Literature Survey on Non-Recovery Coke Ovens

The aim of the project is understanding the coal quality and operational factors which affect coke quality in non-recovery coke ovens and to investigate means of ameliorating inferior coking behaviour.

Coke is primarily consumed by the steel industry where it is the principal fuel used in the production of molten iron in blast furnace. Coke also serves as a porous supporting medium in the blast furnace to allow circulation of hot gases and percolation of molten material. It also provides the reductant for the oxide burden.

Over the last 100 years, the by-product oven, which produces both coke and by-products of tar, pitch, light oil, ammonium phosphate or sulphate, has been the dominant coke making technology in the industrialised world. However, several factors have led to a re-evaluation of other methods of producing coke. The reasons for the re-evaluation of these technologies are complex and include a possible future coke shortage, environmental concerns, occupational health and safety issues and lower prices for by-products.

It was predicted in the recent years that the coke shortages would occur worldwide. It is, however, interesting that the predictions for coke shortages have so far not been fulfilled. There is currently a surplus world supply of coke in the order of 40 million tonnes. This is partly the result of the collapse of the steel industry in the United States where total blast furnace iron production decreased 50% from 1978 to 1986. As a result from 1980 to 1990 approximately 40% of cokemaking capacity in the United States was shut down. Also since 1990, China increased exports of coke by almost 400% to 4.7 mty. In Europe there is currently a slight excess in capacity. In Japan and other parts of Asia, there is an excess of relatively recently installed capacity. Finally, throughout the world, modern coke oven repair technology, such as ceramic welding, is extending the life of batteries beyond what was previously believed possible.

Particularly in the United States and Europe the re-evaluation of methods of coke making, is also being pushed because of public concern about the environmental, and occupational health and safety problems that by-product ovens create. This concern has been expressed in the United States with the introduction of the 1990 Clean Air Act Amendments. The act considers coke oven plant emissions as hazardous air pollutants. The output of these must be lowered to prescribed limited by 1998. Attaining these standards will require expenditure of several million dollars per battery. Austria and the Netherlands have even tighter restrictions currently in place.

Finally, the value of by-products has constantly decreased over the recent years. This has been the result of the petrochemical industry developing processes to produce many of the same products as by-product plants, but at higher purity levels.