Energy Efficiency Improvement through Technology Optimisation and Low Grade Heat Recovery - Industrial Application

Small and Medium-sized Enterprises (SMEs) form the backbone of national economies and especially of the food industry, which in Ireland is made up of over 90 % SMEs. These foods related SMEs have very similar structures, usually containing a small or medium boiler, ovens, chillers, heat exchangers and an extended water network. Another common characteristic is the low energy efficiency due not only to the relatively small size of equipment but also to the non optimisation of the heat network and substantial waste heat and effluent emissions. Therefore, it is an excellent environment to apply system analysis, process integration and optimisation methods, waste heat recovery and waste emission reduction technology with expected high economic and environmental impacts. In this paper the opportunities for energy efficiency improvement with the example of a medium-sized company which produces sliced cooked meats are presented. For this purpose a complex analysis of the heat network is carried out using guided redesign of the technology based on Process Integration, improving the internal heat exchange in order to increase and consequently to minimise the exit exergy (available useful heat) reducing the energy supply. Additionally the application of an advanced technology for boiler flue gas low grade heat recovery with preliminary humidification of the combustion air using waste heat is proposed. As a result an overall efficiency improvement of 20-25 % (respectively less fuel consumption and carbon emission reduction), about 68 % water consumption and effluent reduction and up to 3.8 times less NOx gas emissions is estimated.