It has been realized that the core of urea synthesis reaction is dehydrating carbamate into urea in the liquid phase. This reaction is the main one in urea synthesis and is called urea formation reaction for short hereafter. The goal is to push the reaction to proceed in an ideal direction (equilibrium).
However, in industrial production scale, there are lots of difficulties and interferences which hinder the reaction to proceed in an ideal direction. The main cause hindering the main reaction from becoming an ideal one is that there are two synthesis reactions interfering each other and these are combined with very complex chemical processes.