PROCESS AND APPARATUS FOR PRODUCING CARBON BLACK

Abstract: Process and apparatus for producing carbon black by pyrolysis of oil feedstock with hot combustion gases by in­ troduction of the oil feedstock into the hot combustion gases from longitudinally spaced apart positions.

Description: Background of the Invention In one aspect, the invention relates to the production of carbon black. In another aspect, the invention relates to a furnace which is especially well adapted for producing carbon black. In furnace processes for the production of carbon black, a carbonaceous make oil is pyrolyzed with hot combustion gases formed by combusting a fuel, such as natural gas or residual oil with an oxidant, usually air. The carbon forming reaction occurs in a refractory lined tunnel which constitutes the bulk of the reactor. Different grades of carbon black are produced by manipulating the amount of fuel, oxidant and carbonaceous feed introduced into the reactor, the positions at which they are introduced, and the interior dimensions of the reactor tunnel. Reactors in which the properties of the carbon black produced can be relatively independently manipulated are very desirable. Reactors in which the production of undesired product, such as grit, is maintained at a low level are very desirable. Reactors characterized by a high degree of thermal efficiency are very desirable. The applications EP-A 102 072 and EP-A 136 629 disclose carbon black furnaces having a combustion chamber, converging section, throat and pyrolysis chamber. Means are provided for introducing a feedstock into the conical section and throat of these reactors, however these means are not sufficient for achieving the desired control of the carbon black properties as intended in the present invention. EP-A 184 819 relates to an air distributor for a carbon black reactor in which incoming combustion air is diverted in an upstream direction to achieve better air distribution. The problems of achieving variously desired properties of the product carbon black are not discussed. Objects of the Invention It is an object of this invention to provide an apparatus and process for producing carbon black in which the properties of the carbon black are easily controlled by manipulating input parameters. It is another object of this invention to provide an apparatus and process for the production of carbon black having low levels of grit contaminant. It is a further object of this invention to provide and apparatus for the production of carbon black on which the reactants come together to produce carbon black in a highly efficient manner. It is yet another object of this invention to provide an apparatus and process for producing carbon black in which the tint of the carbon black is easily controlled. According to the present invention a carbon black reactor is provided comprising a generally cylindrical combustion zone. a converging zone; and a reactor throat as defined in Claim 1. The converging zone connects the generally cylindrical combustion zone with the reactor throat. A generally cylindrical pyrolysis zone is situated downstream of the reactor throat, said pyrolysis zone having a diameter in the range of 1.5 to 5 times the diameter of the reactor throat; the combustion zone, the converging zone, the throat and the pyrolysis zone being determined by a sidewall defining a reaction flow passage having a longitudinal axis to the reactor. There is at least one generally annular wall positioned between the reactor throat and the pyrolysis zone, said generally annular wall facing in the downstream direction. The reactor includes means for providing hot combustion gases which flow from the generally cylindrical combustion zone to the generally cylindrical pyrolysis zone. At the downstream end of the generally cylindrical pyrolysis zone are means for introducing a quench fluid. A plurality of ports extend generally radially inwardly towards the longituginal axis of the reactor for the insertion of feedstrock injectors, there being at least one of these ports in the converging zone; at least one in the throat and at least one in the pyrolysis zone. The invention is also directed to a process for producing carbon black as claimed in the accompanying Claims 11 to 18. Brief Description of the Drawing FIGURE 1 is a side cross sectional representation of carbon black reactor embodying certain features of the present invention. FIGURE 2 represents a cross sectional view of the reactor of FIGURE 1 as would appear when viewed along lines 2-2. FIGURE 3 represents a cross sectional view of the reactor of FIGURE 1 as would appear when viewed along lines 3-3. Detailed Description of the Invention According to certain aspects of the invention, a carbon black reactor designated generally by the reference numeral 2 is formed to a large extent by refractory sections 3, 4, 5, 6, 7, 8, 9 and 10 which form a sidewall which defines the reaction flow path 13 through the reactor 2. The reaction flow path through the reactor 2 is symmetric about a longitudinal axis 11 of the reactor 2. The tunnel or flow path 13 has the following zones in sequential, general axial alignment. A first generally cylindrical zone 12 has a first end 14 and a second end 16. A converging zone 15 has a first end 18 connected to the second end 16 of the zone 12, and a second end 20. A reactor throat 22 has a first end 24 connected to the second end 20 of the converging zone 15 and a second end 26. A generally cylindrical pyrolysis zone 34 has a first end 36 connected to the second end 26 of the choke 22, and a second end 38. The second end 38 of the zone 34 is determined by the position of a means 40 for introducing a quench fluid into the zone 34, which serves as the pyrolysis zone for the reactor. A generally annular wall 42 is positioned between the reactor throat 22 and the pyrolysis zone 34. The generally annular wall 42 faces in the downstream direction and forms the upstream end of the pyrolyis zone. The pyrolysis zone 34 will generally have a diameter in the range of from 1.5 to 5 times the diameter of the reactor throat 22 at its narrowest point. The reactor further comprises a means designated generally by the numeral 41 for establishing a generally axial flow of hot combustion gases which flow from the first generally cylindrical combustion zone 12 to the generally cylindrical pyrolysis zone 34 and means designated generally by the reference numeral 44 for introducing a carbonaceous feedstock generally radially inwardly into the hot combustion gases at spaced apart longitudinal positions along the reaction flow path. In one embodiment, the means 41 has an air plenum 46 which can be radial with respect to the reactor axis and a fuel tube 48 which can be along the reactor axis. The air plenum 46 is connected to an oxidizing gas source 50 which has preferably been preheated such as by indirect heat exchange with reactor tail gases. The fuel tube 48 is connected with a suitable source of fuel 52 such as natural gas. A plate 54 which can be circular seals the end of the fuel tube 48 and forms a flange, which can be annular, with respect to the tube 48, the downstream face of which acts as a flame holder. Fuel is emitted from the tube 48 through apertures 56 located near flange 54. Refractory section 3 is cast in the form of a choke which can have a frustoconical converging inside surface leading to the upstream end of the refractory section 4. The upstream end 14 of the generally cylindrical combustion zone 12 is in the shape of an annular wall which also serves as a flame holder. The means 44 for introducing the carbonaceous feedstock into the reactor flow path generally comprises a plurality of ports 59 opening into the flow passage generally radially inwardly through the side wall of the reactor at longitudinally spaced apart positions with respect to the longitudinal axis 11 of the reactor. A plurality of feedstock injectors illustrated by reference 62 in FIGURE 2 are positioned in at least a portion of said ports 59. The feedstock injectors 62 are connected to sources 60 of carbonaceous feedstock and a conduit means 61 connects the sources 60 to carbonaceous feedstock with the injectors 62. Each injector 62 can be terminated in any desired manner which results in introduction of the feedstock with sufficient penetration to clear the wall but insufficient penetration to result in liquid impingement on the opposite wall so as to cause coke buildup. For example, the injector 62 can be terminated so as to emit coherent jets of feedstock, or sprays of feedstock having a cone shaped spray pattern or, atomizing bifluid nozzles can be used which emit a mist or fog of atomized oil and steam or other light gas. Preferably, the injectors are terminated so as to emit sprays of feedstock having a cone shaped spray pattern where the cone diverges at an included angle in the range of from 30° to 120°, since using nozzle tips which emits such sprays has provided good results. Nozzle tips are represented by numeral 64 in the drawing. In accordance with the the invention, the ports 59 are arranged in a first set 63 at a first longitudinal position with respect to the reactor axis, a second set 65 at second longitudinal position with respect to the reactor axis, and a third set 67 at a third longitudinal position with respect to the reactor axis 11. The first set of ports 63 when in a plurality are preferably circumferentially spaced apart around and open into the reactor flow passage in the converging zone 15. The second set of ports 65 when in a plurality are preferably circumferentially spaced apart around and open into the reaction flow passage in the reactor throat 22. The third set of ports 67 when in a plurality are preferably circumferentially spaced apart and open into the reaction flow passage through the wall of the pyrolysis zone 34. In a preferred embodiment of the invention, a fourth set of ports 69 is provided at fourth longitudinal position with respect to the reactor axis 11 opening into the converging zone 15 and positioned upstream from the first set of ports 63. When in a plurality, the ports of the fourth set 69 are preferably circumferentially spaced apart. Any desired number of circumferentially spaced apart ports can be used in forming a set 63, 65, 67 or 69. For convenience, the number of ports will generally be between 1 and 16 in each set. Preferably, each set is formed by in the range of from 1 to 6 ports 59 since good results can be achieved with a small number of ports and injectors positioned in a portion of them. In accordance with the invention, feedstock is introduced simultaneously through injectors positioned in different sets of ports. The process (claim 11) of the present invention, however, excludes the feedstock being introduced through ports at said first and second locations as the sole feedstock source. At least one injector 62 will be positioned in a port 59 of a set in use. Preferably, injectors 62 will be positioned in at least three different sets of ports for simultaneous feedstock injection. For example, at least one feedstock injector 62 could be positioned in a port 59 of set 69 and one each in ports 59 of set 65 and set 67. As another example a feedstock injector 62 could be positioned in a port 59 of set 63, a port 59 of set 65 and a port 59 of set 67. Generally speaking, a set 67 of ports 59 in the pyrolysis zone will be positioned within about 4 reactor throat diameters, usually within 2 reactor throat diameters, at its narrowest point, from the upstream end 36 of the pyrolysis zone 34. Generally, no more than about 6 reactor throat diameters, as measured at its narrowest point, will separate the most upstream set 69 of ports 59 from the most downstream set 67 of ports 59. Usually, the distance separating the most upstream set from the most downstream set when the invention is utilized will be in the range of from 2 to 6 reactor throat diameters, preferably in the range of 3 to 6 reactor throat diameters. Usually, the source 60 carbonaceous feedstock will comprise a storage tank, a pump capable of generating a pressure of at least 0.34 MPa (50 psig), usually in the range of from 0.69 to 3.4 MPa (100 to 500 psig), and a heater for preheating the carbonaceous feedstock to a temperature in the range of from 93°C to 315°C (200°F to 600°F). The spray nozzle 64 mounted on the ends of tubes 62 are preferably removable and easily changeable to provide an additional parameter (spray type) which can be manipulated to influence product properties. Carbonaceous feedstock pressure and/or nozzle orifice size are adjusted so that the feedstock emitted from the injector does not impinge on the opposite wall. The means 40 for introducing quench fluid into the pyrolysis zone generally comprises a tubular member 66 extending through the sidewall which defines the pyrolysis zone 34 usually in a generally radially inward direction. The tubular member 66 is connected to a suitable source 68 of quench fluid, usually water since it is convenient and effective. Where water is used as a quench fluid, the tube 66 will generally be provided with a spray nozzle 69 at its outlet end having an orifice size and a spray angle sufficient to cool the effluent in the pyrolysis zone to below carbon forming temperatures without excessive impingement on the far wall of the reactor. Although the size of the reactor throat is not critical in the present invention, commercial sized reactors constructed in accordance with the present invention will usually have a throat 22 diameter in the range of from 10cm to 41cm (4 inches to 16 inches), usually between 13cm to 25cm (5 inches and 10 inches) at the narrowest point. The size of the throat will be related to the capacity of the air source 50. Generally, a relationship between the throat 22 and the means 50 will be such that that hourly volume of hot combustion gases at a 50 percent excess air rate (150% of the amount required for stoichiometric combustion of the fuel) as measured at standard temperature and pressure conditions (SCFH) will be between about 10,000 r 2.3 and about 14,000 r 2.3 , where r is the radius of the reactor throat 22 in inches. Sufficient oil is introduced via means 44 so as to maintain an air/oil ratio in the range of 1.50 to 6.0 m³/ℓ (200 to 800 SCF/gal,), depending on the desired product. The generally cylindrical zone 12 will generally have a diameter in the range of from 2 to 5 throat diameters, usually between 2.5 and 3.5 throat diameters. It is preferred that the diameter of the zone 12 be toward the larger end of the described ranges where a liquid fuel is to be used. The length of the generally cylindrical zone 12 should be sufficient to provide for the desired degree of combustion of the fuel used with the oxidant gas. Usually, the zone 12 will have a length of at least 2 times the throat diameter, preferably in the range of from 2 to 10 times the throat diameter. The converging zone 15 is preferably formed from a frustoconical reactor section having an included cone angle in the range of from about 30° to about 90°, preferably from about 45° to about 80°. The length of the converging section 15 is, of course, dependent upon the included cone angle and the respective diameters of the zones 12 and 22 but will generally be in the range of from about 2 to about 10 throat diameters. The throat 22 will generally have a length in the range of 0.3 to 3 throat diameters. The zone 34 generally has a diameter in the range of from 1.5 to 5 throat diameters, usually in the range of from 2 to 4 throat diameters. The reactor refractory can be cast in sections along the lines as generally indicated in the FIGURE 1 and separated with expansion paper as is known to those in the art. The reactor tunnel can be lined with chrome alumina refractory at its upstream end around the zones 12 and 15 as well as for the downstream portions of the zone 34. The throat 22 and upstream end of the zone 34 can be formed from a high alumina rammable refractory such as Jade Pak 88P available from A. P. Green. The refractory surrounding the air plenum and fuel inlet of the upstream end of the reactor can be formed from Kaokast refractory available from Babcock and Wilcox and Purotab refractory which is higher alumina content than Kaokast can be used to insulate the tunnel liner. 1.27 cm (One-half inch) thick steel can be used for the reactor shell. EXAMPLE A carbon black reactor according to the invention has dimensions shown in Table I. Four sets of radial oil injection nozzle ports were provided on the above reactor. On the inventive reactor set of ports were located 61 cm (24 inches) upstream from throat outlet (set 69 in FIGURE 1), hereinafter "A"; 41 cm (16 inches) upstream from throat outlet (set 63 in FIGURE 1), hereinafter "B"; 7.6 cm (3 inches) upstream from throat outlet (set 65 in FIGURE 1), hereinafter "C"; and 35 cm (13 11/16 inches) downstream from throat outlet (set 67 in FIGURE 1), hereinafter "D". Oil nozzle spray angle was kept between 45° and 100°, and oil nozzle pressure was kept between 1.0 and 1.65 MPa (140 and 240 psig). Oil quality was: Air rate, quench position, heat input, nozzle spray angle, and percent oil at different positions were changed in an attempt to maximize modulus results while maintaining the necessary CTAB, C-DBP, and tint residual values. Air rate, quench position, and heat input were found to have very little effect on modulus. Increasing the oil nozzle spray angle from 45° to 100° reduced modulus values. The maximum modulus was found when operating with all the oil injected at B position, but this condition also gave tint values too high for N-347. It became apparent that compromises were necessary. The properties and corrected values for this series of tests are shown in Table II. Some things have become apparent as far as N-347 production are concerned. 1. Some oil has to be injected at A or D to reduce the tint sufficiently. 2. No more than 25% of the oil can be injected at D or 325 mesh grit values begin increasing above 100 ppm. 3. For low structure carbon blacks (e.g. N-326) it is very difficult to get enough KNO₃ into the reactor if position A is used. With this in mind and with the information in Table II, it appears the best conditions for producing N-347 is with some combination of oil nozzles at A, B, C, or C-D with A-C-D locations being of secondary importance. Referring to the corrected values in Table II the following conclusions can be drawn. When operating with all oil injected at B position the tint is too high for N-347. When operating with all oil injected in B and C positions the tint is also too high. Injecting oil at A, B, C and D positions simultaneously produces modulus too low. Injecting oil at B-D and A-D gives low modulus. Injecting oil at A-C-D produces tint just on the borderline of being too high. If the A, B, C positions are used at the same time the highest percentage of oil should be injected at B to keep modulus high. In Table III, use of a reactor as described earlier in this example for the production of N-326 carbon black is illustrated. Table IV illustrates derived relationships between certain input parameters and carbon black product properties. An explanation of the variables used in Table IV is given in the following Table.

Claims: A carbon black reactor comprising: a generally cylindrical combustion zone (12); a converging zone (15); a reactor throat (22); the converging zone connecting the generally cylindrical combustion zone with the reactor throat; a generally cylindrical pyrolysis zone (34) downstream of the reactor throat, said pyrolysis zone having a diameter in the range of from 1.5 to 5 times the diameter of the reactor throat; the combustion zone, the converging zone, the throat and the pyrolysis zone being determined by a sidewall defining a reaction flow passage having a longitudinal axis (11) to the reactor; at least one generally annular wall (42) positioned between the reactor throat and the pyrolysis zone, said generally annular wall facing in the downstream direction; a means (41) for providing hot combustion gases which flow from the generally cylindrical combustion zone to the generally cylindrical pyrolysis zone; a means (40) for introducing a quench fluid at the downstream end of the generally cylindrical pyrolysis zone; a plurality of ports (59) extending generally radially inwardly towards the longitudinal axis of the reactor for the insertion of feedstock injectors; characterized by at least one port (59) being in the converging zone (15); at least one port (59) being in the throat (22) and at least one port (59) being in the pyrolysis zone (34). A reactor as claimed in Claim 1 and comprising: a first set of said ports (59) circumferentially spaced in the converging zone (15) at a first longitudinal position with respect to the longitudinal axis of the reactor; a second set of said ports (59) circumferentially spaced in the reactor throat (22) at a second longitudinal position with respect to the longitudinal axis of the reactor; and a third set of said ports (59) circumferentially spaced in the pyrolysis zone (34) at a third longitudinal position with respect to the longitudinal axis of the reactor. A reactor as claimed in Claim 2 and wherein said third longitudinal position is at a distance of about 4 throat diameters from said generally annular wall (42). A reactor as claimed in Claim 2 or Claim 3 and comprising a fourth set of said ports (59) circumferentially spaced at a fourth longitudinal position with respect to the longitudinal axis of the reactor, said fourth set of ports (59) being in the converging zone (15) upstream from said first set of ports (59). A reactor as claimed in Claim 4 wherein the distance separating the fourth set of ports from the third set of ports is no greater than about six reactor throat diameters. A reactor as claimed in Claim 5 wherein the distance separating the fourth set of ports from the third set of ports is in the range of three to six reactor throat diameters. A reactor as claimed in any one of Claims 2 to 6 including at least one feedstock injector (62) in a port (59) at each of at least two of said longitudinal positions; a source of carbonaceous feedstock; and conduit means connecting said source of carbonaceous feedstock with said feedstock injectors. A reactor as claimed in Claim 7 wherein each feedstock injector has means for emitting a coherent jet of feedstock. A reactor as claimed in Claim 7 wherein each feedstock injector has means for emitting a spray of feedstock in a cone shaped pattern. A reactor as claimed in Claim 9 wherein each feedstock injector has means whereby said cone shaped pattern has an included angle in the range of 30° to 120°. A process for producing carbon black wherein hot combustion gases are formed in the combustion zone (12) of the reactor claimed in one of Claims 2 to 10; flowing said hot combustion gases from said combustion zone (12) through said converging zone (15) and said reactor throat (22) into said pyrolysis zone (34); and introducing a carbonaceous feedstock into the hot combustion gases by means of feedstock injectors (62) selectively positioned by means of said ports (59), at at least two of said longitudinal positions. with the proviso that the feedstock shall not be introduced through ports at said first and second locations as the sole feedstock source. A process in accordance with Claim 11 wherein said feedstock is introduced through feedstock injectors in ports at said second and at said third longitudinal position. Process in accordance with Claim 11 or 12 wherein said feedstock is introduced through feedstock injectors in ports at said first and at said third longitudinal positions. Process in accordance with Claim 11 using an apparatus in accordance with Claim 4 or one of the claims referring to Claim 4, wherein said feedstock is introduced through feedstock injectors in ports at said fourth, first and second longitudinal positions. Process in accordance with Claim 11 using an apparatus in accordance with Claim 4 or one of the claims referring to Claim 4, wherein said feedstock is introduced through feedstock injectors in ports at said fourth, second and third longitudinal positions. A process according to one of Claims 11 to 15 wherein the carbonaceous feedstock is sprayed into at least one of the two longitudinal positions in the converging zone and at least one of the reactor throat and the pyrolysis zone. A process according to one of claims 11 to 15 wherein the carbonaceous feedstock is sprayed generally radially inwardly into the hot combustion gases from the side wall following each of the converging zone, the reactor zone and the pyrolysis zone. A process as claimed in one of Claims 11 to 17 wherein feedstock is introduced into the hot combustion gases over a longitudinal distance in the range of from 2 to 6 reactor throat diameters.

Inventors: GRAVLEY, MARK LEE, HENDERSON, EULAS WEBB
Applicants: DEGUSSA AKTIENGESELLSCHAFT
Application year: 1986
Main classification: C09C1
IPC codes: C09C1