Use of Nut Coke in a blast furnace Apr27

Use of Nut Coke in a blast furnace...

Use of Nut Coke in a blast furnace Metallurgical coke is produced during the carbonization of coking coal blend in a coke oven battery. This coke is produced normally in three size fractions namely coke breeze (size – 10 mm), nut coke (size +10 mm to – 25 mm) and blast furnace (BF) coke (+ 25 mm to – 80 mm).  BF coke is one of the most important factors which affect the economic efficiency of a blast furnace. It also constitutes a great portion of the production costs of the hot metal. The use of nut coke in blast furnace is the essential factor to reduce the costs of iron making. The consumption of the BF coke is strongly related to the CO2 emissions. History Earlier there was no use of nut coke in an integrated steel plant and it was sold to other users. Prof. V. I. Loginov suggested in 1960s to charge nut coke into the blast furnace in mixture with sinter.  Though this idea was successfully tested, yet there was initial resistance to use nut coke in blast furnace. In mid 90s Visakhapatnam Steel Plant started using nut coke in their blast furnaces and soon achieved a monthly specific consumption level of over 50 Kg/tHM. The blast furnace of Neelachal Ispat Nigam Limited which was commissioned in February 2002 achieved by 2004-05 a monthly average specific consumption level of over 100 Kg/tHM. Presently the use of nut coke in blast furnace as a substitute of a part of BF coke is considered as a proven technology and nut coke is being used extensively in blast furnaces all over the world. Modern blast furnaces use nut coke in different amount (10-140 Kg/tHM) and in different size of nut coke (10-40 mm)....

Metallurgical coke

Metallurgical coke Metallurgical coke or Met coke in short is a hard carbon material produced in the process of the “destructive distillation” of various blends of bituminous coal. It is produced by carbonization of coal at high temperatures (1100°C) in an oxygen deficient atmosphere in a coke oven. A good quality coke is generally made from carbonization of good quality coking coals. Coking coals are defined as those coals that on carbonization pass through softening, swelling, and re-solidification to coke. One important consideration in selecting a coal blend is that it should not exert a high coke oven wall pressure and should contract sufficiently to allow the coke to be pushed from the oven. The properties of coke and coke oven pushing performance are influenced by following coal quality and battery operating variables: rank of coal, petrographic, chemical and rheologic characteristics of coal, particle size, moisture content, bulk density, weathering of coal, coking temperature and coking rate, soaking time, quenching practice, and coke handling. Coke quality variability is low if all these factors are controlled. The coal-to-coke transformation takes place as follows: The heat is transferred from the heated brick walls into the coal charge. From about 375°C to 475°C, the coal decomposes to form plastic layers near each wall. At about 475°C to 600°C, there is a marked evolution of tar, and aromatic hydrocarbon compounds, followed by re-solidification of the plastic mass into semi-coke. At 600°C to 1100°C, the coke stabilization phase begins. This is characterized by contraction of coke mass, structural development of coke and final hydrogen evolution. During the plastic stage, the plastic layers move from each wall towards the center of the oven trapping the liberated gas and creating in gas pressure build up which is transferred to the heating...