Near-wall phenomena in entrained-flow slagging gasifiers

This paper deals with near-wall particle segregation phenomena in entrained-flow slagging coal gasifiers. The recent literature has addressed the fate of char particles by assessing the relative importance of coal conversion associated with the entrained-flow of carbon particles in a lean-dispersed phase and the segregated flow of char particles in a near-wall dense-dispersed phase. Different micromechanical char–slag interaction patterns may establish, depending on the stickiness of the wall layer and of the impinging char particle. The main objective of this study is to use the tool of the physical modelling, to give a contribution in the development of a phenomenological scenario of the fate of coal/ash particles in entrained-flow slagging coal gasifiers, which considers the establishment of a particle segregated phase in the near-wall region of the gasifier. Different scales of investigation were pursued, relevant to study the fluid dynamic conditions which lead to near-wall particle segregation, as well as the particle–wall micromechanical interactions. Montan wax was used to mimic, at atmospheric conditions, particle–wall interactions relevant in entrained-flow gasifiers. As a matter of fact, this wax had rheological/mechanical properties resembling those of a typical coal slag (under molten state) and those of char particles (under solid state).