Thermodynamic Simulation Of Heavy Metal Behavior In Waste Disposal

With the rapid development of economy,consumption continue increased,the large amounts of waste which difficult to deal with become a big problem,the incineration brings a new problem,the fly ash which contains a large number of harmful substances and heavy metal has pose a threat to the environment,the study shows that the cement rotary kiln is a feasible and effective way to remove harmful substances and fixed heavy metal in the clinker due to its high temperature conditions.This paper simulated the thermodynamic behavior of heavy metal in the process of As,Cd,Sb,Pb and compared with the laboratory calcination conditions,actual industrial production monitoring data by relevant literature data,found that the different flow direction of heavy metals leads to the difference of the final fixation rate.By comparing the data of thermodynamic simulation and laboratory calcination condition,we found that the fixed rate of heavy metals was approximately 78%,42%,53%,5% respectively,however,there is a large deviation from the field test data,more than 90% of the heavy metal fixed in the clinker,the emission of heavy metals into the atmosphere is less than 0.01~1%.In the process of actual product,kiln dust accounted for 15% of the total amount of raw materials,kiln dust contains a large number of high volatility of heavy metals such as Pb,Cd,the result show that the kiln dust cycle has a significant effect on the fixation of heavy metals which with a high volatilization in simulation and laboratory,and after a number of cycles,the fixation rate of higher volatilization heavy metals gradually increased and eventually stabilized.In the circulation process,chose 4 replacement rate of fly ash,1%,5%,10% and 20%,respectively.The different substitution rates have a little effect on the concentration of As,but the change of Cd,Sb and Pb in kiln dust and clinker was very obvious.In the unsteady state,set the circulation rate of kiln dust as 0.4 and 1,found that the fixation rate of heavy metals in the clinker showed an obvious curve increasing trend.The higher the cycle rate,the higher the volatilization rate of the heavy metals,the more times the cycle,the more obvious of the curve trend,especially for Cd and Pb,shows that the heavy metal with high volatility will be attached to the kiln ash and finally fixed in the clinker after several cycles.