OCR Text |
Show of iron compound accumulation and to reduce the accumulation of iron compounds on the furnace floor. II. CHEMICAL REACTIONS OF IRON COMPOUNDS IN THE BURNING COAL Iron in coal is usually in the forms of FeS- and FeS. They are partially reduced during combustion to become free iron because of the presence of CO. The possible routes for the formation of free iron are (A) C + 02 ^s C02 CO + C ^ 2C0 2FeS2 + 6.5 02 + S~Fe203 + 5S02 [1] so2 +io2^ so3 Fe20 + 3C0 - ^ 2Fe + 3C02 (B) FeS + CO -5=^C0S + Fe [3] However, from the study of the properties of the slag from the Big Bend Power Plant of Tampa Electric Co., it is found that the specific gravity of the slag is 4.93, and its paramagnetic property is much weaker than that of pure iron. Because the specific gravity is different for different substances, it is a reliable method for the determination of an unknown substance from the measurement of its specific gravity. From 51st Handbook of Chemistry and Physics published by The Chemical Rubber Co., the specific gravities of iron and its compounds are found to be 7.86 for Fe, 4.74 for FeS, 5.0 for FeS and 5.24 for F e ^ . From this, it is easily seen that the iron in the coal ash is still mostly in the pyritic form. This fact is further supported by the paper by Wright and Roffman (1976) [2]. That means, during the combustion of coal, most of FeS? and FeS do not have the chemical reactions stated above. III. THE REDUCTION OF IRON ACCUMULATION ON THE FURNACE FLOOR Two general approaches may be considered to reduce the accumulation of iron on the furnace floor. One way is to let the pyrites to converted completely into Fe203 which can be carried away by exhaust gas as flying ash. Another way is to melt the ashes completely and let them flow out of furnace through the exit hole on the floor. In order to carry out the first method, the coal particles must stay in the air for a long period that will allow the particles containing 3 |