Utilization of high temperature heat using a calcium oxide / lead oxide / carbon dioxide chemical heat pump

Abstract

A new chemical heat pump designed to utilize high-temperature heat above 800°C generated from a high-temperature gas nuclear reactor or other high-temperature industrial process is presented. Based on experimental results, a heat pump that uses a calcium oxide / lead oxide / carbon dioxide reaction system appears to be a suitable system. To demonstrate the validity of the heat pump, the equilibrium relationship and kinetics of calcium oxide / carbon dioxide and lead oxide / carbon dioxide, which comprise the reaction system of the heat pump, are studied experimentally. A study of the equilibrium relationship of lead oxide / carbon dioxide, which consists of a three-step equilibrium, reveals that the highest temperature equilibrium relationship of the three-step equilibrium is associated with optimal heat pump operation. The practical operation conditions of the heat pump are determined based on the equilibrium relationship and kinetic experiments. The proposed heat pump may be able to operate as a heat transformation-type heat pump, and is capable of storing heat above approximately 830°C and transforming the heat to a higher temperature of more than 870°C under sub-atmospheric pressure and thermal driving conditions with no mechanical work. The calculated mean heat output and heat output amount are 670 W/kg-CaCO3 and 1200 kJ/kg-CaCO3, respectively, at 870°C, 1 atm for 30 min. Thus, the new heat pump can be applied to a heat storage and heat transformation system for high temperature processes.