Novel technique for assessing the burnout potential of pulverized coals/coal blends for blast furnace injection

Tiwari, H. P.; Das, Arijit; Singh, Uttam

doi:10.1016/j.applthermaleng.2017.11.115

Cited by 19 publications

(9 citation statements)

References 44 publications

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“…The latter is calculated using an equation based on the carbon, hydrogen, ash, and moisture content necessary to achieve a replacement of coke with an equivalent carbon content of 87.5% [4]. In addition, the volatile matter content, which is a measure of the coal thermal pyrolysis products, is known to have an important effect on the blast furnace stability by influencing the gas/char combustion and consumption of oxygen in the raceway region [11,12]. The choice of coals injected in the furnace depend on their availability, cost, and properties and are often used as blends, variations of which can impact the stability [13].…”

Section: Introductionmentioning

confidence: 99%

A Comparison of Laboratory Coal Testing with the Blast Furnace Process and Coal Injection

Steer

Greenslade

Marsh

2021

Metals

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The injection of coal through tuyeres into a blast furnace is widely adopted throughout the industry to reduce the amount of coke used and to improve the efficiency of the iron making process. Coals are selected depending on their availability, cost, and the physical and chemical properties determined by tests, such as the volatile matter content, fixed carbon, and ash content. This paper describes research comparing the laboratory measured properties of injection coals that were used over a two-month production period compared to the process variables and measurements of the blast furnace during that study period. In addition to the standard tests, a drop tube furnace (DTF) was used to compare the burnout of coals and the char properties against the production data using a range of statistical techniques. Linear regression modelling indicated that the coal type was the most important predictor of the coal rate but that the properties measured using laboratory tests of those coals were a minor feature in the model. However, comparisons of the Spearman’s correlations between different variables indicated that the reverse Boudouard reactivity of the chars, prepared in the DTF from the coals, did appear to be related to some extent to the coal and coke rates on production. It appears that the constant process adjustments made by the process control systems on the furnace make it difficult to identify strong correlations with the laboratory data and that the frequency of coal sampling and the coal blend variability are likely to contribute to this difficulty.

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Section: Introductionmentioning

confidence: 99%

A Comparison of Laboratory Coal Testing with the Blast Furnace Process and Coal Injection

Steer

Greenslade

Marsh

2021

Metals

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“…For the chars shown in Table 4, formed at 35ms in the DTF, the higher coal burnouts give partially burnt chars with higher gasification reactivity. It is expected that at the higher O:C ratio and burnouts the particles reach higher temperatures due to the 'high temperature rapid combustion field' of volatile matter noted by other authors [5,48,49]. In turn the difference in the environment surrounding the particles leads to differences in the type of carbon-oxygen bonding described in Table 4, carbon sp 2 content and higher gasification reactivities.…”

Section: The Relationship Between the Char Properties And Reactivity mentioning

confidence: 88%

“…Other papers have shown how coal burnout varies considerably in the raceway region of the furnace due to the short particle residence time, coal reactivity and the limited oxygen available for combustion [5,28]. Because of this, it is probable that considerable quantities of partially burnt coal chars make their way into the furnace shaft potentially altering the gas flow through the burden and contributing to other competing reactions which will have an important effect on the process.…”

Section: The Relationship Between Burnout and Gasification Reactivitiesmentioning

confidence: 99%

“…There is a trend for those coals with the highest burnout to form chars with higher gasification reactivity (lowest t0.5 time). The raceway formed by the hot blast is characterised by short particle residence times due to the high blast velocities in the order of 180m/s, and research suggests that residence times are typically in the region of 20-50ms [5,28,29]. But it has also been pointed out by other researchers that the gas flow may be very turbulent in this region, and in certain circumstances this could contribute to particle circulation and longer residence times [30].…”

Section: The Relationship Between Burnout and Gasification Reactivitiesmentioning

confidence: 99%

“…This limits the opportunity for coal to combust completely, which can result in limited burnout of the injected coals leading to partially burnt chars being carried into other regions of the furnace or out of the top as dust emissions in the off gas system where they can impact gas permeability through the coke and iron ore burden and thermal stability [2,3]. Much research work has concentrated on the importance of coal burnout reactivity but with respect to combustion [4,5], specifically Kalkreuth et al explained how higher volatile matter coals produce more reactive chars [6]. Work has also been carried out on the effect of those volatiles, by Ross et al [7] and Hayhurst et al [8], who showed how the reaction environment and conditions influence the fuel particle devolatilisation behaviour especially under oxidizing conditions…”

Section: Introductionmentioning

confidence: 99%

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A comparison of partially burnt coal chars and the implications of their properties on the blast furnace process

Steer

Marsh

Sexton

et al. 2018

Fuel Processing Technology

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Blast furnace coal injection is a vital part of modern ironmaking, reducing the amount of coke reductant required in the process and increasing its efficiency. However the injection of different coals or their blends, into the raceway formed by the hot blast, has technical issues due to the very short particle residence times and the limited availability of oxygen in this region. This makes complete burnout difficult and limits the range of coals suitable for this application, leading to partially burnt chars being carried out of the raceway into the blast furnace shaft and potentially into the offgas system. This paper explores the fate of these chars, from a range of different coals, looking at how this influences the selection for injection and the implication of these on the blast furnace. In particular, we have looked beyond the limitations of selecting coals based on proximate analysis alone by examining in more detail other physical and chemical properties and their potential effect on the process. A drop tube furnace (DTF) has been used to synthesise chars in a high heating rate environment, and although burnout and volatile loss values suggest suitability of some coals for blast furnace injection, additional problematic effects have been identified and measured such as char swelling and agglomeration which may impact the gas permeability of the furnace. A TGA/DSC has been used to measure the gasification of chars by the Boudouard reaction and compare the thermal impact of more reactive samples. Whilst other studies have concentrated on the combustion of injection coals to determine their suitability, this one focuses on the implications of the partially burnt chars formed by incomplete reaction in the raceway.

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Blast Furnace: Most Efficient Technologies for Greenhouse Emissions Abatement

Cavaliere

2019

Clean Ironmaking and Steelmaking Processes

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Novel technique for assessing the burnout potential of pulverized coals/coal blends for blast furnace injection

Cited by 19 publications

References 44 publications

A Comparison of Laboratory Coal Testing with the Blast Furnace Process and Coal Injection

A Comparison of Laboratory Coal Testing with the Blast Furnace Process and Coal Injection

A comparison of partially burnt coal chars and the implications of their properties on the blast furnace process

Blast Furnace: Most Efficient Technologies for Greenhouse Emissions Abatement

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