A Review of Research on Vapour Recovery Technology 4

As requirements for oil and gas recovery efficiency, emission standards, safety, and economic viability continue to rise, research and application of oil and gas recovery technology are evolving toward more efficient, cost-effective, and integrated solutions. Single-technology approaches are increasingly inadequate to meet these demands. Two-stage or multi-stage integrated processes developed from these recovery technologies can combine the advantages of multiple techniques, ensuring operational safety while reducing costs and meeting increasingly stringent emission standards. Currently, two-stage integrated processes include condensation + adsorption, condensation + membrane separation, and absorption + adsorption. In addition to these two-stage integrated processes, multi-stage integrated processes are also continuously developing. Multi-stage oil and gas recovery technology utilizes the characteristics of different technologies for treating oil and gas of varying concentrations, with high-concentration oil and gas undergoing different treatment stages sequentially to achieve high-efficiency recovery and utilization. Compared to single-stage or two-stage recovery technologies, multi-stage oil and gas recovery technology offers significant advantages in terms of technological diversity, and also allows for greater flexibility in technology selection during actual production and use. Currently, multi-stage integrated processes include condensation + membrane separation + adsorption, condensation + adsorption + catalytic combustion, and condensation + absorption + adsorption, among others. However, due to the limited research on multi-stage integrated processes, which are mostly in the experimental research or preliminary application stage, there is a lack of systematic data and mature case studies to support a comprehensive review. In the future, as research deepens and technology matures, multi-stage integrated processes are expected to find broader application in the oil and gas recovery field. The following will focus on two-stage integrated processes.

The condensation method + adsorption method oil and gas recovery process has been widely applied in gas stations. This integrated process leverages the stable and efficient characteristics of the condensation method when handling high-concentration oil and gas, while the adsorption method can control the oil and gas volume fraction within a very low range. This avoids the issues associated with using the two technologies separately, such as the high costs and operational expenses of condensation technology, as well as safety concerns when using adsorption technology to handle high-concentration gases. Chen Yunfeng and Li Zhezhen both pointed out that after the application of the condensation-adsorption integrated process oil and gas recovery system at gas stations, it can reduce oil and gas losses, environmental pollution, and initial investment while improving the safety and reliability of gas stations. The current condensation + adsorption oil and gas recovery process is a highly efficient recovery method. Research on this process holds significant value for improving energy efficiency and oil and gas recovery rates. Numerous scholars have conducted in-depth studies through simulation and experimentation, aiming to optimize the process equipment. Research indicates that this process can achieve oil and gas recovery rates of 99% or higher. Huang Weiqiu et al. studied the condensation method + adsorption method oil and gas treatment technology using Aspen simulation software and experimental methods, finding that this technology can achieve a 99.2% oil and gas recovery rate, with exhaust gas mass concentration controlled at 11.2 g/m³. Fu Suhong et al. developed an oil and gas recovery device utilizing an integrated condensation and resin adsorption recovery process. In practical applications, the mass concentration of emitted oil and gas can be reduced to below 5 g/m³, with a recovery rate of 99%, and energy consumption is 10% lower than that of similar products. Shi Li et al. proposed an integrated oil and gas condensation and adsorption recovery process and validated its recovery efficiency through simulation and experimental studies. The device achieves an oil and gas recovery rate of 99%, with the mass concentration of oil and gas at the outlet below 7.7 g/m³, meeting the standards. Jing Haibo et al. developed an integrated oil and gas recovery system combining condensation, adsorption, catalytic combustion, and ammonia water absorption refrigeration technologies. Research indicates that the recovery rate and energy consumption of the system decrease as the secondary condensation temperature increases, with energy consumption reduced by approximately 30% compared to traditional condensation-adsorption processes, and the recovery rate decreasing by approximately 2%. Zhang Yanxin optimized the condensation temperature in the activated carbon adsorption-condensation recovery process parameters. After optimization, the pre-cooler temperature was set to 0°C, the first-stage condenser temperature to -20°C, and the second-stage condenser temperature to -45°C, achieving an oil and gas recovery rate of 99%. Zhang Lu developed a combined oil and gas recovery device using activated carbon adsorption and a -40°C low-temperature condensation method. After using this device, the recovery rate of ambient temperature light diesel oil was calculated to exceed 95%. Xu Dongsheng et al. proposed a cold cascade-type three-stage condensation adsorption combined oil and gas recovery device. By utilizing the residual heat from the third stage to cool the pre-cooler, designing the first-stage cold box with A and B stages in a 1-to-1 standby configuration, and adding a cascade compression refrigeration system, they achieved optimized temperature control. Operational results showed that the oil and gas recovery rate reached 98.80%, the exhaust gas emission concentration was reduced to 11.415 g/m³, and energy consumption decreased from 145 kW/h to 130 kW/h. Su Lushu et al. applied a combined oil and gas recovery process of "desulfurization + condensation + adsorption" during oil and gas loading, finding that it could achieve on-site emission of exhaust gas after meeting emission standards. Pan Taixing et al. analyzed the condensation method + adsorption method recovery process and concluded that this process not only demonstrates excellent performance in efficient emission control,but also has certain advantages in comprehensive exhaust gas treatment, resource recovery and energy conservation, reduction of gas loss, and safety and reliability. In actual application, the synergistic optimization of condensation and adsorption processes is challenging, and the two processes are difficult to achieve optimal matching, limiting the overall improvement in recovery efficiency. Existing process equipment lacks adaptability when handling oil and gas under different operating conditions, and recovery efficiency becomes unstable when oil and gas concentrations fluctuate significantly. Gong Zhonghao conducted research on the condensation method + adsorption method oil and gas recovery process currently in use on the market and identified existing issues. Currently, the condensation temperature for this process on the market generally exceeds -80°C, leading to a gradual increase in the concentration of C3 components at the outlet; the vacuum extraction capacity of the adsorption section is insufficient, making it difficult for the adsorbent to achieve effective desorption; and the small activated carbon adsorption tanks at the rear end cannot meet the treatment requirements for low-concentration organic compounds after condensation at the front end. Future research should focus on in-depth exploration of the coupling mechanism between condensation and adsorption, and the development of modular, intelligent equipment to enhance adaptability to different operating conditions.