CN114105232B - Silicon steel magnesium oxide wastewater treatment and recycling method - Google Patents

Silicon steel magnesium oxide wastewater treatment and recycling method Download PDF

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Publication number
CN114105232B
CN114105232B CN202010891343.7A CN202010891343A CN114105232B CN 114105232 B CN114105232 B CN 114105232B CN 202010891343 A CN202010891343 A CN 202010891343A CN 114105232 B CN114105232 B CN 114105232B
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water
filter
wastewater
magnesium oxide
recycling
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CN114105232A (en
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侯红娟
侯长俊
武晟
尹婷婷
胡钧
李恩超
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Baoshan Iron and Steel Co Ltd
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    • 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
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/13—Treatment of sludge; Devices therefor by de-watering, drying or thickening by heating
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/02—Aerobic processes
    • C02F3/10—Packings; Fillings; Grids
    • C02F3/105—Characterized by the chemical composition
    • C02F3/107—Inorganic materials, e.g. sand, silicates
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/06—Sludge reduction, e.g. by lysis
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/10—Biological treatment of water, waste water, or sewage

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Inorganic Chemistry (AREA)
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  • General Chemical & Material Sciences (AREA)
  • Biodiversity & Conservation Biology (AREA)
  • Microbiology (AREA)
  • Removal Of Specific Substances (AREA)
  • Filtration Of Liquid (AREA)
  • Water Treatment By Sorption (AREA)

Abstract

The invention belongs to the technical field of water treatment, and particularly relates to a method for treating and recycling silicon steel magnesia wastewater, which comprises the following steps: the silicon steel magnesia wastewater is conveyed to a filtration, sludge concentration and drying integrated system, and after being treated by the filtration, sludge concentration and drying integrated system, a filter cake is discharged, qualified water is produced, and the qualified water is discharged to a water production tank; mixing, stirring, granulating and drying the discharged filter cake and powdered activated carbon generated by a flue gas desulfurization and denitrification process; and taking the dried magnesia particles as a filler of the biological aerated filter, and discharging water after the nitrification reaction from the upper part of the filter. After the treatment of the invention, the magnesia wastewater can meet the recycling requirement, and returns to a unit for recycling, thereby realizing the recycling of the wastewater; the produced precipitated sludge and the powdered activated carbon produced by sintering flue gas desulfurization and denitrification are manufactured into magnesium oxide particles which are used as the filler of the biological aeration filter tank, so that the recycling utilization of the magnesium oxide wastewater precipitated sludge is realized.

Description

Silicon steel magnesium oxide wastewater treatment and recycling method
Technical Field
The invention belongs to the technical field of water treatment, and particularly relates to a silicon steel magnesium oxide wastewater treatment and recycling process.
Background
The surface of the incoming material of the silicon steel hot stretching flattening unit is provided with magnesia powder. The magnesium oxide brushing section mainly cleans MgO powder on the surface of the strip steel, and the MgO powder on the surface of the strip steel is brushed off through the brushing groove, so that the clean strip steel enters the inlet loop, and the inlet loop is prevented from being polluted. The inside of the brushing tank is generally brushed by industrial water, and magnesia powder can remain in the water after brushing. In order to save water resources, the used magnesia wastewater is generally treated, magnesia powder in the wastewater is removed, and the wastewater is returned to a unit for recycling.
The main pollutant in the magnesium oxide wastewater of the silicon steel is magnesium oxide powder, and according to the analysis of the particle size of suspended matters in the magnesium oxide wastewater of a certain iron and steel enterprise, the particle size range is 1-50 mu m, and the average particle size is 10.7 mu m. The processes commonly used for the treatment of suspended matter are precipitation, air flotation and filtration.
The most commonly used process is precipitation, but most of the particles in the wastewater are tiny, the particles are difficult to remove by natural sedimentation precipitation, in order to strengthen the removal effect of suspended substances, chemical agents such as coagulant, coagulant aid and the like are generally added, most of the added chemical agents are precipitated into sludge, a small amount of the added chemical agents remain in supernatant, and if the treated water is recycled, the residual coagulant and coagulant aid in the water are more and more, so that the recycling of the water is influenced; in addition, the chemical agent is precipitated into the sludge, so that on one hand, the yield of the sludge is increased, and on the other hand, the purity of the sludge is affected, and the recycling of the sludge is adversely affected.
The air floatation is a process of using highly dispersed micro air-gown as a carrier to adhere to suspended pollutants in wastewater, so that the buoyancy of the suspended pollutants is larger than gravity and resistance, the pollutants float to the water surface to form foam, and then scraping the foam from the water surface by using a slag scraping device to realize solid-liquid or liquid-liquid separation. The coagulation agent is required to be added in the air floatation process, so that the same problems as precipitation exist.
The filtering is that water passes through a filter medium with micro-pore channels, the pressure at two sides of the filter medium is different, the water passes through the micro-pore channels under the action of pressure difference driving force, and particulate matters and gelatinous matters are blocked by the medium and cannot pass through the medium. The filtering technology for removing suspended matters includes sand filtration, microfiltration and other technologies. The sand filtration process needs backwashing after filtration saturation; the microfiltration process produces concentrate and requires chemical cleaning after contamination.
The sludge produced by the coagulating sedimentation, air floatation and filtering processes is sludge with high water content, the water content of the sludge of the coagulating sedimentation and air floatation is generally above 99%, the water content of sand filtration backwash water and micro filtration concentrated solution is above 99.9%, and further concentration and dehydration are required for the sludge.
With the increasing strictness of national environmental protection standards, the over-current denitration of sintering flue gas has become a necessary choice for many iron and steel enterprises, and the active carbon (coke) process can simultaneously satisfy desulfurization and desulfurization, so that the process is widely applied, about 5% of powdered active carbon can be produced in the active carbon regeneration process, and the active carbon cannot be recycled.
The waste water containing ammonia and nitrogen is a common waste water, biological nitrification is a common, economical and efficient biochemical treatment process, but the alkalinity is consumed in the nitrifying reaction process, the pH is reduced, and chemical agents such as sodium hydroxide, sodium carbonate and the like are generally added to supplement the alkalinity in order to ensure the stable progress of the biochemical reaction.
Disclosure of Invention
The invention aims to provide a method for treating and recycling silicon steel magnesium oxide wastewater, which can meet the recycling requirement and return to a unit for recycling, thereby realizing the recycling of wastewater; the produced precipitated sludge and the powdered activated carbon produced by sintering flue gas desulfurization and denitrification are manufactured into magnesium oxide particles which are used as the filler of the biological aeration filter tank, so that the recycling utilization of the magnesium oxide wastewater precipitated sludge is realized.
The technical scheme of the invention is as follows:
a method for treating and recycling silicon steel magnesia wastewater comprises the following steps:
(1) The silicon steel magnesia wastewater is conveyed to a filtration, sludge concentration and drying integrated system, and after being treated by the filtration, sludge concentration and drying integrated system, a filter cake is discharged, qualified water is produced, and the qualified water is discharged to a water production tank; the content of suspended matters in the silicon steel magnesia wastewater is 50-500 mg/L, and the particle size of the suspended matters is 1-50 mu m.
(2) Mixing and stirring the filter cake discharged in the step (1) and powdered activated carbon generated by a flue gas desulfurization and denitrification process, wherein the proportion of the filter cake is 60-80%, and the proportion of the activated carbon is 20-40%; granulating in a granulator after mixing, and drying, wherein the particle size of the granulated particles is 5-10 mm;
(3) Taking the dried magnesium oxide particles in the step (2) as a filler of a biological aerated filter, filling gravel with the particle size of 10-50 mm at the bottom of the filter as a supporting layer, and filling the dried magnesium oxide particles at the upper part of the supporting layer, wherein at least one layer is arranged in each of the supporting layer and the filler layer in a reaction column; the upper part of the supporting layer is provided with a filter screen, the aperture of the filter screen is 0.5-2.5 mm, and the aperture ratio is 20-80%; the water after the nitration reaction is discharged from the upper part of the filter tank, and the hydraulic retention time in the filter tank is 8-50 h; the ratio of the aerated air to the water is controlled to be 3-8:1.
Further, the treatment process of the silicon steel magnesia wastewater in the filtration, sludge concentration and drying integrated system is as follows:
(1) Prefiltering: the silicon steel magnesia waste water enters a filter container, particles with larger pore diameters than the filter cloth in the waste water generate a bridging effect on the surface of the filter cloth, and the particles with smaller pore diameters than the filter cloth penetrate the filter cloth to remain in the water when passing through the filter cloth and return to the regulating tank, and the prefiltering time is 0.5-5 min;
(2) The filtering process comprises the following steps: the magnesia wastewater enters a filtering procedure after being clarified gradually in a prefiltering stage, a filter cake becomes a main filtering layer, fine particles are intercepted, and the magnesia wastewater flows into a water producing tank; with the extension of the filtering time, the filter cake is thicker and thicker, the filtering resistance is increased, the water yield is gradually reduced, and the filtering is stopped when the water yield is reduced to 60-80% of the original water yield;
(3) And (3) drying a filter cake: after stopping filtering, evacuating water in the filtering container to the regulating tank, then introducing compressed air in the same direction as the filtering, forcing the compressed air to pass through the filter cake, discharging filtrate in the filter cake by gas, compressing the filter cake, wherein the water content of the filter cake is 22-28%;
(4) Back blowing mud-discharging device: after the filter cake is dried, the reverse compressed air is introduced, and the dosage of the compressed air is 2-10 Nm 3 /min·m 2 The ventilation time is 0.5-2 min, and the filter cake falls off from the filter cloth and is discharged.
According to the method for treating and recycling the silicon steel magnesia wastewater, the qualified water generated in the filtering stage is discharged to a water production tank and is conveyed to a magnesia scrubbing unit for recycling.
The invention relates to a method for treating and recycling silicon steel magnesia wastewater, which further comprises a filter cake drying stage, wherein the dosage of compressed air is 1-5 Nm 3 /min·m 2 The ventilation time is 0.5-5 min,
according to the method for treating and recycling the silicon steel magnesium oxide wastewater, in the step (2), granulated magnesium oxide particles are laid on a cool and ventilated ground for natural drying, the thickness is controlled to be 0.5-2 cm, and when the water content is reduced to 5-10%, the dried magnesium oxide particles are collected and packaged.
According to the method for treating and recycling the silicon steel magnesium oxide wastewater, the drying time is more than 5-7 days, and if the water content is reduced to below 5-10% when the drying time is less than 5-7 days, water needs to be sprayed on the surfaces of magnesium oxide particles, so that the drying time is prolonged to more than 5-7 days.
According to the method for treating and recycling the silicon steel magnesium oxide wastewater, in the step (3), gravel with the particle size of 20-30 mm is filled at the bottom of the filter tank to serve as a supporting layer.
According to the method for treating and recycling the silicon steel magnesium oxide wastewater, in the step (3), the aperture ratio of the filter screen is 50-70%.
According to the method for treating and recycling the silicon steel magnesium oxide wastewater, in the step (3), the filter screen is made of stainless steel, ceramic and plastic materials.
According to the method for treating and recycling the silicon steel magnesium oxide wastewater, in the step (3), the height of the packing layer is 5-10 times of the height of the supporting layer.
Detailed description of the invention:
the content of suspended matters in the silicon steel magnesia wastewater is 50-500 mg/L, and the particle size of the suspended matters is 1-50 mu m.
The magnesia waste water is conveyed to a filtration, sludge concentration and drying integrated system by a lift pump, and the system mainly comprises a filtration container, a filter support tube, filter cloth, an air compressor, an air nozzle, a turbidity meter, an automatic control system and the like. The operation process flow of the system is as follows:
(1) Prefiltering: the magnesia waste water enters a filter container, particles with larger pore diameters than the filter cloth in the waste water have a bridging effect on the surface of the filter cloth, and the particles with smaller pore diameters than the filter cloth penetrate the filter cloth to remain in the water when passing through the filter cloth, so that the water can not meet the filter requirement, and returns to the regulating tank for prefiltering for 0.5-5 min.
(2) The filtering process comprises the following steps: the magnesia wastewater enters a filtering procedure after being clarified gradually in a prefiltering stage, a filter cake becomes a main filtering layer, fine particles are intercepted, and the produced filtered water meets the requirement and flows into a water production tank automatically; with the extension of the filtering time, the filter cake is thicker, the filtering resistance is increased, the water yield is gradually reduced, and the filtering is stopped when the water yield is reduced to 60-80% of the original water yield.
(3) And (3) drying a filter cake: after stopping the filtration, the water in the filtration vessel is drained to a regulating tank, and then compressed air is introduced in the same direction as the filtration, wherein the dosage of the compressed air is 1-5 Nm 3 /min·m 2 The aeration time is 0.5-5 min, the compressed air is forced to pass through the filter cake, and the filtrate in the filter cake is discharged by gas, so that the filter cake is compressed, the water content of the filter cake is reduced, the sludge yield is reduced, and the water content of the filter cake is 22-28%.
(4) Back-blowing mud discharge: after the filter cake is dried, the reverse compressed air is introduced, and the dosage of the compressed air is 2-10 Nm 3 /min·m 2 The ventilation time is 0.5-2 min, and the filter cake cracks due to the expansion of the filter cloth and falls off and is discharged from the filter cloth.
And then enter the next filtering cycle.
After being treated by the filtration, sludge concentration and drying integrated system, qualified water generated in the filtration stage is discharged to a water production tank and is conveyed to a magnesium oxide scrubbing unit for recycling. After the process is adopted, no medicament is added into the water, so that the treated water can be recycled, and the ion enrichment problem is avoided.
The discharged filter cake contains magnesium oxide as main component, and part of titanium dioxide, small amount of ferrite and silicon dioxide. Mixing and stirring the filter cake discharged by the previous system and the powdered activated carbon generated by the flue gas desulfurization and denitrification process, wherein the proportion of the filter cake is 60-80%, and the proportion of the activated carbon is 20-40%. And (3) granulating in a granulator after the mixing is finished, wherein the particle size of the granulated particles is 5-10 mm.
The granulated magnesia particles are laid on the cool and ventilated ground for natural drying, and the thickness is controlled to be 0.5-2 cm. And detecting the water content every day, and collecting and bagging the dried magnesium oxide particles when the water content is reduced to 5-10%. And the drying time is 5-15 days, if the water content is reduced to below 5% when the drying time is less than 5 days, water needs to be sprayed on the surfaces of the magnesium oxide particles, and the drying time is prolonged to above 5 days.
Taking the dried magnesium oxide particles as a filler of the biological aerated filter, filling gravel with the particle size of 10-50 mm (preferably 20-30 mm) at the bottom of the filter as a supporting layer, and filling the dried magnesium oxide particles at the upper part of the supporting layer, wherein at least one supporting layer and at least one filler layer are respectively arranged in a reaction column; the upper part of the supporting layer is provided with a filter screen, the aperture of the filter screen is 0.5-2.5 mm, the aperture ratio is 20-80% (preferably 50-70%), and the filter screen is made of stainless steel, ceramic, plastic and other materials; the height of the packing layer is 5-10 times of the height of the supporting layer; the water after the nitration reaction is discharged from the upper part of the filter tank, and the hydraulic retention time in the filter tank is 8-50 h; the ratio of the aerated air to the water is controlled to be 3-8:1.
In the filter tank, microorganisms adhere to the surfaces of magnesium oxide particles to form a biological film, and organic matter oxidation and nitration reactions occur in the biological film; in the reaction process, the pH value gradually decreases along with the degradation of ammonia nitrogen, magnesium oxide particles are slowly corroded under the double action of aeration flushing, mgO released along with the falling biological film can be used as a weak alkaline substance to supplement alkalinity, and the stable operation of biochemical reaction is ensured; in addition, the released activated carbon powder can adsorb organic matters in water, so that the organic matter removal effect is improved.
Beneficial technical effects
The invention provides a treatment and recycling process of silicon steel magnesia wastewater, after the treatment of the invention, the magnesia wastewater can meet the recycling requirement, and the magnesia wastewater returns to a unit for recycling, thereby realizing the recycling of the wastewater; the produced precipitated sludge and the powdered activated carbon produced by sintering flue gas desulfurization and denitrification are manufactured into magnesium oxide particles which are used as the filler of the biological aeration filter tank, so that the recycling utilization of the magnesium oxide wastewater precipitated sludge is realized. The invention has the double effects of economy and environmental protection, and has good social benefit and environmental benefit.
Drawings
FIG. 1 is a flow chart of a process for treating and recycling waste water of silicon steel and magnesia.
Detailed Description
For a better understanding of the present invention, the following examples are set forth to illustrate the present invention further, but are not to be construed as limiting the present invention.
Example 1
A method for treating and recycling silicon steel magnesium oxide wastewater comprises the following steps:
the content of suspended matters in the silicon steel magnesia wastewater is 50mg/L, and the particle size of the suspended matters is 1-50 mu m.
The prefiltering time of the integrated system of filtering, sludge concentration and drying is 5min; stopping filtering when the water yield of the filtration is reduced to 60%, and returning the suspended matters in the filtered water to the unit for recycling, wherein the concentration of the suspended matters in the filtered water is 8mg/L; after stopping the filtration, the water in the filtration vessel was drained to the original water tank, and then compressed air was introduced in the same direction as the filtration, the amount of the compressed air was 2Nm 3 /min·m 2 The aeration time is 0.5min, compressed air is forced to pass through the filter cake, and filtrate in the filter cake is discharged by gas, so that the filter cake is compressed, the water content of the filter cake is reduced, the sludge yield is reduced, and the water content of the filter cake is 28%; after the cake was dried, the reverse compressed air was introduced at a pressure of 10Nm 3 /min·m 2 During ventilationAnd (5) 0.5min later, generating cracks on the filter cake, and falling off and discharging from the filter cloth.
The discharged filter cake and the powdery activated carbon generated by the sintering flue gas desulfurization and denitrification process are mixed according to the following ratio of 60:40, and after the mixing, granulating in a granulator, wherein the particle size of the granulated particles is 5mm.
The granulated magnesium oxide particles are laid on a cool and ventilated ground for natural drying, the thickness is 1cm, and the water content is reduced to 8% after 5 days.
Filling the dried magnesium oxide particles into a biological aerated filter, filling gravel with the particle size of 10mm at the bottom of the filter as a supporting layer, and filling the dried magnesium oxide particles at the upper part of the supporting layer to be 100mm thick; a filter screen is arranged on the upper part of the supporting layer, the aperture of the filter screen is 0.5mm, and the aperture ratio is 50%; the water after the nitration reaction is discharged from the upper part of the filter tank, and the hydraulic retention time in the filter tank is 8h; the ratio of the aerated gas to the water is controlled to be 3:1. The COD of the inflow water of the aeration biological filter tank is 360mg/L, and the ammonia nitrogen is 48mg/L; the COD of the effluent is 65mg/L, and the ammonia nitrogen is 3.4mg/L.
Example 2
A method for treating and recycling silicon steel magnesium oxide wastewater comprises the following steps:
the content of suspended matters in the silicon steel magnesia wastewater is 325mg/L, and the particle size of the suspended matters is 1-50 mu m.
The prefiltering time of the integrated system of filtering, sludge concentration and drying is 1min; stopping filtering when the water yield of the filtered water is reduced to 70%, and returning the filtered water to the unit for recycling, wherein the concentration of suspended matters in the filtered water is 6mg/L; after stopping the filtration, the water in the filtration vessel was drained to the original water tank, and then compressed air was introduced in the same direction as the filtration, the amount of the compressed air was 1Nm 3 /min·m 2 The aeration time is 2min, compressed air is forced to pass through the filter cake, and the filtrate in the filter cake is discharged by gas, so that the filter cake is compressed, the water content of the filter cake is reduced, the sludge yield is reduced, and the water content of the filter cake is 22%; after the cake was dried, the reverse compressed air was introduced in an amount of 7Nm 3 /min·m 2 The ventilation time is 2min, cracks are generated in the filter cake, and the filter cake falls off from the filter cloth and is discharged.
The discharged filter cake and the powdery activated carbon generated by the sintering flue gas desulfurization and denitrification process are mixed according to the following ratio of 70:30, and after the mixing, granulating in a granulator, wherein the particle size of the granulated particles is 8mm.
The granulated magnesium oxide particles are laid on a cool and ventilated ground for natural drying, the thickness is 1.5cm, and the water content is reduced to 7% after 7 days.
Filling the dried magnesium oxide particles into a biological aerated filter, filling gravel with the particle size of 30mm at the bottom of the filter as a supporting layer, and filling the dried magnesium oxide particles at the upper part of the supporting layer to the thickness of 150mm; a filter screen is arranged on the upper part of the supporting layer, the aperture of the filter screen is 2mm, and the aperture ratio is 20%; the water after the nitration reaction is discharged from the upper part of the filter tank, and the hydraulic retention time in the filter tank is 30h; the ratio of the aerated gas to the water is controlled to be 5:1. COD670mg/L of inflow water of the biological aerated filter and 96mg/L of ammonia nitrogen; the COD of the effluent is 87mg/L, and the ammonia nitrogen is 4.8mg/L.
Example 3
A method for treating and recycling silicon steel magnesium oxide wastewater comprises the following steps:
the content of suspended matters in the silicon steel magnesia wastewater is 500mg/L, and the particle size of the suspended matters is 1-50 mu m.
The prefiltering time of the filtration, sludge concentration and drying integrated system is 0.5min; stopping filtering when the water yield of the filtration is reduced to 60%, and returning the suspended solids concentration in the filtered water to the unit for recycling; after stopping the filtration, the water in the filtration vessel was drained to the original water tank, and then compressed air was introduced in the same direction as the filtration, the amount of the compressed air was 2Nm 3 /min·m 2 The aeration time is 1min, compressed air is forced to pass through the filter cake, and filtrate in the filter cake is discharged by gas, so that the filter cake is compressed, the water content of the filter cake is reduced, the sludge yield is reduced, and the water content of the filter cake is 25%; after the cake was dried, the reverse compressed air was introduced at a pressure of 10Nm 3 /min·m 2 The ventilation time is 0.5min, cracks are generated in the filter cake, and the filter cake falls off from the filter cloth and is discharged.
The discharged filter cake and the powdery activated carbon produced by the sintering flue gas desulfurization and denitrification process are mixed according to 80:20, and after the mixing is completed, the mixture enters a granulator for granulation, and the particle size of the granulated particles is 10mm.
The granulated magnesium oxide particles are laid on a cool and ventilated ground for natural drying, the thickness is 2cm, and the water content is reduced to 8% after 7 days.
Filling the dried magnesium oxide particles into a biological aerated filter, filling gravel with the particle size of 50mm at the bottom of the filter as a supporting layer, and filling the dried magnesium oxide particles at the upper part of the supporting layer, wherein the thickness of the supporting layer is 200mm; a filter screen is arranged on the upper part of the supporting layer, the aperture of the filter screen is 5mm, and the aperture ratio is 80%; the water after the nitration reaction is discharged from the upper part of the filter tank, and the hydraulic retention time in the filter tank is 50h; the ratio of the aerated gas to the water is controlled at 8:1. COD980mg/L of inflow water of the biological aerated filter and ammonia nitrogen 156mg/L; the COD of the effluent is 72mg/L, and the ammonia nitrogen is 2.8mg/L.
It will of course be appreciated by those skilled in the art that the above-described embodiments are provided for illustration only and not as limitations of the present invention, and that variations and modifications of the above-described embodiments will fall within the scope of the appended claims.

Claims (8)

1. A method for treating and recycling silicon steel magnesia wastewater is characterized by comprising the following steps:
(1) The silicon steel magnesia wastewater is conveyed to a filtration, sludge concentration and drying integrated system, and after being treated by the filtration, sludge concentration and drying integrated system, a filter cake is discharged, qualified water is produced, and the qualified water is discharged to a water production tank; the content of suspended matters in the silicon steel magnesia wastewater is 50-500 mg/L, and the particle size of the suspended matters is 1-50 mu m;
(2) Mixing and stirring the filter cake discharged in the step (1) and powdered activated carbon generated by a flue gas desulfurization and denitrification process, wherein the mass percentage of the filter cake is 60-80%, and the mass percentage of the activated carbon is 20-40%; granulating in a granulator after mixing, drying, and granulating to obtain granules with the particle size of 5-10 mm; in the step, the granulated magnesia particles are flatly paved on a cool and ventilated ground for natural drying, the thickness is controlled to be 0.5-2 cm, and when the water content is reduced to 5-10%, the dried magnesia particles are collected and packaged; drying time is 5-15 days, if the water content is reduced to below 5% when the drying time is less than 5 days, water needs to be sprayed on the surfaces of the magnesium oxide particles, and the drying time is prolonged to above 5 days;
(3) Taking the dried magnesium oxide particles in the step (2) as a filler of a biological aerated filter, filling gravel with the particle size of 10-50 mm at the bottom of the filter as a supporting layer, and filling the dried magnesium oxide particles at the upper part of the supporting layer, wherein at least one layer is arranged in each of the supporting layer and the filler layer in a reaction column; the upper part of the supporting layer is provided with a filter screen, the aperture of the filter screen is 0.5-2.5 mm, and the aperture ratio is 20-80%; the water after the nitration reaction is discharged from the upper part of the filter tank, and the hydraulic retention time in the filter tank is 8-50 h; the ratio of the aerated air to the water is controlled to be 3-8:1.
2. The method for treating and recycling the silicon steel magnesium oxide wastewater according to claim 1, wherein the treatment process of the silicon steel magnesium oxide wastewater in the integrated system of filtration, sludge concentration and drying comprises the following steps:
(1) Prefiltering: the silicon steel magnesium oxide wastewater enters a filtering container, the suspension of large particles in the wastewater generates a bridging effect on the surface of filter cloth, small particles penetrate the filter cloth to remain in water after passing through the filter cloth and return to an adjusting tank, and the prefiltering time is 0.5-5 min;
(2) The filtering process comprises the following steps: the magnesia wastewater enters a filtering procedure after being clarified gradually in a prefiltering stage, a filter cake becomes a main filtering layer, fine particles are intercepted, and produced water flows into a water producing tank; with the extension of the filtering time, the filter cake is thicker and thicker, the filtering resistance is increased, the water yield is gradually reduced, and the filtering is stopped when the water yield is reduced to 60-80% of the original water yield;
(3) And (3) drying a filter cake: after stopping filtering, evacuating the water in the filtering container to a regulating tank, and then introducing compressed air in the same direction as the filtering to compress a filter cake, wherein the water content of the filter cake is 22-28%;
(4) Back-blowing mud discharge: after the filter cake is dried, the reverse compressed air is introduced, and the dosage of the compressed air is 2-10 Nm 3 /min·m 2 The ventilation time is 0.5-2 min, and the filter cake falls off from the filter cloth and is discharged.
3. The method for treating and recycling silicon steel magnesia wastewater according to claim 2, wherein the qualified water produced in the filtering stage in the step (2) is discharged to a water production tank and is conveyed to a magnesia scrubbing unit for recycling.
4. The method for treating and recycling waste water of magnesium oxide in silicon steel according to claim 2, wherein the amount of compressed air used in the cake drying stage in the step (3) is 1-5 Nm 3 /min·m 2 The ventilation time is 0.5-5 min.
5. The method for treating and recycling silicon steel magnesium oxide wastewater according to claim 1, wherein in the step (3), gravel with a particle size of 20-30 mm is filled in the bottom of the filter tank as a supporting layer.
6. The method for treating and recycling silicon steel magnesium oxide wastewater according to claim 1, wherein in the step (3), the aperture ratio of the filter screen is 50-70%.
7. The method for treating and recycling magnesium oxide wastewater of silicon steel according to claim 1, wherein in the step (3), the filter screen is made of stainless steel, ceramic or plastic material.
8. The method for treating and recycling silicon steel magnesium oxide wastewater according to claim 1, wherein in the step (3), the height of the filler layer is 5-10 times the height of the supporting layer.
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