Full analysis of VOCs emissions from gas stations: how to coordinate the treatment of unloading, refueling, and tank respiration

The volatile organic compounds (VOCs) emissions from gas stations do not only come from one point, but run through three stages: unloading, refueling, and tank respiration. The emission characteristics of each link are different, and the governance methods are also different. Only by clearly understanding the three links can we comprehend the role of the tertiary oil and gas recovery device in the entire system. The Wohong WHSH series tertiary oil and gas recovery device is specifically designed to solve the problem of high concentration oil and gas emissions in the tank breathing process.

Unloading process: high concentration oil and gas replaced by oil tanker trucks

When the oil tanker unloads oil from the storage tank, the liquid level inside the tank rises, and the oil and gas that originally occupied the space are displaced and discharged. The high concentration and instantaneous quantity of oil and gas in this process are important sources of VOCs emissions from gas stations. The oil and gas recovery system recovers the oil and gas discharged from the oil tank truck through the oil and gas recovery pipeline and carries it away with the truck, reducing emissions from the source. The key to the oil unloading process is the tightness of the pipeline and the sealing of the oil and gas recovery interface. Poor sealing can directly cause leakage.

Refueling process: Replacement of fuel and gas in the car's fuel tank and dripping

When refueling, gasoline enters the car's fuel tank, and the oil and gas in the tank are replaced into the recovery pipeline of the refueling gun. The secondary oil and gas recovery system recovers it to the storage tank through the built-in vacuum pump of the refueling machine. The concentration of oil and gas in this stage is relatively low, but the frequency of occurrence is extremely high, and every refueling is carried out. The recycling efficiency of secondary recycling is affected by the sealing cup of the fuel gun, the status of the vacuum pump, and the smoothness of the pipeline. Daily maintenance should be given special attention.

Tank breathing process: the part that requires the most three recycling treatments

Even if the first and second recycling processes are normal, there will still be breathing emissions inside the storage tank due to temperature differences between day and night and oil unloading disturbances, commonly known as small breathing and large breathing. This part of the oil and gas has a high concentration, and direct discharge is neither environmentally friendly nor a waste of oil products. The three-stage oil and gas recovery device collects and processes the oil and gas discharged from the tank breathing valve: compresses and condenses to recover liquid oil products, membrane separates and concentrates the remaining gas, and stabilizes the exhaust gas concentration below 10 grams per cubic meter. The WHSH series adopts a lever mounted design, which can be flexibly arranged near the storage tank area.

How to collaborate among the three stages

Triple recycling is not a replacement for primary and secondary recycling, but a supplement. To cover the entire chain of VOCs emissions from gas stations, the first stage involves unloading oil from the recycling pipe, the second stage involves refueling with the recycling pipe, and the third stage involves breathing in the storage tank of the recycling pipe. Any missing or failed section will result in an overall emission level exceeding the standard. Therefore, the environmental management of gas stations should integrate the three systems for comprehensive inspection.

Understanding the three emission stages of VOCs is the complete puzzle of environmental governance at gas stations. You can have a clear understanding of equipment selection, maintenance, and inspection.