HRS heat exchangers creates anaerobic digestion plant for Muntons
HRS: ‘Heat which is generated or used in one part of an F&B process is lost rather than reused’
One of the most common situations where heat is wasted is where businesses have installed an AD plant to manage their food waste and factory by-products, said Matt Hale, international sales manager, HRS Heat Exchangers.
Heineken, Weetabix, Maltesers & Ovaltine
“In most cases the primary energy output is electricity supported by Feed-in-Tariffs (FITs) which is used on site or exported to the grid,” he added.
“The electricity is generated by a gas engine combined heat and power plant, but what happens to the heat? In some cases it is used for processing or heating the food factory, but often not to its full potential.
“Implementing HRS heat exchanger technology, to use waste heat from one process to fuel another, could save food factories 7.5 pence per kWh² used.”
One such company is Muntons malted ingredients based in Suffolk, UK which supplies malt to Heineken beer, Weetabix, Maltesers and Ovaltine.
The firm uses 250,000 tonnes of barley to manufacture 180,000 tonnes of malt pa, which it sells the brewing and distilling industry and makes a range of malted ingredients used in food, confectionery and baking.
The company is currently putting the finishing touches to its £5.4m on-site anaerobic digestion (AD) plant. Integral to the success of the 499 kW facility is a 3 Tank Batch Sludge Pasteuriser System with Energy Recovery from HRS Heat Exchangers, which will help turn 80,000 tonnes of Muntons’ liquid malt waste into biogas and organic fertiliser.
This biofertiliser will be then be applied to local farmland, helping the company’s network of growers to produce the barley needed to make Muntons’ malt.
“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 and our heat exchangers will provide at least 40% heat regeneration,” said Hale.
AD is a fast-growing industry in the UK
He added AD is a fast-growing industry in the UK and has seen a steep rise in operational plants: from 192 in 2009 to 335 in January 2015. AD could deliver 10% of Britain’s domestic gas demands and reduce UK greenhouse gas emissions by 2%+ if industry reaches its potential: 40TWh of energy.
“There are many AD facilities treating municipal food waste, farm waste and sewage waste, but there is also a growing trend for on-site AD plants at food and drink manufacturing facilities,” said Hale.
“Companies such as Nestlé, Diageo, Barfoots, QV Foods and Wyke Farms have all developed on-site AD plants with wide reaching benefits: energy and heat generation; better waste management; production of a quality biofertiliser; and, not least, revenue from the sale of energy to the national grid, and from government incentives such as the Feed-in Tariff and Renewable Heat Incentive.”
Muntons first became interested in AD after analysis showed 60% of the carbon footprint of its supply chain came from the artificial fertiliser used by its barley growers.
Three tank principle
The firm realised processing its liquid malt waste through an on-site AD plant would produce a high quality digestate for its farmers to use instead of artificial fertiliser, but also cut 3,000 tanker movements per year as there would be no need to transport its liquid waste off-site.
The HRS system works on a three tank principle; while one tank is being filled, the second tank holds the digestate sludge at 70°C (the optimum temperature for pasteurisation), at the same time as the third tank is being emptied – each process lasts one hour.
Waste cooling water from the CHP engine (which converts the biogas into heat and power) is used to heat the sludge in corrugated tube-in-tube heat exchangers; this is more efficient than heating an entire tank of digestate.
HRS has also incorporated an energy recovery section into the process: energy is transferred from the hotter (pasteurised) sludge to the colder (unpasteurised) sludge, reducing energy consumption by up to 70% compared to normal systems.
