CN114702188B

CN114702188B - Method and system for cooperatively treating high-salt solid waste ash and acid wastewater of steel plant

Info

Publication number: CN114702188B
Application number: CN202210499585.0A
Authority: CN
Inventors: 叶恒棣; 颜旭; 杨本涛; 魏进超; 柴立元; 刘彦廷; 冯哲愚
Original assignee: Central South University; Zhongye Changtian International Engineering Co Ltd
Current assignee: Central South University; Zhongye Changtian International Engineering Co Ltd
Priority date: 2021-09-07
Filing date: 2022-05-09
Publication date: 2023-10-10
Anticipated expiration: 2042-05-09
Also published as: CN114702188A; WO2023036053A1

Abstract

The invention discloses a method and a treatment system for cooperatively treating high-salt solid waste ash and acid wastewater of a steel plant, which utilize the high-salt solid waste ash produced by the steel enterprise to produce high-purity potassium chloride. Meanwhile, based on the characteristics of high heavy metals such as thallium and the like, high ammonia nitrogen concentration and high sulfate radical concentration of conventional high-salt solid waste ash water washing waste water, the characteristics of a large amount of sulfite ions (flue gas washing waste water) or iron ions (cold rolling rinsing waste water) and low acidity are combined, on the basis of the existing high-salt solid waste ash water washing and waste water recycling process, the aims of the high-salt solid waste ash and the acid waste water cooperative treatment and recycling of the steel plant are fulfilled by the synergistic effects of acid waste water sectional supply ash washing, sulfur removal and ammonia nitrogen removal, iron carbon micro-electrolysis deep thallium oxide, COD (chemical oxygen demand) and ammonia nitrogen, countercurrent evaporation potassium and sodium separation and the like. Meanwhile, the technical scheme provided by the invention has the advantages of simple process conditions, low energy consumption, no wastewater discharge and the like.

Description

Method and system for cooperatively treating high-salt solid waste ash and acid wastewater of steel plant

Technical Field

The invention relates to solid waste and wastewater treatment in the steel industry, in particular to a method and a treatment system for cooperatively treating high-salt solid waste ash and acid wastewater of a steel plant, belonging to the technical field of solid waste ash and wastewater cooperative recycling treatment in the steel industry.

Background

At present, for high-salt solid waste ash (such as sintering electric field ash, blast furnace cloth bag ash, rotary kiln surface cooling ash, waste incineration fly ash and the like) generated by a steel plant, alkali and chlorine metals are usually removed by adopting a water washing mode, for example, chinese patent CN103435073A (method for producing potassium chloride by using blast furnace gas ash of steel enterprises) reports that tap water is used for leaching the blast furnace gas ash, so that potassium and chlorine in the blast furnace gas ash are greatly reduced, and the leaching solution is used for preparing potassium chloride and sodium chloride. Chinese patent CN101234766A (method for producing potassium chloride by utilizing sintered electric dust of iron and steel enterprises) reports a method for leaching high-salt solid waste ash by adopting tap water and SDD inhibitor compound solution, wherein the leaching rate of potassium and sodium can reach 95-99.5%. The high-salt solid waste after water washing leaching can be returned to high-temperature furnaces such as sintering, a blast furnace, a rotary kiln and the like for further treatment after dehydration. However, in the process of leaching high-salt solid waste by water washing, a large amount of high-salt leaching waste water is generated, and can be used for preparing potassium chloride and sodium chloride. The high-salt wastewater is generally used for evaporating and crystallizing potassium sodium salt after heavy metal and chromaticity are removed by pretreatment. In the actual operation process, since the high-salt wastewater contains a large amount of sulfate radicals (the concentration is generally about 2 g/L), if the sulfate radicals are not removed, the high-salt wastewater finally enters potassium chloride, so that the salt quality is reduced, and an evaporation system is blocked by forming glaserite. In addition, the high-salt wastewater also contains thallium, ammonia nitrogen and other pollutants. If these contaminants are deeply removed, there is a disadvantage in that the treatment process flow is long, which causes a drastic increase in the treatment cost.

The method aims at removing sulfate radical in the wastewater in a plurality of ways, such as a barium chloride method, a nanofiltration method and a calcium oxide method for removing sulfuric acid. However, these methods have different disadvantages and are not suitable for removing pollutants in ash washing water. For example, chinese patent CN110342710A, high-chlorine low-sulfate wastewater treatment system and process thereof, describes a method for removing sulfate by precipitation in a mode of adding calcium chloride, and sulfate can be reduced from 6000ppm to 2000ppm. However, this method is not suitable for the above-mentioned ash washing water, because the sulfate radical concentration in the above-mentioned ash washing water is generally 1500-3000 ppm, and this method cannot realize the deep removal of sulfate radical in the ash washing water. In order to realize the deep removal of sulfate radicals, chinese patent CN111592148A, a process method for converting high-salinity wastewater into NaOH solution, reports that the high-efficiency removal of sulfate radicals is realized by adopting the calcium-aluminum composite salt under the high-alkalinity condition. However, when the method is used for removing sulfate radical in ash washing water, the pH value of the solution is too high, a large amount of hydrochloric acid is required to be recovered, and meanwhile, the formed particles are finer and the defect of filtering and removing is overcome.

The method for removing ammonia nitrogen in the wastewater comprises an ammonia distillation method, a magnesium ammonium phosphate method, a stripping method and the like, wherein the ammonia distillation method and the stripping method require building additional devices and treating the recovered ammonia, and the investment and the operation cost are high. The magnesium ammonium phosphate method has the defects of difficult operation and high operation cost because phosphate radicals and magnesium ions are required to be introduced.

The removal of thallium from high-salt wastewater mainly comprises sodium sulfide precipitation, an oxidation precipitation method and an electrochemical precipitation method, wherein the oxidation precipitation method is the most commonly used method. For example, chinese patent CN106977013a discloses a purification treatment method of high-chlorine thallium-containing wastewater and application thereof, wherein after oxidizing Tl (I) with an oxidizing agent, pretreatment of Tl (III) is performed by an ion exchange resin, and then deep removal of Tl (III) is performed by sodium sulfide. However, tl (III) forms stable [ TlCl4 ] with chlorine in high-salt wastewater ^- ]Because the complex is relatively stable, the complex is difficult to thoroughly remove by adopting a precipitation method.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a method and a treatment system for cooperatively treating high-salt solid waste ash and acid waste water (flue gas washing waste water, cold rolling rinsing waste water and the like) of a steel plant, which can produce high-purity potassium chloride by utilizing waste water and high-salt solid waste ash generated in a sintering process of a steel enterprise, and simultaneously avoid the problems of equipment corrosion and kiln formation caused by the entering of alkali metal and chlorine into high-temperature kilns such as sintering, a blast furnace, a rotary kiln and the like. Meanwhile, based on the characteristics of high heavy metals such as thallium and the like, high ammonia nitrogen concentration and high sulfate radical concentration, and combined with the characteristics of a large amount of sulfite ions (flue gas washing wastewater) or iron ions (cold rolling rinsing wastewater) and low acidity of the wastewater of the iron and steel plant, the method realizes the aims of cooperative treatment and recycling of the high-salt solid wastewater and the acidic wastewater of the iron and steel plant by the synergistic effects of the acid wastewater of the iron and steel plant such as sectional supply of the wastewater for ash washing, sulfur removal and ammonia nitrogen removal, iron carbon micro-electrolysis deep thallium oxide and COD, countercurrent evaporation and potassium and sodium separation and the like on the basis of the existing high-salt solid wastewater washing and wastewater recycling process. Meanwhile, the technical scheme provided by the invention has the advantages of simple process conditions, low energy consumption, no wastewater discharge and the like.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:

according to a first embodiment of the present invention, a method for the co-treatment of high-salt solid waste ash and acid wastewater from steel plants is provided.

A method for cooperatively treating high-salt solid waste ash and acid wastewater of a steel plant, which comprises the following steps:

1) And (3) ash washing treatment: mixing industrial water and part of flue gas washing wastewater to obtain acidic mixed water, washing high-salt solid waste ash by adopting the acidic mixed water, carrying out solid-liquid separation to obtain a filter cake and ash washing wastewater, carrying out outward treatment on the filter cake, mixing the ash washing wastewater with the rest of flue gas washing wastewater to obtain mixed wastewater, and carrying out next-stage treatment.

Or washing the high-salt solid waste ash by adopting part of cold-rolling rinsing wastewater, carrying out solid-liquid separation to obtain a filter cake and ash washing wastewater, carrying out outward treatment on the filter cake, mixing the ash washing wastewater with the rest cold-rolling rinsing wastewater, heating to carry out precipitation reaction, carrying out solid-liquid separation to obtain mixed wastewater and slag phase after the reaction is finished, carrying out outward treatment on the slag phase, and carrying out next stage treatment on the mixed wastewater.

2) And (3) micro-electrolysis treatment: and (3) performing iron-carbon micro-electrolysis treatment on the mixed wastewater obtained in the step (1).

3) Advanced pretreatment of wastewater: adding a mixed reagent into the mixed wastewater after the micro-electrolysis treatment, regulating the mixed wastewater to be alkaline, carrying out weight and hardness removal precipitation reaction on the mixed wastewater, obtaining high-salt wastewater and residues after solid-liquid separation, carrying out outward transportation treatment on the residues, and carrying out next-stage treatment on the high-salt wastewater.

4) Countercurrent evaporation treatment: heating the high-salt wastewater, concentrating and crystallizing, and separating solid from liquid to obtain sodium chloride and filtrate I. And cooling and crystallizing the filtrate I, and carrying out solid-liquid separation to obtain potassium chloride and filtrate II.

Preferably, the method further comprises:

5) And (3) cyclic evaporation treatment: mixing the filtrate II produced in the step 4) with the high-salt wastewater produced in the step 3), and then continuing the countercurrent evaporation treatment. Or returning the filtrate II generated in the step 4) to the step 1) to participate in the water washing and mixing.

Preferably, in step 1), the flue gas washing wastewater is acid flue gas washing wastewater, preferably flue gas washing wastewater generated by the activated carbon method desorption gas washing.

Preferably, in the step 1), the cold-rolling rinsing wastewater is FeCl-containing wastewater generated in the rinsing section of the cold-rolling strip steel pickling process ₃ And HCl, preferably a pH < 2.5, preferably a pH < 2.

Preferably, in step 1), the high-salt solid waste ash comprises one or more of sintering electric field ash, blast furnace cloth bag ash, rotary kiln surface cooling ash and waste incineration fly ash, preferably sintering electric field ash.

Preferably, in step 1), the water-to-ash mass ratio of the acidic mixed water and the high-salt solid waste ash or the water-to-ash mass ratio of the cold-rolling rinse wastewater and the high-salt solid waste ash is 1-6:1, preferably 2-4:1.

Preferably, in step 1), the flue gas washing wastewater or cold-rolling rinsing wastewater is added in such an amount that the pH value of the mixed wastewater is 2 to 4, preferably 2.5 to 3.5.

Preferably, in step 1), the heating is performed to perform the precipitation reaction by heating to 80-100 ℃ for 1-8 hours, preferably to 85-95 ℃ for 2-5 hours.

Preferably, in step 1), the precipitation reaction is carried out by adding a soluble iron salt (e.g. FeCl) ₃ ) So that the mol ratio of sulfate ions, ammonia nitrogen and iron ions in the wastewater is 0.4-0.8:0.2-0.5:1, preferably 0.5-0.7:0.25-0.4:1.

Preferably, in step 2), the pH of the mixed wastewater is adjusted to 3-5, preferably 3.5-4, with a base prior to subjecting the mixed wastewater to iron-carbon micro-electrolysis. The duration of the iron-carbon micro-electrolysis treatment is not less than 20min, preferably 30-60min. Aeration backflushing is required to be carried out periodically in the iron-carbon micro-electrolysis process.

Preferably, in step 2), the base is sodium hydroxide and/or potassium hydroxide.

Preferably, in step 3), the mixed agent is sodium hydroxide and/or potassium hydroxide, sodium carbonate and/or potassium carbonate, sodium sulfide and/or potassium sulfate, and the recapturing agent (preferably xanthate recapturing agent or dithiocarbamate recapturing agent) is formed together. Wherein: the amount of sodium hydroxide and/or potassium hydroxide added is such that the pH of the mixed wastewater is 7-9, preferably 7.5-8. The addition amount of the sodium carbonate and/or the potassium carbonate is 3-10g/L, preferably 4-8g/L. The addition amount of sodium sulfide and/or potassium sulfide is 1-7g/L, preferably 1.5-6g/L. The adding amount of the recapturing agent is 1-8g/L, preferably 2-5g/L.

Preferably, in step 3), the high-salt wastewater has a potassium-sodium content ratio of not less than 4, preferably not less than 5.

Preferably, in step 3), the mixed wastewater is subjected to the weight and hardness removal precipitation reaction for a period of not less than 10 minutes, preferably 15 to 40 minutes.

Preferably, in step 4), countercurrent evaporation is carried out using a multi-effect evaporator having a number of stages ranging from 2 to 6, preferably from 3 to 5. The heating of the high-salt wastewater is to heat the high-salt wastewater to 80-100 ℃, preferably 90-95 ℃. The liquid I is cooled to be lower than 60 ℃ by adopting a flash evaporation or heat exchange mode, and the temperature is preferably 20-55 ℃.

Preferably, the washing in the ash washing treatment is a multistage washing treatment, preferably a three-stage countercurrent washing treatment. The method comprises the following steps: first, carrying out primary water washing on high-salt solid waste ash, and carrying out primary filter pressing dehydration to obtain primary filtrate and primary filter residue, wherein the primary filtrate is subjected to subsequent micro-electrolysis treatment. The primary filter residue enters secondary washing, a secondary washing water source is tertiary filtrate, the secondary washing water is dehydrated through secondary filter pressing after the secondary washing, and secondary filtrate and secondary filter residue are obtained, and the secondary filtrate is discharged to the primary washing for recycling. The secondary filter residue enters tertiary washing, the water source of the tertiary washing is acid mixed water mixed by industrial water and flue gas washing wastewater, tertiary filter pressing and dehydration are carried out after the tertiary washing, tertiary filtrate and tertiary filter residue are obtained, the tertiary filtrate is discharged to the secondary washing for recycling, and the tertiary filter residue is discharged for outward transportation.

According to a second embodiment of the invention, a system for the co-treatment of high-salt solid waste ash and acid wastewater from a steel plant is provided.

A system for cooperatively treating high-salt solid waste ash and acid wastewater of a steel plant comprises a countercurrent water washing device, an adjusting tank, an iron-carbon micro-electrolysis tank, a weight and hardness removal tank and a countercurrent multi-effect evaporator. The wastewater inlet pipeline is communicated with the water inlet of the countercurrent washing device. The water outlet of the countercurrent water washing device is communicated with the water inlet of the regulating tank through a first pipeline. The water outlet of the regulating tank is communicated with the water inlet of the iron-carbon micro-electrolysis tank through a second pipeline. The water outlet of the iron-carbon micro-electrolysis cell is communicated with the water inlet of the weight and hardness removal cell through a third pipeline. The water outlet of the heavy and hard removing pool is communicated with the water inlet of the countercurrent multi-effect evaporator through a fourth pipeline. The countercurrent water washing device is also provided with a high-salt solid waste ash inlet.

Preferably, the waste water inlet pipeline is also provided with a waste water branch pipe which is communicated with the water inlet of the regulating tank. The regulating tank is also provided with at least one dosing port. The regulating tank is also provided with a heating unit, a first pH detector and a temperature detector. Preferably, the heating unit is an electric heating unit or a steam heating unit.

Preferably, the weight and hardness removing tank is also provided with at least one mixed dosing port. A second pH detector is arranged in the weight and hardness removing tank.

Preferably, the countercurrent multiple-effect evaporator comprises a heating unit, a cooling unit and a panning unit. The liquid outlet of the heating unit is communicated with the liquid inlet of the cooling unit through a fifth pipeline. The liquid outlet of the cooling unit is communicated with the water inlet of the heating unit through a circulating infusion tube. The heating unit is also provided with a sodium salt outlet which is communicated with the sodium salt conveying device. The cooling unit is also provided with a potassium salt outlet which is communicated with the elutriation unit through a potassium salt conveying device. The discharge outlet of the elutriation unit is communicated with a pure salt conveying device.

Preferably, the steam outlet of the countercurrent multi-effect evaporator is communicated with the regulating tank through a steam conveying pipeline.

In the prior art, in order to avoid the problems that alkali metal, chlorine element and the like in high-salt solid waste ash can cause equipment corrosion, kiln setting and other adverse conditions, a water washing mode is adopted to remove the alkali and chlorine metal and recycle potassium and sodium salts. But due to high salt solid wastesThe ash composition is complex, so that the ash washing water has complex components, such as a large amount of metal ions, ammonia nitrogen, sulfate radical and the like. In this regard, metal ions and ammonia nitrogen are often removed by making the ash wash water alkaline, but studies have shown that thallium in the high salt solid ash wash water readily forms under alkaline conditions [ TlCl ] ₄ ^- ]Due to [ TlCl ] ₄ ^- ]Is relatively stable, and once formed, is relatively difficult to handle by conventional removal processes. The recovered potassium salt has more impurities and relatively lower purity, which affects the utilization of the potassium salt. Aiming at the high-salt solid waste ash washing wastewater with more potassium than sodium, potassium salt is generally precipitated firstly, and then sodium salt is precipitated, on one hand, the potassium salt is precipitated firstly, impurity pollutants are easily precipitated along with the precipitation of the potassium salt, the quality of the potassium salt is reduced, and on the other hand, the subsequent precipitation of the sodium salt also needs to be continuously heated, concentrated and crystallized, so that the energy consumption is increased. If sodium salt is precipitated first, potassium salt is likely to be precipitated first because the content of potassium is more than that of sodium, so that the quality of sodium salt is reduced, and the yield of potassium salt is also reduced.

In the invention, the process flow specifically comprises the following steps: firstly, acid mixed water (which is formed by mixing part of flue gas washing wastewater and industrial water) or part of cold rolling rinsing wastewater is adopted to perform three-stage countercurrent water washing process dechlorination treatment on high-salt solid waste ash. Carrying out outward transportation treatment on the filter cake obtained after water washing, mixing the ash washing wastewater obtained after water washing with the rest part of flue gas washing wastewater or cold rolling rinsing wastewater, and enabling the pH value of the mixed wastewater to be 2-4 (preferably 2.5-3.5); at the same time, by adding soluble iron salts (preferably FeCl ₃ ) Adjusting the mole ratio of sulfate ions, ammonia nitrogen and iron ions in the mixed wastewater to be 0.4-0.8:0.2-0.5:1 (preferably 0.5-0.7:0.25-0.4:1), and heating the mixed wastewater to 80-100 ℃ (preferably 85-95 ℃) for 1-8 hours (preferably 2-5 hours) to remove the ammonia nitrogen, sulfate radicals and the like in the mixed wastewater. Then adding alkali (sodium hydroxide or potassium hydroxide) into the mixed wastewater to adjust the pH value to 3-4, and then entering an iron-carbon micro-electrolysis reactor to carry out micro-electrolysis reaction, wherein the iron-carbon micro-electrolysis reactor is subjected to aeration back flushing periodically. Due to Tl ³⁺ Ratio Tl ⁺ Easier to remove and, in general, pretreatment can be carried out by oxidation. Iron carbon micro-electrolysis with synergismThe effects of weight removal and oxidation are achieved. After the iron-carbon micro-electrolysis is completed, tl can be changed into a form which is easier to remove. Meanwhile, a large amount of metal ions in the ash washing water can be replaced by the iron simple substance, so that the removal is realized, and a large amount of ferrous iron and ferric iron are generated in the solution. In addition, the iron carbon is favorable for efficiently removing fluoride ions in the wastewater. Adding a mixed reagent (for example, a mixed reagent consisting of sodium hydroxide, sodium carbonate, sodium sulfide and a recapture agent sequentially) into the wastewater after iron-carbon micro-electrolysis, wherein the adding amount of the sodium hydroxide is mainly used for adjusting the pH value of the solution to 7-10 (preferably 7-9), and the sodium carbonate, the sodium sulfide, the recapture agent and the like are used for carrying out heavy and hard removal precipitation reaction of the wastewater to separate heavy metal ions, calcium and magnesium and other precipitates in the water, so that deep removal of ammonia nitrogen, calcium and magnesium and heavy metals is sequentially realized in the process. The treated wastewater is filtered through a filter press together with the precipitate. And (5) treating filter residues as heavy metal sludge by carrying out outward. The filtrate is high-salt wastewater. And (3) homogenizing the high-salt wastewater, and then conveying the homogenized high-salt wastewater into a multi-effect evaporator. The multi-effect evaporator adopts countercurrent design, namely the high-salt solution sequentially passes through a multi-effect reactor, a two-effect reactor and a one-effect reactor, and the temperature of the solution is increased from normal temperature to 95-100 ℃. After evaporation, sodium salt is precipitated after reaching a saturated precipitation point of the sodium salt, the recovery of the sodium salt can be realized through centrifugal separation, and mother solution obtained through centrifugal separation returns to the one-effect evaporator for circulating concentration. Concentrating to potassium salt saturation precipitation point, cooling, reducing the solution temperature to below 60deg.C to precipitate potassium salt, centrifuging to recover potassium salt, and concentrating mother liquor by centrifuging in a multi-effect evaporator. Further, the precipitated potassium chloride solid can be fed into a elutriation device, and washed by saturated potassium chloride solution to further purify the potassium chloride, and the high-purity potassium chloride is obtained after centrifugal separation.

In the invention, since the high-salt solid waste ash is high-potassium low-sodium ash, the potassium-sodium ratio in the conventional water washing solution is generally more than 4 (preferably more than 5). According to the principle of potassium-sodium variable temperature salt separation, the method is suitable for concurrent evaporation, namely potassium-sodium salt phase diagram analysis is performed through variable temperature evaporation, and potassium salt is separated out firstly after high-potassium low-sodium solution is concentrated through evaporation, so that the salt separation mode of high-salt solid waste ash washing water is generally concurrent evaporation. I.e. the solution is gradually cooled during the evaporation process. At the multi-effect outlet, the potassium salt is discharged first. The evaporation mode can lead to precipitation of pollutants along with precipitation of potassium, the quality of potassium can be reduced, and meanwhile, the subsequent precipitation of sodium salt requires two-stage evaporation, so that the investment is increased, and the energy consumption is high. Therefore, the invention introduces the flue gas washing wastewater (containing sodium) to be mixed with industrial water to be used as high-salt solid waste ash water washing water, so that the content ratio of potassium to sodium in the ash washing wastewater is close to 1:1, or the invention introduces the acidic cold rolling rinsing wastewater to enable the content ratio of potassium to sodium in the ash washing wastewater to be close to 2:1. And then potassium salt is separated out through cooling, and residual pollutants are separated out along with the separation of sodium in an evaporation mode (the pollutants mainly enter the sodium salt due to countercurrent evaporation only through one-stage concentration) and cannot enter the potassium salt, so that the quality of the potassium is improved. Meanwhile, the whole evaporation only utilizes one section of evaporation system, so that the method is applicable to the change of different evaporation amounts, and has stronger applicability to raw materials and lower investment.

In the invention, the flue gas washing wastewater comprises suspended matters, metal ions, ammonia nitrogen and fluorine chlorine. The metal ions comprise one or more of sodium, iron, copper, lead, calcium, zinc, cadmium, cobalt, nickel and aluminum. The industrial water and part of the acidic flue gas wash wastewater are first mixed and the mixed water is made acidic (e.g. pH 1-3). Thallium is generally readily formed in high-salt wastewater [ TlCl ] under alkaline conditions ₄ ^- ]Due to [ TlCl ] ₄ ^- ]Is relatively stable, and once formed, is relatively difficult to handle by conventional removal processes. Because the flue gas washing wastewater has stronger acidity, when the flue gas washing wastewater is used for washing ash, on one hand, the solution of the ash washing water can be reduced, and the ash washing water becomes acidic, thereby preventing the formation of stable [ TlCl ] ₄ ^- ]. On the other hand, the flue gas washing wastewater contains thiosulfate radical, and thallium can be removed after the thiosulfate radical is added. Thereby realizing the source inhibition of thalliumAnd (5) preparing. Studies show that the conventional industrial water is adopted for ash washing, and the thallium content in ash washing water is about 30 mg/L. After the acidic washing wastewater is introduced, the thallium content in the ash washing water can be reduced to about 1 mg/L. The invention adopts acid flue gas washing wastewater to cooperatively treat high-salt solid waste ash, on one hand, the potassium-sodium ratio is regulated to be close to 1:1, the countercurrent evaporation is realized, the quality of potassium salt is improved, on the other hand, thallium is reduced from the source, the purity of the potassium salt is further ensured, and the value of the potassium salt is improved.

In the invention, the cold rolling rinsing wastewater is FeCl-containing wastewater generated in the rinsing section of the cold rolling strip steel pickling process ₃ And HCl, generally acidic at a pH of < 2.5 (preferably pH < 2). Based on the characteristics of high thallium and other heavy metals, high ammonia nitrogen concentration and high sulfate radical concentration in the high-salt solid waste ash water washing wastewater (ammonia nitrogen concentration in the ash washing water is generally 1000-4000 mg/L and sulfate radical concentration is generally 500-3000 mg/L), and the characteristics of a large amount of ferric iron and low acidity in the cold-rolling rinsing wastewater are combined, the iron and sulfate radicals can react with potassium, sodium and ammonia nitrogen to form jarosite, sodium jarosite and ammonium jarosite. Therefore, the waste water can be heated (the heat source can be electric heating or the steam waste heat of a subsequent evaporation system) to 80-100 ℃ so as to remove ammonia nitrogen and sulfate radical in the waste water. Secondly, cold-rolling rinsing wastewater is used as high-salt solid waste ash water washing water, thallium control of ash washing wastewater is realized by utilizing the acidity of the cold-rolling rinsing wastewater, and as the acidic cold-rolling rinsing wastewater has stronger acidity, when the cold-rolling rinsing wastewater is used for ash washing, on one hand, the solution of the ash washing water can be reduced, so that the ash washing water becomes acidic, thereby preventing the formation of stable [ TlCl4 ] ^- ]. After the cold rolling rinsing wastewater is introduced, the thallium content in the ash washing water can be reduced to about 5 mg/L. The thallium source is reduced and the dissolution is realized. On the other hand, the research shows that when the concentration of chloride ions in water is not higher than 15000mg/L, the enrichment of chloride in solid waste after water washing is not caused. Therefore, the cold rolling rinsing wastewater is adopted to completely replace industrial water, and deep removal of chlorine in the high-salt solid waste ash can be realized. The effect of treating waste by waste is achieved.

In the invention, impurity removal is also carried out by iron-carbon micro-electrolysis, due to Tl ³⁺ Ratio Tl ⁺ Easier to remove, in generalPretreatment may be performed by oxidation. The iron-carbon micro-electrolysis has the synergistic effects of removing heavy and oxidizing. After passing through the iron carbon, tl can be changed to a more easily removable form. Meanwhile, a large amount of metal ions in the ash washing water can be replaced by the iron simple substance, so that the removal is realized, and a large amount of ferrous iron and ferric iron are generated in the solution. In addition, the iron carbon is favorable for efficiently removing fluoride ions in the wastewater. Further, since the acidic flue gas washing wastewater also contains sulfite, iron and carbon release ferrous iron. And (3) adjusting the ash washing wastewater to alkalescence by adopting alkali (such as sodium hydroxide), and after adjusting the solution to alkalescence, enabling ammonia nitrogen to react with sulfite and ferrous rapidly to form ferrous ammonium sulfite precipitate, so that the deep removal of ammonia nitrogen is realized. Meanwhile, ferric iron and partial calcium and magnesium ions can be removed under the weak base condition. The purpose of adding sodium carbonate is to remove calcium and magnesium. The purpose of adding sodium sulfide and recapturing agent is to realize deep removal of trace heavy metals.

In the invention, the water washing of the high-salt solid waste ash is multi-stage water washing, generally trimerization countercurrent water washing, the three-stage countercurrent water washing process is that the high-salt solid waste ash is subjected to one-stage water washing and then one-stage filter pressing dehydration, filtrate is discharged to enter a subsequent wastewater recycling treatment system (namely, directly enter iron-carbon micro electrolysis), and filter residues enter the two-stage water washing. The water source of the second-stage water washing is water produced by three-stage filter pressing, the second-stage water washing is carried out, the water is dehydrated by the second-stage filter pressing, the filtrate is discharged to the first-stage water washing for recycling, and filter residues enter the three-stage water washing. The third-stage water washing source is a mixed solution of industrial water and evaporated and recovered condensed water, the third-stage water washing source is dehydrated through third-stage filter pressing, filtrate is discharged to the second-stage water washing for recycling, and filter residues are discharged from the system and transported to the outside for disposal. Further, mother liquor after potassium salt is separated out by the multi-effect countercurrent evaporator returns to the multi-effect countercurrent evaporator for circulating concentration or returns to the water washing process to participate in water washing, so that zero emission of wastewater is realized.

In the system for cooperatively treating the high-salt solid waste ash and the acid waste water of the steel plant, when the flue gas washing waste water is used as the ash washing water of the high-salt solid waste ash, the regulating tank is only used for mixing the ash washing waste water with the residual flue gas washing waste water, and the pH place of the mixed waste water is regulated; when cold rolling rinsing wastewater is used as high saltIn addition to the above-mentioned use of the regulating tank, the solid waste ash can also be used as ash washing water to which soluble ferric salt (for example FeCl ₃ ) And heating the place where the precipitation reaction is performed.

Compared with the prior art, the invention has the following beneficial technical effects:

1: according to the invention, aiming at the characteristics of the high-salt solid waste ash and the acid waste water (flue gas washing waste water or cold rolling rinsing waste water) of the steel plant, the waste ash and the waste water are treated in a cooperative resource way, on one hand, the leaching of thallium in the high-salt solid waste ash is inhibited by the acid flue gas washing waste water or the acid cold rolling rinsing waste water, the thallium content in the ash washing waste water is reduced from the source, and the quality of the subsequent potassium salt is improved; secondly, sodium contained in the acidic flue gas washing wastewater is utilized, so that the content ratio of potassium to sodium in the ash washing wastewater is close to 1:1, multi-effect countercurrent evaporation is realized, the quality of potassium salt is further improved, and the recycling value of the potassium salt is improved; or ferric iron contained in the acidic cold rolling rinsing wastewater is also utilized to remove ammonia nitrogen and sulfate radical in the wastewater; meanwhile, the defect of high potassium-sodium ratio in the conventional ash washing wastewater is avoided, the quality of the potassium salt is greatly improved,

2: the invention adopts the method of iron-carbon micro-electrolysis and adding the mixed medicament, realizes the synergistic thallium oxide, deep ammonia nitrogen removal and heavy removal with low cost, greatly reduces the treatment flow of the ash washing wastewater, prevents the pollution of the potassium salt by pollutants, greatly reduces the energy consumption and improves the production efficiency.

3: compared with the traditional process, the scheme of the invention can avoid introducing other ions when directly removing impurities in the wastewater and removing ammonia nitrogen, thallium, heavy metals and the like which affect the recovery of potassium salt at low cost by improving an evaporation mechanism and a process route, further improve the quality of the recovered potassium salt, and prevent pollutants from entering the potassium salt, thereby improving the value of potassium chloride products. Meanwhile, the invention has the advantages of low cost and simple operation, does not additionally increase equipment and energy consumption, reasonably utilizes the resources in the system, realizes digestion in the system and greatly reduces the emission of pollutants.

Drawings

FIG. 1 is a process flow diagram of the method for the synergistic treatment of high-salt solid waste ash and flue gas washing wastewater.

FIG. 2 is a process flow diagram of the method for cooperatively treating high-salt solid waste ash and cold-rolling rinsing wastewater.

FIG. 3 is a schematic diagram of a system for the co-treatment of high salt solid waste ash and acid wastewater from steel works according to the present invention.

FIG. 4 is a schematic diagram of a heating unit of the treatment system of the present invention, which is an electrical heating device.

Reference numerals: 1: a countercurrent water washing device; 2: an adjusting tank; 201: a medicine adding port; 202: a heating unit; 203: a first pH meter; 204: a temperature detector; 3: an iron-carbon micro-electrolysis cell; 4: removing weight and hardness; 401: a mixed medicine adding port; 402: a second pH meter; 5: a countercurrent multiple effect evaporator; 501: a heating unit; 502: a cooling unit; 503: a panning unit; 504: a circulating transfusion tube; 505: sodium salt conveying device; 506: potassium salt conveying device; 507: pure salt conveying device; l0: a wastewater inlet pipe; l01: a waste water branch pipe; l1: a first pipe; l2: a second pipe; l3: a third conduit; l4: a fourth conduit; l5: a fifth pipe; l6: a steam delivery conduit.

Detailed Description

The following examples illustrate the technical aspects of the invention, and the scope of the invention claimed includes but is not limited to the following examples.

A system for cooperatively treating high-salt solid waste ash and acid wastewater of a steel plant comprises a countercurrent washing device 1, an adjusting tank 2, an iron-carbon micro-electrolysis tank 3, a heavy and hard removing tank 4 and a countercurrent multi-effect evaporator 5. The wastewater inlet pipeline L0 is communicated with the water inlet of the countercurrent water washing device 1. The water outlet of the countercurrent water washing device 1 is communicated with the water inlet of the regulating tank 2 through a first pipeline L1. The water outlet of the regulating tank 2 is communicated with the water inlet of the iron-carbon micro-electrolysis tank 3 through a second pipeline L2. The water outlet of the iron-carbon micro-electrolytic cell 3 is communicated with the water inlet of the weight and hardness removing cell 4 through a third pipeline L3. The water outlet of the heavy and hard removing tank 4 is communicated with the water inlet of the countercurrent multi-effect evaporator 5 through a fourth pipeline L4. The countercurrent water washing device 1 is also provided with a high-salt solid waste ash inlet 101.

Preferably, the waste water inlet pipeline L0 is also provided with a waste water branch pipe L01 which is communicated with the water inlet of the regulating tank 2. The regulating reservoir 2 is further provided with at least one dosing port 201. The regulating tank 2 is further provided with a heating unit 202, a first pH meter 203, and a temperature meter 204. Preferably, the heating unit 202 is an electric heating unit or a steam heating unit.

Preferably, the weight-removing and hardness-removing tank 4 is further provided with at least one mixing and dosing port 401. A second pH meter 402 is provided in the weight removal hard tank 4.

Preferably, the countercurrent multiple-effect evaporator 5 includes a heating unit 501, a cooling unit 502, and a panning unit 503. The liquid outlet of the heating unit 501 is communicated with the liquid inlet of the cooling unit 502 through a fifth pipe L5. The liquid outlet of the cooling unit 502 is communicated with the water inlet of the heating unit 501 through a circulating infusion pipe 504. The heating unit 501 is further provided with a sodium salt outlet, and the sodium salt outlet is communicated with a sodium salt conveying device 505. The cooling unit 502 is further provided with a potassium salt outlet, which is in communication with the panning unit 503 via a potassium salt conveying device 506. The discharge port of the elutriation unit 503 is communicated with a pure salt conveying device 507.

Preferably, the steam outlet of the countercurrent multiple-effect evaporator 5 is in communication with the conditioning tank 2 through a steam delivery line L6.

Example 1

As shown in fig. 1, a method for cooperatively treating high-salt solid waste ash and flue gas washing wastewater comprises the following steps:

1) Washing: mixing industrial water and flue gas washing wastewater to obtain acidic mixed water, washing high-salt solid waste ash by adopting the acidic mixed water, carrying out solid-liquid separation to obtain a filter cake and ash washing wastewater, carrying out outward transportation treatment on the filter cake, and carrying out next-stage treatment on the ash washing wastewater.

2) And (3) micro-electrolysis treatment: and performing iron-carbon micro-electrolysis treatment on the ash washing wastewater.

3) Advanced pretreatment of wastewater: adding a mixed reagent into the ash washing wastewater subjected to micro-electrolysis treatment, adjusting the ash washing wastewater to be alkaline, carrying out weight and hardness removal precipitation reaction on the ash washing wastewater, and carrying out solid-liquid separation to obtain high-salt wastewater.

4) Countercurrent evaporation: heating the high-salt wastewater, concentrating and crystallizing, and separating solid from liquid to obtain sodium chloride and filtrate I. And cooling and crystallizing the filtrate I, and carrying out solid-liquid separation to obtain potassium chloride and filtrate II.

Example 2

5) And (3) cyclic evaporation: mixing the filtrate II produced in the step 4) with the high-salt wastewater produced in the step 3), and then continuing the countercurrent evaporation treatment.

Example 3

5) And (3) cyclic evaporation: and returning the filtrate II generated in the step 4) to the step 1) to participate in washing the material.

Example 4

As shown in fig. 2, a method for cooperatively treating high-salt solid waste ash and cold-rolling rinsing wastewater comprises the following steps:

1) And (3) ash washing treatment: and (3) washing the high-salt solid waste ash by adopting part of cold rolling rinsing wastewater, carrying out solid-liquid separation to obtain a filter cake and ash washing wastewater, carrying out outward treatment on the filter cake, and carrying out next-stage treatment on the ash washing wastewater.

2) Sulfur and ammonia nitrogen removal treatment: mixing the ash washing wastewater with the rest cold rolling rinsing wastewater to obtain mixed wastewater, heating the mixed solution to perform precipitation reaction, performing solid-liquid separation to obtain supernatant waste liquid and slag phase after the reaction is completed, carrying out outward transportation treatment on the slag phase, and performing next-stage treatment on the supernatant waste liquid.

3) And (3) micro-electrolysis treatment: and (3) performing iron-carbon micro-electrolysis treatment on the supernatant waste liquid obtained in the step (2).

4) Advanced pretreatment of wastewater: adding a mixed reagent into the supernatant waste liquid after the micro-electrolysis treatment, regulating the supernatant waste liquid to be alkaline, carrying out weight and hardness removal precipitation reaction on the supernatant waste liquid, and carrying out solid-liquid separation to obtain high-salt waste water and residues, carrying out outward transportation treatment on the residues, and carrying out next-stage treatment on the high-salt waste water.

5) Countercurrent evaporation treatment: heating the high-salt wastewater, concentrating and crystallizing, and separating solid from liquid to obtain sodium chloride and filtrate I. And cooling and crystallizing the filtrate I, and carrying out solid-liquid separation to obtain potassium chloride and filtrate II.

Example 5

6) And (3) cyclic evaporation treatment: and adding the filtrate II generated in the step 5) into the high-salt wastewater obtained in the step 4), and continuing countercurrent evaporation treatment along with the high-salt wastewater.

Example 6

As shown in fig. 3-4, a system for cooperatively treating high-salt solid waste ash and acid wastewater of a steel plant comprises a countercurrent water washing device 1, an adjusting tank 2, an iron-carbon micro-electrolysis tank 3, a heavy and hard removing tank 4 and a countercurrent multi-effect evaporator 5. The wastewater inlet pipeline L0 is communicated with the water inlet of the countercurrent water washing device 1. The water outlet of the countercurrent water washing device 1 is communicated with the water inlet of the regulating tank 2 through a first pipeline L1. The water outlet of the regulating tank 2 is communicated with the water inlet of the iron-carbon micro-electrolysis tank 3 through a second pipeline L2. The water outlet of the iron-carbon micro-electrolytic cell 3 is communicated with the water inlet of the weight and hardness removing cell 4 through a third pipeline L3. The water outlet of the heavy and hard removing tank 4 is communicated with the water inlet of the countercurrent multi-effect evaporator 5 through a fourth pipeline L4. The countercurrent water washing device 1 is also provided with a high-salt solid waste ash inlet 101.

Example 7

Example 6 was repeated except that a waste water branch pipe L01 was also branched from the waste water inlet pipe L0 and communicated with the water inlet of the regulating tank 2. The regulating reservoir 2 is further provided with at least one dosing port 201. The regulating tank 2 is further provided with a heating unit 202, a first pH meter 203, and a temperature meter 204.

Example 8

Example 7 is repeated except that the heating unit 202 is an electric heating unit or a steam heating unit.

Example 9

Example 8 is repeated except that at least one mixing dosing port 401 is also provided on the weight removal hard tank 4. A second pH meter 402 is provided in the weight removal hard tank 4.

Example 10

Example 9 is repeated except that the countercurrent multiple-effect evaporator 5 includes a heating unit 501, a cooling unit 502, and a elutriation unit 503. The liquid outlet of the heating unit 501 is communicated with the liquid inlet of the cooling unit 502 through a fifth pipe L5. The liquid outlet of the cooling unit 502 is communicated with the water inlet of the heating unit 501 through a circulating infusion pipe 504. The heating unit 501 is further provided with a sodium salt outlet, and the sodium salt outlet is communicated with a sodium salt conveying device 505. The cooling unit 502 is further provided with a potassium salt outlet, which is in communication with the panning unit 503 via a potassium salt conveying device 506. The discharge port of the elutriation unit 503 is communicated with a pure salt conveying device 507.

Example 11

Example 10 was repeated except that the vapor outlet of the countercurrent multiple-effect evaporator 5 was in communication with the regulating reservoir 2 via vapor delivery line L6.

Application example 1

Firstly, mixing industrial water and flue gas washing wastewater by an activated carbon method to obtain acid mixed water, then adopting the acid mixed water to perform three-stage countercurrent water washing on 100kg of sintered power plant ash (with the potassium content of 24.8 percent and the sodium content of 3.2 percent), obtaining a filter cake and about 310L of ash washing wastewater (with the potassium-sodium content ratio of about 5.4) after filter pressing, and carrying out outward treatment on the filter cake; and then adding sodium hydroxide into the ash washing wastewater to adjust the pH value of the ash washing wastewater to 3 (the addition amount of the activated carbon flue gas washing wastewater and the sodium hydroxide is such that the potassium-sodium content ratio in the ash washing wastewater is close to 1:1), introducing the adjusted ash washing wastewater into an iron-carbon micro-electrolysis reactor for treatment for 40min, and carrying out aeration back flushing on the iron-carbon micro-electrolysis reactor periodically during the treatment. After the micro-electrolysis treatment is finished, adding sodium hydroxide again to adjust the pH value of the ash washing wastewater to 8, then sequentially adding 2kg of sodium carbonate, 620g of sodium sulfide and 550g of dithiocarbamate recapturing agent, and stirring and mixing for reaction for 30min; and after filter pressing, obtaining high-salt wastewater. Heating high-salt wastewater to 95 ℃ in a multi-effect countercurrent evaporator, concentrating and crystallizing, and centrifugally separating to obtain sodium chloride and filtrate I. And cooling the filtrate I to below 60 ℃ to precipitate crystals, and centrifugally separating to obtain a potassium chloride crude product and filtrate II. Returning filtrate II to a countercurrent evaporation inlet for circular evaporation treatment; and (3) washing the crude potassium chloride product for multiple times by adopting a saturated potassium chloride solution, and centrifugally separating to obtain high-purity potassium chloride (the purity is 99.92%).

Application example 2

Firstly, mixing industrial water and flue gas washing wastewater by an activated carbon method to obtain acid mixed water, then adopting the acid mixed water to carry out three-stage countercurrent water washing on 120kg of blast furnace cloth bag ash (the potassium content is 29.4 percent and the sodium content is 4.0 percent), obtaining a filter cake and about 380L of ash washing wastewater (the potassium-sodium content ratio is about 6.3) after filter pressing, and carrying out outward treatment on the filter cake; and then adding sodium hydroxide into the ash washing wastewater to adjust the pH value of the ash washing wastewater to be 4 (the addition amount of the activated carbon flue gas washing wastewater and the sodium hydroxide is such that the potassium-sodium content ratio in the ash washing wastewater is close to 1:1), introducing the adjusted ash washing wastewater into an iron-carbon micro-electrolysis reactor to treat for 40min, and carrying out aeration back flushing on the iron-carbon micro-electrolysis reactor periodically during the treatment. After the micro-electrolysis treatment is finished, adding sodium hydroxide again to adjust the pH value of the ash washing wastewater to 9, then sequentially adding 3kg of sodium carbonate, 665g of sodium sulfide and 450g of dithiocarbamate recapturing agent, and stirring and mixing for reaction for 30min; and after filter pressing, obtaining high-salt wastewater. Heating high-salt wastewater to 95 ℃ in a multi-effect countercurrent evaporator, concentrating and crystallizing, and centrifugally separating to obtain sodium chloride and filtrate I. And cooling the filtrate I to below 60 ℃ to precipitate crystals, and centrifugally separating to obtain a potassium chloride crude product and filtrate II. Returning filtrate II to a countercurrent evaporation inlet for circular evaporation treatment; and (3) washing the crude potassium chloride product for multiple times by adopting a saturated potassium chloride solution, and centrifugally separating to obtain high-purity potassium chloride (the purity is 99.90%).

Application example 3

Carrying out three-stage countercurrent water washing on 100kg of sintering electric field ash (with the potassium content of 24.8 percent and the sodium content of 3.2 percent) by 380kg of cold rolling rinsing wastewater (pH less than 2), obtaining a filter cake and ash washing wastewater (with the potassium-sodium content ratio of about 5.1) after filter pressing, and carrying out outward treatment on the filter cake; then continuously adding cold rolling rinsing wastewater (pH is less than 2) into the ash washing wastewater to enable the pH of the mixed wastewater to be 2-3; feCl is then added to the mixed wastewater ₃ So that the molar ratio of sulfate ions, ammonia nitrogen and ferric ions in the mixed wastewater is close to 2:1:3; then, introducing hot steam into the mixed wastewater to heat the mixed wastewater to 90 ℃ for continuous reaction for 3.5 hours, and after the reaction is finished, performing filter pressing to obtain supernatant and a slag phase, and carrying out external transportation treatment on the slag phase; the pH of the supernatant was adjusted to 3 with sodium hydroxide, and then the supernatant was introduced into the iron-carbon micro-electrolysis reactor for 30min, during which aeration back flushing was periodically performed on the iron-carbon micro-electrolysis reactor. After the micro-electrolysis treatment is finished, adding sodium hydroxide again to adjust the pH value of the ash washing wastewater to 8, then sequentially adding sodium carbonate (the addition standard is 6 g/L), sodium sulfide (the addition standard is 4.8 g/L) and a dithiocarbamate recapture agent (the addition standard is 4.2 g/L), and stirring and mixing for reaction for 30min; and (3) performing filter pressing after the reaction is finished to obtain high-salt wastewater (the content ratio of potassium to sodium in the high-salt wastewater is measured to be about 1.5:1). Heating high-salt wastewater to 95 ℃ in a multi-effect countercurrent evaporator, concentrating and crystallizing, and centrifugally separating to obtain sodium chloride and filtrate I. And cooling the filtrate I to below 60 ℃ to precipitate crystals, and centrifugally separating to obtain a potassium chloride crude product and filtrate II. Returning filtrate II to a countercurrent evaporation inlet for circular evaporation treatment; and (3) washing the crude potassium chloride product for multiple times by adopting a saturated potassium chloride solution, and centrifugally separating to obtain high-purity potassium chloride (the purity is 99.97%).

Application example 4

Adopting 420kg cold rolling rinsing wastewater (pH is less than 2) to carry out three-stage countercurrent water washing on 100kg blast furnace cloth bag ash (with potassium content of 29.4 percent and sodium content of 4.0 percent), and obtaining a filter cake after filter pressingAnd ash washing waste water (the content ratio of potassium to sodium is about 5.7), and carrying out outward treatment on the filter cake; then continuously adding cold rolling rinsing wastewater (pH is less than 2) into the ash washing wastewater to enable the pH of the mixed wastewater to be 2-3; feCl is then added to the mixed wastewater ₃ So that the molar ratio of sulfate ions, ammonia nitrogen and ferric ions in the mixed wastewater is close to 2:1:3; then, introducing hot steam into the mixed wastewater to heat the mixed wastewater to 90 ℃ for continuous reaction for 3.5 hours, and after the reaction is finished, performing filter pressing to obtain supernatant and a slag phase, and carrying out external transportation treatment on the slag phase; the pH of the supernatant was adjusted to 3 with sodium hydroxide, and then the supernatant was introduced into the iron-carbon micro-electrolysis reactor for 30min, during which aeration back flushing was periodically performed on the iron-carbon micro-electrolysis reactor. After the micro-electrolysis treatment is finished, adding sodium hydroxide again to adjust the pH value of the ash washing wastewater to 8, then adding sodium carbonate (the addition standard is 5.8 g/L), sodium sulfide (the addition standard is 4.0 g/L) and a dithiocarbamate recapture agent (the addition standard is 4.0 g/L) in sequence, stirring and mixing for reaction for 30min; and (3) performing filter pressing after the reaction is finished to obtain high-salt wastewater (the content ratio of potassium to sodium in the high-salt wastewater is measured to be about 1.8:1). Heating high-salt wastewater to 95 ℃ in a multi-effect countercurrent evaporator, concentrating and crystallizing, and centrifugally separating to obtain sodium chloride and filtrate I. And cooling the filtrate I to below 60 ℃ to precipitate crystals, and centrifugally separating to obtain a potassium chloride crude product and filtrate II. Returning filtrate II to a countercurrent evaporation inlet for circular evaporation treatment; and (3) washing the crude potassium chloride product for multiple times by adopting a saturated potassium chloride solution, and centrifugally separating to obtain high-purity potassium chloride (the purity is 99.96%).

Claims

1. A method for cooperatively treating high-salt solid waste ash and acid wastewater of a steel plant is characterized by comprising the following steps: the method comprises the following steps:

1) And (3) ash washing treatment: mixing industrial water and part of flue gas washing wastewater to obtain acidic mixed water, washing high-salt solid waste ash by adopting the acidic mixed water, carrying out solid-liquid separation to obtain a filter cake and ash washing wastewater, carrying out outward treatment on the filter cake, mixing the ash washing wastewater with the rest of flue gas washing wastewater to obtain mixed wastewater, and carrying out next-stage treatment; the flue gas washing wastewater is acid flue gas washing wastewater generated by analyzing gas washing by an activated carbon method;

or washing high-salt solid waste ash by adopting part of cold-rolling rinsing wastewater, carrying out solid-liquid separation to obtain a filter cake and ash washing wastewater, carrying out outward treatment on the filter cake, mixing the ash washing wastewater with the rest cold-rolling rinsing wastewater, heating to carry out precipitation reaction, carrying out solid-liquid separation to obtain mixed wastewater and slag phase after the reaction is finished, carrying out outward treatment on the slag phase, and carrying out next stage treatment on the mixed wastewater; the cold rolling rinsing wastewater is FeCl-containing wastewater generated in the rinsing section of the cold rolling strip steel pickling process ₃ And HCl, pH < 2.5;

the addition amount of the flue gas washing wastewater or the cold rolling rinsing wastewater is that the pH value of the mixed wastewater is 2-4;

2) And (3) micro-electrolysis treatment: performing iron-carbon micro-electrolysis treatment on the mixed wastewater obtained in the step 1);

3) Advanced pretreatment of wastewater: adding a mixed reagent into the mixed wastewater subjected to micro-electrolysis treatment, regulating the mixed wastewater to be alkaline, carrying out weight and hardness removal precipitation reaction on the mixed wastewater, carrying out solid-liquid separation to obtain high-salt wastewater and residues, carrying out outward transportation treatment on the residues, and carrying out next-stage treatment on the high-salt wastewater; the mixed medicament is composed of sodium hydroxide and/or potassium hydroxide, sodium carbonate and/or potassium carbonate, sodium sulfide and/or potassium sulfide and a recapturing agent;

4) Countercurrent evaporation treatment: heating high-salt wastewater, concentrating and crystallizing, and separating solid from liquid to obtain sodium chloride and filtrate I; cooling and crystallizing the filtrate I, and carrying out solid-liquid separation to obtain potassium chloride and filtrate II;

in the step 1), the high-salt solid waste ash contains thallium, and comprises one or more of sintering electric field ash, blast furnace cloth bag ash, rotary kiln surface cooling ash and waste incineration fly ash; the heating to carry out precipitation reaction is heating to 80-100 ℃ to carry out precipitation reaction for 1-8h; in the step 1), before heating to perform precipitation reaction, soluble ferric salt is added to make the mol ratio of sulfate ions, ammonia nitrogen and iron ions in the wastewater be 0.4-0.8:0.2-0.5:1; the soluble ferric salt is FeCl ₃ 。

2. The method according to claim 1, characterized in that: the method further comprises the steps of: 5) And (3) cyclic evaporation treatment: mixing the filtrate II generated in the step 4) with the high-salt wastewater generated in the step 3), and then continuing countercurrent evaporation treatment; or returning the filtrate II generated in the step 4) to the step 1) to participate in the water washing and mixing.

3. The method according to claim 1 or 2, characterized in that: the water ash mass ratio of the acid mixed water to the high-salt solid waste ash or the water ash mass ratio of the cold rolling rinsing wastewater to the high-salt solid waste ash is 1-6:1.

4. A method according to claim 3, characterized in that: in the step 2), alkali is adopted to adjust the pH value of the mixed wastewater to 3-5 before the mixed wastewater is subjected to iron-carbon micro-electrolysis; the duration of the iron-carbon micro-electrolysis treatment is not less than 20min; aeration backflushing is required to be carried out regularly in the iron-carbon micro-electrolysis process; the alkali is sodium hydroxide and/or potassium hydroxide.

5. The method according to any one of claims 1-2, 4, characterized in that: in step 3), the addition amount of sodium hydroxide and/or potassium hydroxide is such that the pH of the mixed wastewater is 7-9; the addition amount of the sodium carbonate and/or the potassium carbonate is 3-10g/L; the addition amount of the sodium sulfide and/or the potassium sulfide is 1-7g/L; the adding amount of the recapturing agent is 1-8g/L; and/or

The content ratio of potassium to sodium in the high-salt wastewater is not lower than 5; and/or

The duration of the reaction for removing the heavy and the hard precipitates of the mixed wastewater is not less than 10 minutes.

6. The method according to any one of claims 1-2, 4, characterized in that: in the step 4), countercurrent evaporation is carried out by adopting a multi-effect evaporator, wherein the number of stages of the multi-effect evaporator is 2-6; the heating of the high-salt wastewater is to heat the high-salt wastewater to 80-100 ℃; the liquid I is cooled to be below 60 ℃ by adopting a flash evaporation or heat exchange mode.

7. The method according to any one of claims 1-2, 4, characterized in that: the water washing in the ash washing treatment is three-stage countercurrent water washing treatment; the method comprises the following steps: firstly, carrying out primary water washing on high-salt solid waste ash, carrying out primary filter pressing dehydration to obtain primary filtrate and primary filter residue, and carrying out subsequent micro-electrolysis treatment on the primary filtrate; the first-stage filter residue enters a second-stage water washing process, a second-stage water washing water source is a third-stage filtrate, the second-stage filtrate and the second-stage filter residue are obtained through second-stage filter pressing and dehydration after the second-stage water washing process, and the second-stage filtrate is discharged to the first-stage water washing process for recycling; the secondary filter residue enters tertiary washing, the water source of the tertiary washing is acid mixed water mixed by industrial water and flue gas washing wastewater, tertiary filter pressing and dehydration are carried out after the tertiary washing, tertiary filtrate and tertiary filter residue are obtained, the tertiary filtrate is discharged to the secondary washing for recycling, and the tertiary filter residue is discharged for outward transportation.

8. A system for the co-treatment of high salt solid waste ash as defined in any one of claims 1 to 7 with steel plant acid waste water, characterized in that: the system comprises a countercurrent washing device (1), an adjusting tank (2), an iron-carbon micro-electrolysis tank (3), a weight and hardness removal tank (4) and a countercurrent multi-effect evaporator (5); the wastewater inlet pipeline (L0) is communicated with a water inlet of the countercurrent water washing device (1); the water outlet of the countercurrent water washing device (1) is communicated with the water inlet of the regulating tank (2) through a first pipeline (L1); the water outlet of the regulating tank (2) is communicated with the water inlet of the iron-carbon micro-electrolysis tank (3) through a second pipeline (L2); the water outlet of the iron-carbon micro-electrolysis cell (3) is communicated with the water inlet of the weight and hardness removal cell (4) through a third pipeline (L3); the water outlet of the weight and hardness removing tank (4) is communicated with the water inlet of the countercurrent multi-effect evaporator (5) through a fourth pipeline (L4); the countercurrent water washing device (1) is also provided with a high-salt solid waste ash inlet (101).

9. The system according to claim 8, wherein: a waste water branch pipe (L01) is also separated from the waste water inlet pipeline (L0) and is communicated with a water inlet of the regulating tank (2); at least one dosing port (201) is also arranged on the regulating tank (2); a heating unit (202), a first pH detector (203) and a temperature detector (204) are also arranged in the regulating tank (2); the heating unit (202) is an electric heating unit or a steam heating unit; and/or

At least one mixed dosing port (401) is also arranged on the weight and hardness removing tank (4); a second pH detector (402) is arranged in the weight and hardness removing tank (4).

10. The system according to claim 8 or 9, characterized in that: the countercurrent multi-effect evaporator (5) comprises a heating unit (501), a cooling unit (502) and a elutriation unit (503); the liquid outlet of the heating unit (501) is communicated with the liquid inlet of the cooling unit (502) through a fifth pipeline (L5); the liquid outlet of the cooling unit (502) is communicated with the water inlet of the heating unit (501) through a circulating infusion tube (504); the heating unit (501) is also provided with a sodium salt outlet which is communicated with a sodium salt conveying device (505); the cooling unit (502) is also provided with a potassium salt outlet which is communicated with the elutriation unit (503) through a potassium salt conveying device (506); the discharge port of the elutriation unit (503) is communicated with a pure salt conveying device (507);

the steam outlet of the countercurrent multi-effect evaporator (5) is communicated with the regulating tank (2) through a steam conveying pipeline (L6).