- Case Study
Concrete slab plant
- Hose pumps replace PC and centrifugal pumps at concrete slab plants
- Some pumps run almost continuously six days a week
- Pumps helping leading manufacturer meet sustainability goals
A number of Bredel hose pumps are proving highly successful in the circulation and transfer of waste return slurry from concrete slab manufacturing processes. With its Ytong, Silka and Hebel brands, Xella is one of the world’s largest manufacturers of autoclaved aerated concrete (AAC).
As part of the company’s manufacturing process, the reuse of otherwise waste slurry streams is a priority. The raw materials for AAC include quartz sand, calcined gypsum and lime (mineral), which are mixed with water to an aqueous suspension. The aerating agent is aluminium powder, which is added at the end of the process to a concentration of 0.05-0.08% by volume, depending on the pre-specified density. Finally, the mix is poured into moulds. When the forms are removed from the material, it is solid but still soft. The material is then cut into blocks or panels, and placed in an autoclave chamber for 12 hours.
After cutting, the waste falls into a sump. This is diluted with water and flows to an underground tank, from where it is circulated and transferred by Bredel pumps. The slurry has a specific gravity (SG) of between 1.45 and 1.7 at ambient temperature, along with a viscosity of approximately 100-150 cPs and a solid content 723 g/l.
In the Netherlands, a Bredel 80 pump runs 90% of the time, circulating the slurry in the tank underneath the cutting machine at a rate of 14.5 m3/hr. The slurry in this tank overflows into a back-up tank, which is where another Bredel 80 pump is deployed, pumping the slurry to a bulk storage tank.
At Rotenburg in Germany, the Bredel pump application involves circulation and transfer of ‘schlamm’ or cement slurry using a higher flow Bredel 100. During the slurry transfer, the outlet is into a tank which is mounted on a load cell, while the pump is located near the tank where the cement slurry is mixed by an agitator.
Xella overcame the issues of conveying the abrasive cement slurry seen in the previously deployed progressive cavity (PC) and centrifugal pumps and now benefit from lower pump maintenance costs and greatly reduced downtime, at both the Netherlands and German production sites.