Co-production Of Soda Ash And Yinyl Chloride By Chemical Looping Of NH₄Cl Decomposition With MgO

Soda ash (Na2CO3) and vinyl chloride (CH2CHCl) are widely used as raw materials in chemical industry. During the production processes, both of them contain the same unit-limeston (CaCO3) calcination, which provides the raw material-CO2for the production of soda ash (Na2CO3), and quicklime (CaO) for the production of calcium carbide (CaC2). However, when ammonia (NH3) is regenerated by the reaction of quicklime and ammonium chloride (NH4Cl), calcium chloride is also produced as residue. While in the production process of vinyl chloride, CO2is a waste gas during the limestone (CaCO3) calcinations, which aims to produce quicklime as the raw material by acetylene method. The production processes of soda ash and vinyl chloride could share the same unit of calcination if they are integrated:CO2is for soda ash production and quicklime is for calcium carbide production, therefore the residue and CO2emission could be avoided. Meanwhile, the byproduct ammonium chloride in soda ash production process could be used as chlorine source for vinyl chloride production, thus the traditional energy-intensive electrolysis alkali process could be eliminated. The key of the integration is to decompose NH4Cl into NH3and HC1. In this investigation, the author used magnesium oxide (MgO) as chemical carrier to decompose NH4Cl into NH3and HCl by chemical looping method, with the former gas returned to soda ash production process and the latter returned to vinyl chloride production process. Based on it, this work had a study on soda and vinyl chloride integration processes.First, the author used HSC Chemistry thermodynamics software to analysis the feasibility that ammonium chloride could release NH3and HCl with MgO as chemical carrier. Also, thermodynamic conditions such as the temperature of releasing NH3reaction (MgO absorbing HCl from NH4Cl decomposition to release NH3) and HCl reaction (carriers absorbed HCl decomposing to release HCl), the mole ratio of ammonia to water were determined. Whereafter, experiments of releasing NH3and releasing HCl reactions which were investigated in a fixed-bed reactor was conducted. In these experiments, the results about the effect of the carrier types and reaction conditions were got, and high yield of85～90%of the two gases were obtained. MgO were characterized by technologies, such as thermo-gravimetry, X-ray diffraction, determination of specific surface, particle size distribution, etc. And the activity of various MgO was evaluated. The adsorption performance of MgO absorbents were evaluated after several cyclic runs. The results show that powdered light MgO has the highest activity due to its high specific surface and pore volume. And they still have relatively high activity after11cyclic runs with the particle size changed little. Finally, Aspen Plus software was used for simulation and material balance of sodaash and vinyl chloride integration processes. Reasonable suggestions for energy integrated utilization were provided, and the concept of soda ash-vinyl chloride co-production process was proposed.