(29b) Heat Exchangers Network Retrofit for Energy Efficiency Enhancement in a Crude Oil Refinery

World-wide industrial facilities energy efficiency optimization’ practices and measures are underway by most of the major energy; chemical & petrochemical companies, where well-structured energy efficiency programs are making a difference in such industrial facilities.  Energy efficiency in most of the big industrial companies has been established and organized through engineering procedures for conducting energy assessment studies for existing facilities and grassroots ones followed by actual projects to realize significant reductions in energy resources and energy-based GHG emissions.

Heat exchanger network (HEN) retrofit plays an important role in energy saving in process industry. Many design methods for the retrofit of heat exchanger networks have been proposed during the last three decades. Conventional retrofit methods rely heavily on topology modifications which often result in a long retrofit duration and high initial costs. Moreover, the addition of extra surface area to the heat exchanger can prove difficult due to topology, safety and downtime constraints. Both of these problems can be avoided through the use of heat transfer enhancement in heat exchanger network retrofit. Crude distillation units (CDUs) in crude oil refineries are major consumers of energy because of the high energy consumption of the crude furnace in the crude preheat train. This paper uses the new Heat exchangers network “Retrofitability” concept, HEN retrofit-with-future-retrofit-in-mind through an actual project recently implemented in integrated atmospheric and vacuum distillation units (ADU/VDU). Heat transfer enhancement is used aside with increased heat exchanger network surface area to reduce retrofit capital investment cost and hence modification duration and payback period are reduced. Simulation models has been developed to find the appropriate heat exchangers to be enhanced with minimal additional surface areas required to optimize the heat integration trains and minimize the fuel required in crude furnace.

The case study identified the most cost effective potential energy saving and enhancement initiatives through optimizing Refinery ADU/VDU Plant heat integration in the crude preheat section at minimum capital and operating cost requirements, this would enable a considerable reduction in the required furnace duties by 56.8 MM Btu/h and corresponding reduction in fuel gas consumption equivalent to approximately 1.8 MMSCFD. Moreover, this study considered modifications on both unit design and operation to achieve the ultimate goal of improved energy efficiency for ADU/VDU and an overall improvement of the refinery’s energy intensity index.