Mass flow and heat transfer characteristics of lift tube technology

An innovative vertical transport tube system has been developed to enhance heat transfer between fluidized beds and axial solids circulation within a fluidized bed reactor. Vertical lift tubes pick up particles from the bottom of the reactor, carry them through a fluidized bed burner before discharging them above the reactor bed surface. A full-scale experimental setup was designed to test the effects of different operating conditions on the solids flow through the lift tube. The heat transfer and mass flowrate through the lift tube are altered by varying the fluidization conditions, the motive gas flowrate and the location of a motive gas nozzle with respect to the tube. Increasing the pressure downstream of the lift tube reduces the solids flow. A preliminary study on the heat transfer benefit of the lift tubes was also performed on another laboratory apparatus: implementation of a single lift tube increased the heat transfer coefficient between the central and annular bed from 25 to 400 W/m2 K at optimal flow conditions. This technology has been successfully implemented in a full-scale annular pyrolysis reactor.