The simulation of existing crude oil distillation processes is distinctive and difficult owing to its complex nature and interactions, including variable feedstocks, highly integrated processes, tight cuts specifications, and environmental limitations. This study introduces a systematic simulation-based algorithm for retrofitting an existing crude distillation column. The algorithm accounts for all details of the associated heat recovery system. Both distillation unit and HEN (heat exchanger network) are addressed simultaneously in the simulation. The proposed procedure is applied to simulate an existing CDU (crude distillation unit) processing 100,000 bbl/d crude oil of an Arabian origin. The rigorous simulation model achieved can fully describe the existing plant performance, and for this it is thus validated with the actual data for column operation parameters, cuts flow and specification, and for all details of heat exchanger network. The results are found in a good agreement with the actual data. The model is then applied for optimisation and revamping projects to minimise the energy consumption and the amount of CO2 emissions from the refinery. The advantage of the simulation model is its relevance to refining industries in performing any future revamping studies, modification tests, product changes, and capacity enhancement. (C) 2015 Elsevier Ltd. All rights reserved.