A lab-scale cold flow model reactor to investigate near-wall particle segregation relevant to entrained-flow slagging coal gasifiers

The particle deposition rate at the wall and the partitioning of wax droplets between the lean-dispersed phase and the wall liquid layer have been assessed under a range of operating conditions. Temperatures of the atomized wax, of the mainstream air and of the reactor wall have been set in a range of values (120-155 degrees C) at which the wax was fluid. Experiments with wax feeding rate of 0.2 g s(-1) and flow rate of atomizing air in the order of 0.30 m(3) h(-1) demonstrated that the fractional mass of wax in the dispersed phase decreased from 91% to 12% as the reactor length increased from 0.03 m to 0.27 m. The velocity of the descending wall liquid layer, whose thickness was in the order of 0.2 mm, ranged between 3 mm s(-1) and 6 mm s(-1). The effects of the flow rate of atomization air and of the nozzle temperature were limited. (C) 2013 Elsevier Ltd. All rights reserved.

This paper reports on preliminary results of an experimental investigation aimed at the development of a phenomenological model of the fate of coal/ash particles in entrained-flow slagging coal gasifiers. The study specifically addresses the interaction between the lean-dispersed particle phase and the reactor walls, and the establishment of a particle segregated phase in the near-wall region of the gasifier. Better mechanistic understanding of particle-wall interaction patterns in entrained-flow gasifiers is pursued using the tool of physical modeling. To this end a lab-scale cold flow reactor (0.04 m-ID) has been designed and set up, where molten wax is air-atomized (droplets of 50-100 mu m size) into a mainstream of air to simulate the near-wall fate of char/ash particles in a real hot environment. Preliminary characterization of the hydrodynamics of the lean-dispersed phase, of its interaction with the wall, of the buildup of the liquid wall layer has been accomplished with a focus on the "sticky wall-sticky particle'' sub-regime.