The oil gas recovery process employs the principle of condensation plus pressure swing adsorption: condensation utilizes refrigeration technology to extract the heat from oil and gas, achieving a direct conversion of oil and gas components from the gaseous phase to the liquid phase. By utilizing the vapor pressure differences of hydrocarbon substances at different temperatures, cooling down the oil and gas causes some hydrocarbon vapors to reach a supersaturated state, where the supersaturated vapor condenses into a liquid, enabling the recovery of oil and gas. Generally, a multi-stage continuous cooling method is used to lower the temperature of the oil and gas, allowing it to condense into a liquid for recovery. The low temperature of the condensation unit is determined based on the composition of the volatile gases, the required recovery rate, and the concentration limits of organic compounds in the exhaust gases released into the atmosphere. The condensation is typically achieved through pre-cooling and mechanical refrigeration steps. The pre-cooling stage is designed to reduce the operating energy consumption of the recovery unit, lowering the temperature of the incoming gas from ambient to approximately 5°C, causing most of the water vapor in the gas to condense into water and remove moisture. After pre-cooling, the oil and gas enter the shallow cooling stage, where the gas temperature can be cooled to around -35°C, allowing 70-80% of the hydrocarbon components in the oil and gas to liquefy. Post-shallow cooling, the oil and gas move into the deep cooling stage, where they can be cooled to around -70°C, enabling the recovery of over 95% of the oil and gas.

- After condensation at -70°C, the residual gas still contains a small amount of hydrocarbon components, which does not meet the national standard's emission limits. To achieve standard emissions by solely using condensation for oil and gas treatment, the temperature must be reduced to approximately -110°C, resulting in only a 3-4% increase in recovery, but with an approximately 30% increase in energy consumption, making it highly cost-ineffective. Therefore, for the residual gas after -70°C, the process of pressure swing adsorption is employed, introducing it into an activated carbon adsorption unit for adsorption. After enrichment and concentration, the gas is then condensed for further treatment to meet the tail gas emission standards. When the adsorber becomes saturated, a vacuum pump is used to evacuate the adsorber, reducing the internal pressure, disrupting the adsorption equilibrium, and releasing the adsorbed oil and gas from the adsorber. These are then sent through the vacuum pump to the front of the condensation process for additional condensation and recovery.

In reality, VOCs emissions occur in two states: one is low flow with high concentration (flow below 2000 m³/h, concentration above 500 g/m³), and the other is high flow with low concentration (flow between 2000 and tens of thousands of m³/h, concentration in the low g/m³ range or less). For the former emission state, a "condensation + adsorption" process is used, first condensing and liquefying for recovery; for the latter, an "adsorption + condensation" process is applied, initially using an adsorbent to concentrate hydrocarbon components, allowing for the release of a large amount of air, and then desorbing the concentrated hydrocarbon components to obtain enriched organic gas, which is then condensed and liquefied for recovery. Since the oil storage and transportation process primarily falls into the former emission state and treatment method, commonly referred to as oil vapor recovery, we will mainly introduce the "condensation + adsorption" process here. As the adsorption process uses pressure swing adsorption, it is also known as the "condensation + pressure swing adsorption" process.

This concludes the information on VOCs recovery compiled by the editor at Heze Huawang Technology & Trade Co., Ltd. We hope this information has been helpful to you.