Recovering heat from sulphuric acid plant - by absorbing sulphur tri:oxide in sulphuric acid

摘要

gas obtd. from the first oxidn. stage of an SO2 to SO3 catalytic convertor is fed to a heat recovery tower . 98-102% conc. H2SO4 at above 120 deg.C is passed to the tower and sprayed onto its packing for contact with rising SO3 gas. Downwardly flowing H2SO4 exothermically absorbs SO3. H2SO4 e.g. at upto 240 deg.C, is removed from the tower and pumped to a heat exchanger for heat removal and recirculation (91) to the tower. An SO3 depleted stream (88) is obtd. from the tower top. Heat exchanger is fabricated from alloys with a low corrosion rate w.r.t. hot conc. H2SO4. Heat recovery towerand exchanger are esp. made from alloys which have compsns. with a corrosion index (C.I.) of larger than 39 . Heat recovery tower can opt. be of ceramic lined corbon steel. Stainless steel alloys are esp. pref. for both tower and exchanger.