Recovery method and recovery device for mercury in mercury-containing solid waste

Abstract

The invention discloses a method and a device for recovering mercury in mercury-containing solid waste, the method comprises the following steps: the mercury-containing solid waste is sequentially subjected to first-stage dry distillation and second-stage dry distillation in an air atmosphere to obtain pyrolysis gas, the temperature of the first-stage dry distillation is lower than that of the second-stage dry distillation, and the pyrolysis gas is sequentially subjected to first-stage condensation and second-stage condensation to obtain the mercury in the mercury-containing solid waste. The method comprises the following steps: purifying crude mercury to obtain liquid crude mercury and gaseous tail gas, purifying the liquid crude mercury, and treating the gaseous tail gas by using metal oxide modified activated carbon to complete recovery of mercury in mercury-containing solid waste. According to the method, when the metal oxide modified activated carbon acts with SO2, adsorption of pyrolyzed SO2 is achieved, design is reasonable, operation is convenient and fast, and the recovery rate is high.

Description

Technical Field

[0001] This invention belongs to the field of mercury-containing solid waste recycling technology, and relates to a method and device for recycling mercury from mercury-containing solid waste. Background Technology

[0002] Mercury and many of its compounds are highly toxic, with elemental mercury classified as a Class I (extremely hazardous) toxic substance. For example, expired mercury removal agents from gas fields, mercury-containing zinc-manganese batteries, mercury-containing fluorescent lamps, mercuric chloride catalysts, and dehydrated mercury-containing sludge all contain a certain amount of mercury. In particular, natural gas mercury removal agents are mostly non-renewable. These non-renewable agents are primarily sulfur-loaded activated carbon and metal sulfides. While metal sulfides have some mercury removal effect, the material after mercury removal using metal sulfides becomes hazardous waste if not effectively treated. Furthermore, with the increasing operation of high-mercury-content gas fields, the use of mercury removal agents is also increasing, resulting in a large amount of expired mercury removal agents. Expired mercury removal agents contain almost no hydrocarbon organic matter; the mercury exists mainly in the form of HgS, making it a type of mercury-containing hazardous waste. To reduce the impact of expired mercury removal agents on the environment and human health, further harmless treatment is necessary. Theoretically, HgS can be dissolved by aqua regia or aerobic pyrolysis, but aqua regia will simultaneously dissolve activated carbon, complicating subsequent processes and wasting activated carbon. In addition, some methods for regenerating metal sulfide mercury removal agents have been reported. Chinese patent application CN106215843A discloses a method for regenerating a copper-based mercury removal agent. This involves mixing the agent with CuCl2 / SiO2, introducing a mixture of HCl, N2, and O2, performing high-temperature mercury removal, followed by sieving, ultrasonic acid washing, sulfur-based / hydroxyl impregnation, low-temperature drying, and calcination to obtain the regenerated copper-based mercury removal agent. However, this method is complex, consumes large amounts of resources and energy, and generates significant amounts of wastewater, making it difficult for industrial application. Chinese patent application CN109092277A discloses a method for regenerating metal sulfide mercury removal agents (lead, zinc, copper, iron, manganese, molybdenum, cobalt, nickel, etc.) using heated mercury removal and CuCl2 / SiO2. 2+ The solution immersion activation regeneration method adds immersion, filtration, washing, and drying processes, and generates a large amount of wastewater. Most of these methods focus on the regeneration of mercury removal agents, while mercury recovery from these agents is rarely mentioned. However, mercury recovery makes a significant contribution to resource reuse and sustainable development.

[0003] In addition, regarding mercury recovery devices, Chinese patent application CN109043898A discloses an indirect thermal desorption remediation system and method for treating mercury-containing solid waste and soil. This method includes a feeding unit, a thermal desorption unit, a high-temperature dust removal unit, a tail gas treatment unit, a process water treatment unit, and a discharge unit. This method is specifically designed for mercury-containing solid waste and mercury-contaminated soil in the chlor-alkali industry. Mercury in the treatment medium mainly exists in the form of HgCl, HgO, and elemental mercury. This invention can effectively treat these forms of mercury, and the pyrolysis process does not produce harmful SO2 tail gas. However, mercury in gas field mercury adsorbents mainly exists in the form of black HgS, which produces a large amount of SO2 during pyrolysis, causing secondary pollution. Chinese patent application CN106007297A discloses a thermal treatment method for mercury-containing sludge. The method includes a sludge conditioner, a dewatering machine, a screw conveyor, a heat exchange unit, a dust collector, a spray condenser, an aggregator, and a tail gas treatment device. This method is specifically designed for the harmless treatment of mercury-containing sludge from oil and gas fields. To reduce energy consumption, the method uses vacuum anaerobic pyrolysis, which is beneficial for the pyrolysis of mercury-containing sludge. However, the temperature required for anaerobic pyrolysis of HgS is higher than that for aerobic pyrolysis. If this device is used for the harmless treatment of expired mercury removal agents in gas fields, it will increase the energy consumption of the equipment. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method and apparatus for recovering mercury from mercury-containing solid waste, thereby solving the technical problem that existing methods for regenerating mercury-containing solid waste cannot effectively recover mercury, resulting in resource waste. At the same time, it also solves the technical problem that existing mercury recovery devices consume a lot of energy when processing mercury-containing solid waste, especially mercury from sulfur-containing mercury removal agents.

[0005] This invention is achieved through the following technical solution:

[0006] A method for recovering mercury from mercury-containing solid waste involves dry distillation of the mercury-containing solid waste in an air atmosphere to obtain pyrolysis gas, condensation treatment of the pyrolysis gas to obtain liquid crude mercury and gaseous tail gas, purification of the liquid crude mercury, and treatment of the gaseous tail gas with metal oxide-modified activated carbon to complete the recovery of mercury from the mercury-containing solid waste.

[0007] Preferably, the mercury-containing solid waste includes any one of the following: gas field demercured mercury removal agent, mercury-containing zinc-manganese battery, mercury-containing fluorescent lamp, mercuric chloride catalyst, and dehydrated mercury-containing sludge; the moisture content of the mercury-containing solid waste is not greater than 20%.

[0008] Preferably, the dry distillation includes primary dry distillation and secondary dry distillation; the temperature of the primary dry distillation is lower than the temperature of the secondary dry distillation; the condensation includes primary condensation and secondary condensation.

[0009] Preferably, before performing primary dry distillation on the mercury-containing solid waste, the mercury-containing solid waste is pulverized, and the size of the pulverized mercury-containing solid waste is 10-40 mm.

[0010] Preferably, the temperature of the first-stage dry distillation is 100-200℃ and the time is 20-30 min; the temperature of the second-stage dry distillation is 600-750℃ and the time is 40-60 min.

[0011] Preferably, during the first-stage condensation, the temperature of the pyrolysis gas is reduced to 80-90°C; during the second-stage condensation, the temperature of the pyrolysis gas is reduced to 25-30°C.

[0012] Preferably, the liquid crude mercury is purified using a solid-liquid separation mercury removal ecological membrane.

[0013] Preferably, the metal oxide in the metal oxide-modified activated carbon is at least one of Al2O3 and CuO.

[0014] A recovery apparatus for implementing the above-mentioned recovery method includes a feed assembly, a dry distillation system, a mercury recovery system, and a tail gas treatment system that are sequentially and sealed together.

[0015] The feed inlet of the pyrolysis system is connected to the feed assembly;

[0016] The mercury recovery system includes a condensation component and a liquid mercury purification component connected together, and the inlet of the condensation component is connected to the outlet of the dry distillation system.

[0017] The exhaust gas treatment system includes a desulfurization component, which contains a metal oxide-modified activated carbon adsorption component; the gas phase outlet of the condensation component is connected to the inlet of the desulfurization component.

[0018] The condensation assembly includes a primary condensation assembly and a secondary condensation assembly connected in sequence; the feed inlet of the primary condensation assembly is connected to the discharge outlet of the dry distillation system, and the gas phase discharge outlet of the secondary condensation assembly is connected to the feed inlet of the desulfurization assembly.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] This invention discloses a method for recovering mercury from mercury-containing solid waste. The method involves removing free water, low-boiling-point substances, bound water, elemental mercury, and hydrocarbon organic matter from the mercury-containing solid waste through dry distillation. The dry distillation process is carried out in air, where HgS in the mercury-containing solid waste undergoes a continuous oxidation reaction with oxygen in the air at high temperature, yielding a pyrolysis gas containing gaseous HgO and SO2. The gaseous HgO and SO2 are then condensed sequentially. Under a continuously low-temperature environment, the gaseous HgO rapidly decomposes into liquid elemental mercury and oxygen. The liquid elemental mercury is purified and collected, while the SO2 in the pyrolysis gas is adsorbed by metal oxide-modified activated carbon. When the metal oxide-modified activated carbon reacts with SO2, its porous structure increases the adsorption area, and the metal oxide further oxidizes the SO2 to SO4. 2- This method enables the recovery of mercury from mercury-containing solid waste. It is reasonably designed, easy to operate, and has a high recovery rate.

[0021] Furthermore, the mercury-containing solid waste includes any one of the following: gas field demercured mercury removal agent, mercury-containing zinc-manganese battery, mercury-containing fluorescent lamp, mercuric chloride catalyst, and dehydrated mercury-containing sludge. The moisture content of the mercury-containing solid waste is no more than 20%, which allows the moisture to be quickly evaporated during primary dry distillation.

[0022] Furthermore, the pyrolysis includes primary pyrolysis and secondary pyrolysis; the temperature of the primary pyrolysis is lower than that of the secondary pyrolysis; primary pyrolysis is carried out at a lower temperature to remove free water contained in mercury-containing solid waste, and secondary pyrolysis is carried out again at a higher temperature to remove low-boiling-point substances, bound water, elemental mercury, and hydrocarbon organic matter, which can effectively save energy, reduce energy consumption, and improve the effect of pyrolysis.

[0023] Furthermore, before performing primary dry distillation on the mercury-containing solid waste, the mercury-containing solid waste is pulverized. After pulverization, the size of the mercury-containing solid waste is 10-40 mm, which reduces the diameter of the raw material particles and improves the effect of subsequent dry distillation.

[0024] Furthermore, the temperature of the first-stage dry distillation is 100–200°C and the time is 20–30 min, which can remove most of the water and elemental mercury from the mercury-containing solid waste; the temperature of the second-stage dry distillation is 600–750°C and the time is 40–60 min, which can pyrolyze the HgO in the mercury-containing solid waste into mercury vapor.

[0025] Furthermore, during the first-stage condensation, the temperature of the pyrolysis gas is reduced to 80-90°C; during the second-stage condensation, the temperature of the pyrolysis gas is reduced to 25-30°C, which allows the mercury vapor in the flue gas to be cooled and transformed into liquid mercury.

[0026] Furthermore, the use of a solid-liquid separation mercury removal ecological membrane to purify the liquid crude mercury can further purify the crude mercury and remove its associated minute impurities.

[0027] Furthermore, the metal oxide in the metal oxide-modified activated carbon is at least one of Al2O3 and CuO, which can reduce SO2 in the exhaust gas to the level permissible for atmospheric emissions.

[0028] In addition, this invention also discloses a recovery device for implementing the above-mentioned recovery method, comprising a feeding assembly, a pyrolysis system, a mercury recovery system, and a tail gas treatment system connected in sequence and sealed. The pyrolysis system is used to perform the pyrolysis process of the material. The mercury recovery system includes a condensation assembly and a liquid mercury purification assembly connected together, effectively realizing the condensation of the pyrolysis gas after pyrolysis and the decomposition and recovery of gaseous mercury oxide. The metal oxide-modified activated carbon adsorption assembly in the tail gas treatment system effectively solves the treatment of sulfur dioxide tail gas, effectively avoiding secondary pollution caused by the tail gas. This device has a simple structure, reasonable design, high recovery rate, secondary purification, and low pollution, and has broad application and promotion value.

[0029] Furthermore, the condensation assembly includes a primary condensation assembly and a secondary condensation assembly connected in sequence; the inlet of the primary condensation assembly is connected to the outlet of the dry distillation system, and the gas phase outlet of the secondary condensation assembly is connected to the inlet of the desulfurization assembly, effectively achieving full condensation of the material. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic flowchart of a method for mercury recovery from mercury-containing solid waste according to the present invention;

[0032] Figure 2 This is a schematic diagram of a mercury recovery device for mercury-containing solid waste according to the present invention;

[0033] Figure 3 This is a schematic diagram of the structure of the dry distillation component in this invention.

[0034] The components are as follows: 1. Feeding assembly, 2. Crushing assembly, 3. Screw conveyor belt, 4. Dry distillation assembly, 5. Air purging port, 6. Collection hopper, 7. Residue collection tank, 8. Fuel gas inlet, 9. Micron-level thermal filter, 10. Primary condenser assembly, 11. Secondary condenser assembly, 12. Settling tank, 13. Hydrocyclone, 14. Liquid mercury purification assembly, 15. Pump, 16. Mercury collection tank, 17. Demister, 18. Desulfurization assembly, 19. Mercury deep adsorber, 41. Dry distillation chamber, 42. Dry distillation gas outlet, 43. Feed inlet, 44. Heating gap, 45. Flue gas outlet, 46. Discharge outlet. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0036] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0037] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0038] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0039] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0040] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0041] The present invention will now be described in further detail with reference to the accompanying drawings:

[0042] Example 1

[0043] like Figure 1 As shown, this invention discloses a method for recovering mercury from mercury-containing solid waste, comprising the following steps:

[0044] S1: Mercury-containing solid waste is dry distilled in air to obtain pyrolysis gas;

[0045] S2: The pyrolysis gas is condensed to obtain liquid crude mercury and gaseous tail gas;

[0046] S3: The liquid crude mercury is purified, and the gaseous tail gas is treated with activated carbon modified with metal oxides to complete the recovery of mercury from mercury-containing solid waste.

[0047] This invention discloses a method for recovering mercury from a failed mercury removal agent. Specifically, the method involves: passing mercury-containing solid waste through a primary and secondary dry distillation process in air to obtain pyrolysis gas, wherein the temperature of the primary dry distillation is lower than that of the secondary dry distillation; passing the pyrolysis gas through a primary and secondary condensation process to obtain liquid crude mercury and gaseous tail gas; purifying the liquid crude mercury; and treating the gaseous tail gas with metal oxide-modified activated carbon to complete the recovery of mercury from the mercury-containing solid waste.

[0048] Taking the recovery of mercury from spent mercury removal agents as an example, when the carrier of the spent mercury removal agent is activated carbon, the main component of the pyrolysis residue after pyrolysis is coke; when the carrier is Al2O3, since Al2O3 has a decomposition temperature of 2056℃ and is extremely stable, the pyrolysis residue is Al2O3. The chemical reaction of the pyrolysis reaction is as follows:

[0049]

[0050] The mercury-containing solid waste in this invention can be any of the following: mercury removal agents from gas fields, mercury-containing zinc-manganese batteries, mercury-containing fluorescent lamps, mercuric chloride catalysts, and dehydrated mercury-containing sludge. The moisture content of the aforementioned mercury-containing solid waste is no more than 20%. The moisture content of mercury-containing solid waste refers to the mass ratio of water in the waste, that is, the ratio of the mass of water contained in the material to the mass of the material after drying. This indicator helps to understand the humidity level of the mercury-containing solid waste, thus providing a reference for its treatment and disposal. In this invention, the moisture content of the mercury-containing solid waste is no more than 20%, which allows for rapid evaporation of water during primary distillation, improving treatment efficiency.

[0051] More preferably, the mercury-containing solid waste is pulverized before primary pyrolysis. This pulverization process is typically performed on the solid waste before primary pyrolysis. The purpose of this step is primarily to improve the efficiency and effectiveness of pyrolysis, ensuring that mercury and its compounds in the solid waste can be more effectively recovered or treated. Pulverization can be achieved through various methods, such as mechanical crushing and grinding. These methods break the solid waste into smaller particles or powder, thereby increasing the contact area between the solid waste and the heat source, allowing the organic matter and mercury and its compounds in the solid waste to be decomposed more quickly and completely during pyrolysis. Pulverization improves pyrolysis efficiency; the pulverized solid waste has a larger specific surface area, enabling it to receive and transfer heat more quickly, thus increasing the reaction rate and efficiency of pyrolysis. Furthermore, it promotes mercury recovery. Mercury and its compounds typically exist in solid or liquid forms in solid waste; pulverization disrupts the physical structure of these substances, making them easier to release and recover during pyrolysis. It can also reduce energy consumption. Because the pulverization process improves the pyrolysis efficiency of solid waste, more solid waste can be processed in the same amount of time, thus reducing equipment operating time and energy consumption. Simultaneously, it reduces environmental pollution. By combining pulverization and primary pyrolysis, harmful substances in solid waste can be converted into forms that are easier to treat or recycle, thereby reducing environmental pollution and harm. Pulverization before primary pyrolysis of mercury-containing solid waste is an important pretreatment step that improves the efficiency and effectiveness of pyrolysis, ensuring that mercury and its compounds in the solid waste can be more effectively recovered or treated. In this invention, the size of the mercury-containing solid waste after pulverization is 10–40 mm, which reduces the particle diameter of the raw material and improves the effect of subsequent pyrolysis.

[0052] Dry distillation is a reaction process in which solids or organic matter are heated and decomposed under anaerobic conditions. This process produces various gases, vapors, and solid residues. A mixture of gases and vapors can be separated into gaseous and liquid components upon cooling. Dry distillation of mercury-containing solid waste refers to heating mercury-containing solid waste under anaerobic or low-air conditions to decompose the organic matter and generate high-temperature gases. During this process, mercury and its compounds may volatilize along with the decomposition of organic matter, thus allowing for collection and treatment. Because anaerobic treatment involves high temperatures and high energy consumption, this invention employs dry distillation in an air atmosphere. During dry distillation, temperature and time must be carefully controlled to ensure that mercury and its compounds can be effectively volatilized and collected. In a preferred embodiment of this invention, the temperature of the first-stage dry distillation is 100–200°C, and the time is 20–30 minutes, which allows most of the water and elemental mercury to be removed from the mercury-containing solid waste; the temperature of the second-stage dry distillation is 600–750°C, and the time is 40–60 minutes, which allows the HgO in the mercury-containing solid waste to pyrolyze into mercury vapor.

[0053] The pyrolysis gas from the dry distillation of mercury-containing solid waste undergoes a primary condenser and a secondary condenser to obtain liquid crude mercury and gaseous tail gas. During the dry distillation of mercury-containing solid waste, the organic matter in the waste decomposes under high-temperature treatment, while mercury and its compounds volatilize to form pyrolysis gas. This pyrolysis gas then undergoes a condensation step to separate and recover the mercury. Specifically, the pyrolysis gas first undergoes a primary condenser. In the primary condenser, the higher-temperature pyrolysis gas is cooled, causing some of the mercury vapor to condense into liquid, forming liquid crude mercury. Liquid crude mercury is the initial mercury product recovered, but it may still contain other impurities and requires further purification. After the primary condenser, the pyrolysis gas still contains uncondensed mercury vapor and other gaseous components. These gases then enter the secondary condenser. In the secondary condenser, the pyrolysis gas is further cooled, causing the remaining mercury vapor to condense into purer liquid or solid mercury. Simultaneously, other gaseous components are also condensed, forming gaseous tail gas. Gaseous exhaust gases may contain uncondensed mercury vapor, other volatile organic compounds, and inorganic gases. These exhaust gases require further treatment to prevent the release of mercury vapor and other harmful substances into the atmosphere and causing pollution. Through the combined action of primary and secondary condensation, mercury in mercury-containing solid waste can be effectively recovered, reducing its environmental harm and providing a possibility for the resource utilization of mercury-containing solid waste. In this invention, after primary condensation, the temperature of the pyrolysis gas is reduced to 80–90°C, and after secondary condensation, the temperature of the pyrolysis gas is reduced to 25–30°C.

[0054] After completing the above steps, the liquid crude mercury is purified, and the gaseous tail gas is treated with activated carbon modified with metal oxides to complete the recovery of mercury from mercury-containing solid waste.

[0055] After completing the dry distillation, primary condensation, and secondary condensation steps of mercury-containing solid waste, the resulting liquid crude mercury needs to be further purified to obtain higher purity mercury. At the same time, the gaseous tail gas also needs to be treated to remove mercury vapor and other harmful substances.

[0056] Generally, the purification of liquid crude mercury involves multiple steps, including distillation, electrolytic refining, and chemical refining. These steps aim to remove impurities from the crude mercury, such as other metals, non-metallic elements, and organic matter, to improve the purity of the mercury. Distillation is a commonly used method for purifying liquid metals. By heating the liquid crude mercury, the mercury vapor is volatilized and then condensed and collected. Since different substances have different boiling points, mercury can be separated from other impurities by controlling the temperature and pressure of distillation. Electrolytic refining is another commonly used purification method. In electrolytic refining, liquid crude mercury is used as the anode, while pure mercury or other inert metals are used as the cathode. During electrolysis, mercury ions are reduced to pure mercury at the cathode, while impurities remain at the anode or are electrolyzed into other substances. Chemical refining is a method of removing impurities from crude mercury through chemical reactions. For example, certain chemical reagents can be used to react with impurities, generating soluble compounds or precipitates, which are then separated from the mercury through steps such as filtration and washing. The above-mentioned purification methods are all relatively complex and inefficient. The present invention preferably uses a solid-liquid separation mercury removal ecological membrane to purify the liquid crude mercury. Using a solid-liquid separation mercury removal ecological membrane to purify liquid crude mercury is an advanced purification technology. It combines the principles of solid-liquid separation and the selective permeability of ecological membranes, which can effectively remove impurities from liquid crude mercury and improve the purity of mercury.

[0057] The solid-liquid separation mercury removal ecological membrane is a special membrane material with high selectivity and permeability, allowing mercury molecules to pass through while blocking other impurity molecules. In the purification process, liquid crude mercury is fed into a device containing the solid-liquid separation mercury removal ecological membrane. On one side of the membrane, the liquid crude mercury contacts the membrane, while the other side is a container for collecting pure mercury. When the liquid crude mercury flows through the solid-liquid separation mercury removal ecological membrane, mercury molecules, due to their small size and high chemical affinity, pass through the membrane pores into the pure mercury collection container. Simultaneously, due to the membrane's selective permeability, other impurity molecules, such as metal ions, non-metallic elements, and organic matter, are blocked on the other side of the membrane, thus achieving the separation of mercury from impurities. The high selectivity of the solid-liquid separation mercury removal ecological membrane ensures the collection of high-purity mercury while reducing the content of impurities. Secondly, the method is simple to operate, requiring no complex equipment or chemical reagents, reducing production costs and environmental pollution. Furthermore, the solid-liquid separation mercury removal ecological membrane has good stability and reusability, maintaining high purification efficiency over a long period. Using a solid-liquid separation and mercury removal ecological membrane to purify liquid crude mercury can efficiently remove impurities from the liquid crude mercury, improve the purity of mercury, and provide strong support for the resource utilization of mercury-containing solid waste.

[0058] In this invention, mercury in the mercury-containing solid waste mainly exists as mercury sulfide. Therefore, after dry distillation, the gaseous tail gas is mainly sulfur dioxide. Activated carbon is a porous material with a large specific surface area and adsorption capacity. By loading metal oxides (such as Al2O3 and / or CuO) onto its surface, its adsorption capacity for sulfur dioxide can be further enhanced. This is because metal oxides and sulfur dioxide can undergo a chemical reaction to form stable compounds, which are then adsorbed by the activated carbon. The metal oxides (such as Al2O3 and CuO) loaded on the activated carbon surface can act as catalysts, promoting the reaction of sulfur dioxide with oxygen to produce sulfuric acid or sulfates. These reaction products form stable compounds on the activated carbon surface, thereby achieving effective adsorption of sulfur dioxide. Loading with metal oxides can also improve the surface properties of activated carbon, increasing its active sites and polarity, further enhancing its adsorption capacity for sulfur dioxide. Simultaneously, activated carbon loaded with metal oxides also exhibits good thermal and chemical stability, maintaining high adsorption performance over a wide range of temperature and chemical environments. By loading metal oxides (such as Al2O3 and / or CuO) onto the surface of activated carbon, its adsorption capacity for sulfur dioxide in the tail gas after the dry distillation of mercury sulfide solid waste can be significantly improved, providing an efficient and environmentally friendly method for the resource utilization of mercury-containing solid waste.

[0059] Example 2

[0060] like Figure 2 As shown, the present invention also discloses a recovery device for implementing the above-mentioned recovery method, comprising a feed assembly 1, a dry distillation system, a mercury recovery system, and a tail gas treatment system connected in sequence and sealed together; the dry distillation system includes a dry distillation assembly 4, the inlet of which is connected to the feed assembly 1; the mercury recovery system includes a primary condensation assembly 10, a secondary condensation assembly 11, and a liquid mercury purification assembly 14 connected in sequence; the inlet of the primary condensation assembly 10 is connected to the outlet of the dry distillation assembly 4; the tail gas treatment system includes a desulfurization assembly 18, which contains a metal oxide-modified activated carbon adsorption assembly; the gas phase outlet of the secondary condensation assembly 11 is connected to the inlet of the desulfurization assembly 18. That is, the desulfurization assembly 18 can be an activated carbon desulfurization tower.

[0061] In a preferred embodiment, a crushing component 2 is further provided between the feeding assembly 1 and the dry distillation assembly 4. This crushing component 2 can be a crusher. Mass transfer between the feeding hopper and the crusher is achieved using a screw conveyor belt 3. Similarly, mass transfer between the crusher and the dry distillation system is also achieved using a screw conveyor belt 3. This is to prevent the processed medium from contacting air and to provide a closed environment. The crusher is a hammer mill that uses the relative motion between a high-speed rotating moving hammer and a fixed ring to crush solids. The feeding assembly 1 can be a feeding hopper. Mercury-containing solid waste enters the crusher via the feeding hopper and the screw conveyor belt 3 for crushing. The crushed, ineffective mercury removal agent is then conveyed in a closed system via the screw conveyor belt into the rotary dry distillation system.

[0062] The pyrolysis system is located after the crusher and includes a pyrolysis component 4, a collection hopper 6, and a residue collection tank 7. The pyrolysis component 4 can be a rotary pyrolysis furnace. The pyrolysis component 4 is equipped with an air purging port 5, which is connected to a blower. The solid phase outlet of the pyrolysis component 4 is connected to the collection hopper 6 and the residue collection tank 7, and the gas phase outlet is connected to the mercury recovery system. The pyrolysis component 4 adopts a rotary pyrolysis furnace, which stirs the spent mercury removal agent by rotating the furnace body while pyrolyzing it at high temperature, so that the pyrolysis is more complete.

[0063] This rotary distillation furnace mainly consists of an indirect heating system, a stirring system, a distillation chamber, and an air purging system, etc. Specifically, for example... Figure 3 As shown, the rotary distillation furnace includes a distillation chamber 41, which is equipped with an air purging port 5, a fuel gas inlet 8, a distillation gas outlet 42, and a feed inlet 43. The distillation chamber 41 includes an inner liner and an outer shell, with a heating gap 44 between the inner liner and the outer shell. The fuel gas inlet 8 is connected to the heating gap 44. The distillation chamber 41 also has a flue gas outlet 45 and a discharge port 46. High-temperature flue gas heats the material inside the furnace through the heating gap 44, while the air purging port 5 continuously blows air into the distillation chamber 41 to provide an oxygen-rich environment. The distillation gas exits from the distillation gas outlet 42 to the high-temperature dust filter, and the residue after distillation is sent to a residue collection tank from the discharge port 46.

[0064] The mercury recovery system and tail gas treatment system are located downstream of the pyrolysis system. The mercury recovery system mainly includes a primary condensation unit 10, a secondary condensation unit 11, and a liquid mercury purification unit 14. The liquid mercury purification unit 14 can be a high-efficiency solid-liquid separation mercury removal ecological membrane (VPI-UF). The cold source for the primary condensation unit 10 is air, and the cold source for the secondary condensation unit 11 is cooling water. When HgO in the tail gas comes into contact with the cold air, it can be rapidly decomposed into elemental mercury and oxygen. The elemental mercury condenses into mercury beads and enters the settling tank.

[0065] In a further preferred embodiment, a micron-level thermal filter 9 is included before the primary condenser assembly 10 to remove entrained solid ash and some mercury droplets. The integrated solid ash and mercury droplets are returned to the pyrolysis furnace. The pyrolysis gas, after ash removal, enters a two-stage condenser for condensation. Additionally, the mercury recovery system includes a settling tank 12, a hydrocyclone 13, and a mercury collection tank 16. Liquid mercury, after passing through the settling tank 12 and hydrocyclone 13, enters the liquid mercury purification assembly 14. Finally, the purified liquid mercury from the purification assembly 14 enters the mercury collection tank 16. A pump 15 is also provided between the liquid mercury purification assembly 14 and the settling tank 12, which allows cooling water to flow back into the settling tank.

[0066] The exhaust gas treatment system includes a desulfurization component 18, which contains a metal oxide-modified activated carbon adsorption component. The desulfurization component 18 can be an activated carbon adsorption tower. This recovery method generates a large amount of SO2, but the device operates intermittently and requires periodic start-up and shutdown. Dry activated carbon desulfurization is less affected by start-up and shutdown. Using metal oxide-modified activated carbon for adsorption, the activated carbon needs to be regenerated or replaced periodically after it becomes saturated with SO2. In addition, a demister 17 is installed before the desulfurization component 18, and a mercury deep adsorber 19 is installed after the desulfurization component 18.

[0067] Example 3

[0068] The mercury in the mercury-containing solid waste of this invention exists in the form of black mercuric sulfide. The decomposition temperature of black mercuric sulfide is around 300°C, and the final release temperature is around 600°C. Therefore, the temperature of the rotary distillation furnace is controlled at 600-750°C, and the pressure is atmospheric pressure. The furnace body keeps rotating during the entire operation of the distillation furnace. The heating source is provided by a natural gas burner. In the initial stage of distillation, the temperature inside the furnace is first controlled at around 100°C to remove the free water contained in the ineffective mercury removal agent. After the drying stage is completed, the temperature is gradually raised to around 650°C. During this process, the low-boiling-point substances in the ineffective mercury removal agent are released first, and the bound water, elemental mercury, and hydrocarbon organic matter are transferred to the pyrolysis gas in sequence. At the same time, the black HgS in the ineffective mercury removal agent reacts with the oxygen in the purge air at high temperature to generate gaseous HgO and SO2, which are transferred to the pyrolysis gas. The furnace temperature is maintained at around 650℃ and dry distillation is continued for 40 minutes. During this period, the pyrolysis flue gas is discharged from the top of the dry distillation furnace to the tail gas treatment unit. After the dry distillation is completed, the mercury removal agent residue from the pyrolysis enters the collection hopper 6 from the bottom of the dry distillation furnace and finally enters the mercury removal agent residue collection tank 7.

[0069] In the exhaust gas treatment unit, the pyrolysis gas first passes through a micron-level thermal filter 9 to remove the entrained solid ash and some mercury droplets. The integrated solid ash and mercury droplets are returned to the pyrolysis furnace. The pyrolysis gas with the ash removed enters a two-stage condenser for condensation. The first-stage condenser 10 uses air cooling to reduce the temperature of the pyrolysis gas to about 80°C, and the second-stage condenser 11 uses water cooling to reduce the temperature of the pyrolysis gas to 25°C. The HgO in the pyrolysis gas is rapidly decomposed into liquid mercury and oxygen upon cooling. In addition, the condensate also contains condensate water and a small amount of pyrolysis oil. The condensed droplets enter the settling tank 12 and are initially separated from the mercury using the principle of density difference. Then, the mercury is finely separated by a high-efficiency solid-liquid separation mercury removal ecological membrane and enters the mercury collection tank 16. The condensed non-condensable gas enters the demister 17 to remove the entrained suspended water and mercury droplets. Then, the desulfurization component 18 absorbs SO2 and other substances produced by the pyrolysis reaction. Finally, the gas is treated by the mercury deep adsorber 19 to meet the exhaust gas emission standards before being discharged into the atmosphere. Once activated carbon becomes saturated with SO2, it needs to be regenerated or replaced periodically.

[0070] In this invention, mercury-containing solid waste is first crushed into powder using a crusher before thermal treatment. This powder accelerates the reaction of HgS and oxygen during pyrolysis, reducing energy consumption. The mercury-containing solid waste is sealed from the feed hopper to the retort furnace. Once inside the furnace, air is continuously blown into the furnace through air purging ports, ensuring no mercury comes into contact with the outside environment and preventing mercury vapor leakage, thus guaranteeing safety. This method not only recovers mercury from the waste but also renders it harmless, yielding elemental mercury with economic value while avoiding environmental pollution. Metal oxide-modified activated carbon is used to adsorb SO2. The modified carbon material enriches its surface with SO2 adsorption sites and enhances its SO2 oxidation capacity. This invention enables the harmless treatment of expired mercury removal agents in gas fields, reduces processing energy consumption, saves third-party processing costs, and improves the economic benefits of gas fields.

[0071] Example 4

[0072] This embodiment takes a gas field expired mercury removal agent as an example. The processing volume of the expired mercury removal agent is 250 kg. The mercury exists in the form of black HgS. The total mercury content of the expired mercury removal agent before dry distillation is 18000 mg / kg, and the water content is ≤20% (if the water content is higher than 20%, dehydration treatment is required); the oil content is ≤10%.

[0073] After the spent mercury removal agent was treated by a dry distillation unit, the residue weighed 210 kg, a reduction of 16%; the mercury content after treatment was less than 1 mg / kg; according to the "Integrated Emission Standard for Air Pollutants," the mercury content in the exhaust gas emitted by the dry distillation unit should be less than 0.012 mg / m³. 3 SO2 content is less than 80 mg / m³ 3 .

[0074] The method for recovering mercury from the depleted mercury removal agent includes a feeding system for feeding and crushing the depleted mercury removal agent, a pyrolysis system for removing mercury from the depleted mercury removal agent, and a mercury recovery and tail gas treatment system for the pyrolysis gas. The depleted mercury removal agent or mercury-containing solid waste with a moisture content of less than 20% is fed into the crusher via a feed hopper and screw conveyor belt 3. The crushed depleted mercury removal agent is then fed into a rotary pyrolysis furnace via screw conveyor belt 3. After entering the pyrolysis furnace, the feed inlet is closed using a valve, the pyrolysis furnace is purged with air, the furnace is set to rotate, and the burner is turned on to heat the outside of the pyrolysis furnace. Indirect heating is achieved in the insulated combustion chamber by arranging burners fueled by natural gas, diesel, or propane. The furnace temperature is initially controlled at around 100°C to remove free water contained in the ineffective mercury removal agent. After the drying stage, the temperature is gradually increased to around 750°C. During this process, low-boiling-point substances in the ineffective mercury removal agent are released first, followed by bound water, elemental mercury, organic matter, and heavy hydrocarbons, which are then transferred to the pyrolysis gas. The furnace temperature is then maintained at around 750°C and dry distillation continues for 50 minutes. During this stage, HgS in the ineffective mercury removal agent undergoes a redox reaction with O2 in the air under high-temperature conditions to generate SO2 and gaseous HgO. While the dry distillation unit is operating, the dry distillation gas enters the micron-level thermal filter 9 from the dry distillation furnace to remove some of the entrained ash and mercury droplets. It then sequentially enters the primary condenser 10 to cool to 80°C, and the secondary condenser 11 to cool to 25°C. During condensation, gaseous HgO decomposes directly into liquid mercury and oxygen upon cooling. The non-condensable gas continues to enter the demister 17 to remove any entrained suspended water. The primary condenser 10, secondary condenser 11, and demister 17 separate droplets into a mixture of liquid mercury, oil, and water. This condensate enters the settling tank. Because mercury's density is much greater than that of water and oil, the liquid mercury collects at the bottom of the settling tank 12. After the settling tank 12 has been left to stand for a few minutes, the bottom valve is opened, allowing the liquid mercury to flow out from the bottom of the settling tank. Part of it is then returned through the hydrocyclone 13 and enters the high-efficiency solid-liquid separation and mercury removal ecological membrane for fine separation. The separated liquid mercury enters the mercury collection tank 16 for sealed storage, while the water is returned to the settling tank 12. The elemental mercury in mercury collection tank 16 may contain some dust or small amounts of other metals. It can be rinsed with a 10% nitric acid solution to obtain pure elemental mercury. After the non-condensable gas passes through demister 17 to remove entrained droplets, it enters the activated carbon desulfurization tower for desulfurization treatment. The non-condensable gas flows upwards within the tower. SO2 in the tail gas is first adsorbed by the activated carbon and then oxidized to SO3. The generated SO3 reacts with water vapor to produce sulfuric acid. When the activated carbon becomes saturated with SO2, it needs to be regenerated or replaced periodically. The desulfurized tail gas passes through a mercury deep adsorber 19 to remove residual mercury before being discharged into the atmosphere. The mercury content in the tail gas is less than 0.012 mg / m³. 3 SO2 content is less than 80 mg / m³ 3The process meets the requirements of the "Integrated Emission Standard for Air Pollutants". After the dry distillation is completed, stop the rotation of the dry distillation furnace and close the gas valve to stop the heating. Continue to purge the dry distillation furnace with air for 10 minutes to remove the residual dry distillation gas in the system. After the air purging is completed, open the valve at the bottom of the dry distillation furnace to discharge the pyrolysis residue of the ineffective mercury removal agent into the collection tank for storage.

[0075] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for recovering mercury from mercury-containing solid waste, characterized in that, Mercury-containing solid waste is dry-distilled in air to obtain pyrolysis gas. The pyrolysis gas is then condensed to obtain liquid crude mercury and gaseous tail gas. The liquid crude mercury is purified, and the gaseous tail gas is treated with activated carbon modified with metal oxides, thus completing the recovery of mercury from the mercury-containing solid waste.

2. The method for recovering mercury from mercury-containing solid waste according to claim 1, characterized in that, The mercury-containing solid waste includes any one of the following: gas field waste mercury removal agent, mercury-containing zinc-manganese battery, mercury-containing fluorescent lamp, mercuric chloride catalyst, and dehydrated mercury-containing sludge; the moisture content of the mercury-containing solid waste is not greater than 20%.

3. The method for recovering mercury from mercury-containing solid waste according to claim 1, characterized in that, The dry distillation includes primary dry distillation and secondary dry distillation; the temperature of the primary dry distillation is lower than the temperature of the secondary dry distillation; the condensation includes primary condensation and secondary condensation.

4. The method for recovering mercury from mercury-containing solid waste according to claim 3, characterized in that, Before the mercury-containing solid waste undergoes primary dry distillation, it is pulverized to a size of 10–40 mm.

5. The method for recovering mercury from mercury-containing solid waste according to claim 3, characterized in that, The temperature of the first-stage dry distillation is 100–200℃, and the time is 20–30 min; the temperature of the second-stage dry distillation is 600–750℃, and the time is 40–60 min.

6. The method for recovering mercury from mercury-containing solid waste according to claim 3, characterized in that, During the first-stage condensation, the temperature of the pyrolysis gas is reduced to 80-90°C; during the second-stage condensation, the temperature of the pyrolysis gas is reduced to 25-30°C.

7. The method for recovering mercury from mercury-containing solid waste according to claim 1, characterized in that, The liquid crude mercury is purified using a solid-liquid separation mercury removal ecological membrane.

8. The method for recovering mercury from mercury-containing solid waste according to claim 1, characterized in that, The metal oxide in the metal oxide-modified activated carbon is at least one of Al2O3 and CuO.

9. A recycling apparatus for implementing the recycling method according to any one of claims 1 to 8, characterized in that, It includes a feed assembly (1), a dry distillation system, a mercury recovery system, and a tail gas treatment system that are sequentially sealed and connected. The feed inlet of the pyrolysis system is connected to the feed assembly (1); The mercury recovery system includes a condensation component and a liquid mercury purification component (14) connected together, and the inlet of the condensation component is connected to the outlet of the dry distillation system. The exhaust gas treatment system includes a desulfurization component (18), which is equipped with a metal oxide modified activated carbon adsorption component; the gas phase outlet of the condensation component is connected to the inlet of the desulfurization component (18).

10. A recycling device according to claim 9, characterized in that, The condensation assembly includes a primary condensation assembly (10) and a secondary condensation assembly (11) connected in sequence; the inlet of the primary condensation assembly (10) is connected to the outlet of the dry distillation system, and the gas phase outlet of the secondary condensation assembly (11) is connected to the inlet of the desulfurization assembly (18).

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