2005 SACHE Faculty Workshop

2005 SACHE Faculty Workshop
Chemical Reactivity Hazards:

Chemical Reactivity Hazards: foresee avoid control

Syllabus The worst process industry disasters worldwide have involved uncontrolled chemical reactions Chemical reactivity hazards must be anticipated and recognized before controls can be engineered Reactivity hazards that are eliminated will not need engineering and administrative controls SACHE has many products that can help educate engineers to understand and safeguard against uncontrolled reactions

Pretest Key Concepts 1 Midterm Exam Key Concepts 2 Open-Book Final
Class Schedule Course Texts Pretest Key Concepts 1 Midterm Exam Key Concepts 2 Open-Book Final Extra-Credit Activities

Course Texts

Texts CCPS Safety Alert 2001.
Reactive Material Hazards: What You Need to Know. New York: AIChE. 10 p. Download for free at

Texts Johnson, Rudy, Unwin 2003.
Essential Practices for Managing Chemical Reactivity Hazards. New York: AIChE. 193 p. Register for free access at

Texts CCPS 1995. Guidelines for Chemical Reactivity Evaluation and Application to Process Design. New York: AIChE. 210 p. AIChE members can access for free at

Texts CCPS 1995. Guidelines for Safe Storage and Handling of Reactive Materials. New York: AIChE. 364 p. AIChE members can access for free at

Texts Process Safety in Batch Reaction Systems. CCPS 1999.
Guidelines for Process Safety in Batch Reaction Systems. New York: AIChE. 171 p. AIChE members can access for free at

Texts Hazard Investigation 2002. Improving Reactive Hazard Management.
Washington, D.C.: U.S. Chemical Safety and Hazard Investigation Board. 150 p. Download for free at

Texts HarsBook: A technical guide for the assessment of thermal hazards in highly reactive chemical systems. HarsNet Thematic Network on Hazard Assessment of Highly Reactive Systems. 143 p. Download for free at

Texts P.G. Urben (ed.) Bretherick’s Handbook of Reactive Chemical Hazards (2 vols). Oxford: Butterworth-Heinemann. 2,532 p. ~$250 from AIChE/CCPS; also available electronically

Pretest

Pretest Q1 On the NFPA ‘diamond’, which color(s) or position(s) are associated with chemical reactivity hazards? 4 3 W OX

Pretest A1 Flammability 4 3 Toxicity Instability W OX Special Hazards

Pretest Q2 What should you do first?
Your new research calls for the piloting of a process involving acetone cyanohydrin. What should you do first?

Pretest A2 First, Don’t Panic.

Pretest A2 First, Don’t Panic. Next, find out the inherent hazards of acetone cyanohydrin. C4H7NO

Pretest A2 First, Don’t Panic. Next, find out the inherent hazards of acetone cyanohydrin. CH3 C O + HCN CH3

Pretest A2 First, Don’t Panic. Next, find out the inherent hazards of acetone cyanohydrin. CH3 OH C CH3 C N

2 3 1 Acetone Cyanohydrin Severe health hazard; combustible;
NFPA 49 Severe health hazard; combustible; readily decomposes, producing HCN; no “special hazards”; reacts with acids, alkalis, oxidizing materials, reducing agents 2 3 1

1 4 2 Acetone Cyanohydrin Extremely toxic, Class IIIB combustible,
International Chemical Safety Card Extremely toxic, Class IIIB combustible, unstable at elevated temp, decomposes in water 1 4 2

Acetone Cyanohydrin DOT Class 6.1 Poisonous material

Acetone Cyanohydrin DOT Emergency Response Guidebook 2004
A water-reactive material that produces large amounts of HCN when spilled in water

Acetone Cyanohydrin NOAA Chemical Reactivity Worksheet
Chemical Profile Readily decomposes to acetone and poisonous hydrogen cyanide gas on contact with water, acids (sulfuric acid) or when exposed to heat. Should be kept cool and slightly acidic (pH 4-5) [Sax, 2nd ed., 1965, p. 388]. Slowly dissociates to acetone, a flammable liquid, and hydrogen cyanide, a flammable poisonous gas, under normal storage and transportation conditions. Rate of dissociation increased by contact with alkalis and/or heat. Special Hazards · Water-Reactive No rapid reaction with Air Air and Water Reactions Soluble in water. Readily decomposes on contact with water to form acetone and poisonous hydrogen cyanide. General Description A colorless liquid. Flash point 165°F. Lethal by inhalation and highly toxic or lethal by skin absorption. Density 7.8 lb / gal (less dense than water). Vapors heavier than air. Produces toxic oxides of nitrogen during combustion (© AAR, 1999).

Acetone Cyanohydrin NIOSH Pocket Guide to Chemical Hazards
Incompatibilities & Reactivities: Sulfuric acid, caustics Note: Slowly decomposes to acetone & HCN at room temperatures; rate is accelerated by an increase in pH, water content, or temperature.

Acetone Cyanohydrin CHRIS

Acetone Cyanohydrin

Acetone Cyanohydrin Conclusions
Extremely toxic; must keep contained and avoid all contact Combustible; must avoid flame, ignition Dissociates to produce highly toxic and flammable gases; dissociation increases with heat, moisture, alkalinity Must prevent spills into drains, etc. Must avoid incompatible materials

Key Concepts

Key Concepts From 2005 SACHE module on Chemical Reactivity Hazards

(etc.)

The NOAA Chemical Reactivity Worksheet predicts the results of mixing any binary combination of the 6,080 chemicals in the CAMEO database, including many common mixtures and solutions. For each substance, a general description and chemical profile are given, along with special hazards such as air and water reactivity. The NOAA Worksheet not only indicates the hazards of individual substances, such as shown here for sodium hydrosulfite, ...

CRWorksheet Limitations
Only binary combinations considered Consequences predicted only for ambient temperature, atmospheric pressure Possible effects of confinement, catalysts, contaminants, or materials of construction not included Reaction products not predicted, though flammable or toxic gas generation may be suggested

Preliminary Screen for Chemical Reactivity Hazards
Summary Flowchart Source: Johnson et al. 2003

Incident April 21, 1995 5 worker fatalities ~300 evacuated
Facility destroyed Surrounding businesses damaged As I’m sure you’re aware, an uncontrolled chemical reaction did occur at the Napp Technologies facility. The incident resulted in multiple fatalities and extensive property damage. But again, the purpose of this retrospective example was only to illustrate the preliminary screening method for this type of operation, and show that a probable need for managing chemical reactivity hazards at similar mixing facilities would be indicated. Ed Hill, The Bergen Record Used with permission

WHY? Those hazards that are not eliminated or reduced to insignificance must be managed throughout the lifetime of the facility, to avoid uncontrolled chemical reactions that can result directly or indirectly in serious harm to people, property or the environment.

Inherently Cleaner, Safer Plants
Processes Pollution Prevention Waste Management Environ- mental Restoration POTENTIAL RELEASE AFTERMATH Processes Safer Inherently Prevention Mitigation Recovery Accident And finally, we have come to an emphasis on inherently safer processes, to reduce the underlying loss potentials in our facilities. We know how to measure it, we know why we need it, and now we need to make it a reality. Thank you.

Safe Operation (with respect to Chemical Reactivity Hazards) Contain and control all chemical reactivity hazards throughout entire facility lifetime Reduce hazards or design safeguards such that even if hazard containment or control were lost, no injuries, property damage, environmental damage or business interruption would occur Eliminate chemical reactivity hazards

Inherently Safer Strategies
MINIMIZE SUBSTITUTE MODERATE SIMPLIFY Another approach is to focus on the inherent safety design strategies of MINIMIZE, SUBSTITUTE, MODERATE, and SIMPLIFY. These strategies are included in CCHS' current ISO Guidance document.

Foresee, Avoid, Control Anticipate chemical reactivity hazards
Identify all reactive materials and all possible reactive interactions Do whatever it takes to fully understand intended and unintended reactions Boundaries of safe operation Calculations, literature, testing, experts Design and operate to avoid unintended reactions and control intended reactions

Some chemical reactivity hazards--
some potentials for causing harm and loss-- are best avoided altogether.

Managing Chemical Reactivity Hazards
Section 4.1 Develop/Document System to Manage Chemical Reactivity Hazards START Managing Chemical Reactivity Hazards 4.2 Collect Reactivity Hazard Information 4.9 Investigate Chemical Reactivity Incidents 4.10 Review, Audit, Manage Change, Improve Hazard Management Practices/Program 4.3 Identify Chemical Reactivity Hazards 4.4 Test for Chemical Reactivity IMPLEMENT; OPERATE FACILITY NO Sufficient information to evaluate 4.8 Communicate and Train on Chemical Reactivity Hazards hazard? YES Let’s look at this from the perspective of a management system. Here’s a flowchart from CCPS’ Concept Book for implementing chemical reactivity hazard management. 4.5 Assess Chemical Reactivity Risks 4.6 Identify Process Controls and Risk Management Options 4.7 Document Chemical Reactivity Risks and Management Decisions

IMPLEMENT; OPERATE FACILITY
Identify, Characterize Hazards 4.2 Collect Reactivity Hazard Information 4.9 Investigate Chemical Reactivity Incidents 4.10 Review, Audit, Manage Change, Improve Hazard Management Practices/Program 4.3 Identify Chemical Reactivity Hazards 4.4 Test for Chemical Reactivity IMPLEMENT; OPERATE FACILITY NO Sufficient information to evaluate 4.8 Communicate and Train on Chemical Reactivity Hazards hazard? Note that this PROCESS of Hazard Analysis is a dominant part of managing chemical reactivity hazards. YES 4.5 Assess Chemical Reactivity Risks 4.6 Identify Process Controls and Risk Management Options 4.7 Document Chemical Reactivity Risks and Management Decisions

Chemical Reaction Hazard Identification
D.C. Hendershot “A Checklist for Inherently Safer Chemical Reaction Process Design and Operation.” CCPS International Symposium on Risk, Reliability and Security.

Reaction Hazard Identification
1 Know the heat of reaction for the intended and other potential chemical reactions. There are a number of techniques for measuring or estimating heat of reaction, including various calorimeters, plant heat and energy balances for processes already in operation, analogy with similar chemistry (confirmed by a chemist who is familiar with the chemistry), literature resources, supplier contacts, and thermodynamic estimation techniques. You should identify all potential reactions that could occur in the reaction mixture and understand the heat of reaction of these reactions.

2 Calculate the maximum adiabatic temperature for the reaction mixture. Use the measured or estimated heat of reaction, assume no heat removal, and that 100% of the reactants actually react. Compare this temperature to the boiling point of the reaction mixture. If the maximum adiabatic reaction temperature exceeds the reaction mixture boiling point, the reaction is capable of generating pressure in a closed vessel and you will have to evaluate safeguards to prevent uncontrolled reaction and consider the need for emergency pressure relief systems.

3 Determine the stability of all individual components of the reaction mixture at the maximum adiabatic reaction temperature. This might be done through literature searching, supplier contacts, or experimentation. Note that this does not ensure the stability of the reaction mixture because it does not account for any reaction among components, or decomposition promoted by combinations of components. It will tell you if any of the individual components of the reaction mixture can decompose at temperatures which are theoretically attainable.

3 (continued) If any components can decompose at the maximum adiabatic reaction temperature, you will have to under-stand the nature of this decomposition and evaluate the need for safeguards including emergency pressure relief systems.

4 Understand the stability of the reaction mixture at the maximum adiabatic reaction temperature. Are there any chemical reactions, other than the intended reaction, which can occur at the maximum adiabatic reaction temperature? Consider possible decomposition reactions, particularly those which generate gaseous products. These are a particular concern because a small mass of reacting condensed liquid can generate a very large volume of gas from the reaction products, resulting in rapid pressure generation in a closed vessel.

4 (continued) Again, if this is possible, you will have to understand how these reactions will impact the need for safeguards, including emergency pressure relief systems. Understanding the stability of a mixture of components may require laboratory testing.

5 Determine the heat addition and heat removal capabilities of the pilot plant or production reactor. Don’t forget to consider the reactor agitator as a source of energy – about 2550 Btu/hour/horsepower. Understand the impact of variation in conditions on heat transfer capability. Consider factors such as reactor fill level, agitation, fouling of internal and external heat transfer surfaces, variation in the temperature of heating and cooling media, variation in flow rate of heating and cooling fluids.

6 Identify potential reaction contaminants. In particular, consider possible contaminants which are ubiquitous in a plant environment, such as air, water, rust, oil and grease. Think about possible catalytic effects of trace metal ions such as sodium, calcium, and others commonly present in process water. These may also be left behind from cleaning operations such as cleaning equipment with aqueous sodium hydroxide. Determine if these materials will catalyze any decomposition or other reactions, either at normal conditions or at the maximum adiabatic reaction temperature.

7 Consider the impact of possible deviations from intended reactant charges and operating conditions. For example, is a double charge of one of the reactants a possible deviation, and, if so, what is the impact? This kind of deviation might affect the chemistry which occurs in the reactor – for example, the excess material charged may react with the product of the intended reaction or with a reaction solvent. The resulting unanticipated chemical reactions could be energetic, generate gases, or produce unstable products. Consider the impact of loss of cooling, agitation, and temperature control, insufficient solvent or fluidizing media, and reverse flow into feed piping or storage tanks.

8 Identify all heat sources connected to the reaction vessel and determine their maximum temperature. Assume all control systems on the reactor heating systems fail to the maximum temperature. If this temperature is higher than the maximum adiabatic reaction temperature, review the stability and reactivity information with respect to the maximum temperature to which the reactor contents could be heated by the vessel heat sources.

9 Determine the minimum temperature to which the reactor cooling sources could cool the reaction mixture. Consider potential hazards resulting from too much cooling, such as freezing of reaction mixture components, fouling of heat transfer surfaces, increase in reaction mixture viscosity reducing mixing and heat transfer, precipitation of dissolved solids from the reaction mixture, and a reduced rate of reaction resulting in a hazardous accumulation of unreacted material.

10 Consider the impact of higher temperature gradients in plant scale equipment compared to a laboratory or pilot plant reactor. Agitation is almost certain to be less effective in a plant reactor, and the temperature of the reaction mixture near heat transfer surfaces may be higher (for systems being heated) or lower (for systems being cooled) than the bulk mixture temperature. For exothermic reactions, the temperature may also be higher near the point of introduction of reactants because of poor mixing and localized reaction at the point of reactant contact.

10 (continued) The location of the reactor temperature sensor relative to the agitator, and to heating and cooling surfaces may impact its ability to provide good information about the actual average reactor temperature. These problems will be more severe for very viscous systems, or if the reaction mixture includes solids which can foul temperature measurement devices or heat transfer surfaces. Either a local high temperature or a local low temperature could cause a problem. A high temperature, for example, near a heating surface, could result in a different chemical reaction or decomposition at the higher temperature.

10 (continued) A low temperature near a cooling coil could result in slower reaction and a buildup of unreacted material, increasing the potential chemical energy of reaction available in the reactor. If this material is subsequently reacted because of an increase in temperature or other change in reactor conditions, there is a possibility of an uncontrolled reaction due to the unexpectedly high quantity of unreacted material available.

11 Understand the rate of all chemical reactions. It is not necessary to develop complete kinetic models with rate constants and other details, but you should understand how fast reactants are consumed and generally how the rate of reaction increases with temperature. Thermal hazard calorimetry testing can provide useful kinetic data.

12 Consider possible vapor phase reactions. These might include combustion reactions, other vapor phase reactions such as the reaction of organic vapors with a chlorine atmosphere, and vapor phase decomposition of materials such as ethylene oxide or organic peroxide.

13 Understand the hazards of the products of both intended and unintended reactions. For example, does the intended reaction, or a possible unintended reaction, form viscous materials, solids, gases, corrosive products, highly toxic products, or materials which will swell or degrade gaskets, pipe linings, or other polymer components of a system? If you find an unexpected material in reaction equipment, determine what it is and what impact it might have on system hazards. For example, in an oxidation reactor, solids were known to be present, but nobody knew what they were. It turned out that the solids were pyrophoric, and they caused a fire in the reactor.

14 Consider doing a Chemical Interaction Matrix and/or a Chemistry Hazard Analysis. These techniques can be applied at any stage in the process life cycle, from early research through an operating plant (Mosley et al. 2000). They are intended to provide a systematic method to identify chemical interaction hazards and hazards resulting from deviations from intended operating conditions.

ASTM E “Standard Guide for the Preparation of a Binary Chemical Compatibility Chart” Scenario-based This approach has similarities to a relatively recent ASTM standard for preparing binary compatibility charts. The ASTM Standard emphasizes that chemical compatibility depends heavily on the mixing scenario.

Inadvertent Mixing Scenarios
In PHAs, incompatibility scenarios may need to be developed along with other process deviation scenarios. Two examples are reproduced in Table 3 of our paper. Johnson and Lodal, "Screen Your Facilities for Chemical Reactivity Hazards," CEP, Aug. 2003

2 Inadvertently pump up to 1400 kg of 38°C cyclohexane at 0.3 kg/s into closed, temperature-controlled storage tank of between 700 and 2800 kg of acrylic acid with 200 ppm MEHQ inhibitor, maintained at 20°C I’d like to highlight just the second of these two scenarios. [ADVANCE] Note that the postulated scenario gives equipment, quantities, temperatures, rates, and compositions.

No Most compatibility data in the literature describe what would happen if materials are combined under ambient, unconfined conditions.

? Since this scenario involves confinement and elevated temperatures, we probably can’t use literature data to judge the likely outcome.

Compatibility information only known for ambient conditions; no reaction with cyclohexane expected, but may be hot enough to increase dimer formation and possibly initiate polymerization This scenario illustrates that [ADVANCE] analyzing scenarios involving inadvertent mixing of incompatible materials is likely to identify unknowns that may require additional testing.

Boicourt emphasizes that a good PHA, through the application of appropriate techniques, can identify abnormal processing conditions, but the reactive hazards that result can often be determined only through testing. G.W. Boicourt, “Experimental Safety: What You Need for Effective Process Safety Evaluation,” Proceed. 30th Annual Loss Prev. Symp., 2/96.

A full analysis of these scenarios in the context of a PHA would assess the likelihood and severity of each scenario and the adequacy of safeguards. AS WELL AS Cyclohexane Added Connecting valve left open

Chemistry Hazard Analysis Scenarios
A good place to start is early in the design process. Rohm & Haas authors have published a suggested practice of analyzing the process chemistry at the early development stages of a new process. The authors suggest a “chemistry hazard analysis” approach to identifying deviations and consequences, as illustrated in Table 1 in our paper. Similar to a HAZOP study, this approach studies deviations from an intended chemical reaction using typical HAZOP guidewords. This is done to ensure the consequences of deviating from the intended reaction are understood. Mosley, Ness, and Hendershot, "Screen Reactive Chemical Hazards Early in Process Development," CEP, Nov. 2000

IMPLEMENT; OPERATE FACILITY PHAs; Ensure Risk Control
4.2 Collect Reactivity Hazard Information 4.9 Investigate Chemical Reactivity Incidents 4.10 Review, Audit, Manage Change, Improve Hazard Management Practices/Program 4.3 Identify Chemical Reactivity Hazards 4.4 Test for Chemical Reactivity IMPLEMENT; OPERATE FACILITY NO Sufficient information to evaluate 4.8 Communicate and Train on Chemical Reactivity Hazards hazard? Note that this PROCESS of Hazard Analysis is a dominant part of managing chemical reactivity hazards. YES PHAs; Ensure Risk Control 4.5 Assess Chemical Reactivity Risks 4.6 Identify Process Controls and Risk Management Options 4.7 Document Chemical Reactivity Risks and Management Decisions

Intentional Chemistry Unintentional Chemistry
Materials Reactive with Ubiquitous Substances Spontaneously Combustible Peroxide Forming Water Reactive Oxidizing Self-Reactive Materials Polymerizing Decomposing Rearranging Reactive Interactions Incompatibilities Abnormal Conditions Chemical Reactivity Hazards But it’s harder to get your arms around what’s “in the box” when chemical reactivity hazards are involved. There’s just a whole lot of ways to have uncontrolled chemical reactions! Here’s a breakdown that may be helpful. Control could be lost of a reaction that’s intentionally going on in your facility, [ADVANCE] OR… An unintentional chemical reaction could take place. This could involve either [ADVANCE] various kinds of reactive materials [ADVANCE], or [ADVANCE] reactive interactions. Identify, characterize hazards

Normal Situation - Reactives
Reactive materials contained Reactive interactions (incompatibilities) avoided Intended reactions controlled Chemical Reactivity Hazards When everything is normal, these potentials are contained and controlled, and loss events are not occurring. However, the potential for harm and loss is still there, as long as the hazardous materials and energies are present. Potential Loss Event Impacts People Property Environment

Abnormal Situation - Reactives
Loss of containment Reactive interaction (incompatibility) Loss of reaction control Chemical Reactivity Cause Hazards Various errors and failures can initiate abnormal situations when chemical reactivity hazards are present, resulting in deviations from intended operation. Some typical causes and deviations for intentional chemistry processes are listed in Tables 4 and 5 of our paper. Deviation

Chemical Reactivity: Loss Events
Johnson and Unwin, “Addressing Chemical Reactivity Hazards in Process Hazard Analysis,” 18th Annual International CCPS Conference, NY: AIChE, Sept Table 6 at the end of our paper gives a listing of loss events associated with the various kinds of chemical reactivity hazards-- --what can happen when a chemical reaction gets out of control. For many chemical reactivity incidents, it is not the uncontrolled reaction itself but the pressure buildup and vessel rupture explosion that’s likely to cause harm. Domino effects are also possible with most of the loss events. Loss Event Fire Explosion Release

Loss Events Associated with Reactivity Hazards

Extra- Credit Activities

SACHE Reactivity Products
Case Histories Batch Polystyrene Reactor Runaway The Bhopal Disaster Methacrylic Acid Tankcar Explosion (video) Explosion and Fire Caused By a Runaway Decomposition Mini Case Histories

Hazards Awareness and Reduction An Introduction to Reactive and Explosive Materials (video) Acrylic Monomers Handling The Hazards of Hydroxylamine Chemical Reactivity Hazards (web-based) Introduction to Inherently Safer Design

Emergency Relief Systems Design for Overpressure and Underpressure Protection Unit Operations Laboratory Experiment for Runaway Reactions and Vent Sizing Relief System Design for Single- and Two-Phase Flow

RMR Reactivity Management Roundtable Kickoff Meeting Las Vegas, Nevada
October 23, 2003 Most Recent Meeting Houston, Texas June 1, 2005

DIERS Users Group AIChE Design Institute for Emergency Relief Systems
DIERS Users Group Meetings See for schedule

DIERS Conference 3rd International Symposium on Runaway Reactions and Pressure Relief Design Cincinnati, Ohio October 31 - November 4, 2005 To be held in conjunction with 2005 AIChE Annual Meeting

DIERS Conference Topics
1 Theoretical and Experimental Reactivity Screening 2 Best Practices and Standards for Managing Chemical Reactivity ERS Design for Reactive Systems 3 – Computational Methods 4 – Experimental Methods 5 – Fire Exposure 6 Effluent Handling Design for Reactive Systems

Loss Prevention Symposium
40th Annual Loss Prevention Symposium Orlando, Florida April 23-26, 2006 Loss Prevention: Past, Present, and Future Fire, Explosion and Reactive Hazards Hazard Aspects of Combustion Equipment Hazards & Risks Associated with Alternate Energy Systems Mechanical Integrity Case Histories and Lessons Learned

Continuing Education Courses
AIChE / ASME “Identifying and Managing Chemical Reactivity Hazards” Mary Kay O’Connor Process Safety Ctr ABS Group / Walt Frank

Chemical Reactivity Hazards

Contact Information Robert W. Johnson Unwin Company 1920 Northwest Blvd, Suite 201 Columbus, OH USA (614)

2005 SACHE Faculty Workshop

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