Arsenic-containing acid wastewater treatment system

Abstract

The utility model relates to an arsenic-containing acid wastewater treatment system which comprises a vulcanization reaction tank and a neutralization reaction tank connected with the vulcanization reaction tank, a vulcanization thickener and a ceramic filter press are sequentially connected between the vulcanization reaction tank and the neutralization reaction tank, an outlet of the neutralization reaction tank is further sequentially connected with the thickener and the filter press, and the ceramic filter press is connected with the thickener. The filter press is sequentially connected with a calcium removal tank, a fluorine removal tank and a Gore membrane filtration system, and the Gore membrane filtration system is connected with a water return system. According to the treatment system, the SO2 recovery system and the neutralization filtrate treatment system are additionally arranged, so that recycling of gases such as SO2 is realized, meanwhile, calcium removal, fluorine removal and fine particle separation treatment are further performed on the neutralization filtrate, the problems caused by the filtrate containing calcium and fluorine to subsequent equipment are solved, the wastewater treatment effect is key improved, and the treatment cost is reduced. The treated effluent can stably reach the national discharge standard, and the content of harmful substances in the effluent is far lower than the national discharge standard, so that the recycling of the return water is realized.

Description

Technical Field

[0001] The utility model relates to the technical field of wastewater treatment, in particular to a system for treating arsenic acid wastewater. Background Art

[0002] In the process of pyrite roasting and acid production, a large amount of acidic wastewater is generated, which mainly comes from the acidic wastewater from the acid production section, the waste acid from the purification section, various acidic washing liquids, condensation and absorbent flue spray dirty acid collection, and acidic wastewater from sulfuric acid sales tank leakage. These acidic wastewaters contain a large amount of heavy metal ions (such as arsenic ions), sulfates, calcium ions and other harmful substances, which pose a serious threat to the environment and human health. How to effectively treat the wastewater from pyrite roasting and acid production has become an important task in the current environmental protection field.

[0003] At present, the main methods for treating arsenic-containing wastewater include lime iron salt method, sulfidation method, ion exchange method, electrodialysis method, micro-

[0004] Biological method, membrane separation method, etc. The company's existing arsenic acid wastewater treatment system is as follows: Figure 2 As shown in the figure, sulfide + lime neutralization is mainly used. Although it can reduce the content of harmful substances in wastewater to a certain extent, there are problems such as poor treatment effect, excessive residual harmful components, and unstable compliance of wastewater discharge. For example, a large amount of calcium ions generated after the neutralization reaction have not been treated, which often leads to blockage of the pipes introduced into the return water system section, and a large amount of fluoride ions remain. The strong corrosiveness of fluoride ions will corrode the return water system and related equipment for return water reuse.

[0005] In response to the above problems, this application proposes an arsenic acid wastewater treatment system, which will be improved on the basis of the existing treatment system, improve the treatment effect, minimize harmful substances in the wastewater, ensure that the wastewater meets the national emission standards in a long-term and stable manner, and realize the recycling of wastewater. Utility Model Content

[0006] The utility model provides a system for treating arsenic acid wastewater.

[0007] The specific technical scheme of the utility model is: an arsenic acid wastewater treatment system, comprising a sulfidation reaction tank and a neutralization reaction tank connected thereto, wherein a sulfidation thickener and a ceramic filter press are sequentially connected between the sulfidation reaction tank and the neutralization reaction tank, and an outlet of the neutralization reaction tank is also sequentially connected to a thickener and a filter press, and the filter press is sequentially connected to a decalcification tank, a defluorination tank and a Gore membrane filtration system, and the Gore membrane filtration system is connected to a return water system.

[0008] Furthermore, preferably, a stripping tower is also included, wherein the liquid outlet of the stripping tower is connected to the inlet of the sulfidation reaction tank, and the gas outlet of the stripping tower is connected to the purification section to realize the recovery and utilization of the generated SO2 gas.

[0009] The beneficial effects of the utility model are as follows: the treatment system realizes the recovery and utilization of gases such as SO2 by adding a SO2 recovery system and a neutralization filtrate treatment system, and further performs calcium removal, fluorine removal and fine particle separation treatment on the neutralization filtrate, thereby solving the problems caused by the calcium and fluorine-containing filtrate to subsequent equipment, and crucially improving the wastewater treatment effect. The treated effluent can not only stably meet the national emission standards, but also the content of harmful substances in the effluent is far lower than the national emission standards, so that the return water can be recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is an equipment association diagram of an arsenic acid wastewater treatment system of the utility model;

[0011] Figure 2 It is the equipment association diagram of the existing arsenic acid wastewater treatment system;

[0012] In the figure: 1- desorption tower, 2- sulfidation reaction tank, 3- sulfidation thickener, 4- ceramic filter press, 5- neutralization reaction tank, 6- thickener, 7- filter press, 8- decalcification tank, 9- defluorination tank, 10- Gore membrane filtration system, 11- return water system, 12- purification section. DETAILED DESCRIPTION

[0013] In order to make the technical problems and technical solutions solved by the utility model more clearly understood, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0014] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0015] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", and "connect" 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 it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0016] like Figure 1 As shown, the present embodiment provides an arsenic acid wastewater treatment system, which is based on the existing arsenic acid wastewater treatment system (such as Figure 2 ) on the basis of adding a SO2 recovery system and a neutralization filtrate treatment system to improve the treatment effect, which may reduce harmful substances in the wastewater, ensure that the wastewater meets the national emission standards in a long-term and stable manner, and realize the recycling of wastewater.

[0017] The system includes a sulfidation reaction tank 2 and a neutralization reaction tank 5 connected thereto, wherein a sulfidation thickener 3 and a ceramic filter press 4 are sequentially connected between the sulfidation reaction tank 2 and the neutralization reaction tank 5, and the outlet of the neutralization reaction tank 5 is also sequentially connected to a thickener 6 and a filter press 6, which is the prior art. The filter press 7 is sequentially connected to a decalcification tank 8, a defluorination tank 9 and a Gore membrane filtration system 10, and the Gore membrane filtration system 10 is connected to a return water system 11. At the same time, a desorption tower 1 is also arranged in front of the sulfidation reaction tank 2, wherein the liquid outlet of the desorption tower 1 is connected to the inlet of the sulfidation reaction tank 2, and the gas outlet of the desorption tower 1 is connected to a purification section 12, so as to realize the recovery and utilization of the generated SO2 gas.

[0018] Among them, the decalcification tank 8 can react with the calcium ions in the neutralization filtrate by adding ammonium fluoride to achieve the decalcification effect; the defluorination tank 9 removes the fluoride ions in the neutralization filtrate by adding PAM and aluminum salt; the Gore membrane filtration system 10, as an existing advanced solid-liquid separation technology, can efficiently separate small-size particles, heavy metal precipitates, suspended matter and other substances in chemical treatment wastewater to ensure that the effluent is stable and meets the standards. After the wastewater is chemically treated and filtered by the Gore membrane, the content of pollutants in the clear water is lower than the national sewage comprehensive discharge level 1 standard (GB8979-1996), which is conducive to the recycling of wastewater; compared with the traditional smelting wastewater treatment process, the filtration system has the advantages of good treatment effect, short process flow, small footprint, high degree of automation, low labor intensity, and saving of reagent costs.

[0019] The above treatment system is used to treat arsenic acid wastewater. The specific treatment process is as follows:

[0020] The collected arsenic-containing acid wastewater is pumped into the stripping tower 1 through a pressure pump to desorb the dissolved SO2 from the acid wastewater, and the SO2 is introduced into the purification section 12 for recovery and treatment to realize the utilization of SO2 gas. At the same time, the stripping tower 1 can also remove dissolved gases such as oxygen and carbon dioxide to avoid entering the subsequent treatment links, thereby improving the water purification efficiency.

[0021] The degassed wastewater is then introduced into the sulfidation reaction tank 2, and sodium sulfide is added to carry out the sulfidation reaction:

[0022] ①Na2S+H2SO4→H2S↑+Na2SO4

[0023] ②3H2S+2HAsO2→As2S3↓+4H2O

[0024] ③Cu 2+ +H2S→CuS↓+2H +

[0025] ④Na2S+HF→H2S↑+NaF2+Na2SO4

[0026] Under acidic conditions, arsenic exists in the form of cations. Sodium sulfide reacts with sulfuric acid to generate hydrogen sulfide. Arsenic (As) reacts with hydrogen sulfide to generate As2S3 precipitate. Fluoride ions mainly exist in the form of hydrogen fluoride and react with sodium sulfide to generate hydrogen sulfide and sodium fluoride. However, sodium fluoride is easily soluble under acidic conditions and has limited fluoride removal effect. Other heavy metal elements react with hydrogen sulfide to generate other sulfide precipitates. The arsenic filter cake and sulfide filtrate (mainly containing arsenic and fluorine) are separated by sulfide thickener 3 and ceramic filter press 4.

[0027] The sulfide filtrate is transferred to the neutralization reaction tank 5, and lime milk is added to carry out neutralization reaction:

[0028] ①Ca(OH)2+H2SO4=CaSO4↓+2H2O

[0029] ②3Ca(OH)2+2H3A S O3=Ca(A S O3)2↓+6H2O

[0030] ③Ca(OH)2+H3A S O4=Ca(A S O4)2↓+2H2O

[0031] ④Fe 3+ +3OH→Fe(OH)3↓

[0032] ⑤Ca(OH)2+2HF=CaF2+2H2O

[0033] Calcium hydroxide neutralizes the acid to form an alkaline environment and As 3+ 、As 5+ A precipitate is formed, and hydroxide and Fe 3+ The reaction generates iron hydroxide precipitation, while calcium hydroxide can remove part of the fluoride ions, further removing arsenic, iron and fluoride ions. A coagulant can be added during the reaction to accelerate the reaction precipitation. The reactants are separated into neutralization filter cake and neutralization filtrate (mainly containing fluoride) through a thickener 6 and a filter press 7.

[0034] The neutralized filtrate is transferred to the decalcification tank 8 and ammonium fluoride is added to carry out the decalcification reaction: Ca2 + +2F -→ CaF2↓, remove calcium ions, and then transfer the reactants to the defluorination tank 9, add PAM and aluminum salt to remove fluoride ions: Al 3+ +3F - →AlF3↓, PAM can accelerate the formation and sedimentation of precipitates and improve the defluorination effect. The reactants are deeply treated by the Gore membrane filtration system to separate the fluorine filter cake and other tiny substances and clear liquid. The clear liquid enters the return water system 11 for recycling.

[0035] The treatment effect of the treated wastewater is shown in Table 1:

[0036] Table 1: Comparison of data before and after wastewater treatment

[0037] Test items pH Asmg / L Camg / L Fmg / L CODmg / L BOD5mg / L SSmg / L Cumg / L Before wastewater treatment 1.6 521 1250 2600 100 150 256 5 After wastewater treatment 7.8 0.052 6.89 1.2 1.2 1.1 5 0.01 Emission standards 6-9 0.5 100 10 30 10 20 0.5 Removal rate% / 99.99 99.45 99.95 98.80 99.27 98.05 99.80

[0038] It can be seen from Table 1 that the treatment system of the present application can effectively treat arsenic acid wastewater. The effluent after treatment meets the national emission standards, and the content of various harmful substances in the effluent is far lower than the national emission standards. The removal rates of arsenic, calcium, fluoride and other ions are all above 99%, and the effluent can be recycled.

[0039] The present invention is described in detail above through specific and preferred embodiments, but those skilled in the art should understand that the present invention is not limited to the embodiments described above, and any modifications, equivalent substitutions, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A system for treating arsenic acid wastewater, comprising a sulfidation reaction tank (2) and a neutralization reaction tank (5) connected thereto, wherein a sulfidation thickener (3) and a ceramic filter press (4) are sequentially connected between the sulfidation reaction tank (2) and the neutralization reaction tank (5), and an outlet of the neutralization reaction tank (5) is also sequentially connected to a thickener (6) and a filter press (7), characterized in that: The filter press (7) is sequentially connected to a decalcification tank (8), a defluorination tank (9) and a Gore membrane filtration system (10), and the Gore membrane filtration system (10) is connected to a return water system (11).

2. The arsenic acid wastewater treatment system according to claim 1, characterized in that: It also comprises a stripping tower (1), wherein a liquid outlet of the stripping tower (1) is connected to an inlet of a sulfidation reaction tank (2), and a gas outlet of the stripping tower (1) is connected to a purification section (12), so as to realize the recovery and utilization of the generated SO2 gas.

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