphthalene with the free ammonia component in the ammonia water, it absorbs and removes naphthalene vapor from the waste gas. The naphthalene-containing condensate containing naphthalene and impurities such as coal powder and coke powder is sent out from the liquid phase discharge port at the bottom of the separator 7 to the vent tank for unified treatment.

[0019] The clean exhaust gas, from which dust and naphthalene have been removed, is discharged from the top gas phase outlet of separator 7. The conveying path is selected according to the existing equipment configuration in the plant: when the plant is equipped with a scrubbing tower, the exhaust gas is sent into the gas pipeline before the scrubbing tower, and flows through the scrubbing tower, primary cooler, and electrostatic precipitator for further purification along with the gas flow; when the plant is not equipped with a scrubbing tower, the exhaust gas is directly sent into the gas pipeline before the primary cooler, and flows through the primary cooler and electrostatic precipitator for purification along with the gas flow, and is finally connected to the plant's coke oven gas negative pressure pipeline for unified treatment.

[0020] Using the above system and process, VOCs waste gas undergoes pre-naphthalene and pre-dust removal before being incorporated into the gas pipeline. The pipeline operates under a slight positive pressure and constant temperature throughout, effectively solving the safety hazards of naphthalene crystallization clogging the pipeline and negative pressure air intake, and ensuring the long-term stable operation of the gas purification device.

Claims

1. A pre-treatment naphthalene removal and anti-clogging VOCs recovery system, characterized in that, This system includes a Fisher pressure regulator, a nitrogen heater, a nitrogen blanketing control valve, a pressure control valve, a VOCs main pipe, tank venting gas channels, a separator, a hot ammonia spray pipe, pressure measuring points, temperature measuring points, and a steam regulating valve. The nitrogen inlet pipe connects to the Fisher pressure regulator, and the outlet of the Fisher pressure regulator connects to the nitrogen heater. The steam regulating valve is installed on the steam supply pipe of the nitrogen heater, and the outlet pipe of the nitrogen heater is connected to the VOCs main pipe via the nitrogen blanketing control valve. The heated nitrogen mixes with the exhaust gas to maintain the pipe temperature and inhibit naphthalene crystallization. Multiple tank venting gas channels are connected in parallel and then converged to the VOCs main pipe. The main VOCs pipe is equipped with pressure measuring points, temperature measuring points, and pressure control valves. The pressure measuring points are interlocked with the pressure control valve to maintain a slight positive pressure in the VOCs main pipe, and the temperature measuring points are interlocked with the steam regulating valve to maintain the pipeline temperature and inhibit naphthalene crystallization. The end pipe of the VOCs main pipe is connected to the upper air inlet of the separator. The hot ammonia water spraying pipe is installed inside the separator chamber. The spraying medium is ammonia-containing hot ammonia water. The ammonia-containing hot ammonia water comes into countercurrent contact with the waste gas to remove coal powder, coke powder, and naphthalene vapor. The gas phase outlet of the separator can be connected to the gas pipeline before the scrubbing tower or the gas pipeline before the primary cooler. A liquid phase discharge interface is set at the bottom of the separator.

2. The pre-treatment naphthalene removal and anti-clogging VOCs recovery system according to claim 1, characterized in that, The temperature measuring point can realize high and low temperature alarms. The measuring point signal is interlocked with the steam regulating valve. By adjusting the steam supply, the temperature of the nitrogen and waste gas mixture is stabilized in a temperature range that can suppress the formation of naphthalene crystals.

3. The pre-treatment naphthalene removal and anti-clogging VOCs recovery system according to claim 1, characterized in that, The pressure measuring point can realize high and low pressure alarms. The measuring point signal is interlocked with the nitrogen sealing regulating valve and the pressure control valve to maintain the internal pressure of the VOCs main pipe in the set slightly positive pressure range. Under normal working conditions, the pressure control valve is the main regulator, and when the pressure drops, the nitrogen sealing regulating valve opens to assist in nitrogen replenishment.

4. The pre-treatment naphthalene removal and anti-clogging VOCs recovery system according to claim 1, characterized in that, The hot ammonia water spraying pipe sprays ammonia-containing hot ammonia water into the separation tank. The waste gas comes into countercurrent contact with the ammonia-containing hot ammonia water. The hot ammonia water physically traps coal powder and coke powder and absorbs naphthalene vapor through the similarity between free ammonia and naphthalene.

5. The pre-treatment naphthalene removal and anti-clogging VOCs recovery system according to claim 1, characterized in that, The gas phase outlet of the separator is connected to the gas pipeline in front of the scrubbing tower. The purified waste gas flows through the scrubbing tower, primary cooler, and electrostatic precipitator for further purification along with the gas.

6. A pre-treatment naphthalene removal and anti-clogging VOCs recovery process, characterized in that, The pre-naphthalene removal and anti-clogging VOCs recovery system according to any one of claims 1-5 includes the following operating steps: S1. Collection and stabilization of exhaust gas from coking tanks: The VOCs exhaust gas generated by each coking tank is collected into the VOCs main pipe through its corresponding tank exhaust gas channel. Nitrogen is continuously introduced through the nitrogen sealing regulating valve and, in conjunction with the pressure control valve, a slight positive pressure is maintained in the gas phase inside the VOCs main pipe. S2. Nitrogen pressure regulation and heating and mixing with exhaust gas: High-pressure nitrogen is introduced into the Fisher pressure regulator to complete the pressure reduction, and low-pressure nitrogen enters the nitrogen heater for heat exchange and heating. Temperature measurement points collect pipeline temperature in real time and interlock the steam regulating valve to dynamically adjust the steam supply. The temperature-regulated nitrogen is sent into the VOCs main pipe to mix fully with the exhaust gas to maintain the pipeline temperature and inhibit naphthalene crystal precipitation. S3, VOCs main pipe pressure stabilization and control: The pressure measuring point monitors the internal pressure of the VOCs main pipe in real time. When the pressure deviates from the set range, an alarm is triggered and the pressure control valve is interlocked to adjust the opening to maintain a slight positive pressure inside the VOCs main pipe. Under normal operating conditions, the pressure control valve is the main regulator. When the pressure drops, the nitrogen sealing regulating valve opens to assist in nitrogen replenishment. S4. Hot ammonia water washing to remove coal powder and naphthalene: VOCs waste gas after constant temperature and pressure regulation is sent into the separator. Hot ammonia water spray pipe continuously sprays ammonia-containing hot ammonia water. The waste gas and hot ammonia water come into counter-current contact to remove coal powder, coke powder and naphthalene vapor from the waste gas. The liquid medium containing impurities is discharged from the bottom of the separator. S5. Purified waste gas transportation: The waste gas that has completed the removal of impurities and naphthalene is transported through the selected transportation path according to the equipment configuration of the plant. When the plant is equipped with a scrubbing tower, it is sent to the gas pipeline in front of the scrubbing tower. When the plant is not equipped with a scrubbing tower, it is sent to the gas pipeline in front of the primary cooler and finally connected to the coke oven gas negative pressure pipeline for unified treatment.

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