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Патент USA US2406748

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sept. 3, 1946.
2,406,748
N. L. DlcKlNsoN
DESALTING 01?’ HYDROCARBON OÍIÍLS~
Filed Dec. 29, 1943
NJ?,
'
' In vem‘dr:
l
Norman L. Dickin‘s‘on
BSN
Afforney
i V
Patented Sept. 3, i946
2,406,748 .
UNITED STATES PATENT «- OFFICE
2,406,748
Y
nnsAL'rrNG oF HrDRocanBoN oiLs
lNorman L. Dickinson, Baskîng Ridge, N. J., as
signor to Standard Oil Company, Chicago, Ill.,
a corporation of Indiana
Application Decembeiï 29, 1943, serial No. 516,057
5 Claims. (Cl. 196-5)
.
~
1
2
A
extremely important consideration in catalytic
This invention relates to the desalting of hydro
conversion processes and the frequent replace
carbon oils and it pertains more particularly to
the desalting of reduced crudes for the prepara
i ment of catalyst because of salt contamination
tion of charging stock to catalytic cracking proc
esses.
Many crude petroleum oils contain large
5
Would be economically prohibitive.
The problem of removing salt from crude pe
troleum oils has confronted the industry from its
amounts of salts, particularly sodium chloride,
very beginning and enormous amounts of re
calcium chloride and magnesium chloride. The
search have been conducted in an effort to solve
amount Voi such salts varies with the crudes, Some
this problem. Numerous processes have been pro
crudes containing only traces of salt, others con- 10 posed and some of them used with varying de
taining about .0l to .2 pound per barrel and some
grees of- success but all of them are expensive
containing as much as 5 pounds or more per barand for the most part they do not reduce the
rel.` Thesalt content of typical Mid-Continent
crudes is usuallyV within the approximate range
salt content to the extent suliicient for charging
stocks in catalytic cracking processes. An object
of .04 to .l5 pound per barrel. Since thisr salt is 15 of my invention is to provide an improved method
largely concentrated in the residuum on distillaand means for removing salt from oils and par
tion and the residuum or reduced crude is fre'ticularly from reduced .crudes which method will
quently 50% to 15% of the total crude it will be
be characterized by lower capital investment costs
seen that the amount of salt in the residuum may
and operating costs than any processes heretofore
range from about 0.1 to `1 pound per barrel even 20 known. A further object is to obtain higher yields
in the case of Mid-Continent crudes and may be
of desalted charging stocks from reduced crudes
from .5 to 5 or more pounds per barrel in the case
than could be obtained by any other known'proc
of crudes initially higher in quantities of salt.
ess. A further object is to provide a desalted
An object of my invention is to provide an imcharging stock of higher quality and speciñcally
proved method and means forremoving salt from 25 to avoid the existence of cracking conditions in
such oils and particularly from such reduced
the desalting ystep so that no low octane number
crudes.
gasoline will be produced and so that the value
The salt removal problem is particularly aggraof the charging stock will not be otherwise im
vating in the preparation of charging stocks for
paired. '
è
catalytic cracking processes. Heretofore catalytic 30 A further object is to remove along with the
cracking has been eiïected only on distillate oils
salt certain high molecular Weight substances
or the vaporizable portions of reduced crudes. It
which are deleterious' in catalytic cracking oper
is impossible'to effect complete vaporization of reations but which may serve a useful purpose for
duced crudes Without carbonization and if such
other uses even in the presence of removed salt.
vaporization is effected by thermal means it re- 35 Other objects Will be apparent as the detailed
'suits in the production of loW boiling oils of undesirably low knock rating, i. e. gasolines having
description of the invention proceeds.
I have discovered that when a reduced crude of
an A. S. T. M. octane number of the order of 55
high salt content is admixed With propane in
to 60. In order to vavoid this undesirable thermal k
amounts of about 3 to 5 liquid volumes of propane
cracking oi residual cracking stocks it has been 40 per volume of reduced crude, heated to a tem
proposed to inject these stocks directly into a
perature Within the approximate range of 140jto
catalytic cracking reactor to'which the necessary
185° F. under sufñcient pressure to prevent va
heat for conversion is supplied by other means.
porization of the propane, and introduced into an
Provision can be made for burning the additional
`eii‘icient settling zone which is likewise main
carbonaceous deposits which are laid down in 45 tained under sufficient pressure to prevent pro
such operations but the accumulation on the catpane vaporization, the salt can be carried out of
alyst of inorganic salts from salt-bearing oils
the solution With other propane insoluble mate
ruins the catalysts. An> object of my invention
rials which are present in the reduced crude and
is t0 provide a method and means for the cata-
Withdrawn as a separate stream from the base of
lytic cracking of such heavy reduced crudes of 50 the settling zone. While propane is the preferred
high salt content Without «formation of low antisettling agent for this desalting operation, other
knock gasolines and without deleteriously afiectnormally gaseous hydrocarbons or mixtures
ing the .activity of the catalyst.r The importance
thereof may be employed, higher temperatures
of safeguarding catalyst activity can not be over-
and lower pressures being used in the case of bu
'emphasized because the cost of the catalyst isan 55 tane and lower temperatures and higher pressures
2,406,74s
4
3
distributed in streams flowing between these
in the case of ethane. The normally gaseous hy
drocarbons should preferably be saturated al
baflles so that the baffles do not impede flow but
though the presence of oleflns is not as objection
do avoid possible turbulence and provide surfaces
on which settled droplets may coalesce and run
able in this process as in the process for producing
lubricating oils by conventional propane deas 5 down to the base of the settler without inter
fering with the settling operation. By using such
phalting methods. The amount of normally gas
sloping baliles each particle only has to settle a
eous hydrocarbon employed should be Within
rather closely deiined limits which in the case of
propane are from 3 to 5 volumes, about 4 volumes
per- volume of reduced crude being preferred.
The high propane-to-oil ratios employed in pro
pane deresining processes for lubricating oil man
ufacture are unnecessary and undesirable in the
propane desalting operation, and the reduced
crudes for desalting are usually not of the same
type as those used for the manufacture `oi lubri
eating oils. The invention will be more clearly
understood from the following descriptionbf a
14,250 barrel per stream day deasphalting plant
employed for the preparation from a salt-bearing
reduced crude of a charging stock for a iluid cata
lytic cracking system.
The accompanying drawing which forms a part
`of .this specification is a diagrammatic ilow sheet
of a commercial desalting plant,
Any salt-bearing reduced crude may be em
ployed as a charge to the system, examples being
an 18.7° A. P. I. East Texas-Magnolia reduced
crude, a 21.2° A. P. I. gravity South Louisiana re
duced crude, a 16.2° A. P. I. gravity New Mexico
reduced crude, etc.
few inches before it is coalesced on one of the
collecting plates and thus effectively removed
from the solution. Any eflicient type of settler
may be used but the sloping baille type herein
above described has been found to be very efûcient
and to give excellent results.
The salt is entrained or carried by the heavy
materials which settle out in settlers 22 and 22’
and these settled liquids are withdrawn through
lines 23 and 23’. The relatively salt-free pro
pane solution is removed from the opposite side
of the settler and preferably from the top thereof
through lines 24 and 24’. These solutions pass
through pressure reducing valves 25 and 25’
wherein the pressure is reduced to approximately
280 pounds and the temperature reduced to ap
proximately 136° F. Each of the salt-free streams
after the pressure reducing step will contain about
82,300 pounds per hour of oil, 122,500 pounds per
hour of liquid propane, 85,500 pounds of propane
vapor. These streams are then introduced by
lines 29 and 26’ into depropanizers 21 and 21’
30 Which operate at about 180° F. and about 280
These reduced crudes are
pounds gauge. pressure.
The depropanizers are
preferably about 15 to 30% of the total crude and
their salt contents may range from .05 to 1, usual
ly from .1 to .5 pound per barrel. Such charge is
heated by steam coils 28 and 28’. About 182,400
introduced from source l0 at a temperature of
line 29 and line 29', this propane being returned
through back pressure valve 30, line 3I and con
denser system 32 and finally returned at a tem
perature of about 120° F. to storage tank I I.
The liquid stream which flows over bañ‘les 33
and 33’ is Withdrawn in amounts regulated by
liquid level control valves 34 and 3'4’ through lines
35 and 35’ to depropanizers 36 and 36’. These
depropanizers are likewise heated by steam coils
37 and 37’ `for maintaining a temperature of
about 260° F. and a pressure of about 270 pounds
gauge. About 15,650 pounds per hour of propane
vapor is withdrawn from the top of depropanizers
36 and 36’ through lines 38 and 38', this pro
pane vapor then being passed through lines 39
and 40 to line 3 I, condensed system 32 and storage
tank II.
The liquid which flows over baffles 4I and 4I’
is then Withdrawn in amounts regulated by liquid
level control valves 42 and 42’ and introduced
through line 43 to desalted oil stripping tower 44.
About 164,600 pounds per hour of oil containing
about 13,900 pounds per hour of propane is thus
charged to the stripper which is maintained at a
about 200° F.
The propane in this example is a technical
grade which may contain about 1 to 3% oi
ethane and small amounts of isobutane and bu
tane. The word “propane” is used herein and in 40
the accompanying claims is intended to mean a
normally gaseous hydrocarbon of substantially
the characteristics of propane, i. e., to include
mixtures of propane with small amounts of other ,
normally gaseous hydrocarbons. The propane is 45
`stored in tank II at a temperature of about 120o
F. and a pressureof about 255 pounds per square
inch (all pressures being gauge pressures).
y57,000 barrels per day or 424,000 pounds per hour
of propane are Withdrawn from tank I I through 50
line I2, one half of it being pumped by pump
I3 to line I4 and the other half being pumped
by pump I5 to line I5. The 14,250 barrels per
day or 194,000 pounds per day of charge are in
troduced to the system through pump I'I, half 55
of the charging stock being introduced through
110W control valve I8 to line I4 and the other half
being introduced through iiow control valve I9
pounds per hour of propane vapor is removed
from the top of these depropanizers through
to line I6. If desired of course separate pumps
temperature of about 250° F. and a pressure of
may be used for introducing charge and in fact 60 about 5 pounds gauge. Live steam is introduced
one charging stock may be treated in one portion
through line 45 for stripping the propane from
of my system while another charging stock is
the oil, the propane and steam being taken over
being treated in another part. The propane
head through lines 46 and 41 to jet condenser
charging stock streams from lines I4 and I6 are
48 for condensation of the stripping steam.
raised from a temperat-ure of 137° F. to 185° F. by 65 Desalted oil is withdrawn from the base of
steamheaters 20 and 20', and at this tempera
stripper 44 through line 49 by pump 5I) which op
ture the mixture is introduced through lines 2|
erates to maintain a constant liquid level in the
and 2 I ’ into settlers 22 and 22' which are designed
lower part of the stripper, The desalted oil
to operate at a temperature of 185° F. and a pres
amounts to about 12,350 barrels per stream day
sure of 525 pounds per square inch. These settlers 70 and it is substantially free from salt. Thus a
are preferably large cylindrical tanks mounted at
charging stock which contains .35 pound of salt
a slight angle to the horizontal and they are pref
per barrel can be desalted in this system so effec
erably provided `with sloping lbaffles at intervals
tively that the salt content on the finished oil
ofß or 4 inches, the slope of the baiiies being ,_ Y Will- be less than .0017 pound per barrel which
about 45 degrees. The charge to the settlers is 75 is less than l/zou of the amount of salt in the
. 2,406,1148 ,
6
original charge and is so small as to be prac#
tically negligible.
L
' '
The heavy liquid containing salt may be passed
from lines 2'3 and 23’ thru coils 5l and 5I' in
furnace 52 and'heated from an entering'temper
ature of about 185° F. to a transfer line temper
ature of about 400° F. The streams are then com
bined and introduced by line 53 into flash or vapor
separation drum 5d Vwhich is operated at a tern
perature of about 400° F. and pressure of about 10
270 pounds per square inch. Propane vapor is
withdrawn from the top of this drum at the rate
of about'l3,300 lbs. per hour and conveyed by line
55 to lines 4'0- and’ 3! for condensation and return
tostorage drum il.
The remaining salt-containing liquid», about
29,400 pounds per hour of salt plus heavy com
ponents from the reduced crude, and about ’700
pounds per hour of liquid propane, is withdrawn
ple. The catalyst may be rendered more stable
at high temperatures by the addition thereto of
zirconia, aluminum Vfluosilicate or other stabilizer.
The catalytic cracking is effected at a temper
ature within the approximate range of '750 to
1050° F., preferably about 900 to 950° F., e. g.
about 925° F. The pressure at which catalytic
cracking is eifected may be of the order of atmos
pheric to 50 pounds or more per square inch,
preferably about 5 to 15 pounds per square inch,
e. g. about 10 pounds per square inch (gauge
pressure in all cases). The flow rate or time of
contact Will depend somewhat upon the catalyst,
charging stock, and system employed and in a
fixed or a moving bed system it may be within
the approximate range of .3 to 3, for example
about l volume of liquid charge per hour per
volume of catalyst in the reactor with an on
stream within the general` vicinity of 10 to 30
through line 56, through liquid lever controlled 20 minutesl or more. In the fluid-type or powdered
catalyst vsystem' the catalyst-to-oil weight ratio
valve 5T and> introduced into stripper 58 which
in the stream entering the "reactor may range
operates at about 400° F. and about 5 pounds per
from about 1:1 to 25:1 and the Weight space
square inch pressure. Live steam is introduced
velocity in the reactor itself may be within the
through line 59' and the stripped propane and
steam is taken overhead through lines 59 and 25 approximate range of .3 to 3 pounds of charging
stock per hour per pound of catalyst in the re
41T to jet condenser 48. Water is introduced into
actor.
jet condenser 48 which isr operated at about 2
The catalyst is periodically regenerated by
pounds per square inch pressure. Water is intro
combustion of carbonaceous deposits therefrom
duced into the jet condenser through line bi'> at
about 85° F. and this water together with con 30 usually at temperatures within the approximate
range of 950 to 1150° F., care being taken to»k avoid
densedA steam is removed from thel base of the
unduly high temperatures. The heat of combus
jet condenser> at about 110° F. through linev 62.
tion may be vemployed for preheating and/or
The overhead which consists of about 14,600
vaperizing charging stock as well a-s for supply
pounds per hour of propane vapor is passed by
line VE33 to trapout drum 04 which is operated 35 ing at least a part of the endothermic heat of
cracking. When salt-bearing reduced crudes are
at about l pound pressure and about 100° F., any
employed as charging stock there is not only
aqueous condensate being removed through line
excessively large amounts of carbonaceous mate
65. Propane vapor from the top of this trap is
rial deposited on the catalyst but there is also a
passed by line 65 to compressor 66- and thence by
lines 6l and> 3l back to the condenser system 40 deposit of salt on the catalyst and this salt de
activates the catalyst in a relatively short time
and propane storage drum.
and makes it necessary for the entire catalyst to
The depropanized material leaves the base of
bel discarded. Since the cost of the catalyst is
stripper 53 through line 68, pump 63 maintain
one of the most important items in catalytic
ing a constant liquid level in- the lower part of
45 cracking processes, it is essential that this cata
stripper 53.
lyst poisoning be avoided. Heretofore salt-bear
The desaltedVv oil removed through line 49 is
ing reduced crudes could not be used as charging
excellent charging stock for catalytic cracking
stocks and when overhead fractions were taken
processes and- particularly for processes employ
therefrom said fractions resulted in undesirably
ing the so-called' huid-type operation although
low yields of products characterized Vby undesir
it may be used as charging stock for fixed bed
ably low octane numbers. My invention makes
units of the Houdry'type or moving bed units
possible a substantial increase in the total amount
which are commonly known to the art as the
of high octane number motor fuel obtainable
“Thermofor" catalytic (process. The catalysts
from such reduced crudes andv at the same time
employed> in all of-these processes is of substan
it makes possible the use of salt-bearing crudes
tially the same type and in all cases it is essential
that the charging stock be substantially free from
salt. The catalytic cracking may be effected with
catalysts of the so-called natural or clay type
which is an acid treated or activated Bentonite
or Montmorillonitek clay or it may be a synthetic
without rapidly deteriorating'or ruining the cata
‘ lyst.
My process is particularly advantageous for
reduced crudes containing upwards of about .1
pound of salt per barrel of reduced crude and «
silica-alumina or synthetic silica-magnesia cata
it is advantageous on charging stocks containing
lyst.
only .05 pound per barrel or as low as .0l pound
per barrel. The salt content is substantially
A suitable catalyst may be prepared by ball
eliminated by my process so that desalted oils are
milling silica hydrogel» with alumina or mag
nesia using 2' to 30%, for example about 15% of 65 obtained in which the salt content is less than
.005 pound per barrel and is usually less than
alumina or magnesia, the ball-milled dough being
dried at aV temperature of about 240° F. and then
activated by heating to a temperature of about
900l to 1000° F. Alternatively, the catalyst may be
prepared by Aforming a gel from dilute sodium 70
silicate in the presence of an aluminum salt by
the addition of excess sulfuric acid, boiling the
.002 pound per barrel.
At the same time I re
move from the charging stock the high molecular
weight components which are objectionable in
the catalytic cracking charge but may be very
useful for other purposes.
Y
_
The reduced crudes are preferably about 10 to
30% of the total crude and are thus substantially
resulting gel for an hour or two with an excess
free from hydrocarbons of low or intermediate
of dilutey ammonium hydroxide solution, wash-`
ing', drying and heating as in the previous exam 75 boiling range. The A. P. I. gravities of such re
_7,
2,406,748
8
duced crudes may be within the approximate
range of 15 to 25° although beneficial results may
described.' The salt may be separated from the
solution of oil in normally gaseous diluent by
be obtained on stocks of higher or lower gravities.
means of centrifuges or other separation means.
While specific operating conditions have been
The diluent may be recovered in other manners,
described in connection with the particular ex
and in fact at least a part of the diluent may be
ample hereinabove set forth, it should be under
left in the oil which is charged to the catalytic
cracking system. The invention is particularly
stood that operating conditions will vary for dif
ferent stocks processed and that various modiñ
applicable to salt-bearing reduced crudes which
are not «satisfactory for the manufacture of lubri
cations and alternativesl may be employed both
with regard to the operating system and to the 10 eating oils but are to be used as cracking stocks for
gasoline manufacture. Outstanding features of
conditions employed therein. I have found that
the invention are the low construction and oper~
the salt can be almost completely removed from
the solution in the settling drum regardless of the
ating costs, the remarkable effectiveness of the
salt removal, and the increased yields of high
amount of heavy materials, asphaltic materials
octane number cracked gasoline that are obtain
and the like which may be separated and removed
therewith. Simultaneously with the desalting I
able from any given reduced crude without dele
terious eifect on the catalyst employed in the
may therefore effect varying degrees of deasphalt
cracking operation.
ing. The effect of propane ratio on the amount
I claim:
of asphalt precipitated depends to some extent
1.‘ The method of desalting reduced crude
upon the nature of the reduced crude but usually
which comprises maintaining a quantity of pro
has the effect of decreasing the amount of asphalt
pane in storage at a temperature of about 120°
as the propane ratio is increased. On very short
F., pumping about 4 volumes of propane from
heavy reduced crudes, increasing the propane ra
said storage and about 1 volume of a salt~beartio in the range between 3:1 to 5:1 may have the
elïect of increasing the asphalt Iwhereas a further 25 ing reduced crude through a heating Zone to in
crease the temperature of the mixture to at least
increase above 5:1 tends to decrease the amount
about 140° F. but not more than about 185° F.,
of asphalt. My desalting plant is not designed
introducing the heated solution into a settling
with the idea of having propane-to-oil ratio as a
zone maintained at a temperature Within the
controllable variable, but it is well to understand
what can be expected to occur if the propane 30 approximate range of 140 to 185° F. and under a
pressure suniciently high to prevent vaporization,
ratio does vary.
Operating temperature on the settling system
separating the salt together with undissolved
high molecular weight components of the re
duced cruded from the propane solution of dis
is intended as a controllable variable and has a
deñnite effect upon the amount of asphalt pre 35 solved components in the settling zone, remov
cipitated. Contrary to the usual solution laws an
ing the solution from the settling zone, reducing
increase in temperatures causes a decrease in the
the pressure on the withdrawn solution but main
taining the reduced pressure higher than pro
solubility of asphalt and thus increase in the
amount of asphalt precipitated. With a given
pane storage pressure, heating said solution for
type of reduced crude and a given propane ratio, 40 vaporizing propane therefrom, condensing said
the higher the settling temperature the greater
vaporized propane and returning it to said stor
will be the amount of asphalt separated.
age, reducing the pressure on the remaining pro
The range of temperature in the settling ves
pane solution to approximately 5 pounds per
sels may vary Within the approximate limits of
square inch, stripping said solution with steam
140 to 185° F., 140° F. giving minimum asphalt 45 for removing propane therefrom, condensing the
production and 185° F. giving maximum asphalt
stripping steam with a jet of relatively cool Wa
production which is usually desired along with
ter, separating water from propane vapors, com
the desalting of the reduced crude.
pressing, condensing and returning said propane
It is essential that the propane be kept in liquid
vapors to said propane storage.
condition in the settling zone since the vaporiza~ 50 2. The method of desalting a reduced crude
tion of any propane in the settlers Iwill prevent
which comprises main-taining a quantity of pro
proper settling of the lower phase and thus inter
pane in storage at elevated pressure and at an
within the limits for which the plant is designed
fere with the desired desalting operation.
Usu
elevated temperature which is substantially be
ally a reasonable pressure on the settling Zone is
low about 140° F., mixing about 3 to ’5 volumes
maintained above the amount calculated for com 55 of propane from said storage with about 1 volume
plete liquid phase conditions and it is important
of a salt-bearing reduced crude, heating said mix
in determining the pressure to take into account
ture and holding it in a settling zone at a tem
any small amounts of ethane that may be present
perature within the range of about 140° to 185°
in the propane. With the exception of the two
F. under a pressure sufficiently high to prevent
strippers and the jet condenser the pressures em
vaporization for a time sumcient to effect sepa
ployed at various stages following the settlers are
controlled primarily by the pressure maintained
ration of salt together with undissolved high
molecular weight components of the reduced
on the propane storage tank. The high pressure
crude from the propane solution of dissolved com
ñashpropane recovery units can be said to “float”
ponents in the settling zone, removing the solu
on the propane storage tank, i. e. to carry such 65 tion from the settling zone, reducing 4the pres
pressure as is necessary to make the vapors from
these vessels move through the lines and con
densers back to the storage tank. The pressure
on the two strippers and on the jet condenser
is reduced to atmospheric pressure in order to
facilitate complete vaporization of propane and
the propane thus released is compressed for re~
turn to the condenser and sto-rage system.
As above stated, my invention is not limited to
the precise system and conditions hereinabove
sure on the withdrawn solution but maintaining
the reduced pressure higher than the propane
storage pressure, heating said solution for vapor
lzing propane therefrom, condensing said vapor»
ized propane and returning it without compres
sion to said storage, reducing the pressure on
the remaining propane solution to a level from
about atmospheric to about 5 pounds per square
inch gauge, stripping said solution at the reduced
75 pressure with steam for removing propane there'
2,406,748
from, condensing the stripping steam from pro
pane vapors liberated in the stripping step and
compressing, condensing and returning said pro
pane vapors to said propane storage.
3. The method of claim 2 wherein the salt
bearing reduced crude contains onli»T the residual
components of a crude petroleum oil after vapor
izable components have been removed to the ex
tent of at least about 50% of the total crude.
4. The method of claim 2 wherein the salt
bearing reduced crude contains at least about .05
pound of salt per barrel.
5. The method of claim 2 which includes the
10
from the settling zone to a heating zone, heat
ing said materials to atemperature of lapproxi
mately 400° F., separating propane vapors from
the heated materials at a pressure which is high
er than the propane storage pressure, condens
ing the separated vapors and returning them to
said propane storage, reducing the pressure of
the remaining materials to about atmospheric to
about 5 pounds per square inch, stripping said
materials with steam at said reduced pressure for
removing residual propane vapors, condensing
and separating steam from said residual propane
_vapors and compressing, condensing and return
ing said propane vapors to said propane stor
steps of passing separated salt and undissolved
high molecular Weight components of the reduced 15 age.
crude together with propane associated therewith
NORMAN L. DICKINSON.
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