|Title||Synthesis of heat exchanger networks at subambient conditions with compression and expansion of process streams|
|Publication Type||Journal Article|
|Year of Publication||2011|
|Authors||Wechsung, A., A. Aspelund, T. Gundersen, and P. I. Barton|
|Keywords||carbon dioxide, CCS, exergy, heat exchanger network, heat recovery, LNG, natural gas, Optimization, pinch analysis, pressure recovery, process design|
This paper presents an optimization formulation for the synthesis of heat exchanger networks where pressure levels of process streams can be adjusted to improve heat integration. Especially important at subambient conditions, this allows for the interconversion of work, temperature and pressure based exergy and leads to reduced usage of expensive cold utility. Furthermore, stream temperatures and pressures are tuned for close tracking of the composite curves yielding increased exergy efficiency. The formulation is showcased on a simple example and applied to a case study drawn from the design of an offshore natural gas liquefaction process. Aided by the optimization, it is demonstrated how the process can extract exergy from liquid nitrogen and carbon dioxide streams to support the liquefaction of a natural gas stream without additional utilities. This process is part of a liquefied energy chain which supplies natural gas for power generation while facilitating carbon dioxide sequestration.