Electronic Marshalling Slashes Costs for Sulfuric Acid Maker

By Jim Montague, Executive Editor

If you had to build a new process plant, you might dream about needing 50% less wiring and installation labor, but then you'd likely wake up. Well, some users are now living that dream, thanks to Emerson Process Management's electronic marshalling technology. Launched two years ago, this new approach to control system I/O, which features single-channel, highly flexible characterization modules (CHARMs), is now proving its potential in a growing number of real-world applications.

For instance, Southern States Chemical built and opened its new sulfuric acid plant in Wilmington, N.C., just one year ago, and CHARMs dramatically simplified and streamlined the entire project, according to Bryan Beyer, Southern's acid operations manager. He described Southern's efforts during a Tuesday press briefing at the Emerson Global Users Exchange this week in Nashville.

Though as the largest East Coast supplier of sulfuric acid, it runs other facilities, Southern needed the new plant to meet growing demand for its product. Beyer reports that sulfuric acid is the most widely traded chemical commodity in the world because practically every process application from pulp and paper to chemical production to brewing beer uses large amounts of it. The compact 120-ft x 100-ft plant was also needed to supply reliable, high-pressure steam to Invista's specialty chemical plant next door.

Sulfuric acid is made from water, sulfur and air in a series of oxidation and absorption steps. Measured variables include a range of temperatures, pressures, flow rates and conductivities. "Temperature control of the SO2 converters is especially critical because they use a catalyst and have to make several passes," explained Beyer. "So we decided to install 10 CHARMs cabinets in areas with the highest I/O concentration."

Engineering and integration firms, Control Southern and R.F. Mason, helped Southern States design and integrate the new plant.

In the end, Beyer says his company saved about 50% on wiring and instrumentation installation labor thanks to electronic marshalling. For example, instead of having to bring I/O signals 200 feet back to its control room, many could simply be tied into the existing Ethernet backbone in just a couple of hours. "We were even able to secure some digital inputs, install a horn in the control room and have a whole-plant evacuation system for just $2,000," added Beyer.

To get CHARMS and the rest of its new process control system up and running, Beyer adds that his team had to cope with Southern's long tradition of mostly manual control. "The company used very little automation before, so the operators really weren't used to performing control functions in a control room," he added. "However, after about two weeks of training, they found it was pretty easy to understand." 

In addition, Emerson's chief strategic officer, Peter Zornio, announced that today, October 25, it's adding intrinsically safe (IS) CHARMs to the company's electronic marshalling offering. By eliminating the separate wiring and cabinet space needed for stand-alone IS barriers, IS CHARMs are expected to deliver even greater savings in system design, installation cost and ease of maintenance for hazardous environments.

"Electronic marshalling allows process manufacturers to shorten project schedules, accommodate late project changes, eliminate equipment and cabinets, and dramatically simplify the I/O and marshalling design process," explained Zornio. "With the addition of IS CHARMs, we're bringing this same flexibility and savings to some of the most challenging process environments, in which flexibility and reliability are needed most."

Finally, Zornio revealed that Emerson also is working on a safety instrumented system (SIS) version of CHARMs. He reported that a prototype is even being demonstrated on the event's exhibit floor this week, but so far no release schedule has been announced.