Process Cooling System Helps rPlanet Earth “Close the Loop” on Recycling Post-consumer Plastics


rPlanet Earth in Vernon, California, is the only vertically integrated facility able to convert polyethylene terephthalate (PET) packaging waste into recycled PET (rPET) packaging for food and beverage industries such as bottle preforms, strawberry containers, and drinking cups. The plant’s process cooling system delivers chilled water at precise temperatures at all times.

rPlanet Earth is a rarity in the plastics recycling and manufacturing industry. After all, its operation in Vernon, California, is the world’s only vertically integrated facility able to convert polyethylene terephthalate (PET) packaging waste into recycled PET (rPET) packaging for food and beverage industries. Yet, rPlanet Earth is much like any other plastics company in one key aspect: it must maintain production efficiencies to meet growing demand for its high-quality products. 

With a unique business model in place and clear goals for production, rPlanet Earth (www.rplanetearth.com) partnered with engineering firm Woodard & Curran to design and build its state-of-the-art facility in 2018. The plant features a host of advanced technologies including a process cooling system designed to deliver chilled water at the precise temperatures at all times. “The cooling system,” said rPlanet Earth Vice President of Engineering Andrew Lopez, “plays a pivotal role in allowing our company to meet its production goals – and plans for growth.”

“Cooling is a really huge factor in our overall efficiency. It also allows us to ensure consistency in our product, ” Lopez said, adding the company is on track for strong growth. “Our long-term plan is to double our capacity at this plant by 2023 and also establish more high-volume plants around the United States.”

 

High-quality Packaging with Lowest Carbon Footprint

Turning recycled plastics into containers and packages for the food and beverage industries traditionally involves separate facilities to perform the work. However, rPlanet Earth combined these disparate operations into one as it strives to “close the loop” for the recycling and reuse of post-consumer plastics. 

“Everything we’re doing at rPlanet Earth is typically done at three to five different facilities, depending on how you cut it. Our vertical integration and the use of post-consumer plastics as feedstock allows us to produce high-quality packaging with the lowest carbon footprint,” Lopez said. 

rPlanet Earth’s 302,000-square-foot facility, which grew from ten employees in 2017 to 180 employees today, acts as a recycling operation and separate manufacturing facility under one roof. The plant operates 24 hours per day, seven days a week, and is capable of processing over 80-plus million pounds of post-consumer PET annually.

rPlanet Earth’s 302,000-square-foot facility acts as a recycling operation and separate manufacturing facility under one roof.

The recycling operation receives bales of post-consumer plastics from various curbside collection programs throughout California. It then sorts and grinds the material into flake, which is stored in silos until needed. The flake is subsequently washed and routed through a decontamination and solid stating process to convert the non-food grade material into flake that meets rPlanet Earth’s own quality standards, which exceeds the Food and Drug Administration’s requirements for direct food contact applications. 

The manufacturing component of the facility is comprised of three primary production streams – injection molding machines produce bottle preforms; sheet extrusion machines produce rolled extruded sheet; and thermoforming equipment manufactures thermoformed containers, including rPlanet Earth’s own brand of drink cups and deli containers. 

“What’s also unique about us is our ability to process B-grade, curbside bales,” Lopez said. “Other companies in California recycle PET containers but they’re only able to use bales supplied by deposit centers. If it wasn’t for us, those B-grade plastics would be downcycled into lower quality applications and potentially end up in landfills. Our goal is to close the loop and have zero plastic waste on the planet.”

 

Precise Temperature Control a Must

rPlanet Earth turned to Woodard & Curran to design and build its facility from start to finish, which included everything from site selection, utility and permitting considerations, to equipment selection. 

The process cooling system at the plant is designed to ensure precise temperature control given its impact on cycle times, said Bert Wesley, Senior Principal and Industrial Plant Engineering Practice Leader at Woodard & Curran.

“The temperature of chilled water delivered to the machines needs to be exact to ensure uptime as the machines cycle from one process to the next,” Wesley said. “For example, an injection molding machine will turn out 96 preforms every eight seconds. If that water is one-half degree out of spec it’s going to make 96 defective preforms in eight seconds. It’s easy to see how it adds up.”

Lopez, like Wesley, said accurate temperature control of chilled water is crucial, especially when cycle times are decreased to meet production and quality goals.

“Precise temperature control is going to drive that cycle time down and give us consistent product,” Lopez said. “If you speed up cycle times without precise temperature control then you can have quality defects in your product and you can lose valuable line time to troubleshoot an issue.”

 

Working with a Limited Footprint and Varied Flow Rates

When designing the plant, rPlanet’s desire to maximize the area for manufacturing meant there was limited room for utilities. Additionally, Woodward & Curran needed to prioritize storage for PET flake and process equipment versus utilities, such as the cooling system.

“As needs for production processes evolved in the planning phase, we began to explore how we could save space by not having both a hot tank and a cold tank for the cooling system in addition to the pumping systems that goes with it,” Wesley said. 

Woodard & Curran also wanted to guarantee delivery of chilled water at the proper temperatures, even with a wide range of demand for chilled water at the plant. Flow requirements at the plant range from as low as 100 gallons per minute (gpm) to 960 gpm based on the status of varied production process. 

“We need the system to deliver a thermal sink that’s always ready and always within spec as different machines come online,” Wesley said. “When a line operator hits the start button on the machine, they expect chilled water at the proper temperature to be available in whatever volume they need to circulate through their machine and they need it immediately.”

 

System Features Chillers with Enhanced-flow Management Technology  

The cooling system at rPlanet includes a single, two-cell 1,380-ton EVAPCO open cooling tower, as well as two water-cooled Trane centrifugal chillers rated at 600 tons each. The chillers are arranged in a variable primary chiller plant design, using supply pumps with Variable Frequency Drives (VFDs) to adjust flow rate to meet production demand. Other key components include a 2,500-gallon surge tank, pump system and master Programmable Logic Controller (PLC). A single surge tank eliminated the need for a hot and a cold tank, as well as additional pumps. 

The tower supplies cooling water at 80oF (26.6oC) to the two water-cooled Trane centrifugal chillers that lower the water temperature to 44oF (6.6oC) for delivery to process machines. The towers also supply water through a separate cooling circuit directly to the plant’s compressed air system and manufacturing equipment since they do not require 44oF (6.6oC) water. 

The chilled water loop uses solenoid valves to tie together the chilled water supply line with the hot water return line. At all times, temperature sensors keep tabs on the water temperature in the loop. When seeing an increase in temperature, the PLC opens the valves to allow chilled water from the supply line to flow to the return line until the proper temperature is reached, resulting in constant and proper water temperature regardless of demand.

Each chiller is equipped with Trane’s exclusive Flow Management Package, which uses a variable water-flow compensation algorithm, to deliver chilled water at targeted temperatures even during an increase or decrease in flow of up to 50% per minute. Other chiller manufacturers are limited to a maximum of 10% per minute rate of change of flow and increases beyond that will send those chillers into alarm, knock them offline, or produce off-target temperatures. By using the enhanced-flow management technology, the chillers can quickly ramp up when called upon and deliver water at the specified temperature without faltering, Wesley said.

Trane’s centrifugal chillers at rPlanet Earth’s plant use an enhanced-flow management package, which allows them to deliver chilled water at targeted temperatures at an increase in flow of up to 50% per minute.

“If every machine turns on immediately and starts calling for chilled water, the chillers are able to easily compensate for that rate of rise in flow and ensure water in the system stays at the set temperature,” he said. 

At the plant, cooling water is routed from the surge tank to the chillers and throughout the pipeline network for delivery directly to process machines. Pipeline valving allows the system to reroute additional chilled water generated by the chillers from time to time back to the surge tank. The surge tank, which contains hot water previously routed to it from the return line, serves as a way for the plant to pre-chill the water before it’s routed to the chillers for further cooling as part of the continuous loop. The result is energy efficiency, Wesley said. 

“We’re able to send 100% water at the specified temperature to the manufacturing process while also having a reserve capacity in the surge tank available at all times,” Wesley said. “It also means the chillers have to do less work with that same molecule of water when the water comes back around from the surge tank and flows through them before being sent to the process.”

 

Getting It Right On the Front End

Wesley said the design of the process cooling system involved close collaboration to ensure the design and installation of an optimized system. The system also aligns with rPlanet Earth’s goals tied to energy efficiency. 

“We sat with Trane and EVAPCO to work through how to optimize the size of the equipment across the board and also ensure everything works together seamlessly,” Wesley said, adding the system installed goes beyond the traditional system.

A 1,380-ton EVAPCO open cooling tower supplies cooling water to two water-cooled Trane centrifugal chillers, which further cool tower water for delivery to process machines at rPlanet Earth. The tower also supplies cooling water directly to the facility’s compressed air system and equipment that doesn’t need chilled water at a lower temperature than that provided by the chillers.

“What most would’ve done is to not have a chiller with a flow-management package, and instead, pump the water needed and let the chiller trim it every once and awhile and move on with it. But we didn’t need to pump 960 gpm a minute, 24 hours a day, seven days a week,” he said. “The plant only needs to pump the chilled water based on what’s actually running, and therefore, it’s very energy efficient from an electrical and refrigeration standpoint.”

Wesley said Woodard & Curran specified chillers with an enhanced-flow management package to match its goals for ensuring chilled water at all times.

“Chilled water usage is not constant. It all depends on what complement of machines they’re running,” he said. “Without the package, the chillers wouldn’t give us the guarantee we could deliver water at spec 100% of the time.”

The cooling system overall satisfies the plant’s process cooling goals and business objectives, Wesley said.

“It’s a combination of giving the manufacturing process what they need  all the time, while being energy efficient. And it gives them a lower lifecycle cost, which is worth spending the time and effort up front to get it right.”

Woodard & Curran

Founded in 1979 and headquartered in Portland, Maine, Woodard & Curran is an integrated engineering, science, and operations firm born to address needs arising out of the Clean Water Act. Privately held and steadily growing, the firm specializes in water and environmental-related projects. It has more than 1,100 employees in offices and utility facilities who serve public and private clients across the country.

Woodard & Curran is a nationwide firm specializing in water and environmental-related projects.

The company’s mission is to create a healthy work environment, deliver high-quality services, and promote environmental stewardship. These concepts guide the services it provides and the work it delivers across a range of sectors. In working with industrial clients, Woodard & Curran helps them do more with less, conserve resources, and minimize waste and emissions. The firm clearly understands that the more efficient and productive a company is, the more competitive it can be. 

Utility systems essential to the manufacturing process are often a frequent source of inefficiency and avoidable expense. Woodward & Curran experts have decades of experience identifying opportunities to save energy, reduce waste, implement efficient generation technologies, and reuse heat or water to save money. The company helps clients in a wide range of manufacturing setting reassess utility systems and design infrastructure to get their best return on investment. To learn more, visit www.woodardcurran.com.

 

Another Step Closer to Zero Plastic Waste

Lopez said rPlanet Earth made the right choice in partnering with the Woodard & Curran, citing the cooling system as one example.

“We’ve had a very positive experience with temperature control with our entire cooling system for the plant,” he said, adding rPlanet Earth anticipates a bright future.

“We’re continuing to make significant progress in using previously landfilled post-consumer plastics streams in our process. We’re now looking at re-using and recycling thermoformed containers, which is important because a lot of it ends up in the landfill, “Lopez said. “We’ve always worked toward a circular economy in plastics. We’re very excited about our goal, which is to have zero plastic waste on the planet.”
 

Chiller & Cooling Best Practices Magazine wishes to thank Bert J. Wesley, P.E. of Woodard & Curran for sharing invaluable insights for this article. All photos courtesy of rPlanet Earth.

To read similar plastics industry articles visit https://coolingbestpractices.com/industries/plastics-and-rubber. For similar chiller technology articles visit https://coolingbestpractices.com/technology/chillers.

 

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