Please check the PDF attachment.

Thank you Dr Singh. I have already gone through the document.

Dear Dr. Borah,

(1)   Urea absorbs moisture from the atmosphere and therefore is typically stored either in closed or sealed bags on pallets or, if stored in bulk, under cover with a tarpaulin. As with most solid fertilizers, storage in a cool, dry, well-ventilated area is recommended. Urea is neither combustible nor explosive. It can be stored safely with no loss of quality under normal circumstances.

(2)   Critical Relative Humidity (CRH) is the value of the relative humidity of the surrounding air, above which a fertilizer will absorb moisture and below which it does not absorb moisture. CRH value of fertilizer is required while designing controlled humidity of storage areas for a fertilizer. Critical relative humidity of urea is high (70 to 75 at 30°C) compared to the Ammonium Nitrate and Calcium Ammonium Nitrate (CAN). So, it can withstand the hot and humid conditions in India.

(3)   Urea should not be stored with ammonium nitrate, since CRH of urea and ammonium nitrate mixture is 18. These materials (urea and ammonium nitrate), when in contact, rapidly absorb water when the relative humidity is above 18%. Upto 0.3% moisture content of urea is ideal to avoid physical quality problems like caking. Moisture content above 0.3% results in deterioration of urea in storage.

Drying and storage of NPK granular fertilisers based on superphosphate and containing urea as a plant nutrient by R. E. Jewell DOI: 10.1002/jsfa.274013080  . Here is the abstract: 

In an investigation of the properties of NPK fertilisers which contain urea as a plant food, the effects of free moisture, free acidity, urea content and temperature on their stability during storage have been studied  .

It is concluded that to ensure complete stability of NPK fertilisers (N 10, P2O5, 10, K,2O 18%) containing superphosphate and urea (2-15%).

Other conclusions are that (a) losses of nitrogen during storage are negligible, and that (b) insoluble phosphates formed during storage are in ‚available’ forms as determined by the neutral ammonium citrate test.

(1)a maximum granule temperature of 70°G is preferable during the drying process, although temperatures up to 90°G could be tolerated if the drying time is limited to about 15 min.

(2)for incorporation with urea, ammonium sulphate is somewhat preferable to ammonium nitrate, as it gives a more stable product

(3)the fertilisers should be stored at 35° or lower

Polyethylene-coated urea. 1. Improved storage and handling properties by Omar A. Salman, Ind. Eng. Chem. Res., 1989, 28 (5), pp 630–632, DOI: 10.1021/ie00089a021

A PDF enclosed for further reading ..

Dr Kundu Sir,

Thanks a lot for the information. I also came across these information while reviewing. I just wanted to know if any quantitative estimates had been done of N loss during storage of urea fertilizers.  Your kind interest and inputs are highly appreciated and acknowledged.

Regards

Dr Anoop Sir,

We appreciate and thank you profusely for your inputs. There is another report on hygroscopicity of urea during storage, which observed significant increase at RH 92% following exposure of more than 6 hours (attached file). The information that negligible loss occurs during storage was helpful. We, for academic interest, just wanted to know if it was ever quantified.

Thanks and regards

Dr Nilay , i got an interesting work related somewhere to your on-going discussion , so i thought , must share with you , interesting on e. 

Dr Anoop Sir,

Thanks. I have got this article. Anyway thanks a lot for your gesture, interest and effort.

Regards

Dr Nilay Borah

I'am Anisa Putri from Indonesia. I'm studying now about UREA storage, and I have same question with you about N-Urea loss during storage of UREA fertilizer.

Have you found any info about this topic, sir?

Thank you so much for your attention

Dr Anisa Putri,

We have not done any work on it. I have also not come across any article reporting on loss of N from urea fertilizer during storage after putting my question. The aspect may be included as a part of your current work.

Thanks