1995 Volume 21 Issue 6 Pages 1170-1178
The extent to which a polluted reforming catalyst affects the hydrogen generation in a DIR-MCFC has been experimentally studied. It has been found that the amount of generated hydrogen decreased exponentially with increasing pollution.
In order to identify the process by which catalyst pollution can induce hydrogen depletion, we adopted the approach of reaction kinetics and carried out a surface analysis of the catalyst, assuming the following three processes may be the answer. (1) transition from reaction-controlled stage to diffusion-controlled stage, (2) decrease in the active surface of the reforming catalyst, and (3) Ni changed compound. The main results are; (1) reaction stage can be reaction-controlled because Effective factor _??_ 1 and drop ratio of partial pressure of CH4 both in the bulk and the catalyst surface is 23%, (2) from EPMA and XRD, it was found that the Ni in the catalyst was not a compound but pure, and that the Ni concentration on the catalyst's surface decreased with increasing pollution.
Therefore, it can be concluded that the pollution of the catalyst is caused mainly by the decrease of its active surface, due to the physical absorption of molten carbonate by the Ni included in the catalyst.
In addition, we have also studied the upper limit of the pollution in operating a DIR-MCFC and found that a DIR-MCFC cannot be normally operated when the pollution exceeds about 2 cut.