Method for removing phosphorus from cold rolling pickling waste liquid

Abstract

The invention relates to the technical field of cold rolling pickling waste liquid treatment, in particular to a method for removing phosphorus from cold rolling pickling waste liquid. The method comprises the following steps: (1) neutralization treatment: putting an iron material into a neutralization tank, adding pickling waste liquid into the neutralization tank for neutralization treatment, and discharging a neutralization liquid after the reaction is completed; (2) phosphorus content grading pretreatment: detecting the phosphorus content in the neutralization solution, and if the phosphorus content is greater than 40mg / L in terms of P2O5, sequentially carrying out oxidation, pH regulation and flocculent precipitation treatment; if the phosphorus content is not more than 40mg / L, cooling to not more than 50 DEG C; and (3) dephosphorization treatment: enabling the pretreated solution to enter a resin unit for dephosphorization treatment. According to the method, the resin unit is adopted for dephosphorization treatment, and compared with dephosphorization of the iron oxide powder product, the front-end treatment method is more economical and reasonable.

Description

Technical Field

[0001] The present invention relates to the technical field of cold rolling pickling waste liquid treatment, and in particular to a method for removing phosphorus from cold rolling pickling waste liquid. Background Art

[0002] During the production of cold-rolled steel sheets, pickling is typically used to remove oxides from the surface of the raw coils, primarily using hydrochloric acid. As production progresses, the hydrochloric acid concentration decreases, requiring some of the acid to be discharged and replenished with high-concentration hydrochloric acid to maintain a consistent rate of oxide removal. This discharged acid is commonly referred to as pickling wastewater. This pickling wastewater is treated in an acid regeneration system to produce regenerated hydrochloric acid and iron oxide powder.

[0003] Iron oxide powder is a key raw material in the magnetic materials industry. Purchasers have strict requirements for the content of elements like silicon and phosphorus, which serve as a marker for categorizing different grades of iron oxide powder. For example, the YHT4 standard for iron oxide used in ferrites (GB / T 24244-2009) specifies a reference P2O5 content of no more than 0.03%. As the grade increases, to YHT1, the P2O5 content is required to be no more than 0.005%. This places even higher demands on phosphorus removal in the acid regeneration system.

[0004] In order to meet the needs of the high-end market, the commonly used phosphorus removal methods at present are solid-phase phosphorus removal and liquid-phase phosphorus removal. For solid-phase phosphorus removal, patent CN201410083131.0 discloses a method for dephosphorizing iron oxide powder, a by-product of steel mill pickling waste liquid regeneration, which uses a method of acid leaching after mixed roasting of calcium oxide for phosphorus removal. This method has high energy consumption, and pickling and cleaning produce waste acid and wastewater pollution. For liquid-phase phosphorus removal, patent CN200910065782.6 discloses a treatment process for aluminum substrate pickling and alkali washing waste liquid. The two waste liquids are pre-treated for oil removal, iron removal, and phosphorus and silicon removal. After mixing, neutralization, and separation, the oily filter residue can be used as fuel, the filter cake can be recycled, and the wastewater meets the discharge standards. This method has poor adaptability to high-iron acidic environments and a long process, resulting in high operating costs and difficulty in industrial promotion.

[0005] In summary, there is an urgent need to develop a new process for phosphorus removal from pickling wastewater that can adapt to high-acid and high-iron environments, take into account both phosphorus removal efficiency and iron recovery rate, and has no secondary pollution. Summary of the Invention

[0006] The present invention aims to provide a method for removing phosphorus from cold-rolled pickling wastewater. The method adopts a resin unit for phosphorus removal. After neutralization, the pickling wastewater is sequentially subjected to oxidation, pH adjustment, flocculation and precipitation, and resin process unit treatment to reduce the phosphorus content in the wastewater. At the same time, for the liquid phase with a low phosphorus content after neutralization, it only needs to be cooled and then passed through the resin unit, thereby shortening the process flow and reducing process costs.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows:

[0008] The present invention provides a method for removing phosphorus from cold-rolling pickling wastewater, the method comprising the following steps:

[0009] (1) Neutralization treatment: iron material is placed in the neutralization tank, pickling waste liquid is added to the neutralization tank for neutralization treatment, and the neutralization liquid is discharged after the reaction is completed;

[0010] (2) Phosphorus content classification pretreatment: Detect the phosphorus content in the neutralized solution, calculated as P2O5. If the phosphorus content is greater than 40 mg / L, treat it by oxidation, pH adjustment, and flocculation precipitation in sequence; if the phosphorus content is ≤40 mg / L, cool it to ≤50°C;

[0011] (3) Phosphorus removal: The pretreated solution enters the resin unit for phosphorus removal.

[0012] In the above technical solution, further, in step (1), in the pickling wastewater, Fe 2+ The content is 110-130 g / L, the mass content of hydrochloric acid is 10%-15%, and the phosphorus content is 80-200 mg / L calculated as P2O5.

[0013] In the above technical solution, further, in step (1), the volume of the iron material accounts for 60% to 80% of the volume of the neutralization tank; the phosphorus content of the iron material is ≤0.01% by mass in terms of P2O5;

[0014] The liquid level of the pickling waste liquid does not exceed the iron material;

[0015] The pH of the neutralization solution is ≥1.

[0016] In the above technical solution, further, in step (2), the oxidant used in the oxidation is one of air, O2, O3, and H2O2; Fe 3+ The content is 2 to 10 g / L. The purpose of oxidation treatment is to remove part of the Fe 2+ Oxidized to Fe 3+ , however, excessive Fe 3+ Although the content of Fe in the solution is beneficial to the removal of phosphorus by the neutralization solution, it will reduce the output of iron oxide powder. Therefore, the oxidation process controls the content of Fe in the solution. 3+ The content is 2-10g / L.

[0017] In the above technical solution, further, in step (2), ammonia water is used to adjust the pH of the oxidized solution to make Fe 3+ Precipitation, the pH is the initial pH ~ 4, so as to achieve the purpose of removing phosphorus in the solution, different Fe 3+The initial precipitation pH value is different. In order to prevent the local precipitation from agglomerating due to improper addition of ammonia water, the initial pH is calculated using the following formula:

[0018] pH = 1.732-1g [C (Fe 3+ )] 1 / 3

[0019] Where: C(Fe 3+ ) is the Fe in the solution after oxidation 3+ Content, g / L.

[0020] In the above technical solution, further, in step (2), the flocculant used in the flocculation precipitation is polyacrylamide (PAM), and the dosage is 0.3-0.5 mg / L.

[0021] In the above technical solution, further, in step (3), during the phosphorus removal treatment, the solution flow rate is calculated according to the following formula:

[0022] v=0.0005C 2 -0.1301C+11.427

[0023] Where:

[0024] v is the flow rate of the solution through the resin unit, BV / h;

[0025] C is the phosphorus content in the solution, mg / L.

[0026] In the above technical solution, further, the pretreated solution passes through the resin unit n times, n≥1, until the phosphorus content is ≤15 mg / L.

[0027] The beneficial effects of the present invention are:

[0028] (1) The method of the present invention adopts a resin unit for dephosphorization treatment. After the pickling waste liquid is neutralized, it is sequentially subjected to oxidation, pH adjustment, flocculation precipitation and resin process unit treatment to achieve the purpose of reducing the phosphorus content in the waste liquid. Compared with the dephosphorization of the iron oxide powder product, the front-end treatment method is more economical and reasonable. At the same time, for the liquid phase with a low phosphorus content after neutralization, it only needs to be cooled and then passed through the resin unit, which reduces the number of pre-treatment units, shortens the process flow, and reduces the process cost.

[0029] (2) The oxidant of the present invention will not remain in the solution, thereby avoiding the introduction of other impurities into the iron oxide powder product.

[0030] (3) The present invention determines the operating range of pH through the initial sedimentation pH control formula, thereby avoiding the addition of an inappropriate amount of ammonia water, which leads to agglomeration of the precipitate and an excessive decrease in the iron content in the solution, thereby causing a decrease in the yield of iron oxide powder.

[0031] (4) The present invention avoids the problem of insufficient phosphorus removal capacity due to excessive flow rate by using the phosphorus removal resin unit flow rate formula, and at the same time sets a multiple resin unit flow rate mechanism to ensure that the phosphorus content of the solution reaches the control value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The figure is a process flow chart of the method for removing phosphorus from cold-rolled pickling wastewater according to the present invention. DETAILED DESCRIPTION

[0033] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0034] Example 1

[0035] (1) Add iron material into the neutralization tank, the volume of the iron material accounts for 80% of the volume of the neutralization tank, the phosphorus content of the iron material is 0.01%, and add pickling waste liquid into the neutralization tank. 2+ The content is 115g / L, the mass content of hydrochloric acid is 14%, the phosphorus content (calculated as P2O5) is 200mg / L, the pickling waste liquid level is lower than the upper surface of the iron material, and after neutralization, the pH of the neutralized liquid is 1.0;

[0036] (2) The phosphorus content of the neutralized solution (in terms of P2O5) was 150 mg / L. The neutralized solution entered the oxidation tank and H2O2 was added to the oxidation tank to control the Fe 3+ The content is 10g / L. After oxidation, it enters the regulating tank. The initial precipitation pH of the regulating tank is calculated to be 1.40. The precipitation range is determined to be 1.4-4.0. Ammonia water is added to the regulating tank. When the pH reaches 1.4, ammonia water is slowly added until the pH reaches 3.0. It then enters the flocculation sedimentation tank. PAM is added in the flocculation sedimentation tank at a dosage of 0.5mg / L. The phosphorus content of the solution after precipitation (calculated as P2O5) is 90mg / L.

[0037] (3) The flow rate through the resin unit is calculated to be 3.8 BV / h. The phosphorus content (in terms of P2O5) of the solution after the first resin unit is 25 mg / L. Subsequently, the solution is passed through the resin unit twice. The phosphorus content (in terms of P2O5) of the solution after the second resin unit is 14 mg / L.

[0038] The content of P2O5 in the iron oxide powder after roasting the pickling waste liquid after dephosphorization treatment is 0.0074%.

[0039] Example 2

[0040] (1) Add iron material into the neutralization tank, the volume of the iron material accounts for 70% of the volume of the neutralization tank, the mass percentage of phosphorus in the iron material is 0.005%, and add pickling waste liquid into the neutralization tank. 2+The content is 125g / L, the mass content of hydrochloric acid is 12%, the phosphorus content (calculated as P2O5) is 150mg / L, the pickling waste liquid level is lower than the upper surface of the iron material, and after neutralization, the solution pH = 1.2;

[0041] (2) The phosphorus content of the neutralized solution (in terms of P2O5) was 100 mg / L. The neutralized solution entered the oxidation tank and air was blown into the oxidation tank to control the Fe 3+ The content is 6g / L. After oxidation, it enters the regulating tank. The initial precipitation pH of the regulating tank is calculated to be 1.47, and the precipitation range is 1.47-4.0. Ammonia water is added to the regulating tank. When the pH reaches 1.47, ammonia water is slowly added until the pH reaches 3.5. It then enters the flocculation sedimentation tank. PAM is added in the flocculation sedimentation tank at a dosage of 0.3mg / L. The phosphorus content of the solution after precipitation (calculated as P2O5) is 50mg / L.

[0042] (3) The flow rate of the phosphorus removal resin is calculated to be 6.2 BV / h, and the phosphorus content (in terms of P2O5) of the solution after passing through the resin unit once is 10 mg / L.

[0043] The content of P2O5 in the iron oxide powder after roasting the pickling waste liquid after dephosphorization treatment is 0.0048%.

[0044] Example 3

[0045] (1) Add iron material into the neutralization tank. The volume of the iron material accounts for 60% of the volume of the neutralization tank. The phosphorus content (mass percentage) of the iron material is 0.002%. Add pickling waste liquid into the neutralization tank. The Fe content in the pickling waste liquid is 0.002%. 2+ The content is 130g / L, the mass content of hydrochloric acid is 10%, the phosphorus content (calculated as P2O5) is 80mg / L, the level of the pickling waste liquid is lower than the upper surface of the iron material, and after neutralization, the solution pH = 1.3;

[0046] (2) The phosphorus content (in terms of P2O5) of the neutralized solution was 35 mg / L at a temperature of 55°C, after cooling to 50°C;

[0047] (3) The flow rate through the resin unit is calculated to be 7.5 BV / h, and the phosphorus content (in terms of P2O5) of the solution after passing through the phosphorus removal resin once is 5 mg / L.

[0048] The content of P2O5 in the iron oxide powder after roasting the pickling waste liquid after dephosphorization treatment is 0.0030%.

[0049] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope defined in the claims. Other variations or modifications may be made based on the above description. Obvious variations or modifications derived therefrom shall remain within the scope of protection of the present invention.

Claims

1. A method for removing phosphorus from cold-rolled pickling wastewater, characterized in that: The method comprises the following steps: (1) Neutralization treatment: iron material is placed in the neutralization tank, pickling waste liquid is added to the neutralization tank for neutralization treatment, and the neutralization liquid is discharged after the reaction is completed; (2) Phosphorus content classification pretreatment: Detect the phosphorus content in the neutralized solution, calculated as P2O5. If the phosphorus content is greater than 40 mg / L, treat it by oxidation, pH adjustment, and flocculation precipitation in sequence; if the phosphorus content is ≤40 mg / L, cool it to ≤50°C; (3) Phosphorus removal: The pretreated solution enters the resin unit for phosphorus removal.

2. The method for removing phosphorus from cold-rolled pickling wastewater according to claim 1, characterized in that: In step (1), in the pickling wastewater, Fe 2+ The content is 110-130 g / L, the mass content of hydrochloric acid is 10%-15%, and the phosphorus content is 80-200 mg / L calculated as P2O5.

3. The method for removing phosphorus from cold-rolled pickling wastewater according to claim 1, characterized in that: In step (1), the volume of the iron material accounts for 60% to 80% of the volume of the neutralization tank; the phosphorus content of the iron material is ≤0.01% by mass, calculated as P2O5; The liquid level of the pickling waste liquid does not exceed the iron material; The pH of the neutralization solution is ≥1.

4. The method for removing phosphorus from cold-rolled pickling wastewater according to claim 1, characterized in that: In step (2), the oxidant used in the oxidation is one of air, O2, O3, and H2O2; Fe 3+ The content is 2-10g / L.

5. The method for removing phosphorus from cold-rolled pickling wastewater according to claim 1, characterized in that: In step (2), the pH of the oxidized solution is adjusted to an initial pH of 4 using aqueous ammonia; The initial pH is calculated using the following formula: pH=1.732-lg[C(Fe 3+ )] 1 / 3 Where: C(Fe 3+ ) is the Fe in the solution after oxidation 3+ Content, g / L.

6. The method for removing phosphorus from cold rolling pickling wastewater according to claim 1, characterized in that: In step (2), the flocculant used in the flocculation precipitation is polyacrylamide, and the dosage is 0.3-0.5 mg / L.

7. The method for removing phosphorus from cold rolling pickling wastewater according to claim 1, characterized in that: In step (3), during the phosphorus removal treatment, the solution flow rate is calculated according to the following formula: v=0.0005C 2 -0.1301C+11.427 Where: v is the flow rate of the solution through the resin unit, BV / h; C is the phosphorus content in the solution, mg / L.

8. The method for removing phosphorus from cold rolling pickling wastewater according to claim 1, characterized in that: The pretreated solution passes through the resin unit n times, n ≥ 1, until the phosphorus content is ≤ 15 mg / L.

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