Plant emissions can be impacted by factors anywhere from fuel combustion to stack monitoring, so it is important to look at the whole picture when evaluating SCR system performance. Environex’s Full SCR System Evaluation leaves no stone unturned so that you can have the peace of mind to operate reliably and know that you are addressing the real cause when a problem arises. Our comprehensive evaluations enable us to pinpoint remaining catalyst life, identify causes of performance loss, determine the limiting operating case for your system, and distinguish system problems from catalyst problems before they bring your plant offline.
Our time-tested methodology includes a combination of catalyst core sample “mapping”, detailed operating data analysis, and a thorough system inspection. This combination provides us with a complete set of data and the proper perspective for evaluating all factors that impact stack emissions. Our experience ranges from internal combustion engines and aero-derivative peaker units to large Frame combined cycle plants and coal boilers (and everything in-between), so we have seen it all.
Our engineers collect a representative set of catalyst core samples from various locations throughout the entire catalyst cross-section to “map” overall catalyst activity. This enables us to account for any variation in bulk catalyst activity caused by deviations in flow patterns, temperature gradients, and contaminant loading. It also eliminates the uncertainty caused by sample-to-sample variation and ensures that you are not relying on a single location when making critical catalyst replacement decisions.
Each catalyst sample is tested for NOx conversion performance, chemical contaminant levels, and physical characteristics. Since the SCR reaction is temperature-dependent, the performance tests are run across a range of temperatures that represent the full range of plant operating conditions so that we may project catalyst performance under all operating scenarios.
In addition to catalyst test results, we look at detailed plant operating data for a set of parameters that characterize overall plant emissions performance. This analysis allows us to evaluate overall plant emissions performance and identify the catalyst performance requirements and operating conditions for the full range of plant operations (turndown, full load, duct-fired, etc.).
The catalyst performance test results are evaluated in light of the different performance requirements and operating conditions identified in the operating analysis to determine which operating mode is limiting for your unique system. Inconsistencies between the catalyst test results and operating data analysis enable us to identify system (non-catalyst) problems that are impacting plant emissions and recommend a plan of action to optimize SCR system performance.
While our engineers are on-site to collect catalyst samples they perform a complete inspection of the overall emissions control system. The inspection focuses on the physical condition of the bulk catalyst, the catalyst housing and seals, the operability of the reagent injection system, and other upstream and downstream system components. CO catalysts are also inspected if they are included in your system. Maintenance recommendations that will improve overall emissions performance are identified during the site inspection. Any hardware issues that may be negatively impacting system performance are also identified.
For systems that include a CO oxidation catalyst, the CO catalyst should be tested in conjunction with the SCR catalyst. There are inherent trade-offs in NOx and CO formation during fuel combustion, so performance of the SCR and CO catalysts must be balanced to ensure reliable overall emissions performance. In some cases, combustion tuning may be appropriate if one catalyst is performing significantly better or worse than the other.
The CO catalyst may also have other impacts on SCR system performance, including potential flow distribution issues due to plugging or SCR catalyst poisoning issues due to migration of the active CO catalyst washcoat material onto the SCR catalyst. SCR and CO catalysts are inextricably linked, so they should be evaluated together.