Comparison of Alternative Cogeneration Power Systems for Three Industrial Sites

Three alternative on-site cogeneration power systems were evaluated against technical and economic criteria for three industrial sites. Technical factors included plant sizing to meet process thermal loads, fuel utilization, power output, siting consideration, fuel savings, etc. Economic factors included capital cost, return on equity, and ownership/financing options among others. Each cogeneration plant was evaluated by comparison with the current separate generation scheme. The technologies considered were 1) conventional coal-fired, steam topping cycles; 2) coal-fired, atmospheric fluidized bed/closed-cycle gas turbines; and 3) coal-fired, atmospheric fluidized bed/open cycle gas turbines. These approaches were optimized for three sites 1) an agricultural chemical plant, 2) a brewery, and 3) a kraft paper mill. The results showed that the closed cycle gas turbines yielded the best economics, primarily due to a lower initial cost. The open cycle gas turbine, when combined with a steam bottoming cycle, resulted in larger power outputs than would be realized in the closed cycle or steam turbine cases. None of the plants studied matched the plant electrical load while following the thermal load.