Heat transfer and bubble characteristics in a fluidized bed with immersed horizontal tube bundle

http://www.nt.ntnu.no/users/skoge/prost/proceedings/aiche-2004/pdffiles/papers/280c.pdf

A review of gas–solid dispersion and mass transfer coefficient correlations in circulating fluidized beds

Flow behavior and regime transition in a high-density circulating fluidized bed riser

Solid circulation and loop-seal characteristics of a dual circulating fluidized bed: Experiments and CFD simulation

Effects of particle properties on solids recycle in loop-seal of a circulating fluidized bed

The hydrodynamics of solids (FCC) recycle in a loop-seal (0.08 m) at the bottom of the downcomer (0.08 m-I.D.x4.0 m-high) in a circulating fluidized bed (0.1 m-I.D.x 5.3 m-high) have been determined. Solid flow rate through the loop-seal increases linearly with increasing aeration rate. At the same aeration rate, the maximum solid flow rate can be obtained at a loop-seal height-to-diameter ratio of 2.5. The effects of solid inventory, solid circulation rate and gas velocity on pressure balance around the CFB have been determined. At a given gas velocity and solid circulation rate, pressure drops across the downcomer and loop-seal increase linearly with increasing solids inventory in the bed. At a constant solid inventory, pressure drops across the riser and the downcomer increase with increasing solid circulation rate but decrease with increasing gas velocity in the riser. The obtained solid flow rate has been correlated with pressure drop across the loop-seal.

Solids flow characteristics in loop-seal of a circulating fluidized bed

Gas backmixing in a circulating fluidized bed

Flow regimes and axial pressure profiles in a circulating fluidized bed

The effects of secondary air ratio (0–50%), height of injection port (1.5–2.5 m) and injection types (radial and tangential) on the axial solid holdup distribution have been determined in a circulating fluidized bed (0.1 m I.D. × 5.3 m high). As the secondary air ratio is increased, solid holdup increases below the secondary air port, whereas it decreases slightly above the secondary air injection port. The dense bed height increases with increasing height of the secondary air injection port. Different types of secondary air injection system do not produce any significant difference in the overall axial solid holdup distribution. However, solid holdup just above the injection port in a tangential secondary air injection system exhibits somewhat higher values than those of radial secondary air injection system. The effect of secondary air injection on the axial solid holdup distribution in a circulating fluidized bed can be predicted by a modified freeboard-entrainment model with decay constants determined from the proposed correlation.

Effect of secondary air injection on axial solid holdup distribution in a circulating fluidized bed

Solid recycle characteristics through a conventional and a newly developed loop-seal (0.08 m i.d.) system are determined in a circulating fluidized bed of FCC or silica sand particles. In the loop-seal developed in this paper, gas was injected downward tangentially to the wall of the loop-seal to increase solids mass flux with stable flow. For conventional loop-seal, solids mass fluxes increase linearly with increasing aeration rate but it reaches a maximum value. At the same aeration rate with different aeration locations (0.1-0.6 m) in a conventional loop-seal, a maximum solids mass flux is seen at a height to diameter ratio of 2.5. For the newly developed loop-seal, mass fluxes of FCC and sand particles are higher and more stable than in conventional loop-seal at the same aeration rate. The solid mass fluxes obtained have been correlated with the aeration rate and Archimedes number.

Won Namkung

Papers

Solids flow characteristics in loop-seal of a circulating fluidized bed

Gas backmixing in a circulating fluidized bed

Flow regimes and axial pressure profiles in a circulating fluidized bed

Effect of secondary air injection on axial solid holdup distribution in a circulating fluidized bed

Solid Recycle Characteristics of Loop-seals in a Circulating Fluidized Bed