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

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。

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

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.