Chapter 66. Corrosion of Ceramic Filters for Hot Cleaning in Thermal Power Plants

Summary

The durability of the ceramic candles used for hot cleaning of coal combustion gases are one of the fundamental requirements for the design of the filter units in pressurised fluidised bed combustion power plants. The behaviour of three commercial candle filters, two made of silicon carbide added with a clay-based binder, one made of alumina and mullite, was investigated in the presence of three different ashes, as received from thermal power plants. The study mainly dealt with the chemical interactions which could occur at the interface between the ash grains and the filter surface induced by the presence of low-softening glassy phase in both ashes and filters at high temperature (1000–1100°C). Even if a generalisation of the results is limited by the considerable difference in composition, particle size distribution, glassy phase nature and amount of the ashes, dependent on the starting coal, the three investigated filters showed a promising behaviour in view of their industrial application. Etching was essentially observed on the clay-based binder phase present in one of the SiC filters.