Separating unwanted materials like clay, silt, and slime from valuable sand, gravel, and crushed aggregate has been a tricky problem in processing operations since time immemorial. Wash equipment has been designed and perfected to solve this issue while also assuring that construction aggregates and sand can meet ever more stringent specifications and be saleable.
But washing is not the end of the processing circuit—at least, the addition of water to material in order to clean, size, classify, or separate it is not the final step in a processing operation. Dewatering is an important consideration that every operator, especially those of fine aggregates and sand production businesses, must make following washing. Today we’re taking a closer look at the basics of dewatering and the equipment that achieves this state.
What is Dewatering and Why is it Done?
In short, dewatering is precisely what it sounds like—it is the extraction of water following the “wet” stages of washing and classifying material. It serves two main purposes: additional material recovery and the sufficient reduction of moisture content prior to stockpiling.
Dewatering is Especially Important for Sand Production
Sand production involves the use of horizontal sand classifying tanks that rely on water and the principles of gravity to separate material that has been screened smaller than number 8 mesh. Because hydraulic separation is necessary to claim the smallest sand particles, water becomes a significant force to contend with, and dewatering cannot merely be an afterthought. Luckily sand is easily processed through dewatering screens and may also be dewatered with sand screws, among other equipment.
Dewatering Equipment Options
Traditionally achieved with dewatering screens (in both aggregates and industrial sand production), some washing solutions tend to integrate dewatering into a single piece of equipment, such as sand screw plants, which use single or twin dewatering screws to recover fines and dry product. Bucket wheels are another popular piece of dewatering equipment, which boast sand recovery up to 99.5%.
Because dewatering screens are designed to produce a consistent, drip-free product and are capable of removing dirt and silt while retaining sand down to 100 or even 200 mesh sizing, they tend to be the go-to equipment for dewatering. In fact, dewatering screens can typically achieve much better drying than screws or other, less commonly utilized dewatering equipment.
It is important to note that many washing equipment solutions now include dewatering equipment – either in the form of screens or screws – integrated into a single module. This washing equipment may consist of sand screws, bucket wheel plants, and even hydrocyclone technology.
More About Dewatering Screens
So, how do dewatering screens work? Essentially, they facilitate rapid drainage as slurry is fed onto the screen surface, which is inclined downward. Pit & Quarry University’s lesson on washing and classifying describes what happens next:
“Counter-rotating motors create a linear motion, driving solids uphill, while liquid drains through the screen media. The uphill slope of the screen, along with a discharge weir, creates a deep bed that acts as a filter medium, allowing retention of material much finer than the screen openings.”
Trust Kemper Equipment to Help You Find the Best Dewatering Solutions
Many operators are curious about how to optimize their dewatering screens. While these hardworking pieces of equipment are typically designed to be relatively simple to operate, it is crucial to think about the type of material you’re working with, the feed rate, and other factors. The best way to achieve desired moisture content for your operation’s needs, whether you’re using dewatering screens or another washing/dewatering solution, is to work hand-in-hand with equipment experts like us at Kemper Equipment.