Wood dust is not only a nuisance to industrial facilities but can also be deadly. Combustible wood dust can cause explosions in equipment and building compartments under specific conditions. The five elements of a dust explosion are: fuel, oxygen, ignition source, suspension of the fuel in a dust cloud and containment. Removal of one item eliminates the chance of a combustible dust explosion. Eliminating fuel, oxygen or the ignition source prevents combustion from occurring. Removing suspension reduces the rate of combustion and possibly fuel ignition. If containment is not present, a flash fire or deflagration can still occur but pressure will not accumulate. It is the accumulation of pressure in a confined volume that can lead to catastrophic failure or an explosion.
Among the various methods to protect against a dust explosion, deflagration relief venting is the simplest and most common. Deflagration venting consists of a designed weak point in the protected enclosure, typically a door or panel, which quickly opens at a predefined pressure. This allows the internal pressure and active deflagration generated by rapid combustion of dust to exit the vessel before accumulating and exceeding the enclosure failure strength. Deflagration vents are sized and selected by knowledgeable application specialists according to a standard such as NFPA 68 (Standard on Explosion Protection by Deflagration Venting). Deflagration venting is a reliable, passive method of explosion protection for exterior vessels located in unoccupied areas. Extreme care and caution must be considered with respect to the orientation of deflagration vents as the effects of successful explosion protection include rapid discharge of pressure and fireball from the vents up to as much as 60 meters. An open deflagration inside a facility not only poses a risk associated with fire and pressure discharge but also the potential of a secondary explosion on the building itself from residual dust layers.
Flameless venting was invented by REMBE in the 1990s as a safe, passive explosion venting solution for vessels located inside facilities or in areas where conventional venting was not safe. Flameless venting is a two-part explosion venting system: rupture panel and flame arrestor. The rupture panel functions like a conventional deflagration vent panel that opens under the internal pressure rise of a protected vessel. The flame arrestor is a matrix of stainless steel mesh that allows the vented fireball and gases to pass through to the exterior, but not before removing the flame. This is accomplished through heat transfer from the burning fireball to the layered network of steel mesh. The high surface area of the mesh rapidly absorbs the fireball heat energy below the flash point, allowing only gases to exhaust. The mesh also serves as a retention barrier for unburnt dust expelled from the vented vessel which would otherwise continue to fuel a propagating fireball.
Flameless vents effectively control the external hazards resultant from conventional explosion vents, including fireballs and potential vent panel and unburnt material projection. It is important to note that a complete explosion protection strategy must also include isolation to prevent an explosion from propagating to other interconnected equipment and areas.
The mesh of a flameless vent imposes some restriction to venting the deflagration. This must be accounted for in determining the appropriate relief vent area to protect the vessel. Flameless vents must be tested and certified by a credible organization for suitability and reliability under various parameters, including the combustible dust material, vessel size, pressures and effective vent area compensating for the restriction imposed by the mesh. The European standard EN 16009 is the generally accepted test standard for flameless venting devices and meets the certification requirement of NFPA 68 for flame arresting and particulate retention venting devices.&nbsp;
Flameless venting is extremely advantageous in the wood industry, especially in biomass, pellets and panel board processing involving significant handling and manipulation of fine, dry wood material. Typical equipment with explosion hazards often located inside plants include covered conveyers, dryer systems, hammer mills, bins, sifters and even silos, cyclones and baghouses located in occupied areas. Flameless venting offers a safe, reliable explosion protection solution with virtually no maintenance. Flameless vents are easy to install and can be applied to new equipment or retrofit on site.
In the event of an explosion, it is critical to minimize down time; flameless vents are designed with this in mind. In addition to protecting the integrity of the equipment, flameless vents can be reinstalled following a visual inspection, washdown and spare rupture panels from the plant stores. A protected process could be back online within hours following an explosion without expensive, time-consuming technician startup required by some other explosion protection systems. Author: Jeramy Slaunwhite, P.Eng North American Explosion Safety Consultant REMBE Inc. 902-220-6396 jeramy.slaunwhite@rembe.us

REMBE Q-Box flameless explosion protection installed on covered conveyors.

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A functional illustration of the REMBE Q-Box 
flameless vent. 

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SPOTLIGHT: When passive explosion venting is needed inside a pellet facility, or in areas where conventional venting is unsafe, REMBE has a reliable, maintenance-free solution that is easily installed on a variety of hazard-prone equipment.  

Flameless Explosion Protection for Combustible Wood Dust

Dust explosions and fires in the biomass industry, including pellet manufacturing plants, are not unusual occurrences. The elements needed for an explosion, usually multiple things working together&mdash;fuel, oxygen, confinement and dust dispersion&mdash;can originate in multiple equipment areas within the facility: hammermills, conveyors, dryers, coolers or storage vessels. After that, the only missing ingredient needed for a potentially devastating explosion is an ignition source. One process vessel most prone to dust explosions is the air-material separator (AMS), which in a pellet plant can be a dust collector/baghouse or cyclone.
The purpose of the AMS is to separate the fines from the airstream, which makes these vessels among the most susceptible to explosions within the entire process. The driest and finest dust within the process stream is usually found in these vessels&mdash;the smaller and drier the particle, the lower the ignition energy required to initiate an event. Adding to this threat is the smaller the particle size for a given product, the more surface area by volume is available for heat absorption, resulting in a more dynamic explosion with a higher deflagration index. Another significant risk is that many pellet processes use a central dust collector, aspirating off several vessels. An explosion in the dust collector can propagate through the inlet duct to multiple vessels upstream, causing secondary explosions with devastating results.
For any facility, the first line of defense must be prevention. This should include many of the following practices:
&bull; Proper grounding and bonding for static control
&bull; Magnetic separators or other means to identify and remove tramp metal
&bull; Bearing temperature monitoring or linear heat detection
&bull; Electrical equipment rated for the hazard area
&bull; Housekeeping to minimize residual dust buildup
&bull; Spark detection and suppression on conveyors and dust lines
&bull; Hazardous awareness training A dust hazard analysis (DHA) should be conducted to identify areas of risk within the facility and indicate strategies to minimize the potential for an explosion during normal operating and upset conditions. Because abnormal conditions can happen, NFPA 652 (Fundamentals of Combustible Dust) and NFPA 664 (Wood Processing Facilities) require that the AMS be equipped with explosion protection. The most common forms of protection found in pellet plants are explosion venting, flameless venting, suppression and isolation.
Explosion vents are panels that are strategically located on the sides of the baghouse, or on top of the cyclone. These panels rupture from deflagration pressures, creating an opening that will release a fireball as well as burnt and unburnt dust. Venting is designed to reduce the pressure buildup within the protected vessel to below that which would cause vessel rupture. Typically, vents are of two styles: flat (normal for baghouses) or domed (an option for pressure-cycling vessels).&nbsp;
When considering explosion vents, the most important factor must be whether the vented fireball can be directed to a safe outside area where no equipment, buildings or personnel may be present. The fireball from a vented explosion can eject 50 feet or more. Flame ejection calculation formulas are found in NFPA 68 (Deflagration Venting).&nbsp;
Flameless venting combines an explosion relief vent with a metal mesh trap. Like a standard explosion relief vent, the flameless vent's membrane, installed on the process vessel, opens during a deflagration. But unlike a standard relief vent, the flame and most of the heat from the deflagration is absorbed by the mesh trap, with the deflagration overpressure discharged outside the vessel. Note that a safety perimeter must still be established around the flameless vent to protect workers from the discharge.
An explosion suppression system detects the incipient deflagration and, within milliseconds, injects a dry chemical extinguishing agent into the protected vessel to suppress the explosion before damaging pressure buildup can occur. These systems typically use pressure sensors as a means of detection. Static detectors with a set pressure setting have been commonly used in the past, but rate-of-pressure-rise detectors are becoming much more prevalent due to their high immunity against inadvertent operation from normal operating pressure fluctuations.
Regardless of the protection solution used, flame propagation to connected vessels remains a high threat unless explosion isolation is installed. Passive solutions can include a rotary gate valve that meets the requirements of NFPA 69 (Explosion Prevention), or a flap-style isolation valve on the AMS inlet. Flap valves are closed by the pressure wave preceding the flame propagating through the duct, to prevent the fireball from moving further upstream. When considering flap-style isolation valves, care must be taken to ensure that the valve is designed and approved for the specific application.
Two active explosion isolation techniques are also options. Chemical explosion isolation is typically used in conjunction with explosion suppression systems, or on vessels equipped with explosion venting where flap valves cannot be employed, such as on vertical ducts. High-speed gate valves can also be used for isolation, although because of their cost, these valves are less frequently employed in pellet plants than other isolation techniques.
While the AMS is critical to maintain good housekeeping and reducing the risk of a secondary explosion inside the facility, it is one of the most susceptible vessels to an explosion at the plant.&nbsp; Developing sound explosion prevention strategies, combined with suitable explosion protection, will help limit the explosion risk to operators and the facility. Contact: David Grandaw Vice President of Sales IEP Technologies david.grandaw@hoerbiger.com

Explosion isolation extinguisher on a dust collection line at a DRAX pellet plant.


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Sound explosion prevention and protection strategies are critical in the most susceptible areas of a pellet plant. One process vessel especially prone to a dust explosion is the air-material separator, due to the very dry, fine dust it pulls in. 

Explosion Protection for Dust Collection

According to the National Fire Protection Association, more than 37,000 industrial and manufacturing fires break out each year in the United States. Fire and explosion protection for manufacturing facilities is of extreme importance for companies. Common causes of these fires are heat, sparks, embers and hot particles.
One of the most efficient measures to prevent fire or dust explosion is the early identification of ignition sources. With the new Intelligent Detection Technology (IDT), Fagus GreCon offers a high-performance detector to wood pellet producers. The new DLD 1/9 detector identifies ignition sources in every environment, and it is able to differentiate between sudden interfering light and ignition sources such as sparks or embers.
Sparks and embers are often the source of larger fire and explosion events. Statistics clearly show that such fires and explosions in production facilities often destroy much more than the flames actually reach. Companies incur significant financial losses. And not all consequences of a fire can be insured. This is why a fire often indirectly results in insolvency.
Preventive fire and explosion protection is an important measure, not only to protect production, but also the company and the people working within. Innovating for more than 40 years, Fagus GreCon, headquartered in Alfeld, Germany, with offices worldwide including Charlotte, North Carolina, is bringing enhanced safety to U.S. pellet mills with its spark detection and extinguishing systems equipped with IDT.&nbsp;
Deployed in the DLD 1/9 detector, IDT not only identifies hazardous moving ignition sources before a fire breaks out, but is also able to differentiate between dangerous sparks or harmless incidences of extraneous light due to porous/damaged pipes or an opening of an inspection flap. "With this DLD 1/9 detector, we achieve an optimal detection performance for all ignition sources in every environment, and we continue to expand our pioneering role in preventive fire protection," says Mario Haas, manager of Fagus GreCon&rsquo;s fire protection division.
The GreCon spark detection and extinguishing system provides excellent protection, as it does not wait for an actual fire or explosion to erupt. The system prevents the development of a fire or explosion by the early detection and elimination of the ignition source. With a GreCon system it is possible to detect and eliminate ignition sources before a fire or a dust explosion occurs. Infrared detectors monitor the conveying paths and activate high-speed water extinguishing within milliseconds. The diversion or shutoff of product flow is possible if extinguishing with water is not possible for the application.
A four-level progressive alarm system ensures countermeasures are triggered quickly without interruption of the production process, in most cases. Thus, damages and the resulting downtimes are minimized or eliminated without disturbing the production process unnecessarily.
Additionally, dust collectors and silos can be monitored for fires or spontaneous ignition. When an alarm event happens, the system triggers extinguishing countermeasures even before the plant operator or fire brigade notices the fire.
The integration of the GreCon control console into the customer&rsquo;s control system is possible via Ethernet IP, thereby a decentralized plant architecture is possible. The safety equipment event data is easily linked with the process control data. This is an important contribution on the way to Industry 4.0.
Today, safety is of great importance in modern production plants. High-value production equipment must be running continuously, especially under strong international competitive pressures and economically difficult times. A higher level of operational safety is reached with GreCon spark detection and extinguishing systems.

The GreCon DLD 1/9 spark detector with Intelligent Detector Technology (IDT) is designed to identify hazardous moving ignition sources before fires break out.

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SPOTLIGHT: Fagus GreCon delivers smart technology that identifies and squelches potential sources of fires and explosions before it's too late. The system can differentiate between dangerous sparks and harmless incidences of extraneous light.   

Intelligent Spark Detection and Extinguishing   

Numerous standards exist to prevent dust fires and explosions. In the United States, the National Fire Protection Association is charged with creating and maintaining standards for fire prevention, including standards associated with combustible dust. Many of these standards have seen updates or revisions recently, with the biggest changes focused on the requirements for conducting a dust hazard analysis (DHA). In fact, significant proposed changes are currently in the works.
NFPA maintains over 300 codes and standards covering all aspects of electrical, fire and explosion safety. While NFPA has no enforcement power of its own, authorities having jurisdiction (AHJs) often reference NFPA standards in their own regulations. AHJs include the Occupational Safety and Health Administration (OSHA), as well as local fire marshals and building permitting and inspection offices. In the United States, maintaining compliance with NFPA&rsquo;s combustible dust standards generally falls on the individual facility rather than on equipment manufacturers. Facilities must determine if they have combustible dusts, what standards they would fall under, and what requirements they must comply with based on the equipment they operate in their operation. This differs from, for example, the European ATEX standards which require detailed certification processes on the equipment vendors for all equipment utilized for combustible dust.
The NFPA standards for combustible dust that pertains most directly to pellet and biomass industries are as follows:
&bull; NFPA 652: Standard on the Fundamentals of Combustible Dust, 2019 Edition
&bull; NFPA 664: Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities, 2020 Edition
&bull; NFPA 61: Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities, 2020 Edition
&bull; NFPA 654: Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, 2020 Edition
&bull; NFPA 68: Standard on Explosion Protection by Deflagration Venting, 2018 Edition
&bull; NFPA 69: Standard on Explosion Prevention Systems, 2019 Edition NFPA 61, 654, and 664 are called the commodity-specific standards. The purpose of these standards is to give specific industry types combustible dust standards based on their type of operation. A wood pellet facility would utilize NFPA 664, while an agriculturally based pellet mill (e.g. peanut shells) would utilize NFPA 61. NFPA 654 exists for general manufacturing facilities that do not have their own specific commodity standard.
With so many standards that could be used, it is easy to get confused on which to follow, especially as recommendations can vary across the standards. For this reason, NFPA created NFPA 652: Standard on the Fundamentals of Combustible Dust in 2015. The purpose of NFPA 652 was to serve as the overarching standard that applies to all facilities with combustible dusts, and be the starting point for each facility. NFPA 652 was the first standard to issue the requirement for conducting a DHA. In the current 2019 edition of NFPA 652, the deadline for completion of the DHA is September 7, 2020. The current editions of NFPA 61, 654, and 664 have all worked to integrate NFPA 652 into their standard.
The goal from each of the commodity standards was to reduce the reliance on two different standards: NFPA 652 and their standard. However, this still can lead to confusion. The 2020 edition of NFPA 654 restated NFPA 652&rsquo;s DHA completion deadline of September 7, 2020. NFPA 664 does not state the deadline, but instead refers directly to NFPA 652. The 2020 edition of NFPA 61 states that the deadline for food and agricultural facilities is January 1, 2022. NFPA&rsquo;s guidelines state that when there are differences between 652 and the specific commodity standard, the user can choose either standard.
The commodity-specific standards have always contained numerous &ldquo;prescriptive requirements.&rdquo; These are the specific sets of requirements for types of equipment. For example, each of the standards have requirements for dust collectors that include explosion protection and other monitors, alarms, etc. There has also been the option for &ldquo;performance-based design options&rdquo; which, historically, utilized a process hazard analysis (PHA) type approach. The 2020 editions of these standards are no different in that both prescriptive and performance-based options are still incorporated. However, what we see in all these standards are further explanations and guidance leading toward conducting the DHA, and using those results to determine where the prescriptive requirements should be incorporated. For example, if utilizing only the prescriptive requirements (or the checklist DHA examples provided in some of the standards), you would install explosion protection on all your specific equipment with a prescriptive requirement. But, if you were to conduct a detailed DHA that examined the potential for hazardous atmospheres and hazardous ignition sources, you may find that some equipment at your facility does not have the potential for a hazardous atmosphere, or there are no potential ignition sources. If that is the case, you may not need to implement the prescriptive requirements for that piece of equipment. While these performance-based design options have always been acceptable, current versions of the standards have made their viability clearer than before.
In summary, the major NFPA requirement affecting the pellet and biomass industry is the need to conduct a DHA, with a deadline that is fast approaching. Facilities utilizing wood-based products have until September 7, 2020 to have a DHA completed for their existing operations. Those facilities using agriculturally based products will have until January 1, 2022 to complete their DHAs. Furthermore, these DHAs must be revalidated every five years. Lastly, any facility installing new equipment/processes or modifying existing equipment/processes must conduct a DHA of the equipment/process prior to startup.
Looking into the future, there could be some significant changes to these standards. The long-term goal of NFPA 652 is to incorporate all the commodity-specific standards into 652. It is looking like this may occur under the next edition of NFPA 652, meaning there would be no future standalone editions of the individual NFPA 61, 654, and 664 standards. Instead, these would be incorporated as chapters within NFPA 652. This will likely be a significant undertaking by NFPA and the technical committees for these standards, but it would certainly streamline the combustible dust standards and, hopefully, reduce the confusion that exists within the separate standards. For those interested in the status of NFPA standards, or participating, the meetings are open to the public and comments can be submitted through NFPA&rsquo;s site for future edition drafts. Author: Jeff Davis, PE Director of Engineering Conversion Technologies Inc. 770-263-6330 ext 116

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According to National Fire Protection Association standards for combustible dust, facilities utilizing wood-based products, including pellet mills and other biomass processing plants, must have a dust hazard analysis completed by early September. 

Changes to Dust Fire and Explosion Standards

Two years ago, well ahead of the Sept. 7, 2020, deadline set by the National Fire Protection Association, Greene Team Pellet Fuel Co. contracted Bernard Schonbach of BHS Technical Service LLC to perform a dust hazard analysis (DHA) on its 50,000-ton wood pellet mill in Carmichaels, Pennsylvania. &ldquo;They didn&rsquo;t find any glaring issues, but it was good to have it done&mdash;to truly map out every pneumatic line,&rdquo; says Andy Galis, Greene Team Pellet Fuel&rsquo;s vice president of operations.
The plant is feedstock flexible and receives at least five different types of hardwood material for pelleting, including sawmill cutoffs; green sawdust; wood chips; dry sawdust from hardwood flooring mills, cabinet manufacturers and veneer plants; and whole logs. Part of the DHA included material testing, from green feedstock to dry fines and the pellets themselves.
&ldquo;We gained a much better understanding of where our concerns should be,&rdquo; Galis tells Pellet Mill Magazine. &ldquo;We found out that some areas we were concerned about, even in an upset condition, had no chance of exploding. It allowed us to focus on where we could have an issue. That was the biggest takeaway.&rdquo;&nbsp;
Greene Team Pellet Fuel&rsquo;s comprehensive dust control and mitigation strategy includes a Mac PowerHouse baghouse dust collector, model no. 361. &ldquo;We bought it used from a hardwood flooring plant in North Carolina,&rdquo; Galis says. &ldquo;It&rsquo;s massively oversized for what we ask it to do, and that&rsquo;s a good thing as we&rsquo;ve added product lines over the years. We try to contain everything we can through that.&rdquo; The mill also employs suction hoods over dusty areas to minimize fines from becoming airborne.
&ldquo;The other thing we do differently is once our sawdust is dried, we exclusively convey pneumatically&mdash;no drag chain or belt conveyors,&rdquo; Galis says. This, he adds, eliminates the possibility of dust leakage from tail pulleys or auger holes. &ldquo;Those pneumatic lines go to the baghouse for a closed loop [return],&rdquo; Galis says. &ldquo;A positive-pressure blower conveys the pellets, and that vessel has suction from another fan on it. That four-inch positive line goes into the vessel that has a suction line on it, so it&rsquo;s not pressurizing the vessel and causing sawdust to leak out of it.&rdquo;
Before reaching the baghouse, all positive-pressure lines in the plant blow into cyclones to help capture the larger particles, leaving only the finest dust particles for the Mac 361 baghouse. Naturally, the cyclone return lines are all negative pressure.
&ldquo;We also have an explosion-proof industrial vacuum that we use for clean-up of the dust that&rsquo;s not contained,&rdquo; Galis says. &ldquo;It&rsquo;s impossible to catch everything.&rdquo; Even if Greene Team Pellet Fuel were to contain 99.99 percent of the dust created at its mill, this would still lead to 130 pounds per week of highly explosive dust fines becoming airborne in the plant, according to Galis.
Much like boxing, the secondary explosion in a pellet mill can be the knockout shot in the one-two combo, with the initial explosion acting much like a jarring jab, setting the scene for what&rsquo;s to come. Once an initial deflagration occurs, this can shake dust off the rafters and this newly airborne dust can &ldquo;blow the top off the building,&rdquo; Galis says.
&ldquo;We were doing our very best to continually vacuum the rafters, trying to keep the dust down,&rdquo; he says. &ldquo;But this was a futile exercise without a control system in place. We would completely shut down power, blow down and constantly vacuum. It was super labor intensive and didn&rsquo;t do that good of a job.&rdquo;
Galis and his team began researching better options. &ldquo;We were looking at bigger-type fans, like you&rsquo;d see in a gym,&rdquo; he says. &ldquo;Then we stumbled upon SonicAire. When we watched the videos and talked to the salesmen, it seemed like a no-brainer. We installed the SonicAire fans in summer 2018, just a few weeks before our DHA. We knew it would be a major improvement, and we didn&rsquo;t want the DHA to focus on the dust settled on the rafters.&rdquo; SonicAire Founded by Brad Carr, SonicAire has been manufacturing dust control fans for more than 15 years. Jordan Newton, chief operating officer for SonicAire, says the company had originally focused on lint control at textile factories and commercial laundry facilities. &ldquo;Brad knew this was bigger than lint and textiles,&rdquo; Newton says. &ldquo;He knew there were other industries that have problems with dust.&rdquo; Wood processing industries were primed for the taking.
&ldquo;What our fans offer is similar to a vertical air curtain, but it&rsquo;s flipped sideways to create a horizontal air barrier,&rdquo; Newton says. &ldquo;We call it &lsquo;BarrierAire Technology,&rsquo; and we trademarked that. We create an air barrier that prevents dust generated in process from reaching the ceiling, which can then be swept up with operations at the floor level so there&rsquo;s no ceiling or deep cleaning needed.&rdquo;
Greene Team Pellet Fuel has four SonicAire dust control fans throughout its facility, and a fifth atop a pellet storage silo. &ldquo;SonicAire performed a study of our building, took measurements and made recommendations,&rdquo; Galis says. &ldquo;The fans are not necessarily placed over the machines, but more in a fashion to get overall coverage of the ceiling area. Our 150-foot by 75-foot rectangle building has an evenly spaced, diamond-shaped layout of four SonicAire fans.&rdquo;
SonicAire fans add another layer of protection to a wood pellet plant&rsquo;s dust mitigation and control strategy, Newton explains. &ldquo;This really works in any industry,&rdquo; he says. &ldquo;They can be an additive&mdash;you can spot treat with them or do a full system to cover the entire facility. We take care of your overhead spaces to control fugitive dust.&rdquo;
Although Newton has been with SonicAire for the past 10 years, he says he started his career in forensic engineering, focusing a great deal on fire science, and fire and explosion investigations. &ldquo;Almost all combustible dust events&mdash;every single one I&rsquo;ve studied&mdash;are due to fugitive dust that escapes,&rdquo; he says. &ldquo;This problem is almost always due to dust being in overhead spaces. If you can prevent that, then you can help protect your facility from those kinds of events.&rdquo;
The SonicAire dust control fans with BarrierAire Technology are designed to move robotically, oscillating up and down, based on the customer&rsquo;s range needs. &ldquo;They rotate 360 degrees continuously, which creates an overhead barrier,&rdquo; Newton says. &ldquo;It&rsquo;s really high-velocity airflow, reaching out a good distance.&rdquo;
SonicAire has its own line of controls to manage the fans or, if preferred, they can be integrated into the customer&rsquo;s PLC system. &ldquo;In accordance with NFPA, they are interlocked with the plant&rsquo;s fire protection system,&rdquo; Newton says. &ldquo;If there&rsquo;s a fire event, the fans shut down.&rdquo; The integrated control system runs the fans when the plant is operating, and when operations shut down, so do the fans.
More important than the high functionality of SonicAire&rsquo;s fans is the company&rsquo;s team of engineering support, Newton says. &ldquo;We design a truly engineered system for the customer, based on their individual needs,&rdquo; he says. &ldquo;We have multiple fan models, mounting equipment, controls, and a full tech support and service team.&rdquo;
Newton adds that SonicAire launched a new product line of fans this year that are more robust and help reduce noise. &ldquo;They feature new components that add to the longevity and life expectancy of the equipment,&rdquo; he says. &ldquo;They&rsquo;re really built for highly industrialized settings.&rdquo;
According to Newton, SonicAire&rsquo;s dust control fans are integrated into nearly a dozen pellet manufacturing facilities in North America, including some of the largest. &ldquo;It&rsquo;s fulfilling to be part of a company I know is making a difference in people&rsquo;s lives,&rdquo; he says. &ldquo;I hate waste&mdash;repeating laborious jobs with no return on investment or added value. It&rsquo;s great to be part of something that does that but also impacts people&rsquo;s lives.&rdquo; BossTek Beyond its cool name, BossTek is known for its dust suppression cannons. Mike Lewis, BossTek&rsquo;s vice president of sales, says the company started in 2004 servicing demolition sites, offering its powerful DustBoss cannons to control fugitive dust. Since then, the cannons have been used in a variety of exterior settings, including ports to suppress dust from loading wood pellets onto cargo ships.
Featuring its DustBoss Surge center nozzle jet accompanied by mister rings, DustBoss cannons atomize water to knock down visible dust. &ldquo;Our nozzles break down the water droplets to between 50 and 200 microns,&rdquo; Lewis says. &ldquo;The atomized water agglomerates with dust, making it heavy and drop to the ground.&rdquo; Lewis says pellet mill applications for cannons may include loading trucks or railcars, and anywhere there&rsquo;s transfer points on conveyor lines&mdash;perhaps even in the woodyard.
In addition to its cannons, BossTek also manufactures a line of rings&mdash;like those on the rims of its cannons but separate&mdash;and misters. The DB-Rings feature 30 nozzles and may sit at the underbelly of a conveyor or a telescopic shoot, for example, with the product passing through the misting ring as it journeys off the conveyor or down the shoot and into a pile, helping to minimize fugitive dust. For other transfer points, BossTek&rsquo;s misters, the DB-M Mini, are attached to two-foot booms with nine nozzle misting heads and U-bolts for versatile setup. The DB-M Minis mist out about a half-gallon of water per minute, Lewis says.
Although Lewis says he&rsquo;s not aware of any DB-M Minis, DB-Rings or cannons used inside pellet plants&mdash;as &ldquo;the moisture might disturb baghouse filters,&rdquo; he says&mdash;Galis says he would consider such machines if Greene Team Pellet Fuel Co. had product dropping in the open air inside the building. &ldquo;But we don&rsquo;t do that,&rdquo; Galis says. &ldquo;I&rsquo;ve heard of them being used at plants that receive dry sawdust on tipping trailers. When they dump, they have atomized water misted onto the fugitive dust to get rid of it. We don&rsquo;t do that with our dry sawdust though. We bring that in on walking floors, which produces minimal dust.&rdquo;
The pellet industry is no doubt highly competitive, &ldquo;but we&rsquo;re also one industry,&rdquo; Galis says. For this reason, Galis is willing to share his experience with dust control. &ldquo;If we lose producers because their plants blow up, or insurance rates go super high and we&rsquo;re lumped in with others who don&rsquo;t have [these controls], then that&rsquo;s not good for us. I think the SonicAire fans are a massive improvement as far as the safety of our plant goes.&rdquo;&nbsp; Author: Ron Kotrba Senior Editor, Pellet Mill Magazine 218-745-8347 rkotrba@bbiinternational.com

Andy Galis, vice president of operations at the 50,000-ton Greene Team Pellet Fuel Co. in Carmichaels, Pennsylvania, had a Dust Hazard Analysis performed in 2018. Just weeks before, he had several SonicAire dust control fans installed, which he says 

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Installation of SonicAire dust control fans at Greene Team Pellet Fuel greatly reduced dust buildup on the rafters, improving the safety of the facility. 

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Before Greene Team Pellet Fuel installed SonicAire dust control fans, the plantâ€™s overhead rafters were laden with combustible dust, which posed a significant risk for a secondary explosion. 

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BossTekâ€™s DB-M Mini line of misters can help suppress localized dust at transfer points inside a facility. 

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The Greene Team Pellet Fuel mill takes in at least five types of hardwood, including sawmill cutoffs, green sawdust, wood chips, dry sawdust and whole logs. 

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BossTekâ€™s dust suppression cannons shoot atomized water that agglomerate to dust particles, helping to minimize fugitive dust from escaping.

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A Pennsylvania pellet plant reduced its chances of incurring a dangerous explosion by installing oscillating fans that create a horizontal air barrier inside the structure, preventing combustible dust from settling up high in the rafters.  

Driving Down Pellet Plant Dust

In the aftermath of a 2019 grain silo fire and explosion that resulted in the death of a firefighter and serious injury of an employee, many conclusions were made in a subsequent OSHA investigation report. Discernible from those conclusions was that each violation had a common thread: &ldquo;inappropriate or incomplete lines of communication.&rdquo; Unfortunately, inadequate communication extended beyond the worksite, having detrimental effects on the emergency response outcome. Specifically, &ldquo;definitive roles and duties within the incident command system were not clear or appropriate,&rdquo; and essential information firefighting personnel needed in the event of the emergency was not collected. This included the amount and type of grain in the silo and that it had been smoldering for two days, the assessment of explosion risk and height of bridged product, and the existence and configuration of an inspection port along the side of the silo. This lack of information caused changes to the emergency response and limited strategies to fight the fire, resulting in a catastrophic outcome.
Working with a highly combustible material is the nature of wood pellet manufacturing, and while there is no across-the-board instruction manual on how to prepare for and respond to emergencies, as a jumping off point, there are general recommendations and guidelines for both firefighting personnel and facilities with combustible dust. &ldquo;OSHA&rsquo;s publication, Firefighting Precautions at Facilities with Combustible Dust, indicates that a pre-incident survey forms the basis of how emergency responders plan for and handle incidents,&rdquo; an OSHA spokesperson tells Pellet Mill Magazine. &ldquo;Employers and firefighters must understand that the more specific the information that is shared, the more comprehensive and valuable the pre-incident survey will be.&rdquo;
OSHA does not mandate communication between an establishment processing combustible dusts and emergency responders, the spokesperson adds, but strongly encourages communication and coordination to ensure employees and emergency responders remain safe during emergency situations. Doing so could prevent injury or deaths, but also citations and fines. &ldquo;To abate hazards at facilities processing combustible dusts, OSHA may issue citations for violations of OSHA standards and Section 5(a)(1), the General Duty Clause, which requires employers handling combustible dusts to comply with several agency standards, including housekeeping, exit routes, emergency action plans and fire prevention plans, as well as materials handling and storage, and toxic and hazardous substances.&rdquo;
Even abiding by professional guidelines and recommendations, it leaves the responsibility of formulating, practicing and executing a plan up to each individual facility. &ldquo;There are a lot of unique components for every specific plant, but there are some things all of them can be prepared for,&rdquo; says Fahimeh Yazdan Panah, director of research and technical development for the Wood Pellet Association of Canada. &ldquo;Development of fire and emergency response is very important, as a lot of conventional practices to extinguish fires are not really applicable in general for biomass storage.&rdquo;
For high-capacity facilities, a heavy focus should be placed on silos, according to Panah, and that includes outreach to local fire departments to ensure they have the knowledge and equipment needed in the case of an emergency. Preparation and Communication &ldquo;Wood pellet storage tends to self-heat, and is prone to spontaneous combustion,&rdquo; Panah says. &ldquo;It very much depends on the condition of the storage and environment around the storage&mdash;for example, the temperature, and if the pellets are exposed to moisture. These fires don&rsquo;t happen often, but when they do, they are usually a catastrophic event.&rdquo;
&nbsp;Panah underlines many &ldquo;don&rsquo;ts&rdquo; that may not be obvious when it comes to combatting self-heating or fires in silos, including that they should never be opened, water shouldn&rsquo;t be used, and employees or emergency personnel should never work on top of the silo. &ldquo;When self-heating happens, gases are being produced&mdash;carbon dioxide (CO2), carbon monoxide (CO), and methane. The CO is an early sign; you may not even see any smoldering, especially if the self-heating is happening deep in the silo. That&rsquo;s why it&rsquo;s very important to constantly measure the concentration of gases in the headspace of the silo and around it&mdash;if you read a higher concentration, you know something&rsquo;s happening.&rdquo;
In the event the incident has accelerated to visible smoldering with a strong odor&mdash;an indication pyrolysis has begun&mdash;plants should take immediate action, following an emergency response plan that has been practiced with their local fire department. &ldquo;When the fire department comes to the plant, personnel should be able to explain the observations made, the gases measured and whether there is smoke, so they have a good idea of the scenario,&rdquo; Panah says. &ldquo;Other things firefighting personnel should know include the type of silo, whether it&rsquo;s connected to a ventilation system (which should be shut down), access points for nitrogen injection and the rate of flow it should be sent into the silo.
&nbsp;In some cases, firefighters may not be aware that liquid nitrogen, rather than water, is needed. &ldquo;They should know&mdash;in advance of an incident&mdash;that they need to bring this and a vaporization unit with them,&rdquo; Panah advises. &ldquo;Things like this are what they should practice, or at the very least, be aware of.&rdquo; This knowledge could make a significant difference in the amount of damage a facility undergoes during an incident, especially in locations that are long distances from mobile nitrogen systems. &ldquo;For some plants in British Columbia, it&rsquo;s an eight-hour drive to get nitrogen to the plant,&rdquo; she says. &ldquo;And there have been some cases where there has been smoldering, but two days&rsquo; time to get nitrogen. The very first 24 or 48 hours are critical to have access, and the fire department needs to know this. Nitrogen inerting should be done from the bottom of the silo, discharging material to break down the hot area in the silo.&rdquo;
CO2 can also be used, Panah adds, but nitrogen is highly recommended for a variety of reasons. Perhaps most importantly, if the silo temperature is very high and CO and methane are being produced, CO2 may change the direction of some reactions, producing an excess of hydrogen. In that case, if the silo is opened and exposed to enough oxygen, it will explode. &ldquo;This is another thing the fire department and plant need to review together and have a system or plan in place in the case something happens,&rdquo; Panah says.
There are additional things the fire department and plant personnel should know, including that water can&rsquo;t be put in a silo of wood pellets or biomass. &ldquo;It&rsquo;s not a conventional silo, or an open flame&mdash;pellets will absorb the water and expand, and the silo may burst,&rdquo; Panah says. And, nobody should ever work on top of the silo or open it, as there will be a high level of flammable gas in the headspace of the silo, which is not only poisoning and dangerous, but will explode if oxygen is introduced.
Wood pellet silo fires&mdash;which can take days, or even a week to safely extinguish&mdash;don&rsquo;t happen often, so all these things should be communicated with the local fire department, Panah reiterates. She gives the example at an incident at a Prince George, British Columbia, pellet manufacturing facility that had reviewed and practiced its emergency response plan with the local fire department, which resulted in saving the plant and keeping all personnel safe.
Each plant has its own unique scenario, Panah adds. &ldquo;This is why all of this should be done together with the fire department, with everyone working together. It should be practiced before any incident happens, or it&rsquo;s going to be quite challenging.&rdquo;
Industrial wood pellet producer Enviva has eight operating industrial wood pellet plants in the Southeast U.S., and with two more under construction, the company continues to invest heavily in safety, training and professional manufacturing practices, according to Christopher Seifert, Enviva vice president of environmental health and safety. For new employees, safety and emergency training begins on day one.
Industrial Insight &ldquo;Beginning at new hire orientation, all Enviva employees receive training on their location&rsquo;s emergency response plan, as well as our combustible dust and housekeeping standards,&rdquo; Seifert says. &ldquo;To gain access to the facility&rsquo;s operating areas without direct supervision, employees are required to complete the general plant safety certification process, which entails successfully demonstrating procedures for cleaning combustible dust, activating the emergency action plan, identifying evacuation routes, and locating and using fire extinguishers and fire hoses.&rdquo;
Beyond initial certification, Enviva schedules annual refresher training for all employees, and emergency response drills are conducted annually at each facility for each shift. The local fire department participates in at least one drill per facility each year, according to Seifert, and in conjunction with those drills, employees are required to participate in a walk-through of the facility to flag all fire and explosion hazards, identify where hydrants and firefighting equipment are located, as well as update employees on all entry and exit routes.
The drills with fire departments are reviewed and evaluated by a regional or corporate member of Enviva&rsquo;s operations management team, and improvements are made after each drill&mdash;or actual event, Seifert says. &ldquo;After each drill or event, we debrief and evaluate what went well and what didn&rsquo;t with the collective team, and depending on the findings, our employee training, drills and emergency response plans are updated accordingly.&rdquo;
Seifert says that while safety is a vital objective at all the company&rsquo;s plants, developing and establishing processes and protocols to safeguard employees across all operating facilities is easier said than done. He emphasizes that a key component in successfully crafting and executing these plans is instilling strict protocol in its safety culture at every level of the company. &ldquo;This is from the CEO&rsquo;s office to the factory floor,&rdquo; he says. &ldquo;For example, Enviva uses an emergency notification system with predefined templates and distribution groups that all employees can access to initiate a conference call with key leaders within seconds. There are tiered levels of emergency alerts based on the severity of the incident, and the system ensures the right safety, engineering and operations leadership are notified and engaged in a timely manner to assist the on-site team in the event an emergency response is needed.&rdquo;
Perhaps the most important aspect of emergency response training, according to Seifert, is conducting proactive practice drills critical to ensuring employees are confident in identifying emergencies, know the appropriate steps to take, and follow necessary precautions to keep safe. &ldquo;When possible, all practice drills should be carried out as if they were happening in real-time,&rdquo; he adds. &ldquo;During a drill, we try to simulate a real emergency experience and have all employees run through a full scenario as a team.&rdquo;
Even if a wood pellet facility doesn&rsquo;t have a silo or a collective workforce the size of Enviva&rsquo;s, employees should still become very well-versed and proactive about safety around the plant and material from day one when they come in, says Cory Schrock, general manager of Fiber By-Products, a 50,000-ton plant in White Pigeon, Michigan. Residential Perspective Every new employee at Fiber By-Products receives a copy of, and reviews with HR, the facility&rsquo;s emergency evacuation plan, Schrock says. This includes protocol regarding what to do and where to go, as well as a map that outlines all locations of fire extinguishers, gas and fuel dangers, and shut-off valves. &ldquo;We also have group meetings and walk-throughs to go over procedures, and what to do in the case of a fire,&rdquo; he says. &ldquo;During these meetings, we remind and retrain on things including proper personal protective equipment usage and lockout-tagout procedures, and we have incident report forms that show fire extinguisher use along with other safety or equipment damage-related incidents.
These are turned over to supervisors to review or retrain if necessary, and to ensure that if a fire extinguisher was used, it gets replaced right away. We conduct monthly fire extinguisher checks and replace any outdated or damaged extinguishers, and we have a full-time employee that takes all wheel-loaders out of service in sequence on a daily basis for inspection and cleaning of engine compartments, and anywhere that heat and dust collect during normal operations.&rdquo;
On collaboration with the local fire department, Schrock says it&rsquo;s mostly made up of volunteers with close ties with the facility. &ldquo;The chief works and lives just a couple of miles from the facility and was a full-time employee with us in the past, and we currently employ one of his volunteers on our wood pellet production team,&rdquo; he says. &ldquo;Most of their current staff are familiar with our plant, operations and procedures, and have done walk-throughs of our facility and know where our dangers are, as well as electrical and gas shutoffs and fire hydrants.&rdquo;
Fire department personnel also have the code to the plant&rsquo;s front gate and access to a master key of the facility, according to Schrock.&nbsp;
Beyond the facility&rsquo;s employee education and training and collaboration with the fire department, Schrock highlights the facility&rsquo;s robust spark and fire detection and extinguishing system. All aspects of employee safety practices, training and emergency response are very important, Schrock adds, but this system plays a vital role in preventing fires, explosions or catastrophic events. &ldquo;Real protection comes from this very important piece of our facility.&rdquo; Author: Anna Simet Editor, Pellet Mill Magazine asimet@bbiinternational.com 701-738-4961

A core component of Envivaâ€™s incident prevention and response training is conducting proactive practice drills to ensure employees are confident in identifying an emergency, know the appropriate steps to take and follow necessary precautions to kee

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Coupled with realistic practices drills, Enviva employees are required to participate in facility walk-throughs to flag fire and explosion hazards, locate hydrants and firefighting equipment and identify entry and exit routes.


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The lines of communication between pellet facility employees, management and local fire and emergency response personnel begin with robust training and planning. But even the best-laid plans are only as good as a plant's practice regimen. 

Pellet Plant Safety Rooted in Planning, Practice

Enviva posts strong Q1 results, produces through pandemic With new workplace safety procedures in place to mitigate the risk of COVID-19 exposure in its U.S. pellet mills, Enviva Partners LP is continuing operations after announcing excellent first quarter financials in late April.
Enviva reported April 30 that its operational and financial results have not been materially impacted by COVID-19 and, in fact, the company&rsquo;s Q1 2020 net revenue was up nearly 30% overall, or $46 million above the same quarter last year, with net revenue from product sales up $41 million. The company sold 1,004,000 metric tons of wood pellets in the first quarter, compared to 843,000 metric tons the previous year. The sales uptick resulted in net income of $7.6 million, as compared to a net loss of $8.9 million for the first quarter of 2019.
&ldquo;Despite the COVID-19 pandemic in what is typically our most seasonally challenging quarter, we reported strong first quarter 2020 results representing a significant improvement over the first quarter of 2019,&rdquo; said John Keppler, chairman and CEO of Enviva. &ldquo;Thanks to the hard work as well as good, safe decisions and work practices of our teams, our operations continue largely unaffected. While uncertainty remains in the COVID-19 environment, we believe we are well-positioned to continue to maintain stable, growing cash flows that enable us to increase distributions sustainably over time.&rdquo;
Enviva noted that government-issued guidance identifies biomass and pellet manufacturing facilities as &ldquo;critical infrastructure,&rdquo; and that guidance has been followed by states where its plants and terminals are located, meaning its production output has been largely unaffected by the pandemic.&nbsp;&nbsp;
Financially sound, Drax donates to US communities in need&nbsp;&nbsp; Just days after helping communities in need near its U.S. facilities, Drax Group plc released a trading statement in late April confirming the company&rsquo;s strong financial and operational position and ability to continue supporting its employees and customers during the COVID-19 crisis.
&ldquo;At present, there has been no disruption to production caused by COVID-19, although the state of Louisiana is experiencing a high number of cases,&rdquo; the company said in its April 22 trading statement. &ldquo;The semi-automated nature of the pellet production process limits the need for individuals to be in contact with each other, and this has been enhanced by robust business continuity procedures to further reduce the risk to employees and contractors.&rdquo;
The company also reported that its biomass supply chain has a high level of operational redundancy designed to mitigate potential disruptions. In addition to its own U.S. plants, Drax also sources biomass from across North America and Europe.
A week before announcing its solid operational and financial footing, the company&rsquo;s U.S. subsidiary Drax Biomass donated $30,000 to help COVID-19- and tornado-impacted families in northeastern Louisiana and southwestern Mississippi.
Matt White, Drax Biomass senior vice president, said, &ldquo;The tornadoes experienced by communities across the region in recent days have been devastating and they come at a difficult time as we are all dealing with the impact of the coronavirus pandemic. It&rsquo;s important to support the people and businesses in the areas where we operate. Our thoughts are with all of those affected by these events.&rdquo;

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Business Briefs

In late March, as the impact of the coronavirus really started to accrue, I jotted down a list of the attributes of the wood pellet sector that other sectors might envy as they, too, navigate business during the pandemic.
First, as producers of a home heating fuel, the risk of an immediate demand shock is low. As stay-at-home provisions were implemented across the country, demand for transportation fuels plummeted, and oil and gas prices quickly followed. If sheltering in place had any impact on demand for home heating fuels, it was likely an increase, as homeowners found themselves heating their homes all day instead of just evenings and weekends.
Second, as the outbreak really began to accelerate in mid-March, the home heating season was well on its way to winding down. Consumers had the pellets they needed to get through the last few weeks of a winter that had been fizzling for a month anyway, and orders from retailers were drying up.&nbsp; Any factors with the potential to negatively impact wood pellet demand for the coming heating season have five months to sort themselves out. The most obvious threat is the potential for ultra-low heating oil prices next fall. The speed and depth of oil&rsquo;s price fall has been dizzying and heating oil prices have fallen with the price of crude, but will these historic lows last until next fall? As states move to reopen their economies in the coming months, gasoline demand will begin to recover and, with it, the price of oil. While everyone suspects wood pellets will have to compete with cheaper heating oil next season, no one can say with certainty just how cheap heating oil is likely to be, or if it will be cheap enough to motivate those consumers who have retained their oil appliances to use them.
 For now, the biggest risk facing the wood pellet sector is the availability of wood fiber from upstream forest products manufacturing. As sawmills, pallet operations and flooring manufacturers throttle back to match their own demand turn downs, their chip and sawdust output slows. For some producers, these impacts are already being felt, but it is far from universal with some producers finding that other manufacturers with whom they normally compete for wood fiber are not currently operating as they are not classified as an essential business. As surprising as it may sound, there are wood pellet producers with access to more fiber than they can currently use. Historically, wood pellet output ebbs in March and April, but it doesn&rsquo;t stop altogether. In 2019, producers manufactured 280,000 tons over the period, and to ensure adequate supply this fall, the industry will need to hold as close to these production figures as it can. Additionally, demand for wood products will need to recover quickly or the challenge of fiber availability will become more widespread as the sector ramps up production to lay in inventories in anticipation of the early buying season later this summer.
Finally, wood pellet manufacturers have found the deployment of social distancing guidelines at their operations to be minimally disruptive.&nbsp; Producers have moved to contact free inbound and outbound trucking, have stepped up plant cleaning protocols and have closed their offices to vendors and package delivery.
The coronavirus pandemic has brought with it economic challenges previously impossible to imagine, and the idea that any industry will escape without injury seems like a fantasy. That said, our sector must take good fortune where it can be found. Next fall, people will need to heat their homes, regardless of what happens with the pandemic. So long as upstream forest products manufacturing recovers and generates the fiber wood pellet producers rely on, the sector will be well-positioned to serve them. Author: Tim Portz Executive Director, Pellet Fuels Institute tim@pelletheat.org www.pelletheat.org

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Next fall, people will need to heat their homes, regardless of the pandemic. So long as the upstream forest products manufacturing sector recovers and generates the fiber wood pellet producers rely on, the industry will be ready and able to supply. 

Pellet Industry Remains Positioned to Deliver 

When it comes to biomass fuels, it really doesn’t matter which market you serve, ash content is always a very important parameter. For residential pellet-burning appliances, very low ash is generally desired, as the amount of ash directly relates to how often a stove needs to be cleaned. For power markets, higher amounts of ash are manageable, but how much ash can be managed is dependent on the type of combustion system, as well as the mineral composition of the ash, which is related to slagging. While the concept of ash seems simple, there are a lot of factors that determine how much ash will be present and how it will affect a combustion system.&nbsp;When freshly harvested, a tree contains minerals such as potassium, sodium and calcium, which are brought up into the tree through the root system. These minerals are non-combustible so when the wood is burned these minerals remain in the form of ash. For softwoods, the ash content of clean fiber will generally range from about 0.15% to 0.35%, and for hardwoods it will range from about 0.35% to 0.55%. Mineral composition of the ash will vary, but for clean wood fiber, the mineral composition is generally such that there will not be a slagging problem.Now let’s add bark. The simple nature of bark is that it is exposed to the atmosphere during the life of the tree, so it is free to pick up particulates from the air. Additionally, when the tree is felled, it can pick up dirt and debris from the forest floor, so the inclusion of bark in a fuel mix can and often does significantly increase the amount of ash contained within the fuel. When tested by itself, coarse bark generally contains several percent ash. However, when blended with the tree (e.g. a whole tree chip), if the materials are kept reasonably clean during the harvest, ash content will generally be in the 1 to 2% range. Mineral composition of bark ash is highly varied and largely dependent on the prevailing soil types of the region. Slagging may be associated with bark, especially in regions with silicon-based soils.Next, let’s add dirt. Dirt is a major contaminant, as it is almost all ash. To the fullest extent possible, dirt should be kept out of the fuel mix. This is not always easy if the materials used include land clearing debris. Materials with poor dirt control often range from 2% to 6% ash and can even be over 10% ash. These materials are also highly likely to have slagging issues.Finally, let’s add airborne particulate matter. Let’s say, for example, that your fiber source is expected to be very clean (no bark, no dirt), but your ash content is tracking higher than the baseline levels mentioned above. Chances are, an elevated ash content is the result of airborne dirt/dust particles finding their way into your fiber. A good example is to picture a clean fiber pile located close to a gravel road. As a car passes, there is a cloud of dust that wafts into the air. That dust can easily settle on your fiber, whether it is under cover or in the open air. This mechanism of dust accumulation is very apparent with agricultural residues. Typically, clean ag residues range from about 1% to 3% ash, however it is very common for ash to be 4% to 6%, or even higher.A few words about slagging. It no doubt seems odd that a fuel can have a very high ash content, but still not have a slagging problem. Conversely, materials can sometimes have lower amounts of ash (even below 1%) and have a slagging problem. This is because slagging is not necessarily caused by ash, but rather the mineral composition of the ash, along with combustion temperature. Calcium is a common mineral component of ash, which has very favorable ash fusion characteristics (melts at very high temperatures). When calcium comprises a high percentage of the ash there are generally no problems with slagging. Conversely, silica has the opposite effect—complex silicates generally melt at low temperatures—and is easily present when dirt and airborne dusts find their way into wood fuels. In most instances, slagging problems are the result of silica contamination.Finally, remember that the end user’s experience with ash is also a function of the efficiency of the combustion system. The relative percentages I have described above are representative of ideal conditions in the laboratory. When combustion systems are operated in less-than-optimal conditions (e.g., not enough air flow), the fuel may not completely burn. Dark, or even black, ash is likely the result of incomplete combustion, which can greatly increase ash, facilitate slagging, etc.&nbsp;In summary, if you are struggling with ash, either the overall amount or via the slagging of a combustion system, it is likely the solution can be found in the management of your sources of contamination.&nbsp;&nbsp; Author: Chris Wiberg Manager, Biomass Energy Laboratory 218-428-3583 cwiberg@tpinspection.com

2020-05-26 - Understanding Ash  (Biomass Magazine)

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For operations struggling with ash and slagging, the solution can often be found in the management of potential contamination sources. It's important to understand differences between tree species, and varying inclusion rates of bark, dirt and dust. 

Understanding Ash 

When it comes to preventing and mitigating pellet mill fires and explosions, redundancy is a good thing. So, if a few stories in this issue seem to echo similar guidance and best practices, consider it by design. After all, when it comes to safeguarding human lives, it&rsquo;s wise to have multiple options and opinions that confirm, rather than challenge, industry assumptions.
We drop into this month&rsquo;s safety and prevention theme with a useful look at the&nbsp; necessity of teamwork, training and communication between pellet facility personnel and local emergency response groups. In &ldquo;Flattening the Learning Curve,&rdquo; on page 10, Pellet Mill Magazine Editor Anna Simet reports that while OSHA does not necessarily mandate communication between a pellet plant and its local fire department, the safety agency strongly encourages it&mdash;not just to keep people safe, but to avoid actual violations. Ultimately, the onus of communication lies with the plant; and it&rsquo;s up to facility management to make sure fire crews and first responders know the plant&rsquo;s access points, danger zones and available fire prevention equipment and technologies.&nbsp;&nbsp;
In &ldquo;Driving Down Dust,&rdquo; on page 14, we explain the measures one Pennsylvania wood pellet manufacturer has taken to manage combustible dust and substantively decrease its chances of disaster. As Senior Editor Ron Kotrba reports, Greene Team Pellet Fuel Co.&rsquo;s plan began with the sure footing of a dust hazard analysis (DHA), which not only identified where explosion-prone areas of the plant were, but also where they were probably not. From there, planners were able to suggest equipment installations that made the facility much easier to keep safe. In addition to an oversized baghouse, pneumatic conveying and industrial cyclones and vacuums, the plant remedied a high-maintenance problem&mdash;dust up high in the rafters&mdash;with high-tech oscillating fans that effectively create a horizontal air barrier inside the structure, stopping fugitive dust from reaching the ceiling. Those smart fans, along with possible new equipment additions, make the facility&rsquo;s dust suppression strategy worth of a closer look.
For those looking for a deeper dive into DHAs, contributing writer Jeff Davis of Conversion Technologies Inc., explains some looming fall deadlines (i.e., NFPA 652) pellet producers need to be aware of in &ldquo;Changes to Dust Fire and Explosion Standards,&rdquo; on page 20. Additional on-theme stories continue on page 22, with REMBE, Fagus GreCon and IEP offering even more insight on fire detection and explosion protection for pellet plants.
Stay safe. Enjoy the reading.
Tom Bryan President BBI International

Issue 3

Business Briefs

Business Briefs

Columns

Pellet Industry Remains Positioned to Deliver

Understanding Ash

Programs of Protection

Featured

Driving Down Pellet Plant Dust

Pellet Plant Safety Rooted in Planning, Practice

Contributions

Flameless Explosion Protection for Combustible Wood Dust

Explosion Protection for Dust Collection

Intelligent Spark Detection and Extinguishing

Changes to Dust Fire and Explosion Standards

Issue 3.css-7jxktu{position:absolute;bottom:0px;left:0px;right:0px;height:3px;border-radius:3px;background-color:var(--chakra-colors-brandBlack);}

Business Briefs

Business Briefs

Columns

Pellet Industry Remains Positioned to Deliver

Understanding Ash

Programs of Protection

Featured

Driving Down Pellet Plant Dust

Pellet Plant Safety Rooted in Planning, Practice

Contributions

Flameless Explosion Protection for Combustible Wood Dust

Explosion Protection for Dust Collection

Intelligent Spark Detection and Extinguishing

Changes to Dust Fire and Explosion Standards

Issue 3