aluminium melting furnace

详情

1.Summary of heat storage technology With the advancement of equipment and materials, regenerative heat exchanging technology has got revolutionary development and great progress. At present, this technology is widely used for heating furnace and ladle baker in metallurgical enterprises. This article is to introduce the function of heat storage technology for aluminum melting furnace, explaining that regenerative heat exchanging technology has advantages to improve the aluminum quality, speed up the aluminum speed, reduce the discharge of pollutants and save energy consumption, etc. This technology will have wide application prospect in non-ferrous metallurgy industry. 2. Principle of regenerative heat exchanging technology Regenerative burners exist in pairs, and two opposite burners are a group (group A burner, group B burner). After the normal temperature air from blowers is switched into regenerative burner 1 and 4 by reversing valve, it is heated when passing the ceramic glomerulus in burner 1 and 4, and with a very short time the normal temperature air reaches to furnace temperature (generally ****0%). When the heated air goes into the furnace, it absorbs the flue gas around to form a rarefied, lean-oxygen and high-temperature airflow with the oxygen content lower than *1%, and at the same time and inject fuels into the high-temperature air to make the fuel burn under lean-oxygen condition. Meanwhile, the hot gas inside the furnace is emitted into the air through the other two burners, 2 and 3, and the high-temperature gas is stored in the heat retailers of burner 2 and 3, and then discharged through the reversing valve as low- temperature gas which is below **0?. When the heat stored in the heat retailer is saturated, the reversing valve exchange the direction and make the regenerative burners change its situations between heat storage and working, thus save energy and reduce the discharge of NOX, etc. Regenerative heat exchanging technology has changed the traditional combustion mode; the fuel and air enter into the furnace from different ways with proper speed and mix with the combustion products in the furnace; *1% of the O2 is diluted and the fuels burn at high-temperature (above ***0?) and oxygen deficient atmosphere (5~6.5%). This combustion mode has brought many advantages. With remarkable energy-saving effect, saving *0% more than traditional melting furnace As the heat retailer can recover most of the waste heat of fuel gas and take them back to the furnace through medium in the process of combustion, which can greatly reduce the heat consumption of furnace, thus the furnace employing regenerative heat exchanging technology is more energy-saving than the traditional melting furnace. Eliminating partial high-temperature regions, making the furnace temperature uniform The fuel burn under high-temperature and oxygen-deficient condition, forming diffusion flame without steady flames, which removes the partial high-temperature regions led to by steady flame; the flames nearly occupy the whole furnace, the furnace temperature more uniform. The working state of regenerative burner changes frequently, leading to frequent change of the location of flames and the flow direction of furnace gas, strengthening the furnace gas convection, reducing dead angle inside the furnace and make the furnace temperature more uniform. Improving the heating quality Uniform furnace temperature makes aluminum ingot heating more even, reducing the volatilization and oxidation effect of partial high temperature and oxygen-rich condition to molten aluminum. Prolonging the service life of furnace refractory The uniform furnace temperature and the removal of partial high-temperature regions make the heating of refractory uniform, and also limit the refractory to suitable temperature range all the time. The air is pre-heated nearly up to the furnace hearth temperature before entering into the furnace, which greatly reduce the thermal vibration effect on the refractory. Reducing the emission of greenhouse gas CO2 and formation amount of NOX When the fuel saves *0%, the corresponding emission of CO2 also reduces *0%. As the removal of partial high-temp regions, the formation amount of NOX effectively reduced. Application and effect At present, as the resources and environment problems are becoming increasingly obvious, it is required all enterprises to fully implement efficient, energy-saving and clean production technology. Regenerative heat exchanging technology is the most advanced technology in the whole world today, which can greatly enhance the energy utilization of enterprises, realize proper use of low heat value gas, and reduce the discharge of pollutants to the most extent. Our country has successfully applied this technology to aluminum melting furnaces in recent years. Now we will take a *0 t/ch melting furnace of some factory as an example to explain the application of regenerative heat exchanging technology. This furnace adopts two groups of heat-storage burners (the max gas ability for each burner is Nm3/h), the fuel is natural gas (***0 kcal/Nm3). The heat retainer uses small *-diameter ceramic balls with the switch time of **0s. Due to the production process needs, the furnace begin to load stuffs when its temperature rises to **0 ?, the loading quantity is *5 ton and the time will last for *0mins, and then the temperature drops to about **0 ?. The melting process can be divided into 3 phases. Phase 1, when the furnace is under temperature rising, the furnace temperature and the joined aluminum temperature are all low, the gas quantity for this time is **0 Nm3/h and the time lasts *0mins. Phase 2, the furnace temperature reaching its upper limit (**0 ?~**0 ?), the furnace starts to reserve heat. The gas quantity for this time is **0 Nm3/h and the time lasts for **0mins. Phase 3, the furnace begin to cool down before the molten aluminum reaching the set temperature. The gas quantity for this time is *5 Nm3/h and the time lasts *0mins for this phase. In view of heat balance, the fuel-saving rate of the melting furnace adopting regenerative heat exchanging technology is related to the heat reserve of the furnace masonry envelope and the surface heat radiating loss of furnace body. As the burner recovers waste heat through flue gas, the reduction of the heat reserve of furnace body will lead to less loss of surface heat radiating, thus when the flue gas amount becomes more, the fuel-saving rate will be higher. At the same time, as the melting furnace presents intermittent feature at work, the furnace temperature, the air velocity of the heat retainer and the outlet temperature of fume will undulate greatly under different working conditions. Thus the switch time of burners will also change with the working conditions change, which will optimize the utilization of the heat retainer and make the recovery of waste heat gain the best effect. As the air temperature rises after going through the heat retainer, bringing into the furnace much amount of sensible heat, which will increase the theoretical combustion temperature of the fuels. When using the same furnace type and fuels, the heat-reserve furnace has quicker and higher heating temperature than traditional furnaces. The direct economic benefit brought by employing regenerative heat exchanging technology is that it can save fuels. If the price for natural gas is 2.6Yuan/m3 and the fuel-saving rate is 5%, melting a ton of aluminum will save **5.4Yuan. If the annual output is ****0 tons, the fuels saving for each year will be ******0Yuan. As the partial high-temperature areas have been removed, the furnace temperature is uniform, which can prolong the service time of refractory, and at the same time develop the heating quality and reduce oxidation loss. The economic benefits brought from these factors are very considerable. From the environmental protection perspective, saving *5% of fuels will lead to a corresponding *5% reduction of the greenhouse gas like CO2, etc. At the meanwhile, as the fuels are under high-temperature and oxygen-lean conditions, the NOX production reduced. All in all, the application of regenerative heat exchanging technology to melting furnace has very good energy-saving effect; also it can reduce the discharge of CO2 and NOX, and alleviate environmental pollution. But this technology will be further researched to achieve better energy-saving and environmental protection effect.