North Ridge Pumps: New transfer pump for AD plant doubles flow rates and cuts fertiliser use

This article contains paid for content produced in collaboration with North Ridge Pumps.

For anaerobic digestion plants in particular, the challenges include maintaining feedstock supply right through to maximising total process efficiency.

This drive for better performance led one anaerobic digestion (AD) plant operator to contact Notts-based pump specialists North Ridge Pumps. They were looking for ways to ramp up transfer rates, reduce fertiliser use and utilise digestate throughout their farm more efficiently.

Digestate is an impressive fertiliser containing all the nutrients and micronutrients needed for successful modern farming, including potassium, nitrogen and phosphorus. Moreover, none of these important nutrients are lost during the AD process. This means that farmers can reuse these essential minerals, and close what they call the nutrient cycle.

In fact, digestate brings big benefits to modern farming – and the environment. It can drastically reduce the use of artificial fertilisers. According to the UK Anaerobic Digestion and Bioresources Association, 1 metric tonne of artificial fertiliser replaced by digestate saves a remarkable 1 tonne of oil, 108 tonnes of water and 7 tonnes of CO2 emissions.

Digestate can do all of this and massively reduce greenhouse gas emissions in the agricultural feed, food and beverage sectors. That’s because organic fertilisers like digestate release very low (or even zero) greenhouse gas emissions during production compared with energy-intensive mineral fertilisers.In short, using digestate instead of synthetic mineral fertilisers made from natural gas can save energy, cut fossil fuel consumption and reduce our carbon footprint.

In this application, the AD plant operator wanted to boost the rate of transfer from their digestate pond to a nursing tank at their AD plant. The liquid being moved was mechanically-separated anaerobic digestate containing only 5% solids, small amounts of sand, plus screed less than 1mm in size.

They were extracting the digestate liquid from a lagoon 4m in height and 18m away. The digestate transfer pipeline was over 300m long and fed into the nursing tank, and digestate tanks.The operators wanted to double their existing flow rate up to 200m³h and hydraulically mix their lagoon at the same time. They were looking for a heavy-duty transfer pump of proven design and reliability to achieve this.

What pump was specified?

North Ridge Pumps have over 25 years of experience in providing engineered pumps for a range of applications. Their specialist pumps are used across a wide range of industries and sectors handling fluids as diverse as fuel, chemicals, food, slurries and sludge.

With over 100 successful commissions for UK and international clients, North Ridge can specify from a wide range of pumps for a variety of industrial and commercial environments. For this particular job they specified their XR625 – a 6” Solid Handing Self Priming Pump which was built and supplied it in just over 6 weeks.

The XR pump range are heavy-duty self-priming pumps which are efficient and extremely durable. They easily handle solids thanks to the armoured volute which surrounds the double curved impeller and protects the pump casing from wear.

What’s more, that double curved impeller boosts pump efficiency. Here for instance, the existing site pump achieved a flow rate of just 100m³h with a 25kw motor. The new North Ridge pump delivered 200m³h with a motor power of only 18.5Kw.

In addition, North Ridge advised the client that to maximise output flow, they should run the pump at 60Hz through a frequency inverter to achieve the required flow and pressure.

Protected against corrosion

Another important factor to consider was the material properties of the digestate being pumped, which can be extremely corrosive. When specifying the pump, North Ridge made sure that all internal parts were easily accessible and weren’t held in place by screws which can corrode and need replacement over time.

According to Zac Paull at North Ridge Pumps this was a tricky specification needing careful consideration, “This was quite a challenge, but thanks to our application expertise across numerous sectors, we can specify from a wide range of pumps – and we’re not tied down to just one type of pump technology. We can develop a bespoke solution, not something picked off the shelf. This means that every time we’re asked, we can select the most appropriate pump for that application at the lowest lifetime cost.”

If you have an upcoming application and are unsure of the correct solution, call North Ridge Pumps on 01773 302 660 or visit www.northridgepumps.com to see how we can help.