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Патент USA US2133338

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Patented Oct. 18, 1938
o s
Paul D. Barton, Scarsdale, N. Y., assignor, by
mesne assignments, to Sun Oil Company, Phil
adelphia, Pa., a corporation of New Jersey
Application January 22, 1934, Serial No. 707,637
5 Claims.
My invention relates to a dewaxing process and
(Cl. 196-18)
more particularly to a multi-stage dewaxing proc
Wax crystals solidified and from which separator
a selected upper portion of the oil from which
ess utilizing an excess of a solvent diluent in the
some of the wax has been crystallized and pre
first stage.
Generally speaking, in a process for dewaxing
hydrocarbon oils containing a large percentage
of paraiiin Wax which utilizes a normally gaseous
liquifled hydrocarbon solvent such as propane to
secure dilution, chilling and resultant crystalliza
10 tion of the wax, considerable difficulty has been
experienced in transferring through pumps, pipe
lines and other pieces of equipment associated
with the process, the wax-bearing oil diluted in
the customary manner. The viscosity of oil sol
15 Vent mixture under the usual dilution conditions
of, for example, one part oil and three parts pro
pane is such as to preclude a satisfactory com
mercial rate of dewaxing in a continuous process.
It is an object of my invention to provide a
20 process for dewaxing hydrocarbon oils containing
a. high percentage of wax not readily removed by
cipitated by the chilled solvent, is removed, fil
tered, and then completely or partially denuded
of the solvent diluent before subsequent further
dewaxing. The removal of a predetermined
amount of the solvent at this point is necessary
before further dewaxing is attempted in order
that the proper concentration of the oil in the 10
diluent for most favorable wax crystallization
conditions may be secured. It may be desirable
as an alternative to remove all of the initial
solvent at this point and utilize a different solvent
of higher vapor pressure for the subsequent fur- l5
ther dewaxing operation. The remaining oil wax
slurry from the separating tank is passed through
filters, the filtrate from which is combined with
the partially dewaxed undenuded oil while the
slurry from the filters is denuded of this propane 20
solvent and passed to storage as first wax or
a continuous process involving low dilution of the
oil with a hydrocarbon solvent because of me
The partially dewaxed oil with solvent diluent
for the desired concentration, is cooled by indi
rect heat exchange from surrounding evaporating 25`
propane and passed into a crystallizer tank where
evaporation is prevented by pressure of a lighter
gas and where the time, temperature conditions
chanical difficulties incident to pumping and fil
25 tration.
Another object of my invention is to provide a
multi-stage dewaxing process in which a hydro
carbon oil bearing a high percentage of wax is
highly diluted with a hydrocarbon solvent, chilled
30 and partially dewaxed, the concentration of the
partially dewaxed oil in the solvent then being
increased by denuding the mixture of some sol
vent, the oil again chilled to a lower wax precipi
tating temperature and additional wax removed
35 to givethe desired low cold test oil.
Other and further objects of my invention will
be seen from the following description.
The accompanying drawing which forms part
of the instant specification and is to be read in
40 conjunction therewith is a schematic drawing of
one form of apparatus capable of carrying out the
process of my invention.
In general, I mix a stock bearing a high per~
centage of wax with a liquefied, normally gaseous
45 hydrocarbon solvent such as propane, for example,
under such conditions as will secure an initial di
lution sufficient to obtain a solution and permit
more ready transfer of the solution to a second
mixing chamber where a. large amount of solvent
50 diluent which has been separately chilled to a
predetermined low wax precipitating temperature
is mixed with the first oil diluent solution. This
highly diluted and chilled solution is held under
pressure in a separating tank which permits a
55€ preliminary settling of the larger and heavier
necessary for crystallization are maintained.
This process of chilling and crystallizing under 30
pressure is carried on through a number of steps,
the temperature and pressure decreasing and
the amount of crystallized wax increasing in each
step. The final desired crystal formation is
achieved in the last crystallizer Where the diluent 35`
is caused to evaporate either from direct pressure
relief or as the result of a light gas partial pres
sure effect to secure the proper oil concentration
in the solvent. Some temperature reduction may
occur as the result of incidental auto-refrigera- 40
tion in the last crystallizer though indirect heat
exchange may be used. The oil, bearing the crys
tallized wax, is then passed through a series of
filters of desired type, the filtrate of dewaxed oil
being taken off, denuded of diluent in a distilla- 45 l
tion zone, and then sent to storage as finished de
waxed oil of the desired low cold test. The slurry
from the filters is collected and pumped to a dis
tillation zone for the removal of the diluent, the
denuded material being sent to storage as the sec- 50
ond wax or petrolatum.
It is to be noted that I maintain the pressure
on the initial separating tank sufficient to prevent
evaporation of the propane attendant in the in
itial oil propane solution, thus inhibiting auto- 55!
refrigeration by evaporation of a part of the di
The gas serving as a pressure medium on
this settling tank and on the crystallizers in the
second stage of crystallization is selected from
5 a gas having relatively 10W solubility in the oil
propane mixture. This gas may be, for example,
carbon dioxide or methane.
The latter is espe
cially desirable for securing propane evaporation
by partial'pressure reduction inthe later crystal
unit 33 is withdrawn through the line 35 con
necting to the line 45 which passes to a distilla
tion unit 46 serving to remove the diluent which
passes oi’ic through the line 42 While the denuded
Wax or petrolatum passes 01T through the line 41
to storage.
The partially dewaxed oil is passed to a mixing
chamber 59, either from tank 44 or through line
Diluent Which may be the same or have a
higher vapor pressure is withdrawn from the 10
10 lizers.
tank 5 (or a separate tank, not shown) through
Referring now more particularly to the draw
ing, a wax-bearing stock from tank I ispumped the-line 5| having apump 52 and mixed with the
through a line 2 by pump 3 toa mixing chamber l oil in the mixing chamber 59 in the desired ratio
to give the required higher oil concentration for
4 where it is mixed with a normally gaseous liqui
15 fied hydrocarbon solvent diluent such as propane loW cold test oil product. The oil diluent mix 15
or the like, taken from tank 5 - and pumped ' ture passes through line 53 and heat exchanger 541,
through the line 5 by pump 1. The oil diluent to the crystallizer 551. The oil Withdrawn from
solution is transferred through-the line 8 to a .the crystallizer 551 passes through lines 53 and a
second mixing chamber 9. Diluent is Withdrawn
20 from the tank 5 through the line ||l and -injected
into thechiller il Where it is cooled as a-result of
evaporationof a portion of the diluent, the gas
series of heat exchangers 542, 543, 544, and crys
ltallizers 552,` 553, 554' arranged in series. Liquid 20
diluent is, introduced to each of the heat ex
changers 54 through the lines 55,` permitted. to
evaporate and escape through the lines 51 hav
valve i3. The chilled diluentfrom the chiller ` ing pressure relief valves 58. These lines are
25 «,II is ¿pumped through a line I4 having a pump connected to a main 59 running to the inlet side
I5 to the` mixing chamber_9. The highly diluted of the pump of the compressor Si]V to the outlet
oil diluent solution from the chamber 9 passes of which is connected a line 6| passing -through
heat exchanger 62 to the diluentvsupply tank 5.
through the line | a separating tank |1 hav
ing a series of baiiie plates .lßarranged to mini
Pressure is maintained on each of the crystalliz
ßofimize agitation resulting. from eddy currents set ers 55 by compressed light gas injected through
escaping throughjline I2 having a pressure relief
up in the tank.
A compressor I9 serves to pump a light gas such
as carbon dioxide or methane to tank »|9a„ñtted
Gas from tank |9a passes
35 nthrough the line 29 and branch line 2| to the sep
arating tank I1 at a pressure suñicient to pre
vent evaporation ofthe diluent in the tank. As
'a result of the interchange of sensible heat be
tween the oil and subcooled diluent, some of the
25 :i
the lines 53. Branch lines may be provided for
injecting light gas directly into the oil diluentH
solution if desired to secure diluent evaporation
by partial pressure eiîect in the last crystallizer.
A series of escape lines 54 provided with pres
sure relief valves 55 yare connected toa common
main 66 which returns the gaseous diluent to the
intake side of the compressor i9.
Each of the crystallizers 551, 552, 553, 554, is
40. Wax in the oil is crystallized, settles andincreases provided with liquid level controls 911, 912, 913, 40
914, respectively, for operating the valves 981, 982,
the percentage of Wax crystals in the lower por
tion of the oil solution in tank |1. A layer of 983, 984, respectively, for controlling the pressure
and iiow of the liquid into the respective crys
partiallyl dewaxed oil is Withdrawn from the up
per >level of the tank through the line 22 and tallizers 551, 552, 553, and 554.
The oil bearing the crystallized Wax is With 1.1.5V
45 injected intoVv a ñlter unit of the desired type as
23. A ñltrate of partiallyrdewaxed oil -is With » drawn from the last crystallizer 554 through the
drawn from the filter `unit 23 `through Yline 24 line> 61 having a pump 98. Branch lines 69, 10,
connected to a filtrate main 25 passing to an ac
cumulator tank 26.
The oil Wax slurry in the
50~lower portion of the ñlter unit 23 vis Withdrawn
through lthe> line 21 and combines With oil Wax
slurry being withdrawn from the tank- l1 through
the -liner 28. This-slurry is passed through the
line 29 to the‘ñlter unit 30 from which filtrate
5 ,may be withdrawn through the line 3| and slurry
through the line 32. The slurry is further ñltered
in the» lilter unit 33, filtrate being Withdrawn
through the line 34and slurry through the line
35. The ñltrate being Withdrawn from the units
60.» through the> lines v3| and 34 is passed into the
main 25 connecting With the accumulator tank
25. Valves 36 and 31 are provided in the line` 28
permitting the units 38 and 33 to be operated in
series or cut out as‘desired.
The partially dewaxed oil is Withdrawn from
the tank 26 through the line 38 having a pump
39„ passed through the heat exchanger 48 to a
distillation ,unit-4| _Where the diluent is Wholly
or partially distilled oiîand collected in the main
7013.42. `The partially `dewaxed oilv denuded of its dil
uent is then sent through the liner 43 to a. tank
1| and 12 connect the linel S1 with the filter units Y
13,14, 15 and 16. Withdrawal linesf11, 18, 19
and 89 connect the bottom of the ñlter units with 50
the line 51 which is also provided with the valvesy
8h82,Y 83 and 84 which permit the ñlter units
to be operated eitherin series or cut out as de
The filtrate from the ñlter units is re- »
moved through the line 85 and passed into a dis
tillation unit 86 from which the diluent is re
moved through the lines 86a and 42, and the
iinished dewaxed oil removed through the line
81. It will be understood that if a diiîerent dil
uent from that in tank 5 is used, line 86a will re
turn the same to its oWn tank (not shown). rl‘he
wax-diluent slurry from the iilter unit is passed
through the line 88a >to Vthe tank 88 from which
it is removed through a line 89 having a pump 90
and sent to a distillation unit 9| from which the 65
diluent is. removed through the line 42 and the
wax or petrolatum removed through the line 92.
The accumulated diluent` from the` distillation
units 44,46, 9| and 86 maybe collected in the line s
42 and passed through-a branch line 93, cooled' 70x
in heat exchanger 94, to an accumulator 95 fromY `
44. _ Alternatively, the partially denuded oil may which it is returned through the line 96v and heat
be introducedgdirectly to the ñrst indirect solu » exchanger- 49 to the diluent supply tankr5.
tion chiller 54 through a. by pass 43a, controlled
One example of the operationV of my process
75;;by». valve„43b. >The Wax slurryfrom the >filter , is as follows:
The wax-bearing stock and` diluent such >as
propane from tanks I and 5 respectively are
combined in the mixing chamber 4 in ratio of
about one to three parts by volume. This solu
tion, as a result of sensible heat exchange (and
the operation of an external Water cooled heat
exchange means, if desired, (not shown) will be
cooled to a temperature of about '15° F. Diluent
withdrawn from the tank 5 is sub-cooled to
10 _45° F., for example, in the chiller II by evap
oration of a portion thereof, the sub-cooled
diluent then being mixed with the first oil
diluent solution in the chamber 9 in a ratio of
two to twenty, for example. The entire solution
15 now reaches a temperature of about _30° F.
in the separating chamber I1 where the diluent
is kept from evaporating as a result of the re
straining action of the carbon dioxide or meth
ane at a pressure which may be as high as 200#
20 maintained by the compressor I9 on the separat
ing tank I1. ’I'here will be a slight rise in temp
'erature of the filtrate from the filter units 23,
30 and 33, the partially dewaxed oil in the ac
cumulator 2B being, for example, in the neigh
25 borhood of _25° F. This oil, after passage
under pressure throughthe heat exchanger 40
and distillation unit 4I, will be at a temperature
governed by available cooling water, say about
80° F. and at a pressure in the neighborhood
30 of 175#.
The oil is either completely denuded
of `diluent in distillation unit 4I and then accumu
lated prior to redilution with a diluent of higher
vapor pressure, or sufiicient diluent is removed
to secure a concentration of the oil-diluent ratio
35 which will insure proper crystal growth in the
subsequent dewaxing step.
The oil, if completely denuded of diluent is
withdrawn from the accumulator 44 and mixed
with a different diluent from the tank 5 or a sep
40 arate tank (not shown) in a ratio of substan
tially one part oil to three parts of diluent by
volume. The temperature of the mixture will
be around ’70° F. and this will be cooled in pass
ing through the indirect solution cooler 541 to
45 a temperature of +30 F. as a result of the evap
oration of diluent in the indirect solution cooler
541, which diluent will be at a temperature of
from 0 to _15° F. The wax oil solution from
in tank 88 and pumped through line 89 to dis
tillation unit 9| where the diluent is removed.
The petrolatum is sent to storage through line 92.
It will be understood that certain features and
subcombinations are of utility and may be ern
ployed with reference to other features and sub
combinations. This is contemplated by and is
within the scope of my claims. It is further ob
vious that various changes may be made in de
tails within the scope of my claims without de 10
parting from the spirit of my invention. It is,
therefore, to be understood that my invention is
not to be limited to the specific details shown
and described.
Having thus described my invention, what I 15
claim is:
1. A process for dewaxing hydrocarbon oils
comprising diluting the oil with a hydrocarbon
solvent, chilling the oil-diluent solution to secure
partial crystallization of the wax, separating the 20
wax from the oil, denuding the partially de
waxed oil of the solvent, diluting the partially
dewaxed oil with a different hydrocarbon sol
vent of higher vapor pressure than said ñrst sol
vent, chilling the oil-diluent solution to crystal
lize a further portion of the wax and removing
the wax from the oil.
2. A process for dewaxing hydrocarbon oils
comprising diluting the oil with a hydrocarbon
solvent, further diluting the oil-solvent solution 30
with a chilled hydrocarbon solvent to secure
crystallization of a portion of the contained wax,
separating the wax from a selected portion of
the oil, denuding the partially dewaxed oil of the
hydrocarbon solvent, diluting the partially de
waxed oil with a different hydrocarbon solvent of
higher vapor pressure than said first solvent,
chilling the oil-.diluent solution to a. temperature
lower than that achieved in the first stage of
dewaxing and removing the wax from the oil.
3. A process for dewaxing hydrocarbon oils
comprising diluting the oil with a solvent di
luent, chilling a solvent diluent by auto-refrig
eration, further diluting the oil-diluent solution
with the chilled diluent, introducing the highly 45
diluted chilled solution to a separating stage,
maintaining a ‘pressure in the separating stage
with a gas substantially insoluble in the solu
the first crystallizer 55, will be cooled in passing
50 through the second indirect solution cooler 542
to a temperature of 0° F., in passing through
the third indirect solution cooler 543 to a temp
erature of _10° F., and in passing through the
tion sufiicient to prevent evaporation of the di
luent, removing a selected portion of solution
from the separating stage and introducing it to 50
a filtering stage, removing the iiltrate and par
tially denuding it of the solvent diluent in a dis
fourth solution cooler 544 to a temperature of
Each of the crystallizers 55 is main
tained under pressure by the gas from tank
I9a to prevent evaporation of the diluent in the
crystallizers. This pressure may be less in each
centration in the solution, progressively chilling 55
the solution and crystallizing the Wax in a series
of heat exchange and time crystallization stages
55 _20° F.
crystallizer due to the progressively decreasing
60 temperature of the mixtures. For example, the
first crystallizer 551 may be at 200# pressure, the
second 552 at 150# pressure and the third 553
at 100# pressure. The fourth crystallizer 554
will be at atmospheric pressure and diluent will
65 be permitted to evaporate from the mixture
either by the reduction to atmospheric pressure
or as the result of injected light gas to secure
the desired concentration of mother liquor giv
ing favorable crystal growth. The oil-wax dil
70 uent mixture removed from the last crystallizer
55 is filtered in the selected filter units, the ñl
trate removed through line 85 being denuded of
its diluent in the distillation unit 86 and sent to
storage as finished dewaxed oil through the line
75 81. The slurry from units 13-16 is accumulated
tillation stage, to secure a much higher oil con
while maintaining a super atmospheric pressure
in the crystallizing stages with a gas substan
tially insoluble in the solution, evaporating the 60
diluent from the mixture in the last stage of
crystallization to secure the desired concentra
tion of oil, removing the mixture from the crys
tallizer and introducing it to a filtration stage,
removing the filtrate and denuding the wax free 65
oil of the diluent in a distillation stage.
4. The process of claim 3 in which the first
oil-diluent solution is in substantially the ratio
of one to three parts by volume, in which the
second oil-diluent solution is in the ratio of sub
stantially two to twenty parts by volume and
in which the partially denuded oil-diluent solu
tion is in the ratio of substantially one to three
parts by volume.
5. A process of dewaxing hydrocarbon oils 75
2,133,338 Y1
mospherîc pressureon the solution, then evap
comprising preparing a highlyidiluted oilîsoln
vent solution, chilling the solution, ñltering the
orating a portion of the diluent to secure a pre
solution to secure ,a partially»` devvaxed4 Cil di
determined oil to solvent ratio higher than in
saidzfirst solution and thefinal desired crystal
formation, and vremoving the Wax from the
solution >to a vp1"e«.'ìetermined temperature lower - mixture.
than said ñrst chilling temperature by lindirect
heat exchange While maintaining a,V super ya1:
luent filtrate, removing .a portion of?the diluent
:from the ñltrate, chilling the: íiltratesdiluent
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