首页|Recovery of phosphate from carbonized sewage sludge by chlorination
Recovery of phosphate from carbonized sewage sludge by chlorination
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NETL
NSTL
Elsevier
The objective of this study was to develop a method for selective separation and recovery of phosphorus from carbonized sewage sludge (SSC) by the volatile chloride process. First, char was prepared from sewage sludge, and P existed as FeP_2 in SSC. Next, the volatilization behavior of the constituent elements during chlorination of SSC was investigated in detail: volatilization of Fe and P in SSC was observed above 573 K, and their volatilization rates reached >90 % at 973-1273 K. On the other hand, Si, Al, and K also volatilized above 873 K, and some Mg volatilized above 1173 K, but Ca was thermally stable. Therefore, selective separation of P was attempted to separate the Fe and P compounds by holding at 773 K, and found that it was possible to volatilize 70 % of Fe and P while suppressing the volatilization of Si, Al, and K. At 873 K, the volatilization rate of Fe and P reached more than 90 %, but 10-20 % of Si and Al were volatilized. Thus, it was found that optimum chlorination condition is 773 K holding for selective P separation. As a result of examining the possibility of separation of volatilized Fe and P species at 773 K, 20min holding, most of the volatilized Fe species precipitated on the inner wall of the reactor. Half of the volatilized P precipitated on the inner wall of the reactor, and the rest was concentrated in a water trap installed in a subsequent stage. These results indicate the possibility of separation and recovery of gaseous P and Fe species.
NETL
NSTL
Elsevier
