Filtration performance at high temperatures and analysis of ceramic filter elements during biomass gasification

During the CHRISGAS project, various experimental campaigns were performed with the aim to study the hot gas filtration process during steam-O2 biomass gasification at Delft University of Technology. The test-rig consists of a 100 kW thermal atmospheric circulating fluidized-bed gasifier and a high temperature filter unit which contains 3 rigid ceramic candles with an outer diameter of 60 mm, 10 mm wall thickness and a length of 1520 mm. This paper gives an overview of tests performed with different fuels (A-wood, B-wood, miscanthus) and with sand and magnesite used as bed materials. Dia-Schumalith1 candles were operated in the temperature range between 600 °C and 800 °C for more than 50 h. The filtration performance was studied through continuous observation of the increasing differential pressure while the filter cake formed on the surface of the candles. Gas face velocities ranged between 3 cm s−1 and 5 cm s−1. Stable filtration was achieved during some tests. Dust cake analysis indicated formation of calcium phosphates and silicates and potassium silicates. ⺠A high temperature filtration unit was operated during biomass gasification. ⺠Ceramic candles showed stable filtration with constant baseline pressure drop. ⺠Penetration of fine ash material in the membrane's pores caused unstable filtration. ⺠Ash analyses showed formation of silicates with accommodation of alkali metals.