Equipment innovations and monitoring solutions help chemical processors create more effective dust collection systems
Uncontrolled dust can lead to several complications, including health and safety concerns, product quality problems, regulatory compliance issues and legal ramifications. Although dust should not be ignored, many chemical processors struggle with dust control. Here, dust collection experts share their insight on how to remain compliant when developing dust collection systems, as well as the latest innovations and monitoring solutions designed to help chemical processors create dust collection systems that are more efficient and effective so they can maintain safe, cost-efficient, dust-free facilities.
Managing dust challenges
“Safety is the most important reason for proper dust collection,” says Tara Brown, equipment project engineer with U.S. Air Filtration, Inc. (Tyler, Tex.; usairfiltration.com). “Processes that generate dust can create potential safety issues that should be taken seriously. Dust from chemical processing can cause serious health conditions, including respiratory, skin and eye issues.”
Further, adds Chris Watson, general manager with U.S. Air Filtration, toxic dusts are a big concern in the chemical process industries, because they can have significant health and environmental concerns, so efficient capture and filtration are a high priority.
Jacques Kregting, technical sales and applications engineer with RoboVent (Sterling Heights, Mich.; robovent.com), explains that U.S. Occupational Safety & Health Administration (OSHA; Washington, D.C.; www.osha.gov) sets Permissible Exposure Limits (PELs) for many chemical products that are enforceable by law. “Employers must ensure that workers are not exposed to inhalable dust at levels above the PEL, although many employers aim for lower limits, such as those recommended by other scientific bodies, such as the U.S. Centers for Disease Control and Prevention (CDC)’s National Institute for Occupational Safety & Health (NIOSH) or the American Conference of Governmental Industrial Hygienists (ACGIH; Cincinnati, Ohio; www.acgih.org),” says Kregting. “Even if dust is not considered toxic, OSHA sets limits on so-called ‘nuisance dusts’ to protect workers. The PEL for ‘Particulates Not Otherwise Regulated’ (PNOR) is 15 mg per cubic meter (mg/m 3) for total particulate matter and 5 mg/m3 of air for the respirable fraction.”
Catastrophic failures due to fires and explosions are another important safety concern, because many of the chemicals being processed may be combustible. “Combustible dust faces unique challenges, including potential combustibility, concentration and identifying possible ignition sources,” says U.S. Air Filtration’s Watson. “Understanding a dust’s explosive potential, or Kst value, is critical to getting the appropriate equipment to mitigate an explosion. Identifying ignition sources is another factor that should be carefully considered as additions like spark traps, isolation dampers and abort gates may be needed to prevent or mitigate an explosion.”
Because combustible dusts have the potential for catastrophe, processors dealing with combustible dust are required to complete a dust hazard analysis (DHA) and put mitigations in place that comply with guidelines laid out by the National Fire Protection Association (NFPA; Quincy, Mass.; www.nfpa.org) Standard 562 (Standard on the Fundamentals of Combustible Dust), says RoboVent’s Kregting. “These mitigations include reducing the concentration of dust in the air and preventing the formation of dust clouds in enclosed spaces,” he says.
To determine exactly what your facility requires in the way of combustible-dust control, Tony Galvin, pharmaceutical segment manager with Camfil Air Pollution Control (Jonesboro, Ark.; camfilapc.com), says process owners, as part of their overall risk assessment and strategy, need to be mindful that they perform a “complete” DHA.
“DHAs are often misunderstood as a simple requirement of having process dust tested, which is only one component,” he says. “When authorities having jurisdiction (AHJs) ask for a DHA, they are looking for a complete report that includes dust testing results with the full details on which equipment may pose dust and/or fire risks, the locations within the facility that are also at risk, including electrical area ratings (Class I Division II) and detailed priority-oriented steps and timelines for remediating these issues,” explains Galvin. “DHAs, as described in NFPA 652, are repeated at least every five years and must include administrative practices with ongoing documentation and training.”
Other important concerns regarding dust control include maintaining product quality, avoiding contamination, equipment longevity, satisfying regulatory requirements and the environmental impact of chemicals and waste, points out U.S. Air Filtration’s Brown.
In addition to the dust-related safety hazards, explosion risk and product contamination issues cited by Brown, dust can also create housekeeping issues. “Chemicals and specialty chemicals can generate dust byproducts during production cycles,” says Galvin. “Chemical dust tends to be very fine and, if not properly controlled, can float high up in the facility and settle onto rafters, overhead HVAC [heating, ventilation and air conditioning] ductwork and light fixtures. In addition to creating safety hazards and cross contamination issues, this dust can pose challenges with housekeeping, requiring more downtime to clean.”
“Mitigating dust throughout the production process will assist with all of these challenges and a dust collection system (Figure 1) is a great way to accomplish that,” says U.S. Air Filtration’s Brown. “Keeping equipment and production areas clean and free of nuisance dust will reduce the risk of cross-contamination, health and safety issues and the potential for combustion.”
FIGURE 1. CleanFlo cartridge dust collectors from U.S. Air Filtration, Inc., are modular, compact industrial air filtration systems designed to capture fine dust particulate. They are ideally suited for applications with small to moderate dust load, fine dust particulate (<0.5-micron dust size), height and space restrictions, and airflow temperatures below 245°F.
Effective, compliant dust control
“Local exhaust ventilation (LEV) is the term for engineering controls that capture dust at the point of generation,” says Camfil’s Galvin. “Capturing dust as close as possible to the point of generation will economize the air volume required for capture and greatly reduce the chance of dust migration. Because rogue noxious dust can be captured where it is created, it can be managed safely and efficiently removed from the process, which is the ultimate goal. Dust collectors (Figure 2) receive and manage this material, which can act as a fuel source in combustible events and should be part of safety strategies so that the overall process and employees are not impacted.”
FIGURE 2. Camfil APC’s premium-quality dust collectors cost effectively collect many types of chemical dust, including toxic dusts, combustible dusts, cross-contaminant dusts and nuisance dusts. They ensure that all employees can work safely in facilities where dust is present
“This is why agencies, such as the U.S. Environmental Protection Agency (EPA), OSHA and NFPA, all recommend or require dust collection systems,” says U.S. Air Filtration’s Brown.
It should be noted that regulations for dust control in the chemical industry, as well as other industries, are always changing, both in the U.S. and internationally, says RoboVent’s Kregting. “One big change coming later this year from NFPA is that they are consolidating several of their basic and industry-specific combustible dust standards into a new standard, NFPA 660, which is expected to go into effect in fall 2024. This consolidates NFPA standards 61, 484, 652, 655 and 664. However, the consolidated standard does not represent a major departure from existing standards.”
In addition, chemical manufacturers must be aware of changing health, safety and environmental emission standards that impact their specific products and materials, notes Kregting. “For example, the EPA’s Toxic Substances Control Act (TSCA) is due for inventory updates in 2025, which may introduce new additions to the chemicals included under these regulations. OSHA is also continually evaluating PELs for chemical substances based on new scientific evidence.
“As regulations change, dust collection systems may need to be updated to ensure continued compliance with PELs and emissions standards,” Kregting says.
Once the dust-related risks and the appropriate standards have been identified, it is then possible to determine what type of dust collection system will best manage and mitigate the problems. “There are a lot of decisions to be made in dust-collection-system design and there are no one-size-fits-all solutions,” explains Alysha Yinger, director of engineering with RoboVent. “The system must be tailored to the type and volume of dust produced, the hazard level and applicable PELs, process hazards and requirements, facility constraints and air quality goals.
“It is usually best to work with a qualified engineering firm that can look at all the variables and design a system that is safe, efficient and effective. Make sure the engineering firm complies with guidelines and standards laid out by organizations such as ACGIH, American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) and NFPA,” Yinger advises.
That said, some key decisions when creating a dust collection system, according to Yinger, include:
Source capture versus ambient collection. For most chemical manufacturers, a source-capture system is recommended to prevent chemical dust from propagating throughout the facility. Source capture is also more efficient, as it reduces the volume of air that must be moved.
Dust collector type. For most chemical processors, a cartridge-style dust collector is an effective and versatile choice. These systems use cylindrical, pleated cartridge filters to capture airborne contaminants and can be configured for a wide range of needs. When compared to baghouse collectors with similar airflow ratings, cartridge collectors tend to be smaller and more energy efficient. However, there are situations where a baghouse collector or specialty equipment, such as a wet collector, may be recommended.
Filters. Filter selection is very important in overall system effectiveness and efficiency. Filters come in a range of efficiency ratings. For fine and potentially hazardous chemical dust, a filter with a high efficiency rating — MERV (minimum efficiency reporting value) of 15 or higher — is usually recommended. For highly hazardous dust types, a HEPA [high-efficiency particulate air] filter may be used. If vapors or gas-phase emissions are present, manufacturers may want to consider an activated carbon after-filter. It is also important to consider other characteristics. For example, is the dust abrasive, sticky, hygroscopic or electrostatic? Specialized filter media and coatings can help manage these situations.
System sizing and airflow. Dust collection systems are sized based on the volume of airflow required for effective dust capture — measured in cubic feet per minute (ft3/min), or CFM — and the area of filter media needed per unit of airflow, or air-to-cloth ratio. Sizing is dictated by dust volume and characteristics and the total volume of air that must be moved.
Innovative technologies
“While the basics of dust collection and industrial air filtration haven’t changed much in decades, there are some new innovations that make systems more efficient, more effective and easier to maintain,” notes Yinger.
Among them are modular designs in modern cartridge dust collectors that make it easy to size and customize a system for a specific application. “For example, RoboVent Senturion (Figure 3), a dust collector for chemical and other industries producing large volumes of dust, is a versatile dust collection system built on a modular platform with components that fit together like building blocks,” says Kregting. The modular design allows the creation of a dust collection system that can be adapted for virtually any dust or fume collection application and configured around the physical constraints of the facility. When combined with RoboVent’s PleatLock filter technology, which allows for 35% more usable filter media in the same cartridge space, Senturion offers the smallest footprint for the ft3/min available, he says.
FIGURE 3. The RoboVent Senturion, a dust collector for chemical and other industries producing large volumes of dust, is a modular system with components that fit together like building blocks
Other advances in filters, include an entirely new class of filters developed by W.L. Gore (Putzbrunn, Germany; www.gore.com), says Ed Harrington, strategic account manager with Gore. “Our Low-Drag technology offers new materials that are inherently less resistant to airflow and more efficient, requiring less energy to drive air through during filtration while providing the industry’s best particulate capture efficiency. Using Low-Drag technology (Figure 4) allows users to increase airflow, reduce system pressure drop, lower electricity costs or further increase service life,” says Harrington. “This flexibility allows users to choose the benefit that is most valuable to their process.”
FIGURE 4. Low-Drag filter technology from W.L. Gore allows end users to increase airflow, reduce system pressure drop, lower electricity costs or further increase service life, giving users the ability to choose the benefit that is most valuable to the process
And because energy efficiency is indeed a growing concern, some collection systems offer variable frequency drives (VFD) as an option. “VFD can be added to control panels to help manage blower motor energy based on operational needs,” says Camfil’s Galvin. “Historically, exhaust blowers, when started, would ramp up to their maximum designed speed and remain at 100% until being shut down, whether this was required or not. A VFD will regulate power to the motor based on need and will cycle up and down based on changes to pressure drop, which is the differential pressure inside the collector. VFDs on continuous-operation dust collectors can positively impact operational costs by paying for themselves within the first 12 months.”
Trend toward monitoring
“Integration of dust collection equipment into other monitoring systems within a facility is becoming more common,” says U.S. Air Filtration’s Brown. “Considering dust collection equipment plays a critical role in a facility’s operation, it makes sense to monitor it closely.
“Sensors such as differential pressure gages, emission monitors and broken bag detectors can all be tied into a facility’s PLC, allowing for real-time monitoring,” Brown continues. “This ensures the system is operating efficiently and allows the operator to identify potential maintenance, safety or emission issues quickly.”
“In addition to the use of a monitoring or controls solution, such as differential pressure transmitters that help track the functionality of the dust-collector-system efficiency and that filtration elements are performing properly, monitoring and controls solutions can also be implemented so the system can be optimized to reduce compressed air usage, prolong the lifetime of the filter bags and valves and even include visualization and maintenance alerts,” adds Samuele Oliva, product marketing manager, dust collector systems for Discrete Automation at Emerson (Charlottesville, Va.; emerson.com).
Oliva continues: “Added technologies in dust collector systems, like particulate sensors, are becoming more popular to showcase the functionality of the dust collector system and provide data about the filtering process, such as how much particulate matter is passing through the system.
“More advanced controls are another trend where, through more honed differential-pressure methods, the pulse valves (Figure 5) can be pulsed only when needed in the pulse-jet style of cleaning,” says Oliva. “Visualization and alerts can assist with maintenance of the system, reducing downtime and even translating the system data into reports that can be sent to government regulators.”
FIGURE 5. Emerson’s ASCO dust collector tanks, dust pulse valves (shown here), dust collector controllers and PACSystems PLCs, HMIs and Movicon HMI/SCADA are essential components of quality, cost effective dust control applications
Because the dust collection needs of each facility differ, dust collection systems are custom designed for a particular use case and understanding the dust characteristics and production nuances can mean the difference between a system that works efficiently and with minimal maintenance and one that does not provide adequate control and is a maintenance nightmare. Whether a facility opts to embrace the latest innovations or continue with a traditional dust collection system, a suitable and compliant dust control solution is an essential part of the safety of employees and the facility, as well as the quality of products.
Joy LePree