With the implementation of China’s first mandatory national standard for air pollutant emissions in the foundry industry, Emission Standard of Air Pollutants for Foundry Industry (GB 39726—2020), on January 1, 2021, many foundries have felt a growing sense of urgency in recent years: environmental protection is no longer optional! But how exactly should it be done? With emission limits clearly defined, how can companies meet these requirements? To address this question, the new standard Guideline on Available Techniques of Pollution Prevention and Control for Foundry Industry (HJ 1292—2023) was recently officially released and will come into effect on June 1, 2023.
What Is the “Guideline on Available Techniques of Pollution Prevention and Control”?
Although presented in the form of an environmental standard, the Guideline on Available Techniques of Pollution Prevention and Control does not set emission limits. Instead, it serves as a guide for polluters on how to control and manage pollution and how to meet the established emission limits. To draw an analogy, if emission limits are seen as production or sales targets—KPIs—then the Guideline on Available Techniques is the operational manual or work instructions. As you may have noticed, for enterprises, this Guideline is more practical than the emission limits themselves.
Many industries in China have already issued their own Guidelines on Available Techniques for pollution prevention and control. For instance, the thermal power industry had one as early as 2017. The foundry industry started its environmental protection efforts relatively late, and various environmental requirements are gradually being refined. This Guideline on Available Techniques of Pollution Prevention and Control for Foundry Industry (HJ 1292—2023) will undoubtedly play a crucial guiding role in the environmental protection work of foundries.
What Does the Guideline Require Foundries to Do for Pollution Prevention and Control?
Unlike general enterprises that view environmental protection merely as installing pollution control equipment, this Guideline dedicates significant篇幅 to introducing technologies for preventing pollution at the source through raw materials, auxiliary materials, and process equipment. This fully reflects the fundamental principle of “prevention first” in China’s environmental protection efforts. If pollutant generation during production is unavoidable, can it be reduced in quantity or variety?
To stably meet national pollutant emission standards, enterprises need not only pollution control technologies but also integrated adoption of pollution prevention technologies and environmental management measures.
This Guideline addresses air pollution in the foundry industry primarily through four aspects: pollution prevention, pollution control, fugitive emission management, and mobile source control.
Pollution Prevention: Which Raw Materials and Processes Are More Environmentally Friendly?
The Guideline recommends a range of greener products or technologies in two areas: raw/auxiliary materials and equipment/processes. In recent years, not only foundries but also foundry equipment and material suppliers have deeply felt that non-“green” products are becoming harder to sell. So, which products or technologies are truly more environmentally friendly? This Guideline provides official guidance.
In terms of raw/auxiliary materials, the Guideline recommends six practices:
Substituting clay sand additives with reduced/no coal powder.
Using modified resin binders (including curing agents).
Replacing with ceramic sand.
Substituting with inorganic binders.
Using water-based mold coatings.
Adopting low/no-VOCs coatings.
In terms of equipment/processes, the Guideline recommends eight practices:
Integrated furnace cover and dust removal.
Designated treatment of molten metal.
Low-nitrogen combustion.
Micro-spraying.
Enclosed transfer of molten metal.
Electrostatic spraying.
Cathode electrophoresis.
Wet machining.
Enterprises can refer to the above technologies when selecting processes and purchasing raw/auxiliary materials. If a company is undergoing technical or green upgrades, these products and technologies with pollution prevention effects are ideal choices.
Pollution Control: What Pollution Control Equipment Should Foundries Choose?
Source reduction is the priority, but pollution control must also be implemented. The main air pollution control tasks in the foundry industry include particulate matter control, sulfur dioxide control, and VOCs control. Die-casting enterprises also need to specially consider oil mist control. This Guideline proposes a series of air pollution control technologies suitable for foundries.
For fugitive emission issues, efforts should be made to achieve enclosed material handling and ensure the effective operation of exhaust gas collection systems.
The Guideline provides detailed feasible technologies for air pollution control in various stages of foundry production, including metal melting, molding and core-making, pouring, shakeout and cleaning, sand treatment and waste sand regeneration, and heat treatment of castings. By following these recommended technical solutions, foundries can meet standard requirements or achieve even lower emissions.
Metal Melting: Solutions are provided for cupolas, electric furnaces, and gas-fired furnaces, focusing on dust removal, generally achieving达标排放 (standard-compliant emissions) of 5~20 mg/m³ for particulate matter.
Molding and Core-Making: Dust removal is the primary method. When using resin sand, technologies like modified resins, ceramic sand substitution, and inorganic binder substitution are effective for prevention. For organic binders, absorption or adsorption after dust removal is essential.
Pouring: Detailed control technical routes are provided, with the most complex equipment needed when binders contain organic compounds.
Shakeout, Cleaning, Sand Treatment, Waste Sand Regeneration, and Heat Treatment: Bag/filter cartridge dust removal can be used. For aluminum/magnesium alloy castings, wet dust removal is also an option.
Surface Coating: As the main source of VOCs, coating processes require corresponding control equipment. For traditional paints, thorough combustion for VOCs removal is necessary unless existing high-temperature environments (e.g., continuous annealing furnaces) can be utilized. Using water-based coatings only requires simple paint mist treatment.
Summary: How Much Pollution Control Equipment Should a Foundry Install?
This Guideline is user-friendly for foundries. They simply need to identify their production departments and match them with the required air pollution control equipment as outlined. For example, a sand casting enterprise using clay sand or resin sand, with in-house heat treatment and still using paint for surface coating, may need the following to meet emission standards:
At least 8 sets of dust removal equipment.
1 set of physical adsorption (with wastewater treatment).
1 set of adsorption + catalytic combustion equipment for VOCs control.
This does not account for multiple production units within a department requiring multiple sets of equipment or the possibility of sharing equipment across departments. While the actual situation may be complex, this Guideline will help foundries easily find their direction.
How does your enterprise measure up? Try comparing it with this Guideline!
With the implementation of this Guideline, the foundry industry now has a初步形成 (preliminarily formed) system of national or Ministry of Ecology and Environment standards, including pollutant emission limits,排污许可 (pollution discharge permits), and self-monitoring guidelines. Supervision is gradually becoming law-based. The environmental protection efforts in the foundry industry are steadily advancing, and enterprises should act quickly!