Exergy Analysis of Charcoal Charging Operation of Blast Furnace

Nogami, Hiroshi; Yagi, Jun‐ichiro; Sampaio, Ronaldo Santos

doi:10.2355/isijinternational.44.1646

Cited by 34 publications

(25 citation statements)

References 14 publications

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“…[9][10][11] Others have estimated that charcoal injection rates of 200-225 kg/t-HM may be feasible for large BFs. 12,13) Mathieson et al 6) conducted a heat and mass balance study to estimate BF performance using various biomassderived solid (torrefied wood and charcoal types) and liquid injectants (ethanol, biodiesel) in comparison with conventional coal types (from lignite to anthracite). At an injection rate of 140 kg/t-HM, the study predicted that normal low-ash charcoal types have high replacement ratios, producing calculated decreases in coke and fuel rates of at least 20 kg/t-HM, compared with the injection of a conventional high volatile matter (VM) coal.…”

Section: Introductionmentioning

confidence: 99%

Reducing Net CO2 Emissions Using Charcoal as a Blast Furnace Tuyere Injectant

Mathieson¹,

Rogers²,

Somerville

et al. 2012

ISIJ Int.

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The replacement of coal-based fuels by renewable fuels such as charcoal is an attractive way to reduce net greenhouse gas emissions from the integrated steelmaking route. Our previous studies have indicated that the potential for savings in net CO2 emissions ranges from 32 to 58 percent, with use as a BF tuyere injectant being the largest application. The current study considered the combustibility of four types of charcoal in comparison with PCI coal under simulated BF raceway conditions. The major findings were that burnouts under standard conditions (air-cooled coaxial lance, O/C = 2.0) were comparable or better than that of the high volatile matter PCI coal studied, and a comparison with the trend line for burnout with injectant volatile matter previously established for coals, indicated that the hardwood charcoals studied had burnouts 40% (abs) higher than those of equivalent coals, and the softwood charcoal studied was higher again. A study of the effects of oxygen enrichment indicated that small increases were effective, and particularly so for the least combustible charcoal. Overall, the burnout results indicated that higherthan-coal injection rates should be possible in industrial practice, and in combination with the previous heat and mass balance results, they indicated the potential for increased BF productivity. The brief study of the combustion of coal-charcoal mixtures indicated good combustibility and predictable burnouts. The microscopic examination of both the charcoal injectants and their combustion chars indicated that there was significant fragmentation of the charcoals during combustion, boosting their already high surface areas and combustibility.

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Section: Introductionmentioning

confidence: 99%

Reducing Net CO2 Emissions Using Charcoal as a Blast Furnace Tuyere Injectant

Mathieson¹,

Rogers²,

Somerville

et al. 2012

ISIJ Int.

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show abstract

“…While the potential use of charcoal in various stages of steel production have been investigated both conceptually 8) and experimentally, e.g. sintering, 5,9) iron ore reduction, 10) very little has been published on the environmental and economic aspects of charcoal use in steelmaking.…”

Section: Introductionmentioning

confidence: 99%

Environmental and Economic Aspects of Charcoal Use in Steelmaking

2009

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The use of charcoal as a fuel and reductant in ironmaking and steelmaking in place of fossil fuel-based carbon sources has been assessed from both an environmental and economic point of view. Life cycle assessment methodology has been used to indicate potential reductions in greenhouse gas emissions resulting from charcoal substitution rates up to 100 % in the integrated, direct smelting and mini-mill routes for steelmaking. The results indicated that based on typical costs of charcoal and coal, charcoal is not competitive with coal in the steelmaking applications considered. However, the introduction of a carbon trading scheme or carbon taxes can be expected to improve the competitiveness of charcoal compared to coal. Based on a long-term price of $US90/t for metallurgical coal, a carbon tax in the order of US$30-35/t CO 2 would be required with the direct smelting and integrated routes for the overall charcoal and coal costs to be roughly equal, including a charcoal electricity co-product credit. However, if the recent increase in price of metallurgical coal is sustained for an extended period of time, the required carbon tax rate would fall to about US$18/t CO 2 .KEY WORDS: charcoal; steelmaking; life cycle assessment; greenhouse gases; costs; carbon taxes. © 2009 ISIJ Steelmaking and Opportunities for Charcoal UseThe integrated steelmaking route begins with iron ore extracted from the earth. After crushing and screening, the iron ore fines are either sintered or pelletised and then fed into the blast furnace along with iron ore lump. Coke, produced from coal in the coke ovens, is used as a fuel and reductant in the blast furnace together with fluxes to produce pig iron. Natural gas is also commonly used as a supplementary fuel in the blast furnace. The pig iron is transferred to the basic oxygen furnace (BOF) along with steel scrap, where oxygen is used to refine the pig iron into steel by reducing the carbon content.In direct smelting processes, smelting takes place in a single reactor where ore and coal are both charged into the same melt or bath (hence the name "bath smelting"). The processes utilise post combustion of the process offgases, the heat released being transferred back to the bath to compensate for the endothermic smelting reactions. The HIsmelt process produces molten iron utilising fine iron ores (and other iron-bearing fines) and non-coking coals. The iron oxides are rapidly reduced by the bath whilst carbon from the coal dissolves in the bath. The primary product from the HIsmelt process is hot metal (iron). This iron is tapped continuously through an open forehearth and is slagfree. It can be used as direct feed to steelmaking processes or cast into pig iron.The main opportunities for the use of biomass in the integrated route for steelmaking would appear to be:• replacement of coke as a reductant and fuel in the blast furnace; • replacement of coal and natural gas as a fuel in the blast furnace; • replacement of coke as a fuel in sintering and pelletising. However, it has been suggested ...

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“…The aim is to reduce the CO 2 emissions to the level where this might be needed in the post-Kyoto period. NOGAMI et al discussed that the injection of fine charcoals into the BFs tuyeres can reduce more than 30% of the net CO 2 emission compared with the traditional ironmaking process 8 .…”

Section: Introductionmentioning

confidence: 99%

Reactivity of brazilian coal, charcoal, imported coal and blends aiming to their injection into blast furnaces

2010

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For about 10 years the steel industry in Brazil has used pulverized coal injection (PCI) technology in the blast furnaces based on imported coals. In order to decrease the dependence on imported coals, Brazilian coal, which has limited use due to high ash content, was suggested to be mixed with imported coal and charcoal. The aim was to examine the reactivity of the samples. The charcoal use in the steel industry contributes to the CO 2 emission reduction, since it represents a renewable source of energy. The reactivity of the coals, charcoal and mixtures was evaluated through simultaneous thermal analyses. Results of this study are presented and discussed.

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Exergy Analysis of Charcoal Charging Operation of Blast Furnace

Cited by 34 publications

References 14 publications

Reducing Net CO2 Emissions Using Charcoal as a Blast Furnace Tuyere Injectant

Reducing Net CO2 Emissions Using Charcoal as a Blast Furnace Tuyere Injectant

Environmental and Economic Aspects of Charcoal Use in Steelmaking

Reactivity of brazilian coal, charcoal, imported coal and blends aiming to their injection into blast furnaces

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