H2S Gas Mixtures Research Articles

Hydrate phase equilibrium conditions for H2S and CO2 gas mixture removal from natural gas: modeling and optimization study

In this study, for the first time, a comprehensive mathematical modeling of the optimal conditions for the gas hydrates formation of hydrogen sulfide (H2S) and carbon dioxide (СО2) was carried out with the aim of them removing from natural gas. The study was carried out on a model gas mixture close to the natural gas composition: CH4 – C2H6 – С3Н8 – n-С4Н10 – СО2 – H2S – N2. A temperature range of 268.15–283.15 К and a pressure range of 2.00–8.00 MPa were investigated. The efficiency was assessed based on the gas hydrate distribution coefficients. It was found that the gas hydrate extraction of H2S is more significantly affected by the concentration of H2S in the initial gas mixture. The gas hydrate extraction of СО2 is more significantly affected by the temperature and pressure of the gas separation unit. The maximum gas hydrate distribution coefficient of H2S is 42.05 at T = 268.15 K, p = 8.00 MPa. The maximum gas hydrate distribution coefficient of СО2 is 0.49 at T = 283.15 K, p = 8.00 MPa. Due to the small amounts of CO2 entrapped in gas hydrates, a scheme that combines a multi-stage hydrate-based and membrane technology has been suggested to purify natural gas further.

Growth of Highly Oriented (VNbMoTaW)S2 Layers.

Compositional tunability, an indispensable parameter for modifying the properties of materials, can open up new applications for van der Waals (vdW) layered materials such as transition-metal dichalcogenides (TMDCs). To date, multielement alloy TMDC layers are obtained via exfoliation from bulk polycrystalline powders. Here, we demonstrate direct deposition of high-entropy alloy disulfide, (VNbMoTaW)S2, layers with controllable thicknesses on free-standing graphene membranes and on bare and hBN-covered Al2O3(0001) substrates via ultra-high-vacuum reactive dc magnetron sputtering of the VNbMoTaW target in Kr and H2S gas mixtures. Using a combination of density functional theory calculations, Raman spectroscopy, X-ray diffraction, scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, we determine that the as-deposited layers are single-phase, 2H-structured, and 0001-oriented (V0.10Nb0.16Mo0.19Ta0.28W0.27)S2.44. Our synthesis route is general and applicable for heteroepitaxial growth of a wide variety of TMDC alloys and potentially other multielement alloy vdW compounds with the desired compositions.

Towards net-zero: CO2 capture and biogas purification through electric potential swing desorption to achieve SDGs 7 and 13

Currently, the potential of biomethane derived from biogas is substantial, positioning it to fulfill a considerable share of the United Kingdom’s total energy needs. The primary challenge associated with raw biogas lies in purifying it to produce biomethane, a process that necessitates the removal of carbon dioxide and hydrogen sulfide. Among the various methods, adsorption of activated carbon (AC) stands out as a particularly effective and cost-efficient approach for converting biogas into biomethane, provided that the regeneration of AC proves economically viable. In this research, a segment of activated carbon was utilized to assess the adsorption properties when exposed to a gas mixture of CO2, H2S, and N2 within a regenerative activated carbon setup. This investigation encompassed the analysis of adsorption and desorption behaviors, process capacities, and the impact of regeneration. To enhance the adsorption of CO2, electro-conductive polymers (ECPs) were incorporated into the AC samples, leading to an extension in breakthrough time. Subsequent to adsorption, the electric potential swing desorption (EPSD) was employed for in situ regeneration of activated carbon samples, involving potentials of up to 30 V. The findings exhibited that the newly introduced EPSD technique considerably diminished desorption durations for both H2S and CO2. Moreover, it successfully rejuvenated the accessible adsorption sites, resulting in reduced desorption times compared to the initial breakthrough time during adsorption. Consequently, the EPSD system proves to be a promising candidate for in situ regeneration of activated carbon to eliminate CO2 and H2S from biogas. Notably, this approach offers inherent advantages over conventional methods including thermal swing adsorption (TSA) and pressure swing adsorption (PSA) in terms of regeneration. The demonstrated method underscores the potential for more efficient and economically viable cycles of adsorption and desorption, thereby enhancing the overall biogas-to-biomethane conversion process to achieve SDGs 7 and 13 for clean and green energy applications.

Hydrogen sulfide measurement of combustion gaseous product using ultraviolet absorption spectroscopy

Measurement of hydrogen sulfide (H2S) in gaseous product can provide direct reference for high-temperature corrosion of industrial combustion equipment. Aiming at the interference effect of overlapping measurement of absorption spectrum for H2S and other combustion gas components in UV absorption spectroscopy, the simulation calculation of ultraviolet band absorption spectrum of the typical gaseous products of coal combustion were carried out. The cross interference effects of combustion gaseous products were analyzed in detail. Due to the SO2 and H2S gas under typical combustion condition have equivalent absorption strength in the 228 nm-233 nm band, the influence of SO2 on H2S concentration inversion must be emphatically considered, and the inversion algorithm of H2S gas concentration under the background interference of combustion gaseous products SO2 was put forward. In order to validate the measurement accuracy by the inversion algorithm, the measurement experiments of gas mixture of H2S and SO2 were carried out. The results show that the algorithm can effectively solve the problem of cross interference between the detection of H2S and SO2 in the combustion gaseous products by UV absorption spectroscopy. On this basis, the sampling, pre-treatment and H2S gas concentration measurement system for boiler flue gas near the wall was developed and applied to measure H2S concentration of flue gas near the wall in a 1000 MW ultra-supercritical coal-fired power generation boiler. The results can provide important references for combustion adjustment and high-temperature corrosion prevention of boiler.

The effect of the presence of water on sulfur removal capacity during H2S removal from syngas using ZnO adsorbent

ABSTRACT Compared to extensive studies on affecting parameters in sulfur removal with ZnO adsorbents from coal gasification syngas, similar studies conducted for biomass gasification syngas (BGS) are quite rare. Thus, considering the BGSs with high water content, this study was performed to investigate the effect of H2O presence in syngas on sulfur removal capacity (SRC) of ZnO adsorbents. Initially, the effect of gas composition and temperature on SRC in binary gas mixture was investigated. While H2O decreased the SRC, as expected, the highest reduction in the capacity occurred in the CO–H2S gas mixture due to observed COS formation. Second, the SRCs and resulting COS formation were compared for synthetic syngas mixtures having different water contents and for different amounts of adsorbents. Finally, the separate and combined effects of temperature and H2O on SRC and COS formation in synthetic syngas were investigated by comparing SRCs of typical syngas under wet and dry conditions. The results showed that increasing the amount of adsorbent and temperature results in higher SRC due to a reduction in COS formation through the reactions of COS with H2 and H2O. This indicates that it is critical to control the residence time of syngas and temperature to reduce COS formation during ZnO adsorption.

Modeling solubility of sulfur in pure hydrogen sulfide and sour gas mixtures using rigorous machine learning methods

Accurate determination of sulfur solubility in pure hydrogen sulfide (H2S) and sour gas mixtures has a leading role and a fundamental importance in handling and addressing sulfur deposition issues. In this study, rigorous paradigms based on two artificial neural network (ANN) types, namely multilayer perceptron (MLP) and cascaded forward neural network (CFNN), optimized by Levenberg–Marquardt (LM) algorithm were proposed as machine learning (ML) modeling tools to predict the solubility of sulfur in sour gas mixtures and pure H2S. Besides, explicit and simple-to-use correlations were established using gene expression programming (GEP). The paradigms derived from the methods aforementioned were developed using widespread experimental database. The obtained results indicated that the outcomes gained from the proposed MLP, CFNN and GEP-based correlations are in a high coherence and agreement with the experimental data. In addition, it was found that among the all suggested schemes, CFNN models are the most accurate paradigms for estimating the solubility of sulfur in sour gas mixtures and pure H2S with root mean square error (RMSE) of 0.0232 and 3.8101, respectively. Furthermore, a comparison between the performance of CFNN and the prior alternatives demonstrated that the CFNN models predict the solubility of sulfur in sour gas mixtures and pure H2S more accurately. Moreover, based on the trend analysis, it was concluded that the predictions of CFNN follow the real tendency of sulfur solubility in pure H2S and sour gas mixtures with respect to the input parameters. Besides, the sensitivity analysis dictated that pressure and temperature have the most significant impact on sulfur solubility calculation in pure H2S and sour gas mixtures. The results reported in this investigation revealed that implication of the considered soft computing approaches in the estimation of sulfur solubility in sour gas mixtures and pure H2S can lead to the generation of more reliable predictive paradigms which can be integrated in other related applications. Lastly, the findings of this study can help for effective prediction of the solubility of sulfur in sour gas mixtures and pure H2S while simulating different natural gas processes.

Plasma Diagnostics in Reactive High-Power Impulse Magnetron Sputtering System Working in Ar + H2S Gas Mixture

A reactive high-power impulse magnetron sputtering system (HiPIMS) working in Ar + H2S gas mixture was investigated as a source for the deposition of iron sulfide thin films. As a sputtering material, a pure Fe target was used. Plasma parameters in this system were investigated by a time-resolved Langmuir probe, radio-frequency (RF) ion flux probe, quartz crystal monitor modified for measurement of the ionized fraction of depositing particles, and by optical emission spectroscopy. A wide range of mass flow rates of reactive gas H2S was used for the investigation of the deposition process. It was found that the deposition rate of iron sulfide thin films is not influenced by the flow rate of H2S reactive gas fed into the magnetron discharge although the target is covered by iron sulfide compound. The ionized fraction of depositing particles decreases from r ≈ 40% to r ≈ 20% as the flow rate of H2S, QH2S, changes from 0 to 19 sccm at the gas pressure around p ≈ 1 Pa in the reactor chamber. The electron concentration ne measured by the Langmuir probe at the position of the substrate decreases over this change of QH2S from 1018 down to 1017 m−3

Experimental Analysis and Model Validation on the Performance of Impregnated Activated Carbons for the Removal of Hydrogen Sulfide (H2S) from Sewage Biogas

Organic waste exploitation is crucial for waste emissions restraint in air, soil and water. This type of waste can be exploited to produce biogas, a valuable fuel exploitable for energy purposes. A circular approach for energy production is much cleaner and more sustainable than the traditional linear approach. In this work, organic waste was used for biogas production to feed a highly efficient solid oxide fuel cell power generator, which requires an ultra-purified fuel. Commercial sorbents were experimentally studied in conjunction with a dynamic adsorption model to predict the breakthrough time and organize the material change-over. In the presence of 0.1% oxygen in the gas mixture, AirDep® CKC showed a marked increase in the adsorption capacity (from 3.91 to 84.87 mg/g), overcoming SulfaTrap® R8G (49.91 mg/g). The effect of several operating parameters on adsorption capacity was evaluated: inlet H2S concentration, filter geometry and gas mixture velocity. Experimental data revealed that adsorption capacity increases with initial H2S concentration, following the typical trend of the Langmuir isotherm. Model simulations were in good agreement compared to experimental results, with an average relative error lower than 7%. A sensitivity analysis on the adsorption capacity was accomplished considering parameters from operational and empirical correlations.

Quantitative analysis of SO2, H2S and CS2 mixed gases based on ultraviolet differential absorption spectrometry.

SO2, H2S and CS2 are the decomposition components of insulating gas SF6. The detection of these gases is significant for the online monitoring and fault diagnosis of SF6 electrical equipment. In this study, an ultraviolet differential optical absorption spectrometry (UV-DOAS) platform for detecting the concentration of SO2, H2S and CS2 mixed gases was established and a quantitatively detecting method was proposed. Firstly, the concentration of SO2 was calculated by the spectrum data at 300 nm band. Then the gas mixture spectra of H2S and CS2 at 200 nm band were obtained after linear deduction of SO2 spectrum. By wavelet extraction and fourier transform, the spectral information of H2S and CS2 was separated and the concentrations of the two gases were calculated. The method can detect the concentrations of SO2 (1-20 ppm), H2S (1-20 ppm) and CS2 (0.01-2 ppm) ternary gas mixture and the detection limits of SO2, H2S and CS2 are 0.44 ppm, 0.49 ppm and 3.23 ppb. This method has good detection sensitivity and high detection precision, which is suitable for the on-line monitoring of SF6 gas insulated equipment.

Investigation of selective desulfurization performance of sterically hindered amines

We investigated the H2S/CO2 gas mixture absorption rate and selectivity of 2-(tert-butylamino)ethanol (TBE) and 2-amino-2-methyl-1-propanol (AMP) using a static gas absorption method. The H2S and CO2 gas mixture was pumped into a reaction kettle filled with sterically hindered amines solubilized in water. The influence of time on the H2S absorption rate and selectivity of the sterically hindered amine solutions was investigated.

Hydrogen Sulfide Gas Detection via Multivariate Optical Computing.

Hydrogen-sulfide gas is a toxic, colorless gas with a pungent odor that occurs naturally as a decomposition by-product. It is critical to monitor the concentration of hydrogen sulfide. Multivariate optical computing (MOC) is a method that can monitor analytes while minimizing responses to interferences. MOC is a technique by which an analogue calculation is performed entirely in the optical domain, which simplifies instrument design, prevents the drift of a calibration, and increases the strength and durability of spectroscopic instrumentation against physical perturbation when used for chemical detection and identification. This paper discusses the detection of hydrogen-sulfide gas in the ultraviolet (UV) spectral region in the presence of interfering gaseous species. A laboratory spectroscopic measurement system was set up to acquire the UV spectra of H2S and interference gas mixtures in high-pressure/high-temperature (HPHT) conditions. These spectra were used to guide the design and fabrication of a multivariate optical element (MOE), which has an expected measurement relative accuracy of 3.3% for H2S, with a concentration in the range of 0–150 nmol/mL. An MOC validation system with the MOE was used to test three samples of H2S and mercaptans mixtures under various pressures, and the relative accuracy of H2S measurement was determined to be 8.05%.

ZnO and Cu-based adsorbents for biogas desulfurization at room temperature

Synthesis and structural characterization of ZnO and Cu based materials were done in order to compare chemical, morphological and microstructural effects in sorbent materials for gas-phase desulfurization reaction at room temperatures as a potential application in biogas cleaning. The materials were synthesized through two wet chemical routes, firstly using zinc nitrate, hexamethylenetetramine and NaOH reagents at 70 and 90 °C for ZnO flower-like and rod-like structures, respectively; and secondly a typical calcination of metallic copper to obtain CuO. Powder X-ray diffraction, X-ray fluorescent spectroscopy analysis were realized. Results showed a unique zincite phase for ZnO and three phases in copper samples: Cu0, Cu2O and CuO (76.3, 18.3 and 5.4 wt%). The size of crystal domains varied from 180 to 1600 nm, while the particle size varied from 660 to 1020 nm. These materials were tested in desulfurization reactions at room temperature using a fixed-bed glass reactor. In order to avoid poisoning and asphyxiation risks a non-desulfurized biogas influent was simulated by a gas mixture of N2 and H2S (100 ppm). The reactor was fed with the gas mixture at rate of 450 ml/min (GHSV 9120 h−1). The composition of effluent gas was determined using a biogas detector, coupled with an electrochemical H2S sensor. Results show that CuO and ZnO could be feasible adsorbents for the removal of hydrogen sulfide; however, they became saturated after 300 s while high surface area materials, evidenced by SEM, showed higher saturation capacity. Characterization of wasted adsorbents using electron microscopy techniques and fluorescence X-ray spectroscopy evidenced the presence of metallic sulfides at amounts less than 0.05 wt%, although no crystalline phases were detected in further analysis.

Simultaneous measurement absorption of CO2 and H2S mixture into aqueous solutions containing Diisopropanolamine blended with 1-butyl-3-methylimidazolium acetate ionic liquid

In environmental industry, capturing of acid gases, particularly CO2, has always been a major problem. The different techniques such as absorption and adsorption processes have been used for removal of acid gases from flue and natural gases. In recent years, a new type of solvent, known as green solvent or ionic liquid (IL), due to its notable properties has been introduced. In this work, the mixtures of aqueous solutions of Diisopropanolamine (DIPA) blended with 1-butyl-3-methylimidazolium acetate ([bmim][acetate]) ionic liquid (IL) are used. Using a static high pressure equilibrium cell, the simultaneous absorption of a gas mixture of CO2 (70mol%) and H2S (30mol%) into aqueous solutions of DIPA blended with [bmim][acetate] was measured. The gas compositions were chosen in close to highest sour natural gas streams in gas treatment plants. The weight percent of the aqueous DIPA+ionic liquid systems are (50wt%+5wt%), (50wt%+10wt%), (30wt%+5wt%), (30wt%+10wt%) and (50wt%+50wt%), respectively. The experiments were carried out at 323.15 and 348.15K and in total pressure range of about 0.2–2.5MPa. The results illustrate that an increase in temperature and decrease in DIPA concentration lead to lower solubility of the both acid gases. Moreover, it can be deduced from the results that using ionic liquid at low concentrations leads to lower solubility of CO2 because of diminishing the solution alkalinity. However, at high IL concentrations, more CO2 absorption takes place through physical absorption. On the other hand, H2S solubility enhances at the whole range of ionic liquid mass percent, because the present IL is more selective towards H2S that leads to intensify physical absorption.

Simultaneous Removal of PH3, H2S, and Dust by Corona Discharge

Conversion of PH3 and H2S and simultaneous removal of dust by corona discharge were studied in a wire-cylinder corona discharge reactor. Under the corona discharge, the removal efficiencies of PH3, H2S, and dust reached 99.5, 99.0, and 99.9%, respectively. The results of this study indicated that high conversion of PH3 and H2S was achieved under high SIE (specific input energy). The required SIE for PH3 was lower than that for H2S to achieve the same conversion efficiency, partially because the chemical bond energy of PH3 is lower than that of H2S. Low content of O2 was favorable for removing PH3 and H2S due to the energy consumption of O2 in the electric field. PH3 was converted to elemental phosphorus, H2, and H3PO4, and H2S was converted to elemental sulfur, H2, and SO2 or SO42– when PH3 only or H2S only gas was treated with corona discharge under very low O2 content condition (0.1 vol %). The gas mixture of PH3 and H2S under low O2 content condition generated H2, H3PO4, P4S10, elemental sulfur, and SO...

Modeling of stability conditions of natural gas clathrate hydrates using least squares support vector machine approach

This paper concerns a novel computer-based approach namely Least Square version of Support Vector Machine (LSSVM) algorithm to estimate/represent hydrate forming/dissociating conditions of various gases in the presence of pure water or aqueous solutions of salt(s) and/or alcohol(s). To this end, several models have been presented to predict the hydrate dissociating temperature (HDT) of C1, C2, C3, i-C4, CO2, H2S, N2, and natural gas mixtures in pure water or additive containing solutions. For modeling purpose, an extensive database comprising more than 3900 experimental data have been gathered from the literate from 1940 to 2013. The collected databank covers wide range of experimental conditions at solid/liquid/vapor or solid/ice/vapor equilibrium of distinct hydrate systems. All the proposed models reproduce the targets with R2 of greater than 0.97. The predictions of the developed LSSVM models for hydrate systems of C1, C2, C3, i-C4, CO2, H2S, N2, and natural gas mixtures are in good agreement with corresponding experimental data with the average absolute relative deviation percent (%AARD) equal to %0.22, %0.33, %0.26, %0.07, %0.47, %0.56, %0.08, and %0.34, respectively.

Kinetics and Microstructure of Sulfonitriding of Die-Steels

Sulfonitriding is one of the surface treatments of die made of steels for forging and casting. In this surface treatment, annealing under NH3 and H2S containing atmosphere provides the formation of top sulfide layer on the nitrided zone. The surface sulfide zone has anti-seizure and lubrication effects during forging and casting processes. In this study, microstructure development and its kinetics in sulfonitriding of die-steels. Commercial die-steels, JIS-SKT4 and JIS-SKD61, were used. Those steels were annealed under gas-mixture of N2 and H2S at 520°C for 0.5 h and NH3for 2.5 h. Microstructure of the samples was observed by using scanning electron microscopy (SEM) and electron probe micro-analyzer (EPMA). Phase identification of the samples was conducted with X-ray diffraction (XRD). Chemical profile from the surface was obtained by using glow discharge spectroscopy (GDS). A thin continuous layer with 2 -3 μm in thickness was developed on the surface of die-steels. XRD revealed the formation of FeS after sulfonitriding process. The FeS layer was so dense without significant pore network. Results of GDS and EPMA shows that the surface FeS layer include nitrogen and Cr. Inner nitrided zone consisted of mainly Fe3N. Repeating the sulfonitriding process, thickness of the top FeS layer and Fe3N zone increase parabolically. As a result of the marker experiments with Al2O3 particles, top FeS layer was developed by the outward diffusion of Fe and Fe3N zone was grown with inward diffusion of N. Because open pore network in the top FeS layer was not observed, inward diffuses of nitrogen passing through the top FeS layer occurs during sulfonitriding process.

Solubility of CO2 + H2S gas mixture into different aqueous N-methyldiethanolamine solutions blended with 1-butyl-3-methylimidazolium acetate ionic liquid

In this work, the simultaneous solubility of a gas mixture of CO2+H2S (70+30mol%) into the aqueous solutions of N-methyldiethanolamine (MDEA) blended with 1-butyl-3-methylimidazolium acetate [bmim][acetate] is measured using a static high pressure equilibrium cell. The solvent mixture consists of MDEA (30, 50wt%) and [bmim][acetate] (5, 10, 50wt%). The experiments are carried out at 323.15 and 348.15K and in total pressure range of about 2–25bar. The solubility data is tabulated and presented as acid gas partial pressures against its molality and mole fraction.The results illustrate that an increase in temperature and decrease in MDEA concentration lead to lower solubility of the both acid gases. At low ionic liquid mass fractions region, increasing [bmim][acetate] cause to reduce solubility of the both acid gases. Nevertheless at high IL mass fraction, the reduction of CO2 solubility is observed, but for H2S extend of its solubility depends on temperature. In the other words, more increase in ionic liquid leads to enhance H2S solubility through reduction temperature; and at given ionic liquid (IL) weight percent, the H2S solubility is reduced by increasing temperature. Finally, it can be concluded in the presence of CO2 the selectivity of MDEA+IL is toward H2S at all IL weight fractions.

Prediction of the early breakthrough of a diluted H2S and dry gas mixture when treated by Sulfatreat commercial sorbent

Among the available technologies, gas clean up by adsorption on commercial sorbents is largely employed, although the overall process efficiency is often lowered by operation at fuel compositions and process conditions far from the advised specifications.This work reports on the removal mechanism of one of the most technically harmful trace compounds of biogas, hydrogen sulfide (H2S), when treated at dilute concentrations in a dry gas mixture by the commercial Sulfatreat iron oxide sorbent. A kinetic study is presented, which aims to predict the early breakthrough of H2S during fixed bed adsorption and, therefore, to provide the fundamental design tools for its integration into a fuel cell power system.On the basis of a simple schematization of the Sulfatreat pellet, the initial rate of adsorption of H2S was studied by employing a differential reactor set up; the contribution of both the external mass transport and the intrinsic chemical reaction has been investigated by carrying out specific, low conversion, pseudo steady state tests by means of a dedicated adsorption rig.Results from complete saturation of the sorbent material show that the initial breakthrough is controlled by occurrence of a fast reaction (order 0.53) between H2S and the external surface of the active iron oxide granules, which evolves towards a slower, diffusive mass transport controlled, first order reaction.Modelling work here reported shows that the initial breakthrough of H2S can be predicted beyond fuel cells typical tolerance levels by a non linear kinetic expression, which takes into account of both reaction mechanisms.

Widely-tunable mid-infrared fiber-coupled quartz-enhanced photoacoustic sensor for environmental monitoring.

A compact widely-tunable fiber-coupled sensor for trace gas detection of hydrogen sulfide (H₂S) in the mid infrared is reported. The sensor is based on an external-cavity quantum cascade laser (EC-QCL) tunable between 7.6 and 8.3 μm wavelengths coupled into a single-mode hollow-core waveguide. Quartz-enhanced photoacoustic spectroscopy has been selected as detecting technique. The fiber coupling system converts the astigmatic beam exiting the laser into a TEM(00) mode. During a full laser scan, we observed no misalignment between the optical beam and the tuning fork, thus making our system applicable for multi-gas or broad absorber detections. The sensor has been tested on N₂:H₂S gas mixtures. The minimum detectable H₂S concentration is 450 ppb in ~3 s integration time, which is the best value till now reported in literature for H₂S optical sensors.

Influence of traces of gaseous sulphur on carburisation rate of iron in CO–H2 mixtures

The influence of traces of gaseous sulphur on the carburisation rate of a pure iron plate in CO–H2–H2S gas mixtures was examined at 920–1200°C to clarify the carburisation behaviour in the blast furnace utilising hydrogen or the direct reduction processes. The initial rates were analysed based on two chemical reactions for gas carburisation and the chemisorption equilibrium of sulphur atoms on the surface of iron. Traces of sulphur in gas mixtures significantly decreased the carburisation rate as the sulphur content increased. The carburisation was found to proceed to a small extent dependent on temperature and gas composition even under sulphur saturated chemisorption. The higher sulphur gas mixtures caused simultaneous reactions of carburisation and sulphurisation. When 50% of the CO was substituted by hydrogen, the rates were roughly twice as large as the condition without hydrogen, and approximately independent of the existence of sulphur. With rising temperature, the carburisation rates without sulphur tended to increase until around 1000°C and decrease beyond 1100°C, while the rates under sulphur saturated chemisorption increased gradually with rising temperature. The results are discussed relating to the carburisation behaviour inside the blast furnace utilising hydrogen or the direct reduction processes.