This work presents a comprehensive computer simulation study for the hydrolytic polymerization of epsilon-caprolactam with the vaporization of both water and e-caprolactam in an industrial semibatch reactor. It incorporates various correlations for heat and mass transfer, desorption from the free surface as well as bubbly desorption, and the build-up of pressure in the reactor. The solution of the mass and energy balance equations is carried out using Gear’s algorithm. Optimal values of five parameters are obtained using the Box complex technique with industrial data for a feed-water concentration of 3.45 mass%. Simulation results are then obtained for two other feed-water concentrations using these curve-fitted parameter values. Excellent agreement is obtained with the corresponding industrial data. The activity coefficients of the monomer and water have been correlated with monomer conversion in this study. This eliminates infeasible solutions under certain conditions. The sensitivity of the model results to changes in the values of several parameters is also studied. The model developed can be used to optimize the performance of the reactor.