Blast Furnace Report

7/27/2019 Blast Furnace Report

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Utilizing the blast furnace in an efficient way can help the future of steel makingproduction. The blast furnace is utilized as a means to take in a feed of iron ore, coke, andfluxes (such as limestone to remove impurities) and allow a reaction between burningcoke and the iron ore. As the coke burns due to inserted air, CO is formed and reacts withthe iron ore (which is heated to melt). A series of reductions of the iron ore takes place

due to the presence of near-pure carbon (coke) and this results in the production of ironmetal. Higher quality of raw materials leads to optimal results form the blast furnace.Hence, the carbon content of the coke is important in terms of how the quality of the hotmetal. About 65% of todays steel-making processes utilizes the blast furnace approach.Steel produced in the blast furnace cost $700/t, which is less expensive than the electricarc furnace.

During the production of steel, the iron making process (the operation of the blastfurnace) is the step with the greatest CO2 emission value. The products of the blastfurnace are molten metal, slag, and flue gases that leave the furnace. The flue gascomprises of 20-28% CO, 1-5% H2, 50-55% N2, 17-25% CO2, some sulpher and cyanide

compounds, and a lot of dust from impurities of coal and the iron ore

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. Depending on thefurnace, the production the flue gas ranges from about 1200-2000 Nm3/t pig iron.

The Corex process utilizes the most recent method of producing pig iron, which is smeltreduction. This process combines the gasification of coal with the melt reduction of ironore. This process also utilizes non-coking coal, which takes away the need for a cokingplant. No coke ovens mean elimination byproducts of coal tar. No dust problemsassociated with blast furnaces since the export gas in the Corex process is used as fuel(electricity/other heating purposes). Corex utilizes lumpy ores as raw material instead offine pieces, which takes away the need for a sinter plant. A briquetting machine is alsoused for the fine ores that are remaining to utilize them as well.

To understand how these processes work, we take a look at the materials consumed andcompare them to see which works better or worse. We look at a specific furnace from aplant in JSW Steel Ltd, which shows the consumption of raw materials between theCorex and Blast Furnace processes 11.


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We also have the following thermal and electrical balance (for 1Mtpa hot metal) in thefollowing tables respectively, also by SIEMENS VAI 12,

They also provide information on the CO2, declaring less than 1, 250 kg/tiron12.

We can compare the Corex process to the SSAB Tunnplat AB steel plants Blast furnacesystem. They provide the CO2 emission factor used for indirect emissions from processesoutside the system boundary (kg CO2/t). They also demonstrate the CO2 emissions forvarious cases of changed production practices and integration of new equipment.

We have the outside boundary emissions,


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the schematic of the different process routes taken,

the processes taken,

and the summarized emissions,


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, along with the route alternatives

we see a large difference from the max and min of the Corex route due to the usagerecovery possibilities of the export gas. By replacing the BF with the Corex, we see aCO2 emission of 2580-3500 kg/t steel. The big difference is due to the use of completelydifferent raw materials 9.

The Finex process is another smelting reduction technology based on the direct use ofcoal and fine ore. This process utilizes low-grade ore and low ranked coal making it morecost efficient. Finex eliminated the need for a sinter and coking plant since it uses non-coking coal. There is a direct input of non-coking coal into a melter-gasifier afterbriquetting as well as input of the remaining fine ores through a series of fluidized beds.Siemens Vai gives a detailed presentation on the performance of the Finex technologyand proved a comparison between the Finex process, the Corex process, and thetraditional Blast Furnace.

The operational performance is given of a 1.5M Finex plant as of Mar. 2008 14,


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The Finex process leads to lower coal consumption due to off gas recycling with CO2(less than 700kg/thm of coal consumption) 14.

The CO2 removal equipment from the off-gas is brought out at 0.7-1.0 bar.g splitting 2

ways, one way to the power plant and another through a series of filters leading back tothe fluidized bed reactors. Here is a schematic 14,

The following results have been made available as well,a) The off-gas composition is 36% CO, 33% CO2, 15% H2, and 11% N2 (this is theamount that will be recycled from the process)b) The product has comprises of 53% CO, 3%CO2, 25% H2, and 18%N2 (this will goback in to the reactors and as we see, the CO composition is high as required for the

reducing gasc) The tail gas comprises of 17% CO, 66% CO2, 4%H2, and 3%N2

The total energy gain due to the removal of CO2 and the off gas utilization give thefollowing results 14,a) After the product gas reenters the reactors we have 1190 Mcal/thm and 710Mcal/thmused for reduction, which leaves a 480 Mcal/thm recoveryb) There is a 170 Mcal/thm consumption of electricity for compressing the gasc) Leaving a Final Gain by CO2 removal of 310 Mcal/thm

Using the BF (greenfield 3.0MT) and the FINEX (greenfield 1.5MT) an Energy Balancestarting with 720kg/t 14,a) The combined cycle power plant energy consumption for the BF is 180Mwh and297Mwh for FINEXb) 92Mwh is recycled back in the Finex process compared to 48Mwh for the BF


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c) Coke Dry Quenching and the Top pressure recovery turbine gives off 17MWh in theBF and the TRT and heat recovery steam generator gives off 15MWh in Finexd) The 15Mwh and 17MWh join with 110MWh and 94MWh to give 113Mwh and 125MWh , respectively, of electrical powere) The air separation unit recycles 95MWh and 38MWh for Finex and the BF

respectively

We have the following life cycle assessment of dust, SOx, and NOx emissions by theCorex, Finex, and BF 13,

We observe that the Corex and Finex technologies reduce emissions that the blast furnaceotherwise does not by a significant amount. The Corex and Finex technologies seem to be

in par with each other and the traditional blast furnace route seems to be at a loss.

A further life cycle assessment shows the following danger potentials at certain impactcategories 13,Acidification Potential - Corex route shows the most danger for this area of danger andthe BF and Finex route show little to no dangerAbiotic resource depletion - The Blast Furnace route shows the most danger followed byfinex and then corex; all show a significant depletion potential

Global Warming potential - All show a significant amount of gw potential with the BFroute taking the lead

Photochemical Ozone creation - The finex route shows no sign of this, but the BF routeand Corex route show a significant potential of this dangerEutrophication potential - Only the BF and Finex route show a little potential for thisdanger, but not really that significant


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Based on a 1998 Eco Tech plant of the International Iron and Steel Institute, we have thefollowing energy intensity values of the processes from the material preparation to theend of the blast furnace processes. This data is based on the assumption that 1.389 tneeded to produce 1 t hot rolled steel 8. We see that most of the energy is consumed infueling the furnace.

Based on the Corex plant at POSCOs Pohang site in Korea, we have the followingenergy intensity values from the material preparation to the iron making 8. We observethat most of the energy is consumed fueling the furnace and is higher than the blastfurnace at the Eco Tech plant.


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Blast Furnace Report