Treatment system for potassium salt production discharged wastewater in chlor-alkali industry

Abstract

The utility model provides a system for treating wastewater discharged during potassium salt production in the chlor-alkali industry. According to the utility model, wastewater is separated into produced water containing sodium chloride and potassium chloride and concentrated water containing sodium sulfate by the nanofiltration assembly in advance, so that the content of sodium chloride in the wastewater is reduced, the wastewater can be changed into the produced water for producing sodium chloride, and then the produced water is evaporated and crystallized by the sodium chloride evaporation and crystallization assembly to obtain a byproduct sodium chloride; meanwhile, in order to improve the purity of the byproduct sodium chloride, mother liquor is discharged when the byproduct sodium chloride is prepared, and at the moment, the potassium chloride freezing assembly cools the mother liquor and extracts the byproduct potassium chloride, so that the potassium chloride in the wastewater is indirectly recycled, and therefore, the potassium chloride in the wastewater is recycled. The resource waste is effectively reduced; the utility model belongs to the technical field of wastewater treatment systems.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of wastewater treatment system especially relates to a kind of potassium salt effluent wastewater treatment system of chlor-alkali industry production. BACKGROUND

[0002] ‌Chlor-alkali industry‌ refers to the preparation of sodium hydroxide, chlorine and hydrogen by electrolysis of saturated sodium chloride solution, and a series of chemical products are produced based on these raw materials, while chlor-alkali industry is one of the most basic chemical industries, and its products are widely used in light industry, textile industry, metallurgical industry and petrochemical industry.

[0003] In the production of sodium chloride product process, in order to maintain purity, part of mother liquor needs to be discharged, which contains sodium chloride, sodium sulfate, potassium chloride and other three kinds of salt, if the discharged mother liquor is directly discharged, the drainage will cause serious pollution to the surrounding water resources due to excessive chlorine ions and high salt content, at the same time, it contains sodium chloride, sodium sulfate, potassium chloride and other inorganic salts, causing waste of resources. INVENTION CONTENTS

[0004] The utility model aims at providing a kind of potassium salt effluent wastewater treatment system of chlor-alkali industry production to solve the technical problem described in the background.

[0005] The said potassium salt effluent wastewater treatment system of chlor-alkali industry production includes nanofiltration component, the nanofiltration component is used to separate wastewater into water containing sodium chloride and potassium chloride and concentrated water containing sodium sulfate, the nanofiltration component is connected with water storage by pipeline, the water storage is connected with sodium chloride evaporation crystallization component by pipeline, the water storage is used to store the water sent by the nanofiltration component and send the water to the sodium chloride evaporation crystallization component, the sodium chloride evaporation crystallization component is connected with potassium chloride freezing component by pipeline, the sodium chloride evaporation crystallization component is used to evaporate the water to get byproduct sodium chloride and send the discharged mother liquor to the potassium chloride freezing component, the potassium chloride freezing component is used to cool the mother liquor to get and return the mother liquor to the water storage.

[0006] According to the technical solution, the utility model realizes the following beneficial effects:

[0007] 1, nanofiltration component is separated into water containing sodium chloride and potassium chloride and concentrated water containing sodium sulfate in advance, so as to reduce the sodium chloride content of wastewater, so that the wastewater can become water that can be used for the production of sodium chloride, then, sodium chloride evaporation crystallization component is evaporated to get byproduct sodium chloride, so as to realize the recovery of sodium chloride in wastewater and reduce the waste of resources;

[0008] 2. In order to improve the purity of by-product sodium chloride, when the by-product sodium chloride is produced, the mother liquor is discharged, at this time, the potassium chloride freezing assembly cools and extracts the by-product potassium chloride from the mother liquor, thereby indirectly recovering potassium chloride in the wastewater, so as to further reduce the waste of resources;

[0009] 3. Since the potassium chloride freezing assembly can return the mother liquor after extracting potassium chloride to the water production reservoir as secondary water production, so as to further extract potassium chloride and sodium chloride from the secondary water production, thereby further purifying potassium chloride and sodium chloride until the content of potassium chloride and sodium chloride in all water production (mother liquor) is reduced, so that the water production (mother liquor) can be used for factory recycling, irrigation, etc. or reduce the pollution to the surrounding water resources when discharged.

[0010] In order to further optimize the above technical solutions, one or more of the following embodiments can be combined without conflict.

[0011] In some embodiments, the nanofiltration assembly is simultaneously connected with a sodium sulfate evaporation crystallization assembly, the sodium sulfate evaporation crystallization assembly and the water production reservoir are respectively and independently connected with the nanofiltration assembly, and the sodium sulfate evaporation crystallization assembly is used for evaporating and crystallizing the concentrated water supplied by the nanofiltration assembly and obtaining by-product sodium sulfate;

[0012] Since the nanofiltration assembly previously separates the wastewater into water production containing sodium chloride and potassium chloride and concentrated water containing sodium sulfate, that is, the concentrated water does not contain sodium chloride and potassium chloride, only sodium sulfate remains, at this time, the sodium sulfate evaporation crystallization assembly evaporates and crystallizes the concentrated water and obtains by-product sodium sulfate, thereby recovering sodium sulfate in the wastewater, and at the same time, the sodium sulfate in the wastewater (concentrated water) can be reduced, so that the wastewater (concentrated water) can be used for factory recycling, irrigation, etc. or reduce the pollution to the surrounding water resources when discharged.

[0013] In some embodiments, the sodium sulfate evaporation crystallization assembly is connected with a sodium sulfate centrifuge, and the sodium sulfate centrifuge is used for processing the by-product sodium sulfate;

[0014] According to the technical solution, the sodium sulfate centrifuge can efficiently and stably separate sodium sulfate from the concentrated water.

[0015] In some embodiments, the sodium sulfate evaporation crystallization assembly is provided with a condensate recycling supply pipe for connecting with the workshop pipeline;

[0016] According to the technical solution, the condensate of the water produced when the sodium sulfate evaporation crystallization assembly crystallizes sodium sulfate can be supplied to the factory for recycling, irrigation, etc. through the recycling supply pipe, thereby realizing the reasonable use of water resources.

[0017] In some embodiments, the potassium chloride freezing assembly is connected with a potassium chloride centrifuge, the potassium chloride centrifuge is provided with a backflow pipeline connected with the product water reservoir, and the potassium chloride centrifuge is used to separate the mother liquor from the by-product potassium chloride crystals and backflow the mother liquor to the product water reservoir.

[0018] According to the technical scheme, the potassium chloride centrifuge can stably and efficiently separate the potassium chloride from the mother liquor before the mother liquor is backflowed to the product water reservoir, so as to further reduce the potassium chloride content in the mother liquor.

[0019] In some embodiments, the sodium chloride evaporation crystallization assembly is connected with a sodium chloride centrifuge, and the sodium chloride centrifuge is used to separate the product water from the by-product sodium chloride.

[0020] According to the technical scheme, the sodium chloride centrifuge can stably and efficiently separate the sodium chloride in the product water.

[0021] In some embodiments, the nanofiltration assembly is provided with a nanofiltration membrane group used to separate sulfate radicals.

[0022] According to the technical scheme, the nanofiltration assembly can separate the sulfate radicals in the wastewater, and since monovalent ions have high selective permeability, the sulfate ions are intercepted, at this time, the charge balance in the product water can be maintained, so that more chloride ions permeate the membrane into the product water end, and therefore, the chloride ion concentration in the product water is higher than that in the raw water. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the specific embodiments in the present application, the following will briefly describe the drawings and labels used in the description of the specific embodiments.

[0024] Figure 1 is a structural layout diagram of the present application.

[0025] Reference signs:

[0026] 1, nanofiltration assembly; 12, nanofiltration membrane group; 2, product water reservoir; 3, sodium chloride evaporation crystallization assembly; 31, sodium chloride centrifuge; 4, potassium chloride freezing assembly; 41, potassium chloride centrifuge; 5, sodium sulfate evaporation crystallization assembly; 51, sodium sulfate centrifuge. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the following will be illustrated with reference to the drawings.

[0028] As Figure 1 shown, the present specific embodiment provides a potassium salt discharge wastewater treatment system in chlor-alkali industry, which comprises a nanofiltration assembly 1.

[0029] The wastewater containing three kinds of salt solution enters the nanofiltration assembly 1, which is used for separating the wastewater into water containing sodium chloride and potassium chloride and concentrated water containing sodium sulfate, wherein the water mainly contains sodium chloride and potassium chloride, and the concentrated water mainly contains sodium sulfate <0.05%, and the nanofiltration assembly 1 is provided with a nanofiltration membrane group 12 for separating sulfate. The nanofiltration assembly 1 is connected with a water storage tank 2 and a sodium sulfate evaporation crystallization assembly 5 in a pipeline, and the sodium sulfate evaporation crystallization assembly 5 and the water storage tank 2 are respectively and independently connected with the nanofiltration assembly 1.

[0030] The water storage tank 2 is connected with a sodium chloride evaporation crystallization assembly 3 in a pipeline, and the water storage tank 2 is used for storing the water from the nanofiltration assembly 1 and conveying the water to the sodium chloride evaporation crystallization assembly 3. The sodium chloride evaporation crystallization assembly 3 is connected with a sodium chloride centrifuge 31 and a potassium chloride freezing assembly 4 in a pipeline. The potassium chloride freezing assembly 4 is connected with a potassium chloride centrifuge 41 in a pipeline, and the potassium chloride centrifuge 41 is provided with a backflow pipeline connected with the water storage tank 2 in a pipeline.

[0031] When the nanofiltration water enters the sodium chloride evaporation crystallization assembly 3, evaporation crystallization is first carried out by using an evaporation system and is conveyed to the sodium chloride centrifuge 31 to obtain a by-product sodium chloride and is conveyed to; in order to ensure the purity of sodium chloride, at this time, part of the mother liquor needs to be discharged, and at this time, the control points are the mutual solubility of sodium chloride and potassium chloride (100℃, sodium chloride 16%, potassium chloride 21.7%), and the potassium chloride content in the discharged mother liquor solution is controlled to be <21.7%, so as to ensure the purity of sodium chloride. Subsequently, the mother liquor is conveyed to the potassium chloride freezing assembly 4, the potassium chloride freezing assembly 4 cools the mother liquor to 20℃, a large amount of potassium chloride is precipitated, the control point is the mutual solubility (20℃, sodium chloride 20.7%, potassium chloride 10.4%), and the potassium chloride centrifuge 41 is used to obtain the potassium chloride by-product, and at the same time, the potassium chloride centrifuge 41 returns the mother liquor after separating the potassium chloride by-product to the water storage tank 2 to recover sodium chloride.

[0032] The sodium sulfate evaporation crystallization assembly 5 is connected with a sodium sulfate centrifuge 51 in a pipeline, and the sodium sulfate evaporation crystallization assembly 5 can be selectively provided with a condensed water recycling supply pipe connected with a workshop pipeline. The sodium sulfate evaporation crystallization assembly 5 crystallizes sodium sulfate by using a sodium sulfate evaporation crystallization technology and using the sodium sulfate centrifuge 51 when the nanofiltration concentrated water is used, so as to obtain a by-product sodium sulfate; and the condensed water during this period can be recycled by the workshop or the body system.

Claims

1. A chlor-alkali industry potassium salt effluent wastewater treatment system, characterized by: The nanofiltration assembly is connected with a sodium sulfate evaporation crystallization assembly, the sodium sulfate evaporation crystallization assembly and the product water storage tank are respectively and independently connected with the nanofiltration assembly, and the sodium sulfate evaporation crystallization assembly is used for evaporating and crystallizing the product water supplied by the nanofiltration assembly and obtaining by-product sodium sulfate.

2. A system for treating effluent water produced in chlor-alkali industry, according to claim 1, characterized in that: The sodium sulfate evaporation crystallization assembly is connected with a sodium sulfate centrifuge, and the sodium sulfate centrifuge is used for processing the by-product sodium sulfate.

3. A system for treating effluent water produced in chlor-alkali industry as claimed in claim 2, wherein: The sodium sulfate evaporation crystallization assembly is provided with a condensed water recycling supply pipe for being connected with a workshop pipeline.

4. A system for treating effluent water produced in chlor-alkali industry as claimed in claim 2, wherein: The potassium chloride freezing assembly is connected with a potassium chloride centrifuge, the potassium chloride centrifuge is provided with a reflux pipeline connected with the product water storage tank, and the potassium chloride centrifuge is used for separating the by-product potassium chloride crystals from the mother liquor and refluxing the mother liquor to the product water storage tank.

5. A system for treating effluent water produced in chlor-alkali industry as claimed in claim 1, wherein: The sodium chloride evaporation crystallization assembly is connected with a sodium chloride centrifuge, and the sodium chloride centrifuge is used for separating the by-product sodium chloride from the product water.

6. A system for treating effluent water produced in chlor-alkali industry as claimed in claim 1, wherein: The nanofiltration assembly is provided with a nanofiltration membrane group for separating sulfate.

7. A system for treating effluent water produced in the chlor-alkali industry, according to claim 1, characterized in that: ​

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