DE2444641B2 - DRYING AND INCINERATOR FOR SOLID MATERIALS, SUCH AS SLURRY AND THE LIKE - Google Patents

Description

The invention relates to a drying and Incinerator for solids-containing materials such as sludge and the like, having at least one substantially horizontal hearth, a rotatable central one extending up through the center of the hearth Shaft on which at least one agitating arm is attached, which extends radially outward over the hearth, and with Mixing teeth that extend from the mixing arms to almost the bottom of the stove and downwards relative to the Longitudinal axis of their associated agitator arms are arranged obliquely to the material to be treated with a radial and a circumferential flow component to push over the hearth. The inventive concept is particularly suitable in addition to other possible applications, e.g. B. waste or sewage sludge, To treat roasted ores and the like.

In order to avoid the problem of air pollution, the invention is particularly directed to one substantial reduction of particulate matter, Hydrocarbons, carbonyls, visible smoke and other contaminants in the exhaust gas ovens. Up to now, these gases have contained particles, undesirable gaseous components and stable organic ones Aerosols (including tar vapor or tar fumes), these are essentially contaminants

Were the result of incomplete combustion. As they are known to have harmful effects on health can exercise, they pose a significant problem in terms of air pollution. In In this context, it should be noted that the minimum requirements with regard to the permissible, to The harmful substances released into the atmosphere are constantly being tightened by government agencies.

GB 4 68 887 already discloses a drying and incineration furnace with the structure mentioned at the beginning known, in which the material to be treated in one or more floors arranged one above the other subjected to a stirring action by means of stirring arms with stirring teeth extending over the individual floors is, the stirring teeth are aligned with respect to the longitudinal axis of the stirring arms so that the material to be treated, flowing from floor to floor, is alternately pushed in and out will. However, practice has shown that such an arrangement alone is not sufficient to provide a complete Ensure drying and incineration of the material on the individual hearth floors. These Incompleteness is essentially the result of a non-uniform distribution of the material to be treated over the floor surfaces, this uneven distribution in multi-floor ovens in addition has the disadvantage that it is from the top floor in a similar way to the material distribution in the underlying floors. Furthermore, the uneven distribution of the material results in poor utilization the available stove area and thus an undesirable reduction in the oven capacity.

In contrast, the invention is based on the object of a drying and incineration furnace of the type mentioned at the outset, in which a uniform distribution of the to be treated Material is ensured over the surface of both single and multi-floor ovens.

This object is achieved in that independent devices for generating a additional circumferential flow component are provided for the material to be treated on the hearth floor.

In the case of an oven with several stoves arranged vertically at a distance from one another and several with Distance from one another at that extending through the center of the oven and through each hearth rotatable central shaft attached agitating arms which extend radially outwardly above each hearth, alternating foci arranged in the area of the central shaft and the falling bores in between Have foci in the area of their outer circumference arranged drop bores and the inclined Arrangement of the stirring teeth with respect to the longitudinal axis of the stirring arms is chosen so that the radial flow component successive flocks alternate inwards and outwards, d. H. each in the direction to the associated drop bores, it is proposed according to a development of the invention that the Means for generating an additional circumferential flow component on at least one of the upper hu Flocks are arranged.

In the context of the invention, a uniform, planar distribution means that there is an essentially uniform flow of material over the entire surface of the treatment zone. The material h_s has essentially the same depth in all quadrants of a furnace floor for any furnace diameter, possibly with the exception of the extreme inner or outer circumferential areas, which are equipped with the drop bores in multi-floor furnaces. Nonetheless, a tangled flow of material is also ensured here, so that dead zones are avoided and an uneven flow rate over part of the furnace relative to the other zones is kept to a minimum. Regardless of whether the invention is implemented in a single or multi-floor oven, the uniform distribution of the material to be treated over the hearth or bases is achieved by independent devices which give the material to be treated an additional circumferential flow component. To set up the setting angle of the stirring teeth so that there is both a suitable radial and circumferential material flow, namely proves to be very difficult, if not even impossible. This is due in particular to the fact that the material to be treated undergoes continuous changes in the course of its time, in particular with regard to its physical properties. So far, the angle has been set so that there was an excessive radial flow, which was intended to ensure that the material does not remain on a hearth base and thus does not get in or out to the drop bores and from there to the subsequent hearth base below. This procedure, which has been practiced up to now, has the result that there is excessive radial movement and only a slight circumferential movement of the material during normal operation. By providing, according to the invention, a separate, independent device for applying an additional circumferential flow component to the material, it is distributed from a highly equipped sector of a circular furnace to a less equipped sector, so that the material is completely dried and burned over the entire surface of a hearth base is ensured. In the case of multi-floor ovens, this also ensures that there is a similar distribution of material in the lower-lying oven floors, so that the capacity of the oven is fully utilized.

Therefore, it has been found in many plants that when there is a uniform material distribution in one of the upper hearth floors has the same even distribution on the following hearth floors continues without repeated means in the latter for creating additional circumferential flow components must be provided. For other systems, however, it is advisable to use the above-mentioned facilities repeatedly to arrange the lower base of the oven. For ovens where z. B. the inner drop hole and the central shaft not are exactly concentric to one another, the even distribution once achieved may otherwise possibly be due to a non-uniform material structure, e.g. B. in the form of slag, on the periphery of the Falling hole are negatively influenced, since the flow primarily over the larger area of the drop hole and takes place to a lesser extent over the area of the drop hole, which is the center of the shaft at next lies. When burning lime, for example, or roasting sulphide ores, the lighter one Roasted river zone before the heavier river zones, so that the area of the lower herd that follows the Material obtained from the lighter river zones is wasted, since here already finished material is again the Treatment. Even in cases where

significant heat reactions take place, the massive temperature differences in the case of considerable amounts of gas can cause an early termination of the reaction in the lighter flow zones to one Overheating of the material in these zones will result once the reaction has finished.

In cases where the activation and reactivation of carbon is concerned, the material is in the Low flow zones implemented at least to a state of low exploitation with high ash content and possibly completely incinerated while activating for the remaining material in the High flow zones are still in the state of completion.

When incinerating and drying sewage sludge or other substances for which certain Components of the gas flow, such as oxygen from the air, during combustion is largely consumed, it is important that in many cases the gas is laminar along the top of the furnace flows so that the gas flow in the first quadrant of a hearth base in the first quadrant of the upward direction following hearth remains. The heavy flow zone, however, turns from a hearth to the next. Hence a quarter of the gas flow associates the heavy flow from a hearth the next and completely frees it of oxygen or other reaction gases, while the Gas in the light flow quadrant still contains oxygen or other reactive components that are in the zone of severe reactions are not available. Due to the local differences in the combustion The air required, for example, can produce dark smoke, even though the entire smoke is readily available Gas flow contain more than the stoichiometric oxygen demand can.

According to a further development of the invention, the device is for generating the additional circumferential flow component of the material to be treated is placed on the topmost hearth.

The term "uppermost hearth" refers to the topmost critical treatment zone, since in some ovens the device according to the invention for generating the additional circumferential flow component only needs to be provided for these hearth zones, but not in those for which it is of secondary importance whether that Material here is evenly distributed over the entire stove surface or not. The supply of heat or a reaction with the combustion gas can be harmful or uneconomical in these zones. It is therefore important that the device according to the invention is provided as soon as the material reaches the critical hearth zones in order to distribute it evenly over the entire hearth base without the formation of dead zones.

The device for creating the additional circumferential flow component can be elongated rod-shaped elements which are attached to the clock teeth and are essentially parallel extend to the longitudinal axis of the associated agitator arms.

According to another further development of the invention, the stirring teeth are only arranged obliquely to the longitudinal axis of some of the stirring arms and the device for generating the additional circumferential flow component of the material to be processed consists of several stirring teeth which extend down from the remaining stirring arms to close to the hearth base extend and their associated agitator arms are arranged substantially parallel to the longitudinal axis.

Another alternative to providing the additional circumferential flow component is that the Device for generating the same consists of stirring chains s. It is from DTPS 8 81927 known in principle to distribute muddy material agglomerated by means of chains. These well-known However, chains hang from the inner surface of a rotating drum and do not create additional ones ίο circumferential flow component.

Finally, another alternative is characterized in that the device for generating the additional circumferential flow component from a rope with several spaced apart is shoveling that is between two agitator arms is arranged.

With regard to other developments of the invention, reference is made to subclaims 5 and 9 to 13.

Embodiments of the invention are explained in more detail below with reference to the drawing. It shows

F i g. 1 is an axially sectioned view of a furnace with a plurality of cookers,

Figure 2 is a cross-sectional view of an upper inflow cooker with representation of the material distribution with a known procedure,

Figure 3 is a cross-sectional view of an upper inflow cooker with representation of the material distribution when using the concept according to the invention,

Figure 4 is a cross-sectional view of an upper outflow cooker with representation of the material distribution according to the conventional procedure,

Figure 5 is a cross-sectional view of an upper outflow cooker with representation of the material distribution using the concept according to the invention, Fig. 6 is a sectional view of the upper part of a furnace provided with the invention,

7 shows a section along the section line 7-7 Fig. 6,

8 shows an enlarged view of a chain according to the invention arranged between agitator arms,

Fig. 9 is a perspective view of an upper range of an oven showing the operative ones Position of the chain,

Fig. 10 is a perspective view of an upper range similar to Fig. 9 showing a manner of attachment of the RUhrkcttcn,

Fig. II is a perspective view of an upper Cooker similar to FIG. 9 with a device designed in the form of ropes with blades for creating a even material distribution,

FIG. 12 is a perspective view of an upper range similar to FIG. 9 with device in the form of elongated rod-shaped elements for creating an even material distribution, and SS Fig. 13 a perspective view of an upper stove similar to Pig, 9, in which the teeth on alternating stirring arms are correspondingly aligned to create a circumferential or radial material flow .

do in the drawing and in particular in FIG. 1 the upper part of a furnace 10 is shown with a plurality of hearths, the furnace having a basically cylindrical shape. The furnace consists of a tubular outer steel jacket 12, which, as ^{indicated at 14 r} > s, is covered with firebrick or a similar protective layer Material is lined. Although burner nozzles are only provided in one or two lower trays in some systems, the present

the embodiment of each stove equipped with a plurality of burner nozzles 16, which are both axially also extend tangentially into the hearth. With the outlets of various individually controlled, Burner nozzles, not shown, connected to burner assemblies are distributed over the furnace 10 and serve to create and / or maintain appropriate temperature and atmospheric conditions in the different zones of the oven to provide the specific treatment desired. Further special work doors and windows 18 are provided to permit operation of the oven at each hearth level monitor.

The interior of the oven 10 is divided into a plurality of vertically oriented cookers by means of hearth floors 20 and 22 divided, with only the top four flocks shown. Each hearth base consists of a fireproof one Material and is preferably formed slightly curved, so that the floor has a self-supporting property is awarded in the oven. Near the outer shell 12 of the furnace are outer circumferentially extending ones Drop bores 24 are provided while near the center of the furnace in alternating hearth bottoms 22 central drop bores 26 are formed. Although in Fig. 1 the topmost or first hearth as an outflow hearth is shown, it goes without saying that the inventive concept applies equally to a furnace with a first single-flow range or a lower range of a multi-range oven can.

As shown in Fig. 1, a rotatable vertical central shaft 28 extends axially through the furnace 10. The shaft 28 is, as indicated at 30, supported by an upper bearing and a lower bearing, not shown. It is rotated by a suitable drive device of known type, not shown. A plurality of spaced apart agitator arms 32 are attached to the central shaft 28 as indicated at 34, with the agitator arms in each hearth extending outwardly above the hearth floor. Agitator teeth are molded onto the agitator arms and extend down to near the bottom of the stove. The agitator teeth are inclined to the longitudinal axis of their associated agitator arms, so that when the agitator arms 32 move as a result of the rotation of the central shaft 28, the agitator teeth 36 continuously scrape through the material to be treated on the respective hearth base and this gradually to the drop bores 24 and 26 in the hearth bases to force.

The materini to be treated is fed into the furnace at its upper end by means of a belt conveyor 38 and a filling inlet 40. When the top hearth is an exhaust hearth, as shown in Figure 1, the fill inlet 40 is near the center of the furnace. However, if the top stove is a single-flow stove, the filling chamber is moved towards the periphery of the stove. The material generally moves downward through the furnace in a serpentine manner and is drained from the bottom of the furnace. At the top of the furnace there is provided an oas outlet port 42 through which oase and other products of combustion formed in the furnace during operation can be discharged.

FI g. 2 shows the flow of the material to be treated according to the prior art, the first hearth being a single-flow hearth 22. The material, generally designated 44, enters the hearth from above through a feed inlet 46 and is moved partially around the hearth as indicated by arrow 48 as a result of the stirring teeth rotating in the direction of arrow 49 so that the material finally passes through the central drop bore 26 falls. The agitator teeth are inclined to the longitudinal axis of the agitator arm concerned, so that the material movement has a relatively large radially inwardly directed flow component 50 and a relatively small circumferentially directed flow component 52, whereby a substantial part or portion of the

ίο Cooker uncovered or only very thin with material remains coated, as indicated by reference number 54.

In contrast to FIG. 2 shows F i g. 3 the material flow according to the invention, wherein the first hearth a Single-flow hearth 22 represents. The material, generally designated 56, enters the hearth from above the feed inlet 46 and is moved completely over the hearth according to the arrow 58 and falls through the central drop hole 26 essentially along its entire circumference. According to the invention is thus a Measure taken to the radial flow sector or the material component 60 and further are separate and independent means provided to control the circumferential flow sector or material component 62.

In this way, the two river sections can be selected individually so that the material to an even distribution over the entire stove without creating dead zones, whereby this takes place by means of the independent selection of the two components. In addition, the material residence time in the hearth between entry and exit according to the material and the treatment concerned influence in a targeted manner.

In Figure 4, an outflow hearth 20 is shown, the Material flow is indicated according to known techniques. The material 64 enters the hearth from above through an inlet 66 and is distributed, as indicated by the arrow 68, by means of the in the direction of the Arrow 70 rotating stirring teeth only partially over the stove before it through the circumferentially arranged Falling hole 24 falls. It should be noted that the stirring teeth to the longitudinal axis of the relevant Agitator arm are inclined so that a relatively large radially outwardly directed Mntcrinlflusskompentc or creating a vector 72 and a relatively small circumferential flow component or vector 74, and thus a substantial part 76 of the hearth uncovered or only thinly with that to be treated Material remains covered.

In contrast to the known flow configuration according to FIG. 4, FIG. 5 shows the flow formation in an outflow source 20 with the material treatment according to the invention. The material, generally designated 78, enters the hearth from above through feed inlet 66 and moves completely around the hearth as indicated by arrow 80 and falls substantially along its entire circumference through circumferential bore 24. As will be explained in more detail below, are means provided to the radial flux vector or the

Ao Materlalkomponerite 82 to control and further are separate or independent means are provided for the circumferential flow vector or material component 84 steer. It follows that the circumference component 84 according to the invention is substantially larger than the circumference »·

'· <Component 74 in the prior art, so that a uniform flow distribution without dead zones is present over the entire hearth. This fact becomes through it ensures that the control of the circumferential component

709 6S1 / 2B4

nente 84 independent of the control of the radial component 82 independent of the control of the Radial component 82 is. In addition, the material dwell time on the stove can be targeted accordingly the material and the process in use can be controlled.

The in the F i g. 2 and 4, in contrast to that shown in FIGS. 3 and 5 shown technology according to the invention to diverse problems. For example, there is a waste Oven zone, which reduces the effective oven area. Due to the uneven combustion the life of the furnace lining material is further shortened. So it was found that at one side of the range tended to ignite or burn while the other side tended to ignite was in a smoldering or smoldering state; d. H. on one side of the stove lies the in Material placed on a stove in a burning state while it is on the treatment other side of the oven did not reach the burning state until it moved to a lower hearth would have. So there was a burn on one side of the stove and the other Material was still drying out. This led to difficulties in controlling the residence time at the different stoves and made it practically impossible to find the burner and the atmospheric To control the conditions including the turbulence in each hearth so specifically that a clean distribution of the gas entered above the stove. This consequently led to overheating of the material in some furnace zones and underheating in other zones, which is a poor product for some treatments Had a consequence. When attempting to roast zinc sulfide to obtain zinc oxide, for example, zinc sulfate resulted, which is difficult to remove from the oven. In addition, it goes without saying that a clean burn is about the entire hearth zone a better heat transfer and thus a more economical use of the Brings fuel. In connection with the treatment of waste or sewage sludge one prevents clean combustion over the entire stove, the emission of odorous substances and the formation of blue smoke or tar fumes too fine to pass through currently operating Tugesskrubbcr to be removed. This further reduces or reduces the need to provide afterburners even switched off what were previously necessary to comply with legal requirements, such as the Environmental Protection Agency's Visual Appearance Code.

In order to create an even distribution of the material to be treated over the hearth according to PIg, 3 and 5 , a device is provided to separately control the circumferential vector or the circumferential movement component of the material with respect to the radial vector or the radial movement component. In the FI g. 6 to 9 the two upper hearths of the furnace are shown, the stirring teeth 36 being inclined to the longitudinal axis of their respective stirring arms so that they form a substantial part of the radial component 60, PIg. 3, or 82, P1 g. 4, the movement of the material to be treated on the flocks. As best from PI g. 7 and 9, adjacent agitator arms are connected with agitator chains 86 around a substantial part of the peripheral component 62, PIg.3, or 84, FIg. 5, to create. That is, the stirring teeth act as a means to control radial movement and the chains act as a means to control the circumferential movement of the material on the hearth. Accordingly, when the central shaft 28 is rotated in the direction of arrow 88 as shown in FIGS. Each end of a stirring chain 86 is thereby attached to a stirring tooth 36 in which a shackle 90, FIG. 8, is passed through a ring nut 92 which is connected to the stirring tooth by a nut 94 and screw 96. The chains are moved so that one end of the stirring wing near the perimeter extends, ₅ and the other end to the inner end of the next adjacent stirring wing is attached. The chain slackens a little, but not so far that it drags on the floor of the stove. When installing the chain, a gap of the order of about 2.54 cm is left on the screw%, so that an adjustment is possible by turning the screw. A 6.25 mm chain with a total length of about 3.2 m is suitable for a furnace with an outside diameter in the range of about 6.7 m Shaft is rotated, but the combination of the two components acting on the material to be treated brushes this evenly over a hearth to a drop hole, where the Materia! falls through it onto the next lower hearth and is then pushed evenly over this hearth to its drop hole and this process continues successively from the upper to the lower end of the oven.

In the embodiment of the invention according to FIG. 10, a stirring chain 98 is provided, one end of which is attached to the stirring arm 36 arranged on the outer circumference of the stirring arm 32, as indicated by the reference numeral 100 , while the other ₄ ü end of the chain is attached to the central one Shaft 28 is connected at 102 . The chain 98 is also arranged with a certain slack, which however is not so great that the chain drags on the floor 22. If accordingly, as indicated by the arrow 104 , the central shaft 28 is rotated, the agitator chain acts essentially as a peripheral flux component and the agitator teeth, which are inclined to the longitudinal axis of their respective agitator arm, act essentially as a radial flux component on the solid material and thus create one Uniform and uniform moterial distribution over the hearth base 22 without the formation of dead zones. Although Fig. 10 shows a single-flow hearth, the inventive concept of this embodiment is equally applicable to an Sj-flow-out hearth.

In the embodiment of the invention according to Fl g. create the stirring teeth 36, which are to the longitudinal axes of your concerned agitator arms are inclined, a substantial part of the radial component of the material to be treated over the hearth 22. Between adjacent agitator arms 32 extends, for example, from the Make 114 and 116 a cable 112 that carries a variety of Paddles 118 carries, as a means for generating a substantial portion of the peripheral flow component 6s of the material to be treated on the stove. Thus, the appropriate coordination of the inclination of the stirring teeth and the arrangement of the cable 112 ene Coordination and independent control of the radial

and circumferential flow components of the material to be treated so that it is evenly and uniformly distributed over the hearth base 22 without the formation of dead zones when the agitator arms 32 are rotated in the direction of arrow 120 by means of the central shaft 28. Although Fig. 11 shows a single-flow hearth, the concept of this embodiment is equally applicable to an exhaust-flow hearth.

F i g. 12 shows another means for evenly and uniformly distributing the material to be treated over the hearth base 22. In this embodiment, the stirring teeth 36 are again inclined to the longitudinal axes of their associated stirring arms and create a substantial part of the radial flow component of the material on the hearth 22 during a Stir bar 122 serves as a separate or independent means of providing a substantial portion of the peripheral flow component of the material. The stir bar 122 is attached to the leading edge of the stir teeth at 124 and extends radially from near the center of the range to the periphery thereof. The vertical height of stir bar 122 depends on the desired size of the circumferential flow component for the material being treated. In most facilities there will be some flow of material above and below the rod. However, in some facilities it may be desirable to have flow only under the rod. Careful selection of the inclination of the stirring teeth 36 and the height of the stirring rod 122 results in a coordination and independent control of the radial and circumferential flow components for the material to be treated, so that it is evenly distributed over the hearth base 22 without dead zones when the stirring arms 32 pass through the central shaft 28 can be rotated in the direction of arrow 126. Although Fig. 12 shows a single-flow hearth, it should be understood that the same concept is applicable to an exhaust-flow hearth.

In the following embodiment of the invention according to FIG. 13, an inflow hearth 22 with a central downhole 26 is shown. The agitating arms 32 carry agitating teeth 36 which, as usual, are inclined to the longitudinal axes of their respective agitating towers and essentially generate the entire radial flow component for the material to be treated. As a scpnrntc independent device for creating the circumferential flow component for the material, stirring teeth 128 are provided on alternating stirring arms 32 'which are not inclined but extend essentially parallel to the longitudinal axis of their stirring arms. By suitable selection of the number, the distance and the inclination of the stirring teeth 36 and the number and the distance between the stirring teeth 128 , a coordination and independent control of the radial and circumferential flow components for the material to be treated can be created, so that it is evenly distributed over the hearth base 22 is distributed without dead zones and the desired material residence time on the stove is present when the agitator arms 32 and 32 'are rotated by the central shaft 28 in the direction of arrow 130. Although Fig. 13 relates to an inflow stove, the concept of this embodiment is equally applicable to an outflow stove. Furthermore, it goes without saying that the first or topmost hearth of the oven can be either an inflow or an outflow hearth. In the treatment of certain materials it may be necessary that only the means for separately controlling the radial and circumferential flow components for the movement of the material be placed on the first or uppermost hearth or the first and second uppermost hearths, since once the material is uniform has been distributed over an upper hearth, it is in this one

ίο uniform distribution also in the following lower flocks remain. When treating other materials, however, it may be possible it is not necessary to provide such means for controlling the material flow components on the first hearth, but these means for controlling the flow components at one or more of the lower ones to order other flocks. The principles according to the invention are also applied to an oven Applicable to a single hearth, with either a radial inflow or outflow of the to be treated Material is present.

The device described for controlling the radial and circumferential material flow components separately is particularly suitable for treating waste material such as sewage sludge.

In some urban communities, the drying of the mud is done during part of the year required, the remaining components being used as fertilizers. Is the fertilizer recycling not in question, the lamb is dried, incinerated or burned at other times of the year. The principles of the present invention apply to both drying and drying Ashing method applicable. According to the invention

For this purpose, the wet sewage sludge is continuously fed into the upper end of the furnace, the sludge fed to a first zone in the upper part of the furnace for drying by passing the sludge over one of the uppermost foci with a radial flow component and

at the same time over this stove with an independent circumferential flow component is forced so that the mud in more uniform and even in a distributed manner in the direction of the relevant downhole according to FIGS. 3 and 5 flows. After that, will the sludge successively passed over each hearth and through the associated drop hole the next one below lying hearth in the first zone, the sludge being in essentially the same drying state is kept above each stove. If only that

if drying of the sewage sludge is concerned, the sludge thus dried is removed from the lower end of the first zone of the furnace. In the process which includes both ashing and drying , the slumber dried in the above becomes one

ss second zone in the lower part of the furnace is fed to incineration, placing the sludge successively over each Hearth and through the relevant drop hole to the next hearth below in this zone arrives, with the sludge in essentially the

Ao same crash condition over every stove in the Zone remains and more than one stove In a controlled amount of heat is supplied to the drying and To incinerate the sludge,

In addition 6 sheets of drawings

Claims (14)

Patent claims: 1. Drying and incinerator for solids Materials such as sludge and the like, with at least one substantially horizontal Hearth, a rotatable central one extending up through the center of the hearth Shaft on which at least one agitating arm extending radially outward over the hearth is attached, and with stirring teeth that extend from the stirring arms to ic extend almost down to the hearth base and relative to the longitudinal axis of their associated agitator arms are arranged obliquely to the material to be treated with a radial and a circumferential flow component to push over the stove, characterized ι> that independent bodies (86, 98, 106, 118, 122, 128) to generate an additional circumferential flow component for the material to be treated are provided on the stove (20, 22). 2. Oven according to claim 1, with a plurality of vertically spaced apart cookers and several at a distance from each other on the through attached to the center of the oven and rotatable central shaft extending through each hearth Mixing arms that extend radially outward over each hearth, with alternating hearths in the Drop bores arranged in the area of the central shaft and the foci in between in the Have drop bores arranged in the area of their outer circumference and the inclined arrangement the agitator teeth with respect to the longitudinal axis of the agitator arms is chosen so that the radial flow component successive flocks alternate inwards and outwards, d. H. each in Direction to the assigned drop bores, characterized in that the devices (86, 98, 106, 118, 122, 128) for generating an additional circumferential flow component on at least one of the upper hearths (20, 22) are arranged. 3. Oven according to one of the preceding claims, characterized in that the device (86, 98, 106, 118, 122, 128) for generating the additional circumferential flow component of the to be treated Material is arranged on the uppermost hearth (20). 4. Oven according to one of the preceding claims, characterized in that the device to generate the additional circumferential flow component of the material to be treated from elongated Rod-shaped elements (122) is formed, which are attached to the stirring teeth (36) and extend essentially parallel to the longitudinal axis of the associated agitator arms (32). 5. Oven according to claim 4, characterized in that the height and inclination of the elongated rod-shaped elements (122) for controlling the circumferential flow component is adjustable. 6. Oven according to one of claims 1 to 3, characterized in that the stirring teeth (36) only when some agitator arms (32) are arranged obliquely to their longitudinal axis, and that the device for Generating the additional circumferential flow component of the material to be machined from several fts There are stirring teeth (128) which extend from the remaining stirring arms (32 ') to close to the hearth base extend below and essentially parallel to the longitudinal axis of their associated agitator arms (32 ') are arranged. 7. Oven according to one of claims 1 to 3, characterized in that the means for generating the additional circumferential flow component consists of agitator chains («6,98,106). 8. Oven according to claim 7, characterized in that means (90,92,94,96) for adjusting the Tension of the agitator chains (86, 98, 106) are provided. 9. Oven according to claim 7 or 8, characterized in that the agitator chains (86) between the agitator arms (32) are arranged. 10. Oven according to one of claims 7 to 8, characterized in that each agitator chain (86) with one end at the outer end of a stirring arm (32) and with its other end at the inner end of the adjacent agitator arm (32) is attached. U. Oven according to one of claims 7 to 9, characterized in that each agitator chain (86) between the innermost stirring tooth (36) of a stirring arm (32) and the outermost stirring tooth (36) of the next adjacent agitator arm (32) is arranged. 12. Oven according to claim 7 or 8, characterized in that one end of each agitator chain (98) with the central shaft (28) and the other end of the agitator chain (98) off-center a stirring arm (32) is attached. 13. Oven according to claim 12, characterized in that the chain between the outermost Agitator tooth (36) of an agitator arm (32) and the central shaft (28) is arranged. 14. Oven according to one of claims 1 to 3, characterized in that the device for Generating the additional circumferential flow component from a rope (112) with several spaced apart mutually arranged blades (118), which is arranged between two agitator arms (32).