Volume Change of Solid Substances in CaCl2/CH3NH2 Gas-Solid Reaction Used for Driving a Chemical Heat Pump

The apparent volume of a reaction bed and the real volume of solid substances have been measured at 303.2K for CaCl2/CH3NH2 gas-solid reaction which is used for driving a chemical heat pump. A sixfold expansion of the bed volume has been observed in the initial reaction (CaCl2→CaCl2·6CH3NH2), while its variation was reduced to half of the initial volume change in the repeated reaction (CaCl2.2CH3NH2↔CaCl2·6CH3NH2).The volume of CaCl2.1.6CH3NH2, CaCl2.2CH3NH2 or CaCl2.6CH3NH2 was obtained by subtracting the vacant volume in the reactor, which was measured by introducing nitrogen gas into it, from its total volume. The volume of the solid substances varies proportionally with the moles of methylamine reacted, and one mole of methylamine in the solid occupies a space equivalent to 95% of the molar volume of liquid methylamine. By analyzing the density data of hydrated and ammoniated salts, it has also been confirmed that the proportionality of the volume expansion depends upon the substance reacted with each salt.