465 / 2018-09-05 19:51:47

Biomass Gasification in a Drop Tube Furnace: Experiments and Modelling

全体主题 > 生物质固体成型燃料

The main objective of this work is to study the effects of temperature and gasifying agent during the gasification of wheat straw in a drop tube furnace (DTF), with a length and diameter of 1.75 m and 0.036 m, respectively. The gasification tests were conducted in mixtures of air and nitrogen, and steam and nitrogen, over a temperature range from 900 to 1200 ºC. Both char and soot particles were collected at the exit of the DTF and analysed with a scanning electron microscope (SEM). The resultant syngas of each experiment was analysed in a gas chromatograph and the performance of the gasification was evaluated through the producer gas composition and high heating value (HHV), the gas and solid yields and the carbon conversion efficiency. Preliminary tests showed that the production of CO and CO2 is enhanced in the presence of air, while H2 and CH4 gaseous species are favoured in the presence of steam. In parallel with the experimental tests, a kinetic-diffusion controlled model was implemented in MATLAB using the Cantera reaction kinetics library. Since pyrolysis is the utmost important step in gasification, the Bio-PoliMi pyrolysis mechanism and a tar cracking model were also implemented as a pre-stage of the gasification process. As for the gasification stage, distinct chemical reactions were considered to account for the effects of each atmosphere. The char gasification kinetic parameters of each reaction were optimized to the experimental results using a two-step fitting procedure. Figure 1 shows the flow process of the gasification kinetic-diffusion controlled model. Overall, the proposed model is able to predict the thermochemical and diffusional processes occurring during the gasification of wheat straw and to evaluate the influence of the operating parameters, i.e temperature and gasifying agent on the performance of the process.