Equipment & Systems
Pulpwood to biomass: Batch processing to spec
By Del Williams
Automating procedures with greater operator control and visibility can minimize human error, while improving quality and productivity
By Del Williams
Today, a large share of pulp and paper production in North America and Europe derives from pine trees in sustainably managed forests.
In the kraft pulp production process common in the industry, two notable pine chemical product streams are generated: crude sulphate turpentine (CST) and crude tall oil (CTO).
Kraton Corporation is a developer, manufacturer and marketer of pine chemicals and other bio-based chemicals and specialty polymers worldwide.
In dealing with pine chemicals, their process displaces petroleum dependence for equivalent products, but in so doing, must account for the inherent variability in biomass feedstocks to their process.
The company operates a network of nine strategically located manufacturing facilities in North America and Europe.
However, at Kraton’s Savannah, Georgia facility, too many batches were produced out of spec and required correction, and the issue could not be pinpointed to a certain product or work shift.
Challenges with the automation system
The plant’s 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 might still require the operator’s manual attention to start and stop heating.
After a thorough review, it was determined that product quality could be significantly improved by optimizing the execution of manual tasks.
Operators would get interrupted or busy with other tasks and, for example, 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 the starting and stopping of heaters and other time-sensitive procedural steps.
While the resulting off-spec product could be corrected, making the necessary adjustments took extra time, labour, material and line capacity, which reduced productivity and profitability.
Implementing a new DCS
Kraton uses three different distributed control system (DCS) platforms to filter, centrifuge and distill the feedstocks into resin precursors.
To control their reactor processes, the company now uses the D/3 DCS from Owings Mills, Maryland–based NovaTech, a specialist in batch process automation, for the flexibility of the Sequence and Batch Language (SABL) that the D/3 controllers use, and for an S88-based layered batch management package called FlexBatch.
The NovaTech D/3 operator interface displays real-time process information and allows 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 .doc and .pdf formats, which were embedded within graphics or in help menus.
For manual tasks, operators would 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,” says 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.”
Adding automation to batch programs
Later, Kraton added a layered procedural automation software package called Paperless Procedures (PLP) to the D/3, also from NovaTech.
The software solution allowed manual tasks and automated tasks to be integrated into the same SABL batch programs, an innovation that NovaTech has patented.
“This hybrid approach has improved product quality while reducing batch cycle times.”
PLP provides operators with a standard operating procedure-like checklist interface that merges manual and automated tasks in real time, that adapts dynamically to real-time process data, and which 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,” says Cox. “This hybrid approach has improved product quality while reducing batch cycle times.”
Faster process control
With this approach, the operator can modify recipe parameters, recipe procedures, production schedule, batch start rules, equipment utilization or scale batch amount at any point during recipe development and execution.
Recipe values are automatically entered into the system, and all the operator needs to do is click on the reactor to use and which vessel to pull from. This is safer, more intuitive, and speeds the process because the operator selects all the equipment to be used before starting the procedure.
“We are basically eliminating some of burden on operators to interpret the process,” says Cox. “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 provides higher yields, reduced errors, improved safety and profitability. This has enabled Kraton to capitalize and expand their bio-sourced operations.
More reliable batch processing and greater productivity with renewable products will help the pulp and paper and biomass industries more successfully compete in a challenging marketplace.
Del Williams is a technical writer based in Torrance, California. He writes about health, business, technology and educational issues.