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Патент USA US2119132

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May 3l, 1938.
ì
J. <3` HATMAN
RECOVERY OF TAR ACIDS
Filed April 15, 1935
Y
'2,119,132v
*2,119,132l
Patented May 31, 1938
UNITED STATES
ArsN'r OFFICE
2,119,132
RECOVERY or TAR ACIDS
Julius George Hatman, Elkins Park, Pa., assignor
to The Sharples Specialty Company, Philadel
phia, Pa., a corporation of Delaware
Application April 13, 1935, Serial No. 16,240'
8 Claims.
This invention relates to- the art of recovering
tar acids from tar and particularly to a process
by which the tar acids may be separated in a
simple, economical manner from the tar pro
duced incidental to the manufacture of coke. An
arrangement of apparatus that it has been found
advantageous to use in the performance of the
new process is also a part of this invention.
In accordance with the usual process of manu
facturing coke, a. quantity of tarry material re
sults as a by-product. This tarry material, or
crude tar as it will hereafter be called, has a
speciñc gravity of around 1.06 to 1.18 and ordi
narily contains from 21/2 to 6% of tar acids and
up to about 10% of water. The tar acids, which
consist mainly of phenol and its homologues, such
as the cresols and xylenols, are valuable commer
cially but are quite diliìcult to isolate according
to known procedures.
The practice heretofore has usually been to
dehydrate the crude tar either by evaporating off
the water or centrifuging. After dehydrating, the
crude tar is distilled in a tar still and separated
into two fractions, the fraction boiling below
25 270° C. being known as tar oil and the remain
der simply as tar, or as tar residue.
The tar
acids are substantially wholly contained in the
tar oil and are present thereinin a concentration
of between 15 and 25%.
This tar oil fraction is subjected to further
30
treatment to separate these acids. Such treat
ment ordinarily consists in intermixing the tar
oil with an aqueous caustic soda solution of a
concentration suiîlcient to convert the tar acids
into phenolates, cresolates and the like. These
compounds, which will hereafter be referred to
generally as phenolates, dissolve readily in the
caustic solution and are subsequently separated
from the tar oil by allowing the mixture to settle
into an aqueous layer and an oil layer and then
(Cl. 7260-154)
these refineries must be equipped to carry out
the relatively long and involved process outlined
above.
The present process has been conceived to
overcome difficulties involved in the practice of
>the process now in use and to produce relatively
pure tar acids simply and expeditiously, directly
from the original tarry material as it is pro
duced by the coke plant. According to an appli
cation Serial No. 754,718, filed by Charles M. 10
Ambler, Jr. and-Charles E. Underwood on No
vember 26, 1934 which has matured into Patent
#2,081,692, it has been found that if this original
tarry material is mixed directly with a basic
solution such as an aqueous solution of caustic 15
soda or caustic potash, capable of converting the
tar acids into the corresponding phenolates, and
thereafter separated from such solution with
sufñcient promptness to avoid emulsion difficul
ties, such separation can be effected and the sepa
rated solution will contain substantially all of
the tar acids in the form of soluble phenolates.
These compounds may thereafter be reconverted
into tar acids by the addition of acid, and sepa
rated.
25
The present invention is an improvement upon
the process and apparatus described in the Ambler
et al. application and provides a modified proc
ess according to which the aqueous solution of
phenolates formed by the action of water and 30
caustic soda upon the tar, is recycled until the
concentration of phenolates therein isv greatly
increased and-'the eii'ìciency with which these
phenolates may be separated from the aqueous
solution is materially bettered. Furthermore, the g5
present invention provides a system of apparatus
by which this novel process may be performed
either continuously or by the batch. Further de
tails that add to the efüciency or desirability of
the new process and apparatus will appear more A
through it, or may be treated with an acid, usu
fully from a consideration of the following de
tailed description of the preferred mode of prac
ticing the invention and of the system of appa
ally sulphuric, to convert the dissolved com
The tar acids, being
insoluble, are thereafter separated from the re
sulting solution of sodium carbonate or sodium
ratus which has been found especially adapted
for the performance of this process.
45
In the drawing, forming a part of this applica
tion, the new process and system of apparatus
decanting.
The aqueous solution so obtained is
thereafter treated by blowing carbon dioxide gas
45 pounds back into tar acids.
sulphate by gravity settling.
for performing it are illustrated in their pre
ferred form by a flow sheet. According to this
50 quires a dehydration and. distillation of the heavy ` ilow sheet the original raw materials are water,
tarry material which is difñcult and troublesome tar, caustic soda solution and stack gas from the
and which many coke plants are not equipped coke ovens. In place of at least part of the water,
to accomplish. Hence the tar must often be after the process has been started in operation,
sold without extracting the tar acids therefrom, a solution of phenolates from previously extract
The difficulty with such a process is that it re
to refineries especially equipped for this work and
ed tar is supplied.
'
2
2,119,132
According to illustrated process, a caustic soda
solution, usually of a concentration of about 8%
by weight is supplied to the mixer through a
constant head pump and a proportioningfmeter
in approximately the ratio of one gallon of caus
tic solution to each iive or six gallons of tar,
the tar also being fed through a constant head
pump and the proportioning meter. At the same
time an aqueous liquid, either Water or pheno
10 late solution from a previous extraction or a
mixture of the two, is fed through another` con
stant head pump and the proportioning meter
into the mixer. The aqueous liquid may either
enter the mixer with the caustic solution and
the tar or may be supplied to theseconstituents
after they have been partially mixed, in accord
ance with the process described in the above
mentioned application. The ratio of the aque
ous liquid to the tar is usually about 2 to l by
volume but may be as low as 1 to 1. The ratio
of caustic solution to tar is preferably adjusted
so that approximately 1.4 pounds of caustic soda
are added for every gallon of tar acids in the
tar.
After the mixing has been completed, prefer
ably in the manner described by the above men
tioned application, although it may be done in
any other manner found convenient, the mix
ture is brought to a temperature of around 80°
C. and centrifuged to separate the tar from the
aqueous solution of phenolates formed by the
reaction of the caustic soda solution upon the
tar acids in the tar.
The resulting aqueous solution of phenolates
t-n LA is passed into a storage tank from which it may
be returned by a pump and be recycled through
the same process. As this recycling is continued
the supply of water to the system may be d_i
minished or stopped altogether, with the result
40 that the concentration of phenolates in the so
lution increases until a concentration is reached
at which the phenolate solution contains a suf
ficient percentage of phenolates to enable their
recovery to be efliciently made. At that time
the whole of the phenolate solution may be di
rected into other apparatus for recovering the
tar acids therefrom, or a portion of the pheno
lates may be directed into such apparatus and
the remainder recycled to collect more tar acids.
The concentration of phenolates in the solution
will not increase indefinitely, for the caustic soda
solution added tends to dilute the phenolate
solution and thus to reduce the concentration
and in addition a certain amount of water is ex
tracted from the tar itself. Usually there is
around six to ten percent of water in the tar
as it is originally received and of this all but
about 0.5 to 1.5 percent is extracted and passes
into the phenolate solution.
As the phenolate solution is recycled, the ad
60
dition of caustic soda solution may be discon
tinued, if desired, and sufficient caustic soda,
in solid form, added to the phenolate solution
to maintain the desired concentration. Alterna
tively the addition of the caustic soda solution
may be continued and the rate of addition ad
justed to maintain the proper concentration,
namely, around 1.4 pounds ofcaustic soda per
the phenolates in the phenolate solution Will be
substantially constant. A point of equilibrium
will also be reached if water is added at a deli
nite rate with the recycled phenolate solution
and a suflicient quantity of the phenolate solu
tion is Withdrawn continuously to balance this
water, as well as the water taken from the tar
and the caustic solution.
The phenolate solution taken from the above
described section of the system passes through a
pump and suitable heating apparatus which
raises its temperature to around 90° C. to a
springing tower where it passes countercurrent
to gas from coke oven stacks.
In so doing the
phenolate solution absorbs carbon dioxide and 15
the tar acids are re-formed. Some of the water
and a portion of the tar acids are Volatilized and
pass off through the top of the tower, but these
are condensed in a suitable condenser and passed
to a settling tank together with the portion of 20
the tar acids and water solution that remains
liquid. In the settling tank the re-formed tar
acids separate from the aqueous solution of car
bonates formed in the springing tower. The
carbonate solution is passed to suitable appa 25
ratus where it is regenerated into caustic soda
by treatment with lime.
The tar acids, which still contain some residue
and some Water are distilled to obtain three por
tions, residue, dry tar acids and a mixture of 30
tar acids and water. The residue is discarded,
and the tar acid and water mixture permitted
to settle. Upon settling a quantity of water is
recovered which may be discarded or added back
to the phenolate solution being recycled. There 35
remains crude tar acids which together with the
tar acids recovered directly from the distilla
tion, may be treated in any suitable manner to
further refine them or to separate them into the
individual tar acids.
40
While the process and system of apparatus
described above are the preferred form, it is to
be understood that considerable modifications
may be made in both the process and the appa
ratus without departing from the principles of 45
this invention. For example, any suitable device
may be substituted for the constant head pumps
and the proportioning meter, for feeding accu
rately-proportioned amountsrof caustic soda so
lution, tar and phenolate solution or water to 50
the mixer, The phenolate solution or Water may
be added at any time during the mixing and
the constituents may be heated either before or
after mixing to a temperature of around 80° C‘.,
or the process may be performed without the 55
application of heat to the constituents prior to
the centrifuging. Also, although it is definitely
preferred to use a centrifuge to separate the
phenolate solution from the tar, other means of
separation, such as gravity or filtration may con 60
ceivably be employed.
As has already been indicated, the phenolate
solution resulting from the treat-ment is re
cycled either in whole or in part and this re
cycling may be carried out to any desired ex 65
tent, thus building up a concentration of pheno
lates in the solution of anywhere from 5 to 40%
or even greater. Preferably, in order to make
If an amount of phenolate solution equal to
the amount of caustic added plus the amount of
water extracted from the tar, is removed to the
recovery apparatus continuously and no addi
tional water is added, the system will‘reach an
the process economical, the concentration is built
up to at least 15 or 20% and may be much higher. 70
1f the process is to be performed by the batch,
all ofthe phenolate solution or at least a major
part of it will ordinarily be drawn> off at one
time, whereas> if the process is to be performed
equilibrium point at which the concentration of
continuously a smaller portion, usually from 5 ,
gallon of tar.-
Y
`
2,119,132
to 15%, by volume will be removed to the re
covery apparatus continuously.
In the recovery of the tar acids from the
phenolate solution the steps and the apparatus
may also be modiñed. Thus, the phenolate so
lution may be passed to the springing tower with
out previous heating or the phenolate solution
may be treated with sulphuric acid instead of
stack gas to liberate the tar acids. If desired,
10 the tar acids may be taken directly from the ñrst
settling tank without any further distillation and
used in this condition or passed to other appa
ratus for puriiication.
I claim:
15
l. A process of removing tar acids from tar
that comprises separately mixing with the tar
3
phase to the process to be mixed with the tar; and
continuously withdrawing a portion of the
aqueous phase and recovering tar acids there
from.
6. A process for the recovery of tar acids from
tar that comprises mixing with tar an aqueous
caustic soda solution containing about 8% caustic
soda by weight and in such proportion that ap
proximately 1.4 pounds of caustic soda are added
for each gallon of tar acids in the tar, mixing 10
with these two constituents water in the propor
tion of approximately two gallons of the aqueous
liquid to each gallon of tar, heating the mixture
to approximately 80° C., centrifuging to resolve
a constant proportion of an aqueous caustic soda
solution and a constant proportion of water, cen
the mixture into a tarry portion and an aqueous 15
portion, recycling the aqueous portion as at least
a part of the aqueous liquid added to the tar and
caustic soda solution, and thereafter passing the
trifuging the resulting mixture to remove the tar,
said aqueous portion into contact with a gas con
20 recycling the aqueous liquid recovered from the
taining carbon dioxide whereby the tar acids are
centrifuge by mixing it with additional tar and
recovering the tar acids from the recycled
aqueous liquid.
2. A process of removing tar acids from tar
25 that comprises separately mixing with the tar a
precipitated therefrom, settling to separate the
constant proportion of an aqueous caustic soda
solution and a constant proportion of water,
centrifuging the resulting mixture to remove the
tar, recycling the aqueous liquid recovered from
30 the centrifuge by mixing it with additional tar
and additional caustic soda solution, and recover
ing the tar acids from the recycled aqueous liquid.
3. A process of removing tar acids from tar that
comprises mixing with the tar a constant propor
35 tion of caustic soda and a constant proportion of
Water, centrifuging the resulting mixture to re
move the tar, recycling the aqueous liquid re
covered from the centrifuge a plurality of times
by mixing it with additional tar and recovering
40 the tar acids from the recycled aqueous liquid.
4. A process of removing tar acids from tar
that comprises separately mixing with the tar a
constant proportion of an aqueous caustic soda
solution and a constant proportion of water,
tar acids from the aqueous solution and distilling
the tar acids so separated.
'7. A continuous process for the removal of tar
acids from crude undistilled tar having a speciiic 25
gravity in excess of 1.06 that comprises continu
ously mixing the crude tar with an aqueous al
kaline solutionv to convert the tar acid content
of said crude tar into the corresponding salts of
said tar acids, passing the mixture of crude tar 30
and the aqueous solution of said salts formed by
a reaction of the alkaline solution with said tar
acids continuously through a centrifugal sepa
rator and thereby separating the mixture into a
tarry and an aqueous phase, continuously re 35
turning a portion of the aqueous phase sepa
rated from the centrifugal separator into con
fluence with alkali and a further quantity of
said crude tar and continuously withdrawing a
portion of the aqueous phase and recovering tar 40
acids therefrom.
8. A process for the removal of tar acids from
crude undistilled tar having a speciñc gravity in
excess of 1.06 that comprises mixing the crude
45 heating the mixture to around 80° C., centrifuging
tar with an aqueous alkaline solution to con
the resulting mixture to remove the tar, recycling
the aqueous liquid recovered from the centrifuge
a plurality of times by mixing it with additional
tar and additional caustic soda solution, and re
50 covering the tar acids from the recycled aqueous
vert the tar acid content of said crude tar into
liquid.
5. A continuous process for the removal of tar
acids from tar that comprises continuously and
separately mixing with tar an aqueous caustic
55 soda solution and water in predetermined pro
portions, heating the mixture to around 80° C.,
continuously centrifuging to separate the mix
ture so formed into a tarry and an aqueous phase,
' continuously returning a portion of the aqueous
45
the corresponding salts of said tar acids, passing
the mixture of crude tar and the aqueous solu
tion of said salts formed by a reaction of the
alkaline solution with said tar acids through a 50
centrifugal separator and thereby separating
the mixture into a tarry and an aqueous phase,
returning a portion of the aqueous phase sepa
rated from the centrifugal separator into con
fluence with alkali and a further quantity of said 55
crude tar and withdrawing a portion of the
aqueous phase and recovering tar acids there
from.
JULIUS GEORGE HATMAN.
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