Modeling Of CO₂ Stripper In Urea-Synthesis Process

Urea fertilizer has the largest commercial tonnage of all nitrogen fertilizer. Nowadays, the prospects for a sustained development in the Urea industry are much brighter than they have been for many years. Demands for energy conservation and environmental control must be answered by the Urea process licensors.CO₂ stripper is one of the most important units in the Urea-synthesis process. COa stripping process aims to decompose the carbamate so as to fulfill recycling the unreacted NHs and CO2 from the Urea solution. Therefore, Rigorous simulation of COi stripper is necessary and significant for design, modification and optimization of the Urea production process. The main contents of this paper are as follows:I In this paper, ACWU thermodynamic models involved in Urea-synthesis process which were presented by formers are summarized. The modified UNIQUAC equation which was used by Isla et. al. is applied to calculate vapor-liquid equilibrium (VLE) of NH3-CO2-H2O-Urea thermodynamic system involved in the Urea process system. The results of thermodynamic model agree well with experimental data. The model can be used to predict the behavior of the systems NHs-COa-HbO and NH3-CO2-H2O-Urea over a wide range of composition and temperature.II Based on rigorous thermodynamic model, an equilibrium stage model is developed to simulate CO₂ stripper. The results agree well with design values and the running plant data. The results also accord well with the conclusions obtained by the analysis of the high-pressure phase graph. In addition, calculation model can be used to simulate other types of strippers in the Urea plant. The thermodynamic model is also proved applicably.III The non-equilibrium stage model of CO₂ stripper is proposed. And the related methods of getting kinetics parameters are proposed.IV To simplify calculation and save calculation time, ANN is applied to simulate CC>2 stripper. Rigorous model is replaced by 'black box' model. The forecast results show that this model can reflect the rigorous model exactly and it is helpful to optimize the whole Urea process.