(181d) Application of a Process Model-Free Analysis to Thermochemical Systems for Large-Scale Hydrogen Production

Our previously reported analysis of energy efficiency^a has been applied to several different Sulfur-Iodine processes for thermochemical water decomposition in order to demonstrate how the method can provide a common basis for comparing them. The procedure calculates a set of upper-limit efficiencies that minimizes model dependence and maximizes generality through careful statements of overall, sectional and equipment-based system reversibilities and integrated energy utilization. The basic calculations assume reversibility within the process sections and use standardized input and output flow rates and computed thermodynamic properties from standardized conditions. Heat flows between sections as well as source energy and heat rejection to the surroundings are found and compared. The effects of recycle, changes of conditions and sensitivity of properties models are given. Then, irreversibilities are put in via estimates of entropy generation (equivalent to lost work) to show their impact.

The presentation shows current progress toward a reliable benchmark procedure for more objectively evaluating alternative processes, a more transparent way to improve existing processes, and a path for focusing on needed fundamental research. For example, a few extensions are made to determine the consequences of process changes of flows and states and by corrections to property model predictions.

^a AIChE Annual Meeting, Cincinnati, OH, November 2005