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Dear Sir,
what is the maximum permissible oil content in product liquid ammonia?
Is there any specific limits?
If yes, what are the reasons for the same?Dear Rajkumar,
Yes, there is ammonia specific limit of oil contents is 5 ppm by weight but not more than 10 ppm (max).
For Refrigerant grade anhydrous ammonia
It is at least 99.95 percent pure ammonia. Water cannot have a content above 33 parts per million (ppm) and oil cannot have a content above 2 ppm. Preserving the purity of the ammonia is essential to ensure proper function of the refrigeration system.
Disadvantage oil in Ammonia
1. Ammonia vapors are a fire and explosion hazard at concentrations between 16% and 25%. Mixtures involving ammonia contaminated with lubricating oil from the system, however, may have a much broader explosive range. A study conducted to determine the influence of oil on the flammability limits of ammonia found that oil reduced the lower flammability limit as low as 8%, depending on the type and concentration of oil.
2. Ammonia is also flammable at concentrations of approximately 15 to 28% by volume in air. When mixed with lubricating oils, its flammable concentration range is increased. It can explode if released in an enclosed space with a source of ignition present, or if a vessel containing anhydrous ammonia is exposed to fire.
3. The fire hazard from ammonia is increased by the presence of oil or other combustible materials.
4. In Urea Plant, ammonia taken in ammonia receiver, the ammonia is volatile and oil is less it accumulated in bottom parts of vessel and sometime it will choke of PT of ammonia Feed pump it is very dangerous.
5. The heat exchanger heat transfer efficiency reduces because hard scale with emulsion.Regards,
Prem BabooRtd. from Dangote Fertilizers, Nigeria and National Fertilizers ,India, Fellow of Institution of Engineers (Indi), Sr Member of AIChE(USA) and an expert of ureaknowhow com
As a post-script, if the ammonia is used as feedstock to a nitric acid plant, the potential to poison the catalyst gauze needs to be considered. The maximum limit that I’ve come across before is 5 ppm (wt), in line with something like this:
https://www.hillbrothers.com/pdf/Product-Profiles/Commercial-Grade.pdfMany refrigeration circuits use oil flooded screw compressors, so at first pass, a specification of 2 ppm reads to be rather stringent to me.
Tighter specifications can be found, such as:
https://www.linde-gas.com/en/images/linde-datasheet-01-ammonia-June-2017_tcm17-417364.pdf
but that’s for use in a sensitive industrial process, such as the production of Si3N4 bearings and other high performance ceramics.Fertilizer grade (i.e. direct application) anhydrous ammonia is specified to a nominal 20 ppm:
https://www.nagarjunafertilizers.com/solutions_snb_products.htm
or just doesn’t rate a mention, such as:
https://iowafertilizer.com/assets/uploads/2015/09/Anhydrous-Ammonia-Fertilizer-Grade-Spec-Sheet-1.pdfSo, the oil quality required will depend on the end use. So, this is a question to ask your customer.
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