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SePt- 3, 1945.>
J. 1_.wooD ETAL
2,406,935
PREPARATION OF FUSIONS CONTAV'INING MAGNESIUM CHLORIDE .
Filed oct. 1e. 1941
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INVENToRsl
Patented Sept. 3, _1946
2,406,935
UNITED STATES PATENT OFFICE
`
V2,406,935
PREPARATION OF FUSIONS CONTAINING.
MAGNESIUM CHLORIfDE
Joseph Leonard Wood and Robert B. MaeMullin,
Niagara Falls, N. Y., assîgnors to The Mathieson
Alkali Works, Inc., NeuT York, N. Y., a corpora
tion of Virginia
Application 0ctober 16, 1941, Serial No. 415,270
’7 Claims.y (Cl. 204--70)
l
2
,
This invention relates to improvements in the
decomposition of the magnesium chloride, with
preparation of anhydrous fusions containing
resulting formation of magnesium oxide and lib
magnesium chloride, particularly for the electro
eration of hydrogen chloride, proceeds rapidly
lytic production of metallic magnesium.
due to the relatively large area of the >hydrous
The electrolysis of magnesium chloride fusions 5 magnesium chloride exposed to the atmosphereî
liberates magnesium at the cathode and chlorine
above the fregion of dehydratiomboth as the hy
at the anode. This electrolysis is usually carried
drous salt moves through this atmosphere and as
out with fusions somewhat heavier than magne
it floats on the surface of Vthefused- body of salt.
sium metal at operating temperature containing,
The decomposition losses involved in supplying
in addition to the magnesium chloride, various 10 pulverulent hydrous magnesium chloride to the
halide diluents modifying the solidiñcation point,
fusion range upwards from about 10% «or 15%
the fluidity, `the density or other properties of the
to as much as 50% or more. By supplying `hy
fusion under conditions such that only the mag-`
drous magnesium chloride to the fusion in accord
nesium chloride is electrolytically decomposed.
ance with this invention, however, suchA decom
The magnesium chloride thus consumed must be
position losses can be reduced to as little as 5%
replaced as the operation continues. Since the
presence of water in the region of electrolysis in
The operating steps of this invention comprise
volves losses of liberated magnesium through for
the charging of hydrous magnesium chloride into
mation of the oxide, decomposition vof the chlo- ‘
a fusion consisting essentially of magnesium chlo
ride with formation of hydrogen .chloride and
ride and a substantial proportion of halide dilu
the oxide and power losses otherwise useful for
ent, the magnesium chloride in proportion not ex
the production of magnesium, the fusion under
ceeding about 50% by weight, through itsv upper
going electrolysis should be anhydrous. The
surface as dense aggregates wettable by the fusion
usual processes for the production of magnesium
and of a density approximating 0.9-1.5 or better
chloride produce, initially, aqueous solutions and. 25 0.9-1.1, the maintenance of an atmosphere of
although dehydration of such magnesium chlo
chlorine or hydrogen `chloride above the region
ride solutions to produce the dihydrate can be
of dehydration and the introduction of chlorine or
carried out efficiently and-economically, ordinary
hydrogen chloride into the fusion in the region of
dehydration much beyond this point involves dif
addition of the hydrous material, and the main
ficulties including decomposition ofthe hydrous 30 tenance of the presence of pulverulent carbon in
magnesium chloride with liberation of hydrogen
the region of dehydration, by incorporationof a
proportion of pulverulent carbon not exceeding
chloride and formation of the oxide.`
This invention includes certain operating steps,
about 1% by weight in the dense aggregate of
magnesium chloride with particular advantage,
hereinafter described, which make it possible to
prepare anhydrous fusions containing magnesium
or by maintenance of a blanket of pulverulent
chloride from the hydrous salt, the dihydrate for
carbon on the upper surface of the fusion in the
example, with at most but limited decomposition
region of addition ofthe hydrous material.
of the magnesium chloride.
If, instead of being supplied as a pulverulent
material of relatively low apparent density, the
It has hitherto been proposed to su‘pply the re
quired magnesium chloride by introducing the 40 hydrous magnesium chloride is supplied as aggre-r
gates having an apparent density of the indicated
hydrous salt, magnesium chloride dihydrate for
order, the hydrous magnesium chloride moves
example, into a part of the fused body of salt
through the atmosphere above the region of de
separated from the region of electrolysis, taking
hydration with a minimum of exposure to that
01T the water vapor liberated from theresulting
atmosphere and, being readily Wettable by the
dehydration and causing the thus dehydrated
fusion in this form, moves immediately through
magnesium chloride to move in the fused body
of salt into the region of electrolysis. In carrying
the surface of the fusion so that, even though
these dense aggregates remain at or near the sur-V
out such proposals, the hydrous magnesium chlo
face of the fusion until they are themselves de
ride necessarily moves into the fusion through
an atmosphere consisting essentially of the water 50 hydrated and melted, the hydrousY salt thus sup
plied is separated from the atmosphere above the
vapor liberated by the dehydration, Further, if
region of dehydration by the surface of the fused
the hydrous magnesium chloride is supplied in
body of salt except for the brief period of passage
forms produced by ordinary processing it tends to
or
float, without being immediately wetted, on the
surface of the fusion.
less.
`
`
y
_
through this atmosphere into the fusion.> Also,
Under these conditions 55 by supplying the hydrous magnesium chloride as
2,406,935
4
3
ature of 700°-800° C.
aggregates of the indicated density, the hydrous
magnesium chloride remains at or near the sur
face of the fusion until dehydated and melted,
permitting immediate escape of liberated Water
vapor, eliminating another cause of decomposi
tion of magnesium chloride added as the hydrous
material or previously dehydrated magnesium
chloride present in the fusion.
Such aggregates of hydrous magnesium chlo
ride, of a density approximating 0.9-1.5 or better
The molten magnesium
is withdrawn from compartment 8. Dense ag
gregates of hydrous magnesium chloride are sup
plied through connection H and sealing mecha
nism I2, a star valve for example, to the com
partment E3 on the other side of the upper end
of the cell, the gas space in this compartment be
ing separated from the gas space in the anode
compartment by the partition I4. The fused body
10 of salt circulates upwardly from the lower part
0.9-1.1, are conveniently and advantageously
formed by briquetting aqueous magnesium chlo
ride reduced approximately to the dihydrate by
« of the cell around the anode into the anode com
partment 9, thence beneath the partition I4 into
the supply compartment I3, and thence down
wardly into the lower part of the cell. A blanket
|spray-drying in concurrent flow with a stream
of furnace gases at a temperature, for example, 15 of pulverulent carbon, maintained by appropriate
additions from time to time, either as such or as
of 650°-750° C. and controlling the apparent den
a component of the dense aggregates of hydrous
sity of the aggregates by controlling the effective
magnesium chloride, may be maintained on the
pressure of the briquetting operation. By this
surface of the fused salt body in the cell in the
step alone, the introduction of the hydrous` mag
nesium chloride as dense aggregates wettable by 20 compartment I3, Chlorine or hydrogen chlo
ride is either introduced over the surface ol‘ the
the fusion and of the indicated density through
fused salt body in the compartment I3 through
the upper surface of a fused body of 'salt contain
connection I8 or into the fused salt body in this
inga substantial proportion, not less than about
region through connection I9. The water vapor
50% by Weight, of halide diluent as Iwell as mag
nesium chloride, substantial suppression of de» 25 liberated by the dehydration, together with un»
composition of the magnesium chloride can be
accomplished. Further suppression of such de
composition is effected, in accordance with this
invention, by maintaining an atmosphere of
chlorine or hydrogen chloride above the region 30
of dehydration. This is'accomplished by intro
ducing chlorine or hydrogen chloride over the
surface of the fused body of salt in this region
or, with particular advantage, by introducin
reacted chlorine or hydrogen chloride, is dic
charged through connection I5. Chlorine liber
ated in the anode compartment 9 is discharged
through connection I6. The dense aggregates of
hydrous magnesium chloride charged through
connection I I traverse the gas space in compart
ment I3 and then immediately pass through the
upper Surface of the fused salt body in this com
partment, being readily lwetted by the fusion, so
chlorine or hydrogen chloride into the fused body 35 that the hydro-us magnesium chloride suffers but
a minimum exposure to the atmosphere in the
of salt, beneath its upper surface, in the region
compartment I3. These aggregates then remain
of addition of the anhydrous material. By main
close to the surface of the fusion in this com»
taining the presence of pulverulent carbon in the
partment until, upon dehydration and melting,
region of dehydration, particularly as a compo
nent of the magnesium chloride aggregates, the 40 they bec-o-me a part of the fusion as anhydrous
magnesium chloride. Decomposition of the an
decomposition of the magnesium chloride is fur
hydrous magnesium chloride is thus suppressed,
ther suppressed and additional advantages are
and such decomposition is further suppressed by
secured in the elimination of traces of Water from
the introduction of chlorine or hydrogen chloride
the fused salt mixture undergoing electrolysis.
The operating `steps of this invention may be 45 and by the maintenance of the presence of pul
verulent carbon in this region.
applied to the maintenance of a fused body of
The vessel I, in Figure 1, is arranged in a gas
salt in the cell in which the electrolysis is carried
fired furnace chamber to facilitate initiation of
out or they may be applied to the preparation
the electrolysis. The heat ofthe electrolysis is
of a fusion in a separate Vessel from which the
fused anhydrous salt is supplied to the body of 50 usually suñicient to maintain the fusion temper
ature in the cell.
salt in the cell. Two forms of apparatus in
The apparatus illustrated in Figure 2 comprises
which the operating steps of this invention may
a fusion vessel 2 arranged in a gas fired furnace
be carried out are illustrated, diagrammatically,
chamber to maintain the fusion temperature. A
in elevation and partly in section, in the accom
panying drawing. The electrolytic cell illustrat 55 baffle 3 is arranged to separate the region in
which dehydration is effected, generally desig
ed 'in the accompanying drawing and described
nated 20, from a region, generally designated 2l,
generally'below is the invention of William C.
through which the anhydrous fusion can be with
Gardiner. The apparatus illustrated in Figure
drawn, for example, to be supplied to an ap
1 ls an electrolytic cell, and the apparatus illus
propriate electrolytic cell. A hood 22 is provided
trated in Figure 2 is a separate fusion vessel.
to carry away liberated water and escaping
The apparatus illustrated in Figure 1 com»
chlorine or hydrogen chloride. A body of fused
prises a cast steel vessel I, a cathode made up of
salt consisting essentially of halide diluent and
a plurality of steel rods 4 annularly arranged and
magnesium chloride, the latter in proportion not
depending from a steel plate beneath the parti
tion 5, and an anode, a carbon rod 6, suspended 65 exceeding about 50% by weight, is maintained at
or above the fusion temperature, 650°-800° C, for
throughy an opening in the partition 5. An an
example, in the vessel 2. A blanket of pulverulent
nular baille 'I extending downwardly from an
carbon may be maintained on the fused body of
opening in the partition 5 traps off metallic mag
salt above the region 20. Chlorine or hydrogen
nesium liberated at the cathode, Ithe vmagnesium
chloride is introduced either over the surface of
ñoating on the fused salt body in the cell, and
the fused body of salt above the region 20 or into
causes it to flow into a compartment 8 at one
the fused body of salt in the region 2i) through
side of the upper end of the cell, separated from
from the anode compartment 9 by a partition IEE.
connection 23 or connection 24, respectively.
Dense aggregates of hydrous magnesium chloride
The fused body of salt, halide diluent as well as
magnesium chloride, is maintained at a temper
are charged into the fused body of salt through
12,406,935
i5
6
’thefsurface of the fused saltbody above the
through its uppér surface a'charge ofbriquetted
Vas required through region 20. The operation of a
the charge being wettable by the fusion and hav
ing a’density approximating 0.9-1.5, and taking
hydrous magnesium’chloride, the briquettes of
Aregion 20.» The, anhydrous fusion containing
magnesium chloride _thus prepared is withdrawn
'separate fusionvessel such as that illustrated in C1 off the thus liberated water.
Figure 2 can' be combined with the operation of
2. In the preparation of anhydrous fusions
a recovery vessel. That is, the mixture of fused
containing magnesium chloride, the improve
salt containing magnesium chloride and mag
ment which comprises maintaining a fused body
nesium oxide accumulating in the lower part of
consisting essentially of halide diluent and mag
theelectrolytic cell, 'such as the cell illustrated in ~10 nesium chloride, the body having a density some
Figure 1, may from time to time be removed from
what exceeding that of magnesium metal at the
the electrolytic cell and charged into the separate . temperature of said fused body> and containing
fusion vessel 2 along with the dense aggregates
magnesium chloride in proportions not exceeding
of hydrous magnesium chloride and the recovery
about 50% by weight, maintaining over the body
of -magnesium values of thismixture thus com
an atmosphere containing a gas selected from the
bined with the preparation of the anhydrous
fusion containing magnesium chloride for elec
trolysis.
The halide diluents useful in carrying out this
invention include the chlorides of sodium, potas 20
groupv consisting of chlorine and hydrogen chlo
ride, introducing into said body through its upper
surface a charge of briquetted hydrous magne
sium chloride, the briquettes of the charge being
wettable by the fusion, and having a density ap
sium, calcium and barium and the fluorides of
sodium and calcium. In general the chlorides are
to be preferred to the fluorides. The composition
of the fusion may conform to established prac
tices. It is essential, however, in carrying out
this invention, that a substantial proportion, not
less than about 50% by weight, of the fusion be
made up of halide diluent and that the total mag
nesium chloride present in the fusion be corre
proximating 0.9-1.5 and taking off the thus lib- .
about
hydrous magnesium chloride, the briquettes of
erated water.
3. In the preparation of anhydrous fusions
containing magnesium chloride, the improve
ment which comprises maintaining a fused body
consisting essentially of halide diluent and mag..
nesium chloride, the body having a density some
what exceeding that of magnesium metal at the
temperature of said fused body and containing
spondingly limited.
30 magnesium chloride in proportions not exceeding
In actual practice of `this invention, charging
about 50% by weight, introducing into said body
hydrous magnesium chloride corresponding to
through its upper surface a charge of briquetted
MgC12.1.85I-I2O to MgC12.2.38H2O
the charge being wettable by the fusion and hav
35 ing a density approximating 0.9-1.5, introducing
and containing about 0.5-1.0% by weight of car
into the body in the region of the addition of
bon, anhydrous fusions were prepared with de
the briquetted magnesium chloride a gas selected
composition losses of magnesium chloride of less ~ from the group consisting of chlorine and hydro
than 3% with the introduction of chlorine over
gen chloride, and taking off the thus liberated
the surface of or into the fused salt body and 40 water.
with substantially no decomposition losses of
4. In the preparation of anhydrous fusions
magnesium chloride with the introduction of
containing magnesium chloride, the improvement
hydrogen chloride. With proportions of carbon
which comprises maintaining a fused body con
not exceeding about 1% by weight incorporated
sisting essentially of halide diluent and magne
in the magnesium chloride aggregates, substan
sium chloride, the body having a density some
tially al1 of the carbon is consumed leaving none
what exceeding that of magnesium metal at the
by mischance to be entrained in the dehydrated
temperature of said fused body and containing
fusion moving into the region of electrolysis.
magnesium chloride in proportions not exceeding
When a blanket of pulverulent carbon is used, it
about 50% by Weight, maintaining a layer of
should be limited to the surface over the region
pulverulent carbon on the upper surface of the
of active dehydration to minimize any such en
trainment.
Notwithstanding the maintenance of fusion
temperatures upwards of 650° C., traces of water
nevertheless appear in such halide fusions con
taining Inagnesium chloride to which magnesium
chloride is supplied in hydrated form unless
they are heated to temperatures approximating
1000" C. This is evidenced by the decomposition
body and an atmosphere of chlorine over the
A’btody, introducing into said body through its
upper surface a charge of briquetted hydrous
magnesium chloride, the briquettes of the charge
being wettable bythe fusion, and having a den
sity approximating 0.9-1.5, and taking oiî the
thus liberated water.
5. In the preparation of anhydrous fusions
‘containing magnesium chloride, the improve
of magnesium added as the metal to such fusions. 60 ment which comprises maintaining a fused body
The maintenance of the presence of pulverulent
consisting essentially of halide diluent and mag
carbon in the region of dehydration in accordance
nesium chloride, the body having a density some- ‘
with this invention, however, has the further ad
what exceeding that of magnesium metal at the
vantage of eliminating such residual traces of
temperature of said fused body and containing
water at temperatures approximating 700°-800° C.
magnesium chloride in proportions not exceeding
We claim:
Á
1. In the preparation of anhydrous fusions
about 50% by weight, introducing into said body
through its upper surface a charge of briquetted
containing magnesium chloride, the improve
hydrous magnesium chloride containing finely
ment which comprises maintaining a fused body
consisting essentially of halide diluent and mag
nesium chloride, the body having a density some
what exceeding that of magnesium metal at the
temperature of said fused bodyA and containing
magnesium chloride in proportions not exceeding
divided carbon in proportions not exceeding
about 1% by weight, the briquettes cf the charge
being wettable by the fusion, and having a den
sity approximating 0.9-1.5, and taking off the
thus liberated water.
6. In the preparation of anhydrous fusions
about 50% by Weight, introducing into said body
containing magnesium chloride, the improve
2,406,935
7
ment which comprises maintaining a fused body
consisting essentially of halide diluent and mag_
nesium chloride, the body having a density some
What exceeding that of magnesium metal at the
temperature of said fused body and containing
magnesium chloride in proportions not exceed
ing about 50% by' Weight, introducing into said
8
what exceeding that of magnesium metal at the
temperature of said fused body and containing
magnesium chloride in proportions not exceeding
about 50% by Weight, maintaining a layer of
pulverulent carbon on the upper surface of the
body, maintaining over the body an atmosphere
containing a gas selected from the group con
sisting of chlorine and hydrogen chloride, intro
ducing into said body through its upper surface
quetted hydrous magnesium chloride, the bri
quettes of the charge being Wettable by the fu l0 a charge of briquetted hydrous magnesium chlo
ride, the briquettes of the charge being wettable
sion and having a density approximating 0.9-1.1,
by the fusion and having a density approximat
and taking off the thus liberated Water.
ing 0.9-1.5 and taking oiî the thus liberated
7. In the preparation of anhydrous fusions
Water.
containing magnesium chloride, the improve
JOSEPH LEONARD WOOD.
ment which comprises maintaining a fused body 15
consisting essentially of halide diluent and mag
ROBERT B. MACMULLIN.
nesium chloride, the body having a density some
body through its upper surface a charge of bri
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