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The behaviour of mineral matter from pulverised coal injection in the blast furnace raceway

Herbert, Julian 2019. The behaviour of mineral matter from pulverised coal injection in the blast furnace raceway. PhD Thesis, Cardiff University.
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Coal injection into the blast furnace is used as a means of reducing cost, and improving output and energy efficiency. However, the coals injected all contain mineral matter which converts to ash upon heating and has various effects in the blast furnace. Ash investigated in this thesis contained quartz, kaolinite, illite, calcite, dolomite, apatite and gypsum. The elements silicon, aluminium, iron, calcium, potassium, sodium, sulphur, titanium and phosphorus were identified in varying proportions. The behaviour of the ash and elements in the blast furnace is dependent on their relative amounts. It was found that high fusion temperature (FT) occurred due to high levels of silicon and aluminium, found in quartz and clays, whereas low fusion temperatures were related to high calcium and magnesium, found in calcite and dolomite. A drop-tube furnace (DTF) was used to prepare chars from coals and it was observed that the fusion temperature of the char ash increased with temperature and residence time. This was attributed to mullite formation and amorphous material formation in the DTF. The mullite and amorphous material were linked to increased ash fusion temperature. In the DTF, alkali volatilisation generally increased with temperature and residence time. However in low FT ash, it was observed that volatilisation decreased at high residence time for two low FT ashes, thus these ashes were able to retain alkalis. Sulphur release from the ash was found to increase with temperature and residence time in the DTF. Coals containing calcium in the form of carbonate minerals were able to fix sulphur into the ash in the form of anhydrite. Combustion reactivity of ash added to coal was measured using Thermal Gravimetric Analysis (TGA), and found to act as diluent. The effect of ash on coke gasification reactivity was catalytic. Ashes with higher calcium showed higher catalytic behaviour.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: blast furnace; pulverised coal injection; coal mineral matter; drop tube furnace; ash fusion temperature; sulphur volatilisation.
Date of First Compliant Deposit: 7 May 2020
Last Modified: 13 Mar 2021 02:20

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