As people pay more and more attention to industrial pollution, environmental laws and regulations in many countries are becoming more and more strict. Sand casting is a processing and manufacturing method that melts metal or alloy into liquid state by melting method and directly solidifies in the mold to obtain rough embryo with certain shape, size and performance. Studies have shown that nearly one-third of the world’s energy consumption and 36% of carbon dioxide emissions are caused by manufacturing. Accordingly, strict rules and regulations force manufacturing enterprises to take specific measures to achieve green production. Although the total carbon dioxide emissions have been effectively reduced through the implementation of existing high-tech manufacturing technologies, the carbon emissions of the foundry industry still need to be optimized from many aspects in order to further reduce the impact of the manufacturing process on the environment. Among them, sand casting, as a basic manufacturing process of manufacturing industry, plays an indispensable role in manufacturing industry, but its environmental problems are more serious than other manufacturing technologies.
Contaminants | Pollutant emissions per ton of castings produced |
Dust | 50Kg |
Waste residue | 200Kg |
Exhaust gas | 20M3 |
Foundry waste sand | 1.3-1.5t |
Sand casting is one of the oldest manufacturing processes, which has the characteristics of high energy consumption and great environmental impact. The principle of sand casting is to pour molten metal into the mold cavity, wait for it to solidify, and then get the required casting products through post-treatment. The modern typical sand casting process is divided into several stages: mold making, modeling, pouring, solidification and cleaning. Casting is also one of the most energy intensive manufacturing processes, in which the energy consumed by metal melting process accounts for more than half of the total energy. Most castings are produced by small and medium-sized enterprises, and their energy efficiency is affected by scale differences. Therefore, the overall energy efficiency of the casting industry is not high.
In the casting process, the sand for sand casting is recycled more and more frequently in the metallurgical industry. When the quality of sand used in sand casting decreases and is not suitable for further casting production, it shall be removed from the sand casting industry and treated as waste. However, the landfill treatment of sand for sand mold casting will lead to high metal content in groundwater in some parts. The pyrolysis of binder in resin sand will also produce a variety of by-products, including some harmful air pollutants. Harmful air pollutants produced by pyrolysis of sand casting materials usually include benzene, toluene, ethylbenzene and xylene. In addition, through the comparative analysis of the emission of harmful air pollutants produced by sand casting materials, it is found that 8-10 kinds of harmful air pollutants determined in the test account for 65-98% (by weight) of the total emission of harmful air pollutants quantified in the demonstration scale pouring emission test.
In addition, untreated sand dust is toxic to the respiratory system. A large amount of dust will be produced during sand casting production, which is harmful to macrophages and may lead to silicosis, lung cancer and other related health diseases. 60% – 70% of the world’s castings are cast by sand mold. The amount of pollutants produced in the production process of each ton of castings is shown in the table. Obviously, the sand casting industry has become one of the main sources of energy consumption and carbon emission. The casting industry is one of the most energy intensive industries in the industry, but it has great energy-saving potential. Therefore, energy conservation and emission reduction is an important issue that needs to be solved urgently in the sand casting industry.