Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD FOR PRODUCING CARBON BLACK
Field of the Invention
The present invention relates to a novel and improved furnace process for easily and
steadily producing carbon blacks having lower specific surface area and structure levels l;han it
is possible to produce in a conventional furnace carbon black process. The carbon blacks
produced by the process of the present invention are suitable for various applications inciuding
fillers, reinforcing agents and color pigments in rubbers and plastics.
Back~rolmd
In a conventional furnace process for producing carbon black, liquid hydrocarbonfeefletor~ is pyrolyzed by a hot primary combustion gas stream generated from a mixture of
fuel and oxidant, such as preheated air or the like, to form an effluent stream. Pyrolysis of the
feeAetot~- is stopped by a quench and carbon black products are separated and recovered from
the qllellth~l gas stream.
The specific surface area of carbon black produced by furnace process depen~e7
generally, upon decom~osition reaction temperature which is controlled by primary combustion
gas l~ dlul~ and the amount of feer~etcr~ introduced.
Generally, the specific surface area of carbon black decreases with falling reaction
temperature, which decreases with falling primary combustion gas telll~ld~ul~ and with an
increase in the amount of fee~letock introduced. However, temperature of the primary
combustion gas cannot be decreased without any limitation, because the primary combustion
gas supplies energy for decomposition of the fee-letock Therefore, production of carbon
blacks having such a low specific area in furnace process is generally accomplished by
increasing the amount of feedstock introduced which leads to a need to shut down the reactor
for cleaning as a result of carbon black adhering to the inside of the reactor walls as indicated
by low light trcansmittance of toluene discoloration.
Provided that the amount of feedstock introduced is increclsed, the amount of carbon
black produced per unit volume of the reactor is increased and as a result, promoted coke
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formation leads to increased grit as an impurity which means deterioration of carbon black
quality. In order to resolve this problem, the reaction zone may be e~cp~ntlecl but expansion of
the reaction zone may lead to a new problem of accumulation of carbon black formed due to
slowdown of effluent gas speed in the reactor and also an undesirable economic problem
~oris~tç~l with the need for enlarged facilities.
Primary particle diameter of the carbon black is generally dependent upon the reaction
temperature. The higher the reaction temperature, the smaller is the primary particle diameter of
the carbon black formed. The higher the structure of a carbon black, the lower is the specific
area of the carbon black at a given particle size. This means that low structure blacks have
higher specific surface area at a given primary particle size than high structure blacks.
Restriction of carbon black structure development is zltt~linçti in conventional processes
by introduction of alkali metals ion into the reactor, but this method generally causes an
increase of specific surface area simultaneously with dec~ ing structure because the primary
particle diameter remains generally constant. It will, therefore, be recognized that production
of carbon blacks having both low structure and low specific surface area is difficult in
heretofore conventional furnace processes.
For the purpose of solving this type of problem, U.S. Patent No. 5,190,739 givesimportant suggestions of production method of carbon blacks having both low structure and
low specific surface area at a given overall combustion level, which gives an illl~l l~lt
suggestion to a method for ~ Jdfillg carbon blacks having both low structure and low specific
surface area at a given feedstock level introduced. This method is carried out by adding an
auxiliary hydl ~cal bol1 such as an auxiliary hydrocarbon having high molar hydrogen-to-carbon
ratio or hydrogen.
Technology relating to the introduction of water or steam into furnace carbon black
reactors is disclosed in U.S. Patent No. 4,283,378 and U.S. Patent No. 4,631,180.
Technology relating to introduction of water or steam as an improved method for producing
carbon black based on furnace process, was also described in J~p~n~se Patent Publication No.
ShoS4-7634, Japanese Patent Laid Open No. ShoS6-'74455, and Japanese Patent Laid Open
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No. Hei 3-1289'74 etc. All of these inventions generally rela~e, however, to produetion of
carbon blacks having higher specific surface areas than the earbon blacks produced in a similar
manner in, the absence of steam activation. Thus, the objective of these inventions is quite
different f rom that of the present invention relating to production of carbon blacks having lower
specifie surface areas than carbon blacks produced in a similar manner in the absence of steam
activation
Accordingly, an object of the present invention is to develop an improved furnaee
carbon black process in order to produce easily and steadily carbon blacks having both low
specifie surface area and low structure which have been regarded as being difficult to produce
by eonventional furnace proeess.
Summary of the Invention
Thle above-mentioned object, and other advantages are ~ttZlin~d by an improved furnace
earbon bla~ck proeess featuring restraint both of specific surface area and structure
developments by means of introduction of steam at or near the position of introduction of
feeAsto~l~ in furnace earbon black proeess. According to the process of the present invenltion,
in a furnace carbon black production proeess comprising introduction of hydrocarbon
feeA~tQcl~ preferably in liquid form, into hot primary combustion gas stream, pyrolysis and
quenching, steam is introduced into the combustion gas stream at, or near (u~ or
downstream), the point of the injeetion of the hydrocarbon fee~tock into the gas stream sueh
that the ra~io L/D (as hereinafter defined) ranges from O to less than 1Ø
Brief Description of the Drawin~s
, Figure 1 is a cross-sectional view of a portion of one type of furnace carbon black
reaetor which may be utilized to perform the process of the present invention.
Detailed Description of the Invention
The present invention may be better understood with reference to Figure 1 which
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illustrates one type of furnace carbon black reactor which may be utilized to perform the
process of the present invention.
Figure 1 illustrates a carbon black reactor having combustion zone, 1 where fuel from
probe 2, and an oxidant, such as air or the like, circ~ ting in space 3, are reacted to form a hot
combustion gas stream. Among the fuels suitable for use in contacting the oxidant stream in
combustion zone 1 to generate the hot combustion gases are any of the readily combustible gas,
vapor, or liquid streams such as natural gas, hydrogen, carbon monoxide, methane, acetylene,
alcohol, or kerosene. It is generally preferred, however, to utilize fuels having a high content
of carbon-cont~ining components and in particular, hydrocarbons. The ratio of air to natural
gas utilized to produce the carbon blacks of the present invention may preferably be from about
10:1 to about 100:1. To facilitate the generation of hot combustion gases, the oxidant stream
may be preh~te~l
The direction of the flow of hot combustion gases is shown in the figure by the arrow.
The hot combustion gas stream travels from zone 1, dowl,sl,~ll into a transition zone, 20
having a diameter "D". A liquid hydrocarbon fee~1~tor~ is introduced at point 4 in zone 20.
Suitable for use herein as carbon black-yielding hy~ c~l,on feefl~to~, which are readily
v~ tili7~hle under the conditions of the reaction, are unsaturated hydrocarbons such as
acetylene; olefins such as ethylene, propylene, butylene; aromatics such as benzene, toluene
and xylene; certain saturated hydrocarbons; and other hydrocarbons such as kerosenes,
n~phth~lenes, terpenes, ethylene tars, aromatic cycle stocks and the like. Generally, carbon
black-yielding fee~l~tock is injected in the form of a plurality of streams which penetrate into the
interior regions of the hot combustion gas stream to insure a high rate of mixing and shearing
of the hot combustion gases and the carbon black-yielding feedstock so as to rapidly and
completely decompose and convert the feedstock to carbon black.
Steam is introduced at point 6 in zone 20, which in Figure 1 is downstream from the
point of feedstock injection 4. "L" is the distance from point 4, upstream or downstream to
point 6. When, feedstock and steam are introduced at the same point, L=0 and therefore
L/D=0. Although, in the process depicted in Figure 1, the point of steam introduction is
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do~.lsLl~ll of the point of feeti~tock introduction, according to the process of the present
inventiom, the point of steam introduction may be located u~l-ea..., downstream or at the point
of feedsl;ock introduction, provided L/D ranges from 0 to less than 1Ø Preferably, the point
of steam introduction is located U~ Ull of the point of feedstock introduction.
After introduction of fee~1etor~ and steam the resulting effluent travels downstream into
zone 30. Quench 5, located in zone 30 injects a quenching fluid, such as water to stop the
reaction when carbon blacks having the desired p~u~;~lies are formed. The location of quench
5 may be determined in any ~ me. known to the art for selecting the position of a quench to
stop pyrolysis. One method for determining the position of the quench to stop pyrolysis is by
determiming the point at which an acceptable toluene extract level for the carbon black is
reached. Toluene extract level may be measured by using ASTM Test D1618-83 "Carbon
Black Extractables - Toluene DiscolorationU.
S1 is the distance f3rom point of fuel introduction through probe 2, to the point of
feedstock introduction at point 4. S2 is the f1ist~n-~e from the point of fee~3~tock introduction,
point 4, to the quench 5. S3 is the distance from quench 5 to the end of zone 30.
After the mixture of hot combustion gases and carbon black-yielding feedstock isquenched, the cooled gases pass dow.~ll~ull into any conventional cooling and separating
means whereby the carbon blacks are recovered. The separation of the carbon black from the
gas stream is readily accomplished by conventional means such as a precipitator, cyclone
separator or bag filter. This separation may be followed by pelletizing using, for example, a
wet pelletizer.
As set forth above, in combustion zone 1 of the first section (Sl), hot primary
combustion gas is generated by mixing and reaction of fuel from probe 2, with oxidant in space
3, such as preheated air or the like. In the second zone (S2) adjacent to the first section,
pyrolysis of fee~3~tock, formation of precursor of carbon black and growth of primary particle
of carbon black advance, subsequently to the introduction of liquid hydrocarbon feedstock into
the primary combustion gas stream. Finally, in the third zone (S3), the effluent is quenched by
cooling rnedium from quench 5 such as water or the like to terrninate the reaction and produce
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carbon black.
We have discovered that steam, introduced from a position, 6, near to or at the position
of fee l~tock introduction, 4, can restrain both specific surface area and structure developments
of carbon black formed. More particularly, we have found that the position of introduction of
steam is important to restrain both specific surface area and structure developments of carbon
black and thus produce carbon black products having lower surface areas and structure than are
produced in a similar manner in the absence of steam introduction.
According to the process of the present invention the distance (L) from the position of
introduction of fee~l~tock to that of introduction of steam, U~ ~UIl or downstream, from the
position of feeA~tor,k introduction must be smaller than diameter (D) of the throat where
feedstock is introduced such that L/D ranges from O to less than 1Ø
The diameter of the throat into which feedstock is introduced is generally optimized
according to intrinsic factor for individual reactor in a furnace carbon black process.
Regardless of the shape of the reactor, the same results are obtained in all cases of steam
introduction wherein L/D ranges from O to less than 1Ø
Where the amount of steam introduced is less than 1% by weight of feedstock
introduced, the effect of steam introduction on restraint both of specific surface area and
structure of carbon black is slight. The degree of restraint of specific surface area and structure
development of carbon black is approximately proportional to the increase of steam level
introduced. Where an extremely high level of steam is introduced, formation of carbon black
itself is restrained by severe obstruction of formation of carbon black precursor due to
excessive steam. It is difficult to introduce steam in an amount more than 15% by weight of
the feedstock introduced while carrying on the production of carbon black. Therefore in a
preferred process of the present invention, the aTnount of steam introduced into the combustion
gas stream ranges from 1 to 15%, by weight, of the amount of feedstock introduced.
The following testing procedures are used in evaluating the analytical and physical
~, o~. lies of the carbon blacks produced in the following Examples.
As measures of specific surface area and structure of carbon black in every actual and
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colllld~l examples described herein, data obtained by the following testing procedures are
adopted.
Slpecific Surface Area by Nitrogen Absorption: Based on BEI method (N2SA). This
was determined in acco,d~lce with ASTM D3037 for E~xample I and Example II.
Iodine Absorption No.: This was determined in accordance with JIS K-6221 for
Example I and in acc~ ce with ASTM D1510 for Examplc II.
DBP (Dibutyl Phth~l~te) Absorption No.: This was determined in accord~,ce with JIS
K-6221 for Example I and in accordance with ASTM D3493 for Example II.
C~J~ sed DBP Absorption No. was determined after compression treatment of four
times repe~ted by 24,000 psi load. This was determined in acccordance with ASTM D3493 for
Example I.
The effectiveness and advantages of the present invention will be further illustrated by
the follovring examples.
Example ][.
This Example illustrates the process of the present invention wherein L/D is greater than
0, and less than 1.0, in comparison to processes without steam introduction.
Experiments were con~1ucteDd in a reactor depicted in Fig. 1. Length of the first zone
(S 1) of reactor is 3000mm, length of the second zone (S2) is 15000mm and diameter of throat
(D) where feedstock is introduced is 200mm. Primary ~upe~ies of fuel and feedstock
employed are listed in Table 1. An aqueous solution of potassium ion, for structure control, is
added to the feedstock both for actual and contrast examples.
I
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Table 1
FUEL AND FEEDSTOCK ADOPTED
FUEL ¦ FEEDSTOCK r
Type Liquid Hydrocarbon
Density(15~C) [g/cm3] 0.970 1.057
Viscosity (50~C) [c St] 5 15
C-atom [wt %] 89.8 91.1
H-atom [wt %] 10.1 8.6
Total Calorific Value [kcal/kg] 9920 11230
Data obtained based on actual examples are shown in Table 2 and those on contrast
examples in Table 3.
Additionally the specific surface area of a carbon black is dependent upon its structure.
There is also a lowest limit of specific surface area of a carbon black produced in a furnace
process due to operational limits of the reactor employed. In a furnace process there must,
therefore, exist a minimum specific surface area corresponding to a given structure. This
mh.illlulll specific surface area is designated "Limited Specific Surface Area" hereinafter. The
Limited Specific Surface Area value varies according to the different shape of the reactor. In
the case of the reactor employed for the actual and contrast examples of Tables 2 and 3, the
limit specific surface areais calculated using the following equation (1):
[Limited Specific Surface Area] = 78.5-0.748 x [Compressed DBP] Equation (1)where nitrogen surface area data, compressed DBP data and operation conditions adopted were
taken into consideration.
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TAPLE2
Actual Cx~", l~s 1 2 3 4 5 6
Combustion Air Rate (Nm3Au) 3530 3530 3530 3530 3530 3530
Fuel Rate (kg/hr) 80 80 80 80 80 80
FeGd~ocl; Rate (kg/hr) 1800 1770 1800 1870 1620 1590
Potassium Rate (g/hr) o 128 0 9 9 15
Position of rae-l~lock and Ste~m Intro~uced
Dist;mce from Position (L) (mm) 30 30 30 30 1 ~0 150
(L)/(D) 0.15 0.15 0.15 0.15 0.75 0.75
Steam Rate Introduced (kgAlr) 30 50 70 50 85 200
Steam/Feedstock (%wt) 1.7 2.8 3.9 2.7 5.2 12.6
ugen Sp. Sur. Area (m2/g) 22.3 22.5 19.1 18.0 26.1 29.8
lodine Adsorption No. (mg/g) 22.6 18.2 17.1 11.5 25.6 32.8
DBP Absor~tion No. (cc/100g) 100-6 60.4 79.0 89.2 84.3 81.2
t,ou"~ressed DBP (cc/100g) 71.7 56.2 60.5 65.7 63.9 64.6
Umit Specific Surface Area (m2/g) 24.9 36.5 33.2 29.4 30.7 30.2
Limit Specific Surface Area Index (m2/g) -2.6 -14.0 -14.1 -11.4 -4.6 -0.4
TABLE3
Contrast [Xdl l l, 'c s CE 1 CE 2 CE 3
CombustionAirRate (Nm3/hr) 3530 3170 3170
Fuel Rate (kg/hr) 80 70 70
Feedstnck Rato (kgAlr) 1870 1760 1800
Potassium Rate (gAlr) 27 3408 12150
Position of FeGdsloclc and Steam I ~troduced
Di:~tance from Position (L) (mm) NA NA NA
(L)/(D) NA NA NA
$team Rate Introduced (kg/hr) 0 0 0
Steam/Feedstock (% wt) 0 0 0
Nilrugell Sp. Sur. Area (m2/g) 26.5 40.6 44.2
IDdine Adsorption No. (mg/g) 22.9 38.2 36.7
DBP Abso-~,lion No. (cc/100g) 106.5 78.3 76.0
Cc,-.. ,urt:ssed DBP (cc/100g)73.7 67.8 67.0
Limlt Specific Surface Area (m2/g) 23.4 27.8 28.4
Limit Specific Surface Area Index (m2/g) 3.1 12.8 15.8
NA = Not ,~p,~'ic ' '~
As shown in case of contrast examples, difference from nitrogen specific surface area
to limit specific surface area is positive because limit specific surface area is possible minimum
value as specific surface area for conventional furnace black, and it means also the smaller
absolute value of the difference the closer to limit of the reactor operation conditions. Then, the
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difference is defined as limit specific surface area index by means of the following equation (2):
tLimit Specific Surface Area Index] = Equation (2)
tNitrogen Specific Surface Area]- [Limit Specific Surface Area]
When limit specific surface area and limit specific surface area index of actual examples
are calculated using equations (1) and (2), all of limit specific surface area indices are negative.
This means that by the introduction of steam, carbon blacks having lower specific surface areas
than the minimum Limit Specific Surface Area of the reactor adopted are obtained, and it is
obvious that the present invention is very effective to produce carbon blacks having low
specific surface area.
Since, in the case of the actual examples, the absolute value of Limit Specific Surface
Area index demonstrates directly the effect of steam introduction on restraint of specific surface
area, it proves, for in~t,tn~e referring to actual examples, that the introduction of about 3%
steam can restrain specific surface area at least by about 14 m2/g or more.
Adopting the method of the present invention, as shown in actual example 4 of Table 2,
carbon blacks having specific surface areas as low as that of thermal black, which has been
regarded as difficult to produce by conventional furnace process, are able to be manufactured.
Furthermore, these blacks have much higher structure than thermal black and havecharacteristics which cannot be found in conventional furnace black.
Example II.
This Example illustrates the process of the present invention wherein L/D equals 0, in
cc,n~p~ison to processes without steam introduction.
Experiments were cont~llcted in a reactor typical of the type utilized in conventional
carbon black production processes and similar in configuration to the reactor depicted in Fig. 1.
The diameter of throat (D) where feedstock was introduced was 50.8 millimeters (mm).
Feedstock was introduced through three tips 0.838 mm in diameter located in orifices spaced
evenly around the outer periphery of the throat. In the runs where steam was introduced, the
steam was introduced through a sheath annulus surrounding each feedstock injection tip. As
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will be noted, however, this is merely exempla~y and is not intended to be limiting of the
methods usable for introducing steam.
T he effluent was quenched through the use of a quench located 5.44 meters from the
point of fee~tQck introduction.
Plimary p~ lies of fuel and fee~l~toc~ employed are listed in Table 4. Potassium ion
aqueous solution as alkali metal ion for structure control is added to feedstock both for actual
and contrast examples.
Table 4
FUEL AND FEEDSTOCK ADOP~ED
FUEL FEEDSTOCK
Type Natural GasLiquid Hydrocarbon
Density~15~C) [g/cm3] 0.583 1.105
Viscosity (50~C) [c St] NotAvailable130.0 (estim~tç~)
C-atom lwt %] 73.1 90.6
H-atom lwt%] 23.8 7.5
Total Ca]orific Value [kcal/kg] 12800 9700
Thle results of the expeTimçnt~l runs are shown in Table 5, which includes two runs
exemplary of the process of the present invention wherein I~)=0 and one control run without
steam introduction.
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TABLE5
Cx~,l,, 'ss CE 4 7 8
Combustion Air Rate (Nm3/hr) 375 375 375
Comb. Air Preheat ~C 482 482 482
Fuel Rate (kg/hr) 12.2 12.2 12.2
Feed:-'uckRate (kg/hr) 115.7 115.7 115.7
Primary Combusion % 250 250 250
Overall Combustion % 28 28 28
Position of Feedstock and Steam I 1troduced
Distance from Position (L) (mm) o 0 0
(L)/(D) 0 0 0
Steam Rate Introduced (kg/hr) 0 4.5 13.5
Steam/Feedstc-ck (% wt) 0 3.9 11.7
N ogel1 Sp. Sur. Area (m2/g) 74.9 63.3 57.3
lodine Adsol~liol- No. (mg/g) 77.7 62.3 55.6
DBP Abso~ iull No. (cc/100g) 131.9 121.1 115.0
As shown in Table 5, introduction of steam, according to the process of the present
invention wherein L/D=0, results in carbon blacks having reduced surface area and reduced
structure. The reduction in surface area is shown by Example Runs 7 and 8, of the process of
the present invention, having decreased N2 Surface Areas and Iodine Adsorption Nos. in
colllpalison to contrast example 4 (CE 4) wherein no steam was introduced. The reduction in
structure is shown by Example Runs 7 and 8, of the process of the present invention, having
decreased DBP Absorption Nos. in c~,lllpalison to contrast example 4 (CE 4) wherein no steam
was introduced.
As also shown in Table 5, by a comparison of the results for Example Runs 7 and 8 of
the process of the present invention, increasing the rate of steam introduction, results in a
greater decrease in surface area and structure.
It should be clearly understood that the forrns of the present invention herein described
are illustrative only and are not intended to limit the scope of the invention.
