Operation of thermocompressors in subatmospheric conditions is not uncommon in food processing due to the thermal sensitivity of most foods. A prime example is the evaporation of dairy and other food products, such as the tomato paste application described in detail below. Many chemical evaporators also operate below atmosphere. Fox is the major supplier to some of the most widely known evaporator manufacturers. Manufacturers of desalini-zation equipment have been important Fox customers for many years.
Some evaporator processes require positive pressure operation. The Fox thermocompressor design allows a wide range of operating conditions. The compression of low pressure steam to higher, usable levels can eliminate the need for reboilers.
Not only can thermocompressors reclaim energy stored in waste steam, but also that stored in waste condensate. Typically, condensate can be collected, flashed, and compressed by a single unit to a higher pressure level to meet the demand of other processes, eliminating the use of more expensive, generated steam.
Evaporation Case Study
Concentrating Freshly Squeezed Tomatoes
Evaporation is an important process in the manufacturing of ketchup. Water is removed from the tomato slurry to produce a concentrate that is then stored for later use in ketchup or other sauces and purees. The water is evaporated from the tomato slurry at below atmospheric pressure and, therefore, at cooler temperatures. This protects the product from taste degradation that would result from higher temperatures.
When a large food manufacturer was retrofitting their Canadian facility, they selected Fox Valve to design and build three 20″ thermocompressors to reclaim the waste steam resulting from the evaporation, using its associated heat value and compressing it up to a suitable pressure/temperature to minimize live steam usage. A total of 65,000 lbs/hr of “waste steam” was reclaimed, reducing the live steam required, thus saving thousands of dollars per day in operating costs and simultaneously increasing evaporator efficiency.
The steam used for heating could be considered as “low grade;” however, it is perfect for this application because it raises the temperature of the product without degradation. Most food evaporation processes operate at temperatures and pressures requiring motive/load ratios of 1:1 or less. Fox thermocompressors can be designed to suit your retrofit or new evaporator application.
