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This paper considers comparative assessment of combined-heat-and-power (CHP) performance of three small-scale aero-derivative industrial gas turbine cycles in the petrochemical industry. The bulk of supposedly waste exhaust heat associated with gas turbine operation has necessitated the need for CHP application for greater fuel efficiency. This would render gas turbine cycles environmentally-friendly, and more economical. However, choosing a particular engine cycle option for small-scale CHP requires information about performances of CHP engine cycle options. The investigation encompasses comparative assessment of simple cycle (SC), recuperated (RC), and intercooled-recuperated (ICR) small-scale aero-derivative industrial gas turbines combined-heat-andpower (SS-ADIGT-CHP). Small-scale ADIGT engines of 1.567 MW derived from helicopter gas turbines are herein analysed in combined-heat-and-power (CHP) application. It was found that in this category of ADIGT engines, better CHP efficiency is exhibited by RC and ICR cycles than SC engine. The CHP efficiencies of RC, ICR, and SC small-scale ADIGT-CHP cycles were found to be 71%, 60%, and 56% respectively. Also, RC engine produces the highest heat recovery steam generator (HRSG) duty. The HRSG duties were found to be 3171.3 kW for RC, 2621.6 kW for ICR, and 3063.1 kW for SC. These outcomes would actually meet the objective of aiding informed preliminary choice of small-scale ADIGT engine cycle options for CHP application.

The main objective of this work is to assess the performance of two heat exchanger units (Stripper/Gas Overhead Condenser and Methanator Effluent Cooler) operating under steady state conditions in two stages. Two different methods are employed in monitoring the heat exchanger fouling, namely dirt factor trend method and a statistical control technique where a Cumulative Sum (CuSum) chart is used to check the stability of the process. Data were obtained through steady state monitoring and direct measurements from the plant. The data were analyzed using various energy equations and a computer program to determine the overall heat transfer coefficient, heat duty, capacity ratio, corrected log-mean-temperature difference, fouling factor, temperature range of both fluids and effectiveness. The result shows that for the Stripper/Gas Overhead Condenser, the overall heat transfer coefficient was 63.13% less than the design value in stage1 and 12.59% less in stage2. For the Methanator Effluent Cooler the value of heat duty and the overall heat transfer coefficient were 51.76% and 59.62% less respectively than the design value in stage1 and 30.72% and 30.16% less respectively in stage2. This was traceable to increase in heat transfer rate as a result of injecting the tubes of the exchangers with NALCO fluid. In order to detect small changes in the heat exchanger operation and to know the actual time fouling starts to build up, a Cusum chart is used. This work made use of QI Macros software to check the stability of the heat exchanger units and to know if processes are on-target.

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.