JPH11181323A - Production of carbon black - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an equipment and a process for producing carbon black having a small primary particle diameter, a small agglomerate diameter and a narrow agglomerate distribution in which the ratio agglomerates with a large diameter is small. SOLUTION: In the process for producing carbon black in the equipment having a first reaction zone for forming a combustion gas stream; a second reaction zone for mixing the obtained combustion gas stream with a hydrocarbon to form carbon black; and a third reaction zone situated downstream of the second reaction zone and used for stopping the reaction, there is no substantial disturbance to the flow state of the gas stream within 1.5 ms after the introduction of the hydrocarbon into the apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of carbon black used for various uses such as a filling material, a reinforcing material, a conductive material and a color pigment, and a production apparatus and a production method effective for controlling the physical properties thereof. It is about.

[0002]

2. Description of the Related Art Carbon black is widely used as a pigment, a filler, a reinforcing pigment, and a weather resistance improver. Generally, carbon black is produced in a first reaction zone of a cylindrical carbon black production furnace in a furnace axial direction. Alternatively, the oxygen-containing gas and the fuel are introduced tangentially, and the high-temperature combustion gas stream obtained by the combustion is supplied to the first reaction zone, and subsequently to the first reaction zone having the reduced cross-sectional area having a reduced cross-sectional area. A furnace type production method is known in which a raw material hydrocarbon is introduced into the gas stream while moving to a second reaction zone to generate carbon black, and a reaction gas is rapidly cooled in a third reaction zone to stop the reaction. I have.

[0003] Carbon black used as a colorant in resin colorants, printing inks and paints is required to have excellent blackness, dispersibility, gloss and coloring power, and is mainly used as a reinforcing agent for automobile tires. The carbon black to be used is required to have excellent wear resistance. Blackness and tinting strength depend greatly on the primary particle size of carbon black,
It is known that the smaller the primary particle diameter, the higher the blackness. For example, the relationship between blackness and primary particle size is disclosed in
No. 68992. Further, it is known that such carbon black exhibits a high degree of wear resistance when used as a tire reinforcing agent.

[0004] In order to obtain carbon black having a small particle size, it is necessary to spray raw material hydrocarbons into a high-speed gas stream in a choke portion, and use the motion and heat energy of the gas to atomize a liquid feedstock. It is well known that it works. Further, the distribution of the primary particle diameter also has a significant effect on the rubber properties, particularly on the tire tread rubber composition which is required to have high abrasion resistance, and it is said that the narrower the primary particle diameter distribution is, the more preferable. In general, the smaller the average particle size, the narrower the distribution. However, a method for narrowing the primary particle size distribution is also disclosed.

For example, Japanese Patent Application Laid-Open No. 3-33167 discloses that a chalk having a length sufficient to allow the carbon black formation reaction to be substantially completed is formed at an enlarged outlet portion of the chalk. There is disclosed a method of obtaining carbon black having a relatively narrow particle size distribution by a method that does not exert the influence of swirling current, so-called "back mixing", during the carbon black producing reaction.

[0006] Aggregates are factors that affect the properties of carbon black as well as the primary particle size. The size of the agglomerates greatly affects the tensile stress and extrusion characteristics when compounded with rubber, the dispersibility, blackness and viscosity when compounded with ink and paint vehicles and resins. Carbon black is ultimately composed of aggregates of many primary particles, and controlling the size and shape of these aggregates leads to controlling the properties of carbon black itself, As important as controlling the primary particle size.

Regarding the effect of aggregates, the size and distribution of the aggregates are quantified by regarding the aggregates as simple particles. By treating the aggregates as particles, various particle diameter measurement techniques can be applied, and the size of the aggregate measured in this way is expressed as the aggregate diameter. Aggregates have a significant effect on the properties of carbon black, and it has become clear that many of the properties of carbon black, previously thought to be due to primary particle size, can be better explained by the aggregate size. Have been. For example, it is considered that the diameter of the aggregate plays a large role in optical properties such as coloring power and dynamic viscoelastic properties and reinforcing properties of the compounded rubber composition. It is known that the smaller the agglomerate diameter, the higher the degree of blackness when viewed in resin coloring applications.

In general, in order to reduce the diameter of aggregates, an alkali metal salt or a solution thereof is added to a raw material oil, or is burned or introduced into a reaction zone. However, when incorporated into vehicles and resins of inks and coatings, the reduction in particle size and the size of aggregates cause deterioration in dispersibility and fluidity. It is the functional group on the particle surface that improves the dispersibility and the deterioration of the fluidity due to the reduction in the particle size and the size of the aggregate, and the dispersibility is improved more and more. For example, Japanese Patent Publication No. 46-18368 discloses a method of oxidizing carbon black with ozone. In addition,
No. 13808 discloses a method of oxidizing carbon black with hydrogen peroxide, but not all such acidic carbon blacks show excellent dispersibility in vehicles.

Therefore, regarding the relationship between the properties of carbon black and the physical properties of the resin, it is important to satisfy the blackness and dispersibility, which are generally in a trade-off relationship.

[0010]

SUMMARY OF THE INVENTION The present invention provides a method for producing carbon black satisfying both high blackness and good dispersibility. The present invention has a small primary particle size,
Provided are a production apparatus and a method for obtaining carbon black having a small aggregate diameter, a small aggregate distribution width, and a large aggregate small diameter.

[0011]

Means for Solving the Problems The present inventors analyze the dispersion behavior of carbon black in a matrix and the factors affecting blackness to obtain carbon black having higher blackness and better dispersibility than before. Therefore, as a result of various studies, it was found that carbon black having fine aggregates having no adverse effect on dispersion and uniform aggregates without large aggregates having an adverse effect on blackness had high blackness and good dispersibility. That is, the present inventors have found that carbon black having a small particle diameter, a small aggregate diameter and a sharp distribution of the aggregate diameter and having no large aggregate diameter has high blackness and good dispersibility. The inventors have found that the above object can be achieved by setting the gas flow after the introduction of the raw material hydrocarbon into the apparatus into a specific flow state, and have accomplished the present invention.

The present invention provides a first reaction zone for forming a combustion gas stream, a second reaction zone for mixing a raw material hydrocarbon with the obtained combustion gas stream to produce carbon black, and a second reaction zone for forming carbon black.
When producing carbon black in a carbon black producing apparatus having a third reaction zone downstream of the reaction zone and stopping the reaction, the flow of the gas stream is reduced within 1.5 ms after the raw material hydrocarbon is introduced into the apparatus. A method for producing carbon black characterized by substantially not disturbing the state, and a first reaction zone for forming a combustion gas flow,
An apparatus for producing carbon black, comprising: a second reaction zone for mixing raw hydrocarbons with the obtained combustion gas stream to produce carbon black; and a third reaction zone downstream of the second reaction zone for stopping the reaction. The carbon black producing apparatus is characterized in that the shape of the gas flow path within 1.5 ms from the introduction position of the raw hydrocarbon does not substantially disturb the flow state of the gas flow.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
FIG. 1 is a schematic longitudinal sectional view of a main part showing an example of the carbon black producing apparatus of the present invention. The furnace has, in a longitudinal direction, a first reaction zone 1 for forming a combustion gas stream, and a second reaction zone 2 having a choke section for mixing raw hydrocarbon with the obtained high-temperature combustion gas stream to produce carbon black. And a third reaction zone 3 downstream of the second reaction zone, which stops the reaction. The process itself in each reaction zone can basically adopt the same method as in the prior art.

In the first reaction zone, fuel hydrocarbons and an oxygen-containing gas are generally introduced from the combustion nozzle 5 to generate a combustion gas flow. Air, oxygen or mixtures thereof are used as the oxygen-containing gas, and hydrogen, carbon monoxide, natural gas, petroleum gas and petroleum liquid fuels such as heavy oil, coal-based liquid fuels such as creosote oil are used as fuel hydrocarbons. Is used.

In the second reaction zone, the raw hydrocarbon is sprayed and introduced into the choke section from the raw hydrocarbon introduction nozzle 6 provided in parallel or in the lateral direction with the combustion gas flow obtained in the first reaction zone.
The raw hydrocarbon is pyrolyzed and converted into carbon black. As raw material hydrocarbons, aromatic hydrocarbons such as benzene, toluene, xylene, naphthalene, and anthracene;
Coal-based hydrocarbons such as creosote oil and carboxylic acid oil, heavy petroleum oils such as ethylene heavy-end oil and FCC oil, acetylene-based unsaturated hydrocarbons, ethylene-based hydrocarbons, and aliphatic saturated carbons such as pentane and hexane Hydrogen or the like is preferably used.

The second reaction zone generally includes a choke portion whose inside diameter is sharply reduced as compared with the portion before and after the second reaction zone, and this mode is adopted in the present invention. In the third reaction zone, water or the like is sprayed from the reaction stop fluid introducing nozzle 7 in order to cool the high-temperature reaction gas to 1000 to 800 ° C. or lower. The cooled carbon black is subjected to a known general process such as separation and recovery from gas with a collecting bag filter or the like.

Here, the present invention is characterized in that the flow state of the gas stream is not substantially disturbed within a predetermined time after the raw material hydrocarbon is introduced into the apparatus. In the present invention, “does not substantially disturb the flow state of the gas flow” specifically means the following. Generally, in terms of hydrodynamics, "turbulence" refers to turbulent energy (m ^ 2 / s ^ 2) and eddy dissipation rate
It is represented by the size of (m ^ 2 / s ^ 3). The present inventors performed various experiments and numerical simulations applying fluid dynamics, and examined various experimental conditions in association with physical quantities of flow. As a result, especially in order to prevent the formation of aggregates having a large aggregate diameter, at least one of the turbulent flow energy and the eddy dissipation rate must be increased within 1.5 ms after the feed oil (feed hydrocarbon) is introduced. It has been found that keeping the rate within 10% is effective for not substantially disturbing the flow state of the gas stream. That is, by suppressing at least one of the increase rate of the turbulent flow energy and the eddy dissipation rate within 10%, the disturbance of the flow state of the gas flow is substantially suppressed, and the large aggregates are formed in the process of carbon black aggregate formation. It is believed that the development of aggregates of a diameter can be substantially suppressed.

As an example, a more detailed description will be given with reference to FIG. 2 which shows how the turbulent flow energy at the center of the flow path changes. At the choke inlet, the turbulent flow energy shows a peak due to a decrease in the flow path cross-sectional area (A), and then gradually decreases. The peak at the enlarged portion of the choke outlet again shows a peak (C). 1.5 m after introduction of the raw material hydrocarbon
Within s, the rate of increase of the turbulent energy or the eddy dissipation rate is suppressed to 10% or less. "In FIG. 2, the time from the feedstock introduction point B to the point C at which the turbulent energy increased in FIG. 5 ms or more, or the ratio of the turbulence energy value D immediately before point C to the maximum value E of turbulence energy at point C, E / D, is 1.1 or more.

In this example, the turbulent flow energy decreases monotonically from B to immediately before C, but the present invention is not limited to the monotonic decrease. According to the present invention, the reaction in which the primary particles and agglomerates of the carbon black are maintained after the supply of the raw material hydrocarbon is continued until the primary particles and the agglomerates of the carbon black are generated. It is considered that carbon black having a uniform aggregate diameter and having no large aggregate diameter can be obtained since high disturbance due to a significant change in the cross-sectional shape of the flow channel or the like is prevented before the completion of the process.

That is, the aggregates of carbon black are formed by condensing the raw material hydrocarbons after thermal decomposition, agglomerating into droplets, forming a precursor serving as a nucleus, generating primary particles, and then subjecting the particles to mutual collision. It is considered to be formed by fusion carbonization. Therefore, it is considered that it is desirable that the choke portion is long and that the aggregate formation region does not have a high disturbance field due to a change in the flow path of the throttle portion or the like. The inventors of the present invention have clarified that it is necessary to control for a longer time when controlling the distribution of aggregates than when controlling the particle size distribution. In the present invention, this problem has been achieved by the fact that the flow path shape of the gas flow within 1.5 ms after the introduction of the raw material hydrocarbon does not substantially disturb the flow state of the gas flow. If disturbance occurs due to a significant change in the shape of the channel within 1.5 ms after the introduction of the raw material hydrocarbon, the formation of aggregates having a large aggregate diameter cannot be ignored, and the carbon black aggregate distribution is broad. It will be something.

Further, in the present invention, it has been found that the diameter of the aggregate of carbon black is also affected by the diameter of the choke, and the smaller the diameter of the choke, the sharper the distribution of the aggregate. The diameter of the chalk is 30 to 170 mm, preferably 50 to 150 mm. 170 in diameter
If it exceeds mm, the aggregate distribution of the obtained carbon black tends to be broader.

A method for obtaining a carbon black having a relatively narrow particle size distribution while keeping the chalk length long is disclosed in JP-A-3-3.
No. 3167. However, there is no description about the effect on the aggregate size distribution, which is the most important factor affecting the properties of carbon black, and the preferred size of the chalk is 7 to 10 inches in diameter. There is only. The present invention
By reducing the diameter of the chalk and lengthening the length of the chalk, the aggregate diameter is small and the distribution is sharp, and the carbon black with a large aggregate diameter is reduced,
The content is different from the above publication.

The higher the gas flow rate in the choke, the better. After introduction of the raw material hydrocarbons, they are atomized by the motion and heat energy of the combustion gas. The speed of the combustion gas at that time is preferably as high as possible, preferably at least 250 m / s,
m / s is preferred. In order to uniformly disperse the raw material hydrocarbons in the furnace, it is preferable that the raw material hydrocarbons are introduced into the furnace from two or more nozzles. Keeping the gas in the chalk at a high speed makes it possible to use the kinetic energy and heat energy of the combustion gas to refine the raw material hydrocarbons, resulting in a carbon black with a small particle size and the turbulence in the chalk. By flow mixing, the atmosphere in which the carbon black generation reaction occurs becomes uniform, and carbon black having a narrow particle size distribution can be obtained. In addition, since the heat energy of the combustion gas can be efficiently used for the carbon black generation reaction, the reaction speed is increased and the reaction field is uniform, and as a result, carbon black having a small aggregate diameter can be produced. .

The introduction position of the raw material hydrocarbon is preferably within 1 ms, preferably within 0.6 ms, based on the cross-sectional average flow velocity of the combustion gas from the choke portion and from the choke inlet. Suitable for producing uniform carbon black. In this case, the chalk entrance means a position where the chalk reaches the narrowest part. It is desirable to suppress the oxygen concentration in the combustion gas as much as possible. The presence of oxygen in the combustion gas causes a partial combustion of the feed hydrocarbons in the second reaction zone, resulting in a non-uniform reaction zone. The oxygen concentration in the combustion gas is preferably 3 vol% or less, more preferably 0.05 to 1 vol%.

The temperature of the combustion zone is desirably a sufficiently high temperature atmosphere in order to uniformly vaporize and thermally decompose the raw material hydrocarbons, preferably from 1600 to 1800 ° C. or more, more preferably from 1700 to 2400 ° C. As an evaluation index for aggregates, centrifugal sedimentation in an aqueous dispersion of cDBP or carbon black and electron microscopic analysis are known. Recently, centrifugal sedimentation has been frequently used to evaluate the size and distribution of aggregates. I have. In the present invention, the ratio of the half-width D1 _{/ 2} of the maximum frequency Stokes equivalent diameter D _mod and the maximum frequency Stokes equivalent diameter in the aggregate Stokes equivalent diameter distribution by centrifugal sedimentation as an index of the sharpness of the aggregate diameter. and using D ₇₅ as an indication that there is no large agglomerates diameter.

When the above method is used, the average particle diameter is 25 n
m or less, the ratio of the half-width of the maximum frequency Stokes equivalent diameter D _mod and the maximum frequency Stokes equivalent diameter in the aggregate Stokes equivalent diameter distribution by the centrifugal sedimentation method, that is, the ratio of D _1/2 / D _mod is 0.6 or less, volume 75% diameter and D _mod ratio D ₇₅ / D _mod
Is 1.3 or less, it is possible to obtain carbon black having a small particle diameter, a small aggregate diameter, a sharp aggregate diameter distribution, and a small number of large aggregate diameters. Further, it is more preferable that the particle diameter is 20 nm or less in order to increase the PVC blackness.

[0027]

The present invention will be described below with reference to examples of the present invention.
The present invention is not limited to this. (Examples 1 to 4) A first reaction zone having an inner diameter of 500 mm and a length of 1400 mm provided with an air introduction duct and a combustion burner,
A second reaction zone, which is connected to the first reaction zone and has a plurality of raw material nozzles penetrating from the periphery and has an inner diameter of 60 mm and a length of 800 mm, and an inner diameter of 100 m equipped with a quench device.
A carbon black production apparatus having a structure in which a third reaction zone having an m length of 6000 mm and a control valve having an inner valve diameter of 80 mm as a throttle mechanism were sequentially connected was installed. (Example 5) A carbon black producing apparatus in which the choke portion in Example 1 to 4 had a tapered shape having an inner diameter of 50 mm at the inlet and an inner diameter of 100 mm at the outlet was installed.

Using each of the production apparatuses of Examples 1 to 5, creosote oil was used as fuel and raw material hydrocarbon, and carbon black was produced under the conditions shown in Table 1. Table 2 shows various characteristics of the obtained carbon black. The following test method was used to determine the analytical properties of the carbon black produced according to the present invention. (Specific surface area) The specific surface area (N ₂ SA) is ASTM D3037-8
Determined according to 8. (CDBP) Crushed DBP absorption number (cDBP) is ASTM
Determined according to D-3493-88. (D _mod , D _1/2 ) Maximum frequency Stokes equivalent diameter (D _mod )
The Stokes equivalent diameter _half width (D _1/2 ) was determined as follows.

A 20% ethanol solution was used as a spin solution, and the Stokes equivalent diameter was measured by a centrifugal sedimentation type flow rate distribution measuring device (DCF3 type manufactured by JL Automation), and the Stokes equivalent diameter was measured relative to the given sample. A histogram of the target occurrence frequency (FIG. 5) is created. A line (B) is drawn from the peak (A) of the histogram to the X-axis in parallel to the touch, and ends at the point (C) on the X-axis of the histogram. The Stokes diameter at point (C) is the maximum frequency Stokes equivalent diameter D _mod . Further, the midpoint (F) of the obtained line (B) is determined, and a line (G) is drawn through the midpoint (F) and parallel to the X axis. The line (G) intersects the histogram distribution curve at two points D and E. The absolute value of the difference between the two Stokes diameters of the two points D and E of the carbon black particles is the Stokes equivalent diameter half width D
_1/2 value. (D ₇₅ ) The volume 75% diameter (D ₇₅ ) was determined as follows.

In the above method of determining the maximum frequency Stokes diameter, a histogram of the equivalent Stokes diameter versus the relative frequency of occurrence of the sample The volume was obtained from each Stokes diameter and frequency from FIG. Make a graph showing the total volume of the sample. (FIG. 6) Therefore, the middle point (A) in FIG. 3 represents the sum of the volumes of all the samples. Here, a point (B) having a value of 75% of the total volume is determined, and a line is drawn from the point (B) to the X axis until the curve intersects the equilibrium. A line is equilibrium drawn from the point (C) to the Y axis, and the value at the point (D) crossing the X axis is the volume 75% diameter (D ₇₅ ). (PVC Blackness) The PVC blackness is determined by adding the carbon black of the present invention to a PVC resin, dispersing and sheeting with two rolls, and using Mitsubishi Chemical Corporation carbon black “# 40”.
The blackness of "# 45" was set to 1 point and 10 points, respectively, and a reference value was determined, and the blackness of the material was evaluated by visual perception. (Dispersion index) The dispersion index was evaluated by the following method. PE
The state of dispersion in the resin was observed, and the number of undispersed aggregates was counted. The larger the number, that is, the larger the dispersion index, the worse the dispersibility.

LDP with 250cc Banbury mixer
E-resin mixed with 40% of sample carbon black and 115
Knead at 4 ° C for 4 minutes. Mixing conditions LDPE resin 101.89 g Calcium stearate 1.39 g Irganox 1010 0.87 g Sample carbon black 69.43 g Next, the mixture is diluted with a two-roll mill at 120 ° C. so that the carbon black concentration becomes 1%.

Conditions for preparing diluted compound LDPE resin 58.3 g Calcium stearate 0.2 g Carbon black 40% blended resin 1.5 g A sheet having a slit width of 0.3 mm was cut into chips, which were cut into chips and placed on a hot plate at 240 ° C. for 65 mm. ± 3μm
Into a film. The diameter distribution of undispersed aggregates having a diameter of 0.2 mm or more in a 3.6 mm × 4.7 mm field of view is measured with an optical microscope having a magnification of 20 ×, and the total area is calculated. This area is calculated by dividing the total area by the reference area based on the area of the undispersed aggregate having a diameter of 0.35 mm as the number of reference particles. This is observed in 16 or more visual fields, and the average value is used as the dispersion index. (Particle size) According to electron microscopy. Electron microscopy is a method described below. The carbon black is put into chloroform and irradiated with ultrasonic waves of 200 KHz for 20 minutes to disperse, and then the dispersion sample is fixed to the supporting film. This is photographed with a transmission electron microscope, and the particle diameter is calculated from the diameter on the photograph and the magnification of the photograph. This operation is performed about 1500 times, and the values are obtained by arithmetic averaging. (Comparative Example 1) The carbon black of Comparative Examples 1 and 2 was manufactured under the conditions shown in Table 1 by using a manufacturing furnace in which the length of the choke portion of the carbon black manufacturing furnace used in the examples was changed to 500 mm. Table 2 shows the physical properties. Comparative Example 3,
Comparative Example 4 showed physical properties of commercially available carbon blacks “# 990” and “# 960” of Mitsubishi Chemical Corporation.

When the carbon black according to the present invention is compared with that of the comparative example, as shown in Table 2, in Comparative Examples 1 and 2, significant disturbance was caused by the spraying of the raw oil (as shown in FIG. 2, the disturbance was substantially ignored). Since the time until the gas flow is disturbed to an extent that is not possible is less than 1.5 ms, the formation of aggregates having a large particle size cannot be suppressed. Therefore, the carbon black obtained in the examples is smaller than that of the comparative example. , D _1/2 / D _mod is small, and the distribution of the aggregate diameter is sharp. Also, D ₇₅ is small,
There are few large aggregates. In addition, it exhibits high blackness, has a low dispersion index, and has good dispersibility.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

As described above, when the carbon black obtained by the present invention is used as a black pigment in resin colorants, printing inks, and paints, the ratio of black has conventionally been considered to be difficult due to transfer. Satisfies degree and dispersibility.
Therefore, it is very useful as a black pigment in resin colorants, printing inks and paints.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an apparatus for producing carbon black in the present invention.

FIG. 2 is a diagram showing an example of a state of a change in turbulent flow energy.

FIG. 3 is a diagram showing a method of obtaining a maximum frequency Stokes equivalent diameter (D _mod ) and a Stokes equivalent diameter _half width (D _1/2 ).

FIG. 4 is a diagram showing a method for obtaining a volume 75% diameter.

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Susumu Nakajima 1000 Kamoshita-cho, Aoba-ku, Yokohama-shi Mitsubishi Chemical Corporation Yokohama Research Laboratory

Claims (7)

[Claims] 1. A first reaction zone for forming a combustion gas stream;
In a carbon black producing apparatus having a second reaction zone for mixing raw hydrocarbons with the obtained combustion gas stream to produce carbon black, and a third reaction zone downstream of the second reaction zone for stopping the reaction, A method for producing carbon black, which does not substantially disturb the flow state of a gas flow within 1.5 ms after the raw hydrocarbon is introduced into the apparatus when producing black. 2. The method for producing carbon black according to claim 1, wherein the second reaction zone has a choke portion having a major axis of 30 to 170 mm. 3. The flow rate of the combustion gas in the choke portion is 250 m.
3. The method for producing carbon black according to claim 2, wherein the carbon black is not less than / s. 4. The method for producing carbon black according to claim 1, wherein the introduction position of the starting hydrocarbon is within the chalk portion and within 1 ms from the chalk inlet. 5. The method for producing carbon black according to claim 1, wherein the oxygen concentration in the combustion gas at the feed hydrocarbon introduction position is 3 vol% or less. 6. A first reaction zone for forming a combustion gas stream;
An apparatus for producing carbon black, comprising: a second reaction zone for mixing raw hydrocarbons with the obtained combustion gas stream to produce carbon black; and a third reaction zone downstream of the second reaction zone for stopping the reaction. An apparatus for producing carbon black, characterized in that the flow path shape of the gas flow within 1.5 ms from the introduction position of the raw hydrocarbon does not substantially disturb the flow state of the gas flow. 7. The apparatus according to claim 6, wherein the second reaction zone has a choke portion having a major axis of 30 to 170 mm.