Business professionals suggest conducting in-depth research on the sources and characteristics of zinc dross in various regions, and entrusting qualified hazardous waste identification agencies to identify the hazardous waste characteristics of hot-dip galvanized dross. Until the identification conclusion is reached, zinc dross will not be included in the exclusion management list for the time being.
A draft for soliciting opinions has caused concern among enterprises engaged in solid waste disposal.
On September 28th, the Ministry of Ecology and Environment publicly solicited opinions on the "List of Hazardous Waste Exclusion Management (2021 Edition)" (draft for comments). According to the drafting team for soliciting opinions, "the solid waste included in this list does not belong to hazardous waste".
This draft for soliciting opinions lists six types of solid waste, namely hot-dip galvanizing slag and bottom slag; Wastewater based drilling mud; Wastewater treatment sludge generated during the production process of aluminum electrode foil; Waste from cutting scraps of wind turbine blades; Waste generated during the production process of seven types of resins; De ink residue.
The first type of solid waste that has caused controversy in the industry is hot-dip galvanizing slag and bottom slag.
According to the compilation team, zinc dross mainly occurs during the process of immersing the workpiece into a zinc bath in a zinc pot. It usually floats on the surface of molten zinc and is manually removed; Zinc bottom slag is the sediment formed by the aggregation of iron zinc alloy layers at the bottom of the zinc pot during the reaction. The analysis of the hazardous characteristics of both shows that they do not have hazardous characteristics.
However, the lead addition process may result in excessive levels of heavy metal lead in solid waste, and the resulting zinc floating slag and bottom slag are not included in the list.
Dangerous characteristics mainly refer to the absence of toxicity, corrosiveness, flammability, reactivity, or infectivity, and controllable environmental risks.
The preparation team introduced that currently, zinc floating slag and zinc bottom slag are mainly sold to downstream enterprises for comprehensive utilization at a discount of 60-90% of the market price of pure zinc ingots, producing products such as zinc oxide, secondary zinc oxide, and zinc ingots. Reuse production mainly involves the process of metal smelting, which is managed in accordance with the requirements of the "Emission Standards for Industrial Pollutants of Recycled Copper, Aluminum, Lead, and Zinc", and the environmental risks are controllable.
However, some people from solid waste disposal companies have expressed that zinc dross should be classified as hazardous waste and should not be included in the list.
On October 3rd, the person in charge of a zinc industry limited company in Weifang, Shandong, told First Financial reporters that zinc dross is a hazardous solid waste clearly identified in the "National Hazardous Waste List (2021 Edition)". The waste category is "HW23 zinc containing waste", with the code 336-103-23, which is expressed as "waste generated during hot-dip galvanizing process and dust collected by plating melting (dissolving) agents and dust collection (removal) devices".
The person in charge said that ammonium chloride and zinc chloride are commonly used as auxiliary plating solvents in the galvanizing process, among which zinc chloride is corrosive and highly toxic. During the collection process of zinc dross, it is inevitable to bring out zinc chloride, zinc oxide, and particulate zinc, forming a mixture (with a zinc chloride content of 5-15%).
Zinc dross generally has toxic and hazardous characteristics. "The person in charge said that in March 2017, the company commissioned a third party to conduct leaching toxicity tests on zinc ash produced by a company in Shandong. The results showed that the total zinc concentration was more than 10 times higher than the standard, and the chlorine concentration had leaching toxicity characteristics.
In addition, the quantitative analysis of zinc ash and zinc content in a company in Shandong using energy dispersive spectroscopy showed 63.2% and 10.4%, respectively; The zinc ash of a company in Texas has a zinc content of 69.8% and a chlorine content of 16.0%; The zinc ash of a company in Tianjin has a zinc content of 34.4%, lead content of 23.0%, and chlorine content of 20.6%.
The person in charge said that zinc dross contains metallic zinc powder, which is flammable when in contact with water. Containing zinc ash that is flammable when in contact with water, as well as zinc chloride, a mixture of the two is more likely to cause fires. In addition, the temperature during the processing and separation of zinc ash is high, and it often self ignites during the reproduction process, which poses a high risk and requires key management. The zinc particles sorted from zinc dross are prone to secondary pollution caused by excessive lead, cadmium and other elements during the smelting process, resulting in high environmental risk control costs.
On October 3rd, a person in charge of a zinc industry limited company in Anqiu City, Shandong Province, also told First Financial reporters that "there is a large amount of zinc chloride in hot-dip galvanizing slag, which poses a great environmental hazard" and "there are differences in hot-dip galvanizing processes, resulting in complex composition of hot-dip galvanizing slag".
The person in charge also told First Financial reporters that hot-dip galvanizing enterprises are widely distributed across the country, with thousands of them, and the amount of zinc slag (zinc ash) produced is huge. There are over 300 hot-dip galvanizing enterprises in Beijing Tianjin Hebei, Shandong, and Jiangsu alone, producing approximately 500000 tons of zinc dross annually.
Another Shandong Rizhao Environmental Protection Technology Co., Ltd. provided a written opinion to the First Financial Journalist, stating that "after deducting National Day and Sundays, only 7 working days are allowed, and the time limit for soliciting opinions is unreasonable." "The preliminary research was not made public, and convincing detailed information was not disclosed.
In 2020, the Ministry of Ecology and Environment, together with the National Development and Reform Commission, the Ministry of Public Security, the Ministry of Transport, and the National Health Commission, revised and released the "National Hazardous Waste List (2021 Edition)". In May of this year, the General Office of the State Council issued the "Implementation Plan for Strengthening the Supervision, Utilization and Disposal Capacity Reform of Hazardous Waste", proposing the establishment of a list of hazardous waste elimination and management.
The above-mentioned preparation team introduces the scientific assessment of environmental risks of hazardous waste, the implementation of graded and classified management, and the inclusion of solid waste that does not have environmental risks or has controllable environmental risks in the exclusion management list. This is conducive to focusing regulatory efforts on high-risk hazardous waste, efficiently utilizing management resources, reducing management costs, and achieving maximum control of environmental risks within existing management capabilities.
The above-mentioned business professionals suggest conducting in-depth research on the sources and characteristics of zinc dross in various regions, and entrusting qualified hazardous waste identification agencies to identify the hazardous waste characteristics of hot-dip galvanized dross. Until the identification conclusion is reached, zinc dross will not be included in the exclusion management list for the time being.
On the evening of the 3rd, an industry insider stated in an interview with First Financial News that further scientific evidence is needed to determine whether zinc dross should be classified as hazardous waste. This person analyzed that the reason why companies disposing of hazardous waste have different opinions is partly because these companies have already obtained hazardous waste disposal permits. If zinc floating slag is classified as general solid waste, any company can collect and dispose of it, which will inevitably take a share of the hazardous waste disposal enterprises. On the other hand, hazardous waste disposal enterprises have invested a considerable amount of funds in storage and transportation facilities, but the corresponding subsidies are not significant.
