Oil dryer and device for mass and volume reduction of water- and carbon-containing waste materials with such an oil dryer and a fixed bed gasifier

Abstract

The invention relates to an oil dryer and to a device for the mass and volume reduction of water- and carbon-containing waste materials with such an oil dryer and a fixed bed gasifier. Water- and carbon-containing waste materials, such as, for example, sewage sludge and food waste, are very heavy due to the high water content, and cannot be thermally recycled without prior drying. It is therefore desirable to reduce the mass and volume of these waste materials. As a result of the direct heating of the mixture of oil and waste materials in the drying container (2) by means of an integrated heat exchange device (15), it is not necessary to supply heated oil from an oil storage tank. It is therefore possible to control the temperature in the mixture of waste materials and oil more precisely in the drying container (2), which in turn significantly improves the drying of the water- and carbon-containing waste materials. Furthermore, the more accurate temperature control in the drying container (2) permits a targeted and effective heating of the moist waste materials with a high proportion of solids. The use of a direct heating device (15) in the drying container (2) therefore eliminates the difficulties and high expense otherwise associated with oil conveying and the controlling of the oil temperature.

Description

[0001] Oil dryer and device for mass and volume reduction of water- and carbon-containing waste materials with such an oil dryer and a fixed-bed gasifier

[0002] Description

[0003] The present invention relates to an oil dryer according to claim 1 and a device for reducing the mass and volume of water- and carbon-containing waste materials with such an oil dryer and a fixed-bed gasifier according to claim 14.

[0004] Water- and carbon-containing waste materials, such as sewage sludge and food waste in particular, are very heavy due to their high water content and cannot be thermally recycled without prior drying. Food waste can be recycled through wet digestion. Sewage sludge presents the additional problem of pollutant contamination, which sometimes necessitates its disposal in hazardous landfills. Therefore, it is desirable to reduce the mass and volume of these waste materials.

[0005] An oil dryer for drying water- and carbon-containing waste materials is known from KR100965288B1. The oil dryer comprises a drying vessel, a feed device for the water- and carbon-containing waste materials into the drying vessel, an oil feed into the drying vessel, a heating device for heating the mixture of oil and waste materials in the drying vessel, a screw conveyor for discharging the heated mixture of oil and waste materials from the drying vessel, and a gas outlet for removing gaseous components from the heated mixture of oil and waste materials. The screw conveyor has an inner section and an outer section, with the inner section being arranged in the drying vessel and the outer section outside the drying vessel, and the outer section ending in a mixture outlet. The drying vessel is heated by heating the oil in or from an oil storage tank.This results in the temperature being the mixing temperature of the oil-waste mixture in the drying container and the temperature of the oil supplied from the oil storage tank. Control of the oil temperature and thus also of the drying performance is therefore inaccurate. Conveying or pumping the contaminated oil is either not possible at all or requires considerable effort. Based on KR100965288B1, the object of the present invention is therefore to provide an oil dryer for drying water- and carbon-containing waste materials and a device for reducing the mass and volume of water- and carbon-containing waste materials with such an oil dryer, which enables more efficient drying of the water- and carbon-containing waste materials.

[0006] This problem is solved by the features of claim 1 and 14 respectively.

[0007] By directly heating the mixture of oil and waste materials in the drying vessel using an integrated heat exchanger, the need to supply heated oil from an oil storage tank is eliminated. This enables more precise control of the temperature in the mixture of waste materials and oil in the drying vessel, which in turn significantly improves the drying of the water- and carbon-containing waste materials. Furthermore, the more precise temperature control in the drying vessel facilitates targeted and effective heating of the moist waste materials with high solids content. The use of a direct heating device in the drying vessel therefore eliminates the difficulties and considerable effort otherwise associated with oil extraction and oil temperature control. A gas outlet allows water vapor and other gaseous components, in particular, to be removed from the drying vessel.The oil-waste mixture is removed from the drying vessel via a screw conveyor. The bulk residue mixed with oil, which has a smaller volume and, in particular, a lower mass due to the water removal, is discharged via a mixture outlet at the end of the screw conveyor. The heating device preferably comprises a burner arranged outside the drying vessel with an exhaust outlet, wherein the exhaust line is thermally coupled to the heat exchanger inside the drying vessel. The external arrangement of the burner enables the use of a commercially available gas or oil burner, and the thermal coupling of the exhaust line to the heat exchanger inside the drying vessel enables more precise temperature control of the oil / waste mixture - claim 2.The thermal coupling between the hot exhaust gas and the heat exchanger is achieved in a simple manner by using heating pipes as the heat exchanger, through which the hot exhaust gases from the burner's exhaust outlet flow - claim 3. The heating output of the heating pipes depends on the temperature of the hot exhaust gas, the flow velocity of the exhaust gas in the heating pipes, and the heating surface. To prevent decomposition of the oil, the specific heating output (heat output per unit area) must not exceed an upper limit dependent on the particular oil used. Since the temperature of the hot exhaust gas drops due to the heat transfer to the oil / waste mixture, the heating output along the heating pipes also drops. This uneven heat transfer is undesirable because it is ineffective.By gradually reducing the cross-section of the heating pipes between the beginning and end, the flow velocity of the hot exhaust gas in the heating pipes increases steadily, and the heating output per unit area (specific heating output) remains approximately constant. This results in an approximately constant heating output over the entire length of the heating pipes, thus ensuring uniform heating of the oil / waste mixture - claim 4.

[0008] The gas outlet in the outer section, and particularly at the top end of the first screw conveyor, has the advantage that no additional opening is required for the removal of water vapor from the drying vessel. Since the first screw conveyor would always discharge water vapor, the removal of water vapor from the first screw conveyor must be provided anyway. - Claims 5 and 6.

[0009] The gas scrubber with condenser and oil separator at the gas outlet of the first screw conveyor condenses the water vapor expelled from the aqueous, carbonaceous waste in the oil dryer and removes any entrained oil via the oil separator. The condensate is discharged to the wastewater, and the separated oil is returned to the drying tank - claim 7.

[0010] Due to the inclined upward arrangement of the first screw conveyor, the water vapor and the gases can flow out through the gas outlet and at the same time, the oil conveyed along with it can flow back into the drying container due to gravity, so that less oil needs to be refilled into the drying container - claim 8.

[0011] The design according to claims 9 and 10 ensures that no oil / waste mixture remains in the drying tank. This is achieved by the V-shaped design of the drying tank's side walls, which open into an ascending trough at the lower end. As a result, all solids collect at the lower end of the drying tank due to gravity. The conveyor screw, which runs upwards in the trough, thus inevitably captures all the solids that have sunk to the bottom and carries them upwards.

[0012] The pelletizing device according to claim 11 ensures that the dried oil / waste mixture discharged by the first screw conveyor is granular and free-flowing and is suitable as fuel for a fixed-bed gasifier.

[0013] The thermal insulation according to claim 12 prevents heat losses.

[0014] The advantageous embodiment according to claim 13 is particularly suitable for drying waste materials that contain floating components in the oil / waste mixture. This applies, for example, to kitchen waste. These floating components are fed to the first screw conveyor by the second screw conveyor and discharged by the first screw conveyor.

[0015] The oil dryer according to claims 1 to 13 already enables a considerable reduction in the mass and volume of the water- and carbon-containing waste materials. The process for reducing the mass and volume of water- and carbon-containing waste materials according to claim 14, in which an oil dryer according to claims 1 to 11 is used in combination with a known fixed-bed gasifier, leads to a further reduction in the mass and volume of the water- and carbon-containing waste materials. The pourable waste materials dried in the oil dryer are processed in the fixed-bed gasifier to produce product gas and residue. This means that considerably smaller masses and volumes of residues, i.e., ash and slag from the fixed-bed gasifier, need to be deposited or further processed. This is particularly advantageous if the water- and carbon-containing waste materials and thus the residues from the fixed-bed gasifier are contaminated with toxic substances, e.g.contaminated with heavy metals, as the required landfill volume is much lower.

[0016] By using a gas burner as a heating device, the product gas generated in the fixed-bed gasifier can be used to heat the oil / waste mixture in the drying vessel, which increases the efficiency and environmental compatibility of the device - claims 14 and 15.

[0017] The filter devices according to claims 15, 16 and 17 prevent oil or other pollutants from entering the environment.

[0018] The device according to claims 14 to 17 is particularly suitable for reducing the mass and volume of sewage sludge, thereby significantly reducing the required landfill space. The invention achieves a volume reduction of approximately 60% and a mass reduction of 80% to 85% for sewage sludge. - Claim 17.

[0019] Further advantages and features of the present invention will become apparent from the following description with reference to the accompanying drawings. It shows:

[0020] Fig. 1 is a perspective view of an exemplary embodiment of an oil dryer according to the present invention;

[0021] Fig. 2 shows a section through the oil dryer according to Fig. 1;

[0022] Fig. 3 shows a section through the drying container of the oil dryer according to Figs. 1 and 2;

[0023] Fig. 4 shows a detailed view of the heating tubes of the heating device according to a first embodiment; Fig. 5 shows a detailed view of the heating tubes of the heating device according to a second embodiment;

[0024] Fig. 6 is a sectional view corresponding to Fig. 2 of a third embodiment of an oil dryer;

[0025] Fig. 7 is a sectional view of the second embodiment according to Fig. 6 along the line A - A; and

[0026] Fig. 8 is a block diagram of the combination of an oil dryer according to Fig. 1 to 7 with a fixed bed gasifier for producing product gas.

[0027] A first embodiment of an oil dryer 1 is shown in Figures 1 to 4. The oil dryer 1 comprises a closed drying vessel 2, which is provided with a feed device 4 for water- and carbon-containing waste materials. The waste materials are roughly dewatered and still have a moisture content of up to 70% by weight. The feed device 4 comprises a lockable, funnel-shaped waste container 6, which opens into a pelletizing device 8. The pelletizing device 8 is located on top of the drying vessel 2, opens into the drying vessel 2, and is driven by an electric motor. The drying vessel 2 is provided with an oil feed 10. A level gauge 12 is arranged in the drying vessel 2. The oil feed 10 and the level gauge 12 maintain the level 13 of the mixture of oil and pelletized waste materials within a desired range.The oil / waste mixture is heated by a heating device 14, and the water it contains is evaporated. The heating device 14 comprises a heat exchanger 15 immersed in the oil / waste mixture in the drying container 2 and a burner 16 arranged outside the drying container 2 with an air supply 16-1 and an exhaust gas outlet 16-2. The heat exchanger 15 comprises two heating pipes 15-1 connected in parallel, which are connected on the inlet side to the

[0028] Exhaust gas outlet 16-2 of the burner 16 and on the output side are connected to an exhaust 15-2 which leads out of the drying vessel 2 - see Fig. 2 and 4. The hot exhaust gases from the burner 16 flow through the heating pipes 15-1 and are discharged to the environment via an exhaust 15-2 on the outside of the drying vessel 2.

[0029] The drying vessel 2 has a wedge-shaped, funnel-shaped bottom 18 which extends downwards and is provided with a straight and inclined central trough 20, as can be seen in Fig. 3. The heated oil / waste / steam mixture is discharged via a first screw conveyor 22. The screw conveyor 22 has an inner section 23 and an outer section 24. The inner section 23 is arranged in the trough 20. The outer section 24 extends diagonally upwards away from the drying vessel 2 and ends with a downwardly open mixture outlet 26. In the end region of the outer section 24, on the upper side of the outer section 24, a gas outlet 28 is provided through which the steam and other gaseous components of the hot oil / waste / steam mixture can escape from the first screw conveyor 22.The first screw conveyor 22 runs straight and diagonally upwards so that the water vapor flows through the first screw conveyor 22 to the gas outlet 28.

[0030] The pelletizing device 8 ensures that the oil / waste mixture can be discharged smoothly through the screw conveyor 22. The first screw conveyor 22, which runs at an angle upwards, allows oil to flow back into the drying container 2, so that the oil content of the dried waste materials does not become too high. Both the drying container 2 and the outer section 24 of the first screw conveyor 22 are provided with thermal insulation 29, which reduces heat loss.

[0031] Fig. 5 shows an alternative meandering design of the heating tubes 15-1, whose cross-section continuously decreases between the beginning and the end. The heating output of the heating tubes 15-1 depends on the temperature of the hot exhaust gas, the flow velocity of the exhaust gas in the heating tubes 15-1, and the heat transfer surface of the heating tubes 15-1. To prevent decomposition of the oil, the heating output must not exceed an upper limit dependent on the oil used. Since the temperature of the hot exhaust gas drops due to heat dissipation, the heating output along the heating tubes 15-1 would also decrease if the tube cross-section remained constant. This uneven heat dissipation is undesirable because it corresponds to a lower heating output.By successively reducing the cross-section of the heating pipes 15-1, the flow velocity of the hot exhaust gas in the heating pipes 15-1 increases steadily, and the heating output per unit area (specific heating output) remains approximately constant. This results in an approximately constant heating output over the entire length of the heating pipes and thus a uniform heating of the oil / waste mixture. This cross-section reduction according to the second embodiment can also be applied to the heating pipes 15-1 shown in Fig. 4. Likewise, the heating pipes 15-1 shown in Fig. 5 can consist of two heating pipes 15-1 connected in parallel, analogous to Fig. 4.

[0032] Figures 6 and 7 schematically show a third embodiment of the oil dryer 1, which differs from the first and second embodiments essentially in that a second screw conveyor 30 is arranged in the area of ​​the surface 13 of the oil / waste mixture, which second screw conveyor 30 opens into the first screw conveyor 22 in the area of ​​the transition from the inner section 23 to the outer section 24. Solid components floating on the oil / waste mixture are conveyed by the second screw conveyor 30 into the first screw conveyor 22 and discharged to the outside. The second embodiment is particularly suitable for reducing the volume and mass of kitchen waste that contains floating components.

[0033] During drying, sewage sludge with a solids content of 40 to 60% by weight passes through a sticky, viscous phase, also known as the glue phase. In this glue phase, the drying sewage sludge tends to stick and form clumps, making drying more difficult and potentially leading to critical operating conditions. For this reason, a portion of the dried solids is usually diverted at the end of the dryer, recycled, and mixed with the incoming sewage sludge paste so that the solids content in the drying apparatus is always above the critical composition of the glue phase. This is not necessary with the oil dryer according to the present invention. Due to the rapid surface drying of the pelletized sewage sludge particles (up to 15 mm), which are also constantly surrounded by steam or oil, a short-term glue-like state inside the particle has no negative effects, i.e., clumping does not occur.

[0034] The pourable and dried oil / waste mixture exiting the mixture outlet 26 is used as fuel for a fixed-bed gasifier 32 to generate a product gas. Fig. 8 shows a block diagram of such a combination of the oil dryer 1 according to the present invention and a suitable fixed-bed gasifier 32. The fixed-bed gasifier 32 further reduces the mass and volume of the original water- and carbon-containing waste materials. The water- and carbon-containing waste materials are crushed and pelletized in the feed device 4 by the pelletizing device 8 and fed to the drying vessel 2. Oil is fed to the drying vessel 2 via the oil feed 10.The oil / waste mixture in the drying tank 2 is heated using heat supplied via the heating pipes 15-1. The expelled steam is fed via the gas outlet 28 to a gas scrubber 34 with a condenser 34-1 and an oil separator 34-2. The condensate is fed to the oil separator 34-2 via a condensate line 34-3. The oil contained in the condensed water is separated in the oil separator 34-2, collected, and can be fed back to the oil dryer 1 via an oil outlet 34-4. The cleaned water from the oil separator 34-2 is fed to the wastewater network via a wastewater outlet 34-5. The dried oil / waste mixture or granulate discharged from the screw conveyor 22 via the mixture outlet 26 is fed to the fixed bed gasifier 32. Air is supplied to the fixed bed gasifier 32 via an air supply 32-1.The ash and slag produced by gasification are discharged from the fixed bed gasifier 32 via a residue discharge 32-2 and can be disposed of. The still contaminated product gas is fed as raw gas to a particle filter 36 via a raw gas outlet 32-3. Solid or ash particles contained in the raw gas are filtered out in the particle filter 36 and discharged via a fine ash outlet 36-1. The purified, combustible product gas is discharged via a clean gas outlet 36-2 and fed to the burner 16. Combustion air is supplied to the burner 16 via the air supply 16-1. The air / gas mixture is then combusted in the burner 16 and fed to the heating tubes 15-1 via the exhaust gas outlet 16-2. The hot exhaust gases heat the oil / waste mixture in the drying container 2 and the water contained in the waste is expelled in vapor form.

[0035] An exhaust gas filter 38 is provided between the end of the heating pipes 15-1 and the exhaust 15-2, so that purified exhaust gas is released into the environment via the exhaust 15-2.

[0036] The double reduction in volume and mass significantly reduces the amount of waste to be disposed of, thus reducing the need for landfills. For sewage sludge, this results in a volume reduction of approximately 60% and a mass reduction of 80% to 85%.

[0037] An overview of suitable fixed-bed gasifiers can be found in the presentation "Fixed-Bed Gasification - State of the Art (Overview)" by Lettner, Haselbacher, and Timmerer at the conference "Thermo-Chemical Biomass Gasification for Efficient Electricity / Fuel Supply - Current Findings 2007" in February 2007 in Leipzig (http: / / www.holzgasjournal.de / download / 2_Stufen_vergaser_1.pdf). This overview describes a cocurrent shaft gasifier in which the biomass particles are fed into the gasifier vessel from above by gravity. In such a fixed-bed gasifier, the drying, pyrolysis, oxidation, and reduction zones form from top to bottom, with the reduction zone located directly above the grate. The product gas is extracted from the area of ​​the gasifier vessel below the grate, where the small-particle ash falling through the grate also collects. A suitable fixed bed gasifier is also known from WO2016091835A1 and DE102019218310A1.

[0038] Well-known devices can be used as gas scrubbers, such as those sold by the company Prantner (htps: / / www.prantner.de / de / produkte / abluftreinigung / abluftwascher-gaswascher / ).

[0039] Reference train symbol

[0040] 1 oil dryer

[0041] 2 drying containers

[0042] 4 Feeding device for water and carbon-containing waste materials

[0043] 6 funnel-shaped waste bins

[0044] 8 Pelletizing device

[0045] 10 Oil supply

[0046] 12 level gauges in 2

[0047] 13 Level or surface of the oil / waste mixture in 2

[0048] 14 Heating device

[0049] 15 Heat exchanger

[0050] 15-1 Heating pipes

[0051] 15-2 exhaust

[0052] 16 burners

[0053] 16-1 Air supply

[0054] 16-2 Exhaust outlet

[0055] 18 Bottom of 2 0 Trough in 18 2 First screw conveyor 3 Inner section of 22 4 Outer section of 22 6 Mixture outlet of 22 8 Gas outlet of 22 9 Thermal insulation 0 Second screw conveyor 2 Fixed bed gasifier 2-1 Air supply 2-2 Residue discharge of 32 2-3 Raw gas outlet of 32 4 Gas scrubber 4-1 Condenser 4-2 Oil separator 34-3 Condensate line

[0056] 34-4 Oil outlet

[0057] 34-5 Wastewater outlet

[0058] 36 Particle filter 36-1 Fine ash outlet

[0059] 36-2 Clean gas outlet

[0060] 38 exhaust filters

Claims

Claims 1. Oil dryer (1) for drying water- and carbon-containing waste materials, comprising a drying container (2), a feed device (4) for the water- and carbon-containing waste materials into the drying container (2), an oil feed (10) into the drying container (2), a heating device (14) for heating the mixture of oil and Waste materials in the drying container (2), a first screw conveyor (22) for discharging the heated mixture of oil and waste materials from the drying container (2), wherein the first screw conveyor (22) has an inner section (23) and an outer section (24), the inner section (23) is arranged in the drying container (2) and the outer section (24) is arranged outside the drying container (2), and wherein the outer section (24) ends in a mixture outlet (26), and a gas outlet (28) for discharging gaseous components from the heated mixture of oil and waste materials, characterized in that the heating device (14) comprises a heat exchange device (15) which is arranged entirely within the drying container (2).

2. Oil dryer according to claim 1, characterized in that the heating device (14) comprises a burner (16) with an exhaust gas outlet (16-2), that the burner (16) is arranged outside the drying container (2), and that the exhaust gas outlet (16-2) is thermally coupled to the heat exchange device (15).

3. Oil dryer according to claim 1 or 2, characterized in that the heat exchange device (15) comprises heating pipes (15-1) with a beginning and an end, that the beginning of the heating pipes (15-1) is connected to the exhaust gas outlet (16-2) of the burner (16), and that the end of the heating pipes (15-1) is connected to an exhaust (15-2), which leads out of the drying container (2).

4. Oil dryer according to claim 3, characterized in that the heating pipes (15-1) have a successively decreasing cross-section between the beginning and the end.

5. Oil dryer according to one of the preceding claims, characterized in that the gas outlet (28) is arranged in the outer section (24) of the first screw conveyor (22), 6. Oil dryer according to claim 5, characterized in that the gas outlet (28) is arranged in the end region on the upper side of the outer section (24) of the first screw conveyor (22).

7. Oil dryer according to one of the preceding claims, characterized in that a gas scrubber (34) with a condenser (34-1) and an oil separator (34-2) is connected downstream of the gas outlet (28).

8. Oil dryer according to one of the preceding claims, characterized in that the first screw conveyor (22) is arranged to extend obliquely upwards.

9. Oil dryer according to one of the preceding claims, characterized in that the inner section (23) of the first screw conveyor (22) is arranged in the bottom region of the drying container (2).

10. Oil dryer according to one of the preceding claims, characterized in that the drying container (2) forms a channel (20) in the region of the inner section (23) of the first screw conveyor (22).

11. Oil dryer according to one of the preceding claims, characterized in that the feed device (4) for water- and carbon-containing waste materials comprises a pelletizing device (8).

12. Oil dryer according to one of the preceding claims, characterized in that the outer section (24) of the first screw conveyor (22) and the drying container (2) are thermally insulated (29) from the outside.

13. Oil dryer according to one of the preceding claims, characterized in that a second screw conveyor (30) is provided in the upper region of the drying container (2) in order to feed solid particles floating on the oil / waste mixture to the first screw conveyor (22).

14. Apparatus for mass and volume reduction of water- and carbon-containing waste materials, with an oil dryer (1) according to one of the preceding claims for drying the water- and carbon-containing waste materials and a fixed-bed gasifier (32) for generating product gas from the dried waste materials as fuel, wherein the fixed-bed gasifier (32) is connected to the oil dryer (1) via the mixture outlet (26).

15. Device according to claim 14, characterized in that the fixed bed gasifier (32) comprises an air supply (32-1), a solids discharge (32-2) and a raw gas outlet (32-3), that the raw gas outlet (32-3) is connected to a particle filter (36) for separating fine ash particles, and that the particle filter (36) comprises a fine ash outlet (36-1) and a clean gas outlet (36-2).

16. Device according to claim 14 or 15, characterized in that the burner (16) of the heating device (14) is a gas burner, and that the raw gas outlet (32-2) of the fixed bed gasifier or the clean gas outlet (36-2) of the particle filter (36) is connected to the gas burner (16).

17. Device according to one of claims 14 to 16, characterized in that an exhaust gas filter (38) is connected upstream of the exhaust (15-2).

Images