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Патент USA US3078166

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United States Patent 0 " ICC
Patented Feb. 19, 1963
2 ,
all the added Nazo radicals would act eifectively on the
de?uorinating reaction. It has also been found that, with
increase of P205 presenting as sodium phosphate, the
Onoda, Yamaguchi prefecture, Japan
the sintered product increases also its refractoriness and
the practical operation in the rotary kiln can be made
Taro Yariraguchi, 4 of No. 1341 Marukouchi Ohaza,
No Drawing. ,, Filed Oct. 16, 1957, Ser. No. 690,451
2 Claims; (Cl. 71-44)
de?uorination proceeds rapidly at a low temperature, and -
extremely easily.
The present invention is based on this newly estab
lished knowledge and characterized in that the de?uori
ing ‘?uorine from phosphate rock, more particular phos 10 nation of phosphate rock by sintering the crude rock in
The present invention relates to a method of eliminat
phate rock consisting mainly of tricalcium phosphate of
apatite structure.
the coexistence of water vapour is effected at a low tem
perature when NazO- and. P2O5~radicals are added to.
the phosphate rock consisting mainly of tricalcium phos
An object of the present invention is to eliminate a
phate of apatite structure and then nearly the whole P205
?uorine content remarkably efficiently from phosphate
rock which consists mainly of tricalcium phosphate of 15 radicals added is caused to exist in the form of sodium
apatite structure.
Further, when according to the present invention, NaOz '
Another object of this invention is to perform the
radical as well .as P205 radical is added to phosphate.
de?uorination rapidly at low'temperature after the ad
rock as described above and nearly thewhole of the
dition of Na2O and P205 radicals to the crude rock, and
in the presence of almost all the added P205 radical in 20 added P205 radicals is caused to exist in the form of so
dium phosphate, the deiluorinationis carried out rapidly
the form of sodium phosphate.
at low temperatures, and it has also been vproved that
Further" objects, features and advantages of this inven
a relatively small amount of NazO radicals is sufficient
tion will be’apparent‘ from the‘ following descriptions.
for this purpose. With reference to such additional
Hitherto, an attempt of eliminating ?uorine from phos
phate rock by heating in. the presence of water vapour 25 amounts, various experiments have been conducted in
both- laboratory and practical operation, and as a result
after adding silicic acid thereto has been made since long.
thereof, amounts of additions of P2O5— and .Nazo-radicals .
have been found as follows:
cannot be practiced industrially,‘ unless the adding amount
P205 radical-05 to 1.2 mols to 3 mols of CaO other
of silicic acid has been considerably increased and the 30
than CaO which combine with phosphoric acid in the
fusion points of the mixture have been raised.
phosphate rock to form tricalcium phosphate.
Also, with respect to the procedure for the similar
Na2O radical—0.5 to 1.5 mols to one mol of ?uorine in
treatment with addition of both silicic acid and sodium
the phosphate rock. \
In‘ such a procedure, however, an extremely high treat
ing temperature is required. Therefore, such a procedure '
salt, various procedures have been proposed. However, 35
in this case, it is needexi to control ‘additions of silicic
acid and sodium salt so that CaO, Na2O, P2O5‘and SiO2
in the mixture may produce two complex compounds,
In the practical application of the present method,_
it is most simple to add sodium phosphate or sodium
phosphate and sodium salt, such as Glauber’s salt or so
Accordingly, the
dium carbonate, directly to the phosphate rock, and
Even though the attempt of eliminating fluorine from
ing from a room temperature to 60—7()° C. in the pres~
ence of water. It is, however, possibleto cause sodium
phosphate to form during the course of the manufacture
as in the following manner:
2CaO.Na2O.P2O5 and 2CaO.SiOz.
amount of addition of sodium salt will become exceed; 40 knead the admixture, for example, at a temperature rang
ingly high.
phosphate rock under heating in the presence of water
vapour has been made since long, such attempt requires
(1) Phosphoric acid solution is added to'a mixture of'
a considerably high temperature for treatment, which 45
phosphate rock with Glauber’s salt-or- soda~ash~ and
leads to a remarkably large amount of silicic acid to
mixed by kneading in the condition as described above.
be added. Consequently, this procedure can only be
Sodium phosphate is then produced according to the fol
effected with di?iculty in an industrial practice, unless
lowing reactions:
the fusing points of the mixture have been raised.
It is true that the addition of sodium salt lowers the 50
detluorinating temperature for phosphate rock and ac
celerates the de?uorinating velocity remarkably effec
tively. With regard to the reason why a large quantity
of additions is required in the practical operation in a
(2) Sodium salts, such as NaOl and NaNO3 easily de
rotary kiln, the inventor considers as follows: Namely, 55
composable by heating in the presence of acid substance
the lime other than that which forms in the phosphate
is mixed with. the phosphate rock, to which phosphoric
rock tricalcium phosphate [Ca3(PO4)2] and caliurn ?uo
acid solution is added. The mixture thus obtained pro
ride [Cal-T2] (hereinafter called “free lime”) and SiO2
duces sodium phosphate according to the following re
react with Na2O~atloW temperatures, which is produced
by the ‘decomposition of added sodium salt, to produce 60 actions at a low temperature of 300 to 400° C. in the '
course of sintering up to the order of 1350°~C.~:
a ternary compound of Na2O—CaO—SiOz system, i.e.
sodium calcium glass, which leads to reducing de?uori
nating action of Na2O and ‘balling up of the mixture,
thus disturbing Water vapor from diffusion to the interior
0110121304) + NaOI -———-> NaHzPOi + Cal-IP04 + H81
of the mixture.
Hence, the present inventor has tried to prevent the
formation of above-mentioned ternary compound by ?x
On the contrary, when phosphoric acid solution is
ing free lime in the crude rock by causing added NazO
added to the phosphate rock, dried and mixed with
radical partly or entirely to present in the form of so
Glauber’s salt, for instance in the above case (1), sodium
dium phosphate. With a result, it has been ascertained 70 phosphate Would be hard to form both in the course of
that a tendency of the mixture to balling up in the course
mixing and in the course of sintering, and with a result,
of heating in a rotary kiln decreases, whereby it seemed
the detiuorination would not be sufficient in the practical
operation in the rotary kiln, even when the predetermined
amounts of P2O5- and Nazo-radicals have been added.
additional amount of Na2O was 0.91 mol to 1 mol of F2
in crude nook, and the ratio of Na2O and P205 in the
Further, the amount of silicic acid to be coexistent in
the present method is above 1 mol per mol of NazO radi
cal. Generally, as phosphate rock contains a considerable
amount of silicic acid, it is not necessary in most cases
mixture was 0.32.
The result of the experiment was as follows:
to add silicic acid speci?cally.
Thus, according to this invention the ?uorine in phos
phate rock can be eliminated very effectively.
The present invention is further ‘described in the fol
lowing examples, which are illustrative but not limitive.
‘The phosphate rock used in the following examples is
Rate of de?uorination ______________________ .._ 99.4
that which is produced in Florida and its chemical com
position is as follows:
Ignition loss
3&8 ................................ __
1 47. 69
F2 in the sintered material ___________________ __ 0.02
Example 3
11 parts of anhydrous Glauber’s salt was added to 100
parts of crude rock, to which was further added 22.5 parts
of phosphoric acid solution containing 40% of P205, and
mixed by kneading and then charged at 1000” C. in the
furnace, wherein the mixture was heated up to 13,500“ C.
15 in 1 hour with passing water vapour, and immediately
thereafter :drawn out of the furnace and cooled rapidly.
In this mixture, the additional amount of P205 radicals
was 1.03 mols to 3 mols of lime other than that which
forms tricalcium phosphate, and the additional amount of
Na2O radicals was 0.84 mol to 1 mol of F2 in crude rock,
and the mol ratio of NazO and P205 in the mixture was
3. 51
013030 other than that which is contained in tricalcium phosphate
The result of the experiment is as follows:
1 . 1 0.
Example 1
F2 in the baking substance ___________________ .. 0.01
20 parts of sodium phosphate (NaH2PO4-2H20) was
added to 100 parts of crude rock, mixed thoroughly and
Rate of de?uorination ______________________ __ 99.7
Example 4
then heated in a quartz tube inserted in an electric tube
furnace with passing water vapour raising from a pre
determined temperature up to 1300” C. in one hour, im
15 parts of table salt was added and mixed with 100
parts of crude rock, to which was further added 22.5
mediately thereafter withdrawn and cooled rapidly. The
parts of phosphoric acid solution containing 40% of P205,
additional amount of P205 radicals in this mixture was
and mixed thoroughly, and then treated similarly as in
1.03 mols to 3 mols of lime other than that which forms
tricalciumphosphate. The additional amount of Nazo
Example 3. The ?uorine content in the sintered material
was 0.02% and the rate of de?uorination was 99.3%.
radicals was 0.69 mol ‘to 1 mol of ?uorine in the crude
rock, and the mol ratio of Na2O and P205 in the com
posed mixture was 0.22. Further, the amount of water
vapour passed through the tube during the heating was
chosen 1.0 g. per minute and air passed therethrough was
6 liters per minute.
The result of the experiment is as follows:
In this mixture, the additional amount of P205 radicals
was 1.02 mols to 3 mols of lime other than which forms
tricalcium phosphate, and the additional amount of Nazo
and the
1. In
was 1.47 mols to 1 mol of F2 in the crude rock,
mol ratio of NaZO- and P2O5-radicals was 0.47.
I claim is:
a method of de?uorinating phosphate rock con
sisting mainly of tricalcium phosphate of apatite struc~
ture by heating the rock in the presence of a sodium salt,
Time re
Starting temperature for heating, ° 0.
quired to
heat up to
F1 content
in sintered
the improvement which comprises contacting the rock
with a sodium phosphate in such quantity as to establish
a concentration of 1 to 3 mols of sodium per mol of
diatomic fluorine in the rock, there being 1 to 2.4 mols of
sodium phosphate per mol of calcium in the rock other
1,200° G ,
0. O6
0. 04
0. 01
50 thereafter sintering the mixture in the presence of water
vapor, the phosphate of the sodium phosphate greatly
reducing the quantity of sodium salt needed for de?uorina~
tion, and recovering from the process a deiluorinated
than the calcium which is present as tricalcium phosphate,
Example 2
30 parts of disodium phosphate (Na2HPO4-l2I-I2O)
was mixed with 100 parts of crude rock, mixed thor
oughly and then sintered in a similar apparatus and con
ditions as in Example 1. The mixture was charged in the
furnace of the sintering temperature of 1000° C., heated
to 1300° C. in 90 minutes with passing Water vapour and
immediately thereafter withdrawn out of the furnace and 60
cooled rapidly. The additional amount of P205 in the
mixture thus composed was 0.68 mol to 3 mols of lime
other than that which forms tricalcium phosphate. The
phosphate rock.
2. In a method as claimed in claim 1, the step of form
ing the sodium phosphate in situ.
References Cited in the ?le of this patent
Rothe et a1 _____________ _.. Oct. 4, 1932
Maust et al ___________ _._ Aug. 16, 1949
Hollingsworth ________ __ July 31, 1951
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