US2829951A - Process and apparatus for the production of carbon black - Google Patents

Description

E. WAGNER ET AL April 8, 1958 PROCESS AND APPARATUS FOR THE PRODUCTION. OF CARBON BLACK Filed July 10, 1953 JNVENTORS ERNST WAGNER FRIEDRICH EN DTER ATTORNEYS much as it has United States Patent @fiice PROCESS AND APPARATUS FOR THE PRODUC- TION OF CARBON BLACK Ernst Wagner, Rheinfelden, Baden, and Friedrich Endter, Konstanz, Baden, Germany, assignors to Deutsche Goldund Silher-Scheideanstalt vorrnals Roessler, Frankfurt am Main, Germany, a corporation of Germany Application .l'uly 10, 1953, Serial No. 367,294 Claims priority, application Germany July 23, M52 1 Claim. (Cl. 23-209.6)

The present invention comprises a new and improved process for manufacturing carbon black from gaseous or vaporized hydrocarbons in the presence of oxygen or of gaseous mixtures containing oxygen, with or without the addition of combustible gases that may contain in the manufacture of carbon black by the so-called furnace black process, the procedure has hitherto generally been followed by introducing carbon compounds or by drocarbons, in the form of a mist, into a comparatively large flame, thereby tion and simultaneous formation of carbon black. In this process, the distribution of hydrocarbon in the flame region has not of course been homogeneous, so that the conditions of formation of carbon black at various points in the flame are necessarily quite different and it has been diificult to obtain a uniform product with respect to particle size and structure. Furthermore, the process of combustion of the hydrocarbon or combustible gas must supply not only the energy of decomposition for the formation of carbon black but also the heat of evaporation of the liquid hydrocarbon, which incidentally, owing to the very considerable increase of surface tension with decreasing diameter of droplets, may exceed the available energy of the constituents of the reaction.

There have previously been proposals for vaporizing hydrocarbons which are liquid under ordinary conditions and supplying them to the flame in vaporized form, separately from the combustible gases and the gaseous mixtures supplying the oxygen. While this may serve to improve the heat efilciency of the combustion process itself with respect to the cracking reaction, the method does not eliminate the difficulties resulting from non-homogeneous distribution of the constituents in the flame when separately introduced. This procedure likewise fails to ensure a uniform product and optimum yield. It has now been found that the production of carbo black from hydrocarbons in the presence of gaseous mixtures containing oxygen, with or without combustible gases in particular containing hydrogen, can be substantially simplified, improved in the direction of a more homogeneous and uniform high-grade product, and rendered more economical, by first homogeneously mixing the constituents and then causing them to react together in the flame. This process has been by no means obvious, inashitherto been considered necessary for processes involving reactions attended by a combustion to be carried on essentially in a preferential flame zone, especially when heat is withdrawn from the flame by a cracking reaction attendant upon the combustion. Separate introduction of the constituents has generally been considered desirable for the further reason that, according to the generally accepted view, a gaseous mixture supplied to a flame in homogeneously mixed form is liable to backfiring and to obstructions due to premature precipitation of the solid cracking-product. Surprisingly enough, it has been found that introduction of the constituents to the flame in homogeneous mixture not only does not entail hydrogen.

cracking them with partial combusthereby inhibiting 2,329,951 Patented Apr. 8, 1958 these disadvantages, but permits a safer, and more productive process, high-grade carbon black.

In the process of the invention, especially when oxygen as such or in the form of gaseous mixtures is introduced in at least sufficient quantity for complete combustion of the hydrogen content of the combustible gas, a comparatively small flame with maximum heat concentration is formed, wherein losses due to radiation are reduced to a minimum, and a maximum of energy is available for cracking the hydrocarbon.

The introduction of the constituents in a homogeneous mixture according to this invention has the further advantage that, owing to the resulting comparatively small size of the flame, the time of exposure of the carbon black formed to the flame can be shortened, thus permitting avoidance of undesirable surface modifications of the carbon particles. The formation of short flames, with a high ratio of flame volume to flame area or depth as indicated by the concept of the invention, can be further promoted by the aid of special burners, for example, a rosette burner.

In fact, for the successful practice of the process according to the invention, the use of suitably designed burners is of considerable importance. In the design of the burners, it is especially important that the mixture of the components be intimate and homogeneous, and that this be introduced into the flame in a uniform, smooth and preferably laminar flow from the common burner orifice. Therefore, the most suitable burners are those which, in addition to a mixing chamber for the gases taking part in the reaction, are provided with means by whichthe flow of gas can be rectified and stabilized. It may also be necessary to provide the burners with means by which the burner orifices can reliably be kept free from carbon deposits, without impairing the homogeneous composition of the flame to any major extent. For this purpose, the burner orifice may be fitted with mechanical scraper devices, for example a concentrically shaped movably mounted ring, or the rate of ignition of the issuing gases may be reduced, but only in the immediate vicinity of the rim of the burner, as by means of a stream of inert gas annularly traversing the mouth of the burner, the reaction in that region. The use of such a gas current, preferably of air, serves to keep the reaction away from the rim of the burner and/or to dilute the reaction mixture below the ignition point, and thus functions both mechanically and physically.

A tube burner which has proved eminently suited to the process of this invention has been selected for purposes of illustration and is shown in the accompanying drawings, in which:

Fig. 1 is a view of the burner in longitudinal section,

Fig. 2 is a view in cross section on the line 22 of Fig. 1, and

Fig. 3 is a fragmentary sectional view showing the nozzle of the burner equipped with a scraper.

The burner is indicated as directed into the open unobstructed combustion space 10 shown in dot-and-dash lines. It comprises a tube 11 having an open mouth or nozzle 12 at its inner end and a mixing chamber 13 in its outer end. The components of combustion are brought to the mixing chamber 13 by an inlet duct 14 which enters the mixing chamber 13 tangentially and an inlet duct 15 leading axially into the tube in offset relation. The entering gases or vapors are vigorously agitated by the tangential entry of the components delivered by the duct 14. For example, make gas such as natural gas or vaporized hydrocarbon oil may be admitted tanentially by the duct 14 while air or other oxygen-containing gas may be admitted by the duct 15.

Between the mixing chamber 13 and the ilame, a conmore economical while producing a uniform rectifying and stabilizing path.

' ous purposes.

siderable portion 16 of the tube is occupied by a series of bafiles 17 forming an elongated flow-rectifying chamber. An arrangement of the bafiies 17 is shown by way of example in the sectional view of Fig. 2. The baflles are in this case star-shaped sheets or barriers arranged symmetrically opposite each other with respect to the longitudinal axis of the tube as indicated in Fig. 2 by the lines 17' and so direct the mixed gases in a circuitous, In Fig. 2 it is suggested that the gas inlet 14 may be sub-divided and provided with a branch 14' in case it should be desired to conduct two components of the mixture separately to the burner.

For carrying out the process of the invention the axial inlet 15 is not essential. Alternatively, the gaseous fuel charged with hydrocarbon may be introduced through the inlet 14 and air or oxygen through the branch 14 without interfering with thorough mixing. Alternatively, air and/or oxygen may be introduced into the mixing chamber 13 partly through the branch 14 and partly through the duct 15.

In Fig. 1 the mouth or nozzle of the burner is shown as provided with a jacket 18 providing a con-centric chamber 19 and an annular outlet slit 20. Inert gas may be supplied to the jacket 19 by a duct 21, and by surrounding the flame at the nozzle of the burner the rate of ignition of the issuing gas may be reduced in the immediate vicinity of the rim of the burner. In this way the burner is kept free of objectionable carbon deposits and the flame confined in circumference.

Alternatively, the nozzle of the burner may be mechanically cleaned as suggested in Fig. 3 where it is shown as provided with a ring 23 having scraping fingers 24 shaped to engage the inner cylindrical face of the burner tube. The ring 23 is shown as provided with gear teeth by which it may be rotated or oscillated by means not herein shown.

The process according to the invention further permits the use of gaseous mixtures which, in addition to gaseous or vaporized hydrocarbon with or without combustible gases, contain oxygen only; i. e. the reaction may be carried on effectively and safely with the use of pure oxygen.

An advantage of this procedure is that the gaseous products of the combustion and/or cracking reaction are free from nitrogen, which is otherwise introduced with the combustion air. In a particularly advantageous embodiment of the process according to the invention as carried on with the use of pure oxygen, superheated steam may then be introduced into the reaction field,

namely in that part of the latter where the temperature of the gaseous reaction products remains at least 1000 C. The steam reacts with a portion of the carbon black formed according to the water gas reaction, forming carbon monoxide and hydrogen, at the same time permitting adjustment of the water gas equilibrium to convert any carbon dioxide contained in the exhaust to carbon monoxide. Thus the reaction of the steam with the carbon particles eifects a sort of etching of the surface of the particles, and hence a desirable activation of the carbon formed.

The introduction of steam serves to enrich the exhaust as a whole with carbon monoxide and hydrogen, thus giving it a composition permitting its utilization for vari- This gaseous mixture may, for example, be employed as a synthesis gas, or for vaporizing liquid hydrocarbons, or even as a combustible gas for the manufacture of the carbon black itself. The entire process of manufacture is thus rendered substantially more economical through the production of useful by-product gases, particularly when the gaseous exhaust mixture, after separation of carbon black and condensable com- 4 ponents, especially water, is returned into the closed circuit of the process.

In order to freeze or stabilize the water gas equilibrium established and to prevent the reverse formation of carbon dioxide, according to the Boudouard equilibrium, in the direction 2CO C+CO or otherwise, it is desirable to subject the reaction products, before they leave the reaction field proper, to sudden cooling by injection of water, without however lowering the temperatures of the gaseous mixture to or beyond the dew point of the latter.

If the process of the invention is carried on in a combustion chamber whose walls consist of a heat-radiating material, in particular ceramic, the carbon black formed may be calcined with resulting reduction of empyreumatic content. In this case, however, it is advisable to locate the calcining section between the flame itself and the point of injection of superheated steam intended to enrich the exhaust in carbon monoxide and hydrogen.

The raw material for the production of carbon black by the process of the invention may comprise hydrocarbons which are gaseous, or alternatively normally liquid but readily vaporizable under ordinary conditions, the term gaseous as used herein including vaporized liquid as well as normally gaseous hydrocarbons. The content of such liquid hydrocarbons with respect to non-volatile components should not as a rule be more than 8%, and preferably not more than 6%. The present invention contemplates the employment of mixtures of anthracenc oils and anthracene residues, naphthalene, aromatic recycle oils from petroleum refining, and similar liquid hydrocarbons.

The combustible gases added should, for efficiently carrying out the process of the invention, have a heat value of not less than 2000 heal. and preferably more than 3000 kcal. Hydrogen may be used as well as various commercial mixtures such as illuminating gas, cokeoven gas or water gas.

The burner disclosed is not claimed herein but constitutes the subject-matter of the co-pending application of Ernst Wagner Ser. No. 689,427, filed October 10, 1957.

Having thus disclosed our invention and described in detail illustrative apparatus for carrying it out, we claim as new and desire to secure by Letters Patent:

A process for the manufacture of carbon black from gaseous hydrocarbons in the presence of oxygen and combustible gases, which is characterized by continuously intimately mixing the reactant hydrocarbon gas with an oxygen-containing gas and a combustible gas, thus forming a homogeneous mixture of said unburned constituents, conducting the previously formed homogeneous mixture through an extended circuitous, stabilizing, flowrectifying zone thus stabilizing the gas flow and producing a laminar gas flow; then burning the homogeneous mixture in a flame beginning at the end of the flowrectifying zone and having a high ratio of volume to area.

References Cited in the file of this patent UNITED STATES PATENTS 914,193 Schumacher Mar. 2, 1909 943,927 Gehring et al. Dec. 21, 1909 1,071,053 Hunter Aug. 26, 1913 1,109,272 Wierum Sept. 1, 1914 1,134,416 Pictet Apr. 6, 1915 1,177,027 Perrier Mar. 28, 1916 1,194,740 Hunter Aug. 15, 1916 1,448,655 Darrah Mar. 13, 1923 1,811,854 Lewis June 30, 1931 2,121,463 Wisdom June 21, 1938 2,375,795 Krejci May 15, 1945 2,599,981 Eckholm June 10, 1952

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