A power plant desulfurization wastewater extraction process system and method

Abstract

The application discloses a power plant desulfurization wastewater extraction process system and method. A sodium bed softening unit is arranged at the front end of the extraction process, and Ca 2+ The formation of calcium sulfate scale is avoided from the root, the scaling rate of the extraction device and the pipeline is significantly reduced, the risk of equipment fouling is reduced, the long-term stable operation of the positive extraction centrifuge is ensured, and the equipment maintenance cost is reduced; after the sodium bed softening treatment, Mg 2+ In the desulfurization wastewater, Mg 2+ The continuous enrichment phenomenon does not occur when the treated dechlorination wastewater is reused to the flue gas desulfurization system, and the foaming of the desulfurization slurry is effectively inhibited; the sodium chloride solution generated in the back extraction reaction is mixed with the sodium chloride aqueous solution obtained after the softening treatment of the regeneration liquid, and is used as a sodium bed regeneration supplement liquid for recycling, so that the reagent consumption cost is significantly reduced; meanwhile, the desulfurization wastewater is reused, the waste of water resources is reduced, and the energy saving and environmental protection requirements are met.

Description

Technical Field

[0001] This invention relates to the field of advanced treatment technology for desulfurization wastewater, and in particular to an extraction process system and method for power plant desulfurization wastewater. Background Technology

[0002] In the "three-stage tank + extraction dechlorination" process for desulfurization wastewater in power plants, the desulfurization wastewater still contains a high concentration of Ca after treatment by the three-stage tank. 2+ Existing technologies require acidification of the extractant before extraction, with sulfuric acid being a commonly used acidifying agent. This acidification process introduces a large amount of SO4 into the system. 2- After extraction and dechlorination, a large amount of calcium sulfate precipitates in the system due to the common ion effect, significantly increasing the scaling rate of the extraction unit and causing it to become clogged and unable to operate normally. Meanwhile, the "three-tank + extraction and dechlorination" treatment process for Mg... 2+ The removal rate is limited, and the treated desulfurization wastewater is reused in the flue gas desulfurization system. Mg in the desulfurization tower... 2+ The continuous accumulation of Mg leads to foaming in the desulfurization slurry, affecting desulfurization efficiency. Therefore, there is an urgent need to develop a solution to address scaling in the extraction unit and Mg... 2+ Extraction process system and method for desulfurization wastewater with continuous enrichment problems. Summary of the Invention

[0003] The present invention aims to at least partially solve one of the technical problems in the related art.

[0004] Therefore, embodiments of the present invention propose an extraction process system and method for power plant desulfurization wastewater. This addresses the problem of severe scaling and Mg content in existing desulfurization wastewater extraction and dechlorination technologies. 2+ To address the problem of continuous enrichment, this invention provides an extraction process system and method for power plant desulfurization wastewater. By setting up a sodium bed at the front end of the extraction process, the calcium in the desulfurization wastewater after triple-tank treatment is extracted. 2+ and Mg 2+ Remove and prevent the formation of calcium sulfate and Mg. 2+ Bubbles in the desulfurization slurry caused by continuous enrichment.

[0005] In a first aspect, the present invention proposes a process system and method for extracting desulfurization wastewater from power plants, comprising:

[0006] A sodium bed softening unit, wherein a three-compartment pretreatment unit is provided upstream of the sodium bed softening unit; The positive extraction centrifuge is located downstream of the sodium bed softening unit. A flue gas desulfurization system is installed at the aqueous phase outlet end of the positive extraction centrifuge, and a back extraction centrifuge is installed at the organic phase outlet end. An extractant acidification device is provided, in which the extractant is acidified before entering the positive extraction centrifuge; A sodium hydroxide dosing device is provided, wherein the first outlet of the sodium hydroxide dosing device is connected to the back-extraction centrifuge, the aqueous phase outlet of the back-extraction centrifuge is connected to the sodium chloride dosing device, the organic phase outlet is connected to the extractant acidification device, the second outlet of the sodium hydroxide dosing device is connected to the regenerated liquor softening device, the liquid phase outlet of the regenerated liquor softening device is connected to the sodium chloride dosing device, the solid phase outlet is connected to the sludge treatment system, and the outlet of the sodium chloride dosing device is connected to the sodium bed softening unit. A sodium carbonate dosing device, the outlet of which is connected to the regenerated liquid softening device.

[0007] Furthermore, after being treated by the aforementioned triplex pretreatment unit, the desulfurization wastewater enters the sodium bed softening unit to remove Ca. 2+ and Mg 2+ .

[0008] Furthermore, the sodium chloride dosing device is used to introduce sodium chloride solution into the sodium bed softening unit to regenerate the sodium bed and generate regenerated liquid.

[0009] Furthermore, the regenerated liquid enters the regenerated liquid softening device, where sodium carbonate solution and sodium hydroxide solution are added to the regenerated liquid softening device using the sodium carbonate dosing device and the sodium hydroxide dosing device, respectively, to soften the regenerated liquid and produce an aqueous sodium chloride solution and a solid precipitate.

[0010] Furthermore, the aqueous sodium chloride solution is recycled into the sodium chloride dosing device, and the solid precipitate is fed into the sludge treatment system.

[0011] Furthermore, a sulfuric acid dosing device is provided at the upstream inlet of the extractant acidification device. The extractant trioctylamine is acidified with sulfuric acid in the extractant acidification device to obtain ammonium sulfate, which then enters the positive extraction centrifuge.

[0012] Furthermore, the SO4 in the ammonium sulfate salt during the positive extraction centrifuge 2 Cl in the aqueous phase The exchange process generates the extract R3NHCl, which ultimately forms the R3NHCl organic phase. After dechlorination, it contains a large amount of SO4. 2 The aqueous phase.

[0013] Furthermore, the dechlorinated material contains a large amount of SO4. 2 The aqueous phase enters the flue gas desulfurization system, and the R3NHCl organic phase enters the back-extraction centrifuge.

[0014] Furthermore, sodium hydroxide solution is introduced into the back-extraction centrifuge using the sodium hydroxide dosing device to regenerate the extractant, producing a regenerated extractant and a sodium chloride solution. The regenerated extractant is recycled into the extractant acidification device, and the sodium chloride solution is recycled into the sodium chloride dosing device.

[0015] Secondly, this invention proposes a method for extracting desulfurization wastewater from power plants, utilizing the power plant desulfurization wastewater extraction process system proposed in the first aspect, comprising the following steps: After pretreatment in a three-stage tank, the desulfurization wastewater from the power plant enters the sodium bed softening unit to remove Ca. 2+ and Mg 2+ Then it enters the extraction centrifuge; In the aforementioned extraction centrifuge, the extractant trioctylamine, after being acidified and protonated by sulfuric acid, undergoes an exchange reaction with chloride ions in the wastewater to achieve dechlorination, forming an R3NHCl organic phase. This dechlorinated phase contains a large amount of SO4. 2 The aqueous phase, after dechlorination, contains a large amount of SO4. 2 The aqueous phase enters the flue gas desulfurization system, and the R3NHCl organic phase enters the back-extraction centrifuge for regeneration. A sodium hydroxide solution is introduced into the back-extraction centrifuge to regenerate the extractant, producing a regenerated extractant and a sodium chloride solution, which are then recycled. Sodium chloride solution is introduced into the sodium bed softening unit to regenerate it. The regenerated liquid from the sodium bed softening unit enters the regenerated liquid softening device. The softening process produces an aqueous sodium chloride solution and a solid precipitate. The aqueous sodium chloride solution enters the sodium chloride dosing device for recycling, and the solid precipitate enters the sludge treatment system.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention incorporates a sodium bed softening unit at the upstream end of the extraction process to remove Ca from the effluent of the triplex tank in advance. 2+ This method avoids the formation of calcium sulfate scale at the source, significantly reduces the scaling rate of extraction devices and pipelines, reduces the risk of equipment clogging, ensures the long-term stable operation of the extraction centrifuge, and reduces equipment maintenance costs.

[0017] This invention reduces the Mg content in desulfurization wastewater after sodium bed softening treatment. 2+ When the dechlorinated wastewater is efficiently removed and treated, it will not contain Mg when reused in the flue gas desulfurization system. 2+ The continuous enrichment phenomenon effectively inhibits foaming of desulfurization slurry.

[0018] The sodium chloride solution produced by the back-extraction reaction of the present invention is mixed with the sodium chloride aqueous solution obtained after softening the regenerated liquid and used as a sodium bed regeneration replenishment liquid for recycling, which significantly reduces the cost of reagent consumption; at the same time, it realizes the reuse of desulfurization wastewater, reduces water waste, and meets the requirements of energy conservation and environmental protection. Attached Figure Description

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the power plant desulfurization wastewater extraction process system of the present invention. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] The following description, in conjunction with the accompanying drawings, describes the extraction process system and method for power plant desulfurization wastewater proposed in this invention.

[0022] like Figure 1 As shown, the power plant desulfurization wastewater extraction process system of the present invention includes a three-compartment pretreatment unit, a sodium bed softening unit, a forward extraction centrifuge, a reverse extraction centrifuge, and a regenerated liquid softening device.

[0023] The triplet pretreatment unit is located upstream of the sodium bed softening unit. The desulfurization wastewater from the power plant enters the sodium bed softening unit after pretreatment in the triplet pretreatment unit. The triplet treatment process is a conventional desulfurization wastewater treatment process, comprising a neutralization tank, a reaction tank, and a flocculation tank. The neutralization tank is used to adjust the pH and remove fluoride ions, while the reaction tank is used to remove heavy metals such as Hg, Pb, and Cd, which will not be detailed here.

[0024] After being treated by the triplex pretreatment unit, the desulfurization wastewater enters the sodium bed softening unit to remove Ca. 2+ and Mg 2+ The softened sodium bed permeate is obtained. The core of sodium bed softening is ion exchange, where calcium and magnesium ions in the water are replaced by sodium ions on a sodium-type cation exchange resin. The principle of calcium and magnesium ion replacement by sodium-type resin (R–Na) is as follows: , .

[0025] The forward extraction centrifuge is located downstream of the sodium bed softening unit, and the softened sodium bed permeate enters the forward extraction centrifuge. The sulfuric acid dosing unit and the extractant acidification unit are located upstream of the forward extraction centrifuge, one upstream and one downstream. The extractant trioctylamine (N235) is acidified with sulfuric acid in the extractant acidification unit to obtain ammonium sulfate, which then enters the forward extraction centrifuge. A flue gas desulfurization system is installed at the aqueous phase outlet of the forward extraction centrifuge, and a reverse extraction centrifuge is installed at the organic phase outlet.

[0026] SO4 in ammonium sulfate in positive extraction centrifuge 2 Cl in the aqueous phase The exchange process generates the extract R3NHCl, which ultimately forms the R3NHCl organic phase. After dechlorination, it contains a large amount of SO4. 2 The aqueous phase contains a large amount of SO4 after dechlorination. 2 The aqueous phase enters the flue gas desulfurization system, and the R3NHCl organic phase enters the back-extraction centrifuge.

[0027] N235 is protonated by H2SO4 to produce SO4-containing compounds. 2 The reaction equation for the amine salt (R3NH)2SO4 is shown in equation (1), where R is n-octyl (-C8H). 17 ).

[0028]

[0029] SO4 in ammonium salt (R3NH)2SO4 2 Cl in the aqueous phase The exchange process produces the extract R3NHCl, and the reaction equation is shown in equation (2).

[0030] The extractant is regenerated in a back-extraction centrifuge. Specifically, the first outlet of the sodium hydroxide dosing device is connected to the back-extraction centrifuge, the aqueous phase outlet of the back-extraction centrifuge is connected to the sodium chloride dosing device, and the organic phase outlet is connected to the extractant acidification device. Sodium hydroxide solution is introduced into the back-extraction centrifuge using the sodium hydroxide dosing device. The sodium hydroxide solution reacts with the extractant, resulting in the regeneration of the extractant into regenerated extractant and sodium chloride solution. The aqueous phase sodium chloride solution flows out of the aqueous phase outlet of the back-extraction centrifuge and is recycled back into the sodium chloride dosing device. The regenerated organic phase extractant flows out of the organic phase outlet of the back-extraction centrifuge and is recycled back into the extractant acidification device.

[0031] The mechanism of back-extraction is as follows: After the sodium bed softening unit has been running for a period of time, a sodium chloride solution is introduced into the sodium bed through a sodium chloride dosing device for regeneration. Specifically, the outlet of the sodium chloride dosing device is connected to the sodium bed softening unit, and the sodium chloride solution is introduced into the unit to regenerate the sodium bed and produce a regenerated solution. After the sodium bed resin is saturated with calcium and magnesium, it is regenerated with saturated brine (NaCl), as follows:

[0032]

[0033] The sodium bed softening unit generates a regenerated solution during the regeneration process. This regenerated solution is a mixed solution of calcium chloride and magnesium chloride. The regenerated solution outlet of the sodium bed softening unit is connected to a regenerated solution softening device, where the regenerated solution undergoes softening treatment.

[0034] Specifically, the second outlet of the sodium hydroxide dosing device is connected to the regenerated liquid softening device, the outlet of the sodium carbonate dosing device is connected to the regenerated liquid softening device, the liquid phase outlet of the regenerated liquid softening device is connected to the sodium chloride dosing device, and the solid phase outlet is connected to the sludge treatment system. Sodium carbonate solution and sodium hydroxide solution are added to the regenerated liquid softening device using the sodium carbonate dosing device and sodium hydroxide dosing device, respectively. The sodium carbonate solution and sodium hydroxide solution soften the regenerated liquid, reducing the CaO content in the regenerated liquid. 2+ and Mg 2+ The solid sludge produced during the softening process forms a precipitate and enters the sludge treatment system for further processing. The sodium chloride aqueous solution produced after softening enters the sodium chloride dosing device and is used as a makeup liquid in the regeneration process of the sodium bed, along with the sodium chloride solution produced during the back-extraction process.

[0035] The method for extracting desulfurization wastewater from power plants, utilizing the power plant desulfurization wastewater extraction process system of the present invention, includes the following steps: (1) After pretreatment in a three-stage tank, the desulfurization wastewater from the power plant enters the sodium bed softening unit to remove Ca. 2+ and Mg 2+ Then it enters the extraction centrifuge; (2) In the positive extraction centrifuge, the extractant trioctylamine, after being acidified and protonated by sulfuric acid, undergoes an exchange reaction with chloride ions in the wastewater to achieve dechlorination, forming an R3NHCl organic phase. After dechlorination, it contains a large amount of SO4. 2 The aqueous phase, after dechlorination, contains a large amount of SO4. 2 The aqueous phase enters the flue gas desulfurization system, and the R3NHCl organic phase enters the back-extraction centrifuge for regeneration. (3) Sodium hydroxide solution is introduced into the back-extraction centrifuge to regenerate the extractant and generate regenerated extractant and sodium chloride solution, which are then recycled. (4) Sodium chloride solution is introduced into the sodium bed softening unit to regenerate it. The regenerated liquid of the sodium bed softening unit enters the regenerated liquid softening device. The softening process produces aqueous sodium chloride solution and solid precipitate. The aqueous sodium chloride solution enters the sodium chloride dosing device for recycling, and the solid precipitate enters the sludge treatment system.

[0036] Step (1) is the pretreatment process for power plant desulfurization wastewater. After the desulfurization wastewater is pretreated in a three-stage tank to remove heavy metals such as Hg, Pb, and Cd, it enters the sodium bed softening unit to remove Ca. 2+ and Mg 2+ The softened sodium bed permeate is then obtained and enters the positive extraction centrifuge.

[0037] Step (2) is the positive extraction dechlorination process. The extractant trioctylamine (N235) is acidified with sulfuric acid in the extractant acidification device to obtain ammonium sulfate, which then enters the positive extraction centrifuge. In the positive extraction centrifuge, the SO4 in the ammonium sulfate is removed. 2 Cl in the aqueous phase The exchange process generates the extract R3NHCl, which ultimately forms the R3NHCl organic phase. After dechlorination, it contains a large amount of SO4. 2 The aqueous phase contains a large amount of SO4 after dechlorination. 2 The aqueous phase enters the flue gas desulfurization system, while the organic phase R3NHCl enters the back-extraction centrifuge for regeneration.

[0038] Step (3) is the back-extraction process. Sodium hydroxide solution is introduced into the back-extraction centrifuge using a sodium hydroxide dosing device. The sodium hydroxide solution reacts with the extractant to regenerate the extractant, producing a regenerated extractant and a sodium chloride solution. The aqueous sodium chloride solution flows out of the aqueous phase outlet of the back-extraction centrifuge and is recycled into the sodium chloride dosing device. The organic phase regenerated extractant flows out of the organic phase outlet of the back-extraction centrifuge and is recycled into the extractant acidification device.

[0039] Step (4) is the sodium bed regeneration solution treatment process. The sodium bed softening unit generates regeneration solution during the regeneration process. The regeneration solution is a mixed solution of calcium chloride and magnesium chloride. Sodium carbonate solution and sodium hydroxide solution are added to the regeneration solution softening device using sodium carbonate dosing device and sodium hydroxide dosing device, respectively. The sodium carbonate solution and sodium hydroxide solution soften the regeneration solution, reducing the Ca content in the regeneration solution. 2+ and Mg 2+ The solid sludge produced during the softening process forms a precipitate and enters the sludge treatment system for further processing. The sodium chloride aqueous solution produced after softening enters the sodium chloride dosing device and is used as a makeup liquid in the regeneration process of the sodium bed, along with the sodium chloride solution produced during the back-extraction process.

[0040] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0042] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A power plant desulfurization wastewater extraction process system, characterized in that, include: A sodium bed softening unit, wherein a three-compartment pretreatment unit is provided upstream of the sodium bed softening unit; The positive extraction centrifuge is located downstream of the sodium bed softening unit. A flue gas desulfurization system is installed at the aqueous phase outlet end of the positive extraction centrifuge, and a back extraction centrifuge is installed at the organic phase outlet end. An extractant acidification device is provided, in which the extractant is acidified before entering the positive extraction centrifuge; A sodium hydroxide dosing device is provided, wherein the first outlet of the sodium hydroxide dosing device is connected to the back-extraction centrifuge, the aqueous phase outlet of the back-extraction centrifuge is connected to the sodium chloride dosing device, the organic phase outlet is connected to the extractant acidification device, the second outlet of the sodium hydroxide dosing device is connected to the regenerated liquor softening device, the liquid phase outlet of the regenerated liquor softening device is connected to the sodium chloride dosing device, the solid phase outlet is connected to the sludge treatment system, and the outlet of the sodium chloride dosing device is connected to the sodium bed softening unit. A sodium carbonate dosing device, the outlet of which is connected to the regenerated liquid softening device.

2. The power plant desulfurization wastewater extraction process system as described in claim 1, characterized in that, After being treated by the aforementioned triplex pretreatment unit, the desulfurization wastewater enters the sodium bed softening unit to remove Ca. 2+ and Mg 2+ .

3. The power plant desulfurization wastewater extraction process system as described in claim 1, characterized in that, The sodium chloride solution is introduced into the sodium bed softening unit using the sodium chloride dosing device to regenerate the sodium bed and generate a regenerated liquid.

4. The power plant desulfurization wastewater extraction process system as described in claim 3, characterized in that, The regenerated liquid enters the regenerated liquid softening device, where sodium carbonate solution and sodium hydroxide solution are added to the regenerated liquid softening device using the sodium carbonate dosing device and the sodium hydroxide dosing device, respectively, to soften the regenerated liquid and produce an aqueous sodium chloride solution and a solid precipitate.

5. The power plant desulfurization wastewater extraction process system as described in claim 4, characterized in that, The aqueous sodium chloride solution is recycled into the sodium chloride dosing device, and the solid precipitate is fed into the sludge treatment system.

6. The power plant desulfurization wastewater extraction process system as described in claim 1, characterized in that, A sulfuric acid dosing device is installed at the upstream inlet of the extractant acidification device. The extractant trioctylamine is acidified with sulfuric acid in the extractant acidification device to obtain ammonium sulfate, which then enters the positive extraction centrifuge.

7. The power plant desulfurization wastewater extraction process system as described in claim 6, characterized in that, SO4 in the ammonium sulfate in the positive extraction centrifuge 2 Cl in the aqueous phase The exchange process generates the extract R3NHCl, which ultimately forms the R3NHCl organic phase. After dechlorination, it contains a large amount of SO4. 2 The aqueous phase.

8. The power plant desulfurization wastewater extraction process system as described in claim 7, characterized in that, The dechlorinated material contains a large amount of SO4. 2 The aqueous phase enters the flue gas desulfurization system, and the R3NHCl organic phase enters the back-extraction centrifuge.

9. The power plant desulfurization wastewater extraction process system as described in claim 1, characterized in that, The sodium hydroxide solution is introduced into the back-extraction centrifuge using the sodium hydroxide dosing device to regenerate the extractant, producing a regenerated extractant and a sodium chloride solution. The regenerated extractant is recycled into the extractant acidification device, and the sodium chloride solution is recycled into the sodium chloride dosing device.

10. A method for extracting desulfurization wastewater from a power plant, characterized in that, The power plant desulfurization wastewater extraction process system according to any one of claims 1 to 9 includes the following steps: After pretreatment in a three-stage tank, the desulfurization wastewater from the power plant enters the sodium bed softening unit to remove Ca. 2+ and Mg 2+ Then it enters the extraction centrifuge; In the aforementioned extraction centrifuge, the extractant trioctylamine, after being acidified and protonated by sulfuric acid, undergoes an exchange reaction with chloride ions in the wastewater to achieve dechlorination, forming an R3NHCl organic phase. This dechlorinated phase contains a large amount of SO4. 2 The aqueous phase, after dechlorination, contains a large amount of SO4. 2 The aqueous phase enters the flue gas desulfurization system, and the R3NHCl organic phase enters the back-extraction centrifuge for regeneration. A sodium hydroxide solution is introduced into the back-extraction centrifuge to regenerate the extractant, producing a regenerated extractant and a sodium chloride solution, which are then recycled. Sodium chloride solution is introduced into the sodium bed softening unit to regenerate it. The regenerated liquid from the sodium bed softening unit enters the regenerated liquid softening device. The softening process produces an aqueous sodium chloride solution and a solid precipitate. The aqueous sodium chloride solution enters the sodium chloride dosing device for recycling, and the solid precipitate enters the sludge treatment system.

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