(69b) Opportunities for Energy Savings on Thermal Coupling CDU and DCU Grassroot Designs

Crude oil distillation unit (CDU) and Delayed coking unit (DCU) present significant energy consumption in a refinery, given the high flow rates involved on process streams. As refiners are increasing the process of opportunity crudes, heat integration on these units becomes more relevant.

Because DCU is essentially a semi-continuous process, heat integration involving its hot streams may impact considerably the CDU operation. However, thermal coupling between CDU and DCU can be explored through the evaluation of adequate DCU feed temperature. By increasing vacuum residue temperature to DCU, the DCU cooling demand increases while CDU cooling demand decreases. As pinch location on each unit is relatively high, little influence on heating demand is expected, unless the pinch is modified by variation on vacuum residue temperature to DCU. Capital costs are supposed to suffer variations as well, especially on DCU, due to the required area to preheat the feed and to cool the product streams.

This work presents the evaluation of DCU feed temperature relevance on both CDU and DCU overall costs and utility consumption, considering grassroot designs, based on Pinch Analysis approach in a conceptual design.

The paper also investigates the potential of medium pressure steam generation on each unit, discussing the impacts on both processes.