Abstract:

Experiments were carried out to examine the ash depositon characteristics in a bench-scale circulating fluidized bed (CFB). The influence of ash particle sizes, flue gas temperatures and heat exchange tube surfaces temperature (500℃, 550℃, 600℃ and 650℃) on ash deposit formation rate was investigated. The results indicated that with the increase of particle size, the content of CaO and SO₃ in the loose-like fouling ash gradually decreased, while the content of SiO₂ and Al₂O₃ increased gradually. The contents of the alkali metals Na and K and the halogen Cl were the highest in the ash with a smaller particle size. The ash deposition is mainly rich in elements such as Ca, S, Si and Al. The content of CaO and SO₃ in the ash is higher than that in the fouling ash, while the content of Al₂O₃ and SiO₂ is lower. The deposition mass increases as the temperature of the flue gas increases, and decrease as the particle size range of the fly ash increases. The effect of particle size on ash deposition is significant. Large-size ash particles are difficult to deposit while small-size ash particles are easy to deposit. The deposition mass achieve a minimum at the probe surface temperature of 600℃. The content of CaO and SO₃ decreases as the probe surface increases, while the content of refractory Al₂O₃ and SiO₂ increases as the wall temperature increases.

Key words: fluidized-bed, waste treatment, deposition, convection heating surfaces, alkali metals

摘要：

在自行搭建的小型流化床积灰试验台上选用流化床垃圾焚烧炉对流管束浮灰，模拟焚烧炉烟气环境下开展飞灰沉积实验。首先分析浮灰理化特性，结果表明：随着粒径增大，浮灰中CaO和SO₃含量逐渐降低，而SiO₂和Al₂O₃的含量逐渐增加；碱金属Na和K以及卤素Cl的含量在粒径较小的浮灰中含量最高。其次重点研究了浮灰粒径、烟气温度和换热管表面温度对飞灰沉积特性的影响规律，结果表明：积灰中主要富含Ca、S、Si和Al等元素，积灰中CaO和SO₃含量比浮灰高，而Al₂O₃和SiO₂含量比浮灰低；积灰量随着烟气温度升高而增加；粒径对灰沉积影响作用显著，大粒径灰颗粒难沉积而小粒径灰粒易沉积；管壁温度在600℃时，积灰量最小。积灰中CaO和SO₃的含量随着管壁温度升高而减少，而难熔Al₂O₃和SiO₂的含量随着管壁温度升高而增加。

关键词: 流化床, 废物处理, 沉积物, 对流受热面, 碱金属