Reactive chemical hazards

1. Reactive chemical hazards This module provides a systematic and simplified way to tounderstand andidentifyreactive chemical hazards (RCHinshort).

2. About the module • Thismoduleisdevelopedfor undergraduate Chemical Engineering students prior to plant design project. • Thegoalofthismoduleisto: • RaiseawarenessofRCHstudy • MotivatestudentstostudyRCHbyshowcasetheconsequencesfromRCH • HelpstudentstounderstandthenatureofRCH • ProvidetoolsforstudentstoidentifyRCH • ProvideexamplesforstudentstoestimatetheextentofRCH • Control and Prevention of RCH will not be discussed in details in this module as it involves substantialtechnicalandtheoreticallearning.

3. Whatcanhappen?

4. Table of Contents • Introduction • DefinitionofHazard and Risk • DefinitionofReactive Chemical Hazards (RCH) • Desired and Undesired Reactions • TypeofRCH • Process of RCH Studies • Understanding • QualifyRCH • QuantifyRCH • ControlandPrevention • References

5. Hazard and Risk Definition • “•“ An intrinsic chemical, physical, societal, economic or political condition that has the potential for causing damage to a risk receptor (people, property or the environment)” • •“A measure of the human injury, environmental damage or economic loss in terms of both the frequency and the magnitude of the loss of injury” • • • -- Definition from the Centre for Chemical Process Safety Introduction Process of RCH Studies References Type of RCH

6. ReactiveChemicalHazard(RCH)Definition • Reactivity: • Tendencyofsubstancestoundergochemicalchange • A reactivechemicalhazard (RCH) is a situation with the potential for an UNCONTROLLED chemical reaction – with significant increases in Temperature, Pressure, and/or gas evolution – that can result directly or indirectly in serious harm to people, property or the environment Introduction Process of RCH Studies References Type of RCH

7. Nature of RCH… • Chemical reactionsinvolveenergychanges • Mostreactionsliberateenergyasheat–exothermic • Someenergyisabsorbedintoproducts–endothermic • RCHinvolveshighratesofenergyrelease • Toohightobeabsorbedbytheimmediateenvironmentofthereactingsystem • Resultindamages • Safeguarding information is provided later in this presentation Introduction Process of RCH Studies References Type of RCH

8. Desired and Undesired Reactions • Desired reactions can be controlled • Process Hazards Analysis – assess effect of deviations on process conditions • E.g. temperature, feed rate, pressure, etc… • Undesired reactions must be prevented • Types of undesired reactions: • Sidereactions • Mixing of incompatible chemicals • Formation of self-reacting chemicals • Unintended decomposition Introduction Process of RCH Studies References Type of RCH

9. Significant Disasters in History Introduction Process of RCH Studies References Type of RCH

10. Recap • Afterreading the case studies,which of the following is NOT a cause from chemical reactivity disasters? • Untrained labours • False alarm • Uncontrolled reaction • Lack of responsibility • None of the above ALL contributes to a potential disaster!!! Introduction Process of RCH Studies References Type of RCH

11. Types of RCH? • Self-Reactingimpact-sensitive or thermally sensitivematerials • Runaway reactions • Chemical incompatibility Introduction Process of RCH Studies References Type of RCH

12. Self-Reactingimpact-sensitiveorthermallysensitivematerials • When subjected to heat or impact, these chemicals may rapidly decompose, resulting in a potentially explosive release of energy. • Theseareundesiredorunintentionalreactions • Examples: • organicperoxides • copperacetylide Introduction Process of RCH Studies References Type of RCH

13. ChemicalIncompatibility • Between two or more substances • These hazards occur when a chemical is suddenly mixed or comes into contact with another chemical, resulting in a violent reaction. • Theseareundesiredandunintentionalreactions • Examples: • Strongacidsandstrongbases • Waterreactivematerials(sodiummetalandwater) • Pyrophoricmaterials(ironsulfideandoxygen) Introduction Process of RCH Studies References Type of RCH

14. Runaway Reactions • Predominantlyinvolvesdesired/intentionalreactions • Self-reactivechemicalsormixtures • In an out-of-control reaction involving a chemical or chemical mixture, the rate at which heat is generated exceeds the rate at which it is removed through cooling media and surroundings. Forexample: • Polystyrenebatchreactionandlossofjacketedcoolingcontrol • Acetylenehydrogenationreactionandinadequateheatremovalpergasflowthroughreactor • Usuallyoccurduringscale-upasthesystembecomesmoreadiabaticasitincreasesinsize Introduction Process of RCH Studies References Type of RCH

15. Recap • “In order to prevent RCHfor undesired chemical reactions, we need to establish sufficient control via safety mechanisms” True or False? • Answer: False • “In order to prevent Reactive Chemical Hazards for undesired chemical reactions,theeasiestwayisto PREVENT incompatible materials from contacting” Introduction Process of RCH Studies References Type of RCH

16. Break time Bhopal disaster made into a movie (watchthetrailerhere) Introduction Process of RCH Studies References Type of RCH

17. ProcessforRCHStudies Step 1: What reactivity hazard question is being studied? Desired Concern for runaway Undesired Single chemical: instability More than one chemical: incompatibility Step 2: Conduct Literature Research (qualitative review) Step 3: Is information researched sufficient to make a definitive decision on reactivity hazard for specific situation under consideration? Use qualified labs to conduct controlled/safe lab testing. Quantification can involve calorimetry test for heat release and kinetics Conclude investigation, document findings and necessary recommendations YES NO Introduction Process of RCH Studies References Type of RCH

18. Step 1: Understanding • Afterdefiningthesystemboundary,askthisquestion: Which ofthetwoscenarioisinvolved? • Chemical reacting by design/Desiredreaction • e.g. desired production • Chemical reacting by accident/Undesiredreaction • e.g. inadvertentmixingofchemicals Introduction Process of RCH Studies References Type of RCH

19. Step 2: Qualify RCH – a screening tool • SourcestoIdentifyRCH • ReactiveFunctionalGroups • MSDS (Material Safety Data Sheet) • International Chemical Safety Data Card • NOAA reactivity worksheet • S2S RCH online assessment • Oxygen Balance Introduction Process of RCH Studies References Type of RCH

20. Reactive Functional Groups • The presence of certain functional groups is considered an indicator of reactivity. • Some examples of chemicals containing functional groups can be considered potentially reactive: • -NO2 organic nitro compounds • N=N=N organic/inorganic azides, a linear anion • -O-O-, -O-OH organic/inorganic peroxide and hydroperoxide compounds • -C≡C- triple bonded carbon atoms as in acetylene and acetylenic compounds Introduction Process of RCH Studies References Type of RCH

21. Reactive Functional Groups • Simplest reactivity screening method possible and serves as a guideline for further analysis. • CornellUniversity’sEHSwebsite • ListofFunctionalGroupsPropertiesandHazards, including Reactivity Hazards Introduction Process of RCH Studies References Type of RCH

22. Recap • Whichofthefollowingfunctional group reacts vigorously with concentrated mineral acids? (Hint: available in Cornell’s EHS website) • A.aldehydes • B. aliphatic amines • C. alicyclic hydrocarbons • D. alcohols • Answer: • B. aliphatic amines Introduction Process of RCH Studies References Type of RCH

23. Reactive Functional Groups • Useful source: EPA’sChemical Compatibility Chart • Todeterminingthecompatibilityofchemicalsandthe resultofmixing Introduction Process of RCH Studies References Type of RCH

24. EPA Chemical Compatibility Chart Available Here: Introduction Process of RCH Studies References Type of RCH

25. Recap Q:Using the EPA compatibility chart, what will happen by mixing amides and oxidizing mineral acids? Introduction Process of RCH Studies References Type of RCH

26. RecapSolution Answer: Toxic gas formation and Heat Introduction Process of RCH Studies References Type of RCH

27. MSDS (Material Safety Data Sheet) • Contact your supplier for MSDS first • Under Section‘StabilityandReactivity’ • Limiteddetails Introduction Process of RCH Studies References Type of RCH

28. InternationalChemicalSafetyCard • If MSDS is not available, this is the secondary source • AvailableonILO(InternationalLabourOrganization) Website • ORGoogle international chemical safety data card • CDC(CentersforDiseaseControlandPrevention)website • Startsearch: Introduction Process of RCH Studies References Type of RCH

29. Recap • UsingICSD cards, findoutatleastonekeyreactive hazardforleadchromate. • Solution: • Decomposes on heating. This produces toxic fumes including lead oxides. • Reacts violently with many substances such as combustible substances, amines, bases and metals. This generates fire and explosion hazard.  Introduction Process of RCH Studies References Type of RCH

30. NOAA Reactivity Worksheet (CRW) • Asoftwaretofindouthazardsof: • Chemicals:a database of reactivity information for more than 5,000 common hazardous chemicals • ReactiveGroups:chemicals are assigned to 64reactivegroupsto generatereactivitypredictions • Mixturesofchemicals:rule-based algorithm allowing you to virtually “mix” chemicals to determine compatibility of two or more chemicals • Availableonline Introduction Process of RCH Studies References Type of RCH

31. NOAA: Use functional groups instead of chemicals when… • You know the chemical class of a chemical, but not its exact name or CAS (Chemical Abstracts Service) registry number. • For instance, you may be able to tell that it's a powdered metal • A new compound that hasn't yet been included in major chemical databases. • You work with (or store) proprietary chemicals that are not included in the CRW's chemical database. In this case, you can either use a reactive group to approximate the chemical or you could create a custom chemical datasheet in the CRW. Introduction Process of RCH Studies References Type of RCH

32. NOAA Example-Singlechemical Search SearchResults When working with mixture, seenextslide Introduction Process of RCH Studies References Type of RCH

33. NOAA Example Continued… Canobtainsummaryhere 2.Searchcompounds,thenaddtomixture,repeatwithmultiplecompounds 1.Createnewmixture 3.Willshowcompatibilitychart Introduction Process of RCH Studies References Type of RCH

34. Recap: TrythisonNOAA… • Mixsodiumhypochloriteandhydrogenperoxidetogether • Whatarethepredictedhazards? Introduction Process of RCH Studies References Type of RCH

35. S2SRCHOnlineAssessment • Toassess the hazardous properties of your substances or the hazardous properties of your process. • Select “SelfassessmentReactivityHazards” Introduction Process of RCH Studies References Type of RCH

36. S2SRCHOnlineAssessment • FollowthepromptfromS2Sonlineassessment,practicewithsodiumazide: NaN3 • YoucanusefactsregardingNaN3 in MSDS or ICSC • Resultsin asummaryreportindicating: • Deficiencies in Good Practice • Adequate fulfillment of needs • Insufficient Knowledge and Practices • Instruction: • Take a screenshotofyourassessmentandsubmitHERE. Introduction Process of RCH Studies References Type of RCH

37. OxygenBalance(OB,orOB%) • Usedtoindicatedegreetowhichanexplosivecanbeoxidized • Ifanexplosivemoleculecontainsjustenoughchemically-bonded oxygentoconvertallofitscarbontocarbondioxide,allofitshydrogentowater,andallofitsmetaltometaloxidewithNOEXCESS,themoleculeissaidtohaveazerooxygenbalance • PositiveOB:moleculecontainsmorechemically-bonded oxygenthanisneeded. • NegativeOB:moleculecontainslesschemically-bonded oxygenthanisneeded. • ForOB>-200,itisconsideredpotentialhighrisk • Important clarification - Use of the oxygen-balance tool implies the presence of oxidizing groups (functional groups) like nitro, nitrate, chlorate, peroxy in the molecule.  • *Using the oxygen balance without this additional information often will lead in wrong (nonsensical) results. Introduction Process of RCH Studies References Type of RCH

38. OxygenBalance(OB,orOB%) LothropandHandrick(1949)definedOBandwillbecalculatedas: For an organic compound: CxHyOz+ (x+y/4 - z/2) O2 ⇒ x CO2 + y/2 H2O and M is the molecular weight. CanalsobecalculatedonS2Swebsite Introduction Process of RCH Studies References Type of RCH

39. Break time T2 Laboratory Runaway Watch Online: https://www.youtube.com/watch?v=C561PCq5E1g Introduction Process of RCH Studies References Type of RCH

40. Step 3: Quantify RCH – an estimating tool Tools to Quantify RCH • Calorimetry • Adopting TCPA (Toxic Catastrophe Prevention Act) • CalculatedAdiabaticReactionTemperature(CART) • ASTMCHETAHprogram Introduction Process of RCH Studies References Type of RCH

41. Calorimetry • Tomeasure the heat effect of： • Physical changes (melting, evaporation, dehydration) • Chemical changes (acid-base reaction, dissolving, solid-state reaction, crystal phase transition) • It can be used to determine: • Enthalpy formation trends • Phase stability • Heat capacity • Surface effect • According to relationship between time and heat release per mole, we can, for intended reactions, design the safety response accordingly (e.g. cooling rate, set pressure alarm, etc.) Introduction Process of RCH Studies References Type of RCH

42. Calorimeter • An instrument determines heat effect in it by measuring temperature. • Based on state of system, classified into two types: • Adiabatic • Directly measures the temperature change in insulated system • Non-adiabatic • Measures heat flow of the system, with heat transfer to surrounding • Based on working conditions, classified into two types: • Constant pressure (e.g. coffee cup calorimeter) • Constant volume (e.g. bomb calorimeter) • Other types: solution calorimetry, scanning calorimetry

43. Schematic of a simplified calorimeter Reactant Stirrer Thermometer Calorimeter liquid Heater Picture reference: Calorimetry: Fundamentals, Instrumentation and Applications, 1st ed. (Stefan M. Sarge, Gunther W. H. Hohne, and Wolfgang Hemminger.

44. Calorimetry Example • When 0.7022 g of oxalic acid (C2O4H2) is burnt in the calorimeter under the same conditions as Example 6, the temperature increased by 1.602°C. The heat capacity of the calorimeter is 1.238 kJ/K. Calculate dH°combustion. • Solution: • The balanced equation and various quantities calculated are given in a logical order below: • C2O4H2(s) + 0.5 O2(g) 2 CO2 (g) + H2O(l) • dn = 1.5 q = C dT = 1.238*1.602 = 1.984 kJ • n of oxalic acid = 0.7022/90 = 0.00780 mol • dE = -1.984 / 0.00780 = -354.4 kJ/mol • dH = dE + dnRT • = -254.4 kJ + 1.5 mol * 0.008314 kJ/(K mol)* 298 K • = -250.6 kJ/mol Similarly, temperature increase can be calculated knowing the reaction, amount of reactants, heat capacity, and energy release. Introduction Process of RCH Studies References Type of RCH

45. Adopting TCPA (New Jersey) (Toxic Catastrophe Prevention Act) • TCPA’s goal:Protectthepublicfromcatastrophicreleasesofextraordinarilyhazardoussubstances(EHS). • TCPAincludestwocategoriesofreactivechemicals: • ReactiveHazardSubstances(RHS),listofchemicals • ReactiveHazardSubstanceMixtures(RHSM)determinedbyfunctionalgroups Thresholdquantityiscalculatedas: TQ=thresholdquantityoftheRHS,lb; D=distancetopropertyline,ft; E=energyofexplosionoftheRHS; 24=scaleddistanceforthemassofTNTthatresultsinablastpressureof2.3psi; 1024=energyofexplosionofTNT,cal/g. Introduction Process of RCH Studies References Type of RCH

46. Threshold for IndividualRHS Introduction Process of RCH Studies References Type of RCH

47. CalculationadoptingfromTCPA • Reactionthreshold can be calculated with heat of reaction ΔH,andobtainusingthetablebelow: • Distancefromthereactortothepropertylinecanalsobecalculatedadoptingthismethod. NOTE: TCPA is not our center of attention, it is the calculation that can be adopted to help with RCH evaluation. Introduction Process of RCH Studies References Type of RCH

48. Recap:TCPA Example • Now,practicewiththefollowingcopolymerizationexample: • Styreneandacrylonitrile formsSAN(styrene-acrylonitrile) • Literaturevalue: • Heatofreactionis-261kcal/molwith70:30feedweightratio • Find out: • Forareactorfilledwith8500lbofSAN,whatwouldbetheminimumdistanceforustokeepthereactorfrom? • Solution: Introduction Process of RCH Studies References Type of RCH

49. CalculatedAdiabaticReactionTemperature(CART) • Alsoknownasadiabaticflametemperature • “Foracombustionprocessthattakesplaceadiabaticallywithnoshaftwork,thetemperatureoftheproductsisreferredtoastheadiabaticflametemperature.” Δh1+Δh2=Δhadiabatic=0 fornoworkdoneandnoheatexchanged(overallenthalpyfrominitialtofinalstateiszero). Introduction Process of RCH Studies References Type of RCH

50. CalculatedAdiabaticReactionTemperature(CART) • CART relates to reaction mechanism and KNOWN stoichiometry • Energy release, HRXN • The ioMosaic Reactivity Hazard Index can then be used to compare/rank reactivity hazards • “Neglible Reactivity Hazard” • HRXNnomore negative than – 100 cal/g, and • CART  700 K • “Low Reactivity Hazard” (energetic reaction but not likely to be explosive) • HRXNbetween – 100 and – 287 cal/g, and • CART 700 K • “Intermediate Reactivity Hazard” (energetic reaction but not likely to be explosive) • HRXNbetween –287 and – 717 cal/g, or • 700 < CART 1600 K • “High Reactivity Hazard” (strong potential for being explosive reaction) • HRXN more negative than – 717 cal/g, or • CART1600 K Introduction Process of RCH Studies References Type of RCH