Industrial Ammonia & Urea: Glossary of Terms

A

  • Anhydrous Ammonia (NH3): Pure, water-free ammonia. At room temperature and atmospheric pressure, it is a pungent gas. For industrial use, it is stored as a liquid under high pressure.
  • Aqueous Ammonia (NH4OH): Also known as Ammonium Hydroxide or "Aqua." A solution of ammonia in water, typically handled at concentrations of 19%, 24.5%, or 29%.
  • ASME Section VIII: The portion of the ASME Boiler and Pressure Vessel Code that governs the design, fabrication, and inspection of pressure vessels used in ammonia service.

C

  • CAS Number: The Chemical Abstracts Service registry number. For Anhydrous Ammonia, it is 7664-41-7.
  • Chloramination: A water treatment process where ammonia is added to chlorinated water to create chloramines, which are longer-lasting disinfectants than free chlorine.
  • CUI (Corrosion Under Insulation): A severe form of localized external corrosion that occurs in insulated piping due to moisture ingress. A major concern for refrigerated ammonia systems.

E

  • ESD (Emergency Shutdown System): An integrated safety system designed to automatically isolate ammonia storage and stop flow in the event of a leak, overpressure, or power failure.

H

  • Hydrolysis: The chemical process used in Urea-to-Ammonia (U2A) systems to convert urea into ammonia using heat and water.

I

  • IIAR (International Institute of Ammonia Refrigeration): The primary organization that sets the standards for the design, installation, and maintenance of ammonia-based systems.
  • Inerting: The process of replacing the atmosphere in a tank or pipe with an unreactive gas (like Nitrogen) to prevent the formation of an explosive mixture or to prepare for maintenance.

M

  • Metallurgical Grade: A high-purity grade of anhydrous ammonia ($99.99%+) typically used in heat-treating and metal-processing applications.

N

  • NOx (Nitrogen Oxides): Harmful atmospheric pollutants (NO and NO2) produced during high-temperature combustion. Ammonia and Urea are the primary reagents used to neutralize these in SCR systems.

P

  • P&ID (Piping and Instrumentation Diagram): A detailed diagram showing the technical interconnection of piping, vessels, and control instrumentation for a process system.
  • PHA (Process Hazard Analysis): A systematic effort to identify and analyze the significance of potential hazards associated with the processing or handling of highly hazardous chemicals.
  • PSM (Process Safety Management): A set of OSHA regulations (29 CFR 1910.119) intended to prevent the unexpected release of toxic, reactive, or flammable liquids and gases.

R

  • RMP (Risk Management Plan): An EPA regulation (40 CFR Part 68) that requires facilities to assess their chemical risks and develop emergency response plans for the surrounding community.

S

  • SCC (Stress Corrosion Cracking): A type of intergranular cracking in carbon steel caused by the combined effects of tensile stress and the corrosive environment of anhydrous ammonia.
  • SCR (Selective Catalytic Reduction): An emissions control system that injects a reagent (Ammonia or Urea) through a catalyst into the exhaust stream of a boiler or engine to convert NOx into nitrogen and water.