The most effective method for identifying process unit energy efficiency improvements
is to carry out a process flow diagram (PFD) review [1]. This can be considered a
“structured brainstorming” activity, similar to hierarchical process reviews [2]. A PFD
should be developed for each process unit (e.g., hydrotreater and crude unit) to show the
major equipment items and their interconnections, together with the basic heat and
material balance across the unit. All fired heaters, columns, and heat exchangers should
be shown, with temperatures, flow rates, and pressures labeled on the inlets and outlets of
each piece of equipment. Ideally, the duty for each fired heater, heat exchanger, or block
of exchangers should be shown. In addition, any place where steam is used for heating
or stripping, or where steam is generated, should be indicated on the PFD with flow
rates labeled.