Simulation And Analysis For Low-atmospheric Pressure Recycle System And Desorber Of Urea Process

The urea process is involved in two important systems NH3-CO2-H2O(ACW) and NH3-CO2-H2O-Urea(ACWU), of which the experimental data and thermodynamic calculation models were collected in the paper.The ELECNRTL property method was chosen, and the binary interaction parameters of ELECNRTL model about ACW system were regressed based on the experimental data from reference. The accuracy of the regressed parameters was verified. And the SRK equation of state was used to describe the gas phase behavior of related systems.Taking some domestic urea plant as an example, the problems about low-pressure recovery system in CO2-Striping urea process were pointed, while the simulation process of low-pressure recovery system was established using Aspen Plus Chemical simulation software. For the absorption effective of atmospheric absorber was poor, absorption with pressure method was proposed. That was to say, the atmospheric absorber should be merged into low-pressure system to enhance the absorbing. The pressurized absorber was analysed by simulating to guide the actual product. By comparing the production data before and after reforming of the atmospheric absorber, more ammonia was recycled, resulting that the ammonia consumption of per ton urea decreased by3kilogram, which meant that1620liquid ammonia could be saved, that equal to2105tons of standard coal. The simulation results proved to be effective.Because of desorption-hydrolyzation system running overload, the desorption column operation was unstable, which was carried out with simulation analysis. The vapor-liquid flow rate distribution, the temperature distribution and the vapor composition distribution in the desorption column were given, at the same time, the desorbing effective was calculated. At last, the influence on the top concentration of temperature in desorption column was investigated.