LNG production using mixed refrigerant and trigeneration precooling
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Process Description Feedstock – compressed NG is treated from acidic components and water vapors in unit 1, mixed with boiled- off gas, cooled in heat exchanger 4, and divided into two streams. The first and second streams are cooled in heat exchangers 6 and 7, respectively, combined, pressure is reduced by means of a reducing valve or expander 8, and they are separated in separator 10 to produce LNG and boil- off gas, which is heated in heat exchanger 6, part is sent to unit 1 as purge gas, and the regeneration gas is supplied as fuel gas to drives 11. Compressor drives 11 are connected along the spent gas stream to an absorption refrigeration machine 12, which supplies cooled water to heat exchangers 4 and 5. The main part of the boil-off gas is supplied by compressor 2 for mixing. Heat exchanger 7 is cooled by the head transfer medium circulating in a closed circuit through heat exchanger 5 and expander 9 using compressor 3. A mixed freon or hydrocarbon refrigerant is used.
Process features
Three cooling cycles: external – trigeneration and mixed refrigerant, in-line cycle –nitrogen-methane
High degree of liquefaction
High energy efficiency
Low capital investment and operating costs
Technical Specification
NG Temperature: 5–25 °С
Pressure 6.0–10.0 МPа
LNG capacity 1–20, 20–120, 120–800 t/h
Products: LNG of "A", "B" brands
Energy efficiency of liquefaction: 0.22-0.27 kWh/t of LNG
Patents of the Russian Federation No. 2767848, 2023107109