Not all gas coolers are equal

Whether you want to recover waste heat from exhaust gases or remove moisture from biogas to improve plant performance and operational longevity, various designs of heat exchanger are available. However, these gas mixtures are often highly corrosive, meaning that when comparing possible heat exchanger or dehumidification systems, it is important to consider the design and materials used to ensure the chosen equipment lasts as expected.

Exhaust gas heat recovery has become common in many industries, providing cost savings and environmental benefits. With as much as 35% of an engine’s fuel being wasted as exhaust heat, there can be considerable savings to be made from exhausts or flues with heat exchangers, meaning the initial capital outlay can quickly be recouped.

Similarly, as the global use of anaerobic digestion and energy generation from landfill gas has increased, so too has awareness of the issues caused by the water contained in biogas, such as corrosion and cavitation in CHP engines and generators. As a result, HRS Heat Exchangers has seen increased demand for its Biogas Dehumidification System (BDS).

Raw biogas and exhaust gas contain a mixture of different compounds, from relatively inert substances like as carbon dioxide and nitrogen to oxides of nitrogen and sulphur, and siloxanes (which can react to form highly corrosive or abrasive materials) and organic compounds, particulates and heavy metals (which can increase the fouling potential of the gas).

Unless a heat exchanger or other system has been specifically designed for use in such aggressive situations, it can quickly succumb to fouling, corrosion or complete failure. At best this means lower operating efficiency, and in the worst cases that such heat exchangers will need replacing sooner – possibly after months instead of years.

Unlike cheaper heat exchangers which are constructed from carbon steel, the HRS K Series and G Series of Gas Cooling Heat Exchangers are constructed from AISI 304 and AISI 316L stainless steel to withstand corrosion and utilise our corrugated tube technology which increases heat transfer and reduces fouling. This means that in practice we have seen the HRS G Series last 3- or 4-times longer in aggressive operating environments compared to lower cost carbon steel heat exchangers.

These benefits explain why companies such LMS Energy and Melbourne Water have installed stainless steel HRS K Series corrugated shell and tube heat exchangers and Biogas Dehumidification System (BDS) respectively.

With systems for digester heating, pasteurisation, digestate concentration, biogas dehumidification, and sludge and exhaust gas heat recovery. HRS equipment is installed at more than 200 biogas plants worldwide, helping operators to improve their efficiency and overall operation.