A Membrane Separation Process for Nitrogen-Containing Natural Gas with Enhanced Permeation Selectivity at Low Temperature

Abstract

The invention provides a nitrogen-containing natural gas membrane separation process with enhanced permeation selectivity at low temperature, which belongs to the field of petrochemical industry. Nitrogen-containing natural gas undergoes pretreatment such as compression and dehydration, and then achieves high-efficiency and high-yield methane concentration through a multi-stage low-temperature membrane process to produce commercial natural gas with a nitrogen content of <4.0vol%. The separation process of the present invention significantly improves the permeation selectivity by reducing the operating temperature of the membrane, thereby improving the separation efficiency and methane recovery rate; throttling refrigeration through membrane permeation, expansion refrigeration of high-pressure tail gas, and compression refrigeration driven by turbines , to provide sufficient cooling capacity for the low-temperature membrane process, and avoid consuming external energy to drive the refrigeration system. Using the membrane separation process provided by the invention, the unit power consumption for production is about 0.22kWh / Nm 3 For feed gas with a nitrogen content of about 30 vol%, the methane recovery rate exceeds 75.0%.

Description

technical field [0001] The invention relates to a nitrogen-containing natural gas membrane separation process coupled with turbo expansion refrigeration and gas membrane separation, which utilizes low temperature to enhance permeation selectivity, and belongs to the field of petrochemical industry. Nitrogen-containing natural gas enters the cold box after compression and dehydration, and enters the multi-stage membrane separation unit with the rubbery polymer membrane as the core after cooling down to obtain natural gas with a methane content of more than 96vol%, which meets the Chinese national standard "Natural Gas GB17820-2012" Requirements; the remaining nitrogen-rich tail gas enters the turbo expansion refrigeration, synchronously drives the vapor compression refrigeration system, and provides refrigeration for the cooling of nitrogen-containing natural gas. The process enhances the permeation selectivity of the rubbery polymer membrane at low temperature, which can separ...

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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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