CN114105232A - Silicon steel magnesium oxide wastewater treatment and recycling method - Google Patents
Silicon steel magnesium oxide wastewater treatment and recycling method Download PDFInfo
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Abstract
The invention belongs to the technical field of water treatment, and particularly relates to a silicon steel magnesium oxide wastewater treatment and recycling method, which comprises the following steps: conveying the silicon steel magnesium oxide wastewater to a filtering, sludge concentrating and drying integrated system, treating by the filtering, sludge concentrating and drying integrated system, discharging filter cakes and generating qualified water, and discharging the qualified water 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; the dried magnesium oxide particles are used as the filler of the biological aerated filter, and the water after nitration is discharged from the upper part of the filter. After the treatment of the invention, the magnesium oxide wastewater can meet the recycling requirement and returns to the unit for recycling, thereby realizing the reclamation of the wastewater; the generated precipitated sludge and powdered activated carbon generated by desulfurization and denitrification of the sintering flue gas are prepared into magnesium oxide particles which are used as fillers of the biological aeration filter, so that the resource utilization of the precipitated sludge of the magnesium oxide wastewater is realized.
Description
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-drawing leveling unit is provided with magnesium oxide powder. The magnesium oxide brushing section mainly removes MgO powder on the surface of the strip steel, and the MgO powder on the surface of the strip steel is brushed and washed by the brushing groove, so that the clean strip steel enters the inlet loop, and the pollution to the inlet loop is avoided. The inside of the brushing groove is generally brushed by industrial water, and the magnesium oxide powder is remained in the water after brushing. In order to save water resources, the used magnesium oxide wastewater is generally treated, and magnesium oxide powder in the wastewater is removed and then returned to a unit for recycling.
The main pollutant in the silicon steel magnesia wastewater is magnesia powder, and according to the analysis of the particle size of suspended matters in the magnesia wastewater of certain steel enterprises, the particle size range is 1-50 mu m, and the average particle size is 10.7 mu m. The treatment of suspended matter is usually carried out by precipitation, air flotation and filtration.
Precipitation is the most commonly used process, but most of particulate matters in wastewater are fine and difficult to remove by natural precipitation, chemical agents such as coagulant and coagulant aid are generally added to enhance the removal effect of suspended matters, most of the added chemical agents are precipitated into sludge, a small amount of the added chemical agents are remained in supernate, and if the treated water is recycled, more and more coagulants and coagulant aids remain in the water, so that the recycling of the water is influenced; in addition, the chemical agent is precipitated in the sludge, so that the yield of the sludge is increased, the purity of the sludge is influenced, and the resource utilization of the sludge is adversely affected.
The air floatation is a process of utilizing highly dispersed micro air-robes as carriers to adhere to suspended pollutants in the wastewater, enabling the buoyancy of the suspended pollutants to be larger than the gravity and the resistance, enabling the pollutants to float up to the water surface to form foams, and then scraping the foams from the water surface by using slag scraping equipment to realize solid-liquid or liquid-liquid separation. The air floatation process also needs to add a coagulating agent, so that the problem of the air floatation process is the same as that of precipitation.
The filtration is that water passes through a filter medium with a micro-pore passage, the pressure at two sides of the filter medium is different, the water passes through the micro-pore passage under the action of differential pressure driving force, and particulate matters and colloidal matters are blocked by the medium and cannot pass through the medium. The filtering process for removing the suspended matters includes sand filtering, microfiltration and the like. Backwashing is needed after the sand filtration process is saturated; the microfiltration process produces a concentrate which, after contamination, also requires chemical cleaning.
The sludge produced by the coagulating sedimentation, air flotation and filtration processes is sludge with high water content, the water content of the sludge for sedimentation and air flotation is generally more than 99%, the water content of sand filtration backwashing water and microfiltration concentrated solution is more than 99.9%, and the sludge needs to be further concentrated and dewatered.
With the stricter national environmental protection standards, the over-current denitration of sintering flue gas becomes a necessary choice for many steel enterprises, and the activated carbon (coke) process can meet the requirements of desulfurization and desulfurization at the same time, so that the process is widely applied, and about 5% of powdered activated carbon can be generated in the activated carbon regeneration process and cannot be recycled.
The waste water containing ammonia nitrogen is a common waste water, biological nitrification is a common, economical and efficient biochemical treatment process, but alkalinity is consumed in the nitrification reaction process to cause pH reduction, and in order to ensure the stable operation of the biochemical reaction, chemical agents such as sodium hydroxide, sodium carbonate and the like are usually added to supplement the alkalinity.
Disclosure of Invention
The invention aims to provide a method for treating and recycling silicon steel magnesium oxide wastewater, the treated silicon steel magnesium oxide wastewater can meet the recycling requirement and is returned to a unit for recycling, and the recycling of the wastewater is realized; the generated precipitated sludge and powdered activated carbon generated by desulfurization and denitrification of the sintering flue gas are prepared into magnesium oxide particles which are used as fillers of the biological aeration filter, so that the resource utilization of the precipitated sludge of the magnesium oxide wastewater is realized.
The technical scheme of the invention is as follows:
a silicon steel magnesium oxide wastewater treatment and recycling method comprises the following steps:
(1) conveying the silicon steel magnesium oxide wastewater to a filtering, sludge concentrating and drying integrated system, treating by the filtering, sludge concentrating and drying integrated system, discharging filter cakes and generating qualified water, and discharging the qualified water to a water production tank; the content of suspended matters in the silicon steel magnesium oxide 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%; after mixing, granulating in a granulator, and drying, wherein the particle size of the granulated particles is 5-10 mm;
(3) taking the dried magnesium oxide particles obtained in the step (2) as a filler of the biological aerated filter, filling gravels with the particle size of 10-50 mm at the bottom of the filter as a supporting layer, filling the dried magnesium oxide particles at the upper part of the supporting layer, and arranging at least one layer of the supporting layer and at least one layer of a packing layer in the reaction column; a filter screen is arranged on the upper part of the supporting layer, the aperture of the filter screen is 0.5-2.5 mm, and the aperture ratio is 20-80%; water after the nitration reaction is discharged from the upper part of the filter, and the hydraulic retention time in the filter is 8-50 h; the gas-water ratio of aeration is controlled to be 3-8: 1.
Further, the treatment process of the silicon steel magnesium oxide wastewater in the integrated system of filtering, sludge concentration and drying is as follows:
(1) pre-filtering: the silicon steel magnesium oxide wastewater enters a filtering container, particles with the pore diameter larger than that of the filtering cloth in the wastewater generate a bridging effect on the surface of the filtering cloth, and particles with the pore diameter smaller than that of the filtering cloth pass through the filtering cloth and remain in the water, and return to the regulating reservoir, wherein the pre-filtering time is 0.5-5 min;
(2) and (3) filtering: the magnesium oxide wastewater enters a filtering procedure after being gradually clarified in the pre-filtering stage, a filter cake becomes a main filtering layer, fine particles are intercepted, and the generated magnesium oxide wastewater flows into a water production tank; with the prolonging of the filtering time, the filter cake becomes 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 to 80 percent of the initial water yield;
(3) and (3) drying a filter cake: after filtering is stopped, draining water in the filtering container to a regulating tank, introducing compressed air in the same direction as filtering, forcing the compressed air to pass through a filter cake, discharging filtrate in the filter cake by gas, and compressing the filter cake, wherein the water content of the filter cake is 22-28%;
(4) back flushing and sludge discharging: after the filter cake is dried, introducing reverse compressed air, wherein the using amount of the compressed air is 2-10 Nm3/min·m2And (4) ventilating for 0.5-2 min, and discharging the filter cake after the filter cloth falls off.
According to the silicon steel magnesium oxide wastewater treatment and recycling method provided by the invention, further, qualified water generated in the filtering stage is discharged to a water production tank and conveyed to a magnesium oxide scrubbing unit for recycling.
According to the silicon steel magnesium oxide wastewater treatment and recycling method provided by the invention, further, in a filter cake drying stage, the amount of compressed air is 1-5 Nm3/min·m2The aeration time is 0.5-5 min,
according to the silicon steel magnesium oxide wastewater treatment and recycling method provided by the invention, further, in the step (2), the granulated magnesium oxide particles are flatly 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 bagged.
According to the silicon steel magnesium oxide wastewater treatment and recycling method provided by the invention, further, the drying time is more than 5-7 days, if the water content is reduced to be less than 5-10% when the drying time is less than 5-7 days, water needs to be sprayed on the surfaces of magnesium oxide particles, and the drying time is prolonged to be more than 5-7 days.
According to the silicon steel magnesium oxide wastewater treatment and recycling method provided by the invention, furthermore, in the step (3), gravels with the particle size of 20-30 mm are filled at the bottom of the filter pool and are used as a supporting layer.
According to the silicon steel magnesium oxide wastewater treatment and recycling method provided by the invention, further, in the step (3), the aperture ratio of the filter screen is 50-70%.
According to the silicon steel magnesium oxide wastewater treatment and recycling method provided by the invention, further, in the step (3), the filter screen is made of stainless steel, ceramic or plastic materials.
According to the silicon steel magnesium oxide wastewater treatment and recycling method provided by the invention, further, in the step (3), the height of the packing layer is 5-10 times of that of the supporting layer.
Detailed description of the invention:
the content of suspended matters in the silicon steel magnesium oxide wastewater is 50-500 mg/L, and the particle size of the suspended matters is 1-50 mu m.
The magnesium oxide wastewater is conveyed to a filtering, sludge concentrating and drying integrated system by a lifting pump, and the system mainly comprises a filtering container, a filter supporting 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) pre-filtering: and (3) allowing the magnesium oxide wastewater to enter a filtering container, wherein particles with the pore diameter larger than that of the filtering cloth in the wastewater generate a bridging effect on the surface of the filtering cloth, and the particles with the pore diameter smaller than that of the filtering cloth penetrate through the filtering cloth and remain in the water, so that part of water cannot meet the filtering requirement, and returns to the regulating tank, and the pre-filtering time is 0.5-5 min.
(2) And (3) filtering: the magnesium oxide wastewater enters a filtering procedure after being gradually clarified in the pre-filtering stage, a filter cake becomes a main filtering layer, fine particles are intercepted, and the generated filtered water meets the requirement and automatically flows into a water production tank; and (3) with the prolonging of the filtering time, the filter cake becomes 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 initial water yield.
(3) And (3) drying a filter cake: after the filtration is stopped, emptying the water in the filtration container to a regulating tank, and then introducing compressed air in the same direction as the filtration, wherein the usage amount of the compressed air is 1-5 Nm3/min·m2Ventilating for 0.5-5 min, and pressingThe compressed air is forced to pass through the filter cake, and the filtrate in the filter cake is discharged by the 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 flushing and sludge discharging: after the filter cake is dried, introducing reverse compressed air, wherein the using amount of the compressed air is 2-10 Nm3/min·m2And (3) ventilating for 0.5-2 min, wherein the filter cake is cracked due to expansion of the filter cloth and falls off from the filter cloth to be discharged.
And then proceed to the next filtration cycle.
After being treated by the integrated system of filtering, sludge concentrating and drying, qualified water produced in the filtering stage is discharged to a water production tank and 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 problem of ion enrichment does not exist.
The discharged filter cake contains magnesium oxide as a main component, and also contains a part of titanium dioxide and a small amount of ferrite compounds, silica, and the like. Mixing and stirring filter cakes discharged by the previous system and powdered activated carbon generated by a flue gas desulfurization and denitrification process, wherein the proportion of the filter cakes is 60-80%, and the proportion of the activated carbon is 20-40%. And after mixing, the mixture enters a granulator for granulation, and the particle size of the granulated particles is 5-10 mm.
And (3) spreading the granulated magnesium oxide particles on a cool and ventilated ground for natural drying, wherein the thickness is controlled to be 0.5-2 cm. 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 (3) drying for 5-15 days, and if the water content is reduced to below 5% when the drying time is less than 5 days, spraying water on the surfaces of the magnesium oxide particles, and prolonging the drying time to above 5 days.
The dried magnesium oxide particles are used as a filler of the biological aerated filter, gravels with the particle size of 10-50 mm (preferably 20-30 mm) are filled at the bottom of the filter and are used as a supporting layer, the dried magnesium oxide particles are filled at the upper part of the supporting layer, and at least one layer is arranged on the supporting layer and the filler layer in the reaction column respectively; a filter screen is arranged on the upper part of the supporting layer, the aperture of the filter screen is 0.5-2.5 mm, the aperture ratio is 20-80% (preferably 50-70%), and the material is stainless steel, ceramic, plastic and other materials; the height of the packing layer is 5-10 times of that of the supporting layer; water after the nitration reaction is discharged from the upper part of the filter, and the hydraulic retention time in the filter is 8-50 h; the gas-water ratio of aeration is controlled to be 3-8: 1.
In the filter, microorganisms are attached to the surfaces of magnesium oxide particles to form a biological membrane, and organic oxidation and nitration reactions occur in the biological membrane; in the reaction process, the pH value is gradually reduced along with the degradation of ammonia nitrogen, magnesium oxide particles are slowly corroded under the double action of aeration scouring, MgO released along with a fallen biological membrane is used as a weak alkaline substance to supplement the alkalinity, and the stable operation of biochemical reaction is ensured; in addition, the released activated carbon powder can adsorb organic matters in water, and the removal effect of the organic matters is improved.
Advantageous technical effects
The invention provides a process for treating and recycling silicon steel magnesium oxide wastewater, and after the treatment of the process, the magnesium oxide wastewater can meet the recycling requirement and returns to a unit for recycling, so that the recycling of the wastewater is realized; the generated precipitated sludge and powdered activated carbon generated by desulfurization and denitrification of the sintering flue gas are prepared into magnesium oxide particles which are used as fillers of the biological aeration filter, so that the resource utilization of the precipitated sludge of the magnesium oxide wastewater 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 silicon steel magnesium oxide wastewater treatment and recycling process provided by the invention.
Detailed Description
In order to better understand the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.
Example 1
A silicon steel magnesium oxide wastewater treatment and recycling method comprises the following steps:
the content of suspended matters in the silicon steel magnesium oxide wastewater is 50mg/L, and the particle size of the suspended matters is 1-50 mu m.
Filtration, sludge concentration, mummification integration systemPre-filtering for 5 min; stopping filtering when the water yield of the filter is reduced to 60%, and returning the filtered water to the unit for recycling, wherein the concentration of suspended matters in the filtered water is 8 mg/L; after the filtration is stopped, the water in the filtration container is emptied to the original water tank, and then compressed air is introduced in the same direction as the filtration, wherein the amount of the compressed air is 2Nm3/min·m2The aeration time is 0.5min, 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 28%; after the filter cake is dried, compressed air is introduced reversely, and the dosage of the compressed air is 10Nm3/min·m2And (3) ventilating for 0.5min, generating cracks on a filter cake, and discharging the filter cake after falling off from the filter cloth.
The discharged filter cake and powdered activated carbon generated by the sintering flue gas desulfurization and denitrification process are mixed according to the mixing ratio of 60: 40, and after mixing, granulating in a granulator, wherein the particle size of the granules after granulation is 5 mm.
And (3) spreading the granulated magnesium oxide particles on a cool and ventilated ground for natural drying, wherein the thickness is 1cm, and the water content is reduced to 8% after 5 days.
Filling dried magnesium oxide particles into a biological aerated filter, filling gravels with the particle size of 10mm at the bottom of the filter as a supporting layer, and filling the dried magnesium oxide particles with the thickness of 100mm at the upper part of the supporting layer; 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%; water after nitration is discharged from the upper part of the filter tank, and the hydraulic retention time in the filter tank is 8 hours; the gas-water ratio of aeration is controlled to be 3: 1. The influent COD of the biological aerated filter is 360mg/L, and the ammonia nitrogen is 48 mg/L; the effluent COD is 65mg/L, and the ammonia nitrogen is 3.4 mg/L.
Example 2
A silicon steel magnesium oxide wastewater treatment and recycling method comprises the following steps:
the content of suspended matters in the silicon steel magnesium oxide wastewater is 325mg/L, and the particle size of the suspended matters is 1-50 mu m.
The pre-filtering time of the filtering, sludge concentration and drying integrated system is 1 min; stopping filtering when the water yield of the filtering is reduced to 70 percent, and returning the suspended substance in the filtered water to the unit for recycling, wherein the concentration of the suspended substance in the filtered water is 6 mg/L; stopping filtrationThen, the water in the filter container is emptied into the raw water tank, and then compressed air is introduced in the same direction as the filtration, the amount of the compressed air being 1Nm3/min·m2The ventilation 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 filter cake is dried, compressed air in the reverse direction is introduced, and the using amount of the compressed air is 7Nm3/min·m2And (3) ventilating for 2min, generating cracks on a filter cake, and discharging the filter cake after falling off from the filter cloth.
The discharged filter cake and powdered activated carbon generated by the sintering flue gas desulfurization and denitrification process are mixed according to the weight ratio of 70: 30, and after mixing, granulating in a granulator, wherein the particle size of the granulated particles is 8 mm.
The granulated magnesium oxide particles are spread on a cool and ventilated ground for natural drying, the thickness is 1.5cm, and the water content is reduced to 7 percent after 7 days.
Filling dried magnesium oxide particles into a biological aerated filter, filling gravels with the particle size of 30mm at the bottom of the filter as a supporting layer, and filling the dried magnesium oxide particles with the thickness of 150mm at the upper part of the supporting layer; 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%; water after nitration is discharged from the upper part of the filter, and the hydraulic retention time in the filter is 30 h; the gas-water ratio of aeration is controlled to be 5: 1. The influent COD of the biological aerated filter is 670mg/L, and the ammonia nitrogen is 96 mg/L; effluent COD is 87mg/L, and ammonia nitrogen is 4.8 mg/L.
Example 3
A silicon steel magnesium oxide wastewater treatment and recycling method comprises the following steps:
the content of suspended matters in the silicon steel magnesium oxide wastewater is 500mg/L, and the particle size of the suspended matters is 1-50 mu m.
The pre-filtering time of the filtering, sludge concentration and drying integrated system is 0.5 min; stopping filtering when the water yield of the filtering is reduced to 60 percent, and returning the suspended substance in the filtered water to the unit for recycling, wherein the concentration of the suspended substance in the filtered water is 9 mg/L; after the filtration is stopped, the water in the filtration container is emptied to the original water tank, and then compressed air is introduced in the same direction as the filtration, wherein the amount of the compressed air is 2Nm3/min·m2The ventilation time is 1min, 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 25%; after the filter cake is dried, compressed air is introduced reversely, and the dosage of the compressed air is 10Nm3/min·m2And (3) ventilating for 0.5min, generating cracks on a filter cake, and discharging the filter cake after falling off from the filter cloth.
The discharged filter cake and powdered activated carbon generated by the sintering flue gas desulfurization and denitrification process are mixed according to the weight ratio of 80: 20, and after mixing, granulating in a granulator, wherein the particle size of the granulated particles is 10 mm.
And (3) spreading the granulated magnesium oxide particles on a cool and ventilated ground for natural drying, wherein the thickness is 2cm, and the water content is reduced to 8% after 7 days.
Filling dried magnesium oxide particles into a biological aerated filter, filling gravels with the particle size of 50mm at the bottom of the filter as a supporting layer, and filling the dried magnesium oxide particles with the thickness of 200mm at the upper part of the supporting layer; 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%; water after nitration is discharged from the upper part of the filter tank, and the hydraulic retention time in the filter tank is 50 h; the gas-water ratio of aeration is controlled at 8: 1. The influent COD of the biological aerated filter is 980mg/L and the ammonia nitrogen is 156 mg/L; the COD of the effluent is 72mg/L, and the ammonia nitrogen is 2.8 mg/L.
Of course, those skilled in the art should recognize that the above-described embodiments are illustrative only, and not limiting, and that changes and modifications can be made within the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A silicon steel magnesium oxide wastewater treatment and recycling method is characterized by comprising the following steps:
(1) conveying the silicon steel magnesium oxide wastewater to a filtering, sludge concentrating and drying integrated system, treating by the filtering, sludge concentrating and drying integrated system, discharging filter cakes and generating qualified water, and discharging the qualified water to a water production tank; the content of suspended matters in the silicon steel magnesium oxide 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%; after mixing, granulating in a granulator, and drying, wherein the particle size of the granulated particles is 5-10 mm;
(3) taking the dried magnesium oxide particles obtained in the step (2) as a filler of the biological aerated filter, filling gravels with the particle size of 10-50 mm at the bottom of the filter as a supporting layer, filling the dried magnesium oxide particles at the upper part of the supporting layer, and arranging at least one layer of the supporting layer and at least one layer of a packing layer in the reaction column; a filter screen is arranged on the upper part of the supporting layer, the aperture of the filter screen is 0.5-2.5 mm, and the aperture ratio is 20-80%; water after the nitration reaction is discharged from the upper part of the filter, and the hydraulic retention time in the filter is 8-50 h; the gas-water ratio of aeration is controlled to be 3-8: 1.
2. The silicon steel magnesium oxide wastewater treatment and recycling method 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) pre-filtering: the silicon steel magnesium oxide wastewater enters a filtering container, large-particle suspended matters in the wastewater generate a bridging effect on the surface of the filter cloth, small particles penetrate through the filter cloth and remain in the water after passing through the filter cloth, and the silicon steel magnesium oxide wastewater returns to an adjusting tank, wherein the pre-filtering time is 0.5-5 min;
(2) and (3) filtering: the magnesium oxide wastewater enters a filtering procedure after being gradually clarified in the pre-filtering stage, a filter cake becomes a main filtering layer, fine particles are intercepted, and produced water flows into a water production tank; with the prolonging of the filtering time, the filter cake becomes 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 to 80 percent of the initial water yield;
(3) and (3) drying a filter cake: after filtering is stopped, draining water in the filtering container to a regulating tank, introducing compressed air in the same direction as filtering, and compressing a filter cake, wherein the water content of the filter cake is 22-28%;
(4) inverse directionBlowing and discharging sludge: after the filter cake is dried, introducing reverse compressed air, wherein the using amount of the compressed air is 2-10 Nm3/min·m2And (4) ventilating for 0.5-2 min, and discharging the filter cake after the filter cloth falls off.
3. The silicon steel magnesia wastewater treatment and reclamation method as recited in claim 2, wherein the qualified water produced in the filtering stage in the step (2) is discharged to a water production tank and conveyed to a magnesia scrubbing unit for recycling.
4. The silicon steel magnesium oxide wastewater treatment and recycling method according to claim 2, wherein in the filter cake drying stage in the step (3), the amount of compressed air is 1-5 Nm3/min·m2And the ventilation time is 0.5-5 min.
5. The silicon steel magnesium oxide wastewater treatment and recycling method according to claim 1, wherein in the step (2), the granulated magnesium oxide particles are spread 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 bagged.
6. The silicon steel magnesium oxide wastewater treatment and recycling method according to claim 5, wherein 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 magnesium oxide particles, and the drying time is prolonged to above 5 days.
7. The silicon steel magnesium oxide wastewater treatment and recycling method according to claim 1, wherein in the step (3), gravels with the particle size of 20-30 mm are filled at the bottom of the filter pool to serve as a supporting layer.
8. The silicon steel magnesium oxide wastewater treatment and recycling method according to claim 1, wherein in the step (3), the aperture ratio of the filter screen is 50-70%.
9. The silicon steel magnesium oxide wastewater treatment and recycling method according to claim 1, wherein in the step (3), the material of the filter screen is stainless steel, ceramic or plastic.
10. The silicon steel magnesium oxide wastewater treatment and recycling method according to claim 1, wherein in the step (3), the height of the packing layer is 5-10 times of that of the support layer.
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