Thursday, April 18, 2013

Texas Explosion Highlights Dangers of Anhydrous Ammonia

Nat Geo - A fertilizer plant in the community of West, Texas that exploded on Wednesday to deadly effect was known to produce and store a volatile and potentially dangerous form of nitrogen-based fertilizer known as anhydrous ammonia. 

Many fertilizer plants either produce or use anhydrous ammonia—a gas that is one part nitrogen and three parts hydrogen—as a base for creating different fertilizer types, said Kurt Steinke, a soil scientist at Michigan State University (MSU).

"Anhydrous ammonia can be combined with different compounds, such as nitric acid, sulfuric acid, or even carbon dioxide from the atmosphere to produce the different kinds of fertilizers that we use today," he said.

Anhydrous ammonia—often referred to as simply ammonia—can be cheaply manufactured and is an effective fertilizer in its own right. But producing it requires intense heat and it must be stored at high pressures.

"When used in agriculture anhydrous ammonia is compressed into a liquid and must be stored under high pressure in specially designed tanks.  When the air temperature around the tank increases the temperature of the liquid inside the tank increases causing the liquid to expand thus increasing the internal tank pressure," Steinke said. "If you have a leak in the ammonia tank ... the liquid can quickly convert to a gas rapidly combining with body moisture to cause severe dehydration and chemical burns."