# Presentation: 571464

## How Can Reactive Chemical Incidents Be Prevented?

**Dennis C. Hendershot (speaker)**
**Albert Ness**
**Rohm and Haas Company**
**Engineering Division**
**Croydon, PA, USA**
**Dhendershot@rohmhaas.com**
**For presentation at the**
**Joint EFCOG/DOE Chemical Management Workshop**
**March 8-10, 2005**
**Washington, DC**

## Agenda

- Discuss three reactive chemistry incidents
- In all three cases, no chemical reaction was ***INTENDED.***
- Review two tools for identifying reactive chemistry hazards
- Briefly review checklist for design of reactive chemistry processes

## Three incidents

- Scrubber packing failure due to reaction with process materials
- Decomposition during a blending operation
- Fire from mixing of solid spills

## Three incidents

***Scrubber packing failure due to reaction with process materials***
- Decomposition during a blending operation
- Fire from mixing of solid spills

## Scrubber packing failure due to reaction with process materials

## What happened

- Power failure shuts off recirculation pumps and process water; SO2 blower (steam driven) continued to run
- Acid vapors continued to flow to absorbers
- Flow not shutoff manually per instructions
- When power was restored acid unit  restarted –
- high temperature observed at top of acid scrubber
- abnormal pH readings observed (Temp high but within range)

## Consequences

- SO3 reacted with scrubber packing
- Plant had to be run at reduced rates for several months
- Cost was high enough to appear in company annual report

## Why?

- Reaction between SO3 and Polypropylene unknown to personnel reviewing process
- Reaction known others in company, but not at this location
- Scenario not identified in the Process Hazard Analysis (PHA)
- Unit shifted to keeping blower on to get vapors to the stack for environmental purposes

## Three incidents

- Scrubber packing failure due to reaction with process materials
***Decomposition during a blending operation***
- Fire from mixing of solid spills

## Process description

- Blending only, no reaction intended
-  50/50 weight % mixture of Linseed Oil and Cyclohexanone Oxime
- Dissolve the solid oxime at elevated temperature
- Rapidly cool solution in an external heat exchanger to make specified particle size slurry

- Linseed Oil – a mixture of glycerides of unsaturated C18 fatty acids:
-  Oleic acid (1 double bond)
-  Linoleic acid (2 double bonds)
-  Linolenic acid (3 double bonds)

## Old production unit

## New production unit

## Process change

- Mix vessel temperature increased from ~95 C to ~130 C
- Increased heat loss in longer pipe from mix vessel to heat exchanger in new system
- Same heat exchanger inlet temperature
-  Management of change review held
-  Did not identify any hazard associated with increased temperature

## First batch at higher temperature

- Temperature increased steadily over several hours from ~133 C to ~138 C
- Then, rate of temperature increase began to accelerate, ultimately reaching > 170 C
- Pressure increase opened reactor relief valve on mix vessel discharging a two phase mixture to the atmosphere

## Consequences

- Relief valve size was adequate to protect the vessel from rupture
- By good luck, NOT DESIGN
- Relief valve not designed for unknown reaction
- No injuries
- Contaminated neighboring property
- Significant government agency involvement

## Results of laboratory ARC tests

-  Cyclohexanone Oxime thermal stability
-  Decomposition occurs at ~ 180 C
-  Oxime/oil 50/50 mixture
-  Decomposition occurs at ~ 128 C
-  Normal product, without any contamination or other abnormal processing

## ARC results – oxime

## ARC results - mixture

## What happened?

- Increasing the batch temperature from 95 C to 130 C exceeded the decomposition temperature for a normal product mixture
- Decomposition did not require contamination or other process upset

## Specific actions

- Review all other products manufactured in the plant for potential decomposition hazards
- Improve management of change procedures to better recognize potential decomposition hazards from future changes
- Review all future new products for potential decomposition hazards

## Three incidents

- Scrubber packing failure due to reaction with process materials
- Decomposition during a blending operation
***Fire from mixing of solid spills***

## Fire from mixing of solid spills 

- Fire in production area near reactor
- Fire occurred under panel box
- Electrical and instrument wiring severely damaged
- 2 Reactor trains down for 1 month
- Total cost ~ $1 Million

## Consequences

## What happened

*** These can react, generating heat and fire**

## Common theme

**	****There is a common theme in all three incidents:**
**	****THE PEOPLE OPERATING THE PROCESS WERE NOT AWARE OF THE POTENTIAL FOR A REACTIVE CHEMISTRY INCIDENT.**

## General lessons

- In a process hazard or management of change review, confirm that all materials and mixtures are stable at the maximum credible process temperature
- Absence of data does not mean that there is no decomposition or reaction, it may mean that nobody has done any testing
- Understand potential chemical interactions, even if you do not intend for a reaction to occur

## General lessons

- Be suspicious of energetic and potentially reactive chemical structures
- Double bonds, multiple double bonds, triple bonds
- Reactive groups
- Nitro groups, oximes, peroxides, etc.
- Strained ring structures, ring structures containing nitrogen, sulfur, oxygen, anything other than carbon
- Get advice from a chemist with experience with thermal decomposition, stability

## Some examples

## Free on-line resource

- _[http://info.knovel.com/ccps/](http://info.knovel.com/ccps/)_
- Available free courtesy of  US OSHA, US EPA, American Chemistry Council (ACC), Synthetic Organic Chemical Manufacturers Association (SOCMA), Center for Chemical Process Safety (CCPS), and Knovel

## Overall process

## Two specific tools

- Interaction Matrix
- Chemistry Hazard Analysis

## Generic chemical reaction

## Partial interaction matrix

**Notes:**
The interaction matrix has been described elsewhere, for example by 
Leggett, D. J.  in Process Safety Progress (Spring 1997
“Management of Chemical Plants Using Chemical Compatibility Information.” 16, 1), 8-13

It   lists all of the materials, materials of construction, likely contaminants, potential sources of energy, process utilities (such as steam, water, nitrogen, compressed air, ethylene glycol coolant and heat transfer oil), and other relevant parameters along each axis of the matrix. 
Then, ask what happens for each interaction where the matrix columns and rows intersect and document the answers. 
An interaction matrix for our example reaction is given in the paper.

## A famous process

**Double, double toil and trouble;**
**Fire burn, and cauldron bubble.**
**Fillet of a fenny snake,**
**In the cauldron boil and bake;**
**Eye of newt and toe of frog,**
**Wool of bat and tongue of dog,**
**Adder's fork and blind-worm's sting,**
**Lizard's leg and owlet's wing,**
**For a charm of powerful trouble****,**
**Like a hell-broth boil and bubble.**
**Double, double toil and trouble;**
**Fire burn, and cauldron bubble.**
**- Macbeth, Act IV, Scene 1**

## Interaction matrix

## NOAA Chemical Reactivity Worksheet results for Incident 1 (SO3/Polypropylene)

| Chemical | Sulfur Trioxide | Polypropylene |
| --- | --- | --- |
| Sulfur Trioxide | Water & Air Reactive | B1, C1, D4 |
| Polypropylene | B1, C1, D4 | --- |

**B1 - May cause fire**
**C1 - Heat generation by chemical reaction, may cause pressurization**
**D4 - Nonflammable gas generation; causes pressurization**

**Notes:**
This is part of the compatibility chart for the polymerization of MMA in an extruder. More examples and an article about creating them are in your notes. Sometimes you will see a 1, 2, or 3 rating for level of hazard instead of the letters shown here.
Be sure to include:
Materials of construction, steel in this example
utilities - air
common materials in the area  - gear oil
as well as the reactants, intermediates and products. 

Emphasize - We are striving to have compatibility charts made for all projects and processes. It’s development should begin in research as soon as a reaction route is identified.
We have a computer program with 4000 compounds. It is Desktop1 approved. Handout sheet on program
Do you have any questions about it?
Time = 3 - 5 minutes.

## NOAA Chemical Reactivity Worksheet

## Chemistry Hazard Analysis

- Abbreviated “HAZOP” of Chemistry
- Start with the chemical reaction:

## Chemistry Hazard Analysis procedure

- Apply HAZOP Guidewords to the reaction
- 	No		 Reverse
- 	More		 As Well As
- 	Less		 Other
- Not necessary to identify causes
- List consequences
- Make comments or recommendations

## Some examples

- NO reactant A, NO reactant B, NO Solvent, NO catalyst, NO reaction....
- MORE A, MORE B, MORE catalyst, MORE concentrated, MORE (HIGH) Temperature, MORE Feed time....
- LESS A, LESS B, LESS temperature, LESS reaction, LESS feed time.....
- REVERSE reaction, REVERSE order of addition...
- Other material AS WELL AS intended materials, Impurities AS WELL AS intended materials...
- OTHER – completely wrong material, no mixing, no cooling....

## Reactive Chemistry Design Checklist

## Questions to understand reactivity hazards

- What is the heat of reaction for all intended reactions? How about possible, but not intended reactions?
- What is the maximum adiabatic reaction temperature?

## Questions to understand reactivity hazards

- What is the maximum temperature from all process heating systems (assuming failure of all controls)?
- What is the maximum temperature to which the process material can be heated from other energy sources?
- For example, mechanical energy from pumping, agitation, grinding; microwave energy; other energy sources

## Questions to understand reactivity hazards

- Are all individual components of the mixture stable at the maximum attainable temperature?
- Raw materials, intermediates, products, by-products, catalysts, solvents, etc.
- Is the mixture stable at the maximum attainable temperature?

## Questions to understand reactivity hazards

- What is the minimum temperature from all process cooling systems (assuming failure of all controls)?
- What happens to the mixture at this temperature
- Freezing, precipitation, loss of reaction with accumulation of reactants, etc.

## Questions to understand reactivity hazards

- What is the effect of larger temperature and concentration gradients in production scale equipment?
- If you intend to do a chemical reaction, what are the reaction kinetics (intended reaction, side reactions, unintended reactions)?

## More detailed discussion

- See CCPS Safety Alert:  “A Checklist for Inherently Safer Chemical Reaction Process Design and Operation”
- Can be downloaded from
- _[http://www.aiche.org/ccps/safetyalerts.htm](http://www.aiche.org/ccps/safetyalerts.htm)_

## Chemistry haiku

**	****Laboratory.**
**	****Someone mixes chemicals.**
**	****Look! A reaction.**
**- Neil Dickinson**

**Don’t be surprised by a reaction!**