H2S In Biogas Research Articles

Prediction of hydrogen sulphide production during anaerobic digestion of organic substrates

The main objective of this study was to develop a methodology to predict the hydrogen sulphide content of raw biogas produced during anaerobic mono-digestion of a bioenergy feedstock. Detailed chemical and biological analyses were made on 37 different feedstocks originating from urban wastewater treatment plants, farms, agri-food facilities and municipal wastes. Total sulphur content ranged from 1 to 29.6mgS/kg of total solids, and 66% of the feedstocks analysed contained less than 5mgS/kg of total solids. The biochemical methanogenic potential and biochemical biogas potential of each feedstock combined with its S content were used to predict appearance of H2S in the raw biogas. A model to link H2S in biogas with the carbon:sulphur ratio was established. Based on this model, a minimum carbon:sulphur ratio of 40 is required in feedstock to limit the concentration of hydrogen sulphide in raw biogas to less than 2% (volume/volume).

Experimental Study of Biological H<sub>2</sub>S Removal in Biogas

Removal of hydrogen sulfide from waste and energy-rich gases is required not only because of environmental health and safety reasons, but also because of operational reasons. Biotrickling filter is one of the most promising clean technologies for removing H2S. This study attempted to remove H2S in biogas using a laboratory-scale biotrickling filter. The performance and the influence caused by different concentrations of pH, CODCr, sulfate, external nitrate source in the nutrient solution were systematically analyzed. Optimal operating conditions were obtained by the following: pH 2.0~8.0, COD 400~500mg/L, cumulative sulfate concentration 250mg/L, external nitrogen concentration 7.5mg /L.

Pretreatment of municipal waste activated sludge for volatile sulfur compounds control in anaerobic digestion

The effect of combination of mechanical and chemical pretreatment of municipal waste activated sludge (WAS) prior to anaerobic digestion was studied using a laboratory scale system with an objective to decrease volatile sulfur compounds in biogas and digested sludge. Mechanical pretreatment was conducted using depressurization of WAS through a valve from a batch pretreatment reactor pressurized at 75±1psi, while combined pretreatments were conducted using six different dosages of hydrogen peroxide (H2O2) and ferrous chloride (FeCl2) along with mechanical pretreatment. About 37–46% removal of H2S in biogas occurred for different combined pretreatment conditions. Sludge solubilization achieved due to the mechanical pretreatment increased total cumulative methane production by 8–10% after 30days during the biochemical methane potential (BMP) test. The pretreatment also improved dewaterability in terms of time to filter (TTF), and decreased methyl mercaptan generation potential of the digested sludge.

On-site removal of H2S from biogas produced by food waste using an aerobic sludge biofilter for steam reforming processing

H2S in biogas was removed by sludge-loaded biofiltration, rendering the biogas suitable for catalytic reforming into a mixture of CO and H2 syngas that was then applied for the generation of electricity using a solid oxide fuel cell or for the chemical synthesis of methanol. The biogas was anaerobically produced in a 2 m3 bioreactor at 35°C for 2 years using restaurant food waste from Korea Advanced Institute of Science and Technology (KAIST), and the concentration of H2S in the biogas ranged from 612 to 1,500 ppmv (Avg. 1,060 ppmv). Two immobilized cell bioreactors 0.2 and 8.5 L in volume were loaded with aerobic sludge and used to study characteristics of H2S removal from biogas. At a retention time of 400 sec, the removal efficiency of H2S was over 99% following initial stabilization for 7 days in the 8.5 L bioreactor installed at the on-site biogas facility. The maximum rate of H2S removal in this study was 359 g-H2S/m3/h with an average mass loading rate of 14.7 g-H2S/m3/h (kinetic analysis: Vm = 842.6 g-H2S/m3/h and Ks = 2.2 mg/L). Therefore, purified biogas with a negligible concentration H2S was efficiently reformed to syngas. This study demonstrates the feasibility of biogas purification as a part of high-quality syngas production.

Biodegradação de resíduos lignocelulósicos gerados na bananicultura e sua valorização para a produção de biogás

Propôs-se, neste trabalho, avaliar a potencialidade do uso de resíduos lignocelulósicos da bananicultura como substrato de fermentação do processo de metanização. Os resíduos casca de banana, engaço, folhas e pseudocaule da bananeira Musa cavendischii, foram biodegradados a 30 °C e pH 7,2, em diferentes volumes de trabalho, empregando-se como biodigestor frascos Erlenmeyer, garrafas plásticas e biorreator de bancada. A composição ideal do substrato para a metanização foi definida como: 50% m m-1 de cascas, 25% de folhas e 25% de pseudocaule. O engaço, por apresentar baixa velocidade de biodegradação em comparação com as demais biomassas, não foi recomendado para a metanização conjunta dos resíduos. A hidrólise ácida prévia do substrato foi prejudicial à produção de biogás visto que, além de conduzir à formação de H2S no biogás gerado, inibiu a formação de CH4. O rendimento máximo em biogás, obtido em biodigestor de bancada empregando-se substrato in natura, foi de 244 LCNTP kg-1ST com 66,8% v v-1 de CH4.

Removal of H2S from Biogas by Iron (Fe3+) Doped MgO on Ceramic Honeycomb Catalyst using Double Packed Columns System

Biogas, a clean environment fuel, is produced by anaerobic digestion of biological wastes. The presence of hydrogen sulfide (H2S) in biogas has a toxic and corrosive to most equipment such as piping, boilers, and powergenerating machine. H2S removal from biogas is of crucial importance to guarantee better performances in biogas exploitation processes, and to reduce environmental impact of gaseous emissions. Iron (Fe 3+ ) doped magnesium oxide (MgO) catalyst was synthesized using sol–gel dip coating process on foam ceramic honeycomb for removal of H2S in biogas. The synthesis catalyst was characterized by XRD and SEM techniques. Double packed columns containing absorption column and catalytic column were used to remove H2S in biogas in this paper. The absorption column using water absorbent was run with counter current mode to absorb H2S from biogas. The synthesized catalyst was packed in catalytic column to continuously degrade the H2S in water absorbent liquid and regenerated by air flow. The results showed that the double packed columns system was effectively performed in H2S removal from biogas. The L/G ratio of 0.6, biogas flow rate of 1 l/min and 10 pieces of catalyst were optimum operating condition of the double packed columns system to get the highest H2S removal efficiency of 72% without any loss of CH4 in the biogas.

Packed-Bed Reactor for Biogas H2S Removal and for Methane-Dependent Effluent Nitrate Removal Applied to High Strength Organic Wastewater Treatment Process.

In a wastewater treatment process consisting of a UASB reactor and aerobic post treatment, excess biogas is produced during the warm season. Methane-dependent nitrate removal using a biogas scrubber would be an efficient way to utilize the excess biogas. The performance of the plastic media-filled packed-bed reactor was examined for biogas scrubbing and methane-dependent nitrate removal. A bench-scale packed-bed reactor was installed in a swine wastewater treatment plant consisting of a UASB reactor and a trickling filter. The biogas from the UASB reactor was supplied from the bottom (3.4-9.4 m d-1), and the trickling filter effluent was spread from the top (9.4-26.1m3 m-2 d-1) . The concentration of H2S dropped from 1200-2500 ppm to less than 2 ppm. The plastic media covered with biofilm were then collected from the reactor and filled into a laboratory scale packed-bed reactor. Inorganic medium containing 40 mg-N l-1 nitrate was spread from the top of this reactor (1.4 m3 m-2 d-1), and gas was supplied from the bottom (25-36.5 m d-1) . The nitrate concentration dropped significantly when CH4 (93%v/v) and O2 (7%v/v) were supplied simultaneously. In contrast, nitrate removal scarcely occurred when only CH4 or He was supplied. These results suggest that simultaneous biogas scrubbing and methane-dependent nitrate removal are possible with the packed-bed reactor.