糠醛渣流化床燃烧过程中碱金属析出迁移特性

THE EMISSION AND TRANSFORMATION OF ALKALI METALS DURING FLUIDIZED BED COMBUSTION OF FURFURAL RESIDUE

为研究床温对糠醛渣流化床燃烧中碱金属析出迁移特性的影响，在小型鼓泡流化床试验台上以糠醛渣为原料进行不同温度（750、800、850、900℃）下的燃烧试验，试验后采用ICP-OES测定各工况下的床料和飞灰中碱金属K的份额，并结合糠醛渣原料中的K的份额，计算气相中K的份额。结果表明：在所研究的床温范围内，K主要存在于气相中。随床温的升高，气相和床料中K的份额均升高，并且在750～800℃之间气相有较大幅度的升高，而在飞灰中的份额会降低。通过对试验后糠醛渣灰的x射线衍射（XRD）分析表明，不同床温下K在床料、飞灰和气相中的份额不同的根本原因在于，灰中钾盐存在的形式不同，750℃为KCl，800℃为KCl和K2SO4的混合物，800℃以L则为含碱金属K的复杂硅酸盐。

In order to study the impact of bed temperature on mechanism of emission and transformation of alkali metal during fluidized bed combustion of furfural residue, normal operations at 750, 800, 850 and 900℃ were tested on a bench-scale bubbling fluidized bed. The alkali metal potassium content in bed material and flyash under different bed temperatures after combustion was determined by Inductive Coupled Plasma Spectrometer （ICP-OES）, basing on which as well as total potassium in furfural residue the alkali metal potassium content in gas phase is calculated. The results indicated that the potassium mainly exists in gas phase after combustion in the experiment temperature. It was found that the alkali metal potassium content in gas phase and bed material increase with the increasing bed temperature, and there was a rapid release in gas phase between 750-800℃, while the alkali metal potassium content in flyash decreases with the increasing of bed temperature. XRD analysis on furfural residue after combustion suggested that the different compositions of alkali metal potassium salt in ash at different bed temperatures is the main reason that causes the alkali metal potassium content having different proportion in bed material flyash and gas phase. The main composition of alkali metal potassium salt is KCl at 750 ℃, mixture of KCI and K2SO4 at 800 ℃, complex silicate compounds with potassium above 800℃.