The issue of water-soluble phosphorus in the production process of diammonium phosphate
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We produce diammonium phosphate using traditional methods, with a nutrient content of over 62%. Currently, the ratio of water-soluble phosphorus to total available phosphorus in the final product is around 75%, which does not meet the requirement of 80%. We are not sure what causes this issue; we hope everyone can offer some suggestions.
The total nitrogen content in the diammonium form is low; if it goes any lower, it becomes ammonium-based. I haven’t encountered a situation where the water-soluble phosphorus level is low.
Check the solid content of the concentrated acid coming from the phosphoric acid workshop to see if it exceeds the limit; I’m not too familiar with the other aspects.
Thank you for the help from above. So, what is the typical range for the solid content in concentrated phosphoric acid?
We haven’t produced diammonium phosphate for seven or eight years now, and the relevant figures aren’t clear. You can compare them with the previous data from your phosphate production unit to see if the levels have been high recently
It mainly depends on the grade of phosphate rock, or whether the amount of phosphoric acid in the solid phase exceeds the limit
My opinion: The neutralization reaction time should be adjusted； Otherwise, the neutralization reactor should be redesigned. There will be a certain increase under certain conditions of phosphate.
Primarily, the high content of impurities such as iron, magnesium, and aluminum in phosphoric acid leads to the formation of various complex compounds during the ammoniation process. These compounds affect the viscosity of the slurry, as well as the composition, physical properties of the ammonium phosphate product, and its solubility in P2O5.
Since the pH value of diammonium is around 5.8, components such as iron phosphate, aluminum phosphate, and magnesium ammonium phosphate are formed at this point, resulting in issues related to water-soluble phosphorus. A comprehensive analysis of the acid used as a raw material can be conducted to determine the reasons for the low level of water-soluble phosphorus. Solutions include: first, optimizing the mineral composition； Second, increase the phosphate concentration ； Third, increasing the aging time of the concentrated acid allows the precipitated salts to separate from the acid, thereby improving the quality of the diammonium product.
The solid content should be below 2; 2 is the ideal value； The MER value should be less than 0.1; the lower the Mg content, the better
With the decline in phosphate ore grades, the issue of water-soluble phosphorus is likely to be a challenge for the industry in the future. At present, the phosphate ammonium in Yunnan is of better quality, but I’ve heard that the cost of using water-soluble phosphorus through tubes is higher; Dayukou is a great example of this.