蔗糖脱硝对模拟动力堆高放废液煅烧产物性能及结构的影响

Effect of Denitration with Sucrose on Property and Structure of Calcinate of Simulated PWR High-level Liquid Waste

高放废液玻璃固化前需进行脱硝处理,常用的脱硝剂有甲酸、甲醛、蔗糖等。本文针对蔗糖的脱硝作用开展了模拟高放废液回转煅烧脱硝实验,研究了温度、糖硝比对煅烧产物性能及结构的影响。煅烧产物的X射线荧光光谱分析表明,温度和糖硝比对脱硝效果有明显影响,当温度≥500℃、糖硝比≥1∶8时,N含量低于仪器检测下限,C含量(质量分数)<1.42%;扫描电子显微图像表明,蔗糖能使煅烧产物形成疏松的泡沫形态,在高温和物理作用下形成致密颗粒团聚物;X射线衍射谱表明,温度≥500℃、糖硝比≥1∶8能提高产物结晶程度,并形成锆镧氧化物、钡锶钼氧化物和钇铈氧化物;热重、微分热重曲线表明,煅烧过程分为以下3个阶段:游离水和结合水蒸发析出阶段、硝酸盐和蔗糖分解阶段、无机盐煅烧阶段;红外光谱和X射线光电子能谱分析结果表明:蔗糖特征官能团C—O—C、C—C、C—OH与NO_(3)在高温下逐渐消失,并可能生成中间产物金属氢氧化物和碳酸盐,进一步分解为金属氧化物。

Denitration treatment is required before the high-level liquid waste vitrification,conventional denitration agents are formic acid,formaldehyde,sucrose,etc.According to the denitration effect of sucrose,a simulated PWR high-level liquid waste rotary calcination experiments were conducted to investigate the effects of temperature and ratio of sugar to nitrate on the properties and structure of the calcinate.X-ray fluorescence spectrometer(XRF)analysis indicates that temperature and ratio of sugar to nitrate has significant effects on denitration,when temperature≥500℃and ratio of sugar to nitrate≥1∶8,N content(mass fraction)is lower than the detection limit,C content is<1.42%.Scanning electron microscope(SEM)images show that sucrose can make the calcinate form a loose foam shape,and then form dense particle agglomerates under high temperature and rotation.X-ray diffractometer(XRD)spectrum reveals that when the temperature≥500℃and ratio of sugar to nitrate≥1∶8,the degree of crystallization of the calcinate significant increases,and zirconium lanthanum oxide,barium strontium molybdenum oxide and yttrium cerium oxide are formed.Thermogravimetric/derivative thermogravimetric(TG/DTG)curves present that the calcination process is divided into the following three stages:the evaporation of free water and bound water,the decomposition of nitrate and sucrose,and the decomposition and calcination of inorganic salts.Fourier transform infrared spectrometer(FT-IR)and X-ray photoelectron spectroscopy(XPS)analysis results reveal that the characteristic functional groups of sucrose,such as C—O—C,C—C,C—OH,and NO_(3)gradually disappear at high temperature producing metal hydroxide,carbonates as an intermediate product further decomposes into metal oxides.The characteristic functional groups of C—O—C,C—C,C—OH and NO_(3)of sucrose gradually disappear at high temperature,and may generate metal hydroxides and carbonates as intermediate products,are further decomposed into metal oxides.