Conveying Boric Acid at Boron Mine in California

General Description

Boron has many uses in everyday applications including ceramics, fertilizer, detergent, permanent magnets, nuclear reactors, and cosmetics. Permanent magnet composition includes rare earths, iron, and Boron. The demand for electric vehicles has greatly increased the demand for Boron. Boron is also used to manufacture solar modules, and wind turbines.

Geologically, Boron is difficult to find, with deposits forming from a combination of volcanic activity near an evaporated inland sea in tectonically active areas. The San Andreas fault that runs through California contains Boron deposits. Boron is extremely hard and is only surpassed by diamonds. It is heat resistant to 3,000ºF and if infused with other metals the corrosion propensity decreases.

KWS provided a shaftless screw conveyor for transferring Boric Acid Wet Cake from a vacuum belt filter to a dryer and a shafted screw conveyor to convey dry Boric Acid from the dryer to a bagging operation.

Design Parameters

1. Product Type: Boric Acid Wet Cake and Dry Boric Acid
2. Material Density: 86 – 88 pcf (wet) and 50 – 60 (dry)
3. Capacity: 8 CFH (wet) and 10 CFH (dry)
4. Duty: 8 Hours per Day, 6 Days per Week

KWS Advantages

KWS and the consulting engineer met multiple times with the end user to review the application and develop long term and cost-effective solutions. KWS coordinated the layout and dimensions, so the screw conveyors fit perfectly within the existing space without compromising the process or functionality. KWS modeled the area including the new screw conveyors and interfacing equipment such as the vacuum filter and dryer to ensure proper equipment layout with an allowance for maintenance.

KWS Special Features

The KWS shaftless screw conveyor was very efficient for conveying wet boric acid cake up a 27-degree incline from the vacuum filter to the dryer. Wet clumps of material were easily broken up during the conveying process. KWS provided an inlet transition that mounted directly to the vacuum belt filter without additional work, saving time and money.

Dry boric acid is free-flowing and best conveyed using a shafted screw conveyor. Both new KWS screw conveyors were constructed from 304 stainless steel for corrosion resistance. Covers were bolted on 12-inch centers to contain the Boric Acid and prevent access to rotating components.

Connections were supplied on each conveyor so maintenance personnel could wash out the units as they deem necessary. KWS designed and supplied structural supports for each screw conveyor, making field installation easy. Hinged doors with safety grating were provided over the discharges for inspection purposes. KWS also supplied a Binswitch capacitance level indicator to monitor plugging and zero-speed switches to monitor screw rotation.

KWS also supplied a Y-type diverter valve so that dry Boric Acid could be discharged to the bagging system. If one bag was full, material could be diverted to an empty bag while the full bag was removed and replaced.