FR2474043A1 - PROCESS AND DEVICE FOR MANUFACTURING CARBON BLACK AND CARBON BLACK OBTAINED - Google Patents

Abstract

The invention facilitates the use of completely or substantially non-exothermically decomposing hydrocarbons, in particular of benzene, for producing carbon blacks of the same quality as acetylene blacks. This is achieved by introducing the gaseous or atomised hydrocarbon into an air and/or nitrogen plasma. The invention further relates to apparatus for carrying out the process and to the carbon black obtained.

Description

 The subject of the invention is a process for the production of carbon blacks from hydrocarbon, in which the hydrocarbon is injected or sprayed in an enclosure brought to a flame temperature by the introduction of a heat-carrier and / or oxidant gas. of the hydrocarbon and the products of the dissociation are entrained by means of the reaction gases acting as vectors, after which the solid particles are extracted therefrom. It also relates to a device for implementing the invention and the carbon blacks obtained.

 The invention relates more particularly, but not exclusively, to a process for producing carbon black having at least the properties of the so-called black acetylene class.

 It is known that the now conventional processes for the manufacture of carbon black employ the flame technique and that the particularly advantageous properties of acetylene black are due to the exceptional conditions prevailing within the producing flame.

We will refer to the study: Yvan Schwob, Acetylene Black,
Chemistry and Physics of Carbon, vol. 15, pp. 109-218, (1979), Ph. Walker, Peter A. Thrown, Ed. Marcel Dekker,
NY, which shows that, compared with current carbon blacks, acetylene blacks are formed by a very high reaction thermal density. In particular, the highly exothermic nature of the decomposition of acetylene leads to a flame whose specific power is close to that of the oxy-acetylenic torch.

 This notion of thermal density, expressed as a ratio of the standard reaction heat to the standard molar volume of the gaseous constituents produced, has proved to be fruitful in explaining the particular properties of these blacks whose micrographitic character leads to a high absorbency and electrical conductivity. high. It is known that these qualities, combined with the equally exceptional purity of the products, make it a hitherto irreplaceable raw material for the constitution of cathodic masses of dry cells.

 The above study shows how this notion made it possible to develop a process for the production of acetylene black by controlled combustion in the gaseous phase and in the presence of oxygen of an ethylenic or aromatic hydrocarbon, in particular ethylene, benzene, toluene and xyne, the process described in the published French patent 2,229,744. While the reaction thermal density, as defined above, reaches a value close to 1.6 cal / mole in the case of the oxy-acetylenic torch, we have showed that the thermal decomposition of the acetylene-air mixtures easily reached this value whereas the benzene-oxygen mixtures for example, even preheated, did not exceed 0.5, but that this was sufficient for the black products to enter the range However, this method has the disadvantage of consuming, by combustion, a portion of the hydrocarbon, which makes the process expensive.

 The object of the invention is to propose a new process for producing carbon black, and more particularly a black having the appearance and properties of an acetylene black from carbon-rich hydrocarbon. which is not necessarily of strong exothermic decomposition, such as acetylene, but may be for example benzene or other carbide, and even carbons with endothermic decomposition, such as saturated aliphatics.

 This object is achieved, in a process of the type described at the beginning, thanks to the fact that the coolant and / or oxidant gas is introduced into the chamber in the plasma state. In this way, the amount of energy required to compensate for the heat deficit resulting from the replacement of acetyene by a lower formation heat hydrocarbon is introduced into the reaction medium, so that, thanks to the In the present invention, flame reactions can be carried out between a carbon-rich hydrocarbon and a carrier gas in which the thermal densities are equal to or even higher than those obtained in the processes employing the thermal decomposition of acetylene.

 The current means of generating plasmas. of gases can easily introduce such energy into a gas and the subsequent mixtures of this energy carrier gas with a hydrocarbon whose raw molar composition is comparable to that of acetylene, lead to flame reactions similar to those of thermal decomposition of acetylene-based mixtures. In particular, the carbon concentration of the product aerosol is of the same order and the reaction thermal density may even be greater.

 It is according to the invention that the heat transfer and / or oxidizing gas is constituted by nitrogen and / or oxygen in all desired proportions, the case for example.

 It is advantageous that the heat stored by Nm3 gas is of the order of 3 to 6 kwh.

 It is also in accordance with the invention that the starting hydrocarbon is a compound or mixture of hydrocarbon compounds having an overall molar composition of O / E ratio close to 1, especially gaseous benzene.

A device for implementing the invention comprises:
an oven comprising an orifice for introducing a hydrocarbon gas or sprayed and an orifice for introducing a heat-transfer and / or combustion gas,
- Preheating means respectively of the gaseous or sprayed hydrocarbon and the heat transfer gas and / or oxidant in communication respectively with the introduction orifices in the oven,
a pipe for driving the products obtained out of the oven, by pneumatic transport using the gaseous products,
a means for separating the particles from the gaseous products, and the means for preheating the heat-transfer and / or oxidizing gas comprise a plasma torch, which is preferably a plasma-blown torch.

 The method of the invention thus makes it possible to achieve the fixed goal, but it also makes it possible to have an additional adjustment means with respect to the use of acetylene, whose heat of decomposition is fixed and whose thermal instability makes it almost impossible to preheat. It is thus possible, by means of the technique of the invention, to obtain a wider range of micrographitic blacks, which are absorbent and conductive, whose application qualities are markedly improved, in particular in their use for the constitution of cathode-battery masses. dry.

 In addition, the economy of these fabrications is improved. The carbon yield is increased, easily exceeding 9 kP / o of the theory, whereas in the known processes starting from aromatic hydrocarbons, as in patent FR 2,229,744, it reaches barely 50%.

 Other features and advantages of the invention will emerge from the description of examples and an installation which will be given below without limitation.

For the description of the installation, reference will be made to the single appended figure which schematically shows an installation according to the invention for the implementation of the method according to the invention.

 The thermodynamic data of the acetylene dissociation reaction in acetylene black manufacture will first be discussed.

Thermodynamic data of the dissociation reaction of acetylene
In Table I relating to the acetylene-air mixtures, the factors resulting from the use of x moles of air, namely x moles of oxygen and 4 x moles of nitrogen, including, in particular, moles of acetylene, were used. the standard reaction heat Q in cal / mol, ive molar feather resulting V in 1, the reaction thermal density expressed by the quotient Q / 22s4 x V, the carbon concentration in the aerosol product expressed in kg of carbon per kg of gas and the carbon yield as a percentage of the total carbon involved. The amounts are expressed in moles. (See Table I).

 T A B L E A U I (1) = consumption in kg of C per kg of C produced. (2) = yield in C.

(1) (2)
C2H2 + xO2 + 4xN2 = 2 (1-x) C + H2 + 2xCO + 4xN2 QVQ kg / kg C% 22.4 V 1 0 0 2 1 0 0 55 1 2.46 12 100 1 0.02 0.08 1.96 1 0.04 0.08 56.18 1.12 2.24 2.75 98 1 0.04 0.16 1.92 1 0.08 0.16 57.16 1.24 2.06 1 , 55 96 1 0.06 0.24 1.88 1 0.12 0.24 58.24 1.36 1.91 1.08 94 1 0.08 0.32 1.84 1 0.16 0.32 59.32 1.48 1.79 0.83 92 1 0.1 0.4 1.80 1 0.2 0.4 60.40 1.6 1.69 0.67 90 1 0.2 0.8 1.60 1 0.4 0.8 65.80 2.2 1.34 0.35 80 1 0.5 2.0 1 1 1 2 82.00 4 0.92 0.14 50 1 1 4 0 1 2 4 109 7 0.70 0 0
TABLE II (1) = consumption in kg of C per kg of C produced. (2) = yield in C.

(1) (2) 1 / 3C6H6 + xO2 + 4xN2 = 2 (1-x) C + H2 + 2xCO + 4xN2 VQ q WW / x W / c kg / kg 22.4v (q + W) C% 1 0, 04 0.16 1.92 1 0.08 0.16 1.24 2.06 6.26 50.90 50.90 1272 26.51 1.55 96 1 0.06 0.24 1.88 1 0, 12 0.24 1.36 1.91 7.34 50.90 58.24 848 27.07 1.08 94 1 0.08 0.32 1.84 1 0.16 0.32 1.48 1.79 8.42 50.90 59.32 636 27.66 0.83 92 1 0.10 0.40 1.80 1 0.20 0.40 1.60 1.69 9.50 50.90 60.40 509 28.28 0.67 90 1 0.20 0.80 1.60 1 0.40 0.80 2.20 1.34 14.90 50.90 65.80 254 31.81 0.35 80
The practical areas of work are in the range 0.04 <z <0.2 with theoretical carbon yields of between 90% and 95%.

Thermodynamic data in the process of the invention
Table II shows the figures resulting from the use of a mixture of benzene and an air plasma according to the invention, in which the benzene is in the non-superheated vapor state. The reaction is expressed in a form comparable to the previous one by writing 1/3 C6X6 instead of CS 2. The reaction heat was calculated under the sign q, but this time the value W, expressed in calories, of the energy provided by the carrier gas consisting of air plasma. The sum q + W becomes Q, which is intentionally given the same value as in Table I. To keep within the practical limits, the calculations were limited to the values of x between 0.04 and 0.2.

 In Table II was added the ratio W / x corresponding to the energy expressed in calories per volume of air used and in another column the ratio W / c expressing the number of calories per mole of carbon produced. It will be recalled that the reaction thermal density of the oxy-acetylenic torch, calculated in a similar manner, is established without preheating the gases, at 1.62.

The comparison of Tables I and II shows that for the values of W taken into consideration, a deep similarity exists, both in the thermal densities, the carbon concentrations and the carbon yields between the two means used, namely the flame. classic for acetylene and air plasma for benzene.

In practice, this time expressed differently, this means that 26 grams of gaseous benzene treated with air volumes between 0.04 and 0.2 times 22.4 1, storing W cal, may be suitable for obtain common acetylene blacks from the. best quality.

If we take as an example that of the fourth line of Table II and that it is related to 1 kg of black produced with gaseous benzene: the consumptions will be the following ones
1 1000. Benzene: 26 xx = 1,203 grams. Air: 22.4 x 0.5 x = 518 liters
26 1000 1. Kwh: 28.28 xx = 2.87 Kwh 12 820
By overheating the gaseous benzene by 500 for example, the saving in Kwh will be approximately 0.2 of 500 x 1.2 x = 0.15 Kwh.

820
In summary, and for the example chosen, a consumption of energy per air plasma of the order of 3 Kwh will obtain 1 kg of black with a consumption of benzene slightly greater than 1.2 kg. An air plasma generator of 100 Kw will provide sufficient flow to obtain 33.3 kg of black per hour, or about 800 kg per day, in continuous operation.

 The applicants' experience verifies these facts and also confirms that it is easy to obtain these values for W thanks to the gas plasma generators currently available on the market.

 The implementation of the process according to the invention consists in preceding the chamber producing acetylene black, a gas plasma generating device and a gaseous hydrocarbon feed whose preheating obviously only knows the stability limit of the raw material used. The characteristics of the flames thus produced are such that all the other members of the installations are usable without modification, in particular the cooling, collection and waste gas recovery members.

 It is clear to those skilled in the art that the hydrocarbon may be different from benzene, it being understood that the heat of formation specific to the hydrocarbon used must be taken into account in the calculation of the reaction thermal densities. , its preheating temperature and the gaseous reaction volumes, always to maintain a similarity in the conditions of generation of the aerosol.

 The hydrocarbon serving as raw material is advantageously constituted by n compound or a mixture of compounds whose overall molar composition is in a C / E ratio close to 1.

The plasma technique also allows the use of high boilers which can then be sprayed in the liquid state rather than vaporized,
Similarly, air, chosen as an example, can be replaced by another gas. It will only be necessary to take into account the different conditions resulting from the modification of the parameters of the reactions. Without oxygen, the heat of formation of CO is obviously to be subtracted from calculations. With an oxygenated gas, or even with pure oxygen, or with superoxygenated air, the calculations can easily be made in the manner described in Table II, again in order to maintain the similarity in the essential conditions of formation of acetylene black thermal density and carbon concentration of the aerosol.

The fact that a gas plasma contains a large part of atomic constituents or, in the case of the presence of nitrogen, nitrous gas, does not in any way impede the development of the flame which is established in contact with the atom. hydrocarbon, as was clearly demonstrated in the study mentioned at the beginning,
Thus, whether in terms of economy or that of the variety of the range of blacks as possible, the method of the invention has a character of particularly advantageous flexibility. In practice, the use of an aromatic hydrocarbon and an air plasma easily achieves flame temperatures of between 15,000 and 30,000, widely included in the usual areas of micrographitic particle formation characteristic of blacks. 'acetylene.

- EX PLUE 1
Figure 1 shows a schematic view of the device according to the invention used. A cylindrical continuous production furnace 1, with a capacity of approximately 100 l, is preceded by a feed device 2 in gaseous or vaporized benzene and an air plasma generator 3 with a power of 100 kW and a flow rate of 17 Nm3 per hour. The liquid benzene is introduced into the vaporizer 2 via a line 8 and the air into the generator 3 via the inter-electrode space of a blown plasma torch 9. The vaporized benzene and the air plasma are fed, respectively via lines 12 and 13 to the orifices 14 and 15 of a nozzle 4, in the form of a burner, arranged at the top of the production furnace 1, in which the flame reaction The gaseous products of the furnace constitute a black entrainment vector formed by a line 8 to a separator 5. The collection of the black formed, after cooling the aerosol, at the tip of the separator 5 makes it possible to recover at output 6, 33 kg of a black whose essential characteristics are as follows
. Volatile substances .......... 0.1%
. Ashes ..................... Traces
. BET specific surface area 90 m2 / gram
. Carbon content ........... 99.8%
. STIFFNESS absorption index 60
The operating method of the BET method is recalled in the aforementioned article Yvan SCXWOB. That of the determination of the Stiffness index is described in the same article, appendix D, pO 213.

 The waste gas escapes through the orifice 7 of the separator 5.

The yield of carbon production reaches 90%, which, given the losses, gives rise to the following:
. Benzene 1,210 grams
. KWh 2.93 - EXAMPLE 2
Working under the same conditions as in Example 1, but with an air flow of 25 Nm3 per hour instead of 17.

The yield of carbon formation falls to about 85%, or 31.3 kg per hour of a product with the following essential characteristics:
. Volatiles 0.05%
. Ash Traces
. Specific surface RET 110 m2 / gr
. Carbon content 99.9%
. Absorption index Stiffness: 75 - EXAMPLE 3
Working under the same conditions as in Example 1, but with a nitrogen flow of 20 Nm3.

 Still with a power of 100 KW, the carbon yields are identical to those of Example I and the blacks produced have similar characteristics.

 Those skilled in the art will understand that by properly adjusting the characteristics of gas plasmas, a significant improvement in the qualities of the blacks can be targeted, particularly for the use of these products in the manufacture of cathodic masses for high performance dry cells. .

It will also be noted that the consumption of Kwh in the process of the invention is advantageously compared with the production of acetylene by means of calcium carbide. This comes from essen causes
following factors: the energy efficiency of a kiln to
carbide does not exceed 505o ', the decomposition of benzene
gas is exothermic, the partial combustion of hydro-
carbide leads to a contribution of calories to the process,
Thus, compared to known methods of
manufacture of acetylene blacks, the process according to the invention is presented economically, so as to
particularly advantageous.

The process can be extended to the pro
production of ordinary carbon blacks with adapta
flow of air plasma and / or nitrogen to the heat of
dissociation of carbides used more or less noble so that the reaction temperature prevailing in the furnace
is lowered to 1200 to 15500C, temperatures below
those necessary for the equilibrium of gas to water
are totally moved towards the formation of the only
oxides of carbon and hydrogen.

In all cases the addition of a
additional energy by air plasma will achieve substantial hydrocarbon savings.

Claims (8)

REVENDICAlIONS  1) Process for producing carbon blacks from hydrocarbon, in which the hydrocarbon is injected or sprayed into an enclosure heated to a flame temperature by introducing a heat-carrier gas and / or oxidant of the hydrocarbon and the products of the dissociation are entrained by means of the reaction gases acting as vectors, after which the solid particles are extracted therefrom, characterized in that the heat-carrying and / or oxidizing gas is introduced into the chamber in the state of plasma.  2) Process according to claim 1, characterized in that the gas introduced in the plasma state consists of nitrogen and / or oxygen in all regulated proportions.  3) Process according to claim 2, characterized in that the gas introduced in the plasma state is air.  4) Process according to any one of claims 2 and 3, characterized in that the heat stored by Nm3 gas is of the order of 3 to 6 kwh.  5) Process according to claim 1 characterized in that the starting hydrocarbon is a compound or mixture of hydrocarbon compounds having a total molar composition of about C / E = I ratio.  6) Process according to claim 5, characterized in that the hydrocarbon is benzene gas.  7) Apparatus for carrying out the method according to any one of claims 1 to 6 comprising:  - An oven (1) having an orifice (14) for introducing a hydrocarbon gas or sprayed and an orifice (15) for introducing a coolant gas and / or com burant,  - Preheating means respectively (2) of the hydrocarbon gas or sprayed and (3) heat transfer gas and / or oxidant in communication respectively with the orifices (14, 15) for introduction into the oven (1).  a means for separating (5) the particles of the gaseous products, characterized in that the means for preheating the heat-transfer and / or oxidizing gas comprise a plasma torch (9).  a pipe (8) for driving the products obtained out of the oven, by pneumatic transport using the gaseous products,  8) Device according to claim 7, characterized in that the plasma torch (9) is a blown plasma torch.