In LNG (liquefied natural gas) production, the control standard of oil content of feed gas is extremely strict. According to industry norms and actual production needs, the oil content in LNG feed gas usually needs to be controlled below 1 mg/m & sup3; (I. e. not more than 1ppm). The following is a detailed analysis:
technical background of 1. oil content control standard
- liquefaction Process Requirements:
- LNG is formed by cryogenic liquefaction (-162 ℃), and the oil is easy to solidify at this low temperature, which may block equipment and pipelines.
- Product purity requirements:
- LNG needs to meet the high calorific value (about 36-40MJ/m & sup3;) and combustion efficiency, and the oil residue will reduce the energy efficiency.
- Safety specification:
- oil may decompose at high temperature to produce harmful substances, affecting the safety of use.
2. oil content detection and control method
- detection means:
- adopt infrared spectrophotometry, Through gas sampling and laboratory analysis, it can accurately detect the oil content of μg/m & sup3; level.
- pretreatment process:
- filtration separation: The inlet is equipped with a high-efficiency filter to remove mechanical impurities and free oil droplets.
- adsorption dehydration simultaneous removal of moisture and trace oil by molecular sieve adsorbent.
- deep purification: Special adsorbent for mercury removal tower further reduces oil content to 0.01 μg/m & sup3; Below.
3. international benchmarking and industrial practice
- international Standard Reference:
- although the European standard EN1160 does not directly specify the oil content, it requires the methane content to be> 75%, and indirectly requires strict control of impurities (including oil).
- Domestic Practice Cases:
- for example, in the Xiangguosi Gas Storage Project in Chongqing, the oil content of the feed gas was reduced from 10.6 mg/m & sup3; to 8.5 mg/m & sup3;(still higher than 1ppm, further treatment is required) through multi-stage compression and deep purification.
Risk of Excessive 4. and Countermeasures
- consequences of exceeding the standard:
- oil residue may lead to LNG storage tank blockage, gasification efficiency decline, and even lead to equipment failure.
- Countermeasures:
- increase activated carbon adsorption unit or membrane separation technology, enhanced oil removal.
- Regularly detect the oil content of the feed gas and optimize the pretreatment process parameters.
5. Summary
the oil content of LNG feed gas should be controlled below 1ppm to ensure the stability of the liquefaction process, product purity and safety. In actual production, it is necessary to combine high-efficiency pretreatment technology and precise detection methods to achieve deep removal of oil.
