The effect of limestone particle size on sulphur dioxide retention in a fluidized bed combustor

Abstract

This paper reports on the effect of limestone particle size and operating parameters on the reduction of sulphur dioxide emissions in a fluidized bed combustor operating under unstaged combustion conditions. The experimental rig consisted of a stainless steel combustor, 2 m high and 0.3 m square in section. The experiments were carried out at overall fluidizing velocities between 1–2 m/s, bed temperature 830–880°C, 20–40% excess air level, bed particle size of 665 μm and limestone particle size between 0.8–3 mm mean diameter. An uncooled sampling probe located at the cyclone exit was used to determine sulphur dioxide. The results showed that the bed temperature had the most significant effect on sulphur dioxide retention. An increase in excess air level and decrease in limestone particle size resulted in an increase in sulphur dioxide reduction. Over 70% reduction could be achieved using coarse (1–2 mm) limestone under unstaged combustion conditions.