Unlike traditional, large-scale petrochemical manufacturers that focus on a single product, polymer manufacturers produce many products over a wide range of conditions. Operating a polymer reactor to meet these varying specifications is a complex, non-linear control problem. As a result, operations must focus not only on maintaining the quality of each product during ‘at-grade’ conditions, but also on transitioning from one grade to the next in the most time- and cost-efficient manner. To maximise production and profit across the entire production lifecycle, manufacturers must continuously control the many variables that influence product quality and production rate.
This article will present a case study of a chemical manufacturer - one of the largest integrated energy companies in the world. Its polyethylene business unit is a leading producer of polyethylene with a full range of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) products for the packaging, agricultural, consumer goods, and construction sectors. The company’s European unit makes a wide range of product grades and produces hundreds of thousands of kilotons of LLDPE per year, using its propriety process to produce the chemical. The customer needed a way to meet specific production targets, including increasing LLDPE production, reducing off-spec material, and reducing transition times between grades.
The company learned about the Rockwell Automation advanced process control (APC) solutions during a technical exchange meeting and was impressed with the company’s proven expertise in the polymer industry. Concluding that Rockwell Automation solutions could help the company achieve its quality and production goals, the company implemented the Rockwell Automation FactoryTalk Analytics MPC solution.
FactoryTalk Analytics combines steady-state optimisation with model predictive closed loop control to reduce product variability and transition times, improve reactor stability, and maximise raw material efficiency.
The customer’s specific needs for the software included controlling the gas phase composition in the reactor and managing and controlling instantaneous reactor product quality and transitions between grades. FactoryTalk Analytics creates online predictive models that augment hardware instruments and laboratory analyses to provide real-time estimates of process and product conditions. These virtual instruments provide the feedback and predictive process information needed to keep production on track and prevent process upsets, identifying problems and providing answers quickly¬—without the time and expense of additional laboratory analyses. The customer's specific requirements were to monitor main quality variables such as melt flow index (MFI) and density from actual reactor data.
The first Rockwell Automation solution was installed, implemented, tested, and commissioned at the customer site within 8 months. Rockwell Automation provided most of the engineering expertise with the support of customer personnel, who were trained during project execution.
The benefits of the Rockwell Automation solution – including significant improvements in production levels, reduced disturbances, reduced reactor variance, and transition time savings – were quickly apparent to the customer. The customer also reduced the variability of product properties by 50% because of implementing Rockwell Automation software. “From this we could operate closer to our hardware constraints, resulting in higher throughput,” said a customer representative. The software also decreased transition times by up to 50% (depending on the LLDPE grade produced), increased production by 7%, and increased efficiencies in monomer and catalyst use.
According to the customer representative, the project was a success and delivered additional benefits, which enhanced the profitability of the plant by increasing the range of options.
A customer representative said: “We gained non-APC-related improvements caused by a new understanding of the constraints of the systems. To me, one of the most remarkable improvements is the ability to run new grade transitions which were not possible using the old control scheme. This gives us a higher flexibility in reacting to the needs of our customers.”
Based on the success of the project, Rockwell Automation and the customer formed a strategic alliance to deploy Rockwell Automation advanced process control solutions in the customer’s polyethylene facilities, its joint venture organisations, and its licensees worldwide. In the first two years of the alliance, the customer and its affiliated organisations have successfully deployed 14 projects with Rockwell Automation.
Read the article online at: https://www.hydrocarbonengineering.com/special-reports/29092021/reduce-cycle-time-to-production/
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