Cement Manufacturers Association (CMA)

28 Usage of Slag as alternate rawmaterial has proven to reduce thermal heat in KHD Pre-heaters, where approximately 20-30% of GGBS is used, and because of the reduction of the generated calcination heat, significant thermal heat is reduced. The use of copper ash as an iron component in raw grinding is more popular in terms of reducing the costs and using waste material. Challenges of using alternative fuels in cement production Cement factories offer nearly ideal possibilities for burning most of the alternative fuels. The mineral or ash portion is incorporated into the clinker phase. Toxic organic harmful matter is destroyed at high temperatures and heavy metals bind to the crystal structure after the mortar or concrete hardens, but they also have process limitations that must be addressed. However, the transition to alternative fuels brings several challenges because they have different properties compared to traditional fuels, both physically and chemically, e.g. particle size, moisture content, ash content, volatile matter content, calorific value, heterogeneous properties that make handling difficult. In the table below, some fuels are classified according to their most important characteristics. They all have positive (see green fields) - neutral (yellow) and negative (marked in red) sides. Fuel has its own disadvantages. This may be due to fuel costs, high sulfur or chloride content, or handling and preparation difficulties. Table 4: Characteristics of some solid fuels Description Coal pet coke Anthracite Tyre chips Fluff-RDF Animal Meal Sewage sludge Heat Value A A A A B B C Preparation A B B C C B B Handling A A A C C B B Chlorine Input A A A B C C B Sulphur Input A C A B A A B NOx reduction potential B C C A B A B Fuel costs C B B A A A A A= positive, B= indifferent, C= negative High moisture or low calorific value of the fuel can increase the burning time required for heating and this leads to a higher specific volume of exhaust gas. If the production line does not have margin in fan or gas velocity limits are exceeded at critical points (eg in the kiln inlet chamber), increased use of alternative fuels will reduce the production rate. Fuel properties affect cement production in many ways to influence critical parameters; energy balance, operational stability, clinker quality, and emissions, which are described below. Effect on energy balance • Increase of specific heat consumption (as most AF contain higher moisture and lower HV) • Increased waste gas volumes (higher fuel moisture, fuel chemical composition, higher excess air demand, more fuel to maintain hot sintering zone).