Experimental Study And Process Calculation On The Synthesis Of Chloromethane With Ammonium Chloride And Methanol

China is a big soda producer in the world,and the output of soda by Hou’s process accounts for more than 40%of the total soda output.Hou’s process is a combined process for manufacture of soda ash and ammonium chloride.A large amount of ammonium chloride is by-produced in the process.However,the quantity demanded of ammonium chloride in some applications is very small.In order to find new application fields of ammonium chloride,it is necessary to develop chemically converting methods to produce high added value chemicals,which is of great significance to promote the sustainable development of alkali industry.In the chemically converting methods for ammonium chloride,the reaction with methanol to synthesize methyl chloride possess the characteristics such as relatively low reaction temperature,high conversion rate,high product added value,and being suitable for large-scale industrial production.The synthesis of methyl chloride with ammonium chloride can not only solve the problem of the excess output of ammonium chloride,but also broaden the way to produce methyl chloride and reduce the production cost of methyl chloride.Preliminary researches on the process of synthesizing methyl chloride with ammonium chloride were carried out by relevant foreign companies and research institutions in the last century.This process is not industrialized.In order to solve the wayout of ammonium chloride in China and to build an industrial chain of circular economy to combine the manufacture of soda ash and the process of organosilicon production,our research group started the experimental studies on the synthesis of methyl chloride with ammonium chloride 10 years ago,and has made systematic researches including the development of catalyst,fluidized bed reactor technology and subsequent separation process technology.Based on the table-scale and pilot-scale experiments,we find that there are the following problems to be solved:(1)the decomposition rate of ammonium chloride particles,which involves in the calculation of the inventory of ammonium chloride in the reactor and the design of the industrial fluidized bed reactor;(2)blockage of ammonium chloride feed.Due to the crystalline transformation of ammonium chloride at about 200℃,the blockage of ammonium chloride powder will easily occur during feeding.To this end,the following research works have been carried out in this paper:1)Kinetic researches on the decomposition of ammonium chloride.Based on thermogravimetric-differential thermal analysis of ammonium chloride particles,a thermogravimetric experiments were carried out under higher temperature using a self-made high-capacity thermogravimetric experimental device,and the volume change of single ammonium chloride particle during decomposition were recorded in real-time with a self-made microthermal decomposition device.The shrinkage unreacted core model was used to simulate the decomposition of ammonium chloride,and the kinetic model was obtained.The results show that the decomposition of ammonium chloride is not affected by gas phase diffusion,and its decomposition rate is only related to temperature and reaction surface area.The rate equation is(?):and E=69.55 kJ/mol,A=2.236×106mm/min.2)Experimental studies on the cohesive properties of ammonium chloride under high temperature.Taking the accumulation repose angle of ammonium chloride powder as a characteristic index,the cohesive properties were investigated with ammonium chloride powder,ammonium chloride mixed with alumina powder respectively after heat treatment under 180～300℃ and 20～60 minutes.The experimental results show that the cohesiveness of ammonium chloride powder is affected by temperature,particle dispersibility and heating time,the extrusion force during feed process.The higher the temperature is,the worse the particle dispersion is,the longer the heating time is,and the larger the extrusion pressure between particles is,the easier it is for ammonium chloride to sinter into a hard massive solid.Mixing with 2%alumina powder will reduce the cohesiveness of ammonium chloride powder.3)Development of new feeding devices for ammonium chloride powder.In order to ensure ammonium chloride powder in a dispersed state and under low temperature during the feeding process,four kinds of free-fall vertical feeding devices with different structures have been developed and optimized.The results show that the vertical triple-tube feeding device with water-cooling gives the best results.The optimal operating conditions are the flow rate of inert gas in inner jacket,0.02～0.04 m/s;the flow rate of cooling water in outer jacket,0.1～0.5 cm/s.4)Process calculation for the synthesis of methyl chloride with ammonium chloride with the output of 20 kt/a methyl chloride.Based on the results of above experiments and previous researches in our research group,the process calculations were carried out including the reaction process and product separation process.The structure and size of fluidized bed reactor and some main device were obtained,and the P&ID diagrams,the fluidized bed reactor structure diagram were given.