METHOD OF FRACTIONATING MIXTURES OF LOW MOLECULAR WEIGHT HYDROCARBONS

摘要

The invention relates to the field of membrane gas separation and can be used for the energy-efficient fractionation of hydrocarbon mixtures, including the separation and drying of natural gas and associated petroleum gases. Proposed is a method of fractionating mixtures of low molecular weight hydrocarbons which is based on the capillary condensation of the components of a mixture in the pores of microporous membranes with uniform porosity and a pore diameter in a range of 5-250 nm, wherein, for capillary condensation, the temperature of the membrane and the pressure on the permeate side are kept below the temperature and the pressure of the crude mixture such that the equilibrium pressure of the saturated vapours of the separated components on the permeate side is lower than the partial pressure of the components in the feed stream. This method makes it possible to significantly increase membrane permeability with respect to condensible components (over 500 m3/(m2·h·bar) for n-butane), and also component separation selectivity (the n-С4Н10/СН4 separation coefficient is greater than 60 for a mixture having an associated petroleum gas composition), while also making it possible to dispense with deep cooling of the gas stream fed to a membrane module, and to carry out gas separation under less significant cooling of the membrane on the permeate side (up to -50°С). For more effective gas separation, permeate is collected in a liquid state. The technical result of the invention is the creation of a method that makes it possible to efficiently separate high-boiling hydrocarbons (С3-С6) from natural gas and associated petroleum gases, as well as to obtain gas mixtures with a constant composition.