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Application of the Fuller-Thompson equation in sinter blend design to increase sinter plant productivity

Purnell, Alex 2017. Application of the Fuller-Thompson equation in sinter blend design to increase sinter plant productivity. EngD Thesis, Cardiff University.
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Abstract

TATA Steel Europe are the second largest steel producers in Europe (2015) with operations focused in the UK and Netherlands. The sintering process is an upstream process in the iron and steelmaking chain to create part of the blast furnace burden. A blend of raw materials composing of iron ore, flux, coke breeze and revert materials are sintered on a moving strand to produce an iron rich, strong and porous agglomerate known as sinter. Before sintering, the blend is processed through a mixer and granulator to create granules, which enhances sinter bed permeability. Sinter bed permeability is the driving factor behind sinter strand productivity. Differing compositions of sinter blends are known to impact the sintering process. More specifically concerned in this study is blend particle size distribution (PSD). A new application of the Fuller-Thompson (FT) equation is proposed, which was originally developed for designing the aggregates in concrete and shown to improve properties like strength. The FT equation determines the PSD to create the maximum particle packing density. The FT equation is applied to sinter blend design through the granulation process. During granulation, finer particles are layered around coarser nuclei particles to produce granules. Designing the finer or layering proportion of sinter blends to the FT equation is proposed to create granules with denser and stronger layers. Thus, enabling greater bed permeability during the process and increased sinter strand productivity. The first phase of the Author’s study determined the parameters of the FT equation that gave the optimum granule beds in terms of ‘cold’ bed permeability and efficiency in maintaining ‘cold’ permeability under an applied motion. These were established to be a maximum layering particle size (D) of 0.5mm and a FT exponent (Y) of 0.5. Bimodal sinter blends were used to study the impact of layering PSD spread (n), which is a relative measure for the uniformity of sizes in the distribution on bed permeability and sintering time. Widening the spread of layering particle sizes increased ‘cold’ bed permeability due to the narrowing in granule size distribution spread and increasing mean granule diameter. With the blends investigated the layering PSD spread of the FT blend gave the greatest ‘hot’ permeability and shortest sintering times, as it maintained more permeability than expected based on the trend with mean granule diameter. Industrial base blends were compared with blends designed to the FT equation. At equal layering particle proportions the FT blends increased ‘cold’ permeability by up to 20% and reduced sintering times by up to 9.5%. The FT blends could also incorporate 4wt% more layering particles and still exhibit the same ‘cold’ permeability and sintering times as the base blends. No changes in sinter quality were observed. Full-scale plant trials with FT blend design at Tata Steel Europe showed positive impacts on ignition permeability, flame front speed and net production rate compared to typically used blends. No changes in sinter quality were identified. The methodology is currently being implemented into sinter blend design practice at Tata Steel Europe.

Item Type: Thesis (EngD)
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Granulation; Iron Ore; Sintering; Particle Size Distribution; Fuller-Thompson; Sinter Blends.
Date of First Compliant Deposit: 1 March 2018
Last Modified: 19 Oct 2019 03:05
URI: http://orca-mwe.cf.ac.uk/id/eprint/109631

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