Minnesota-based cheese manufacturer Melrose Dairy Proteins trucks in up to 4 million pounds of milk for processing each day, transforming it into a variety of cheeses for consumption. This process requires a significant amount of energy.
Approximately 40 percent of the dairy’s operating expenses go to electricity, natural gas and water consumption. In 2008, managing partner Land O’Lakes began a corporate initiative to lower the company’s natural resource consumption by 25 percent within 10 years. This meant that Melrose needed to take a closer look at its operation and find ways to lower the plant’s overall resource consumption.
Gartner Refrigeration, a Minnesota-based company specializing in custom industrial refrigeration solutions, was asked to find a way lower the plant’s energy consumption. One solution found was to use waste heat from the compressor oil coolers to heat water at the plant. The challenge to this approach was that the need for hot water was not constant. Gartner had to find a way to keep the compressor oil cool, both when the plant needed hot water and when it did not.
Gerry Anderson, a project manager for Gartner, designed a hybrid oil-cooling solution to accomplish this goal. The first step was to install liquid-injected oil cooling (LIOC) to all the compressors. This also helped the company improve summer operation; the existing thermosyphon system was not keeping up with the oil-cooling load during peak operation. Next, he integrated the LIOC system with a water-based heat recovery system that further reduced costs by using water to cool the plant’s compressors and provide hot water for equipment cleaning.
Anderson relied on his long-standing relationship with vendors such as Baltimore-based Danfoss to help provide consultation on the system upgrade. Anderson used the Danfoss ICF Flexline valve station as a key component in the overall solution.
Streamlined Upgrade Creates Cost Savings
When Anderson assessed Melrose’s existing system, he identified two main issues that, once resolved, would greatly reduce the manufacturer’s consumption of natural resources. The first — and most pressing — issue was that the plant’s existing thermosyphon oil cooling system was undersized and not able to keep the compressors cool enough. This caused the entire system to overheat and shut down during the hot summer months.
To solve this issue, Anderson installed a liquid-injection oil cooling system that would enable Melrose Dairy to operate continuously during hotter months. Anderson explained that the key component to this retrofit was the installation of the Danfoss ICF Flexline valve station for LIOC. This provided Anderson with a way to precisely manage the temperature of the compressors while also preventing the loss of refrigerant by reducing the occurrence of leaks by up to 75 percent.
The Danfoss ICF valve station incorporates several functions into one housing unit, enabling it to replace a series of mechanical, electromechanical and electronically operated valves. For instance, rather than having to weld together a traditional valve train, a process that requires up to twelve welds, the Danfoss ICF control solution required only two welds during installation. Additionally, the compactness of the valve station allowed the team to retrofit an existing compressor package with tight space limitations without sacrificing any of the desired functionality.
Systems Integration Leverages Natural Resources
Water is a natural byproduct of the cheese manufacturing process and the plant already used this water for its clean-in-place (CIP) process. (The plant is required to clean all of its equipment every 24 hours with extremely hot water.) Anderson noticed that the water used in the CIP process was heated by cycling through a boiler using natural gas.
Once the LIOC was successfully operating for several months, Anderson and his team began the second phase of the operation: to implement a water-based heat recovery system and integrate it with the LIOC system.
According to Anderson, the plant’s compressors produced nearly 2,000,000 BTUs in unused heat energy, and using the water to cool the oil would produce the hot water needed for the CIP process. The cost-savings of this procedure were two-fold — it eliminated the need to use natural gas to heat water, and it meant that the LIOC system would only have to operate for 30 percent of the day.
The Danfoss ICF valve system remained an integral component of this solution as the oil-cooling demands required the LIOC to operate intermittently when water was not available during the CIP process. Additionally, the valve system was used as a backup for when the water from the heat-recovery system was too warm to cool the oil in the compressors. The valve station’s motorized valve has the speed and precision to respond to changing control system signals with regard to positioning quickly.
The installation of the valve station along with the water-based heat recovery system has allowed Melrose Dairy to cut costs and become more productive and efficient. The valve station alone has saved the dairy approximately $13,000 in electricity costs each year. Additionally, the dairy saves an estimated $70,000 a year because it no longer purchases natural gas to heat water for the CIP process.
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