Abstract: Wastewater with high-concentration urea can be treated by freeze concentration effectively.The determination of freeze concentration limitation is necessary for forecasting and evaluating the efficiency and maximal water recovery rate of freeze concentration.The phase change of urea solution during the freezing process was analyzed with differential scanning calorimetry (DSC).The solution concentration at the eutectic point of urea was determined by freezing experiment.Urine was adopted as the sample to study the method for determining the freeze concentration limitation of wastewater containing high-concentration urea.It was found that when the urea concentration of wastewater was higher than 26.3%, urea would crystallize with ice before the freeze concentration limitation.The wastewater became glass state at the end point of freeze concentration.The maximal water recovery rate of the freeze concentrate technology and the glass transformation temperature of solution can be determined by DSC. DSC analysis showed that the glass transformation temperature of urine was -108.33℃,the corresponding solution concentration of maximal freeze concentration was 57.92%,and the maximal water recovery rate was 97.75%.

摘要： 冷冻浓缩技术是处理尿素厂废水和尿液等高浓度尿素废水的有效方法之一，浓缩极限的确定则是预测和评价该工艺最高水回收率和工作效率的必要条件.以尿素溶液为研究对象，采用差示扫描量热技术分析了溶液在冷冻过程中的相态变化规律，通过冷冻试验确定了溶液发生尿素共晶析出时的浓度;以尿液为对象，研究了确定高浓度尿素废水冷冻浓缩极限的方法.研究结果表明：尿素废水在达到浓缩极限之前，当尿素浓度高于26.3%时，继冰晶析出之后会共晶析出尿素;尿素废水在浓缩极限处呈玻璃态，由差示扫描量热分析可确定废水玻璃化转变温度、推算冷冻浓缩工艺最高水回收率;尿液的玻璃化转变温度为-108.33 ℃，相应的溶液浓度为57.92%，冷冻浓缩可达到的最高水回收率为97.75%.