Adsorption-type Tertiary Vapor Recovery Unit

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The adsorption-type tertiary Vapor recovery unit is a highly efficient and environmentally friendly device designed to address the problem of Vapor volatilization from gas station storage tanks. This product employs activated carbon adsorption + vacuum desorption technology, utilizing the difference in adsorption capacity between Vapor components and air components by porous adsorbents such as activated carbon, achieving selective separation of Vapor from air. The enriched Vapor is recovered and returned to the storage tank, and the treated exhaust gas meets emission standards.

This product complies with the requirements of the "Emission Standard of Air Pollutants for Gas Stations" (GB 20952-2020), with a treatment efficiency ≥95% and an emission concentration ≤25g/m³. According to the latest policy requirements, gas stations with annual gasoline sales exceeding 2000 tons must complete the installation of this unit by 2027. Adsorption is a general term for activated carbon adsorption combined with vacuum desorption. In the field of tertiary Vapor recovery equipment for gas stations, it has been included as one of the shortlisted technologies by large oil companies such as Sinopec and CNOOC. It is suitable for standard processing capacities of 6 m³/h and 8 m³/h, making it a reliable choice for small and medium-sized gas stations to achieve environmental compliance.

Technical Positioning Explanation: The activated carbon adsorption + vacuum desorption process used in adsorption-type tertiary Vapor recovery devices is one of the two major process types specified in Sinopec Sales Co., Ltd.'s 2025-2026 framework procurement announcement for tertiary Vapor recovery equipment for gas stations. It is combined with absorption methods in high-volume oil turnover scenarios, and with condensation methods in small-scale gas station scenarios. Pure adsorption technology still holds a certain market share in small and medium-sized gas stations. To distinguish it from combined processes, this article focuses on pure adsorption and dual-tank alternating adsorption processes.

2.1 Core Technical Principles
The adsorption method utilizes the difference in binding strength between different components in an oil-gas mixture and an adsorbent (activated carbon) to separate the difficult-to-adsorb and easily-adsorbed components in the mixture. Hydrocarbons are adsorbed by the adsorbent. Activated carbon has a strong adsorption capacity for hydrocarbon molecules in Vapor , but its adsorption capacity for air is extremely weak-activated carbon, silica gel, and other adsorbents have very little adsorption capacity for air. Unadsorbed exhaust gas is discharged through the exhaust pipe-thus achieving selective separation of Vapor from air.

Adsorption Stage: When the oil-gas mixture passes through the adsorption tank, hydrocarbon components are physically adsorbed by the pores on the surface of the activated carbon, and clean air is discharged in compliance with standards. The adsorption process takes place at normal temperature and pressure without any chemical reaction.

Desorption Stage: When the activated carbon is saturated, the system uses a vacuum pump to perform vacuum desorption on the adsorption tank (vacuum degree can reach below -0.095 MPa), releasing the adsorbed hydrocarbons and forming a high-concentration oil-gas mixture that is recovered to the storage tank. After desorption, the activated carbon regains its original function and is ready to perform the next Vapor adsorption cycle.

Alternating Operation: A dual-tank alternating design is adopted. While one tank is adsorbing, the other is desorbing and regenerating, achieving continuous operation through automatic switching. The unit contains two carbon beds that alternately operate and perform the adsorption-desorption-regeneration process, thus forming a continuous Vapor recovery capacity.

2.2 VPSA Method (Vacuum Pressure Swing Adsorption)

VPSA (Vacuum Pressure Swing Adsorption) is an adsorption and recovery method that uses two tower-type adsorption tanks for adsorption at atmospheric pressure and desorption under vacuum. During adsorption in one tower, desorption is performed in the other tower via a vacuum pump. After a certain period, a solenoid valve switches between adsorption and desorption. This process is repeated continuously. Because the pressure loss within the adsorption towers is very small, the Vapor reach the adsorption process using their own pressure, eliminating the need for an additional compressor. The system is simple and efficient.

Startup Conditions: When the Vapor pressure in the underground oil storage tank rises to the set pressure value (usually +150Pa, adjustable) and remains for 10 seconds, the system automatically starts operating. When the Vapor pressure in the gasoline storage tank falls below -50Pa (adjustable), the equipment stops adsorption, enters standby mode, and ends one Vapor recovery process.

Desorption process: A dry vacuum pump is used for vacuum desorption. The desorbed high-concentration Vapor are cooled and returned to the gasoline storage tank as an Vapor mixture. This completes the regeneration of the activated carbon in the adsorption tank. The adsorption tank can then be used for the next Vapor adsorption cycle.

2.4 Multi-stage Adsorption Process

Based on conventional dual-tank alternating adsorption, multi-stage series adsorption can further improve adsorption efficiency: the first stage of the multi-stage adsorption bed is in a saturated state, while the second stage is in a partially saturated state. The vacuum pump only needs to desorb from the first-stage adsorption tank, resulting in a higher concentration of desorbed Vapor . This process ensures that the Vapor are always in a two-stage adsorption state, and the desorption frequency of each activated carbon tank is the same, thus effectively ensuring that the exhaust gas concentration always meets the exhaust gas standards.
 

This product mainly consists of the following core components:

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