Filtration Properties of Dust from Fluidised Bed Gasification Systems

Abstract

Advanced coal-based combined cycle power generation technologies, such as the British Coal Topping Cycle, require hot clean gas to be produced in order to maximise their thermal efficiency. The cleaning is needed to prevent wear of the heavy duty industrial gas turbines which burn the gas and to meet emission requirements.

The British Coal Topping Cycle is based on a pressurised air blown spouted bed gasifier to produce fuel gas with a circulating fluidised bed combustor to burn the char. Hot gas filtration using ceramic filter elements is used to remove particulate material from the fuel gas. Performance of the hot gas filter will be affected by the design of the system, operating conditions and also the nature of the dust from the fluidised bed gasifier.

The work reported in this paper is part of a programme of hot gas filtration studies being carried out at the Coal Research Establishment, Cheltenham. Satisfactory cleaning was achieved for a range of UK and internationally traded coal/sorbent combinations. There was some variation in cleaning behaviour for the dusts but further work is required in order to quantify these effects in terms of the impact upon operation of a multi-element filter unit. The results have highlighted properties of the dust and coal which may have an impact on filtration performance. A programme of additional tests is recommended in order to investigate further the effect of dust properties on filtration performance. Reducing filtration temperature from 600°C to 400°C did not lead to difficult to clean dust cakes and this result suggests that filtration temperature for the demonstration plant will not be a major issue as far as cleaning is concerned.