Fly ash dry method waste salt collecting and purifying process
Through the fly ash dry waste salt collection and purification process, the problem of difficult to effectively deal with high content of chloride in fly ash in the prior art is solved, and the efficient removal of chloride salt and heavy metals is achieved, ensuring the purification of water quality and the high purity of crystalline salts.
Patent Information
- Application Number
- CN202411944425.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-27
- Publication Date
- 2025-06-06
AI Technical Summary
The prior art is difficult to effectively treat high-content chlorides in fly ash, and the water washing and pickling processes will lead to the migration of pollutants such as heavy metals and cause water quality pollution.
The fly ash dry waste salt collection and purification process is adopted, including heating the fly ash in a melting furnace to evaporate the chloride salt, collecting the chloride salt particles through a ceramic filtering high-temperature dust collector, and then performing multi-step processing through dissolution tanks, plate and frame filter pressing equipment, precipitation tanks and MVR evaporators and other equipment to remove the chloride salt and heavy metals, and extract sodium chloride and potassium chloride crystalline salt.
The efficient removal of chloride in fly ash is achieved, water pollution is avoided, and the high purity of crystalline salt is ensured through multiple steps of treatment.
Smart Images
Figure CN120097362A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of fly ash chloride treatment, in particular to a fly ash dry waste salt collection and purification process. Background Art
[0002] As of the end of 2021, the amount of urban domestic waste collected and transported in my country reached 248.68 million tons, with 583 domestic waste incineration power plants, a total designed incineration capacity of 719,553.44 tons / day, and an actual annual incineration treatment capacity of 180.2967 million tons. The incineration of domestic waste in a grate furnace will produce 3-5% of domestic waste incineration fly ash (hereinafter referred to as fly ash). Because domestic waste contains 40%-75% kitchen waste and about 20% plastic, the chloride content in the fly ash is relatively high, and the chlorine content is mostly between 10% and 20%, and can reach up to 30%. At present, the methods for treating chlorides in fly ash include water washing, acid washing, and heat treatment processes.
[0003] The fly ash water washing process can effectively remove soluble chlorine in fly ash, but it is difficult to remove insoluble chlorine. The fly ash acid washing pretreatment process is to add a certain proportion of acid on the basis of the water washing process to convert insoluble chlorine into soluble chlorine and then remove it. The dechlorination effect is better than simple water washing. However, both the water washing and acid washing pretreatment processes inevitably cause heavy metals and other pollutants to migrate from the solid phase to the liquid phase. The wastewater contains a large amount of heavy metal ions and chloride ions, etc., and water purification is required later. Therefore, a fly ash dry waste salt collection and purification process is proposed to solve the above problems. Summary of the invention
[0004] 1. Technical issues to be resolved In view of the deficiencies in the prior art, the present invention provides a fly ash dry waste salt collection and purification process, which has the advantages of ensuring the dust removal efficiency of chloride salts and heavy metal particles in molten flue gas, and solves the problem of being unable to effectively treat chlorides in fly ash.
[0005] (II) Technical solution To achieve the above object, the present invention provides the following technical solution: a fly ash dry waste salt collection and purification process, comprising the following steps: 1) Dry-press the fly ash raw materials into briquettes and put them into a melting furnace, which is continuously heated until all the chloride salts are volatilized; 2) A portion of the chloride salt in the flue gas is discharged through the exhaust port of the melting furnace. The temperature of the exhaust port will cause the chloride to form fine particles. After the flue gas enters the exhaust gas treatment system for treatment, it is discharged into the waste salt collection bin for collection; 3) Another part of the flue gas and chloride salts are wrapped in the glass slag liquid. The vaporized chloride salts are collected by a ceramic filter high-temperature dust collector in the channel between the slag outlet of the melting furnace and the rock wool centrifuge, and discharged into the waste salt collection bin; 3) Discharge the chloride salt and fly ash in the waste salt collection bin into the dissolution tank, and add fresh water to the dissolution tank; 4) Introduce the dissolution tank into the plate and frame filter press equipment, and use the plate and frame filter press to separate and remove the fly ash, impurities, heavy metals, etc. that are insoluble in water to produce sludge; 5) The wastewater is then introduced into a high-density sedimentation tank, and PAM and heavy metal scavengers are added to the high-density sedimentation tank. The (organic sulfur) heavy metal scavenger is added to directly react with most of the heavy metals in the wastewater to form precipitation, thereby removing the heavy metals in the wastewater. Polyacrylamide (PAM) shortens the reaction and sedimentation time; 6) The treated wastewater is diverted to another sedimentation tank, and sodium carbonate is added to the sedimentation tank to reduce the Ca 2+ It reacts with calcium carbonate to form calcium carbonate precipitation, and a large amount of HCO is produced during the hydrolysis process. 3 - OH - and CO 3 2- , which increases the alkalinity in the system and the Ca 2+ With CO 3 2- Formation of CaCO 3 precipitation.
[0006] 7) Introduce the wastewater in the sedimentation tank into the filter, so that the filter can remove the residual particles that cannot settle in the wastewater; 8) Due to the heavy metals and Ca in the washing wastewater 2+ Mg 2+ Most of it is removed, and the main components of the washing liquid are NaCl and KCl. The washing wastewater is introduced into the mechanical vapor recompression (MVR) evaporator. The principle of "high-temperature sodium precipitation and mother liquor circulation" is adopted, and the MVR evaporation technology is used to extract NaCl and KCl. The material concentrated by the MVR evaporator produces sodium chloride crystals and potassium chloride crystals in the separator; 9) The precipitated crystal salt settles to the bottom of the separator and is discharged to the centrifuge. The obtained supernatant is sent to the water washing section. Since the raw materials contain a certain amount of impurities, it is necessary to discharge a small amount of flash crystallization mother liquor to the impurity salt evaporator for separate evaporation to produce a small amount of impurity salt to ensure the purity of the final sodium chloride and potassium chloride crystal salt.
[0007] Preferably, in the step 1), when the temperature of the garbage fly ash in the melting furnace reaches 450°C, the chlorine element in the fly ash begins to function, causing the melting furnace to continue to rise. When the temperature reaches above 830°C, the chloride will be gasified. When the combustion temperature of the melting furnace reaches above 1500°C, all the chloride salts are volatilized.
[0008] Preferably, in step 6), Na 2 CO 3 After dissolving in wastewater, two-step hydrolysis reactions occur, namely: CO 3 2- +H 2 O=HCO 3 - +OH - HCO 3 - +H 2 O=H 2 CO 3 +OH - Preferably, the exhaust gas treatment system in step 2) is composed of a cyclone dust collector and a ceramic filter high-temperature dust collector, and the filtration accuracy of the ceramic filter high-temperature dust collector is 0.3 um.
[0009] Preferably, in step 2), the temperature of the smoke outlet is 200-250°C, the smoke temperature drops below 400°C, and the chlorides form fine particles.
[0010] (III) Beneficial effects Compared with the prior art, the present invention provides a fly ash dry waste salt collection and purification process, which has the following beneficial effects: The fly ash dry waste salt collection and purification process adopts "water washing + water washing liquid pretreatment (heavy metal capture + decalcification + filtration) + evaporation crystallization" to remove the chloride salt and some heavy metals in the water washing liquid. Dioxins are stable in nature, slightly soluble in most organic solvents, and extremely difficult to dissolve in water. They are also resistant to acids, alkalis, oxidants and reductants. The addition of heavy metal capture agents and PAM in the water washing process has minimal changes in the polarity of water and does not affect the solubility of dioxins in water. Therefore, this process will not have a significant elution effect on dioxins in fly ash, and the amount of dioxins entering the water washing liquid is also extremely small. The dioxins in the water washing liquid are mainly attached to the suspended matter in the water. The filter is used to remove the suspended matter in the water in the water washing wastewater treatment process. The treated wastewater enters the MVR evaporation treatment to effectively control the content of dioxins in the crystallized salt. After the water washing liquid is treated, the sodium chloride crystallized salt, potassium chloride crystallized salt and waste salt residue are obtained by evaporation crystallization. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 This is a process flow chart of a chlorine-salt washing system in a fly ash dry waste salt collection and purification process proposed by the present invention; DETAILED DESCRIPTION
[0012] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0013] See also Figure 1 , a fly ash dry waste salt collection and purification process, comprising the following steps: 1) Dry-press the fly ash raw materials and put them into the melting furnace. When the temperature of the garbage fly ash in the melting furnace reaches 450°C, the chlorine element in the fly ash begins to play a role. When the temperature reaches above 830°C, the chloride will be gasified. The combustion temperature of the melting furnace reaches above 1500°C, so that all the chloride salts are volatilized; 2) A part of the chloride salt in the flue gas is discharged through the exhaust port of the melting furnace. The temperature of the exhaust port is 200-250C°. When the flue gas temperature drops below 400C°, the temperature of the exhaust port will cause the chloride to form fine particles. After the flue gas enters the cyclone dust collector and the ceramic filter high-temperature dust collector for treatment, it is discharged into the waste salt collection bin for collection; 3) Another part of the flue gas and chloride salts are wrapped in the glass slag liquid. The vaporized chloride salts are collected by a ceramic filter high-temperature dust collector in the channel between the slag outlet of the melting furnace and the rock wool centrifuge, and discharged into the waste salt collection bin; 3) Discharge the chlorine salt and fly ash in the waste salt collection bin into the dissolving tank, and add fresh water to the dissolving tank. The dissolving tank is used to store washing wastewater and has a homogenizing function; 4) Introduce the dissolution tank into the plate and frame filter press equipment, and use the plate and frame filter press to separate and remove the fly ash, impurities, heavy metals, etc. that are insoluble in water to produce sludge; 5) The wastewater is then introduced into a high-density sedimentation tank, and PAM and heavy metal scavengers are added to the high-density sedimentation tank. The (organic sulfur) heavy metal scavenger is added to directly react with most of the heavy metals in the wastewater to form precipitation, thereby removing the heavy metals in the wastewater. Polyacrylamide (PAM) shortens the reaction and sedimentation time; 6) The treated wastewater is diverted to another sedimentation tank, and sodium carbonate is added to the sedimentation tank to reduce the Ca 2+ It reacts with calcium carbonate to form calcium carbonate precipitation, and a large amount of HCO is produced during the hydrolysis process. 3 - OH - and CO 3 2- , which increases the alkalinity in the system and the Ca 2+ With CO 3 2- Formation of CaCO3 precipitation.
[0014] 7) Introduce the wastewater in the sedimentation tank into the filter, so that the filter can remove the residual particles that cannot settle in the wastewater; 8) Due to the heavy metals and Ca in the washing wastewater 2+ Mg 2+ Most of it is removed, and the main components of the washing liquid are NaCl and KCl. The washing wastewater is introduced into the mechanical vapor recompression (MVR) evaporator. The principle of "high-temperature sodium precipitation and mother liquor circulation" is adopted, and the MVR evaporation technology is used to extract NaCl and KCl. The material concentrated by the MVR evaporator produces sodium chloride crystals and potassium chloride crystals in the separator; 9) The precipitated crystal salt settles to the bottom of the separator and is discharged to the centrifuge. The obtained supernatant is sent to the water washing section. Since the raw materials contain a certain amount of impurities, it is necessary to discharge a small amount of flash crystallization mother liquor to the impurity salt evaporator for separate evaporation to produce a small amount of impurity salt to ensure the purity of the final sodium chloride and potassium chloride crystal salt.
[0015] Among them, the cyclone dust collector, also known as the cyclone separator, is composed of an air inlet pipe, an exhaust pipe, a cylinder, a cone and an ash discharge valve. Among mechanical dust collectors, the cyclone dust collector is the most efficient one. It is suitable for the removal of non-sticky and non-fibrous dust, mostly used to remove particles larger than 20μm. It is a medium-efficiency dust collector and can be used for the purification of high-temperature flue gas. It is a widely used dust collector that can be used for boiler flue gas dust removal, multi-stage dust removal and pre-dust removal. The dust removal efficiency of dust particles with a diameter of more than 20μm can reach more than 80%; the filtration accuracy of the ceramic filter high-temperature dust collector is 0.3um, which can achieve 5mg / Nm 3 To meet the needs of ultra-clean emissions, the dust removal efficiency is as high as 99.9%, achieving near-zero emission requirements. It is widely used in high-temperature dust removal in cement kilns, glass kilns, ceramic kilns, chemical plants and other industries.
[0016] The principle of the mechanical vapor recompression (MVR) evaporator is to use a high-efficiency steam compressor to compress the secondary steam generated by evaporation, convert electrical energy into thermal energy, increase the enthalpy of the secondary steam, and pump the secondary steam with increased thermal energy into the evaporation chamber for heating to achieve the recycling of the existing thermal energy of the secondary steam, so that the purpose of evaporation and concentration can be achieved through the self-circulation of the evaporator without the need for external fresh steam. The system temperature, pressure, motor speed, and system evaporation balance are controlled through PLC, industrial computer (FA), configuration, etc.
[0017] The beneficial effects of the present invention are: High-temperature heat treatment of fly ash can make full use of the high chlorine and heavy metal content of fly ash, and volatilize heavy metals and chlorine into flue gas, and finally capture them in concentrated ash. Then, "water washing + water washing liquid pretreatment (heavy metal capture + decalcification + filtration) + evaporation crystallization" is used to remove the chloride salts and some heavy metals in the water washing liquid. Dioxins are stable in nature, slightly soluble in most organic solvents, and extremely difficult to dissolve in water. They are also resistant to acids, alkalis, oxidants and reductants. Adding heavy metal capture agents and PAM in the water washing process will have little effect on the polarity of water and will not affect the solubility of dioxins in water. Therefore, this process will not have a significant elution effect on dioxins in fly ash, and the amount of dioxins entering the water washing liquid is also very small. Dioxins in the water washing liquid are mainly attached to suspended matter in the water. In the water washing wastewater treatment process, filters are used to remove suspended matter in the water. After treatment, the wastewater enters the MVR evaporation treatment to effectively control the content of dioxins in the crystallized salt. After the water washing liquid is treated, it is evaporated and crystallized to obtain sodium chloride crystal salt, potassium chloride crystal salt and waste salt residue.
[0018] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A fly ash dry waste salt collection and purification process, characterized in that: The following steps are involved: 1) Dry-brick the fly ash raw material and put it into a melting furnace, which is continuously heated until all the chloride salts are volatilized; 2) A portion of the chloride salt in the flue gas is discharged through the exhaust port of the melting furnace. The temperature of the exhaust port will cause the chloride to form fine particles. After the flue gas enters the exhaust gas treatment system for treatment, it is discharged into the waste salt collection bin for collection; 3) Another part of the flue gas and chloride salts are wrapped in the glass slag liquid. The vaporized chloride salts are collected by a ceramic filter high-temperature dust collector in the channel between the slag outlet of the melting furnace and the rock wool centrifuge, and discharged into the waste salt collection bin; 3) Discharge the chloride salt and fly ash in the waste salt collection bin into the dissolution tank, and add fresh water to the dissolution tank; 4) Introducing the dissolution tank into the plate and frame filter press equipment, using the plate and frame filter press to separate and remove the fly ash, impurities, heavy metals, etc. that are insoluble in water, and produce sludge; 5) The wastewater is then introduced into a high-density sedimentation tank, and PAM and heavy metal scavengers are added to the high-density sedimentation tank. The (organic sulfur) heavy metal scavenger is added to directly react with most of the heavy metals in the wastewater to form precipitation, thereby removing the heavy metals in the wastewater. Polyacrylamide (PAM) shortens the reaction and sedimentation time; 6) The treated wastewater is diverted to another sedimentation tank, and sodium carbonate is added to the sedimentation tank to reduce the Ca content in the ash washing wastewater to 2+ It reacts with calcium carbonate to form a precipitate, and a large amount of HCO3 is produced during the hydrolysis process. - OH - and CO3 2- , which increases the alkalinity in the system and the Ca 2+ With CO3 2- A CaCO3 precipitate is formed. 7) Introduce the wastewater in the sedimentation tank into the filter, so that the filter can remove the residual particles in the wastewater that cannot be settled; 8) Due to the heavy metals and Ca in the washing wastewater 2+ Mg 2+ Most of it is removed, and the main components of the washing liquid are NaCl and KCl. The washing wastewater is introduced into the mechanical vapor recompression (MVR) evaporator. The principle of "high-temperature sodium precipitation and mother liquor circulation" is adopted, and the MVR evaporation technology is used to extract NaCl and KCl. The material concentrated by the MVR evaporator produces sodium chloride crystals and potassium chloride crystals in the separator; 9) The precipitated crystal salt settles to the bottom of the separator and is discharged to the centrifuge. The obtained supernatant is sent to the washing section. Since the raw material contains a certain amount of impurities, it is necessary to discharge a small amount of flash crystallization mother liquor to the impurity salt evaporator for separate evaporation to produce a small amount of impurity salt to ensure the purity of the final sodium chloride and potassium chloride crystal salt.
2. A fly ash dry waste salt collection and purification process according to claim 1, characterized in that: In the step 1), when the temperature of the garbage fly ash in the melting furnace reaches 450°C, the chlorine element in the fly ash begins to function, causing the melting furnace to continue to rise. When the temperature reaches above 830°C, the chloride will be gasified. When the combustion temperature of the melting furnace reaches above 1500°C, all the chloride salts are volatilized.
3. A fly ash dry waste salt collection and purification process according to claim 1, characterized in that: In step 6), Na2CO3 is dissolved in wastewater and undergoes two-step hydrolysis reactions, which are: CO3 2- +H2O=HCO3 - +OH - HCO3 - +H2O=H2CO3+OH - 。 4. A fly ash dry waste salt collection and purification process according to claim 1, characterized in that: The exhaust gas treatment system in step 2) is composed of a cyclone dust collector and a ceramic filter high-temperature dust collector.
5. A fly ash dry waste salt collection and purification process according to claim 4, characterized in that: The filtration accuracy of the ceramic filter high temperature dust collector is 0.3um.
6. A fly ash dry waste salt collection and purification process according to claim 1, characterized in that: In the step 2), the temperature of the smoke outlet is 200-250°C, the smoke temperature drops below 400°C, and the chlorides form fine particles.