A Straightforward Optimization Approach for a Baseload Propane-Mixed Refrigerant Process

Abstract

As the energy markets adjust to the increasing demand on liquefied natural gas (LNG) and growing global warming concerns, a compelling need arises to operate existing LNG plants as efficiently as possible. Cryogenic systems, such as those used for natural gas (NG) liquefaction, are very complex. This makes optimizing their performance a frustrating task. In this paper, we propose a simple and systematic optimization approach for cryogenic processes characterized by large numbers of independent variables and sophisticated heat integration schemes. The method is composed of successive optimization levels that rely on shortcut thermodynamic techniques and sequential quadratic programming (SQP). In this paper, we are reporting the results of the proposed approach for optimizing an actualbaseload propane mixed refrigerant (C3MR) process. Results showed a 6 % compression power reduction compared to the plant's current consumed power. The method is currently being tested for a more sophisticated LNG system employing C3MR cycles integrated with natural gas liquids (NGL) recovery, helium extraction, and nitrogen rejection processes.