Hydrogen sulfur-cycle

Physical and Chemical Properties. Information is available on the physical and chemical properties of hydrogen sulfide (ACGIH 1991 Amoore and Hautala 1983 Budavari et al. 1996 HSDB 1998 Leonardos et al. 1969 Lide and Frederikse 1993 NIOSH 1997). However, additional information on those properties that determine the specific fate, transport, and rates of transformation of hydrogen sulfide as part of the larger sulfur cycle would be useful in discerning the environmental fate and behavior of this compound. 

Hundreds of cycles have been studied from the viewpoint of the feasibility of component chemical reactions in terms of conversion ratio or product separation, theoretical thermal efficiency of hydrogen production, etc. [16]. Among them, those that utilize thermal decomposition of sulfuric acid, which are categorized as "sulfur cycles," have been considered one of the most promising cycles. 

A great number of processes and sinks related to the sulfur cycle in a sewer affect to what extent hydrogen sulfide is an odor problem. Figure 4.4 outlines the major pathways that also will be major subjects for detailed descriptions in Chapter 6. Although not all aspects depicted in Figure 4.4 can be easily quantified, they should be included in an evaluation of odor problems associated with sewage transport. 

As far as organic matter transformations are concerned, the process rates are significantly slower compared with aerobic transformations. Basically, readily biodegradable organic matter is preserved and even, to some extent, produced opposite to the situation when aerobic processes proceed. The sulfur cycle, until now included in the sewer process model, is relatively simply described following empirical expressions for sulfide formation. Other important processes in this respect, e.g., hydrogen sulfide emission and sulfide oxidation, still need to be included, however, and, most of all, investigated from a conceptual point of view. 

The integrated aerobic-anaerobic WATS model has changed this situation. As an example, it is possible to use the model in a gravity sewer with changing aerobic and anaerobic conditions. As previously stressed, a number of in-sewer processes still need to be dealt with. Examples are the anoxic transformations and the processes related to the extended sulfur cycle, particularly, the oxidation of sulfide and the emission of hydrogen sulfide into the sewer atmosphere, including its further oxidation at the sewer walls. Combined use of empirical and conceptual models is still needed. 

Figure 4.8. The sulfur cycle where S° is elemental sulfur, H2S is hydrogen sulfide, S2032" is thiosulfate, SO32" is sulfite, SO/- is sulfate, R-OSO3H represents a sulfate ester, R-SO3H a sulfonic acid, R-S-R a thioether, and R-SH a thiol. (Adapted from Coyne MS. Soil Microbiology An Experimental Approach. Boston Delmar Publishers 1999.)...

Hydrogen is one of the constituents of water. It recycles as in other biogeochemical cycles. It is actively involved with the other cycles like the carbon cycle, nitrogen cycle, and sulfur cycle. 

The nitrogen cycle is closely connected with the fluxes of hydrogen, sulfur, and other chemicals (Smith et al., 1998 Dimitroulopoulou and Marsh, 1997 Chapin et al., 2002 Rhee et al., 2005 Stevenson and Cole, 1999). Nitrogen and hydrogen react under great pressure and temperature in the presence of a catalyst to make ammonia. The study of correlations between the cycles of these elements is necessary to improve... 

Cano RJ, Borucki MK (1995) Revival and identification of bacterial spores in 25- to 40-million-year-old Dominican amber. Science 268 1060-1064 Carlson RW, Anderson MS, Johnson RE, Smythe WD, Hendrix AR, Barth CA, Soderblom LA, Hansen GB, McCord TB, Dalton JB, Clark RN, Shirley JH, Ocampo AC, Matson DL (1999a) Hydrogen peroxide on the surface of Europa. Science 283 2062-2064 Carlson RW, Johnson RE, Anderson MS (1999b) Sulfuric acid on Europa and the radiolytic sulfuric cycle. Science 26 97-99 Carney RS (1994) Consideration of the oasis analogy for chemosynthetic communities at Gulf of Mexico hydrocarbon vents. Geo-Marine Lett 14 149-159... 

A possible function of this intracellular sulfur cycle is to buffer, i.e. to homeostatically regulate, the cysteine concentration of the cells. Irrespective of whether sulfate, cysteine, or sulfur dioxide is available as sulfur source, the intracellular sulfur cycle would allow a plant cell to use as much of these compounds as necessary for growth and development. At the same time, it would give a plant cell the possibility to maintain the cysteine pool at an appropriate concentration by emitting excess sulfur into the atmosphere. Thus, emission of hydrogen sulfide may take place when the influx of sulfur in the form of sulfate, cysteine, or sulfur dioxide exceeds the conversion of these sulfur sources into protein, glutathione, methionine, and other sulfur-containing components of the cell. 

Westinghouse Electric Corporation (1980), A Study on the Electrolysis of Sulfur Dioxide and Water for the Sulfur Cycle Hydrogen Production Process, AESD-TME-3043, July. 

Goldstein, S., J.M. Borgard, X. Vitart (2005), Upper Bound and Best Estimate of the Efficiency of the Iodine Sulfur Cycle , Int. J. Hydrogen Energy, 30, 619-626. 

Brecher, L.E., S. Spewock, C.J. Warde (1977), The Westinghouse Sulfur Cycle for the Thermochemical Decomposition of Water , International Journal of Hydrogen Energy, Vol. 2, pp. 7-15, Pergamon Press. 

Russell, J.H., Sedlak, Dr. J.M., General Electric Company, Direct Energy Conversion Programs, Economic Comparison of Hydrogen Production Using Solid Polymer Electrolyte Technology for Sulfur Cycle Water Decomposition and Water Electrolysis, EPRI Research Project 1086-3, Final Report, December 1978. 

In the Sulfur Cycle, hydrogen is produced in a low temperature electrochemical step, wherein sulfuric acid and hydrogen are produced from sulfurous acid, i.e.,... 

This paper will discuss the development status of the Sulfur Cycle Hydrogen Production Process, the results of evaluations of process performance, and the program steps which can lead to commercialization of the system. 

SULFUR CYCLE HYDROGEN PRODUCTION SYSTEM MAJOR PROCESS PARAMETERS FOR A COMMERCIAL SYSTEM... 

SULFUR CYCLE HYDROGEN PRODUCTION PROCESS DEVELOPMENT AREAS... 

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