Study On Kinetics And Reactors For Pyrogenation Reaction Of Magnesium Hydroxide Chloride

Chemical looping of ammonium chloride (NH4CI) is the key technology of soda ash-vinyl chloride co-production process, wherein the chlorine release reaction with high efficiency is of great importance in particular. This thesis studied thermal decomposition of magnesium hydroxide chloride (Mg(OH)Cl), and proposed the kinetics and mechanism. Furthermore, simulation calculation was carried out on reactor to optimize process conditions and configurations of reactor. The result could provide essential data and reactor technology for the industrial application of soda ash-vinyl chloride co-production process.Firstly, the kinetics and mechanism of thermal decomposition of Mg(OH)Cl under nitrogen atmosphere were studied. The thermal decomposition process and product characteristic were analyzed using integrated thermal analysis, X-ray diffraction, scanning electron microscope, etc. The results showed that the thermal decomposition process of Mg(OH)Cl could be divided into two stages. In the first stage, the decomposition reaction was controlled by Avrami-Erofeev function (n=1), the activation energy was 290kJ/mol and the pre-exponential was 2.72×1019 min-1. Relatively, the reaction rate of the second stage-with complex mechanism became slower, which might be caused by diffusion. After calcination of Mg(OH)Cl, magnesium oxide with high purity and high activity was prepared.Secondly, according to the demonstration project about treatment of ammonium chloride with a scale of 100,00t/a, this thesis made a primary design on the thermal decomposition reactor, including the calculation of basic reactor parameters, heat transfer process, energy accounting and other aspects. Especially for regenerative combustion reactor, the basic parameters of the regenerator, pressure drop and other aspects were calculated. These data laid a foundation for numerical simulation and optimization in the further work.Finally, based on the decomposition kinetic of Mg(OH)Cl and the basic reactor parameters, this thesis designed a one-dimensional heat transfer-reaction coupling model, and obtained temperature distribution of gas, concentration and temperature distribution of material by COMSOL software. As for regenerative combustion reactor, the effect of velocity, reactor’s length and switching time on temperature distribution and reaction was studied. As for jacketed reactor, the effect of inlet gas temperature, gas flow, reactor’s length and other factors were evaluated. Optimization of reactor operating conditions manifested that the outlet material temperature of lower than 650℃ and the average Mg(OH)Cl conversion of 92.2% were optimum.