DE7535759U - CENTRIFUGE FOR SPRAYING AND RE-RELEASE OF SUGAR - Google Patents

Description

BRAUNSCHWEIGISCHE MACHINENBAUANSTALT

33 Braunschweig
At the old train station 5

"Centrifuge for spinning off and redissolving sugar"

The invention relates to a centrifuge for spinning off and Redissolving sugar, which has a conical centrifugal basket equipped with a sieve lining on the inside, which around a vertically extending axis driven in rotation and serving as a collecting space for separated liquid within one Housing is arranged and at its upper end has an edge serving for the passage of the sugar crystals, the The centrifugal basket and the housing are arranged within a housing-like outer jacket, through the cover of which a feed device for the filling compound protrudes into an acceleration device attached to the hub of the centrifugal basket.

Very high purity sugar is produced in the sugar industry by passing the previously purified sugar solution through Crystallizers and the resulting filling compound in centrifuges in a liquid phase and in a solid phase - the crystallized sugar - separates. The ones in the starting product

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any impurities still contained remain in the liquid Phase. Certain / extremely small amounts of impurities are still present in the sugar crystals after this process. That is why sugar crystals become this one Species redissolved, crystallized and subjected to a separation treatment In centrifuges when the purity is high Sugar should be achieved. This is done by redissolving recovered sugar solution filtered before crystallization.

There are other uses for sugar solution, which is obtained from already crystallized sugar by redissolving and filtering. On these uses will be referred to in detail at a later point.

The DT-AS 20 25 828 relates to a device of the type mentioned above Art. In this document, a continuously operating centrifuge is described in which the conical The centrifugal basket has a radially elongated edge at the upper end, which extends into what is known as a collecting ring circular tube extends into it, which is arranged coaxially to the axis of rotation of the centrifugal basket and for the reception of the edge has a corresponding slot open towards the centrifugal basket. This collecting ring is filled with liquid loaded; at a suitable point there is a connection for discharging flowable product. The applicant of this document claims for itself that the sugar thrown into the collecting ring into the rotating liquid

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already dissolved again in this ring and thus discharged in a liquid manner will. Practice has shown that only a mixture of liquid and sugar crystals is formed in the collecting ring can be - so it is only mashed -. The liquid-crystal mixture formed is removed from the centrifuge Discharged in a liquid way and must before it can be filtered / by mixing pumps or in appropriate dissolving containers with Agitators can be converted into sugar solution.

The reason why in the known centrifuge only mashed and sugar goes into solution in negligibly small quantities, is that the influence of the time factor was overlooked or not taken into account. The sugar picked up by the collecting ring in the known centrifuge cannot be dissolved within the technically possible dwell time in the rotating liquid ring, because every dissolution process Takes time. Under otherwise identical conditions influencing the dissolving process, the dissolving process can only be shortened in time by acting in a mechanical manner on the crystal-liquid mixture. At the That is to say, dissolving forms layer-like shells of saturated or almost saturated solution immediately around each crystal.

A further dissolving process is only possible when these shells of high concentration are replaced by liquid of low concentration are replaced. Since in sugar solutions with increasing con-

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centration also increases the viscosity, the exchange of the Boundary layers are also made more difficult. The previous practice of sugar solutions resulted from these physical conditions Manufacture solution vessels that are equipped with appropriate mechanical stirring devices. Through the mechanical action the agitators support the exchange of the boundary layers.

In the known centrifuge mentioned, the liquid flows in the collecting ring at a relatively low speed, because at the centrifugal effect would make itself felt at high speed. The sugar thrown into the collecting ring would then sediment in the outer area of the collecting ring and could no longer be entrained by the flow of liquid. the The flow velocity at which this sedimentation is prevented is far too low to be a mechanical effect on the Solid or sugar-liquid mixture to have an influence that noticeably shortens the solution time.

The interpretation mentioned at the beginning therefore represents a centrifugal fugue which in reality is primarily about preventing knots from forming, because when sugar comes out of one continuously centrifuge is discharged dry in the usual way, then knots or sugar lumps are formed almost inevitable. However, these sugar lumps make the subsequent redissolution of the sugar more difficult. By the

so-called liquid discharge of the sugar from the continuously working centrifuge, the formation of knots can be avoided. This creates the possibility of a solid-liquid mixture to produce that can be conveniently promoted. However, this thought is not new. For example, it will be fine US Pat. No. 2,883,054 shows a centrifuge in which the centrifuge thrown from the conical centrifugal drum Sugar can be sprayed with liquid in a collecting ring and rinsed out. Although this is also used in this publication which is physically impossible - speaking of the fact that the sugar could also be dissolved again in this way.

Another example is shown in US Pat. No. 3,301,708. This is also the case with this continuously operating centrifuge A collecting ring surrounds the upper edge of the drum and liquid is poured onto the sugar caught in this ring given up. A rotating nozzle body charged with liquid is used for the purpose of feeding the liquid.

A real and realistic description of the processes within a continuously operating centrifuge is given by the American patent specification No. 3,238,063. In this known centrifuge, an annular tube is arranged at a relatively large axial distance from the upper edge of the conical centrifuge basket and is directed radially outward Has outlet holes or nozzles for liquid. The one over the top

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Sugar thrown off the edge of the centrifugal basket is used in this case Centrifuge caught on resilient baffles, with liquid being sprayed from the ring tube and the nozzles at the same time will. In this way, a solid-liquid mixture is to be created that is comfortable and free of knots the centrifuge can be discharged.

The present invention is based on the object of providing a centrifuge through which the centrifuge from the centrifugal basket drum discarded sugar can still be completely dissolved inside the centrifuge.

To achieve the object on which the invention is based, a centrifuge of the type mentioned at the outset, which according to the invention is characterized in that at an axial distance above the upper edge (6) a circular tube (14) is arranged with nozzles (30) directed towards the edge and that at a certain distance from the edge of the centrifugal basket (3) a baffle ring (18) arranged coaxially to the axis of rotation (2) is provided which is arcuate from an area above the upper edge of the centrifugal basket with respect to the axis of rotation curved, extending radially outwards and downwards, with the concave side facing the centrifugal basket and the radius of curvature from the inner to the outer edge of the PiallrInges (18) smaller and that the outer and at the same time lower end of the impact ring together with a horizontally arranged intermediate plate (20)

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a narrow passage gap (19) for the mixture of sugar solution and sugar crystal residues and air forms and that outside the baffle ring (18) on the intermediate plate (20) an upright annular baffle (22) is placed, the upper edge of which is at a certain distance above the passage slot (19) runs.

It is particularly expedient in terms of production technology if the impact ring Is shaped like a basket base, because standardized construction elements can then be used.

In contrast to the known centrifuges, according to the invention actually achieved complete redissolution of the sugar crystals within the centrifuge. A particular advantage of the Invention is that the sugar solution flowing out of the centrifuge has a concentration of the order of 60 to 70 Brix and more and therefore without any interposition any process steps can be filtered immediately.

The reason why complete dissolution is achieved in the centrifuge designed according to the invention, in contrast to the known prior art, is that all special situations within a continuously operating centrifuge are used in an inventive manner for multiple mechanical action on the liquid-sugar mixture . So it is known that the sugar crystals at the top

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of the conical centrifuge basket have the highest speed prevailing in the centrifuge. For this reason, the dissolving liquid is sprayed under pressure at this point and if possible at an angle, for example at a right angle, onto the sugar crystals that have been thrown off or over the upper edge of the centrifugal basket. The two media meet at the greatest differential speeds and considerable kinetic energies have an effect in the sense of an intensive interfacial exchange. As a result of the unavoidable high air turbulence and the collision with the sugar, the liquid is distributed in very fine droplets and forms a dense mist of finely divided dissolving liquid in the space that is enclosed by the impact ring, which, however, under very violent conditions from the high speed of the Centrifugal drum caused turbulence flows. The sugar crystals have to pass through this turbulent flow mist and are exposed a second time to a mechanical influence, which ensures that the liquid skins or boundary layers on the crystal surfaces are exchanged so that the dissolution process can proceed. After a relatively short flight distance, the crystals collide with the inclined surface of the prail ring. Their momentum carries it over the curved surface of the impact ring of time, thereby the sugar crystals are partially crushed or smashed, but this process takes place at the same time under the influence intensivster turbulent flow of the already repeatedly mentioned liquid mist. It

there is a third effect on the dissolving process, in which the surface, the can come into contact with the dissolving liquid, is enlarged, in addition cause flow or movement over a solid surface and air turbulence cause a further intensive exchange of boundary layers. At the lower and radially outer At the end of the impact ring, the intermediate plate creates a jam. The liquid that is in this stagnation zone is in turn intensely mechanically whirled through. At this point there are only a few isolated small amounts in the liquid Crystal residues, most of the sugar has already been dissolved. Under the influence of the high air turbulence that causes the rotation of the centrifugal basket, the jammed liquid with the residual crystals is between the outer and lower edge of the baffle ring and the intermediate plate pressed through a relatively narrow slot, with air and liquid mist act as admixtures in the sense of a fourth mechanical effect. Outside the impact ring, the liquid must another weir overflow and can be discharged. The functionality of the new process and the new centrifuge has been confirmed in an experiment with the help of a prototype.

A very important further aspect of the invention results from the use of the new centrifuge. For very Namely, liquid sugar of high purity is required for many industrial uses. To prevent crystallization

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this sugar is converted into invert sugar. Before doing this, however, the path of crystallization and redissolution has to be followed and filtration, only sugar solution can be created. Because of the extremely high purity requirements was previously only the use of periodically operating centrifuges guarantees that sugar of the required purity is obtained.

According to the invention, however, a high degree of purity can already be achieved in the continuously operating centrifuge through intensive covering be achieved. The sugar solution discharged from the centrifuge in this mode of operation then only needs after filtration nor to be subjected to the invert treatment in order to be used as Liquid sugar to be usable.

Further advantages and features of the invention emerge from the following description of an exemplary embodiment.

Figure 1 shows a sectional view of an inventively designed, continuously operating centrifuge, which is suitable for carrying out the invented process.

FIG. 2 shows an enlarged detail of the centrifuge according to Figure 1, the for the dissolution of the sugar decisive processes are indicated schematically.

FIG. 1 shows a continuously operating centrifuge 1,

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at, which rotates a conical centrifugal basket 3, which is open at the top, about a vertically extending axis of rotation 2. A drive motor 4 serves to drive it. The centrifugal basket 3 is equipped with a sieve 5 on the inside in über1icher Welse. The centrifugal basket 3 has an upper edge 6.

In the center of the spin basket 3 there is an acceleration and processing device 7, into which a feed device 8 extends, which filling compound 9 consists of a Metering slide 10 is supplied in a selectable amount. The filling compound is freed of the liquid phase when passing the sieve 5 and thrown off over the edge 6. Nozzle pipes 11, the suitable - not shown - feed lines are connected, are used to feed the on the sieve 5 in the direction of the upper edge 6 to apply water or steam to sliding sugar.

The liquid phase separated from the filling compound is collected in a collecting space 12 and drained off. This collecting space 12 is defined by a housing 13 surrounding the centrifugal basket 3.

To with the continuously operating centrifuge formed in the above manner over the upper edge 6 of the centrifuge basket 3, to be able to dissolve thrown sugar again in the centrifuge itself, the following precautions have to be taken: located at a certain axial distance above the edge 6

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det is an annular tube 14, which over a feed line 15 and a metering valve 16 to a feed line 17 for dissolving liquid is connected. The inner edge extends at a slight radial distance from the tube 14 a baffle ring 18, which is curved in the manner of a basket bottom and consequently at the level of the upper edge 6 of the lock 3 presents an inclined surface to the sugar thrown off over the edge 6. The lower end of the impact ring 18 is perpendicular. It ends leaving a narrow passage slot 19 above an intermediate plate 20, which is horizontally within a Outer jacket 21 of the centrifuge and the housing 13 runs. At a certain radial distance outside the impact ring 18 is Arranged on the intermediate plate 20, an annular baffle 22, the upper edge of which is at a certain height above the Passage slot 19 runs.

In the intermediate plate 20 is an outlet opening for sugar solution provided, to which a discharge pipe 23 is connected. The sugar solution is removed from the centrifuge through this discharge pipe 23 1 carried out.

A fine thermometer 24 protrudes into the discharge pipe 23 and is connected to a controller 26 via control connections 25 stands, which in turn has control connections 27 with an actuator 28 of the metering slide 10 and with an actuator 29 of the metering device 16 is in connection.

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The centrifuge described works as follows. The from the metering slide 1O with as constant a temperature as possible in metered The amount of filling compound 9 flowing through the feed device 8 is after passing the acceleration device 7 in the centrifugal bowl 3 in a solid phase, the sugar and a liquid phase, separated in the drain. The sugar is used if necessary covered by water or steam and exits over the edge 6. The annular tube 14 has exit holes or nozzles 30, by which dissolving liquid with a suitable temperature under pressure and by the metering device 16 also in a regulated Quantity sprayed onto the sugar crystals at an angle to the direction of flight will. In FIG. 2, arrows 31 indicate the direction of flight of the sugar crystals, while arrows 32 indicate the direction of the rays the dissolving liquid. In the illustration in Figure 2, it must be taken into account that it is an axial section, so that the directions shown still by a movement component directed perpendicular to the plane of the drawing, the is generated by the rotation of the centrifugal basket 3, would be supplemented.

The sugar crystals that are thrown off in the direction of the arrows 31 and the jets of liquid that are ejected in the direction of the arrows 32 meet at a very high speed, with very high kinetic energies having an effect. It arises in the space enclosed by the baffle ring 18 with the participation of the very violent turbulent air flow that is caused by

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the rotation of the centrifugal basket 3 is caused, a dense liquid mist 33, in which, as in Figure 2 by arrows is indicated, in addition, very violent turbulence and eddies form. With the first contact with the dissolving liquid A very violent exchange of substances takes place in the sugar crystals, which leads to an immediate, intensive start of the dissolution process causes. On the way in the direction of the arrows 31, the sugar crystals are again passed through dense, finely divided liquid Medium, namely the triggering liquid thrown through, so that again an intensive liquid exchange takes place, who further promotes the solution. Meet the sugar crystals then on the impact ring 18 and are due to the inherent energy in approximately the manner indicated by the arrows 34 partly moved in the direction of rotation partly in the direction of the lower end of the impact ring. High mechanical forces are at work here which partly lead to a mechanical crushing of the individual sugar crystals, but also an intensive one Have a mixing and stirring effect on the dissolving liquid that accompanies the crystals in this way. An additional The turbulence and eddies 33 exert an action on the liquid and the migrating crystals. At the bottom of the Impact ring 18, there are hardly any sugar crystals left, but there is almost only sugar solution left. This sugar solution with certain residual crystals forms at the bottom of the Impact ring 18 in front of the narrow passage slot 19 a jam 35. Since the interior of the centrifugal basket 3 via the inlet

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Running device 8 rait steam is applied and since the high speeds of the centrifugal basket 3 cause a ventilation effect, the liquid accumulation 35 is driven through the passage slot 19 under the influence of a pressure or flow effect of liquid mist and air acting approximately in the direction of the arrows 36 in FIG. A liquid, air or moisture mixture through which liquid mist flows intensively occurs approximately in the direction of arrow 37 in FIG. This last mechanical action on the sugar solution created in the meantime also brings the last remaining crystal residues to a complete solution, so that pure, completely dissolved sugar solution flows off through the discharge pipe 23. Tests have shown that s.3hx high sugar concentrations of the order of 60 to 70 Brix or more can be achieved.

The already mentioned fine thermometer 24 is provided to regulate the density of the sugar solution. When regulating the density, based on the idea that the temperature of the sugar solution depends on the temperature and the amount of the inflowing Filling mass and also depends on the temperature and amount of the dissolving liquid supplied. Assuming that the temperature of the filling compound is lower than the temperature of the dissolving liquid, this means a drop in temperature the sugar solution flowing through the discharge pipe 23, that too much filling compound or too little dissolving liquid in the centrifuge is initiated. Accordingly, the density or the

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Brix increase. With an inverse behavior of the temperature The opposite situation would arise with the discharged sugar solution. You can take advantage of this by About the already mentioned controller 26 and the control connections 25, 27 actuators 28 and 29 actuated to the To dose the amount of filling compound and / or the amount of dissolving liquid supplied under pressure. Requirement for the The function of this density regulation of the produced sugar solution are constant temperatures of the dissolving liquid or the Filling compound or corresponding additional controller functions of the controller 26. Should the temperatures of the filling compound and the Dissolving liquid is subject to fluctuations, these would have to be measured and taken into account in the regulation.

In practice it can happen that, as a result of the failure of pumps or the like, a sudden influx of dissolving liquid fails. In practice, this would result in complete clogging and blocking of the centrifuge 1 within a short period of time. For this reason, a pressure gauge 37 is switched on in the supply line 17 and, in terms of control, with a solenoid valve connected, which is able to connect a further feed line 29 for the supply of dissolving liquid, if the Pressure in the feed line 17 suddenly drops. A check valve 40 prevents in this situation that the substitute supplied dissolving liquid flows off in the wrong direction.

Normally, the dissolving liquid used for the dissolving process

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thin juice can be used. But it can also be done with condensate or appropriately treated water, or with suitable concentrated concentrated juices.

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Claims (3)

f ■! '· Protection claims 1. Centrifuge for continuous spinning off and re-dissolving of sugar, which has a conical centrifugal basket equipped with a sieve lining on the inside, which around a vertically extending shaft driven in rotation and inside a collecting space for separated liquid Serving housing is arranged and at its upper end one for the passage of the sugar crystals serving edge, the centrifugal basket and housing arranged within a housing-like outer jacket are, through the cover of a feed device for the filling compound up to one on the hub of the centrifugal basket attached acceleration device protrudes, characterized in that in an axial distance above the upper edge (6) an annular tube (14) with directed against the edge Nozzles (30} is arranged, and that at a certain distance from the edge of the centrifugal basket (3) a coaxial to Axis of rotation '2) arranged impact ring (18) is provided, that of a * 2m area above the upper edge of the Centrifugal basket from arcuately curved with respect to the axis of rotation, extends radially outward and downward, the The concave side facing the centrifugal basket is urtd the radius of curvature from the inner to the outer edge of the impact ring (18) becomes smaller and that the outer and at the same time lower At the end of the impact ring, together with a horizontally arranged intermediate plate (20), a narrow passage gap (19) for the mixture of sugar solution and sugar crystal residues and forms air and that outside the baffle ring (18) on the intermediate plate (20) an upright annular baffle (22) is placed, derei. Upper edge runs at a certain distance above the passage slot (19). 2. Centrifuge according to claim 1, characterized in that that on the intermediate plate (20) a downward and through the outer jacket (21) leading to the outside Drain pipe (23) for the sugar solution connects that in a fine thermometer (24) is arranged in the discharge pipe (23). 3. Centrifuge according to claim 1 and / or 2, characterized in that the impact ring (18) according to Kind of a basket bottom is shaped. J2 Braunschweig, February 14, 1977 7535759 08.0677