Manufactured Sand: A Two-Pronged Approach – the BIVI-TEC®
In Part 1 in our discussion on manufactured sand (mansand) we talked about the Ortner® Sand Washer and its ability to remove unwanted fines from screenings while using very little water. But what if washing is not an option, due to:
- No water available
- Cost of washing sand is too high.
- Unable to obtain permits for washplant, settling ponds, etc.
- Sand plant is currently a dry plant; don’t want to start washing.
If your operation doesn’t use water for washing sand and you would like to keep it that way, or if you are already using too much water and don’t want to (or can’t) add more gpm to the system, then dry-screening might be a great option for you.
The problematic fines in screenings are very fine, minus #200mesh (<0.75 microns). In order to turn screenings into mansand, all that has to be done is to remove the #200mesh fraction, and maybe some of the #100mesh. Conventional vibrating screens are used to make the top cut at ~3/16″, but they are very inefficient at smaller separations and certainly cannot remove the ultra-fines while leaving the rest of the gradation intact. The BIVI-TEC® Screen can be used to remove these powdery ultra-fines and bring your screenings into spec.
The first BIVI-TEC® screens were put into operation in the early 1990’s. Initially designed for wet, sticky material that would blind over a conventional screen, we quickly discovered that the BIVI-TEC® was capable of making cut-points that are far smaller than any other screen on the market.
The system uses a typical counterbalance weight system with a single drive to create an elliptical motion, just like most other vibrating screens. The difference is that the BIVI-TEC® takes the motion from the screen box and amplifies it, setting up a secondary vibration (bi-vi = two-vibrations). One side of each polyurethane screen panel is pulled by the screen-box motion, while the other side of the panel is pulled by the amplified secondary vibration. The result is a trampoline effect that tosses the material into the air and prevents blinding.
In crushed stone quarries, where the moisture in the sand is typically 2%, the BIVI-TEC® Screen can be used in-line with the crusher to produce manufactured sand. The screen is capable of making a separation as low as #100mesh, removing the ultra-fines while leaving the rest of your gradation intact.
A typical sample of screenings will contain 10-15% -#200mesh dust. The BIVI-TEC® can reduce this to 4-5% after a single pass, eliminating the need for washplants with hundreds of gpm of water. A single wash-screen can easily consume 1,000+ gpm of water. That’s a lot of waste-water to handle on-site, especially if you have to obtain additional permits from your friendly local enforcement agency.
Miss part one of our series on mansand? Check it out to learn more about the Ortner® Sand Washer.
If you’d like to see how the Ortner® or BIVI-TEC® can benefit your application, contact Aggregates Equipment, Inc.