CN214537336U

CN214537336U - Rotary kiln

Info

Publication number: CN214537336U
Application number: CN202120247340.XU
Authority: CN
Inventors: 刘征官; 王萍; 刘钧云; 谢楠
Original assignee: Ganzhou Formos Technology Co ltd
Current assignee: Ganzhou Formos Technology Co ltd
Priority date: 2021-01-28
Filing date: 2021-01-28
Publication date: 2021-10-29
Anticipated expiration: 2031-01-28

Abstract

The utility model relates to a rotary kiln belongs to chemical industry equipment technical field. The device comprises a first rotary cylinder (1) and a second rotary cylinder (2), wherein the cross section of the first rotary cylinder (1) or the second rotary cylinder (2) is circular and/or elliptical or polygonal, and the second rotary cylinder (2) is longer than the first rotary cylinder (1); the second rotary cylinder (2) penetrates through the inside of the first rotary cylinder (1), and the outlet end of the second rotary cylinder (2) is positioned outside the first rotary cylinder (1). The utility model has the advantages of simple structure, safe and reliable adjusts the convenience, and production efficiency is high, area is little, need not plus heat basically, with low costs, the neodymium iron boron oxidation rate is high and stable, energy utilization is high, the product composition that obtains is even, and the specially adapted burns various neodymium iron boron waste materials and is favorable to improving the industrialization of the high value element in the neodymium iron boron waste material and retrieves and stably improve its quality.

Description

Rotary kiln

Technical Field

The utility model relates to a rotary kiln. Belongs to the technical field of chemical equipment.

Background

In the production of valuable elements such as rare earth recovered from neodymium iron boron waste, in order to reduce pollution and improve recovery rate, the pretreatment by firing is a common production method. Rotary kilns are common production facilities.

The publication date is 24 months and 12 months in 2014, and the publication number is CN104232905A, namely ' an iron hydroxide base material containing high-value elements and application thereof ' discloses ' an iron hydroxide base material containing high-value elements and application thereof. Belongs to the technical field of resource recycling and hydrometallurgy. The iron hydroxide-based raw material containing the high-value elements mainly comprises iron hydroxide, high-value element compounds and combustible organic matters. Wherein the iron accounts for 3.5-45 wt% of the element, the sum of the high-value elements accounts for 2-32 wt% of the oxide, and Y (Fe)³⁺) the/TFe is more than or equal to 54.47 wt%, the combustible organic matter is less than or equal to 6.5 wt% calculated by C, and the iron hydroxide-based raw material does not spontaneously combust at the temperature of less than or equal to 200 ℃, so that the product is powdery or easily crushed and has the advantages of uniform texture, difficulty in spontaneous combustion, convenience in use, safety and the like. Eliminates the fire hazard of the iron-based waste in the processes of transportation, loading, unloading, storage and production, and realizes safe production. When in use, the dissolution rate of each high-value element is high, and various elements can be prepared into different products, thereby realizing the maximum utilization of resources and being beneficial to the development of circular economy. The patent application does not disclose the production apparatus used and its structure.

The bulletin day is 2011 09 months 21 days, chinese utility model patent of publication No. CN201983601U named "neodymium iron boron waste material high efficiency oxidation calcination rotary kiln" discloses "an energy-concerving and environment-protective novel calcination device, it is made through reforming transform traditional rotary kiln, make the rotary kiln feed inlet be a little higher than the discharge gate, and simultaneously, the welding gear of rotary kiln outside, the rotational speed through controlling external buncher drives the gear, and simultaneously, increase three whirlwind gas wash tower and a water spray set and a pond at the discharge gate, at water spray setThe rear end of the device is additionally provided with a blower, and the rear end of the device is connected with a recovery device; increase a water tank in feed inlet department, and increased twice screening "technical scheme again at the discharge gate, gained" the utility model discloses simple process, processing is convenient, assembles easy "technological effect. However, the technical scheme of the patent application has the defects of complex structure, large occupied area, large energy consumption, high cost, large fluctuation of the oxidation rate of the neodymium iron boron, difficult control, low energy utilization rate and the like. Especially, the lump neodymium iron boron waste oil sludge contains a large amount of inflammable organic matters, has high viscosity, and is in a colloid state and difficult to grind and disperse. The neodymium iron boron at the central position is difficult to contact with air during firing and is difficult to be oxidized. The integral oxidation rate of the neodymium iron boron waste is reduced. Typically, the oxidation rate of the neodymium iron boron waste is about 70%. In order to ensure that the oxidation rate of the neodymium iron boron waste is not less than 90 percent, external heat is required, and the consumption of natural gas is reduced to 0.8M³More than t waste material.

SUMMERY OF THE UTILITY MODEL

To prior art's defect, the utility model provides a rotary kiln adopts following technical scheme:

the device comprises a first rotary cylinder 1 and a second rotary cylinder 2, wherein the cross section of the first rotary cylinder 1 or the second rotary cylinder 2 is circular, elliptical or polygonal, and the second rotary cylinder 2 is longer than the first rotary cylinder 1; the second rotary drum 2 penetrates through the inside of the first rotary drum 1, and the outlet end of the second rotary drum 2 is positioned outside the first rotary drum 1.

The utility model discloses one of preferred technical scheme still includes first draught fan 3 and/or first air-blower 4, the access connection of first draught fan 3 is in 1 exit end of first revolving drum, the exit connection of first air-blower 4 is in 1 entrance point of first revolving drum.

The utility model discloses another preferred technical scheme still includes second draught fan 5 and/or second air-blower 6, the access connection of second draught fan 5 is in 2 exit ends of second revolving drum, the exit connection of second air-blower 6 is in 2 entrance points of second revolving drum.

The utility model discloses another preferred technical scheme, first dust remover 7 and/or second dust remover 8, the access connection of first dust remover 7 is in 1 exit end of first revolving drum, second dust remover 8 is connected in 2 exit ends of second revolving drum.

The utility model discloses a still another preferred technical scheme, first revolving drum 1 and/or second revolving drum 2 still include internals 10, internals 10 is located first revolving drum 1 and/or 2 inner walls of second revolving drum.

The utility model discloses a preferred technical scheme again, internals 10 is "L" shape or "V" shape, has 2 at least in the same cross-section of first revolving drum 1 or second revolving drum 2, evenly distributed in the inner wall of first revolving drum 1 or second revolving drum 2.

In another preferred embodiment of the present invention, the inner member 10 is made of metal or alloy pipe with a suitable diameter. Namely, 10 to 40 percent of the pipe wall is cut off according to the circumference and then fixed on the long edge of one side of a corresponding plate with proper width, and then the long edge of the other side of the plate is fixed on the inner wall of the first rotary drum 1 or the second rotary drum 2, so that the width direction of the plate basically points to the center of the first rotary drum 1 or the second rotary drum 2.

The utility model discloses another preferred technical scheme, interior piece 10 is whole to be rectangular form, and the cross section direction has circular arc 104 and long handle 103, circular arc 104 is connected to the one end of long handle 103. When the device is mounted, the other end of the long handle 103 opposite to the connecting arc 104 is fixed to the inner wall of the first rotary cylinder 1 or the second rotary cylinder 2.

The utility model discloses a preferred technical scheme again, interior piece 10 is whole to be long banding, and the cross section direction has short handle 101, oblique handle 102 and long handle 103, short handle 101 and long handle 103 are connected respectively to the both ends of oblique handle 102. When the device is mounted, the other end of the long handle 103 opposite to the connection inclined handle 102 is fixed to the inner wall of the first rotary cylinder 1 or the second rotary cylinder 2.

In another preferred embodiment of the present invention, the short handle 101 and the inclined handle 102 form an acute angle.

The utility model discloses another preferred technical scheme, internals 10 is along first revolving

drum

1 or 2 length direction dislocation arrangements of second revolving drum.

The utility model discloses another preferred technical scheme still includes reducing mechanism 9, reducing mechanism 9 is located behind the export of first rotary drum 1.

The utility model discloses a still another preferred technical scheme still includes first sieve 11 and/or second sieve 12, first sieve 11 is located under the export of first revolving drum 1 or is located after reducing mechanism 9, second sieve 12 is located after the export of second revolving drum 2.

In another preferred embodiment of the present invention, the length direction of the inner member 10 has an included angle with the horizontal plane. The included angle is preferably 1 to 5 degrees.

The utility model discloses a preferred technical scheme again, the feed inlet and the air intake of first revolving drum 1 are located each one side of first revolving drum 1 respectively. Namely, the advancing direction of the neodymium iron boron waste materials in the first rotary cylinder 1 is opposite to the advancing direction of the air flow.

The utility model discloses another preferred technical scheme still includes cooling jacket 13. The cooling jacket 13 is positioned at the outlet end of the first rotary drum 1 and/or the second rotary drum 2.

The utility model discloses another preferred technical scheme still includes connecting rod 14. The connecting rod 14 fixedly connects the first rotary drum 1 and the second rotary drum 2.

The utility model has the advantages of simple structure, safe and reliable adjusts the convenience, and production efficiency is high, area is little, need not plus heat basically, with low costs, the neodymium iron boron oxidation rate is high and stable, energy utilization is high, the product composition that obtains is even, and the specially adapted burns various neodymium iron boron waste materials and is favorable to improving the industrialization of the high value element in the neodymium iron boron waste material and retrieves and stably improve its quality.

Drawings

Fig. 1 is a schematic view of embodiment 1 to embodiment 10 of the present invention.

Fig. 2 is a schematic view of embodiment 1, embodiment 2 and embodiment 6 to embodiment 10 of the present invention.

FIG. 3 is a schematic view of example 3.

FIG. 4 is a schematic view of examples 4 and 5

Detailed Description

Example 1

A rotary kiln, see fig. 1, 2.

Comprises a first rotary cylinder 1, a second rotary cylinder 2, a Roots blower 4, an internal part 10, a cooling jacket 13, a connecting rod 14 and a transmission system.

The first rotary cylinder 1 and the second rotary cylinder 2 are both cylindrical, one end of the first rotary cylinder is a feeding end, and the other end of the first rotary cylinder is a discharging end. Wherein the diameter of the first rotary cylinder 1 is larger than that of the second rotary cylinder 2, and the second rotary cylinder 2 is longer than the first rotary cylinder 1. The second rotary cylinder 2 penetrates through the first rotary cylinder 1, and two ends of the second rotary cylinder 2 extend out of two ends of the first rotary cylinder 1; the center lines of the first rotary drum 1 and the second rotary drum 2 are substantially in the horizontal plane. One end of the connecting rod 14 is fixed on the inner wall of the first rotary drum 1, and the other end is fixed on the outer wall of the second rotary drum 2, so that the first rotary drum 1 and the second rotary drum 2 are connected into a whole body which can rotate at the same time by a common transmission system (not shown in the figure). The first rotary cylinder 1 and the second rotary cylinder 2 are both internally provided with a plurality of internal parts 10. The inner member 10 is a long handle 103, and is long and rectangular in cross section. The length direction of the installation is consistent with the basic length direction of the first rotary drum 1 or the second rotary drum 2. A plurality of groups of internal parts 10 are respectively arranged in the first rotary cylinder 1 and the second

rotary cylinder

2, and 8 internal parts 10 in each group are uniformly distributed on the inner walls of the first rotary cylinder 1 and the second rotary cylinder 2. When each internal member 10 is installed, one end of the long handle 103 in the width direction is fixed on the inner wall of the first rotary cylinder 1 or the second rotary cylinder 2, and the other end is a non-fixed end; the non-fixed end points to the center of the first rotary cylinder 1 or the second rotary cylinder 2, one side of the feeding end of the long handle 103 in the length direction is a plurality of centimeters higher than one side of the discharging end, and when the projection distance of each symmetrical internal part 10 on the horizontal plane is the maximum, the same included angle is formed between each symmetrical internal part and the horizontal plane. Preferably, each internal member 10 is angled from 1 to 10 degrees (most preferably 3 to 5 degrees) from the horizontal.

And an air outlet of the Roots blower 4 is connected to the discharge end of the first rotary cylinder 1. An air outlet of the first rotary cylinder 1 (positioned at the feed end of the first rotary cylinder 1) is connected with an air inlet of the second rotary cylinder 2 through a pipeline respectively. The cooling jacket 13 is positioned on the outer wall of the outlet end of the second rotary drum 2.

During operation, the roots blower 4 sends cold air into the first rotary cylinder 1 from the discharge end of the first rotary cylinder 1, is heated by heat released by neodymium iron boron reaction, gradually heats up to 200-. The hot air enters the second rotary drum 2 after leaving the first rotary drum 1 and reacts with the neodymium iron boron waste in the second rotary drum 2, and the tail gas after the reaction is cooled by the cooling jacket 13 before leaving the second rotary drum 2. In the reaction process, the neodymium iron boron waste materials are acted by the internal member 10, slide downwards along the inner wall of the first rotary cylinder 1 or the second rotary cylinder 2 after rising to a certain height along with the internal member 10, continuously stir the solid materials in the first rotary cylinder 1 and the second rotary cylinder 2, crush the neodymium iron boron waste material blocks to a certain extent, expose fresh neodymium iron boron waste materials, and promote the release of the contained organic matters. Because one side of the feeding end of the internal part 10 in the length direction is higher than the discharging end, the neodymium iron boron waste materials gradually move from the feeding end to the discharging end along with the rotation of the first rotary cylinder 1 and the second rotary cylinder 2. Meanwhile, the temperature of the neodymium iron boron waste in the first rotary cylinder 1 is controlled to be 600-800 ℃ by adjusting the air volume and/or the quantity and the rotating speed of the neodymium iron boron waste so as to control the reaction speed of the neodymium iron boron waste. If the oxidation rate of the neodymium iron boron waste material leaving the first rotary drum 1 is low, the neodymium iron boron waste material can be transferred to the second rotary drum 2 to control the neodymium iron boron waste material to be continuously oxidized at the temperature of 300-650 ℃. The oxidation reaction is kept to be continuously carried out by means of the heat released by the neodymium iron boron waste material in the production process, and heat is not required to be supplied from the outside.

The hot air after the reaction leaves the first rotary cylinder 1 and immediately enters the second rotary cylinder 2 to continue to react with the neodymium iron boron waste in the second rotary cylinder 2. Neodymium iron boron waste in the second rotary drum 2 accepts on the one hand that 2 transfers of second rotary drum come from the heat that neodymium iron boron waste reacted and emitted in the first rotary drum 1, and on the other hand directly contacts with hot-air, has improved the neodymium iron boron waste in the second rotary drum 2 and has oxidized speed and oxidation rate, and neodymium iron boron waste oxidation rate reaches about 95%. Because the second rotary drum 2 passes through the inside of the first rotary drum 1, the length of the rotary kiln is greatly shortened, and the occupied area is saved.

Can carry out continuous processing to a slice neodymium iron boron waste material in first revolving cylinder 1 and second revolving cylinder 2, also can handle the same or different neodymium iron boron waste material of two copies respectively simultaneously. The neodymium iron boron waste material in the second rotary drum 2 can utilize the reaction heat initiation oxidation reaction of the neodymium iron boron waste material in the first rotary drum 1, saves fuel.

The first rotary cylinder 1 and the second rotary cylinder 2 are reversely rotated for a short time, the discharging end can temporarily stop discharging, and the reaction time of the neodymium iron boron waste is prolonged. The feeding and discharging ends of the first rotary drum 1 and the second rotary drum 2 can be changed.

Example 2

A rotary kiln, see fig. 1, 2.

This embodiment is substantially the same as embodiment 1 except that the non-fixed end of the long handle 103 is directed to the center of the first rotary cylinder 1 or the second rotary cylinder 2 and is tilted upward in the opposite direction to the rotation of the first rotary cylinder 1 or the second rotary cylinder 2.

When the first rotary drum 1 and the second rotary drum 2 rotate, the inner member 10 can bring the ndfeb scrap to a higher position.

Example 3

A rotary kiln, see fig. 1, 3.

This embodiment is substantially the same as embodiment 1 except that the inner piece 10 has a long shank 103 and a circular arc 104. The arc 104 is 3/4 of a pipe, one end of the arc is fixedly connected with the non-fixed end of the long handle 103, and a gap is reserved between the other end of the arc and the long handle 103. Preferably the gap is 1/4 of the inner diameter of the tubing.

When first revolving cylinder 1 and second revolving cylinder 2 are rotatory, circular arc 104 can fall down neodymium iron boron waste material area to the central line of crossing first revolving cylinder 1 or second revolving cylinder 2, spill the outer wall of second revolving cylinder 2 with the partial high temperature neodymium iron boron waste material in first revolving cylinder 1, help improving the temperature of neodymium iron boron waste material in second revolving cylinder 2, and make the neodymium iron boron waste material more even in first revolving cylinder 1 or second revolving cylinder 2, still be favorable to smashing lumpy neodymium iron boron waste material. And more neodymium iron boron scrap is stored in the inner piece 10.

Example 4

A rotary kiln, see fig. 1, 4.

This embodiment is substantially the same as embodiment 3 except that each of the inner pieces 10 is composed of a sloping shank 102 and a long shank 103. One end of the inclined handle 102 is fixedly connected with the non-fixed end of the long handle 103, and the inclined handle 102 and the long handle 103 form an acute angle.

The inner member 10 of the present embodiment is easy to manufacture.

Example 5

A rotary kiln, see fig. 1, 4.

This embodiment is substantially the same as embodiment 4, except that each of the inner members 10 has an "umbrella" shape, and is composed of 2 inclined stems 102 and 1 long stem 103. The 2 inclined handles 102 are respectively and fixedly connected with one side of the non-fixed end of the long handle 103, and each inclined handle 102 and the long handle 103 form an acute angle.

When the first rotary cylinder 1 and the second rotary cylinder 2 rotate forwards or backwards, the efficiency can be kept unchanged.

Example 6

A rotary kiln, see fig. 1, 2.

This embodiment is substantially the same as embodiment 1 except for the absence of the connecting rod 14. The first rotary drum 1 and the second rotary drum 2 are respectively provided with independent transmission systems (not shown in the figure).

In this embodiment, the first rotary drum 1 and the second rotary drum 2 may rotate in the same direction or in opposite directions without interfering with each other.

Example 7

A rotary kiln, see fig. 1, 2.

The present embodiment is substantially the same as embodiment 1, except that a second induced draft fan 5 and a second cyclone separator 8 are further included. And an air inlet of the second induced draft fan 5 is connected with an air outlet of the second rotary cylinder 2, an air outlet of the second induced draft fan is connected with an air inlet of the second cyclone separator 8, and tail gas in the second rotary cylinder 2 is sent into the second cyclone separator 8 to separate dust in the tail gas and then is discharged.

Example 8

A rotary kiln, see fig. 1, 2.

This example is substantially the same as example 7, except that: firstly, the device also comprises a pulverizer 9, a first sieve 11 and a second sieve 12; and the second cyclone separator 8 is replaced by a second pulse bag filter 8.

The pulverizer 9 is provided with 2 sets of pulverizing machines which are respectively positioned behind the discharge ports of the first rotary cylinder 1 and the second rotary cylinder 2. The first screen 11 and the second screen 12 are located after 1 pulverizer, respectively.

The neodymium iron boron waste materials discharged from the first rotary cylinder 1 and the second rotary cylinder 2 are respectively crushed by the crushers 9, then are sieved by the first sieve 11 or the second sieve 12, the neodymium iron boron powder with qualified granularity enters a subsequent working section, and the sieved residues return to the corresponding crushers 9 to be continuously crushed.

And the second pulse bag filter 8 is used for replacing the second cyclone separator 8, so that the dust removal efficiency is higher, and the recovery rate of the neodymium iron boron waste is higher.

Example 9

A rotary kiln, see fig. 1, 2.

Comprises a first rotary drum 1, a second rotary drum 2, a first blower 4, an internal part 10, a cooling jacket 13 and a transmission system.

The first rotary cylinder 1 and the second rotary cylinder 2 are both in a circular truncated cone shape with a small feeding end and a large discharging end. The second rotary cylinder 2 penetrates through the first rotary cylinder 1, and two ends of the second rotary cylinder 2 extend out of two ends of the first rotary cylinder 1; the center lines of the first rotary drum 1 and the second rotary drum 2 are substantially in the horizontal plane. The first rotary cylinder 1 and the second rotary cylinder 2 are both internally provided with a plurality of internal parts 10. The inner member 10 is a long strip and includes a first inner member and a second inner member. The cross section of the second internal part is L-shaped, and the second internal part is provided with a short handle 101, an inclined handle 102 and a long handle 103, wherein the two ends of the short handle 101 are respectively connected with the inclined handle 102 and the long handle 103. The first inner piece is only provided with a long handle 103 and is arranged at the feeding end of the first rotary cylinder 1. The rest parts of the first rotary cylinder 1 and the second rotary cylinder 2 are provided with a second internal part. 6 pieces of internal parts 10 are respectively arranged on a certain section of the first rotary cylinder 1 and the second rotary cylinder 2 and are uniformly distributed on the inner walls of the first rotary cylinder 1 and the second rotary cylinder 2. When each internal member 10 is installed, the other end of the long handle 103 opposite to the connecting short handle 101 or the inclined handle 102 is fixed on the inner wall of the first rotary drum 1 or the second rotary drum 2, and when the projection distance of the symmetrical 2 internal members 10 on the horizontal plane is maximum, the height of the feeding end is basically the same as that of the discharging end.

And an air outlet of the first air blower 4 is connected to the discharge end of the first rotary drum 1. The transmission system has 2 sets (not shown in the figure), and the first rotary drum 1 and the second rotary drum 2 are respectively provided with independent transmission systems.

During operation, the neodymium iron boron waste material moves from the feed end to the discharge end gradually along with the inclination of the inner walls of the first rotary cylinder 1 and the second rotary cylinder 2.

Example 10

A rotary kiln, see fig. 1, 2.

This embodiment is substantially the same as embodiment 9, except that: the cross sections of the first rotary cylinder 1 and the second rotary cylinder 2 are polygonal cylinders; and secondly, the center lines of the first rotary cylinder 1 and the second rotary cylinder 2 are superposed, and form an included angle with the horizontal plane, and the feeding end is higher than the discharging end and is lower than the discharging end. So that the neodymium iron boron waste materials gradually move from the feeding end to the discharging end along with the rotation of the first rotary cylinder 1 and the second rotary cylinder 2.

The above is only several preferred modes enumerated in the utility model, and those skilled in the art should understand, the utility model discloses the embodiment is not limited to above several kinds, and any is in the equivalent transformation of doing on the basis of the utility model, for example in the suitable position of first revolving drum 1 and second revolving drum 2 sets up insulation material and resistant firebrick etc. or with cold air all should belong to the scope of the utility model through cooling jacket preheats etc..

Claims

1. A rotary kiln comprises a first rotary cylinder (1) and a second rotary cylinder (2), wherein the cross section of the first rotary cylinder (1) or the second rotary cylinder (2) is circular, oval or polygonal, and the second rotary cylinder (2) is longer than the first rotary cylinder (1); the device is characterized in that the second rotary cylinder (2) penetrates through the inside of the first rotary cylinder (1), and the outlet end of the second rotary cylinder (2) is positioned outside the first rotary cylinder (1).

2. A rotary kiln according to claim 1, further comprising a first induced draft fan (3) and/or a first blower (4), wherein an inlet of the first induced draft fan (3) is connected to an outlet end of the first rotary drum (1), and an outlet of the first blower (4) is connected to an inlet end of the first rotary drum (1).

3. A rotary kiln according to claim 1, further comprising a second induced draft fan (5) and/or a second blower (6), wherein an inlet of the second induced draft fan (5) is connected to an outlet end of the second rotary drum (2), and an outlet of the second blower (6) is connected to an inlet end of the second rotary drum (2).

4. A rotary kiln according to claim 1, further comprising a first dust collector (7) and/or a second dust collector (8), wherein an inlet of the first dust collector (7) is connected to an outlet end of the first rotary drum (1), and the second dust collector (8) is connected to an outlet end of the second rotary drum (2).

5. A rotary kiln according to claim 1, characterized in that the first rotary drum (1) and/or the second rotary drum (2) further comprises an internal member (10), the internal member (10) being located on the inner wall of the first rotary drum (1) and/or the second rotary drum (2).

6. A rotary kiln according to claim 5, characterized in that the internal member (10) is L-shaped, and at least 2 members are uniformly distributed on the inner wall of the first rotary drum (1) or the second rotary drum (2) at the same section of the first rotary drum (1) or the second rotary drum (2).

7. A rotary kiln according to claim 5 or 6, characterized in that the internals (10) are arranged offset in the direction of the length of the first rotary cylinder (1) or the second rotary cylinder (2).

8. A rotary kiln according to claim 1, further comprising a crushing device (9), the crushing device (9) being located after the outlet of the first rotary drum (1).

9. A rotary kiln according to claim 8, characterized in that it further comprises a first screen (11) and/or a second screen (12), said first screen (11) being located below the outlet of the first rotary drum (1) or after the crushing means (9), said second screen (12) being located after the outlet of the second rotary drum (2).

10. A rotary kiln according to claim 5 or 6, characterized in that the longitudinal direction of the internals (10) is angled in relation to the horizontal plane.