Aggregate Environmental Control Systems


May 1, 2008

From reducing dust to cleaner water, here’s a guide to what can help keep your operation environmentally friendly.

by Tina Grady Barbaccia, Senior Editor

Gravitational, inertial forces

The Mobile Classifier from Buell is composed of the Buell GI-108 Gravitational Inertial Classifier, two cyclones, a filter, fan, air compressor, two discharge conveyors, and a control panel with starters, all of which are situated on a single, flatbed trailer. The system is equipped with hydraulics that allow the system to be set up in about two hours. Ceramic liners are included in certain areas to provide wear protection when processing abrasive materials. The classifier has a 75 tons-per-hour feed rate and combines gravitational, inertial, centrifugal, and aerodynamic forces to efficiently classify materials at cut points ranging from 50 to 200 mesh (300 to 75 microns).

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Uses half the horsepower

The Aggre-Dry FMW (fine material washer) Screen from GreyStone washes and dewaters aggregate material, combining a fine material screw and dewatering screen that the company says produces sand and gravel with a moisture content as low as 8 to 13 percent, by weight, while using less than half the horsepower required to process the same tonnage of spec product using a traditional screen/cyclone system. The dewatering screen features a 0.25-mm screen that reduces the amount of material that can fall through the screen. The feed from the screw allows the material to build to a bed depth of 14 inches on the screen, squeezing additional moisture from the sand as the vibratory motors move it along the length of the screen cloth, further reducing moisture content.

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Monitors thickener bed level

Autofloc controllers from Nalco function as feedback or feed-forward controllers used to monitor and control clarification/thickening operations. The company offers a variety of controller types ranging from one that monitors the thickener bed level and adjusts flocculant dosage accordingly to another that monitors water clarity in ponds and thickeners. The company also offers a third controller that measures floc size in thickener center wells and adjusts polymer dosage.

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Reduces particulate matter 99.9 percent

Huss LLC showcased its Diesel Particle Filters (DPFs) during March’s ConExpo-Con/Agg tradeshow in Las Vegas. The DPFs have been independently proven to reduce 99.9 percent particulate matter (PM), according to the manufacturer. The company offers filter systems with a broad range of regeneration strategies, providing solutions for both retrofit and OEM to help clean diesel exhaust. The MD-System, a diesel particle filter with active diesel injection, combines active and passive DPFs and allows continuous regeneration.

The new wall flow filter is made of liquid-phase sintered silicon carbide (SiC) with 200 cells per square inch density, high mechanical and thermal durability, and high chemical resistance. The filter is made to resist corrosive residues in the fuel and extreme differences in exhaust gas temperatures during operation and while regenerating. It also withstands severe crushes due to uneven terrain. The specially designed triangle channel structure offers nearly 15 percent more filter area compared to the traditional quad.

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Innovative Equipment Solutions
Fully automated, drive-through system

Innovative Equipment Solutions (IES) introduces it new Neptune Series of fully automated, drive-through wheel wash systems, which can be configured with one-, two-, or three-tire revolutions of cleaning to eliminate jobsite trackout. Featuring concrete- or galvanized-steel sidewall construction, the Neptune system works in both permanent and temporary installations. All models are engineered with a fully automated, closed-loop water recycling and solids separation process so that water present at the site entrance does not create any additional issues. The series features a high-volume, low-pressure water design, which prevents overspray and the knocking of oil and grease from the truck chassis. Its extra-wide, 42-inch wash elements flex the tire tread open to allow the high water volume flow to flush the tires clean. Adjustable nozzle assemblies allow for a highly focused spray.

Each system is configured with the appropriately sized water recycling and solid separation tank. A self-priming flocculent pump increases the cleanliness of the recycled water. Solids can be removed with equipment that would typically be on-hand at a site. Pumps are installed using autocouplers that allow the operator to remove the pumps from the tank without the need to dewater the tank, which is a significant savings in time and water during any maintenance or repair.

IES also offers its new portable aboveground Maximus Series, which also offers a fully automated, closed-loop water recycling and solids separation solution.

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Midwest Industrial Supply
Environmentally safe dust control

Haul Pro from Midwest Industrial Supply Inc. is designed as a long-term solution to control dust and surface deterioration on unpaved haul roads. An environmentally safe product, it is effective in controlling PM10 and PM2.5 in large areas. The resin-modified emulsion product’s high-performance chemical properties allow it to be used in a full-range of haul road applications in various climates and weather conditions. It can be applied using a standard spray truck.

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Dual-action spray manifolds

The DirtSquirt Wheel Wash System from Nesco is equipped with galvanized, dual-action spray manifolds that have 200-psi nozzles. According to Nesco, the wheel wash system runs at a much higher pressure than other wheel washes, using less than 60 gallons of water per truck. It can be installed as a stationary wash or housed in a trailer with a surge tank for portable applications. The system uses a 200-psi pump module available in capacities ranging from 40 to 320 gpm to supply spray nozzles that can be configured to wash tires alone or in conjunction with the truck body and undercarriage. A sensor within the armored housing is used to automate the wash and control both the frequency and duration of the wash cycle. A surge tank with a level switch and fill solenoid ensures that the pump is ready to go when a truck enters the wheel wash.

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‘Water miser’ clarifier

The Jadair Settler/Clarifier system provides simple, effective water clarification without requiring any settling ponds for the water or solids or energy-intensive requirements. The company says that this transportable, compact system is a “water miser” and was developed to deal with the inorganic solids that are most often encountered in the mining industry. Dirty water enters in and clarified water exits for immediate reuse. The solids are thick — typically a thick mud — and often only can be removed with the company’s specially designed paddle conveyor system. The solids are handled simply and have been conditioned to continue to release water naturally. The settler/clarifier system can handle 200 gpm to more than 10,000 gpm, and the highly automated controls are now Ethernet capable for integration into overall plant control systems. Use of polymers to enhance the settling characteristics are integral to the system, which is designed on a modular building block approach so that various combinations can be easily readily mixed and matched for particular needs.

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Dust Control Technology
Captures, controls maximum dust

Dust Control Technology featured its flagship DustBoss DB-60 and its smaller DustBoss DB-30 during this year’s ConExpo-Con/Agg in Las Vegas. Both ducted fan units are designed specifically to optimize particle size and velocity for maximum dust capture and control. The DustBoss DB-60 is built to handle bigger jobs, with a throw of more than 200 feet and the capability of blanketing a 21,000-square-foot area with droplets that are 50 to 200 microns in size. The unit is made of a series of 30 specially designed brass nozzles that atomize the water, which is then launched by a 25 horsepower fan that generates 30,000 cfm. It also is equipped with a 10-horsepower booster pump to increase water pressure as much as 150 psi from a 2-inch supply hose. The DB-60 has an adjustable throw angle from 0 to 50 degrees, and the oscillating head delivers 40 degrees of motion. The unit can also be outfitted with a dosing pump to accommodate odor control additives or surfactants to further enhance binding of dust particles. Additional options include explosion-proof motors and stainless steel or nylon nozzles for special applications.

The company’s DustBoss DB-30 — developed for use in smaller jobs — is mounted on a movable carriage and has a 7.5-horsepwer motor that generates 9,200 cfm. The unit also features a ring of 30 specially designed brass nozzles that atomize the water supply to droplets between 50 and 200 microns in size. It has an adjustable throw angle from 0 to 50 degrees elevation and oscillates up to 70 degrees. With a reach of 100 feet, it covers a 5,500-square-foot area from a standard 5/8-inch garden hose. The machine comes with a 1-1/2-inch pre-filter with quick cam release for easy access, and it can be set up to run potable or non-potable water. Options include single phase or international motors, explosion-proof motors, secondary filter system, and dosing pump.

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Internal dilution and settling zone

The Ultrastep Ultra High Rate Thickener from Phoenix Process Equipment Co. has no moving parts, takes up minimal space, and features high underflow solids up to 50 to 60 percent. It also comes completely assembled from the factory to make installation and relocation easier. The thickener features an internal dilution and settling zone to provide optimal, efficient flocculation; a small footprint; no drag chains, making mechanical maintenance necessary; and a consistently thick underflow, resulting in reduced pond storage areas. Increased bed depths enhance the compaction of thickened material at the bottom of the bed, which maximizes the underflow solids concentration.

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