Release Behaviour of Boron during Heat Treatments of Coals

摘要

In a series of studies on coal cleaning, the forms and distribution of boron in coal, and the release behaviorof boron from coal during pyrolysis and gasification were investigated by using 7 types of coal with differentcoal ranks. The sequential leaching of the sample coals by using H_2O, CH_3COOH, and HCl solutions showedthat the content of H_2O soluble boron has an inverse correlation with coal rank. The analysis of the densityseparated coals showed that boron is unevenly distributed in the low density fraction of coal. The releasebehavior of boron was found to vary according to the type of coal during pyrolysis at temperature in therange of 200-1200°C. On the basis of this behavior, boron was classified into 2 group: one group thatreleased boron at temperatures below 900°C and the other group that released boron at temperatures above900°C. No appreciable volatilization was observed for boron during gasification of pyrolyzed chars.