Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Contribution of combustion conditions to deactivation rates

Previous studies of VAB in a circulating fluidised bed plant firing forest residues and a plant firing pulverised wood in Sweden found that after 2100h, when using a conventional honeycomb catalyst 80% of the original activity remained in the circulating fluidised bed boiler but only 20% remained in the pulverised wood boiler. The tendency is that a boiler with short residence time between burnout zone and catalyst and/or high flame temperatures gives a faster deactivation. Elsam has carried out SCR catalyst tests on catalysts exposed to, respectively, high and low-dust conditions, in a pulverized fuel power plant co-firing of straw and coal. The deactivation of catalyst elements was faster than for pure coal firing but lower than for pure biomass firing. Experience with fuels having a high amount of volatile potassium show that the combustion conditions are very important for the speciation of potassium and the deactivation rate.

During full scale tests in slip stream reactor in High-Dust as well as in Low-Dust configuration however actual investigations carried out within this project did not show a significant decrease in catalyst activity during 7% thermal straw addition.

Concerning the release of phosphorus, reducing conditions as for instance during air staging for primary NOx reduction showed no detectable influence on catalyst deactivation during bench scale tests.

In full scale measurements on the behaviour of phosphorus could not detect a certain behaviour, which could solely be contributed to the combustion conditions. However, parameter variations in full scale are extremely difficult given enough time for stabilisation of the equilibrium in the boiler. Parametric studies would have exceeded the budget of the current project.

Reported by

Universität Stuttgart
Pfaffenwaldring 23
70569 Stuttgart
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