Aluminum melting regenerative combustion system

Aluminum melting regenerative combustion system

Aluminum melting regenerative combustion system

Aluminum alloys are widely used in many fields due to their excellent properties.

The energy consumption and combustion efficiency in the aluminum alloy melting process are the focus of the industry.

The regenerative combustion system is increasingly used in the field of aluminum alloy melting due to its advantages of high efficiency, energy saving and pollution reduction. 

The regenerative aluminum melting furnace is a typical application with a regenerative combustion system. 

This article aims to deeply analyze the application, technical characteristics, benefits and development prospects of this system in aluminum melting.

1. Working principle of regenerative combustion system

The regenerative burners are arranged in pairs, and the two opposite burners form a group (burners A and B).

After the normal temperature air from the blower is switched into the regenerative burner A by the reversing valve, it is heated when it flows through the ceramic ball regenerative body of the regenerative burner A.

The normal temperature air is heated to a temperature close to the furnace temperature (generally 80%-90% of the furnace temperature).

After the heated high-temperature air enters the furnace, it draws in the flue gas in the surrounding furnace to form a thin, oxygen-poor, high-temperature airflow with an oxygen content much lower than 21%.

The oxygen-poor, high-temperature air mixes with the injected fuel to achieve combustion of the fuel in an oxygen-poor state;

At the same time, the hot flue gas in the furnace is discharged through the regenerative burner B.

When the high-temperature hot flue gas passes through the regenerative burner B, the sensible heat is stored in the heat storage body of the regenerative burner B, and then it is discharged through the reversing valve as low-temperature flue gas below 150°C.

When the heat stored in the heat storage body reaches saturation, the reversal is performed, and the regenerative burners A and B switch the combustion and heat storage working states, and this cycle is repeated, thereby achieving the goals of energy saving and reducing NOX emissions.

The regenerative combustion technology has changed the traditional combustion method.

The main manifestation is that the fuel and air enter the furnace from different nozzle channels at appropriate speeds and draw in the combustion products in the furnace.

The O2 content in the air is diluted, and the fuel burns under high temperature (above 1000°C) and low oxygen concentration field (5%-6.5%) conditions in the furnace.

The regenerator is the key part of the regenerative combustion technology.

It requires the regenerator to have large heat storage capacity, good heat exchange rate, good high temperature strength, small resistance loss, strong anti-oxidation and anti-slag properties, and economical and durable.

The principle of ceramic balls is to fill the regenerator with many ceramic solid balls of the same diameter, stacked in a fixed bed, and the ball diameter is generally between 15-25mm.

The ceramic ball heat storage body has a large specific surface area.

The numerous small balls divide the airflow into very small streams.

When the airflow flows through the heat storage body, it forms a strong turbulence, which effectively breaks through the boundary layer on the surface of the heat storage body.

Because the ball diameter is very small, the heat transfer radius is small, the thermal resistance is small, the density is high, the thermal conductivity is strong, and the reversing system is uniquely designed, frequent and rapid reversing can be achieved.

Therefore, the heat storage body can be used 30 times/H, and the high-temperature flue gas can be reduced to 150℃ for discharge after passing through the heat storage body bed.

Normal temperature air can be preheated to 50℃ lower than the flue gas temperature in the same path through the heat storage body, and the temperature efficiency is as high as more than 95%.

In addition, because the heat storage body is very small in size and the flow capacity of the small ball bed is strong, even if the resistance of the ash accumulation increases, it will not affect the heat exchange index.

The replacement and cleaning of the ceramic balls are very convenient and can be reused.

2. Application advantages in aluminum melting

Significant energy saving:

It can preheat the combustion air to a temperature close to the flue gas temperature, greatly improve the combustion efficiency and reduce fuel consumption.

Studies have shown that compared with traditional combustion systems, it can save 30% – 50% of energy.

Reduce pollution emissions:

Efficient combustion allows the fuel to react fully and reduces the emission of incomplete combustion products.

At the same time, due to the uniform combustion temperature, the generation of nitrogen oxides (NOx) is reduced, which can generally reduce NOx emissions by 30% – 50%.

Improve the quality of melting and casting:

The stable and high-temperature combustion environment makes the temperature of the aluminum alloy liquid more uniform, reduces the impact of temperature fluctuations on the quality of melting and casting, reduces casting defects, and improves the product yield。

3. Problems and challenges

High initial investment cost:

The cost of purchasing, installing and commissioning the regenerative combustion system equipment is high, which may cause financial pressure for small and medium-sized enterprises with tight funds.

High maintenance requirements:

The heat storage body is easily damaged under long-term high temperature and high-speed flue gas erosion, and needs to be inspected and replaced regularly.

The key components such as switching devices also require regular maintenance, and the maintenance cost and technical requirements are high.

System matching is difficult:

Different aluminum alloy melting and casting processes have different requirements for combustion temperature, atmosphere, etc.

The precise matching of the regenerative combustion system and the melting and casting process requires in-depth research and debugging.

4. Development Trends

Intelligent Control:

Combining advanced sensors and intelligent control systems to achieve real-time monitoring and precise control of the combustion process, further improving combustion efficiency and system stability.

Integration with new energy:

Explore the integrated application of new energy such as solar energy and electric energy, such as using off-peak electricity to preheat thermal storage bodies and reduce dependence on traditional fossil fuels.

Research and development of thermal storage materials:

Research and development of higher performance thermal storage materials to improve thermal storage capacity, thermal shock resistance and service life, and reduce system maintenance costs.

5. Summary

From the perspective of heat balance, the fuel saving rate of a melting furnace using heat storage heat exchange technology is related to the heat storage of the furnace masonry and the surface heat loss of the furnace body.

Because the burner recovers waste heat through flue gas, the heat storage of the furnace body decreases, the less the surface heat loss, the greater the exhaust waste heat, and the higher the fuel saving rate.

At the same time, due to the intermittent working characteristics of the aluminum melting furnace, the furnace temperature, air flow rate in the heat storage body, and flue gas outlet temperature fluctuate greatly in different working states.

In this way, the burner reversing time should also change with the working state, optimize the utilization rate of the heat storage body, and achieve better waste heat recovery.

Since the temperature of the air rises after passing through the heat storage body, a large amount of sensible heat is brought into the furnace, which significantly increases the theoretical combustion temperature of the fuel.

When using the same furnace type and fuel, the heat storage furnace has a higher comprehensive heating temperature and faster heating speed than the conventional furnace.

The direct economic benefit of using heat storage heat exchange technology is mainly fuel saving. Due to the elimination of local high temperature areas, the furnace temperature is evenly distributed, which prolongs the service life of refractory materials, improves the heating quality, and reduces oxidation and burning.

The economic benefits brought by these factors are also considerable.

From the perspective of environmental protection, fuel is saved by 25%, and the total amount of greenhouse gases such as CO2 in the flue gas is also reduced by 25%.

At the same time, because the fuel is in a high-temperature air and oxygen-poor environment, the generation of NOx is reduced.

In short, the application of heat storage technology to aluminum melting furnaces has a good energy-saving effect; it also reduces the emission of CO2 and NOx and alleviates environmental pollution.

At the same time, heat storage technology needs further research to achieve better energy-saving and environmental protection effects.

• 1张明新, 刘日新. 蓄热燃烧技术及其在冶金工业炉中的应用[J]. 工业炉, 2000, 22(2):18-20.

• 2布焕存. 蓄热式高温空气燃烧技术的应用[J]. 钢铁研究学报, 2005, 17(5):1-6.

• 3昝海龙. 蓄热式燃烧技术及自动化控制的应用[J]. 内蒙古石油化工, 2011, 37(10):166-167.

 

June 2, 2025