Patent ID: 6017507
Filing Date: 2000-01-25
Classification: B01D,C01B,Y10S

Abstract:
A process for the oxidation to sulphur of the H.sub.2 S present in a gas in a concentration of between 0.7% and 3% by volume, in which the operation is carried out in a catalytic oxidation unit comprising a plurality of catalytic oxidation stages arranged in series and including an initial stage, a final stage and optionally at least one intermediate stage, each of the stages containing a catalyst promoting the selective oxidation of H.sub.2 S to sulphur and operating at temperatures which are lower than the dew point of the sulphur resulting from the oxidation, wherein the gas to be treated containing H.sub.2 S is introduced at the entry of the initial catalytic oxidation stage and the gas is successively passed through each of the catalytic oxidation stages in contact with the oxidation catalyst and additionally injecting a gas containing free oxygen into each of the initial and intermediate catalytic oxidation stages in order to carry out in each of the initial and intermediate catalytic oxidation stages a partial oxidation of the H.sub.2 S in the gas to sulphur by the oxygen in the gas containing free oxygen, the sulphur formed being deposited on the catalyst in each catalytic oxidation stage, and a purified gas with a low residual content of H.sub.2 S is discharged at the exit of the final catalytic oxidation stage, wherein the gas containing H.sub.2 S is brought to a temperature of between 80.degree. C. and 100.degree. C. before it enters each of the catalytic oxidation stages, the quantity of gas containing free oxygen introduced into the initial stage and each of the optional intermediate stages of catalytic oxidation being substoichiometric with respect to the quantity of hydrogen sulfide in the gas so that the temperature of the gas mixture at the exit of each of the catalytic oxidation stages which operate adiabatically, is at most equal to the maximum temperature .theta.s of the temperature range in which the oxidation catalyst is capable of promoting the required selective oxidation of H.sub.2 S to sulphur and does not exceed 150.degree. C., in that the quantity of gas containing free oxygen which is introduced into the final catalytic oxidation stage is controlled in order to provide an excess of oxygen in the purified gas above that required for a total oxidation of the H.sub.2 S passing through the final stage and wherein the oxidation of the H.sub.2 S in the final catalytic oxidation stage is carried out at temperatures which are at most equal to the temperature .theta.s and not exceeding 150.degree. C., by cooling the final catalytic stage by indirect heat exchange with a cold fluid if required to maintain the required temperature.