Mixing and pelletizing sewage sludge ash (SSA) or municipal solid waste (MSW) fly ash with CaCl2 and
treating these pellets in a rotary reactor at approximately 1000 °C lead to a significant decrease of the heavy
metal concentration.
Experiments were carried out in an indirectly-heated laboratory-scale rotary reactor. From SSA, after 10 min
at 1050 °C, more than 95% of Cu, Pb and Zn could be removed. The heavy metal removal from municipal solid
waste (MSW) fly ash proceeded more slowly and often less efficiently. After 45 min at 1050 °C, 95% Cd, 60%
Cu, 98% Pb and 80% Zn could be removed.
Thermodynamic equilibrium calculations for possible single reactions were carried out. It was found that SiO2,
a main component in sewage sludge ash, accelerates the formation of HCl and Cl2. CaO, which is contained in
CaO-bearing phases in MSW fly ash, decreases the rate of this reaction. Al2O3, also contained in MSW fly
ash-phases, leads to the formation of aluminates. Cd-aluminate can be affected by HCl and Cl2, leading to a
lower removal rate. Zn-aluminate can only be affected by Cl2; Cu-aluminate is stable under chlorination
conditions. I.e., Cu and Zn can easily be incorporated into the MSW fly ash matrix.
Mixing and pelletizing sewage sludge ash (SSA) or municipal solid waste (MSW) fly ash with CaCl2 andtreating these pellets in a rotary reactor at approximately 1000 °C lead to a significant decrease of the heavymetal concentration.Experiments were carried out in an indirectly-heated laboratory-scale rotary reactor. From SSA, after 10 minat 1050 °C, more than 95% of Cu, Pb and Zn could be removed. The heavy metal removal from municipal solidwaste (MSW) fly ash proceeded more slowly and often less efficiently. After 45 min at 1050 °C, 95% Cd, 60%Cu, 98% Pb and 80% Zn could be removed.Thermodynamic equilibrium calculations for possible single reactions were carried out. It was found that SiO2,a main component in sewage sludge ash, accelerates the formation of HCl and Cl2. CaO, which is contained inCaO-bearing phases in MSW fly ash, decreases the rate of this reaction. Al2O3, also contained in MSW flyash-phases, leads to the formation of aluminates. Cd-aluminate can be affected by HCl and Cl2, leading to alower removal rate. Zn-aluminate can only be affected by Cl2; Cu-aluminate is stable under chlorinationconditions. I.e., Cu and Zn can easily be incorporated into the MSW fly ash matrix.
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