Next generation microreactors for ultra-pure H2 production (10244)

The regime transition from bubbling to turbulent fluidization was investigated in five micro fluidized beds with widths of 2 mm, 3 mm, 4 mm, 5 mm and 6 mm using fine particles (d_p=50-150µm, ρ_p=1500kg/m³) using full 3D DPM (Discrete Particle Model) simulations. The sudden change of bed expansion characteristics and the maximum value of standard deviations of local bed voidage and absolute pressure or differential pressure fluctuations indicate that the simulated critical velocities for regime transition are in general one order of magnitude smaller than those reported for conventional large scale fluidized beds. The early transition to the turbulent fluidization regime might be quite advantageous in view of the improved mass (and heat) transfer characteristics. The DPM will be extended with component mass balances to study this in great detail.

Experimental setups with different configurations were constructed for an experimental study on the hydrodynamics and gas mixing in confined gas-solid fluidized beds. Glass beads with different sizes (d_p: 100-600 µm, ρ_p=2500 kg/m³) have been used at different superficial gas velocities (1.2 to 3.5u_mf) to measure their influence on the fluidization characteristics by applying optical, non-intrusive measuring techniques (Particle Image Velocimetry coupled with Digitial Image Analysis, PIV/DIA). In addition, the development of a completely new non-intrusive technique to study gas back-mixing in gas-solid fluidized beds based on infrared (IR) has been initiated (since existing techniques based on gas sample extraction are unsatisfactory for micro-fluidized beds) and preliminary experimental results show that indeed tracer gas concentration profiles can be measured.