Experimental evaluation of lime spray drying for SO<sub>2</sub> absorption

Lawrence Koech; Hilary Rutto; Tumisang Seodigeng; Lawrence Koech; Hilary Rutto; Tumisang Seodigeng

doi:10.3934/environsci.2023019

AIMS Environmental Science

2023, Volume 10, Issue 3: 325-340. doi: 10.3934/environsci.2023019

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Research article

Experimental evaluation of lime spray drying for SO₂ absorption

1.
Department of Chemical and Metallurgical Engineering, Vaal University of Technology, Vanderbijlpark Campus, Private Bag X021, 1911, South Africa
2.
Eskom Power Plant Engineering Institute (EPPEI) Specialization Centre for Emission Control, School of Chemical and Minerals Engineering, Centre of Excellence in Carbon-based Fuels, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa

Received: 26 December 2022 Revised: 02 April 2023 Accepted: 04 April 2023 Published: 17 April 2023

This paper presents the findings of an experimental investigation on the performance of a laboratory-scale spray dryer involving flue gas desulfurization. Using commercial hydrated lime as a sorbent, a systematic set of experiments were performed to evaluate SO₂ absorption capacity of the spray dryer. The experimentation involved accurate measurement of the spray drying characteristics, such as temperature and SO₂ concentration along the spray chamber, by varying the input and output variables. Tests were done to investigate the effects of spray characteristics, i.e., inlet gas phase temperature (120–180 ℃) and calcium-to-sulfur ratio (1–2.5), on SO₂ removal efficiency. The performance of the spray dryer was further evaluated based on the degree of conversion of calcium (sorbent utilization) after SO₂ absorption. Results indicated an increase in SO₂ removal efficiency by increasing the stoichiometric ratio and decreasing the temperature. Absorption efficiency of SO₂ beyond 90% was achieved at a stoichiometric ratio of 2.5. A high degree of conversion of calcium was realized at low stoichiometric ratios, with a maximum utilization of 94% obtained at a stoichiometric ratio of 1.5. The analysis of the final desulfurization product revealed the presence of sulfite with better conversion achieved at a stoichiometric molar ratio of 1.5. A significant amount of unreacted sorbent (63.43%) was observed at a stoichiometric ratio of 2, while samples collected at a stoichiometric ratio of 1.5 had the lowest concentration of unreacted Ca[OH]₂ (41.23%).
- spray drying absorption,
- hydrated lime,
- desulfurization,
- SO2 in air,
- sorbent conversion
Citation: Lawrence Koech, Hilary Rutto, Tumisang Seodigeng. Experimental evaluation of lime spray drying for SO2 absorption[J]. AIMS Environmental Science, 2023, 10(3): 325-340. doi: 10.3934/environsci.2023019

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Abstract

This paper presents the findings of an experimental investigation on the performance of a laboratory-scale spray dryer involving flue gas desulfurization. Using commercial hydrated lime as a sorbent, a systematic set of experiments were performed to evaluate SO₂ absorption capacity of the spray dryer. The experimentation involved accurate measurement of the spray drying characteristics, such as temperature and SO₂ concentration along the spray chamber, by varying the input and output variables. Tests were done to investigate the effects of spray characteristics, i.e., inlet gas phase temperature (120–180 ℃) and calcium-to-sulfur ratio (1–2.5), on SO₂ removal efficiency. The performance of the spray dryer was further evaluated based on the degree of conversion of calcium (sorbent utilization) after SO₂ absorption. Results indicated an increase in SO₂ removal efficiency by increasing the stoichiometric ratio and decreasing the temperature. Absorption efficiency of SO₂ beyond 90% was achieved at a stoichiometric ratio of 2.5. A high degree of conversion of calcium was realized at low stoichiometric ratios, with a maximum utilization of 94% obtained at a stoichiometric ratio of 1.5. The analysis of the final desulfurization product revealed the presence of sulfite with better conversion achieved at a stoichiometric molar ratio of 1.5. A significant amount of unreacted sorbent (63.43%) was observed at a stoichiometric ratio of 2, while samples collected at a stoichiometric ratio of 1.5 had the lowest concentration of unreacted Ca[OH]₂ (41.23%).

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