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Transferring abrasive slurries poses a significant challenge for pumps that cannot run dry or self-prime. A major water, energy, and waste management company discovered this when two centrifugal pumps at a major biomass power plant in Pécs, Hungary, repeatedly failed during operation. The centrifugal pumps broke down when they ran dry, which resulted in extra costs for replacement parts and unplanned maintenance.

The biomass boilers—fuelled by straw and wood waste supplied by local farmers, forestry, and sawmill operators—produce ash as a byproduct of combustion which accumulates beneath the boilers. During a planned maintenance stop, the ash is washed out with high-pressure water, forming a dense slurry of water, soot, sludge, gravel, and metal fragments. The resulting slag wastewater/ash slurry collects in a pit under the boiler and must be pumped out for disposal.

However, the centrifugal pumps used to transfer this slurry were unable to run dry which caused the pumps to break down. Centrifugal pumps typically do not prime when they are dry. Once stopped, the centrifugal pumps could not be restarted due to build up of slag, which caused internal damage and further downtime. This not only disrupted operations with periods of unplanned maintenance downtime but was also costly due to the replacement parts purchased to get the pumps working again.

The power plant in Pécs needed a reliable and durable pump for transferring highly abrasive, dense slurries with solid particles during the planned maintenance stop in the renewable energy production process.

Dissatisfied with the maintenance and frequent replacement parts required by the centrifugal pumps after each use, the water, waste and energy company trialled a Bredel 100 hose pump with NR Transfer hose from Watson-Marlow Fluid Technology Solutions (WMFTS) at the Pécs power plant. The operators found that the Bredel hose pump effectively handled the solid particles in the water, with sizes of up to 2-3 cm, which the centrifugal pumps were unable to transfer previously.

Since 2024, the power plant has been using the Bredel hose pump twice a year for 5-7 consecutive days to remove the slag wastewater/ash slurry, with a solid content up to 50%, from the waste pit (leaving behind the slag) beneath the biomass boiler, thanks to its ability to handle large solids and run dry, with low maintenance requirements.

Bredel hose pumps are engineered to handle sand and slurries with a high solid content, capable of transferring up to 80% solids in suspension.

Ferenc Andri, Sales Engineer at WMFTS in Hungary, said: “The Bredel peristaltic pump replaced centrifugal pumps for a more reliable and low-maintenance operation in pumping the biomass ash waste slurry. The Bredel hose pump efficiently handles the high-density slurries with hard particles with minimal wear and tear in a challenging environment which is what the customer was looking for after the previously used pumps needed repairing every time they were used to pump the slag wastewater. We provided a solution for the company to quickly try out and no other pump could handle this sort of material.”

By switching to a Bredel 100 hose pump, the biomass power plant has improved operational reliability and efficiency.

Two electricity production units in Pécs are fuelled when heat converts water in the biomass boilers to steam. The high-pressure steam turns the blades of a turbine generator to produce electricity, while ash from the burnt fuel is collected beneath the boiler.

The Bredel hose pump is also contributing to the sustainability benefits of the Pécs power plant: electricity produced from renewable resources at Pécs provides sustainable heating for over 30,000 homes and 450 public buildings, while also avoiding the emission of 150,000 metric tonnes of carbon dioxide (CO₂) per year, according to the company. The ash produced by the biomass combustion is also recycled to make fertiliser.

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