JP4876006B2 - Water treatment system - Google Patents

Description

  The present invention is a system for treating exhaust gas dust collection water in a process having a wet dust collector such as an iron blast furnace, a steel making converter, an electric furnace, a cupola, a dust melting furnace, a non-ferrous metal refining furnace, a scrap melting furnace, etc. The present invention relates to a water treatment system for circulating recovery.

  In general, a processing system (hereinafter referred to as a dust collection system) of dust collection water having a high solid content concentration (hereinafter referred to as SS concentration) generated from a wet dust collector of exhaust gas is a wet dust collector as shown in FIG. 1, a thickener 2 that is a dust collection water treatment facility, a treatment water tank 3, and a dust collection water pump 4. Thickener is a sedimentation tank that performs solid-liquid separation processing of solid content and supernatant water in drainage (dust collection return water). In addition, the dust collection system is a closed water circulation recovery system, but the water amount balance is established by appropriately replenishing the amount lost by evaporation and scattering (water amount; γ1).

  On the other hand, wastewater (water amount; α) having a high SS concentration from the sewage supply system 6 may be received by the thickener 2 for treatment. In this case, as described above, since the water balance is established in the dust collection system, if α is larger than γ1, the treated water after acceptance is discharged from the system as surplus water to the outside of the system 5 as it is. Need to be made. Further, in the sewage supply system 6, the amount received by the thickener 2 must be replenished separately from the amount lost by evaporation and scattering (water amount; γ2). In other words, if α is larger than γ1 in the dust collection system, α-γ1 surplus water is always generated, and the sewage supply system 6 always supplies α in addition to the conventional γ2.

  For example, as shown in FIG. 2, the wastewater treatment of the steelmaking converter is performed by the dust collection system A, the blower and the pumps 11, which are composed of the converter wet dust collector 6, the converter thickener 7, the treatment water tank 8, and the dust collection water pump 9. There is a converter circulating water system B composed of a cooling tower 12, which is a circulating water treatment facility, a treated water tank 13, and a cooling washing water pump. The converter circulation water system (hereinafter referred to as circulation system B) includes a discharge system a in which drainage with a concentration equal to the feedwater SS concentration returns and a discharge system b in which drainage with a concentration higher than the feedwater SS concentration returns. Have. Therefore, the waste water in the discharge system a is cooled as it is in the cooling tower 12 and recovered in the treated water tank 13, so that it can be recycled by using the cooling washing water pump 14, but the waste water in the discharge system b is less than the feed water SS concentration. If the solid content is not removed, the cooling tower 12 performs the cooling process and cannot be recovered in the treated water tank 13.

  Until now, wastewater with a high SS concentration generated from the discharge system b has been sent to the converter thickener 7 in the dust collection system A for solid-liquid separation treatment. For this reason, since the dust collection system A is a closed water circulation system, when the waste water (water amount; α) having a high SS concentration is received from the discharge system b, the treated water is treated as described in FIG. It was discharged as it was from the dust collection system A as surplus water (water amount: α-γ1) to the outside of the converter system 10. In the circulation system B, the treated water tank 13 was replenished with an amount of water (water amount; γ2 + α) of wastewater that could not be circulated and collected.

  As described above, in each converter water treatment system having the equipment system configuration as shown in FIG. 1 and FIG.

JP 2006-231115 A

  As an efficient wastewater circulation recovery in the above-described dust collection system A and circulation system B, a circulation recovery method as shown in FIG. 3 has been common. That is, first, in order to collect wastewater having a high SS concentration generated from the discharge system b, the wastewater is subjected to primary precipitation treatment in a coagulation sedimentation facility 15 including a raw water tank 16, a precipitation tank 17, and a treated water tank 18. . Next, there is a method in which the precipitated treated water is pumped and filtered to the sand filter 20 using the filtration pump 19 and subjected to secondary filtration treatment to treated water with low SS concentration that can be reused as cooling washing water. It was.

  According to the above method, wastewater having a high SS concentration generated from the discharge system b can be collected into the treated water tank 13, and the wastewater can be circulated and collected in the dust collection system A and the circulation system B.

  Here, the problem to be solved by the present invention will be described with reference to FIG.

  In the water treatment system shown in FIG. 3, although extra makeup water (water amount; α) in the circulation system B can be reduced, the sand filter 20 is used as the secondary filtration treatment, so a large amount of washing sewage is generated. To do. This is because the filter 20 must periodically clean the inside of the filter 20 with a large amount of water using the outside of the converter system 21 as a water source for the purpose of eliminating clogging of solids captured between the filter media. It is. As a result, the sand filter 20 generates a large amount of washed sewage (water amount; β1) having a high SS concentration, which is a target for aggregation and precipitation.

  Eventually, the sewage is received and processed by the converter thickener 7, and the treated water (water amount; β1) is discharged from the dust collection system A as surplus water to the outside of the converter system 10 as it is. In A, there remains a problem that efficient drainage circulation recovery cannot be performed.

  That is, in the water treatment system shown in FIG. 3, there is no sewage received from the discharge system b in the circulation system B to the converter thickener 7 in the dust collection system A and processed (water amount; α → 0). The amount of make-up water was reduced to the required amount of make-up water (the amount supplementing the amount of water lost due to evaporation etc.) (water amount; γ2 + α → γ2). However, since a large amount of washed sewage (water amount; β1) generated in the filtration process of the sewage is received and processed by the converter thickener 7 in the dust collection system A, a large amount of excess water (water amount; β1) is collected from the dust collection system A. The problem that -γ1) is discharged outside the converter system 10 is not solved.

  In addition, when the sand filter 20 is employed, additional facilities such as a washing water tank for storing water for washing the filter 20, a pump and blower for washing, and a drain tank for receiving washing wastewater are required. For this reason, not only the equipment cost increases, but also the equipment occupying space becomes large. Therefore, when it is installed in a narrow water treatment plant, there is a space problem.

  Accordingly, there has been a demand for a space-saving and inexpensive water treatment facility that collects wastewater with a high SS concentration generated from the circulation system B without discharging excess water from the dust collection system A to the outside of the converter system 10 as much as possible.

  The efficient, space-saving and inexpensive wastewater circulation and recovery system (water treatment system) according to the present invention has been devised in view of various problems in the exhaust gas dust collection system having a wet dust collector.

The present invention has been made in view of the above problems, and the gist thereof is as follows.
(1) Wet dust collector, for supplying said row cormorants solid-liquid separation means to the solid-liquid separation treatment with respect to the dust collecting waste water from the wet dust collector, the treated water solids separated in the solid-liquid separation means to the wet dust collector A dust collection system having a supply means, a circulating water treatment device, a solid-liquid separation treatment means having a filter for performing solid-liquid separation treatment on the waste water from the circulation water treatment device , and a solid content in the solid-liquid separation treatment means supply There supplying a circulation system having a supply means for supplying treated water separated in the circulating water treatment apparatus, a filtration media cleansing dirty water from the filtration unit of the circulatory system, solid-liquid separation means of the dust collecting system a means, the said filtration unit, the water treatment system and carrying out solid-liquid separation process using the flying characteristics filter medium.

(2) The dust-collecting solid-liquid separation means has a thickener that performs solid-liquid separation processing on the dust-collecting wastewater, and the filter medium cleaning sewage from the circulating filter is used as the dust collecting system. supply means for supplying the water treatment system according to the above (1), wherein the supplying the filter material washing dirty water to the thickener.

(3) The solid-liquid separation processing means of the circulation system includes a coagulation sedimentation facility that performs a first solid-liquid separation process on the wastewater containing the solid content, and a second coagulation facility for the wastewater from the aggregation precipitation facility. Waste water supplied to the filter, the solid content concentration of waste water supplied to the coagulation sedimentation facility is 700 mg / L or more and 8000 mg / L or less. The solid content concentration of the water treatment system according to (1) or (2), wherein the solid content concentration is 400 mg / L or less.

  (4) The water treatment system according to (3) above, wherein a solid content concentration of waste water supplied to the filter is 100 mg / L to 400 mg / L.

  (5) The water treatment system according to any one of (1) to (4), wherein the filter medium is spherical or cylindrical.

  (6) The water treatment system according to any one of (1) to (5) above, wherein a specific gravity of the filter medium is smaller than 1.0.

  (7) The water treatment system according to any one of (1) to (6), wherein the size of the filter medium is 0.1 mm to 1.5 mm.

  (8) The water treatment system according to any one of (1) to (7), wherein the wastewater supplied to the filter has a pH of 6 to 12.

  The present invention has a dust collection system having a wet dust collector, and a processing means including a filter that performs solid-liquid separation processing on waste water containing solids, and supplies washing water of the filter to the dust collection system. By adopting a filter using levitating filter media in the water treatment system, it is possible to provide a more efficient, space-saving and inexpensive drainage circulation collection system, and to discharge water to the dust collection system and to the dust collection system. Reduction of makeup water can be done effectively.

  In the following, the best mode for carrying out the present invention will first be outlined with reference to FIG.

  The main configuration of the dust collection system A of the present embodiment includes a wet dust collector 1, a thickener 2, a treated water tank 3, and a dust collection water pump 4. However, as long as the exhaust gas dust collected water is processed using the wet dust collector 1, the type and shape of the individual devices constituting the dust collection system A are not selected. Further, the sewage supply system 6 that supplies the cleaning sewage to the dust collection system A (thickener 2) is a discharge system a in which waste water having a concentration equivalent to the feed water SS concentration returns like the converter circulation system B shown in FIG. And it is not necessary to have two discharge systems b to which drainage with a concentration higher than the feedwater SS concentration returns. For example, any circulatory system can be used as long as sewage with a concentration higher than the feedwater SS concentration is generated and the sewage cannot be reused as feedwater unless it is treated using the treatment facility 7 including a filter.

  Here, in the filter medium washing process of the filter, by applying a filter in which the amount of washing sewage is small as will be described later, washing sewage (water amount; water amount; generated in the sewage supply system 6 (filter) is high. If β) is not brought into the dust collection system A as much as possible, surplus water from the dust collection system A to the outside 5 can be reduced to the maximum.

  That is, if β approaches γ1, excess water can be further reduced. If β is γ1 or less, β becomes a part of makeup water in the dust collection system A (treated water tank 3), and excess water to the outside 5 is Does not occur.

  Next, regarding the best mode for carrying out the present invention, converter dust collection water treatment is shown as an example in FIG. Here, the filtration processing system to which a filter with a small amount of washed sewage for the filter medium is applied will be described in detail.

  First, the device configuration will be described. The equipment configuration in the water treatment of the converter dust collection system A and the circulation system B is the same as that shown in FIG. 3 employing a sand filter.

  The circulation system B has two systems, a discharge system a in which drainage having a concentration equal to the feedwater SS concentration returns and a discharge system b in which drainage having a concentration higher than the feedwater SS concentration returns. 12 is cooled and recovered in the treated water tank 13 to be recycled as cooling washing water. Further, the waste water of the discharge system b is once stored in the raw water tank 16, and then separated into solid content and supernatant water in the precipitation tank 17. Here, the separated primary treated water is stored in the treated water tank 18 and then pumped to the filter 21 filled with the floatable filter medium by using the filtration pump 19. Furthermore, the solid content in the primary treated water is supplemented by the filter 21 and subjected to secondary treatment to treated water having a low SS concentration that can be reused as cooling washing water. Finally, it is cooled in the cooling tower 12 and recovered in the treated water tank 13 to be recycled as cooling washing water.

  Here, when a sand filter is applied to a filter for secondary filtration of wastewater having a high SS concentration generated from the circulation system B, the amount of washing sewage (water amount; β1) becomes large. Therefore, in the present invention, by using the filter 21 in which a floatable filter medium such as expanded polystyrene is filled in the machine, the machine can be washed with raw water flowing into the filter 21 without requiring another water source, It pays attention to the fact that the amount of washing sewage (water amount; β2) can be greatly reduced as compared with the case of using a filter.

  Next, the water amount balance effect in the converter water treatment system of the filtration treatment system to which the filter 21 filled with the floatable filter medium is applied will be described in detail. Here, the filter 21 using the floatable filter medium has a structure in which a filter medium layer is formed with the filter medium that has floated in the filtration tank, and the stock solution is passed through the filter layer in an upward flow.

  Since the washing sewage generated from the sand filter is large, the present inventors have searched for and examined a filtration method that can reduce the amount of sewage. As a result, if the filter 21 using a floatable filter medium is employed, for example, the amount of makeup water in the circulation system B is increased by about 5% compared to the sand filter, but the amount of water in which the washed sewage flows into the converter thickener 7. Was found to be reduced by about 96%.

  That is, since β2 is a very small amount of about 4% of β1 (example: β2 = 0.04 × β1 << β1), the replenishment to the circulatory system B is a fraction of β2 in addition to the conventional γ2 (FIG. 3). However, the increase is as small as about 5% (example: β2 = 0.05 × γ2). In addition, since the difference between β2 and γ1 is reduced, surplus water from the dust collection system A to the outside of the converter system 10 can be significantly reduced compared to the sand filter so that it can be ignored in terms of operation and equipment design (β2 -Γ1 << β1-γ1). Further, if the washing sewage of the floatable filter medium is γ1 or less (β2−γ1 <0), the sewage becomes a part of makeup water in the dust collection system A, and no excess water is generated outside the converter system 10.

  Furthermore, the operation form of this filtration processing system is demonstrated in detail.

  Since the floatable filter medium filled in the filter 21 has a specific gravity smaller than that of sand, mechanical stirring with a stirrer installed in the filter 21 is possible. And since the solid content adhering to the floatable filter medium can be satisfactorily peeled off by stirring with a stirrer stronger than conventional water flow stirring, the amount of washing water of the floatable filter medium is smaller than that of the sand filter medium. As a result, sand filter media need to use relatively low wash water with an SS concentration of about 10 to 100 mg / l, whereas floatable filter media flow into a highly turbid filter with an SS concentration of about 100 to 400 mg / l. Raw water can be used as washing water.

  As a result, the amount of cleaning sewage generated from the cleaning process of the filter 21 and supplied to the converter thickener 7 can be reduced. That is, excess water from the dust collection system A to the outside of the converter system 10 can be significantly reduced. Here, if the amount of washed sewage β2 is less than or equal to the amount of makeup water γ1 in the dust collection system A, surplus water from the dust collection system A to the outside of the converter system 10 is not generated, and more efficient circulation and collection of waste water is achieved. it can.

  Next, as a material of the filter medium showing the floating performance, a foamable polymer resin is preferable. In particular, foamed polyurethane, foamed polypropylene, and foamed polystyrene are suitable.

  As the shape of the filter medium, a spherical shape (a shape whose cross section includes a circle or an ellipse) or a cylindrical shape (a shape whose cross section perpendicular to the longitudinal direction includes a circle or an ellipse) is preferable, and a spherical shape is particularly preferable. In the case of a projection like a cube, the stirring efficiency is deteriorated due to friction at the time of collision in the filter, and therefore a spherical or cylindrical shape with fewer corners is optimal. As the aspect ratio of the cylinder, the aspect ratio is preferably 1: 1 to 3, and particularly preferably 1: 1 to 2.

  The specific gravity of the filter medium is preferably less than 1.0 and more preferably 0.01 to 0.5. In particular, 0.05 is preferable as the bulk specific gravity. If the specific gravity is 1.0 or more, the amount of washing water for the filter medium (that is, the amount of washing sewage β2) for the purpose of eliminating clogging in the filter 21 increases, and the stirring power of the filter medium also increases. Moreover, if specific gravity is smaller than 0.5, the problem of shortening the lifetime by abrasion of a filter medium will arise.

  The size of the filter medium (maximum diameter in the case of a spherical shape, maximum length in the case of a cylindrical shape) is preferably 0.1 mm to 2.0 mm, and particularly preferably 1.0 mm to 2.0 mm. If the size is larger than 2.0 mm, the amount of washing water for the filter medium for the purpose of eliminating clogging in the filter 21 increases, and the stirring power of the filter medium also increases. Further, if the size is smaller than 0.1 mm, there arises a problem that the differential pressure of the filter 21 is likely to stand or the filter medium flows out of the filter 21.

  The applied pH of the filter medium to be used is preferably 6 to 12, particularly 7 to 9. If the pH is 6 or lower and the alkali is 12 or higher, the surface of the filter medium is melted and uneven, resulting in a problem that the solid content capturing efficiency and the cleaning efficiency are lowered.

  The applied SS concentration of the filter medium to be used is preferably 400 mg / l or less, and particularly preferably 100 mg / l or less. If the SS concentration is 400 mg / l or more, the clogging of the floatable filter medium proceeds in a short time, and there arises a problem that the solid content throughput decreases or the filter medium wear progresses as the cleaning time increases. .

  Finally, unlike the sand filtration method, the filter 21 filled with the floatable filter medium uses raw water flowing into the filter 21 as a water source for cleaning the machine, and is stirred and washed with a stirrer installed in the machine. There is no need for backwash equipment such as backwash pumps and backwash blowers. In addition, the floatable filter medium has a smaller specific gravity than sand and can reduce the power of a pump that feeds water to the filter 21, so that the equipment cost is lower and the space is saved compared to the case where a sand filter is used.

  Hereinafter, the effect of this invention which performed the water treatment of the apparatus structure shown in FIG. 5 is demonstrated in detail.

Example 1
In the converter water treatment system, the effect of introducing a filter 21 filled with a floatable filter medium as in the apparatus of FIG. 5 will be described as an example. Here, as shown in Table 1, the amount of sewage α generated from the circulation system B is 3.0 m ³ / min, and the water quality is an SS concentration of 800 to 8,000 mg on the entry side of the coagulation sedimentation facility 15 which is a pretreatment process for filtration. / L and pH 10-11, SS concentration 100-400 mg / l and pH 10-11 at the entrance side of the filter 21.

  Moreover, about the floatable filter medium with which the filter 21 is filled, the material used is a foamed polystyrene, the shape is cylindrical, the specific gravity is 0.05, and the size is 1.1 mm.

  In addition, about the comparative example, the quantity (alpha) and water quality of the wastewater which generate | occur | produce in the circulation system B were made into the same as that of a present Example. Moreover, as a filter medium with which the filter 20 is filled, the material is sand / anthra, the shape is spherical or protruding, the specific gravity is 1.2 to 0.5, and the size is 0.8 to 1.6. did.

  When the filter 21 filled with the floatable filter medium is introduced in the above case, the amount of washing sewage β2 is reduced by about 96% of β1 as compared with the comparative example in which the sand filter 20 is adopted as shown in Table 2. I was able to. As a result, although the supplementary water amount γ (γ2 + β2) in the circulation system B in this example increases by about 5% compared to the comparative example (supplementary water amount γ2), the surplus water (β2−γ1) from the dust collection system A is almost equal. I was able to make it zero. Here, in Table 2, when the value of excess water (β2−γ1) from the dust collection system A is negative, it is indicated as “0”. When the value (β2−γ1) is negative, the cleaning wastewater β2 is a part of makeup water in the dust collection system A.

  Further, there is no need for cleaning equipment such as a backwash pump and a blower for the sand filter 20, and the floatable filter medium has a smaller resistance to water flow than sand and can reduce the power of the pump that sends water to the filter 21. Can be reduced by 30% and installation space by 40%.

(Example 2)
The amount of sewage generated from the circulation system B and the water quality conditions are the same as in Example 1. Moreover, as shown in Table 1, the filter medium filled in the filter 21 was the same in material, shape and size as in Example 1, but a specific gravity of 0.5 was adopted.

  Also in this example, the same effect as in Example 1 was obtained. That is, the amount of washing sewage β2 of the filter 21 can be greatly reduced, and surplus water from the dust collection system A can be made substantially zero.

(Example 3)
The amount of sewage generated from the circulation system B and the water quality conditions are the same as in Example 1. In addition, as shown in Table 1, the filter medium filled in the filter 21 was the same in material, shape, and specific gravity as in Example 1, but a filter having a size of 2.0 mm was used.

  Also in this example, the same effect as in Example 1 was obtained. That is, the amount of washing sewage β2 of the filter 21 can be greatly reduced, and surplus water from the dust collection system A can be made substantially zero.

Schematic showing water balance in wet dust collection system Schematic showing water balance in converter wet dust collection system Schematic showing equipment measures for the converter wet dust collection system of FIG. Schematic showing water balance correction effect of wet dust collection system Schematic showing equipment measures for the converter wet dust collection system of FIG.

Explanation of symbols

A: Dust collection system B: Circulation system 6: Converter wet dust collector 7: Thickener 8: Treated water tank 12: Cooling tower 13: Treated water tank 15: Coagulation sedimentation equipment 21: Filter using a floatable filter medium

Claims (8)

Wet dust collector, row cormorants solid-liquid separation means solid-liquid separation treatment with respect to the dust collecting waste water from the wet dust collector, the supply means for supplying treated water solids separated in the solid-liquid separation means to the wet dust collector A dust collection system,
Circulating water treatment device, solid-liquid separation processing means having a filter for performing solid-liquid separation processing on waste water from the circulating water treatment device, circulating the treated water from which the solid content has been separated by the solid-liquid separation processing means A circulation system having a supply means for supplying to the water treatment device;
The filter material washing dirty water from the filtration unit of the circulatory system has a supply means for supplying a solid-liquid separation means of the dust collection system, said filtration machine, a solid-liquid separation process using the flying characteristics filter medium A water treatment system characterized by performing. The solid-liquid separation means of the dust collection system has a thickener that performs a solid-liquid separation process on the dust collection waste water,
The circulation system supply means for supplying to the dust collecting system the filter media cleaning sewage filtration machine, the water treatment system of claim 1, wherein the supplying the filter material washing dirty water to the thickener. The solid-liquid separation processing means of the circulation system includes a coagulation precipitation facility that performs a first solid-liquid separation process on the wastewater containing the solid content, and a second solid-liquid separation with respect to the wastewater from the aggregation precipitation facility. Having the filter to perform the treatment,
The solid content concentration of the wastewater supplied to the coagulation sedimentation facility is 700 mg / L or more and 8000 mg / L or less,
3. The water treatment system according to claim 1, wherein a solid content concentration of waste water supplied to the filter is 400 mg / L or less.   The water treatment system according to claim 3, wherein the solid content concentration of the waste water supplied to the filter is 100 mg / L to 400 mg / L.   The water treatment system according to claim 1, wherein the filter medium is spherical or cylindrical.   The water treatment system according to claim 1, wherein a specific gravity of the filter medium is smaller than 1.0.   The water treatment system according to any one of claims 1 to 6, wherein a size of the filter medium is 0.1 mm to 1.5 mm.   The water treatment system according to any one of claims 1 to 7, wherein the wastewater supplied to the filter has a pH of 6 to 12.

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