Efficiency improvement through waste heat reduction

This paper aims at proposing a simplified method for the evaluation of the potential heat energy saving in existing industrial systems through technology optimisation and improved heat recovery. For this purpose heat network analysis is carried out using guided redesign of the technology based on process integration. This results in an improvement in the internal heat exchange consequently minimising the exit exergy and in this way reducing the energy supply. For further efficiency improvement the application of enhanced low-grade heat recovery is proposed using direct phase contact heat exchange and pre-humidification of the boiler combustion air at the expense of waste heat. The application of the method and the resulting potential efficiency improvement is presented. A medium-sized company which produces sliced cooked meats is used as an example. This is a very typical case study for the food industry, represented mainly by Small to Medium-sized Enterprises (SMEs), which have relatively low energy efficiency due to non-optimisation of the heat network and substantial waste heat and effluent emissions. A substantial energy efficiency improvement is achieved resulting in about 30% heat saving at 12.1% reduced fuel consumption. Further hot water production at 70 degrees C corresponding to 61% of the original steam production is available without additional fuel consumption, if required. Finally a reduction of 1.9 times effluent and up to 2.7 times NOx gas emissions is estimated. (C) 2014 Elsevier Ltd. All rights reserved.