Kiln dust dechlorination method, kiln dust treatment method and kiln dust treatment system
By combining a primary washing tank and a plate and frame filter press, the effective separation and resource utilization of chloride ions in kiln ash are achieved, solving the problem that kiln ash cannot be used in cement products and ensuring the reliability and environmental friendliness of cement production.
Patent Information
- Application Number
- CN202511095608.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-06
- Publication Date
- 2025-11-11
AI Technical Summary
Existing technologies cannot reliably handle chloride ions in kiln ash, leading to cement kiln crusting and corrosion of refractory materials. Furthermore, the kiln ash cannot enter cement products, affecting cement production.
The method of mixing in a primary water washing tank, solid-liquid separation in a plate and frame filter press, and circulating water washing is adopted. By combining the primary water washing tank with the plate and frame filter press, the chloride ions in the kiln ash are effectively dissolved and separated. The chloride ions are then sent to the raw material mill after being rinsed with clean water and squeezed with compressed air to ensure that the chloride ions meet the emission standards.
It has achieved reliable removal of chloride ions from kiln ash, reduced water consumption, simplified process equipment, ensured the quality of cement production raw materials, and realized zero discharge and resource utilization of kiln ash.
Smart Images
Figure CN120920486A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of kiln ash disposal, specifically to a method for dechlorinating kiln ash, a method for disposing of kiln ash, and a kiln ash disposal system. Background Technology
[0002] In the cement clinker calcination process, the compounds formed by the chemical components such as potassium, sodium, and chloride in the raw materials have low sublimation temperatures. Before entering the kiln, they volatilize into the flue gas due to high temperatures. As the flue gas moves to the upper part of the preheater, they cool and re-condense, mixing into the materials. This cycle repeats, resulting in enrichment. This is the main reason for the crusting of the preheater system and the excessive chloride ions in the clinker. Furthermore, the crusting of the preheater system aggravates the corrosion of refractory materials.
[0003] To reduce the risk of excessive chloride ions in cement kiln crusts and clinker, and to extend the lifespan of refractory materials, the main current measure is to bypass the high-temperature air at the kiln tail. This involves releasing a portion of the high-temperature flue gas from the kiln tail chamber. Because the low-melting-point components such as chloride ions contained in the flue gas escape with the flue gas, they are cooled and condensed in the bypass ventilation system and then mixed into the flue gas dust (kiln ash). The chloride content in the kiln ash collected in this way is tens to hundreds of times higher than that in the raw materials entering the kiln.
[0004] However, with the rapid increase in the use of alternative fuels in cement kilns, the output of kiln ash will increase significantly. Previously, kiln ash could be quantitatively added to cement products through a kiln ash addition system; however, the new version of GB / T175-2023 "General Portland Cement" has removed the provision allowing kiln ash to be added to cement products. Therefore, the reliable disposal of kiln ash is a pressing issue facing cement plants. Summary of the Invention
[0005] The purpose of this invention is to provide a method for dechlorinating kiln ash, a method for disposing of kiln ash, and a system for disposing of kiln ash. This method for dechlorinating kiln ash can reliably remove chloride ions from kiln ash, thereby achieving the goal of reliably disposing of kiln ash.
[0006] To achieve the above objectives, the present invention provides a method for dechlorinating kiln ash, comprising:
[0007] Step 1: Mix kiln ash and water in the primary washing tank;
[0008] Step 2: The slurry in the primary washing tank is fed into the first plate and frame filter press for solid-liquid separation. The resulting filtrate is fed into the first filtrate tank, while the slurry residue remains in the plate and frame filter press.
[0009] Step 3: Input a fixed mass of clean water into the first plate and frame filter press, and input the resulting filtrate into the second filtrate tank. The mass ratio of the input clean water to the mass of the kiln ash added in step 1 is 1.5:1-3:1.
[0010] Step 4: Input the filtrate from the second filtrate tank into the first plate and frame filter press for circulating water washing of the kiln ash;
[0011] After steps 5 and 4 are completed, compressed air is introduced into the diaphragm of the first plate and frame filter press to perform solid-liquid separation. The first plate and frame filter press discharges the slag cake, and the filtrate enters the second filtrate tank.
[0012] In step 1, the water in the primary washing tank comes from the secondary filtrate tank.
[0013] Preferably, the mixing time in step 1 is set to be no less than 30 minutes.
[0014] In step 4, the chloride ion content in the filtrate obtained from water washing is detected, and the water washing cycle is terminated based on the detection results.
[0015] Preferably, in step 1, the added kiln ash is weighed, and a fixed mass of kiln ash is added to the primary washing tank.
[0016] Preferably, in step 5, the residue cake is fed into the raw material mill.
[0017] The present invention also provides a method for treating kiln ash, comprising:
[0018] Step 1: Use the kiln ash dechlorination method described in any one of claims 1-4 to wash the kiln ash with water to remove chloride ions. Chloride ions enter the first filtrate tank, and the dechlorinated kiln ash becomes slag cake and is collected.
[0019] Step 2: Pre-treat the filtrate in the first filtrate tank;
[0020] Step 3: Evaporate the pretreated solution to obtain potassium and sodium salts.
[0021] Preferably, the pretreatment in step 2 includes degravation, dehardening and neutralization, wherein the solids separated after degravation and dehardening are fed into the raw material mill together with the dechlorinated kiln ash in step 1.
[0022] Preferably, in step 3, the evaporation temperature is 80-100℃, an MVR evaporator is used, and potassium chloride crystals are obtained by centrifugal separation.
[0023] Preferably, in step 3, when the sodium chloride concentration in the mother liquor is close to 16.8%, the mother liquor is transported to a vacuum drying machine to obtain mixed salt.
[0024] The present invention also provides a kiln ash disposal system used in the kiln ash disposal method described above, comprising a water washing unit, a water treatment unit, and an evaporation salt production unit. In the kiln ash dechlorination method described in claims 1-4, the water washing unit is used to dechlorinate the kiln ash. The filtrate in the first filtrate tank is transported to the water treatment unit for pretreatment. The filtrate obtained from the pretreatment enters the evaporation salt production unit to obtain potassium salt and sodium salt.
[0025] According to the above technical solution, the present invention mixes kiln ash and water in a primary washing tank to obtain a slurry. Clean water needs to be added during the first mixing in the primary washing tank, wherein the mixing ratio of clean water to kiln ash is 1.5:1-3:1 by mass.
[0026] In the primary washing tank, the chloride ions in the kiln ash are fully dissolved in the water by stirring and introducing compressed air. After mixing, the slurry in the primary washing tank is pumped into the first plate and frame filter press. The solution separated by the first plate and frame filter press enters the first filtrate tank. Then, the first plate and frame filter press is flushed to wash the slurry residue in the plate and frame. After repeated flushing, the first plate and frame filter press is used to separate the slurry from the washing water. The separated solid slag cake is sent back to the raw material mill for use as a raw material in cement production. The separated solution enters the second filtrate tank and is then fed into the primary washing tank to be mixed with the kiln ash to make slurry.
[0027] The second filtrate tank is connected to the first plate and frame filter press. The filtrate from the second filtrate tank is fed into the first plate and frame filter press to wash the slurry residue inside the plates and frames. This allows the residual chloride ions in the slurry residue to dissolve into the filtrate, which then flows back into the second filtrate tank and then back into the first plate and frame filter press. This process is repeated to circulate the solution between the second filtrate tank and the first plate and frame filter press, thus achieving the circulating water washing and dechlorination of the slurry residue inside the plates and frames.
[0028] To ensure sufficient dissolution of chloride ions in the primary washing tank, the mixing time in step 1 is set to no less than 30 minutes. During this mixing time, continuous stirring and the introduction of compressed air into the primary washing tank achieve better dissolution, allowing more chloride ions to dissolve in the solution. Subsequently, the solid-liquid separation of the slurry and slag is effectively achieved through the solid-liquid separation action of the first plate and frame filter press. The separated filtrate enters the first filtrate tank. Therefore, this method enables reliable separation of chloride ions from the kiln ash. Afterward, the chloride-rich solution in the first filtrate tank is recycled, thus recovering the chloride ions from the kiln ash.
[0029] After the first solid-liquid separation in the first plate and frame filter press, chloride ions still remain in the slag cake. By adding clean water to the first plate and frame filter press and using the added clean water to repeatedly wash the slurry in the plate and frame, the residual chloride ions in the slag cake can be continuously dissolved, thereby achieving a reliable dechlorination effect on the kiln ash.
[0030] The amount of clean water added to the first plate and frame filter press is fixed. Preferably, the amount of clean water added is equal to twice the mass of the kiln ash. After all the clean water has been added, the addition of clean water is stopped, and the slurry residue in the first plate and frame filter press is repeatedly washed with the solution in the second filtrate tank. During the repeated washing process, the solution in the second filtrate tank is continuously fed into the inlet of the first plate and frame filter press, while the outlet of the first plate and frame filter press continuously feeds the filtered solution into the second filtrate tank, thereby achieving the effect of circulating water washing of the slurry residue in the plate and frame. During the circulating water washing process, the chloride ion content in the slurry residue continuously decreases until the chloride ion content in the slurry residue is lower than the set value. At this point, compressed air can be introduced into the first plate and frame filter press to squeeze out the water contained in the slurry residue, and the remaining slurry residue is discharged.
[0031] At this time, the amount of solution in the second filtrate tank is the same as the amount of clean water added to the first plate and frame filter press. At the same time, these solutions will be sent to the first-stage washing tank to mix with the kiln ash to form a slurry.
[0032] Therefore, by processing a fixed amount of kiln ash each time and determining whether to discharge slag cake by detecting the chloride ion content, the chloride ion content in the slag cake recycled into the raw material mill meets the system requirements. Thus, this method achieves reliable chloride removal from the kiln ash. Furthermore, by using a first plate and frame filter press, only approximately twice the weight of the kiln ash in clean water is needed each time to reliably remove chloride ions from the kiln ash, greatly saving water resources. Simultaneously, it enables simultaneous water washing and solid-liquid separation, reducing the complexity of the process equipment.
[0033] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description
[0034] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:
[0035] Figure 1 This is a flowchart of a method for dechlorinating kiln ash;
[0036] Figure 2 This is a flowchart of a method for dechlorination and pretreatment of kiln ash.
[0037] Explanation of reference numerals in the attached figures
[0038] 11 Primary washing tank; 12 First plate and frame filter press
[0039] 13 First filtrate tank 14 Second filtrate tank
[0040] 21 Second Plate and Frame Filter Press Detailed Implementation
[0041] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.
[0042] In this invention, unless otherwise stated, directional terms included in the terminology represent only the orientation of the term in its normal use or as commonly understood by those skilled in the art, and should not be regarded as a limitation on the term.
[0043] See Figure 1 The method for removing chlorine from kiln ash includes:
[0044] Step 1: Mix kiln ash and water in primary washing tank 11;
[0045] Step 2: The slurry in the primary washing tank 11 is fed into the first plate and frame filter press 12 for solid-liquid separation. The resulting filtrate is fed into the first filtrate tank 13, while the slurry residue remains in the plate and frame filter press.
[0046] Step 3: Input a fixed mass of clean water into the first plate and frame filter press 12, and input the resulting filtrate into the second filtrate tank 14. The mass ratio of the input clean water to the mass of the kiln ash added in step 1 is 1.5:1-3:1.
[0047] Step 4: Input the filtrate in the second filtrate tank 14 into the first plate and frame filter press 12 to circulate and wash the kiln ash;
[0048] After steps 5 and 4 are completed, compressed air is introduced into the diaphragm of the first plate and frame filter press 12 to perform solid-liquid separation. The first plate and frame filter press 12 discharges the slag cake, and the filtrate enters the second filtrate tank 14.
[0049] In step 1, the water in the primary washing tank 11 comes from the secondary filtrate tank 14.
[0050] By implementing the above technical solution, kiln ash and water are mixed in the primary washing tank 11 to obtain a slurry. Clean water needs to be added during the first mixing in the primary washing tank 11, and the mixing ratio of clean water to kiln ash is 1.5:1-3:1 by mass.
[0051] In the primary washing tank 11, the chloride ions in the kiln ash are fully dissolved in the water by stirring and introducing compressed air. After mixing, the slurry in the primary washing tank 11 is pumped into the first plate and frame filter press 12. The solution separated by the first plate and frame filter press 12 enters the first filtrate tank 13. Then, the first plate and frame filter press 12 is flushed to wash the slurry residue in the plate and frame. After repeated flushing, the first plate and frame filter press 12 is used to separate the slurry from the washing water. The separated solid slag cake is sent back to the raw material mill for use as a raw material for cement production. The separated solution enters the second filtrate tank 14 and is then fed into the primary washing tank 11 to be mixed with the kiln ash to make a slurry.
[0052] The second filtrate tank 14 is connected to the first plate and frame filter press 12. The filtrate from the second filtrate tank 14 is fed into the first plate and frame filter press 12 to wash the slurry residue in the plate and frame, so that the residual chloride ions in the slurry residue dissolve into the filtrate. Then, the filtrate enters the second filtrate tank 14 with the filtrate and enters the first plate and frame filter press 12 again. This process is repeated to circulate the solution between the second filtrate tank 14 and the first plate and frame filter press 12, thereby achieving the circulating water washing and dechlorination of the slurry residue in the plate and frame.
[0053] To ensure sufficient dissolution of chloride ions in the primary washing tank 11, the mixing time in step 1 is set to be no less than 30 minutes. During this mixing time, continuous stirring and the introduction of compressed air into the primary washing tank 11 achieve better dissolution, allowing more chloride ions to dissolve in the solution. Subsequently, the solid-liquid separation of the slurry and slag is effectively achieved through the solid-liquid separation action of the first plate and frame filter press 12. The separated filtrate enters the first filtrate tank 13. Therefore, this method enables reliable separation of chloride ions from the kiln ash. The chloride-rich solution in the first filtrate tank 13 is then recycled, thus recovering the chloride ions from the kiln ash.
[0054] After the first solid-liquid separation in the first plate and frame filter press 12, chloride ions still remain in the slag cake. By adding clean water to the first plate and frame filter press 12 and using the added clean water to repeatedly wash the slurry in the plate and frame, the residual chloride ions in the slag cake can be continuously dissolved, thereby achieving a reliable dechlorination effect on the kiln ash.
[0055] The amount of clean water added to the first plate and frame filter press 12 is fixed. Preferably, the amount of clean water added is equal to twice the mass of kiln ash. After all the clean water has been added, the water addition is stopped, and the slurry in the first plate and frame filter press 12 is repeatedly washed with the solution in the second filtrate tank 14. During the repeated washing process, the solution in the second filtrate tank 14 is continuously fed into the inlet of the first plate and frame filter press 12, and at the same time, the outlet of the first plate and frame filter press 12 continuously feeds the filtered solution into the second filtrate tank 14, thereby achieving the effect of circulating water washing of the slurry in the plate and frame filter press. During the circulating water washing process, the chloride ion content in the slurry continuously decreases until the chloride ion content in the slurry is lower than the set value. At this point, compressed air can be introduced into the first plate and frame filter press 12 to squeeze out the water contained in the slurry and discharge the remaining slurry.
[0056] At this time, the amount of solution in the second filtrate tank 14 is the same as the amount of clean water added to the first plate and frame filter press 12. At the same time, these solutions will be sent to the first-stage washing tank 11 to mix with kiln ash to form a slurry.
[0057] Therefore, by processing a fixed amount of kiln ash each time and determining whether to discharge slag cake by detecting the chloride ion content, the chloride ion content in the slag cake recycled into the raw material mill meets the system requirements. Thus, this method achieves reliable chloride removal from the kiln ash. Furthermore, by using a first plate and frame filter press, only approximately twice the weight of the kiln ash in clean water is needed each time to reliably remove chloride ions from the kiln ash, greatly saving water resources. Simultaneously, it enables simultaneous water washing and solid-liquid separation, reducing the complexity of the process equipment.
[0058] In one embodiment, a sampling point is provided on the connecting pipeline between the first plate and frame filter press and the second filtrate tank 14. By taking a sample at this sampling point and measuring the chloride ion content in the filtrate separated by the first plate and frame filter press, it is determined whether the chloride ion content in the slurry meets the requirements for discharging slag cake.
[0059] Preferably, after the plate and frame filter press has completed the slurry filtration, compressed air is introduced into the diaphragm of the first plate and frame filter press 12. The compressed air will squeeze the slurry residue in the plate and frame filter press, thereby further dewatering the slurry and reducing the water content of the residue cake.
[0060] Moreover, in this way, the amount of clean water added to the first plate and frame filter press 12 is equal to the amount of filtrate in the first filtrate tank 13 and also equal to the amount of filtrate in the second filtrate tank 14. Therefore, each time only a fixed amount of clean water needs to be added to the first plate and frame filter press 12, the same amount of chloride-rich solution can be discharged, and the same amount of solution can be input into the primary washing tank 11.
[0061] Preferably, the mass ratio of clean water to kiln ash is 2:1. The washing unit processes the same mass of kiln ash each time, and the first plate and frame filter press 12 introduces clean water with a mass twice that of kiln ash into the washing unit. By setting the mixing ratio of clean water and kiln ash, the water content in the first filtrate tank 13 is kept stable, avoiding excessive water content in the solution entering the subsequent evaporation and salt production process, which would affect the processing efficiency and increase the system energy consumption.
[0062] Clean water is added to the first plate and frame filter press 12 and circulated between the first plate and frame filter press 12 and the second filtrate tank 14 to repeatedly wash the slurry residue in the first plate and frame filter press 12, so as to continuously dissolve chloride ions in the slurry residue into the filtrate until the chloride ion content in the slurry residue is reduced to below a set value. Then, compressed air is introduced into the first plate and frame filter press 12 to press the slurry residue in the plate and frame into a cake, and the separated filtrate is sent to the second filtrate tank 14. Then, the filtrate in the second filtrate tank 14 is fed into the first water washing tank and mixed with the kiln ash to be treated next to form the next batch of slurry.
[0063] Preferably, two primary washing tanks 11 are provided. After the slurry from one primary washing tank 11 is fed into the first plate and frame filter press 12, the other primary washing tank 11 begins mixing the slurry. After the first plate and frame filter press 12 completes washing, the separated filtrate enters the second filtrate tank 14, and the residue cake is conveyed to the raw material mill. Then, the filtrate in the second filtrate tank 14 is conveyed to the emptied primary washing tank 11, where it begins mixing the slurry. Simultaneously, the mixing work in the other primary washing tank 11 is completed, and the mixed slurry is conveyed to the first plate and frame filter press 12. Therefore, during the operation of the first plate and frame filter press 12, one primary washing tank 11 is simultaneously mixing the slurry, while the other primary washing tank 11 can perform pre-mixing preparation work. After the first plate and frame filter press 12 completes its work, the primary washing tank 11, which simultaneously mixes the slurry, has also completed the slurry mixing process and can supply slurry to the first plate and frame filter press 12, enabling the first plate and frame filter press 12 to operate continuously. At the same time, the solution discharged from the first plate and frame filter press 12 will enter the waiting primary washing tank 11 through the second filtrate tank 14. The primary washing tank 11 will simultaneously mix the slurry with the first plate and frame filter press 12 so that it can supply slurry to the first plate and frame filter press 12 after its work is completed. Therefore, by setting up two primary washing tanks 11, the purpose of continuous operation of the first plate and frame filter press 12 can be achieved, thereby improving the working efficiency of the washing unit.
[0064] Preferably, when the working time of the first plate and frame filter press 12 is less than the mixing time of the primary washing tank 11, more than two primary washing tanks 11 can be set up so that the first plate and frame filter press 12 can work continuously.
[0065] In this embodiment, preferably, the mixing time in step 1 is set to be no less than 30 minutes;
[0066] In step 4, the chloride ion content in the filtrate obtained from water washing is detected, and the water washing cycle is terminated based on the detection results.
[0067] In order to achieve full dissolution of chloride ions in kiln ash, the mixing time in step 1 is set to be no less than 30 minutes. Preferably, the water washing time of the first plate and frame filter press 12 is set to 30-60 minutes. Therefore, the working time of the first plate and frame filter press 12 can cover the mixing time in step 1.
[0068] A fixed amount of clean water is added to the first plate and frame filter press 12. The added clean water is circulated between the first plate and frame filter press 12 and the second filtrate tank 14 to repeatedly wash the slurry residue in the first plate and frame filter press 12. Eventually, this clean water will dissolve the chloride ions in the slurry residue and enter the second filtrate tank 14.
[0069] Subsequently, the slurry in the primary washing tank 11 is fed into the first plate and frame filter press 12. Under the action of the first plate and frame filter press 12, the liquid in the slurry is fed into the first filtrate tank 13. At the same time, the primary washing tank 11 is emptied, and the solution originally stored in the second filtrate tank 14 is fed into the primary washing tank 11.
[0070] In this way, clean water passes through the first plate and frame filter press 12 and sequentially enters the second filtrate tank 14 and the primary washing tank 11, and is finally discharged from the first filtrate tank 13. Throughout the process, chloride ions are enriched in the filtrate. Meanwhile, the chloride ion content in the slurry within the plates and frames of the first plate and frame filter press 12 gradually decreases. By detecting the chloride ion content in the filtrate obtained from the washing process, it can be determined whether the chloride ion content in the slurry has been reduced to the set value. If the measurement result shows that the chloride ion content is very low and meets the discharge requirements of the slurry, compressed air can be introduced into the first plate and frame filter press 12, and then the sludge cake can be discharged.
[0071] Preferably, when the processing time of step 4 reaches the set time, the filtrate obtained from the water washing can be sampled and tested to determine whether the water washing cycle has ended.
[0072] In this embodiment, preferably, in step 1, the added kiln ash is weighed and a fixed mass of kiln ash is added to the primary washing tank 11.
[0073] The first plate and frame filter press 12 processes the same quality of kiln ash each time. This batch processing method for kiln ash can achieve a reliable dechlorination effect, avoiding the unsatisfactory dechlorination effect caused by continuous production line operation.
[0074] Preferably, by setting up multiple primary washing tanks 11 connected to the first plate and frame filter press 12, the first plate and frame filter press 12 can still maintain continuous operation, thereby improving working efficiency.
[0075] In this embodiment, preferably, the slag cake is fed into the raw material mill in step 5.
[0076] After the first plate and frame filter press 12 washes the slag cake, although a lot of chloride ions have been dissolved and separated, a small amount of chloride ions still remain in the slag cake. By feeding these slag cakes into the raw material grinding system, zero chloride ion discharge can be achieved.
[0077] The present invention also provides a method for treating kiln ash, comprising:
[0078] Step 1: Use the kiln ash dechlorination method to wash the kiln ash with water to remove chloride ions. Chloride ions enter the first filtrate tank 13, and the dechlorinated kiln ash becomes slag cake and is collected.
[0079] Step 2: Pre-treat the filtrate in the first filtrate tank 13;
[0080] Step 3: Evaporate the pretreated solution to obtain potassium and sodium salts.
[0081] After the kiln ash is dechlorinated by washing with water, the dechlorinated kiln ash becomes a slag cake and is sent back to the raw material grinding system. This not only achieves zero discharge of chloride ions, but also realizes the recycling and reuse of raw materials. The chloride ions are enriched in the solution, and these solutions are made into potassium salts and sodium salts through subsequent recovery processes, thereby realizing the resource-based treatment of chloride ions in the kiln ash and reliably completing the removal and recovery of chloride ions in the kiln ash.
[0082] In this embodiment, preferably, the pretreatment in step 2 includes degravation, dehardening and neutralization, wherein the solids separated after degravation and dehardening are fed into the raw material mill together with the dechlorinated kiln ash in step 1.
[0083] During the heavy metal removal and hardening treatment process, heavy metal removal agents and sodium carbonate are added to the solution to remove heavy metals and hardening agents, thereby removing calcium from the wastewater. 2+ The concentration was reduced from 1000-3000 mg / L to 50 mg / L. The mixture was then subjected to solid-liquid separation using a second plate and frame filter press 21. The solid phase in the separated mixture was transported to a raw material mill along with the dechlorination kiln ash for use as cement raw material, while the separated liquid phase entered the subsequent neutralization process. In one embodiment, sodium thiosulfate was used as the heavy metal removal agent.
[0084] During the neutralization process, hydrochloric acid is added to the solution to lower the pH value from 13 to 7. After the neutralization process is completed, the solution enters the evaporation salt production unit.
[0085] In this embodiment, preferably, in step 3, the evaporation temperature is 80-100°C, an MVR evaporator is used, and potassium chloride crystals are obtained by centrifugal separation.
[0086] During the evaporation and crystallization process using an MVR evaporator, the MVR evaporator is first started to circulate and crystallize the solution. Pretreated high-salt wastewater is introduced into the evaporator, where water evaporates and the salt solution is concentrated. At the same time, potassium chloride crystals precipitate out. The centrifugal filtration section in the MVR evaporator separates the crystallized potassium chloride by centrifugation and collects the separated potassium chloride. The separated liquid continues to evaporate and crystallize in the MVR evaporator, thus achieving the effect of cyclic evaporation and crystallization.
[0087] During the crystallization of potassium chloride, the evaporation temperature needs to be controlled between 80 and 100°C. Since the Na ion content in the system is low (≤1% based on sodium chloride conversion) and the potassium chloride content is approximately 15 wt%, the system is dominated by potassium chloride. According to the ternary aqueous phase diagram of sodium chloride and potassium chloride, when the sodium chloride content is less than 16.8 wt% at 100°C, the system is in the region where potassium chloride crystals form. Therefore, by controlling the evaporation temperature, potassium chloride (KCl) crystals will preferentially precipitate during this evaporation crystallization process.
[0088] Therefore, during the centrifugal separation process in the MVR evaporator, the centrifuge separates the mixed liquid after evaporation and crystallization to obtain potassium chloride crystals. The separated mother liquor is returned to the MVR evaporator for further concentration. When the sodium chloride content in the mother liquor approaches 16.8 wt%, the circulation is stopped, and the remaining solution is discharged into the vacuum dryer.
[0089] The pretreated mother liquor is fed into the vacuum dryer at a flow rate of 100–250 kg / h, where it undergoes salt drying. The vacuum dryer utilizes steam heating and vacuum negative pressure to remove moisture from the mother liquor, ultimately yielding a mixed salt containing NaCl and KCl with a water content ≤10%.
[0090] In this embodiment, preferably, in step 3, when the sodium chloride concentration in the mother liquor is close to 16.8 wt%, the mother liquor is transported to a vacuum drying machine to obtain mixed salt.
[0091] During the crystallization of potassium chloride, the evaporation temperature needs to be controlled between 80 and 100°C. Since the Na ion content in the system is low (≤1% based on sodium chloride conversion) and the potassium chloride content is approximately 15 wt%, the system is dominated by potassium chloride. According to the ternary aqueous phase diagram of sodium chloride and potassium chloride, when the sodium chloride content is less than 16.8 wt% at 100°C, the system is in the region where potassium chloride crystals are formed. Therefore, by controlling the evaporation temperature, potassium chloride (KCl) crystals are preferentially precipitated from the evaporated product.
[0092] Therefore, during the centrifugal separation process in the MVR evaporator, the centrifuge separates the mixed liquid after evaporation and crystallization to obtain potassium chloride crystals. The separated mother liquor is returned to the MVR evaporator for further concentration. When the sodium chloride content in the mother liquor approaches 16.8 wt%, the circulation is stopped, and the remaining solution is discharged into the vacuum dryer.
[0093] The present invention also provides a kiln ash disposal system for use in a kiln ash disposal method, comprising a water washing unit, a water treatment unit, and an evaporation salt production unit. In the kiln ash dechlorination method, the water washing unit is used to dechlorinate the kiln ash. The filtrate in the first filtrate tank 13 is transported to the water treatment unit for pretreatment. The filtrate obtained from the pretreatment enters the evaporation salt production unit to obtain potassium salt and sodium salt.
[0094] The washing unit includes a primary washing tank 11 and a first plate and frame filter press 12. The primary washing tank 11 and the first plate and frame filter press 12 respectively perform primary washing and circulating washing on the kiln ash. The solution is circulated by setting a second filtrate tank 14 connected to the first plate and frame filter press 12. After circulating washing by the first plate and frame filter press 12, the dechlorinated kiln ash is sent back to the raw material mill system, while the chloride-rich solution is stored in the first filtrate tank 13.
[0095] After the solution in the first filtrate tank 13 enters the water treatment unit, it undergoes degravation and dehardening treatment, followed by neutralization with hydrochloric acid. The resulting solution then enters the evaporation and salt production unit to separate the potassium and sodium salts from the solution.
[0096] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.
[0097] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.
[0098] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.
Claims
1. A method for removing chlorine from kiln ash, characterized in that, include: Step 1: Mix kiln ash and water in the primary washing tank (1); Step 2: Input the slurry in the primary washing tank (1) into the first plate and frame filter press (12) for solid-liquid separation. The resulting filtrate is input into the first filtrate tank (13), while the slurry residue remains in the plate and frame filter press. Step 3: Input a fixed mass of clean water into the first plate and frame filter press (12), and input the resulting filtrate into the second filtrate tank (14). The mass ratio of the input clean water to the mass of the kiln ash added in step 1 is 1.5:1-3:
1. Step 4: Input the filtrate in the second filtrate tank (14) into the first plate and frame filter press (12) to circulate and wash the kiln ash; After steps 5 and 4 are completed, compressed air is introduced into the diaphragm of the first plate and frame filter press (12) to perform solid-liquid separation. The first plate and frame filter press (12) discharges the slag cake and the filtrate enters the second filtrate tank (14). In step 1, the water in the primary washing tank (1) comes from the second filtrate tank (14).
2. The method for dechlorinating kiln ash according to claim 1, characterized in that, The mixing time in step 1 should be set to no less than 30 minutes. In step 4, the chloride ion content in the filtrate obtained from water washing is detected, and the water washing cycle is terminated based on the detection results.
3. The method for dechlorinating kiln ash according to claim 2, characterized in that, In step 1, the kiln ash is weighed and a fixed mass of kiln ash is added to the primary water washing tank (1).
4. The method for dechlorinating kiln ash according to claim 1, characterized in that, In step 5, the residue cake is fed into the raw material mill.
5. A method for treating kiln ash, characterized in that, include: Step 1: Use the kiln ash dechlorination method described in any one of claims 1-4 to wash the kiln ash with water to remove chloride ions. Chloride ions enter the first filtrate tank (13), and the dechlorinated kiln ash becomes slag cake and is collected. Step 2: Pre-treat the filtrate in the first filtrate tank (13); Step 3: Evaporate the pretreated solution to obtain potassium and sodium salts.
6. The method for treating kiln ash according to claim 5, characterized in that, The pretreatment in step 2 includes degravation, dehardening and neutralization. The solids separated after degravation and dehardening are fed into the raw material mill together with the dechlorinated kiln ash from step 1.
7. The method for treating kiln ash according to claim 5, characterized in that, In step 3, the evaporation temperature is 80-100℃, an MVR evaporator is used, and potassium chloride crystals are obtained by centrifugal separation.
8. The method for treating kiln ash according to claim 6, characterized in that, In step 3, when the sodium chloride concentration in the mother liquor is close to 16.8%, the mother liquor is transported to a vacuum drying machine to obtain mixed salt.
9. A kiln ash disposal system used in the kiln ash disposal method according to any one of claims 5-8, characterized in that, It includes a water washing unit, a water treatment unit, and an evaporation salt production unit. The method for dechlorinating kiln ash according to claims 1-4 uses the water washing unit to dechlorinate the kiln ash. The filtrate in the first filtrate tank (13) is transported to the water treatment unit for pretreatment. The filtrate obtained from the pretreatment enters the evaporation salt production unit to obtain potassium salt and sodium salt.