Disposal system for incineration fly ash washing liquid

Abstract

The embodiment of the utility model discloses a disposal system for incineration fly ash washing liquid, which comprises a pretreatment unit, a first-stage decalcification reaction tank, a second-stage decalcification reaction tank, a third-stage decalcification reaction tank, a third-stage decalcification reaction tank and a fourth-stage decalcification reaction tank, the post-treatment unit comprises a secondary decalcification reaction tank connected with a liquid phase outlet of the vertical scraper centrifuge, and the secondary decalcification reaction tank is connected with a plate-and-frame filter press; the primary decalcification reaction tank and the secondary decalcification reaction tank are respectively connected with the sodium sulfate dissolving tank and the sodium carbonate dissolving tank, and a liquid phase outlet of the plate-and-frame filter press is connected with the sodium sulfate dissolving tank and the sodium carbonate dissolving tank. By combining sodium sulfate and sodium carbonate decalcification technologies, the operation cost can be reduced, the product quality can be improved, and production equipment can be effectively protected. The method is helpful for promoting environmental protection and sustainable development, and contributes to long-term prosperity of the chemical industry.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to the technical field of calcium removal from fly ash washing liquid, and particularly to a disposal system for incinerated fly ash washing liquid. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the overall understanding of the present disclosure, and is not necessarily regarded as an admission or any form of implication that this information constitutes related art that has become well-known to those of ordinary skill in the art.

[0003] In the chemical industry, the presence of calcium ions often has an adverse impact on the production process and the final product. It may cause problems such as equipment scaling, pipeline blockage, etc., reduce the heat exchange efficiency, and even affect the quality and performance of the product. With the increasing shortage of global resources and the gradual enhancement of environmental protection awareness, the chemical industry is seeking more green and efficient production methods. In this context, the innovation and development of calcium removal technology play an important role in promoting the green transformation of the chemical industry.

[0004] In the related art, sodium carbonate, as an efficient and economical calcium remover, has been widely used in the chemical industry. However, due to its relatively high reagent cost, long-term and large-scale use will lead to high operating costs. Therefore, with the development of the economy, using sodium sulfate for calcium removal has gradually become a popular trend. The reason why sodium sulfate is favored is mainly due to the high activity of its molecular structure, enabling it to efficiently treat a large amount of calcium ions. At the same time, sodium sulfate also has excellent antioxidant properties, which helps to maintain the activity of calcium ions during the reaction. In addition, sodium sulfate shows good stability in brine, and its reaction products are harmless to the environment, thus ensuring its safety and being applicable to the brine refining process.

[0005] It should be noted that although sodium sulfate can effectively remove calcium ions in water, as the calcium ion concentration decreases, its calcium removal effect may gradually weaken. Therefore, in practical applications, it is necessary to flexibly adjust the dosage of sodium sulfate according to specific situations to achieve the best calcium removal effect. Utility Model Content

[0006] For this reason, embodiments of the present disclosure provide a disposal system and method for incinerated fly ash washing liquid to solve the problems in the related art that it is difficult to remove calcium at low concentrations and the calcium removal efficiency is low due to fly ash washing and calcium removal.

[0007] In order to achieve the purpose of efficient and thorough calcium removal and recycling, the embodiments of the present disclosure provide the following technical solutions:

[0008] In the first aspect of the embodiments of the present disclosure, a disposal system for incinerated fly ash washing liquid is provided, including

[0009] Pretreatment unit: It includes a primary decalcification reaction tank, and the primary decalcification reaction tank is connected to a vertical scraper centrifuge;

[0010] Post-treatment unit: It includes a secondary decalcification reaction tank connected to the liquid phase outlet of the vertical scraper centrifuge, and the secondary decalcification reaction tank is connected to a plate and frame filter press;

[0011] The primary decalcification reaction tank and the secondary decalcification reaction tank are respectively connected to a sodium sulfate dissolution tank and a sodium carbonate dissolution tank, and the liquid phase outlet of the plate and frame filter press is connected to the sodium sulfate dissolution tank and / or the sodium carbonate dissolution tank.

[0012] In one embodiment, the primary decalcification reaction tank is connected to a primary decalcification thickening tank through a liquid pump, and the primary decalcification thickening tank is connected to the vertical scraper centrifuge through an underflow pump.

[0013] In one embodiment, there is an upper tank between the underflow pump and the vertical scraper centrifuge, and the centrifugal liquid phase outlet of the vertical scraper centrifuge is connected to the secondary decalcification reaction tank through a primary decalcification filtrate tank.

[0014] In one embodiment, the bottom liquid phase outlet of the vertical scraper centrifuge is also connected to the primary decalcification thickening tank.

[0015] In one embodiment, the secondary decalcification reaction tank is connected to a secondary decalcification reaction pool through a pump, the secondary decalcification reaction pool is connected to a sludge well, and the sludge well is connected to the plate and frame filter press through a sludge pump.

[0016] In one embodiment, the liquid phase outlet of the plate and frame filter press is connected to a buffer tank, and the buffer tank is connected to the sodium sulfate dissolution tank and the sodium carbonate dissolution tank.

[0017] In one embodiment, the buffer tank is also connected to the secondary decalcification reaction tank.

[0018] In one embodiment, the liquid phase outlet of the sludge well is also connected to the buffer tank.

[0019] In one embodiment, the system further includes a hydrochloric acid tank, the hydrochloric acid tank is connected to a pipeline mixer through a pump, and the pipeline mixer is connected to the buffer tank.

[0020] In the second aspect of the embodiments of the present disclosure, a method for disposing of incineration fly ash washing liquid is provided, which is applied to the above-mentioned incineration fly ash washing liquid disposal system, and includes the following steps:

[0021] Step 1, preparation of the calcium removal solution:

[0022] Sodium sulfate solution: Sodium sulfate solid and the treated chlorine-containing washing liquid are configured in a ratio of 1:10 to form a sodium sulfate mixed solution with a concentration of about 10%, and stored in a sodium sulfate dissolution tank;

[0023] Sodium carbonate solution: Sodium carbonate solid and the treated chlorine-containing washing liquid are configured in a ratio of 1:10 to form a sodium carbonate mixed solution with a concentration of about 10%, and stored in a sodium carbonate dissolution tank;

[0024] Step 2, primary decalcification treatment:

[0025] The chlorine-containing washing liquid of incineration fly ash to be treated is first introduced into the primary decalcification reaction tank. A flowmeter is used to measure the feed flow rate, and an on-line calcium ion detector is used to detect the calcium ion concentration; then the sodium sulfate mixed solution is pumped into the primary decalcification reaction tank by a diaphragm pump, and the flow rate is measured by a flowmeter at the same time. According to the detected calcium ion concentration and the feed flow rate, the flow rate of the required sodium sulfate solution is calculated through the DCS system;

[0026] Step 3, secondary decalcification treatment:

[0027] The filtrate of primary decalcification is pumped and introduced into the secondary decalcification reaction tank together with the supernatant at the top of the primary decalcification thickening tank. An on-line calcium ion detector is installed on the overflow pipeline of the supernatant of the primary decalcification thickening tank, and at this time the calcium ion is approximately 2000 mg / L. Then the sodium carbonate solution is pumped into the secondary decalcification reaction tank by a diaphragm pump, and the flow rate is measured by a flowmeter at the same time. The flow rate of the required sodium carbonate solution is calculated through the DCS system;

[0028] Step 4, solution pH adjustment treatment:

[0029] For the solution in the buffer tank, a part is used for dissolving sodium sulfate and sodium carbonate, and the other part is led out of the system by a buffer pump. At this time, the solution pH is about 12 - 13. A pipeline mixer is installed on the outlet pipeline of the buffer pump, and hydrochloric acid is introduced into the pipeline mixer for neutralization to adjust the pH to 6 - 8; the finally treated clear washing liquid can be further processed or sent to evaporation for salt production according to actual needs.

[0030] According to the embodiments of the present disclosure, the system has the following advantages: It includes a pretreatment unit: including a primary decalcification reaction tank, and the primary decalcification reaction tank is connected to a vertical scraper centrifuge; a post-treatment unit: including a secondary decalcification reaction tank connected to the liquid phase outlet of the vertical scraper centrifuge, and the secondary decalcification reaction tank is connected to a plate and frame filter press; the primary decalcification reaction tank and the secondary decalcification reaction tank are respectively connected to a sodium sulfate dissolution tank and a sodium carbonate dissolution tank, and the liquid phase outlet of the plate and frame filter press is connected to the sodium sulfate dissolution tank and the sodium carbonate dissolution tank. By combining the sodium sulfate and sodium carbonate decalcification technologies, not only can the operating cost be reduced and the product quality be improved, but also the production equipment can be effectively protected. This approach helps to promote environmental protection and sustainable development, and contributes to the long-term prosperity of the chemical industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the related art, the following will briefly introduce the drawings required for use in the description of the embodiments or the related art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can also be obtained based on the provided drawings.

[0032] The structures, ratios, sizes, etc. illustrated in this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present disclosure. Therefore, they do not have substantial technical significance. Any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects that the present disclosure can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present disclosure.

[0033] Figure 1 FIG. 1 is a schematic structural diagram of a disposal system for incineration fly ash washing liquid according to an exemplary embodiment;

[0034] Figure 2 FIG. 2 is a flowchart of a disposal method for incineration fly ash washing liquid according to an exemplary embodiment.

[0035] In the figures: 1, primary decalcification reaction tank; 2, vertical scraper centrifuge; 3, secondary decalcification reaction tank; 4, plate and frame filter press; 5, sodium sulfate dissolution tank; 6, sodium carbonate dissolution tank; 7, primary decalcification thickening tank; 8, underflow pump; 9, upper tank; 10, primary decalcification filtrate tank; 11, secondary decalcification reaction pool; 12, sludge well; 13, buffer tank; 14, hydrochloric acid tank; 15, pipe mixer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The following specific embodiments illustrate the embodiments of the present disclosure. Those familiar with this technology can easily understand other advantages and effects of the present disclosure from the content disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present disclosure.

[0037] The terms such as "upper", "lower", "left", "right", "middle", etc. cited in this specification are only for the convenience of clear narration and are not used to limit the scope of implementation of the present disclosure. The change or adjustment of their relative relationship, without substantial change in the technical content, should also be regarded as the scope that the present disclosure can implement.

[0038] Such asFigure 1 As shown, it shows a schematic structural diagram of a disposal system for incineration fly ash washing liquid shown according to an exemplary embodiment. The system includes

[0039] Pretreatment unit: including a primary decalcification reaction tank 1, and the primary decalcification reaction tank 1 is connected to a vertical scraper centrifuge 2;

[0040] Post-treatment unit: including a secondary decalcification reaction tank 3 connected to the liquid phase outlet of the vertical scraper centrifuge 2, and the secondary decalcification reaction tank 3 is connected to a plate and frame filter press 4;

[0041] The primary decalcification reaction tank 1 and the secondary decalcification reaction tank 3 are respectively connected to a sodium sulfate dissolution tank 5 and a sodium carbonate dissolution tank 6, and the liquid phase outlet of the plate and frame filter press 4 is connected to the sodium sulfate dissolution tank 5 and the sodium carbonate dissolution tank 6.

[0042] The sodium sulfate solution in the sodium sulfate dissolution tank 5 is pumped into the primary decalcification reaction tank 1 by a pump, and reacts with the calcium-containing waste liquid in the primary decalcification reaction tank 1 under the action of a stirrer. The reacted turbid liquid is pumped into the vertical scraper centrifuge 2 for separation. The separated solid phase is calcium sulfate dihydrate and collected. The liquid phase of the primary waste liquid enters the secondary decalcification reaction tank 3. The sodium carbonate solution in the sodium carbonate dissolution tank 6 is pumped into the secondary decalcification reaction tank 3 to react with the primary waste liquid, and then pumped into the plate and frame filter press 4 for separation. The solid phase is calcium carbonate and recovered. The liquid phase of the secondary waste liquid is refluxed to the sodium sulfate dissolution tank 5 and / or the sodium carbonate dissolution tank 6 to dissolve sodium sulfate and / or sodium carbonate.

[0043] By combining the sodium sulfate and sodium carbonate decalcification technologies, not only can the operating cost be reduced and the product quality be improved, but also the production equipment can be effectively protected. This approach helps to promote environmental protection and sustainable development, and contributes to the long-term prosperity of the chemical industry.

[0044] In one embodiment, in order to better obtain precipitates and improve the solid-liquid separation efficiency of the vertical scraper centrifuge 2, the primary reverse decalcification reaction tank is connected to a primary decalcification thickening tank 7 through a liquid pump. After the primary decalcification thickening tank 7 stands for precipitation, the thick slurry is scraped to the discharge port at its bottom through the internal scraper device. The primary decalcification thickening tank 7 is connected to the vertical scraper centrifuge 2 through an underflow pump 8, and the clarified liquid of the precipitation above directly enters the secondary decalcification reaction tank 3.

[0045] In one embodiment, an upper tank 9 is provided between the underflow pump 8 and the vertical scraper centrifuge 2, and the centrifugal liquid phase outlet of the vertical scraper centrifuge 2 is connected to the secondary decalcification reaction tank 3 through a primary decalcification filtrate tank 10.

[0046] The upper tank 9 further concentrates the bottom liquid and serves as a metering device at the same time. The vertical scraper centrifuge 2 operates in batches, and the capacity of one upper tank 9 just meets the usage amount of one decalcification centrifuge at a time. Meanwhile, during the operation of the vertical scraper centrifuge 2, the upper tank 9 is fed, and then the upper tank 9 flows into the decalcification centrifuge by gravity, reducing the feeding time.

[0047] In one embodiment, during the separation process of recovering calcium sulfate dihydrate, in order to prevent some of the filtrate after its filtration from affecting the discharge of calcium sulfate dihydrate and diluting calcium sulfate dihydrate, the bottom liquid phase outlet of the vertical scraper centrifuge 2 is also connected to a primary decalcification thickening tank 7.

[0048] In one embodiment, in order to separate calcium carbonate more effectively, the secondary decalcification reaction tank 3 is connected to the secondary decalcification reaction pool 11 by a pump, so that the calcium carbonate solution can be secondarily deposited in the secondary decalcification reaction pool 11, and through the internal scraper device, the dense slurry is scraped to the discharge port at its bottom. The secondary decalcification reaction pool 11 is connected to a sludge well 12, and the sludge well 12 is connected to a plate and frame filter press 4 by a sludge pump. The liquid phase of the secondary decalcification reaction pool 11 flows back to the sodium sulfate dissolution tank 5 and / or the sodium carbonate dissolution tank 6 to dissolve sodium sulfate and / or sodium carbonate.

[0049] Since, after the pretreatment of the primary decalcification reaction tank 1, there is not much calcium ion in the secondary waste liquid, so setting the sludge well 12 can further sediment the calcium carbonate mixture in large amounts and multiple times. In this embodiment, the mixture in the secondary decalcification reaction pool 11 is pumped into the sludge well 12 from the bottom of the sludge well 12 by a sludge discharge pump, avoiding excessive deposition of calcium carbonate in the sludge well 12 during the long-term static process, which makes its fluidity poor and difficult to pump it into the plate and frame filter press 4. The clarified liquid of the sediment above the sludge well 12 flows back to the sodium sulfate dissolution tank 5 and / or the sodium carbonate dissolution tank 6 to dissolve sodium sulfate and / or sodium carbonate.

[0050] In one embodiment, in order to relieve the situation that all separated liquids enter the sodium sulfate dissolution tank 5 and the sodium carbonate dissolution tank 6, increasing the pressure of the sodium sulfate dissolution tank 5 and the sodium carbonate dissolution tank 6 and affecting the concentration of the dissolved liquid, the liquid phase outlet of the plate and frame filter press 4 is connected to a buffer tank 13, and the buffer tank 13 is connected to the sodium sulfate dissolution tank 5 and the sodium carbonate dissolution tank 6.

[0051] In one embodiment, to avoid saturation of the buffer tank 13, the buffer tank 13 is also connected to the secondary decalcification reaction tank 3 for auxiliary adjustment of the reaction.

[0052] Among them, the liquid phase outlet of the sludge well 12 is also connected to the buffer tank 13, and then is shunted by the buffer tank 13 to avoid liquid accumulation and improve the circulation treatment effect of the separated liquid.

[0053] In one embodiment, to ultimately achieve the safe discharge of the treatment liquid, the system further includes a hydrochloric acid tank 14. The hydrochloric acid tank 14 is connected to a pipeline mixer 15 through a pump. The pipeline mixer 15 is connected to a buffer tank 13. The treatment liquid in the buffer tank 13 enters the pipeline mixer 15 to be neutralized with hydrochloric acid, and after meeting the external discharge standard, the final discharge of the decalcified filtrate is carried out.

[0054] In the second aspect of the embodiments of the present disclosure, a method for disposing of incineration fly ash washing liquid is provided, which is applied to the above-mentioned incineration fly ash washing liquid disposal system, as Figure 2 shown, and includes the following steps:

[0055] Step 1, preparation of the calcium removal solution:

[0056] Sodium sulfate solution: Sodium sulfate solid and the treated chlorine-containing washing liquid are prepared in a ratio of 1:10 to form a sodium sulfate mixed solution with a concentration of about 10%, that is, SO 4 2- with a concentration of about 80000 mg / L. And it is stored in the sodium sulfate dissolution tank.

[0057] Sodium carbonate solution: Sodium carbonate solid and the treated chlorine-containing washing liquid are prepared in a ratio of 1:10 to form a sodium carbonate mixed solution with a concentration of about 10%, that is, CO 3 2- with a concentration of about 68000 mg / L. And it is stored in the sodium carbonate dissolution tank.

[0058] Note: Using the treated chlorine-containing washing liquid to prepare the calcium removal solution can ensure that no new water is introduced into the system and the total amount of the treated chlorine-containing washing liquid is not increased.

[0059] Step 2, primary calcium removal treatment:

[0060] The incineration fly ash chlorine-containing washing liquid to be treated is first introduced into the primary calcium removal reaction tank 1. A flow meter is used to measure the feed flow rate, and an on-line calcium ion detector is used to detect the calcium ion concentration; then the sodium sulfate mixed solution is pumped into the primary calcium removal reaction tank 1 through a diaphragm pump, and the flow rate is also measured by a flow meter. According to the detected calcium ion concentration and the feed flow rate, the required flow rate of the sodium sulfate solution is calculated through the DCS system. The sodium sulfate solution is added to reduce the calcium ion concentration of the feed washing liquid to 2000 mg / L. The calculation formula is:

[0061] Q 2 =Q 1 (C 1 -C 3 ) / (C 2 / 2.4-C 3 )

[0062] Q 1: Feed flow rate of incineration fly ash washing liquid, unit: m 3 / h

[0063] Q 2 : Feed flow rate of sodium sulfate solution, unit: m 3 / h

[0064] C 1 : Calcium ion detection value of incineration fly ash washing liquid feed, unit: mg / L

[0065] C 2 : SO in sodium sulfate solution 4 2- Content, here it is 80000, unit: mg / L

[0066] C 3 : Ca content in the effluent from the first-stage demineralization reaction tank 1 after reaction, here it is 2000, unit: mg / L 2+

[0067] 2.4: Conversion coefficient for the reaction of calcium ions and sulfate ions

[0068] SO in the solution 4 2- reacts with Ca 2+ to form calcium sulfate precipitate. The reaction formula is Ca 2+ +SO 4 2- →CaSO 4 ↓. The generated calcium sulfate suspension is introduced into the first-stage demineralization thickening tank 7 through the first-stage demineralization reaction pump for concentration. In the first-stage demineralization thickening tank 7, the suspended matter settles to the bottom naturally and is then scraped to the center of the bottom of the tank by a sludge scraper for discharging. Here, the design of the first-stage demineralization thickening tank 7 is as follows: sedimentation rate 20 kg / m 2 ·h; solid content in the supernatant 300 mg / L; solid content in the underflow liquid 20%; maximum linear speed of the sludge scraper 0.1 - 0.3 m / s, height of the straight cylinder section of the tank ≤ 3 m, and discharging is carried out through the central cone section. The underflow liquid is transferred to the upper tank 9 through a special underflow pump 8 for buffering 13 and further concentration. The volume of the upper tank 9 is designed to be 2 times the volume of the special demineralization centrifuge. Subsequently, the liquid naturally flows into the special vertical scraper centrifuge 2 for solid-liquid separation. The separated solid phase is gypsum (calcium sulfate dihydrate) product with a water content of 12% to 20%. The filtrate enters the first-stage demineralization filtrate tank 10 for temporary storage.

[0069] Step 3, secondary demineralization treatment:

[0070] ​The primary decalcification filtrate is introduced into the secondary decalcification reaction tank 3 by pumping together with the supernatant at the top of the primary decalcification thickening tank 7. An on-line calcium ion detector is installed on the overflow pipeline of the supernatant of the primary decalcification thickening tank 7, and at this time, the calcium ion is approximately 2000 mg / L. Then, the sodium carbonate solution is pumped into the secondary decalcification reaction tank 3 by a diaphragm pump, and the flow rate is measured by a flow meter at the same time. The required flow rate of the sodium carbonate solution is calculated through the DCS system, and the sodium carbonate solution is added according to the theoretical value of the complete reaction of the remaining calcium ions. The calculation formula is:

[0071] Q 3 =(Q 1 *C 1 +Q 2 *C 2 ) / C 3 / 1.5

[0072] Q 1 : Feed flow rate of incineration fly ash washing liquid, unit: m 3 / h

[0073] Q 2 : Flow rate of treated washing liquid, unit: m 3 / h

[0074] Q 3 : Dosage of sodium carbonate solution, unit: m 3 / h

[0075] C 1 : Detected value of calcium ions in the overflow liquid of the primary decalcification thickening tank 7, unit: mg / L

[0076] C 2 : Detected value of calcium ions in the treated washing liquid, unit: mg / L

[0077] C 3 : Content of CO 3 2- in the sodium carbonate solution, here it is 68000, unit: mg / L

[0078] 1.5: Conversion coefficient of the reaction between calcium ions and carbonate ions

[0079] CO 3 2- in the solution reacts with Ca 2+ to form calcium carbonate precipitate, and the remaining calcium ions are completely removed. The suspension containing calcium carbonate particles is introduced into the secondary decalcification reaction tank 11 for static precipitation and homogenization treatment.

[0080] A sludge scraper is configured in the secondary decalcification reaction tank 11. It can efficiently scrape the sediment at the bottom of the tank to the central position and orderly transport the sediment to the sludge well 12 for temporary storage through a sludge discharge pump. Here, the secondary decalcification reaction tank 11 is designed with an effective volume that meets the 24-hour treatment volume, a sedimentation rate of 5 kg / m 2 ·h; the solid content of the supernatant is 10 mg / L; the solid content of the underflow liquid is 20%; the maximum linear speed of the sludge scraper is 0.1 - 0.3 m / s. Subsequently, the sludge discharge pump of the sludge well 12 is started, and the slurry containing calcium carbonate is sent into the plate and frame filter press 4 through a pipeline for final solid-liquid separation treatment. The filtrate separated by the plate and frame filter press 4 is a turbid liquid before forming a filter cake layer. This part of the turbid liquid is returned to the secondary decalcification reaction tank 11, and after the filtrate becomes clear, it is introduced into the buffer tank 13.

[0081] Step four, pH adjustment treatment of the solution:

[0082] For the solution in the buffer tank 13, a part is used for dissolving sodium sulfate and sodium carbonate, and the other part is led out of the system through the buffer pump 13. At this time, the pH of the solution is about 12 - 13. A pipeline mixer 15 is installed on the outlet pipeline of the buffer pump 13, and hydrochloric acid is introduced into the pipeline mixer 15 for neutralization to adjust the pH to 6 - 8; the finally treated clear washing liquid can be further processed or sent to evaporation for salt production according to actual needs.

[0083] The calcium ion on-line detector, with a measuring range of 0 - 40000 ppm, can ensure the continuous and stable operation of the entire system.

[0084] The detailed treatment process is as follows: The calcium-containing waste liquid to be treated is first introduced into the primary decalcification reaction tank 1 and mixed with the sodium sulfate solution for reaction. The addition amount of sodium sulfate is added according to the removal amount of 30% of the total calcium ion concentration. SO in the solution 4 2- and Ca 2+ react to form calcium sulfate precipitation. The generated calcium sulfate suspension is introduced into the primary decalcification thickening tank 7 through the primary decalcification reaction pump for concentration. In the primary decalcification thickening tank 7, the suspended matter settles to the bottom naturally, and then is scraped to the center of the bottom of the tank body by the sludge scraper for discharging. The solid content of the underflow liquid needs to be increased to more than 20%. The underflow liquid is transferred to the upper tank 9 through a special underflow pump 8 for buffering 13 and further concentration. Subsequently, the liquid naturally flows into the vertical scraper centrifuge 2 for solid-liquid separation. The obtained gypsum (calcium sulfate dihydrate) product has a water content of 12% to 20%.

[0085] The clear filtrate separated by the vertical scraper centrifuge 2 and the supernatant at the top of the primary decalcification thickening tank 7 are introduced into the secondary decalcification reaction tank 3 together. Sodium carbonate solution is added to the secondary decalcification reaction tank 3. CO in the solution 3 2- and Ca 2+A calcium carbonate precipitate is formed by the reaction to completely remove the remaining calcium ions. The suspension containing calcium carbonate particles is introduced into the secondary decalcification reaction tank 11 for homogenization and precipitation treatment.

[0086] A sludge scraper is arranged in the secondary decalcification reaction tank 11, which can efficiently scrape the precipitates at the bottom of the tank to the central position and orderly transport the precipitates to the sludge well 12 for temporary storage through a sludge discharge pump. Subsequently, the sludge discharge pump of the sludge well 12 is started, and the calcium carbonate-containing slurry is sent through a pipeline to the plate and frame filter press 4 for final solid-liquid separation treatment.

[0087] Finally, the separated filter cake is properly disposed of according to the subsequent process flow, while the clear filtrate can be adjusted for pH value or further remove other trace impurities according to actual needs to ensure that the effluent quality meets the subsequent application or discharge standards.

[0088] Calcium ion online detectors are installed on the inlet pipelines of the primary decalcification reaction tank 1 and the secondary decalcification reaction tank 3 and on the filtrate discharge pipeline of the plate and frame filter press 4, with a measurement range from 0 to 40000 ppm, which can ensure the continuous and stable operation of the entire system.

[0089] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising a..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the element.

[0090] Although the present disclosure has been described in detail above with general descriptions and specific embodiments, based on the present disclosure, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present disclosure fall within the scope of protection required by the present disclosure.

Claims

1. A system for treating incineration fly ash washing liquid, characterized in that: include Pre-treatment unit: including a primary decalcification reaction tank, wherein the primary decalcification reaction tank is connected to a vertical scraper centrifuge; Post-processing unit: comprising a secondary decalcification reaction tank connected to the liquid phase outlet of the vertical scraper centrifuge, and the secondary decalcification reaction tank is connected to a plate and frame filter press; The primary decalcification reaction tank and the secondary decalcification reaction tank are connected to the sodium sulfate dissolution tank and the sodium carbonate dissolution tank respectively, and the liquid phase outlet of the plate and frame filter press is connected to the sodium sulfate dissolution tank and / or the sodium carbonate dissolution tank.

2. The incineration fly ash washing liquid disposal system according to claim 1, characterized in that: The primary anti-decalcification reaction tank is connected to the primary decalcification thickening tank via a liquid pump, and the primary decalcification thickening tank is connected to the vertical scraper centrifuge via an underflow pump.

3. The incineration fly ash washing liquid disposal system according to claim 2, characterized in that: An upper tank is arranged between the underflow pump and the vertical scraper centrifuge, and the centrifugal liquid phase outlet of the vertical scraper centrifuge is connected to the secondary decalcification reaction tank through a primary decalcification filtrate tank.

4. The incineration fly ash washing liquid disposal system according to claim 3, characterized in that: The bottom liquid phase outlet of the vertical scraper centrifuge is also connected to the primary decalcification thickening tank.

5. The incineration fly ash washing liquid disposal system according to claim 1, characterized in that: The secondary decalcification reaction tank is connected to the secondary decalcification reaction pool through a pump, the secondary decalcification reaction pool is connected to a sludge well, and the sludge well is connected to the plate and frame filter press through a sludge pump.

6. The incineration fly ash washing liquid disposal system according to claim 5, characterized in that: The liquid phase outlet of the plate and frame filter press is connected to a buffer tank, and the buffer tank is connected to the sodium sulfate dissolution tank and the sodium carbonate dissolution tank.

7. The incineration fly ash washing liquid disposal system according to claim 6, characterized in that: The buffer tank is also connected to the secondary decalcification reaction tank.

8. The incineration fly ash washing liquid disposal system according to claim 7, characterized in that: The liquid phase outlet of the sludge well is also connected to the buffer tank.

9. The incineration fly ash washing liquid disposal system according to claim 8, characterized in that: The system also includes a hydrochloric acid tank, which is connected to a pipeline mixer via a pump, and the pipeline mixer is connected to the buffer tank.

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