Residence time. Besides the driving force and associated formation rates, the residence time crucially determines the degree of CO 2 depletion in the gas phase. The effect of the time it takes for a control volume of gas to flow from the reactor inlet to the outlet, can be investigated by varying mass flow rates while keeping all other parameters the same. To this end, Fig. shows the gas composition at the reactor outlet together with cumulative masses of captured CO 2 versus time for mass flow rates ranging from 0.5-2.0 slm. To allow for a good comparison with Fig. , the process conditions used are identical. This time, however, all experiments are conducted with the same packed bed of solidified dry water. Additionally, the packed bed has already been cycled seven times before this investigation to mitigate the random nature of nucleation.