CS203998B2 - Method of separating the carbon parts from the suspension of the fine carbonaceous material in the water - Google Patents

Abstract

The invention relates to a process for the preparation of dry soot from a suspension with a soot content of from 0.5 to 1.5%w of soot particles in water as obtained when washing gases originating from a process for the preparation of gas by partial combustion of a carbon-containing feed, the suspension being brought to turbulence in an agglomeration zone with addition of a liquid light hydrocarbon or mixture of hydrocarbons, characterized in that the mixture of liquid and agglomerates leaving the agglomeration zone is passed through the drum of a rotary sieve, in which sieve drum the mixture is filtered, the agglomerates leaving the sieve drum having a water content of from 4-5%w and a light hydrocarbon(s) content of from 300800%w, and the agglomerates are de-watered while being transported to the outlet of the drum, after which the light hydrocarbon(s) is (are) recovered by evaporation and condensation.

Description

The invention relates to a process for separating carbonaceous particles from a suspension of fine carbonaceous material in water.

The invention also relates to an apparatus for carrying out this method.

Examples of carbonaceous material are carbon black and coal. A carbon black slurry in water is obtained, for example, from scrubbing gases from incomplete combustion of a carbon-containing feedstock. The coal coal slurry may be prepared from fine coal for transport by pipeline or for further processing. With coal, ash removal is often as important as water removal.

The carbon-containing feedstock for the above incomplete combustion process may be a mineral oil or a fraction thereof, from methane to heavy asphalt. It also includes coal, or fine coal slurry in a liquid of ^one or more slowly oil fraction.

The raw gas obtained as the product contains very fine carbon blacks, the amount of which depends on various circumstances, such as the composition of the feedstock, the ratio of fuel to oxygen during combustion, temperature, pressure. In practice, the carbon black content frequently occurring in the gas is in the range of 2 to 4% by weight. The carbon black may be removed from the gas by scrubbing with water to obtain an aqueous suspension of the carbon black particles. The carbon black content of this suspension is in the range of 0.5 to 1.5 wt. %. Typically, this suspension should be treated to soot-free water. A common and effective way to achieve this is to swirl the suspension in the agglomeration zone with the addition of a light liquid hydrocarbon or a mixture of such hydrocarbons. The carbon black particles then agglomerate to form agglomerates of several millimeters in diameter that can be separated from water. In the case of ash-containing material, the removal of ash and water is carried out at the same time as the ash is removed together with the water in a non-damp form. Common methods for separating agglomerates and water - possibly with ash - include the use of a settling vessel, a vibrating screen or a sieve tray.

It has now been found that, when used on a large scale, this separation of liquid from agglomerates causes difficulties, mainly due to transport problems; the process of the invention indicates how these difficulties can be overcome.

According to the invention, the mixture of liquid and agglomerates leaving the agglomeration zone is passed through a rotary screen drum, in which the screen drum is filtered and the agglomerates are dewatered during transport to exit the drum, whereupon the light hydrocarbon or light hydrocarbons are separated. av shlu203998 p. evaporation and condensation,. to recover them.

The invention therefore relates to a method for separating carbonaceous particles from a slurry of fine carbonaceous material in water by swirling the slurry in an agglomeration zone with the addition of a liquid light hydrocarbon or a mixture of light liquid hydrocarbons, which method is characterized in The agglomeration zone is guided through a rotary screen drum at 5-25 rpm, clumps. The mixture is filtered to remove water, and the light hydrocarbon or light hydrocarbons recovered by evaporation and condensation.

A mixture of liquid - usually water or water containing ash - and clumps must be handled with special care. Clusters of carbon black or coal particles with light hydrocarbons as binders, for example with heavy gasoline or gasoline, are not solid. If the clusters already break down during the separation of the clusters from the liquid, no pure liquid is obtained. Agglomeration using a light hydrocarbon or mixture of light hydrocarbons is advantageous because the relatively expensive binder can easily be recovered and reused. The clusters pass through the drum as a result of the screen rotation. This can be achieved by a helical tape that is perpendicular to the screen wall. By the slight inclination of the drum, along with the rotation, it is also possible to transport the clusters through the drum. It was. It has been found that there are no transport difficulties in the sieve drum regardless of the residence time of the clusters in the drum. There is neither rubbing nor sticking.

Furthermore, it has been found that the water content of the clusters leaving the sieve drum is very low, that is to say 4-5% by weight for the carbon black clusters and much less for the coal clusters. This water content even proves to be theoretically minimal, which is surprising. These clusters have dimensions of a few millimeters. They come from the aquatic environment and because of their small size, many water adheres to their surface, which is also. contained in gaps between clusters. Filtration, also in this rotary screen, is due to the earth's gravity because the screen speed is very low, only 5 to 25 rpm. In conventional separation methods, a lot of water still adheres to the surface of the clusters and between them. In a rotary screen, the clusters constantly roll over one another. This gives each drop of water the ability to touch the surface of the sieve to remove it. This means that all adhering and sealed water is removed. Only the water trapped inside the clusters is not removed in the rotary screen.

Another important advantage of the method according to the invention is that it is technically not a problem to enclose the rotary screen drum in an impermeable, rigid casing, allowing operation under pressure. This is important because agglomeration is usually carried out under pressure. The feed suspension generally has a temperature above 100 ° C. In this case, the open connection of the product gas scrubbing tower to the agglomeration zone and the sieve drum can be provided open, which represents a great advantage since it is technically difficult to convey the dispersions with larger particles through the closures.

Finally, it has been found that the process of the invention can be carried out continuously on any scale. In addition to the abovementioned small amount of water, the carbon black or coal agglomerates thus obtained still contain a light hydrocarbon or light hydrocarbons. Their amount may range from 300 to 800% by weight, based on the carbon black. Can be expelled by heating and recovered by · vapor condensation.

This is preferably done by fluidizing the clusters exiting the sieve drum by means of superheated hydrocarbon or hydrocarbon vapors as used for agglomeration as a fluidizing gas, whereupon the vapors exiting the fluidized bed are condensed. This procedure can be carried out in a vessel in which the same pressure prevails as in the sieve drum. The use of light hydrocarbon or light hydrocarbon vapors, for example heavy naphtha vapor, has the great advantage that the liquid organic product obtained by condensation can be reused immediately for agglomeration and fluidization without any further intermediate steps. During the fluidization, the water enclosed within the clusters is also removed, which, after condensing, is separated from the hydrocarbon or hydrocarbons. It is, of course, also possible to use other gas, such as nitrogen, as fluidizing gas. The clusters remain intact.

The carbon black aggregates thus obtained consist almost entirely of carbon black and can be used for many purposes. By way of example, they may be used as adsorbents.

The process according to the invention also provides the possibility of feeding the clusters leaving the sieve drum by means of a pump to the feedstock used in the gas production process by incomplete combustion. Generally, the feedstock has a temperature above 100 ° C to have a sufficiently low viscosity to allow it to be pumped and converted into tiny droplets in the burner. If water-containing carbon black is added under these conditions, foaming occurs as a result of water vapor escaping. It has now been found that the carbon black obtained from the sieve drum has an already low water content such that foaming does not occur. The binder - light hydrocarbon or light hydrocarbons - can be removed from the fuel by flash evaporation and recovered by condensation. A suitable pump for supplying bursts to the fuel is a pressure pump. With this pump, the clusters can be introduced directly into the hot pressurized fuel, while the clusters are comminuted. Alternatively, the clusters leaving the sieve drum may be first added to the hydrocarbon or hydrocarbons as used for agglomeration and then pumped into the fuel. In this case it will then be possible to use, for example, a rotary vane pump. A disadvantage is that it is necessary to recover a larger amount of hydrocarbon (s).

Typically, the clumps will be conveyed from the sintering zone to the sieve drum by a stream of water. However, it is also possible to report a mixture of water and agglomerates after leaving the agglomeration zone of the separator comprising a lower layer of water and an upper layer of a light-liquid hydrocarbon or light liquid hydrocarbons as used for agglomeration, from which excess water is discharged and the layer containing the clusters is discharged into a sieve drum. Thus, the clusters are conceived of a light hydrocarbon or light hydrocarbons before they are filtered. The advantage of this arrangement is that virtually no adhering water can reach the screen with clumps, so that later water removal is accelerated.

The invention is illustrated by the following examples with reference to the accompanying drawing.

Figure 1 schematically illustrates a process for preparing dry carbon black or coal of the present invention.

FIG. 2 shows a combination of the process of the present invention for preparing dry carbon black with a gas production process.

According to FIG. 1, an aqueous suspension stream 10 is fed to the agglomeration apparatus 11. This apparatus is equipped with a stirrer 12 driven by a motor 13. A binder stream 14, for example a heavy gasoline or a gasoline, is also fed to the sintering device 11. During the swirling, carbon black or coal clusters are formed, which are discharged from the plant together with water through line 15 and which are led to a sieve drum 18. The drum 18 rotates slowly, driven by a motor 17. The drum wall has holes of about 200 ^ rn. The drum is provided with a vertical helical tape inside. Rotation, for example at 6 to 10 rpm, and the inclination of the tape forces the clusters to move toward the outlet 18. Water is discharged through the duct 19. The housing 20 surrounds the drum 16. Any clogging of the drum sieve walls can be removed. , which could be caused by improper operation of this equipment.

The debris-free clusters enter the dryer 22. In this dryer, they are fluidized by the hot gas entering the nozzles 23. The binder, for example, heavy gasoline, is evaporated and its vapors, together with the fluidizing gas, are discharged via line 24. The fluidizing gas is Here, superheated steam hydrocarbons used as binders. The vapors in the conduit 24 pass through a cooler 25. This provides a liquid binder which forms the aforementioned stream 14. A portion of this stream is vaporized in the heat exchanger 28 which then provides the fluidizing gas. Any binder losses are replaced via line 27. Dry clusters are discharged as stream 28.

FIG. 2 shows a reactor 30 for incomplete combustion of the carbon-containing feedstock via line 31 by reaction with oxygen or oxygen-containing gas through line 32 with the addition of water vapor supplied through line 33. The gas obtained is cooled in a cooler 35. the gas is purged through the water supply line 38 to obtain gas removed via line 39 that is no longer carbon black, and the aqueous carbon black slurry discharged through line 40. This carbon black slurry is swirled in an agglomerator 41 equipped with a stirrer and motor 42, together with a liquid light hydrocarbon, such as heavy gasoline, supplied via line 43. The resulting clusters go along with water through line 44 to a rotary sieve drum 45 provided with motor 46, burst outlet 47, water evacuation line 48 and jacket 49 .

In this variation, the dried agglomerates are introduced by a pressure pump into the feedstock stream discharged via line 51. The agglomerates still contain a binder which is removed in a flash evaporator 52. The condensate is condensed in the cooler 53 and the condensate is reused as binder supplied via line 43. and optionally supplemented with fresh binder feed line 54 to compensate for any losses. The binder-free feedstock stream is then fed via line 31 to the reactor 30.

Various variations of this procedure are possible. No evaporation in the evaporator 52.

Example 1

The slurry of carbon black particles in water contained 1.14 wt% carbon black. This suspension originated from gas production by incomplete combustion of residual mineral oil. The slurry stream was then fed to the sinter plant at a rate of 1.12 m 3 / h. The stirrer was rotated at a speed of 1000 rpm. At the same time, 58.8 kg / h of heavy gasoline was added. This supplied 12.77 kg / h. the ratio of heavy gasoline to carbon black was 4.6.

The stream leaving the sinter plant was fed to a rotary screen. The sieve drum had a diameter of 30 cm and was 120 cm. long. The helical vertical tape, moving along the inner wall of the sieve (with 200 μπι holes), had a height of 2.5 cm and a slope of 3 cm. The drum was rotated at 6 rpm.

The clusters leaving the drum were fed into a fluidized bed. The fluidizing gas was a vapor at 180 ° C. Ty203998

8 t of steam was fed at 340 kg / h. The progressive gas velocity was 0.16 m / s.

A dry carbon black stream of 12.04 kg / h was discharged from the dryer. in the form of clusters. Another dry carbon black at 0.29 kg / h. were separated from the gasoline vapor stream in the cyclone.

The experiment lasted for 8 hours and there was no failure or clogging. The clusters were completely dry on the outside. They contained approximately 3% by weight of water.

The following table lists the conditions and results of a series of cluster experiments obtained as described previously without the use of a fluidized bed. Sintering and sintering were carried out under various free conditions.

amount of carbon black feed introduced, 1 / h. 810 810 810 810 810 1200 810 860 1200

Carbon black content in slurry by weight 1.16 1.00 1.02 0.98 0.87 0.89 0.94 0.85 0.88

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203898

At an optimal weight ratio of heavy gasoline to soot agglomeration in the range of 5.6 to 6.0, the water content of the clusters was in the range of 4 to 5% by weight. At a very high ratio of heavy gasoline to soot 9.7 the water content was lower. At a low ratio of heavy gasoline to soot, smaller clusters were obtained. These clusters weigh more water on their surface due to the larger specific surface area per weight unit. It has been found that by increasing the residence time in the rotary screen by increasing its inclination, it has improved drying.

Example 2

The suspension of extractive fine coal in water contained 13% by weight of coal. The ash content of the coal was in the range of 25 to 30% by weight. The slurry stream was passed through an agglomeration apparatus at a rate of 20 L / h. The stirrer was rotated at 1400 rpm. Simultaneously, a stream of 0.41 kg / h of heavy gasoline was added.

The sinter stream was fed to a rotary screen of the same type as in Example 1.

The clusters leaving the drum were fed into a fluidized bed. The fluidizing gas was nitrogen at a temperature in the range of 150-160 ° C, fed at a flow rate of 0.20 m / s.

From this dryer a stream of agglomerates with an ash content of 5% by weight and a water content of 0% by weight came out.

The coal regeneration was 85-90% by weight, the remainder of the coal leaving the sinter plant with water as a waste containing 70-80% by weight of water.

The nitrogen in the fluidized bed can be replaced by heavy gasoline vapors.

Claims (3)

CLAIMS 1. A method for separating carbonaceous particles from a slurry of fine carbonaceous material in water by swirling the slurry in an agglomeration zone with the addition of a liquid light hydrocarbon or a mixture of light liquid hydrocarbons, characterized in that The clusters are dewatered by filtration, and the light hydrocarbon (s) are recovered by evaporation and condensation. 2. A method according to claim 1, characterized in that the clusters leaving the sieve drum are fluidized by superheated hydrocarbon or hydrocarbon vapors used for agglomeration as a fluidizing medium, whereupon the vapors leaving the fluidized bed are condensed. 3. A process according to claim 1, wherein the mixture of water and agglomerates is conducted from the agglomeration zone to a separation zone comprising a lower layer of water and an upper layer of a liquid light hydrocarbon, optionally identical to the hydrocarbons used for agglomeration. the top layer containing clusters is fed to a sieve drum.