Thermodynamic Model of the Urea Synthesis Process

Abstract

A thermodynamic model of the ammonia−carbon dioxide–water–urea system at urea synthesis conditions, that is, at t = (135 to 230) °C, p = (3.5 to 45) MPa, L = n N/n C = (2 to 5.5) and W = ( n H2O – n (NH2)2CO) = n O/n C – 2 = (−0.75 to 1.2) was developed. A liquid phase was described by the UNIQUAC model including urea, ammonium carbamate, and ammonium bicarbonate as compounds; the gas phase was described by a virial equation of state. Bubble point pressures and carbon dioxide to urea conversion data were used for the model parameters optimization. The unique features of the model are the correct description of the saddle azeotrope and intensive use of existing thermodynamic data about constituents and binary subsystems vapor–liquid equilibria data.

Novel Process Design of Synthesizing Propylene Carbonate for Dimethyl Carbonate Production by Indirect Alcoholysis of Urea

“…The vapor–liquid equilibrium (VLE) relationship is described by the UNIQUAC activity coefficient model. In the PC synthesis reaction system, only the thermodynamic data of urea–ammonia and PG–PC pairs are found in the literature. ,, Table lists their binary interaction parameters of the UNIQUAC model. The solubility of ammonia in the reaction mixture is represented by using Henry coefficients.…”

Conversion of Recovered Ammonia and Carbon Dioxide into Urea in the Presence of Catalytically Active Copper Species in Nanospaces of Porous Silica Hollow Spheres

“…The processes of urea synthesis from ammonia and carbon dioxide in gas and liquid phases have been reported. For the processes, high temperatures and/or pressures have been required for a high urea yield. − In the present study, we tried to produce the compounds from the recovered ammonia and carbon dioxide in porous silica hollow spheres under mild conditions.…”

Empirical Modeling of Urea Synthesis Chemical Equilibria

“…Hamidipour et al [6] assumes the gas is ideal and the liquid properties are modeled using Wilson equations. Other papers related to the thermodynamics of urea synthesis are listed in references [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Reactor models also vary in complexity. Irazoqui et al [23] assume that all components are in liquid phase and there is countercurrent flow between the coil and the bulk of the reactor.…”