Cleaner production through exergetic optimisation in a chemical Industry: a case of Tradeco oil Industry, Dar es Salaam

Exergy analysis is a tool for process understanding and optimisation. This analysis was performed on an edible oil processing plant in Dar es Salaam Tanzania. The purpose of the study was to assess the plant performance, propose cleaner production options and asses improvement on applications of the options. The analysis involved material balance; energy balance and exergy balance (using Excel programme for computation). An exergy balance sheet was made for the whole plant. From the sheet, a graph of exergy loss in the unit processes was drawn and the unit processes with high exergy loss were revealed, to be: deodorization (5663.43 MJ), cooling (2528.49 MJ), storage (775.96 MJ), dehydration (704.65 MJ), degumming (333.97 MJ) and neutralisation (437.58 MJ). Exergy optimisation through process modification, re-use and recycling of material including removing the storage process, using hot refined oil to produce heat for degumming and neutralisation instead of steam, and using diathermy fluid to heat crude oil before dehydration is proposed. The proposed modifications were analysed and the results show exergy saving per batch as follows: removing the storage, 68l .59MJ is saved, recycling hot refined oil for degumming and neutralization saves 2044.78MJ of exergy. The dehydration and deodorization processes use less exergy by 236.29MJ and 4771.13MJ respectively. The results indicate that a reduction of waste products by 83.87% and energy requirements by 56.28% is possible. It is concluded that exergy analysis is a powerful tool that may be used to identify process losses and hence process optimisation and cleaner production.