US 3438732 A
Description (OCR text may contain errors)
April 15, 1969' R. MOREL METHOD AND APPARATUS FOR PRODUCTION OF CARBON BLACK Sheet of 2 Filed May 26, 1966 METHOD AND APPARATUS FOR PRODUCTION OF CARBON BLACK Filed May 26, 1966 R. MOREL.
A ril 15, 1969 Z of 2 Sheet United States Patent r 3,438,732 METHOD AND APPARATUS FOR PRODUCTION OF CARBON BLACK Roger More], 3 Rue dAumale, 75,
Paris 9, France Filed May 26, 1966, Ser. No. 553,241 Claims priority, applicatiolbg rance, May 31, 1965,
Int. Cl. C09c N48 US. 'Cl. 23-209.4 8 Claims ABSTRACT OF THE DISCLOSURE The improvements envisaged in the present invention are concerned generally with the manufacture of products through cracking and relate, more particularly, to the production of carbon black by a continuous process, in an oven or in a combustion chamber.
According to a known method of production of carbon black, gas and air are inserted in a combustion chamber to provide a bright flame with the forming of carbon black 1n suspension in the combustion gases.
The combustion gases consist mostly of carbon dioxide, carbon monoxide, hydrogen, nitrogen and steam.
According to another known method of production of carbon black, an air and gas mixture is inserted in a combustion chamber, together with an atomized liquid hydrocarbon; the combustion of the mixture causes one portion of the hydrocarbon to crack into carbon and hydrogen, while a substantial portion of the hydrocarbon burns and produces carbon monoxide.
In either case, the aim is to ensure the production of carbon black by the incomplete combustion of a hydrocarbon in gaseous form or in gaseous and liquid form, attended by the decomposition of a portion of the hydrocarbon through cracking.
Besides, the quality of the resulting carbon black, depends, among other factors, on the degree of dilution of the raw material. The particle dimensions of carbon black decrease when the dilution increases, and the manufacturer wishing to increase the degree of fineness is led, paradoxically, to employ increased volumes of air while trying to obtain an incomplete combustion of the hydrocarbon.
It is well known, for instance, in the existing technique, to use a combustion chamber for liquid and gaseous fuel, wherein the quantity of air inserted is calculated to burn the gas and cause, in theory, the combustion of 35 to 50% of the liquid hydrocarbon or tar, the atomizing of which is effected, moreover, by air compressed to to 10 kg.cm.
Said combustion occurs in part with the forming of CO, which means a greater loss of liquid hydrocarbon.
It is also known, in the current technique, to employ variations ranging from 1 to 3 in the quantity of atomizing air, as well as, sometimes, a number of variations in the quantity of combustion air, intended to alter the quality of carbon black. This resuls in some modifications in the ratio CO/CO Within the tail-gases, the total of these 3,438,732 Patented Apr. 15, 1969 ICC two components representing a more or less constant percentage of said gases, e.g. 19 to 20% for a particular oven, w1th 15 to 16% of hydrogen, the remainder consisting of nitrogen and water, with traces of hydrocarbon.
It is also found that, when the heating gas does not burn well because of a badly adjusted burner, there occurs a very turbulent combustion, the turbulence becoming more pronounced as the supply of tar increases.
The mode of combustion becomes pulsatory, which makes it necessary to stop further increases in supply which might lead to a dangerous pulsating combustion.
This comes from the fact that a portion of the oxygen which was intended for burning the gas, penetrates into the cracking chamber.
Therefore the chamber becomes more charged in oxygen and less charged in CO and the gases contained therein are set alight again, thereby transforming the oven into a pulse-reactor By contrast, when a burner burns well all the heating gas and consumes the corresponding quantity of oxygen, the combustion has very little turbulence and is practically silent, which makes it possible to increase considerably the supply of tar, without causing the above-mentioned drawbacks.
It is therefore advantageous to reduce as much as possible the presence of oxygen within the cracking chamber.
It is found, from an analysis of the tail-gases of a carbon black production plant:
That the CO content of the tail-gases approximates to the CO resulting from the combustion of the heating Also that the CO content approximates to the quantity resulting from a combination of carbon with the excess of oxygen remaining in the gases after combustion of the heating gas;
That the carbon content of the CO, added to the carbon yield as carbon black, corresponds to the total carbon content of the tar.
One comes to the conclusion that the output loss in carbon black is directly relates to the CO content in the tail gases, which content is directly related to the excess of .air in the combustion or atomizing air.
It is also known that the quality of carbon black remains constant for a given temperature before cracking, provided that the supplies of tar, of combustion air and of atomizing air, remain constant in value.
A change in any one of these factors will alter the quality of carbon black.
Therefore, apart from the change in temperature before cracking, the changes in the rates of delivery of the tar, combustion air and atomizing air, produce variations in the gaseous throughput in the cracking chamber, together with variations in velocity, and these variations in velocity or time of contact bring about variations in quality and output.
The French Patent No. 1,438,188 dated Jan. 15, 1964 and its first and second certificates of addition for Method and Apparatus for the Production of Carbon Black" in the name of the present applicant, describe arrangements for avoiding some of the above-mentioned disadvantages, by assigning well-defined functions to the combustion gas and tar, and by ensuring as complete as possible a combustion of the gas, while preventing the tar from participating in that combustion. However, even these arrangements require the use of an important excess of air, for avoiding stoppages, ensuring the transport of the particles of carbon black, and effecting the required dilution.
The present invention has in view means and methods aimed at curing more completely the above-mentioned disadvantages.
These means allow for an easier control of the various production factors and make it possible, more particularly:
To vary the velocity and quality of the atornizing without having to vary the rate of delivery of atornizing air, which air has the unfortunate tendency, even when mixed with tar, to produce only CO in the cracking chamber;
To vary, without changing the kinetic conditions of the system, the excess quantity of oxygen, while maintaining the same velocities of contact, the same temperatures before cracking, and so bring about a reduction in the forming of CO with a corresponding increase in the production of carbon black, while, in the existing plants, more than 50% of the carbon content of the tar goes into the production of CO;
To extend the range of qualities of carbon black obtainable by continuous process and, more particularly, to produce qualities which, until now, could be produced only by the channel and thermic methods.
According to one feature of the invention, the tar is atomized by mechanical means and the velocity of particles of atomized tar is controlled by a regulatable injection of pressurized neutral or inert gas.
According to another feature of the invention, the atomized tar is caused to crack by being brought in contact with a flow of gas having the required temperature and composed, at least in part, of an inert gas.
Preferably, the tail-gases, suitably treated, are used as a source of inert gas. Thus the inert gas may simply consist of the tail-gases from which the hydrogen, carbon monoxide and water have been extracted.
Another embodiment features the catalytic oxidizing of the carbon monoxide and hydrogen, after the water has been extracted.
According to another embodiment, a combustible gas is added to the tail-gases, the mixture is burned, and the products of combustion are used as inert gas.
These various embodiments include preferably a recovery of the heat content found in the tail-gases at their outlet or produced subsequently by burning them.
According to another embodiment the supply of inert gas is drawn from a source other than the tail-gases.
FIGURE 1 of the attached drawing shows, as a nonrestrictive example, the layout of an installation according to the invention.
FIGURE 2 is a graph on which there have been plotted various grades of carbon black produced according to the invention.
FIGURE 1 shows a combustion chamber 1, for producing carbon black, followed by an antechamber of cracking 2a and a cracking chamber 2. Pipes A and G deliver air and a combustible gas respectively to a burner B.
The tar is led into chamber 1 by an atomizer GT fed by a pipe T, which is pressurized by mechanical means, not shown.
The gases produced, containing carbon black in suspension, are quenched, by meansof quenching device 14, and pass through a tubular exchanger 4 which is used for heating the combustion air fed by fan 8 to the combustion chamber, by way of pipes A1 and A. A pipe A2, controlled by a valve V1, enables the air to by-pass exchanger 4. Valve V1, actuated by a temperature detector CT fitted to pipe A, is used for controlling the temperature of the air supplied to the chamber.
The above-sketched arrangements conform to those described in the above-cited patent, but are not necessary to the operating of the present invention, the latter being applicable to any type of cracking installation.
Chamber 1 is suitably dimensioned to facilitate the production of a sufiicient amount of heat for the cracking reaction, bearing in mind that if its volume were unduly reduced, some of the fuel would remain unburnt.
The gases issuing from exchanger 4 pass through cyclones 5 and filters 6, with the carbon black in suspension forming a deposit, and, according to the present invention, the tail-gases issuing from the filters 6 are led by pipe CQ to a cooler 10, wherein their water content is condensed.
Thereafter, they pass through a water separator 11. The condensed water is let out through pipe E and the tail-gases are led by pipe CQl to an incinerator 7, wherein they are mixed with fuel gas supplied by pipe GA, prior to being burned, the combustion heat being recovered in an exchanger 7a.
The combustion air is supplied to the incinerator 7 by a fan 9, after having passed through the cooler 10, where it becomes heated while causing the water of the tailgases to condense.
The neutral gas issuing from the incinerator 7 is sent by fan 12 to pipe GN, and arrives to the burner B of the plant.
A compressor 13 receives one portion of these gases, and compresses and injects them into the tar atomizer GT, by way of a pipe GNl controlled by a vave V2. This affords a regulation of the quantity of neutral gas injected and of the velocity of the particles of atomized tar, with selective alterations in quality of the final product. One can, as an example, increase the quantity of inert gas injected, to pass from HAF grade to ISAF grade of carbon black, according to the grade denominations of the international classification.
According to an alternative way of using the tail-gases as a source of neutral gas, the hydrogen and water are retained at the outlet of filters 6, while the CO is either extracted, together with the hydrogen, or transformed into C0 The neutral gas, consisting of the remaining CO and nitrogen, may be preheated in an exchanger, using the gases issuing from the oven, to be supplied thereafter to the combustion chamber.
According to another alternative, the tail-gases, freed of their water by condensation, are sent on a catalytic bed, together with air, where the CO and hydrogen are oxidized, to give an inert gas, the temperature of which may lie, for instance, between 400 and 500 C.
The example given hereinafter will give an idea of some results achievable through the invention.
Given an oven to which there were supplied heretofore 2350 kg. of combustion air and kg. of atornizing air, together with m. of fuel gas, it is possible, according to the invention, to replace these 2450 kg. of air by 1600 kg. of air and 850 kg. of inert gas, preheated in order to generate in the combustion chamber the same temperature as before, i.e. for instance, 1500 to 1600 C. This being achieved, one may vary the velocities of contact, by varying either the output of tar, or the quantity of inert gas supplied to the system.
Since after the combustion of the fuel gas, the excess quantity of oxygen is considerably reduced in the cracking chamber, the forming of CO will be reduced in proportion and the carbon which will not be able to combine with oxygen will yield carbon black through cracking.
However, the temperatures will tend to fall in the cracking chamber, since the combining of carbon and oxygen into CO generates heat, while the cracking requires a supply of heat.
This will create a state of unbalance since there will be, on one hand, more hydrocarbon to be cracked, therefore an increased quantity of heat to be supplied, while there will be missed the supply of heat previously generated by the forming of CO.
The balance will be re-established by a reduction in the output of tar, i.e. in the amount of heat to be supplied for cracking, or by an increase in the quantity of fuel gas, or, more economically by an increase in temperature of the mixture air-inert gas, such increase being achievable at least in part through the oxidising of the combustible elements of the tail-gases.
In practice, one may choose to keep unchanged the conditions of contact and avoid the stoppages liable to result from an excessive production rate, by reducing the output of tar to such a value that the carbon black yield remains unchanged.
Therefore the invention offers a means of considerably increasing the carbon black yield, relatively to the tar, and of doubling that yield in some cases.
Besides, it eliminates the risks of explosion both during the preheating of the oven and during actual production.
In general, it permits a variation in the physical factors influencing the production, more particularly the pressures, velocities, volumes and temperatures, without requiring a variation in the chemical factors.
It makes it possible to produce in an oven, by continuous process, grades of carbon black identical with those obtained by the channel method, wherein a flame is brought directly in contact with a surface to form a carbon black deposit, or by the discontinuous thermic process.
There have been plotted, on the graph of FIG. 2 a number of points representing grades of carbon black produced by a continuous process according to the invention, with the specific surface and oil absorption of carbon black being measured, respectively, on the x and y axes.
There are also shown on the graph a number of shaded areas corresponding to grades of carbon black currently in demand. The results obtained show that the grades obtainable through the invention extend throughout the existing industrial range of production. Experience shows that with a suitable rate of atomizing, designed to produce prolonged times of contact, the quality of carbon black becomes very comparable to grades SRF-Sterling Sterling S-Regal RRF.
The method and plant according to the invention are not limited to the production of carbon black and may be generally used with advantage in the cracking of liquid or gaseous hydrocarbons.
Thus in the manufacture of acetylene by incomplete combustion of a mixture of oxygen and methane gas, the burning of the tail-gases, followed by their recirculation inside or outside the cracking chamber, may advantageously be used for maintaining the latter at a suitable temperature.
It is understood that the invention is in nowise limited to the arrangements as shown and described, and that it covers all equivalent alternatives thereof.
What I claim is:
1. In a method for continuously producing carbon black by introducing an atomized stream of hydrocarbon within a confined space and cracking said hydrocarbon into carbon black and tail-gas within said space through contact of said hydrocarbon with a hot gas, the improvement comprising the step of freeing said tail-gas of water vapor and combustible components to provide inert tailgas, and recirculating the inert tail-gas to said confined space together with air and a combustible gas to form said hot gas.
2. A method according to claim 1, including the step of admixing part of said inert tail-gas with said hydrocarbon to produce said atomized stream.
3. A method according to claim 1, including the step of heating said inert tail-gas before recirculation by heat exchange with generated tail-gas issuing from said confined space.
4. A method according to claim 1, including the steps of cooling said tail-gas by heat exchange with air for condensing the water vapor content of said tail-gas, extracting said condensate from said tail-gas and burning thereafter the combustible components of said tail-gas with said air to form inert tail-gas.
5. Apparatus for the continuous production of carbon black by cracking an atomized stream of hydrocarbon into carbon black and tail-gas within a confined space, said apparatus comprising a combustion chamber having an air inlet, a combustible gas inlet, a make-up gas inlet, a hydrocarbon inlet, and a carbon black and tail-gas outlet, and further having an installation with an inlet connected to said outlet for receiving said tail-gas and for condensing water vapor therefrom and oxidizing combustible components therefrom whereby to form inert tail-gas, said installation having an outlet connected to said make-up gas inlet for supplying inert tail-gas to said combustion chamber.
6. An apparatus according to claim 5, wherein there is included a heat exchanger having a flux of carbon black and tail-gas from said combustion chamber circulating within said exchanger in heat exchange relationship with a flux of inert tail-gas issuing from said installation.
7. An apparatus according to claim 5, further includ-.
ing means for injecting said inert tail-gas into hydrocarbon for producing said atomized stream of hydrocarbon.
8. An apparatus according to claim 5, further including means for circulating air within said installation in heat exchange relationship with said tail-gas for condensing water vapor therefrom and for admixing thereafter of said air into said water free tail-gas for oxidizing combustible components therefrom.
References Cited UNITED STATES PATENTS 2,672,402 3/1954 Stokes 23209.8 3,075,829 1/1963 Latham et a1. 23--209.4 3,211,532 10/ 1965 Henderson 23259.5 3,362,790 1/1968 Wood et a1. 23259.5
EDWARD J. MEROS, Primary Examiner.
US. Cl. X.R. 23--259.5