Due to rising energy prices and increasing pressure to reduce carbon dioxide emissions in industrial production processes such as printing, there is an increasing demand for more accurate press energy consumption data on the market. At present, the first step has been taken in the form of agreement among printing press manufacturers to calculate the guidelines for the power consumption caused by the production of lithographic printing presses. But for greater transparency and as a method and potential for improvement in identifying energy losses, we recommend an energy audit of the entire printing press. This requires knowledge about the energy flow and the order in which they occur in time during the production process.
In order to obtain a detailed actual energy diagram of a sheet-fed printing press, KBA engineers actually set up camps in the printing workshop for several months and took hundreds of measures. They keep records of the energy input and the resulting energy flow. Then they developed a comprehensive energy audit for the printing press.
KBA eight-color Rapida 106
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Data capture
The printing machine they checked was a eight-color Rapida 106 equipped with multiple additional parts not included in the standard configuration. In particular, these components include a UV drying device and an IR (infrared) hot air (TA) composite drying device, a double-sided printing device and two coating units with appropriate drying devices. Studying this machine (see above) enables them to capture data on equipment parts that consume the most energy in any single printing job at any one time.
The data used to calculate the unique electrical and thermal parameters of Rapida 106 are collected during the routine printing production process. The information is transferred from sensor clusters attached to more than 120 measurement points in separate steps.
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Energy audit
The energy audit of the inspected Rapida 106, detailed below, lasted for a month. It should be noted that the energy consumption depends to a large extent on the structure of the printing job, and the values ​​recorded during the measurement phase only apply to this specific printing press and the printing job it produces. The focus of this energy audit is the five largest energy-consuming devices: UV drying device, IR / TA drying device, printing machine itself, air compression cabinet and multi-function cooling device.
The total power consumption recorded during the one-month time frame reviewed here is 53.91 MWh (Figure 1).
As expected, the readings taken at the power source of the printing press show that there is a significant difference in energy consumption between standstill and operation. During standstill, the printer is switched to an energy-saving idle mode. When the printing press accelerates, the input of energy and the increase in speed are related to each other. The power consumption measured at the printing machine wiring accounts for about 35.6% of the total energy consumption. The total energy consumption includes useful energy and heat generated by friction and released to the printing press or the surrounding air (printing workshop).
The controllable air compression cabinet is one of the largest energy-consuming devices, although it can be turned off when not needed. Click here to view all news pictures
Paying attention to the numbers of auxiliary devices will get very interesting results. It can be clearly seen that a component such as a cooling device consumes as much energy as an air compression cabinet with a much higher rated power. The reason is that the cooling device continues to work, and the air compression cabinet will automatically shut down when it is not needed. And although the connection load of the cooling device and the air compression cabinet is low, their common consumption is as much as the IR / TA drying device. This is because the working period of these two devices will be extended.
About 13.9% of the total energy consumption is attributed to the cooling device, 28% to the air compressor, and the remaining 72% to the circulation pump and metering device. This energy is used to transfer 6.84 MWh of waste heat out of the press and into the return cooling line. In addition, unspecified energy consumption includes useful energy and energy loss. [next]
The controllable air compression cabinet consumes approximately 14.4% of the input energy. This energy is then converted to waste heat and released via the return cooling line (60.5%). In addition, unspecified energy consumption (39.5%) includes useful energy and energy loss. The energy consumption in the air compression cabinet is described in Figure 2.
figure 1
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figure 2
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image 3
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The biggest energy consumer is the dryer. Having said that, the UV drying device in the example cited here plays a smaller role. The type of printed work and the degree of use of the UV drying device during the period of observation are explained. If the energy consumption of the UV drying device is described separately, the following conclusions can be drawn.
The energy consumption of the UV drying device depends on the number of modules participating in the operation at any time. During the one-month observation period, about 6.6% of the electrical energy input was used for the UV drying device. This energy is partly converted into heat, most of which is released through the exhaust (17.5%) or through the return cooling line (55.6%). There is still some unspecified energy consumption (26.8%). This includes the energy used in the drying process, the energy applied to the paper, the energy input into the printing press, and the energy dissipated in the printing shop. The energy consumption in the UV dryer is described on the left (see Figure 3).
Unlike UV dryers, energy-saving IR / TA dryers are operated regularly. The apparent fluctuations in the measured dynamic load during the observation were caused by different types of printing jobs and applied varnishes. The IR / TA dryer consumes about 29.7% of the total electrical energy input. It has been found that the energy generated by entering air in the thermal temperature regulating device is much lower than the exhaust energy released by the printing press. This can be explained by the fact that the exhaust gas from elsewhere in the printing press and from around the printing press is discharged together with the exhaust gas from the IR / A drying device. [next]
For anyone involved in the development of technical processes or concepts for waste gas utilization, auditing the energy emitted through water and air is not a temporary interest. This kind of audit will be a crucial foundation for quantifying the interaction and interaction between these individual processes and concepts.
The waste gas reused through the water cooling line accounts for 13.49 MWh of the energy released. This is equal to about 25% of the total power input. The exhaust pipe emits 16.6 MWh of waste heat. This is about 30.8% of the total electrical energy input. The decomposition of the energy flow in the printing press is given in Figure 4.
The above audit shows that even an electric device connected with a low load will play a significant role in the overall balance. The sustainable concept of reducing power consumption and using energy more efficiently can be implemented by optimizing printing press technology, configuring energy recovery systems and installing more energy-efficient drying devices (such as KBA's newly released VariDryBLUE for large format). For printers keen to improve their energy efficiency, KBA can provide customized services according to their specific job structure.
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