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Process Equipment |
Paper Plant on Gulf Coast Prepares to Take Delivery of Spiral Heat Exchangers
A major paper and pulp plant in the south is preparing to take delivery of two Spiral Heat Exchangers, (SHE), for heat recovery from black liquor. The recent increases in the cost of natural gas have brought heat recovery to the forefront in the paper and pulp industry throughout North America. Heat recovery from black liquor has been considered in the past but was put aside in favor of other easier heat recovery efforts. Black liquor is now one of the most energy wasteful streams in the industry, and with careful planning is proving to be a very fruitful source of recoverable heat. This plant is installing two spiral heat exchangers with over 3000 square feet of heat transfer surface and will recover over 14 million Btu/Hr of heat. Without the SHE this application would be all but impossible. The fouling characteristics of black liquor are similar to that found in sewage sludge, both are digested and organic in nature. The helipical flow path of the spiral keeps the solids laden streams from attaching to the heat transfer surface and fouling & plugging up the heat exchanger. This curved path effect is what gives the SHE its legendary ability to handle the worst flows and stay clean. In this application the channels were almost 1" tall, being able to handle particles up to 5/8" in diameter on both the black liquor and the cold side, in this case filtrate water with high fiber content. The paper industry is no stranger to spiral heat exchangers; the black liquor application is another place in the plant that uses the unique attributes of this kind of equipment to process difficult flows.
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