Sand Washing Plants

Sand Washing comes in many forms and covers a range of feed and products produced, including construction aggregates such as concrete, asphalt, mason, mortar, and plaster sands; sports sands such as for golf courses, ball parks, and race courses; industrial sands, such as glass, filter, foundry, and frac; specialty sands and materials such as anti-skid, roofing granules; deligniting/organics removal; and soils washing for environmental projects.

For customers who are interested in maximizing yield and producing precisely graded products to the end-user's needs and specifications, it is more likely that a custom sand plant is the correct solution. Whether the sands are natural or manufactured, fine or coarse, well or poorly graded, or required for specialty applications, McLanahan can offer a plant specifically designed to suit your needs.

How Sand Washing Plants Work

Sand Washing Plants covers a variety of processes to get the sand from the raw state to a finished state. These process can include:

• Feed Preparation - Before the raw feed can be processed, it must be prepared using a combination of Attrition Cells, Blade Mills, Coarse Material Screw Washers, Log Washers and Rotary Scrubbers. The objective is to bring all materials into suspension, essentially breaking down any clays and clay-bound materials and removing superficial surface contamination.
• Sizing – Prior to and immediately after the feed preparation step, the raw feed must be screened into fractions appropriate for both the downstream process and the products to be produced. Vibratory Screens are typically used.
• Pumping – Centrifugal Slurry Pumps are the preferred means by which slurry is transferred from one plant/process to the next. Pumps are also used for effluent disposal. Although there can be resistance to using a pump over a gravity-fed unit, a gravity-fed unit may not be able to capture saleable materials. These losses go straight to waste and will end up costing you money in the long term.
• Desliming - If a significant amount of liberated ultra-fine material is present in the feed, it is typically desirable to remove this deleterious fraction before classification. Classification efficiency can be adversely impacted by high levels of suspended clays, leading to losses of saleable materials and dirty products. Cyclones are the preferred desliming device due to their high shear and efficient classification. Feed Regulating Sumps are also very appropriate especially where there are high volumes such as would be found in dredging applications. Their controlled overflow can reduce the power consumption for pumping to downstream classification. Occasionally, desliming or simply washing is all that is needed to create the final product by removing the <75µm (<200 mesh) down to a certain level, such as 3-5% passing.
• Classifying – This is the process of separating particulates from one another based on either size or specific gravity. In sand washing, this applies to the <4mesh (<5mm) particulates. The procedure may involve making single sharp separations with our Hydrosizer™, or multiple size classifications with our Classifying Tanks. Where a specialty sand is being produced, such as for glass, frac, sports, filter, foundry, etc., a Hydrosizer™ provides the accuracy needed for the splits in product gradation. Cyclones and Separators™ are also classification devices operating in the 140mesh (105µm) and finer size separation range typically finer than that where a Hydrosizer might be used.
• Deligniting/Organics Removal - This process is the classification of materials based on their specific gravity. In an aggregate application, depending on the overall process design, either a Hydrosizer™ or a LitesOut™ is used to reject +50 x 4mesh organics of 1.4 – 1.8 SG. We use the ASTM C123 test for lightweight materials where a heavy liquid is used to define the specific gravity of the contaminant. Under some circumstances where the specific gravity differential between the sand and the lignite is marginal, we may run a test in our lab to evaluate dense medium separation as in a Hydrosizer™. It should always be understood that final products will not be lignite-free but will pass based on ASTM C123.
• Densifying and Dewatering – Certain types of equipment, like Hydrosizers and Attrition Cells, require a dilute slurry to be concentrated. Cyclones or Separators™ are most commonly used for this purpose. Separators™ are especially suited for this duty with the ability to dial in and under flow density. In the case of dewatering, Fine Material Screws, Dewatering Screens or Separators™ are the most common devices. The lowest moisture content, by far, is obtained with a Dewatering Screen. With improved safety (less cleanup around the conveyors), better housekeeping (almost no water drainage from the stockpile) and more immediate availability, Dewatering Screens have become the equipment of choice for final product dewatering.
• Effluent Treatment – Water is a very valuable commodity, so it is becoming a requirement to include a water recovery circuit as part of any permitting process. The device most common for this purpose is a Thickener. In most cases, 85% of the process water can be recovered for reuse. The most cost-effective storage method is a dedicated water tank to reduce the percolation and evaporation losses associated with ponds. These tanks also save on the power requirement to pump the water out and back.
• Waste Solids Management – While Thickeners can recover process water, the underflow is relatively dilute and is typically be pumped to containment ponds. To finish off the sand washing process and have the waste solids in a conveyable and stackable condition, Filter Presses are typically employed.
• Sampling - Every system requires monitoring and sampling to provide the best results. McLanahan can design a sampling system up front to focus on the key areas. The ability to react faster to process changes helps eliminate waste, improve product quality and troubleshoot problems.

Why McLanahan Sand Washing Plants

Sand Washing comes in many forms and covers a range of feed and products produced, including construction aggregates such as concrete, asphalt, mason, mortar, and plaster sands; sports sands such as for golf courses, ball parks, and race courses; industrial sands, such as glass, filter, foundry, and frac; specialty sands and materials such as anti-skid, roofing granules; deligniting/organics removal; and soils washing for environmental projects.

McLanahan is best known for creating process solutions to address the specific needs of each customer's application. We have one of the largest ranges of robust, field-proven equipment, and we are constantly innovating. Our background and expertise in applications is second to none.

Depending on the application, McLanahan can perform lab scale tests on materials, including sieve analysis, percent solids, attrition scrubbing, sink/float, sand equivalency and durability, Hydrosizer™ based classification, static and dynamic flocculation/settling and Filter Press testing.

With our proprietary simulations, in-house lab and industry expertise, you get a plant designed specifically for your site with capacities to match your need. Our expertise is the envy of the industry, so when you couple this with one of the largest ranges of equipment offerings, we can offer a solution.