In the real operating environment of an SCR catalyst, exhaust gas temperatures, flows, and other factors vary across the catalyst cross-section. These differences cause non-uniform wear and tear on the catalyst. Uncontrolled thermal events and poisons entrained in the exhaust can cause irreversible damage to the catalyst which cannot be seen by the naked eye. Furthermore, as-manufactured variability in catalyst activity may cause single-sample testing to misrepresent the bulk catalyst activity level.
For these reasons, Environex recommends a full system evaluation which includes testing multiple samples from the inlet and outlet sides of the catalyst. This ensures that the catalyst test results are representative of the actual condition of the bulk catalyst in a way that single-sample testing cannot. These results, particularly when combined with operating data analysis, provide a secure foundation from which to make future catalyst maintenance and replacement plans. This level of analysis minimizes the risk of unplanned catalyst maintenance or replacement, which can help you avoid costly environmental fines, forced plant downtime, and expensive expediting costs.
There are some instances when single sample testing may be appropriate. Baseline testing of a new catalyst, interim testing between full system evaluations, and post-mortem failure analysis of a spent catalyst are the most common cases where single sample testing is acceptable.