Note: Descriptions are shown in the official language in which they were submitted.
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The invention releats to an apparatus
for progressively cooling a hot gas stream~. More
particularly, the invention -elates to an
apparatus wherein heat from the gas stream is dissipated
ln a casing by radiation in two steps.
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Conventional systems for dissipating heat in a
casing involve heat exchange devices onithe casing waIl,
which heat exchange devices are welded to the casing
wall and are formed as a function `of the anticipated
operating pressure in the casing. The heat exchange
devices can comprise heating or cooling ducts welded to
the casing wall or lines in the casing wall which can be
a thin or diaphragm wall. For removing different
quantities of heat while maintaining a given outlet
temperature at the casing outlet, special measures have
to be taken. In particular, the cooling circuit control
system must be constructed such that the outlet temper-
ature does not drop below the predetermined outlet
temperature. This is particularly important when the
casing is used for performing reactions wherein the
outlet temperature significantly affects the quality of
the product being produced.
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Casings, employed fo.r perforrn.ing exo-thermic reactions
wherein large and varying ~uantit.i.es of heat are produced .in the
reacti.on zone, require intense cooling of such zone. Conven-
tional heat exchangers cannot e~fectively provide the required
cooling without considerable expendi-ture and effort. Thus,
other solutions have been sought.
One known sys-tem i.nvolves a direct cooling process in
whi.ch a cooling me~i.um is introduced direct:ly into the reacti.on
zone. rl'his process is, for example, used in the production of
10 carbon black by substoichiometric combustion of hydrocarbons.
The cooling medium used is water. However, this process suffers
from the disadvantage that the carbon black produced partly
agglomerates to black grit, which grit. must be ground in a
further operation to permit it to be used.
The present invention provides an apparatus for
progressively cooling a hot gas stream wherein -the temperature
gradient at the outlet of the casing is substantially indepen-
dent of the quantities of heat to be removed at the inle-t of the
casing.
The present invention also provides an apparatus for
progressively cooling a hot gas stream which is simple and
i.nexpensive to construct and opera-te.
According to the present invention there is provided a
casing for progressively cooling a hot gas stream therein, com-
prising: a substantially cylindrical inner jacket surrounding an
i.nner area throughwhich the hot gas stream flows, said inner
jacket having a radiant energy receiving inner surface and a
radiant energy emitting outer surface, said inner jacke-t being
open at axial ends thereof to permi-t the hot gas stream to flow
30completely through said inner jacke-t; a substantially cylindri-
cal outer wall substan-tia~ly uniformly spaced ou-twardly from
said inner jacket with inner and outer surfaces, said inner
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surface of said outer wall facing said inner jacket and forming
a radiant energy receiving surface receiving radiant energy from
said outer sur~ace of said inner jacket; a closed, gene.rally
annular intermediate area defined between said inner jacket and
said outer wall, said in-termediate area being sealed from sald
inner area and the atmosphere and providing an empty space
between said inner jacket and said ou-ter wall; and a hea-t ex-
changer coupled to said ou-ter wall; whereby heat is dissipated
from the hot gas stream by radia-tion to said inner jacket, and
lQ t.hen from said i.nner jacket by radiat.ion to said heat exchanger.
Thus according to the invention in the casing for pro-
gressively cooli.ng a hot gas stream in a casing, the hot gas
stream is conveyed through an inner area of a casing having a
casing wall in fluid contact with a cooling medium and a radiant
surface between the inner area and casing wall. Heat
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from the gas stream is dissipated by radiation to the
surface, and then from the radiation surface by radia-
tion to the cooling mediu~
~ he casing or progressively cooling
a ho-t gas s-tream, -thus comprises an inner
jacket, an outer wall spaced outwardly Erom the inner
jacket and a heat exchanger located on the ou~er surface
of the outer wall. The inner jacket surrounds an inner
area through which the ho-t gas stream ~lows. ~leat is
dissipated from the hot gas stream by racliation to the
inner jacket, and then from the inner jacket by radia-
tion to the heat exchanger.
This casing is particularly effective
for exothermic reactions such as the ignition of a
mixture of air and oil. The heat generated during the
reaction must be dissipated in a dosed manner to ensure
that the temperature of the product at the casing outlet
is within a predetermined, narrow temperature range.
The use of t~o radiation steps, i.e., from the gas to
the inner jacket and from the inner jacket to the outer
wall, provides the required cooling such that the
temperature peaks occuring with different mixing ratios
have only a limited effect on the temperature profile
toward the casing outlet. Thus, the system of the
present invention does not require external control,
i.e~, of the cooling system of the heat exchanger.
Within the context of the present invention, the
term "casing" covers lines and vessels, particularly
reaction vessels, operated by overpressure or under-
pressure and in which high temperatures occur.
A particularly advantageous embodiment o~ the
present invention will be described with reference to
the accompanying drawings wherein:-
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Figure 1 is a schematic, side elevational view insection of a casing for progressively cooling a hot gas
stream in accordance with the present inven-tion; and
Figure 2 is a graph illustra~ing temperature
gradients in the casing of Figure 1 used as a reactor
for producing carbon black.
Figure 1 graphically illustrates a casing 2 con-
structed as a reactor. The casing 2 has an inner area 3
with any desired cross-sectional configuration, e.g.,
circular, rectagonal or polygonal. Inlet E and outlet A
are located on opposite sides of casing 2. The casing
or reactor shown in Figure 1 can be used for producing
carbon black from hydrocarbons by the process according
to the present invention.
Casing 2 comprises an outer wall having a heat
exchanger 5 in the form of a jacket welded to the outer
surface of outer wall 4. However, the heat exchanger 5
can also be constructed in other known ways, for
example, in a form previously described.
The inner area 3 is peripherally bounded by an
inner jacket 6, which jacket is spaced inwardly from
outer wall 4 defining an annular intermediate area 7
therebetween which is a void or is filled with air. On
its outlet side, intermediate area 7 is separated by a
seal 8 from inner area 3. Intermediate area 7 is also
closed or sealed on its inlet side by a cover plate 9.
Inner jacket 6 is fixed to cover plate S by means of a
flange 10 extending towards outer wall 4. Outer wall 4
is connected by a flange 11 to the edge oE cover plate
9.
A connector 12 is provided on the outlet side of
heat exchanger 5. A further connector 13 is provided on
the inlet side of the heat exchanger. The directions of
the illustrated arrows indicate that the cooling medium
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enters at connector 12 and that the cooling medium exits
at connector 13.
A terminating cone 14 is mounted below outer wall 4
having an outlet port 15 connected to downstream appara-
tus required Eor treating the carbon black produced.
Cover plate 9 supports those parts of ~he reactor
with which the oxygen carrier, usually air, and the
hydrocarbons are introduced into the inner area 3. The
oxy~en carrier is fed from an oxygen source 16 through a
line 17 into a distributor 18. The distributor has
openings 19 on its casing side through which the oxygen
carrier is introduced into mixing chambers 20. In the
chambers, the oxygen carrier is mixed with the hydro-
carbons injected through a nozzle 21. The hydrocarbons
are supplied to nozzle 21 through lines 23 from a
storage container 22. The mixture is fed from mixing
chambers 20 into inner area 3.
In the inner area, the mixture is continuously
ignited causing a powerful exothermic reaction. The
heat generated during the reaction must be removed in
dosed manner to ensure that the product temperature at
the outlet is within a predetermined narrow temperature
range. The maintaining of this temperature has a
significant effect on the product quality obtained.
Thus, the gas outlet temperature must be largely inde-
pendent of the quantity of heat released.
The heat transfer from the reaction gas and reac-
tion product takes place by means of radiation to the
inner surface of inner jacket 6. The temperature on the
outer surface of inner jacket 6 is increased by heat
conduction. Inner jacket 6 forms a radiant surface
radiating heat to outer wall 4. Since the heat transfer
by radiation increases with the fourth power of the
temperature, convective and conductive heat transfer of
the gas in the immediate area has only a very minor
effect. The heat absorbed in outer wall 4 is trans-
ferred to a suitable cooling medium, e.g., boiling
water.
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Figure 2 shows the action of the cooling system
according to the present invention comprising the series
connection of two radiation processes, i.e., of the gas
in inner area 3 to inner jacket 6 and from inner jacket
6 to outer wall 4.
Figure 2 illustrates two reactions for producing
two different carbon black qualities. The continuou5
lines show the temperature gradient in the gas over the
length L of inner area 3 from inlet E to outlet A. 'rhe
broken lines show the temperature gradient of inner
jacket 6 for the two operating cases. The dot-dash line
shows the wall temperature of heat exchanger S. In
operating case I with the hiyhest gas temperature of
approximately 1900C, a black quality is produced in
which the oxygen proportion is relatively high. In the
second operating case II with the much lower maximum gas
temperature of approximately 1000~C, a black quality is
produced in which the oxygen proportion is relatively
low.
However, it is apparent from Figure 2 that the
temperature gradient at the outlet A of the reactor is
largely independent of the temperature peak reached at
the reactor inlet E. On modifying the operating condi-
tions in the production of different carbon black types
by widely varying the oil-to-air ratio, varying temper-
ature peaks are obtained which have only a limited
effect on the temperature profile towards reactor outlet
A. No action has to be taken from the outside, i.e., by
the cooling system control. Thus, the desired reaction
conditions towards the reactor outlet A are obtained
largely independently of what happens at the reactor
inlet E without any external action being required.
The cooling process and apparatus of the present
invention is advantageous since thè temperature peaks
occurring during the reaction rapidly drop to a rela-
tively low temperature compared with the high reaction
temperature, and further cooling only takes place
slowly. Due to this selective heat dissipation, the
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quantity of heat, yenerated during the reaction and
dependent on the specific reaction heat and the through
quantity, only has a very limited effect on the outlet
temperature of the reaction yases. In addition, the
ternperature of the cooling medium and outer wall 4 has
virtually no effect on the temperature gradient of the
reaction gas. Thus, the choice of the cooling medium
can be adapted to other requirements, e.g., for a
particularly appropriate further use of the heat.
