A method for producing an iron pigment and hydrochloric acid with reduced or substantially eliminated waste streams includes: providing an iron chloride solution, wherein the iron chloride solution includes one or both of iron (II) chloride and iron (III) chloride; neutralizing the iron chloride solution with one or both of ammonia and ammonium hydroxide to form a slurry of an iron oxide solid component and an ammonium chloride solution; separating the iron oxide solid component from the ammonium chloride solution; drying the iron oxide solid component to form an iron pigment or pigment intermediate; reacting the ammonium chloride solution with an alkaline-earth metal solid to form an alkaline-earth metal chloride solution and to evolve ammonia as a vapor, wherein at least a portion of the evolved ammonia reacts with water to form ammonium hydroxide; recycling one or both of the evolved ammonia and the formed ammonium chloride for use in connection with the neutralization step; and pyrohydrolyzing the alkaline-earth metal chloride solution to form hydrochloric acid and to regenerate the alkaline-earth metal solid. Iron pigment or pigment intermediate produced in accordance with the method may have a yellow, red, or black color.

Disclosed is a system and method for preparing hydrogen chloride and ammonia gas by using ammonium chloride. The system includes a decomposition reactor and at least one regeneration reactor, or includes a reactor that may serve as the decomposition reactor and the regeneration reactor; ammonium chloride in particle form is continuously added to the decomposition reactor via a solid particle feed apparatus, and reacts with molten-state ammonium hydrogen sulfate to generate hydrogen chloride gas and an intermediate material; the intermediate material is discharged to the regeneration reactor, and heated therein to decompose into ammonium hydrogen sulfate and ammonia gas; and the ammonium hydrogen sulfate is returned to the decomposition reactor for recycling. The present disclosure provides an industrial feasible implementation solution for continuous decomposition of ammonium chloride, lowers volatilization of ammonium chloride by continuously and slowly adding ammonium chloride in particle form, and improves utilization rate of the ammonium chloride.

Disclosed is a system and method for preparing hydrogen chloride and ammonia gas by using ammonium chloride. The system includes a decomposition reactor and at least one regeneration reactor, or includes a reactor that may serve as the decomposition reactor and the regeneration reactor; ammonium chloride in particle form is continuously added to the decomposition reactor via a solid particle feed apparatus, and reacts with molten-state ammonium hydrogen sulfate to generate hydrogen chloride gas and an intermediate material; the intermediate material is discharged to the regeneration reactor, and heated therein to decompose into ammonium hydrogen sulfate and ammonia gas; and the ammonium hydrogen sulfate is returned to the decomposition reactor for recycling. The present disclosure provides an industrial feasible implementation solution for continuous decomposition of ammonium chloride, lowers volatilization of ammonium chloride by continuously and slowly adding ammonium chloride in particle form, and improves utilization rate of the ammonium chloride.