OCR Text |
Show The internal and external layer of the Colombian ash deposit do not show any stratification; chemical composition, taking into account chemical analysis error, appears to be the same. We could not infer that some segregation of components could eventually happen after long exposure due to oxigen partial pressure changes and phase modification. For sure, three hours were not long enough to produce significant differentations. The observed greater stickiness of the Colombian deposi t cannot be explained with alkali content, which is low and equal in both fuels. We compared the visual observations with the few fouling and slagging indexes suggested in the Ii terature to see if they matched. Iron-to-calcium and iron-to-dolomi te ratios, dolomi te percentages and Attig and Duzy slagging factors /2/, /8/, /9/, /10/, /11/, are all means of assessing the influence of iron and calcium on the fusibility of coal ash and on slagging tendency. I.rcn/ calci un I.rcn/IX:>lani te IX:>lanite A ttig and f?}.IZY Fe 0 Fe 0 2 3 --2 3 CaO+-r.1gO Base *S Silica *100 CaO CaO+t-1gO Fe 0 ~lgJ+Na OtK 0 Acid Alunina 2 3 2 2 Colombian 3.77 2.10 25.81 0.14 3.16 coal South African 0.77 0.51 55.13 0.22 1.4 coal A ttig and Duzy /2/ al so proposed two foul ing factors to express the fouling tendencies of coals. |