Increase In H2S Concentration Research Articles

Simultaneous capture of NH3 and H2S using TiO2 and ZnO nanoparticles - laboratory evaluation and application in a livestock facility

Simultaneous removal of ammonia (NH3) and hydrogen sulphide (H2S) from pre-mixed gases and stored swine manure gases were investigated in laboratory and semi-pilot scale systems and in a swine production facility, using TiO2 and ZnO nanoparticles. Increase of NH3 concentration in the mixture from 50 to 500 ppmv led to higher breakthrough and equilibrium adsorption capacities, while increase of temperature had an opposite effect. Equilibrium adsorption capacities at 22 °C were in the range 6.92–11.95 mg NH3 g−1 and 1.35–3.57 mg NH3 g−1 at 280 °C. Increase of H2S concentration up to a certain level led to higher equilibrium adsorption capacities but no dependency between breakthrough adsorption capacity and H2S concentration was observed. Both breakthrough and equilibrium adsorption capacities increased with the increase of temperature. The highest equilibrium adsorption capacity of 52.31 mg H2S g−1 was obtained with 550 ppmv H2S in the mixture at 140 °C, while the lowest value was 14.55 mg H2S g−1 with 50 ppmv H2S at 22 °C. At low temperature (22 °C) NH3 adsorption occurred through both physical adsorption and chemisorption, while at 280 °C chemisorption was the dominant mechanism. A sulfidation reaction involving ZnO and H2S that was favored by higher temperatures was evident. Treating gases emitted from stored swine manure in a semi-pilot scale adsorption system led to complete elimination of NH3 and H2S. Application of a nano-based air filtration-circulation system with ZnO and TiO2 nanoparticles in a swine production room during manure handling led to removal efficiencies of 67–100% for H2S and 50–100% for NH3.

A dual-mode fluorescent probe for the separate detection of mercury(II) and hydrogen sulfide

A dual-mode fluorescent probe (Probe 1) was developed for the separate detection of Hg2+ and H2S. Probe 1 could detect Hg2+ and H2S through two different reaction sites, with the mechanism of Probe 1 for Hg2+ depending on the desulfurization reaction and for H2S depending on the nucleophilic addition reaction of an aldehyde with H2S. Separate detection of Hg2+ and H2S was achieved by determining the fluorescence emission wavelength of Probe 1-Hg2+ (443 nm, λab = 247 nm) and Probe 1-H2S (504 nm, λab = 256 nm). The fluorescence intensity of Probe 1 has a linear relationship with the concentration of Hg2+ in the range 0–7 μM and the LOD was 39.28 nM. And H2S in the range 0–110 μM, the LOD was 0.7449 μM. With increasing concentrations of Hg2+, test strips gradually became darker in color. The luminescence intensity of test strips gradually increased with increasing H2S concentration, and the initially colorless Probe 1 solution gradually changed to yellow under natural light with increasing H2S concentration. Probe 1 could be used for Hg2+ and H2S detection in real samples.

CO2 corrosion behavior of sensitized 304 and 316 austenitic stainless steels in 3.5 wt.% NaCl solution and presence of H2S

The CO2 corrosion behavior of sensitized and non-sensitized 304 and 316 stainless steels in the absence and presence of H2S was investigated using cyclic polarization and electrochemical impedance spectroscopy techniques. The sensitization resulted in significant negative shift on pitting potential for both alloys. The general CO2 corrosion rate of sensitized and non-sensitized samples was not significant. However, increasing H2S concentration up to 200 ppm resulted in severe increase in general corrosion rate and also significant negative shift for pitting potential. It was concluded that, the major role of sensitization is influencing the pitting potential and pitting corrosion of both alloys.

Fuel Impurity Poisoning of Ru/γ-Al2O3 Catalyst Packed in the Reformer for Biogas-Fueled SOFC System

In operating biogas-fueled SOFC module, impurities such as H2S and siloxane can poison reforming catalyst and anode. To achieve a stable SOFC operation, fuel impurity poisoning of Ru/γ-Al2O3 catalyst has to be examined. Poisoning test for the reformer and the reformer-SOFC series were performed at 700oC. Humidified simulated biogas with varied concentration of H2S or siloxane was supplied to Ru/γ-Al2O3 beads-packed reformer. H2S poisoning test during biogas steam reforming showed a correlation between the degradation rate of CH4 conversion and the decrease rate of Ru surface area which increased with increasing H2S concentration. In the case of siloxane poisoning test, accumulated-silica covered the catalyst surface, resulting in the degradation of CH4 conversion although milder than the case of H2S. The poisoning tests for the reformer-SOFC series revealed that the degradation rate of cell voltage was considerably lower than that of CH4 conversion in the reformer for both impurities.

Using H2S plasma to modify activated carbon for elemental mercury removal

Non-thermal plasma was applied to modify activated carbons (ACs) in the presence of H2S for improving the elemental mercury (Hg0) removal performance. The physical and chemical properties of raw and modified ACs were characterized by scanning electron microscopy with energy disperse X-ray spectroscopy, Brunauer-Emmett-Teller and X-ray photoelectron spectroscopy. The Hg0 removal performance of modified AC was tested by a bench-scale fixed bed. The results indicated that H2S plasma treatment enhanced S content of raw AC. Moreover, S content and Hg0 removal efficiency of modified AC increased with the increase of H2S concentration. The reason was that higher concentration H2S resulted in more S active sites on modified AC and S active site played a significant role during the Hg0 removal process. Besides, non-thermal plasma treatment in the presence of H2S had a weak impact on BET surface area. By further analysis, it could be inferred that the improvement of Hg0 removal performance was ascribed to the chemisorption rather than physisorption. Combined the results of temperature programmed desorption and XPS analysis, the mechanism of Hg0 removal was that elemental S on the surface of modified AC reacted with Hg0 to form HgS.

A dual-sites fluorescent probe based on symmetric structure of naphthalimide derivative to detect H2S

Hydrogen sulfide (H2S) is a powerful toxin which has a strong stimulating effect on the eye, respiratory system and central nervous system. Therefore, it is essential to detect H2S in biological samples. Fluorescence imaging technology has the advantages of real-time and non-invasive, so it is very advantageous to detect H2S in living cells. In this work, we designed and synthesized a fluorescent probe (named ND-N3) based on naphthalimide derivative with symmetric structure and double recognition sites. The fluorescence intensity at 532 nm of ND-N3 obviously increased with the increase of H2S concentration. Apart from this, the probe showed excellent selectivity and rapid response time. More importantly, ND-N3 can be used to detect endogenous/exogenous H2S in living cells.

Toxicity of hydrogen sulfide toward sulfate-reducing bacteria Desulfovibrio piger Vib-7.

Sulfate-reducing bacteria (SRB) belonging to the intestinal microbiota are the main producers of hydrogen sulfide and their increasing amount due to the accumulation of this compound in the bowel are involved in the initiation and maintenance of inflammatory bowel disease. The purpose of this experiment is to study the relative toxicity of hydrogen sulfide and survival of Desulfovibrio piger Vib-7 through monitoring: sulfate reduction parameters (sulfate consumption, hydrogen sulfide production, lactate consumption and acetate production) and kinetic parameters of these processes. The research is highlighting the survival of intestinal SRB, D. piger Vib-7 under the influence of different hydrogen sulfide concentrations (1-7mM). The highest toxicity of H2S was measured in the presence of concentrations higher than 6mM, where growing was stopped, though metabolic activities were not 100% inhibited. These findings are confirmed by cross correlation and principal component analysis that clearly supported the above mentioned results. The kinetic parameters of bacterial growth and sulfate reduction were inhibited proportionally with increasing H2S concentration. The presence of 5mM H2S resulted in two times longer lag phase and generation time was eight times longer. Maximum rate of growth and hydrogen production was stopped under 4mM, emphasizing the H2S toxicity concentrations to be < 4mM, even for sulfide producing bacteria such as Desulfovibrio. The results are confirming H2S concentrations toxicity toward Desulfovibrio, especially the study novelty should be emphasized where it was found that the exact H2S limits (> 4mM) toward this bacterial strain inhabiting humans and animals intestine.

Removal of hydrogen sulfide on activated carbon supported ionic liquids

In this study, ionic liquid loaded activated carbon was applied as the adsorbent for hydrogen sulfide (H2S) removal under the anaerobic conditions in a fixed bed. The effects of activated carbon substrate, ionic liquid, initial H2S concentration and flow rate on the adsorption process were systematically studied. The experimental results show that the activated carbon named AC-1 having higher surface area and micropore volume is more suitable as the support for ionic liquid. Amongst three ionic liquids studied, the 1-ethyl-3-methylimidazolium acetate loaded activated carbon exhibites the highest H2S sorption capacity performance. As a results of the superior performance of the 1-ethyl-3-methylimidazolium acetate loaded activated carbon, further tests and characterizations were performed on the sorbent. The breakthrough capacity of 1-ethyl-3-methylimidazolium acetate sorbent is two times greater than pure activated carbon. In addition, it is confirmed that increasing H2S concentration enhances H2S adsorption capacity, and the adsorption capacity of H2S decreases significantly with increasing gas flow rate.

Degradation behavior of Ni-YSZ anode-supported solid oxide fuel cell (SOFC) as a function of H2S concentration

This study investigated the effect of H2S concentration (5, 10 and 50 ppm) on the degradation and performance of Ni-YSZ anode supported solid oxide fuel cells. When supplied with hydrogen fuel containing H2S, the cell voltage dropped rapidly, and with increasing H2S concentration, voltage drop % increased (due to higher sulfur coverage on the Ni surface) and saturated more rapidly. A high concentration (50 ppm) of H2S led to an additional, slow rate voltage loss. In all cases, cell performance did not completely recover even after being supplied with H2S-free hydrogen fuel, because of the incomplete desorption of sulfur from the Ni surface. After the performance tests, nickel sulfides were detected on the Ni surface by Raman spectra, which were produced by the reaction of the remaining adsorbed sulfur with Ni during the cooling process. This indicates that the formation of nickel sulfides was not responsible for the secondary voltage drop. SEM/EDS analyses combined with FIB revealed that the reason for the additional 2nd drop was Ni oxidation; at a high sulfur coverage ratio (50 ppm), the outer layer of the Ni particle was oxidized by oxygen ions transported from the electrolyte. This indicates that H2S concentration as well as current density is a critical factor for Ni oxidation, and gives rise to the second voltage drop (irreversible cell degradation). The present work showed that the degradation behavior and phenomenon can differ significantly depending on the concentration of H2S, i.e., permanent changes may or may not occur on the anode (such as Ni oxidation) depending upon H2S concentration.

CO2 and H2S absorption by MEA solution in packed-bed columns under inclined and heaving motion conditions - Hydrodynamics and reactions performance for marine applications

Two-phase countercurrent flow dynamics and simultaneous CO2 and H2S removal performance were studied in countercurrent randomly packed-bed columns with fourth generation Raschig super-Rings exposed to static inclination and heaving motion via an unsteady-state comprehensive three-dimensional model. Gas-liquid countercurrent flow displays a gradual deviation to axial symmetry with the increase of angle of the packed-bed column inclination. CO2 absorption process is negatively impacted in inclined packed-bed columns and the deficit in CO2 removal performance increases with the increase of H2S concentration in gas phase. H2S removal efficiency is marginally reduced and mostly at considerable packed bed inclinations. Under heaving motion of the packed-bed column, an oscillatory two-phase flow and CO2-monoethanolamine (MEA) absorption process performance develop around the steady-state solution of the column stationary state prior to heaving application. As externally-generated packed-bed column oscillations, the heaving motion impacts more CO2 absorption because of very high rate constant of the reaction between H2S and MEA and because the packed-bed column is exposed only to small episodes of time to maximum/minimum heaving acceleration where H2S removal efficiency can be affected.

A systematic study of the iron hydroxide-based adsorbent for removal of hydrogen sulphide from biogas

This study was aimed to evaluate the hydrogen sulfide (H2S) removal efficiency of an economic iron hydroxide-based adsorbent from simulated biogas mixture with an H2S concentration range of 500–10300 ppm. The properties of these porous materials such as crystal structures, surface patterns, surface area, pore volume and pore size were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET measurements. The H2S adsorption capacity (Adscap) is nearly independent of the drying temperature of hydroxide-based adsorbent over the range of temperatures tested (100–200 °C) as well as relative humidity (0–80%) under equal conditions of H2S concentration. In addition, the experimental results revealed that the Adscap increased exponentially from 23.3 to 48.7 wt% with the increased retention time from to 0.5–52.9 s and decreasing space velocity from 7433 to 68 h-1. At the same time, Adscap increased linearly from 20.57 to 35.18 wt% with the increasing H2S concentration from 500 to 10300 ppm.

Hydrogen sulfide removal from biogas by biotrickling filter inoculated with Halothiobacillus neapolitanus

Hydrogen sulfide (H2S), a highly corrosive gas, is found in biogas due to the biodegradation of proteins and other sulfur containing organic compounds present in feed stock during anaerobic digestion. The presence of H2S is one of the biggest factors limiting the use of biogas. It should be removed prior to application of biogas in an electric generator or industrial boiler. The present research evaluated the performance of biotrickling filter inoculated with Halothiobacillus neapolitanus NTV01 (HTN) on the H2S removal from synthetic biogas. HTN, isolated and purified from activated sludge, is a sulfur oxidizing bacteria able to degrade H2S and thiosulfate to elemental sulfur and sulfate, respectively. Operational parameters in a short term operation were varied as following; gas flow rate (0.5–0.75 LPM); EBRT (40–120 s); the inlet H2S concentrations (0–1500 ppmv); liquid recirculation rate (3.6–4.8 L/h). EBRT showed a greater effect to the removal efficiency than increasing H2S concentration. Longer EBRT resulted higher removal efficiency. The changes of liquid recirculation rates did not significantly affect the removal efficiency. In long term operation, the gas flow rate and liquid recirculation rate were fixed at 0.5 LPM (120 s EBRT) and 3.6 L/h; and H2S concentrations were varied (0–2040 ppmv). The maximum elimination capacity was found as 78.57 g H2S/m3 h, which had greater performance than the previous studies.

Reservoir Souring – Latest developments for application and mitigation

Sulphate-reducing prokaryotes (SRP) have been identified in oil field fluids since the 1920s. SRP reduce sulphate to sulphide, a toxic and corrosive species that impacts on operational safety, metallurgy and both capital and operational cost. Differences in water cut, temperature, pressure and fluid chemistry can impact on the observed H2S concentration, meaning that an increase in H2S concentration does not always correlate with activity of SRP. However it wasn’t until the 1990s that SRP activity was accepted as the leading cause of reservoir souring (i.e. an increase in H2S concentrations) in water flooded oil fields.The process of sulphate-reduction has been well documented at the genetic, enzymatic and physiological level in pure cultures under laboratory conditions. DNA sequencing has also identified new groups of microorganisms, such as archaea which are capable of contributing to reservoir souring. This has led to some recent advances in microbial control and detection, however, despite this, many of the methods used routinely for microbial control and detection are over a century old. We therefore look towards emerging and novel mitigation technologies that may be used in mitigating against reservoir souring, along with tried and tested methods. Modelling and prediction is another important but often under-used tool in managing microbial reservoir souring. To be truly predictive, models need to take into account not only microbial H2S generation but also partitioning and mineral scavenging. The increase in ‘big data’ available through increased integration of sensors in the digital oil field and the increase in the DNA sequencing capabilities through next-generation sequencing (NGS) therefore offer a unique opportunity to develop and refine microbial reservoir souring models. We therefore review a number of different reservoir souring models and identify how these can be used in the future.With this comprehensive overview of the current and emerging technologies we will highlight areas where significant development effort could generate rewards that can improve detection, prediction and control of microbial reservoir souring.

Corrosion Behavior of API X100 Steel Material in a Hydrogen Sulfide Environment

Recently, the API X100 steel has emerged as an important pipeline material for transportation of crude oil and natural gas. At the same time, the presence of significant amounts of hydrogen sulfide (H2S) in natural gas and crude oil cause pipeline materials to corrode, which affects their integrity. In this study, the effect of H2S concentration on the corrosion behavior of API X100 in 3.5% NaCl solution is presented. The H2S gas was bubbled into saline solutions for different durations, and the corrosion tests were then performed using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM) techniques were used to characterize the corroded surface. The results indicate that the corrosion rate of API X100 steel decreases with increasing H2S bubbling time due to the increase in H2S concentration in 3.5% NaCl solutions. It is noticed that an accumulation of a critical amount of hydrogen in the metal can result in hydrogen-induced crack initiation and propagation. It was further observed that, when the stress limit of a crystalline layer is exceeded, micro-cracking of the formed protective sulfide layer (mackinawite) occurs on the API X100 steel surface, which may affect the reliability of the pipeline system.

Application of ZnO Nanoparticles in Control of H2S Emission from Low-Temperature Gases and Swine Manure Gas

Zinc oxide nanoparticles were evaluated for the removal of hydrogen sulfide from low-temperature gases, as well as swine manure gas using laboratory and semi-pilot scale systems. Effects of gas flow rate (200 and 450 mL min−1), H2S concentration (90–1500 ppmv), temperature (1–41 °C), and particle size (18, 80–200 nm) were investigated in the laboratory scale system using premixed gases (H2S-balanced N2). The breakthrough and equilibrium adsorption capacities increased with an increase of H2S concentration. Application of high gas flow rates saturated the adsorbent faster and decreased the adsorption capacities. Adsorption capacities of 18 nm particles were higher than those of 80–200 nm. Regardless of H2S concentration, the equilibrium adsorption capacity was not affected by temperature in the range 1 to 22 °C but increased when a higher temperature of 41 °C was applied. Among the evaluated isotherms, Langmuir-Freundlich described the equilibrium data obtained with 18 and 80–200 nm particles with a higher level of accuracy. Experiments in a semi-pilot scale adsorption system with 18 nm ZnO and gases emitted from the stored swine manure demonstrated the effectiveness of ZnO nanoparticles in removal of H2S from these representative gases. Specifically, treatment of manure gas in the semi-pilot scale adsorption system decreased the level of H2S from an average inlet value of 235.7 ± 85.2 ppmv to a negligible level.

The chemistry and saturation states of subsurface fluids during the in situ mineralisation of CO2 and H2S at the CarbFix site in SW-Iceland

In situ carbonation of basaltic rocks could provide a long-term carbon storage solution, which is essential for the success and public acceptance of carbon storage. To demonstrate the viability of this carbon storage solution, 175tonnes (t) of pure CO2 and 73tonnes (t) of a 75% CO2-24% H2S-1% H2-gas mixture were sequentially injected into basaltic rocks at the CarbFix site at Hellisheidi, SW-Iceland from January to August 2012. This paper reports the chemistry and saturation states with respect to potential secondary minerals of sub-surface fluids sampled prior to, during, and after the injections. All gases were dissolved in water during their injection into permeable basalts located at 500–800m depth with temperatures ranging from 20 to 50°C. A pH decrease and dissolved inorganic carbon (DIC) increase was observed in the first monitoring well, HN-04, about two weeks after each injection began. At storage reservoir target depth, this diverted monitoring well is located ∼125m downstream from the injection well. A significant increase in H2S concentration, however, was not observed after the second injection. Sampled fluids from the HN-04 well show a rapid increase in Ca, Mg, and Fe concentration during the injections with a gradual decline in the following months. Calculations indicate that the sampled fluids are saturated with respect to siderite about four weeks after the injections began, and these fluids attained calcite saturation about three months after each injection. Pyrite is supersaturated prior to and during the mixed gas injection and in the following months. In July 2013, the HN-04 fluid sampling pump broke down due to calcite precipitation, verifying the carbonation of the injected CO2. Mass balance calculations, based on the recovery of non-reactive tracers co-injected into the subsurface together with the acid-gases, confirm that more than 95% of the CO2 injected into the subsurface was mineralised within a year, and essentially all of the injected H2S was mineralised within four months of its injection. These results demonstrate the viability of the in situ mineralisation of these gases in basaltic rocks as a long-term and safe storage solution for CO2 and H2S.

Experimental study on electrochemical corrosion of FV520B in natural gas environment

The electrochemical corrosion of the FV520B stainless steel for natural gas compressor impeller is studied by means of the uniform experimental method. The electrochemical corrosion potential, current density and Tafel slope of the material are measured, and the polarization resistance is solved. The experimental results show that FV520B material does not appear passivation area in the presence of the natural gas environment with H2S, and the material has been in the activation and dissolved state. When the temperature is below 130 °C, the corrosion is dominated by the process of the anode reaction, the concentration of H2S is the decisive factor to determine the occurrence of stress corrosion, the increase of H2S concentration significantly accelerates the corrosion process of the specimen, CO2 inhibits the occurrence of the stress corrosion to a certain extent.

Effect of sulfide films formed on X65 steel surface on hydrogen permeation in H2S environments

In this work, the morphology, structure and ion-selectivity of surface sulfide films formed on an X65 pipeline steel in solutions with various pH values and H2S concentrations were characterized, and the effect of the film on hydrogen permeation was investigated. Results demonstrated that crystalline iron sulfide (FeS) and/or mackinawite forms on the steel surface during H2S corrosion, depending on the H2S concentration and the solution pH. The presence of sulfide films blocks the hydrogen permeation through the steel, and the blocking effect increases with the increasing H2S concentration and reducing pH value. Compared to the film containing crystalline FeS only, the mixed compositions of mackinawite and FeS in the film cause an increased effect to block hydrogen permeation. The sulfide films are an n-type semiconductor with the anion selectivity, which, combined with the film thickness, contributes to the blocking effect on hydrogen permeation into the filmed steel.

Colorimetric detection of hydrogen sulfide based on terbium-G-quadruplex-hemin DNAzyme

It is of great importance to simply and sensitively detect hydrogen sulfide (H2S) because of its role in various physiological processes as well as its inherent toxicity. In this work, a colorimetric method for H2S detection was developed by employing terbium-G-quadruplex-hemin (Tb/G4-hemin) DNAzyme as a peroxidase mimic, which can catalyze H2O2-mediated oxidation of 2,2′-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) to produce radical cation (ABTS+). Compared with the G4-hemin DNAzyme promoted by K+ and Na+, Tb/G4-hemin DNAzyme exhibits a higher catalytic activity. In the presence of Ag+, the peroxidase-like activity of Tb/G4-hemin DNAzyme can be inhibited significantly owing to the disruption of G-quadruplex structure. However, the addition of H2S can effectively suppress such negative behavior by competitive binding with Ag+, leading to the recovery of the peroxidase-like activity of Tb/G4-hemin DNAzyme, which can be reflected by an increase in absorbance signal of ABTS+. The absorbance of ABTS+ was enhanced linearly with increasing H2S concentration from 20nM to 2μM. The detection limit for H2S is 13nM, which is much lower than most of previous methods. Moreover, the proposed method possesses the features of simple preparation, easy reproducibility and good biocompatibility. Given the fine performances and striking properties, we believe that the Tb/G4-hemin DNAzyme would have a great promise for analytical applications.

The Effect of Temperature and Acid Gas Loading on Corrosion Behavior of API 5L X52 Carbon Steel in Amine Unit

The effect of temperature and H2S concentration on amine corrosion of API 5L X52 carbon steel in a CO2-saturated 25 wt.% diethanolamine solution was investigated via electrochemical techniques. It was found that increase in temperature from 25 to 80 °C resulted in severe increase in corrosion rate from 0.88 to 16.24 mpy due to increase in degradation rate of amine. Also, it was concluded that increase in H2S concentration led to increase in corrosion rate because of formation of more heat stable amine salts. The effect of temperature on corrosion rate was more significant than acid gas loading.