How Anchor Glass improved plant and energy efficiencies with a modern DCS
Anchor Glass serves the beverage industry with a variety of shapes, colors, and sizes of glass bottles and also produces glass containers for jams, sauces, and salsa for food and beverage companies around the world.
Its Shakopee, Minn., facility is one of six food-grade manufacturing facilities for the company. Here, Anchor Glass takes raw material into the facility-mixing, melting, conditioning, and forming it into a finished glass container-producing up to 600 bottles per minute.
Making a glass bottle
The crushed recycled glass and other raw materials arrive by truck or rail and are offloaded into holding silos. Once the necessary chemicals are added, the glass and other ingredients are sent to a 27-x-46-ft furnace for melting. Here, the glass is heated to 2,700 F to melt it into a molten lava state. This lava is then distributed to different forehearths to be formed, conditioned, and cooled.
After these vast fluctuations in temperature, the glass’s chemical compound has not stabilized and must be reheated to do so. Once the formed glass has reached 1,000 F, it is cooled very slowly to stabilize the chemicals in the glass. This finished product is then inspected for blemishes and inconsistencies before being shipped.
Losing control of temperature
The Shakopee facility produces 300 million bottles per year and was relying on two aging furnaces that were running nonstop. The larger of the two furnaces was 17 years old and needed to be re-bricked.
Aging bricks mean poor insulation. The furnaces were not retaining proper temperatures, which is vital for the glass manufacturing process. Anchor Glass was wasting energy and money trying to maintain temperatures and keep furnaces efficient. With these unstable temperatures, Anchor Glass was also risking lower-quality glass.
The need for improved thermal control was most evident in the furnace reversal process. This process relies on the regenerative furnace to maximize as much energy (heat) as possible. One side of the furnace captures heat then the entire process is reversed, and the captured heat is reused by injecting it back into the furnace. This temperature fluctuation is repeated throughout the day, and without tight control during the process, heat would be lost, which in turn meant that Anchor Glass was losing revenue.
Additionally, the old thermal monitoring system was not user-friendly and required manual adjustments and charting, which was a time-consuming process for operators. The old system only stored two weeks’ worth of data. This lack of visibility into data made monitoring and trending difficult. The limited exposure to historical data and trends prevented valuable analysis to occur. Operators were also relying on an old, analog alarm system with only 12 alarms for the facility.
With so many variables, including furnace pressure, air-to-fuel ratio, and controller stability, Anchor Glass knew it needed a new control system to improve managing its furnace operations and regain control of energy costs.
Advanced process controls
To help design the new system, Anchor Glass turned to system integrator Stone Technologies. Anchor Glass and Stone Technologies had a 15-year history of working together. After hearing the company’s desire for better data collection, tighter controls, and a more intuitive operator interface, Stone Technologies recommended a modern distributed control system (DCS). A scalable, plant-wide control system would help increase furnace efficiency and access to real-time temperature information.
"Everything we do relies on temperature control," said Kyle Fiebelkorn, batch and furnace manager of Anchor Glass. Implementing the new system "gives us improved batch management and data collection to monitor our furnace operations."
The DCS monitors more than 1,000 data tags and 2,600 detailed and manageable alarms. It tracks which alarms go off most frequently, improving predictive maintenance. Historian software integrated into the DCS gathers historical data on furnace temperature, air pressure, and other data points. This information is viewable on an intuitive human-machine interface (HMI) system with detailed sequencing, which allows operators to fine-tune process enhancements to achieve more energy-efficient operations.
The DCS allows for an intuitive control system with consistent faceplates that require less training to operate, which is vital with only six staff members at the Shakopee plant.
To address the loss of energy during the furnace reversal process, Stone Technologies implemented a scalable, controller-based sequencing solution. With the added sequencing capabilities, operators have better control over each step of the reversal process.
Stone Technologies also led Anchor Glass into a new generation of controls for slow processes by utilizing the internal model control (IMC) process function with the new DCS. The advanced process control functions help tremendously in slow acting loops, such as glass-level control and glass-temperature control.
"The IMC for advanced process control applications provides a simplified control algorithm and model to provide better control without reaction to disturbances created by reversal or other factors," said Brad Downen, manufacturing execution system (MES) project manager of Stone Technologies.
Serving up savings, flexibility, quality
Since implementing the new DCS in 2013, Anchor Glass has improved handling the 18 changeovers it does each month.
The increase in visibility allows operators to:
- Better manage temperature stability throughout the day
- Recognize operational trends and patterns
- Easily pinpoint potential problems faster
- Keep furnaces efficient to produce the optimum number of bottles per day.
"Since re-bricking the furnace and implementing the new DCS, we have seen huge savings in our gas and electrical expenses," said Fiebelkorn. "I would estimate an average of 15% of the cost savings to having a better control system on the furnace."
The facility is able to save 350 dekatherms per day, which translates to almost $766,500 in gas savings per year. Additionally, Anchor Glass estimates $337,260 in electrical savings per year.
Operators are also confident they are producing higher quality glass with fewer blemishes.
The Shakopee plant was the first Anchor Glass facility to implement the modern DCS. Since first installing the system, Anchor Glass has put similar systems into three other facilities, using the Shakopee plant as a blueprint.
Jeffrey Warning is a solution architect of integrated architecture for Rockwell Automation. Edited by Emily Guenther, associate content manager, Control Engineering, CFE Media, email@example.com.
- How modern distributed control systems lead to energy efficiency
- The cost savings behind updating control systems
- Advanced process controls and accessing data analysis.
What preventive maintenance measures should be in place to ensure optimal energy efficiency?
See additional stories about preventive maintenance and DCSs linked below.