Browsing by Subject "Hydrogen sulfide"

Hydrogen sulfide (H2S) is a toxic gas and common odor nuisance produced in a variety of chemical and environmental processes. The biological oxidation of H2S to sulfate/sulfuric acid is a well-documented treatment method that is efficient both in removal and cost. Sulfate ions produced in a BTF can interact with various cations, specifically calcium, and form insoluble salts. Gypsum (CaSO4*2H2O) formed within a BTF treating H2S can affect system performance by causing pressure buildup and reducing pollutant mass transfer. An experimental approach was developed to quantify gypsum precipitation in BTFs as a function of critical system parameters. Effluent liquid from one laboratory and four industrial BTFs was used to induce gypsum precipitation at various levels of pH, total sulfate concentration, calcium content, and ionic strength. A computer model was developed to predict gypsum precipitation based on the ionic composition of the reactor trickling liquid. The results support the hypothesis that gypsum precipitation in a BTF treating H2S is a realistic concern for industrial systems. The computer model demonstrates the ability to successfully predict gypsum precipitation within a correction factor of 2. The presence of gypsum and elemental sulfur in solid samples collected from industrial BTFs illustrates the feasibility of mineral deposition in full-scale treatment systems. Ethylene diamine tetraacetic acid (EDTA) shows the potential of being an effective additive for the prevention of gypsum formation within a BTF treating hydrogen sulfide.

Pre-treatment of hydrogen sulfide is required before the utilization of biogas to eliminate the detrimental effects of corrosive hydrogen sulfide to the following combustion engines and pipelines. Biotrickling filters as one of the biotechnological methods have been investigated in desulfurizing biogas in recent years. Although high removal efficiency has been achieved by conventional biotrickling filters, clogging of the biotrickling filter bed due to the accumulation of excess biomass and elemental sulfur, has been widely reported (Janssen et al. 1997, Fortuny et al. 2008). In this context, a novel biotrickling filter using a monolith as its filter bed has been proposed and studied in this work to investigate its performance in removing H2S and solving the bed-clogging problem through pigging, a common method used for pipeline and tubular reactor cleaning. The inlet H2S concentration was controlled around 1000 ppmv, corresponding to a loading rate of 122 g S–H2S m−3 h−1, and the empty bed gas residence time (EBRT) was 41 s. The influence of different H2S/O2 ratios on the removal performance was investigated at these conditions and results indicated that at H2S/O2 molar ratio of 1:2, an average removal efficiency of 95% was obtained. Under all conditions investigated, elemental sulfur and sulfate were measured to be the two dominant products and covered up to 93% of total end products. The monolith bed design also served to demonstrate that the risk of clogging was greatly reduced under this kind of design and bed-clogging problems could be resolved when bed pigging was implemented to remove excess biomass and elemental sulfur accumulated inside the bed. Based on the results reported here, the monolith filter bed can be an effective alternative to the conventional packing material with a high specific surface area and a comparable performance could also be achieved by this novel bioreactor.