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Патент USA US2129787

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Filed Jan._ 25, 1934
Patented Sept". 13,1933
» anni?
Adair Schwalenber/ch, Essen, Germany, assigner,
by mesne assignments. to Kappers Company, a.
corporation ai Delaware v
Application January 25,. 11934, Seriali No. ’iilßdldll
En Germany January 25, i033
il Claim. ‘Íßit 202-393
The invention relates to the removal and re
covery of benzol, its homologues and naphtha
iene from gases, particularly coal distillation
tilling the Washingoil, coming irom the‘scrubber,
in the steam distillation step is subjected before
the rectiñcation to a. pre-distillation for the re
covery of benzol and homologues, which is carried
The object oi the present invention is to pro- , p out at such a temperature that the heavier con
vide such improvements in the removal and re
covery of benzol, its homologues and naphthalene
from gases, particularly coal distillationgases,
that the removal of the said' substances from the
lgas can. be effected. in a single ‘operation and
benzol and homologues and naphthalene on the
other hand can be recovered separately in prac
stituents of the washing oil remain behind, Whilst
the »lighter constituents ci' the washing oil to
gether with benzol, its homologues and naphtha
iene are evaporated. The. vapors produced by>
this- pre-distillation are then conducted Ainto the
grammes benzol and homologues per cubic meter
rectihcaticn apparatus including a still for distil
lation of benzol and homologues, from which
there is withdrawn, after driving off benzol and
homologues, an oil with a content of about 30%
naphthalen'e. From 'this part of the distillation
step oil highlyenri'ched with naphtlialene is pro
duced and there can be separated> a very pure
and about 0.4 to 0.6 gramme naphthalene. For
the removal of benzol and» homologues the gas
room' temperatures above 10° C. which can be
' tically pure condition.
Normal coal distillation gas contains, after the
usual so-called iinal cooling and before ythe
scrubbers serving to remove benzoLabout V25
20 l is Washed with a usual washing oil.
The used
washing oil is subjected to steam distillation.
The vapors òf distillation thus produced contain
about equal quantities by Weight of washing oil
~ and benzol, i. e. about 50% benzol and homo
naphthalene by crystallization with cooling to
obtained directly Without artiilcial cooling.
Ili‘he quantity of heavy constituents of washing
oil which occurs in the pre-.distillation step ac-'
coi-ding to the invention varies. 1n general .it
amounts to about 30 to 90% of the condensed
oil containing benzol and naphthalene introduced
25 logues and about 2% naphthalene. From the - into the pre-distillation apparatus in the case
condensate of the steam distillation» benzol and
homologues are removed by rectiiicatlon, whilst
the naphthalene-containing oil remains behind.
' As the quantity of the napl'ithalene in the re
sidual oil, as stated, only amounts to about 2%,
it -is not possible to separate the naphthalene
from the oil by crystallization whilst cooling to
temperatures still obtainable, having due regard
to favorable economy, Without'artiiicial cooling;
35 Consequently the Washing oil becomes enriched
with naphthalene, which in the usual manner
is used in circulation for renewed Washing 'of
when the main quantity of naphthalene is to be _ »
separated i'rom> the heavier constituents of the '
washing oil in the pre-distillation stage.
aThe heavier constituents oi thevvashln'g oil
remaining inthe pre-distillation stage, are mixed
with the lighter constituents, which remain in
the main distillation stage, after the naphthalene
hasbeenseparated from the lighter constituents '
by cooling, and then are again used together-for 35
washing benzol and naphthalene from the gas.
The invention will now be described with` rei
erence to the accompanying drawing showing,
benzol from the gas, gradually to such a quan
tity that the vapor pressure _of the Washing oil partly in elevation and partly in cross section,Vv
apparatus for practicing the invention.
40 in connection with naphthalene is in equilibrium
with the vapor pressure of the gas as regards " En the arrangement >shown in the drawing used
naphthalene. In the case of normal Washing oil washing oil, containing benzol and naphthalene,
from the container i, of which the function is
thisÍ point lies at about 12% naphthalene. Be
yond this point an enriching of the washing oil -described hereinafter, is supplied through a pipe
line 2 by means of a pump t to a heating device fi.
45 with naphthalene is not possible in the method . -"ll‘he hot Washing oil andthe vapors producedv
of operation hitherto usual.' But even with a
content of naphthalene of 12% the naplithalene during the heating pass from the device il through
cannot be recovered from the washing oilI with
out artiiicial cooling. '
According to the present invention the separa
tion both of benzol and of naphthalene from the
washing oil, which served for bothl the removal ci
the pipe lines d and 0 into _ a firnovvn primary
distilling column apparatus '71. This column» ap
paratus ‘i has a series of bottoms or trays which 50
are `provided'vvith vvapor openings 0 covered by
bells' d, and at the middle each has a liquid over
ñow i0. SteamV is introduced into the bottom
benzol and homologues and also naphthalene
from the gases, is‘rendered fundamentally pos ‘ of the-column apparatus through the pipe line i i. .
sible. in that the condensates derived from dis-v .The steam rises through the openings 0 in the
bottoms of the column apparatus,` »whilst the
washing oil ñows downwardly in the apparatus 'l
from top to bottom through the openings, l0.
Steam and washing oil in this manner come into
intimate Contact with one another, whereby the
washing oil is heated. The vapors produced in
the column apparatus l such as steam, benzol,
its homologues, naphthalene and some oi the
wash oil, escape through the pipe line i2 and
washing oil to be re-used for washing >out benzol ‘
and-naphthalene. Tothe pipe line 38 is also con-`
nected the pipe line 29 so that thus-the whole of
the washing oil freed. from benzol, its homo
logues and naphthalene, which was driven oiî in
_the column apparatus li, is again continued.
There will now be described the path followed
by the used washing oil which is treated in the
apparatus shown in the drawing. The used
The liquid condensates thus formed new
washing oil withdrawn from the scrubbers, not
shown in the drawing, which serve for washing
through the pipe line i0 into a separating tanl:
benzol, its homologues and naphthalene from the
gas. is conducted to a storage tank £0. From this
it ñows through the pipe line M into the cooling
pipe system ci’ the condensing device i3 in which l5
it is used for cooling the vapors escaping from
the column apparatus l, vin this manner there
is obtained simultaneously an advantageous pre
heating of the cold used washing oil. The wash
ing oil thus preheated then passes through the 20
pipe 02 into the tank i, which simultaneously
pass into a condensing device i3 where they are
In the separating tank i0 the water escap
ing from the apparatus 'i separates from the oily
The latter are withdrawn at the up
per end of the separating tank iii through the
pipe line iii, whilst the water passes through the
pipe line il' into the tank i0.
, The
through the pipe line i0 into the still i0. To the
still l0 there are also supplied through the pipe
line 20 those gaseous constituents which were
not condensed in the condensing device i3.
Into the lower part of the still i0 there is sup
25 plied through the pipe lines 2i steam which in
serves as storage tanh and as heat exchanging
rThe used crude washing oil is here
further preheated, the hot unvaporizecl washing
through the pipe line 23a into the dephleg‘mator
oil from the column still l here serving for the 25
preheating. For this purpose there is connected
to the bottom oi’ the column apparatus 'E the
pipe line 03 through which the hot Washing oil
ñows from l into a pipe system located in the in,terior oi the tank i. in the tank i the hot re 30
sidual oil of the column apparatus “i imparts a
portion of its heat to the colder untreated wash
ing oil. rl‘he residual oil pre-cooled in this man
_ner then i‘lows through the pipe line ¿ld into a pipe
35 part 23 oi the apparatus l0, maintained atl a
,cooling apparatus Q55, sprayed with wat/er from 35
the interior of the apparatus flows through ypipe
coils or the like not shown in the drawing. The
condensedwater is withdrawn from these heat
ing pipe coils through the pipe lines 22.
30 liquid in the still l0 is thus heated indirectly.
The vapors thus formed, benzoi, its homologues,
naphthalene, and a small part of the wash oil
vapor condensed from the still it, rise and pass
predetermined temperature, from which they
escape through'the pipe line 2d after passing a
separating bottle 2155> for separating the constit
‘uents condensed in the dephlegmator. The
40 condensate from the separating bottle 2t flows
through the pipe line
bach into the still iS.
For cooling‘the dephlegmator there is preferably
used cold water which flows to a cooling pipe system, located in the interior of the dephlegmator
'23, through a pipe line 2li and flows out through
a pipe line 2t.
The oil which is not evaporated in the still it)
and which mainly consists of the heavier con
stituents of the washing oil and is practically
free from naphthalene, is withdrawn through the
pipe line 20.
The vapors produced in the still iii pass '
, through the pipe line 25 into the main distilla
tion still 30 _which is arranged substantially in
the same manner as the still HQ.
which it passes through the pipe line il@ into the
The re
generated wash oil is pumped continuously inI
cycle baci; to the gas-washing benzol-scrubber
(not shown) through a pipe line 39a. At certain 40
intervals part of the wash oil, circulating from
the benzol scrubber to the distillation plant and
thence to the tanlr 30 for return back to the ben
storage tank 30 for fresh washing oil.
zoi scrubber, must be replaced by new or fresher
wash oil to replacedeterioration. The added oil
may be introduced into tank 3s, or at any other
point in the cycle of flow ofthe benzol-absorbent
wash oil..
The process according to the invention isv car
ried into euect somewhat in the following man
lt is assumed that the gas of a coal distillation
plant is to be treated which has an average of
i000 metric tons oi’ dry coal per day. The colcing
of this coal produces about 300 cubic meters of
gas per ton of coal, that is‘daiiy 300,000 cubic
meters of gas. After the usual ñnal cooling of
the gas this contains before passing into the ben»
aol scrubbers about 50 to 60 grammes naphtha.
-lene per 100 cubic meters. In this case there is
assumed a naphthalene content of the gas or 55
grammes per 100 cubic meters. lThe quantity of
The vapors produced in the main distillation
still, which practically consists only of benzol
and its homologuesf pass through the pipe line
3i into a cooling apparatus 32 in which they are
deposited. Cold water is supplied to the cooling
apparatus 32 through the» pipe line 30, passes
through a cooling pipe system located in the inu
tenor of the apparatus- 32 and ilows out throughl naphthaiene contained ‘ in the gas therefore
the pipe line 3&3. 'I'hecondensates formed in the amounts per day. to lôâkilogrammes. of which’
apparatus 32 are withdrawn from the lower part 150 kilogrammes are washed out per day by the
washing oil.
of the apparatus through the pipe lines 05.
, ’nie content of the gas in benzol and its
The liquid constituents which are not evapof
rated in the main distillation still 30 ñ'ow through ¿homologues amounts to 25 grammes per cubicA
the lpipe line 36 to a naphthalene crystallizing pan meter, that is per day 7500 kilogrammes benzol
31 in which they are cooled to about room tem
perature but above 10° C. As a result solid crys
and homologues..
According tov experience the quantity of wash
talline naphthalene separates from the liquid
ing oil, which passes over in the column appa
ratus 1 when driving off bénzol and its homo
sidual liquid passes from the device 31 through logues in order to obtain a si‘iß‘icient removal
75 the pipe line 38 into the storage tank 39 for the ot benzol and its homologues from the washing 75
which contains about 30% naphthalene. The re- '
on, is the saine as the quantity of benzol driven ` unes 4t, at, «sind sa now only contains 22,500
od. In the example described 7500 kilogrammes kilogrammes oi’ naphthalene per day equal on
an average to 6% naphthalene. This naphtha-~
iene content of the washing oil again iiowing
column apparatus ii. In this quantity of wash
ing oil there is alsoy contained the total naph» back into the'benzol scrubbers remains constant
‘thalenle contained in the oil, so that the‘7500 when carrying out the lprocess according tothe
invention. It is possible with this constant naph
kilogrammes of washing oilv distilled over con
thalene content of the washing oil to remove
tain 8% naphthalene assuming that for wash
ing- benzol, homologues and naphthalene from the naphthalene from the gas up to 5 grammes
_ of Washing oil are thus distilled over daily in the
10 the gas therev was used a. washing oil containing
As the solubility oi naphthalene in the‘wash-4
per 100 cubic metersof gasy during the benzol
scrubbing step.v This content of naphthalene in
the gas is'so slight that a separate subsequent l`
ing oil-at about 20 to 25° C. amounts to about
washingout of naphthalene as a rule is unnec
12%; naphthalene at these~ temperatures, which
essary. Ii", however, for special reasons a stili
further reduction of the naphthalene content
can be obtained without any artiiicial cooling
oi' themfwashing oil, cannot be crystallized out
oi" a washing oil with «8_%„„naphthalene.
of the gas should be necessary this is substan
tially simpler and cheaper as the quantity of
naphthalene, remaining in the gas, after the
application of the process according to the in
naphthalëne therefore'passes, according to the>
llfiitinerto `method .of operation,l together With- the
residual oil vfrointhe rectiiìcation’apparatus for y vention, is only very slight.
benzo'l back' i?t'o the washing oil which then be
, in the foregoing the invention has been de
scribed with reference to an example for carry
ing it into eiïect, without however, the invention
the vapor pressure of the Washing oil with naph
thalene is equal to the vapor pressure of the being limited to the method of carrying it out as
described. On the contrary the process accord
25 gas with naphthalene. As a Eesult it follows ing- to the invention can be modified in various 25
that bythe hitherto usual method of operation .
respects without departing from the scope of
naphthalene cannot be washedfrom the gas to
gether with benzol. On the contrary it 'was the following claim.
li claim:
therefore always necessary to provide beyond the
v'li‘he method of removing and recovering benzoi,`
so benzol scrubber a separate scrubbery for naph its homologues and naphthalene from gases ’con-y 30
According to the' invention the vapor mixture;- taining them, comprising: Washing the gas with
escaping from the column apparatus il, consist-Ñ - wash oil adapted to absorb benzol, its homologues
ing of 7500 kilogrammes benzolandhomoiogues, and naphthalene therefrom; heating spent wash
oil from the gas washin'gostage to drive oiï ab
35 6850 kilogrammes .washing oil constituents and
comes enriched. - This enriching continues until
_fiâii‘kilogrammes> naphthalene, is so decomposed
sorbed benzol, its homologues, naphthalene and
> that as first fraction there'is obtained a washing
a quantity of wash oil about the same as the
oil, «which does not contain' more naphthalene
than the initial washing oil, as second fraction
quantity of benzol, its homologues and naphtha
Iene; condensing the vapors from said heating
a washing oil highly enriched with'naphthalene ‘i st'ep‘and pre-distillingl the condensate at about
and as third fraction benzol and its homologues. 108° C. to remove benzol, its homologues and
F‘or- this purpose the condensate of the vapor naphthalene together with a smal-l portion of the
mixture escaping from the column ’apparatus ‘l - wash oil that comes over with the vapors‘from
is subjected in the pre-distillation stage .it to the aforesaid heating step; condensing the va
a distillation at about 108° C_‘measured at the- pors from the latter pre-distilling step and iinally 45
outlet of the distillation vapors at a, andi'the- redistillingthe condensate'at about Bti-90° C. to
constituents entering the main distillation appa l drive off benzol and its homologues leaving as
ratus 3d to a distillation at about dii-90° C. meas i residuum the naphthalene and _wash -oil that
n >ured at the outlet oi the distillation vapors at a’. icomeso'ver. with the vapors from the-‘pre-dis
With this methodof operation the residual oil,V itilling step; separating naphthalene from the 50
``colle`cting in the pre-distillation stage id and latter residuum by atmospheric cooling to room
Withdrawn vthrough the. pipe line it, contains temperature above 10° C.; separating the solid
395 kilogrammes of naphthalene per day (=6%) naphthalene from ther so cooled wash oil; and
-and the residual oil in the main distillation stage returning the wash `oil combined with the Wash
3d, 255 kilogrammes oi naphthalene per day oii residuum from the first two distilling steps 55
(=2’i'.i%l. From the latter- residual oil there
fare separated in the crystallization device til
to the gas washing stage 'for another cycle, said.
combined Wash oil being of suiiiciently 10W con
150 kilogrammes of naphthaiene per day, v)From _ « >centration
this it follows that the fresh washing oii ñowing
back into the storage tanti 3d, through the pipe
of naphthalene to effect the absorp~-
tion of naphthalene from »the gas.
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