CN114702188A

CN114702188A - Method and system for co-processing high-salinity solid waste ash and acid wastewater of iron and steel plant

Info

Publication number: CN114702188A
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: 2022-07-05
Anticipated expiration: 2042-05-09
Also published as: CN114702188B; WO2023036053A1

Abstract

The invention discloses a method and a treatment system for the cooperative treatment of high-salt solid waste ash and acid wastewater of an iron and steel plant, which are used for producing high-purity potassium chloride by using the high-salt solid waste ash produced by an iron and steel enterprise. Meanwhile, based on the characteristics of high heavy metals, high ammonia nitrogen concentration and high sulfate radical concentration of thallium and the like in the conventional high-salt solid waste ash washing wastewater, the characteristics of containing a large amount of sulfite ions (flue gas washing wastewater) or iron ions (cold rolling rinsing wastewater) and low acidity in the wastewater of the steel plant are combined, on the basis of the existing high-salt solid waste ash washing and wastewater recycling process, the synergistic effects of ash washing, sulfur and ammonia removal, iron-carbon micro-electrolysis deep thallium oxide, COD (chemical oxygen demand) and ammonia nitrogen, countercurrent evaporation potassium-sodium separation and the like are supplied by sections through the acidic wastewater, the purposes of synergistic treatment and recycling of the high-salt solid waste ash and the acidic wastewater of the steel plant are realized, and the quality of the recovered potassium-sodium salt is greatly improved. Meanwhile, the technical scheme provided by the invention also has the advantages of simple process conditions, low energy consumption, no wastewater discharge and the like.

Description

Method and system for cooperatively treating high-salinity solid waste ash and acid wastewater of iron and 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 an iron and steel plant, and belongs to the technical field of cooperative recycling treatment of solid waste ash and wastewater 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 cold ash, waste incineration fly ash and the like) generated in steel plants, alkali and chlorine metal are usually removed by a water washing mode, for example, in chinese patent CN103435073A, "method for producing potassium chloride by using blast furnace ash of steel enterprises", it is reported that tap water is used for leaching blast furnace ash to greatly reduce potassium and chlorine in the blast furnace ash, and leachate is used for preparing potassium chloride and sodium chloride. Chinese patent CN101234766A method for producing potassium chloride by using sintered electric precipitator dust of iron and steel enterprises reports a method for leaching high-salt solid waste ash by using a 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 washing and leaching is dehydrated and then can be returned to high-temperature furnaces such as sintering furnaces, rotary kilns and the like for further treatment. However, during 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. Generally, after heavy metal and chromaticity of high-salinity wastewater are removed through pretreatment, the high-salinity wastewater is used for evaporative crystallization of potassium sodium salt. In the actual operation process, because the high-salinity wastewater contains a large amount of sulfate radicals (the concentration is about 2g/L generally), if the sulfate radicals are not removed, the sulfate radicals can enter potassium chloride finally, the salt quality is reduced, and an evaporation system is blocked due to the formation of glaserite. In addition, the high-salinity wastewater also contains thallium, ammonia nitrogen and other pollutants. If the pollutants are deeply removed, the treatment process is long, and the treatment cost is increased greatly.

Aiming at the removal of sulfate radicals in wastewater, more removal modes are provided, such as a barium chloride method, a nanofiltration method and a calcium oxide method for removing sulfuric acid. However, these methods all have different disadvantages and are not suitable for removing contaminants from the scrubber water. For example, Chinese patent CN110342710A, high-chlorine low-sulfate radical wastewater treatment system and process, describes a method for removing sulfate radicals by precipitation in a manner of adding calcium chloride, and the sulfate radicals can be reduced from more than 6000ppm to 2000 ppm. However, the method cannot be applied to the ash washing water, because the concentration of sulfate radicals in the ash washing water is generally 1500-3000 ppm, the method cannot realize deep removal of sulfate radicals in the ash washing water. In order to realize the deep removal of sulfate radicals, the Chinese patent CN111592148A 'a process method for converting high-salinity wastewater into NaOH solution' reports that the efficient removal of sulfate radicals is realized by adopting calcium-aluminum composite salt under the high-alkaline condition. However, when the method is used for removing sulfate radicals in the ash washing water, the pH value of the solution is too high, a large amount of hydrochloric acid is needed to be adjusted back, and meanwhile, the formed particles are fine and need to be filtered and removed.

The ammonia nitrogen removal method in the wastewater comprises ammonia distillation, magnesium ammonium phosphate method, stripping method and the like, wherein the ammonia distillation and stripping method needs to construct an additional device and process the recovered ammonia gas, and the investment and operation cost is high. The magnesium ammonium phosphate method has the defects of difficult operation and high operating cost because phosphate radical and magnesium ions need to be introduced.

The removal of thallium in the high-salinity wastewater is mainly performed by 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 Tl (I) is oxidized by an oxidant, then the pretreatment of Tl (III) is carried out by ion exchange resin, and then the Tl (III) is deeply removed by sodium sulfide. But because Tl (III) can form stable [ TlCl4 ] with chlorine in high-salinity wastewater^-]Because the complex is relatively stable, the complex is difficult to completely remove by 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 wastewater (flue gas washing wastewater, cold rolling rinsing wastewater and the like) of an iron and steel plant, which can produce high-purity potassium chloride by utilizing wastewater produced in a sintering process of an iron and steel enterprise and the high-salt solid waste ash, and simultaneously avoid the problems of equipment corrosion and kiln caking caused by alkali metal and chlorine entering high-temperature kilns such as a sintering furnace, a blast furnace, a rotary kiln and the like. Meanwhile, based on the characteristics of high content of heavy metals such as thallium and the like, high ammonia nitrogen concentration and high sulfate radical concentration in the high-salt solid waste ash washing wastewater, and the characteristics of containing a large amount of sulfite ions (flue gas washing wastewater) or iron ions (cold rolling rinsing wastewater) and low acidity in the wastewater of the steel plant, on the basis of the existing high-salt solid waste ash washing and wastewater recycling process, the purposes of cooperative treatment and recycling of the high-salt solid waste ash and the acid wastewater of the steel plant are realized through the synergistic effects of sectional supply of the acid wastewater of the steel plant for ash washing and sulfur and ammonia nitrogen removal, iron-carbon micro-electrolysis deep thallium oxide and COD, countercurrent evaporation potassium-sodium separation and the like, and the quality of the recycled potassium-sodium salt is greatly improved. Meanwhile, the technical scheme provided by the invention also has the advantages of simple process conditions, low energy consumption, no wastewater discharge and the like.

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

according to a first embodiment of the invention, a method for the synergistic treatment of high-salinity solid waste ash and acidic wastewater from steel plants is provided.

A method for the cooperative treatment of high-salt solid waste ash and acid wastewater of a steel plant comprises the following steps:

1) ash washing treatment: mixing industrial water and part of the flue gas washing wastewater to obtain acidic mixed water, washing high-salt solid waste ash with the acidic mixed water, performing solid-liquid separation to obtain a filter cake and ash washing wastewater, transporting the filter cake outwards for disposal, mixing the ash washing wastewater with the rest of the flue gas washing wastewater to obtain mixed wastewater, and performing next-stage treatment.

Or washing the high-salt solid waste ash by using part of cold rolling rinsing wastewater, performing solid-liquid separation to obtain a filter cake and ash washing wastewater, transporting the filter cake outwards for disposal, mixing the ash washing wastewater with the rest cold rolling rinsing wastewater, heating for precipitation reaction, performing solid-liquid separation to obtain mixed wastewater and a slag phase after the reaction is finished, transporting the slag phase outwards for disposal, and performing next-stage treatment on the mixed wastewater.

2) Micro-electrolysis treatment: carrying out iron-carbon micro-electrolysis treatment on the mixed wastewater obtained in the step 1).

3) Advanced wastewater pretreatment: adding a mixed medicament into the mixed wastewater after micro-electrolysis treatment, adjusting the mixed wastewater to be alkaline, performing a reaction of removing heavy matters and hard precipitates from the mixed wastewater, performing solid-liquid separation to obtain high-salinity wastewater and residues, transporting the residues for disposal, and performing next-stage treatment on the high-salinity wastewater.

4) And (3) countercurrent evaporation treatment: heating the high-salinity wastewater, concentrating, crystallizing, and performing solid-liquid separation to obtain sodium chloride and filtrate I. And cooling and crystallizing the filtrate I, and performing solid-liquid separation to obtain potassium chloride and a filtrate II.

Preferably, the method further comprises:

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

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

Preferably, in the step 1), the cold-rolling rinsing wastewater is FeCl-containing wastewater generated in the rinsing stage of the cold-rolled strip steel pickling process₃And HCl at a pH of < 2.5, preferably at a pH of < 2.

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

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

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

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

Preferably, in step 1), before the precipitation reaction is carried out by heating, a soluble iron salt (e.g., FeCl) is also added₃) So that the molar 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), before the mixed wastewater is subjected to iron-carbon micro-electrolysis, the pH of the mixed wastewater is adjusted to 3-5, preferably 3.5-4, by using alkali. The duration of the iron-carbon micro-electrolysis treatment is not less than 20min, preferably 30-60 min. The aeration backflushing is required to be carried out regularly 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 composed of sodium hydroxide and/or potassium hydroxide, sodium carbonate and/or potassium carbonate, sodium sulfide and/or potassium sulfate, and a recapture agent (preferably xanthate recapture agent or dithiocarbamate recapture agent). Wherein: the sodium hydroxide and/or potassium hydroxide are added in such an amount that the pH of the mixed wastewater is 7 to 9, preferably 7.5 to 8. The addition amount of the sodium carbonate and/or the potassium carbonate is 3-10g/L, and preferably 4-8 g/L. The addition amount of the sodium sulfide and/or the potassium sulfide is 1-7g/L, and preferably 1.5-6 g/L. The addition amount of the recapture agent is 1-8g/L, preferably 2-5 g/L.

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

Preferably, in the step 3), the mixed wastewater is subjected to the reaction for removing the heavy and hard precipitates for not less than 10min, preferably 15-40 min.

Preferably, in step 4), the countercurrent evaporation is carried out using a multi-effect evaporator, the number of stages of which is 2 to 6, preferably 3 to 5. The high-salinity wastewater is heated to 80-100 ℃, preferably 90-95 ℃. And the liquid I is cooled to be below 60 ℃ by adopting a flash evaporation or heat exchange mode, and preferably to be 20-55 ℃.

Preferably, the washing in the ash washing treatment is a multi-stage washing treatment, and preferably a three-stage counter-current washing treatment. The method comprises the following specific steps: firstly, carrying out primary washing on the 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. And (3) the primary filter residue is subjected to secondary washing, the secondary washing water source is tertiary filtrate, secondary filtrate and secondary filter pressing dehydration are carried out after the secondary washing, secondary filtrate and secondary filter residue are obtained, and the secondary filtrate is discharged to the primary washing for recycling. And the second-stage filter residue enters third-stage washing, the water source of the third-stage washing is acidic mixed water mixed by industrial water and flue gas washing wastewater, third-stage filter pressing dehydration is performed after the third-stage washing to obtain third-stage filtrate and third-stage filter residue, the third-stage filtrate is discharged to the second-stage washing for recycling, and the third-stage filter residue is discharged and transported to the outside for disposal.

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

The utility model provides a system for high salt solid waste ash and acid waste water coprocessing of iron and steel plant, this system includes countercurrent washing device, equalizing basin, little electrolytic bath of iron carbon, removes heavy hard pond and 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 tank is communicated with the water inlet of the weight and hardness removing tank through a third pipeline. The water outlet of the weight and hardness 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 communicated with the water inlet of the regulating tank. The regulating reservoir is also provided with at least one dosing port. Still be provided with heating unit, first pH detector and temperature detector in the equalizing basin. Preferably, the heating unit is an electric heating unit or a steam heating unit.

Preferably, at least one mixed dosing port is further arranged on the weight and hardness removing pool. A second pH detector is arranged in the weight and hardness removing tank.

Preferably, the counter-flow multiple effect evaporator comprises a heating unit, a cooling unit and an elutriation unit. And a liquid outlet of the heating unit is communicated with a 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 liquid conveying pipe. 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 sylvite outlet which is communicated with the elutriation unit through a sylvite conveying device. The discharge port 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, to avoid high salt content in the waste ashAlkali metals, chlorine elements and the like cause the problems of equipment corrosion and kiln caking and the like, and the alkali metals and the chlorine metals are removed by adopting a water washing mode, and the potassium sodium salt is recovered. However, the high-salinity solid waste ash has complex composition, which results in complex components of the ash washing water, such as containing a large amount of metal ions, ammonia nitrogen, sulfate radicals and the like. In this regard, metal ions and ammonia nitrogen are often removed by adjusting the wash water to alkaline, but studies have shown that thallium is readily formed under alkaline conditions in high salinity solid waste grey water wash wastewater₄ ^-]Due to [ TlCl₄ ^-]Is relatively stable and once formed, is difficult to process by conventional removal processes. The recovered sylvite has more impurities and relatively low purity, and the utilization of the sylvite is influenced. Generally, aiming at high-salt solid waste ash washing waste water with more potassium than sodium, potassium salt is generally separated out firstly, and then sodium salt is separated out, on one hand, potassium salt is separated out firstly, impurity pollutants are easy to separate out along with the separation of potassium salt, so that the quality of potassium salt is reduced, on the other hand, the subsequent separation of sodium salt also needs to be continuously heated, concentrated and crystallized, so that the energy consumption is increased. If the sodium salt is precipitated first, the potassium salt is inevitably precipitated first because the content of potassium is more than that of sodium, so that the quality of the sodium salt is reduced, and the yield of the potassium salt is also reduced.

In the invention, the process flow specifically comprises the following steps: firstly, dechlorinating high-salt solid waste ash by using acid mixed water (formed by mixing part of flue gas washing wastewater and industrial water) or by using part of cold rolling rinsing wastewater through a three-stage countercurrent washing process. Carrying out outward transportation treatment on the filter cake obtained after washing, and mixing the ash washing wastewater obtained after washing with the rest of the flue gas washing wastewater or the cold rolling rinsing wastewater to ensure that the pH value of the mixed wastewater is 2-4 (preferably 2.5-3.5); at the same time, by adding soluble iron salts (preferably FeCl)₃) Adjusting the molar ratio of sulfate ions, ammonia nitrogen and iron ions in the mixed wastewater to 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 1-8h (preferably 2-5h) to remove ammonia nitrogen, sulfate 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 for micro-electrolysisAnd (3) reacting, namely periodically carrying out aeration backflushing on the iron-carbon micro-electrolysis reactor. Due to Tl³⁺Ratio Tl⁺Easier removal, in general, pretreatment by oxidation. Iron-carbon microelectrolysis has the synergistic effect of weight removal and oxidation. After iron-carbon micro-electrolysis is sufficient, 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 to realize removal, and a large amount of ferrous iron and ferric iron are generated in the solution. In addition, the iron carbon is beneficial to the efficient removal of fluorine ions in the wastewater. Adding a mixed medicament (for example, adding a mixed medicament consisting of sodium hydroxide, sodium carbonate, sodium sulfide and a recapture agent in sequence into the wastewater after iron-carbon micro-electrolysis, wherein the addition amount of the sodium hydroxide is mainly used for adjusting the pH value of the solution to be 7-10 (preferably 7-9), and the sodium carbonate, the sodium sulfide, the recapture agent and the like are used for carrying out the reaction of removing heavy metal and hard precipitate in the wastewater, so as to separate out heavy metal ions, calcium, magnesium and the like in the water), and sequentially realizing the deep removal of ammonia nitrogen, calcium, magnesium and heavy metal in the process. The treated wastewater is filtered together with the precipitate by a filter press. The filter residue is heavy metal sludge which is transported to the outside for disposal. The filtrate is high-salinity wastewater. After homogenizing the high-salinity wastewater, conveying the high-salinity wastewater into a multi-effect evaporator. The multi-effect evaporator adopts a counter-current design, namely, the high-salt solution sequentially passes through the multi-effect reactor → the two-effect reactor → the one-effect reactor, and the temperature of the solution is increased to 95-100 ℃ from normal temperature. After evaporation, sodium salt is precipitated after reaching a sodium salt saturation precipitation point, the recovery of the sodium salt can be realized through centrifugal separation, and mother liquor obtained through the centrifugal separation is returned to the one-effect evaporator for cyclic concentration. Concentrating to saturation precipitation point of potassium salt, cooling, reducing the temperature of the solution to below 60 ℃ to precipitate potassium salt, realizing recovery of potassium salt through centrifugal separation, and returning the mother liquor obtained through centrifugal separation to the multi-effect evaporator for cyclic concentration. Further, the separated potassium chloride solid can be put into an elutriation device, a saturated potassium chloride solution is adopted for washing so as to realize further purification of potassium chloride, and high-purity potassium chloride is obtained after centrifugal separation.

In the present invention, since the high-salinity 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, through phase diagram analysis of potassium-sodium salt through variable-temperature evaporation, potassium salt is bound to be separated out firstly after a high-potassium low-sodium solution is evaporated and concentrated, and therefore, a salt separation mode of high-salt solid waste ash washing water is generally concurrent evaporation. Namely, the solution is gradually cooled in the evaporation process. And at the multi-effect outlet, discharging the sylvite firstly. The evaporation mode can cause pollutants to be separated out along with the separation of potassium, the quality of the potassium can be reduced, meanwhile, the subsequent sodium salt separation needs two-stage evaporation, the investment is increased, and the energy consumption is large. Therefore, the flue gas washing wastewater (containing sodium) is introduced and 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 acidic cold rolling rinsing wastewater is introduced, so that the content ratio of potassium to sodium in the ash washing wastewater is close to 2:1, under the two conditions, according to phase diagram simulation and experimental verification, the high-salt solid waste ash water washing water is suitable for countercurrent evaporation, namely, sodium salt is preferentially separated after concentration, so that the evaporation process can be adjusted to countercurrent evaporation, namely, the sodium salt is discharged at an effective outlet first. And then cooling to separate out potassium salt, wherein the evaporation mode enables residual pollutants to be separated out along with the separation of sodium (because the counter-current evaporation is only subjected to one-stage concentration, the pollutants mainly enter sodium salt) and cannot enter potassium salt, thereby being beneficial to improving the quality of potassium. Meanwhile, the whole evaporation only utilizes one section of evaporation system, so that the method is suitable for the change of different evaporation amounts, has stronger applicability to raw materials and has lower investment.

In the invention, the flue gas washing wastewater comprises suspended matters, metal ions, ammonia nitrogen and fluorine and chlorine. The metal ions comprise one or more of sodium, iron, copper, lead, calcium, zinc, cadmium, cobalt, nickel and aluminum. The process water and a portion of the acidic flue gas scrubbing wastewater are first mixed and the mixed water is made acidic (e.g., pH 1-3). Generally, thallium is easy to form under alkaline condition in high-salinity wastewater₄ ^-]Due to [ TlCl₄ ^-]Is relatively stable and once formed, is relatively difficult to process 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, so that the ash washing water is changed into acidity, and therefore, the flue gas washing wastewater has stronger acidityTo prevent the formation of stable [ TlCl ]₄ ^-]. On the other hand, the flue gas washing wastewater contains thiosulfate, and thallium removal is facilitated after the thiosulfate is added. Thereby realizing the source inhibition of thallium. Research shows that the thallium content in the ash washing water is about 30mg/L by adopting the conventional industrial ash washing water. When the acidic washing wastewater is introduced, the thallium content in the ash washing water can be reduced to about 1 mg/L. The method adopts the acidic flue gas washing wastewater to cooperatively treat the high-salinity solid waste ash, so that on one hand, the adjustment of the potassium-sodium ratio to be close to 1:1 is realized, the countercurrent evaporation is realized, the quality of the sylvite is improved, on the other hand, thallium is reduced to be dissolved out at the source, the purity of the sylvite is further ensured, and the value of the sylvite is improved.

In the invention, the cold-rolling rinsing wastewater is FeCl-containing wastewater generated in the rinsing stage of the acid-washing process of the cold-rolled strip steel₃And HCl, which is generally acidic with a pH < 2.5 (preferably a pH < 2). Based on the characteristics of high content of heavy metals such as thallium and the like, high ammonia nitrogen concentration and sulfate radical concentration in the washing wastewater of the high-salinity solid-waste ash water (the ammonia nitrogen concentration in the washing wastewater is generally 1000-4000 mg/L, and the sulfate radical concentration is generally 500-3000 mg/L), and by combining the characteristics of large amount of ferric iron and low acidity in the cold rolling rinsing wastewater, the method considers that iron and sulfate radical can react with potassium, sodium and ammonia nitrogen to form jarosite, jarosite and ammoniojarosite. Therefore, the wastewater can be heated (the heat source can be electric heating or steam waste heat of a subsequent evaporation system) to 80-100 ℃, and ammonia nitrogen and sulfate radicals in the wastewater can be removed. Secondly, cold rolling rinsing wastewater is used as high-salt solid waste ash water washing water, the acidity of the cold rolling rinsing wastewater is utilized to realize thallium control on the ash washing wastewater, and since the acidic cold rolling rinsing wastewater has stronger acidity, when the ash is washed, the solution of the ash washing water can be reduced on the one hand, so that the ash washing water is changed into acidity, and stable [ TlCl4 ] is prevented from being formed^-]. When cold rolling rinsing wastewater is introduced, the thallium content in the ash washing water can be reduced to about 5 mg/L. Reduced dissolution of thallium sources is achieved. On the other hand, studies have shown that when the concentration of chlorine ions in water is not higher than 15000mg/L, chlorine enrichment in the solid waste after washing with water does not occur. Therefore, the cold rolling rinsing wastewater is adopted to completely replace industrial water, and the deep removal of chlorine in the high-salinity solid waste ash can be realized. Get up toThe effect of treating wastes with wastes.

In the present invention, the impurity removal is also carried out by iron-carbon microelectrolysis, since Tl³⁺Ratio Tl⁺Easier removal, in general, pretreatment can be carried out by oxidation. Iron-carbon microelectrolysis has the synergistic effect of weight removal and oxidation. After passing through the iron carbon, Tl can be changed into a form more easily removed. 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 also beneficial to the efficient removal of fluorine ions in the wastewater. Further, because the acidic flue gas washing wastewater also contains sulfite, and the iron carbon can release ferrous iron. Alkali (such as sodium hydroxide) is adopted to adjust the ash washing wastewater to be alkalescent, and when the solution is adjusted to be alkalescent, ammonia nitrogen can rapidly react with sulfite and ferrous iron to form ammonium ferrous sulfite precipitate, so that the deep removal of the ammonia nitrogen is realized. Meanwhile, under the condition of weak alkali, the removal of ferric iron and partial calcium and magnesium ions can be realized. Sodium carbonate is added for the purpose of calcium and magnesium removal. The purpose of adding the sodium sulfide and the recapture agent is to realize deep removal of trace heavy metals.

In the invention, the washing of the high-salt solid waste ash is multi-stage washing, generally trimeric countercurrent washing, and the three-stage countercurrent washing process comprises the steps of carrying out primary washing on the high-salt solid waste ash, carrying out primary filter pressing dehydration, discharging filtrate, and allowing the filtrate to enter a subsequent wastewater recycling treatment system (namely directly entering iron-carbon micro-electrolysis), and carrying out secondary washing on filter residues. And the secondary washing water source is tertiary filter pressing water production, secondary washing is performed, secondary filter pressing dehydration is performed, filtrate is discharged to primary washing for recycling, and filter residues enter tertiary washing. And the third-stage water washing source is a mixed solution of industrial water and condensed water recovered by evaporation, the third-stage water washing source is dewatered by three-stage filter pressing after being washed, filtrate is discharged to the second-stage water washing for recycling, and filter residues are discharged from the system and transported outside for disposal. Further, the mother liquor after the potassium salt is separated out by the multiple-effect counter-flow evaporator returns to the multiple-effect counter-flow evaporator for circulating concentration or returns to the water washing procedure for water washing, so that zero discharge of wastewater is realized.

In the system for the synergistic treatment of the high-salt solid waste ash and the acid wastewater of the iron and steel plant, the flue gas is adopted for washingWhen the waste water is used as ash washing water of 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 the ash washing water of high-salt solid waste ash, the conditioning tank can be used for adding soluble iron salt (such as FeCl) in addition to the above-mentioned waste water₃) And heating the place where the precipitation reaction is performed.

Compared with the prior art, this beneficial technological effect of sending out is as follows:

1: according to the invention, aiming at the respective characteristics of high-salt solid waste ash and acid wastewater (flue gas washing wastewater or cold rolling rinsing wastewater) of a steel plant, the waste ash and the wastewater are subjected to cooperative resource treatment, on one hand, the leaching of thallium in the high-salt solid waste ash is inhibited through the acid flue gas washing wastewater or the acid cold rolling rinsing wastewater, the content of thallium in the ash washing wastewater is reduced from the source, and the quality of subsequent sylvite is improved; secondly, sodium contained in the acid 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, multiple-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 realize the removal of ammonia nitrogen and sulfate radical in the wastewater; simultaneously avoids the defect of high ratio of potassium to sodium in the conventional ash washing wastewater, greatly improves the quality of potassium salt,

2: the method adopts the iron-carbon micro-electrolysis and the method of adding the mixed reagent, realizes the synergistic thallium oxide, deep ammonia nitrogen removal and weight removal at low cost, greatly reduces the treatment flow of ash washing wastewater, prevents pollutants from polluting sylvite, greatly reduces 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 influence the recovery of the potassium salt at low cost by improving the evaporation mechanism and the process route, thereby further improving the quality of the recovered potassium salt and preventing pollutants from entering the potassium salt, thereby improving the value of a potassium chloride product. Meanwhile, the invention has the advantages of low cost and simple operation, does not additionally increase equipment and energy consumption, reasonably utilizes 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 co-treatment method of high-salinity solid waste ash and flue gas washing wastewater of the present invention.

FIG. 2 is a process flow chart of the co-treatment method of high-salt solid waste ash and cold-rolling rinsing wastewater of the invention.

FIG. 3 is a schematic structural diagram of a system for the synergistic treatment of high-salinity solid waste ash and acidic wastewater from steel plants.

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

Reference numerals: 1: a countercurrent water washing device; 2: a regulating reservoir; 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: a weight and hardness removing pool; 401: mixing and adding the medicine; 402: a second pH meter; 5: a counter-current multi-effect evaporator; 501: a heating unit; 502: a cooling unit; 503: a elutriation unit; 504: circulating the infusion tube; 505: a sodium salt delivery device; 506: a potassium salt conveying device; 507: a pure salt conveying device; l0: a wastewater inlet pipe; l01: a waste water branch pipe; l1: a first pipe; l2: a second conduit; l3: a third pipeline; l4: a fourth conduit; l5: a fifth pipeline; l6: a steam delivery pipeline.

Detailed Description

The technical solution of the present invention is illustrated below, and the claimed scope of the present invention includes, but is not limited to, the following examples.

The utility model provides a system for high salt solid waste ash and acid waste water coprocessing of iron and steel plant, this system includes countercurrent washing device 1, equalizing basin 2, indisputable carbon micro-electrolysis cell 3, removes heavy hard pond 4 and countercurrent multi-effect evaporator 5 of removing. The wastewater inlet line L0 is in communication with the water inlet of the reverse flow water washing apparatus 1. The water outlet of the reverse flow water washing apparatus 1 is communicated with the water inlet of the regulating reservoir 2 through a first pipe L1. The water outlet of the regulating reservoir 2 is communicated with the water inlet of the iron-carbon micro-electrolysis reservoir 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-removing hard 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.

Preferably, a branched waste water pipe L01 is further connected to the inlet of the regulating reservoir 2 from the waste water inlet pipe L0. The regulating reservoir 2 is also provided with at least one dosing port 201. The adjusting tank 2 is also 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, at least one mixed dosing port 401 is further arranged on the weight and hardness removing pool 4. The second pH meter 402 is provided in the weight-removing hard pool 4.

Preferably, the counter-flow multiple effect evaporator 5 includes a heating unit 501, a cooling unit 502, and an 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 liquid conveying pipe 504. The heating unit 501 is also 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 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.

Preferably, the steam outlet of the countercurrent multi-effect evaporator 5 is communicated with the regulating reservoir 2 through a steam conveying pipeline L6.

Example 1

As shown in figure 1, the method for the synergistic treatment of the high-salinity solid waste ash and the flue gas washing wastewater comprises the following steps:

1) washing with water: mixing industrial water and flue gas washing wastewater to obtain acidic mixed water, washing high-salt solid waste ash with the acidic mixed water, performing solid-liquid separation to obtain a filter cake and ash washing wastewater, transporting the filter cake outwards, and performing next-stage treatment on the ash washing wastewater.

2) Micro-electrolysis treatment: and carrying out iron-carbon micro-electrolysis treatment on the ash washing wastewater.

3) Advanced wastewater pretreatment: adding a mixed medicament into the ash washing wastewater after micro-electrolysis treatment, adjusting the ash washing wastewater to be alkaline, performing a weight removal and hardness removal precipitation reaction on the ash washing wastewater, and performing solid-liquid separation to obtain high-salinity wastewater.

4) And (3) countercurrent evaporation: heating the high-salinity wastewater, concentrating, crystallizing, and performing solid-liquid separation to obtain sodium chloride and filtrate I. And cooling and crystallizing the filtrate I, and performing solid-liquid separation to obtain potassium chloride and a filtrate II.

Example 2

2) Micro-electrolysis treatment: carrying out iron-carbon micro-electrolysis treatment on the ash washing wastewater.

5) Circulating evaporation: mixing the filtrate II generated in the step 4) with the high-salinity wastewater generated in the step 3), and then continuing to perform countercurrent evaporation treatment.

Example 3

4) And (3) countercurrent evaporation: heating the high-salinity wastewater, concentrating, crystallizing, and performing solid-liquid separation to obtain sodium chloride and filtrate I. Cooling and crystallizing the filtrate I, and performing solid-liquid separation to obtain potassium chloride and a filtrate II.

5) Circulating evaporation: returning the filtrate II generated in the step 4) to the step 1) to participate in water washing and stirring.

Example 4

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

1) ash washing treatment: and (3) washing the high-salt solid waste ash by using part of cold rolling rinsing wastewater, performing solid-liquid separation to obtain a filter cake and ash washing wastewater, transporting the filter cake outwards for disposal, and performing next-stage treatment on the ash washing wastewater.

2) And (3) sulfur removal and ammonia nitrogen removal treatment: mixing the ash washing wastewater with the rest cold rolling rinsing wastewater to obtain mixed wastewater, then heating the mixed solution for precipitation reaction, after the reaction is finished, carrying out solid-liquid separation to obtain supernatant wastewater and a slag phase, carrying out outward treatment on the slag phase, and carrying out next-stage treatment on the supernatant wastewater.

3) Micro-electrolysis treatment: carrying out iron-carbon micro-electrolysis treatment on the supernatant liquid obtained in the step 2).

4) Advanced wastewater pretreatment: adding a mixed reagent into the supernatant liquid after micro-electrolysis treatment, adjusting the supernatant liquid to be alkaline, performing a heavy-removal hard-precipitation removal reaction on the supernatant liquid, performing solid-liquid separation to obtain high-salinity wastewater and residues, transporting the residues for outward treatment, and performing next-stage treatment on the high-salinity wastewater.

5) And (3) countercurrent evaporation treatment: heating the high-salinity wastewater, concentrating, crystallizing, and performing solid-liquid separation to obtain sodium chloride and filtrate I. And cooling and crystallizing the filtrate I, and performing solid-liquid separation to obtain potassium chloride and a filtrate II.

Example 5

2) And (3) sulfur removal and ammonia nitrogen removal treatment: mixing the ash washing wastewater with the rest cold rolling rinsing wastewater to obtain mixed wastewater, then heating the mixed solution to perform precipitation reaction, after the reaction is finished, performing solid-liquid separation to obtain supernatant waste liquid and a slag phase, transporting the slag phase outwards, and performing next-stage treatment on the supernatant waste liquid.

5) And (3) countercurrent evaporation treatment: heating the high-salinity wastewater, concentrating, crystallizing, and performing solid-liquid separation to obtain sodium chloride and filtrate I. Cooling and crystallizing the filtrate I, and performing solid-liquid separation to obtain potassium chloride and a filtrate II.

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

Example 6

As shown in figures 3-4, the system for the synergistic treatment of the high-salinity solid waste ash and the acid wastewater of the iron and steel plant comprises a countercurrent water washing device 1, a regulating tank 2, an iron-carbon micro-electrolysis tank 3, a heavy-weight removal hard tank 4 and a countercurrent multi-effect evaporator 5. The wastewater inlet pipe L0 is communicated with the water inlet of the countercurrent water washing device 1. The water outlet of the reverse flow water washing apparatus 1 is communicated with the water inlet of the regulating reservoir 2 through a first pipe L1. The water outlet of the regulating reservoir 2 is communicated with the water inlet of the iron-carbon micro-electrolysis reservoir 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-removing hard 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.

Example 7

Example 6 is repeated, except that a waste water branch pipe L01 is further branched from the waste water inlet pipeline L0 and is communicated with the water inlet of the regulating reservoir 2. The regulating reservoir 2 is also provided with at least one dosing port 201. The adjusting tank 2 is also 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 the weight-removing hard pool 4 is further provided with at least one mixed dosing port 401. The second pH meter 402 is provided in the weight-removing hard pool 4.

Example 10

Example 9 is repeated except that the counter flow multiple effect evaporator 5 comprises a heating unit 501, a cooling unit 502 and an 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 liquid conveying pipe 504. The heating unit 501 is also 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 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.

Example 11

Example 10 was repeated except that the vapor outlet of the countercurrent multi-effect evaporator 5 was communicated with the conditioning tank 2 through a vapor delivery line L6.

Application example 1

Mixing industrial water and flue gas washing wastewater of an activated carbon method to obtain acidic mixed water, then carrying out three-stage countercurrent washing on 100kg of sintering power plant ash (the potassium content is 24.8%, and the sodium content is 3.2%) by using the acidic mixed water, obtaining a filter cake and about 310L of ash washing wastewater (the potassium-sodium content ratio is about 5.4) after filter pressing, and transporting the filter cake outwards for disposal; and then adding sodium hydroxide into the ash washing wastewater to adjust the pH value of the ash washing wastewater to 3 (the adding amount of the flue gas washing wastewater and the sodium hydroxide in the activated carbon method enables the content ratio of potassium to sodium in the ash washing wastewater to be close to 1:1), introducing the adjusted ash washing wastewater into an iron-carbon micro-electrolysis reactor to be treated for 40min, and periodically carrying out aeration back-flushing on the iron-carbon micro-electrolysis reactor in the period. 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 heavy catcher, stirring, mixing and reacting for 30 min; and (4) after filter pressing, obtaining high-salinity wastewater. Heating the high-salinity wastewater to 95 ℃ in a multi-effect counter-current evaporator, concentrating, crystallizing, and centrifugally separating to obtain sodium chloride and filtrate I. And cooling the filtrate I to below 60 ℃ to precipitate crystals, and performing centrifugal separation to obtain a potassium chloride crude product and a filtrate II. Returning the filtrate II to the countercurrent evaporation inlet for cyclic evaporation treatment; and elutriating the crude potassium chloride product by adopting a saturated potassium chloride solution for multiple times, and carrying out centrifugal separation to obtain high-purity potassium chloride (the purity is 99.92%).

Application example 2

Mixing industrial water and flue gas washing wastewater of an activated carbon method to obtain acidic mixed water, then carrying out three-stage countercurrent washing on 120kg of blast furnace cloth bag ash (the potassium content is 29.4 percent, and the sodium content is 4.0 percent) by using the acidic mixed water, obtaining a filter cake and about 380L of ash washing wastewater (the potassium-sodium content ratio is about 6.3) after filter pressing, and transporting the filter cake outwards for disposal; and then adding sodium hydroxide into the ash washing wastewater to adjust the pH value of the ash washing wastewater to 4 (the adding amount of the flue gas washing wastewater and the sodium hydroxide in the activated carbon method enables the content ratio of potassium to sodium in the ash washing wastewater to be close to 1:1), introducing the adjusted ash washing wastewater into an iron-carbon micro-electrolysis reactor to be treated for 40min, and periodically carrying out aeration back-flushing on the iron-carbon micro-electrolysis reactor in the given period. 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 recapture agent, stirring, mixing and reacting for 30 min; and (4) after filter pressing, obtaining high-salinity wastewater. Heating the high-salinity wastewater to 95 ℃ in a multi-effect counter-current evaporator, concentrating, crystallizing, and centrifugally separating to obtain sodium chloride and filtrate I. And cooling the filtrate I to below 60 ℃ to precipitate crystals, and performing centrifugal separation to obtain a potassium chloride crude product and a filtrate II. Returning the filtrate II to the countercurrent evaporation inlet for cyclic evaporation treatment; and elutriating the crude potassium chloride product by adopting a saturated potassium chloride solution for multiple times, and carrying out centrifugal separation to obtain high-purity potassium chloride (the purity is 99.90%).

Application example 3

Carrying out three-stage countercurrent washing on 100kg of sintering electric field ash (the potassium content is 24.8 percent, and the sodium content is 3.2 percent) by adopting 380kg of cold rolling rinsing wastewater (the pH value is less than 2), obtaining a filter cake and ash washing wastewater (the potassium-sodium content ratio is about 5.1) after filter pressing, and transporting the filter cake outwards for disposal; then continuously adding cold rolling rinsing wastewater (the pH value is less than 2) into the ash washing wastewater to ensure that the pH value of the mixed wastewater is 2-3; then adding FeCl into the mixed wastewater₃So 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, after the reaction is finished, performing filter pressing to obtain a supernatant and a slag phase, and transporting the slag phase out for disposal; adjusting the pH value of the supernatant to 3 by using sodium hydroxide, then introducing the supernatant into an iron-carbon micro-electrolysis reactor for treatment for 30min, and periodically carrying out aeration backflushing on the iron-carbon micro-electrolysis reactor in the period. 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 6g/L), sodium sulfide (the addition standard is 4.8g/L) and dithiocarbamate recapture agent (the addition standard is 4.2g/L), stirring, mixing and reacting for 30 min; after the reaction, filter pressing is carried out to obtain high-salinity wastewater (the content ratio of potassium to sodium in the high-salinity wastewater is measured to be about 1.5: 1). Heating the high-salinity wastewater to 95 ℃ in a multi-effect counter-current evaporator, concentrating, crystallizing, and centrifugally separating to obtain sodium chloride and filtrate I. And cooling the filtrate I to below 60 ℃ to precipitate crystals, and performing centrifugal separation to obtain a potassium chloride crude product and a filtrate II. Returning the filtrate II to the countercurrent evaporation inlet for cyclic evaporation treatment; and elutriating the crude potassium chloride product by adopting a saturated potassium chloride solution for multiple times, and performing centrifugal separation to obtain high-purity potassium chloride (the purity is 99.97%).

Application example 4

Carrying out three-stage countercurrent washing on 100kg of blast furnace cloth bag ash (the potassium content is 29.4 percent and the sodium content is 4.0 percent) by adopting 420kg of cold-rolled rinsing wastewater (the pH value is less than 2), obtaining a filter cake and ash washing wastewater (the potassium-sodium content ratio is about 5.7) after filter pressing, and transporting the filter cake outwards for disposal; then continuously adding cold rolling rinsing wastewater (the pH value is less than 2) into the ash washing wastewater to ensure that the pH value of the mixed wastewater is 2-3; then adding FeCl into the mixed wastewater₃So that the molar ratio of sulfate ions, ammonia nitrogen and ferric ions in the mixed wastewater is close to 2:1: 3; introducing hot steam into the mixed wastewater, heating the mixed wastewater to 90 ℃, continuously reacting for 3.5 hours, after the reaction is finished, performing pressure filtration to obtain a supernatant and a slag phase, and transporting the slag phase to outside for disposal; adjusting the pH value of the supernatant to 3 by using sodium hydroxide, then introducing the supernatant into an iron-carbon micro-electrolysis reactor for treatment for 30min, and periodically carrying out aeration backflushing on the iron-carbon micro-electrolysis reactor in the period. 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 5.8g/L), sodium sulfide (the addition standard is 4.0g/L) and dithiocarbamate recapture agent (the addition standard is 4.0g/L), stirring, mixing and reacting for 30 min; after the reaction, filter pressing is carried out to obtain high-salinity wastewater (the content ratio of potassium to sodium in the high-salinity wastewater is measured to be about 1.8: 1). Heating the high-salinity wastewater to 95 ℃ in a multi-effect counter-current evaporator, concentrating, crystallizing, and centrifugally separating to obtain sodium chloride and filtrate I. And cooling the filtrate I to below 60 ℃ to precipitate crystals, and performing centrifugal separation to obtain a potassium chloride crude product and a filtrate II. Returning the filtrate II to the countercurrent evaporation inlet for cyclic evaporation treatment; and elutriating the crude potassium chloride product by adopting a saturated potassium chloride solution for multiple times, and performing centrifugal separation to obtain high-purity potassium chloride (the purity is 99.96%).

Claims

1. A method for the cooperative treatment of 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) ash washing treatment: mixing industrial water and part of the flue gas washing wastewater to obtain acidic mixed water, washing high-salt solid waste ash with the acidic mixed water, performing solid-liquid separation to obtain a filter cake and ash washing wastewater, transporting the filter cake outwards for disposal, mixing the ash washing wastewater with the rest of the flue gas washing wastewater to obtain mixed wastewater, and performing next-stage treatment;

or, washing the high-salt solid waste ash by using part of cold-rolled rinsing wastewater, performing solid-liquid separation to obtain a filter cake and ash washing wastewater, transporting the filter cake outwards for disposal, mixing the ash washing wastewater with the rest cold-rolled rinsing wastewater, heating for precipitation reaction, performing solid-liquid separation to obtain mixed wastewater and a slag phase after the reaction is completed, transporting the slag phase outwards for disposal, and performing next-stage treatment on the mixed wastewater;

2) micro-electrolysis treatment: carrying out iron-carbon micro-electrolysis treatment on the mixed wastewater obtained in the step 1);

3) advanced wastewater pretreatment: adding a mixed medicament into the mixed wastewater after micro-electrolysis treatment, adjusting the mixed wastewater to be alkaline, performing a reaction of removing heavy matters and hard precipitates from the mixed wastewater, performing solid-liquid separation to obtain high-salinity wastewater and residues, transporting the residues for disposal, and performing next-stage treatment on the high-salinity wastewater;

4) and (3) countercurrent evaporation treatment: heating the high-salinity wastewater, concentrating and crystallizing, and performing solid-liquid separation to obtain sodium chloride and filtrate I; and cooling and crystallizing the filtrate I, and performing solid-liquid separation to obtain potassium chloride and a filtrate II.

2. The method of claim 1, wherein: the method further comprises the following steps:

5) and (3) cyclic evaporation treatment: mixing the filtrate II generated in the step 4) with the high-salinity wastewater generated in the step 3), and then continuing to perform countercurrent evaporation treatment; or, returning the filtrate II generated in the step 4) to the step 1) to participate in water washing and stirring.

3. The method according to claim 1 or 2, characterized in that: in the step 1), the flue gas washing wastewater is acidic flue gas washing wastewater generated by washing of the desorption gas by an activated carbon method;

the cold-rolling rinsing wastewater is FeCl-containing wastewater generated in the rinsing section of the cold-rolled strip steel acid-washing process₃And HCl with a pH of less than 2.5; and/or

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; and/or

The water-ash mass ratio of the acidic 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. The method of claim 3, wherein: in the step 1), the addition amount of the flue gas washing wastewater or the cold rolling rinsing wastewater is such that the pH value of the mixed wastewater is 2-4;

in the step 1), the heating for carrying out the precipitation reaction is heating to 80-100 ℃ for carrying out the precipitation reaction for 1-8 h;

in step 1), the precipitation reaction is also carried out by adding a soluble iron salt (e.g. FeCl) before heating₃) So that the molar ratio of sulfate ions, ammonia nitrogen and iron ions in the wastewater is 0.4-0.8:0.2-0.5: 1; and/or

In the step 2), before carrying out iron-carbon micro-electrolysis on the mixed wastewater, alkali is adopted to adjust the pH value of the mixed wastewater to 3-5; the duration of the iron-carbon micro-electrolysis treatment is not less than 20 min; aeration backflushing is required to be carried out periodically 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, wherein: in the step 3), the mixed medicament consists of sodium hydroxide and/or potassium hydroxide, sodium carbonate and/or potassium carbonate, sodium sulfide and/or potassium sulfate and a recapture agent; wherein: the adding amount of the sodium hydroxide and/or the potassium hydroxide is to ensure that the pH value of the mixed wastewater is 7-9; the adding amount of the sodium carbonate and/or the potassium carbonate is 3-10 g/L; the addition amount of the sodium sulfide and/or the potassium sulfide is 1-7 g/L; the addition amount of the recapture agent is 1-8 g/L; and/or

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

The time of the reaction of removing the heavy matters and the hard sediments in the mixed wastewater is not less than 10 min.

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

7. The method according to any one of claims 1-2, 4, wherein: the water washing in the ash washing treatment is three-stage countercurrent water washing treatment; the method specifically comprises the following steps: firstly, carrying out primary washing on high-salt solid waste ash, carrying out primary filter pressing and 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 is subjected to second-stage washing, the water source of the second-stage washing is third-stage filtrate, the second-stage filtrate is subjected to second-stage filter pressing and dehydration after the second-stage washing to obtain second-stage filtrate and second-stage filter residue, and the second-stage filtrate is discharged to the first-stage washing for recycling; and the second-stage filter residue enters third-stage washing, the water source of the third-stage washing is acidic mixed water mixed by industrial water and flue gas washing wastewater, third-stage filter pressing dehydration is performed after the third-stage washing to obtain third-stage filtrate and third-stage filter residue, the third-stage filtrate is discharged to the second-stage washing for recycling, and the third-stage filter residue is discharged and transported to the outside for disposal.

8. A system for the method for the co-treatment of the high-salinity solid waste ash and the acidic wastewater of the steel plant according to any one of claims 1 to 7, wherein the method comprises the following steps: the system comprises a countercurrent water 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 the water inlet of the countercurrent 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 reservoir (2) is communicated with the water inlet of the iron-carbon micro-electrolysis cell (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 removing cell (4) through a third pipeline (L3); the water outlet of the weight and hardness removing pool (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 of claim 8, wherein: a waste water branch pipe (L01) is also arranged on the waste water inlet pipeline (L0) and is communicated with a water inlet of the regulating tank (2); the adjusting tank (2) is also provided with at least one dosing port (201); a heating unit (202), a first pH detector (203) and a temperature detector (204) are also arranged in the adjusting tank (2); the heating unit (202) is an electric heating unit or a steam heating unit; and/or

The weight and hardness removing pool (4) is also provided with at least one mixed medicine adding port (401); a second pH detector (402) is arranged in the weight and hardness removing pool (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 an elutriation unit (503); a liquid outlet of the heating unit (501) is communicated with a liquid inlet of the cooling unit (502) through a fifth pipeline (L5); a liquid outlet of the cooling unit (502) is communicated with a water inlet of the heating unit (501) through a circulating liquid conveying pipe (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 hole 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).