An Optimized Approach to Dust Control in Grain Elevators and Terminals

Over 18 billion bushels of grain are produced and moved through grain handling systems in the US each year. The ability of the United States to feed its populace and livestock, support the biofuels movement, and export excess grain to emerging markets is a point of national pride and strength. The infrastructure for moving grain from one point to another includes small country elevators, larger elevators, large grain terminals, trucks, trains, barges, and ocean going shipping vessels. And every time grain is moved from one of these points to another, dust is generated. Dust which must be controlled, captured, and contained. A proper Dust Collector System Design is imperative to ensure safety, longevity, ease of maintenance and to lower cost of operations.

New Dust Control Solutions

As industry trends push grain handlers to look at dust control as an integral part of their operations, the dust collection industry continues to provide solutions for those demands. In some instances, companies have applied solutions that follow age-old practices and approaches, while others have developed newer and more effective solutions to meet the new demands.

One innovative approach to dust management is to collect and manage dust at the point of generation – at the source. Capturing and controlling dust at its source provides several benefits including:

Reduction or Elimination of waste streams. When captured dust is retained within the pro-cess generating it, it stays as part of the revenue producing product stream. Instead of turning a portion of the product into a pile of wasted dust, it remains as part of the product stream that has economic value.

Reduction or Elimination of waste stream equipment. When dusts produced in a process are separated from the original process stream, they require independent material handling equipment and process equipment. Keeping the dust within the product stream minimizes the cost and maintenance of additional material handling equipment.

Minimizing the amount of duct runs. It takes a tremendous amount of energy to move dust-laden air through long duct runs. Installing point-of-use dust collectors closer to the dust-generating process minimizes or eliminates unnecessary ducts, which saves energy.

Reduced duct maintenance. Minimizing duct runs reduces maintenance costs, eliminates wasted air from leaks in the duct system and eliminates costly lining of ducts.

Easier installation. Less ducting also equates to a simpler and easier installation for dust collection equipment. Smaller, lighter collectors mean less support infrastructure in grain handling facilities where collectors are often not placed on the ground.

Improved uptime and reliability for the system as a whole. With centralized dust collection, when a dust collection system requires servicing the entire dust handling system, and often the entire grain handling facility must be shut down to resolve the problem. With a series of point-of-use collectors, when an individual leg of the process is taken offline for maintenance, the rest of the system continues to operate. This provides a level of redundancy to the system, leading to improved uptimes for the facility. Other potential benefits of point-of-use collectors include:

• Minimizing impact on uptime due to servicing – minimize downtime to allow more flexibility in servicing scheduling (20 minute cycle vs. 4-8 hours); design characteristics that simplify and speed servicing actions.
• Localized systems minimize the impact on total operations when a single component has issues.
• Localized systems improve energy utilization, allowing operations to use energy only when needed to manage dust in each area. This approach eliminates wasted energy used to pull air from areas not handling dust.
• Technologies that extend filter life to reduce service frequency

Supporting a point-of-use innovative dust control solution requires a dust filtration product with a very small footprint, but with robust performance to handle moderate to large air volumes. Traditional bag houses and cartridge collectors are generally either too large for point-of-use installation, or when sized to fit, are unable to handle the necessary air volumes.

Newer products on the market, such as the Donaldson®Torit® PowerCore® CP-Series dust collector, work very well as a point-of-use source collector. As a small, light, easy to maintain collector capable of handling the required air volume, this product offers distinct advantages over the more typical bag house technologies, which have been in use for over 40 years.

Products like this offer the ability to collect materials at the source, and allow dust control with a more manageable investment in energy costs. Point-of-use collectors reduce air volume for dust control; reduce horsepower investment, and minimize operational energy costs. With its smaller size and low profile, the Torit PowerCore CP collector can be installed at multiple locations in new facilities as source collectors, and can squeeze into tight spaces in existing facilities (due to its smaller size) to solve nuisance dust problems.

Dust Control Solutions Comparison Example

To help understand the influence a point-of-use dust control strategy can have on facility’s operational costs, consider a typical grain elevator handling 40,000 bushels per hour of grain, transferring from rail to barges.

FIGURE 1 shows this typical elevator site with a conventional centralized dust control strategy. This facility would utilize 15 centralized bag house dust collectors, moving approximately 99,000 cfm of air anytime the facility is in operation, and the entire operation would need to shut down for periodic dust collector maintenance.

These centralized systems would involve the installation of significant amounts of ducts adding to the installation and maintenance challenge for the facility. The energy costs for air movement alone in this centralized system could exceed $70,000 a year and additionally, the collected dust from the various bag house collectors would require expensive, maintenance-intensive material handling systems.

This centralized approach also creates a lower value waste stream for the collected dust.

FIGURE 3 shows the same typical 40,000 bushel per hour elevator facility with a more contemporary approach leveraging point-of-use source capture in the dust control strategy. The facility would utilize 43 Torit PowerCore CP-Series point-of-use dust collectors and one bag house collector moving the same amount of air when all areas of the facility are running, but individual zones in the facility would be offline when certain processes are not running or when maintenance is required.

Energy costs for this point-of-use strategy would approach $55,000 per year for an energy cost saving of almost 22% compared to a more traditional centralized strategy, just in air movement costs.

In addition, the point-of-use approach does not generate the lower value waste stream. Collected dust is returned to the primary product stream and maintenance of extensive amounts of duct is reduced or eliminated in some areas.

In FIGURE 4 the point-of-use dust control strategy was implemented at a major grain export terminal on the Gulf Coast.

FIGURE 5 shows a close up of a point-of-use collector on a silo. Note that knowledge of best practices is essential to applying a point-of-use strategy, including understanding how to properly select and apply point-of-use equipment. As an example, point-of-use collection directly on the legs of a bucket elevator is not recommended, however a properly selected and designed point-of-use collector can allow captured dusts to be returned to the boot of the elevator offering the benefits of point-of-use source collection in a manner compliant with most standards. (See FIGURE 6)