Utilization method of alkaline washing waste liquid of pickling line and waste liquid treatment device

Abstract

The invention provides a method for utilizing alkali washing waste liquid of a pickling line and a waste liquid treatment device. The utilization method comprises the following steps: carrying out primary neutralization on the acid-containing wastewater to obtain primary neutralized wastewater; and performing secondary neutralization on the primary neutralized wastewater, and adding alkali washing waste liquid in the secondary neutralization process to obtain secondary neutralized wastewater. And adding polyferric sulfate and polyacrylamide into the secondary neutralized wastewater to clarify to obtain clarified waste liquid. The clarified waste liquid is subjected to pH adjustment and filtration, and then water to be treated in a centralized mode is obtained. The alkali washing waste liquid is added into the second neutralization tank, after the alkali washing waste liquid is added, OH <-> is not greatly reduced, and silicic acid in the alkali washing waste liquid subjected to secondary neutralization is in a monomer dispersed state. The silicic acid monomer in the alkali washing waste liquid is used as a coagulant aid and cooperates with polyferric sulfate and polyacrylamide to clarify. The alkali washing waste liquid has a coagulation aiding effect, so that the effect of treating waste with waste is realized, and the wastewater treatment is efficient, low in cost and environment-friendly.

Description

Technical Field

[0001] The invention relates to the field of wastewater treatment, and in particular to a method for utilizing alkali-washing waste liquid of a pickling line and a waste liquid treatment device. Background Art

[0002] In order to increase the added value of products, the proportion of high silicon steel in the product structure of the pickling section of the cold rolling pickling line or the pickling mill combined unit is increasing. However, the silicate in the acid solution of pickling silicon steel can easily cause the pipes, valves, graphite heaters, acid pumps, nozzles, etc. of the cold rolling pickling line or the pickling mill combined unit to be blocked.

[0003] Therefore, alkaline solution is used to wash the pipes, valves, graphite heaters, acid pumps, nozzles, etc. of the acid pipeline system in a circulating manner on a regular basis to wash the silica gel adhering to the pipeline, so that the actual flow diameter of the acid pipeline can be restored. The waste alkaline solution generated in this way is mixed with the acid-containing wastewater generated by the pickling line or the pickling mill combined unit and the acid regeneration in the acid-containing wastewater wastewater pit and discharged into the cold rolling wastewater station. However, this treatment method is prone to blockage of the wastewater treatment pipeline in actual operation. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for utilizing the alkali-washing waste liquid of a pickling line, so as to solve the technical problem that the wastewater treatment pipeline is easily blocked in actual operation.

[0005] To achieve the above object, the present invention provides a method for utilizing the alkali washing waste liquid of the pickling line, comprising the following steps:

[0006] The acid-containing wastewater is subjected to primary neutralization to obtain primary neutralized wastewater. The acid-containing wastewater includes at least one of pickling wastewater and acid regeneration wastewater.

[0007] The primary neutralization wastewater is subjected to secondary neutralization, and alkali washing waste liquid is added during the secondary neutralization process to obtain secondary neutralization wastewater. The alkali washing waste liquid is alkali washing waste liquid from the pickling line.

[0008] Polyferric sulfate and polyacrylamide are added to the secondary neutralization wastewater for clarification to obtain clarified waste liquid.

[0009] The clarified waste liquid is subjected to pH adjustment and filtration to obtain water to be centrally treated.

[0010] According to an embodiment of the present application, the amount of the alkaline washing waste liquid added satisfies that the concentration of silicate ions in the secondary neutralization wastewater is 0.8-1.2 mg / L.

[0011] According to an embodiment of the present application, the mass fraction of free NaOH in the alkali washing waste liquid is 10-20%, and the concentration of silicate ions is 100-200 g / L.

[0012] According to an embodiment of the present application, the pH value of the primary neutralization wastewater is 8-9. The pH value of the secondary neutralization wastewater is 9-10.

[0013] According to the implementation manner of the present application, the amount of polyferric sulfate added is such that the corresponding concentration in the secondary neutralization wastewater is 25 to 35 mg / L, and the amount of polyacrylamide added is such that the corresponding concentration in the secondary neutralization wastewater is 1.5 to 2.5 mg / L.

[0014] According to an embodiment of the present application, the time for adding polyferric sulfate and polyacrylamide to the secondary neutralization wastewater for clarification is 2 to 4 hours.

[0015] According to an embodiment of the present application, in the steps of performing the primary neutralization and the secondary neutralization, lime milk is added for neutralization.

[0016] According to the implementation mode of the present application, it also includes reusing the water to be centrally treated after centralized treatment.

[0017] The present application also provides a waste liquid treatment device, including an alkali liquid collection tank, an acid-base wastewater regulating tank, a primary neutralization tank, a secondary neutralization tank, an acid-base clarification tank, a pH adjustment tank, a filter and a discharge water tank connected in sequence.

[0018] The acid-base wastewater regulating tank is used to receive the acid-containing wastewater, and the acid-containing wastewater includes at least one of pickling wastewater and acid regeneration wastewater.

[0019] The primary neutralization tank is used to perform primary neutralization on the acid-containing wastewater to obtain primary neutralized wastewater.

[0020] The secondary neutralization tank is used to perform secondary neutralization on the primary neutralization wastewater to obtain secondary neutralization wastewater.

[0021] The alkali liquid collection tank is connected to the secondary neutralization tank and is used to pass the alkali washing waste liquid into the secondary neutralization tank for secondary neutralization. The alkali washing waste liquid is the alkali washing waste liquid of the pickling line.

[0022] The acid-base clarification tank is used to receive polyferric sulfate and polyacrylamide, and to clarify the secondary neutralization wastewater to obtain clarified waste liquid.

[0023] The pH adjustment tank and the filter are used to adjust the pH of the clarified waste liquid and filter it to obtain the water to be centrally treated and discharge it into the discharge water tank.

[0024] According to an embodiment of the present application, a metering pump connected between the alkali solution collection tank and the secondary neutralization tank is also included.

[0025] In the above-mentioned method for utilizing the alkali-washing wastewater from the pickling line, the alkali-washing wastewater is added to the second neutralization tank. On the one hand, the H + Compared with the acid-containing wastewater, the content has been reduced, so after the addition of alkaline washing wastewater, OH - There is no significant drop, and there will be no large amount of silica gel precipitation to reduce the effect of monomer silicic acid and block the pipeline, so that the system can operate stably. On the other hand, the next step of the secondary neutralization wastewater is the clarification step. The silicic acid monomer in the alkali washing waste liquid is used as a coagulant to cooperate with polyferric sulfate and polyacrylamide for clarification. The alkali washing waste liquid has a coagulant effect, achieving the effect of treating waste with waste, making the wastewater treatment efficient, low-cost and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0027] Figure 1 The present invention is a process flow chart of treating the alkali-washing waste liquid of the pickling line in the prior art.

[0028] Figure 2 The present invention is a flowchart of a method for utilizing alkali waste liquid from a pickling line according to an embodiment of the present application.

[0029] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with the implementation methods and with reference to the accompanying drawings.

[0030] 100. Alkali liquid collection tank; 110. Acid-base wastewater regulating tank; 120. Primary neutralization tank; 130. Secondary neutralization tank; 140. Acid-base clarification tank; 150. pH adjustment tank; 160. Filter; 170. Discharge pool; 180. Sludge concentration tank. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] It should be noted that all directional indications (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0033] In addition, in the present invention, the descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0034] Furthermore, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in the field. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0035] Generally speaking, the process of alkali cleaning is as follows: each time the pickling line or the pickling rolling mill combined unit is shut down for scheduled maintenance, the acid in the pipeline system is emptied, and a large amount of acid (flake alkali NaOH is prepared into 30% concentration or 30% NaOH liquid alkali is added) is regularly prepared in the alkali circulation tank and heated to 70-85°C with steam, connected to the acid pump inlet, and the existing acid pump is used to circulate the acid pipeline system, and the pipes, valves, graphite heaters, acid pumps, nozzles, etc. of the acid pipeline system are washed, and the silica gel adhered in the washing pipeline is washed to restore the actual flow diameter of the acid pipeline. In fact, the hot alkali solution can quickly dissolve the silica gel and restore the pickling ability, that is, the reaction formula is: 2NaOH+H2SiO3=Na2SiO3+2H2O.

[0036] Hot alkali solution can quickly open silica gel and dissolve it into monomeric silicic acid, and sodium silicate solution can stably exist in a high pH environment. However, once the monomeric silicic acid is easily precipitated and combined to form silica gel under the condition of lower pH and lower temperature, the formed silica gel will not play a role in the flocculation and sedimentation process.

[0037] See also Figure 1In the related art, the waste alkali liquid is mixed with the acid-containing wastewater generated by the pickling line or the pickling mill combined unit and the acid regeneration in the acid-containing wastewater pit and discharged into the cold rolling wastewater station. The study found that due to the long length of the wastewater pipeline from the acid-containing wastewater pit of the pickling line or the pickling mill combined unit to the cold rolling wastewater station, such as more than 500 meters, and the other is that a large amount of Na2SiO3 waste alkali liquid is mixed with acid-containing wastewater, causing the pH value to decrease. In addition, as the temperature drops, silica gel will form in the wastewater pipeline and cause the discharge pipeline to be blocked (for example, the pipeline between the acid-containing wastewater pit and the acid-base wastewater regulating tank, the pipeline between the acid-base wastewater regulating tank and the primary neutralization tank, and the pipeline between the primary neutralization tank and the secondary neutralization tank), resulting in poor drainage. Moreover, since it has re-formed silica gel, it cannot be used as a coagulant to cooperate with other clarifiers to achieve the effect of clarification during the clarification process.

[0038] That is to say, the waste alkali liquid containing a large amount of Na2SiO3 is actually a kind of waste, and it only plays a role in the neutralization of acid-containing wastewater in the wastewater pit and the acid-base neutralization in the acid-base wastewater treatment system.

[0039] In addition, the pipeline between the acid wastewater pit and the acid-base wastewater regulating tank is long (that is, the length of the wastewater pipeline from the acid wastewater pit to the cold rolling wastewater station is long). Due to the blockage, the drainage is not smooth, which can easily affect the production of pickling and acid rolling. The specific manifestation is: the reason is that the acidic wastewater cannot be discharged normally, but normal production continues to produce acidic wastewater.

[0040] 1. The acid discharge pipeline is long, and the blockage point caused by the mixed discharge of alkali washing waste liquid is not easy to find, which brings trouble to the inspection and maintenance work.

[0041] 2. The acid discharge pipeline is discharged together with the alkaline washing waste liquid, causing the silica gel to be continuously deposited in the pipe wall, resulting in the overall reduction of the pipe diameter. The inspection and maintenance work is often repeated and annoying.

[0042] 3. The on-site acid discharge pipeline to the wastewater station is often in the form of double pipelines (one for use and one for backup) to ensure normal acid discharge from the pipeline. When one pipeline is blocked, the other pipeline is activated, and the blocked pipeline is repaired and cleared, or even replaced as a whole. This increases the equipment maintenance cost and a lot of manpower, material and financial resources.

[0043] The reason for the above problems is that the silica gel produced by the mixed discharge of alkaline washing waste liquid and acid-containing wastewater causes pipeline blockage.

[0044] The present invention provides a method for utilizing the waste liquid of pickling line alkali washing, see Figure 2 , including the following steps:

[0045] S100: performing primary neutralization on the acid-containing wastewater to obtain primary neutralized wastewater. The acid-containing wastewater includes at least one of pickling wastewater and acid regeneration wastewater.

[0046] The purpose of neutralization treatment is to add lime milk to neutralize the acid in the acid-base wastewater. The wastewater after neutralization treatment is weakly alkaline, which is convenient for the subsequent clarification process.

[0047] In an embodiment of the present application, a two-stage neutralization treatment is performed, and illustratively, the neutralization treatment is performed in a primary neutralization tank 120 and a secondary neutralization tank 130. The primary neutralization tank 120 is for rough pH adjustment and the secondary neutralization tank 130 is for fine pH adjustment, so that after aeration, the trivalent iron enters the acid-base precipitation tank and the iron hydroxide flocs are precipitated together with oil, silicate, organic matter, and other metal ions. For example, lime milk is added for neutralization reaction. In order to accelerate the mixing and reaction of lime milk with acid-base wastewater, in some embodiments, aeration treatment is performed during the neutralization treatment process.

[0048] The purpose of primary neutralization is to initially neutralize the acidic wastewater and reduce H + The content increases the pH value of the primary neutralization wastewater. The specific primary neutralization method is not specifically limited. The source of the acid-containing wastewater is also not specifically limited, such as including at least one of pickling wastewater and acid regeneration wastewater.

[0049] S200: performing secondary neutralization on the primary neutralization wastewater, and adding alkali washing waste liquid during the secondary neutralization process to obtain secondary neutralization wastewater. The alkali washing waste liquid is alkali washing waste liquid of the pickling line.

[0050] The alkali washing wastewater actually contains a large amount of Na2SiO3. The addition of alkali washing wastewater during the second stage neutralization shortens the flow path of the alkali washing wastewater when it enters the clarification process, and reduces the impact of temperature drop on the precipitation of silicate. + The content has been reduced. In this way, the alkali washing waste liquid is prevented from contacting with the acidic waste water too early and neutralizing to cause OH - In this way, although the pH value of the secondary neutralization wastewater is lower than that of the alkali washing wastewater, it still remains at a high level, so that the silicon element still exists in the form of Na2SiO3.

[0051] S300: Adding polyferric sulfate and polyacrylamide to the secondary neutralized wastewater for clarification to obtain clarified waste liquid.

[0052] In this step, the silicate monomer (SiO2·y(H2O2)) of Na2SiO3 is used as a coagulant. The silicate monomer SiO2·y(H2O2) produces a polycondensation reaction in the solution, which is the result of hydroxyl bridging and oxygen bridging. The anion of the inorganic polymer formed by the polycondensation is a tetrahedral polymer, which can develop into filaments, branched chains or spherical particles. It can only play a flocculating role on negatively charged colloidal particles in water. Therefore, it is often used as a coagulant in combination with aluminum salts and iron salts. It can greatly enhance the flocculation process when used in small amounts, reduce the amount of coagulant, and improve the coagulation effect under low temperature and low alkalinity conditions.

[0053] (1) Polyferric sulfate (PFS)

[0054] PFS is an intermediate product in the process of Fe2(SO4)3 being gradually converted into Fe(OH)3 by hydrolysis, and is polymerized into an inorganic polymer compound through a hydroxyl cross-bridging reaction. There are two performance indicators of PFS, namely alkalinity and polymerization degree. Alkalinity B = [OH] / 3 [Fe], the equivalent ratio of hydroxyl and iron in the compound. Generally speaking, the higher the alkalinity, the more polynuclear complex ions with low charge and high polymerization degree, and the better the flocculation performance of its bonding and bridging. On the contrary, if the alkalinity is low, inorganic polymers with high charge and low polymerization degree will account for the majority, which will compress the double electric layer, neutralize the electricity and achieve a good effect of colloidal destabilization. Generally, the alkalinity of PFS ranges from about 9% to 16%. The use of PFS alone cannot achieve the best coagulation and flocculation effects.

[0055] (2) Polyacrylamide (PAM)

[0056] PAM is a high molecular weight coagulant, which is dispersed into a huge number of linear chain polymers after being dissolved in water. Such huge chain molecules can play a bonding and bridging role, and the charged groups on the molecules play a role in compressing the double electric layer and neutralizing electricity. The anionic type is currently used, and the colloid particles in the wastewater are generally negatively charged. The anionic coagulant can only play a flocculation role in such wastewater. PAM is applicable to a relatively narrow range. If it is used in excessive amounts, a colloid protective effect will occur, which will increase the stability of the colloid and worsen the coagulation effect.

[0057] In this way, silicate monomer, polyferric sulfate and polyacrylamide work together to achieve the effect of clarification. In this way, there is no need to purchase silicate monomers additionally. The characteristics of alkaline wastewater containing a large amount of Na2SiO3 are directly utilized. Combined with the effects of PAM (high molecular weight coagulant) and polyferric sulfate (PFS), the oil and COD in the cold rolling acid-base wastewater are flocculated and precipitated to remove them, thus turning waste into treasure and using waste to smelt waste to make the cold rolling wastewater run efficiently, at low cost and in an environmentally friendly manner.

[0058] The sludge generated during the clarification process is treated separately, such as being regularly transported to the sludge thickening tank 180 by a sludge pump, and then sent from the sludge thickening tank 180 to the filter press.

[0059] S400: After pH adjustment and filtration, the clarified waste liquid is subjected to centralized treatment water.

[0060] Exemplarily, the clarified waste liquid is adjusted in the pH adjustment tank by adding a reagent, and then pumped to the filter 160 for oil removal and filtration, and the effluent flows by gravity to the discharge pool 170 for subsequent centralized treatment.

[0061] The oil removal filter can be a walnut shell filter. The walnut shell filter has a large specific surface area and is effective for oil filtration. Taking the walnut shell filter as an example, clinoptilolite is added to the walnut shell filter. Zeolite is a kind of aluminosilicate, and clinoptilolite is mainly used to remove ammonia nitrogen. Clinoptilolite has a screening effect on ions in wastewater, an exchange adsorption effect, and a strong effect on NH4 + It has strong selectivity and can use exchange adsorption process to remove ammonia nitrogen in water. It is the last step to remove ammonia nitrogen before cold rolling wastewater enters the centralized sewage treatment station.

[0062] Acidic wastewater and alkali washing wastewater are now treated separately and discharged into the wastewater treatment station. For example, acidic wastewater enters the acid-base wastewater regulating tank; alkali washing wastewater enters the alkali liquid collection tank. This greatly reduces the blockage of silica gel in the acid discharge pipeline; the silicic acid in the alkali washing wastewater has a high free alkali concentration and good solubility of sodium silicate, and exists in the alkali washing wastewater as an active monomer silicic acid, which is also conducive to transportation and storage.

[0063] In the above-mentioned method for utilizing the alkali-washing wastewater from the pickling line, the alkali-washing wastewater is added to the second neutralization tank. On the one hand, the H + Compared with the acid-containing wastewater, the content has been reduced, so after the addition of alkaline washing wastewater, OH - There is no significant drop, and there will be no large amount of silica gel precipitation to reduce the effect of monomer silicic acid and block the pipeline, so that the system can operate stably. On the other hand, the next step of the secondary neutralization wastewater is the clarification step. The silicic acid monomer in the alkali washing waste liquid is used as a coagulant to cooperate with polyferric sulfate and polyacrylamide for clarification. The alkali washing waste liquid has a coagulant effect, achieving the effect of treating waste with waste, making the wastewater treatment efficient, low-cost and environmentally friendly.

[0064] According to an embodiment of the present application, the amount of the alkaline washing waste liquid added satisfies that the concentration of silicate ions in the secondary neutralization wastewater is 0.8-1.2 mg / L.

[0065] The concentration of silicate ions in the alkali washing wastewater may fluctuate due to the different metals being treated. Therefore, the amount of addition needs to be adjusted adaptively. The specific amount of addition is based on the concentration of silicate ions in the secondary neutralization wastewater, which is 0.8-1.2 mg / L. Under this condition, the concentration requirement of silicate ions as a coagulant in the subsequent clarification process can be met.

[0066] The components of secondary neutralization wastewater are mainly hydroxides of iron and other metal ions, oil, organic matter, silicate, chloride ions, phosphates, ammonium salts, amines, etc.

[0067] In some embodiments, the mass fraction of free NaOH in the alkali washing waste liquid is 10-20%, and the concentration of silicate ions is 100-200 g / L.

[0068] In some embodiments, the pH value of the primary neutralization wastewater is 8-9. The pH value of the secondary neutralization wastewater is 9-10.

[0069] In some embodiments, the amount of polyferric sulfate added is such that the corresponding concentration in the secondary neutralization wastewater is 25-35 mg / L, and the amount of polyacrylamide added is such that the corresponding concentration in the secondary neutralization wastewater is 1.5-2.5 mg / L.

[0070] The inventors conducted a series of experiments. In the clarification step, different types and amounts of flocculants were used to clarify the acid-base wastewater after neutralization treatment, and the COD content in the clarified liquid was detected. Cr , oil content, calculate COD Cr The removal rate and oil removal rate are shown in Tables 1 and 2.

[0071] Table 1 Addition amount and type of flocculant mg / l

[0072]

[0073]

[0074] Table 2 COD and petroleum removal rates

[0075] Experiment No. <![CDATA[COD in the supernatant liquid Cr > Oil content in clear liquid <![CDATA[COD Cr Removal rate]]> Oil removal rate 1 80.6 52.2 72.2％ 77.7％ 2 100.6 79.3 65.3％ 66.1％ 3 75.4 54.0 74.0％ 76.9％ 4 101.2 78.8 65.1％ 66.3％ 5 112.2 86.1 61.3％ 63.2％

[0076] Among them, COD Cr Removal rate = (1-COD in clear liquid Cr / COD of acid-base wastewater after neutralization treatment Cr )*100%, oil removal rate = (1-oil content in clear liquid / oil content in acid-base wastewater after neutralization treatment)*100%.

[0077] Taking into account the nature of wastewater, treatment effect and cost investment, we can choose to first add activated silica in the secondary neutralization tank and then add PAM and PFS in the high-efficiency reaction clarification tank. The concentrations of activated silica are about 0.8-1.2 mg / l, PAM is about 1.5-2.5 mg / l and PFS is 25-35 mg / l, which can fully achieve the expected treatment effect.

[0078] In some embodiments, the time for adding polyferric sulfate and polyacrylamide to the secondary neutralization wastewater for clarification is 2 to 4 hours.

[0079] In some embodiments, the purpose of adding alkaline waste liquid is to utilize the free NaOH remaining in the alkaline waste liquid to play a neutralizing role. In addition, after the acid-base waste water is neutralized by lime milk, the pH is 8-9, and after the second neutralization, the pH is 9-10. Among them, the first stage of neutralization is a rapid pH rough adjustment; the second stage of neutralization is a slow pH fine adjustment. On the one hand, it reduces the addition of lime milk. The free NaOH in the alkaline waste liquid is alkaline and has a neutralizing effect on acidic waste water or acid-base waste water. The alkaline waste liquid naturally replaces the lime milk to play a neutralizing role, and the addition of lime milk is reduced. On the other hand, the addition of monomer silicic acid at a certain OH - In the case of high concentration, monomer silicic acid is aerated and stirred vigorously in the second stage neutralization, and the volume of the second stage neutralization tank is twice that of the first stage neutralization tank, so the acid-base wastewater in the second stage neutralization tank is retained for a longer time. Monomer silicic acid is fully in contact with Fe(OH)3 flocs, metal ion hydroxides, oil, organic matter, etc. in the acid-base wastewater, and the characteristics of monomer silicic acid are used to greatly promote the effect of subsequent flocculation and sedimentation.

[0080] In some embodiments, see Figure 2 In the steps of primary neutralization and secondary neutralization, lime milk is added for neutralization. This method has good neutralization effect and low cost.

[0081] In some embodiments, see Figure 2 , and also includes reusing the water to be treated centrally after centralized treatment.

[0082] The present application also provides a waste liquid treatment device, see Figure 2 , including an alkali liquid collection tank 100, an acid-base wastewater regulating tank 110, a primary neutralization tank 120, a secondary neutralization tank 130, an acid-base clarification tank 140, a pH regulating tank 150, a filter 160 and a discharge water tank 170 which are connected in sequence.

[0083] The acid-base wastewater regulating tank 110 is used to receive the acid-containing wastewater, and the acid-containing wastewater includes at least one of pickling wastewater and acid regeneration wastewater.

[0084] The primary neutralization tank 120 is used to perform primary neutralization on the acid-containing wastewater to obtain primary neutralized wastewater.

[0085] The secondary neutralization tank 130 is used to perform secondary neutralization on the primary neutralization wastewater to obtain secondary neutralization wastewater.

[0086] The alkali liquid collection tank 100 is connected to the secondary neutralization tank 130, and is used to pass the alkali washing waste liquid into the secondary neutralization tank 130 for secondary neutralization. The alkali washing waste liquid is the alkali washing waste liquid of the pickling line.

[0087] The acid-base clarification tank 140 is used to receive polyferric sulfate and polyacrylamide, and to clarify the secondary neutralization wastewater to obtain clarified waste liquid.

[0088] The pH adjustment tank 150 and the filter 160 are used to adjust the pH of the clarified waste liquid and filter it to obtain the water to be centrally treated and discharge it to the discharge tank 170 .

[0089] The above-mentioned device has the technical effect corresponding to the above-mentioned method for utilizing the alkali washing waste liquid of the pickling line, which will not be repeated.

[0090] In some embodiments, a metering pump connected between the alkali solution collection tank 100 and the secondary neutralization tank 130 is also included.

[0091] The specific method is that the waste liquid in the alkali liquid collection tank 100 liquid circulation tank is discharged into the alkali liquid collection tank 100 by a newly added separate discharge pump, and the alkali liquid of sodium silicate containing monomer silicic acid is pumped into the secondary neutralization tank in the acid-base wastewater treatment system in proportion by a metering pump.

[0092] The alkali liquid collection tank is used to collect the alkali liquid generated during alkali cleaning of the pickling line and the pickling section of the pickling mill, and is usually used as a tank for preparing Na2SiO3. In some embodiments, to ensure continuous treatment of acid-base wastewater, monomer active silicate is continuously added, and when the pickling line and the pickling section of the pickling mill are not subjected to alkali cleaning, Na2SiO3 is prepared to meet the dosage requirements.

[0093] In some specific embodiments, after the acid-base wastewater is neutralized by lime milk, the pH is 8-9, and then adjusted to 9-10. The acid-base wastewater system has a processing capacity of 100-150 cubic meters per hour, and the concentration of silicate ions (i.e., monomer activated silicic acid) in the secondary neutralization wastewater is 0.8-1.2 mg / L. When the concentration of silicate ions in the alkali washing wastewater is 100 g / L, the metering pump continuously adds 800-1800 liters of alkali washing wastewater to the secondary neutralization tank per hour; when the concentration of silicate ions in the alkali washing wastewater is 200 g / L, the metering pump continuously adds 400-900 liters of alkali washing wastewater to the secondary neutralization tank per hour.

[0094] The above technical solutions of the present invention are only preferred embodiments of the present invention, and the patent scope of the present invention is not limited thereto. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for utilizing alkali-washing waste liquid from a pickling line, characterized in that: The following steps are involved: The acid-containing wastewater is subjected to primary neutralization to obtain primary neutralized wastewater; the acid-containing wastewater includes at least one of pickling wastewater and acid regeneration wastewater; The primary neutralization wastewater is subjected to secondary neutralization, and alkali washing waste liquid is added during the secondary neutralization process to obtain secondary neutralization wastewater; the alkali washing waste liquid is alkali washing waste liquid of the pickling line; Adding polyferric sulfate and polyacrylamide to the secondary neutralization wastewater for clarification to obtain clarified waste liquid; The clarified waste liquid is subjected to pH adjustment and filtration to obtain water to be centrally treated.

2. The method for utilizing the alkali waste liquid of the pickling line according to claim 1, characterized in that: The amount of the alkaline washing waste liquid added is such that the concentration of silicate ions in the secondary neutralization waste water is 0.8-1.2 mg / L.

3. The method for utilizing the alkali waste liquid of the pickling line according to claim 1, characterized in that: The mass fraction of free NaOH in the alkaline washing waste liquid is 10-20%, and the concentration of silicate ions is 100-200 g / L.

4. The method for utilizing the pickling line alkali washing waste liquid according to claim 1, characterized in that: The pH of the primary neutralization wastewater is 8-9; the pH of the secondary neutralization wastewater is 9-10.

5. The method for utilizing the pickling line alkali washing waste liquid according to claim 1, characterized in that: The amount of the polyferric sulfate added is such that the corresponding concentration in the secondary neutralization wastewater is 25 to 35 mg / L, and the amount of the polyacrylamide added is such that the corresponding concentration in the secondary neutralization wastewater is 1.5 to 2.5 mg / L.

6. The method for utilizing the alkali waste liquid of the pickling line according to claim 1, characterized in that: The time for adding polyferric sulfate and polyacrylamide to clarify the secondary neutralized wastewater is 2 to 4 hours.

7. The method for utilizing the alkali waste liquid of the pickling line according to claim 1, characterized in that: In the steps of performing the primary neutralization and the secondary neutralization, lime milk is added for neutralization.

8. The method for utilizing the alkali waste liquid of the pickling line according to any one of claims 1 to 7, characterized in that: It also includes the reuse of water to be centrally treated after centralized treatment.

9. A waste liquid treatment device, characterized in that: It includes an alkali liquid collection tank, an acid-base wastewater regulating tank, a primary neutralization tank, a secondary neutralization tank, an acid-base clarification tank, a pH regulating tank, a filter and a discharge water tank which are connected in sequence; The acid-base wastewater regulating tank is used to receive acid-containing wastewater, wherein the acid-containing wastewater includes at least one of pickling wastewater and acid regeneration wastewater; The primary neutralization tank is used to perform primary neutralization on the acid-containing wastewater to obtain primary neutralized wastewater; The secondary neutralization tank is used to perform secondary neutralization on the primary neutralization wastewater to obtain secondary neutralization wastewater; The alkali liquid collection tank is connected to the secondary neutralization tank, and is used to pass the alkali washing waste liquid into the secondary neutralization tank for secondary neutralization; the alkali washing waste liquid is the alkali washing waste liquid of the pickling line; The acid-base clarification tank is used to receive polyferric sulfate and polyacrylamide and to clarify the secondary neutralization wastewater to obtain clarified waste liquid; The pH adjustment tank and the filter are used to adjust the pH of the clarified waste liquid and filter it to obtain the water to be centrally treated and discharge it into the discharge water tank.

10. The waste liquid treatment device according to claim 9, characterized in that: It also includes a metering pump connected between the alkali solution collection tank and the secondary neutralization tank.

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