Phosphate Fertilizers by Calcination Process Experiments with Different Phosphates H.L. MARSHALL, D. S. REYNOLDS, IC. D. JACOB, AND L. F. RADER,JR. Bureau of Chemistry and Soils, Washington, D. C. With phosphate r o c b containing approximately good results were obtained, however, when the silica 4 to 12 per cent of silica, high volatilization of the content of the charge was increased to about 10 per fluorine and conversion of the phosphorus into the cent. The citrate solubility of tricalcium phosphate was cifrate-soluble condition were usually obtained by heating small charges (2.5 grams) of 40 to 80 mesh increased to 85 per cent or more by heating at 1400' material in the presence of water vapor for 30 min- C. either in a moist atmosphere, with or without the addition of silica, or in a dry atmosphere. The utes at 1400' C. Of the domestic phosphates, the best results were citrate solubilities of hydroxyapatite and bone prodobtained with Tennessee brown-rock and Idaho phos- ucts were decreased by heating at 1400" in a moist phates. Little or no citrate-soluble phosphorus was atmosphere in the absence of silica, but were very formed when the low-silica phosphates from Morocco markedly increased by heating at 1400' either in a and various ocean-island deposits were heated alone moist atmosphere in the presence of silica or in a dry at 1400' C. in the presence of water vapor; very atmosphere without silica.
I
N PRECEDING papers of this series (9, 10) it was shown
that nearly complete volatilization of the fluorine and formation of citrate-soluble phosphorus are obtainedwhen silica-bearing Florida land-pebble phosphate is heated a t 1400' C. under the proper conditions. These conditions are (1) an ample supply of water vapor in the furnace atmosphere, (2) particle size within the approximate limits 40 to 80 mesh, (3) a maximum charge weight of 2.5 grams, (4) a minimum heating time of 30 minutes, and ( 5 ) rapid cooling of the product. Further experiments to determine the effect of heating different natural and synthetic phosphates under these conditions have been made, and the results are reported in this paper.
MATERIALS AND EXPERIMENTAL METHOD The majority of the domestic phosphate rocks used in this study were representative of the commercial materials that have been or are now being produced from the deposits. Experiments were also made with fluorapatites from Canada and Virginia, the latter being obtained as a by-product of the preparation of titanium compounds from ilmenite-nelsonite ore mined in Amherst County ( I ) , and with commercial phosphates from Morocco and the islands of CuraCao, Christmas, Makatea, Kauru, and Ocean. The phosphate rocks were ground t o pass a 40 mesh sieve, and the 40 to 80 mesh particles were used. The bone ash, spent bone black, and steamed bone meal were commercial materials. The tricalcium phosphate was prepared by slowly adding, with constant stirring, a solution of pure phosphoric acid to the equivalent quantity of pure calcium oxide in aqueous suspension, evaporating to dryness, and igniting to constant weight a t 900" C., as described by Ross, Jacob, and Beeson (11). The hydroxyapatite was prepared by prolonged boiling, with daily change of water, of an aqueous suspension of the product obtained by precipitating a solution containing an excess of calcium nitrate with a solution of ammonium phosphate containing ammonia in excess of the triammonium phosphate equivalent; boiling was continued until the solid material showed a weight ratio of P~OSto CaO very close to the theoretical ratio (0.760) in hydroxyapatite [Cal~(OH)2(P04)6]. The product was dried
over concentrated sulfuric acid for several weeks. The synthetic aluminum phosphate was prepared by precipitating a solution of aluminum sulfate with a solution of triammonium phosphate (prepared by adding the proper quantity of ammonia to a solution of diammonium phosphate), as described by Bartholomew and Jacob (2). The product was dried a t 50" to 60' C. The natural aluminum phosphate came from a deposit in the Connetable Islands off the coast of French Guiana. This material was formerly used in the manufacture of sodium phosphate by alkali treatment processes. All of these materials were ground to pass a 100 mesh sieve. The 200 mesh silica was a specially purified grade of commercial quartz flour. The 40 t o 80 mesh silica was prepared from pure quartz crystals. Partial chemical analyses of the samples are given in Table I. FArepresents the fluorine in excess of that corresponding t o the fluorapatite [Cal~F2(P04)6]equivalent of the total phosphorus in the rock. FB and F'B represent the fluorine corresponding to the respective atoms of fluorine in the fluorapatite equivalent of the total phosphorus; for convenience these may be designed as the first (FB) and second (F'B) atoms of fluorine. The apparatus and general experimental procedure were the same as those used in previous experiments (9). All experiments were run in duplicate. The product was withdrawn from the furnace a t the final temperature of the experiment and allowed to cool quickly in the laboratory atmosphere. All samples for analysis were ground to pass a 100 mesh sieve.
EFFECT OF w.4TER
PHOSPHATE ROCKS AND FLUORAPATITE When 2.5-gram charges (40 to 80 mesh material) of comVAPOR ON
mercial grades of Florida land-pebble, Tennessee brown-rock, Tennessee blue-rock, Idaho, Montana, and Wyoming phosphates were heated for 30 minutes a t 1400' C. in the presence of water vapor (0.8 gram per minute), more than 97 per cent of the total fluorine was volatilized and upwards of 90 per cent of the phosphorus was converted into the citrate-soluble condition (Table 11) ; the best results were obtained with Tennessee brown-rock phosphate. With the exception of the Montana phosphate which contained 22.01 per cent of total
205
lNDUSTRIAL AND ENGINEERING CHEMISTRY
206
Vol. 27, No. 2
TABLE I. COMPOSITION OF PHOSPHATES (Results on air-dry basis, in per cent) -PzO,Total Citrate sol. F SiOP FezOsb
-TOTAL F AS:--TYPEAND SOURCEOB PHOSPHATE AlzOaC CaO COI FA FA FB F'B 1.99 3.67 5.30 3.10 Tennessee brown rock No. 1 Wales 34.64 1.28 48.88 1.26 15.8 57.9 42.1 3.86 4.54 3.15 2.80 1.52 48.98 1.75 Tennessee brown rock No 2' Mountpleasant 34.66 16.0 58.0 42.0 3.37 2.17 29.50 4.00 7.59 28.14 0.60 Tennessee brown rock, u n b h e d matrix 20.77 14.8 57.3 42.7 3.65 6.48 2.85 1.26 31.69 2.36 49.92 2.40 22.8 61.3 38.7 Tennessee blue rock No. 1 Gordonsburg 3.10 3.18 11.62 1.60 1.05 Tennessee blue rock No. 2 : kidney phosphate, Boma 31.58 44.20 0.79 55.7 44 11.4 3.72 3.67 1.67 0.80 0.60 52.41 2.39 9.0 54.5 45:; Tennessee white rock No. 1 Tomscreek 37.45 3.68 2.55 1.85 49.50 1.98 13.6 56.8 43., 35.46 3.69 1.72 Tennessee white rock No. 2: Qodwin 30.47 4.20 3.67 9.96 1.90 0.63 45.60 3.48 26.0 63.0 37.r) Florida land pebble No. 1 34.56 2.85 3.75 7.44 0.90 1.14 48.62 1.72 17.8 58.9 41.1 Florida land pebble No. 2, Mulberry 35.25 3.83 3.62 4.69 0.88 0.79 2.60 13.2 56.6 49.87 43.4 Florida hard rock, Dunnellon 26.45 5.06 3.41 13.08 1.60 0.93 42.29 4.55 30.8 South Carolina land rock, Johns Island 65.4 34.6 33.56 3.73 3.37 3.93 0.60 0.74 47.94 2.06 11.2 55.6 44.4 Idaho, Conda 2.96 22.01 1.55 28.96 1.99 1.73 39.98 0.96 12.8 56.4 43.8 Montana Garrison 31.29 1.08 3.54 5.00 0.85 0.44 48.18 4.01 60.6 39.4 21.2 Wyoming', Cokeville 0.74 0.30 0.33 52.52 3.59 22.6 61.3 38.7 34.63 5.49 3.99 Morocco d 37.88 5.65 0.91 0.54 0.80 0.39 49.60 3.99 .. .. Curacao Island 39.38 6.22 1.43 0.346 0.60 0.77 53.78 2.39 / Christmas Island 0.34e 0.60 0.48 37.80 5.37 3.24 52.35 2.22 0 48,'O 52:O Makatea Island 38.38 5.03 2.68 0.3ge 0.40 0.23 52.90 2.24 0 36.2 63.8 Nauru Island 0.35 0.13 3.24 2.77 0.28' 53.20 0.91 0 35.9 64.1 39.86 Ocean Island 0.85 3.03 1.25 0.40 0.38 Fluorapatite No. 1 uebec Province Canada 39.38 54.44 0.72 0 42.1 57.9 2.48 3.04 3.96 0.65 0.55 51.75 0.09 0 42.1 67.9 Fluorapatite, No. i,?.mherst Count;, Va. 39.46 .. 53.68 Triralrium phosphate, synthetic 45.61 24.56 .. ... 54.00 41.67 12.80 Hydrox apatite, synthetic .. Steamedl bone meal 34 54 15.58 0:06 0.07 ... Spent bone black from sugar reflnery 34.83 8.53 Bone ash 40.31 4.43 0.05 0:45 0:24 0.00 54:04 0:fO Aluminum phosphate s nthetic 36.49 38.49 0.00 0.03 26.72 ... Aluminum phosphate: zonnetable Islands 42.20 3.76 0.05 1:il 3.43 28.58 0.00 0:OO 0 Total Si b Total Fe. C Total AI. not corrected for Ti. d The fluorine content of this m a t e d 1 corresponded to only 53.8% of that required for 1atom of fluorine in the fluorapatite equivalent of the total phonphorus. e Total material insoluble in 1:l hydrochloric arid. / The fluorine content of this material corresponded to only 81.5% of that required for 1 atom of fluorine in the fluorapatiteequivalent of the total phonphorus.
..
silica, these materials contained about 4.0 to 11.5 per cent of total silica (Table I). With the fluorapatite (No. l ) , Tennessee white-rock (No. l), Morocco, and island phosphates, less than 80 per cent of the total fluorine was volatilized and not more than 28 per cent of the phosphorus was converted into the citrate-soluble condition; all of these phosphates contained less than 2 per cent of silica. Although poor results were invariably obtained when the rock contained less than about 4 per cent of silica, the presence of more than 4 per cent of silica did not always cause a high volatilization of fluorine and production of citrate-soluble phosphorus, as shown by the results obtained with the South
..
:.
+
...
..
...
...
.... ..
.. ..
..
.. .. ..
Carolina rock and the Tennessee brown-rock matrix which contained 13.08 and 29.50 per cent of total silica, respectively. Complete or nearly complete fusion of these phosphates occurred a t 1400" C., with the result that penetration of water vapor into the charges and into the individual particles of rock was greatly hindered. That the high silica content was not alone responsible for the fusion of these phosphates is indicated by the absence of fusion a t 1400' C. in the Montana rock which contained 22.01 per cent of total silica. The high content of iron and aluminum (Table I) in the Tennessee brown-rock matrix probably contributed to the fusion of this material; also, this material did not contain sufficient calcium
TABLE11. EFFECTOF WATERVAPORON PHOSPHATE ROCKSAND FLUORAPATITE [2.5-gram charges of 40 t o 80 mesh materials heated for 30 minutes a t 1400° C. in water vapor (0.8 gram per minute) and air (120 cc. per minute)] COMPOSITION OF PRODUCT TYPEORSOURCEOF Total CitrateTOTALF F'B VOLACITRATE PHOSPHATE PIOa sol. P z O ~ F VOLATILIZED TILIZED SOLY.O F PzOr CONDITION OF PRODUCT
%
%
%
%
%
%
FLORIDA PHOBPHATES
Land pebble No. 1 Land pebble No. 2 Hard rock
34.1 36.8 37.7
31.9 33.3 30.2
0.02 0.08 0.22
Rrnrvn m ~ Nn k 1I.U.. _.". Brown rock No. 2
3 6.1 ..
0.01 0.01
Brown rock, unwashed matrix Blue rock No. 1 Blue rock No. 2 White rock No. 1 White rock No. 2
36.9 . 37.3 22.7 34.7 34.5 39.4 38.2
South Carolina Idaho Montana Wyoming
30.4 38.0 30.2 35.6
13.1 37.2 28.9 32.2
0.74 0.01 0.02 0.08
Fluorapatite No. 1 Fluorapatite No. 2 Morocco Curacao Island Christmas Island Makatea Island Nauru Island Ocean Island
40.0 40.2 37.7 41.3 41.5 41.7 41.9 42.0
9.1 28.7 1.8 11.5 2.8 2.4 2.1 1.8
1.51 0.52 1.41 0.43 0.72 1.18 1.23 1.30
99.5 97.9 94.2
98.6 94.9 86.8
93.5 90.5 80.1
Friable sinter Less sintered than land pebble No. 1 Same
97.8 99.7 7.0 91.6 91.9 17.8 79.3
Less sintered than Florida land uebble No. 1 Same Completely fused About the same as Florida land pebble No. 1 Same Ver slightly sintered Sligxtly sintered
TENNEBSEE PHOSPHATES
37.2 1.6 31.8 31.7 7.0 30.3
0.60 0.06 0.03 0.87 0.17
99.7 99.7 74.7 98.5 99.1 77.5 95.7
99.3 99.3 40.7 96.1 98.0 50.5 90.0
SOUTH C A R O L I N A A N D WESTERN PHOBPHATES
80.8 99.6 99.2 97.9
44.5 99.1 98.2 94.7
43.1 97.9 95.7 90.4
Almost completely fused L e ~ ssintered than Florida land pebble No. 1 About the same as Florida land pebble No. 1 Less aintered than Florida land pebble No. 1
F L U O R A P A T I T E A N D F O R E I Q N PHOSPHATES
51.0 83.2 67.5 56.6 52.3 66.8 57.9 55.4
15.4 71.0 16.0 76.6n 61.1b 36.2 34.0 30.4
22.8 71.4 4.8 27.8 6 7 5.8 5.0 4.3
a The original phosphate contained fluorine corresponding to only 53.8 per cent of that required for 1atom of fluorine in the fluorapatite equivalent of the total phosphorus; the figure 76.8 includes the origipal deflFiency of fluorine (46.2%) and the fluorine volatilized (30.4%), based on the quantity of fluorine corresponding to 1 atom of Buorine in the,Ruorapatite equivalent. b The original phosphate contained fluorine wrrespondine to only 81.5 per cent of that required for 1 atom of fluorine in the fluorapatite equivalent of the total phosphorus. The figure 61.1 includes the original deficiency of fluorine (18.5%) and the fluorine volatilized (42.6%), based on thequantity of fluorine corresponding t o 1 atom of fluorine in the fluorapatite equivalent.
February, 1935
INDUSTRIAL AND ENGINEERING CHEMISTRY
207
TABLE111. EFFECT OF WATERVAPORAND SILICA ON BONE PRODUCTS, ALUMINUMPHOSPHATES, AND SYNTHETIC CALCIUM PHOSPHATES (Charges heated for 30 minutes at 1400° C.)
MATERIAL Tricak?ium phosphate Hydroxyapatite
EXPTL. CONDITIONS" A B C A B
C
Bone aah Spent bone black Steamed bone meal Aluminum phosphate, hynthetic
-
Aluminum phosphate, natural a
A B C A B C A A B C A
, -
Total Pros
COMPO~ITION OF PRODUCTCitrate-sol. Citrate soly. P206 of P z O ~
CITRATE SOLY.OF
P ~ OISN ORIGINAL MATERIAL
%
%
%
%
46.1 42.3 45.9 43.1 40.0 43.6 41.4 38.0 41.6 40.0 36.8 40.5 41.3 56.6 49.6 56.8 56.7
41.6 37.7 42.0 10.0 37.7 40.6 3.4 34.2 37.4 2.6 33.1 34.1 4.5 12.7 13.4 20.2 6.8
90.2 89.1 91.5 23.2 94.3 93.1 8.2 90.0 89.9 6.5 89.9 84.2 10.9 22.4 27.0 35.6 12.0
53.8 30.7
11.0 24.5 45.1 100.0
8.9
CONDITION OF PRODUCT Considerably caked Slightly caked Slightly sintered Slightly caked Considerably sintered Slightly caked Considerably caked Considerably sintered Slightly caked Slightly caked Semi-fused Powder Slightly caked Powder Powder Powder Powder
A 1.5 grams of phosphate material heated in water vapor (0.8 gram per minute) and air (120 cc. per minute). B = 1.5 grams of phosphate material plus 0.15 gram of silica (
