September 1, 2006
by Lynn Petrak
Dairy heat exchangers — built to accommodate processor needs for volume and efficiency.
In dairy processing, there are really are a few important degrees of separation — like the degrees in temperature that can affect product quality and safety, and the degrees in flow rates that can translate into improved efficiency.
Heat exchangers are pivotal in making such differences, because of their function in heating, cooling, pasteurization and heat recovery at various stages in processing. Whether used to handle products like milk, cultured products, cheese, dried products, ice cream bases or whey, or to heat or cool water for purposes like sanitation, heat exchangers can be found at various points within a dairy plant.
There are different types of heat exchangers and, within those categories, a range of unit designs. Plate heat exchangers are the most traditional and common type of heat exchangers used in dairy plants. Such models are typically used for processes for milk, cheese milk, whipping cream, sour cream and ice cream, while some are used to handle byproducts. Scraped-surface heat exchangers and shell and tube heat exchangers, meanwhile, are equipped to handle viscous products or those with large particulates, while tubular heat exchangers are often used in dairies that utilize ultra-high-temperature (UHT) processes and require systems with longer run times and the flexibility for both liquid and particulate-rich products. Heat exchangers today are sold in gasketed, welded and semi-welded form.
Long a workhorse of dairy operations, a heat exchanger generally has a long production cycle. Typically, they are replaced on an as-needed basis or installed as part of new plant construction, addition or renovation.
As a testament to the evolving nature of dairy processing over the past generation or so, those that manufacture heat-transfer equipment have developed new generations of heat exchangers designed for today’s production priorities. Although the basic premise remains similar, the designs are increasingly tailored for processors operations. “Plate heat exchangers have been around for some time, but we are always putting new tweaks on it,” says Paul Hume, national sales manager, processing systems and equipment for Paul Mueller Co., Springfield, Mo., which offers several types of stainless-steel gasketed and semi-welded plate heat exchangers and shell and tube heat exchangers for the dairy industry and other industries, such as chemical and petrochemical industries.
Perhaps one of the largest drivers of new heat exchanger models is the nature of not just the dairy business, but of the U.S. manufacturing industry in general: speed. “What we’ve seen over the last couple of years, just like other pieces of equipment like separators and homogenizers, is that our customers are looking to process higher flow rates in their plate heat exchangers. They are going for a greater economy of scale,” says Don Bohner, manager of heat exchangers for Vernon Hills, Ill.-based global processing and packaging company Tetra Pak Inc., adding that the drive for improved throughput is in turn driven by converging factors, such as greater demand for products.
Hume concurs that the dairy industry is constantly striving to maximize production capability. “They are looking to do more with less and they also want a better process,” he says.
New product development in turn affects new equipment development. “I have seen the evolution of new products, like lower-fat products that are more viscous,” Bohner says. “And certainly, viscosity will affect the sizing of a heat exchanger.”
New and Improved
For the common need for greater capacity, suppliers have developed heat exchangers that can handle today’s type of products and processes. Tetra Pak, for instance, has unveiled a new Tetra Plex C15 stainless-steel frame plate heat exchanger for pasteurizing, heating or cooling liquid food products at high flow rates, with a capacity of 220,000 parts per hundred (pph) for fluid milk/whey pasteurization at 94 percent regeneration and 350,000 pph for cheese milk pasteurization.
Although not currently in use in the dairy industry, Invensys APV, Lake Mills, Wis., in August unveiled what the company calls the “most powerful” heat exchanger on the marketplace. The APV Sirius is a high-capacity machine designed for large-scale plants and features the largest heat transfer area per plate on the market, with flow rates of more than 4,500 cubic meters per hour and porthole sizes of more than 500 millimeters. Titanium plates are available as well for that unit.
In addition to increasing volume, the latest heat exchanger technology reflects the mix of dairy products on the market today. The growth of more viscous products, like yogurts, smoothies and ice cream mixes, requires heat exchangers with reduced flow resistance and with a wider inlet design, among other attributes.
There are several examples of heat exchangers that are going with the lower flow, so to speak. Paul Mueller Co. offers its sanitary shell and tube heat exchangers that range in size from desktop models to those that are 100 feet long, Hume says. “It’s for items with high solids and fruit particulates. We are very much capable of doing applications like that,” he says.
Last year, Alfa Laval Inc., with U.S. offices in Richmond, Va., introduced its ViscoLine Dynamic, a scraped-surface tubular heat exchanger designed to handle high volumes of high-viscosity, sticky or particulate-laden products. The heat exchanger can handle higher product volumes, can be installed vertically or horizontally with product flow in either single-pass or multi-pass configurations and was engineered with a large heat transfer area used for crystallizing and evaporating high-viscosity products.
Waukesha Cherry-Burrell, a unit of Delavan, Wis.-based SPX Process Equipment, has also addressed the viscosity issue with scraped-surface heat exchangers specified for viscous and heat-sensitive products. The heat exchangers include a product tube within a tube; a revolving shaft in the product tube contains a scraper that prevents product from remaining on the heat transfer surface.
Invensys APV, for its part, offers a scraped-surface heat exchangers and its PLC-controlled R5 Quad-Drive plate exchanger that can be used for low-flow applications, designed to solve challenges in handling viscous products.
In addition to units designed for viscous products, other heat exchanger styles have been introduced for very specific product applications, including those that handle different types of dairy ingredients. One example of such specificity comes from Ivarson Inc., Milwaukee, which offers a scraped-surface heat exchanger designed to handle pastry fats, including butterfat, at high pressure applications. “When you make pastries, you need to have a special fat with a good plasticity, and a high melting point. You have to have the moisture evaporate and the fat burn and it all has to happen at a certain temperature,” president Glen Ivarson explains, adding that the heat exchanger equipment allows that to be done and that companies.
Durability and Safety
In addition to larger and more cost-efficient units, heat exchangers are also engineered to be both more durable and easy and quick to clean than older models, with many models designed for clean-in-place (CIP) capability.
Alfa Laval, for its part, focused some of its more recent efforts on its AlfaNova, a heat exchanger constructed with 100 percent stainless steel. The company’s unique brazing technology allows for extreme temperature and pressure conditions.
At Paul Mueller, Hume says older models are being replaced by newer, more sanitation-friendly units. The company’s most popular heat exchangers include the AT20 and AT40 models that include a stainless frame. “Snap-in gaskets are a must now, rather than the old glued-in gaskets because you can take them out,” he says.
Finally, in an energy-conscious time like today, dairies looking to upgrade heat exchangers are also looking to keep a lid on costs as much as possible. Equipment manufacturers are designing heat exchangers for running efficiency as well as volume efficiency. Tetra Pak, for example, offers a larger scraped-surface heat exchanger that allows operators to reduce the number of required cylinders and in the process, reduce maintenance costs. AGC Engineering, Bristow, Va., built its Pro5 line, for improved energy efficiency, with a plate structure that allows for additional plates and a greater heat transfer area. The recently-upgraded Pro5 models are also redesigned to better handle viscous products.
Lynn Petrak is a freelance journalist based in the Chicago area.$OMN_arttitle="Hot Topic";?>