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Патент USA US2089945

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Aug. 17, 1937.
'
,1. D. CONVERSE ET AL
2,039,945
PROCESS OF PROD UCING AMMONII‘JM N'ITRATE AND OTHER FUSIBLE COMPOUNDS
Filed Feb. 6, 1934
2 Sheets-Sheet 1
W17 7'i R V/IPOK
?/VHYDRO us Man's/v ammo/wan
M»
N/TRH r5
John D. Cbn verse
Shin/g9 L Handfor/h INVENTORS
Gem-gel Harris
BY
A TTORNEY.
Aug- 17, 1937-“
J. D. CONVERSE ET AL
2,089,945
PROCESS OF PRODUCING AMMONIUM NITRATE AND OTHER FUSIBLE COMPOUNDS
Filed Feb. 6, 1934
2 Sheets-Sheet 2
Wafe)’ Vapor
Jo'lvézr? D. Converse
'
' Stanley Lh’andfarz‘h INVENTORS
FY mm”,
ATTORNEY
Patented Aug. 17, 1937
2,039,945 -
UNITED STATES PATENT. OFFICE \
2,089,945
PROCESS OF PRODUCING AMIMONIUM NI;
_ TRATE AND OTHER FUSIBLE COMPOUNDS
John D. Converse, Shawinigan Falls, Quebec,
Canada, Stanley L. Handforth, Gordon
. Heights, Del., and George J. Harris, Mount
Royal, Quebec, Canada, nssignors to E. L du
Pont de Nemours. & Company, ~VVilmington,
Del., a, corporation of Delaware
_ Application February 6, 1934,“ Serial No. 709,968
19 Claims.
(Cl. 23-103)
.
more satisfactorily than has been the case here
duction of substantially dry, molten compounds tofore. A further object is such a process in '
from solutions of said compounds in volatilize.
which ammonium nitrate of much lower water
ble solvents. with the removal of the solventby content than is now practical is produced from
$1 evaporation, and more particularly to the pro
aqueous solutions of this salt. A still further
duction of ammonium nitrate of relatively low object is a process for producing fused ammo
water content from its aqueous solutions.
nium nitrate, in which the evaporation‘of large
Up to the present time, ammonium nitrate ‘amounts of ammonium nitrate solution in one
has been recovered from water solutions by one body is unnecessary.- An additional object is
l0 of two processes. By the ?rst of these, the solu- such a process in which the hazards present in . 10
tion is evaporated to a medium water content previous methods are avoided. Further objects
and then cooled. The ammonium nitrate crys- will be disclosed as the invention is-more fully
This invention relates to .a process for the pro
tallized
recovered
in this
mother
way,liquor
is separated,
is further
and dried.
evaporated
The
15 and put through the same cycle. This procedure
described
. We havehereinafter.
found that, the foregoing objects‘ are _
attained and the production of the substantially 15
is wasteful. of heat and also requires consider-
dry, molten compound desired is brought about
able equipment.
The second method consists in evaporating to
by causing the solution of said compound in a
volatilizable solvent to flow at a rapid rate, in
ny relatively low water content, for example, 2
the form of a thin layer or film over a heated
.20 to§:10%., which is really a solution of water in
surface, whereby theevaporation of thewater 20
-
molten ammonium nitrate. This molten mass
is then cooled with agitation so as to obtain a
present is substantially complete. While our
process ‘is applicable to‘various solid --chemica1
grained product. It is thus necessary to evaporate the remaining water from the resultant
compound-s, it is desirable that the material
have'a fusion point without decomposition suf
25 product at a lower temperature so as to obtain
?ciently' low so that it will be in a molten con- 25
an essentially dry ammonium nitrate. The boiling point of fused ammonium nitrate with 10%
water is 147° C., while with 5% water, it is 169°
C. ».Hence, in order to evaporate to this low
39 water content, it has been necessary to hold
large quantities of molten ammonium nitrate at
a high temperature for a considerable length of
dition, even after the removal of the greater
part of the solvent.) The invention has partic
ular application to the production of substan
time, and, even under these conditions, it is
practically impossible to evaporate such a mateas rial to ‘as low a water content. as is desired.
.
tially dry, ammonium nitrate from its aqueous '
solutions.
30
In the latter case, the solution of ammonium
nitrate is passed at a high velocity, in the form
of a thin ?lm, over a heated surface. In this
way, since a minimum of material is exposed
to the necessary elevated temperature for only 35
Moreover at these temperatures ammonium ni-
a very short time, the amount of decomposition
trate decomposes, so that there is loss of valuable material. In addition, ammonium nitrate
is negligible. Also, under these conditions evap
oration is essentially a surface process instead
so processed and containing only small amounts - of a normal boiling. As a result, there is a mini
40 of water will cause any organic material coming mum amount of spray which can be carried away 40
into contact with it to burn with almost explosive violence.
There is, therefore, great danger under certain conditions of the whole mass of ammonium
45 nitrate exploding, which creates a- serious hazard
when any large body of it is so treated. Furthermore, when solutions containing as much
as 5% moisture are cast or ?aked, the high moisture content causes the productto become por50 ous and ‘to disintegrate on storage.
An object of our invention is a process for the
- production of substantially dry, molten chemical
compounds from solutions of such compounds in
,volatilizable solvents, where the removal of the
5' on solvent is ‘brought about more eiliciently and
with the water vapor and lost. We have also
found it advantageous when an extremely low
water content is desired, to pass a rapid stream
of hot inert gas, such as heated air, countercur
rent to the ?lm ?owing rapidly over the heated 45
surface. In this way, the water vapor is con
tinuously removed and evaporation occurs at a
temperature substantially below the normal boil
ing point. By such a process, a material is ob
tained having an ammonium nitrate content of 50
not less than 98%.
For example, ammonium nitrate solutions, as
ordinarily made by the neutralization of am
monia with nitric acid, usually contain from 10
to 50% water. Such a solution is caused to ?ow 56
- 2
2,089,945
down the inside of‘ a vertical pipe in the form
of a_ thin ?lm, while steam at 150 lbs. pressure,
that is with a temperature of 185° C., surrounds
through tube l countercurrent to the ?lm of
solution flowing down over the inner surface
of ‘the tube, and leaves the top chamber 3 by
pipe l0, along with the water vapor driven off
the outside of the tube. As a result, water evap
5 crates from the rapidly ?owing ?lm and leaves from the ammonium nitrate solution by its con
the top of the tube, while the molten ammonium - tact with the hot surface. The molten ammoni- '
nitrate, containing 2 to 10% water, is withdrawn
from the bottom of the tube without the occur
rence of any loss of material, due to decompo
10 sition or to entrainment. .If ‘it is desired to re
move still further amounts of water, this molten
material may, with advantage, be passed through
a second similar tube, up which a rapid current
of heated inert gas, such‘as air, is blown. If
15 the initial concentration‘ is high enough, the
complete evaporation may be carried out in one
stage by the use of a current of gas up through
the tube. By this means,- it is possible to reduce
the water ‘content to even less than 0.5% and
_ 20 obtain a molten ammonium nitrate with a freez
um nitrate leaves chamber 4 through pipe H,
for cooling and solidi?cation in_ any form de
' sired. As previously described, the complete op
eration may be carried out in one step, as shown
in Figure 1, or two such evaporators in series
may be provided as shown in Figure 2, through
the ?rst of ‘which no air is blown, so that pipe 9
is omitted. In this case the eiliuent from pipe ll
of the ?rst evaporator enters a second stage, sim 15
ilar to that shown in theFigure1,inwhichastream
of inert gas is used to drive out the last of the
water.
In other respects, this second stage is a _
duplicate of- the ?rst stage. Thus, I2 is a verti
cal tube with jacket l3, and chambers l4 and 20
l5 at the top and bottom respectively. Am
monium nitrate enters the chamber is through
heating medium no hotter than 185° C., even ' pipe Ii and overflows into the pipe l2 through
though it is practically impossible to reduce a slots l6, passing in an 'even ?lm down the inside
25 fused ammonium nitrate to so low a water con
of ‘pipe i2. Steam enters the outer jacket 25
tent by the ordinary evaporating means, hereto
through inlet I‘! and the condensate leaves by
fore available, since the boiling temperature is outlet pipe I8. Any suitable hot inert gas such
ing point higher than 160° C. and at a tempera
ture of about 180° C. This may be done with a
so high that there is almost complete decompo
sition.
30 With the above procedure, when evaporating
to extremely low water contents, there may be
a slight volatilization of ammonium nitrate and
some loss.
Under such conditions, we have found '
that, by introducing even a trace of ammonia
5 gas into the'heated air, which is ?owing coun
tercurrent to the ?lm of molten nitrate, this loss
may be almost completely prevented, even when
evaporating to as low a water content as 0.2%.
Preferably the ammonia content of the air cur
’? rent should be not greater than 1%.
Ammonium nitrate is customarily produced on
a commercial scale by the neutralization of
aqueous nitric acid with ammonia either as a
gas or in aqueous solution and the subsequent
45 removal of the water from the solution by evap
as air is introduced into chamber l5 through
pipe l9. Water vapor is driven o? from the top
of pipe l2. The-molten‘ammonium nitrate leaves 30
chamber l5 through pipe 2! from which it passes
to the chilled revolving roller 22 and-solidi?es
thereon, and from which it is readily removed
in ?aked anhydrous form.
While the evaporator described in the fore 35,
going consists of a heated tube, it should be
understood that other forms of apparatus may
be employed. For example, a number of tubes
may be placed in one heating jacket, or ?at
plates or sloping surfaces and the like may be 40
used. '
The fused ammonium nitrate, resulting from
the process described heretofore, can‘be solidi?ed
inany form desired. It may, for example, be
poured into molds and solidi?ed in cast forms,orit 45
may be picked up on a chilled rotating roll and
when cooled scraped off as ?akes, or it may be
sprayed to form granules. In any case, the low
oration. The reaction of ammonia with nitric
acid is exothermic and produces a large amount
of heat. This heat of neutralization has been
utilized in a number of recent processes for the I
water content will prevent either a caking or'a
trate solution. It may also, if desired, be used
disintegration of the ?nal solid. With the prod 50
uct of ammonium nitrate solutions, evaporated
50 preliminary concentration of the ammonium ni-_
for bringing about the volatilization of the water
from the ?lm of ammonium nitrate solution ?ow
ing over the heated surface. In this case the
55 heated surface will be located concentrically
within the neutralizer, preferably as an over?ow
' pipe, and heated by the hot reacting products
surrounding it. .In this event, we prefer to op
erate the reaction on the alkaline side, the ex
60 cess ammonia being recovered and returned to
the process.
.
‘
An apparatus suitable for carrying out our
invention is illustrated in the accompanying
drawings, in which Iris a vertical tube. surround
65 ed'by a jacket 2. In communication with this
tube chambers 3 and 4 are provided at the top
and bottom respectively. Ammonium nitrate
enters 3- through inlet pipe 5, rises in this cham
‘ber and. over?ows into the top of pipe I through
in the ordinary way and containing as much as
2% water, the high moisture content would cause
the masses to become porous, to stick together, _
or to disintegrate.
'
>
An advantage of the cast product over forms of
ammonium nitrate previously available lies in its
high apparent density, over 1.5, and practically
equivalent to the absolute density. ‘As a result
of this high density, the material will not ?oat in
a molten ammonium nitrate bath, a property
that makes this cast product especially valuable
for some particular uses of ammonium nitrate, for
example in the manufacture of nitrous oxide.
While we have described our invention for the 65
production of a substantially dry product from
a solution of said product in a volatilizable solvent
in connection with ammonium nitrate particu
larly, it will be apparent that this process of con
' 70 slots 6. From these, which serve as distributors, ' centrating a solution to obtain a dry product, by
70
the solution ?ows in an even ?lm down the in
the passing of a ?lm of such solution over' a
side of pipe I. Steam enters the outer jacket heated surface is applicable with advantage to
through inlet 1 and the condensate leaves by many other products, both inorganic and organic.
outlet pipe 8. Hot air, which enters the bot
Among .the inorganic compounds, to the prepara-.
75 tom chamber 4 through pipe 9, is forced up tion of which the process is applicable, may be
75
cited ammonium acetate, sodium, acetate stantial part of the waterv present, maintaining
the rate of ?ow su?iciently rapid and the time of
(NB-CaHzOz-3 H20), and sodium sul?te. Simi
larly the method may be applied to organic‘com - contact of vthe ?lm with the heated surface sum
pounds, for example to the evaporation of urea ciently short to substantially avoid decomposition
5 andsugar solutions, the concentration of tartaric
of the compound and maintaining'the molten am
acid preliminary to crystallization, and in many
monium nitrate in. substantially anhydrous form
other cases. It is apparent that our invention is
as it leaves the heated surface.
equally applicable to processes in which either
water or other volatilizable solvents are em
to ployed.
}
We intend, therefore, to be limited only as in
dicated in the following patent claims:
Weclaim:
5
-
- -_
6. The process of producing ammonium nitrate
which comprises causing a concentrated aqueous
solution of the ammonium nitrate to ?ow in the 10
form of a continuously moving ?lm over a heated
surface maintained at a temperature suf?ciently
above the melting point of substantially anlw
;
l. The process of producing a substantially dry
15 molten compound which has a tendency to de-'
compose when maintained above its melting
point, which process comprises causing a solution
containing said compound and a volatile ?uid
to ?ow in the form of a continuously moving-?lm
drous ammonium nitrate, whereby to remove suf
?clent of the water present to obtain a ?nal 15
molten product having an ammonium nitrate
content of not less than 98%, and maintaining
the ammonium ‘nitrate in molten form as it
30 over a surface maintained at a temperature above
7. The process of producing molten ammonium
nitrate which comprises causing a concentrated
solution of ammonium nitrate to' ?ow in the
form of a continuously moving film over a heated
the melting point of the compound in the anhy
drous state and maintaining (the rate of flow
su?lcientiy rapid and the time of- contact of the
film with the heated surface su?ciently short
35 to substantially avoid decomposition of the com
pound, but sufficiently long to substantially de-v
hydrate said compound.
.7
2. The process of producing a ‘substantially dry
leaves the heated surface.
a
,
'20
surface maintained atya temperature above the
melting point of the salt in the anhydrous state 25
and maintaining the rate of flow sul?ciently
rapid and the time of contact of the film with
the, heated surface su?iciently short to sub-'
molten compound melting at a ‘temperature at
stantially avoid decomposition of the ammonium
nitrate but sufficiently long to remove by vola 30
30 tainable with superheated steam, which com
tilization the greater part of the ,water present,
prises causing a solution containing said com
and flowing the molten ammonium nitrate from
pound and water to ?ow in the form of a con
tinuously moving ?lm over a surface maintained the heated surface.
8. The process of producing ammonium ni
at a temperature above the melting point of the
35 compound in the anhydrous state and main ' trate of relatively low water content which com 35
talning the rate of now‘ sui?ciently rapid and prises causing an aqueous solution of the ammo
the time of contact of the ?lm with the heated nium nitrate to flow in the form of a continuously
surface sufficiently short to substantially avoid moving ?lm over a heated surface maintained
decomposition of the compound, but sufficiently at a temperature above the melting point of sub
iil'long to substantially dehydrate said compound.
stantially anhydrous ammonium nitrate, coun
3. The process of producing a substantially dry
molten compound which has a tendency to de
compose when maintained above its melting point,
tercurrent to a stream of inert gas and recover
which process comprises causing a solution con45 taining said compound and a volatile fluid to
flow in the form of a continuously moving film
over a heated surface countercurrent to a stream
of heated inert gas while maintaining said sur
' face at a temperature above the melting point of
50 the compound in the anhydrous state and main
taining the rate of ?ow su?iciently rapid and
the contact of the ?lm with the heated surface
su?lciently short to avoid decompositionof the
compound, but sumciently long to substantially
55 dehydrate said compound.
4. The process of producing substantially dry
40
ing ‘molten ammoniu‘m'nitrate substantiallyfree
from water as it leaves the heated surface.
9. The process of producing ammonium nitrate
which comprises causing an aqueous ammonium 45
nitrate solution to ?ow in the form of a contin
uously moving ?lm over a heated surface main
tained at a temperature above the melting point
of substantially anhydrous ammonium nitrate,
countercurrent to a stream of hot inert gas, re
50
moving sumcient of the water present to obtain a
?nal product having an ammonium nitrate con
tent of not less than 98% and recovering the am
. monium nitrate in molten form as it leaves the
heated surface.
10. The process of producing ammonium ni
55 -.
ammonium nitrate in fused form which comprises trate of relatively low water content which com
causing. an. aqueous solution ofqthe ammonium . prises causing a concentrated aqueous solution of
nitrate to flow in the form of a continuously mov
60 mg film over a heated surface maintained at a
temperature above the melting point of the am
monium nitrate in the anhydrous state and main
‘ taining the rate of flow su?iciently rapid and the
time of contact of the him with the heated sur
65 face sumciently short to substantially avoid de
composition of the ammonium nitrate while re
moving the water therefrom.
5. The process of producing molten ammonium
nitrate of relatively low water content which
70 comprises causing a concentrated aqueous solu
tion of the ammonium nitrate to ?ow in the form
of a continuously moving ?lm over a surface
maintained at a temperature sumciently above
' the melting point of substantially anhydrous am
75 monium nitrate to remove by volatilization a sub
ammonium nitrate to flow in the form of a con
tinuously moving ?lm over a surface maintained 60
at a temperature above the melting point of ‘sub
stantially anhydrous ammonium_»nitrate couni
tercurrent to a~stream of hot inert gases to eifect
the removal of a substantial part of the water
present, and maintaining a small ammonia con 65
tent in said gases.
'
_11. The process of producing ammonium ni
trate of relatively low water content which com
prises causing an aqueous solution of the ammo
nium nitrate to ?ow in the form of a continuously 70
moving ?lm over a heated surface for the partial
evaporation of the water present, and then pass~
ing the resulting solution, in the form of a ?lm,
at a rapid rate over a second heated surface
maintained at a temperature above the melting 75
4
2,089,945
point of substantially anhydrous ammonium ni: compound, maintaining the rate of ?ow sum
trate, countercurrent to a stream of heated in
ert gas to remove a further portion of the water
ciently rapid,- and the time of contact of the ?lm '
the heated inert gas has an ammonia content
remove said volatile solvent from said compound,
'with the heated surface su?iciently short to sub
stantially avoid decomposition of said compound,
content.
.
5
12. The process according to claim 11 in which; but su?lciently long to substantially completely
not greater than 1%.
and‘causing the substantially solvent-free com
13. The process of producing solidi?ed ammo
nium nitrate which comprises causing an aque
10 ous-solution of the ammonium nitrate to flow in
the form of a ?lm over a heatedsurface main- 1
tained at a temperature above the melting point
of substantially anhydrous ammonium_ nitrate,
pound to ?ow from said heated surface in a
molten condition.
'
_
-
18. The process of producing a substantially 11
anhydrous molten compound which comprises‘
causing an aqueous solution containing. a sub
stantially non-volatile compound which melts ,
countercurrent to a stream of hot inert gas to ' in the anhydrous state below its decomposition _
15 evaporate a substantial part of the water pres
‘ ent, ?owing the molten ammonium nitrate away
20
temperature, to ?ow in the form ofa continuous
ly moving ?lm over a surface maintained at a
from the surface and converting the resulting
product into a predetermined form and cooling
temperature above the melting point of said
compound in the anhydrous state, but below its
it to a solid in such form.»
14. The process according to claim 13 in which
the molten ammonium nitrate flows into a mold
decomposition temperature, maintaining the rate
and is solidi?ed in predetermined cast form.'
15. The process according to claim 13 in which
the molten ammonium nitrate is chilled to solid
_ g5 i?cation on the surface of a revolving roll and the
solid ?lm is scraped off in the form of a ?aked
product.
y
16. A process for producing substantially dry
ammonium nitrate in fused form, which com
30 prises rapidly ,?owing a concentrated aqueous
solution of said ammonium nitrate, in the form
of a'?lm, over a surface heated to a tempera
ture above the melting point of substantially an
hydrous‘ ammonium nitrate, and of suii‘icient
35 length to provide for removal of substantially all
water from said ammonium nitrate and the fu
sion under heat of the ammonium nitrate, and
of, ?ow su?iciently rapid and the time of contact
of the ?lm with the heated surface su?lciently
short to substantially avoid decomposition of
said compound, but su?iciently long to substan
tially dehydrate said compound, and causing the
substantially'anhydrous compound to ?ow from 25
said heated surface in a molten condition.
19. The process'of producing a substantially
anhydrous molten compound, which process com- 7
prises causing an aqueous solution of a substan
tially non-volatile compound which melts in the 30
anhydrous state below its decomposition temper
ature, to ?ow in the form of a continuously mov
ing ?lm over a surface maintained at a‘ temper
ature above the melting point of said compound
in the anhydrous state, but below the decom 35
position temperature thereof, countercurrent to
?owing the fused ammonium nitrate from said a stream of hot inert ‘gas, maintaining the rate
surface in molten and substantially anhydrous‘ of ?ow substantially rapid and the time of con
tact of the ?lm with the'heated surface su?i
17. The process of producing a substantially ciently short to substantially avoid decomposition 40
solvent-free molten compound, which process‘ of said compound, but sufficiently long to sub
comprises causing a solution containing a volatile stantially dehydrate said compound, and caus
solvent and a substantially non-volatile com
ing the compound to ?ow from said heated sur
45 pound which melts in the pure‘state below'its' ‘ face in a molten, substantially anhydrous con
40 form_..
decomposition temperature, to flow in the form
‘of a continuously moving ?lm over a surface
maintained at a temperature above the melting
point of said compound in the solvent-free state,
50 but below the decomposition temperature of said
dition.
“
45
'
JOHN D. CONVERSE.
_
STANLEY L. HANDFOR'I'I-L'
GEORGE J. HARRIS.
50
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