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0a. 15,1946.-
A. w. sADDlNG-roN
MANUFACTURE OF SODIUM SULPHIDES
Filed oct. 9, '1945, l
2,409,392
Patented Oct. 15, 1946
»_ 2,409,392
UNITED STATES PATENT -OFFICE
2,409,392
MANUFACTURE OF SODIUM SULFIDES
Arthur W. Saddington, Syracuse, N. Y., assign
or to The Solvay Process Company, New York,
N. Y., a corporation of New York
Application October 9, 1943, Serial No. 505,596
10 Claims.
(Cl. ,2S-_134)
l
2
This invention relates to the manufacture of
soda as the source of sodium, coagulation and
sodium hydrosulfide (NaHS) or sodium sulfide
precipitation of metallic impurities are not ob- '
(NazS) or mixtures of both.
tained consistently even when pure Hes gas is
used and even though the liquor has been gassed
with a large excess of H25. Thus, while the prior
art indications are that coagulation and pre
-
It is known that sodium hydroxide may be
reacted with HzS to form NazS which may be
treated with more I-IzS to convert Nass to NaHS,
and it has been proposed to make sodium hydro
sulflde by gassing an NazS-NaHS liquor with
cipitation of metallic impurities may be had by
_ gassing the liquor to such an extent that the liq
pure hydrogen sulfide.
.
'
uor contains no NazS and then using an excess of
In processes of the type to which the inven 10 HzS, I ñnd these conditions are not controlling
tion relates, the source of >sodium is commercial
in all circumstances, and have discovered that
caustic soda which contains appreciable quanti
ties of impurities, such as iron, copper, nickel,
manganese and silicon. These impurities do not ,
discolor caustic soda to any great extent, and 15
NazS contents. While not identified with cer
hence their presence in commercial caustic is un
tainty, indications are that the carbonate of so
coagulation and precipitation of impurities are
dependent upon the composition of the NaI-IS
liquor with respect to carbonate of sodium and
objectionable. However, during HzS gassing of
commercial caustic liquor, such impurities pass
dium present in the system is in the form'of
NazCOa and for convenience will be referred to
thru the process and are carried into the re
as such in this specification.
sulting NaI-IS liquor. Such impurities may be 20 It will be understood that good grades of com
present in the NaHS liquor as soluble salts or
mercial caustic soda contain appreciable
suspended in finely divided condition. While
amounts, sometimes as much as O16-0.20%, of
probably largely sulfides, exact compositions of
NazCOa. Further, synthetic I-IzS gas also con
the impurities are not known, and whatever
tains appreciable quantity of CO2 as an impurity,
their nature, these substances are referred to 25 while the more common hydrogen sulñde gases,
herein as metallic impurities. The presence of
such as those formed in oil refining operations,
even small amounts of these impurities in NazS
or NaHS solutions results in products of very
poor appearance because of the highly colored
often contain as much as 10-25% CO2 by volume.
A principal object of this invention lies in pro
Vision of a process for making sodium hydrosul
nature of the impurities after having been'sub 30 ñde or sodium sulfide, of purity acceptable to the
jected to H2S gassing. Accordingly, a major
trade, from commercial raw materials which con
problem presented in manufacture of relatively
stitute a source of metallic impurities and sodium
pure sodium hydrosulñde has been the elimina
carbonate in the NaHS liquor resulting from HzS
tion of such impurities.
‘
gassing. The invention also aims to provide a
Commercially available hydrogen sulñde gases 35 process which permits use of an HzS gas contain
contain appreciable amounts of carbon dioxide
ing substantial amount of CO2. Further objects
as an impurity. The discoveries constituting this
are provision of a process by which it is possible
to avoid troublesome solid sodium sulfide phase
invention arose out of attempts to manufacture,
in accordance with known procedure, relatively
during the NaHS producing reaction, to operate
pure sodium hydrosulñde from commercial 40 such reaction continuously and at relatively low
caustic soda and hydrogen sulfide gases contain
temperature, and if desired to provide for quan
titative utilization of hydrogen sulñde.
ing carbon dioxide. The prior art indicates that
The process of the invention comprises gener
ally three major stages: first, formation of a
I-I2S sufiicient to convert all of the NazS content
of the liquor to NaHS and gassing is continued 45 suitable NazS-NaHS starting liquor utilizing com
utilizing a substantial excess of I-IzS, the metallic
mercial NaOH as a raw material; second, a re
impurities in the liquor coagulate and precipitate
action stage in which the NazS-NaI-IS liquor is
contacted with hydrogen sulfide gas to convert
in a ñlterable form. _ I noted that, in no instance,
are coagulation and precipitation of metallic im
NazS to NaHS; and third, a purification stage in
purities effected where the sodium hydrosulfide
which the NaHS liquor'discharged fromthe re-`
when an NazS-NaHS liquor is gassed with pure
liquor has been produced from I-I2S gas contain
ing CO2, even if all the NazSy has been converted
to NaHS and a further large excess of H2S has
been employed. This observation- led to a fur
action stage is treated in accordance with certain
principles of the invention to effect (a) reduc
tion of the amount of available sodium carbonate
present in the liquor, and (U) control of the com
ther ñnding that when using commercial caustic 65 position of such liquor with respect to NazS con
2,409,392
3
4
tent, whereby to bring about elimination from
the system of metallic impurities brought into
tinuous operation, and accordingly absorbing
liquor is fed continuously from make-up tank H
the process as impurities in the initial caustic
soda.
The nature of the invention is such that a
major advantage is that H28 gas containing a
substantial amount of CO2 may be employed.
Hence, a preferred embodiment, using H2S con
taining COz, is described below in connection with
into the top of a tower I4 providing a reaction
zone I5 in which the absorbing liquor is contact
ed preferably counter-current with I-IzS gas from
an inlet pipe I6, which gas, in accordance with
the invention, may permissibly contain substan
tial amounts` of carbon dioxide.
I have found that any carbon dioxide contained
the accompanying drawing diagrammatically 10 in the hydrogen sulfide gas reacts substantially
quantitatively with NazS to form a reaction prod
showing suitable apparatus.
In usual practice of the invention, the
NazS-NaHS absorbing liquor in tank II is made
by treating a portion of NaI-IS product liquor of
a previous run with commercial sodium hydroxide
which may contain say 0.l-0.2% or more by
weight of NazCOs. However, to start the process
an aqueous solution of sodium hydroxide of any
suitable concentration, e. g. 50-'70% NaOI-I, may
uct which appears and is herein considered for
purposes of illustration to be sodium carbonate.
I further observe that most of this sodium car
bonate immediately precipitates as a solid read
ily filterable form. Since the H28 gas used may
contain substantial amount of carbon dioxide the
quantity of solid sodium carbonate produced may
be correspondingly substantial. When the proc
be gassed with hydrogen sulfide, preferably pure, 20 ess is carried out as a batch procedure, solid so
dium carbonate readily settles to the bottom of
to such an extent as to form a liquor containing
NazS and a substantial amount of NaHS. In
the reaction vessel and causes no particular op
this preliminary step, the liquor mass should be
erating difficulty. However, to provide for con
tinuous operation throughout, I nnd that be
kept at any suitable temperature, e. g. 70° C. or
upwards depending upon the sodium sulñde con 25 cause of formation of solid sodium carbonate it
is not feasible to carry out the NaHS produc
centration of the liquor, needed to maintain all
ing reaction in the more or less usual type of
of the sodium sulñdes in the liquid phase. Pre
packed. liquor-gas contacting tower. An open
liminary starting liquor, as to composition and
spray tower, containing no packing and provid
temperature, should be similar in all respects to
the absorbing liquor formed during the usual 30 ed at the top with a spray head for introduction
of NazS-NaI-IS absorbing liquor and at the bot
practice of the process which is preferably con
tom an inlet for the HzS gas, may be employed.
tinuous.
Contact towers containing bailles 20 such as in
When the process is under way, a portion of the
dicated on the drawing may be used, although
sodium hydrosulñde liquor discharged from the
I-IzS gassing zone is run continuously thru line 35 in such instance baille arrangement should be
such as to afford good contact of gas and liquor
Iß .into NazS-NaHS absorbing liquor make-up
but at the same time permit downiiow of a rela
tank I I Iwhich may be steam jacketed to keep tem
tively light slurry and discharge of all of the
perature high enough to hold all sodium sulfide
slurry from the bottom of the tower. The type
in liquid phase. While HzS gassing zone efliuent
liquor may contain a limited amount of Nats, 40 of liquor-gas contacting tower suitable for use
in practice of the continuous basis may be de
such liquor is preferably an aqueous solution of
sodium hydrosulfide containing substantially no
fined as an unobstructed reaction chamber, but
it should be understood that the term unob
NazS. A strong solution of NaOH from tank I2
structed is used in the sense that while the re
is likewise continuously fed into make-up tank
I I. Although an absorbing liquor containing any 45 action chamber rnay contain mixing baffles, con~
struction of these baffles is such as not to cause
suitable relative proportions of NazS and NaHS
plugging but permits retarded but steady down
may be employed, it is more desirable to regulate
flow of liquor containing some solids in Isuspen
feed of NaI-IS liquor and sodium hydroxide solu
tion to tank II in such a way as to maintain
sion.
therein an absorbing liquor of certain composi
Hence in the preferred continuous operation,
tion with respect to Na2S and NaHS, purpose of
absorbing liquor of the type described is run into
this feature being to provide an absorbing liquor
the top of a contact tower of suitable design, a
of such composition as to make possible ready
stream of I-IzS gas which may contain carbon
maintenance of sodium sulfide in the liquid phase
dioxide is fed into the bottom, unused and inert
both in tank II and in the subsequent reaction 55 gases leave the top of the tower thru pipe 2I,
stage in which NazS of the absorbing liquor is
and reacted liquor is discharged from the bottom
converted to NaHS, and further to facilitate
into pipe 22 provided with valve 23. Hydrogen
carrying out the HzS contacting operation at
'sulfide and carbon dioxide react with NazS of
relatively low temperatures. To afford accom
the absorbing liquor to form NaHS and sodium
plishment of these ends, feed of sodium hydro 60 carbonate, and any NazCOs impurity contained
sulñde liquor from line l0 and of NaOH solution
in the initial commercial NaOH passes thru
from tank I2 to the make-up tank is regulated to
the contacting Zone unchanged. As a whole, re
provide therein an absorbing liquor desirably con
actions eiiected in the contacting zone are exo
thermic and some heat is developed. Broadly,
taining not more than 15% by weight of NazS.
Especially where it is desired to supply absorbing 65 the absorbing operation may be carried out at
any temperature high enough to keep all so-dium
liquor to the HzS reaction zone at a relatively low
suliide's in the liquor phase under the prevailing
temperature, e. g. 'l0-80° C., and at the same time
conditions of operation. However, temperatures
avoid any solid phase formation either in the
in the reaction zone above about 90° C. are not
absorbing liquor make-up tank or in the reaction
zone, it is preferred to control formation of the 70 desirable because of greatly accelerated corro
sion of equipment. I find that by regulating the
absorbing liquor in such a Way that the liquor
composition of the NazS-NaHS absorbing liquor
contains not more than 10% by weight of NazS
and at least 25% by weight of NaHS.
as in the above indicated preferred conditions, it
is possible to feed the absorbing liquor to the re
While the entire process may be practiced
batchwise, one of the advantages afforded is con 75 action zone at a low temperature, e. g. 'l0-80° C.,
2,409,392
. 5
v6
Y
tial' amount of NazS. The preferred condition
of operation is to bring about substantially com
plete removal `of available carbonate of sodium.
The second factor critical as to effecting coagula
phase but does not exceed the indicated maxi-'
mum temperature and does not require extra Ul tion and precipitation of metallic impurities is the
NazS content 0f the NaHS liquor. I have found
neous cooling.
.
While the carbon dioxide content of the I-IzS
that,`in conjunction With the maximum carbon
in which case the heat developed in the reaction
zone automatically maintains a temperature high
enough> to keep all> sodium sulñdes in the liquid
gas fed to the reaction Zone may vary consider
ably and may be usually about 10% by volume,
ate of sodium tolerance noted above, the NaHSA
liquor should contain not more than 5% by Weight
ordinarily it is preferred thatl such gas contain a 10 of NazS, and preferably substantially noNazS at
predominating amount of I-IzS and not more than
all. The preferred conditions of substantial ab
sence of available carbonate of sodium and of
about 25% CO2 by volume. «
.
In practice of the emb-odiment being described,
substantial absence of NazS, cause the most
thorough and rapid coagulation and precipitation
design of the gas-liquor contacting tower` and
rates of feed thereto of absorbing liquor and HzS 15 of metallic impurities. Other permissible condi
tions, as to available carbonate of sodium and
gas, whether the process is carried out batchwise,
Na2S contents, Within the limits stated bring
countercurrent, or co-current, are vregulated so
about an ultimately satisfactory coagulation and
that during the contacting operation reaction
precipitation of metallic impurities, the overall
of the NazS content of the absorbing liquor-,fed
to the contacting zone is effected to such an ex 20 difference being that as the available carbonate
of sodium and NazS contents increase to the maxi
tent that the reaction zone eñluent NaHS liquor
mum values noted, rates of coagulation and pre
contains not more than 5% by Weight of NazS,
cipitation of metallic impurities correspondingly
and preferably substantially no NazS at all. `Rea
decrease. Hence, briefly, theinvention involves
son for such conversions of the Naas content of
NaI-IS will subsequently appear.
25 formation of sodium hydrosulñde liquor contain
ing Vcertain metallic impurities and also an
In usual operation, employing an I-I2S gas
amount of carbonate of sodium equivalent to more
containing substantial amount of CO2, the NaI-IS
than 0.06% by Weight of CO3 radical, and com
liquor discharged from the bottom of tower i4
prises the steps of reducing the available car
contains a substantial amount of suspended solid
sodium carbonate which is readily separable and 30 bonate of sodium content of the liquor to` an
amount equivalent to not more than 0.06% by
is removed by ñlter 25. The ñltrate in pipe 26
weight of CO3 radical, and controlling the com
contains in solution the metallic impurities such
position of the resulting liquor so that such liquor
as iron, brought into the process as impurities in
contains not more than 5% by Weight of sodium
the commercial sodium hydroxide or picked up
from the liquor make-up or gassing apparatus,
sulfide.
and if any NaHS or NazS product Were recovered
In the more usual practice of the invention
process, i. e. where the HzS gas contains substan
tial amount cf CO2 and the reaction zone liquor
eflluent contains a comparable substantial amount
directly from the filtrate, such products would be
badly discolored and contain these impurities in
amounts in excess of trade specifications.
‘
As above stated, prior literature indicates that 40 of solid sodium carbonate, the clear liquor filtrate
in line 26 contains soluble sodium carbonate to
when an NazS-NaHS liquor is gassed with enough
the point of saturation and may Well contain in
H2S tc convert all NazS to NaHS, plus a substan
. tial excess of HzS, the metallic impurities in the
liquor coagulate and precipitate out in a ñlter
able form. I have found, with respect to con
sistently securing- coagulation and precipitation
of metallic impurities, that the controlling fac
tors are the amounts of carbonate of sodium and
NazS present in the NaHS liquor, and that the
use of an excess of I-I2S is not critical.
For ex
solution say 0.2-0.5% or more by Weight sodium
carbonate. In the modification being described,
à valve 2l in pipe 28 is closed and valve 29 is open.
A portion of the filtrate runs into recycle line l0,
and by suitable adjustment of valves 30 and 3l,
a portion of the filtrate corresponding with the
“make” of one cycle of the process is run thru
5 O valve 3| into a tank 32 in which the NaHS liquor
ample, in one operation, in which a substantial
excess of HzS was employed, and the resulting
is treated in any suitable way to bring the sodium
carbonate content down to the conditions stated.
liquor contained 46% by weight of NaI-IS, no
NazS, and carbonate of sodium in amount equiv
alent to 0.08% by weight of CO3 radical, the liquor
Carbonate
remained dark brown and there was no coagula
tion and precipitation of metallic impurities.
I have found that if sodium hydrosulflde liquor
reduction or elimination may be
effected by treating the filtrate with a compound
of an alkaline earth metal, e. g. calcium com
pound capable of reacting with the soluble sodium
carbonate to precipitate the combined CO3 as
calcium carbonate. The amount of treating ma
terial used should be at least sufficient to reduce
an amount of available (i. e. in solution or both 6 O soluble sodium carbonate content of the NaHS
liquor to an amount equivalent to not more than
in solution and in solid form) carbonate of so
is saturated with carbonate of sodium, or contains
dium equivalent to more than 0.06% by Weight
0.06% by Weight of CO3 radical. Preferably, the
quantity of treating agent employed is that which
of CO3 radical, metallic impurities do not co
is theoretically required to react with all of the
agulate or precipitate even though the liquor con
tains no NazS and has been treated with a large 65 soluble sodium carbonate. The preferred treatñ
ing materialis calcium hydrosulñde, and in this
excess of HzS, and regardless of Whether the
instance sodium carbonate is converted in accord~
liquor has been made by gassing With purel HzS or
ance with the equation
with I-IzS containing carbon dioxide. I ñnd that
if available carbonate of sodium is substantially
completely removed from an NaI-IS liquor, or re
moved to an extent such that the liquor does not
Ca (HS) z-l-NazCOsèCaCOa-i-ZNaHS
70 calcium carbonate being precipitated and the
sodium of the NazCOa being converted to NaHS,
the desired product. The calcium hydrosulfide
dium equivalent to more than 0.06% by weight
treatment does not bring about any increase in
of CO3 radical, metallic impurities coagulate and
the Na2S content of the treated liquor. In this
precipitate even if the liquor contains a substan 75 instance, the control of the treated liquor com
contain an amount of available carbonate of so
2,409,392
8
position, with respect to NazS content, is had by
principles of the invention apply to puriñcation of
regulating the I-I2S gassing in tower I'll so that
the NaI-IS liquor fed to the treating tank con
tains not more than 5% by weight of Naas> or any
lesser amount that may be desired in that particu Cn
NaHS liquors containng an amount of available
lar operation. The foregoing procedure creates
conditions which cause coagulation and precipita
tion of the metallic impurities in. readily filterable
form. The treated liquor is then filtered in ñlter
34 to remove the calcium carbonate and the
carbonate of sodium equivalent to more than
0.06% by weight of CO3 radical, no matter how
such liquors are produced.
It will be understood that if the final product
desired is VNaHS, gassing in the reaction Zone,
and in tank 32 if needed, is carried out to an ex
material such as Ca(OH)2 may be employed. In
this instance Ca(OI-I) 2 reacts with NazC‘Oa to form
CaCOa and NaOH ywhich in turn reacts with NaHS
to form NazS, thus increasing the NazS content
tent surlìcient to convert all the NazS to NaHS.
On the other hand if an NazS product is desired,
except as indicated, complete conversion of NazS
to Nal-IS is unnecessary, since the liquor eil‘luent
of ñlter 34 may be treated with NaOl-I to cut
back the product to NazS. If desired, the NaI-IS
or NazS may be converted to solid form by evapo
ration of the liquors and solidiiication by known
of the NaI-IS liquor Iundergoing
methods.
metallic impurity precipitates.
In place of calcium hydrosuliide, other treating
treatment.
I claim:
Should the quantity of Ca(OI-l) 2 used be suñicient
to raise the NazS content of the treated liquor to
1. The method for producing puriñed sodium
above the maximum permissible Naas value for 20 hydrosulñde from a sodium hydrosuli'lde liquor
that particular operation, after the Ca(OI-I)2
containing (a) at least one metallic impurity of
treatment, the liquor in tank 32 may be gassed
the group consisting of iron, copper, nickel, man
with enough H28, preferably pure, to lower the
ganese and silicon, and (b) an amount of avail
Nags content to the desired amount. In this
able carbonate of sodium equivalent to more than
mode of operation, control of the NazS content of
0.06% by weight of CO3 radical, which method
Ca(OH)2 treated liquid is had partly by gassing
in tower I4 and partly by gassing in tank 32.
comprises treating said liquor with an alkaline
earth compound so as to react with available
It will be noted that even when Ca(HS) 2 is used
carbonate of sodium to precipitate combined CO3
as a treating agent, it is not critically important
thereof as alkaline earth carbonate, the amount
that the NaHS liquor fed into tank 32 contain not 30 of said alkaline earth compound being at least
more than the permissible Nazs maximum for
sufficient to reduce the available carbonate of
that operation. For example, an Nazs liquor con
sodium content of said liquor to an amount equiv
taining say 6% by weight of NazS may be fed
alent to not more than 0.06% by weight of CO3
into tank 32, treated with Ca(I-IS)2, and there
radical, controlling the composition of the result
after gassed with enough H25, preferably pure,
ing liquor so that such liquor contains not more
to reduce the Na2S content to the point desired.
than 5% by weight of sodium sulfide, thereby
Hence, it will be understood that control of the
effecting coagulation and precipitation of metal
composition, with respect to Naz-S content, of the
lic impurities, and separating said metallic im
treated liquor may be elîected either before or
purities from such liquor.
'
after, or partly before and partly after treatment
2. The method for producing purified sodium
with the sodium carbonate content reducing
hydrosuli'lde from a sodium hydrosulñde liquor
agent, and unless speciñcally stated to be con
containing (a) metallic impurities of the type
trary, the appended claims are to be so con
present in commercial sodium hydroxide, and
strued.
(b) an amount of available carbonate of sodium
In some modiñcations the reaction zone ef- f equivalent to more than 0.06% by Weight of CO3
fluent may contain only a relatively small amount
radical, which method comprises treating said
of solid sodium carbonate, e. g. where the HzS
liquor with an alkaline earth compound so as to
gas contains no or only a small amount of CO2.
react with available carbonate of sodium to pre
In these instances, Valve 21 may be opened, valves
cipitate combined CO3 thereof as alkaline earth
23 and 29 closed, ñlter 25 by-passed, and filtration
carbonate, the amount of said alkaline earth
of the reaction eiiluent may be omitted. However,
compound being at least sufficient to reduce the
in such circumstances the amount of treating
available carbonate of sodium content of said
agent used in tank 32 should be sufficient to react
liquor to an amount equivalent to not more than
with all available sodium carbonate (i. e. both
0.06% by weight of CO3 radical, controlling the
solid and soluble) present at the time of addition
composition of the resulting liquor so that such
of the calcium compound to an extent such that
liquor contains not more than 5% by weight of
the treated liquor does not contain more available
sodium suliide, thereby effecting coagulation and
carbonate of sodium than is equivalent to 0.06%
precipitation of metallic impurities, and separat
by weight of CO3 radical. Otherwise, procedure is
ing said metallic impurities from such liquor.
the same.
3. The method of producing puriñed sodium
In practice of the invention, when treating
hydrosulñde which comprises forming an NazS
NaHS liquors, containing as high as L1.2% by
NaHS liquor containing metallic impurities of
weight of NazS, in such a way as to reduce the
the type present in commercial sodium hydroxide,
available carbonate of sodium content substan
contacting Said liquor with an HzS gas under
tially to zero, straw yellow product liquors have
been obtained containing as little as 0.0002%
FezOa and 0.045% SiO2 by weight.
temperature conditions high enough to maintain
sodium sulñde in liquid phase, continuing contact
of the liquor and HzS gas for an interval sufûcient
to elîect conversion of at least a major portion
in connection with use of an H28 gas containing
of the NazS content of said liquor to Nal-IS
CO2, it is noted that the invention is not thus 70 thereby forming an NaI-IS liquor containing, as
restricted. It will be understood that many grades
a result of presence of oxide of carbon impurities
of commercial caustic contain sufficient Na2CO3
in the system, an amount of available carbonate
as an impurity to result in formation of an NaI-IS
of sodium equivalent to more than 0.06% by
liquoi` containing more than the indicated toleraweight of CO3 radical, reducing the available car
While the invention has been described chie-fly
ble maximum of carbonate of sodi-um.
The
bonate of sodium content of said NaHS liquor to
2,409,392
' 9
an amount equivalent to not more than v0.06%
by Weight of CO3 radical, controlling ‘the composi
tion of the resulting NaHS liquor so that such
ing >in solution an amount of carbonate of sodium
equivalent to more than 0.06% by weight of CO3
radical,- treating recovered NaHS liquor with a
liquor contains not more than 5% by weight of
calcium compound'so as to react With soluble car
sodium sulfide, thereby effecting coagulation and
bonate of sodium to precipitate combined CO3
precipitation of metallic impurities, and separat
thereof as calcium carbonate, the amount of said
ing said metallic impurities from such liquor.
calcium compound being at least sufficient to re
4. The method of producing purified sodium
duce the soluble carbonate of sodium content of
hydrosulñde which comprises forming an NazS
said recovered NaHS liquor to an amount equiva
NaI-IS liquor containing metallic impurities of the 10 lent to not more than 0.06% by Weight of` CO3
radical, controlling the composition o_f the. result-`
type present in commercial sodium hydroxide,
ing NaHS liquor so that such liquor contains sub
contacting said liquor with an H25 gas containing
stantially no sodium sulfide, thereby eiîecting
CO2 as an impurity under temperature conditions
coagulation and precipitation of metallic impuri
high enough to maintain sodium sulfide in liquid
phase, continuing contact of the liquor and HZS 15 ties, and separating said metallic impurities from
gas for an interval sufficient to effect conversion
the NaHS liquor.
ì
7. The method of producing puriiied sodium
of at least a major portion of the NazS content
hydrosuliide which comprises forming an NazS
of said liquor to NaHS thereby forming an Nal-IS
NaHS liquor containing metallic impurities of the
liquor containing an amount of available car
bonate of sodium equivalent to substantially more 20 type present in commercial sodium hydroxide,
continuously introducing said liquor into a rela
than 0.06% by weight of CO3 radical, reducing .
tively unobstructed reaction zone and counter
the available carbonate of sodium content of said
currently contacting said liquor therein with a
NaHS liquor to an amount equivalent to not more
gas containing predominantly H2S and a substan
than 0.06% by weight of CO3 radical, controlling
tial amount but not more than 25% by volume
the composition of the resulting Nal-IS liquor so
of CO2 as an impurity under temperature con
that such liquor contains not more than 5% by
Weight of sodium sulñde, thereby effecting coagu
lation and precipitation of metallic impurities,
and separating said metallic impurities from such
liquor.
‘
y
‘
5. The method of producing purified sodium
hydrosulñde which comprises forming an NazS
NaHS liquor containing metallic impurities of the
type present in commercial sodium hydroxide,
contacting said liquor with a gas containing pre
dominantly H2S and a substantial amount of
CO2 as an impurity under temperature conditions
ditions high enough to maintain sodium sulñde
in liquid phase, regulating contacting of liquor
and HzS gas in said zone for an interval suf?
30 cient to effect conversion of NaeS and NaI-IS to
such an extent that the resulting NaHS liquor
contains substantially no NazS, said NaHS liquor
containing carbonate of sodium in solution and
as a solid precipitate, continuously withdrawing
'such NaI-IS liquor and’suspended solid from the
reaction zone, separating solids from said NaI-IS
liquor thereby recovering NaHS liquor contain
high enough to maintain sodium sulfide in liquid
phase, continuing contact of liquor and HzS gas
ing in solution an amount of carbonate of sodium
NaI-IS liquor contains not more than 5% by Weight
of NazS, said NaHS liquor containing carbonate
alent to that needed to precipitate soluble com
bined CO3 as calcium carbonate, thereby effect
equivalent to more than 0.06% by Weight of CO3
'for an interval sufficient to effect conversion of 40 radical, treating recovered NaHS liquor with cal
cium hydrosuliide in amount substantially equiv
NazS to NaHS to such an extent that the resulting
of sodium in solution and as a solid precipitate,
separating solids from said NaHS liquor thereby
ing coagulation and precipitation of metallic im
purities, and separating said metallic impurities
recovering NaI-IS liquorcontaining in solution an
amount of carbonate of sodium equivalent to
from said recovered NaI-IS liquor.
in said zone for an interval suilicient to effect
conversion of Naas and NaHS to such an extent
ganese and silicon, and (b) an amount of avail
able carbonate of sodium equivalent to more than
8. The method of producing puriiied sodium
hydrosulñde from a sodium hydrosuliide liquor
more than 0.06% by weight of CO3 radical, treat
containing (a) atleast one metallic impurity of
ing said recovered NaHS liquor with calcium
hydrosulñde in amount substantially equivalent " the group consisting of iron, copper, nickel, man
ganese and silicon, and (b) an amount of avail
to that needed to precipitate soluble combined
able carbonate of sodium equivalent to more than
C03 as calcium carbonate, thereby eiîecting co
agulation and precipitation of metallic impurities, , 0.06% by weight of CO3 radical, which method
comprises reducing the available carbonate of
and separating said metallic impurities from said
55 sodium content of said liquor to an amount
recovered NaHS liquor.
equivalent to not more than 0.06% by weight of
6. The method of producing puriñed sodium
CO3 radical, controlling the composition of the
hydrosuliide which comprises forming an NazS
resulting liquor so that such liquor contains not .
NaHS liquor containing metallic impurities of the
more than 5% by weight of sodium sulfide, there
type present in commercial sodium hydroxide,
continuously introducing said liquor into a rela 60 by effecting coagulation and precipitation of
metallic impurities, and separating said metallic
tively unobstructed reaction zone and contacting
impurities from such liquor.
said liquor therein with a gas containing pre
9. The method of producing purified sodium
dominantly H25 and a substantial amount of CO2
as an impurity under temperature conditions high 65 hydrosulíide from a sodium hydrosulñde liquor
containing (a) at least one metallic impurity of
enough to maintain sodium sulfide in liquid
the group consisting of iron, copper, nickel, man
phase, regulating contacting of liquor and HzS gas
0.06% by weight of CO3 radical, which method
that the NaI-IS liquor formed contains not more
than 5% by .weight of NazS, said NaHS `liquor 70 comprises treating said liquor with calcium hy
drosulflde in amount substantially equivalent to
containing carbonate of sodium in solution and
that needed to react with available carbonate of `
as a solid precipitate, continuously withdrawing
such NaI-IS liquor and suspended solids from the
sodium to precipitate combined CO3 thereof _as
calcium carbonate, controlling the compositlon
reaction zone, separating solids from said Nal-IS
liquor thereby recovering NaHS liquor contain.1 75 of the resulting liquor so that such liquor con
2,409,392
12
tains not more than 5% by weight of sodium
sulñde, thereby effecting coagulation and precipi
tation of metallic impurities, and separating said
metallic impurities from such liquor.
l0. The method of producing purified sodium
hydrosulñde `from a sodium hydrosulñde liquor
containing (a) metallic impurities of the type
present in commercial sodium hydroxide, and (b)
an amount of available carbonate of sodium
available carbonate of sodium content of said
sodium hydrosulñde liquor to an amount equiva
lent to not more than 0.06% by Weight of CO3
radical, controlling the composition of the result
ing liquor so that such liquor contains not more
than 5% by Weight of sodium sulñde, thereby
effecting coagulation and precipitation of metallic
impurities, and separating said metallic impuri
ties from such liquor.
equivalent to more than 0.06% by weight of CO3 10
radical, which method comprises reducing the
ARTHUR W. SADDINGTON.
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