Note: Descriptions are shown in the official language in which they were submitted.
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Prooess for Producing Carbon Black
Background of the Invention
Carbon black is produoed by the incc,~ lctc combustion of a hydrocarbon
such as petroleum, natural gas and other well-known materials at high lelllp~latures~ When
separated from the reaction gases, the product is a fluffy, carbon black powder.In a typical furnace prooess for the production of carbon black, a fuel and an oxidant such as
air are reacted to provide a stream of hot combustion gases. A hydrocarbon feedstock is injected
into the stream of hot combustion gases resulting in the formation of carbon black. The le~ alure
of the carbon black ~unlai~ g gas stream is then lowered by quenching with any conventional means
such as a water spray. The black is separated from the stream of gases in which it is suspended by
known techniques, such as by cyclones and filters; and then pelletiæd and dried.Carbon black is incorporated into rubber col,.~ul.ds in order to impart reinfo~ ~l.t properties
to the rubber COIl .~ou,ld. Among the many ~ro~xl lies of carbon black which are iln~l l~nt to the
rubber industry is the aggregate size distribution of the carbon black. The rubber industry has found
that for certain purposes blacks having wide ag~ gale size distribution are highly desirable.
Ac~,rdill~,ly, an object of the present invention is to provide a prooess for producing carbon
blacks having a wider aggregate siæ distribution as measured by an increase in the ~ D50 values
of the blacks.
Summary of the Invention
The process of the present In-,en~ion l,--~olves injecting liquid feedstock in the form of
non-~lealoll~zed coherent streams or ~reato"l,2ed streams into a staged (modular) carbon black
forming process at two sepal àle locations. A portion of the feedstock is injected prior to the
combustion gas stream having reached maximum velocity at a point upstream of which no further
'.
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increase in the crushed DBP structure of the carbon black
caused by injecting feedstock in the hot combusion gas stream
prior to the point at which the cQmbustion gas stream has
reached maximum velocity is observed, and also where an
increase in the width of the aggregate size distribution of the
carbon black is achieved. The remainder of the feedstock is
injected at the point where the c~mbustion gas stream has
reached maximum velocity.
While Canadian Patent Application Ser. No. 470,709 filed
December 20, 1984 teaches that the crushed DBP structure of a
carbon black can be increased by injecting liquid feedstock
into a c~mbustion gas stream at a point where maximum velocty
of the combusion gas stream is reached and at a point prior to
that where the m~ximllm velocity of the combustion gas stream is
reached, there is no suggestion that the crushed DBP structure
of the blacks produced by this process would not increase
nfinitely as the distance between feedstock injection points
lncreases.
Brief Description of the Drawings
Figure 1 is a schematic, diagrammatic, longitudinal,
sectional view of a typical carbon black-producing furnace
which was utilized in all of the Examples of the present
application.
Figure 2 is a histogram showing a size distribution curve
of carbon black aggregates and illustrating the ~ D50 of the
aggregate size distribution of a sample of carbon black.
Detailed Description of the Invention
Referring to Figure 1, there is shown a furnace 1 which
is illustrative of the furnaces used to prepare carbon black
using the process of the present invention. Furnace 1 is
camprised generally of four zones, namely, a mixing chamber 3,
a cambustion zone 10, a transition zone 13, and a reaction zone
31.
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- 2a -
Mixing chamber 3 is defined by wall 4, the outer side of
interior partition 9 and upstream wall 6. Attached to the
inner side of partition 9 at the upstream end of the partition
is flame holder 11. Combustion chamber 10 is defined by the
inner side of partition 9, the downstream side of flame holder
11 and terminates at downstream point 12. Through wall 6 is
inserted conduit 8 through which fuel is introduced into mixing
chamber 3. Through sidewall 4 is inserted conduit 5 through
which an oxidant is introduced into chamber 3. Through conduit
8 is inserted internal probe 19 through which feedstock may be
injected into the furnace prior to the point where the hot
combustion gas stream reaches maximum velocity and at the point
where no increase in CDBP structure of the resultant black
caused by injecting feedstock into the hot combustion gas
stream prior to the point at which the hot combustion gas
stream has reached m~imllm velocity is observed. Injection
probe 19 is an axially aligned probe which may be liquid-cooled
and which terminates in the end cap 27. End cap 27
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has a plurality of orifices 29 oriented radially about the ~ ,ce thereof. Downstream from
combustion charnber 10 is transition zone 13 which is defined by wall 17. Cil-u~l~-elltially located
around wall 17 are a plurality of substantially transversely oriented orifices 21 through which
feedstock may be in~cted into zone 13.
Do~llsllealll from transition zone 13 is reaction zone 31 which is defined by wall 37. Zone 31
can be of variable length and aoss-sectional area depending upon the reaction conditions desired. In
this instance reaction zone 31 has an internal diameter of 36 inches. Quench probe 41 is inserted into
reaction zone 31 through wall 37. Water is in~ected through quench probe 41 into reaction zone 31 to
terminate the carbon black forming reaction.
In general, the prooess of the present invention for producing blacks having a wider aggregate
size distribution is achievecl as follows. Into the mixing chamber of the furnace there is introduced
through a fuel conduit a suitable fuel and through an oxidant conduit a suitable oxidant such as air,
oxygen, mixtures of air and oxygen, or the like. Among the fuels suitable for use in the reaction with
the oxidant stream in the wmbustion chamber to gene,ale the hot combustion gases are included any
readily combustible matter whether in gaseous, ~,aporous or liquid form such as hydl ogen, carbon
monoxide, methane, aoetylene, alwhols, keç~sene, liquid hydrocarbon fuels and the like.
As referred to herein, the primary wll.buslion ,~fesenls the amount of oxidant in the first
stage of the modular process divided by the amount of oxidant theoretically r~uiled for the complete
combustion of the fuel present in the first stage of the process to form carbon dioxide and water,
multiplied by 100 to give a }~I .enlage. While the ~l ill .al ~ w~ u~lion may range from 100 to 500%,
the ~,lefelled primary or first stage combustion may vary from about 120 to about 300%. In this
manner there is generated a stream of hot combustion gases flowing at a high linear velocity. It has
furthermore been found that a ~ Ule differential belwé~l~ the cornbustion chamber and the reaction
charnber of at least 1.0 p.s.i. (6.9 kPa) and preferably about 1.5 p.s.i. (10.3 kPa) to 10 p.s.i. (69 kPa) is
desirable. Under these conditions, there is produced a stream of gaseous combustion products
possessing sufficient energy to convert a carbon black-yielding liquid hydrocarbonaceous feedstock into
the desired carbon black products. The lesultant combustion gases emanating from the cornbustion stage
attain a leln~l alurl: of at least aboùt 2400 F, (1350 C) with the most ~l ~f~l I ed l~lnlxrature being at
least above about 3000F (1650 C).
The hot cornbustion gases are propelled in a do~nsl~ealn direction and are discharged
from the downstream end of the combustion chamber at a high linear velocity which is accelerated
by passing the combustion gases Into an enclosed transition zone of smaller diameter which may, if
desired, be tapered or restricted. At a~ luA~ alely the mid-point of the transition zone in the furnace
the combustion gas stream reaches ma~l,ull. velocity.
According to the pro~ess of the present invention, an arnount of liquid feedstock ranging from
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.` 4
about 20 to about 80%, and preferably from about 25 to about 75% of the total amount of the liquid
hydrocarbonaceous feedstock required is injected in the form of non-preatomized coherent streams or
preatomized streams, preferably non-preatomized coherent streams, substantially transversely, in a
direction outwardly or inwardly, into the combustion gas stream from the periphery thereof prior to
the point where ma~mu~l~ velocity of the combustion gas stream is reached and at a point upstream
of which no further increase in crushed DBP structure caused by injecting a portion of the feedstock into
the hot combustion gas stream prior to the point at which the combustion gas stream has reached
maximum velocity is obse, ved and where a wider aggregate size distribution is obtained. When the
liquid feedstock is injected tran~v~, ~ely outwardly into the hot combustion gas stream prior to the
stream having reached maximum velocity, the feedstock is preferably injected through a feedstock
injection probe. At the point where the combustion gas stream has reached rnacimum velocity, the
remaining amount of the liquid hydrocarbon feedstock ranging from about 20 to about 80% of the total
hydrocarbon feedstock, and preferably an amount ranging from about 25 to about 75%, of the total
feedstock is injected. At this point the liquid feedstock is injected in the form of a plurality of
non~ alol, ized coherent streams or preatomized streams, preferably non-~,~alol,uzed, into the hot
combustion gas stream in a direction substantially radial or transverse to the flow of the combustion
gas stream either from the outer or inner periphery of the combustion gas stream. In a preferred
embodiment of the process, the feedstock is injected at the point where the combustion gas stream has
reached II~IIIUIII velocity through a plurality of l~ar~v~, ,ely oriented orifices within the wall of
the transition zone of the furr~ce in a direction radially inwardly to the flow of the combustion gas
stream. Suitable for use herein as hydrocarbon feedstocks are unsaturated hyd,~lbol s such as
acetylene, olefins such as ethylene, propylene, butylene, aromatics such as benzene, toluene, xylene,
certain saturated hydrocarbons and volatilized hydrocarbons such as kerosenes, naphthalenes,
e,les, ethylene tars, aromatic cycle stocks and the like. With respect to the above injections of
feedstock at the defined locations, the feedstock may be the same or different.
The amounts of feedstock, fuel, and/or oxidant employed herein will be adjusted so as to
result in an overall peroent combustion ranging from about 15 to about 60 percent and preferably from
about 15 to about 40 peroent. The overall combustion .~,~,.ts the total amount of oxidant used in the
carbon lo.,,u,.g prooess divided by the amount of oxidant required for the complete cornbustion of the
total amount of fuel and feedstock present in the carbon forrning prooess so as to yield carbon dioxide
and water, multiplied by 100 in order to arrive at a pe.centage.
Sufficient residenoe time is provided to allow the carbon black forrning reactions to occur prior
to termination of the reaction by quenching. An exemplary manner of quenching is accomplished by
injecting water through a quench nozzle. However, there are many other methods known in the art for
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quenching the carbon black fO~llUng process. The hot effluent gases co"la,ning the carbon black products
suspended therein are then subiected to the .vnvenlional steps of cooling, separation and collection of
carbon black. The separation of the carbon black from the gas stream is readily accomplished by any
.vnvenlional means such as a precipitator, cyclone se~ll,toJ, bag filter, or combination thereof.
It has been found that by in~ecting fee~cto-lc at the two locations in accordanoe with the process
of the present invention, blacks having wider aggregate size distribution are produced.
The following test procedures are used in delt ~ Inining the analytical yl oy~, Lies of the blacks
produced by the present invention.
IODINE ADSOKI~l1~NUMBER
The iodine adsorption number of a carbon black sample is del~-l,u,,ed in accordance
with ASTM ~151~81.
-- T~T STR~GTH
The tint sLlenglh of a carbon black sample is deterrnined relative to an industry tint reference
black in accordance with ASTM ~3265-76a.
DIBUIYL PHTHALATE (DBP) ABSORPTION
The DBP absorption number of a carbon black is dele..-~ined in accordance with ASTM D 2414-84.
The results r~yG. led indicate whether the carbon black is in fluffy or pellet form.
CRUSHED DBP ABSORlrrION NUMBER (CDBP)
The CDBP absorption number of a carbon black pellet is determined in accordanoe with ASTM
D-3493-84.
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AGGREGATE SIZE DlSTR~BUTlON (~ D 50)
The aggregate size distribution (~ D 50) of a sarnple of carbon black is determined in the
following manner. A histogram is made of the Stokes diameter of the aggregates of the carbon black
sample versus the relative fr~quency of their occurence in a given sample. As shown in Figure 2, a line
(;B) is drawn from the peak (A) of the histogram in a direction parallel to the Y axis to and ending at
the X-axis at point (C) of the histogram. The midpoint (F) of the resultant line (B) is determined and a
line (G) is drawn through the midpoint (F) thereof parallel to the X-axis. Line (G) intersects the
distribution curve of the histogram at two points D and E. The absolute value of the difference of the
two Stokes diameters of the carbon black particles at points D and E is the ~ D 50 value. The data used
to gnerate the histogram are determined by the use of a disk centrifug such as one manufactured by
loyoe Loebl Co. Ltd. of Tyne and Wear, United Kingdom. The following procedure is a modification of
the procedure described in the instruction manual of the Joyoe Loebl disk centrifuge file reference
DCF 4.008 published on February 1, 1985 and was used in dete-l~ining the data .
PROCEDURE
10 mg of a carbon black sample are weighed in a weighing vessel. 3 drops of a surfactant
produoed and sold by the Shell Chemical Co. under the registered trademark NONIDET P~0 are
added to the carbon black and the resultant mixture is stirred to produce a uniform paste. 50 cc of a
solution of 20% absolute ethanol and 80% distilled water are added to the paste and dis~.aed by
means of ultrasonic energy for 15 ~ lles using a sonifier having the Model No. W385 rn~nl1factl-red by
Heat Systems Ultrasonics Inc. Farrnin~ le New York.
Prior to the the run, the following data are entered into the computer which records the data
from the disk centrifug:
1. The specific gravity of carbon black, taken as 1.86g/cc,
2. The volume of the solution of the carbon black dispersed in the above
solution of water and ethanol, which in this instanoe is 0.5 cc,
3. The volume of spin fluid which, in this instance, is 14 cc of water,
4. The viscosity of the spin fluid which in this instanoe is taken as 0.933 centipoise at 23 C,
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5. The density of the spin fluid which, in this instance, is 0.9975 g/cc at 23 C,
6. The disk speed which, in this instance, is 8,000 rpm,
7. The data sampling interval which, in this instance, is 1 second.
The disk centrifuge is operated at 8000 rpm while the stroboscope is operating. 14 cc of
distilled water are injected into the spinning disk as the spin fluid. The turbidity level is set to 0;
and 1cc of the solution of 20% absolute ethanol and 80% distilled water is injected as a buffer liquid.
The cut and boost buttons of the disk centrifuge are then operated to produce a smooth concentration
gradient between the spin lluid and the buffer liquid and the gradicnt is monilored visually. When
the gradient becomes smooth such that there is no distinguishable boundary between the two fluids,
0.5 cc of the dia~l ~1 carbon black in aqueous ethanol solution is injected into the spinning disk and
data collection is started immediately. If streaming occurs the run is aborted. The disk is spun for 20
minutes following the injection of the dispersed carbon black in aqueous ethanol solution. Following
the 20 minutes of spinning, the disk is stopped, the temperature of the spin fluid is measured, and
the average of the tenl~lature of the spin fluid measured at the beginning of the run and the
temperature of the spin fluid measured at the end of the run is entered into the computer which
records the data from the disk centrifuge. The data is analyzed according to the standard Stokes
equation and presented as a histogram as shown in Figurc 2.
The prooess of the present invention for producing carbon black having wider aggregate size
distribution will be more readily understood by reference to the following examples. There are, of
course, many other embodiments of this invention which will become obvious to one skilled in the art
once the invention has boen fully disclosed and it will accordingly be recognized that the following
examples are given for the purpose of illustration only, and are not to be construed as limiting the
scope of this invention in any way.
The furnace depicted in Figure 1 is illustrative of the furnaces used in each of the following
examples. In examples 1~3 the same liquid hydrocarbon was utilized as a fuel. Furthermore, in examples
1-3 a liquid hydrocarbon different from that used as lhe fuel was utilized throughout as the feedslock.
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: 8
Example 1
Utilizing the furnace shown in Figure 1, there was introduced into mixing chamber 3 air
~lehealed to a le~ ature of 1238F (670C) at a rate of 500 mscflh (3.933 Nm3/sec) and liquid
hydrocarbon fuel at a rate of 238 gal/hr (900 L/h). A stream of hot combustion gases were generated
therefrom having a 154% primary combustion flowing in a downstream direction at a high linear
velocity. Potassium was added to the combustion gases in the form of an aqueous solution such that
84 ppm of potassium was added relative to the total amount of feedstock which was used.
Subsequently, 25% of the total feedstock was introduced in the form of non-preatomized
coherent liquid streams radially outwardly into the hot combustion gas stream through probe 19
prior to the point where the combustion gas stream reached maximum velocity. Probe 19 had an
outside diameter of 2 inches (5.1 cm) and was equipped with a 1/4 inch NPT end cap 27
having six 0.070 inch (1.78 mm) diameter orifioes perpendicularly oriented and located
equiangularly about the circumferenoe thereof. In this example, probe 19 was positioned such
that end cap 27 was 11.8 inches (30 cm) uysl~ of orifices 21.
The remaining 75% of the reedslock was injected radially inwardly in the form ofnon-yrealolllized coherent streams into the hot combustion gas stream through 12 orifices 21 at
the point where the cornbustion gases had reached maximum velocity i.e., at the mid-point
of transition zone 13. Transition zone 13 has a length of 11 inches (27.9 crn) and an internal
diameter of 12.4 inches (31 5 cm). Orifioes 21 were 1~ ansvel æly oriented, each 0.078 inches
(1.99 mm) in diameter and spaoed equiangularly in a single plane about the ~ir~ull~erenoe of
wall 17 of transition zone 13. The total amount of feedstock was injected at a cornbined rate of
1437 gal/hr (5439 L/h).
The process was carried out such that the overall combustion was 205%. Reaction chamber 31
was 36 inches (91 cm) in diameter. Quench nozzle 41 was located at a point about 10 feet (2.45 m)
dow,lsl-eam from orifioes 21. The analytical yl.~l lies of the black are reported in the Table.
Example 2
Carbon black was produced using the appalalus, feedstock and process of Example 1 with the
following exceptions. In this e~alllplc, probe 19 was positioned such that end cap 27 was 19.7
inches (50 cm) ~ ealll of orifioes 21 within transition zone 13 and 123 ppm of potassium relative to
the total amount of feedstock utilized was added in the form of an aqueous solution to the hot
combustion gas stream. Thè analytical properties of the black are rc~ul le~ in the Table.
.
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g
Exalr~e 3
Carbon black was produced using the apparatus, feedstock and process of Example 1 with the
following exoeptions. Internal probe 19 was positioned such that end cap 27 was 23.6 inches (60 cm)
uys~eam of orifices 21 and 123 ppm of potassium relative to the total amount of feedstock utilized
was added in the form of an aqueous solution to the hot combustion gas stream.The analytical
.o~, lies of the black are J`e~l led in the Table.
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Tab]e
Example 1 Example 2 Example 3
Potassium Addition
Relative to Amount of
Feedstock
(ppm) 84 123 123
Separation Distance
of Feedstock Injection
Points 11.8inches 19.7inches 23.6inches
(30 cm) (50 cm) (60 cm)
~D50~ 68 77 83
Tinting Strength% 98 98 96
Iodine No.
rng ~2/g black 60 60
DBP Absorption
Pellets cc/100 ~ 109 1C6 107
CDBP (24M4)
cc/100 g 9~ 88 90
The data in the Table shows that the process of the present invention results in the
production of carbon blacks having increased ~ D50 values while maintaining substantially
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1 1
identical values for structure and surface areas. Furthermore, from the data and the examples
one would conclude that the ~ D50 value of a carbon black could be further increased as the distance
between the two points of feedstock injection of this invention is increased.
In examples 1-3, different amounts of potassium were added in order to achieve a given
level of structure of the carbon black. In so doing the effect of the present invention is shown
indirectly by noting that equal amounts of potassium were required in examples 2 and 3, both of
which exceeded the amount required in example 1 in order to reach the given structure level of the
carbon black. The increase in the amount of potassium used in examples 2 and 3 compared to that used
in example 1 shows that at the separation distance of example 1 the structure was still increasing witl
respect to the increasing distance between feedstock injection points. On further increasin~ the
separation distance between feedstock injection points, the constant amounts of potassium utilized in
examples 2 and 3 show that there has been no further increase in CDBP caused by injection of the portion
of feedstock into the hot combustion gases prior to reaching maximum velocity at the increasing
distances between feedstock injection in examples 2 and 3.
While this invention has bcen described with respect to certain embodiments, it is not so
limited, and it should be understood that variations and modifications thereof may be made
which are obvious to those skilled in the art without departing from the spirit or scope of the
invention.
