1. Petrolum and Gas Refining Engineering Department , College of Petroleum Processes Engineering, Tikrit University , Tikrit , Iraq
2. Studies and Economic Affairs Division , Iraqi National Oil Company , Baghdad , Iraq
3. North Refineries Company, Ministry of Oil , Baiji , Iraq
4. University of Al Mashreq , Baghdad , Iraq
5. Chemical Engineering Department , Faculty of Engineering & Informatics, University of Bradford , Bradford BD7 1DP , UK