Fluidization XVII

Experimental and Modelling Study of the Volatiles Distributor for Improving the Horizontal Gas Distribution in Fluidized Beds

Authors

Lyngfelt, A., Chalmers University of Technology
Linderholm, C., Chalmers University of Technology
Mattisson, T., Chalmers University of Technology
Chemical looping combustion of biomass is an important and promising CO2 capture technology due to its inherent CO2 separation. However, biomass has a high content of volatiles, and if the contact between volatiles and the bed material of oxygen-carrier is insufficient in the fluidized bed used for the fuel reactor, the unconverted combustibles require the costly oxygen polishing step. Therefore, a concept named volatiles distributor (VD) is proposed for achieving a more uniform volatiles distribution over the cross-section, providing better gas-solids contacting and improving the gas conversion in the fuel reactor. The concept could be useful for other solid fuel conversion processes in fluidized-beds.

An experimental study of the VD with different configurations in a circulating fluidized-bed (CFB) cold-flow model has been investigated under different fluidization conditions, which shows that the VD gives a more uniform lateral distribution under higher fluidization velocity. Also, higher volatiles flow gives a more even distribution along the VD. The single bubble regime, i.e. large single bubbles formed at the bottom, and multiple bubble regime, i.e. multiple bubbles with different sizes formed at the bottom, were investigated with the VD. It was found that the VD gives a more uniform lateral distribution in single bubble regime compared to the multiple bubble regime. The installation of internal baffles at the bottom of the VD was found to reduce the bottom air flowing into the VD, thus improving the uniformity of the horizontal distribution of the volatiles and further reducing the risk of volatiles slip below the lower edge of the VD.

A modelling study is being conducted based on the above experimental data with the purpose to better understand the fluid dynamics in the fluidized bed with the VD.