Batch Process Integration: Management of Capacity-Limited Thermal Energy Storage by Optimization of Heat Recovery

Abstract

Integration of batch processes is preferably accomplished by indirect heat recovery using thermal energy storage. Such processes may have brief peaks in energy demand, necessitating high storage capacity within short time periods. However, practical space constraints often limit maximal storage volumes, restricting the potential capacity to recover process heat. Consequently, the required utility costs of storage-limited integration solutions are increased, influencing their economic viability. Given increasing importance in the industry to utilize thermal energy efficiently, process operators may want to explore what is maximally possible energetically, within current space constraints, before contemplating expansion and further capital expenditure. Therefore, linear programming is utilized to determine storage integration solutions which maximize heat recovery per batch for volume-limited sensible stratified storage, specified by an insight-based approach from Pinch Analysis. The results produce a process-specific capacity limitation chart of batch-wise maximal heat recovery as a function of limited capacity, allowing generation of optimal storage loading and unloading profiles. Total batch costs (investment and operating cost per batch) are used to estimate the influence of limited capacity. The methodology is demonstrated in a case study. The resulting capacity limitation chart shows that for a stratified storage with four VSUs, which would require a volume of 97.4 m3 to achieve 100 % of the indirect heat recovery potential, approximately 60 % can be covered by an 8 m3 storage.