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首页> 外文期刊>Journal of Environmental Management >Release dynamic process identification for a cement based material in various leaching conditions. Part II. Modelling the release dynamics for different leaching conditions
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Release dynamic process identification for a cement based material in various leaching conditions. Part II. Modelling the release dynamics for different leaching conditions

机译：在各种浸出条件下发布基于水泥的材料的动态过程识别。第二部分模拟不同浸出条件下的释放动力学

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This paper deals with process identification and model development for the case of a porous reference material leaching under certain hydrodynamic conditions. Four different dynamic leaching tests have been applied in order to take into account different types of solid/liquid contact conditions corresponding to various real leaching scenarios: monolithic and granular material with sequential eluate renewal, and granular material and continuously renewed eluate with different hydrodynamic conditions (dispersion, residence time). A coupled chemical-mass transfer model has been developed to describe the leaching behaviour under all experimental conditions. Diffusion has been considered as the mass transport mechanism inside the saturated porous material and dispersive convection as that in the leachate. Two specific phenomena have been identified and considered in the model: (i) the early surface dissolution of the material which results in high Ca concentration and (ii) the late weak dissolution of Na and K giving rise to a long-term residual release. The intrinsic material parameters such as the initial concentrations in the pore water and solid phases were determined by applying equilibrium leaching tests and geochemical modelling. Diffusion coefficients for different elements and the late solubility of alkalines have been found to reach the same values in the four tests. The estimated values of the surface dissolution kinetic constant have shown a dependence on leachate hydrodynamics when the thickness of the degraded layer is nearly the same in the four tests (intrinsic parameter of the material). The competition between the four main dynamic processes, i.e. diffusion, convection, late dissolution, and surface dissolution, has been emphasized and compared in the four leaching tests: the hydrodynamic dispersion and the residence time had no effect on the leaching behaviour of alkalines, which is controlled by diffusion, whereas the behaviour of calcium (a major element of the material) was strongly influenced. This has significant effects on eluate pH values and on the concentration of Pb (the monitored pollutant). The model was then applied to simulate a landfill scenario in the case of a stabilized/solidified incinerator residue containing heavy metals and chloride. A high rain infiltration level and the use of small blocs are favourable conditions for enhanced pollutant release.
机译：本文针对在某些流体动力学条件下浸出多孔参考材料的情况进行过程识别和模型开发。为了考虑到与各种实际浸出场景相对应的不同类型的固/液接触条件，已经应用了四种不同的动态浸出测试：具有顺序洗脱液更新的整体和颗粒物料，以及具有不同流体动力学条件的颗粒物料和连续更新的洗脱液（分散，停留时间）。已经开发了一种耦合的化学-质量转移模型来描述在所有实验条件下的浸出行为。扩散已被认为是饱和多孔材料内部的传质机理，而扩散对流被认为是渗滤液中的质量对流。在模型中已经确定并考虑了两种特定的现象：（i）材料的早期表面溶解会导致高的Ca浓度；（ii）Na和K的较弱的溶解会导致长期的残留释放。固有的材料参数，例如孔隙水和固相中的初始浓度，是通过应用平衡浸出试验和地球化学模型确定的。在这四个测试中，发现不同元素的扩散系数和碱的后期溶解度达到相同的值。当在四个测试中降解层的厚度几乎相同时（材料的固有参数），表面溶解动力学常数的估计值显示出对渗滤液流体动力学的依赖性。在四个浸出试验中已强调并比较了四个主要动态过程（即扩散，对流，后期溶解和表面溶解）之间的竞争：流体动力分散和停留时间对碱金属的浸出行为没有影响。钙是通过扩散控制的，而钙（材料的主要元素）的行为受到了很大的影响。这对洗脱液的pH值和Pb（受监测的污染物）的浓度有重大影响。然后，在稳定/固化的焚烧炉残留物中含有重金属和氯化物的情况下，将该模型应用于模拟垃圾填埋场。较高的雨水渗透水平和使用小型集团是增加污染物释放的有利条件。

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