Comparison of Methods for Computing Crude Distillation Product Properties in Production Planning and Scheduling

Production planning and scheduling optimize feedstocks usage in refineries by using crude simplified distillation models which relate feed true boiling point (TBP) curves to product TBP curves and from these calculate product yields and properties. We compare product yield and properties calculated by the swing-cut methods (fixed-cut, weight/volume transfer, and light/heavy) with results from the pseudocuts TBP-based method. The latter uses product yields and TBP curves computed via the hybrid distillation model. Swing-cut methods use assumptions which lead to lower accuracy of predicting yields vs hybrid model yields, resulting in errors in computed bulk product properties. If swing-cut methods yields are replaced by the correct yields from hybrid model, all four methods have approximately the same accuracy. Therefore, for a mixture of crudes, by using accurate yields from the hybrid model, product bulk properties can be computed by blending rules as simple as those used by the fixed-cut swing method.