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June '28, v1938.
Filed Dec. 1, 1934
2 Sheets-Sheet 1
_, =
June 28,1938.
Filed Dec. 1_, 1934
2 Sheets-Sheet’ 2
. . , 9m.
mm. .
Cheateni?dams '
I F e
W. 5072a‘
' Patented vJune 28, 1938
2,122,019 '
Chester E. Adams, Hammond, Ind., and ‘FredvW. ,
Scheineinan, Chicago, 111., assignors to Stand-'
, ard Oil Company, Chicago, Ill.,'a corporation
, ..
i1 5 ,
of Indiana
ApplicationDecember 1, 1934, Serial No. 755,602
8 Claims. (o1. [196-18)vv
effectively utilizing available refrigeration and
This invention relates to the separation of wax
from oils and it pertains'more particularly to an “used propane” in this chilling'step, and for pro
improved system for the use of normallyvg'aseous . viding improved-‘methods and means of handling
the slurry during” and subsequent to the chilling
diluent refrigerants, such as liquid propane. ' This
application is a continuation in part of appli
method and means for operating a wax ?ltration
system whereby ‘maximum ?exibility of operation
The object of our invention is to provide a com
mercial'large-scale dewaxing plant for petroleum
may be obtained by the use of a minimum num- ,
ber of pumps, ‘conduits and connections. A fur- ‘l0
‘re?neries in which inflammable volatile diluents
or refrigerants may be used with safety. . In other
ther object is-to provide improved means. for
words, ourob-ject is to provide a closed system and
Washing wax cake, discharging the“ washed cake
from the leaves, and utilizing ‘the used wash
means for regulating the pressure in all parts of
the‘ system so that leakage of propane will be pre
us vented. We want to avoid the necessity for open
ing ?lters and this means, in turn, that we must
provide a system whereby the ?lter leaves will not
propane in the system.
points, and to obtain wax which is substantially
oil free. Other objects will be apparent‘as the
detailed description of our invention proceeds. . >
Certain features of our invention maybe briefly <20
£20 ?lters that will ?t into a specially designed ?lter
system to accomplish the continuous dewaxing of
.characterized as‘ follows: In the ?rst place, ‘we
employ a dewaxing system which is tied together
by a gas‘ line, all parts of said system being op
oil in a closed system which will‘not‘ have to be
frequently interrupted for repair or cleaning.
A further object of our invention is to provide
7,25 an ‘improved system and method of-chilling di
luted oil-wax mixtures so thatthe optimum wax ,
Wcrystal formation may be obtained.
A further objectis to obtain improved ‘lubri- z31'5
eating oils having high ?ash points and low pour
become clogged with amorphous or ?nely divided
wax. Our object is to provide a special design for
A further object is to provide an improved
cants’ copending application ,No. 599,730, ?led
In other
eratively connected with said line. Vaporized
propane from- all parts of the system are sucked (25
from this line by suitable pumps, compressed, con
densed and returned to storage for re-use.‘ This
tying. together of the whole system by suction
. words,. we wantv to determine the sequence of
steps, the'relative volumes of diluent refrigerant
gas lines insures safety, and at the same timerit'
and waxy oil in the several steps‘, the optimum
‘manner and rate of cooling,‘ and the method of
enables the temperature of each ‘respective ele'-' {30
.ment of the combination to be separately con
trolled in a very simple and expeditious manner.
handling’ the crystals ‘which will prevent them‘
‘from being macerated or deformed prior to; ?ltrae 'In other words, the tying together of thewhole
tion. The particularmethod of crystal formation dewaxing system with a suction gas line makes
and the method of handling these crystals is of it possibleto employ volatile and expensive re- $35
,great importance in a commercial dewaxing sys . frigerants and diluents which were heretofore too
dangerous for commercial use and makes it pos
sible to improve the operation of ?lters, chillers,
; ~ A ‘further object of our invention is to provide a
etc. so that the operation is uninterrupted over a
system for [obtaining maximum mechanical,
thermal, and operating efficiency. .Wewant-to
long period of time.
arrange heat exchangers and chillers so that it '
, will be possibleto abstract all of the heat ‘from
wax-bearing oil without the use of the conven
tional wax chillers whereinscrapers are neces
a :45
sary for removing wax from cold walls. ‘We also
want to obtain the'maximum bene?t from the
Another feature of our invention is the com
bination with our suction gas line of an improved, .
closed vertical ?lter in which reverse flow and
pressure regulation co-act to remove the ?lter
cake and clean the ?lter cloth. Another feature
of our invention is the combination of “wash pro
low temperatures of dewaxed oil and diluent'so pane” and “used wash propane”. tanks‘with the
‘that the expense of refrigeration may be reduced chillers and ?lters so thatpractically all of the
to a minimum.
Affurther object is to provide improved means
for eliminating water from all parts of the sys
I A further object is to provide an improved
"method and‘means for chilling the oil-wax mix
ture to obtain readily ?lterable wax crystals, for
oil can be removed from the wax without the re
melting or redissolving the same in oil or diluent. 150‘
.Another feature is our improved heat exchange
' system whereby cold oil-diluent mixtures are used
to coolthe waxy oil without the formation of wax
crystals on the sides ‘of containers so that the
vuse of scrapers is avoided.
Another feature of our invention is the use of
propane may be selectively removed from one of
liquid traps for removing water from the system
these storage chambers through line l4, passed
and for preventing liquids from entering the com
pressors. A further feature is the provision of
safety means to adequately relieve the system of
through heat exchanger l5, and thence into wash
tank I6. The propane is usually at a tempera
ture of 95° F. in line H! and it is cooled in ex
changer E5 to a temperature of about —20° F.
propane gas in case of failure of condenser, Water
The propane in Wash tank I6 is cooled to a tem
Another feature of our invention is the im
perature of -—40° F. by the evaporation of a part
proved system of chillers, ?lter supply tanks and
of the propane, vapors being removed from the
tank through conduit I1 and line E8 to compressor 10
I9 which is designed to maintain atmospheric
pressure in line is. The gases may then be passed
through pipe 20 to compressor 2| which boosts
10 connections from said chillers and supply tanks to ,
the other elements of the system.
' -
Another feature of our invention isithe use of
two banks of ?lters with separate charging
means therefor and with means for obtaining
15 maximum ?exibility of operationhwith a mini
mum number of connecting lines.
them to a pressure of about 200 pounds, or com
pressor I9 may be designed to boost them to this 15
pressure, in which case compressor 2! is cut out
by pipe 22. We prefer to use compressor H! as a
holding compressor and compressor 2! as a chill
ing compressor, as will be hereinafter described.
In any case, ‘the highly compressed vapors are 20
Another fea- ‘
ture is the use of the Wax discharge means as a
means for introducing wax slurry into the ?lter.
A most important feature of our invention is
the method of operating the chilling and the
?ltering system.
The, invention will be more clearly understood
passed through line 23 and condensers 24 back
.to storage tanks I2. The cold propane from Wash
tank I6 is pumped through pipe 25 by pump 26 to
from the following description taken in connec
tion with the accompanying drawings which form
25 a part of the speci?cation and in which similar
parts are designated by like reference characters
throughout the several views. In these drawings:
Figure 1 is a diagrammatic plan of our entire
the ?lter system.
The wax-bearing oil is pumped from storage 25
tank 21 by pump 28 through one branch of pipe
Figure 2 is a modi?cation of the system illus
trated in Figure 1 showing additional liquid trap
out systems and improved chilling and ?ltering
Our invention will be described as used for the
35 separation of wax'from a treated distillate lubri
cating oil from Mid-Continent crude petroleum,
the particular distillate having a viscosity of
about 100 seconds Saybolt at 210° F. and an
A. P. I, gravity of 21.3. It should be understood,
40 however, that the invention is equally applicable
to any wax-bearing oils.
In the description of our preferred embodiment
we will disclose the use of commercial propane
as a combined diluent and refrigerant. It should
45 be understood that other normally gaseous hy
drocarbons, such as butane, isobutane, butylene,
ethane, ethylene, propane, propylene, etc. may be
used either separately or in admixture with each
other. The waxy oil may be diluted all through
50 the system with a smallamount of ?lter naphtha
or other light oil which may be useful as a vis
cosity breaker.
Instead of using, normally gas
eous hydrocarbons we may use normally gas
eous ethers such as methyl ether or we may use
55 chlorinated or ?uorinated hydrocarbons such as
methyl chloride or dichlor-di?uor-methane or
oxygenated compounds such as ethylene oxide;
the last named substances are useful in the de
Waxing process because they have a tendency
.60 to throw wax out of solution. We may use nor
mally liquid antisolvents for wax, such as ace
tone, acid esters, etc; or mixtures of liquid anti
solvents with miscibility agents such as benzene
or mixtures of benzene with naphtha. If liquids
of this type are mixed with the oil they may be
considered in the following description as a part
of the oil. In our preferred embodiment we effect
practically complete dewaxing of the oil by the
use of commercial propane. ‘
The propane enters the system through line
I0 and is introduced by pipes H into storage
tanks l2 which are designed to hold the propane
at temperatures as high as‘ 95° F. at which tem
perature the propane may exert a pressure of 165
117:5 pounds gauge (above atmospheric).
The liquid
29 into one of the gauging tanks 30, one of these
tanks being ?lled While the other is being emp
tied. ‘The oil from the gauging tanks is trans
ferred by pump 3! to mixer 32 where it is mixed 30
with propane, forced by pump 33 through pipe
34, and the mixture of waxy oil and propane
is cooled in exchanger 35 to a temperature of
about 90° F. to 100° F., this temperature being
preferably selected so that the wax will be com
pletely dissolved in the diluted oil.‘ The mixture
of wax and diluent is then selectively introduced
through one of the pipes 36 into one of the chill
chambers A, B, C, or D. When one of these
chambers is about one-third to three-fourths full
the ?ow thereto is cut off and the propane-oil
mixture is introduced into the following cham
ber. While this mixture is being charged into
the tank the vapor outlets 3‘! and 38 are prefer
ably closed so that no appreciable cooling by
evaporation of diluent takes place, and the tanks
are warmed up prior to being ?lled so that “shook
chilling” will be avoided. ‘
The cooling of the oil to effect precipitation of
wax in ?lterable form is not as simple a matter 50
as it might appear. In the ?rst place, oil and
'wax should be in complete solution in the pro
pane before‘the chilling is initiated and since a
chiller which has just been emptied is very cold,
it is necessary to warm up this chiller before add 55
ing a new batch of propane-oil-wax solution.
The bulk of wax precipitates as the solution is
cooled from 100° F. to- about 30° or 0° F. and
cooling throughout this range is effected by the
withdrawal of propane vapors by means of chill 60
ing compressor 2!. At this. time cold “used wash
propane” is introduced into the chiller through
line 39 to make up propane lost through vaporiza
tion and to supply additional‘refrigeration. The
cooled slurry should have about two volumes of 65
propane per volume of oil when the temperature
reaches —40° F. After the introduction of the
cold used propane the ‘evaporative refrigeration is
continued, the propane vapors being discharged --70
through line 40 into compressor 2| and thence to
the condensers 24 and back to storage chambers
12. When the temperature has been reduced to
about —40". F. the vapor outlet conduit 31 is
‘closed. and outlet 33 is opened to vent the chill .575
chamber to the suction gas line and the holding
throughheat exchanger ‘H and heat exchanger
12 to the top plate of the oil heater 13. Heat'may
At about -40° F. the wax slurry is withdrawn -be supplied thereto by steam‘coil 14 so that a
‘through one of the pipes 4|, pump 42, line 43, temperature ofabout 235°, F. at a pressure of 2.00
"and one of the feed pipes 44 to ?lter L, M or N. . pounds is maintained in the heater. Oil is .with- 5.5
‘ The ?lters which are diagrammatically shown in drawnfrom the base of the heater; by pipe 15
the drawings are‘vertical cylinders'containing a > through a regulating. valve 16 to lowpressure
:ilplurality of stationaryv ?lter .leaves, .but it..:.should .?ash drum TI; Regulating valve 16 is automat
.be ‘understood that we may employ continuous ically ‘controlled to maintain a constant. liquid
?lters or ?lters of any» other type which are ‘ level in heater ‘[3. Propane‘ vapors are removedllo
known to the art. The transfer pump 42 should from the ?ash drum to line l8. The oil from the
be of a type which will not unduly macerate‘ or base of the ?ash drum is passed in amounts regu
‘ vbreak up the wax crystals and, in fact, it maybe lated by liquid level control valve 18 into steam
desirable to employ ?uid pressure to, charge the stripping chamber 19 where it is stripped‘ with
?lters or to maintain the chillers and ?lter sup
"steam or other suitable gas.
The steam is with- :15v
plies ata sufficiently elevated position so that the , drawn throughexchanger ‘H. and thence to jet
'liquid head will afford the necessary ?lter pres . condenser .80,—-the liberated propane being re
Filtrate is withdrawn from. the ?lters by
meansof one of the pipes 45, each of which is
connected with header 45. The clear ?ltrate is
then conveyed‘ by gravity through pipes 41 to
?ltrate receiver 48. 'When a su?icient cake is
deposited on the ?lter elements the oil mixture
.is introduced into the next ?lter. or bank of ?lters
‘and the cake in the ?rst ?lter is washed with
propane from wash tank l6, line 25, pump 26 and
one of the feed pipes .49. When the ?lters are be
ing washed with propane the so-called “wash pro;
pane” ?ltrate passes by gravity through pipes 50
30 to “used Wash tank” 5| from which it is trans
ferred by pump 52 into pipes 39. The propane
vin-the “used wash tank” 5| is maintained. at
—40° F. by the vaporization of a partthereof,
‘turned to line. I 8.
The oil from the base of the.‘stripper'lais'withj
drawn through heat exchanger 12 and to oill'20
I storage tank. 8 I.
It will be observed from, the above description
thatuthe ‘chill chambers,. unused wash propane,
used wash‘ propane, ?ltrate receivers and wax
pumping drum are all maintained at temperatures; 25
slightly below dewaxingtemperatures- by the di
rect vaporization-of propane, these vapors being
Withdrawn bypropane line l8 and compressed in
. compressor I!) to about. 200 pounds. -It' will be
‘understood that suitable valves or pressure regu-mll)
‘lating means will be installed betweenfthevarious
:tanks, ?lters,,i chillers, etc. and gas line 18. - The
> chill‘ chambers, ?ltrate receivers and wax pump
the vapors being removed through pipe 53.. to I ing drum will tend to have a temperature, sub- ,
line l8.
stantia'lly equal to the dewaxing temperature,< 35
We connect the ?lters to line l8 by valved pipes,
'54. These valves are closed during actual ?lter
operation, but for purposes of cooling the ?lter or
removing the ?lter cake,. the valves may be‘
Wax is removed from the base of the ?lter in
the manner hereinafter described through one of
pipes 55,. thence through pipe 56 to wax pump
ing drum v5'I. _‘ The wax lines are preferably large
conduits provided-with screw conveyors although
in some instances the'wax slurry may be pumped
by ordinary methods. Wax from drum 51 is
. while the unused wash propane andused wash
.apropanerwill havev a temperature slightly lower
than the dewaxing temperature on account of the‘
vapor pressure of pure propane being higher than '
that. of . a mixture.
Temperatures may be con-(‘x40
trolled, however, by'regulating the valves leading
I to line l8._
If the pressure in the system exceeds about 200
pounds-itwill be released through pressure ‘re
lease valves on the stills or on the lines connectedIAEi
thereto, which valves are preferably connected to
vent or fuel line 82.‘ Pressure release valves on '.
forced by pump ‘58 into high pressure heater 59 . the diluent storage tank are preferably set to open ‘
which is maintained under a pressure of about at about 165 pounds pressure and these valves are
2.50 200 pounds gauge. Steam coil 60 maintains a’ likewise connected to the vent or fuel line. Wez150
temperature in the heater of about 235° F. 1 have diagrammatically illustrated a pressure re
‘Liquid wax, together withlsome propane, is with-“ . lease valve 83 in line 82, but it should be under
drawn from‘ the base of the heater through pipe stood that similar valves will be used wherever
BI and passes through regulating valve‘ 62 into "safety requires them. Pressure in the storage
,55 atmospheric ?ash drum '53. Valve‘ 62 is auto-. tanks I2 is usually about 150 pounds to 165155
matically controlled to maintain a constant liquid - pounds gauge and use mayjbemade of this-pres- '
level in heater 59. vThe propane vaporized in wax ; sure to blow the ?lter cake from the ?lter leaves
heater 59 is withdrawn through pipe 23~which (-as will be hereinafter described), the propane
leads directly to condensers 24. Propane from
atmospheric ?ash drum 63 is withdrawn to line l8.
The wax from the based the ?ash chamber is
gas‘bei'ng conducted through line 84 to the rem60
spective ?ltrate dischargepipes 45, suitable by-“f
passes and valves being provided so that propane
withdrawn in amounts controlled by liquid level ;- can. be used to discharge the ?lter cake, without
operated valve 64 and'i'ntroduced into wax strip
per ‘65 in which, steam or other suitable stripping
gas may be injected; The stearnfrom the top of
the stripper. is condensed by thejwater in- jet con
‘ interfering with the normal ?ltrate discharge. '
If'desired, propane from line' 23 may be lily-(3365
passed into line 84 by line 85. When gasis used
‘ denser 66, the liberated propane being‘ vented to _ to ‘blow back. the?lter cake there will v‘be a con
Tpropane line I8. Finally the wax which has been densation of propane in the ?lter cloth due to its
freed from oil and propane is forced by pump 61 .cold temperature, andthere will be an almost
"instantaneous boiling or revaporizatio-n ‘of ‘this-‘70
through cooler 68 into storage tank 69.
Returning to the ?ltrate in tanks? 48, this propane due to the low pressure on the other side
?ltrate is withdrawn through one of pipes 10 and ‘of the ?lter cakeand, as a¥result, the ?lter cake'is
2 . "pump 10a to heat exchanger [5 wherein it cools quickly and thoroughly removed from the ?lter
the incoming propane which is» to be used in. cloth' and the cloth iswashed by‘ the reversed'i?ow
:75‘ washing the ?lters. The ?ltrate then passes of ‘propane. The same end may be ‘accomplished? .75
"by the reverse ?ow of a ‘slight amount‘of ‘used .passed through line I06 to water trapout tank
wash propane liquid.
ID‘! from which the water is withdrawn through
The ?lters may be either of the vertical cylin .1 line I08 in amounts regulated by liquid level con
drical batch type diagrammatically illustrated in trolled valve I09. Propane from trap IN is with
0% the drawings or they may be of the continuous .drawn through line H0 to Wash tank I6 and L35
pressure rotary type. In either case they will be through line! I I topump 33, line 3d and mixer 32
designed to Withstand considerable pressure, they .as- hereinabove described. Any Water or other
will be heavily insulated and they will be provided immiscible liquid impurity is thus separated from
with means for steaming or washing out the pro . the propane before itis discharged into the plant.
pane therefrom prior to opening for repair or
The next distinguishing feature of Figure 2 isI-‘10
replacement so that there will be no hazard from the arrangement and operation of the chilling
escaping propane gas.
Filtration is continued until a cake about 1/2”
to 1" is built up on the leaf, at which time the
system. The warm propane-oil-wax mixture
from cooler 35 and .line 36 is introduced through
lines H2 to one of a plurality of chillers A, B.
flow of the wax slurry is stopped by closing outlet
In actual commercial use we have found thatelc
valves in line 45, and the wash propane from tank
I6 is introduced at the top of the ?lter through
line 49a. The ?ow of this liquid propane is con
tinued until all of the un?ltered oil in the ?lter
three of such chillers give excellent results, -al
though it should be understood that any .number
may be used. The upper-parts of these chillers
are connected through gas line II 3 so that if
chiller A has just been emptied and chiller B has-‘J20
just been ?lled, the vapor line I I3 between these
chillers may be opened and propane may be
boiled out of chiller B and condensed in chiller. A
thereby warming the latter chiller suf?ciently to
is forced back (through by-pass 42a‘) to the
chillers by displacement. The ?ow of the wash
propane is then changed so as to enter the ?lter
at the bottom and to pass through the wax cake
and the ?lter leaves and out through line 45. The
25 flow of this propane is continued until practically ‘ prevent shock chilling when the propane-oilewaxl‘l-25
all of the oil is washed out of the wax cake. The solution is introduced into it. When equilibrium
?rst wash propane may contain large amounts of has been established between the two chillers, this
oil and it may therefore be discharged with the vapor line isv closed, and propane vapors are re
?ltrate into ?ltrate receivers 48 through pipes 41. moved from the ?lled chiller through .lines 31
30 Later amounts of wash propane are removed from
and 00. When the temperature in this chillerff30
the ?lter leaves through pipe 50 to “used wash ~ for instance chiller B, reaches about 0° to 30° F.,
propane” tank 5|. Propane from the lattertank, cold used propane is introduced into it through
as stated above, is used for diluting incoming lines 39. and H2. The ?nal chilling is. then
waxy oil in chillers A, B, C, etc.
effected by evaporative cooling and when a tem
Finally the ?oW of wash propane from tank I6 perature of —40° F. is reached the wax slurry isi~35
is stopped and the remaining propane liquid .is
pumped from the bottom of the ?lter back-to
wash tank I6. During this operation. a_ small
pressure is maintained inside the ?lter (outside
1" 40 of the leaves) by means of vapors admitted
through lines 84 and 54. To remove the ?lter
, cake we may employ a reverse ?ow of wash pro
pane or we may employ gas from'line 84.
either case, liquid propane will be formed in the
145 ?lter medium and it will be violently expanded by
Withdrawn by opening line M and withdrawing
the cold slurry through main I I0, pipe I I5, main
H6 and pipes II‘! to one of the ?lter supply
tanks H8.
As soon as chiller B is thus emptied
the vapors from chiller A are condensed into ittim
through. line H3 until it is warmed up and then
. additional propane-oil-wax solution is introduced
into it through line‘ I I2.
From the above descriptionit will be seen that
the slurry is ?rst chill-ed by evaporative cooling,».45
opening the valve in pipe 54, this expansion caus
ing the immediate and thorough removal of the
cake from the leaf. The ?lter cake is directed
by the hopper bottom 88 into an enlarged con—
preferably at a rate of about 1/2° to 4° F. per
minute, it is then chilled and diluted by means
of used wash propane and it is ?nally chilled by
duit 56 wherein a screw conveys it to wax sump
supply tank. Before transferring the slurry frome50
evaporative cooling and dropped into the ?lter
5'1. If desired, a spray of liquid propane may be , chiller B to ?lter supply tank I I8, we preferably
used to assist in washing the outside of the leaves. I connect the vapor spaces of these two tanks
Precoats or ?lter aids may be employed to in
through line H9 so that they will be in equilib
crease ?lter rates and prevent clogging. Some rium both as to temperature and pressure when
oils are readily dewaxed with the ordinary ?lter I the slurry is transferred and so that there willh55
elements, but other oils show a “cloud” at low be no shock chilling.- Lines I20 are also con
temperatures after dewaxing. It is highly desir
able that lubricating oil should be “zero-bright.”
Therefore, in some cases we make a slurry of
infusorial earth or other ?lter-aid in propane or
nectedto the top of the ?lter supply tanks and
are‘connected to each other through line I2I so
thatqthis system may be used to equalize the
pressure on ?lter supply tanks as well as to re-mo
light oil, and apply a precoat to the ?lter by - turn ‘cold slurry from the ?lter system back to
spraying or by passing some of the liquid through ‘ the ?lter vsupply tanks. The multiplicity of pipes
the ?lter. Other ?brous or crystalline ?lter aids and valves need not be described in detail, but it
may be used, either as a precoat or admixed with a will be apparent that each chiller may be con
the wax slurry.
nected to‘ chillingvcompressor 2! through lines£Z65
In'the chilling step we may simultaneously re
31 and .40, they may be connected to holding
move propane vapors and add propane liquid to . compressor I9 through line 38, they may be con
the‘ chillers, we may cool by evaporating propane nectedvto each other through line H3, or they
and subsequently adding more cold propane, or qmay be connected to the upper part of ?lter '
7-70 we may add all of the propane before we start supply tanks through lines I IS. The warm pro-i1 70
to chill by evaporation. Our preferred method pane solution may be introduced'into each chiller
of cooling and of operating the ?lter system will K through line 30 and cold used propane may be
now be described in connection with Figure 2.
.introduced thereto through line 39. Slurry from
In the modi?cation shown in Figure 2, the ,pro
any chiller maybe selectively introduced into any
75 pane which is withdrawn from , storage is?rst ?lter supply tankand slurryfromthe ?lter- sys-Ei 15
I38 and I39'to manifold 46 and through lines
tem may be returned to any desired ?lter supply
I38 and I39A to manifold 46A.
It is sometimes desirable to recirculate slurry
from the ?lters back to the ?lter supply tank‘
and for this purpose we employ line I40 which is
connected to manifold I33 through line MI and
Referring now to _ the ?lter system, we have
again diagrammaticallyv shown the use of vertical
. batch ?lters L, M, LL and'MM.
It will be ob
served that the‘?rst two of these filters are con
to manifold I33A through line I4IA. When the
?lter operation is just beginning and the cake is
being formed on the leaves, it may be desirable
. nected in parallel to operate as one bank while
the second two are connected in parallel to oper
ate as another bank. We preferably have four
to have valve I42 open, but as soon as the cake
is built up and a clear ?ltrate is being obtained.
valve £42 may be closed so that the pump which
is. forcing the slurry into the?lter may build up
a-Ipressure of about 50. pounds per square inch
?lters in each bank, but it should be understood
that any number of batch or continuous ?lters
may be, employed "in either bank. Slurry from
?lter supply tanks H8 .is transferred through
line II'I, line I,I,6, line.'I22, pump I23 and line I24
on the-?ltering surface. If the pressure exceeds 15,.
wax discharge line 56, which is used as a
I 15. to
conduit for-introducing this slurry into theibase
' of the ?lters,’
this value, valve ‘I42 maybe slightly opened.
_ The ?lter leaves in ?lters L and M are con
When continuous ?lters are-used,
nected through lines 45 ‘and 46 to ?ltrateline 41
and ?ltrate collector .48; similarly, ?ltrate from
?lters LL and MM pass through lines 45A, 46A
and 41. Cloudy ?ltrate from manifold 46 may be
passed through lines I43 and I44 to line I3I
it will be understood that line I24 will lead to
the wax slurry reservoir in the ?lter chamber.
2.0? For charging wax slurry to the other bank- of
?lters, the slurry is passed through ‘line I25, pump
' I26 and line I 21 to line 56A, which likewise serves
as a wax discharge pipe;
supply tank. Likewise, cloudy ?ltrate from mani
fold 46A may be passed through line i43A to I44
and thence back to the ?lter supply tank. Al
ternatively, the cloudy ?ltrate may be passed from
?lter elements ‘and it is desired to wash the oil
\out ‘of said cake, fresh cold propane from wash
tank I6 is introduced‘ through line 25, line I28,
46A through line 56A back to the used wash
3.9 1
The operation of our ?lter system may be de—~
scribed as follows: The ?lters are ?rst cooled,
preferably by passing cold oil through them or
evaporating, propane in them. Chilled wax slurry
is then-forced throughv line H6 by pump I23 3.5 ;
manifold 46 through line 50 or from manifold
pump I23 and line I24 to ?lters L and M or
through line I29, pump I26 and line‘ I2'I to ?lters
3.0 . LL and MM.
through which it maybe returned to the ?lter
.When a ?lter cake has been built up on the
tank 5|.
. When it is desired to'withdraw wax slurry
from the base of the ?lters, this material may be,
withdrawn through line 56, line I30, pump I23,
line I24v and line I3I .through which it may be
returned to the ?lter supply tanks I I8. Likewise,
slurry from the base of ?lters LL or M may be
- withdrawn through line 56A, line I36A, pump I26,
through lines I24, 56 and 55 into ?lters L and M. .
The slurry is allowed to ?ll the ?lters and to
overflow through lines 54 into manifold I33,>
line I21 and line I3IA which joins with line I3I
and returns to the ?lter supply tanksj If it is ’ thence through recirculating lines I4I and I46
back to the ?lter supply tanks. The initial
' at
desired to empty wash propane out of the ‘?lters,
be cloudy and it may therefore be
the wash propane is withdrawn through line 56, Y ?ltrate‘may
manifold 46 through lines I43
line I30, pump I23, line I24 and line I32 to line
and I44 back to the ?lter supply tank. As soon
propane from ?lters LL and MM may be passed , as the sight glasses on the ?ltrate lines indicate
I ‘ 25 which leads. to wash tank I6.
that it is clear, the valve .in line I43¢is closed and 4.5.
the valve to line 41 is opened allowing the ?ltrate
through line 56A, line I36A, pumpMI26, line I2‘I_
‘ and line I32A, which leads into line I32 for re
to be passed to they ?ltrate collectors 48. ' At this
turning the wash propane to wash tank I6.
If it is desired to introduce wax slurry or wash
propane into the ?lters at the top instead of at
, 59;; the bottom, this may be" accomplished by open
ing the valve in line I33v so that pump I23 may
time the valves in line 54 are'closed so that the
pressure is gradually; built up in the ?lters'to
about 50 pounds per square inch. In about 20
minutes a cake of about 1/2"’ to 1" thick is built
upon the leaves.
force the liquids through line I24 and then
through‘ line I33 which’ acts as a manifold to
whichv ?lters'L and M in the ?rst bank arecony
Similarly, pump ' I26 can .force liquids
through line I27 and line I33A into the upper
' '
_ When the cake of desired thickness has been a
built up, the wax slurry in the ?lters is displaced,
preferably by Propane gas from lines 84, I35 and 5.,51
I33, the .valves in lines 54 being opened for this '
purpose. The displaced wax slurry is withdrawn ’
of ?lters
and MM. by line I34 with'low ' through line 56 and may either be forced back
pressure gas line I8 and this low pressure gas line
is likewise connected to manifold I33A through
line I34A. Thus, positive connection may be made
between the low pressure gas line‘ and the shell of
any ?lter through lines 54, I33 and I34 or lines
I33A and
Manifold‘ I33>is also connected to high pressure
'or blowing gas line 84 through line-I35 and mani
fold I33A is connected thereto through line I35A.
For removing wax ‘cake from the ?lter leaves
it is desirable to vblowyback with propane gas.
“ The ?lter leaves are connected to the low pressure
gas line I8 through lines I36 and I3‘Iywhich lead
to the ?lter supply tank through line‘ I30, pump
I 23, line I24 and line -I3I or may be forced di
rectly back to the ?lter supply tank through lines
56, line I24 and line I3I bythe propane pressure.
The pressure of the propane gas maintains the
wax cake on the ?lter leaves and although a
"small amount of the propane is condensed by the 6.5..
cold wax cake 'we have found that in a short
time interval the condensation is not appreciable.
As soon as the wax slurry has been displaced‘
from the ?lters, cold fresh propane from‘wash
tank. I6 is forced through line'25, line I23, pump‘
ing, the oil out of the ?lter cake onithe leaves.
‘ to manifold 46 and lines I36 and I3'IA which ' The ?rst wash liquid may contain a large amount
lead to manifold 46A. The high pressure or of oil and practically no wax so that it may be
75: blowing gas line 84 is connected through [lines
I23, line I24 and line 56 into the ?lters for wash
passed throughnmanifold46 and line 41 to the 7.5.
?ltrate collector. The bulk of the wash propane
part of the propane storage tanks because'the
is, however, passed through manifold 46 and line
gas therein contains a larger amount of ethane
or a larger amount of air or inert gas and there
50 to the used wash propane tank, from which
tank it is withdrawn at intervals to supply the
chillers as hereinabove described. When the oil
has been washed out of the wax cake, the valves
in lines 54, which were closed during the washing
step, are now opened again and propane gas is
employed to displace the propane from the ?lters
10 back to the fresh cold propane tank I6. This,
again, may be accomplished by direct gas pressure
or it may be accomplished by means of pump
I23 and lines I24 and I32.
Instead of employing propane gas to displace
15 the wax slurry, we may introduce liquid propane
through line I33 from the top of the ?lters while
We are displacing wax slurry from the base there
of through lines I24 and I3I back to the ?lter
supply tank. Instead of introducing wash pro
20 pane at the top and displacing the slurry from
the bottom of the ?lters, we may merely substi
tute the wash propane for the wax slurry which
is being introduced at the base of the ?lter and
We may return the wax slurry to the ?lter supply
25 tank through the recirculating line I40.
modi?cations in operating procedure will be ap
parent from the detailed arrangement of valves,
lines and pumps shown in Figure 2.
When all of the wash liquid has been displaced
30 from the ?lter in the presence of sufficient pro
pane gas pressure to hold the cake on the leaves,
propane gas from lines 84, I36, I31, 46 and 45 is
intermittently blown back from the ?ltrate side
to cause a distending of the ?lter element and
35 the removal of the wax cake therefrom. We may
employ liquid propane for removing the wax
from the cakes, but this is undesirable because it
necessitates an undue amount of propane recov
_ cry.
The wax cake which is discharged from the
fore is less condensible.
The pressure in line 84
may be regulated on the ?lter side of a pressure
reducing valve, as illustrated in Figure l. The ?l
tration pressure has been described as 50 pounds
per square inch, but we may employ pressures as
high as 100 or 150 pounds per ‘square inch.
The ?lters are provided with connections
through which they may be washed out at inter
vals with a warm wax solvent, but since the draw
ings are already quite complicated, the additional
wax solvent washing line will not be illustrated.
Likewise, the ?lters are preferably provided with 15'
steam connections so that they may be steamed
out prior to being opened. Other modi?cations
in operating procedure will be apparent from the
detailed arrangement of valves, lines and pumps
shown in Figure 2‘.
It is desirable in any dewaxing process that
rapid and ef?cient separation of oil from wax be
obtained and this in turn necessitates a careful
regulation of wax crystallizing and ?ltering oper
ations. The wax should be completely dissolved 25
in propane before chilling is commenced and at
no time subsequent to this complete solution step
should the mixture be shock chilled, i. e., come in
contact with any liquid or equipment at a much
lower temperature or be suddenly released from 30
a high pressure into a zone of substantially lower
We have found that the chilling should be‘
effected in three steps: First, the vapor space of
a chiller containing warm solution should be con 35
nected to the vapor space of a cold chiller which’
has just been emptied so that the solution is
chilled by evaporative cooling as the pressures
are‘equalized. Cooling may then be continued
by operating the variable compressor 2| until a
temperature of 30° F. to 0° is reached. Next, the,
40" ?lter elements is conveyed by screw conveyors in
line 56 to wax sump 51, as hereinabove described.
This bank of ?lters is now ready to repeat the 7 cold wash propane (propane which may contain
?ltering operation. The other bank of ?lters some wax or oil) is added at a temperature which
operates in the same manner andfurther de
is lower than that of the wax mixture, butwhich
scription is deemed unnecessary.
We have already described the trap for re
moving water from propane entering the system,
but since steam is usedto strip propane gas in.
‘ the low pressure oil and wax stills, it is necessary
to use special precautions tov keep additional
water from entering the system. The propane
gas from the steam stripping stills is introduced
through line I46 into jet condenser 66 and water
is introduced through line It? at the upper part
The water and condensed steam are
Withdrawn from the base of this jet condenser
through line I48 and We preferably employ a
liquid level controller I49 which may be a simple
, ?oat which mechanically or electrically operates
60 the discharge valve in line I48. Propane gas from
the upper part of the jet condenser is withdrawn
by compressor I50 and forced through line I 5| to
vent 82, high pressure gas line 23 or low pressure
gas line I8.
Another feature of our system is the use of a
liquid trap I52 in line I8 on the suction side of
holding compressor IS. A constant liquid level
may be maintained in this trap by a suitable ?oat
control which operates valve I53 in liquid dis
is not low enough to produce shock chilling. This
makes it possible to utilize effectively the refrig
eration available through. heat exchange and
minimizes the volume of propane which. must be
distilled and recondensed.
The ?nal chilling to -
about —/l0° F. is effectedby evaporative cooling
by means of variable compressor _2I. While we
prefer to use this method of cooling, it should be
understood that the cooling may be effected ,by
conventional heat exchangers or any other means‘
without losing other advantages of our invention 55
hereinabove and hereinafter pointed out.
We have found that it is very desirable to ?lter
the crystallized wax as soon as possible after it
has been chilled to ?ltering temperature. If the
chilled slurry is held for too long a time in ?lter 60
supply tanks H8, we have found that ?ltration‘is'
more di?icult and that yields are decreased.‘ The
?lter supply tank should be well insulated so that
none of the solidi?ed wax will be redissolved and
all valves leading to and from the supply tank
should be extremely tight so that there will not
be any leakage through ?lter valves which would
cause shock chilling and which would thereby
charge pipe I56. This liquid will usually consist
impair ?lter rates.
of propane and it may be returned to one of the
ciprocating block valve pump is quite satisfactory
for transferring slurry from the ?lter supply tank
diluent storage tanks or to the chiller, ?lter sup
ply tanks or other cold propane tanks.
The supply of propane gas for blowing. the
presses is preferably obtained from the upper
We have found that a re
to the ?lters, but even better results may be ob
tained by employing ?uid pressure, such as com
pressed nitrogen, ethane or other gas, for forcing
' 7
tively transferring liquid from said ?lter element
the slurry into the ?lters. Where continuous to said ?ltrate collector or said ?lter supply tank.
?lters are employed'and a relatively low pressure
3. The apparatus of claim 2 which‘ includes a
differential is sufficient, we mount the chillers _ used wash propanetank, means for transferring
and ?lter supply tanks at a higher level than the
liquid from said ?lter element to said tank, and $1
?lters so that the liquid head, due to difference means for transferring liquid from said tank to
in elevation, will be suflicient to force the diluted
oil through the ?lter element.
said closed pressure chilling tank.
4. The apparatus of claim 2 wherein the ?lter
element is also selectively connected to a blow
back line leading from a source of propane gas; 10
5. In a propane dewaxing system wherein a
tillates we may add a small amount of a heavier ' waxy oil is dissolved in propane at elevated tem
lubricating oil stock, a small amount of asphaltic peratures and pressures, cooled to solidify the
material or a wax crystallization regulator of the
wax in readily separable form, mechanically sep
type prepared by condensing chlorinated wax and arated into wax and diluted oil and ?nally freed
naphthalene with aluminum chloride. Amounts from .the propane diluent, the step of periodically
of the latter material as low as .3% have been washing the separation means with kerosene for
found to increase dewaxed oil yields on S. A. E. removing propane and improving separation
Some light ,distillates may tend to give a floc
culent wax cake which is dif?cult to ?lter, giving
10 poor ?lter rates and low oil yields. To such dis
i 20 Mid-Continent distillate from 70% to 84% and i
at the same time have been found to double ?lter
20 rates.
An important feature of our ?lter structure is
the extreme ?exibility of its connections so that
a single pump and a minimum of conduits may
be employed to transfer all types of liquids and
slurries to and from then?lters of the several
storage and supply tanks. Another important
- rates.
6. In apparatus of the class described, a, pro
pane. storage tank, a chiller, a ?lter, a ?ltrate
collector, a low pressure gas line, means for mix- '
ing propane from said storage tank with waxy
oil, and for introducing said mixture into said
chiller, means for venting said chiller to said‘low
pressure gas line'to provide evaporative cooling
in the chiller, means for introducing slurry fromv
feature of the ?lter structure is the fact that , the chiller to said ?lter, means for ‘transferring
each of these ?lters is provided with a line I55 for ?ltrate from the-?lter to the ?ltrate collector, a '
introducing kerosene for washing out the?lters I connection from said ?ltrate collector‘ to said 1
30 before opening them. and/ or for introducing steam
low pressure gas line, a propane recovery system
to blow out all traces of propane.
From a safety
standpoint, it is highly necessary that precautions
and meansfor passing ?ltrate from said. col
be taken to prevent the formation of explosive
lector to said recovery system, means for strip
ping propane from oil with steam in said recov
ery system, means for condensing steam from
oil-propane mixtures.
While we have described in detail preferred
embodiments of our invention, it should be under- ‘
_ stood that we do not limit ourselves to the details
hereinabove set forth except as de?ned by the
following claims, which should be construed as
'40 broadly as the prior art will permit.
We claim:
1. In a propane dewaxing system wherein a
‘waxy oil is dissolved in propane at elevated tem
‘ peratures and pressures, cooled to solidify the
wax in readily separable form, mechanically sep
arated into wax and diluted oil and ?nally freed
from the propane diluent, a ?lter vessel contain
ing a ?lter element, a conduit for withdrawing
wax slurry from said ?lter vessel, positive means
for moving wax through said conduit and means
for forcing a wax slurry into said vessel through
the same conduit through which wax is removed
2. In a propane dewaxing system wherein a
waxy oil is dissolved in propane at elevated tem
peratures and pressures, cooled to solidify the
wax in readily separable form, mechanically sep
arated into wax and diluted oil and ?nally freed
from the propane diluent, a closed pressure chill
said‘stripping step, separating propane ‘therefrom
and returning the propane to said low pressure
gas line, a compressor and condenser connected
between said low pressure gas line and said pro
pane storage tank, a liquid trap interposed imme
diately in front of said compressor for trapping
out and removing any condensate which may col
lect in that part of the propane gas line connected
to the inlet side of the compressor, an inlet to
said trap connected with said low pressure gas 45
line, a connection from vthe upper part of said
trap to the inlet of said compressor, and means
for withdrawing liquid from the lower part of
said trap.
'7. A propane dewaxing system which comprises 50
a propane storage tank, a chiller, a ?lter supply
tank, a cold propane storage tank, a used propane
storage tank, a ?lter, a ?ltrate receiver, means.
for mixing propane from said storage tank with
waxy oil and for introducing said mixture into 55
said chiller, means for transferring cold slurry
to said ?lter supply tank, a pump with its inlet
selectively connected to said chiller, ?lter supply
tank, cold propane tank and ?lter shell, and with
its outlet connected to said ?lter shell, means for'
(30' ing tank, a ?lter supply tank connected with said passing ?ltrate from said ?lter selectively to said
chilling tank, a closed ?lter vessel, a ?lter ele- . ?ltrate collector, ‘to said ?lter supply tank or to
said used propane tank, means for passing pro‘
pane from said used propane tank to said chiller
inlet connections therefor separately connected and means for passing liquids from said ?lter
65 to said cold propane tank and said ?lter supply" to said ?lter supply tank respectively.
ment in said vessel, a fresh cold propane ‘tank, a
?ltrate collector means including a pump and
tank, respectively for selectively introducing into
said ?lter a slurry from said supply tank or fresh
‘ cold propane from said fresh cold propane tank,
means for returning slurry from said ?lter vessel
70 to said ?lter supply tank and means for selec
8. The system of claim 7 which includes a vent
line and a propane blow~back line both selectively
connected, to said ?lter.
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