Where Does Anhydrous Ammonia Come from?

Anhydrous Ammonia

Ammonia in its purest form—without water—is known as anhydrous ammonia and is hygroscopic, which means it readily and hungrily absorbs any moisture with which it comes into contact. This means that it requires very large amounts of water to neutralize the effects of anhydrous ammonia, which is very caustic.

Ammonia is made from nitrogen and hydrogen and is one of the most widely used industrial chemicals in the country. While it is found naturally in the environment (and even in humans), it is also used in both industry and commerce and is essential for many biological processes.

Approximately 80 percent of the anhydrous ammonia that’s produced today is used as an agricultural fertilizer, but it is also used as a refrigerant, for water purification, and in the manufacture of plastic, leather, explosives, textiles, dyes, and pesticides. Anhydrous ammonia is also used in pollution control in a process called DeNOx. Its versatility means that anhydrous ammonia is used in countless applications on farms and in factories and manufacturing plants across the globe.

But where does this chemical come from? When farmers or manufacturers call for an order of anhydrous ammonia, how does this colorless, pungent gas come to be?

How Anhydrous Ammonia Is Transported and Stored?

At room temperature, anhydrous ammonia takes on a gaseous form. It’s clear and colorless but has a strong odor. Just how strong? Ammonia is detectable at very, very low concentrations of only 50 parts per million, which is usually in a gaseous form. However, in most applications, those who use anhydrous ammonia require it to be in liquid form instead of in a gaseous state. When compressed and/or cooled, anhydrous ammonia takes on a liquid state, and so must be stored under extreme pressure, and often at very low temperatures to prevent vaporization. Terminal tanks for anhydrous ammonia must dip below -28 degrees Fahrenheit to keep ammonia in liquid form.

Anhydrous ammonia is incredibly compressed and condensed. Just a cubic foot of anhydrous ammonia in a liquid state is equivalent to 855 cubic feet of ammonia gas. For this reason, retail storage tanks and nurse tanks made for anhydrous ammonia are carefully engineered to withstand high internal pressures and can hold up to at least 250 pounds per square inch. The terminal tanks that store anhydrous ammonia are cooled, which means that the pressure of the liquid anhydrous ammonia decreases dramatically. Terminal tanks that refrigerate ammonia to -28 degrees Fahrenheit have a storage pressure of less than 1 pound per square inch.

How Anhydrous Ammonia Is Produced?

Ammonia is produced naturally when organic material decomposes, including animals, plants, and animal waste—which is why materials like manure and other organic materials like compost are used for fertilizers. While ammonia is a common chemical compound found in our biological world, it must be produced to be used on the scale that manufacturers and growers use the chemical compound today. In 2019, U.S. producers created 16.41 million metric tons of synthetic anhydrous ammonia for industrial uses.

Anhydrous ammonia, also sometimes called “pure ammonia,” since it has not been diluted with water, is commercially manufactured using natural gas, air, and steam. How is anhydrous ammonia made? Producers of anhydrous ammonia start by removing sulfur from natural gas using hydrogen, which creates a byproduct of hydrogen sulfide. This hydrogen sulfide is then removed by passing the gas through “beds of zinc oxide.” This zinc oxide sets off a reaction with the hydrogen sulfide, forming two new byproducts: zinc sulfide and water. What’s left is a natural gas that’s very high in methane.

This high-methane natural gas is then heated to an incredibly high temperature—somewhere around 1,500 degrees Fahrenheit—and then is combined with steam and a catalyst like ferric oxide. These new additions cause the methane and steam to form carbon monoxide and hydrogen, and with enough water present in the steam, this carbon monoxide forms carbon dioxide and hydrogen.

Next, the carbon dioxide and carbon monoxide gas must be removed. This can be accomplished in multiple ways. One way is that the carbon monoxide and carbon dioxide are absorbed with a solution of ethanolamine solution. What’s left is highly pure hydrogen gas.

To this high-purity hydrogen gas, anhydrous ammonia producers add a catalyst like ferric oxide. They also add a very specific amount of air to the hydrogen gas—just enough to provide exactly one nitrogen atom for every three hydrogen atoms present in the gas. Finally, this gaseous mixture is compressed under a very high pressure to produce anhydrous ammonia.

The chemical formula is as follows:

3 H2 + N2 = 2NH3

This anhydrous ammonia can then be stored as a liquid by cooling it to -30 degrees Fahrenheit and maintaining that very high level of constant pressure.

The Haber Process

The production of anhydrous ammonia has a name: The Haber Process or sometimes the Haber-Bosch Process. This process combines nitrogen (which exists in the air) with hydrogen derived from natural methane gas. Unlike some chemical processes, this reaction is reversible. The production of ammonia is exothermic, which means it releases heat.

The Haber-Bosch process was the very first chemical manufacturing process for industrial use that uses high pressure to create a chemical reaction. By using a catalyst like iron (or ferric oxide), the reaction can happen at a lower temperature to make the production process simpler and easier.

Airgas Specialty Products: Your Reliable Anhydrous Ammonia Supplier (And More)

The creation of industrial anhydrous ammonia is a complicated one, but obtaining the pure ammonia you need for your farming, pollution control, refrigerant, or manufacturing processes shouldn’t be.

At Airgas Specialty Products, we not only aim to be your reliable supplier of anhydrous ammonia, but we also offer repairs, pump-outs, tank inspections, and preventative maintenance to keep you in constant operation no matter the reason you use the chemical. We have a fully-functional, dependable nationwide distribution network, which means that no matter where you are, we can get you the pure ammonia you need, and we also offer short-notice and after-hours delivery too.