Printing press with dryer unit and waste heat recovery system and method for optimizing waste heat recovery on a printing press

Abstract

Printing press with dryer unit and waste heat recovery system, wherein the waste heat recovery system (1) includes a heat exchanger (4) and / or a heat pump (2) which heat air and supply it to the dryer unit, wherein a control or regulation is provided to influence an air temperature and / or an air volume flow supplied by the heat exchanger (4) and / or the heat pump (2), characterized by that the drying system contains several drying units, each with individually selectable drying temperatures and that at least one dryer unit of the dryer system is assigned a second air supply flap (13) with which ambient air can be mixed with the air coming from the waste heat recovery system (1).

Description

[0001] The invention relates to a printing press with a dryer device and waste heat utilization system according to the preamble of claim 1 and a method for optimizing the waste heat utilization on a printing press.

[0002] The use of waste heat sources through heat recovery is widely known and established. The use of heat exchangers and heat pumps, in particular, is already common in air conditioning technology. In printing presses, cooling units are primarily operated with heat exchangers.

[0003] From DE 200 08 740 U1, a hot air drying device with a heat exchanger is known, wherein the heat exchanger has a filter on its inlet side which removes impurities from the air supplied to the heat exchanger. A monitoring device is not provided. A disadvantage of this solution is that the operating personnel must observe replacement intervals, and damage may result from failure to do so.

[0004] German patent DE 100 38 801 A1 discloses a method and a device for utilizing the waste heat from a suction and compressed air supply for the infrared or hot air dryer of a printing press. A heat exchanger is used to utilize the waste heat for preheating the dryer air. Furthermore, it is proposed to install a reheater after the heat exchanger to further heat the air. This reheater can be a heat pump. A disadvantage of this solution is the lack of a control system for the heat pump.

[0005] German patent DE 10 2008 042 122 A1 discloses a thermal air drying device for printing presses that proposes the possibility of using the dryer exhaust air for energy recovery. This already increases the energy efficiency of the printing press. A disadvantage of this solution is that the use of waste heat energy cannot be utilized for all printing jobs.

[0006] In all known waste heat recovery systems for printing presses, the air temperature supplied to the dryer from the heat exchanger or heat pump is not regulated. The heat exchanger or heat pump is either in operation or not. The air supplied to the dryer can only be heated by the dryer's heating elements, which means that the heat exchanger or heat pump must be switched off if the dryer temperature specified for the specific job is lower than the air preheated by the exhaust air recovery system.

[0007] Up to now, heat exchangers and heat pumps have been optimized according to energy efficiency criteria, which may lead to energy losses in relation to the overall system.

[0008] The invention is therefore based on the objective of creating an improved printing press with a dryer unit and waste heat recovery system and a method for optimizing waste heat recovery on a printing press, which ensures effective exhaust air utilization.

[0009] According to the invention, the problem is solved by a device with the features of the independent device claim and a method with the features of the independent method claim. Advantageous embodiments are described in the dependent claims, the description, and the drawings.

[0010] The invention has the advantage of increasing the overall machine's energy efficiency, which ultimately reduces total energy consumption. Furthermore, it expands the range of jobs that can be printed energy-efficiently. The heat exchangers and / or heat pumps can also be used at lower dryer temperatures.

[0011] The heat exchanger principle, as used here, refers to the transfer of energy from a medium of higher temperature to a medium of lower temperature via a surface, particularly a metal surface. Control or regulation can be achieved, for example, by activating or deactivating individual heat exchangers when multiple heat exchangers are used. Air is preferably used as the medium in this context.

[0012] The heat pump principle, as used here, refers to the transfer of energy from a medium of higher temperature to a medium of lower temperature via a transfer medium circulating in an intermediate circuit. The temperature of the transfer medium can be raised to a higher value by supplemental heating, particularly using electrical energy. Depending on the transfer medium used, certain temperature ranges are possible. Control or regulation can be achieved primarily by adjusting the temperature of the transfer medium. Air-source heat pumps, designed for large air volumes, are the preferred type of heat pump. These air-source heat pumps typically have their own drives to move these large air volumes and can also be referred to as air-to-air heat pumps.

[0013] Alternatively or additionally to controlling the air temperature, the preheated air supplied to the dryer can be influenced by controlling the air volume flow. This can involve changes in the cross-section of the air duct system, adjusting the transport speed using positive drives, particularly fans, opening or closing bypass lines, and / or adding fresh air. A simple adjustment option is the stepwise activation of dampers located in the air duct system. However, continuously adjustable dampers are preferably used in the air duct system.

[0014] The printing press can be any type of printing press. It can be a letterpress, gravure, offset, and / or screen printing press and can print on either web or sheet-fed substrates. Preferably, the printing press is a sheetfed offset rotary printing press. The waste heat recovery system is connected to the printing press via an air duct system with multiple air channels and can be located in or outside the printing area. Preferably, the waste heat recovery system is located directly adjacent to the printing press as a waste heat recovery module. Particularly preferably, the waste heat recovery module is located in the delivery area, especially above the dryers. Alternatively, it can be located above the printing press on the ceiling of the building. Furthermore, several printing presses can be equipped with a common waste heat recovery system.

[0015] The waste heat recovery system utilizes heat generated in the exhaust air from any process on the printing press to warm the required fresh air. This warmed fresh air is then fed back into the same process or another process. Preferably, the exhaust air heat from the dryers in the delivery unit of the printing press is used to warm the fresh air. This warmed fresh air is then fed back into a process on the printing press, preferably into the drying process. The drying unit preferably has several drying units, on which different drying temperatures can be preselected depending on the print job. These different drying temperatures can be controlled by the machine control system or entered and / or confirmed by the operator at the drying unit.

[0016] In a further development of the invention, an air filter system is integrated into the waste heat recovery system. This air filter system includes a filter that cleans the exhaust air emitted by the printing press, particularly the dryer unit, thus preventing deposits and maintaining a constant efficiency. The filter is arranged such that the incoming exhaust air is cleaned before entering the heat pump or heat exchanger to remove contaminants such as dust, printing powder, or chemical impurities from inks and varnishes. This prevents the downstream equipment, especially the heat pump and heat exchanger, from becoming contaminated or even damaged. Furthermore, no time-consuming cleaning of the equipment or air ducts is required. At the same time, the service life of all equipment, and thus of the waste heat recovery system, is increased.In a preferred embodiment, the air filter system is equipped with a sensor device for monitoring the filter's degree of contamination. This sensor device allows for continuous monitoring of the filter and, if a predefined contamination level is exceeded, can issue a signal, particularly a warning message, or transmit information to the printing press's machine control system.

[0017] In a further embodiment of the invention, the waste heat recovery system includes, in addition to the heat pump, a heat exchanger, which is preferably located downstream of the heat pump. The heat exchanger utilizes the remaining heat in the exhaust air after the heat pump to heat cooler fresh air. This heated fresh air is then used for further processes, particularly as dryer air. The heat exchanger is specifically designed as a cross-flow, cross-counterflow, or rotary heat exchanger. Alternatively, a second heat pump can also be used.

[0018] In a preferred embodiment of the invention, a measuring and control device is assigned to the waste heat recovery system, by means of which the temperature of the fresh air heated by the waste heat recovery system is measured. Depending on the measured temperature, the heating power of the heating elements of one or more dryer units in the delivery area of ​​the printing press is regulated. If the temperature of the heated fresh air is higher, the power of the heating elements can be minimized via the measuring and control device, so that a desired dryer temperature is always maintained. The energy consumption required by the heating element is thus minimized by the measuring and control device.

[0019] In a further preferred embodiment of the invention, the heat pump is connected to a refrigeration circuit of the printing press. The heat pump is equipped with a reverse cycle, enabling it to generate cooling. This cooling can be used for the printing press or other processes to reduce the printing press's energy consumption. The cooling is advantageously used in warmer seasons or near heat sources for cooling or air conditioning rooms. For example, in summer, cooling water can be generated and the waste heat released to the outside air via the evaporator, which then operates as a condenser. The cooling capacity is also intended for cooling specific work areas on the printing press.

[0020] The invention will now be explained by way of example. The accompanying drawings schematically illustrate the following: Fig. 1: Waste heat recovery system with a heat pump and an air filter located upstream of the heat pump; Fig. 2: Waste heat recovery system with a heat pump, an air filter upstream of the heat pump and an additional heat exchanger; Fig. 3: Dryer unit with four dryer units in the delivery of a printing press and waste heat recovery system according to the first figure.

[0021] The Fig. Figure 1 shows, in one embodiment of the invention, a waste heat recovery system 1 with a heat pump 2. The waste heat recovery system 1 further includes an air distribution system with several air distribution channels. Air is supplied to or extracted from the waste heat recovery system 1 in the air distribution channels according to the arrows shown. Heated air from outside the waste heat recovery system 1 is supplied to the heat pump 2 via an exhaust air supply channel 3.1. The exhaust air leaving the heat pump 2 is extracted from the waste heat recovery system 1 via an exhaust air channel 3.2. Fresh air is supplied to the waste heat recovery system 1 via a fresh air supply channel 3.3. A fresh air return channel 3.4 returns the air preheated by the heat pump 2 back to the printing press.

[0022] The structure of heat pump 2 is shown only schematically, with only the evaporator 2.1 and condenser 2.2 depicted. The evaporator 2.1 extracts heat from the environment, in this case, the exhaust air. The condenser 2.2 transfers heat to the environment, in this case, the fresh air. Heat pump 2 also requires a separate drive (not shown) to circulate a medium between evaporator 2.1 and condenser 2.2 in a circuit 2.3. This drive serves to force convection of the medium flowing between evaporator 2.1 and condenser 2.2. The waste heat recovery system 1 also includes an air filter system, which is associated with the exhaust air supply duct 3.1. The air filter system is located upstream of heat pump 2 with respect to the direction of airflow.

[0023] The warm exhaust air from the printing press is fed from the exhaust air supply duct 3.1 to the air filter system and cleaned by an air filter assembly. The air filter system includes an air filter 3.5, which consists of a single mechanical or chemical filter or a combination of a mechanical filter, e.g., a bag filter, and a chemical filter. An activated carbon filter is preferably used as the chemical filter. In a further embodiment of the invention (not shown), a sensor device for monitoring the filter condition, in particular the degree of contamination, is assigned to the air filter system.

[0024] After the air filter 3.5, the exhaust air from the exhaust air supply duct 3.1 is fed to the heat pump 2, specifically to the evaporator 2.1 of the heat pump 2, in order to extract energy from the exhaust air in the form of heat. This energy is then transferred internally by the heat pump 2 to the condenser 2.2, which heats a fresh air stream from the fresh air supply duct 3.3. This fresh air stream can be ambient air, particularly from the building, outside air, or other clean process air. The air heated by the condenser 2.2 of the heat pump 2 is then routed from the fresh air return duct 3.4 to the processes of the printing press.

[0025] The Fig. Figure 2 shows a preferred embodiment of the invention with a heat exchanger 4 arranged downstream of the evaporator 2.1 of the heat pump 2. This additional heat exchanger 4 extracts further energy from the exhaust air downstream of the evaporator 2.1 in order to transfer it to the fresh air flow of the fresh air supply duct 3.3 or to another process. The fresh air heated by the heat exchanger 4 is then either available for heating other objects or is combined with the fresh air flow to the condenser 2.2 of the heat pump 2. The proportions of the air flows are adjusted via a mixing damper 5. The exhaust air in the exhaust air duct 3.2 downstream of the heat pump 2 or heat exchanger 4 can preferably be reused, since it is advantageously filtered and may still retain a certain residual temperature.

[0026] The Fig.Figure 3 shows an embodiment of the invention comprising a delivery dryer 6, in particular an IR hot air dryer, with a waste heat recovery system 1. The delivery dryer 6 contains four dryer units in which the desired drying temperatures can be selected separately. Heating elements 7 for generating the hot air are arranged in the dryer units, where four heating elements 7 are shown, but only one heating element 7 with its associated parts is labelled. The hot air generated by the heating elements 7 is supplied as drying air to the sheets transported in the delivery unit in order to dry the printing and varnish layers applied in the printing press before they are placed on a delivery stack. The supplied air is heated by the heating element 7, for example, to up to 80 °C. The heating in the heating element 7 is electrically powered. The electricity consumption for this is considerable. This energy requirement can be reduced by preheating the air supplied to the heating elements 7.The preheated air provided by the waste heat recovery system 1 can be supplied to the heating registers 7 in whole or in part, and can also supply other processes.

[0027] The air preheated by the waste heat recovery system 1 is supplied from the fresh air return duct 3.4 to the individual dryer units in the display area via a common duct. Each heating coil 7 can be supplied with preheated air via a separately controllable supply air damper 8, so that when a heating coil 7 is deactivated, its air supply can also be shut off via the supply air damper 8. The preheated air can be forced into the heating coil 7 via a supply air fan 9 assigned to each heating coil 7. Furthermore, each heating coil 7 is preferably also assigned an exhaust air fan 10 and an exhaust air damper 11. The heating coils 7 can be controlled separately accordingly. Alternatively, groups of heating coils 7 could also be assigned to a common supply air and / or exhaust air duct.

[0028] Depending on the specific machine configuration, the exhaust air streams from the heating coils 7 and dryers are connected to a common collecting duct 12 via the exhaust air dampers 11, or alternatively, individually fed to the waste heat recovery system 1. When dryer units are not in use, the corresponding exhaust air damper 11 of the heating coil 7 is closed, preventing air from flowing into the collecting duct 12. The exhaust air dampers 11 of active dryer units are opened, allowing the warm exhaust air from the dryer units to flow through the collecting duct 12 and, preferably, later into the exhaust air supply duct 3.1, into the waste heat recovery system 1. The exhaust air flow is actively controlled by exhaust air fans 10. Preferably, the volume flow of the exhaust air is regulated by the exhaust air fans 10 such that a small positive differential pressure exists in the exhaust air collecting duct 12 relative to the ambient pressure.In a further embodiment not shown, different waste heat sources can be used simultaneously. For example, various heat sources of the printing press can be connected to the waste heat recovery system 1. In a further embodiment of the invention, the heat pump 2 of the waste heat recovery system 1 is additionally controlled according to the number of active heating elements 7. The volume and heat flow to and from the waste heat recovery system 1 is adjusted by appropriate actuators, e.g., flaps and / or fans.

[0029] In a preferred embodiment of the invention (not shown), the waste heat recovery system 1 includes a measuring and control device which can be assigned to the heat pump 2. This measuring and control device records the corresponding temperature values ​​of the preheated fresh air after the heat pump 2 and transmits them to the machine control system. The temperature values ​​supplied by the measuring and control device are compared by the machine control system with setpoint values, in particular with the dryer temperatures preselected at the individual dryer units. Based on the evaluation of this data, the measuring and control device influences the heat exchanger 4 and / or the heat pump 2 such that the air temperature supplied by them is optimized to match the dryer temperatures preselected at the respective dryer unit.The heat exchanger 4 and / or heat pump 2 are controlled by directly adjusting or regulating them, encompassing all possible parameters. Alternatively or additionally, the volume flow supplied by the heat exchanger 4 and / or heat pump 2 can be optimized. This can be achieved through an adjustable flow control mechanism, adjustable dampers, etc. As a result of adjusting the air temperature and / or the volume flow of the fresh air, the heating output of the heating coils 7 is optimized accordingly, in particular, regulated, so that the preselected dryer temperature in the dryer units remains constant. According to the invention, the waste heat recovery system 1 is primarily controlled or regulated, and the heating coil 7 is controlled secondarily, thus ensuring a consistently minimal energy consumption of the overall machine.

[0030] The air temperature can be controlled or regulated as follows: The fresh air temperature supplied by the waste heat recovery system 1 (supply air temperature to the heating coils 7) is measured by a temperature sensor in the measuring and control unit and represents the variable to be controlled. The heat pump 2 then internally sets the heating requirement for the heat pump 2, for example, by heating the heat transfer medium. This can be adjusted via an external signal, such as one from the printing press. The machine control thus sends a signal for the desired (preselected) dryer temperature to the heat pump 2, which then adjusts the value for the desired air temperature to be supplied to the dryer unit. If several dryer units are operated with different (preselected) dryer temperatures, the system automatically selects between the individual dryer temperatures.Here, the lowest of all (preselected) dryer temperature setpoints is transferred to heat pump 2. This selection is preferably made by the measuring and control unit. Active cooling of the fresh air by heat pump 2 is not possible in this case. If the lowest preselected dryer temperature is lower than the lowest temperature that heat pump 2 can deliver, heat pump 2 is put into standby mode with pure temperature control, and only cold fresh air is supplied to the dryer, which is then heated to the preselected dryer temperature by means of the heating coils 7. However, volume flow control is preferably used in this case.

[0031] The airflow can be controlled or regulated as follows: Depending on which dryer units are in operation, the machine control system activates the corresponding exhaust air dampers 11, which direct the exhaust air from the dryer unit into the common collection duct 12. Alternatively, if there is no common collection duct 12, only one ventilation damper can be assigned to the exhaust air supply duct 3.1. Whenever the exhaust air from the corresponding dryer unit is in operation, the machine control system opens the associated exhaust air damper 11. When the hot air from a dryer unit is activated, the corresponding supply air damper 8 is also opened by the machine control system.

[0032] In a further development, it is proposed to arrange a second air supply flap 13 on at least one, but preferably every, dryer unit, which is controlled by the machine control system. Depending on how the printer sets the parameters, this second air supply flap 13 is either closed (supply air for the corresponding heating coil 7 comes exclusively from the heat pump 2 or the dryer unit is inactive) or, preferably gradually, opened (heating coil 7 draws a proportion of ambient air if the preselected dryer temperature is lower than the supply air temperature of the heat pump 2). This control system makes it possible to supply each dryer unit individually with the required temperature. This contrasts with the prior art, in which each dryer receives the same amount of air and heat, regardless of whether it needs it or not.In this advanced training, the heat exchanger 4 and / or the heat pump 2 can also supply the maximum preselected dryer temperature, whereby the desired temperature at the dryer unit is set by the second air intake flap 13 through the supply of cold ambient air.

[0033] Regarding the mode of operation: According to the invention, each dryer unit can be individually supplied with heat. For example, the heat pump 2 can provide an air temperature between 40°C and 70°C. The dryer unit can be operated with a number of preselected dryer temperatures, depending on the order. If three dryer units are operated at 30°C, 40°C, and 60°C, the machine control regulates the heat pump 2 to, for example, 40°C. This means that ambient air is mixed into the first dryer unit, the second dryer unit uses only the supply air from the heat pump 2, and in the third dryer unit, the heating element 7 must heat the supply air from the heat pump by a further 20°C. Through the control of the air temperature and / or the volume flow according to the invention, the energy consumption of the overall system is thus optimized, i.e., minimized. List of reference symbols used 1 Waste heat recovery system 2 Heat pump 2.1 Evaporator 2.2 Capacitor 2.3 Circulation 3.1 Exhaust air supply duct 3.2 Exhaust air duct 3.3 Fresh air supply duct 3.4 Fresh air return duct 3.5 Air filter 4 heat exchangers 5 Mixing flap 6 display dryers 7 heating coils 8 Air intake flap 9 Supply air fan 10 Exhaust fan 11 Exhaust flap 12 Collection channel 13 second air intake flap

Claims

[1] Printing press with dryer and waste heat recovery system, wherein the waste heat recovery system (1) includes a heat exchanger (4) and / or a heat pump (2) which heat air and supply it to the dryer, wherein a control or regulation is provided to influence an air temperature and / or an air volume flow supplied by the heat exchanger (4) and / or the heat pump (2), characterized by , that the drying system contains several drying units, each with individually selectable drying temperatures and that at least one dryer unit of the dryer system is assigned a second air supply flap (13) with which ambient air can be mixed with the air coming from the waste heat recovery system (1). [2] Printing press according to claim 1, characterized by, that the control or regulation of the air temperature and / or the air volume flow is carried out depending on a preselected dryer temperature of the dryer unit. [3] Printing press according to claim 1 or 2, characterized by , that the influence on the air volume flow is achieved by ventilation flaps or fans of an air distribution system. [4] Printing press according to at least one of the preceding claims, characterized by , that the control or regulation of the heat pump (2) is carried out in such a way that an energy supply from an energy source to a medium circulating in a circuit (2.3) between an evaporator (2.1) and a condenser (2.2) is set. [5] Printing press according to at least one of the preceding claims, characterized by , that a heat exchanger (4) is connected downstream of the heat pump (2), which utilizes the heat energy remaining in the exhaust air of the heat pump (2). [6] Printing press according to at least one of the preceding claims, characterized by , that the heat pump (2) is connected to a refrigeration circuit of the printing press and is equipped with a reversing circuit, such that the heat pump (2) can be used to generate cooling for the printing press or other processes. [7] Printing press according to at least one of the preceding claims, characterized by , that the waste heat recovery system (1) includes a mechanical and / or a chemical filter for the heat exchanger (4) and / or the heat pump (2), wherein a sensor device is provided for monitoring the degree of contamination of the filter. [8] Method for optimizing waste heat utilization on a printing press, wherein a waste heat utilization system (1) includes a heat exchanger (4) and / or a heat pump (2) which heat air and supply it to a dryer unit, wherein a preselected dryer temperature is set for dryer units of the dryer unit and wherein the heat exchanger (4) and / or the heat pump (2) are controlled or regulated in such a way that they provide a required air temperature and / or a required air volume flow depending on at least one selected dryer temperature, characterized by , that it is intended to arrange a second air inlet flap (13) on at least one or every dryer unit, which is controlled by the machine control, whereby, depending on how the printer sets the parameters, this second air inlet flap (13) is either closed or open or gradually opened. [9] Method according to claim 8, characterized by , that the heat exchanger (4) and / or the heat pump (2) supply the maximum preselected dryer temperature, whereby the desired temperature at the dryer unit is set by the second air intake flap (13) through the supply of cold ambient air. [10] Method according to claim 8 or 9, characterized by , that the dryer unit is operated with a number of preselected dryer temperatures specific to the order.

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