Energy saving technologies and measures for casting production

The foundry industry is a major energy consumer in the mechanical industry, with high energy consumption, low energy utilization, severe pollution, and poor economic benefits constraining its development. Reasonably utilizing energy and vigorously promoting energy conservation is an important task in the foundry industry.
Energy saving technologies and measures include the following aspects.
1、 Recycling and reuse of old sand
In developed industrial countries in Europe and America, the reuse of old sand has always been a major research topic, and has achieved good research results, which have been put into industrial production. When casting non-ferrous metal parts, cast iron parts, and cast steel parts. According to the sintering temperature of the old sand, mechanically regenerate the old sand. Their regeneration rates are roughly 90%, 80%, and 70%, respectively. The combination of old sand reuse and wet regeneration is the most economical and ideal choice, with a two-stage wet regeneration removal rate (Na2O) of 85% to 95%, and a single-stage removal rate of up to 70%. 90% of the old sand is recycled and reused, with a quality close to that of new sand. Richard Company in the UK uses thermal regeneration, which can increase the regeneration rate by about 10-20%. Moreover, the cost recovery period of the complete set of equipment for regenerating old sand by thermal method is relatively short, and the cost can generally be recovered after two years of operation. The recycled zirconium sand that cannot be mechanically regenerated is of better quality than new sand after thermal treatment. In the United States, the annual consumption of sand in the foundry industry is around 5 million tons. BastianKC and AllemanJE found that the old sand used for casting is used as highway subgrade material. It can fully meet the performance requirements of materials used in highway construction. Its performance is also superior to new sand of the same variety.
2、 Recycling and reuse of adhesives
Environmentally friendly inorganic binders for sand cores and sand treatment and regeneration technologies are receiving increasing attention. Laempe's Beach Box inorganic binder is a fluid containing multiple minerals. The core sand is made of 95% sand and 5% binder. For castings, dry core removal is used, and the binder remains in the sand. To activate the binder, only 2.5% water needs to be added, which can be reused multiple times without the need for new binder. This means that the maximum amount of binder added in each batch is only 1.6%. The binder components harden due to chemical reactions caused by water removal, and the usage time is unlimited, but the relative humidity should not exceed 70%. The mixed sand is well sealed and can be stored for a long time. The binders of Foundry Automation and MEG are in powder form and are used for aluminum alloy core making, storage, and casting processes without emitting gas, and without any environmental issues that may be caused by resin binders. The water used for wet sand cleaning can be reused by 85%, and the recovered materials can be reused by 100%.
3、 Regeneration of molds and mold materials
Since the 1990s, countries in the United States and Europe have treated discarded or recycled molds from precision casting manufacturers with special purification processes, and then adjusted the composition according to different user needs to form "recycled recycled molds". The key to this technology lies in the use of advanced multi-stage filtration or centrifugal separation methods to accelerate the operation process and obtain purer molds. MittererC found in his research on aluminum casting molds. Coating a layer of hard film on the surface of steel molds can effectively suppress corrosion, improve resistance to thermal cracking, corrosion and other destructive behaviors by utilizing the protective effect of nitrogen and carbides, and replace thick oxygen based coating materials with thin films, thereby effectively extending the service life of molds. Its core technology is PACVD technology, which is plasma chemical vapor deposition.
4、 Energy saving technology centered on smelting
The energy consumption of the casting melting part accounts for about 50% of the total energy consumption of casting production, and the casting waste caused by melting accounts for about 50% of the total waste. Therefore, adopting advanced and applicable melting equipment and melting processes is the main measure for energy conservation. Taking the energy-saving technology of cast iron smelting as an example.
(1) It is an inevitable trend to promote the use of hot air, water cooling, and continuous operation, and to develop long service blast furnaces towards large-scale and long-term continuous operation. Foreign foundry companies have applied it as an important energy-saving measure. In recent years, a lot of work has been done in these areas in China, and some enterprises have adopted them, achieving significant energy-saving effects. For example, using the double layered air supply blast furnace technology with large spacing can save 20% to 30% of coke, reduce the scrap rate by 5%, and reduce Si and Mn burn losses by 5% and 10% respectively; Water cooled unlined and thin lined blast furnaces have a long continuous operation time and can save energy by more than 30%; Hot air blast furnace is both energy-saving and environmentally friendly.

(2) Promote the dual melting process of blast furnace and electric furnace. The double melting of blast furnace and electric furnace utilizes the advantages of blast furnace preheating, high melting efficiency, and high overheating efficiency of induction furnace to improve the quality of molten iron and achieve the goal of reducing energy consumption. In recent years, with the significant increase in the prices of raw materials such as coke and pig iron, and the increasing demand for casting quality, the use of electric furnaces for smelting has become more and more common. The use of low valley electricity production at night has also achieved good economic and energy-saving effects.

(3) Promote the application of casting coke and blast furnace melting. The use of cast coke fuel is an effective way to improve the temperature and quality of molten iron. Most blast furnaces abroad use cast coke for melting. Due to the high price of casting coke or habitual reasons, most domestic enterprises still use metallurgical coke. Some enterprises even use earth coke, which not only affects the quality of castings but also consumes a large amount of coke. If casting coke is applied, the scrap rate can be reduced by 2%. Therefore, developing the production of cast coke and promoting its application is one of the measures to improve the quality of castings and reduce energy consumption.

(4) When using metallurgical coke in a dehumidified blast furnace, it is difficult to maintain a stable temperature of 1500 ℃ for the molten iron. If 3% oxygen enriched air supply is used, it can be guaranteed, and each ton of molten iron can reduce energy consumption by about 10kg of standard coal. Cupola dehumidification and air supply are usually used in humid areas in the south, which can increase the temperature of molten iron and reduce the burning of elements such as silicon and manganese. Improve the quality and melting rate of molten iron, and reduce coke consumption by 13% to 17%.

(5) The blast furnace adopts computer control technology. The blast furnace adopts computer control, including computer batching, automatic weighing and quantification of furnace materials, and automation control of the melting process. By operating the cupola in an optimized state, high-quality molten iron and suitable molten iron temperature can be obtained. Compared with manual control, it can save 10% to 15% of coke.

(6) Promote the use of high-pressure centrifugal energy-saving fans specifically designed for blast furnaces. At present, there are still many blast furnaces in China that use Roots or Yeats positive displacement fans, which have high energy consumption and noise. By using a dedicated high-pressure centrifugal energy-saving fan for the blast furnace, energy can be saved by 50% to 60%, and the melting rate can be increased by about 33%.