The Role of Limestone in Preventing Agglomeration and Slagging during CFB Combustion of High-Phosphorous Fuels

Conference poster, 2008

ABSTRACT: This paper presents key observations on the role of limestone in preventing bed agglomeration during combustion of a high-phosphorous fuel in CFB boilers. Composition of the bed material samples was analyzed using X-ray fluorescence, and scanning electron microscope combined with an energy dispersive X-ray analyzer (SEM/EDXA). It has been demonstrated that during combustion of the high-phosphorous fuel in CFB conditions, addition of limestone reduces or prevents bed agglomeration and formation of slag by interfering with the ash chemistry, and not by simple dilution of the reacting system. The role of limestone can be summarized as: 1) to provide calcium for the reaction with phosphorous forming high-temperature-melting calcium phosphates instead of low-temperature-melting potassium phosphates, and 2) to coat silica particles preventing the reaction of potassium (calcium) phosphates and silica from fluidizing sand, which can form low-temperature-melting potassium (calcium) silicates, especially relevant for fluidized bed combustion conditions.