Coke (fuel)

Coke ( coke of English ) is a porous, highly carbonaceous fuel with high specific surface area, which in coking plants preferably of low-ash bituminous coal ( lignite or hard coal) due to heat the absence of oxygen (pyrolysis ) is generated. The disturbing sulfur is separated in high-sulfur coal.

The products of pyrolysis and distillation process occur pyrolysis gases ( coke oven crude gas ), pyrolysis and condensable components ( water, tar, sulfur). The process of converting coal into coke is called coking.

If raw lignite cokes, the result Grudekoks. In the 1960s, the BHT process was developed in the GDR because of lack of hüttenfähigem coke. This lignite briquettes are carbonized to produce a blast furnace grade coke from the actually unsuitable lignite.

Coke from coal is used in particular as fuel and as a reducing agent in iron production in blast furnaces. Coal itself is not suitable for this, as are free when they burn too much sulfur, soot and smoke. This contaminates the one hand the iron recovered, and also results in a relatively porous carbon layer in the blast furnace, which quickly breaks under the weight of overlying layers and thus leads to poor mixing.

The process of coking coal to coke takes place in special industrial plants, which are known as coking. The volatile components of the coal are removed by heating in an oven under the exclusion of air at more than 1000 ° C, so that the fixed carbon and residual ash fusion. The volatile components of the coal, however, are expelled and form the coke oven crude gas. Other valuable materials are extracted from the raw coke oven gas, especially coal tar, crude benzene, sulfuric acid and a fuel gas ( coking clean gas ), which was formerly used as town gas and today in any steel works is a valuable energy source.

The coking was developed in 1713 in England, in 1740 the blast furnaces were charged with coke here, an invention of Abraham Darby. In 1796 for the first time in Germany, coke used in Upper Silesia Gliwice for blast furnace firing. In the Ruhr area, the first coke blast furnace 1849 approached, however was processed here ( at Zeche Salzer and Neuack ) as early as 1816 coal into coke. Previously, charcoal was used in the blast furnaces.

Coke is after the erase-before ( cooling with water) in a grain size of about 0 to about 200 mm. Depending on the application area is coke - possibly after breaking - are classified in cokes by sieving. A distinction is made between blast furnace coke, Coke nut and coke breeze. The blast furnace coke ( HK) is in the varieties HK 1 (> 80 mm), HK 2 (> 60 mm), HK 3 (> 40 mm) and HK 4 divided ( > 20 or 25 mm). Today, the variety HK 4 is the common Hochofenkokssorte, the lower grain boundary at 20 and the top is set at 100 mm. The Coke nut (RK ) is in the varieties RK 1 ( 100-60 mm), RK 2 ( 60-40 mm), RK 3 ( 40-20 mm), RK 4 ( 20-10 mm) and RC 5 (10 - 6 mm ) was prepared. Coke breeze usually has a grain size of 10-0 mm.

For firing in the household Coke nut 2 or 3 crushed coke is common. For small grain falls through the grate, too much grain can hinder slipping.

In metallurgy, a distinction metallurgical coke, foundry coke (which is slightly longer coked at a lower temperature ) and Special types, as well as Bergwerkskoks ( from coal ) and lignite.

Coke has a calorific value of 23-31 MJ / kg.