Assessing Opportunities to Apply Advanced Control

ModelingAndControl.com blog’s Greg McMillan copied me on two presentations he recently gave to a major chemical manufacturer. Being a blogger and firmly believing that great content should be shared with the world, I asked Greg if I could upload the files to my slideshare account. Greg graciously agreed.

Here’s one of them, Opportunity Assessment and Advanced Control:

Greg listed the benefits that advanced process control can bring, based on his experience and 33 year career in the chemical manufacturing industry. These included:

  • Improved yield (better selectivity)*
  • Less blending, scrap, and rework or higher price for higher grade*
  • Lower utility costs (energy minimization)
  • Higher production rate (feed maximization)
  • Increased on stream time (fewer shutdowns)
  • Reduced maintenance (less stress on equipment)
  • Safer operation (fewer shutdowns and less stress on equipment)

*The benefits for improved yield and less scrap or rework can be taken as an increase in capacity or a reduction in raw materials

The presentation is rich with guidance for opportunity sizing and assessment, common myths and misconceptions, lessons learned, rules of thumb, and of course, Greg’s famous top 10 lists. I’ll highlight just the opportunity assessment portion of the presentation and leave the rest for your perusal.

Greg showed a chart of three companies who benchmarked their regulatory and batch control, advanced control, and data management. The total improvement in cost of goods sold (COGS) across these three categories was 8%.

Greg advised to begin with a thorough opportunity sizing before the opportunity assessment using cost sheets, product prices, historical trends, business plans, research reports, technical studies, and simulations to establish actual, practical, and theoretical performance–like yields and capacity improvements–with operations and technology.

Next, he counseled to work with the plant process engineers to go through the process, identify constraints, and offer ideas on opportunities to reduce gaps identified in the opportunity sizing exercise to see and work way out of the current process box. You’ll want to avoid the temptation of a canned solution or to come to conclusions before the plant personnel thoroughly discuss peculiarities and special problems. Greg felt that it’s important for knowledgeable people to speak first and ask questions–and to hold off on solutions. Instead, offer concepts that people can use to generate solutions and be a good listener during this phase.

And from the process itself, use the automation system and the historian to find loops in manual, limit cycles, slow or oscillatory set point and load responses, and controller outputs running near limits.

Your next step is to look for opportunities to infer compositions from fast, lower maintenance measurements such as density, viscosity, mass spectrometers, microwave, and nuclear magnetic resonance. Seek applications of accurate mass flow ratios for material balance knowledge and control.

You’ll want to ask the operations folks what would happen if a set point or operating mode were changed. When developing possible solutions, pick control technologies to address opportunities and give relative estimates of implementation cost and time (e.g. high, medium, low) and percent of gap addressed. For a sanity check, ask plant process engineers to estimate percentage of gap addressed by each solution.

Greg’s closing thoughts for this assessment process were to take advantage of momentum and group enthusiasm by starting on “quick hits” immediately and setting definitive schedules and assignments for others (to avoid inertia of waiting for a quote or study.) Finally, take the action to tune the loops and improve the loops.

If you view or download the presentation, look at some of the questions you should ask during this assessment on slides 16 and 17. Hopefully you’ll find some nuggets on how and where to apply APC to reduce your COGS.

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Posted Tuesday, November 11th, 2008 under Education, Process Optimization.

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