Xiren Xu

Study on the Gasification and Melting Characteristics of Electronic Waste

The disposal of WEEE (waste electrical and electronic equipment) or “electronic waste” is an important issue in the whole world. Its gasification and melting characteristics were studied here. The experiments proved that over 50% of WEEE would be decomposed through gasification or pyrolysis and its total heat value could amount to more than 20000MJ/Kg. After gasification stage, the abundant metals, such as Fe, Cu, etc., would be more convenient to be recovered. Then melting would be a good method to dispose of the remainders of WEEE. The final melting production would be fairly stable because some metals would be solidified into various compounds that are difficult to be digested. Thus, by means of gasification and melting, it is potential to realize the energy utilization, metal recovery as well as pollution avoidance of heavy metals for the WEEE.

Experimental Study on the Conversion of Desulfurization Residues into Sulphoaluminate Cement

According to the complex compositions (with high contents of sulfur and calcium) of the desulfurization residues from coal-burning power plants, a possible idea is put forward to use them as the materials of sulfoaluminate cement. Through experiments, it is proved that the desulfurization residues, added to by some CaO or CaCO3, can be converted into sulfoaluminate cement at about 1300°C. In this way, the disadvantageous minerals in the desulfurization residues, such as free CaO, CaCO3, Ca(OH)2 as well as sulfur-containing minerals like CaSO3 and CaSO4, can all be completely utilized and converted into minerals of sulfoaluminate cement clinker, such as calcium sulfoaluminate(Ca4Al6O12SO4) and dicalcium silicate(Ca2SiO4), etc. In addition, the unburned carbon in the ashes can also be made good use of through further combustion. Therefore, this new utilization method, which can take out the maximum value of the desulfurization residues, is a high- efficiency way and may have bright prospects.

Study on a New Utilization Method for Dry and Semi-Dry Desulfurization FDG Residues

At present, most of the dry and semi-dry flue gas desulfurization (FGD) residues are simply stored and have become an obstacle to the popularization of the FGD technologies. The utilization of these residues needs to be solved urgently. Based on sufficient studies of the composition properties of the FGD residues, a completely new utilization method was put forward to produce sulfoaluminate cement in this paper, and experiments were carried out. In the experiments, the residues and some other materials were utilized to prepare raw meals according to appropriate element matching proportion. It was proved that, on a certain calcining condition, the raw materials could be converted to cement clinkers with mineral compositions being calcium sulfoaluminate (Ca 4 Al 6 O 12 SO 4 ) and dicalcium silicate (Ca 2 SiO 4 ), and with excellent mechanical strength properties. This utilization method, which can consume massive these residues, may have a wide prospect of application.