It is observed that there are differences in the cost reported in the work of Ajao and Akande and this study. This can be due to the fact that Ajao and Akande obtained their operating cost, capital cost and total cost in Naira. As at year 2009, dollar conversion to naira exchange rate was between N145 and N 171 to $1, hence, an average value of N158 per $1 was used to convert the results of Ajao and Akande from naira to dollar equivalence. It was nevertheless not clear, the conversion factor used by the authors to convert from dollars to Naira. Another possible reason for the difference in cost obtained is that the authors did not state the number of hot streams and the number of cold streams identified in the process flow sheet. Moreover, the network structure of the optimized CDU was not shown in the study of Ajao and Akande .