Stagewise expansion
Cognis expands DeltaV system at UK site

Specialty chemicals and nutritional ingredients manufacturer Cognis is in the process of migrating existing control systems at its site at Hythe, UK, to an Emerson DeltaV digital automation system. Work began in late 2002 and will continue at least until the end of this year.

The Cognis plant at Hythe is the world’s leading producer of hydroxy monomers, reactive intermediates that are sold globally and used primarily in high performance automotive paints and high-gloss product lacquers. Cognis also manufacture high-purity products for contact lens and biomedical applications as well as multifunctional methacrylate monomers used in niche applications such as adhesives, rubber compounds and superabsorbent polymers in disposable nappies. The products require high levels of consistency and tight control. High levels of manufacturing availability are required to meet the demand for the products.

The Hythe plant has experienced tighter control and greater consistency since migrating from its existing control systems to the DeltaV digital automation system from Emerson Process Management. Other benefits so far include improved safety, greater ease of use and lower maintenance costs thanks to the DeltaV’s Windows-based technology. The DeltaV system now has five operator stations controlling four plants, with more to follow this year. Future plans include an expansion of Emerson’s PlantWeb technology with Foundation fieldbus.
The story of the control upgrade began in late 2002 on one of the site’s two Multifunctional Monomers production units, a batch plant known as MMU2. While its sister plant, MMU3, is controlled by a Rosemount System 3 (RS3) process automation system from Emerson that is still performing well, MMU2 was controlled by ageing multiloop controllers.
The need for changewas there
Certain components within the existing controllers on MMU2 were becoming difficult to source, leading to concerns about plant availability. There were also issues surrounding the engineering support of the older controllers, including fewer technicians able to program the DOS-based software. In addition, one of the site control rooms had to be moved, and the cost of hard wiring the controllers into a new location was prohibitive.
“To address the MMU2 issues we decided to install a DeltaV digital automation system,” says Pepita Monk, the site’s Project Instrument/Electrical Engineer. “We chose DeltaV for several reasons. It was the most economic solution for us, and we could use the existing site local area network to enable the engineering and operator stations within the new control room to communicate with the controllers located in the termination room on the plant. Use of the DeltaV system also prepares our plant to use the benefits of Foundation fieldbus technology and PlantWeb digital plant architecture for future expansions.”
“We also knew from our System 3 that Emerson gives very good support, and that was definitely a factor in choosing the new system,” says Monk.
“Emerson continued to give us very good help throughout the project,” she continues. “They spent a lot of time helping us prepare a specification before we placed the order, as well as running training sessions to ensure our engineers were comfortable with the technology. When we installed the new control system, we used the existing field wiring and termination panels to minimize costs. These were then wired directly to the DeltaV I/O. Emerson assisted us in commissioning, and helped with operator training. By using DeltaV simulate, we were able to configure a training demo to resemble the new architecture that we were installing.”The new system was commissioned in February 2003 and has worked smoothly ever since. “This is not a large plant, with around 50 I/O points,” says Monk, “but we had the operators trained within a week and we lost only four or five days of production.”
Gradual expansion in the number of control loops
There are no plans at the moment to replace the RS3 controller on MMU3, but it may soon be linked to the DeltaV system using DeltaV Operate for RS3 software, which will enable raw material inventory data to be shared by both systems. Other changes include a gradual expansion in the number of control loops and a trial of Emerson’s AMS Suite Intelligent Device Manager software, in which around 60 intelligent field devices pass diagnostic information on their condition through to the plant maintenance technicians.
Though there was originally no firm plan to expand the DeltaV system beyond the MMU2 plant, says Monk, it was clear from the start that the Hythe site offered plenty of opportunities for better process control.
Soon after the system had demonstrated its success on the MMU2 plant, Cognis decided to extend it to another three reactors. These alkoxylation reactors use ethylene oxide and propylene oxide, whose addition rates need careful control if the plant is to operate safely. “The existing system relied on rather dated charts of the safe operating region,” says Monk. “Now with the DeltaV system we are able to control the addition rates based on the reactor pressure, so safety has improved.” Recipe management is also better with the new system. Previously, ingredient quantities and reaction profiles had to be keyed in individually by the operator. “It generally worked well, but mistakes were not unknown,” says Monk. “The revamp didn’t justify a complete recipe management system, but we manage very well by storing the recipe details in a spreadsheet and downloading that to the DeltaV system.”
The next control systems to be upgraded are those for the unloading and distribution facilities for ethylene oxide and propylene oxide, which should be completed in June this year. By the end of the year, the company also plans to have upgraded control of the utilities system.
“It’s an ongoing project,” says Monk, “we’re always tweaking the system and adding to it, often just one or two loops at a time.“