Thermoeconomic analysis for a trigeneration system in a soluble coffee industry

Abstract

Considering that a trigeneration system tends to result in higher thermal efficiency than electricity, heating and cooling generation in separated ways, the purpose of this study is to perform a thermoeconomic analysis of a trigeneration system in a soluble coffee industry in order to improve its energy and economic performance. The current thermal system has a steam generator that provides heating utility for the soluble coffee production, including a refrigeration plant using ammonia/water absorption, while the electricity is bought from the energy concessionary. The proposal is to include an extraction-condensing steam turbine providing 5100 kW of electricity to the industrial plant, besides keeping the same energy demands in the current plant. Heat, cold and power were evaluated for their costs per unit of exergy in the current plant and compared to the proposal of the trigeneration system. The results show that the proposal to integrate a turbo-generator is technically and economically viable, resulting in reduction in the costs for heating, cooling and electricity of up to 72% in a payback period of only 24 months.