Sigurd Weidemann Løvseth

Annotated bibliography—Use of optimization in LNG process design and operation

Abstract This paper provides a review of the literature on applications of optimization for design and operation of processes for liquefaction of natural gas and a few related subjects. The review takes the form of an annotated bibliography. A short summary of each of the 186 published works published up to and including 2013 is combined with a classification of the different contributions. While the main focus is design and optimization of processes for liquefaction of natural gas, a selection of publications considering optimization of other parts of the LNG value chain and optimization of other sub-ambient refrigeration processes is also included.

Formulating the optimization problem when using sequential quadratic programming applied to a simple LNG process

Abstract Sequential quadratic programming (SQP) may be very efficient compared with other techniques for the optimization of simple processes for the liquefaction of natural gas (LNG), and can be combined with process evaluation using commercial flowsheet simulators. However, the level of success is dependent on the formulation of the problem. In this work, effects of varying different aspects of the optimization problem formulation is investigated, such as variable selection, formulae for the estimation of derivatives, initial values, variable bounds, and formulation of constraints. Especially the formulation of the constraint for the temperature difference between the hot and cold composite curve is essential. The commonly used minimum temperature difference constraint should generally not be employed in gradient based optimization. Recommendations regarding optimization of simple LNG processes using SQP and flowsheet simulators are provided.