Changing oil tubes in a carbon black reactor
BACKGROUND OF THE INVENTION 
     In one aspect, the invention relates to carbon black production. In another aspect, the invention relates to an apparatus for producing carbon black. In yet another aspect, the invention relates to changing out feed tubes in a furnace. 
     In the production of carbon black from a carbonaceous make oil, it is frequently desirable to change the nozzle through which the make oil is emitted into the reaction flow passage of the reactor. This is because the properties of the carbon black being produced can be varied by changing the nozzles. For example, in certain types of carbon black reactors, changing from a nozzle which emits a 20° cone-shaped spray of feedstock to a nozzle which emits a 90° cone spray dramatically changes the properties of the black produced. Also, nozzles sometimes become plugged or burn off in the reactor and must be removed for repair or replacement. Further, the pressure drop across a set of nozzles can be altered by changing out one of them. 
     In many plant production systems, it could take operators an hour or more to change over the feedstock nozzles. During this time period, if the reactor were equipped with multiple nozzles, the carbon black being produced would not be on specification and thus could not be easily sold. Were the furnace to be shut down to replace the feedstock nozzle, the subsequent cooling of downstream processing equipment could make possible the formation of acidic condensate which can damage downstream equipment such as the filter bags. Also, downstream processes which rely upon the heat of the reactor such as the wet pellet dryer would encounter operational difficulties. 
     In reactors where the oil nozzle is exposed, shutting down the oil flow to remove the nozzle allows excessive heating of the nozzle by the reactor combustion gases and sometimes the nozzle is thereby damaged. The oil nozzle can also be damaged when it is inserted into the reactor without flow of oil going through it due to overheating. 
     A process to avoid overheating of the oil nozzles during changeout operations would be very desirable. A process which provides for changing out the oil nozzles without shutting down the reactor would be very desirable. A process which provides for rapid changeout of oil nozzles with minimal production of altered product would also be very desirable. 
     OBJECTS OF THE INVENTION 
     It is an object of this invention to provide an apparatus in which the oil nozzles can be changed without shutdown of operation. 
     It is a further object of this invention to provide an apparatus in which nozzle changeout can be carried out with minimal production of off-specification product. 
     It is yet another object of this invention to provide an apparatus in which the nozzles can be changed out with little danger of exposing the nozzle to excessively high temperatures. 
     It is another object of this invention to provide a process in which the above objects are satisfied. 
     STATEMENT OF THE INVENTION 
     In one aspect, there is provided a first tubular member having first and second ends with a nozzle attached to the first end. An oil source and a cooling fluid source are operatively associated with the first tubular member by a means for simultaneously or alternatively connecting the oil source and the cooling fluid source to the second end of the tubular member. When the apparatus is deployed in a furnace such as a carbon black reactor for the injection of oil, it can be removed for changeout of the nozzle by initiating the flow of cooling fluid, terminating the flow of oil and pulling the oil tube from the furnace. Where three of more of the oil tubes are deployed in a single furnace the cessation of oil flow through one of them will not alter product properties to an unacceptable extent. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The FIGURE schematically illustrates a cross-sectional view of a carbon black reactor employing transverse injection of feedstock in the plane of the drawing. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     According to the invention, oil injectors 2 are provided for introducing a carbonaceous feedstock into a carbon black reactor 4. It is expected that equally good results will be obtained when the invention is applied to introduce most any combustible fluid into a furnace where temperatures are so high that the nozzle can be damaged by cessation of flow of combustible fluid through the nozzle. 
     The injectors 2 are connected to a source 6 of combustible fluid. For carbon black production, the fluid generally comprises a highly aromatic high boiling oil such as a coal tar or refinery residuum. A source 8 of a cooling fluid, preferably a gas, to avoid the formation of deposits during evaporation is also connected to each injector 2. The source 8 most preferably comprises steam because it is readily available and cheap, although other light gas such as nitrogen or air could be used, although air flow could cause problems such as ignition of the combustible deposits in the oil tube if any were present. Preferably, a source of continuous cooling gas flow, such as air source 10 is also connected to the injector assembly 2 to provide a sheath around the oil tube and assist in avoiding overheating the nozzle. 
     Each of the injectors 2 comprises a first tubular member 12, which can be an oil tube, having a first end 14 and a second end 16. A nozzle 18 is affixed to the first end 14 of the tubular member 12. Preferably, the nozzle 18 is of the monofluid type, although bifluid nozzles could also be utilized if desired. In the event that the invention were practiced with a bifluid nozzle, the nozzle would additionally be connected to the steam source or other atomizing gas by a separate line, not shown. The tubular member 12 is connected to the oil source 6 and the steam source 8 by a means 20 for the simultaneous or alternative connections of the tubular member 12 to the oil source 6 and the steam source 8. 
     Preferably, the means 20 comprises a conduit 22 which forms a flow path between the oil source 6 and the nozzle 18 and a conduit 24 which forms a flow path between the steam or other cooling gas source 8 and the nozzle 18. The conduit 22 preferably has a valve 26 positioned therein for control of the flow of oil therethrough. The conduit 24 preferably is provided with a valve 28 positioned therein to control the flow of steam therethrough. The valves 26 and 28 are preferably of the manual type. The conduits 22 and 24 are connected to the tubular member 12 so as to supply fluids to the nozzle 18. 
     For rapid nozzle changeout, it is preferred that a flexible conduit 30 be positioned between the conduits 22 and 24 and the tubular member 12. In one embodiment, the conduits 22 and 24 are connected to the tubular member 12 through a tee fitting 32. The conduit 22 is connected to the first branch of the tee fitting, the conduit 24 is connected to the second branch of the tee fitting 32, and the tubular member 12 is connected to the third branch of the tee fitting 32, preferably via the flexible hose 30. 
     In a preferred embodiment, a second tubular member 34 is positioned coaxially around a first tubular member 12 so that an annulus 36 is formed between the tubular member 12 and the tubular member 34. The air source 10 is connected to the annulus 36 by a suitable conduit means 38. The tubular member 34 has a first end 40 positioned adjacent the nozzle 18 generally flush with the reactor wall and a second end 42 with a valve 44 mounted thereon. The valve 44 contains a gate or plug member which is movable from a first position in which the tubular member 34 is opened to receipt of the tubular member 12 to a second position in which the tubular member 34 is closed to receipt of the tubular member 12. During nozzle changeout the gate or plug of the valve 44 is moved into the second position to close the flow passage and prevent the escape of reactor gases. A packing 46 is positioned adjacent the second end 16 of the tubular member to seal off the annulus 36 and the inside of the reactor from the outside when the valve 44 is in second position. A suitable packing can be formed with a gasket and the exterior of the tubular member 12 can be provided with an annular flange to engage a drawdown nut, not shown. 
     Preferably, the reactor 4 is provided with three or more of the oil tubes or injectors 2 so that the cessation of oil flow through one of the injectors will not have an intolerably large influence on the properties of carbon black being produced, as long as changeout is reasonably fast. Preferably, six injectors are used, although four will provide good results and are cheaper than six. Four or more oil tubes should be used for good results. The reactor 4 is generally formed from a generally tubular mass of refractory 48 which defines a flow passage 50 having a longitudinal axis 52. The tubes 12 are preferably oriented so that their longitudinal axes are perpendicular to the axis 52 of the reaction flow passage 50. 
     In operation, the oil tubes 12 are easily removed from the reactor when fouling or nozzle damage has occurred or where a change in the type of nozzle 18 being utilized is desired. To change out the oil tubes the valve 28 is opened and the valve 26 is closed to initiate the flow of steam into the oil tube and terminate the flow of oil. The flow of steam will prevent excessive heating of the nozzle 18. The oil tube 12 can be pulled from the reactor after the loosening of the packing 46. As the first end of the tube 12 clears the plug or gate in the valve 44, the valve 44 is placed in the closed position to prevent escape of gases from the reaction flow passage 50. Steam flow can be terminated and withdrawal or removal of the oil tube from the reactor completed readily. 
     Generally the flow of air annularly to the tube 12 is not interrupted because the flow of air assists in keeping the nozzle 18 cool and helps to prevent escape of reactor content through the valve 44. 
     Once the nozzle 18 has cleared the reaction flow passage the flow of steam can be terminated or, in any event, terminated prior to changing of the nozzle 18 once the oil tube has been removed from the reactor. 
     The procedure is simply reversed in order to install the oil tube. 
     The invention is illustrated by the following example. 
     EXAMPLE 
     Four oil feed tubes, which are 2&#39;6&#34; lengths of 3/8&#34; Sch 80 316 stainless steel, with appropriate pipe fittings attached to each end, were used to feed oil radially to a carbon black reactor. A convenient length of 316 SS, Sch 80, 3/4&#34; dia. single braid flexible oil hose was attached to a first end of each oil tube. Fulljet spray nozzles, 3/8  G 9.5, available from Spraying Systems Co., 3201 Randolph St., Bellwood, IL, were attached to the second end of three of the oil tubes, and a 1/8 G 5 fulljet spray nozzle, also from Spraying Systems Co., was attached to the second end of the fourth oil feed tube. 
     The 3/8&#34; oil tubes entered the reactor through an assembly comprising in seriatim; a 1&#34; dia. Sch 80 pipe nipple PEXSE, 3&#34; long welded to the reactor shell; a 1&#34; dia full bore gate valve (VOGT 13111); a second 1&#34; dia Sch 80 pipe nipple SEXSE, 3&#34; long; a 1&#34; dia WECO F18 200 pipe union; four 3/16&#34;×3/16&#34; asbestos packing rings; a 21/4&#34; long packing gland, and a 13/4&#34; long bushing. Thickness of the reactor wall, including shell, insulation, and refractory, was 151/4&#34; at the point where the oil tubes were located. 
     The oil was sprayed into a reaction zone which converged from a 21&#34; dia to an 8&#34; dia (throat) over a length of 181/2&#34;. Conduits for supplying oil, steam and purge air to the reactor were as shown in FIG. 1, except that the location of the oil injectors was rotated 45° to provide sufficient ground clearance. 
     With the reactor hot and operating, steam flow was initiated to one of the oil injectors and oil flow was terminated. With steam flow of 75 lb/hr at 100 psig through the oil tube, the bushing holding the packing gland in place was loosened; the gate valve 44 in FIG. 1 was open, the oil tube was pulled from the reactor, and the gate valve was closed. After changing out the nozzle on the oil tube that was removed from the reactor, the procedure was reversed in order to reinstall the oil tube. Time required for changing out the spray nozzle was from 3 to 5 minutes. 
     Reactor operating conditions and collected product specifications maintained while changing out the spray nozzle are shown in the table below: 
     
                       TABLE                                                       
______________________________________                                    
Total Air           248,499 SCFH                                          
Gas                 16,067 SCFH                                           
Oil                 555 GPH                                               
API.sup.1           -2.3                                                  
BMCI.sup.2          127                                                   
Air Temp            1220° F.                                       
Oil Temp            259° F.                                        
Tailpipe Temp       1435° F.                                       
Oil Noz. Pres       139 psig                                              
Oil No.sup.2 Types  3 G 9.5 &amp; 1 G 5                                       
I.sub.2.sup.3 (No)  84.7                                                  
CTAB.sup.4 (m.sup.2 /g)                                                   
                    90                                                    
DBP.sup.5 (cc/100 g)                                                      
                    111.1                                                 
24M4.sup.6 (cc/100 g)                                                     
                    89.7                                                  
Tint.sup.7 (% 1RB#3)                                                      
                    109.6                                                 
Tint Residual.sup.8 4.0                                                   
Grit.sup.9 (Wt. %)  .0040                                                 
Type                N330                                                  
______________________________________                                    
 .sup.1 API at 60° F.                                              
 .sup.2 Bureau of Mines Correlation Index                                 
 .sup.3 ASTM 151076                                                       
 .sup.4 ASTM D3765-79                                                     
 .sup.5 ASTM D2414-76                                                     
 .sup.6 ASTM D3493-76                                                     
 .sup.7 ASTM D3265-76                                                     
 .sup.8 TR = T[56.0 + 1.057(CTAB)  0.002745(CTAB).sup.20.2596(24M4)       
 0.201(N.sub.2 SACTAB)                                                    
 where TR = tint residual                                                 
 CTAB  See footnote.sup.4 above                                           
 N.sub.2 SA  Nitrogen surface area per ASTM D3037-76                      
 24M4  See footnote.sup.6 above                                           
 .sup.9 ASTM D1514-79