PROCESS FOR PURIFYING AN OXIDATION WASTE GAS WITH RECOVERY OF ENERGY

摘要

21 The invention relates to a process for the purification of an off gas which originates from a reaction process operated under pressure and in particular from an oxidation process operated using oxygen-containing gas and which is contaminated with aliphatic and/or aromatic substances, with at least partial recovery of the energy contained in the off gas, in which process the off gas stream is expanded in an expansion turbine for generating mechanical or electrical energy. The off gas to be purified originates in particular from the oxidation of para-xylene (p-X) with air by the so-called Witten DMT process for the preparation of dimethyl terephthalate (DMT). The invention envisages that the off gas is burned under pressure and the resulting flue gases are used for generating mechanical or electrical energy in an expansion turbine. The invention preferably comprises the following main steps: a) Partial condensation of the substances to be washed out, at about 35-60.degree.C; b) Absorption with methyl para-toluate (p-TE) or with a mixture of p-TE and methyl benzoate (BME); c) Absorption with BME and/or methanol; d) Absorption with water; e) Combustion under pressure, if necessary with the supply of oxygen and combustible products.