Understanding Acrylonitrile

This "Chemical of the Quarter" excerpt is from the U.S. Coast Guard “Proceedings of the Marine Safety & Security Council” magazine, by LCDR Gretchen Bailey, Marine Inspector, U.S. Coast Guard Hazardous Materials Standards Division

What is it?
Acrylonitrile is a colorless to pale yellow volatile liquid that is soluble in water and used in common solvents. Technical-grade acrylonitrile is more than 99 percent pure and always contains a polymerization inhibitor.

Acrylonitrile is a reactive chemical that polymerizes (converts one compound into another) spontaneously, either when heated or in the presence of a strong alkali. I

How is it shipped?
Acrylonitrile is typically shipped as a liquid in low-pressure tank railcars, as liquid in tank barges, or by truck as liquid in non-pressure liquid tanks.

Why should I care?
Shipping concerns.
Acrylonitrile is a polymerizing cargo that can become explosive when heated or involved in a fire. This product has a very low flash point—30 degrees Fahrenheit—and using water to fight the fire may be inefficient. When this cargo is heated or burned, it may produce a toxic vapor of hydrogen cyanide gas, so it is essential to keep a safe distance during a fire. Additionally, its vapor is heavier than air and has been known to travel a considerable distance to an ignition source, then flash back to the spill.

Health concerns.
It is very toxic by ingestion, inhalation, or absorption through the skin. Symptoms of poisoning will begin with irritation of the eyes, limb weakness, difficulty in breathing, dizziness, and impaired judgment. If the degree of poisoning increases, the symptoms will progress to cyanosis, nausea, collapse and loss of consciousness, irregular breathing, convulsions, and respiratory arrest.

Because it is lighter than water, acrylonitrile will form a light surface sheen when spilled on the water. Sorbent booms, pillows, and other containment tools will be contaminated and must not be handled without appropriate personnel protective equipment. However, due to its moderately high solubility, acrylonitrile will quickly dissolve into the water column.

Fire or explosion concerns.
Acrylonitrile is flammable and has the capability to explode. This happens when the cargo is heated, causing a polymerization reaction, which is highly exothermic. If the cargo is involved with a fire, the fumes from the cargo are a poisonous gas and should be avoided.

It is essential for emergency responders to wear self-contained breathing apparatus and rubber overclothing (including gloves), and to combat the fire from a safe distance or protected location. The most efficient way to extinguish the fire is with dry chemical foam, alcohol foam, or carbon dioxide. With water, use spray or fog; do not use straight stream.

What is the Coast Guard doing about it?
Acrylonitrile is categorized as a “Subchapter D” cargo, regulated in 46 Code of Federal Regulations Part 30.25. This cargo is carried in tank barges and ships that are required to be inspected by the Coast Guard.

Required design and construction standards for these vessels include:
· being double-skinned,
· having spacing between the hull and the inner tank wall,
· employing individual tank manifolds and pumps to avoid cross-contamination,
· utilizing a separate tank venting facility,
· being capable of internally circulating the tanks,
· being capable of being ventilated.

For more information:
Full article is available at http://www.uscg.mil/proceedings/fall2010.

Subscribe online at http://www.uscg.mil/proceedings/subscribe.asp.