Sulfur dioxide disproportionation for sulfur based thermochemical energy storage. (August 2015)

• Record Type: Journal Article
• Authors: Wong, Bunsen; Brown, Lloyd; Buckingham, Robert; Sweet, Wendi; Russ, B.; Gorensek, Max
• Is Part Of: Solar energy. Volume 118(2015)
• Page Start: 134
• Page End: 144
• Publication Date: 2015-08
• Subjects: Thermochemical processes -- Sulfur storage -- CSP energy storage; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2015.04.037
• Languages: English
• ISSNs: 0038-092X

Abstract

Highlights: Sulfur dioxide disproportion is key to converting high temperature solar heat into internal energy in elemental sulfur. Iodine was identified as catalyst to achieve fast disproportionation. A kinetic equation for disproportion was established. Full recovery of iodine catalyst has been demonstrated. A conceptual disproportion reaction system design was introduced. Abstract: Sulfur dioxide disproportionation is one of three reaction steps that make up the sulfur based thermochemical cycle used for thermal energy storage of concentrated solar power. The characteristics of this reaction were studied using thermodynamic modeling and laboratory measurements. Modeling results showed full disproportionation can only be achieved at pressure. The reaction driving force is enhanced by system pressure but declines with increasing temperature. Appropriate water to sulfur dioxide ratio also drives disproportionation. Batch experiments showed that reaction rate increases with temperature. A catalyst survey identified homogenous iodides as catalysts that can improve the reaction rate by up to twenty times while increasing the apparent extent of disproportionation. The dependence of disproportionation rate on sulfuric acid concentration was established via constant pressure experiments. Means to recover the iodide catalyst from sulfuric acid and molten sulfur for reuse were demonstrated. Modeling and test results were used to establish a design concept for a sulfur dioxide disproportionation reactor system capable of rapidly generating sulfur as required for the sulfur based thermochemical energy storage technology.