Aging Heat Exchanger Began to Corrode and Fail
As part of its sludge treatment process, the site at Avonmouth uses acid phase digestion (APD) to produce biogas and digestate. The heat for this process was provided by an aging carbon steel heat exchanger which had begun to corrode, and which was starting to fail – allowing sludge to pass into the heating water.
From Emergency Fix to Permanent Replacement
HRS Heat Exchangers were initially contacted by YTL Group to provide temporary heat exchangers as an emergency fix. These proved to be so effective that we were asked to quote to provide a complete, permanent replacement.
However, the overall operations at the Avonmouth site meant that YTL Construction and their engineering partner Mills Engineering Services Ltd had a strict deadline of just 72 hours for the installation of the new heat exchanger in a relatively small space, within a highly congested area of the site.
A 4.3 MW Array of HRS DTI Series Heat Exchangers
The provided solution is a 4.3 MW array of HRS DTI Series heat exchangers which pre-heats the incoming sludge prior to APD. Because HRS heat exchangers are manufactured from high quality 316L stainless steel, the replacement unit has much better corrosion resistance than the old unit it is replacing.
- Stainless Steel BellowsAnother feature of the unit design is the use of stainless steel bellows to replace the previous rubber fittings, which will also increase the operational life of the unit.
- Hinged HatchesTo facilitate easy and fast inspection and cleaning of the tube side of the heat exchangers, the end of each unit features hinged hatches secured with Victaulic connections, meaning that only two bolts need to be removed.
- Same FootprintTo fit the tight space available, and minimise crucial downtime during the installation period the heat exchanger was designed to the same footprint as the previous unit, as well as keeping all pipework and connections in the same locations.
60 Heat Exchangers in Series
The finished unit contains 60 heat exchangers, each of which is 6 meters long, with total operating length of 360 meters, giving a total heat transfer surface area of 303 m². The sludge passes through the unit in a single line moving through all 60 heat exchangers in series. The service water runs in three parallel lines (as occurred in the original unit) which allowed for rapid installation without the need to modify the existing water pipework.
Two Thermal Duties in One Unit
The heat exchanger performs two different functions (duties). Not only does it heat the raw sludge entering the reactor, but it also batch-heats the reactor to ensure the sludge is at the correct temperature – an operation which is controlled by the Avonmouth site itself.
Installed Despite High Winds and Torrential Rain
Despite challenging weather conditions which included high winds and torrential rain, the unit was successfully installed by YTL Construction and Mills Engineering Services Ltd at the beginning of June 2026, and has been successfully carrying out both required thermal duties since.
About HRS Heat Exchangers
Located in the UK, HRS Heat Exchangers is part of the EIL Group (Exchanger Industries Limited) which operates at the forefront of thermal technology. HRS offers innovative heat transfer solutions worldwide across a diverse range of industries. With more than 40 years’ experience in the anaerobic digestion and biogas sector, specialising in the design and manufacture of an extensive range of turnkey systems and components, incorporating our corrugated tubular and scraped surface heat exchanger technology, HRS products are compliant with global design and industry standards. HRS has a network of offices throughout the world: Australia, Canada, UK, Spain, USA, Malaysia and India; with manufacturing plants in India, Spain and Canada.
- GroupEIL Group (Exchanger Industries Limited)
- ExperienceMore than 40 years’ experience in the anaerobic digestion and biogas sector
- OfficesAustraliaCanadaUKSpainUSAMalaysiaIndia
- Manufacturing plantsIndiaSpainCanada
