Study On Nuclear Industry Wastewater Treatment With Low-temperature Evaporation

Nuclear industry wastewater is a kind of untreatable wastewater that contains not only a great deal of dissolved salt but also some quantity of radioactive substance. Nowdays, it is still a difficult problem in wastewater treatment field to treat effectively the nuclear industry wastewater. The radioactive wastewater from the North Nuclear Fuel Component Limited Company is mostly refining uranium wastewater from this company's nuclear fuel component preparation process that contains uranium and ammonium nitrate. This wastewater still contains small quantity of radioactive substance and a great deal of dissolved salt after treated with silica gel adsorption.To resolve the difficult problem of treating the radioactive wastewater from the North Nuclear Fuel Component Limited Company, this paper put forward treating nuclear industry wastewater with low-temperature evaporation refer to the features of this wastewater. The pollution of the nuclear industry wasteater to environment will be eliminated entirely if the wastewater is evaporated at low temperature, the condensate is collected and utilized and the residual wastewater crystal is cement solidificated in turn. Furthmore, a process for treating nuclear industry wastewater with low-temperatrue evaporation has been developed refer to the wastewater's discharge, which supplys referrence for resolving the difficult problem of treating the radioactive wastewater of the North Nuclear Fuel Component Limited Company.The low-temperatrue evaporation was studied to treat the nuclear industry wastewater. The process parameters of low-temperatrue evaporation were optimized with orthogonal experiment. In terms of various factors, higher vacuum degree avails decreasing operating temperature,reducing consumption of energy and heightening processing capacity but also augments the condensate's chemical oxygen demand(COD);lower pH value can reduce the ammonia nitrogen concentration of the condensate but augments its chemical oxygen demand;lower ratio of wastewater feeded is helpful for improving condensate's quailty but decreases handling wastewater capacity. The major substances contaminating the condensate are evaporable organics and free ammonia as well as steam entrainment in the tempestuous ebullition. As a result, the water quality of condensate from initial and later evaportion stage is bad while the water quality of condensate from middle evaportion stage is good. Thus, it is feasible to separate collect and utilize the condensate from different evaporation stage. Under the opotimal operating parameters, namely, regulating nuclear industry wastewater's pH value to be 3.0, adjusting working vacuum degree to be 0.060MPa, taking continuously feeding wastewater as feeding mode, the wastewater was evaporated to the volume of the residue went down to one-fifth of raw wastewater's, the residue can crystalize entirely after cooled and the crystal is suitable to be cement solidificated.The condensate does not contain any radioactive substance, and the TDS, COD, chromaticity and turbidity of the condensate are respectively 130.56mg/L, 55.36mg/L, 0 times and under 3 NTU, so it is suitable for reusing as water for planting in the within site.Finally, a process design and equipment selection of the low-temperature evaporation process for treating wastewater from North Nuclear Fuel Component Limited Company has been finished based on the experimental results, which lays the foundation for the industrial application of this technology.