Hydrolysis of Urea for Ammonia-Based Wet Flue Gas Desulfurization

Nowadays, the ammonia-based wet flue gas desulfurization is gaining more popularity. In this study, the ammoniabased wet flue gas desulfurization obtained ammonia resource from urea hydrolysis instead of anhydrous ammonia and aqueous ammonia, which was beneficial for the development of circular economy. An electric-heating reactor was employed as the hydrolysis reactor instead of traditional ones using hot air or water vapor as the heat carrier. The effects of temperature, pressure, urea solution concentration, and time on urea hydrolysis were investigated, and the optimum hydrolysis condition was estimated to be 30 (wt, %) urea solution hydrolyzing for 4 h at 140 degrees C, 0.4 MPa. The desulfurization experiment was conducted in a bubbling reactor. The effects of SO2 concentration and liquid gas ratio on desulfurization were investigated. The ammonia-based absorbent for desulfurization was prepared by the ammonia produced from the 30 (wt, %) urea solution hydrolyzing for 4 h at 140 degrees C, 0.4 MPa. The experimental results showed that all desulfurization efficiencies at different SO2 concentrations exceeded 99%, and a higher liquid-gas ratio could raise the desulfurization efficiency. The suitable pH range for this ammoniabased absorbent is 6.5-7.5. It was also found that higher SO2 concentration and lower liquid gas ratio could promote the generation of high added-value ammonium sulfate.