Modern Tobacco industry relies on a large amount of compressed air in the production process. The energy consumption of air compressor accounts for a high proportion of the energy consumption of equipment system, and the rest heat emission becomes an important source of energy waste. With the implementation of energy conservation policies and the acceleration of industrial green transformation, waste heat recovery and utilization technology has gradually become an important link for enterprises to improve energy efficiency. The technological process of cigarette factory has stable demand for hot water, humidity control air and daily energy, so that waste heat recovery has a good application Foundation. Studying the technical logic, system composition and engineering application value of waste heat recovery of air compressor is helpful to guide enterprises to carry out energy-saving transformation and build an efficient energy management system.
I. Mechanism of waste heat generation of air compressor and analysis of energy demand characteristics of cigarette factory
The air compression process is essentially the conversion of energy from electric energy to compressed air potential energy, and this conversion is accompanied by a significant temperature rise process, which makes a considerable part of the input electric energy be dissipated in the form of heat. When the air compressor compresses air, the multistage compression chamber and lubrication system are continuously affected by the combined effects of gas compression, friction and mechanical load, so that the exhaust temperature can usually reach 90℃ to 110℃. As a common equipment in cigarette factories, the compression efficiency of Screw Air Compressor is affected by air Volume fluctuation, lubrication conditions and compression ratio changes, with high heat emission ratio, body heat dissipation, cooling oil circulation and post-treatment equipment have become the main sources of waste heat emission. The mechanism of waste heat generation can be summarized as three paths of heat transfer in the process of compression work conversion heat, mechanical loss conversion heat and oil-gas separation. The energy demand of cigarette factories has the characteristics of strong process continuity and high temperature and humidity control requirements. The silk making section needs to stabilize the process environment of temperature and humidity. The rebaking section has certain requirements for hot air conditioning. The equipment cleaning and feeding system usually needs medium temperature hot water, the living area and office area also have stable hot water supply demand. Traditional processes mostly rely on steam boilers or electric heating to provide hot water, and the energy supply cost is relatively high. When the waste heat of the air compressor can be converted into available heat through efficient heat equator exchange facility, the energy utilization efficiency can be improved without changing the structure of the main system, the boiler load can be reduced, and the purchased energy cost can be reduced. In the overall energy structure of cigarette factories, compressed air systems usually account for a relatively high proportion, so waste heat recovery has considerable energy saving potential. Clarifying the matching relationship between waste heat source structure and process requirements is the key premise for building waste heat recovery system and an important basis for engineering design.
II. Structural design and key technical path of air compressor waste heat recovery system
The waste heat recovery system usually consists of heat equator exchange facility, oil circuit transformation module, control system and heat energy utilization unit. Its design needs to take into account safety, stability and energy matching. The heat source side is mainly composed of air compressor lubricating oil and exhaust system, and heat is extracted through high-efficiency plate heat exchanger or casing heat exchanger, so that the oil temperature and exhaust temperature are gradually reduced and stabilized in the working interval. Heat equator exchange facility must have the characteristics of high temperature resistance, low resistance and not easy to scale to meet the long-cycle operation requirements. The oil circuit transformation module builds an oil-water heat exchange circuit through bypass valve and circulating pump, so that the heat exchange process can be carried out without affecting the performance of the air compressor body. In order to avoid the influence of oil temperature fluctuation on the stability of air compressor, the system generally needs to set up thermostat valve and heating regulating unit to keep the oil temperature within the ideal range. The control system undertakes the functions of real-time monitoring and process regulation. Through the analysis of temperature, flow and pressure data, the hot water output and heat exchange efficiency are dynamically adjusted to adapt to the changes of production demand. The heat energy utilization unit can include process hot water tank, domestic hot water system, air humidity control module or process waste heat reuse equipment according to process requirements. In the process of system design, attention should be paid to load fluctuation, so that the waste heat recovery effect can maintain a dynamic balance with the heat demand of cigarette factories. In order to improve energy utilization efficiency, the waste heat recovery system can interact with the energy management platform to realize scheduling optimization through Operation curve analysis and load forecasting. In order to ensure safety, the system should set up pressure protection, temperature limit and cycle failure alarm mechanism to avoid thermal shock caused by insufficient water or abnormal cycle of heat exchange unit. Based on reasonable structural design and technical selection, the waste heat recovery system can realize efficient conversion and continuous output of heat energy without affecting the operation stability of the air compressor.
III. Engineering application mode and Operation effect analysis of waste heat recovery of air compressor
In the practical application of cigarette factories, waste heat recovery mainly forms three typical modes: hot water supply, process humidity control and air conditioning. The hot water supply mode converts waste heat into medium temperature hot water of 45℃ to 70℃, providing heat source for equipment cleaning, living area water and some low temperature processes. In the energy-saving renovation project, waste heat recovery is used to replace the original boiler load, which significantly reduces the energy cost. The process humidity adjustment mode combines the air conditioning requirements of silk making and redrying section, heating fresh air through waste heat, making temperature and humidity control more stable and reducing the usage of steam and electric heating. The air conditioning mode uses waste heat to heat the winter workshop or improve the local environment, improving the comfort level of the working area and reducing the heating energy consumption. In engineering application, the operation effect of the waste heat recovery system is affected by the load change of the air compressor, the heat exchange efficiency, the matching degree between the circulating water volume and the heat demand. Therefore, the operation data analysis and system verification are required. In a typical cigarette factory project, the waste heat recovery can make the oil temperature of the air compressor more stable, improve the lubrication effect and prolong the maintenance period of the equipment. According to the operation monitoring data, the utilization rate of system waste heat can reach more than 60% under stable working conditions, and the annual energy saving is significant. Engineering application also shows that there are some differences in the output level of the waste heat recovery system in different seasons, which can play a greater role in the case of high technological demand in winter, however, in the summer heat load reduction stage, the system stability needs to be maintained through intelligent scheduling. In some projects, the day and night load balance is realized through the hot water energy storage device to improve the utilization rate of waste heat. The operation of the system shows that waste heat recovery not only has economic benefits, but also improves the working environment of the air compressor, reduces the heat dissipation load, and helps to improve the efficiency of the air compressor and the service life of the equipment.
IV. Optimization direction of waste heat recovery technology and coordination strategy of cigarette factory energy system
With the development of energy management in cigarette factories towards intelligence, the waste heat recovery system needs to be continuously optimized in terms of efficiency improvement, control precision and system coordination. With the development of heat exchange technology, the new high-efficiency plate heat exchanger has higher heat transfer efficiency and pollution resistance, which can reduce the problem of efficiency decline caused by long-term operation. In terms of system flow control, through frequency conversion circulating pump, intelligent thermostat valve and heat load prediction technology, the heat exchange process can be more accurate and efficient. In order to further improve the stability of the system, the intelligent prediction model of oil temperature can be introduced. Through the deep analysis of the operation data of the air compressor, the operation parameters of the system can be adjusted before the load fluctuation, so that the heat exchange process is always in the best range. Through the construction of digital monitoring platform, the air compressor data, heat exchange system data and energy management system are integrated to realize cross-system coordination, so that waste heat recovery can automatically match output according to process requirements. The future development direction also includes cascade design of waste heat utilization, using heat energy of different temperature levels in different scenarios to make energy utilization more hierarchical; Building energy storage modules to adapt to seasonal demand changes; the modular design of the propulsion system makes the waste heat device suitable for cigarette factories of different scales. In the aspect of coordination strategy, the waste heat recovery of Air compressor can be integrated with boiler system, HVAC system and process humidity control system to form closed-loop utilization of heat energy between different links and promote the integration of energy management. Through continuous technological upgrading and system coordination, the waste heat recovery system will become an important support for green manufacturing in cigarette factories and promote the industry to make greater breakthroughs in energy structure optimization.
V. Summary
Air compressor waste heat recovery technology has significant energy saving potential and engineering application value in cigarette factories. Through effective system design and reasonable engineering implementation, a large amount of waste heat energy can be converted into available resources, reduce boiler load and energy consumption. With the improvement of tobacco industry’s requirements for green manufacturing, energy saving and consumption reduction, waste heat recovery technology will have a broader application prospect in the future. Through continuous optimization in heat exchange efficiency, control strategy and system coordination, the energy utilization rate can be further improved, and the refinement and intelligence of energy management can be realized. Waste Heat Recovery is not only an important part of energy saving technology, but also a key link to promote cigarette factories to build an efficient energy system. In the future, through the dual drive of engineering practice and technological innovation, the energy structure of cigarette factories will be more reasonable, laying a solid foundation for the sustainable development of the industry.