System and method for treating ash of waste alkali furnace of POSM device

Abstract

The invention relates to the technical field of waste alkali furnace ash treatment, and particularly discloses a POSM device waste alkali furnace ash treatment system and method.The POSM device waste alkali furnace ash treatment system comprises a coagulation settling tank, the coagulation settling tank is connected with a buffer tank, the buffer tank is connected with a saline water tank, and the saline water tank is connected with a separation system through an eighth pipeline; a third pipeline is further connected to the eighth pipeline, the separation system is connected with a sodium salt multi-effect evaporation system through a sixth pipeline, the sixth pipeline is connected with a saline water tank through a fifth pipeline, and a fourth pipeline is further connected to the fifth pipeline. Finally, sodium carbonate in the furnace ash is recycled in a solid form, other carnallite is treated as solid hazardous waste, and the disposal amount of the hazardous waste in the device is greatly reduced; and in addition, condensate water and other solutions produced by the salt separation treatment unit are recycled into the furnace ash dissolving system, so that zero discharge of wastewater is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of waste alkali furnace ash treatment, and specifically to a treatment system and method for the waste alkali furnace ash of a POSM device. Background Technique

[0002] Due to the expansion of the domestic PO market demand, it has greatly promoted the growth of China's PO production capacity. The PO / SM method co-produces styrene, and the main raw materials are ethylene, benzene, propylene, etc., including peroxidation, epoxidation, propylene oxide refining, ethylbenzene recovery, acetophenone hydrogenation, dehydration of methylbenzyl alcohol, and styrene refining processes. For every 1t of propylene oxide produced, 1 - 2t of wastewater is generated. The organic matter content in the wastewater is too high, containing benzene ring substances, which are difficult to treat, and generally incineration method or advanced oxidation method (such as wet oxidation) is used for treatment. At present, for the furnace ash after incineration in domestic PO / SM devices, it is basically disposed of as hazardous waste, and the sodium salts in the furnace ash are not recovered, resulting in direct economic losses and increasing the pollution hazards in the chemical industry. Currently, the waste alkali incinerator generates a large amount of furnace ash every year. The bag dust collector of the waste alkali incinerator is provided with furnace ash collection, and there are two problems: First, the on-site bagging operation volume is large, the number of operating personnel is large, and it belongs to dust-related operations. It is not suitable to maintain this operating state in the high-temperature furnace area for a long time; Second, the amount of outsourced hazardous waste disposal is high, and the disposal cost is high. Calculated at a disposal cost of 3000 yuan per ton, 26.4 million yuan is required every year. Therefore, a treatment system and method for the waste alkali furnace ash of a POSM device are provided. Summary of the Invention

[0003] The purpose of the present invention is to address the deficiencies of the prior art and provide a treatment system and method for the waste alkali furnace ash of a POSM device to solve the problems raised in the above background technique.

[0004] To achieve the above purpose, the present invention provides the following technical solution: A treatment system for the waste alkali furnace ash of a POSM device, including a coagulation sedimentation tank, the coagulation sedimentation tank is connected to a buffer tank, the buffer tank is connected to a brine tank, the brine tank is connected to a separation system through an eighth pipeline, a third pipeline is also connected to the eighth pipeline, the separation system is connected to a sodium salt multi-effect evaporation system through a sixth pipeline, the sixth pipeline is connected to the brine tank through a fifth pipeline, a fourth pipeline is also connected to the fifth pipeline, the sodium salt multi-effect evaporation system is respectively connected to a miscellaneous salt separation and crystallization system and a miscellaneous salt filtration and evaporation system through a seventh pipeline, the miscellaneous salt filtration and evaporation system is connected to the brine tank through a first pipeline, and the coagulation sedimentation tank is connected to a miscellaneous salt sludge adsorption system through a second pipeline.

[0005] As a preferred technical solution of the present invention, a second heat exchanger is connected to the miscellaneous salt separation and crystallization system, and the miscellaneous salt separation and crystallization system is connected to the miscellaneous salt filtration and evaporation system.

[0006] As a preferred technical solution of the present invention, one end of the fourth pipeline is connected to the sodium hydroxide solution pipeline, and both the sodium hydroxide solution pipeline and the concentrated brine conveying pipeline from the incinerator are connected to the coagulation sedimentation tank.

[0007] As a preferred technical solution of the present invention, a miscellaneous salt sludge pump is installed on the second pipeline, and a miscellaneous salt recovery pipeline is connected to the miscellaneous salt filtration and evaporation system; the sodium salt multi-effect evaporation system is connected to the sodium salt filtration and evaporation system through a sodium salt conveying pipeline, and a sodium salt feeding pump is installed on the sodium salt conveying pipeline. The second pipeline is also connected to a PAM or PFS conveying pipeline. The buffer tank is connected to the second pipeline through a connecting pipeline, and a miscellaneous salt sludge pump is installed on the connecting pipeline.

[0008] As a preferred technical solution of the present invention, one end of the third pipeline is connected to the sulfuric acid conveying pipeline and the DW conveying pipeline, and the third pipeline is also connected to the brine tank.

[0009] As a preferred technical solution of the present invention, a backwash water tank and a backwash water feeding pump are installed on the fifth pipeline, a brine feeding pump is installed on the eighth pipeline, the eighth pipeline between the brine feeding pump and the separation system is connected to the third pipeline, and a first heat exchanger is also installed on the sixth pipeline.

[0010] A method for treating the waste alkali furnace ash of the POSM device by using the above treatment system is as follows:

[0011] Step 1: Precipitation and filtration to preliminarily separate miscellaneous salts and sodium salts;

[0012] After adjusting the pH of the concentrated brine from the incinerator with sodium hydroxide solution, it is first sent to the coagulation sedimentation tank for coagulation sedimentation to remove heavy metal insoluble substances in the brine; additional flocculant is added to strengthen the flocculation effect; after preliminary separation, the sodium salt solution passes through the buffer tank, while the miscellaneous salts are in the form of heavy metal insoluble substances. After being preliminarily separated from the sodium salt solution by the flocculant, the heavy metal insoluble substances are transported to the second pipeline by the miscellaneous salt sludge pump and sent to the miscellaneous salt sludge adsorption system by the miscellaneous salt sludge pump, and the filtrate flows to the brine tank by gravity;

[0013] Step 2: Adsorption:

[0014] The miscellaneous salt sludge undergoes exchange adsorption in the miscellaneous salt sludge adsorption system. The water produced by the adsorption system is used as the feed water for sodium salt multi-effect evaporation and crystallization in the subsequent sodium salt multi-effect evaporation system. After the adsorption system is saturated, cleaning and regeneration operations are carried out; the regeneration reagent is unpacked and enters the dissolution tank, and after being configured into a regeneration solution in the dissolution tank, it is pumped to the miscellaneous salt sludge adsorption system for desorption operation; the desorbed solution obtained after desorption is temporarily stored in the miscellaneous salt sludge adsorption system, and the regeneration solution is configured 1-2 times a day;

[0015] Step 3: Sodium carbonate crystallization;

[0016] Evaporation crystallization control mainly includes evaporation control, crystal size control, product purity control, and sludge production control. Evaporation control mainly controls the temperature and pressure of evaporation. A temperature above 65 degrees Celsius ensures the crystallization of monohydrate sodium carbonate. The countercurrent multi-effect method is adopted. By controlling the total amount of incoming materials for evaporation and the daily operation experience parameters, the flow rate into the miscellaneous salt evaporator is controlled, ensuring the product purity and recovery rate.

[0017] The effluent from the miscellaneous salt sludge adsorption system is lifted into the sodium salt multi-effect evaporation system. After evaporation crystallization, monohydrate sodium carbonate is obtained. The monohydrate sodium carbonate is dried to obtain anhydrous sodium carbonate products. The products are packaged in ton bags and sold externally. The condensed water obtained from evaporation crystallization is collected in the condensate tank. The finally obtained mother liquor is lifted into the sodium salt multi-effect evaporation system for treatment by a water pump. The countercurrent evaporation process is adopted to recover sodium carbonate crystals with a recovery rate of 80 - 90% or above.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] The present invention performs salt separation treatment on the furnace ash generated by the waste alkali incinerator, finally recovers the sodium carbonate in the furnace ash in solid form, and treats other miscellaneous salts as solid hazardous waste, greatly reducing the amount of hazardous waste disposal in the device. In addition, the condensate water and other solutions produced by the salt separation treatment unit are recycled into the furnace ash dissolution system, achieving zero wastewater discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of the present invention.

[0021] In the figure: 1 - Coagulation sedimentation tank; 2 - Brine tank; 3 - Separation system; 4 - Backwash water tank; 5 - Sodium salt multi-effect evaporation system; 61 - First heat exchanger; 62 - Second heat exchanger; 7 - Sodium salt filtration evaporation system; 8 - Miscellaneous salt separation crystallization system; 9 - Miscellaneous salt filtration evaporation system; 10 - Miscellaneous salt sludge adsorption system; 11 - Brine feed pump; 12 - Backwash water feed pump; 13 - Miscellaneous salt sludge pump; 14 - Buffer tank; 15 - Miscellaneous salt sludge pump; 16 - Sodium salt feed pump; 101 - First pipeline; 102 - Second pipeline; 103 - Third pipeline; 104 - Fourth pipeline; 105 - Fifth pipeline; 106 - Sixth pipeline; 107 - Seventh pipeline; 108 - Eighth pipeline. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The following elaborates on the preferred embodiments of the present invention in detail with reference to the drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0023] Please refer to Figure 1, the present invention provides a technical solution: a treatment system for the furnace ash of a POSM device waste alkali furnace, which includes a coagulation sedimentation tank 1. The coagulation sedimentation tank 1 is connected to a buffer tank 14, the buffer tank 14 is connected to a brine tank 2, and the brine tank 2 is connected to a separation system 3 through an eighth pipeline 108. The separation system 3 is used to separate sodium ions from other metal ions to obtain a higher-purity inorganic sodium salt. A third pipeline 103 is also connected to the eighth pipeline 108. The separation system 3 is connected to a sodium salt multi-effect evaporation system 5 through a sixth pipeline 106. The sodium salt multi-effect evaporation system 5 is used to recover sodium ions as much as possible, thereby reducing the amount of solid waste. According to the crystallization temperatures of different sodium salts, sodium carbonate, sodium sulfate, and sodium molybdate are separated. The sixth pipeline 106 is connected to the brine tank 2 through a fifth pipeline 105. A fourth pipeline 104 is also connected to the fifth pipeline 105. The sodium salt multi-effect evaporation system 5 is respectively connected to a miscellaneous salt separation and crystallization system 8 and a miscellaneous salt filtration and evaporation system 9 through a seventh pipeline 107. The miscellaneous salt separation and crystallization system 8 is used to finally treat the miscellaneous salt in the form of a by-product. The crystallization treatment reduces the water content and other impurities in the miscellaneous salt and improves the quality of the miscellaneous salt. The miscellaneous salt filtration and evaporation system 9 reduces the water content in the miscellaneous salt to ensure the quality of the miscellaneous salt. The miscellaneous salt filtration and evaporation system 9 is connected to the brine tank 2 through a first pipeline 101. The coagulation sedimentation tank 1 is connected to a miscellaneous salt sludge adsorption system 10 through a second pipeline 102. The miscellaneous salt sludge adsorption system 10 reduces the amount of sludge generated during the miscellaneous salt separation process and reduces the amount of hazardous waste to be treated.

[0024] A second heat exchanger 62 is connected to the miscellaneous salt separation and crystallization system 8, and the miscellaneous salt separation and crystallization system 8 and the miscellaneous salt filtration and evaporation system 9 are connected.

[0025] One end of the fourth pipeline 104 is connected to a sodium hydroxide solution pipeline, and both the sodium hydroxide solution pipeline and the concentrated brine conveying pipeline from the incinerator are connected to the coagulation sedimentation tank 1.

[0026] A miscellaneous salt sludge pump 13 is installed on the second pipeline 102, and a miscellaneous salt recovery pipeline is connected to the miscellaneous salt filtration and evaporation system 9. The sodium salt multi-effect evaporation system 5 is connected to a sodium salt filtration and evaporation system 7 through a sodium salt conveying pipeline, and a sodium salt feeding pump 16 is installed on the sodium salt conveying pipeline. The second pipeline 102 is also connected to a PAM or PFS conveying pipeline. Both PAM and PFS are flocculants. PAM is polyacrylamide, and PFS is polyferric sulfate. The flocculant mainly has positively (negatively) charged groups that approach some particles or granules with negatively (positively) charged and difficult-to-separate in water, reduce their electric potential, make them in an unstable state, and use their polymerization properties to concentrate these particles and separate them by physical or chemical methods. The buffer tank 14 is connected to the second pipeline 102 through a connecting pipeline, and a miscellaneous salt sludge pump 15 is installed on the connecting pipeline.

[0027] One end of the third pipeline 103 is connected to the sulfuric acid delivery pipeline and the DW delivery pipeline to supplement water for dissolving ions, and the third pipeline 103 is also connected to the brine tank 2.

[0028] An anti-washing water tank 4 and an anti-washing water feeding pump 12 are installed on the fifth pipeline 105, and a brine feeding pump 11 is installed on the eighth pipeline 108. The eighth pipeline 108 between the brine feeding pump 11 and the separation system 3 is connected to the third pipeline 103. A first heat exchanger 61 is also installed on the sixth pipeline 106 to increase the temperature and the solubility of salt. At the same time, preheating also improves the heating efficiency of the sodium salt multi-effect evaporation system.

[0029] As Figure 1 shown, a method for treating the waste alkali furnace ash of the POSM device by using the above treatment system is as follows:

[0030] Step 1: Precipitation and filtration to preliminarily separate out miscellaneous salts and sodium salts;

[0031] After adjusting the pH of the concentrated brine from the incinerator with sodium hydroxide solution, it is first sent to the coagulation sedimentation tank 1 for coagulation sedimentation to remove heavy metal insoluble substances in the brine; additional flocculant is added to strengthen the flocculation effect; after preliminary separation, the sodium salt solution passes through the buffer tank 14, while the miscellaneous salts are in the form of heavy metal insoluble substances. After being preliminarily separated from the sodium salt solution by the flocculant, the heavy metal insoluble substances are transported to the second pipeline 102 by the miscellaneous salt sludge pump 15 and sent to the miscellaneous salt sludge adsorption system 10 by the miscellaneous salt sludge pump 13. The filtrate flows to the brine tank 2 by gravity;

[0032] Step 2: Adsorption:

[0033] The miscellaneous salt sludge undergoes exchange adsorption in the miscellaneous salt sludge adsorption system 10. The water produced by the adsorption system serves as the feed water for sodium salt multi-effect evaporation and crystallization in the subsequent sodium salt multi-effect evaporation system 5. After the adsorption system is saturated, cleaning and regeneration operations are carried out; after the regeneration agent is unpacked, it enters the dissolution tank, and after being configured into a regeneration solution in the dissolution tank, it is lifted by a pump to the miscellaneous salt sludge adsorption system 10 for desorption operation; the desorbed solution obtained after desorption is temporarily stored in the miscellaneous salt sludge adsorption system 10, and the regeneration solution is configured 1-2 times a day;

[0034] Step 3: Sodium carbonate crystallization;

[0035] The evaporation crystallization control mainly includes evaporation control, crystal size control, product purity control, and sludge production control. Evaporation control mainly controls the evaporation temperature and pressure. A temperature above 65 degrees ensures the crystallization of monohydrate sodium carbonate. Using countercurrent multi-effect, by controlling the total amount of incoming materials for evaporation and the daily operation experience parameters, the flow rate into the miscellaneous salt evaporator is controlled, ensuring the product purity and recovery rate;

[0036] The effluent water inside the miscellaneous salt sludge adsorption system 10 is lifted and enters the sodium salt multi-effect evaporation system 5. After evaporation and crystallization, sodium carbonate monohydrate is obtained. After drying, anhydrous sodium carbonate products are obtained. The products are packaged in ton bags and sold externally. The condensed water obtained from evaporation and crystallization is collected in the condensate water tank. The finally obtained mother liquor is lifted by a water pump into the sodium salt multi-effect evaporation system 5 for treatment, and a countercurrent evaporation process is adopted to recover sodium carbonate crystals with a recovery rate of 80 - 90% or above.

[0037] Sulfuric acid is used in the chemical cleaning process of the filtration device; sodium hydroxide is used to adjust the pH to maintain a good recovery rate and product purity of the system; PAM is used to condition heavy metal sludge mainly composed of copper hydroxide to increase the solid content rate of the sludge.

[0038] As Figure 1 shown, the remaining route process is as follows:

[0039] Coagulation sedimentation tank 1 to buffer tank 14: The brine in the coagulation sedimentation tank 1 flows into the brine tank 2 by gravity. To better separate insoluble substances, multiple (1 - 10 levels) buffer tanks 14 are added on the path where the brine is sent to the brine tank 2.

[0040] Buffer tank 14 to brine tank 2: The brine in the buffer tank 14 flows by gravity to the brine tank 2.

[0041] Brine tank 2 to separation system 3: The brine entering the brine tank 2 has removed large - particle suspended substances, which can ensure the stability of the subsequent evaporation and crystallization inlet water. The brine in the brine tank 2 is pressurized by the brine feed pump 11 and enters the ultrafiltration membrane following the separation system 3.

[0042] Separation system 3 to sodium salt multi - effect evaporation system 5: Two sets of ultrafiltration membranes are used in a one - standby mode, which can filter out fine particles larger than 0.45 microns, further improve the purity of sodium carbonate products and reduce heavy metal crystallization in the evaporation system. The ultrafiltered brine enters the sodium salt multi - effect evaporation system 5 for evaporation and crystallization to recover sodium carbonate.

[0043] Backwash water tank 4 to brine tank 2: Ultrafiltration can be backwashed with deionized water DW and air. When the effect of pure water backwashing cannot reach the requirement according to the cleaning cycle (8 h / time), dilute sulfuric acid is used for chemical cleaning. The sewage from pure water cleaning is stored in the backwash water tank 4 and then returned to the brine tank 2 in a small flow rate.

[0044] Example 1: Analysis data of furnace ash composition: sodium carbonate 79.3%, moisture 16.56%, sodium molybdate 1.67%, chromium 0.0045%, sodium chloride 0.0031%, sodium sulfate 1.287%, water - insoluble substances 0%.

[0045] Pretreatment: Prepare a brine solution with a mass concentration of 25%, a solution temperature of 40°C, and a pH of 10 from the brine solution coming from the soda ash dissolution unit. When the pH is lower than 9, the feeding valve of sodium hydroxide will remain open to add sodium hydroxide into the pipeline to maintain the pH stable at about 9.5 - 11.5. When the pH is higher than 10.5, the feeding valve of sodium hydroxide will be closed. In this way, the automatic operation of pretreatment and the non-separate treatment of backwash water avoid the discharge of heavy metal wastewater and a separate waste treatment system, reduce the management content of the system, and can ensure the stability of subsequent processes.

[0046] Remove the insoluble substances in the brine through the coagulation sedimentation tank 1, and the brine is sent to the brine tank 2. To better remove the insoluble substances in the brine, PAM is added into the sedimentation tank 1 to strengthen the flocculation and precipitation effect. The brine in the sedimentation tank 1 flows into the brine tank 2 by gravity. To better separate the insoluble substances, multiple stages (1 - 10 stages) of buffer tanks 14 are added on the path where the brine is sent to the brine tank 2. The brine in the buffer tank 14 flows to the brine tank 2 by self-gravity. The miscellaneous salt sludge in the buffer tank 14 is sent to the miscellaneous salt sludge adsorption system 10 through the miscellaneous salt sludge pump 15. The miscellaneous salt sludge discharged from the sedimentation tank 1 is transported to the miscellaneous salt sludge adsorption system 10 through the miscellaneous salt sludge pump 13.

[0047] The miscellaneous salt sludge is further concentrated and evaporated and dehydrated in the miscellaneous salt filtration and evaporation system 9. The solid dry miscellaneous salt cake after dehydration and evaporation in the miscellaneous salt filtration and evaporation system 9 is handed over to a third party for disposal as hazardous waste. The liquid miscellaneous salt sludge is crystallized in the miscellaneous salt separation and crystallization system 8, and the crystallized solid miscellaneous salt is sent to the miscellaneous salt filtration and evaporation system 9 for disposal by a third party. Operating parameters of the miscellaneous salt crystallization system: Feed rate: 500 kg / h; Heating temperature: 95°C; Heating pressure: 0.04 MPa G. The filtrate generated after dehydration and filtration in the miscellaneous salt filtration and evaporation system 9 is collected and then returned to the brine tank 2. By operating in this way repeatedly, the purpose is to recover more sodium salts.

[0048] The brine entering the brine tank 2 has removed large suspended particles, which can ensure the relatively stable water inlet for subsequent evaporation and crystallization. The brine in the brine tank 2 is pressurized by the brine feeding pump 11 and enters the subsequent ultrafiltration membrane 3. Two groups of ultrafiltration membranes are used alternately, which can filter out fine particles larger than 0.45 microns, further improve the purity of sodium carbonate products, and reduce the heavy metal crystallization in the evaporation system. The ultrafiltered brine enters the multi-effect evaporation system 5 for evaporation and crystallization to recover sodium carbonate. A triple-effect evaporator is used this time, and its operating parameters are as follows: Feed rate: Triple-effect 5000 kg / h; Second-effect: 3999 kg / h; First-effect: 2400 kg / h. Heating temperature: Triple-effect 75°C, Second-effect 95°C, First-effect 115°C. Heating pressure: Triple-effect: -0.07 MPa G, Second-effect: -0.04 MPa G; First-effect: 0.04 MPa G.

[0049] Ultrafiltration can be backwashed with deionized water DW and air. When backwashing with clean water according to the cleaning cycle (once every 8 hours) fails to achieve the effect, chemical cleaning is carried out with dilute sulfuric acid. The sewage from the clean water cleaning is stored in the backwash water tank 4 and then returned to the brine tank 2 at a small flow rate.

[0050] The miscellaneous salts from the sodium salt multi-effect evaporation system are separated and then separated and crystallized again in the miscellaneous salt separation and crystallization system 8 to improve the output rate of solid materials.

[0051] Example 2: Analysis data of furnace ash composition: sodium carbonate 95.51%, moisture 0.064%, sodium molybdate 2.17%, chromium 0.007%, sodium chloride 0.0042%, sodium sulfate 1.51%, water-insoluble matter 0.037%.

[0052] Pretreatment: The brine solution from the alkali ash dissolution unit is configured to have a mass concentration of 22%, a solution temperature of 40°C, and a pH of 9. When the pH is lower than 8, the feeding valve of sodium hydroxide will remain open to add sodium hydroxide into the pipeline to maintain the pH stable at about 8.5 - 12.5. When the pH is higher than 11, the feeding valve of sodium hydroxide will be closed. In this way, the automatic operation of pretreatment and the non-separate treatment of backwash water avoid the discharge of heavy metal wastewater and a separate waste treatment system, reduce the management content of the system, and can ensure the stability of subsequent processes.

[0053] The insoluble substances in the brine are removed by the coagulation sedimentation tank 1, and the brine is sent to the brine tank 2. To better remove the insoluble substances in the brine, PFS is added to the sedimentation tank 1 to enhance the flocculation and precipitation effect. The brine in the sedimentation tank 1 flows into the brine tank 2 by gravity. To better separate the insoluble substances, two-stage buffer tanks 14 are added to the path where the brine is sent to the brine tank 2. The brine in the buffer tank 14 flows to the brine tank 2 by self-gravity. The miscellaneous salt sludge in the buffer tank 14 is sent to the miscellaneous salt sludge adsorption system 10 by the miscellaneous salt sludge pump 15. The miscellaneous salt sludge discharged from the sedimentation tank 1 is transported to the miscellaneous salt sludge adsorption system 10 by the miscellaneous salt sludge pump 13.

[0054] The miscellaneous salt sludge is further concentrated and evaporated and dehydrated in the miscellaneous salt filtration and evaporation system 9. The solid dry miscellaneous salt cake after dehydration and evaporation in the miscellaneous salt filtration and evaporation system 9 is handed over to a third party for disposal as hazardous waste. The liquid miscellaneous salt sludge is crystallized in the miscellaneous salt separation and crystallization system 8, and the crystallized solid miscellaneous salt is then sent to the miscellaneous salt filtration and evaporation system 9 for disposal by a third party. Operating parameters of the miscellaneous salt crystallization system: feed rate: 300 kg / h; heating temperature 100°C; heating pressure: 0.045 MPa G. The filtrate generated after dehydration and filtration in the miscellaneous salt filtration and evaporation system 9 is collected and then returned to the brine tank 2. Such repeated operations aim to recover more sodium salts.

[0055] The brine entering the brine tank 2 has removed large particulate suspended matter, which can ensure the stability of the subsequent evaporation crystallization feed water. The brine in the brine tank 2 is pressurized by the brine feed pump 11 and enters the subsequent ultrafiltration membrane 3. Two groups of ultrafiltration membranes are used in rotation, with one in use and the other in reserve, which can filter out fine particles larger than 0.45 microns, further improve the purity of sodium carbonate products and reduce the heavy metal crystallization in the evaporation system. The ultrafiltered brine enters the multi-effect evaporation system 5 for evaporation crystallization to recover sodium carbonate. A triple-effect evaporator is used this time, and its operating parameters are as follows: Feed rate: 4890 kg / h for the third effect; 3789 kg / h for the second effect; 2230 kg / h for the first effect. Heating temperature: 68 °C for the third effect, 98 °C for the second effect, 105 °C for the first effect. Heating pressure: -0.08 MPa G for the third effect, -0.03 MPa G for the second effect; 0.045 MPa G for the first effect.

[0056] The ultrafiltration can be backwashed with deionized water DW and air. When the clear water backwashing cannot achieve the effect according to the cleaning cycle (6 h / time), dilute sulfuric acid is used for chemical cleaning. The sewage from the clear water cleaning is stored in the backwash water tank 4 and then returned to the brine tank 2 at a small flow rate.

[0057] The miscellaneous salts from the multi-effect evaporation system of sodium salts are separated and then separated and crystallized again in the miscellaneous salt separation and crystallization system 8 to improve the yield of solid materials.

[0058] The above embodiments only illustrate the implementation modes of the present invention, and the description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A system for treating ash from a spent alkali furnace of a POSM device, comprising a coagulation and sedimentation tank (1), characterized in that: The coagulation and sedimentation tank (1) is connected to the buffer tank (14), the buffer tank (14) is connected to the brine tank (2), the brine tank (2) is connected to the separation system (3) via an eighth pipeline (108), the eighth pipeline (108) is also connected to the third pipeline (103), the separation system (3) is connected to the sodium salt multiple-effect evaporation system (5) via a sixth pipeline (106), the sixth pipeline (106) is connected to the brine tank (2) via a fifth pipeline (105), The sodium salt multiple-effect evaporation system (5) is connected to a salt separation and crystallization system (8) and a salt filtration and evaporation system (9) through a seventh pipeline (107); the salt filtration and evaporation system (9) is connected to the brine tank (2) through a first pipeline (101); and the coagulation and sedimentation tank (1) is connected to the salt sludge adsorption system (10) through a second pipeline (102).

2. The processing system of the spent alkali furnace ash of the POSM device according to claim 1, characterized in that: The impure salt separation and crystallization system (8) is connected to a second heat exchanger (62), and the impure salt separation and crystallization system (8) and the impure salt filtration and evaporation system (9) are connected.

3. The processing system of the spent alkali furnace ash of the POSM device according to claim 1, characterized in that: One end of the fourth pipeline (104) is connected to the sodium hydroxide solution pipeline, and the sodium hydroxide solution pipeline and the concentrated brine delivery pipeline from the incinerator are both connected to the coagulation sedimentation tank (1).

4. The processing system of the spent alkali furnace ash of the POSM device according to claim 1, characterized in that: The second pipeline (102) is equipped with a foreign salt sludge pump (13), and the foreign salt filtration and evaporation system (9) is connected to a foreign salt recovery pipeline; the sodium salt multiple-effect evaporation system (5) is connected to the sodium salt filtration and evaporation system (7) via a sodium salt delivery pipeline, and a sodium salt feed pump (16) is installed on the sodium salt delivery pipeline; the second pipeline (102) is also connected to a PAM or PFS delivery pipeline; the buffer tank (14) is connected to the second pipeline (102) via a connecting pipeline, and a foreign salt sludge pump (15) is installed on the connecting pipeline.

5. The processing system of the spent alkali furnace ash of the POSM device according to claim 1 is characterized in that: One end of the third pipeline (103) is connected to the sulfuric acid delivery pipeline and the DW delivery pipeline, and the third pipeline (103) is also connected to the brine tank (2).

6. The processing system of the spent alkali furnace ash of the POSM device according to claim 1 is characterized in that: The fifth pipeline (105) is installed with a backwash water tank (4) and a backwash water feed pump (12), the eighth pipeline (108) is installed with a brine feed pump (11), the eighth pipeline (108) between the brine feed pump (11) and the separation system (3) is connected to the third pipeline (103), and the sixth pipeline (106) is also installed with a first heat exchanger (61).

7. A method for treating ash from a spent alkali furnace of a POSM device using the treatment system according to any one of claims 1 to 6, characterized in that: The specific steps are as follows: Step 1: Preliminary separation of impurity salts and sodium salts by precipitation and filtration; After the pH of the concentrated brine from the incinerator is adjusted by sodium hydroxide solution, it is first sent to the coagulation and sedimentation tank (1) for coagulation and sedimentation to remove the insoluble heavy metals in the brine; additional flocculants are added to enhance the flocculation effect; After preliminary separation, the sodium salt solution passes through a buffer tank (14), while the impure salts are in the form of heavy metal insolubles. After preliminary separation from the sodium salt solution by a flocculant, the heavy metal insolubles are transported to a second pipeline (102) via an impure salt sludge pump (15), and are then transported to an impure salt sludge adsorption system (10) via an impure salt sludge pump (13), and the filtrate flows to a brine tank (2) by gravity; Step 2: Adsorption: The mixed salt sludge is exchanged and adsorbed in the mixed salt sludge adsorption system (10), and the water produced by the adsorption system is used as the water for the sodium salt multi-effect evaporation crystallization in the subsequent sodium salt multi-effect evaporation system (5). After the adsorption system is saturated, it is cleaned and regenerated; the regeneration agent is unpacked and enters the dissolution tank, and after being configured into the regeneration liquid in the dissolution tank, it is pumped to the mixed salt sludge adsorption system (10) for analysis; the analysis liquid obtained after analysis is temporarily stored in the mixed salt sludge adsorption system (10), and the regeneration liquid is configured 1-2 times a day; Step 3: sodium carbonate crystallization; Evaporation and crystallization control mainly includes evaporation control, crystal size control, product purity control, and sludge output control. Evaporation control mainly controls the temperature and pressure of evaporation. The temperature above 65 degrees ensures the crystallization of sodium carbonate monohydrate. Countercurrent multi-effect is adopted. The total amount of material evaporated and the daily operation experience parameters are used to control the flow rate discharged into the mixed salt evaporator, thereby ensuring the purity and recovery rate of the product. The effluent from the mixed salt sludge adsorption system (10) is lifted and introduced into the sodium salt multiple-effect evaporation system (5), and after evaporation and crystallization, sodium carbonate monohydrate is obtained. After the sodium carbonate monohydrate is dried, anhydrous sodium carbonate products are obtained, and the products are packaged in ton bags and sold to the outside. The condensed water obtained by evaporation and crystallization is collected in a condensed water tank. The mother liquor finally obtained is lifted by a water pump into the sodium salt multiple-effect evaporation system (5) for treatment, and a countercurrent evaporation process is adopted to recover sodium carbonate crystals with a recovery rate of 80-90% or more.

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