A method for removing solid impurities from acid gas

Abstract

This invention discloses a method for removing solid impurities from acidic gas, relating to the field of acidic gas impurity removal. Through a synergistic process of low-temperature plasma pretreatment, multi-stage gradient washing with a composite chelating agent, graded gas-liquid separation, and deep purification via membrane filtration, a stepwise and efficient removal of solid impurities is achieved. Low-temperature plasma pretreatment disrupts the adsorption membrane on the surface of solid impurities and weakens the binding force between ammonia and impurities, laying the foundation for subsequent separation. The composite chelating agent, through graded addition and dynamic replenishment, precisely captures solid impurities and ammonia at different temperature ranges. The graded cross-flow filtration of ceramic microfiltration membranes and organic ultrafiltration membranes deeply removes solid particles, effectively preventing scaling and blockage in downstream pipelines, ensuring continuous operation of the acidic gas treatment unit, and solving a key technical bottleneck restricting the stable operation of the acidic gas recovery process from refinery wastewater.

Description

Technical Field

[0001] This invention relates to acid gas impurity removal technology, specifically to a method for removing solid impurities from acid gas. Background Technology

[0002] During the operation of various refining and chemical production units in the oil refining industry, refining wastewater containing sulfides, ammonia nitrogen, and some soluble solid impurities is continuously generated. In order to achieve the resource recovery of acid gas in the wastewater and the subsequent treatment of wastewater to meet standards, the industry generally adopts distillation process to treat this type of refining wastewater. In the process of distilling and recovering acid gas, soluble solid impurities in the wastewater are easily carried out with the acid gas, eventually forming a mixed acid gas with sulfides and ammonia as the main components and mixed with soluble solid impurities.

[0003] However, when mixed acidic gas containing soluble solid impurities enters the downstream acidic gas treatment unit, the soluble solid impurities in the mixed acidic gas are easily deposited and scaled in the pipeline after undergoing oxidation under the high-temperature reaction conditions, which in turn causes blockage of the pipelines in the downstream acidic gas treatment system. This problem directly affects the continuous operation of the acidic gas treatment unit and has become the core technical problem restricting the stable and efficient operation of the entire process of acidic gas recovery from refinery wastewater. Summary of the Invention

[0004] The purpose of this invention is to provide a method for removing solid impurities from acidic gas, in order to solve the problem in the prior art that soluble solid impurities in mixed acidic gas are easily deposited and scaled in pipelines after undergoing oxidation under high-temperature reaction conditions, which in turn causes blockage of pipelines in downstream acidic gas treatment systems.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for removing solid impurities with acidic gas, comprising the following steps:

[0006] Step S1: The acidic gas containing solid impurities and ammonia generated in the oil refining and distillation process is subjected to low-temperature plasma pretreatment. The plasma bombardment destroys the adsorption film on the surface of the solid impurities and weakens the binding force between ammonia and the impurities.

[0007] Step S2: The pretreated acidic gas is introduced into a multi-stage gradient scrubbing tower, and a scrubbing liquid containing a composite chelating agent is introduced into the tower. The solid impurities and ammonia are transferred to the scrubbing liquid in steps by gradient cooling scrubbing.

[0008] Step S3: Pass the washed gas-liquid mixture through primary gravity separation and secondary centrifugal separation in sequence;

[0009] Step S4: The separated liquid phase containing impurities is subjected to membrane filtration and low-temperature distillation, and solid impurities and ammonia resources are recovered simultaneously;

[0010] Step S5: The separated gas phase is treated by a combination of high-efficiency demisting and catalytic ammonia removal before being exported to downstream equipment.

[0011] Further, step S1 includes the following steps:

[0012] Step S11: The acid gas is introduced into the buffer tank, where a built-in metal wire mesh primary filter intercepts larger solid particles with a pore size of 50-100μm. The acid gas temperature is then adjusted to 80-100℃ and the pressure is stabilized at 0.3-0.5MPa by a plate heat exchanger.

[0013] Step S12: The pretreated acidic gas is introduced into the pulsed corona plasma reaction chamber. A dual-electrode structure is adopted, with the cathode material being titanium alloy and the anode being porous stainless steel. The discharge voltage is adjusted to 20-30kV and the frequency to 1-5kHz. The residence time of the acidic gas in the reaction chamber is controlled to be 3-5s. The adsorption membrane is destroyed and the ammonia binding force is weakened by bombardment of active particles such as high-energy electrons and hydroxyl radicals.

[0014] Step S13: Real-time monitoring is performed using a laser particle size analyzer and an online ammonia concentration detector at the inlet and outlet of the reaction chamber. Stable operation is achieved when the outlet ammonia concentration is more than 30% higher than the inlet concentration and the average particle size of impurities is reduced by 15-20%. If the standard is not met, the discharge voltage ±2kV and the gas residence time ±1s are adjusted.

[0015] Further, step S2 includes the following steps:

[0016] Step S21: A vertical three-stage series washing tower is adopted, with a high temperature section of 120-130℃, a medium temperature section of 80-90℃, and a low temperature section of 40-50℃ set from top to bottom. The tower is filled with porous ceramic packing with a specific surface area ≥500m² / m³.

[0017] Step S22: Prepare a composite chelating agent of ATMP and HEDTA with a mass ratio of 3:2 and a chelating agent concentration controlled at 0.8-1.2 mol / L. The composite chelating agent is added in stages, and fresh chelating agent is added dynamically according to the monitoring results of the washing liquid turbidity ≥200 NTU and ammonia concentration ≥0.5 mol / L.

[0018] Step S23: High-pressure atomization spraying and countercurrent contact are adopted in each stage of the tower. The spraying pressure of the washing liquid is 0.6-0.8MPa, the atomization particle size is 50-100μm, and the gas-liquid volume ratio is adjusted to 1:8-1:10. A baffle plate demister is added between the medium temperature section and the low temperature section to intercept entrained droplets.

[0019] Further, step S3 includes the following steps:

[0020] Step S31: The gas-liquid mixture is introduced into a gravity separator with a volume of 5-8 m³, with an inclined baffle at an angle of 30°. The temperature inside the separator is maintained at 50-60℃ and the pressure at 0.2-0.3 MPa. The gas residence time is controlled at 10-15 s and the liquid residence time at 30-40 s. The gas-liquid density difference is used for preliminary separation.

[0021] Step S32: Introduce the pre-separated gas phase into a high-speed centrifuge at a speed of 8000-10000 r / min, with a separation factor ≥1000. A dual-chamber separation structure is adopted, with the inner chamber being the centrifugal separation zone and the outer chamber being the liquid collection zone. The speed is adjusted in real time according to the inlet air flow rate. For every 10% increase in flow rate, the speed is increased by 5% to ensure a separation efficiency ≥99.5%.

[0022] Step S33: Install a high-efficiency wire mesh demister made of polytetrafluoroethylene at the outlet of the centrifuge with a pore size of 5μm. A liquid collection tank is set at the bottom to collect entrained liquid. The differential pressure monitor is used to monitor in real time. When the inlet and outlet pressure difference is ≥0.05MPa, the nitrogen backflushing device is activated to prevent blockage. The backflushing pressure is 0.4MPa.

[0023] Further, step S4 includes the following steps:

[0024] Step S41: A graded cross-flow filtration system using ceramic microfiltration membranes and organic ultrafiltration membranes is employed. The ceramic microfiltration membrane has a pore size of 0.1-0.2 μm, a temperature resistance of ≥150℃, a filtration pressure of 0.3-0.4 MPa, and a flow rate of 2-3 m³ / h to remove solid impurities with a particle size ≥0.1 μm. The organic ultrafiltration membrane has a molecular weight cutoff of 1000-5000 Da, a filtration pressure of 0.1-0.2 MPa, and a flow rate of 1.5-2 m³ / h to remove fine colloidal impurities and chelating agent-metal ion complexes.

[0025] Step S42: The filtered solid impurities are washed three times with deionized water, dried at 120°C for 2 hours and then recovered. The membrane filtration permeate is introduced into a vacuum low-temperature distillation column.

[0026] Step S43: The vacuum cryogenic distillation column operates at a pressure of -0.08 to -0.09 MPa and a temperature of 60-70°C. The column bottom is heated by steam at a temperature of 80-90°C. The vapor phase at the top of the column is condensed into liquid ammonia by a condenser at 10-15°C. If the concentration of chelating agent in the column bottom residue is ≥0.5 mol / L, it is recycled for replenishment in the washing column; otherwise, it is subjected to harmless treatment.

[0027] Step S44: Liquid ammonia is introduced into the distillation purification tower, and the reflux ratio is adjusted to 3:1-5:1. The purified ammonia is pressurized to 1.0-1.2MPa and cooled to 20-30℃ before being reused in the oil refining distillation process.

[0028] Further, step S5 includes the following steps:

[0029] Step S51: A high-efficiency wire mesh demister is used to perform deep demisting of the gas phase. The material is polytetrafluoroethylene with a pore size of 3-5μm. The intercepted droplets are returned to the scrubbing tower.

[0030] Step S52: The demisted gas phase is introduced into the catalytic residual ammonia removal reactor. A supported copper-based catalyst is used, with γ-Al2O3 as the support and copper loading of 6-8%. The residual ammonia reacts with trace oxygen in the gas phase to generate N2 and H2O at room temperature (25-35℃) and atmospheric pressure. The catalyst bed is a fixed bed structure and the gas phase residence time is 2-3s.

[0031] Step S53: Monitor the residual ammonia content at the outlet in real time using an online ammonia concentration monitor. When the residual ammonia content is >10mg / m³, switch to the standby catalyst bed. The original bed is regenerated by purging with hot air at 120-150℃ for 30 minutes.

[0032] Step S54: Detect the treated gas phase. The residual ammonia should be ≤10mg / m³, particulate matter ≤5mg / m³, and humidity ≤5%. After confirming that the standards are met, export the gas to downstream equipment. If the standards are exceeded, emergency treatment should be carried out by activated carbon adsorption.

[0033] Furthermore, the liquid phase separated by centrifugation in step S32 is combined with the liquid phase discharged from the gravity separator and transported through a pipeline to the membrane filtration system in step 4. The liquid collected in the accumulation tank is returned to the gravity separator for recycling.

[0034] Furthermore, in S41, the ceramic microfiltration membrane and the organic ultrafiltration membrane are backwashed using deionized water. The backwashing pressure is 0.1 MPa lower than the filtration pressure, and the backwashing frequency is 10 minutes every 2 hours of operation.

[0035] Furthermore, the graded dosing in S22 specifically involves the following dosages: 40% for the high-temperature stage, 35% for the medium-temperature stage, and 25% for the low-temperature stage.

[0036] Furthermore, in S54, the activated carbon adsorption emergency treatment uses granular activated carbon with an iodine adsorption value ≥800mg / g. After adsorption saturation, it is recycled through thermal regeneration at a temperature of 180-200℃. The emergency treatment unit and the main treatment process can be automatically switched via a three-way valve.

[0037] Compared with existing technologies, the present invention provides a method for removing solid impurities from acidic gas. Through a synergistic process of low-temperature plasma pretreatment, multi-stage gradient washing with composite chelating agents, staged gas-liquid separation, and membrane filtration for deep purification, it achieves a stepwise and efficient removal of solid impurities. Low-temperature plasma pretreatment can destroy the adsorption film on the surface of solid impurities and weaken the binding force between ammonia and impurities, laying the foundation for subsequent separation. The composite chelating agent, through staged addition and dynamic replenishment, accurately captures solid impurities and ammonia at different temperature ranges. The staged cross-flow filtration of ceramic microfiltration membrane and organic ultrafiltration membrane can deeply remove solid particles, effectively avoiding scaling and blockage in downstream pipelines, ensuring the continuous operation of the acidic gas treatment unit, and solving the key technical bottleneck restricting the stable operation of the acidic gas recovery process of refinery wastewater.

[0038] While efficiently removing impurities, a complete resource recovery system for ammonia, solid impurities, and chelating agents has been established, specifically addressing the problem of resource waste in traditional processes. Through vacuum low-temperature distillation and rectification purification, the ammonia recovery rate has been significantly improved. The purified ammonia can be directly reused in the oil refining distillation process. The chelating agent in the washing liquid can be recycled and replenished after the distillation residue test meets the standards. Under the premise of ensuring process stability, both economic benefits and environmental friendliness are taken into account. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0040] Figure 1 This is a schematic diagram of the steps provided in an embodiment of the present invention. Detailed Implementation

[0041] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0042] To address the issue of soluble solid impurities in mixed acidic gases undergoing oxidation under high-temperature reaction conditions, easily depositing and forming scale in pipelines, and subsequently causing blockages in downstream acidic gas treatment systems, please refer to [link to relevant documentation]. Figure 1 The following preferred technical solutions are provided.

[0043] Example 1

[0044] This embodiment provides a method for removing solid impurities with acidic gas, the specific steps of which are as follows:

[0045] 1. Low-temperature plasma pretreatment

[0046] Acidic gas containing solid impurities and ammonia generated during the oil refining and distillation process is introduced into a buffer tank. Larger solid particles are intercepted by a built-in metal wire mesh primary filter with a pore size of 50μm. The acidic gas temperature is then adjusted to 80℃ and the pressure is stabilized at 0.3MPa by a plate heat exchanger.

[0047] The pretreated acidic gas was introduced into the pulsed corona plasma reaction chamber. The cathode was made of titanium alloy and the anode was made of porous stainless steel. The discharge voltage was adjusted to 20kV and the frequency to 1kHz, and the residence time of the acidic gas in the reaction chamber was controlled to be 3s.

[0048] Real-time monitoring using laser particle size analyzers and online ammonia concentration detectors at the inlet and outlet of the reaction chamber showed that the outlet ammonia concentration was 32% higher than the inlet concentration, and the average particle size of impurities was reduced by 15%, meeting the compliance requirements and maintaining stable operation.

[0049] 2. Multi-stage gradient washing

[0050] A vertical three-stage series scrubbing tower is adopted, with a high temperature section of 120℃, a medium temperature section of 80℃, and a low temperature section of 40℃ set from top to bottom. The tower is filled with porous ceramic packing with a specific surface area of ​​500m² / m³.

[0051] A composite chelating agent of ATMP and HEDTA was prepared with a mass ratio of 3:2 and the concentration of the chelating agent was controlled at 0.8 mol / L. The agent was added in stages, with 40% added in the high-temperature stage, 35% in the medium-temperature stage, and 25% in the low-temperature stage. Fresh chelating agent was added dynamically when the turbidity of the washing liquid reached 200 NTU and the ammonia concentration reached 0.5 mol / L.

[0052] Each stage of the tower adopts high-pressure atomization spraying and countercurrent contact. The scrubbing liquid spraying pressure is 0.6MPa, the atomization particle size is 50μm, the gas-liquid volume ratio is adjusted to 1:8, and a baffle plate demister is added between the medium temperature section and the low temperature section to intercept entrained droplets.

[0053] 3. Gas-liquid separation

[0054] The gas-liquid mixture is introduced into a gravity separator with a volume of 5m³. An inclined baffle with a 30° inclination is installed inside the separator to maintain a temperature of 50℃ and a pressure of 0.2MPa. The gas residence time is controlled to be 10s and the liquid residence time to be 30s. The gas-liquid density difference is used for preliminary separation.

[0055] The initially separated gas phase is introduced into a high-speed centrifuge with a dual-chamber separation structure. The inner chamber is the centrifugal separation zone, and the outer chamber is the liquid collection zone. The initial speed is 8000 r / min, and the separation factor is 1000. The speed is adjusted in real time according to the inlet flow rate. For every 10% increase in flow rate, the speed increases by 5%. The liquid phase after centrifugal separation is combined with the liquid phase discharged from the gravity separator and transported to the membrane filtration system.

[0056] A high-efficiency wire mesh demister made of polytetrafluoroethylene with a pore size of 5μm is installed at the outlet of the centrifuge. A liquid collection tank is installed at the bottom to collect the entrained liquid. The differential pressure is monitored in real time by a differential pressure monitor. The inlet and outlet pressure difference is 0.03MPa. The nitrogen backflushing device is not activated. The liquid collected in the liquid collection tank is returned to the gravity separator for recycling.

[0057] 4. Membrane filtration and resource recycling

[0058] A staged cross-flow filtration system using ceramic microfiltration membranes and organic ultrafiltration membranes was employed. The ceramic microfiltration membrane has a pore size of 0.1 μm, a temperature resistance of 150℃, a filtration pressure of 0.3 MPa, and a flow rate of 2 m³ / h. The organic ultrafiltration membrane has a molecular weight cutoff of 1000 Da, a filtration pressure of 0.1 MPa, and a flow rate of 1.5 m³ / h. Both membranes were backwashed online using deionized water as the backwash medium. The backwash pressure was 0.1 MPa lower than the filtration pressure, and the backwash frequency was 10 minutes every 2 hours of operation.

[0059] The filtered solid impurities were washed three times with deionized water, dried at 120°C for 2 hours, and then recovered.

[0060] The permeate from the membrane filtration is introduced into a vacuum cryogenic distillation column, operating at a pressure of -0.08 MPa and a temperature of 60°C. The column bottom is heated by steam at a temperature of 80°C. The vapor phase at the top of the column is condensed into liquid ammonia by a 10°C condenser. The concentration of chelating agent in the residual liquid at the bottom of the column is 0.5 mol / L, which is then reused for replenishment in the washing column.

[0061] Liquid ammonia is introduced into a distillation purification tower, and the reflux ratio is adjusted to 3:1. The purified ammonia is pressurized to 1.0 MPa and cooled to 20°C before being reused in the oil refining distillation process.

[0062] 5. Demisting and catalytic removal of residual ammonia

[0063] A high-efficiency wire mesh demister made of polytetrafluoroethylene is used to perform deep demisting of the gas phase. The pore size is 3μm, and the intercepted droplets are returned to the scrubbing tower.

[0064] The demisted gas phase is passed into the catalytic residual ammonia removal reactor. A supported copper-based catalyst is used, with γ-Al2O3 as the support and 6% copper loading. The residual ammonia reacts with trace oxygen in the gas phase to generate N2 and H2O at room temperature 25℃ and atmospheric pressure. The catalyst bed is a fixed bed structure with a gas phase residence time of 2s.

[0065] The residual ammonia content at the outlet was monitored in real time by an online ammonia concentration monitor. The residual ammonia content was 8 mg / m³, and the switch to the standby catalytic bed was not performed.

[0066] Step S54: The treated gas phase was tested, and the residual ammonia content was 8 mg / m³, the particulate matter content was 3 mg / m³, and the humidity was 4%, all of which met the requirements. The gas was then exported to downstream equipment.

[0067] Example 2

[0068] This embodiment provides a method for removing solid impurities with acidic gas, the specific steps of which are as follows:

[0069] 1. Low-temperature plasma pretreatment

[0070] Acidic gas containing solid impurities and ammonia generated during the oil refining and distillation process is introduced into a buffer tank. Larger solid particles are intercepted by a built-in metal wire mesh primary filter with a pore size of 75μm. The acidic gas temperature is then adjusted to 90℃ and the pressure is stabilized at 0.4MPa by a plate heat exchanger.

[0071] The pretreated acidic gas was introduced into the pulsed corona plasma reaction chamber. The cathode was made of titanium alloy and the anode was made of porous stainless steel. The discharge voltage was adjusted to 25kV and the frequency to 3kHz, and the residence time of the acidic gas in the reaction chamber was controlled to 4s.

[0072] Real-time monitoring using laser particle size analyzers and online ammonia concentration detectors at the inlet and outlet of the reaction chamber showed that the outlet ammonia concentration was 35% higher than the inlet concentration, and the average particle size of impurities was reduced by 18%, meeting the compliance requirements and maintaining stable operation.

[0073] 2. Multi-stage gradient washing

[0074] A vertical three-stage series scrubbing tower is adopted, with a high temperature section of 125℃, a medium temperature section of 85℃, and a low temperature section of 45℃ set from top to bottom. The tower is filled with porous ceramic packing with a specific surface area of ​​550m² / m³.

[0075] A composite chelating agent of ATMP and HEDTA was prepared with a mass ratio of 3:2 and the concentration of the chelating agent was controlled at 1.0 mol / L. The agent was added in stages, with 40% added in the high-temperature stage, 35% in the medium-temperature stage, and 25% in the low-temperature stage. Fresh chelating agent was added dynamically when the turbidity of the washing liquid reached 220 NTU and the ammonia concentration reached 0.6 mol / L.

[0076] Each stage of the tower adopts high-pressure atomization spraying and countercurrent contact. The scrubbing liquid spraying pressure is 0.7MPa, the atomization particle size is 75μm, the gas-liquid volume ratio is adjusted to 1:9, and a baffle plate demister is added between the medium temperature section and the low temperature section to intercept entrained droplets.

[0077] 3. Gas-liquid separation

[0078] The gas-liquid mixture is introduced into a gravity separator with a volume of 6.5 m³. An inclined baffle with a 30° inclination is installed inside the separator to maintain a temperature of 55°C and a pressure of 0.25 MPa. The gas residence time is controlled at 12 s and the liquid residence time at 35 s. The gas-liquid density difference is used for preliminary separation.

[0079] The initially separated gas phase is introduced into a high-speed centrifuge with a dual-chamber separation structure. The inner chamber is the centrifugal separation zone, and the outer chamber is the liquid collection zone. The initial speed is 9000 r / min, and the separation factor is 1200. The speed is adjusted in real time according to the inlet flow rate. For every 10% increase in flow rate, the speed increases by 5%. The liquid phase after centrifugal separation is combined with the liquid phase discharged from the gravity separator and transported to the membrane filtration system.

[0080] A high-efficiency wire mesh demister made of polytetrafluoroethylene with a pore size of 5μm is installed at the outlet of the centrifuge. A liquid collection tank is set at the bottom to collect the entrained liquid. The differential pressure is monitored in real time by a differential pressure monitor. The inlet and outlet pressure difference is 0.04MPa. The nitrogen backflushing device is not activated. The liquid collected in the liquid collection tank is returned to the gravity separator for recycling.

[0081] 4. Membrane filtration and resource recycling

[0082] A staged cross-flow filtration system using ceramic microfiltration membranes and organic ultrafiltration membranes was employed. The ceramic microfiltration membrane has a pore size of 0.15 μm, a temperature resistance of 160℃, a filtration pressure of 0.35 MPa, and a flow rate of 2.5 m³ / h. The organic ultrafiltration membrane has a molecular weight cutoff of 3000 Da, a filtration pressure of 0.15 MPa, and a flow rate of 1.75 m³ / h. Both membranes were backwashed online using deionized water as the backwash medium. The backwash pressure was 0.1 MPa lower than the filtration pressure, and the backwash frequency was 10 minutes every 2 hours of operation.

[0083] The filtered solid impurities were washed three times with deionized water, dried at 120°C for 2 hours, and then recovered.

[0084] The permeate from the membrane filtration is introduced into a vacuum cryogenic distillation column, with an operating pressure of -0.085 MPa and a temperature of 65°C. The column bottom is heated by steam at a temperature of 85°C. The vapor phase at the top of the column is condensed into liquid ammonia by a 12°C condenser. The concentration of chelating agent in the residual liquid at the bottom of the column is 0.7 mol / L, which is recycled for replenishment in the washing column.

[0085] Liquid ammonia is introduced into a distillation purification tower, and the reflux ratio is adjusted to 4:1. The purified ammonia is pressurized to 1.1 MPa and cooled to 25°C before being reused in the oil refining distillation process.

[0086] 5. Demisting and catalytic removal of residual ammonia

[0087] A high-efficiency wire mesh demister made of polytetrafluoroethylene is used to perform deep demisting of the gas phase. The pore size is 4μm, and the intercepted droplets are returned to the scrubbing tower.

[0088] The demisted gas phase is passed into a catalytic residual ammonia removal reactor. A supported copper-based catalyst is used, with γ-Al2O3 as the support and a copper loading of 7%. The residual ammonia reacts with trace amounts of oxygen in the gas phase at room temperature (30℃) and atmospheric pressure to generate N2 and H2O. The catalyst bed is a fixed bed structure with a gas phase residence time of 2.5s.

[0089] The residual ammonia content at the outlet was monitored in real time by an online ammonia concentration monitor. The residual ammonia content was 6 mg / m³, and the switch to the standby catalytic bed was not performed.

[0090] The treated gas phase was tested and found to have a residual ammonia content of 6 mg / m³, a particulate matter content of 2 mg / m³, and a humidity of 3%, all of which met the standards and were then exported to downstream equipment.

[0091] Example 3

[0092] This embodiment provides a method for removing solid impurities with acidic gas, the specific steps of which are as follows:

[0093] 1. Low-temperature plasma pretreatment

[0094] Acidic gas containing solid impurities and ammonia generated during the oil refining and distillation process is introduced into a buffer tank. Larger solid particles are intercepted by a built-in metal wire mesh primary filter with a pore size of 100μm. The acidic gas temperature is then adjusted to 100℃ and the pressure is stabilized at 0.5MPa by a plate heat exchanger.

[0095] The pretreated acidic gas was introduced into the pulsed corona plasma reaction chamber. The cathode was made of titanium alloy and the anode was made of porous stainless steel. The discharge voltage was adjusted to 30kV and the frequency to 5kHz, and the residence time of the acidic gas in the reaction chamber was controlled to be 5s.

[0096] Real-time monitoring using laser particle size analyzers and online ammonia concentration detectors at the inlet and outlet of the reaction chamber showed that the outlet ammonia concentration was 38% higher than the inlet concentration, and the average particle size of impurities was reduced by 20%, meeting the compliance requirements and maintaining stable operation.

[0097] 2. Multi-stage gradient washing

[0098] A vertical three-stage series scrubbing tower is adopted, with a high temperature section of 130℃, a medium temperature section of 90℃, and a low temperature section of 50℃ set from top to bottom. The tower is filled with porous ceramic packing with a specific surface area of ​​600m² / m³.

[0099] A composite chelating agent of ATMP and HEDTA was prepared with a mass ratio of 3:2 and the concentration of the chelating agent was controlled at 1.2 mol / L. The agent was added in stages, with 40% added in the high-temperature stage, 35% in the medium-temperature stage, and 25% in the low-temperature stage. Fresh chelating agent was added dynamically when the turbidity of the washing liquid reached 230 NTU and the ammonia concentration reached 0.7 mol / L.

[0100] Each stage of the tower adopts high-pressure atomization spraying and countercurrent contact. The scrubbing liquid spraying pressure is 0.8MPa, the atomization particle size is 100μm, the gas-liquid volume ratio is adjusted to 1:10, and a baffle plate demister is added between the medium temperature section and the low temperature section to intercept entrained droplets.

[0101] 3. Gas-liquid separation

[0102] The gas-liquid mixture is introduced into a gravity separator with a volume of 8m³. An inclined baffle with a 30° inclination is installed inside the separator to maintain a temperature of 60℃ and a pressure of 0.3MPa. The gas residence time is controlled at 15s and the liquid residence time at 40s. The gas-liquid density difference is used for preliminary separation.

[0103] The initially separated gas phase is introduced into a high-speed centrifuge with a dual-chamber separation structure. The inner chamber is the centrifugal separation zone, and the outer chamber is the liquid collection zone. The initial speed is 10,000 r / min, and the separation factor is 1500. The speed is adjusted in real time according to the inlet flow rate. For every 10% increase in flow rate, the speed increases by 5%. The liquid phase after centrifugal separation is combined with the liquid phase discharged from the gravity separator and transported to the membrane filtration system.

[0104] A high-efficiency wire mesh demister made of polytetrafluoroethylene with a pore size of 5μm is installed at the outlet of the centrifuge. A liquid collection tank is set at the bottom to collect the entrained liquid. The differential pressure is monitored in real time by a differential pressure monitor. The inlet and outlet pressure difference is 0.045MPa. The nitrogen backflushing device is not activated. The liquid collected in the liquid collection tank is returned to the gravity separator for recycling.

[0105] 4. Membrane filtration and resource recycling

[0106] A staged cross-flow filtration system using ceramic microfiltration membranes and organic ultrafiltration membranes was employed. The ceramic microfiltration membrane has a pore size of 0.2 μm, a temperature resistance of 180℃, a filtration pressure of 0.4 MPa, and a flow rate of 3 m³ / h. The organic ultrafiltration membrane has a molecular weight cutoff of 5000 Da, a filtration pressure of 0.2 MPa, and a flow rate of 2 m³ / h. Both membranes were backwashed online using deionized water as the backwash medium. The backwash pressure was 0.1 MPa lower than the filtration pressure, and the backwash frequency was 10 minutes every 2 hours of operation.

[0107] The filtered solid impurities were washed three times with deionized water, dried at 120°C for 2 hours, and then recovered.

[0108] The permeate from the membrane filtration is introduced into a vacuum cryogenic distillation column, operating at a pressure of -0.09 MPa and a temperature of 70°C. The column bottom is heated by steam at a temperature of 90°C. The vapor phase at the top of the column is condensed into liquid ammonia by a 15°C condenser. The concentration of chelating agent in the residual liquid at the bottom of the column is 0.8 mol / L, which is then reused for replenishment in the washing column.

[0109] Liquid ammonia is introduced into a distillation purification tower, and the reflux ratio is adjusted to 5:1. The purified ammonia is pressurized to 1.2 MPa and cooled to 30°C before being reused in the oil refining distillation process.

[0110] 5. Demisting and catalytic removal of residual ammonia

[0111] A high-efficiency wire mesh demister made of polytetrafluoroethylene is used to perform deep demisting of the gas phase. The pore size is 5μm, and the intercepted droplets are returned to the scrubbing tower.

[0112] The demisted gas phase is passed into the catalytic residual ammonia removal reactor. A supported copper-based catalyst is used, with γ-Al2O3 as the support and 8% copper loading. The residual ammonia reacts with trace oxygen in the gas phase to generate N2 and H2O at room temperature (35℃) and atmospheric pressure. The catalyst bed is a fixed bed structure with a gas phase residence time of 3s.

[0113] The residual ammonia content at the outlet was monitored in real time by an online ammonia concentration monitor. The residual ammonia content was 5 mg / m³, and the switch to the standby catalytic bed was not performed.

[0114] The treated gas phase was tested and found to have a residual ammonia content of 5 mg / m³, a particulate matter content of 1 mg / m³, and a humidity of 2%, all of which met the standards and were then exported to downstream equipment.

[0115] Comparative Example 1

[0116] The technical solution of Example 2 is adopted, the difference being that the pulsed corona plasma reaction treatment is omitted in step S1, and only the metal wire mesh primary filtration and temperature and pressure adjustment in step S11 are performed.

[0117] Comparative Example 2

[0118] The technical solution of Example 2 is adopted, the difference being that: in step S2, the composite chelating agent of ATMP and HEDTA is not used, only deionized water is used as the washing liquid, and there is no graded addition or dynamic replenishment.

[0119] Performance testing

[0120] The acidic gases from oil distillation and recovered products treated in Examples 1-3 and Comparative Examples 1-2 were subjected to multi-dimensional performance tests according to relevant national standards. The residual ammonia content was determined using Nessler's reagent spectrophotometry, referring to the "Emission Standard for Odor Pollutants" (GB14554-1993). Lower values ​​indicated better ammonia removal, with ≤10 mg / m³ considered compliant. Particulate matter content was determined using gravimetric analysis, referring to the "Integrated Emission Standard of Air Pollutants" (GB16297-1996). Lower values ​​indicated better solid impurity removal, with ≤5 mg / m³ considered compliant. Humidity was determined using gravimetric analysis, referring to the "Determination of Moisture Content in Gases" (GB / T5832.1-2016). The humidity of the treated gas phase is measured, with lower values ​​indicating better gas-liquid separation; ≤5% is considered acceptable. Secondly, the solid impurity recovery rate is calculated by measuring the total mass of solid impurities in the acidic gas before and after treatment, and then calculating (recovered solid impurity mass / initial solid impurity mass) × 100%. A higher value indicates better solid resource recovery. Similarly, the ammonia recovery rate is calculated by measuring the total mass of ammonia in the acidic gas before and after treatment, and the mass of recovered liquid ammonia, and then calculating (recovered ammonia mass / initial ammonia mass) × 100%. A higher value indicates better ammonia resource recovery. Finally, the scaling condition of the downstream pipeline is determined by observing the condition of the inner wall of the downstream pipeline after 1000 hours of continuous operation, categorized as "no scaling," "moderate scaling," and "significant scaling." No scaling indicates that pipeline blockage can be effectively avoided. Specific test results are shown in the table below.

[0121] Testing items Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Residual ammonia content (mg / m³) 8 6 5 25 18 Particulate matter content (mg / m³) 3 2 1 12 9 humidity(%) 4 3 2 8 7 Solid impurity recovery rate (%) 98.2 98.8 99.3 85.5 88.3 Ammonia recovery rate (%) 97.5 98.2 98.7 90.1 92.4 Downstream pipe scaling No scaling No scaling No scaling Obvious scaling Moderate scaling

[0122] As can be seen from the above test results, the acidic gas method for removing solid impurities in Examples 1-3 of the present invention has the following characteristics: the residual ammonia content in the gas phase after treatment is ≤8mg / m³, the particulate matter content is ≤3mg / m³, and the humidity is ≤4%, all of which meet the standard requirements; the solid impurity recovery rate is ≥98.2%, the ammonia recovery rate is ≥97.5%, and there is no scaling phenomenon in the downstream pipeline after continuous operation for 1000 hours, which effectively solves the problem of pipeline blockage in the prior art.

[0123] Comparative Example 1 omitted pulsed corona plasma reaction treatment, so the adsorption film on the surface of solid impurities was not destroyed, and the binding force between ammonia and impurities was not weakened, resulting in incomplete removal of particulate matter, significantly reduced recovery rates of solid impurities and ammonia, and obvious scaling in downstream pipelines. Comparative Example 2 did not use a composite chelating agent, so the washing liquid had insufficient ability to capture solid impurities and ammonia, which also led to poor treatment effect and moderate scaling in downstream pipelines.

[0124] In summary, this invention achieves efficient removal of solid impurities from acidic gas and recovery of ammonia resources through a combination of low-temperature plasma pretreatment, multi-stage gradient washing with composite chelating agents, staged gas-liquid separation, membrane filtration and low-temperature distillation recovery, and catalytic removal of residual ammonia. This avoids scaling in downstream pipelines and ensures the continuous and stable operation of the acidic gas treatment device.

[0125] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for removing solid impurities with acidic gas, characterized in that, Includes the following steps: Step S1: The acidic gas containing solid impurities and ammonia generated in the oil refining and distillation process is subjected to low-temperature plasma pretreatment. The plasma bombardment destroys the adsorption film on the surface of the solid impurities and weakens the binding force between ammonia and the impurities. Step S2: The pretreated acidic gas is introduced into a multi-stage gradient scrubbing tower, and a scrubbing liquid containing a composite chelating agent is introduced into the tower. The solid impurities and ammonia are transferred to the scrubbing liquid in steps by gradient cooling scrubbing. Step S3: Pass the washed gas-liquid mixture through primary gravity separation and secondary centrifugal separation in sequence; Step S4: The separated liquid phase containing impurities is subjected to membrane filtration and low-temperature distillation, and solid impurities and ammonia resources are recovered simultaneously; Step S5: The separated gas phase is treated by a combination of high-efficiency demisting and catalytic ammonia removal before being exported to downstream equipment.

2. The method for removing solid impurities from acidic gas according to claim 1, characterized in that, Step S1 includes the following steps: Step S11: The acid gas is introduced into the buffer tank, where larger solid particles are intercepted by the built-in metal wire mesh primary filter, and then the temperature of the acid gas is adjusted to 80-100℃ and the pressure is stabilized at 0.3-0.5MPa by the plate heat exchanger. Step S12: The pretreated acidic gas is introduced into the pulsed corona plasma reaction chamber, the discharge voltage is adjusted to 20-30kV and the frequency to 1-5kHz, and the residence time of the acidic gas in the reaction chamber is controlled to be 3-5s. Step S13: Detect the inlet and outlet of the reaction chamber. When the outlet ammonia concentration is more than 30% higher than the inlet and the average particle size of impurities is reduced by 15-20%, the operation is stable. If the standard is not met, adjust the discharge voltage ±2kV and the gas residence time ±1s.

3. The method for removing solid impurities from acidic gas according to claim 1, characterized in that, Step S2 includes the following steps: Step S21: A vertical three-stage series washing tower is adopted, with a high temperature section of 120-130℃, a medium temperature section of 80-90℃, and a low temperature section of 40-50℃ set from top to bottom. The tower is filled with porous ceramic packing with a specific surface area ≥500m² / m³. Step S22: Prepare a composite chelating agent of ATMP and HEDTA with a mass ratio of 3:2 and a chelating agent concentration controlled at 0.8-1.2 mol / L. The composite chelating agent is added in stages, and fresh chelating agent is added dynamically according to the monitoring results of the washing liquid turbidity ≥200 NTU and ammonia concentration ≥0.5 mol / L. Step S23: High-pressure atomization spraying and countercurrent contact are adopted in each stage of the tower. The spraying pressure of the washing liquid is 0.6-0.8MPa, the atomization particle size is 50-100μm, and the gas-liquid volume ratio is adjusted to 1:8-1:

10. A baffle plate demister is added between the medium temperature section and the low temperature section to intercept entrained droplets.

4. The method for removing solid impurities from acidic gas according to claim 1, characterized in that, Step S3 includes the following steps: Step S31: The gas-liquid mixture is introduced into a gravity separator with a volume of 5-8 m³, with an inclined baffle at an angle of 30°. The temperature inside the separator is maintained at 50-60℃ and the pressure at 0.2-0.3 MPa. The gas residence time is controlled at 10-15 s and the liquid residence time at 30-40 s. The gas-liquid density difference is used for preliminary separation. Step S32: Introduce the pre-separated gas phase into a high-speed centrifugal separator, and adjust the rotation speed in real time according to the inlet flow rate. For every 10% increase in flow rate, the rotation speed is increased by 5%. Step S33: Install a high-efficiency wire mesh demister made of polytetrafluoroethylene at the outlet of the centrifugal separator, and set up a liquid collection tank at the bottom to collect the entrained liquid.

5. The method for removing solid impurities from acidic gas according to claim 1, characterized in that, Step S4 includes the following steps: Step S41: A graded cross-flow filtration system using ceramic microfiltration membranes and organic ultrafiltration membranes is employed. The ceramic microfiltration membrane has a pore size of 0.1-0.2 μm, a temperature resistance of ≥150℃, a filtration pressure of 0.3-0.4 MPa, and a flow rate of 2-3 m³ / h. The organic ultrafiltration membrane has a molecular weight cutoff of 1000-5000 Da, a filtration pressure of 0.1-0.2 MPa, and a flow rate of 1.5-2 m³ / h. Step S42: The filtered solid impurities are washed three times with deionized water, dried at 120°C for 2 hours and then recovered. The membrane filtration permeate is introduced into a vacuum low-temperature distillation column. Step S43: The vacuum cryogenic distillation column operates at a pressure of -0.08 to -0.09 MPa and a temperature of 60-70℃. The column bottom is heated by steam. The vapor phase at the top of the column is condensed into liquid ammonia by a condenser at 10-15℃. If the concentration of chelating agent in the column bottom residue is ≥0.5mol / L, it is recycled for replenishment in the washing column. Step S44: Liquid ammonia is introduced into the distillation purification tower, and the reflux ratio is adjusted to 3:1-5:

1. The purified ammonia is pressurized to 1.0-1.2MPa and cooled to 20-30℃ before being reused in the oil refining distillation process.

6. The method for removing solid impurities with acidic gas according to claim 1, characterized in that, Step S5 includes the following steps: Step S51: The gas phase is deeply demisted by a high-efficiency wire mesh demister, and the intercepted droplets are returned to the scrubbing tower; Step S52: The demisted gas phase is introduced into the catalytic residual ammonia removal reactor. A supported copper-based catalyst is used to catalyze the reaction of residual ammonia with trace amounts of oxygen in the gas phase to generate N2 and H2O at room temperature (25-35℃) and atmospheric pressure. The catalyst bed is a fixed bed structure and the gas phase residence time is 2-3 seconds. Step S53: Monitor the residual ammonia content at the outlet in real time using an online ammonia concentration monitor. When the residual ammonia content is >10mg / m³, switch to the standby catalyst bed. The original bed is regenerated by purging with hot air at 120-150℃ for 30 minutes. Step S54: Detect the treated gas phase. If it meets the standard, export it to downstream equipment. If it exceeds the standard, perform emergency treatment by activated carbon adsorption.

7. The method for removing solid impurities from acidic gas according to claim 4, characterized in that, In step S32, the liquid phase separated by centrifugation is combined with the liquid phase discharged from the gravity separator, and the liquid collected in the accumulation tank is returned to the gravity separator for recycling.

8. The method for removing solid impurities with acidic gas according to claim 5, characterized in that, In S41, the ceramic microfiltration membrane and the organic ultrafiltration membrane are backwashed using deionized water. The backwashing pressure is 0.1 MPa lower than the filtration pressure, and the backwashing frequency is 10 minutes every 2 hours of operation.

9. The method for removing solid impurities from acidic gas according to claim 3, characterized in that, Specifically, the graded dosing in S22 is as follows: the dosing amount in the high-temperature stage accounts for 40% of the total amount, the dosing amount in the medium-temperature stage accounts for 35% of the total amount, and the dosing amount in the low-temperature stage accounts for 25% of the total amount.

10. The method for removing solid impurities from acidic gas according to claim 6, characterized in that, The activated carbon adsorption emergency treatment in S54 uses granular activated carbon, which is recycled through thermal regeneration after adsorption saturation.

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