System for preparing sodium carbonate and by-products by using sodium sulfate high-salinity wastewater

Abstract

The utility model discloses a system for preparing sodium carbonate and by-products by using sodium sulfate high-salinity wastewater. The system comprises a high-salinity wastewater concentration device, a reactor, a calcining furnace, a first evaporation concentration device, a cold separation crystallizer and a second evaporation concentration device. According to the device, sodium carbonate, sodium sulfate and ammonium sulfate products with high added values are prepared by adopting a double decomposition method and a circulating evaporation-cooling method, so that the device is a green and pollution-free technical method for harmless treatment and resource utilization of waste water, zero emission and circular economy are really realized, and no waste water is generated in the whole process. The mother liquor is recycled to extract sodium sulfate and ammonium sulfate, so that waste caused by low yield due to the fact that part of sodium bicarbonate is dissolved in the solution is avoided. Sodium bicarbonate, sodium sulfate and ammonium sulfate recovered by the device are high in purity, wherein the purity of sodium bicarbonate is gt; the ammonium sulfate contains nitrogen gt; the purity of sodium sulfate is gt; therefore, remarkable social benefits and economic benefits are obtained.

Description

Technical Field

[0001] The utility model relates to the technical field of water treatment, in particular to a system for preparing sodium carbonate and by-products by utilizing sodium sulfate high-salt wastewater. Background Art

[0002] Industrial wastewater often contains high concentrations of salt, particularly sodium sulfate wastewater. Discharge of this wastewater without treatment can cause severe soil and water pollution, disrupting ecosystems and making subsequent treatment and environmental remediation difficult.

[0003] Traditional treatment methods such as evaporative crystallization, resin adsorption and membrane separation can process sodium sulfate wastewater to a certain extent, but these methods generally have defects such as high energy consumption, high equipment cost and low treatment efficiency, and may even cause secondary pollution. Although direct evaporative crystallization can obtain sodium sulfate solid, this method consumes a lot of energy and the product purity is not high. In view of the limited market capacity of domestic sodium sulfate solid, the economic and environmental benefits of direct evaporative crystallization are not significant. Therefore, the sodium sulfate in the wastewater is recovered and the product with high added value is prepared, which is a technical problem that needs to be solved urgently in this area. Utility Model Content

[0004] This utility model provides a system for producing sodium carbonate and its byproducts from sodium sulfate high-salt wastewater, solving the problem of recovering sodium sulfate from high-salt wastewater. The entire process produces no waste, no wastes, and no environmental benefits, resulting in significant economic and environmental benefits. The purpose of this utility model is achieved through the following technical solutions:

[0005] A system for preparing sodium carbonate and by-products from sodium sulfate high-salt wastewater, comprising:

[0006] High-salt wastewater concentration device, used to concentrate sodium sulfate high-salt wastewater;

[0007] A reactor connected to a high-salt wastewater concentration device; the reactor is used to react the concentrated high-salt wastewater with ammonium bicarbonate; the reactor is provided with a first solid-liquid separator, the first solid-liquid separator is used to perform solid-liquid separation on the reaction product of the high-salt wastewater and ammonium bicarbonate to obtain mother liquor I and solid I;

[0008] a calciner connected to the reactor and used to calcine the solid I to obtain sodium carbonate;

[0009] a first evaporation and concentration device, the first evaporation and concentration device being connected to the liquid outlet of the first solid-liquid separator; the first evaporation and concentration device being used to evaporate and concentrate the mother liquor I; the first evaporation and concentration device being provided with a second solid-liquid separator, the second solid-liquid separator being used to perform solid-liquid separation on the evaporated and concentrated mother liquor I to obtain mother liquor II and solid II;

[0010] a cold crystallizer connected to the liquid outlet of the second solid-liquid separator; the cold crystallizer is used to cool the mother liquor II after solid-liquid separation; the cold crystallizer is provided with a third solid-liquid separator, the third solid-liquid separator is used to perform solid-liquid separation on the cooled mother liquor II to obtain mother liquor III and solid III; the solid outlet of the third solid-liquid separator is connected to the first evaporation and concentration device, so that the solid III is returned to the first evaporation and concentration device;

[0011] The second evaporation and concentration device is connected to the liquid outlet of the third solid-liquid separator and is used to evaporate and concentrate the mother liquor III; the second evaporation and concentration device is provided with a fourth solid-liquid separator, and the fourth solid-liquid separator is used to perform solid-liquid separation on the evaporated and concentrated mother liquor III to obtain mother liquor IV and solid IV; the liquid outlet of the fourth solid-liquid separator is connected to the cold precipitation crystallizer, so that the mother liquor IV is returned to the cold precipitation crystallizer.

[0012] Optionally, the first evaporation and concentration device is further connected to an acid adding device for adjusting the pH of the mother liquor I;

[0013] Preferably, the first evaporation and concentration device is provided with a gas exhaust pipeline, and the gas exhaust pipeline is connected to the reactor.

[0014] Optionally, the first evaporation and concentration device and the second evaporation and concentration device use normal pressure evaporators.

[0015] Optionally, the first evaporation concentration device, the cold precipitation crystallizer, and the second evaporation concentration device are all provided with a stirrer.

[0016] Optionally, the cold crystallizer adopts a cooling kettle.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The utility model recycles high-salt industrial wastewater as a resource and uses it as a raw material for preparing sodium carbonate. The mother liquor after producing sodium carbonate is used to extract sodium sulfate and ammonium sulfate. The condensed water generated by evaporation can also be used as product washing water. This is a green and pollution-free technical method for harmless treatment and resource utilization of wastewater, which truly realizes "zero emission" and circular economy, and no wastewater is generated in the entire process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 This is a device diagram of the utility model. DETAILED DESCRIPTION

[0021] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered a limitation of the present invention, but rather a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only used to describe specific embodiments and are not intended to limit the present invention.

[0022] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0023] Example 1

[0024] This embodiment proposes a system for preparing sodium carbonate and by-products using sodium sulfate high-salt wastewater. Figure 1 As shown, including:

[0025] High-salt wastewater concentration device, used to concentrate high-salt wastewater;

[0026] The reactor is a double decomposition reactor for reacting the concentrated high-salt wastewater with ammonium bicarbonate; the reactor is provided with a first solid-liquid separator, and the first solid-liquid separator is used to perform solid-liquid separation on the high-salt wastewater after the reaction to obtain mother liquor I and sodium bicarbonate solid (solid I);

[0027] Calcination furnace, used for calcining sodium bicarbonate solid to prepare sodium carbonate;

[0028] The first evaporation and concentration device is configured to evaporate and concentrate mother liquor I. The first evaporation and concentration device is equipped with a second solid-liquid separator for performing solid-liquid separation on the evaporated and concentrated mother liquor I to produce mother liquor II and sodium sulfate solid (solid II). In addition to a large amount of ammonium sulfate, the mother liquor I also contains small amounts of residual sodium sulfate, sodium bicarbonate, and ammonium bicarbonate. The first evaporation and concentration device is also connected to an acid addition device for adjusting the pH of mother liquor I to a range of 4 to 5. The first evaporation and concentration device is also connected to a gas exhaust line connected to a reactor for recovering and reusing carbon dioxide and ammonia generated during pH adjustment and heating and evaporation.

[0029] A cold crystallizer is used to cool the mother liquor II after solid-liquid separation; the cold crystallizer is provided with a third solid-liquid separator, and the third solid-liquid separator is used to perform solid-liquid separation on the cooled mother liquor II to obtain mother liquor III and double salt crystals (solid III);

[0030] The second evaporation and concentration device is used to evaporate and concentrate the mother liquor III; the second evaporation and concentration device is provided with a fourth solid-liquid separator, and the fourth solid-liquid separator is used to perform solid-liquid separation on the evaporated and concentrated mother liquor III to obtain mother liquor IV and ammonium sulfate (solid IV); the mother liquor IV is returned to the cold precipitation crystallizer for cooling and crystallization.

[0031] The first evaporation and concentration device and the second evaporation and concentration device adopt normal pressure evaporators; the cold precipitation crystallizer adopts a cooling kettle.

[0032] The reactor is a double decomposition reactor and is provided with a gas inlet pipeline, through which carbon dioxide and ammonia generated in subsequent processes can be introduced into the reactor.

[0033] The first evaporation and concentration device and the second evaporation and concentration device adopt normal pressure evaporators.

[0034] The first evaporation and concentration device is provided with a first agitator, the cold precipitation crystallizer is provided with a second agitator, and the second evaporation and concentration device is provided with a third agitator.

[0035] The working process of the above system includes the following steps:

[0036] Step 1) Pre-treated coking sodium sulfate high-salt wastewater from the factory is concentrated by evaporation at 90°C in a high-salt wastewater concentrator by approximately 7 times under reduced pressure to obtain a concentrated solution nearly saturated with sodium sulfate, with a sodium sulfate content of 27%. Ammonium bicarbonate is added to the concentrated solution in a reactor in two batches at a sodium sulfate to ammonium bicarbonate molar ratio of 0.9:1 to carry out a double decomposition reaction at 32°C for 2 hours to precipitate sodium bicarbonate solid. The wet material is filtered through a first solid-liquid separator to obtain wet sodium bicarbonate and mother liquor I. The wet sodium bicarbonate is washed with water and dried to obtain sodium bicarbonate. The sodium bicarbonate product is calcined in a calciner at 220°C for 2 hours to obtain a sodium carbonate product.

[0037] Step 2) In the first evaporation and concentration device, sulfuric acid is added to the mother liquor I to adjust the pH to 4.5 to remove the remaining bicarbonate in the mother liquor I. At this time, the mother liquor I contains 17.22% sodium sulfate and 10.77% ammonium sulfate.

[0038] Step 3) The mother liquor I is evaporated and concentrated in a first evaporation and concentration device at a temperature of 75° C. to reduce its weight by 58% and precipitate solid sodium sulfate. The mother liquor is then filtered while hot in a second solid-liquid separator to obtain mother liquor II and solid sodium sulfate;

[0039] Step 4) cooling the mother liquor II to 18° C. in a cold crystallizer and stirring at 240 rpm for 20 min to precipitate double salt crystals, filtering in a third solid-liquid separator to separate the solid and liquid to obtain double salt and mother liquor III, wherein the mass of the precipitated double salt is 18% of the mass of the mother liquor II;

[0040] Step 5) The mother liquor III is heated to 55° C. again in a second evaporation and concentration device for evaporation and concentration, with a weight loss of 28% to precipitate solid ammonium sulfate, and the mother liquor IV and solid ammonium sulfate are obtained by filtration in a fourth solid-liquid separator while still hot;

[0041] Step 6) Mother liquor IV is mixed with mother liquor II, and steps 4) and 5) are repeated to cyclically extract sodium sulfate and ammonium sulfate.

[0042] In the reaction of this embodiment, the yield of the sodium bicarbonate product obtained by the reaction was about 60%, the purity of the sodium bicarbonate product was 94%, the purity of the sodium carbonate product after calcination was 91%, the recovery rate of the byproduct sodium sulfate was 74%, the purity was 94%, the recovery rate of ammonium sulfate was 22%, and the nitrogen content was 19.6%.

[0043] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A system for preparing sodium carbonate and by-products using sodium sulfate high-salt wastewater, characterized in that: include: High-salt wastewater concentration device, used to concentrate sodium sulfate high-salt wastewater; A reactor connected to a high-salt wastewater concentration device; The reactor is used to react the concentrated high-salt wastewater with ammonium bicarbonate; the reactor is provided with a first solid-liquid separator, and the first solid-liquid separator is used to perform solid-liquid separation on the reaction product of the high-salt wastewater and ammonium bicarbonate to obtain mother liquor I and solid I; a calciner connected to the reactor and used to calcine the solid I to obtain sodium carbonate; a first evaporation and concentration device, the first evaporation and concentration device being connected to the liquid outlet of the first solid-liquid separator; the first evaporation and concentration device being used to evaporate and concentrate the mother liquor I; the first evaporation and concentration device being provided with a second solid-liquid separator, the second solid-liquid separator being used to perform solid-liquid separation on the evaporated and concentrated mother liquor I to obtain mother liquor II and solid II; a cold crystallizer connected to the liquid outlet of the second solid-liquid separator; the cold crystallizer is used to cool the mother liquor II after solid-liquid separation; the cold crystallizer is provided with a third solid-liquid separator, the third solid-liquid separator is used to perform solid-liquid separation on the cooled mother liquor II to obtain mother liquor III and solid III; the solid outlet of the third solid-liquid separator is connected to the first evaporation and concentration device, so that the solid III is returned to the first evaporation and concentration device; The second evaporation and concentration device is connected to the liquid outlet of the third solid-liquid separator and is used to evaporate and concentrate the mother liquor III; the second evaporation and concentration device is provided with a fourth solid-liquid separator, and the fourth solid-liquid separator is used to perform solid-liquid separation on the evaporated and concentrated mother liquor III to obtain mother liquor IV and solid IV; the liquid outlet of the fourth solid-liquid separator is connected to the cold precipitation crystallizer, so that the mother liquor IV is returned to the cold precipitation crystallizer.

2. A system for preparing sodium carbonate and by-products using sodium sulfate high-salt wastewater according to claim 1, characterized in that: The first evaporation and concentration device is also connected to an acid adding device for adjusting the pH of the mother liquor I.

3. A system for preparing sodium carbonate and by-products using sodium sulfate high-salt wastewater according to claim 1, characterized in that: The first evaporation and concentration device is provided with a gas exhaust pipeline, and the gas exhaust pipeline is connected to the reactor.

4. A system for preparing sodium carbonate and by-products using sodium sulfate high-salt wastewater according to claim 1, characterized in that: The first evaporation and concentration device and the second evaporation and concentration device both adopt normal pressure evaporators.

5. The system for preparing sodium carbonate and by-products by utilizing sodium sulfate high-salt wastewater according to claim 1, characterized in that: The first evaporation and concentration device, the cold precipitation crystallizer and the second evaporation and concentration device are all provided with a stirrer.

6. The system for preparing sodium carbonate and by-products by utilizing sodium sulfate high-salt wastewater according to claim 1, characterized in that: The cold precipitation crystallizer adopts a cooling kettle.

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