GB1120063A - Process for producing sulphur trioxide and/or sulphuric acid from gases which contain sulphur dioxide by the catalytic oxidation of the sulphur dioxide - Google Patents

Abstract

<PICT:1120063/C1/1> A process for the catalytic conversion of SO2-containing gases having an SO2 content below 9% per volume to form SO3, and/or sulphuric acid, comprises cleaning and drying the gases, preheating the SO2-containing gases by heat exchange with hot SO3-containing gases produced in the process, subjecting the preheated gases to a catalytic conversion in the first stage of a two-stage catalytic converter, each stage of which comprises two contact hurdles, to effect a conversion of 70 to 80% by volume of the total SO2 contained in the starting gases, effecting an intermediate absorption of the SO3 formed in the first conversion stage including cooling the gases before the absorption and then reheating them after the absorption, subjecting the gases to the second catalytic conversion in the second stage of the converter, and absorbing the SO3 formed in the second conversion stage; the preheating of the SO2-containing gases being effected by preheating a first and major part of the gases by heat exchange with the hot SO3-containing gases from the second converter stage before the absorption of the SO3 contained in such gases, and preheating a second part of the gases by a heat exchange with the hot SO3-containing gases from the first contact hurdle of the second converter stage before such SO3-containing gases are passed to the second contact hurdle of the second converter stage, such preheated starting gases being then combined and brought to the required reaction temperature for the first converter stage by heat exchange with hot SO3-containing gases obtained from the first converter stage. In an example, SO2-containing gases are cooled, cleaned and dried at 60 DEG C., passed via conduit 1 into the converter. A partial stream is passed through 2 to a heat exchanger 3 and heated, and thence through 4 into heat exchanger 5 and further heated to 430 DEG C. The heated gases pass through 6 into a first hurdle 7 of converter 8 and leave through 9 to a mixing chamber 10 where a partial stream of starting gases are added through 32 to the second stage 33 of heat exchanger 16, 33. From 10 the gases pass through 12 to a heat exchanger 5 and are cooled before entering the second contact hurdle 14. After conversion of nearly 80% the gases pass through 15 to the first stage of heat exchanger 16, 33. After leaving 33 through 17 the gases enter the absorber 18 and then pass through 19 to heat exchanger 16 and thence through 20 to a third contact hurdle 21. The gases are then cooled in heat exchanger 23 with a partial stream of starting gas entering through 24. The converted gases then enter the last contact hurdle 26 and leave through 28, passing to heat exchanger 3, and thus cooled, it passes through 29 to final absorber 30. The partial stream of starting gas entering at 24 leaves 23 by way of 27, passes through 4 and is combined with a main stream of starting gas.