| With the improvement of people’s living standard and the rapid development of electronic and information technology, waste electrical and electronic waste (WEEE) has become one of the world’s fastest-growing solid waste. Printed circuit boards (PCBs) that are widely used in all kinds of electronic equipments is an important part of WEEE. Because of its high content of precious metals, PCBs have much high value of recovery and utilization. As some conventional recovery methods of PCBs-such as simple dismantled, open burning, chemical method et al-are easily to environmental pollution, exploring reasonable method of PCBs’recycling and disposal has become an important subject that all countries have to face.Pyrometallurgy technology is an effective method to realize resource utilization of PCBs, because it’s many advantages, like large in handling capacity, simple process, easy to operate, high recovery rate of precious metals, quantity of heat contains in the resin and combustible component can be made full use of, et al. But because of bromide flame retardants, it’s easy to generate corrosive gas-inorganic bromide-and polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) during PCBs’ combustion. Based on this backgrounds, the aim of this paper is to investigate the transformation and conversion characteristics of bromine and the generation and emission characteristics of PBDD/Fs in WPCBs at high temperature.The weight loss and gas emission characteristics during thermal composition of PCBs have been studied by TG-FTIR under nitrogen and oxygen atmosphere, respectively. The results show that there is only one quick weight loss process during pyrolysis, which is caused by the release of volatile, while there are two quick weight loss processes during combustion, which are caused by the release of volatile and the combustion of fixed carbon, respectively.Then the influence of temperature, calcium base additives and sulfur on the transformation and conversion of bromine during PCBs’combustion was investigated with the tubular furnace. The results indicated that the higher the temperature, the higher the Bromide molecular’s conversion rate, while the lower the Hydrogen bromide’s conversion rate. Calcium base additives’ impact on the conversion rate of HBr was not too much, but all improved the inorganic bromide’s conversion, and the promoting effect is Ca (OH)2> CaO> CaCO3. The addition of sulfur had two impacts, on the one hand, it promoted Br2conversing to HBr, on the other hand, it reduced the inorganic bromide’s conversion rate.The impact of temperature, calcium base additives and sulfur on PBDD/Fs emission during PCBs’ combustion was also researched with the tubular furnace. It turned out that PBDFs predominate in PBDD/Fs products between800℃and1100℃. The Toxic Equivalent Quantity (TEQ) was the largest at900℃, while PBDDFs generation at1000℃, and they both greatly reduced at1100℃. The addition of calcium base additives and sulfur both improved the proportion of PBDDs in the total amount of PBDD/Fs. The concentration of PBDD/Fs and TEQ reduced at all conditions with the additives, except at Ca/Br≧1with CaCO3, and the inhibition effect of the additives was CaO>S>Ca(OH)2>CaCO3. In addition, this paper had founded that there was no obvious relevance between the characteristics of bromide’s transformation and conversion and that of PBDD/Fs’ generation and emission by comparison and analysis of the data. |
