TRPO污溶剂净化树脂吸附床穿透时间确定新方法研究

Method Study for Determination of Penetration Time of Resin-fixed Beds Utilized in TRPO Solvent Purification

  • 摘要: 三烷基氧膦(TRPO)污溶剂净化工艺是我国自主开发的高放废液处理流程,为大幅降低成本和放射性废物量,生成的大量污溶剂需要净化后进行复用。树脂固定床吸附净化技术是TRPO污溶剂有效净化的途径之一,其设计需要基于准确的、不同操作条件下的穿透时间才能进行。但在放射性限制下,获取大量辐射降解污溶剂存在困难,无法通过大量试验确定系列条件下的穿透时间。为解决该难题,本文采用微分床技术,利用少量辐射降解污溶剂,通过少量试验确定树脂净化吸附热力学和动力学关键参数—树脂吸附平衡曲线和树脂吸附传质系数,并据此建立固定床吸附传质模型,获得系列穿透曲线。结果表明,TRPO污溶剂净化树脂吸附床操作穿透时间(tp)和树脂饱和吸附时间(ts)之间存在线性关系(tp=3.94ts−9.64×103),其中树脂吸附饱和时间可根据操作条件简单计算得到。本文提出的方法为避免放射性限制,快速确定TRPO污溶剂净化树脂吸附床的穿透时间提供了一条可行途径。

     

    Abstract: The TRPO process is a treatment methodology for high-level waste liquid that has been independently developed in China. This process uses TRPO as an extractant to remove long-lived isotopes such as transuranic elements and highly toxic isotopes such as strontium and cesium from high-level waste liquid. However, TRPO undergoes a series of physical and chemical changes after irradiation, resulting in a decrease in quality and affecting extraction performance. Nevertheless traditional alkali washing and water washing methods are ineffective in removing the strong complex products generated by irradiation in TRPO. Consequently, the issue of retention of heavy metal nuclides, such as plutonium, resulting from these strong complex products cannot be adequately addressed through alkali and water washing alone. To significantly reduce both the costs and the volume of radioactive waste, it is essential to purify the dirty TRPO solvent generated during this process for potential reuse. The resin-fixed bed is emerged as an effective approach for purifying the dirty TRPO solvent. When designing a resin-fixed bed, it is necessary to accurately determine the penetration time under varying operational conditions. However, the high-level radioactivity poses a challenge in acquiring a sufficient quantity of radiation-degraded dirty solvents, making it difficult to ascertain penetration times through extensive testing. To address this challenge, a differential bed technique was employed utilizing a minimal amount of radiation-degraded dirty solvent. Through limited experimental trials, key thermodynamic and kinetic parameters for resin purification adsorption were determined, specifically the resin adsorption equilibrium curve and the mass transfer coefficient of the adsorption process. Based on these parameters, a mass transfer model for resin-fixed beds adsorption was established, through which a series of pentration curves were obtained. Furthermore, a mass transfer model available for resin-fixed beds was established, which facilitates the generation of penetration curves. The effects of resin-fixed bed length, feed rate, and feed concentration on the dynamic evolution of resin-fixed bed adsorption and penetration time were systematically examined through a total of 120 simulations in this study. A linear relationship between penetration time (tp) and resin saturation adsorption time (ts) was determined which is tp=3.94ts−9.64×103. The resin adsorption saturation time can be calculated based on operational conditions. In addition, the adsorption equilibrium curve and the liquid-solid mass transfer coefficient can be expressed as q=8.017×10−4+0.1804co−7.390×10−3c_\mathrmo^2 +1.177×10−4c_\mathrmo^3 and εKLa=−0.021+1.32U−5.56U2, respectively. The novel method proposed in this research offers a solution to circumvent radioactive limitations and rapidly determine penetration time of resin-fixed bed during the dirtty TRPO solvent purification.

     

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