US3211532A - Carbon black furnace - Google Patents

Description

1965 E. w. HENDERSON CARBON BLACK FURNACE 2 Sheets-Sheet 1 Filed March 12, 1962 Oct. 12, 1965 E, w. HENDERSON CARBON BLACK FURNACE 2 Sheets-Sheet 2 Filed March 12, 1962 INVENTOR. E. W. HENDERSON BY A:

A TTORNEKS 3,211,532 Ice Patented Oct. 12, 1965 3,211,532 CARBON BLACK FURNACE Eulas W. Henderson, Phillips, Tex., assignor to Phillips Petroleum Company, a corporation of Delaware Filed Mar. 12, 1962, Ser. No. 179,006 8 Claims. (Cl. 23-2595) This invention relates toimprovements in carbon black furnaces and processes of operating the same. In one aspect it relates to such furnaces and processes as applied to the use of a heavy residual hydrocarbon oil of API gravity less than 15, especially when the oil is a heavy residual aromatic tar hydrocarbon oil having a Bureau of Mines Correlation Index (BMCI) of 85 to about 160, when such oil is used as a fuel to produce hot combustion gases which pyrolyze a portion of such oil to form carbon black. The expression heavy residual hydrocarbon oil, when used in the present specification in the field of making carbon black by a furnace process, is defined as an essentially hydrocarbon oil having a distillation range under atmospheric pressure, or corrected to atmospheric pressure, with a percent distilled point of at least 550 F., and at least 10 percent of which will not distill at atmospheric pressure without cracking.

In the prior art, as represented by US. Patent 2,961,300 to R. E. Dollinger of November 22, 1960, it is old to have a carbon black furnace comprising in combination a first cylindrical chamber of greater diameter than length and a second cylindrical coaxial chamber of less diameter communicating therewith, said second chamber being of greater length than diameter, a hydrocarbon injector being disposed to discharge a stream of hydrocarbons predominantly axially into said first chamber and therethrough into said second chamber, and to have at least one generally cylindrical oil burner chamber having an axial outlet communicating with said first chamber predominantly tangent to the cylindrical inner Wall thereof. However, in said prior art when using a heavy residual hydrocarbon oil of API gravity less than 15, or especially a heavy residual aromatic tar hydrocarbon oil having a BMCI of 85 to about 160, as the fuel to the tangentially disposed oil burner chamber, a rapid deposition of carbonaceous and tarry material occurs in the oil burner chamber which reduces the length of time that the carbon black-forming reaction can continue without shutting down the furnace and cleaning out the deposit. This shutting down and cleaning out is quite expensive in that the furnace cannot produce carbon black while being cleaned out and that considerable time of the operators is lost in cleaning out the furnace. In said Dollinger patent in column 5, lines 1924, and column 6, Table I, it will be noted that while a heavy residual aromatic tar hydrocarbon oil having an API gravity of about 1 and a BMCI of about 122, designated as 8-2 tar, is employed as an axial feedstock, a light r distill-ate less-aromatic hydrocarbon oil of an API gravity of about and a BMCI of about 80 is employed as the tangential fuel.

The present invention is the discovery that heavy residual hydrocarbon oil of API gravity less than 15, even heavy residual aromatic tar hydrocarbon oil having a BMCI of 85 to about 160, can be employed as the tangential fuel as well as the axial feedstock in such a furnace without rapid deposit of carbonaceous material if the central portion of the tangential combustion chamber is enlarged, especially if the tangential fuel is atomized into said enlarged portion of the tangential combustion section by injecting gas under pressure into said tangential fuel, said gas under pressure being either air or an inert gas, but preferably an inert gas comprising the combustion gases formed in the carbon black-pro ducing process. Such combustion gases consist mainly of mixtures of carbon dioxide, carbon monoxide, nitrogen and water vapor, although minor proportions of hydrogen, methane, acetylene and other hydrocarbons in trace quantities may be present and may be used as formed, although it is preferred to separate such water as may be readily condensed by cooling to a temperature as little above atmospheric temperature as may be convenient.

One object of the present invention is to provide a new and useful carbon black furnace.

Another object is to provide new methods of operating a carbon black furnace.

Another object is to provide a carbon black furnace and method of operating the same which will permit the use of heavy residual hydrocarbon oil of API gravity less than 15, such as a heavy residual aromatic tar hydrocarbon oil of API gravity less than 15 and having a BMCI of to about 160, as both the axial feedstock to be converted to carbon black and as the tangential fuel to produce the hot combustion gases which pyrolyze the axial feedstock into carbon black.

Another object is to provide a suitable tangential burner for burning such heavy oil without substantial carbon deposits in said burner.

Another object is to provide means for utilizing such heavy oil with gas pressure so that it will burn in such a tangential burner with even less tendency to deposit oarbonaceous material.

Numerous other objects and advantages will be apparent to those skilled in the art upon reading the accompanying specification, claims and drawings.

In the drawings:

FIGURE 1 is an elevational view of a carbon black furnace embodying the present invention with parts broken away to show details of construction.

FIGURE 2 is an end view of the furnace of FIGURE 1 with parts broken away to show the details of construction.

FIGURE 3 is a cross-sectional view of one type of oil spray nozzle which may be employed as either the axial or tangential oil nozzles in the furnace of FIGURES 1 and 2.

FIGURE 4 is a cross section of FIGURE 3 taken along the line 4-4 looking in the direction indicated.

It will be noted that FIGURE 3 is a cross section taken along the line 33 of FIGURE 4 looking in the direction indicated, and the carbon black furnace portion of FIG- URE 1 is taken along the line 1-1 of FIGURE 2 looking in the direction indicated, except for a part of 19 not broken away.

The furnace and process of the present invention pen mits the substitution of cheaper heavy oil for the more expensive light distillate oil used in tangential firing in the prior art and thus accomplishes large savings in cost for a large carbon black plant.

In FIGURE 1 a carbon black furnace, generally designated as 6, comprises in combination a first cylindrical chamber 7 of greater diameter than length and a second cylindrical coaxial chamber 8 of from /2 to A the diameter of said first chamber (shown as /3 the diameter of said first chamber) communicating therewith. Said second chamber 8 is of greater length than diameter. A hydrocarbon injector 9 is disposed to discharge a stream of hydrocarbons predominantly axially into said first chamber 7 and therethrough into said second chamber 8. At least one generally cylindrical oil burner chamber 11 is provided having an axial outlet 12 communicating with said first chamber 7 predominantly tangential to the cylindrical inner wall thereof.

As shown in FIGURE 2, the oil burner chamber 11 is for-med with its outlet 12 of a diameter B from /2 to 1 /2 times the diameter of said second chamber 8 (shown as about the same diameter), said oil burner chamber 11 comprising in combination, in axial communication in series, means generally designated as 13 for supplying air under pressure, an inlet 14, a combustion section 16, a reducing section 17 and said outlet 12.

The combustion section 16 has a length C at least as great as its diameter and a diameter A from 1 /2 to 3 times the diameter B of said outlet 12 (shown as about twice the diameter), and a liquid hydrocarbon injector 18 is disposed in said combustion section 16 to discharge a stream of hydrocarbon predominantly axially thereof towards said outlet 12. Obviously, the spray nozzle 29 of injector 18 should be located adjacent the inlet 14 of the chamber of combustion section 16 to enable the combustion shown by dotted lines 20 in FIGURE 2 to occur as shown in said figure. The dimensions A, B and C are critical, but the dimensions D and E are not critical, as the length D of reducing section 17 may be of any length permitting converging flow of gases, from combustion section 16 through outlet 12 into chamber 7, and the diameter E of inlet 14 may range anywhere between the diameter A of combustion section 16 and about half the diameter of B outlet 12, preferably about A the diameter of B. Inlet 14 (when used) merely tends to increase the turbulence and completeness of burning of hydrocarbon 20 in combustion section 16. The diameter A should be at least 1% times the axial length of the precombustion chamber 7.

The means 13 for supplying air under pressure may be any such means known in the prior art, but preferably comprises a cylindrical wind box 19, preferably of at least as great diameter as said combustion section 16, and compression means comprising a compressor 21 (lower part of FIGURE 1) having an intake conduit 22 communicating with the atmosphere and an outlet conduit 23 connected to at least one air supply conduit 24 of about the same diameter F as said outlet 12 connected in communication with said wind box 19 predominantly tangent to its inner cylindrical wall.

While not essential to the practice of the invention, certain details of construction are shown in FIGURE 2. The carbon black furnace 6 could be built entirely of refractory material, but to reduce the cost is preferably constructed with an inner refractory ceramic lining 26, intermediate heat-insulating lining 27 and an outer metal casing 28. The tangential oil injector 18 may be provided with a nozzle 29 (shown in greater detail in FIG- URES 3 and 4), and the pipe 31 leading to injector 18 may be mounted in a stufling box 32 to provide axial adjustment of nozzle 29 in combustion section 16, movement for which is provided by flexible section 33 of conduit 31.

As shown in FIGURE 1, a single source 34 of oil may be employed, said oil being pumped by pump 36 through coil 37 of preheater 38 into oil spray line 39. As a safety measure, line 39 may be provided with a relief valve 41 and a recycle line 42 so that if a predetermined maximum pressure is reached in line 39 some of the oil and the pressure will be relieved through line 42 back to tank 34. The oil in line 39 passes through line 43 and valve 44 into axial injector 9. Axial injector 9 may be a simple pipe but preferably is provided with a nozzle 29 of the type shown in FIGURES 3 and 4.

The oil in line 39 also passes through line 46 and valve 17 and line 31 into tangential injector 18.

While valve 47 may remain closed so that oil from line 46 is passed through line 31 into tangential oil injector 18 merely under pump pressure 36 as controlled by relief valve 41, it is preferred to pass the oil through line 46 into the throat of a gas-powered, venturi-type oil eductor 48, supplied with gas under a pressure of to 500 p.s.i.g., more preferably 25 to 150 p.s.i.g., for example preferably about 75 p.s.i.g., with valve 47 open.

It is not believed necessary to show the details of the gaspowered oil eductor 48, as such eductors are well known in the prior art, and any one of the same gives substantially the same results.

As the heavy oil employed is somewhat difiicult to ignite, it is customary to start with a starting fuel, such as gasoline, injected through line 51 and valve 52. After the combustion section 16 of the tangential burner 11 is heated, valve 52 is closed and valve 17 opened to supply heavy oil to the hydrocarbon injector 18.

While it is only necessary to have one tangential burner 11 discharging through outlet 12 into the first cylindrical chamber 7, known as the precombustion chamber, it is preferable for steady operation to have two tangential burners 11 spaced 180 apart, as shown in FIGURE 2. Of course, more than two burners could be used. While it is possible to operate with only one tangential air inlet 24 in wind box 19, it is preferable to have two such tangential inlets to each wind box 19, as shown in FIGURE 2. Of course, more than two tangential inlets could be used.

It is preferred to quench the hot smoke coming from the second cylindrical chamber 8, often known as the reaction section, by injecting a spray of water into the same through pipe 54, controlled by valve 57 as a primary quench, and if necessary, injecting further water sprays as a secondary quench through pipes 55 and 56 controlled by valves 58 and 59, respectively. The portions 61 and 62 downstream of the first quench 54 are often known as the quench section of the furnace.

When starting the furnace, valve 63 in branch line 64 may be open to by-pass the hot combustion gases which are warming up the furnace, but as soon as the oil from line 43 is injected through axial injector 9 upon opening valve 44, then valve 63 is closed and the smoke in pipe 53 passes into any conventional system known to the prior art for separating carbon black solids from the combustion gases suspending the same. For purposes of illustration, a simple cyclone separator generally designated as 66 is shown as this conventional separating means, the smoke entering tangentially from pipe 53 and the combustion gases, known as elf-gas, passing upwardly through pipe 67 while the solid particles of carbon black, separated from the gas by centrifugal force and gravity, pass downwardly out through the conventional star valve 68.

While the major portion of the off-gas passes through valve 69 to the atmosphere, at least a portion of these combustion gases pass through line 71, either directly to a compressor 72 through line 74 or preferably through line 76 and water separator 77 to said compressor 72. These combustion gases from line 76 contain a large proportion of water vapor. As water separator 77 is not very much above atmospheric temperature and may contain suitable bafiies (not shown), a large proportion of the water vapor condenses to form water and is removed through valve 78 in response to liquid level control 79, thus avoiding water entering compressor 72 or being recycled to the carbon black furnace where it would have a dampening effect on the process.

Compressor 72 may compress the gases to a pressure of 25 to 500 p.s.i.g., preferably 25 to p.s.i.g., and most preferably to about 75 p.s.i.g. The gases compressed can be combustion gas from line 74 or 76 when valve 81 is open and/ or air from lines 23 and 82 when valve 83 is open. The gas compressed by compressor 72 travels through line 84 and valve 47 when used to educt oil from line 46 into eductor 48 and into tangential hydrocarbon injector 18 through line 31.

Sometimes some difficulty is experienced with carbon deposits around the axial hydrocarbon injector 9. While not essential to the invention, Valves 86 and/ or 87 may be opened to permit air from lines 23 and 88, orgas from line 84, respectively, to pass through line 89 into the annular space 91 around injector 9 to reduce the tendency for deposits to form in said annular space 91.

While the injection may be practiced with ordinary injector pipes 9 and 18, it is obviously preferable to have some sort of nozzle 29 on their ends which will provide a suitable spray. While any type of spray head known to the prior art may be employed as nozzle 29, in FIGURES 3 and 4 are shown the preferred nozzle, which nozzle was not invented by the present applicant but merely selected for use from the prior art. Nozzle 29 has threads 92 for connection with pipes 9 or 18; however, any other connection means maybe used. A valve seat 93 and spring-closed check valve 94 is biased against said seat by helical com pression spring 96. The spring retainer 97 contains openings 98 for the passage of oil therethrough. Although not essential, it is desirable to surround openings 98 with a cylindrical screen 99 in order to prevent the passage of foreign matter into the small diameter feed passages 101, which preferably lead tangentially into chamber 102 and thence through orifice 103 in the spray nipple 104 in order to provide a more perfect spray. Plate 106 and spherical surface 107 merely allow for minor self-adjustment of parts to minimize leakage.

While the present invention is directed to an apparatus and process for cleanly burning a heavy residual aromatic tar hydrocarbon oil of API gravity less than 15, having a BMCI of 85 to about 160, in the tangential burners of a carbon black furnace of the general type disclosed in said Dollinger patent, it is obvious that other cleaner burning and more easily combustible oils can be employed as both the axial feedstock injected at 9 and the tangential fuel injected at 18. However, such cleaner burning oils are not as valuable in making carbon black because their BMCI is generally below 85, and generally the higher the BMCI the higher the yield of carbon black is per gallon of oil, and the higher is the quality of the carbon black produced.

Therefore, from a standpoint of economic, it is preferred to use liquid feedstocks having a BMCI of at least 85 and more preferably over 110. The formula used is as follows:

+131.5+API wherein F is the boiling point in degrees Fahrenheit at the 50 percent recovery distillation and API is the American Petroleum Institute gravity at 60 F. It is preferred that the API gravity should be as low as possible at least less than 15.

As an example of one preferred residual feedstock employed, a normally liquid hydrocarbon having a hydrogen-to-carbon atomic ratio below 1.5 and preferably in the range of 0.75 to 1.25, a mean molecular weight above 140 and preferably from 225 to 550, an API gravity less than 10, and a low Conradson carbon residue which, however, may be in excess of 1.5 weight percent or even in excess of 3 weight percent, but not more than 15 and preferably not more than 10 weight percent, is suitable in the practice of this invention. However, any heavy hydrocarbon oil of API gravity less than may be employed in the invention. However, a heavy residual aromatic tar hydrocarbon oil of API gravity less than 15 having a BMCI of 85 to 160 is preferred. The feedstock should be essentially a hydrocarbon oil. However, any small oxygen or nitrogen content appears to only reduce the yield and not affect the quality of the carbon black. Sulfur is not objectionable so far as carbon black quality is concerned, but large amounts can cause corrosion in the equipment, so for commercial purposes the sulfur content should be less than 3 and preferably less than 1 weight percent. Said liquid hydrocarbon feedstock may be a petroleum residual oil or a coal tar residual oil, synthetic tars from catalytic or thermal cracking, cracked residues, or vacuum still tarry residuums.

The use of a large diameter combustion space 16 gives ample room for the complete combustion of the liquid hydrocarbon spray before it reaches the walls of the combustion chamber so that substantial carbon deposits will not occur therein, while the reducing section 17 and outlet 12 allows the air to turn the flame away from the walls of the tangential burner and restores the original velocity to produce a sufiicient tangential velocity to move the combustion gases to the cylindrical wall as they enter the precombustion chamber 7. When employed, the further addition of gas 84 to pressure and atomize the oil emerging from hydrocarbon injector 18 gives a finer and faster burning mist of oil, with an increase in turbulence, to produce more rapid and complete combustion without deposit of carbonaceous material on the inner walls of combustion section 16, reducing section 11, outlet 12, first chamber 7, and second chamber 8.

While specific embodiments of the invention have been discussed in the specification and shown in the drawings for illustrative purposes, the invention is not limited there- 110.

Having described my invention, I claim:

1. In a carbon black furnace comprising in combination a first cylindrical chamber of greater diameter than length and a second cylindrical coaxial chamber of from /2 to A the diameter of said first chamber communicating therewith, said second chamber being of greater length than diameter, a hydrocarbon injector disposed to discharge a stream of hydrocarbons predominantly axially into said first chamber and therethrough into said second chamber, and at least one generally cylindrical oil burner chamber having an axial outlet communicating with said first chamber predominantly tangent to the cylindrical inner wall thereof;

the improvement characterized by forming said oil burner chamber with its said outlet of a diameter from /2 to 1% times the diameter of said second chamber;

said oil burner chamber comprising in combination, in

axial communication in series, means for supplying air under pressure, an inlet, a combustion section, a reducing section, and said outlet;

said combustion section having a length at least as great as its diameter, and a diameter from 1% to 3 times the diameter of said outlet and at least 1% times the axial length of said first cylindrical chamber; and

a liquid hydrocarbon injector disposed in said combustion section to discharge a stream of hydrocarbon from a point adjacent said inlet thereof predominant ly axially thereof toward said outlet.

2. The combination of claim 1 in which the means for supplying air under pressure comprises a cylindrical wind box of at least as great diameter as said combustion section, and air compression means comprising at least one air supply conduit of about the same diameter as said outlet connected in communication with said wind box predominantly tangent to its inner cylindrical wall.

3. The combination of claim 1 with means to supply under pressure the same heavy residual hydrocarbon oil to both said hydrocarbon injector and said liquid hydrocarbon injector.

4. The combination of claim 1 in which the inlet of said oil burner chamber comprises a diaphragm with an orifice of about A the diameter of said outlet.

5. The combination of claim 1 in which there is a means for introducing gas under a high pressure of 25 to 500 p.s.i.g. into said liquid hydrocarbon injector for atomizing said liquid hydrocarbon being injected into said combustion section.

6. The combination of claim 5 in which the inlet of said oil burner chamber comprises a diaphragm with an orifice of about the diameter of said outlet.

7. The combination of claim 5 in which said carbon black furnace includes means to separate the carbon black formed from the combustion gases, and means for compressing at least a portion of said combustion gases to a pressure of 25 to 500 p.s,i.g. and supplying them to said gas introducing means as said gas for atomizing said liquid hydrocarbon.

8. The combination of claim 7 with means to supply under pressure the same heavy residual hydrocarbon oil to both said hydrocarbon injector and said liquid hydrocarbon injector.

References Cited by the Examiner UNITED STATES PATENTS Krejci 23259.5 X Goldtrap 23209.4 Heller 23209.4 Dollinger 23259.5 X Heller et al. 23209.4

MAURICE A. BRINDISI, Primary Examiner.

Claims (1)

1. IN A CARBON BLACK FURNACE COMPRISING IN COMBINATION A FIRST CYLINDRICAL CHAMBER OF GREATER DIAMETER THAN LENGTH AND A SECOND CYLINDRICAL COAXIAL CHAMBER OF FROM 1/2 TO 1/4 THE DIAMETER OF SAID FIRST CHAMBER COMMUNICATING THEREWITH, SAID SECOND CHAMBER BEING OF GREATER LENGTH THAN DIAMETER, A HYDROCARBON INJECTOR DISPOSED TO DISCHARGE A STREAM OF HYDROCARBONS PREDOMINANTLY AXIALLY INTO SAID FIRST CHAMBER AND THERETHROUGH INTO SAID SECOND CHAMBER, AND AT LEAST ONE GENERALLY CYLINDRICAL OIL BURNER CHAMBER HAVING AN AXIAL OUTLET COMMUNICATING WITH SAID FIRST CHAMBER PREDOMINANTLY TANGENT TO THE CYLINCRICAL INNER WALL THEREOF; THE IMPROVEMENT CHARACTERIZED BY FORMING SAID OIL BURNER CHAMBER WITH ITS SAID OUTLET OF A DIAMETER FROM 1/2 TO 1 1/2 TIMES THE DIAMETER OF SAID SECOND CHAMBER; SAID OIL BURNER CHAMBER COMPRISING IN COMBINATION, IN AXIAL COMMUNICATION IN SERIES, MEANS FOR SUPPLYING AIR UNDER PRESSURE, AN INLET, A COMBUSTION SECTION, A REDUCING SECTION, AND SAID OUTLET; SAID COMBUSTION SECTION HAVING A LENGTH AT LEAST AS GREAT AS ITS DIAMETER, AND A DIAMETER FROM 1 1/2 TO 3 TIMES THE DIAMETERE OF SAID OUTLET AND AT LEAST 1 1/4 TIMES THE AXIAL LENGTH OF SAID FIRST CYLINDRICAL CHAMBER; AND A LIQUID HYDROCARBON INJECTOR DISPOSED IN SAID COMBUSTION SECTION TO DISCHARGE A STREAM OF HYDROCARBON FROM A POINT ADJACENT SAID INLET THEREOF PREDOMINANTLY AXIALLY THEREOF TOWARD SAID OUTLET.

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