Loading chutes are in demand for filling vessel holds while avoiding problems with fugitive dust emissions.
In many instances, just suppressing fugitive dust in stockpiles is not enough. Terminals want, or are obliged, to minimise their environmental impact, from pile to loading and discharging.
In this respect, both North and South America have proved successful hunting grounds recently for Cleveland Cascades.
In Brazil, Cleveland engineers supported aluminium maker Alcoa with the commissioning of a refurbished loading chute installed at Alumar Consortium plant in São Luis.
The Cascade chute is one of the 1500 sized systems mounted on a pivoting head chute and luffing boom. The chute is 25m in length when extended, and retracts to 6.4m. The cones are lined with 4mm ceramic tiles for abrasion protection as the system loads alumina at approximately 2,000 tph.
The chute is fitted with a speed reducer for material control at the base of the chute, and to keep dust to a minimum.
After several years of operation, Cascade engineers were called in to assess the current condition of the chute, to ensure the successful installation of spare parts, and to confirm that the chute operation is optimal.
Replacement strops had recently been fitted prior to the engineers’ arrival and, following a functionality inspection, a new shroud was fitted to the speed reducer, and the chute was returned to loading operation.
The Big Easy
In New Orleans, Cleveland completed the installation and commissioning of three identical chutes for ADM Ama Louisiana.
The three chutes are of the 1700 size system at 39.62m extended and 11.62m retracted. The chutes are designed for loading from a fixed head chute and are operated via a remotely mounted drum type hoist system.
They are fitted with a comprehensive suite of electrical components, necessary for safe operation and control, providing signalling for any potential blockages. All of the functions provide feedback to the control system for the shiploader, with safety limits being interlocked with the conveyor system feeding the chute.
The systems are in place to handle wheat, soya beans, milo, corn, cornmeal and dried distillers grains (DDGs) at a maximum capacity of 3,000 m3 an hour. The head chute deflectors are lined with 6mm ceramic tiles and cones lined with 4mm ceramic tiles for abrasion resistance.
Each of the chutes is supplied with a 360-degree trimming spout with a 3.96m outreach from the chute centre line, with manual adjustment for spout inclination used to adjust material trajectory for differing materials.
Further afield, the company helped Christmas Island Phosphates, based on Christmas Island in the Pacific Ocean, to upgrade its twinarmed shiploader. Cleveland installed a chute on the North Arm and extended the South Arm chute.
The South Arm was extended from the original installation to meet with the needs of the vessels being loaded. Having installed and commissioned the North Arm chute, both are now operating loading phosphates at 800-1,000 tph.
The pair of 1100 size chutes are designed for dual use for simultaneous loading, and are 26m in length with a capability to retract to 7.07m. The cones are lined with 6mm UHMWPE for abrasion protection. Both chutes are mounted from a fixed head chute fitted to a shuttling boom.
Each system is fitted with a speed reducer for further slowing of material prior to exit of the chute, thus reducing dust and material degradation, and a resitain valve that prevents the evacuation of material while the chute is being repositioned and loading is not underway.
Following installation, evaluation and cold running trials, both chutes were hot commissioned during a vessel loading.
On the hop
Hoppers are commonly used to transfer powdery, granular or other free-flowing materials. However, controlling dust has always been a challenge with hoppers. Until quite recently, many processing, storage and handling plants had little choice other than to try and cope with a dust-polluted atmosphere. But a new, patented dust-suppression hopper launched last year by British company TH White Projects is claimed to virtually eliminate dust during transfer processes.
The dust suppression hopper is a loading spout, designed to be mounted immediately beneath an existing feed point. The company says it is ideal for use where free-flowing products need to be packed, bagged, or loaded into ships, railway wagons, trucks, silos or storage bins.
The dust suppression hopper funnels material through a restricted orifice and cone, causing it to adopt a swirl. As the material exits the nozzle, a combination of surface tension, compression and the induced vortex holds it together in a tight, highly controlled stream that contains any dust within the column.
The standard version has no internal moving parts and requires no power – it is simply configured before use according to the type of material being dealt with. Where several different types of material may need to be out-loaded from the same conveying system, TH White says there is an advanced model featuring a computerised positional feed control.
Both models are available in a range of 10 sizes and can be made from standard polyethylene, or tougher materials including steel (mild steel, electro-galvanised, Corten or Hardox) where aggressive or abrasive materials are being handled. Stainless steel of 304-grade can also be specified for the handling of warm or abrasive materials, and 316-grade stainless steel specified for food-grade handling and corrosive materials.
Although the design was inspired by the need for safer handling of fertilisers, the firm says that the dust suppression hopper has proved to be equally effective when handling most other freeflowing granular materials. Goods that are already being widely handled with success include cereals, sugar, salt, pet foods, sand, gravel, lime, minerals, pellets and chemical powders.
In terms of applications, the company says the grain processing industry can benefit at storage and handling installations including cooperatives, milling plants, maltings, breweries and distillers.
But it can also be applied in mines, quarries and glassworks, as well as ports, where it can control fugitive dust during shiploading.
Since the launch, TH White has been in contact with decisionmakers in key industries, including agricultural and cereal milling and processing sectors, port operators, chemical plants, mining and quarries.
One company in the feed milling industry undertook a trial using a demonstration unit, and recorded a significant reduction in dust emissions, after which it proceeded with an order.
Andrew Workman, head of business development at TH White Projects, said: “We have been most impressed by the initial response from the market to this innovation. Like our clients, we are confident that as the installed units become operational, they will deliver significant environmental improvements, leading to healthier and safer conditions.”
Cutting all emissions
Atomised water is another common method of dust suppression, particularly for use on stockpiles. However, one of the ironies of using this method is that portable systems require the use of diesel generators, which themselves can be polluting.
But one manufacturer, BossTek, has revamped its line-up of selfpowered dust suppression units. BossTek now uses Tier IV Finalcompliant generators, ensuring compliance in all 50 US states. The company made the announcement with the debut of the new DustBoss DB-60 Fusion, a suppression system driven by a high reliability 25 hp electric motor and paired with a genset powered by a heavy-duty four-cycle indirect injection diesel engine. Designed, engineered and assembled in the US, the generator features a dual-containment fuel cell, heavy gauge lockable enclosure and oversized rushless alternator for easy starting.
Tier IV is the latest emission milestone established by the US Environmental Protection Agency and the California Air Resources Board. The regulations apply to new engines in off-road equipment, including construction, mining and agricultural plant, as well as marine vessels, locomotives and stationary engines used in industrial and power generation applications.
Tier IV-compliant engines are designed to reduce significantly emissions of particulate matter (PM) and oxides of nitrogen (NOx) to near zero levels. Relative to previous emissions standards, Tier IV-compliant engines reduce emissions by over 95% for most agricultural and construction equipment, and just over 86% for much larger applications, such as locomotives and marine vessels. The emission standards are roughly similar to emission reduction requirements for engines that power heavy-duty trucks.
Permanently mounted on a roadworthy trailer, BossTek says the Fusion line-up is proving to be a popular and effective means of delivering versatile, mobile dust suppression to sites that lack a readily available power source. The company expects to unveil two other Fusion models in the coming months, giving customers the ability to select the size and coverage range.
The new generator series is designed with sound attenuation for better noise reduction and a multivoltage switch with utility power outlet in all voltage modes. The digital engine/generator controller is equipped with single button stop/start and an 80-gallon fuel capacity, giving the units a run time of more than 24 hours at a prime rating of 45 kVA. Like the previous Fusion systems, BossTek guarantees the DB-60 Fusion for three years/3,000 hours, with a five-year/5,000 hour coverage on the electric motor, and a twoyear/2,000 hour warranty on the generator.
The DB-60 Fusion drives pressurised water through a circular stainless steel manifold with 30 atomising spray nozzles, and then launches millions of tiny droplets with a powerful fan that produces 30,000 ft3 a minute of air flow. Atomised mist droplets of 50-200 microns are thrown out in a 200ft (60m) cone at an adjustable elevation angle of 0-50 degrees, capturing airborne dust particles and dragging them to the ground.
Less water use
Unlike industrial sprinklers used for the same purpose, which can require hundreds of gallons of water per minute, the DB-60 only uses about 23 gallons/minute to help avoid pooling or run-off. A touchscreen panel for controlling the dust suppression unit is encased in a NEMA 3R cabinet, allowing operators to control oscillation, booster pump, fan and water. The cabinet is constructed for outdoor use, designed to provide protection against solid foreign objects (such as dirt), air (dust, emissions), water (rain, sleet, snow) and ice formation. The system is able to deliver up to 62,800 ft3 of coverage.
“Maintaining air quality is essential for communities near a demolition project, mining operation or other bulk material handling activities, but even in places with little infrastructure, dust can choke worksites and foul equipment,” said project engineer Jason Lesch. “We engineered the Fusion to be highly mobile, with its own power source, so it can be easily towed anywhere on a job site.”
Equipped with an in-line 75 mesh, 200 micron filter, the unit can be specified with special filtration to accommodate nonpotable water sources. In addition, the new design can be optimised with a variable frequency drive to adjust the fan speed precisely. An optional dosing pump is available for precise metering of additives to enhance particle control even further.