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Solids circulation in circulating fluidized beds with low riser aspect ratio and varying total solids inventory

Tove Karlsson (Institutionen för energi och miljö, Energiteknik) ; Xuemin Liu ; David Pallares (Institutionen för energi och miljö, Energiteknik) ; Filip Johnsson (Institutionen för energi och miljö, Energiteknik)
Fluidization XV (2016), Quebec, Canada (2016)
[Konferensbidrag, övrigt]

This paper presents an experimental study with the aim to understand the relation between the flow conditions - the riser pressure drop and fluidization velocity - in a CFB riser and the net (external)solids flux (Gs [kg/m2s]), applying a riser geometry and overall flow conditions similar to CFB boilers. The experiments are carried out in a CFB unit operated under ambient conditions. The riser has a cross section of 0.7 m x 0.12 m and a height of 8.5 m, yielding a riser height-to-width aspect ratio of 10.6 (in the wide dimension), similar to that of CFB boilers. The unit is equipped with densely spaced pressure taps providing a fine resolution of the measured vertical pressure profile along the riser and an automatic system to accurately measure Gs. The experiments cover fluidization velocities of 0.3-7 m/s, riser pressure drops of 1.7-10.5 kPa and loopseal fluidization velocities of 0.12-0.54 m/s (secondary air flows are not considered). These ranges correspond to conditions both with and without a dense bottom region. The results show that Gs is determined by the solids concentration at the riser top, which depends riser pressure drop and fluidization velocity, and the backflow effect, which depends on the configuration and flow conditions of the loop seal and the exit region. For operating conditions with a dense bottom bed present, Gs is independent of riser pressure drop, whereas when operating without a dense bed an increase in riser pressure drop yields an increase in Gs.

Nyckelord: circulating fluidized bed, solids circulation, solids entrainment, solids elutriation, dense bottom bed



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Denna post skapades 2016-07-04.
CPL Pubid: 238912

 

Institutioner (Chalmers)

Institutionen för energi och miljö, Energiteknik

Ämnesområden

Energi
Energiteknik

Chalmers infrastruktur