Flue Gas Desulphurization in Circulating Fluidized Beds

• Main Authors: Yimin Deng, Renaud Ansart, Jan Baeyens, Huili Zhang
• Format: Article
• Language: English
• Published: MDPI AG 2019-10-01
• Series: Energies
• Subjects: so₂ abatement; dry or semi-dry reaction; calcium oxide; model; efficiency
• Online Access: https://www.mdpi.com/1996-1073/12/20/3908

Sulphur dioxide (SO₂) is mostly emitted from coal-fueled power plants, from waste incineration, from sulphuric acid manufacturing, from clay brick plants and from treating nonferrous metals. The emission of SO₂ needs to be abated. Both wet scrubbing (absorption) and dry or semi-dry (reaction) systems are used. In the dry process, both bubbling and circulating fluidized beds (BFB, CFB) can be used as contactor. Experimental results demonstrate a SO₂-removal efficiency in excess of 94% in a CFB application. A general model of the heterogeneous reaction is proposed, combining the external diffusion of SO₂ across the gas film, the internal diffusion of SO₂ in the porous particles and the reaction as such (irreversible, 1st order). For the reaction of SO₂ with a fine particulate reactant, the reaction rate constant and the relevant contact time are the dominant parameters. Application of the model equations reveals that the circulating fluidized bed is the most appropriate technique, where the high solid to gas ratio guarantees a high conversion in a short reaction time. For the CFB operation, the required gas contact time in a CFB at given superficial gas velocities and solids circulation rates will determine the SO₂ removal rate.