Research and Industrial Application of Energy-Saving Technologies for 95+ High-Efficiency Ultra-Pure Industrial Furnaces

Thread Content

I. Background: One of the tasks outlined in the **report of March 2019 was to strengthen pollution control and ecological development, and to promote green growth vigorously. Reform and improve relevant systems to jointly promote high-quality development and ecological environment protection. Strengthen key scientific and technological efforts in pollution prevention and control, reform and improve environmental economic policies, and enhance the emission rights trading system. As the main entities responsible for pollution prevention and control, enterprises must fulfill their environmental protection obligations in accordance with the law. A series of laws, regulations and policies have been introduced, such as the Energy Conservation Law of the People’s Republic of China (Decree No. 77), the Law of the People’s Republic of China on Promoting Clean Production (Decree No. 72), the Environmental Protection Law of the People’s Republic of China (effective as of January 1, 2015), the Measures for the Management of Energy Conservation in Industry (Order No. 33 issued by the Ministry of Industry and Information Technology), the Notice of the State Council on Issuing the Comprehensive Work Plan for Energy Conservation and Emission Reduction during the 13th Five-Year Plan Period (Guo Fa [2016] No. 74), and the Notice on Fully Launching the Paid Use and Trading System for Energy Use Rights in Zhejiang Province (Zhejiang Development and Reform Commission Energy Department [2018] No. 621), all of which require enterprises to fulfill their social environmental protection responsibilities in accordance with the law. Faced with increasingly dwindling energy resources, energy conservation and emission reduction are the themes of contemporary social development. As an important energy-consuming device in petrochemical enterprises, the flame heating furnace accounts for over 70% of the plant’s production costs; it directly determines the efficiency of the plant. It is also a focus of environmental protection efforts. The research and application of innovative technologies for heating furnaces can yield dual benefits in terms of energy savings and environmental protection. Therefore, improving the thermal efficiency of heating furnaces means saving fuel, reducing energy consumption of the equipment, and lowering pollutant emissions. The main measures taken recently to improve the thermal efficiency of heating furnaces include: reducing the flue gas temperature, lowering the excess air coefficient, minimizing losses due to incomplete combustion, and reducing heat loss. To reduce the flue gas temperature, new heating furnaces are now installed in facilities, including catalytic reforming units; generally, a waste heat recovery system is added to recover this waste heat. However, due to the sulfur content in the fuel of the heating furnace, sulfur (S) in the fuel is converted into sulfur dioxide (SO2) during combustion. A small amount of this SO2 is further oxidized to sulfur trioxide (SO3), which then reacts with water vapor in the flue gases to form sulfuric acid (H2SO4). The dew point of flue gas containing sulfuric acid vapor rises significantly. When the wall temperature of the heating surface is below this dew point, the sulfuric acid-containing vapor condenses on the heating surface to form a sulfuric acid-containing liquid, causing severe corrosion to the heating surface. Since it occurs on the heated surface at lower temperatures, it is called low-temperature corrosion. Since this type of corrosion occurs only after dew forms on the heated surface, it is also known as dew point corrosion. To prevent corrosion caused by the dew point of flue gases, which could affect the proper operation of downstream equipment such as preheaters, exhaust fans, and flue gas ducts, and taking into account the sulfur content in the fuel used in oil refining units, the exhaust temperature of newly built oil refining facilities is generally around 140°C. Under the premise of ensuring the continuous operation of the equipment, how to further reduce the flue gas temperature is the development direction of energy-saving technologies for heating furnaces. The advancement of the flue gas waste heat recovery system in a heating furnace is the main factor determining its thermal efficiency. At present, domestic reheating furnace waste heat recovery systems mostly adopt a single-stage waste heat recovery system. The characteristic of this system is that it features only one air preheater; the exhaust fan is located at the rear end of the air preheater, and it draws in the flue gas from the top of the convection section into the air preheater to exchange heat with the cooler air, thereby reducing the temperature of the exhaust gases. Since the exhaust temperature has a direct impact on the thermal efficiency of the heating furnace, the lower the exhaust temperature, the higher the thermal efficiency; however, a lower exhaust temperature also leads to more severe dew point corrosion. Therefore, the improvements to the waste heat recovery systems in domestic heating furnaces focus on addressing the dew point corrosion issue of air preheaters by reducing the flue gas temperature. II. By adopting the currently widely used waste heat recovery technologies at home and abroad to carry out energy-saving upgrades to the heating furnace in this project, it is difficult for the thermal efficiency to exceed 93%. The “95+ High-Efficiency Ultra-Pure Industrial Furnace Technology” effectively addresses the current bottleneck in improving the thermal efficiency of heating furnaces. III. Analysis of Application Prospects: The introduction of a series of laws and regulations such as the Energy Conservation Law of the People’s Republic of China (Decree No. 77), the Measures for Industrial Energy Conservation (Ministry of Industry and Information Technology Decree No. 33), the Notice of the State Council on Issuing the Comprehensive Work Plan for Energy Conservation and Emission Reduction during the 13th Five-Year Plan Period (State Council Document [2016] No. 74), and the Notice on Fully Launching the System of Paid Use and Trading of Energy Use Rights in Zhejiang Province (Zhejiang Development and Reform Commission Energy Department Document [2018] No. 621) requires enterprises to fulfill their social responsibilities regarding energy conservation and environmental protection in accordance with the law. The application of 95+ high-efficiency ultra-pure heating furnace energy-saving technologies is in line with the call for **energy conservation and emission reduction, and it can also meet the energy-saving and emission-reduction needs of enterprises; therefore, it holds broad application prospects.