Dry Dust Collection vs. Wet Dust Extraction:
Which Bulk Material Dust Control Do You Need?
Dry dust collection vs. wet dust extraction is a choice you have to make when fugitive dry dust in industrial operations can pose a serious threat to worker health and factory operations, including explosive potential if left unchecked. Bulk material handling will always generate dust, making it an ever-present concern. Whether from bag handling, conveying, drying, storing, or transporting by truck, bulk material dust can originate anywhere throughout an operation. If left unresolved, its impact on production, compliance, and maintenance will affect time, labor, and financial resources.
Dust also can pose grave hazards to personal safety. For example, in May 2021, Dust Safety Science noted 1,000 combustible dust-related incidents in its fifth annual review and analysis of these events. In that same month, a Georgia biofuel firm, an Iowa grain elevator, and an Idaho grain storage site were rocked by dust-related explosions.
In 2018, according to a Purdue University report, explosions at U.S. grain handling, feed manufacturing, and biofuel facilities were reported as increasing, although with fewer injuries and fatalities than in 2017. The report’s lead author pointed out that grain dust acted as the explosions’ fuel at the grain handling facilities, requiring only a spark to ignite.
Years earlier, in 2008, a massive explosion and fire at the Imperial Sugar Factory in Georgia killed 14 people and injured dozens more, including victims with severe and life-threatening burns. The blast had been caused by the igniting of massive accumulations of sugar dust throughout the packaging building.
The disaster prompted OSHA to reissue its Combustible Dust National Emphasis Program, imposing stricter worker safety regulations for plants that handle combustible dust. Unfortunately, the sugar factory – built in 1916 – also came to represent what had been a growing problem: older facilities using outdated equipment without safety measures for combustible dust.
Even after the sugar-factory explosion and OSHA response, the U.S. Chemical Safety Board continued documenting more plant explosions and resulting deaths and injuries. Statistics about dust-related explosions also are believed to be under-reported, as some may be quietly resolved if no deaths or injuries are involved.
The problems with dust further extend to what it can do to the body when inhaled and to workers’ vision when too much is airborne. Effective bulk material dust control is required for a safe, productive, and profitable operation. The question becomes which dust control method is best suited for a particular facility.
Dry Dust Collection vs. Wet Dust Extraction
Dust collection is the primary way an operation controls airborne and combustible dust. When introducing a fugitive dust control system or retrofitting one for compliance, a facility will need to determine whether wet extraction or dry collection is the proper dust control technique.
For example, facilities that process metals might produce combustible dust such as titanium or niobium. In these cases, wet dust extraction would be the method for preventing explosions. However, wet dust extraction will not control all dust types, nor will it always be the most efficient dust control technique.
No two bulk materials are the same, and each conveying system will have its traits. Therefore, determining optimal dust control requires assessing a bulk material handling system’s construction, volume, and characteristics; the operating environment; and the EPA, OSHA, or NFPA compliance required.
An initial step in planning total dust management might be a Dust Hazards Analysis (DHA) in which an expert examines the facility. The inspection will look for a plant’s potential risks, such as possible sparks from static electricity that could ignite airborne dust (e.g., from an ungrounded shop vacuum). Because many explosions originate within the equipment, a DHA will typically include thorough equipment inspections.
A material’s physical properties should be examined and tested as well. For example, all materials have a minimum and maximum moisture content concerning dust suppression. Proper testing will reveal the water-content percentage needed for dust control of bulk material.
Dry dust collection typically involves drawing and removing dust and particulates from the air using a filter that captures and separates the matter. It then discharges purified air back into the work or production area.
Many dry dust collectors will include a blower, a dust filter, a filter cleaning system, a dust receptacle, and a dust removal system. Five common dry dust collection equipment types are fabric filter baghouses, inertial separators (e.g., mechanical cyclones), cartridge collectors, wet scrubbers, and electrostatic precipitators.
A dry dust collection system’s effectiveness will rely on the filter and filter media, air pressure, particle type, and size of bulk material. Because of their great efficiency, baghouse dust collectors are the most common dry dust collection system.
Dry dust collection does not require water as a means of removal, and its applications are broad. It can be especially productive with medium-to-large particulate matter and dusts with low-to-medium combustion potential.
Most dust control systems use dry dust collection at bulk material handling operations unless a DHA determines the bulk material emits light, fine, sticky, or highly combustible dust.
Dry dust collection will not remove toxic components of any dusty gases the process might generate. It also can create secondary flying dust if the equipment is mishandled.
In other cases, a dry dust collector may gather excess product while operating at a high volume. Conversely, volumes below industry standards can cause dust to fall out in ducts and clog them. Filters can plug or tear during dry dust collection as well.
Controlling the airflow’s temperature is often vital with dry dust collection. If the temperature is too high, it can result in problems such as bag sticking and pipe blocking. If it is too low, generated dust can harden and create blockages. Any dust that is moist also can survive, leading to possible equipment corrosion and attrition.
Wet dust extraction uses water as the primary dust control medium. A wet dust extractor’s main components include a motor, a fan impeller, bifurcated housing, a knit mesh–screen extraction panel, and a louvered demister panel.
The fan draws air into the extractor’s inlet end, where dust is captured with hoods and transported through ductwork to the extractor. Water is then injected at the inlet of the fan impeller and spun with incoming air and dust to impact powerfully against the fan housing.
Water, dust, and air pass through the bifurcated housing to the extraction panel, removing water and trapped dust to a discharge sump at the bottom. The louvered demister panel captures over-spray from the extraction panel. The filtered air then exits the extractor’s exhaust end.
Wet dust extraction is particularly efficient for light, fine, sticky, and highly combustible dust.
Benetech: Total Dust Management
As pioneers of safer, more productive bulk material handling, Benetech specializes in dust control technologies and services that adapt to your specific challenge.
Benetech can provide your facility with a dust collection assessment that determines the dust control method to give you command of your challenges.
Our field engineers can:
- survey your existing systems
- identify problem areas and sources of dust
- develop solutions specific to items requiring remediation
- implement the solution right at the site
- install a new system if needed
Benetech: Your Ally in Bulk Material Handling
We welcome each opportunity to answer your questions about making your operation safe, compliant, and profitable. If you would like to discuss bulk material dust control further, including dry dust collection and wet dust extraction, contact us at (630) 844-1300 to speak with a specialist.