| 摘要 |
A gas stream is fed (48) into the catalytic reactor (50) and wherein a contaminant removal unit (75) is provided upstream of the catalytic reactor. The presence of a contaminant in the gas stream is detected by providing at least one contaminant trap (80) either upstream or downstream of the contaminant removal unit (75), and passing at least part of the gas stream through the or each contaminant trap (80) for at least some of the time. By monitoring (89, 92) the quantity of the gas that passes through each contaminant trap (80), and monitoring the presence of the contaminant material trapped in the contaminant trap (80), the presence and concentration of the contaminant in the gas stream can be assessed. |
