TECHNICAL FIELD

The present invention relates to a method for controlling the oxidation of wet beaded carbon black in a screw conveyor. It has surprisingly been found that the motor current used to drive the conveyor screw is an indicator for the destruction of the wet beaded carbon black during the oxidation. The inventive method as well as control device utilize said motor current and adepts the rotational speed of the screw.

TECHNICAL BACKGROUND

Carbon blacks are fine powders that are difficult to store, transport or process. To avoid these difficulties, carbon black powders are often provided as pellets or beads having an increased bulk density.

One process to provide these beads is known as wet-beading, where the carbon black powder is agitated with water and dried afterwards. Such a process is described in GB 839,918.

Dry beading in a drum and feeding an oxidation agent directly in the dry beading drum is known in the prior art. However, this technology is not applicable for rubber customers, due to the low pellet strength of dry beaded products.

On the other hand, wet beaded carbon black can be beneficially used for rubber compositions since an increased pellet strength is achieved. The oxidation and the subsequent wet beading of carbon black are described in US 2019/0161621 A1. The produced carbon black is pulverized and subjected to a second reactor, where a carbon black/water mixture is obtained. The carbon black in the mixture is then oxidized and thereafter beaded in a pelletizer. The obtained oxidized beaded carbon black is transferred via a screw conveyer to a dryer.

However, the drawback of beading and drying the oxidized carbon black is that the degree of oxidation, i.e. the amount of function groups of the surface of the carbon black beads, is decreased during the process. Accordingly, it is difficult to control the desired degree of oxidation of the carbon black beads.

Therefore, a screw conveyor has been developed as the oxidation unit for wet beaded carbon blacks. Even though the destruction of wet beaded carbon black can be reduced in a screw conveyor, a control device and a method should be provided that can detect and avoid the destruction of the beads during the oxidation. It has surprisingly been found that the above objective can be achieved by a control device as well as method that detects the motor current required for a set rotational speed, determine the difference between the required motor current and the motor current that is needed for the set rotational speed without pellet destruction, and adept the rotational speed based on said difference.

SUMMARY OF THE INVENTION

Particularly, the above objective can be achieved by method for controlling a rotational speed n(t) and an ozone flow q _OZ one(n,t) of a screw conveyor (200, 300) for producing oxidized wet beaded carbon black (202), wherein the screw conveyor (200, 300) comprises an electrical motor (215) for driving a conveyor screw (213), the conveyor screw (213) conveying wet beaded carbon black (201) from a material inlet (210) towards a material outlet (202) passing a reaction chamber (218) comprising ozone, wherein the reaction chamber (218) further comprises at least one ozone inlet (216) configured to adapt an ozone flow q _OZ one(n,t) into the reaction chamber (218), wherein the method comprises a current regulated power control of the motor depending on predetermined correlations of set values for a specific carbon black product. The present invention also relates to a control device (900) for controlling a rotational speed n(t) and an ozone flow q _OZ one(n,t) of a screw conveyor (200, 300) for producing oxidized wet beaded carbon black (202), wherein the screw conveyor (200, 300) comprises an electrical motor (215) for driving a conveyor screw (213), the conveyor screw (213) conveying wet beaded carbon black (201) from a material inlet (210) towards a material outlet (202) passing a reaction chamber (218) comprising ozone, wherein the reaction chamber (218) further comprises at least one ozone inlet (216) configured to adapt an ozone flow q _OZ one(n,t) into the reaction chamber (218), wherein the control device (900) is configured to perform a current regulated power control of the motor depending on predetermined correlations of set values for a specific carbon black product.

These and other optional features and advantages of the present invention are described in more detail in the following description, figures, aspects and claims.

FIGURES

Figure 1 (FIG. 1): Process (100) for the production of oxidized wet beaded carbon black (202).

Figure 2 (FIG. 2): Inner section of a screw conveyor (200, 300) for the production of oxidized wet beaded carbon black. Figure 3 (FIG. 3): Outer section of a screw conveyor (200, 300) for the production of oxidized wet beaded carbon black.

Figure 4 (FIG. 4): Section of a conveyor screw (400).

Figure 5 (FIG. 5): Section of a conveyor screw (500) having a second helical conveyor blade (501) forming a circumferential clearance (503).

Figure 6 (FIG. 6): Section of a conveyor screw (600) having segments (601 , 602, 603) of different helical conveyor blades (501 , 502).

Figure 7 (FIG. 7): Section of a conveyor screw (700) having a second helical conveyor blade (501) forming a circumferential clearance (503) and turners (702, 703).

Figure 8 (FIG. 8): Section of a conveyor screw (700) having a second helical conveyor blade (501) forming a circumferential clearance (503) and turners (702, 703) including angles and the rotation direction.

Figure 9 (FIG. 9): Image of oxidized wet beaded carbon black (202).

Figure 10 (FIG. 10) A method for controlling a rotational speed n(t) and an ozone flow q _O zone(n,t) of a screw conveyor (200, 300).

DETAILED DESCRIPTION

It has been found that the rotational speed of a screw conveyor has an influence on the pellet strength, pellet attrition, as well as the fines content and thus, an influence on the pellet destruction. If the energy consumption of the electrical motor is too high, an increased pellet destruction will be observed. Accordingly, a device (or control device) and method has been developed that can adapt to the conditions during the oxidation. It is now possible to continuously oxidize the wet beaded carbon black in a screw conveyor as oxidation unit without damaging the pellets. Accordingly, the resulting oxidized wet beaded carbon black has improved pellet strength, lower pellet attrition, as well as a lower fines content. Moreover, a screw conveyor utilizing the inventive method and device is more versatile since the system can adept to an increased input of wet beaded carbon black feed by increasing or lowering the screw rotational speed. It is desired that the output of the oxidized wet beaded carbon black is maximized without negatively affect the properties of the beads.

Thus an inventive control device for controlling a rotational speed n(t) and an ozone flow q _OZ one(n,t) of a screw conveyor for producing oxidized wet beaded carbon black is provided, wherein the screw conveyor comprises an electrical motor for driving a conveyor screw, the conveyor screw conveying wet beaded carbon black from a material inlet towards a material outlet passing a reaction chamber comprising ozone, wherein the reaction chamber further comprises at least one ozone inlet configured to adapt an ozone flow q _OZ one(n,t) into the reaction chamber, wherein the control device is configured to perform a current regulated power control of the motor depending on predetermined correlations of set values for a specific carbon black product.

The control device can further comprise a primary controller, means for detecting and/or monitoring the actual motor current during operation, means for detecting and/or monitoring and/or controlling rotational speed and data storage means comprising a database for product specific power setting values of the screw conveyor.

The control device can further comprise a flow controller, configured to control the flow q _O zone(n,t) based on the set ozone flow q _OZ one,set(n,t).

Moreover, the invention relates to a method for controlling a rotational speed n(t) and an ozone flow q _OZ one(n,t) of a screw conveyor for producing oxidized wet beaded carbon black, wherein the screw conveyor comprises an electrical motor for driving a conveyor screw, the conveyor screw conveying wet beaded carbon black from a material inlet towards a material outlet passing a reaction chamber comprising ozone, wherein the reaction chamber further comprises at least one ozone inlet configured to adapt an ozone flow q _OZ one(n,t) into the reaction chamber, wherein the method comprises a current regulated power control of the motor depending on predetermined correlations of set values for a specific carbon black product.

The current regulated power control of the motor is used to adapt the actual rotational speed n(t) of the screw of the screw conveyor and the actual motor current l(t). The adaption of n(t) and l(t) depend on predetermined correlations of set values comprising a set rational speed n _se t(t) and a correlated set motor current l _se t(t) preferably for a specific carbon black product compared to actual motor current l(t).

The at least one ozone inlet configured to adapt an ozone flow q _OZ one(n,t) into the reaction chamber can comprise a valve that is able to adapt an ozone flow q _OZ one(n,t) into the reaction chamber.

The current regulated power control can be used to adapt the rotational speed of the conveyor screw based on the energy consumption of the electrical motor of the screw conveyor by comparing the actual energy consumption with a predetermined energy consumption, wherein preferably the predetermined energy consumption is measured for the specific oxidized carbon black to be produced for multiply rotational speeds, and the predetermined energy consumption is preferably stored in a look up table.

Furthermore the method can comprise the steps: (A) determining and setting a set rotational speed n _se t(t) and a set ozone flow q _OZ one,set(n,t) for a specific oxidized wet beaded carbon black to be produced from said predetermined correlations, (B) detecting the actual motor current l(t) of the electrical motor during operation, (C) comparing the actual motor current l(t) with a first predetermined set motor current l _se t(t) from said predetermined correlations of set values; (D) adjusting the set rotational speed n _se t(t) to n(t) based on a result (Al) of said comparison, preferably using a primary controller, (E) determining a corrected second set motor current and a corrected set ozone flow based on the adjusted rotational speed and (F) generating a set ozone flow q _OZ one,set(n,t) from the rotational speed n(t) and (G) adapting the ozone flow into the reaction chamber accordingly.

It is desired that the control device as well as the method utilizes a screw conveyor, wherein the conditions are measured for different oxidized wet beaded carbon black that are desired to be produced. Accordingly, a user should collect data that are optimal for the production of the desired oxidized wet beaded carbon black for the specific screw conveyor. The data can be stored in a look up table by defining a set rotational speed n _set (t) and a respective set motor current I _se t(t) that is required for the electrical motor of the screw conveyor. In other words, the data in the look up table for the oxidized wet beaded carbon black to be produced can consider the screw conveyor. For instance, the screw conveyor receives a wet beaded carbon black feed and several different rotational speeds are applied and the corresponding motor current is measured and stored. Accordingly, a look up table can store the correlated values for the rotational speed n _se t(t) and motor current l _se t(t) for the specific screw conveyor (for instance first look up table). The correlations of rotational speed and rotational speed can be stored as the set rotational speed n _se t(t) and set motor current I _se t(t). Additionally, for each correlation or relation a set ozone flow q _OZ one,set(n,t) is also stored in the look up table (for instance in a second look up table). The set ozone flow q _OZ one,set(n,t) defines the desired degree of oxidation and depends on the desired oxidized wet beaded carbon black that should be produced. However, the rotational speed has an influence on the time in which the wet beaded carbon black is present in the reaction chamber and thus, the degree of oxidation. Generally, the longer the wet beaded carbon black is present in the reaction chamber of the screw conveyor, the higher the degree of oxidation (provided that the ozone flow is the same). Accordingly, the set ozone flow q _OZ one,set(n,t) is determined for each set rotational speed n _se t(t) for the production of the desired oxidized wet beaded carbon black. During the oxidation process, a flow sensor can measure the ozone flow q _OZ one(n,t) so that the flow controller can adjust the ozone flow q _OZ one(n,t) or the set ozone flOW qozone,set(n,t) .

Accordingly, it is desired that the look up table comprises data about a correlated set rotational speed n _se t(t) and set motor current I _se t(t) including a set ozone flow q _OZ one,set(n,t). Moreover, a first look up table can comprise data representing a plurality of correlated values for n _se t(t) and l _se t(t) for at least one specific product. A second look up table can comprise data representing a plurality of correlated values for n(t) and q _OZ one,set(n,t). Preferably, the look up table or each look up table comprises data about several, such as 2 to 1000 data points, correlated set rotational speed n _se t(t) and set motor current l _se t(t) data including a set ozone flow q _OZ one,set(n,t), wherein each data point relates to a different rotational speed. In other words, it is desired that the look up table comprises data about set rotational speed n _set (t), the set motor current l _se t(t) and set ozone flow q _OZ one,set(n,t) for the production of the desired oxidized wet beaded carbon black. However, it is possible that a database or data storage means comprising the look up table or the first and/or second look up table can extrapolate data points that are not explicitly measured. It should be noted that the look up table or the first and/or second look up table preferably comprises for each specific oxidized wet beaded carbon black product several, such as 2 to 1000 data points, correlated set rotational speed n _set (t) and set motor current l _se t(t) data including a set ozone flow q _OZ one,set(n,t), wherein each data point relates to a different rotational speed. The look up table can store for each desired product a different set of data points.

The look up table can comprise data about the relationship between the set rotational speed n _set (t) and the set motor current I _se t(t) as well as the set ozone flow q _OZ one,set(n,t) required for the set rotational speed n _set (t) for the production of the desired oxidized wet beaded carbon black. The relationship between the set rotational speed n _se t(t) and the set motor current l _set (t) as well as the set ozone flow q _OZ one,set(n,t) required for the set rotational speed n _set (t) for the production of the desired oxidized wet beaded carbon black can be determined for each desired oxidized wet beaded carbon black produced in the screw conveyor. The relationship between the set rotational speed n _set (t) and the set motor current l _se t(t) as well as the set ozone flow q _OZ one,set(n,t) required for the set rotational speed n _se t(t) for the production of the desired oxidized wet beaded carbon black can be determined for each desired oxidized wet beaded carbon black produced in the screw conveyor and stored in the look up table. Preferably a first look up table can comprise data representing a plurality of correlated values for n _se t(t) and I _se t(t) for at least one specific product. A second look up table can comprise data representing a plurality of correlated values for n(t) and q _OZ one,set(n,t). The database or the look up table can also extrapolate the data points of the related set motor current l _set (t) and set rotational speed n _S et(t) if not no value is stored for this specific rotational speed n _se t(t).

The data in the look up table for the oxidized wet beaded carbon black to be produced should consider a condition of the screw conveyor, where the wet beaded carbon black is not crushed. However, as mentioned above, it is desired that multiply data points are stored in the look up table, wherein each data point relates to a specific rotational speed, where the wet beaded carbon black is preferably not crushed.

Generally a user can select the desired oxidized wet beaded carbon black to be produced so that the set rotational speed n _set (t) and a set ozone flow q _OZ one,set(n,t) is received. The electrical motor uses the set rotational speed n _se t(t) and the a set ozone flow q _OZ one,set(n,t) is applied.

The result (Al) in step (D) can be used in the following step (E) to determining a corrected second set motor current and a corrected set ozone flow based on the adjusted rotational speed. For instance, if the result Al or difference current Al reveals that the motor current l(t) is lower than the set motor current l _se t(t), the set rotational speed n _se t(t) can be increased, preferably in each loop until the difference current Al is zero or very low. Similarly, if the difference current Al reveals that the motor current l(t) is higher than the set motor current l _set (t), the set rotational speed n _se t(t) can be decreased, preferably in each loop until the difference current Al is zero or very low.

The adjustment of the set rotational speed n _se t(t) to n(t) can be done by decreasing or increasing the rotational speed n(t) in predetermined increments, preferably in increments of 1 to 99 %, preferably 2 to 80 %, more preferably 3 to 50 %, most preferably 5 to 10 %. Generally, the electrical motor drives the conveyor screw with the rotational speed n(t). Preferably, the adjustment of the rotational speed n(t) is done by decreasing the rotational speed n(t) to an amount based on the result Al or difference current Al. For instance, if the result Al or difference current Al reveals that the motor current I (t) is 10 % lower than the set motor current l _se t(t), the rotational speed n(t) can be lowered by 10 %. However, the specific reduction is not limited to a specific value. Accordingly, the inventive method and device can adjust the rotational speed during the oxidization and prevents the destruction of the wet beaded carbon black. Additionally, fluctuations of the wet beaded carbon black feed can be compensated. It is also possible that the amount of wet beaded carbon black injected to the screw conveyor via the material inlet is controlled and/or measured. The adjustment is done contentiously during the oxidation of the wet beaded carbon black in the screw conveyor. A new user input may be necessary if another product is desired or another degree of oxidation is required. If another product is desired, another set of data points will be received from the data base or data storage means.

The adjustment of the rotational speed or the decrease of the rotational speed n _se t(t) can be done in predetermined time can be done intermittently, preferably in intervals of 1 second to 30 minutes, preferably of 5 seconds to 20 minutes, more preferably of 30 seconds to 10 minutes, most preferably in intervals of 1 minute to 5 minutes.

Generally, the rotational speed of the conveyor screw is adjusted in response to a detection of the actual motor current based on predetermined correlations for the specific carbon black product between motor current and rotational speed. Moreover, it is desired that further the ozone flow is adjusted in response to the adjusted rotational speed based on predetermined correlations for the specific carbon black product between rotational speed and ozone flow. For instance, in step (E) data is received from a first lookup table and/or second look up table comprising data representing a plurality of correlated values for n _se t(t) and I _se t(t) for at least one specific product. This means that for the adjusted set rotational speed n _se t(t) to n(t) in step (D) a correlated predetermined set motor current lset(t) is used. This correlated predetermined set motor current I _se t(t) can be used as a new set motor current l _se t(t) for the further comparison with the actual motor current I (t) that is required for the correlated the set rotational speed n _set (t).

“Carbon black” as referred to herein means a material composed substantially, e.g. to more than 80 wt.%, or more than 90 wt.% or more than 95 wt.%, based on its total weight of carbon that is produced by thermal oxidative pyrolysis or thermal cleavage of a carbon feedstock. Different industrial processes are known for the production of carbon blacks such as the furnace process, gas black process, acetylene black process, thermal black process or lamp black process. The production of carbon blacks is per se well known in the art and for example outlined in J.-B. Donnet et al., “Carbon Black:Science and Technology”, 2 ^nd edition, therefore being not described herein in more detail. Carbon black refers to carbon black in a powder form unless otherwise indicated. Wet carbon black refers to carbon black powder that comprises water and optionally binders. Beaded carbon black refers to either dry or wet beaded carbon black. Oxidized wet beaded carbon black refers to the carbon black produced according to the invention, where carbon black is first beaded and subsequently oxidized, unless otherwise indicated. The term beads and pellets are used synonymously. Oxidized carbon blacks generally have a notable oxygen content and have oxygen-containing functional groups, which can be exemplified, but are not limited to, quinone, carboxyl, phenol, lactol, lactone, anhydride and ketone groups. The screw conveyor according to the invention is a screw conveyor designed for the oxidation of carbon black beads. Diameter always refers to the inner diameter unless otherwise indicated.

The process for the production of oxidized wet beaded carbon black comprising the following steps: (a) providing carbon black, (b) wet beading the carbon black obtained in step (a) to obtain wet beaded carbon black, and (c) oxidizing the wet beaded carbon black obtained in step (b) in a reaction chamber to obtain oxidized wet beaded carbon black.

The obtained oxidized wet beaded carbon black has inter alia a high pellet crush strength and a low pellet attrition. At the same time, the volatiles can be controlled during the production without the risk to lose volatiles (i.e. decrease the degree of oxidation) during the drying process or beading process.

The oxidation in step (c) can be carried out in a screw conveyor comprising the reaction chamber mentioned in step (c) and at least one ozone inlet to supply ozone to the reaction chamber. The wet beaded carbon black obtained in step (a) can be supplied to the screw conveyor, particularly to the reaction chamber of the screw conveyor. The screw conveyor is further described below.

It is desired that the speed of the screw (screw of the screw conveyor) is 0.01 to 10 rpm, preferably 0.1 to 5 rpm, more preferably 0.2 to 3 rpm, even more preferably 0.3 to 2.5 rpm and most preferably 0.4 to 1 rpm. Generally, the screw rotational speed is not limited to a specific value. The rotational speed of the screw can have an influence of the properties of the produced oxidized wet beaded carbon black. For instance, a low rotational speed of the screw results in a higher volatiles content of the produced oxidized wet beaded carbon black since the wet beaded carbon black is longer present in the reaction chamber. Accordingly, a lower rotational speed of the screw may require a lower supply of ozone (or ozone flow, such as set ozone flow) if the desired volatiles content should be constant. It is desired that the rotational speed of the screw is set to a value where no or only a minimal destruction of the beads is observed. The optimal rotational speed may depend on the specific wet beaded carbon black material to be oxidized. Accordingly, it is recommended to measure the optimal rotational speed of the screw of the specific screw conveyor as well as the wet beaded carbon black. The measured values can be stored in a look up table as a set rotational speed n _set (t) and the set motor current l _se t(t) that is required for the set rotational speed n _set (t). As mentioned above, the set rotational speed n _S et(t) should be a rotational speed where no or only a minimal destruction of the beads is observed. Additionally, the required flow of the oxidation agent (such as ozone) can be determined and stored in the look up (for instance in a second look up table) for the desired oxidized wet beaded carbon black. During the oxidation step (c), at least 80 %, preferably 90 %, more preferably 95 %, of the pellets should not be crushed.

The carbon black in step (a) is generally provided as a powder. Any kind of carbon black powder material can be used according to the invention, for instance, acetylene black, channel black, furnace black, lamp black and thermal black. Furnace black is particularly preferred. A crusher can further pulverize the carbon black powder before the wet beading.

For the oxidation any oxidation agent can be used. According the inventive process is not limited to a specific oxidation agent. Ozone, H2O2 and/or NOx (such as HNO3) can be used for the oxidation. Ozone is particularly preferred since ozone can be easily obtained from an ozone generator using air. Moreover, a reduced oxidation/corrosion of the equipment is observed by using of ozone instead of NOx. This is particularly useful for a screw conveyor comprising moving parts such as the screw. However, if specific functional groups are desired on the surface of the carbon black, a different oxidation agent can be used such as NOx.

High concentrations of ozone can be used in the reaction chamber for the oxidation. The concentration or amount of ozone in the reaction chamber depends on the desired degree of oxidation (amount of volatiles). The concentration of ozone should be the highest at the ozone inlets and decreases towards the outlet for the produced oxidized wet beaded carbon black. It is desired that the ozone completely reacts with the wet beaded carbon black. Thus, it is desired that substantially no ozone or no ozone is present at the outlet of the reaction chamber, or the amount of ozone is below 0.1 wt.-% of the gas present at the outlet of the reaction chamber. The ozone concentration or amount can be adjusted by the ozone flow into the reaction chamber. It is desired that 0.1 to 95 wt.-%, preferably 0.5 to 20 wt.-%, more preferably 1 to15 wt.-%, even more preferably 1 .5 to 15 wt.-%, most preferably 2 to 10 wt.-%, of the gas present in the reaction chamber is ozone and/or of the gas subjected to the reaction chamber via the ozone inlet is ozone. Usually 0.5 to 5 wt.-% of the gas present in the reaction chamber is ozone. Particularly, ozone enriched air is used for the oxidation step comprising the amount or concentration mentioned herein. The concentration of ozone in the reaction chamber or the concentration of ozone that is subjected to the reaction chamber via the ozone inlets can be 1 to 300 g/m ³ , such as 1 to 200 g/m ³ , 1 to 50 g/m ³ , 1 to 60 g/m ³ , 15 to 60 g/m ³ , 15 to 60 g/m ³ , or 15 to 50 g/m ³ . The ozone concentration or the amount of ozone in the reaction chamber can consider a concentration gradient in the reaction chamber. Thus, the overall ozone concentration or amount of ozone in the entire reaction chamber is generally considered. Accordingly, it is possible that the ozone concentration at the ozone inlet is above the aforementioned maximum values or below the above minimum values at the outlet as long as the overall concentration is according the aforementioned ranges. The ozone flow can be 100 to 50000 g/h, such as 300 to 5000 g/h, 300 to 30000 g/h, 500 to 10000 g/h, 800 to 5000 g/h, 5000 to 30000 g/h, or 1000 to 30000 g/h. The ozone flow can be adjusted as desired for the degree of oxidization. Moreover, the ozone flow depends on the size of the screw conveyor. If a large screw conveyor is intended to use, a higher ozone flow should be utilized. The ozone that is subjected to the reaction chamber via said ozone inlets can be derived from air or liquid oxygen.

Generally, the ozone concentration is adjusted/controlled in such a way that the volatile content measured at 950°C is 1 to 25 wt.-%, such as 1.5 to 20 wt.-%, 1 to 10 wt.-%, 1.5 to 10 wt.-%, 1.5 to 20 wt.-%, 2 to 10 wt.-%, 2 to 15 wt.-%, 5 to 15 wt.-%, 2.5 to 10 wt.-%, 3 to 7 wt.-%, or 3.5 to 7 wt.-%. Accordingly, the ozone concentration in the reaction chamber should be adjusted/controlled so that the desired volatile content is achieved. For instance, the ozone flow into the reactor can be adjusted/controlled to adjust/control the ozone concentration. The ozone concentration should refer to the ozone concentration at which the wet beaded carbon black is treated. For example, the ozone concentration in the reactor or in the reactor chamber.

The volatile content at 950 °C can also adjusted/controlled by the air flow and the dwell time of the wet beaded carbon black. The dwell time of the wet beaded carbon black can be adjusted by the feed rate of the wet beaded carbon black and/or the screw rotational speed.

Generally, the air flow is adjusted/controlled in such a way that the volatile content measured at 950°C is 1 to 25 wt.-%, such as 1.5 to 20 wt.-%, 1 to 10 wt.-%, 1.5 to 10 wt.- %, 1.5 to 20 wt.-%, 2 to 10 wt.-%, 2 to 15 wt.-%, 5 to 15 wt.-%, 2.5 to 10 wt.-%, 3 to 7 wt.- %, or 3.5 to 7 wt.-%. For instance, the air flow into a reaction chamber.

Generally, the dwell time of the wet beaded carbon black is adjusted/controlled in such a way that the volatile content measured at 950°C is 1 to 25 wt.-%, such as 1.5 to 20 wt.-%, 1 to 10 wt.-%, 1.5 to 10 wt.-%, 1.5 to 20 wt.-%, 2 to 10 wt.-%, 2 to 15 wt.-%, 5 to 15 wt.- %, 2.5 to 10 wt.-%, 3 to 7 wt.-%, or 3.5 to 7 wt.-%. For instance, the dwell time of the wet beaded carbon black in a reaction chamber.

Generally, the screw rotational speed is adjusted/controlled in such a way that the volatile content measured at 950°C is 1 to 25 wt.-%, such as 1.5 to 20 wt.-%, 1 to 10 wt.-%, 1.5 to 10 wt.-%, 1.5 to 20 wt.-%, 2 to 10 wt.-%, 2 to 15 wt.-%, 5 to 15 wt.-%, 2.5 to 10 wt.-%, 3 to 7 wt.-%, or 3.5 to 7 wt.-%. For instance, the screw rotational speed of a screw conveyor.

It is possible that the ozone concentration, the air flow, the dwell time of the wet beaded carbon black and/or the screw rotational speed, is (are) adjusted/controlled in such a way that the volatile content measured at 950°C is 1 to 25 wt.-%, such as 1.5 to 20 wt.-%, 1 to 10 wt.-%, 1.5 to 10 wt.-%, 1.5 to 20 wt.-%, 2 to 10 wt.-%, 2 to 15 wt.-%, 5 to 15 wt.-%, 2.5 to 10 wt.-%, 3 to 7 wt.-%, or 3.5 to 7 wt.-%.

It is preferred that the volatile content measured at 950°C of the wet beaded carbon black is 2.2 to 25 wt.-%, preferably 2.2 to 20 wt.-%, more preferably 2.2 to 15 wt.-%, even more preferably 3 to 15 wt.-% and most preferably 3 to 10 wt.-%.

Furthermore, the screw conveyor can comprise means to generate ozone. The means to generate ozone should be in connection with the at least one ozone inlet.

Volatiles at 950°C can be measured using a thermogravimetric instrument of Fa. LECO Instrumente GmbH (TGA-701) according to the following protocol: Pans are dried at 650°C for 30 min. The carbon black materials are stored in a desiccator equipped with desiccant prior to measurements. Baked-out pans are loaded in the instrument, fared and filled with between 0.5 g to 10 g carbon black material. Then, the oven of the TGA instrument loaded with the sample-filled pans is gradually heated up to 105°C by automated software control and the samples are dried until a constant mass is achieved. Subsequently, the pans are closed by lids, the oven is purged with nitrogen (99.9 vol% grade) and heated up to 950°C. The oven temperature is kept at 950°C for 7 min. The content of volatiles at 950°C is calculated using the following equation:

_T . , . .. m( rior to heating~)-m(after 7 minutes@950°C') .

Volatiles = — - m(p —ri —or t —o h -eating) - ■ 100%. The volatile content can also be measured according to DIN 53552:1977-09.

The weight ratio of the wet beaded carbon black (such as dry weight of the carbon black) to ozone for the oxidation in step (c) should be over 1, preferably 3 or more, more preferably 4 or more. Particularly, the weight ratio of the wet beaded carbon black (such as dry weight of the carbon black) to ozone for the oxidation in step (c) should be 1 :1 to 15:1 , preferably 1.1:1 to 13:1 , more preferably 1.5:1 to 10:1 , even more preferably 2:1 to 8:1, most preferably 3:1 to 6:1.

The temperature for the oxidation in step (c) is 10 to 60 °C, preferably 20 to 50 °C, more preferably 30 to 45 °C. Particularly, the temperature in the reaction chamber is 10 to 60 °C, preferably 20 to 50 °C, more preferably 30 to 45 °C. The temperature in the screw conveyor can be controlled by a liquid or fluid, such as water, attached to the screw conveyor or the barrel of the screw conveyor. Accordingly, the screw conveyor can comprise temperature control unit for cooling or heating. It is desired that the temperature in the reaction chamber or for the oxidation is controlled so that no loss of volatiles during the oxidation occurs. Generally, the oxidation of wet beaded carbon black is an exothermic reaction so that heat should be dissipated. This can be particularly relevant for a process in which a highly oxidated carbon black or a highly oxidated wet beaded carbon black is to be obtained. However, in a process in which a low oxidized carbon black is to be obtained, it can be beneficial if additional heat is transferred to the reaction chamber for the oxidation step.

The wet beading (b) comprises generally the following steps: (b1) treating the carbon black with water to obtain wet carbon black, (b2) beading the wet carbon black to obtain beaded carbon black comprising water, and (b3) drying the beaded carbon black to obtain wet beaded carbon black (201).

The water content of the wet beaded carbon black should be less than 10 wt.-%, more preferably less than 5 wt.-%, even more preferably 0.001 to 4 wt.-%, and most preferably 0.01 to 1 wt.-%. This means that after the aforementioned drying step, most of the water content is removed so that the oxidation is performed using already dried wet beaded carbon black. Thus, it is preferred that the oxidation is performed using dried wet beaded carbon black.

Wet beading is usually carried out in a “wet beading box” equipped with a multiplicity of agitator pins secured to a shaft extending longitudinally through the body and rotating a speed up to about 240 rpm depending on the type of carbon black powder to be treaded. The action of the pins causes the moist carbon black to form into beads or pellets which are subsequently dried in a dryer. However, every type of wet beading apparatus may be used for the wet beading.

The weight of water used for the beading is usually equal to the weight of the carbon black powder to be beaded. The range can be 5 wt.-% to 1000 wt.-%, based on the total weight of the carbon black. Preferably 20 to 200 wt.-%, more preferably 50 to 150 wt.-%, based on the total weight of the carbon black.

The water for the wet beading usually comprises a binder, preferably the binder comprises molasse, and/or lignosulfonates. Such binders are uniformly dispersed through the beads. A binder can increase the crushing strength and packing point of carbon black beads. The binder can be present in an amount of 0.01 to 1.00 wt.-%, preferably 0.05 to 0.9 wt.-%, more preferably 0.1 to 0.80 wt.-%, based on the total weight of the carbon black, particularly the carbon black for the wet beading. The weight ratio of the binder to the carbon black for the wet beading is from 1/10000 to 1/100, preferably 1 to 1/2000 to 1/110, more preferably 1/1000 to 1/125.

The air flow to the reaction chamber should be 5 to 1000 Nm ³ /h, such as 5 to 200 Nm ³ /h, 10 to 150 Nm ³ /h, 15 to 100 Nm ³ /h, 20 to 50 Nm ³ /h, 10 to 600 Nm ³ /h, 15 to 300 Nm ³ /h, 10 to 600 Nm ³ /h, 100 to 800 Nm ³ /h, or 200 to 600 Nm ³ /h. The air flow generally depends on the set ozone flow. Moreover, the air flow depends on the size of the reaction chamber. A larger reaction chamber usually requires a higher air flow. The wet beaded carbon black feed to the reaction chamber can be 0.01 to 1000 g/s, such as 1 to 500 g/s, 100 to 600 g/s, 0.05 to 50 g/s, 0.08 to 20 g/s, or 0.08 to 5 g/s.

The oxidized wet beaded carbon black can have an average pellet crush strength of pellets with a diameter of 1 .0 to 1 ,4 mm of from 4 to 80 cN, preferably 5 to 40 cN, and more preferably 10 to 30 cN. The oxidized wet beaded carbon black can have an average pellet crush strength of pellets with a diameter of 1 ,4 to 1 ,7 mm of from 3 to 80 cN, preferably 4 to 40 cN, and more preferably 5 to 30.

The pellet crush strength, such as the average pellet crush strength, can be measured according to ASTM D5230-19.

It is particularly desired that the average pellet crush strength of pellets with a diameter is from 0.71 to 1 ,0 mm is from 4 to 80 cN, preferably 5 to 40 cN, and more preferably 10 to 30 cN, and the average pellet crush strength of pellets with a diameter of 1.0 to 1 ,4 mm is from 4 to 80 cN, preferably 5 to 40 cN, and more preferably 10 to 30 cN, and the average pellet crush strength of pellets with a diameter of 1 ,4 to 1 ,7 mm is from 3 to 80 cN, preferably 4 to 40 cN, and more preferably 5 to 30.

It is particularly desired that the average 5 hardest pellets with a diameter of 0.71 - 1 .0 mm has a pellet crush strength of 10 to 110 cN, preferably 12 to 80 cN, more preferably 15 to 60 cN, and most preferably 17 to 50 cN. The hardest pellet with a diameter of 0.71 - 1.0 mm should have a pellet crush strength of 10 to 110 cN, preferably 12 to 80 cN, more preferably 15 to 60 cN, and most preferably 17 to 50 cN. The average 5 hardest pellets with a diameter of 1.0 - 1.4 mm should have a pellet crush strength of 10 to 110 cN, preferably 12 to 80 cN, more preferably 15 to 60 cN, and most preferably 17 to 50 cN. The hardest pellet with a diameter of 1.0 - 1.4 mm should have a pellet crush strength of 10 to 110 cN, preferably 12 to 80 cN, more preferably 15 to 60 cN, and most preferably 17 to 50 cN.

The fines content of the oxidized wet beaded carbon black may be 0.1 to 50 %, preferably 1 to 10 %, and more preferably 1 to 5 %. The fines contend can be measured according to ASTM D1508-02. A low fines content is an indicator for avoiding the destruction of the bead/pellets during the oxidation step.

The pellet attrition should be below 6.5 %, preferably 0.1 to 5 %, more preferably 0.2 to 3 %, and most preferably 0.5 to 2 %. The pellet attrition can be measured according to ASTM D1508-02. A low pellet attrition is desired so that the transportation and mixing of the beads is improved. Additionally, a low pellet attrition prevents the destruction of the pellets during the transportation or handling.

The screw conveyor for the production of oxidized wet beaded carbon black and that is used for the inventive method and control device usually comprises a reaction chamber and at least one ozone inlet to supply ozone to the reaction chamber.

The screw conveyor is usually tube containing a “spiral blade” coiled around a shaft. The screw conveyor is further modified to allow the oxidation of wet beaded carbon black. Accordingly, the screw conveyor comprises and at least one ozone inlet to supply ozone to the chamber of the screw conveyor. The chamber of the screw conveyor is thus a reaction chamber, where the oxidation agent, such as ozone, can oxidize the wet beaded carbon black.

Accordingly, the screw conveyor can comprise ozone in the reaction chamber, preferably 0.1 to 80 wt.-%, more preferably 0.5 to 20 wt.-%, most preferably 1 to 10 wt.-%, of the gas present in the reaction chamber is ozone. The ozone inlet further comprises means to control and/or determine the supply of ozone to the reaction chamber to adjust the concentration of ozone in the reaction chamber. Additionally, the reaction chamber can comprise wet beaded carbon black and/or oxidized wet beaded carbon black. In sum, the reaction chamber should comprise wet beaded carbon black, oxidized wet beaded carbon black as well as ozone, preferably in the aforementioned amount/concentration. The ozone inlets are preferably located at the bottom of the vessel of the screw conveyor.

The screw of the screw conveyor (conveyor screw) can be a conventional helical screw blade. The screw of the screw conveyor has a thread (or helical screw blade), said thread can have 2 to 100 windings, preferably 5 to 50 windings. The thread may have a pitch between 0.1 to 5, preferably a continuous or a constant increasing/decreasing pitch.

The screw conveyor can comprise at least one temperature control unit for cooling or heating the reaction chamber. During the oxidation of the wet beaded carbon black, the temperature may increase. To avoid the risk of losing volatiles (decrease the degree of oxidization) the temperature of the reaction chamber can be controlled by the temperature control unit. However, in a process in which a low oxidized carbon black is to be obtained, it can be beneficial if additional heat is transferred to the reaction chamber for the oxidation step. It is preferred that temperature control units are attached on the outer surface of the reaction chamber or barrel.

The screw of the screw conveyor (conveyor screw) can be a conventional helical screw blade. The screw of the screw conveyor has a thread (or helical screw blade), said thread can have 2 to 100 windings, preferably 5 to 50 windings. The thread may have a continuous or a constant increasing/decreasing pitch. Generally, the screw comprises a shaft and a helical conveyor blade thereon. However, it is also possible that the screw is a shaftless helical conveyor blade. Thus, the blade can be directly driven by a motor. The screw conveyor can comprise a helical conveyor blade. The screw generally has at least one screw flight extending radially and helically from and along the shaft.

The screw can be configurated at least partly as a flight, preferably at least partly as a single flight, more preferably at least partly as a double flight, wherein the screw comprises at least one second helical conveyor blade (second flight) and if the screw is configurated at least partly as double flight ribbon, further comprises at least one first helical conveyor blade (first flight).

The screw conveyor or the helical conveyor blade can comprise at least one first helical conveyor blade and/or at least one second helical conveyor blade. The first and second helical conveyor blade can be configured in sequence and thus form a single thread. It is also desired that the first and second helical conveyor blade form a twin thread (or double-start thread, or double flight). For instance, the first and second helical conveyor blade can form a high-low thread, wherein the first helical conveyor blade is the low thread and the second helical conveyor blade is the high thread. Individual turns of said first conveyor blade can extend at least over a partial length of the shaft between subsequent individual turns of said second conveyor blade. If a twin thread is present, both threads do not have to start simultaneously.

The second helical conveyor blade can extend at least over a partial length of said shaft with a radial distance to said shaft thereby forming a circumferential clearance between said shaft and said second helical conveyor blade. A helical conveyor blade having the aforementioned clearance is generally called a flight ribbon. Thus, the screw can be configurated at least partly as a flight ribbon, preferably at least partly as a single flight ribbon, more preferably at least partly as a double flight ribbon.

The screw can be configurated at least partly as a flight ribbon, preferably at least partly as a single flight ribbon, more preferably at least partly as a double flight ribbon, wherein the screw comprises at least one second helical conveyor blade (second flight) and if the screw is configurated at least partly as double flight ribbon, further comprises at least one first helical conveyor blade (first flight).

The screw can be configurated as a flight ribbon, preferably a single flight ribbon, more preferably a double flight, wherein one flight comprises at least partly a flight ribbon, wherein the screw comprises at least one second helical conveyor blade (second flight) and if the screw is configurated double ribbon, further comprises at least one first helical conveyor blade (first flight), wherein the at least one second helical conveyor blade (second flight) is configurated at least partly as the flight ribbon.

It is particularly preferred that the screw can be configurated as a double flight, wherein the screw comprises at least one second helical conveyor blade (second flight) and at least one first helical conveyor blade (first flight), wherein the at least one second helical conveyor blade (second flight) is configurated at least partly as the flight ribbon (preferably as the second segment). It is preferred that the flight ribbon is present adjacent to the ozone inlets.

It is also preferred that the screw can be configurated as a flight, wherein the screw comprises at least one second helical conveyor blade (second flight), wherein the at least one second helical conveyor blade (second flight) is configurated at least partly as a flight ribbon (preferably as the second segment), preferably the at least one second helical conveyor blade (second flight) has three segments, wherein the first segment is a flight directly and continuously attached to the shaft, the second segment is the flight ribbon, and the third segment is a flight directly and continuously attached to the shaft. It is preferred that the flight ribbon is present adjacent to the ozone inlets. The second segment should be located between the first and second segment.

It is particularly preferred that the screw can be configurated as a double flight, wherein the screw comprises at least one second helical conveyor blade (second flight) and at least one first helical conveyor blade (first flight), wherein the at least one second helical conveyor blade (second flight) is configurated at least partly as a flight ribbon (preferably as the second segment), preferably the at least one second helical conveyor blade (second flight) has three segments, wherein the first segment is a flight directly and continuously attached to the shaft, the second segment is the flight ribbon, and the third segment is a flight directly and continuously attached to the shaft, preferably wherein the at least one first helical conveyor blade (first flight) is a flight directly and continuously attached to the shaft. It is preferred that the flight ribbon is present adjacent to the ozone inlets. The second segment should be located between the first and second segment. A clearance between the shaft and the helical conveyor blade in a conventional screw conveyor would have the disadvantage that the ability of conveying material would be decreased. In other words, the main purpose of a conventional screw conveyor is the transportation of material, e.g. for overcoming a slope. However, the screw conveyor according to the invention is not only used for conveying the material but also to oxidize the feed material. Such a blade with clearance between the shaft and the helical conveyor blade can be beneficially used for the oxidation. The oxidation agent can be better distributed through the reaction chamber and the wet beaded carbon black can be uniformly mixed. A uniform mixing during the oxidation allows an improved and uniform oxidation of the wet beaded carbon black.

It is particularly preferred that the second helical conveyor blade with a radial distance to said shaft thereby forming a circumferential clearance between said shaft and said second helical conveyor blade extend at least over a partial length of said shaft where the ozone inlets are located.

It is possible that the second helical conveyor blade comprises a first segment comprising a helical conveyor blade directly attached to the shaft, and a second segment comprising a helical conveyor blade extending at least over a partial length of said shaft, preferably where the ozone inlets are located, with a radial distance to said shaft thereby forming a circumferential clearance between said shaft and said second helical conveyor blade. Moreover, it is desired that the second helical conveyor blade comprises a first segment comprising a helical conveyor blade directly attached to the shaft, a second segment comprising a helical conveyor blade extending at least over a partial length of said shaft, preferably where the ozone inlets are located, with a radial distance to said shaft thereby forming a circumferential clearance between said shaft and said second helical conveyor blade, and a third segment comprising a helical conveyor blade directly attached to the shaft. It is preferred that the second helical conveyor blade comprises the segments in the following order, first segment, second segment and third segment. The first helical conveyor blade can form a second thread of the screw, wherein the diameter (or outer diameter) of the first helical conveyor blade is smaller than the diameter (outer diameter) of the second helical conveyor blade.

Said second conveyor blade can be attached at least over a partial length of said shaft to said shaft via spacer bars radially extending from said shaft, preferably via three or more bars. Particularly, the second conveyor blade with a radial distance to said shaft thereby forming a circumferential clearance between said shaft and said second helical conveyor blade can be attached at least over a partial length of said shaft to said shaft via spacer bars radially extending from said shaft, preferably via three or more bars. This means that the segment of the second conveyor blade having said clearance should be attached at least over a partial length of said shaft to said shaft via spacer bars radially extending from said shaft, preferably via three or more bars.

The radial distance to a shaft thereby forming a circumferential clearance between said shaft and the second helical conveyor blade should be 10 to 200 mm, preferably 20 to 150 mm, more preferably 30 to 100 mm, even more preferably 40 to 80 mm, and most preferably 45 to 70 mm.

A radial distance to a shaft thereby forming a circumferential clearance between said shaft and a helical conveyor blade clearance in a conventional screw conveyor would have the disadvantage that the ability of conveying material would be decreased. In other words, the main purpose of a conventional screw conveyor is the transportation of material, for instance overcoming a slope. However, the screw conveyor according to the invention is not only used for conveying the material but also to oxidize the feed material. Such a blade with said clearance can be beneficially used for the oxidation. The oxidation agent can be better distributed through the reaction chamber and the wet beaded carbon black can be uniformly mixed. A uniform mixing during the oxidation allows an improved and uniform oxidation of the wet beaded carbon black.

It is preferred that the first conveyor blade has a first outer diameter and said second conveyor blade has a second outer diameter and wherein preferably the first and second outer diameters differ from each other. Particularly said first outer diameter is smaller than said second outer diameter. A spacing (lead) of said second conveyor blade at least over a partial length of the shaft should be smaller than a spacing (lead) of said first conveyor blade.

The screw conveyor can comprise a drive and a driven screw, said extending within a barrel forming said reaction chamber, the screw comprising a shaft and at least one first helical conveyor blade. The drive should be configured to drive the driven screw.

Generally, the screw of the screw conveyor comprises a shaft and at least one first helical conveyor blade. Alternatively, or additional, the screw of the screw conveyor comprises a shaft and at least one second helical conveyor blade.

The screw of the screw conveyor and/or the reaction chamber may have a length of 0.1 to 100 m, such as 1 to 20 m, 5 to 15, 2 to 4 m 10 to 90 m, or 20 to 80 m. The volume of the reaction chamber can be 1 to 10000 L, such as 10 to 1000 L, 20 to 100 L, 2 to 50 L, 100 to 9000 L, or 500 to 5000 L. The volume of the reaction chamber can be chosen as desired for the process. A higher input of the wet beaded carbon black feed requires a lager reaction chamber. The screw conveyor can comprise a drive and a driven screw, said extending within a barrel forming said reaction chamber. The screw conveyor usually comprises an inlet for the wet beaded carbon black to the reaction chamber. Similarly, the screw conveyor usually comprises an outlet for the produced oxidized wet beaded carbon black, wherein the outlet is positioned at the opposite side of the reaction chamber with respect to the inlet. The inlet should be arranged on the top of the screw conveyor and the outlet should be arranged on the bottom of the screw conveyor.

The diameter of the screw can be 50 to 300 mm, preferably 60 to 250 mm, more preferably 70 to 200 mm, even more preferably 80 to 150 mm, and most preferably 90 to 130 mm. The diameter of the at least one first and/or at least one second helical conveyor blade can be 50 to 1000 mm, preferably 100 to 800 mm, more preferably 150 to 700 mm, even more preferably 200 to 600 mm, and most preferably 250 to 400 mm. The diameter of at least one first helical conveyor blade can be 25 to 500 mm, preferably 50 to 400 mm, more preferably 75 to 350 mm, even more preferably 100 to 300 mm, and most preferably 150 to 300 mm. The inner diameter of the barrel can be 50 to 3000 mm, such as 100 to 800 mm, 150 to 700 mm, 200 to 600 mm, 250 to 400 mm, 100 to 2000 mm, or 150 to 1000 mm, preferably the inner diameter of the barrel is higher than the diameter of the at least one first and/or at least one second helical conveyor blade. The inner diameter of the at least one second helical conveyor blade can be 40 to 900 mm, preferably 80 to 750 mm, more preferably 130 to 650 mm, even more preferably 180 to 550 mm, and most preferably 230 to 350 mm. The outer diameter of the at least one second helical conveyor blade should be 50 to 1000 mm, preferably 100 to 800 mm, more preferably 150 to 700 mm, even more preferably 200 to 600 mm, and most preferably 250 to 400 mm.

Generally, the respective size of the components of the screw conveyor should be chosen with respect to the size of the screw conveyor. A large screw conveyor usually comprises larger components and larger dimensions of the components. Thus, the size and dimensions of the specific components or parts of the screw conveyor are usually matched.

The gap between the helical conveyor blade and the inner surface of the reactor chamber can be 0 mm (or more than 0 mm) to 200 mm, preferably 1 mm to 100 mm, more preferably 2 mm to 80 mm, even more preferably 5 to 50 mm, and most preferably 10 to 40 mm.

The at least one first and/or at least one second helical conveyor blade can comprise at least one turner attached thereto on a surface facing opposite the conveying direction. The turner should be able to lift a part of the wet beaded carbon black material so that the mixing of the material is improved. This allows a uniform mixing of the material so that the oxidization is enhanced.

The at least one first and/or at least one second helical conveyor blade can comprise at least one first turner and at least one second turner. The at least one first and the at least one second turner can are alternating attached on at least one first and/or at least one second helical conveyor blade. The angle of the at least one first turner should be higher than the angle of the at least one second turner, wherein the turners extend in an angle relative to a tangent to the circumference of said second conveyor blade (shown in FIG. 8). The angle of the at least one first turner can be 30 to 100°, preferably 35 to 90°, more preferably 40 to 80°, even more preferably 50 to 70°, and most preferably 55 to 65°. The angle of the at least one second turner is 10 to 60°, preferably 15 to 55°, more preferably 20 to 50°, even more preferably 25 to 45°, and most preferably 35 to 45°, wherein the turners extend in an angle relative to a tangent to the circumference of said second conveyor blade.

The invention will now be described with reference to the accompanying figures which do not limit the scope and ambit of the invention. The description provided is purely by way of example and illustration. However, specific features exemplified in the figures can be used to further restrict the scope of the invention and claims.

FIG. 1 relates to the process for the production of oxidized wet beaded carbon black (202). First, the carbon black is provided (101), preferably as a powder. As mentioned above, the carbon black powder is preferably a furnace black. However, any kind of carbon black materials can be used according to the invention, including mixtures of carbon black materials. In the second step, the carbon black is wet beaded. Wet beading may include the subjection of the carbon black powder with water and optionally a binder. Subsequently, the mixture is beaded and dried to provide the wet beaded carbon black (102). The beads are then subjected to an oxidizing step (103) to obtain oxidized wet beaded carbon black (202). The oxidizing step is preferably carried out in a screw conveyor (200, 300) according to the invention. However, the particular means for the oxidation is not limited to the screw conveyor. Preferably ozone is used as oxidizing agent.

Referring to FIG. 2, an inner section of the screw conveyor (200) according to the invention is shown. The screw conveyor (200) comprises at least one first helical conveyor blade (214, 502) attached to a shaft (213) that is connected to an electric motor (215) that drives said screw. Alternatively, the helical conveyor blade shown in FIG. 2 is at least one second helical conveyor blade (501). The screw conveyor (200) further comprises a barrel (211) that defines the reaction chamber (218) or provides a barrier defining the reaction chamber (218). The screw conveyor (200) comprises an inlet (210) for the wet beaded carbon black (201) and an outlet (212) for the produced oxidized wet beaded carbon black (202). On the bottom of the screw conveyor (200) several ozone inlets (216) are attached to supply ozone (217) into the reaction chamber (218). The screw comprises at least one first helical conveyor blade (214) to transport feed material from the inlet in the direction to the outlet. If a second helical conveyor blade (501) that extends at least over a partial length of said shaft with a radial distance to said shaft (213) thereby forming a circumferential clearance (503) between said shaft (213) and said second helical conveyor blade (501) is present, it will be desired that said clearance (i.e. with a radial distance to said shaft (213) thereby forming a circumferential clearance (503) between said shaft (213) and said second helical conveyor blade (501)) is located over a partial length of said shaft where the ozone inlets are located. The longitudinal direction (220) of the screw is indicated in FIG. 1.

Referring to FIG. 3, an outer section of the screw conveyor (300) according to the invention is shown. In this view, three temperature control units (301) are visible that are attached on the outer wall of the screw conveyor (300), i.e. on the outer wall of the barrel (211). The temperature control units extend to the opposite side of the screw conveyor (300) that is not shown in this figure. Each temperature control unit (301) comprises an inlet (302) for a fluid, such as water, and an outlet (303) for the fluid, such as water. The inlet (301) and the outlet (302) can be interchanged. Furthermore, the barriers (304) are shown as dashed lines that indicate a flow passage of the fluid. Thus, each barrier has at least one opening for defining the flow passage so that the fluid can be transported from the inlet (302) to the outlet (303). Some openings are not shown in the figure since they are present on the opposite side of the temperature control units (301).

FIG. 4 shows a section of a screw (400) comprising at least one first helical conveyor blade (214, 502) attached to a shaft (213). In this view, a screw configured as single flight (at least partly) is shown. The at least one first helical conveyor blade (214, 502) are attached directly to the shaft (213) without a radial distance to said shaft (213) and thus, without forming a circumferential clearance (503) between said shaft (213) and said first helical conveyor blade (214, 502). Alternatively, the helical conveyor blade shown in FIG. 2 is at least one second helical conveyor blade (501). The spacing of said first conveyor blade (214, 502) is indicated in the figure. The spacing of the first conveyor blade is the lead. The spacing of a specific conveyor blade or the lead of a specific conveyor blade is the distance along the screw's axis that is covered by one complete rotation of said conveyor blade. If the screw comprises only one conveyor blade, the lead and the pitch are the same (single start thread). In FIG. 4 the flight directly and continuously attached to the shaft (without a clearance, not a flight ribbon).

FIG. 5 reveals a section of a screw (500) comprising a shaft (213) and at least one first helical conveyor blade (502) and at least one second helical conveyor blade (501) extends at least over a partial length of said shaft with a radial distance to said shaft (213) thereby forming a circumferential clearance (503) between said shaft (213) and said second helical conveyor blade (501). Accordingly, the screw is designed as a twin thread (or double-start thread), wherein the first helical conveyor (502) is the low thread and the second helical conveyor is the high thread (501). This means that individual turns of said first conveyor blade (214, 502) at least over a partial length of the shaft extend between subsequent individual turns of said second conveyor blade (501). It is desired that this configuration is present where the ozone inlets are located. Thus, the described screw (500) is preferably arranged in the middle section of the screw, preferably where the inlets for the ozone (216) are located. Accordingly, the ozone (217) that is subjected via the inlets (216) can be easily distributed inside the reaction chamber (218) and an improved and uniform oxidation is achieved. It should be noted that the at least one second helical conveyor blade (501) extends at least over a partial length of said shaft with a radial distance to said shaft (213) thereby forming a circumferential clearance (503) between said shaft (213) and said second helical conveyor blade (501) can be attached to the screw via bars (spacer bars) that are not shown in the figure. The bars (spacer bars) can support the structure. However, any possible means to attach the at least one second helical conveyor blade (501) to the screw can be used. The spacing (504) or lead (504) of the at least one first helical conveyor blade (502) is indicated in FIG. 5. The spacing (505) or lead (505) of the at least one second helical conveyor blade (501) is indicated in FIG. 5. In this view, a screw configured as double flight (at least partly) that has a ribbon flight is shown. The ribbon flight is the at least one second the second helical conveyor (501).

Referring to FIG. 6, a screw (600) is shown that has different segments of helical conveyor blades (601, 602, 603). In this configuration the screw comprises a shaft (213) and at least one first helical conveyor blade (502) and at least one second helical conveyor blade (501) extends at least over a partial length of said shaft with a radial distance to said shaft (213) thereby forming a circumferential clearance (503) between said shaft (213) and said second helical conveyor blade (501). The screw is designed as a twin thread (or double-start thread), wherein the first helical conveyor (502) is the low thread and the second helical conveyor is the high thread (501). Accordingly, the second helical conveyor blade (501) extends only partly over a length of said shaft with a radial distance to said shaft (213) thereby forming a circumferential clearance (503) between said shaft (213) and said second helical conveyor blade (501). This part is indicated as segment (602). Thus, the second helical conveyor blade (501) in segments (601) and (603) are directly attaches to the shaft (213). A smooth transition of a segment of the second helical conveyor blade (501) directly connected to the shaft (213) to a segment that extends at least over a partial length of said shaft with a radial distance to said shaft (213) thereby forming a circumferential clearance (503) between said shaft (213) and said second helical conveyor blade (501) is generally formed.

FIG. 7 and FIG 8 reveal a cross section of a screw comprising a shaft (213), at least one first helical conveyor blade (502), at least one second helical conveyor blade (501) extends at least over a partial length of said shaft with a radial distance to said shaft (213) thereby forming a circumferential clearance (503) between said shaft (213) and said second helical conveyor blade (501) as well as turners (702, 703). The at least one second helical conveyor blade (501) extends at least over a partial length of said shaft with a radial distance to said shaft (213) thereby forming a circumferential clearance (503) between said shaft (213) and said second helical conveyor blade (501)are attached to the screw (213) via spacer bars (701). The number 502 indicates the at least one first helical conveyor blade (502) has a lower diameter. The respective diameters of the respective helical conveyor blades as well as said clearance (503) is indicated in FIG. 8. The inner diameter (804) of the at least one second helical conveyor blade (501) extends at least over a partial length of said shaft with a radial distance to said shaft (213) thereby forming a circumferential clearance (503) between said shaft (213) and said second helical conveyor blade (501) defines at the same time said clearance (503) between said second helical conveyor blade (501) and the shaft (213). It should be noted that the diameters mentioned herein refer to a diameter of the helical conveyor blades considering the cross-section as shown in e.g. FIG. 7. Furthermore, the outer diameter (803) of at least one second helical conveyor blade (501) extends at least over a partial length of said shaft with a radial distance to said shaft (213) thereby forming a circumferential clearance (503) between said shaft (213) and said second helical conveyor blade (501), the distance (807) between the at least one first helical conveyor blade (502) and the at least one second helical conveyor blade (501), the diameter (806) of the at least one first helical conveyor blade (502), as well as the distance (805) between the inner diameter and the outer diameter of the at least one second helical conveyor blade (501) is indicated in FIG. 8. As can be seen from FIG. 8, the turners (702, 703) are attached to the at least one second helical conveyor blade (501 in a specific angle (801 , 802). The respective angle is the angle at which the turners extend in an angle relative to a tangent to the circumference of said second conveyor blade, particularly as indicated in FIG. 8. As mentioned above, the turners (702, 703) can also be attached to the at least one first helical conveyor blade (214, 502).

FIG. 9 shows oxidized wet beaded carbon black prepared according to the invention. As can be seen from the image, it is possible to oxidize wet beaded carbon black without destroying the beads.

FIG. 10 is directed to the inventive control device and method (900). A user can select (901) the desired oxidized wet beaded carbon black to be produced. The three look up tables represent first look up tables for different products indicated as product 1 , product 2 and product 3. A set motor current I _se t(t) and a set rotational speed n _se t(t) is received by the inventive method or control device (902). The current sensor (911) detects the motor current l(t) that is used by the electrical motor (215) to apply and/or maintain the set rotational speed n _se t(t). The set motor current l _se t(t) and the motor current l(t) is then compared using a primary controller (910) and the difference between said currents (i.e. the result Al or difference current Al) is used to adjust the set rotational speed n _se t(t) to n(t). The new or adjusted rotational speed n(t) is then communicated to the electrical motor (215) of the screw conveyor (200). A new or corrected second set motor current is received from a first look up table (920) for the desired product to be produced based on the adjusted rotational speed n(t). Additionally, a set ozone flow q _OZ one,set(n,t) is generated from the rotational speed n(t) (i.e. the adjusted rotational speed n(t)), preferably by receiving the set ozone flow q _OZ one,set(n,t) from a second look up table (921) based on the rotational speed n(t) (i.e. the adjusted rotational speed n(t)).

EXAMPLES

Example 1 : Production of oxidized wet beaded carbon black according to the invention

The carbon black powder used for the production of the oxidized wet beaded carbon black in Examples A to I (Ex. A to I) is N234.

In Examples A to H, the carbon black powder is wet beaded by subjecting water to the carbon black powder, beading the wet carbon black powder and subsequently drying the resulting wet beaded carbon black.

The wet beaded carbon black is then subjected to a screw conveyer for the oxidization. Ozone is supplied to the reaction chamber of the screw conveyer to oxidize the wet beaded carbon black. The settings and the results of the production of the oxidized wet beaded carbon black are indicated in table 1. The ozone flow indicates the target ozone flow in the reaction chamber. The reaction chamber of the screw conveyor is cooled with water. In Comparative Example I (Comp. Ex. I) the carbon black powder is first oxidized and then dry beaded to avoid reducing the volatiles of the carbon black beads.

Table 1 : Production of oxidized wet beaded carbon black.

¹ The pellet crush strength is measured according to ASTM D5230-19 ² Fines contend measured according to ASTM D1508-02; ³ Volatiles are measured at 950 °C for 7 min as described below; ⁴ BET surface area is measured according to ASTM D6556-17; ⁵ STSA surface area is measured according to ASTM D6556-17; ⁶ lodine adsorption number is measured according to ASTM D1510-17; ⁷ Pellet attrition is measured according to ASTM D1508-02; ⁸ pH-value is measured according to ASTM D1512-15b, Test Method B - Sonic Slurry; ⁹ Oil absorption number is measured according to ASTM D2414-18; ¹⁰ weight ratio of carbon black to ozone.

Volatiles at 950°C were measured using a thermogravimetric instrument of Fa. LEGO Instrumente GmbH (TGA-701) according to the following protocol: Pans were dried at 650°C for 30 min. The carbon black materials were stored in a desiccator equipped with desiccant prior to measurements. Baked-out pans were loaded in the instrument, fared and filled with between 0.5 g to 10 g carbon black material. Then, the oven of the TGA instrument loaded with the sample-filled pans was gradually heated up to 105°C by automated software control and the samples were dried until a constant mass was achieved. Subsequently, the pans were closed by lids, the oven was purged with nitrogen

(99.9 vol% grade) and heated up to 950°C. The oven temperature was kept at 950°C for

7 min. The content of volatiles at 950°C was calculated using the following equation:

The produced oxidized wet beaded carbon black has a remarkable pellet crush strength compared to the beads obtained in Comparative Example I. This indicated that the beads are not destroyed during the oxidation treatment in a screw conveyor. The pellet crush strength is particularly high by using a low screw rotational speed such as 0.5 rpm instead of 3 rpm. On the other hand, the fines content is lower by using a higher screw rotational speed. The BET, STSA and CTAB surface area of the produced oxidized wet beaded carbon black is higher compared to palletized carbon black according to the Comp. Ex. I. Furthermore, the pellet attrition and the OAN is improved compared to palletized carbon black according to the Comp. Ex. I. FIG. 11 reveals the oxidized wet beaded carbon black produced according to Example A.

The data provided in Examples A to H can be used for a look up table to obtain the set rotational speed n _set (t) and the set motor current l _se t(t) as well as the set ozone flow q _O zone,set(n,t) required for the set rotational speed n _se t(t) for the production of the desired oxidized wet beaded carbon black, wherein the carbon black beads are not crushed.