Carbothermal Reduction Of Iron-containing Raw Materials In The Microwave Field Basic And Small-scale Experimental Research

In recent years,the global efforts to reduce greenhouse gas emissions and reduce energy consumption have led to a boom in scientific and industrial research on the technology of making direct reduced iron.Direct reduced iron is produced by removing oxygen from solid iron-bearing materials.Based on the characteristics of abundant coal resources and shortage of natural gas resources in China,coal-based direct reduced iron technology is the development direction.Taking advantage of the characteristics of microwave equipment with low investment,small occupation of land,easy to instal,control and move,the application of microwave heating technology to making direct reduced iron can realize the production mode of mobile factory,which can not only reduce emission and consumption,but also bring convenience for occupying and exploiting resources rapidly,and reducing the transportation costs.In this paper,the microwave heating technology was applied to make the direct reducing iron with anthracite,iron concentrate and mill scale.The basic research and pilot-scale experiment in the microwave field were carried out.The main research contents of this paper are as follows:1.The heating characteristics and dielectric properties of iron concentrate,mill scale and anthracite in microwave field were studied.With the increase of temperature,the change trend of microwave penetration depth in the material layer is generally decreased.The depth range of microwave penetration through the mixture layer is2.15cm⁷5.99cm,which provides a basis for the design of pilot-scale experiment microwave equipment.2.The process of direct reduction by microwave heating was study.The reduction of iron oxide still follows the reduction sequence of Fe₂O₃?Fe₃O₄?FeO?Fe,and the main reduction reaction is in the range of 750?⁹00?.The non-isothermal kinetics study was used to obtain kinetic parameters,that the materials were heated 800?⁹50?by conventional heating method,reaction fraction is6.94%²4.73%,the apparent activation energy was 155.66 kJ/mol,and microwave heating temperature at 600?⁷50?,the fraction was 33.61%⁴5.22%,the apparent activation energy was 58.33 kJ/mol,significantly reduced the apparent activation energy,so the microwave heating can accelerate the reaction rate,reduce the reaction apparent activation energy.3.The process experiment was carried out in the microwave field,the influencing rules of the reduction temperature,reduction time,ratio of anthracite,iron oxide ratio and the ratio of desulfurizer for reduction product grade and metallization rate were obtained,when the iron concentrate?mill scale=40?60,22%anthracite temperature 1100?,reduction time 60min,the grade of product was 78.36%,the metallization rate was 96.65%.It provides important technical parameters for pilot scale experimental study.4.This paper analyzed and designed the main components of the expansion experiment equipment for making direct reduced iron in the microwave field,and processed a set of pilot-scale experiment equipment.The characteristic of the equipment is that the microwave source distribute respectively under the chamber and the upper side.5.The pilot-scale experiment of making direct reduced iron by microwave heating was carried out.Firstly,through static pilot-scale experiment,the temperature rise of the material in the equipment cavity was mastered,and the appropriate height of layer,reduced time and the amount of reductant were obtained.Under the experimental conditions of iron concentrate?mill scale=40?60,anthracite ratio25%,reduction temperature 1100?,material layer height 40mm,6 plates of mixture at the same time,direct reduced iron grade is 91.40%,metallization rate is 92.76%,reduction process cycle is 375min,reduction process time is shortened 91.1%,microwave energy thermal efficiency is 75.39%.A reasonable microwave reduction operation system was developed,which provided an important reference for further industrialization of making direct reduced iron by microwave heating.