A customized propylene glycol process chiller is allowing a juice maker to increase efficiency and process control.



"We couldn’t afford to sacrifice anything. Cranberry juice is like red gold; a drum is worth thousands of dollars,” said Tom DeThomas, director of engineering for Clement Pappas, a leading producer of fruit juice, fruit drinks and cranberry sauce located in Seabrook, N.J. The company’s plant, covering more than 400,000 ft 2, is not only a processing facility but also a cold storage and bottling operation that produces millions of gallons of juice per year.

“Precise temperature control is essential to production, so we needed to upgrade our 1930s chilling technology to guarantee reliability. We also knew our facility was consuming too much energy,” DeThomas said. These factors led to the decision to install a new process chiller in the facility.

Traditional Cooling Process

The Clement Pappas plant was a pre-World War II vegetable processing plant that had been converted into a juice and cranberry sauce processing facility and cold storage warehouse. Before the retrofit, the operation used an ammonia system with three Frick HDI reciprocating compressors and a cooled salt brine solution to remove heat from the processing plant. Three heat exchangers were used between the product and the refrigerant, along with three cooling mediums -- R-717 (anhydrous ammonia) to a salt-brine solution, the salt-brine solution to propylene glycol, and propylene glycol to the product. The brine solution was piped underground to the processing plant, and the evaporators were located in the processing and storage rooms.

This system provided a less than optimum control strategy for several reasons. First, 5,500 lb of ammonia were required to cool 30,000 gal of brine. Clement Pappas wanted to eliminate ammonia from the system because the plant is in a residential area, and an ammonia leak can be dangerous to employees or surrounding neighbors. Additionally, the system was highly inefficient. Prior to the upgrade, the system was consuming approximately 250,000 kWh per month.

The Danfoss EKC331T electronic controller loads and unloads the reciprocating compressor and allows the cranberry juice to be maintained at a 1°F temperature differential.

A Customized System

The company turned to Devault Refrigeration, a design/build contractor located in Colmar, Pa. Bil Sauer, sales engineer and project manager at Devault Refrigeration, worked with DeThomas and his engineering staff to design a solution for replacing the system with a new propylene glycol, R-22 process chiller. Devault designed and built a customized package chiller on a skid that contained a Frick screw compressor and a Vilter reciprocating compressor. An evaporative condenser was located remotely, and a plate-frame heat exchanger was used to chill the cranberry juice to a precise temperature with propylene glycol. According to the company, by eliminating the brine and its associated heat exchanger, the system has less pumping loss and leak potential, and it consumes less energy. “This system is basically a mini-engine room on a skid. It can be moved relatively easily if the plant expands the operation or moves location,” Sauer pointed out.

“We had some very interesting challenges with this project,” he explained. “Juice plants are unique because shelf-life considerations, design changes and many of the parameters are variable.”

Clement Pappas runs three lines, and in eight hours can produce 50 different labels and 15 different formulas of juice or cranberry sauce. Accurate temperature control is paramount in processing juices. At Clement Pappas, the juice must be held at 34°F (1°C). The product is batched, then pasteurized and bottled. Pasteurization is a critical control point where the product needs to be heated, filled and cooled immediately. The bottle temperature must be brought down from 182 to 100°F (83 to 37°C) quickly to preserve juice quality.

Because it is batch processing, the raw juice processing plant can be idle or can produce at a rate of 35 gal/min. “We essentially used two different manufacturers' compressors to handle the load,” explained Sauer. To design the system within the budget specifications, both screw and reciprocating compressors were used on the package. The Frick screw compressor is the lead compressor on the job. When the glycol pump turns on, it activates the screw compressor. If the screw compressor is in anti-recycle delay mode and unavailable to turn on, or if additional cooling capacity is required to achieve the target temperature, a Danfoss EKC331T electronic controller will signal the Vilter reciprocating compressor to turn on. The Danfoss controller then will load and unload the reciprocating compressor with steps of 100, 75, 50 and 25 percent. A Danfoss AKC21W temperature sensor monitors the glycol's leaving temperature to determine when the compressors need to run.

“The system was designed with no flywheel effect, which means the entire volume of glycol is turned over in eight minutes,” remarked Sauer. “There is very little reserve glycol in the system, so tight refrigerant control is crucial. There is only one other compressor sequencing with the screw, and it is a reciprocating [design]. A microprocessor sequencing panel did not fit within our project budget, so the Danfoss EKC was an ideal solution. For a fraction of the cost, we were able to achieve the same result.”

According to Brian Davis, vice president of Danfoss Industrial Refrigeration, this application was well-suited for the Danfoss EKC331T. “We were able to provide the link between the screw and the reciprocating compressors to achieve stable control and system efficiency,” he said. The controller works harmoniously with the other Danfoss valves and sensors that also were installed on the package.

The mobile skid package system was delivered to Clement Pappas on a flatbed truck. The system was designed so that it could be moved if the facility is expanded or relocated.

Smooth Startup

The mobile skid package system was delivered to the Clement Pappas facility on the back of a flatbed trailer and started up in March 2005. Bill Carrington and Tim Schrauger were part of the startup team who were onsite when the system arrived.

This was the first project Devault had handled using Danfoss controls, and the company was pleased with the results. “The 'blackbox' [EKC331T] was a very cost-effective solution, and it works,” said Schrauger. Bill Carrington, who was instrumental in carrying out the design, commented further that the Danfoss controller allowed the plant to maintain a 1°F temperature differential on the product with the reciprocating compressor -- a critical factor because the application requires such precise control.

According to DeThomas, once the skid package was started up, Clement Pappas noticed efficiency improvements immediately. “We are using 25 percent less energy in processing than the old reciprocating units that had been in place. The energy cost of cooling the juice was reduced to approximately one cent per gallon.”

The revamped system's reduced energy consumption is a benefit to both Clement Pappas and the environment. But the ecological impact goes beyond energy consumption. Eliminating the external water-cooled condenser allowed Clement Pappas to reduce water consumption by approximately 20 percent. The skid package design also allowed the company to reduce its wastewater purging. “Our disposal of wastewater has been reduced by approximately 300 gal/min,” said DeThomas.

Looking back over the retrofit process, Devault's Bil Sauer commented, “We always strive to stay current on the latest technology so we can help solve our customers' unique challenges. And that's exactly what we were able to do on this project by working with Danfoss. The controller allowed us to provide a unique control strategy, and the staff provided excellent support during the entire process.”

DeThomas also was pleased with results of the project. “Devault was able to design a system that met my budget and our specific needs. I was able to save money with the reciprocating compressor and the controller, but I didn't sacrifice anything in the control processing side.”

Since installing the new system, Clement Pappas' overall energy consumption has dropped by 25 percent, and the plant no longer requires 5,500 lb of ammonia or 30,000 gal of salt-brine solution. Best of all, the company has compressor redundancy to protect its red gold.

Baltimore-based Danfoss manufactures mechanical and electronic products and controls for refrigeration and air conditioning, heating and motion-control systems. For more information, call (410) 513-1133; e-mail baltimore@danfoss.com; or visit www.danfoss.com.

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