Wilmington, N.C.-based Southern States Chemical (www.sschemical.com), a division of Dulany Industries Inc., is the Southeastern United States' largest provider of sulfuric acid. Two locations (Savannah, Ga., and Wilmington, N.C.) combine to produce over 1800 tons per day, with total marketable tons exceeding 750,000 annually, and combined storage capacity exceeding 35,000 tons.
The company's existing Wilmington plant had produced around 500,000 tons of product per year, but the aging plant was almost entirely manually operated, and meeting EPA emissions limits was a concern. So to expand production capacity and ensure conscientious environmental stewardship, the company looked beyond expanding and upgrading the existing facility to building a new state-of-the-art plant on a 15-acre site next to the old plant with ready road and rail access to transport raw materials and finished product.
Another important consideration was the fact that this particular site meant that the principal byproduct of the sulfuric acid manufacturing process—steam—could be converted into a marketable commodity energy source. The new plant is located adjacent to the plant of Invista Wilmington, a large synthetic polymer and fiber manufacturer, which made a ready customer for a reliable supply of clean, high-pressure steam. The new plant would have three absorbing towers, a sulfur furnace, two waste heat boilers, two SO2-to-SO3 converters, gas-gas heat exchangers, four liquid heat exchangers, four storage tanks, and truck and rail loading facilities.
Southern States also went all in with high-tech tools, abandoning its largely manual operations in favor of the latest in automation technology, including HART communications, remote terminal displays, flow elements, DeviceNet networking and a DeltaV automation system from Emerson Process Management (www.emersonprocess.com) along with Emerson's electronic marshalling system, the new characterization modules (CHARMs). All this technology comes together to regulate temperature, pressure, flow, level, conductivity and weight by means of around 235 I/O points.
Shopping in Wisconsin
The company was challenged with keeping down the expense of building a new plant from the ground up. Among the solutions it found was the recycling of major components from a decommissioned government munitions plant in Baraboo, Wis., and transporting them to the Wilmington site. The Baraboo "imports" included all three towers, two gas heat exchangers, some acid pumps and most of the structural steel. To this equipment were added two new converters, a new furnace, new waste heat boilers, two new economizers, a new cooling tower and new storage tanks. This recycling effort gave the new plant its name—Wilbara, in recognition of the two contributing cities located 1100 miles apart. It also saved Southern States an estimated 20% on the cost of the new facility.
Relocating the old equipment and integrating it with the new was only the first challenge. With Southern States' new supplier relationship, reliability became a crucial parameter for the new plant. Southern States not only had to be a reliable supplier to sulfuric acid customers, but also reliable as a supplier of steam under a contract with its neighbor. The company could not afford to have delivery delays caused by start-up glitches or problems getting employees up to speed on the new systems.
Furthermore, Southern States had little previous automation infrastructure within the corporation. Everyone from upper management to the junior operators had to be shown how to look at things from an automation point of view. Training the on-the-ground personnel to operate the new system from a computer screen was another challenge. Working with automated equipment was a completely new experience for them and a challenge to the new plant's operational schedule. But staff took to the new equipment thanks to hands-on, in-the-field training.
Another potential challenge to the new system and technology's installation and start-up was the fact that Southern States was working with two different firms for system configuration and support, so coordinating the two teams' efforts without costly overlap, omission or schedule deviation was a concern.
Integration of technology between the two different companies went smoothly. Process automation consulting and engineering firms Control Southern of Suwanee, Ga. (www.controlsouthern.com), and R.E. Mason of Charlotte, N.C. (www.remason.com), the local distributor of Emerson and Fisher valve products, worked together during the entire project to provide a seamless handoff from inception to operation. The former firm ordered all the field devices, performed programming and graphics design. The latter was involved in the initial concept, FAT, on-site installation and commissioning, then took over all on-going programming and site support. One R.E. Mason employee worked with Control Southern from the beginning to get an overall perspective on the project, and then the Mason team took over completely upon start-up.
The Heart of the System
To automate its processes, Southern States implemented Emerson's DeltaV v11 digital automation system. While that system has proven itself a reliable performer, Southern States took a leap of faith in the system's new CHARM technology. In fact, this project was one of North America's first installations of the new I/O technology.