Phosphoric acid

[Karishma Attarkar 11CHE1007]

http://www.slideshare.net/Donal_Tunks/phosphoric-acid-process-comparison-paper

The above link provides the comparison between different types of phosphoric acid manufacturing processes, their comparison between them, the recovery of P2O5 from the rock, their annual cost and rate of return, etc.

[Vishwanath Dalvi]

Nice link.  But summarize it here also.

[Karishma Attarkar 11CHE1007]

Phosphoric acid can be manufactured by the following processes and are classified according to the gypsum product obtained and the advantages are as follows:

1. Di-hydrate- 28% P2O5 required, with the extraction capacity of 95%, annual profit:$80 million

2. Hemihydrate: It is carried out at higher temp, high P2O5 capacity. It requires lower grinding(due to high temp.), lower clarification and storage capacity required as high concentration of acid obtained, 46% less evaporator capacity but 92% extraction capacity. profit: $88 million

3. Hemi-dihydrate: Overcome lattice loss of hemi and provide higher concentration as dihydrate. First hemi is produced and the crystallized to dihydrate. Additional cost of recrystallization tank, filter building, higher amount of air needed to be scrubbed is added. profit:$99 million

4. Di-hemihydrate: Similar to earlier just the sequence is altered. Gypsum recovered is pure and can be used in construction.

5. Nitrophosphate: Rock phosphate+ HNO3 = Calcium nitrate tetrahydrate(0-20oC) + H3PO4 and is filtered and H3PO4 is stored. The CO2 is passed through slurry and CaCO3 formed is ammoniated to give Calcium ammonium nitrate(fertilizer). But, the HNO3, NH3,CAN granulation plant needs to be installed. profit:$369 million

6. Electric furnace and furnace: Furnace method is better than electric as petroleum fuel are cheaper than electricity required. Even though, if furnace provided lower P2O5 extraction i.e. 87% than 92% by thermal it was found to be more profitable. profit:$103 million

7. HCl acid route: Not profitable at all. Due to cost of HCl, environmental impact much higher than due to gypsum.

Considering the various parameter i.e. operating cost, installation cost and the annual profit the maximum rate of return is provided by di-hydrate i.e. 36.5%