Experimental studies on Chemical-looping combustion in a packed-fluidized bed: Effects of packing type and bed height

Examensarbete för masterexamen
Sustainable energy systems (MPSES), MSc
Tsuji, Yukari
Chemical Looping Combustion (CLC) is a technology that can be used as a gas separation technology for Carbon Capture and Storage (CCS). Compared to other alternatives, it is considered to have lower investment and operational costs per amount of CO2 captured. CLC utilizes fuel and air reactors where the use of fluidized beds can be an advantage. For industrial applications, fuel conversion rates for higher bed heights need to be improved. One possible solution could be to add packings in the reactors to inhibit bubble growth and possibly increase the fuel conversion rate by increasing the mass transfer rate. This project investigated possible improvements of fuel conversion rate in a packed fluidized bed for Chemical Looping Combustion(CLC). Two types of fuel, Syngas and CO, were tested with two different types of packings, RMSR and Hiflow® ring, as well as without packings. All tests were conducted with a small laboratory scale reactor and bed heights between 10 and 60 cm. The results show that the fuel and CO conversion rates increase as the bed height increases. This could be due to spouting or insufficient fluidization when having a lower bed height, leading to a shorter reaction path. The relative increases in conversion rate are the highest for lower bed heights. However, for taller beds the conversion rates are above 96 % without packings and approach 100 % with. A fluidized bed equipped with RMSR has the best overall fuel conversion rates but use of packings in general showed an improvement when compared to the experiments without them. For higher beds without packings there were some observations indicating large bubble formation. The lack of similar observations when packings were used could indicate that the they are inhibiting the formation of large bubbles as intended. In conclusion, the use of packings in a fluidized bed for CLC seems to increase the the fuel conversion rate, possibly through the inhibition of bubble growth. Further studies, with taller beds as well as with other packings with different geometries and materials, under different operating temperatures and pressures, are recommended. Study of bubble formation and inhibition with packings in a fluidized bed can also contribute to the understanding of the effect of packings for bubble inhibition and hence the rates of mass transfer and fuel conversion.
Packed-fluidized bed , Chemical-looping combustion , CCS , metal random packing , fuel conversion
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