Vehlow Jürgen, Bergfeldt Britta, Hunsinger Hans, Seifert Helmut, Mark Frank E
Forschungszentrum Karlsruhe GmbH, Institute for Technical Chemistry, Karlsruhe, Germany.
Environ Sci Pollut Res Int. 2003;10(5):329-34. doi: 10.1065/espr2003.02.147.
INTENTION, GOAL, SCOPE, BACKGROUND: The halogen bromine is far less abundant than chlorine, but it can be found at high concentrations in special materials like flame retarded plastics. The fate and effects of Br in waste incineration are not well understood. It may have similar implications like Cl for the volatilisation of heavy metals and the formation of low volatile organic compounds. Due to its lower oxidation potential, there is a risk of formation of elementary Br2 in the offgas.
Co-combustion tests of different types of Br containing plastic waste materials (up to 22%) and MSW in the TAMARA pilot plant for waste incineration were conducted to investigate the Br partitioning and the influence of Br on metal volatilisation.
The Br inventory of the fuel mix was elevated to approx. 1 wt-%. All input and output mass flows of the furnace have been sampled and the partitioning of Cl, Br, S, and a number of heavy metals, has been calculated on the basis of closed mass balances.
Organically-bound Br was typically released to more than 90% into the raw gas. Elementary Br2 was detected at high Br levels. Its presence was always analysed when all SO2 in the raw gas was oxidised to SO3. Br enhances the volatilisation of metals like K, Zn, Cd, Sn, Sb, and Pb out of the fuel bed principally in the same way as Cl. The tests gave strong indication that the promoting influence of the halogens on metal volatilisation is more pronounced than that of the fuel bed temperature. The volatilised metals are condensated on the fly ashes and are discharged along with the filter ashes.
As long as a surplus of SO2 is present in the raw gas no Br2 is formed. Although the halogen induced transfer out of the fuel bed causes high concentrations of volatile metals in the filter ashes, a recovery is not economically feasible for the time being. The volatilisation gives no rise to metal emission problems as long as efficient dedusting is achieved.
If there is a risk of Br2 formation, in wet scrubbing a reducing agent has to be added to the neutral scrubber for efficient abatement. Filter ashes should be disposed of in a way that enables access for recovery in the future. The exact volatilisation characteristics of the various metals have to be studied in future using specifically tailored experiments.
目的、目标、范围、背景：卤素溴的含量远低于氯，但在阻燃塑料等特殊材料中能以高浓度存在。溴在垃圾焚烧中的归宿和影响尚未得到充分了解。它对重金属挥发和低挥发性有机化合物形成的影响可能与氯类似。由于其较低的氧化电位，在废气中存在形成单质溴的风险。
在用于垃圾焚烧的TAMARA中试装置中，对不同类型含溴塑料废料（含量高达22%）与城市固体废弃物进行共燃烧试验，以研究溴的分配以及溴对金属挥发的影响。
将燃料混合物中的溴含量提高到约1 wt-%。对炉膛的所有输入和输出质量流进行了采样，并基于封闭质量平衡计算了氯、溴、硫以及多种重金属的分配情况。
有机结合的溴通常有超过90%释放到原气体中。在高溴含量时检测到了单质溴。当原气体中的所有二氧化硫都被氧化为三氧化硫时，总会对其存在情况进行分析。溴主要以与氯相同的方式增强钾、锌、镉、锡、锑和铅等金属从燃料床中的挥发。试验有力地表明，卤素对金属挥发的促进作用比燃料床温度的影响更为显著。挥发的金属凝结在飞灰上，并与过滤灰一起排出。
只要原气体中存在过量的二氧化硫，就不会形成溴。尽管卤素诱导的从燃料床中的转移导致过滤灰中挥发性金属浓度较高，但目前回收在经济上不可行。只要实现高效除尘，挥发就不会引发金属排放问题。
如果存在形成溴的风险，在湿式洗涤中必须向中性洗涤器中添加还原剂以实现有效减排。过滤灰的处置方式应便于未来进行回收利用。未来必须通过专门设计的实验研究各种金属的确切挥发特性。
