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“3*
c. w. STRATFORD
2,126,420
METHOD FOR HEATING AND FRACTIONATING HYDROCARBON OILS ‘
' Filed Dec. 18, 1933
C57R6U/9DE
2 Sheets-Sheet 1
%
INVENTOR
‘
GM “Sf/‘afford
c. w. STRATFORD
2,126,420
METHOD FOR HEATING AND FRACTIONATING HYDROCARBON ‘OILS
Filed Dec. 18, 1935
2 Sheets-Sheet 2
ENVENTOR
-
CW. Sr‘rzvfora’
.13" ’» /
ATTOR “ EY
Patented Aug. 9, 1938
2,126,426
UNITED STATES
PATENT OFFICE
2,126,420
ll/IETHOD FOR HEATING AND- FRACTIONAT
ING HYDROC'ARBON OILS
Charles W. Stratford, Paris, France, assignor to
Stratford Development Corporation, Kansas
City, Mo., a corporation of Delaware
Application December 18, 1933, Serial No. 702,883
4 Claims.
My invention relates to a method for heat—
ing and fractionating hydrocarbon oils.
In the processes and apparatus of the prior
art wherein oil is heated and ?ashed into a
5 vlfractionating zone in a single ?ash operation,
dif?culty is experienced in obtaining maxi
mum yields of desired products. The charging
rate can be varied only through certain limits.
Diiferent types of crudes have di?erent boiling
10- ranges which fact makes it necessary to espe
a. The charging rate.
b. The type of oil.
Another object of my invention is to provide
a method of fractionating oils in which the re
boiling load may be varied from zero to the 5
maximum permitted by the capacity of the heater.
Another object of my invention is to provide a
method of operating a heater to clean it by flow
ing oil in such a manner as to preclude carbon
particular type of crude used in processes involv
ing conventional methods. When pipe stills are
deposition on the heating surfaces.
10
Another object of my invention is to provide
a fractionating method which will permit the
securing of maximum yields of desired products
used as a means for heating the oil, the furnace
of great uniformity and over a Wide range.
cially design fractionating‘ equipment for the
l5‘ temperature to which a pipe still must be ?red
is governed by the charging rate, the type of oil
charged and the amount of oil to be vaporized.
In fractionating problems where a number of re
boilers are used for supplying heat in the bottom
20 of the fractionating towers, the heat for reboiling
cannot readily be supplied by the pipe still which
heats the oil for fractionation, since varying
quantities of heat must be supplied for reboiling.
It will be seen that the present systems of heat
25‘ ing and fractionating oils are not ?exible. The
type of crude upon which they operate can be
varied only. within certain limits. The charging
rate at which the plant is to be operated can be
varied within comparatively narrow limits.
In heaters which employ brickwork, the re
fractory material becomes highly heated and,
when it is desired to shut down the furnace, it is
necessary to keep on circulating oil even after
the ?re has been extinguished. Then, too, in fur
35 naces employing brick work, the cost of main
taining the brick work is considerable, due to the
high temperatures of ?ring.
One object of my invention is to provide a
method of fractionating hydrocarbon oils which
40 vpossess flexibility of,
a. Control.
I). Desired products.
0. Charging rate.
4511
(Cl. 196-73)
(1. Charging stock.
Another object of my invention is to provide
a method of heating oil in which the oil flows
in a thin ?lm at progressively increasing velocity.
Another object of my invention is to provide
a novel method of furnishing the heat of reboil
‘ing which will permit a ?exibility and accurate
control.
Another object of my invention is to provide
a heating method having a high ei?ciency.
Anotherv object of my invention is to provide
55 ‘i a method for heating oil independent of,
In the accompanying drawings which form part 15'
of the instant speci?cation and which are to be
read in conjunction therewith and in which like
reference numerals are used in the various views
to represent like parts:
Figure 1 is a diagrammatic representation of
one mode of apparatus capable of carrying out
the process of my invention.
Figure 2 is a diagrammatic sectional elevation
of the heater used in my process.
Figure 3 is a sectional view taken on a line
25
3-3 of Figure 2.
Figure 4 is a sectional view taken on a line
4--4 of Figure 2.
Figure 5 is a sectional View taken on a line
5-5 of Figure 2.
30
Figure 6 is an enlarged fragmentary sectional
View of the portion of the heater shown in
Figure 2.
In general, my invention contemplates the es
tablishing of a circulating stream of a fairly 35
heavy oil from a reservoir through a heater and
back to the reservoir. The circulating oil is that
previously separated from the process and may
comprise a crude from which the desired lighter
products such as gasoline, naphtha, kerosene, and 40
gas oil have been removed. The absence of light
products insures that the oil may be heated to
desired temperatures without the formation of
vapors so- that the heater will always be operated
completely full of liquid precluding the formation
of vapor in the heater which would tend to insu
late the oil to be heated from the heating sur
faces. The stream of oil is circulated at high
velocity and at a constant rate. Another pump
takes suction from the reservoir and discharges
to any desired number of heating units through
which the oil to be heated passes in heat ex
change. From the various heating. units, the oil
is returned to the common reservoir.
It will be
seen that the quantity of oil passing through the
2
2,126,420
heater may remain constant while the reboiling
load may vary from zero to the maximum.
The heater comprises structure which will per
mit a mass of oil to be ?owed at high and pro
gressively increasing velocity toward the ?red end
of the heater. A convection section is ?tted to
the heater. The crude is charged through a
series of heat exchangers through the convec
tion section and into the ?rst fractionating tower
in which a desired light product such as gasoline
is removed. In the ?rst tower, the bottoms are
reboiled by means of heat supplied by a stream
of oil withdrawn from the reservoir. It will be
appreciated that in this manner close control
15 and great ?exibility are achieved.
By main
taining the bottom of the tower at a predeter
mined temperature, maximum yields of the de
sired product can be obtained. The partially
topped crude is then heated by heat exchange
20 with a second stream of oil drawn from the reser
voir, and passed into a second tower from which
a second desired product is withdrawn overhead.
The bottom of the tower is reboiled by a third
stream of oil withdrawn from the bottom of the
25 reservoir. The topped crude is then introduced
directly into the heated stream of oil which is
circulating from the heater. The oil is heated
to the desired point in the heater to permit of
the vaporization of gas oil and lighter fractions.
The quantity of oil flowing through the heater
is comparatively great in proportion to the topped
crude being admixed with the heated oil. The
hot oil will vaporize the gas oil fractions and those
lighter, and the admixed vapors and oil are sep
35 arated in a separating zone which is preferably
situated at the top of the reservoir. The un
vaporized oil will pass to the body of oil in the
reservoir. The vapors are taken overhead and
fractionated in a tower in which a desired light
product, as for example, a naphtha or kerosene,
may be recovered overhead while the heavier
products such as gas oil may be withdrawn at
any desired point.
The unvaporized condensate
bottoms of the tower are stripped either in an
external or internal stripping zone. The
45 stripped condensate bottoms may be then reheat
ed in a vacuum still for vacuum distillation as is
the customary practice, or otherwise processed.
More particularly referring now to the draw
ings, oil from the lower portion of separator
reservoir l is pumped by pump 2 through line 3
into the inlet ring 4 of the radiant section 5 of
the heater 6 which will be more fully described
hereinafter. The oil is withdrawn from the out
let 1 of the heater and passed through line 8 into
the upper portion of the separator reservoir I
through tangentially disposed inlet 9, through
spiral separator Ill. The oil collects in gutter I l,
over?ows on to humped plate l2 and rejoins the
body of oil [4 in the reservoir portion of tower
60
l. The oil circulation just described is continu
ous, the same quantity of oil being constantly
withdrawn and returned. The crude oil to be
fractionated, it being understood of course that
any oil may be used, crude being taken merely by
way of example, from storage tank I6, is pumped
by pump I‘! through heat exchanger I8, through
heat exchanger l9, through heat exchanger 25,
through heat exchanger 2|, through heat ex
70 changer 22, into the convection tubes 23 of the
heater from which it leaves through line 24 and
is discharged into fractionating tower 25. It
will be observed that the oil flows through the
various heat exchangers in counter?ow relation.
75 Vapors formed by the heating of the oil are re
moved from the fractionating tower 25 through
line 26, passed through heat exchanger !8,
through condenser 27, into separator 28.
In sep
arator 28 water is removed through line 25; gas
is vented through line 3:3 and the desired product
which may be gasoline, for example, is removed
through line 3 l.
A portion of the gasoline passes
through line 32 to the re?ux reservoir 33 formed
in the lower portion of the separator, re?ux be
ing pumped by pump 36 through line 35, as is
well known in the art. The bottom oi tower 25
is maintained at a predetermined temperature by
means of heat supplied thereto in reboiler 36
which is substantially a vertical heat exchanger.
Pump 37 withdraws oil. from the body of oil I4 15
within separator reservoir ! from which it is
pumped through line 38, through line 39, con
trolled by valve 45, through reboiler 35. Valve
as may be a temperature controlled valve so that,
as the temperature of the bottom of the tower 25 20
drops, the valve Ml will tend to open, permitting
a greater quantity of hot oil to circulate through
the reboiler. The tower bottoms pass through
line all, through the reboiler, and return to the
tower through line 42 by thermo-siphon flow.
25
It will be observed that the unvaporized oil
withdrawn from the bottom of fractionating tower
25 through line 53 is the crude minus the desired
light fraction. The partially topped crude is
pumped by pump 44 through heat exchanger 45 30
in which it is heated by hot oil from the body of
oil l4 coming from line 38 through line 4B,
through line 41, in counter?ow with the partially _
topped crude in heat exchanger 45, through line
48, where it joins the oil coming from reboiler 36, 35
through line 49. The oil from reboiler 35 and
heat exchanger ‘i5 passes through line 55 into line
5|, which discharges into separator reservoir into
the gutter l I thereof. The partially topped crude,
heated in heat exchanger 45 passes through line
52 and is discharged into fractionating tower 53.
The bottom of fractionating tower 53 is main
tained at a. given temperature by means of re
boiler 54 which acts similar to reboiler 36 and is
supplied with hot oil from the body of oil I4 by 45
oil withdrawn from line 45 through line 55, which
is controlled by valve 56 and is returned through
the reboiler and line 5'! which communicates with
line 5|.
Line 5| is the common line for return
ing all of the oil, with exception of oil to HJI 50
through line 86, that is withdrawn from the body
of oil I4 by pump 31, to the body of oil. The bot
tom of the tower being maintained at a given
temperature, a maximum yield of the ' desired
product will be obtained. Vapors of the desired 55
product are taken overhead through line 58, pass
‘through heat exchanger l9 into condenser 59 and
thence into separator 65, which is similar to sepa
rator 28. Re?ux from the re?ux accumulator 6|
in the bottom of separator 65 is pumped by pump 60
62 through line 63 controlled by valve 64 into
tower 53. The desired product is withdrawn
through line 65 and passed to storage. It will be
observed that both towers 25 and 53 are provided
with lines 66 and 6'5 controlled by valves 68 and 65
69. These lines are for the purpose of admitting
steam into the bottom of towers 25 and 53. In
event it is desired to repair, clean or inspect re
boilers 36 and 54, these lines may be also used in
starting. It is to be understood, of course, that in 70
normal operation the reboilers are used and not
steam from lines 66 and 61.
The topped crude
passes from the bottom of fractionating tower 53
through line 70. Normally, tower 53 will be posi
tioned above separator reservoir I so that oil from 75
2,126,420
the bottom of fractionating tower 53 may flow
through line 70 by gravity. In the drawings, a
pump 'H is shown. The topped crude passes
through valve controlled line 12 and is discharged
into the circulating stream of hot oil in line 8.
It will be observed that the oil circulating in
the primary circulating stream, that is, the oil
from the reservoir through the heater back to
the reservoir, is highly heated. The oil in the
3
the quantity of oil in reservoir I is substantially
constant. The vapors passing into fractionating
tower 15 are fractionated, the desired product
being tatken overhead through line 90 and pass
ing through heat exchanger 20 and condenser 9|
into separator 02, the lower portion of which
forms a re?ux accumulator 03 similar to sepa
rators 28 and 60, re?ux being pumped by pump
04 through line 05 to tower 15. The desired
110' reservoir is usually maintained at about 600° F. product, which may be kerosene, for example, is
The ‘oil leaving the radiant heat section of the withdrawn through line 96 and passed to storage.
heater through line 8 is usually only a few de
The gas oil fraction may be withdrawn from the
grees higher in temperature than the oil entering tower through side stream drawo? and passes
the heater due to the fact that the circulation through line 91 through heat exchanger 2|,
; rate is very high. For example, if the rate of through cooler 93, through line 99, to storage.
?ow of the topped crude be about 50 gallons per The heaviest liquid is withdrawn from fraction
minute, the circulation rate through the heater ating tower 75 through line I00 and is discharged
in the primary circulating stream will be about together with the oil being bled from the sepa
3000 gallons per minute. It is obvious therefore rator reservoir through line 86 into ‘stripping
20: that a large quantity of hot oil ?owing through tower lill in which the heavy fractions are
the heater will heat the topped crude joining the stripped with steam entering tower l0! through
circulating stream through line 12 to a tempera
line £02. The vapors and stripping steam are
ture in the vicinity of 600° F. The hydrocarbons passed into fractionating tower 75 through line
boiling below this temperature will be vaporized. M3. The stripped bottoms are withdrawn from
The oil and vapors are discharged tangentially the stripping tower by pump I00 and passed
through a spiral passageway 10 in the top of the through line I 05, through heat exchanger 22,
separator reservoir I. It will be observed further through cooler I06, and withdrawn through line
that steam may be discharged into a spiral pas
I01. Line I01 may pass to the heater of a vac
sageway through valve controlled line 13 to fur
uum distillation system or to other processing
3,6 ,1 ther assist in the removal of light products from as is well known in the art. In a typical exam
the topped crude. The result of this procedure is ple, in which a Roumanian crude was processed,
that the unvaporized oil is separated from the oil the oil in the primary circulating stream through
vapors. The oil vapors will be withdrawn from heater 6 entered the heater at about 320° C. and
the separator reservoir through line ‘M and passed left the same at about 325° C. The bottom of
j; to fractionating tower 75. The unvaporized oil fractionating tower 25 was maintained at about
will join the main body of oil l4 in the reservoir 180° C. giving a gasoline having an end point of
portion of the separator reservoir. It will be about 140° C. The partially topped crude is
observed further that the oil in the reservoir and heated in heat exchanger 45 and passed into
forming the body of oil I4 is denuded of all prod
fractionating tower 53 from which a naphtha
ucts boiling below the vicinity of 600° F. so that having an end point of 185° C. was removed, the
the oil being circulated through the heater is of bottom of the tower 53 being reboiled to a tem 40"
such a nature that it will not become vaporized perature of 250° C. The vapors passing into
when heated to temperatures in the vicinity of fracticnating tower 15 through line 74 resulted
600° F. This results in keeping the heating spaces in an overhead product of a kerosene having an
i. of the heater liquid full.
end point of 275° C. The gas oil was withdrawn
Pumps 2 and 31 are mounted from ?anges through line 01.
‘
which are welded to tubular member 16 as will
Referring now to Figure 2, a cylindrical shell
be appreciated from the drawings. Pumps 2 and 200 is provided with slots 2M and embraced by
31 are driven by electric motors T! and 18, which an annular member 4 provided with a ?ange
:3 are secured to the pumps, the assemblies being connection 202 into which the oil to be heated
supported from tubular member 16. The tubular passes. Disposed within and surrounded by shell 50
member 16 passes through the reservoir in the 200, I ?t a second cylindrical shell 203, disposed
manner illustrated. Within the reservoir, the in spaced relation to shell 200 adapted to form a
tubular member is provided with a number of manifold into which oil through slots 20! passes.
wholes or openings 00 which are covered by a By reference to Figure 6 it will be seen that
coarse screen 8i which in turn is covered with shell 203 is ?tted with nozzles 204. These nozzles
a ?ne screen 82. The liquid level of the oil in are disposed completely around the shell 203 at
the reservoir is indicated at 03. This level is spaced intervals. It will be appreciated that oil
maintained by means of level control 84. Just from manifold 205 formed by shells 200 and 203
60 “below the liquid level 83 swirl plates 85 are ?tted. will pass through the nozzles 204 throughout the
60'
The pumps 2 and 31 take suction through the entire area. Disposed in spaced relation within
tubular member l?which is supplied from the shell 203 is a third shell 205 which may be cor»
reservoir through the holes 80, as will readily be rugated in the manner shown. The space be
appreciated by reference to the drawings. The tween shell 203 and shell 206 forms a thin annu
'rliquid level operates in the following manner. lar oil passageway. An annular outlet ring ‘I 65
A bleeder line 86 communicates with the dis~
charge of pump 37. If the level of the liquid
drops, air line 0? communicating with level con
trol chamber 0d acts to put pressure on dia
70 glphragm valve 80 tending to close the valve and
reducing the amount of liquid bled through line
86. If the level rises above the predetermined
point, the action is reversed, the valve 88 tending
to open and permitting a greater quantity of oil to
75 be bled through line 86. It is thus assured. that
communicates with the oil passage 20'! and is
provided with a connection member 208. A
burner 200 is disposed to ?re the surface of shell
206 which forms in effect a combustion cham
ber Zlll. A volute 2H supplies air through air 70
register 2l2 of the burner and is adapted to give
the products of combustion a whirling motion.
A transition ?ue 2|3 joins a casing 2H5 to the
construction just described. Within member 2M
a plurality of tubes 23 are disposed forming a 75
2,126,420
convection section, it being observed that the
?rst portion of the furnace described above forms
a radiant heat section.
A second transition ?ue 2l5 joins an air pre
heater 2|‘! of any suitable construction to the
convection section. The air preheater 2|‘! is con
nected to a stack ‘MB. A blower fan 219 passes
air in heat exchange with the hot products of
combustion in air preheater 2 l1 and supplies the
10 preheated air through duct 220 to the volute 2| I.
The duct 229 is ?tted with a suitable damper 22L
In operation, oil to be heated flows through
connection 2% around annular oil inlet member
4, through slots ZOI into manifold 205 and is
15 jetted by nozzles 204 against the corrugated sur
face of shell Z‘UES. Since all of the oil must flow
into outlet ring 1, it will be observed that the
oil ?owing through the ?red end in Figure 2
flows in a thin annular sheet to which addi
tional oil is constantly and progressively being
added, the oil at the convection section end be
ing supplied by one ring of nozzles. As the oil
passes to the left, more and more oil is added
to the ?owing sheet. Inasmuch as the volume
of the passageway is substantially constant, the
addition of an increasing quantity of oil will
result in an increased velocity in order to take
care of the increased mass of oil being supplied.
Just before the oil enters the annular outlet
30 member ‘I, the oil passageway 29'! is enlarged
by tapering the cylindrical shell 20% at 222 for
collecting the oil. The combustion gases have
been given a whirling motion as pointed out
above. rI‘he rate of heat transfer is extremely
85 high due to the fact that the oil is flowing from
'an extended surface in counterflow to the heat
ing medium and owing to high velocity flow of
impinged 011 against the heated shell. There
is minimum loss of radiant heat due to the fact
40 that the heating surface completely surrounds
the source of radiant heat. The jetting of the
oil against the heating surface and the high
rate of flow prevent carbon deposition and in a
measure act as an automatic cleaning means,
45
carbon deposits being prevented by maintenance
of Very low flow temperature.
The heater is
easily and inexpensively installed, maintained,
and repaired, inasmuch as there is a minimum
of brick work. Furthermore, when the furnace
is shut down, there is a minimum of radiant
50 heated brick work to continue heating the oil.
The cost of brick work maintenance is avoided.
A heater of my design has a very high efficiency,
being between 87 and 90%. I have used an
experimental heater of the type shown for a
period of one year and a half, without the ne
cessity of cleaning it once.
It will be observed that I have accomplished
the objects of my invention. I have provided
60
a method of distillation in which maximum yields
of desired products are obtained while providing
for ?exibility with respect to control and with
respect to the types of crudes which can be
processed. I am enabled to operate my unit at
any charging rate from zero to the maximum.
I am enabled to reboil in an ef?cient and flexible
manner. It will be observed that the quantity
of oil passing through the primary circulation
ring in which heat is supplied is unchanged while
the reboiling load may be varied at will. Due
to the fact that all light products are removed
from the primary circulating stream, the heater
operates liquid full. Due to the high velocity
of flow in my heater, low ?lm temperatures are
obtained so that parasitic cracking is avoided.
It will be understood that certain features and
sub-combinations are of utility and may be em
ployed without reference to other features and
sub-combinations. This is contemplated by and
is within the scope of my claims. It is further
obvious that various changes may be made in
details within the scope of my claims without
departing from the spirit of my invention. It 10
is, therefore, to be understood that my invention
is not to be limited to the speci?c details shown
and described.
Having thus described my invention, what I
claim is:
15
1. A method of fractionating hydrocarbon oil
including the steps of circulating a stream of
oil from and to a body of oil, supplying heat to
said stream of oil, heating the oil to be frac
tionated and fractionating the same in a ?rst
fractionating zone, removing vapors from said
zone, passing the unvaporized oil in said zone
in heat exchange with a second stream of oil
circulated from and to said body of oil to reboil
the unvaporized oil in said ?rst fractionating
zone, removing the unvaporized oil from said
zone and passing the same in heat exchange
with a third stream of oil circulated from and
to said body of oil, fractionating the thus heated
oil, and removing oil vapors from the fractionat
ing zone.
2. A method as in claim 1 wherein the unva
porized oil in the second fractionating zone is
reboiled by heat exchange with a fourth stream
of oil circulated from and to said body of oil,
the unvaporized oil is withdrawn from the sec
ond fractionating zone and introduced into the
?rst stream of oil whereby vapors are formed,
the vapors separated from unvaporized oil, which
is returned to said body of oil and the vapors are 40
fractionated.
3. A method of fractionating hydrocarbon oil
including the steps of circulating a stream of
oil from and to a body of oil, circulating a second
stream of oil from and to said body of oil, sup 45
plying heat to said ?rst circulating stream of
oil, heating oil to be fractionated by heat ex
change with said second circulating stream of
oil, fractionating the heated oil, withdrawing oil
vapors from the fractionating zone, separately
removing liquid fractions from the fractionating 60
zone, circulating a third stream of oil from and
to said body of oil, and passing the liquid frac
tions in said fractionating zone in heat exchange
with said third circulating stream of oil to re
65
boil the liquid fractions.
4. A method of fractionating hydrocarbon oil
including the steps of circulating a stream of oil
from and to a body of oil, circulating a second
stream of oil from and to said body of oil, sup 60
plying heat to said ?rst circulating stream of
oil, heating oil to be fractionated by heat ex
change with said second circulating stream of
oil, fractionating the heated oil, withdrawing oil
vapors from the fractionating zone, separately
removing liquid fractions from the fractionating 65
zone, introducing said liquid fractions into the
heated ?rst circulating stream of oil whereby
vapors are formed, separating the vapors from
the liquid oil, passing the liquid oil to said body
of oil and fractionating the second mentioned 70
vapors in a second fractionating zone.
CHARLES W. STRATFORD.
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