Westinghouse sulfur process

Carty R, Cox K, Punk J, Soliman M, Conger W (1977) Process sensitivity studies of the Westinghouse sulfur cycle... 

The hybrid sulfur process (also known as Westinghouse GA-22 and Ispra Mark 11) has a single electrochemical step that completes the cycle ... 

In the initial thiocyanate-complex Hquid—Hquid extraction process (42,43), the thiocyanate complexes of hafnium and zirconium were extracted with ether from a dilute sulfuric acid solution of zirconium and hafnium to obtain hafnium. This process was modified in 1949—1950 by an Oak Ridge team and is stiH used in the United States. A solution of thiocyanic acid in methyl isobutyl ketone (MIBK) is used to extract hafnium preferentially from a concentrated zirconium—hafnium oxide chloride solution which also contains thiocyanic acid. The separated metals are recovered by precipitation as basic zirconium sulfate and hydrous hafnium oxide, respectively, and calcined to the oxide (44,45). This process is used by Teledyne Wah Chang Albany Corporation and Western Zirconium Division of Westinghouse, and was used by Carbomndum Metals Company, Reactive Metals Inc., AMAX Specialty Metals, Toyo Zirconium in Japan, and Pechiney Ugine Kuhlmann in France. 

Westinghouse A proposed thermochemical process for decomposing water to oxygen and hydrogen by electrolysis, coupled with the high-temperature decomposition of sulfuric acid ... 

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. 

The system (Figure 12) is based on sulfuric acid (H2SO4) synthesis and decomposition process (the Westinghouse process) developed earlier. The sulfur trioxide (SO3) decomposition process is facilitated by electrolysis with ionic oxygen conductive solid electrolyte to reduce the operation temperature 200°C-300°C lower than the Westinghouse process. 

Thermochemical hybrid cycles offer the possibility of running low-temperature reactions on electricity. The expectations for realization of hybrid processes are similar to those for purely thermochemical processes. Various hybrid processes are energetically possible, but not always practicable. Important criteria are the minimum voltage for the electrolysis step, realizability, efficiency. The sulfuric acid hybrid or Westinghouse process is expected to reduce material streams as compared with the IS process. The electric energy demand here is a factor of 7 (in reality 3 - 4) lower than in the electrolytic water splitting process. Technological improvements are still possible. 

The sulfuric acid hybrid cycle (Westinghouse process) is given by the reaction equations... 

Many types of thermochemical processes for H2 production exist. All of the competitive processes require heat input at temperatures above 750°C. The sulfuric acid processes (sulfur-iodine and Westinghouse hybrid) are the leading candidates. In each of these processes, the high-temperature, low-pressure endothermic (heat-absorbing) reaction is the catalytic thermal decomposition of sulfuric acid to produce oxygen ... 

Electrochemical oxidation of aqueous SO2 on the electrode surface has also aroused interest in the large-scale hydrogen production processes via a hybrid sulfur cycle which was patented as Westinghouse Process. The electrochemical oxidation of aqueous sulfur dioxide with respect to the hybrid sulfur cycle has recently been reviewed and shown the importance of the mechanism of the oxidation of sulfur dioxide on the electrode surface. Platinum, gold, and carbon materials as electrocatalysts have been reviewed to compare the catalytic activity for SO2 oxidation [16]. The first step in the Westinghouse Process is the dissociation of H2SO4 into SO2 and O2 by thermal cracking at about 1,000 °C ... 

Of all these methods indirect oxidation of SO2 using redox mediators and electrochemically promoted oxidation seem to be the nearest alternatives to the commercial applications. The removal of SO2 by using redox mediators has already been tested in commercial scale in the processes named Peracidox and Ispra Mark HI. Westinghouse Process is another commercial application in terms of hydrogen production via hybrid sulfur cycle. 

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