Heat exchanger and organic waste treatment system

Abstract

The present invention relates to a heat exchanger having a plurality of heat transfer surface tubes 16 arranged in at least one tube row 16 and an end element. The heat exchanger 10 has a casing 11 around the row of tubes 16. The tubes 16 are straight. In the heat exchanger 10, a substance to be heated or cooled is configured to flow within the tubes 16, and stationary heat transfer media 20, 21 are located between the tubes 16 within an interior volume 19 of the casing 11, with each end of the tube 16 removably attached to an end element. The present invention also relates to a system for treating organic waste by hydrothermal carbonization under given process conditions, comprising at least one organic waste source, at least one wet organic waste tank, at least one thermal reactor for hydrothermal carbonization, and the heat exchanger 10. The at least one wet organic waste tank and the at least one thermal reactor are in flow connection with a heat exchanger 10, which is configured to heat the organic waste being treated in the thermal reactor by hydrothermal carbonization, and to cool biochar sludge received from the thermal reactor as a result of the hydrothermal carbonization.

Description

[Technical Field]

[0001] The present invention relates generally to a heat exchanger and an organic waste treatment system. The present invention particularly relates to a heat exchanger and an organic waste treatment system according to the preamble of independent claim 1. [Background technology]

[0002] Heat exchangers known from the prior art generally have tubes and jacket sides, and heat is transferred from one medium to another by heat transfer surface tubes, which are typically provided as primary and secondary tubes for the heat transfer medium. Prior art heat exchangers, in the context of organic waste treatment systems, generally have an overly complex configuration, which also often leads to an increase in the size of the heat exchanger, thus making them inconvenient to use in applications where space is limited.

[0003] Hydrothermal carbonization processes for organic waste treatment are well known. In hydrothermal carbonization processes, heat exchangers are used to heat and / or cool the organic waste. Heat exchangers known from the prior art generally have tube and shell sides, and heat is transferred from one material to another through heat transfer tubes. Pre-pressurization of the feed material, i.e., organic waste, is achieved by recovering heat through a heat exchanger used to cool the treated discharged waste sludge. Due to the high temperature of the discharged waste sludge, organic material can easily accumulate on the heat exchanger surface and even obstruct the flow of organic material between the heat exchanger tubes, which can eventually reduce the overall energy efficiency of the process and thus hinder the operation of the heat exchanger. Furthermore, when used in a compartmented heat exchanger, the high solid content of the waste can cause obstructions.

[0004] Known hydrothermal carbonization systems are often complex and involve multi-stage processes. Thus, organic waste treatment systems often have very complicated configurations. Attempts have been made to improve efficiency, for example, by cyclic processes and by reusing energy from one process stage to another. However, known systems often remain inefficient and result in significant losses of thermal energy.

[0005] In heat exchangers known from the prior art used in organic waste treatment systems, problems have arisen due to the high solids content of the material being treated, which causes poor flow characteristics and therefore insufficient pumping capacity. This high solids content causes blockages in the heat exchanger, thus leading to the need for cleaning. Heat exchangers known from the prior art are almost impossible to clean. Therefore, there is a great need for heat exchangers that are easy to clean.

[0006] In published patent application EP 3514218 A1, a system for treating organic waste by hydrothermal carbonization under given process conditions is disclosed, the system comprising at least one organic waste source, at least one wet (or aqueous) waste tank, a wet waste mixing tank, at least a first thermal reactor and a second thermal reactor, a biochar cooler, and at least one steam conduit provided with a valve to provide a connection between the first and second thermal reactors to supply steam alternately from the first to the second thermal reactor or from the second to the first thermal reactor to provide heat and pressure for the thermohydrolysis process. The system further includes at least one water conduit with a pump for providing a connection between the first and second thermal reactors to supply hot pressurized water alternately from the first to the second thermal reactor or from the second to the first thermal reactor to achieve given process conditions. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent Application Publication No. 3514218(A1) Summary of the Invention [Problem to be solved by the invention]

[0008] It is an object of the present invention to eliminate or at least minimize the above-mentioned problems and drawbacks of prior art heat exchangers.

[0009] A further object of the present invention is to simplify the construction of the heat exchanger.

[0010] It is an object of the present invention to eliminate or at least minimize the above-mentioned problems and drawbacks of prior art organic waste treatment systems.

[0011] A further object of the present invention is to simplify the construction of an organic waste treatment system.

[0012] A particular object of the present invention is to create a heat exchanger with reduced size and footprint. [Means for solving the problem]

[0013] To achieve the above-mentioned and other objects that will become apparent later, the heat exchanger according to the invention is mainly characterized by what is presented in the characterizing part of the independent heat exchanger claim. The organic waste treatment system according to the invention is also mainly characterized by what is presented in the characterizing part of the independent system claim. Advantageous features of the invention are defined in the dependent claims.

[0014] At a general level, the present invention also relates to a hydrothermal carbonization process, which is a thermochemical process for a given process time (duration), in which organic material is decomposed into carbon ions by raising the temperature in a sealed vessel to about 200-250°C, whereby the pressure is also raised to about 20-25 bar. The organic material decomposes, and the resulting carbon recondenses into aromatic carbon compounds. The end product of this process is biochar or hydrochar, whose chemical composition is similar to that of fossil coal. The main given process conditions are temperature, pressure, and process time (duration). The process conditions may also be called process parameters.

[0015] According to the present invention, a heat exchanger has heat transfer surface tubes arranged in at least one tube row (row of tubes) and end elements, the heat exchanger has a casing around the tube row, and the heat exchanger is configured so that the substance to be heated or cooled flows within the tubes, the tubes are straight, a stationary heat transfer medium is located between the tubes within the internal volume of the casing, and each end of the tubes is removably attached to an end element.

[0016] According to an advantageous feature of the invention, the heat exchanger has a primary side and a secondary side formed by channels located in the end elements, and the heat exchanger is configured to heat and cool two different substances by flowing the two different substances through the primary and secondary sides on opposite sides, i.e., the hot side and the cold side. This design therefore allows for the simultaneous heating and cooling of two different substances, for example, two different sludge-like material streams, both of which may have a very high solids content.

[0017] According to an advantageous feature of the invention, the end elements are formed from a tube plate and a turn chamber plate, which plates are sealed by a seal located between the plates.

[0018] According to an advantageous feature of the invention, the channels located in the end element are located in the tube plate of the end element and in the turn chamber plate.

[0019] According to an advantageous feature of the invention, the end element can be opened by means of a removable attachment and the tube is adapted to be cleaned when the end element is removed.

[0020] According to an advantageous feature of the invention, the heat transfer medium comprises a mass-like and / or pasty material and / or a solid material. Particularly advantageous is a combination of a mass-like or pasty material with a solid material, in which case the solid-form heat transfer medium also supports the structure of the heat exchanger. The solid-form heat transfer medium can be configured, for example, as a profile. The solid-form material is selected from materials with good thermal conductivity and good manufacturing properties, for example, good formability, and in particular an aluminum profile / several aluminum profiles are preferred.

[0021] According to the present invention, an organic waste treatment system is a system for treating organic waste by hydrothermal carbonization, the system comprising at least one organic waste source, at least one wet organic waste tank, at least one thermal reactor for hydrothermal carbonization, and a heat exchanger, wherein the at least one wet organic waste tank and the at least one thermal reactor are in flow connection with the heat exchanger, the heat exchanger being configured to heat the organic waste to be treated in the thermal reactor by hydrothermal carbonization and to cool the biochar sludge received from the thermal reactor as a result of the hydrothermal carbonization, the heat exchanger having heat transfer surface tubes arranged in at least one tube row and end elements, the heat exchanger having a casing around the tube row, wherein the heat exchanger is configured such that the substance to be heated and / or cooled in the heat exchanger flows in the tubes, the tubes are straight, a stationary heat transfer medium is located between the tubes within the interior volume of the casing, and each end of the tubes is removably attached to an end element.

[0022] According to an advantageous feature of the invention, the system comprises a discharge line pressurization unit for pre-pressurizing the discharge of at least one of the thermal reactors.

[0023] According to an advantageous feature of the invention, the heat exchanger is connected to a heat exchange monitoring unit, which is configured to monitor the pressure drop increase and the thermal efficiency of the heat exchanger based on measurement results received at measuring means, e.g. sensors, provided in the heat exchanger.

[0024] According to an advantageous feature of the invention, the system comprises a viscosity and / or solids content control unit and a heat exchanger control unit, which are connected to a common control unit of the system or which are formed as separate control units connected to the common control unit of the system.

[0025] According to an advantageous aspect of the invention, in the heat exchanger the substances to be heated and cooled are not connected to each other by the walls of the tubes as in heat exchangers known from the prior art, but instead the substances to be heated and cooled flow in their own tubes and the heat transfer medium is located between the tubes.

[0026] In heat exchangers known from the prior art, the purpose is generally to heat or cool a substance, so that on the primary side the substance to be heated / cooled is located and on the secondary side the heat transfer medium is located.

[0027] In a heat exchanger for a hydrothermal carbonization process, the objective is to warm a low-temperature material and cool a high-temperature material. Since both materials have a high solids content, the pressure drop in the material flow is high, and therefore the secondary side is quickly blocked by the solids, making it impossible to use systems known from the prior art. Therefore, according to an advantageous aspect of the present invention, straight tubes are used, thereby achieving smooth flow on both the primary and secondary sides. The heat transfer medium is arranged by a stationary, i.e., static but replaceable, heat transfer medium located around / between the tubes. The heat transfer medium does not flow out of or into the heat exchanger during use, but remains inside the heat exchanger, around / between the tubes of the heat exchanger.

[0028] According to an advantageous aspect of the invention, the heat exchanger has straight tubes removably attached at each end to end elements. Advantageously, the end elements are formed from a tube plate and a turn chamber plate, and a seal is formed between the plates. Advantageously, between the two end elements, the attached tubes are formed into at least one bank of tubes, for example by mangling, welding, pressing, etc. Thus, the heat exchanger has at least one bank of tubes. The heat exchanger has a primary side and a secondary side formed by channels located in the end elements, the tubes connecting said elements. The channels in the end elements are sealed to the plates by seals.

[0029] According to an advantageous aspect of the invention, in the heat exchanger, the material flows in the tubes and the heat transfer medium is located between the tubes, which are located in a heat transfer volume inside the casing with respect to the tube row, so that the heat is transferred to the inside of the casing fitted around the tubes, the casing volume between the tubes being filled with the heat transfer medium, which provides for an increased heat transfer surface and therefore a more efficient heat transfer compared to solutions known from the prior art.

[0030] According to an advantageous aspect of the invention, the heat exchanger has tubes, which are advantageously straight, through which the substance to be heated and / or cooled flows. The tubes are removably attached to end elements at each end of the tube. The end elements can be opened, so that the tubes can be easily cleaned by separating the removably attached end elements.

[0031] According to an advantageous embodiment, the organic waste treatment system comprises means for pre-pressurizing the discharge conduit to control the discharge flow from the thermal reactor, advantageously by, for example, pumping water into the discharge conduit of the organic waste treatment system until the pressure in the discharge conduit approaches the pressure inside the thermal reactor of the organic waste treatment system that is about to be discharged.

[0032] The heat exchanger and organic waste treatment system according to the present invention, and their advantageous features, achieve many advantages, namely, a compact system that optimizes energy use within the system itself. This system is therefore particularly advantageous for installation on ships where space is limited and external energy supplies are unavailable. The design of the heat exchanger consists of straight pipes without partitions, reducing the risk of blockages and eliminating the risk of buildup on the secondary side. Because the heat exchanger consists primarily of straight piping and because the stationary heat transfer medium is located around / between the piping, the heat exchanger is easy to clean. The design also eliminates the need for heat exchangers that run thermal oil or similar active heat transfer media. In the organic waste treatment system, pre-pressurization of the discharge conduit reduces flow control issues for the thermal reactor discharge during discharge. Furthermore, potential "pressure shocks" are prevented by the pre-pressurization measures.

[0033] Regardless, aspects of the present invention, together with further objects and advantages thereof, will best be understood from the following description of several illustrative embodiments when read in conjunction with the accompanying drawings, in which: [Brief explanation of the drawings]

[0034] [Figure 1A] 1 shows a schematic diagram of an advantageous embodiment of a heat exchanger according to the invention; [Figure 1B] 1 shows a schematic diagram of an advantageous embodiment of a heat exchanger according to the invention; [Figure 1C] 1 shows a schematic diagram of an advantageous embodiment of a heat exchanger according to the invention; [Figure 2] 1A-1C in an isometric view, schematically illustrating an advantageous embodiment of the heat exchanger according to the invention; [Figure 3] 1A-1C show schematic cutaway views of the advantageous embodiment of the heat exchanger according to the invention; [Figure 4A]3A-3C show schematic views of an alternative embodiment of detail E of FIG. 3 of the advantageous embodiment of the heat exchanger according to the invention shown in FIGS. [Figure 4B] 3A-3C show schematic views of an alternative embodiment of detail E of FIG. 3 of the advantageous embodiment of the heat exchanger according to the invention shown in FIGS. [Figure 5] 1 is a diagram showing a schematic diagram of an advantageous embodiment of an organic waste treatment system according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0035] Throughout this specification, like numbers and characters are used to identify like elements through the various figures illustrating the invention. Repetition of some reference characters may be omitted in the figures for reasons of clarity.

[0036] 1A-3 and 4A-4B show an example of a heat exchanger 10. The heat exchanger 10 has heat transfer surface tubes 16 and end elements formed from a tube sheet 12, turn-chamber plates 13 and 14, and seals 15. Advantageously, the tubes 16 are formed as at least one row of tubes 16 arranged inside a casing 11 by crushing, welding, pressing, or the like. The tubes 16 are straight. Thus, the heat exchanger has at least one row of straight tubes 16, each row arranged inside the casing 11, which is thus mounted around the row of tubes 16. The heat exchanger 10 has a primary side 17 and a secondary side 18 formed by channels in the tube sheet 12 and turn-chamber plates 13 and 14 located in the end elements. The channels in the tube sheet 12 and turn-chamber plates 13 and 14 of the end elements are sealed by seals. In the heat exchanger 10, a substance to be heated and / or cooled flows within the tubes 16, and the volume 19 between the tubes 16 within the casing 11 is filled with a stationary heat transfer medium 20, 21. The heat transfer medium is stationary, i.e., static, but replaceable, and is located around / between the tubes. The heat transfer medium does not flow out of or into the heat exchanger 10 during use, but remains inside the heat exchanger 10 around / between the tubes 16 of the heat exchanger 10. The heat exchanger 10 is configured to simultaneously heat and cool two different substances by flowing the two different substances on opposite sides of the primary side 17 and the secondary side 18. The substance to be heated / cooled is introduced into the heat exchanger 10 via an inlet channel, and the heated / cooled substance is removed from the heat exchanger via an outlet channel. The heat exchanger 10 can be easily cleaned because the tubes 16 are straight and the heat transfer surface tubes 16 are removably attached to end elements at the ends of the heat transfer surface tubes 16, and the end elements can be opened.

[0037] In FIG. 4A, within the casing 11, the volumes 19 between the tubes 16 are filled with a stationary heat transfer medium 20, which in this example comprises a mass-like and / or pasty substance.

[0038] 4B, the volumes 19 between the tubes 16 within the casing 11 are filled with stationary heat transfer media 20, 21, which in this example comprise a mass and / or paste-like substance 20 and a solid material 21 with high thermal conductivity. The solid material 21 can be, for example, a material profile made of a material with good thermal conductivity, such as an aluminum profile. In addition to providing heat transfer, the solid material 21 acts as a heat transfer medium and provides support for the structure of the heat exchanger.

[0039] 5, an advantageous embodiment of an organic waste treatment system 100 is shown diagrammatically. The organic waste treatment system 100 by hydrothermal carbonization includes at least a source of organic waste 30, which is supplied to the system 100 via an inlet channel 50. The organic waste 30 is generally in a wet state. The organic waste is supplied via the inlet channel 50 to a first tank, designated by the reference numeral 31. The first tank 31 has a mixing means for mixing the wet organic waste 30 to provide a mixed wet waste for further processing. The wet organic waste can be, for example, in the form of so-called biosludge and food waste. The first tank 31 can advantageously have viscosity and / or solids measuring means, such as a sensor, whose measurement results are transferred to the viscosity and / or solids content control unit 45 via a connection 51.

[0040] The mixed wet organic waste 30 is then fed by a pump 41 from the first tank 31 through a feed conduit 51 to the heat exchanger 10 for heating. From the heat exchanger, the wet organic waste 30 is alternately fed via a feed conduit 52 to a feed conduit 53 of the first thermal reactor 33 and a feed conduit 54 of the second thermal reactor 34, respectively. In the organic waste treatment system by hydrothermal carbonization, the initial process is carried out alternately in the first thermal reactor 33 and the second thermal reactor 34.

[0041] In a first initial stage, an initial batch of mixed wet organic waste 30 is alternately fed from a first tank 31 by a high-pressure pump 41 via a feed conduit 52 through respective feed conduits 53 and 54 to a first thermal reactor 33 and a second thermal reactor 34. The first thermal reactor 33 and the second thermal reactor 34 are respectively provided with mixing devices 33M, 34M for providing continuous mixing of the received mixed wet waste.

[0042] The process temperature in the first thermal reactor 33 and the second thermal reactor 34 is provided by the heat exchanger 10 and is raised to a given temperature level, typically above 200°C, by an external energy source, for example, by electrical heating. The pressure level in the first thermal reactor 33 and the second thermal reactor 34 typically exceeds 20 bar depending on the selected temperature value. The mixed wet organic waste in the first thermal reactor 33 and the second thermal reactor 34 is continuously mixed by the mixing devices 33M and 34M, respectively, while being held in the first thermal reactor 33 and the second thermal reactor 34 for a given process time of a set number of hours. The given temperature level, given pressure level, and given process time discussed above are hereinafter referred to as given process conditions, in other words, desired process conditions. Because the hydrothermal carbonization process is an exothermic reaction, heat energy is released by the chemical reaction. In addition, an external heat source is used to ensure high temperatures. The reactors provide a closed system after feeding the mixed wet waste into the reactors.

[0043] Upon completion of the processes in the first and second thermal reactors 33 and 34, the mixed waste is carbonized into biochar sludge. The biochar sludge is then led from the first and second thermal reactors 33 and 34 through discharge conduits 55 and 56, respectively, and through discharge conduit 57 to the heat exchanger 10 for cooling. The discharge conduit 57 is connected via a connecting line 72 to a discharge line pressurization unit 47 for pre-pressurizing the discharge. For example, pre-pressurization can be achieved by pumping water into the discharge conduit 57 until the pressure in the discharge conduit 57 approaches the pressure inside the thermal reactors 53 and 54 to be discharged.

[0044] After the biochar sludge has cooled sufficiently in the heat exchanger 10, the biochar sludge is discharged from the heat exchanger 10 into a storage tank 35 which has a mixing means for mixing the biochar sludge.

[0045] From the storage tank 35, the biochar sludge is conducted to a drying process by the drying means 36 via a transfer conduit 59 provided by a high-pressure pump, pump 42. The drying means 36 provides mechanical drying to separate the water and char solids. From the drying process, the dried char 38 from the drying means 36 is discharged to an external storage via a discharge conduit 61, and the separated water, known as reject water, is conducted to a reject water tank 37 via a transfer conduit 60. From the reject water tank 37, the reject water is conducted to further processing 39 via a discharge conduit 62 provided by a high-pressure pump, pump 43.

[0046] The first thermal reactor 33 and the second thermal reactor 34 have exhaust connections 63, 64, respectively, to control the pressure in the thermal reactors 33, 34. If the pressure rises too high in the thermal reactors 33 and 34, the gas can be removed via the exhaust conduits 63, 64, respectively, and directed via the transfer conduit 65 back to the first tank 31.

[0047] The heat exchanger 10 provides, on the one hand, for heating the organic waste to be treated in the thermal reactors 33, 34 by hydrothermal carbonization, and, on the other hand, for cooling the biochar sludge received from the thermal reactors 33, 34 as a result of the hydrothermal carbonization.

[0048] The heat exchanger 10 is advantageously connected to a heat exchanger control unit 46, which monitors the pressure drop increase and thermal efficiency of the heat exchanger 10 based on measurements received at measuring means, e.g. sensors, provided in the heat exchanger 10.

[0049] The viscosity and / or solids content control unit 45 and the heat exchanger control unit 46 can be connected to a common control unit of the system 100 or can be formed as separate control units connected to the common control unit of the system 100.

[0050] In the above description, some functions have been described with reference to particular features, but those functions may be performed by other features, whether or not described. Although features have been described with reference to particular embodiments or examples, those features may also be present in other embodiments or examples, whether or not described. While the present invention has been described with reference to certain advantageous embodiments, it should not be construed as being limited strictly to those embodiments. Many modifications and variations are possible within the scope of the present invention, as defined by the appended claims.

Claims

1. A heat exchanger having a plurality of heat transfer surface tubes (16) arranged in rows of at least one tube (16) and end elements, The heat exchanger (10) has a casing (11) around the row of tubes (16), the tubes (16) are straight, the substance to be heated or cooled in the heat exchanger (10) is configured to flow within the tubes (16), a stationary heat transfer medium (20, 21) is disposed between the tubes (16) in a volume (19) inside the casing (11), and each end of the tubes (16) is removably attached to the end element.

2. 2. The heat exchanger of claim 1, wherein the heat exchanger (10) has a primary side (17) and a secondary side (18) formed by channels arranged in the end elements, and the primary side (17) and the secondary side (18) allow the heat exchanger (10) to heat and cool two different substances by passing the two different substances in opposite directions through the primary side (17) and the secondary side (18).

3. 3. A heat exchanger according to claim 1 or 2, characterized in that the end elements are formed from a tube plate (12) and turn chamber plates (13, 14), the plates (12, 13, 14) being sealed by seals (15) arranged between the plates (12, 13, 14).

4. 4. A heat exchanger according to claim 3, characterized in that the channels arranged in the end elements are arranged in the tube plates (12) and the turn chamber plates (13, 14) of the end elements.

5. 5. A heat exchanger according to any one of claims 1 to 4, characterized in that the end elements can be opened by means of a removable attachment and the tubes (16) are adapted to be cleaned when the end elements are removed.

6. 6. Heat exchanger according to any one of claims 1 to 5, characterized in that the heat transfer medium comprises a mass and / or pasty substance (20) and / or a solid substance (21).

7. An organic waste treatment system, the system being an organic waste treatment system by hydrothermal carbonization, the system comprising at least one organic waste source, at least one wet organic waste tank (31), at least one thermal reactor (33, 34) for the hydrothermal carbonization, and a heat exchanger (10); The at least one wet organic waste tank (31) and the at least one thermal reactor (33, 34) are in flow connection (53, 54) with the heat exchanger (10), which is configured to heat the organic waste treated in the thermal reactor (33, 34) by hydrothermal carbonization and to cool the biochar sludge received from the thermal reactor (33, 34) as a result of the hydrothermal carbonization, and the heat exchanger (10) is configured to have a plurality of heat exchangers arranged as an array of at least one tube (16).

1. An organic waste treatment system comprising: transfer surface tubes (16) and end elements, the heat exchanger (10) having a casing (11) around the row of the tubes (16), the tubes (16) being straight, the heat exchanger (10) being configured such that a substance to be heated and / or cooled flows within the tubes (16), a stationary heat transfer medium (20, 21) being disposed between the tubes (16) in an internal volume (19) of the casing (11), and each end of the tubes (16) being removably attached to the end elements.

8. 8. The organic waste treatment system according to claim 7, characterized in that the system comprises a discharge line pressurization unit (47) for pre-pressurizing the discharge from at least one of the thermal reactors (33, 34).

9. 9. The organic waste treatment system according to claim 7 or 8, characterized in that the heat transfer medium comprises a mass and / or a pasty substance (20) and / or a solid substance (21).

10. 10. The organic waste treatment system according to claim 7, wherein the heat exchanger (10) is connected to a heat exchange monitoring unit (46), and the monitoring unit (46) is configured to monitor the pressure drop increase and thermal efficiency of the heat exchanger (10) based on measurement results received by a measuring means, for example a sensor, provided in the heat exchanger (10).

11. 11. The organic waste treatment system according to claim 7, characterized in that the system comprises a viscosity and / or solids content control unit (45) and a heat exchanger control unit (46) connected to a common control unit of the system (100) or formed as separate control units connected to the common control unit of the system (100).

Images