Combustible Dust Safety in the Recycling Industry – Part 2

Dominick DalSanto is a guest contributor to the EES blog.  Dominick is an environmental technologies expert for www.baghouse.com and has authored numerous articles, whitepapers, and blogs on dust collection systems for industrial sources.  This is Part 2 of his series on combustible dust safety.

Selecting a Dust Collector

To begin your search it is vital to look for a company who can provide you with the best possible solution to your facility’s unique dust collection needs.  It is helpful if you can find a firm that is both an equipment supplier and a service provider.  This is useful for two reasons, (1) improperly installing your system can have detrimental effects on its efficiency, and (2) this will provide you with advantages in both expertise and price.  It will also be essential for you to have already researched and documented any and all regulations and standards that will apply to your site.  A good dust collector supplier should be able to help you in this regard should you need assistance.  Some applicable regulations that may apply to a recycling facility include:

  • National Fire Prevention Association (NFPA)
  • OSHA’s Combustible Dust National Emphasis Program (CDNEP)
  • EPA’s National Ambient Air Quality Standards (NAAQS)
  • Other EPA standards covering any toxic compounds processed and/or generated on site e.g. mercury, lead, etc…

NFPA standards will be the primary point of reference for all above referenced regulatory agencies, insurance underwriters and other authorities having jurisdiction.  In certain jurisdictions, testing is required of all compounds that are going to be collected.  If applicable, collect a sample of dust from the site, and send it to an accredited firm to be tested.

Next to be considered is the actual collector itself.  Baghouse selection and design should be the work of both the equipment supplier and the customer.  The customer will need to provide the equipment supplier with information such as a detailed floor plan, amount of fugitive dust emissions and the amount of dust that needs to be collected.

Other factors that will need to be taken into consideration while designing the system will include the potential for sparks in the system.  These can be caused by the type of shredding mechanism (e.g. hammer mill), and the RPMs of the shredding equipment itself.  This may require special equipment such as spark arrestors to be installed in the ductwork prior to entry into the Baghouse.

In cases where the local jurisdiction finds the material to be above certain combustibility levels (Kst value), and the system has a high potential for the generation of ignition sources (e.g. sparks), the system may be required to have explosive protection installed or be explosion proof.  This can range from explosion relief vents on the Baghouse itself, to additional collection hoods throughout the facility.  In these instances the NFPA Standard 68 on Explosive Protection by Deflagration Venting may apply.

Finally, after these factors have been taken into consideration, the dust collector supplier should be able to furnish you with a few recommendations.  Some of the different options they may present should include the following things, with explanations of the pros and cons of each recommendation.

Collector Type:

Pulse-jet, reverse-air, or shaker.

Filter Fabric and Treatments:

Examples include: polyester, fiberglass, PPS, Nomex, etc… Treatments include: antistatic, moisture repellent, ePTFE Membrane (Teflon) etc…

Filter Configurations

Standard filter bags, pleated elements, or cartridges.

Fan and Ducting

Motor type, power requirements, etc…

Misc

Pre-Filters e.g. cyclone collectors, baffle plates, spark arrestors, explosion vents, etc…

Closing Comments

When reviewing supplier recommendations, it is wise to consider the following questions:

  • Will this system meet my current and extended collection needs?

Ensure that the proposed system actually meets not only current production levels, but also projected growth and expansion.

  • Will it enable the facility to meet/exceed all current applicable environmental regulations?

These may include EPA standards such as NAAQS, NESHAPs, and process specific mercury MACT, Lead MACT, OSHA Workplace Safety standards, NFPA (National Fire Protection Agency) combustible dust standards, etc…

  • Does it account for foreseeable changes in environmental regulations? e.g. will it be able to meet environmental standards in 5, 10, or 20 years?

Regulations are always changing, and they are nearly always becoming stricter.  If the system will only achieve acceptable levels according to current legislation, more than likely in a few years the entire system may need to be retrofitted or replaced in order to meet any new standards that may come into effect.

A dust collection system can be a large investment for any facility regardless of size.  Some choose to cut corners in an attempt to save precious funds.  However, by taking the time to research the matter fully, facility managers can ensure that their system not only is affordable, but that in the end it helps increase efficiency, reduce risks from safety hazards, and fines from governmental regulatory bodies over air emissions.  A little time, money, and effort spent on your dust collector will always pay for it self many times over in the long run.

 

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One Response to Combustible Dust Safety in the Recycling Industry – Part 2

  1. DominickD says:

    From a LinkedIn Post:

    uday verma • It is necessary to have anti -static filter bags and the system handling the dust must be properly grounded to avoid any static charge build up.Also,integral to the system should have some sort of monitor and alarm to warn against excessive concentration,temperature,fire and smoke.