- By Chris Kourliouros
When chemical processors—including those creating plastic, polymer, or rubber products—use batch reactors, following the recipe from batch-to-batch and plant-to-plant is critical to reliably and cost-effectively manufacture high value-added materials to spec. This typically involves charging the reactor, manipulating operating conditions to meet processing criteria, and shutting down and emptying the reactor.
Even when certain procedures and processes are standardized and automated, numerous key steps in and around the automation may still depend on operator input or manual intervention. Unfortunately, when the operator is interrupted to handle other tasks or when responses vary from operator to operator, off-spec product can result. This can cause costly corrective steps or wasted product that must be disposed.
As a solution, some chemical producers are automating their standard operating procedures (SOPs) while providing operators with greater control and visibility. This helps chemical processors perform more consistently reliable batch processing to spec, which enhances quality, productivity, and profit.
Batches of biomass-derived specialty chemicals
Kraton Corporation develops, manufactures, and markets biobased chemicals and specialty polymers worldwide and has more than 800 customers across a diverse range of end markets in more than 70 countries. The company is also a global producer of styrenic block copolymers and pine chemicals. In January 2016, Kraton Corporation completed the acquisition of Arizona Chemical, a global producer of high-value performance products and specialty chemicals derived from nonhydrocarbon, renewable raw materials.
Renewable biomass derivatives from paper production (referred to as “soap”) are used to produce a variety of specialty chemicals for 3M, HB Filler, and other clients: rosins used in inks, adhesives, road paint, construction, packaging, personal care, and other applications. The process displaces petroleum dependence for equivalent products, but in so doing must account for the inherent variability in biomass feedstocks to their process.
Kraton operates a network of nine manufacturing facilities in North America and Europe, but its Savannah, Ga., facility was producing too many out-of-spec batches and required correction. Although the issue could not be pinpointed to a certain product or work shift, the previous automation system consisted of a series of programs that still required operator intervention at key junctures. For example, an automated procedure could charge a reactor with a particular product, but it might still require the operator’s manual attention to start and stop heating.
Optimize execution of manual tasks
After a thorough review, the Kraton team determined that product quality could be significantly improved by optimizing the execution of manual tasks. Operators would be interrupted or become busy with other tasks. For example, they would be unable to hold a material at a certain steady melt point, because they had to unstick a valve by running steam into a line to free it up.
Natural human variability in operator response was also causing inconsistencies, for instance, in starting and stopping heaters and in other time-sensitive procedural steps. While the resulting off-spec product could be corrected, making the necessary adjustments took extra time, labor, material, and line capacity, which reduced productivity and profitability.
Kraton uses three different distributed control system (DCS) platforms to filter, centrifuge, and distill the feedstocks into resin precursors. To control its reactor processes, Kraton uses the D/3 DCS from Owings Mills, Md.–based NovaTech LLC Process Division. The D/3 system was chosen for three main reasons: the company’s expertise in batch process automation; the flexibility of the Sequence and Batch Language (SABL) that the D/3 controllers use; and for an ISA-88-based layered batch management package called FlexBatch.
The NovaTech D/3 operator interface displays real-time process information and makes it easy for the operator to control the process, enter information, and interact with sequence programs. In addition to the real-time process graphics and the FlexBatch interface, operators had access to standard operating procedures in standard document .doc and .pdf formats, which were embedded within graphics or in Help menus. For manual tasks, operators could type answers to enter values, such as which vessel was used to supply the materials to produce a given product.
“I have not seen any DCS that can handle nearly as many loops and as much programming per controller as the D/3,” explained Gregg Cox, the senior controls engineer who designed the operator interface. “We run about 3,000 I/O points on five process control modules here, and we could probably do it on two.”
Paperless procedure automation
Kraton added a layered procedural automation software package, Paperless Procedures (PLP) from NovaTech, to the D/3. The software solution allowed manual tasks and automated tasks to be seamlessly integrated into the same SABL batch programs, an innovation that NovaTech patented.
PLP provides operators with an intuitive SOP-like checklist interface that merges manual and automated tasks in real time, that adapts dynamically to real-time process data, and that can be viewed from any PC, tablet, smartphone, or other device. PLP also provides secure, time-stamped records of every procedure step to support compliance requirements and continuous improvement efforts. The combination of tools has allowed Kraton to achieve more accurate, consistent, and repeatable batches.
“The final product is completed with scheduled campaigns on FlexBatch that are completed with batches run with PLP,” explained Cox. “This hybrid approach has improved product quality while reducing batch cycle times.”
With this approach, the operator can modify recipe parameters, recipe procedures, production schedules, batch start rules, and equipment utilization, or scale batch amount at any point during recipe development and execution. Recipe values are automatically entered into the system, and the operator only needs to select the reactor and which vessel to pull from. This safer, more intuitive approach speeds the process because the operator selects all the equipment to be used before starting the procedure.
“We are basically eliminating some of [the] burden on operators to interpret the process,” Cox said. “This has resulted in batch cycles that are more consistently executed with the proper timing and procedure. As a result, we can begin looking at the overall design of our processes and engineer out some of the ‘wiggle room’ that had to be there to account for operators’ varying interpretations of what to do next and when.”
According to Cox, filling in the gaps in the system’s automation process ultimately brings higher yields, reduced errors, improved safety, and greater profitability. Kraton can capitalize and expand its operations over both petroleum-based and other biosourced competitors.
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