PURIFIED PHOSPHORIC ACID PROCESSES A THESIS Presented to The Faculty of the Graduate ...

151 Pages·2006·12.02 MB·English

PURIFIED PHOSPHORIC ACID PROCESSES
A THESIS
Presented to
The Faculty of the Graduate Division
by
Amitava Roy
In Partial Fulfillment
of the Requirements for the Degree
Doctor of Philosophy in the School of Chemical Engineering
Georgia Institute of Technology
March 1976
PURIFIED PHOSPHORIC ACID PROCESSES
\
Approved:
G.L. Bridger, Chairman
D. Muzzf^(/
H.C. Ward
3
. A<//7 4
Date approved by Chairman:
11
ACKNOWLEDGMENTS
In the long and fitful preparation of this work, the understanding,
patience and support of several people merit acknowledgment. The
transposition of this work from experimental notes to printed page
occurred with guidance and helpful discussion with my thesis advisor,
Dr. G.L. Bridger. I wish to thank him for making possible the financial
support received by me while working on this thesis.
I want to express my gratitude to the Union Carbide Corporation,
Allied Chemicals, DuPont Co. and Kaiser Chemical Company for providing
financial assistance through industrial fellowships.
I am deeply indebted to Dr. C.B. Drees, who very generously helped
in supplying the much needed knowledge concerning the quantitative chemical
analytical methods used in this work.
I would like to express my sincere thanks to Dr. J.D. Muzzy and
Dr. H.C. Ward for serving in the reading committee and for the assistance
they contributed to the completion of this work.
I am very grateful to my parents for their many years of sacrifice,
love, and understanding, sufficient thanks for what they have done for me
could never be adequately expressed.
Finally, I must especially thank "The Lady", for her unfailing
love and encouragement during the preparation of this thesis.
TABLE OF CONTENTS
ACKNOWLEDMENTS . . ..
LIST OF TABLES . . .
LIST OF FIGURES . . .
SUMMARY
Chapter
I. INTRODUCTION
General Information and Statement of Problem
Objectives
Literature Survey
II. EXPERIMENTAL PROCEDURES AND MATERIALS
Preparation of Wet Process Orthophosphoric Acid for
Subsequent Preparation of Monocalcium Phosphate
Preparation of Monocalcium Phosphate
Monocalcium Phosphate Dissociation Experiments
Preparation of Wet Process Phosphoric Acid by Direct
Acidulation of Phosphatic Material with Sulfuric
Acid or Oleum
Particle Size Reduction of Materials
Materials
General Description of the Chemical Analytical Methods
III. EXPERIMENTAL RESULTS AND DISCUSSION
Stagewise Dissociation Using Methanol and Acetone
Dissociation of Monocalcium Phosphate Prepared from
Various Phosphatic Materials with Methanol and Acetone
Exploratory Experimentation for the Production of High
Purity Phosphoric Acid of a Desired Concentration by
Direct Acidulation of Phosphate Rock with Sulfuric Acid
Near Optimum Reaction and Extraction Conditions for the
Direct Acidulation Process Using Methanol and Acetone
Production of High Purity Phosphoric Acid of a Desired
Concentration by Direct Acidulation of Low Grade Phos
phatic Byproducts and Wastes
TABLE OF CONTENTS (Continued)
Chapter page
IV. CHEMICAL PROCESS FLOW DIAGRAMS 81
Low Impurity Phosphoric Acid of a Desired Concentration
by Direct Acidulation of Phosphate Rock with Sulfuric
Acid
V. CONCLUSIONS AND RECOMMENDATIONS 89
Conclusions
Recommendat ions
APPENDICES
A. Chemical Compositions and Particle Size Distribution of
Dried Monocalcium Phosphate Materials and Dried
Acidulate 94
B. Experimental Filtrate P 0_ Yields, Impurity Rejections
9
and Filtration for Stagewise Dissociation of Mono-
calcium Phosphate in Methanol and Acetone 100
C. Experimental Filtrate P0 . Yields, Impurity Rejections
9 [
and Filtration Rates for Dissociation of Monocalcium
Phosphate Prepared from Various Grades of Phosphatic
Materials in Methanol and Acetone 121
D. Experimental Filtrate ? ®5 Yield i-n the Stagewise
2
Extraction of Phosphoric Acid from Dried Acidulate
with Methanol or Acetone 129
E. Sample Calculation ,. 133
BIBLIOGRAPHY 136
V
LIST OF TABLES
Table Page
1. Composition of Typical Commercial Concentrated Wet Process
Orthophosphoric Acids 5
2. Bulk Price of Commercial Chemicals Purchased by Tankcar • • • • 31
3. Chemical Composition of Experimental Phosphatic Materials ... 33
4. Particle Size Distribution of Experimental Phosphatic
Materials 34
5. Stagewise Dissociation of Crude Monocalcium Phosphate Containing
32 Percent PrjO- with Methanol at Different Solvent Ratios ... 41
6. Stagewise Dissociation of Crude Monocalcium Phosphate Containing
47 Pecent P 0c with Methanol at Different Solvent Ratios ... 43
9
7. Stagewise Dissociation of Crude Monocalcium Phosphate Containing
32 Percent PrjO- with Acetone at Different Solvent Ratios ... 49
8. Stagewise Dissociation of Crude Monocalcium Phosphate Containing
47 Percent P-^Oj- with Acetone at Different Solvent Ratios ... 51
9. Stagewise Dissociation of Crude Monocalcium Phosphate with
Either Acetone or Methanol at Optimum Solvent Ratios in Each
Stage 55
10. Dissociation of Crude Monocalcium Phosphate, Prepared from
Various Grades of Phosphatic Materials, with Methanol or
Acetone 57
11. Production of Phosphoric Acid by Stagewise Extraction of
Dried Acidulate with Methanol 63
12. Production of Phosphoric Acid by Stagewise Extraction of
Dried Acidulate with Acetone 54
13. P9O5 Concentration, Impurity Concentrations in the Product
Phosphoric Acid and Phosphoric Acid containing 54% P2O5 from
Stagewise extraction of Dried Acidulate with Methanol 66
14. P9O5 Concentration, Impurity Concentrations in the Product
Phosphoric Acid and Phosphoric Acid Containing 54% P9O5 from
Stagewise Extraction of Dried Acidulate with Acetone 71
vi
LIST OF TABLES (Continued)
Table Page
15. Stagewise Extraction of Dried Acidulate, Prepared from
Various Grades of Phosphatic Materials, with Methanol . . .. 77
16. Stagewise Extraction of Dried Acidulate, Prepared from
Various Grades of Phosphatic Materials, with Acetone . . .. 78
17. Process Flow Rates for the Production of Low Impurity
Phosphoric Acid by Stagewise Extraction of Dried
Acidulate, Prepared from Florida Phosphate Rock, with
Methanol 84
18. Process Flow Rates for the Production of Low Impurity
Phosphoric Acid by Stagewise Extraction of Dried
Acidulate, Prepared from Florida Phosphate Rock, with
Acetone 86
19. Chemical Composition of Dried Monocalcium Phosphate and
Dried Acidulate 95
20. Particle Size Distribution of Dried Monocalcium Phosphate
and Dried or Denned Acidulate 98
21. Variation of P2O5 Yield, Impurity Concentration and
Filtration Rate for Phosphoric Acid from First Stage
in Stagewise Dissociation of Crude Monocalcium Phosphate
with Methanol at Different Solvent Ratios 101
22. Variation of P 0c Yield, Impurity Concentration and
?
Filtration Rate for Phosphoric Acid from First Stage in
Stagewise Dissociation of Crude Monocalcium Phosphate
with Acetone at Different Solvent Ratios 102
23. Variation of P0O5 Yield, Impurity Concentration and
Filtration Rate for Phosphoric Acid from Second
Stage in Stagewise Dissociation of Crude Monocalcium
Phosphate with Methanol at Different Solvent Ratios 104
24. Variation of P9O5 Yield, Impurity Concentration and
Filtration Rate for Phosphoric Acid from Second Stage
in Stagewise Dissociation of Crude Monocalcium
Phosphosphate with Acetone at Different Solvent Ratios . . . 106
25. Variation of P^Oc Yield, Impurity Concentration and
Filtration Rate for Phosphoric Acid from Third Stage in
Stagewise Dissociation of Crude Monocalcium Phosphate
with Methanol at Different Solvent Ratios 108
vii
LIST OF TABLES (Continued)
Table Page
26. Variation of Po0,_ Yield, Impurity Concentration and
Filtration Rate for Phosphoric Acid from Third Stage in
Stagewise Dissociation of Crude Monocalcium Phosphate with
Acetone at Different Solvent Ratios 109
27. Variation of P„0r Yield, Impurity Concentration and Fil
tration Rate for Phosphoric Acid from First Stage in
Stagewise Dissociation of Crude Monocalcium Phosphate with
Methanol at Different Solvent Ratios Ill
28. Variation of P2O5 Yield, Impurity Concentration and Fil
tration Rate for Phosphoric Acid from First Stage in
Stagewise Dissociation of Crude Monocalcium Phosphate
with Acetone at Different Solvent Ratios 112
29. Variation of P„0c Yield, Impurity Concentration and
Filtration Rate for Phosphoric Acid from Second Stage
in Stagewise Dissociation of Crude Monocalcium
Phosphate with Methanol at Different Solvent Ratios 113
30. Variation of P0O5 Yield, Impurity Concentration and
Filtration Rate for Phosphoric Acid from Second Stage
in Stagewise Dissociation of Crude Monocalcium Phos
phate with Acetone at Different Solvent Ratios 115
31. Variation of P0O5 Yield, Impurity Concentration and
Filtration Rate for Phosphoric Acid from Third Stage
in Stagewise Dissociation of Crude Monocalcium Phos
phate with Methanol at Different Solvent Ratios 118
32. Variation of P„0r Yield, Impurity Concentration and
Filtration Rate for Phosphoric Acid from. Third Stage
in Stagewise Dissociation of Crude Monocalcium Phos
phate with Acetone at Different Solvent Ratios 119
33. Variation of PoO,- Yield, Impurity Concentration and
Filtration Rate for Phosphoric Acid from Dissocia
tion of Crude Monocalcium Phosphate, Prepared from
Various Grades of Phosphatic Materials, in Methanol
and Acetone 122
34. Variation of PoOc Yield in the Stagewise Extraction
of Phosphoric Acid from Dried Acidulate with Either
Acetone or Methanol at Different Overall Contact Time . . .. 130
viii
LIST OF FIGURES
Figure Page
1. Schematic Diagram for the Dissociation Process 8
2. Schematic Diagram for the Direct Acidulation Process 13
3. P7O5 Yield, ^2^^ Concentration and Impurity Concentration
as a function of Sulfuric Acid Concentration when Acidulate
is Extracted with Methanol 68
4. P?^S Yield, P0O5 Concentration and Impurity Concentration as
a Function of Sulfuric Acid Concentration when Acidulate
is Extracted with Acetone 70
5. Schematic Diagram for the Acidulation Process with Low
Impurity Phosphoric Acid Product 82
6. PQ^S Yield as a Function of Total Contact Time when Acidulate
is Extracted with Acetone or Methanol 131
IX
SUMMARY
One of the fastest growing segments of the fertilizer industry
has been the area of liquid mixed fertilizers. Coupled with this growth
has been increased emphasis on the quality of the phosphoric acid used
for production of liquid mixed fertilizers. Of the two major commerical
processes which are presently used for the manufacture of phosphoric acid
both have certain disadvantages. Electric furnace grade phosphoric acid
is chemically and physically well suited to be used as the source of
phosphorus for clear liquid mixed fertilizers but is relatively expensive.
Wet process phosphoric acid, on the other hand, is less expensive but
when this acid is used, it is virtually impossible to manufacture a clear
liquid mixed fertilizer that does not eventually precipitate solids or
form a gel due to the impurities present in the acid. Therefore, a
potential market exists in the area of clear liquid mixed fertilizer
production for a phosphoric acid which is purer than commerical wet
process acid but less expensive than commercial electric furnace acid.
The overall objective of this study was to investigate the
technical feasibility of producing low impurity, high concentration
phosphoric acid by using two chemical routes.
The first process is essentially the one developed by Dr. C.B.
Drees (11). This process produces low impurity phosphoric acid by a
chemical route which uses the conventional wet process method as a
starting point and is based on the dissociation of monocalcium phosphate
into phosphoric acid and dicalcium phosphate in the presence of an organic