Water dual temperature exchange, hydrogen sulfide

In many respects, the case history presented by D. W. Jones and J. B. Jones of the DuPont Company is typical, They reported studies conducted on a pair of columns in use at Dana, Indiana, and Savannah River, Georgia, for a heavy-water process using dual temperature exchange of deuterium between water and hydrogen sulfide at elevated pressures. 

Figure 11 Illustrates a simplified arrangement of components and the magnitude of operating parameters for the concentration of deuterium by dual-temperature exchange between hydrogen sulfide gas and liquid water. H2S Is circulated In a closed loop counter-current to a descending stream of water. In the colder column deuterium concentrates In the liquid phase the equilibrium constant for the exchange at the cold temperature, 30°C, is 2.20.

In the dual-temperature H2O/H2S process (61,62), exchange of deuterium between H20(l) and H2S(g) is carried out at pressures of ca 2 MPa (20 atm). At elevated temperatures deuterium tends to displace hydrogen in the hydrogen sulfide and thus concentrates in the gas. At lower temperatures the driving force is reversed and the deuterium concentrates in H2S in contact with water on the tiquid phase. 

All of the previously mentioned plants except those employing distillation of water were parasitic to a synthetic anunonia plant. Their deuterium-production rate is limited by the amount of deuterium in ammonia synthesis gas. To produce heavy water at a sufficient rate, a growing industry of heavy-water reactors requires a deuterium-containing feed available in even greater quantity than ammonia synthesis gas. Of the possible candidates, water, natural gas, and petroleum hydrocarbons, water is the only one for which an economic process has been devised, and the dual-temperature hydrogen sulfide-water exchange process is the most economic of the processes that have been developed. 

DUAL-TEMPERATURE WATER-HYDROGEN SULFIDE EXCHANGE PROCESS... 

Hydrogen sulfide is conserved by returning depleted Hj S from the top of the cold tower to the bottom of the hot. Heat is conserved by heat exchange between hot and cold liquid and between hot and cold vapor. In principle, no materials other than feed water are consumed in the dual-temperature system energy consumption can be reduced by efficient heat exchange, with a lower bound set by the minimum required by thermodynamics for the separation. 

The dual temperature process is based on the atomic exchange of hydrogen and deuterium between hydrogen sulfide gas (H2S) and fresh water with a deuterium concentration of approximately 148 parts per million. 

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