Integral to the success of the 499kW facility is a three-tank batch sludge pasteuriser system, with energy recovery, from HRS Heat Exchangers, which will help convert up to 80,000 tonnes of Muntons' liquid malt waste into quality organic fertiliser meeting PAS 110 standards.
This will be used on local farmland, helping the company's network of growers to produce some of the 250,000 tonnes of barley needed to make Muntons' malt.
According to Lawrence Howes, project engineer at Muntons, the firm was impressed by the comprehensiveness of HRS's proposal and the system itself – which is capable of saving up to 70% of heat energy compared to conventional systems, while also delivering a half flow rate mode, should the volume of digestate stock reduce.
"The fact that the HRS system offers batch reporting was also a big draw: traceability is very important to us," comments Howes.
The HRS system works on a three tank principle: while one tank is being filled, the second tank holds the sludge at 70°C at the same time as the third tank is being emptied. Each process lasts one hour.
Cooling water from the CHP (combined heat and power) engine is used to heat the sludge in corrugated tube-in-tube heat exchangers.
As for the energy recovery system, that works by transferring energy from the hotter (pasteurised) sludge to the colder (unpasteurised) sludge.
"Using [HRS's] solution enables us to make use of an abundance of waste hot water," states Howes.
"Not only does the tube-in-tube technique deliver improved performance, but they're also more resistant to fouling, which means less downtime and maintenance," he continues.
"In addition, we had a short deadline – just 16 weeks – which HRS was able to meet easily."
The AD plant is currently undergoing commissioning and will become fully operational later this spring.