Design and optimization of alcohol-ketone-hydrogen chemical heat pumps

Abstract

The performance of the Alcohol–Ketone–Hydrogen working fluid system for chemical heat pumps was studied using steady state simulation, focusing on three systems: isopropanol–acetone–hydrogen, 2-butanol–methyl ethyl ketone–hydrogen and 2-Pentanol–methyl propyl ketone–hydrogen. Performance parameters such as Coefficient of Performance based on heat quantity ($COP$), Coefficient of Performance based on electric work input ($CO{P}_W$), and Exergy efficiency (${\eta }_{25}$, ${\eta }_{78}$) at reference temperatures 25 °C and 78 °C were calculated for different endothermic temperatures (∼130 °C to 200 °C) at temperature lift of 25 °C, 50 °C, 75 °C and 100 °C. For each operating scenario (e.g. the combination of the temperature of available waste heat and the desired temperature lift), the optimal design parameters such as feed tray locations, purity of distillate and bottom streams, and the ratio of hydrogen and Ketone at the exothermic reactor inlet were found through optimization techniques. Overall, the isopropanol–acetone–hydrogen working fluid system offers better performance in terms of $COP$, $CO{P}_W$, ${\eta }_{25}$ and ${\eta }_{78}$ compared to the other considered chemical systems for most of the temperature range. In the best use cases, ${\eta }_{78}$ reached as high as 70 % and $CO{P}_W$ reached as high as 15.