Análise termoeconômica de um sistema de trigeração em uma indústria de alimentos

Abstract

Food industry usually requires amounts of thermal energy to develop different unit operations such as heating, drying, evaporation, refrigeration and freezing. In addition, the cost and availability of energy inputs are crucial for determining the level of competitiveness of this sector. Trigeneration is the simultaneous production of power, heat and cooling from a single fuel source and is seen as an alternative to reduce costs and increase energy efficiency of industrial plants. In this context, the purpose of this study is apply the thermoeconomic analysis method for a trigeneration system for a case study in a soluble coffee industry in order to aggregate benefits in the energy and economic performance of the plant. The thermal system current includes a steam generator that provides thermal energy for two ammonia/water absorption refrigeration plants and for soluble coffee production. Considering the thermal energy demands, the exergetic specific cost (Speco) of the products generated by the thermal system, heat, cooling and power were evaluated and compared with the products generated by integrating the trigeneration system. The optimization of process utilities consumption was made by applying the Pinch analysis, which is a method of thermal integration of current processes by providing the best setting for the implementation of a network of heat exchangers for energy recovery. The results showed that the proposal to integrate a turbogenerator of 4.5 MW is technically and economically viable, resulting in reduction in the Speco for all products evaluated (heat, cooling and power), with a payback period of investment 14.5 months. With the application of Pinch analysis in the extraction process, which was appointed as critical point due to the high consumption of steam, a reduction of up to 6 tons of steam was obtained, incorporating a 15% increase in power generation. The significant reduction in the cost of electricity (70%) with the trigeneration, considering the high quality and high costs of this energy source, makes attractive cogeneration. The methodology used to assess feasibility of cogeneration/trigeneration systems for soluble coffee industry can be extended to any segment of the food chain and drinks.