Gas stations, as places for storing and selling oil products, have concentrated sources of volatile organic compounds (VOCs) emissions and clear requirements for their management. Many gas station owners equate VOCs treatment with buying a tertiary oil and gas recovery device to install. In fact, a complete and reliable treatment project starts with gas source identification, and goes through the entire process management from scheme design, equipment selection, on-site installation to acceptance and operation. This article compiles a set of implementation procedures that can be followed for reference when planning and renovating fuel stations.
Before governance, it is necessary to clarify where the oil and gas come from and how much they are in quantity. VOCs at gas stations mainly come from three stages: unloading, refueling, and tank respiration. The tertiary oil and gas recovery device focuses on processing the gas exhaled from the tank breathing valve, so it is necessary to first calculate the exhaled gas volume of the tank, add up the capacity of a single tank or the entire station, and estimate the peak flow rate based on temperature fluctuations and unloading rhythm. The processing capacity of WHSH series devices covers 4 to 20 cubic meters per hour. By falling within this range, the equipment specifications can be preliminarily determined.
After determining the processing capacity, enter the process and equipment selection stage. The three-stage oil and gas recovery adopts a combined process of compression condensation and membrane separation. Condensation is responsible for converting most of the oil and gas into liquid and returning it to the tank, while membrane separation controls the emission concentration of residual light components. When selecting, in addition to processing capacity, it is also necessary to check the emission concentration indicators, power supply conditions, basic requirements, and installation space of the device. Skid mounted structures are a common choice for retrofitting existing sites due to their small footprint, high integration, and low on-site installation workload. When selecting, compare the processing capacity curve, gas concentration, and on-site installation conditions together.
After the equipment arrives, it enters the installation phase. The tertiary device is generally installed at the breathing valve of the storage tank, with the intake pipe connected to the breathing valve pipeline, the return pipe connected to the storage tank, and then connected to the power and signal lines. During installation, a shut-off valve and flame arrester should be installed on the intake pipeline, and a shut-off valve and check valve should be installed on the return pipeline. After the pipeline is completed, an air tightness test should be conducted. The equipment foundation should be flat, above the ground, and reserved for drainage. The grounding resistance of electrical grounding should meet the requirements, and explosion-proof wiring and distribution should be carried out in accordance with hazardous area regulations. These details directly determine whether the device can operate stably.
After installation, it must undergo debugging and acceptance before it can be officially put into use. During debugging, check the phase sequence, confirm that the system can start and stop normally, and ensure that the exhaust concentration is within the production range before putting it into use. After operation, it is recommended to establish an inspection system, with exhaust concentration, membrane pressure, and processing capacity as fixed inspection items, record trends, and promptly identify problems. Membrane components are consumables with a service life, and replacement should be arranged when the cycle or performance decreases during operation. Only by solidly following the entire process can the VOCs control at gas stations truly achieve the expected results.
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