Iron and steel enterprise high-salt wastewater and high-salt solid waste collaborative resource utilization system

Abstract

The invention provides an iron and steel enterprise high-salt wastewater and high-salt solid waste collaborative resource utilization system which is characterized in that firstly, non-magnetic fly ash in sintering machine head fly ash is screened out through a pretreatment module; carrying out multi-stage washing and filter pressing treatment on slurry obtained by mixing the non-magnetic dedusting ash, the blast furnace gas condensate water and the strong brine of the desalting water station through a multi-stage washing and filter pressing module to obtain multi-stage washing ash and multi-stage ash washing brine; finally, carrying out purification and separation treatment on the multi-stage ash washing brine through a purification and separation module to obtain industrial-grade NaCl, industrial-grade KCl and devitrification mother liquor; according to the method, non-magnetic fly ash, blast furnace gas condensate water and strong brine of a desalting water station are used as raw materials, the problem of enrichment of alkali metal and chloride ions in a sintering machine system is solved through a series of co-processing technologies, and meanwhile industrial-grade NaCl and industrial-grade KCl are extracted from the blast furnace gas condensate water and the strong brine of the desalting water station. Therefore, the resource utilization rate is improved, and benefits are increased for iron and steel enterprises.

Description

Technical Field

[0001] The present invention relates to the technical field of coking wastewater treatment, and in particular to a coordinated resource utilization system for high-salt wastewater and high-salt solid waste in a steel enterprise. Background Art

[0002] Iron and steel enterprises are high-energy-consuming and high-polluting enterprises, which produce a large amount of high-salt wastewater and high-salt solid waste. High-salt wastewater such as blast furnace gas condensate and desalted water station concentrated brine is mainly used for blast furnace slag flushing. However, the high concentration of chloride ions in the high-salt wastewater affects the normal operation of the blast furnace slag flushing equipment and the quality of the slag, making it difficult to dispose of the high-salt wastewater.

[0003] High-salt solid waste such as sintering machine head ash is mainly recycled directly, but the machine head ash contains a large amount of alkali metals and chloride ions. Direct recycling will cause the enrichment of alkali metals and chloride ions in the sintering machine, causing "grate bars" in the sintering machine, reducing the output and quality of sintered ore. When low-quality sintered ore enters the blast furnace system, it will cause the blast furnace to be corroded, seriously affecting the service life of the blast furnace.

[0004] Therefore, there is an urgent need for a coordinated resource utilization system for high-salt wastewater and high-salt solid waste in steel enterprises to solve the problem of effective disposal of high-salt wastewater and high-salt solid waste in steel enterprises. Summary of the invention

[0005] In view of this, the present application provides a coordinated resource utilization system for high-salt wastewater and high-salt solid waste in steel enterprises to solve the technical problem that existing steel enterprises generate a large amount of high-salt wastewater and high-salt solid waste which cannot be effectively disposed of.

[0006] The object of the present invention is achieved through the following technical solutions: In order to achieve the above technical objectives, this application adopts the following technical solutions: The present invention provides a high-salt wastewater and high-salt solid waste collaborative resource utilization system for a steel enterprise, comprising a pretreatment module, a multi-stage water washing and filter pressing module and a purification and separation module connected in sequence; Among them, the pretreatment module is used to screen out non-magnetic dust removal ash in the sintering machine head dust removal ash; the multi-stage water washing filter press module is used to perform multi-stage water washing filter press treatment on the slurry mixed with non-magnetic dust removal ash, blast furnace gas condensate and concentrated brine from the desalting water station to obtain multi-stage water washed ash and multi-stage ash washing brine, and return the multi-stage water washed ash to the sintering machine; the purification and separation module is used to purify and separate the multi-stage ash washing brine to obtain industrial-grade NaCl, industrial-grade KCl and crystallization mother liquor.

[0007] Preferably, the sintering machine head dust removal ash includes No. 1 electric field dust removal ash, No. 2 electric field dust removal ash, No. 3 electric field dust removal ash and No. 4 electric field dust removal ash, and the pretreatment module is used to perform magnetic separation treatment on No. 1 electric field dust removal ash to obtain magnetic particle ore and the first dust removal ash; Among them, the non-magnetic dust removal ash includes the first dust removal ash, No. 2 electric field dust removal ash, No. 3 electric field dust removal ash and No. 4 electric field dust removal ash.

[0008] Preferably, the pretreatment module is a dry magnetic separation device with a magnetic field strength of 500-3000 Gs.

[0009] Preferably, the multi-stage water washing and filter pressing module comprises a primary alkaline water washing unit, a primary filter pressing unit, a secondary water washing unit, a secondary filter pressing unit, a tertiary water washing unit and a tertiary filter pressing unit connected in sequence; Among them, the primary alkaline water washing unit is used to perform primary alkaline water washing treatment on the first slurry obtained by mixing the first dust removal ash, blast furnace gas condensate and concentrated brine from the desalting water station to obtain the first mixed slurry; the primary filter press unit is used to perform primary filter press treatment on the first mixed slurry to obtain primary water-washed ash and primary ash-washing brine after solid-liquid separation, and return the primary water-washed ash to the sintering machine; the secondary water washing unit is used to perform secondary water washing treatment on the second slurry obtained by mixing the No. 2 electric field dust removal ash and the primary ash-washing brine to obtain the second mixed slurry; the secondary water washing unit is used to perform secondary water washing treatment on the second slurry obtained by mixing the No. 2 electric field dust removal ash and the primary ash-washing brine to obtain the second mixed slurry; The first-stage filter press unit is used to perform a second-stage filter press treatment on the second mixed slurry, and obtain second-stage water-washed ash and second-stage ash-washing brine after solid-liquid separation, and return the second-stage water-washed ash to the sintering machine; the tertiary water washing unit is used to perform a tertiary water washing treatment on the third slurry mixed with No. 3 electric field dust removal ash, No. 4 electric field dust removal ash and second-stage ash-washing brine to obtain a third mixed slurry; the tertiary filter press unit is used to perform a tertiary filter press treatment on the third mixed slurry, and obtain third-stage water-washed ash and third-stage ash-washing brine after solid-liquid separation, and return the tertiary water-washed ash to the sintering machine.

[0010] Preferably, the water-cement ratio in the primary alkaline water washing unit is (1-3):1, the reaction pH value is 7-9, and the reaction time is 0.5-1.5h; the reaction time in the secondary water washing unit is 0.5-1.5h; and the reaction time in the tertiary water washing unit is 0.5-1.5h.

[0011] Preferably, the purification and separation module comprises a multi-effect purification treatment submodule connected to the three-stage filter press unit and a salt separation and crystallization submodule connected to the multi-effect purification treatment submodule; Among them, the multi-effect purification treatment submodule is used to perform multi-effect purification treatment on the tertiary ash washing brine to obtain crystallization mother liquor, multi-stage sedimentation sludge and condensed water; the salt separation and crystallization submodule is used to perform separation and crystallization treatment on the crystallization mother liquor to obtain industrial-grade NaCl, industrial-grade KCl and crystallization mother liquor.

[0012] Preferably, the multi-effect purification treatment submodule comprises an ultrasonic electrocatalytic oxidation unit, a primary desulfurization and magnesium and fluorine removal unit, a secondary desulfurization and calcium and weight removal unit, and a triple-effect countercurrent evaporation unit connected in sequence; Among them, the ultrasonic electrocatalytic oxidation unit is used to ultrasonically oxidize the tertiary ash washing brine to obtain ultrasonic oxidized brine; the primary desulfurization and magnesium removal and fluorine removal unit is used to remove SO in the ultrasonic oxidized brine. 4 2- Perform a rough removal and simultaneously ultrasonically oxidize the Mg in the brine 2+ and F - After removal, the first-level impurity-removing brine and the first-level sedimentation sludge are obtained. The reagent added to the first-level desulfurization, magnesium removal and fluorine removal unit is Ca(OH) 2 , PAC and PAM; secondary desulfurization and decalcification and deweighting units are used to remove SO in the primary impurity removal brine. 4 2- Carry out secondary fine removal, and at the same time remove Ca in the primary impurity removal brine 2+ After the removal of heavy metal ions, secondary impurity removal brine and secondary sedimentation sludge are obtained. The reagent added to the secondary desulfurization and calcium removal and weight removal unit is Na 2 CO 3 、Na 2 S, BaCl 2 , PAC and PAM; the three-effect countercurrent evaporation unit is used to perform countercurrent step-by-step temperature evaporation on the secondary impurity-removing brine to obtain crystallization mother liquor and condensed water.

[0013] Preferably, in the ultrasonic electrocatalytic oxidation unit: the frequency of the ultrasonic device is 50-500 kHz, the catalyst is TiO 2 The catalyst dosage is 100-300 mg / L, the pH value is 6-7; the reaction time of the reaction zone of the primary desulfurization and magnesium and fluorine removal units is 0.4-0.6 h; the reaction time of the reaction zone of the secondary desulfurization and calcium and weight removal units is 0.3-0.7 h; the temperature of the triple-effect countercurrent evaporation unit is 70-100 °C.

[0014] Preferably, the salt separation and crystallization submodule comprises a sodium salt centrifugal separation unit, a freezing crystallization unit and a potassium salt centrifugal separation unit which are connected in sequence; Among them, the sodium salt centrifugal separation unit is used to obtain industrial-grade NaCl and centrifugal mother liquor after centrifugal treatment of the crystallization mother liquor; the frozen crystallization unit is used to obtain potassium salt mixed liquor after frozen crystallization treatment of the centrifugal mother liquor; the potassium salt centrifugal separation unit is used to obtain industrial-grade KCl and crystallization mother liquor after centrifugal treatment of the potassium salt mixed liquor, and the crystallization mother liquor is transported to the triple-effect countercurrent evaporation unit for internal reuse.

[0015] Preferably, the temperature of the freezing crystallization unit is 0-50°C.

[0016] Beneficial effect: The present invention provides a high-salt wastewater and high-salt solid waste collaborative resource utilization system for a steel enterprise, which first screens out non-magnetic dust removal ash in the sintering machine head dust removal ash through a pretreatment module, then performs multi-stage water washing and filter pressing treatment on a slurry obtained by mixing non-magnetic dust removal ash, blast furnace gas condensate and concentrated brine from a desalting water station through a multi-stage water washing and filter pressing module to obtain multi-stage water washing ash and multi-stage ash washing brine, and finally performs purification and separation treatment on the multi-stage ash washing brine through a purification and separation module to obtain industrial-grade NaCl, industrial-grade KCl and crystallization mother liquor; Ming uses non-magnetic dust ash screened by the pretreatment module, blast furnace gas condensate and concentrated brine from the desalting station as raw materials through a series of coordinated disposal technologies. On the one hand, the multi-stage water-washed ash after multi-stage water washing and filtration treatment is returned to the sintering machine for utilization, solving the problem of alkali metal and chloride ion enrichment in the sintering machine system. On the other hand, the multi-stage ash-washing brine extracted from blast furnace gas condensate and concentrated brine from the desalting station is purified and separated to obtain industrial-grade NaCl and industrial-grade KCl, thereby improving resource utilization and increasing benefits for steel companies. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A structural framework diagram of a coordinated resource utilization system for high-salt wastewater and high-salt solid waste in a steel enterprise provided in an embodiment of the present application; Figure 2 This is a process flow chart of the system for collaborative resource utilization of high-salt wastewater and high-salt solid waste from steel enterprises provided in Example 1 of the present application. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] This is aimed at the problem that existing steel enterprises generate large amounts of high-salt wastewater and high-salt solid waste which cannot be effectively disposed of.

[0020] The present invention uses blast furnace gas condensate, concentrated brine from a desalting station and sintering machine head ash as raw materials and uses a series of coordinated treatment technologies. On the one hand, the washed ash from which alkali metals and chloride ions have been removed is returned to the sintering machine for utilization, thereby solving the problem of alkali metal and chloride ion enrichment in the sintering machine system. On the other hand, salt is extracted from blast furnace gas condensate and concentrated brine from a desalting station and purified to generate condensed water, which is then reused in the industrial water system to improve the utilization rate of water resources. At the same time, the salt extracted from the above high-salt wastewater and high-salt solid waste is prepared into potassium chloride and sodium chloride products for sale, thereby improving the utilization rate of resources and increasing the benefits of steel enterprises.

[0021] The present invention solves the environmental protection pain points and difficulties of high-salt wastewater and high-salt solid waste in steel enterprises, and is of great significance to protecting the ecological environment and the high-quality sustainable development of production enterprises.

[0022] See also Figure 1 , Figure 1 A structural framework diagram of a system for collaborative resource utilization of high-salt wastewater and high-salt solid waste in a steel enterprise provided in an embodiment of the present application; wherein the system for collaborative resource utilization of high-salt wastewater and high-salt solid waste in a steel enterprise provided by the present invention comprises a pretreatment module, a multi-stage water washing and filter pressing module, and a purification and separation module connected in sequence; Among them, the pretreatment module is used to screen out non-magnetic dust removal ash in the sintering machine head dust removal ash; the multi-stage water washing filter press module is used to perform multi-stage water washing filter press treatment on the slurry mixed with non-magnetic dust removal ash, blast furnace gas condensate and concentrated brine from the desalting water station to obtain multi-stage water washed ash and multi-stage ash washing brine, and return the multi-stage water washed ash to the sintering machine; the purification and separation module is used to purify and separate the multi-stage ash washing brine to obtain industrial-grade NaCl, industrial-grade KCl and crystallization mother liquor.

[0023] In the embodiment of the present invention, sintering machine head dust removal refers to the dust removal process of the waste gas discharged from the sintering machine head in the sintering process of steel production. Sintering machine head dust removal usually adopts various dust removal equipment and technologies, such as electrostatic precipitator, bag filter, electric bag composite dust collector, etc., to separate the dust in the waste gas by physical or chemical methods, so that the purified waste gas can meet the environmental emission standards before being discharged, and the collected dust can be further processed or recycled.

[0024] Specifically, sintering machine head ash is generally set with a four-level electric field for dust removal, wherein the iron content of the sintering machine head ash decreases step by step with the increase of the electric field level, while the salt content increases step by step.

[0025] Preferably, the sintering machine head dust removal ash includes No. 1 electric field dust removal ash, No. 2 electric field dust removal ash, No. 3 electric field dust removal ash and No. 4 electric field dust removal ash, and the pretreatment module is used to perform magnetic separation treatment on No. 1 electric field dust removal ash to obtain magnetic particle ore and the first dust removal ash; Among them, the non-magnetic dust removal ash includes the first dust removal ash, No. 2 electric field dust removal ash, No. 3 electric field dust removal ash and No. 4 electric field dust removal ash.

[0026] Preferably, the pretreatment module is a dry magnetic separation device with a magnetic field strength of 500~3000Gs; this range of magnetic field strength can meet the magnetic separation requirements of different types of materials. For materials with weaker magnetism, effective separation can be performed at a lower magnetic field strength; while for materials with stronger magnetism, a higher magnetic field strength can ensure a more thorough separation effect.

[0027] In an embodiment of the present invention, the multi-stage water washing and filter pressing module comprises a primary alkaline water washing unit, a primary filter pressing unit, a secondary water washing unit, a secondary filter pressing unit, a tertiary water washing unit and a tertiary filter pressing unit connected in sequence; Among them, the primary alkaline water washing unit is used to perform primary alkaline water washing treatment on the first slurry obtained by mixing the first dust removal ash, blast furnace gas condensate and concentrated brine from the desalted water station to obtain the first mixed slurry.

[0028] Specifically, when a blast furnace is used to make iron, the blast furnace gas produced contains a large amount of water vapor. During the gas purification and transportation process, as the gas temperature gradually decreases, the water vapor condenses to form liquid water, namely, blast furnace gas condensate. The main components of blast furnace gas condensate include acidic substances, suspended matter and heavy metals.

[0029] Specifically, desalted water stations usually use reverse osmosis, ion exchange and other processes to remove impurities in water to produce desalted water that meets specific requirements. In this process, most of the salt and other impurities in the raw water are intercepted to form concentrated brine.

[0030] Specifically, NaOH is added to the primary alkaline water washing unit to adjust the alkali, and air stirring and mechanical stirring are used to perform the primary alkaline water washing reaction on the first slurry, and the first mixed slurry is obtained after the salt is dissolved in water. The main reaction equation is as follows: 4Fe 2+ +O 2 +2H 2 O→4Fe 3+ +4OH - ; Fe 3+ +3OH - →Fe(OH) 3 ↓.

[0031] Furthermore, the water-to-cement ratio in the primary alkaline water washing unit is (1-3):1, the reaction pH value is 7-9, and the reaction time is 0.5-1.5h; wherein, a reasonable water-to-cement ratio range can avoid excessive water use while ensuring the cleaning effect, thereby reducing the water load and cost of subsequent treatment; the pH value is controlled at 7-9, which is relatively mild, which can effectively remove impurities while avoiding the adverse effects of excessive alkalinity on equipment and subsequent treatment, such as corrosion of equipment and increased difficulty in treatment; the reaction time of 0.5-1.5h can ensure that the impurities in the ash have enough time to fully contact, dissolve and react with water.

[0032] In an embodiment of the present invention, the primary filter press unit is used to perform primary filter press treatment on the first mixed slurry, and primary water-washed ash and primary ash-washing brine are obtained after solid-liquid separation, and the primary water-washed ash is returned to the sintering machine.

[0033] In an embodiment of the present invention, the secondary water washing unit is used to perform secondary water washing treatment on the second slurry obtained by mixing the No. 2 electric field dust removal ash and the primary ash washing brine to obtain a second mixed slurry; wherein the reaction time in the secondary water washing unit is 0.5 to 1.5 hours.

[0034] In an embodiment of the present invention, the secondary filter press unit is used to perform secondary filter press treatment on the second mixed slurry, and secondary water-washed ash and secondary ash-washing brine are obtained after solid-liquid separation, and the secondary water-washed ash is returned to the sintering machine.

[0035] In an embodiment of the present invention, the tertiary water washing unit is used to perform tertiary water washing treatment on the third slurry obtained by mixing No. 3 electric field dust removal ash, No. 4 electric field dust removal ash and secondary ash washing brine to obtain a third mixed slurry; wherein the reaction time in the tertiary water washing unit is 0.5 to 1.5 hours.

[0036] In an embodiment of the present invention, the three-stage filter press unit is used to perform three-stage filter press treatment on the third mixed slurry, and after solid-liquid separation, three-stage water-washed ash and three-stage ash-washing brine are obtained, and the three-stage water-washed ash is returned to the sintering machine.

[0037] In the embodiment of the present invention, the purification and separation module includes a multi-effect purification treatment submodule connected to the three-stage filter press unit and a salt separation and crystallization submodule connected to the multi-effect purification treatment submodule; Among them, the multi-effect purification treatment submodule is used to perform multi-effect purification treatment on the tertiary ash washing brine to obtain crystallization mother liquor, multi-stage sedimentation sludge and condensed water; the salt separation and crystallization submodule is used to perform separation and crystallization treatment on the crystallization mother liquor to obtain industrial-grade NaCl, industrial-grade KCl and crystallization mother liquor.

[0038] Specifically, the multi-effect purification treatment submodule includes an ultrasonic electrocatalytic oxidation unit, a primary desulfurization and magnesium and fluorine removal unit, a secondary desulfurization and calcium and weight removal unit, and a three-effect countercurrent evaporation unit connected in sequence; Among them, the ultrasonic electrocatalytic oxidation unit is used to perform ultrasonic oxidation treatment on the tertiary ash washing brine to obtain ultrasonic oxidized brine.

[0039] Specifically, an ultrasonic generator, an electrochemical oxidation device and a catalyst are arranged in the ultrasonic catalytic oxidation unit to remove COD (Chemical Oxygen Demand) and NH 4 + On the one hand, the tertiary ash washing brine is cavitated and turbulently activated, and the treated ultrasonic oxidation brine is sent to the primary desulfurization and magnesium removal and defluorination unit. The main reaction equation in the ultrasonic catalytic oxidation unit is as follows: 2Cl - -2e - →Cl 2 ; Cl 2 +H 2 O → HCl + HClO; 2NH 4 + +3HClO→N 2 ↑+3H 2 O+5H + +3Cl - .

[0040] Preferably, in the ultrasonic electrocatalytic oxidation unit: the frequency of the ultrasonic device is 50-500 kHz, the catalyst is TiO 2 , the catalyst dosage is 100-300 mg / L, and the pH value is 6-7; ultrasonic waves can generate enough energy in this frequency range to cause cavitation effect in the solution. The cavitation effect can produce local high temperature, high pressure and strong shock waves, which helps to destroy the molecular structure of organic matter and promote the oxidation reaction; under certain conditions, TiO 2 It can absorb light energy to generate electron-hole pairs. These electrons and holes can react with dissolved oxygen and water molecules in water to produce active species such as hydroxyl free radicals with strong oxidizing properties, thereby effectively oxidizing and decomposing organic matter. Under neutral to weakly acidic conditions with a pH value of 6 to 7, TiO 2 The catalytic activity is relatively high. At this time, the charge state of the catalyst surface and the efficiency of generating active species are more suitable, which is conducive to the oxidation reaction.

[0041] In the embodiment of the present invention, the primary desulfurization and magnesium removal and fluorine removal unit is used to ultrasonically oxidize SO in the brine. 4 2- Perform a rough removal and simultaneously ultrasonically oxidize the Mg in the brine 2+ and F - After removal, primary impurity-removing brine and primary sedimentation sludge are obtained; the primary sedimentation sludge is dehydrated and transported for disposal, and the reaction time of the reaction zone of the primary desulfurization and magnesium removal and fluorine removal unit is 0.4-0.6h; wherein, a reaction zone, a coagulation zone and a sedimentation zone are set in the primary desulfurization and magnesium removal and fluorine removal unit, and Ca(OH) is added. 2 , PAC (Polyaluminium Chloride) and PAM (Polyacrylamide) for SO 4 2- Perform a rough removal to remove Mg 2+ and F - To remove, the main reaction equation is as follows: Ca 2+ +SO 4 2- →CaSO 4 ↓; Ca 2+ +2F - →CaF 2 ↓; Mg 2+ +2OH - →Mg(OH) 2 ↓.

[0042] In the embodiment of the present invention, the secondary desulfurization and decalcification and deweighting unit is used to remove SO in the primary impurity removal brine. 4 2- Carry out secondary fine removal, and at the same time remove Ca in the primary impurity removal brine 2+ After the removal of heavy metal ions, secondary impurity-removing brine and secondary sedimentation sludge are obtained; the secondary sedimentation sludge is dehydrated and transported out for disposal. The reaction time of the reaction zone of the secondary desulfurization and calcium and weight removal units is 0.3 to 0.7 hours.

[0043] Specifically, a reaction zone, a coagulation zone and a precipitation zone are set in the secondary desulfurization and decalcification and deweighting unit, and Na 2 CO 3 、Na 2 S, BaCl 2 , PAC and PAM, for SO 4 2- Perform secondary fine removal to remove Ca 2+ and heavy metal ions (such as Cu 2+ , Pb 2+ 、Zn 2+ ) is removed, and its main reaction equation is as follows: Ba 2+ +SO 4 2- →BaSO 4 ↓; Ca 2+ +CO 3 2+ →CaCO 3 ↓; Cu 2+ +S 2- →CuS↓; Pb 2+ +S 2- →PbS↓; Zn 2+ +S 2- →ZnS↓.

[0044] In an embodiment of the present invention, a triple-effect countercurrent evaporation unit is used to perform a countercurrent step-by-step temperature-rising evaporation treatment on the secondary impurity-removing brine to obtain a crystallization mother liquor and condensed water, and the temperature of the triple-effect countercurrent evaporation unit is 70-100°C; in the triple-effect countercurrent evaporation unit, a countercurrent step-by-step temperature-rising evaporation reaction is performed, NaCl is preferentially precipitated, and the evaporated water vapor is condensed to form condensed water for reuse, and the generated crystallization mother liquor is sent to the sodium salt centrifugal separation unit.

[0045] In an embodiment of the present invention, the salt separation and crystallization submodule includes a sodium salt centrifugal separation unit, a freezing crystallization unit and a potassium salt centrifugal separation unit which are connected in sequence.

[0046] Specifically, the sodium salt centrifugal separation unit is used to obtain industrial-grade NaCl and centrifugal mother liquor after centrifugal treatment of the crystallization mother liquor; in the sodium salt centrifugal separation unit, solid-liquid separation is completed by a centrifugal device, and the NaCl crystals are separated and sent to the sodium salt drying unit for dehydration and drying, and then dried into industrial-grade NaCl products for sale.

[0047] Specifically, the freezing crystallization unit is used to obtain a potassium salt mixed solution after freezing and crystallizing the centrifugal mother liquor; the freezing crystallization unit precipitates KCl in the centrifugal mother liquor by cooling, and sends the potassium salt mixed solution with precipitated KCl to the potassium salt centrifugal separation unit; wherein the temperature of the freezing crystallization unit is 0~50°C.

[0048] Specifically, after the potassium salt centrifugal separation unit completes the solid-liquid separation of the potassium salt mixed liquid through a centrifugal device, the KCl crystals are separated and sent to the potassium salt drying sub-unit for dehydration and drying, and then dried into industrial-grade KCl products for sale; at the same time, the potassium salt centrifugal separation unit transports the obtained crystallization mother liquor to the triple-effect countercurrent evaporation unit for internal reuse.

[0049] The technical solution of the present invention is now further described in conjunction with specific embodiments.

[0050] Embodiment 1: See also Figure 1 The high-salt wastewater and high-salt solid waste collaborative resource utilization system provided by the present invention comprises a pretreatment module, a multi-stage water washing and filter pressing module and a purification and separation module connected in sequence; Among them, the pretreatment module is used to screen out non-magnetic dust removal ash in the sintering machine head dust removal ash; the multi-stage water washing filter press module is used to perform multi-stage water washing filter press treatment on the slurry mixed with non-magnetic dust removal ash, blast furnace gas condensate and concentrated brine from the desalting water station to obtain multi-stage water washed ash and multi-stage ash washing brine, and return the multi-stage water washed ash to the sintering machine; the purification and separation module is used to purify and separate the multi-stage ash washing brine to obtain industrial-grade NaCl, industrial-grade KCl and crystallization mother liquor.

[0051] See also Figure 2 , Figure 2 The process flow chart of the coordinated resource utilization system of high-salt wastewater and high-salt solid waste of steel enterprises provided in Example 1 of the present invention; the specific process steps are as follows Figure 2 As shown: (1) First, the 1# electric field dust removal ash from the sintering machine head of the sintering plant is sent to the magnetic separation unit in the pretreatment module to separate the magnetic particle ore and return it to the sintering machine for reuse. The remaining first dust removal ash is mixed with the blast furnace gas condensate and the concentrated brine from the desalting water station to the first slurry sent to the primary alkaline water washing unit. NaOH is added to the primary alkaline water washing unit for alkali adjustment, and air stirring and mechanical stirring are used for reaction. After the salt is dissolved in water, the obtained first mixed slurry is sent to the primary filter press unit to complete the solid-liquid separation. The dehydrated first water washing ash is returned to the sintering machine, and the first water washing brine with dissolved salt is sent to the secondary water washing unit. The main reaction equations are as follows: 4Fe 2+ +O 2 +2H 2 O→4Fe 3+ +4OH - ; Fe 3+ +3OH - →Fe(OH) 3 ↓; Specifically, sintering machine head ash is generally set up with 4 levels of electric field for dust removal. The composition of dust removal ash from electric field No. 1 to No. 4 of a certain steel enterprise is shown in Table 1. It can be found from Table 1 that the composition of machine head ash at each level of electric field is significantly different, among which the iron content decreases step by step with the increase of the electric field level, while the salt content increases step by step.

[0052] Table 1: Composition of typical sintering machine No. 1 to No. 4 electric field dust removal ash in steel enterprises

[0053] After the above analysis, the following three reasons are considered to separate the quality of the dust from No. 1 to No. 4 electric field dust removal and wash them with water: First: The Fe element in the sintering machine head ash is mainly Fe 2 O 3 and Fe 3 O 4 The particle size of the dust from the electric field at each level was analyzed, and it was found that the particle size of the dust from the electric field No. 1 was relatively large. If it was directly washed with water and then filtered, it would easily cause a large amount of sedimentation in the washing tank, which would then block the equipment. At the same time, due to the large difference in particle size from other ashes, there was a problem of difficulty in filtering. Therefore, the dust from the electric field No. 1 was first separated by magnetic separation to remove the large particles of Fe 2 O 3 and Fe 3 O 4 Prioritize separation and directly return the ore to solve the above problems.

[0054] Second: The weight ratio of the 4 electric field ashes is as follows: No. 1 electric field dust removal ash: No. 2 electric field dust removal ash: No. 3 electric field dust removal ash: No. 4 electric field dust removal ash = 10:8:1:1. Because the water washing process requires a certain water-to-ash ratio, generally (1~4):1, the quality-separated series water washing can reduce the amount of water by about 50% compared with mixing the 4 electric field dust removal ashes before water washing, which can greatly reduce the scale of the subsequent impurity removal process and evaporation and salt separation process, thereby reducing investment and operating costs.

[0055] Third: The four electric field dust removal ashes are washed according to the order of increasing salt content. Compared with mixing the four electric field ashes and then washing them together, the separated water washing can achieve a higher water washing concentration gradient. This can greatly promote the water solubility of salt and promote the separation of salt in the sintering machine head dust removal ash into multi-stage ash washing brine, which can better solve the problem of alkali metal ion enrichment in the sintering machine and recover valuable metals at a higher proportion.

[0056] Specifically, the water quality of blast furnace gas condensate of a steel company is shown in Table 2: Table 2: Water quality of blast furnace gas condensate in a steel company

[0057] According to the water quality, blast furnace gas condensate and desalted water station concentrated brine are used as water sources for water washing. There are three main reasons: First, from the composition of the sintering machine head ash, it can be seen that the molar ratio of alkali metal ions to chloride ions is about 1.2:1, which is still a certain distance from 1:1, and a certain proportion of chloride ions needs to be supplemented. The blast furnace gas condensate and the concentrated brine of the desalted water station contain high concentrations of chloride ions, which can just solve the above problem.

[0058] Second: The target effective element in sintered ore is Fe. The condensate of blast furnace gas contains high concentrations of divalent iron ions and trivalent iron ions. Through air oxidation and alkaline precipitation, a large amount of iron hydroxide mud is formed, which is separated into water-washed ash through filter pressing and then returned to the sintered ore. In this way, the iron element in the wastewater is recovered and the iron grade in the sintered ore is improved.

[0059] Third, the particle size of the sintering machine head ash is very small, belonging to the submicron dust particles, and its surface is highly hydrophobic, which is easy to agglomerate in the water washing unit, resulting in a reduction in the dissolution effect of potassium and sodium salts. The concentrated brine of the desalting station contains a certain amount of surfactants, such as hexadecyl ammonium bromide, etc. The surfactant can disperse the ash particles of the sintering machine head ash, increase the contact area between the ash particles and water, and promote the dissolution of salt in the ash.

[0060] (2) Secondly, the second slurry obtained by mixing the No. 2 electric field dust removal ash from the sintering machine head and the first-level ash washing brine is sent to the second-level water washing unit. After being fully stirred and reacted in the second-level water washing unit and the salt is dissolved in water, the obtained second mixed slurry is sent to the second-level filter press unit to complete solid-liquid separation. The dehydrated second-level water-washed ash is returned to the sintering machine, and the salt-dissolved second-level ash washing brine is sent to the tertiary water washing unit.

[0061] (3) The third slurry obtained by mixing the No. 3 electric field dust removal ash of the sintering machine head, the No. 4 electric field dust removal ash of the sintering machine head and the secondary ash washing brine is sent to the tertiary water washing unit, and is fully stirred and reacted in the tertiary water washing unit. After the salt is dissolved in water, the obtained third mixed slurry is sent to the tertiary filter press unit to complete solid-liquid separation. The dehydrated tertiary water washing ash is returned to the sintering machine, and the salt-dissolved tertiary ash washing brine is sent to the ultrasonic electrocatalytic oxidation unit.

[0062] (4) An ultrasonic generator, an electrochemical oxidation device and a catalyst are installed in the ultrasonic catalytic oxidation unit to remove COD and NH 4 + On the one hand, the tertiary ash washing brine is cavitated and turbulently activated, and the ultrasonic oxidation brine obtained after treatment is sent to the primary desulfurization and magnesium and fluorine removal unit. The main reaction equation in the ultrasonic catalytic oxidation unit is as follows: 2Cl - -2e - →Cl 2 ; Cl 2 +H 2 O → HCl + HClO; 2NH 4 + +3HClO→N 2 ↑+3H 2 O+5H + +3Cl - .

[0063] Specifically, ultrasonic electrocatalytic oxidation is mainly considered for the following three reasons: First, the viscosity coefficient of the tertiary ash washing brine is relatively large, which is not conducive to the reaction, while ultrasound has the effect of cavitation and turbulence activation of the water body, which can greatly promote the reaction rate of catalytic oxidation and subsequent units.

[0064] Second: Since the tertiary ash washing brine contains a certain amount of COD, in order to avoid it affecting the quality of subsequent potassium and sodium salts, it must be removed in the previous process. If the Fenton process (an advanced oxidation technology, mainly used to treat difficult-to-degrade organic wastewater) is adopted, a large amount of impurity ions will be introduced, which will bring a greater burden to the subsequent treatment process. Therefore, electrocatalytic oxidation is adopted, which has a higher organic matter removal rate in high brine and avoids the introduction of new impurity ions.

[0065] Third: Due to the use of blast furnace gas condensate, if a certain amount of ammonia nitrogen is introduced, it needs to be removed. When the electrocatalytic oxidation process is used to treat wastewater containing a large amount of chloride ions, a large amount of hypochlorous acid will be produced. Hypochlorous acid will react with ammonia nitrogen through the "breakpoint chlorination" principle, oxidizing it into nitrogen and removing the ammonia nitrogen.

[0066] (5) Set up a reaction zone, a coagulation zone and a precipitation zone in the primary desulfurization, magnesium removal and fluorine removal unit, and add Ca(OH) 2 , PAC and PAM, for SO 4 2- Perform a rough removal to remove Mg 2+ and F - After removal, the primary impurity removal brine and primary sedimentation sludge are obtained. The main reaction equations are as follows: Ca 2+ +SO 4 2- →CaSO 4 ↓; Ca 2+ +2F - →CaF 2 ↓; Mg 2+ +2OH - →Mg(OH) 2 ↓.

[0067] (6) The first-level impurity-removing brine after treatment in the primary desulfurization and magnesium and fluorine removal unit is sent to the secondary desulfurization and calcium and weight removal unit, and the generated primary sedimentation sludge is dehydrated and transported for disposal. The reaction zone, coagulation zone and sedimentation zone are set in the secondary desulfurization and calcium and weight removal unit, and Na 2 CO 3 、Na 2 S, BaCl 2 , PAC and PAM, for SO 4 2- Perform secondary fine removal to remove Ca 2+ and heavy metal ions (such as Cu 2+ , Pb 2+ 、Zn 2+ ) is removed to obtain secondary impurity removal brine and secondary sedimentation sludge. The main reaction equation is as follows: Ba 2+ +SO 4 2- →BaSO 4 ↓; Ca 2+ +CO 3 2+ →CaCO 3 ↓; Cu 2+ +S 2- →CuS↓; Pb 2+ +S 2- →PbS↓; Zn 2+ +S 2- →ZnS↓.

[0068] (7) The secondary impurity-removing brine after treatment by the secondary desulfurization and calcium and weight removal units is sent to the three-effect countercurrent evaporation unit, and the secondary precipitated sludge produced is dehydrated and transported for disposal. In the three-effect countercurrent evaporation unit, a countercurrent step-by-step temperature rise evaporation reaction is carried out, and NaCl is precipitated first. The evaporated water vapor is condensed to form condensed water for reuse, and the resulting crystallization mother liquor is sent to the sodium salt centrifugal separation unit.

[0069] (8) In the sodium salt centrifugal separation unit, the crystallization mother liquor is separated into solid and liquid by a centrifugal device, and the NaCl crystals are separated and sent to the sodium salt drying unit for dehydration and drying, and then dried into industrial-grade NaCl products for sale. The centrifugal mother liquor obtained after solid-liquid separation is sent to the freezing crystallization unit, and KCl is precipitated by cooling. The mixed solution of precipitated KCl is sent to the potassium salt centrifugal separation unit, and the solid-liquid separation is completed by a centrifugal device, and the KCl crystals are separated and sent to the potassium salt drying unit for dehydration and drying, and then dried into industrial-grade KCl products for sale. The crystallization mother liquor obtained by solid-liquid separation in the potassium salt centrifugal separation unit is sent to the triple-effect countercurrent evaporation unit for internal reuse.

[0070] In summary, different from the prior art, the present invention has the following advantages after adopting the above technical solution: (1) High resource coupling: Through the invented method, two kinds of wastes that are difficult to dispose of in steel enterprises undergo a series of coupling reactions, and high-salt wastewater and high-salt solid waste that originally needed to be treated and disposed of separately are treated in a coordinated manner. When high-salt wastewater is treated separately to achieve zero discharge, a separate process flow of pretreatment + membrane treatment + evaporation treatment is required, which requires a large amount of investment and operating costs. When high-salt solid waste is washed with industrial water alone, on the one hand, a large amount of new industrial water is consumed, and on the other hand, washing + impurity removal + evaporation is also required. At the same time, chloride ions need to be added to adjust the ratio of alkali metal: chloride ions to complete the recovery of alkali metals. Compared with the investment and operating costs of the above separate treatments, the coordinated resource utilization method of the present invention reduces investment by 30% to 50% and reduces operating costs by 10% to 20%.

[0071] (2) Turning waste into treasure and reducing carbon emissions: The iron ions in the blast furnace gas condensate are recycled into the sintering system to improve the iron grade of the sintered ore; a multi-stage water washing process is used to extract the potassium and sodium salts in the sintering machine head ash into the ash washing brine to the maximum extent, and then the impurity removal + evaporation and salt separation method is used to produce potassium chloride and sodium chloride salt products, and the condensate is reused, thereby improving the resource utilization rate of the steel enterprise.

[0072] (3) High synergistic benefits of environmental protection and economy: The high-salt wastewater and high-salt solid waste in the steel enterprise are materially coupled with the main sintering process line to form an internal cycle, while producing high value-added products, reducing costs and increasing efficiency for the enterprise. It not only solves the environmental protection pain points and difficulties of wastewater and solid waste in steel enterprises, protects the ecological environment, but also generates good economic benefits, reduces operating costs, and increases product value. It is of great significance to the high-quality and sustainable development of production enterprises.

[0073] The above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A coordinated resource utilization system for high-salt wastewater and high-salt solid waste in steel enterprises, characterized in that: It includes a pre-treatment module, a multi-stage water washing and filter pressing module and a purification and separation module which are connected in sequence; Among them, the pretreatment module is used to screen out non-magnetic dust removal ash in the sintering machine head dust removal ash; the multi-stage water washing filter press module is used to perform multi-stage water washing filter press treatment on the slurry obtained by mixing the non-magnetic dust removal ash, blast furnace gas condensate and concentrated brine from the desalting water station to obtain multi-stage water washed ash and multi-stage ash washing brine, and return the multi-stage water washed ash to the sintering machine; the purification and separation module is used to perform purification and separation treatment on the multi-stage ash washing brine to obtain industrial-grade NaCl, industrial-grade KCl and crystallization mother liquor.

2. The high-salt wastewater and high-salt solid waste collaborative resource utilization system of a steel enterprise according to claim 1 is characterized in that: The sintering machine head dust removal ash includes No. 1 electric field dust removal ash, No. 2 electric field dust removal ash, No. 3 electric field dust removal ash and No. 4 electric field dust removal ash, and the pretreatment module is used to perform magnetic separation treatment on the No. 1 electric field dust removal ash to obtain magnetic particle ore and the first dust removal ash; Among them, the non-magnetic dust removal ash includes the first dust removal ash, the No. 2 electric field dust removal ash, the No. 3 electric field dust removal ash and the No. 4 electric field dust removal ash.

3. The high-salt wastewater and high-salt solid waste collaborative resource utilization system of a steel enterprise according to claim 2 is characterized in that: The pretreatment module is a dry magnetic separation device with a magnetic field strength of 500-3000 Gs.

4. The high-salt wastewater and high-salt solid waste collaborative resource utilization system of a steel enterprise according to claim 2 is characterized in that: The multi-stage water washing and filter pressing module comprises a primary alkaline water washing unit, a primary filter pressing unit, a secondary water washing unit, a secondary filter pressing unit, a tertiary water washing unit and a tertiary filter pressing unit which are connected in sequence; Among them, the primary alkaline water washing unit is used to perform a primary alkaline water washing treatment on the first slurry obtained by mixing the first dust removal ash, the blast furnace gas condensate and the concentrated brine of the desalted water station to obtain a first mixed slurry; the primary filter press unit is used to perform a primary filter press treatment on the first mixed slurry to obtain primary water-washed ash and primary ash-washing brine after solid-liquid separation, and return the primary water-washed ash to the sintering machine; the secondary water washing unit is used to perform a secondary water washing treatment on the second slurry obtained by mixing the No. 2 electric field dust removal ash and the primary ash-washing brine to obtain a second mixed slurry; The secondary filter press unit is used to perform secondary filter press treatment on the second mixed slurry, and obtain secondary water-washed ash and secondary ash-washing brine after solid-liquid separation, and return the secondary water-washed ash to the sintering machine; the tertiary water washing unit is used to perform tertiary water washing treatment on the third slurry obtained by mixing the No. 3 electric field dust removal ash, the No. 4 electric field dust removal ash and the secondary ash-washing brine to obtain a third mixed slurry; the tertiary filter press unit is used to perform tertiary filter press treatment on the third mixed slurry, and obtain tertiary water-washed ash and tertiary ash-washing brine after solid-liquid separation, and return the tertiary water-washed ash to the sintering machine.

5. The high-salt wastewater and high-salt solid waste collaborative resource utilization system of a steel enterprise according to claim 4 is characterized in that: The water-cement ratio in the primary alkaline water washing unit is (1-3):1, the reaction pH value is 7-9, and the reaction time is 0.5-1.5h; the reaction time in the secondary water washing unit is 0.5-1.5h; and the reaction time in the tertiary water washing unit is 0.5-1.5h.

6. The high-salt wastewater and high-salt solid waste collaborative resource utilization system of a steel enterprise according to claim 4 is characterized in that: The purification and separation module includes a multi-effect purification treatment submodule connected to the three-stage filter press unit and a salt separation and crystallization submodule connected to the multi-effect purification treatment submodule; Among them, the multi-effect purification treatment submodule is used to perform multi-effect purification treatment on the three-stage ash washing brine to obtain crystallization mother liquor, multi-stage sedimentation sludge and condensed water; the salt separation and crystallization submodule is used to perform separation and crystallization treatment on the crystallization mother liquor to obtain the industrial-grade NaCl, the industrial-grade KCl and the crystallization mother liquor.

7. The high-salt wastewater and high-salt solid waste collaborative resource utilization system of a steel enterprise according to claim 6 is characterized in that: The multi-effect purification treatment submodule includes an ultrasonic electrocatalytic oxidation unit, a primary desulfurization and magnesium and fluorine removal unit, a secondary desulfurization and calcium and weight removal unit, and a three-effect countercurrent evaporation unit connected in sequence; The ultrasonic electrocatalytic oxidation unit is used to ultrasonically oxidize the tertiary ash washing brine to obtain ultrasonic oxidized brine; the primary desulfurization and magnesium removal and fluorine removal unit is used to remove SO4 2- A rough removal is performed, and at the same time, the Mg in the ultrasonic oxidation brine is 2+ and F - After removal, primary desulfurization brine and primary sedimentation sludge are obtained. The reagents added to the primary desulfurization and magnesium and fluorine removal units are Ca(OH)2, PAC and PAM; the secondary desulfurization and calcium and weight removal units are used to remove SO4 in the primary desulfurization brine. 2- Perform secondary fine removal, and at the same time remove the Ca 2+ After removing the heavy metal ions, secondary impurity removal brine and secondary sedimentation sludge are obtained. The reagents added to the secondary desulfurization and calcium removal and weight removal units are Na2CO3, Na2S, BaCl2, PAC and PAM; the three-effect countercurrent evaporation unit is used to perform countercurrent step-by-step temperature evaporation treatment on the secondary impurity removal brine to obtain the crystallization mother liquor and the condensed water.

8. The high-salt wastewater and high-salt solid waste collaborative resource utilization system of a steel enterprise according to claim 7, characterized in that: In the ultrasonic electrocatalytic oxidation unit: the frequency of the ultrasonic device is 50~500kHz, the catalyst is TiO2, the catalyst dosage is 100~300mg / L, and the pH value is 6~7; the reaction time of the reaction zone of the primary desulfurization and magnesium and fluorine removal units is 0.4~0.6h; the reaction time of the reaction zone of the secondary desulfurization and calcium and weight removal units is 0.3~0.7h; the temperature of the triple-effect countercurrent evaporation unit is 70~100℃.

9. The high-salt wastewater and high-salt solid waste collaborative resource utilization system of a steel enterprise according to claim 7, characterized in that: The salt separation and crystallization submodule comprises a sodium salt centrifugal separation unit, a freezing crystallization unit and a potassium salt centrifugal separation unit connected in sequence; Among them, the sodium salt centrifugal separation unit is used to obtain the industrial-grade NaCl and the centrifugal mother liquor after centrifugal treatment of the crystallization mother liquor; the frozen crystallization unit is used to obtain the potassium salt mixed liquor after frozen crystallization treatment of the centrifugal mother liquor; the potassium salt centrifugal separation unit is used to obtain the industrial-grade KCl and the crystallization mother liquor after centrifugal treatment of the potassium salt mixed liquor, and transport the crystallization mother liquor to the triple-effect countercurrent evaporation unit for internal reuse.

10. The high-salt wastewater and high-salt solid waste collaborative resource utilization system of a steel enterprise according to claim 9, characterized in that: The temperature of the freezing crystallization unit is 0-50°C.

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