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

doi:10.1016/j.compchemeng.2015.06.003

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

2015-11-01

Per Eilif Wahl *

Sigurd Weidemann Løvseth

DOI：10.1016/j.compchemeng.2015.06.003

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Abstract

En 中文

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. (C) 2015 Elsevier Ltd. All rights reserved.

Keywords:

LNG

PRICO

Optimization

Sequential quadratic programming

Formulation of constraints

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