Using HPA (heteropoly acid), namely Na2HPMo12O40, as absorbent in form of aqueous solution, a promising resolution to SO2 containing gas purification was developed. In this study, experiments were conducted concerning the additive effect for maximizing the desulfurization efficiency of HPA absorbent system and the performance of absorbent regeneration. As a consequence, all additives including NaCl, H3PO4, MnSO4, CuSO4, ZnSO4 and NH4VO3 were found to have positive effects on the improvement of the desulfurization efficiency of HPA solution. Among them, the effect of NaCl is the most significant. The following two couples i.e. NaCl vs H3PO4 and Zn2+ vs Mn2+, were found to have interactions. Based on orthogonal experiments, the optimum additive/HPA molar ratio in multi-component absorbent system was gained. The process of HPA regeneration by air stream is strongly influenced by operation temperature, whereby the optimum regeneration temperature was found to be ca. 51oC. The desulfurization efficiency of single HPA shows excellent reproducibility during long time operation of 6 absorption-regeneration cycles. The resultant solution of single HPA after desulfurization can also be effectively regenerated by gas stream containing NOx, which shows better effect than that by air stream.

An innovative approach to H2S 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 H2S to elemental sulfur and to be regenerated by air. The presence of Na2CO3 in HPAS system can improve the absorption rate of H2S, and the contribution of NaCl lies in its 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 H2S 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 H2S was proposed to be: H2S Na3PMo(VI)12O400/S Na3H2PMo(VI)10Mo(V)2O40 i.e. there are two Mo(VI) atoms reduced to Mo(V). As a further work, the characteristic and efficiency of H2S removal with HPAS solution systems were investigated in a counter-current packed column. The effects of absorbent concentration, operation temperature, inlet H2S concentration, flow rate of inlet gas stream and absorbent spray density on the absorption of H2S are presented. The absorbent consisting of HPAS and additives including NaVO3, Na2 CO3 and NaCl shows better performance than that of HPAS only. Although the H2S 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.

In order to achieve a comprehensive understanding of the performance of the heteropoly compound (HPC) absorbent systems for H2S removal developed before this study, a comparable study was made concerning the desulfurization characteristics, sulfur loading capacity (SLC) and desulfurization product composition, taking Fe-EDTA system as a standard. The desulfurization effect of HPC multicomponent absorbent system can be greater than that of Fe-EDTA system during long time of operation; the regeneration effects of HPC and Fe-EDTA system are similar. The SLC of single HPC is almost the same as that of the Fe-EDTA system, and the multicomponent system of HPC has SLC which is 12.93% higher. Furthermore, the desulfurization product from HPC system contains sulfur mainly, which is superior to that from Fe-EDTA system. Hence, HPC absorbent system developed would be of promising application value.

A new method of naturalgas desulfurization has been developed by employing the heteropoly compound of the rich elements of our country. This method enables hydrogen sulfide to be removed and element sulfur to be recovered simaltaneously. The thermodynamic feasibility of simultaneous desulfurization and sulfur recovery from naturalgas with the solution of heteropoly compound was proved to be applicable by the experimentalresult of potential2pH curves. At present, no proof was given on the exact number of electron transferred during the redox reaction betw een sodium phosphomolybdate and reductants including hydrogen sulfide. The research here also reveals the reaction mechanism betw een sodium phosphomolybdate and hydrogen sulfide. With the aid of ISE, DSC and EM S, themechanism of desulfurization reaction was studied. The reaction products contain little deposition compounds of molybdenum and vanadium, indicating that sodium phosphomolybdate is stillmuch stable in its chemical property aftermany times of absorption-regeneration cycles, the agent loss ismuch lower than that of the chelateiron method. The chemical equation of sodium phosphomolybdate and H2S was p roposed to be: H2S+ Na2HPMoÎ 12O40 S↓+Na2H3PMoÎ 10MoÍ 2O40 i. e., there are twoMo (Î) atom s reduced toMo (Í). Therefore, the theoretical saturation sulfur loading capacity of sodium phosphomolybdate is twice that of chelateiron with the same molar concentration.