1. Linear Screens
WesTech has built a solid reputation for reliable process equipment and superior service worldwide. We design, engineer, and manufacture quality equipment for municipal, mining, and industrial treatment applications. This presentation will focus on linear screening equipment in the mining industry along with a brief discussion of other mining equipment.
Presented by:
WesTech Engineering, Inc.

2. World Headquarters – Salt Lake City, Utah - USA
Who are we…
World Headquarters – Salt Lake City, Utah - USA
Process Equipment. Process Driven. Since 1973, WesTech has gained extensive experience in water and wastewater treatment for a wide range of equipment and processes. Prior to making a treatment recommendation for a particular application, WesTech works closely with customers to gather necessary information for the entire process. This process driven approach, along with the combined experience of our process and
application engineers, ensures a successful facility that accomplishes clients’ essential treatment goals.
Now celebrating 40 years, WesTech has enjoyed steady growth since its founding and has maintained a financially sound position throughout. With an Employee Stock Ownership Plan (ESOP) holding a large part of the company’s stock, WesTech employees have a strong commitment to the success of the company. WesTech’s management is progressive and responsive to the needs of its customers, employees, and the industry at large.
WesTech was founded in 1973
WesTech is ISO certified
WesTech supplies equipment worldwide
WesTech is employee owned

3. Locations
WesTech World Headquarters
WesTech Regional Office
WesTech Global Partner
Global Presence: WesTech equipment is supported by a global network of experienced engineers and qualified sales agents. WesTech maintains offices and partnerships throughout the world to give you access to our products and services. Contact WesTech to arrange a visit with our local representative in your area.

4. Minerals Products Thickening and Clarification Polishing (Filtration)
Thickeners & Clarifiers
High Rate Thickeners
Ultra High Rate Thickeners
Paste Thickeners
Solids Contact Clarifiers
Vacuum Filtration
Scraper Drum Filters
Conventional Disc Filters
Ceramic Disc Filters
Drum Belt Filters
Horizontal Belt Filters
Precoat Drum Filters
Polishing (Filtration)
Buoyant Media Clarifiers
Granular Media Filters
SuperSand Filters
Pressure Filtration
Belt Presses
Filter Presses
Tower Presses
Screens
Carbon Retention Screens
Linear Screens
Spare Parts & Service
These are the major equipment lines WesTech offers to the Minerals industry. The remainder of this presentation will briefly discuss the application and process advantages of the various pieces of equipment.

5. Typical Minerals Applications
Gold CCD
CIP / CIL
Potash
Soda Ash
Mineral Concentrates
Mineral Tailings
Backfill
Process Streams
Industrial Minerals
Acid Mine Drainage
Underground Mine Water
Pile Runoff
Oil Sands
WesTech’s experienced technical staff performs on‑site bench-scale testing or in-house laboratory testing to determine appropriate settling rates, unit areas, and other key design parameters. WesTech’s experience has been applied to many minerals applications.

6. Applications – Gold CIL
This presentation focuses on carbon retention screens in the carbon-in leach circuit as well as trash screens at the front end and carbon safety screens at the end of the circuits. A brief discussion is included for thickeners and paste thickeners in the flowsheet.
Carbon-in-Leach Circuit (CIL)
For over a hundred years, miners have used dilute alkaline cyanide solutions (e.g., sodium cyanide [NaCN] around pH 10-11) to leach (dissolve) gold and other precious metals, from their ores. The gold is usually in the form of small flakes mixed with other minerals. It is difficult to separate mechanically, so it is dissolved and then recovered by other means.
Activated carbon removes gold out of dilute cyanide solution by adsorption (sticking). Carbon adsorption (with other extraction steps) is often the best method to follow gold cyanidation.*†
Carbon-in-leach process adds the leaching agent (cyanide solution) and activated carbon together into the slurry of ore and water. This prevents other carbonaceous materials (wood, clay, etc.) in the ores from adsorbing the gold first (“preg-robbing”).
In this step:
Mills grind the ore, exposing gold particles.
Water joins the ore to form slurry.
A trash linear screen rejects wood and debris so that it does not disrupt later operations.
A high-rate thickener removes excess water from the grinding stage.
This process includes several vessels where:
Cyanide solution leaches the gold from the slurry so that it can be adsorbed by carbon. ‡
Slurry flows downstream (pumped or by gravity). Carbon retention screens keep the larger-sized carbon from going downstream, at each stage.
Pumps force the carbon-rich slurry upstream.
Countercurrent net transfer: slurry flows downstream – with less gold at each stage; carbon flows upstream – loaded with more gold at each stage.
A high-rate or paste thickener dewaters the tails (waste), before disposal in a tailings pond, or as a paste deposition.
This process includes:
Elution – A hot, concentrated cyanide solution pulls the gold from the carbon.
Regeneration – A kiln reactivates carbon before the circuit reuses it.
Electrowinning – Electricity passes through the gold-loaded (pregnant) solution, causing gold to form at a cathode, and cyanide at an anode. A smelter refines the gold.
Carbon Fines Recovery
Slurry leaves the final adsorption stage through a linear screen, which catches any residual carbon fragments. These are recycled.
A carbon sizing, linear screen ejects the carbon fines from the adsorption circuit.
A settling tank (e.g., AltaFloTM Thickener) or filter collects carbon fines, and reclaims water.
*But if the silver content in the ore is high, see “CCD – Merrill-Crowe Gold Silver” flow sheet.
†There are three subsets of the carbon adsorption approach:
Carbon-in-Pulp – Most efficient for slurries. Process leaches the gold first, adds carbon separately.
Carbon-in-Leach – Effective for carbonaceous ore slurries. Process adds leaching agent and carbon together, keeping ‘preg-robbing’ material (like wood) from adsorbing the gold.
Carbon-in-Column – For non-slurries, solution-only. Typical for heap leach applications.
‡Leaching detention time is dependent on:
Particle Size – Finer particles dissolve quicker, less time needed
Dissolved Oxygen – Rate of dissolution is directly proportional to amount of oxygen present.

7. Linear Trash Screen
Linear trash screens were originally developed to remove tramp material in CIP/CIL processes. Since then they have been applied to various mining and chemical applications.

8. What are Linear Screens?
A revolutionary screening system which has solved a major problem in the CIP/CIL processes in gold plants. Since then it has been applied to other applications.
It removes the wood fiber and tramp oversize from milled gold slurries. And it is capable of screening between 500 and 2,000 microns.

9. Where Do Linear Screens Fit?
Typical Uses
The main applications for linear screens are as trash screens and safety screens in gold circuits.

10. Where Do Linear Screens Fit?
The main applications for linear screens are as trash screens and safety screens in gold circuits.

11. WesTech Linear Screens
Features:
Low maintenance
No vibration – low noise
High screening efficiency
Continuous cloth washing
Sizes:
10 to 300 ft2
Screen openings from 500 to 2,000 microns
Screen was developed to remove wood fiber and tramp oversize from milled gold slurries and is capable of screening between 150 and 2,000 microns. >98% removal of wood material and tramp oversize compared to 40-70% from other systems.

12. What Do They Look Like? Feedbox Filter Cloth Feed Oversize
The standard linear screen consists of an endless polyester screen cloth, supported on rollers to prevent pooling of the feed slurry and driven by a head pulley that is coupled to a drive unit. Slurry is fed into the feed box and then passes through a series of holes in a distributor plate on to the moving cloth. The feed distributor plate spreads the feed slurry over the width of the cloth and obviates flooding. The undersize material drains by gravity through the cloth and is collected from the screen under pan. The oversize fraction discharges from the belt at the drive pulley with the aid of wash water sprayed from the underside of the cloth. This spray serves the additional function of continuously cleaning and un-blinding the cloth. The cloth returns to accept further feed via an automatic tracking system and a dynamic tensioner mechanism.
Screen Underpan
Cloth Wash
Cloth Tracker
Screened Slurry

13. Advantages Removes over 95% of trash material Availability exceeds 98%
No vibration, hence smaller civil and support steel requirements than vibrating screens
No scaling
Low noise levels
Low power consumption
Relatively low maintenance costs

14. Wood Fibre Reduction Linear Screen Installed
Since the linear screen operates with no vibration, this prevents realignment of oversize material with the cloth aperture, ensuring retention of all oversize material. This results in over 98% removal of wood fiber as shown in this slide.

15. Linear Screen Applications
Gold
Platinum
Asbestos
Copper
Oil Sands
Any slurry circuit
There are a number of applications where the linear screen can be applied. Some are shown above.
By making a careful selection of the aperture, weave and open area of the screen cloth, the cut point, capacity and general performance of the linear screen can be matched to the specific application.
When handling more viscous pulps and/or finer cut sizes, some undersized material might become entrained within the bed of oversize material retained on the screen cloth. In such instances an additional series of wash water jets can be installed across and also under the screen cloth. These water jets disturb the bed and liberate more misplaced fines for passage through the screen cloth.

16. Trash Screen Oil Sands Bitumen Slurry
Bitumen screen in the oil sands industry is one of the most difficult applications to date. Three 12m2 linear screens were installed to remove trash from bitumen product so that downstream pumps would not plug.

17. Trash Screen Oil Sands Bitumen Slurry
The screens worked in a range of slurry viscosities – even on bad days.
Bad Day
Good Day

18. Tek Pogo
This application was to remove trash from a thickener feed screen. A 3m2 linear screen was installed.

19. Rosebel
This 25m2 screen was installed on gold CIL as a trash screen.

20. Other Services Equipment application Laboratory testing
Pilot plant testing
Spare parts
Field service
Instrumentation and controls
Our technical staff can aid in solving many of the problems encountered in today’s sophisticated and automated flow sheets.
WesTech strongly believes in the use of pilot and laboratory size equipment when required to accurately determine customer needs. We encourage our clients to use our testing services.
A full line of accessory and instrumentation is available to complement your equipment needs. WesTech electrical controls are built from stock components providing you with one source supply and establishing system responsibility. Filters and accessories that are skid mounted can be shipped fully plumbed and wired for your installation convenience.

21. © WesTech Engineering, Inc. 2016