| China is rich in magnesium resources in salt lakes.The reserves of magnesium salt in Qaidam Basin are about 5 billion tons,slightly higher than the reserves of magnesite resources in China.Compared with magnesite,Salt Lake magnesium has less impurities and is the preferred raw material for the production of magnesium intensive processing products.However,the magnesium products produced by Salt Lake magnesium in China and even the world are less than 10%at present.Due to the blank of Salt Lake magnesium resource technology,Salt Lake magnesium,as the preferred raw material for the production of high-quality magnesium products,has not been effectively resourced,forming a"magnesium hazard".Until 2004,Xu Hui of Central South University put forward the technology of Salt Lake magnesium resource utilization and implemented it in the Western magnesium industry,creating a precedent for the utilization of Salt Lake magnesium in China.The core of the technology is to add precipitant to the brine first,and then fully calcine the solid precipitation of basic magnesium carbonate or magnesium hydroxide obtained from the reaction to obtain light burned magnesium oxide.It is true that the two-step method is a technological change.However,from the principle of chemical reaction,magnesium in Salt Lake can be directly produced by one-step method.Although the academic circles have discussed it for more than ten years,they have not solved this theoretical and technical problem so far.Based on this,the research team has joined the Northeastern University and Liaoning Dongda Powder Engineering Technology Co.,Ltd.,based on the technical requirements of the Western magnesium industry,and based on the practice of Liaoning Dongda Powder Engineering Technology Co.,Ltd.in powder engineering in the past 30 years,the integrated spray pyrolysis process is proposed,and the atomizing pyrolysis furnace is developed.This paper studies the atomization theory in this technical breakthrough,so as to provide theoretical support for the follow-up pilot project and technical breakthrough.The main research contents and innovations are as follows.(1)According to the atomization requirement of the pyrolysis furnace,the internal mixing two phase flow nozzle with solid spray shape was determined,and the atomizing experimental platform with a volume of 100L/h was built and the atomization characteristics of the nozzle were preliminarily studied.The experimental results show that the gas-liquid mass ratio,gas supply pressure and liquid injection hole diameter of the nozzle are the main factors affecting the atomization quality.Among them,with the increase of gas-liquid mass ratio and gas supply pressure and the decreases of the diameter of liquid injection hole,the atomization cone angle increases.Under experimental conditions,when the air supply pressure is kept constant,the gas-liquid mass ratio increases from 0.023 to 0.094,and the atomization cone angle increases from 15.4°to 39.7°;When the treatment capacity and gas supply pressure are kept constant,the diameter of liquid injection hole increases from 1.0mm to 2.0mm,the area of liquid injection channel increases from 0.79mm~2to 3.14mm~2,the atomization cone angle decreases from 29.8°to 19.6°.(2)In order to further study the atomization characteristics,a numerical calculation model based on Euler-Euler method is established to study the fluid characteristics in the nozzle;Based on the Euler-Lagrange method,the spray characteristics of the nozzle outside the nozzle are studied.The results show that the main factors affecting the atomization quality are the diameter of injection holes,the number of injection holes,the ratio of mixing chamber length to nozzle outlet diameter,air supply pressure and treatment capacity/liquid flow.Among them,when the volume of processing and the pressure of the gas supply is constant,the injection hole diameter increases from 1.0mm to 2.5mm,the area of the liquid injection channel increases from 0.79mm~2to 4.91mm~2,the atomization cone angle decreases,the spray penetration distance,the arithmetic mean diameter AMD and the Salter mean diameter SMD increase.When the injection hole increases from 3 to 6,the area of the gas injection channel increases from 9.42mm~2to 18.85mm~2,the spray penetration distance decreases,and the spray cone angle changes little.AMD and SMD decrease first and then increase.When the mixing chamber length and the nozzle outlet diameter ratio increases from 3 to 4.5,the spray cone angle increases,the spray penetration distance and AMD change little,SMD decreases first and then increases.When the volume and nozzle structure parameters are constant,the pressure of the gas supply increases from 0.2MPa to 0.5MPa,the air flow rate increases from0.50m~3/h to 1.31m~3/h,the gas-liquid mass ratio increases from 0.016 to 0.104,the atomization cone angle and spray penetration distance increase,AMD and SMD decrease.When the air pressure and nozzle structure parameters are fixed,the throughput increases from 40L/h to100L/h,the gas-liquid mass ratio decreases from 0.149 to 0.023,atomization cone angle decreases,spray penetration distance,AMD and SMD increase.(3)According to the experimental and numerical calculation results,the suitable parameters of the nozzle with a treatment capacity of 80L/h are determined as follows.The diameter of the liquid injection hole is 1.0mm,the gas injection hole with a diameter of 2.0mm is 4,the ratio of the length of the mixing chamber to the diameter of the nozzle outlet is 4.5,and the air supply pressure is 0.5MPa.At this time,the SMD can reach 40.58μm.The atomization quality is the highest. |
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