ES2870666T3 - Belt drying system with two drying planes - Google Patents

Abstract

Belt drying installation (10) for drying bulk material (12), such as sawmills, in which a first upper drying plane (20) is provided for pre-drying relatively wet bulk material (12), a second plane drying machine (26) to subsequently dry bulk material (12) already previously dried in the upper drying plane (20) and an air duct (68, 70, 72, 74) of hot air is provided, with which Hot air can be led first through the lower drying plane (26) and then through the upper drying plane (20), in which the hot air can be led through the air duct (68, 70, 72, 74) from top to bottom circulating through the respective drying plane (20, 26), and under the respective drying planes (20 and 26) various suction equipment (58, 60, 62, 64, 66, 86) are provided , 88, 90, 92, 94) to suck hot air from top to bottom as exhaust air, in which the plane d The upper drying (20) is divided into several sections (30, 32, 34, 36, 38), in which an upper air inlet is provided, by means of which outlet air can be fed as inlet air from the lower drying plane (26) to at least one section of the upper drying plane (20), characterized in that, by means of the upper air inlet, fresh air (56) from the environment can also be fed to at least one other section ( 30, 32, 34, 36, 38) of the upper drying plane (20).

Description

DESCRIPTION

belt drying system with two drying planes

Background of the invention

The invention relates to a belt drying installation for drying bulk material, such as saws, OSB cords or the like, in which a first upper drying plane is provided for the pre-drying of relatively wet bulk material, a second lower drying plane for subsequent drying of bulk material that has already been dried previously in the upper drying plane and a hot air duct, with which hot air can first be led through the lower drying plane and then through the upper drying plane.

In belt drying plants, there is generally the problem that the bulk material to be dried in them, such as particularly sawmills, sewage sludge or cereals, must be dried simultaneously in the gentlest, most uniform and efficient way possible. In addition, high demands are placed on the lowest possible energy consumption and the lowest possible dust discharge from the belt drying plant. Finally, an installation space as small as possible is also desirable, in particular with regard to a small adjustment surface for the belt drying installation.

From SE 0 900 475 A1 a dryer is known for drying chopped wood material, such as saws. In this case, a first upper belt is provided on which a material is guided through a first drying section for pre-drying, and a second lower belt on which the material previously dried on the upper belt is guided through of a second drying section for subsequent drying. Furthermore, an air duct is provided with which the heated dried air can be led first through the lower drying section and then through the upper drying section respectively from top to bottom. In this case, a respective fan is provided to generate depression in the respective drying air. Furthermore, a dryer with the same base structure is known which is configured with several modules extending along an upper conveyor belt and a lower conveyor belt. In this case, a respective fan can be used for two respective modules.

Base problem

The invention is based on the problem of configuring a generic type belt drying installation such that, however, on a small adjustment surface an effective drying of bulk material is possible.

Solution according to the invention

This problem is solved according to the invention with a belt drying installation for drying bulk material according to claim 1.

The invention is based on the knowledge that for a space-saving or simply space-saving configuration of a belt drying installation it is almost essential to design it with several planes, in particular an upper drying plane and a lower drying plane. The two drying planes preferably have in this case a respective independent peripheral drying belt on which the bulk material to be dried lies and through which this bulk material passes through the belt drying installation. In this construction according to the invention of a belt drying device, said material is advantageously pre-dried in the upper drying plane and subsequently dried in the lower drying plane. The advantage in this case is that the bulk material to be dried can flow downward from the upper drying plane to the lower drying plane solely due to its weight and the force of gravity. It is not necessary to lift the bulk material, for example, from the bottom up, as would be necessary with other types of construction of belt drying plants, if these, for example, are pre-dried from the bottom and then dried from the top. At the same time, the invention uses an air duct in which the hot air used to dry the bulk material is transported from top to bottom by circulating through the bulk material to be dried in the respective drying plane. For air conduction, the hot air used must first be led through the post-drying zone first and then, when the hot air is already partially humidified, it must be led through the pre-drying zone. Therefore, in the belt drying installation according to the invention it would be basically simpler to guide the hot air from the bottom up through the lower drying plane, and again from the bottom up through the upper drying plane. On the contrary, the solution according to the invention takes a different path and guides the hot air respectively from top to bottom through the bulk material to be dried. Air duct of this type is certainly more laborious than an air duct in which hot air is conveyed through the drying planes from the bottom up, but the air duct according to the invention is also more efficient in this case. . In particular, the air duct according to the invention is advantageous when it comes to keeping the proportion of dust in the hot air flowing through the bulk material to be dried low and also of keeping the outlet air coming out of the drying plant. tape as dust-free as possible. The air duct according to the invention means that the bulk material to be dried remains compact and is not swirled by the hot air. Furthermore, dust particles enter the bulk material to be dried from above, but can be difficult to exit from below due to the conveyor belt located there.

This effect of sucking the exhaust air downwards is further reinforced or improved in the solution according to the invention in that several suction devices are provided below the respective drying plane to suck the hot air as exhaust air from top to bottom. The suction can be carried out in sections by means of the suction equipment. The suction generates in the bulk material to be dried a depression that further facilitates the local evaporation of the humidity towards the outlet air to be evacuated.

In the belt drying installation according to the invention, a first heating device is preferably further provided to heat the hot air before it is fed to the upper drying plane. By means of the first heating equipment, the re-fed hot air can rise with respect to its temperature level and thus can be prepared to absorb additional moisture.

This first heating device can work in this case at a relatively low temperature level and heat re-fed hot air preferably at a temperature of up to 130 ° C. In this way, in particular the danger of ignition of the bulk material to be dried can be kept low. In this case, the first heating device can be designed in an energetically favorable manner as a heat exchanger, in particular as a fluid heat exchanger. Likewise, process flows that are available in other parts of the installation as a source of waste heat can preferably be used for the heat exchanger.

In order to feed the inlet air to the upper drying plane of the belt drying installation according to the invention, a mixing device is also preferably provided for mixing fresh air with the hot air fed to the upper drying plane. The mixing equipment mixes preferably between 10 and 50 percent by weight, preferably between 20 and 40 percent by weight, and particularly preferably between 25 and 35 percent by weight of fresh air with the hot air fed to the upper drying plane. With said intake of fresh air coming from the environment of the belt drying installation, relatively dry air reaches the re-fed hot air. With the addition of fresh air, more air can be used in the pre-drying zone, thus more water or moisture can be discharged.

Alternatively or additionally, in the belt drying installation according to the invention, a second heating device is also advantageously provided for heating only the fresh mixed air before feeding it to the upper drying plane. Heating of this type only of the fresh mixed air has the advantage that only a relatively small amount of air is heated. In addition, it can work with high heating temperatures and a high temperature drop, so that the heating equipment to be used can be kept relatively small. For heating, it can be worked simultaneously with high heating temperature, without the danger of ignition in the respective fresh air supplied free of dust.

The second heating device is preferably configured as a fuel heater, in particular as a fluid burner. The fluid in this case heated or burned is preferably fuel gas, in particular natural gas or a combustible liquid, in particular oil or petroleum derivatives (benzine, diesel, heating oil) or biofuels.

The first and second heating devices can advantageously also be configured as a single heating device. In this case, both the re-fed exhaust air as well as the supplied fresh air are heated by this heating equipment, before they are fed to the upper heating plane and, in this case, are led from top to bottom through the material to bulk to dry there present.

The lower drying plane of the belt drying installation according to the invention is preferably divided into several sections and a lower air outlet is provided, by means of which exhaust air can be conveyed as inlet air from the lower drying plane of at least one section up to the upper drying plane and by means of which exhaust air can also be evacuated to the environment from at least one other section of the lower drying plane, in particular the fifth last section in the direction of flow of the material to bulk to dry. With the air outlet of this type, not all the outlet air is fed back from the lower sectioned drying plane to the upper drying plane, but a part of the outlet air is discharged to the environment. This part of the exhaust air comes in particular from the central area of the entire belt drying installation, preferably in the fifth last section of the lower drying plane. The exhaust air evacuated to the environment advantageously evacuates moisture from the bulk material to be dried to the environment. This evacuation of moisture is advantageously carried out in this case in that area of the belt drying installation, in which the dust load in the drying air that passes through the bulk material is still relatively small.

In the belt drying plant according to the invention, the upper drying plane is further divided into several sections and an upper air inlet is provided, by means of which exhaust air can be conveyed as inlet air from the drying plane lower to at least one section of the upper drying plane and by means of which fresh ambient air can also be fed to at least one other section of the upper drying plane, in particular the fifth section, considered in the direction of circulation of the material in bulk to dry. With the air inlet of this type, not all the outlet air from the lower drying plane is returned to the sectioned upper drying plane, but a part of the inlet air for the drying plane is extracted from the environment. higher. This part of the inlet air is fed in particular to the central area of the entire belt drying installation, preferably to the fifth section of the upper drying plane. The incoming air fed from the environment has only a very low moisture content and a low dust load and thus contributes in particular to the drying of the bulk material to be dried. This relatively dry inlet air supply is advantageously carried out in this case in that area of the belt drying plant according to the invention in which the bulk material to be dried is still relatively humid and therefore can discharge little moisture at relatively small temperature.

In a particularly advantageous manner, both the lower drying plane and the upper drying plane are divided into several sections and a lower air outlet and an upper air inlet are provided, by means of which outlet air and air can be conveyed. inlet from the last section of the lower drying plane, considered in the direction of circulation of the bulk material to be dried, to the first section of the upper drying plane, considered in the direction of circulation of the bulk material to be dried. Preferably, by means of the air outlet and the air inlet, outlet air can also be conveyed as inlet air from the penultimate section of the lower drying plane, considered in the direction of flow of the bulk material to be dried, to the second section of the upper drying plane, considered in the direction of circulation of the bulk material to be dried. Preferably, outlet air can also be conveyed as inlet air from the third last section of the lower drying plane, considered in the direction of flow of the bulk material to be dried, to the third section of the upper drying plane, considered in the direction circulation of the bulk material to be dried, and / or outlet air can be conveyed as inlet air from the fourth last section of the lower drying plane, considered in the direction of circulation of the bulk material to be dried, to the fourth section of the upper drying plane, considered in the direction of circulation of the bulk material to be dried. Sectional evacuation and feeding of this type have the advantage that very dry air is distributed respectively to the relatively humid bulk material and less dry air to the relatively even less humid bulk material. The sectioned feedback of this type of exhaust air as intake air is here deliberately carried out in four sections, which has been considered surprisingly advantageous with regard to the overall energy situation.

Brief description of the drawings

An exemplary embodiment of the solution according to the invention is explained in more detail below with the aid of the attached schematic drawings. The figure shows a greatly simplified longitudinal section of a belt drying plant according to the invention.

Detailed description of the realization example

A belt drying installation 10 for drying bulk material 12 in the form of saw cuts is configured with a loading device 14 by means of which the bulk material to be dried 12 can be distributed on an upper drying belt 16. The drying belt Upper 16 is an endless belt by means of which the bulk material 12 applied thereon can be conveyed in a broad horizontal direction from left to right, referred to in the figure, through an upper drying zone 18. The drying zone Upper 18 and upper drying belt 16 thus form an upper drying plane 20 which serves to pre-dry the bulk material 12.

From the upper drying plane 20, the bulk material 12 at the right end of the drying belt 16 reaches a lower drying belt 22 due to its weight and the downward force of gravity. This drying belt 22 extends from right to left, in reference to the figure, through a lower drying zone 24, thereby forming a lower drying plane 26 to a large extent horizontal. The lower drying plane 26 serves for the subsequent drying of the bulk material 12. At the left end of the lower drying belt 22, the subsequently dried bulk material 12 then exits the belt drying installation 10 by means of a discharge device 28.

The upper drying plane 20 is divided into five sections 30, 32, 34, 36 and 38, which are successively traversed by the bulk material 12 and of which correspondingly section 30 forms a first upper section, section 32 forms a second upper section, section 34 forms a third upper section, section 36 forms a fourth upper section, and section 38 forms a fifth upper section. The sections 30, 32, 34, 36 and 38 are spaced apart from each other, such that they can be traversed by the bulk material 12 on the upper drying belt 16, but are otherwise widely spaced from each other. This separation is particularly applicable for hot air which is conducted in the sections through the bulk material 12 present there to dry it, as explained more clearly below.

The lower drying plane 26 is also divided into five sections, namely sections 40, 42, 44, 46 and 48. From these sections, section 40 correspondingly forms a first lower or fifth last section, section 42 forms a second lower or fourth last section, section 44 forms a third lower or third last section, section 46 forms a fourth lower or penultimate section, and section 48 forms a fifth lower or last section. The sequence data of sections 30, 32, 34, 36, 38, 40, 42, 44, 46 and 48 refer in this case to a flow direction 50 of the bulk material to be dried 12 on the upper drying plane 20 and the lower drying plane 26.

To supply hot air to the belt drying installation 10 for drying the bulk material 12, a first lower fresh air supply unit 52 and a second lower fresh air supply unit 54 are provided on the lower drying plane 26 Thanks to both fresh air supply units 52 and 54, fresh air 56 can be fed from the environment of the belt drying installation 10 from above and towards sections 40, 42, 44, 46 and 48. The fresh air 56 serves as inlet air for these sections, as explained below, it is first heated and then sucked in by means of lower suction equipment 58, 60, 62, 64 and 66 sectionally from above and below through the bulk material 12 located on the lower drying plane 26.

Thanks to the lower suction device 58, which is assigned to the fifth last section 40, the exhaust air of this type is evacuated directly to the environment of the belt drying installation 10. On the other hand, thanks to the lower suction devices 60, 62, 64 and 66, the outlet air from the lower sections 42, 44, 46 and 48 is transported to the upper sections 36, 34, 32 or 30 sectionally by means of a respective associated air duct 68, 70, 72 or 74. The outlet air from the last section 48 is thus conveyed as the intake air to the first section 30. The outlet air from the penultimate section 46 is conveyed to the second section 32. The outlet air from the third last section 44 is conveyed to the third section 34 and the exhaust air from the fourth last section 42 is conveyed to the fourth section 36. The relatively very dry exhaust air from the last section 48 thus reaches the first section 30 , in which the largest p art of water or humidity. The exhaust air from the penultimate section 46, with only relatively slightly humid exhaust air, reaches the second station 32 where a little less water or humidity etc. evaporates. In general, the total amount of water per section or station can be kept roughly the same in this way.

Furthermore, in the upper drying plane 20 a mixing equipment 76 is provided by means of which fresh air 56 from the environment of the belt drying installation 10 can be fed to the sections present there 30, 32, 34, 36 and 38. In this case, only said fresh air 56 as inlet air is fed to section 38, but not as outlet air from the lower drying plane 26 because the outlet air from section 40 is already relatively intensely saturated with humidity.

To heat the fresh air fed 56 and the exhaust air fed back from the lower drying plane 26 to the upper drying plane 20, several lower heating equipment are associated with each of the sections 40, 42, 44, 46 and 48. 78 and to each of the sections 30, 32, 34, 36 and 38, several upper heating equipment 80 are associated. The heating equipment 78 and 80 are respectively located on the corresponding conveyor belt 22 or 16 in the feeding zone of air, so that, in particular, by means of the heating equipment 80, both the returned exhaust air from the lower sections 42, 44, 46 and 48 as well as the supplied fresh air 56 are heated.

The heating equipment 78 and 80 are respectively configured as a heat exchanger, through which hot water or steam can be transported by means of a hot water supply 82.

Finally, below the conveyor belt 16, in sections 30, 32, 34, 36 and 38, respectively a first upper suction device 86, a second upper suction device 88, a third upper suction device 90 or a fourth upper suction equipment 94. By means of these suction equipment 86, 88, 90, 92 and 94, the exhaust air is evacuated from the respective sections to the outside towards the environment of the belt drying installation 10.

Finally, it should be taken into account that a first belt blowing device 96 in the extreme right zone of the upper drying belt 16 is fed with the inlet air of the fifth last section 40 and a second belt blowing device 98 in the The extreme left area of the lower drying belt 22 is supplied with the inlet air of the last section 48. Furthermore, in the belt drying installation 10 a first belt cleaning device 100 is provided for the upper drying belt 16, a second belt cleaning device 102 for the lower drying belt 22 and, for both drying belts 16 and 22, a quench water equipment 104.

Reference symbols list

10 Belt drying facility

12 Bulk material

14 Charging device

16 Top drying belt

18 Upper drying zone

20 Top drying plane

22 Lower drying belt

24 Lower drying area

Lower drying plane

Discharge device

First section of the upper drying plane

Second section of the upper drying plane

Third section of the upper drying plane

Fourth section of the upper drying plane

Fifth section of the upper drying plane

First or fifth last section of the lower drying plane Second or fourth last section of the lower drying plane Third or third last section of the lower drying plane Fourth or penultimate section of the lower drying plane Fifth or last section of the lower drying plane Direction of circulation of the bulk material to be dried First lower fresh air supply device Second lower fresh air supply device Fresh air from the environment of the belt drying installation First lower suction device

Second bottom suction equipment

Third bottom suction kit

Fourth lower suction equipment

Fifth bottom suction equipment

Air conduction

Air conduction

Air conduction

Air conduction

Mixer equipment

Bottom heating equipment

Top heating equipment

Hot water supply

Heat exchanger

First top suction equipment

Second top suction equipment

Third top suction equipment

Fourth upper suction equipment

Fifth top suction equipment

First tape blowing device

Second tape blowing device

First belt cleaning device Second belt cleaning device Extinguishing water device

Claims (9)

1. Belt drying installation (10) for drying bulk material (12), such as sawmills, in which a first upper drying plane (20) is provided for pre-drying relatively wet bulk material (12), a second lower drying plane (26) to subsequently dry bulk material (12) already previously dried in the upper drying plane (20) and an air duct (68, 70, 72, 74) of hot air is provided, with where hot air can be led first through the lower drying plane (26) and then through the upper drying plane (20), in which hot air can be led through the air duct (68, 70, 72, 74) from top to bottom circulating through the respective drying plane (20, 26), and below the respective drying planes (20 and 26) various suction equipment (58, 60, 62, 64, 66) are provided. , 86, 88, 90, 92, 94) to suck the hot air from top to bottom as exhaust air, in which the plan or upper drying (20) is divided into several sections (30, 32, 34, 36, 38), in which an upper air inlet is provided, by means of which outlet air can be fed as inlet air from the lower drying plane (26) to at least one section of the upper drying plane (20), characterized in that, by means of the upper air inlet, fresh air (56) from the environment can also be fed to at least one other section (30, 32, 34, 36, 38) of the upper drying plane (20). 2. Belt drying plant according to claim 1, characterized in that a first heating equipment (80) is provided to heat the hot air before feeding it to the upper drying plane (20). 3. Belt drying installation according to claim 2, characterized in that the first heating equipment (80) is configured as a heat exchanger (84), in particular as a fluid heat exchanger. Belt drying plant according to one of Claims 1 to 3, characterized in that a mixing equipment (76) is provided to mix fresh air with the hot air fed to the upper drying plane (20). Belt drying plant according to claim 4, characterized in that a second heating equipment (78) is provided to heat the mixed fresh air before feeding it to the upper drying plane (20). Belt drying plant according to claim 5, characterized in that the second heating equipment (78) is configured as a combustion heater, in particular as a fluid burner. Belt drying plant according to one of Claims 1 to 6, characterized in that the lower drying plane (26) is divided into several sections (40, 42, 44, 46, 48) and a lower air outlet is provided, by means of which outlet air can be conveyed as inlet air from the lower drying plane (26) of at least one section (40, 42, 44, 46, 48) to the upper drying plane (20) and by means of which exhaust air can also be evacuated to the environment from the minus another section (40, 42, 44, 46, 48) of the lower drying plane (26), in particular of the fifth last section (48), considered in the direction of circulation (50) of the bulk material to be dried ( 12). Belt drying plant according to one of Claims 1 to 7, characterized in that, by means of the upper air inlet, fresh air (56) from the environment can also be fed to at least one other section (30, 32, 34, 36, 38) of the upper drying plane (20) of the fifth section (38), considered in the direction of circulation (50) of the bulk material to be dried (12). Belt drying plant according to one of Claims 1 to 8, characterized in that the lower drying plane (26) is divided into several sections (40, 42, 44, 46, 48) and the upper drying plane (20) is divided into several sections (30, 32, 34, 36, 38) and a lower air outlet and an upper air inlet are provided, by means of which outlet air can be conveyed as inlet air from the last section (48) of the first lower drying plane (26), considered in the direction of circulation (50) of the bulk material to be dried (12), up to the first section (30) of the upper drying plane (20), considered in the direction of circulation (50) of the bulk material to be dried (12 ), and / or by means of which outlet air can transport as inlet air from the penultimate section (46) of the lower drying plane (26), considered in the direction of circulation (50) of the bulk material to be dried (12), up to the second section (32) of the upper drying plane (20), considered in the direction of circulation. n (50) of the bulk material to be dried (12), and / or by means of which outlet air can be conveyed as inlet air from the third last section (44) from the lower drying plane (26), considered in the direction of circulation (50) of the bulk material to be dried (12), to the third section (34) of the upper drying plane (20), considered in the direction of circulation (50) of the bulk material to be dried (12), and / or by means of which outlet air can be conveyed as inlet air from the fourth last section (42) of the lower drying plane (26), considered in the direction of circulation (50) of the bulk product to be dried (12), up to the fourth section (36) of the upper drying plane (20), considered in the direction of circulation (50) of the bulk material to be dried (12) .