Controlled utilization of coal slag in the MHD topping cycle
Abstract
Slag coating development for structural protection from gas dynamic erosion, and from current concentrations in the MHD channel, is described. Experimental and analytical study of the behavior of coal ash on the wall structures of MHD systems has resulted in an understanding of controlling transport processes. Experimental measurements under both subsonic and supersonic conditions indicate that on a wettable wall structure, operating at temperatures well below 250 K, slag develops by deposition from the gas flow at a predictable rate. A layer equilibrates with a viscosity-temperature distribution defined by balancing of local mass flow in the layer with skin friction and pressure gradient forces driving it. Typically, at 0.3 wt% mineral matter in a Mach 1.4 flow, equilibration time is about 40 min. This is somewhat greater than predicted by simple theory, due to the existence of a finite rate of reentrainment prior to equilibration. The steady-state layer is on the order of one mm thick, with surface temperature about 1800 K. Effects of ash composition, combustion stoichiometry, flow field, and wall structure are discussed, together with corresponding analyses.
- Publication:
-
In: Ash deposits and corrosion due to impurities in combustion gases; Proceedings of the International Conference
- Pub Date:
- 1978
- Bibcode:
- 1978adcd.proc..665S
- Keywords:
-
- Coal Utilization;
- Fluid Dynamics;
- Magnetohydrodynamic Generators;
- Protective Coatings;
- Slags;
- Topping Cycle Engines;
- Energy Technology;
- Mass Flow Factors;
- Steady State;
- Supersonic Flow;
- Transient Response;
- Walls;
- Plasma Physics