Q.42
The production of single superphosphate (SSP) involves following operations:
(A) . The powdered rock phosphate (containing 30%-38% total POs) is mixed with sulphuric
acid (65%-75% H»SOa) to form a slurry.
(B) . The wet material is subjected to final curing, when some of the slow reactions reach a state of near completion and
the excess water evaporates. The curing time is 2-6 weeks
(C) . Solidification of the slurry in a den (denning), where continued reactions and crystallization of monocalcium
phosphate take place (time required 0.5 to 4 hours)
(D) . If granular SSP is desired, it can be granulated either before or after it is cured
Choose the correct answer from the options given below:
- Slurry Formation (A): Powdered rock phosphate (containing 30%–38% total $P_2O_5$) is reacted with sulfuric acid (65%–75% $H_2SO_4$) in an acidulator to produce soluble monocalcium phosphate and calcium sulfate.
- Denning Process (C): The reacting slurry is discharged into a den where solidification, continued acidulation, and initial crystallization of monocalcium phosphate occur over 0.5 to 4 hours.
- Curing (B): The solidified porous superphosphate mass is excavated and transferred to storage piles for 2 to 6 weeks of curing, allowing slow chemical reactions to reach equilibrium and excess free acid/moisture to dissipate.
- Granulation (D): If granular SSP is required, the cured or uncured powder can be granulated with water/steam in a rotary drum granulator.
- Conclusion: All operations (A), (B), (C), and (D) are integral components of single superphosphate manufacture. (Correct answer: Option 3)
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