EP3640572A2 - Method and drying installation for wet wood and the like with improved exhaust quality - Google Patents

Abstract

Method for operating a drying plant for moist wood and comparable bio-materials, consisting of at least one grate dryer (2, 2a-c) with a material entry (3, 16) for the material to be dried, the grate dryer (2, 2a-c ) formed material bed (16, 26) is interspersed with a mixed gas (45) which consists of the mixture of the boiler gas (47) derived from the boiler (1) and the recirculation gas (43) discharged from the grate dryer (2, 2a-c) is generated, the at least one material bed (16, 26) through which the mixed gas (45) flows from bottom to top, the mixed gas quantity 19 being drawn off from the primary gas chamber 48 and from the secondary gas chamber 49.

Description

The invention relates to a method and a device for operating a drying plant for damp wood and the like lumpy and granular comminuted material, the invention of its own EP 3 351 885 A1 going out.

In the method described there, there is the problem that the hot gas or boiler gas generated by the boiler is introduced into a mixing chamber into which a recirculated gas is introduced, the mixed gas generated at the outlet of the mixing chamber running in the direction from above onto the material bed arranged in the dryer .

It has been shown that the flow of material with a mixed gas flow from above has serious disadvantages.

It was found that solid particles are torn down from the material flow through which the material flows and are deposited on the bottom of the dryer and can only be removed with great effort.

It was also found that the condensate in the bulk material was discharged down to the bottom of the dryer and had to be drained off, which either resulted in waste water contaminated with toxins, which had to be discharged or had to be neutralized with a complex treatment.

It was also found that the solids portions torn out of the material bed - due to the flow of the material beds from top to bottom - are undesirably introduced into the downstream filter, thereby reducing the effective filter area is reduced and to compensate for this deposit the filter must be made larger.

There is also an increased proportion of filter ash, which must also be discharged.

In the EP 3 351 885 A1 there were two opposing screws as a transport route for loading the dryer and for conveying away, one screw conveyor feeding the material onto the grate of the dryer, while the other screw, which was driven separately, brought the material out of the dryer. This meant a high level of machine expenditure and, in addition, a dry material shredded to granulate size, the shredding of which was only possible with additional machine expenditure.

The invention is therefore opposite to its own EP 3 351 885 A1 the task of developing a method and a device for carrying out the method so that different moist materials can be dried even in a comminuted state in the manner of sawdust or in lumpy material size with significantly better efficiency and thereby a better cleaned exhaust gas with a lower proportion of residues (ash and condensate) is reached.

To achieve the object, the invention is characterized by the technical teaching of claim 1.

A preferred feature of the invention is that the material bed is flowed through from the bottom to the top by the mixed gas, which means that the mixed gas generated downstream of the mixing chamber now flows from below through the bed of material stored on the grate of the drying chamber, whereby significant advantages are achieved.

A first advantage of this first embodiment is that with the flow of material from bottom to top, the flow from the Material with entrained solids are carried upwards into the gas space of the grate dryer and no longer fall to the bottom of the dryer. The result of this is that the upward torn material particles settle again on the surface of the material bed, are dried again and thus no longer reach the bottom of the dryer.

The condensate formed during drying is also carried upwards out of the material bed and falls back into the material bed, so that the condensate in the material bed is dried without the risk that condensate parts fall down into the dryer and are disposed of there at great expense have to. This means that the exhaust gas is no longer polluted.

Another advantage is that the filter is no longer burdened by the condensate and residual ash. Therefore, only small amounts of ash or solids get into the filter, because the heavier ash and solid parts sink back to the surface of the material bed due to gravity and do not reach the area of the filter.

This means that more effective filters can be used with a smaller filter area, and the service life of the filters is extended because only a lower solids content has to be removed in the filters.

It is also advantageous that the temperature in the material bed can now be chosen relatively freely because the mixing temperature can be freely selected and is maintained within certain limits.

In addition to the flow of material from top to bottom, another embodiment claims that this flow takes place in combination with a reverse flow in a dryer connected downstream of it, which was not previously known.

Accordingly, a series connection of dryers is proposed in various exemplary embodiments - with regard to the material flow of the material beds - a second preferred embodiment in a first Drying stage flows through the material bed from top to bottom and in the subsequent drying stage the material bed is flowed through from bottom to top. This also achieves the advantages of the invention and improves the filter performance because double filtering takes place through two layers of a material bed connected in series.

In a third embodiment, a reverse method is provided in which the mixed gas flows from bottom to top through the material bed in the first layer and in the second, downstream material bed the drying gas originating from the first material bed flowing through now flows through the second material bed from top to bottom . The advantages of the invention are also achieved here.

Both versions therefore have in common that at least two material beds connected in series in the conveying direction of the material share a common grate dryer, in particular its primary chamber, and are divided into at least two material beds divided in terms of flow.

The drying stream formed from the mixed gas flows through the first material bed in one direction - preferably from top to bottom - while the drying stream leaving the first material bed and enriched with moisture now flows through the second material bed - preferably from bottom to top. It is preferred that the material bed which is flowed through from bottom to top is located below the filter and the chimney. This achieves the previously described advantages that material and condensation particles that are torn upward from the bed of material flowing through from below upwards now fall down onto the bed of material due to gravity and are rendered harmless there.

In a kinematic reversal of the flow directions described above, however, it can be provided in another embodiment that the first material bed from bottom to top and the second material bed from flow through the top down. The advantages of the invention are then also achieved in that the material bed flowing through from bottom to top is located below the filter and chimney and thus a smaller and cleaned amount of exhaust gas is produced.

In a further exemplary embodiment of the invention, it is provided that the layers of the material beds are arranged, so to speak, one above the other, while in the aforementioned exemplary embodiment the layers of the material beds are arranged side by side.

With the embodiment of the material beds lying one above the other, which, however, are connected in series in terms of flow, there is the advantage of a smaller space requirement for the dryer. Here, too, the advantage is achieved that condensate components that arise always fall back into the material bed and never reach the bottom of the drying chamber, where they have to be disposed of at great expense.

In a further embodiment it is provided that the two drying sections with the two grids connected in series are connected in series, so that the grates are flowed through from bottom to top on both sides and only the effective area of the grilles is doubled if the grates are of the same size going out.

Here, too, an improved filter performance is achieved and there is no condensation on the bottom of the drying chamber.

With all variants of the serial connection of drying grates, there is the advantage that higher material layers can be run in the dryer with the same heat output of the boiler, which improves the separation effect of the ash and the solids in the material bed and thus either no longer requires or only the filters used be charged much less.

In a development of the invention, a device is provided in which - as from the EP 3 351 885 A1 known - feed and discharge screws are dispensed with. Instead, push floors or comparable hydraulically or pneumatically driven slides are now proposed, which always ensure a constant fill level of the material beds in the dryer.

The moving floor conveyors preferably work intermittently depending on the fill levels of the material fillings to be described later, which has the advantage that granular drying goods no longer have to be used, as in the case of the EP 3 351 885 A1 known, but it can be used lumpy moist material goods such. B. lump wood, uncrushed bark, sawdust and the like.

In the EP 3 351 885 A1 however, only moist pieces of material the size of wood chips could be dried. Accordingly, the invention has the advantage that even large material denominations can be used, which is possible thanks to the push floor technology or comparable intermittently working slides.

In many cases, a moving floor conveyor is already installed in silos in a manner known per se and is used as a discharge device, and such a moving floor silo can therefore be used advantageously for carrying out the method.

What was previously referred to as the material feed chute can therefore be designed as a moving floor silo. H. a silo body with a moving floor conveyor as a discharge device, which intermittently delivers depending on the height of the downstream material bed.

In a device according to the invention, it is preferred if the two material beds connected in series in the conveying direction are arranged on grate dryers of different heights. This allows the material flow from the higher material bed due to gravity to the lower material bed and it is useful to To form a vertical partition between the two material beds, which forms a level-controlled chute, which on the one hand forms a buffer storage and on the other hand ensures that the material is mixed during the transition from one to the other material bed.

It is also provided that the inlet area of the foremost material bed in the conveying direction is equipped with a material feed chute serving as a buffer store, the fill level of which is regulated by a sensor which regulates the material flow of the sliding floor slide forming the bottom of the material feed chute.

The advantage is that all denominations of wet materials from the wood industry can be processed. Another advantage is that the device works with the same conveyor technology, namely the use of an intermittent moving floor conveyor or an equivalent slide. There is therefore no need for complex feed and discharge screws.

The subject matter of the present invention results not only from the subject matter of the individual patent claims, but also from the combination of the individual patent claims with one another.

All of the information and features disclosed in the documents, including the summary, in particular the spatial configuration illustrated in the drawings, could be claimed as essential to the invention, insofar as they are new to the prior art, individually or in combination. The use of the terms “essential” or “according to the invention” or “essential to the invention” is subjective and does not imply that the features named in this way must necessarily be part of one or more patent claims.

In the following, the invention will be explained in more detail with reference to drawings showing only one embodiment. Here go from the drawings and their description further essential features and advantages of the invention.

Figur 1:

ein erstes bevorzugtes Verfahrensschema für ein erstes Ausführungsbeispiel

Figur 2a:

ein gegenüber Figur 1 abgewandeltes Ausführungsbeispiel, bei dem eine serielle Hintereinanderschaltung von zwei Rosttrocknern verwendet wird

Figur 2b:

ein gegenüber Figur 2a abgewandelten Strömungsverlauf

Figur 3a:

ein gegenüber den Figuren 2a und 2b abgewandeltes Verfahrensschema mit übereinander angeordneten Rosttrocknern

Figur 3b:

ein gegenüber Figur 3a abgewandelten Strömungsverlauf

Figur 4:

ein abgewandeltes Verfahrensschema, bei dem im Wesentlichen die Rostflächen hintereinander geschalteter Roste vergrößert sind und zu einem einzigen Rosttrockner 2c vereinigt ist

Show it:

Figure 1:

a first preferred method scheme for a first embodiment

Figure 2a:

one opposite Figure 1 modified embodiment in which a serial connection of two grate dryers is used

Figure 2b:

one opposite Figure 2a modified flow

Figure 3a:

one versus the Figures 2a and 2 B modified process diagram with grate dryers arranged one above the other

Figure 3b:

one opposite Figure 3a modified flow

Figure 4:

a modified method scheme, in which the grate surfaces of grids connected in series are essentially enlarged and combined into a single grate dryer 2c

43

Rezirkulationsgas

43'

Rezirkulationsleitung

45

Mischgas

45'

Mischgasleitung

46

Reingas

46'

Reingasleitung

47

Heissgas

47'

Heissgasleitung

Although the following description of the Figures 1 to 4 are self-contained representations, it is possible to the individual embodiments of the Figures 1 to 4 to combine with each other in any way. Accordingly, each exemplary embodiment should enjoy protection in isolation, but also in any combination with the other designs. The following double terms were used for reference numerals 43 45, 46, 47:

43

Recirculation gas

43 '

Recirculation line

45

Mixed gas

45 '

Mixed gas line

46

Clean gas

46 '

Clean gas line

47

Hot gas

47 '

Hot gas pipe

The entire drying system 2, 2a-2c is preferably operated in negative pressure in all exemplary embodiments, because the exhaust gas fan 17 connected upstream of the chimney 25 generates such negative pressure in the entire drying system.

Figure 1: Rust dryer first variant

The hot exhaust gases with the temperature T1 flow from the boiler 1 to the mixing chamber 15. In the dryer 2, grids 5 or 6 or more than two are installed. It is also possible to use only a single dryer.
The grids 5, 6 are designed in the position and in height to be adjustable about the axes 7, 8 (arrow direction 9, 9a). The length and width of the grids 5, 6 can be freely selected. The surfaces of the grids 5 and 6 are usually identical, but can also be different.

A material feed chute 3 or a moving floor silo is arranged in front of the dryer 2. In position 3, the material 16 to be dried is temporarily stored. The level probe LC1 shows the material level. With the level LC1 in the feed chute 3, the gas tightness of the dryer 2 is ensured to the outside.

The material 16 is pushed further from the position 3 onto the grate 5 or 6 or more with the sliding floor slide 20 or a comparable slide.

At the entrance to the gas space 23 above the bed there is a height-adjustable metering bar 11. The layer height of the bed 16 can thus be adjusted.

The level probe LC2 is arranged in the chute 12. Depending on the level LC2 z. B. the sliding floor slide 20 promote the material on the gratings 5, 6 or more.

The sliding floor slide 20 or the comparable slide is driven hydraulically via a working cylinder 4, but can also be done electrically by means of a geared motor.

At the bottom of the chute 12, a screw conveyor 21 or a push floor 22 can take care of the removal of the dried material. It is advantageous if the screw conveyor 21 is designed as a stuffing screw or the push floor 22 as a cutting slide. With these versions, the gas-side closure to the outside is guaranteed.

In order to reach a selectable temperature T2 before the boilers 47 enter the dryer 2 via the boiler gas line 47 ′, they have to be re-circulated with part of the gas quantity after flowing through the layer 16 in the direction of arrow 13 with the recirculation fan 14 as recirculation gas 43 via the recirculation line 43 'sucked off and mixed in the mixing chamber 15. The temperature T2 of the mixed gas 45 in the mixed gas line 45 ′ is thus reached at the inlet into the dryer 2.

The mixing temperature T2 is selectable and can e.g. B. between 80 and 100 ° C, without limiting it.

The mixed gas 45 with the mixed gas quantity 19 flows through the material bed 16 from bottom to top and there absorbs moisture from the material to be dried until it is fully saturated with water and steam. The temperature T3 in the gas space 23 above the material bed 16 can be between 40 to 70 ° C. in normal operation, but is not limited thereby.

In particular, the larger solid parts of the gas quantity 19 of the mixed gas 45 are retained in the material bed 16. The exhaust gases in the gas space 23 are thus pre-cleaned. The solid parts separated in the material bed 16 are discharged with the dry material into the chute 12.

If even lower solids contents are required in the clean gas 46 of the clean gas line 46 ', a suitable filter type 18 can be arranged at the outlet from the gas space 23 in the clean gas line 46'.

In this arrangement, the filter 18 flows from bottom to top. Separated solids fall directly into the material bed 16 underneath. If condensate occurs in the filter 18, this flows back directly into the material bed 16 and therefore does not have to be disposed of in a complex manner.

With the exhaust gas fan 17, the grate dryer 2 and - if present - the filter 18 are operated in negative pressure. If necessary, a condensation stage 24 can be installed after the filter 18 in order to obtain additional energy from the exhaust gases.

The exhaust gases flow into the surroundings via the chimney 25. A clearing moving floor 25 can be installed on the bottom of the grate dryer for discharging the separated ash parts.

In Figure 1 A flow variant is shown, which in an alternative embodiment - which is not shown in the drawing - can be changed in the same way as the flow conditions in the comparison between the Figures 2a and 2 B or the flow conditions in the comparison between the Figures 3a and 3b can be trained.

It follows that the in Figure 1 The mixed gas line 45 shown, which opens into the primary gas chamber 48 on the bottom side, is now introduced into the upper side of the dryer in the alternative embodiment, which is not shown in the drawing, namely into the gas space 23, from which it follows that the material bed 16 is now from above is flowed downwards, ie exactly in the opposite direction to the arrow direction 13 shown.

The arrangement of double grates 5, 6 and 5a, 6a and their mutual influence in the embodiments according to FIGS. 2 to 4

For all embodiments of the Figures 2a , 2 B , 3a , 3b , 4th It is binding that double grates 5, 6 and 5a, 6a are used to enlarge the dryer area. These are each arranged in the same plane and are covered either by the material bed 16 or 26. Thus, instead of the double grates, single grates 5 or 6 or 5a or 6a could also be provided. For the sake of simplicity of description, the following description therefore assumes grates 5, 5a and 6, 6a, although these are double gratings which, as explained above, can also be designed as single gratings.

The effect of two grates 5, 5a and 6, 6a separated from one another in terms of flow technology is as follows:
In the arrangement of two grids 5, 6; 5a, 6a, in a preferred embodiment, after flowing through the first bed of material 26, the amount of gas 19, which corresponds to up to 2/3 of the volume of the initial volume, is fed into the mixing chamber 15 and the remaining amount of gas remains about 1/3 of the initial volume is, flows through the second material bed 16, whereby an additional exhaust gas cleaning and heat recovery take place.

Figure 2a: grate dryer second variant (lying side by side)

The hot boiler gases 47 flow from the boiler 1 in the boiler gas line 47 ′ at the temperature T1 to the mixing chamber 15.

The grates 5 or 6 and more are installed in the grate dryer 2b. The grids can be adjusted and adjusted in height around the axes 7, 8 (arrow direction 9). The length and width of the grids 5, 6 can be freely selected.

The surfaces of the grids 5 and 6 or more are generally identical, but can also be different.

A material feed chute 3 or a moving floor silo are arranged in front of the grate dryer 2b. In the material feed chute 3, the material to be dried Well stored. The level probe LC1 indicates the material level 41. With the level LC1 in the feed shaft 3, the gas tightness of the grate dryer 2b is secured to the outside.

With the sliding floor slide 20 or a comparable slide, the material is pushed further from the material feed chute 3 onto the grate 5 and 6 or more. At the entry into the gas space 23b above the material bed 16 there is a height-adjustable metering bar 11. This allows the layer height of the material bed 16 to be adjusted.

The level sensor LC2 is arranged in the chute 12. Depending on the level LC2 z. B. the sliding floor slide 20a promote the material from the material feed chute 3 on the gratings 5, 6 or more.

The sliding floor slide 20a or the comparable slide is driven hydraulically with the drive cylinder, but can also be done electrically by means of a geared motor.

In front of the dryer grates 5a and 6a or more, a material feed chute 12 is arranged in which the somewhat pre-dried material is temporarily stored. The level probe LC2 regulates the fill level in the material feed chute 12. The level LC2 in the feed chute 12 ensures the gas tightness of the dryer 2a, 2b to the outside.

With the sliding floor slide 20a or a comparable slide, the material is pushed further from the material feed chute 12 onto the grate 5, 6 or more. At the entry into the gas space 23a above the material bed 26 there is a height-adjustable metering bar 27. The layer height of the material bed 26 can thus be adjusted.

The level sensor LC3 is arranged in the drop shaft 28. Depending on the level LC3 z. B. the sliding floor slide 20a promote the material from the chute 12 onto the gratings 5a, 6a or more.

At the bottom of the chute 28, a screw conveyor 29 and / or a push floor 30 can take care of the removal of the dried material. It is advantageous if the screw conveyor 29 is designed as a stuffing screw or the push floor 30 as a cutting slide. With these versions, the gas-side closure to the outside is guaranteed.

In order to achieve a selectable temperature before the mixed gases 45 enter the mixed gas line 45 ′ into the gas space 23a, they must be recirculated gas 43 via the recirculation line 43 ′ from the recirculation fan 14 with part of the gas quantity after flowing through the layer 26 in the direction of arrow 13 suctioned off and mixed in the mixing chamber 15. The temperature T2 of the mixed gas 45 in the mixed gas line 45 ′ is thus reached at the inlet into the dryer 2a.

The mixing temperature T2 can be selected and is preferably between 80 and 100 ° C, but is therefore not limited.

The mixed gas 45 flows through the material bed 26 from top to bottom in the direction of the arrow 13a and there absorbs moisture from the material to be dried until it is fully saturated with water and steam.

The temperature under the material bed 26 and below the grids 5a, 6a in the connecting chamber 44 formed there can preferably be between 40 to 70 ° C. in normal operation, but is not limited thereby.

In particular, the larger solid parts of the gas mixture are retained in the material bed 26, the exhaust gases are thereby pre-cleaned. The material bed 26 thus acts like a first filter stage. The solid parts separated in the material bed 26 are discharged with the dry material into the chute 28.

From the connecting chamber 44, which is also referred to as the primary gas chamber 48, which is formed under the dryer grates 5, 6, 6a and more, the volume necessary for cooling the hot boiler gases 47 from the boiler 1 becomes of the recirculation gas 43 is sucked off via the recirculation line 43 ′ with the recirculation fan 14 and conveyed into the mixing chamber 15 and mixed with the hot boiler gases 47. The extracted volume corresponds to half the volume flow of the gas after flowing through the material bed 26.

The remaining gases are deflected in the connecting chamber 44 and then flow through the grids 5, 6 or more with the material bed 16 in the grate dryer 2b from bottom to top in the direction of the arrow 13b.

The area of the grids 5, 6 or more in the grate dryer 2b corresponds to the area of the grates 5a, 5b or more in the grate dryer 2a. Since this amount of gas through the bed of material 26 only has approximately up to 1/3 volume, the residence time of the gas in the bed of material 26 is considerably longer. This results in an additional separation of solids in the material bed 26. The gas is still cooled in the material bed 16.

If even lower solids contents in the exhaust gas in the chimney 25 are required, a suitable filter type, preferably a wet electrostatic filter 32, can be arranged at the outlet from the gas space 23b.

In this arrangement, the filter 32 is ideally flowed from bottom to top. Separated solids fall directly into the material bed 16 underneath. If condensate accumulates in the filter 32, this flows directly into the material bed 16 and therefore does not have to be disposed of in a complex manner.

At the bottom of the connecting chamber 44 of the grate dryers 2a, 2b, a clearing floor 31 can be installed for the discharge of the separated ash parts.

With the exhaust gas fan 17, the grate dryers 2a, 2b and, if present, the following apparatus are operated in negative pressure. If necessary, a condensation stage 24 can be installed after the filter 32 in order to add additional ones To gain energy from the exhaust gases. The exhaust gases flow into the surroundings via the chimney 25.

In a variant that is not shown in the drawing, it can be provided that the gas entry at the temperature T2 from the mixed gas line 45 ′ takes place via the gas space 23b and the gas exit consequently takes place after the gas space 23a. The flow directions 13a, 13b are thereby reversed by 180 degrees.

In the embodiments of the Figures 2a , 2 B and 3a , 3b and 4th a partition 40 is provided between the grate dryers lying next to each other.

It is important that two different material beds 16, 26 are arranged on both sides of the vertical partition 40, which are separated from one another by the partition 40. This has the advantage that the partition wall forms a first throughflow chamber for the first grate dryer, which is provided with the material bed 16, that the heating gases are then diverted and then flow through the second material bed 26 in the opposite direction.

The two material beds 16, 26 are accordingly separated by the partition 40, and the two dryers 1 and dryer 2 formed therefrom are separated from one another in terms of flow. The arrangement of the partition 40 accordingly prevents a short circuit of the flow gases between the dryer 2 and the dryer 1.

According to a further feature of the invention, it is provided that the two material beds 16 and 26 flow and connect to the partition wall 40 to form a seal, and thus a gas seal between the two gas spaces 23a and 23b is possible.

A short circuit between the two gas spaces 23a and 23b is thus avoided and a defined guidance of the heating gases through the material beds 16 and 26 is ensured.

The advantage of the measures after the division of a drying process into two driers 1 and 2 connected in series with one another in terms of flow is that additional separation of the solids in the material bed 26 can take place and heat recovery can also take place therein, which was not previously known.

The fact that preferably about half of the amount of gas present there is preferably withdrawn from the connecting chamber 44 via the recirculation line 43 ′ and is fed back to the mixing chamber 15 furthermore means that the material bed 26 that follows the material bed 16 only now is flowed through at half the flow rate and thus an additional solid separation takes place in the overlying material bed 26 without the risk that the material particles are torn away from the material bed 26 upwards due to high flow rates.

An improved cleaning effect of the exhaust gases is thus achieved, and an additional drying effect can be achieved by further reducing the temperature in the material bed 26.

Figure 2b: grate dryer second variant (lying side by side)

The difference in Figure 2b to Figure 2a is that there is in principle a reverse flow pattern, because the mixed gases flowing from the mixing chamber 15 via the mixed gas line 45 'with the temperature T2 are now fed directly onto the grate dryers 5 and 6 and thus the material bed 16 in the direction of the arrow 13a from above is flowed through below. 16 particles are entrained downward in the direction of arrow 13a from the material bed and reach the bottom side of the grate dryer 2a, 2b.

The two grate dryers 2a, 2b are arranged side by side and are arranged in a connecting chamber 44 connecting the two dryers. The connecting chamber 44 can also be referred to as the primary gas chamber 48.

Starting from the connecting chamber 44, the material bed 16 is thus flowed through in the direction of the arrow 13a, and the gas laden with particles flows in the opposite direction 13b via the grate dryers 5a and 6a.

Because the recirculation gas 43 is discharged from the connection chamber 44 via the recirculation line 43 ′, a smaller volume of air is kept in the connection chamber 44, which means that with the same grate surface, the grate dryer 5a and 6a has half the flow rate for the material bed arranged there 26 is given. This improves the drying effect and improves exhaust gas purification. It follows that the downstream wet electrostatic precipitator 32 is only optionally required and in many cases can be completely eliminated.

The difference between the Figure 2a and the Figure 2b thus lies in the reverse flow behavior of the mixed gases from the mixed gas line 45 ', which is carried in different variants.

Figure 3a: grate dryer 2a + 2b, third variant in tier arrangement

According to Figure 3a the hot boiler gases 47 flow from the boiler 1 with the temperature T1 via the boiler gas line 47 'to the mixing chamber 15. The grates 5a or 6a and several are installed in the first grate dryer 2a.

As in all of the exemplary embodiments, there may also be more than two gratings 5a, 6a. The grids 5a, 6a can be adjusted in position and height about the axes 7, 8 (arrow direction 9a, 9b). The length and width of the grids 5a, 6a can be selected.

The surfaces of the grids 5, 5a and 6, 6a or more are generally identical, but can also be different.

A material feed chute 3 or a moving floor silo is arranged in front of the dryer 2b. The material to be dried is temporarily stored in the material feed chute 3. The level probe LC1 regulates the material level. With the Level LC1 in the material feed chute 3 ensures the gas tightness of the dryer 2b to the outside.

With the sliding floor slide 20 or a comparable slide, the material is pushed further from the material feed chute 3 onto the grate 5 or 6 or more.

At the entry into the gas space 23b above the material bed 16 there is a height-adjustable metering bar 11. The layer height of the material bed 16 can thus be adjusted.

The level sensor LC2 is arranged in the chute 12. Depending on the level, z. B. the sliding floor slide 20 promote the material from the material feed shaft 3 on the grids 5, 6 or more.

The sliding floor slide 20 or the comparable slide is driven hydraulically via drive cylinder 4, but can also be done electrically by means of a geared motor.

The second grate dryer 2a is preferably arranged below the first grate dryer 2b. This results in a double flow through the material bed 16 in the upper grate dryer 2b, because the material bed is additionally flowed through by the drying gases flowing through the lower material bed 26.

In the lower grate dryer 2a, a material feed chute 12 is arranged in front of the grates 6a and 6b, which contains the material pre-dried via the first grate dryer 2b. The pre-dried material from the first grate dryer 2b is temporarily stored in the chute 12. The level probe LC2 regulates the material level in the chute 12. The level in the chute 12 ensures the gas tightness of the dryer 2b to the outside.

The material is pushed further from the chute 12 onto the grate 6a and 5a or more of the lower grate dryer 2a with the sliding floor slide 20a or a comparable slide.

The grids 5a and 6a can be adjusted in position and height about the axes 7 and 8 (arrow direction 9a, 9b). The length and width of the gratings can be selected.

The surfaces of the grids 5a and 6a or more are generally identical, but can also be different.

The sliding floor slide 20a or the comparable slide is driven hydraulically via drive cylinder 4a, but can also be done electrically by means of a geared motor.

At the entrance to the gas space 23a above the material bed 26 there is a height-adjustable metering bar 27. The layer height of the material bed 26 can thus be adjusted.

The level sensor LC3, which regulates the level, is arranged in the drop shaft 28. Depending on the level, z. B. the sliding floor slide 20a convey the material from the chute 12 onto the grids 6a, 5a or more for drying on the grate dryer 2a.

At the bottom of the chute 28, a screw conveyor 21 or a push floor 22 can take care of the removal of the dried material.

It is advantageous if the screw conveyor 21 is designed as a stuffing screw or the push floor 22 as a cutting slide. With these versions, the gas-side closure to the outside is guaranteed.

In order to achieve a selectable temperature T2 in the mixed gas line 45 ′ before the boiler gases 47 enter the grate dryer 2a from the boiler gas line 47 ′, they have to be mixed with part of the gas quantity of the rizurculation gas 43 from the recirculation line 43 ′ after flowing through the material bed 26 in Direction of arrow 13b suctioned off with the recirculation fan 14 and mixed in the mixing chamber 15. The temperature T2 of a mixed gas 45 in the mixed gas line 45 ′ is thus reached at the inlet into the dryer 2a.

The mixing temperature T2 of the mixed gas 45 can be selected and is preferably between 80 and 100 ° C. without thereby limiting it.

The mixed gas 45 flows through the material bed 26 in the direction of the arrow 13b from bottom to top and there absorbs moisture from the material to be dried until it is fully saturated with water and steam.

The temperature T4 in the gas space 23b above the material bed 16 is preferably between 40 to 70 ° C. in normal operation, but is not limited thereby.

Above all, the larger solid parts of the gas mixture are retained in the material bed 26, the exhaust gases are thus pre-cleaned before they flow through the further material bed 16 in the red dryer 2b. The solid parts separated in the material bed 26 are discharged with the dry material into the chute 28.

From the gas space 23a forming the secondary gas chamber under the grate dryer 2b, the volume required for cooling the hot exhaust gases from the boiler 1 is extracted with the fan 14 and conveyed into the mixing chamber 15 and mixed with the hot boiler gases 47. The extracted volume of the recirculation gas 43 in the recirculation line 43 ′ corresponds to approximately 2/3 of the volume flow of the gas after flowing through the material bed 26.

The remaining gas quantities in the gas space 23a then flow through the grates 5, 6 or more in the grate dryer 2b and the material bed 16 arranged there from bottom to top in the direction of the arrow 13.

The area of the grids 5, 6 in the grate dryer 2b corresponds to the area of the grates 5a, 6a in the grate dryer 2a. Since the amount of gas through the bed of material 16 is only about half the volume, the dwell time of the gas in the bed of material 16 is also considerably longer. This results in an additional separation of solids in the material bed 16, as a result of which the gas is still cooled.

If even lower solids contents in the exhaust gas are required, a suitable filter type, preferably a wet electrostatic filter 32, can be arranged at the outlet from the gas space 23b.

In this arrangement, the filter 32 is ideally flowed from bottom to top. Separated solids fall directly into the layer of material bed 16 underneath. If condensate accumulates in filter 32, this flows directly onto material bed 16 and therefore does not have to be disposed of in a complex manner.

With the exhaust gas fan 17, the grate dryers 2a, 2b and - if present - the following apparatuses are also operated in negative pressure. If necessary, a condensation stage 24 can be installed after the filter 32 in order to obtain additional energy from the exhaust gases.

At the bottom of the grate dryer 2a, a clearing floor 31 can be installed to discharge the separated ash parts. The exhaust gases flow into the surroundings via the chimney 25.

In a variant not shown in the drawing Figure 3 a can also be compared to Figure 3a Reverse flow pattern of the grates 5, 6 and 5a, 6a of the two grate dryers 2a, 2b arranged above or below one another can be provided.

From the comparison of the Figure 3a with the procedural scheme of Figure 3b it follows that also - analogous to the description of the Figures 2a and 2 B - Reverse heating gas flow is possible.

The tracking of the heating gases Figure 3a can therefore in Figure 3b can be reversed by providing that the mixed gas line 45 'with the mixed gas 45 flowing there now flows into the gas space 23a of the floor dryer consisting of the grate dryers 2a and 2b stacked one above the other on the floor.

The material bed 16, which is supported on the upper grate dryer 2b, consisting of the grates 5 and 6, is flowed through from top to bottom in the direction of the arrow 13a, and the gases thus enter the gas space 23b and immediately further onto the surface of the material bed 26 adjoining it.

The difference in Figure 3a and 3b to the Figures 2a and 2 B is accordingly, inter alia, that the material beds 16, 26 lie directly one below the other and are therefore flowed through in a serial manner.

It follows from Figure 3b that the gases flowing through the upper grate dryer 2b in the flow direction 13a now directly reach the surface of the lower material bed 26 and the lower grates 5a and 6a are flowed through in the arrow directions 13 from top to bottom.

The drying gases thus enter a primary gas chamber of the grate dryer 2a and the solid particles that accumulate there can be removed via the clearing floor 31.

The big advantage of the arrangement according to Figure 3a is that, due to the temperature in the primary gas chamber 48, no condensate is produced and therefore no condensate has to be disposed of.

The in Figure 3a drawn-in clearing floor 31 can in itself also be omitted because there is no risk that particles can fall downward from the material bed 26 which flows through from bottom to top. Such a clearing floor can also be optionally available.

In the Figure 3b the arrangement of the clearing floor 3 is preferred because, due to the flow through the lower grate dryer 2a in the direction of arrow 13b, particles are increasingly introduced into the primary gas chamber 48, then fall onto the clearing floor 31 and can be removed therefrom from the primary gas chamber 48.

In the Figure 3a however, no condensate will accumulate in the primary gas chamber 48, while with condensate formation in the process diagram Figure 3b may be expected.

Figure 4 - Variant grate dryer 2c (flow from bottom to top)

The hot hot gases 47 with the temperature T1 flow from the boiler 1 to the mixing chamber 15. The grates 5, 6, 5a, 6a and several are installed in the grate dryer 2c.

The gratings 5, 6, 5a and 6a and also others can be extended. The grids are adjustable in position and height about the axes 7, 8 (arrow direction 9, 9a, 9b). The length and width of the gratings can be selected. The surfaces of the grids 5, 5a, 6, 6a are generally identical, but can also be different.

The grate 5, 6 with the material beds 16 and 26 lying thereon are flowed through from bottom to top in the direction of arrow 13.

The material to be dried is temporarily stored in the material feed chute 3 depending on the fill level LC1.

The material feed chute 3 or a moving floor silo are arranged in front of the gas space 23.
With a minimum level in the material feed chute 3, the gas tightness of the dryer 2c is secured to the outside.

The height of the material bed 16 is adjusted with the height-adjustable metering bar 11.

In order not to compress the material bed 16 after the grates 5, 6 and several, a chute 12 with a fill level monitoring LC2 is arranged in the space between the grates 5, 6 and 5a, 6a.

Depending on the level LC2, the material bed 16 is pushed onto the gratings 5, 6 or more by the slide system of the sliding floor slide 20.

With the sliding floor slide 20a or a comparable slide, the material is pushed from the feed chute 12 onto the gratings 5a, 6a and several.

At the entrance above the gas space 23 above the second material bed 26 there is a height-adjustable metering bar 27. The layer height of the material bed 26 can thus be adjusted.

The drive 4a of the sliding floor slide 20a or the comparable slide is hydraulic, but can also be done electrically by means of a geared motor.

At the bottom of the chute 28, a screw conveyor 29 or a push floor 30 can take care of the removal of the dried material. It is advantageous if the screw conveyor 29 is designed as a stuffing screw or the push floor 30 as a cutting slide. These measures ensure the gas-side closure.

A moving floor 31 can be installed on the bottom of the dryer 2c, which comprises both material beds 16, 26 in order to remove the material from the exhaust gas or the grates 5, 6 and 5a. 6a to be carried out.

In order to achieve a selectable temperature T2 before the hot gases enter the grids 5, 5a, 6, 6a of the dryer 2c, they have to be exhausted by the recirculation fan 14 with part of the gas quantity (recirculation gas 43) after flowing through the material beds 16 and 26 are sucked out of the gas space 23 and mixed in the mixing chamber 15. In order to the temperature T3 for the mixed gas 45 is determined in the in the mixed gas line 45 'for entry into the grate dryer 2c below the grates 5, 6 and 5a, 6a.

The mixing temperature T3 can be selected and is preferably between 80 and 100 ° C, without limiting it.

The temperature T4 of the clean gas 46 in the clean gas line 46 'can be between 40 to 70 ° C. in normal operation, but is not limited thereby.

Above all, the larger solid parts of the gas quantity are retained in the material beds 16 and 26 lying next to one another, as a result of which the exhaust gases are cleaned. The material beds 16 and 26 act like filters. The solid parts separated in the material beds 16, 26 are discharged with the dry material.

A suitable filter type, preferably a wet electrostatic filter 32, can be arranged at the outlet from the gas space 23 for even lower solids contents in the exhaust gas.

In this arrangement, the wet electrostatic filter 32 is ideally flowed from bottom to top. Separated solids fall directly into the layer of material beds 16, 26 underneath.

The exhaust fan 17 operates the dryer 2c and, if present, the filter 18 in negative pressure.

If necessary, a condensation stage 24 can be installed after the filter 18 in order to obtain additional energy from the exhaust gases. The exhaust gases flow into the surroundings via the chimney 25.

Drawing legend

1

boiler

2nd

Grate dryer 2a, 2b, 2c

3rd

Material feed chute

4th

Drive cylinder 4a

5

Rust 5a

6

Rust 6a

7

Swivel axis

8th

Swivel axis

9

Arrow direction (swivel axis)

10th

Arrow direction (swivel axis)

11

Dosing bar

12th

Chute

13

Direction of arrow (gas) 13a, 13b

14

Recirculation fan

15

Mixing chamber

16

Bulk material

17th

Exhaust fan

18th

Wet electrostatic precipitator

19th

Mixed gas amount

20th

Sliding floor slide 20a

21

Auger

22

Moving floor

23

Gas space 23a, 23b

24th

Condensation level

25th

stack

26

Bulk material

27

Dosing bar

28

Chute

29

Auger

30th

Moving floor

31

Clearing floor

32

Wet electrostatic precipitator

33

34

35

Gas space

36

 

37

38

39

40

partition wall

41

Material level

42

Material feed chute

43

Recirculation gas; 43 'recirculation line

44

Connecting chamber

45

Mixed gas; 45 'Mixed gas line

46

Clean gas; 46 'Clean gas line

47

Boiler gas; 47 'Boiler gas line

48

Primary gas chamber

49

Secondary gas chamber

Claims (10)

Method for operating a drying plant for moist wood and comparable bio-materials, consisting of at least one grate dryer (2, 2a-c) with a material entry (3, 16) for the material to be dried, the grate dryer (2, 2a-c ) formed material bed (16, 26) is interspersed with a mixed gas (45) which consists of the mixture of the boiler gas (47) derived from the boiler (1) and the recirculation gas (43) discharged from the grate dryer (2, 2a-c) is generated, characterized in that the at least one material bed (16, 26) flows through from the mixed gas (45) from bottom to top. A method according to claim 1, characterized in that with the flow through the material bed (16, 26) from bottom to top, the solid particles entrained in the material bed (16, 26) upwards in the direction of the gas space (23, 23a, 23b) of the grate dryer ( 2, 2a-c) are worn. A method according to claim 1 or 2, characterized in that in the arrangement of two grids (5, 6; 5a, 6a) arranged approximately one above the other after the flow through the first material bed (26), the amount of gas (19) which is up to Corresponds to 2/3 of the volume of the initial volume, is led into the mixing chamber (15) and that the remaining amount of gas flows up to about 1/3 of the initial volume through the second material bed (16), whereby an additional exhaust gas purification and heat recovery take place. Method according to one of Claims 1 to 3, characterized in that in the first material bed (16, 26) the mixed gas (45) flows from bottom to top through the material bed (16, 26) and the second material bed (26, 16) from which the drying gas originating from the first flow of material (16, 26) flows from top to bottom, as a result of which the exhaust gases are additionally cleaned and heat is recovered. Method according to one of claims 1 to 4, characterized in that for temperature control T2 from a primary gas chamber (48) connecting the two grate dryers (2a, 2b, 2c) on the bottom side and the secondary gas chamber (49) of the gas quantity (45) approximately up to 2 / 3 of the gas volume after the flow through the material bed (16/26) (45) is removed via a mixed gas line (45 '), as a result of which the residence time in the material bed (16, 26) is considerably extended. Device for operating a drying system for moist, shredded and / or shredded wood and comparable bio-materials, consisting of at least one grate dryer (2, 2a-c) with a material entry (3) for the material to be dried, the grate dryer (2 , 2a-c) formed material bed (16, 26) is interspersed with a mixed gas (45) which is derived from the mixture of the boiler gas (47) derived from the boiler (1) and from the grate dryer (2, 2a-c) Recirculation gas (43) can be generated, characterized in that the mixed gas (45) flows through a first material bed (16, 26) from top to bottom and can be introduced into a primary gas chamber (48) arranged below the first material bed (16, 26) and there after the flow through the second material bed (16, 26) can be introduced into a gas space (23a, 23b) arranged above the material bed (16, 26) and fed there to a chimney (25) via an exhaust gas fan (17) is YOURSELFSOFTWAREUPDAT E. Apparatus according to claim 6, characterized in that there is a series connection of grate dryers (2a-2c), the first material bed (16, 26) in a first dryer stage from top to bottom and in the subsequent dryer stage the second material bed (16, 26) can be flowed through from bottom to top. Device according to one of claims 6 to 7, characterized in that the layers of the material beds (16, 26) are arranged one above the other in stages, (Figure 3a, 3b). Device according to one of claims 6 to 7, characterized in that the layers of the material beds (16, 26) are separated from each other by a vertical partition (40) and are arranged in series in the flow direction. Device according to one of claims 6 to 9, characterized in that the material entry (3) in the grate dryer (s) (2, 2a-c) is formed by a level-controlled sliding floor slide (20, 20a).

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