WO2023216471A1 - 一种钢铁厂多源废水协同处理零排放的工艺 - Google Patents

一种钢铁厂多源废水协同处理零排放的工艺 Download PDF

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WO2023216471A1
WO2023216471A1 PCT/CN2022/116896 CN2022116896W WO2023216471A1 WO 2023216471 A1 WO2023216471 A1 WO 2023216471A1 CN 2022116896 W CN2022116896 W CN 2022116896W WO 2023216471 A1 WO2023216471 A1 WO 2023216471A1
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wastewater
water
ash
washing
salt
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French (fr)
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杨本涛
刘彦廷
陈瑶
刘佰越
魏进超
冯哲愚
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中冶长天国际工程有限责任公司
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D3/00—Halides of sodium, potassium or alkali metals in general
    • C01D3/04—Chlorides
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
    • C02F5/02—Softening water by precipitation of the hardness
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/58—Treatment of water, waste water, or sewage by removing specified dissolved compounds
    • C02F1/60—Silicon compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/101—Sulfur compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/105—Phosphorus compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/16—Nitrogen compounds, e.g. ammonia
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/16—Nature of the water, waste water, sewage or sludge to be treated from metallurgical processes, i.e. from the production, refining or treatment of metals, e.g. galvanic wastes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
    • C02F5/08—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents

Definitions

  • the invention relates to the treatment of wastewater and solid waste in steel plants, and specifically relates to a zero-discharge process for collaborative treatment of multi-source wastewater in steel plants, and belongs to the technical field of collaborative resource treatment of wastewater in the steel industry.
  • the zero-discharge system of wastewater generally mainly solves the problem of reverse osmosis brine and coking wastewater in the reuse water system, and uses hard removal, ultrafiltration, silicon removal, oxidation, membrane systems and other means to resource sulfate and chlorine in the wastewater.
  • the current zero wastewater discharge technology mainly focuses on recovering sodium salts, such as sodium sulfate and sodium chloride.
  • sodium salts such as sodium sulfate and sodium chloride.
  • the zero-discharge wastewater project mainly suffered losses.
  • wastewater emissions, and ultra-low flue gas emissions in order to build a green steel plant with "no solid waste leaving the factory, zero wastewater emissions, and ultra-low flue gas emissions".
  • Environmentally friendly disposal should be carried out in a coordinated manner between water, gas and solid phases. In this mode, the final reflection is the efficient removal and resource utilization of chlorine in the entire plant.
  • the sources of chlorine include, in addition to the reverse osmosis brine and coking wastewater from the reuse water system that have been disposed of earlier, wet/dry desulfurization wastewater, gas condensate, cold rolling rinse water, softened wastewater and high-salt solid waste. Wait.
  • Chinese patent CN111825259A realizes wastewater reuse through softening pretreatment, ultrafiltration, reverse osmosis concentration system, ozone oxidation system, nanofiltration, and reverse osmosis membrane salt separation.
  • the concentrated water from nanofiltration is disposed together with the crystallization system of the coking concentrated water station.
  • the reverse osmosis concentrated water realizes the recovery of sodium chloride through fluorine and silicon removal, electrodialysis concentration and evaporation crystallization.
  • Chinese patent CN112939321A realizes wastewater treatment through softening pretreatment, first-level salt concentration, resin adsorption, membrane salt separation, reverse osmosis membrane concentration, electrodialysis and evaporation crystallization.
  • the first-level salt concentration uses reverse osmosis, and the produced water is used for industrial applications.
  • the water is reused and the concentrated water enters the resin adsorption system.
  • Two-stage nanofiltration is used for membrane salt separation.
  • the concentrated water is used for converter slag washing, and the fresh water is concentrated by high-pressure reverse osmosis membrane.
  • sodium chloride is obtained through evaporation and crystallization.
  • the present invention analyzes the characteristics of the presence of chlorine elements in the entire steel plant wastewater and the difficulty of disposal, designs and provides a A zero-discharge process for the collaborative treatment of multi-source wastewater in steel plants.
  • the process has the following features: selective mass separation of desalted water and gas condensate water from the softening station, high-pressure nanofiltration concentrated water, collaborative cold-rolling rinse wastewater recovery of yellow sodium ferrosite, and high-pressure reaction
  • selective mass separation of desalted water and gas condensate water from the softening station high-pressure nanofiltration concentrated water
  • collaborative cold-rolling rinse wastewater recovery of yellow sodium ferrosite and high-pressure reaction
  • a zero-discharge process for collaborative treatment of multi-source wastewater in steel plants specifically includes the following steps:
  • step 2) First, add a heavy-removing agent (such as sulfide or dithiocarbamate recapture agent) and a hard-removing agent (soluble carbonate, such as sodium carbonate or potassium carbonate) to the mixed concentrated salt wastewater obtained in step 1)
  • a heavy-removing agent such as sulfide or dithiocarbamate recapture agent
  • a hard-removing agent soluble carbonate, such as sodium carbonate or potassium carbonate
  • the secondary reverse osmosis treatment and high-pressure nanofiltration treatment are performed sequentially to obtain high-pressure nanofiltration concentrated water and high-pressure nanofiltration fresh water.
  • step 3 Mix the high-pressure nanofiltration concentrated water obtained in step 2) with the cold rolling rinsing wastewater to obtain mixed acidic wastewater, and then heat the mixed acidic wastewater to perform a precipitation reaction. After the reaction is completed, solid-liquid separation is performed to obtain yellow sodium ferrosite and residual liquid. Yellow sodium ferrosite is comprehensively disposed of in the factory, and the residual liquid is returned to step 1) to participate in homogenization treatment.
  • step 4 Perform high-pressure reverse osmosis treatment on the high-pressure nanofiltration fresh water obtained in step 2) to obtain high-pressure reverse osmosis concentrated water and reused fresh water.
  • the high-pressure reverse osmosis concentrated water is used for washing treatment of high-salt solid waste ash, and the fresh water is recycled to any water-demanding process in the steel plant.
  • the high-quality wastewater is softening station desalted water and/or gas condensate water with a conductivity greater than 10,000 ⁇ S/cm, preferably desalted water and/or gas condensation water of a softening station with a conductivity greater than 12,000 ⁇ S/cm. Condensation water.
  • the concentrated brine of the desalted water station is neutral concentrated water containing sulfate and chloride ions produced when the steel plant uses reverse osmosis to desalinize circulating water.
  • the cold rolling rinsing wastewater is wastewater with a pH of ⁇ 2.5 containing FeCl3 and HCl produced in the rinsing section of the cold-rolled strip pickling process, preferably with a pH of ⁇ 2.
  • the pH of the mixed acidic wastewater is 2-4, preferably the pH is 2-3.
  • the method of heating the mixed acidic wastewater to perform the precipitation reaction specifically involves heating the mixed acidic wastewater to 80-100°C for 1-8 hours, preferably heating to 85-95°C for 2-5 hours.
  • step 3 before heating the mixed acidic wastewater to perform the precipitation reaction, the molar ratio of iron ions and sulfate ions in the mixed acidic wastewater is adjusted to 1:0.4- by adding a soluble iron salt (preferably ferric chloride). 0.8, preferably 1:0.5-0.7.
  • a soluble iron salt preferably ferric chloride
  • step 4 the use of high-pressure reverse osmosis concentrated water for the water washing treatment of high-salt solid waste ash is specifically:
  • the impurity removal wastewater is subjected to iron-carbon micro-electrolysis treatment. Then, mixed chemicals are added to the impurity removal wastewater after micro-electrolysis treatment, the impurity removal wastewater is adjusted to alkalinity, and the impurity removal wastewater is subjected to a degravity and hard precipitation reaction. After solid-liquid separation, high-salt wastewater and residue are obtained. The residue is integrated in the plant. Disposal, high-salt wastewater enters the next process.
  • the desulfurization wastewater is first evaporated and concentrated to obtain suspended solids-containing wastewater, and then an ammonia nitrogen precipitant is added to the suspended solids-containing wastewater for precipitation treatment, and finally solid-liquid treatment is performed. Obtained after separation.
  • the evaporation concentration is to use multi-stage evaporation concentration equipment to concentrate the wet desulfurization wastewater 3-6 times.
  • the ammonia nitrogen precipitating agent is soluble ferrous salt and soluble sulfite.
  • the wet desulfurization wastewater is the wastewater produced when flue gas is treated by limestone/gypsum method.
  • the desulfurization wastewater is the wastewater after the activated carbon process wastewater has been diverted. Specifically, 1/4 to 1/2 of the activated carbon process wastewater is used to mix with high-pressure reverse osmosis concentrated water to wash the high-salt solid waste ash, and the remaining Part of the wastewater is used to adjust the ash washing wastewater to acidity.
  • the activated carbon method wastewater is acidic flue gas scrubbing wastewater produced by activated carbon adsorption analysis gas scrubbing.
  • the wet desulfurization wastewater is evaporated and concentrated into a multi-stage evaporation concentration in which the evaporation temperature is gradually reduced and the vacuum degree is gradually increased.
  • the evaporation temperature of the first stage evaporation concentration is 80-100°C, and the vacuum degree is -40-5kPa.
  • the evaporation temperature of the second stage evaporation concentration is 50 ⁇ 80°C, and the vacuum degree is -70 ⁇ -40kPa.
  • the evaporation temperature of the third stage evaporation concentration is 30 ⁇ 50°C, and the vacuum degree is -100 ⁇ -70kPa.
  • the soluble ferrous salt is one or more of ferrous chloride, ferrous sulfate, and elemental iron powder.
  • the soluble sulfite is one or more of sodium sulfite, sodium bisulfite, and potassium sulfite.
  • the order of adding the soluble ferrous salt and the soluble sulfite is sequential addition.
  • the hot steam generated by evaporation and concentration is used to heat the mixed acidic wastewater in step 3) and/or is used to heat the ash washing wastewater in step 4b).
  • adjusting the ash washing wastewater to acidity means adjusting the pH of the ash washing wastewater to 2-4, preferably the pH is 2-3.
  • the heating of the ash washing wastewater to perform the precipitation reaction specifically involves heating the ash washing wastewater to 80-100°C for 1-8 hours, preferably heating to 85-95°C for 2-5 hours.
  • step 4b) before heating the ash washing wastewater to perform the precipitation reaction, the molar ratio of iron ions, sulfate ions, and ammonia nitrogen in the ash washing waste water is adjusted to 1:0.4-0.8:0.2-0.6 by adding soluble iron salts. , preferably 1:0.5-0.7:0.3-0.5.
  • an alkali needs to be used to adjust the pH of the impurity removal wastewater to 3-5, preferably 3.5-4.
  • the base is sodium hydroxide and/or potassium hydroxide.
  • the mixed agent is sodium hydroxide and/or potassium hydroxide, sodium carbonate and/or potassium carbonate, sodium sulfide and/or potassium sulfate, recapture agent (preferably xanthate ester Recapture agent or dithiocarbamate recapture agent).
  • the amount of sodium hydroxide and/or potassium hydroxide added is such that the pH of the impurity removal wastewater is 7-9, preferably 7.5-8.
  • the addition amount of sodium carbonate and/or potassium carbonate is 3-10g/L, preferably 4-8g/L.
  • the added amount of sodium sulfide and/or potassium sulfide is 1-7g/L, preferably 1.5-6g/L.
  • the added amount of the recapture agent is 1-8g/L, preferably 2-5g/L.
  • the high-salt solid waste ash includes one or more of sintered electric field ash, blast furnace bag ash, rotary kiln surface cooled ash, and garbage incineration fly ash, preferably sintered electric field ash.
  • the water washing of the high-salt solid waste ash is a three-stage countercurrent water washing process.
  • the high-salt solid waste ash is first washed with one-level water, and dehydrated through one-level press filtration to obtain the first-level filtrate and the first-level filter residue.
  • the first-level filtrate is ash washing wastewater.
  • the first-level filter residue enters the second-level water washing.
  • the water source of the second-level water washing is the third-level filtrate, high-pressure reverse osmosis concentrated water and desulfurization wastewater.
  • After the second-level water washing it is dehydrated through the second-level press filtration to obtain the second-level filtrate and the second-level filter residue.
  • the second-level filtrate is discharged Use it in a first-level wash cycle.
  • the second-level filter residue enters the third-level water washing.
  • the water source of the third-level water washing is industrial water.
  • After the third-level water washing it is dehydrated through the third-level filter press to obtain the third-level filtrate and the third-level filter residue.
  • the third-level filtrate is discharged to the second-level water washing for recycling, and the third-level filter residue is Comprehensive disposal in the factory.
  • a multi-effect counter-current evaporation device is used to treat the high-salt wastewater.
  • the number of stages of the multi-effect counter-current evaporation device is 2-6, preferably 3-4.
  • the heating of the high-salt wastewater is to heat the high-salt wastewater to 80-100°C, preferably 90-95°C.
  • the primary filtrate is cooled by flash evaporation or heat exchange to a temperature below 60°C, preferably 20-55°C.
  • the hot steam generated by the multi-effect countercurrent evaporation device is used to heat the mixed acidic wastewater in step 3) and/or is used to heat the ash washing wastewater in step 4b).
  • the existing technology for the resource treatment of multi-source wastewater from different processes in steel plants, the existing technology can often only carry out simple resource treatment of a certain type of wastewater.
  • the existing technology In order to achieve the standard discharge or zero discharge of factory wastewater, it is often necessary to Multiple sets of different wastewater treatment equipment need to be established to meet the treatment needs of wastewater discharged from different processes in steel plants, resulting in high input costs for wastewater treatment and low added value of by-products.
  • the gas condensation water mainly comes from the condensation water produced during the transportation process of blast furnace, converter and coking gas, and contains a certain amount of sulfate and chloride ions, but the specific water quality characteristics are closely related to the drainage time and the gas transportation distance.
  • the desalted water in the softening station mainly comes from the concentrated water produced when ion exchangers are used to remove chlorine and sulfate radicals in wastewater.
  • General gas condensate and demineralized water from softening stations are often biochemically treated together with biodegradable wastewater.
  • the present invention performs selective mass separation and zero discharge of gas condensation water and demineralized water from the softening station. That is, real-time detection of conductivity is first used, and water with a conductivity greater than 10,000 ⁇ S/cm (preferably greater than 12,000 ⁇ S/cm) is carried out. Quality separation, and after pretreatment and membrane concentration and salt separation, they participate in high-value recovery of yellow sodium ferrosite and collaborative dust washing respectively.
  • nanofiltration concentrated water containing high-concentration sulfate radicals can finally be obtained.
  • high-pressure reverse osmosis concentrated water containing high concentrations of chloride ions Nanofiltration concentrated water generally uses evaporation crystallization + freezing to recover sodium sulfate.
  • this process has the disadvantages of high energy consumption and low added value of sodium sulfate.
  • the cold rolling rinsing water contains a large amount of ferric iron, iron and sulfate will react with sodium to form yellow sodium ferrosite.
  • the cold rolling rinse water is strongly acidic wastewater, which can provide unique conditions for the occurrence of this reaction. Therefore, the waste heat steam from the evaporation system (wet desulfurization wastewater evaporation concentration system and high-salt wastewater countercurrent evaporation dilute salt system) is used to heat the mixed wastewater (high-pressure nanofiltration concentrated water and cold rolling rinsing wastewater mixed) to 80-100°C to achieve High-value recovery of sulfate radicals in concentrated water through nanofiltration, while absorbing cold rolling rinse water.
  • the mixed wastewater high-pressure nanofiltration concentrated water and cold rolling rinsing wastewater mixed
  • the molar ratio of iron ions and sulfate ions in the mixed wastewater can also be adjusted to 1:0.4-0.8 (preferably 1:0.5-0.7) by adding soluble iron salts (preferably ferric chloride), thereby promoting the reaction. .
  • the high-pressure reverse osmosis concentrated water is mainly composed of sodium chloride. Studies have shown that using the high-pressure reverse osmosis concentrated water to participate in the washing of high-salt solid waste ash can reduce the alkalinity of the ash washing water and make it close to medium. sex. Therefore, the present invention uses high-pressure reverse osmosis concentrated water and acidic wastewater from other processes to perform collaborative ash washing (high-salt solid waste ash) treatment, which is beneficial to improving the water quality of the ash washing wastewater. Generally, when the desulfurization wastewater is mainly wet desulfurization wastewater, it is concentrated (generally concentrated 3-6 times) before being washed.
  • the concentrated wet desulfurization wastewater is highly acidic, it is not compatible with high-pressure reverse osmosis. After the concentrated water is mixed, on the one hand, the solution of the gray wash water can be reduced, making the gray wash water weakly acidic, thus preventing the formation of stable [TlCl 4 - ]. On the other hand, since the concentrated wet desulfurization wastewater contains a large amount of sulfite, its addition will cause thallium to be weakly reduced and destroy the complex, which is conducive to the removal of thallium, thereby achieving source suppression of thallium.
  • the desulfurization wastewater is mainly activated carbon process wastewater
  • the activated carbon process wastewater has strong acidity, when using it for dust washing, on the one hand, it can reduce the solution of the dust washing water and make the dust washing water acidic, thereby preventing Stable [TlCl 4 - ] is formed.
  • acidic washing wastewater contains thiosulfate, its addition will also facilitate the removal of thallium. Therefore, the co-processing of high-pressure reverse osmosis concentrated water, desulfurization wastewater (wet desulfurization wastewater or activated carbon wastewater) and high-salt solid waste ash can greatly improve the quality of the graywash water and reduce the dissolution of pollutants.
  • the main composition of high-pressure reverse osmosis concentrated water and desulfurization wastewater is similar to that of gray washing water. Co-processing can significantly reduce the water consumption of high-salt solid waste.
  • the wet/dry desulfurization wastewater, gas condensate, desalted water from the softening station and high-salt solid waste ash all contain different concentrations of ammonia nitrogen. It will eventually be enriched in the graywash water, thus affecting the quality of the recovered product salt.
  • the present invention provides a new technology of two-stage deamination. First paragraph: The concentration of ammonia nitrogen in wet desulfurization wastewater after concentration will reach 10-30g/L. For the precipitation and removal of high-concentration ammonia nitrogen, it can be removed by the ferrous ammonium sulfite method and the magnesium ammonium phosphate method.
  • the ferrous ammonium sulfite method is that under the condition that the solution pH is 5 to 8, ammonia nitrogen will combine with ferrous iron and sulfite to form ferrous ammonium sulfite precipitation.
  • the cold rolling rinse water contains a large amount of ferric iron.
  • iron and sulfate radicals will react with potassium, sodium, and ammonia nitrogen to form jarosite, jarosite, and jarosite. Therefore, cold rolling rinsing wastewater can be added to the ash washing wastewater, and the waste heat of the evaporation system can be used to heat the wastewater to 80-100°C to achieve the removal of ammonia nitrogen in the wastewater.
  • the ammonia nitrogen precipitation reaction can be promoted by additional addition of ferrous ions and sulfite ions.
  • the potassium-sodium ratio in its conventional water washing solution is generally greater than 4 (preferably greater than 5).
  • the principle of temperature-changing salt separation of potassium and sodium it is suitable for downstream evaporation, that is, through temperature-changing evaporation, potassium and sodium salts are separated.
  • Phase diagram analysis shows that after a solution with high potassium and low sodium is concentrated by evaporation, potassium salt will inevitably precipitate first. Therefore, for high-salt solids
  • the salt separation method of waste ash washing water is generally downstream evaporation. That is, the evaporation process of the solution is a gradual cooling process. At the multi-effect outlet, the potassium salt is discharged first.
  • the present invention introduces high-pressure infiltration concentrated water (mainly containing sodium chloride) and desulfurization wastewater (containing sodium) as high-salt solid waste ash washing water, thereby making the potassium and sodium content ratio in the ash washing wastewater close to 1:1.
  • impurities are also removed through iron-carbon micro-electrolysis (the iron-carbon reaction time should not be less than 20 minutes). Since Tl 3+ is easier to remove than Tl + , generally speaking, pretreatment can be performed by oxidation. Iron-carbon micro-electrolysis has synergistic effects of weight removal and oxidation. After passing through iron and carbon, Tl can be changed into a form that is easier to remove. At the same time, a large number of metal ions in the gray wash water will be replaced by iron elements, thereby achieving removal, and a large amount of ferrous iron and ferric iron will be produced in the solution. In addition, iron-carbon is also beneficial to the efficient removal of fluoride ions in wastewater.
  • the iron carbon will release ferrous iron.
  • alkali such as sodium hydroxide
  • ammonia nitrogen will quickly react with sulfite and ferrous iron to form ammonium ferrous sulfite precipitate, thereby achieving the removal of ammonia nitrogen. Deep removal.
  • the purpose of adding sodium carbonate is to remove calcium and magnesium.
  • the purpose of adding sodium sulfide and recapture agent is to achieve deep removal of trace heavy metals.
  • This invention performs quality and graded treatment of high-salt wastewater from steel plants.
  • the main disposal objects include desalted water from the softening station, gas condensate water, concentrated brine from the desalted water station, cold rolling rinsing wastewater, desulfurization wastewater, etc. Compared with traditional zero-emission technology, the treatment objects are more complete and comprehensive.
  • the present invention co-disposes high-salt wastewater and high-salt solid waste ash, greatly reducing the content of pollutants in the ash washing water, thereby reducing the cost of subsequent wastewater treatment, while reducing the amount of wastewater used, and greatly reducing the disposal cost.
  • the present invention realizes high-value recovery of sulfate radicals in high-pressure nanofiltration concentrated water through the ferrite method based on the acidity and large amounts of ferric iron in the cold rolling rinse water. At the same time, based on the characteristics of cold rolling rinse water, it can remove ammonia nitrogen and sulfate radicals in gray wash water, improve the purity of salt products, and has the advantages of low cost and simple operation.
  • the present invention combines the analysis of the characteristics of the graywash water produced by the collaborative graywashing of high-salt solid waste and wastewater. Based on the iron-carbon micro-electrolysis pretreatment, the present invention realizes collaborative thallium oxidation and de-gravity treatment, greatly reducing the wastewater treatment process, and at the same time targeting The characteristics and process design of each wastewater realize the collaborative resource treatment of multi-source wastewater and achieve zero discharge of wastewater.
  • the potassium salt recovered by the present invention is of high quality.
  • ammonia nitrogen, thallium, sulfate and other pollutants can be removed at low cost through wastewater pretreatment, preventing contamination of the potassium salt.
  • the potassium-sodium ratio in the ash washing water changes, which makes it suitable to use countercurrent evaporation, which can prevent pollutants from entering the potassium salt, thereby increasing the value of the salt product.
  • Figure 1 is a flow outline diagram of the multi-source wastewater collaborative treatment with zero discharge in a steel plant according to the present invention.
  • Figure 2 is a detailed flowchart of the zero-discharge collaborative treatment of multi-source wastewater in a steel plant according to the present invention.
  • a zero-discharge process for collaborative treatment of multi-source wastewater in steel plants specifically includes the following steps:
  • step 2) First, add degravity, hardness removal agent and desilicon treatment to the mixed concentrated salt wastewater obtained in step 1), and then perform secondary reverse osmosis treatment and high-pressure nanofiltration treatment in sequence to obtain high-pressure nanofiltration concentrated water and high-pressure sodium filtration treatment. Filter fresh water.
  • step 3 Mix the high-pressure nanofiltration concentrated water obtained in step 2) with the cold rolling rinsing wastewater to obtain mixed acidic wastewater, and then heat the mixed acidic wastewater to perform a precipitation reaction. After the reaction is completed, solid-liquid separation is performed to obtain yellow sodium ferrosite and residual liquid. Yellow sodium ferrosite is comprehensively disposed of in the factory, and the residual liquid is returned to step 1) to participate in homogenization treatment.
  • step 4 Perform high-pressure reverse osmosis treatment on the high-pressure nanofiltration fresh water obtained in step 2) to obtain high-pressure reverse osmosis concentrated water and reused fresh water.
  • the high-pressure reverse osmosis concentrated water is used for washing treatment of high-salt solid waste ash, and the fresh water is recycled to any water-demanding process in the steel plant.
  • step 1) the high-quality wastewater is softening station desalted water and gas condensate water with a conductivity greater than 10,000 ⁇ S/cm.
  • step 1) the high-quality wastewater is demineralized water and gas condensation water from the softening station with a conductivity greater than 12000 ⁇ S/cm.
  • the cold rolling rinsing wastewater is wastewater containing FeCl 3 and HCl with a pH of ⁇ 2.5 produced in the rinsing section of the cold rolled strip pickling process.
  • step 3 the pH of the mixed acidic wastewater is 3.
  • the heating of the mixed acidic wastewater to perform the precipitation reaction specifically involves heating the mixed acidic wastewater to 90° C. for 4 hours.
  • step 3 before heating the mixed acidic wastewater to perform the precipitation reaction, the molar ratio of iron ions and sulfate ions in the mixed acidic wastewater is adjusted to 3:2 by adding ferric chloride.
  • step 4 the use of high-pressure reverse osmosis concentrated water for the water washing treatment of high-salt solid waste ash is specifically:
  • the impurity removal wastewater is subjected to iron-carbon micro-electrolysis treatment. Then, mixed chemicals are added to the impurity removal wastewater after micro-electrolysis treatment, the impurity removal wastewater is adjusted to alkalinity, and the impurity removal wastewater is subjected to a degravity and hard precipitation reaction. After solid-liquid separation, high-salt wastewater and residue are obtained. The residue is integrated in the plant. Disposal, high-salt wastewater enters the next process.
  • the desulfurization wastewater is obtained by first evaporating and concentrating the wet desulfurization wastewater 5 times to obtain suspended solids-containing wastewater, and then adding ferrous chloride and ferrous chloride to the suspended solids-containing wastewater. Sodium sulfite is subjected to precipitation treatment, and finally the wastewater is obtained after solid-liquid separation.
  • the wet desulfurization wastewater is evaporated and concentrated as follows: the evaporation temperature of the first stage of evaporation and concentration is 80 to 100°C, and the vacuum degree is -40 to -5 kPa.
  • the evaporation temperature of the second stage evaporation concentration is 50 ⁇ 80°C, and the vacuum degree is -70 ⁇ -40kPa.
  • the evaporation temperature of the third stage evaporation concentration is 30 ⁇ 50°C, and the vacuum degree is -100 ⁇ -70kPa.
  • Example 9 Repeat Example 9, except that the hot steam generated by evaporating and concentrating the wet desulfurization wastewater is used to heat the mixed acidic wastewater.
  • step 4b the step of adjusting the ash washing wastewater to acidity is to adjust the pH of the ash washing wastewater to 3, and the heating of the ash washing wastewater to perform a precipitation reaction specifically involves heating the ash washing wastewater to 90°C for 4 hours. .
  • step 4b before heating the ash washing wastewater to perform the precipitation reaction, the molar ratio of iron ions, sulfate ions, and ammonia nitrogen in the ash washing wastewater is adjusted to 3:2:1 by adding soluble iron salts.
  • the mixed agent is composed of sodium hydroxide and potassium hydroxide, sodium carbonate and potassium carbonate, sodium sulfide and potassium sulfate, and dithiocarbamate recapture agents.
  • the addition amount of sodium hydroxide and potassium hydroxide is such that the pH of the impurity removal wastewater is 8.
  • the addition amount of sodium carbonate and potassium carbonate is 7g/L.
  • the addition amount of sodium sulfide and potassium sulfide is 3.5g/L.
  • the added amount of the dithiocarbamate recapture agent is 3.6g/L.
  • Example 13 Repeat Example 13, except that the high-salt solid waste ash includes sintered electric field ash.
  • the water washing of the high-salt solid waste ash is a three-stage countercurrent water washing process. Specifically, the high-salt solid waste ash is first washed with one-level water, and dehydrated through one-level press filtration to obtain the first-level filtrate and the first-level filter residue.
  • the first-level filtrate is ash washing wastewater.
  • the first-level filter residue enters the second-level water washing.
  • the water source of the second-level water washing is the third-level filtrate, high-pressure reverse osmosis concentrated water and desulfurization wastewater.
  • After the second-level water washing it is dehydrated through the second-level press filtration to obtain the second-level filtrate and the second-level filter residue.
  • the second-level filtrate is discharged Use it in a first-level wash cycle.
  • the second-level filter residue enters the third-level water washing.
  • the water source of the third-level water washing is industrial water.
  • After the third-level water washing it is dehydrated through the third-level filter press to obtain the third-level filtrate and the third-level filter residue.
  • the third-level filtrate is discharged to the second-level water washing for recycling, and the third-level filter residue is Comprehensive disposal in the factory.
  • step 4d a 3-stage multi-effect countercurrent evaporation device is used to treat high-salt wastewater.
  • the heating of high-salt wastewater is heating of high-salt wastewater to 95°C.
  • the primary filtrate is cooled to below 60°C by flash evaporation or heat exchange.
  • Example 16 Repeat Example 16, except that the hot steam generated by the multi-effect countercurrent evaporation device is used to heat the ash washing wastewater.
  • step 4c the impurity removal wastewater is subjected to iron-carbon micro-electrolysis treatment for not less than 20 minutes.
  • step 4c) after the mixed reagent is added to the impurity removal wastewater, the duration of the weight removal and hard precipitation reaction on the impurity removal wastewater is not less than 10 minutes.
  • Example 6 The process described in Example 6 is used to perform collaborative resource treatment on desalted wastewater from the softening station of the steel plant, gas condensate water, concentrated brine from the desalinated station and cold rolling rinsing wastewater:
  • the conductivity of desalted water and gas condensate water from the softening station is tested respectively, and high-quality desalted water from the softening station and high-quality gas condensate water with a conductivity greater than 12,000 ⁇ S/cm are mixed to obtain high-quality wastewater; for conductivity lower than 12,000 ⁇ S/cm
  • the desalted water and low-quality gas condensate from the low-quality softening station can be sent for routine biochemical treatment.
  • Example 18 The process described in Example 18 is used to collaboratively process multi-source wastewater from steel plants with zero discharge and collaboratively process high-salt solid waste ash:
  • the cake is returned to the sintering process for batching disposal; then cold rolling rinsing wastewater is added to the ash washing wastewater to adjust the pH of the ash washing wastewater to 3, and ferric chloride is added to the ash washing wastewater to make iron ions, sulfate ions,
  • the molar ratio of ammonia nitrogen is close to 3:2:1; then hot steam is introduced into the ash washing wastewater to heat the ash washing wastewater to 90°C and the reaction continues for 4 hours.
  • the ammonium resources in the slag phase can be used to reduce the source of sintering nitrogen oxides, and the sulfate radicals in the slag can be absorbed by converting into sulfur dioxide;
  • the adjusted impurity removal wastewater is passed into the iron-carbon micro-electrolysis reactor for treatment for 40 minutes. During this period, the iron-carbon micro-electrolysis reactor is regularly aerated and backflushed. After the micro-electrolysis treatment is completed, add sodium hydroxide again to adjust the pH of the impurity removal wastewater to 8, then add 2.45kg sodium carbonate, 1.23kg sodium sulfide, and 1.26kg dithiocarbamate recapture agent in sequence, and stir and mix the reaction. 30 minutes; after press filtration, high-salt wastewater is obtained (the potassium and sodium content ratio in high-salt wastewater is measured to be approximately 1.1:1).
  • the evaporation temperature of the first-stage evaporation concentration is 95°C and the vacuum degree is -20kPa.
  • the evaporation temperature of the second-stage evaporation concentration is 75°C and the vacuum degree is -60kPa.
  • the evaporation temperature of the third stage evaporation concentration is 40°C and the vacuum degree is -90kPa); during this period, sodium chloride and primary filtrate are obtained through centrifugal separation.
  • the primary filtrate is cooled to below 60°C to precipitate crystals, and centrifuged to obtain crude potassium chloride and secondary filtrate.
  • the secondary filtrate is returned to the countercurrent evaporation inlet for cyclic evaporation treatment; the crude potassium chloride is washed multiple times with saturated potassium chloride solution and centrifuged to obtain high-purity potassium chloride (purity: 99.95%).

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Abstract

本发明公开了一种钢铁厂多源废水协同处理零排放的工艺，该工艺具备软化站除盐水和煤气冷凝水选择性分质零排、高压纳滤浓水协同冷轧漂洗废水回收黄钠铁矾、高压反渗透浓水与脱硫废水及高盐固废灰协同处置以及氨氮低成本处置的特点。同时还将多源废水与高盐固废灰协同处置，可大幅降低洗灰水中污染物含量，从而减少了后续废水处理成本和废水使用量，极大的降低了固废和废水的处置成本，实现了多源废水的内部消纳和废水零排放。

Description

一种钢铁厂多源废水协同处理零排放的工艺 技术领域
本发明涉及钢铁厂废水及固废处理，具体涉及一种钢铁厂多源废水协同处理零排放的工艺，属于钢铁行业废水协同资源化处理技术领域。
背景技术
当前，钢铁厂对废水回用率要求越来越高，而且随着环保标准的加严，钢铁厂废水零排放势在必行。目前，废水的零排放系统一般主要解决回用水系统的反渗透浓盐水和焦化废水，通过除硬、超滤、除硅、氧化、膜系统等手段进行废水中硫酸根和氯的资源化。
当前废水零排放技术以回收钠盐为主，如硫酸钠、氯化钠。但由于钠盐附加值不高，加之废水蒸发成本较高，导致废水零排放项目主要为亏损。此外在新时期背景下，为打造“固废不出厂、废水零排放、烟气超低排”的绿色钢厂。环保处置应该向着水气固相协调的方式进行，而这种模式下，最终反映出来就是全厂氯元素的高效去除及资源化。氯元素的来源，除了有早前已经处置的回用水系统的反渗透浓盐水和焦化废水外，还包括湿法/干法脱硫废水、煤气冷凝水、冷轧漂洗水、软化废水及高盐固废等。中国专利CN111825259A通过软化预处理、超滤、反渗透浓缩系统、臭氧氧化系统、纳滤、反渗透膜分盐实现废水的回用，其中纳滤的浓缩水与焦化浓水站结晶系统一同处置，而反渗透浓水通过氟硅去除、电渗析浓缩和蒸发结晶实现氯化钠的回收。中国专利CN112939321A通过软化预处理、一级盐浓缩、树脂吸附、膜分盐、反渗透膜浓缩、电渗析和蒸发结晶实现废水的处理，其中一级盐浓缩采用反渗透，产水用于工业新水回用，浓水进入到树脂吸附系统。膜分盐采用两级纳滤，浓水用于转炉冲渣，淡水进行高压反渗透膜浓缩，最终通过蒸发结晶得到氯化钠。
综上所述，由于钢铁厂不同工序废水的不同特点，以及不同废水的性质的差异，现有技术往往仅能针对单一工序的废水进行资源化处理，而且对于一些组分复杂的废水，其资源化效果并不理想，且投入成本较大。目前，发明人尚未发现有针对钢铁厂多源废水进行低成本协同处置实现零排放的相关技术报道。
发明内容
针对现有技术的不足，本发明为提高零排放盐产品的附加值和加大钢铁厂废水处理的覆盖面，基于钢厂全厂废水中氯元素存在的特征及处置难度进行分析，设计并提供了一种钢铁厂多源废水协同处理零排放的工艺，该工艺具备软化站除盐水和煤气冷凝水选择性分质零排、高压纳滤浓水协同冷轧漂洗废水回收黄钠铁矾、高压反渗透浓水与脱硫废水及高盐固废灰协 同处置以及氨氮低成本处置的特点。
为实现上述目的，本发明所采用的技术方案具体如下所述：
一种钢铁厂多源废水协同处理零排放的工艺，该工艺具体包括如下步骤：
1)将高质废水与除盐水站浓盐水进行均质混合后获得混合浓盐废水。
2)先将步骤1)获得的混合浓盐废水投加除重药剂(如硫化物或二硫代氨基甲酸盐类重捕剂)、除硬药剂(可溶性碳酸盐，如碳酸钠或碳酸钾)及脱硅处理(脱硅药剂为镁剂或铁盐)后，然后再依次进行二级反渗透处理和高压纳滤处理，获得高压纳滤浓水和高压纳滤淡水。
3)将步骤2)获得的高压纳滤浓水与冷轧漂洗废水混合获得混合酸性废水，然后加热混合酸性废水进行沉淀反应，反应完成后进行固液分离，获得黄钠铁矾和残液。黄钠铁矾厂内综合处置，残液返回步骤1)参与均质处理。
4)将步骤2)获得的高压纳滤淡水进行高压反渗透处理，获得高压反渗透浓水和回用淡水。将高压反渗透浓水用于高盐固废灰的水洗处理，回用淡水循环至钢铁厂任意需水工序。
作为优选，在步骤1)中，所述高质废水为电导率大于10000μS/cm的软化站除盐水和/或煤气冷凝水，优选为电导率大于12000μS/cm的软化站除盐水和/或煤气冷凝水。
作为优选，在步骤1)中，所述除盐水站浓盐水为钢铁厂在对循环水采用反渗透除盐时产生的含有硫酸根和氯离子的中性浓水。
作为优选，在步骤3)中，所述冷轧漂洗废水为冷轧带钢酸洗工艺漂洗段产生的含有FeCl 3和HCl的pH＜2.5的废水，优选为pH＜2的废水。
作为优选，在步骤3)中，所述混合酸性废水的pH为2-4，优选pH为2-3。所述加热混合酸性废水进行沉淀反应具体为加热混合酸性废水至80-100℃反应1-8h，优选为加热至85-95℃反应2-5h。
作为优选，在步骤3)中，在加热混合酸性废水进行沉淀反应前，还通过添加可溶性铁盐(优选为氯化铁)调节混合酸性废水中铁离子与硫酸根离子的摩尔比为1:0.4-0.8，优选为1:0.5-0.7。
作为优选，在步骤4)中，所述将高压反渗透浓水用于高盐固废灰的水洗处理具体为：
4a)将高压反渗透浓水与脱硫废水混合后对高盐固废灰进行水洗，固液分离后获得滤饼和洗灰废水，滤饼厂内综合处置，洗灰废水进入下一工序。
4b)采用脱硫废水或冷轧漂洗废水调节洗灰废水至酸性，然后加热洗灰废水进行沉淀反应，反应完成后，固液分离获得除杂废水和渣相，渣相厂内综合处置，除杂废水进入下一工序。
4c)先将除杂废水进行铁碳微电解处理。然后向微电解处理后的除杂废水中加入混合药 剂，调节除杂废水至碱性并对除杂废水进行除重除硬沉淀反应，固液分离后获得高盐废水和残渣，残渣厂内综合处置，高盐废水进入下一工序。
4d)先加热高盐废水，进行浓缩析晶，固液分离后获得氯化钠和一次滤液。然后再将一次滤液进行冷却析晶，固液分离后获得氯化钾和二次滤液。最后将二次滤液与高盐废水混合后循环进行加热析盐处理。
作为优选，在步骤4a)中，所述脱硫废水是通过先将湿法脱硫废水进行蒸发浓缩得到含悬浮物废水，然后再向含悬浮物废水中加入氨氮沉淀剂进行沉淀处理，最后经固液分离后得到的。所述蒸发浓缩为采用多级蒸发浓缩设备将湿法脱硫废水浓缩3-6倍。所述氨氮沉淀剂为可溶性亚铁盐和可溶性亚硫酸盐。所述湿法脱硫废水为用石灰石/石膏法处理烟气时产生的废水。
或者，所述脱硫废水为活性炭法废水进行分流处理后的废水，具体为将1/4～1/2的活性炭法废水用于与高压反渗透浓水混合对高盐固废灰进行水洗，剩余部分废水则用于调节洗灰废水至酸性。所述活性炭法废水为对活性炭吸附法解析气体洗涤产生的酸性烟气洗涤废水。
作为优选，将湿法脱硫废水进行蒸发浓缩为蒸发温度逐级降低、而真空度逐级提高的多级蒸发浓缩。优选为：第一级蒸发浓缩的蒸发温度为80～100℃，真空度为-40～-5kPa。第二级蒸发浓缩的蒸发温度为50～80℃，真空度为-70～-40kPa。第三级蒸发浓缩的蒸发温度为30～50℃，真空度为-100～-70kPa。
作为优选，所述可溶性亚铁盐为氯化亚铁、硫酸亚铁、单质铁粉中的一种或多种。所述可溶性亚硫酸盐为亚硫酸钠、亚硫酸氢钠、亚硫酸钾中的一种或多种。优选，可溶性亚铁盐和可溶性亚硫酸盐的添加顺序为顺次加入。
作为优选，蒸发浓缩产生的热蒸汽用于步骤3)中加热混合酸性废水和/或用于步骤4b)中加热洗灰废水。
作为优选，在步骤4b)中，所述调节洗灰废水至酸性为调节洗灰废水的pH为2-4，优选pH为2-3。所述加热洗灰废水进行沉淀反应具体为加热洗灰废水至80-100℃反应1-8h，优选为加热至85-95℃反应2-5h。
作为优选，在步骤4b)中，在加热洗灰废水进行沉淀反应前，还通过添加可溶性铁盐调节洗灰废水中铁离子、硫酸根离子、氨氮的摩尔比为1:0.4-0.8:0.2-0.6，优选为1:0.5-0.7:0.3-0.5。
作为优选，在步骤4c)中，在将除杂废水进行铁碳微电解前需采用碱调节除杂废水的pH为3-5，优选为3.5-4。优选，所述碱为氢氧化钠和/或氢氧化钾。
作为优选，在步骤4c)中，所述混合药剂为氢氧化钠和/或氢氧化钾、碳酸钠和/或碳酸钾、硫化钠和/或硫酸钾、重捕剂(优选为黄原酸酯类重捕剂或二硫代氨基甲酸盐类重捕剂)共同 组成。其中：氢氧化钠和/或氢氧化钾的加入量为使得除杂废水的pH为7-9，优选为7.5-8。所述碳酸钠和/或碳酸钾的加入量为3-10g/L，优选为4-8g/L。所述硫化钠和/或硫化钾的加入量为1-7g/L，优选为1.5-6g/L。所述重捕剂的加入量为1-8g/L，优选为2-5g/L。
作为优选，所述高盐固废灰包括烧结电场灰、高炉布袋灰、回转窑表冷灰、垃圾焚烧飞灰中的一种或多种，优选烧结电场灰。
作为优选，所述高盐固废灰的水洗为三级逆流水洗处理。具体为：先将高盐固废灰进行一级水洗，并通过一级压滤脱水，获得一级滤液和一级滤渣，一级滤液为洗灰废水。一级滤渣进入二级水洗，二级水洗水源为三级滤液和高压反渗透浓水以及脱硫废水，二级水洗后通过二级压滤脱水，获得二级滤液和二级滤渣，二级滤液排至一级水洗循环使用。二级滤渣进入三级水洗，三级水洗水源为工业水，三级水洗后通过三级压滤脱水，获得三级滤液和三级滤渣，三级滤液排至二级水洗循环使用，三级滤渣在厂内综合处置。
作为优选，在步骤4d)中，采用多效逆流蒸发装置对高盐废水进行处理，所述多效逆流蒸发装置的级数为2-6级，优选为3-4级。所述加热高盐废水为加热高盐废水至80-100℃，优选为90-95℃。所述一次滤液进行冷却为采用闪蒸或换热的方式降温至60℃以下，优选为20-55℃。
作为优选，多效逆流蒸发装置产生的热蒸汽用于步骤3)中加热混合酸性废水和/或用于步骤4b)中加热洗灰废水。
在现有技术中，针对钢铁厂不同工序的多源废水的资源化处理，现有技术往往仅能针对某一种废水进行简单的资源化处理，为实现出厂废水的达标排放或零排放，往往需要建立多套不同的废水处理设备以满足钢铁厂不同工序排放废水的处理需求，导致废水处理投入成本较大且副产品附加值低。
在本发明中，煤气冷凝水主要来源于高炉、转炉、焦化煤气输送过程中产生的冷凝水，均含有一定量的硫酸根和氯离子，但具体水质特征与排水时间、煤气输送距离密切相关。软化站除盐水主要来源于采用离子交换器去除废水中的氯、硫酸根时产生的浓水。一般的煤气冷凝水和软化站除盐水，常与可生化的废水一同进行生化处理。但对钢厂全厂煤气冷凝水和软化站除盐水的水质分析发现，这两股水中均为存在大量的氯离子的高浓度废水，最高有200g/L，这么高盐分废水进入生化系统，势必会导致生物中毒，因此，本发明对煤气冷凝水及软化站除盐水进行选择性分质零排，即先采用电导率实时检测，对大于10000μS/cm(优选为大于12000μS/cm)的水进行分质，并经预处理及膜浓缩分盐后分别参与高值化回收黄钠铁矾和协同洗灰。
在本发明中，含高浓度盐分的煤气冷凝水和软化站除盐水与除盐水站浓盐水混合后，通过预处理+膜浓缩分盐，最终可得到含高浓度硫酸根的高压纳滤浓水和含高浓度氯离子的高压反渗透浓水。纳滤浓水一般采用蒸发结晶+冷冻的方式回收硫酸钠。但该工艺存在能耗高、硫酸钠附加值低的不足。考虑到冷轧漂洗水中含有大量的三价铁，而铁、硫酸根会与钠发生反应，形成黄钠铁矾。加上冷轧漂洗水为强酸性废水，可为本反应的发生提供得天独厚的条件。因此，利用蒸发系统(湿法脱硫废水蒸发浓缩系统和高盐废水逆流蒸发稀盐系统)的余热蒸汽将混合废水(高压纳滤浓水与冷轧漂洗废水混合)加热至80～100℃，实现纳滤浓水硫酸根的高值化回收，同时消纳冷轧漂洗水。一般地，还可通过添加可溶性铁盐(优选为氯化铁)调节混合废水中铁离子与硫酸根离子的摩尔比为1:0.4-0.8(优选为1:0.5-0.7)，进而促进反应的进行。
在本发明中，高压反渗透浓水主要由氯化钠组成，研究表明，采用该高压反渗透浓水参与高盐固废灰的水洗可降低洗灰水的碱度，使其趋近于中性。因此，本发明采用高压反渗透浓水与其他流程的酸性废水混合进行协同洗灰(高盐固废灰)处理，有利于改善洗灰废水的水质。一般地，当脱硫废水主要为湿法脱硫废水时，将其通过浓缩(一般浓缩3-6倍)后再进行洗灰，由于浓缩后的湿法脱硫废水具有较强的酸性，与高压反渗透浓水进行混合后，一方面可降低洗灰水的溶液，使洗灰水变为弱酸性，从而防止形成稳定的[TlCl 4 -]。另一方面，由于浓缩后的湿法脱硫废水含有大量亚硫酸根，其加入后，会使铊被弱还原，而破坏络合体，有利于铊的去除，从而实现铊的源头抑制。而当脱硫废水主要为活性炭法废水时，同理，由于活性炭法废水具有较强的酸性，采用其洗灰时，一方面可降低洗灰水的溶液，使洗灰水变为酸性，从而防止形成稳定的[TlCl 4 -]。另一方面，由于酸性洗涤废水含有硫代硫酸根，其加入后，也会利于铊的去除。因此，通过将高压反渗透浓水、脱硫废水(湿法脱硫废水或活性炭法废水)与高盐固废灰协同处置可以大幅的改善洗灰水的水质，降低污染物的溶出。且高压反渗透浓水、脱硫废水主要组成与洗灰水类似，协同处置可大幅降低高盐固废耗水量。
在本发明中，根据研究表明，因为钢铁厂原料和反应特性，产生的湿法/干法脱硫废水、煤气冷凝水、软化站除盐水及高盐固废灰中均有不同浓度的氨氮，其最终会在洗灰水中富集，从而影响回收的产品盐品质。针对氨氮的去除，本发明提供了两段脱氨的新技术。第一段：湿法脱硫废水浓缩后的氨氮浓度会达到10～30g/L，针对高浓度氨氮的沉淀去除，可以通过亚硫酸亚铁铵法和磷酸铵镁法进行去除。其中亚硫酸亚铁铵法为在溶液pH为5～8的条件下，氨氮会与亚铁和亚硫酸根结合，形成亚硫酸亚铁铵沉淀。第二段：由于冷轧漂洗水中含有大量的三价铁。考虑到铁、硫酸根会与钾、钠、氨氮发生反应，形成黄钾铁矾、黄钠铁矾、黄铵铁矾。因此，可向洗灰废水中加入冷轧漂洗废水，并利用蒸发系统的余热将废水加热至 80～100℃，实现废水中氨氮的去除。同理，在第二段脱氨氮的过程中，可以通过额外添加亚铁离子和亚硫酸根离子的方式促进氨氮沉淀反应的进行。
在本发明中，由于高盐固废灰为高钾低钠灰，其常规水洗溶液中钾钠比一般大于4(优选大于5)。根据钾钠变温分盐的原理，其适合顺流蒸发，即通过变温蒸发分钾钠盐相图分析，高钾低钠的溶液通过蒸发浓缩后，势必会先析出钾盐，因此针对高盐固废灰洗灰水的分盐方式，一般为顺流蒸发。即溶液在蒸发过程为逐步降温的过程。在多效出口，先排出钾盐。这种蒸发方式会导致污染物随着钾的析出而析出，会降低钾品质，同时后续钠盐析出需要二段蒸发，投资增大，能耗大。因此，本发明通过引入高压渗透浓水(主要含氯化钠)，与脱硫废水(含钠)作为高盐固废灰水洗用水，进而可使得洗灰废水中钾钠含量比接近1:1，在这种条件下，根据相图模拟及实验验证，其适合逆流蒸发，即通过浓缩后，优先分离出钠盐，可使得蒸发工艺可调整为逆流蒸发，即在一效的出口，先排出钠盐。然后再通过降温冷却析出钾盐，这种蒸发方式使得残留的污染物随着钠的析出而析出(由于逆流蒸发只经过一段浓缩，其污染物主要进入到钠盐)，不会进入到钾盐中，有利于提高钾的品质。同时整个蒸发仅利用一段蒸发系统，可适用于不同蒸发量的变化，对原料的适用性更强，且投资较低。
在本发明中，还通过铁碳微电解进行除杂(铁碳反应的时间应不低于20min)，由于Tl 3+比Tl +更容易去除，一般来说，可通过氧化进行预处理。铁碳微电解具有协同除重和氧化的作用。通过铁碳后，可将Tl变为更加易于去除的形态。同时，洗灰水中的大量金属离子会被铁单质置换，进而实现去除，并在溶液中产生大量的亚铁和三价铁。另外，铁碳有还利于废水中氟离子的高效去除。进一步地，由于酸性烟气洗涤废水中还含有亚硫酸根，而铁碳会释放出亚铁。采用碱(例如氢氧化钠)调节洗灰废水至弱碱性，当调节溶液至弱碱后，氨氮会与亚硫酸根、亚铁发生快速反应，形成亚硫酸亚铁铵沉淀，从而实现氨氮的深度脱除。同时，在弱碱条件下，可实现三价铁及部分钙镁离子的去除。加入碳酸钠目的为除钙镁。加入硫化钠和重捕剂的目的为实现微量重金属的深度去除。
与现有技术相比较，本发的有益技术效果如下：
1：本发明将钢厂高盐废水进行分质分级处理，主要处置对象包括软化站除盐水、煤气冷凝水、除盐水站浓盐水、冷轧漂洗废水、脱硫废水等。相对传统零排放技术，处理对象更加完善全面。
2：本发明将高盐废水与高盐固废灰协同处置，大幅降低洗灰水中污染物含量，从而减少了后续废水处理成本，同时减少废水使用量，极大的降低处置成本。
3：本发明针对硫酸盐附加值低的特点，基于冷轧漂洗水中酸性和含有大量三价铁的特征， 通过铁矾法实现高压纳滤浓水中硫酸根的高值化回收。同时还基于冷轧漂洗水的这一特征，可实现洗灰水中氨氮、硫酸根的去除，可提高盐产品纯度，具有成本低，操作简单的优点。
4：本发明结合高盐固废与废水协同洗灰产生的洗灰水特征分析，基于铁碳微电解预处理，实现协同氧化铊、除重处理，大幅的减少了废水的处理流程，同时针对个废水的特性和工艺设计，实现了多源废水的协同资源化处理，实现了废水的零排放。
5：本发明回收的钾盐品质较高，一方面氨氮、铊、硫酸根等污染物通过废水预处理可低成本的去除，防止了污染钾盐。另外一方面，通过引入含钠废水协同洗灰处理，使得洗灰水中的钾钠比发生变化，进而适合采用逆流蒸发，可避免污染物进入到钾盐，从而提高盐产品的价值。
附图说明
图1为本发明钢铁厂多源废水协同处理零排放的流程大纲图。
图2为本发明钢铁厂多源废水协同处理零排放的流程详解图。
具体实施方式
下面对本发明的技术方案进行举例说明，本发明请求保护的范围包括但不限于以下实施例。
实施例1
一种钢铁厂多源废水协同处理零排放的工艺，该工艺具体包括如下步骤：
1)将高质废水与除盐水站浓盐水进行均质混合后获得混合浓盐废水。
2)先将步骤1)获得的混合浓盐废水投加除重、除硬药剂及脱硅处理后，然后再依次进行二级反渗透处理和高压纳滤处理，获得高压纳滤浓水和高压纳滤淡水。
3)将步骤2)获得的高压纳滤浓水与冷轧漂洗废水混合获得混合酸性废水，然后加热混合酸性废水进行沉淀反应，反应完成后进行固液分离，获得黄钠铁矾和残液。黄钠铁矾厂内综合处置，残液返回步骤1)参与均质处理。
4)将步骤2)获得的高压纳滤淡水进行高压反渗透处理，获得高压反渗透浓水和回用淡水。将高压反渗透浓水用于高盐固废灰的水洗处理，回用淡水循环至钢铁厂任意需水工序。
实施例2
重复实施例1，只是在步骤1)中，所述高质废水为电导率大于10000μS/cm的软化站除盐水和煤气冷凝水。
实施例3
重复实施例1，只是在步骤1)中，所述高质废水为电导率大于12000μS/cm的软化站除 盐水和煤气冷凝水。
实施例4
重复实施例3，只是在步骤3)中，所述冷轧漂洗废水为冷轧带钢酸洗工艺漂洗段产生的含有FeCl 3和HCl的pH＜2.5的废水。
实施例5
重复实施例3，只是在步骤3)中，所述混合酸性废水的pH为3。所述加热混合酸性废水进行沉淀反应具体为加热混合酸性废水至90℃反应4h。
实施例6
重复实施例5，只是在步骤3)中，在加热混合酸性废水进行沉淀反应前，还通过添加可氯化铁调节混合酸性废水中铁离子与硫酸根离子的摩尔比为3:2。
实施例7
重复实施例6，只是在步骤4)中，所述将高压反渗透浓水用于高盐固废灰的水洗处理具体为：
4a)将高压反渗透浓水与脱硫废水混合后对高盐固废灰进行水洗，固液分离后获得滤饼和洗灰废水，滤饼厂内综合处置，洗灰废水进入下一工序。
4b)采用脱硫废水或冷轧漂洗废水调节洗灰废水至酸性，然后加热洗灰废水进行沉淀反应，反应完成后，固液分离获得除杂废水和渣相，渣相厂内综合处置，除杂废水进入下一工序。
4c)先将除杂废水进行铁碳微电解处理。然后向微电解处理后的除杂废水中加入混合药剂，调节除杂废水至碱性并对除杂废水进行除重除硬沉淀反应，固液分离后获得高盐废水和残渣，残渣厂内综合处置，高盐废水进入下一工序。
4d)先加热高盐废水，进行浓缩析晶，固液分离后获得氯化钠和一次滤液。然后再将一次滤液进行冷却析晶，固液分离后获得氯化钾和二次滤液。最后将二次滤液与高盐废水混合后循环进行加热析盐处理。
实施例8
重复实施例7，只是在步骤4a)中，所述脱硫废水是通过先将湿法脱硫废水进行蒸发浓缩5倍后得到含悬浮物废水，然后再向含悬浮物废水中加入氯化亚铁和亚硫酸钠进行沉淀处理，最后经固液分离后得到的废水。
实施例9
重复实施例8，只是将湿法脱硫废水进行蒸发浓缩具体为：第一级蒸发浓缩的蒸发温度为80～100℃，真空度为-40～-5kPa。第二级蒸发浓缩的蒸发温度为50～80℃，真空度为 -70～-40kPa。第三级蒸发浓缩的蒸发温度为30～50℃，真空度为-100～-70kPa。
实施例10
重复实施例9，只是将湿法脱硫废水进行蒸发浓缩产生的热蒸汽用于加热混合酸性废水。
实施例11
重复实施例10，只是在步骤4b)中，所述调节洗灰废水至酸性为调节洗灰废水的pH为3，所述加热洗灰废水进行沉淀反应具体为加热洗灰废水至90℃反应4h。
实施例12
重复实施例11，只是在步骤4b)中，在加热洗灰废水进行沉淀反应前，还通过添加可溶性铁盐调节洗灰废水中铁离子、硫酸根离子、氨氮的摩尔比为3:2:1。
实施例13
重复实施例12，只是在步骤4c)中，所述混合药剂为氢氧化钠和氢氧化钾、碳酸钠和碳酸钾、硫化钠和硫酸钾、二硫代氨基甲酸盐类重捕剂共同组成。其中：氢氧化钠和氢氧化钾的加入量为使得除杂废水的pH为8。所述碳酸钠和碳酸钾的加入量为7g/L。所述硫化钠和硫化钾的加入量为3.5g/L。所述二硫代氨基甲酸盐类重捕剂的加入量为3.6g/L。
实施例14
重复实施例13，只是所述高盐固废灰包括烧结电场灰。
实施例15
重复实施例14，只是所述高盐固废灰的水洗为三级逆流水洗处理。具体为：先将高盐固废灰进行一级水洗，并通过一级压滤脱水，获得一级滤液和一级滤渣，一级滤液为洗灰废水。一级滤渣进入二级水洗，二级水洗水源为三级滤液和高压反渗透浓水以及脱硫废水，二级水洗后通过二级压滤脱水，获得二级滤液和二级滤渣，二级滤液排至一级水洗循环使用。二级滤渣进入三级水洗，三级水洗水源为工业水，三级水洗后通过三级压滤脱水，获得三级滤液和三级滤渣，三级滤液排至二级水洗循环使用，三级滤渣在厂内综合处置。
实施例16
重复实施例15，只是在步骤4d)中，采用3级多效逆流蒸发装置对高盐废水进行处理。所述加热高盐废水为加热高盐废水至95℃。所述一次滤液进行冷却为采用闪蒸或换热的方式降温至60℃以下。
实施例17
重复实施例16，只是将多效逆流蒸发装置产生的热蒸汽用于加热洗灰废水。
实施例18
重复实施例17，只是在步骤4c)中，除杂废水进行铁碳微电解处理的时长不低于20min。
实施例19
重复实施例18，只是在步骤4c)中，除杂废水中加入混合药剂后，对除杂废水进行除重除硬沉淀反应的时长不低于10min。
应用实施例1
采用实施例6所述工艺对钢铁厂软化站除盐废水、煤气冷凝水、除盐水站浓盐水以及冷轧漂洗废水进行协同资源化处理：
分别对软化站除盐水、煤气冷凝水进行电导率检测，并将电导率大于12000μS/cm的高质软化站除盐水和高质煤气冷凝水混合获得高质废水；对于电导率低于12000μS/cm的低质软化站除盐水和低质煤气冷凝水送进行常规生化处理即可。
将高质废水和除盐水站浓盐水在均质池中搅拌混合进行均质化；然后向均质池中加入除重药剂(硫化钠)、除硬药剂(碳酸钠或碳酸钾)以及脱硅药剂(氯化铁)进行除重、除硬以及脱硅处理；固液分离后，将滤液依次进行二级反渗透处理和高压纳滤处理，获得高压纳滤浓水和高压纳滤淡水；高压纳滤淡水再经高压反渗透处理后获得可循环使用的回用淡水和用于高盐固废灰水洗用的高压反渗透浓水；
向高压纳滤浓水中加入冷轧漂洗废水，并使得混合酸性废水的pH为3；然后采用热蒸汽加热混合酸性废水至90℃反应4h；反应完成后，固液分离获得高纯度黄钠铁矾，滤液返回均质池进行循环处理。所得黄钠铁矾运至焦化废水氧化处理环节，作为Fenton氧化剂催化降解难降解有机污染物。
应用实施例2
采用实施例18所述工艺对钢铁厂多源废水协同处理零排放及协同处理高盐固废灰：
先将应用实施例1获得的高压反渗透浓水和部分活性炭法烟气洗涤废水混合获得酸性混合水，然后采用酸性混合水对100kg高盐固废灰(烧结电厂灰和高炉布袋灰的混合灰，检测到混合灰中钾含量约为27.6％，钠含量约为5.1％)进行三级逆流水洗，压滤后获得滤饼和约350L洗灰废水(其中钾钠含量比约为5.7)，将滤饼返回烧结工序配料处置；然后先向洗灰废水中加入冷轧漂洗废水调节洗灰废水的pH为3，同时向洗灰废水中加入氯化铁，使得洗灰废水中铁离子、硫酸根离子、氨氮的摩尔比接近3:2:1；然后向洗灰废水中通入热蒸汽加热洗灰废水至90℃持续反应4h，反应完成后，进行压滤获得除杂废水和渣相，渣相运至烧结配料，可利用渣相中的铵资源实现烧结氮氧化物源头减量，以及渣中的硫酸根可通过转化为二氧化硫而被消纳；
采用氢氧化钠调节除杂废水的pH为3，调节后的除杂废水通入到铁碳微电解反应器中处理40min，期间对铁碳微电解反应器定期进行曝气反冲。微电解处理完成后，再次加入氢氧 化钠调节除杂废水的pH为8，然后再依次加入2.45kg碳酸钠、1.23kg硫化钠、1.26kg二硫代氨基甲酸盐类重捕剂，搅拌混合反应30min；压滤后，获得高盐废水(测得高盐废水中钾钠含量比约为1.1:1)。在三级多效逆流蒸发器中进行浓缩析晶(第一级蒸发浓缩的蒸发温度为95℃，真空度为-20kPa。第二级蒸发浓缩的蒸发温度为75℃，真空度为-60kPa。第三级蒸发浓缩的蒸发温度为40℃，真空度为-90kPa)；期间通过离心分离获得氯化钠和一次滤液。将一次滤液冷却至60℃以下析出晶体，离心分离获得氯化钾粗品和二次滤液。二次滤液返回至逆流蒸发入口进行循环蒸发处理；将氯化钾粗品采用饱和氯化钾溶液淘洗多次，离心分离，获得高纯氯化钾(纯度为99.95％)。

Claims (10)

  1. 一种钢铁厂多源废水协同处理零排放的工艺，其特征在于：该工艺具体包括如下步骤：
    1)将高质废水与除盐水站浓盐水进行均质混合后获得混合浓盐废水；
    2)先向步骤1)获得的混合浓盐废水投加除重、除硬药剂及脱硅处理后；再依次进行二级反渗透处理和高压纳滤处理，获得高压纳滤浓水和高压纳滤淡水；
    3)将步骤2)获得的高压纳滤浓水与冷轧漂洗废水混合获得混合酸性废水，然后加热混合酸性废水进行沉淀反应，反应完成后进行固液分离，获得黄钠铁矾和残液；黄钠铁矾厂内综合处置，残液返回步骤1)参与均质处理；
    4)将步骤2)获得的高压纳滤淡水进行高压反渗透处理，获得高压反渗透浓水和回用淡水；将高压反渗透浓水用于高盐固废灰的水洗处理，回用淡水循环至钢铁厂任意需水工序。
  2. 根据权利要求1所述的工艺，其特征在于：在步骤1)中，所述高质废水为电导率大于10000μS/cm的软化站除盐水和/或煤气冷凝水，优选为电导率大于12000μS/cm的软化站除盐水和/或煤气冷凝水；和/或
    在步骤1)中，所述除盐水站浓盐水为钢铁厂在对循环水采用反渗透除盐时产生的含有硫酸根和氯离子的中性浓水；
    在步骤3)中，所述冷轧漂洗废水为冷轧带钢酸洗工艺漂洗段产生的含有FeCl 3和HCl的pH＜2.5的废水，优选为pH＜2的废水。
  3. 根据权利要求1或2所述的工艺，其特征在于：在步骤3)中，所述混合酸性废水的pH为2-4，优选pH为2-3；所述加热混合酸性废水进行沉淀反应具体为加热混合酸性废水至80-100℃反应1-8h，优选为加热至85-95℃反应2-5h；
    作为优选，在加热混合酸性废水进行沉淀反应前，还通过添加可溶性铁盐(优选为氯化铁)调节混合酸性废水中铁离子与硫酸根离子的摩尔比为1:0.4-0.8，优选为1:0.5-0.7。
  4. 根据权利要求1-3中任一项所述的工艺，其特征在于：在步骤4)中，所述将高压反渗透浓水用于高盐固废灰的水洗处理具体为：
    4a)将高压反渗透浓水与脱硫废水混合后对高盐固废灰进行水洗，固液分离后获得滤饼和洗灰废水，滤饼厂内综合处置，洗灰废水进入下一工序；
    4b)采用脱硫废水或冷轧漂洗废水调节洗灰废水至酸性，然后加热洗灰废水进行沉淀反应，反应完成后，固液分离获得除杂废水和渣相，渣相厂内综合处置，除杂废水进入下一工序；
    4c)先将除杂废水进行铁碳微电解处理；然后向微电解处理后的除杂废水中加入混合药剂，调节除杂废水至碱性并对除杂废水进行除重除硬沉淀反应，固液分离后获得高盐废水和残渣，残渣厂内综合处置，高盐废水进入下一工序；
    4d)先加热高盐废水，进行浓缩析晶，固液分离后获得氯化钠和一次滤液；然后再将一次滤液进行冷却析晶，固液分离后获得氯化钾和二次滤液；最后将二次滤液与高盐废水混合后循环进行加热析盐处理。
  5. 根据权利要求4所述的工艺，其特征在于：在步骤4a)中，所述脱硫废水是通过先将湿法脱硫废水进行蒸发浓缩得到含悬浮物废水，然后再向含悬浮物废水中加入氨氮沉淀剂进行沉淀处理，最后经固液分离后得到的；所述蒸发浓缩为采用多级蒸发浓缩设备将湿法脱硫废水浓缩3-6倍；所述氨氮沉淀剂为可溶性亚铁盐和可溶性亚硫酸盐；所述湿法脱硫废水为用石灰石/石膏法处理烟气时产生的废水；
    或者，所述脱硫废水为活性炭法废水进行分流处理后的废水，具体为将1/4～1/2的活性炭法废水用于与高压反渗透浓水混合对高盐固废灰进行水洗，剩余部分废水则用于调节洗灰废水至酸性；所述活性炭法废水为对活性炭吸附法解析气体洗涤产生的酸性烟气洗涤废水。
  6. 根据权利要求5所述的工艺，其特征在于：将湿法脱硫废水进行蒸发浓缩为蒸发温度逐级降低、而真空度逐级提高的多级蒸发浓缩；优选为：第一级蒸发浓缩的蒸发温度为80～100℃，真空度为-40～-5kPa；第二级蒸发浓缩的蒸发温度为50～80℃，真空度为-70～-40kPa；第三级蒸发浓缩的蒸发温度为30～50℃，真空度为-100～-70kPa；和/或
    所述可溶性亚铁盐为氯化亚铁、硫酸亚铁、单质铁粉中的一种或多种；所述可溶性亚硫酸盐为亚硫酸钠、亚硫酸氢钠、亚硫酸钾中的一种或多种；优选，可溶性亚铁盐和可溶性亚硫酸盐的添加顺序为顺次加入；
    作为优选，蒸发浓缩产生的热蒸汽用于步骤3)中加热混合酸性废水和/或用于步骤4b)中加热洗灰废水。
  7. 根据权利要求4-6中任一项所述的工艺，其特征在于：在步骤4b)中，所述调节洗灰废水至酸性为调节洗灰废水的pH为2-4，优选pH为2-3；所述加热洗灰废水进行沉淀反应具体为加热洗灰废水至80-100℃反应1-8h，优选为加热至85-95℃反应2-5h；
    作为优选，在加热洗灰废水进行沉淀反应前，还通过添加可溶性铁盐调节洗灰废水中铁离子、硫酸根离子、氨氮的摩尔比为1:0.4-0.8:0.2-0.6，优选为1:0.5-0.7:0.3-0.5。
  8. 根据权利要求4-7中任一项所述的工艺，其特征在于：在步骤4c)中，在将除杂废水进行铁碳微电解前需采用碱调节除杂废水的pH为3-5，优选为3.5-4；优选，所述碱为氢氧化钠和/或氢氧化钾；和/或
    所述混合药剂为氢氧化钠和/或氢氧化钾、碳酸钠和/或碳酸钾、硫化钠和/或硫酸钾、重捕剂(优选为黄原酸酯类重捕剂或二硫代氨基甲酸盐类重捕剂)共同组成；其中：氢氧化钠和/或氢氧化钾的加入量为使得除杂废水的pH为7-9，优选为7.5-8；所述碳酸钠和/或碳酸钾 的加入量为3-10g/L，优选为4-8g/L；所述硫化钠和/或硫化钾的加入量为1-7g/L，优选为1.5-6g/L；所述重捕剂的加入量为1-8g/L，优选为2-5g/L。
  9. 根据权利要求4-8中任一项所述的工艺，其特征在于：所述高盐固废灰包括烧结电场灰、高炉布袋灰、回转窑表冷灰、垃圾焚烧飞灰中的一种或多种，优选烧结电场灰；和/或
    所述高盐固废灰的水洗为三级逆流水洗处理；具体为：先将高盐固废灰进行一级水洗，并通过一级压滤脱水，获得一级滤液和一级滤渣，一级滤液为洗灰废水；一级滤渣进入二级水洗，二级水洗水源为三级滤液和高压反渗透浓水以及脱硫废水，二级水洗后通过二级压滤脱水，获得二级滤液和二级滤渣，二级滤液排至一级水洗循环使用；二级滤渣进入三级水洗，三级水洗水源为工业水，三级水洗后通过三级压滤脱水，获得三级滤液和三级滤渣，三级滤液排至二级水洗循环使用，三级滤渣在厂内综合处置。
  10. 根据权利要求9所述的工艺，其特征在于：在步骤4d)中，采用多效逆流蒸发装置对高盐废水进行处理，所述多效逆流蒸发装置的级数为2-6级，优选为3-4级；所述加热高盐废水为加热高盐废水至80-100℃，优选为90-95℃；所述一次滤液进行冷却为采用闪蒸或换热的方式降温至60℃以下，优选为20-55℃；
    作为优选，多效逆流蒸发装置产生的热蒸汽用于步骤3)中加热混合酸性废水和/或用于步骤4b)中加热洗灰废水。
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