With regulatory changes for reducing carbon dioxide emissions likely coming into force, many plants will revisit energy integration to reduce net heat use. One oft-mentioned idea is to add inter-reboilers to towers. This allows for using lower-temperature heat sources to provide part of the duty to the tower. The objective is to usefully recover lower-temperature heat instead of rejecting it to air or water.
Figure 1 shows a product splitter with two inter-reboilers added. The first (E32AB) used two small exchangers with the plant’s low-pressure steam — which otherwise would be vented — to provide heat to the tower. This reduced hot-oil duty demand by 3.5 million Btu/hr. The inter-reboiler worked well.
Andrew Sloley is a Chemical Processing contributing editor. You can e-mail him at [email protected].