添加剂对秸秆燃烧过程中碱金属行为的影响

Effect of additives on behavior of alkali metals during straw combustion

在小型燃烧装置上对秸秆及秸秆与添加剂混合物进行了燃烧试验,并对燃烧过程中凝结在金属管道表面的沉积物和分离器灰进行了分析.添加剂包括:高岭土(AI2Si2O5(OH)4)、燃煤飞灰、硅藻土(SiO2)、氢氧化铝(Al(OH)3)和碳酸钙(CaCO3).试验结果表明,高岭土、燃煤飞灰和硅藻土,可以减少沉积物中水溶性钾和氯的质量分数.对纯秸秆和以高岭土为添加剂的沉积物和灰进行了SEM-EDX分析,SEM图片显示沉积物中主要是由被黏接物黏在一起的圆形球状颗粒组成.EDX测试结果表明,燃烧纯秸秆的球形颗粒主要由钾、硅和钙组成,而以高岭土为添加剂的秸秆燃烧沉积物中的球形颗粒主要由钾、硅和铝组成,两个样品中的黏接物主要是由氯化钾(KCI)组成,由此证明了合适的添加剂可以和气态的KCI反应并减少其在沉积物中的质量分数,进而减轻了秸秆燃烧过程中由碱金属引起的沉积所造成的腐蚀.

Experiment on combustion of pure pulverized straw and experiments on pulverized straw with additives were carried out in a pilot plant, where the deposits and ashes from the experiments were analysed. The additives included kaolin, fly ash from coal combustion, celite（porous SiO2 ）, aluminium hydroxide and calcium carbonate. The results showed that adding of kaolin, fly ash, celite and quartz reduces the amounts of water soluble potassium and chlorine in the deposits. SEM-EDX measurements were performed on deposits and ashes from experiments with combustion of pure straw and with adding of kaolin. The SEM pictures showed that deposits consisting of spherical particles are connected by a coherent material. EDX-measurements revealed that the spherical particles from the experiment with combustion of pure straw consist mainly of potassium, silicium and calcium. The spherical particles from the experiment with kaolin addition consist mainly of potassium, silicium and aluminium. The coherent material turned out to be potassium chloride in both samples. This shows that volatilised KCl can react with additives and reduce the content of chlorine in deposit, and therefore corrosion can be reduced by applying a suitable additive.