A new targeting method for the retrofit of heat exchangers networks is
presented. II combines existing targeting and design methods for retr
ofit with the concept of zoning used in grassroots design. The structu
ral targeting retrofit method gives targets not only for the utility s
aving and exchanger area investment, but also for the extent and locat
ions of the required modifications. This targeting requires a Special
way of zoning based on the existing network. This zoning is extensivel
y discussed. Practical aspects like functionality, lay-out and operabi
lity can be taken into account. Two case studies are presented: a simp
lified aromatics and a real C3/C4 separation case. Both cases illustra
te that structural targeting is an effective method to identify parts
of the original network with a high saving to investment potential. Th
e method favours simple adaptations and is especially effective for la
rge networks. The C3/C4-case also shows how structural targeting provi
des a number of alternatives, many of which are independent of each ot
her, to adapt the existing network. The retrofit design effort is sign
ificantly reduced compared to existing methods. (C) 1998 Elsevier Scie
nce Ltd. All rights reserved.