Nader Jand

Catalytic gasification of biomass to produce hydrogen rich gas

Abstract Catalytic biomass steam gasification runs were performed in a bench scale plant consisting essentially of a fluidised bed gasifier and a secondary catalytic fixed bed reactor. This secondary reactor employed alternatively two different steam reforming catalysts and calcined dolomite. The operating conditions in the gasifier (temperature, biomass/steam ratio and biomass feed rate) were kept constant for all the runs (770 °C, 1 and 764 kg of biomass per hour per m3 of bed, respectively). The influence of the operating conditions in the catalytic converter on the production of gases, especially H2, was investigated over the temperature range of 660–830 °C, for Gas Hourly Space Velocities (GHSV) in the range 9000–27,700 h−1. About 2 m3 of dry gas (at ambient conditions) per kg of daf biomass were obtained by utilising the fresh catalyst at the highest temperature level, with more than 60% by volume being hydrogen. The lowest tar residue was 0.45 g/kg of daf biomass, which increased slightly over the three hours gasification time. Substantial carbon deposition was observed, mainly on the catalyst layers contacting the inlet gas. On the basis of these results, a process configuration suitable for industrial applications is discussed.

Cold model characterisation of a fluidised bed catalytic reactor by means of instantaneous pressure measurements

Abstract The analysis of instantaneous pressure fluctuations is utilised in a cold modelling study of a pilot scale fluidised bed catalytic reactor for ethane oxychlorination. It is demonstrated that the fluid dynamic behaviour of a cold model of this fine particle (Geldart group A) system is well characterised by the frequency spectrum, the standard deviation and the cross-correlation of pressure signals detected at different locations within the bed and in the freeboard. The influence of operating parameters, such as gas flow rate, initial bed height, reactor configuration (internals) and average value of the local pressure, is investigated, and a comparison is made with the features exhibited by Geldart group B systems (fluidised bed combustors) for which the same diagnostic techniques have been applied. Finally, the applicability to fine particle suspensions of literature correlations for dominant frequency and propagation velocity of pressure waves is discussed with reference to the combined influence of the eruption of many small bubbles at the bed surface, and the compressibility of the gas contained within the particle-bed interstices.