1. The current situation of the casting industry

China is a major casting country with over 30000 casting enterprises, ranking among the top in the world for many consecutive years since 2000. In 2013, the total production of various types of castings in China was 44.5 million tons, accounting for approximately 40% of the world's production.

The casting industry belongs to an industry with high energy consumption and severe pollution. The energy consumption of the casting industry accounts for 25-30% of the total energy consumption of the mechanical industry. The most serious environmental pollution caused by casting enterprises during the production process is solid waste and air pollution. The emissions of three wastes per ton of casting production in China are 10 times that of some industrialized countries. According to statistics, the total amount of pollutants emitted by the casting industry in China in 2013 was approximately 2.2 million tons of dust, 4.5-90 billion m3 of exhaust gas, 50 million tons of waste sand, and 13 million tons of waste slag.

The pollution control technology and facilities in China's foundry industry are still relatively backward. In developed countries, the investment in environmental protection by foundries accounts for 20-30% of the equipment investment in foundries, while China only accounts for 5-8%. Areas with developed casting enterprises, such as Jiangsu, Shandong, Zhejiang, Shanghai, Hubei, Chongqing, etc., have caused serious environmental pollution during the production process.

2. Air pollution emitted by foundry enterprises

The characteristics of air pollution in foundries include dispersed pollution sources, low concentrations, and large amounts of gas. Out of a total of 188 hazardous air pollutants listed by the US Environmental Protection Agency, more than 40 have been detected in foundry waste gas, posing significant risks to the environment and human health.

The HAP produced during casting, cooling and sand falling comes from the pyrolysis of pulverized coal and organic binder during casting.

3. Control of Harmful Gases in Foundry Enterprises

There are several methods for treating waste gas generated in the production process of casting enterprises, each with its advantages and disadvantages:

a. Activated carbon adsorption;

b. Chemical dissolution method;

c. Biodegradation method;

d. Plasma method;

e. Plant liquid spraying method;

f. Catalytic combustion method;

g. Catalytic oxidation method;

h. Acid alkali neutralization method;

i. UV photolysis purification method

The current state of waste gas treatment is characterized by low efficiency and high cost in end treatment. The real solution is to avoid the generation of harmful exhaust gases from the source, which will be introduced later in the Yangtze River environmentally friendly low odor coated sand and Yangtze River CITEK inorganic sand.

4. New Technology of Environmentally Friendly Resin Coated Sand

1) Yangtze River environmentally friendly low odor coated sand

2) Low odor: Compared to ordinary resin coated sand, the ammonia emission of the odor gas phase during core making is more than 85% lower, and the high-temperature thermal cracking gas phase emission during pouring is about 30% lower

3) Low gas generation: reduces gas generation by about 10% compared to ordinary resin coated sand

4) Low expansion: The thermal expansion of resin coated sand is about 5% lower than that of ordinary resin coated sand

5) Good sand production performance: It is easier to clean sand than ordinary resin coated sand, and the cleaning time can be shortened by about 30%

6) Changjiang CITEK inorganic sand: 920 ° C Curie point thermal cracking gas phase organic matter test results show that compared to organic resin sand, gas phase pollutants are reduced by more than 92%, basically avoiding the generation of harmful gases in casting.

5. The Current Situation of Casting Waste Sand Dumping Pollution

Waste sand is the most serious and significant source of environmental pollution in the production process of casting enterprises.

6. Pollution and Harm of Casting Waste Sand

1) The hazards of waste sand include dust pollution, chemical pollution, soil desertification, land occupation, and waste of silica sand resources;

2) Dust pollution: A large number of small particles (including PM2.5) contained in waste sand, which can be blown away by the wind when exposed, posing a great danger;

3) Chemical pollution: Waste sand contains persistent harmful organic pollutants, and the waste sand disposed of in landfills will pollute soil and water for a long time.

7. Solution to pollution of foundry waste sand: cyclic regeneration treatment

1) Technically, it reduces the thermal expansion coefficient, enhances the activation of the sand surface, removes the fine powder content in the sand, thereby reducing the amount of resin added to the molding sand and reducing casting defects such as veins and pores on the casting surface;

2) Economically, it can significantly reduce the amount of new sand used, protect sand resources, and save transportation costs. Reduce casting defects, thereby reducing the overall cost of castings. Reduce the cost of C02 emissions.

3) From an environmental perspective, government regulations are becoming increasingly stringent. The regeneration treatment of waste sand can greatly reduce the indiscriminate discharge of mixed waste sand containing harmful substances, greatly reducing pollution to soil and water sources.

8. Waste sand regeneration treatment technology

1) The usual regeneration technology and equipment thermal method (with horizontal and vertical furnaces, problem: only processing resin sand, energy consumption is still high)

Mechanical (with friction and impact, problem: only dealing with a single waste sand, low regeneration efficiency)

Wet method (also known as water washing method, problems: large land area, resin cannot be treated, serious secondary pollution, winter freezing, high investment and operating costs)

2) The thermal mechanical combined regeneration technology of Chongqing Changjiang Group is efficient and low consumption. The waste heat can be reused multiple times to treat various types of waste sand, such as resin sand, tidal film sand, and inorganic sand. The regenerated sand has high quality and can replace new sand for core making. Zero emission: dust reuse, waste gas treatment.

9. Environmental issues in waste sand recycling treatment

The domestic recycling equipment, technology, and process are uneven, resulting in uneven quality, recycling costs, and environmental protection measures of recycled sand; Many casting enterprises are not familiar with recycling technology, resulting in low equipment utilization, poor quality of recycled sand, high comprehensive costs, and serious secondary pollution. In regeneration treatment, there are mainly changes in the migration of pollutants (organic pollutants, heavy metals) and secondary pollutants (waste gas: dioxins, PM2; dust; heavy metals; wastewater; organic pollutants)

10. Zero emission solution for foundry waste sand pollution: cyclic regeneration treatment

11. Zero discharge regeneration treatment technology for foundry waste sand

Chongqing Changjiang Group has monitored the waste gas generated during the regeneration process and the mechanism of the main components.

The basic principle of Changjiang Group's waste gas treatment is to degrade the harmful factors in the waste gas into harmless factors, fundamentally eliminating the generation of secondary air pollution and achieving zero emissions.

The waste generated during the regeneration process includes dust, waste residue, waste metal, etc. The separation and collection of secondary waste should be strictly regulated; Classify materials, avoid secondary pollution during transmission and processing, and conduct harmless treatment and reuse of dust to fundamentally achieve zero emissions.

12. The Recycling Treatment Mode of Casting Waste Sand in Chongqing Changjiang Group

1) Chongqing Changjiang has invested in the construction of a waste sand recycling and treatment production line near casting enterprises, responsible for daily production and operation. Foundry enterprises send waste sand to the recycling treatment center and recycle the recycled sand that meets the technical requirements after treatment;

2) Casting enterprises have no worries about emissions, no equipment investment risks, no production management, recycled sand quality, equipment maintenance and other issues;

3) Scaled and specialized production is conducive to the treatment of secondary waste, reducing secondary pollution, and achieving zero emissions;

4) It is beneficial for the government's environmental protection department to monitor and manage the treatment of foundry waste sand.