This work presents a dynamic simulation and a design control system for the thermal decomposition of nitrogen trichloride during electrolytic chlorine production. Nitrogen trichloride is an extremely unstable and explosive compound and the decomposition process has two main problems: variability of the reactor temperature and loss of solvent. The process was simulated using the AspenTech (R) simulator and the simulations were validated with industrial plant data. The dynamic analysis showed that the process presents integrating behavior and that the loss of the solvent is strongly affected by the dynamics. The implementation of the results of this work at the industrial plant resulted in a significant decrease in the variability of the reactor temperature as well as reducing solvent loss.