Examining the economic viability of an absorption heat transformer in energy intensive industries

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.

Absorption heat transformers are closed cycle thermodynamic systems which are capable of upgrading the temperature of waste heat energy and, allowing it to be recycled within a plant. An industrial case study is conducted which examines the economic viability of installing a triple absorption heat transformer in a small oil refinery. Particular attention is paid to determining the suitability of different waste heat streams which have been made available. In the refinery examined, two waste streams of interest have been identified; a viscous residue oil line and a condensing Naphtha stream. A relatively large increase in temperature is required by the company in order that the recycled waste heat energy may be incorporated into its existing heat exchange network (HEN), and thus a triple stage heat transformer is being designed. Results obtained during this study indicate that the physical properties of the residue oil stream make it unsuitable for use in such heat recovery technology, while the Naphtha condensation may be utilised with more favourable outcomes. Based upon the current gas price being quoted by the refinery, it is demonstrated that this Naphtha stream on its own does not contain sufficient quantities of recyclable energy to ensure that the system is capable of generating an acceptable return upon investment. The suitability of such heat recovery to larger, more energy intensive sites is highlighted however, and it is demonstrated that if the quantity of suitable energy available were to increase by a factor of two or four then the economic indicators begin to show substantially more favourable results. Thus it may be concluded that at the current low gas price, the use of a triple stage absorption heat transformer is mainly suited to larger plants with sufficient waste energy available for recycling