Disposal methods for discarded catalysts
Publishdate：2018-07-12 Views：15
1. Recycling metal resources
Recycling and reusing valuable metal resources contained in discarded catalysts. This is the best way to solve the problem of waste catalysts. However, it is difficult to achieve in practical operation because of the following problems: 1) collection and transportation issues; 2) Complex ingredients, difficult to separate and recover; 3) Determine the scale and location of the factory construction; 4) Disposal of heavy metals in dust and other related issues. The above issues make it difficult to achieve recycling and reuse.
1.1 Collection, storage, and transportation issues
Although the annual production of catalysts in China reached over 340000 cubic meters in 2014, and the accumulated amount of discarded catalysts over the years can be said to be close to astronomical figures, these catalysts are distributed throughout the country and in different industries, such as power plants and chemical plants. Moreover, in situations where the time of damage is uncertain, it is difficult to collect and handle it all in a unified manner; Secondly, there is the issue of storage, where a large amount of heavy metal dust is attached to discarded catalysts. How to effectively store them and prevent secondary pollution of heavy metals and dust; The third transportation problem is that due to the large amount of dust containing heavy metals attached to the surface of the catalyst, especially during long-distance transportation, it is difficult to ensure that the dust does not fly everywhere, which becomes a mobile pollution source and pollutes the surrounding environment.
1.2 Complex ingredients, difficult to separate, and recyclable
Catalyst production involves mixing, shaping, drying, calcining, and cutting TiO2, V2O5, WO3, MoO3, and other materials. Its main components are shown in Table 2.
From the table, it can be seen that the main costs of catalysts are TiO2, V2O5, WO3, MoO3, etc. However, it is difficult to separate titanium, vanadium, molybdenum, tungsten, etc., especially since molybdenum and tungsten are both lanthanide elements with similar properties, making it more difficult to separate them.
1.3 Factory scale and site selection
If industrial recovery is carried out using waste catalysts as raw materials, a fixed production scale is required to maintain its normal production. The sufficient supply of raw materials for discarded catalysts is a prerequisite for ensuring industrialization. But in reality, it is difficult to obtain sufficient waste catalysts as raw materials to ensure continuous production. With 3 × For example, for a 600MW unit, each unit requires approximately 600m3 of catalyst. Generally, the catalyst has a service life of about three years (without considering regeneration, if the regeneration time is longer), then approximately 1800m3 of waste catalyst is available every three years. This obviously cannot maintain the normal production of the enterprise. Although the annual production of domestically produced catalysts reaches several hundred thousand cubic meters, and the accumulated amount of discarded catalysts over the years can be said to be close to astronomical figures, these catalysts are distributed throughout the country and in different industries, such as power plants and chemical plants. Moreover, it is difficult to collect and handle all the damages in a situation where the time of damage is uncertain. Therefore, the determination of production scale and factory location is crucial.
Due to the inability of a single power plant to meet production needs with discarded catalysts. So, multiple power plants and cement plants are needed to ensure normal production, so the site should be selected with multiple nearby power plants (or cement plants). Reduce transportation costs while preventing the generation of new mobile pollution sources.
1.4 Disposal of heavy metals in dust
The discarded catalyst adheres to a large amount of dust as shown in the figure, which contains a large amount of heavy metals. The disposal of these dust containing heavy metals has become a difficult and challenging problem to solve.
2. Landfill
Landfilling is a simple way to solve waste catalysts. However, in the recently released "Technical Specification for Thermal Power Plant Smoke Denitration Engineering - Selective Catalytic Reduction Method", the treatment method for SCR waste catalysts is crushing and landfill. However, SCR waste catalysts are classified as hazardous solid waste and cannot be disposed of arbitrarily due to the presence of toxic metals such as V2O5 and WO3, as well as heavy metals attached during use, According to the Special Provisions on the Prevention and Control of Hazardous Waste Pollution in the Solid Waste Pollution Environmental Prevention and Control Law of China, the regulations stipulate that units producing hazardous waste must bear the disposal costs. This indicates that power plants, chemical plants, and other units that use denitrification catalysts, as well as denitrification engineering companies (as the implementation and operation and maintenance units of denitrification projects), must bear the disposal costs of SCR waste catalysts, This will undoubtedly impose an economic burden on power plants, chemical plants, and engineering companies. In fact, the landfill treatment method does not comply with the requirements of the Recycling and Resource Utilization Industry Model in the Circular Economy Promotion Law of the People's Republic of China. SCR waste catalysts themselves are resources with high recyclable value and should be recycled and reused.
3. Other methods
There are currently no reports on other treatment methods for SCR waste catalysts, which can be crushed and thoroughly mixed with cement to produce concrete products such as cement floor tiles, cement pipelines, and cement poles.
1. Recycling metal resources
Recycling and reusing valuable metal resources contained in discarded catalysts. This is the best way to solve the problem of waste catalysts. However, it is difficult to achieve in practical operation because of the following problems: 1) collection and transportation issues; 2) Complex ingredients, difficult to separate and recover; 3) Determine the scale and location of the factory construction; 4) Disposal of heavy metals in dust and other related issues. The above issues make it difficult to achieve recycling and reuse.
1.1 Collection, storage, and transportation issues
Although the annual production of catalysts in China reached over 340000 cubic meters in 2014, and the accumulated amount of discarded catalysts over the years can be said to be close to astronomical figures, these catalysts are distributed throughout the country and in different industries, such as power plants and chemical plants. Moreover, in situations where the time of damage is uncertain, it is difficult to collect and handle it all in a unified manner; Secondly, there is the issue of storage, where a large amount of heavy metal dust is attached to discarded catalysts. How to effectively store them and prevent secondary pollution of heavy metals and dust; The third transportation problem is that due to the large amount of dust containing heavy metals attached to the surface of the catalyst, especially during long-distance transportation, it is difficult to ensure that the dust does not fly everywhere, which becomes a mobile pollution source and pollutes the surrounding environment.
1.2 Complex ingredients, difficult to separate, and recyclable
Catalyst production involves mixing, shaping, drying, calcining, and cutting TiO2, V2O5, WO3, MoO3, and other materials. Its main components are shown in Table 2.
From the table, it can be seen that the main costs of catalysts are TiO2, V2O5, WO3, MoO3, etc. However, it is difficult to separate titanium, vanadium, molybdenum, tungsten, etc., especially since molybdenum and tungsten are both lanthanide elements with similar properties, making it more difficult to separate them.
1.3 Factory scale and site selection
If industrial recovery is carried out using waste catalysts as raw materials, a fixed production scale is required to maintain its normal production. The sufficient supply of raw materials for discarded catalysts is a prerequisite for ensuring industrialization. But in reality, it is difficult to obtain sufficient waste catalysts as raw materials to ensure continuous production. With 3 × For example, for a 600MW unit, each unit requires approximately 600m3 of catalyst. Generally, the catalyst has a service life of about three years (without considering regeneration, if the regeneration time is longer), then approximately 1800m3 of waste catalyst is available every three years. This obviously cannot maintain the normal production of the enterprise. Although the annual production of domestically produced catalysts reaches several hundred thousand cubic meters, and the accumulated amount of discarded catalysts over the years can be said to be close to astronomical figures, these catalysts are distributed throughout the country and in different industries, such as power plants and chemical plants. Moreover, it is difficult to collect and handle all the damages in a situation where the time of damage is uncertain. Therefore, the determination of production scale and factory location is crucial.
Due to the inability of a single power plant to meet production needs with discarded catalysts. So, multiple power plants and cement plants are needed to ensure normal production, so the site should be selected with multiple nearby power plants (or cement plants). Reduce transportation costs while preventing the generation of new mobile pollution sources.
1.4 Disposal of heavy metals in dust
The discarded catalyst adheres to a large amount of dust as shown in the figure, which contains a large amount of heavy metals. The disposal of these dust containing heavy metals has become a difficult and challenging problem to solve.
2. Landfill
Landfilling is a simple way to solve waste catalysts. However, in the recently released "Technical Specification for Thermal Power Plant Smoke Denitration Engineering - Selective Catalytic Reduction Method", the treatment method for SCR waste catalysts is crushing and landfill. However, SCR waste catalysts are classified as hazardous solid waste and cannot be disposed of arbitrarily due to the presence of toxic metals such as V2O5 and WO3, as well as heavy metals attached during use, According to the Special Provisions on the Prevention and Control of Hazardous Waste Pollution in the Solid Waste Pollution Environmental Prevention and Control Law of China, the regulations stipulate that units producing hazardous waste must bear the disposal costs. This indicates that power plants, chemical plants, and other units that use denitrification catalysts, as well as denitrification engineering companies (as the implementation and operation and maintenance units of denitrification projects), must bear the disposal costs of SCR waste catalysts, This will undoubtedly impose an economic burden on power plants, chemical plants, and engineering companies. In fact, the landfill treatment method does not comply with the requirements of the Recycling and Resource Utilization Industry Model in the Circular Economy Promotion Law of the People's Republic of China. SCR waste catalysts themselves are resources with high recyclable value and should be recycled and reused.
3. Other methods
There are currently no reports on other treatment methods for SCR waste catalysts, which can be crushed and thoroughly mixed with cement to produce concrete products such as cement floor tiles, cement pipelines, and cement poles.
