LU85695A1 - PROCESS FOR PRODUCING CARBON BLACKS - Google Patents

Abstract

This disclosure relates to an improved furnace process for producing carbon blacks by the incomplete combustion of hydrocarbonaceous feedstock by varying the process described in U.S. Reissue Patent No. 28974 by carrying out the injection of a portion of the liquid hydrocarbon feedstock into the combustion gas stream as solid streams substantially radially at a location where the combustion gas stream has not attained maximum velocity whereby the resultant blacks have increased CDBP values and have properties which impart improved hysteresis to rubber formulations in which the blacks are incorporated.

Description

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The present invention relates to the production of carbon blacks in the oven having many important applications. These include the use as fillers, pigments and reinforcing agents in rubber and plastics. In general, the oven process for the preparation of carbon nuts involves cracking and / or incomplete combustion of a hydrocarbon feedstock such as natural gas or a recycling feedstock in a closed area of conver-10 sior. at temperatures above ': Z56 ° K (982 ° C) to produce carbon black. The carbon black entrained in the gases emanating from the conversion zone is then cooled and collected by any suitable means commonly used in industry. It has however been desirable, although difficult, to produce baking blacks having similar properties, capable of imparting better hysteresis properties to rubber formulations.

Consequently, the main object of the present invention is a new and improved process for the preparation of carbon blacks which are characterized in that they have properties indicating better hysteresis capacities.

Another subject of the present invention is an improved process for the preparation of carbon blacks having lower tinting powers and higher values for crushed DBP (dibutyl phthalate) (CDBP).

Another subject of the present invention is a 2

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process for controlling the tinting and CDBP values of carbon blacks.

Other objects, advantages and characteristics of the invention will become more apparent to those skilled in the art by considering the detailed description which follows.

According to the invention, it has been found that the above objectives and others still are obtained by modifying a modular or stepwise process for the production of carbon black of the type disclosed in the reissue of US Patent No. 28,974 The stage process comprises an initially prepared primary combustion zone (first stage) where a stream of hot gaseous products of combustion is formed; a second zone or transition zone where a feedstock of liquid hydrocarbon in the form of solid streams (coherent jets) is injected substantially transversely from the external or internal periphery of the combustion gas stream into the preformed stream of hot gases ; and a third zone (the reaction zone) where the formation of carbon black occurs before the end of the reaction by rapid cooling.

In processes of the above-mentioned type where feedstock is injected from the outer periphery of the flue gas stream, there is a possibility that the flue gases will pass through the system without being used. This will happen, for example, if the hydrocarbon feedstock does not completely fill the area through which the flue gases flow, thereby allowing unused heat to escape in the form of gas combustion. This tends to happen quite strongly as the size of the reactor increases. To prevent this uneconomic loss of combustion gases, it is disclosed in US Patent No. 3,922,335, to inject an additional supply charge into the interior region 3 of the combustion gas stream where the charge of feed injected from the outer periphery of the transition zone cannot arrive. The patent describes the use of a suitable device such as a probe through which the feedstock of additional liquid hydrocarbon will be injected into the core of the flue gas stream in a substantially transverse manner, and in a direction from the center or core of the flue gas stream outward to the reactor walls.

By doing so, it is shown that the combustion gases will be fully used for the intended purpose of shearing, atomizing and dispersing the oil droplets. The injection of the feedstock into the interior region of the flue gas stream occurs in the same plane as that through which the feedstock is injected from the outer periphery of the inward transition zone of the flue gas stream. The process described in US Patent No. 3,922,335 is reported to produce exceptionally high throughput and high yields and to have the ability to produce high quality carbon blacks.

There are, however, cases where it is desired to produce carbon blacks in a similar manner to the above two methods, but to produce carbon blacks having different properties. In particular, it may be desirable to produce carbon blacks with reduced tinting and increased CDBP value, which indicate increased rebound and better hysteresis properties. The modification of the present modular or stepwise process 30, which allows the preparation of the blacks having better hysteresis, consists in injecting a portion of the feedstock of liquid hydrocarbon into the stream of combustion gases under form of solid streams substantially radially at a location 35 where the stream of combustion gas has not reached its maximum speed. The feedstock may be injected from the outer or inner periphery of the flue gas stream, substantially radially into the flue gas stream at lower speed. However, it is preferable to inject the solid streams of the feedstock into the flue gas stream at a lower speed, from the inner periphery radially outward into the flue gas stream.

In the present step process, the maximum speed of the flue gas stream is reached approximately in the middle of the transition zone. Thus, for example, if the injection is made by a probe, the modification can be carried out by withdrawing the probe in the first zone or primary combustion so that the feedstock, injected radially, whether inward or outward, enters a stream of combustion gas having a lower speed. The actual point or plane where the feedstock is injected into the stream of combustion gas at a lower speed in a radial direction can be varied considerably depending on the specific quality or type of carbon black desired. It is believed that the radially inward or outward injection of the solid streams of the liquid feedstock into a lower velocity stream of combustion gas results in the formation of more oil droplets. large dimensions which appear to be associated with increased CDBP values.

In the preparation of the hot combustion gases used to prepare the blacks of the present invention, a liquid or gaseous fuel and a suitable oxidizing current such as air, oxygen are reacted in a suitable combustion chamber. , mixtures of air and oxygen or the like. Among the fuels suitable for use for a reaction with the oxidizing stream 35 in the combustion chamber to produce the hot combustion gases 5, there can be mentioned any stream of easily combustible gases, vapors or liquids such as hydrogen, carbon monoxide, methane, acetylene, alcohols and kerosene. It is, however, generally preferable to use fuels having a high content of components containing carbon and in particular hydrocarbons. For example, methane-rich streams such as natural gas and modified or enriched natural gas are excellent fuels as well as other streams containing high amounts of hydrocarbons such as various gaseous and liquid hydrocarbons and refinery by-products. comprising fractions of ethane, propane, butane and pentane, fuel oils and the like. In the present case, the primary combustion represents the quantity of the oxidizing agent used in the first stage of the modular process compared to the quantity of the oxidizing agent theoretically required for the complete combustion of the hydrocarbon of the first stage to form carbon dioxide and water. In this way there is produced a stream of hot combustion gases flowing at a high linear speed. It has further been found that a pressure difference between the combustion chamber and the reaction chamber of at least 6.9 kPa and preferably from about 10.3 kPa to 69 kPa is desirable. Under these conditions, a stream of gaseous combustion products is produced having sufficient kinetic energy to atomize a liquid hydrocarbon feedstock giving carbon black, good enough to obtain the desired carbon blacks. The resulting stream of combustion gases emanating from the primary combustion zone reaches a temperature of at least about 1316 ° C, the most preferable temperatures being at least above "649 ° C. The hot combustion gases are propelled down at a high linear speed which is accelerated by the introduction of the combustion gases into a closed transition stage of smaller diameter which can, if desired, be tapered or restricted for example by means of a conventional venturi.

In the present process, a portion of the liquid feedstock is injected in the form of a number of solid streams, from the inner or outer periphery of the flue gas stream in a direction substantially radially outward or inward in the flue gases at a point in the process where the flue gas stream has not reached its maximum velocity, i.e., about the middle of the transition zone. The remainder of the liquid feedstock is injected as a number of solid streams substantially radially approximately in the middle of the transition zone in the flue gases, the outer or inner periphery of the gas stream combustion, preferring an injection of the external periphery. By this technique for injecting the feedstock, the tinting and CDBP levels of the carbon blacks produced are changed in a direction promoting better hysteresis.

In the second stage of the process, the flue gases flow at a rapid rate and there is a kinetic charge of the gases of at least about 6.9 kPa. The portion of the carbon black liquid hydrocarbon feedstock which is injected in the form of solid streams into the combustion gases in the transition zone or second zone must be injected at a pressure sufficient to obtain proper penetration to thereby ensure a high rate of mixing and shearing of the hot combustion gases and the liquid hydrocarbon feedstock. The liquid feedstock is injected substantially transversely from the external or internal periphery of the stream of hot combustion gases 35 in the form of a number of solid streams (coherent jets) which penetrate well into the interior region, or core, of the flue gas stream.

As hydrocarbon feedstocks suitable for use herein, which are readily volatilizable under reaction conditions, there may be mentioned unsaturated hydrocarbons such as acetylene; olefins such as ethylene, propylene and butylene; aromatics such as benzene, toluene and xylene; certain saturated hydrocarbons; and volatilized hydro-10 carbides such as kerosene, naphthalenes, terpenes, ethyl tars, aromatic recycling charges and the like.

The third stage of the modular process is a reaction zone which will allow sufficient residence time for the carbon black formation reaction to occur before the reaction is terminated by quenching or rapid cooling. The residence time in each case depends on the particular conditions of the process and the particular black desired.

Following the reaction for forming carbon black for the desired time, the reaction is terminated by spraying an extinguishing liquid such as water thereon, using at least one group of injectors. The effluent hot gases containing the carbon blacks 25 produced in suspension then pass downstream where the stages of cooling, separation and recovery of the carbon black are carried out in a conventional manner. For example, the separation of carbon black from the gas stream is easily accomplished by conventional means such as a precipitator, a cyclone separator, a bag filter or combinations thereof.

When practicing the present invention, the quantities of feedstock injected into the primary combustion zone and at point 35 where the combustion gases have reached their maximum speed 8 are all the quantities or proportions resulting that the process produces carbon blacks with increased CDBP values. On the other hand, blacks will impart better hysteresis properties to a rubber composition containing blacks. It is preferable to inject about 20 to about 80% of the liquid feedstock as solid streams into the primary combustion zone, the remaining amount of the feedstock being injected as solid currents at about the point of the transition zone where the flue gas stream has reached its maximum speed. In a particularly preferred embodiment, an amount of about 40 to about 60% of the feedstock is injected into the primary combustion zone, the remaining amount of the feedstock being injected approximately at the point in the transition zone where the flue gas stream has reached maximum speed.

The following test procedures are used to assess the analytical and physical properties of the blacks produced by the present invention.

IODE ADSORPTION INDEX It is determined according to the American standard ASTM D-1510-70.

25 TINT POWER

The tinting power of a carbon black sample is determined relative to an industry standard shade black according to the American standard ASm D3265-76a.

30 DIBUTYL PHTHALATE ABSORPTION INDEX (DBP) The DBP absorption index of a carbon black is determined according to the American standard ASTM D 2414-76.

The reported results indicate whether or not the carbon black is fluffy or in the form of 35 pellets.

9 DBP ECRASE ABSORPTION INDEX (CDBP)

A carbon black pellet is subjected to an action of the crushing type and the structure is then v measured according to the American standard ASTM D 3493-79 ·

5 MODULE AND TRACTION

These physical properties are determined according to the processes described in American standard ASTM D 412. In short, the measurement of the modulus relates to the tension, in KPa, observed when a sample of vulcanized rubber is stretched to 300% of its length of origin. The tensile measurement is a determination of the traction in KPa which it takes to break or break a sample of vulcanized rubber in a tension test, SHRINKING ON EXTRUSION

It is determined according to the American standard ASTM D-2230-37 (method B).

REBOUND

It is determined according to the process indicated in the American standard ASTM D-1054.

The invention will be better understood by referring to the examples which follow. There are, of course, many other forms of the invention which will become apparent to those skilled in the art, when the invention has been fully disclosed, and it will therefore be recognized that these examples are given simply for illustrate the invention and must in no case limit its scope.

EXAMPLE 1

In this example, a suitable reaction device 30 is used, provided with means for introducing the reactants producing combustion gases, i.e. a fuel and an oxidizing agent, either in the form of separate streams or in the form of gaseous reaction products pre-burned in the primary combustion zone, and also means for introducing the hydrocarbon feedstock giving carbon black, which are mobile in order to allow the location of the l radially inwardly outwardly injected 5 of the feedstock into the flue gas stream before the point where maximum speed is reached. The device can be constructed of any suitable material such as metal and be either provided with refractory insulation or else surrounded by a cooling means such as a recirculating liquid which is preferably water. In addition, the reaction device is equipped with means for recording temperature and pressure, means for quenching the carbon black formation reaction, such as injectors, a means for cooling the carbon black produced and means for separating and recovering the carbon black from other unwanted by-products. For the implementation of the present example, any suitable burner can be used in primary or first stage combustion where a primary combustion of 150% can be obtained. The first stage combustion gases having a primary combustion of 150% are formed by introducing, into the combustion zone of the device, air preheated to a temperature of 649 ° C (922 ° K) at a flow rate of 3,736 m ^ / s, and natural gas at a rate of 0.256 m ^ / s to thereby produce a stream of hot combustion gases flowing downstream at a high linear speed. The rapidly flowing stream of flue gases flows into a second transition zone or zone of smaller cross-sectional diameter to increase the linear velocity of the flue gas stream. A suitable liquid hydrocarbon feedstock is then introduced substantially transversely into the stream resulting from the hot combustion gases. The feedstock is injected in the form of solid streams 11 times from the outer periphery radially inward towards the core of the combustion gases through twelve unobstructed orifices each of which has a dimension of 1, 50 mm, and from the inner periphery radially towards the outside in the stream of combustion gas by six unobstructed orifices each of which has a dimension of 1.50 mm.

Consequently, in this test, one third of the feedstock is injected outside, from the internal periphery, the remaining two thirds being injected inside, from the external periphery of the stream of combustion gas. The total feedstock injection occurs in the same plane, i.e. roughly in the middle of the transition zone, at a combined rate of 1.02 l / s and under conditions sufficient to ensure an appropriate degree of penetration into the flue gas stream so that coke formation does not occur in the reactor. The transition zone of the device has a diameter of 315 mm and a length of 279 mm. The section of the reactor had a diameter of 57 mm and a length of 2.74 m, before rapid cooling or quenching of the reaction.

The reaction is carried out so that the total combustion of the process is 26.1% or an equivalence ratio of 3.83 and quenching with water to complete the reaction is placed at a point at 2.74 meters from the location of the feedstock injection. The analysis and performance characteristics of this black are indicated in Table I. Furthermore, this ncir is used here as a control for Example 2 since the feedstock has been completely introduced in the middle of the transition zone where the maximum speed of the flue gas stream was reached.

EXAMPLE 2

The process of Example 1 is followed using the same device. The main difference of this example 12 compared to example 1, consists in modifying the location at which the injection of the feedstock of liquid hydrocarbon in the form of solid currents from the internal periphery radially towards the outside in the flue gas stream is performed. In this test, the partial injection of the liquid feedstock from the internal periphery occurs at a location where the flow of combustion gas has not yet reached its maximum speed, i.e. before roughly the middle of the transition zone. More particularly, combustion air, preheated to 649 ° C (922 ° K) is introduced into the primary combustion zone at the rate of 3.736 m ^ / s or natural gas is introduced at the rate of 0.156 m ^ / s to produce primary combustion or to the first stage 15 having a primary combustion of 274%. In this test, the total rate at which the liquid hydrocarbon feedstock is injected into the fuel gas stream is 1.03l / s. Here, as in Example 1, the liquid feedstock is injected in the form of solid streams (coherent jets) from the outer periphery and the inner purge of the combustion gas stream. More specifically, 50% of the feedstock is injected approximately in the middle of the transition zone through three unobstructed orifices each of which is 2.74 mm in size from the outer periphery, radially towards the inside in the flue gas stream. The remaining 50% of the liquid feedstock is injected in the form of solid streams from the internal periphery of the gas stream is combusted in a radially outward direction in the flue gas stream through three unobstructed orifices, each has a dimension of 2.87 mm. However, the injection of the liquid feedstock of the internal periphery in this test is carried out at a location which is 457 mm upstream of the plane where the maximum speed of the combustion gas stream 13 is reached, that is to say i.e. roughly in the middle of the transition zone. The current resulting from combustion gases passes into the reaction zone where the carbon black formation reaction is stopped with water 5 at a point located 2.74 meters downstream of the plane where the maximum speed of the gas is reached. flue gas stream, i.e. roughly in the middle of the transition zone. The total percentage of combustion in the test is 27.8%. The analytical and physical properties of this black are reported in Table I.

TABLE I

Example 12 15 ---

Iodine value, mgl2 / g black 89 82

Tinting power,% 112 99

DBP absorption, pellets, 20 cc / 100 g 134 129 CBBP (24M4), cc / 100 g 103 105 The suitability of the blacks of the present invention 25 as low hysteresis reinforcing agents for rubber compositions is clearly shown in the table II which follows. To assess blacks, rubber formulations are easy to prepare by conventional methods. For example, the rubber and carbon black are intimately mixed together on a conventional mixing machine of the type normally used for mixing rubber or plastics such as a Banbury mixer and / or a roller mixer in order to ensure satisfactory dispersion.

The rubber formulations are combined according to 14 industry standard formulations for a formulation containing natural rubber or synthetic rubber. The resulting vulcanizates are cured for the specified time to determine the particular physical property.

In evaluating the performance of the carbon blacks of the present invention, the following formulation is used where the amounts are specified in parts by weight. The rubber formulation specifically used here is the synthetic rubber formula of American standard 10 ASTM-D-3191-79 and is characterized as follows:

Ingredient Quantity 15 Polymer (SBR 1500 / 23.590 styrene, 76.5% butadiene) 100

Zinc oxide 3 20 -

Sulfur 1.75

Stearic acid 1 N-tert-butyl-2 benzothiazole 25 sulfenamide 1

Carbon black 50

In Table II which follows, the advantageous and unexpected results obtained by using the carbon blacks produced described above as additives in rubber formulations are demonstrated. It will of course be apparent that the examples should not limit or restrict the invention.

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TABLE II

Physical properties of synthetic rubber vulcanisates 5 --—- · £ ·

Carbon black sample Ex. 1 Ex. 1

Module at 300%, 35 min, MPa +4.068 +2.103

Module at 300%, 50 min, MPa +4.621 +2.310 10

Traction, 50 min, MPa +2.034 +0.379 Extrusion shrinkage,% 89 89

Rebound, 60 min,% -3.9 -1.4 # 15 Data are relative to IRB R ° 5

Consideration of the data presented above reveals that the blacks produced by the present process exhibit the desired properties. When incorporated into rubber formulations, there is a marked improvement in rebound property, which indicates a rubber vulcanizate having better hysteresis.

Claims (4)

16 1.- A modular process for the production of carbon blacks in an oven in which a fuel and an oxidizing agent are reacted in a first zone in order to produce a stream of hot primary combustion gases having sufficient energy to convert a charge of liquid hydrocarbon feed giving carbon black to carbon black and where in a second zone, a liquid hydrocarbon feedstock is peripherally injected, in the form of a number of solid streams (coherent jets) , in the flue gas stream at a location where the flue gas stream has reached its maximum speed, in a direction substantially transverse to the direction of flow of the flue gas stream and at a pressure. sufficient to obtain the degree of penetration required for good shearing and good mixing of the feedstock, and where in a third area the feedstock is decomposed posed and converted into carbon black before the end of the reaction for forming carbon black by quenching, then cooling, separation and recovery of the resulting carbon black, characterized in that one introduces, in the form of a number of solid streams, a sufficient portion of the total amount of liquid hydrocarbon feedstock substantially radially into the stream of combustion gas from its periphery, before the point where the stream of combustion reaches its maximum speed, thereby producing carbon blacks with increased CDBP values. 2. Method according to claim 1, characterized in that an amount of approximately 20 to approximately 80% of the total quantity of the liquid feed charge is injected into the flue gas stream before the location. where the maximum speed of the flue gas stream is reached, the remainder being added approximately at the point where the flue gas stream has reached its maximum speed. 3. Method according to claim 1, characterized in that an amount of the order of 40 to about 60% of the total amount of the liquid feedstock is injected into the combustion gas stream before the location where the maximum speed of the flue gas stream is reached, the remainder being added approximately at the point where the flue gas stream has reached its maximum speed. 4. ~ A method according to claim 1, characterized in that the liquid hydrocarbon feedstock which is injected into the flue gas stream before the point where the flue gas stream has reached its maximum speed is injected in a substantially transverse direction, outwardly, from the inner periphery of the flue gas stream. 5. A method according to claim 1, characterized in that the liquid hydrocarbon feedstock which is injected into the flue gas stream at about the point where the maximum speed is reached is injected in a direction substantially inwardly transverse to the outer periphery of the flue gas stream. 6.- Method according to claim 1, characterized in that the liquid hydrocarbon feedstock cui is injected into the combustion gas stream before the point where the combustion gas stream has reached its maximum speed is injected in a substantially transverse direction, outwards / from the internal periphery of the stream, this combustion gas and the feedstock of liquid hydrocarbon which is injected into the stream of combustion gas Ί 18 at about the point where the speed maximum is reached is injected in a substantially transverse direction, towards the inside, of the external periphery of the flue gas stream.