H2S Removal Efficiency Research Articles

Simultaneous removal of ammonia and hydrogen sulfide gases using biofilter media from the biodehydration stage and curing stage of composting.

Biofiltration of NH3 and H2S with different packing media, biodehydration stage compost (BSC), and curing stage compost (CSC) was studied. Meanwhile, fluorescence excitation-emission matrix (EEM) spectroscopy was used to characterize the conversion mechanisms of organic matter during these biofiltration processes. Both biofilters were effective for the simultaneous removal of NH3 and H2S when inlet concentrations of NH3 and H2S were 0-50 and 50-250mg/m3, respectively. An abrupt increase in the inlet gas concentrations of NH3 and H2S to 100-150 and 200-250mg/m3, respectively, caused the decrease in the removal efficiencies (REs) of NH3 and H2S in the BSC biofilter, followed by a slow upturn. By contrast, relatively steady REs of both NH3 and H2S were observed in the CSC biofilter. After 60days of operation, the average REs of NH3 and H2S were more than 95% in the CSC biofilter. During the operation of CSC, nitrate and nitrite peaked around the 30th day, whereas sulfate showed a steady increase. The excitation-emission matrix fluorescence and parallel factor analysis (EEM-PARAFAC) indicated that the simultaneous inlet of NH3 and H2S facilitated the degradation of protein-like substances, whereas humic-like substances played an important role in the packing filters for the treatment of the two odorous pollutants.

Microfluidic cold stripping of H2S from crude oil in low temperature and natural gas consumption

This study presents the results of removing H2S from crude oil using a micro scale stripper. The main issue in this work is reduction of natural gas consumption and use of low operational temperature. The effects of various operational parameters (such as: crude oil flow rate, natural gas flow rate and temperature of crude oil) on H2S removal efficiency (efficiency) and Specific Energy Consumption (S.E.C) are evaluated. The obtained results, even for lower amounts of the used gas (about one-third) and lower gas temperature (about 18 °C), show a higher efficiency of cold stripping using microchannel compared with other type of strippers. This superior result, with an efficiency of 77.80%, is related to efficient mixing by the employed microchannel at the proposed condition. It has been demonstrated that the efficiency increases with increasing the temperature of crude oil and natural gas flow rate, while temperature does not show a considerable effect on S.E.C. The efficiency and SEC have decreasing trend with increase in flow rate of crude oil at constant temperature and gas flow rate. The mathematical modeling is proposed for H2S removal and the relation between the parameters was determined using Response Surface Methodology (RSM) with Central Composite Design (CCD) method. The values of R2 and lack of fit (LOF), obtained from the mathematical model for efficiency, are 0.9589 and 0.2126, respectively. In addition, the values of R2 and LOF for S.E.C are 0.9981 and 0.0606.

Valorization of MSWI bottom ash for biogas desulfurization: Influence of biogas water content

In this study an alternative valorization of Municipal Solid Waste Incineration (MSWI) Bottom Ash (BA) for H2S elimination from landfill biogas was evaluated. Emphasis was given to the influence of water content in biogas on H2S removal efficiency by BA. A small-scale pilot was developed and implemented in a landfill site located in France. A new biogas analyzer was used and allowed real-time continuous measurement of CH4, CO2, O2, H2S and H2O in raw and treated biogas. The H2S removal efficiency of bottom ash was evaluated for different inlet biogas humidities: from 4 to 24gwater/m3. The biogas water content was found to greatly affect bottom ash efficiency regarding H2S removal. With humid inlet biogas the H2S removal was almost 3 times higher than with a dry inlet biogas. Best removal capacity obtained was 56gH2S/kgdryBA. A humid inlet biogas allows to conserve the bottom ash moisture content for a maximum H2S retention.

Effect of S/N Ratio on the Removal of Hydrogen Sulfide from Biogas in Anoxic Bioreactors

Both biogas desulfurization and wastewater denitrification can be achieved simultaneously, when nitrate/nitrite is used as the electron acceptor for H2S oxidation. The main objective of this study was to investigate the influence of the molar ratio of sulfide/nitrate (S/N) on biogas desulfurization performance in a biotrickling filter (BTF) and a biobubble column (BBC). The results show that with the decrease of the S/N ratios from 3.6 to 0.7, the removal efficiencies of H2S increased from about 66 to 100%, while the removal of nitrate decreased from 100 to 70% in the two bioreactors. The BTF has a better and more stable desulfurization performance than the BBC does, which could be attributed to their different gas-liquid contacting modes. With the increase of the S/N ratios from 1.0 to 2.5 in the BTFs, the removal of H2S in biogas was affected slightly, while the percentages of the produced sulfate decreased evidently. In addition, different supplying methods of nitrate wastewater, i.e., intermittent and continuous, did not affect the removal of H2S significantly, while the intermittent addition of nitrate wastewater increased the percentages of sulfate and denitrification performance.

Study on selective hydrogen sulfide removal over carbon dioxide by catalytic oxidative absorption method with chelated iron as the catalyst

H2S is a detrimental impurity that must be removed for upgrading biogas to biomethane. H2S removal selectivity over CO2 employing catalytic oxidative absorption method and its influence factors were studied in this work. The desulfurization experiments were performed in a laboratory apparatus using EDTA-Fe as the catalyst and metered mixture of 60% (v/v) CH4, 33% (v/v) CO2 and 2000–3000 ppmv H2S balanced by N2 as the simulated biogas. It was found that for a given catalytic oxidative desulfurization system, it exists a critical pH, at which desulfurization selectivity achieves the highest. It was also observed that desulfurization selectivity increased along with the increase of chelated iron concentration, gas flow rate, and ratio of gas flow rate to liquid flow rate (G/L). This demonstrated that high selectivity and high efficiency for biogas desulfurization could both be achieved through optimizing these parameters. Specific to the desulfurization system of this work, when the gas flow rate was set as 1.1 L/min, after optimizing the above mentioned parameters, i.e. EDTA-Fe concentration of 0.084 mol/L, absorption solution pH of 7.8, and G/L of 55, the desulfurization selectivity factor reached 142.1 with H2S removal efficiency attained 96.7%.

Kinetics and the mass transfer mechanism of hydrogen sulfide removal by biochar derived from rice hull

ABSTRACTThe biochar derived from rice hull was evaluated for its abilities to remove hydrogen sulfide (H2S) from gas phase. The surface area and pH of the biochar were compared. The biochar derived from rice hull was evaluated for its abilities to remove hydrogen sulfide (H2S) from gas phase. The surface area and pH of the biochar were compared. The different pyrolysis temperature has great influence on the adsorption of H2S. At the different pyrolysis temperature, the H2S removal efficiency of rice hull-derived biochar was different. The adsorption capacities of biochar were 2.09 mg·g–1, 2.65 mg·g–1, 16.30 mg·g–1, 20.80 mg·g–1, and 382.70 mg·g–1, which their pyrolysis temperatures were 100 °C, 200 °C, 300 °C, 400 °C and 500 °C respectively. Based on the Yoon-Nelson model, it analyzed the mass transfer mechanism of hydrogen sulfide adsorption by biochar.Implications: The paper focuses on the biochar derived from rice hull–removed hydrogen sulfide (H2S) from gas phase. The surface area and pH of the biochar were compared. The different pyrolysis temperatures have great influence on the adsorption of H2S. At the different pyrolysis temperatures, the H2S removal efficiency of rice hull–derived biohar was different. The adsorption capacities of biochar were 2.09, 2.65, 16.30, 20.80, and 382.70 mg·g−1, and their pyrolysis temperatures were 100, 200, 300, 400, and 500 °C, respectively. Based on the Yoon-Nelson model, the mass transfer mechanism of hydrogen sulfide adsorption by biochar was analyzed.

Modeling an aerobic biotrickling filter for biogas desulfurization through a multi-step oxidation mechanism

A dynamic model describing physical–chemical and biological processes for the removal of high loads of H2S from biogas streams in biotrickling filters (BTFs) was developed, calibrated and validated for a wide range of experimental conditions in a lab-scale BTF. The model considers the main processes occurring in the three phases of a BTF (gas, liquid and biofilm) in a co-current flow mode configuration. Furthermore, this model attempts to describe accurately the intermediate (thiosulfate and elemental sulfur) and final products (sulfate) of H2S oxidation. A sensitivity analysis was performed in order to focus parameters estimation efforts on those parameters that showed the highest influence on the estimation of the H2S removal efficiency, the accumulated mass of sulfur and the sulfate concentration in the liquid phase. Biofilm and liquid layer thicknesses, specific growth rate of biomass over elemental sulfur and the H2S global mass transfer coefficient were the parameters that showed the highest influence on model outputs. Experimental data for model calibration corresponded to the operation of the BTF under stepwise increasing H2S concentrations between 2000 and 10,000ppmv. Once the model was calibrated, validation was performed by simulating a stationary feeding period of 42days of operation of the BTF at an average concentration of 2000ppmv and a dynamic operation period where the BTF was operated under variable inlet H2S concentration between 1000 and 5000ppmv to simulate load fluctuations occurring in industrial facilities. The model described the reactor performance in terms of H2S removal and predicted satisfactorily the main intermediate and final products produced during the biological oxidation process.

Avaliação de lavador de gases do tipo Venturi, operando com solução de hidróxido de sódio, para dessulfuração de biogás com altas concentrações de H2S

RESUMO O processo de metanização tem sido empregado com sucesso como tratamento biológico de distintas tipologias de efluentes orgânicos. Para conversão do biogás em energia, o sulfeto de hidrogênio (H2S) é o principal composto a ser removido. A metanização da vinhaça, principal efluente do setor sucroenergético, gera um biogás com concentrações de H2S que podem ultrapassar os 30.000 ppmV, com grande variação devido às condições operacionais das usinas. Processos químicos de dessulfuração apresentam-se como uma alternativa que alia robustez e maior controle operacional do processo, além de não resultarem em diluição da concentração de metano, como ocorre em processos biológicos. Entretanto, a principal desvantagem desses processos é a demanda de compostos químicos, resultando em custos operacionais elevados. Esse trabalho teve como objetivo avaliar a viabilidade técnica de se realizar uma dessulfuração química de biogás com altas concentrações de H2S, além de determinar as concentrações de hidróxido de sódio (NaOH) em meio aquoso que proporcionassem altas eficiências de remoção de H2S e que possibilite que o efluente desse processo seja passível de regeneração por microrganismos sulfo-oxidantes. Foi utilizado um lavador do tipo Venturi, com uma solução de 5,00 x 10-2 mol.L-1 de NaOH. Na faixa de pH de crescimento desses microrganismos, as eficiências de remoção de H2S variaram de 99,3 a 99,9%. Constatou-se que é possível atingir eficiências máximas de remoção de H2S utilizando soluções de 5,00 x 10-3 mol.L-1 de NaOH, obtendo um efluente com pH adequado ao crescimento de microrganismos sulfo-oxidantes. Verificou-se, ainda, que o CO2 exerce grande influência na competição pelas hidroxilas presentes no meio.

Metagenomic analysis of a desulphurisation system used to treat biogas from vinasse methanisation

We investigated the response of microbial community to changes in H2S loading rate in a microaerated desulphurisation system treating biogas from vinasse methanisation. H2S removal efficiency was high, and both COD and DO seemed to be important parameters to biomass activity. DGGE analysis retrieved sequences of sulphide-oxidising bacteria (SOB), such as Thioalkalimicrobium sp. Deep sequencing analysis revealed that the microbial community was complex and remained constant throughout the experiment. Most sequences belonged to Firmicutes and Proteobacteria, and, to a lesser extent, Bacteroidetes, Chloroflexi, and Synergistetes. Despite the high sulphide removal efficiency, the abundance of the taxa of SOB was low, and was negatively affected by the high sulphide loading rate.

Monolithic Zn–Co–Ti based sorbents for hot syngas desulfurization

Charge of monolithic Zn–Co–Ti–O based sorbent was manufactured using natural clay as a binder and tested in model hot syngas desulfurization. Fresh and regenerated sorbent was characterized by XRD, SEM–EDX, XPS, mercury porosimetry, and TPRH2. After four cycles of desulfurization (at 540°C) and regeneration (540–650°C), monoliths retained the mechanical integrity and their geometry did not change. Monolithic sorbent captured 5.3gS/100g in the first cycle and 13.8gS/100g in the last one. Concentration of H2S in the treated gas was lowered from 6000ppmv to 3ppmv and the H2S removal efficiency was min. 99.6%. Fresh sorbent contains Zn2Ti3O8 (dominant phase), TiO2 and SiO2, while in the regenerated one always occurs: TiO2 (dominant phase), ZnTiO3, Zn2Ti3O8; SiO2; Zn2SiO4 and ZnAl2O4. Reducibility and the amount of sulfates formed in the used sorbent depend on its position in the bed. After tests, small amounts of free ZnO are present on the surface of the used monoliths. During regeneration the zinc oxide (from Zn–Ti–O mixed oxides) reacts with Al2O3 or SiO2 (clay components), and forms compounds more resistant to deactivation, such as Zn2SiO4 and ZnAl2O4.

Biogas upgrading from vinasse digesters: a comparison between an anoxic biotrickling filter and an algal‐bacterial photobioreactor

AbstractBACKGROUNDBiological technologies for biogas upgrading such as anoxic biotrickling filters (BTF) and algal–bacterial photobioreactors (PBR) constitute a cost‐effective, environmentally friendly alternative to conventional physical–chemical methods. Nonetheless, there is a lack of studies comparing their performance when treating real biogas.RESULTSA H2S removal efficiency >98% was consistently recorded in both systems, with elimination capacities up to 26 and 12.4 g S‐H2S m−3 h−1 in the BTF and PBR, respectively, at empty bed residence times (EBRTs) of ∼ 30 min. Both bioreactors demonstrated a high robustness towards fluctuations in biogas composition and flowrate, maintaining nearly complete desulfurization despite the variations in sulfur load and EBRT. The BTF also showed an immediate recovery from a 15 days operational shut‐down, and the ability to utilize the nutrients from nitrate‐supplemented digestate during biogas desulfurization. In addition, the PBR supported an average CO2 removal of 23.0 ± 11.8%, increasing to 62% at higher pH of 8.1, with a carbon fixation rate of 285 mg CO2 L−1 d−1.CONCLUSIONSThe BTF was confirmed as a robust technology for the desulfurization of real biogas, even when supplemented with effluent from the digester. High H2S removal was also achieved in the PBR, the CO2 fixation capacity of microalgae enhancing biogas purification. © 2015 Society of Chemical Industry

Biofiltration of H2S-rich biogas using Acidithiobacillus thiooxidans

Biogas has limited use in energy generation mainly due to the presence of hydrogen sulfide (H2S). Currently, most of the techniques employed in the removal of H2S from biogas have a chemical base, with high material costs and generating secondary pollutants. Biological processes for H2S removal have become effective and economical alternative techniques to traditional gas-treatment systems based on physicochemical techniques. Therefore, the aim of this work was to investigate the performance of a bench-scale biofilter for the removal of H2S present in synthetic biogas. In addition, CO2 and CH4 concentrations in the outlet biogas were evaluated. The inoculum used in the experiment was composed of Acidithiobacillus thiooxidans fixed on a packing of wood chips. Synthetic biogas was supplied to the system with a composition of 60 % CH4, 39 % CO2 and 1 % H2S. The biofilter operated continuously for 37 days with an average H2S removal efficiency of 75 ± 13 % and maximum of 97 %. The elimination capacity of the system reached an average of 130 ± 23 g m−3 h−1 and a maximum of 169 g m3 h−1. The biofiltration system showed an average reduction of only 6 % in CH4 concentration from biogas. Thus, besides being efficient in the removal of H2S, the system was able to maintain the biogas energy value.

Simultaneous hydrogen sulphide and ammonia removal in a biotrickling filter: Crossed inhibitory effects among selected pollutants and microbial community change

A coal slag-packed biotrickling filter inoculated with autotrophic sulphide oxidizing and ammonia oxidizing bacteria was successfully operated for co-treating hydrogen sulphide (H2S) and ammonia (NH3). Excellent removal efficiencies of H2S (98.5%) and NH3 (99.9%) were obtained at loadings of up to 120g H2Sm−3h−1 and 80g NH3m−3h−1, respectively. The inhibitory effects of selected pollutants and metabolic products on the treatment performance were evaluated through mass balance and bacterial community analyses. The presence of NH3 significantly affected the composition of metabolic products of sulphide oxidation. Elemental sulphur was the dominant metabolite that ranged from 35% to 65%, whereas the amount of sulphite and thiosulphate generally increased up to 20%. However, a similar trend in the distribution of by-products to the results of nitrogen mass balance from sole NH3 removal was observed. The predominant bacteria were also changed with different loading ratios (H2S:NH3).

Selective absorption of H2S from a gas mixture with CO2 in a microporous tube-in-tube microchannel reactor

In industrial gas processing, there is an increasing interest in gas absorption processes for the selective removal of H2S from gas streams with a high CO2/H2S ratio. In this work, the selective absorption of H2S from a gas mixture with CO2 into N-methyldiethanolamine (MDEA) in a microporous tube-in-tube microchannel reactor (MTMCR) was studied. A high H2S removal efficiency of 99.85% could be achieved. The effects of various parameters such as MDEA concentration, liquid and gas flow rates, gas–liquid ratio, absorbent temperature, mean micropore size and annular channel width of MTMCR on H2S removal efficiency and selectivity were explored. The results indicated that MDEA concentration, liquid and gas flow rates had significant influence on H2S removal efficiency and selectivity. With the increase of MDEA concentration and liquid flow rate, H2S removal efficiency increased while selectivity decreased. Increasing gas flow rate resulted in H2S removal efficiency decrease and the selectivity increase. The smaller micropore size and annular channel width led to higher H2S removal efficiency and lower selectivity. Furthermore, the micropore size had a bigger effect on H2S selective removal process than the annular channel width. The results obtained imply a great potential for MTMCR applied to the selective absorption of H2S.

Sorptive Removal of Hydrogen Sulfide from Gas Streams by an Mg‐Al Layered Double Hydroxide

Mg‐Al layered double hydroxides (Mg‐Al LDHs) were used as an adsorbent for hydrogen sulfide (H2S) removal. Removal efficiency of H2S by the Mg‐Al LDH has been investigated at different temperatures and humidity. The results have shown Mg‐Al LDH to be highly promising as an adsorbent for H2S removal. Research results about sorption mechanisms indicate that at lower temperatures (20 ºC), H2S removal by Mg‐Al LDHs is mainly a physical sorption process; however, at higher temperature (> 40 ºC), it is dominated by chemical reactions involving ion exchange. Confirmation of the redox reaction between H2S and Mg‐Al LDHs was provided by XPS data. The results obtained demonstrate that the H2S removal efficiency of Mg‐Al LDHs increases with the temperature increasing, and decreases with the water vapour content increasing.

The selective removal of H2S over CO2 from biogas in a bubble column using pretreated digester effluent

Raw biogas purification can be achieved using various physicochemical techniques. Unfortunately, techniques for the simultaneous absorption of CO2 and H2S are susceptible to the corrosive nature of H2S. Furthermore, the absorbents utilized are often expensive, thus requiring regeneration. Concurrently, on farm digesters are now moving toward the incorporation of NH3 recovery. One such process, air stripping, requires elevation of pH, which as a result produces an alkaline effluent. Due to this, a physicochemical H2S removal process was investigated in a bubble column reactor using this manure based alkaline absorbent. Selective removal of H2S over CO2 increased nearly 50% by altering the sparger configuration. Additional selectivity was achieved by decreasing the effluent height in the bubble column and increasing the superficial gas velocity. Continuous countercurrent mode of operation was tested and relatively high H2S removal efficiency (84%) was achieved at a biogas-to-effluent ratio (v/v) of 20:1, close to that typically found on dairy digesters.

Microbial Analysis and Efficiency of Biofiltration Packing Systems for Hydrogen Sulfide Removal from Wastewater Off Gas

Hydrogen sulfide (H2S) is commonly detected among waste gases from wastewater treatment plants causing atmospheric pollution, which affects human and environmental health. The aim of this study is to characterize the microbial diversity present within two different H2S biofiltration systems packed with either pozzolan or marble and to assess their efficiency for H2S removal. Few examples were reported about the relationship between the characteristics of the packing material and biofilter performance. Physicochemical parameters such as sulfate concentrations and pH are measured along this study. Sulfate concentrations produced by H2S oxidation were higher using marble biofilter and a higher efficiency of H2S removal was observed. Microbial diversity was characterized using a culture-independent 16S rRNA gene approach. Our results show that the biofilter packed with marble is very acidic (pH <3) and exhibits a higher bacterial diversity with three dominant bacterial families: Xanthomonadaceae, Hydrogenophilaceae, and Spirillaceae. However the biofilter packed with pozzolan is less acidic (pH 5.7–6.8) and shows completely different phylotypes where the plastid 16S rRNA gene of the red algae Cyanidium caldarium and Acidithiobacillus bacterium were retrieved. Such results show that the selection of an appropriate packing material is essential to the odor removal performance of a biofilter system and should allow for the design of better reactor with optimal operating conditions.

The effect of oxygen supply on the dual growth kinetics of Acidithiobacillus thiooxidans under acidic conditions for biogas desulfurization.

In this study, to simulate a biogas desulfurization process, a modified Monod-Gompertz kinetic model incorporating a dissolved oxygen (DO) effect was proposed for a sulfur-oxidizing bacterial (SOB) strain, Acidithiobacillus thiooxidans, under extremely acidic conditions of pH 2. The kinetic model was calibrated and validated using experimental data obtained from a bubble-column bioreactor. The SOB strain was effective for H2S degradation, but the H2S removal efficiency dropped rapidly at DO concentrations less than 2.0 mg/L. A low H2S loading was effectively treated with oxygen supplied in a range of 2%–6%, but a H2S guideline of 10 ppm could not be met, even with an oxygen supply greater than 6%, when the H2S loading was high at a short gas retention time of 1 min and a H2S inlet concentration of 5000 ppm. The oxygen supply should be increased in the aerobic desulfurization to meet the H2S guideline; however, the excess oxygen above the optimum was not effective because of the decline in oxygen efficiency. The model estimation indicated that the maximum H2S removal rate was approximately 400 ppm/%-O2 at the influent oxygen concentration of 4.9% under the given condition. The kinetic model with a low DO threshold for the interacting substrates was a useful tool to simulate the effect of the oxygen supply on the H2S removal and to determine the optimal oxygen concentration.

Bio-desulfurization of biogas using acidic biotrickling filter with dissolved oxygen in step feed recirculation

Triple stage and single stage biotrickling filters (T-BTF and S-BTF) were operated with oxygenated liquid recirculation to enhance bio-desulfurization of biogas. Empty bed retention time (EBRT 100–180s) and liquid recirculation velocity (q 2.4–7.1m/h) were applied. H2S removal and sulfuric acid recovery increased with higher EBRT and q. But the highest q at 7.1m/h induced large amount of liquid through the media, causing a reduction in bed porosity in S-BTF and H2S removal. Equivalent performance of S-BTF and T-BTF was obtained under the lowest loading of 165gH2S/m3/h. In the subsequent continuous operation test, it was found that T-BTF could maintain higher H2S elimination capacity and removal efficiency at 175.6±41.6gH2S/m3/h and 89.0±6.8% versus S-BTF at 159.9±42.8gH2S/m3/h and 80.1±10.2%, respectively. Finally, the relationship between outlet concentration and bed height was modeled. Step feeding of oxygenated liquid recirculation in multiple stages clearly demonstrated an advantage for sulfide oxidation.

Mathematical Modeling and Genetic Algorithm Optimization of Reactive Absorption of H2S

AbstractA rate‐based mathematical model was developed for the reactive absorption of H2S in NaOH, with NaOCl or H2O2 as the chemical oxidant solutions in a packed column. A modified mass transfer coefficient in the gas phase was obtained by genetic algorithm and implemented in the model to correct the assumption of instantaneous reactions. The effects of different operating variables including the inlet H2S concentration, inlet gas mass flux, initial NaOH, concentrations of the chemical oxidants in the scrubbing solutions, and liquid‐to‐gas ratio on the H2S removal efficiency were studied. A genetic algorithm was employed to optimize the operating variables in order to obtain maximum removal efficiency of H2S. The model results were in good agreement with the experimental data.