Bielefeld, 02.06.2020, Findings of a customer-oriented problem solution led to a significant improvement in the cleaning performance of the FilterMaster system when cleaning heavily loaded large filters. The patented FilterMaster process can now also be used successfully for non-catalytically loaded CRT filters.
Kipp Umwelttechnik solves cleaning problems with CRT filters that are heavily contaminated with inorganic ash and installed downstream of a NOX catalytic converter with its patented FilterMaster system and subsequent innovative, material-friendly post-treatment. These do not normally have a catalytically active coating.
Several large filters of a customer, which always showed a rapid increase in contamination and were known to the customer as problematic, were cleaned with the FilterMaster standard process and showed a clear weight loss after cleaning, which was almost the same for all filters. The differential pressure values corresponded to a new filter. The filters were cleaned and returned to the customer.
However, it was found that the operating time of the cleaned filters was significantly reduced compared to the operating time of new filters. The customer then provided Kipp Umwelttechnik with a filter to investigate the causes.
The filter housing was cut open and samples of the CRT filter crystal were taken. It was found that the channels of the CRT filter were largely permeable, but still had residues on the inner walls. The residues were examined using the analytical methods SEM / EDX. These were the usual inorganic residues from the combustion of diesel fuel, engine oil and coolant. The unusually high amount of inorganic ash can be explained by the increased combustion of engine oil and coolant, as these have a significantly higher inorganic additive content.
Crystals on the sintered filter wall
This study provided two important findings.
1. the opening of a filter has shown that our previous test methods (differential pressure test, volume flow measurement) in this case primarily provide information about the cleaning success of the upstream NOX catalytic converter.
Reason: The total cross-section of the NOX catalytic converter’s passage openings appears significantly smaller in relation to the total cross-section of the CRT filter’s passage openings. The NOX catalytic converter and CRT filter are installed at a very small distance from each other. Since the area with the smallest cross-section determines the volume flow, the NOX catalytic converter is decisive here as long as the air passage of the filter crystal is higher than that of the catalytic converter. However, this is probably also the case if the filter walls still have a high inorganic coating. The aforementioned tests therefore did not provide any suitable information about the cleaning quality of the CRT filter. The weight measurement, which is also included in our test procedure, can only provide an indication here, as the filter loads are not the same and the weight of new filters is subject to considerable series variation.
2 Our patented FilterMaster standard process gently removes soot and ash from catalytic-coated CRT filters in a single operation at relatively low drying temperatures. This results in a complete decomposition of soot. Inorganic ash is practically completely discharged. In the case of uncoated CRT filters with an upstream NOX catalytic converter, the soot is converted, but the inorganic ash is only partially loosened in powder form. A very small proportion also remains firmly attached to the filter walls of the diffuser channels.
In this respect, ways had to be found for successful post-treatment after using our standard procedure that do not impair the performance of the NOX catalytic converter. The total costs for this were borne by Kipp Umwelttechnik.
With some effort, we have found solutions to both problems. The customer has now also been provided with several filters that have been cleaned according to the new findings. As a result, we were able to remove considerable additional quantities of the residues listed in the analysis and also generate an audit factor. From our point of view, the filters are now almost as good as new. If required / for other filter types, cleaning procedures and test procedures can now be readjusted at any time.
The entire process is now available to the market.
