compare and contrast combustion of phosphorus and wood.
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.Recent studies show that deposit formation and agglomeration in fluidized bed boilers may be aggravated by a high phosphorus content besides alkali metals, chlorine and sulphur in a fuel. This paper presents the fate of phosphorus during co-combustion of wood chips and wood pellets with rapeseed cake pellets, a high phosphorus fuel in a 12MW CFB boiler. 12 hour tests with 12% and 18% (energy basis) of rapeseed cake with wood were performed with and without limestone addition. All fuels were characterised by means of standard fuel analyses combined with chemical fractionation. . Analyses of bed material particle cross-sections showed phosphorus compounds present within a K-silicates matrix between the agglomerated sand particles, indicating direct attack of gaseous potassium compounds on the bed surface followed by adhesion of rich in phosphorus ash particles. Build-up of the deposits took place mainly on the windward side of the probe; where up to 9 wt-% of phosphorus was present. SEMlEDXA shows that rapeseed cake addition caused an increase of K, Na besides P indicating presence of low melting phosphate salts in the deposits. During limestone addition in the deposit samples the increase of CI could be noticed however no significant change in P content was observed. This paper shows that agglomeration and fouling when co-firing rapeseed cake may be linked to its high content of organically bonded phosphorus — phytic acid salts; together with high content of water soluble fraction of alkali metals chlorides and sulphates in the fuel mixture. Keywordsrapeseed cake-co-combustion-phosphorus-agglomeration-fouling