Advanced and Enhanced

Automation experts estimate perhaps half the ethanol industry has migrated to newer, more powerful distributed control systems (DCS). Many of the older systems remaining are getting extended lives, however, through targeted advanced regulatory controls.

DCS migration is a big project—financially and systematically—comprised not only of computer upgrades but new sensors and software. “It’s a large system connected to 3,000 individual sensors that have to be replaced,” says Carson Merkwan, business development manager for Direct Automation. “We do it in two days and check it out and they’re ready to go.” Advanced control systems forestall the need for the big migration project, reducing cost and targeting the application. “Advanced process control is a very powerful tool that’s been around a while,” Merkwan says. “And it’s a lot less expensive than it used to be. It used to cost $1 million and now is about $50,000 for targeted areas.”

“What we’ve seen as a trend in recent years is plants utilizing existing control architecture more, without resorting to third-party controls, but pulling some of that advanced control into the DCS controller,” explains Rick Tenor, product management lead at Trident Automation.

While 10 years ago, the advanced controls were considered mostly for the larger, 100 MMgy plants, the development of a modular approach has made it technically and financially feasible for midsize plants, says Gary Jubien, senior product marketing manager at Honeywell. “There’s a minimum level where you have to be able to write from a computer and control a set point. If that can’t be done, you can’t implement, but a lot of systems will support that.”

Basics to Advanced
Every plant has basic automation with multiple proportional integral derivative (PID) loops. Jubien likens a PID loop to cruise control in a car. The basic automation offered by single PID loops are often linked in cascade loops where one PID controls a second loop.

PIDs are reactive, however, compared to advanced controls that learn key upstream indicators and respond more quickly. Tenor explains the difference using the example of dryer temperature control. “As long as everything is stable and you have a steady flow coming in and there’s nothing disturbing your system, it’s pretty easy to control the temperature in the dryer with a simple control loop. But let’s say, for some reason, the flow going through centrifuges increases 20 percent, introducing more cold product into the dryers. It’s going to drop the temperature, which the loop is going to see. It will crank up the natural gas to increase the temperature, probably overshoot and get things a little too hot for a while before coming back down.” That sort of temperature variability can make it difficult to maintain consistent moisture in the DDGS, he says.

“But if you knew that change in flow was coming before it happened, then you can compensate by increasing temperature a little bit in advance and try to keep up as it happens. You can keep the temperature in the dryer nice and even and your product moisture isn’t going to change all that much. That’s what we can do with advanced regulatory control—use that feed coming out of the centrifuge as an indicator that something’s going to change and react before it happens.”

Besides the dryers, two other areas that are good targets for advanced controls include slurry to maintain the optimal ground corn-to-water ratio, and in distillation to maintain temperature differentials.  

Honeywell documented the benefits of advanced controls installed at one 50 MMgy plant. Energy savings in distillation improved profits by $71,000 annually and better 200 proof control improved them by $80,000. Fermentation yield improvements added $188,000 to the bottom line and the incremental increase in throughput of 0.6 percent brought in $126,000.  

Integrated management
Management of the data being recorded by the control system is also getting more sophisticated. “Data is flowing in like mad and getting processed automatically, coming out in meaningful format for decision-making,” Merkwan says. More plants are making use of predictive analytics, he adds, plugging historical data into an Aspen model to see whether a proposed change, such as adding a molecular sieve, would deliver the desired results or whether other tweaks are needed to capture the full benefits.

Data integration is big, Merkwan says. Direct Automation has implemented its tool, Pi in the Sky, at a number of plants, making the data available in the cloud to those with proper access. “It takes data from their automation system and from the lab, the maintenance management software and commodities and internet data like weather forecasts and aggregates it in one master database. From that, we can generate any report they want.” The reports are available in the control room, the office, or even on managers’ cell phones. “The average user is on the site 1.5 hours a day,” he adds.

Honeywell is also putting more solutions in the cloud. “The buzzword is IIOT—the industrial internet of things,” Jubien says. “Honeywell is adding analytic capabilities to our products. The data on the cloud is available not only to the plant operators, but to Honeywell. We can detect when something is going wrong—maybe the board operator isn’t using the application as well as it could be or maybe the application isn’t matching the plant as well as it can. We use analytics that look at data and automatically generate an alert that is sent to the customer. Then we can jointly work to solve it.”

Another trend Honeywell is working with taps into the capabilities of artificial intelligence. “We found a lot of applications were turned off because the operator didn’t understand what it was doing,” Jubien explains. “Being able to answer that is key to addressing the comfort level of operators.”

Even as the industry continues to install new and more powerful DCS and advanced controls, attention to the basics is important. Merkwan recommends just cleaning up existing systems. “There’s been so many things coming out that people need to clean it up and get it working well,” he says. “There are so many systems where cable management is bad, alarm management is bad, the sequencing and coding needs to be cleaned up. A lot of times, if they have an engineer there for a month or two cleaning the system up and restoring the old system, it will make a difference.”

Another opportunity for improvement is in implementing sequences, Tenor says, pointing to 10 sequences Trident Automation has implemented at various plants.  “An example is shifting from one mash train to another, which is a series of opening and closing valves. If you do it by hand, it could be 30 mouse clicks to get it done. If you build a sequence, it just does it with one click.”

Hands-On Vs. Automation
While it can be helpful to automate sequences whose repetition can be mind-numbing, balance is needed, Tenor says. “You want human interaction and operators with their eyes on everything.” That said, it can be beneficial to automate critical sequences so the procedure is done the same way every time, regardless of shift changes or new or experienced operators.

Experience will outweigh automation in some cases where plant managers and operators turn off automation. “Some don’t use them because they like to have their fingers on the system instead of doing it with automation,” Merkwan says. “Stereotypically, the guys that have been around a while, that have been in the system for 20 years, they know what a good-sounding plant sounds like. They can walk into a place and hear the motors running and know if everything is running right. They do a good job. And if it works, it works. As the newer guys come in, we’re starting to see movement towards automation.”

Built upon the historical data of a plant, advanced process controls essentially are replicating what the best operators do. “Advanced control is just trying to do slightly better than what the operator does,” Jubien says. “Over a day, [the advanced controller] is making 1,000 small adjustments. Even the most patient, dedicated operator can’t apply that level of focus. That’s why the advance control can do a little better in most cases. I’ll use the cruise control analogy. I know my cruise control can hold the 65 miles per hour a little more steadily than I can. But it’s not necessarily a better driver.”



Author: Susanne Retka Schill
Freelance Journalist
[email protected]