Method for recovering heat energy in material drying process, heat recovery system and device for drying material

Abstract

The invention relates to a method for recovering heat energy in a material drying process. The method comprises the following steps: providing a material to be dried containing a liquid component; providing thermal energy to vaporize at least a portion of the liquid from the material; providing a dry gas stream to carry vapor from the vaporized liquid of the material and associated latent heat; collecting the gas stream carrying the steam and the latent heat; recovering at least a majority or substantially all of the vapours carried by the gas stream to at least a majority or substantially all of the vapour components in the gas stream collected by condensing to obtain a recovered liquid and a recovered gas stream; recovering the thermal energy for evaporation and the latent heat of the steam carried by the gas stream by heat exchange and condensation to obtain recovered thermal energy; recycling at least a portion of the recovered thermal energy as the thermal energy 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 comprising liquid components.

Description

Technical Field

[0001] The present invention generally relates to drying processes and drying apparatus. More particularly, the present invention relates to a method for recovering heat energy during a drying process, a heat recovery unit and an apparatus for drying a material containing a liquid component, wherein heat energy can be recovered and substantially all or at least a large part of the spent liquid and / or gas can also be recovered. Background Art

[0002] Many manufacturing processes require drying of materials containing liquid components. Various processes involve drying of a mixture of fibers (such as cellulose fibers) and one or more liquids. Examples of such processes are papermaking processes and processes for making yarn or filaments from cellulose fibers. Water is mixed with the raw material (e.g., fibers) to form a mixture, which is then dried by providing heat and air.

[0003] Such manufacturing processes involve the demand for a large number of resources, such as water, air and energy. Traditionally, many manufacturing processes are associated with adverse environmental impacts. For example, water and energy are valuable resources that should be conserved. These resources are also expensive and increase the overall manufacturing cost. However, the processes of the prior art involve the treatment of air, which contains latent heat from the dried material and the evaporated liquid. Therefore, this heat and liquid cannot be reused.

[0004] For drying materials, more environmentally sustainable processes are needed. Summary of the invention

[0005] The object of the present invention is to alleviate at least some of the problems of the prior art. According to one aspect of the present invention, there is provided a method for recovering heat energy during a material drying process, the method comprising, after at least an initial phase of obtaining an initial volume of liquid and an initial amount of airflow,

[0006] - providing a material to be dried containing a liquid component,

[0007] - providing thermal energy to evaporate at least a portion of the liquid from the material,

[0008] - provide a drying gas stream to carry the vapor and associated latent heat of the evaporated liquid from the material,

[0009] - Collect the air flow carrying steam and latent heat,

[0010] - recovering at least a major part or substantially all of the vapor carried by the gas stream by condensing at least a major part or substantially all of the vapor component in the collected gas stream to obtain recovered liquid and a recovered gas stream,

[0011] - recovering the heat energy used for evaporation and the latent heat of the steam carried by the gas stream by heat exchange and condensation to obtain the heat energy recovered by heat exchange and condensation,

[0012] - recycling at least part of the recovered heat energy as heat energy for evaporation, and / or

[0013] - recirculating at least part of the recovered gas stream as a drying gas stream, and / or

[0014] At least a portion of the recovered liquid is recycled to the material to be dried comprising a liquid component.

[0015] According to independent claim 11 there is also provided a heat recovery system, and according to independent claim 16 there is provided an apparatus for receiving a material comprising a liquid component and drying said material.

[0016] By means of the invention, a method for heat recovery can be implemented while drying a material containing a liquid component, wherein the total amount of liquid, air and / or energy required for the drying process is reduced, for example during the service life of the relevant manufacturing facility, or within a specific time period for producing a certain amount of dry material. The cost of producing the dry material can then be lower than in known methods for producing the corresponding dry material or product.

[0017] Liquids, gases and / or energy used in drying can be recovered rather than wasted and can thereafter be reused in the drying process or provided to other processes. This can provide a more efficient way to conserve these resources than prior art, resulting in a more environmentally friendly process.

[0018] In one embodiment, the method can be a closed process with respect to the liquid. Here, substantially all or at least 90%, preferably at least 99%, of the liquid can be recycled to the material to be dried which contains a liquid component.

[0019] In one embodiment, the method may be a closed process with respect to the gas stream.Substantially all or at least 90%, preferably at least 99%, of the gas stream may be recycled as a dry gas stream.

[0020] In the prior art methods, a large portion or at least a portion of the liquid and gas stream greater than that in the present invention is not recovered and / or recycled, so that most of the liquid and / or most of the gas stream is wasted and cannot be reused. For example, it is well known that many prior art manufacturing facilities discharge a large amount of water vapor into the environment after drying the material containing the liquid component.

[0021] The manufacturing facility for manufacturing materials or providing dry materials according to the invention can be smaller in size than the manufacturing facilities of the prior art. This is due to the possibility of reducing the amount of infrastructure required for the circulation of energy, liquids and / or gases, since these are largely recirculated in the invention. For example, in the facility according to the invention, the machine room for the gases can be much smaller than in the prior art.

[0022] In one embodiment, the method may include recovering at least 50%, preferably at least 60%, more preferably at least 70% or 80% of the heat energy used for evaporation, and preferably recycling at least a portion of the recovered heat energy as heat energy for evaporating liquid from the material. In one embodiment, at least most or substantially all of the recovered heat energy is recycled as heat energy for evaporating liquid from the material. In other embodiments, only a portion of the heat energy required for evaporating liquid from the material is provided as recovered heat energy, and a portion of the heat energy required to maintain the process after the initial stage will be obtained from an external source during the process. Here, in order to provide excess heat energy directed to the process, it may be advantageous to recycle only a portion of the recovered heat energy as heat energy for evaporating liquid from the material. The remaining recovered heat energy can be directed to an external process.

[0023] Thus, in some embodiments, in addition to recycling the recovered energy and reusing it in the process of drying the material, or in addition, at least a portion of the recovered heat 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 of the recovered heat energy (such as 5%-70%, for example about 10%-30%) may be directed to an external process for reuse, while the remaining recovered heat energy may be recycled as heat energy for drying the material. At least a portion of the recovered heat energy may be sold to a third party. For example, the third party may be a district heating provider.

[0024] Embodiments of the invention may involve materials comprising fibers, for example fibers made from natural raw materials, such as cellulose. The one or more liquids used may comprise at least water. The method may comprise providing a mixture comprising at least cellulose fibers and water as the material to be dried.

[0025] The method may involve a method of making filaments from a material to be dried, such as by extruding the material to be dried from one or more nozzles and providing the material to be dried to a drying surface.

[0026] In one embodiment, the thermal energy is provided to a drying surface configured to receive the material to be dried.In addition to being recycled to the drying gas stream, at least a portion of the recovered thermal energy may also be recycled to the drying surface.

[0027] The method may include directing the gas stream carrying the vapor and latent heat to a heat recovery unit including at least a condensing heat exchanger unit. The condensing heat exchanger unit may utilize a cooling fluid to condense liquid at the condensing heat exchanger unit so as to recover the thermal energy and latent heat carried by the gas stream. Using the condensing heat exchanger, at least a majority or substantially all of the evaporated liquid may be recovered. In the prior art, a majority of the evaporated liquid may typically be provided in a waste air stream.

[0028] The cooling fluid can be provided by a cooling fluid providing device, which is preferably a device separate from the condensing heat exchanger unit, for providing cooling fluid to the condensing heat exchanger unit to exchange heat from the dry gas flow through the heat exchanger, thereby cooling the gas flow and condensing the liquid carried by the gas flow, so as to further recover the latent heat from the gas flow, and direct at least a part of the recovered heat energy obtained thereby to the cooling fluid.

[0029] In one embodiment, the cooling fluid of the condensing heat exchanger unit is provided by a heat pump unit, and the method may include directing at least a portion of the recovered heat energy obtained at the condensing heat exchanger unit to the heat pump unit to recover additional heat energy, so as to recover additional heat energy from the recovered heat energy obtained at the condensing heat exchanger unit, thereby obtaining further recovered heat energy, and directing the recovered additional heat energy to an external unit and / or recycling the additional recovered heat energy as heat energy for evaporating and / or treating the material to be dried. The heat pump unit may provide the heat exchanger unit with a sufficiently cold refrigerant fluid to enable the evaporated liquid to condense.

[0030] In one embodiment, at least a portion of the recovered heat energy can be provided to at least the drying gas stream and the drying gas stream can be heated to a temperature below 200°C, preferably below 150°C or below 100°C. Thus, embodiments of the present invention may be advantageous in processes involving drying materials, where the used drying gas stream can be maintained at a temperature of, for example, below 150°C. An example is drying a mixture comprising at least cellulose fibers and water, where it may be advantageous to maintain the temperature of the drying gas stream below a threshold temperature, for example below 100°C, such as below 90°C or below 80°C. Such embodiments can be easily implemented using known heat pumps. However, the method for drying materials according to the present invention is not limited to such temperatures, and higher temperatures can also be provided, particularly with respect to embodiments in which an enhanced heat pump unit can be provided. However, in processes where the drying gas stream temperature or other temperatures that can be utilized in the drying process can be maintained, for example, below 150°C, the present invention can provide particular advantages, and the amount of recovered heat energy, recovered liquid and / or recovered gas stream can be increased compared to existing similar processes.

[0031] The term "unit" may refer herein to a separate physical entity configured to perform a specified function, or may refer to one or more other elements of a heat recovery system or apparatus capable of performing the function in question.

[0032] Drying of a material refers to the evaporation of at least a portion of the liquid components contained in the material. After the material has been dried, the material may be completely free of liquid, but may still contain some residual portions of liquid. The dried material may, for example, contain 0.1% wt.-5% wt., preferably 0.1% wt.-1% wt. of liquid. This may refer to the amount of liquid in the material immediately after the drying process, while the dried material may start to absorb moisture from the environment essentially immediately after the drying process and contain larger amounts of liquid, for example during storage. However, the present invention may also be used in combination with a method for drying a material, wherein the "dried" material may also contain larger amounts of liquid, the drying referring to the partial evaporation of the liquid components.

[0033] The novel features which are believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with further objects and advantages thereof, will be best understood from the following description of specific exemplary embodiments when read in conjunction with the accompanying drawings.

[0034] As will be appreciated by a person skilled in the art, the considerations presented with respect to the various embodiments of the method may be flexibly applied mutatis mutandis to embodiments of the heat recovery system or device, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In the following, the invention will be described in more detail with reference to exemplary embodiments according to the accompanying drawings, in which:

[0036] Figure 1 Schematically illustrates a flow chart of the method of the invention according to one embodiment utilizing at least a portion of a heat recovery system, wherein heat energy, gas streams and / or liquids can be recycled,

[0037] Figure 2 A flow chart showing a method of the invention according to one embodiment utilizing at least a portion of a heat recovery system, wherein thermal energy can be recycled,

[0038] Figure 3 Schematically shows at least a part of a device according to yet another embodiment of the present invention,

[0039] Figure 4 A flow chart showing a method of the present invention utilizing at least a portion of a heat recovery system according to one embodiment, wherein airflow and heat energy can be recycled,

[0040] Figure 5A flow chart showing a method of the present invention utilizing at least a portion of a heat recovery system according to one embodiment, wherein heat energy and liquid can be recycled, and

[0041] Figure 6 A flow chart is shown of a method of the present invention utilizing at least a portion of a heat recovery system according to one embodiment, wherein heat energy, gas streams and liquids may be recycled. DETAILED DESCRIPTION

[0042] Figure 1 A flow chart of a method of the present invention using at least a portion of a heat recovery system according to one embodiment is schematically shown, wherein heat energy, airflow and / or liquid can be recycled. The method is shown in conjunction with a material manufacturing process including at least a drying process. Recycling can refer to recycling the recovered heat energy, airflow and / or liquid back into the material manufacturing process (including processes before and / or after the drying process and / or evaporation process, i.e., recycling can also be post-processing of wet material processing and / or dry products).

[0043] In a wet process, one or more solid materials constituting the material to be dried (and therefore the major part of the final product produced in the material manufacturing process) may be mixed with optional additives and a liquid substance which may be a carrier liquid or solvent to provide a material to be dried comprising a liquid component. The liquid may be a pure substance or a mixture of substances in liquid form, which is used as a carrier liquid or solvent in a wet process.

[0044] The drying process can be thought of as a process where the liquid content of the material received from the wet process is reduced by evaporation, producing steam, which is the gaseous form of the evaporated liquid.

[0045] The diagram depicts at least a portion of a heat recovery system that may be used in embodiments of the present invention. Figure 1 Also provided is a diagram of how different heat, gas and / or liquid flows can be directed in the method and related processes. Heat, gas and / or liquid or other used media can be manipulated between different units of the system by a (re)circulation or transport system (e.g. comprising conduits).

[0046] Through embodiments of the present invention, heat, gas, and / or liquid may be recycled. The recycling of any of the foregoing may be partial. In addition to being recycled for use in a drying process or product manufacturing process, the recovered heat, gas, and / or liquid may also be directed to some other external process. For example, in Figure 1 In an example, the thermal energy may be directed to an external use, such as district heating. A portion of the recovered gas and / or recovered liquid may be directed to an external entity as waste gas or output liquid.

[0047] As previously mentioned, the recovered heat, gases and / or liquids can be recycled to one or more sub-processes within the manufacturing process. Figure 1 In the example of , the recovered gas is shown as possibly being recycled to the drying process, the recovered liquid is shown as being recycled to the wet process, and the recovered heat is shown as being recycled (at least partially) to at least the drying process. Additionally or alternatively, the recovered heat can be recycled to the wet process and / or post-processing of the dried product.

[0048] The present invention relates at least to a heat recovery system, which can be configured to recover heat energy during a material drying process for drying a material containing a liquid component. Thus, the heat recovery system can be configured to receive a drying gas stream carrying vapor and associated latent heat of evaporated liquid from the material containing a liquid component, the liquid component having been evaporated from the material containing the liquid component using heat energy, and to transfer heat from the drying gas stream through a heat exchanger to cool the drying gas stream, condensing substantially all or at least a majority of the vapor, thereby providing recovered liquid, recovered gas stream, and recovered heat energy through heat exchange and condensation.

[0049] The heat recovery system may include one or more elements or units that can work together to provide heat exchange and condensation. A unit may also include multiple elements. For example, a heat exchange unit may include multiple heat exchangers.

[0050] In one embodiment, the heat recovery system includes at least one condensing heat exchanger unit 102 and a device 104 for providing a cooling fluid to the condensing heat exchanger unit 102. The cooling fluid may be delivered to the heat exchanger unit 102 via a cooling fluid delivery system 106.

[0051] The heat exchanger unit 102 is configured to receive a drying gas stream carrying vapor and latent heat from the material to be dried. Using a cooling fluid, the heat exchanger unit 102 can cool the drying gas stream and condense evaporated liquid to obtain recovered liquid and recovered heat energy. The drying gas stream / carrier gas can be cooled to at least the dew point temperature of the gas stream to recover latent heat by condensation.

[0052] The condensing heat exchanger unit 102 may include a plurality of heat exchangers, at least one of which is a condensing heat exchanger.

[0053] Various embodiments of the drying process can be achieved using a heat recovery system, such as suspending the material to be dried in an air space so that the heated drying air flow can be used to evaporate the liquid, or a drying surface can be used, which will be discussed further below.

[0054] In some embodiments, the device 104 for providing a cooling fluid can be any type of unit configured to provide a cooling fluid. The cooling fluid device 104 can be, for example, a cooling system 104 that delivers a cooling fluid from an external source. In an advantageous embodiment, the device 104 is a heat pump unit. The heat recovery system may include a heat energy delivery system 108 (e.g., implemented using a pipeline), and the condensing heat exchanger unit 102 may be configured to direct at least a portion of the recovered heat energy obtained to the heat pump unit 104 to recover further heat energy from the recovered heat energy obtained at the condensing heat exchanger unit 102, thereby obtaining additional recovered heat energy.

[0055] The heat pump unit 104 can then be configured to direct the recovered additional heat energy to an external unit and / or utilize a heat energy recycling system (e.g., including conduits that can transport heat energy via a fluid medium) to recycle the additional recovered heat energy as heat energy for evaporation and / or processing the material to be dried.

[0056] The cooling fluid device 104 is advantageously a separate device from the condensing heat exchanger unit 102, i.e. the device 104 is not integrated with the condensing heat exchanger unit 102 and is provided as an external device 104. The condensing heat exchanger unit 102 may be arranged in connection with or closer to other parts of the heat recovery system, while the device 104 may be located at a distance from the condensing heat exchanger unit 102. The device 104 (such as a heat pump unit) and the condensing heat exchanger unit 102 may be coupled only via the cooling fluid delivery system 106 and the thermal energy delivery system 108.

[0057] For example, a production facility that performs a material drying process may include a production building, the drying process is performed in the production building, and at least the condensing heat exchanger unit 102 may be located in the production building. Then the equipment that provides the cooling fluid (such as the heat pump unit 104) may be located in a separate building or structure.

[0058] The distance between the device 104 and the rest of the heat recovery system may be, for example, tens of meters or several kilometers.The cooling fluid delivery system 106 and the thermal energy delivery system 108 may then couple these devices.

[0059] For example, since the heat pump unit 104 is provided as a separate device and is separated from the condensing heat exchanger unit 102, one heat pump unit 104 can serve one heat recovery unit or one drying process, but it can also serve multiple heat recovery units or drying processes, which may be similar processes or may be different types of drying processes.

[0060] By providing a separate facility for the cooling fluid device 104, or at least by providing a separate cooling fluid device 104, a device 104 can be utilized in situations that exceed the capabilities of using a dedicated and integrated cooling fluid device 104 when associated with a drying process and a heat recovery unit.

[0061] The heat recovery system may additionally include a liquid recycling system configured to receive the recovered liquid and recirculate the recovered liquid to the mixing unit for mixing the feed with the liquid to provide the feed including the liquid component.

[0062] The heat recovery unit may additionally include an airflow recirculation system configured to receive the recovered airflow and recirculate the recovered airflow as a drying airflow for use in the process of drying the material.

[0063] Figure 2 A flow chart of a method of the present invention utilizing at least a portion of a heat recovery system according to one embodiment is shown, wherein the thermal energy can be recycled. In this embodiment, the gas and liquid are not recycled, and the recovered liquid and recovered gas are provided as output liquid and exhaust gas, which can be directed, for example, to some external entity or the environment or a waste treatment facility.

[0064] Figure 3 An example of an apparatus for receiving a material containing a liquid component and drying the material is schematically shown. The apparatus includes at least a heat recovery system, which may be similar to Figure 1 or Figure 2 Heat recovery system. Figure 3 It can be considered as depicting at least a portion of the equipment that may be used in a material manufacturing process including sub-processes such as wet processing and dry processing. Figure 3 The embodiments may be considered particularly suitable for Figure 2 Embodiment of heat recycling.

[0065] The device may additionally include 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 include at least one airflow element 112, which is configured to provide a dry airflow to carry the evaporated liquid and the latent heat from the material. The thermal energy from the heating element 110 can be provided to at least the airflow element 112 so that the dry airflow is a heated dry airflow. The heating element 110 can also be included in association with the airflow element 112. The heating element 110 can be configured to receive at least a portion of the energy used from an external source. At least a portion of the energy used can also be recycled recovered heat energy and is recovered heat energy recovered by a heat recovery system.

[0066] The gas stream may include a pure substance or a mixture of substances in gaseous form used in the drying process to dry the material and to receive the vapor (liquid evaporated from a material containing a liquid component) and carry it out of the drying process. In addition, the gas stream may be used to carry heat during the drying process. Typically, the gas is air and may contain volatile additives and / or impurities. The gas stream is also typically a heated gas stream.

[0067] The apparatus may be configured to receive a material comprising a liquid component. Figure 2 In an example of the apparatus, the apparatus includes a drying surface 114 configured to receive a material to be dried that includes a liquid component. For example, the drying surface 114 may include a metal material or some other material that conducts thermal energy. The drying surface 114 may be configured to be movable relative to other elements of the apparatus so that the material to be dried may also be movable relative to other elements of the apparatus. The drying surface 114 is movable along a machine axis X.

[0068] In this example, the heating element 110 is configured to provide heat to or via the airflow and the surface heating element 116. The device may also include a plurality of airflow elements and / or surface heating elements. The surface heating element 116 may be thermally connected to the drying surface 114. The heating element 110 may be considered as a separate heating element 110 as shown, or each of the one or more surface heating elements 116 and the one or more airflow elements 112a, 112b, 112c may include the separate heating element 110 or be connected to the separate heating element.

[0069] In one embodiment, the drying gas stream may be heated to less than 150° C. or less than 100° C. During drying of the mixture of cellulosic fibers and water to form yarns or filaments, it may be advantageous to maintain the temperature of the drying gas stream below 90° C.

[0070] In embodiments having multiple air streams, the drying air streams may be substantially similar or some or all of the drying air streams may be different from one another.

[0071] The amount of thermal energy provided to the at least one surface heating element 116 can advantageously be such that the temperature of the drying surface 114 is maintained below 100° C. This can be useful in processes where a mixture of cellulose-derived fibers and water is dried and the final product after drying is filaments, because the integrity or quality of the resulting filaments can be higher if the water is not boiling.

[0072] When the material is dried, the vapor and the associated latent heat of the evaporated liquid from the material are transferred to the drying gas stream. The drying gas stream carrying 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 to the condensing heat exchanger unit 102. This directing can be achieved by a drying gas stream collection system, for example by using one or more suction devices and ducts, such as near or located at the gas flow element 112.

[0073] Heat recovery systems can be combined with Figure 1 Operating as described for the thermal energy recycling system, wherein the recycling system may include, for example, different components or conduits for conducting the thermal energy, at least a portion of the recovered thermal energy obtained may be recycled to the at least one heating element 110. Of course, the heat may additionally be recycled to the wet process or post-processing of the dry product.

[0074] The heat recovery system may additionally comprise a liquid recirculation system for recirculating at least a portion of the recovered liquid to the wet process.

[0075] The wet process can be implemented using at least one mixing unit configured to receive a material and mix the material with a liquid to obtain a material comprising a liquid component. The mixing unit may be external to the device or the device may include the mixing unit. The mixing unit may include or, for example, may be connected to one or more nozzles that provide the material to be dried, for example, to a drying surface 114. In one embodiment, the mixing unit further includes a heating element 110 or is coupled to the heating element so that the material comprising a liquid component can be preheated.

[0076] The heat recovery system may additionally include an airflow recirculation system configured to receive the recovered airflow and recirculate the recovered airflow as a drying airflow in the drying process (to one or more airflow elements 112). The recirculation system is not depicted in the figure or is only schematically depicted, and it should be apparent to a person skilled in the art how such a system involves, for example, ducts that can be implemented for transporting recovered heat energy, liquid and / or airflow.

[0077] The device may additionally include a control entity (not depicted) configured to receive one or more determined parameters, which may, for example, include measured parameters, such as one or more determined temperatures or humidities, and the control entity may be configured to control the amount of thermal energy provided by the at least one heating element 110 and / or control the amount of airflow provided by the at least one airflow element 112 and / or control the amount of liquid received by the mixing unit based on the determined parameters.

[0078] The control unit may include one or more processors and may be executed via, for example, one or more computing devices, which may be connected to any other components of the apparatus by wire or wirelessly.

[0079] The control entity may utilize one or more temperatures of the drying surface 114 and / or one or more temperatures and / or humidities of the drying airflow carrying steam and latent heat. The control entity may be configured to maintain the temperature or humidity at or near a predetermined value through the control system components. For example, if the temperature of the drying surface 114 at a certain measurement location is lower than a predetermined value, the control entity may control the heating element 110 to direct more heat energy to the measurement location.

[0080] Additionally or alternatively, the control entity may receive a request from one or more components of the device (such as a mixing unit or heating element 110) to provide, for example, a requested amount of liquid or thermal energy. The control entity may be configured to control the liquid recirculation system, the thermal energy recirculation system, and / or the airflow recirculation system based on the process control logic and / or the request from the system components so that the drying method is optimized to

[0081] The apparatus may be configured to receive a starting volume of liquid, a starting amount of energy and a starting amount of gas flow from an external source and / or from outside the system at the start of the method / process. After the process is started, the process may be a closed process, at least with respect to the liquid and / or gas, in which no additional liquid and / or gas is required from an external source for a given amount of process time.

[0082] In some embodiments, the control entity may be used to provide an appropriate amount of starting amount of liquid, gas, and / or heat for a given process, depending on, for example, the amount of material to be dried.

[0083] The control entity may be configured to control the amount of recovered heat energy, recovered liquid and / or recovered gas flow that is recycled.

[0084] Figure 4-6 Various embodiments of the invention are shown in which used heat (thermal energy), liquids and / or gas streams may be recovered and recycled back into the manufacturing process (wet and / or dry processes) or recovered and directed to an external entity for use.

[0085] exist Figure 4 In the process, the airflow and the heat energy can be at least partially recycled in the material manufacturing process. The recovered airflow can be directed to an external entity and / or provided to the environment in the exhaust gas flow.

[0086] Figure 5 A process is depicted whereby heat energy and liquid may be recycled while the recovered gas stream is provided as exhaust gas to one or more external entities or into the environment.

[0087] exist Figure 6 In embodiments of the present invention, the heat energy, gas flow and liquid can be recycled to the manufacturing process. The device 104 for providing cooling fluid to the condensing heat exchanger unit 102 is a cooling system, which can be some other cooling system other than a heat pump unit. Here, the cooling system can be considered as an external cooling system, while in some embodiments, it can also be considered as being included in the heat recovery system. Figure 6 Embodiments of the invention may be depicted in which the additional heat energy directed to the cooling fluid is not recovered and directed to an external unit and / or recycled into the drying process. The cooling system 104 may be, for example, a cooling system that utilizes a cooling fluid obtained from the environment, such as water from a lake or a river, as the cooling fluid delivered to the condensing heat exchanger unit 102.

[0088] Figure 6 The cooling system 104 may also be replaced with a heat pump unit 104 to provide a process in which additional thermal energy directed to the cooling fluid is also recovered and put to use, as previously discussed.

[0089] The invention has been explained above with reference to the aforementioned embodiments and several advantages of the invention have been demonstrated. It is obvious that the invention is not limited to these embodiments only but comprises all possible embodiments within the spirit and scope of the inventive idea and the following patent claims.

[0090] Unless explicitly stated otherwise, the features recited in the dependent claims are mutually freely combinable.

Claims

1. A method for recovering heat energy during a material drying process, the method comprising: At least after an initial phase of obtaining a starting volume of liquid and a starting amount of gas flow, - providing a material to be dried containing a liquid component, - providing thermal energy to evaporate at least a portion of the liquid from said material, - providing a drying gas stream to carry the vapor and the associated latent heat of the evaporated liquid from the material, - collecting said gas flow carrying said steam and said latent heat, - recovering at least a major part or substantially all of the vapour carried by the collected gas stream by condensing at least a major part or substantially all of the vapour component in said gas stream to obtain recovered liquid and a recovered gas stream, - recovering said heat energy for evaporation and said latent heat of the steam carried by said gas stream by heat exchange and condensation to obtain heat energy recovered by said heat exchange and condensation, - recycling at least part of the recovered heat energy as the heat energy for evaporation, and / or - recycling at least part of the recovered gas stream as the drying gas stream, and / or - Recirculating at least a portion of the recovered liquid to the material to be dried comprising a liquid component.

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

3. A method according to any preceding claim, wherein the method is a closed process with respect to the gas stream and comprises recycling at least a major part or substantially all of the recovered gas stream as a dry gas stream.

4. A method according to any preceding claim, wherein the method comprises directing the gas stream carrying the steam and the latent heat to a heat recovery unit comprising at least a condensing heat exchanger unit, wherein the cooling fluid is provided by a cooling fluid providing device, which is preferably a device separate from the condensing heat exchanger unit, for providing cooling fluid to the condensing heat exchanger unit to exchange the heat from the drying gas stream through the heat exchanger and thereby cool the gas stream and condense the liquid carried by the gas stream to further recover the latent heat from the gas stream, and directing at least a portion of the recovered thermal energy obtained thereby to the cooling fluid.

5. A 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 heat energy obtained at the condensing heat exchanger unit to the heat pump unit, recovering additional heat energy from the recovered heat energy obtained at the condensing heat exchanger unit to obtain further recovered heat energy, and directing the recovered additional heat energy to an external unit and / or recycling the additional recovered heat energy as heat energy for evaporating and / or treating the material to be dried.

6. A method according to any preceding claim, wherein the method comprises recovering at least 50%, preferably at least 60% and more preferably at least 70% or 80% of the heat energy used for evaporation.

7. A method according to any preceding claim, wherein at least part of the recovered heat energy is provided at least to the dry gas stream, the method comprising heating the dry gas stream to a temperature below 200°C, preferably below 150°C or below 100°C.

8. A method according to any preceding claim, wherein the material is a mixture comprising fibres, preferably cellulosic fibres, and a liquid, the method comprising mixing the fibres and at least one liquid, the at least one liquid comprising water.

9. A method according to any preceding claim, wherein the thermal energy is provided at least to the drying gas stream and optionally to a drying surface on which the material is received.

10. A method according to any preceding claim, wherein the gas stream carrying the steam and the latent heat is cooled to at least the dew point temperature of the gas stream in order to recover the latent heat by the condensation.

11. A heat recovery system for recovering heat energy used in a material drying process, the heat recovery system being configured to receive a dry gas stream carrying vapor and associated latent heat of evaporated liquid from a material containing a liquid component, the liquid component having been evaporated from the material containing the liquid component using heat energy, and to transfer heat from the dry gas stream through a heat exchanger to cool the dry gas stream, causing substantially all or at least a majority of the vapor to condense, thereby providing recovered liquid, recovered gas stream, and recovered heat energy through the heat exchange and condensation.

12. A 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 supplying a cooling fluid to the condensing heat exchanger unit to exchange the heat from the dry gas stream through the heat exchanger, and thereby cool the gas stream and condense the liquid carried by the gas stream to further recover the latent heat from the gas stream, and to direct at least a portion of the recovered thermal energy obtained thereby to the cooling fluid.

13. The heat recovery system according to claim 12, additionally comprising a heat energy recycling system, and the device for providing the cooling fluid is a heat pump unit, wherein the condensing heat exchanger unit is configured to direct at least a portion of the obtained recovered heat energy to the heat pump unit to recover further heat energy from the recovered heat energy obtained at the condensing heat exchanger unit to obtain additional recovered heat energy, and the heat pump unit is configured to direct the recovered additional heat energy to an external unit and / or recycle the additional recovered heat energy as heat energy for evaporating and / or treating the material to be dried.

14. The heat recovery system according to any one of claims 11-13, additionally comprising a liquid recycling system, wherein the liquid recycling system is configured to receive the recovered liquid and recirculate the recovered liquid to a mixing unit for mixing the material with the liquid to provide the material containing the liquid component.

15. The heat recovery system according to any one of claims 11 to 14, further comprising an airflow recirculation system, wherein the airflow recirculation system is configured to receive the recovered airflow and recirculate the recovered airflow as the drying airflow in a process for drying materials.

16. An apparatus for receiving a material containing a liquid component and drying the material, the apparatus comprising at least one heat recovery system according to any one of claims 11 to 15 and at least one air flow element for providing a drying air flow and at least one heating element for providing thermal energy to evaporate the liquid from the material.

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

18. Apparatus according to claim 16 or 17, additionally comprising a drying surface configured to receive the material to be dried, wherein at least a portion of the thermal energy is preferably provided to the drying surface.

19. An apparatus according to any one of claims 16 to 18, further comprising a control entity configured to receive one or more determined parameters, the determined parameters preferably comprising at least one determined temperature, optionally configured to receive the temperature of a drying surface of the material and / or the temperature of the drying gas flow carrying the vapor of the evaporated liquid and the associated latent heat, wherein the control entity is configured to control the amount of thermal energy provided by the at least one heating element and / or the amount of air flow provided by the at least one air flow element based on the determined parameters.

Images