Installation for producing corrugated paperboard, and method for operating such an installation

Abstract

The invention specifies a method for operating an installation (2), wherein the installation (2) has a corrugator (4) for producing corrugated paperboard (6), wherein the installation (2) has a printing installation (8) for printing a print on a paper ply (10), wherein the installation (2) has a thermal engine (12) for generating thermal power (Pth) and electrical power (Pel), wherein the corrugator (4) and the printing installation (8) form a combination and are thus jointly supplied with thermal power (Pth) and with electrical power (Pel) by the thermal engine (12). The invention also specifies a corresponding installation (2).

Description

[0001] Description

[0002] Plant for the production of corrugated cardboard and method for operating such a plant

[0003] The invention relates to a method for operating a plant designed to produce corrugated cardboard, as well as to a corresponding plant.

[0004] During the production of corrugated board, several layers of paper are combined into a corrugated board web using a corrugator, and then optionally finished. For example, to produce double-layer (or two-part) corrugated board, two layers of paper are each corrugated using a corrugating roller and then alternately glued to form a stack with three non-corrugated paper layers. The corrugated board web is then finished and cut into individual blanks, for example. During the production of corrugated board, energy is required in the various processing stations of the corrugator. On the one hand, electrical power (power) is needed to drive the corrugator, and on the other hand, thermal power (heat) is needed for drying or steam generation at various points, e.g. when producing a corrugated paper web using a corrugator roller.The need for thermal power usually significantly exceeds the need for electrical power.

[0005] Fundamentally, it is desirable to make the production of corrugated board as energy-efficient and economical as possible and to utilize the primary energy used to operate the corrugated board plant as fully as possible. The concept of combined heat and power (CHP) or even combined heat, power, and cooling (CHCC) generally offers the advantage that, in an integrated process, the primary energy used (e.g., natural gas) is essentially completely converted into both heat and electricity, making it usable accordingly. However, the ratio of electrical power to thermal power achieved in this way cannot be adjusted at will, but is predetermined by the primary energy conversion process, meaning that CHP or CHCC is not necessarily ideal for every process.

[0006] Against this background, one object of the invention is to make the production of corrugated board as energy-efficient as possible. In particular, a combined heat and power (CHP) process or even a combined heat and power (CHCC) process is to be used. For this purpose, a correspondingly improved plant for the production of corrugated board and a method for its operation are to be specified.

[0007] The object is achieved according to the invention by a method having the features according to claim 1 and by a system having the features according to claim 18. Advantageous embodiments, refinements, and variants are the subject of the dependent claims. The statements in connection with the method also apply mutatis mutandis to the system, and vice versa. If steps of the method are described below, expedient embodiments for the system result from the system being designed to carry out one or more of these steps. For this purpose, the system has, in particular, a correspondingly designed control unit.

[0008] A key idea of ​​the invention is in particular to combine a corrugated board plant with a printing plant and then to operate these jointly with a heat engine. In other words: a corrugated board plant, a printing plant and a heat engine are energetically coupled with one another. This is based on the knowledge that the ratio of thermal output to electrical output (i.e. the power ratio) of a heat engine optimally reflects the total thermal and electrical power requirements of a corrugated board plant in conjunction with a printing plant. In contrast, a heat engine is not really suitable for supplying just one printing plant or just one corrugated board plant, since their respective power requirement ratio (ratio of thermal to electrical power requirement) does not correspond individually to the power ratio of the heat engine.

[0009] The method according to the invention serves to operate a system. The system has a corrugator for producing corrugated board. The corrugated board is produced, for example, as a continuous web of corrugated board or as prefabricated blanks. In addition, the system has a printing system for printing a paper layer with a print, in particular by means of a print head. The printing system and the corrugator are in particular operated simultaneously. The paper layer is preferably used to produce the corrugated board and is transferred from the printing system to the corrugator for this purpose, but this is not mandatory. Printing preferably takes place before the paper layer is further processed, in particular before it is combined with other paper layers to form corrugated board. Alternatively, the paper layer is printed if it has already been combined with one or more other paper layers.The printing system is preferably a digital printing system; this is assumed below without restriction of generality, although other printing systems are also suitable in principle.

[0010] Overall, in an advantageous embodiment, the system is used for producing printed corrugated board. The printing system and the corrugator are preferably operated inline (inline operation), i.e. the paper layer to be printed passes through the printing system and the corrugator without being wound and unwound in between. With regard to controlling the conveyor speed, the printing system preferably follows the corrugator, i.e. the corrugator sets a conveyor speed, which is then adopted by the printing system. The conveyor speed varies, in particular, depending on the current production order for the system, so that the thermal and electrical power requirements may also vary accordingly within certain limits.

[0011] As an alternative to the aforementioned inline operation, a configuration is also suitable in which the printing system and the corrugator are operated separately from one another, i.e., the paper layer is not transferred directly to the corrugator and, in one possible configuration, is even used for another purpose and not further processed in the corrugator. For example, the printing system and the corrugator produce, completely independently of one another, a printed paper layer and, on the other hand, corrugated board. In a suitable configuration, the printing system is operated in roll-to-roll operation, i.e., the paper layer is unrolled at the inlet of the printing system, then printed by the printing system, and finally wound up again into a roll at the end of the printing system. This roll is then transferred to the corrugator and unrolled there to produce corrugated board, or the roll is used for a completely different purpose, e.g.in another corrugator. Alternatively or additionally, the corrugator is operated in a roll-to-sheet mode. In any case, the respective conveyor speed of the printing system and / or the corrugator varies regularly depending on the current production order, so that the thermal and electrical power requirements may also vary within certain limits.

[0012] The plant further comprises a heat engine for generating thermal and electrical power. Preferably, the heat engine comprises a gas turbine and, in particular, also a generator. The gas turbine is operated with gas as the primary energy source (i.e., chemically supplied primary energy) and, when gas is burned, generates predominantly thermal power and, on the other hand, mechanical power, which drives the generator, which then generates electrical power. Without limiting the generality, the following assumes a gas turbine with a generator; however, other heat engines are also suitable in principle. Preferably, only a single primary energy source with the lowest possible carbon footprint (e.g., SNG, biogas, or green hydrogen) is used for the entire plant.

[0013] The corrugated board plant and the printing plant now form a network and are thus jointly supplied with thermal and electrical power by the heat engine, i.e. the thermal and electrical power generated by the heat engine are distributed between the corrugated board plant and the printing plant. In particular, both the corrugated board plant and the printing plant consume both thermal and electrical power. As already indicated above, it is of secondary importance whether the printing plant and the corrugated board plant are operated inline or separately. The only important thing is that the network of printing plant and corrugated board plant is jointly supplied with both thermal and electrical power by the heat engine.

[0014] A key advantage of the invention is that the power requirement ratio of the combination of corrugated board plant and printing plant corresponds particularly well to the power ratio of the heat engine. When the printing plant and the corrugated board plant are operated simultaneously, their thermal and electrical power requirements add up and can then be served jointly by a single heat engine, as described. By combining the corrugated board plant with the printing plant, the disadvantage that these, viewed on their own, are difficult to utilize in a cogeneration or CHP process is advantageously eliminated. It has been observed, for example, that a gas turbine has a power ratio of approximately 2:1 (e.g. 3.7 MW thermal and 1.8 MW electrical), whereas a corrugated board plant typically has a power requirement ratio of approximately 10:1 (e.g. 2.5 MW thermal and 250 kW electrical) and a printing plant of approximately 1:1 (e.g. 1 MW each thermal and electrical).In combination, however, this results in a power requirement ratio of around 2.8:1, so that in a network consisting of a corrugator and a printing plant, the use of a CHP or CHCC process is particularly economical. The heat engine accordingly has a corresponding ratio of thermal to electrical power, whereby a small deviation from the ideal ratio is tolerated, particularly if there is a surplus of electrical power, as this can be fed into a grid particularly easily. Accordingly, a heat engine with a power ratio of 2:1 to 3:1 (thermal to electrical) is already advantageous. As explained in more detail below, the power requirement ratio of the network can be adjusted within certain limits, so that further optimization and approximation to the power ratio of the heat engine is possible.This results in a significant increase in efficiency compared to operating the corrugated board plant and printing plant separately, as the combined heat and power (CHP) process maximizes the utilization of chemical primary energy. Operating costs for the combined plant are also reduced. If a CO2-neutral primary energy source is used, the CO2 emissions from corrugated board production are correspondingly reduced.

[0015] To ensure the most economical operation of the plant, it is designed in such a way that as many simultaneous consumers as possible are available for the thermal and electrical output of the heat engine (demand simultaneity factor). This is particularly optimal in the combination of a corrugated board plant and a printing plant described here, thus offering not only an economical but also a potentially CO2-neutral energy supply process. However, even the use of fossil natural gas in the heat engine results in a significant reduction in CO2 emissions comparable to the power plant.

[0016] The heat engine preferably provides the thermal output in the form of a hot gas, of which a first hot gas portion is used in the printing system, in particular directly for drying the paper layer and / or the print, and a second hot gas portion is used to generate process steam for the corrugator. In the case of a gas turbine, the hot gas is flue gas generated during the combustion of the primary energy source. This flue gas has a temperature in the range of 500°C to 600°C. The thermal output of the heat engine is therefore used in two different ways, i.e. the system is a bivalent system in this respect: on the one hand, the hot gas is used directly for drying in the printing system (direct heat utilization) and, on the other hand, for the simultaneous generation of process steam for the corrugator (indirect heat utilization).Downstream of the heat engine, the hot gas flow is divided into two partial flows, one is led to the pressure plant, the other to a waste heat boiler, which generates process steam for the corrugator, in particular by means of the sensible heat in the waste heat boiler.

[0017] The first hot gas portion is preferably fed at least partially to a pre-dryer in the printing system for drying the paper layer before printing, in particular to pre-condition the paper web for a more stable process. Alternatively or additionally, the first hot gas portion is at least partially fed to a hot air dryer in the printing system for drying the print, i.e. for drying after printing. The pre-dryer and the hot air dryer are each generally referred to as dryers. The dryers are preferably each designed as convection dryers, i.e. they emit warm drying air which comes into direct contact with the paper layer and optionally the print (direct gas drying). The hot gas from the heat engine is particularly suitable for this type of direct, thermal convection drying in the printing system because, by its very nature, the hot gas is free of particles or similar pollutants.The hot gas is also sterile and essentially contains CO2, N2, and water vapor. This direct gas drying process advantageously eliminates the need for a heat exchanger, which would generate heat transfer losses; such a heat exchanger is conveniently omitted. A further advantage of using direct gas is that internal recirculation can be omitted for reasons of energy efficiency and is also expediently omitted. In the recirculation air, the water vapor partial pressure and relative humidity would increase, which would fundamentally inhibit the drying / evaporation of solvents in the print. Eliminating recirculation in the dryer also eliminates the need for complex piping systems and radial fans for the supply and recirculation air. Furthermore, the drying air has a nearly constant moisture content, which has a positive effect on the drying characteristics of the print.

[0018] Preferably, the printing process in the printing system is based on an inkjet process. The printing system preferably uses only one or more water-based inks to print the paper layer. This avoids flammable solvent mixtures in combination with the hot gas, which contributes to explosion protection.

[0019] The temperature of the respective drying air, i.e. the drying temperature, in the respective dryer is in particular adjustable and is expediently set in the range from 100°C to 600°C as required. The drying temperature is preferably set by admixing fresh air. In a preferred embodiment, the drying temperature in the hot air dryer is controlled or even regulated as a function of a conveying speed of the paper layer through the printing system. This is based on the consideration that when the conveying speed changes, the period over which the paper layer and the print are in contact with the drying air also changes. To achieve a consistent drying result, the drying temperature is then expediently adjusted accordingly, i.e. reduced at lower conveying speeds and conversely increased at higher conveying speeds.

[0020] In a suitable embodiment, an exhaust air stream from the hot air dryer is fed to the pre-dryer to dry the paper layer before printing. The drying air is guided onto the paper layer in the hot air dryer and then discharged as an exhaust air stream. Since the drying air may not transfer all of its heat to the paper layer under pressure, the exhaust air stream has a corresponding amount of residual heat (e.g. a temperature in the range of 100°C to 200°C), which is then used in the pre-dryer. Alternatively or additionally, depending on its temperature, the exhaust air stream from the hot air dryer is expediently used either in an exhaust air recuperator (in particular an air / air recuperator) at a high temperature, in particular in the range of 200°C to 400°C and / or to generate process cooling, e.g. in an absorption chiller, at a low temperature, in particular in the range of 100°C to 200°C.The same applies analogously to a corresponding exhaust air flow from the pre-dryer, if one is available.

[0021] In addition to the first hot gas portion for direct gas utilization, the second hot gas portion is fed in particular to the aforementioned waste heat boiler (also referred to as a partial flow waste heat boiler), suitably via a controlled hot gas bypass which is designed, for example, with a valve for dividing the hot gas between the two hot gas portions (the valve then “bypasses” the direct gas utilization and feeds the hot gas to the waste heat boiler instead, or vice versa). The distribution of the hot gas between the two hot gas portions, i.e. a ratio of first to second hot gas portion, is expediently controlled, in particular with the hot gas bypass. Suitably, this is controlled according to the medium with the highest added value. This is, in particular, process steam. Expediently, when the system is put into operation, it is measured which maximum volume flow of hot gas (first hot gas portion) must be branched off for direct gas utilization for drying in the pressure system.The remaining hot gas is fed into the waste heat boiler (second hot gas portion). The design is carried out as part of a process balancing analysis. The heat engine is then dimensioned accordingly in terms of its power ratio. If the respective thermal power requirements of the corrugator and the printing system fluctuate, the distribution of the hot gas between the first and second hot gas portions is preferably regulated in such a way that the corrugator, in particular, is always supplied with sufficient thermal power and thus has priority over the supply of thermal power to the printing system. In other words, the thermal power requirement of the corrugator is met first, and this therefore takes priority over the thermal power requirement of the printing system.A possible deficit in the supply of thermal power to the printing system is suitably compensated by supplying additional thermal power which is generated separately from the thermal power of the heat engine, in particular with a heating element, e.g. a gas burner or an electric heating register or the like. The latter has the advantage that electrical power from the heat engine is expediently used, which may already be available in slight surplus. The corrugator's requirement for process steam therefore has overall priority, i.e. if more power is suddenly required to generate process steam, the first hot gas portion is reduced accordingly compared to the second hot gas portion, i.e. less hot gas is fed into the printing system for drying. The reduction in the first hot gas portion is suitably compensated by additional thermal power as described.

[0022] It is fundamentally advantageous to feed the hot gas for direct air drying to one or more dryers in a continuous flow operation and to discharge it from there as exhaust air and, if necessary, to use any residual heat elsewhere. Another advantageous variant is one in which one or more dryers in the printing system are operated at least temporarily or even permanently in recirculation mode, i.e. the supplied hot gas is not simply passed through and then discharged as exhaust air, but is continuously circulated, at least in part. Recirculation mode is particularly advantageous if, as described above, a deficit in the thermal output of the printing system is compensated for by supplying additional thermal output with a heating element (e.g. gas burner, electric heating register or the like).Recirculation mode therefore advantageously reduces the supplied hot gas flow because the recirculation temperature, which cools down due to heat losses, only needs to be kept constant. Overall, at least the following two variants are advantageous. In the first variant, drying takes place in continuous operation. Compared to recirculation mode, the required hot gas flow is higher but the required temperature is lower because the volume flow must be comparatively large in order to achieve a certain required blow-out speed at the outlet (e.g. dryer nozzles) of the dryer (in recirculation mode this is achieved with a separate recirculation fan). In a second variant, partial recirculation mode (mixed operation) is used. Compared to continuous operation, the required hot gas flow is now significantly lower, but the temperature must be higher to compensate for the heat losses from recirculation mode.In particular, the heating element is used solely to compensate for the aforementioned deficit and thus represents a backup solution to compensate for any peaks in thermal power demand as needed.

[0023] In an advantageous embodiment, however, the recirculation mode is used alternatively or additionally in a different way as follows: since the hot gas from the heat engine regularly has a significantly higher temperature than is required for drying, this hot gas can also be used in recirculation mode for a certain period of time or even permanently before the temperature has dropped below a minimum temperature required for drying. In an advantageous embodiment, at least a portion of the hot gas from the heat engine is fed to a hot air dryer (preferably the hot air dryer already mentioned above) of the printing system, and the hot air dryer is then operated in recirculation mode. The minimum temperature is in particular a temperature at least required for drying and is preferably in the range between 200 °C and 300 °C.In contrast, the hot gas from the heat engine has a significantly higher temperature, preferably in the range of 500°C to 600°C, or is 200°C to 400°C hotter than the minimum temperature, resulting in a correspondingly large amount of heat available for recirculation. When the temperature of the hot gas in the hot air dryer reaches the minimum temperature, the now "used" hot gas is discharged as exhaust air, and the process can be restarted as needed.

[0024] Partial recirculation mode (also known as mixed mode) is also suitable for recirculation operation. In this mode, only a portion of the hot gas is circulated in the hot air dryer and the other portion is discharged as exhaust air and then expediently replaced with fresh hot gas. 100% (fully closed) recirculation mode is typically not possible, as this would result in solvents (mainly water vapor) concentrating in the recirculated air. Therefore, in recirculation mode, cold, uncontaminated fresh air is preferably supplied and contaminated, hot exhaust air is discharged, but both volume flows are kept as low as possible. Partial recirculation mode is preferably used when there is too little hot gas available for drying in the printing system. In this mode, additional heating elements such as gas burners, etc. are also required.in the circulating air and are preferably used, which would not be possible with direct continuous drying.

[0025] The waste heat boiler generates saturated steam, e.g. at 16 bar, and thus advantageously serves the entire process steam requirement of the corrugated board plant and thus in particular also its entire thermal power requirement.

[0026] This second part of the bivalent heat utilization significantly increases the overall efficiency of the system.

[0027] The process steam for the corrugator is suitably first led from the waste heat boiler to a steam distributor, which then forwards the process steam at a suitable pressure to a respective processing station of the corrugator. The corrugator has, in particular, one or more of the following processing stations: a preheater, for preheating one or more paper layers, e.g., prior to gluing; a laminating unit and / or a heating and pulling section, each for gluing several paper layers together; a module facer (e.g., with a corrugating roller) for corrugating a paper layer. One or more of the aforementioned processing stations have a heating device and / or a humidification device, which require process steam, e.g., a heating plate or a spray bar.

[0028] As already indicated at the beginning, the thermal power requirement of the network may vary depending on the current production order. Therefore, the plant is suitable for having a steam storage facility, which compensates for the time-varying thermal power requirement of the network. In other words: the heat engine generates a predominantly constant amount of thermal and electrical power, whereas the network may have varying thermal and electrical power requirements depending on the production order. Any excess thermal power is then diverted to the steam storage facility, or conversely, thermal power is withdrawn from it if the thermal power requirement of the network exceeds the thermal output of the heat engine (with regard to electrical power, a similar procedure is followed, for example, using the public grid instead of the steam storage facility).Hot gas (more precisely: hot gas from the second hot gas stream) from the heat engine is stored in the steam accumulator and called upon as needed for the printing plant or the corrugator, or both. In a practical embodiment, hot water or superheated steam is extracted from the waste heat boiler or the steam accumulator as needed and used to generate process cooling. In an advantageous embodiment, the superheated steam is used as saturated steam for rehumidification and / or for adjusting a cross-sectional moisture profile in the printing plant.

[0029] In a suitable embodiment, the ratio of the thermal outputs of the first and second hot gas components is 3:4 to 1:4, i.e., the larger portion of the thermal output is fed to the waste heat boiler and / or steam storage and used, in particular, as process steam for the corrugator, while only approximately 20% to 45% of the thermal output is used for the printing system. For example, the thermal output of the direct gas utilization (first hot gas stream) is 1.6 MW, and the remaining thermal output (second hot gas stream) is 2.5 MW, which corresponds to a ratio of approximately 2:3.

[0030] In an advantageous embodiment, the system is designed to generate process cooling and, for this purpose, comprises, in particular, an absorption chiller and / or a compression chiller. The process cooling is expediently used to cool one or more components of the printing system and / or the corrugated board system, e.g., to operate a cooling roller for cooling the paper layer in the printing system. The process cooling is supplied, for example, by means of cooling water, which is cooled by an absorption chiller and / or a compression chiller.

[0031] The absorption chiller is operated with thermal power, e.g., as described above, with exhaust air from the pressurized plant, or with hot water or superheated steam from the waste heat boiler or steam storage, or even directly with hot gas from the heat engine. The compression chiller, on the other hand, is operated with electrical power, which in particular comes directly from the heat engine. Accordingly, process cooling can be generated flexibly in different ways depending on the availability of thermal and electrical power.Accordingly, in an advantageous embodiment, the system for generating process cooling comprises both an absorption chiller operated with thermal power and a compression chiller operated with electrical power. The respective power consumption of the absorption chiller and the compression chiller is controlled such that the thermal power requirement and the electrical power requirement of the system are optimally adapted to the electrical power and thermal power of the heat engine. In other words, a given amount of process cooling is generated proportionally by the absorption chiller and the compression chiller in such a way that the thermal and electrical power of the heat engine are utilized as optimally as possible.The power consumption of the absorption chiller and the compression chiller is therefore controlled depending on what type of power is still available at a given time, so that the power requirement ratio of the network is optimized overall. This is based on the consideration that the method of generation of process cooling is irrelevant for the use of the process cooling. For example, if there is no thermal power available to generate process cooling at a given time, but electrical power is available, the process cooling is generated using the compression chiller. Conversely, if there is a surplus of thermal power, the process cooling is generated using the absorption chiller. The amount of process cooling generated preferably remains constant. Mixed operation is also possible and, depending on the respective power availability, can be advantageous.

[0032] As long as sufficient thermal capacity is available, the absorption chiller is preferably operated as a once-through chiller, which is designed for the highest possible number of operating hours. The compression chiller is preferably activated only to cover peak cooling loads and otherwise remains inactive. The compression chiller is therefore a type of emergency unit and is only activated in exceptional cases to meet peak loads, while the absorption chiller primarily serves a base load continuously.

[0033] Just like the thermal power, the electrical power of the heat engine is also used by both the printing system and the corrugator. In a preferred embodiment, the electrical power is used to operate at least one IR dryer (i.e. infrared dryer) of the printing system, at least one drive of the printing system and / or the corrugator (i.e. for conveying one or more paper layers, the corrugated board or intermediate products thereof) and at least one processing station, e.g. a wet end or a dry end of the corrugator. The dry end preferably has one or more of the following processing stations: cross cutter, longitudinal cutter, slitting device, creasing device.The dry end is connected to the wet end of the corrugated board plant and refers to the part of the corrugated board plant to which the paper layers joined together to form a corrugated board web are fed for further processing, in particular finishing, i.e. the paper layers are no longer present individually in the dry end, but are connected to form the corrugated board web.

[0034] The IR dryer in the printing system is primarily used to dry the print. Compared to convection drying, an IR dryer has the advantage that it does not smudge the freshly printed image. Therefore, an IR dryer is preferably located immediately downstream of a print head in the printing system. Disadvantages of an IR dryer, however, are its high electrical power consumption (usually in the range of approximately 500 kW to 1000 kW), its relatively short lifespan (limited lifespan of carbon filaments, for example), and the fact that the effectiveness of the drying depends on the absorption coefficient of the printed ink and is therefore sometimes color-dependent. To overcome the aforementioned disadvantages of an IR dryer and to integrate an additional heat sink into the system, it is advantageous to combine an IR dryer with a hot air dryer in the printing system.Instead of using an IR dryer exclusively for drying, it is dimensioned smaller and combined with a hot air dryer in order to achieve at least the required drying performance. In an advantageous embodiment, the printing system therefore has at least one IR dryer and at least one hot air dryer (in particular as already described above) for drying the print, and the IR dryer is arranged upstream of the hot air dryer with respect to a conveying direction of the paper layer being printed. In this way, the print is pre-dried using the IR dryer before the necessary remaining drying takes place with the hot air dryer. Pre-drying with the IR dryer advantageously prevents smudging of the print during drying in the hot air dryer.The hot air dryer also reduces the electrical power requirements of the printing system and requires less maintenance than the IR dryer.

[0035] Preferably, the printing system has at least two IR dryers, namely a first IR dryer upstream and a second IR dryer downstream (with respect to the conveying direction of the paper layer) of the hot air dryer.

[0036] Analogous to the combination of an absorption chiller and a compression chiller for generating process cooling, the combination of an IR dryer and a dryer also advantageously enables an optimization of the power requirement ratio of the system and thus an adjustment of the thermal and electrical power requirements to the actually available thermal and electrical power, if necessary also in response to a change in operation, e.g. due to a change in the production order for the system. The above statements on the generation of process cooling also apply analogously to drying and vice versa. In an advantageous embodiment, the printing system for drying the print has an IR dryer, which is operated with electrical power, and a dryer (hot air dryer), which is operated with thermal power.The IR dryer and the dryer preferably correspond to the IR dryer and hot air dryer described above, respectively. The respective power consumption of the IR dryer and the dryer is then controlled such that the thermal power requirement and the electrical power requirement of the combination are adapted to the electrical power and thermal power of the heat engine. For example, if there is an excess of thermal power, the power requirement of the dryer is increased and the power requirement of the IR dryer is reduced (and vice versa if there is an excess of electrical power), suitably such that the drying performance of the combination of dryer and IR dryer remains constant.Analogous to the combination of absorption chiller and compression chiller, a configuration in which one of the dryers, particularly the hot air dryer, serves a base load in terms of drying, while the other dryer, particularly the IR dryer, only serves a peak load as needed, is also advantageous. However, the detailed control of the various dryers depends on the design of the entire system (number, type, and output of the various dryers) and the process balancing (distribution of thermal and electrical power between the corrugator and the printing system).

[0037] A preferred embodiment of the system is described below by way of illustration. A layer of paper is fed to the printing system, e.g. from a unwinder. The layer of paper is first optionally pre-dried using a pre-dryer. The layer of paper is then printed on using a number of print heads, i.e. provided with a print, which is then dried first with an IR dryer and then with a hot air dryer. This is optionally followed by a further IR dryer as a booster in order to achieve a particularly high overall drying performance, e.g. at a particularly high conveying speed. The printed and dried layer of paper is finally cooled using one or more cooling rollers and then transferred directly to the corrugator.In this, the paper layer is glued to other paper layers in the wet end to form a corrugated board web and then, if necessary, finished in the dry end. The finished corrugated board is then output from the corrugator either as continuous product or in multiple copies. The thermal output of the heat engine is divided between the pre-dryer and the hot air dryer on the one hand, and a waste heat boiler and, optionally, a steam storage unit on the other. Various processing stations in the corrugator are supplied with process steam from the waste heat boiler for joining the paper layers to form the corrugated board. Optionally, part of the thermal output and / or one or more exhaust air streams from the printing system can be used to generate process cooling and / or fed to an exhaust air recuperator to preheat fresh air for the heat engine. The cooled, but still warm exhaust air from the exhaust air recuperator is used, for example, to generate process cooling.The electrical power of the heat engine is distributed between the printing system's IR dryers and one or more drive units of the printing system and the corrugator. The dry end is also supplied with electrical power for finishing the corrugated board web, e.g., cutting and / or creasing. Any excess electrical power is fed into the public grid.

[0038] In the following, exemplary embodiments of the invention are explained in more detail with reference to a drawing. In each case, the following schematically show:

[0039] Fig. 1 a process diagram for the operation of a plant,

[0040] Fig. 2 shows a process balance for the plant from Fig. 1 .

[0041] The system 2 shown in Fig. 1 has a corrugated board system 4 for producing corrugated board 6, which is produced, for example, as a continuous corrugated board web or as prefabricated blanks. In addition, the system 2 has a printing system 8, here a digital printing system, with a number of print heads (not explicitly shown) for printing a paper layer 10 with a print. In the exemplary embodiment shown here, inline operation is realized, in which the printed paper layer 10 is transferred directly from the printing system 8 to the corrugated board system 4 in order to use the paper layer 10 in the production of the corrugated board 6. In an alternative embodiment not explicitly shown, however, the printing system 8 and the corrugated board system 4 are operated separately from one another and the printing system 8 is operated, for example, in a roll-to-roll mode.Regardless of whether the printing system 8 and the corrugator 4 are operated inline or separately, they are always operated simultaneously.

[0042] In the illustrated embodiment, printing occurs before the paper layer 10 is combined with other paper layers to form corrugated board 6. Overall, the system 2 thus serves to produce printed corrugated board 6. The printing system 8 and the corrugating board system 4 are operated inline, i.e., the paper layer 10 being printed passes through the printing system 8 and the corrugating board system 4 without being wound and unwound in between. If the paper layer 10 is not used to produce corrugated board 6 with the corrugating board system 4, the system 2 serves to produce a printed paper layer 10 on the one hand and corrugated board 6 on the other.

[0043] Plant 2 further comprises a heat engine 12 for generating thermal power Pth and electrical power Pel from an input chemical power Pchem. In the illustrated embodiment, heat engine 12 comprises a gas turbine (not explicitly shown) and a generator (also not explicitly shown). The gas turbine is operated with gas as the primary energy source 14.

[0044] The corrugated board plant 4 and the printing plant 8 now form a network and are thus jointly supplied with thermal power Pth and electrical power Pel by the heat engine 12, i.e. the thermal and electrical power Pth, Pel generated by the heat engine 12 are distributed between the corrugated board plant 6 and the printing plant 8, which each consume both thermal and electrical power. A possible process balance for distributing the thermal and electrical power Pth, Pel is shown in Fig. 2. In the exemplary embodiment in Fig. 2, the electrical power Pel is 1.9 MW and the thermal power Pth is 4.1 MW, so that the power ratio of the heat engine 12 is approximately 2:1. The thermal power Pth is then again distributed, for example, in a ratio of 2:3 between the printing plant 8 and the corrugated board plant 6, with the corrugated board plant 6 receiving the larger share.However, depending on the specific design of the entire system 2, the values ​​and ratios mentioned may vary.

[0045] The heat engine 12 shown here provides the thermal output Pth in the form of a hot gas at, for example, 550 °C, of ​​which a first hot gas portion 16 is used directly in the printing system 8 to dry the paper layer 10 and / or the print. A second hot gas portion 18 of the hot gas is used to generate process steam 20 for the corrugator 6. The thermal output Pth is used in two different ways: firstly, for drying in the printing system 8 (direct heat utilization) and, secondly, for the simultaneous generation of process steam for the corrugator 4 (indirect heat utilization). Downstream of the heat engine 12, the hot gas stream is split into two partial streams 16, 18 by a hot gas bypass 21 (here implemented with a valve). One is fed to the printing system 8, the other to a waste heat boiler 22, with which the process steam 20 for the corrugator 4 is generated.

[0046] The first hot gas portion 16 is partially fed to a pre-dryer 24 for drying the paper layer 10 before printing. In addition, in Fig. 1 the first hot gas portion 16 is also partially fed to a hot air dryer 26 for drying the print, i.e. for drying after printing. The pre-dryer 24 and the hot air dryer 26 are generally each also referred to as dryers. The dryers 24, 26 are each designed as convection dryers, i.e. they flow out warm drying air which comes into direct contact with the paper layer 10 and optionally the print (direct gas drying). The temperature of the respective drying air, i.e. the drying temperature, in the respective dryer 24, 26 is adjustable and in the embodiment shown is set as required in the range from 100°C to 600°C, in this case by admixing fresh air 28, e.g. with a temperature of 20°C.

[0047] The following calculation example is intended to roughly illustrate the design of system 2: the heat engine 12 provides hot gas with a mass flow in the range of 5 to 10 kg / s, which is distributed between the printing system 8 and the corrugator 6 in a ratio of approximately 2:3, as shown in Fig. 2. Knowing the temperature of the hot gas, the corresponding volume flow can be calculated and distributed among the various tasks, primarily the dryers 24, 26. The volume flow for the printing system 8 and its temperature are adjusted via the fresh air 28, which is dimensioned according to the specific requirements. For example, approximately half the hot gas temperature is selected as the temperature for the dryers 24, 26, and for this purpose, the first hot gas portion 16 is mixed with fresh air 28 in a ratio of approximately 3:1 (volume flow ratio) in order to obtain a sufficient quantity of hot air with a sufficient temperature for drying.

[0048] In addition, in Fig. 1, an exhaust air stream 30 from the hot-air dryer 26 is fed to the pre-dryer 24 for drying the paper layer 10 prior to printing. The drying air is directed onto the paper layer in the hot-air dryer and then discharged as exhaust air stream 30. Alternatively or additionally, in an embodiment not shown, the exhaust air stream 30 is used, depending on its temperature, either in an exhaust air recuperator and / or to generate process cooling 44. The same applies analogously to a corresponding exhaust air stream from the pre-dryer 24, if one is present.

[0049] In addition to the first hot gas portion 16 for direct gas utilization, the second hot gas portion 18 is fed to the waste heat boiler 22. This generates saturated steam and thus serves the entire process steam requirement of the corrugated board plant 4. The process steam 20 for the corrugated board plant 4 is first fed from the waste heat boiler 22 to a steam distributor 32, which then forwards the process steam 20 at a suitable pressure to a respective processing station of the corrugated board plant 4. The corrugated board plant 4 shown here as an example has the following processing stations: a preheater 34 for preheating one or more paper layers; a module facer 36 for corrugating a paper layer; a laminating unit 38; and a heating and pulling section 40, each for gluing several paper layers together.

[0050] Depending on the current production order, the thermal power requirement of the network may vary. Therefore, system 2 in Fig. 1 additionally has a steam accumulator 42, which compensates for the time-varying thermal power requirement of the network. Hot gas is stored in the steam accumulator 42 and called up as needed. In the embodiment shown here, hot water or superheated steam is even extracted from the waste heat boiler 22 or from the steam accumulator 42 as needed and used to generate process cooling 44. In an advantageous embodiment, the superheated steam is used as saturated steam for rehumidification and / or for adjusting a cross-sectional moisture profile in the printing system.

[0051] As already indicated, the system 2 shown here is designed to generate process cooling 44 and, for this purpose, has an absorption chiller 46 and a compression chiller 48. The process cooling 44 is used to cool one or more components of the printing system 8 and / or the corrugated board system 4, in Fig. 1 specifically to operate a cooling roller 50 for cooling the paper layer 10 in the printing system 8. The process cooling 44 is supplied, for example, by means of cooling water 52, which is cooled by the absorption chiller 46 and the compression chiller 48.

[0052] The absorption chiller 46 is operated with thermal power Pth, while the compression chiller 48 is operated with electrical power Pel. Accordingly, process cooling 44 can be flexibly generated in different ways depending on the availability of thermal and electrical power Pth, Pel. Accordingly, the respective power consumption of the absorption chiller 46 and the compression chiller 48 is controlled in such a way that the thermal power demand and the electrical power demand of the network are adapted as optimally as possible to the electrical power Pel and the thermal power Pth of the heat engine 12. The power consumption of the absorption chiller 46 and the compression chiller 48 is therefore controlled depending on which type of power Pth, Pel is available at a given time, so that the power demand ratio of the network is optimized overall.

[0053] Just like the thermal power Pth, the electrical power Pel is also used by both the printing system 8 and the corrugator 4. In the exemplary embodiment shown, the electrical power Pel is used to operate two IR dryers 54, 56 (i.e. infrared dryers) of the printing system 8, as well as to operate a respective drive 62 of the printing system 8 and the corrugator 4, and also to operate at least one processing station of a dry end 58 of the corrugator 4. The dry end 58 has one or more of the following processing stations: cross cutter, longitudinal cutter, slitting device, creasing device. These are not explicitly shown here for the sake of simplicity. The dry end 58 is connected to the wet end 60 of the corrugator 4.

[0054] The IR dryer 54 is arranged directly downstream of a print head of the printing system 8. This is combined with the hot-air dryer 26 as an additional heat sink in the printing system 8. The IR dryer 54 is arranged upstream of the hot-air dryer 26 with respect to a conveying direction of the paper layer 10 being printed, as shown in Fig. 1. In this way, the print is pre-dried by the IR dryer 54 before the remaining drying takes place with the hot-air dryer 26. In addition, the printing system 8 shown here also has the second IR dryer 56 downstream of the hot-air dryer 26.

[0055] Analogous to the combination of absorption chiller 46 and compression chiller 48 for generating process cooling 44, the combination of an IR dryer 54, 56 and a dryer 24, 26 also enables optimization of the power requirement ratio of the system and thus adaptation of the thermal and electrical power requirements to the actually available thermal and electrical power Pth, Pel. The statements regarding the generation of process cooling 44 also apply analogously to drying, and vice versa. The respective power consumption of the IR dryers 54, 56 and the dryers 24, 26 is now controlled such that a thermal power requirement and an electrical power requirement of the system are adapted to the electrical power Pel and the thermal power Pth of the heat engine 12.

[0056] Excess electrical power Pel is fed into the public grid 64 if necessary.

[0057] 2 Appendix

[0058] 4 Corrugated board line

[0059] 6 Corrugated cardboard

[0060] 8 Printing system

[0061] 10 paper layers

[0062] 12 Heat engine

[0063] 14 primary energy sources

[0064] 16 first hot gas portion

[0065] 18 second hot gas component

[0066] 20 Process steam

[0067] 22 waste heat boilers

[0068] 24 pre-dryers, dryers

[0069] 26 hot air dryers, dryers

[0070] 28 Fresh air

[0071] 30 exhaust air flow

[0072] 32 steam distributors

[0073] 34 preheaters

[0074] 36 Module Facer

[0075] 38 Laminating plant

[0076] 40 Heating and draft section

[0077] 42 steam storage tanks

[0078] 44 Process cooling

[0079] 46 Absorption chiller

[0080] 48 compression refrigeration machine

[0081] 50 cooling rollers

[0082] 52 Cooling water

[0083] 54 IR dryers

[0084] 56 IR dryers

[0085] 58 Dry End

[0086] 60 wet end

[0087] 62 public network Pchem chemical power

[0088] Pel electrical power

[0089] Pth thermal power

Claims

Claims Method for operating a plant (2), - wherein the plant (2) comprises a corrugated board plant (4) for producing corrugated board (6), - wherein the system (2) comprises a printing system (8) for printing a paper layer (10) with a print, - wherein the plant (2) comprises a heat engine (12) for generating thermal power (Pth) and electrical power (Pel), - wherein the corrugated cardboard system (4) and the printing system (8) form a network and are thus jointly supplied with thermal power (Pth) and electrical power (Pel) by the heat engine (12). Method according to claim 1, wherein the heat engine (12) provides the thermal power (Pth) in the form of a hot gas, of which a first hot gas portion (16) is used for drying in the printing system (8) and a second hot gas portion (18) is used to generate process steam (20) for the corrugated cardboard system (4).Method according to claim 2, wherein, when a respective thermal power requirement of the corrugated cardboard system (6) and the printing system (8) fluctuates, the distribution of the hot gas between the first and the second hot gas portion (16, 18) is regulated such that the corrugated cardboard system (6) is supplied with sufficient thermal power (Pth) and thus has priority over the supply of thermal power (Pth) to the printing system (8), wherein a possible deficit in the supply of thermal power to the printing system (8) is compensated by supplying additional thermal power which is generated separately from the thermal power (Pth) of the heat engine (12). Method according to claim 2 or 3, wherein the first hot gas portion (16) is at least partially fed to a pre-dryer (24) of the printing system (8) for drying the paper layer (10) before printing. Method according to one of claims 2 to 4, wherein the first hot gas portion (16) is at least partially fed to a hot-air dryer (26) of the printing system (8) for drying the print. Method according to claim 4 and claim 5, wherein an exhaust air stream (30) of the hot-air dryer (26) is fed to the pre-dryer (24). Method according to claim 5, wherein a drying temperature in the hot-air dryer (26) is controlled as a function of a conveying speed of the paper layer (10) through the printing system (8). Method according to one of claims 1 to 7, wherein at least a portion of the hot gas from the heat engine (12) is supplied to a hot air dryer (26) of the printing system (8) and the hot air dryer (26) is then operated therewith in a recirculation mode.Method according to one of claims 1 to 8, wherein the system (2) comprises a steam accumulator (42) with which a time-varying thermal power requirement of the network is compensated. Method according to one of claims 1 to 9, wherein the system for generating process cooling (44) comprises an absorption chiller (46) which operates with thermal power (Pth). and a compression refrigeration machine (48) which is operated with electrical power (Pel), wherein a respective power consumption of the absorption refrigeration machine (46) and the compression refrigeration machine (48) is controlled such that a thermal power requirement and an electrical power requirement of the compound are adapted to the electrical power (Pel) and the thermal power (Pth) of the heat engine (12). Method according to one of claims 1 to 10, wherein the electrical power (Pel) is used for operating - at least one IR dryer (54, 56) of the printing system (8), - at least one drive of the printing system (8) and / or the corrugated board system (4) and - at least one processing station of the corrugated cardboard system (4). The method according to one of claims 1 to 11, wherein the printing system (8) has at least one IR dryer (54) and at least one hot-air dryer (26) for drying the print, wherein the IR dryer (54) is arranged upstream of the hot-air dryer (28) with respect to a conveying direction of the paper layer (10). Method according to one of claims 1 to 12, wherein the printing system (8) for drying the print has an IR dryer (54, 56) which is operated with electrical power (Pel), and a dryer (24, 26) which is operated with thermal power (Pth), wherein a respective power consumption of the IR dryer (54, 56) and of the dryer (24, 26) is controlled such that a thermal power requirement and an electrical power requirement of the combination are adapted to the electrical power (Pel) and the thermal power (Pth) of the heat engine (12).Method according to one of claims 1 to 13. wherein the heat engine (12) comprises a gas turbine. Method according to one of claims 1 to 14, wherein the printing system (8) is a digital printing system. Method according to one of claims 1 to 15, wherein the printing system (8) and the corrugated board system (4) are operated inline. Method according to one of claims 1 to 15, wherein the printing system (8) and the corrugated board system (4) are operated separately from one another. wherein the printing system (8) and / or the corrugated board system (4) is / are operated in particular in a roll-to-roll operation and / or a roll-to-sheet operation. System (2) which is designed to operate according to a method according to one of claims 1 to 17

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