On January 3, 2024, the Ministry of Ecology and Environment solicited opinions on the National Hazardous Waste List (Revised Draft), which is the fourth revision of the hazardous waste list and the specific implementation of the dynamic adjustment requirements of the national hazardous waste list after the promulgation of the new environmental protection law.
From the general idea of this revision, the hazardous waste directory is more accurate in determining the category of hazardous waste, and the waste that is reflected in the daily management work is also revised in a timely manner, which can be seen that the next step of hazardous waste management is to be managed from the perspective of refinement, and at the same time, the frequency of dynamic adjustment will be more rapid than before.
The changes in this revision are mainly reflected in the following aspects:
1) The wastewater treatment sludge in the process of gas production has been restricted, and the wastewater treatment sludge produced by fluidized bed gasification technology and flow-bed gasification technology coal-to-gas has been removed from the list.
In the revised draft of the new list, the wastewater treatment sludge (excluding wastewater biochemical treatment sludge) generated in the gas production process is revised to the wastewater treatment sludge (excluding wastewater biochemical treatment sludge) generated in the process of gas production by fixed bed gasification technology, and the coal-to-gas wastewater treatment sludge generated by fluidized bed and airflow bed gasification technology is removed from the list.
For the coal chemical industry, coal gasification technology can be said to be the basic core of modern coal chemical industry, almost all modern coal chemical industry chain is based on coal gasification as the process source, therefore, except for coal direct liquefaction projects, almost all modern coal chemical industry involves the application of coal gasification technology.
The wastewater produced by coal chemical industry usually gives people the impression of high-concentration, high-pollution, toxic, and refractory industrial wastewater. As a result, wastewater treatment sludge from the gas production process was considered a hazardous waste in the previous list. However, according to some practices of coal chemical enterprises in actual production and operation, the pollution characteristics of chemical wastewater produced by different gasification technologies are very different.
In the coal gasification process, the temperature of the gas is reduced by the circulating water cooling spray system at the outlet of the gas furnace, and at the same time, the organic impurities, undecomposed gasifier (water vapor) and tar carried in the gas that can be dissolved in water or slightly soluble in water are condensed, and the ash in the gas is washed down, so as to produce a large amount of coal-to-gas wastewater, which is the main source of coal-to-gas wastewater.
The cleanliness of coal gas has a direct impact on coal gasification wastewater, and the water quality of coal-to-gas wastewater produced by different processes and different raw materials is also very different. At present, modern coal gasification technology can be roughly divided into three types: fixed-bed gasification technology, fluidized bed gasification technology, and flow-bed gasification technology.
As the world's earliest gasification technology developed and applied, fixed-bed gasification technology has a wide range of applications in the field of coal gasification, however, due to its relatively low pyrolysis temperature and complex water quality of gas-making wastewater, some fixed-bed gasification processes can be as high as 10000 20000 mg L, and also contain a large number of phenolic esters, alkanes, polycyclic aromatic hydrocarbons and heterocyclic substances such as pyridine and quinapyridine that are inhibitive and toxic to biological metabolism.
Airflow bed gasification technology is a new gasification technology developed in the early 50s of the 20th century, using superheated steam and oxygen as gasifiers, carrying coal-water slurry or pulverized coal particles through a special nozzle to spray into the gasifier at high speed, instantaneous flame reaction, because of its excellent production capacity and gasification efficiency, has been widely used in the world.
Due to the high gasification temperature, the temperature of the gasification reaction zone is as high as 2000, the concentration of organic matter in wastewater is low, the COD concentration is generally 500 mg L, and most of the pollutants are small molecule organic matter, which has good biodegradability and relatively clean wastewater quality.
The amount of wastewater produced by the fluidized bed gasification process is relatively small, and because of its higher temperature and pressure than the fixed bed, the water quality contains tar, oil, and phenol are cracked at high temperatures, and there are fewer such pollutants, low CODCR concentration, and lower wastewater water pollution, which is between the fixed bed and the airflow bed.
From the perspective of the three types of gasification processes, the pollution of gas-making wastewater from fixed-bed gasification technology is very high, and a large number of toxic and harmful heterocyclic substances containing oil, and a large number of toxic and harmful substances are easily adsorbed in the sludge in the wastewater treatment process.
However, due to the high temperature of the airflow bed and the fluidized bed, the heterocyclic substances are basically decomposed into small molecule organic matter at high temperature, and the concentration of toxic and harmful substances is low.
Almost all modern coal chemical industry is inseparable from coal gasification technology, from the current revision of ideas, can greatly reduce the pressure of hazardous waste management in the modern coal chemical industry, but also for the modern coal chemical industry solid waste management more refined and scientific.
2) The cyanide tailings of the ** industry have been restricted, and only the cyanide tailings of gold concentrate and cyanide-containing wastewater treatment sewage have been included in the list, and the cyanide tailings of gold ore have been removed from the list.
For the industry, there is a major change in this revision, that is, the "cyanide tailings and cyanide-containing wastewater treatment sludge produced in the beneficiation process using cyanide" is revised to "the cyanide tailings and cyanide-containing wastewater treatment sludge produced in the beneficiation process of gold concentrate and cyanide-containing wastewater produced in the beneficiation process using cyanide".
This is a huge change.
Cyanide tailings is a solid waste generated by the first production enterprise using the cyanide gold extraction method and refining the first batch of cyanide such as cyanide. The cyanide gold extraction method has a history of more than 100 years, and occupies a dominant position in the world's leading industry due to its simple process and high gold rate.
On August 1, 2016, the "National Hazardous Waste List (2016 Edition)" was released, which characterized "the cyanide tailings and cyanide-containing wastewater treatment sludge produced in the process of using cyanide in the beneficiation process" as hazardous waste.
For the ** industry where 1 ton of gold ore can only be refined 30-100mg, the amount of cyanide tailings produced is very large, and it can be said that the content of gangue in 1 ton of gold ore is close to 100%, even for mining enterprises in the process of producing gold ore powder, the amount of tailings produced is huge.
Such a large amount of cyanide tailings are characterized as hazardous waste, which basically touches the "life and death valve" of the industry, and many companies question whether the content of cyanide in the tailings is already very low in terms of the first industry process treatment level, and whether it is necessary to turn it into a list of hazardous wastes, so the first enterprise has a strong voice.
Under the appeal and organization of China's leading associations, major groups and major enterprises, the Chinese Academy of Environmental Sciences and the Changchun ** Research Institute have carried out a lot of research work on cyanide tailings, and issued the "Technical Specifications for Cyanide Pollution Control in the Industry", which has played a positive role in standardizing the management of cyanide tailings, and at the same time, promoted the exemption of cyanide tailings in the 2021 version of the list.
Although the 2021 edition of the "National Hazardous Waste List" still includes cyanide tailings in the list of hazardous wastes, the 2021 version of the list exempts the management of cyanide tailings, stipulating that the disposal process of cyanide tailings is not managed according to hazardous waste when it meets the requirements of the "Technical Specifications for Cyanide Pollution Control in the Industry" and enters the tailings pond for disposal or cement kiln for co-disposal.
Until this revision, the fine management of cyanide tailings in the ** industry has been further promoted, and the gold ore cyanide tailings (the gold ore without separation operation or the tailings of gold ore after separation operation as raw materials, after crushing and pretreatment, cyanide leaching and gold extraction after cyanidation) are directly removed from the list, and only the gold concentrate cyanide tailings are included in the list.
According to relevant enterprises, scientific research institutions and relevant testing data, the cyanide content of gold ore cyanide tailings is extremely low, which can basically rule out its toxic characteristics, which may also be the reason for the revision of gold ore cyanide tailings to be removed from the list.
3) Restriction on ion exchange resin regenerated sludge, waste incineration bottom slag, fly ash, wastewater treatment sludge, and paint slag in the process of painting.
Modify "wastewater treatment sludge generated during the regeneration process of ion exchange devices (excluding drinking water, industrial pure water and boiler softened water preparation units)" to "wastewater treatment sludge generated during the regeneration process of ion exchange devices (excluding drinking water, industrial pure water and boiler softened water preparation units, and ion exchange devices in complete wastewater treatment processes)."
The scope of the exclusion of wastewater treatment sludge from the ion exchange plant regeneration process has been expanded to cover sludge generated by ion exchange plant regeneration in the wastewater treatment package.
This has to do with the way ion exchange resins are managed.
In the 2016 edition of the Hazardous Waste List, discarded ion exchange resins were classified as hazardous waste, regardless of the quality of the treated raw water, and were managed as hazardous waste** 900-015-13, mainly because of the possibility of heavy metals in the example exchange resins, so they were classified as hazardous waste management.
Since the implementation of the 2016 version of the list, local ecological and environmental authorities have received a large number of inquiries from enterprises about whether the waste ion exchange resin generated in the preparation of pure water and boiler softened water is a hazardous waste, because the raw water treated by it basically does not contain harmful substances or has a very low content of harmful substances.
On the basis of a large number of feedback on such problems, the "Hazardous Waste List" (2021 Edition) restricts ion exchange resins, stipulating that the list no longer includes ion exchange resins for drinking water, industrial pure water and boiler softened water preparation units. In the implementation of the implementation of drinking water, industrial pure water and boiler demineralized water preparation units of ion exchange resins are no longer managed as hazardous waste, some places, such as Shanghai, directly clarify that such ion exchange resins are managed according to general industrial solid waste.
In this revision, 900-015-13 has not been revised, but the sludge generated by the ion exchange resin regeneration process that is not listed in 900-046-49 has been expanded.
"Bottom slag, fly ash and wastewater treatment sludge produced by hazardous waste incineration, pyrolysis and other disposal processes" is revised to "bottom slag produced by toxic and infectious hazardous waste incineration, pyrolysis and other disposal processes (excluding bottom slag produced by domestic waste incinerator co-disposal of infectious medical waste), fly ash and wastewater treatment sludge".
For hazardous waste incineration, the bottom residue, wastewater and wastewater treatment sludge produced by incineration are limited, and only incinerated toxic and infectious hazardous wastes are included, which means that the bottom residue, fly ash and wastewater treatment sludge after incineration of hazardous wastes with corrosive, reactive and flammable properties are no longer included in the list.
At the same time, since medical waste is also a kind of hazardous waste, the bottom slag produced by the co-disposal of infectious medical waste by domestic waste incinerators in this revision is not directly included in the list, but for this type of bottom slag, according to the understanding that it is not included in the list, this kind of bottom slag needs to be managed by identifying and determining the attributes.
The above is only a personal opinion for the reference of all enterprises.
References:
1] Li Dedi, Liu Jianzhong, Wu Hongli, et al. Component characteristics analysis of coal gasification wastewater[J].Coal Technology, 2017(9):3doi:10.13301/j.cnki.ct.2017.09.109.
2] Before getting the "gold medal for avoiding death", the heart-wrenching experience of cyanide tailings. Gold Miner, 202012.