21 Bredel hose pumps in sustainable energy project

Bredel hose pumps have been installed as part of a landmark abrasive handling project at the combined heat and power (CHP) plant in Denmark. The project has seen the facility switch from coal to biomass fuel in line with its ambition to supply sustainable energy.

• Ørsted switches major plant from coal to biomass
• 21 pumps in use, some of which run continuously
• Unusual application pumping highly abrasive fly ash slurry

Bredel used in sustainable energy project

Process change

In converting from coal to biomass (wood pellets) Ørsted required the construction of a plant facility for firing ash from coal combustion to achieve the optimum binding of alkali in the flue gas. This would also serve to spare the boiler walls from scale/slag accumulation, corrosion as well as reduce poisoning of the deNOx catalyst.

For this purpose, fly ash is mixed with 35% water, fed to the dosing tanks (each with a recirculation line) through a 650m-long pipeline and finally injected to the pellet mills. Inside, to avoid settlement, four Bredel 80 hose pumps are deployed to circulate the fly ash slurry, which is then dosed from the recirculation line into a Babcock boiler.

The ash slurry is dosed via four wood pellet mills, each mounted with a Bredel 40 pump. In total, the installation involves 21 Bredel pumps of mixed sizes, some of which run continuously. Extending hose life to enable maximum uptime

It was evident at an early stage in the project that the potential for hose wear was high. Project co-operation between WMFTG, Eurocon and Ørsted saw the delivery of an optimised solution that would potentially result in huge financial savings – fly ash is traditionally handled by large double-acting hydraulic pumps costing circa £500,000 each.

By making subtle changes to the process, it was found that the life of the hose elements in use at Ørsted could be maximised. With good engineering support from WMFTG, the system back pressure versus shimming was optimised, reducing mechanical stress on the pump hoses.

The introduction of pulsation dampeners to overcome cavitation further on in the line has also provided a positive change to the pumps’ installation. As a result of the pulsation dampeners and the reduced flow, system back pressure was decreased by 50%. This does not affect process speeds as the four Bredel 80 pumps are only circulating fly ash slurry to keep it in suspension.

Optimised solution

“To summarise, the effect of abrasiveness on hose life is low—the effect of factors such as dry solid content and pump speed is much higher,” says Edo van der Meulen, Bredel product specialist. “The dry solids content of the fly ash entering the system is controlled automatically—when it exceeds the limit at which the slurry can be successfully pumped, a Bredel 40 is activated to add water until the B100 [used to transfer the prepared slurry from a buffer tank to the storage tanks] can pump again.”

In a final statement, Edo van der Meulen reminds Bredel pump users such as Ørsted in Denmark “Pump speed has an almost linear effect on hose life: half the speed is double the hose life.”

Bredel hose pumps