Host: The Society of Chemical Engineers, Japan
An experimental study has been conducted on the structural properties of reactor beds packed with CaCl2 reactive salt particles with a view of evaluating the heat transfer mechanism in porous particle beds. Particulate and bed properties of CaCl2 reactive particles, which are CaCl2/CH3OH, CaCl2/CH3NH2 and CaCl2/NH3 reactive salts applicable to driving chemical heat pumps, have been studied by means of mercury porosimetry and SEM as well as bed volume measurements. From the porosimetry measurements, it was found that the void fraction inside particles of CaCl2/CH3OH salt varied from 0.2 to 0.6 with increasing the moles of methanol reacted with CaCl2, while the void fraction outside particles was kept almost constant during reaction cycles. Based on the experimental results of CaCl2/CH3OH particles, the void fraction inside particles was estimated, varying from 0 to 0.8 in CaCl2/CH3NH2 and from 0.3 to 0.7 in CaCl2/NH3 particles. SEM observations revealed that after several reaction cycles a drastic change took place in pellet structure; the shape and the state of aggregation of the grains in a pellet had changed to completely different ones from those of the original unreacted CaCl2. Such changes in grain and pellet structures may cause the considerable decrease in the thermal conductivity of these reactive salts observed in our previous study.
