Kinetics of hydrogen sulfide decomposition in a DBD plasma reactor operated at high temperature

The present study investigates the kinetics of hydrogen sulfide (H 2 S) decomposition into hydrogen and sulfur carried out in a nonthermal plasma dielectric barrier discharge (NTP-DBD) reactor operated at ∼ 430 K for in situ removal of sulfur condensed inside the reactor walls. The dissociation of H 2 S was primarily initiated by the excitation of carrier gas (Ar) through electron collisions which appeared to be the rate determining step. The experiments were carried out with initial concentration of H 2 S varied between 5 and 25 vol% at 150 mL/min (at standard temperature and pressure) flow rate in the input power range of 0.5 to 2 W. The reaction rate model based on continuous stirred tank reactor (CSTR) model failed to explain the global kinetics of H 2 S decomposition, probably due to the multiple complex reactions involved in H 2 S decomposition, whereas Michaelis-Menten model was satisfactory. Typical results indicated that the reaction order approached zero with increasing inlet concentration

Photochemical Decomposition of Hydrogen Sulfide

Hydrogen sulfide is an extremely toxic gas which is generated from both nature factors and human factors. A proper method for the efficient decomposition of hydrogen is of great importance. Using traditional Claus process, hydrogen sulfide could be decomposed into hydrogen oxide and sulfur. One drawback of this process is that the energy stored in hydrogen sulfide is partially wasted by the formation of hydrogen oxide. In fact, the energy could be utilized for the generation of hydrogen, a potential energy source in future, or other chemical products. Various methods that could possibly make better use of hydrogen sulfide have been studied in recent years, like thermal decomposition, plasma method, electrochemical method, and photochemical method. In particular, there have been high hopes in photochemical method due to the possible direct solar energy conversion into chemical energy. Unlike traditional photocatalytic water splitting, hydrogen sulfide decomposition is more accessible from the thermodynamic point of view. Photocatalytic hydrogen sulfide decomposition could occur in both gas phase and solution phase and various systems have been reported. Besides, the photoelectrochemical decomposition of hydrogen sulfide is also highlighted. In this chapter, we will simply introduce the current situation for photochemical decomposition of hydrogen sulfide

Production of Hydrogen by Superadiabatic Decomposition of Hydrogen Sulfide - Final Technical Report for the Period June 1, 1999 - September 30, 2000

The objective of this program is to develop an economical process for hydrogen production, with no additional carbon dioxide emission, through the thermal decomposition of hydrogen sulfide (H{sub 2}S) in H{sub 2}S-rich waste streams to high-purity hydrogen and elemental sulfur. The novel feature of the process being developed is the superadiabatic combustion (SAC) of part of the H{sub 2}S in the waste stream to provide the thermal energy required for the decomposition reaction such that no additional energy is required. The program is divided into two phases. In Phase 1, detailed thermochemical and kinetic modeling of the SAC reactor with H{sub 2}S-rich fuel gas and air/enriched air feeds is undertaken to evaluate the effects of operating conditions on exit gas products and conversion efficiency, and to identify key process parameters. Preliminary modeling results are used as a basis to conduct a thorough evaluation of SAC process design options, including reactor configuration, operating conditions, and productivity-product separation schemes, with respect to potential product yields, thermal efficiency, capital and operating costs, and reliability, ultimately leading to the preparation of a design package and cost estimate for a bench-scale reactor testing system to be assembled and tested in Phase 2 of the program. A detailed parametric testing plan was also developed for process design optimization and model verification in Phase 2. During Phase 2 of this program, IGT, UIC, and industry advisors UOP and BP Amoco will validate the SAC concept through construction of the bench-scale unit and parametric testing. The computer model developed in Phase 1 will be updated with the experimental data and used in future scale-up efforts. The process design will be refined and the cost estimate updated. Market survey and assessment will continue so that a commercial demonstration project can be identified

A Membrane Reactor for H2S Decomposition

This program consisted of experimental evaluation of new metal- membrane compositions, experimental evaluation of the corrosion resistance of structural alloys and coatings for use in fabricating membrane reactors, development and evaluation of new membrane reactor designs, and economic analysis of the membrane reactor-based process for H{sub 2}S thermolysis and membrane-reactor fabrication. The results are described. Preliminary economic analyses indicate that the membrane-reactor process will ultimately be a cost-effective, energy-efficient, and environmentally acceptable means for the separation and treatment of H{sub 2}S from hot coal-gasifier streams. We estimate that the proposed process will separate and decompose H{sub 2}S at a cost that is one-half to one-fifth that of conventional technology for this application-amine scrubbers coupled with the Claus process

Thermodynamic Analysis of Carbon Capture and Pumped Heat Electricity Storage

This work can be divided into two parts: the first part is focused on carbon capture; the second part is devoted to the study of pumped heat electricity storage processes. Thermodynamic analysis of energy requirement for adsorption and chemical looping processes is investigated. It enables us to compare various technology platforms under the same separation target. Sorption-enhanced reaction is a novel intensified process by combining catalyst and adsorbent in a single fixed bed reactor. Experimental studies of sorption-enhanced water gas shift and steam methane reforming have been done by previous members of our group. Here numerical studies on the interactions between reaction and sorption in a sorption-enhanced reactor are carried out. Water-gas shift reaction, hydrogen sulfide decomposition and propene metathesis reaction are studied. Our results suggest that the produce purity depend on factors such a reaction kinetics, stoichiometry, equilibrium and adsorption isotherm. Mass transfer resistance can also play an important role in product purity. Experimental studies on high temperature carbon dioxide capture by pressure swing adsorption using Na-promoted alumina are undertaken for the first time. The effects of steam during regeneration are discussed. Pumped heat electricity storage processes are a novel thermal energy storage technique recently proposed. It does not require specific geological structure sites and is environmentally friendly. When combined with renewable energy resources, e.g. solar, wind and tidal, it can supply stable power throughout the day. During the charging and delivery cycle a cyclic steady state temperature distribution is formed inside the storage tank. In order to reduce the computing time to simulate this process, a novel matrix exponential solution is provided. Dimensionless analysis on the process performance is discussed

Gas-Phase Photochemical Overall H2 S Splitting by UV Light Irradiation

[EN] Splitting of hydrogen sulfide is achieved to produce valueadded chemicals. Upon irradiation at 254 nm in the gas phase and in the absence of catalysts or photocatalysts at near room temperature, H2S splits into stoichiometric amounts of H2 and S with a quantum efficiency close to 50%. No influence of the presence of CH4 and CO2 (typical components in natural gas and biogas in which H2S is an unwanted component) on the efficiency of overall H2S splitting was observed. A mechanism for the H2 and S formation is proposed.Financial support by the Spanish Ministry of Economy and R1) and Generalitat Valenciana (Prometeo 2013-014) is gratefully acknowledged. Thanks are due to Dr. J. A. Agullo-Macia for performing a preliminary experiment.Garcia-Baldovi, H.; Albero-Sancho, J.; Ferrer Ribera, RB.; Mateo-Mateo, D.; Alvaro Rodríguez, MM.; García Gómez, H. (2017). Gas-Phase Photochemical Overall H2 S Splitting by UV Light Irradiation. ChemSusChem. 10(9):1996-2000. https://doi.org/10.1002/cssc.201700294S1996200010

Development of Fe-based Catalysts for Purification of Coke Oven Gases

Fe-based catalysts of different geometry are developed for the purification of coke oven gases: bulk, supported on alumina and supported on alumina silicate monoliths. Adsorption and decomposition of H2S on the catalysts developed are studied. Influence of active component content, type of support material and modification by Mn and Mo on the catalyst activity in de-H2S process is elucidated. Supported monolith catalysts show superior activity over bulk and supported spherical catalysts in H2S decomposition reaction and demonstrate stable operation in ammonia decomposition process during 2 hours at 900 °C giving 100% ammonia conversion

Material screening for two-step thermochemical splitting of H2S using metal sulfide

Associated with the rise in energy demand is the increase in the amount of H2S evolved to the environment. H2S is toxic and dangerous to life and the environment, thus, the need to develop efficient and costeffective ways of disposing of the H2S gas has become all-important. To this end, a two-step thermochemical H2S splitting cycle is proposed in this work which does more than just getting rid of the toxic gas but has the potential to produce valuable H2 gas as well as store the solar heat energy. Studies have proved that the type of material used, such as metal sulfides, is critical to the efficiency of this thermochemical splitting process. As follows, this study focuses on establishing a criterion to aid in selecting favorable metal sulfides for application and further development in the H2S thermochemical decomposition sphere. Using a computational approach, via the HSC Chemistry 8®, evaluations such as the equilibrium yield from the sulfurization and decomposition reaction steps, the temperature required for reaction spontaneity, and the Reversibility Index were determined. Investigations proved that sulfides of Zirconium, Niobium, and Nickel were auspicious candidates for the thermochemical decomposition

NUMERICAL SIMULATION OF A FLAT-TUBE HIGH POWER DENSITY SOLID OXIDE FUEL CELL

In recent years, fuel cells have been deemed to be a low-polluting fuel consuming power-generation technology with high efficiency. They are an important technology for a potentially wide variety of applications. Among fuel cell types, solid oxide fuel cells (SOFC) have the recognized potential to be one of most promising distributed power generation technologies. Tubular SOFCs have evolved over last two decades, and work is currently underway to reduce cell cost toward commercialization. Further SOFC development is needed in order to achieve a commercially competitive cell and stack cost. A flat-tube high power density (HPD) SOFC is a newly designed cell of a different geometry from a tubular SOFC. It has increased power density, but still maintains the tubular SOFC¡¯s beneficial feature of secure sealing. In this study, heat/mass transfer and fluid flow in a single flat-tube high power density SOFC is investigated using a self-developed code in FORTRAN. The temperature fields, concentration fields and velocity fields in different chambers of a flat¨Ctube HPD SOFC are studied.Based on the temperature fields and species concentration fields, an overall electrical performance of a flat-tube high power density SOFC is performed using a commercial tool for electrical circuit analysis. The effects of the stack chamber numbers, stack shape and other stack features on the performance of the flat-tube HPD SOFC are also studied. The results show that the performance of a flat-tube HPD SOFC is better than a tubular SOFC with the same active cell surface, and that increasing the chamber number can improve the overall performance and power/volume rating for a flat-tube HPD SOFC. The study helps to design and optimize the flat-tube HPD SOFC for practical applications so as to achieve widespread utilization of SOFCs. In this study, one interesting application example for the SOFC is also presented