Heat exchangers used for exhaust gas heat recovery need to be robust in order to cope with the physical and chemical stresses imposed on them from the exhaust gases, which are both hot and corrosive.

Nowhere was this truer than at an anaerobic digestion (AD) site belonging to a waste management company in the United Kingdom, The digester is used to transform approximately 45,000 metric tons of food waste from domestic and commercial sources into renewable electricity and high value digestate biofertiliser.

When the original heat exchanger fitted to the exhaust system failed after a few years of operation, the company asked HRS Heat Exchangers to provide a replacement. The company recommended its G Series gas cooling heat exchanger, a stainless-steel multi-tube unit designed for exhaust gas cooling and thermal recovery.

Now in place at the digester, the heat exchanger is cools the exhaust gas from 980 to 600°F (527 to 316°C). The hot exhaust gases flow through the interior tubes of the heat exchanger while the service fluid (in this case water) flows though the surrounding shell. The heat recaptured from the process is used in the anaerobic digestion facility and to provide hot water around the site.