EP0917640B1 - Rotary drum for drying pourable goods - Google Patents

Description

The invention relates to a rotary drum for drying free-flowing material according to the Preamble of claim 1.

Such a rotary drum is from DE-C 33 45 118 known.

When drying free-flowing material, especially when drying wood chips and strands, directly heated rotary drums are used. The good and that Drying gas abandoned at the inlet of the rotating drum and the dried good and that Drying gas drawn off at the outlet.

To achieve a good heat transfer from the drying gas to the good is from the Book: K Kröll "dryer and drying process", Springer-Verlag 1959, pages 475 to 479, known to provide the rotary drums with internals. The internals serve this purpose. the Good to split into several sub-piles, to distribute it evenly in the drum cross-section, to give it a large surface and keep it across the gas flow let it trickle through. The cross internals described there are from Applicant often used for drying wood chips.

Cross internals are also known from DE-B 23 62 725 and from DE-B 29 11 137. They are for drying strands, 5 to 50 mm wide and 75 to 150 mm long wooden parts, OSB boards are not made from. A rotary drum with tight arranged cross internals, as used for drying wood chips, would easily clog when drying strands. If you increase the Distance between the cross internals, so the heat transfer from the drying gas to the goods too low. In addition, they have the disadvantage of relatively high manufacturing and installation costs.

Further trickle internals for a rotary drum are described in DE-B 18 04 154. These trickle internals have radially inserted, partially permeable, the cross section of Drum row walls dividing into equal sectors, which over openings consistently connected with each other. The cell walls are on their inside According to the direction of rotation of the drum on the rear side equipped with webs, soft running almost vertically on the walls and parallel to the drum axis are arranged. Furthermore, are on the inner periphery of each sector Lifting paddles arranged. With this arrangement, the material trickles from the internals of a sector almost at the same time. In the last part of the drum rotation are the Sectors therefore only slightly filled. The distribution of the goods over the cross section of the Drum is uneven. Exist within a sector, at least with drums large cross-section, too long falling distances, in which the material is due to the drying gas can be carried away. If the openings in the cell walls are chosen too large, then so if the effect increases, if you choose it too small, there is a risk of constipation.

In a drum known from DE-B 1 230 703 divide partitions, as from DE-B 18 04 154 known, the cross section of the drum in mutually identical sectors. It exists however no connection between the individual sectors, so that the good only within a sector is circulated. The entire good cannot be circulated. Due to the arrangement and small number of sheets on the sectors exist within the sectors Partition walls and large falls in the circumference, in which the goods are carried away can.

In the drying drum known from DE-C 423 753: the cross section is also divided into cells by built-in cells. Intermediate sheets that serve as throwing bars are all of a shape and size. You divide that by an outside or an or several inner drum tubes formed circular mantles in cells. Disadvantage of this strong The division into cells is the lack of circulation of the entire good. A Uniformization of a different degree of moisture of the incoming goods in the Different cells are not possible in the course of drying.

In a drum known from DE-C 288 896, they have the cross section of Drum dividing walls into cells on the inside and outside of each two Lifting blades on. The crop flow is strong due to the lifting blades attached on both sides led, which prevent a uniform trickle. This arrangement leads to one small number and extension of the lifting blades to large fall distances or harbors larger number of lifting blades the risk of clogging. The denser the assembly with lifting blades, the greater the design effort.

From DE-C 33 45 118 is a generic device for drying sugar known with a rotary tube. The rotary tube is inside with several Circumferential sets of outer, evenly distributed trickle blades equipped. All outer trickle blades of a circumferential set extend in the axial direction a certain length of the rotary tube. The outer trickle scoops in a row arranged circumferential sets are staggered. At the center of the Rotary tube is an installation fastened to the rotary tube with an elongated support, which is provided on the outside with inner, approximately radiating trickle blades, intended. These trickle internals are also for drying the lighter wood chips and beaches not suitable. The fall distances inside the rotary tube are too large. Is too the total area of the internals is too small for effective heat emission.

The object of the invention is a rotary drum for drying free-flowing material to develop according to the preamble of claim 1 for drying wood chips and is suitable for drying strands, good heat transfer from Allows drying gas on the goods and their manufacturing and assembly costs are at least not higher than those of cross internals.

The object is achieved by the characterizing features of claim 1.

A rotary drum according to the invention is particularly suitable for drying wood chips and beaches and chip material with long chips, but also for drying other, free-flowing Suitable material.

According to the invention, the internals extend from the circumference in the direction Drum center in the form of a beam over a larger area of the drum radius. The area is at least 60% and at most 85% of the drum radius. Compared to Cross fittings are somewhat cheaper to manufacture. Instead of To manufacture welded cross internals can be radiating internals For example, be made from folded sheets. The radiating internals can, if they consist of one part, only be attached to the circumference of the rotating drum. They can also consist of two parts, the outer part on the circumference of the Rotary drum is attached and the inner inside, for example on an inner tube. In both cases, the assembly is easier than that of cross internals.

The material is broken down into several sub-piles by the radiation-shaped internals. The Extension of the internals over 60 to 85% of the drum radius enables a large one Installation area. The larger the installation area, the sooner the surface of the goods and the Dwell time of the goods in the rotating drum can be increased, and the better Heat transfer. In the case of radial installations, there is also a faster one Uniform distribution of the goods over the drum cross-section instead of as with cross installations.

The more coarse that is to be dried, the smaller the number of radiation-shaped internals Good is. With a similar drum cross-section, the number of radiation-shaped ones is Fittings for drying strands only 0.5 to 0.8 times those for Drying wood chips.

The radial internals form from the circumference to the center of the drum at least two pockets. A bag becomes two in one in the direction of rotation itself opening angle, for example 90 degrees, arranged to each other Sections of the radiating internals formed. The first section is one Pocket often arranged approximately radially. The second section of the first bag closes either directly, in the case of one-piece radial installations, or after one small, e.g. B. bridged by a baffle, the first section of the gap second bag. The second or, if there are several pockets, the last pocket can be used connect another section. Training with bags and one more Section leads to a cascade-shaped configuration of the radiation-shaped internals. The goods are further divided by the pockets and when they trickle out of the pockets distributed over the drum cross-section during the rotary movement. You decrease that Stretch free fall and ensure that the goods are circulated and loosened up.

The course of the radial internals begins approximately on the radial beam their attachment point on the circumference and continues by training the pockets in front of the Radial jet away. If you divide the drum cross section into by the attachment points limited sectors, so paint over the radiating internals on their way to Drum center at least half of their sector in front of the radial beam. Especially at A large number of radiating internals can cover the entire sector paint over and protrude towards the middle of the drum into the next sector. This course of radiating internals causes their pockets to be emptied one after the other during operation be, especially that in half of the drum cross-section to the direction of rotation well, trickles well out of the pockets.

The extension up to the middle of the drum, the formation of at least two Bags and the course of the radiation-like internals in the upstream sector enable a homogeneous distribution of the trickling material over the drum cross-section, a large drying area and thus good heat transfer from the drying gas on the estate.

Structurally simple and thus easy to manufacture and assemble, are one-piece, radiating internals each from a mounting sheet according to claim 2. Zur Stabilization are the mounting plates of a set on one or more, along the Drum axis one behind the other, for example at three points, one in the Start area, one in the middle and one in the end area, by circular arranged Connected to each other. Through these connectors also balls that form when drying long, low density beaches can, dissolved or adhering good parts detached from each other. As Pipe sections with a round diameter are particularly suitable.

The arrangement of one or more rings according to claim 3, for example at the beginning, in the middle and at the end of a sentence, at which the ends of all radiating internals or the ends of a part of equal length are used for further stabilization. By lifting blades, which according to claim 4 additionally between the radial Installations are arranged, there is a further division of the goods and a Improvement of the distribution of the trickling material over the cross section. The lifting blades are arranged at a slightly positive or at a negative angle to the radial beam and flat or angled in the direction of rotation.

An offset of the radiating internals in accordance with sentences arranged Claim 5, for example by half the sector width, leads to a shift of the goods, thus increasing the dwell time and improving the Heat transfer.

According to claim 6 before or after a set or between sets of radiating Built-in zones with curved lifting vanes, angled in the direction of rotation, the length of which is approximately 20% of the length of the radial internals of a set, to avoid clogging at the transition from one sentence to another.

The arrangement of baffle plates in front of or behind a set of radial Installations according to claim 7, wherein a baffle plate as a round, central disc or as middle or outer ring can be formed, extended by stowing the goods Dwell time.

For different types of radiating internals with different lengths or with different number, shape and arrangement of the pockets according to claim 8 the trickling of the goods out of the pockets can be varied even more. The emptying the different pockets can be pulled apart better in time, so that the Distribution of the material flowing through the cross section is even more homogeneous.

Fixtures with different lengths, some of the fixtures closer to The middle of the drum protrudes than the others and has the advantage that the product is without Risk of blockage is evenly distributed in the middle of the drum.

The features of claims 9 to 11 are particularly for wood chips and beaches and goods, which have a similar drying and trickling behavior as this, suitable.

Opening angle of the pockets from 70 to 140 degrees according to claim 9, position angle of the Pockets from 10 to -30 degrees to the radial beam, the angle between the radial beam through the top edge of the first section and the first section a pocket is defined and the tracing of the position angle to the direction of rotation is related, according to claim 10 and the heights and widths of the bag, which by the Lengths of the first and second sections are set according to claim 11 a homogeneous distribution of the material flowing through the cross section.

The invention will be further illustrated by examples shown schematically in the drawing explained.

Figure 1 is a process diagram of a plant for drying wood chips or beaches.

FIG. 2 shows an interrupted longitudinal section through a rotary drum of an example 1 for drying strands and FIGS. 3, 4, 5 and 6 show cross sections A-A, B-B, C-C, D-D by the rotary drum at the locations marked in Figure 2. In Figure 7 is a Cross section through a rotating drum of an example 2 for drying wood chips shown.

A plant for drying wood chips or beaches has, if necessary Lines connected in series, a combustion chamber 1, a mixing chamber 2 Power tube 3, a rotating drum 4, and a cyclone 5. One leads from cyclone 5 Return gas line 7 having fan 6 to the mixing chamber 2. Behind the fan 6 a line 9 leading to the chimney 8 branches off from the return gas line 7. In FIG. 1 also A wet material feed 10 and a coarse material lock 11 are indicated, both on the flow tube 3, and a dry material discharge 12 on the cyclone 5.

The rotary drum 4 is divided into an inlet, a central part 13, and an outlet, wherein the inlet has a first part 14 with a diameter smaller than the drum diameter of the middle part 13 and a second, conically widening part 15 and the outlet a first, conically tapering part 16 and a second part 17 with a smaller one Have diameter.

On the parts 14, 17 with a smaller diameter of the inlet and the outlet Races 18, which are supported on bearings 19, attached. A bearing 19 points for example, bearings with rollers.

The rotary drum 4 can also be used without a conically widening or conically tapering Parts 15, 16 may be formed. At the end of the rotary drum 4, a failure housing for the dried good can be provided.

The rotary drum 4 is arranged horizontally in Examples 1 and 2. You can also in Direction of conveyance be inclined.

In operation, the material to be dried is passed to the flow tube 3 through the wet material feed 10 supplied, in the flow tube 3 through the coming from the combustion chamber 1 and with recycled vapors pre-dried in the mixing chamber 2 mixed drying gases and rotating, for example at 1 to 10 revolutions per minute Rotary drum 4 dried to final moisture.

The dried material is drawn off in cyclone 5. A part of the brothers is in the Mixing chamber 2 returned, the rest leaves the system, possibly after one Cleaning, by the chimney 8.

In particular for drying strands, the system can be designed without a flow tube 3 his.

Example 1 (Figures 2 to 6):

A rotary drum 4 for drying strands has a double jacket 20 in the inlet and distributed in the inlet and outlet over the circumference, as lifting and transport blades trained internals 21, 22, the internals 21 in the second part 15 of the inlet are arranged slightly helically. The rotary drum 4 can also be a simple one Have coat.

Inside the middle part 13 of the rotary drum 4 there is at least one set 23 of its own In the direction of the drum axis 24 extending internally distributed internals. The Installations of a set 23 project radially from the circumference of the rotary drum 4 towards the middle of the drum. The area covered by the internals is 60 to 85% of the drum radius. The radiating internals run outside the circumference essentially in the direction of rotation 25 in front of one by its attachment point 26 Circumferential radial beam and form in their course from the circumference to the center of the drum at least two pockets.

The radiating internals each consist of a mounting plate, the axial Length corresponds to the length of a set 23. In this example there are a total of twelve cascade-shaped mounting plates, namely six of two different types A, B, alternately, distributed over the circumference. Type A mounting plates are longer and form more pockets than those of type B.

The type A mounting plates form three pockets and extend over them a range of 75% of the drum radius. For this purpose, a type A mounting plate is provided in seven, sections 27, 28, 29, 30, 31, 32 and 33 arranged at an angle to each other divided, with the mounting plate attached to the circumference with the section 27 and with the last section 33 protrudes into the middle of the drum. Sections 27 and 28 form the first and the second section of the first pocket, sections 29 and 30 the first and second section of the second pocket and sections 31 and 32 the first and second Section of the third pocket.

The type B mounting plates form two pockets and extend over them an area of 64% of the drum radius. The type B mounting plate is in five Sections 34, 35, 36, 37 and 38 divided, the mounting plate with the section 34 attached to the circumference and protrudes with the last section 38 in the middle of the drum. The Sections 34 and 35 form the first and second sections of the first pocket and sections 36 and 37 the first and second sections of the second pocket.

The opening angles of the bags are 70 to 140 degrees. The opening angle of the Pockets of the type A mounting plate differ only slightly and are in the range of 90 degrees. The pockets of the type B mounting plate differ more, at least one opening angle is greater than 100 degrees.

The mounting plates are shaped so that the pockets are at an angle of 10 degrees are arranged up to -30 degrees to the radial with respect to the direction of rotation, with inner Bags tend to have a negative attitude angle. If the opening angle of the Little difference between pockets of a mounting plate, as with type A, the position angle is the Bags from the outside in are becoming increasingly negative. The lengths of the first sections of the Pockets are 0.15 to 0.25 times and the lengths of the second sections of the Bags 0.05 to 0.15 times the drum radius.

The three pockets of the type A mounting plate have opening angles of 95 degrees, 90 Degrees and 90 degrees and are under attitude angles of 0 degrees, -7 degrees and -13 degrees arranged. The lengths of their first sections 27, 29, 31 are each 0.21 times and that of its second portions 28, 30, 32 0.13 times, 0.1 times and that 0.05 times the drum radius. The last section 33 of the mounting sheet is under one Position angle of -20 degrees arranged. Its length is 0.11 times that Drum radius.

The two pockets of the type B panel have opening angles of 95 degrees and 118 degrees up and are arranged at angles of 0 degrees and -7 degrees. The lengths its first sections are 0.21 times and 0.15 times and the lengths of their second sections both 0.13 times the drum radius. The last section is 38 arranged at an angle of 2 degrees. Its length is 0.11 times that Drum radius.

Through this formation of the installation sheets of both types A, B, their course begins in each case the radial beam through the attachment point 26 and continues by training the Pockets away from the radial. If you divide the drum cross section into Fastening points 26 limited twelve sectors, so paint over the mounting plates their way to the middle of the drum two thirds of their sector, in the case of type A, and half their sector, in the case of type B, in front of the radial beam.

The mounting plates of a set 23 are in three places, one in each Direction of conveyance 39 in the beginning area, in the middle and in the end area of the set 23 circularly arranged connectors 40 connected to each other. As Connectors 40 are tubular sections with a round cross section. The Connectors 40 are at a distance of 40 to 60% of the drum radius Drum axis 24, arranged within the outer two pockets of the mounting plates. she are in this example near the second pocket of the type A and B mounting plates arranged on half the drum radius.

A set 23 also has three, centered at the beginning, in the middle and at the end of the Set 23 arranged rings 41 on which the ends of the sections 33 of the internals of the longer type A are attached. The radius of the rings 41 is depending on the length of the mounting plates attached to them 25 to 30% of the drum radius.

Between the mounting plates there are twelve at a position angle of, for example, -9 degrees straight lifting blades 42 arranged.

In FIGS. 2 to 6 there is a circumferential ring located at the end of the set 23 43 to see.

In the rotating drum 4 are eight sets 23 of one behind the other in the conveying direction 39 radiating internals, of which only five in Figure 2 due to the interruption see are arranged. The radiating internals, i.e. the mounting plates, one on top of the other The following sentences 23 are installed offset from one another. Here are how the comparison of the Figures 3 and 4 shows the mounting plates of the second set 23 by half a sector width rotated about those of the first set 23 about the drum axis 24. Also the Installation baffles of the following sentences 23 are half of the previous ones Sector width rotated.

Between the sets 23 there are zones 44 in which twelve curved, namely angled in the direction of rotation, lifting blades 45 are attached. The length of one Zone 44 is approximately 20% the length of a set 23.

A total of three baffle plates 46, 47, 48 are inserted in the rotary drum 4, the annular, an area between the ring 41 and about the middle of the second pockets of the Baffle plate 46 covering mounting plates (FIG. 4) in conveying direction 39 before the second Set 23 and the two centric, covering the central area up to the ring 41 Baffle plates 47, 48 are arranged behind the second and behind the seventh set 23.

The arrangement of the baffle plates 46, 47, 48 in the rotary drum 4 can vary. In the However, the first three sets 23 of a rotary drum is always one or more Baffle plates arranged. For rotary drums 4 with a larger diameter are the Baffle plates arranged further forward than those with a smaller diameter. It baffle plates, which are designed as an outer ring, are also used.

In operation, the material to be dried is divided by the internals 21 in the inlet the installation sheets again and again transversely to the conveying direction 39, homogeneously over the cross section distributed moved and dried by contact with the drying gas. The Displacement of the mounting plates of different sets 23 and the baffle plates 46, 47, 48 a long dwell time.

Example 2 (Figure 7):

A rotary drum 4 of Example 2 for drying wood chips is essentially like constructed a rotary drum 4 of Example 1. It differs from it in that a total of twenty cascade-shaped mounting plates, ten each two different types A and B are installed. Type A mounting plates are also longer than that of type B, with type A mounting plates over a range of 82% and that of type B extend over a range of 73% of the drum radius. The Installation sheets of both types A and B form two pockets in the course of which they each are divided into five sections 49, 50, 51 52, 53 (type A) and 54, 55, 56, 57, 58 (type B).

The two pockets of the type A mounting plate have an opening angle of 83 degrees and 90 degrees and are arranged at angles of 0 degrees and -1.5 degrees. The lengths its first portions 49 and 51 are 0.27 times and 0.30 times and theirs second sections 50 and 52 0.10 times and 0.08 times the drum radius. The last section 53 of the mounting plate is arranged at a position angle of -8 degrees. Its length is 0.28 times the drum radius.

The two pockets of the type B mounting plate also have an opening angle of 83 Degrees and 90 degrees and are arranged under position angles of 0 degrees and -2 degrees. The Lengths of their first sections 54 and 56 are 0.19 times and 0.30 times and Lengths of the second sections 55 and 57 0.10 times and 0.09 times the Drum radius. The last section 38 is arranged at a position angle of 5 degrees. Its length is 0.27 times the drum radius.

In this example, the opening angles of the pockets are both types A and B. equal to each other and in the range of 90 degrees. For the longer mounting plates of the type A, the second pockets are arranged further towards the drum axis 24 than those of type B.

Connectors 59 are outside of the second sections 52 and 57 of the second Pockets of the mounting plates at a distance of about 60% of the drum radius Drum axis 24 arranged.

In contrast to example 1, the ends of the last sections 38 are the shorter Type B mounting plates attached to rings 60.

In addition, the sets 23 each have an inner tube 61, which by means of struts 62 with the Rings 60 is connected.

Type A mounting plates cover the entire sector in front of their radial beam and those of type B about two thirds of the sector in front of their radial beam.

Alternating between the mounting plates are two types C and D of lifting blades 63, 64, the lifting blades 63 of type C are straight and those of type D in Conveying direction 39 are angled.

The wood chips are always in operation during drying due to the internals again evenly distributed over the cross section of the rotary drum 4.

Reference symbol list:

1

Combustion chamber

2nd

Mixing chamber

3rd

Power pipe

4th

Rotary drum

5

cyclone

6

fan

7

Return gas line

8th

stack

9

management

10th

Wet feed

11

Coarse material lock

12th

Dry goods deduction

13

Middle section

14

First part of the inlet

15

Second part of the inlet

16

First part of the outlet

17th

Second part of the outlet

18th

Race

19th

storage

20th

Double jacket

21

Built-in inlet

22

Built-in outlet

23

Set of radiating internals

24th

Drum axis

25th

Direction of rotation

26

Attachment point

27

First section first pocket

28

Second section first pocket

29

First section second pocket

30th

Second section second pocket

31

First section third pocket

32

Second section third pocket

33

Last section

34

First section first pocket

35

Second section first pocket

36

First section second pocket

37

Second section second pocket

38

Last section

39

Direction of conveyance

40

Connector

41

ring

42

Lifting bucket

43

Circumferential ring

44

Zone

45

Lifting bucket

46

Baffle plate

47

Baffle plate

48

Baffle plate

49

First section first pocket

50

Second section first pocket

51

First section second pocket

52

Second section second pocket

53

Last section

54

First section first pocket

55

Second section first pocket

56

First section second pocket

57

Second section second pocket

58

Last section

59

Connector

60

ring

61

Inner tube

62

Strive

63

Straight lifting bucket

64

Angled lifting bucket

Claims (11)

1. A rotary drum (4) for drying pourable material, comprising at least one set (23) of axially extending baffles distributed over the circumference inside the rotary drum (4), characterised in that the baffles extend radially over a range from 60% to 85% of the radius of the rotary drum (4), starting from the circumference and extending towards the centre of the drum, and that the baffles except in the vicinity of the circumference extend substantially in sense of rotation (25) upstream of their radial extent which starts from the fixing point (26), and have a cascade structure owing to the formation of at least two pockets.
2. A device according to claim 1, characterised in that the radiating baffles each comprise a baffle plate, the baffle plates of one set (23) being interconnected at one or more points by circular connecting pieces (40, 59).
3. A device according to either one of claims 1 and 2, characterised in that at least some of the baffle plates of a set (23) are fixed to a ring (41, 60) at one or more points at their inner ends.
4. A device according to any one of claims 1 to 3, characterised in that lifting blades (42, 63, 64) are arranged between the radiating baffles.
5. A device according to any one of claims 1 to 4, wherein a plurality of sets of radiating baffles are arranged one behind the other, characterised in that the radiating baffles of consecutive sets (23) are mutually offset.
6. A device according to any one of claims 1 to 5, characterised in that the rotary drum (4) has zones (44) upstream or downstream of a set (23) or between sets of radiating baffles, the zones (44) being provided with curved lifting blades (45).
7. A device according to any one of claims 1 to 6, characterised in that static plates (46, 47, 48) are arranged upstream or downstream of a set (23) of radiating baffles.
8. A device according to any one of claims 1 to 7, characterised in that two types of radiating baffle are arranged alternately, the two types differing in one or more of the features of length of the baffles, number, shape or arrangement of the pockets.
9. A device according to any one of claims 1 to 8, characterised in that opening angles of the pockets are 70 to 140 degrees.
10. A device according to any one of claims 1 to 9, characterised in that the pockets are arranged at an orientation angle of 10 to -30 degrees to the radial extent relative to the direction of rotation.
11. A device according to any one of claims 1 to 10, characterised in that the length of the first portions (27, 29, 31, 34, 36, 49, 51, 54, 56) of the pockets is 0.15 to 0.25 times the drum radius, and the length of the second portions (28, 30, 32, 35, 37, 50, 52, 55, 57) of the pockets is 0.05 to 0.15 times the drum radius.

Images