Seja a primeira pessoa a gostar disto
This paper is an update of a previous publication in Spanish . One of the current trends in the production of
metallurgical coke is the comeback of non-recovery ovens. This is driven by less interest in byproducts, smaller investment per annual ton, better environmental performance. The development took place particularly in China, India, USA, Brazil, Australia and Colombia . In the USA, one important factor promoting this technology was that EPA declared it as Maximum Achievable Current technology in 1990. This technology arises from the classic beehive ovens which supplied since the XVIII century the coke for the industrial revolution. Those ovens were manually operated, with small heat recovery, just for heating the oven. Now, non-recovery ovens are modern construction, with highly mechanized operation, and automated to a certain degree. Gases generated by the combustion of the volatile matter are sent through downcomers and further burnt to heat the oven bottom and sides; in many cases, mostly when the plant is built within or closed to a steelmaking facility, the hot gas is used for vapor generation and electric power production. Main differences between conventional and non-recovery/heat recovery processes are shown in figure 1. In conventional process, the coal charged receives the heat indirectly through the furnace walls, by combustion of external gas; inside the oven, positive pressure develops. Gas generated in the coking process is sent to the
by-products plant. In non-recovery ovens, coking proceeds from the top through direct heating by the partial
combustion of the volatile matter over the coal bed, and from the bottom by heat coming from full combustion of gases escaping from the oven. In these plants, the offgas is treated and sent to the stack, in many cases after recovering sensible heat to produce vapor and electric power. Installed capacity for these furnaces was esteemed in 2005 in 22 M metric tons per year, probably including
beehive ovens . In table 1, some of the non-recovery coke plants currently operating are listed. Some plants
belong to companies with coal mining as its core business; others are independent coke producers, purchasing coal and selling coke; then there is some joint ventures between coke producers and steelmakers,
and finally, captive coke plants belonging to steel companies.