Magnetohydrodynamics has very low air-pollution potential. In pilot plant tests in which a 2.2 wt-pct sulfur coal was burned in a cyclone furnace at 200 lbs/hr and 4,000 deg f (2,500 deg k) at a seed concentration of 1 g-mole k2co3/kg coal, 99.8% Removal of so2 was obtained with only 5 ppm so2 in the gaseous effluent. Operating the combustor with 95% of stoichiometric oxygen and ambient air admitted at 2,000 deg f (1,370 deg k), nox emissions decreased to 150 ppm or 0.12 Lb NO2/million btu. This represents a 94% reduction from single-stage operation at 102% of stoichiometric oxygen. It is expected that a commercial plant would experience even lower nox emissions. A mathematical model using the zeldovich mechanism was adequate to follow the nox decomposition in the air-rich system; an extended zeldovich was more appropriate in the fuel-rich regime. Experiments showed that at high slag-rejection rates of greater than 90%, recovery of the potassium seed by aqueous extraction was better than 99%. Cost estimates of a 1,000-mwe mhd-steam plant, in which the spent seed is recovered by aqueous extraction and then regenerated with reducing gases to remove the sulfur, showed an operating cost of the seed recovery-sulfur removal steps of 8% of the overall power costs of 10.3 Mills/kwh. Seed make-up costs have a marginal impact even at potassium recoveries as low as 95%. The capital costs of so2 removal is $10.4/Kw, approximately one-fifth of that in conventional power plants.
13th Symp. Eng. Aspects of Magnetohydrodynamics, Stanford Univ., 3/26-28/73, PP. VII.1-VII.1.10