Nitrogen-containing natural gas membrane separation process with low-temperature enhancement of permeation selectivity

Abstract

The invention provides a nitrogen-containing natural gas membrane separation process with low-temperature enhancement of permeation selectivity, and belongs to the field of petrochemical industry. Nitrogen-containing natural gas is subjected to pretreatment such as compression and dehydration, then high-efficiency and high-yield methane concentration is realized through a multi-stage low-temperature membrane process, and commercial natural gas with the nitrogen content being less than 4.0 vol% is produced. According to the separation process disclosed by the invention, the permeation selectivity is remarkably improved by reducing the operation temperature of a membrane, so that the separation efficiency and the methane recovery rate are improved; and through throttling refrigeration of membrane permeation, expansion refrigeration of high-pressure tail gas and compression refrigeration driven by a turbine, sufficient cooling capacity is provided for the low-temperature membrane process, and it is avoided that external energy is consumed to drive a refrigeration system. By adopting the membrane separation process provided by the invention, feed gas with the single power consumption of about 0.22 kWh / Nm<3> and the nitrogen content of about 30 vol% is produced, and the methane recovery rate exceeds 75.0%.

Description

Technical field [0001] The present invention relates to an expandable membrane separating the gas turbine coupled to the refrigerant, using a low temperature process to strengthen the nitrogen gas permeation selectivity of the membrane separation, petrochemical field belongs. Compressed nitrogen gas, dehydration entering the cold box, after cooling into the multistage membrane separation unit to the core rubbery polymer film, the isolated methane gas content exceeds 96vol%, to meet the Chinese national standard "Gas GB17820-2012" requirements; the remaining nitrogen-rich exhaust gas into the turbine expansion refrigeration, synchronously driven vapor compression refrigeration system to provide refrigeration to cool the nitrogen-containing gas. The process by cryogenic rubbery polymer reinforced permselective membranes, can be more efficient separation of nitrogen and methane, thereby improving the recovery rate of the nitrogen-containing gas. Background technique [0002] Natural...

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Problems solved by technology

[0010] Aiming at the key problem that technologies such as cryogenic separation, pressure swing adsorption, and normal temperature membrane separation are difficult to meet the needs of efficient separation and concentration of nitrogen-containing natural gas, this invention proposes a combination of turbo expansion refrigeration and gas membrane separation, which uses low temperature to enhance permeation selectivity. Membrane separation process for nitrogen and natural gas

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