High Concentrations Of H2S Research Articles

Corrosion Behavior of X52 Anti-H2S Pipeline Steel Exposed to High H2S Concentration Solutions at 90 °C

Initial corrosion kinetics of X52 anti-H2S pipeline steel exposed to 90 °C/1.61 MPa H2S solutions was investigated through high temperature and high pressure immersion tests. Corrosion rates were obtained based on weight loss calculation. The corrosion products were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and electron probe micro-analysis (EPMA). The initial corrosion kinetics was found to obey the exponential law. With increasing immersion time, the main corrosion products changed from iron-rich mackinawite to sulfur-rich pyrrhotite. The corrosion films had two layers: an inner fine-grained layer rich in iron and an outer columnar-grained layer rich in sulfur. The corrosion film formed through the combination of outward diffusion of Fe2+ ions and inward diffusion of HS− ions. The variation of the corrosion products and compaction of the corrosion layer resulted in a decrease in the diffusion coefficient with increasing immersion time. The double-layered corrosion film formed after long time immersion acted as an effective barrier against diffusion.

Spatial distribution of hydrogen sulfide from two geothermal power plants in complex terrain

Concerns have arisen about the health impact and odor annoyance of hydrogen sulfide (H2S) emissions associated with geothermal power production. Measurements have been made at stationary measuring stations in inhabited areas but little is known about the spatial behavior of the H2S plumes. This study presents field measurements of the spatial distribution of the ground concentration of H2S within a 30 km radius of two geothermal power plants during 20 distinct events spanning one year. The results showed that high H2S concentration was correlated with high air stability, low wind speed and absence of precipitation. The odor threshold (11 μg m−3) was exceeded in all events. The instantaneous measurements exceeded the 24-h average national health limit (50 μg m−3) up to 26 km from the power plants. The shape of the measured plumes at the same location was similar between events, indicating repeated patterns in plume distribution. Convergence of plumes was observed due to spatial variability in wind direction. Plumes were found to follow mountain passes and accumulate alongside a mountain range. AERMOD modeling demonstrated that narrower plumes with higher concentration can be expected for smoother terrain, such as lakes, consistent with measurements.

Corrosion behavior about tubing steel in environment with high H2S and CO2 content

The corrosion behavior of C100 steel in simulated environments with high H2S and CO2 content was studied through high-temperature and high-pressure autoclave, and the H2S stress corrosion cracking (SSC) resistance of C100 steel was evaluated by SSC tests. Scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD) technique were employed to characterize the corrosion products and the metal matrix. The results indicate that all of the corrosion products in this investigation are mainly composed of different types of iron sulfide such as Fe0.95S, FeS0.9, Fe0.985S, Fe7S8 and FeS, and the absence of iron carbonate in the corrosion scales suggests that the corrosion process is governed by H2S corrosion. The corrosion rate decreases in the initial stage and then increases with the enhancement of the temperature. There exists a minimum corrosion rate at about 110 °C. Under the partial pressure of H2S lower than 9 MPa, the corrosion rate decreases with the increase of \(P_{H_2 S} \) While over 9 MPa, a higher \(P_{H_2 S} \) will result in a faster corrosion process. When the applied stress is 72%, 80% and 85% of actual yield strength (AYS), all tested specimens show no crack, which reveals a superior SSC resistance.

Characterisation of corrosion products formed on copper exposed at indoor and outdoor sites with high H2S concentrations

Corrosion products formed on copper exposed indoors and outdoors at sites with high hydrogen sulphide (H2S) concentrations were characterised using several analytical techniques. The crystalline corrosion products that formed on the copper exposed indoors were chalcocite (Cu2S) and cuprite (Cu2O), while those that formed on the copper exposed outdoors were chalcocite, cuprite and basic copper sulphates. Surface analysis by X-ray photoelectron spectroscopy revealed differences between the copper exposed indoors and outdoors that are explained by the composition, localisation and oxidation of the corrosion products. The surface morphologies of the corrosion products also differed. Elemental depth profiling by glow discharge optical emission spectroscopy revealed that the corrosion products that formed indoors were mainly chalcocite with cuprite only at and near the surface. In contrast, the corrosion products that formed outdoors were a mixture of chalcocite and cuprite. These differences in corrosion products are attributed to the differences in relative humidity during exposure.

P03 Effect of S-adenosyl-l-methionine (SAM), an allosteric activator of cystathionine-β-synthase (CBS) on colorectal cancer cell proliferation and bioenergetics in vitro

Several series of in vitro and in vivo data presented at the current Meeting support the conclusion that colon cancer cells selectively overexpress CBS, which produces H2S, to maintain cellular bioenergetics, thereby supporting tumor growth and to promote angiogenesis and vasorelaxation. These studies, taken together, identify CBS-derived H2S as a tumor promoting factor and a potential future anticancer drug target. The purpose of the current study was to investigate the effect of S-adenosyl-l-methionine (SAM) on the proliferation and bioenergetics of the colon cancer cell line HCT116 in vitro. The non-transformed, the non-tumorigenic colon epithelial cell line NCM356, derived from the normal margin of a rectal cancer specimen, was used as a control. HCT116 cells were cultured in McCoy’s 5A medium, while NCM356 cells were cultured in DMEM supplemented with 10% fetal bovine serum. For assessment of cell proliferation, the xCELLigence system (Roche) was used. For the measurement of bioenergetic function, the XF24 Extracellular Flux Analyzer (Seahorse) was used. Oxygen consumption rate (OCR) after oligomycin (1.5 μg/ml) was used to assess ATP production rate and OCR after FCCP (0.5 μM) to assess maximal mitochondrial respiratory capacity. 2-deoxyglucose (100 mM) was used to estimate cellular glycolytic dependency and antimycin A (2 μg/m) and rotenone (2 μM) were used to inhibit the flux of electrons through complex III and I, to detect residual non-mitochondrial activity. Addition of SAM (0.1–1 mM) to HCT116 cells (which show a high expression of CBS) induced a concentration-dependent increase in cell proliferation between 0–50 h, while higher concentrations of SAM (3 mM) inhibited cell proliferation. However, at time periods between 50–100 h, the cells treated with intermediary concentrations of SAM (0.3–1 mM) showed a suppression of cell proliferation compared to the vehicle control; the proliferation-enhancing effect of SAM was only maintained throughout the entire experimental period with the 0.1 mM concentration of SAM. In contrast to HCT116 cells, NCM356 cells (which have only a low-level expression of CBS) were proliferating at a substantially slower rate, and SAM failed to stimulate their proliferation. Extracellular Flux Analysis of the effect of acute exposure of HCT116 cells to SAM (0.1–1 mM) induced a concentration-dependent increase in their oxygen consumption and bioenergetic function, while in NCM356 cells SAM failed to enhance oxygen consumption and cellular bioenergetics. Longer-term exposure of HCT116 cells to both low concentrations of SAM (0.1 mM) and high concentrations of SAM (1 mM) suppressed cellular bioenergetic responses. Studies presented at the current meeting demonstrate that the H2S-producing enzyme CBS is selectively overexpressed in human colorectal cancer cells, and significantly contributes to their proliferation, migration and invasion in vitro. The present data, demonstrating that short-term exposure of SAM to HCT116 cells exerts proliferative and positive bioenergetic effects that are in line with the effects of exogenously administered H2S in the same experimental system further support the view that CBS in colon cancer cells produces H2S in a regulated fashion, and that this H2S serves as an endogenous cancer cell proliferation and bioenergetic factor. Higher local concentrations of H2S are known to be antiproliferative, at least in part due to their inhibitory on mitochondrial function. Therefore, the longer-term inhibition of cell proliferation and bioenergetic function noted with SAM in the present experiments may either be attributed to the adverse autocrine effects of high concentrations of H2S, produced when CBS is ‘over-activated’ by SAM, or, alternatively, may be related to additional, CBS-independent pharmacological effects of SAM.

Corrosion behaviour of X52 pipeline steel in high H2S concentration solutions at temperatures ranging from 25°C to 140°C

High temperature and high pressure immersion tests in an autoclave were employed to study the corrosion behaviour of X52 pipeline steel in aqueous solutions containing high concentrations of H2S. The corrosion products generated were characterised using scanning electron microscope, energy dispersive spectroscopy and X-ray diffraction. It was seen that at a constant H2S concentration of 22 g/l, the corrosion rate increased with increasing temperature up to 90°C, thereafter decreased at 120°C and slightly increased again at 140°C while the corrosion rate increased with H2S concentration at a temperature of 90°C. When the temperature and H2S concentration increased, the corrosion product converted from iron rich to sulphur rich products in the following sequence: mackinawite→troilite→pyrrhotite, where the microstructure and stability of the corrosion products had an important effect on the corrosion rate. The corrosion film was formed through the combination of the outward diffusion of Fe2+ ions and the inward diffusion of H2S and HS− species.

Elimination of high concentration hydrogen sulfide and biogas purification by chemical–biological process

A chemical–biological process was performed to remove a high concentration of H2S in biogas. The high iron concentration tolerance (20gL−1) of Acidithiobacillus ferrooxidans CP9 provided sufficient ferric iron level for stable and efficient H2S elimination. A laboratory-scale apparatus was setup for a 45 d operation to analyze the optimal conditions. The results reveal that the H2S removal efficiency reached 98% for 1500ppm H2S. The optimal ferric iron concentration was kept between 9 and 11gL−1 with a cell density of 108CFUg−1 granular activated carbon and a loading of 15gSm−3h−1. In pilot-scale studies for biogas purification, the average inlet H2S concentration was 1645ppm with a removal efficiency of up to 97% for a 311d operation and an inlet loading 40.8gSm−3h−1. When 0.1% glucose was added, the cell density increased twofold under the loading of 65.1gSm−3h−1 with an H2S removal efficiency still above 96%. The analysis results of the distribution of microorganisms in the biological reactor by DGGE show that microorganism populations of 96.7% and 62.7% were identical to the original strain at day 200 and day 311, respectively. These results clearly demonstrate that ferric iron reduction by H2S and ferrous iron oxidation by A. ferrooxidans CP9 are feasible processes for the removal of H2S from biogas.

Characteristics and Origin of Natural Gases in the Puguang and Maoba Gas Fields, NE Sichuan Basin, China

Northeastern Sichuan Basin is one of the most significant areas for natural gas exploration in China, and Puguang and Maoba are the two most important and typical gas fields there. The common characteristics of the natural gases in the Puguang and Maoba gas fields include extremely high dryness, high H2S contents, high δ13C1 values, with a wide range of δ13C2 values. Based on gas composition and stable carbon isotope values, natural gases in the study area are classified into three genetic groups, derived from type III kerogen, type II kerogen and those with a complex origin. The latter group is most likely the result of mixing between low maturity ethane inherited from earlier oil accumulation and high maturity methane generated from subsequent in-reservoir oil cracking and thermochemical sulfate reduction. In conjunction with regional source rock data, the Upper Permian Longtan Formation is considered to be the main source rock for the gases in the Feixianguan-Changxing reservoirs of the Puguang and Maoba gas fields.

A multicenter retrospective survey on a suicide trend using hydrogen sulfide in Japan

Context. In Japan, suicide by inhaling hydrogen sulfide (H2S) by mixing commercial products escalated into a nationwide trend in April 2008. Objective. We conducted a multicenter retrospective survey on the demographics, clinical features, treatments, and outcomes of patients exposed to H2S suicide attempts. Materials and methods. Subjects included patients transported to emergency facilities in Japan from January 2005 to December 2011 following H2S suicide attempts. Among 277 facilities to which a letter requesting data collection was sent, questionnaires were sent to and filled out by the 47 (18%) facilities that agreed to provide data. Questionnaires were collected and data were extracted at Kitasato University. Results. A total of 156 patients were included in this survey. Patients involved in an H2S suicide attempt increased from 1 in 2007 to 51 in 2008, and gradually decreased from 44 in 2009 to 37 in 2010 and 23 in 2011. Ninety-two patients attempted H2S suicide (primary exposure group), and 64 were secondarily affected by the suicide attempt (secondary exposure group). Patients in the primary exposure group were young (mean, 30.3 years (10.9)), and male patients (n = 62) were approximately two times more likely to attempt H2S suicide than females (n = 30). Forty-eight patients in cardiopulmonary arrest at the scene did not survive. Five non-cardiopulmonary arrest patients died, and five patients who presented with a Glasgow coma scale (GCS) < 8 and lactic acidosis had neurological or cardiac signs or symptoms at discharge. Antidote therapy was performed on 26 of the primary group patients, but with poor outcomes. None of the secondary group patients were in cardiopulmonary arrest at the scene, five received antidotal therapy after arriving at the hospital, and all completely recovered from H2S exposure. Discussion and conclusion. Mortality (58%) among patients who attempted H2S suicide was very high, likely resulting from inhaling high concentrations of H2S after mixing commercial products in a sealed and confined space.

Impacts of meteorological factors on hydrogen sulfide concentration downwind of geothermal power plants

Hydrogen sulfide (H2S) concentration in the city of Reykjavik, downwind of geothermal power plants has been studied with respect to meteorological factors as the odor and other effects are starting to become a nuisance. The main sources of H2S in Reykjavik City were the Nesjavellir and Hellisheidi Geothermal Power Plants, which are both less than 35 km east of the city. The H2S concentration in Reykjavik was correlated with the H2S emissions from the power plants but was also heavily influenced by weather conditions. The results showed that the H2S concentration at the Grensasvegur Measuring Station was elevated when the wind direction was from 54° to 125°, especially when the wind direction was stable for several hours. The H2S concentration in Reykjavik was highest when the wind speed in the city was between 1.5 and 4 m s−1, and decreased rapidly with higher wind speeds. H2S concentration showed correlation with the air temperature in the city below 3 °C and the concentration rose as the temperature decreased, and the air became more stable and was highest when there was a temperature inversion. The quantitative effects of precipitation on H2S concentration could not be determined in this study although the events with the highest H2S concentration occurred when there was no precipitation. The results showed that favorable conditions for high H2S events can be expected in Reykjavik 2–6 times per year and events with H2S concentration exceeding 50 μg m−3 might be expected on average about 2 times per year. The results also indicate that events with high H2S concentration can be predicted by using a current weather forecast.

The Experiment Research of Corrosion Behavior about Tubing Steel in Environment with High H&lt;sub&gt;2&lt;/sub&gt;S and CO&lt;sub&gt;2&lt;/sub&gt; Content

The corrosion behavior of C100 steel in simulated environments with high H2S and CO2 content was studied through high-temperature and high-pressure autoclave, and the H2S stress corrosion cracking (SSC) resistance of C100 steel was evaluated by SSC tests. Scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD) technique were employed to characterize the corrosion products and the metal matrix. The results indicate that all of the corrosion products in this investigation are mainly composed of different types of iron sulfide such as Fe0.95S, FeS0.9, Fe0.985S, Fe7S8 and FeS, and the absence of iron carbonate in the corrosion scales suggests that the corrosion process is governed by H2S corrosion. The corrosion rate decreases in the initial stage and then increases with the enhance of the temperature. There exists a minimum corrosion rate at about 110°C. Under the partial pressure of H2S lower than 9MPa, the corrosion rate decreases with the increase of P . While over 9MPa, a higher P will result in a faster corrosion process. When the applied stress is 72 %, 80 % and 85 % of actual yield strength (AYS), all tested specimens show no crack, which reveals a superior SSC resistance. The precipitation of the second phase particles at the grain boundary or in crystal grain, the dislocation tangle and the dislocation pinning of the dispersion carbonide hinder the SSC cracks to propagate.

Simulation of gas kick with high H2S content in deep well

The phase transition, from a subcritical state to a gaseous state, of the natural gas with high H2S content and the solubility of the H2S component in the drilling fluid will make the multiphase flow behavior very different from the pure natural gas-drilling fluid two-phase flow under the gas kick condition in a deep well. With consideration of the phase transition and the solubility of the H2S component in the natural gas, a multiphase flow model is established. The simulation analysis results indicate that, for a typical case of a well depth of 4 325 m, the density of the 100%-H2S natural gas can be 4 times higher than that of the 0%-H2S natural gas, and the solubility of the 100%-H2S natural gas is 130 times higher than that of the 0%-H2S natural gas. These will make the detection of the gas invasion more difficult. While the invasion gas moves up along the wellbore to a certain position, the phase transition and the release of the dissolved gas may cause a rapid volume expansion, increasing the blowout risk. The calculation results also show that the risks of a gas kick can be reduced by increasing the wellhead back pressure.

A Study on Hydrogen Sulphide as Potential Tracer in Landfill Gas Monitoring

Municipal solid waste (MSW) landfills are one of the major source of hydrogen sulphide (H2S) which is the offensive odours potentially creating annoyance in adjacent communities. This project focuses on H2S emission from landfills in Perlis, Malaysia. Landfill gas (LFG) samples were collected and analyzed accordance with NIOSH method 6013. The mean concentrations of H2S in Kuala Perlis Landfill and Padang Siding Landfill are 210.68 ppm and 242.85 ppm respectively. High concentrations of H2S may be a concern for employees working on the landfill site. These results indicate that workers should use proper personal protection at landfill when involved in excavation, landfill gas collection, and refuse compaction. The formation of H2S most likely to be contributed by the biological conversion of sulfate from gypsum-rich soils and landfill wastewater treatment sludges by sulfate-reducing bacteria (SRB) which can utilize dissolved sulfate as an electron acceptor. H2S is conveniently detected by hand held analyzer, such Jerome meter, landfill gas analyzer. In the organic range, in the ease of detection range in the dispersion rate within the landfill site, the monitored H2S gas form a very noticeable concentration with the travelling wind direction. It proved that the dispersion rate of H2S are suitable as tracer to detect route of travelling in a certain distance.

Handling Jurassic Field Sour Gas Creates Challenges Upstream and Downstream

This article, written by Editorial Manager Adam Wilson, contains highlights of paper SPE 154452, ’Challenges in Sour-Gas Handling for Kuwait Jurassic Sour Gas,’ by Bader Nasser Al Qaoud, SPE, Kuwait Oil Company, prepared for the 2012 SPE Middle East Unconventional Gas Conference and Exhibition, Abu Dhabi, 23-25 January. The paper has not been peer reviewed. Kuwait Oil Company started free gas production from its Jurassic sour-gas field in May 2008 with the commissioning of Early Production Facility (EPF) 50. The field produces sour gas and light crude from a deep high-pressure/high-temperature naturally fractured carbonate reservoir with low permeability and low porosity. The well fluid is characterized by high hydrogen sulfide (H2S) (5%) and carbon dioxide (CO2) (5%) content. Handling such highly corrosive well fluid creates a wide range of challenges, from upstream at the wellhead to downstream at the processing facility. Upstream Challenges Upstream challenges for the Jurassic gas field have been related mostly to subsurface corrosion of tubing, unplanned well downtime because of hydrate formation during winter, and failure of automated chokes for some wells. Subsurface Tubing Corrosion. A moderate to severe corrosion rate has been indicated by corrosion logs in the production tubing because of the high H2S and CO2 content of the well fluid. Plans exist for existing carbon-steel tubing for four wells to be replaced by corrosion-resistant alloy material, and regular corrosion logs are being run for other suspect wells. Hydrate Formation in Flowlines. Hydrate formation has been observed in flowlines during winter for 11 wells when flowline temperature drops to 65°F. This has resulted in unplanned production loss and substantial well downtime. The best mitigation option implemented was the injection of kinetic hydrate inhibitor (KHI) at the wellhead at the onset of winter for the identified wells, and a good degree of success has been achieved. However, KHI is not very effective in controlling hydrates at temperatures below 4°C, and this is a problem that needs to be addressed as a priority. Flowline insulation at the point of restriction and heat tracing also have been implemented for four wells, with a fair amount of success. Challenges With Automated Chokes. Automated chokes were first installed in the field in April 2011. The purpose of automation was to improve control of remotely located wells, enhance safety, and ensure better control of field production. Sixteen Jurassic wells are currently on automated chokes of three different makes—M1, M2, and M3. Challenges With Make M1. The factory-set choke opening did not match actual choke opening. Choke adjustments had to be made with flowing wellhead pressure (FWHP) as a reference, and this leads to inaccurate settings. Scale formation also has been observed in-side the choke body, causing restricted flow and inaccurate FWHP readings and, therefore, poor monitoring of well performance.

Sulfide induces apoptosis and Rho kinase-dependent cell blebbing in Jurkat cells

Hydrogen sulfide (H₂S) is a toxic gaseous substance, and accidental exposure to high concentrations of H₂S has been reported to be lethal to humans. Inhaled and absorbed H₂S is partially dissolved within the circulation and causes toxic effects on lymphocytes. However, the mechanisms involved in H₂S toxicity have not been well documented. In this study, we examined the cellular uptake and injury of sulfide-exposed human T lymphocytes (Jurkat). Cells were exposed to a H₂S donor, sodium hydroxysulfide (NaHS), at pH 6.0, 7.0, or 8.0 for 1 h at 37 °C in a sealed conical tube to avoid the loss of dissolved H₂S gas. Cytotoxicity and cellular sulfide concentrations increased dramatically as the pH of the NaHS solution decreased. Sulfide enhanced the cleavage of caspase-3 and poly (ADP-ribose) polymerase and induced early cellular apoptosis. A pan-caspase inhibitor reduced sulfide-induced apoptosis. These results indicate that sulfide induces pH-dependent and caspase-dependent apoptosis. We also found that blebbing of the plasma membrane occurred in sulfide-exposed cells. Both ROCK-1 and ROCK-2 (Rho kinases) were activated by sulfide, and sulfide-induced cell blebbing was suppressed by a ROCK inhibitor, suggesting that a Rho pathway is involved in sulfide-induced blebbing in lymphocytes.

Biotrickling filters for biogas sweetening: Oxygen transfer improvement for a reliable operation

An industrial-scale biotrickling filter for the removal of high concentrations of H2S is described in this work. The system has been operating at H2S inlet concentrations between 1000 and 3000ppmv at acidic conditions. A decrease of pH from 2.6 to 1.8 did not affect the biological activity inside the biofilter while reducing the water make-up consumption up to 75%. The current oxygen supply system, based on direct injection of air to the liquid phase, has demonstrated to be inefficient for a long-term operation leading to elemental sulfur accumulation in the packing material (i.e. promoting clogging episodes). The present study demonstrates it is possible to partially remove (40.3%) the deposited elemental sulfur by bio-oxidation when biogas is not fed. In normal operation conditions, the implementation of an aeration system based on jet-venturi devices has shown quite promising results in terms of oxygen transfer efficiency and robustness. Such improvement of oxygen transfer was translated in a better conversion of H2S to sulfate, which increased around 17%, prolonging the lifespan operation at low-pressure drop.

The Inhibitory Role of Hydrogen Sulfide in Airway Hyperresponsiveness and Inflammation in a Mouse Model of Asthma

Cystathionine γ-lyase (CSE) is one of the major enzymes producing hydrogen sulfide (H2S) in lungs, participating in the regulation of respiratory functions. The role of CSE-derived H2S in eosinophil-dominant inflammation in allergic diseases has been unclear. The objective of this study was to explore the protective role of H2S against allergen-induced airway hyperresponsiveness (AHR) and inflammation. CSE expression and H2S production rate were assessed in mouse lung tissues with ovalbumin (OVA)-induced acute asthma. AHR, airway inflammation, and Th2 response in wild-type (WT) mice were compared with those in CSE gene knockout (KO) mice. The effect of NaHS, an exogenous H2S donor, was also evaluated on these parameters. CSE expression was absent and H2S production rate was significantly lower in the lungs of CSE KO mice when compared with WT littermates. OVA challenge decreased lung CSE expression and H2S production in WT mice. CSE deficiency resulted in aggravated AHR, increased airway inflammation, and elevated levels of Th2 cytokines such as IL-5, IL-13, and eotaxin-1 in bronchoalveolar lavage fluid after OVA challenge. The aforementioned alterations were reversed by exogenous H2S treatment. More importantly, NaHS supplement rescued CSE KO mice from the aggravated pathological process of asthma. The CSE/H2S system plays a critical protective role in the development of asthma. A new therapeutic potential for asthma via targeting CSE/H2S metabolism is indicated.

Optimization of Oxygen Transfer through Membrane Diffusers for Biological Sweetening of Biogas

AbstractBiological techniques for the removal of gaseous pollutants such as hydrogen sulfide (H2S) have proved to be effective, environmentally friendly, and economically viable. However, when high concentrations of H2S are treated, the process is severely restricted by the oxygen deficit in the liquid phase. The oxygen transfer efficiency provided by a membrane diffuser is evaluated under typical pressure and salinity conditions used for the biological treatment of H2S in biogas. The optimal operating parameters for enhanced oxygen transfer were determined. The addition of pure oxygen with a membrane diffuser to increase the oxygen transfer rate and the use of a nonaqueous phase to improve oxygen transfer in a bioscrubber system are also evaluated.

Evaluation of the Effect of Sulfur on Iron-Ore Oxygen Carrier in Chemical-Looping Combustion

Chemical-looping combustion (CLC) is an emerging combustion technology that can be used to meet the demand of energy production with inherent separation of CO2. Because of the presence of sulfur contaminants in fossil fuels, the gaseous products of sulfur species and the interactions between these sulfur contaminants and the oxygen carrier are significant concerns in chemical-looping combustion. Experiments on chemical-looping combustion of a sulfur-containing gaseous fuel with iron ore as the oxygen carrier were performed by thermogravimetric analysis and Fourier transform infrared (TGA–FTIR) spectroscopy. The effects of reaction atmosphere (N2 and CO2), H2S concentration, and pressure on the reactivity of iron ore in the presence of H2S were investigated. The evolution of gaseous sulfur species was also investigated in both N2 and CO2 atmospheres. With a higher concentration of H2S in the gaseous fuel, the weight loss was slower, and a weight gain was even observed due to the sulfidation of iron ore. Sulfidation of iron ore was observed in both N2 and CO2 atmospheres, and elevated pressure contributed to a higher sulfidation rate. Compared with N2 atmosphere, CO2 atmosphere gave higher concentrations of COS and an initial SO2 peak but a lower concentration of CS2. Furthermore, the effect of sulfidation on the structure of the iron ore was investigated in a fluidized bed, and scanning electron microscopy with energy-dispersive analysis by X-rays (SEM-EDAX) and X-ray diffraction (XRD) were utilized to characterize the iron ore. The sulfidation of iron ore caused a decrease in both surface area and pore volume, and the porous surface of the oxygen carrier became smoother and almost imperforate. FeS was the only iron sulfide observed during the sulfidation process. The vulcanized iron ore could be regenerated with air calcination treatment, and the addition of H2O in the gaseous fuel could prevent the sulfidation of iron ore. The addition of CaO in the oxygen carrier was effective in mitigating the sulfidation and reducing the emission of gaseous sulfur species.

Technical and Energetic Assessment of a Three-Stage Thermochemical Treatment for Sewage Sludge

A three-stage thermochemical process comprising torrefaction, pyrolysis, and char activation is proposed for the treatment of dry sewage sludge or biomass materials. To assess the feasibility of the process, lab-scale experiments were carried out with dried sewage sludge as feedstock, and mass and energy balances were calculated. In the process, 19.3% of the sewage sludge initial weight was transformed into a bio-oil with three distinct phases and reduced water content (66.1% of water content in the aqueous phase compared to 73.8% in a single-step fast pyrolysis). The product gases had a high H2S content but also enough heating value to be combusted. After being activated by the torrefaction vapors, the solid fraction (48.2% of the initial sludge weight) showed certain pore development and might be suitable for adsorption applications. Regarding the energy balance, it was found that the combustion of part of the product gas would provide the necessary heat to drive the process (1019 kJ/kg of dry sewage sludge).