Blast furnace heat balance

Rist, A and Meyson, N, 1967. A dual graphic representation of blast furnace heat and mass balances. Journal of Metals, 19 50-59. 

Thermochemistry. From an overall heat and mass balance point of view, the main chemical reactions of the blast furnace include oxidation of carbon in the zone in front of the tuyeres (raceway) to give CO plus heat. 

Mass and energy balances are used to evaluate blast furnace performance. Many companies now use sophisticated computeri2ed data acquisition and analysis systems to automatically gather the required data for daily calculation of the mass and heat balances. Typical mass and heat balances are shown in Figure 4 and Table 5, respectively. 

A heat balance for the blast furnace produced by Michard et al. (1967), shows tlrat nearly 80% of the heat generated in tire furnace is used to produce and melt the iron and slag. The gas which emerges from tire first zone is further used to pre-heat the ah injected in the tuyeres in large stoves. The process thus runs at a vety high efficiency, botlr from tire point of view of tire amount of metal and slag produced and from the heat generation and utilization. 

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Calculation of the heat balance results in the stated heat transfer efficiencies. The cold blast cupola shows an efficiency of <30 %. The application of oxygen or secondary air increases the efficiency to 37 - 40 %. The hot blast cupola shows a further increased efficiency, providing the furnace wall is refractory lined. In liningless operation, the efficiency drops below 40 %, which may be somewhat compensated for by adding oxygen. The cokeless cupola with inductive superheating results in a very high efficiency, close to 60 %. 

The heat-balance and chemical changes in the blast-furnace were studied on the basis of Bunsen and Playfair s work by Isaac Lothian Bell (Newcastle on Tyne, 15 February 1816-Northallerton, 20 December 1904), a Durham iron-master who studied in Edinburgh and Paris, F.R.S. 1874, baronet 1885, who published books and important papers on ferrous metallurgy and allied subjects. ... 

Actual fuelling requirements can be established from detailed heat and mass balances for a particular furnace. However, for a typical lead blast furnace, a fuelUng level of 90 kg/t of sinter would appear to be a reasonable figure for efficient operation. If the top gas COiCOj ratio is 0.4 then 2.286 kg of oxygen are required per kilogram of carbon burned. This is supplied by reduction of sinter and by the air blast... 

For the above illustration the overall heat balance for the blast furnace will be as shown in Table 5.4. 

The manner in which carbon is utilised for zinc production is affected by heat balance issues as well as chemical requirements for metal reduction. The heat balance is influenced by the amount of slag produced, the blast preheat and the preheat achieved in coke and sinter. Apart from the quantity of zinc oxide reduced, the chemical factors include the lead and iron contents of sinter and the moisture entering the furnace in blast air and in sinter or additives. Based on typical operating conditions as indicated above and a lead production of close to 50 per cent of the zinc production, the empirical formula used to relate carbon consumption to zinc production is given by Equation 6.1 ... 

Figure 6.5.11 shows the mass and heat balance of a typical blast furnace. The furnace is operated with the injection of 160 kg pulverized coal per t of hot metal (HM). Coke consumption is 326 kg per t HM, and 43 m of oxygen (as air) per t HM are added into the cold blast to achieve a sufficient temperature. The top gas leaves the blast furnace at a rate of 4.75 GJ per t HM. About two-thirds of the gas is... 

Tested super sulfated cements comprise mainly recycled industrial by-products blast furnace slag (Table 1) and heat-activated chemical gypsum, Kerysten K Co (the estimated CO2 balance (excluding transport) is 50 kg/t of manufactured SSC). Tests were conducted on the basis of standard mortar (binder/sand mass ratio = 1/3) with two W/B ratios (0.4 and 0.5), which correspond to characteristics of the old and new standards for SSC. 

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