Profit Optimization of a Refrigerated Gas Plant

The operation of a gas processing plant with tight profit margin and rigid contractual constraints at both ends poses a challenging problem. The problem is further compounded by continuous fluctuations in the feed compositions and economic conditions of the plant. To widen its profit margin, the plant needs to operate more efficiently. This requires continuous re-evaluation of the operating conditions through an efficient optimization algorithm. The success of solving the optimization problem rests on the accuracy of the plant model used, as well as the inclusion of technical and business aspects of the plant operation.

This paper proposes means for optimizing a refrigerated gas plant (RGP) based on a steady-state simulation model. The RGP is simulated using AspenTech HYSYS and calibrated with the actual plant data. Key optimization variables are prudently identified in order to induce maximization of a profit function. Four case studies namely the base case (1B), one-feed (1F), two-feed (2F) and three-feed (3F) inlet streams are carried out. As compared with Case 1B, the profit margins rise by 9.3%, 12.3% and 13.4% for Cases 1F, 2F and 3F, respectively. It is observed that the best option for this RGP is to focus on balancing the feed gas supplies while respecting the plant constraints. In addition, it is found that optimizing utility consumption results in insignificant savings. The utilities only contribute less than 2.4% of the total expenses in all four case studies.