PROBLEM TO BE SOLVED: To provide a method capable of treating cement kiln waste gas dust in a closed system to recycle it as a harmless cement raw material and recovering also the removed component to have a recyclable grade as an industrial raw material.;SOLUTION: In a 1st stage, (a) the cement kiln waste gas dust is washed, (b) the resultant cleaning water is pH adjusted and a sulfidizing agent is added thereinto to be solid-liquid separated into precipitate and a liquid component and (c) the liquid component is concentrated by heating and cooled to deposit and recover potassium chloride. In a 2nd stage, (a) hydrochloric acid is added into a dehydrated cake after washing in the (a) process in the 1st stage to dissolve and exude and the obtained slurry after adjusted to pH ≤1 is solid- liquid separated into residue and a hydrochloric acid exuded liquid, (b) the residue is washed and remaining solid portion is recovered, (c) the hydrochloric acid exuded liquid is pH adjusted and after a sulfidizing agent is added, solid- liquid separated into precipitate and a liquid component, and (d) the separated precipitate and the precipitate separated in the (b) process of the 1st stage are washed to recover a solid portion.;COPYRIGHT: (C)2001,JPO
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