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

Steer, Julian Mark, Marsh, Richard, Sexton, D and Greenslade, M. 2018. A comparison of partially burnt coal chars and the implications of their properties on the blast furnace process. Fuel Processing Technology 176 , pp. 230-239. 10.1016/j.fuproc.2018.03.027

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Abstract

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 off-gas 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. While 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.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Engineering
Publisher: Elsevier
ISSN: 0378-3820
Date of First Compliant Deposit: 19 April 2018
Date of Acceptance: 24 March 2018
Last Modified: 06 Apr 2019 01:52
URI: http://orca.cf.ac.uk/id/eprint/110683

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