Cement Energy and Environment

• • • How wil l the alternative fuel affect the operation of the kiln sys tem? Will it redu ce c li nker production ? Will it increase maintenance requirements? Will the alternative fuel produce ash? If so, how wi ll it affect the chemistry of the clinker produced? How will the ash affect the operation of the kiln system?ln some cases, ash may contain high levels of silica, aluminium or iron that may be beneficial. It may, in some cases, allow the plant to reduce consumption of a more expensive raw material. Will the alternati ve fuel generate any additional pollutants? If so, what are the consequences of these pollutants? Are special permits required? Potential savings resulting from using an alternative fuel are shown in Table 6. It is important to note that the cost of alternati ve fuels varies significantly. In some Table 6. Potential savings resuJting from using an alternate fuel Before After change change Primary fuel cost, 8.00 8.00 US$/million kcal Alternative fuel cost, 4.00 4.00 US$/millionkcal Fuel substitution, alt. 0% 40% fuel kcaVtotal kcal Fuel cbst, US$/ 8.00 6.40 million kcal Effect - - - - -1.60 I cases, the cement plant may be paid to use alternative fuel s. Potential savings and benefits are as follows: US$ 396 000/yr can be saved in fuel costs for a plant producing 330 000 tpa of clinker at 750 kcal/kg. There may be social benefits from using alternative fuels, such as safe di sposal of domestic and industrial was tes. Conclusion Thi s article has presented a number of examples of potential savings achievable by operational changes and small capital investments, including; optimi sing heat transfer, optimi sing combustion condi tions and using alternati ve fuels.These potential savings provide an order of magnitude saving, which may vary according to existing plant operating conditions and production. It is important to stress that these are only a selection of examples on relatively small kiln systems, and that many more areas of potential savings and benefits ex ist that are applicable to the kiln system and other sections of the producti on process. It is also important that larger equipment capaciti es will show larger returns on investment for simil ar operati ona l changes and modifications. Plants are recommended to undergo an audit by technical experts to evaluate existing systems in order to optimise and maintain low operating costs using proven theoretical and practical tools. • Technology Trends THERE'S CASH IN THAT TRASH· FRENCH CEMENT I PRODUCERS BURNWASTE, LOWERPRODUCTIONCOSTS* I I . A few decades ago, cement industry used to be dubbed as highly polluting. This concept has undergone a rapid change during the last decade, thanks to tlze industry's continuous efforts in abating pollution from particulate emission. Most modern plants today are symbols of cleanliness and pollution free environment. In addition, the cement rotary kiln has turned put to be an excellent incinerator of all types of wastes including the waste derived fuels (WDF). The European Cement plants have earned a distinction in this regard by utilising large quantities of sludges, pharmaceutical wastes, hazardous chemical wastes etc. The French experience is described in this article -Ed. * Courtesy : Cement Americas, Oct. 1999 14