Simulation Of Urea Hydrolysis With Improved Thermodynamic Model

Urea is one of the most simple organic compounds, whose nitrogen content is the highest among solid nitrogen fertilizer and is widely used in the agricultural sector. During the urea synthesis process, a large number of process condensed fluid is discharged directly into the environment which would cause environmental pollution and waste of resources. Adding desorption hydrolysis unit in the urea production process is an inevitable choice to reduce environmental pollution to reduce material consumption and to improve the market competitiveness of products. Most research reports on urea thermodynamics focused on urea synthesis process, desorption hydrolysis is rarely reported. It is very necessary to develop a new thermodynamic model for this procedure in order to study process condensate processing better.In this paper, both intermolecular associations in vapor phase and complex system in the liquid phase with multi-electrolyte were studied. In order to accurately describe the vapor-liquid equilibrium phenomenon in urea hydrolysis process, truncated virial equation was improved to describe the non-ideal vapor phase and the extended UNIQUAC equation was streamlined and applied to describe the non-ideal properties of the liquid phase. A new thermodynamic equation was established using an equilibrium-based model. The predicted data and their trends of the model were well consistent with the plant data, indicating the validity of the model. Several key operating parameters, which were considered impacting on the efficiency of urea hydrolysis performance, were studied. The results of the work showed that both inlet wastewater temperature and steam flow rate have a positive correlation with the urea removal efficiency.Full Tower thermodynamic equilibrium stage model of Stamicarbon process path for condensate processing is established. The calculated concentration and temperature of each gas and liquid stream in each unit is compared with the plant parameters respectively. The model can be used to study the influence of feed flow rate, inlet temperature, high and low pressure steam flow and reflux ratio of urea hydrolysis tower. Any parameter which can improve circulation flow temperature of the system, such as the process condensate feed temperature, high and low pressure steam flow, reducing the reflux ratio and other operations, will help to improve the efficiency of hydrolysis and the removal rate of ammonia and carbon dioxide.