Halit Z. Kuyumcu

Stamped coal cakes in cokemaking technology: Part 1 – A parameter study on stampability

Abstract 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 pyrolysis in the so called stamp charge operation. Using stamp charging not only improves the flexibility of the coke making plant using cost efficient raw materials, but oven throughput is also increased. 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 depending on the stamping energy. The first part of this paper defines the overall process objectives and presents results from systematic investigations of the effects of several coal properties on the so called stampability as the integral model parameter for compacting. Surface moisture, coal granulometry and mechanical properties have significant influence on the densification. The incorporation of these parameters into the model allows the differentiated calculation of the cake density.

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

Abstract 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.

Investigations on the Sorting of Very Fine Particles by Biocoagulation

The Technical University Berlin is involved in the EU RTD-project “Biotechnology for Metal bearing materials in Europe (BioMinE)”. The provided results are part of the field “microbioengineering”, possibly called “micro-biotechnology”. In this context inorganic particles in micrometer size and in form of element or element compounds (minerals) play an important role. By using microbiologic functions in the microscopic scale for developing technological methods, bridging between the living and the non-living nature takes place. For the scientific work, it is necessary to increase the understanding of the inorganic and the organic matter as well as their interaction with the aim to establish a new technological thinking. The idea for the project follows from identified technological limits of the classic mineral processing. The technical relevant sorting processes, like density, magnetic or electrical separation and flotation respectively, require a narrow particle-size distribution in order to eliminate overlapping effects. Because of the rapid decrease of the mass forces with declining particle size the well-known sorting processes are not applicable to an effective separation of particle sizes smaller than 10 μm. For obtaining a selective enrichment and recovery respectively of sorting products in that particle size range usually chemical dissolving or leaching processes are used, which often lead to higher processing costs and negative environmental effects. Moreover, the necessity of sorting processes for finely dispersed solid systems increases. Additionally new sorting processes are useful in the cleaning of wastewater to remove a variety of suspended particles. The approach of using the charge of cell walls of microorganisms for selective coagulation of solid particles on microbes is novel. The project targets differ from well-known processes like biosorption, bioaccumulation etc. of dissolved substances. Therefore the new micro-process is called biocoagulation, as the aim is to attach valuable particles to microorganisms producing larger biocoagulates, which can be separated a lot easier by applying mechanical processes. The investigations are divided into three major steps (Fig. 1): At first the microbes are described, which are able to retain the selected particles at their surface, the so-called biocoagulation. The second step is the separation of the biocoagulated substances from the pulp. Thirdly the connection between the extracted substance and the microorganisms is suspended. Sorting products Microorganisms Loading by Biocoagulation

A novel process for sorting fine-sized sulphide minerals by biocoagulation

Abstract Based on a process design idea, investigations at Technical University of Berlin confirm that the biocoagulation of microorganisms and solid particles would be a new method to generate coarser particles suitable for sorting. The procedure of selective biocoagulation of microorganisms, e.g. yeasts like Saccharomyces cerevisiae and Yarrowia lipolytica respectively, and micro-dispersed solids, e.g. minerals like galena and sphalerite, has been analyzed as a basis for a novel sorting process. Therefore, especially the characteristics of the cell surface of the microorganisms, e.g. the electrostatic charge and the composition of extracellular polymeric substances, as well as their influence on the selective biocoagulation were studied. Experimental investigations show that the microorganisms and the sulphide particles below 10 µm coagulate effectively. Furthermore, the flotation is suitable for the separation of the selectively formed biocoagulates. With the designed column flotation, satisfying recovery rates are reached.

Biocoagulation and its Application Potentials for Mineral Bioprocessing

Based on a process design idea, investigations confirm that the biocoagulation of microorganisms and solid particles can be used to generate coarser sized coagulates which are more suitable for sorting. Experimental investigations showed that microorganisms like Saccharomyces cerevisiae and Yarrowia lipolytica and sulphide particles like galena and sphalerite below 10 � m coagulate effectively. Theoretical thermodynamic and extended DLVO theory calculations are in good agreement with microorganisms adhesion onto metal sulphides but not on silicates and selective biocoagulation of sulphides. Furthermore it has been demonstrated that flotation is suitable for the separation of the selectively formed biocoagulates.

Effect of Particle-Size Distribution and Degree of Saturation on Coal-Compacting Processes within a Coke-Making Operation

The bulk density of an oven charge is a very important factor for the selection of the coking coals and coke quality in a coke-making process for producing blast furnace coke. Major factors influencing the bulk density of coal are moisture content, particle surface properties, particle shape, particle-size distribution, and particle density. The bulk density can be increased significantly through compacting the coal to a coal cake prior to oven charging. The objective of the compaction processes is the production of a cake with high density and as well as a sufficient mechanical strength in order to ensure a trouble-free cake charging into the coke oven. The present article deals with the evaluation of the compaction process based on lab-scale test work. The two subprocesses of densification and strengthening during both stamping and pressing were theoretically and experimentally investigated using compaction test units in combination with a strength-test device. Systematic investigations showed that particle-size distribution and degree of saturation have significant influence on cake density and mechanical properties of the coal cake.