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Патент USA US2115835

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May 3, 1938.
2,1 15,835
D. J. YOUNG
SULPHATE PULP PROCESS
Filed Sept. 15, 1937
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Patented May 3, 1938
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UNITED STATES PATENT OFFICE I
- 2,115,835
SULPHATE PULP PROCESS
Daniel J. Young, Tacoma, Wash.,> assignor to
Young-.Whitwell
Gas
Tacoma, Wash.
Process
Company,
’
Application September 15, 1937, Serial No. 163,973
3` Claims. (Cl. 92--9)
The invention relates to improvements in the
process of treating wood and like cellulosic mate-
would be a distinct asset to the community pro
vided the obectionable odors resulting therefrom
rial for the formation of pulp, and more partic-
could be eliminated.
ularly to the elimination of objectionable odors
5 which are especially characteristic of the manu-
facture of pulp by the sulphate procesjs. It is.
known that the‘ gases resulting from sulphate
pulp manufacture contain certain non-conden-
-
The primary object of the present inventio
is to withdraw the objectionable gases directly Ul
from the digester before they have become diluted
with air and to preferably burn them or other
wise dispose of them in a manner which is not
sible components having an extremely nauseating
10 odor and consisting largely of combustible mercaptans and the like.’
In the ordinary method of manufacture of sulphate pulp the cellulosic materials to be treated-
objectionable. 'I'he ordinary equipment may be
maintained practically without change, it-being 10only necessary to add a condenser communicat
ing with the top of the digester through a valve
connection, the condenser being equipped with
(usually Wood chips) together with the usual
15 chemicals are placed in the digester and steam is
a gas offtake leading to a gas holder or the like
to which the non-condensed vapors are conveyed 15 ~
admitted at or near the bottom of the digester
until the pressure within the digester reaches
about 125 to 135 pounds with the consequent tem-
perature within the digester from 350° to 400° F.
and from which they may be withdrawn for
burning or other unobjectionable disposal.
The invention will be more readily understood
by reference to the accompanying drawing in
20 This condition may be maintained for a period
of about one and one-half hours and is known as
the “cook”. When the pulp has been suiiiciently
cooked the steam is turned orf, the bottom of the
digester is opened and the pulp is discharged' into
which there is illustrated somewhat diagram 20
matically a sulphate pulp digester of conven
tional type equipped with the improved connec
tions whereby the malodorous gases may be with
drawn and disposed of without pollution of the
25 a closed. tank generally known as the blow pit,
atmosphere.
in which tank the liquor containing the chemicals and the pulp are held and the excess steam
and gases resulting from the cook are carried
away and condensed, the non-condensible gases
30 being then usually discharged at the base of the
Referring to the drawing the reference nu- “
meral I0 denotes a digester of any desired type
being approximately 10 feet in diameter and 60
feet high although obviously- not limited to these
proportions. The digester is i'llled with wood 30
boiler stack, coming out of the top of the stack
with the gases from the boiler.
As the process is nowv carried outy a large
amount of air is taken in with the gases and
35 steam so that the gas as admitted to the bottom
of the stack is practically> all air though containing the mercaptans. These mercaptan gases
being combustible, many eiïorts have been made
to burn them at this time but due to the extent
40 of dilution with air such attempts have proved
unsuccessful.
~ o
The total amount of mercaptans produced
during the process is relatively small, that produced in a digester approximately ten feet in
45 diameter and sixty feet high, which was studied
in connection with the present invention, being
about 100 to 150 cubic feet each time the digester
_ is blown, a blow taking place about once an hour.
However, when these gases are allowed to pass
50 unburned into the atmosphere the objectionable
odor may be observed for a. distance of many
.
'
n
chips and chemicals to a level II at approx
imately two-thirds the height of the digester’.
The steam inlet I2 may be provided near'the
bottom of the digester and a removable lcap I3
is shown at the top to permit charging of the
digester and also for the preliminary discharge
of air prior to the digestion proper. The digester
is provided with a bottom I4 through which the
digested materials may be discharged into a blow
pit I5 of conventional form. The blow pit is 40
shown as provided with an offtake I6 for gas and
steam leading to a condenser I1 provided with
a liquid outlet I8 and a gas outlet I9. Ordinarily
the gases passing from the outlet I9’are so diluted
with air that it is impossible to burn the mer- 45
captans contained therein.
'
According to my invention an outlet pipe 20 for
gas and steam is provided at the top of the di
gester, such outlet being preferably provided
with a. valve 2|. The pine 20 is preferably of 50
relatively small diameter so as not to interfere
miles. The nuisance is so great that in many with the pressure which is maintained within the
communities sulphate plants are not permitted digester. The pipe 20 leads to a condenser 22
to operate simply on account of the odor al- _ which may be of the surface type or of the type
55 though from a business standpoint such a plant commonly used in gas plants and referred> to 5'5
Z
2,115,835
as the scrubber. The condenser is equipped with
a liquid outlet pipe 23 and- with an ofitake pipe.
' 24 for non-condensible gases.
These gases in
clude the mercaptans in sumcient quantity for
combustion. 'I'he pipe 24 communicates with
a gas holder 25 which may be of conventional
type and which is shown as equipped with an
offtake 26 controlled by a valve 21. 'I'he oiïtake
26 may lead to a suitable burner Where the mer
10 captans or other malodorous gases are disposed
of instead of being discharged directly into the
atmosphere.
According to my method after the digester has
been charged steam is admitted at the bottom
15 of the digester and the cap I3 is left open for a
short time until the air has been swept out of
the digester by the steam. The cap I3 is then
closed thereby maintaining the digester air-tight.
Further steam under pressure is admitted to the
20 digester and continues to ilow in sufiicient amount
to maintain the pressure in the digester from
125 to 135 pounds more or less. As this steam
ilows upward through the pulp and liquor it will
force the steam and gases which are above the
25 liquor out through the pipe 20 into the con
denser 22 where the steam and other condensible
portions will be separated from the non-con
densible gases, which are being conducted to the
gas holder from which they may be periodically
withdrawn for burning. According to this meth
od no air will be present with the gases and
they can be satisfactorily burned. During the
cooking process the valve 2| may be opened either
intermittently or constantly. If desired two or
more digesters may be used in battery, the steam
and gases from one digester passing into a sec
ond one thus more eillciently utilizing the heat`
of the steam.
After the digesting process is completedr‘the
40 pulp and liquor from which the malodorous gases
have been substantially completely driven will
be discharged into the blow pit in the usual man
ner and any gases remaining n therein will be
passed to the condenser I1. Since the mercap
tans have been eliminated during the digesting
period there is no objection to passage-of the
non-condensible gases through the outlet I9 di
rectly to the atmosphere, since such gases-are
substantially wholly air.
60
The invention has been described in detail with
reference to a particular form of apparatus but
it will be understood that many diiîerent coni
binations of operation may be employed without
departing from the spirit of the invention which
55 consists brieiLv in withdrawing the gas and suill
cient steam to carry the gas, from _the digester
during the digesting operation, condensing the
steam from the gas and conducting the gas to a
place where it may be burned, care being exer
cised to prevent an excess of dilution byair, the
gas being at all times kept in closed containers
or pipes until it is burned. thereby preventing
malodorous gases from escaping into the at
mosphere.
I claimz-
'
1. The improvement in the process of treating
sulphate cellulosic pulp contained in a digester,
for the purpose of avoiding contamination of
the atmosphere with malodorous sulphur con
taining gases; which comprises sweeping out sub
stantially all of the air from the digester prior 10
to the commencement of the cooking process,
then admitting to the digester steam under pres
sure to perform the cooking operation, and dur
ing the cooking stage withdrawing the resulting
gases and vapors from the digester substantially
free from air, separating the condensible from
the non-condensible portions containing the mal
odorous constituents without introduction of air,
and burning said non-condensible portion.
‘
2. A combined process for treating sulphate 20
cellulosic pulp contained in a digester and dis
posing of the resulting malodorous sulphur con
taininggases without contamination of the at
mosphere; which comprises sweeping out sub
stantially all the air from the digester prior to 25
lthe cooking process. then cooking the pulp and
during the cooking process and prior to dis
charging the pulp _from the digester, withdraw
ing the gases and vapors resulting from the cook
ing operation substantially free from air, sep 30
arating the condensible portions from the non
condensible portions containing the malodorous
constituents without introduction of air, and
burning said- non-condensible portion whereby
the malodorous gases are destroyed.
3. A. combined process for treating sulphate
cellulosic pulp contained in a digester, and for
eliminating the resulting malodorous sulphur
containing gases without contaminating the at
mosphere; which comprises conducting the treat 40
ment of the pulp in the digester in two distinct
stages, the ilrst of which comprises sweeping out
substantially all of the air from the pulp prior
to the commencement of the cooking process, and
the second of which comprises cookingl the pulp 45
from which air has been driven off while avoid
ing the admission of further air, and during the
cooking process and prior to discharging the pulp
from the digester, withdrawing the gases and
vapors resulting from the cooking operation from 60
the top of the digester, separating the condensi
ble from the non-condensible portions contain
ing the malodorous constituents without intro
duction of air, and burning the combustible con
stituents or said non-condensible portion where
55
by the malodorous gases are destroyed; the pulp _
being discharged from the bottom o'f the di
gester after the gases and vapors have been with
drawn.
DANIEL J. YOUNG.
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