摘要
为给熔盐氧化法处理废树脂的工程化应用提供理论指导,本文采用处理能力为1.25 kg/批次的实验室规模处理装置对与核电厂使用的同类型废混合离子交换树脂进行处理。结果表明,该方法处理废树脂的优越性主要体现在对酸性尾气的吸收作用(将N、S元素以硝酸盐和硫酸盐的形式截留)和对废树脂体积的高效减容。针对核电厂常用的混合离子交换树脂(由强碱性阴离子交换树脂和强酸性阳离子交换树脂组成),熔盐氧化装置处理结果表明,酸性气体产物(NO、NO_(2)、SO_(2)、H_(2)S)在反应开始0.5 h后即能降低至10 mg/m^(3),0.5 h后气体产物主要为CO_(2)。SEM图像表明,树脂结构在熔盐氧化后由完整的球状变为破碎的颗粒,氧化后废盐中仍剩余62.1%的碳酸盐,树脂中的S、N元素在废盐中的截留率分别为22.77%和59.6%。XRD结果表明,碳酸熔盐能吸收SO_(2)并将其转化为硫酸盐。对Li_(2)CO_(3)、Na_(2)CO_(3)、K_(2)CO_(3)在不同温度下与SO_(2)生成硫酸盐的反应吉布斯自由能(ΔG)进行了热力学计算,结果表明在200~800℃范围内3种碳酸盐均能与SO_(2)自发反应,ΔG随着温度的升高而降低,800℃时Li_(2)CO_(3)、Na_(2)CO_(3)、K_(2)CO_(3)的ΔG分别为-2.800、-41.626、-69.590 KJ/mol,K_(2)CO_(3)是SO_(2)主要的吸收剂。经熔盐氧化后,树脂降解率达98.36%,减容比(氧化前树脂体积/氧化后废盐体积)达6.9。以上结果表明,熔盐氧化是一种理想的处理废混合离子交换树脂方法,有较大的工程应用潜力。
In order to provide theoretical guidance for the engineering application of molten salt oxidation(MSO)for spent mixed ion exchange resins(MRs)treatment,a bench-scale MSO plant with a treatment capacity of 1.25 kg/batch was used to treat the same type of spent MRs used in nuclear power plants(NPPs).The superiority of MSO in the treatment of spent resins was mainly reflected in the adsorption of acid tail gas(carbonate was consumed,N and S elements were trapped in the form of nitrate and sulfate)and the efficient volume reduction ratio of spent resins.The MRs commonly used in NPPs(consisting of strong basic anion exchange resin and strong acid cation exchange resin)were treated by bench-scale MSO plant.The results show that the acid gas(NO,NO_(2),SO_(2),H_(2)S)can decrease to 10 mg/m^(3)and the main gas product is CO_(2)after 0.5 h in the process of MSO.This means that the first 0.5 hours mainly involve the decomposition of functional groups,followed by the destruction of the resin skeleton.Scanning electron microscope(SEM)images show that the resin structure changes from spherical to broken particle after MSO.The content of carbonate in waste salt is 62.1%after MSO.Moreover,the retention rates of sulfur and nitrogen in resins in waste salt are_(2)2.77%and 59.6%,respectively.X-ray diffraction(XRD)results show that the molten carbonate salts could convert sulfur dioxide gas into sulfate in the waste salt.The Gibbs free energy(ΔG)of Li_(2)CO_(3),Na_(2)CO_(3)and K_(2)CO_(3)reacting with SO_(2)at different temperatures was calculated thermodynamically.The calculation results show that all the three carbonates could spontaneously react with SO_(2)in the temperature range of 200℃to 800℃,and theΔG decreases with the increase of temperature.At 800℃,theΔG of Li_(2)CO_(3),Na_(2)CO_(3)and K_(2)CO_(3)react with SO_(2)is-2.800,-41.626 and-69.590 KJ/mol,respectively.Moreover,theΔG of K_(2)CO_(3)is the lowest among the three carbonates,indicating that K_(2)CO_(3)is the main adsorbent of SO_(2).The results also provide a theoretical basis for the adsorption reaction process of SO_(2)by ternary carbonate system.After MSO,the degradation rate and the volume reduction ratio(resin volume ratio before and after MSO)of MRs are 98.36%and 6.9,respectively.The above results show that MSO is an ideal treatment method for spent MRs,which has great development potential for industrial scale application.
作者
王跃霖
薛云
郑仰海
马福秋
张密林
颜永得
WANG Yuelin;XUE Yun;ZHENG Yanghai;MA Fuqiu;ZHANG Milin;YAN Yongde(Harbin Engineering University,Harbin 150001,China;Yantai Research Institute,Harbin Engineering University,Yantai 264006,China)
出处
《原子能科学技术》
EI
CAS
CSCD
北大核心
2024年第2期320-327,共8页
Atomic Energy Science and Technology
基金
山东省重点研发计划“核动未来”科技示范工程项目(2022SFGC0501)
国家自然科学基金(22176045)。
关键词
熔盐氧化
混合树脂
放射性固体废物
molten salt oxidation
mixed resin
radioactive solid waste
