Abstract
A novel concept called volatiles distributor (VD), with the purpose to achieve an even distribution of volatiles over the cross-section of a fluidized-bed and better contact between volatiles and bed materials, has been investigated. The concept could be useful for chemical- looping combustion, as well as other solid fuel conversion processes in fluidized-beds. An experimental study of the VD in a circulating fluidized-bed (CFB) cold-flow model was conducted under different fluidization velocities and flows of simulated volatiles. In the reference case without VD, a local plume of volatiles is formed and the maldistribution becomes more pronounced at higher fluidization velocity in the range from 1 m/s to 4 m/s. Conversely, higher fluidization velocity gives a more even volatiles distribution in the presence of VD. The relative standard deviation of volatiles horizontal distribution decreases from 131% in absence of VD to 22% in presence of VD at the fluidization velocity of 4 m/s. There is no significant effect of volatiles flow rate on VD performance at a fluidization velocity 1 m/s. As the fluidization velocity and volatiles flow rate increase, the bed level inside VD is lowered and the volatiles inside the VD become less diluted, because less air from the main fluidization passes through the VD.
Highlights
Chemical-looping combustion (CLC) separates conventional com bustion into two steps, avoids the direct contact between fuel and air, and allows for inherent CO2 separation
The performance of the volatiles distributor (VD) is the focus of this work, the typical solid density profile and the simulated volatiles distribution in absence of the VD were first investigated as reference cases
The results from two methods are in the same order of magnitude, and show the same trend, i.e. decreasing flow and velocity with increased volatiles flow. This initial experimental study performed in a circulating fluidizedbed cold-flow model validates the effectiveness of a volatiles distributor
Summary
Chemical-looping combustion (CLC) separates conventional com bustion into two steps, avoids the direct contact between fuel and air, and allows for inherent CO2 separation. CLC has potential for a significant breakthrough in carbon capture and storage area in order to alleviate climate change. Since the CLC concept was coined in 1987, it was initially developed for gaseous fuels [1]. Its application was extended to solid fuels like coal, since solid fuels are still the major energy source in the medium-term all over the world. The use of biomass in CLC is receiving increasing interest. Chemical-looping com bustion of biomass together with the CO2 capture and storage process can give negative CO2 emissions because the captured CO2 originates from the atmosphere through the photosynthesis of plants
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