Indirect cooling of gas streams is often preferable because it eliminates the possibility of contamination of the stream being cooled. Other times, the versatility of a direct cooler to provide gas cleaning in addition to cooling can provide process benefits, saving time and money. Kimre Kon-Tane® Scrubber and Tower Packing and Kimre B-GON® Mist Eliminators are perfectly suited to provide effective cooling and cleaning in a direct contact cooler.
A specialty chemicals manufacturer used a recycled nitrogen stream that was cooled from 60 °C to 20 °C. They had been using an indirect cooler for a number of years, but 1000 mg/cubic meter of insoluble polymer in the 70,000-cubic-meter per hour nitrogen stream clogged the heat exchanger and required extensive annual maintenance to clean the unit.
The chemical company considered other options and decided on a direct cooled system. The system consisted of an evaporative cooling section, a two-stage sensible cooling system using Kimre Kon-Tane® Scrubber and Tower Packing and a Kimre B-GON® Mist Eliminator. The evaporative cooling section sprayed 24,000 kg/hr of water into the gas stream, evaporating 435 kg/hr to reduce the gas temperature from 60 °C to 40 °C. This also reduced a small amount of the particulate. In the sensible cooling section, two stages of Kimre Kon-Tane® Scrubber and Tower structured monofilament packing were sprayed with 10 °C chilled water to achieve the required 20 °C outlet temperature, while removing over 90% of the entrained solids. The sensible cooling section was followed by a structured Kimre B-GON® mist eliminator, which effectively removed all the entrained water droplets and mist generated in the cooling operation.
The system was installed and operated successfully at a pressure drop of less than 150 mm of water. It has continued to run for over two years and has required no maintenance.
In conclusion, the use of direct contact coolers is an effective way to reduce the temperature dirty gas streams. Unwanted contaminants can be removed, and the gas stream directed to downstream equipment or recycled into the process.