By Billy Thinnes
DALLAS -- Pemex hired KBC Advanced Technologies to help it improve the profitability and reliability of its national refining system. A major focus for this project was an upgrade to the linear program (LP) model for Pemex's refining system, and the quest to improve production planning work processes.
The LP upgrade project involved upgrading the process unit LP representations in all six Pemex refineries, which constitute the backbone of the company's 1.3-MMbpd refining system. It took place from December 2010 to July 2012.
Pemex's Ihali Crespo led off a presentation at the AFPM Q&A and Technology Forum by confirming the six refineries that received attention: Madero, Salina Cruz, Cadereyta, Tula, Minatitlán and Samanca.
Michael Tucker, one of the KBC leads on the project, followed Ms. Crespo and noted that each phase at each refinery had an onsite review of LP system parameters, structures, stream routings, process limits and blending options. Process unit table updates were mainly based on KBC's PetroSIM flowsheet base-case simulation.
Mr. Tucker and his team also debugged the model using LP system validation diagnostics, meaning that they tested all modeled features including crude oil options, product options and cutpoints. When all was said and done, the modeling indicated a minimal deviation on gasoline, diesel and fuel oil within the system.
Ms. Crespo noted that the objective of the project was to maximize profit. However, she readily acknowledged the constraints facing the team, including capacities, product qualities and environmental regulations. She also shared the product demand and distribution landscape for Pemex within the LP: demand is associated with 77 markets, passing through 85 transference nodes that are connected by barge, pipeline, truck and rail modes of transport. Ms. Crespo also informed audience members that there are six gasoline types in Mexico.
Mr. Tucker then explained that one of KBC's objectives was to tune up the process unit area. By utilizing the PetroSIM system, his team was able to offer a new crude assay yield; updated crude unit cutpoints; upgraded property index formulas; and upgraded mass balances, blending options and stream routings.
Benefits and lessons learned. Mr. Tucker said improvements were made to the accuracy of the model by tuning up the yields and adding more swing cuts to the crude tower. This was a significant change, he said, as the team eventually added five swing cuts to the model. Other upgrade activities of note were corrected steam routings, mass balance equalization and other error reductions in decision-making.
According to Mr. Tucker, the project execution efficiency benefited from previous KBC/Pemex projects and relationships. "We've been working together on various configuration projects for over 10 years," Mr. Tucker said.
He noted that there were some interesting problems with the data. "We had to go through a lot of reconciliation to get these simulators calibrated," Mr. Tucker said.
Mr. Tucker summarized his presentation by saying that the Pemex global LP is an ideal application for the optimization of a large domestic crude supply, refining and product distribution system. It now allows for optimized crude supply and distribution, inter-refinery transfers, product distribution and imports/exports.
To clarify, Petro-SIM is KBC's refinery-wide process simulation software, complete with multiple process unit simulation models for each location. Petro-SIM allows process engineers to model all of their refinery assets, enabling them to optimize, analyze and evaluate complex refinery interactions. Petro-SIM can be used to determine the impact of different feedstocks and operating targets, monitor process performance, conduct investment studies or update an LP model.
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