ELA997: Unit 1 - Ammonium Nitrate, Hydrogen and Ethylene ...

Copyright ©American Institute of Chemical Engineers 2018. All rights reserved.

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SAChE® Certificate Program

Level 3, Course 3.3: Common Chemicals and Their Major Hazards

Unit 1 – Ammonium Nitrate, Hydrogen and Ethylene

Narration:

[No narration]


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Getting Started

Narration (male voice):

If this is your first time taking a SAChE course, please take a few minutes to explore the interface.

This slide will explain how to use the controls to navigate through the course. All of the units in

the course use the same interface.

This interface has four main features that you should be aware of:

• Here is the left navigation bar. It contains a list of the slides as well as the narrative

transcript. At any point in the course, if you would like to revisit any content, click the

slide title to jump back.

• You may also use the Previous button on the bottom of the player. To advance forward,

use the Next button.

• The Search feature allows you to search for content using any word in the current unit.

• On the top menu bar you will find the Help, Abbreviations, Glossary, Resources and Exit

options. The resources included in this course include any unit-specific attachment as


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well as a printable copy of the unit slides and narrative. Use the Exit tab to leave this

unit at any time.

Click the arrows if you want to learn more about the interface features. Click ‘Next’ when you’re

ready to continue.


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About This Training Program

Narration (female voice):

Welcome to the American Institute of Chemical Engineers’ online Process Safety training

program. This course will introduce you to some common industrial chemicals and their major

hazards.

In this course, we will examine nine common chemicals:

1. Ammonium nitrate;

2. Hydrogen;

3. Ethylene;

4. Chlorine;

5. Ammonia;

6. Benzoyl peroxide as an example organic peroxide;

7. Ethylene oxide as an example epoxide;

8. Hydrogen fluoride; and

9. Sulfuric acid.

These chemicals are being covered in this course because they have played a role in numerous


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industrial or transportation incidents that resulted in injury or death. They are also ubiquitous;

due to their wide usage and/or large production volumes, you are likely to encounter these in

your career. When you do, it is important that you are aware of the hazards associated with

them. These are obviously not the only hazardous materials you will encounter in your work but

they are some of the most common.

Technology exists to handle these chemicals safely. As an engineer, you will be part of the team

responsible for ensuring that they are handled properly.


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Course Introduction


This course is divided into four units:

• Unit 1 – Ammonium Nitrate, Hydrogen and Ethylene;

• Unit 2 – Chlorine and Ammonia;

• Unit 3 – Organic Peroxides and Epoxides; and

• Unit 4 – Hydrogen Fluoride and Sulfuric Acid.

We have included the discussion of two to three chemicals in each unit simply for the purpose

of organizing the material into four units. The pairing of chemicals in each unit does not imply

that there is a unique relationship between them.

Each unit takes about 30 to 45 minutes to complete. At the end of each unit, you will be

presented with a quiz. You must pass the quiz in order to have the unit marked as complete so

be sure to pay close attention to the content and answer all of the review questions along the

way. After completing all of the units in the course, you will take a final exam. You must pass the

exam to have the course marked as completed.


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Objectives


By the end of each unit of this course, you will be able to do the following for all of the

chemicals covered in that unit:

• Identify their common names, the physical states in which they are generally stored and

shipped, and their primary applications;

• Identify the primary hazards associated with the chemicals;

• Identify the inherent characteristics of these chemicals that make them hazardous; and

• Describe incidents that have occurred involving these chemicals.


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Types of Hazards


Before we begin to explore individual chemicals, let’s review some key hazard terms. As you

know, hazards in the process industries include:

• Flammability;

• Toxicity;

• Instability; and

• Corrosivity.

[Male voice]

Click each term to review its meaning.


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Flammability (Slide Layer)

[When “Flammability” is clicked…]

Flammability is the ability of a substance to ignite and be consumed by fire.


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Toxicity (Slide Layer)

[When “Toxicity” is clicked…]

Toxicity is the quality, state, or degree to which a substance is poisonous and/or may chemically

produce an injurious or deadly effect upon introduction into a living organism.


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Instability (Slide Layer)

[When “Instability” is clicked…]

Instability is the degree of intrinsic susceptibility of a material to release energy through self-

reaction (polymerizing, decomposing or rearranging).


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Corrosivity (Slide Layer)

[When “Corrosivity” is clicked…]

Corrosivity is the ability of a material to cause visible destruction of, or irreversible damage to,

living tissue by chemical action at the site of contact. These materials can begin to cause

damage as soon as they touch the skin, eyes, respiratory tract or digestive tract.


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SECTION 1: Ammonium Nitrate

Narration:

[No narration]


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Description


Let’s begin our exploration of common chemicals with an introduction to ammonium nitrate.

Ammonium nitrate (often referred to by its abbreviation, AN) is a colorless or white crystalline

solid. It’s often sold in the form of a pellet.

AN is a commonly used fertilizer. However, when heated to high temperature, it can become

dangerously unstable and potentially detonate. Later in this section, we’ll review some major

incidents that occurred due to this instability.


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Chemical Structure and Properties


Ammonium nitrate has the chemical formula NH4NO3, as illustrated here.

AN is the nitrate salt of the ammonium cation. The nitrate anion makes AN a strong oxidizer.

While not flammable itself, as an oxidizer, AN will accelerate the combustion of other materials.


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NFPA 704 Diamond


The National Fire Protection Association (NFPA) Standard 704 diamond is shown here.

The health (left blue), flammability (top red) and instability (right yellow) hazards of a material

are ranked from zero to four with four indicating the highest hazard level. Symbols in the

bottom white diamond indicate special hazards.

The NFPA diamond is intended for use by first responders. It provides a simple, pictorial

summary of the hazards associated with a material under emergency conditions, such as fire or

loss of containment.

For more information on the NFPA diamond, see the SAChE course on Fire Hazards.


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NFPA 704 Diamond (continued)


By looking at the NFPA 704 diamond for AN shown here, you can see that AN has a high level of

instability hazard, has no significant health hazard, and is not flammable but can participate in

fire as oxidizer.

[Male voice]

Explore the hazards associated with AN by clicking each colored diamond. When you do, you

will see the NFPA definition of the hazard number shown.


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Red diamond (Slide Layer)

[When the red-0 diamond is clicked…]

Will not burn under typical fire conditions.


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Yellow diamond (Slide Layer)

[When the yellow-3 diamond is clicked…]

Capable of detonation or explosive decomposition or explosive reaction but requires a strong

initiating source or heating to high temperature under confinement before initiation.


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White diamond (Slide Layer)

[When the white-OX diamond is clicked…]

Possesses oxidizing properties.


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Blue diamond (Slide Layer)

[When the blue 0 diamond is clicked…]

No hazard beyond that of ordinary combustible material.


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Ammonium Nitrate Applications


Now let’s look at applications for ammonium nitrate.

We mentioned that AN is a common fertilizer. The agricultural industry is the largest user of

ammonium nitrate. It’s used directly as a fertilizer and it is also used to produce other fertilizers.


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Production of Explosives


Ammonium nitrate is also used as an oxidizer in the production of commercial explosives for

uses such as rock blasting. When ammonium nitrate is combined or contaminated with a

combustible material, such as fuel oil, an explosive mixture exists since the mixture contains

both a fuel and an oxidizer. Since ammonium nitrate and fuel oil are readily available, this

mixture has been used by terrorists, such as the Oklahoma City bomber.


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Other Applications


Smaller quantities of ammonium nitrate are used in various other applications, such as:

• A raw material for the production of nitrous oxide gas;

• In the production of vehicle air bags;

• In medical instant cold packs; and

• As a nutrient in the production of antibiotics and yeasts.


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Hazards of Ammonium Nitrate


Now let’s look at hazards posed by ammonium nitrate in more detail.

First, as we noted, AN is capable of detonation or explosive decomposition when exposed to a

strong initiating source.

As an oxidizer, AN can react with combustible materials, allowing them to burn without an air

supply (oxygen for combustion is available from the nitrate anion in the AN molecule). If a

material is burning in air, AN can accelerate the combustion. Thus, it is dangerous to store AN

near combustible materials.


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Thermal Instability


The greatest hazard of AN is thermal instability. This material is subject to rapid decomposition;

the mechanism and rate of decomposition vary with temperature.

Pure AN is stable at room temperature. Low temperature AN decomposition is endothermic.

The heat input required for this reaction is comparable to that required to boil water. Small

amounts of ammonia and nitric acid vapor may be released at ambient temperatures but this

reaction is not self-accelerating.


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Thermal Instability (continued)


Above about 200°C, AN becomes thermally unstable. Decomposition at this temperature

becomes exothermic and self-accelerating. Toxic oxides of nitrogen (NO, NO2, and N2O) plus

water, O2 and N2 are produced. Large volumes of gas are generated.

If a fire is the source of the high temperature, the produced oxygen and nitrogen oxides can

escalate the event by supporting the existing fire as oxidizers.


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With Increasing Temperature…


As the temperature rises…

• The rate of decomposition increases; and

• The decomposition reaction becomes more exothermic.

Under the right conditions, the decomposition reaction can reach detonation velocities. Recall

that a detonation occurs when the reaction front moves faster than the speed of sound. The

resulting explosion is much more forceful than other types of explosions. We’ll see some

examples of the force of an AN explosion in a few minutes, when we review incidents involving

this material.

For more information on detonation, see the SAChE course on Explosion Hazards.


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Detonation


The detonation of AN can be initiated by:

• A shock produced by an explosive charge; or by

• Heating of the AN to a high temperature under confinement.


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Incidents Involving Ammonium Nitrate


We’ll conclude our discussion of ammonium nitrate by presenting a couple of incidents involving

this chemical:

• The SS Grandcamp explosion in Texas City, Texas; and

• The West Texas Fertilizer explosion.


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SS Grandcamp, Texas City, Texas


A disaster that occurred in Texas City, Texas shortly after the end of World War II is generally

considered the worst industrial incident in American history. On April 16, 1947, the cargo ship,

SS Grandcamp, was docked in the port of Texas City, Texas. The vessel’s cargo included

approximately 2,100 metric tons of ammonium nitrate packaged in paper bags.

Around 8:00 a.m., smoke was spotted in the cargo hold. Over the next hour, attempts to

extinguish the fire or bring it under control failed.

At 9:12, the vessel detonated, causing enormous destruction throughout the port. The blast

leveled nearly 1,000 buildings and even knocked two planes out of the sky. The official casualty

estimate was 567. More than 5,000 people were injured, with 1,784 admitted to 21 area

hospitals.

You will recall that a strong initiator is required to detonate AN. In this case, the initiator was

high temperature along with confinement. The high temperature was generated by the

preceding fire and the use of steam to try to extinguish the fire. The necessary confinement was

provided by the bags of AN packed together inside the ship’s hold.


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Part 2


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West Fertilizer Company Explosion


On April 17, 2013 a fire broke out in a fertilizer storage and distribution facility in the town of

West, Texas. The facility stored large amounts of ammonium nitrate for use as a fertilizer. The

fire caused approximately 27 metric tons of ammonium nitrate to detonate. The initiator was

the same as at Texas City in 1947 – fire-induced high temperature and confined material.

The site itself and buildings near the site were destroyed. The explosion caused 15 fatalities –

most of them firefighters – and many more injuries. It led to extensive damage and destruction

in the town.

[Male voice]

For more details on this event, click the video icon to watch a video produced by the U.S.

Chemical Safety Board (CSB).


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Part 2


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Part 3


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Part 4


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West Texas Video (Slide Layer)


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SECTION 2: Hydrogen

Narration:

[No narration]


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Description


Here in Section 2, we’ll discuss hydrogen.

At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic,

but highly flammable gas. It can be liquefied for storage and transportation. With a normal

boiling point of 20°K, it is cryogenic when in its liquid state.

Hydrogen is widely used in industry.


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Chemical Structure and Properties


Hydrogen has the chemical formula H2 and is sometimes referred to by that formula rather than

its full name. With its low molecular weight, it is much lighter than air at ambient conditions.

A large number of tragic industrial incidents have begun with the release of a flammable gas or

vapor. Hydrogen is a highly flammable gas that is used in large quantities. It is easily ignited and

more likely than most other gases to transition from deflagration to detonation when ignited in

a congested area.


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NFPA 704 Diamond


The NFPA 704 diamond for H2 is shown here. You can see that flammability is the only

significant hazard of H2 – but it is a serious hazard.

[Male voice]

Click on the colored diamonds if you would like to see the NFPA definitions of the hazard levels

given for H2.


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Burns readily. Rapidly or completely vaporizes at atmospheric pressure and normal ambient

temperature.


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Normally stable, even under fire conditions.


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[When the white diamond is clicked…]

No special hazards.


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[When the blue-0 diamond is clicked…]

No hazard beyond that of ordinary combustible material.


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Hydrogen Applications


The primary use of hydrogen is in the production of ammonia.

The next largest single user of hydrogen is oil refineries. These facilities use hydrogen in

processes such as reforming and hydrotreating.

Hydrogen is also used in the production of other chemicals for a variety of industries.


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Vehicle Fuel


Liquid hydrogen has long been used as fuel for space travel. Liquid and gaseous hydrogen are

now being used as a fuel for road transportation and in fuel cells.


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Hazards of Hydrogen


Now let’s discuss what makes hydrogen so flammable.

The flammability hazard of hydrogen can be quantified using a number of parameters. Let’s look

first at flammability range. A wide range of hydrogen/air mixtures will ignite. In other words,

hydrogen has a large flammability range. The range is much larger than that of typical

hydrocarbons, as you can see by the lower flammable limits (LFLs) and upper flammable limits

(UFLs) listed in this table.


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Easily Ignited (Low MIE)


Hydrogen is also easily ignited. Note from this table that hydrogen has a much lower minimum

ignition energy (MIE) than that typical of hydrocarbons.


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Minimum Oxygen Required


Hydrogen does not need a lot of oxygen to burn. The limiting oxygen concentration (LOC) of

hydrogen is lower than that typical of hydrocarbons.


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Explosion Potential, Particularly in Congested Areas


Once ignited, hydrogen has the potential to produce violent vapor cloud explosions (VCEs).

Beware of the use or storage of hydrogen in congested process areas or near pipe racks, as

these areas are particularly susceptible to hydrogen vapor cloud explosions.


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High Flame Speed


Additionally, due to hydrogen’s high flame speed, it is more likely than most gases to transition

from a deflagration to detonation in a congested area.


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Potential Mitigating Factor – Density


A mitigating factor with regards to hydrogen’s flammability hazard is its density. Being much

lighter than air, hydrogen will disperse quickly if it can escape upward when released.

This is not true of hydrogen vaporizing from spilled liquid. The very low temperature of the

vapor initially causes it to be heavier than ambient air until it warms up.


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Leaks are Difficult to Detect


Hydrogen has an additional fire hazard. As we mentioned, H2 is a colorless, odorless gas. It

burns with a pale blue, almost invisible flame. Thus, a hydrogen leak is difficult to detect.

The use of flame resistant clothing (FRC) is critical when working anywhere hydrogen is used or

stored since you could walk into a hydrogen flame without seeing it!


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Incidents Involving Hydrogen


On the next couple of slides, we’ll review two incidents involving hydrogen:

• The Hindenburg airship disaster; and

• The Silver Eagle Refinery incident.


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Hindenburg Airship Disaster


In May of 1937, the Hindenburg was completing its flight from Frankfurt, Germany to Lakehurst,

New Jersey. Onboard the large airship were 36 passengers and 61 crew members.

While attempting to moor, the airship suddenly burst into flames. A spark may have ignited the

hydrogen used to provide lift for the airship. Rapidly falling 200 feet to the ground, the fabric

skin of the vessel incinerated within seconds. Thirteen passengers, 21 crewmen, and one civilian

member of the ground crew died. Most of the survivors suffered substantial injuries.

After this event, airship travel was no longer popular. Modern blimps are filled with helium, an

inert gas, rather than hydrogen.


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Part 2


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Part 3


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Silver Eagle Refinery


A massive explosion and fire occurred at the Silver Eagle Refinery on November 4, 2009, in

Woods Cross, Utah. The incident was caused by a rupture of a pipe that had become

dangerously thin from corrosion.

The catastrophic rupture occurred in a ten-inch pipe at the bottom of a reactor. The rupture led

to a massive release of hydrogen, which caught fire quickly. A vapor cloud explosion (VCE) sent a

blast wave across the refinery into a subdivision. The blast wave damaged over 100 homes, two

severely. One home was knocked off its foundation.

Fortunately, no one was seriously injured. There were four workers near the process unit at the

time of the explosion. They were blown to the ground but were not seriously injured. A fifth

worker escaped injury by just minutes, having been taking readings next to the pipe that failed

just one to two minutes before the release.


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SECTION 3: Ethylene

Narration:

[No narration]


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Description


In this last section of Unit 1, we’ll discuss ethylene. Ethylene is a highly flammable, colorless gas.

It is called ethene by the International Union of Pure and Applied Chemistry (IUPAC).

Ethylene is widely used as an intermediate in the chemical industry. It is one of the largest

volume organic chemicals produced globally.

Ethylene is typically transported as a compressed gas or as a cryogenic liquid with a boiling point

of -104°C.

The primary hazards of ethylene are fire and explosion. It is important to know that, like

hydrogen, ethylene is more likely than most gases to transition from deflagration to detonation

when ignited in a congested area. Unlike hydrogen, ethylene has significant instability and

toxicity hazards as well.


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Chemical Structure


The chemical formula for ethylene is C2H4. The double carbon-carbon bond makes ethylene

more reactive than alkanes like ethane. The breaking of this bond is accompanied by a high

energy release.


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NFPA 704 Diamond


The NFPA 704 diamond for ethylene is shown here. Note the high flammability hazard and less

severe toxicity and instability hazards.

[Male voice]

Click on the colored diamonds to see the definitions of the hazard levels shown.


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Burns readily. Rapidly or completely vaporizes at atmospheric pressure and normal ambient

temperature.


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Readily undergoes violent chemical changes at elevated temperatures and pressures.


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[When the white diamond is clicked…]

No special hazards.


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[When the blue-2 diamond is clicked…]

Can cause temporary incapacitation or residual injury.


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Ethylene Applications


Ethylene is primarily used as a monomer for the production of polyethylene. Large quantities of

ethylene are required because polyethylene is the most widely used plastic in the world.

Ethylene is also widely used as an intermediate in the chemical industry, including in the

production of other plastics, anti-freeze solutions and solvents.


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Hazards of Ethylene


There are flammability, instability, and health concerns associated with ethylene.

Ethylene is highly flammable; therefore, fire and explosion are its primary hazards.

Ethylene also has polymerization and decomposition hazards, but elevated temperature is

required for these reactions to occur.

Finally, ethylene is toxic, but exposure to relatively high concentrations is required for there to

be adverse health effects. Exposure to thousands of parts per million may cause headache,

dizziness, anesthesia, drowsiness, or other central nervous system effects.


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Flammable and Explosive


Some of the properties of ethylene that cause it to be a highly flammable gas are its wide

flammability range and low minimum ignition energy, or MIE.

The flammability range at atmospheric pressure is about three to 36%, broader than the two to

10% range typical of hydrocarbons.

Ethylene’s MIE is low – just 0.06 millijoules. This is not as low as the 0.018 millijoules of

hydrogen but well below that of methane at 0.28 millijoules. This low MIE means it does not

take a very strong ignition source to ignite ethylene.

Finally, like hydrogen, ethylene is more likely than other gases to transition from a deflagration

to detonation in congested areas. This means that ethylene explosions can, under certain

conditions, be very forceful.


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Dispersion


Unlike hydrogen, ethylene does not disperse easily. At ambient temperature, ethylene is only

slightly lighter than air and cold ethylene gas evolved from cryogenic liquid is heavier than air.

The American Chemistry Council (ACC) reports that a flammable ethylene cloud can extend up

to 0.8 kilometers beyond the visible fog of a large low temperature leak.


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Instability


Hazardous polymerization of ethylene can occur at high temperatures or in the presence of

materials such as activated carbon or molecular sieve.

Decomposition with rapid pressure build-up can occur at temperatures above 180°C and

pressure above 1136 kilopascal.

Explosions have occurred in pipelines due to heating by compression and during ethylene drying

operations.


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Incident Involving Ethylene


Before we conclude our discussion of ethylene, let’s examine an incident that demonstrates the

force with which ethylene can explode.


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Phillips 66


On October 23, 1989, a massive explosion demolished the Phillips 66 Company polyethylene

plant in Pasadena, Texas (a Houston suburb), when more than 38,500 kilograms of ethylene

dissolved in isobutane was instantaneously released to the atmosphere.

The incident investigation indicated that a block valve thought to be closed during a

maintenance operation on a high density polyethylene reactor was actually open. A product

plug was all that kept the high temperature/high pressure reactor contents from venting to the

atmosphere. At about 1:00 pm, more than 99% of the reactor contents were released almost

instantaneously when the plug apparently broke loose.

Within 90 to 120 seconds, this gas mixture found an unidentified ignition source and exploded

with the force of 2.2 metric tons of TNT. The initial explosion threw debris 8 kilometers and

shattered windows a kilometer away. It registered between 3 and 4 on the Richter scale on

Houston’s Rice University seismographs. Following this initial explosion, there was a series of

further explosions and fires. One eye-witness reported hearing ten explosions that afternoon.

In all, 23 lives were lost and 314 people were injured. More than 100 workers trapped by the


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fire were rescued by U.S. Coast Guard fireboats and evacuated across the Houston Ship Canal.

Capital losses were initially estimated at over $715 million. Business disruption losses were

nearly as great, $700 million.

Part 2


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Part 3


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Part 4


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Part 5


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Part 6


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Part 7


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Unit 1 Summary


We’ve reached the end of the first unit in the Common Chemicals and Their Major Hazards

course. Having completed this unit, titled “Ammonium Nitrate, Hydrogen and Ethylene,” you

should now be able to do the following for each of the three chemicals discussed in this unit:

• Identify their common names, the physical states in which they are generally stored and

shipped, and their primary applications;

• Identify the primary hazards associated with the chemicals;

• Identify the inherent characteristics of these chemicals that make them hazardous; and

• Describe incidents that have occurred involving these chemicals.

In Unit 2, we’ll explore chlorine and ammonia. But first, please take the quiz for Unit 1 beginning

on the next slide.

ELA997: Unit 1 - Ammonium Nitrate, Hydrogen and Ethylene ...

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