Study on Characteristics of Change of Urea and Biuret Content by Temperature Variation in Urea Solution

요소수(Urea solution)의 온도변화에 따른 요소 및 뷰렛함량 변화 특성 연구

Abstract

As interests in the air pollution increases, many kinds of researches are underway on the reduction of air pollutants. The removal of nitrogen oxides from the emission gas of diesel vehicles using urea solution has shown a great effect. The quality of urea solution is strictly defined by domestic law, but the increase of impurities in urea solution reduces the effect of reducing nitrogen oxides. Therefore, in this study, the change of physical properties of urea solution was analyzed after heating the urea solution for a certain temperature and time. Also, the changes of physical properties of urea solution were analyzed according to kinds of storage container and temperature for storing the urea solution. After heating the urea solution for a certain period of time, the biuret content in urea solution increased and the content of urea decreased. As the urea content decreased, both density and refractive index decreased. In the storage stability test carried out at a constant temperature with iron and PET containers, no change in physical properties was observed.

대기오염에 대한 관심이 증대하면서 대기오염물질의 저감에 관한 많은 연구가 진행되고 있다. 차량용 요소수(Urea solution)를 이용한 디젤 차량의 질소산화물(NOx) 제거는 큰 효과를 나타내고 있다. 요소수의 품질은 국내법으로 엄격히 규정하고 있으나 요소수 내 불순물의 증대는 질소산화물 저감 효과를 감소시키게 된다. 따라서 본 연구에서는 일정 온도와 시간동안 요소수를 가열한 후 요소수의 물성변화를 분석하였다. 또한, 요소수를 보관하는 저장용기와 저장온도의 변화에 따른 요소수 물성변화도 함께 분석하였다. 요소수를 일정시간 가열한 후 요소수 내 뷰렛함량은 증가하고 요소함량은 감소하였으며, 요소함량감소에 따라 밀도와 굴절률도 함께 감소하였다. 철제 및 PET 용기와 일정온도($30^{\circ}C$, $50^{\circ}C$)에서 실시한 저장안정성 시험에서는 물성변화가 나타나지 않았다.

Fig. 1. Procedure of the urea solution analysis by heating process.

Fig. 2. Procedure of the urea solution analysis by storage experiment.

Fig. 1. Results of refractive index and density analysis according to heating time.

Fig. 2. Results of biuret analysis according to heating time

Fig. 3. Samples after biuret analysis according to heating time

Fig. 4. Results of urea content analysis according to heating time.

Fig. 5. Comparison of urea and biuret contents according to heating time.

Fig. 6. Comparison of urea content and refractive index according to heating time.

Fig. 7. Results of refractive index analysis according to product container and temperature variation.

Fig. 8. Results of density analysis according to product container and temperature variation.

Fig. 9. Results of density analysis according to product container and temperature variation.

Fig. 10. Results of urea content analysis according to product container and temperature variation.

Table 1. Criteria of aqueous urea solution at Clean Air Conservation Act in Korea

Table 2. Test methods and equipment criteria for analyzing the urea solution

Table 3. Results of the urea solution analysis for using the automotive diesel vehicle

Table 4. Results of refractive index and density analysis according to heating time

Table 5. Results of biuret and urea contents analysis according to heating time

Table 6. Physical/chemical properties of urea and biuret

Table 7. Results of refractive index analysis according to product container and temperature variation

Table 8. Results of density analysis according to product container and temperature variation

Table 9. Results of biuret analysis according to product container and temperature variation

Table 10. Results of urea contents according to product container and temperature variation