Method for using desalted water in galvanizing line and galvanized sheet production equipment

Abstract

The application provides a utilization method of desalted water of a galvanizing line and a galvanized sheet production equipment. The utilization method comprises the following steps: introducing the desalted water into a finishing machine, collecting generated finishing waste water, introducing the finishing waste water into a first sedimentation and ultrafiltration mechanism for treatment, and obtaining first treated desalted water; introducing the first treated desalted water into a tension leveler, collecting generated tension leveler waste water, introducing the tension leveler waste water into a second sedimentation and ultrafiltration mechanism for treatment, and obtaining second treated desalted water; introducing the second treated desalted water into a water quenching tank and a desalted water circulation tank for circulation, collecting part of generated water quenching waste water, introducing the water quenching waste water into a third sedimentation and ultrafiltration mechanism for treatment, and obtaining third treated desalted water; and introducing the third treated desalted water into a cleaning section for use. The desalted water is utilized in series, the use amount of the desalted water is saved, waste water discharge is reduced, the treatment load, treatment scale and treatment cost of oil-containing waste water are reduced, and the water production and water supply pressure of the desalted water are relieved.

Description

Technical Field

[0001] This invention relates to the field of cold-rolled galvanizing line production, and more particularly to a method for utilizing desalinated water from galvanizing lines and equipment for producing galvanized sheets. Background Technology

[0002] The finishing, leveling, water quenching, and cleaning sections of the cold-rolled galvanizing line all require demineralized water. The cleaning section is divided into an electrolytic degreasing section, an alkaline brushing section, and a hot water rinsing section. Among these, the demineralized water used in the finishing and leveling sections is directly discharged as wastewater, resulting in a large overall consumption of demineralized water and a large total volume of wastewater generated, which puts significant pressure on subsequent wastewater treatment. Summary of the Invention

[0003] The main objective of this invention is to provide a method for utilizing demineralized water from a galvanizing line and galvanized sheet production equipment, in order to solve the technical problems of large demineralized water consumption and large total wastewater generation in existing cold-rolled galvanizing lines.

[0004] To achieve the above objectives, the present invention provides a method for utilizing desalinated water from a galvanizing line, comprising the following steps:

[0005] The demineralized water is fed into the polishing machine and the resulting polishing wastewater is collected. The polishing wastewater is then treated by a first sedimentation ultrafiltration mechanism to obtain the first treated demineralized water.

[0006] The first-treated demineralized water is fed into the straightening machine for use and the resulting straightening wastewater is collected. The straightening wastewater is then treated by the second sedimentation ultrafiltration mechanism to obtain the second-treated demineralized water.

[0007] The second-treatment demineralized water is circulated into the galvanizing line's water quenching tank and the demineralized water circulation tank to collect a portion of the generated water quenching wastewater. The water quenching wastewater is then treated by a third sedimentation ultrafiltration mechanism to obtain the third-treatment demineralized water.

[0008] The demineralized water from the third treatment process is then fed into the cleaning section.

[0009] The filtration components of the first precipitation ultrafiltration mechanism, the second precipitation ultrafiltration mechanism, and the third precipitation ultrafiltration mechanism include inorganic ceramic membranes, and the filtration accuracy of the inorganic ceramic membranes is 50 nm.

[0010] According to embodiments of this application, at least one of the following steps is also included:

[0011] A portion of the first-treatment demineralized water is fed into the optical finishing machine for recycling.

[0012] A portion of the second-treatment desalinated water is fed into the straightening machine for recycling.

[0013] A portion of the third-stage demineralized water is circulated into the galvanizing line's water quenching tank and demineralized water circulation tank.

[0014] According to the embodiments of this application, the finishing wastewater, the straightening wastewater, and the water quenching wastewater are pressurized to 0.3-0.4 MPa and filtered by the filtration components of the first precipitation ultrafiltration mechanism, the second precipitation ultrafiltration mechanism, and the third precipitation ultrafiltration mechanism, respectively.

[0015] According to the embodiments of this application, the method further includes collecting the steam condensate generated by each hot air drying device in the galvanizing line and passing it into a third precipitation ultrafiltration unit for treatment to obtain steam condensate desalinated water.

[0016] According to the embodiments of this application, the flow rate of the demineralized water is 18-20 cubic meters per hour, the flow rate of the first treated demineralized water is 16-18 cubic meters per hour, the flow rate of the second treated demineralized water is 15-17 cubic meters per hour, and the flow rate of the third treated demineralized water is 15-16 cubic meters per hour.

[0017] According to the embodiments of this application, the first precipitation ultrafiltration mechanism, the second precipitation ultrafiltration mechanism and the third precipitation ultrafiltration mechanism each include an inclined plate sedimentation tank, a filter assembly, a clear water tank, an acid washing tank, an alkali washing tank and a rinsing tank.

[0018] The inclined plate sedimentation tank is used for sedimentation and stratification of wastewater, and the filter assembly is connected to the inclined plate sedimentation tank; the clear water tank collects the filtrate of the filter assembly; the inclined plate sedimentation tank collects the residual filtrate of the filter assembly; the acid washing tank, alkaline washing tank and rinsing tank are respectively connected to the filter assembly and supply liquid to wash the filter assembly.

[0019] According to an embodiment of this application, the method further includes a step of cleaning the filter assembly, the cleaning step comprising:

[0020] The filter components are switched, rinsed, alkaline washed, rinsed, acid washed, rinsed, and switched again in sequence.

[0021] The acid and alkali contents of the cleaning solutions used for alkaline washing and acid washing are 1% to 2% by mass, respectively. The water temperature of the cleaning solutions is 50-60℃.

[0022] The rinsing water temperature is 30-40℃.

[0023] According to an embodiment of this application, the step of introducing the third treated demineralized water into the cleaning section includes:

[0024] A portion of the desalinated water from the third treatment process is mixed with a degreasing agent and preheated in the annealing furnace before being subjected to electrolytic cleaning.

[0025] Then, a portion of the desalinated water from the third treatment is mixed with a degreasing agent and preheated in the annealing furnace before being subjected to alkaline scrubbing.

[0026] Then, a portion of the demineralized water from the third treatment is preheated in the annealing furnace and rinsed with hot water.

[0027] According to an embodiment of this application, it further includes:

[0028] The oily wastewater from electrolytic cleaning and the alkaline wastewater from alkaline washing are sent to the cold rolling wastewater station for treatment.

[0029] This application also provides a galvanized sheet production equipment, comprising a cleaning section, a drying equipment, a continuous annealing furnace, a zinc pot, a galvanizing line water quenching tank, a first hot air drying equipment, a finishing machine, a straightening machine, a second hot air drying equipment, a passivation machine, a third hot air drying equipment, and a demineralized water supply equipment arranged in sequence. The demineralized water supply equipment operates according to the above-described method for utilizing demineralized water from a galvanizing line.

[0030] In the aforementioned method for utilizing desalinated water from a galvanizing line, based on the cleanliness requirements of the finishing, straightening, water quenching, and cleaning sections, the used desalinated water is treated to remove only zinc powder and oil, which have a significant impact on subsequent processes. Then, the desalinated water and the supply sequence of each treatment process are rationally arranged. In other words, the desalinated water is utilized in a cascade manner, saving on the amount of desalinated water used and reducing wastewater discharge. This lowers the load, scale, and cost of oily wastewater treatment, and alleviates the pressure on desalinated water production and supply. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0032] Figure 1 This is an application flowchart of the method for utilizing desalinated water from a galvanizing line according to an embodiment of this application.

[0033] Figure 2 This is a schematic diagram of the precipitation ultrafiltration mechanism according to one embodiment of this application;

[0034] Figure 3 This is a schematic diagram of the operation of the precipitation ultrafiltration mechanism according to one embodiment of this application.

[0035] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] It should be noted that all directional indicators (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0038] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0039] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0040] In existing technologies, the finishing, straightening, and water quenching sections all directly use demineralized water. The demineralized water used in the finishing and straightening sections is directly discharged as wastewater. The amount of demineralized water used in each stage is relatively large. For example, in some processes, the washing section uses approximately 20 cubic meters per hour of demineralized water, and the water quenching tank section uses 15-17 cubic meters per hour. This usage is mainly adjusted based on the cooling capacity of the demineralized water cooler. The finishing and straightening sections use 18-20 cubic meters per hour and 16-18 cubic meters per hour, respectively.

[0041] This results in a large overall consumption of desalinated water and a large total volume of wastewater generated. However, the applicant's research revealed that the finishing wastewater and straightening wastewater after use in the finishing and straightening sections have excellent water quality, as shown in Table 1. After simple treatment, they are suitable for reuse. For example, simply filtering out oil and zinc powder can meet the desalinated water requirements of the finishing and straightening sections. The table below shows the water quality of the desalinated water after use in the water quenching section and the finishing and straightening sections.

[0042] Table 1. Desalinated water quality after use of the existing water quenching section and finishing / straightening section.

[0043] detection indicators Water quenching tank wastewater Finishing and straightening machine wastewater Suspended solids (mg / L) 23 13 pH 7.70 7.98 Electrical conductivity (μs / cm) 3.74 4.01 Total hardness (mg / L) none none Calcium hardness (mg / L) 0.017 0.014 Chloride ions (mg / L) 1.14 1.83 Sulfate (mg / L) none none Soluble SiO2 (mg / L) none none Total iron (mg / L) none none Total oil (mg / L) 0.27 0.79 Zinc (mg / L) none none Anionic surfactants (mg / L) 0.007 0.003

[0044] If the wastewater is directly discharged and then treated at a wastewater treatment plant, not only will the total volume of wastewater be large, but the treatment cost will also be high. The specific reasons are as follows: Wastewater treatment plants handle a variety of wastewater types, and in order to ensure that the treated wastewater meets the discharge standards, multiple types of treatment methods are required. However, in fact, finishing wastewater does not require this type of treatment, which increases the treatment cost.

[0045] Furthermore, this method does not collect the zinc powder in the wastewater; instead, it enters the wastewater treatment plant as wastewater, resulting in wastewater with high zinc content and even the presence of lead ions. Collecting the zinc powder would enable the recycling of zinc resources.

[0046] Besides the high post-treatment costs, the actual production costs of using large quantities of desalinated water are also very high. In some methods, the process of producing desalinated water includes:

[0047] The source water first passes through an inclined plate filter to settle sediment, then is pressurized by a pump and enters a multi-media filter (containing quartz sand and activated carbon) for initial filtration. Next, it passes through a precision filter (containing vertical tube filter cartridges made of PP cotton with a filtration accuracy of 5μm) for further initial filtration. Then, it is pressurized to 1MPa and enters the reverse osmosis unit. Afterward, it passes through ion exchange beds (cation bed, anion bed, and mixed bed), and finally, utilizing the height difference, it passes through a resin trap to remove ion exchange resin before entering the product water tank. This water production process is energy-intensive, involves multiple steps, and has numerous bottlenecks, thus limiting the water production capacity.

[0048] Because the demineralized water produced by the desalination plant near the cold rolling mill has always been a bottleneck resource, specifically reflected in the following aspects: 1) Numerous users: In addition to the users of the cold rolling pickling line, pickling line, single stand, three galvanizing lines, and the leveling unit, the demineralized water supplied also includes three units in the power generation workshop and the coking dry quenching workshop; 2) Seasonal changes: In addition, the demineralized water production capacity is affected by seasonal changes (affected by the thermal expansion and contraction of the reverse osmosis membrane); 3) Limited water production capacity: On the one hand, the water production process is complex (such as primary and precision filtration, reverse osmosis, cation bed, anion bed, mixed bed, etc.); on the other hand, the water production process has high energy consumption, such as increasing the water pressure to 1MPa before entering the reverse osmosis unit; on the other hand, the design capacity is limited; and on the other hand, the investment in adding new demineralized water production capacity is large.

[0049] Based on this, the present invention provides a method for utilizing desalinated water from a galvanizing line, see [link to relevant documentation]. Figure 1 This includes the following steps:

[0050] S100: The demineralized water is fed into the polishing machine for use and the polishing wastewater generated is collected. The polishing wastewater is then treated by the first sedimentation ultrafiltration mechanism to obtain the first treated demineralized water.

[0051] The finishing section uses a large volume of demineralized water (18-20 cubic meters / hour), and it is essential to use demineralized water because it has extremely low conductivity and low salt content, preventing scaling on the dried galvanized steel strip surface. Furthermore, the demineralized water used in the finishing machine needs to be pressurized to nearly 10 MPa, and the nozzles are small and cannot be clogged; therefore, the water quality requirements for demineralized water are high. Moreover, since finishing requires the use of work rollers to press the galvanized steel strip, the demineralized water also acts as a lubricant during the pressing process, thus requiring even higher cleanliness of the water used; otherwise, marks such as pits may be left on the galvanized steel strip. Therefore, this application selects to use demineralized water in the finishing section, rather than demineralized water obtained from treated desalination wastewater.

[0052] At the inlet of the finishing mill, four rows of demineralized water nozzles simultaneously spray water onto the upper support roller, upper working roller, lower working roller, and lower support roller. Their functions include: 1) lubricating the galvanized strip and rollers; and 2) removing zinc powder adhering to the rollers. At the outlet of the finishing mill, high-pressure water spray (demineralized water) is applied in two rows at low flow rate and high pressure between the support roller and working roller. Its main function is to remove zinc powder adhering to the rollers.

[0053] Finishing wastewater is typically collected in a designated pit on-site and then treated by a first-stage sedimentation ultrafiltration unit. As analyzed above, the finishing wastewater has a relatively high water quality. Therefore, by using the first-stage sedimentation ultrafiltration unit to remove oil and zinc powder from the wastewater, for example, the wastewater, which already has low conductivity, only needs to be pressurized to 0.3-0.4 MPa by a pump and passed through the filter components of the first-stage sedimentation ultrafiltration unit to obtain a solution with low conductivity, low oil content, and low zinc powder content, meeting the water requirements of the straightening machine. The filter components include an inorganic ceramic membrane with a filtration precision of 50 nm.

[0054] Inorganic ceramic membranes have excellent capabilities in removing oil and zinc powder. In addition, ceramic membranes are less susceptible to fouling, have strong continuous operation capabilities, and have high membrane flux that is not easily degraded.

[0055] S200: The first treated demineralized water is fed into the straightening machine for use and the generated straightening wastewater is collected. The straightening wastewater is then treated by the second sedimentation ultrafiltration mechanism to obtain the second treated demineralized water.

[0056] The water consumption required by the straightening machine is similar to that of the finishing section, at 16-18 cubic meters per hour. It also needs to be pressurized before being introduced into the nozzles, therefore the water quality requirements are relatively higher, slightly lower than those for the finishing machine.

[0057] The collection and treatment process of straightening wastewater through the second sedimentation ultrafiltration unit is similar to that of finishing wastewater, and will not be described in detail here.

[0058] S300: The second-processed demineralized water is circulated into the galvanizing line water quenching tank and the demineralized water circulation tank to collect part of the generated water quenching wastewater. The water quenching wastewater is then treated by the third sedimentation ultrafiltration mechanism to obtain the third-processed demineralized water.

[0059] The water consumption of the galvanizing line's water quenching tank is large (15-17 cubic meters / hour, depending primarily on the cooling capacity of the demineralized water cooler). The second-stage demineralized water circulates between the galvanizing line's water quenching tank and the demineralized water circulation tank. In the galvanizing line's water quenching tank, the second-stage demineralized water continuously contacts and cools the galvanized sheet. During this cooling process, zinc powder from the surface of the galvanized sheet continuously enters the second-stage demineralized water, and the temperature of the second-stage demineralized water continuously rises before being cooled again in the demineralized water circulation tank. Specifically, heat exchange occurs with the external circulating water, reducing some of the temperature.

[0060] The collection and treatment process of water-quenched wastewater by the third precipitation ultrafiltration unit is similar to that of finishing wastewater and will not be described in detail here. The filtration components of the first, second, and third precipitation ultrafiltration units include inorganic ceramic membranes with a filtration accuracy of 50 nm.

[0061] S400: The third treated demineralized water is introduced into the cleaning section for use. The filtration components of the first, second, and third precipitation ultrafiltration mechanisms include inorganic ceramic membranes with a filtration accuracy of 50 nm.

[0062] The cleaning section uses a relatively large amount of water (approximately 20 cubic meters per hour) and is divided into an electrolytic degreasing section, an alkaline brushing section, and a hot water rinsing section. The electrolytic degreasing section removes oil and grease adhering to the strip surface using electrolysis. The alkaline brushing section removes the degreasing substances carried over from the degreasing process. The degreasing function removes iron powder, dust, and other impurities from the strip surface. The alkaline brushing section first uses spray brushing to clean the strip surface, further removing impurities and oil, and rinsing away the alkaline solution. The hot water rinsing section, which follows the three-stage rinsing, uses spraying to further clean the remaining alkaline solution and impurities on the strip surface, ensuring a good cleaning effect.

[0063] In the technical solution of this application, a sedimentation ultrafiltration mechanism is used to filter out zinc powder and oil content from the desalinated water after use in the finishing, straightening, and water quenching sections of the galvanizing line, and then reuse the desalinated water in these sections. This solves the problem of tight desalinated water supply, realizes the resource recycling of this bottleneck, reduces the amount of oily wastewater, alleviates the load on the oily wastewater treatment plant (because the oily wastewater is treated biologically in the first stage, the biological treatment load is reduced, the treatment time in the biological process is increased, and the treated wastewater is easier to meet the discharge standards), and lowers the treatment cost of oily wastewater.

[0064] This aligns with the national trend of energy conservation and emission reduction. Previously, the desalinated water used in the finishing and leveling sections was not reused after single-use, leading to a shortage of desalinated water at the desalination plant and consequently, a shortage of desalinated water for the cold rolling mills, making communication and coordination difficult. Furthermore, the wastewater treatment plant had a heavy load on oily wastewater, frequently resulting in effluent quality exceeding standards. Through practical application, these technical issues have been resolved.

[0065] Existing technologies require 30-40 cubic meters of demineralized water per hour for a single galvanizing line, while the proposed solution reduces this to 15-20 cubic meters per hour. This significantly reduces the demineralized water consumption per ton of steel for a single galvanizing line, whereas a cold rolling mill typically has two or even four galvanizing lines. This application achieves self-circulation and cascade utilization of demineralized water, comprehensively considering water conservation across the entire demineralization line. This substantially reduces the demineralized water consumption per ton of steel galvanized, saving on demineralized water production costs and significantly reducing investment required for expanding the demineralized water production capacity (which typically involves substantial investment).

[0066] In the aforementioned method for utilizing desalinated water from a galvanizing line, based on the cleanliness requirements of the finishing, straightening, water quenching, and cleaning sections, the used desalinated water is treated to remove only zinc powder and oil, which have a significant impact on subsequent processes. Then, the desalinated water and the supply sequence of each treatment process are rationally arranged. In other words, the desalinated water is utilized in a cascade manner, saving on the amount of desalinated water used and reducing wastewater discharge. This lowers the load, scale, and cost of oily wastewater treatment, and alleviates the pressure on desalinated water production and supply.

[0067] In some embodiments, see Figure 1 It also includes at least one of the following steps:

[0068] A portion of the first-treatment demineralized water is fed into the optical finishing machine for recycling.

[0069] A portion of the second-treatment desalinated water is fed into the straightening machine for recycling.

[0070] A portion of the third-stage demineralized water is circulated into the galvanizing line's water quenching tank and demineralized water circulation tank.

[0071] In addition to being used in the next process for cascade processing, the first, second, and third treatment demineralized water can all be self-circulated according to the water demand of their respective stages of use to achieve water balance. For example, when the water demand of the straightening machine decreases while the water demand of the finishing machine increases, some of the first treatment demineralized water can be fed into the finishing machine for recycling.

[0072] In some embodiments, see Figure 1The finishing wastewater, the straightening wastewater, and the water quenching wastewater are pressurized to 0.3-0.4 MPa and filtered through the filtration components of the first precipitation ultrafiltration mechanism, the second precipitation ultrafiltration mechanism, and the third precipitation ultrafiltration mechanism, respectively. This method has high filtration efficiency and high filtration quality.

[0073] In some embodiments, the method further includes collecting the steam condensate generated by each hot air drying device in the galvanizing line and passing it through a third precipitation ultrafiltration unit for treatment to obtain steam condensate desalinated water.

[0074] For example, the condensate from the hot air dryer above the water quenching tank, the hot air dryer after finishing and straightening, and the hot air dryer after passivation is collected. The condensate has a high temperature, and therefore carries some iron ions and iron filings as it flows through the pipes. Furthermore, its composition is similar to demineralized water. Therefore, the presence of iron ions and some iron filings makes it unsuitable for finishing or straightening. For example, iron filings can cause pits on the surface of the strip after finishing, and iron ions can cause the surface of the strip to turn yellow due to oxidation after straightening.

[0075] Steam condensate is fed into the third sedimentation and ultrafiltration unit for treatment, which increases the total amount of demineralized water in the third treatment and helps to balance the water consumption of the cleaning section, which has a large water consumption.

[0076] Each cycle of demineralized water (considered as one cycle after use and treatment by the sedimentation ultrafiltration unit) results in a 10-15% decrease in water volume. The flow rate of the third-stage demineralized water is approximately 15 cubic meters per hour, which, with the addition of steam condensate, can basically meet the water demand of the cleaning section at approximately 20 cubic meters per hour. In other words, the steam condensate demineralized water serves both as a supplement to the water volume and heat of the third-stage demineralized water.

[0077] In some embodiments, the flow rate of the demineralized water is 18-20 cubic meters per hour, the flow rate of the first treated demineralized water is 15-18 cubic meters per hour, the flow rate of the second treated demineralized water is 15-17 cubic meters per hour, and the flow rate of the third treated demineralized water is 15-16 cubic meters per hour.

[0078] In some embodiments, see Figure 2 and Figure 3 The first precipitation ultrafiltration mechanism, the second precipitation ultrafiltration mechanism and the third precipitation ultrafiltration mechanism each include an inclined plate sedimentation tank, a filter assembly, a clear water tank, an acid washing tank, an alkaline washing tank and a rinsing tank;

[0079] The inclined plate sedimentation tank is used for sedimentation and stratification of wastewater, and the filter assembly is connected to the inclined plate sedimentation tank; the clear water tank collects the filtrate of the filter assembly; the inclined plate sedimentation tank collects the residual filtrate of the filter assembly; the acid washing tank, alkaline washing tank and rinsing tank are respectively connected to the filter assembly and supply liquid to wash the filter assembly.

[0080] The desalinated water from the finishing, straightening, and water quenching processes can be collected in their respective collection tanks and then pumped into the inclined plate settling tank for stratification. Oil stains on the roller surfaces and bearings of the finishing and straightening machines exist as floating oil in the water. The inclined plate settling tank controls the liquid level to allow overflow, allowing the floating oil to flow by gravity into the collection tank next to the oil press and then into the oily wastewater treatment system of the wastewater treatment station. Zinc powder and ash are collected by natural sedimentation. The clear liquid in the middle is pumped into the filter assembly for circulating filtration. The feed liquid undergoes cross-flow filtration through the inorganic ceramic membrane of the filter assembly; part of it forms filtrate that flows by gravity into the clear water tank, while the other part flows back to the inclined plate settling tank via the return pipeline. The clear liquid in the middle continuously circulates, constantly generating permeate to achieve separation. The clear liquid in the clear water tank is pumped to each user point.

[0081] Taking finishing wastewater as an example, after collection, the wastewater enters an inclined plate sedimentation tank where it settles and separates into layers. The upper layer consists of oily substances, the middle layer is the water to be filtered, and the bottom layer is zinc powder. The oily substances and zinc powder are collected separately. The water to be filtered is pressurized and then passed through a filter assembly for filtration. The filter assembly includes an inorganic ceramic membrane. The filtrate is the first-stage demineralized water, and the residual filtrate from the filter assembly is returned to the inclined plate sedimentation tank for further sedimentation and stratification.

[0082] After a certain period of use, the filter components need to be cleaned, thus requiring acid washing tanks, alkali washing tanks, and rinsing tanks. These tanks store some of the clarified liquid for preparing the alkali, acid, and rinsing solutions used to clean the membrane tubes.

[0083] In some embodiments, see Figure 2 and Figure 3 It also includes a step of cleaning the filter assembly, the cleaning step comprising:

[0084] The filter assembly is sequentially switched, rinsed, alkaline washed, rinsed, acid washed, rinsed, and switched again. The acid and alkali contents of the cleaning solutions used for alkaline and acid washing are 1%–2% by mass, respectively. The water temperature of the cleaning solutions is 50–60°C. The water temperature for rinsing is 30–40°C.

[0085] After a certain operating cycle, the membrane needs to be cleaned to restore the permeate flux. Cleaning a ceramic membrane filtration unit generally includes switching, rinsing, alkaline washing, and acid washing. The acid and alkali content of the cleaning solution is generally controlled at around 1%-2% by mass. The general cleaning steps are: switching, rinsing, alkaline washing, rinsing, acid washing, rinsing, and switching.

[0086] Switching refers to the transition between normal membrane filtration and membrane cleaning states. For example, during cleaning, switching involves changing from normal operation to membrane cleaning. This includes replacing waste demineralized water with a suitable rinsing solution (which can be clean demineralized water) to clean the membrane. Rinsing is an intermediate process between different washing methods to prevent cross-contamination, such as acid washing after alkaline washing, or rinsing before the membrane enters normal operation after acid washing.

[0087] The water temperature for chemical cleaning is generally controlled at 50-60℃, and the switching water temperature is controlled at 30-40℃. The cleaning time is approximately 2.0 to 4.0 hours. If the flow rate does not recover, chemical cleaning and rinsing can be performed again.

[0088] In some embodiments, see Figure 3 The step of introducing the third-treatment demineralized water into the cleaning section includes:

[0089] A portion of the desalinated water from the third treatment process is mixed with a degreasing agent and preheated in the annealing furnace before being subjected to electrolytic cleaning.

[0090] Then, a portion of the desalinated water from the third treatment is mixed with a degreasing agent and preheated in the annealing furnace before being subjected to alkaline scrubbing.

[0091] Then, a portion of the demineralized water from the third treatment is preheated in the annealing furnace and rinsed with hot water.

[0092] In some embodiments, it also includes:

[0093] The oily wastewater from electrolytic cleaning and the alkaline wastewater from alkaline washing are sent to the cold rolling wastewater station for treatment.

[0094] This application also provides a galvanized sheet production equipment, comprising a cleaning section, a drying equipment, a continuous annealing furnace, a zinc pot, a galvanizing line water quenching tank, a first hot air drying equipment, a finishing machine, a straightening machine, a second hot air drying equipment, a passivation machine, a third hot air drying equipment, and a demineralized water supply equipment arranged in sequence. The demineralized water supply equipment operates according to the above-described method for utilizing demineralized water from a galvanizing line.

[0095] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for utilizing desalinated water from a galvanizing line, characterized in that, Includes the following steps: The demineralized water is fed into the polishing machine and the resulting polishing wastewater is collected. The polishing wastewater is then treated by the first sedimentation ultrafiltration mechanism to obtain the first treated demineralized water. The desalinated water supplied to the optical finishing machine is not desalinated wastewater that has undergone treatment; The first treated demineralized water is fed into the straightening machine and the resulting straightening wastewater is collected. The straightening wastewater is then treated by the second sedimentation ultrafiltration mechanism to obtain the second treated demineralized water. The second-processed demineralized water is circulated into the quenching tank and demineralized water circulation tank of the galvanizing line to collect part of the generated quenching wastewater. The quenching wastewater is then treated by the third sedimentation ultrafiltration mechanism to obtain the third-processed demineralized water. The steam condensate generated by each hot air drying device in the galvanizing line is collected and treated by the third sedimentation ultrafiltration mechanism to obtain steam condensation demineralized water. The steam condensation demineralized water replenishes the water volume and heat of the third-processed demineralized water. The demineralized water from the third treatment process is then fed into the cleaning section. The step of introducing the third-treatment desalinated water into the cleaning section includes: mixing a portion of the third-treatment desalinated water with a degreasing agent and heating it with the residual heat of the annealing furnace before electrolytic cleaning; Then, a portion of the demineralized water from the third treatment is mixed with a degreasing agent and heated by the residual heat of the annealing furnace, followed by alkaline scrubbing; then, a portion of the demineralized water from the third treatment is heated by the residual heat of the annealing furnace and rinsed with hot water. The filtration components of the first precipitation ultrafiltration mechanism, the second precipitation ultrafiltration mechanism and the third precipitation ultrafiltration mechanism include inorganic ceramic membranes. The inorganic ceramic membranes have a filtration accuracy of 50 nm and the inorganic ceramic membranes have the ability to remove oil and zinc powder.

2. The method for utilizing desalinated water from a galvanizing line according to claim 1, characterized in that, It also includes at least one of the following steps: A portion of the first-treatment demineralized water is circulated into the optical finishing machine for reuse. A portion of the demineralized water from the second treatment process is circulated into the tension leveler for reuse. A portion of the third-stage demineralized water is circulated into the galvanizing line's water quenching tank and demineralized water circulation tank.

3. The method for utilizing desalinated water from a galvanizing line according to claim 1, characterized in that, The finishing wastewater, the straightening wastewater, and the water quenching wastewater are pressurized to 0.3-0.4 MPa and filtered by the filtration components of the first precipitation ultrafiltration mechanism, the second precipitation ultrafiltration mechanism, and the third precipitation ultrafiltration mechanism, respectively.

4. The method for utilizing desalinated water from a galvanizing line according to claim 1, characterized in that, The flow rate of the demineralized water is 18-20 cubic meters per hour, the flow rate of the first demineralized water is 16-18 cubic meters per hour, the flow rate of the second demineralized water is 15-17 cubic meters per hour, and the flow rate of the third demineralized water is 15-16 cubic meters per hour.

5. The method for utilizing desalinated water from a galvanizing line according to claim 1, characterized in that, The first precipitation ultrafiltration mechanism, the second precipitation ultrafiltration mechanism, and the third precipitation ultrafiltration mechanism each include an inclined plate sedimentation tank, a filter assembly, a clear water tank, an acid washing tank, an alkaline washing tank, and a rinsing tank; The inclined plate sedimentation tank is used for sedimentation and stratification of wastewater, and the filter assembly is connected to the inclined plate sedimentation tank; the clear water tank collects the filtrate of the filter assembly; the inclined plate sedimentation tank collects the residual filtrate of the filter assembly; the acid washing tank, alkaline washing tank and rinsing tank are respectively connected to the filter assembly and supply liquid to wash the filter assembly.

6. The method for utilizing desalinated water from a galvanizing line according to claim 5, characterized in that, The method also includes a step of cleaning the filter assembly, the cleaning step comprising: The filter components are switched, rinsed, alkaline washed, rinsed, acid washed, rinsed, and switched in sequence. The alkaline and acidic cleaning solutions have an alkali content and an acid content of 1% to 2% by mass, respectively; and the water temperature of the cleaning solution is 50-60℃. The rinsing water temperature is 30-40℃.

7. The method for utilizing desalinated water from a galvanizing line according to claim 1, characterized in that, Also includes: The oily wastewater from electrolytic cleaning and the alkaline wastewater from alkaline washing are sent to the cold rolling wastewater station for treatment.

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