Natural Gas Sulfur Research Articles

Solubility evolution of elemental sulfur in natural gas with a varying H2S content.

The solubility variations of elemental sulfur are of great importance in the prevention of sulfur deposition during the development of high-sulfur gas formations. It has been observed that the solubility varies with H2S content, which is the main solvent of elemental sulfur in natural gas. Moreover, the addition of small amounts of CH4 and/or CO2 in H2S leads to a dramatic solubility reduction of which the mechanism remains unclear. Using a modified direct coexistence method, molecular dynamics simulations are conducted to uncover the molecular mechanism of the solubility reduction. The observed solubility variations with H2S content are reproduced, and the solubility reduction is interpreted by the antisolvent effect of CH4 and CO2. While the H2S content varies in a wide range in the known high-sulfur gas formation, our simulations provide useful information for controlling the sulfur deposition in gas development. Molecular dynamics simulations are carried out using the LAMMPS package. The initial models are constructed with the Packmol software. The Ballone and Jones' potential is used for S8, the Galliero's potential for H2S and CO2, and the transferable potentials for phase equilibria-united atom (TraPPE-UA) force field for CH4. The time step is set to 1fs, and the molecular trajectories of additional 2ns after equilibrium are collected for analysis.

Molecular mechanism of elemental sulfur dissolution in H2S under stratal conditions.

Resulting from the solubility reduction of elemental sulfur during the development of high sulfur gas formations, sulfur deposition often occurs to reduce the gas production and threaten the safety of gas wells. Understanding the dissolution mechanism of elemental sulfur in natural gas is essential to reduce the risk caused by sulfur deposition. Because of the harsh conditions in the high-sulfur formations, it remains challenging to in situ characterize the dissolution-precipitation processes, making deficient the knowledge of sulfur dissolution mechanism. The dissolution of sulfur allotropes (SN, N = 2, 4, 6 and 8) in H2S, the main solvent of sulfur in natural gas, is studied in this work by means of first-principles calculations and molecular dynamics simulations. While S6 and S8 undergo physical interaction with H2S under the conditions corresponding to those at 1-6 km stratigraphic depths, S2 and S4 react with H2S and form stable polysulfides. Unravelling the mechanism would be helpful for understanding and controlling the sulfur deposition in high-sulfur gas development.

Roles of Carbon Dioxide and Methane in the Dissolution of Elemental Sulfur in Natural Gas

Roles of Carbon Dioxide and Methane in the Dissolution of Elemental Sulfur in Natural Gas

Molecular simulation of the adsorption characteristics of H2S in calcite slit-like pores

Hydrogen sulfide (H2S) in acid gas reservoirs is an important source of sulfur deposition in rock reservoirs. Studying the adsorption behavior of H2S in calcite slit-like pore is of great significance for predicting the amount of sulfur in natural gas. In this paper, the grand canonical Monte Carlo (GCMC) method is used to investigate the adsorption of H2S in calcite with slit-like pore. Moreover, the effects of different pressures, temperatures and pore sizes on the adsorption characteristics are discussed. The results showed that the adsorption of H2S goes up with the increasing of the pressure and gradually reaches a saturation level. And the adsorption of H2S decreases with the increasing of the temperature. The excess adsorption of H2S first increases and then decreases with the increasing of the pressure. The effect of the size on the excess adsorption capacity changes with the pressure. Meanwhile, the peak of the adsorbate near the surface of the adsorbent shows a nonmonotonic trend with the pressure.

Solution Mechanism of Elemental Sulfur in Hydrogen Sulfide under Conditions of Natural Gas Transmission

Predicting the solubility of elemental sulfur in natural gas is an important task in the prevention of sulfur deposition. The knowledge of the sulfur solution mechanism in hydrogen sulfide is of gr...

A system consisted of flame ionization detector and sulfur chemiluminescence detector for interference free determination of total sulfur in natural gas

A new detection system consisted of a flame ionization detector (FID) and a sulfur chemiluminescence detector (SCD) was developed for sensitive and interference free determination of total sulfur in natural gas by non-separation gas chromatography. In this system, sulfur containing compounds and hydrocarbons were firstly burned in the FID using oxygen rich flame and converted to SO2, CO2 and H2O, respectively. The products from FID were transported into the SCD with hydrogen rich atmosphere wherein only SO2 could be reduced to SO and reacted with O3 to produce characteristic chemiluminescence. Therefore, the chemiluminescence of CO found in conventional SCD were eliminated because CO2 could not be reduced to CO under these conditions. The experimental parameters were systematically investigated. Limit of detection obtained by the proposed system is better than 0.5μmol/mol for total sulfur and superior to those previously reported. The proposed method not only retains the advantages of the conventional SCD but also provides several unique advantages including no hydrocarbon interference, better stability, and easier calculation. The utility of this technique was demonstrated by the determination of total sulfur in real samples and two certified reference materials (GBW 06332 and GBW (E) 061320).

Removal of sulfur from sulfur-bearing natural gas to produce clean jet fuel

ABSTRACTDespite the low percentage of trace level sulfur in natural gas (NG), its use as a jet fuel for reduction from the ultra level is very important. Clean and efficient NG as a fuel has major advantages and importance. If the sulfur content of natural gas will decrease in how much it is substantially upgraded. The main problems and difficulties encountered method of removing minor amounts of sulfur remaining in gases after conversion of the major portion of the sulfur content of the gas to elemental sulfur by the Claus or Stretford methods, or any method. Low-quality NG contains hydrogen sulfide, carbon dioxide, and nitrogen, but is not suitable for treatment using current conventional gas treating methods due to economic and environmental challenges. To remove sulfur from natural gas as the most common on the Claus process is applied. However, the Claus process itself is not sufficient for removal of sulfur in the ultra level. The tail gas from the Claus reaction is then passed through a catalytic hydrogenation reactor together with a supply of hydrogen to reduce the sulfur and sulfur compounds to hydrogen sulfide. As a results, hydrogen sulfide is completely removed from the NG streams by washing with alkanolamine solutions.

Results of Testing Various Natural Gas Desulfurization Adsorbents

This article presents the results of testing many commercially available and some experimental sulfur adsorbents. The desired result of our testing was to find an effective method to reduce the quantity of sulfur in natural gas to less than 100 ppb volume (0.1 ppm volume). An amount of 100 ppb sulfur is the maximum limit permitted for Siemens Westinghouse solid oxide fuel cells (SOFCs). The tested adsorbents include some that rely only on physical adsorption such as activated carbon, some that rely on chemisorption such as heated zinc oxide, and some that may use both processes. The testing was performed on an engineering scale with beds larger than those used for typical laboratory tests. All tests were done at about 3.45 barg (50 psig). The natural gas used for testing was from the local pipeline in Pittsburgh and averaged 6 ppm volume total sulfur. The primary sulfur species were dimethyl sulfide (DMS), isopropyl mercaptan, tertiary butyl mercaptan, and tetrahydrothiophene. Some tests required several months to achieve a sulfur breakthrough of the bed. It was found that DMS always came through a desulfurizer bed first, independent of adsorption process. Since the breakthrough of DMS always exceeds the 100 ppb SOFC sulfur limit before other sulfurs were detected, an index was created to rate the adsorbents in units of ppm DMS × absorbent bed volume. This index is useful for calculating the expected adsorbent bed lifetime before sulfur breakthrough when the inlet natural gas DMS content is known. The adsorbents that are included in these reports were obtained from suppliers in the United States, the Netherlands, Japan, and England. Three activated carbons from different suppliers were found to have identical performance in removing DMS. One of these activated carbons was operated at four different space velocities and again showed the same performance. When using activated carbon as the basis of comparison for other adsorbents, three high-performance adsorbents were found that removed about 100 to 150 times as much DMS as activated carbon before breakthrough.

Determination of sulfur components in natural gas: A review

AbstractMore stringent environmental regulations as well as higher demands presently being imposed on the sulfur content of natural gas feed‐stocks for chemical processes necessitate the development of new analytical procedures for sulfur determination in natural gas. Only analytical procedures based on gas chromatography can meet the sensitivity and accuracy requirements dictated by environmental regulation institutions and modern chemical industry. The complexity of the natural gas matrix as well as the extremely low concentration levels at which the sulfur species occur make the development of these analytical methods a true challenge. In this review the three steps common for analytical methods for trace analysis in complex matrices, i.e. pretreatment, chromatographic separation, and detection, are discussed in detail. Possible methods for calibration of the system are discussed in the final section.Various techniques to determine sulfur in natural gas are described. Depending on the application, the most suitable system has to be selected. For example, for on‐line application in a hazardous area a simple and rugged system is required, i.e. a simple gas chromatograph with a flame photometric detector, while for laboratory application a more complex instrument including preconcentration, column switching, and more exotic detection systems could be more suitable. Therefore it is crucial to define the requirements of the instrument at an early stage and use the information in this review article to develop/select a dedicated instrument/procedure for the problem at hand.