Exergetic analysis of breakfast cereal production in Nigeria

Abstract

This work comprehensively studied energy and exergy analyses of breakfast cereal production in Nigeria. The process analysis method of energy accounting was used to evaluate the energy requirement for each of the five defined unit operations. The total energy used in the operation is 1,287.94 MJ. The types of energy used in breakfast cereal production were electrical, thermal and manual and the respective percentages are 48.87%, 50.53% and 0.60%. It was estimated that an average energy intensity of 11.27 MJ/kg was required for the production of breakfast cereals. The most energy intensive operation was identified as the mixing operation followed by milling with energy intensities of 665.10 MJ/kg and 383.04 MJ/kg, respectively. The exergy analysis revealed that the roller dryer was responsible for most of the inefficiency (over 65.94%) followed by the wet mixer (27.40%). Suggestions for energy saving which will help in the reducing the high expenditure on energy and thus improve the profit margin were provided.Keywords : Energy, Exergy, Efficiency Breakfast Cereal  1. INTRODUCTION Energy is the driving force required for any activity or process. It has become the major element of an economy and a factor that not only determines the growth but has also an indicator of the development of the economy. Energy which can be classified as renewable -solar, wind, hydroelectric, biomass, tidal and geothermal energy or non-renewable -fossil fuels and nuclear energy [1] is consumed by all the sectors of an economy. The industrial and residential sectors have the greatest consumption value of Nigeria's domestic energy [2]. Most production industries worldwide depend heavily on energy derived from non-renewable resources [3]. In the south-western Nigeria, gasoline consumption is highest in Lagos and Oyo states with 24,200,352 litres (59.3%) and 6,260,901 litres (15.3%), respectively, due to industrial processes [4]. The food industry is one of the energy-intensive industries. In the food industry, energy is consumed to various degrees by different unit operations like handling, cleaning, sorting/grading, milling, mixing, pelletizing, drying, blanching, frying, cooking, pasteurizing, packaging, etc. Of all these operations, milling and  drying operations have been recognized to have high energy demand even as they are also least energyefficient [5,6]. Energy consumption in food production/crop processing industry has been identified to be affected by factors like production scale; type of equipment; efficiency of machine; maintenance; automation; grain properties; size of screen holes for milling operations; speed of operation; feeding rate [6 -11]. Presently, energy studies are not been limited to methods of consumption and transformation but also to the effectiveness of energy utilization, energy usage pattern and efficiency. Energy efficiency has attracted increasing attention in the food industry [6 -10]; hence, researches have been geared towards identifying the causes of energy loss in different industrial prod...