Hazards of Energetic Reactions, aka Why Things Go Boom

Transcription

1 Hazards of Energetic Reactions, aka Why Things Go Boom David Frurip, PhD MSU Consultant Midland, MI 1

2 My Background Retired as the Technical Leader of Dow s Reactive Chemicals Discipline 32 Years at Dow Involved in Reactive Chemicals the entire time Former Chair of ASTM E-27 (RC hazards of chemicals) Former Chair of Dow Michigan Operations RCPHA Committee 65 Publications CHETAH expert training Promoted Reactive Chemicals techniques at many companies and universities

3 Fate! Little did I know then, I would spend a career in Reactive Chemicals

4 Examples of Events in Academia Univ. of Hawaii hydrogen explosion. Researcher lost her arm 4

5 Examples of Events in Academia Fatality at UCLA spill of pyrophoric t-butyllithium 5

6 Would You Know Better? Acetone + H2O2 TATP 6

7 Many Events Involve Wastes Aluminum sample holders added to acidic waste (hydrogen generation) Recent letter to CEN Safety Forum: Conc nitric acid added to glass waste jug with a EtOH residue led to explosion 7

8 First Steps: Recognize/ID Reactive Chemicals (RC) hazards Energy release potential Inherent energy in reactants/raw materials Inherent energy of intended chemistry Inherent energy from process upsets (high temperature decomposition) Flammability Flash Point! Dust explosion (more relevant to industry) 8

9 This is not necessarily Rocket Science! Common Sense Approach Three simple questions: 1. How much energy can be released 2. Under what circumstances 3. How fast can it happen? Example: recognition of hazardous functional groups: HO OH OH versus HO OH NO 2 9

10 Understanding the concept of the safe operating envelope Success defined: Having sufficient knowledge about the process to assure that the process operates in a safe zone NOT risk free! but acceptable risk Process Upset, worst case Safe Operating Envelope Normal Process Conditions 10 Looking for the nail that sticks up! Minor Process Upset

11 Common High Energy Functional Groups and Chemistries Groups: -NO2 Azo, Azide Peroxide C-N heterocycles diazonium salts Many more Chemistries: Redox reactions hydrogenations oxidations Polymerizations Nitrations Many others 11 Dilution: We don t care about 100 ppm TNT in a non-volatile solvent!!!

12 First Questions 12 How Much Energy Can It Liberate? (thermodynamics) How Fast Can it Go? (kinetics) A rusting pipe is very hot chemistry but very slow!

13 Vicious Cycle for Exothermic Reactions (Runaway Reactions) Reaction Goes Faster at Higher Temperatures Heat Given Off by Reaction Heat Raises Temperature of System 13 Runaway reaction definition: Heat gains exceed heat losses Pressure from rxn products, vapor pressure eventually vents or ruptures vessel

14 Calculations - Used to Understand Thermodynamics Literature Calculated Heats of Reaction Open Literature heats Analog Reactions NIST WebBook Useful for rxn heats 14

15 Quick and Easy Ways to Evaluate Your Chemistry and Process for Reactive Chemicals Hazards No Surprise WIKI! (not Wiki Leaks ) Chemical Reactivity Worksheet (CRW) Joint development Dow Chemical and NOAA Free download here 15 Other sources you have access to

16 Example: Diazonium Salts 16

17 Example : Hydrogen Flammability Hazards 17

18 MSU Training (Power Point Training Slides) Hydrogen Flammability LN2 Hazards SOP s for: H2 handling Tube Furnaces CO handling more 18

19 CCPS-CRW Useful for compatibility information Also useful for general reactivity of chemicals 19

20 But - Why Doesn t EVERY Exothermic Reaction Run Away? 20

21 Heat Loss!!!! Reaction Goes Faster at Higher Temperatures Heat Given Off by Reaction Heat Lost to the Surroundings Heat Raises Temperature of System TNR = Temperature of No Return

22 Heat is Lost From Vessels At Different Rates Why are R&D events typically pretty spectacular? 22

23 Worst Case Scenario Concept What: Plausible events that can result in an uncontrolled chemical reaction Potential to cause loss, injury or environmental harm. How: Examine the chemical process in detail. Looking for possible uncontrolled conditions that might occur 23

24 Worst case Examples for Lab Operations Fire due to flask breaking and release of flammable solvent Burst reactor due to runaway reaction with overpressure Explosion of a shock sensitive peroxide in an old solvent bottle 24

25 Which of the Following is an Appropriate Worst Case Scenario? Loss of Cooling Resulting in a Thermal Runaway (ΔT = 185 ºC) Loss of Cooling Resulting in a Thermal Runaway (ΔT = 1.85 ºC) Inherently safe design: Operate as dilute as practical Loss of Vacuum in Distillation resulting in a Flammable Mix & Explosion. DC-9 landing on my Reactor 25

26 Lines of Defense/ Layers of Protection 26 Things or actions to be employed to avoid reactive chemicals accidents If the hazard is serious, you should have multiple lines of defense! The last line of defense might be the fire extinguisher!

27 Lines of Defense Examples for Lab Operations 27 Fire due to flask breaking and release of flammable solvent No ignition source in hood non-flammable solvent chosen Burst reactor due to runaway reaction with overpressure High T cutoff of jacket Excess solvent used to prevent high T during runaway Explosion of a shock sensitive peroxide in an old solvent bottle Proper lab chemical management Peroxide forming materials are properly sealed

28 Which of the Following is an Appropriate Line of Defense? Scenario: Adiabatic Temp. Rise due to loss of cooling = 150 ºC. Flow restriction on feed line to reactor Temperature alarms at ΔT = 20 ºC High boiling solvent The Post-Doc is really really good at handling these situations 28

29 Laboratory Incident 2017 at MSU Researcher used LN2 to cool a glass vessel containing cellulose and SO2 Removed a Teflon valve stem for 5 minutes to facilitate adding small amounts of organic acids After replacing the valve stem and sealing the vessel, still in LN2, pumped the system by opening a valve attached to a pump for a few seconds, closing the valve and repeating ten times Note: the researcher was aware of the potential hazards of LO2 but assumed the amount of LO2 formed would be small and the pumping would remove it. 29

30 Schematic of Apparatus 30

31 Laboratory Incident 2017 at MSU, cont d 31 Upon warming the sealed system, the vessel exploded and injured the researcher An inherently safe (vessel was sealed with rubber septa to provide a relief) reenactment of the experiment showed: In 5 minutes of air exposure the vessel accumulated ca cc of LO2. After performing the ten consecutive pumping steps, most of the LO2 in the vessel remained! Root cause: the vessel burst from significant overpressure as the LO2 warmed up

32 If you observe condensed liquid in a LN2 cooled trap or vessel Move vented trap or vessel behind a shield in a hood 2. Inform co-workers to avoid the area 3. Allow to warm slowly as O2 boils off 4. If any solids remain treat carefully as the material may now contain unstable oxygenated species (peroxides etc.) Use good chemical sense here or consult with EHS or others Dissolve any solids with copious amounts of water or other solvent Consider testing the solids/solution for the presence of peroxides

33 Flame Sealing Ampoules Hazard A relatively common lab technique involves flame sealing glass ampoules By definition the ampoules will be sealed and unvented Never use LN2 as a cooling medium If not possible to avoid LN2 the ampoule MUST BE sealed with a continuous N2 purge DURING the sealing After sealing immediately check for LO2 in the ampoule. If present score and break the neck while still cold and allow the LO2 to vaporize 33

34 How I Can Help You? Evaluate your process (current and proposed) for Reactive Hazards can do by phone! Quick questions (phone call or dfrurip@charter.net or frurip@msu.edu ) It s free (to you!) Possible training of various topics 34

35 Safety Culture in Industry Industrial safety in the chemical industry is a religion It s the only way to do business! Stringent adherence to the safety (and reactive chemicals) policies is a condition of employment! Being a champion for lab safety will be a resume enhancer! 35

36 Inspirational Poster 36

37 Conclusions Reactive Chemicals management is a key part to the success of projects in the lab It need not and should not slow down activities A common sense risk based approach is optimum DO NOT hesitate to contact me 37