OVERALL INTEGRATION OF THE MANAGEMENT OF H2AND CO2WITHIN REFINERY PLANNING USING RIGOROUS PROCESS MODELS

Computational Experience with Piecewise Linear Relaxations for Petroleum Refinery Planning

Refinery planning optimization is a challenging problem as regards handling the nonconvex bilinearity, mainly due to pooling operations in processes such as crude oil distillation and product blending. This work investigated the performance of several representative piecewise linear (or piecewise affine) relaxation schemes (referred to as McCormick, bm, nf5, and nf6t) and de (which is a new approach proposed based on eigenvector decomposition) that mainly give rise to mixed-integer optimization programs to convexify a bilinear term using predetermined univariate partitioning for instances of uniform and non-uniform partition sizes. The computational results showed that applying these schemes improves the relaxation tightness compared to only applying convex and concave envelopes as estimators. Uniform partition sizes typically perform better in terms of relaxation solution quality and convergence behavior. It was also seen that there is a limit on the number of partitions that contribute to relaxation tightness, which does not necessarily correspond to a larger number of partitions, while a direct relationship between relaxation size and tightness does not always hold for non-uniform partition sizes.

Mathematical Modeling and Analysis of Distributed Energy Systems for a Refinery in Kuwait

In this study, a model is developed to optimally integrate various energy generation technologies within a refinery to help reduce economic costs as well as mitigate carbon emissions. The combined heat and power system was found to reduce 80 Mton of CO₂ emissions while saving $2.61 billion dollars over 30 years as opposed to utilizing boilers and grid-connected electricity. Maximum carbon emissions can be prevented by installing wind turbines to reduce further 49 Mton of carbon emissions, saving at an added cost of $53.4 million. Purchasing electricity completely from the grid was found to be the most expensive option, resulting in a monthly average of $25 million. Changes in various factors such as the land available for installation of technology, electricity tariffs, and efficiency of modules and their impacts on the total project costs and emissions were studied. It was found that solar photovoltaic (PV) modules can be a more economical and environmentally friendly option than wind technology if they were equally efficient. Moreover, grid-connected electricity would only be the most economical option if it were purchased at $0.03/kWh or lower. However, it is currently sold at close to $0.10/kWh, making CHP the most economic option for refineries.