EP0134538A2 - Process for mixing soot with a high-viscosity fluid - Google Patents

Abstract

The soot mass for mixing with a high-viscosity fluid to give a suspension or dispersion without splashing and foaming contains a liquid (water, gasoline, alcohols, esters or a solvent mixture) whose boiling point is below the temperature of the hot high-viscosity fluid which can be a mineral oil, a distillation residue oil, bitumen, asphalt or another high-viscosity hydrocarbon. The soot is uniformly and finely dispersed in the hot high-viscosity fluid and is in the form which is also suitable for the production of synthesis gas by partial combustion. The fluid-containing soot mass is introduced with continuous intensive stirring into the hot high-viscosity fluid and dispersed, preferably in a high-powered disperser generating a shear force. The hot high-viscosity fluid is under a pressure which is lower than the vapour pressure of the fluid contained in the soot mass at the temperature of the hot fluid. The process is reliable and safe in operation and is economical on a large industrial scale, without expensive pretreatment of the soot mass.

Description

The invention relates to a process for mixing a carbon black mass with a highly viscous liquid to form a suspension or dispersion in which the carbon black is uniformly and finely distributed, the carbon black mass containing a liquid whose boiling temperature is below the temperature of the hot, highly viscous liquid.

The invention aims to make the process reliable and economical on an industrial scale.

As is known, larger amounts of soot are produced, for example, in the partial oxidation of gaseous and liquid hydrocarbons, generally 1 to 2% of the starting material (Ullmanns Enzyklopadie der Technische Chemie, 4th edition, vol. 14, page 394 ff.). This also applies to hydrocarbon pyrolysis and the arc process for the production of acetylene (Ullmanns Encyclopedia of Industrial Chemistry, 4th Edition, Vol. 7, page 47 ff.). The resulting soot is usually washed out of the reaction gases with water or deposited in cyclones or filters. From the resulting aqueous soot suspensions, the soot can be agglomerated with an auxiliary such as. B. light oil or residual oil and separated by filtration from the aqueous phase (DE-PS 10 42 793). The soot-oil agglomerates so produced generally contain up to 20% water. The separation of soot from a soot-water mixture by flotation, filtration, sedimentation or centrifugation (DE-OS 29 49 286, DE-OS 26 06 098) leads to soot concentrates with high residual moisture (more than about 60%), which can only be removed by further expensive drying (DE-PS 23 11 102).

In other processes, soot masses can be formed which, in addition to water or instead of water, contain other low-boiling liquids - mostly hydrocarbons.

Soot as a valuable product can be used for various purposes. On the one hand, it can be obtained from soot masses as a practically foreign product. On the other hand, a liquid-containing carbon black mass can be incorporated into other liquids and can be reused in this form.

Soot is suitable, for example, as a feedstock in partial combustion plants for the production of synthesis gas or in total combustion plants for the production of energy (DE-PS 20 41 227). In the first case, it is necessary to enter, mix and suspend the liquid, solid, semi-solid or flowable soot mass without costly pretreatment, such as degassing or drying, and to break it down into gasifiable particle sizes. The introduction of a liquid-containing soot mass is unproblematic in the case of liquids whose temperature is below the boiling point of that contained in the soot mass. Liquid is provided that the liquid has a viscosity that is sufficiently low for its delivery.

In the case of heavy mineral oil, distillation residue oil, bitumen, asphalt and other highly viscous hydrocarbons, which only have the low viscosity required for their pumpability by pumping at high temperatures, a liquid must be added soot mass containing such soot oil with foaming and heavy splashing are to be expected if the boiling temperature of the liquid contained in the soot mass is below the temperature of the liquid into which the soot mass is to be introduced. For this purpose, it has been proposed, for example (DE-AS 22 28 5Q5), to introduce and mix the soot mass into the hot liquid under increased pressure; in some cases, it is necessary to pulverize the soot mass beforehand. The suspension, dispersion and homogenization necessary for gasification are not taken into account.

Furthermore, carbon black - as a pigment or filler - can be incorporated in the form of a liquid-containing carbon black mass into highly viscous liquids such as melted or dissolved polymers, which are then sprayed in the molten or dissolved state, for example, and processed as soot-containing powder. Although the liquid contained in the carbon black mass largely evaporates when sprayed, it is also necessary in this process to prevent foaming and spraying when the liquid carbon black mass is incorporated into the hot polymer melt.

The task thus arises of developing a process for the foam-free and splash-free introduction and mixing of a liquid-containing soot mass into a hot liquid, with which a uniform soot distribution with a particle size which may also be suitable for gasification is achieved with the shortest possible residence time in the mixing container and in the homogenizer becomes.

• - Erhitzen der hochviskosen Flüssigkeit auf eine Temperatur, bei der die Flüssigkeit hinreichend fließfähig ist,
• - Einrühren der flüssigkeitshaltigen Rußmasse in die heiße Flüssigkeit, die unter einem Druck steht, der niedriger ist als der Dampfdruck der in der Rußmasse enthaltenen Flüssigkeit bei der Temperatur der heißen Flüssigkeit,
• - intensives ständiges Rühren der Flüssigkeit, bis der Ruß suspendiert ist,
• - Homogenisieren der Suspension.

According to the invention, this object is achieved by a method with the following characteristic features:

• Heating the highly viscous liquid to a temperature at which the liquid is sufficiently free-flowing,
• Stirring the liquid soot mass into the hot liquid, which is under a pressure which is lower than the vapor pressure of the liquid contained in the soot mass at the temperature of the hot liquid,
• - constant stirring of the liquid until the soot is suspended,
• - Homogenize the suspension.

The liquid-containing carbon black mass to be stirred in can be present as an uncompressed or compressed carbon black mass in the form of an agglomerate, granules, concentrates, extrudates, filter residue or in another solid, semi-solid or flowable form in which the carbon black is obtained or obtained in soot-producing processes. The liquid in the soot mass can be water and / or a relatively low-boiling hydrocarbon or a mixture of relatively low-boiling hydrocarbons, for example gasoline, methanol, benzene and solvent mixtures.

The carbon black mass can contain, for example, up to 50% by weight of water, up to 30% methanol, up to 40% gasoline or up to 50% benzene.

The soot mass is - if necessary through a pressure lock - introduced and stirred into the hot liquid, which is a mineral oil, distillation residue oil, bitumen, asphalt or another at least at the selected temperature for its conveyance and the further conveyance of the suspension sufficiently flowable hydrocarbon; the kinematic viscosity of the hot liquid is generally 1 cm ² / s or less.

In other cases, the liquid-containing carbon black mass can be introduced into a molten or dissolved polymer and stirred in.

The selection of the conveying device depends on the consistency of the liquid-containing soot mass and on the pressure against which the soot mass is to be introduced into the hot liquid. In general, screw conveyors or single-screw extruders are sufficient.

The selection of the dispersing device depends on the degree of division and distribution of the soot particles necessary for the further processing of the suspension or dispersion.

The liquid-containing soot mass is conveyed into a stirred tank, which may be under pressure, and mixed with the hot liquid. The suspension is stirred vigorously and continuously and / or is kept in intensive motion by pumping around the suspension partially withdrawn from the container and injecting it back into the suspension. The hot liquid-soot mixture is then conveyed into a homogenizer.

The homogenizer is either a mechanical or static homogenizer, or a shear force-producing disperser that applies a shredding power of 50 to 250 megawatts per cubic meter of the device volume filled with suspension, or an ultrasound device.

The residence time of the suspension in the shear-generating disperser is between 0.05 and 0.5 seconds; during this time the suspension is homogenized and the soot is crushed.

If the soot dispersion is to be used in a partial combustion plant for the production of synthesis gas, with an average particle size of at most 70 pm at least 95% of all soot particles must be less than 100 pm be; No particles should be detectable above 600 pm. For other uses of the soot suspension or soot dispersion, less stringent particle size distribution conditions may be sufficient.

The mechanical homogenizer is, for example, a high-speed mixer or a centrifugal pump. Commercially available shear force generating devices, in which further sprockets rotate at high speed between concentrically arranged fixed sprockets, are significantly more effective. All commercially available devices with sufficient power are suitable for homogenization in the ultrasonic field.

The homogenizers can either be used on their own or as successive devices acting on the suspension.

Surprisingly, when the liquid-containing carbon black mass is stirred into the hot liquid, the temperature of which is above the boiling point of the liquid contained in the carbon black mass under the present pressure, depending on the stirring intensity, little or no foam occurs; furthermore, the liquid splashes little or not at all. In this process, foaming and spraying can be influenced and suppressed using the stirring intensity. This effect is presumably related to a slow transfer of heat from the hot liquid to the liquid-containing soot particles, which results in an only moderately high evaporation rate of the liquid contained in the soot.

The viscosity of the suspension can increase significantly with increasing soot concentration. For a soot concentration above about 3%, it has therefore proven useful not to completely free the soot mass from the liquid contained in the stirred tank and only moderately to disperse. In the subsequent homogenization stage, the liquid still contained in the suspension then has a lower viscosity than that which is obtained with the same but liquid-free suspension.

• - Es erfordert einen kleineren apparativen Aufwand als vergleichbare Verfahren, bei denen die Rußmasse unter erhöhtem Druck in die heiße Flüssigkeit eingetragen wird.
• - Die Behandlung der heißen Suspension in einem scherkrafterzeugenden Dispergiergerät ergibt eine wesentlich günstigere Teilchengrößenverteilung als eine Behandlung der Rußmasse (z. B. Pulverisierung) vor dem Eintragen in die heiße Flüssigkeit.
• - Es kann kontinuierlich, halbkontinuierlich oder diskontinuierlich betrieben werden.
• - Es erlaubt, die in der Rußmasse enthaltene Flüssigkeit vollständig, weitgehend oder nur teilweise aus der Suspension zu entfernen.
• - Weil beim Einrühren der Rußmasse in die heiße Flüssigkeit das Spritzen und Schäumen weitgehend verhindert wird, läßt sich die Suspension ohne Kavitationserscheinung an den Geräten rühren, fördern und homogenisieren.

The method according to the invention has the following advantages:

• - It requires less equipment than comparable processes in which the soot mass is introduced into the hot liquid under increased pressure.
• - The treatment of the hot suspension in a shear force-producing dispersing device results in a much more favorable particle size distribution than a treatment of the soot mass (e.g. pulverization) before being introduced into the hot liquid.
• - It can be operated continuously, semi-continuously or discontinuously.
• - It allows the liquid contained in the soot mass to be completely, largely or only partially removed from the suspension.
• - Because splashing and foaming is largely prevented when the soot mass is stirred into the hot liquid, the suspension can be stirred, conveyed and homogenized on the devices without any signs of cavitation.

The method according to the invention is illustrated in the figure for the case of continuous operation, without being limited to this embodiment.

The soot mass to be introduced is conveyed by means of the conveying device (4) into the - optionally heatable - stirred tank (1); if the stirred tank is depressurized, the Fall free of the soot into the container. The mixing container is only about two thirds of its total height filled with the hot liquid; this is fed continuously via line (5) and stirred intensively by means of the stirrer. The intensive mixing of the liquid can be supported by injecting the hot liquid from line (5). The vapor escaping during the stirring of the liquid contained in the soot mass is drawn off via line (7), optionally with the aid of a gas stream from line (6) or with the aid of a suction device (not shown).

The suspension is continuously removed from the stirred tank via line (8). If the soot is already sufficiently suspended in the stirred tank, the suspension can be used for further use.

If the suspension - e.g. B. because of the large soot concentration - to be further homogenized, it is conveyed via line (8) and generally by means of a pump (2) into a downstream homogenizer (3). If the suspension still contains part of the undevaporated liquid contained in the soot mass and this liquid is to remain in the suspension, the suspension is further dispersed in the homogenizer under a correspondingly high pressure. The suspension is removed via line (9) from the homogenizer and fed to further use, for example fed into a synthesis gas reactor.

The implementation of the method is further explained using the examples.

example 1

In an open laboratory vessel with a diameter of 90 mm and a height of 230 mm, a blade stirrer with a diameter of 80 mm and a Leaf height of 20 mm had stirred in a water-containing soot mass, which contained approx. 18% water, in approx. 180 ° C hot vacuum oil. The filling height was 40 mm at the start of the tests. When the carbon black mass was added, the temperature of the liquid was kept approximately constant by heating the stirred tank. In about 10 minutes, the same amount by weight of water-containing carbon black mass was sprinkled in as was introduced into hot vacuum residue oil.

At a stirrer speed of 50 rpm, a foam height of approx. 10 cm arose, at 100 rpm of approx. 5 cm and at 200 rpm of approx. 2 cm. At 350 rpm there was practically no foam to be observed.

The suspension obtained consisted of 3.2% carbon black and 96% vacuum residue oil; it was practically anhydrous. After stirring for 30 minutes at 350 rpm, the soot was evenly distributed in the oil; 78% of the soot particles were smaller than 100 µm. Some soot particles were larger than 2 mm.

Example 2

A closed, heated stirring vessel with a volume of 12 m ³ was charged at 3.7 bar with 8.7 m3 / h of distillation residue oil heated to 205 ° C. and 4.3 m ³ / h of liquid-containing carbon black mass. The carbon black mass consisted of 37% carbon black and 63% hydrocarbon mixture which had a boiling range of 103 ° C. to 143 ° C. at 3.7 bar and which contained predominantly xylenes. The average residence time of the suspension in the stirred vessel, which was only about half full, was about 30 minutes.

The carbon black mass could be stirred in at a stirrer speed of 200 rpm without foaming and spraying.

The suspension obtained consisted of 14.2% carbon black and% oil. The soot was evenly distributed in the oil. 72% of the soot particles were smaller than 100 µm. Only a few soot particles were larger than 2 mm.

Example 3

Before being used further, the suspension obtained in Example 2 was pumped at 3.7 bar through a high-performance shear force-generating device and further dispersed therein. The gear chamber of the device had a volume of 0.9 liters. The drive power of the gears was 86 kW, which resulted in a shredding power of 96 MW / m ³ . With a throughput of 13 m3 / h, the residence time of the suspension in the gear chamber was approximately 0.25 seconds.

The soot was very evenly distributed in the suspension removed from the disperser. 95% of all particles were smaller than 90 pm. No particles larger than 480 µm were found. The soot particles were therefore of a size suitable for gasification.

Claims (6)

1. A method for mixing a liquid-containing carbon black mass with a highly viscous liquid to form a suspension or dispersion in which the carbon black is evenly distributed, characterized by Heating the highly viscous liquid to a temperature at which the liquid is sufficiently free-flowing, Stirring the liquid soot mass into the hot liquid, which is under a pressure which is lower than the vapor pressure of the liquid contained in the soot mass at the temperature of the hot liquid, - intensive and constant filling of the liquid until the soot is suspended, - Homogenize the suspension. 2. The method according to claim 1, characterized by - Stirring a liquid-containing, possibly compacted, carbon black mass in solid, semi-solid or flowable form into the hot liquid, which can be a mineral oil, distillation residue oil, bitumen, asphalt or another sufficiently flowable hydrocarbon. 3. The method according to claims 1 and 2, characterized by - Stir in a soot mass containing up to 30 weight percent low-boiling hydrocarbons. 4. The method according to claims 1 to 3. characterized by - Stir in a soot mass that contains up to 50 weight percent water. 5. The method according to claims 1 to 4, characterized by - Intensive constant stirring of the liquid in a stirred container and / or by injecting the hot liquid or the suspension partially withdrawn from the container back into the suspension. 6. The method according to claims 1 to 5, characterized by - Homogenization of the suspension in a mechanical or static mixer and / or in a shear force-producing disperser with a shredding capacity of 50 to 250 MW / m ^{3 of} the device volume filled with suspension and / or in an ultrasound device.

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