Effects of Municipal Sewage Sludge on Fixation of Cr, Ni, Cu, and Zn during Co-processing of Heavy Metal-containing Waste in Cement Kilns

Application Status of Co-Processing Municipal Sewage Sludge in Cement Kilns in China

“…With the drying process of sludge, the content of heavy metals in the exchangeable state and carbonate binding state in the sludge decreased significantly, reducing the release of heavy metals in the collaborative disposal process of sludge [21]. However, when MSS and heavy metal-rich waste were treated simultaneously, the fixed ratio of heavy metal declined due to the trace element composition of MSS [9]. Therefore, attention should be paid to pollutant emission when cement kilns are used to coordinate the disposal of various wastes.…”

“…There are many factors that affect the selection of co-processing technique routes of cement plants, such as distinct features of different processes, MSS properties, and social situations [6,9]. The primary routes used in mainland China can be summarized as follows: In the first route, MSS is…”

“…There are many factors that affect the selection of co-processing technique routes of cement plants, such as distinct features of different processes, MSS properties, and social situations [6,9]. The primary routes used in mainland China can be summarized as follows: In the first route, MSS is added to a cement kiln from a transition chamber using special pumps (Route 1), and the typical case is the co-processing project in a cement plant in Guangxi; In the second route, MSS is dewatered by direct thermal drying, and after that it is added to the cement kiln from a precalciner via a plate chain conveyor (Route 2) and the typical application case is the co-processing project in Guangdong; In the third route, after indirect drying pretreatment, MSS is added to the cement kiln from a precalciner via a plate chain conveyor (Route 3), and Beijing Cement Plant adopted this route.…”

“…Compared with other disposal methods, co-processing MSS in cement kilns is more environmentally friendly. High kiln temperatures destroy dioxins or furans produced during combustion, acidic gaseous pollutants can be effectively removed by the suspended fine limestone particles, and heavy metals from the sludge are adsorbed onto the particles or solidified in clinkers [8,9]. Furthermore, organics in MSS can contribute extra heating value to the cement kiln, resulting in their serving as alternative fuels for the kiln.…”