Reducing System Migration Risk for Refinery Blend and Tank Farm Operations

Emerson's Murali Krishnan

Emerson's Patrick Truesdale

Regulatory bodies across the globe continue to impose stricter specifications for transportation fuels to reduce combustion byproducts. Emerson’s Murali Krishnan and Patrick Truesdale shared a story with me of an Asian refiner who needed to modernize its blend and tank farm operations to meet the sulfur-related regulations and other seasonal volatility specifications.

For refiners, blending and their associated tank farm operations are quite complex since they require close coordination and collaboration among different groups—planning, operations, lab and engineering.

To improve the efficiency and reliability of their operations, this refiner worked with the Emerson refining consultants and project team to develop and execute a plan to migrate and enhance blending and tank farm operations. To meet the tighter specifications, the plan required that the control system be modernized, automatic tank gauging systems (ATGS) be modified, and on-line blend and optimization systems be added. Also required was information integration between the control system, data historian, laboratory information management system (LIMS), ATGS, and other sources of data in the production process.

For the project from initial design through commissioning, the Emerson team included an overall project manager, blending and optimization consultants, DeltaV distributed control system and SmartProcess Blend project engineers, as well as safety, quality, planning & scheduling, order, and procurement support. The project also had to meet performance guarantees. For the unleaded gasoline grade specifications, those were Research Octane Number (RON) ±0.15 and Reid Vapor Pressure (RVP) ±0.5 bar. This collaborative project effort with the plant staff helped to reduce the risks associated with the system migration and blend process improvements.

The team identified several challenges to overcome at the start of the project. The drawings that were associated with the existing instrumentation and controls required significant updating to reflect the current state of the refinery. The data from the LIMS system used long-term property component data instead of current data based on the feedstock. This fixed data was used in the blend recipe, creating more opportunity for off-spec gasoline blends to be produced.

The existing refinery blend control strategy was based on ratio control with offline measurements. The project scope included online analyzer measurements—Fourier-transform near-infrared spectroscopy (FT-NIR) and RVP to perform real-time optimization.

The scope also included a “hot cutover” to migrate from the legacy control system to the DeltaV system. This meant that the refinery would continue to operate while each control loop was transferred over from the old system to the new system. The project team carefully planned how this would be done to reduce the risk of any unplanned outages during the hot cutover.

The refinery staff and Emerson project team successfully performed the hot cutover and migration of the control system, measurement device and analyzer on time and with no incidents. The optimized refinery blend operations provided reduced variability in the finished products. By reducing variability, quality touchups were eliminated, quality giveaways were reduced, and inventory levels were more effectively managed.

The performance guarantees for the project were successfully achieved. Refinery planners had minimal deviations from recipe and blend component usage and were better able to provide on-time delivery based on commitments made. Overall, the refinery experienced lower blending costs and more efficient and reliable operations.

Visit the Refinery Blending section of the Emerson website for more information. You can also connect and interact with other refining industry experts in the Refining group in the Emerson Exchange 365 community.

Posted Wednesday, January 24th, 2018 under Refining.

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