Comparative Study of Sorbents for Spray Dry Scrubbing of SO2 from Flue Gases

Lawrence Koech; Raymond C Everson; Burgert Hattingh; Hilary Rutto; Letsabisa Lerotholi; Hein Wjp Neomagus

doi:10.1021/acsomega.3c00064

Comparative Study of Sorbents for Spray Dry Scrubbing of SO₂ from Flue Gases

ACS Omega. 2023 Jun 23;8(26):23401-23411. doi: 10.1021/acsomega.3c00064. eCollection 2023 Jul 4.

Authors

Lawrence Koech^{1

2}, Raymond C Everson¹, Burgert Hattingh¹, Hilary Rutto^{1

2}, Letsabisa Lerotholi^{1

2}, Hein Wjp Neomagus¹

Affiliations

¹ 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.
² Department of Chemical and Metallurgical Engineering, Vaal University of Technology, Vanderbijlpark Campus, Private Bag X021, Vanderbijlpark 1900, South Africa.

Abstract

This study presents the findings of an investigation involving the absorption of SO₂ from flue gases, using three different sorbents, in a spray dryer. Experimentation involved the evaluation of three sorbents, i.e., hydrated lime (Ca[OH]₂), limestone (CaCO₃), and trona (Na₂CO₃·NaHCO₃·2H₂O), and their relevant properties, for flue gas desulfurization by spray dry scrubbing. Experiments were conducted to explore the effects of spray characteristics in the spray drying scrubber on SO₂ removal efficiency using the selected sorbents. The ranges of various operating parameters were considered, including the stoichiometric molar ratio of (1.0-2.5), the inlet gas phase temperature of (120-180 °C), and an inlet SO₂ concentration of 1000 ppm. The use of trona gave better SO₂ removal characteristics; a high SO₂ removal efficiency of 94% was recorded at an inlet gas phase temperature of 120 °C and a stoichiometric molar ratio of 1.5. Under the same operating conditions, Ca[OH]₂ and CaCO₃ gave 82 and 76% SO₂ removal efficiency, respectively. Analysis of the desulfurization products by X-ray fluorescence (XRF) and Fourier transform infrared (FTIR) spectroscopy revealed the presence of CaSO₃/Na₂SO₃, a product of the semidry desulfurization reaction. A significant proportion of unreacted sorbent was observed when Ca[OH]₂ and CaCO₃ sorbents were used at a stoichiometric ratio of 2.0. Trona also gave the highest degree of conversion (96%) at a stoichiometric molar ratio of 1.0. Ca[OH]₂ and CaCO₃ gave 63 and 59%, respectively, under the same operating conditions.