Explosion Risks from Nanomaterials

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1 Explosion Risks from Nanomaterials Jacques BOUILLARD & A. VIGNES, INERIS O. Duffaud, L Perrin & D. Thomas, LSGC, NANCY

2 INERIS Ile-de-France (Parisian region), ( Northern Regional Delegate Parc Technologique Alata - BP Verneuil en Halatte 600 employees 60 M Expert in environmental and industrial risks

3 How to Evaluate the Accidental Risk? R = P I V R =Explosion Risk P = Hazard Probability I = Intensity of the phenomenon V = Target Vulnerability (workers in our case) Remark : Existence and efficiency of various barriers: Prevention (P), Mitigation (I) et Protection (V)

4 INERIS and the EU NanoSafe2 Project Objectives How to characterize Physical and chemical Parameters of Nanoparticles Physical aspects: size, shape, specific surface, density Chemical Aspects: Chemical speciation (volumic and surfacic) How to Evaluate Accidental Effects: What are the important parameters, New Metrics to consider? Current Characterization tools: Are they pertinent for nanopowders? NAN SAFE2 «Safe production and use of nanomaterials Financial Support from FP6-NMP2-CT , and French Ministry of Ecology and Sustained Development.

5 n 400 ATD - ATG 135 INERIS is evaluating the Explosibility and Flammability Characterization Methodologies Current techniques and tools are evaluated for nanopowders Différence de température entre l'échantillon et le témoin ( C) Température du témoin ( C ) 2 Poids (%) Ignition Differential Thermal Analysis Isothermal Tests Minimal Ignition Energy Explosion 20 liter Sphere Already, some technical limitations are appearing

6 INERIS has developed combustion models for Carbon Nanotubes Study of Ignition and Combustion of CNT dx dt = E A A. exp. O X 2 RT ( ) n P.( 1 )2 1 X 1 dh = d H dt Ea=150 kj/mol et n=1.4 Réaction essentially lateral on the nanotube surface

7 INERIS Explores the Nanometric Domain Thermal Combustion of Nanomaterials ATG, DSC Analysis CNT + Carbon Blacks 2 ρ 1 pd p Tinf =. 6 τ Aluminum HcombEa Nuλg 1/ Image de fond : CNRS Photothèque, Température Didier Cot / Georges de début Nabias de réaction( C) NTC Surface spécifique(m²/g) Conclusion: Onset Temperature decreases with the particle size Température de début de réaction ( C) Diamètre des particules(nm)

8 Évaluation of Explosion Severity of Nanopowders Kst = dp dt V max -1/3 Kst: Explosibility constant of a powder calculated from the pressure rise rate (dp/dt )max) and the volume of the vessel Goal: Rank the explosive Character of the powdere as function of their Kst. MEC: Smallest concentration in air at which an explosion is observed P (bars) P m Event (dp/dt) m 0 Temps(ms) Entrée d eau Courbe de vitesse de montée en pression 20-Liter sphere apparatus Allumeurs Disperseur Electrovanne Sortie d eau Capteurs de pression Résevoir de poudre Air comprimée

9 INERIS Obtained New Safety Parameters for Nanopowders S BET (m²/g) d BET (nm) d aggl (nm) ~80000 Explosion Severity Low for agglomerated nanomaterials (ex CB) Very High for metallic compounds =>Possible Detonation

10 INERIS in International Collaboration to develop New tools of Characterization 100 Energie minimale d'inflammation (mj) 10 1 Kwok (2002) Field (1982) Al nanométrique Traore (2007) Babrauskas (2006) d 32 (µm)

11 Conclusions Évaluations of Minimal Ignition Energy (MIE) and explosion severity (Kst) performed for Carbone Nanotubes, Carbon Blacks and Aluminum. Have shown that Radiation Driven Detonation (RDD) Hazards with metallic nanoparticles are possible in certains conditions. Agglomeration phenomena can lead to an under-estimation of the explosion hazard. In order to obtain reliable safety parameters, a better understanding of dispersion phenomenology of nanopowders is required for: The development of new tools allowing a stricter control of dispersion/agglomeration, a better securisation and possibly a miniaturisation of these instruments.