DE102012005441B4 - Belt drying plant for drying bulk material - Google Patents

Abstract

Belt drying plant (10) for drying bulk material, such as sawdust, in which a first, lower drying level (24) for predrying comparatively moist material and a second, upper drying level (36) for after-drying already pre-dried at the lower drying level (24) Good are provided, characterized in that the two drying levels (24, 36) are formed with a single circulating drying belt (20).

Description

Background of the invention

The invention relates to a belt drying plant for drying bulk material, in particular sawdust, in which a first, lower drying level for predrying comparatively moist material and a second, upper drying level are provided for subsequent drying of already pre-dried on the lower drying level Good. Such a generic belt drying plant is out EP 2 218 997 A1 known.

Out DE 20 2009 001 935 U1 is a cover dryer for the drying of z. As sawdust or wood sawdust with hot air, in which a conveyor of the goods is divided into several sections. The sections are separated from each other by air flow. The sections each have their own exhaust fan. Thus, the heating and air power should be able to be graded in sections to the respectively desired, possibly different temperature values. To further save energy, a part of the hot air is to be circulated.

Underlying task

The invention has for its object to provide a belt drying plant, by means of a particularly energy-saving and low-dust drying of bulk materials is possible.

Inventive solution

This object is achieved according to the invention with a belt drying plant for drying bulk material such as sawdust, in which a first, lower drying level for pre-drying of relatively moist material and a second, upper drying level are provided for subsequent drying of already pre-dried at the lower drying level.

According to the invention, a belt drying plant is provided with which it is possible in a particularly space-saving manner to reduce both the dust emissions of the belt drying plant and the energy required for drying by means of heat recovery. For this purpose, according to the invention, the material to be dried is supplied to a lower drying level of the belt drying plant and in this lower drying level then takes place a first pre-drying of the goods. Subsequently, the material is transported to an overlying second drying level and dried there. In this case, the material to be dried is flowed through at the upper drying level of hot air, which is advantageously subsequently passed through the lower drying level.

This ensures that the hot air from top to bottom is initially promoted by comparatively dry and thus slightly dusty Good. The hot air accumulates with dust and moisture and is advantageously subsequently passed from above through the lower drying level. The already slightly moistened and laden with dust wet air flows through the still comparatively moist material in the lower drying level. The hot air that is drawn through the moist material in such a way is thereby filtered and freed of dust, before finally entering the environment of such belt drying plant. At the same time, the warm air from the comparatively dry material, which had not yet been completely saturated with water, in the lower drying level and there in stock, very moist material is strongly saturated with moisture. Thus, in the warm air, a higher saturation with moisture is achieved, whereby the energy requirement of the overall system can be kept particularly low.

In an advantageous development of the strip drying system according to the invention an air duct of hot air is provided in accordance with the drying, with which the hot air is first to be guided through the upper drying level and then through the lower drying level.

Particularly advantageously, the lower drying level is formed only on a first portion of the longitudinal extent of the upper drying level. Thus, it is possible that in the lower section of the material to be dried is flowed through at the beginning of hot air from the end of the upper drying level and in the upper drying level only the warm air is passed to the lower drying level, which comes from the end of the band pass of the belt drying plant.

Advantageously, according to further provided for drying an air duct of hot air through both drying levels only in the first section of the upper drying level and in the remaining second section of the upper drying level an air duct of hot air is formed by only this upper drying level. In the second section, the hot air thus flows through only one drying level and then passes (without another passage through the material to be dried) directly into the environment of the belt drying plant.

The strip drying plant according to the invention is in terms of their internal promotion of the material to be dried in both drying levels with designed a single circulating drying belt. The only one drying belt has the advantage that the cost of the drive and the control of the promotion of the goods can be significantly reduced.

In the lower drying level preferably only a part of the longitudinal extent of the drying belt is to be used in this drying plane for drying the material. In the lower drying level, the transport path of the material to be dried is therefore shorter than on the upper level. This has the advantage that within the belt drying plant at the lower level sufficient space for a high promotion of the goods in the upper drying level is available. Furthermore, the drying is then carried out in the lower drying level only in a partial area, which, as will be explained in more detail below, is advantageous in view of the then possible air flow of the hot air.

Furthermore, a belt cleaning between the lower drying level and the upper drying level is preferably provided at the strip drying plant according to the invention. The belt cleaning is particularly preferably designed as a continuous dry belt cleaning with blowing through the perforated drying belt. It is preferably arranged behind the discharge of the goods at the lower drying level. The belt cleaning is then carried out within the passage of the goods through the belt drying plant, preferably in a range of 1/4 to 1/2 of the entire drying path, preferably at about 1/3 of the drying path. Thus, the drying belt is cleaned after being transported for a while comparatively moist material and before it is transported to the comparatively dry good. This type of cleaning has proven to be particularly advantageous in view of the cleaning quality then achieved on the drying belt. Furthermore, the belt cleaning is preferably arranged after the discharge of the goods at the upper drying level. Thus, the drying belt is cleaned again after it was transported for a while comparatively dry good.

Particularly advantageous for further cleaning of the drying belt, the belt cleaning designed as a discontinuous wet cleaning. Such a wet cleaning is preferably designed with rotating annular nozzles, which are supplied by a high-pressure pump with cleaning water at a pressure of about 180 bar. The resulting jets remove even sticky deposits such as resins, lignins and greases from the drying belt. The wet cleaning also works during the drying process, so that no downtimes occur.

In order to raise the material to be dried from the lower drying level to the upper drying level of the belt drying plant according to the invention, a separate conveyor is particularly preferably provided. This conveyor can be operated depending on the capacity of the drying belt and thus ensure a coordinated transport of the goods to be dried by the belt drying plant according to the invention.

Particularly preferably, the conveyor is designed with a screw. With the screw, larger differences in height between the drying levels can be overcome in a cost effective manner with little effort.

Also advantageous is the use of a turning device at the upper drying level. With the turning device, the material to be dried is redeployed. This mixes the drier top layer of the product with the moister bottom layer. This measure ensures a very homogeneous dry material. Depending on the size of the belt drying plant, several turning devices can also be installed.

Preference is also the use of a moisture control automatic. After measuring the moisture content of the dry material at the outlet of the belt drying plant, a control and monitoring of the throughput time of the goods takes place. For this purpose, the movement speed of the drying belt is finely adjusted via a frequency-driven geared motor. At high moisture content, the belt speed and thus the throughput are reduced, whereas at low moisture content the belt speed is increased. This regulation ensures a constant dry material moisture and optimal utilization of the heat energy supplied.

Brief description of the drawings

An exemplary embodiment of the solution according to the invention will be explained in more detail below with reference to the attached schematic drawings. It shows:

1 the left part of a longitudinal section of a belt drying plant according to the invention and

2 the right part of the longitudinal section according to 1 ,

Detailed description of the embodiment

In the 1 and 2 is a belt drying plant 10 illustrated with an outer case 12 and an air-ducting Dryer tunnel or inner housing 14 is formed. Inside the outer housing 12 is located right in front of the inner housing 14 a feeding station 16 for a material to be dried, in the present sawdust or similar products. The feeding station 16 is with two distribution screws 18 formed, which the supplied moist Good, the so-called wet product 19 , on one in the outer housing 12 circulating drying belt 20 give up and distribute there.

The drying belt 20 is by means of roles 22 guided and thereby from the Aufgabestation 16 starting initially on a lower drying level 24 through a section 26 down horizontally through the inner housing 14 passed. At the left end of the lower part of the inner housing 14 becomes the good of the drying belt 20 in a collecting screw 28 and subsequently in a screw conveyor 30 spent.

With the screw conveyor 30 The estate is from the lower drying level 24 diagonally upwards to another feeding station 32 brought where it by means of two distribution screws 34 at an upper drying level 36 back on the drying belt 20 is distributed.

The already pre-dried material then passes through on the upper drying level 36 again the inner housing 14 This time from left to right, this pass is over the entire length of the inner housing 14 extends.

At the right end of the upper drying level 36 then the completely dried good from the drying belt 20 in another collecting screw 37 promoted, from where it as dry matter 39 from the belt drying plant 10 is promoted.

For the guidance and the drive of the one drying belt 20 are beyond the roles 22 also two rubberized drive rollers 38 provided, one of which is at the left end of the lower drying level 24 and one at the right end of the upper drying level 36 located. The drive rollers 38 So are arranged so that they are the drying belt 20 each pass through the associated drying area.

Further, for the tape guide is a motor-operated belt running control 40 provided with at least one of the rollers 22 can be moved to a running of the drying belt 20 counteract. The band progression control 40 is at the lower drying level 24 in the transport direction behind the collecting screw 28 before the transfer of the drying belt 20 arranged from bottom to top.

In this area of the drying belt 20 is also a discontinuous band cleaning 46 , which as wet cleaning with a lower and an upper nozzle row 48 is provided. The nozzle rows 48 be using a pneumatic piston-cylinder arrangement 42 by means of a valve arrangement 44 and supplied compressed air 45 can be operated, constantly from one side of the drying belt 20 driven to the other side. The nozzle rows 48 be doing with cleaning water 49 supplied under pressure, which by a water catch 50 as wastewater 51 drains again. Further, located on the drying belt 20 immediately behind the drive roller 38 the lower drying level 24 a dry cleaning 52 by means of air nozzles 53 is realized. The air nozzles 53 be with a fan 54 from the front of the upper drying level 36 Air supplied, then through the drying belt 20 is blown to clean this. The case of the drying belt 20 blown off dust gets into the collecting screw 28 spent on the further to be dried good. Another dry cleaning 55 is at the end of the upper drying level 36 immediately behind the drive roller 38 , At this dry cleaning 55 is from another fan 58 Air from the rear of the upper drying level 36 taken. The air is passing through the drying belt 20 blown from behind to also the dust blown there in the other collecting screw 37 to promote and with the discharged dried good from the belt drying plant 10 out, without it can come to a dust in their environment.

To secure a possible fire is located at the upper drying level 36 above the local drying belt 20 a sprinkler system 56 , the extinguishing water 57 can be supplied. Furthermore, there is at the upper drying level 36 a turning device 65 ,

For drying on the drying belt 20 good is outside air 59 in and through the inner housing 14 directed. outside air 59 is by means of a heat exchanger 60 warmed up to warm air, by means of a hot water inlet 61 and a hot water drain 62 Heat energy can be supplied. Other heating media, such as steam, oil, gas or biomass, are possible.

The inner case 14 is separated into two sections, a left section 63 and a right section 64 , The right section 64 comprises about 3/5 of the total longitudinal extent of the inner housing 14 , At this section 64 becomes the wet product 19 at the lower drying level 24 supplied from the right and at the upper drying level 36 to the right as dry material 39 dissipated. The left section 63 of the inner casing 14 extends over about 2/5 of the longitudinal extent of the inner housing 14 and includes only the upper drying level 36 ,

At the bottom of the inner housing 14 There are a total of five fans 66 for hot air extraction, two of which are in the left section 63 and three in the right section 64 are arranged. The drying belt 20 is so through the two sections 63 and 64 led, in the right section 64 the hot air first through the drying belt 20 as well as the already strongly dried material at the upper drying level 36 and subsequently through the drying belt 20 as well as the local still strongly moist good at the lower drying level 24 is sucked. In the left section 63 is, however, from the local fans 66 the hot air alone once through the drying belt 20 and the estate at the upper drying level 36 sucked.

In this way, in particular, dust from the heavily dried material of the upper drying level 36 into the still wet material at the lower drying level 24 recycled. Further, the hot air in this passage in the section 64 through two drying levels 24 and 36 particularly strongly enriched with moisture.

Finally, it should be noted that all the features that are mentioned in the application documents and in particular in the dependent claims, in spite of the formal reference back to one or more specific claims, even individually or in any combination should receive independent protection.

LIST OF REFERENCE NUMBERS

10

Band dryer

12

outer casing

14

inner housing

16

feeding station

18

Distribution screw at the feed station

19

wet product

20

drying belt

22

Roll of the drying belt

24

lower drying level

26

part Of

28

collection coil

30

Auger

32

further feeding station

34

Distribution screw at the further feed station

36

upper drying level

37

another collecting screw

38

Drive roller of the drying belt

39

dry material

40

Tape path control

42

Piston-cylinder arrangement

44

valve assembly

45

compressed air

46

belt cleaning

48

nozzle row

49

cleaning water

50

water collection

51

sewage

52

Dry cleaning

53

air nozzles

54

Fan for dry cleaning

55

further dry cleaning

56

sprinkler system

57

fire water

58

another fan

59

outside air

60

Heat exchanger

61

Hot water supply

62

Hot water discharge

63

left section of the inner housing

64

right section of the inner housing

65

turning device

66

Fan for hot air extraction

Claims (9)

Belt drying plant ( 10 ) for drying bulk material, such as sawdust, in which a first, lower drying level ( 24 ) for pre-drying relatively moist material and a second, upper drying level ( 36 ) for subsequent drying of already at the lower drying level ( 24 ) are provided in advance, characterized in that the two drying levels ( 24 . 36 ) with a single circulating drying belt ( 20 ) are formed. Belt drying installation according to Claim 1, in which an air duct ( 14 . 63 . 64 . 66 ) is provided by hot air, with the warm air first through the upper drying level ( 36 ) and then through the lower drying level ( 24 ) is to lead. Belt drying plant according to claim 1 or 2, wherein the lower drying level ( 24 ) only on a first subsection ( 26 . 64 ) of the longitudinal extent of the upper drying level ( 36 ) is trained. Belt drying installation according to Claim 3, in which an air duct ( 14 . 63 . 64 . 66 ) of hot air through both drying levels ( 24 . 36 ) only in the first subsection ( 26 . 64 ) of the upper drying level ( 36 ) and in the remaining second subsection ( 63 ) of the upper drying level ( 36 ) an air duct ( 14 . 63 . 64 . 66 ) of hot air through only this upper drying level ( 36 ) is trained. Belt drying plant according to one of claims 1 to 4, in which in the lower drying level ( 24 ) just a part ( 26 ) of the longitudinal extent of the drying belt ( 20 ) in this drying level ( 24 ) is to use for drying the goods. Belt drying system according to one of claims 1 to 5, in which a belt cleaning ( 46 ) between the lower drying level ( 24 ) and the upper drying level ( 36 ) is provided. Belt drying system according to claim 6, wherein the belt cleaning ( 46 ) is designed as a wet cleaning. Belt drying installation according to one of Claims 1 to 7, in which a conveyor device ( 30 ) for transporting the material from the lower drying level ( 24 ) to the upper drying level ( 36 ) is provided. Belt drying installation according to Claim 8, in which the conveyor device ( 30 ) is designed with a screw.

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