EXPLOSION PROTECTION USING THE DATABASE. Maria Molnarne. formerly at BAM Federal Institute for Materials Research and Testing, Berlin, Germany

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1 EXPLOSION PROTECTION USING THE DATABASE Maria Molnarne formerly at BAM Federal Institute for Materials Research and Testing, Berlin, Germany

2 Department - Chemical Safety Engineering

3 Outline Database CHEMSAFE Safety characteristics Explosion protection primary, secondary, tertiary (constructive) explosion protection Examples Summary

4 CHEMSAFE database for evaluated safety characteristics of app flammable substances: liquids, gases, dusts and their mixtures project partners: BAM, DECHEMA, PTB updated yearly, languages: German / English

5 CHEMSAFE contains 1. Safety characteristics for fire & explosion protection, its definitions and information about test methods 2. Occupation safety data 3. Classification and labelling 4. Substance identification and specifications: Synonyms, CAS-,, EC-,, Index- and UN-No., No., particle size distributions 5. References, Recommendation of experts 6. Estimation methods (e.g. ISO flammability and oxizing potential), graphical tools, data exchange

6 Example - Benzene

7 Explosion region of a ternary system

8 Primary explosion protection Safety characteristics for assessing the explosiveness (flammability) of gases & liquids: Explosion limits Limiting values of explosion region (MOC, LOC, MXC, Tci), inerting Limiting values for chemically unstable substances (maximum stability ratio) Explosion point, Flash point

9 Test apparatus for determination of explosion limits of gases EN 1839-T T (tube) min. 100 mm

10 Apparatus in EN 1839 EN 1839 B B Bomb method -closed vessel -spherical or cylindrical -internal volume of at least 5 Liters -spark or fusing wire igniter EN T T Tube method -open vessel -tube ( ( 80 mm, minimum length 300 mm) -spark igniter

11 Temperature influence on explosion limits 25 Brenngasanteil in Mol-% UEL UEG Methan OEG Methan UEG Ethan OEG Ethan UEG Propan OEG Propan UEG Benzen OEG Benzen LEL 0 Source: BAM, CHEMSAFE Temperatur in o C Temperature in C

12 Pressure influence on explosion limits 70 UEG, OEG in vol% Methanol Cyclohexan Aceton Ethanol Source: : PTB, CHEMSAFE 0 0,0 0,2 0,4 0,6 0,8 1,0 p in bar

13 Explosion diagram with limiting values flammable gas 100 [mol %] UEL [mol %] MOC 0 MOC (LOC) IAR measured data + expl. curve MOC-line ICR-line IAR-line SCO-line inert gas SCO LEL explosionrange Explosion MAI oxygen A [mol %] ICR MXC (Tc i ) MXC 100 0

14 Inerting 0 Brenngas in Mol-% Explosionsbereich IAR C Oxidator MAI 40 in Mol-% 30 MOC ICR Inertgas in Mol-% Total inerting area (area under LEL and ICR- line) Other areas outside explosion region are partially inerted. MXC

15 Explosion region: Ethylene oxide/n 2 /air Decomposition C 2H 4O CO CH 4 Combustion 5 C2H 4O O2 2CO2 2H 2O 2 Explosion explosive without air Decomposition Initial conditions: 100 C, 40 kpa Test method: EN 1839-B Combustion

16 Explosion region of the system Ethene/H 2 O/air at different temperatures

17 Explosion region of the ternary system CH 4 /N 2 /air at 10 bar and 100 bar

18 Explosion region of ethane/n 2 with different oxidizing gases oxidizing gas 0 oxidiser 10 chlorine nitrous oxide nitric oxide air nitrogen trifluoride ethane in mol% ethane oxidiser in mol% 50 nitrogen in mol% N 2

19 Calculation method for flammability (ISO 10156) Flammable component n i 1 A i 100 Tc i 1 Inert component m j 1 B j K j If this condition fulfilled the mixture is classified as non-flammable

20 Determination of Tc i from x-y diagram Explosion range methane/nitrogen/air measurement by Schulz BAM Lab. II.22 (1996) 0 % air Tci (ISO) methane in mol % Tci (BAM) = 8.4 mol% T ci -value explosion range LEL : 4.2 mol % UEL : 16.3 mol % T Ci : 8.49 mol % nitrogen in mol % ISO (1996) Tci value for methane was 14.3 mol in %

21 Acetylene Chemically unstable gas

22 Stability pressure limits for acetylene with other gases Stability pressure limit in bar Stabilitätsgrenzdruck in bar H 2 N 2 CH 4 Wasserstoff Stickstoff Methan Propan Ignition energy: 70 Ws C 3 H Stoffmengenanteil Acetylen in % Acetylene in mol%

23 Dust explosion accident February 8, 2008 Sugar factory Savannah, Georgia, USA

24 Dust explosion test in BAM 20-liter sphere 1- cubic meter vessel

25 Search for sugar in CHEMSAFE

26 Secondary explosion protection Safety characteristics to assess the ignitability of substances Autoignition temperature of gases & vapors Minimum ignition temperatures of dusts (clouds, layer, heaps) Minimum ignition energy

27 Autoignition temperature of flammable liquids in function of pressure (autoclave) Tz in C T1 T2 Methylacetat Ethylacetate Propylacetate Butylacetate Pentylacetate T2 T3 Quelle: PTB, CHEMSAFE p in bar

28 Constructive explosion protection Safety characteristics to assess the severity of an explosion Maximum explosion pressure Maximum rate of pressure rise (dp/dt) max K G value for gases and vapors: K G -value = (dp/dt) max * V 1/3 (cubic law) K st value for dust, Dust explosion class Maximum experimental safe gap

29 Constructive explosion protection 50-liter spherical autoclave designed for pressures up to bar in BAM Investigation of detonation phenomena

30 Explosion pressure in function of concentration of methane in air 9,00 8,00 7,00 TUD 20 C TUD 100 C TUD 120 C TUD 200 C 6,00 TUD 240 C pex/pi [-] 5,00 4,00 3,00 2,00 1,00 0,00 3,00 5,00 7,00 9,00 11,00 13,00 15,00 17,00 19,00 CH 4 [mol-%] Data from SAFEKINEX EU-Project, TU Delft, NL- CHEMSAFE

31 K G values in functions of the test vessel and the hydrogen composition in air BAM 2.8-dm^3 BAM 6.0-dm^3 BAM 14.0-dm^3 800 KG [bar m/s] ,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00 80,00 90,00 H 2 [mol-%] Data from SAFEKINEX EU-Project, CHEMSAFE

32 Experimental setup (IEC ) 1) Inner (1) and outer (2) volume is filled with the same flammable mixture. Concentration of the flammable mixture is varied Width of the gap (3) is varied by turning the screw (6) Ignition occurs in the centre of the inner volume; Power of the ignition source (5) is about 10 J Criterion: flame transmission through the gap observed through window (4) maximum experimental safe gap (MESG)

33 Determination and estimation of MESG of mixtures Only a few MESG of mixtures are experimentally determined MESG determination is time consuming Using the lowest MESG of the mixture components rises often technical problems Based on some 150 measurements of different mixtures an estimation method was developed

34 MESG - measured and estimated 1,2 Lines mean linear interpolations at 40 C C and 120 C 1,2 1,0 1,0 MESG in mm 0,8 0,6 0,4 0,2 measured at 120 C estimated measured at 40 C estimated 0,0 0,0 0,00 0,25 0,50 0,75 1,00 0,8 0,6 0,4 0,2 Relative molar amount CH 4 Mixture of methane and dioxane

35 Minimum ignition energy maximum experimental safe gap Substance MIE in mj MESG in mm Hydrogen Acetylene Diethyl ether Propane Methane Ammonia

36 Summary Safety characteristics of hazardous substances needed under process conditions Chemically unstable gases represent further difficulties by explosion protection Dust explosion data are needed with particle size distribution CHEMSAFE contains this information and data evaluation is given by experts

37 Acknowledgement The author would like to thank Dr. M. Sam Mannan, Director of the Mary O Connor Process Safety Center for the financial support of this presentation and BAM for the presentation materials.

38 BAM Test Site Technical Safety Thank you for attention!

39 Limiting values of flammable mixture LEL UEL MAI MXC MOC SCO lower explosion limits (mol%) upper explosion limits (mol%) minimum required amount of inert gas in inert gas-oxidizer mixtures (mol%) maximum permissible amount of flammable gas in inert gas-flammable gas mixture in mol% (if nitrogen then Tci) maximum (permissible) oxidizing gas content in mol% (if air then LOC) stoichiometric concentration for the oxidizing reaction (mol%) ICR minimum inert gas-combustible ratio (-) IAR minimum inert gas/oxidizer (air) ratio (-)