Regeneration of Bentonite Slurries

Bentonite mud regeneration plant for hydro shield tunnel boring machines

The bentonite suspension serves two purposes; on the one hand, as a shield-protector and on the other hand in the hydraulic removal of drillwaste. The subsequent cleaning of the mud is divided into three stages as follows: the first stage is concerned with the pre-screening of coarse particles (larger than 4 mm). The second and third stages are served by a combination of two connected hydrocyclones i.e. the overflow from the cyclone in the first stage provides the feed for the cyclone in the second stage. The underflows from both stage are fed onto a dewatering screen, where the coarser particles separated in stage one serve as a precoat layer, onto which the finely-grained underflow from the second cyclone stage will be fed. A further cleaning (third stage) can be done in case of high clay and silt content in the soil by centrifuging a part of the slurry.

Engineering of optimal adapted Regeneration Systems Based on the particle size distribution of the envisaged soil for slot walls, tunnels or drill holes, we at AKW A+V engineer the optimum technical and economical system for our clients:

• For gravel and coarse sand in the range of 2 - 100 mm mere screening is sufficient.
• For sandy material down to approx. 0,1 mm we recommend the addition of a one-stage hydrocyclone plant including a dewatering screen.
• For the separation of very fine sands and silt down to approx. 0.02 mm a second hydrocyclone stage has been proved to be necessary.

The modular system of our equipment also caters for the extension of existing plants for further
application under more difficult conditions.
Our plants are designed to cope with strongly fluctuating feed conditions.
We develop new solutions for problems in storing used slurries.