From secondary to tertiary oil and gas recovery: upgrading path and key points for VOCs treatment in gas stations

Many gas stations have completed secondary oil and gas recovery renovations, and with the increasing environmental requirements, upgrading to tertiary oil and gas recovery has become a trend. Many people understand secondary and tertiary as simply overlapping, but in fact, they target different stages and accomplish different missions. The secondary recovery mainly solves the oil and gas recovery during the unloading and refueling process, while the tertiary recovery focuses on the centralized treatment of the gas exhaled from the storage tank at the breathing valve. Understanding this upgrade path can help gas stations scientifically plan renovation plans.

Division of labor between secondary and tertiary

The secondary oil and gas recovery mainly relies on the recovery pipe buried in the refueling gun to collect the oil and gas generated during the unloading and refueling of the oil tanker, which belongs to the process recovery. The tertiary oil and gas recovery device is installed at the breathing valve of the storage tank, processing the portion of exhaled gas discharged from the breathing valve during daily temperature rise and oil unloading. It can be said that the second person is responsible for keeping most of the oil and gas in the system, and the third person is responsible for cleaning up the residual exhaled gas before discharging it. Only by working together can the entire site achieve a high recycling rate.

Access method during upgrade

The tertiary device and the secondary system are not in conflict, but rather complement each other. When upgrading, simply connect the intake pipe of the tertiary device to the tank breathing valve pipeline, the return pipe to the storage tank, and then connect the power and signal lines. Generally, there is no need to modify the existing secondary system. The WHSH series three oil and gas recovery device is a pry mounted structure, which is convenient for layout on existing sites. Before connecting, it should be verified whether the outgoing gas volume of the storage tank falls within the processing range of 4 to 20 cubic meters per hour, and the on-site power supply and basic conditions should be confirmed.

Four key points for renovating the site

There are four details on the upgrade and renovation site that are easily overlooked. Firstly, a shut-off valve and flame arrester should be installed in the intake pipeline, and a shut-off valve and check valve should be installed in the return pipeline. After the pipeline is completed, an air tightness test should be conducted; Secondly, the installation location of the device should be flat and ventilated, higher than the ground, with reserved drainage, and sufficient safety distance from the walls and buildings; Thirdly, electrical grounding must meet the requirements, explosion-proof wiring and distribution must be carried out in accordance with hazardous area regulations, and the explosion-proof surface of the explosion-proof box must be sealed properly; Fourthly, warning signs and guardrails should be installed on the equipment to prevent unrelated personnel from approaching. Only by solidly implementing these points can the upgraded recycling system run stably.

Expected effect after upgrading

After completing three upgrades, the storage tank can maintain a state close to atmospheric pressure, and the exhaled gas is no longer directly discharged into the atmosphere. The on-site odor and volatilization losses will be significantly improved. The system runs automatically throughout the entire process and is unmanned. Daily inspections of membrane components, grounding, and pipeline status only need to be carried out according to the plan. For gas stations that plan to move towards higher standards, this is a controllable and effective technological upgrade path.