Ammonia R717, NH₃ – what is it?

Ammonia is produced through the synthesis of nitrogen and hydrogen. This inorganic chemical compound also forms naturally as a result of the decomposition of protein substances. In industrial settings, it is obtained using the Haber‑Bosch method by synthesizing nitrogen and hydrogen over iron catalysts.

What are the properties of ammonia used for cooling?

Chemical properties of ammonia

• colorless gas
• strongly alkaline
• has a distinctive, pungent odor
• easily soluble in water
• flammable, burns with a characteristic yellow flame
• chemically active
• boiling point: −33.4°C
• reacts with acids to form ammonium salts, and with chemically active metals to form amides
• lighter than air – accumulates in the upper parts of rooms

Ammonia in industry

Ammonia has a wide range of applications. Although artificial fertilizers are the first association, this is far from its only use. It is also employed in the production of explosives and synthetic fabrics. Moreover, its favorable thermodynamic properties make ammonia an effective refrigerant for cooling installations.

Ammonia in refrigeration – advantages of ammonia as a refrigerant

• High energy efficiency: Ammonia is one of the most energy‑efficient refrigerants. For example, 1 kg of ammonia can absorb 1347 kJ during evaporation, whereas 1 kg of R22 absorbs only 222 kJ.
• Environmental impact: Ammonia has the lowest impact on ozone depletion and the environment compared with all known refrigerants. This ensures that ammonia‑based installations are not subject to the restrictions imposed on synthetic refrigerants.
• Cost of ammonia: The price of 1 kg of ammonia is significantly lower than the price of 1 kg of chemical refrigerants (freons) — approximately a hundredfold difference. Additionally, liquid ammonia has a much lower density than chemical refrigerants.
• Smaller pipe diameters: Ammonia requires smaller diameters of discharge and suction pipes compared to chemical refrigerants.
• Heat transfer: This is one of ammonia’s most significant advantages. It exhibits much higher heat transfer efficiency than chemical refrigerants. As a result, ammonia heat exchangers require significantly smaller heat exchange surfaces than those used for chemical refrigerants.

Refrigeration installations – ammonia as an optimal alternative to F‑gases

According to EU Regulation 517/2014 on F‑gases, the threshold limits determining the frequency of refrigeration equipment inspections are defined in CO₂ equivalent:

• 5 to 50 tonnes CO₂‑eq: at least once every 12 months, or once every 24 months if equipped with a leak‑detection system. Hermetically sealed systems containing fewer than 10 tonnes CO₂‑eq of F‑gases, labeled accordingly, are exempt from leak checks.
• 50 to 500 tonnes CO₂‑eq: at least once every 6 months, or once every 12 months with leak detection.
• Above 500 tonnes CO₂‑eq: at least once every 3 months, or once every 6 months with leak detection.

The regulation has also prohibited the use of refrigerant R22 since January 1, 2015. By 2018, the industry was required to reduce total F‑gas consumption by 37%.
The goal for 2030 is to reduce F‑gas production to 21% of 2015 levels.

Refrigerant R404A has been banned since 2020. Additional stricter requirements regarding leak detection and inspection regimes will also be introduced. Investing in F‑gas‑based refrigeration installations is not economically feasible, especially since further regulations remain unknown. For industrial refrigeration systems, ammonia remains the only reasonable alternative.

Ammonia refrigeration – operating principle

Ammonia refrigeration systems operate on a fairly simple principle. Liquid ammonia flows from a storage vessel to a separator. There, it undergoes compaction and depressurization. It then passes through a throttle valve, where it mixes with hot gaseous ammonia and decreases in temperature. It absorbs heat from water flowing through the evaporator and transitions to a gaseous state. This process repeats continuously, maintaining cooling.

Ammonia refrigeration installation – diagram and secondary‑side detection point

On the diagram below:
B – location of ammonia leak detection on the secondary side

Safety of ammonia refrigeration systems

Safety in ammonia installations is not only about protecting industrial facilities but, above all, safeguarding human health and life.

This article outlines safety requirements for the technological installation itself. To ensure proper operation, an Installation Operation Logbook must be maintained. Correct entries should include:

• date of service/repair work, including maintenance of proper NH₃ detection on the secondary side
• detailed description of performed work
• information on personnel performing the tasks
• data and name of the service/repair company

Ammonia installations – regulations

Detailed requirements for the above records are defined in PN‑EN‑378‑4.

Additional important information is contained in the Regulation of the Minister of Labour and Social Policy of November 29, 2002, on maximum permissible concentrations and intensities of harmful factors in the work environment (Dz.U. 2002.217.1833).

Ammonia in the secondary circuit

A limitation of using R717 is its effect on metals. While anhydrous ammonia and its aqueous solutions do not affect iron and its alloys, moist ammonia reacts with zinc, copper, and copper alloys. This is particularly important when designing secondary refrigeration circuits. Therefore, ammonia detection on the secondary side is used in ammonia‑based systems.

To ensure proper NH₃ ion detection, the installation should operate in an alkaline range (pH 8–9).

Practical application of the ammoniadetector

The following is based on the experience gained through JUMO Sp. z o.o.’s long-standing collaboration with a key supplier in the ammonia refrigeration industry – GEA Refrigeration Poland Sp. z o.o.

Safety in case of a leak – ammonia sensor for leak detection in liquid solutions

Servicing an ammonia detector is relatively simple, but it is recommended that it be performed by authorized service personnel or trained specialists. A good practice is to service the detector during each semi‑annual system inspection.

The ammonia sensor can operate between −8 … +30°C. Versions for −55 … +30°C are also available. The sensor should be installed in a pressure‑free system, e.g., a bypass when using conventional fittings. For more demanding systems, self‑sealing fittings with a double chamber are used, allowing installation in a pressurized system of 2–3 bar (max. 6 bar). This is the recommended practice.

Fitting for ammonia sensor

The fitting allows the ammonia sensor to be removed from the system without interrupting system operation and protects the sensor from pressure damage. The medium itself should be clean, free of solid contaminants, oils, etc. If necessary, use filters.

Summary

Given the growing popularity of ammonia technology and its associated benefits and challenges, ammonia‑based systems appear to be the only economically justified solution. It is essential to remember the operational requirements of such systems, including the secondary circuit. Neglecting the secondary side can result in significant financial losses and system downtime. To ensure safe and optimal long‑term operation, regular servicing is crucial.