铁基载氧体与干化市政污泥二元混合物流化特性

Fluidization characteristics of binary mixtures of iron-based oxygen carrier and dried sewage sludge

化学链燃烧技术处置污泥可有效抑制有害气体排放,但干化污泥与铁基载氧体的物理性质相差较大,在流化床内会产生混合分离等问题。在内径(φ)为100 mm的有机玻璃冷态流化床装置上,进行了干化污泥与载氧体二元颗粒流化实验,讨论了颗粒粒径大小、干化污泥与载氧体质量比和操作风速对二元颗粒流化特性的影响。结果表明,污泥与平均粒径为0.66 mm的载氧体能实现混合流化,最小流化速度Umf和最小混合操作风速Um相等;污泥与平均粒径为1.46 mm的载氧体流化时,随操作风速增大,逐渐由分离流化状态过渡到混合流化状态,Um>Umf;污泥与平均粒径为2.43 mm的载氧体流化时,始终保持分离流化状态。基于提出的表征混合/分离流化状态的无量纲数Gd,当0<Gd<0.8时处于混合流化,Gd>0.8时处于分离流化。

Chemical looping combustion technology can effectively decrease the pollutant emissions from the dried sewage sludge incineration. The mixing and separation of binary mixtures of dried sludge and iron-based oxygen carrier are involved in the fluidized bed due to their big difference in physical properties. The fluidization experiments of binary mixtures of dried sewage sludge and ironbased oxygen carrier were carried out in a plexiglass cold fluidized bed with 100 mminner diameter in this study. The effects of particle size, mass ratio of dried sewage sludge and oxygen carrier and operating velocity on the fluidization characteristics were investigated. The results showed that the sludge can be mixed well with the oxygen carrier with mean particle size of 0.66 mm, and the minimum fluidization velocity(Umf) was equal to the minimum mixing operation velocity(Um). When the mean particle size of oxygen carrier was 1.46 mm, it gradually transited from the separated fluidization state to the mixed fluidization state as the operating velocity increased, and the Um was greater than U?mf in this condition. When the mean particle size of oxygen carrier was 2.43 mm, the separated fluidization state was always maintained. Based on a proposed dimensionless number Gd for judging the mixed/separated fluidization state of binary mixtures of dried sewage sludge and iron-based oxygen carrier, the binary mixtures were in a mixed fluidization state while 0<Gd<0.8, and the binary mixtures were in a separated fluidization state while Gd>0.8.