DRYING SYSTEM AND METHOD FOR DRYING DEWATERED SEWAGE SLUDGE

Abstract

A drying system includes a disk contact dryer, which includes an inlet for the sewage sludge, a drying chamber for temporarily accommodating the sewage sludge, multiple disks in the drying chamber, a drive for rotating the disks at a defined rotational speed, a heater for heating the disks, an outlet for the sewage sludge dried in the drying chamber, and an incineration system for the dried sludge. The drying system includes an input sensor for determining the initial moisture of the sewage sludge, an output sensor for determining the final moisture of the sewage sludge, and a controller for regulating the rotational speed of the disks and/or the heat output of the heater and/or the amount of sewage sludge entering the inlet, and/or the amount of dry sewage sludge exiting the outlet based on the measurements of the input sensor and of the output sensor.

Claims

1. A drying system for drying partially dewatered sewage sludge, the drying system comprising: a disk contact dryer that includes an inlet configured for receiving the partially dewatered sewage sludge that is to be dried, a drying chamber adjoining the inlet and connected to the inlet and configured for temporarily accommodating the partially dewatered sewage sludge to be dried that has been received via the inlet, a plurality of disks, which are arranged adjacent to one another within the drying chamber and disposed to come in contact with the partially dewatered sewage sludge during the operation of the disk contact dryer, and an outlet connected to the drying chamber and configured for receiving sewage sludge dried in the drying chamber to exit from the drying chamber; a drive connected to the disk contact dryer and configured for rotating the plurality of disks at a predefined rotational speed; a heater configured to act upon the disks with a predefined heating power to supply heat to the partially dewatered sewage sludge to be dried and effectuate an evaporation of liquid present in the partially dewatered sewage sludge to be dried to yield dried sewage sludge; and an input sensor configured for determining an initial measure of the moisture of the partially dewatered sewage sludge to be dried; an output sensor configured for determining a final measure of the moisture of the dried sewage sludge in the drying chamber; a controller connected to the input sensor and to the output sensor and configured for regulating the rotational speed of the plurality of disks and the amount of partially dewatered sewage sludge to be dried entering the drying chamber via the inlet based on the initial measure of the input sensor and the final measure of the output sensor.

2. The drying system of claim 1, further comprising an input screw conveyor connected to the inlet and configured for transporting partially dewatered sewage sludge through the inlet and into the drying chamber.

3. The drying system of claim 1, further comprising an output screw conveyor connected to the outlet and configured for transporting the dried sewage sludge away from the outlet.

4. The drying system of claim 1, further comprising an output hopper connected to the outlet and configured for the intermediate storage of the dried sewage sludge exiting through the outlet before further processing of the dried sewage sludge.

5. The drying system of claim 4, wherein the output hopper includes a hopper screw conveyor that is configured to transport at least a portion of the dried sewage sludge from the outlet and into the output hopper during the operation of the drying system.

6. The drying system of claim 4, wherein the output sensor is disposed to measure the moisture of the dried sewage sludge in the output hopper during the operation of the drying system.

7. The drying system of claim 4, wherein the output sensor is arranged near the outlet or near the output hopper.

8. The drying system claim 1, wherein the input sensor or the output sensor is a microwave sensor or a near-infrared sensor.

9. The drying system of claim 1, further comprising an input hopper connected between the inlet and the drying chamber and configured for the intermediate storage, before drying, of the partially dewatered sewage sludge to be dried.

10. The drying system of claim 9, wherein the input sensor is disposed to measure the moisture of the partially dewatered sewage sludge near the inlet or near the input hopper.

11. The drying system of claim 1, wherein the controller is connected to the heater and configured for regulating the heat supplied by the heater to the plurality of disks within the drying chamber.

12. The drying system of claim 1, further comprising an incineration system connected to the disk contact dryer and configured for incinerating the dried sewage sludge from the drying chamber; wherein the incineration system is configured for operating according to multiple process variables, wherein the incineration system is connected to the controller, which is configured for regulating the multiple process variables of the operation of the incineration system.

13. A method for operating a drying system that includes a disk contact dryer having a drying chamber for drying partially dewatered sewage sludge, and having a plurality of disks arranged adjacent to one another within the drying chamber and rotatable at a defined rotational speed, which disks are in contact with the sewage sludge during the operation of the disk contact dryer, the method comprising the steps of: using an input sensor to determine the initial moisture of the partially dewatered sewage sludge before entry of the partially dewatered sewage sludge into the drying chamber; introducing an amount of partially dewatered sewage sludge into the drying chamber; applying a defined heating power to the plurality of disks to supply heat to the partially dewatered sewage sludge to effectuate an evaporation of the liquid from the partially dewatered sewage sludge introduced into the drying chamber and transform the partially dewatered sewage sludge to dried sewage sludge; removing the dried sewage sludge from the drying chamber; using an output sensor to determine the final moisture of the dried sewage sludge removed from the drying chamber; and regulating the rotational speed of the disks and the amount of the partially dewatered sewage sludge introduced into the drying chamber based on the initial moisture of the sewage sludge to be dried and the final moisture of the dried sewage sludge.

14. The method of claim 13, wherein the defined heating power and the amount of the partially dewatered sewage sludge introduced into the drying chamber is regulated in such a way that the dried sewage sludge has a final moisture between 55% and 60% moisture.

15. The method of claim 13, wherein the defined heating power and the amount of the partially dewatered sewage sludge introduced into the drying chamber is regulated in such a way that the dried sewage sludge has a final moisture between 5% and 10% moisture.

16. The method of claim 13, further comprising the step of regulating the defined heating power applied to the plurality of disks in addition to the step of regulating the rotational speed of the disks and the amount of the partially dewatered sewage sludge introduced into the drying chamber based on the initial moisture of the sewage sludge to be dried and the final moisture of the dried sewage sludge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate at least one presently preferred embodiment of the invention as well as features applicable to some alternative embodiments. These drawings, together with the written description, explain the principles of the invention but by no means are intended to be exhaustive of every possible embodiment of the invention. A full and enabling disclosure of the present invention is set forth more particularly in this specification, including reference to the accompanying figures, in which:

[0037] FIG. 1 schematically shows a drying system according to the invention.

[0038] FIG. 2 schematically shows details of components of a drying system according to the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

[0039] Reference now will be made in detail to present exemplary embodiments of the invention, wherein one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and/or letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the embodiments of the invention.

[0040] Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

[0041] It is to be understood that the ranges and limits mentioned herein include all sub-ranges located within the prescribed limits, inclusive of the limits themselves unless otherwise stated. For instance, a range from 100 to 1200 also includes all possible sub-ranges, examples of which are from 100 to 150, 170 to 190, 153 to 162, 145.3 to 149.6, and 187 to 1200. Further, a limit of up to 7 also includes a limit of up to 5, up to 3, and up to 4.5, as well as all sub-ranges within the limit, such as from about 0 to 5, which includes 0 and includes 5 and from 5.2 to 7, which includes 5.2 and includes 7.

[0042] FIG. 1 schematically shows a drying system 1 according to the invention for drying sewage sludge 3. The drying system 1 includes a disk contact dryer 2 having a drying chamber 5 and a plurality of disks 6 arranged within the drying chamber 5. The disks 6 are arranged adjacent to one another within the drying chamber 50 and disposed to come in contact with the partially dewatered sewage sludge 3 during the operation of the disk contact dryer 2. The disks 6 desirably are connected to an exterior surface that defines a shaft 23, which extends axially along the length of the drying chamber 5. A drive 20 is connected to the shaft 23 and configured for rotating the shaft 23 and the plurality of disks 6 during the operation of the disk contact dryer 2 in order to optimize the heat transfer from the disks 6 to the sewage sludge 3.

[0043] A heater is configured to act upon the disks 6 with a predefined heating power to supply heat to the partially dewatered sewage sludge 3 to be dried and effectuate an evaporation of liquid present in the partially dewatered sewage sludge 3 to be dried to yield dried sewage sludge. In order to heat the disks 6, the disks 6 desirably are connected to a heating medium inlet 22 schematically shown in FIG. 1. A heated liquid, for example, water or a heat transfer oil, or heated steam, desirably is supplied via the interior of the shaft 23 to the interior of the disks 6 in order to heat the disks 6. The moisture emerging from the sewage sludge 3 during the drying process finally reaches the outside of the drying chamber 5 via a vapor escape 21.

[0044] Moreover, as schematically shown in FIG. 1, the disk contact dryer 2 includes an inlet 4 connected to the drying chamber 5 and configured for receiving partially dewatered sludge 3 to be dried that enters the drying chamber 5. The disk contact dryer 2 includes an outlet 7 connected to the drying chamber 5 and configured for the receiving sewage sludge that has been dried in the drying chamber 5 and discharging of the dried sewage sludge exiting from the drying chamber 5.

[0045] As schematically shown in FIG. 1, the inlet 4 in the exemplary embodiment shown is connected via an input sludge line 11 to an input storage tank 15, in which the sewage sludge 3 to be dried is stored for the drying process that is to occur within the drying chamber 5. In the example shown, the drying system 1 includes an input conveyor device 12, which is configured to transport the sewage sludge 3 from the input storage tank 15 into the drying chamber 5 via the input sludge line 11.

[0046] Alternatively, the input storage tank 15 can also be omitted when the sewage sludge 3 to be dried is continuously transported to the disk contact dryer 2, for example, via a conveyor device, which is connected to a device delivering the sewage sludge 3.

[0047] The outlet 7 in the exemplary embodiment shown schematically in FIG. 1 is connected to an output sludge line 13. The dried sewage sludge 3 is discharged from the drying chamber 5 via the output sludge line 13. An output conveyor device 14 desirably is connected to the output sludge line 13 and configured to transport the dried sewage sludge 3 to a further device, in which the dried sewage sludge 3 is further processed.

[0048] It is also conceivable that the output conveyor device 14 is utilized for conveying the dried sewage sludge 3 into an output facility (not represented) of the drying system 1, from which output facility the dried sewage sludge 3 is transported away.

[0049] Moreover, as schematically shown in FIG. 1, the output sludge line 13 can empty into an incineration system 18, wherein a conveyor device for the sewage sludge 3 also could be present in this region of the output sludge line 13.

[0050] Additionally, as schematically shown in FIG. 1, it is conceivable that the output sludge line 13 empties into an output storage tank 16, which is a hopper that is configured and disposed to be utilized for temporarily storing the dried sewage sludge 3. According to this embodiment, it is advantageous when the output storage tank 16 includes a storage-tank conveyor device 17, which ensures a movement of the sewage sludge 3 from the output sludge line 13 into the output storage tank 16. One further advantage of the storage-tank conveyor device 17 is described further below in conjunction with FIG. 2.

[0051] The described devices (output conveyor device 14, incineration system 18, output storage tank 16) can be present individually or in any combination in the drying system 1 according to the invention, wherein the combination of the drying system 1 and the incineration system 18 would form a combined installation according to the invention. In this case, as schematically shown in FIG. 1, the combined installation and/or the incineration system 18 alone can include a separate control unit 19, with the aid of which separate control unit 19, the incineration of the dried sludge 3 can be performed.

[0052] In order to be able to reliably regulate the drying process of the sewage sludge 3 within the drying chamber 5, the drying system 1 includes an input sensor 8 that is configured and disposed for measuring the initial moisture of the sewage sludge 3 entering the drying chamber 5. Additionally, the drying system 1 includes an output sensor 9 that is configured and disposed for determining the final moisture of the dried sewage sludge 3 at or after the outlet 7. With respect to possible sensors 8, 9, reference is made to the preceding description.

[0053] In particular, it is advantageous when the input sensor 8 is integrated into the input sludge line 11. It likewise is advantageous when the output sensor 9 is integrated into the output sludge line 13.

[0054] Both the input sensor 8 and the output sensor 9 are connected to a controller 10. The controller 10 is configured to evaluate the measured data of the sensors 8, 9. The controller is further configured to employ the measured data from one or both of the sensors 8, 9 as a basis of regulating the heat output of the disk contact dryer 2 and/or the mass flow rate of the sewage sludge 3 entering the drying chamber 5 via the inlet 4 and/or the mass flow rate of the sewage sludge 3 exiting the drying chamber 5. Thus, as schematically shown in FIG. 1, the controller 10 desirably is connected to and configured to control operation of the input conveyor device 12 and the output conveyor device 14. Moreover, the controller 10 desirably is connected to and configured to control operation of the device supplying the heat via the heating medium inlet 22. The controller 10 desirably is connected to and configured to control operation of the drive 20 that is connected to the shaft 23 and configured for rotating the shaft 23 and the plurality of disks 6 during the operation of the disk contact dryer 2 in order to optimize the heat transfer from the disks 6 to the sewage sludge 3.

[0055] For example, it would be possible, furthermore, that the aforementioned control unit 19 regulates the oxygen supply and/or the air supply of the incineration system 18 based on the data of the input sensor 8 and/or of the output sensor 9. In particular, the control unit 19 can be directly connected to the aforementioned sensors 8, 9, and a connection to a controller 10 of the drying system 1 is also contemplated.

[0056] FIG. 2 schematically shows one alternative to the embodiment in FIG. 1, in which the disk contact dryer 2 is connected to an output storage tank 16, wherein only one section of the drying system 1 is represented. The disk contact dryer 2 includes, in the vicinity of its outlet 7, an output conveyor device 14 that is configured to route the dried sewage sludge 3 out of the drying chamber 5 and into a storage-tank conveyor device 17. The controller 10 desirably is connected to and configured to control operation of the storage-tank conveyor device 17 and the output conveyor device 14. In the view schematically depicted in FIG. 2, the output conveyor device 14 desirably is provided in the form of a screw conveyor, which is depicted from the perspective of a plane that is normal to the axis of rotation of the screw.

[0057] The storage-tank conveyor device 17 in the example shown includes a screw conveyor, which is connected to a drive unit 25. In the view schematically depicted in FIG. 2, the storage-tank conveyor device 17 is depicted from the perspective of a plane that is parallel to the axis of rotation of the screw. With the aid of the screw conveyor of the storage-tank conveyor device 17, the sewage sludge 3 coming from the drying chamber 5 is transported into the output storage tank 16. In this embodiment, the output sensor 9 is preferably annularly located around the storage-tank conveyor device 17 so that the output sensor 9 is disposed for determining the moisture content of the sewage sludge 3 passing through the storage-tank conveyor device 17. In a further alternative embodiment, a portion of the sewage sludge 3 emerging from the outlet 7 can also flow past or fall past the storage-tank conveyor device 17 into the output storage tank 16, and so only a portion of the aforementioned dried sewage sludge 3 is conveyed by the storage-tank conveyor device 17.

[0058] In particular, the output sensor 9 in the examples shown is designed as a microwave sensor, with the aid of which the final moisture of the sewage sludge 3 can be determined. As a result, a particularly reliable measurement of the final moisture of the sewage sludge 3 is possible, since the sewage sludge 3 is transported by the storage-tank conveyor device 17 at a constant and predictable mass flow rate.

[0059] While at least one presently preferred embodiment of the invention has been described using specific terms, such description is for illustrative purposes only. It is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims. This written description uses examples to disclose the invention, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that the present disclosure puts into the possession of those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.