METHOD FOR EXTRACTION OF LIQUEFIED HYDROCARBON GASES FROM NATURAL GAS OF MAIN GAS PIPELINES AND PLANT FOR ITS IMPLEMENTATION Russian patent published in 2018 - IPC F25J3/02 

FIELD: oil and gas industry.

SUBSTANCE: flow of natural gas is sequentially cooled and sent to a first low temperature separation stage, then gas separated in the first stage is expanded in a turbo expander and sent to a second low temperature separation stage. Liquid hydrocarbon fraction produced at the first separation stage is also sent after throttling to the second separation stage. The flow of separated gas of methane-ethane fraction is directed by reverse flow for natural gas cooling. The produced liquid flow is fed to the top of deethaniser column, from which gas flow of methane-ethane fraction is taken and after throttling it is combined with reverse gas flow of methane-ethane fraction produced at the second separation stage, then after recuperation of cold, combined flow of methane-ethane gas is additionally cooled and withdrawn from the plant as a commercial gas. After throttling, liquid fraction C₃₊ produced in the deethaniser column is sent to the middle part of the depropanizer column, from which the gas flow of propane fraction is sent to reflux, after that the produced liquid propane fraction is divided into two flows, the smaller one is fed into the upper part of the depropanizer column as a reflux, and the larger one is withdrawn from the plant. After throttling, liquid flow of C₄₊ fraction from the bottom of the depropanizer column is sent to the middle part of the debutanizer column, from the top of which the gas flow of butane fraction is sent to reflux. After that, the produced liquid butane fraction is divided into two flows, the smaller one is fed into the upper part of the debutanizer column as reflux, the larger one is cooled and removed from the plant, and after cooling the flow of C₅₊ liquid fraction is withdrawn from the plant from the bottom of the debutanizer column. The plant comprises two recuperative heat exchangers, two low temperature separators, the deethanizer column, the depropanizer column equipped with reflux condenser including a third recuperative heat exchanger and a separator, the debutanizer column equipped with dephlegmator including water cooler and a separator, three pumps, three air-cooling devices, turbo-expander, four throttles and connecting pipelines.

EFFECT: increased gas processing efficiency, possibility for production propane and butane fractions separately.

2 cl, 1 dwg