垃圾焚烧中硫化合物对重金属Cd迁移分布影响

INFLUENCE OF SULPHUR COMPOUNDS IN MSW INCINERITION UPON TRANSFER AND DISTRIBUTION OF HEAVY METAL Cd

采用管式炉模拟垃圾焚烧研究垃圾中不同硫化合物、焚烧温度、Cd初始浓度以及垃圾焚烧停留时间对Cd迁移分布特性的影响。结果表明,硫化合物种类、焚烧温度以及Cd初始浓度对Cd的迁移分布有着重要影响。氧化性气氛下S和Na2S更易使Cd在底渣中分布,Na2SO3和Na2SO4更易使Cd在飞灰中分布;硫化合物对Cd的挥发性影响能力大小依次为Na2S<S<Na2SO3<Na2SO4;温度的升高使得Cd的挥发性增强,逐渐向飞灰中分布。当焚烧温度达到950℃时,Cd开始在烟气中分布;850℃以前,Cd在烟气中的分布近乎为0。Cd初始浓度的增加使得Cd在底渣中的分布比例逐渐升高,而在飞灰中的分布比例逐渐下降。随着垃圾焚烧停留时间的增加,Cd从底渣逐渐转移到飞灰中,底渣中的分布逐渐减少。

By using tubular furnace, the municipal solid wastes（MSW） incineration has been simulated. The infuence of different sulphur compounds, incineration temperature, initial concentration of Cd, and remaining time of MSW incineration upon transfer and distribution behavier of the heavy metal Cd being studied. Results show that the kinds of sulphur compounds, incineration temperature, and initial concentration of Cd have important influence upon the transfer and distribution of Cd. Under oxidizing atomosphere, S and Na2S tend to increase Cd distribution in the bottom slag, Na2SO3 and Na2SO4 tend to increase Cd distribution in the fly ash. The effects of sulphur compounds upon volatility of Cd are successively in the order of Na2S〈S〈Na2SO3 〈Na2SO4 ; the increase of temperature makes the volatility of Cd to be stronger, making Cd gradually to distribute into fly ash. When the incineration temperature reaches 950 ℃, the Cd begins distribute into flue gas, but before 850 ℃ ,the distribution of Cd in flue gas is nearly to be zero, The increase of initial concentration of Cd makes the distribution ratio of Cd in bottom slag gradually to be rised, while making the distribution ratio of Cd in fly ash gradually to be reduced. Along with the increase of remaining time in MSW incineration, the Cd is gradually transfering from bottom slag into fly ash, the distribution of Cd in bottom slag is to be gradually reduced.