Use Of Coal Petrography Blast Furnace Coal Blending Mechanism

Pulverized coal inject into BF is a great technology revolution in modern iron making. Low coal rate and UPC's exist because of the imperfection combust of coal in BF besides of the blindness in the choice of coal used to spew are the questions conquered to iron makers.The mechanism study of the coal blending in BF injection using coal petrography is the transfer of the petrography coal blend in coking techniques, with the DGC mechanical separation of coal macerals and combust experimentation under the BF inject environment tried to found the relationship between the coal mecrals and the coal combustibility in BF inject condition so as to set up the coal petrography blending theory about coals used in BF injection, offer some theory gist to boost the coal combustibility in BF inject and reduce the mass of UPC in BF, so we can enhance the coal inject count and reduce the pig iron cost.The coals used in this work were LePing, Shen Fu, Hong Qiang, Tai Xi, Bao Qiao, Fang Shan and Yang QuanThe coal sample preparation was carried through planetary ball mill, saved in nitrogen-filled black class bottle after drying. The separation of coal macerals was accomplished by DGC method (Density gradient centrifugation)The devises used in experimentation were :LBH75250 type air compressor, vacuum pump; 10-liter sieve flask; galvanothermy blast evaporation box; 1200-model coal powder combust furnace.Some examination parameters were sirocco temperature: 1000℃temperature in burning furnace: 1400℃sirocco flux: 10Nm3/h Cold wind pressure: 0.2MpaBecause of the aim of this examination was to investigate the relationship between the coal maceral and coal combustibility and based on the fact that vitrinite was majored in all of the coals used in examination, the principle to draw experimentation is assure the even distributing between 0 and 100%.Two formulas to calculate the coal powder combustibility were: combust mass balance method and ash balance method.After experiments and the analysis of the result of the experiments we can found something as follows:The coal powder combustibility became lower along with the improve of the vitrinite content, colligate consider with fusinite coal powder has the highest combustibility at the content 35%. The H/C rate in vir was higher than in fus just as the volatilizations content and felt character, so when the coal was heat up, vitrinite change into coal cell and the density became low, vitrinite would flee away with the wind flow, the coal combust became incomplete and the coal powder combustibility became lower. The combustibility of fusinite has some differences with vitrinite's. There was a max count on the curve and before and after the count the coal powder combustibility become lower. When the content of fusinite was about 60%, the coal has the highest combustibility count about 80%. Because of the great inner surface and cavity the fusinite was direct combust without fuse, volatilization and compact constriction, there is low UPC content in ash from fusinite. But the fusinite exhausted combust temperature is high, so fusinite's combustibility became bad when its content became higher because it could not get enough quantity heat from the surrounding.Exinite content in most kinds of coal was low and even lack, but ex was very easy to fire and combust, enhance the content of ex was propitious to improve the coal combustibility. Exinite has the lowest hydrogen content and the highest volatilize mass, it became soft and decomposed at very low temperature, so we could not find any mass come from Exinite in coal ash. The influence to the coal combustibility aroused from Exinite is very tiny.Mineral has double function to the coal pyrogenation, this character rest on the mineral and maceral compose. Original mineral's influence to volatilize produce rate is relate to the maceral, but the mineral is the main source of coal ash, so the exist of mineral has restrain function to the coal combustibility in radically.With the help of coal powder combust experiment and the analyze of the relationship between the coal macerals and the combustibility we found that when the content of vitrinite is high (85%), the combustibility become lower with the fusinite content become higher; but when the content of vitrinite is low (50%), the fusinite would improve the coal combustibility. When the coal used to inject into BF is purer vitrinite, the influence to combustibility from the other macerals could be ignored. The content of fusinite (20%), when the vitrinite content below in 75%, the presence of vitrinite restrained the combust of coal powder, but above 75%, boosted it. The combustibility variety because of vitrinite is about 15%. When the fusinite content is above 40%, with the higher of vitrinite ,the combustibility became lower.With the analyze about the photo of coke we found that different maceral form different structure coke and different coke structure blending relevant to different maceral blending. In the resident of coal burned, the tiny changed coal, anisotropism, block, break up, porework come from the vitrinite of the coal, but the cranny and framework come from the fusinite, the dash came from the mineral in the coal. Vitrinite is the main source of UPC under the condition about BF tyuere injection.The coal combustibility in the condition of BF tyuere injection is related to its maceral component, rational maceral component could improve about 30% of the combustibility and make a very advantaged condition for improve the coal rate greatly. The content of coal about vitrinite 35% and fusinite 60% has the highest combustibility.