Abstract: An alkali metal-containing spent liquor is treated to recover the alkali metal content for reuse without the need for recycling furnace ash and forming solid pellets therefrom. A mixture of aluminum hydrate and alkali metal-containing waste liquor is directed through a heated furnace and dried to form granules of the aluminum hydrate and waste liquor solids, and the organic content of the granules are combusted and reacted to form granular alkali metal aluminate furnace ash. The granular furnace ash is removed from the furnace and treated to recover the alkali metal and to produce aluminum hydrate for reuse in the process.

Abstract: A process and apparatus for treating concentrated alkali metal-containing waste liquor to recover the alkali metal content for reuse includes the following steps and apparatus. Concentrated alkali metal-containing waste liquor is mixed with recycled alumina and formed into solid pellets by mixing the concentrated liquor-alumina mixture with recycled alkali metal aluminate furnace ash. The solid pellets are fed through a furnace operating at a temperature below the fusion temperature of the aluminate for combusting the organic portion of the pellets and reacting the alkali metal content thereof with the alumina to form additional alkali metal aluminate ash. A portion of the furnace ash is recycled for reuse in the formation of pellets, while another portion of the ash is dissolved in water to form a solution of alkali metal aluminate. The alkali metal aluminate solution is mixed with slurry recycled from later in the process to initiate limited precipitation of alumina from the alkali metal aluminate.