Flow Hydrodynamics in a Scaled Cold Flow CFB Model
Typ
Examensarbete för masterexamen
Program
Innovative and sustainable chemical engineering (MPISC), MSc
Publicerad
2018
Författare
Sellgren, Christoffer
Andersson, Viktor
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
One way to tackle the ever increasing threat of disasters due to global warming and other environmental issues could be implementation of circulating fluidized bed (CFB) technology, in which there is a need to improve the available knowledge regardingtheflowstructureandscaleupprocesses. Inordertomoreeasilyinvestigate this, the Institute of Energy Systems and Technology at Darmstadt Technical University constructed a scaled, 0.36:1, cold flow model of a hot 1 MWth pilot plant located at campus. The cold flow model and most of its experimental parameters are scaled according to the simplified Glicksman scaling laws. Previous studies have been conducted without scaling the size of the particles used as bed material, which is the focus in this study. However, the density ratio is not scaled accordingly, with the motivation that the hot pilot operates in the viscous limit regime and thus the particle densities might be negligible [1]. Profile measurements of particle concentrations and velocities are conducted at various heights within the cold flow model using a capacitance probe system. The results are validated using continuously conducted pressure profiles, material properties, different entrance points on the riser as well as repeating measurements. As expected in CFB systems with relatively low particle concentrations and superficialgasvelocities(<10m/s),thecore-annularflowstructureispresentinmost of the resulting velocity- and concentration profiles. Depending on the superficial gas velocity and particle size distributions, the core-annular flow structure is often obstructed in the lower regions of the riser. This is believed to be caused by the highamountofrecirculatingbedmaterialthroughtheloopseal,togetherwithahigh resistance particle filter at the air distribution plate, causing particle accumulation in the center of the riser. The capacitance probe results were well comparable to the hot pilot plant results and showed good accordance to the simplified Glicksman scaling laws. The minorvariationininventory, smallchangeinphysicalpropertiesofthematerialand displayedconsistencyoftheequipmentallindicatethattheacquireddataissuitable for further processing.