Research Of Exergy Balance Analysis And Energy Saving For Cement Rotary Kiln

The cement industry in China is an industry that consumes a considerable quantity of resources and energy, the requirements of energy conservation and emissions reduction for cement industry is improving. Therefore, many studies on the efficient use of energy were carried out in the past. Indeed, some energy savings can be achieved in the short term, but the direction of long-term energy saving is still unclear. In this study, taking the 2500t/d clinker production line in Shandong for example, exergy analysis method were applied to clinker production process, which aims to analyze and evaluate actual energy utilization rate and provide theoretical basis and technical measures in energy-saving schemes.The system is divided into preheater & calciner, rotary kiln and cooler three subsystems, and established exergy balance model and calculate its heat balance and exergy balance. Exergy loss is from combustion, chemical reaction and gas-solid heat transfer process. the results shows that the inherent exergy loss are 625.67 kJ/kg、704.08 kJ/kg and 96.87 kJ/kg, respectively. The system analysis shows that the clinker formation heat is 1836.26 kJ/kg, the burning heat consumption is 3126.6kJ/kg.cl, and the thermal efficiency is 58.65%. The result also shows that clinker formation exergy is 1160.45 kJ/kg, general and objective exergy efficiencies are 54.3%、36.95%, respectively. The objective exergy efficiency is much lower than the thermal efficiency, which indicates that exergy analysis based on both the first and the second laws of thermodynamics can reveal the real utilization of energy. Exergy analysis indicate both the energy transformation and the location of energy degradation, then it provide reliable basis for the evaluation and long-term energy saving.Three subsystems exergy loss analysis is investigated and the energy-saving control link is determined, results suggest that the exergy losses are949.76 kJ/kg,748.15 kJ/kg and 322.42 kJ/kg, exergy loss coefficient is 29.32%,23.09% and 9.95%, respectively. Exergy efficiency and exergy loss coefficient impact factor of preheater & calciner is maximum, which shows that reducing the exergy loss of preheater & calciner have the greatest effects on improving the system exergy efficiency.It is advised to use the technology of preheating with high solid-gas ratio to reduce system inherent exergy lose significantly. Heat exergy loss of rotary kiln shell is the biggest part, and shares 48.65% of total heat exergy loss. Considering the deficiencies of the prior heat collector, a new collector design coupled with radiation and convection heat transfer was proposed. According to existing exhaust gas utilization, step utilization of cooler exhaust gas was presented.