The urea plant of Hebei Cangzhou Dahua Group Co., Ltd. is a large-sized urea production plant with capacity of 1620 mtpd, imported in 1973 and using CO2 stripping process. In the original design, the off-gas from the low-pressure (LP) section is directly vented. Via a technical revamp of the plant in 1988, the LP section is provided with an atmospheric absorption section, which can absorb the off-gas from the LP section and the hydrolysis section at atmospheric pressure. After the plant modifications were implemented and put into service, the plant had a lot of technical problems, such as much liquid in the vent pipe, poor performance in scrubbing and absorption. Additionally after increasing the plant load the incremental vent flows of the LP and hydrolysis sections resulted in higher energy consumption figures.
To improve the absorption performance of the atmospheric absorption section, reduce the consumption figures and the amount of off-gas vented, and to increase economic and environmental benefits, the urea plant was again technically revamped in 2011: The atmospheric absorption section was upgraded as the LP one. As a result, the said problems have been successfully solved.