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Патент USA US3062629

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Nov. 6, 1962
H. A. BEEKHUIS
3,062,619
CONVERSION OF METAL CHLORIDES TO THE CORRESPONDING METAL NITRATES
Filed Sept. 26, 1960
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United States Patent
ICQ
A
3,052,619
‘Patented Nov. 6, 1952
2
1
recycle stream of nitric acid containing from 50%, to
65% by weight of nitric acid on a salt-free basis, prefer
ably from 50% to 60% nitric acid, which stream prefer
ably is the mother liquor from which the potassium
3,062,619
CONVERSION OF METAL CHLORIDES T0 COR
RESPONDING METAL NITRATES
Herman A. Beekhuis, Mount Alvemo Road, Media, Pa.
nitrate crystal product ‘has been separated, is passed
Filed Sept. 26, 1960, Ser. No. 58,518
8 Claims. (Cl. 23-102)
through this column to maintain the acid concentration
therein at a level to give high yields of potassium nitrate.
The vapors consisting of chlorine and nitrogen dioxide
are taken off overhead from the top of the column, main
This invention relates to the conversion of alkali metal
and alkaline earth metal chlorides (particularly potas
sium chloride) to the corresponding alkali and alkaline 10 tained at a temperature of from —5° C. to -—l0° C.,
earth metal nitrates.
condensed and a portion of the condensate returned as
Potassium nitrate, as is well known, is useful as a
re?ux. The amount thus returned is preferably from
fertilizer, a constituent of mixed fertilizers, and as a raw
40% to 60% of the total condensate removed overhead.
material in many processes. This invention will herein
The amount of re?ux returned to the column can be re
after be described in connection with the conversion of 15 duced by inserting a Water cooled coil about halfway
potassium chloride to potassium nitrate, 1but it will be
between the nitric acid feed point and the top of the
understood, it is not limited thereto and includes the
column. The remainder of this condensate consisting of
conversion of other alkali metal chlorides, such as sodium,
a mixture of chlorine and nitrogen dioxide in the pro
and alkaline earth metal chlorides, such as calcium, to
portions of 2 mols of nitrogen dioxide per mol of chlorine
20 may be fractionated to remove chlorine as product. The
the corresponding nitrates.
The reaction of potassium chloride with nitric acid to
nitrogen dioxide may be reacted with‘ water and oxygen
produce potassium nitrate, nitrosyl chloride and chlorine,
to form nitric acid employed in the process.
the oxidation of the nitrosyl chloride to produce nitrogen
The bottoms from this column contains potassium
dioxide (ZNOZSNQOQ and chlorine, the separation of
nitrate, some sodium nitrate formed from the sodium
the nitrogen dioxide from the chlorine and the reaction 25 chloride invariably present as an impurity in the potas
of the nitrogen dioxide thus separated with potassium
sium chloride, water and nitric acid, the latter in amount
chloride in the presence of nitric acid or with water and
oxygen to produce nitric acid for use in the process has
of from 45% to 55% by weight on a salt-free basis.
When the reaction is carried out in the ?rst stage so
been suggested.
'
that the bottoms contain less than 55% nitric acid on
It is amongr the objects of the present invention to 30 a salt-free basis, say about 50%, the bottoms will also
provide a process of converting potassium chloride to
potassium nitrate which results in economically attractive
high yields of potassium nitrate and yet eliminates the
contain hydrogen chloride in amount of about 0.1% by
.‘weight.
On the other hand, when the reaction is con
ducted so as to produce as bottoms a reaction mixture
containing about 55% nitric acid or more on a salt~free
necessity of employing an oxidation treatment compara
ble to the oxidation of nitrosyl chloride employed in 35 basis, then the hydrogen chloride concentration will be
heretofore known procedures.
It is another object of this invention to provide such
less than about 0.05% by weight. In the latter case, the
‘hydrogen chloride in the bottoms can conveniently be
taken off overhead in step 2 as hereinafter described.
process which is comparatively simple to carry out and
requires for its practice less equipment than prior known
techniques for producing potassium nitrate from potas
Should the reaction mixture removed as bottoms from
step 1 contain more than about 0.1% hydrogen chloride,
the hydrogen chloride is removed‘ in step 2 and recycled
to the distillation column in step 1 where it reacts with
sium chloride.
Still another obfect of this invention is to provide such
process which results in the production of acid liquors
nitric acid forming chlorine, nitrogen dioxide and water,
of a character such as to minimize corrosion problems in
which chlorine and nitrogen dioxide are removed over
the handling thereof, particularly in the crystallizer and 45 head from the distillation column in step 1.
equipment associated therewith for effecting separation of
Step 2: The reaction mixture removed as bottoms from
the potassium nitrate crystals from the mother liquor.
step 1 is introduced into a distillation column where it
Other objects and advantages of this invention will be
is subjected to distillation ?owing downwardly in the
apparent from the following detailed description thereof
base portion of the column countercurrent' to a rising
taken in connection with the accompanying drawings in 50 stream of vapor produced by boilingv the reaction mix
which:
'IGURE 1 is a diagrammatic layout of the equipment
for practicing one embodiment of the invention; and
FIGURE 2 is a diagrammatic layout of the equipment
for practicing another embodiment of the invention.
The process of this invention involves three stages or
55
ture at the base of the column. This column is main
tained at a temperature of about 120° C. at the base
and 100° C. at its top. Operating with the ‘reactor bot
toms containing about 50% nitric acid on a salt-free
basis, and hence containing about 0.1 % hydrochloric acid,
as the vapors rise in the column ‘they tend to become
more and more concentrated with respect to their hydro
steps, which will be numbered sequentially for purposes
chloric acid content. At‘ a point in the column approxi
of facilitating a description of the invention. It will be
mately one-third from the top, a vapor mixture is formed
appreciated the process is continuous. These stages take
place concurrently and the numbers do not indicate any 60 containing approximately 3 mols‘ of hydrochloric acid
sequence in the point of time.
v
per mol of nitric acid.
Above this point little or no hy
drochloric acid is present. At the top of the column
In the ?rst stage, potassium chloride is reacted with
the vapors consist substantially entirely of water. These
nitric acid having a strength of at least 75% by‘ weight,
vapors are removed, condensed and a portion returned
preferably from 80% to 100% by weight, in the propor
tions of about 2 mols of nitric acid per mol of potassium 65 as re?ux. The amount thus returned is from 25% to
chloride by ?owing the nitric acid introduced near the
50% of the vapors removed overhead.
At the point of the column where the hydrochloric
top of a distillation column and they potassium chloride
introduced at a point below the nitric acid downwardly
acid vapors concentrate and are present in approximately
countercurrent to a rising stream ‘of vapors of nitrogen
the proportions of 3 mols of hydrochloric acid per mol
dioxide, nitrosyl chloride and chlorine produced by‘boil 70 of nitric acid, a‘ side stream is removed and introduced
ing the reaction mixture at the base of the column. A
into the distillation column employed in the ?rst stage
3,062,619
3
4
where the hydrochloric acid reacts with the nitric acid
to produce chlorine, nitrogen dioxide and water; this side
stream contains up to about 12% hydrochloric acid.
In the alternative procedure in which the reaction mix
ture removed as bottoms contains 55% by weight or
more of nitric acid on a salt-free basis, the chloride
removed as bottoms through line 42 and can be reacted
with water and oxygen to produce nitric acid to supply
fresh nitric acid for the process.
FIGURE 1 differs from FIGURE 2 chie?y in that the
acid concentrator 21 is provided with a line 43 leading
to the reactor 10. A side stream is removed through
content is so low that it can be e?iciently removed over
this line from the acid concentrator, which stream con
head from the concentrating column employed in step 2.
In this mode of operation, the temperatures in the column
tains 2 to 3 mols of hydrochloric acid per mol of nitric
acid.
are substantially the same as in the ?rst described method 10
The following examples are given for purposes of
in which a side stream is removed from the concentrat
illustrating the invention. It will be understood the in
ing column and is fed to the reactor column. No side
vention is not limited to these examples. In these ex
stream is removed from the concentrating column in
this alternative mode of operation. The overhead vapors
amples all pound values are pounds per hour, percent
ages are on a weight basis, and temperatures are in ° C.
containing a small amount of hydrochloric acid are con
densed, from 25% to 50% of the condensate returned
as re?ux and the remainder of the condensate may be
passed to waste.
Step 3: The concentrated reaction mixture from step
2 containing from 55% to 65% by Weight of nitric acid
on a salt-free basis is passed to the crystallizer where
the potassium nitrate is crystallized. These crystals are
separated from the mother liquor. The mother liquor
containing from 55% to 65% by weight of nitric acid
on a salt-free basis, as hereinabove described, is recycled
through the distillation column employed in step 1.
In FIGURE 1 of the drawing, 10 is a distillation
column provided with a boiler 11 at its base. A con
denser 12 is arranged to receive the vapor stream com
ing off from the top of distillation column 10. The
condensate from condenser 12 is divided into two streams,
one of which is returned as re?ux through line 13 and
the other pumped by pump 14 to the chlorine still 15.
Fresh nitric acid is supplied to the reactor 10 through
line 16. The potassium chloride feed is supplied by line
17 to a slurry mixer 17' into which the recycle acid is
supplied through line 18. The resultant slurrv enters
the reactor 10 through line 19.
In the base of reactor
Example I
This example is carried out in equipment of the type
shown in FIGURE 1.
Step 1: 157.5 pounds of nitric acid of 80% concentra
tion containing 126 pounds (2 mols) of nitric acid and
31.5 pounds of water are introduced into the potassium
chloride reactor at a point where the temperature is
about 90° C. Introduced into this reactor at approxi
mately its midpoint, which is below the point of introduc
tion of the nitric acid, is a slurry of potassium chloride
produced by mixing 74.5 pounds (1 mol) of potassium
chloride with the recycle acid stream in amount of 866.5
pounds consisting of 315 pounds nitric acid, 257.5 pounds
water, 206.0 pounds potassium nitrate and 88.0 pounds
sodium nitrate. This recycle acid stream contains 55%
nitric acid on a salt-free basis.
The temperature at the
base of the reactor is 115° C. and at the top —5° C.
Also introduced into the reactor is a side stream re
moved from the acid concentrator employed in step 2
which side stream is in amount of 10.0 pounds and con
sists of 0.5 pound of nitric acid, 8.9 pounds water and
0.6 pound hydrochloric acid.
The vapors taken off overhead are cooled to a tem
10 the mixture is maintained at its boiling point which,
when the column is operated under atmospheric pressure 40 perature of ~25° C. The condensate thus produced
is divided into two streams. One stream in amount of
conditions, is approximately 115° C. The top of this
81.5 pounds consisting of 35.5 pounds of chlorine and
column is at a temperature of ——5° C. to —10° C., pref
46.0 pounds nitrogen dioxide is returned as re?ux. The
erably —7° C. The fresh nitric acid is introduced
other or second stream in amount of 81.5 pounds con
through line 16 at a point in the column where the
sisting
of 35.5 pounds chlorine and 46.0 pounds nitrogen
temperature is about 90° C.
dioxide is passed to the chlorine still where the nitrogen
The recycle acid concentrator 21 is in the form of a
dioxide is separated from the chlorine.
distillation column which communicates through .line 22
1027.0 pounds of reactor bottoms is removed con
with the base of the potassium chloride reactor 10 so
taining 50% nitric acid on a salt-free basis. The re
that the ‘bottoms from this reactor ?ow continuously
through line 22 leading into column 21 at point 23. A 50 actor bottoms contain 315.5 pounds nitric acid, 315.9
pounds water, 0.6 pound hydrochloric acid, 307 pounds
boiler 24 communicates with the base of this column
for maintainin" the reaction products at the boiling point,
i.e.. about 120° C.
The ton of this column communicates with a con
denser 25 for condensing the vapor leaving the column.
The condensate is divided into two streams. one of which
is returned as re?ux through line 26 and the other is
removed through line 27.
Pump 31 pumps the concentrated slurrv from con
centrator 21 through the circulating svstem 32 of the 60
crvstallizer 33: circulating system 32 comprises a cooler
34. The cooled liquid is mixed with the concentrated
slurrv and the mixture is pumned into the crvstallizer
33. Crvstals are withdrawn from the base of the
crvstallizer 33 through the line 35 and enter the centrifuge
36 which effects the separation of the potassium nitrate
crystals from the mother liquor. The mother liquor
is pumped by pump 38 through the line 37 into the
slurry mixer 17'.
potassium nitrate and 88 pounds sodium nitrate.
Step 2: The reactor bottoms are introduced into the
acid concentrator operated at a temperature of 120° C.
at its base and 100° C. at its top. The vapors taken over
head are condensed and the condensate divided into two
streams. One of these is returned as re?ux in amount
of 34.6 pounds consisting entirely of water. The other
stream consisting of 49.5 pounds water is passed to
waste.
Bottoms from the acid concentrator are removed
in amount of 967.5 pounds consisting of 315 pounds nitric
acid, 257.5 pounds Water, 307 pounds potassium nitrate
and 88 pounds sodium nitrate. It contains 55 weight
percent nitric acid on a salt-free basis.
Step 3: The bottoms from the acid concentrator are
cooled to 40° C. and introduced into the crystallizer.
A slurry of crystals are withdrawn from the crystallizer
and passed through a centrifuge. 101 pounds of potas
sium nitrate (1 mol) are removed from the centrifuge.
The overhead from the reactor 10 is pumped into 70 The mother liquor in amount of 866.5 pounds consisting
of 315 pounds nitric acid, 257.5 pounds water, 206
chlorine still 15 where it is fractionated, the chlorine
pounds potassium nitrate and 88 pounds sodium nitrate
going off overhead and condensed in condenser 39. A
portion of the chlorine is returned to chlorine still 15
is recycled to the potassium chloride reactor. It con
through line 40 as re?ux liquid and the remainder re
tains about 55 weight percent nitric acid on a salt-free
moved as product through line 41. Nitrogen oxides are 75 basis.
3,062,619
5
Example 11
This example is also carried out in equipment of
the type shown in FIGURE 1.
Step 1: 157.5 pounds of nitric acid of 80% concen
tration containing 126 pounds (2 mols) of nitric acid and
31.5 pounds of water are introduced into the potassium
chloride reactor at a point where the temperature is
about 90° C. Introduced into this reactor at approxi
The vapors taken off overhead are cooled tov a tem
perature of —25° C. The condensate thus produced is
divided into two streams.
One stream is returned as
re?ux and the other stream is passed to the chlorine still
where the nitrogen is separated from the chlorine. Each
stream is in amount of 81.1 pounds consisting of 35.3
pounds chlorine and 45.8 pounds nitrogen dioxide.
975.2 pounds of reactor bottoms are removed contain
ing 55% nitric acid on a salt—free basis. The reactor bot
mately its midpoint, which is below the point of introduc
tion of the nitric acid, is a slurry of potassium chloride 10 toms contain 330 pounds nitric acid, 269.5 pounds water,
produced by mixing 74.5 pounds (1 mol) of potassium
chloride with the recycle acid stream in amount of
405.8 pounds consisting of 161 pounds nitric acid, 107.3
pounds water, 97 pounds potassium nitrate and 40.5
0.2 pound hydrochloric acid, 299 pounds potassium
nitrate and 76.5 pounds sodium nitrate.
Step 2: The reactor bottoms are introduced into the
acid concentrator operated at a temperature of 120° C.
pounds sodium nitrate. This recycle acid stream con 15 at its base and 100° C. at its top. The vapors taken over
head are condensed and the condensate divided into two
tains 60% nitric acid on a salt-free basis. The tempera
ture at the base of the reactor is 115 ° C. and at the top
—5° C.
streams.
One of these is returned as re?ux in amount of
34,96 pounds consistingof 34.65 pounds water, 0.14 pound
hydrochloric acid and 0.17 pound nitric acid. The other
Also introduced into the reactor is a side stream re
moved from the acid concentrator employed in step 2 20 stream in amount of 49.95 pounds consisting of 49.5
pounds water, 0.2 pound hydrochloric acid and 0.25
which side stream is in amount of 5 pounds and consists
pound nitric acid is passed to waste. Bottoms from the
of 0.25 pound nitric acid, 4.45 pounds Water, and 0.3
pound hydrochloric acid.
The vapors taken off overhead are cooled to a tern
acid concentrator are removed in amount of 925.25
pounds consisting of 329.75 pounds nitric acid, 220 pounds
perature of —25° C. The condensate thus produced is 25 water, 299 pounds potassium nitrate and 76.5 pounds so
dium nitrate. It contains 60 weight percent nitric acid
divided into two equal streams. One stream is returned
on a salt-free basis.
as re?ux, and the other stream is passed to the chlorine
Step 3: The bottoms from the acid concentrator are
still where the nitrogen dioxide is separated from the
cooled to 40° C. and introduced into the crystallizer. A
chlorine. Each stream is in amount of about 81.5
slurry of crystals are withdrawn from the crystallizer and
pounds consisting of 35.5 pounds chlorine and 46.0
passed through a centrifuge. 101 pounds of potassium
pounds nitrogen dioxide.
nitrate (1 mol) are removed from the centrifuge. The
561.3 pounds of reactor bottoms are removed con
mother liquor in amount of 824.25 pounds consisting of
taining 50% nitric acid on a salt-free basis. The reactor
329.75 pounds nitric acid, 220 pounds water, 198 pounds
bottoms contain 161.25 pounds nitric acid, 161.25 pounds
water, 0.3 pound hydrochloric acid, 198 pounds potas 35 potassium nitrate and 76.5 pounds sodium nitrate is
recycled to the potassium chloride reactor. It contains
sium nitrate and 40.5 pounds sodium nitrate.
60 weight percent nitric acid on a salt-free basis.
Step 2: The reactor bottoms are introduced into the
acid concentrator operated at a temperature of 120° C.
Example IV
at its base and 100° C. at its top. The vapors taken
This
example
is
carried
out in equipment of the type
overhead are condensed and the condensate divided 40
shown
in
FIGURE
2.
into two streams. One of these is returned as re
?ux in amount of 34.65 pounds consisting entirely of
water. The other stream consisting of 49.5 pounds water
is passed to waste. Bottoms from the acid concentrator
are removed in amount of 506.8 pounds consisting of
161 pounds nitric acid, 107.3 pounds water, 198 pounds
potassium nitrate and 40.5 pounds sodium nitrate. It
Step 1: 157.5 pounds of nitric acid of 80° concentra
tion containing 126 pounds (2 mols) of nitric acid and
31.5 pounds of water are introduced into the potassium
chloride reactor at a point where the temperature is
about 90° C. Introduced into this reactor at approxi
mately its midpoint, which is below the point of intro
duction of the nitric acid, is a slurry of potassium chloride
contains 60 weight percent nitric acid on a salt-free basis.
Step 3: The bottoms from the acid concentrator are
cooled to 40° C. and introduced into the crystallizer.
chloride with the recycle acid stream in amount of 412.5
weight percent nitric acid on a salt-free basis.
vided into two streams. One stream is returned as re?ux
produced by mixing 74.5 pounds (1 mol) of potassium
pounds consisting of 177 pounds nitric acid, 95.5 pounds
A slurry of crystals are withdrawn from the crystallizer
water, 98 pounds potassium nitrate and 42 pounds sodium
and passed through a centrifuge. 101 pounds of potas
nitrate. This recycle acid stream contains 65% nitric
sium nitrate (1 mol) are removed from the centrifuge.
acid on a salt-free basis. The temperature at the base of
The mother liquor in amount of 405.8 pounds consisting
55
the reactor is 115° C. and at the top —5° C.
of 161 pounds nitric acid, 107.3 pounds water, 97 pounds
The vapors taken off overhead are cooled to a tempera
potassium nitrate and 40.5 pounds sodium nitrate is re
ture of —25° C. The condensate thus produced is di
cycled to the potassium chloride reactor. It contains 60
Example 111
This example is carried out in equipment of the type
shown in FIGURE 2.
Step 1: 157.5 pounds of nitric acid of 80% concen
tration containing 126 pounds (2 mols) of nitric acid and
and the other stream is passed to the chlorine still where
60 the nitrogen dioxide is separated from the chlorine. Each
stream is in amount of 81.3 pounds consisting of 35.4
pounds chlorine and 45.9 pounds nitrogen dioxide.
563.1 pounds of reactor bottoms are removed contain
ing 55% nitric acid on a salt-free basis. The reactor
31.5 pounds of water are introduced into the potassium 65 bottoms contain 177 pounds nitric acid, 145 pounds water,
0.1 pound hydrochloric acid, 199 pounds potassium ni
chloride reactor at a point where the temperature is about
trate and 42 pounds sodium nitrate.
90° C. Introduced into this reactor at approximately
Step 2: The reactor bottoms are introduced into the
its midpoint, which is below the point of introduction of
acid concentrator operated at a temperature of 120° C.
the nitric acid, is a slurry of potassium chloride with the
recycle acid stream in amount of 824.25 pounds consist 70 at its base and 100° C. at its top. The vapors taken over;
head are condensed and the condensate divided into two
ing of 329.75 pounds nitric acid, 220 pounds water, 198
streams. One of these is returned as reflux in amount
pounds potassium nitrate and 76.5 pounds sodium nitrate.
of 34.84 pounds consisting of 34.65 pounds water, 0.07
This recycle acid stream contains 60% nitric acid on a
pound hydrochloric acid and 0.12 pound nitric‘acid. The
salt-free basis. The temperature at the base of the reac
75 other stream in amount of 49.77 pounds ‘consisting of 49.5
tor is 115° C. and at the top —5° C.
sperms
7
8
pounds water, 0.1 pound hydrochloric acid and 0.17
2 mols of nitric acid per mol of metal chloride in a dis
pound nitric acid is passed to waste. Bottoms from the
acid concentrator are removed in amount of 513.5 pounds
tillation column by ?owing the nitric acid and metal
consisting of 177 pounds nitric acid,- 95.5 pounds water,
199 pounds potassium nitrate and 42 pounds sodium
said column produced by boiling the reaction mixture
while recycling through said column nitric acid having a
nitrate. It contains 65 weight percent nitric acid on a
salt-free basis.
concentration of from 50% to 65% by weight on a salt
free basis, thus producing in said column as the vapor
product of reaction only chlorine and nitrogen dioxide,
said recycled nitric acid being obtained as the mother
Step 3: The bottoms from the acid concentrator are
cooled to 40° C. and introduced into the crystallizer. A
chloride countercurrent to a rising stream of vapors in
slurry of crystals are withdrawn from the crystallizer 10 liquor in the crystallization of metal nitrate from the
and passed through a centrifuge. 101 pounds of potas
reaction mixture produced in said column.
2. The process of converting potassium chloride to
sium nitrate (1 mol) are removed from the centrifuge.
The mother liquor in amount of 412.5 pounds consisting
the corresponding nitrate which comprises reacting nitric
of 177 pounds nitric acid, 95.5 pounds water, 98 pounds
acid of at least 75% by weight concentration with said
potassium nitrate and 42 pounds sodium nitrate is re
potassium chloride in the proportions of about 2 mols
cycled to the potassium chloride reactor. It contains 65
of nitric acid per mol of potassium chloride in a dis
weight percent nitric acid on a salt-free basis.
tillation column by ?owing the nitric acid and potassium
It will be noted that the present invention provides a
chloride countercurrent to a rising stream of vapors in
process of converting potassium chloride and other alkali
said column produced by boiling the reaction mixture
metal and alkaline earth metal chlorides to the cor-re 20 while recycling through said column nitric acid having a
sponding metal nitrate, which process results in high yields
concentration of from 50% to 65 % by weight on a salt
of metal nitrate in that substantially all of the alkali metal
free basis, thus producing in said column as the vapor
product of reaction only chlorine and nitrogen dioxide,
and alkaline earth metal is utilized in the process and
said recycled nitric acid being obtained as the mother
this without producing nitrosyl chloride which, as a prac
tical matter, must be oxidized to recover the nitrogen 25 liquor in the crystallization of potassium chloride from
values thereof. Hence the present invention can be car
the reaction mixture produced in said column.
ried out in more simple and less expensive equipment,
3. The process of converting a metal chloride from the
because it eliminates the necessity of using oxidation
group consisting of alkali metal and alkaline earth metal
equipment comparable to the nitrosyl chloride oxidizers.
chlorides to the corresponding nitrate which comprises:
Moreover, the liquors produced in the processes of 30 step 1, feeding to a distillation column nitric acid of at
least 80% concentration by weight and said metal chlo
the present invention are of such character as to mini
mize corrosion problems entailed in their handling. In
ride in the proportions of about 2 mols of nitric acid per
one modi?cation involving the production of a reac
mol of metal chloride, passing the metal chloride and
nitric acid downwardly through said column counter
tion mixture in the ?rst stage containing about 50 weight
current to a rising stream of vapors produced by heating
percent nitric acid on a salt-free basis and accordingly
containing appreciable amounts of hydrochloric acid, the
the reaction mixture to its boiling point near the base of
hydrochloric acid is concentrated in the distillation col
said column, condensing the vapors containing chlorine
umn employed in step 2 and a side stream containing the
and nitrogen dioxide leaving the top of said column
hydrochloric acid is removed from this distillation column
and returning as re?ux to the top of said column a por
and passed to the potassium chloride reactor. Thus the
tion of the condensate, maintaining the top of said col
umn at a temperature of —5° C. to -—10° C., recycling
concentrated reaction mixture fed to the crystallizer is
through said column mother liquor derived from step
free of chloride, minimizing corrosion problems in the
3 containing from 50% to 65 % by weight ‘of nitric acid
crystallizer, centrifugal separator, or other separating
equipment employed in association with the crystallizer.
on a salt—free basis; step 2, concentrating the reaction mix
In the other modi?cation in which the reaction mix 45 ture from step 1 in a distillation column to drive off over
ture removed from step 1 contains about 55 or more
head water and remove as bottoms concentrated reaction
mixture containing from 50% to 65% by weight nitric
weight percent nitric acid on a salt-free basis, the chloride
content of this reaction mixture is so low that all of the
acid on a salt-free basis, and step 3, crystallizing metal
chloride can conveniently be removed overhead in the
nitrate from the concentrated reaction mixture from step
2, separating the metal nitrate crystals from the mother
distillation column eitecting concentration of the reaction
liquor and recycling the mother liquor through step 1.
mixture. Here also the concentrated reaction mixture fed
4. The process of converting potassium chloride to
to the crystallizer is free of chloride.
potassium nitrate which comprises: step 1, feeding to a
Since certain changes may be made in carrying out the
above described method of converting alkali metal and
distillation column nitric acid of at least 80% concentra~
alkaline earth metal chlorides to the corresponding nitrates 55 tion by weight and potassium chloride in the proportions
of about 2 mols of nitric acid per mol of potassium
without departing from the scope of this invention, it is
intended that all matter contained in the above descrip
chloride, passing the potassium chloride and nitric acid
tion or shown in the accompanying drawings shall oe
downwardly through said column countercurrent to a
interpreted as illustrative and not in a limiting sense.
rising stream of vapors produced by heating the reaction
Thus while the invention has been described in connec 60 mixture to its boiling point near the base of said column,
tion with operations in the potassium chloride reactor and
acid concentrator under atmospheric pressure conditions
(pressure of about 1 atmosphere at the top of each col
umn), these columns may be operated under pressures of
condensing the vapors containing chlorine and nitrogen di
oxide leaving the top of said column and returning as
re?ux to the top of said colum a portion of the condensate,
pressures. The temperatures will, of course, be changed
correspondingly; the mixtures in the bottoms of these
mother liquor derived from step 3 containing from 50%
columns are maintained boiling under the pressure condi
step 2, concentrating the reaction mixture from step 1
tions existing therein.
in a distillation column to drive off overhead water and
maintaining the top of said column at a temperature of
two or three atmospheres or even higher superatmospheric 65 —5° C. to —10° C., recycling through said column
to 65% by weight of nitric acid on a salt-free basis;
What is claimed is:
70 remove as bottoms concentrated reaction mixture con
taining from 50% to 65% by weight nitric acid on a
1. The process of converting a metal chloride from the
salt-free basis; and step 3, crystallizing potassium nitrate
group consisting of alkali metal and alkaline earth metal
from the concentrated reaction mixture from step 2, sepa
chlorides to the corresponding nitrate which comprises
rating the potassium nitrate crystals from the mother
reacting nitric acid of at least 75% by weight concentra
tion with said metal chloride in the proportions of about 75 liquor and recycling the mother liquor through step 1.
3,062,619
10
5. The process of converting potassium chloride to
potassium nitrate which comprises: step 1, feeding to a
distillation column nitric acid of about 80% by weight
concentration and potassium chloride in the proportions
of about 2 mols of nitric acid per mol of potassium chlo
ride, passing the potassium chloride and nitric acid doWn~
wardly through said column countercurrent to a rising
7. The process of converting potassium chloride to
potassium nitrate which comprises: step 1, feeding to a
distillation column nitric acid of about 80% by weight
concentration and potassium chloride in the proportions
of about 2 mols of nitric acid per mol of potassium chlo
ride, passing the potassium chloride and nitric acid down
wardly through said column countercurrent to a rising
stream of vapors of chlorine and nitrogen dioxide pro
stream of vapors of chlorine and nitrogen dioxide pro
duced by heating the reaction mixture to its boiling point
duced by heating the reaction mixture to its boiling point
near the base of said column, condensing said vapors
leaving the top of said column and returning as a re?ux
to the top of said column a portion of the condensate,
maintaining the top of said column at a temperature of
near the base of said column, condensing said vapors
leaving the top of said column and returning a portion
nitric acid on a salt-free basis; step 2, concentrating the
centrating the reaction mixture from step 1 in a distilla
tion column to drive o? water overhead, and removing
of the condensate as re?ux to the top of said column at
a temperature of about —5° C., recycling through said
column mother liquor derived from step 3 containing 60%
about ———5° C., recycling through said column mother
liquor derived from step 3 containing 55% by weight of 15 by weight of nitric acid on a salt-free basis; step 2, con
reaction mixture from step 1 in a distillation column to
drive off water overhead, removing a side stream from
said column containing hydrochloric acid and introducing
as bottoms from said column of step'2 a concentrated
reaction mixture containing 60% nitric acid on a salt
said side stream into the distillation column employed in 20 free basis; and step 3, crystallizing the potassium nitrate
from the concentrated reaction mixture removed from
step 1 and removing as bottoms from said column of
step 2, separating the potassium nitrate crystals from the
step 2 a concentrated reaction mixture containing 55%
mother liquor containing 60% by weight nitric acid on
nitric acid on a salt-free basis; and step 3, crystallizing
a salt-free basis and recycling the mother liquor through
the potassium nitrate from the concentrated reaction mix
ture removed from step 2, separating the potassium nitrate 25 the distillation column employed in step 1.
8. The process of converting potassium chloride to
crystals from the mother liquor containing 55% by weight
potassium nitrate which comprises: step 1, feeding to a
nitric acid on a salt-free basis and recycling the mother
liquor through the distillation column employed in step 1.
distillation column nitric acid of about 80% by weight
concentration and potassium chloride in the proportions
6. The process of converting potassium chloride to
potassium nitrate which comprises: step 1, feeding to a 30 of about 2 mols of nitric acid per mol of potassium chlo
ride, passing the potassium chloride and nitric acid down
distillation column nitric acid of about 80% by weight
wardly through said column countercurrent to a rising
concentration and potassium chloride in the proportions
stream of vapors of chlorine and nitrogen dioxide pro—
of about 2 mols of nitric acid per mol of potassium chlo
duced by heating the reaction mixture to its boiling point
ride, passing the potassium chloride and nitric acid down
wardly through said column countercurrent to a rising 35 near the base of said column, condensing said vapors
leaving the top of said column and returning as re?ux
stream of vapors of chlorine and nitrogen dioxide pro
duced by heating the reaction mixture to its boiling point
to the top of said column a portion of the condensate,
maintaining the top of said column at a temperature of
near the base of said column and returning as re?ux to
about —5° C., recycling through said column mother
the top of said column a portion of the condensate,
liquor derived from step 3 containing 65% by weight of
maintaining the top of said column at a temperature of
nitric acid on a salt-free basis; step 2, concentrating the
about —5° 0, recycling through said column mother
liquor derived from step 3 containing 60% by Weight of
nitric acid on a salt-free basis; step 2, concentrating the
reaction mixture from step 1 in a distillation column to
drive olf water overhead, and removing as bottoms from
said column of step 2 a concentrated reaction mixture
reaction mixture from step 1 in a distillation column to
drive off overhead water, removing a side stream from 45 containing 65% nitric acid on a salt-free basis; and step 3,
said column containing up to about 12% hydrochloric
acid and introducing said side stream into the distillation
column employed in step 1 and removing as bottoms from
crystallizing the potassium nitrate from the concentrated
reaction mixture removed from step 2, separating the
potassium nitrate crystals from the mother liquor con
taining 65% by weight nitric acid on a salt-free basis and
said column of step 2 a concentrated reaction mixture
containing 60% nitric acid on a salt-free basis; and 50 recycling the mother liquor through the distillation col
step 3, crystallizing the potassium nitrate from the con
umn employed in step 1.
centrated reaction mixture removed from step 2, separat
ing the potassium nitrate crystals from the mother liquor
containing 60% by weight nitric acid on a salt-free basis
and recycling the mother liquor through the distillation
column employed in step 1.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,138,016
Beekhuis ____________ __ Nov. 29, 1938
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