A Review of Research on Vapour Recovery Technology 3

The absorption method separates oil and gas components based on differences in their solubility in the absorbent, separating the light hydrocarbon components that are easily soluble in the absorbent from the other components that are difficult to dissolve, thereby achieving oil and gas recovery. It is suitable for treating high-concentration, medium-flow oil and gas recovery [47-48]. This method can recover useful oil and gas components, but may face challenges in selecting the appropriate absorbent and may result in

secondary pollution issues. In absorption method research, the regeneration efficiency of the absorbent significantly impacts the method's efficiency, economic costs, and the stability and safety of the production process. Currently, various absorbent regeneration methods are being

studied and applied. Zheng Zongneng et al. introduced commonly used regeneration methods for absorbents, including heating desorption, vacuum desorption, ultrasonic desorption, negative pressure desorption, and microwave radiation desorption, as well as integrated regeneration methods combining heating and vacuum, microwave heating and vacuum, ultrasonic and vacuum, and ultrasonic and microwave. Research has found that method integration often improves regeneration efficiency, further confirming the importance of optimizing regeneration methods for enhancing absorption method performance.

Numerous scholars have conducted research on optimizing absorption process flows, selecting appropriate absorbents, and determining optimal operating parameters, achieving a series of significant results. Liao Changjian et al. utilized ASPEN PLUS software to conduct an in-depth analysis of the low-temperature diesel absorption process for oil and gas, optimizing multiple parameters including temperature, pressure, liquid-to-gas ratio, packing layer height, and diesel properties. After optimization, the total hydrocarbon recovery rate of the exhaust gas exceeded 95%. Li Yuzhong et al. constructed a pressurized absorption process flow and found that pressurized absorption effectively improves absorption efficiency and reduces outlet concentration. When pressurized to 0.2 MPa, the absorption effect was optimal. Niu Ruiping et al. pointed out that optimizing the absorption process flow, reducing the absorption liquid concentration, and selecting appropriate absorption liquids all contribute to improving absorption efficiency. Cai Yawen [54] conducted an optimized design of the absorption recovery process. Experimental studies revealed that the influence of three factors-absorbent type, absorption liquid spray volume, and crude oil vapor temperature-on crude oil vapor absorption gradually decreases. The selection of absorbents must comprehensively consider factors such as their solubility in oil vapors, regeneration performance, cost implications, and secondary pollution. These multiple factors limit the selection of absorbent materials and their widespread application. Research on absorption methods will focus on developing new, efficient, environmentally friendly, and economical absorbents, studying more effective regeneration technologies to reduce costs and pollution, exploring methods for integrated treatment of low-concentration oil and gas with other technologies, and expanding the scope of application.

Membrane separation is a physical separation method that utilizes the preferential permeability of specific polymer membrane materials to oil and gas molecules. By creating a pressure difference across the membrane, hydrocarbon molecules that are easily soluble in the membrane migrate from the high-pressure side to the low-pressure side, while air components are retained on the membrane surface due to their inability to pass through, thereby achieving effective separation of organic compounds from air. Membrane separation technology offers advantages such as low energy consumption, compact footprint, simple operation, and no secondary pollution, making it suitable for recovering oil and gas of varying concentrations and flow rates.

Membrane separation technology is increasingly applied in the field of oil and gas recovery. Zheng Fei et al. conducted a comparative analysis of two common membrane separation technologies-spiral-wound and stacked-and found that both technologies feature simple operation, straightforward process flows, stable performance, and high treatment efficiency, making them suitable for gas stations with low oil and gas evaporation rates or limited space. Shen Yunhui studied the principles, process flow, and recovery efficiency of membrane-based recovery technology. The results showed that membrane technology demonstrates broad applicability and high efficiency in the recovery of "three benzenes" oil and gas in the refining and chemical industries. Li Hongwei et al. addressed the issues of high water content in the absorbent and high absorbent temperature in summer

, designed a low-temperature critical absorption technology to address the high temperature issue, replaced the mist eliminator at the top of the absorption tower, and added a water separation filter before the membrane to resolve the high moisture content issue. This resulted in lower exhaust gas emission concentrations and oil vapor recovery rates exceeding 95%. The selection and development of separation membrane materials are key research focuses in membrane separation technology. Currently, new membrane materials are continuously emerging, significantly driving the advancement of membrane separation technology. Suo Jizhan et al., Zhou Shiyi, and Gao Feng introduced the principles of permeation vaporization membrane separation technology and its applications in the petrochemical industry, highlighting its advantages of simple process, high economic efficiency, and strong stability. Wei Xin et al. conducted experiments using high-polymer membranes with polyvinylidene fluoride flat sheets as the base membrane, introducing inorganic particles into the modified polydimethylsiloxane functional layer to enhance separation performance for aromatic hydrocarbons. When treating process exhaust gas with high concentration fluctuations and high load conditions, this technology can stably control the mass concentration of non-methane total hydrocarbons below 80 mg/m³, while the mass concentrations of benzene, toluene, and xylene are below 4, 15, and 20 mg/m³, respectively, meeting emission standards. Yang Chengcheng participated in the development of a perfluorinated AF glassy material composite membrane, which can meet the emission requirements of gas stations for small treatment volumes and mixed gases with an inlet oil gas volume fraction of 10% to 30%.

Many scholars have conducted in-depth studies on the factors affecting the recovery efficiency of membrane separation technology and have clearly identified that factors such as temperature, pressure, and feed concentration have a significant impact on recovery efficiency. By precisely controlling these factors, the recovery effect can be optimized. Xie Lingling et al. pointed out that increased environmental temperature causes membrane separation units to operate beyond capacity, leading to emissions exceeding standards, which can be addressed by adding more membrane separation units. Lu Yongliang and Liu Yuwei explored the key factors influencing membrane technology in oil and gas recovery, finding that by precisely controlling temperature, pressure, and feed concentration, membrane technology can effectively enhance oil and gas recovery rates. Jia Qiongqing analyzed that the separation rate of organic hydrocarbons can be improved by increasing the membrane permeability of VOC components and increasing the pressure difference before and after the membrane. Under the premise of meeting emission standards, the exhaust volume of oil and gas vapor can be appropriately increased, and the inlet pressure of the membrane can be increased to improve the separation efficiency of the membrane.

Currently, membrane separation technology faces technical challenges such as high costs, membrane material selectivity and stability, and membrane cleaning and replacement [68]. Membrane separation technology should continue to develop low-cost, high-selectivity, and high-stability membrane materials, reduce costs, and improve performance through innovative preparation processes and optimized formulations. Simultaneously, efficient membrane cleaning and maintenance technologies should be developed to effectively remove pollutants, extend membrane lifespan, and reduce downtime.

The absorption method separates oil and gas components based on differences in their solubility in the absorbent, separating the light hydrocarbon components that are easily soluble in the absorbent from the other components that are difficult to dissolve, thereby achieving oil and gas recovery. It is suitable for treating high-concentration, medium-flow oil and gas recovery [47-48]. This method can recover useful oil and gas components, but may face challenges in selecting the appropriate absorbent and may result in

secondary pollution issues. In absorption method research, the regeneration efficiency of the absorbent significantly impacts the method's efficiency, economic costs, and the stability and safety of the production process. Currently, various absorbent regeneration methods are being

studied and applied. Zheng Zongneng et al. introduced commonly used regeneration methods for absorbents, including heating desorption, vacuum desorption, ultrasonic desorption, negative pressure desorption, and microwave radiation desorption, as well as integrated regeneration methods combining heating and vacuum, microwave heating and vacuum, ultrasonic and vacuum, and ultrasonic and microwave. Research has found that method integration often improves regeneration efficiency, further confirming the importance of optimizing regeneration methods for enhancing absorption method performance.

Numerous scholars have conducted research on optimizing absorption process flows, selecting appropriate absorbents, and determining optimal operating parameters, achieving a series of significant results. Liao Changjian et al. utilized ASPEN PLUS software to conduct an in-depth analysis of the low-temperature diesel absorption process for oil and gas, optimizing multiple parameters including temperature, pressure, liquid-to-gas ratio, packing layer height, and diesel properties. After optimization, the total hydrocarbon recovery rate of the exhaust gas exceeded 95%. Li Yuzhong et al. constructed a pressurized absorption process flow and found that pressurized absorption effectively improves absorption efficiency and reduces outlet concentration. When pressurized to 0.2 MPa, the absorption effect was optimal. Niu Ruiping et al. pointed out that optimizing the absorption process flow, reducing the absorption liquid concentration, and selecting appropriate absorption liquids all contribute to improving absorption efficiency. Cai Yawen [54] conducted an optimized design of the absorption recovery process. Experimental studies revealed that the influence of three factors-absorbent type, absorption liquid spray volume, and crude oil vapor temperature-on crude oil vapor absorption gradually decreases. The selection of absorbents must comprehensively consider factors such as their solubility in oil vapors, regeneration performance, cost implications, and secondary pollution. These multiple factors limit the selection of absorbent materials and their widespread application. Research on absorption methods will focus on developing new, efficient, environmentally friendly, and economical absorbents, studying more effective regeneration technologies to reduce costs and pollution, exploring methods for integrated treatment of low-concentration oil and gas with other technologies, and expanding the scope of application.

Membrane separation is a physical separation method that utilizes the preferential permeability of specific polymer membrane materials to oil and gas molecules. By creating a pressure difference across the membrane, hydrocarbon molecules that are easily soluble in the membrane migrate from the high-pressure side to the low-pressure side, while air components are retained on the membrane surface due to their inability to pass through, thereby achieving effective separation of organic compounds from air. Membrane separation technology offers advantages such as low energy consumption, compact footprint, simple operation, and no secondary pollution, making it suitable for recovering oil and gas of varying concentrations and flow rates.

Membrane separation technology is increasingly applied in the field of oil and gas recovery. Zheng Fei et al. conducted a comparative analysis of two common membrane separation technologies-spiral-wound and stacked-and found that both technologies feature simple operation, straightforward process flows, stable performance, and high treatment efficiency, making them suitable for gas stations with low oil and gas evaporation rates or limited space. Shen Yunhui studied the principles, process flow, and recovery efficiency of membrane-based recovery technology. The results showed that membrane technology demonstrates broad applicability and high efficiency in the recovery of "three benzenes" oil and gas in the refining and chemical industries. Li Hongwei et al. addressed the issues of high water content in the absorbent and high absorbent temperature in summer

, designed a low-temperature critical absorption technology to address the high temperature issue, replaced the mist eliminator at the top of the absorption tower, and added a water separation filter before the membrane to resolve the high moisture content issue. This resulted in lower exhaust gas emission concentrations and oil vapor recovery rates exceeding 95%. The selection and development of separation membrane materials are key research focuses in membrane separation technology. Currently, new membrane materials are continuously emerging, significantly driving the advancement of membrane separation technology. Suo Jizhan et al., Zhou Shiyi, and Gao Feng introduced the principles of permeation vaporization membrane separation technology and its applications in the petrochemical industry, highlighting its advantages of simple process, high economic efficiency, and strong stability. Wei Xin et al. conducted experiments using high-polymer membranes with polyvinylidene fluoride flat sheets as the base membrane, introducing inorganic particles into the modified polydimethylsiloxane functional layer to enhance separation performance for aromatic hydrocarbons. When treating process exhaust gas with high concentration fluctuations and high load conditions, this technology can stably control the mass concentration of non-methane total hydrocarbons below 80 mg/m³, while the mass concentrations of benzene, toluene, and xylene are below 4, 15, and 20 mg/m³, respectively, meeting emission standards. Yang Chengcheng participated in the development of a perfluorinated AF glassy material composite membrane, which can meet the emission requirements of gas stations for small treatment volumes and mixed gases with an inlet oil gas volume fraction of 10% to 30%.

Many scholars have conducted in-depth studies on the factors affecting the recovery efficiency of membrane separation technology and have clearly identified that factors such as temperature, pressure, and feed concentration have a significant impact on recovery efficiency. By precisely controlling these factors, the recovery effect can be optimized. Xie Lingling et al. pointed out that increased environmental temperature causes membrane separation units to operate beyond capacity, leading to emissions exceeding standards, which can be addressed by adding more membrane separation units. Lu Yongliang and Liu Yuwei explored the key factors influencing membrane technology in oil and gas recovery, finding that by precisely controlling temperature, pressure, and feed concentration, membrane technology can effectively enhance oil and gas recovery rates. Jia Qiongqing analyzed that the separation rate of organic hydrocarbons can be improved by increasing the membrane permeability of VOC components and increasing the pressure difference before and after the membrane. Under the premise of meeting emission standards, the exhaust volume of oil and gas vapor can be appropriately increased, and the inlet pressure of the membrane can be increased to improve the separation efficiency of the membrane.

Currently, membrane separation technology faces technical challenges such as high costs, membrane material selectivity and stability, and membrane cleaning and replacement [68]. Membrane separation technology should continue to develop low-cost, high-selectivity, and high-stability membrane materials, reduce costs, and improve performance through innovative preparation processes and optimized formulations. Simultaneously, efficient membrane cleaning and maintenance technologies should be developed to effectively remove pollutants, extend membrane lifespan, and reduce downtime.