Mathematical Modeling Of Reverse Osmosis Treatment Of Low And Intermediate Level Radioactive Waste And Its Verification

In recent years, there is a great concern over the membrane technologytreatment the nuclear radioactive liquid waste. Research work is usuallyrestricted by safety and cost, and using cold experiment instead of heatexperiment. The currently used radioactive wastewater discharge standards(coastal is3700Bq/L, inland is37Bq/L), the concentration of treatmentradioactive waste is very low, which is difficult to detect. In order to facilitatetesting, research usually used high concentrations, but this method isunrepresentative and the value is not high. Therefore, studying the membranemass transfer model of ultra-low concentrations has a crucial significance for theapplication of membrane technology treatment radioactive wastewater.In this thesis, we use reverse osmosis technology to treat low-medium levelradioactive waste (choose radioactive nuclide cobalt as research object), systemmass balances and solution-diffusion model have been used to simulate theseparation process of low concentrations of cobalt. The effect of systemvariables on the retention efficiency of non-active nuclides cobalt ions andmembrane permeation flux were explored under different concentrations andoperating pressures. The effects of treatment capacity on the reverse osmosisperformance were explored under continuous operating conditions. The use ofsolution-diffusion model and the material balance to simulation the behavior of the reverse osmosis removal cobalt ions.The results showed that:(1) the experimental investigated the effect ofoperating pressure, feed concentration and processing capacity on the membraneflux and rejection. When the feed concentration was low, the flux mainlyaffected by the operating pressure, and the relation between pressure and themembrane flux is linear. With the operating pressure increasing, the membraneflux almost linearly increase and the retention also increased slightly. The effectof concentration on the membrane flux and rejection rate is very small, with theconcentration increasing, membrane flux and rejection decreased. With theprocessing capacity increasing, and membrane flux almost constant, osmoticconcentration and the average concentration of permeated liquid graduallyincreased, osmotic concentration permeate increased faster than the averageconcentration of permeated liquid.(2) The solution-diffusion model was used topredict the behavior of reverse osmosis membrane, when used for the removalof cobalt from low and medium level radioactive wastewater. Thesolution-diffusion model has been used to simulate the separation process of lowconcentrations of cobalt. Model equation constants were obtained when thecobalt concentration was high, and then compared the experimental data withsimulated data when the cobalt concentration was low. The results showed thatthe osmolality simulation and experimental values relative error does not exceed14%, the permeate flux simulation and experimental values relative error doesnot exceed15%, the retention simulated and experimental values relative errordoes not exceed0.5%, the experimental data and simulation relative data errordoes not exceed15%.Good agreement between the experimental and thepredicted suggests that the solution-diffusion model can be used to well predictosmotic concentration even when the concentration of cobalt is low.(3) Theproposed model combines material balances on the feed tank, membrane moduleand product tank with membrane mass transfer models. Simulation thesecondary treating process, and compared the experimental data with simulateddata. The results showed that the osmolality simulation and experimental values relative error does not exceed5%, and the flux simulation and experimentalvalues relative error does not exceed8%. The permeated osmotic concentrationand average concentration simulation and experimental values relative errordoes not exceed10%. Secondary fluid simulation, the feed concentrationsimulation and experimental value relative error does not exceed10%, the fluxsimulation and experimental value relative error does not exceed3%. Themathematical model can be used in simulation the process of membranetechnology treatment cobalt ion, and can be used to predict the effect of reverseosmosis performance when the concentration of cobalt is low.