Cement Manufacturers Association (CMA)

29 • Higher amount of primary air (transport air) and leakage air, decrease of recuperation air from clinker cooler. • Increased heat losses by radiation (shifting temperature profile of kiln-to-kiln inlet chamber). • High amounts of alkalis, Sulphur and/or chlorides may affect kiln operation. Gas bypass may be required if these quantities can’t be absorbed in clinker. Exhaust gas volumes increase, and energy consumption will go up Effect on plant operation stability • High demands on fuel dosing equipment, and continuous fuel feed. • The large fuel particles may not have suffcient time for complete burnout and unburned fuel may therefore fall into the clinker bed and continue combustion causing local reducing conditions, which results in unstable calcinedr and Kiln operation • Formation of build-ups in the case of Cl- and S-rich alternative fuels in the area kiln inlet, riser duct, and bottommost cyclone. More manual cleaning efforts or Bypass System is necessary • High moisture in hazardous wastes can limit the production capacity of the kiln and an increase in specific heat consumption. Effect on clinker quality • “Raining” of un-burnt fuel out of the kiln flame to the clinker bed => reduced burning conditions. • Cooling down of the sintering zone. • Possible enrichment of harmful elements in clinker, e.g. MgO, P2O5 (depending on Alternative Fuel ash composition). • One potential constraint on the implementation of alternative fuels is the final clinker composition since the combustion by- products and fuel ash are incorporated into the clinker. Fuel ashes can lead to reducing effects on the clinker bed Effect on emissions • Some AF have a positive influence on avoiding NOx formation and/or NOx reduction. • CO formation in case of inadequate calcinedr technology or unsuitable alternative fuels • Saving of primary fuel related CO 2 emissions. • Adaption of raw mix, e.g. high Silica and Fe- content in Alternative Fuel. Conclusion Several years of experience have shown that the use of waste as AF in cement factories is justified both ecologically and economically. The use of AF helps to reduce the cost of cement production. The average energy requirement to produce one ton of cement is around 3.3 GJ, which corresponds to 120 kilograms of coal with a calorific value of 27.5 MJ/kg. Energy costs make up 30-40 percent of the total costs of cement production. Replacing fossil fuels with AF helps reduce energy costs and gives a cement plant using this energy source a competitive advantage. In addition, less waste needs to be dumped or incinerated, which means fewer landfills. Therefore, the use of AF in cement plants is also beneficial for the environment. The conditions of rotary kilns, such as high temperature, high gas flow and long particle retention time, ensure that the use of AF is environmentally safe. Co- processing in the cement industry is the optimal way to recover energy and material from waste. It offers a safe and acceptable solution to society, the environment, and the cement industry by replacing non-renewable natural resources with society’s waste under strictly controlled conditions. Desired fuel waste is usually available within the state or country. The price of waste used as fuel does not exceed the cost price of fossil fuels. Usage of Alternative raw materials like Slag, fly ash, Calcinedd clay, Boiler ash, etc. has been increased in the last decade but its maximum utilisation potential yet to be explored as there are some reference plants in the world where about 30% raw material substitution is achieved with a saving of Specific heat about 100-150 Kcal/kg of clinker. In Indian context it becomes more important in view of conserving natural reserves of limestone and other materials and substitution of raw materials with by-products of Steel, Power, and other industries. Looking to the trend of competitive environment and today’s requirement for operating efficiency, it will be a necessity in future cement plants to have comprehensive combination of technology where co-generation of renewable energy, Alternative fuel and Raw materials, environment protection techniques well adopted.