Simulation And Improvement For Urea Hydrolyzed System

About0.7tons of process condensate will generated to produce one ton of urea inurea production process, which contains a considerable amount of ammonia, carbondioxide and urea and should be purified before discharge. Process condensate is treatedby urea hydrolysis system. Urea be hydrolyzed to water and carbon dioxide byhigh-pressure steam, then concentrated by distillation to obtain aqueous solution ofammonia and carbon dioxide returned to the synthesis system. In this process so muchsteam is consumed. So it is significant for environmental protection and energy savingto operating hydrolysis system well.This paper introduces the mathematical model used to calculate the urea hydrolysissystem in detail, including the vapor-liquid equilibrium model, the kinetic model of ureahydrolysis and the model of complex distillation column. The key points of theequilibrium is the true species composition in liquid and the activity coefficientcalculation; Calculating the enthalpy of logistics requires setting the same standard stateand a reasonable changing way in order to obtain the relative values of enthalpy; as themedium in the urea hydrolysis system is low concentration and weak electrolyte system,the low concentration kinetic model is used for the hydrolysis of urea; Complexdistillation column model is relatively mature, but there is a chemical reaction inhydrolysis column, and the balance of material and heat has changed.Based on the above mathematical model, FORTRAN language was used tocomplete the hydrolysis rigorous system simulation. The results showed that themathematical model could describe the urea hydrolysis system well. Through theanalysis of various factors such as steam flow and operating pressure, the operationadjustment direction of the existing hydrolysis system was proposed.Finally, the improvements of the existing process was suggested, and thesimulation was carried out. The results showed that the treatment effect was very goodafter the transformation, which proved the feasibility of reconstruction, and pointed outthe direction of the column selected to lay a foundation for the equipment renovation.