Wastewater treatment system for lime coupling calcium sulfate crystallization

Abstract

The utility model discloses a wastewater treatment system for coupling lime with calcium sulfate crystals. A regulating reservoir of the wastewater treatment system homogenizes and equalizes to-be-treated wastewater; the pretreatment unit is used for removing turbidity of the wastewater homogenized and homogenized in the regulating tank; the reverse osmosis membrane unit is used for concentrating the wastewater subjected to turbidity removal by the pretreatment unit; the calcium sulfate crystallization unit generates magnesium hydroxide precipitate by adding lime so as to remove magnesium ions in the wastewater, generates sodium hydroxide through causticization reaction, and induces calcium sulfate in the wastewater to be separated out in a precipitate form by adding seed crystal; the high-density pool unit is used for introducing carbon dioxide into the wastewater treated by the calcium sulfate crystallization unit so as to soften residual calcium ions; and the concentration and crystallization unit is used for concentrating and crystallizing the wastewater softened by the high-density pool unit. According to the utility model, lime agent softening and calcium sulfate induced crystallization are combined, so that the addition of a large amount of sodium hydroxide and sodium carbonate is reduced, and the agent adding cost is greatly reduced.

Description

Technical Field

[0001] The utility model relates to a wastewater treatment system for lime-coupled calcium sulfate crystallization, belonging to the technical field of wastewater treatment. Background Art

[0002] Currently, the advanced wastewater treatment process primarily consists of a front-end pretreatment unit and a subsequent concentration and crystallization unit. Membrane concentration is an essential process step. Insoluble salts in wastewater can easily cause membrane scaling, leading to reduced membrane performance. Therefore, advanced pretreatment is necessary to remove scaling ions and other factors to ensure the proper operation of subsequent units.

[0003] Currently, conventional pretreatment solutions include the lime-soda ash method and the caustic soda-soda ash method. These processes are characterized by fast reaction rates and mature technology, but their greatest limitations are the high cost of caustic soda and soda ash. Furthermore, their production requires high energy consumption and generates significant carbon emissions. Therefore, it is necessary to find more economical and low-carbon wastewater softening treatment solutions. Utility Model Content

[0004] The utility model aims at the deficiencies in the prior art and provides a wastewater treatment system by coupling lime with calcium sulfate crystallization, thereby solving the problem of high cost of softening agents in traditional water treatment solutions.

[0005] The utility model solves the above technical problems with the following technical solutions: A wastewater treatment system for lime-coupled calcium sulfate crystallization comprises a regulating tank, a pretreatment unit, a reverse osmosis membrane unit, a calcium sulfate crystallization unit, a high-density tank unit and a concentration crystallization unit;

[0006] The regulating tank is connected to the pretreatment unit through a delivery pipeline, and the regulating tank is used to homogenize and weigh the wastewater to be treated; the pretreatment unit is used to remove turbidity from the wastewater after homogenization and weighing in the regulating tank;

[0007] The pretreatment unit is connected to the reverse osmosis membrane unit through a delivery pipeline, and the reverse osmosis membrane unit is used to concentrate the wastewater after turbidity removal by the pretreatment unit;

[0008] The concentrate outlet of the reverse osmosis membrane unit is connected to the calcium sulfate crystallization unit through a delivery pipeline. The calcium sulfate crystallization unit is used to generate magnesium hydroxide precipitation by adding lime to remove magnesium ions in the wastewater, and to produce sodium hydroxide through a causticization reaction, and to induce the precipitation of calcium sulfate in the wastewater by adding seed crystals;

[0009] The calcium sulfate crystallization unit is connected to the high-density pool unit through a delivery pipeline, and the high-density pool unit is used to introduce carbon dioxide into the wastewater treated by the calcium sulfate crystallization unit to soften the remaining calcium ions;

[0010] The high-density pool unit is connected to the concentration crystallization unit through a conveying pipeline, and the concentration crystallization unit is used to concentrate and crystallize the wastewater softened by the high-density pool unit.

[0011] As a preferred solution for the wastewater treatment system of lime-coupled calcium sulfate crystallization, the calcium sulfate saturation in the concentrated water produced by the reverse osmosis membrane unit is between 200% and 800%.

[0012] As a preferred solution for the wastewater treatment system of lime-coupled calcium sulfate crystallization, the calcium sulfate saturation in the effluent of the calcium sulfate crystallization unit is between 100% and 200%.

[0013] As a preferred solution for the wastewater treatment system of lime-coupled calcium sulfate crystallization, lime is added to the calcium sulfate crystallization unit to form magnesium hydroxide precipitation to remove magnesium ions in the wastewater.

[0014] As a preferred solution for the wastewater treatment system of lime-coupled calcium sulfate crystallization, the calcium sulfate crystallization unit is connected to a filter press unit through a conveying pipeline. The filter press unit is used to filter the magnesium hydroxide and calcium sulfate slurry produced by the calcium sulfate crystallization unit to obtain filler or cement filler for building coatings.

[0015] The beneficial effects of the utility model are as follows:

[0016] By combining lime reagent softening with calcium sulfate induced crystallization, a large amount of sodium hydroxide and sodium carbonate addition is reduced, thereby significantly reducing the cost of adding drugs. The amount of water and salt entering the subsequent concentrated crystallization unit will also be greatly reduced, which can reduce a lot of energy consumption and achieve the purpose of cost reduction. By combining the lime reagent softening method with calcium sulfate induced crystallization technology, the reaction time is shortened, the equipment investment cost is reduced, the equipment maintenance and repair are facilitated, and it has higher social and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0018] The structures, proportions, sizes, etc. illustrated in this specification are intended solely to complement the contents disclosed herein and to facilitate understanding and reading by persons familiar with the art. They are not intended to limit the conditions under which the present invention may be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in size, without affecting the efficacy and objectives of the present invention, shall remain within the scope of the technical contents disclosed herein.

[0019] Figure 1 This is a schematic diagram of a wastewater treatment system for lime-coupled calcium sulfate crystallization provided in an embodiment of the present invention.

[0020] In the figure, 1. Equalization tank; 2. Pretreatment unit; 3. Reverse osmosis membrane unit; 4. Calcium sulfate crystallization unit; 5. High-density tank unit; 6. Concentration crystallization unit; 7. Filter press unit. DETAILED DESCRIPTION

[0021] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of specific embodiments of the present invention is provided in conjunction with the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of this invention are intended only to describe specific embodiments and are not intended to limit this invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] See also Figure 1 The embodiment of the utility model provides a wastewater treatment system of lime coupled calcium sulfate crystallization, comprising a regulating tank 1, a pretreatment unit 2, a reverse osmosis membrane unit 3, a calcium sulfate crystallization unit 4, a high-density tank unit 5 and a concentration crystallization unit 6;

[0024] The regulating tank 1 is connected to the pretreatment unit 2 through a conveying pipeline. The regulating tank 1 is used to homogenize and weigh the wastewater to be treated; the pretreatment unit 2 is used to remove turbidity from the wastewater after homogenization and weighing in the regulating tank 1.

[0025] The pretreatment unit 2 is connected to the reverse osmosis membrane unit 3 through a delivery pipeline, and the reverse osmosis membrane unit 3 is used to concentrate the wastewater after the turbidity is removed by the pretreatment unit 2;

[0026] The concentrated water outlet of the reverse osmosis membrane unit 3 is connected to the calcium sulfate crystallization unit 4 through a delivery pipeline. The calcium sulfate crystallization unit 4 is used to generate magnesium hydroxide precipitation by adding lime to remove magnesium ions in the wastewater, and to produce sodium hydroxide through a causticization reaction, and to induce the precipitation of calcium sulfate in the wastewater by adding seed crystals;

[0027] The calcium sulfate crystallization unit 4 is connected to the high-density pool unit 5 through a delivery pipeline. The high-density pool unit 5 is used to introduce carbon dioxide into the wastewater treated by the calcium sulfate crystallization unit 4 to soften the remaining calcium ions.

[0028] The high-density tank unit 5 is connected to the concentration crystallization unit 6 through a conveying pipeline, and the concentration crystallization unit 6 is used to concentrate and crystallize the wastewater softened by the high-density tank unit 5 .

[0029] In this embodiment, the calcium sulfate saturation in the concentrated water produced by the reverse osmosis membrane unit 3 is between 200% and 800%. The calcium sulfate saturation in the effluent from the calcium sulfate crystallization unit 4 is between 100% and 200%. Lime is added to the calcium sulfate crystallization unit 4 to form a magnesium hydroxide precipitate to remove magnesium ions from the wastewater. The calcium sulfate crystallization unit 4 is connected to a filter press unit 7 via a delivery pipeline. The filter press unit 7 is used to filter the magnesium hydroxide and calcium sulfate slurry produced by the calcium sulfate crystallization unit 4 to obtain a filler for architectural coatings or cement fillers.

[0030] The principle of this utility model is as follows:

[0031] After being homogenized and weighed in the regulating tank 1, the wastewater to be treated enters the pretreatment unit 2 for preliminary turbidity removal treatment, and the effluent enters the reverse osmosis membrane unit 3 for high-concentration. The recovery rate of the reverse osmosis membrane unit 3 is controlled to ensure that the calcium sulfate saturation of the concentrated water of the reverse osmosis membrane unit 3 is between 200% and 800%. Calcium sulfate within this concentration range will achieve a good crystallization effect in the subsequent calcium sulfate crystallization unit 4.

[0032] The concentrated water from the reverse osmosis membrane unit 3 enters the calcium sulfate crystallization unit 4. Lime is added to the calcium sulfate crystallization unit 4, and the following reaction occurs:

[0033] Ca(OH)2+MgSO4→CaSO4+Mg(OH)2↓

[0034] Ca(OH)2+Na2SO4→CaSO4+2NaOH

[0035] Thus, Mg is removed from wastewater 2+Sodium hydroxide is produced. Seed crystals are then added to the reaction system of calcium sulfate crystallization unit 4 to accelerate the reaction and induce the precipitation of calcium sulfate in the water, effectively removing a large amount of calcium and magnesium hardness and sulfate radicals from the system. The calcium and magnesium slurry produced by calcium sulfate crystallization unit 4 can be used as a raw material for wet desulfurization of boiler flue gas. After filter pressing and dehydration, it can be used as a filler for architectural coatings or cement fillers, achieving efficient resource utilization of solid waste.

[0036] The saturation of calcium sulfate in the effluent of calcium sulfate crystallization unit 4 is between 100% and 200%, and further treatment is required to meet the requirements of the subsequent concentration crystallization unit 6. The effluent of calcium sulfate crystallization unit 4 is introduced into the high-density tank unit 5 for further softening treatment. Carbon dioxide is introduced into the high-density tank unit 5, and the following reaction occurs:

[0037] 2NaOH+CO2→Na2CO3+H2O, Na2CO3+Ca 2+ →CaCO3↓+2Na +

[0038] Thus, the remaining Ca in the wastewater can be removed 2+ The carbon dioxide can be sourced from lime kiln gas or purchased from outside sources. Enterprises with their own power plants can also use flue gas. Furthermore, by combining the lime reagent softening method with calcium sulfate-induced crystallization technology, the amount of sodium hydroxide and sodium carbonate added is reduced. The amount of water and salt entering the subsequent concentration and crystallization unit 6 is also significantly reduced, significantly reducing dosing costs and ultimately lowering overall process costs.

[0039] In summary, the utility model is provided with a regulating tank 1, a pretreatment unit 2, a reverse osmosis membrane unit 3, a calcium sulfate crystallization unit 4, a high-density tank unit 5 and a concentration crystallization unit 6; the regulating tank 1 is connected to the pretreatment unit 2 through a transmission pipeline, and the regulating tank 1 is used to homogenize and equalize the wastewater to be treated; the pretreatment unit 2 is used to remove turbidity from the wastewater after homogenization and equalization in the regulating tank 1; the pretreatment unit 2 is connected to the reverse osmosis membrane unit 3 through a transmission pipeline, and the reverse osmosis membrane unit 3 is used to concentrate the wastewater after turbidity removal from the pretreatment unit 2; the concentrated water outlet of the reverse osmosis membrane unit 3 is connected to the calcium sulfate crystallization unit 4 through a transmission pipeline. Unit 4, the calcium sulfate crystallization unit 4, is used to remove magnesium ions from the wastewater by adding lime to generate magnesium hydroxide precipitation, and to produce sodium hydroxide through a causticizing reaction, and to induce the precipitation of calcium sulfate in the wastewater by adding seed crystals. The calcium sulfate crystallization unit 4 is connected to the high-density tank unit 5 via a transmission pipeline. The high-density tank unit 5 is used to introduce carbon dioxide into the wastewater treated by the calcium sulfate crystallization unit 4 to soften the remaining calcium ions. The high-density tank unit 5 is connected to the concentration crystallization unit 6 via a transmission pipeline. The concentration crystallization unit 6 is used to concentrate and crystallize the wastewater softened by the high-density tank unit 5. The utility model combines lime reagent softening with calcium sulfate induced crystallization, thereby reducing the large amount of sodium hydroxide and sodium carbonate added, thereby significantly reducing the dosing cost. The amount of water and salt entering the subsequent concentration crystallization unit 6 is also significantly reduced, which can significantly reduce energy consumption and achieve the purpose of cost reduction. By combining the lime reagent softening method with the calcium sulfate induced crystallization technology, the reaction time is shortened, the equipment investment cost is reduced, and the equipment maintenance and repair are facilitated, which has high social and environmental benefits.

[0040] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0041] The above-described embodiments merely represent several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the present utility model patent shall be determined by the appended claims.

Claims

1. A wastewater treatment system for lime-coupled calcium sulfate crystallization, characterized in that: It includes a regulating tank (1), a pretreatment unit (2), a reverse osmosis membrane unit (3), a calcium sulfate crystallization unit (4), a high-density tank unit (5) and a concentration crystallization unit (6); The regulating tank (1) is connected to the pretreatment unit (2) via a delivery pipeline, and the regulating tank (1) is used to homogenize and weigh the wastewater to be treated; the pretreatment unit (2) is used to remove turbidity from the wastewater after homogenization and weighing in the regulating tank (1); The pretreatment unit (2) is connected to the reverse osmosis membrane unit (3) via a delivery pipeline, and the reverse osmosis membrane unit (3) is used to concentrate the wastewater after turbidity removal by the pretreatment unit (2); The concentrated water outlet of the reverse osmosis membrane unit (3) is connected to the calcium sulfate crystallization unit (4) through a conveying pipeline. The calcium sulfate crystallization unit (4) is used to generate magnesium hydroxide precipitation by adding lime to remove magnesium ions in the wastewater, and to generate sodium hydroxide by a causticizing reaction, and to induce the precipitation of calcium sulfate in the wastewater in the form of precipitation by adding seed crystals; The calcium sulfate crystallization unit (4) is connected to the high-density pool unit (5) via a conveying pipeline, and the high-density pool unit (5) is used to introduce carbon dioxide into the wastewater treated by the calcium sulfate crystallization unit (4) to soften the remaining calcium ions; The high-density tank unit (5) is connected to the concentration crystallization unit (6) via a conveying pipeline, and the concentration crystallization unit (6) is used to concentrate and crystallize the wastewater softened by the high-density tank unit (5).

2. A wastewater treatment system for lime-coupled calcium sulfate crystallization according to claim 1, characterized in that: The calcium sulfate saturation in the concentrated water produced by the reverse osmosis membrane unit (3) is between 200% and 800%.

3. A wastewater treatment system for lime-coupled calcium sulfate crystallization according to claim 1, characterized in that: The calcium sulfate saturation in the effluent of the calcium sulfate crystallization unit (4) is between 100% and 200%.

4. A wastewater treatment system for lime-coupled calcium sulfate crystallization according to claim 1, characterized in that: Lime is added to the calcium sulfate crystallization unit (4) to form magnesium hydroxide precipitation to remove magnesium ions in the wastewater.

5. A wastewater treatment system for lime-coupled calcium sulfate crystallization according to claim 4, characterized in that: The calcium sulfate crystallization unit (4) is connected to a filter press unit (7) via a delivery pipeline. The filter press unit (7) is used to filter the magnesium hydroxide and calcium sulfate slurry produced by the calcium sulfate crystallization unit (4) to obtain a filler for building coatings or a cement filler.

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