| Mg(NO3)2·6H2O is a secondary resource produced in the laterite nickel ore wet metallurgy process,and its resource utilization is one of the key technologies to realize the laterite nickel ore wet metallurgy green.The main way to utilize Mg(NO3)2·6H2O is to produce MgO and NOx through pyrolysis.Among them,NOx is used to produce acid and return to the hydrometallurgical process.At present,there is almost no research on Mg(NO3)2·6H2O pyrolysis at home and abroad.Based on this,this paper relies on the school enterprise cooperation project of the key technologies of the pilot scale pyrolysis system of magnesium nitrate hydrate,and takes Meishan Yingli Pilot Project as the research object,using experiments and numerical calculation methods to develop Mg(NO3)2·6H2O pyrolysis reaction mechanism and other basic theoretical research.Based on this,the process flow of Mg(NO3)2·6H2O pyrolysis resource utilization was established,the key pyrolysis process parameters were determined,in order to lay a theoretical foundation for the design and debugging of Meishan pilot project system.Main research contents and conclusions:(1)Using TG-FTIR and other analytical methods,research on the pyrolysis reaction mechanism of Mg(NO3)2·6H2O was carried out.The results show that:1)The pyrolysis process of Mg(NO3)2·6H2O can be divided into two processes:dehydration and decomposition,which are reflected in three stages.Among them,the dehydration process is divided into two stages:at 68～170℃,Mg(NO3)2·6H2O loses 4 crystal waters and becomes Mg(NO3)2·2H2O;at 170～389℃ Mg(NO3)2·2H2O loses 2 crystal waters and becomes Mg(NO3)2;Decomposition process:In the range of 389～510℃,Mg(NO3)2 decomposes to form MgO,NO2,O2.2)TG experiments based on different heating rates The thermal analysis kinetics method was run to solve the kinetic parameters of the three stages of the Mg(NO3)2·6H2O pyrolysis process,and a pyrolysis kinetic model was established.(2)Based on the research on the pyrolysis mechanism,a process flow for the Mg Mg(NO3)2·6H2O pyrolysis to acid is constructed-a pyrolysis gas self-circulating spray pyrolysis process;the process mainly includes:raw material melting system,spray Pyrolysis system,gas dust removal system,gas heating system,MgO powder waste heat recovery system and acid production system.Among them,the pyrolysis system has a vertical entrained bed,and the gas heating system uses a regenerative hot-air stove;its main feature is that it uses pyrolysis gas as a pyrolysis heat carrier,which provides extremely convenient conditions for subsequent exhaust gas treatment.(3)Through the calculation of the energy balance of the logistics and chemical reactions,supplemented by numerical calculations,the preliminary determination is made:1)Process parameters of the pyrolysis system:200kg/h of raw material processing capacity,234Nm3/h of pyrolysis gas generation,temperature of 500℃,Among them,the volume fraction of NOx is 41%;the temperature of the gas entering the acid-making system is 400℃ and the flow rate is 234Nm3/h;the temperature of the gas as the heat carrier is 1000℃ and the flow rate is 1772Nm3/h;The solution time is 4～5s;the atomizing nozzle is a single nozzle with 8 nozzles,and the ratio of compressed air to solution is 75Nm3:1000kg.2)The structural parameters of the pyrolytic furnace foundation are furnace height 10 m,furnace diameter 2 m and spray angle 60 degrees.(4)The Euler-Lagrange method is used to perform numerical simulation of the flow mixing process of the droplets and circulating gas in the spraying process in the pyrolysis furnace.The circulating gas enters tangentially from the top entrance of the pyrolysis furnace,forming some spiral downward thirst around the central axis of the decomposition furnace,which makes the gas descend in a spiral manner,the speed gradually decreases,and there is an obvious vortex phenomenon in the furnace,which can make the flow field The gases and materials in the mixture are thoroughly mixed.The droplets are well dispersed in the decomposition furnace,and almost fill the entire space of the furnace body. |
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