The Experimental Investigation And Simulation On The Leaching Behavior Of Metals In Fly Ash Of Power Plant

Coal is the major energy resource in China. The development of large-scale coal-fired power plants leads to a notable increase in fly ash production. Coal ash has been found to have significant impacts on the environment. Much of the ash is disposed of in settling ponds for a long time, which occupies a lot of land and affects natural landscape. Furthermore, fly ash contains significant quantities of various toxic heavy elements. The main leachants of the disposed ash are rainwater and slurry water. The toxic elements carried with leachants will pollute the soil and the water and harm human health. Therefore, much concern has been paid to the leaching behavior of metals in fly ash. However, little progress has been achieved up to now.This thesis aims to investigate the leaching behavior of metals in fly ash both theoretically and experimentally. First, the fly ash formation mechanisms, the species and hazards of heavy metals, and the enrichment of heavy metals are summarized. The current research results of the leaching behavior of metals are briefly reviewed.Second, base on the wide application of electrostatic precipitator, the serial batch leaching method is used to elucidate the leaching behavior of metals in fly ash, which is collected in three electrostatic precipitators of a real power plant boiler. The differences in the physical and chemical properties of fly ash are studied in detail. The distributions and leaching behavior of different metals, such as Al, Ca, Mg, Cd, Cr, Cu, Pb and Ni, in fly ash are discussed. The various pH values and leaching time are used to assess their influence on the leaching behavior of the metals.Finally, the Visual MINTEQA program is used to simulate the leaching behavior of some metals, such as Ca, Al, Pb, Cd and Ni, in fly ash under various pH values for substituting for the complicated experiment. The results show a good agreement with the experiment data.