Chlor-alkali industry salty mud resource utilization device and method

Abstract

The invention relates to the technical field of chlor-alkali industry, in particular to a chlor-alkali industry salty mud resource utilization device and method.The chlor-alkali industry salty mud resource utilization device comprises a washing pool used for washing salty mud to melt sodium chloride in the salty mud; the first filter press is used for separating a solution containing sodium chloride from the dry salty mud material; the calcium chloride production device comprises a reaction tank for the reaction of limestone and hydrochloric acid, and a neutralization tank for adding alkali for neutralization, the reaction tank is used for receiving the separated dry salty mud material; according to the chlor-alkali industry salty mud resource utilization device and method, calcium ions in calcium carbonate are recycled, and sodium chloride and magnesium hydroxide are recycled, so that recycling is more thorough.

Description

Technical Field

[0001] This invention relates to the field of chlor-alkali industry technology, specifically to a device and method for the resource utilization of salt mud in the chlor-alkali industry. Background Technology

[0002] The chlor-alkali industry is a chemical industrial process that produces caustic soda (sodium hydroxide), chlorine, and hydrogen by electrolyzing saturated brine. The salt mud generated during the chlor-alkali production process is classified as solid waste. The amount of mud produced by the ion-exchange membrane production unit varies depending on the type of salt used, generally ranging from 10 kg to 60 kg per ton of caustic soda produced. The salt mud contains a large amount of salts such as calcium carbonate, magnesium hydroxide, and sodium chloride. Salt mud is highly susceptible to soil pollution and impacts the ecological environment. Its disposal requires proper three-proof treatment, which increases the production costs of enterprises.

[0003] Patent application number 201510478757.6 discloses a system and method for treating salt mud, a byproduct of chlor-alkali production. This system first treats the chlor-alkali calcium carbonate salt mud with hydrochloric acid to remove carbonate ions. The generated carbon dioxide is then transported to an absorption tower to react with caustic soda to produce soda ash for brine purification. The solution can be further purified by adding caustic soda to adjust the pH, precipitating acid-insoluble substances and magnesium ions. After pressure filtration, a clear calcium chloride solution is obtained, which can be used as a refrigerant in membrane denitrification refrigeration units and sold externally. The waste residue and acid-insoluble residue obtained after pressure filtration are sent to cement plants, and magnesium hydroxide is calcined at high temperature to obtain magnesium oxide, achieving zero emissions of pollutants.

[0004] The patent application with application number 201510478757.6 only recovers calcium ions from calcium carbonate, but does not recover magnesium ions from magnesium hydroxide or sodium chloride, resulting in incomplete recycling. Summary of the Invention

[0005] The main objective of this invention is to provide a device and method for the resource utilization of salt mud in the chlor-alkali industry, so as to solve the problem that the existing chlor-alkali industry salt mud treatment system only recovers calcium ions from calcium carbonate, and does not recover magnesium ions from magnesium hydroxide or sodium chloride, resulting in incomplete recovery.

[0006] To achieve the above objectives, the present invention provides a device for the resource utilization of salt mud in the chlor-alkali industry, comprising: The washing pool is used to wash the salt mud, so that the sodium chloride in the salt mud melts. The first filter press is used to separate the solution containing sodium chloride from the dry salt mud. The calcium chloride production unit includes a reaction tank for reacting limestone and hydrochloric acid, and a neutralization tank for adding alkali to neutralize the limestone; the reaction tank is used to receive the separated dry salt mud.

[0007] Furthermore, it also includes the raw salt dissolving tank of the chlor-alkali industrial production equipment; the raw salt dissolving tank receives the separated solution containing sodium chloride.

[0008] Furthermore, a mixer is installed in the washing tank, which is connected to the material inlet of the first filter press via a pipe, and the filtrate outlet of the first filter press is connected to the raw salt dissolving tank via a pipe.

[0009] Furthermore, the calcium chloride production unit also includes a second filter press, which is connected to a neutralization tank via a pipeline; the neutralization tank is connected to a reaction tank via a pipeline.

[0010] Furthermore, a first filter press is set on a filter press platform, and a conical sludge collection hopper for recovering dry salt mud is provided below the first filter press. The outlet of the sludge collection hopper faces the inlet of the auger, and the outlet of the auger faces the reaction tank.

[0011] This invention also provides a method for the resource utilization of salt mud from the chlor-alkali industry, using the aforementioned chlor-alkali industry salt mud resource utilization device, comprising the following steps: S1. Add the salt mud to the washing tank, pass demineralized water into the washing tank, stir thoroughly, and wash the salt mud so that the sodium chloride in the salt mud dissolves into the demineralized water. S2. Pass the mixture of salt mud and deionized water in the washing tank into the first filter press to separate the solution containing sodium chloride from the dry salt mud. S3. Pass the dry salt mud into the reaction tank of the calcium chloride production unit for the reaction of limestone and hydrochloric acid; S4. The reaction tank contains limestone and hydrochloric acid. The main component of limestone is calcium carbonate, and limestone contains iron impurities. Calcium carbonate reacts with hydrochloric acid to produce calcium chloride solution. The reaction equation is: CaCO3 + 2HCl = CaCl2 + H2O + CO2↑. Calcium carbonate in the dry salt mud reacts with hydrochloric acid to produce calcium chloride solution, and magnesium hydroxide in the salt mud reacts with hydrochloric acid to produce magnesium chloride. S5. Pass the mixture in the reaction tank into the neutralization tank, adjust the pH of the neutralization tank, and magnesium ions in the solution will form magnesium hydroxide and begin to precipitate; iron impurities in the solution will form Fe(OH)3, and magnesium hydroxide will co-precipitate with iron impurities during precipitation; S6. Separate the precipitates of magnesium hydroxide and Fe(OH)3.

[0012] Further, in step S5, calcium hydroxide is added when adjusting the pH in the reaction tank; the pH value is adjusted to 9-9.5.

[0013] Furthermore, in step S6, the mixture in the neutralization tank is passed into a second filter press to separate magnesium hydroxide and Fe(OH)3 precipitates and other insoluble substances; the filtrate obtained by the filter press is used as a liquid calcium chloride product, or the filtrate is used to continue the production of solid calcium chloride.

[0014] Furthermore, in step S3, a solution containing sodium chloride is introduced into the raw salt dissolving tank (3) of the chlor-alkali industrial production equipment.

[0015] The beneficial effects of this invention are: The device and method for resource utilization of salt mud in the chlor-alkali industry not only recovers calcium ions from calcium carbonate, but also recovers sodium chloride and magnesium hydroxide, thus achieving more thorough recovery.

[0016] This invention recovers calcium ions from calcium carbonate for use in a calcium chloride production system to produce calcium chloride; recovers sodium chloride for use in the raw salt dissolving tank of chlor-alkali industrial production equipment, thus recycling solid waste generated in the chlor-alkali industry within the original system; and recovers magnesium hydroxide for use in the calcium chloride production system to co-precipitate with iron impurities in the calcium chloride production system, thereby removing iron impurities. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] Figure 1 This is a schematic diagram of the structure of the chlor-alkali industry salt mud resource utilization device in the embodiment; In the diagram: 1. Washing tank; 101. Mixer; 2. First filter press; 3. Raw salt dissolving tank; 4. Calcium chloride production unit; 401. Reaction tank; 402. Neutralization tank; 403. Second filter press; 5. Screw conveyor; 6. Sludge collection hopper. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] Example 1 like Figure 1 As shown, a device for the resource utilization of salt mud in the chlor-alkali industry includes: Washing tank 1 is used to wash the salt mud, so that the sodium chloride in the salt mud melts; First filter press 2 is used to separate the solution containing sodium chloride from the dry salt mud; first filter press 2 is a chamber filter press; The calcium chloride production unit 4 includes a reaction tank 401 for reacting limestone and hydrochloric acid, and a neutralization tank 402 for neutralizing with alkali; the reaction tank 401 is used to receive the separated dry salt mud.

[0021] The washing tank 1 is equipped with a mixer 101, which is a top-entry paddle mixer; the washing tank 1 is connected to the material inlet of the first filter press 2 through a pipeline, and a conveying pump is installed on the pipeline.

[0022] Example 2 like Figure 1 As shown, a chlor-alkali industrial salt mud resource utilization device differs from the chlor-alkali industrial salt mud resource utilization device in Example 1 only in that: It also includes a raw salt dissolving tank 3 for chlor-alkali industrial production equipment; the raw salt dissolving tank 3 receives the separated solution containing sodium chloride; the filtrate outlet of the first filter press 2 is connected to the raw salt dissolving tank 3 via a pipeline.

[0023] Example 3 like Figure 1 As shown, the chlor-alkali industrial salt mud resource utilization device differs from the chlor-alkali industrial salt mud resource utilization device in Example 2 only in that: The calcium chloride production unit 4 also includes a second filter press 403, which is a diaphragm filter press. The second filter press 403 is connected to a neutralization tank 402 via a pipeline. The neutralization tank 402 is connected to a reaction tank 401 via a pipeline.

[0024] Example 4 like Figure 1 As shown, the chlor-alkali industrial salt mud resource utilization device differs from the chlor-alkali industrial salt mud resource utilization device in Example 3 only in that: The first filter press 2 is set on the filter press platform. Below the first filter press 2 is a conical mud collection hopper 6 for recovering dry salt mud. The bottom outlet of the mud collection hopper 6 faces the inlet of the screw conveyor 5, and the outlet of the screw conveyor 5 faces the reaction tank 401.

[0025] Example 5 A method for the resource utilization of chlor-alkali industrial salt mud, using the chlor-alkali industrial salt mud resource utilization device in Example 1, includes the following steps: S1. The salt mud mainly contains CaCO3, Mg(OH)2, and NaCl, and also contains a small amount of insoluble substances such as mud, sand, and silicates. Add the salt mud to washing tank 1 and pass demineralized water into washing tank 1. Stir thoroughly to wash the salt mud and dissolve the sodium chloride in the salt mud into the demineralized water. S2. The mixture of salt mud and demineralized water in washing tank 1 is fed into the first filter press 2 to separate the solution containing sodium chloride from the dry salt mud. S3. Pass the dry salt mud into the reaction tank 401 of the calcium chloride production unit 4 for the reaction of limestone and hydrochloric acid. S4. Limestone and hydrochloric acid are present in reaction tank 401. The main component of limestone is calcium carbonate, and limestone contains iron impurities. Calcium carbonate reacts with hydrochloric acid to produce calcium chloride solution. The reaction equation is: CaCO3 + 2HCl = CaCl2 + H2O + CO2↑. Calcium carbonate in the dry salt mud reacts with hydrochloric acid to produce calcium chloride solution, and magnesium hydroxide in the salt mud reacts with hydrochloric acid to produce magnesium chloride. S5. Pass the mixture in reaction tank 401 into neutralization tank 402, add calcium hydroxide, adjust the pH of neutralization tank 402 to 9-9.5, magnesium ions in the solution will form magnesium hydroxide and begin to precipitate; iron impurities in the solution will form Fe(OH)3, and magnesium hydroxide will co-precipitate with iron impurities during precipitation. S6. Separate the precipitates of magnesium hydroxide and Fe(OH)3.

[0026] The principle behind the co-precipitation of magnesium hydroxide with iron impurities is: The newly formed magnesium hydroxide precipitate is an amorphous, loose, gel-like precipitate with a very large specific surface area and extremely high surface energy; this high surface energy strongly adsorbs other ions or molecules in the solution to lower its own energy. Iron ions (Fe2+) in the solution... 3+ ) or its preliminary hydrolysis products (such as Fe(OH) 2+ The iron will be effectively adsorbed on the surface of the magnesium hydroxide precipitate particles; as the magnesium hydroxide precipitate particles grow and settle, they act like countless "small brooms" to "sweep" iron impurities in the solution during the settling process and wrap them inside the precipitate. This process is also called "sweeping coprecipitation".

[0027] Example 6 Example 6 also provides a method for the resource utilization of salt mud in the chlor-alkali industry, which differs from the method in Example 5 only in that: In step S6, the mixture in the neutralization tank 402 is passed into the second filter press 403 to separate magnesium hydroxide and Fe(OH)3 precipitates and other insoluble substances; the filtrate obtained by pressure filtration is used as a calcium chloride liquid product, or the calcium chloride filtrate is concentrated and dried to produce calcium chloride solid.

[0028] Example 7 Example 7 also provides a method for the resource utilization of salt mud from the chlor-alkali industry, which differs from the method in Example 6 only in that: In step S3, a solution containing sodium chloride is introduced into the raw salt dissolving tank 3 of the chlor-alkali industrial production equipment.

[0029] The above-described embodiment of the chlor-alkali industrial salt mud resource utilization device and method not only recovers calcium ions from calcium carbonate, but also recovers and utilizes sodium chloride and magnesium hydroxide, thus achieving more thorough recovery.

[0030] The above embodiments recover calcium ions from calcium carbonate for use in the calcium chloride production system to produce calcium chloride; recover sodium chloride for use in the raw salt dissolving tank of the chlor-alkali industry production equipment, thus applying the solid waste generated by the chlor-alkali industry to the original system for recycling; and recover magnesium hydroxide for use in the calcium chloride production system to co-precipitate with iron impurities in the calcium chloride production system, thereby removing the iron impurities.

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for the resource utilization of salt mud in the chlor-alkali industry, characterized in that, include: Washing pool (1) is used to wash the salt mud and melt the sodium chloride in the salt mud; The first filter press (2) is used to separate the solution containing sodium chloride from the dry salt mud. The calcium chloride production unit (4) includes a reaction tank (401) for reacting limestone and hydrochloric acid, and a neutralization tank (402) for neutralizing with alkali; the reaction tank (401) is used to receive the separated dry salt mud.

2. The chlor-alkali industrial salt mud resource utilization device as described in claim 1, characterized in that, It also includes a raw salt dissolving tank (3) of chlor-alkali industrial production equipment; the raw salt dissolving tank (3) receives the separated solution containing sodium chloride.

3. The chlor-alkali industrial salt mud resource utilization device as described in claim 1, characterized in that, The washing tank (1) is equipped with a mixer (101). The washing tank (1) is connected to the material inlet of the first filter press (2) through a pipe. The filtrate outlet of the first filter press (2) is connected to the raw salt dissolving tank (3) through a pipe.

4. The chlor-alkali industrial salt mud resource utilization device as described in claim 1, characterized in that, The calcium chloride production unit (4) further includes a second filter press (403), which is connected to a neutralization tank (402) via a pipeline; the neutralization tank (402) is connected to a reaction tank (401) via a pipeline.

5. The chlor-alkali industrial salt mud resource utilization device as described in claim 1, characterized in that, The first filter press (2) is set on the filter press platform. Below the first filter press (2) is a conical mud collection hopper (6) for recovering dry salt mud. The outlet of the mud collection hopper (6) faces the inlet of the screw conveyor (5), and the outlet of the screw conveyor (5) faces the reaction tank (401).

6. A method for the resource utilization of salt mud from the chlor-alkali industry, characterized in that, The chlor-alkali industrial salt mud resource utilization device described in claim 1 includes the following steps: S1. Add the salt mud to the washing tank (1), pass demineralized water into the washing tank (1), stir thoroughly, wash the salt mud, and dissolve the sodium chloride in the salt mud into the demineralized water. S2. Pass the mixture of salt mud and deionized water in the washing tank (1) into the first filter press (2) to separate the solution containing sodium chloride from the dry salt mud. S3. The dry salt mud is fed into the reaction tank (401) of the calcium chloride production unit (4) for the reaction of limestone and hydrochloric acid. S4. Limestone and hydrochloric acid are present in the reaction tank (401). The main component of limestone is calcium carbonate. Limestone contains iron impurities. Calcium carbonate reacts with hydrochloric acid to produce calcium chloride solution. The reaction equation is: CaCO3 + 2HCl = CaCl2 + H2O + CO2↑. Calcium carbonate in the dry salt mud reacts with hydrochloric acid to produce calcium chloride solution. Magnesium hydroxide in the salt mud reacts with hydrochloric acid to produce magnesium chloride. S5. Pass the mixture in the reaction tank (401) into the neutralization tank (402) and adjust the pH of the neutralization tank (402). Magnesium ions in the solution will form magnesium hydroxide and begin to precipitate. Iron impurities in the solution will form Fe(OH)3. When magnesium hydroxide precipitates, it will co-precipitate with the iron impurities. S6. Separate the precipitates of magnesium hydroxide and Fe(OH)3.

7. The method for resource utilization of salt mud in the chlor-alkali industry as described in claim 6, characterized in that, In step S5, calcium hydroxide is added when adjusting the pH in the reaction tank (401); the pH value is adjusted to 9-9.

5.

8. The method for resource utilization of salt mud in the chlor-alkali industry as described in claim 6, characterized in that, In step S6, the mixture in the neutralization tank (402) is passed into the second filter press (403) to separate magnesium hydroxide and Fe(OH)3 precipitate and other insoluble substances; the filtrate is used as calcium chloride liquid product, or the filtrate is used to continue producing calcium chloride solid.

9. The method for resource utilization of salt mud in the chlor-alkali industry as described in claim 6, characterized in that, In step S3, a solution containing sodium chloride is introduced into the raw salt dissolving tank (3) of the chlor-alkali industrial production equipment.

Images