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Oil and gas recovery is an energy-saving and environmentally friendly new technology. It utilizes this technology to capture the oil and gas emitted during storage, transportation, and loading/unloading processes, thereby preventing air pollution caused by the evaporation of such gases and eliminating potential safety hazards. By improving the efficiency of energy utilization, it reduces economic losses and thus yields significant benefits. Common methods include systems such as adsorption, absorption, condensation, and membrane separation. The function of the oil and gas recovery system in tank trucks is to achieve fully enclosed gas recovery during the loading and unloading process of tank trucks, thereby preventing oil and gas from being released into the atmosphere. That is, the oil transfer pipes and vapor recovery pipes between the oil tank truck and the oil storage tank form a sealed vapor recovery pipeline. While the tank truck unloads oil through the unloading pipeline, the oil and gas in the gas station’s tanks return to the tank truck via the return pipeline. The tank truck transports the oil and gas back to the oil depot for processing, thereby achieving oil and gas recovery. When oil is introduced, fluctuations in the oil level can increase the evaporation and leakage of oil and gas; therefore, the oil injection pipe must extend below the oil level to minimize disturbances in it. The opening of the oil and vapor recovery pipe is equipped with special devices for opening it; only when the oil and vapor recovery pipeline of the tank truck is properly connected to the oil tank does the recovery port open, while the exhaust pipe closes, allowing the oil and vapor in the oil tank to be completely returned to the tank truck through the recovery port. Oil and gas recovery at oil depots refers to the process of collecting the volatile oil and gas from oil depots as well as that released during loading via transfer pipes. This collected gas is then treated using one or a combination of methods such as absorption, adsorption, or condensation, either to reduce pollution caused by this gas or to convert it from a gaseous state to a liquid state, thereby turning it back into gasoline for reuse. The 5 commonly used methods currently, along with their advantages and disadvantages. 1. The adsorption method utilizes the varying adsorption capacity of adsorbents such as activated carbon, silica gel, or active fibers to separate oil and gas from air. The oil and gas pass through adsorbents such as activated carbon; the components of the oil and gas get adsorbed on the surface of these adsorbents. Subsequently, desorption is carried out under reduced pressure or using steam, and the concentrated oil and gas is pumped into oil tanks using vacuum pumps or liquefied by other methods ； Adsorbents such as activated carbon have very low adsorption capacity for air, and the unadsorbed exhaust gases are released through the exhaust pipe. Advantages: The adsorption method can achieve a high treatment efficiency ； The emission concentration is low, and can reach very low values. Disadvantage: Triphenyls can easily deactivate activated carbon, and secondary pollution occurs once the activated carbon is deactivated ； The adsorption capacity of domestically produced activated carbon is generally only around 7%, and its lifespan is short – it usually needs to be replaced every 2 years or so. 2. The absorption method separates oil and gas from air based on the differences in solubility of various components in the mixed oil and gas within the absorbent. Poor-quality fuels such as diesel are generally used as absorbents. Generally, countercurrent contact is employed between the oil and gas and the absorbent sprayed from the top of the absorption tower; the absorbent selectively absorbs the hydrocarbon components, while the unabsorbed gas is discharged through a flame arrester. The absorbent then enters a vacuum desorption tank for desorption, after which the enriched oil and gas are absorbed using oil products. Advantages: Simple process and low investment cost. Disadvantage: The recovery rate is too low, typically only reaching around 80%, failing to meet the current **standards ； The equipment requires a large amount of space ； High energy consumption ； The absorbent is consumed in large quantities, so it needs to be replenished continuously ； The pressure drop is too high, around 5000 pascals. 3. The condensation method utilizes refrigeration technology to remove the heat from the oil and gas, enabling a direct conversion of the oil and gas components from the gas phase to the liquid phase. The condensation method is a technique for recovering oil and gas by taking advantage of the difference in vapor pressures of hydrocarbons at different temperatures; by cooling, the vapor pressure of certain hydrocarbons in the oil and gas is brought to a supersaturated state, and the supersaturated vapor condenses into a liquid state. A multi-stage continuous cooling method is generally used to lower the temperature of the oil and gas, causing them to condense into a liquid for recovery. The minimum temperature of the condensation device is determined based on the composition of the volatile gases, the desired recovery rate, and the allowable concentration limits of organic compounds in the exhaust gases released into the atmosphere. It is generally achieved through steps such as pre-cooling and mechanical refrigeration. The pre-cooler is a single-stage cooling device. To reduce the operational energy consumption of the recovery unit, a technology for reusing cold energy has been developed, which lowers the temperature of the gas entering the recovery unit from the ambient temperature to around 4°C, allowing most of the water vapor in the gas to condense into water and be removed. After leaving the pre-cooler, the gas enters the shallow cooling stage. The gas temperature can be cooled to –30°C to –50°C, and as required, nearly half of the hydrocarbons in the oil and gas can be recovered. The slightly cold oil and gas proceed to the deep-cold stage, where they can be cooled to temperatures ranging from –73°C to –110°C. The temperature is set according to specific requirements, and the compressors are configured accordingly. Advantages: Simple process principle, highest economic benefits ； The recovered liquid oil can be seen visually ； High security ； High level of automation. Disadvantage: High initial investment. Refrigeration consumes a lot of energy; at least two condensers are needed to work in alternation, so the machine must be turned on in advance to start cooling! 4. Direct combustion method: This approach involves directly oxidizing and burning the hydrocarbon-containing gases generated during storage and transportation; the carbon dioxide, water, and air produced as a result of combustion are then released directly as purified gases. This process flow serves only as a measure to control oil and gas emissions; it cannot recover oil products and has no economic value. 5. The membrane separation method takes advantage of the property that special polymer membranes allow hydrocarbons to pass through more easily. Under the influence of a certain pressure, the hydrocarbon molecules in the gas mixture pass through the polymer membrane first, while the air components are retained and removed. The concentrated hydrocarbons are then transferred back to the oil tank or liquefied using other methods. Advantages: Advanced technology, relatively simple process ； The recovered liquid oil can be seen visually ； High security ； Disadvantage of high automation level: Membrane separation devices require gas with stable flow and pressure. Shenzhen Aotuwell Technology Co., Ltd. ------- has an excellent design team for oil and gas recovery equipment as well as numerous practical project examples.