Method for separating chlorine salt from waste incineration fly ash through multi-stage washing

Abstract

The invention belongs to the technical field of waste incineration treatment, and discloses a method for separating chlorine salt from waste incineration fly ash through multi-stage washing, which comprises the following steps: taking waste incineration fly ash, carrying out multi-stage washing and solid-liquid separation to obtain washing liquid and washing fly ash, carrying out purification treatment and membrane filtration on the washing liquid to obtain a salt solution, the salt solution is subjected to evaporation, salt separation and crystallization treatment, and chlorine salt is obtained through separation; the content of chlorine in the waste incineration fly ash is 10-20%, the content of CaO is 30-40%, and the content of MgO is 1-3%. According to the method, the separation effect of chloride ions in fly ash can be improved by controlling the treatment process parameters of multi-stage washing, and then the salt solution with specific ion content is subjected to evaporation, salt separation and crystallization treatment, so that the recovery rate of chlorine salt can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of waste incineration treatment, and in particular relates to a method for separating chloride salts from waste incineration fly ash by multi-stage water washing. Background Art

[0002] Waste incineration fly ash is the collection of flue gas purification systems and bottom ash settled at the bottom of flues and chimneys during the incineration of municipal domestic waste. my country's large and medium-sized cities produce a large amount of fly ash and have scarce land resources. The main disposal method of landfill is no longer sustainable. With the implementation of relevant policies, national and local policies have gradually shifted to resource utilization.

[0003] The common treatment processes for waste incineration fly ash in the existing technology generally include a series of production processes such as water washing, filter pressing, drying, high-temperature calcination and evaporation, which can effectively remove harmful factors in fly ash, solidify heavy metals and dioxins, and produce industrial salt, caustic soda, sodium chloride, potassium chloride, calcium oxide, industrial-grade new materials and other products, thereby achieving harmlessness, reduction and resource reuse of fly ash.

[0004] Soluble chloride salts are a difficult point in the harmless and resource-based disposal of fly ash. They not only increase the leaching toxicity and migration risk of heavy metals, but also reduce the strength and stability of resource-based products. During the high-temperature melting / sintering process, the soluble salts in the fly ash will volatilize into the flue gas, causing equipment blockage, corrosion, crusting and other problems. At present, most people are concerned about the removal of chloride ions. In fact, the chloride ions in fly ash mostly exist in the form of soluble chlorides or chlorates, with a content of generally 10% to 30%, and up to about 40%. If these soluble chlorides or chlorates are not recovered, it will cause great waste. In addition, fly ash contains not only a large amount of chlorine, but also a large amount of calcium and magnesium compounds. These calcium and magnesium compounds are easy to affect the dissolution effect of chloride ions, and then affect the separation of chloride salts.

[0005] In summary, it is an urgent problem to provide a method for separating chloride salts from waste incineration fly ash by multi-stage water washing, while improving the separation effect of chloride ions in fly ash and the recovery rate of chloride salts. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the existing technology and provide a method for separating chloride salts from fly ash from waste incineration by multi-stage water washing. The separation effect of chloride ions in fly ash can be improved by controlling the processing parameters of the multi-stage water washing. Then, a salt solution with a specific ion content is evaporated and crystallized to improve the recovery rate of chloride salts.

[0007] To achieve the above object, the present invention adopts the following technical solutions: A method for separating chloride salt from waste incineration fly ash by multi-stage water washing, comprising the following steps: taking waste incineration fly ash (in a 150-200r / min mixer) and performing multi-stage water washing, obtaining washing liquid and washed fly ash after solid-liquid separation, obtaining salt solution after purification and membrane filtration of the washing liquid, and performing evaporation, salt separation and crystallization treatment on the salt solution to separate the chloride salt.

[0008] The chlorine content of the waste incineration fly ash is 10-20%, the CaO content is 30-40%, and the MgO content is 1-3%. Preferably, the chlorine content of the waste incineration fly ash is 15%, the CaO content is 36%, and the MgO content is 1.7%.

[0009] Preferably, the liquid-to-solid ratio of the multi-stage water washing is 9-12 L / Kg, the water washing time is 16-26 min, and the water washing temperature is 70-90°C.

[0010] Preferably, the multi-stage water washing is six-stage water washing, the liquid-solid ratio of the first-stage water washing is 12 L / Kg, the washing time is 26 min, and the washing temperature is 80°C; the liquid-solid ratio of the second-stage water washing is 9 L / Kg, the washing time is 16 min, and the washing temperature is 70°C; the liquid-solid ratio of the third-stage water washing is 12 L / Kg, the washing time is 21 min, and the washing temperature is 90°C; the liquid-solid ratio of the fourth-stage water washing is 11L / Kg, the washing time is 20 min, and the washing temperature is 75°C; the liquid-solid ratio of the fifth-stage water washing is 10 L / Kg, the washing time is 18 min, and the washing temperature is 70°C; the liquid-solid ratio of the sixth-stage water washing is 9 L / Kg, the washing time is 25 min, and the washing temperature is 70°C.

[0011] Preferably, the pH value of the waste incineration fly ash is 11-13.

[0012] Preferably, the purification treatment includes heavy metal removal treatment and flocculation sedimentation treatment in sequence.

[0013] The heavy metal removal treatment is specifically as follows: a heavy metal capture agent is added to the water washing liquid for treatment, wherein the heavy metal capture agent is sodium sulfide or sodium thiosulfate, and the added amount thereof is 3-9% of the mass of the waste incineration fly ash.

[0014] The flocculation and precipitation treatment is specifically as follows: a flocculant is added to the liquid treated with heavy metals for precipitation, wherein the flocculant is aluminum sulfate, ferrous sulfate, polyaluminum chloride, polysilicic acid flocculant, polyaluminum chloride phosphorus or polyacrylamide, and the amount of the flocculant added is 0.1-1% of the mass of the liquid treated with heavy metals.

[0015] Preferably, the pore size of the membrane filtration is 0.01-10 μm.

[0016] The present invention also provides an evaporation salt separation and crystallization treatment method in a method for separating chloride salts by multi-stage water washing of waste incineration fly ash, comprising: (1) Pretreatment for removing calcium and magnesium ions: The carbonate aqueous solution (mass concentration of 15-30%) is transported to a thickener filled with salt solution. After the reaction, a precipitate is formed. The precipitate is removed by centrifugation and the pH of the supernatant is adjusted to 6 to obtain a pretreated solution. (2) After preheating (70-90°C) and gas-liquid separation, the pretreated liquid is transported to an evaporator for evaporation to obtain a crystal slurry. The crystal slurry is centrifuged and filtered to obtain sodium chloride crystals. The supernatant then enters a cooling crystallization device to precipitate potassium chloride crystals.

[0017] Preferably, the salt solution has an initial chloride ion content of 5-10 g / L, an initial calcium ion content of 2-6 g / L, and an initial magnesium ion content of 0.1-0.3 g / L.

[0018] Preferably, in step (1), the amount of carbonate added is 5-10% of the mass of the salt solution, and the carbonate is sodium carbonate or potassium carbonate.

[0019] Preferably, in step (2), the evaporator comprises a first-stage falling film evaporator and a second-stage forced circulation evaporator, the initial concentration of the feed liquid in the first-stage falling film evaporator is 1.00-1.39%, and the first-stage evaporation capacity is 28-36 t / h; the initial concentration of the feed liquid in the second-stage forced circulation evaporator is 4.5-5.2%, and the second-stage evaporation capacity is 8-12 t / h.

[0020] Preferably, the cooling crystallization device comprises a first-stage cooling crystallization device and a second-stage cooling crystallization device, the temperature in the first-stage cooling crystallization device is not higher than 45°C, and the temperature in the second-stage cooling crystallization device is not higher than 25°C.

[0021] The beneficial effects of the present invention are: (1) The content of each element in the washing process will have an impact on the washing process. The present invention performs multi-stage washing on waste incineration fly ash with a specific component content. By controlling process parameters such as the liquid-to-solid ratio, washing time, and washing temperature during the washing process, the removal rate of chloride salts in the fly ash can be improved.

[0022] (2) After the fly ash is washed with water, the washing liquid contains calcium and magnesium ions, especially a large amount of calcium ions, which affect the crystallization process of chloride salt. Therefore, when the washing liquid is subjected to evaporation and salt separation and crystallization treatment, carbonate is first used for pretreatment, which can react to form solid salt precipitation and effectively remove Ca in the washing liquid. 2+ Mg 2+. The initial chloride ion content and magnesium ion content in the salt solution have a great influence on the pretreatment of calcium and magnesium ion removal. The present application can improve the calcium and magnesium removal effect in the salt solution by limiting the initial calcium ion content in the salt solution to 2-6 g / L, the initial magnesium ion content to 0.1-0.3 g / L, and controlling the amount of carbonate added.

[0023] (3) The chloride ion content in the salt solution obtained by washing and purifying the fly ash has a significant effect on the effect of the evaporation and salt crystallization treatment. When the present invention performs the evaporation and salt crystallization treatment, the initial chloride ion content of the water washing liquid is controlled to be 5-10 g / L, which can obtain a better evaporation and crystallization effect. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. 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.

[0025] Unless otherwise specified, the reagents involved in the embodiments of the present invention are all commercially available products and can be purchased through commercial channels. Example 1

[0026] The waste incineration fly ash used in this embodiment has a chlorine content of 15%, a CaO content of 36%, and a MgO content of 1.7%. The pH of the waste incineration fly ash is 11-13.

[0027] The present embodiment provides a method for separating chloride salts from waste incineration fly ash by multi-stage water washing, comprising the following steps: taking waste incineration fly ash (in a 170r / min mixer) and performing multi-stage water washing to obtain a washing liquid and washed fly ash after solid-liquid separation, purifying the washing liquid and performing membrane filtration to obtain a salt solution, and performing evaporation and salt separation and crystallization on the salt solution to separate the chloride salts.

[0028] The multi-stage water washing is a three-stage water washing, the liquid-to-solid ratio of each stage of water washing is 9 L / Kg, the water washing time is 16 minutes, and the water washing temperature is 70°C.

[0029] The purification treatment includes heavy metal removal treatment and flocculation sedimentation treatment in sequence.

[0030] The specific heavy metal removal treatment is: adding heavy metal capture agent sodium sulfide to the water washing liquid for treatment, and the amount of sodium sulfide added is 5% of the mass of the waste incineration fly ash.

[0031] The flocculation and sedimentation treatment is specifically as follows: adding a flocculant, polyaluminium chloride, to the liquid treated with heavy metals for precipitation, and the amount of the flocculant added is 0.5% of the mass of the liquid treated with heavy metals.

[0032] The initial chloride ion content of the salt solution was 8 g / L, the initial calcium ion content was 3 g / L, and the initial magnesium ion content was 0.2 g / L.

[0033] The evaporation salt crystallization treatment method includes: (1) Pretreatment for removing calcium and magnesium ions: Sodium carbonate or potassium carbonate aqueous solution (mass concentration of 20%, added in an amount of 7% of the mass of the salt solution) is transported to a thickener filled with salt solution, and a precipitate is formed after the reaction. The precipitate is removed by centrifugation, and the pH of the supernatant is adjusted to 6 to obtain a pretreated solution; (2) After preheating (80°C) and gas-liquid separation, the pretreated liquid is transported to an evaporator for evaporation to obtain a crystal slurry. The crystal slurry is centrifuged and filtered to obtain sodium chloride crystals. The supernatant then enters a cooling crystallization device to precipitate potassium chloride crystals.

[0034] The evaporator includes a first-stage falling film evaporator and a second-stage forced circulation evaporator. The initial concentration of the feed liquid in the first-stage falling film evaporator is 1.2%, and the first-stage evaporation capacity is 32 t / h; the initial concentration of the feed liquid in the second-stage forced circulation evaporator is 4.8%, and the second-stage evaporation capacity is 10 t / h.

[0035] The cooling crystallization device comprises a first-stage cooling crystallization device and a second-stage cooling crystallization device, the temperature in the first-stage cooling crystallization device is not higher than 45°C, and the temperature in the second-stage cooling crystallization device is not higher than 25°C. Example 2

[0036] The difference between this embodiment and embodiment 1 is that the multi-stage water washing is six-stage water washing, the liquid-to-solid ratio of each stage of water washing is 9 L / Kg, the water washing time is 16 min, and the water washing temperature is 70°C. Example 3

[0037] The waste incineration fly ash used in this embodiment has a chlorine content of 10%, a CaO content of 30%, and a MgO content of 1%. The pH of the waste incineration fly ash is 11-13.

[0038] The present embodiment provides a method for separating chloride salts from waste incineration fly ash by multi-stage water washing, comprising the following steps: taking waste incineration fly ash (in a 150r / min mixer) and performing multi-stage water washing to obtain a washing liquid and washed fly ash after solid-liquid separation, purifying the washing liquid and performing membrane filtration to obtain a salt solution, and performing evaporation and salt separation and crystallization on the salt solution to separate the chloride salts.

[0039] The multi-stage water washing is a six-stage water washing, the liquid-to-solid ratio of each stage of water washing is 10 L / Kg, the water washing time is 21 minutes, and the water washing temperature is 90°C.

[0040] The purification treatment includes heavy metal removal treatment and flocculation sedimentation treatment in sequence.

[0041] The specific heavy metal removal treatment is: adding heavy metal capture agent sodium sulfide to the water washing liquid for treatment, and the amount of sodium sulfide added is 5% of the mass of the waste incineration fly ash.

[0042] The flocculation and sedimentation treatment is specifically as follows: a flocculant polyaluminum chlorinated phosphorus is added to the liquid treated with heavy metals for precipitation, and the amount of the flocculant added is 0.3% of the mass of the liquid treated with heavy metals.

[0043] The initial chloride ion content of the salt solution is 5 g / L, the initial calcium ion content is 2 g / L, and the initial magnesium ion content is 0.1 g / L. The evaporation salt crystallization treatment method includes: (1) Pretreatment for removing calcium and magnesium ions: Sodium carbonate or potassium carbonate aqueous solution (mass concentration of 15%, added in an amount of 10% of the mass of the salt solution) is transported to a thickener filled with salt solution, and a precipitate is formed after the reaction. The precipitate is removed by centrifugation, and the pH of the supernatant is adjusted to 6 to obtain a pretreated solution; (2) After preheating (70°C) and gas-liquid separation, the pretreated liquid is transported to an evaporator for evaporation to obtain a crystal slurry. The crystal slurry is centrifuged and filtered to obtain sodium chloride crystals. The supernatant then enters a cooling crystallization device to precipitate potassium chloride crystals.

[0044] The evaporator includes a first-stage falling film evaporator and a second-stage forced circulation evaporator. The initial concentration of the feed liquid in the first-stage falling film evaporator is 1.00%, and the first-stage evaporation capacity is 28 t / h; the initial concentration of the feed liquid in the second-stage forced circulation evaporator is 4.5%, and the second-stage evaporation capacity is 8 t / h.

[0045] The cooling crystallization device comprises a first-stage cooling crystallization device and a second-stage cooling crystallization device, the temperature in the first-stage cooling crystallization device is not higher than 45°C, and the temperature in the second-stage cooling crystallization device is not higher than 25°C. Example 4

[0046] The waste incineration fly ash used in this embodiment has a chlorine content of 20%, a CaO content of 40%, and a MgO content of 3%. The pH of the waste incineration fly ash is 11-13.

[0047] The present embodiment provides a method for separating chloride salts from waste incineration fly ash by multi-stage water washing, comprising the following steps: taking waste incineration fly ash (in a 200r / min mixer) and performing multi-stage water washing to obtain a washing liquid and washed fly ash after solid-liquid separation, purifying the washing liquid and performing membrane filtration to obtain a salt solution, and performing evaporation and salt separation and crystallization on the salt solution to separate the chloride salts.

[0048] The multi-stage water washing is a six-stage water washing, the liquid-to-solid ratio of each stage of water washing is 12 L / Kg, the water washing time is 26 minutes, and the water washing temperature is 80°C.

[0049] The purification treatment includes heavy metal removal treatment and flocculation sedimentation treatment in sequence.

[0050] The specific heavy metal removal treatment is: adding heavy metal capture agent sodium sulfide to the water washing liquid for treatment, and the amount of sodium sulfide added is 3% of the mass of the waste incineration fly ash.

[0051] The flocculation and sedimentation treatment is specifically as follows: adding a flocculant polyacrylamide to the liquid treated with heavy metals for precipitation, and the amount of the flocculant added is 0.6% of the mass of the liquid treated with heavy metals.

[0052] The initial chloride ion content of the salt solution is 10 g / L, the initial calcium ion content is 6 g / L, and the initial magnesium ion content is 0.3 g / L. The evaporation salt crystallization treatment method includes: (1) Pretreatment for removing calcium and magnesium ions: Sodium carbonate or potassium carbonate aqueous solution (mass concentration of 30%, added in an amount of 5% of the mass of the salt solution) is transported to a thickener filled with salt solution, and a precipitate is formed after the reaction. The precipitate is removed by centrifugation, and the pH of the supernatant is adjusted to 6 to obtain a pretreated solution; (2) After preheating (90°C) and gas-liquid separation, the pretreated liquid is transported to an evaporator for evaporation to obtain a crystal slurry. The crystal slurry is centrifuged and filtered to obtain sodium chloride crystals. The supernatant then enters a cooling crystallization device to precipitate potassium chloride crystals.

[0053] The evaporator includes a first-stage falling film evaporator and a second-stage forced circulation evaporator. The initial concentration of the feed liquid in the first-stage falling film evaporator is 1.39%, and the first-stage evaporation capacity is 36 t / h; the initial concentration of the feed liquid in the second-stage forced circulation evaporator is 5.2%, and the second-stage evaporation capacity is 12 t / h.

[0054] The cooling crystallization device comprises a first-stage cooling crystallization device and a second-stage cooling crystallization device, the temperature in the first-stage cooling crystallization device is not higher than 45°C, and the temperature in the second-stage cooling crystallization device is not higher than 25°C. Example 5

[0055] The difference between this embodiment and embodiment 1 is that the multi-stage water washing is six-stage water washing, the liquid-solid ratio of the first-stage water washing is 12 L / Kg, the washing time is 26 min, and the washing temperature is 80°C; the liquid-solid ratio of the second-stage water washing is 9 L / Kg, the washing time is 16 min, and the washing temperature is 70°C; the liquid-solid ratio of the third-stage water washing is 12 L / Kg, the washing time is 21 min, and the washing temperature is 90°C; the liquid-solid ratio of the fourth-stage water washing is 11 L / Kg, the washing time is 20 min, and the washing temperature is 75°C; the liquid-solid ratio of the fifth-stage water washing is 10 L / Kg, the washing time is 18 min, and the washing temperature is 70°C; the liquid-solid ratio of the sixth-stage water washing is 9 L / Kg, the washing time is 25 min, and the washing temperature is 70°C.

[0056] Comparative Example 1 Compared with Example 2, the chlorine content in the waste incineration fly ash is 7%.

[0057] Comparative Example 2 Compared with Example 2, the chlorine content in the waste incineration fly ash is 23%.

[0058] Comparative Example 3 Compared with Example 2, the CaO content in the waste incineration fly ash is 25%.

[0059] Comparative Example 4 Compared with Example 2, the CaO content in the waste incineration fly ash is 45%.

[0060] Comparative Example 5 Compared with Example 2, the MgO content in the waste incineration fly ash is 0.7%.

[0061] Comparative Example 6 Compared with Example 2, the MgO content in the waste incineration fly ash is 3.5%.

[0062] Comparative Example 7 Compared with Example 2, the water-to-solid ratio of each stage of washing is 8 L / Kg.

[0063] Comparative Example 8 Compared with Example 2, the water-solid ratio of each stage of washing is 13 L / Kg.

[0064] Comparative Example 9 Compared with Example 2, the washing time for each stage is 12 minutes.

[0065] Comparative Example 10 Compared with Example 2, the washing time for each stage is 30 minutes.

[0066] Comparative Example 11 Compared with Example 2, the water washing temperature of each stage is 60°C.

[0067] Comparative Example 12 Compared with Example 2, the water washing temperature of each stage is 95°C.

[0068] Comparative Example 13 Compared with Example 5, the initial chloride ion content of the salt solution is 3 g / L.

[0069] Comparative Example 14 Compared with Example 5, the initial chloride ion content of the salt solution is 12 g / L.

[0070] Comparative Example 15 Compared with Example 5, the initial calcium ion content of the salt solution is 1 g / L.

[0071] Comparative Example 16 Compared with Example 5, the initial calcium ion content of the salt solution is 7 g / L.

[0072] Comparative Example 17 Compared with Example 5, the initial magnesium ion content of the salt solution is 0.05 g / L.

[0073] Comparative Example 18 Compared with Example 5, the initial magnesium ion content of the salt solution is 0.4 g / L.

[0074] Comparative Example 19 Compared with Example 5, the amount of carbonate added is 3% of the mass of the salt solution.

[0075] Comparative Example 20 Compared with Example 5, the amount of carbonate added is 12% of the mass of the salt solution.

[0076] 1. Chlorine removal rate in fly ash after multi-stage water washing The fly ash was washed with water in multiple stages using the methods of Examples 1-5 and Comparative Examples 1-12, filtered and dried after washing, the chlorine content in the washed fly ash was measured, and the chlorine removal rate was calculated. The results are shown in Table 1 below.

[0077] Table 1

[0078] As can be seen from Table 1, the chlorine removal rates of Examples 1-5 of the present invention on fly ash are in the range of 93.2-98.8%, and in particular, the chlorine removal rate of Example 5 is as high as 98.8%.

[0079] Compared with Example 2, Comparative Examples 1-12 respectively changed the chlorine content, CaO content, MgO content in the waste incineration fly ash, as well as the liquid-to-solid ratio of each stage of water washing, water washing time, water washing temperature and other process parameters. As a result, the chlorine removal rate in the fly ash decreased to varying degrees, indicating that these parameters will affect the chlorine removal rate.

[0080] 2. Effect of removing calcium and magnesium ions from salt solution after washing The methods of Example 5 and Comparative Examples 15-20 were used to pretreat the salt solution obtained after multi-stage water washing and purification of fly ash to remove calcium and magnesium ions. The calcium and magnesium ion contents in the pretreated solution were determined, and the calcium and magnesium ion removal rates were calculated. The results are shown in Table 2 below.

[0081] Table 2

[0082] As can be seen from Table 2, the removal rates of calcium and magnesium ions in the salt solution in Example 5 of the present invention reached 97.7% and 96.5%, respectively, showing a good calcium and magnesium removal effect.

[0083] Compared with Example 5, Comparative Examples 15-20 respectively changed the initial calcium and magnesium ion contents in the salt solution and the amount of carbonate added, and as a result, the calcium and magnesium ion removal rates were reduced.

[0084] 3. Determination of sodium chloride and potassium chloride obtained by evaporation and crystallization 1. Recovery rate of sodium chloride and potassium chloride The fly ash was subjected to multi-stage water washing and evaporation and salt separation crystallization treatments using the methods of Examples 1-5 and Comparative Examples 13-20, respectively. The amounts of sodium chloride and potassium chloride crystals obtained were measured, and the recovery rates were calculated. The results are shown in Table 3 below.

[0085] Table 3

[0086] As can be seen from Table 3, the recovery rates of sodium chloride in fly ash in Examples 1-5 of the present invention are in the range of 91.3-98.1%, and the recovery rates of potassium chloride are in the range of 92.2-97.5%. In particular, the recovery rate of sodium chloride in Example 5 is as high as 98.1%, and the recovery rate of potassium chloride is as high as 97.5%.

[0087] Compared with Example 5, Comparative Examples 13-20 respectively changed the initial chloride ion content, initial calcium and magnesium ion content, and the amount of carbonate added in the salt solution, resulting in reduced recovery rates of sodium chloride and potassium chloride.

[0088] 2. Quality testing of sodium chloride and potassium chloride The sodium chloride and potassium chloride crystals obtained by the present invention were subjected to quality inspection. The sodium chloride product was tested with reference to the industrial dry salt standard "Industrial Salt" (GB / T5462-2015), and the potassium chloride product was tested with reference to the standard "Industrial Potassium Chloride" (GB / T 7118-2008). The results are shown in Table 4 below.

[0089] Table 4

[0090] As shown in Table 4, the sodium chloride and potassium chloride obtained by evaporation and crystallization of the present invention both meet the first-class indicators of the corresponding standards and are of excellent quality.

[0091] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for separating chloride salts from fly ash from garbage incineration by multi-stage water washing, characterized in that: The following steps are involved: The fly ash from garbage incineration is washed with water in multiple stages, and washing liquid and washed fly ash are obtained after solid-liquid separation. The washing liquid is purified and membrane filtered to obtain a salt solution, and the salt solution is evaporated and crystallized to separate the chloride salt; The waste incineration fly ash contains 10-20% chlorine, 30-40% CaO and 1-3% MgO.

2. The method according to claim 1, characterized in that: The waste incineration fly ash contains 15% chlorine, 36% CaO and 1.7% MgO.

3. The method according to claim 1, characterized in that: The pH value of the waste incineration fly ash is 11-13.

4. The method according to claim 1, characterized in that: The liquid-to-solid ratio of the multi-stage water washing is 9-12 L / Kg, the water washing time is 16-26 min, and the water washing temperature is 70-90°C.

5. The method according to claim 4, characterized in that: The multi-stage water washing is six-stage water washing, the liquid-solid ratio of the first-stage water washing is 12 L / Kg, the washing time is 26 min, and the washing temperature is 80°C; the liquid-solid ratio of the second-stage water washing is 9 L / Kg, the washing time is 16 min, and the washing temperature is 70°C; the liquid-solid ratio of the third-stage water washing is 12 L / Kg, the washing time is 21 min, and the washing temperature is 90°C; the liquid-solid ratio of the fourth-stage water washing is 11 L / Kg, the washing time is 20 min, and the washing temperature is 75°C; the liquid-solid ratio of the fifth-stage water washing is 10 L / Kg, the washing time is 18 min, and the washing temperature is 70°C; the liquid-solid ratio of the sixth-stage water washing is 9 L / Kg, the washing time is 25 min, and the washing temperature is 70°C.

6. A method for evaporation and salt separation and crystallization according to claim 1, characterized in that: The evaporation and salt separation crystallization treatment step comprises: (1) Pretreatment for removing calcium and magnesium ions: The carbonate aqueous solution is transported to a thickener filled with a salt solution, where a precipitate is formed after the reaction, and the precipitate is removed by centrifugation to obtain a pretreated solution; (2) After preheating and gas-liquid separation, the pretreated liquid is transported to an evaporator for evaporation to obtain a crystal slurry. The crystal slurry is centrifuged and filtered to obtain sodium chloride crystals. The supernatant then enters a cooling crystallization device to precipitate potassium chloride crystals.

7. The method according to claim 6, characterized in that: The salt solution has an initial chloride ion content of 5-10 g / L, an initial calcium ion content of 2-6 g / L, and an initial magnesium ion content of 0.1-0.3 g / L.

8. The method according to claim 6, characterized in that: In step (1), the amount of carbonate added is 5-10% of the mass of the salt solution, and the carbonate is sodium carbonate or potassium carbonate.

9. The method according to claim 6, characterized in that: In step (2), the evaporator includes a first-stage falling film evaporator and a second-stage forced circulation evaporator. The initial concentration of the feed liquid in the first-stage falling film evaporator is 1.00-1.39%, and the first-stage evaporation capacity is 28-36 t / h; the initial concentration of the feed liquid in the second-stage forced circulation evaporator is 4.5-5.2%, and the second-stage evaporation capacity is 8-12 t / h.

10. The method according to claim 6, characterized in that: The cooling crystallization device comprises a first-stage cooling crystallization device and a second-stage cooling crystallization device, the temperature in the first-stage cooling crystallization device is not higher than 45°C, and the temperature in the second-stage cooling crystallization device is not higher than 25°C.

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