A device and method for capturing carbon dioxide in industrial waste gas and producing caustic soda

Abstract

The application relates to a device and a method for capturing carbon dioxide in industrial waste gas and producing alkali, and belongs to the technical field of industrial waste gas treatment. The method for capturing carbon dioxide in industrial waste gas and producing alkali comprises the following steps: treating the industrial waste gas, capturing carbon dioxide CO2 and ammonia NH3 in the industrial waste gas; introducing the carbon dioxide CO2 and the ammonia NH3 in the industrial waste gas into a carbonization cleaning tower to generate ammonium carbonate (NH4)2CO3; in a reaction tower, ammonium carbonate (NH4)2CO3 and sodium chloride NaCl solution are reacted to generate sodium bicarbonate NaHCO3 and ammonium chloride NH4Cl, and the sodium bicarbonate NaHCO3 and the ammonium chloride NH4Cl are separated; the separated sodium bicarbonate NaHCO3 is steam calcined to generate Na2CO3 products, and the ammonium chloride NH4Cl is cooled and crystallized to generate NH4Cl products. The application can not only realize effective recovery and cyclic utilization of carbon dioxide, but also generate valuable chemical products through multiple reactions and resource conversion, thereby achieving a good balance between environmental protection and economic benefits.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of industrial waste gas treatment, and particularly relates to a device for capturing carbon dioxide in industrial waste gas and producing caustic soda and a method thereof. BACKGROUND

[0002] Capturing carbon dioxide from industrial waste gas is of great significance, not only can it effectively reduce the total amount of greenhouse gas emissions into the atmosphere, but also can achieve effective recycling of resources, which is highly consistent with the advanced concept of sustainable development.

[0003] The caustic soda industry has always played a vital role in the chemical industry. The traditional caustic soda production process has always been strongly dependent on high-purity carbon dioxide gas sources. However, industrial waste gas contains a considerable amount of carbon dioxide resources, which undoubtedly creates an excellent opportunity for carbon dioxide capture and caustic soda production. With the increasingly stringent environmental standards and the deep-rooted concept of resource recycling in society, the research and breakthrough of carbon dioxide capture and caustic soda production technology from industrial waste gas is of great significance in promoting the green transformation of the chemical industry and actively responding to the crisis caused by climate change. SUMMARY

[0004] The present application provides a device for capturing carbon dioxide in industrial waste gas and producing caustic soda and a method thereof, which aims to partially or completely solve the technical problem of how to capture carbon dioxide in industrial waste gas and produce caustic soda in the prior art. The technical solution of the present application is as follows:

[0005] In a first aspect, a device for capturing carbon dioxide in industrial waste gas and producing caustic soda includes: a capture unit that processes industrial waste gas to capture carbon dioxide CO2 and ammonia NH3 in the industrial waste gas; a first reaction unit that introduces carbon dioxide CO2 and ammonia NH3 in the industrial waste gas into a carbonation washing tower to react and generate ammonium carbonate (NH4)2CO3; a second reaction unit that reacts ammonium carbonate (NH4)2CO3 with sodium chloride NaCl solution to generate sodium bicarbonate NaHCO3 and ammonium chloride NH4Cl, and separates sodium bicarbonate NaHCO3 and ammonium chloride NH4Cl; a third reaction unit one that steam calcines the separated sodium bicarbonate NaHCO3 to generate Na2CO3 product; and a third reaction unit two that cools and crystallizes the separated ammonium chloride NH4Cl to generate NH4Cl product.

[0006] Optionally, the device for capturing carbon dioxide in industrial waste gas and producing caustic soda further includes a dissolution unit and a third reaction unit three, the dissolution unit dissolves the Na2CO3 product to form a Na2CO3 solution, and the third reaction unit three reacts the Na2CO3 solution with urea CO(NH2)2 to generate NaOCN product.

[0007] Optionally, the industrial waste gas carbon dioxide capture and alkali production device further comprises: a carbon dioxide capture and delivery unit and an ammonia gas capture and delivery unit, the carbon dioxide capture and delivery unit captures sodium bicarbonate NaHCO3 for steam calcination to generate carbon dioxide, and the carbon dioxide is delivered into the first reaction unit; the ammonia gas capture and delivery unit captures ammonia gas generated by the decomposition of the NH4Cl product, and the ammonia gas is delivered into the first reaction unit.

[0008] Optionally, the industrial waste gas carbon dioxide capture and alkali production device further comprises: a carbon dioxide and ammonia gas capture and delivery unit, which captures carbon dioxide and ammonia gas generated by the reaction of Na2CO3 solution and urea CO(NH2)2, and delivers the carbon dioxide and ammonia gas into the first reaction unit.

[0009] In a second aspect, a method for capturing carbon dioxide from industrial waste gas and producing alkali, comprising the following steps:

[0010] Step S100: treating the industrial waste gas to capture carbon dioxide CO2 and ammonia gas NH3 in the industrial waste gas;

[0011] Step S200: passing the carbon dioxide CO2 and ammonia gas NH3 in the industrial waste gas into a carbonation washing tower to generate ammonium carbonate (NH4)2CO3;

[0012] Step S300: reacting the ammonium carbonate (NH4)2CO3 and sodium chloride NaCl solution in a reaction tower to generate sodium bicarbonate NaHCO3 and ammonium chloride NH4Cl, and separating the sodium bicarbonate NaHCO3 and ammonium chloride NH4Cl;

[0013] Step S400: steam calcining the separated sodium bicarbonate NaHCO3 to generate Na2CO3 product, and cooling and crystallizing the ammonium chloride NH4Cl to generate NH4Cl product.

[0014] Optionally, in step S400, during the steam calcination of NaHCO3, flue gas is released after condensation and washing to release carbon dioxide CO2, which is delivered into the carbonation washing tower.

[0015] Optionally, step S400 comprises:

[0016] Step S401: cooling the ammonium chloride solution: when the ammonium chloride solution reaches a saturated state, gradually cool the solution by controlling the temperature, as the temperature decreases, the solubility of ammonium chloride decreases, and the ammonium chloride in the solution will precipitate from the solution to form ammonium chloride solid crystals;

[0017] Step S402: drying treatment: the separated ammonium chloride crystals need to be dried to remove residual moisture, and through the method of recrystallization, the dissolved crystals are filtered to remove impurities, and then cooled and crystallized again to obtain ammonium chloride with higher purity;

[0018] Step S403: NH4Cl product: the dried pure ammonium chloride crystals form the NH4Cl product.

[0019] Optionally, the method for capturing carbon dioxide in industrial waste gas to produce alkali also includes step S500: decomposing ammonium chloride NH4Cl to produce ammonia NH3, which can enter the carbonization washing tower.

[0020] Optionally, the method for capturing carbon dioxide in industrial waste gas to produce alkali also includes step S600: sending Na2CO3 product into a solution alkali machine to form a Na2CO3 solution, and reacting the Na2CO3 solution with urea CO(NH2)2 to generate NaOCN product.

[0021] Optionally, in the reaction of the Na2CO3 solution and the urea CO(NH2)2 in step S600, the generated carbon dioxide CO2 and ammonia NH3 can be supplemented as carbon dioxide CO2 and ammonia NH3 in the industrial waste gas.

[0022] The beneficial effects obtained by the present application are as follows:

[0023] (1) In the present application, in step S400, the carbon dioxide CO2 generated by steam calcining NaHCO3 is captured and transported back to the carbonization washing tower to further supplement and recover the carbon dioxide CO2 in the industrial waste gas, in step S500, after the decomposition of ammonium chloride NH4Cl to generate ammonia, the ammonia NH3 is captured and sent back to the carbonization washing tower to further supplement and recover the ammonia NH3 in the industrial waste gas, in step S600, the generated sodium cyanate NaOCN and the generated carbon dioxide CO2 and ammonia NH3 can further supplement and recover the carbon dioxide CO2 and ammonia NH3 in the industrial waste gas, forming a carbon dioxide CO2 recycling closed loop, an ammonia NH3 recycling closed loop and a carbon dioxide CO2 and ammonia NH3 recycling closed loop, the capture and recovery of carbon dioxide CO2 not only reduces the emission of waste gas, reduces the influence of greenhouse gases, and reduces the pollution to the environment.

[0024] (2) In the present application, in step S200, carbon dioxide reacts with ammonia to form ammonium carbonate (NH4)2CO3, in step S300, ammonium carbonate (NH4)2CO3 reacts with sodium chloride NaCl to form sodium bicarbonate NaHCO3 and ammonium chloride NH4Cl, in step S400, NaHCO3 is reacted by steam calcination to form sodium carbonate Na2CO3 (soda ash), NH4Cl is obtained by cooling crystallization to obtain pure chloride, in step S600, Na2CO3 solution reacts with urea to form sodium cyanate NaOCN, carbon dioxide CO2 and ammonia NH3 in industrial waste gas are converted into valuable chemical products: sodium carbonate Na2CO3 product, ammonium chloride NH4Cl product, sodium cyanate NaOCN product, which are widely used in chemical fertilizer production, chemical synthesis, agriculture and other industrial fields, and can provide important raw materials for related industries and improve industrial efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1 It is a composition schematic diagram of the present application for an industrial waste gas carbon dioxide capture and alkali production device.

[0027] Figure 2 It is a flowchart schematic diagram of the present application for an industrial waste gas carbon dioxide capture and alkali production method.

[0028] Figure 3 It is a principle schematic diagram of the present application for an industrial waste gas carbon dioxide capture and alkali production method.

[0029] The drawings are used to provide further understanding of the present application, and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application, and do not constitute a limitation of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0031] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In order to make the purpose, technical scheme and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0032] In some embodiments, the first reaction unit comprises a carbonation washing tower, the carbonation washing tower is provided with a gas inlet for introducing carbon dioxide and ammonia in the industrial waste gas respectively; the carbonation washing tower is provided with a gas distributor to uniformly mix and fully contact the carbon dioxide and ammonia; the carbonation washing tower is also provided with a plurality of spraying devices to spray appropriate amount of water mist to make the carbon dioxide CO2 and ammonia NH3 react to generate ammonium carbonate (NH4)2CO3, and the reacted ammonium carbonate (NH4)2CO3 can be discharged from the bottom outlet of the carbonation washing tower. Figure 1 The industrial waste gas carbon dioxide capture and alkali production device comprises: a capture unit for treating the industrial waste gas to capture carbon dioxide CO2 and ammonia NH3 in the industrial waste gas; a first reaction unit for introducing the carbon dioxide CO2 and ammonia NH3 in the industrial waste gas into a carbonation washing tower to react to generate ammonium carbonate (NH4)2CO3; a second reaction unit for reacting the ammonium carbonate (NH4)2CO3 with a sodium chloride NaCl solution to generate sodium bicarbonate NaHCO3 and ammonium chloride NH4Cl, and separating the sodium bicarbonate NaHCO3 and ammonium chloride NH4Cl; a third reaction unit one for steam calcining the separated sodium bicarbonate NaHCO3 to generate Na2CO3 product; and a third reaction unit two for cooling and crystallizing the separated ammonium chloride NH4Cl to generate NH4Cl product.

[0033] In some embodiments, the first reaction unit comprises a carbonation washing tower, the carbonation washing tower is provided with a gas inlet for introducing carbon dioxide and ammonia in the industrial waste gas respectively; the carbonation washing tower is provided with a gas distributor to uniformly mix and fully contact the carbon dioxide and ammonia; the carbonation washing tower is also provided with a plurality of spraying devices to spray appropriate amount of water mist to make the carbon dioxide CO2 and ammonia NH3 react to generate ammonium carbonate (NH4)2CO3, and the reacted ammonium carbonate (NH4)2CO3 can be discharged from the bottom outlet of the carbonation washing tower.

[0034] In some embodiments, the second reaction unit comprises a reaction kettle, the reaction kettle is provided with an ammonium carbonate solution inlet and a sodium chloride solution inlet, and a pipeline is connected to an accurate metering device to ensure that the two are fed in proportion. The reaction kettle is provided with a powerful stirrer to mix the solutions quickly and fully. The reacted mixed solution flows into a settling tank, which can use a caustic washing machine to separate the sodium bicarbonate and ammonium chloride according to their solubility difference, the sodium bicarbonate is precipitated at the bottom of the tank, and the ammonium chloride solution is in the upper layer. The tank bottom is connected to a filter through a discharge port to filter out impurities to obtain relatively pure sodium bicarbonate. The upper layer of ammonium chloride solution enters the subsequent processing device through an overflow pipeline, and can be subjected to crystallization and other operations to obtain ammonium chloride crystals.

[0035] In some embodiments, the third reaction unit one 301 comprises a steam calcination furnace, which is internally provided with a material tray that is resistant to high temperature and uniformly distributed, for placing sodium bicarbonate material; the steam calcination furnace comprises a steam generating device, which controls the steam input amount and temperature, so that the steam can fully contact with the sodium bicarbonate to perform the calcination reaction; the steam calcination furnace is provided at the top with an exhaust port, which can discharge the furnace gas generated in the reaction, which contains carbon dioxide, water vapor and possibly some impurity gases; the steam calcination furnace is provided at the bottom with a discharge port, through which the calcined sodium carbonate product can be discharged and enter the subsequent cooling and packaging processes; the whole furnace body structure of the steam calcination furnace is well sealed, which ensures that the reaction environment is stable and safe.

[0036] In some embodiments, the third reaction unit two 402 comprises a cooling crystallizer, which comprises a tank body provided with a jacket, the jacket can be connected with a cooling medium such as cooling water to control the cooling temperature in the tank, and the tank body is provided with a stirring paddle to uniformly cool the ammonium chloride solution and prevent local supercooling; the tank body is provided at the top with a solution inlet connected with an ammonium chloride solution source, and is provided at the bottom with a discharge port for discharging the crystallized ammonium chloride product; the cooling crystallizer can further comprise a temperature sensor and a liquid level meter to monitor and control the crystallization process in real time, so as to ensure that the produced ammonium chloride product has high purity and uniform particle size.

[0037] Therefore, in the industrial waste gas carbon dioxide capture and alkali production device of the present application, through the integration of multiple reaction units, the capture unit can accurately process industrial waste gas, rapidly capture carbon dioxide CO2 and ammonia NH3 therein, and effectively remove harmful gases in the waste gas to reduce environmental pollution; the first reaction unit generates ammonium carbonate (NH4)2CO3 by reacting carbon dioxide and ammonia through the carbonation washing tower, providing high-purity raw materials for subsequent reactions; the second reaction unit generates sodium bicarbonate and ammonium chloride by reacting sodium chloride solution and ammonium carbonate, and effectively separates them through the caustic washing machine; the third reaction unit one converts sodium bicarbonate into sodium carbonate through steam calcination technology, and the third reaction unit two produces high-purity ammonium chloride through cooling crystallization technology, realizing the production of sodium carbonate Na2CO3 product and ammonium chloride NH4Cl product, which not only realizes the effective recovery and recycling of carbon dioxide, but also generates valuable chemical products through multiple reactions and resource conversion, achieving a good balance between environmental protection and economic benefits, and greatly adapting to the sustainable development needs of current industrial production.

[0038] Optionally, the industrial waste gas carbon dioxide capture and alkali production device further comprises a dissolving unit and a third reaction unit three, the dissolving unit dissolves the Na2CO3 product to form a Na2CO3 solution, and the third reaction unit three reacts the Na2CO3 solution with urea CO(NH2)2 to generate a NaOCN product.

[0039] In some embodiments, the dissolving unit includes a dissolving tank, a Na2CO3 product feeding port and a solvent water feeding port are arranged at the top of the dissolving tank, and flow control devices are arranged for the two feeding ports. A stirrer is arranged in the dissolving tank to promote dissolution. A discharge port is arranged at the bottom of the dissolving tank. Meanwhile, the third reaction unit 403 includes a reaction tank. A stirring device is arranged in the reaction tank to enable the sodium carbonate solution and urea to be fully mixed. A feeding port is arranged at the top of the reaction tank, and conveying pipelines for the sodium carbonate solution and urea are connected to the feeding port, respectively. Precise metering devices are arranged to control the feeding ratio. The tank body of the reaction tank can be wrapped with a heating jacket to adjust and maintain the required temperature for the reaction. A discharge port is arranged at the bottom of the reaction tank, and a filter is connected to the discharge port to separate the NaOCN product generated by the reaction from other impurities or substances that are not completely reacted. A pressure monitoring and safety valve is arranged to ensure that the reaction is safely and stably carried out.

[0040] In the present application, sodium cyanate NaOCN is generated by the reaction of urea and Na2CO3, which further improves the added value of the sodium carbonate product. Sodium cyanate can be used in various industries such as chemical fertilizers and plastics, which promotes the recycling of resources. While effectively capturing carbon dioxide and generating sodium carbonate and ammonium chloride, the dissolution and reaction process generates higher value products, achieving the goals of resource utilization and environmental protection in the waste gas treatment process, and further improving economic benefits and environmental protection effects.

[0041] Optionally, the industrial waste gas carbon dioxide capture and alkali production device further includes a carbon dioxide capture and conveying unit and an ammonia gas capture and conveying unit. The carbon dioxide capture and conveying unit captures sodium bicarbonate NaHCO3 after steam calcination to generate carbon dioxide, and conveys the carbon dioxide to the first reaction unit. The ammonia gas capture and conveying unit captures ammonia gas generated by the decomposition of the NH4Cl product, and conveys the ammonia gas to the first reaction unit.

[0042] In some embodiments, the ammonia gas capture and conveying unit includes a gas collecting hood, a condenser tube, a gas conveying pipe and a fan. The gas collecting hood collects ammonia gas generated by the decomposition of ammonium chloride. The condenser tube removes water vapor impurities in the ammonia gas. The gas conveying pipe connects the gas collecting hood and the first reaction unit. The fan provides power to promote the stable conveying of the ammonia gas along the pipeline to the first reaction unit, ensuring the recycling and reuse of the ammonia gas.

[0043] In the present application, the carbon dioxide capture and delivery unit can efficiently capture the carbon dioxide generated in the sodium bicarbonate NaHCO3 vapor calcination process and timely deliver it to the first reaction unit (carbonation washing tower) for secondary recycling. This not only reduces carbon dioxide emissions, but also improves the utilization rate and reaction efficiency of carbon dioxide in the ammonium carbonate (NH4)2CO reaction process in the first reaction unit, and improves the efficiency and quality of ammonium carbonate production. The ammonia capture and delivery unit can capture and deliver the ammonia released during the decomposition of NH4Cl product, and return it to the first reaction unit to ensure the utilization rate and reaction efficiency of ammonia in the ammonium carbonate (NH4)2CO reaction process in the first reaction unit, and improve the efficiency and quality of ammonium carbonate production. Therefore, through efficient recovery and recycling of carbon dioxide and ammonia, the production process of sodium carbonate and ammonium chloride is optimized, and the stability, economy and environmental friendliness of the production process are enhanced.

[0044] Optionally, the carbon dioxide capture and delivery unit in the industrial waste gas also includes a carbon dioxide and ammonia capture and delivery unit that captures the carbon dioxide and ammonia generated by the reaction of Na2CO3 solution and urea CO(NH2)2, and delivers the carbon dioxide and ammonia to the first reaction unit.

[0045] In some embodiments, the carbon dioxide and ammonia capture and delivery unit includes a gas collection hood, a gas pipeline, a compressor and a purification device. The gas collection hood is located above the third reaction unit three 403 to collect reaction completed carbon dioxide, ammonia and other gases. The gas pipeline is connected to the gas collection hood, the compressor is installed on the gas pipeline to provide gas delivery power, and the purification device is used to remove impurities and moisture in the gas to ensure gas purity. The purified carbon dioxide and ammonia are delivered to the carbonation washing tower of the first reaction unit through the pipeline.

[0046] In the present application, the carbon dioxide and ammonia capture and delivery unit can efficiently capture the carbon dioxide and ammonia generated in the reaction of Na2CO3 solution and urea, and timely deliver it to the first reaction unit, realizing double gas capture and delivery, avoiding waste of carbon dioxide and ammonia, and ensuring optimal ratio of carbon dioxide and ammonia in the ammonium carbonate (NH4)2CO reaction process in the first reaction unit, improving the efficiency and quality of ammonium carbonate production, and enhancing the environmental performance and sustainability of the carbon dioxide capture and delivery unit in the industrial waste gas.

[0047] In a second aspect, as shown in Figure 2 The method for capturing carbon dioxide in industrial waste gas and producing alkali includes:

[0048] Step S100: treating the industrial waste gas to capture carbon dioxide CO2 and ammonia NH3 in the industrial waste gas;

[0049] Specifically, step S100 includes: the industrial waste gas treatment process covers multiple treatment operations, at least including dust removal, filtration and separation of the industrial waste gas, etc. to obtain carbon dioxide CO2 and ammonia NH3 in the industrial waste gas. In this way, through the operations of dust removal, filtration and separation, impurity particles, harmful pollutants, etc. in the waste gas can be effectively removed, the waste gas is purified, the pollution emission to the environment is reduced, and the environmental quality requirements are met. When obtaining carbon dioxide and ammonia, a way for resource recycling is opened up, the resource utilization rate is improved, and the raw material cost of enterprises is reduced. Carbon dioxide and ammonia can be extracted, making the subsequent carbon dioxide capture more efficient, the alkali production raw materials more sufficient and the quality guaranteed, effectively promoting the smooth progress of the alkali production process, and improving the stability and economy of the entire production process.

[0050] Step S200: carbon dioxide CO2 and ammonia NH3 in the industrial waste gas are introduced into a carbonation washing tower to generate ammonium carbonate (NH4)2CO3;

[0051] Specifically, step S200 includes:

[0052] In the industrial waste gas treatment process, when the industrial waste gas rich in carbon dioxide CO2 and ammonia NH3 is introduced into the carbonation washing tower, the carbon dioxide CO2 and ammonia NH3 in the industrial waste gas meet the water H2O in the carbonation washing tower under the internal environmental conditions of the carbonation washing tower. Under the synergistic action of suitable temperature, pressure, and uniform mixing chemical conditions, chemical reaction occurs to generate ammonium carbonate (NH4)2CO3. The reaction process equation is:

[0053] 2NH3+ CO2+ H2O→ (NH4)2CO3.

[0054] Therefore, this chemical reaction has relatively mild reaction conditions and does not require extremely harsh equipment, reducing the difficulty and cost of industrial implementation. It can efficiently convert carbon dioxide and ammonia in the waste gas, realize preliminary integrated utilization of resources, reduce harmful gas emissions, and meet environmental protection concepts. At the same time, the carbon dioxide CO2 and ammonia NH3 originally existing in the industrial waste gas in gaseous form are converted into ammonium carbonate (NH4)2CO3, which is relatively stable and easy to handle and utilize subsequently. It is an important intermediate product for subsequent alkali production processes, provides a key link for the entire industrial waste gas treatment and resource recycling chain, and helps to improve the quality and yield of alkali production products.

[0055] Step S300: In the reaction tower, ammonium carbonate (NH4)2CO3 and sodium chloride NaCl solution react to generate sodium bicarbonate NaHCO3 and ammonium chloride NH4Cl, and sodium bicarbonate NaHCO3 and ammonium chloride NH4Cl are separated;

[0056] Specifically, step S300 includes:

[0057] In the reaction tower, ammonium carbonate (NH4)2CO3 and sodium chloride NaCl solution react to generate sodium bicarbonate NaHCO3 and ammonium chloride NH4Cl, and sodium bicarbonate NaHCO3 and ammonium chloride NH4Cl are separated;

[0058] (NH4)2CO 3+2 NaCl→2NaHCO3+2NH4Cl.

[0059] In some embodiments, sodium bicarbonate NaHCO3 and ammonium chloride NH4Cl are separated by a caustic washing machine, which generally refers to a device used for the treatment of alkali substances such as sodium bicarbonate, sodium hydroxide, etc. In production, this device is often used to remove by-products such as ammonium chloride from the solution to improve the purity of the main product. The caustic washing machine device can be a simple filtration device or a complex continuous flow system, depending on the properties of the mixture being treated and the separation requirements. Specifically, in the separation process of sodium bicarbonate (NaHCO3) and ammonium chloride (NH4Cl), the caustic washing machine utilizes the difference in solubility of different substances in solution by adjusting the temperature, pH value, etc. of the solution, through filtration, cleaning and washing steps, to ultimately separate sodium bicarbonate (NaHCO3) and ammonium chloride (NH4Cl), thereby obtaining pure products.

[0060] Thus, in the present application, firstly, the raw materials ammonium carbonate and sodium chloride used in the chemical reaction are relatively cheap and easy to obtain, and the reaction process can produce two products with wide application: sodium bicarbonate and ammonium chloride. Sodium bicarbonate can be widely used in cleaning agents, food leavening agents and pharmaceutical products, while ammonium chloride can be widely used in agricultural fertilizers, chemical reagents and metal surface treatment. Secondly, the reaction process is simple and the reaction conditions are mild. The reaction is carried out at room temperature, avoiding the energy consumption and equipment wear caused by high temperature operation. The reaction occurs in an aqueous solution, which has good reaction controllability and can optimize the yield of the product by adjusting the concentration of the reactants and the reaction time. In addition, the sodium bicarbonate generated in the reaction is usually precipitated in solid form, which is easy to separate and purify, so that the yield of sodium bicarbonate product is high. The generated ammonium chloride is dissolved in water and can be further extracted by evaporation and concentration, ensuring the quality of the product. In addition, the reaction has little effect on the environment and belongs to green chemistry. There is no harmful waste gas or pollutant generated in the reaction process, which has great application potential in industrial production, reduces the production cost and environmental pollution risk, and has outstanding performance in the comprehensive benefits of chemical production.

[0061] Step S400: Steam calcination of the separated sodium bicarbonate NaHCO3 to generate Na2CO3 product, and cooling crystallization of ammonium chloride NH4Cl to generate NH4Cl product.

[0062] Specifically, step S400 includes:

[0063] The reaction equation of sodium bicarbonate NaHCO3 in the solution after the reaction is:

[0064] 2NaHCO3→ Na2CO3+ CO2+ H2O.

[0065] Thus, firstly, the calcination or thermal decomposition reaction of sodium bicarbonate is usually carried out under high temperature conditions, and the temperature needs to reach between 300°C and 400°C to ensure the high efficiency of the reaction and the high purity of the product; after heating, sodium bicarbonate will decompose into sodium carbonate, carbon dioxide and water, that is, the calcination reaction can convert sodium bicarbonate into more stable and widely used sodium carbonate Na2CO3 (soda ash), which can be widely used in the technical fields of glass manufacturing, fertilizer production, detergents and chemical synthesis, etc. Thus, the calcination reaction of sodium bicarbonate NaHCO3 not only provides an effective way for the production of sodium carbonate, but also can help the recovery and utilization of carbon dioxide; in addition, by controlling the temperature of the ammonium chloride solution, ammonium chloride will be precipitated from the saturated solution to form crystals, and impurities can be effectively excluded, ensuring the high purity of the prepared ammonium chloride product, and ammonium chloride can be precipitated in solid form, which is convenient for subsequent separation, drying and packaging, thereby improving the production efficiency of ammonium chloride product, and without the need for complex equipment and high energy consumption, the operation is simple and the cost is low, and ammonium chloride can be widely used as a fertilizer or industrial raw material.

[0066] Optionally, in step S400, during the steam calcination process of NaHCO3, the furnace gas is released after condensation and washing to release carbon dioxide CO2, which is transported to the carbonation washing tower.

[0067] In some embodiments, firstly, in the aforementioned steam calcination furnace, sodium bicarbonate (NaHCO3) is decomposed into sodium carbonate (Na2CO3), carbon dioxide (CO2) and water (H2O) by heating, and the calcination process is usually carried out at high temperature (about 300°C to 400°C), and the furnace gas contains carbon dioxide, water vapor and possibly some impurity gases; then, the furnace gas first enters a cooling device (such as a cooling tower, a cooler, etc.), and during the cooling process, the gas temperature gradually decreases, and the water vapor condenses into liquid water; the cooled furnace gas enters a washing device, which is usually filled with a washing liquid (such as water or a weak acid solution), and the washing liquid can absorb the soluble substances, dust and impurities in the furnace gas when the furnace gas passes through the washing tower, ensuring the purity of the carbon dioxide; finally, after condensation and washing, the carbon dioxide in the furnace gas is separated from the mixed gas, and a relatively pure carbon dioxide gas stream is obtained, which can be further treated or compressed, stored or transported to the carbonation washing tower to participate in subsequent chemical reactions. Thus, the carbon dioxide is extracted from the furnace gas and recaptured, which helps to save resources and can reduce the emission of greenhouse gases, and the purity of the carbon dioxide after washing is relatively high, the recycling of carbon dioxide can promote the continuous progress of the reaction, and the carbon dioxide can be used as a raw material to participate in the synthesis of ammonium carbonate (NH4)2CO3, thereby improving the economic efficiency and production efficiency of the reaction.

[0068] Optionally, in step S400, the cooling and crystallization of ammonium chloride NH4Cl to obtain the NH4Cl product comprises the following steps.

[0069] Step S401: cooling the ammonium chloride solution: when the ammonium chloride solution reaches the saturated state, the solution is gradually cooled by controlling the temperature, and as the temperature decreases, the solubility of ammonium chloride decreases, and the ammonium chloride in the solution precipitates from the solution to form ammonium chloride solid crystals. The crystallization process is affected by temperature and solution concentration. The cooled ammonium chloride crystals usually deposit at the bottom of the solution and can be separated from the mother liquor by filtration, centrifugation, etc.

[0070] Step S402: drying treatment: if there are impurities in the crystallization process, the impurities can be removed by re-crystallization, filtration, and cooling and crystallization again. The separated ammonium chloride crystals need to be dried to remove residual moisture. Common drying methods include hot air drying, vacuum drying, etc. Higher purity ammonium chloride is obtained.

[0071] Step S403: NH4Cl product: the dried pure ammonium chloride crystals form the NH4Cl product. The NH4Cl product can be crushed and packaged as needed for further use as a fertilizer or chemical reagent.

[0072] In the present application, cooling and crystallization is a mature separation and purification method, which is simple to operate and has relatively low equipment investment. High-purity ammonium chloride products can be obtained by cooling and crystallization, which is suitable for the production of high-purity chemical reagents or fertilizers. The cooling and crystallization process is energy-saving and does not produce a large amount of waste gas or wastewater, which has important application value in industrial production.

[0073] Optionally, the method for capturing carbon dioxide in industrial waste gas to produce alkali further comprises step S500: decomposing ammonium chloride NH4Cl to produce ammonia gas NH3, which can enter the carbonization washing tower.

[0074] In some embodiments, ammonium chloride NH4Cl is decomposed at high temperature to generate ammonia gas NH3 and hydrogen chloride HCl, which is usually carried out at a temperature of about 350-450°C, and the reaction formula is:

[0075] NH4Cl→NH3+HCl.

[0076] In some embodiments, the generated ammonia gas NH3 and hydrogen chloride HCl usually coexist in the reaction furnace. In order to ensure the purity of ammonia gas, the hydrogen chloride HCl and other impurities can be removed by gas separation method. After cooling and purification, the ammonia gas NH3 enters the carbonization washing tower, where it reacts with water and carbon dioxide CO2 to form ammonium carbonate (NH4)2CO3.

[0077] In the present application, ammonia is generated by ammonium chloride decomposition, and the ammonia is introduced into the carbonization washing tower to supplement the content of ammonia, which not only helps to form ammonium carbonate (NH4)2CO3, but also can be recycled to improve production efficiency and reduce pollution.

[0078] Optionally, the method for producing alkali from carbon dioxide in industrial waste gas further comprises a step S600 of sending the Na2CO3 product into a caustic soda dissolving machine to form a Na2CO3 solution, and reacting the Na2CO3 solution with urea CO(NH2)2 to generate a NaOCN product.

[0079] In some embodiments, the sodium carbonate Na2CO3 product is sent into a caustic soda dissolving machine to form a Na2CO3 solution, and then the Na2CO3 solution is reacted with urea CO(NH2)2 to generate a NaOCN (sodium cyanate) product. Specifically, the caustic soda dissolving machine is a device for dissolving alkaline substances, usually using water or other solvents, and under certain temperature and pressure, the Na2CO3 product is completely dissolved in water or other solvents, and the sodium carbonate Na2CO3 product is finally converted into a Na2CO3 saturated solution or a Na2CO3 concentrated solution.

[0080] In some embodiments, the Na2CO3 solution is mixed with urea CO(NH2)2, which is usually carried out at moderate temperature, and the reaction can also be promoted under heating conditions, and the reaction generates sodium cyanate NaOCN and ammonia NH3, and the reaction equation is:

[0081] Na2CO3 + CO(NH2)2 → NaOCN + NH3 + CO2.

[0082] After the reaction is completed, sodium cyanate NaOCN can be separated by filtration, crystallization, drying, etc. to obtain pure NaOCN product, and the sodium cyanate NaOCN product can be widely used in the fields of chemical fertilizer, pesticide production, chemical synthesis, etc.

[0083] Optionally, in the reaction of the Na2CO3 solution and urea CO(NH2)2 in step S600, carbon dioxide CO2 and ammonia NH3 are generated, which can supplement the carbon dioxide CO2 and ammonia NH3 in the industrial waste gas.

[0084] In some embodiments, the carbon dioxide CO2 and ammonia NH3 generated by the reaction of the Na2CO3 solution and urea CO(NH2)2 not only can provide raw materials for chemical synthesis and fertilizer production, but also can effectively supplement and recover carbon dioxide in industrial waste gas, effectively reduce the emission of industrial waste gas, and reduce the impact of greenhouse gases,

[0085] Therefore, in the method for capturing carbon dioxide in industrial waste gas to produce alkali, the carbon dioxide CO2 generated by steam calcination of NaHCO3 is captured and sent back to the carbonation washing tower to further supplement and recover the carbon dioxide CO2 in the industrial waste gas in step S400, the ammonia NH3 generated after decomposition of ammonium chloride NH4Cl is captured and sent back to the carbonation washing tower to further supplement and recover the ammonia NH3 in the industrial waste gas in step S500, and the carbon dioxide CO2 and ammonia NH3 generated simultaneously when sodium cyanate NaOCN is generated can also further supplement and recover the carbon dioxide CO2 and ammonia NH3 in the industrial waste gas in step S600, forming a carbon dioxide CO2 recycling closed loop, an ammonia NH3 recycling closed loop, and a carbon dioxide CO2 and ammonia NH3 recycling closed loop, so that the capture and recovery of carbon dioxide CO2 not only reduces the emission of waste gas, reduces the impact of greenhouse gases, and reduces environmental pollution; in addition, in step S200, the carbon dioxide reacts with the ammonia to generate ammonium carbonate (NH4)2CO3, in step S300, the ammonium carbonate (NH4)2CO3 reacts with sodium chloride NaCl to generate sodium bicarbonate NaHCO3 and ammonium chloride NH4Cl, in step S400, NaHCO3 is reacted by steam calcination to generate sodium carbonate Na2CO3 (soda ash), NH4Cl is cooled and crystallized to obtain pure chloride, and in step S600, the Na2CO3 solution reacts with urea to generate sodium cyanate NaOCN, so that the carbon dioxide CO2 and ammonia NH3 in the industrial waste gas are converted into valuable chemical products: sodium carbonate Na2CO3 product, ammonium chloride NH4Cl product, and sodium cyanate NaOCN product, which are widely used in fertilizer production, chemical synthesis, agriculture, and other industrial fields, and can provide important raw materials for related industries and improve industrial efficiency.

[0086] Therefore, the method for capturing carbon dioxide in industrial waste gas to produce alkali can not only achieve effective recovery and recycling of carbon dioxide, but also generate valuable chemical products through multiple reactions and resource conversion, achieving a good balance between environmental protection and economic benefits, reducing waste gas emissions, improving resource utilization efficiency, reducing environmental pollution, and improving enterprise efficiency, and greatly meeting the sustainable development needs of current industrial production.

[0087] The application and its embodiments have been described above, which is not restrictive, and the embodiments shown in the drawings are only one of the embodiments of the application, and the actual structure is not limited thereto. In general, if a person skilled in the art is inspired by it, without departing from the creative purpose of the application, without creative design, similar structure and embodiments of the technical solution can be designed, which should belong to the protection scope of the application.

Claims

1. A device for capturing carbon dioxide from industrial exhaust gas and producing caustic soda, comprising: a capturing unit for dust removal, purification and separation of industrial exhaust gas to capture carbon dioxide CO2 and ammonia NH3 therein; a first reaction unit, which is a carbonation washing tower, is provided with a gas distributor and a multi-layer spraying device, so that the CO2 and NH3 react to generate ammonium carbonate (NH4) 2CO3 in an aqueous phase; a second reaction unit is provided with an ammonium carbonate solution inlet and a sodium chloride solution inlet, for reacting (NH4) 2CO3 with NaCl to generate NaHCO3 and NH4Cl, and separating NaHCO3 and NH4Cl by means of a caustic soda washing machine according to solubility difference; a third reaction unit one, which is a steam calcination furnace, uses superheated steam to calcine the NaHCO3 to generate Na2CO3; a third reaction unit two, which is a cooling crystallization and drying system, is used for cooling crystallization and drying of NH4Cl solution to obtain NH4Cl product; a dissolving unit for dissolving Na2CO3 product to form Na2CO3 solution; a third reaction unit three, which is a reaction tank for reacting with urea CO(NH2)2, is used for reacting Na2CO3 solution with urea to generate NaOCN; characterized in that it further comprises three sets of closed-loop capture and conveying units in parallel communication with the first reaction unit: (i) a carbon dioxide capture and conveying unit for capturing CO2 after condensation and washing of the calcination furnace gas of the third reaction unit one and conveying it to the carbonation washing tower; (ii) an ammonia gas capture and conveying unit for purifying the ammonia-containing gas generated by the decomposition of NH4Cl to remove HCl and then conveying NH3 to the carbonation washing tower; (iii) a carbon dioxide / ammonia gas capture and conveying unit for collecting CO2 and NH3 generated in the reaction process of the third reaction unit three, and introducing them into the carbonation washing tower after compression and purification. 2.The device according to claim 1, wherein the second reaction unit comprises a stirred reaction kettle and a caustic soda washing machine in communication therewith, and the washing machine performs solid-liquid separation on the mixed solution obtained by reaction and reduces the NaCl content in NaHCO3 by washing. 3.The device according to claim 1, wherein the carbon dioxide capture and conveying unit comprises a cooler, a gas washing tower and a conveying pipeline, and the conveying pipeline is in communication with the gas inlet of the carbonation washing tower. 4.The device according to claim 1, wherein the ammonia gas capture and conveying unit comprises a gas collection hood, a condenser and a purification device, and the purification device is used to remove hydrogen chloride and then introduce NH3 into the gas inlet of the carbonation washing tower. 5.The device according to claim 1, wherein the carbon dioxide / ammonia gas capture and conveying unit comprises a gas collection hood, a compressor and a purification device, and the purified CO2 and NH3 are introduced into the gas inlet of the carbonation washing tower, respectively. 6.A method for capturing carbon dioxide from industrial exhaust gas and producing caustic soda, which is implemented by using the device according to claim 1, comprising: S100 treating industrial exhaust gas to capture CO2 and NH3 therein; S200 introducing the CO2 and NH3 into a carbonation washing tower to generate (NH4) 2CO3; S300 reacting (NH4)2CO3 with NaCl solution in a reaction tower to generate NaHCO3 and NH4Cl, and separating NaHCO3 and NH4Cl; S400 steam calcining NaHCO3 to obtain Na2CO3 product, and cooling and crystallizing NH4Cl solution and drying to obtain NH4Cl product; S500 decomposing NH4Cl and purifying to remove HCl, and then returning NH3 to the carbonation washing tower; S600 dissolving Na2CO3 product and reacting with urea CO(NH2)2 to generate NaOCN, and simultaneously capturing CO2 and NH3 released in the reaction and returning to the carbonation washing tower, to realize CO2 closed loop, NH3 closed loop and CO2 / NH3 closed loop.

7. The method according to claim 6, wherein the gas obtained by decomposing NH4Cl is purified to remove HCl before being returned.

8. The method of claim 6, wherein the S600 comprises: Na2CO3 product is sent into a solution alkali machine to form Na2CO3 solution; Na2CO3 solution is reacted with urea CO(NH2)2 in a reaction tank with stirring to generate NaOCN.

9. The method according to any one of claims 6-8, wherein CO2 and NH3 generated in the S600 process are collected by a gas collection hood and returned after being compressed and purified as raw gas of the carbonation washing tower.

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