| Magnesite is one of the strategic mineral resources in China,and its reserves,output and export rank first in the world.Magnesite resources are concentrated in China,and more than85%of its reserves are distributed in Liaoning Province.Light burned magnesia is the raw material of most magnesia materials.Flash dynamic roasting furnace is a revolutionary roasting furnace,which changes hourly roasting into second roasting and lump ore roasting into micro-rice flour roasting,which makes the product activity higher,the energy consumption per ton of product lower and the environmental protection treatment cost lower.Admittedly,the flash baking furnace is a technological change,but it still has some disadvantages,such as insufficient gas-solid contact in the furnace feeding area caused by furnace feed segregation,which leads to furnace blanking and uneven gas-solid contact in the main furnace,which leads to unstable baking quality.Based on the introduction of gas-liquid jet technology by my research team,a jet feed structure is proposed.Relying on the Liaoning Province Key R&D Project(2021jh1/10400030),It is proposed to study the gas-solid two-phase material flow characteristics in the resistance feeding region under different jet structure types by experimental means,and further study the effects of jet structure types,structure parameters and operation parameters on the gas-solid flow characteristics,so as to provide theoretical support for the subsequent design of feeding structure.The main research contents and innovations are as follows:(1)According to the thermodynamics requirement of light-burned magnesia powder roasting in the flash roaster,the feeding requirement and evaluation index of the flash roaster are determined,and then the structure type of the jet feeding structure is determined.The research shows that the feed rate of the flash roaster should be controllable,and the materials can be suspended in the air flow without dropping.Indicators for evaluating the feeding effect include speed,pressure,residence time and particle concentration.The jet feed structure is determined to be composed of air inlet pipe,nozzle,suction chamber,feed pipe,throat pipe and expansion pipe.(2)According to the principle of similarity,considering many factors and levels,such as throat distance,nozzle diameter and air intake,a jet feed structure was designed and established,and a test device with a treatment capacity of 30kg/h was designed.The structural parameters of the jet-type feeding structure of the device are as follows:the inclined angle of the feeding pipe is 60°,the diameter of the nozzle is 16mm,the distance between the throat and the nozzle is 90mm,the length-diameter ratio of the throat is 2,and the operating parameters are as follows:the air intake is 200m~3/h,the flow rate in the furnace is 13.6m/s,and the particle size of the material is 15μm.(3)Through experimental research,the main factors that affect the feeding effect and their influencing rules are preliminarily explored.The experiments show that:1)the jet feed structure can effectively promote the mixing of material particles and gas.2)The main factors that affect the feeding effect are throat distance,nozzle diameter and inlet air volume in descending order.Among them,the feed efficiency increases with the increase of throat-nozzle distance,and the rate of increase of feed efficiency slows down when the throat-nozzle distance is more than 200mm;The feed efficiency decreases with the increase of nozzle diameter.When the nozzle diameter is greater than 20mm,the decrease rate increases.The feed efficiency increases with the increase of intake air volume.When the intake air volume is greater than 200m~3/h,the increase of feed efficiency slows down.(4)According to the experimental research,it is preliminarily determined that the jet feed structure of a flash roaster with an annual output of 100000 tons of light-burned magnesia powder adopts a four-inlet jet feed structure.Its structural parameters include nozzle diameter of 220mm,throat-to-throat distance of 3000mm,suction chamber diameter of 1500mm,throat diameter of 1040mm,operating parameters of air intake of 44138m~3/h,feed rate of 26.50t/h and particle size of 78μm. |
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