MOE Key Laboratory of Thermo-Fluid Science and Engineering, Xi'an Jiaotong University, Xi'an, China.
MOE Key Laboratory of Thermo-Fluid Science and Engineering, Xi'an Jiaotong University, Xi'an, China.
J Environ Manage. 2020 Sep 1;269:110799. doi: 10.1016/j.jenvman.2020.110799. Epub 2020 May 26.
The high content of sodium in coal ash can induce severe ash deposit problems on heated surface. Vermiculite has been investigated to solve this problem in drop-tube furnace recently. In this work, the effects of vermiculite and perlite on appearances, inorganic mineral transformation, elemental composition change and Na capture efficiency of ash deposit were investigated. The results show that the molten deposit obtained by drop-tube furnace at 1373 K was transformed into weakly-condensed deposit and strongly-sticky deposit respectively when vermiculite and perlite were added separately. Vermiculite has a better effect on improving the ash deposition than perlite. The mechanism of alleviating the ash deposition by vermiculite and perlite is proposed as follows: (1) The interaction between ash particles is inhibited due to the combination reactions of thermal expansion additive particles with coal ash particles. (2) The coal ash particles attach to the surface and the gap of thermal expansion additive particles, forming a porous structure. (3) With vermiculite added, MgSiO (forsterite) increases the fusion point of ash deposit. NaCaMgAl(SiAl)O(OH) (pargasite) and MgFeSiO (forsterite ferroan) result in the weak viscosity of ash deposit. (4) With perlite added, silicate and sodium aluminosilicate in perlite react with coal ash to produce a large amount of amorphous substance, which can flow downwards to make the bottom deposit molten and lead to the strong viscosity of total deposit. (5) Vermiculite has a strong capacity for Na capture at 1023 K, and perlite has a strong capacity for Na capture at 1373 K.
煤灰中高含量的钠会导致受热面严重积灰。最近，在滴管炉中研究了蛭石来解决这个问题。在这项工作中，研究了蛭石和珍珠岩对灰沉积外观、无机矿物转化、元素组成变化和 Na 捕获效率的影响。结果表明，在 1373 K 下通过滴管炉获得的熔融沉积物在分别添加蛭石和珍珠岩时分别转化为弱凝结沉积物和强粘性沉积物。蛭石对改善积灰的效果优于珍珠岩。提出了蛭石和珍珠岩缓解积灰的机理如下：（1）由于热膨胀添加剂颗粒与煤灰颗粒的结合反应，抑制了灰颗粒之间的相互作用。（2）煤灰颗粒附着在热膨胀添加剂颗粒的表面和间隙上，形成多孔结构。（3）添加蛭石后，MgSiO（镁橄榄石）增加了灰沉积的熔点。NaCaMgAl(SiAl)O(OH)（钠钙镁铝硅羟化物）和 MgFeSiO（镁铁橄榄石）导致灰沉积的弱粘性。（4）添加珍珠岩后，珍珠岩中的硅酸盐和硅酸钠与煤灰反应生成大量无定形物质，可向下流动使底部沉积物熔融，导致总沉积物的强粘性。（5）蛭石在 1023 K 时具有很强的 Na 捕获能力，而珍珠岩在 1373 K 时具有很强的 Na 捕获能力。
