The journey is often more important than the destination, and this is especially true for lifecycle management in blending and movement automation (BMA) applications. "Overall, process control system lifecycle management seeks to provide the greatest ROI over the life of the system," says Paul Singh, Ph.D., global blending and oil movement specialist at Chevron Corp. Singh presented "Control System Lifecycle Management and BMA Upgrades at Chevron" in June at Honeywell Users Group 2013.
Singh reports Chevron's BMA applications at its refineries strive for standardized, online, closed-loop, real-time optimization. This is achieved with multi-blend optimization (MBO) scheduling and planning at the enterprise level, which downloads objectives and recipes to blend property controls (BPCs) at the operator stations. Planners figure out optimum processes to perform and then run them on the refinery's DCS and its blend ratio controls (BRCs), related instruments and analyzers.
Chevron's DCS and blending applications process 50,000 bpd to 800,000 bpd and use vintage and new equipment, including:
- BRC v44.3 through Experion Blend Control (EBC) and BMA 320.7 for BRC;
- BPC v54.0 through OpenBPC BMA 320.7 for BPC and optimization;
- SDM v44.2 through Inventory Monitor BMA 320.7 for inventory monitoring; and
- Knock engines through Raman spectrographic analyzers from Process Systems Inc.
Singh adds that blending optimization at Chevron since 2005 has been a continuous process aided by several programs, including: multi-product, multi-period, non-linear optimization implementation and upgrades; and migration from NIR and other online analyzers to Raman modeling and online analyzers.
"We gained a lot of benefits with the Raman analyzers, which are easier to maintain. We've been using them for about 32 months, including between blends, and had virtually no downtime," says Singh. "So what's the motivation for all these upgrades? Well, our first priority is safety and the environment. We also want to use the same systems, and make products that are at least 95% on-spec, which we've achieved because we're usually 98% on-spec.
"We also found that, as we improve safety and environmental performance, profit improves as well. For example, the difference between the top quarter of performers and the bottom quarter can be more than $1.50 to $2 per barrel, while a performance variation of just 10 cents can add up to about $5 million per year for a typical refinery. And you can lose $500,000 in one day of doing a process wrong, or gain it if you do what's right."
Singh adds that Chevron's applications must be as nimble as possible. "Large refineries can't make blends and analyze them later," he explains. "We need to be flexible to reduce downtime between blends. We have one refinery with barely a half hour between blends.
"Gone are the days when we made the same product day in and day out. Now refineries make 50 to 80 products, and they must meet just as many specs. So, we use predictive properties and account for opt-ins, such as adding ethanol. In the future, we'll see even more operational complexity, as well as increasing regulations of conventional fuels and reformulated blendstock for oxygenate blending (RBOB) now; E15, E85 and biofuels on the horizon and tighter rules for data capture and retention."
Fortunately, Chevron is becoming even more proficient in its lifecycle and BMA practices. For example, Singh reports it completed a BMA320 upgrade about three years ago by implementing redundant C300 controllers on multiple blenders and adding EBCs and OpenBPCs. "We completed our mogas blender cutover in just 16 hours," adds Singh. "This upgrade produced significant economic benefits, including increasing uptime and decreasing deviation from maximum profit by 50%."