Energy conservation and waste utilization in the cement industry serve the green technology and environment

The cement industry is one of the most energy-intensive industries consuming 4 GJ/ton of cement, i.e. 12-15% of the energy use in total industry. Energy cost accounts for 30% of the total cost of cement production. Seventy-five per cent of this energy is due to the thermal energy for clinker production. It is also found that 35% of this supplied thermal energy is lost in flue gas streams. Most modern kilns use pet coke or coal as their primary fuel. Instead, the municipal waste in landfills offer a cheap source of energy and reduce the environmental effects of dumping solid waste. The calcination and drying processes and the kiln need large quantities of thermal energy. About 40% of the total energy input is lost in the hot flue gases and cooling the stack plus the kiln shell. Hence, it is suitable to use an organic Rankine cycle (ORC) to recover the exhaust energy from the kiln. Alternatively, a 15MW gas turbine engine combined with a steam turbine could be utilized. It was found that ORC produces 5MW with a capital cost recovery period of 1.26 years. However, the gas turbine combined system produces 21.45MW with a maximum recovery period of 2.66 years.