Assessment of a Kalina cycle for waste heat recovery in the cement industry

The evaluation of a Kalina cycle that is presented in the sequence aimed to estimate the potential of electricity generation from the exhaust gases of the cyclone preheater of the rotary kiln of a Brazilian cement factory with a daily production capacity of 2.1 thousand tons clinker. The thermodynamic, heat transfer, cost estimation, and optimization models we developed in the EES to estimate the dimensioning of the cycle pieces of equipment and to evaluate the Kalina cycle performance doing its optimization regarding net power, thermal and exergetic efficiency, and specific electricity generation cost. It observed that the increasing the ammonia concentration at the outlet of the evaporator and reducing the pinch point in the evaporator leads to the increase in net power, while the increasing in the turbine inlet pressure decrease the cost of the electricity generated. The heat recovery boiler and the condenser are decisive (together with the turbine) in estimating the investment cost of the cogeneration plant for waste heat recovery in the cement industry. With slightly higher cost in the specific electricity generation, the maximizing power generation is the appropriate objective function for the optimization of the studied Kalina cycle. The values of power generation, 2429.056 kW, thermal efficiency (0.233) and exergetic (0.478) are also very promising. In the Brazilian tariff market, the cost values obtained (similar to 0.2847 R$/kWh and 5507 RS/kW) are competitive in the scenario of the Brazilian electricity sector in the second decade of the 21st century.