Recovery and regeneration of spent MHD seed material by the formate process

In an MHD method involving combustion of a sulfur-containing fossil fuel to produce a high-temperature flue gas wherein the gas is seeded with an ionizable alkali metal salt to render the gas electrically conductive by ionization of the alkali metal salt therein to enable generation of electricity by passage of the conductive gas through a magnetic field at a high velocity, and wherein alkali metal ions in the gas react with sulfur dioxide and slag produced by combustion of the fuel to form solid combustion products including a spent seed material containing the alkali metal sulfate and a slag material containing alkali metal aluminosilicates, an improvement in the method of recovering the alkali metal from the combustion products and regenerating the alkali metal to a sulfur-free form suitable for use in providing the seed material which comprises collecting the combustion products from the gas, dissolving the alkali metal sulfate from the spent seed in water to provide an aqueous solution thereof, reacting the alkali metal sulfate in the solution with calcium hydroxide and carbon monoxide to form an alkali metal formate and calcium sulfate, adjusting the pH of the alkali metal formate solution to promote precipitation of any dissolved calcium salts and to suppress subsequent formation of formic acid, and employing the alkali metal formate solution as a source for the alkali metal salt seed material.