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Factors affecting the gas separation membrane separation process: 1. Effect of membrane area on the separation process – The larger the membrane area, the lower the concentration of the permeate gas, and the greater the flow rate of the permeate gas; consequently, the recovery rate is higher. 2. The influence of the separation coefficient on the separation process: At a constant gas production rate, the higher the separation coefficient of the membrane module, the higher the concentration of the permeate gas, and the larger the membrane area required for the membrane module. Once the separation coefficient reaches a certain value, it has little effect on the concentration of the permeate gas. When the separation coefficient is high, the separation process is mainly completed in the first half of the separator. Therefore, in the separator, the first half completes the concentration process, while the second half is primarily aimed at increasing the recovery rate. When the feed gas flow rate, feed gas concentration, pressure on the feed side, pressure on the permeate side, and permeate gas concentration remain constant, as the separation coefficient increases, the recovery rate that can be achieved by the system rises, while the required membrane area increases. From an economic perspective in engineering, the membrane separation process has its own optimal operating conditions. When the concentration of the product gas remains constant, even if the separation efficiency of the membrane module improves significantly, the increase in recovery rate will lead to a sharp rise in the system cost. 3. The effect of temperature on the separation process: An increase in temperature greatly accelerates the penetration process. As the temperature increases, the movement speed of molecules accelerates, and the vibration frequency as well as the amplitude of vibration of the polymer chain segments in the membrane increase. As a result, molecules can pass through the membrane more quickly and easily. However, the increased vibration amplitude of the polymer chain segments reduces the membrane’s ability to selectively allow certain gas molecules to pass through, that is, the separation coefficient decreases. Generally, as the temperature increases, the ultimate result is a significant increase in the recovery rate and a decrease in the concentration of the permeate gas. 4. Effect of pressure difference on the separation process: Since the driving force for the osmosis process is the pressure difference between the gas molecules on both sides of the membrane, an increase in pressure difference enhances this driving force, resulting in an increase in the volume of the product gas. At the same time, the concentration of the product gas also increases slightly. What was mentioned above refers to the positive pressure difference. In membrane design, the membranes are made very thin in order to reduce the resistance to gas molecule permeation through them. At the same time, to meet the requirements regarding their pressure resistance in practical applications, a support layer with a looser structure is added beneath the membrane. When subjected to positive pressure, the membrane is supported by this layer and thus not damaged. However, when faced with negative pressure, the membrane is prone to damage. 5. Influence of pressure ratio on the separation process: An increase in the pressure ratio will directly lead to an increase in the concentration of the product gas. In the membrane separation process, the pressure ratio is very important; operating under conditions with a higher pressure ratio yields better separation results. However, once the pressure ratio exceeds 6, its significance diminishes. As a qualitative understanding, increasing the pressure ratio is similar to increasing the membrane’s separation coefficient, while increasing the pressure difference is similar to increasing the membrane’s permeability coefficient. 6. Effect of raw gas flow rate on the separation process: The higher the flow rate of the raw gas, the higher the concentration of the permeate gas and the greater the total amount of hydrogen that can be recovered. However, the recovery rate decreases. In this case, if the concentration of the permeate gas is higher than the required concentration for the product gas, it is possible to increase the number of membrane modules in order to improve the recovery rate; other methods such as raising the operating temperature or increasing the pressure difference can also be employed. But if the concentration of the permeate gas is not higher than the required level, then increasing the recovery rate can only be achieved by increasing the pressure difference or pressure ratio. When the flow rate of the feed gas decreases, reducing the number of membrane modules is a good approach to maintain the concentration of the permeate gas and maximize the performance of the membrane modules. 7. Influence of operating conditions on exhaust gas condensation: In refineries, exhaust gas condensation has a significant impact on the performance of membrane modules; therefore, it is discussed separately here. The fewer the poorly condensable gas components such as hydrogen in the exhaust gas, the higher the partial pressure of the easily condensable gases such as C4+, and the greater the likelihood that they will condense on the membrane surface. And these C4+ condensates cause severe damage to the membrane; therefore, it is essential to prevent C4+ from condensing inside the membrane module during operation. The following are the main factors that cause condensation of exhaust gases within the membrane module: (1) An increase in the C4+ concentration in the feed gas. ⑵The flow rate of the feed gas decreases. ⑶The number of membrane modules increases. ⑷The pressure of the feed gas increases. ⑸The permeate gas pressure decreases. ⑹The temperature of the feed gas increases. All of the above 6 factors can lead to the condensation of exhaust gases within the membrane module; therefore, when such situations occur, it is necessary to conduct a comprehensive analysis of the components of the exhaust gases, and determine whether condensation will take place within the membrane module by calculating the dew point. If exhaust gases condense inside the membrane module, we can avoid this by reducing the number of membrane modules.