Revamp study of crude distillation unit heat exchanger network: Energy integration potential of delayed coking unit free hot streams

This work addresses the revamp study of the crude distillation unit (CDU) heat exchanger network (HEN) of a typical refinery with and without the consideration of the free hot streams available in the delayed coking unit (DCU). Based on pinch design method, two sub-cases of revamp study have been considered namely (a) installation of new heat exchangers for the entire network and (b) reutilization of existing heat exchangers. Based on the study, it has been evaluated that the revamp design of existing CDU HEN without considering the DCU free hot streams allows the enhancement of heat integration by 4.73% with respect to that available for the base case. On the other hand, the heat integration potential of DCU free hot streams is evaluated to enhance energy integration by 15.66% (with respect to the base case) with a simultaneous reduction of furnace duty by 37.1% and cooling water duties by 89.8%. Of various cases considered, the most attractive option corresponds to the partial revamp of CDU HEN along with DCU free hot streams that involve the reutilization of existing heat exchangers. The profitability analysis of this option concludes that the revamp design needs an additional investment of 2.68 M$ to enhance annual profit by 1.58 M$ with a payback period of 1.9 years. Thereby, the heat integration potential of DCU free hot streams is inferred to be significant and marks an important choice amongst different key revamp parameters associated to heat exchanger networks.