Three times of oil and gas recovery condense the evaporated oil and gas back into liquid. These recovered liquids are treated as waste at many stations, while some stations try to reuse them in the oil tank. Both methods have prerequisites: whether they can be reused and what path to reuse them depends on the quality judgment of the recovered liquid, rather than on how much the device itself has recovered. It is a sequence to avoid subsequent troubles by first understanding the quality and then deciding on the destination.
Where does the recycled liquid come from
The recovered liquid mainly comes from three sources: the oil and gas collected during the unloading and refueling processes, which are liquefied after condensation or adsorption; the condensate from the tank breathing gas processed by the recovery device; and the liquid accumulated at low points in the pipeline and in the condensate collection tank. The components of the three sources are not exactly the same. The former two are mainly hydrocarbons, while the pipeline condensate may contain water and impurities.
The differences in composition directly dictate that they should be treated differently during reuse. Mixing all recycled liquids in one tank and then making a unified judgment often leads to a conservative conclusion, rejecting parts that could otherwise be reused.
Why can't it be reused directly
The reclaimed liquid appears similar to gasoline, but the actual difference lies in the content of water and impurities. Oil and gas inevitably contain water, which will liquefy along with hydrocarbons during the condensation process. Rust products and dissolved substances from sealing materials in pipelines and storage tanks may also enter the liquid. These components can affect the quality of oil products, gas station equipment, and vehicle fuel systems. Therefore, it is necessary to accurately determine their content before reuse.
Which items need to be tested
The setting of testing items revolves around two questions: "Can it enter the oil tank?" and "Will there be any impact after entering the tank?" It is not necessary to pursue complete items, but to focus on the key items required for judgment.
Three steps of detection and sampling
- Sample by tank according to the source. Do not mix the recovery liquids from different sources initially, otherwise the sampling will lose its distinguishing significance;
- Submit the sample for inspection as soon as possible after sampling, and record the operating conditions and liquid level during sampling for result traceability;
- Take several consecutive batches from the same source, first examine the stability between batches, and then evaluate the results of each individual batch.
How to interpret the test results
The core of judgment lies in comparison: comparing the test results of the recovered fluid with the quality requirements of the oil products sold in the station to see if the key items are within an acceptable range. This comparison needs to be done by an institution with testing capabilities, and the conclusion should be based on the test report.
| Type of testing item | focus | Impact on reuse |
|---|---|---|
| Component composition | Ratio of hydrocarbons to other components | Decide whether it is suitable to reuse based on the oil product |
| moisture content | Situation of free water and dissolved water | When the water content is relatively high, it is necessary to first treat or adjust the reuse path |
| Impurities and particulate matter | Mechanical impurities, rust products, etc | If the value is on the high side, it is necessary to add a filtering step |
| Color and appearance | Is there any abnormal color change | In case of anomalies, it is necessary to identify the source |
| Batch stability | Fluctuations across multiple batches from the same source | When there is significant volatility, the basis for judgment needs to be more conservative |
How to choose the reuse path
There are three common paths. First, after testing and confirmation, it can be reused in the corresponding oil tank at a certain proportion. Second, it can be stored separately for low-grade use. Third, if it does not meet the conditions for reuse, it should be disposed of by a qualified unit according to hazardous waste management regulations. Which path to choose depends on the test results and the management requirements of the station. The three paths are not mutually exclusive, and they may coexist in the same station.
It should be noted that the reuse ratio and method should be fixed and written into the station's operating procedures to avoid individual judgments by different shifts. The records of the reuse process should be archived together with the inspection reports, serving as the basis for subsequent traceability.
Frequently Asked Questions
Must the recovered liquid be tested before reuse?
When it comes to reusing oil tanks, the test results should serve as the basis, with conclusions issued by institutions that meet the testing requirements. Direct reuse without testing basis poses significant risks and potential future troubles.
Can recycled liquids from different sources be mixed together?
It is not recommended to mix before testing. Separate sampling is necessary to determine which part can be reused, as mixing will only yield a generally conservative overall conclusion.
How to determine the testing frequency?
It can be conducted in batches or at fixed intervals. Additional testing should be performed in case of process adjustments, equipment maintenance, or abnormal appearance of the recovered liquid.
This article is compiled by Luoyang Wohong Petrochemical Equipment Co., Ltd. The company provides design and manufacturing, skid-mounted customization, installation and commissioning, as well as after-sales operation and maintenance services for three-time oil and gas recovery equipment to gas stations and oil depots. If you need on-site inspection or scheme configuration, please feel free to contact us for discussion.