| 摘要 |
Process for purifying aq. urea solns., partic. for regenerating those flowing in closed circuit in a dewatering plant comprises adding, esp. to a fraction withdrawn from the circuit, ammonia to concn. of 1-10 wt.%. This soln is then held at 110-170 degrees C for 30-240 min., then excess NH3 and CO2 are eliminated, if necessary, before recycling to the dewaxing plant. Pref. NH3 added is that obtd. from a previously purified stream, esp. that liberated by expansion of the warm purified soln. Pref. absorption, purification, sepn. of CO2 and opt. excess NH3 and opt. sepn. of CO2 from NH3 are all effected in a single operative stage in a single reactor. Appts. for the process is also claimed. Condensation prods. such as biuret are destroyed and urea losses are reduced, e.g. by 50-80%. |
