Chapter 8: Crowl & Louvar CBE 465 4/12/2017 Chemical Reactivity Chapter 8: Crowl & Louvar

Chemical Reactive Hazard CBE 465 Chemical Reactive Hazard 4/12/2017 Chemical reactivity hazard: situation with potential for an uncontrolled chemical reaction, resulting in harm to people, equipment, or environment. Result could be: Violent release of heat, toxic or flammable materials Build up of excessive pressure Reaction could be: Self-reacting chemical (i.e., monomer) With other chemicals; intentional or otherwise Catalyzed by contamination, construction materials Exothermic and/or gas producing Due to incompatibility

Screening for Reactive Hazards CBE 465 Screening for Reactive Hazards 4/12/2017 Figure 8-1 Screening flowchart for reactive chemical hazards. An answer of “yes” at any decision point moves more toward reactive chemisty. See Section 8.2 for more details. (Source: R.W. Johnson, S.W. Rudy, and S. D. Unwin, Essential Practices for Managing Chemical Reactivity Hazards (New York: AIChE Center for Chemical Process Safety, 2003.))

Specific Chemical Reactive Hazard CBE 465 Specific Chemical Reactive Hazard 4/12/2017

Specific Chemical Reactive Hazard CBE 465 Specific Chemical Reactive Hazard 4/12/2017

Specific Chemical Reactive Hazard CBE 465 Specific Chemical Reactive Hazard 4/12/2017 http://response.restoration.noaa.gov/chemaids/react.html

Specific Chemical Reactive Hazard CBE 465 Specific Chemical Reactive Hazard 4/12/2017 Table AF-1: A few pyrophoric and spontaneously combustible categories and chemicals (these materials combust on exposure to air). Table AF-2: Some chemical structures susceptible to peroxide formation (the peroxides formed may become unstable and explode when disturbed). Table AF-3: Chemical categories susceptible to water reactivity. Table AF-4: Common water-reactive chemicals. Table AF-5: Typical oxidizers. Table AF-6: Some polymerizing compounds (these chemicals may polymerize rapidly with release of large amounts of heat).

Reactive Functional Groups CBE 465 Reactive Functional Groups 4/12/2017

Sources of Information CBE 465 Sources of Information 4/12/2017

Understanding Reactive Systems CBE 465 Understanding Reactive Systems 4/12/2017 Cooling Water Exothermic Reaction Runaway reactions can occur whenever exothermic chemistry is used. Why important: Common problem with exothermic reactions.

Understanding Reactive Systems CBE 465 Understanding Reactive Systems 4/12/2017

Runaway Reactions How? 1. Loss of coolant. 2. Increased temperature. CBE 465 Runaway Reactions 4/12/2017 How? 1. Loss of coolant. 2. Increased temperature. 3. Increased energy generation. High pressure due to: Vapor pressure of liquid. Vapor decomposition products. Larger vessels respond faster - less heat transfer thru walls!!! Some chemicals can achieve self heat rates of 100’s deg. C/min! Styrene, Acrylic Acid There are lots of ways for runaway reactions to occur. People somehow do not realize that a larger vessel will runaway faster since it has a lower surface to volume ratio with less heat losses.

Runaway Reactions Some ways for runaways to occur: Loss of cooling. CBE 465 Runaway Reactions 4/12/2017 Some ways for runaways to occur: Loss of cooling. Overcharge reactant. External fire. Mis-charge reactant. Low reaction temperature in semi-batch reactor. This is called a sleeping reactor. Loss of agitation. Some ways for this to occur. Two phase flow is a very challenging engineering problem. Most reactive runaways result in 2-phase flow thru relief and require a relief area 2 to 10 times larger than single phase relief.

Understanding Reactive Systems CBE 465 Understanding Reactive Systems 4/12/2017

Application of Calorimeter Data CBE 465 Application of Calorimeter Data 4/12/2017 Heat exchanger duty to achieve required reactor cooling Cooling water requirements and cooling water pump size Condenser size in a reactor reflux system Max conc. Of reactants to prevent overpressure in the reactor Reactor vessel size and pressure rating Type of reactor (batch, semi-batch, tubular) Reactor temperature control and sequencing Semi-batch reactor reactant feed rates Catalyst concentrations; max fill for batch and semi-batch reactors Alarm/shutdown setpoints Operating and emergency procedures Relief sizing and effluent treatment systems Solvent concentrations required to control reactor temperature Page 415 C&L 3rd ed.

Improving Reactive Safety CBE 465 Improving Reactive Safety 4/12/2017

4/12/2017 CBE 465

Improving Reactive Safety CBE 465 Improving Reactive Safety 4/12/2017

CBE 465 In-Class Exercise 4/12/2017 A company had a spray painting operation to paint automotive parts. The spray painting was done in a paint booth to reduce worker’s exposure and to collect any paint droplets that might be entrained in the exhaust air. The paint droplets were collected by fibrous filters. At the end of each day, the filters were removed, placed in plastic bags, and stored for disposal in a separate building. Due to environmental concerns over volatile emissions from paint solvents, the paint supplier reformulated the paint to use a less volatile solvent. This change was done in consultation with the paint company. Several test were done to ensure the reformulated paint worked well with the existing spray equipment and that the quality was satisfactory. The company switched to the reformulated paint. Several days later the disposal building caught on fire, apparently due to a fire started by the paint filters. Can you explain how this might have happened. Any suggestions for prevention?

CBE 465 In-Class Exercise 4/12/2017 A university lab expansion includes installation of a distribution system to provide gaseous oxygen from manifolded cylinders to a biochemical engineering laboratory. No chemical reactivity hazards have been previously identified for the lab facilities. Apply the screening method of Figure 8-1 to determine if any chemical reactivity hazards are expected.

Runaway Reactions - 4 CBE 465 4/12/2017 A picture from the 1940s showing a relief discharge thru the roof of a building.