Energy-saving hot water preheating extrusion ingot technology

In 2019, the global total output of aluminum extrusion products is about 37 million tons, China is about 20.5 million tons, North America is about 2.5 million tons, Japan is about 810,000 tons, and Germany is about 620,000 tons. They are all products produced by hot extrusion. The ingot is heated to 320°C to 520°C before hot extrusion. The allowable maximum heating temperature for different alloys is also different. For example, the 1 series alloy is 400℃～470℃; the 2 series alloy is 320℃～460℃; the 6 series alloy is 480℃～520℃, which is the highest allowable extrusion temperature The maximum allowable temperature of 6061, 6063 alloy can reach 520℃, but such high temperature is not commonly used, generally around 500℃. These two alloys are also the most commonly used alloys, and their output accounts for 75% of the world's total output. ; The output of 2 series and 7 series alloy extruded materials is less than 8% of the total output, most of which are aerospace, military and other stressed structural materials.

In the production process of extrusion materials, the processes that require heating and energy consumption include: smelting, ingot heating before extrusion, heating of extrusion cylinders and molds, heating and heat preservation of offline solution treatment and aging treatment. The heat source used can be electric heating (resistance or induction heating), or gas heating. In the past 10 years, Extrutec GmbH in Radolfzell has made great achievements in rapid gas heating systems. For example, the most prominent among recent innovations is the ESU (Eco Shower Unit), which is an energy-saving hydrothermal device connected to a long ingot gas heating furnace. It has been installed in Germany in 2019. It has been promoted with the Middle East and has a greater energy-saving effect and has been well received.

Economical spray heating technology

The Esu heating system of Extrusion Technology Company has a greater energy-saving effect. It has a long ingot conveyor preheated by water, which is located on the line with a gas furnace and forms a whole. Aluminum and aluminum alloys have high thermal conductivity (238 W/m﹒K at 0℃～100℃), which can absorb a large amount of heat in a short time and increase the temperature. However, the energy density of the furnace gas (energy density) ) Is low, and the temperature of the aluminum ingot cannot be increased in a short time. If the heat exchanger is used, this idea can be realized. The engineer of S. Beer (Stefan Beer) of Extrusion Technology Company invented the Esu heating system based on this idea. Therefore, the system can be translated as an economic spray heater. The heating method of this long aluminum ingot is: first heat the water in the heat exchanger with a gas fire of 360℃, the water temperature can rise to 90℃, when the ingot passes through the spray chamber, spray the water at 90℃ to On the slowly advancing ingot. The time for the long ingot to pass through the spray heating chamber is 4min to 5min, the length of the ingot heated to 90°C is 3 times the length of the short ingot to be extruded, and the water is circulated. The temperature of the flue gas coming out of the heat exchanger is 120°C to 130°C, instead of 250°C to 300°C, which is usually emitted by gas stoves. The use of the Esu heating system can save energy by about 15%, which is not a small number. For an enterprise with an annual output of several hundred thousand tons of extruded materials, it cannot be ignored.

After the long ingot is heated to 90°C by spraying water, it enters a conventional gas heating chamber or induction heating furnace, is heated to the extrusion temperature, is cut into a specified length and then sent into the extrusion cylinder. The contaminated water sprayed on the long ingot flows into the filter, and is recycled after filtration, while washing the surface of the ingot completely.

Heating the aluminum extruded ingots with hot water not only saves energy, but also reduces the emission of greenhouse gas CO2, because the amount of liquefied gas used as fuel has decreased. Another advantage is that the length of the heating furnace can be shortened because the number of zones of the heating furnace can be reduced, and the length of the general furnace can be shorter by 1.5 meters.

Practical application

By the end of 2019, there are 4 aluminum extrusion plants in the world using or about to put into production the Ezu long ingot heating system, and 3 plants in Germany: Aluminium-Werke Wutoschingen (AWW), which is under construction New extrusion lines: Erbosloh Aluminium GmbH (Erbosloh Aluminium GmbH) in Velbert; Extrutec GmbH. Another plant is an aluminum alloy profile extrusion company in the United Arab Emirates, which also ordered one. The practice of these companies shows that the investment in the construction of hot water heating ingot equipment can be recovered in less than a year, and the payback period is so short, which is really rare.

The application shows that this cutting-edge new technology has four advantages: one is that the gas furnace can be made shorter, which is the shortest furnace on the market; the other is that the ingot cleaning system can remove all dirt and adhered particles on its surface Removal is conducive to prolonging the life of the mold; third, all existing equipment and methods can be used without waste; fourth, various temperatures can be accurately controlled. In addition, the German government also attaches great importance to the promotion of this technology, and the Federal Ministry of Environment gives certain rewards to companies that apply this technology.

Conclusion

The economic spray hot water heating technology of long ingots for extrusion is a new cutting-edge technology with a small investment and can be recovered in about 1 year. It is an energy-saving and emission-reduction project. It can be applied not only to new extrusion production lines, but also applicable Upgrade and transformation of existing production lines. my country is building large-scale aluminum extrusion projects in Heilongjiang and Guangdong. It is best to learn about this technology, can you introduce one and try, and hope that the existing aluminum extrusion enterprises will understand this.