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F CASE STUDY

CASE STUDY

HRS Heat Exchangers help Muntons close the loop Muntons is a company with sustainability at its core and this project will create a closed loop system, exemplifying the circular economy.

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alted ingredients company Muntons (Stowmarket, Suffolk) is putting the finishing touches to its £5.4 million on-site anaerobic digestion (AD) plant which will help reduce the firm’s CO2 emissions from 27,264 to 26,605 tonnes per annum. Integral to the success of the 499 kW facility is a three Tank Batch Sludge Pasteuriser System with Energy Recovery from HRS Heat Exchangers, which will help turn up to 80,000 tonnes of Muntons’ liquid malt waste into quality organic fertiliser (known as digestate). 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, around 180,000 tonnes per annum. Muntons is a company with sustainability at its core and this project will create a closed loop system, exemplifying the circular economy. The company became interested in AD after analysis showed that 60 percent of the carbon footprint of its supply chain came from the artificial fertiliser used by its barley growers. The firm realised that using its liquid malt waste as feedstock for an on-site AD plant would not only produce a high quality digestate for its farmers to use instead of artificial fertiliser, it would also cut

66 | December 2015 - Milling and Grain

3,000 tanker movements per year and generate 25 percent of the site’s electricity demand. The digestate will be pasteurised to meet stringent PAS 110 standards using the HRS Heat Exchangers three Tank Batch system, ensuring that the final fertiliser is free from plant pathogens or other biological contaminants. The beauty of the closed-loop system is that the waste feedstock which is turned into digestate during the AD process has come only from the processing of barley. It is then applied to the next barley crops for use in the factory. As well as a comprehensive proposal, the Muntons’ team was impressed by the HRS system, which can save up to 70 percent of heat required, as well as its ability to run at a half flow rate, should the volume of digestate stock reduce. Additionally, the equipment’s monitoring feature enables Muntons to track every batch of digestate back to the feedstock from which it was produced. “The fact that the HRS system offers batch reporting was also a big draw; traceability is very important to us,” remarks Lawrence Howes, Project Engineer at Muntons. Matt Hale, International Sales Manager at HRS: “For Muntons, this whole project has been about maximising efficiency. Although they have an abundance of heat, they still wanted to recapture what they could - our heat exchangers will provide at least 40 percent heat regeneration.” 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). Waste cooling water from the CHP engine is used to heat the sludge in corrugated tube-in-tube heat exchangers, which

Dec 2015 - Milling and Grain magazine  
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