Method for recovering thermal energy in a material drying process, heat recovery system, and apparatus for drying a material

Abstract

A method for recovering thermal energy in a material drying process, the method comprising: providing a material to be dried containing a liquid component; providing thermal energy to evaporate at least a portion of the liquid from the material; providing a drying gas stream to convey the vapor of the liquid evaporated from the material and the associated latent heat; collecting the gas stream conveying the vapor and latent heat; recovering at least a majority or substantially all of the vapor conveyed by the gas stream and condensing at least a majority or substantially all of the vapor component in the collected gas stream to obtain a recovered liquid and a recovered gas stream; recovering the thermal energy used for evaporation and the latent heat of the vapor conveyed by the gas stream by heat exchange and condensation to obtain the thermal energy recovered by heat exchange and condensation; recycling at least a portion of the recovered thermal energy as the thermal energy used for evaporation, and / or recycling at least a portion of the recovered gas stream as the drying gas stream, and / or recycling at least a portion of the recovered liquid to the material to be dried containing the liquid component.

Description

Technical Field

[0001] The present invention generally relates to drying processes and equipment. More particularly, the present invention relates to a method for recovering thermal energy in a drying process, a heat recovery unit, and an apparatus for drying a material containing a liquid component, where thermal energy can be recovered while substantially all or at least a majority of the used liquid and / or gas can also be recovered.

Background Art

[0002] In many manufacturing processes, a dried material containing a liquid component is required. In various processes, drying of a mixture of fibers such as cellulose fibers and one or more liquids is involved. Examples of such processes include the papermaking process and the process for producing yarn or filament from cellulose fibers. Water is mixed with raw materials, for example, fibers, to form a mixture, and then dried by providing heat and air.

[0003] Such manufacturing processes involve the need for large amounts of resources such as water, air, and energy. Traditionally, many manufacturing processes are associated with adverse environmental impacts. For example, water and energy are precious resources that should be conserved. These resources are also costly and are added to the total manufacturing cost. However, prior art processes involve disposing of the dried material and air containing the latent heat from the evaporated liquid. Thus, this heat and liquid are not reusable.

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is a need for a more environmentally sustainable process for drying materials.

Means for Solving the Problems

[0005] The object of the present invention is to mitigate at least some of the problems in the prior art. According to one aspect of the present invention, there is provided a method for recovering thermal energy in a material drying process, the method comprising, at least after an initial stage in which an initial volume of liquid and an initial amount of gas flow are obtained, - providing a material to be dried containing a liquid component; - providing thermal energy to evaporate at least a part of the liquid from the material; - providing a drying gas flow to convey the vapor of the liquid evaporated from the material and the associated latent heat; - collecting the gas flow conveying the vapor and the latent heat; - recovering at least most or substantially all of the vapor conveyed by the gas flow and condensing at least most or substantially all of the vapor fraction in the collected gas flow to obtain a recovered liquid and a recovered gas flow; - recovering the thermal energy used for evaporation and the latent heat of the vapor conveyed by the gas flow by heat exchange and condensation to obtain the thermal energy recovered by heat exchange and condensation; - recycling at least a part of the recovered thermal energy as the thermal energy used for evaporation, and / or - recycling at least a part of the recovered gas flow as the drying gas flow, and / or recycling at least a part of the recovered liquid to the material to be dried containing the liquid component.

[0006] There is also provided a heat recovery system according to independent claim 11, and there is provided an apparatus for receiving a material containing a liquid component and drying the material according to independent claim 16.

[0007] Through the present invention, it may be possible to implement a method for thermal energy recovery while drying a material containing a liquid component, where, for example, during the lifespan of the associated manufacturing facility, or during a given period for manufacturing a specific amount of dried material, the overall amount of liquid, air, and / or energy required for the drying process decreases. Subsequently, the cost of manufacturing the dried material can be lower than that of known methods for manufacturing the corresponding dried material or product.

[0008] The liquid, gas, and / or energy used in drying is recovered without waste and can then be reused in the drying process or provided to other processes. This can provide a way for these resources to be conserved more efficiently than in the prior art, leading to a more environmentally friendly process.

[0009] In one embodiment, the method may be a closed process with respect to the liquid. Here, essentially all or at least 90%, preferably at least 99% of the liquid may be recycled to the material to be dried containing the liquid component.

[0010] In one embodiment, the method may be a closed process with respect to the gas stream. Essentially all or at least 90%, preferably at least 99% of the gas stream may be recycled as the drying gas stream.

[0011] In prior art methods, most of the liquid and gas streams used, or at least a portion more than that of the present invention, are not recovered and / or recycled, so most of the liquid and / or gas streams are wasted and cannot be reused. For example, it is well known that many prior art manufacturing facilities discharge a huge amount of water vapor into the environment after a material containing a liquid component is dried.

[0012] Manufacturing equipment according to the present invention for manufacturing a material or providing a dried material may be smaller than prior art manufacturing equipment. This is because it may reduce the amount of infrastructure required for the circulation of energy, liquid, and / or gas, and in the present invention, these are highly recycled. For example, the engine room for gas may be significantly smaller in the facility according to the present invention than in the prior art.

[0013] In one embodiment, the method may include recovering at least 50%, preferably at least 60%, more preferably at least 70% or 80% of the thermal energy used for evaporation, and preferably recycling at least a portion of the recovered thermal energy as thermal energy for evaporating liquid from the material. In one embodiment, at least most or essentially all of the recovered thermal energy is recycled as thermal energy for evaporating liquid from the material. In other embodiments, only a portion of the thermal energy required to evaporate liquid from the material is provided as the recovered thermal energy, and a portion of the thermal energy required to maintain the process after the starting phase is required from an external source during the process. Here, to provide the extra thermal energy induced into the process, it may be advantageous to recycle only a portion of the recovered thermal energy as thermal energy for evaporating liquid from the material. The remainder of the recovered thermal energy may be induced into an external process.

[0014] Thus, in some embodiments, rather than or in addition to recycling the recovered energy and reusing it in the process of drying the material, at least a portion of the recovered thermal energy may be reused in some other process or may be directed to an external process for reuse. For example, in one embodiment, at least a portion (5% - 70%, for example, about 10% - 30%) of the recovered thermal energy may be directed to an external process for reuse, and the remainder of the thermal energy recovered as thermal energy for drying the material may be recycled. At least a portion of the recovered thermal energy may be sold to a third party. The third party may be, for example, a district heating provider.

[0015] Embodiments of the present invention may involve materials that include fibers, for example, fibers made from natural raw materials such as cellulose. The one or more liquids used may include at least water. The method may include providing a mixture including at least cellulose fibers and water as the material to be dried.

[0016] The method may relate to a method of manufacturing filaments from the material to be dried, such as by extruding the material to be dried from one or more nozzles to provide the material to be dried onto a drying surface.

[0017] In one embodiment, thermal energy is provided to a drying surface configured to receive the material to be dried. In addition to at least a portion of the recovered thermal energy being recycled into the drying gas stream, it may be recycled to the drying surface.

[0018] This method may include inducing a gas stream that conveys vapor and latent heat into a heat recovery unit having at least a condensation heat exchanger unit. To recover the thermal energy and the latent heat conveyed by the gas stream, the condensation heat exchanger unit may utilize a cooling fluid to condense a liquid in the condensation heat exchanger unit. Using the condensation heat exchanger, at least most or essentially all of the evaporated liquid may be recovered. In the prior art, a larger portion of the evaporated liquid may typically be provided by a waste air stream.

[0019] The cooling fluid may be provided by a cooling fluid supply device, which is preferably a device separated from the condensation heat exchanger unit, and provides the cooling fluid to the condensation heat exchanger unit for exchanging heat from the dry gas stream by the heat exchanger, thereby cooling the gas stream, condensing the liquid conveyed by the gas stream, recovering the latent heat from the gas stream, and at least part of the recovered thermal energy thus obtained may be induced into the cooling fluid.

[0020] In one embodiment, the cooling fluid of the condensation heat exchanger unit is provided by a heat pump unit, and this method includes inducing at least part of the recovered thermal energy obtained in the condensation heat exchanger unit into the heat pump unit to recover additional thermal energy from the recovered thermal energy obtained in the condensation heat exchanger unit to obtain further recovered thermal energy, and inducing the recovered additional thermal energy to an external unit and / or recycling the recovered additional thermal energy as the thermal energy used for evaporation and / or treatment of the material to be dried. The heat pump unit may provide a refrigerant fluid cooled sufficiently to enable condensation of the evaporated liquid to the heat exchanger unit.

[0021] In one embodiment, at least a portion of the recovered thermal energy may be provided to at least a dry gas stream, and the dry gas stream may be heated to a temperature of less than 200 °C, preferably less than 150 °C, or less than 100 °C. Thus, embodiments of the present invention may be advantageous in processes involving dry materials where the dry gas stream used can be maintained at a temperature of, for example, 150 °C. One example is drying a mixture containing at least cellulose fibers and water, where it may be advantageous to keep the temperature of the dry gas stream at a threshold temperature, for example, less than 100 °C, for example, less than 90 °C, or less than 80 °C. Such embodiments can be easily enabled using known heat pumps. However, the method of drying materials according to the present invention is not limited to such temperatures, and in particular, higher temperatures may be provided, especially in embodiments where it is possible to provide an improved heat pump unit. However, the present invention may provide certain advantages in processes that keep the temperature of the dry gas stream or other temperatures that can be utilized in the drying process, for example, at 150 °C or less, and improve the amount of recovered thermal energy, recovered liquid, and / or recovered gas stream compared to existing similar processes.

[0022] As used herein, the term "unit" may refer to a distinct physical entity configured to perform a specified function, or to one or more other elements of a heat recovery system or apparatus capable of performing the discussed function.

[0023] The drying of a material refers to the evaporation of at least a part of the liquid content in the material. After the material is dried, the liquid may completely disappear from the material, or it may contain some residual part of the liquid. The dried material may be, for example, 0.1 wt% to 5 wt%, preferably 0.1 wt% to 1 wt% of liquid. This may refer to the amount of liquid in the material immediately after the drying process is completed. On the other hand, the dried material may start to essentially absorb moisture from the environment immediately after the drying process is completed and may contain a larger amount of liquid, for example, during the storage period. However, the present invention may also be utilized in relation to the drying process of a material where the "dried" material may also contain a larger amount of liquid, and drying refers to the evaporation of a part of the liquid content.

[0024] The novel features considered to be characteristic of the invention are set forth particularly in the appended claims. However, the invention itself, as well as its additional objects and advantages, will be best understood from the following description of specific exemplary embodiments when read in connection with the accompanying drawings, regarding both its construction and its method of operation.

[0025] As will be understood by those skilled in the art, the presented considerations regarding various embodiments of the method may be flexibly applied to embodiments of a heat recovery system or apparatus, and vice versa.

[0026] Next, the present invention will be described in more detail with reference to exemplary embodiments according to the accompanying drawings.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0028] FIG. 1 schematically shows a process diagram of a method of the present invention that utilizes at least a part of a heat recovery system according to one embodiment, in which thermal energy, gas flow, and / or liquid can be recycled. This method is shown in relation to a material manufacturing process that includes at least a drying process. Recycling may refer to the recycling of the recovered thermal energy, gas flow, and / or liquid to the material manufacturing process (including processes before and / or after the drying process and / or evaporation process, i.e., recycling can also be a wet material treatment and / or post-treatment of the dried product).

[0029] In the wet process, one or more solid materials including the material to be dried (thus, the main part of the final product produced in the material manufacturing process) may be mixed with an optional additive and a liquid substance that can be a carrier liquid or a solvent, and a material to be dried containing a liquid component may be provided. The liquid may be a pure substance or a mixture of substances in liquid form used as a carrier fluid or a solvent within the wet process.

[0030] The drying process can be considered as a process in which the liquid component of the material received from the wet process is reduced by evaporation, producing vapor which is the gaseous form of the evaporated liquid.

[0031] The figure shows at least a part of a heat recovery system that can be utilized in an embodiment of the present invention. Figure 1 also provides an example showing how different flows of thermal energy, gas, and / or liquid can be induced in a method and related processes. Thermal energy, gas, and / or liquid, or other media used, may be handled, for example, between different units of the system via a (re)circulation or delivery system equipped with conduits.

[0032] According to an embodiment of the present invention, thermal energy, gas flow, and / or liquid can be recirculated. Any one of the aforementioned recirculations may be partial. In addition to being recirculated for use in a drying process or a product manufacturing process, the recovered heat, gas, and / or liquid may also be directed to several other external processes. For example, in the example of Figure 1, the thermal energy may be directed to external uses such as district heating. A part of the recovered gas and / or the recovered liquid may be directed to an external entity as exhaust gas or output liquid.

[0033] As described above, the recovered thermal energy, gas, and / or liquid may be recirculated to one or more sub - processes in a manufacturing process. In the example of Figure 1, it is shown that the recovered gas may be recirculated to a drying process, the recovered liquid may be recirculated to a wet process, and the recovered thermal energy is shown to be (at least partially) recirculated to at least the drying process. The recovered thermal energy may be additionally or alternatively recirculated to a wet process and / or post - treatment of the dried product.

[0034] The present invention relates to a heat recovery system that can be configured to be utilized at least for recovering thermal energy in a material drying process for drying a material containing a liquid component. Accordingly, the heat recovery system can be configured to receive a drying gas stream that conveys the vapor of the evaporated liquid and the associated latent heat from a material containing the liquid component that has evaporated using thermal energy, transfer heat from the drying gas stream by a heat exchanger to cool the drying gas stream, condense essentially all or at least a majority of the vapor, and be configured to provide the recovered liquid, the recovered gas stream, and the recovered thermal energy by heat exchange and condensation.

[0035] The heat recovery system may comprise one or more elements or units that can cooperate to provide heat exchange and condensation. One unit may also comprise a plurality of elements. For example, the heat exchange unit may comprise a plurality of heat exchangers.

[0036] In one embodiment, the heat recovery system comprises at least one condensation heat exchanger unit 102 and a device 104 for providing a cooling fluid to the condensation heat exchanger unit 102. The cooling fluid may be delivered to the heat exchanger unit 102 via a cooling fluid delivery system 106.

[0037] The heat exchanger unit 102 is configured to receive a drying gas stream that conveys vapor and latent heat from the material to be dried. The heat exchanger unit 102 may utilize the cooling fluid to cool the drying gas stream, condense the evaporated liquid, and obtain the recovered liquid and the recovered thermal energy. The drying gas stream / carrier gas may be cooled to at least the dew point temperature of the gas stream in order to recover the latent heat by condensation.

[0038] The condensation heat exchanger unit 102 may comprise a plurality of heat exchangers, at least one of which is a condensation heat exchanger.

[0039] It is possible to have various implementations of the drying process in the heat recovery system, such as suspending the material to be dried in the air space so as to use a heated dry gas stream to evaporate the liquid or, as further described below, to utilize a drying surface.

[0040] The device 104 for providing the cooling fluid may, in some embodiments, be any type of unit configured to provide the cooling fluid. The cooling fluid device 104 may be, for example, a cooling system 104 that delivers the cooling fluid from an external source. In an advantageous embodiment, the device 104 is a heat pump unit. The heat recovery system may comprise a thermal energy delivery system 108 (implemented, for example, using conduits), and the condensation heat exchanger unit 102 may direct at least a portion of the recovered thermal energy obtained to the heat pump unit 104 and may be configured to recover further thermal energy from the recovered thermal energy obtained in the condensation heat exchanger unit 102 to obtain additional recovered thermal energy.

[0041] The heat pump unit 104 may then be configured to direct the additional recovered thermal energy to an external unit and / or to recycle the additional recovered thermal energy as thermal energy used for the evaporation and / or treatment of the material to be dried, for example, using a thermal energy recirculation system comprising conduits through which the thermal energy can be delivered, for example, via a fluid medium.

[0042] The cooling fluid device 104 is preferably a device separated from the condensation heat exchanger unit 102. That is, the device 104 is not integrated with the condensation heat exchanger unit 102 and is provided as an external device 104. The condensation heat exchanger unit 102 may be provided in relation to or in proximity to other parts of the heat recovery system, while the device 104 may then be located away from the condensation heat exchanger unit 102. The device 104, such as a heat pump unit, and the condensation heat exchanger unit 102 may be coupled only via a cooling fluid delivery system 106 and a thermal energy delivery system 108.

[0043] For example, a production facility where a process for drying materials is carried out may include a production building where the drying process takes place and where, for example, at least the condensation heat exchanger unit 102 may be present. Further, a device providing a cooling fluid, such as the heat pump unit 104, may be located in a separate building or structure.

[0044] The distance between the device 104 and other parts of the heat recovery system may be, for example, several tens of meters or several kilometers. Further, the cooling fluid delivery system 106 and the thermal energy delivery system 108 may couple the devices.

[0045] For example, since the heat pump unit 104 is provided as a separate device and separated from the condensation heat exchanger unit 102, one heat pump unit 104 may serve one heat recovery unit or one drying process, but it may also serve multiple heat recovery units or drying processes that may be similar processes or different types of drying processes.

[0046] Using a separate installation for the cooling fluid device 104 or by providing at least a separate cooling fluid device 104, one device 104 may be utilized in a capacity exceeding the capacity of using a dedicated and integrated cooling fluid device 104 in relation to one drying process and one heat recovery unit.

[0047] The heat recovery system may additionally comprise a liquid recirculation system configured to receive the recovered liquid and recirculate the recovered liquid to a mixing unit for mixing the material with the liquid to provide a material containing a liquid component.

[0048] The heat recovery unit may additionally comprise a gas flow recirculation system configured to receive the recovered gas flow and recirculate the recovered gas flow as a dried gas flow in the process of drying the material.

[0049] FIG. 2 shows a process diagram of a method of the present invention that utilizes at least a portion of a heat recovery system according to an embodiment in which thermal energy can be recycled. In this embodiment, the gas and liquid are not recycled, and the recovered liquid and the recovered gas are provided as an output liquid and an exhaust gas that can be directed, for example, to some external entity, or to the environment or a waste facility.

[0050] FIG. 3 schematically shows an example of an apparatus for receiving a material containing a liquid component and drying the material. This apparatus may comprise at least a heat recovery system, which may be similar to the heat recovery system of FIG. 1 or FIG. 2. FIG. 3 can be considered to show at least a portion of the equipment that can be used in a material manufacturing process including sub-processes of a wet process and a drying process. The embodiment of FIG. 3 may be considered applicable particularly in relation to the embodiment of FIG. 2 in which heat is recycled.

[0051] This device may additionally comprise at least one heating element 110 for providing thermal energy to evaporate at least a portion of the liquid from the material. The device may also comprise at least one gas flow element 112 configured to provide a dry gas flow for transporting the evaporated liquid and latent heat from the material. The thermal energy from the heating element 110 may be provided to at least the gas flow element 112 such that the dry gas flow is heated dry gas flow. The heating element 110 may be configured in relation to the gas flow element 112. The heating element 110 may be configured to receive at least a portion of the energy used from an external source. At least a portion of the energy used may also be thermal energy, and the thermal energy may be recycled and be the recovered thermal energy recovered by a heat recovery system.

[0052] The gas flow may include a pure substance or a mixture of substances in gaseous form used in the drying process to dry the material, receive the vapor (evaporated liquid from the liquid-containing material), and convey it away from the drying process. Additionally, the gas flow may be used to transport heat in the drying process. Typically, the gas is air and may contain volatile additives and / or impurities. The gas flow is typically also a heated gas flow.

[0053] The device may be configured to receive a material containing a liquid component. In the example of FIG. 2, the device comprises a drying surface 114 configured to receive the material to be dried containing a liquid component. The drying surface 114 may include, for example, a metallic material or any other material that conducts thermal energy. The drying surface 114 may be configured to be movable relative to other elements of the device, whereby the material to be dried may also be movable relative to other elements of the device. The drying surface 114 may be movable within the mechanical axis X.

[0054] In this example, the heating element 110 is configured to provide thermal energy to the gas flow and the surface heating element 116, or through them. The apparatus may comprise a plurality of gas flow elements and / or surface heating elements. The surface heating element 116 may be in thermal connection with the drying surface 114. The heating element 110 may be considered as a separate heating element 110 as shown, or each of one or more surface heating elements 116 and one or more gas flow elements 112a, 112b, 112c may comprise or be associated with a separate heating element 110.

[0055] In one embodiment, the drying gas flow may be heated to less than 150 °C or less than 100 °C. In a use case where a mixture of cellulose fibers and water is dried in a process to form a yarn or filament, it may be advantageous to keep the temperature of the drying gas flow below 90 °C.

[0056] In embodiments having a plurality of gas flows, the drying gas flows may be essentially similar, or some or all of the drying gas flows may differ from each other.

[0057] The amount of thermal energy provided to at least one surface heating element 116 may advantageously be such that the temperature of the drying surface 114 is maintained below 100 °C. This may be useful when drying a mixture of cellulose-derived fibers and water in a process where the dried end product is a filament, and the integrity or quality of the resulting filament may be higher if the water does not boil.

[0058] As the material dries, the vapor of the evaporated liquid and the associated latent heat from the material are transferred to the drying gas flow(s). The drying gas flow that conveys the evaporated liquid and the latent heat from the material is directed to a heat recovery system or at least one unit of a heat recovery system, advantageously a condensation heat exchanger unit 102. Such direction may be enabled, for example, by using one or more suction devices and conduits, for example, via a drying gas flow collection system near or in the vicinity of the gas flow element(s) 112.

[0059] The heat recovery system may operate as described in connection with FIG. 1 and may recycle at least a portion of the recovered thermal energy to at least one heating element 110, for example, using a recirculation system that may include different components or conduits to induce thermal energy. Of course, heat may additionally be recycled to the wet process or post-treatment of the dried product.

[0060] The heat recovery system may additionally include a liquid recirculation system for recirculating at least a portion of the recovered liquid to the wet process.

[0061] The wet process may be implemented using at least one mixing unit configured to receive a material, mix the material with a liquid, and obtain a material containing a liquid component. The mixing unit may be external to the apparatus or the apparatus may include the mixing unit. The mixing unit may include, for example, one or more nozzles for providing the material to be dried to the drying surface 114 or may be coupled to, for example, one or more nozzles. In one embodiment, the mixing unit also includes or is coupled to a heating element 110 such that the material containing the liquid component can be preheated.

[0062] The heat recovery system may additionally include a gas flow recirculation system configured to receive the recovered gas flow and recycle the recovered gas flow as the drying gas flow (to one or more gas flow elements 112) during the drying process. The recirculation system is not shown or is shown only schematically, and how such a system, for example, with conduits for transporting the recovered thermal energy, liquid, and / or gas flow, can be implemented will be apparent to those skilled in the art.

[0063] The device may additionally comprise a control entity (not shown) configured to receive one or more measured parameters, which may include, for example, one or more determined temperatures or humidities. The control entity may be configured to control the amount of thermal energy provided by at least one heating element 110 and / or to control the amount of gas flow provided by at least one gas flow element 112 based on the determined parameters and / or to control the amount of liquid received by the mixing unit.

[0064] The control unit may comprise one or more processors and may be implemented via one or more computing devices that can communicate, either wired or wirelessly, with any of the other components of the device.

[0065] One or more temperatures of the drying surface 114 and / or one or more temperatures and / or humidities of the drying gas flow carrying vapor and latent heat may be utilized by the control entity. The control entity may be configured to maintain the temperature or humidity at or near a predetermined value by controlling system components. For example, if the temperature of the drying surface 114 at a particular measurement location is lower than a predetermined value, the control entity may control the heating element 110 to direct more thermal energy to that measurement location.

[0066] Additionally or alternatively, the control entity may receive requests from one or more components of the device, such as the mixing unit or the heating element 110, and provide the requested amount of, for example, liquid or thermal energy. The control entity may be configured to control a liquid recirculation system, a thermal energy recirculation system, and / or a gas flow recirculation system such that the drying process is optimized based on process control logic and / or requests from system components.

[0067] The device may be configured to receive, at the start of the method / process, an initial amount of liquid volume, an initial amount of energy, and an initial amount of gas flow from an external source and / or outside of the system. After the process has started, the process may be a closed process, taking into account at least the liquid and / or gas, where no additional liquid and / or gas from an external source is required for a given amount of process time.

[0068] In some embodiments, for example, a control entity may be utilized to provide an appropriate initial amount of liquid, gas, and / or thermal energy for a given process, depending on the amount of material to be dried.

[0069] The control entity may be configured to control the amount of recovered thermal energy, recovered liquid, and / or recovered gas flow that is recycled.

[0070] Figures 4 - 6 illustrate different embodiments of the present invention, where the heat (thermal energy), liquid, and / or gas flow used can be recovered and recycled into the manufacturing process (wet and / or drying process), or can be recovered and directed to an external entity for use.

[0071] In the process of Figure 4, the gas flow and thermal energy may be at least partially recycled in the material manufacturing process. The recovered gas flow may be directed to an external entity as an exhaust gas flow and / or provided into the environment.

[0072] Figure 5 shows a process where thermal energy and liquid can be recycled, while the recovered gas flow is provided to one or more external entities as exhaust gas or into the environment.

[0073] In the embodiment of FIG. 6, thermal energy, gas flow, and liquid can be recycled in the manufacturing process. The device 104 for providing the cooling fluid to the condensation heat exchanger unit 102 is a cooling system that can be some other cooling systems other than the heat pump unit. Here, the cooling system may be considered as an external cooling system, while in some embodiments, it may also be considered as being provided in the heat recovery system. FIG. 6 can show an embodiment of the present invention in which additional thermal energy induced in the cooling fluid is not recovered, but is induced into an external unit and / or recycled to the drying process. The cooling system 104 may be, for example, a cooling system that utilizes cooling fluid obtained from the environment such as water from a lake or a river as the cooling fluid induced into the condensation heat exchanger unit 102.

[0074] The cooling system 104 in FIG. 6 can be replaced with a heat pump unit 104 to provide a process for recovering and using additional thermal energy induced in the cooling fluid as described above.

[0075] The present invention has been described above with reference to the foregoing embodiments, and some advantages of the present invention have been demonstrated. It is clear that the present invention is not limited to these embodiments, but includes all possible embodiments within the spirit and scope of the concept of the present invention and the following claims.

[0076] The features recited according to the claims can be freely combined with each other unless otherwise explicitly stated.

Claims

1. A method for recovering thermal energy in a material drying process, wherein at least after an initial step in which the initial volume of liquid and the initial amount of gas flow are obtained, the method is performed. - To provide a material to be dried that contains liquid components, - Provide thermal energy to evaporate at least a portion of the liquid from the material to be dried, - To provide a flow of dry gas to transport the vapor of the evaporated liquid and associated latent heat from the material to be dried, - Collecting the gas flow that transports the steam and the latent heat, - To recover at least a large portion or essentially all of the vapor transported by the gas flow, and to condense at least a large portion or essentially all of the vapor in the collected gas flow, thereby obtaining a recovered liquid and a recovered gas flow. - The thermal energy used for evaporation and the latent heat of the vapor transported by the gas flow are recovered by heat exchange and condensation to obtain the thermal energy recovered by heat exchange and condensation. - At least a portion of the recovered thermal energy is recycled as thermal energy used for evaporation, and / or - Recirculate at least a portion of the recovered gas flow as the dry gas flow, and / or A method comprising: recirculating at least a portion of the recovered liquid to the material to be dried, which contains the liquid component.

2. The method according to claim 1, wherein the method is a closing process with respect to the liquid.

3. The method according to claim 1 or 2, wherein the method is a closed process with respect to the gas flow, and the method includes recirculating at least a large portion or essentially all of the recovered gas flow as the dry gas flow.

4. The method according to claim 1 or 2, wherein the method includes guiding the gas flow carrying the steam and the latent heat to a heat recovery unit including at least a condensing heat exchanger unit, wherein a cooling fluid is provided by a cooling fluid providing device, the cooling fluid providing device is a device separated from the condensing heat exchanger unit, and the method is for cooling the gas flow, condensing the liquid carried by the gas flow, recovering the latent heat from the gas flow, and guiding at least a portion of the recovered thermal energy thus obtained to the cooling fluid.

5. The method according to claim 4, wherein the cooling fluid is provided by a heat pump unit, and the method includes: directing at least a portion of the recovered thermal energy obtained in the condensing heat exchanger unit to the heat pump unit to recover additional thermal energy from the recovered thermal energy obtained in the condensing heat exchanger unit to obtain further recovered thermal energy; and directing the recovered additional thermal energy to an external unit and / or recirculating the additional recovered thermal energy as the thermal energy used for evaporation and / or processing of the material to be dried.

6. The method according to claim 1 or claim 2, wherein the method includes recovering at least 50% of the thermal energy used for evaporation.

7. The method according to claim 1 or 2, wherein at least a portion of the recovered thermal energy is supplied to at least the dry gas flow, and the method includes heating the dry gas flow to a temperature of less than 200°C.

8. The method according to claim 1 or 2, wherein the material to be dried is a mixture comprising fibers and a liquid, and the method comprises mixing the fibers with at least one liquid, wherein the at least one liquid comprises water.

9. The method according to claim 1 or claim 2, wherein the thermal energy is provided at least to the dry gas flow and to the drying surface on which the material to be dried is received.

10. The method according to claim 1 or 2, wherein the gas flow that transports the steam and the latent heat is cooled to at least the dew point temperature of the gas flow in order to recover the latent heat by condensation.

11. A heat recovery system for recovering thermal energy used in a material drying process, wherein a dry gas stream carrying evaporated liquid vapor and associated latent heat is configured to receive from a material containing the liquid component, the liquid component having evaporated using thermal energy, and a heat exchanger cools the dry gas stream by transferring heat from it, thereby condensing essentially all or at least most of the vapor, and providing a liquid recovered by heat exchange and condensation, a recovered gas stream, and recovered thermal energy.

12. The heat recovery system according to claim 11, wherein the heat recovery system comprises at least a condensing heat exchanger unit (102) and a device (104) for providing a cooling fluid to the condensing heat exchanger unit for cooling the gas flow by exchanging heat from the dry gas flow with the heat exchanger, and for condensing the liquid transported by the gas flow to recover the latent heat from the gas flow, thereby guiding at least a portion of the recovered thermal energy obtained in this manner to the cooling fluid.

13. The heat recovery system according to claim 12, further comprising a thermal energy recirculation system, wherein the device for providing the cooling fluid is a heat pump unit, the condensing heat exchanger unit is configured to guide at least a portion of the recovered thermal energy obtained to the heat pump unit to recover further thermal energy from the recovered thermal energy obtained in the condensing heat exchanger unit to obtain additional recovered thermal energy, the heat pump unit is configured to guide the additional recovered thermal energy to an external unit and / or recirculate the additional recovered thermal energy as thermal energy used for processing the material to be evaporated and / or dried.

14. The heat recovery system according to any one of claims 11 to 13, further comprising a liquid recirculation system configured to receive the recovered liquid and recirculate the recovered liquid to a mixing unit for mixing the material with the liquid to provide a material containing the liquid.

15. The heat recovery system according to any one of claims 11 to 13, further comprising a gas flow recirculation system configured to receive the recovered gas flow in a process for drying the material and to recirculate the recovered gas flow as the dry gas flow.

16. An apparatus for receiving a material containing a liquid component and drying the material, wherein the apparatus comprises a heat recovery system according to any one of claims 11 to 13, at least one gas flow element for providing a dry gas flow, and at least one heating element for providing thermal energy for evaporating the liquid from the material.

17. The apparatus according to claim 16, further comprising a mixing unit configured to receive a material and mix the material with the liquid to obtain a material containing the liquid.

18. The apparatus according to claim 16, wherein the apparatus further comprises a drying surface configured to receive the material to be dried, and at least a portion of the thermal energy is provided to the drying surface.

19. The apparatus according to claim 16, further comprising a control entity configured to receive one or more determined parameters, wherein the determined parameters include at least one determined temperature, the temperature of a drying surface configured to receive the material, and / or the temperature of the drying gas flow that carries the vapor or associated latent heat of the evaporated liquid, and the control entity is configured to control the amount of thermal energy provided by the at least one heating element and / or, based on the determined parameters, the amount of gas flow provided by the at least one gas flow element.

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