Imfluehcimo of the Plastic Properties of Steam Coal by Means of Setumisous Additives

Summary

It is a well-known fact that when coal has a low gas content and inadequate coking capacity the coke quality can be considerably improved by adding binding agents such as pitch, bitumen or asphalt. It is generally assumed that the additive acts by increasing the plasticity of the “molten coal” during pyrolysis.

The present report provides results of laboratory studies of blends of steam coal and various types of carbo-pitch and petro-pitch as well as bitumen extract from the same coal* It examines the changes in:

• Gieseler plasticity

• dilatoaeter readings

• Roga Index.

• both types of bitumen increase dilatation, but oil bitumen is less effective than solid bitumen

• oil bitumen lowers the Roga Index whereas solid bitumen increases it.

In order to establish the effect of bitumen extracted from the same coal on the coking properties, the influence of both bitumen removed and bitumen addition is examined. The findings show that the pressure extraction treatment for obtaining the coal extract causes much greater changes in coking behaviour than actual bitumen removal.

Comparative tests with the oil bitumen and solid bitumen isolated from steam coal bitumen show that

• both types of bitumen increase dilatation, but oil bitumen is less effective than solid bitumen

• oil bitumen lowers the Roga Index whereas solid bitumen increases it.