Waste to Energy
30°C and viscosity of 500cPs, with 9-12% dry content, although potentially up to 60%, creating very high abrasion. T is temperature rises to between 40-55°C in the second stage of the digestion, but with a consequentially reduced viscosity. After pasteurisation, the temperature increases again to 70°C. Bredel pumps transfer viscous and
abrasive slurries and sludge with up to 80% solids in suspension. Pump capacity is entirely independent of suction and discharge conditions, and this application the choice of natural rubber hose means that fl uids with temperatures up to 80°C can be pumped. Hoses have a soft inner bore which cushions large and abrasive particles, whilst the multiple layers of reinforcing nylon and the tough outer rubber of the hose, provide excellent performance and long hose life.
Low TCO T e relatively low Bredel pump running speed of 14rpm in this application relates to uptime and total cost of ownership (TCO) requirements. Low maintenance is paramount in biogas plants, which are highly automated with few human employees. T e plant only has a staff of three, for example. T e potential for repeated maintenance with PC pumps is high. For instance, the stator is destroyed within seconds if the pump accidently runs dry. Factors such as pressure, abrasive content and temperature can all negatively aff ect PC pump performance. In contrast, the Bredel pump is
One of the largest biogas plants in France has Bredel 65 hose pumps at its core
17-21 days typically), not just because of the lower processing temperatures involved, but because vegetable matter, which takes longer to digest, accounts for 20% of content. T is vegetable matter also means that volume reduction after digestion is just 20%, rather than 50%, which is a more typical waste volume reduction in biogas plants.
Design and planning Bredel 65 pumps fulfi l three principal process transfer applications at the French plant: from buff er input to buff er tank via heat exchangers; from buff er input to buff er tank through pasteurisers; and from buff er tank to digester via heat exchangers.
T e pumps’ installation needed consideration for the pipework system from buff er input to the 5m high buff er tank (via heat exchangers), through considerable discharge pipe lengths and bends. T e impact on back pressure due to the long pipe runs could negatively aff ect many other pump types. However, Bredel pumps maintain constant fl ow against pressure, over the whole life of the hose. At this biomethane production site,
Bredel 65 pumps run at relatively low speeds of 14rpm to generate a fl ow of 4m3/h. In the fi rst part of the process, the slurry has a temperature of around
foolproof in that it is impossible to make mistakes such as run dry. Furthermore, there is only one wear part – the hose – which only takes around 30 minutes to replace (in-situ) and does not require the services of skilled personnel. Importantly, hose life is repeatable, ensuring that biogas plants can plan preventative maintenance accordingly. Ultimately, digestate from the French biogas plant is reused as a natural organic fertiliser for 20,000 hectares of surrounding farmland, reducing the need to procure 60 tonnes of chemical fertilisers and representing annual cost savings up to €15,000 for each of the 17 adjacent farmers. Furthermore, the digestion process reduces carbon emissions by 4,222 tons of CO2
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