Magnesia Additive Performance in Oil Fired Boilers -Kinetics of the MgO/SO₃ Reaction

Abstract

Magnesia powder injected into the flue gas airheater inlet (or outlet) on oil-fired power plant is being evaluated as a possible palliative to H₂SO₄ deposition and acid smut emission problems. This paper considers laboratory scale and theoretical work aimed at quantifying one of the mechanisms influencing additive performance, namely the reaction between sulphuric acid vapour and magnesia particles suspended in the flue gas. The model derived lo describe the sulphation kinetics has been usedto estimate the amount of acid vapour likely to be neutralized by commercial additives. The results have been compared with measurements of H₂SO₄ vapour depletion between the airheater and stack of a 500 MW(e) unit. This work provides guidelines for estimating the extent of the reduction in sulphuric acid vapour concentrations which may be attained provided that the additive powder residence times and size spectrum are well established