Electroplating hexavalent chromium wastewater treatment and recycling system

Abstract

The utility model discloses an electroplating hexavalent chromium wastewater treatment and recycling system, which relates to the technical field of sewage treatment and comprises a pretreatment system, a reduction sedimentation system and a chromium sludge calcining system, the pretreatment system comprises a water pump, a first neutralization tank, a first coagulation tank, a first sedimentation tank, a sludge concentration tank, a first diaphragm pump and a first filter press which are connected in sequence, and effluent of the first filter press flows back into the first neutralization tank; the reduction sedimentation system comprises an acidification tank, a reduction tank, a second neutralization tank, a second coagulation tank, a second sedimentation tank, a chromium sludge concentration tank, a second diaphragm pump and a second filter press which are connected in sequence, and supernate of the first sedimentation tank enters the acidification tank; and the chromium sludge calcining system comprises a conveyor and calcining equipment which are connected in sequence. According to the utility model, the chromium-containing wastewater is treated by adopting the three-stage system, namely the pretreatment system, the reduction settling system and the chromium sludge calcining system, so that recyclable pigment-level chromium oxide can be directly obtained.

Description

Technical Field

[0001] The utility model relates to the technical field of sewage treatment, in particular to a system for treating and recycling electroplating hexavalent chromium wastewater. Background Technique

[0002] The water quality components of electroplating chromium-containing wastewater are complex, mainly existing in the form of hexavalent chromium, and there are also some other pollution factors such as Cr 3+ , Zn 2+ , Cu 2+ , Fe 3+ , Ni 2+ etc. If directly discharged without treatment, it will cause great pollution to the surrounding water bodies, thus endangering aquatic animals and plants, as well as the crops, animals and humans that depend on them for survival. At present, the conventional method for treating chromium-containing water is the reduction-neutralization flocculation method. First, under acidic conditions, a reducing agent is added to reduce Cr 6+ to Cr 3+ , and then alkali or lime is added to adjust the pH value of the wastewater, so that metal ions are all converted into corresponding hydroxide precipitates and removed. The chromium sludge obtained by this method has complex components and low chromium concentration, and the secondary utilization effect is poor.

[0003] As an inorganic chemical raw material, Cr2O3 (chromium trioxide) is a green crystalline powder. Pigment-grade chromium oxide can be used as the glaze of enamel and ceramics, the colorant of artificial leather, building materials, etc., and the catalyst for organic synthesis. It can also be used to manufacture lightfast coatings, abrasive materials, green polishing paste and special ink for printing banknotes, etc. From the above content, it can be seen that pigment-grade chromium oxide has high requirements and large demand, and electroplating hexavalent chromium wastewater contains a large amount of chromium resources. The conventional wastewater treatment method cannot effectively utilize chromium resources. If it can not only treat electroplating chromium-containing wastewater but also be used as a raw material to prepare pigment-grade chromium oxide, this system has great application significance compared with the traditional method for treating wastewater. Summary of the Utility Model

[0004] The purpose of the utility model is to provide a system for treating and recycling electroplating hexavalent chromium wastewater to solve the problems existing in the above-mentioned prior art, and to be able to effectively separate and recycle the Cr 6+ in the chromium-containing wastewater.

[0005] To achieve the above purpose, the utility model provides the following scheme:

[0006] A system for treating and recycling electroplating hexavalent chromium wastewater includes a pretreatment system, a reduction and sedimentation system, and a chromium sludge calcination system;

[0007] The pretreatment system includes a water pump, a first neutralization tank, a first coagulation tank, a first sedimentation tank, a sludge thickening tank, a first diaphragm pump and a first filter press connected in sequence. The water discharged from the first filter press flows back into the first neutralization tank;

[0008] The reduction and sedimentation system includes an acidification tank, a reduction tank, a second neutralization tank, a second coagulation tank, a second sedimentation tank, a chromium sludge thickening tank, a second diaphragm pump, and a second filter press, which are connected in sequence. The supernatant of the first sedimentation tank enters the acidification tank, and the supernatant of the second sedimentation tank and the effluent of the second filter press enter the SCR system;

[0009] The chromium sludge calcination system includes a conveyor and a calcination device, which are connected in sequence. The sludge discharged from the second filter press enters the conveyor.

[0010] Preferably, it further includes a first chemical feeding device connected to the first neutralization tank and the second neutralization tank.

[0011] Preferably, pH meters are provided in the first neutralization tank and the second neutralization tank, and the chemical agent provided by the first chemical feeding device is 30% lye.

[0012] The interiors of the first coagulation tank and the second coagulation tank are divided into a coagulation zone and a flocculation zone, and the coagulation zone and the flocculation zone are interconnected.

[0013] Preferably, it further includes a second chemical feeding device connected to the first coagulation tank and the second coagulation tank. The second chemical feeding device provides a coagulant and a flocculant for the coagulation zone and the flocculation zone respectively.

[0014] Preferably, it further includes a third chemical feeding device connected to the acidification tank.

[0015] Preferably, a pH meter is provided in the acidification tank, and the chemical agent provided by the third chemical feeding device is 20% sulfuric acid.

[0016] Preferably, it further includes a fourth chemical feeding device connected to the reduction tank.

[0017] Preferably, an ORP potentiometer is provided in the reduction tank, and the chemical agent provided by the fourth chemical feeding device is 10% sodium metabisulfite.

[0018] Preferably, stirring devices are provided in the first neutralization tank, the first coagulation tank, the first sedimentation tank, the sludge thickening tank, as well as the acidification tank, the reduction tank, the second neutralization tank, the second coagulation tank, the second sedimentation tank, and the chromium sludge thickening tank.

[0019] The utility model has achieved the following technical effects compared with the prior art:

[0020] In the present utility model, first, the chromium-containing wastewater is fed into a pretreatment system. Metal ions in the wastewater react with alkali to produce precipitates, which are then filtered by a filter press. The supernatant obtained is then fed into a reduction and sedimentation system. The supernatant is acidified by adding acid, and then sodium metabisulfite is added to reduce hexavalent chromium to trivalent chromium, followed by neutralization and sedimentation treatment. After the filter press filters to obtain chromium hydroxide sludge, the sludge is washed with reclaimed water to remove salts and then transferred to a chromium sludge calcination system. It is conveyed by a conveyor belt to a calcination device for calcination to obtain pigment-grade chromium green, effectively separating and recycling the resources in the chromium-containing wastewater. It has the advantages of simple structure, high treatment efficiency, and good treatment effect. 6+ BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 FIG. 1 is a schematic structural diagram of the electroplating hexavalent chromium wastewater treatment and resource recovery system disclosed by the present utility model;

[0023] Wherein, 1, water pump; 2, first neutralization tank; 3, first coagulation tank; 4, first sedimentation tank; 5, sludge thickening tank; 6, first diaphragm pump; 7, first filter press; 8, acidification tank; 9, reduction tank; 10, second neutralization tank; 11, second coagulation tank; 12, second sedimentation tank; 13, chromium sludge thickening tank; 14, second diaphragm pump; 15, second filter press; 16, conveyor; 17, calcination device; 18, first chemical feeding device; 19, second chemical feeding device; 20, third chemical feeding device; 21, fourth chemical feeding device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present utility model with reference to the drawings in the embodiments of the present utility model. Those familiar with this technology can easily understand other advantages and effects of the present utility model from the content disclosed in this specification. Obviously, the described embodiments are only some embodiments of the present utility model, rather than all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present utility model.

[0025] ​It should be noted that the structures, proportions, sizes, etc. depicted in the attached drawings of this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present utility model. Therefore, they do not have substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects that the present utility model can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present utility model. In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by terms such as "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the attached drawings, and is only for the convenience of describing the present utility model, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation to the present utility model. In addition, terms such as "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present utility model, unless otherwise stated, the meaning of "a plurality" is two or more.

[0026] It should also be noted that in the embodiments of this application, the same reference numeral is used to represent the same component or the same part.

[0027] The purpose of the present utility model is to provide a system for treating and recycling electroplating hexavalent chromium wastewater to solve the problems existing in the prior art and be able to effectively separate and recycle the Cr in the chromium-containing wastewater. 6+ for resource recovery treatment.

[0028] To make the above objects, features, and advantages of the present utility model more obvious and understandable, the present utility model will be further described in detail below with reference to the attached drawings and specific embodiments.

[0029] Please refer to Figure 1 , this embodiment provides a system for treating and recycling electroplating hexavalent chromium wastewater, including a pretreatment system, a reduction and sedimentation system, and a chromium sludge calcination system.

[0030] The pretreatment system includes a water pump 1, a first neutralization tank 2, a first coagulation tank 3, a first sedimentation tank 4, a sludge thickening tank 5, a first diaphragm pump 6, and a first filter press 7. The chromium-containing wastewater enters the first neutralization tank 2 through the water pump 1. The water pump 1, the first neutralization tank 2, the first coagulation tank 3, the first sedimentation tank 4, and the first sludge thickening tank 5 are connected in sequence through pipelines. The sludge thickening tank 5 is connected to the first diaphragm pump 6, the first diaphragm pump 6 is connected to the first filter press 7, and the effluent of the first filter press 7 flows into the first neutralization tank 2.

[0031] The reduction sedimentation system includes an acidification tank 8, a reduction tank 9, a second neutralization tank 10, a second coagulation tank 11, a second sedimentation tank 12, a chromium sludge thickening tank 13, a second diaphragm pump 14 and a second filter press 15. The supernatant of the first sedimentation tank 4 in the pretreatment system enters the acidification tank 8. The acidification tank 8, the reduction tank 9, the second neutralization tank 10, the second coagulation tank 11, the second sedimentation tank 12 and the chromium sludge thickening tank 13 are connected in sequence through pipelines. The chromium sludge thickening tank 13 is connected to the second diaphragm pump 14, and the second diaphragm pump 14 is connected to the second filter press 15. The medium water pipeline is connected to the second filter press 15. The supernatant of the second sedimentation tank 12 and the water discharged from the second filter press 15 enter the SCR system. The water in the medium water pipeline is the water produced by the SCR system.

[0032] As a preferred solution of this embodiment, a first chemical supply device 18 connected to the first neutralization tank 2 and the second neutralization tank 10 is also provided. The chemical agent provided by the first chemical supply device 18 is 30% lye. pH meters are arranged in both the first neutralization tank 2 and the second neutralization tank 10 to control the pH value in the first neutralization tank 2 to be 9.0 - 9.5 and the pH value in the second neutralization tank 10 to be 8.5 - 9.0.

[0033] The first coagulation tank 3 and the second coagulation tank 11 are internally divided into a coagulation zone and a flocculation zone, and the coagulation zone and the flocculation zone are interconnected. The second chemical supply device 19 connected to the first coagulation tank 3 and the second coagulation tank 11 provides a coagulant and a flocculant for the coagulation zone and the flocculation zone respectively. The coagulant is polyaluminum chloride, and the flocculant is polyacrylamide.

[0034] A third chemical supply device 20 connected to the acidification tank 8 is also provided. The chemical agent provided by the third chemical supply device 20 is 20% sulfuric acid. A pH meter is arranged in the acidification tank 8, and the pH value in the acidification tank 8 is set to be 2.0 - 2.5.

[0035] A fourth chemical supply device 21 connected to the reduction tank 9 is also provided. The chemical agent provided by the fourth chemical supply device 21 is 10% sodium metabisulfite. An ORP potentiometer is arranged in the reduction tank 9, and the potential value in the reduction tank 9 is set to be 230 - 250 mv.

[0036] As a preferred solution of this embodiment, stirring devices are arranged in the first neutralization tank 2, the first coagulation tank 3, the first sedimentation tank 4, the sludge thickening tank 5, as well as the acidification tank 8, the reduction tank 9, the second neutralization tank 10, the second coagulation tank 11, the second sedimentation tank 12 and the chromium sludge thickening tank 13.

[0037] The first filter press 7 and the second filter press 15 are plate and frame filter presses.

[0038] The chromium sludge calcination system package includes a conveyor 16 and a calcination device 17 connected in sequence. The conveyor 16 is connected to the calcination device 17. The sludge discharged from the second filter press 15 is sent into the calcination device 17 through the conveyor 16 for calcination. The calcination temperature is 1100 °C and the calcination time is 4 h.

[0039] The working principle and process of this embodiment are as follows:

[0040] Pretreatment stage: The hexavalent chromium-containing wastewater is pumped into the first neutralization tank 2 by a water pump 1. Liquid alkali is added in the first neutralization tank 2. After removing other metal ions, it enters the first coagulation tank 3. Poly aluminum chloride and polyacrylamide are added. Precipitation is carried out in the first sedimentation tank 4. The sediment flows into the sludge thickening tank 5. The sediment in the sludge thickening tank 5 is pumped to the first filter press 7 by the first diaphragm pump 6 for pressure filtration. The obtained sludge is sent out for treatment. The water produced by the first filter press 7 returns to the first neutralization tank 2.

[0041] Reduction and sedimentation stage: The supernatant of the first sedimentation tank 4 flows into the acidification tank 8. Sulfuric acid is added in the acidification tank 8 to adjust the acidity. Sodium metabisulfite is added in the reduction tank 9 to reduce hexavalent chromium to trivalent chromium. Liquid alkali is added in the second neutralization tank 10 to make trivalent chromium into chromium hydroxide precipitation. Poly aluminum chloride and polyacrylamide are added in the second coagulation tank 11. Precipitation is carried out in the second sedimentation tank 12. The sediment flows into the chromium sludge thickening tank 13. The sediment in the chromium sludge thickening tank 13 is pumped to the second filter press 15 by the second diaphragm pump 14 for pressure filtration. The supernatant of the second sedimentation tank 12 and the water produced by the second filter press 15 flow into the SCR system for further treatment.

[0042] Chromium sludge calcination stage: When the second filter press 15 is full of sludge, the middle water pipeline valve is opened to wash the sludge in the second filter press 15 to remove salts. The washed sludge is conveyed to the calcination device 17 through the conveyor 16 for calcination, and finally chromium green products are obtained.

[0043] In this embodiment, the chromium-containing wastewater is first subjected to a pretreatment system. The metal ions in the wastewater react with alkali to produce precipitation, which is pressure-filtered by a filter press. The obtained supernatant then enters the reduction and sedimentation system. Acid is added to the supernatant for acidification, and then sodium metabisulfite is added to reduce hexavalent chromium to trivalent chromium and then neutralization and sedimentation treatment is carried out. After the chromium hydroxide sludge is obtained by pressure filtration of the filter press and the salts are washed with middle water, it is transferred to the chromium sludge calcination system and conveyed to the calcination device by a conveyor belt for calcination to obtain pigment-grade chromium green, effectively separating and recycling the resources in the chromium-containing wastewater, and having the advantages of simple structure, high treatment efficiency and good treatment effect. 6+ Separate resource recovery and treatment, with the advantages of simple structure, high treatment efficiency and good treatment effect.

[0044] In the description of the present application, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0045] If the present utility model discloses or involves components or structural parts that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (such as using bolts or screws), or it can also be understood as: a non-detachable fixed connection (such as riveting, welding). Of course, the mutually fixed connection can also be replaced by an integral structure (such as manufactured integrally by a casting process) (except when it is clearly impossible to adopt an integral forming process).

[0046] In addition, unless otherwise stated, the terms used to represent positional relationships or shapes in any of the technical solutions disclosed in the present utility model include states or shapes that are approximate, similar, or close to them.

[0047] Any component provided by the present utility model can either be assembled from multiple individual components or be a single component manufactured by an integral forming process.

[0048] Adaptations made according to actual needs are all within the protection scope of the present utility model.

[0049] It should be noted that for those skilled in the art, it is obvious that the present utility model is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present utility model, the present utility model can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present utility model is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed by the present utility model. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0050] Specific examples are used in the present utility model to illustrate the principles and implementation manners of the present utility model. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present utility model; at the same time, for those of ordinary skill in the art, according to the idea of the present utility model, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be understood as a limitation to the present utility model.

Claims

1. A system for treating and recycling electroplating hexavalent chromium wastewater, characterized in that: It includes a pretreatment system, a reduction and sedimentation system, and a chromium sludge calcination system; The pretreatment system includes a water pump, a first neutralization tank, a first coagulation tank, a first sedimentation tank, a sludge thickening tank, a first diaphragm pump, and a first filter press that are connected in sequence. The effluent of the first filter press flows back into the first neutralization tank; The reduction and sedimentation system includes an acidification tank, a reduction tank, a second neutralization tank, a second coagulation tank, a second sedimentation tank, a chromium sludge thickening tank, a second diaphragm pump, and a second filter press that are connected in sequence. The supernatant of the first sedimentation tank enters the acidification tank, and the supernatant of the second sedimentation tank and the effluent of the second filter press enter the SCR system; The chromium sludge calcination system includes a conveyor and a calcination device that are connected in sequence. The sludge discharged from the second filter press enters the conveyor.

2. The electroplating hexavalent chromium wastewater treatment and resource utilization system according to claim 1, wherein: It also includes a first chemical feeding device connected to the first neutralization tank and the second neutralization tank.

3. The electroplating hexavalent chromium wastewater treatment and resource utilization system according to claim 2, wherein: pH meters are installed in the first neutralization tank and the second neutralization tank, and the chemical agent provided by the first chemical feeding device is 30% alkali solution.

4. The electroplating hexavalent chromium wastewater treatment and resource utilization system according to claim 1, wherein: The interiors of the first coagulation tank and the second coagulation tank are divided into a coagulation zone and a flocculation zone, and the coagulation zone and the flocculation zone are interconnected.

5. The electroplating hexavalent chromium wastewater treatment and resource utilization system according to claim 4, characterized in that: It also includes a second chemical feeding device connected to the first coagulation tank and the second coagulation tank. The second chemical feeding device provides a coagulant and a flocculant for the coagulation zone and the flocculation zone respectively.

6. The electroplating hexavalent chromium wastewater treatment and resource recovery system according to claim 1, characterized in that: It also includes a third chemical feeding device connected to the acidification tank.

7. The electroplating hexavalent chromium wastewater treatment and resource utilization system according to claim 6, characterized in that: A pH meter is installed in the acidification tank, and the chemical agent provided by the third chemical feeding device is 20% sulfuric acid.

8. The electroplating hexavalent chromium wastewater treatment and resource utilization system according to claim 1, characterized in that: It also includes a fourth chemical feeding device connected to the reduction tank.

9. The electroplating hexavalent chromium wastewater treatment and resource utilization system according to claim 8, characterized in that: An ORP potentiometer is installed in the reduction tank, and the chemical agent provided by the fourth chemical feeding device is 10% sodium metabisulfite.

10. The electroplating hexavalent chromium wastewater treatment and resource utilization system according to any one of claims 1-9, characterized in that: Stirring devices are installed in the first neutralization tank, the first coagulation tank, the first sedimentation tank, the sludge thickening tank, as well as the acidification tank, the reduction tank, the second neutralization tank, the second coagulation tank, the second sedimentation tank, and the chromium sludge thickening tank.

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