05 Ecologically Sound Disposal Methods in Ammonia Technology // Umweltgerechte Entsorgung in der Ammoniak-Technik

Disposing of ammonia and its effect on the environment

Please note that these are German guidelines. You can observe them, but you should comply with the regulations in your own country.

These guidelines examine the use of operating fluids in ammonia systems only (i.e. ammonia as a refrigerant and the cold machine oil). It does not deal with the disposal of systems and their components.

1.         Ammonia (NH₃)

1.1       Effect of NH₃ emissions

           Ammonia is a natural, environmentally compatible substance.  

           Ammonia is not included in the German Technical Instructions on Air Quality Control (TA Luft).

           The workplace exposure limit (WEL) for ammonia is 14 mg/m³ = 20 ppm
           (0.7 mg/m³/1 Vppm).

           Environmental damage must not be caused if ammonia is emitted into the atmosphere. The                        ERGP-2 limit is 150 ppm = 105 mg/m³ (ERGP = Emergency Response Planning Guidelines).

           It can thus be released into the atmosphere.

           If the concentration in exhaust air increases above the limit approved by local authorities, the                      ammonia content must be reduced by cleaning with water in the air or by applying water                               directly to the leakage point.

In such cases, you must observe the following:

• Collect the water/ammonia mix (ammonia solution) in suitable containers or collecting tanks
• Ammonia only reacts with water to a limited extent as per the equation NH₃ + H₂O → NH₄OH → NH₄⁺ + OH^-. Such circumstances produce an alkaline reaction in the solution.
• Most of the ammonia is absorbed by the water, thus producing heat. (Note: ammonia in the system may also suck in water due to the high absorption capacity)
• You must take into account the high vapour pressure of NH₃ compared to the vapour pressure of water (warning: possible pressure increase in closed tanks, particularly if the temperature rises).
• Ammonia is neutralised with hydrochloric acid or diluted sulphuric acid to a pH value of 7 or 8 and released into the connected sewage treatment plant via the sewer (consult treatment plant operator; do not discharge directly into surface water).
• The exhaust air system is automated by connecting a gas scrubber to the installed gas warning system. Heavily diluted sulphuric acid ( 12%) should be used as the scrubbing solution. This gas scrubber washes out any ammonia in the indoor air, holding it in a chemical bond. The chemical bond formed holds the ammonia permanently. The ammonia can no longer be released from the scrubbing solution. The bond produced is non-critical (chemical fertiliser).

Diluted sulphuric acid = WHC 1 water hazard class Xi (irritant)

• The excess washing solution should be disposed of correctly. Local regulations must be observed in individual cases.
• It is recommended that the scrubber tank should have a double wall and an automatic monitoring system.

1.2     Disposal when systems are decommissioned or refrigerant content is reduced
           (Warning: when you drain the ammonia, residual quantities of liquid ammonia are often left behind.            Due to the high enthalpy of evaporation, extra heat input is required to evaporate the ammonia.)

1.2.1 Disposal of returnable containers

           In cases of need, NH₃ suppliers provide returnable containers to dispose of used ammonia. The            returns system is designed to make commercial reuse of containers.

1.2.2   Reclaiming as ammonia solution
           The ammonia being disposed is vaporised at ambient temperature. Contaminants remain in the            evaporator due to the partial pressure. The pure NH₃ is absorbed in demineralised water and                      processed to form ammonia solution (25% NH₃). The heat produced is discharged.

1.2.3   Take into account:

            You always need to check whether national laws and regulations stipulate other requirements.

2.         Ammonia refrigeration machine oil

• Refrigeration machine oil from NH₃ refrigeration systems comes under Section 5a of the German Ordinance on Waste Oils. Consequently, it is not a recyclable material (like machine oils in other types of refrigeration system which do not use NH₃ as refrigerant). Such oil is subject to a complex disposal procedure.
• Since waste oils from NH₃ systems do not contain PCB or halogens, they are assigned disposal code AVV130506 and can be treated as mineral machine oils on disposal.
• NH₃-soluble oils (PAG oils) are assigned the disposal code 1AVV30208.
• Waste oils from NH₃ systems may contain up to 5–7% ammonia. The level may be even higher in PAG oils. For this reason, before changing the oil, the warm refrigeration machine oil should be evacuated or the degassing times must be observed before sealing the transport containers.

            Disposal procedure:

• Collection by authorised carriers (licensed to collect or convey waste as per Section 12 German Waste Management Act [AbfG]).
• Oil is handed over to the carrier with a dock receipt.
• Reconditioned in authorised system.