Anhydrous vs. Aqueous Ammonia: What the Difference Means for Removal

Two very different products

Anhydrous ammonia is pure anhydrous ammonia, stored as a liquefied gas under pressure. It is the refrigerant in nearly every large industrial cold storage plant, food processor and packing house in California.

Aqueous ammonia is ammonia dissolved in water, typically at 19% or 29% concentration, stored in atmospheric or low-pressure tanks. It is the reagent used in SCR and other NOx control systems at power plants, cogeneration facilities, biomass plants and water treatment sites.

How removal differs

Anhydrous removal is a pressure problem. You are working with a two-phase system, and both liquid and vapor have to be recovered, usually with push/pull compression and careful vessel-by-vessel sequencing.

Aqueous removal is closer to a liquid transfer. Pumps move the solution into tankers or totes, and the main concerns are vapor control at the tank opening, containment under every connection, and recovering the heel at the bottom of the tank so it can be cleaned or inspected.

Shared hazards

Both products are corrosive to skin, eyes and the respiratory tract, and both produce hazardous vapor. Aqueous ammonia is frequently underestimated because it sits in an unpressurized tank, but an open 29% tank on a hot Central Valley afternoon will produce vapor concentrations that require respiratory protection.

Gas monitoring, full PPE, exclusion zones and a written plan apply to both jobs, every time.

Getting the scope right

Before quoting either job, we confirm concentration, total volume, vessel fittings, site access for a tanker, and where the product is going afterward. Those five answers determine crew size, equipment and duration.