Development of Moisture Tolerant Rock Dust for Improved Mine Safety August 26, 2015 Dave Anstine - Senior Technical Leader, Building and Chemicals

Development Background Tragic explosion at the Upper Big Branch Mine in West Virginia in 2010 Extensive investigations were launched by the Mine Safety and Health Administration (MSHA) and found:  Mine was poorly dusted  78.92% were out of compliance with the federal standard The significance of the analysis and the role that Rock Dust played in the Upper Big Branch Mine explosion prompted MSHA to ask NIOSH to evaluate current Rock Dusts in North America and their compliance to specifications and its use in greater detail  47% of Rock Dust Samples did not meet the particle size requirement  All Rock Dust Samples tested, caked when wetted & dried and did not disperse with a light blast of air 30 CFR 75.2 Rock Dust Definition  Pulverized limestone, dolomite, gypsum, anhydrite, shale, adobe, or other inert material  Particle Size: ‒ 100% minus 20 Mesh ‒ Minimum 70% minus 200 Mesh  Particles of which when wetted & dried will not cohere to form a cake which will not be dispersed into particles by a light blast of air  Does not contain more than 5 percent combustible matter  Does not contain more than a total of 4 percent free and combined silica(SiO2) 04/12/2015Development of Moisture Tolerant Rockdust2

Current Rock Dust Samples Subjected to “Wet” Conditions 04/12/2015Development of Moisture Tolerant Rockdust3

Rock Dust Simple Caking Test 04/12/2015Development of Moisture Tolerant Rockdust4

NIOSH Dust Dispersion Chamber A laboratory dust dispersion chamber was developed by NIOSH to provide a reproducible air pulse across the surface of the sample to compare relative dispersibility of Rock Dust samples All test samples were subjected to the same 0.3-second pulse from a 40psi compressed air source to give a peak dynamic pressure of approximately 4.2 psi.. Sample trays were weighed before and after each air pulse to determine the amount of dust dispersed.. While this apparatus and test procedure cannot hope to duplicate the dust dispersal mechanism in advance of a propagating mine explosion, it does provide a repeatable dynamic pressure source and quantitative measure of the relative mass loss and dispersibility of dusts under controlled dispersion conditions. pressure. 04/12/2015Development of Moisture Tolerant Rockdust5

NIOSH Dust Dispersion Chamber 04/12/2015Development of Moisture Tolerant Rockdust6

NIOSH Dust Dispersion Trays with Rock Dust: After and Before Dispersion 04/12/2015Development of Moisture Tolerant Rockdust7

NIOSH Dust Dispersion Trays: Dry, Wet & Wet with Filter Paper 04/12/2015Development of Moisture Tolerant Rockdust8

NIOSH Dust Dispersion Chamber “Wet” Test Results: Current Rock Dust Samples 04/12/2015Development of Moisture Tolerant Rockdust9 Sample Identification Particle Size d(50) microns Dry Weight Loss (%) Wet Weight Loss (%) Imerys ImerWhite Competitive Sample # Competitive Sample # Competitive Sample # Competitive Sample # Competitive Sample # Competitive Sample # Competitive Sample #

Humidity Chamber 04/12/2015Development of Moisture Tolerant Rockdust10

NIOSH Dust Dispersion Chamber “Wet” Test Results: Moisture Tolerant Samples 04/12/2015Development of Moisture Tolerant Rockdust11 Imerys Sample #Particle Size d(50) MicronsDry Weight Loss (%)Wet Weight Loss (%) 2A075K-925R A125K-875R A125S-875R A075S-925R A075S A075S-925M A125S-875M A125K A125S A075S A125K-875M A125S A075K-925M A075K

NIOSH Dust Dispersion Chamber “Wet & Humid” Test Results: Moisture Tolerant Samples 04/12/2015Development of Moisture Tolerant Rockdust12 Imerys Sample #Particle Size d(50) MicronsWeight Loss (%) 0 Days7 Days14 Days21 Days 2C100S-900M B075K SU125K-875M C075S-925M S-900M C100K-900M B125K-875M B100K C075K-925M K-875M B100S B100S B075S C075S

Imerys Samples Tested in NIOSH 20L Explosibility Chamber 04/12/2015Development of Moisture Tolerant Rockdust13 Coal Concentration(g/cu.m) Rockdust Concentration(%) Imerys Sample No. #2B075K-9258dntgono-nodnt gono-nodnt gono-no #2B100S-9008dntgo-gono-no dntgono-nodnt gono-no #2B125S-8758dntgono-nodnt gono-nodnt gono-no #2B125K-875Mdntgono-nodnt gono-nodntgono-nono #2B075K-925Mdntgono-nodnt gono-nodntgono-nono #2B100S-90010dntgono-nodntgono-gonodntgono-nono #2B125S-87510dntgono-nodntgono-nonodntgono-nono #3125K-875Mgono-gono-nodntgono-gono-nodntgono-gono-no #3100S-90010dntgono-nodntgono-gono-nodntgono-nono #3100S-900Mdntgono-nodntgono-gono-nodntgono-nono #SU125K-875Mdntgono-nodnt gono-nodnt gono-no ImerWhite dntgo-gono-nodnt gono-nodnt gono-no no-no = two tests conducted and both inerted the coal dust go = explosion no = no explosion, dnt = did not test

Modified & Current Rock Dusts: After “Wet” and Humid Conditions 04/12/2015Development of Moisture Tolerant Rockdust14

Imerys Rock Dust Samples Comparison to 30 CFR /12/2015Development of Moisture Tolerant Rockdust15 Imerys Sample #Particle Size d(50) um Sieve Retains:Combustible Material % % SiO2 Free & Combined 20% Mesh200% Mesh 30CFR (max)30 (max)5 (max)4 (max) 2A075S-925R <0.2<0.7 2A125K-875R <0.2<0.7 2B075S <0.2<0.7 2B100K <0.2<0.7 2B125K <0.2<0.7 2C075S-925M <0.2<0.7 2C100S-900M <0.2<0.7 2C100K-900M <0.2< S-900M <0.2< S <0.1<0.2<0.7 SU125K-875M <0.2<0.7 2B125K-875M <0.2<0.7 2B125K-875M13.80<0.1<0.2<0.7 2B125S <0.1<0.2<0.7

Summary All samples have shown greatly improved dispersibility over the current Rock Dusts being used in North American coal mines when subjected to moisture and high humidity and then dried. The samples performed as well as the current Rock Dusts in their ability to inert explosions All samples meet the current requirements for 30CFR 75.2 Moisture Tolerant Rock Dust has been applied to a section of a Rib at the Bruceton Experimental Mine on the NIOSH Campus in Pittsburgh, PA  Compared to ImerWhite which was on a different section of a Rib  The Moisture Tolerant Rock Dust has been applied for over 6 months and is still dispersing with a light puff of air 04/12/2015Development of Moisture Tolerant Rockdust16

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