Energy Audit of a Wheat Processing Plant in Rivers State, Nigeria

In this study, energy audit of a wheat processing plant in Rivers State, Nigeria has been carried out.  A walked-through energy audit method was undertaken to identify the major sources of energy in use, identify the lapses in energy usage, identify areas to improve energy usage, determine the level of energy consumption of the various energy sources and recommending policy measures that will enhance energy savings in the industry. The analysis showed that eight defined unit operations were required for the production of wheat flour; Truck Loading, Intake or Storage, Cleaning, Tempering or Conditioning, Holding Bin, Milling, Finished Product and Packaging. The types of energy used were electrical, thermal (diesel and gas), and manual energies with proportions of 14.63%, 85.31% and 0.05% respectively of total energy input. Average energy intensity was estimated to be 1.3GJ/tonnes for the production of wheat flour for the 5 years (2011-2015) study period. The most energy intensive operation was identified as the milling process with percentage energy input of 44.39% (123837.60MJ) followed by Finished Product Storage process with percentage energy input of 36.17% (100885.92MJ). It was observed that the industry under review did not sufficiently utilize energy as the energy used ratio is below 1. This was as a result of some factors that contributed to energy waste and energy use inefficiency in the industry. Among these factors are: electric motor that dissipate much heat, use of electric motors that have been rewound more than twice and generation of electricity more than needed in the industry by some generators. The exergy analysis showed that the roller dryer accounted for the major loss in the process with an inefficiency of 44.8%.  The useful work was 5.3kJ; exergy loss expended is 15.68kJ in the roller dryer. The study concluded that energy is not sufficiently utilized in the industry resulting in high energy waste and high pricing of wheat flour products.