生物质灰烧结熔融规律实验研究

Experiment Study of Biomass Ash Sintering and Melting

根据稻秆、玉米芯、棕榈壳、麦秆酶解残渣灰样烧结熔融实验,分析了生物质烧结熔融温度的变化规律。结果表明：灰分在受热烧结熔融过程中发生元素迁移和化学反应,KCl在800℃以上明显挥发,部分K、Na元素与灰中的SiO_2、Al_2O_3反应形成不易挥发的长石系化合物;灰分中某种元素对烧结温度影响取决于其氧化物熔点、相关化学反应和共熔体的性质,其中Al、Ca、K、Na、S元素使烧结温度降低,Mg、Fe、P元素使烧结温度升高;Si元素含量变化对灰渣烧结熔融温度影响较小。对于以SiO_2为主要成分的生物质灰,可以按照烧结温度约等于0.9倍软化温度估算。拟合得到由灰样中主要组分估算烧结温度的公式,适用烧结温度范围为950~1 200℃,R2为0.967,偏差为25.6℃。

Release and reactions of elements in biomass ash of rice straw,corn cob,palm kernel shell and wheat straw enzymatic hydrolysis residue were investigated by experiments of biomass ash sintering and melting. The ash was considered to be sintering as the Mohs＇ scale of hardness was up to 3,which would block the burner or gasifier. The ash in this paper was prepared at 600℃,and put into the tubular furnace of 700 ~ 1 200℃ in order to evaluate the temperature of sintering and melting. The ash was put into the tubular furnace at the sintering temperature for 5 ~ 30 min,which showed the process of sintering. According to the analysis of ash by XRF and XRD,volatilization of KCl became obvious after800℃. Parts of K and Na stayed in the ash,forming alkali feldspars in the reactions with SiO_2 and Al_2O_3. Volatilization of alkali metals would cause an increase of melting temperature in TG-DSC and fusion test,which is different from the character of coal ash. The method of evaluating the coal ash sintering temperature is unreliable for the ash of biomass. Different elements in the ash have different characteristics of melting and reactions, which decides the sintering temperature. The sintering temperature decreases with more Al,Ca,K,Na,S or less Mg,Fe,P,while the influence of Si is weak.As the main composition of biomass ash is SiO_2,the sintering temperature can be estimated to be 0. 9times of sintering temperature. Using the data of four kinds of biomass ash in the experiment,the linear regression fits for the sintering temperature against the mass percentage of ash components was obtained with R2 of 0. 967 and error of 25. 6℃ for the sintering temperature range of 950 ~ 1 200℃.