Evaluation of Energy and Exergy Efficiency of Steam Generation and Utilization in Nigerian Pharmaceutical Industries

Abstract

The results of the evaluation of energy-exergy efficiency of pharmaceutical plants in Nigeria have been presented. Two pharmaceutical plants at JUHEL and DANA in Awka, Anambra state and Minna Niger state were considered. The energy and exergy analyses of these pharmaceutical industries were used to determine the utilization efficiency of the process heat at different operating conditions. The exergy of the component system was evaluated and analysed with an engineering equation software (EES). The JUHEL boiler energy and exergy efficiencies were found to be 30.4% and 17.5% while the distillation unit recoded 42.3% energy and 22.6% exergy efficiencies. Similarly, DANA boiler energy and exergy efficiencies were found to be 22.4% and 16.6% by the autoclave unit which recorded 37.3% and 34.3% efficiencies. Other components of the plants with low energy and exergy efficiencies include; the steam headers, condensers and preheaters. Total exergy destruction for JUHEL and DANA plants was found at 13532kJ/hr for JUHEL and 14086KJ for DANA.  Exergy destruction in JUHEL and DANA boilers were found at 6778 kJ/hr and 7789.5kJ/hr which accounted for 38% and 42.3% of the plants total exergy destruction respectively. However, the condenser and autoclave recorded 16% and 5% of the total exergy destruction in JUHEL plant while the same components recorded 15% and 5% of total destruction in DANA plant. The study also showed that for a 1^oC increase in ambient temperature, the exergy destruction in both plants increased by about 0.9%. However, variations in boiler inlet pressure showed that the rate of exergy destruction reduced with increased in boiler inlet pressure.  The result of evaluation of the effect of flue gas constituents on boiler combustion efficiency showed that at 3.4% oxygen in flue gas, an optimal value of 14% excess air was recorded which resulted in optimal combustion efficiencies of 75% and 78%% for JUHEL and DANA plants respectively. The study suggests a retrofitting of the existing pharmaceutical plants and a time series analysis will be necessary to show how the plant’s irreversibilities change with time for proper optimization.

Keywords: Energy, Exergy, Exergy Destruction, Combustion efficiency.