Cement and Energy

Sulphur in lignite is present in organic combination as part of the substance and in inorganic combination as pyrite or marcasite and as calcium sulphate. These forms of sulphur are commonly referred to as organic, pyritic and sulphate sulphur. The su lphur from lignite may be partly removed by physical method or chemical process. Generally physical methods are used to remove pyritic and non– pyritic (sulphate) sulphur. Chemical treatment is needed to remove largely the organic su lphur. In some cases, a comhination of physical and chemical methods is preferred for removing all these forms of sulphur from lignite. In the chemical method, treatment is given at specified operating and process conditions in a fluidised bed reactor where I ignite structure changes during the chemical reaction. C0111"1esy: Nwional Council for Cement and Building Materials Three techniques, viz. selective crushing and screening, steam-air treatment in fluidised bed reactor and ferric sulphate treatment followed by pyrolysis were considered for partly removing of sulphur from lignite. The results of experiments of chemical treatment with a specified fraction of lignite are highly encouraging with sulphur reducing to the extent of 45 - 50% and product recovery of around 60%. The lower size fraction of lignite below 1 mm containing high pyritic and sulphate sulphur can be treated with ferric sulphate solution and then pyrolysed at 400° C for effective desulphurisation up to 75%. The steam-air technique has enabled the reduction of sulphur in Lignite to the extent that it can rationally be utilised after blending with coal in cement and other untappped and unutilised reserves of li gnite as an excellent source of energy in a most effective manner. REDUCING ENERGY COSTS IN BALL MILLS G rinding plants are designed for efficient production of a certain product at a specified quality, and in order to do this, energy is required, However, on ly a small amount of energy can be utilised for this process because energy is inevitably wasted through wear, heating the product and noise. Reduction of these energy losses and an increase in energy utilisation is therefore desired. The energy consumption of a grinding plant is dependent on: • Process design and plant layout • Feed material and the fini shed products • Design and condition of the mill internals • Operation mode of the mill Grinding plants cannot always achieve the optimum rate in producti on and energy consumption because it is impossible to obtain them under the same operating conditions. Maximum production rate and minimum energy consumption are not constant values for a mill and can be influenced particularly by the design and condition of the mill internals. Energy consumption and wear are indirectly related - higher energy consumption results proportionally in higher wear. In consequence, any energy reduction in the grinding process automatically results in reduction of this specific wear. Mill internals consist of the mill shell lining, the intermediate and discharge diaphragms and a grinding ball charge. The mill shell lining has to transfer the mill tube's rotational energy into the grinding ball charge. The shell plates must be designed in accordance with indi vidual operating conditions to achieve optimum energy transfer and grinding efficiency for the relevan t 4 ...