Optimization design of waste heat power generation systems for cement plants based on the thermal resistances analyses.

Heat loss from the cement production accounts for a large amount of the energy consumption in energy-intensive industry. In order to recover the heat loss, a waste heat power generation system is proposed in this work. The system contains a suspension preheater boiler, an air quenching cooler boiler, a condenser, a turbine and a heat recovery system with nine heat recovery exchangers. Then, integration of the thermodynamic and thermal resistance analyses yields physical model relations between the system requirements and the design parameters, i.e. the thermal conductance and the mass flow rates, which form the constraint equation group of a global optimization model. With the aid of the conditional extremum principles, the equation group is solved to obtain the optimal structural and operational parameters for the heat power generation system. Besides, experimental measurements are investigated to determine the heat transfer characteristics of the heat recovery exchangers. Finally, an optimization case of a practical system is studied and some factors that affect the optimal results are discussed. The results illustrate that the global optimization method can obtain the optimal design parameters for each component in the waste heat power generation system. The required thermal conductance of the heat recovery system could reduce by 22% compared with the values before optimization. The vaporization temperature will decrease as the total mass flow rate and the work output of the turbine increase. Besides, the total thermal conductance will increase as the inlet temperature of the cooling water in the condenser and the work output in the turbine increase. [ABSTRACT FROM AUTHOR]