Development of an Anti-Caking Rock Dust

Details

• Personal Author:
  Anstine D ; Doidge N
• Description:
  The overall objective of the project was to develop modified limestone based rock dust blend(s) capable of effectively 1) dispersing in the NIOSH dust dispersion chamber after being wetted, then dried, and 2) inerting coal dust in the NIOSH 20-L explosibility chamber. Dozens of blends of fine treated limestone with coarser untreated limestone were evaluated to determine the most desired combination. The blends were constructed upon the premise that fine treated limestone particles would fill the voids between the larger untreated limestone particles and prevent or inhibit the migration of water throughout the blend, and subsequently pass the dust dispersion chamber test. Seven commercially available limestone products were used throughout the study (5 coarse untreated limestone products and two fine treated limestone products). The study was broken down into several phases as the optimization work focused in on specific blend components and ratios. Particle size, chemistry and stearic acid treatment levels were measured to validate that the blends were correctly proportioned. In addition, contact angle, ASTM D-698 (Proctor test) and dust dispersion chamber testing was conducted on the blends at various humidities to determine their hydrophobicity and ability to re-disperse after being wetted and dried. Finally selected blends were evaluated for their effectiveness in inerting Pittsburgh pulverized coal (PPC) dust in NIOSH's 20-L chamber. In this study, regardless of the blend components or their ratios, all the wetted then dried rock dust blends dispersed when compared to conventional rock dusts which formed essentially a non-dispersible cake when tested in the NIOSH developed dust dispersion chamber. Initial concerns regarding the use of a treated component and the possible adverse effects of free stearic acid was investigated, and not found to be an issue at the levels tested with the base and blend samples. Blends containing greater than 12.5% of the treated limestone component offered little additional advantage when tested for 'dust dispersion' and 'inerting'. Contact angle and ASTM D-698 testing suggest blends containing <7.5% of the treated component are more susceptible to moisture pick up. The NIOSH designed dust dispersion chamber and test protocols developed for this study were an excellent indicator of whether a rock dust would disperse into separate particles by a defined pulse of air. Contact angle measurements were beneficial for determining whether a blend demonstrated hydrophobic properties but the contact angle results did not correlate well with the dust dispersion results. As the study progressed, several base components and their blends (Drikalite, #8 White & RO-40) were eliminated based on performance or economic factors. The remaining blends based on#10 White and Micro-White 100, all inerted the Pittsburgh pulverized coal (PPC) dust at the 75% inertant concentration within the NIOSH 20-L chamber. Individual test results coupled with economic considerations led to the recommendation of a 20-25 um untreated rock dust (Micro-White 100) blended with 10% + 2.5% of a 3 um treated component (Kotamite). A large 20 ton scale-up sample of this blend was subsequently manufactured for more extensive testing within an area of NIOSH's Safety Research Coal Mine or similar facility. The scale-up blend sample along with an untreated rock dust (Micro-White 100) and two blends of the untreated rock dust with Kotamite (at 10% and 20%) were evaluated by NIOSH within the Bruceton Experimental Mine. The results showed that the untreated rock dust immediately wicked moisture from the mine strata and was not dispersible when wet or later when dried. All of the treated rock dust blends dispersed immediately after application and continue to disperse over time. [Description provided by NIOSH]
• Subjects:
  Coal Dust Explosions Occupational Health Particulate Matter Safety
• Keywords:
  Coal-dust Dusts Explosion-prevention Explosive-dusts Particulates Statistical-analysis Stone-processing
• Series:
  Mining Publications
• Publisher:
  National Institute for Occupational Safety and Health
• Document Type:
  Text
• Funding:
  Contract
• Genre:
  Final Contract Report
• Place as Subject:
  Georgia ; OSHA Region 3 ; OSHA Region 4 ; Pennsylvania
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-65
• NIOSHTIC Number:
  nn:20046358
• NTIS Accession Number:
  PB2015-105153
• Citation:
  Pittsburgh, PA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Contract 200-2012-52496, 2014 Apr; :1-65
• Contact Point Address:
  Neil Doidge, IMERYS Marble, Inc., IMERYS Carbonates, LLC., ECCA Calcium Products, Inc., 100 Mansell Court East, Suite 300, Roswell, GA 30076
• Email:
  Neil.Doidge@imerys.com
• Federal Fiscal Year:
  2014
• Performing Organization:
  IMERYS Carbonates, Roswell, Georgia
• Peer Reviewed:
  False
• Start Date:
  20120919
• Source Full Name:
  National Institute for Occupational Safety and Health
• End Date:
  20140331
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:e69ec2e1059b2ffd62875d909e6db2c51294b7962bafc60faeea3bc0791c0c8449fef75ce6105bef54d200f5e6d45d87d0be535bbdc60bffd16bfeb229127321
• Download URL:
  https://stacks.cdc.gov/view/cdc/228135/cdc_228135_DS1.pdf
• File Type:
  [PDF - 1.56 MB ]