Process for controlling the porosity of carbon blacks

Abstract

The present invention relates to a furnace black having a STSA surface area of at 130 m.sup.2/g to 350 m.sup.2/g wherein the ratio of BET surface area to STSA surface area is less than 1.1 if the STSA surface area is in the range of 130 m.sup.2/g to 150 m.sup.2/g, the ratio of BET surface area to STSA surface area is less than 1.2 if the STSA surface area is greater than 150 m.sup.2/g to 180 m.sup.2/g, the ratio of BET surface area to STSA surface area is less than 1.3 if the STSA surface area is greater than 180 m.sup.2/g, and
the STSA surface area and the BET surface area are measured according to ASTM D 6556 and to a furnace process wherein the stoichiometric ratio of combustible material to O.sub.2 when forming a combustion gas stream is adjusted to obtain a k factor of less than 1.2 and the inert gas concentration in the reactor is increased while limiting the CO.sub.2 amount fed to the reactor. Also provided is an apparatus for conducting the process according to the present invention.

Claims

1. A process for the production of carbon black with a furnace reactor, wherein the furnace reactor comprises, as three distinct zones, and in order in a flow direction: a combustion zone, a reaction zone that extends from a point where carbon black feedstock material is first injected to a point where cooling of formed carbon black begins, and a quench zone in which carbon black formation is terminated, wherein a cross-section of the quench zone is larger than a cross-section of the reaction zone, the process comprises: feeding combined gas streams comprising an O.sub.2-containing gas stream and a fuel stream comprising combustible material to the combustion zone of the furnace reactor, wherein the combined gas streams are fed to the combustion zone in amounts that provide a k factor of less than 1.2, the k factor being defined as the ratio of O.sub.2 theoretically necessary for stoichiometric combustion of all combustible material in the combustion zone to the total O.sub.2 fed to the combustion zone; combusting the combustible material in the fuel stream in a combustion step in the combustion zone to provide a hot flue gas stream, and passing the hot flue gas stream to the reaction zone; introducing a carbon black feedstock into the reaction zone, and contacting the carbon black feedstock with the hot flue gas stream passed from the combustion zone in a reaction step in the reaction zone to form carbon black; and terminating carbon black formation reaction by quenching in a terminating step in the quench zone; wherein an inert gas stream is fed to at least one of the combustion zone in the combustion step, the reaction zone in the reaction step, and the quench zone in the terminating step, the inert gas comprising a combined amount of components selected from oxygen containing compounds of at most 16 vol.-% based on the total volume of gaseous components excluding combustible components fed to the combustion step.

2. The process of claim 1, wherein the inert gas stream is fed to: a supply line for the O.sub.2-containing gas stream; a supply line for the fuel stream; a supply line for the carbon black feedstock; a supply line for a quench material used in the terminating step; or a combination thereof.

3. The process of claim 2, wherein the furnace reactor further comprises a pre-heater for the O.sub.2-containing gas stream; and the process further comprises feeding the inert gas stream to a supply line for the O.sub.2-containing gas stream at a location upstream of the heat exchanger.

4. The process of claim 1, wherein the inert gas is selected from N.sub.2-containing gases comprising at least 84 vol.-% N.sub.2 based on the total volume of gaseous components excluding combustible components fed to the combustion step, and ammonia.

5. The process of claim 4, wherein the inert gas is selected from N.sub.2-containing gases comprising 84-99.9999 vol.-% N.sub.2 based on the total volume of gaseous components excluding combustible components fed to the combustion step.

6. The process of claim 5, wherein the inert gas is selected from N.sub.2-containing gases comprising 90-99.99 vol.-% N.sub.2 based on the total volume of gaseous components excluding combustible components fed to the combustion step.

7. The process of claim 6, wherein the inert gas is selected from N.sub.2-containing gases comprising 92-99.99 vol.-% N.sub.2 based on the total volume of gaseous components excluding combustible components fed to the combustion step.

8. The process of claim 7, wherein the inert gas is selected from N.sub.2-containing gases comprising 95-99 vol.-% N.sub.2 based on the total volume of gaseous components excluding combustible components fed to the combustion step.

9. The process of claim 1, further comprising separating air in an air separation unit into a nitrogen-containing gas stream and an oxygen-enriched gas stream, wherein the nitrogen-containing gas stream is employed as the inert gas stream.

10. The process of claim 9, wherein the air separation unit is a pressure swing adsorption unit or a membrane separation unit.

11. A process for the production of carbon black with a furnace reactor, wherein the furnace reactor comprises, as three distinct zones, and in order in a flow direction: a combustion zone, a reaction zone that extends from a point where carbon black feedstock material is first injected to a point where cooling of formed carbon black begins, and a quench zone in which carbon black formation is terminated, wherein a cross-section of the quench zone is larger than a cross-section of the reaction zone, the process comprises: feeding combined gas streams comprising an O.sub.2-containing gas stream and a fuel stream comprising combustible material to the combustion zone of the furnace reactor, wherein the combined gas streams are fed to the combustion zone in amounts that provide a k factor of less than 1.2, the k factor being defined as the ratio of O.sub.2 theoretically necessary for stoichiometric combustion of all combustible material in the combustion zone to the total O.sub.2 fed to the combustion zone; combusting the combustible material in the fuel stream in a combustion step in the combustion zone to provide a hot flue gas stream, and passing the hot flue gas stream to the reaction zone; introducing a carbon black feedstock into the reaction zone, and contacting the carbon black feedstock with the hot flue gas stream passed from the combustion zone in a reaction step in the reaction zone to form carbon black; and terminating carbon black formation reaction by quenching in a terminating step in the quench zone; wherein the combined gas streams fed to the combustion step contain less than 20.5 vol.-% O.sub.2 and less than 3.5 vol.-% of carbon dioxide based on the total volume of gaseous components excluding combustible components fed to the combustion step.

12. The process of claim 11, wherein an inert gas stream is fed to at least one of the combustion zone in the combustion step, the reaction zone in the reaction step, and the quench zone in the terminating step, the inert gas comprising a combined amount of components selected from oxygen containing compounds of at most 16 vol.-% based on the total volume of gaseous components excluding combustible components fed to the combustion step.

13. The process of claim 11, wherein the k factor is in a range from 0.15 to 1.2.

14. The process of claim 13, wherein the k factor is in a range from 0.3 to 1.15.

15. The process of claim 14 wherein the k factor is in a range from 0.15 to 1.2.

16. The process of claim 15 wherein the k factor is in a range from 0.3 to 1.15.

17. The process of claim 16 wherein the k factor is in a range from 0.75 to 1.15.

18. The process of claim 17 wherein the k factor is in a range from 0.85 to 1.1.

19. The process of claim 18 wherein the k factor is in a range from 0.95 to 1.05.

20. The process of claim 11, wherein the combined streams fed to the combustion step comprise 1.0 to 20.0 vol.-% O.sub.2 and/or less than 2.0 vol.-% of carbon dioxide based on the total volume of gaseous components excluding combustible components fed to the combustion step.

21. The process of claim 20, wherein the combined streams fed to the combustion step comprise 2.5 to 19.5 vol.-% O.sub.2 and/or less than 1.0 vol.-% of carbon dioxide based on the total volume of gaseous components excluding combustible components fed to the combustion step.

22. The process of claim 21, wherein the combined streams fed to the combustion step comprise 5.0 to 19.0 vol.-% O.sub.2 and/or less than 0.5 vol.-% of carbon dioxide based on the total volume of gaseous components excluding combustible components fed to the combustion step.

23. The process of claim 11, wherein the O.sub.2-containing gas stream is air.

24. The process of claim 11, wherein the fuel stream comprises natural gas.

Description

(1) The present invention will now be explained in more detail with reference to the figures and to the examples.

(2) FIG. 1 shows a schematic representation of the process and the apparatus according to the present invention.

(3) As depicted in FIG. 1, the process according to the present invention is conducted in a furnace reactor 1 having in flow direction three distinct reaction zones. To the first reaction zone 2, also referred to as the combustion zone, a fuel stream comprising combustible material is fed via line 5 and an O.sub.2 containing gas stream via line 6. The fuel stream is subjected in the first reaction zone 2 to combustion in order to provide hot flue gases. As shown in FIG. 1, the diameter of the furnace reactor is narrowed, forming a second reaction zone 3 where carbon black feedstock is contacted with the hot flue gases. The carbon black feedstock is fed via line 7 to the second reaction zone 3 in the narrow part of the furnace reactor. This can be achieved by a plurality of radially arranged injection ports like oil lances (not shown). Alternatively or in addition, carbon black feedstock material can also be injected into the second reaction zone 3 via axial lances. In the second reaction zone 3 carbon black is formed by decomposition of the carbon black feedstock material. The thereby produced pyrolysis reaction mixture enters the third reaction zone 4 that is also referred to as the quenching zone. The quench material can be fed to a plurality of positions via the quench material line 8 to the quench zone. In the quenching zone 4 the reaction mixture is cooled down to a temperature that is low enough to essentially terminate the carbon black formation reaction. At this point, the reaction mixture is a dispersion of carbon black particles in a continuous gas phase of the reaction gases. The reaction mixture, after leaving the furnace reactor, is directed to one (FIG. 1) or more heat exchange units 11, in order to further reduce the temperature of the reaction mixture. The heat that is thereby removed from the reaction mixture is used to preheat the O.sub.2-containing gas stream prior to entry into the first reaction zone 2. The cold O.sub.2-containing gas stream is fed via line 13 to the heat exchange unit 11 and the preheated oxygen-containing gas stream is fed via lines 6 to the first reaction zone 2.

(4) FIG. 1 shows possible positions for feeding the inert gas stream to the reactor. One suitable position is to feed the inert gas from an inert gas storage or production unit 9 via line 10 to line 13 of the cold O.sub.2-containing gas prior to entry into the heat exchanger 11. As discussed above, unit 9 is preferably a pressure swing adsorption unit. Alternatively, the inert gas is fed via line 10 to line 6 feeding the preheated O.sub.2-containing gas stream to the first reaction zone 2. It is also possible to feed the inert gas stream via line 10 directly to the reactor 1 into the first reaction zone 2. Most preferably, the inert gas stream is fed via line 10 to line 13 of the cold O.sub.2-containing gas prior to entry into the heat exchanger 11.

(5) The cooled solid/gaseous reaction mixture leaving the heat exchanger unit 11 is directed to a separation unit 14 where the carbon black particles are recovered from the reaction mixture. The separation unit 14 is preferably a filter unit. The solid carbon black is further conducted to a discharge unit 15 for further processing and storage. The separated gas phase is then also directed to further processing units for cooling and gas treatment before it is released to the environment.

(6) In the examples as presented an apparatus as shown in FIG. 1 is used, wherein the carbon black feedstock is injected via 4 radially oriented oil lances into the second reaction zone 3. As inert gas nitrogen is used that is directly fed to line 13 of the cold O.sub.2-containing gas prior to entry into the heat exchanger 11, 12. The process parameters and the properties of the obtained carbon blacks are shown in Table 1.

(7) TABLE-US-00001 TABLE 1 Example Unit CE1 E1 E2 Process parameter k-Factor 0.75 0.75 1.0 combustion air flow Nm.sup.3/h 2302 2299 2302 combustion air temperature C. 651 650 650 nitrogen gas flow Nm.sup.3/h 0 246.6 246.4 fuel (natural gas) flow Nm.sup.3/h 178.0 177.8 237.5 carbon black feedstock kg/h 493 493 493 temperature oil lance (A-D) C. 116.5 116.5 116.4 pre-quench stream l/h 657 656 656 post-quench stream m.sup.3/h 0.304 0.29 0.287 temperature reactor exit C. 795 794 795 temperature pre-combustion C. 1786 1703 1828 chamber measured by IR molar fraction of CO in the % 13.03 11.1 9.09 water free tail gas .sup.1 sulfur flow in tail gas .sup.2 kg/h 1.8 1.8 1.6 Carbon black properties Iodine mg/g 207.1 180.7 166.6 BET m.sup.2/g 186.7 159.8 146.3 STSA m.sup.2/g 147.7 139.3 134.4 BET:STSA 1.26 1.15 1.09 OAN ml/100 g 142.1 140.2 153 .sup.1 Tail gas is extracted from the production line and filtered to remove carbon black. Subsequently the tail gas is cooled to +4 C. to freeze out water and thereafter is passed through phosphorous pentoxide to remove water completely. The water free tailgas composition is analyzed with an Inficon 3000 Micro GC Gas Analyzer to obtain the molar fraction of CO. The Inficon 3000 Micro GC Gas Analyzer is frequently calibrated with specified reference gas. .sup.2 Sulfur flow in tail gas is calculated via a mass balance. The sulfur flow of carbon black is subtracted from the sulfur flow of the feedstock. The difference is the sulfur flow of tail gas. The sulfur content of feedstock and carbon black is analyzed with an,, vario EL cube CHNS - elemental analyzer from,, Elementar Analysesysteme GmbH. The sulfur flow of feedstock and carbon black is calculated taking into account the mass flows of feedstock and carbon black and the sulfur concentration in feedstock and carbon black.