Drying plant for biomass and / or sludge

Abstract

Drying plant for biomass and / or sludge (material to be dried) comprising a drying hall (18) with a heated floor and a building envelope that converts at least partial solar radiation into heat energy, a feeding device (1, 2, 3, 4) for feeding the drying hall (18) with material to be dried, a distribution and transport device (5) for moving the material to be dried through the drying hall (18) and for distributing and circulating the material to be dried, characterized in that the roof surface of the building envelope comprises air chambers from a volume surrounded by a film, wherein the air chambers are formed from at least two different films, namely an outwardly facing film made of a translucent and tear-resistant material with UV (ultraviolet) stabilizers and an inwardly facing film made of a translucent and tear-resistant material with anti-dew additives as well as IR (infrared) additives,wherein the foils of the roof surface are arranged so that the air chambers form thermal insulation and direct solar heating is provided in the event of solar radiation and wherein the drying hall (18) is divided into two separate rooms arranged one above the other by a suspended ceiling, wherein the lower room is the actual drying room and the upper room serves to preheat intake air.

Description

BACKGROUND OF THE INVENTION AREA OF THE INVENTION

[0001] The present invention relates to a drying plant for biomass and / or sludge according to the preamble of claim 1. STATE OF THE ART

[0002] German patent application DE 103 11 554 B4 relates to a conventional sludge drying plant comprising a drying hall with a heated floor and a building envelope that converts at least some solar radiation into heat energy, a feeding device for supplying the drying hall with sludge, and a distribution and transport device for moving the sludge through the drying hall and for distributing and circulating the material being dried. German patent application EP 0 899 529 B1 further discloses a solar dryer with a turning device for sludge, wherein a drying hall is designed that has a building envelope and a floor, the building envelope being made of a transparent and heat-insulating plastic film, such as PE bubble wrap.In addition, the publication DE 197 04 201 C2 describes another device for dewatering and drying sewage sludge, in which a dewatering basin and a drying basin are directly connected to each other, wherein the dewatering basin is divided into an upper chamber and a lower chamber by a filter layer (filter fabric, sieve belt, sieve cloth) and the drying basin by a grid, and wherein the drying basin and / or the dewatering basin can be covered by a sunlight-permeable cover / hood.

[0003] The publication EP 1 150 083 A1 relates to a method and a device for drying moist material, in particular sewage sludge, in a drying stage using drying air. The drying plant shown therein has a drying hall in which warm drying air can be supplied to the moist material across the entire floor area of ​​the drying bed. The drying hall is enclosed by a building envelope that converts at least some solar radiation into heat energy. To enable the use of solar radiation to support the drying process, the building envelope can be designed in the form of a greenhouse.The casing can be double-walled and at least partially transparent, with the double-walled design ensuring good insulation. The air intended for drying is drawn into the space between the walls of the casing and preheated or pre-dried using solar radiation. Solar collectors can also be incorporated to heat the drying air via a heating medium.

[0004] Document DE 89 00 214 U1 discloses a greenhouse film for covering film greenhouses, consisting of two individual films connected by film ribs, wherein air-fillable chambers are defined by the film ribs, the enclosed air volume of which forms an efficient insulating layer. The outer film is a film with good UV light transmission properties, for example polyethylene, and the inner film has good insulating properties, i.e., it can reflect infrared radiation inwards to a high degree, and has anti-condensation properties to prevent droplet formation.

[0005] Conventional devices for drying sludge are also known, for example, from DE 10 2006 021 131 A1, DE 43 15 321 A1, DE 34 40 484 A1, DE 10 2007 032 117 A1 and DE 20 2008 005 798 U1.

[0006] In these known drying plants for biomass and / or sludge, the material to be dried (dry material) is spread out on a heated floor of a drying hall and moved by appropriate conveying equipment in the drying hall from a loading side, where the material to be dried is brought into the drying hall, to a discharge side, where the dried material (dry material) is removed from the plant.

[0007] Furthermore, it is known from the prior art to design drying halls in such a way that, when exposed to sunlight, solar energy is used to heat and thus dry the goods being dried. For example, such drying halls can be designed in the manner of a greenhouse.

[0008] Although such drying plants can already be used to dry biomass and sludge, there is a constant need to improve the efficiency of such plants, i.e. to reduce the energy required for drying and / or to use readily available energy.

[0009] Furthermore, the known drying plants cause considerable odor pollution in the environment, which can lead to low acceptance of such plants. REVELATION OF THE INVENTIONAL TASK OF INVENTION

[0010] It is therefore an object of the present invention to provide a drying plant for biomass and / or sludge in which the aforementioned problems of the prior art can be avoided or requirements arising from the prior art can be met. In particular, a drying plant is to be provided which enables a simple reduction in the energy consumption of such a drying plant and / or allows for the efficient use of available energy. In addition, the problem of odor nuisance from such plants is to be reduced or eliminated. TECHNICAL SOLUTION

[0011] This problem is solved by a drying system with the features of claim 1. Advantageous embodiments are the subject of the dependent claims.

[0012] The drying system according to the invention is characterized in that, in order to increase energy efficiency, the roof surface of the building envelope comprises air chambers, wherein the air chambers are formed by a volume surrounded by at least two different films.

[0013] The roof membranes, namely an outward-facing membrane made of a translucent and tear-resistant material with UV (ultraviolet) stabilizers and an inward-facing membrane made of a translucent and tear-resistant material with anti-dew additives and IR (infrared) additives, are designed so that the air chambers form thermal insulation and direct solar heating is provided when exposed to sunlight.

[0014] Furthermore, a suspended ceiling is installed in the drying hall, effectively dividing it into two superimposed spaces. The lower space serves as the actual drying chamber, while the upper space is used to preheat the intake air. This design limits the volume of the drying chamber, requiring less heat for heating. Additionally, the intake air is preheated in the upper space, resulting in increased energy efficiency when combined with the improved thermal insulation.

[0015] Furthermore, the exhaust air enriched with the moisture of the goods to be dried cannot simply be released into the environment, but the contained heat energy can be used for further drying of the goods through heat recovery and / or the exhaust air can be cleaned to avoid emissions.

[0016] Various measures can be taken to create a system that is as closed as possible and largely avoids emissions. For example, an automated removal device for the dried material, such as a conveyor system for storing the dried material in a closed container for transport, such as a silo, or in particular a silo trailer for a truck, can be installed, in which a displacement air recirculation system is provided. As can easily be seen, in a closed container, such as a silo tank, into which something is being filled, at least some of the air must escape. Due to the form of the dried material, which is preferably in the form of dry granules, simply filling an open container can generate dust emissions that escape from the open container.In a discharge system where the dried material is placed in a closed container for transport, the emission of dust can be prevented by recirculating the air back into the drying hall. Furthermore, no odorous gases are released into the environment. The dust can also be removed from the air during the recirculation process using a filter.

[0017] Furthermore, a feeding device with a lockable receiving hopper can be arranged to ensure that no emissions leave the drying plant. The lockable receiving hopper can either be a closed system, in which, for example, the material to be dried is filled directly into the receiving hopper from a closed container of the delivery vehicle via a hose, thus preventing any emissions from being released. Alternatively, the lockable receiving hopper can be briefly opened for feeding and then quickly closed again.

[0018] The exhaust air purification system, which is arranged in the drying plant according to the invention, can comprise a humidifier, scrubber, conditioner, and / or droplet separator. The scrubber achieves initial purification, and the chemical composition of the exhaust air can be adjusted by a suitable conditioner. For example, if the NH3 content is too high, acid can be added to the scrubber water to enable appropriate adjustment of the chemical composition for subsequent process steps.

[0019] The exhaust air purification system can thus include one or more biofilter modules, in which the exhaust air can be purified via appropriate biochemical processes.

[0020] Furthermore, the exhaust air purification system may include a step in which the exhaust air is further purified by photolytic oxidation in order to avoid contamination of the environment or odor nuisance in the environment.

[0021] The drying system can be operated fully automatically, whereby a control and / or regulation device can control and / or regulate the corresponding process sequence with suitable heating of the drying surface in the drying hall, coordinated adjustment of the bulk thickness of the material to be dried on the heating surface and adjustment of the movement speed of the material to be dried through the drying hall, and can be adjusted to the specified drying target.

[0022] In particular, the movement speed of the biomass and / or sludge to be dried can be slow at the beginning of the process, i.e., on the feed side of the drying hall, while towards the end of the process, i.e., on the discharge side, the movement can be faster than on the feed side. This also allows the layer thickness of the material to be dried to be greater on the feed side than on the discharge side. Thus, at the beginning of the drying process, the material to be dried can be arranged in a greater thickness, while towards the end of the drying process it is present in a relatively thin layer to ensure complete drying.

[0023] Furthermore, the use of waste heat, especially from biogas production, for heating the drying plant is an aspect that can be realized using the drying plant. BRIEF DESCRIPTION OF THE FIGURE

[0024] Further advantages, characteristics, and features of the present invention will become clear in the following detailed description of an exemplary embodiment with reference to the accompanying drawing. The single figure in the drawing provides a schematic overview of the structure of a drying system according to the invention. EXAMPLE OF EXECUTION

[0025] The figure shows a schematic top view of a drying plant according to the invention, in which material to be dried (drying material), such as biomass, sludge, and in particular sewage sludge, can be introduced via a receiving hopper 11. The receiving hopper 11 has a closure (not shown), so that the receiving hopper 11 is normally closed. Only when material to be dried is to be filled into the receiving hopper 11, for example, when sewage sludge is delivered by vehicle, is the receiving hopper 11 briefly opened, the vehicle load filled into the receiving hopper 11, and the receiving hopper 11 immediately closed again to prevent emissions from the receiving hopper 11.Preferably, the receiving bunker 11 can also be designed in such a way that vehicle loads are filled directly into the receiving bunker 11 via a closed system, for example a hose system or the like, in order to avoid emissions.

[0026] In the receiving hopper 11, a moving floor 1 is provided, which moves the material being loaded towards a high-density conveying pump 2. The high-density conveying pump 2 directs the material to be dried onto a horizontal conveyor belt 3, 4, so that the material to be dried can be distributed across the width of a drying hall 18. One section 3 of the horizontal conveyor belt 3, 4 is rigid, while the other section 4 is automatically adjustable to determine the width of the drying hall 18 to which the material to be dried is fed. Accordingly, the automatically adjustable section 4 of the horizontal conveyor belt 3, 4 can be retracted, so that material only passes through the rigid section 3 of the horizontal conveyor belt 3, 4 into a specific section, e.g., half of the drying hall 18.

[0027] The drying hall 18 is divided into a large number of heating surfaces 17, which can be controlled and operated independently of each other, so that the corresponding temperature and amount of heat can be set as desired for each heating surface 17.

[0028] The heating surfaces 17 have a corresponding underfloor heating system, which can be implemented, for example, by laying heating coils in the floor of the drying hall 18.

[0029] The drying system according to the invention is preferably heated by waste heat from a biogas plant, so that the biomass generated as waste from the biogas plant can preferably be dried with waste heat from the biogas plant.

[0030] In the drying hall 18, two longitudinal scrapers 5 are arranged in the illustrated embodiment. These scrapers convey the material to be dried from the feed side at the horizontal conveyor belt 3, 4 to the discharge side via a dry material discharge distributor screw 8. Instead of the two longitudinal scrapers 5 shown in the embodiment, more or fewer longitudinal scrapers can be used. The longitudinal scrapers 5 can be designed in any suitable shape, for example, with corresponding teeth, shields, and the like, whereby the longitudinal scrapers 5 can also cause agitation and mixing of the material to be dried.Accordingly, the longitudinal scrapers 5 can not only perform a linear movement to transport the material to be dried from one side to the other of the drying hall 18, but also superimposed transverse movements, resulting in certain zigzag movements and allowing the material to be dried to move in a direction perpendicular to the main direction of movement and be mixed with other material to be dried. The longitudinal scrapers 5 can include endless conveyor belts that move in a circle and can have corresponding carriers for transporting the material to be dried.

[0031] The longitudinal scrapers 5 can also be designed to move the material to be dried, regardless of its thickness or height. This can be adjusted as needed.

[0032] Furthermore, the longitudinal scrapers 5 can also be designed so that the movement speed can be varied from the inlet side to the outlet side. Thus, the movement speed can initially be set low in the inlet area, while it is set higher in the outlet area. With a continuous material flow, this also results in the thickness or height of the material to be dried decreasing towards the outlet side on the drying surface in drying hall 18, so that after initial dehumidification at the inlet side, final drying to the desired residual moisture content takes place at the outlet side.

[0033] Overall, the drying properties to be achieved in the drying system can be adjusted by setting the temperature in the individual heating surfaces 17, the pile height of the material to be dried and the conveying speed of the material to be dried from the input side to the output side, in order to produce fuel from sludge, for example.

[0034] In addition to the drying area with the heating surfaces 17 in the form of underfloor heating under or in a concrete slab, the drying hall 18 has a building envelope with a steel structure, in which at least partially the side and / or gable walls are formed with transparent plastic hollow chamber panels, in particular PVC hollow chamber panels, which on the one hand ensure good thermal insulation and on the other hand guarantee heat generation when exposed to sunlight.

[0035] Drying hall 18 is also insulated in the area of ​​the base plate to prevent heat loss downwards.

[0036] The roof structure can be designed as a gable roof or in any other suitable roof shape.

[0037] Air chambers are formed on the roof surfaces, which also provide good thermal insulation. These air chambers are created by two essentially overlapping films joined at the sides. The space enclosed by the films is inflatable, resulting in thermally insulating air chambers. The films forming the air chambers have different surfaces on the top and bottom.

[0038] An outward-facing film consists of a translucent and tear-resistant material with UV (ultraviolet) stabilizers. An inward-facing film is a special co-extruded film made of a translucent and tear-resistant material with anti-dew additives and IR (infrared) additives.

[0039] Drying hall 18 is divided into two separate rooms, one above the other, by a suspended ceiling. The lower room is the actual drying room, while in the upper room, the required intake air is preheated by being transported along the length of drying hall 18. The suspended ceiling also allows the actual drying room to be small in volume, thus minimizing the energy required for heating it.

[0040] At the end of drying hall 18, i.e., at the discharge side where the material to be dried is removed from drying hall 18, a cross conveyor 6 is arranged, which moves the material towards a centrally located discharge conveyor 7. The cross conveyor 6 can be embedded in the floor and heated, allowing for reheating of the material to sanitize it. This ensures a germ-free end product in the form of granules.

[0041] The dry material discharge conveyor 7 conveys the dry material to the dry material discharge distribution screw 8, which distributes the dry material via a transport container, for example a silo tank trailer 9.

[0042] The silo tank trailer 9 is connected to the drying hall 18 via a displacement air line 10, so that when the silo tank trailer is filled, the displacement air produced is returned to the drying hall 18. This prevents emissions when the dried material is dispensed. A dust filter can be installed in the displacement air line 10 to remove dust from the returned air.

[0043] By combining the measures taken in the drying system according to the invention, namely with regard to the formation of a closed system and the avoidance of emissions, as well as energy optimization with the utilization of solar energy and waste heat to reduce energy requirements, and fully automated material flow control with correspondingly adjustable and / or controllable settings of the drying parameters, an optimally dried product can be achieved with low energy consumption and the avoidance of unwanted emissions.

[0044] This is further aided by the fact that the exhaust air from the drying hall 18, which contains moisture extracted from the material being dried, is routed through a heat recovery system with an exhaust air heat exchanger (air-to-air heat exchanger) 15 to cool the exhaust gases and heat the intake air, thus further reducing energy consumption. This also ensures that the exhaust gas temperature remains constant, enabling optimal conditions in the downstream biofilter modules 16.

[0045] The cooled gas is introduced into a humidifier / scrubber, conditioner, and droplet separator 12, where the exhaust gas is scrubbed. Water or a conditioning agent serves as the scrubbing medium. If the exhaust gas contains more than 30 mg / m³ of NH₃, further processing is required. 3 The water can be additionally acidified. A scrubber can be used when the NH3 content is less than 10 mg / m³. 3 can also be dispensed with.

[0046] After passing through the scrubber, where the exhaust gas remains for at least 2 to 5 seconds, the gas enters biofilter modules 16 for further purification. The exhaust gas flows through biofilter material, which is piled or stacked in a container and can consist of shredded root wood and a layer of spruce bark. At a temperature of 18 °C to 30 °C, the gas flows through the biofilter for at least 30 seconds. A reaction of the exhaust gas within the biofilter, such as biochemical oxidation by bacteria, fungi, or yeasts, purifies the exhaust gas and, in particular, reduces odor emissions.

[0047] As can be seen from the attached figure, several biofilter modules 16 can be connected in series.

[0048] In the illustrated embodiment, a reactor 14 for photolytic oxidation (UV-C sterilization) is also arranged, in which the oxidation of organic material results in sterilization and the removal of odorous substances. Accordingly, purified exhaust air can be released into the environment via a chimney 13, causing no adverse effects on the surroundings.

[0049] Overall, the drying system according to the invention provides a system that operates very efficiently with regard to energy balance and achieves high acceptance by avoiding emissions.

[0050] Although the present invention has been described in detail with reference to the exemplary embodiment, it is obvious to a person skilled in the art that the invention is not limited to this embodiment, but rather that, within the scope of protection of the appended claims, modifications can be made such that different combinations of individual features presented, as well as the omission of individual features, can be made without departing from the scope of protection. The present invention specifically claims any combination of all the presented features.

Claims

[1] Drying plant for biomass and / or sludge (drying material) with a drying hall (18) with a heated floor and a building shell which at least partially converts solar radiation into thermal energy, a feeding device (1, 2, 3, 4) for feeding the drying hall (18) with drying material, a distribution and transport device (5) for moving the drying material through the drying hall (18) and for distributing and circulating the drying material, characterized byin that the roof surface of the building envelope comprises air chambers made of a volume surrounded by a film, wherein the air chambers are formed from at least two different films, namely an outward-facing film made of a translucent and tear-resistant material with UV (ultraviolet) stabilizers and an inward-facing film made of a translucent and tear-resistant material with anti-dew additives and IR (infrared) additives, wherein the films of the roof surface are adjusted in such a way that the air chambers form thermal insulation and direct solar heating is provided when solar radiation occurs, and wherein the drying hall (18) is divided by a suspended ceiling into two separate rooms arranged one above the other, wherein the lower room represents the actual drying room and the upper room serves to preheat intake air. [2] Drying plant according to claim 1, characterized bythat an automated removal device (6,7,8) for the dried material with displacement air return (10) is arranged. [3] Drying plant according to claim 1 or 2, characterized by that the feeding device (1,2,3,4) comprises a lockable receiving bunker (11). [4] Drying plant according to one of the preceding claims, characterized by that an exhaust air heat exchanger (15) and / or an exhaust air purification system (12,14,16) is arranged. [5] Drying plant according to claim 4, characterized by that the exhaust air purification system (12,14,16) comprises a humidifier, scrubber, conditioner and / or droplet eliminator (12). [6] Drying plant according to one of claims 4 or 5, characterized by that the exhaust air purification system (12,14,16) comprises several biofilter modules (16). [7] Drying plant according to one of claims 4 to 6, characterized bythat the exhaust air purification system (12,14,16) comprises a reactor (14) for photolytic oxidation of the exhaust air. [8] Drying plant according to one of the preceding claims, characterized by that the building envelope includes additional transparent parts through which direct solar heating is provided.

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