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Патент USA US2106168

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2,106,18
Patented Jan. 25, 1938
UNITED STTES
r
PTENT OFF-IE
2,106,168
PRODUCTION OF ALKALI METAL NITRATES
Alfred Stevens Denny, Hopewell, Va., assignor,
by memo assignments, to The Solvay Process
Company, New York, N. Y., a corporation of
New York
No Drawing. Application October 2, 1931,
Serial No. 566,583
10 Claims. (01. 23-102)
This invention relates to the production of al
kali metal nitrates, more particularly to a proc
ess for the preparation of sodium nitrate free
from a carbonate of sodium and includes corre
lated improvements and discoveries whereby the
production of pure sodium nitrate is facilitated.
The production of an alkali metal nitrate, for
example, the production of sodium nitrate by
the absorption of oxides of nitrogen in an alka
10 line liquor, gives, in the ?nal stages, a resulting
liquor which usually, in order to obviate the cor
rosive action of acid liquor on piping, is slightly
alkaline due to sodium carbonate or caustic al
kali. The liquor is then subjected to evapora
15 tion in order to concentrate it for subsequent
crystallization of the sodium nitrate. During the
evaporation procedure, the sodium carbonate and
sodium bicarbonate that may be present tend
to accumulate in the mother liquor and are held
in solution. When the sodium nitrate has crys
phate, or ammonium chloride. It is preferred to
employ ammonium nitrate which accomplishes
the removal ‘of the sodium carbonate Without
introducing any impurity into the sodium ni
trate. The addition of the salt may be made dur
ing the evaporation or concentration of the liquor
prior to crystallization of the sodium nitrate or
the salt may be introduced prior to-the evapora
tion of the'liquor. There is thereby effected a
decomposition of the carbonate of sodium with 10
the formation of ammonium carbonate, which
in a boiling solution of sodium nitrate decom
poses into ammonia and carbon dioxide which
pass 01? from the boiling solution.
By employing a salt of the type described above 15
for the treatment of sodium nitrate liquor con
taining sodium‘ carbonate, it is possible to remove
the sodium carbonate in a simple efficacious
manner.
As an illustrative embodiment of a manner in
tallized and is subsequently separated by ?ltra
tion, the ?ltering operation does not completely
which the process may be carried out in practice,
remove all of the mother liquor from the crys
tale. The dry salt therefore contains a small
amount of a carbonate of sodium. The presence
A sodium nitrate liquor containing, for ex
ample, an amount of a carbonate of sodium
of the small amount of this impurity is disadvan
tageous when the sodium nitrate is utilized for
certain purposes, and accordingly it is an object
of this invention to obviate such disadvantages.
It is an objectof this invention to provide a
process for the treatment of basic liquors con
taining an alkali metal nitrate for the produc
tion therefrom of a satisfactory solid nitrate
product. More particularly, it is an object of
the invention to provide a process in accordance
with which sodium nitrate substantially free
from sodium carbonate and sodium bicarbonate
may be obtained readily and ei?ciently on a com
mercial scale.
Other objects of the invention will in part be
obvious and will in part appear hereinafter.
The invention accordingly comprises the sev~
eral steps and the relation of one or more of such
steps with respect to each of the others thereof,
45 which will be exempli?ed in the process herein
after disclosed, and the scope of the invention
will be indicated in the claims.
In the practice of the invention, an alkali metal
nitrate liquor obtained in the course of manu
v50 facture, and particularly a sodium nitrate liquor
containing a carbonate of sodium may be re
acted With an ammonium salt. Examples of
salts suitable for addition to the nitrate liquor
in accordance with this: invention are ammonium
nitrate, ammonium sulfate, ammonium phos
the following example is given:
equivalent to about 2 grams per liter of NazCOs 25
is passed into an evaporator, as a three-effect
multiple evaporator, and therein concentrated.
This sodium nitrate liquor during the concentra
tion in the evaporator, and more particularly in
the third, or last effect thereof, is reacted with
ammonium nitrate. The ammonium nitrate is
added in the proportions of about 3 grams am
monium nitrate per liter of, original solution be
fore evaporation. This corresponds to stoichio
metric proportions of ammonium nitrate and so 35
dium carbonate in solution. There is thereby
eiiected a reaction with the sodium carbonate
and/or sodium bicarbonate which may be pres
ent, and their removal whereby the carbonate is
prevented from passing into the mother liquor 40
and being present in the sodium nitrate whenit
is obtained in dry, crystalline form. The sodium
nitrate which crystallizes from the evaporated
liquor, is separated by ?ltration and subsequently
dried in a suitable drier.
45
The ammonium salt may also be added to the
nitrate liquor by forming the salt in situ within
the liquor. Thus, for example, an acid nitrate
liquor containing free nitric acid and prior to
?nal addition of sodium carbonate may be treat 50
ed with ammonia to form the desired quantity
of ammonium nitrate by reaction'with a portion
of the free nitric acid in the liquor and the resid-v
ual nitric acid then reacted with additional so
dium carbonate." During the concentration of 55
2
2,106,168
the thus treated liquor, the ammonium nitrate
reacts with the sodium carbonate and/or sodium
bicarbonate which may be present to remove the
carbonate and result in the production of a so
dium nitrate substantially free from carbonate.
By the process above described, the sodium car
bonate and/or sodium bicarbonate content of a
sodium nitrate liquor may be substantially en
tirely removed and such removal is considered to
be brought about in the manner set forth by the
following equations:
4. In a process for the production‘ of sodium 10
nitrate from an aqueous solution containing the
same together with a small proportion of an al
kaline material from the group consisting of
sodium carbonate and sodium hydroxide, that
improvement which comprises reacting said alka 16
15
As will appear from the above equations the
amount of the salt added will be preferably that
which is required to fully react with the car.
bonate of sodium present in the sodium nitrate
liquor.
»
Sodium nitrate produced in the foregoing man
ner is substantially free from a carbonate of so
dium and a nitrate containing not more than
0.02 per cent. of sodium carbonate may be ob
25 tained on a commercial scale.
Since certain‘ changes may be made in carry
ing out the above process without departing from
the scope of the invention, it is intended that all
matter contained in the above description shall
30 be interpreted as ilustrative and not in a limiting
sense. For example, when the nitrate liquor
contains a base such as sodium hydroxide to ren
der it slightly basic in reaction and non-corro
sive to the evaporator, the liquor may be treated
35 in accordance‘ with this invention by the addi
tion thereto ofan ammonium salt and heating
to evolve ammonia, thus removing excess base
from the liquor and enabling the manufacturer
to produce a satisfactory crystalline sodium ni
40 trate product. This invention is likewise appli
cable to the production of alkali metal nitrates
in general, and in particular to potassium nitrate
from a basic liquor containing the same together
with potassium carbonate or other alkaline
45 material.
I claim:
1. In a process for the production of an alkali
metal nitrate from an aqueous solution of the
same containing a small proportion of an alkaline
50 material from the group consisting of the alkali
metal carbonates and hydroxides, that improve
ment which comprises treating said solution with
an inorganic ammonium salt and heating the
thus treated solution to concentrate it until said
55 alkaline material is substantially completely re
moved therefrom.
2. In a process for the production of an‘ alkali
metal nitrate from an aqueous solution contain
ing the same together with a small proportion of
an alkaline material from the group consisting
of the alkali metal carbonates and hydroxides,
that improvement which comprises treating said
solution with an ammonium salt belonging to the
group consisting of ammonium nitrate, ammo
nium, sulfate, ammonium chloride and ammo
nium phosphate and heating the thus treated
solution to evaporate water therefromyuntil said
70
solution with an ammonium salt belonging to
the group consisting of ammonium nitrate,
ammonium sulfate, ammonium chloride and
ammonium phosphate in amount corresponding
to about stoichiometric proportions to the alka
line material present in the solution and heating
the thus treated solution to evaporate water
therefrom until said alkaline material is substan
tially completely removed therefrom.
line material in the solution with an ammonium
salt belonging to the group consisting of am
monium nitrate, ammonium sulfate, ammonium
chloride and ammonium phosphate and heating
the thus treated solution to evaporate water 20
therefrom until said alkaline material is sub
stantially completely removed from the solution.
5. In a process for the production of sodium
nitrate from an aqueous solution containing the
same together with a small proportion of an al
kaline material from the group consisting of so
dium carbonate and sodium hydroxide, that im_
provement which comprises treating said solu
tion with an ammonium salt belonging to the
group consisting of ammonium nitrate, ammo 80
nium sulfate, ammonium chloride andammo
nium phosphate in amount corresponding to
about stoichiometric proportions to the alkaline
material present in the solution and heating the
thus treated solution to evaporate water there 35
from until said alkaline material is substantially
completely removed therefrom.
6. In a process for the production of sodium
nitrate from an aqueous solution of the same
containing a small proportion of an alkaline ma
terial-from the group consisting of sodium car
bonate and sodium hydroxide, that improvement
which comprises reacting said alkaline material
in the solution with ammonium nitrate and heat
ing the solution under conditions such that am
monia is evolved from the solution until the al
kaline material is substantially completely re
moved therefrom.
7. In a process for the production of sodium
nitrate from an aqueous solution of the same
containing a small proportion of an alkaline
material from the group consisting of sodium
carbonate and sodium hydroxide, that improve
ment which comprises reacting said alkaline ma
terial in the solution with ammonium nitrate and 55
heating the solution to evaporate it until said
alkaline material is substantially completely re
moved therefrom.
8. In a process for the production of sodium, ni
trate from an aqueous solution of the same con
taining a small proportion of sodium carbonate,
that improvement which comprises reacting the
sodium carbonate in the solution with ammonium
nitrate and heating the solution to evaporate
water therefrom until the solution is substan
tially completely freed of carbonate.
alkaline material is substantially completely re
moved from the solution.
9. In a process for the production of sodium
nitrate from an aqueous solution of the same
containing a small proportion of sodium car
3. In a process for the production of an alkali
metal nitrate from an aqueous solution contain
ing the same together with a small proportion ‘of
ing the sodium carbonate in the solution with
about stoichiometric proportions of ammonium
an alkaline material from the groupconsisting
of the alkali metal carbonates and hydroxides,
nitrate, and heating the solution to evaporate
water therefrom until the solution is substan
that improvement which comprisestreating said
tially freed of carbonate.
bonate, that improvement which comprises react 70
75
2,106,168
10. In a process for the production of sodium
nitrate that improvement which comprises re
acting ammonia With an aqueous sodium ni
trate solution containing free nitric acid, adding
sodium carbonate to the thus treated solution
until it is basic but contains sufficient ammonium
3
salt to fully react with the sodium carbonate
present and heating said basic solution to evap
orate water therefrom until the carbonate is
substantially completely removed from the solu
tion.
ALFRED STEVENS DENNY.
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