一套完整的油气回收体系，通常分三个阶段，构成一道立体防线：

A complete oil and gas recovery system is usually divided into three stages, forming a three-dimensional defense line:

第一阶段：卸油回收

Phase 1: Unloading and Recycling of Oil

目标：油罐车向地下储油罐卸油时，置换出的油气。

Objective: The oil and gas displaced when the oil tanker unloads oil from the underground storage tank.

原理：通过密闭管线，将地下油罐内被液体挤出的油气，“反向”输送回油罐车的空余空间。实现了“你来我往”的平衡交换，杜绝了卸油时油气外逸。

Principle: The oil and gas squeezed out of the underground oil tank by the liquid are transported back to the empty space of the oil tanker in the "reverse" direction through a closed pipeline. Realized a balanced exchange of 'you come and I go', eliminating the escape of oil and gas during oil unloading.

第二阶段：储油与加油回收

Phase 2: Storage and Refueling Recovery

目标：日常储存及为汽车加油过程中产生的油气。

Goal: Daily storage and refueling of oil and gas generated during the process of refueling the car.

原理：核心在于“压力平衡”。在加油时，通过 specially designed 的真空泵（如基于真空辅助或油气平衡原理），将汽车油箱内溢出的油气，经油枪上的特殊回收孔、地下管道抽回至储油罐内存储。此阶段技术要求最高，是日常控制排放的主力。

Principle: The core lies in "pressure balance". When refueling, the oil and gas overflowing from the car's fuel tank are pumped back into the storage tank through a specially designed vacuum pump (such as based on vacuum assist or oil gas balance principle) through a special recovery hole on the oil gun and underground pipeline. This stage has the highest technical requirements and is the main force for daily emission control.

第三阶段：末端深度处理与回收

Phase 3: End of pipe deep processing and recycling

目标：对储油罐内积聚的、富集的油气进行集中净化处理。

Objective: To concentrate and purify the accumulated and enriched oil and gas in the oil storage tank.

原理：当罐内气压达到设定值时，油气进入处理装置。主流技术包括：

Principle: When the pressure inside the tank reaches the set value, oil and gas enter the processing device. The mainstream technologies include:

冷凝法：将油气深度冷却至零下数十度，使其冷凝为液态油。回收纯度高，是当前的主流和推荐技术。

Condensation method: Deeply cool the oil and gas to tens of degrees below zero to condense it into liquid oil. Recycling with high purity is currently the mainstream and recommended technology.

吸附法：利用活性炭等吸附剂吸收油气，后再进行脱附回收。技术成熟，但可能存在二次废物。

Adsorption method: using activated carbon and other adsorbents to absorb oil and gas, followed by desorption and recovery. The technology is mature, but there may be secondary waste.

膜分离法：利用特殊薄膜对油气分子的选择性透过进行分离。适用于高浓度油气。

Membrane separation method: using a special thin film to selectively separate oil and gas molecules. Suitable for high concentration oil and gas.

三个阶段环环相扣，构成了从产生到收集再到最终回收的闭环。

The three stages are interrelated, forming a closed loop from generation to collection and ultimately to recycling.