Heat pump technology for energy savings in satellite flexo presses
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Heat pump technology is known as one of the energy technologies of the 21st century. It is no exaggeration, because the use of heat pump technology can improve energy efficiency, which includes two meanings: the first layer, from the environmental point of view, the use of heat pump technology can reduce greenhouse gas emissions, reduce environmental damage; Heat pump technology can solve high power load. Therefore, the heat pump technology has gradually gained attention in the packaging and printing industry by virtue of energy saving and consumption reduction. So, what benefits can heat pump technology bring to packaging and printing companies?
As we all know, packaging and printing workshops often need constant temperature and humidity, office buildings and other places need air conditioning and refrigeration in the hot summer, while printing, coating and other processes need to dry hot air, and the use of heat pump technology can achieve effective energy utilization. The heat pump works on a heat booster that acts from the heat in the western zone of the surrounding environment and passes it to the heated object. This is like using a water pump to direct water from a low place to a high place. A heat pump can be used for a part of the office building and the like, and the heat generated by the heating end can be used for the printing and drying system, which can greatly save electricity costs. It is a good solution for environmental protection and energy conservation, and it is worth promoting. The author takes the application of heat pump technology on the satellite flexo printing machine as an example.
Application principle of heat pump on satellite flexo printing machine
The application of flexographic printing technology in China's printing industry is getting more and more attention. The green environmental protection of flexographic printing technology is undoubted, but its high energy consumption during drying has always been one of the factors restricting its development. The combination of heat pump technology and its application can effectively Solve this problem and bring more benefits to the printing industry.
At present, the air-energy heat pump water heater is used in the packaging and printing industry. The equipment obtains low-temperature heat source through natural energy (air heat storage), and uses the air cooled by the low-temperature heat source for workshops, office buildings, blown film machines, etc. Refrigeration; the heat released by the condenser is used to heat water, heat or supply hot water to the heat exchanger of the printing machine and the coating machine drying system to heat the oven air intake, and the whole system has high heat collection efficiency.
The drying principle of the satellite flexo printing ink is generally to heat the air by using a heat source (such as steam heating, electric heating, natural gas heating, etc.), and then blowing the hot air to the surface of the substrate at a certain wind speed, taking away the solvent in the ink. Achieve ink drying. The heat pump is applied to the satellite flexo press to realize the heating process: the heat pump heating device extracts heat from the satellite flexo dryer drying oven exhaust, and transfers the heat to the fresh air that needs to be heated, thereby reducing the heat required for heating the heat source, thereby To achieve energy saving purposes. In addition to the obvious energy-saving effect, heat pump drying is also a uniform low-temperature dehumidification drying method, which can greatly improve the yield and the quality of printed products compared with the traditional hot air drying method.
How to choose heat pump for satellite flexo printing machine
In general, the satellite flexo press requires two drying units. A portion is between the printing color groups, commonly referred to as an inter-color drying device, the purpose of which is to allow the previous color ink layer to dry as quickly and thoroughly as possible before the print enters the next printing color group to avoid the latter color. The ink is mixed with the previous color ink during overprinting; the other part is after all the printing color groups, usually called the centralized drying device, the purpose is to completely eliminate the solvent in the printing ink layer, further consolidate the drying of the ink, so as not to Quality problems such as back smearing during rewinding or post-processing. The two principles of the satellite flexo press should follow the following guidelines when selecting a heat pump unit.
(1) Drying between colors is generally carried out by a low temperature, high wind speed drying method, the temperature is generally not higher than 60 ° C, and the wind speed is greater than 45 m / sec. Therefore, when using a heat pump, a high-pressure fan is also required to control the wind speed. In addition, in order to avoid the hot air from overflowing from the wind chamber, causing the dry plate phenomenon, a fan must also be equipped to discharge all the air into the air to avoid hot air overflow. According to the comprehensive evaluation, the temperature required for drying between the colors is not high, the energy saving effect of using the heat pump is not obvious, and the comprehensive manufacturing cost is high, so the heat pump is not recommended.
(2) Centralized drying generally adopts a high temperature, high wind speed drying method. The temperature is generally between 70 and 80 ° C. When using a heat pump, an electric heater is required to ensure the hot air temperature. The air velocity of the oven tuyere is generally not less than 30 m / s, so the heat pump can be equipped with a high-pressure fan here. The specific installation and use form is shown in Figure 1. The fresh air enters the fresh air inlet, passes through the sensible heat exchanger, absorbs the condensation heat from the temperature, and the relative humidity decreases. Then it is sent to the heater through the fan to heat it to the preset temperature and then sent to the drying oven. The tuyere takes away the solvent evaporated from the substrate; then, the air passes through the atherbore heat exchanger and the heat recovery heat exchanger again through the air return port of the oven, so that the two heat exchangers respectively absorb heat for heating the fresh air; The waste air is discharged through the exhaust vent.
Heat pump benefits
Through the actual test and verification on the satellite flexo press, the comprehensive energy-saving efficiency achieved by using the heat pump is about 50% to 70%. Simple calculations can be made as follows.
Assume that the heating power of the centralized drying device of the satellite flexo printing machine is 72kW, the actual operating rate of the centralized drying device is 60%, the satellite flexo printing machine is turned on for 18 hours every day, the annual operating days are 300 days, and the industrial electricity cost is 1 yuan/degree. Calculation, annual operating cost = 72 × 60% × 18 × 300 × 1 = 233,280 yuan. Calculated according to the minimum energy saving efficiency of the heat pump 50%, the annual energy saving cost = 233280 × 50% = 116640 yuan. The heat pump heating device used in the satellite flexo printing machine costs about 150,000 yuan. Then, the investment return period = annual energy saving cost / heat pump heating device cost = 15/11.664 ≈ 1.3 years.
The application of heat pump technology can change the current situation of high energy consumption of satellite flexo printing machines and reduce the large operating costs for packaging and printing enterprises. At the same time, the intelligent and automatic control of the heat pump reduces the labor intensity of the operator; the integrated design eliminates the cumbersome piping and improves the aesthetics of the whole machine. The combination of heat pump technology and flexo printing technology is a project that can bring long-term benefits to packaging and printing enterprises. It is believed that it will be favored and selected by more packaging and printing enterprises.