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Hearth coke bed buoyancy in the blast furnace: experimental study with a 3-dimensional cold model
2006 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The effect of buoyancy forces acting on the hearth coke bed or the “deadman” of the blast furnace has attracted a great deal of interest during recent years of blast furnace research. This thesis presents an effort to elucidate the particle movement patterns connected to formation of a coke free layer in the hearth. In the work, the impact of different pressure distributions on the behaviour of the particle bed was studied with an experimental 3D-cold blast furnace hearth model. The bases for the work were the results from tests along with two different numerical models from a previous study, Hearth coke bed buoyancy, a preliminary investigation, made in 2004 at Bluescope Steel Research, Port Kembla, Australia. In the model, a bed of plastic particles in water were subjected to different pressure distributions, and float-sink motions induced by accumulation and drainage of the water through a valve in the bottom. The results showed that the bed was quite resistant to internal particle movements, when subjected to different linear pressure distributions along the radius. However, previous studies have suggested the downward pressure under the raceways to be severely reduced, and when going below 15:85 in pressure ratio between the peripheral and central area, it was observed that the particles moved internally. As the central load was descending in the bed, upward particle movements were observed along the walls, as well as from the centre towards the walls on the bottom. Particle movements were strongly dependent on the sink-float motions, and moved relative to one another only during drainage, when particles under the central weight moved down faster than under the peripheral reduced pressure area. This mechanism resulted in formation of a peripheral free space in the bottom of the hearth. Addition of an agglomerate of particles to the bottom of the particle bed, resulted in less particle movements and retarded formation of the peripheral free space. Initially it was intended to carry out these tests also numerically using Bluescope Steel’s particle simulation package DPSim. Because of problems with validating DPSim for the application with float-sink motions induced by buoyancy forces, this section was constrained to a sensitivity analysis on the program. The study showed that the float-sink behaviour of the particle bed was insensitive to friction parameter adjustments in the tested range. It was also discovered that the assigned simulation time was of significant importance. This indicates that the common practise of reducing the runtime may not be valid for this application.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Blast furnaces, Hearths, Experimental cold models, Iron, Buoyancy, Deadman, Coke, Iron and steel making, Metallurgy
Keyword [sv]
URN: urn:nbn:se:ltu:diva-55907ISRN: LTU-EX--06/235--SELocal ID: cb6c324b-3812-42c4-ae68-87ffb7b7efb5OAI: diva2:1029291
Subject / course
Student thesis, at least 30 credits
Educational program
Chemical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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