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Патент USA US2111380

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Mmh 15, 193s.
2,111,380
M. W. BARNES`
HEATING OF FLUIDS
Filed May 4, 1955
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INVENTOR
MARION W. BARNES
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Patented Mar.’ 15, 1938
f UNITED STATES -PATENT
OFFICE
2,111,380
HEATING _or FLUrDs
Marion W. Barnes, Chicago, Ill., assignor to Uni
versal Oil Products Company, Chicago, Ill., a
corporation-of Delaware
Application May 4, 1933, Serial No. 669,325
11 Claims. (Cl. 19,'6-51)
This invention particularly refers to an im
proved method and means of heating ñuids such
as hydrocarbon oils to the high temperatures
required for their conversion and more particu
5 larly refers to improvements in the type of fur
nace wherein separate combustion zones are
employed, heat derived from one zone, primarily
, by radiation, being utilized to quickly heat the
oil tothe desired conversion temperature while
heat derived from the other~ combustion zone,
also primarily by radiation, is utilized to main
_ equal streams, parallel rows of tubes of the usual
size being employed-for the two streams. This
necessitates the use ofboth exposed and shielded
tubes in that portion of the fluid conduit where
heat is absorbed principally by radiation.
Obviously, if one stream of hydrocarbon oil
is passed through the shielded row of tubes and p
the other stream through the exposed row of
tubes, both streams will not be subjected to the
same heating conditions, the stream in the ex 10
posed row being subjected to a higher rate of
tain the oil at a fairly constant conversion tem
perature for a predetermined time and combus
tion gases from both combustion zones being
utilized to heat the incoming oil to a temperature
below the desired conversion temperature at
tained by the oil in the ñrst mentionedcombusf
heating and consequently heated to a higher
temperature than the stream in the shielded row.`
Under these conditions a portion (one stream) of
tion zone.
such unequal heating are accumulative. - The in
'
the oil would be subjected to a much more severe -
cracking condition than another portion (the ~
other stream) of the same oil and the effects of
creased vaporization of the more highly heated
stream increases the velocity and friction through 20
that portion of the fluid conduit through which
it passes thereby causing a larger proportion of
the oil to pass through that portion .of the ñuid
or near the attained temperature for a prede
conduit which is subjected to less severe heating
termined time, has been the'large drop in pres
conditions and further decreasing the rate of 25
' sure due to friction through the iluid conduit,
which is necessarily of unusual length due to ' heating and the temperature to which the oil
the time element required in the soaking section, is heated in this portion of the ñuid conduit. '
One of the principal problems in the design of
20 furnaces of the character above described.
wherein the oil is first heated to the desired
conversion temperature and then maintained at
i. e. that section wherein the oil is maintained
at a. fairly constant temperature for a prede
termined time. This necessitates exceptionally
high pressures in the ñrst heating stages in order
This tends to bring about a condition wherein a
predominant quantity\ of the _total oil passes
through the shielded row of tubes andA is heat 30
ed therein vto a temperature substantially below
to maintain the desired conversion pressure in " that desired, while only a smalLquantity of the
total oil passes through -the exposed „row of
the soaking section and obviously greatly in
creases pumping costs as well aslnecessitating tubes in a highly Vaporous condition and is
35 the use of thicker wall tubes and fittings to main
tain the proper safety factor and obviate un
usual fire and explosion hazard.> An increase in
the diameter of the fluid conduit for the purpose
of reducing the pressure drop for a given volume
of oil _flowing therethrough, due to friction,
greatly reduces the effectiveness _of the heating
surface measured over a given tube area, since
the cross-sectional area, which determines the
volume of the tube, increases out of proportion
’ to- the increased circumference, which deter
heated to a temperature greatly in excess of that 35
desired.
'
-
`
.In the present invention in order to effect
substantially equal heating in the Atwo streams
and to maintain the quantities of oil in each
stream substantially equal, a criss-cross flow is
employed through the shielded and exposed
rows of tubes,„ each of the two streams passing l
first'through a tube in the exposed row >and then
through a tube in the shielded row, then through
another tube in the exposed row and so,A on
mines the heating surface. Therefore, the heat ' throughout the length of the two‘ro'ws of tubes,
ing surface per unit volume of oil undergoing different streams of oil` flowing through adjacent
treatment is decreased by increasing the tube tubes in each row, the number of shielded tubes
and the number of exposed tubes in each stream
In the present invention in order to maintain being equal. In this manner regardless of dif 50
the desired ratio of heating surface to tube ferent heating conditions in the exposed and
volume and still minimize the pressure drop, due shielded rows and even though heating condi-l
to friction through the iiuid conduit, the stream tions may vary indifferent portions of the same
of oil during its passage through a portion of row, substantially equal heating is obtained in _
the fluid conduit is divided into two substantially both' streams and, due4 to equal heating- and
diameter.
'
f
-
.
2
2,111,380
equal friction in the two streams, a substantially
equal quantity of oil may be maintained in both
streams.
.
In the preferred embodiment of the invention
the oil tobe subjected to ‘conversion is divided
into two substantially equal streams which pass
simultaneously and in series through an equal
number of tubes. comprising similar portions of
the fluid conduit located in the convection sec
10 tion of the furnace, wherein the two streams
are subjected to equal heating by fluid heat de
rived from the combustion gases from both com
bustion zones of the furnace. The two streams
of oil then join and the commingled stream
passes in series through adjacent tubes compris
ing single rowsrof tubes adjacent the floor and
>adjacent the roof of one combustion zone,
whereby the oil is quickly brought to the desired
conversion temperature primarily by `radiant
20 heat derived from the hot combustion gases and
` the refractory walls of the furnace. il The oil is
then again divided into two substantially equal
streams, the flow of which forms a criss-cross
path, as previously described, through adjacentY
tubes comprising an exposed and a shielded row'
of oil are subjected to substantially equal heat
ing.
The «accompanying diagrammatic drawing is a
sectional elevation in cross-section of one specific
form of furnace embodying the various features
of 'the present invention and in which the proc
ess of the invention and the desired results may
be accomplished.
Referring to the drawing, the outer walls of
the furnace are indicated at I and comprise the 10
usual side walls, end walls, roof and floor of
any desired standard construction. The interior
of the furnace comprises two combustion zones
designated, respectively, as 2 and 3 and a fluid
heating or convection zone 4, which latter is sep
arated from the combustion zones 2 ,and 3 by the
respective bridge walls 5 and 6.
Fuel is supplied by means of any suitable form
, of
burners,
(not
shown)
through
one
or
a
plurality of firing tunnels l to each of the com 20
bustion zones 2 and 3. Any suitablefuel such as
oil, gas or pulverized solid fuel being supplied,
together with a portion of the air required for
combustion, through the central portions 8 of the
tunnels while the desired auxiliary air or steam or
both is supplied to the combustion zone through
tunnels 9 and l0 adjacent the central tunnel ii.
and regulated by means of suitable dempers ll.
of tubes adjacent the roof and adjacent the floor
‘of the other combustion zone of the furnace,
whereby the two streams are subjected to sub
stantially equal heating by means of primarily
radiant heat derived from the combustion gases
and refractory furnace walls of this portion of
the furnace, the heating in this latter stage be- l
ing of sufficient intensity to maintain the oil at
The air and/or steam admitted through tunnels 9
and I0 commingles with the fuel and air under 30
going combustion from tunnei 8, assisting in con
trolling the combustion conditions and particu
larly the character of the flame in combustion
a substantially uniform conversion temperature
during its passage therethrough,y said uniform
zones 2 and 3 of the furnace.
The materials undergoing combustion in zones
Yconversion temperature being not appreciably ’ 2 and 3 of the furnace give up a major portion
(say 50° F.) aboveor below the maximum tem
perature attained in the preceding> portion of
' th'e fluid conduit.
.
’
Series flow through tubes arranged in single
exposed rows in that portion of the fluid conduit
wherein the oil is brought to the desired con
version temperature is preferred in order to main
tain a high velocity and a high rate of heating
in this portion of the heating stage of the proc
ess while split flow, such as described, is pre
lferred in the soaking section of the fluid conduit
where such a high rate of heating is not re
quired, due to the fact that the oil is simply
50 maintained at a substantially constant tempera
40
ture in this portion of the, heating stage, and
split flow may also be employed in the so-called
convection heating zone of the furnacewherein
fluid heat from the combustion gases is imparted
55 to the oil, due> to the fact that most of the latent
heat of vaporization and of cracking is> added
in subsequent portions of the heating coil, ob
viating the necessity of high rates of heating
in the convection section.
60
,
One feature of the invention embodies, in
conjunction with a ñuid conduit comprising
shielded and exposed rows of tubes subjected to
heating primarily by radiation, the `improved
flow therethrough obtained by connecting diagon
65 ally adjacent tubes in the different rows and
of their radiant energy to the fluid conduit lo
cated along the floor’and roof of the combustion
zones, as will be later more fully described, by
means of Ywhich radiant heat is transmitted to
the oil passing through the fluid conduit. rThe
combustion gases pass from combustion zones 2
and 3 over the bridge walls 5 and B, respectively,
and pass thence downward through the so-called
convection heating zone 4 of the furnace where
vthey give up fluid heat largely by convection,
although to some extent by radiation, to the fluid
conduit in this portion of the furnace and to the
oil passing therethrough. The spent combustion
gases pass from convection zone 4 through flue l2
toa stack (not shown)`.
The bridge walls 5 and 6, in the particular case
here illustrated, are of the suspended Wall type
with spaces 5’ and 6', respectively, provided be
tween their front and back Walls to accommo
date supporting steel structure (not shown), and.
when desired, air may be circulated through the
openings 5’ and 6', for the purpose of cooling the
steel structure and, when desired, the air thus
circulated Vand thereby heated may be utilized
-as a portion or all of the air required for com
bustion in zones 2l and 3 of the furnace, although
Well known means for circulating the air through
spaces 5’ and 6’ and for supplying to> zones 2
and 3 and/or to ñring tunnels 'l are not shown in
alternate tubes in the same row in series and
the drawing.
passing therethrough substantially equal quan
A bank I3 of tubes I4 is located in the ccn
vection zone E of the furnace and consists of
tities of _oil in separate streams in such a man
ner that the number of shielded tubes in each
70 stream is equal to the number- of shielded tubes
in the other stream and the number of exposed
tubes in each stream is equal to the number of
exposed tubes in the other stream so that each
, of the streams of substantially equal quantities
superimposed horizontally parallel rows of hori
zontal tubes. The tube bank i3 is divided into
two similar sections I3’ and I3" each contain
ing the same number of tubes and each hav
ing the same number of tubes in each horizontal
row.
Adjacent tubes in each row and end tubes
in adjacent rows of each of the two heating coils
3
l 2,111,380
I 3’ and I3’f are connected in series at'their ends
by means of suitable headers or` return bends
(not shown), and located outside of the heat
ing zone, The single lines LIE and »I6 indicate
the path ofv ñow of the fluidlthrough the heating
coil, solid portions of the lines- indicating the
tions in different zones along the heating coil
will not produce different heating conditions in
the two streams; furthermore, the number of
shielded tubes in each stream is equal to the num- _
ber of shielded tubes in the other stream and the
number .of exposed tubes in each stream is equal
to the number of exposed tubes in the other
connections between the tubes on the near side
of the furnace and the dotted lines indicating the stream, insuring no inequality in the'heating of
connections on the far side of the furnace. The the two streams, due to the different heating con
10 arrows indicate the direction or flow of the fluid. ' ditions in the shielded and exposed rows of tubes. 10
It will be understood that various modifications
The two streams- of oil I5 and I6 of substantially
of the specific form of apparatus illustrated and
the specific ñow above described may be employed
where they are subjected/to substantially ¿equal without departing from the scope of the inven
heating by fluid heat absorbed from the combus- ' tion. For example, the flow of oil through bank
i3 may be Aconcurrent instead of countercurrent
tion gases from both of the combustion zones 2
and 3, the oil passing through this zone, in the tothe flow of combustion gases through zone It
particular case illustrated,` in a general direction ofthe furnace also, when desired, the 'direction
of fl'ow of the oil through rows lll and it and/or
‘ counter-current to the flow of combustion gases
vequal quantities pass through the respective
banks i3’ and 'I3"_ in zone 4 of the furnace
20
therethrough.
.
'
A single row of horizontal tubes i4 comprises
the floor bank I1 located adjacent the floor of
combustion zone 2 and preferably, as here illus
trated, depressed somewhat below the outlet from
ñring tunnel 'l and out of the direct path of the
products undergoing combustion in this zone. A
roof bank Ill located adjacent the roof of com
bustion zone 2 comprises a single horizontal row
of horizontal tubes I 4. Adjacent tubes in rows
30 .il and I8 are connected‘at their ends in series 4
and the commingled streams of oil designated as
l5 and i6 pass first through the iioor bank I'I and
then through the roof bank I8, wherein the oil is
brought to the desired conversion temperature
t@ Ch derived, to- some extent,'by convection but ”pri~
marily by radiation from the combustion gases
and the heated ,refractory furnace walls.
Two parallel horizontal rows i9 and 20 of tubes
la comprise the roof _bank of the soaking section
40 of the ñuid conduit located Íadjacent the roof
of combustion zone 3. The commingled streams
of oil l5 and I6 flowing through tube I4' are
again split into two substantially equal streams
the sequence of these two rows may be changed. 20.
It is also specifically within the scope of the in
vention lto omit the tubes in rows VI3, i9 and 2l]
which are located above and opposed to the tubes
in bank i3.
When these tubes are omitted a'
higher proportion of radiant heat will be irn
parted to the tubes in the upper rows of bank I3
and consequently a somewhat higherv rate of
heating will occur in this portion of the fluid con
duit.
,
'
l claim as my invention:
30
n 1. A furnace for heating Huid which comprises,
in combination, two combustion zones, means for
independently controlling the heating conditions
in each combustion zone, a convection zone lo
cated between the combustion zones, means for 35
supplying combustion gases from both of the
combustion zones to the convection zone, fluid
conduits comprising a plurality of elongated
tubular elements located >Within the convection
zone, means for heating said ñuid conduits by 40
fluid heat from the combustion gases, fluid con
duits comprising a plurality of elongated tubular
elements located in each combustion zone, means
whichgare designated as I5' and lû'.- Stream l5’ for heating the latter fluid conduits predom
enters the end'tube of the exposed row 20 and ' inantly by radiant heat from the respective com
stream I6’ enters the adjacent tube in the same bustion'zones, means for passing the ñuid to be
heated in a plurality lof substantially equal
row. The respective streams then pass in paral
lel though adjacent tubes in shielded row lil streams through the fluid conduits in the con
thence throughthe-next two adjacent tubes in vection zone in such a manner that each stream
is subjected _to substantially equal heating con 50
-50 exposed row 2li and s_o on throughout this portion
ditions therein, means for passing the fluid in a
of the-fluid- conduit.
,
w
Parallel horizontal rows 2l and i2 of tubes ld single stream through the fluid conduit in one comprise the remainder of the soaking-section combustion zone, and means for passing the fluid
of the fluid conduit located adjacent the floor of in a plurality of substantially equal streams
combustion zone 3 and, as in the case of iloor through the fluid conduit in the other combustion 55
bank Ill, these tubes are preferably depressed zone, whereby each stream is subjected to sub
‘ somewhat below the outlet from the 'firing tunnel stantially equal heating conditions in this zone.
2. A furnace for heating fluid which comprises,
to remove them from the direct path of the
materials
undergoing combustion. `The
two
60 streams of oil l5’ and I6’ flow through the tubes
in the shielded and> exposed rows 2i and 22, -re
spectively, of the floor bank in a manner similar
to that described in connection with rows I9 and
2li of the roof bank, the two streams commingling
65 again in the ñnal shielded tube i4" of the floor
bank from which the heated> oil is discharged to
any desired further stage of the cracking process.
It will be noted that the two substantially equal
streams I 5' and I6’ are subjected to substantially
70 equal heating conditions in the soaking section
of the fluid conduit, comprising shielded rows i9
and 2l and exposed rows 2l] and 22, in combustion
zone ‘3. The ,two streams ñow in parallel through
adjacent tubes in both the shielded and exposed
76 rows, insuring that any unequal heating condi- »
in combination, two combustion zones, means for
independently controlling the heating conditions
in each combustion zone, a convection zone l'o
cated between the two combustion zones, means
for supplying combustion gases from both of the
combustion zones to the convection zone, fluid
conduits `comprising a plurality of elongated 65
tubular 'elements located within the convection
zone, .means for heating said fluid conduits by
fluid heat from the combustion gases, fluid con
duits comprising a plurality of elongated tubular
elements located in each combustion zonekmeans
for heating the latter fluid conduits predom
inantly byrradiant heat from the respective com
bustion zones', means for passing the fluid to be
heated in a plurality of substantially equal
‘streams through the fluid conduits in the con
if
ze
4
2,111,380
vection zone d in such a manner that each stream
is subjected to substantially equal heating condi
passing the heated fluid fßom the latter zone in
two substantially equal streams through both the
tions therein, means for passing' the heated fluid
shielded» and exposed tubes in the other com
from the convection zone in a single stream
through the fluid conduit in one combustion zone.
bustion zone whereby each stream passes through
and means for finally passing the heated fluid
from the latter in a plurality of substantially
equal streams through the fluid conduit in the
an equal number of exposed tubes and an equal 5
number of shielded .tubes-and the two streams
flow in parallel through adjacent tubes in the
shielded rows and adjacent tubes in the exposed
other combustion zone, whereby each stream is '
rows.
10 subjected to substantially equal heating condi
tions in this zone.
-
v
5. A process for the heating of hydrocarbon
'
3. A furnace for heating fluid, ‘which com,
prises, in combination, two combustion zones,
means for independently controlling the heating
conditions in each combustion zone, a convection
ñuids which comprises heating a flowing stream
of the fluid to conversion 'temperature in a fur
nace, then dividing the stream into two sub
stantially equal streams, passing the latter
streams simultaneously through a fluid conduit
zone located between the combustion zones,
located within the furnace, said fluid conduit
means for _supplying combustion gases from both
comprising a shielded row and an exposed row of
of the combustion zones to the convection zone,
parallel elongated tubular elements subjected to
fluid conduits comprising a plurality of elongated
tubular elements located within the convection
heating primarily by radiation, passing each
zone, means for heating said fluid conduits by
fluid heat from the combustion gases, a fluid con
duit comprising a single row of elongated tubular .
elements located adjacent the floor of one com,
25 bustion zone and a single row of elongated tubu
lar elements located `adjacent the roof of the
same combustion zone, a fluid conduit comprising
a shielded row and an exposed row of elongated
tubular elements located adjacent the roof of
30 the other combustion zone and a shielded row and
exposed row of elongated tubular elements lo
cated adjacent the floor of the latter combustion
stream through diagonally adjacent tubes in the
two rows and through alternate tubes in each
row, the two streams passing in parallel through
adjacent tubes in the same row in such a mañ
ner that each stream flows through the same
number of exposed tubes and through the same
number of shielded tubes, whereby a substantially
equal quantity of fluid passes through each
stream and each stream is subjected to substan
tially equal heating conditions.
6. In the heating of hydrocarbon fluid in fur~ 30
naces of the type having a pair of independently
fired combustion zones and a convection zone
zone, means for passing the fluid to be heated in I receiving combustion gases from both the com
a plurality of substantially equal streams through bustion zones; the method which comprises first
the fluid conduits in the convection zone whereby passing the hydrocarbon fluid through the con 35
each stream is subjected to substantially equal vection zone and subjecting the same therein to
heating conditions therein, means for passing the convection heating from said gases, then passing
heated fluid from the convection zone in a single the fluid in a stream through one of said com
stream through the fluid conduit in the first bustion zones and further heating the same there
,mentioned combustion zone,
and means for in predominantly Iby radiant heat, raising the
finally passing the heated fluid from the latter ‘ fluid to conversion temperature during 'its flow 40
zone in two substantially equal streams through
both the shielded and exposed tubes in the other
combustion zone in such aymanner that each
stream is subjected to substantially equal heating
conditions in this zone.
4. A furnace for heating fluid, which comprises,
in combination, two combustion zones, means for
independently controlling theheating conditions
in each combustion zone, a convection zone lo
cated> between the combustion zones, ineans for
supplying combustion gases from both of the
combustion zones to the convection zone, fluid
conduits comprising a plurality of elongated
55 >tubular
elements located within the convection
through the convection zone and the last named
combustion zone, dividing said stream, after ele
vation of the fluid to conversion temperature,
into a plurality of substantially equal streams
and passing the latter through the other of said
combustion zones wherein the fluid is main
tained at conversion temperature predominantly
by radiant heat, and subjecting the equal streams
to substantially uniform heating conditions dur 50
ing their passage through the last named com
bustion zone.
'1. 1n the heating of hydrocarbon uuid in fur-naces of the type having a pair of independentlyr `
fired combustion zones and a convection zone
zone,y` means for heating said fluid conduits by receiving combustion gases from both the com- '
fluid heat from the combustion gases, a fluid con
>bustion zones; the method which comprisesflrst
duit comprising a single row of elongated tubular passing the hydrocarbon fluid through the con
elements located adjacent the floor of one com
vection zone in a plurality of streams and subf
bustion zone and a single row of elongated tubular jecting the same therein to convection heating
elements located adjacent the roof of the same from said gases, then uniting said streams and
combustion Vzone, a fluid conduit comprising a passingthe resultant composite stream through
shielded row and an exposed row of elongated
one of said combustion zones, heating the com
tubular elements located adjacent the roof of the posite stream in the last named combustion zone
other combustion zone and a shielded row and
exposed row of elongated tubular elements lo
cated adjacent the floor of the latter combustion
zone, means for passing the fluid to be heated in
a plurality of substantially equal streams through
the fluid conduits in the convection zone whereby
each stream is subjected to substantially equal
heating conditions therein, means for passing the
heated fluid from the convection zone in a single
stream through the fluid conduit in the first
75 mentioned combustion zone, and means for finally
to conversion temperature predominantly by ra 65
diant heat, then- dividing the composite stream
into a plurality of substantially equal streams
and passing the latter through the other of said
combustion zones wherein the iluidf‘ is> main
tained at conversion temperature predominantly 70
by radiant heat, and subjecting the equal/streams
to substantially uniform heating conditions dur
ing their passage through the last named com
bustionzone.
'
8. In the heating and subjection of hydrocar 75
l allinea
the latter through one tube bant: adjacent the
root and through another adjacent the door oi
radiant heat zones and a convection heating >zone - the other ot said radiant heat zones, and sub
jecting the equal streams to substantially unl»
receiving combustion gases from both the radi
ant heat zones, the method which comprises hrst form radiant heating conditions during their how
through said other radiant heat zone.
passing the hydrocarbon Huid through said con
10. ln the heating oi hydrocarbon uuid in iur
vection zone, then passing the huid in a single
stream through one tube bank adjacent the door naces oi the type having a pair of independently
bon huida to conversion temperatures in iurnaces
oi the type having a pair of independently iired
and through another adjacent the root oi‘ one
10 of said radiant heat Zones and heating the same
in this zone predominantly by radiation, then
dividing saidsingle stream into a plurality oij
substantially equal streams and passing the lat
ter through one tube bank adjacent the root and
15 through another adjacent the Hoor of the other
oi said radiant heat Zones, and subjecting the
equal streams to substantially uniform radiant
heating conditions during their ilovv through said
other radiant heat zone.
20
fired combustion zones and a- convection zone re
ceiving combustion gases from both the combus lll
tion zones ; the method whicheomprises- heating
the hydrocarbon fluid to conversion temperature
by passage through the convection zone and one
of said combustion zones, the fluid being heated
predominantly by convection from said gases in
the convection zone and predominantly by radi
ant heat in the combustion zone and the huid
being passed through the latter none in a single
stream, dividing said single stream, after eleva
9. lin the heating and subjection of hydrocar
tion thereof to conversion temperature, into a 20
bon iiuids to conversion temperatures in furnaces
plurality of substantially equal streams and‘pass
ing the latter through the other oi said com
bustion Zones wherein the Huid is maintained
at conversion temperature predominantly by ra
diant heat, and subjecting the equal streams to 25
of the type having a pair of independently fired
radiant heat zones and a convection heating zone
receiving combustion gases from both the radi«
ant heat zones, the method which comprises ñrst
passing the hydrocarbon huid through said con
substantially uniform heating conditions during
vection zone in a plurality oi streams, then com
' their passage through the last named combustion
bining said streams and passing the resultant
single stream through one tube bank adjacent
30 the door and through another adjacent the root
ol" one oi said radiant heat zones and heating
the same in this zone predominantly by radia
tion, then dividing said single stream into a plu
rality oi' substantially equal streams and passing
ZODB.
ll. The method as dehned in claim l0 furthercharacterized in that the hydrocarbon huid un 30
dergoing heating is passed through the convec- Y
tion zone in a plurality oi streams.
ON W. BARNES.
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