PROCESS AND DEVICE FOR PURIFYING A GAS STREAM BY MEANS OF HOLLOW-FIBRE MEMBRANE CONTACTOR(S)

摘要

The invention relates to a process and a device for purifying a gas stream comprising an acidic gas to be removed, comprising a first membrane module comprising at least one dense-skin membrane which is selectively permeable to an acidic gas compared with a volatile basic species, wherein the membrane is defined by a reverse selectivity for ammonia or any other volatile basic species and defines a first part and a second part comprising a liquid phase comprising ammonia, wherein the liquid phase is in contact with the membrane which is chemically stable in a concentrated ammoniacal medium between 1% and 15% by weight, the membrane being suitable so that, when the gas stream is circulated in the first part, the acidic gas is absorbed by the liquid phase so as to form a first permeate and a first retentate which is the gas stream depleted of acidic gas, the liquid phase being confined without ever being in direct contact with the gas stream during the absorption, the membrane consisting of a hollow polymer fibre covered with a dense skin of small thickness typically less than two micrometres, with a physical structure free of pores of diameter greater than 0.4 nm, of organic, carbon-based, inorganic or polymer type, having little or no physicochemical affinities with ammonia while at the same time having a molecular structure defined by a large free volume fraction greater than 0.18 and a reverse selectivity favouring transport of the acidic gas compared with ammonia.