Mercury recovery device and method

Abstract

The invention relates to the technical field of mercury-containing waste disposal and mercury resource recovery, in particular to a mercury recovery device and method. The invention provides a mercury recovery device which comprises a hopper 1, a metering scale 2 located below the hopper 1, a microwave plasma reactor 3 communicated with the hopper 1, a first-stage retarder 4 communicated with the microwave plasma reactor 3, a second-stage main condenser 5 communicated with the first-stage retarder 4 and a third-stage fine condenser 6 communicated with the second-stage main condenser 5. The monitoring system and the tail gas purifier 8 are sequentially communicated with the third-stage fine condenser 6; the mercury recovery device further comprises a collection bottle 7 communicated with the first-stage retarder 4, the second-stage main condenser 5 and the third-stage fine condenser 6. The device provided by the invention can realize rapid gasification and release of mercury in the mercury-containing waste, and efficient condensation in different areas, so that high-purity liquid mercury is directly obtained, and secondary conversion and complex post-treatment are avoided.

Description

Technical Field

[0001] This invention relates to the field of mercury-containing waste disposal and mercury resource recovery technology, specifically to a mercury recovery device and method. Background Technology

[0002] Mercury (Hg) is volatile and exists in multiple valence states and multiple forms (Hg0, Hg2, Hg3). 2+ Organic mercury (Methylmercury) readily migrates in the environment and bioaccumulates through the food chain. Methylmercury, in particular, poses significant risks to the central nervous system and fetal development and has been listed as a globally prioritized pollutant under the Minamata Convention. Various mercury-containing wastes mainly originate from mercury catalysts, waste batteries, fluorescent lamp powder, and metallurgical tailings. Data from the World Health Organization and the United Nations Environment Programme indicate that mercury can have toxic effects on the nervous, digestive, and immune systems, as well as the lungs, kidneys, skin, and eyes, with long-term exposure to MeHg posing a significant risk.

[0003] Currently, the main methods for the harmless treatment of mercury-containing waste are thermal desorption / vacuum distillation / dry distillation for mercury recovery and solidification / stabilization. Thermal desorption / vacuum distillation / dry distillation for mercury recovery involves heating mercury-containing solid waste or contaminated soil at temperatures up to 800°C, causing the mercury to volatilize and then condense for recovery, and incorporating tail gas dust removal, washing, and activated carbon adsorption units. This type of process has mature equipment and high recovery efficiency, but it suffers from high energy consumption, poor adaptability to high water content or viscous materials, and corrosion / safety issues with halogen systems. Furthermore, the removal of organic mercury and complexed mercury often requires higher temperatures or pretreatment, increasing overall operating costs. Solidification / stabilization treatment involves solidification with cement / asphalt, stabilization with phosphate ceramics (CBPC) and sulfur-containing / thiol-based adsorbents, or the final conversion of mercury into mercury compounds—mercury sulfide (HgS)—for "terminal" treatment. This can quickly reduce the risk of leaching. However, the long-term stability of the material treated by this method is affected by environmental media (such as high chloride / thiosulfate, dissolved organic matter, and sulfur / iron redox cycles), and there is still a risk of re-release. Furthermore, the overall cost of subsequent landfilling is high.

[0004] Besides the aforementioned high-temperature desorption and condensation recovery and landfill solidification methods, a related invention patent CN104032137 A utilizes chemical solution leaching to dissolve various forms of mercury in mercury-containing tailings in a thiosulfate solution. Alkali metal selenides are then added to the solution containing mercury and hexasulfate complex ions, converting the mercury into a stable, low-solubility, and low-toxicity mercury selenide precipitate. This method still follows the solidification approach, but the introduction of metal selenides introduces new metallic impurities into the solution; furthermore, during the solidification of the mercury complex, no solutions are provided for the potential re-release of other acid radicals (SO2, Cl2, etc.) present in the solution.

[0005] In summary, the difficulties in mercury recovery from existing mercury-containing waste are: (1) mercury is easily volatilized at room temperature, and direct thermal treatment poses a risk of secondary pollution; (2) the waste is loaded with components (oxides, sulfides, organic complexes); and (3) selective extraction of mercury is required to avoid the generation of large-scale byproducts, thereby increasing the risk of secondary pollution. Therefore, it is necessary to develop a new method and device for mercury recovery from mercury-containing waste. Summary of the Invention

[0006] In view of this, the present invention provides a mercury recovery device and method. The device provided by the present invention can realize the rapid vaporization and release of mercury in mercury-containing waste, efficient condensation in different zones, and thus directly obtain high-purity liquid mercury, avoiding secondary conversion and complex post-processing, and realizing efficient, clean and continuous resource recovery of mercury-containing waste.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: The present invention provides a mercury recovery device, including a hopper 1, a weighing scale 2 located below the hopper 1, a microwave plasma reactor 3 connected to the hopper 1, a primary retarder 4 connected to the microwave plasma reactor 3, a secondary main condenser 5 connected to the primary retarder 4, a tertiary fine condenser 6 connected to the secondary main condenser 5, and a monitoring system and an exhaust gas purifier 8 connected in sequence to the tertiary fine condenser 6. The mercury recovery device also includes a collection bottle 7 connected to the primary retarder 4, the secondary main condenser 5, and the tertiary fine condenser 6.

[0008] Preferably, the monitoring system includes an online mercury detector 9, a temperature sensor 10, a flow sensor 11, and a pressure sensor 12.

[0009] The present invention also provides a method for recovering mercury using the mercury recovery device described above, comprising the following steps: Mercury-containing waste is pretreated to obtain pretreated mercury-containing waste. The pretreated mercury-containing waste is continuously fed into a microwave plasma reactor, where plasma is generated under an inert atmosphere to treat the mercury-containing waste and release the mercury in the form of vapor. The tail gas carrying mercury is sequentially passed through a primary condenser, a secondary main condenser, and a tertiary fine condenser for condensation to obtain liquid mercury and the condensed tail gas; the liquid mercury is collected into a collection bottle. The condensed exhaust gas is purified by an exhaust gas purifier before being discharged.

[0010] Preferably, the pretreatment involves sequential crushing, sieving, and drying; the particle size of the powder after crushing and sieving is <2mm.

[0011] Preferably, the moisture content of the pretreated mercury-containing waste is <5%.

[0012] Preferably, the conditions for plasma treatment are: inert atmosphere: N2 or Ar; power: 0.5~3.0 kW; reaction pressure: 50~80 Pa; treatment temperature: 120~280℃; time: 2~15 min.

[0013] Preferably, the temperature of the primary retarder is set to 0~-20 ℃.

[0014] Preferably, the temperature of the secondary condenser is set to -50 to -80 ℃.

[0015] Preferably, the temperature for the three-stage fine condensation is set to -90 to -120 ℃.

[0016] Compared with the prior art, the present invention has the following advantages: (1) This invention proposes a novel “microwave plasma-assisted release” method, which utilizes high-energy electrons and active particles in plasma to break chemical bonds such as Hg-S, Hg-O, and Hg-Cl at relatively low temperatures (120~280℃) to achieve rapid vaporization and release of mercury in mercury-containing waste, significantly reducing energy consumption and shortening the treatment cycle.

[0017] (2) The present invention proposes a “multi-stage cold trap fine condensation” strategy, which introduces mercury vapor into cold traps of different temperature zones (0~-20℃, -50~-80℃, -90~-120℃) in sequence to achieve efficient condensation in zones, and obtains high-purity liquid mercury directly in the collection bottle, avoiding secondary conversion and complex post-processing.

[0018] (3) By adding a tail gas purification and monitoring system after the three-stage cold trap, the present invention not only ensures that the mercury concentration in the tail gas is stable and meets the standard for a long time, but also allows the device to switch flexibly between continuous and intermittent operation modes, which has good adaptability and industrial promotion value. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a mercury recovery device, where 1-hopper, 2-weighing scale, 3-microwave plasma reactor, 4-primary retarder, 5-secondary main condenser, 6-tertiary fine condenser, 7-collection bottle, 8-tail gas purifier, 9-online mercury detector, 10-temperature sensor, 11-flow sensor, and 12-pressure sensor. Detailed Implementation

[0020] This invention provides a mercury recovery device (see...) Figure 1The system includes a hopper 1, a weighing scale 2 located below the hopper 1, a microwave plasma reactor 3 connected to the hopper 1, a primary retarder 4 connected to the microwave plasma reactor 3, a secondary main condenser 5 connected to the primary retarder 4, a tertiary fine condenser 6 connected to the secondary main condenser 5, and a monitoring system and an exhaust gas purifier 8 connected in sequence to the tertiary fine condenser 6. The mercury recovery device also includes a collection bottle 7 connected to the primary retarder 4, the secondary main condenser 5, and the tertiary fine condenser 6.

[0021] In one embodiment of the present invention, the monitoring system includes an online mercury detector 9, a temperature sensor 10, a flow sensor 11, and a pressure sensor 12. In another embodiment of the present invention, the exhaust gas purifier 8 is preferably an activated carbon bed.

[0022] The present invention also provides a method for recovering mercury using the mercury recovery device described above, comprising the following steps: Mercury-containing waste is pretreated to obtain pretreated mercury-containing waste. The pretreated mercury-containing waste is continuously fed into a microwave plasma reactor, where plasma is generated under an inert atmosphere to treat the mercury-containing waste and release the mercury in the form of vapor. The tail gas carrying mercury is sequentially passed through a primary condenser, a secondary main condenser, and a tertiary fine condenser for condensation to obtain liquid mercury and the condensed tail gas; the liquid mercury is collected into a collection bottle. The condensed exhaust gas is purified by an exhaust gas purifier before being discharged. In one embodiment of the present invention, the pretreatment is preferably performed by crushing, sieving, and drying in sequence; the drying is preferably carried out under a protective atmosphere; the particle size of the powder after crushing and sieving is less than 2 mm; and the protective atmosphere is preferably N2 or Ar.

[0023] In one embodiment of the present invention, the moisture content of the pretreated mercury-containing waste is <5%; As one embodiment of the present invention, the preferred conditions for plasma treatment are: inert atmosphere: N2 or Ar; power: 0.5~3.0 kW; reaction pressure: 50~80 Pa; treatment temperature: 120~280 ℃; and time: 2~15 min.

[0024] In one embodiment of the present invention, the temperature of the primary retarder is preferably set to 0~-20℃, the temperature of the secondary primary condenser is preferably set to -50~-80℃, and the temperature of the tertiary fine condenser is preferably set to -90~-120℃.

[0025] In this invention, mercury-carrying exhaust gas is sequentially passed through a three-stage cold trap: a first-stage condenser to remove water vapor / high-boiling impurities; a second-stage main condenser to condense and recover the main mercury; and a third-stage fine condenser to capture trace amounts of mercury. Liquid mercury can be directly obtained from the collection bottles at the second and third-stage cold traps (i.e., the second-stage main condenser 5 and the third-stage fine condenser 6); condensate can be collected from the collection bottle at the first-stage cold trap (first-stage condenser 4).

[0026] To further illustrate the present invention, the technical content provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0027] Example 1 The mercury-containing waste was crushed and sieved (the particle size of the sieved waste was 1 mm) and dried under a nitrogen atmosphere to obtain pretreated mercury-containing waste with a moisture content of 3%. The pretreated mercury-containing waste was continuously fed into a microwave plasma reactor, where stable plasma was generated under nitrogen atmosphere to treat the mercury-containing waste (power: 1 kW, reaction pressure: 60 Pa, plasma treatment time: 10 min), causing the mercury to be released in the form of vapor. The tail gas carrying mercury is sequentially passed through a primary retarder (temperature -20℃), a secondary main condenser (temperature -50℃), and a tertiary fine condenser (temperature -90℃) for condensation to obtain liquid mercury and the condensed tail gas; the liquid mercury is collected in a collection bottle with a purity of 90%; The condensed exhaust gas is purified by an activated carbon bed before being discharged, and the mercury concentration at the outlet is consistently within the standard.

[0028] The above process uses a monitoring system (online mercury detector, temperature sensor, flow sensor, and pressure sensor) to automatically and dynamically adjust microwave power, gas flow rate, and cold trap load to monitor mercury concentration, reaction chamber pressure, cold trap (first-stage retarder, second-stage main condenser, and third-stage fine condenser) and pipeline flow signals.

[0029] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A mercury recovery device, comprising a hopper (1), a weighing scale (2) located below the hopper (1), a microwave plasma reactor (3) connected to the hopper (1), a primary retarder (4) connected to the microwave plasma reactor (3), a secondary main condenser (5) connected to the primary retarder (4), a tertiary fine condenser (6) connected to the secondary main condenser (5), a monitoring system and a tail gas purifier (8) sequentially connected to the tertiary fine condenser (6); The mercury recovery device also includes a collection bottle (7) connected to the primary retarder (4), the secondary main condenser (5), and the tertiary fine condenser (6).

2. The mercury recovery device according to claim 1, characterized in that, The monitoring system includes an online mercury detector (9), a temperature sensor (10), a flow sensor (11), and a pressure sensor (12).

3. A method for recovering mercury using the mercury recovery device described above, comprising the following steps: Mercury-containing waste is pretreated to obtain pretreated mercury-containing waste. The pretreated mercury-containing waste is continuously fed into a microwave plasma reactor, where plasma is generated under an inert atmosphere to treat the mercury-containing waste and release the mercury in the form of vapor. The tail gas carrying mercury is sequentially passed through a primary condenser, a secondary main condenser, and a tertiary fine condenser for condensation to obtain liquid mercury and the condensed tail gas; the liquid mercury is collected into a collection bottle. The condensed exhaust gas is purified by an exhaust gas purifier before being discharged.

4. The method according to claim 3, characterized in that, The pretreatment involves sequential crushing, sieving, and drying; the particle size of the powder after crushing and sieving is <2 mm.

5. The method according to claim 3, characterized in that, The moisture content of the pretreated mercury-containing waste is <5%.

6. The method according to claim 3, characterized in that, The conditions for plasma treatment are as follows: inert atmosphere: N2 or Ar; power: 0.5~3.0 kW; reaction pressure: 50~80 Pa; treatment temperature: 120~280℃; time: 2~15 min.

7. The method according to claim 3, characterized in that, The temperature of the primary retarder is set to 0~-20 ℃.

8. The method according to claim 3, characterized in that, The temperature of the secondary condenser is set to -50 to -80 ℃.

9. The method according to claim 3, characterized in that, The temperature for the three-stage fine condensation is set to -90 to -120 ℃.

Images