METHOD AND SYSTEM FOR FEEDING PROPELLANT SLURRY

METHODE ET SYSTEME D'ALIMENTATION D'UN PROPULSEUR SOUS FORME DE BOUILLIE

English Abstract

ABSTRACT OF THE DISCLOSURE
A method and system are provided for feeding a
slurry of energetic wastes, such as propellants or
explosives, dissolved in a volatile solvent such as acetone,
for introduction into a molten salt for destruction of such
waste, without vaporization of the solvent in the feeding
device or injector, and without deposition of explosive
residue on the inside surface of such injector. This is
achieved by introducing carbon dioxide liquid into the
slurry feeding device or injector, and into heat exchange
relation with the feed slurry to cool the slurry and prevent
vaporization of the volatile solvent, and to thereby prevent
deposition of explosive solid residue in the feed injector.
The injector is mounted on the vessel which contains the
molten salt and such vessel is positioned in a furnace for
heating the molten salt to reaction temperature. Although
the injector for feeding the propellant slurry is heated by
the furnace, sufficient cooling is achieved by the liquid
carbon dioxide within the injector to prevent vaporization
of the volatile solvent.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In the process of feeding a slurry of a propellant
or explosive dissolved in a volatile solvent through a
feeding device and into a molten salt system for destruction
of said propellant or explosive, the improvement for
preventing vaporization of said solvent and preventing
formation of an explosive residue in the feeding device,
comprising passing carbon dioxide liquid into heat exchange
relation with said slurry to cool same and to maintain said
solvent in liquid form.
2. The process of claim 1, wherein said solvent is
selected from the group consisting of ketones, ethers,
acetates, and mixtures thereof.
3. The process of claim 1, wherein said solvent is
acetone.
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4. The process of claim 1, wherein said feeding
device feed is an actively-cooled injector having a central
passage, and including passing carbon dioxide liquid into an
annulus of the injector around said feed passage to cool the
slurry therein, and vaporizing said carbon dioxide liquid
and discharging the resulting carbon dioxide gas from said
annulus.
5. The process of claim 4, and including passing air
through a second annulus around said annulus containing said
carbon dioxide liquid and gas.
6. The process of claim 5, wherein said solvent is
selected from the group consisting of ketones, ethers,
acetates, and mixtures thereof.
7. The process of claim 5, wherein said solvent is
acetone.
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8. The process of feeding a slurry of a propellant or
explosive dissolved in a volatile solvent into a molten salt
system for destruction of said propellant or explosive while
preventing vaporization of said solvent and preventing
formation of an explosive residue, comprising
passing said feed slurry through a central feed
passage in an injector disposed within a furnace containing
a molten salt bath,
passing carbon dioxide liquid downwardly through a
tube and into an annulus around said feed passage to cool
said slurry and to maintain said solvent in liquid form and
prevent formation of a residue in said feed passage,
vaporizing said carbon dioxide liquid, said annulus being
closed at the lower end of said injector,
discharging the resulting carbon dioxide gas from
the upper end of said injector, and
discharging said slurry from the lower end of said
feed passage into said molten salt bath.
9. The process of claim 8, wherein said volatile
solvent is acetone.
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10. The process of claim 8, and including passing air
downwardly through a second annulus around said annulus
containing said carbon dioxide liquid and gas, and
discharging said air from the lower end of said second
annulus, into said molten salt bath.
11. A system for feeding a slurry of a propellant or
explosive dissolved in a volatile solvent into a molten salt
system for destruction of said propellant or explosive while
preventing vaporization of said solvent and preventing
formation of an explosive residue, which comprises
an injector,
a molten salt system,
a containment vessel for said molten salt system,
said injector mounted at the upper end of said
vessel, said injector comprising
a central tube for passage of a feed slurry of a
propellant or explosive dissolved in a volatile solvent, the
lower end of said central tube being open and communicating
with said molten salt system,
a second tube disposed around and concentric with
said central tube and forming an annulus between said tubes,
said second tube being closed at its lower end and open at
- 12 -

(Claim 11 continued)
its upper end,
a third small diameter tube extending into said
annulus and open at its lower end for communication with
said annulus, and
means for feeding carbon dioxide liquid into the
upper end of said third tube for passage at its lower end
into said annulus and into heat exchange relation with the
feed slurry in said central tube to cool said slurry and for
discharge of the resulting carbon dioxide gas from the upper
end of said annulus.
12. The system of claim 11, and including a fourth
tube around and concentric with said second tube and forming
a second annulus between said second and fourth tubes, said
fourth tube being open at opposite ends for passage of air
through said injector and into said molten salt system.
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13. The system of claim 12, and including a downcomer
for passage of cooled feed slurry and air from the lower end
of said injector and through said molten salt system.
14. The system of claim 13, said molten salt system,
said containment vessel, said injector and said downcomer
being mounted in an electric furnace.
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Description

93R043
~-` 21209~2
Docket 1842
METHOD AND~SYSTEM FOR FEEDING PROPBLLANT SLURRY
Richard L. Gay
Jerold (n~i) Guon
John C. Newcomb
BACKGROUND OF THE INVENTION
. _
1. Field of the Invention
This invention relates to the destruction of
explosives and propellants, and is particularly directed to
an improved process for feeding a slurry of energetic
wastes, such as a propellant or explosive, dissolved in a
volatile solvent into a waste destruction system, while
preventing vaporization of the solvent and leaving an
explosive solid residue on the feeding device.
2. Description of the Prior Art
Propellants and explosives are energetic systems
containing energetic groups such as nitrate and azide
groups, and finely-divided metal particles. The problem is
to dispose of these materials as a waste. The use of a
molten salt bath containing alkali metal carbonate for
destroying propellant and explosive wastes has been
developed. Because these materials are so sensitive as
solids to potential detonation, the practice has been to
dissolve them in an organic solvent such as ketones (e.9.
~r ~ ~ ~ t

212 0 9 9 2 93R043
acetone),ethers and acetates, to make a pumpable slurry.
However, since ketones, ethers and acetates
used to for~ the slurry are very volatile, where a feed
injector is located within a heated vessel in a molten salt
waste destruction system, the heat transferred to the feed
injector is such that it is likely to vaporize the organic
solvent and leave a solid residue on the inside of the
injector piping and which may potentially detonate.
SUMMARY OF THE INVENTION
_ . _
The present invention provides a method and system
for actively cooling the injector for feeding the energetic
waste slurry of a propellant or explosive containing a
volatile organic solvent such as acetone, while the slurry
is being heated, so that the solvent in the slurry does not
evaporate and no explosive residue forms and the slurry is
discharged from the feed injector for passage to the waste
destruction system, such as a molten salt bath.
According to the invention, such cooling of the
energetic waste is achieved using carbon dioxide liquid. ~.
The carbon dioxide liquid is introduced into an annulus of
the injector for heat exchange with the waste
slurry passing through a central tube in the injector.
Since the feed injector is normally mounted within a furnace
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-- 2~20992
containing a molten salt waste destruction bath, common
aqueous coolants such as water could not be employed because
if a leak developed in the injector, water would be
introduced into the molten salt bath which could result in a
steam explosion. Where carbon dioxide liquid is employed
according to the present invention, it will vaporize during
heat exchange cooling with the waste slurry in the injector,
and no stea~ or other explosion potential is presented.
Common cooling gases such as air or helium cannot be used
because insufficient heat can be removed in the gas phase.
OBJECTS OF THE INVENTION
It is accordingly an object of the present
invention to provide an improved process for feeding a waste
slurry of a propellant or explosive dissolved in a volatile
solvent to a waste destruction system.
Another object is the provision of a process for
feeding a waste slurry of a propellant or explosive
dissolved in acetone or other volatile organic solvent
through a feeding device into a molten salt bath for
destruction of the propellant or explosive, without
vaporization of the acetone or other volatile organic
solvent during passage of the waste slurry through the feed
system.
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2120992 93R043
Yet another object is the provision of a system
for carrying out the invention process.
Other objects and advantages of the invention will
be apparent or made obvious by the description below of a
preferred embodiment of the invention.
DESCRIPTION OF THE DRAWINGS
,
Fig. 1 is an elevational view of an
actively-cooled slurry injector for carrying out the
invention process, and
Fig. 2 shows the slurry injector of Fig. 1
positioned within an electric furnace containing a molten
salt bath for discharge of the feed slurry into such bath.
DETAILED DESCRIPTION OF A ~;
PREFERRED EMBODIMENT OF THE INVENTION
Referring to Fig. 1 of the drawing, the actively
cooled slurry injector according to the invention, indicated
at 10, is comprised of a central tube 12 for passage of the
feed slurry, and which is open at both ends. A second
larger diameter tube 14 is positioned around tube 12
concentrically therewith. The bottom of tube 14 is sealed
at 16 but is open at its upper end. A third small diameter
tube 18 is positioned in the annulus 20 between tubes 12 and

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~ 2120992
14, and extends downwardly into the annulus close to the
bottom thereof. Carbon dioxide liquid is fed downwardly
through the small tube 18 and is discharged from the bottom
thereof into the annulus 20 and passes in heat exchange
relation with the feed slurry in the central tube 12,
cooling same and causing vaporization of the CO2. The
liquid carbon dioxide fed to tube 18 and into annulus 20 is
usually under pressure, e.g. 800 psi, and at a temperature
of the order of about 0C or below. The CO2 gas is
discharged from the top of tube 14 since it is sealed at the
bottom. In this process it flows around the outside of the
central tube 12 and removes heat therefrom.
While the slurry injector is normally positioned
inside a furnace, as shown in Fig. 2 and described below, so
that it is subjected to heating from the outside, the ~ -
cooling capacity of the carbon dioxide liquid is still
sufficient to maintain the feed slurry sufficiently cooled
so that the volatile solvent therein, such as acetone, does
not evaporate.
A fourth tube 22 having a diameter greater than
tube 14 is positioned concentrically around tubes 12 and 14.
Tube 22 is open at both ends and functions for passage of
air downwardly in the annulus 24 between tubes 14 and 22 and
exits at the bottom of tube 22. The air passing through

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2120992
annulus 24 and discharging at the bottom thereof functions
as process air for passage to the molten salt bath as shown
in Fig. 2, and also aids to a minor extent in cooling of the
central feed tube 12.
Referring now to Fig. 2, it is seen that the
slurry injector 10 of Fig. 1 is mounted within the upper end
of a containment vessel 26 containing a ~olten salt bath 28
at the bottom. The slurry injector 10 is mounted within the
upper end of a downcomer 34 which communicates at its lower
end with the molten salt bath 28. The molten salt bath 28
contains an alkali metal carbonate such as sodium carbonate,
or an alkali metal chloride such as sodium chloride or
mixtures thereof. In preferred practice a mixture of sodium -
carbonate and sodium chloride chiefly sodium carbonate, is
employed. Temperature of the molten salt bath 28 can be
maintained from about 300 to about 1,000C for submerged
reactive contact of the waste feed with the molten salt and
decomposition of the waste propellant or explosive feed to
form essentially CO2 r nitrogen and water vapor, which can be
vented. Such molten salt compositions are well known in the
art and described, for example, in U. S. Patent 3,778,320.
To maintain the above noted molten salt
temperatures, the containment vessel 26 is positioned within
a retainer vessel 30 and the entire assembly including the

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~ 212~992
molten salt 28, the slurry injector 10 and downcomer 34 is
positioned within an electric furnace 32.
Waste feed slurry containing volatile solvent
such as acetone is fed from the supply tank 36 via line 38
and a pump 40 to the central tube 12 of the slurry injector
10. Process air is fed from an air inlet 42 into the outer
tube 22 and the annulus 24. The feed slurry and the process
air are discharged from the lower end of the injector 10 ::
through the downcomer 34 and forced through the salt bath 28
for reaction therewith. Reactive off-gas containing CO2, N2
and water vapor are discharged from an off-gas outlet 44 at
the upper end of the retainer vessel 30.
It will be noted that although the injector 10
mounted within the electric furnace 32 is being heated
therein, the cooling effect of the carbon dioxide liquid on
the feed slurry within the central tube 12 of the injector
is sufficient to maintain the volatile organic solvent such
as acetone in the feed slurry in liquid form without
vaporization thereof, so that no explosive or propellant
residue is deposited within the central tube 12, and the
slurry which is fed into the upper end of the central tube
12 of the slurry injector, remains as a slurry throughout
its passage through the injector and is discharged as a
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--'` 2120992
slurry from the bottom of the slurry injector without
vaporization of the acetone therein.
It is understood that although acetone is a
preferred organic solvent for the energetic waste slurry,
other ketones, ethers or acetates, and mixtures thereof, and
which are volatile can be used, such as methyl ethyl ketone,
diethyl ether, tetrahydrofuran, ethyl acetate, anc mixtures
thereof.
From the foregoing, it is seen that the invention
provides an improved method and system for feeding a slurry
of energetic waste solids dissolved in a volatile solvent
such as acetone, to a molten salt for destruction of such
waste, without evaporation of the solvent in the feeding
device or injector, and without depositing an explosive
solid residue on the inside surface of the injectcr.
It is to be understood that what has been
described is merely illustrative of the principles of the
invention and that numerous arrangements in accorcance with
this invention may be devised by one skilled in the art
without departing from the spirit and scope thereof.

Representative Drawing