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 furnace black having a STSA surface area of 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.

2. The furnace black of claim 1 having a STSA surface area of 140 m.sup.2/g to 300 m.sup.2/g, preferably 150 m.sup.2/g to 280 m.sup.2/g, more preferred 160 m.sup.2/g to 250 m.sup.2/g.

3. The furnace black according to claim 1, wherein the ratio of BET surface area to STSA surface area is less than 1.09 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 1.15 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 1.25 if the STSA surface area is greater than 180 m.sup.2/g.

4. The furnace black according to claim 1 having a STSA surface area of 140 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, preferably less than 1.09 if the STSA surface area is in the range of 140 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, preferably less than 1.15 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, preferably less than 1.25 if the STSA surface area is greater than 180 m.sup.2/g.

5. The furnace black according to claim 1, having an OAN value measured according to ASTM D2414 of 20-200 ml/100 g, preferably 30-170 ml/100 g, more preferred 100-170 ml/100 g.

6. A furnace process for the production of carbon black comprising: feeding an O.sub.2-containing gas stream, a fuel stream comprising combustible material and optionally one or more further gas streams to a furnace reactor; subjecting the combustible material to combustion in a combustion step to provide a hot flue gas stream, wherein the O.sub.2-containing gas stream, the fuel stream comprising combustible material and optionally the at least one further gas stream are fed to the combustion step in amounts providing a k factor of less than 1.2, wherein the k factor is defined as the ratio of O.sub.2 theoretically necessary for stoichiometric combustion of all combustible material in the combustion step to the total O.sub.2 fed to the combustion step; contacting a carbon black feed stock with the hot flue gas stream in a reaction step to form carbon black; terminating the carbon black formation reaction in a terminating step; wherein the combined 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; and/or an inert gas stream comprising a combined amount of components selected from oxygen containing compounds of at most 16 vol.-% is fed to at least one of the reaction step and the terminating step.

7. The process of claim 6, wherein the k factor is 0.15 to 1.2, preferably 0.3 to 1.15, more preferred 0.75 to 1.15, even more preferred 0.85 to 1.1, most preferred 0.95 to 1.05.

8. The process of claim 6, wherein the combined streams fed to the combustion step comprise 1.0 to 20.0, preferably 2.5 to 19.5, more preferred 5.0 to 19.0 vol.-% O.sub.2 and/or less than 2.0, preferably less than 1.0, more preferred less than 0.5 vol. % of carbon dioxide based on the total volume of gaseous components excluding combustible components fed to the combustion step.

9. The process of claim 6, wherein the O.sub.2-containing gas stream is air optionally oxygen enriched, or oxygen depleted air.

10. The process of claim 6, wherein the fuel stream comprises natural gas.

11. The process of claim 6, wherein an inert gas stream comprising a combined amount of components selected from oxygen containing compounds of at most 16 vol.-% is fed to any of the combustion step, the reaction step, the termination step, to any of the supply lines for the O.sub.2-containing gas stream, the fuel stream, the carbon black feedstock or if a quench material is used in the terminating step to the quench material or a combination thereof, preferably the furnace reactor further comprises a pre-heater for the O.sub.2-containing gas stream and the inert gas stream is fed to the supply line for the O.sub.2-containing gas stream prior to entry into the heat exchanger.

12. The process of claim 6, wherein the inert gas is selected from N.sub.2-containing gases comprising at least 84 vol.-% N.sub.2, and ammonia, preferably the inert gas stream comprises 84-99.9999 vol.-% N.sub.2, more preferred 90-99.99 vol.-% N.sub.2, even more preferred 92-99.99 vol.-% N.sub.2, most preferred 95-99 vol.-% N.sub.2.

13. The process of claim 6, further comprising separating air in an air separation unit, preferably a pressure swing adsorption unit or membrane separation unit into a nitrogen-containing gas stream and an oxygen-enriched gas stream, wherein the nitrogen-containing gas stream is employed as inert gas stream and the oxygen-enriched gas stream is optionally utilized in the process for the production of carbon black.

14. An apparatus for producing of carbon black, comprising a) a furnace reactor comprising a first reaction zone for generating a hot flue gas stream and at least one line in flow connection with the first reaction zone for feeding an O.sub.2-containing gas stream to the first reaction zone and at least one line in flow connection with the first reaction zone for feeding a fuel stream comprising combustible material to the first reaction zone; a second reaction zone for contacting the hot flue gas stream with the carbon black feed stock downstream of and in flow connection with the first reaction zone and at least one line in flow connection with the second reaction zone for feeding carbon black feed stock to the second reaction zone; and a third reaction zone for terminating the carbon black formation reaction downstream of and in flow connection with the second reaction zone comprising means for quenching the carbon black formation reaction; and b) an inert gas supply unit; and c) at least one line connecting the inert gas supply unit to the reactor or to any of the feeding lines for feeding material to the reactor in order to feed an inert gas stream to the reactor, wherein the inert gas supply unit is a supply line connecting an external inert gas production facility to the apparatus, a storage unit, or an air separation unit.

15. The apparatus of claim 14, further comprising a pre-heater for the oxygen-containing gas stream and/or at least one feeding line in flow connection with the third reaction zone for feeding a quench material to the third reaction zone.

16. The apparatus of claim 14, wherein the air separation unit is a pressure swing adsorption unit or a membrane separation unit and the inert gas supply unit is connected via the at least one line for feeding the inert gas stream to any of: the line for feeding the O.sub.2-containing gas stream prior to entry into the pre-heater; the line for feeding the O.sub.2-containing gas stream down-stream of the pre-heater; the line for feeding the fuel stream; the line for feeding carbon black feedstock; the means for quenching the carbon black formation reaction, in the form of a line for feeding quench material; the first reaction zone; the second reaction zone; the third reaction zone; or a combination thereof, preferably to the line for feeding the oxygen-containing gas stream prior to entry into the pre-heater.

Description

[0076] The present invention will now be explained in more detail with reference to the figures and to the examples.

[0077] FIG. 1 shows a schematic representation of the process and the apparatus according to the present invention.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

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.