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Crystallization


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#1 Celopsin.Khan

Celopsin.Khan

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Posted 07 October 2017 - 10:17 PM

I am a Graduate Chemical Engineer, and have 3 years experience at Nitro-phosphate Fertilizer (22-20-0) Plant Operations.

 

Nitrophos is produced at our plant through Odda Process. Acidulation of Rock Phosphate (Tri Calcium Phosphate) with Nitric Acid (60%) is carried out, forming Phosphoric acid and Calcium Nitrate (CN), this CN is then crystallized as tetra hydrate crystals by cooling it in batch type crystallizer for 8 hrs using 25% ammonical soln. as coolant.

 

The CN Tetra hydrate crystals are then filtered from Phosphoric Acid through Rotary Drum Vacuum Filters. The phosphoric acid then collected as mother liquor is then neutralized to form Compound Fertilizers (MAP, DAP, MCP, DCP,) and then prilled as NP product after evaporation.

 

PROBLEM:

We are experiencing a unique previously unknown phenomenon of poor crystallization, causing High Vacuum and cake droppage on Rotary Drum, leading to heavy production loss. Recently we have observed foaming in our crystallizers after filling, and as soon as coolant is applied to the filled crystallizer, foaming die out instantaneously. if coolant is not applied soon after filling the crystallizer, foam die out naturally in 25 mins (avg). 

 

After this observation, we are now giving delay time of 30 min in coolant application to all crystallizers after filling, and now the High Vacuum Issue on drums have disappeared completely.

 

We are now interested in what actually can be the cause/explanation behind this phenomenon and what has caused the improvement.



#2 Bobby Strain

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Posted 08 October 2017 - 02:40 PM

You might start by reviewing the operations before and after the problem. Many organizations use a group and formal procedure to do this.  In detail. Including reaction components. Sometimes something obvious will be the result of your analysis. Sometimes you experience a one-of-a-kind problem that nobody else has experienced. It happens all the time in manufacturing operations.

 

Bobby






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