Experiment of Microwave Heating on Self-FluxingPellet Containing Coal

J. Iron Steel Res, IntMay 2003Experiment of microwave Heating on Self-FluxingPellet Containing CoalCHEN Jin', LIU Liu, ZENG Jia-qinLIU Jin-ying, REn Rui-gang(1. Central Iron and Steel Research Institute, Beijing 100081, China; 2. Beijing Vacuum Electronics ResearchInstitute, Beijing 100016, China; 3. Xuanhua Iron and Steel Group Co, Xuanhua 175100, China)Abstract: The self-fluxing pellets containing coal possess an independent self-reducing and selfslag-making system. A high metallization rate can be achieved without external reduction condition at high temperature and it looks like a micro-blast-furnace by itself. The essential condition to use it is to supply heat to the pellet rapidly and uniformly and keep it at a certain tem-perature. Microwave heating can meet the need of rapid and uniform heating. The resulshow that the temperature of the pellet with a certain weight increases as the microwave powerincreases. The heating rate of the pellet is increased from 9 17 K/min( 5 kW)to 71.65 K/minKey words: microwave heating i pellet containing coal self-fluxing smelting reductionSelf-fluxing pellets containing coal( SFPC )areMicrowave energy can act directly on chemicalartificial iron ore with unique properties of self-re- system and promote the chemical reaction. The miduction at high temperature. At high temperature a crowave heating of inorganic solid phase has becomevery high metallization rate can be reached rapidly a new field of applications which is widely usedal reduction condition so the pellets the industrial drying sterilization sintering synthelook like micro-blast-furnace. The reduction rate of sis and other fields. The microwave heating can afthe pellet is higher at higher temperature with fect pellets at different depths at same time. Thensmaller diameter of pellet, finer coal particles and the uniform and rapid heating is realized with energysmaller size of the raw materialL. However the savingreduction reaction is an endothermic process andMicrowave heating is different from other heatthe supply of heat from the surface of pellet to the ing methods and the heat is generated by dielectriccore determines the rate of the overall reactionloss of substance in electromagnetic field. The caloTherefore the high temperature and rapid supply of rific effect of microwave on substances depends oheat is the key point to reduce the pellets for a short the dielectric characteristics of substancetime21The conventional heating methods such as heat- 1 Characteristics of Raw Materialng by conduction and radiation can not meet therequirement of rapid and uniform heating. For imThe main components of the self-fluxing pelletsproper heating, the strength of the pellets decreases containing coal are iron ore fine, pulverized coalsharply at medium temperature( 700-1 000 C). flux powder binder and water and so on. It is ineven at low temperature( 400-600 C ) Consequently portant to investigate the microwave absorbing charit displays its fatal weakness low strength and high acteristics of those raw materials in microwave fieldself-pulverization rate. It is reported that the highThe ability of metal oxides to absorbmicrowavestrength of the pellets containing coal comes from is obviously different according to their componentsthe network of iron-jointing crystal[]. The iron- and molecular structures. Then the heating rate ofJointing crystal in pellets can be formed only at high oxide powder in microwave field is related to the mispeed and uniform heating. In this way, the com- crowave absorbing properties of their molecules. Thepression resistance and grind resistance of the pellets oxides can be classified into three types according toI have the advantage over other pellets. B中国煤化工O, Ni,O and Srnecessary to heat the pellets as required and the ad- etcCN MH Gb microwave and highvantage can be developeddielectric loss 2 )Oxides with medium polar bondFoundation item: Item Sponsored by National Natural Science Foundation of China( 50274033)and Shanghai Baoshan Iron and Steel groupBiography: CHEN Jin(1955), Male, Doctor candidate Associate professor; Received date: October 10, 2001J. Iron Steel Res. , I1Vol 10such as Fe3O4, Fe, O3, Cr,O3 and V2 Os, etc. their are shown in Table 14)ability to absorb microwave is weak at the beginningAccording to Table 1 there are a high heatingand becomes stronger after a period ;(3 )Oxideate for coal magnetite and manganese ore in micro-with weak polar bond such as AlO3, TiO2 and wave field a medium rate for lime and siderite andMoO2, etc. are transparent to microwave, anda. In addition, water and sometheir temperature increases very slowly or even does organic compounds are good at absorbing microwavenot increase 41. The heating rates of some substances energy (see Table 2)Table 1 Heating rate of some substancesMolecular Heating temperature Heating temperature Heating time T-273)/tAmorphous carbon(