Investigation of a new liquid redox method for H_2S removal and sulfur recovery with heteropoly compound

摘要

An inovative approach to H_2S removal and sulfur recovery involving the use of heteropoly compounds was investigated systematically in this study. The favorable redox potential of sodium phosphomolybdate (HPAS) makes it thermodynamically feasible for it to oxidate H_2S to elemental sulfur and to be regnerated by air. The presence of Na_2CO_3 in HPAS system can improve the absorption rate of H_2S, and the contribution of NaCl lies in this catalytic effect on HPAS regeneration. The absorption efficiency of HPAS decreases slightly with the increase in operation temperature and good absorption effect can be achieved at room temperature. The regeneration time decreases with the increase in absorbent concentration, temperature and regeneration air flow rate, and it increases with the increase in feed gas H_2S concentration. HPAS is still much stable in its chemical property during multiple absorption-regeneration cycles, the desulfurization product is confirmed to be elemental sulfur. The chemical reaction between HPAS and H_2S was proposed to be: H_2S + Na_3PMo(VI)_(12)O_(40) + Na_3H_2PMo(V)_2O_(40) i.e. there are two Mo(VI) atoms reduced to Mo(V). As a further work, the characteristic and efficiency of H_2S removal with HPAS solution systems were investigated in a counter-current packed column. The effects of absorbent concentration, operation temperature, inlet H_2S cocnentration, flow rate of inlet gas stream and absorbent spray density on the absorption of H_2S are presented. The absorbent consisting of HPAS and additives including NaVO_3, Na_2CO_3 and NaCl shows better performance than that of HPAS only. Although the H_2S removal efficiency of HPAS absorbent system is several percentage lower than that of Fe-EDTA during 12 absorption-regeneration cycles, the sulfur content (i.e. elemental sulfur) in the sedimentation product of the former was confirmed to be much higher than the latter with the aid of energy Spectrum. In addition, the absorbent loss of the former is much lower too.