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Патент USA US2403493

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Patented July 9, 1946
2,403,493
UNITED sTATEs PATENT oFElcE
2,403,493
MANUFACTU ING NITROCELLULOSE
Frederick J. Bouchard, Radford, Va., Robert C.
Gunness, Chicago, Ill., and Raphael L. Stern,
South River, N. J., assignors to Hercules Pow
der Company, Wilmington, Del., a corporation
v of Delaware
Application May 19, 1943, Serial No. 487,558
12 Claims. (Cl. 260--220)
1
2
This invention relates to the manufacture of
nitrocellulose and more particularly it relates to
the recovery of spent nitrating acid adhering to
nitrocellulose after separation of the nitrocellu
lose from the major portion of the spent acid
supernatant-spent acid. In accordance with this
formed in the nitration step.
~
invention, nitrocellulose wet with such adhering
spent acid is drowned by admixture with a
quenching or drowning volume of an aqueous
Y mixed acid (nitric and sulphuric acids), having
a concentration between about 10% and about
Nitrocellulose is prepared by nitrating cellu
25%, the volume thereof being sufficient to
lose in a large excess such as 30-65 times by
reduce the concentrationof the resulting acid in
and on the nitrocellulose from above about 75%
weight of the cellulose of “mixed acid.” “Mixed
acid” is a mixture of nitricfacid, sulphuric acid
and a relatively small proportionof water. The
spent acid from the nitration is slightly weak-v
ened in nitric acid and slightly increased in
water content. It is absolutely essential that it
be recovered for fortification and re-use.
The
major part of the spent `acid is relatively easily
separated from `the nitrocellulose. However, it is
quite diñ'ìcult to recover the-remaining portion
wetting the nitrocellulose without damaging the
quality of the nitrocellulose.
It has been proposed to wash nitrocellulose
containing strong spent acid with progressively
more dilute spent acid so as to lose a minimum>
_ to between about 10% and about 25% substan
tially instantaneously. The nitrocellulose is then
removed from the drowning acid and spent acid`
remainingtherein may be displaced, or other
wise removed by water or other washing liquid
essentially water, or both. The dilute acid formed
by such washing may be added to the drowning
acid to permit and to aid in maintaining the
concentrationY in the 10 to about 25% range.
Nitric acid is evaporated from a portion ofy the
drowning acid to recover a nitric acid fraction.
A sulphuric acid fraction may be recovered from
the evaporation residuum.
It has been found that the drowning acid of
10-25% concentration unexpectedly has substan
25 tially no denitrating effect, i. e., denitration is
of nitric acid. This method has the serious ob
jection that the nitrocellulose is subjected to de
nitrating conditions and becomes nonuniform and
negligible in the period of a few minutes or few
variable in ultimate degree of nitration. It has
hours between drowning and complete separation
also been proposed to use wash water repeatedly
_of the drowning acid. At the same time it has
until its acid concentration permitted treatment
been found practical to recover the nitric acid
with ferrous sulphate or like reducing agent to 30 and sulphuric acid from the drowning acid by
recover nitric oxide. This method has the objec
evaporative fractionation.
~`
'tion of nonuniform treatment of succeeding
> The process in accordance with this invention
batches of nitrocellulose, is inefficient in nitric
may be more completely described in connection
acid recovery, and loses sulphuric acid present.
with the accompanying drawing which illustrates
the process diagrammatically.
These and other methods for recovery of lspent
acid -have either subjected the nitrocellulose to
Referring to the drawing the flow of pertinent
varying periods of treatment with acid Vor to vary
material is shown as originating in a nitrator I
ing concentrations causing serious nonuni
from which the nitration mixture passes to'a
formity.
separator 2, which may be a centrifuge, squeeze
Thus, in practical operation, nitrated cellulose 40 roll equipment or the like, and which removes the
has been removed from supernatant acid by cen
greater part of the spent acid from the nitrated
trifuging, squeezing or the like, to obtain nitro
cellulose. The free spent acid so obtained is ledcellulose wet with one to three times its weight
to storage for fortification and re--use. The nitro
cellulose with adhering spent acid passes to the
of adhering spent acid. Thismaterial has then
been drowned in a large volume of water to 45 drowning equipment 3 Where it is rapidly mixed
decrease the concentration of the'acid in contact
with a large volume of drowning liquor, which
with the nitrocellulose to below~2 or 3% very rap
reduces the concentration of the acid wetting
idly to prevent denitration by intermediate
strength acid. The retained or adhering spent
acid has been lost and has caused disposal dif
ñcu-lties since it has been diluted too greatly for
recovery.
-
I
' The process according to this invention is con
cerned with the recovery ofthe spent acid ad
the nitrocellulose substantially instantaneously to
below denitrating'levels. The nitrocellulose and
" drowning acids pass to a rotary filter 4 which sep
arates‘the‘nitrocellulose from the drowning acid.
Portions of drowning acid remaining in the nitro
cellulose after-the initial separation are washed
with water, or with vapor condensate, which is
hering-to nitrocellulose after its separation from' 55; essentiallyfwater, or preferably, first with the
2,403,493 l
3
4
vapor condensate and then further with water,
the vapor condensate being obtained as herein
after described. The vapor condensate and/or
The nitrocellulose is removed from the drown
ing acid by a rotary filter, washed on the iilter
by displacement first with a water vapor con
densate containing about 1% nitric acid and
water form a dilute acid in the washing oper
ation, which dilute acid is admixed with sep
fil then by a small amount of pure Water.
arated drowning acid. The drowning acid flows
from the filter back to the drowning equipment
either directly7 or, preferably, through sedimenta
It is then
treated, in thefusual manner for stabilization,
viscosity adjustment and dehydration.
The
drowning acid is recycled through a sedimenta
tion tank removing most of any associated nitro
tion equipment or a filter to remove nitrocellu
lose iines. The washed nitrocellulose passes from 10 cellulose fibers. A portion of the drowning acid,
substantially equivalent to the quantity added by
the filter into a slurry tank 5 in which Vit is sus
the strong acid wetting the nitrocellulose and
the Wash water, is withdrawn and initially con
centrated tovabout 45% total acid concentra
tion equipment 6.
A portion of the drowning acid separated from 15 tion. It is .then evaporated to strip it of nearly
all of its nitric acid to form a nitric acid water
the nitrocellulose, preferably a quantity about
vapor fraction equivalent to about 30% nitric
equivalent to that added in the nitrocellulose and
acid and a liquid residual fraction of about 65%
Wash liquid, is bled off and passed to a concen
sulphuric acid. The sulphuric acid is denitrated
trator which consists of a concentration column
8 and an operatively associated evaporator 9 20 to free it of residual nitric acid by steam to yield
a oki-68% sulphuric acid. The nitric acid vapors
equipped with a suitable heating coil. The con
pended in water for subsequent purification
usually in a series of tubs represented as purifica
centralìor separates the drowning acid portion
are concentrated to form a concentrated nitric
acid of (S5-67% `nitric acid content and a vapor
into the vapor fraction, essentially Water vapor
essentially water but containing about 1% of
with a> small content of nitric acid, and a liquid
fraction _of mixed acid of increased concentration. 25 nitric acid. Thevapors from the concentrators
This mixed acid passes` to an evaporator l0
equipped with a suitable heating coil. The ma
jor portion of the nitric acid in the mixedacid
is evaporated from the drowning acid portion in
this evaporator to form a vapor fraction contain 30
ing nitric acid and water. The liquid residuum
leaving the evaporator is apartiallyV concentrated
sulphuric _acid fraction containing a small amount
of nitric acid. This liquid passesto a sulphuric
are condensed, cooled and used as nitrocellulose
wash Water to recover the nitric acid content of
the drowned filtered nitrocellulose and to aid in
maintaining the concentration of the drowning
acid in the range desired.
It will be appreciated that it is not essential
to use vapor condensate for Washing thev nitro
cellulose. However, such operation permits sub
stantial recovery of the small nitric acid con
acid denitrator i3 where, bythe action of steam, 35 tent of the vapor condensate and it further pro
vides a means of maintaining the drowning acid
remaining vnitric acid is evaporated to form'> an
in the' lll-25% rangein which it is effective in
aqueousnitric acid vapor. The sulphuric acid
drowning the nitrocellulose and at the same time
liquid 4fraction leaves in a denitrated form. The
recoverable. The vapor condensate in general
aqueous nitric acid vapor leaving the evaporator
I0 and the nitric acid vapor leaving the denitra 40 will include nitric acid in any quantity up to
about 3%. It will be appreciated that the vapor
tor i3 pass with partial or no condensation to a
condensate may be returned directly to the drown
nitric acid concentrator which consists of the
ing acid without use for washing.
concentrator column H and an operatively asso
Under most conditions of operation, it is nec
ciated evaporator l2 provided with a suitable
. essary to add small quantities of water to the
heating coil, The nitric acid concentrator re
system to prevent the drowning acid from build
solves the nitric acid fractions fed thereto into
ing up in concentration to a level at which deni
a liquid concentrated nitric acid fraction and a
tration of nitrocellulose aft-er drowning ceases to
vapor Vfraction consisting essentially- of water 4
be negligible. Such make-up water is conven
vapor but in most cases containing a `small
amount of nitric acid. The vapors from one or 50 iently added by using pure water as a final wash
for thenitrocellulose on the filter and merging
both of the concentrators 8 and ll may be led
to a condenser I4 where theyform a vapor con
the resultant Wash water with the drowning acid. '
By this expedient, substantially all of the drown
ing acid is removed and recovered from the nitro
be used in Washing nitrocellulose on the rotary 55 cellulose.
The nitric acid may be recovered by distilla
filter 4, thereby permitting complete recovery of
tion from the 10-25% mixed drowning acid and
the drowning acid from the nitrocellulose and
subsequently further concentrated. However, it
recovery of the small amount, of nitric acid in
has been found that preconcentration to form a
the vapor condensate. The columns 8 and Il
may be of packed or bubble-cap construction. 60 mixed acid of about 35% to about 60% concentra
tion greatly Aimproves the eñ‘iciency of the steps
In a typical operation serving as an example
of evaporating or distilling the nitric acid and
of the process, cellulose is nitrated with 45 times
subsequently concentrating it. Such preconcen
its weight of mixed acid to form a spent mixed
tration Yalso makes practicable subsequent deni
acid containing about 25% nitric acid, about 55%
sulphuric acid and about 20% water. The nitra 65 tration of the residual sulphuric acid. The con
centration is accomplished by evaporation of
tion mixture is centrifuged, eliminating the ma
essentially water from> the acid.
jor portion of the spent acid, but leaving a quan
Usually the aqueous nitric acid fraction ob
tity in the nitrocellulose of about 1.1 times the
tained is concentrated to (iO-68%. The fraction
weight ofthe nitrocellulose. The wetnitrocel
lulose is then drowned with mixed 4acid dilutedl 70 may first be condensed but Ypreferably the vapor
ous fraction with partial or no condensation is
to 20% total acid concentration in a quantity
introduced directly into a concentrating column.
of approximately 50 times the weight ofthe
Thev sulphuric acid> fraction is conveniently
nitrocellulose (dry basis). The increase in con
brought to 50-'75%` as denitrated and may then
centration in the drowning acid produced by the
strong. acid wetting. nitrocellulose> is- about 2%. 75 be further concentrated in other equipment when
densate containing a small amountof >nitric acid.
This condensate, preferably cooled, may then
2,403,493
.v6
stronger'. acid is desired. The denitration' step
separates the small residual quantity of nitricacid, which is less than 5% of the residual frac
tion, from the sulphuric acid to permit. ready
loseiis separated from supernatant spent mixed
acid-of~above about '75% total acid concentra
tion by weight, drowned to reduce- the concen
tration of acid wetting thenitrocellulose rapidly
to below. concentrations causing substantial de
nitration, and then .puriñed a process which _com
It is essential that the concentration of th
prises'carrying out the drowning of the said sep
drowning acid be held within therange herein
arated nitrocellulose wet with spent acid by mix
above specified. The concentration must be no
ing it with a quenching volume of aqueous mixed
greater than about 25% since otherwise denitra
tion of the nitrocellulose 'occurs during and after 10 nitric and sulphuric acid having a concentration
of about 10 to about 25% by'weight of total acid,
drowning in a variable and unpredictable man
said'volume'being sufficient to reduce .the con
ner. `At below concentrations of 25% and with
centration of the spent acid on and .in the nitro
use of vthe drowning acid in a volume to insure
concentration of the sulphuric acid. ~
that the mixture resulting is below about 25%,
cellulose to between about 10% and about"25%
substantially'no denitration occursand further 15 substantially instantaneously,> removing the
drowned nitrocellulose from the drowning acid,
more, the nitrocelluloseobtained is highly uni
and evaporating nitric acid from a portion of
formxfrom'batch to batch. Concentrations of
the drowning acid.
'
drowning acid below about 10% do- not permit
2.' In a procedure for manufacturing nitro
obtaining the economies of the present invention
since 'recovery ofthe component nitric and sul 20 cellulose in which cellulose is nitrated in an
excess of mixed acid and the resulting nitrocellu
phuric acids fromthe acid is impractical. A con
lose is separated from supernatant spent mixed
centration between 15% and 20% is preferred.
, The mixed acid wetting the nitrocellulose -after
its removal from the major portion of the spent
acid will have a total acid concentration in ex
cessrof about 75%. The ratio of sulphuric acid
to nitric acid will be between about 4: 1 and about
acid of above about 75% total acid concentration
by weight, drowned to reduce the concentration
25 of‘acid wetting the nitrocellulose rapidly to be
low concentrations causing substantial denitra
tion, and then purified, a process which com
0.5:1, usually between 3:1 and 1:1', by weight.
prises carrying out the drowning of the said sep
'I‘he same relationship between sulphuric acid and
arated nitrocellulose wet with' spent acid by mix
nitric acid will apply in the drowning acid.
30 ing it with a quenching volume of aqueous mixed
nitric and sulphuric acid having'a concentration
The elîectiveness of `the present process in
economic recovery of spent acid is in no »small
part dependent upon recovery of the drowning
acid wetting the drowned nitrocellulose by means
ofthe rotary lilter which provides a filter sur
face through which the drowning acid may be
drained, and which further provides for eñicient
displacement of residual acidthroughthe ñlter
of about 10 to about 25% by weight of total acid',
said volume being suñîcient to reduce the concen
tration of the spent acid on and 'in the nitro
35 cellulose to between about 10% and about 25%
substantially
instantaneously,
removing ' the
drowned nitrocellulose from the drowning acid,
washing the nitrocellulose with essentially water
thereby obtaining a dilute acid, adding said dilute
surface with the essentially pure water of the con
densedvapor obtained from the 'acid concen 40 acid to the drowning mixed acid in a quantity no
more than that maintaining the drowning acid
trators and with the iinal wash of pure water.
The Viilter further provides a very convenient
’ between about 10% and about 25% in total acid
manner for introducing an amount of water to the
concentration, and evaporating nitric acid from a
drowning acid suiiîcient or nearly suñicient to
portion of the drowning acid.
'
'
maintain the concentration of the drowning acid
3. In a procedure for manufacturing nitrocel
in the critical range by compensating for the
lulose in which cellulose is nitrated in an excess
effect of the addition of strong acid in the nitro
of mixed acid and the resulting nitrocellulose is
cellulose.
However, it will be appreciated that
separated from supernatant spent mixed acid of
water added as such or in the form‘oi dilute
above about 75% total acid concentration by
acid will be in a quantity- no more than that 50 weight, drowned to reduce the concentration of
quantity which is required to maintain the con
centration at the desired level in the critical
range.
'
By maintenance of the drowning acid substan
tially constant in concentration, a highly uni
form nitrocellulose product is obtained. It has
been found that the method of this invention pro
duces a uniform nitrocellulose of a quality fully
acid wetting the nitrocellulose rapidly to below
concentrations causing substantial denitration,
and then puriñed, a process which comprises car-`
rymg- out the drowning of the said separated ni-trocellulose wet with spent acid by mixing it with
a quenching volume of aqueous mixed nitric and
sulphuric acid having a concentration of about
10 to about 25% by weight of'total acid, said
volume being sufficient to reduce the concentra
equivalent to material obtained by drowning as
heretofore with water involving complete loss of 60 tion of the spent acid on and in the nitrocellu
retained acid.
'
lose to between about 10% and about 25% sub
The present process is'of particular usefulness
stantially instantaneously, removing the drowned
in permitting direct and simple recovery of- the
nitrocellulose from the drowning acid, washing
nitric acid contained in the retained spent acid,
the >nitrocellulose. with a condensed vapor essen
and furthermore it leads to recovery of both the 65 tially water thereby obtaining a dilute acid, add- nitric acid and the sulphuric acid therein. AIn
ing said dilute acid to the drowning mixed acid,
addition, the problem of Vdisposal of waste dilute
evaporating a portion of the drowning acid to
acid is avoided.
Y
form an evaporated nitric acid fraction and a
All acid concentrations herein and in the claims
fraction of essentially water vapor, and condens
are in percent by weight.
>
u .
70 ing the water vapor fraction to form the afore
What we claim and desire to protect by Letters
said condensed vapor.
Patent is:
.
.v
4. In a procedure for >manufacturing nitro
1. In a procedure forl manufacturing nitro
cellulose in which cellulose is nitrated in Yan ex
cess >of mixed acid and the resulting nitrocellu
cess'of _mixed acid `.and the -resulting nitrocellu
lose'v is separated: ‘from supernatant- spent vmixed
cellulose in which cellulose isvnitrated in an ex
2514035493
7
8
acid of above about '75% total 'acidconcentra
tion by weight, drowned to reduce the concen~
tration vof .acid wetting the'nitroce'llulose rapidly
ofïmixed .acid and .fthe resulting .nitrocellulose is
separated fromisupernatant spent mixedacidiof
above about 75% total .acid concentration by
Weight, drowned to .reduce .thefconcentration of
to below concentrations causing.‘substantialv ‘de-V
nitra'tion, and then purified, alprocessiwhi‘ch >com
Ul
prises icarrying .out the drowning :of the .saidrsepe
aratedxnitrocellul'ose `wet with spent .acid by mix
ing it with a quenching volume .of .aqueous mixed
nitric -and sulphuric acid having aconcentration
of about 10 to about 25% by Weight of total acid,
said volume being suiiicient to reduce the con~
centration of the spent acid'on and in the >»nitro
cellulose to betweenabout 10% and about25% sub
acid wetting the nitrocellulose rapidlyto. below
concentrations causing substantial . denitration,
and. then puriñed,` aprocess .which comprises car
rying 'out fthe. drowning yof the .said separated vni
trocellulosev wet with .spent acid .by mixing 'it .with
O aquenching 'volume of .aqueous .mixed .nitric and
sulphuric acid having a. concentration vof :about
10.-to about-25% byzweight of .total acid, said
volume .being >:suñicien't .toreduce .the concentra
tion of thespent .acid `on and. in -the .nitrocellu
stantially instantaneously, :removing the drowned
nitrocellulose from the drowning acid, evaporat
. lose to between„about.l0%.and about .25% sub
ing a _portion of the drowning acidltoj form-»a
fraction o_f essentially water vapor, 'condensing
the Vapor fraction, and returning condensed Vapor
to the drowningv acid in an `amount permitting the
concentration of the drowningv'acid to be `main 20
tained between about 10% and about 25% Vby
Weight.
stantially instantaneously, .removing :the drowned
nitrocellulose Vfrom thedrowningacid, .evaporate
ing nitric acid from a .portion of the drowning
acid, :and recovering a ysulphuric acidiractionof
increased concentration frornthesaid portion;
8; In aprocedurefor manufacturingnitrocellu
lose .in which cellulose is nitrated .inv an excess 4:of
mixed acid and the .resultingnitrocellulose is
separated from supernatant spent mixed acid of
v5. In a proceduce .for manufacturingnitrocel
lulose in which cellulose is nitrated in an excess
of.mixed acid and the resulting nitrocellulose 25. above about 75% total acid concentration by
weight, drowned to'reduce the concentration `.of
acid wetting the nitrocellulose rapidly `to .below
of above about 75% total acid concentration by
weight, drowned to reduce the concentration of
concentrations causing substantial denitration,
acid wetting the nitrocellulose rapidly to below
and then purified, a process which comprises car
rying out the drowningof thesaidseparated .ni
concentrations causing> substantial denitration,
and then pur'iiied, a process which comprises .car
trocellulose wet with spent acidby mixing it .with
is .separated from supernatant spentmixed acid
rying out the drowning ofthe said separated ni
trocellulose wet with spent acid by mixing it with
a quenching volume of aqueous lmixed Anitric and
a quenching `volume of aqueous mixed nitric 'and
sulphuric acid having a concentration of about
10 to about 25% by weight of total acid, said
volume being suiiicient to reduce the concentra
35
sulphuric acid havingfa concentrationof .about
l0 to about 25% by weight of totalacid, said
volume being sufficient to reduce the/concentra
tion of the spent acid on and Vin the` nitrocel1u~
lose to between about 10%` and about 25% sub
tion ofthe spent acid on and in the nitrocellu
stantially instantaneously, removing ,thedrowned
lose to between about 10% and about 25% sub
stantially instantaneously', removing the drowned
nitrocellulose. from the drowning acid, «concen
trating a portion of the drowning acid, andevap
orating .nitric acid from the concentratedpor
nitrocellulose from thewdrowning acid, evaporat
ing a portion of the drowning acid -to form a .ni
tionto recover a nitric acid fraction and a sul
tric acid fraction, concentrating .the .nitric acid
phuric .acid Aresidual fraction. .
fraction to form a concentrated acid-fraction and
9. In a `procedure for manufacturing .nitrocel
lulose .in which cellulose is nitrated in .an excess :of
a .fraction essentially Water vapor, condensing the
said water vapor fraction, Vand returningthere
sulting. .condensate .to thedrowning acidrin an
amount permitting the concentration of the
drowning acid to be maintained between about
10%. and about .25% by Weight.
mixed acid >and the: resulting nitrocellulose .is
separated from supernatant spent .mixed acid of
abovev about 75% total- acid concentration .by
Weight, drowned to reduce the concentration .of
acid wetting'the nitrocellulose. rapidly to below
6.> In a procedure .for manufacturing nitrocel
lulose in which cellulose is .nitrated' in van excess
concentrations causing; substantial 'denitration.,
of mixed acid and the .resulting-.nitrocellulose is
separated -from supernatant spent mixed acid :of
above about '75% total acid» concentration by 5
weight, drowned to reduce the. concentration Yof
nitrocellulose wet withV spent acid .by mixing it
with a quenching volume oî‘aqueous .mixed nitric
and then purified, a process which comprises
carrying out the drowning of the said separated
and sulphuric acidv having a concentration of
acid wetting the nitrocelluloserapidly to vbelow
about 10 to about V25% .by weight'of totalaci'd, vsaid
concentrations causing substantial denitration,
volume .being `suiîicient to reduce the concentra'
and then’puriiied, a process which .comprisescar‘
rying out the drowning of 'the said separated .ni
trocellulose wet with spent acid bymixing it with
tion‘of thefspent acid. yon andin'the nitrocellulose
to between about 10% and. about 25% substan
a quenching volume of aqueous mixed :nitricand
sulphuric acid having a concentration of about
trocellulose from. the drowningacid, concentrat
10 to about >25% by weight of total. acid, saidfvol
urne being sufficient to reduce. the concentration
of the spent acid on andl inthe nitrocelluloseto
between about 10%. and` about 25%.»substantially
ing nitric acid .from the concentrated portion to
instantaneously, removing-«the drowningacid from:
the nitrocellulose fibers -bydrainage- through aA
filter surface and by displacement .of;residual«acid„
from the nitrocellulose through fthe :iilter :surface
with essentially water, >and .evaporating nitric acid
from .a portion of-.the drowning acid.;
7. y In Va procedure . for 'manufacturing :nitrocel-.y
tially instantaneously, removing the .drowned .ni- _
ing-a portion >ofthe drowning acid, and evaporat
, recover-.a nitricv acid >fraction and a sulphuric acid
residual fraction and concentrating the nitric
acid fraction to 60-69%..
10. In a procedure for manufacturing nitro
cel-lulose'in‘which‘ `cellulose iS.»n-itrated in an vex
cess of mixed acid and the resulting- nitrocellulose
isseparated from supernatant spent mixed acid'of
above about '75% total acid concentration by
weight, drowned tol reduce theiconcentrationof
acid ¿wetting the vnitrocellulose rapidly to below
lulose .in which celluloseV is nitrated 'in :an excessv 75 concentrations. causing> substantialVV denitration,
2,403,493
10
and then puriñed, a process which comprises car
treated, concentrating the nitric acid fraction to
rying out the drowning of the said separated ni
trocellulose wet with spent acid by mixing it with
a quenching volume of aqueous mixed nitric and
sulphuric acid having a concentration of about
10 to about 25% by weight of total acid, sai-cl vol
form a concentrated nitric acid fraction and a
second vapor fraction essentially water vapor with
a small content of nitric acid, condensing the two
essentially Water vapor fractions, and returning
the condensate to the drowning mixed acid in an
amount permitting the total acid concentration
of the drowning acid to be maintained between
ume being sufficient to reduce the concentration
of the spent acid on and in the nitrocellulose to
between about 10% and about 25% substantially
about 10% and about 25%.
instantaneously, removing the drowned nitrocel 10
l2. In a procedure for manufacturing nitrocel
lulose from the drowning acid, concentrating a
lulose in which cellulose is nitrated in an excess of
portion of the drowning acid, subjecting the re
mixed acid and the resulting nitrocellulose is sep
sulting acid to evaporation to form a vapor frac
arated from supernatant spent mixed acid of
tion of water and a major portion of the nitric
above about 75% total acid concentration by
acid in the drowning acid concentrate and a liquid 15 weight, drowned to reduce the concentration of
fraction of aqueous sulphuric acid containing the
acid wetting the nitrocellulose rapidly to below
remaining nitric acid, denitrating the sulphuric
concentrations causing substantial .denitration,
acid fraction to form an aqueous nitric acid vapor,
and then puriñed, a process which comprises car
and subjecting the tWo said nitric vapors to con
rying out the drowning of the said separated rli
centration to form and recover a concentrated 20 trocellulose wet with spent acid by mixing it with
nitric acid fraction.
a quenching volume of aqueous mixed nitric and
11. In a procedure for manufacturing nitrocel
sulphuric acid having a concentration of about
lulose in which cellulose is nitrated in an excess of
10 to about 25% by weight of total acid, said vol
mixed acid and the resulting nitrocellulose is
separated from supernatant spent mixed acid of ,
above about '75% total acid con-centration by
weight, drowned to reduce the concentration
of acid wetting the nitrocellulose rapidly to
below concentrations causing substantial de
ume being suilicient to reduce the concentration
of the spent acid on and in the nitrocellulose to
between about 10% and about 25% substantially
instantaneously, removing the drowned nitrocel
lulose from the drowning acid, concentrating a
nitration, and then purified, a process which ,
comprises carrying out the drowning of the
said separated nitrocellulose wet with spent
acid by mixing it with a quenching volume of
aqueous mixed nitric and sulphuric acid having a
concentration of about 10 to about 25% by weight
of total acid, said volume being suñicient to re
duce the concentration of the spent acid on and
portion of the drowning acid to form an acid con
centrate fraction and a vapor fraction essentially
water vapor with a small content of nitric acid,
subjecting the acid concentrate to evaporation to
form an aqueous nitric acid vapor fraction and
a residual fraction containing the sulphuric acid
of the drowning acid portion treated, concentrat
in the nitrocellulose to lbetween about 10% and `
ing the nitric acid fraction to form a concentrated
nitric acid fraction and a second vapor fraction
essentially water vapor with a small content of
about 25% substantially instantaneously, remov
nitric acid, condensing the two essentially water
ing the drowned nitrocellulose from the drowning~ 40 vapor fractions, washing nitrocellulose Wet with
acid, concentrating a portion of the drowning acid
residual drowning acid to remove said residual
to form an acid concentrate fraction and a vapor
fraction essentially water vapor with a small con
acid and to form therewith a diluted acid, and
adding said diluted acid to the drowning acid.
tent of nitric acid, subjecting the acid concentrate
to evaporation to form an aqueous nitric acid va
por fraction and a residual fraction containing
the 'sulphuric acid of the drowning acid portion
45
FREDERICK J. BOUCHARD.
ROBERT C. GUNNESS.
RAPHAEL L. STERN.
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