CA1336475C - Process for producing carbon black - Google Patents

Abstract

The invention relates to an improved process for producing furnace carbon blacks wherein a fuel and an oxidant are reacted so as to provide a stream of hot primary combustion gases possessing sufficient energy to convert a carbon black yielding liquid hydrocarbon feedstock to carbon black, and wherein liquid hydrocarbon feedstock is peripherally injected, in the form of a plurality of non-preatomized coherent streams or preatomized streams, into the stream of gaseous combustion products at a point where the combustion gas stream has reached maximum velocity in a direction substantially transverse to the direction of flow of the stream of combustion gases and under sufficient pressure to achieve a degree of penetration required for proper shearing and mixing of the feedstock. The feedstock is decomposed and converted into carbon black prior to termination of the carbon forming reaction by quenching, and then cooling, separating and recovering the resultant carbon black. According to the invention, a sufficient portion of the total amount of liquid hydrocarbon feedstock is introduced into the combustion gas stream prior to the point at which the stream of combustion gases reaches maximum velocity and at a point upstream of which no further increase of the CDBP of the resultant carbon black caused by injecting feedstock into the hot combustion gas stream prior to the point at which the combustion gas stream has reached maximum velocity is observed to thereby produce carbon blacks having wider aggregate size distribution. The process of the invention enables one to produce carbon blacks having wider aggregate size distribution.

Description

Prooess for Producing Carbon Black Background of the Invention Carbon black is produoed by the incc,~ lctc combustion of a hydrocarbon such as petroleum, natural gas and other well-known materials at high lelllp~latures~ When separated from the reaction gases, the product is a fluffy, carbon black powder.In a typical furnace prooess for the production of carbon black, a fuel and an oxidant such as air are reacted to provide a stream of hot combustion gases. A hydrocarbon feedstock is injected into the stream of hot combustion gases resulting in the formation of carbon black. The le~ alure of the carbon black ~unlai~ g gas stream is then lowered by quenching with any conventional means such as a water spray. The black is separated from the stream of gases in which it is suspended by known techniques, such as by cyclones and filters; and then pelletiæd and dried.Carbon black is incorporated into rubber col,.~ul.ds in order to impart reinfo~ ~l.t properties to the rubber COIl .~ou,ld. Among the many ~ro~xl lies of carbon black which are iln~l l~nt to the rubber industry is the aggregate size distribution of the carbon black. The rubber industry has found that for certain purposes blacks having wide ag~ gale size distribution are highly desirable.
Ac~,rdill~,ly, an object of the present invention is to provide a prooess for producing carbon blacks having a wider aggregate siæ distribution as measured by an increase in the ~ D50 values of the blacks.

Summary of the Invention The process of the present In-,en~ion l,--~olves injecting liquid feedstock in the form of non-~lealoll~zed coherent streams or ~reato"l,2ed streams into a staged (modular) carbon black forming process at two sepal àle locations. A portion of the feedstock is injected prior to the combustion gas stream having reached maximum velocity at a point upstream of which no further '.
~

increase in the crushed DBP structure of the carbon black caused by injecting feedstock in the hot combusion gas stream prior to the point at which the cQmbustion gas stream has reached maximum velocity is observed, and also where an increase in the width of the aggregate size distribution of the carbon black is achieved. The remainder of the feedstock is injected at the point where the c~mbustion gas stream has reached maximum velocity.
While Canadian Patent Application Ser. No. 470,709 filed December 20, 1984 teaches that the crushed DBP structure of a carbon black can be increased by injecting liquid feedstock into a c~mbustion gas stream at a point where maximum velocty of the combusion gas stream is reached and at a point prior to that where the m~ximllm velocity of the combustion gas stream is reached, there is no suggestion that the crushed DBP structure of the blacks produced by this process would not increase nfinitely as the distance between feedstock injection points lncreases.
Brief Description of the Drawings Figure 1 is a schematic, diagrammatic, longitudinal, sectional view of a typical carbon black-producing furnace which was utilized in all of the Examples of the present application.
Figure 2 is a histogram showing a size distribution curve of carbon black aggregates and illustrating the ~ D50 of the aggregate size distribution of a sample of carbon black.
Detailed Description of the Invention Referring to Figure 1, there is shown a furnace 1 which is illustrative of the furnaces used to prepare carbon black using the process of the present invention. Furnace 1 is camprised generally of four zones, namely, a mixing chamber 3, a cambustion zone 10, a transition zone 13, and a reaction zone 31.

- 2a -Mixing chamber 3 is defined by wall 4, the outer side of interior partition 9 and upstream wall 6. Attached to the inner side of partition 9 at the upstream end of the partition is flame holder 11. Combustion chamber 10 is defined by the inner side of partition 9, the downstream side of flame holder 11 and terminates at downstream point 12. Through wall 6 is inserted conduit 8 through which fuel is introduced into mixing chamber 3. Through sidewall 4 is inserted conduit 5 through which an oxidant is introduced into chamber 3. Through conduit 8 is inserted internal probe 19 through which feedstock may be injected into the furnace prior to the point where the hot combustion gas stream reaches maximum velocity and at the point where no increase in CDBP structure of the resultant black caused by injecting feedstock into the hot combustion gas stream prior to the point at which the hot combustion gas stream has reached m~imllm velocity is observed. Injection probe 19 is an axially aligned probe which may be liquid-cooled and which terminates in the end cap 27. End cap 27 3 l 336475 has a plurality of orifices 29 oriented radially about the ~ ,ce thereof. Downstream from combustion charnber 10 is transition zone 13 which is defined by wall 17. Cil-u~l~-elltially located around wall 17 are a plurality of substantially transversely oriented orifices 21 through which feedstock may be in~cted into zone 13.
Do~llsllealll from transition zone 13 is reaction zone 31 which is defined by wall 37. Zone 31 can be of variable length and aoss-sectional area depending upon the reaction conditions desired. In this instance reaction zone 31 has an internal diameter of 36 inches. Quench probe 41 is inserted into reaction zone 31 through wall 37. Water is in~ected through quench probe 41 into reaction zone 31 to terminate the carbon black forming reaction.
In general, the prooess of the present invention for producing blacks having a wider aggregate size distribution is achievecl as follows. Into the mixing chamber of the furnace there is introduced through a fuel conduit a suitable fuel and through an oxidant conduit a suitable oxidant such as air, oxygen, mixtures of air and oxygen, or the like. Among the fuels suitable for use in the reaction with the oxidant stream in the wmbustion chamber to gene,ale the hot combustion gases are included any readily combustible matter whether in gaseous, ~,aporous or liquid form such as hydl ogen, carbon monoxide, methane, aoetylene, alwhols, keç~sene, liquid hydrocarbon fuels and the like.
As referred to herein, the primary wll.buslion ,~fesenls the amount of oxidant in the first stage of the modular process divided by the amount of oxidant theoretically r~uiled for the complete combustion of the fuel present in the first stage of the process to form carbon dioxide and water, multiplied by 100 to give a }~I .enlage. While the ~l ill .al ~ w~ u~lion may range from 100 to 500%, the ~,lefelled primary or first stage combustion may vary from about 120 to about 300%. In this manner there is generated a stream of hot combustion gases flowing at a high linear velocity. It has furthermore been found that a ~ Ule differential belwé~l~ the cornbustion chamber and the reaction charnber of at least 1.0 p.s.i. (6.9 kPa) and preferably about 1.5 p.s.i. (10.3 kPa) to 10 p.s.i. (69 kPa) is desirable. Under these conditions, there is produced a stream of gaseous combustion products possessing sufficient energy to convert a carbon black-yielding liquid hydrocarbonaceous feedstock into the desired carbon black products. The lesultant combustion gases emanating from the cornbustion stage attain a leln~l alurl: of at least aboùt 2400 F, (1350 C) with the most ~l ~f~l I ed l~lnlxrature being at least above about 3000F (1650 C).
The hot cornbustion gases are propelled in a do~nsl~ealn direction and are discharged from the downstream end of the combustion chamber at a high linear velocity which is accelerated by passing the combustion gases Into an enclosed transition zone of smaller diameter which may, if desired, be tapered or restricted. At a~ luA~ alely the mid-point of the transition zone in the furnace the combustion gas stream reaches ma~l,ull. velocity.
According to the pro~ess of the present invention, an arnount of liquid feedstock ranging from 1 336~75 .` 4 about 20 to about 80%, and preferably from about 25 to about 75% of the total amount of the liquid hydrocarbonaceous feedstock required is injected in the form of non-preatomized coherent streams or preatomized streams, preferably non-preatomized coherent streams, substantially transversely, in a direction outwardly or inwardly, into the combustion gas stream from the periphery thereof prior to the point where ma~mu~l~ velocity of the combustion gas stream is reached and at a point upstream of which no further increase in crushed DBP structure caused by injecting a portion of the feedstock into the hot combustion gas stream prior to the point at which the combustion gas stream has reached maximum velocity is obse, ved and where a wider aggregate size distribution is obtained. When the liquid feedstock is injected tran~v~, ~ely outwardly into the hot combustion gas stream prior to the stream having reached maximum velocity, the feedstock is preferably injected through a feedstock injection probe. At the point where the combustion gas stream has reached rnacimum velocity, the remaining amount of the liquid hydrocarbon feedstock ranging from about 20 to about 80% of the total hydrocarbon feedstock, and preferably an amount ranging from about 25 to about 75%, of the total feedstock is injected. At this point the liquid feedstock is injected in the form of a plurality of non~ alol, ized coherent streams or preatomized streams, preferably non-~,~alol,uzed, into the hot combustion gas stream in a direction substantially radial or transverse to the flow of the combustion gas stream either from the outer or inner periphery of the combustion gas stream. In a preferred embodiment of the process, the feedstock is injected at the point where the combustion gas stream has reached II~IIIUIII velocity through a plurality of l~ar~v~, ,ely oriented orifices within the wall of the transition zone of the furr~ce in a direction radially inwardly to the flow of the combustion gas stream. Suitable for use herein as hydrocarbon feedstocks are unsaturated hyd,~lbol s such as acetylene, olefins such as ethylene, propylene, butylene, aromatics such as benzene, toluene, xylene, certain saturated hydrocarbons and volatilized hydrocarbons such as kerosenes, naphthalenes, e,les, ethylene tars, aromatic cycle stocks and the like. With respect to the above injections of feedstock at the defined locations, the feedstock may be the same or different.
The amounts of feedstock, fuel, and/or oxidant employed herein will be adjusted so as to result in an overall peroent combustion ranging from about 15 to about 60 percent and preferably from about 15 to about 40 peroent. The overall combustion .~,~,.ts the total amount of oxidant used in the carbon lo.,,u,.g prooess divided by the amount of oxidant required for the complete cornbustion of the total amount of fuel and feedstock present in the carbon forrning prooess so as to yield carbon dioxide and water, multiplied by 100 in order to arrive at a pe.centage.
Sufficient residenoe time is provided to allow the carbon black forrning reactions to occur prior to termination of the reaction by quenching. An exemplary manner of quenching is accomplished by injecting water through a quench nozzle. However, there are many other methods known in the art for quenching the carbon black fO~llUng process. The hot effluent gases co"la,ning the carbon black products suspended therein are then subiected to the .vnvenlional steps of cooling, separation and collection of carbon black. The separation of the carbon black from the gas stream is readily accomplished by any .vnvenlional means such as a precipitator, cyclone se~ll,toJ, bag filter, or combination thereof.
It has been found that by in~ecting fee~cto-lc at the two locations in accordanoe with the process of the present invention, blacks having wider aggregate size distribution are produced.
The following test procedures are used in delt ~ Inining the analytical yl oy~, Lies of the blacks produced by the present invention.

IODINE ADSOKI~l1~NUMBER

The iodine adsorption number of a carbon black sample is del~-l,u,,ed in accordance with ASTM ~151~81.

-- T~T STR~GTH

The tint sLlenglh of a carbon black sample is deterrnined relative to an industry tint reference black in accordance with ASTM ~3265-76a.

DIBUIYL PHTHALATE (DBP) ABSORPTION

The DBP absorption number of a carbon black is dele..-~ined in accordance with ASTM D 2414-84.
The results r~yG. led indicate whether the carbon black is in fluffy or pellet form.

CRUSHED DBP ABSORlrrION NUMBER (CDBP) The CDBP absorption number of a carbon black pellet is determined in accordanoe with ASTM
D-3493-84.

AGGREGATE SIZE DlSTR~BUTlON (~ D 50) The aggregate size distribution (~ D 50) of a sarnple of carbon black is determined in the following manner. A histogram is made of the Stokes diameter of the aggregates of the carbon black sample versus the relative fr~quency of their occurence in a given sample. As shown in Figure 2, a line (;B) is drawn from the peak (A) of the histogram in a direction parallel to the Y axis to and ending at the X-axis at point (C) of the histogram. The midpoint (F) of the resultant line (B) is determined and a line (G) is drawn through the midpoint (F) thereof parallel to the X-axis. Line (G) intersects the distribution curve of the histogram at two points D and E. The absolute value of the difference of the two Stokes diameters of the carbon black particles at points D and E is the ~ D 50 value. The data used to gnerate the histogram are determined by the use of a disk centrifug such as one manufactured by loyoe Loebl Co. Ltd. of Tyne and Wear, United Kingdom. The following procedure is a modification of the procedure described in the instruction manual of the Joyoe Loebl disk centrifuge file reference DCF 4.008 published on February 1, 1985 and was used in dete-l~ining the data .

PROCEDURE
10 mg of a carbon black sample are weighed in a weighing vessel. 3 drops of a surfactant produoed and sold by the Shell Chemical Co. under the registered trademark NONIDET P~0 are added to the carbon black and the resultant mixture is stirred to produce a uniform paste. 50 cc of a solution of 20% absolute ethanol and 80% distilled water are added to the paste and dis~.aed by means of ultrasonic energy for 15 ~ lles using a sonifier having the Model No. W385 rn~nl1factl-red by Heat Systems Ultrasonics Inc. Farrnin~ le New York.
Prior to the the run, the following data are entered into the computer which records the data from the disk centrifug:

1. The specific gravity of carbon black, taken as 1.86g/cc, 2. The volume of the solution of the carbon black dispersed in the above solution of water and ethanol, which in this instanoe is 0.5 cc, 3. The volume of spin fluid which, in this instance, is 14 cc of water, 4. The viscosity of the spin fluid which in this instanoe is taken as 0.933 centipoise at 23 C, 5. The density of the spin fluid which, in this instance, is 0.9975 g/cc at 23 C, 6. The disk speed which, in this instance, is 8,000 rpm, 7. The data sampling interval which, in this instance, is 1 second.

The disk centrifuge is operated at 8000 rpm while the stroboscope is operating. 14 cc of distilled water are injected into the spinning disk as the spin fluid. The turbidity level is set to 0;
and 1cc of the solution of 20% absolute ethanol and 80% distilled water is injected as a buffer liquid.
The cut and boost buttons of the disk centrifuge are then operated to produce a smooth concentration gradient between the spin lluid and the buffer liquid and the gradicnt is monilored visually. When the gradient becomes smooth such that there is no distinguishable boundary between the two fluids, 0.5 cc of the dia~l ~1 carbon black in aqueous ethanol solution is injected into the spinning disk and data collection is started immediately. If streaming occurs the run is aborted. The disk is spun for 20 minutes following the injection of the dispersed carbon black in aqueous ethanol solution. Following the 20 minutes of spinning, the disk is stopped, the temperature of the spin fluid is measured, and the average of the tenl~lature of the spin fluid measured at the beginning of the run and the temperature of the spin fluid measured at the end of the run is entered into the computer which records the data from the disk centrifuge. The data is analyzed according to the standard Stokes equation and presented as a histogram as shown in Figurc 2.

The prooess of the present invention for producing carbon black having wider aggregate size distribution will be more readily understood by reference to the following examples. There are, of course, many other embodiments of this invention which will become obvious to one skilled in the art once the invention has boen fully disclosed and it will accordingly be recognized that the following examples are given for the purpose of illustration only, and are not to be construed as limiting the scope of this invention in any way.
The furnace depicted in Figure 1 is illustrative of the furnaces used in each of the following examples. In examples 1~3 the same liquid hydrocarbon was utilized as a fuel. Furthermore, in examples 1-3 a liquid hydrocarbon different from that used as lhe fuel was utilized throughout as the feedslock.

: 8 Example 1 Utilizing the furnace shown in Figure 1, there was introduced into mixing chamber 3 air ~lehealed to a le~ ature of 1238F (670C) at a rate of 500 mscflh (3.933 Nm3/sec) and liquid hydrocarbon fuel at a rate of 238 gal/hr (900 L/h). A stream of hot combustion gases were generated therefrom having a 154% primary combustion flowing in a downstream direction at a high linear velocity. Potassium was added to the combustion gases in the form of an aqueous solution such that 84 ppm of potassium was added relative to the total amount of feedstock which was used.
Subsequently, 25% of the total feedstock was introduced in the form of non-preatomized coherent liquid streams radially outwardly into the hot combustion gas stream through probe 19 prior to the point where the combustion gas stream reached maximum velocity. Probe 19 had an outside diameter of 2 inches (5.1 cm) and was equipped with a 1/4 inch NPT end cap 27 having six 0.070 inch (1.78 mm) diameter orifioes perpendicularly oriented and located equiangularly about the circumferenoe thereof. In this example, probe 19 was positioned such that end cap 27 was 11.8 inches (30 cm) uysl~ of orifices 21.
The remaining 75% of the reedslock was injected radially inwardly in the form ofnon-yrealolllized coherent streams into the hot combustion gas stream through 12 orifices 21 at the point where the cornbustion gases had reached maximum velocity i.e., at the mid-point of transition zone 13. Transition zone 13 has a length of 11 inches (27.9 crn) and an internal diameter of 12.4 inches (31 5 cm). Orifioes 21 were 1~ ansvel æly oriented, each 0.078 inches (1.99 mm) in diameter and spaoed equiangularly in a single plane about the ~ir~ull~erenoe of wall 17 of transition zone 13. The total amount of feedstock was injected at a cornbined rate of 1437 gal/hr (5439 L/h).
The process was carried out such that the overall combustion was 205%. Reaction chamber 31 was 36 inches (91 cm) in diameter. Quench nozzle 41 was located at a point about 10 feet (2.45 m) dow,lsl-eam from orifioes 21. The analytical yl.~l lies of the black are reported in the Table.

Example 2 Carbon black was produced using the appalalus, feedstock and process of Example 1 with the following exceptions. In this e~alllplc, probe 19 was positioned such that end cap 27 was 19.7 inches (50 cm) ~ ealll of orifioes 21 within transition zone 13 and 123 ppm of potassium relative to the total amount of feedstock utilized was added in the form of an aqueous solution to the hot combustion gas stream. Thè analytical properties of the black are rc~ul le~ in the Table.
.

g Exalr~e 3 Carbon black was produced using the apparatus, feedstock and process of Example 1 with the following exoeptions. Internal probe 19 was positioned such that end cap 27 was 23.6 inches (60 cm) uys~eam of orifices 21 and 123 ppm of potassium relative to the total amount of feedstock utilized was added in the form of an aqueous solution to the hot combustion gas stream.The analytical .o~, lies of the black are J`e~l led in the Table.

- - - 1 33647~

Tab]e Example 1 Example 2 Example 3 Potassium Addition Relative to Amount of Feedstock (ppm) 84 123 123 Separation Distance of Feedstock Injection Points 11.8inches 19.7inches 23.6inches (30 cm) (50 cm) (60 cm) ~D50~ 68 77 83 Tinting Strength% 98 98 96 Iodine No.
rng ~2/g black 60 60 DBP Absorption Pellets cc/100 ~ 109 1C6 107 CDBP (24M4) cc/100 g 9~ 88 90 The data in the Table shows that the process of the present invention results in the production of carbon blacks having increased ~ D50 values while maintaining substantially identical values for structure and surface areas. Furthermore, from the data and the examples one would conclude that the ~ D50 value of a carbon black could be further increased as the distance between the two points of feedstock injection of this invention is increased.
In examples 1-3, different amounts of potassium were added in order to achieve a given level of structure of the carbon black. In so doing the effect of the present invention is shown indirectly by noting that equal amounts of potassium were required in examples 2 and 3, both of which exceeded the amount required in example 1 in order to reach the given structure level of the carbon black. The increase in the amount of potassium used in examples 2 and 3 compared to that used in example 1 shows that at the separation distance of example 1 the structure was still increasing witl respect to the increasing distance between feedstock injection points. On further increasin~ the separation distance between feedstock injection points, the constant amounts of potassium utilized in examples 2 and 3 show that there has been no further increase in CDBP caused by injection of the portion of feedstock into the hot combustion gases prior to reaching maximum velocity at the increasing distances between feedstock injection in examples 2 and 3.
While this invention has bcen described with respect to certain embodiments, it is not so limited, and it should be understood that variations and modifications thereof may be made which are obvious to those skilled in the art without departing from the spirit or scope of the invention.

Claims (7)

1. In a modular process for producing furnace carbon blacks wherein a fuel and an oxidant are reacted so as to provide a stream of hot primary combustion gases possessing sufficient energy to convert a carbon black yielding liquid hydrocarbon feedstock to carbon black, and wherein liquid hydrocarbon feedstock is peripherally injected, in the form of a plurality of non-preatomized coherent streams or preatomized streams, into the stream of gaseous combustion products at a point where the combustion gas stream has reached maximum velocity in a direction substantially transverse to the direction of flow of the stream of combustion gases and under sufficient pressure to achieve a degree of penetration required for proper shearing and mixing of the feedstock, and wherein the feedstock is decomposed and converted into carbon black prior to termination of the carbon forming reaction by quenching, and then cooling, separating and recovering the resultant carbon black, the improvement which comprises introducing a sufficient portion of the total amount of liquid hydrocarbon feedstock into the combustion gas stream prior to the point at which the stream of combustion gases reaches maximum velocity and at a point upstream of which no further increase of the CDBP of the resultant carbon black caused by injecting feedstock into the hot combustion gas stream prior to the point at which the combustion gas stream has reached maximum velocity is observed to thereby produce carbon blacks having wider aggregate size distribution.

2. A process as defined in claim 1 wherein an amount of from about 20 to about 80% of the total amount of liquid feedstock is injected into the combustion gas stream prior to the point where maximum velocity of the combustion gas stream is reached and and upstream of which no further increase of the CDBP of the resultant carbon black caused by injecting feedstock into the hot combustion gas stream prior to the point at which the combustion gas stream has reached maximum velocity is observed, with the remainder of the feedstock being added at the point where the combustion gas stream has reached maximum velocity.

3. A prooess as defined in claim 1 wherein an amount of from about 25 to about 75% of the total amount of liquid feedstock is injected into the combustion gas stream prior to the point where maximum velocity of the combustion gas stream is reached and upstream of which no further increase in the CDBP of the resultant carbon black caused by injecting feedstock into the hot combustion gas stream prior to the point at which the combustion gas stream has reached maximum velocity is observed, with the remainder of the feedstock being added at the point where the combustion gas stream has reached maximum velocity.

4. A process as defined in claim 1 wherein the feedstock which is injected into the hot combustion gas stream at the point where the hot combustion gas stream has reached maximum velocity is in the form of non-preatomized, coherent streams.

5. A process as defined in claim 1 wherein the liquid hydrocarbon feedstock which is injected into the stream of hot combustion gases prior to the point at which the stream of combustion gases has reached maximum velocity and upstream of which no further increase in the CDBP of the resultant carbon black caused by injecting feedstock into the hot combustion gas stream prior to the point at which the combustion gas stream has reached maximum velocity is observed, is injected in a substantially transverse direction to the flow of the hot combustion gas stream and the feedstock is in the form of non-preatomized coherent streams.

6. A process as defined in claim 5 wherein the liquid hydrocarbon feedstock which is injected into the stream of hot combustion gases prior to the point at which the stream of combustion gases has reached maximum velocity and upstream of which no further increase in the CDBP of the resultant carbon black caused by injecting feedstock into the hot combustion gas stream prior to the point at which the combustion gas stream has reached maximum velocity is observed, is injected outwardly from the inner periphery of the hot combustion gas stream.

7. A process as defined in claim 1 wherein the liquid hydrocarbon feedstock is injected in the form of non-preatomized coherent streams in a substantially transverse direction outwardly from the inner periphery of the combustion gas stream into the stream of combustion gases prior to the point at which the stream of combustion gases has reached maximum velocity and upstream of which no further increase in the CDBP of the resultant carbon black caused by injecting feedstock into the hot combustion gas stream prior to the point at which the combustion gas stream has reached maximum velocity is observed, and the liquid hydrocarbon feedstock is injected in the form of non-preatomized coherent streams in a substantially transverse direction inwardly from the outer periphery of the hot combustion gas stream into the combustion gas stream at the point where maximum velocity of the combustion gas stream is reached.