Stamped coal cakes in cokemaking technology: Part 2 – The investigation of cake strength

Coking of coal blends using high volatile coals with poor caking properties to produce a high quality coke for blast furnace application can be achieved by compacting the whole coal blend before the pyrolysis in the so called stamp charge operation. Using stamp charging not only improves the flexibility of the cokemaking plant using cost efficient raw materials, but also increases oven throughput. Therefore, in recent years, densification of coals has been introduced even to coals with good carbonisation properties when heat recovery ovens are used. At the Department for Mechanical Process Engineering and Solids Processing of the Technical University Berlin, the two subprocesses, densification and strengthening during stamping, were theoretically and experimentally investigated. The research work aims on the development of an integrated mathematical model, allowing the calculation of cake density and strength of the coal cake for a given coal blend and as a function of the stamping energy. In the first part of the paper, investigations on the stampability of coal blends were reported. In this paper, the development of a new strength test device for the systematic investigation of mechanical strength of coal compacts produced by stamping is described. Results from compressive strength tests indicate an elastic–plastic behaviour with failure by plastic fracture. Shear test results show similarity to the yield limit description in soil mechanics.