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Патент USA US2403563

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Patented July 9, 1946
2,403,563
UNITED STATES PATENT OFFICE
2,403,563
SURGE TANK SYSTEM
Marshall R. Sprinkle, Edwardsville, and Robert S.
MacDuli’, Alton, Ill., assignors to Shell De
velopment Company, San Francisco, Calif., a
corporation of Delaware
Application October 4, 1943, Serial No. 504,984
7 Claims. (Cl. 137-78)
l
2
The present invention relates to surge tank sys
in sour hydrocarbon distillates, and more particu
tems and more particularly to surge tank sys
larly in gasoline distillates, are extracted with
tems for use in processes wherein absorption of
solutizer solution, i. e, aqueous solutions of alkali
small quantities of air or oxygen by the reactants
metal hydroxides containing solutizers, is well
in passing through a surge tank system is dele 6 known. The solutizer process has been described
terious or undesirable.`
and the several compounds particularly suitable
In the majority of industrial chemical proc
.as solutizers have been enumerated in the gen
esses involving process ñows it has been found
eral literature, for example, Rei-incr and Natural
advantageous to include surge tanks Within the
Gasoline Manufacturer, May 1939, pages 171 to
flow system. These tanks serve to minimize or 10 176 and March 1940, pages 73 to 76; Industrial
eliminate ñuctuations in ñow rates throughout
and Engineering Chemistry, vol. 32, pages 257
the system and conventionally comprise a sim
to 262, February 1940; Chemical and Metallurgi
ple reservoir from which fluid material to be
cal Engineering,` vol. 47, pages 776 to 778, Novem
treated or reacted may be withdrawn at a con~
ber 1940, etc. As shown in these references, the
stant rate regardless of variations of input iiow
solutizer process involves the extraction of mer
to the reservoir. However, since the liquid level
captans whereby a spent solutizer solution is pro
Within the surge tank is either continuously or
duced which is continuously regenerated as by
periodically changing, it is necessary to provide
steam stripping, and the regenerated solution is
a vent or breather arrangement in order to avoid
then re-used for further extraction of mercap
substantial pressure changes within the system. 20 tans. The principal purpose of the process is
In some instances, particularly where the ma
to sweeten sour gasoline distillates,
.
terial passing through the surge tank tends to
It has been observed that in the course of
absorb air, difficulties in the operation of the'
such treatment, hydrocarbon distillates, e. g. gas
process are encountered as a result of the` air
oline, may deteriorate in color and the solutizer
absorbed in thesurge tank, usually in the form 25 solutions, i. e. alkali metal hydroxide solutions
of undesirable side reactions, excessive foaming,
containing solutizers, at times tend to form rela
sludging, or the like.
tively stable emulsions with the hydrocarbon oil
It is an object of the present invention to
under treatment, probably due to gradual ac
provide a surge tank system wherein contami
cumulation of emulsiñers believed to be resinous
30
substances not removable by steam stripping,
therethrough is substantially eliminated. Other
which emulsions either reduce the throughput
objects, together with some of the advantages to
due to retarded settling or cause carry-over of
be derived from operating according to the pres
valuable solutizer.
ent invention, will become apparent from the
It has been found, however, that the trouble-vfollowing detailed description thereof, taken to 35 some substances, emulsiñers as well as the color
gether with the accompanying drawing which is
bodies, are formed through oxidation, probably
a schematic flow diagram of a speciñc application
of some components contained in the hydrocar
of one embodiment of the invention.
bon oil to be treated. One of the principal places
In the present improved surge tank system,
wherein undesirable oxidation and/or oxygen ab
nation, by air absorption, of materials passing
fluctuation in the content of the surge tank due 40 sorption normally occurs is in the surge tank
to inconstant rate of liquid input thereto is com
system of the process as usually operated.
pensated by interñow of an aqueous displacement
According to the present invention such unde
medium, preferably water,lbetween the surge tank
sirable oxidation may be avoided, for example in
and an auxiliary tank in accordance with ñow
the manner disclosed in the accompanying draw
rate variations to the surge tank, and air is ex 45 ing. Sour hydrocarbon liquid free from ab
cluded from the surge tank by maintaining a va
sorbed airor oxygen is passed from conduit l5
por blanket over the liquid level in the auxiliary
into surge tank I from whence it passes through
tank, as will be explained in detail below.
conduit 2 into extractor 3 wherein it is counter
For purposes of illustration, the invention will
currently contacted with fresh sclutizer solution
50
be described in relation to its application to a
entering through conduit 8, Spent solutizer so
specific process wherein a surge tank is normally
lution passes out of extractor 3 through conduit
included and wherein air absorption by materials
9 and thence through conduit Il to be regener
passing through the surge tank is objectionable.
ated. Treated hydrocarbon liquid and small
The solutizer process, by means of which mer
amounts of entrained solutizer solution pass out
captans and other weak organic acids contained 55 of extractor 3 through` conduit 4 to washer 5
2,403,563
3
4
other material which is normally in a vapor state
at the temperature of operation, is relatively in
soluble in water, and does not contain air or oxy
wherein they are countercurrently contacted with
water entering washer 5 through conduit 1. The
wash water, including spent solutizer solution re
moved from the hydrocarbon stream, passes out
gen, may be utilized.
Suitable examples of such
materials include, for example, nitrogen, meth
ane, ethane, butane, propane and the like.
Although the present improved surge tank sys
of washer 5 through conduit Iû to contact I I, the
treated and washed hydrocarbon liquid passing
through >condu-it 6 to utilization, storage or fur- ,
tem has been described with particular reference
lto its use in combination with the solutizer gaso
line sweetening process, it will be readily under
ther treatment.
A water level is maintained in surge tank I
and in tank I3, conduit I2 permitting passage of
stood that the principles of operation and con
struction have wide applicability in any surge
tank `arrangement wherein it is necessary or de
water in lboth directions. A blanket of fuel gas
is maintained above the water level in tank I3.
In normal operation, sour hydrocarbon liquid is
withdrawn from surge tank I through conduit 2,
the rate of flow being controlled by valve I1 or
other suitable means. If the rate of flow of sour
hydrocarbon liquid to surge tank I through con
duit I5 should temporarily exceed the rate of
sirable to exclude oxygen from a system wherein
a water-immiscible liquid is passed through a
surge tank.
For example, the problem of oxygen exclusion
also arises in the separation of butadiene, pen
tadiene, hexadiene, etc., from other C4, C5 and
withdrawal from surge tank I, water is displaced
from surge tank I and forced through conduit 20 Ce hydrocarbons respectively, oxygen causing the
formation of gummy materials as well as foam
I2 'to tank I3, in turn forcing fuel gas from the
ing and emulsifying agents; or in the separation
top of tank I3 to a gas reservoir (not shown),
of benzene, toluene, xylenes, etc. from narrow
such as a conventional water-sealed gasholder,
boiling hydrocarbon mixtures containing them
for example, which delivers gas under a slight
positive pressure.
Conversely, when the rate of 25 by extractive distillation with phenol, oxygen in
this case causing corrosio-n in the reboiler of the
extractor, or sludging of the phenol, or both;
or in the polymerization of oleñns with phos
phoric acid or other solid catalyst, oxygen caus
withdrawal from surge tank I is less than the
rate of input, the water level in surge tank I
will rise, water flowing by gravity from tank it
through conduit I2, and an equivalent quantity
of fuel gas will pass through conduit I4 to replace
the water` exiting from tank I3.
A purging conduit IB `including valve I9 is also
provided in tank I3 in order to avoid entrap
ment of an .air pocket when starting operations.
Thus, in putting the unit in operation, the sys
tem may be first charged with fuel gas admitted
through conduit I4, valves I6, i9, 23 and 25 being
closed during this purging operation. Valves 2l!
and 2| are then opened and a quantity of water
admitted to tank I3 through conduit I6, and to
surge tank I through conduit I2, valve I9 being
opened meanwhile for a suflicient period of time
to insure escape of any air entrapped in tank
I3. When a suitable liquid level has been at
tained in surge tank I, valve 23 is opened and
flow of sour hydrocarbon liquid to surge tank I
permitted, resulting in a back pressure within
surge tank I and preventing further flow of water
thereto from -tank I3 and permitting the desired
liquid level to 'be attained in tank I3, whereupon
valve 2| is closed. The system will then operate
automatically to take care of fluctuation in feed
rate to surge tank I, as described above. Water
may be withdrawn from the surge tank system,
ing gumming of the catalyst, thereby shortening
its useful life, etc. In virtually all commercial
plants wherein processes such as those above
described are carried out it is both necessary and
desirable to include one or more surge tank sys
35 tems, and it is in such systems that contamina
tion o-f the product or reactants with oxygen
often occur. Such contamination may be en
tirely obviated by use of the surge tank system
described in the present specification.
40
We claim as our invention:
l. In an arrangement for minimizing iiow fluc
tuations in a flow system the combination com
prising a closed surge tank, a closed auxiliary
tank, flow communication means between said
45 surge tank and said auxiliary tank, an Iaqueous
displacement medium comprising water in said
surge tank and said auxiliary tank, said flow com
munication means terminating beneath the liq
uid level of said aqueous displacement medium
50 in said surge tank and said auxiliary tank, means
lfor introducing a substantially water-immisci
ble oxidizable fluid material having a density less
than that of water to said surge tank, means for
withdrawing said substantially water-immiscible
when desired, through conduit 24 by >opening 55 oxidizable ñuid material from said Vsurge tank
and means for maintaining an oxygen excluding
valve 25.
vapor blanket above the liquid level of vsaid aque
ous displacement medium in said auxiliary tank.
2. In -an arrangement for minimizing flow
if desired or useful for a particular purpose, as 60 fluctuations in a flow system the combination
comprising a closed surge tank, a closed auxiliary
for example it may be advantageous to include
tank, flow communication means between said
varying amounts of salts, acids, alkalis, wetting
surge tank and said vauxiliary tank, an vaqueous
agents or alcohols and the like in the displace
displacement medium in said surge tank and said
ment medium for various purposes.
auxiliary tank, said flow communication means
It has been found that the maintenance of an
terminating at each end beneath the liquid level
inert blanket over the water in tank I3 is an es
of said aqueous displacement medium in said
sential feature of the invention since, in the ab
surge tank and the liquid level of said aqueous
sence of such a blanket, suiiicient air is absorbed
displacement medium in said auxiliary tank, re
by the water in tank I3 and transmitted to surge
tank I, wherein it is taken up ‘by the hydrocarbon 70 spectively, said aqueous displacement medium
normally tending to ñnd a common level by grav
material, to seriously interfere with the opera
ity flow through said flow communication means,
tion of the sweetening process. Although fuel
means for introducing a substantially water-im
‘gas is a particularly suitable material for the
miscible oxidi'zable fluid material having a `den
purpose of forming an inert blanket over the
water in tank I, it will be appreciated that any 75 sity less than that of water to said ‘surge tank,
Although Water alone is generally to be pre
ferred as the aqueous displacement medium,
other primarily aqueous media may be employed
5
2,403,663
means for withdrawing said substantially water
immiscible oxidizable ñuid material from said
surge tank and kmeans for maintaining an oxygen
excluding vapor blanket above said liquid level
of aqueous displacement medium -in said auxil
iary tank.
iary tank, ilow communication means between
' said surge tank and said auxiliary tank, water
bodies in said surge tank and said auxiliary tank,
said flow communication means terminating at
one end beneath the water level of said water
body in said surge tank and at the other end be
neath the water level of said body of water in
3. In an arrangement for minimizing ñow
fluctuations in a 'flow system, the combination
said auxiliary tank, said water bodies normally
comprising a closed surge tank, a closed auxiliary
tending to ñnd a common level by gravity iiow
tank, flow communication means between said 10 through said iiow communication means, means
surge tank and said auxiliary tank, water bodies
for continuously introducing to said surge tank
in said surge tank and said auxiliary tank, said
liquid hydrocarbon material having a .density
i'low communication means terminating at one
less than that of water, said hydrocarbon mate
end beneath the water level of said water body
rial being of such nature as to necessitate exclu
in said surge tanke and at'the other end beneath 15 sion of contact thereof with oxygen, means for
the water level of said body `>of water in said aux
continuously withdrawing said liquid hydrocar
iliary tank, said water bodies normally tending
bon material from said surge tank, and means
to find a common level by gravity ñow through
for maintaining an oxygen-excluding vapor
said ñow communication means, means for con
blanket under pressure above said water level in
tinuously introducing to saidsurge tank liquid 20 said auxiliary tank.
hydrocarbon material having a density less than
5. The system according to claim 3 wherein
that of water, said hydrocarbon material being
the oxygen excluding vapor blanket comprises
of such nature as to necessitate exclusion of con
a normally gaseous hydrocarbon.
f
tact thereof with oxygen, means for continuous
6. The system according to claim 3 wherein
ly withdrawing said liquid hydrocarbon mate 25 the oxygen excluding vapor blanket comprises
rial from said surge tank at controlled ñow rates
nitrogen.
and means for maintaining an oxygen-excluding
7. The system according to claim 3 ¿wherein
vapor blanket above said water level in said aux
the oxygen excluding vapor blanket comprises
iliary tank.
4. In an arrangement for minimizing flow 30
iluctuations in a ñow system, the combination
comprising a closed surge tank, a closed auxil
fuel gas.
MARSHALL R. SPRINKLE.
ROBERT S. MACDUFF.
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