RockRoadRecycle staff writer
Around the globe, the mining, minerals, recycling and construction industries are encountering a variety of challenges based on ever changing customer requirements. This has meant that there is now a growing need to meet today’s stringent specifications for cleaner and higher quality aggregates — whether virgin or recycled — while using more effective water recycling processes. Based on industry requirements there is a need for material processing companies to invest in the latest washing plants that are more productive and intelligent than ever before.
Major reasons for this are stricter aggregates specifications as well as a need to make the best use of `extracted material, driving the greater use of washing equipment. However, the latest technology means that this growth does not have to significantly impact energy consumption or water usage. The washing of aggregate is also enabling quarries (and recycling centers to a lesser extent) to meet the demand for sand, as naturally occurring sand reserves are declining and are protected in many countries. Modern washing techniques mean that with the aid of advanced crushing and screening technology sand can be manufactured — with advanced washing plants being essential to the process.
Furthermore, as quarries develop through usage, the more easily extracted material has generally been used. As demand for construction materials increases globally, quarries are having to process material with a higher level of contaminant. This is incentivizing construction companies (as well as legislation) to recycle inert construction materials resulting from demolition or excavations, etc. Many in the industry believe that wet and dry classifying is likely to be a big growth area in the coming years, with many manufacturers, quarries and contractors looking to expand their washing capabilities to meet the demand.
The decision on what equipment a quarry or recycling center needs has to be considered in the context of both the feed material and the final product. This has to take into account normal production volumes and a realistic appraisal of future targets. In effect there is no “one size fits all” when it comes to a wash plant and companies need to carefully match their requirements with those of their customers in order to recommend the right equipment.
Minimizing water usage
Other developments have seen dewatering screens become more popular in recent years. Quarries and recyclers recognized that a drier product is more profitable and allows more water to be recycled. This matches the trend towards considering the environmental impact of material treatment, including reducing run off, which has driven wider use of dewatering screens and water reclamation techniques. There is also a focus on more energy efficient techniques, so many companies now use a standard dewatering screw to discharge onto a dewatering screen which reduces the moisture content and returns any material that falls through the screen back onto the screen. This removes the need for a cyclone, thereby using less energy.
Manufacturers of all shapes and sizes
Fortunately, there are many manufacturers of equipment who are able to supply a wide variety of washing plant. A typical washing set-up will be used when the material does not require scrubbing — only rinsing — to remove small particles of silt and fines to produce a clean end product. The scrubbing process is required when dry and other deleterious materials are present. The process of high speed scrubbing has become an accepted method. Scrubbing works on the principle of working material against material to remove clay and other elements from stone, before moving on to the next stage of the process. With this in mind, and noting the variety of washing plant solutions available, we outline a selection of manufacturers and their offerings.
Some manufacturers have many years of experience in the industry, being in effect washing plant specialists, but some are relatively new entrants into the market, developing advanced systems based on customer demand. As demand for more stringent material specifications grows and quarries progress further into their reserves, the need to wash aggregate materials increases. This saw Superior acquire Greystone Inc. in 2014. Since then, the company has been supplying wet processing solutions from its Columbus, NE, plant. Superior inherited an experienced team of engineers and manufacturing personnel along with a wide range of equipment purpose-designed for washing and classifying bulk materials to a high specification.
Superior’s range now includes classifying systems and tanks, stationary, skid or portable mounted; density separators, fine material washing and dewatering equipment. This includes its patented Aggredry™ washer, fine washing screws, dewatering screens, coarse material washer and so forth. All are designed to provide an offset feed, which eliminates turbulence, with surfaces lined with cast polyurethane. Of particular note is the company’s Helix™ cyclone, designed to remove unwanted fines and recapture fines lost during washing
A recent development from Superior is its new Alliance™ low water washer. This is said to be a first of its kind for aggregate producers, with a unique low water washer being capable of accepting a dry feed directly within a crushing circuit. These fines are then pressure washed and dewatered for production of sellable manufactured sands. “Historically, all of the machinery used to wash crusher fines has been traditional sand screws,” said John Bennington, director of wet processing technology at Superior. “That typically means material producers are handling and hauling the material to a separate wash site, which adds cost quickly.”
During operation, an agitator section accepts the feed where it is mixed with water to produce thick slurry. This slurry is then dumped onto a dewatering screen with a series of spray bars to help clean and wash out the fines. The end result is saleable manufactured sand with just 8 percent moisture content. “The Alliance low water washer is designed specifically for washing crusher fines and uses 80 percent less water than the traditional screw/screen combination,” Bennington says.
A relatively new entrant into the market, McCloskey Washing Systems’ (MWS) AggStorm™ range provides robust and reliable equipment for the most challenging applications. The AggStorm™150 is a modular-design plant designed to remove harsh clay contaminants from natural and crushed gravel, stone and ore feeds that cannot be removed by rinsing or screening alone. This makes it an effective solution for the aggregate and mining industries. The log shafts rotate in opposite directions and are timed to obtain an overlap of the paddle shoes for maximum scrubbing action. The AggStorm’s™ design features ensure smart performance in the harshest environments as well as transforming material into a premium end product.
Haver & Boecker
The company acquired the Tyler range of equipment with its hydro-clean washing plants being designed to minimize water consumption with lower electricity costs for aggregate operations. These units may be incorporated in a plant or can be used as a mobile washing plant. The equipment has been developed to reduce water consumption by as much as 75 percent when compared to traditional washing systems, such as log washers and other aggregate washing systems. Modular components save energy costs by as much as 15 percent, minimizing the effect on the environment. The innovative cleaning capability allows operators to produce higher quality products and create new products from previously unsellable material.
The company’s Hydro-Clean 1000 washing plant features the Hydro-Clean together with a Tyler L-Class 6×16 horizontal rinse screen mounted on a semi portable skid structure, delivering up to 200tph of sellable, washed aggregates. During the cleaning process, the washed material works its way down the HC1000’s drum and exits onto a discharge conveyor that leads to the rinse screen. The screen removes any remaining dirt or clay still on the stone as it classifies the material.
Kolberg Pioneer and Johnson Crushing
KPI-JCI has a wide range of product lines, including crushing, screening, material handling, washing and classifying, track mounted, stationary and portable equipment. They offer comprehensive solutions for a variety of markets. KPI-JCI and Astec Mobile Screens is part of Astec Industries’ Aggregate and Mining Group, having developed expertise in the area of washing plants designed to deal with even the most agglomerated deposits. Its innovative log washers include an exclusive reverse involution design that has paddles arranged in a spiral pattern along the shaft, producing a much more effective scrubbing action to remove tough, plastic-soluble clays and other unwanted coatings. This unique motion ensures that some portion of material is constantly moving, leveling power demand while reducing power consumption.
Its coarse material washers are engineered to quickly adapt to producers’ ever-changing needs. Both single and twin spiral designs can be easily reconfigured, with numerous bolt-on paddle and flight arrangements to satisfy even the most precise specifications. Coarse material washers are equipped with a high-efficiency drive and offer a throughput of 500TPH for increased productivity. The company’s blademills are designed for seamless compatibility with producers’ existing processing plants. An innovative double-pitch flights and ribbed paddle design efficiently convey material through the blademill to break up sticky clay and muddy clumps. Fine material washers deliver productivity and are engineered with high efficiency drives, and a resulting low horsepower requirement reduces operating costs while increasing throughput.
Efficient aggregate processing is delivered through the company’s portable Series 1800 screening and washing plants. These offer leading fine material washers an array of configurations including inclined or horizontal wet single, double or triple shaft screens with two or three decks and a blademill — all on a single chassis. Standard and custom-built skid mounted or stationary plants are available with a wide variety of configurations and options.
Adding to the company’s offering is its dewatering screens, which are designed to dewater sand products to a level typically not possible with fine material washers. Depending on product gradation and other material characteristics, the dewatering screens will produce material with a moisture content as low as 8 percent. Single deck, adjustable incline linear motion screens are available in sizes ranging from 2 x 7 feet to 8 x 16 feet with processing rates up to 400TPH on a single unit.
The company also provides full plants — the Series 9000 products — which are custom engineered and built for each application. Products include classifying cyclones, dewatering screens, dewatering cyclones, pumps, attrition cells, density classifiers and sieve bend screens. The complete systems incorporate products into a single, custom engineered system created to match customer specifications.
Terex Washing Systems
Terex Washing Systems (TWS) recently launched the AggWash™ 300, a screening, scrubbing, sizing and sand recovery for recyclable aggregates, all on one modular chassis. Terex AquaClear™ is the first water management treatment system from Terex. TWS Director Oliver Donnelly commented, “Terex Washing Systems is focused on bringing to market products that deliver value to our customers and offer solutions that serve their needs. The AggWash™ 300 and AquaClear™ do just that.”
The AggWash™ was designed to address higher production requirements for recycling customers and quarry owners, particularly in the construction, demolition and excavation waste recycling market. The high performance solution brings together rinsing, screening, scrubbing and sand washing capabilities on a single plant. While its readily portable format makes it particularly suitable for green field applications, contractor use and temporary planning permission sites, operators more used to static installations will still appreciate the small footprint and minimal site preparations required.
The AggWash™ incorporates two 4.9m x 1.5m (16’ x 5’) triple deck Terex Cedarapids LJ-TS Series horizontal screens, incorporating a triple shaft vibrator mechanism that provides high G-force along with efficient oval motion. The compact installation height of horizontal screens compared to conventional inclined circular motion screens is conducive to the condensed working envelope of the AggWash 300. The “rolling chutes” feature provides easy access for screen maintenance. The machine boasts a high capacity log washer with twin shaft angle adjustment to scrub gravel fraction and float out organics and adhered contaminants. Additionally, there is a 1.8m x 1.2m (6’ x 4’) trash screen for dewatering of lightweight contaminants from the log washer and the plant has an integrated sand plant incorporating rubber lined pumps and hydro cyclones, available in various configurations and capacities.
The AquaClear ™ further enables TWS to offer end-to-end solutions for washing and water management from a single supplier. The range includes clarifying tanks, flocculent dosing systems, filter presses and all associated equipment. Donnelly commented, “TWS is due to begin manufacturing the Terex AquaClear water management solution in Dungannon, Northern Ireland, later this year, working alongside strategic alliance partners in the U.S. We are already handling enquiries for AquaClear from Europe and North America markets. Through our strategic alliance [for North American customers], we can send a filter press fully built up rather than in its component parts in containers. Working with partners who have been in the industry for many years, we are confident that we have the technical capability to devise optimized solutions which present customers with a unique opportunity to maximize their return on investment.”
As can be seen from the brief overview of manufacturer offerings, there is no one definite solution to aggregate and material washing. What is common to all the companies looked at is a drive to produce efficient, effective, economical and environmentally friendly equipment. As the latest developments show, the processing of sand is noted, as is the drive to produce modular solutions to meet the very specific requirements of individual customers.