A system and method for recycling metal resources in waste SCR denitration catalyst

Abstract

The present invention discloses a system and method for recycling metal resources in waste SCR denitration catalysts, including a pretreatment system for removing surface impurities from waste SCR denitration catalysts, the outlet of the pretreatment system is connected to a ball milling system, the outlet of the ball milling system is connected to a calcining system, the outlet of the calcining system is connected to a molten salt hot dip and electrodeposition system for extracting and recovering metals V, Mo and W, and the residue outlet of the molten salt hot dip and electrodeposition system is connected to a molten salt electrolysis system for extracting and recovering metal Ti. The present invention can realize the single-substance separation, extraction and recycling of metal elements in waste SCR denitration catalysts.

Description

Technical Field

[0001] The present invention relates to the field of solid waste treatment, and in particular to a system and method for recycling metal resources in a discarded SCR denitration catalyst. Background Art

[0002] The large amount of nitrogen oxides emitted from coal-fired power plants will lead to pollution problems such as acid rain, photochemical smog and haze, which will pose a serious threat to the quality of the atmospheric environment and human health. Therefore, controlling the emission of nitrogen oxides has always been an important issue that governments around the world are extremely concerned about.

[0003] Due to its high denitration efficiency and mature technology, the SCR method is the most widely used flue gas denitration post-treatment technology in coal-fired power plants at home and abroad. In the entire SCR denitration system, the denitration catalyst is the core, and its cost accounts for 30% to 40% of the total investment of the denitration device. The main component of the carrier in the denitration catalyst is TiO2, and the active components are mainly V2O5, WO3 and MoO3. In the actual operation of the SCR system, as the operating time increases, the denitration catalyst will inevitably have problems such as reduced activity and shortened life, resulting in reduced denitration efficiency. Although some denitration catalysts can be reused through regeneration, after multiple (3) regenerations, their original structure will be severely damaged and cannot be used normally, and eventually become waste.

[0004] Waste SCR denitration catalysts contain toxic metal oxides such as V2O5, WO3 or MoO3, which are hazardous solid wastes. Landfilling them will not only occupy a large amount of land resources, but also bring potential pollution risks to the environment. Titanium, vanadium, tungsten, molybdenum, etc. are important metal resources required for human economic and social development, and vanadium, tungsten and molybdenum are called rare metals due to their low abundance in the earth's crust. Therefore, the effective recycling of metal resources in waste denitration catalysts not only has significant environmental benefits but also has strong economic value.

[0005] At present, the main methods for recycling metal resources in waste SCR denitration catalysts include sodium (calcium) roasting-water leaching, wet acid leaching, alkali leaching, etc., which not only consume a large amount of chemical agents, but also the recovered products are mostly metal oxides, and the economic added value of the products is low. There is no report on the technology of separating and extracting the main metal elements Ti, V, W, and Mo in the waste SCR denitration catalyst in single state. Summary of the invention

[0006] The purpose of the present invention is to provide a system and method for recycling metal resources in waste SCR denitration catalysts to overcome the problems existing in the prior art. The present invention can achieve the separation, extraction and recycling of metal elements in the waste SCR denitration catalyst in a single substance state.

[0007] In order to achieve the above object, the present invention adopts the following technical scheme:

[0008] A system for recycling metal resources in waste SCR denitration catalysts, comprising a pretreatment system for removing surface impurities from the waste SCR denitration catalysts, wherein the outlet of the pretreatment system is connected to a ball milling system, the outlet of the ball milling system is connected to a calcining system, the outlet of the calcining system is connected to a molten salt hot dip and electrodeposition system for extracting and recovering metals V, Mo and W, and the residue outlet of the molten salt hot dip and electrodeposition system is connected to a molten salt electrolysis system for extracting and recovering metal Ti.

[0009] Furthermore, the pretreatment system includes a high-pressure air gun for purging the waste SCR denitration catalyst, a water washing device for washing the purged catalyst with water, and a drying device for drying the washed catalyst.

[0010] Furthermore, the calcining system includes a heating device using a ring heating method, and a thermocouple placed at the same horizontal position as the calcined material.

[0011] Furthermore, the molten salt hot dip and electrodeposition system includes an electrolysis device, which includes an electrolysis cell. The electrolysis cell is placed in a reactor, and the reactor is placed in a high-temperature electric furnace. The air inlet on the reactor is connected to a gas distribution system for providing inert gas through a gas drying device, and the air outlet on the reactor is respectively connected to a vacuum pump and an exhaust gas recovery system. The reactor is also connected to a control system, which includes a temperature control system for controlling the heating temperature and heating rate of the high-temperature electric furnace, and a reaction control system for controlling reaction process parameters.

[0012] A method for recycling metal resources in a discarded SCR denitration catalyst comprises the following steps:

[0013] Step 1: pre-treating the waste SCR denitration catalyst to remove impurities on the catalyst surface;

[0014] Step 2: mixing the pretreated waste SCR denitration catalyst and the alkali metal oxide and ball milling them to reduce the particle size and make them uniform;

[0015] Step 3: calcining the mixture of the waste SCR denitration catalyst and the alkali metal oxide after ball milling, and wrapping the calcined material with a mesh bag of high temperature resistant material with porosity after calcination;

[0016] Step 4: placing the net bag wrapped with the reaction material in a molten salt for hot dipping, dissolving the metals V, Mo and W in the molten salt, and electro-depositing the molten salt containing the metals V, Mo and W under different conditions, transferring the molten salt electro-deposited product to an inert atmosphere and cooling it to room temperature, removing the electrolyte in the product with deionized water, and drying it under vacuum conditions to extract the metals V, Mo and W respectively;

[0017] Step 5: Make the residue in the net bag into a reaction cathode for molten salt electrolysis, transfer the molten salt electrolysis product to an inert atmosphere and cool it to room temperature, use deionized water to remove the electrolyte in the reaction product, and dry it under vacuum conditions to extract metal Ti.

[0018] Furthermore, the pretreatment in step one includes a high-pressure air gun blowing and a water washing process; in step two, the pretreated waste SCR denitrification catalyst and the alkali metal oxide are placed in a ball mill at a molar ratio of 1:1, and ball milling is performed for 24 hours at a rotation speed of 300 rpm.

[0019] Furthermore, in step 2, the alkali metal oxide is one of lithium oxide, potassium oxide, sodium oxide, calcium oxide and magnesium oxide.

[0020] Furthermore, in step three, the calcination temperature is 650-850° C., and the calcination time is 6 hours.

[0021] Furthermore, step four is specifically as follows: placing the net bag wrapped with the reaction material in molten salt for hot dipping, so that the metal elements V, Mo and W are dissolved in the molten salt, and then using a high temperature resistant conductive material as a reaction cathode and a soluble or insoluble material as a reaction anode, applying different reaction potentials or reaction voltages in succession, that is, electro-deposition recovery of the metal elements V, Mo, and W respectively.

[0022] Furthermore, step five is specifically as follows: using a soluble or insoluble material as a reaction anode, applying a reaction voltage between the reaction cathode and the reaction anode and performing electrolysis, that is, obtaining an electrolysis product Ti at the cathode.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] The system of the present invention has a simple device, a short process flow and is easy to operate. (1) First, through the thermochemical reaction between the metal oxide component and the alkali metal oxide in the waste SCR denitration catalyst, the transformation of the component composition in the waste SCR denitration catalyst is achieved to increase the solubility of some components in the molten salt; (2) By utilizing the different solubilities of different components in the product after the thermochemical reaction in the molten salt, the separation of V, Mo, W elements and Ti elements is achieved through molten salt immersion; (3) By utilizing the difference in the electrodeposition potential between the V, Mo and W elements in the ionic state after immersion and dissolution in the molten salt, metal V, Mo and W can be obtained respectively by applying different reaction potentials or reaction voltages in succession, thereby achieving the separation and recovery of V, Mo and W elements in the waste SCR denitration catalyst; (4) The solid residual material after immersion in the molten salt is used as the reaction cathode, and the molten salt electrolysis solid-state reduction method is adopted to prepare metal Ti, thereby achieving the separation, extraction and recovery of the metal element Ti in the waste SCR denitration catalyst.

[0025] The present invention does not consume or discharge acid and alkali reagents, and the recovery process has the characteristics and advantages of being green and low-pollution; the metal resources V, Mo, W and Ti in the waste SCR catalyst can be efficiently separated, extracted and recovered in the form of metal elements, the product purity is high, and the recovered product has high economic added value. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a process flow chart of separating, extracting and recycling metal resources in waste SCR denitration catalysts according to the present invention.

[0027] Figure 2 It is a schematic diagram of a system for separating, extracting and recycling metal resources in waste SCR denitration catalysts according to the present invention.

[0028] Figure 3 It is a schematic diagram of a molten salt hot dipping and electrodeposition system in the process of separating, extracting and recycling metal resources in a discarded SCR denitration catalyst according to the present invention. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments:

[0030] See also Figure 1 A system for recycling metal resources in waste SCR denitration catalysts mainly includes a pretreatment system, a ball milling system, a calcination system, a molten salt hot dip and electrodeposition system and a molten salt electrolysis system; the pretreatment system is connected to the ball milling system, the ball milled product enters the calcination system, the calcined product is wrapped and sent to the molten salt hot dip and electrodeposition system to achieve the extraction and recovery of metals V, Mo and W; the residue after molten salt hot dip enters the molten salt electrolysis system to achieve the extraction and recovery of metal Ti.

[0031] The pretreatment system mainly uses mechanical methods to treat the waste catalyst, including high-pressure air gun blowing and water washing processes. The pretreatment system also includes a drying device for drying the waste catalyst after water washing. The pretreated waste catalyst is sent to the ball milling system. The ball milling jar and ball milling beads used in the ball milling system are made of agate to reduce the contamination of other metal elements on the waste catalyst. Ball milling can be done by dry grinding or wet grinding. The liquid used in the wet grinding process is ethanol and other volatile solvents that do not react with the raw materials. The calcination system adopts the degree temperature control method to achieve standard program control of the heating process and heating rate. The internal ring resistance wire ensures that the calcined material is heated evenly; a thermocouple is placed at the same horizontal position of the calcined material to achieve accurate monitoring of the heating temperature and accurate control of the heating rate. The calcination temperature used is 650-850℃. Before the calcined waste SCR catalyst enters the molten salt hot dip and molten salt electrodeposition system, it is necessary to wrap the waste SCR catalyst with a high temperature resistant material with a certain porosity, on the one hand to ensure sufficient contact reaction between the waste SCR catalyst and the molten salt, and on the other hand to ensure that the components that do not react thermochemically with the molten salt are retained in the high temperature resistant material, which is convenient for the subsequent removal of the molten salt. The molten salt hot dip and electrodeposition system can respectively realize the molten salt hot dip process and the molten salt electrodeposition process. The device consists of a high temperature electric furnace, a reactor, an electrolytic cell, a thermocouple, etc. The high temperature electric furnace can heat the reactor; the reactor is built into the high temperature electric furnace, and the material is a high temperature resistant metal material, a ceramic material or graphite. The top of the reactor is provided with an anode port, a cathode port, an observation port, an air inlet, an air outlet, and a circulating cooling water inlet and outlet; the corresponding anode and cathode materials can be placed at the anode port and the cathode port, respectively. The observation port can observe the internal state of the reactor in real time; the circulating cooling water can cool the top of the reactor to prevent potential safety risks caused by the high temperature at the top of the reactor. The thermocouple is built between the high-temperature electric furnace and the reactor, and the reaction temperature of the electrolysis system can be monitored in real time. The reaction electrolytic cell is built into the reactor and is made of ceramic material or graphite. The anode material and cathode material used in the reaction electrolytic cell are inserted into the electrolytic cell through the anode port and cathode port of the reactor, and the depth of immersion in the electrolyte and the distance between the cathode and cathode are fixed. The molten salt hot dip and electrodeposition system is connected to the temperature control device and the reaction control device; the temperature control system can control the heating temperature and heating rate of the high-temperature electric furnace in real time; the main body of the reaction control system is the reaction power supply, which is mainly a DC regulated power supply, and is connected to the reaction anode and reaction cathode through wires. The reaction control system can control the reaction current, reaction voltage, reaction time and reaction electricity to achieve the control of the reaction rate and the degree of deoxidation. The molten salt hot dip and electrodeposition system is connected to a gas distribution system, which mainly transports inert gases such as Ar gas to the molten salt hot dip and molten salt electrodeposition system to prevent the oxidation of the reactor and the electrolysis products under high temperature conditions.A gas drying device is provided between the gas distribution system and the molten salt hot dip and electrodeposition system to dry the gas entering the molten salt hot dip and electrodeposition system. The molten salt electrolysis system is similar to the molten salt hot dip and electrodeposition system in terms of device composition, except that the operation and recovery principle of metal recovery are different. The main purpose of the molten salt hot dip and electrodeposition system is to extract V, Mo, and W. It includes two steps of molten salt hot dip and electrodeposition, which must be carried out in one system. The overall process is to soak the material in the molten salt hot dip and electrodeposition system, and the soluble substances (including V, Mo, and W substances) will dissolve into the molten salt hot dip and electrodeposition system, and then the electrodeposition operation is carried out in the molten salt hot dip and electrodeposition system, and the dissolved V, Mo, and W are respectively recovered by electrodeposition (the same system, two steps in succession); and the insoluble substances after hot dip exist in the form of solid residue, which are first removed from the molten salt hot dip and electrodeposition system, and then subjected to molten salt electrolysis in the molten salt electrolysis system to achieve Ti recovery.

[0032] A method for recycling metal resources in waste SCR denitration catalysts, specifically comprising:

[0033] The waste SCR denitration catalyst with the main components of V2O5 / MoO3 / WO3 / TiO2 is placed in the pretreatment system to remove impurities on the catalyst surface. Then it is sent to the ball milling system with alkali metal oxides (one of lithium oxide, potassium oxide, sodium oxide, calcium oxide and magnesium oxide) and mixed with a certain proportion of alkali metal oxides to make the components evenly mixed. The ball-milled reaction material is placed in the calcination system and calcined at a suitable reaction temperature for a certain period of time. Then a mesh bag with a high-temperature resistant material with a certain porosity is used to wrap the calcined material.

[0034] The reacted materials after encapsulation are sent to the molten salt hot dip and electrodeposition system. After a certain period of thermochemical reaction, the metal elements V, Mo, and W migrate into the reaction electrolyte in ionic state. The compound corresponding to the metal element Ti still exists in the encapsulated material and is removed from the molten salt hot dip and electrodeposition system. Since the metal elements V, Mo, and W in ionic state in the reaction electrolyte have different reduction potentials, the high temperature resistant conductive material is used as the reaction cathode, and the soluble or insoluble material is used as the reaction anode. Different reaction potentials or reaction voltages E1, E2, and E3 are applied successively, and the metal elements V, Mo, and W can be respectively recovered by electrodeposition.

[0035] The compound corresponding to the metal element Ti is used as the reaction cathode, and the soluble or insoluble material is used as the reaction anode. The reaction cathode and the reaction anode are placed in a molten salt electrolysis system, and a suitable reaction voltage is applied between the cathode and the cathode and a suitable reaction time is selected for electrolysis, and the electrolysis product Ti can be obtained at the cathode.

[0036] The present invention is further described in detail below in conjunction with specific embodiments:

[0037] Example 1

[0038] The waste SCR denitration catalyst was pretreated by high-pressure air gun and water washing to remove surface impurities. After drying, 5g of waste SCR denitration catalyst and calcium oxide were weighed in a molar ratio of 1:1 and placed in a ball mill at a speed of 300rpm for 24 hours. The mixed material after ball milling was placed in a calcination device, the temperature was raised to 850℃, and calcined for 6 hours. The calcined reaction material was wrapped with a metal mesh bag made of high-temperature resistant material, and the whole was fixed on the operating rod of high-temperature resistant material.

[0039] 500g of CaCl2 was used as the reaction electrolyte and placed in an alumina crucible to form a reaction electrolytic cell. The reaction electrolytic cell was built into a graphite crucible. The use of a graphite crucible can prevent leakage from damaging the furnace and consume a certain amount of oxygen to control the atmosphere in the reactor. CaCl2 was dried at 300℃ for 48h. Then, under the protection of argon gas and cooling water, the reaction was continued at 5℃min. -1 The temperature is slowly raised to 850°C at a heating rate, at which time the molten salt is in a molten state.

[0040] The metal mesh bag wrapped with the reaction material is placed in the molten salt hot dip and molten salt electrodeposition device. After 4 hours of reaction, the metal mesh bag is removed from the molten salt. Since the metal compounds corresponding to the metal elements vanadium, molybdenum and tungsten in the reaction material after calcination have a large solubility in the molten salt, their corresponding compounds will be dissolved and transferred to the reaction electrolyte CaCl2 in an ionic state. The compound corresponding to the metal titanium has a low solubility and will be retained in the metal mesh bag in a solid form. Thus, the initial separation of the components is achieved.

[0041] A graphite rod was used as the anode and stainless steel was used as the cathode in a reaction electrolyte CaCl2. At 850°C, an electrolysis voltage of 1.6V was applied between the cathode and the cathode. After 10 hours of reaction, the current value remained basically stable and there was no obvious metal precipitation. The stainless steel cathode was slowly removed from the reaction electrolyte CaCl2 and cooled in an inert atmosphere. The deposited product on the surface of the stainless steel cathode was cleaned with deionized water to remove a small amount of electrolyte and dried under vacuum conditions. The main component of the obtained product was metallic molybdenum.

[0042] A new stainless steel cathode was replaced and placed in the previous reaction electrolyte CaCl2. At 850°C, an electrolysis voltage of 1.65V was applied between the anode and cathode. After 10 hours of reaction, the current value remained basically stable, and there was no obvious metal precipitation. The stainless steel cathode was slowly removed from the reaction electrolyte CaCl2 and cooled in an inert atmosphere. The stainless steel cathode product was cleaned with deionized water to remove a small amount of electrolyte and dried under vacuum conditions. The main component of the obtained product was metallic tungsten.

[0043] A new stainless steel cathode was replaced and placed in the previous reaction electrolyte CaCl2. At 850°C, an electrolysis voltage of 1.75V was applied between the anode and cathode. After 10 hours of reaction, the current value remained basically stable and there was no obvious metal precipitation. The stainless steel cathode was slowly removed from the reaction electrolyte CaCl2 and cooled in an inert atmosphere. The stainless steel cathode product was cleaned with deionized water to remove a small amount of electrolyte and dried under vacuum conditions. The main component of the obtained product was metallic vanadium.

[0044] Weigh 1.5g of the residual reaction material in the metal mesh bag and press the cathode test piece (diameter 20mm) under 10MPa pressure. Wrap the cathode test piece with nickel foam and fix it to the cathode current collector molybdenum rod with molybdenum wire. Using CaCl2 as the reaction electrolyte and graphite as the reaction anode, the reaction electrolyte, reaction cathode and reaction anode are placed in a molten salt electrolysis device. At 850℃, an electrolysis voltage of 3.0V is applied between the cathode and the cathode. After 10h of reaction, the cathode test piece is slowly taken out and cooled under inert atmosphere. The stainless steel cathode product is cleaned with deionized water to remove a small amount of electrolyte and dried under vacuum. The main component of the obtained product is metallic titanium.

[0045] Example 2

[0046] The waste SCR denitration catalyst was pretreated by high-pressure air gun and water washing to remove surface impurities. After drying, 5g of the waste SCR denitration catalyst and sodium oxide were weighed in a molar ratio of 1:1 and placed in a ball mill at a speed of 300rpm for 24 hours. The mixed material after ball milling was placed in a heatable reaction device, the temperature was raised to 650℃, and calcined for 6 hours. The calcined reaction material was wrapped with a metal mesh bag made of high-temperature resistant material, and the whole was fixed on the operating rod of high-temperature resistant material.

[0047] 500g of CaCl2-NaCl mixed salt was used as the reaction electrolyte and placed in an alumina crucible to form a reaction electrolytic cell. The reaction electrolytic cell was built into a graphite crucible. The use of a graphite crucible can prevent leakage from damaging the furnace and consume a certain amount of oxygen to control the atmosphere in the reactor. The CaCl2-NaCl was dried at 300℃ for 48h. Then, under the protection of argon gas and cooling water, the reaction was continued at 5℃min. -1 The temperature is slowly raised to 750°C at a heating rate, at which time the molten salt is in a molten state.

[0048] The metal mesh bag wrapped with the reaction material is placed in a molten salt hot dip and molten salt electrodeposition device. After 8 hours of reaction, the metal mesh bag is removed from the molten salt. Since the metal compounds corresponding to the metal elements vanadium, molybdenum and tungsten in the reaction material after calcination have a large solubility in the molten salt, their corresponding compounds will be dissolved and transferred to the reaction electrolyte CaCl2-NaCl in an ionic state. The compound corresponding to the metal titanium has a low solubility and will be retained in the metal mesh bag in a solid form. Thus, the initial separation of the components is achieved.

[0049] A graphite rod was used as the anode and stainless steel was used as the cathode in a reaction electrolyte CaCl2-NaCl. At 750°C, an electrolysis voltage of 1.9V was applied between the cathode and the cathode. After 12 hours of reaction, the current value remained basically stable and there was no obvious metal precipitation. The stainless steel cathode was slowly removed from the reaction electrolyte CaCl2-NaCl and cooled in an inert atmosphere. The deposited product on the surface of the stainless steel cathode was cleaned with deionized water to remove a small amount of electrolyte and dried under vacuum conditions. The main component of the obtained product was metallic molybdenum.

[0050] A new stainless steel cathode was replaced and placed in the previous reaction electrolyte CaCl2-NaCl. At 750°C, an electrolysis voltage of 1.95V was applied between the anode and cathode. After 12 hours of reaction, the current value remained basically stable and there was no obvious metal precipitation. The stainless steel cathode was slowly removed from the reaction electrolyte CaCl2-NaCl and cooled in an inert atmosphere. The stainless steel cathode product was cleaned with deionized water to remove a small amount of electrolyte and dried under vacuum conditions. The main component of the obtained product was metallic tungsten.

[0051] A new stainless steel cathode was replaced and placed in the previous reaction electrolyte CaCl2-NaCl. At 750°C, an electrolysis voltage of 2.1V was applied between the anode and cathode. After 12 hours of reaction, the current value remained basically stable and there was no obvious metal precipitation. The stainless steel cathode was slowly removed from the reaction electrolyte CaCl2-NaCl and cooled in an inert atmosphere. The stainless steel cathode product was cleaned with deionized water to remove a small amount of electrolyte and dried under vacuum conditions. The main component of the obtained product was metallic vanadium.

[0052] Weigh 1.5g of the residual reaction material in the metal mesh bag and press the cathode test piece (diameter 20mm) under 10MPa pressure. Wrap the cathode test piece with nickel foam and fix it to the cathode current collector molybdenum rod with molybdenum wire. Use graphite as the reaction anode and CaCl2-NaCl as the reaction electrolyte. Place the reaction anode, reaction cathode and reaction electrolyte in a molten salt electrolysis device. Raise the reaction temperature to 900℃, apply 3.0V electrolysis voltage between the cathode and cathode. After 10h of reaction, slowly take out the cathode test piece, cool it under inert atmosphere, use deionized water to clean the stainless steel cathode product to remove a small amount of electrolyte, and dry it under vacuum. The main component of the obtained product is metallic titanium.

[0053] Example 3

[0054] The waste SCR denitration catalyst was pretreated by high-pressure air gun and water washing to remove surface impurities. After drying, 5g of waste SCR denitration catalyst and lithium oxide were weighed in a molar ratio of 1:1 and placed in a ball mill at a speed of 300rpm for 24 hours. The mixed material after ball milling was placed in a heatable reaction device, the temperature was raised to 725℃, and calcined for 6 hours. The calcined reaction material was wrapped with a metal mesh bag made of high-temperature resistant material, and the whole was fixed on the operating rod of high-temperature resistant material.

[0055] 500g of CaCl2-LiCl mixed salt was used as the reaction electrolyte and placed in an alumina crucible to form a reaction electrolytic cell. The reaction electrolytic cell was built into a graphite crucible. The use of a graphite crucible can prevent leakage from damaging the furnace and consume a certain amount of oxygen to control the atmosphere in the reactor. The CaCl2-LiCl was dried at 300℃ for 48h. Then, under the protection of argon gas and cooling water, the reaction was continued at 5℃min. -1 The temperature is slowly raised to 800°C at a heating rate, at which time the molten salt is in a molten state.

[0056] The metal mesh bag wrapped with the reaction material is placed in a molten salt hot dip and molten salt electrodeposition device. After 6 hours of reaction, the metal mesh bag is removed from the molten salt. Since the metal compounds corresponding to the metal elements vanadium, molybdenum and tungsten in the reaction material after calcination have a large solubility in the molten salt, their corresponding compounds will be dissolved and transferred to the reaction electrolyte CaCl2-LiCl in an ionic state. The compound corresponding to the metal titanium has a low solubility and will be retained in the metal mesh bag in a solid form. Thus, the initial separation of the components is achieved.

[0057] A graphite rod was used as the anode and stainless steel was used as the cathode in a reaction electrolyte CaCl2-LiCl. At 800°C, an electrolysis voltage of 1.7V was applied between the cathode and cathode. After 12 hours of reaction, the current value remained basically stable and there was no obvious metal precipitation. The stainless steel cathode was slowly removed from the reaction electrolyte CaCl2-LiCl and cooled in an inert atmosphere. The deposited product on the surface of the stainless steel cathode was cleaned with deionized water to remove a small amount of electrolyte and dried under vacuum conditions. The main component of the obtained product was metallic molybdenum.

[0058] A new stainless steel cathode was replaced and placed in the previous reaction electrolyte CaCl2-LiCl. At 800°C, an electrolysis voltage of 1.75V was applied between the anode and cathode. After 12 hours of reaction, the current value remained basically stable and there was no obvious metal precipitation. The stainless steel cathode was slowly removed from the reaction electrolyte CaCl2-LiCl and cooled in an inert atmosphere. The stainless steel cathode product was cleaned with deionized water to remove a small amount of electrolyte and dried under vacuum conditions. The main component of the obtained product was metallic tungsten.

[0059] A new stainless steel cathode was replaced and placed in the previous reaction electrolyte CaCl2-LiCl. At 800°C, an electrolysis voltage of 1.85V was applied between the anode and cathode. After 12 hours of reaction, the current value remained basically stable and there was no obvious metal precipitation. The stainless steel cathode was slowly removed from the reaction electrolyte CaCl2-LiCl and cooled in an inert atmosphere. The stainless steel cathode product was cleaned with deionized water to remove a small amount of electrolyte and dried under vacuum conditions. The main component of the obtained product was metallic vanadium.

[0060] Weigh 1.5g of the residual reaction material in the metal mesh bag and press the cathode test piece (diameter 20mm) under 10MPa pressure. Wrap the cathode test piece with nickel foam and fix it to the cathode current collector molybdenum rod with molybdenum wire. Use graphite as the reaction anode and CaCl2-LiCl as the reaction electrolyte. Place the reaction anode, reaction cathode and reaction electrolyte in a molten salt electrolysis device. Raise the reaction temperature to 900℃, apply 3.0V electrolysis voltage between the cathode and cathode. After 10h of reaction, slowly take out the cathode test piece, cool it under inert atmosphere, use deionized water to clean the stainless steel cathode product to remove a small amount of electrolyte, and dry it under vacuum. The main component of the obtained product is metallic titanium.

Claims

1. A method for recycling metal resources in waste SCR denitration catalysts, characterized in that: The following steps are involved: Step 1: pre-treating the waste SCR denitration catalyst to remove impurities on the catalyst surface; wherein the pre-treatment includes high-pressure air gun blowing and water washing processes; Step 2: The pretreated waste SCR denitration catalyst and the alkali metal oxide are mixed and ball-milled to reduce the particle size and make it uniform. Specifically, the pretreated waste SCR denitration catalyst and the alkali metal oxide are placed in a ball mill at a molar ratio of 1:1 and ball-milled for 24 hours at a rotation speed of 300 rpm; Step 3: calcining the mixture of the waste SCR denitration catalyst and the alkali metal oxide after ball milling, and wrapping the calcined material with a mesh bag of high-temperature resistant material with porosity, wherein the calcination temperature is 650-850° C. and the calcination time is 6 hours; Step 4: placing the net bag wrapped with the reaction material in a molten salt for hot dipping, dissolving the metals V, Mo and W in the molten salt, and electro-depositing the molten salt containing the metals V, Mo and W under different conditions, transferring the molten salt electro-deposited product to an inert atmosphere and cooling it to room temperature, removing the electrolyte in the product with deionized water, and drying it under vacuum conditions to extract the metals V, Mo and W respectively; Step 5: Make the residue in the net bag into a reaction cathode for molten salt electrolysis, transfer the molten salt electrolysis product to an inert atmosphere and cool it to room temperature, use deionized water to remove the electrolyte in the reaction product, and dry it under vacuum conditions to extract metal Ti.

2. The method for recycling metal resources in a waste SCR denitration catalyst according to claim 1, characterized in that: In step 2, the alkali metal oxide is one of lithium oxide, potassium oxide, sodium oxide, calcium oxide and magnesium oxide.

3. The method for recycling metal resources in a waste SCR denitration catalyst according to claim 1, characterized in that: Step four is as follows: placing the net bag wrapped with the reaction material in molten salt for hot dipping, dissolving the metal elements V, Mo and W in the molten salt, and then using a high temperature resistant conductive material as a reaction cathode and a soluble or insoluble material as a reaction anode, applying different reaction potentials or reaction voltages in succession, that is, electro-depositing and recovering the metal elements V, Mo and W respectively.

4. The method for recycling metal resources in a waste SCR denitration catalyst according to claim 1, characterized in that: Step five is specifically as follows: using a soluble or insoluble material as a reaction anode, applying a reaction voltage between the reaction cathode and the reaction anode and performing electrolysis, that is, obtaining an electrolysis product Ti at the cathode.

5. The method for recycling metal resources in a waste SCR denitration catalyst according to claim 1, characterized in that: The method is implemented by using a system for recycling metal resources in waste SCR denitration catalysts, including a pretreatment system for removing surface impurities from waste SCR denitration catalysts, wherein the outlet of the pretreatment system is connected to a ball milling system, the outlet of the ball milling system is connected to a calcining system, the outlet of the calcining system is connected to a molten salt hot-dip and electro-deposition system for extracting and recovering metals V, Mo and W, and the residue outlet of the molten salt hot-dip and electro-deposition system is connected to a molten salt electrolysis system for extracting and recovering metal Ti.

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