PROCESS FOR RECOVERING SULFATE AND CHLORIDE SALTS FROM WASTEWATER, MIXED SALTS, AND BRINES

摘要

A process is described for recovering alkali-chloride and alkali-sulfate salts from a salt solution. The salt solution comprises alkali metal, chloride and sulfate ions and is directed to a hydrous salt crystallization unit which crystallizes hydrated sulfate salts that comprise sulfate and at least one alkali metal. A purged solution from the hydrous salt crystallization unit is directed to a chloride salt crystallization unit while the hydrated sulfate salt crystals are melted to form an aqueous sulfate solution which is directed to a sulfate crystallization unit. Anhydrous sulfate salts are crystallized from the aqueous sulfate solution to form sulfate salt crystals comprising sulfate and at least one alkali metal. In the chloride salt crystallization unit, chloride salt is crystallized to form chloride salt crystals. A purge from the chloride salt crystallization unit is directed to the hydrous salt crystallization unit.

主权项

1. A method for treating wastewater from a coal to chemical or coal to liquid process, comprising:
converting coal to chemical or liquid and producing a wastewater; concentrating the wastewater to form a salt solution; directing the salt solution comprising an alkali metal, chloride, and sulfate to a hydrous salt crystallization unit and crystallizing hydrated sulfate salts to form hydrated sulfate salt crystals comprising sulfate and at least one alkali metal, and a hydrous salt crystallization unit solution; melting the hydrated sulfate salt crystals to form an aqueous sulfate solution; directing the aqueous sulfate solution to a sulfate crystallization unit and crystallizing anhydrous sulfate salts from the aqueous sulfate solution to form sulfate salt crystals comprising sulfate and at least one alkali metal, and a sulfate crystallization unit solution; directing at least a portion of the sulfate crystallization unit solution to the hydrous salt crystallization unit; directing at least a portion of the hydrous salt crystallization unit solution or at least a portion of the sulfate crystallization unit solution to a chloride salt crystallization unit and crystallizing chloride salt from the hydrous salt crystallization unit solution or the sulfate crystallization unit solution to form chloride salt crystals comprising chloride and at least one alkali metal, and a chloride salt crystallization unit solution; and directing at least a portion of the chloride salt crystallization unit solution to the hydrous salt crystallization unit.