Machine and method for producing or treating a fibrous web, having a heat pump

Abstract

The invention relates to a machine (1) and to a method for producing or treating a fibrous web (F), in particular a paper, cardboard or tissue web (F), comprising at least one drying section (2, 4) and at least one first steam and condensate system (5) and at least one first thermal energy recovery system (6), and wherein the at least one drying section (2, 4) comprises at least one first and one further drying group (21, 22, 23, 24, 25, 41, 42), and wherein the thermal energy recovery system (6) comprises at least one heat pump (90), and the at least one heat pump (90) partially extracts residual thermal energy from an exhaust air stream (84), preferably from the at least one drying section (2, 4) and / or a further machine section (3) and a heating medium is heated by additionally supplying electrical energy (80), and wherein the at least first drying group (21, 22, 41) can be connected to the at least one first steam and condensate system (5) and can be heated substantially completely with steam. According to the invention, it is provided that the heat pump (90), the at least one heat pump (90), is arranged such that the at least one first steam and condensate system (5) can be supplied by the at least one heat pump (90), and provides steam for the at least first drying group (21, 22, 41) as the heating medium, and that the at least one further drying group (23, 24, 25, 42) is not connected to the at least first steam and condensate system (5) and can be supplied by a heating system separate from the at least first steam and condensate system (5).

Description

[0001] Machine and process for the production or treatment of a fibrous web using a heat pump

[0002] The invention relates to a machine for producing or treating a fibrous web, in particular paper, cardboard, or tissue web, comprising at least one drying section, at least one first steam and condensate system, and at least one first heat energy recovery system, wherein the at least one drying section comprises at least one first and one further drying group, and wherein the heat energy recovery system comprises at least one heat pump, and the at least one heat pump partially extracts residual heat energy from an exhaust air stream, preferably from the at least one drying section and / or a further machine section, and heats a heating medium with the additional supply of electrical energy, and wherein the at least first drying group is connectable to the at least one first steam and condensate system and is substantially completely heatable with steam.

[0003] The invention also relates to a method for use in a machine according to the invention.

[0004] Document DE10 2015 219 379 A1 discloses a machine and a method for operating a machine, wherein a medium for drying a fibrous web is supplied to a drying area and the medium is discharged downstream of the drying area and supplied as a heat source to a heat pump, by means of which a second medium is heated and supplied further downstream to a smoothing cylinder within the drying area.

[0005] Document DE10 2015 219 381 A1 discloses a machine and a method for operating a machine, wherein a medium for drying a fibrous web is supplied to a drying area and the medium is discharged from the drying area downstream of the drying area and used as

[0006] - 1 - Heat source of a heat pump is supplied, by means of which the same medium is heated with the supply of further energy and is supplied back to the drying area at the beginning.

[0007] Document WO 2020 / 079 326 A1 discloses a heat pump installation in a recirculating air system and a recirculating air process for a drying section of a cardboard or machine. The system comprises at least three air recirculation sections connected in series to a drying section hood in the direction of travel of a web-shaped material. Each recirculating air section includes one or more heat recovery units. Each heat recovery unit comprises a recirculating air fan for drawing moist exhaust air from the drying section hood through the heat recovery unit and for supplying at least a portion of the conditioned moist exhaust air to the drying section hood, and an air-fluid heat exchanger for conditioning the moist exhaust air by cooling and reducing its moisture content.

[0008] Document DE10 2007 051165 A1 discloses a machine and a method with a wet section and a dry section, wherein the dry section includes a drying compartment and a drying hood for the paper web. Energy from the exhaust air of the dry section is used to heat supply air in a heating device located in the wet section via a heat pump.

[0009] Document DE 26 30 853 A1 , 1976, discloses a drying section for a machine, wherein a heat pump is connected between the inlet line with fresh, hot supply air and the outlet line with moist exhaust air, thereby enabling energy recovery from the exhaust air and transfer of the energy to the inlet line of the drying section.

[0010] Various drying devices are used to dry fibrous webs, for example in the paper industry. These include

[0011] - 2 - for example, contact drying units or non-contact drying units. Contact drying units include, for example, single-row and double-row drying cylinder units, while non-contact drying units include, for example, air drying devices or infrared drying units. In the case of steam input, such as with steam-heated drying cylinders, this is often taken from a steam generator fired with fossil fuels, for example, a combined cycle gas turbine (CCGT) power plant.

[0012] However, the aforementioned solutions have a number of disadvantages.

[0013] Machines for the production of fiber webs using a conventional wet laying process have a very high demand for water and therefore also for drying or evaporation capacities for the water contained in the fiber web.

[0014] This energy requirement is currently met primarily by fossil fuels, especially natural gas, for drying the fiber web, with the expected disadvantages in terms of cost and environment. Rising procurement costs, as well as increasingly stringent CO2 regulations and taxes, represent a significant portion of the production costs. Furthermore, global crises often raise concerns about the availability and reputation of these fuels with regard to their impact on the global climate.

[0015] A further disadvantage, particularly during the hot summer periods that occur more frequently even in temperate latitudes, is that the available water for the manufacturing process and for cooling the power plants is limited.

[0016] - 3 - Another disadvantage for residents in the immediate vicinity of the machines for the production of a fiber web is the nuisance caused by the saturated, moist exhaust air from the drying sections in the form of so-called steam formation.

[0017] The solutions mentioned in the prior art reveal the use of a heat pump within a drying section, but at the operating point of the heat pump in an energetically unfavorable arrangement for efficient operation of the machine or even for partial use, in parallel with the use of fossil fuel-fired drying devices.

[0018] Another disadvantage is that heat pumps are limited in providing the required increased energy levels from the perspective of an efficient operating point (COP). This results in a limited heating temperature and pressure generation by the heat pump if one still wants to achieve acceptable efficiency values.

[0019] As part of decarbonization or CO2 emission reduction, ideally a complete electrical supply of the drying sections should be achieved, but this presents numerous challenges for an optimized arrangement and combination of the available systems, such as a heat pump and / or electrically heated components in the machine, as well as the selection of the correct operating modes of the components used.

[0020] The object of the invention is to provide a machine and a method for the production and / or treatment of a fibrous web, in particular a paper, cardboard, or tissue web, with a reduced influence and impact on the environment.

[0021] - 4 - Here, a first aspect focuses on the heat energy recovery of the machine and the partial or complete CO2-free generation of the required heat energy for a drying section.

[0022] Improved heat energy recovery enables the decarbonization of the machine and significantly reduces or eliminates the need for fossil fuels, especially natural gas, in drying a fiber web. Reducing or completely avoiding CO2 emissions reduces the machine's environmental footprint, while simultaneously lowering operating costs and reducing the risk of dependence on a single fuel source or supplier.

[0023] A second aspect focuses on the recovery of water used in the manufacturing process.

[0024] The high proportion of the exhaust air stream discharged from the drying section has a very high residual moisture content and therefore has a negative impact on the immediate surroundings with regard to so-called steam formation and also through increased fresh water consumption.

[0025] The object of the invention is achieved by a machine and a method according to the independent claims, comprising at least one arrangement of an electric heat pump in a heat energy recovery system. Further advantageous embodiments of the present invention are found in the dependent claims.

[0026] The inventors recognized that an advantageous arrangement of electrically operated heating devices in the machine and an optimized operating procedure could eliminate the disadvantages.

[0027] The machine according to the invention is characterized in that the at least one heat pump is arranged such that the at least one

[0028] - 5 - Heat pump that can supply at least one first steam and condensate system, and provides steam as a heating medium for the at least first dry group, and that the at least one further dry group is free from a connection to the at least first steam and condensate system and can be supplied by a heating system separate from the at least first steam and condensate system.

[0029] For an advantageous first phase of decarbonizing machine 1, the existing steam and condensate system 5 of machine 1, which typically uses conventional steam generation (e.g., with fossil fuels), can be very efficiently converted to steam generation with a heat pump for the first drying groups 21, 22, 41 of the drying section 2,4 during modernization or conversion. The first drying groups of a drying section are characterized by lower temperatures and / or lower steam pressures compared to the subsequent drying groups. Lower temperatures and / or steam pressures can be achieved very efficiently with a higher heat pump efficiency and thus have a positive impact on CO2 savings and the decarbonization of the machine.

[0030] Partial decarbonization of the machine is preferably considered for conversions and modernizations of a large proportion of existing machines and ensures a gradual, cost-effective conversion of existing systems.

[0031] In an alternative embodiment, the machine is characterized in that at least one heat exchanger is arranged upstream of the at least one heat pump in an exhaust air duct, preferably an air-to-air heat exchanger or an air-to-heat transfer medium heat exchanger.

[0032] - 6 - Advantageously, the heat pump is arranged in the exhaust air stream after one or two heat exchangers in order to utilize the waste heat in the condensation area at the highest possible temperature in the exhaust air stream.

[0033] In an alternative embodiment, the machine is characterized in that the at least one heat pump is designed such that a steam requirement required in normal operation of the machine, preferably a steam temperature and a steam mass flow rate, is provided in the at least one first steam and condensate system solely by the heat pump.

[0034] In an alternative embodiment, the machine is characterized in that a steam generator, preferably a passively functioning or electrically operated steam generator, is arranged downstream of the at least one heat pump and is included in the first steam and condensate system. The steam generator is designed to convert condensate heated to steam temperature by the heat pump into steam.

[0035] In an alternative embodiment, the machine is characterized in that the at least one heat pump is designed such that the at least one first steam and condensate system can be supplied with a steam pressure of less than or equal to 4 bar above ambient pressure, preferably less than or equal to 3 bar above ambient pressure.

[0036] Advantageously, when generating steam using a heat pump, additional electrical energy is used according to the efficiency of the heat pump and the required temperature increase by utilizing the thermal energy of the exhaust air stream.

[0037] Compared to a conventionally used steam and condensate system, which also has losses, the losses are higher when using steam generated electrically by a heat pump and also when using purely electrically heated additional drying groups.

[0038] - 7 - more electrical energy is needed to achieve the same evaporation performance.

[0039] However, this disadvantage can be turned into an advantage or significantly reduced through optimal machine design by increasing the degree of heat recovery, while simultaneously enabling complete decarbonization of the machine.

[0040] For optimal heat recovery from the heat pump, the vapor pressure generated by the heat pump should be lower than in a conventional steam and condensate system.

[0041] In an alternative embodiment, the machine is characterized by the fact that a second heat pump is arranged in the exhaust air stream, such that a secondary consumer system can be supplied and / or the residual moisture content of the exhaust air stream is reduced to a residual moisture content of less than or equal to 80%, preferably less than or equal to 70%.

[0042] In an alternative embodiment, the machine is characterized in that the at least one further drying group can be supplied by at least one second steam and condensate system, which can be supplied with a steam pressure of less than or equal to 10 bar and greater than 4 bar.

[0043] In an alternative embodiment, the machine is characterized in that the at least one further drying group is at least one further electrically, preferably purely electrically, heated drying group and can be supplied by electrical energy.

[0044] For complete decarbonization and reduction of CO2 emissions from the drying sections of a machine, at least one additional drying group is advantageously used, preferably the additional drying groups that have a higher

[0045] - 8 - Drying temperature or a higher vapor pressure than the level generated by the first steam and condensate system with a heat pump require electrical heating.

[0046] Advantageously, these drying groups are heated purely electrically, which eliminates the need for a complex and costly installation of a secondary system, such as a second steam and condensate system for new buildings.

[0047] In an alternative embodiment, the machine is characterized in that the drying section comprises at least as many, preferably two, three or more, further electrically heated drying groups, such that a proportion of the further electrically heated drying groups in the drying, in particular in the evaporation performance, in the drying section is greater than or equal to 30%, preferably greater than or equal to 40%, and less than or equal to 70%, preferably less than or equal to 60%, of the total drying performance of the drying section.

[0048] To achieve the highest possible heat recovery, the proportion of electrically heated drying groups should ideally be between 30% and 70% of the total evaporation capacity of the drying section.

[0049] A completely decarbonized drying section of a machine can also be achieved with increased effort in modernizations, but ideally a completely decarbonized system, preferably with electric heating devices such as heat pumps and purely electric drying cylinders, is considered for new buildings.

[0050] In an alternative embodiment, the machine is characterized in that the at least one electrically heated drying group comprises at least one electrically heated drying cylinder, and that the electrically heated drying group is free from any connection with the at least first steam and condensate system.

[0051] - 9 - Advantageously, the electrically heated drying units are arranged and constructed in the usual manner, so no effects on the flow of the fiber web are to be expected. The electrically heated drying units comprise purely electrically heated drying cylinders and are free from any connection to a steam and condensate system.

[0052] In an alternative embodiment, the machine is characterized in that the at least one electrically heated drying cylinder comprises internal electrical heating devices, preferably at least one induction heating device and / or at least one resistance heating device.

[0053] Advantageously, the drying cylinders, which are otherwise steam-heated, are equipped with an internal electric heating device, such as an induction heater or a resistance heater, spanning the entire width of the cylinder. Depending on the width and diameter of the drying cylinders, several of these heating devices can be arranged within a single cylinder.

[0054] Advantageously, the first heat pump is designed such that it only needs to achieve a slight increase in temperature and / or pressure in the steam and condensate system. This has a positive effect on the achievable efficiency of the first heat pump and enables higher heat energy recovery and lower electrical energy consumption in the overall drying section.

[0055] Method for producing or treating a fibrous web, in particular a paper, cardboard or tissue web, in an alternative embodiment, the machine is characterized in that the at least one heat pump supplies the first steam and condensate system of the at least

[0056] - 10 - a first, steam-heated drying group supplied with a steam pressure of less than or equal to 4 bar above ambient pressure, preferably less than or equal to 3 bar above ambient pressure, such that the fibrous web is dried to a temperature corresponding to the steam pressure.

[0057] Advantageously, the at least one steam and condensate system 5 is fully supplied by the at least one heat pump 90 only up to an optimal operating range for the heat pump 90, while maintaining an efficient operating point for the heat pump 90. Maintaining the efficient operating point of the heat pump limits the achievable steam pressure and thus also the achievable temperature of the steam-heated drying sections 21, 41. Advantageously, during the drying of a fiber web F, the temperature is successively increased along the machine direction MD and is therefore at a lower temperature level at the beginning of the drying section 2, 4 than at the end of the drying section 2, 4. This advantageously allows for conventional steam heating of the first drying sections while maintaining the usual steam and condensate system 5, thus providing a simple way to modernize an existing machine.At the same time, the steam, which is usually generated by a gas-fired power plant, can be electrically operated using renewable energies via the heat pump 90, with a view to saving CO2.

[0058] In an alternative embodiment, the method is characterized in that the fibrous web is dried with at least one further electrically heated drying unit and that the at least one further electrically heated drying unit achieves a proportion of the total drying capacity of the drying section, in particular a proportion of the total evaporation capacity of the drying section, of greater than or equal to 30%, preferably greater than or equal to 40%, and less than or equal to 70%, preferably less than or equal to 60%.

[0059] - 11 - The combination of classic steam-heated drying groups at the beginning of the drying sections, which are supplied via an electrically operated heat pump, and a further drying group heated purely electrically for higher required fiber web drying temperatures, allows for optimal, very efficient operation of the machine in terms of operating costs and heat recovery aspects, which is possible purely electrically and therefore completely CO2 neutral under given circumstances.

[0060] In an alternative embodiment, the method is characterized in that a second heat pump is downstream of the at least one heat pump in an exhaust air stream, such that the second heat pump cools the exhaust air stream to an exhaust air temperature of less than or equal to 50°C, preferably less than or equal to 40°C, in such a way that any water vapor or residual moisture contained in the exhaust air stream is completely or partially condensed.

[0061] A disadvantage in a drying section 2, 4 is that the drying of the fiber web F produces a warm or hot exhaust air that is essentially completely saturated with water vapor, which can usually be recovered to a small extent by heat exchangers arranged in the exhaust air stream.

[0062] Advantageously, by arranging a second heat pump 91 in an exhaust air stream 84 of a drying section 2, 4, it is possible to cool the exhaust air stream 84 to a very low exhaust air temperature, compared to a pure heat exchanger arrangement.

[0063] By installing a second heat pump 91, the residual moisture content or water vapor contained in the exhaust air stream 84 can, in a first aspect, be largely or almost completely recovered or condensed as water, and in a second aspect, an efficient supply can be provided to the secondary consumer systems 71 included in machine 1, which operate at a low temperature. These low-temperature secondary consumer systems 71 include, for example, machine hall ventilation, machine hall heating, or production process water heating.

[0064] Water recovery is particularly advantageous at warm ambient temperatures, such as during hot summer periods, because the quantities of water required for the production of the fiber web F are no longer available from the natural resources often found in the surrounding area, such as rivers, due to low water levels during droughts, or must be purchased at high cost.

[0065] By recovering water from the exhaust air stream 84, the supply of fresh water for the manufacturing process of the fiber web F can be minimized, with the unused water being advantageously available for the operation, in particular cooling, of the power plant to provide energy in the form of electricity and / or steam, or the fresh water being available for other purposes for public water supply and / or supply to agriculture.

[0066] In an alternative embodiment, the method is characterized in that the second heat pump, via a further heat exchanger downstream of the second heat pump, reheats the exhaust air stream cooled by the second heat pump to an exhaust air temperature of less than or equal to 50°C, in such a way that the reheated exhaust air stream has a further reduced residual moisture content of less than or equal to 80%, preferably less than or equal to 70%.

[0067] Advantageously, the recovered heat energy can be reheated, preferably slightly, by the second heat pump 91 and thus the cooled exhaust air stream 84, in order to reduce the residual moisture content of the air released into the environment.

[0068] - 13 - to reduce the outgoing exhaust air stream 84. A slight warming of the exhaust air of 3°C or greater, in particular 5°C or greater, may be sufficient to reduce the residual moisture content to 80% or less and to reduce or completely eliminate the formation of steam from the exhaust air stream 84 when it exits into the environment.

[0069] Furthermore, the reduction of the residual moisture content of the exhaust air stream and the almost complete recovery of the water in the exhaust air stream result in a reduction of the nuisance to residents and the surrounding area caused by so-called steam formation from the exhaust air ducts of machine 1, which usually occurs due to the condensation of the residual moisture with the cooler and drier ambient air.

[0070] In an alternative embodiment, the method is characterized in that a second steam and condensate system is included with a bypass control loop, and the bypass control loop is connectable to the first steam and condensate system, such that i) when the machine is started up, the bypass control loop is opened in such a way that the second steam and condensate system heats the first steam and condensate system until an operating temperature is reached; ii) during normal operation of the machine, preferably when the operating temperature of the first steam and condensate system is reached, the bypass control loop is closed in such a way that the first steam and condensate system is supplied solely by the at least one heat pump.

[0071] Advantageously, in an embodiment with a second steam and condensate system 5', preferably a steam generation system already present in the machine, redundancy is provided with the first steam and condensate system 5 with a heat pump 90. The second steam and condensate system 5' can advantageously handle the energy-intensive start-up phase of the

[0072] - 14 - Take over machine 1 and thus provide full drying capacity from the start.

[0073] In an embodiment without a second steam and condensate system 5' or with only one steam and condensate system 5 for the at least one first drying group 21 , 22, 41 , wherein the first steam and condensate system 5 can be supplied completely or partially by a heat pump 90 and in a combination with further electric drying groups 23, 24 ,25, 42, when starting up the machine 1, the steam generation by the heat pump 90 is increased over time.

[0074] The heat pump reduces the temperature and residual heat energy of available exhaust air to such an extent that the moisture absorbed during the drying process condenses at least partially, and preferably completely. Simultaneously, the heat extracted from the exhaust air flowing through the outlet duct is transferred at a higher level to a heat consumer circuit, such as a steam and condensate system and / or a secondary system consumer. The heat energy required for the drying process can be achieved entirely electrically or with non-fossil fuels at a lower energy consumption. By extracting moisture from the exhaust air in the form of condensate, a significant reduction in water consumption is achieved, for example, in the aforementioned paper mill. At the same time, the environmental impact is reduced, which in many cases is caused by the rising steam plumes resulting from the moist exhaust air.

[0075] The invention expressly extends to embodiments which are not given by combinations of features from explicit cross-references of the claims, whereby the disclosed features of the invention can be combined with one another — insofar as this is technically meaningful.

[0076] - 15 - Corresponding elements of the embodiments shown in the figures are provided with the same reference numerals. The functions of such elements in the individual figures correspond to each other, unless otherwise described and this does not lead to contradictions. Therefore, a repeated description is omitted.

[0077] It should also be noted that the differing features of the illustrated embodiments can be interchanged and combined. The invention is therefore not limited to the combinations of features shown in the illustrated embodiments.

[0078] Further features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the drawings.

[0079] Character description

[0080] The invention will be explained below with reference to the following figures.

[0081] Figure 1 shows a schematic arrangement of the machine according to the invention, with a heat pump in the first steam and condensate system and a second steam and condensate system for the further drying groups;

[0082] Figure 2 shows a schematically illustrated arrangement of the machine according to the invention, with a heat pump in the first steam and condensate system and further electrical drying groups;

[0083] Figure 3 shows a schematic representation of an arrangement with two heat pumps in one machine.

[0084] Figures 1, 2 and 3 illustrate, in a schematic and highly simplified representation, the basic structure and basic function of a device according to the invention.

[0085] - 16 - machine 1 for the production or treatment of a fibrous web F, in particular a paper, cardboard or tissue web F with a heat pump 90 for supplying at least a first steam and condensate system 5.

[0086] The machine 1 comprises at least one drying section 2, 4. In the exemplary arrangement, two drying sections 2, 4 are shown, with at least one further machine section 3 arranged between the two drying sections 2, 4. This further section 3 is, for example, an application device or a calender. The machine 1 is shown schematically and in a highly simplified manner, and only the components relevant to the invention are depicted. The other usual upstream and downstream machine sections or components of a machine 1 for the production or treatment of a fibrous web F, such as a headbox, a former, a press, an application device, a calender, a smoothing device, and a winding unit, are not shown, as these are assumed to be known.Typically, after leaving the last drying section 4, the fiber web F is transferred to a subsequent machine section such as a smoothing device and / or the winding unit.

[0087] To clarify the individual directions, a Cartesian coordinate system is used. The x-direction represents the longitudinal direction, also known as the machine direction (MD). The y-direction corresponds to the direction perpendicular to the machine direction and is called the cross-direction (CD), while the z-direction corresponds to the vertical direction.

[0088] The flow directions of the different media are illustrated in the figures by a directional arrow in the pipes or connections.

[0089] The fiber web F comes from a previous machine section 3, for example a forming section 3 with a vacuum blower 31, which

[0090] - 17 - another possible source for an exhaust air stream 84 in another machine section 3 of the machine 1 is shown. In this case, a forming section 3 usually includes so-called vacuum blowers of the forming section 31 for dewatering the fiber web F, which provide a further exhaust air 84 with residual heat.

[0091] This is followed by another machine section 3, usually a press section, before the fiber web F typically enters a first drying section 2, as shown. The first drying section 2 is divided into several drying groups, and a total of five drying groups 21, 22, 23, 24, 25 are shown. Within the first drying section 2, the drying groups are further enclosed by a drying hood 29, which collects or captures the heat energy released and not consumed in the drying groups in the form of an exhaust air stream 84.

[0092] The drying section 2, 4 can, for example, be configured as a single-row and / or double-row drying cylinder drying group 21, 22, 23, 24, 25, 41, 42 with surrounding drying hoods 29, 49. Furthermore, the drying section can, for example, be configured in a tissue machine as a high-performance drying hood 29, 49 on a Yankee drying cylinder, the Yankee drying cylinder forming a drying group.

[0093] The drying hoods 29, 49 shown are connectable to a supply air duct 82 and an exhaust air duct 84, wherein a warmed, dry fresh air stream 82 is preferably supplied through the supply air duct 82 to better absorb any released moisture. The warmed and moist air from the drying of the fiber web is carried away again as an exhaust air stream 84 through the connected exhaust air duct 84.

[0094] It is advantageous to connect several exhaust air ducts 84 together, for example to obtain a larger exhaust air volume flow and / or alternatively, if the available heat is significantly higher than the temperatures required for efficient heat energy recovery, to further blend or mix them in order to achieve an optimal output temperature level.

[0095] - 18 - to provide with a higher volume flow for efficient heat energy recovery.

[0096] The machine 1 further comprises a first steam and condensate system 5, a heat energy recovery system 6, and, as a possible alternative embodiment, a second steam and condensate system 5'. The first steam and condensate system 5 is typically used to supply the drying sections 2, 4 with heat in the form of heated, superheated, and / or heated steam. The first steam and condensate system 5 is connected to the first drying groups 21, 22, 41 within the drying section 2, 4 via a steam supply line 57 and a condensate return line 58. The first steam and condensate system 5 is designed to provide steam at a maximum pressure of 4 bar with a volume or mass flow rate sufficient to supply the connected drying groups. The steam consumed in the drying groups is returned to the closed steam and condensate system 5 in the form of condensate via a condensate return line 58.

[0097] The second drying section 4 is shown, for example, in Figure 1 with a single drying group 41 and a drying hood 49.

[0098] The possible alternative embodiment with a second steam and condensate system 5' comprises, like the first steam and condensate system 5, a steam supply line 57 and a condensate return line 58, wherein the second steam and condensate system 5' can provide steam at a pressure greater than 4 bar, preferably up to 10 bar, and thus can provide more drying capacity or evaporation capacity than the first steam and condensate system 5. The second steam and condensate system 5' can be connected to and supplies the further drying groups 23, 24, 25, which are designed analogously to the first drying groups 21, 22, 41. The second steam and condensate system 5' can advantageously be connected to the first steam and condensate system 5' by a bypass control loop 51.

[0099] - 19 - Condensate system 5 can be connected to enable control depending on the operating state of machine 1.

[0100] For efficient utilization of the residual heat, the exhaust air streams 84 are each individually fed to a separate heat recovery system 6. Advantageously, each exhaust air duct 84 has a separate heat recovery system, which can also be advantageously interconnected and mixed again on the consumer side, for example, to achieve the desired temperatures in a secondary system consumer 70, 71. Another resulting advantage is, for example, when the existing exhaust air volume flows 84, as in the case of a vacuum blower in a forming section 31, are so large that the dimensions of the exhaust air ducts 84, for example in diameter, have to be routed over long distances of the machine 1 and become too complex in terms of cost and manufacturing.In this process, a heat exchanger 60, preferably an air-to-water heat transfer medium heat exchanger 60, is installed upstream in the exhaust air duct, which is kept as short as possible. This heat exchanger advantageously transfers the heat with minimal losses to a heat transfer medium intermediate circuit 86. The heat transfer medium 86, preferably water 86, has a high specific heat capacity compared to the exhaust air, making transport over longer distances within the machine 1 easier.

[0101] To achieve particularly efficient operation of machine 1, machine 1 comprises a heat energy recovery system 6 with at least one heat pump 90 for supplying the first steam and condensate system 5 for the first drying groups 21, 22, 41 of the drying section 2, 4 with heat, which extracts the necessary heat from an exhaust air line 84 from a machine section. Preferably, the exhaust air 84 is taken from a drying section 2, 4 and / or directly from a drying group, for example, an enclosed vacuum suction box or an impact air or hot air drying group. The residual heat or temperatures found there are in the

[0102] - 20 - Compared to other exhaust air streams, the volume is higher than, for example, an exhaust air stream 84 from a vacuum blower in a forming section 31. If higher volume flows are required in the exhaust air stream 84, it is advantageous to mix air from different exhaust air lines 84 along the entire heat energy recovery system / process 6. Ideally, the outlet temperatures of the mixed exhaust air streams 84 are still above the dew point, thus enabling advantageous recovery of the condensation heat contained therein.

[0103] Additional required air is drawn from the environment 88 of machine 1, the environment having an ambient temperature and ambient pressure, usually essentially 1 atm (atmosphere) or 1 bar.

[0104] Figure 1 shows an arrangement of the heat pump 90 within the heat energy recovery system 6, which is marked by a dashed box. The exhaust air duct 84 from the machine 1, with a typical temperature of 75°C to 90°C, is fed to a first heat exchanger 60 located upstream of the heat pump 90. In the illustrated arrangement, a first portion of the residual heat still contained in the exhaust air 84 is transferred to the supply air 82 flowing from the environment of the machine 1, or to the supply air duct 82.

[0105] Advantageously, in this arrangement the upstream or first heat exchanger 60 is designed as an air-to-air heat exchanger 60.

[0106] The exhaust air 84' leaving the first heat exchanger 60 now has a lower temperature T_84' than the temperature T_84 of the incoming exhaust air 84.

[0107] The exhaust air stream 84', which passes through the first, upstream heat exchanger 60, is now fed to the heat pump 90, or rather to the first heat exchanger of the heat pump 90, via the heat source supply line, thus further utilizing a further portion of the residual heat still contained in the exhaust air 84'. Simultaneously, the heating medium to be heated is supplied to the heat pump 90 via the condensate return line 58 at a temperature T_58 through the heating medium supply line. By simultaneously supplying electrical energy 80,

[0108] - 21 - the heating medium is heated by the heat pump 90 to a higher temperature level T_58' in the heating medium discharge 91 and the exhaust air 84' is cooled to a lower temperature, here to ambient temperature T_88 or discharged into the environment 88 through the heat source discharge.

[0109] Advantageously, the heat pump 90 is suitable for recovering heat energy in a particularly energy-efficient manner at a temperature T_84 in the exhaust air duct 84 of greater than or equal to 55°C, preferably greater than or equal to 60°C, and less than or equal to 80°C, preferably less than or equal to 70°C.

[0110] In an alternative embodiment, the first steam and condensate system 5 comprises a steam generator 53, wherein the steam generator 53 is located downstream of the heat pump 90, and the steam generator 53 is optionally indicated by a dashed bypass line. The steam generator 53 can be passively or electrically heated, and the steam generator 53 can be configured such that it can convert heated condensate in the condensate return line 58' downstream of the heat pump 90 into steam with no or only a small amount of electrical energy input. Typically, the heat pump is designed to directly achieve a phase transition from liquid condensate to gaseous steam when the temperature of the condensate from the condensate return line 58 to heated condensate in the condensate return line 58'.

[0111] Figure 2 shows a possible, fully decarbonized or electric drying section 2, 4 with most of the elements already described in Figure 1.

[0112] In contrast to Figure 1, Figure 2 contains a further drying group 42 in the second drying section 4 and all further drying groups 23, 24, 25, 42 are heated by an electrical energy source 80.

[0113] The second steam and condensate system 5' is completely omitted in Figure 2, as is the optional steam generator 53 shown in Figure 1. Whereas the optional

[0114] - 22 - electric or passive steam generators 53 may be an alternative embodiment of Figure 2 not shown.

[0115] Figure 3 shows a possible arrangement of a first heat pump 90 and a second heat pump 91 in the machine 1. The heat pumps 90, 91 are advantageously enclosed in the at least one heat energy recovery system 6 of the machine 1, which is marked by a dashed box. The heat energy recovery systems 6 of the machine 1 are also advantageously used for the energy-efficient supply of required heat to further secondary system consumers 70, 71.

[0116] Figure 3 shows an arrangement of a first heat pump 90, which is downstream of a first heat exchanger 60 and a second heat exchanger 61. The exhaust air stream 84 is passed through a first heat exchanger 60, followed by a second heat pump 91 and a third heat exchanger 62 into the environment 88.

[0117] To achieve the most energy-efficient heat energy recovery and cost-effective integration, the first heat exchanger 60 is designed as an air-to-water heat exchanger 60, which can be used to supply a secondary consumer 70, preferably the hall heating system 70. Since the hall heating system 70 is only used on cold days, the heat energy for the first heat pump 90, located in the secondary system consumer circuit 70, can be individually consumed and controlled.

[0118] The first air-water heat exchanger 60 is followed by a second water-air heat exchanger 61, which enables efficient heating of the fresh supply air 82 for the drying sections 2, 4 or the drying hoods 29, 49 from the environment 88.

[0119] Other secondary system consumers 70, 71 with reduced or low

[0120] Temperature levels can, for example, affect the air supply to the hair dryer hood (82°C), which

[0121] - 23 - Process water heating, hall ventilation or hall heating and the supply of steam blow boxes in the drying sections.

[0122] The first heat pump 90 is located downstream of the second heat exchanger 62 and supplies or heats the first steam and condensate system 5.

[0123] The second heat pump 91 is downstream of the first air-to-water heat exchanger and extracts further heat energy from the exhaust air stream 84' at a reduced temperature, thus further reducing the temperature of the exhaust air stream 84".

[0124] The second heat pump 91 is used to supply further secondary system consumers 70, 71 with reduced or low

[0125] Temperature levels used.

[0126] As a combination or on its own, a third heat exchanger 62 can be connected downstream of the second heat pump 91. This third heat exchanger is supplied directly by the second heat pump 91 and transfers the heat energy back to the exhaust air stream 84 at a temperature of less than or equal to 50°C, preferably less than or equal to 40°C. Since condensate forms during the cooling stages of the exhaust air stream 84 in the first heat exchanger 60 and the second heat pump 91, a large portion of the water vapor contained in the exhaust air stream 84 has already been removed.

[0127] For particularly effective vapor reduction, the third heat exchanger 62 raises the temperature of the exhaust air stream 84 to a higher level, preferably greater than or equal to 2°C. This reduces the relative residual moisture content of the exhaust air stream 88 discharged into the environment to less than or equal to 80%, thereby reducing or completely eliminating condensation in the ambient air.

[0128] The addition or removal of thermal energy into or from a "pipe" means that the medium moving in the pipe at a certain temperature and with a certain mass and volume flow rate, for example air, water,

[0129] - 24 - preferably steam and / or condensate or a special heat transfer medium that releases or absorbs heat energy.

[0130] The "optimal COP" of a heat pump refers to the point at which the heat pump operates at its most efficient point with the highest efficiency for the required temperature difference dT, thus providing a multiple of the heat energy from a given input, typically electrical energy. The optimal COP increases with a smaller required temperature difference. For example, with a temperature difference of dT = 60 K, a COP of approximately 3 is theoretically achievable, while with a temperature difference of dT = 15 K, a COP of approximately 10 is theoretically possible. This is measured as the temperature difference between the first and second heat exchangers of the heat pump. To achieve the most energy-efficient operation possible, it is advantageous to position the heat pump as early as possible in the system to recover condensation heat from the exhaust air stream.

[0131] A "cold start" of a machine means that all possible storage devices have been depleted and the temperature of the machine and its components is essentially the same as the ambient temperature. This is typically the case after a prolonged period of inactivity, such as during modernization or modification.

[0132] The term “heat source” is understood to mean a media flow or a heat transfer medium flow, preferably an exhaust air flow 84 and / or water flow 86, with residual heat from a machine section 2, 3, 4 of the machine 1, wherein the residual heat from the “heat source” is used.

[0133] A "heat sink" or "heat consumer" is defined as a medium flow or a heating medium flow, preferably a supply air flow 82 and / or water, steam and condensate flow 57, 58, preferably for a heat consumer such as a steam condensate system 5 or a so-called

[0134] - 25 - Secondary system consumers 70, 71, for example, a hair dryer supply air heating 82, where heat is supplied to the heat sink.

[0135] The "dew point" temperature is the temperature in a medium, preferably a heat transfer medium, in particular moist exhaust air 84, 84', 84", above which condensation of the contained gaseous component, preferably the moisture, takes place. The dew point is characterized by the fact that the vapor saturation pressure equals the vapor partial pressure of the medium.

[0136] Reference symbol list

[0137] 1 machine

[0138] 2 Dry section

[0139] 21 first, steam-heated drying group

[0140] 22 second, steam-heated drying group

[0141] 23 more dry group

[0142] 24 more dry group

[0143] 25 more dry group

[0144] 29 Hair dryer hood

[0145] 3 more machine parts, for example a strike part

[0146] 31 vacuum blowers of a forming section

[0147] 4 Dry section

[0148] 41 first, steam-heated drying group

[0149] 42 more, dry group

[0150] 49 Hair dryer hood

[0151] 5 first steam and condensate system

[0152] 5' second steam and condensate system

[0153] 50 conventional, fossil-fueled steam generators

[0154] 51 Bypass control loop

[0155] - 26 - 53 Steam generators, optional

[0156] 57 Steam supply line

[0157] 58 Condensate return

[0158] 6 Heat energy recovery system

[0159] 60 heat exchangers

[0160] 61 additional heat exchangers

[0161] 62 additional heat exchangers

[0162] 70 secondary system consumers

[0163] 71 additional secondary system consumers

[0164] 80 electrical power supply

[0165] 82 Air supply duct for hair dryer hood, air supply flow

[0166] 84 Exhaust duct for hair dryer hood, exhaust air flow

[0167] 84' Low temperature exhaust duct compared to 84

[0168] (T_84>=T84'>=T84")

[0169] 84" low temperature exhaust duct compared to 84'

[0170] (T_84>=T84'>=T84")

[0171] 88 Environment, ambient temperature, ambient pressure

[0172] 90 Heat pump

[0173] 91 second heat pump

[0174] F Fibre web

[0175] Temperature

[0176] MD Machine direction of travel

[0177] CD Machine transverse direction x, y, z coordinates

[0178] - 27 -

Claims

- 28 - Patent claims 1. Machine (1) for producing or treating a fibrous web (F), in particular a paper, board or tissue web (F), comprising at least one drying section (2, 4) and a first steam and condensate system (5) and a second steam and condensate system (5') and at least one first heat energy recovery system (6), wherein the at least first heat energy recovery system (6) is connectable to the first steam and condensate system (5) and comprises at least one heat pump (90), and the at least one heat pump (90) partially extracts residual heat energy from an exhaust air stream (84), preferably from the at least one drying section (2, 4) and / or a further machine section (3), and heats a heating medium with the additional supply of electrical energy (80), and wherein the at least one drying section (2, 4) comprises at least one first and one further drying group (21, 22, 23, 24, 25, 41, 42) includes,and wherein the at least first drying group (21, 22, 41) is connectable to the first steam and condensate system (5) and is substantially entirely heatable with steam, and the at least one further drying group (23, 24, 25) is supplyable with the second steam and condensate system (5'), characterized in that the at least one heat pump (90) is arranged such that the first steam and condensate system (5) can be supplied by the at least one heat pump (90), and provides steam as a heating medium for the at least one first drying group (21, 22, 41), and that the at least one further drying group (23, 24, 25, 42) is free from a connection to the at least first steam and condensate system (5) and can be supplied by a second steam and condensate system separate from the at least first steam and condensate system (5).

2. Machine (1 ) according to claim 1, characterized in that at least one heat exchanger (60) is arranged upstream of the at least one heat pump (90) in an exhaust air duct (84), preferably an air-to-air heat exchanger (60) or an air-to-heat transfer medium heat exchanger (60).

3. Machine (1 ) according to claim 1 or 2, characterized in that the at least one heat pump (90) is designed such that a steam requirement required in normal operation of the machine (1 ), preferably a steam temperature and a steam mass flow, is provided in the at least one first steam and condensate system (5) solely by the heat pump (90).

4. Machine (1 ) according to claim 1 or 2, characterized in that a steam generator (53) comprising the first steam and condensate system (5) is arranged downstream of the at least one heat pump (90), preferably a passively functioning or electrically operated steam generator (53), which is designed to convert a condensate (58') heated to steam temperature by the heat pump (90) into steam.

5. Machine (1 ) according to one of the preceding claims, characterized in that the at least one heat pump (90) is designed such that the at least one first steam and condensate system (5) can be supplied with a steam pressure of less than or equal to 4 bar above ambient pressure, preferably less than or equal to 3 bar above ambient pressure.

6. Machine (1 ) according to one of the preceding claims, characterized in that a second heat pump (91 ) is arranged in the exhaust air stream (84) such that a secondary consumer system (70, 71 ) can be supplied and / or the residual moisture content of the exhaust air stream (84) is reduced to a residual moisture content of less than or equal to 80%, preferably less than or equal to 70%. - 29 - 7. Machine (1 ) according to one of the preceding claims, characterized in that the at least one further drying group (23, 24, 25, 42) can be supplied by at least one second steam and condensate system (5') which can be supplied with a steam pressure of greater than or equal to 4 bar, preferably less than or equal to 10 bar.

8. Machine (1 ) according to one of claims 1 to 5, characterized in that the at least one further drying group (23, 24, 25, 42) is at least one further electrically, preferably purely electrically, heated drying group (23, 24, 25, 42) and can be supplied by electrical energy (80).

9. Machine (1) according to claim 8, characterized in that the drying section (2, 4) comprises at least as many, preferably two, three or more, further electrically heated drying groups (23, 24, 25, 42) such that a proportion of the further electrically heated drying groups in the drying, in particular in the evaporation capacity, in the drying section (2, 4) is greater than or equal to 30%, preferably greater than or equal to 40%, and less than or equal to 70%, preferably less than or equal to 60%, of the total drying capacity of the drying section (2, 4).

10. Machine (1 ) according to claim 8, characterized in that the at least one electrically heated drying group (23, 24, 25, 42) comprises at least one electrically heated drying cylinder, and that the electrically heated drying group is free from a connection with the at least first steam and condensate system (5). - 30 - 11. Machine (1) according to claim 10, characterized in that the at least one electrically heated drying cylinder comprises internal electrical heating devices, preferably at least one induction heating device and / or at least one Includes resistance heating device.

12. Method for producing or treating a fibrous web (F), in particular a paper, cardboard or tissue web (F), in a machine (1) according to claim 1, characterized in that the at least one heat pump (90) supplies the first steam and condensate system (5) of the at least one first steam-heated drying group (21 , 22, 41 ) with a steam pressure of less than or equal to 4 bar above ambient pressure, preferably less than or equal to 3 bar above ambient pressure, such that the fibrous web (F) is dried to a temperature corresponding to the steam pressure.

13. Method according to claim 11, characterized in that the fibrous web (F) is dried with at least one further electrically heated drying group (23, 24, 25, 42) and that the at least one further electrically heated drying group (23, 24, 25, 42) achieves a proportion of the total drying capacity of the drying section (2,4), in particular a proportion of the total evaporation capacity of the drying section (2,4), of greater than or equal to 30%, preferably greater than or equal to 40%, and less than or equal to 70%, preferably less than or equal to 60%.

14. Method according to claim 13, characterized in that a second heat pump (91) is arranged downstream of the at least one heat pump (90) in an exhaust air stream (84) such that the second heat pump (91) cools the exhaust air stream (84) to an exhaust air temperature of less than or equal to 50°C, preferably less than or equal to 40°C, such that - 31 - - 32 - any water vapor or residual moisture contained in the exhaust air stream (84) is completely or partially condensed.

15. Method according to claim 13, characterized in that the second heat pump (91 ) via a further heat exchanger (62) downstream of the second heat pump (91 ) reheats the exhaust air stream (84) cooled by the second heat pump (91 ) to an exhaust air temperature of less than or equal to 50°C, such that the reheated exhaust air stream (84) has a further reduced residual moisture content of less than or equal to 80%, preferably less than or equal to 70%.

16. Method according to claim 11, characterized in that a second steam and condensate system (5') is comprised with a bypass control loop (51) and the bypass control loop (51) is connectable to the first steam and condensate system (5) such that i) when the machine (1) is started up, the bypass control loop (51) is opened, such that the second steam and condensate system (5') heats the first steam and condensate system (5) until an operating temperature is reached; ii) during normal operation of the machine (1), preferably when the operating temperature of the first steam and condensate system (5) is reached, the bypass control loop (51) is closed, such that the first steam and condensate system (5) is supplied solely by the at least one heat pump (90). - 32 -

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