Dust Extraction & Collection: Live Safely in Dusty Environments

Dust is a term used to describe all airborne particles – these can be wood, stone, flour, concrete, grain, mold or asbestos particles as well as fumes and chemicals. Many activities create dust. Larger dust particles get lodged in the nose and throat while the smaller more dangerous particles get lodged deep in the lungs – these dust particles are the ones that can cause fatal diseases. It is a legal requirement to assess and monitor the dust risk in a work environment where the creation of dust is “part of the job”. After the risk is assessed, dust extraction and suppression equipment can then be installed and utilized. In order to lower your risk in terms of dust exposure attempt to implement the following ideas – try to avoid creating dust by investigating different ways of doing a dust-creating job; try to prevent your exposure to dust or use dust extracting methods and equipment; however, if it’s not possible to avoid dust completely, try to minimize your exposure as much as possible. Remember, dust is dangerous – work safely.

A dust collector is a system used to enhance the quality of air released from industrial and commercial processes by collecting dust and other impurities from air or gas. Designed to handle high-volume dust loads, a dust collector system consists of a blower, dust filter, a filter-cleaning system, and a dust receptacle or dust removal system. It is distinguished from air cleaners, which use disposable filters to remove dust.

Five principal types of industrial dust collectors are:

·         Inertial separators

·         Fabric filters

·         Wet scrubbers

·         Electrostatic precipitators

·         Unit collectors

Dust collectors vary widely in design, operation, effectiveness, space requirements, construction, and capital, operating, and maintenance costs. Each type has advantages and disadvantages. However, the selection of a dust collector should be based on the following general factors:

·         Dust concentration and particle size - For minerals processing operations, the dust concentration can range from 0.1 to 5.0 grains (0.32 g) of dust per cubic feet of air (0.23 to 11.44 grams per standard cubic meter), and the particle size can vary from 0.5 to 100 µm.

·         Degree of dust collection required - The degree of dust collection required depends on its potential as a health hazard or public nuisance, the plant location, the allowable emission rate, the nature of the dust, its salvage value, and so forth. The selection of a collector should be based on the efficiency required and should consider the need for high-efficiency, high-cost equipment, such as electrostatic precipitators; high-efficiency, moderate-cost equipment, such as baghouses or wet scrubbers; or lower cost, primary units, such as dry centrifugal collectors.

·         Characteristics of airstream - The characteristics of the airstream can have a significant impact on collector selection. For example, cotton fabric filters cannot be used where air temperatures exceed 180°F (82°C). Also, condensation of steam or water vapor can blind bags. Various chemicals can attach fabric or metal and cause corrosion in wet scrubbers.

·         Characteristics of dust - Moderate to heavy concentrations of many dusts (such as dust from silica sand or metal ores) can be abrasive to dry centrifugal collectors. Hygroscopic material can blind bag collectors. Sticky material can adhere to collector elements and plug passages. Some particle sizes and shapes may rule out certain types of fabric collectors. The combustible nature of many fine materials rules out the use of electrostatic precipitators.

·         Methods of disposal - Methods of dust removal and disposal vary with the material, plant process, volume, and type of collector used. Collectors can unload continuously or in batches. Dry materials can create secondary dust problems during unloading and disposal that do not occur with wet collectors. Disposal of wet slurry or sludge can be an additional material-handling problem; sewer or water pollution problems can result if wastewater is not treated properly.

Dust collectors are used in many processes to either recover valuable granular solid or powder from process streams, or to remove granular solid pollutants from exhaust gases prior to venting to the atmosphere. Dust collection is an online process for collecting any process-generated dust from the source point on a continuous basis. Dust collectors may be of single unit construction, or a collection of devices used to separate particulate matter from the process air. They are often used as an air pollution control device to maintain or improve air quality.

Dust collectors remove particulate matter in the form of fine liquid droplets from the air. They are often used for the collection of metal working fluids, and coolant or oil mists. Mist collectors are often used to improve or maintain the quality of air in the workplace environment.

Dust Control: Solutions to Dust & Fume Extraction

It can be relaxing to watch dust particles slide down a sunbeam streaming through the window on a summer day, but for people with asthma or allergies, it might not be very healthy. Dust has been the subject of many studies and recently was found to be a cause of irritation to upper-respiratory airways and the reason behind increased emergency room visits and hospital admissions. But for the most part, this visible form of dust is considered larger particulate matter and not associated with severe health risks. The dust we all take for granted as part of life, especially those living in a desert environment, has a particle size greater than 10 microns and is more a nuisance than a threat.

We commented on the use of mist systems or fog systems for effective dust and odor control. The idea is that when you atomize water to extremely small droplet sizes and distribute them into an area with airborne dust particles, the water will bind with the dust particles and force them to the ground. In many applications, this method of dust suppression is the most efficient option available. The same principle applies for odor suppression.

When properly designed and operated, water in the form of mist or fog is extremely effective at ‘filtering’ the air. One study even showed where a mist system could substantially reduce the amount of CO₂ in the air. So the concept is not limited to dust particles. It can also remove airborne odors and gases.

Traditionally, this method of dust control worked best in an indoor environment where conditions allowed for the installation of a typical overhead mist system. It was not always practical to install such a system in a facility where the dust control requirement was outdoors in an open area.

For these types of applications (which include waste treatment facilities, rock crushing, mining, waste transfer, recycling, construction sites, and structure demolition) a more specialized solution was required. The solution is Spray stream.

The products are engineered for industrial use in the most extreme environments. They include a variety of sizes and options including wall mount units, portable cart units, and completely self-contained trailer units. When developing dust-control solutions for unpaved roads, things to consider include how long the road will be operational and the volume and type of traffic it is expected to bear. There are basically three groups of control options, including restricting vehicle traffic, improving the road surface, and applying surface treatments, such as dust suppressants. Restrictions might include setting speed limits or limiting the weight or number of vehicles that may pass on the road. These measures have shown to provide moderate emission reductions when they are strictly enforced. Paving is a surface improvement that works well but is so costly that it often becomes unaffordable, and in some cases, such as the Boise 8th Street example, it's undesirable for other reasons. Paved roads also generally create more storm water runoff. Chemical dust suppressants offer the least expensive and most efficient option. Reapplication rates vary and are a major item to address in the development of a dust-control solution.

Many office workers have long been aware of “sick building syndrome”, and have suffered from it too. The syndrome occurs when problems with the heating, ventilation, air conditioning systems and in many cases poor lighting and the materials used to construct the building itself combine to sour the atmosphere and produce ailments including eyes, nose, throat and skin irritation, sneezes and sniffles, coughing, tiredness and nausea.

Office blocks are well known as the major culprit when it comes to sick building syndrome, but apartment complexes have also been known to cause it as well. In both cases, the solution is good quality exhaust ventilation systems with effective dust extraction and fume extraction capability.

At the design stage, sick building syndrome can be avoided by making natural ventilation from the air and wind as great a part of the architectural process as possible. However, nature can only go so far, especially in urban areas, so it is incumbent upon the architects to incorporate fume extraction into their designs from the get-go through the addition of proper local exhaust ventilation.

A constant circulation of air throughout the building in question will keep the atmosphere fresh and the occupants happy.

Dust Control Solutions |  Dust and Fume Extraction