Study on whitening of phosphogypsum by low-temperature calcination
Based on the fact that phosphogypsum whiteness had a crucial influence on the subsequent bulk utilization of phosphogypsum,in order to better utilize the phosphogypsum resources,maximize the value of phosphogypsum,and im-prove the phosphogypsum whiteness,the whitening of phosphogypsum by low-temperature calcination was studied.Phospho-gypsum was sieved and calcined under the conditions of no additives,adding single additives(ammonium chloride,hydro-gen peroxide,calcium hydroxide),and composite additives,and the results showed that the whitening effect of ammonium chloride in the single additives was better,and the whiteness of phosphogypsum was increased from 68.3%to 80.5%after adding ammonium chloride with the mass fraction of 1%and calcined at 460℃.At the calcination temperature of 400℃,us-ing ammonium chloride with a mass fraction of 1%and calcium hydroxide with a mass fraction of 2.8%as a composite addi-tive could increase the whiteness of phosphogypsum to 84.2%.In addition,under the condition that the whiteness of phos-phogypsum was above 80.0%,the calcination temperature of phosphogypsum could be reduced to 350℃.This composite ad-ditive could effectively improve the whiteness of phosphogypsum and reduce energy consumption.
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