Method for producing calcium hydroxide desulfurizer with high content and large specific surface area by micro-bead reaction

Abstract

The invention relates to a method for producing a calcium hydroxide desulfurizer with high content and large specific surface area by micro-bead reaction, and belongs to the technical field of calcium hydroxide desulfurizer production. The invention discloses a method for producing calcium hydroxide through reaction of micro liquid beads. According to the method, a sodium hydroxide solution with a certain concentration and a calcium chloride solution with a certain concentration are atomized in a spraying mode and react with each other, and then a nano calcium hydroxide product with high content and large specific surface area is stably prepared. Meanwhile, on the basis of the micro-bead reaction, a novel polyhydroxy small-molecule stabilizer (such as monosaccharides as glucose and disaccharides as cane sugar) is further added, and a hot water cleaning technology and a spray drying technology are combined, so that the content and the specific surface area of the product are further improved. By adopting the micro-liquid bead preparation technology, a calcium hydroxide product with the content of more than 90% and the specific surface area (BET method) of more than 35M < 2 > / g can be stably produced, and the requirements of efficient desulfurization and denitrification can be met.

Description

Technical Field

[0001] The invention relates to a method for producing a high-content and large-specific-surface-area calcium hydroxide desulfurizer by utilizing micro-liquid bead reaction, and belongs to the technical field of calcium hydroxide desulfurizer production. Background Art

[0002] Although clean energy has developed rapidly in recent years, traditional mineral energy such as coal and natural gas is still the mainstream energy and irreplaceable. After burning, mineral energy will release a large amount of carbon dioxide, sulfur oxides (sulfur dioxide, sulfur trioxide, etc.) and a large amount of nitrogen oxides (nitrogen monoxide, nitrogen dioxide, nitrogen trioxide, etc.), and carbon dioxide, sulfur oxides and nitrogen oxides are significant greenhouse gases. More seriously, sulfur oxides and nitrogen oxides react with moisture in the air to convert into corresponding acids, such as sulfuric acid, sulfurous acid, nitrous acid and nitric acid, thereby causing acid pollution of the atmosphere, water bodies and soil. At present, primary energy industry units (such as thermal power plants) have attached importance to post-combustion desulfurization and denitrification treatment. Other energy application industries (such as heating plants, ceramic production enterprises, glass manufacturing enterprises, etc.) and waste incineration enterprises also have the same technical requirements. In terms of desulfurization, calcium carbonate desulfurization was used in the early stage, and its advantages were low price and large output. However, the disadvantages of calcium carbonate desulfurizer are also very obvious, with high desulfurization temperature, complicated operation and low desulfurization efficiency. Later, it was gradually replaced by calcium hydroxide desulfurizer.

[0003] The content and specific surface area of ​​calcium hydroxide are two key technical indicators of calcium hydroxide desulfurizer. Among them, the content of calcium hydroxide determines the theoretical desulfurization capacity of calcium hydroxide desulfurizer. The higher the content of calcium hydroxide, the greater the theoretical desulfurization capacity. The specific surface area of ​​calcium hydroxide determines the desulfurization speed, desulfurization efficiency and operability of calcium hydroxide desulfurizer. The larger the specific surface area of ​​calcium hydroxide desulfurizer, the larger the contact area between unit weight of calcium hydroxide desulfurizer and combustion tail gas, the faster the desulfurization speed, and the higher the desulfurization efficiency of unit weight of desulfurizer. The larger the specific surface area of ​​calcium hydroxide desulfurizer, the easier it is to disperse in water, the better the stability of the aqueous dispersion, the easier it is to desulfurize by spraying, and the easier it is to desulfurize by spraying, which is convenient for desulfurization operation. Therefore, the preparation of calcium hydroxide desulfurizer with high content and large specific surface area is the key to promoting the desulfurization of calcium hydroxide desulfurizer.

[0004] Calcium hydroxide can be prepared by quicklime digestion, calcium hydride hydrolysis, and double decomposition reaction of calcium salts (calcium chloride, calcium nitrate, etc.) with sodium hydroxide. Among them, the reaction of calcium oxide (quicklime) and a certain amount of water is one of the main methods for preparing calcium hydroxide (digestion method). Since the water solubility of the raw material calcium oxide and the product calcium hydroxide is relatively low, the raw material and product of the calcium oxide digestion method will be divided into two parts. The specific surface area of ​​the sedimentation part in water is very small and cannot be used as a desulfurizer. Only the water-soluble part can produce a calcium hydroxide product with a large specific surface area. The water solubility of calcium hydroxide is related to temperature. The low temperature makes calcium hydroxide more soluble, but even when the solubility is maximum at low temperatures, calcium hydroxide products cannot be obtained in batches. Studies have shown that the specific surface area of ​​calcium hydroxide products prepared by the new digestion technology has increased significantly [Xiong Shuang, Yan Jinsheng, Zhou Zhou, et al. (2023) Effect of quicklime digestion reaction conditions on the characteristics of calcium hydroxide. Inorg. Chem. Ind. 2023, 55(12), 50-58.; Shin HG, Kim H., Kim YN, et al, (2009) Preparation and characterization of high surface area calcium hydroxide sorbent for SO 2 removal Curr.Appl.Phys.9,3Supplement,S276-S279.】, but its surface area and output are still difficult to meet the needs of large-scale use.

[0005] Calcium hydride hydrolysis method can prepare nano calcium hydroxide products with special structures to meet the special needs of special fields [Liu TL, Zhu YR, Zhang XZ, et al. (2010) synthesis and characterization of calcium hydroxide nanoparticles by hydrogen plasma-metal reaction method. Mater. Lett. 64 (23), 2575-2577.], but this method needs to use and produce flammable and explosive hydrogen during the reaction process, and the raw material metal calcium or calcium hydride is hygroscopic, flammable and explosive, which is not conducive to storage. Therefore, the safety of production and storage, as well as the problem of high production cost determine that this method can only meet the needs of a small amount of calcium hydroxide application, and is not suitable for industrial production.

[0006] In order to obtain a sufficient amount of calcium hydroxide products with a large specific surface area, the method of reacting calcium chloride or calcium nitrate with sodium hydroxide is currently generally used for preparation. However, since calcium chloride (or calcium nitrate) reacts with sodium hydroxide very quickly, the calcium hydroxide generated first can further react with calcium chloride, resulting in the close accumulation of calcium hydroxide, and causing the particles to gradually grow and the specific surface area to decrease. Moreover, the byproduct of the reaction, sodium chloride, will cause the product content to decrease. If it cannot be effectively removed, the product will not reach the required content. Each calcium hydroxide molecule can bind up to 12 water molecules. The number of bound water molecules is affected by temperature. The higher the temperature, the lower the bound water content. In addition, both the raw material sodium hydroxide and the product calcium hydroxide are easy to absorb carbon dioxide dissolved in the air and water, and finally converted into calcium carbonate, which will lead to a decrease in product content. The bound water content and the generation of calcium carbonate are the key controlling factors for whether the calcium hydroxide desulfurizer can meet the standards. Therefore, the development of calcium hydroxide desulfurizers needs to focus on improving the content and specific surface area of ​​the product.

[0007] In the classic chemical reaction of direct reaction of calcium chloride or calcium nitrate with sodium hydroxide, whether the calcium chloride or calcium nitrate solution is dripped into the sodium hydroxide solution, or the sodium hydroxide solution is dripped into the calcium chloride or calcium nitrate solution, or the sodium hydroxide solution and the calcium chloride or calcium nitrate solution are directly mixed and reacted, it is difficult to obtain a calcium hydroxide product with a large specific surface area, and therefore it cannot be used to prepare a high-efficiency calcium hydroxide desulfurizer.

[0008] Studies have shown that the use of calcium chloride and sodium hydroxide reaction systems with alcohols (ethanol, propanol, isopropanol, diethylene glycol, etc.) as stabilizers to prepare calcium hydroxide can increase the specific surface area of ​​the product to a certain extent. Calcium is a highly oxygen-affinity element. When a certain amount of alcohol solvent is added as a stabilizer to the solution for preparing calcium hydroxide, the surface of the obtained calcium hydroxide particles is adsorbed by alcohol hydroxyl groups. The hydrophobic groups formed on the surface of the particles can prevent the continuous growth of the particles, thereby obtaining relatively small particles and increasing the specific surface area of ​​the product [Li Huizhi, Li Hong, Xiong Yinghui (2008). Study of modified calcium hydroxide for enhancing SO 2removalduring sorbent injection in pulverized coal boilers.Fuel 76(3),257-265.;ShinH.G.,Kim H.,Kim Y.N.,et al.(2009)Preparation and characterization of highsurface area calcium hydroxide sorbent for SO 2removal Curr.Appl.Phys.9(3Supplement),S276-S279.】. The advantage of this method is that the particle size of the product can be controlled by the amount of alcohol solvent added. However, in order to obtain a calcium hydroxide desulfurizer with a large specific surface area, a large amount of organic solvent is required. If the solvent cannot be recovered, the cost will be very high, and a large amount of volatile organic compounds (VOC) will be released to the environment, so the safety of use is not guaranteed. If the solvent is recovered, it is necessary to increase the cleaning and recovery process, which will also increase the cost. Moreover, in the process of recovering the solvent stabilizer, the product particles will also increase, resulting in a significant decrease in the specific surface area. Therefore, there are certain difficulties in mass production of high-quality calcium hydroxide desulfurizer using this process, and the cost is difficult to control. Polyethylene glycol is the most widely used stabilizer for the preparation of calcium hydroxide desulfurizer. When used in small amounts, it can have a similar effect to isopropanol [Hasanova I., Hasanova U., Gasimov E., et al. (2021) PEG-assisted controlledprecipitation of calcium hydroxide and calcium carbonate nanostructure forcement reinforcement Mater.Chem.&Physics,2021,271,Doi:10.1016 / j.matchemphys.2021.124865.; Chen Jianhua, Chen Wenhua, Zhao Junfeng (2010). Effects of adding PEG on the structure and performance of calcium-based flue gas desulfurizer. Coal Conversion, 33(2), 85-87,91.; Hou Ruiqin, Du Yucheng, Liu Zheng, et al. (2010) Preparation, characterization and NO capture performance of nano calcium hydroxide particles. 33(5): 5-7,12.; Wang Ziming, Peng Wen'an, Sun Qing, et al. (2018) Improvement of the preparation method of nano calcium hydroxide and a preliminary study on its biosafety as a root canal treatment paste. Oral Medicine Research, 34(4): 428-43.]. However, whether using small molecule alcohol stabilizers such as ethanol and isopropanol, or macromolecular stabilizers such as polyethylene glycol, the increase in the specific surface area of ​​calcium hydroxide products is limited, generally not more than 16M 2 / g

Yao Yong, Li Shizhu, Zheng Dongchen, et al. (2023). Preparation, evaluation and application research of new low-carbon emission desulfurization agent nano calcium hydroxide. Inorganic Salt Chemical Industry, 55(4), 38-44.

[0009] Further research found that the calcium chloride and sodium hydroxide reaction system with oligoethylenediamine as stabilizer can produce calcium hydroxide products with a large specific surface area. The researchers believe that oligoamines can form complexes with calcium, thus effectively preventing the growth of calcium hydroxide particles. The specific surface area of ​​the prepared calcium hydroxide desulfurizer can be as high as 28M 2 / g, and the reported desulfurization efficiency is over 98% (Yao Yong, Li Shizhu, Zheng Dongchen et al. (2023), Preparation, Evaluation and Application Research of New Low-carbon Emission Desulfurizer Nano Calcium Hydroxide. Inorganic Salt Chemical Industry, 55(4), 38-44.). However, this product does not use high content of calcium hydroxide to achieve high desulfurization efficiency, but uses calcium hydroxide combined with oligomeric organic amines to achieve efficient desulfurization, and its safety is questionable. If the operating temperature is too high, the oligomeric amines will be oxidized to generate nitrogen oxides, increasing the difficulty of denitrification. If the operating temperature is not high, the oligomeric amines will react with nitrogen oxides to generate highly carcinogenic nitrosamine compounds, which are difficult to handle later.

[0010] Other studies have found that using natural polymer materials (such as gelatin, cactus juice, etc.) and modified polymer materials (such as sodium carboxymethyl cellulose, etc.) as stabilizers for double decomposition reactions can produce calcium hydroxide products with large specific surface areas. For example, calcium nitrate and sodium hydroxide can react to form nano calcium hydroxide with large specific surface areas when sodium carboxymethyl cellulose is used as a stabilizer. However, since sodium carboxymethyl cellulose reacts with calcium hydroxide to form calcium carboxymethyl cellulose, it is difficult to remove it after the reaction, which in turn affects the purity of the product [Zhang HY, Liu RQ, Ning TY et al. (2018). Higher CO 2 absorption using a new class of calcium hydroxide(Ca(OH) 2)nanoparticles.16,1095-1100.]. At the same time, gelatin [Darroudi M., Bagherpour M., Hosseinie HA, et al (2016). Biopolymer-assisted green synthesis and characterization of calciumhydroxide nanoparticles. Ceram Int, 42:3816–3819. https: / / doi.org / 10.1016 / j.ceramint.2015.11.045.] or cactus juice [Rodriguez-Navarro C., Ruiz-Agudo E., Burgos-Cara A., et al (2017). Crystallization and colloidal stabilization of Ca(OH) 2 The presence of Nopal juice (Opuntia ficus indica): implications in architectural heritage conservation. Langmuir 33: 10936–10950. https: / / doi.org / 10.1021 / acs.langmuir.7b02423.] and other natural polymer compounds also have a good stabilizing effect on calcium hydroxide products and are conducive to the formation of calcium hydroxide products with a large specific surface area. However, the source of this type of polymer is obviously not as good as carboxymethyl cellulose, and its wide use is limited.

[0011] In addition, adding a stabilizer during the double decomposition reaction of calcium salt and sodium hydroxide can significantly improve the quality of calcium hydroxide desulfurizer. However, in order to ensure the product content, the stabilizer and the by-products of the reaction must be removed after the reaction is completed. The washing process of the product will cause the physical and chemical properties of the product (such as particle size, specific surface area, etc.) to change. After washing, the use of different drying and powdering technologies will also lead to significant differences in the physical and chemical properties of the product [Xu Jing, Qian Qingrong, Chen Qinghua, etc. (2008). Research on anti-agglomeration drying of nano calcium hydroxide. New Chemical Materials, 10: 93-96.; Choi MK, Cho JS, Jo SMetal. (2007). Effect of Several Factors on the Synthesis of Calcium HydroxidePrepared by Spray Drying Method Using Limestone. Mat. Sci. Forum Vols. 544-545.]. It usually increases the particle size and reduces the specific surface area, which is not conducive to the production of high-performance calcium hydroxide products.

[0012] In summary, the existing methods for preparing calcium hydroxide desulfurizers all have different problems, which leads to certain difficulties in large-scale production of calcium hydroxide desulfurizers with high content and large specific surface area. Therefore, it is necessary to develop new methods to prepare calcium hydroxide desulfurizers with high content and large specific surface area. Summary of the invention

[0013] In order to overcome the shortcomings of the above-mentioned prior art, the present invention proposes a new technology for producing a calcium hydroxide desulfurizer with high content and large specific surface area by using a micro-liquid bead synthesis method. The technology can stably produce a calcium hydroxide desulfurizer with a content of more than 90% and a specific surface area (BET method) of more than 35M 2 / g of calcium hydroxide products can meet the needs of efficient desulfurization and denitrification.

[0014] In order to achieve the above object, the technical solution adopted by the present invention is:

[0015] The present invention provides a method for producing a high-content and large-specific-surface-area calcium hydroxide desulfurizer by using a micro-liquid bead reaction, the method comprising the following steps:

[0016] S1, dissolving calcium chloride and a low-cost natural polyhydroxy stabilizer in a certain amount of water to prepare a calcium chloride-stabilizer aqueous solution;

[0017] S2, dissolving sodium hydroxide in a certain amount of water to obtain a sodium hydroxide aqueous solution;

[0018] S3, spraying the calcium hydroxide-stabilizer aqueous solution and the sodium hydroxide aqueous solution into the reaction container at a certain speed in a spraying manner to perform a micro-bead reaction;

[0019] S4. Filter the aqueous dispersion of the product after the reaction is completed, and wash it with hot water for no less than 3 times to remove the possible unreacted raw materials and the by-products of the reaction, sodium chloride and stabilizer, so as to obtain a high-content calcium hydroxide-bound water product;

[0020] S5. After the cleaning is completed, the obtained calcium hydroxide product is dispersed again in a certain amount of water to obtain a calcium hydroxide aqueous dispersion, and then the calcium hydroxide aqueous dispersion is spray-dried according to the viscous liquid spray drying conditions to obtain a calcium hydroxide desulfurizer product with a high content and a large specific surface area that can meet the requirements of efficient desulfurization.

[0021] The present invention provides a new technology for synthesizing a high-content and large-specific-surface-area calcium hydroxide desulfurizer by using micro-liquid beads. On this basis, a new type of polyhydroxy small molecule stabilizer is further added, and hot water cleaning technology and spray drying technology are combined, so that a high-content and large-specific-surface-area nano calcium hydroxide product can be stably prepared, and a high-content (content greater than 90%) and large-specific-surface-area (greater than 35M) nano calcium hydroxide product can be stably mass-produced. 2 / g) of calcium hydroxide desulfurizer products can meet the needs of energy production enterprises for effective desulfurization and environmental protection.

[0022] Preferably, the low-cost natural polyhydroxy stabilizer includes monosaccharides or disaccharides, wherein the monosaccharides include glucose, arabinose, fructose, xylose, xylitol and other monosaccharides, and the disaccharides include sucrose, lactose, maltose and other disaccharides. Monosaccharides (such as glucose) and disaccharides (such as sucrose) are efficient and inexpensive new stabilizers for preparing high-content and large specific surface area calcium hydroxide desulfurizers.

[0023] More preferably, the low-cost natural polyhydroxy stabilizer is sucrose, and the mass ratio of calcium chloride to sucrose is 111g:10g-15g.

[0024] More preferably, the low-cost natural polyhydroxy stabilizer is glucose, and the mass ratio of calcium chloride to glucose is 111g:10g-20g.

[0025] Preferably, the molar ratio of calcium chloride to sodium hydroxide is 1:2.12-2.75.

[0026] Preferably, in S1, the concentration of calcium chloride in the calcium chloride-stabilizer aqueous solution is 111-222 g g / 2000-4000 mL.

[0027] Preferably, in S2, the concentration of sodium hydroxide in the sodium hydroxide aqueous solution is 165-444 g / 4000-8000 mL.

[0028] Preferably, in S5, the spray parameters are: fan, 60-80; temperature setting, 200-220°C, pump speed, 7-15; needle passing, 8-12S.

[0029] Preferably, the solid-liquid ratio between the mass of the calcium hydroxide product in S5 and the volume of water is 1:15-25.

[0030] The invention also provides a high-content and large-specific-surface-area calcium hydroxide desulfurizing agent prepared by the method.

[0031] The research found that the micro-liquid bead method of the present invention can be used to produce calcium hydroxide desulfurizer with a stable content of more than 90% and a specific surface area (BET method) of more than 35M 2 / g of calcium hydroxide product can meet the needs of efficient desulfurization and denitrification.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention discloses a method for producing a calcium hydroxide desulfurizer by using a micro-liquid bead reaction. The method is to atomize a sodium hydroxide solution of a certain concentration and a calcium chloride solution of a certain concentration in a spraying manner and react with each other, thereby stably preparing a nano calcium hydroxide product with a high content and a large specific surface area. At the same time, on the basis of the micro-liquid bead reaction, a new type of polyhydroxy small molecule stabilizer (such as monosaccharides such as glucose, disaccharides such as sucrose) is further added, and combined with hot water cleaning technology and spray drying technology, the content and specific surface area of ​​the product are further improved. Among them, compared with traditional organic amine stabilizers, polyhydroxy stabilizers can more effectively prevent the process of calcium hydroxide dissolution and precipitation equilibrium, which is conducive to the preparation of calcium hydroxide products with a large specific surface area; hot water cleaning can efficiently remove reaction by-products and stabilizers, prevent excessive calcium carbonate from being generated, and can prevent the ripening and growth of calcium hydroxide particles; spray drying can effectively prevent the agglomeration growth of particles during the drying process, which is conducive to the preparation of powdered calcium hydroxide products with good dispersibility. Through the above-mentioned micro-liquid bead preparation technology of the present invention, a calcium hydroxide product with a content greater than 90% and a specific surface area (BET method) greater than 35M can be stably produced. 2 / g of calcium hydroxide products can better meet the needs of efficient desulfurization and denitrification. DETAILED DESCRIPTION

[0034] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] The reagents and instruments involved in the following examples are as follows:

[0036] (1) Reagents: Calcium chloride (cp, 25kg package) was produced by Erdos Group, sodium hydroxide (cp25kg package) was produced by Shandong Hehuang Haihua. Glucose and sucrose (AR) were produced by Shanghai Sinopharm Group. The experimental water was obtained from high-quality tap water (in line with the national first-level drinking water standard) of the R&D unit.

[0037] (2) Instruments: The double spray synthesis equipment is composed of two 30° nozzles and a 25kg plastic bucket with a lid, in which the double nozzles are arranged at 120° to the vertical plane. SPECTRO ARCTRO induced coupled plasma emission spectrometer (ICP, METEK material Analysis Division, USA) is used to determine the purity of the product. Micrometrics ASAP 2460 specific surface area analyzer (BET) (produced in California, USA) is used to test the specific surface area of ​​the product. JJ-1A 90W electric stirrer (produced by Jintan Xicheng Xinrui Instrument Factory) is used for conventional synthesis method research. 78-1 magnetic heating stirrer (Changzhou Yuexin Instrument Manufacturing Co., Ltd.) is used to ensure the stability of calcium hydroxide dispersion. YM-8600B spray dryer used for product drying is produced by Shanghai Yuming Instrument Co., Ltd. CNC ultrasonic cleaner (Dongguan Kangshijie) is used for ultrasonic dispersion of products. Circulating water vacuum pump (Gongyi Yuhua Instrument Co., Ltd.) and other equipment including sand core funnels (12cm, 18cm, 22cm,), 1000±0.01g electronic balance, large sheets of medium-speed filter paper, etc. are used for product cleaning.

[0038] In order to overcome the problem that the prior art cannot produce high-content, large-specific-surface-area calcium hydroxide desulfurizer on a large scale, the following embodiment develops a new technology for producing high-content, large-specific-surface-area calcium hydroxide desulfurizer.

[0039] In the process of preparing calcium hydroxide desulfurizer by solution method using sodium hydroxide and calcium chloride, if calcium hydroxide is prepared in a large volume solution, the first generated particles will gradually increase as the reaction proceeds, or the fine particles are easy to quickly agglomerate and reorganize, which will cause the product specific surface area to decrease. Therefore, how to react sodium hydroxide with calcium chloride of limited concentration in a limited volume is the key to preparing calcium hydroxide with fine particles and large specific surface area. To this end, the present invention proposes a strategy for preparing a high-content and large specific surface area calcium hydroxide desulfurizer using a double spray synthesis technology, which can enable the reaction of sodium hydroxide and calcium chloride to be completed in a very short time. Specifically, a certain concentration of sodium hydroxide solution and a certain concentration of calcium chloride solution are atomized in a spraying manner and react with each other. During the flight, the atomized sodium hydroxide solution micro-liquid beads and the calcium chloride solution micro-liquid beads merge with each other, and the sodium hydroxide and calcium chloride in the fused droplets react rapidly to generate calcium hydroxide particles, and produce sodium chloride byproducts. The calcium hydroxide particles produced will not continue to grow in the process of flight because there is no more reaction raw material to supplement, and the particles produced can be wrapped by the stabilizer and then gathered in the product collector and difficult to continue to grow, thereby ensuring that the preparation process can produce a calcium hydroxide product with a large specific surface area.

[0040] Further, on the basis of preparing calcium hydroxide desulfurizer by double spraying, low-cost polyhydroxy natural new stabilizers, such as glucose, sucrose, etc., are added to prevent the calcium hydroxide particles from increasing during the storage process before the product is collected and cleaned. Calcium hydroxide is soluble in water, but the solubility is not very large. Therefore, in a solution without adding a stabilizer, the smaller the particle size, the greater the surface energy, and the more soluble it is in water. When the concentration of calcium hydroxide soluble in water is greater than the solubility of calcium hydroxide, the excess part will precipitate on the surface of large particles with less solubility, resulting in particle enlargement and reduced specific surface area. Therefore, adding a stabilizer to the reaction solution can prevent the process of dissolution and precipitation equilibrium, which is conducive to the preparation of calcium hydroxide products with large specific surface area. At the same time, compared with the affinity for nitrogen elements in organic amines, calcium elements have a stronger affinity for oxygen elements in hydroxyl compounds, and the stability of calcium oxygen complexes is stronger than that of calcium nitrogen complexes, so polyhydroxy compounds are better stabilizers for calcium hydroxide. Moreover, this type of stabilizer is cheap, the raw materials are easy to obtain, and it is easy to remove without any subsequent pollution.

[0041] Further, on the basis of preparing calcium hydroxide desulfurizer by double spraying, byproduct sodium chloride and stabilizer are removed by hot water cleaning, which is more conducive to improving product purity and obtaining high-content calcium hydroxide desulfurizer. Unlike other chemical products, the solubility of calcium hydroxide in water decreases with increasing temperature, while the solubility of byproduct sodium chloride and stabilizer in water increases with increasing temperature of the aqueous solution. Therefore, hot water cleaning can quickly remove the byproducts and stabilizers of the reaction, reduce the loss of calcium hydroxide, and delay the dissolution and precipitation balance in the cleaning process, preventing the increase of particle size and causing a decrease in specific surface area. Moreover, the solubility of carbon dioxide in hot water is small, and cleaning with hot water can prevent the generation of calcium carbonate, which is conducive to improving product purity.

[0042] Furthermore, based on the preparation of calcium hydroxide desulfurizer by double spraying, the product is dried by spray drying technology. The specific surface area of ​​calcium hydroxide products is not only related to the synthesis method, storage and cleaning process, but also affected by the drying method. Spray drying technology can effectively ensure that after removing by-products and stabilizers, the particles of calcium hydroxide desulfurizer will not grow significantly during the drying process, and no agglomeration between particles will occur, thereby ensuring the acquisition of high-quality products with good dispersibility and large specific surface area.

[0043] Research has found that the present invention can stably produce high-content (content greater than 90%) and large specific surface area (greater than 35M) calcium hydroxide desulfurizers in batches by adding a low-cost polyhydroxy natural new stabilizer based on the preparation of calcium hydroxide desulfurizers by double spraying, and combining hot water cleaning and spray drying technology. 2 / g) of calcium hydroxide desulfurizer products can better meet the needs of energy production companies for effective desulfurization and environmental protection.

[0044] In order to further clearly present the process of the present invention developing a new technology for producing a high-content, large specific surface area calcium hydroxide desulfurizer, a detailed description is given below.

[0045] Example 1: Synthesis of traditional calcium hydroxide desulfurizer

[0046] (1) Method 1: Weigh 55.5g (0.5 mole) of calcium chloride in a 2000mL beaker, add 500mL of tap water, start an electric stirrer, and completely dissolve the calcium chloride. In addition, add 40g of sodium hydroxide (1 mole) in a 1000mL beaker, add 500mL of tap water, and stir to completely dissolve the sodium hydroxide. Then adjust the stirring speed of the electric stirrer to 500 rpm, transfer the sodium hydroxide solution into the calcium chloride solution at once, and the reaction proceeds rapidly to produce a white precipitate. After about 10 minutes, stop stirring, filter the product dispersion, and wash it with tap water several times. Transfer the filter cake of the obtained calcium hydroxide product to a beaker and bake it at 120°C for 24 hours to obtain a block solid (recorded as P1). This product is crushed with a steel mill and analyzed for specific surface area (BET method).

[0047] (2) Method 2: Weigh 55.5 g (0.5 mole) of calcium chloride in a 2000 mL beaker, add 500 mL of tap water, start an electric stirrer, and completely dissolve the calcium chloride. In addition, add 40 g of sodium hydroxide (1 mole) in a 1000 mL beaker, add 500 mL of tap water, and stir to completely dissolve the sodium hydroxide. Then adjust the stirring speed of the electric stirrer to 150 rpm, and drip the sodium hydroxide solution into the calcium chloride solution at a rate of about 40 mL per minute to react and produce a white precipitate. Stop stirring after the sodium hydroxide solution has dripped. Filter the product aqueous dispersion and wash it with tap water several times. Transfer the filter cake of the obtained calcium hydroxide product to a beaker and bake it at 120°C for 24 hours to obtain a block solid (recorded as P2). This product is crushed with a steel mill and analyzed for specific surface area.

[0048] (3) Method 3: Weigh 55.5 g (0.5 mole) of calcium chloride in a 2000 mL beaker, add 500 mL of tap water, start an electric stirrer, and dissolve the calcium chloride completely. In addition, add 40 g of sodium hydroxide (1 mole) in a 1000 mL beaker, add 500 mL of tap water, and stir to dissolve the sodium hydroxide completely. Then adjust the stirring speed of the electric stirrer to 150 rpm, and drip the sodium hydroxide solution into the calcium chloride solution at a rate of about 40 mL per minute to react and produce a white precipitate. Stop stirring after the sodium hydroxide solution has dripped. Filter the product aqueous dispersion and wash it with tap water several times. The obtained product filter cake is then ultrasonically dispersed in 200 mL of water and then spray dried. The spray conditions of the spray dryer are: fan, 70 (70% of the full working state); temperature setting, 190°C; pump speed, 10 (10 mL / min); needle pass, 10S. During the spray drying process, the product dispersion was always stirred by an electromagnetic stirrer to make the product dispersion uniform. After spray drying, a powder with good dispersibility (denoted as P3) was obtained, and the specific surface area of ​​the product was finally analyzed by BET.

[0049] Example 2: Spraying synthetic calcium hydroxide desulfurizer without stabilizer

[0050] (1) Method 1: Dissolve 222g of calcium chloride in 4000mL of water and store it in a calcium chloride solution storage tank; dissolve 165g of sodium hydroxide in 4000mL of water and store the sodium hydroxide solution in an alkali solution storage tank. Then spray the sodium hydroxide solution into the calcium chloride solution to react with it (single spray synthesis). The spray reaction is completed within 25min-30min to obtain a product aqueous dispersion. Filter the product, remove the reaction aqueous solution, and wash the filter cake with cold water. Then transfer the obtained filter cake into cold water, disperse it evenly, and dry it again using the above-mentioned spray drying conditions to obtain a calcium hydroxide product (denoted as P4). Finally, measure the specific surface area of ​​the product.

[0051] (2) Method 2: Dissolve 222g of calcium chloride in 4000mL of water and store it in a calcium chloride solution storage tank; dissolve 165g of sodium hydroxide in 4000mL of water and store it in a sodium hydroxide solution storage tank. Then, atomize the calcium chloride solution and the sodium hydroxide solution and spray them into the product collector at the same time (double spray synthesis). The spray reaction is completed within 25min-30min to obtain a product aqueous dispersion. Filter the product, remove the reaction aqueous solution, and wash the filter cake with cold water. Disperse the obtained filter cake into 2000mL of water, stir and mix with electromagnetic stirring, and then spray dry to obtain a calcium hydroxide product (denoted as P5). The parameters of the spray dryer are set as follows: fan, 70; temperature setting, 210℃, pump speed, 10; needle pass, 10S. Finally, the specific surface area of ​​the product is measured by a specific surface analyzer.

[0052] (3) Method 3: Dissolve 222g of calcium chloride in 4000mL of water and store it in a calcium chloride solution storage tank; dissolve 220g of sodium hydroxide in 4000mL of water and store it in a sodium hydroxide solution storage tank. Then, atomize the calcium chloride solution and the sodium hydroxide solution and spray them into the product collector at the same time. The spray reaction is completed within 25min-30min to obtain a product aqueous dispersion. Filter the product, remove the reaction aqueous solution, and wash the filter cake with cold water. Then disperse the obtained filter cake in 2000mL of water, stir and mix it by electromagnetic stirring, and then spray dry it to obtain a calcium hydroxide product (recorded as P6). The parameters of the spray dryer are set as follows: fan, 70; temperature setting, 210℃, pump speed, 10; needle pass, 10S. Finally, the specific surface area of ​​the product is measured by a specific surface analyzer.

[0053] Example 3: Adding stabilizer to spray synthesize calcium hydroxide desulfurizer

[0054] (1) Method 1: Dissolve 222g of calcium chloride and 20g of different types of stabilizers [oligoethylenediamine (final product is recorded as P7), sucrose (final product is recorded as P8), polyethylene glycol 400 (final product is recorded as P9), glucose (final product is recorded as P10)] in 4000mL of water and store them in a calcium chloride-stabilizer solution storage tank; dissolve 165g of sodium hydroxide in 4000mL of water and store them in a sodium hydroxide solution storage tank. Then, the calcium chloride-stabilizer solution and the sodium hydroxide solution are atomized and sprayed into the product collector at the same time. The spray reaction is completed within 25min-30min to obtain a product aqueous dispersion. Filter the product, remove the reaction aqueous solution, and wash the filter cake with cold water. Disperse the obtained filter cake in 2000mL of water, stir and mix with electromagnetic stirring, and then spray dry. The parameters of the spray dryer are set as follows: fan, 70; temperature setting, 210℃, pump speed, 10; needle pass, 10S. Finally, the specific surface areas of the four products were measured using a specific surface analyzer.

[0055] (2) Method 2: Dissolve 222g of calcium chloride and 20g (the final product is recorded as P11), 30g (the final product is recorded as P12), and 40g (the final product is recorded as P13) of sucrose in 4000mL of water and store them in a calcium chloride-sucrose solution storage tank; dissolve 220g of sodium hydroxide in 4000mL of water and store them in a sodium hydroxide solution storage tank. Then, the calcium chloride-sucrose solution and the sodium hydroxide solution are atomized and sprayed into the product collector at the same time. The spray reaction is completed within 25min-30min to obtain a product aqueous dispersion. Filter the product, remove the reaction aqueous solution, and wash the filter cake with cold water. Then disperse the obtained filter cake in 1000mL of water, stir it with electromagnetic stirring, and then spray dry it. The parameters of the spray dryer are set as follows: fan, 70; temperature setting, 210℃, pump speed, 10; needle passing, 10S. Finally, the specific surface area of ​​the three products is measured by a specific surface analyzer.

[0056] (3) Method 3: Dissolve 222g of calcium chloride and 20g (the final product is recorded as P14), 30g (the final product is recorded as p15), and 40g (the final product is recorded as P16) of glucose in 4000mL of water, and transfer the solution to the calcium chloride-glucose solution storage tank; dissolve 165g of sodium hydroxide in 4000mL of water, and transfer the solution to the sodium hydroxide solution storage tank. Then, the calcium chloride-glucose solution and the sodium hydroxide solution are atomized and sprayed into the product collector at the same time. The spray reaction is completed within 25min-30min to obtain the product water dispersion. Filter the product, remove the reaction aqueous solution, and wash the filter cake with tap water. Then disperse the obtained filter cake in 1000mL of water, stir it with electromagnetic stirring, and then spray dry it. The parameters of the spray dryer are set as follows: fan, 70; temperature setting, 210℃, pump speed, 10; needle passing, 10S. Finally, the specific surface area of ​​the three products is measured by a specific surface analyzer.

[0057] (4) Method 4: Dissolve 444g of calcium chloride and 60g of glucose in 8000mL of water, and transfer the solution to a calcium chloride-glucose storage tank. In addition, dissolve 444g of sodium hydroxide in 8000mL of water and transfer it to a sodium hydroxide solution storage tank. Then atomize them separately, react, filter and wash the product, and then transfer the product to 2000mL of water to make a product dispersion. After electromagnetic stirring and mixing, spray drying is performed to obtain a calcium hydroxide product (denoted as P17). The parameters of the spray dryer are set as follows: fan, 70; temperature setting, 21050 degrees to 70, pump speed, 10; needle passing, 10S. Finally, the specific surface area of ​​the product is measured using a specific surface analyzer.

[0058] (5) Method 5: Dissolve 444 g of calcium chloride and 60 g of glucose in 8000 mL of water, and transfer the solution to a calcium chloride-glucose storage tank. Dissolve 330 g of sodium hydroxide in 8000 mL of water, and transfer the solution to a sodium hydroxide solution storage tank. Then atomize and react with each other, filter and wash the product naturally, wash the product with tap water 4 times, and measure the solid content of the obtained product (recorded as P18). Then repeat the synthesis once according to the same method, wash the product with hot water (50-70°C) 4 times, and measure the solid content of the obtained product.

[0059] (6) Method 6: 444 g of calcium chloride and 60 g of glucose were dissolved in 8000 mL of water, and the solution was transferred to a calcium chloride-glucose storage tank. In addition, 330 g of sodium hydroxide was dissolved in 8000 mL of water and transferred to a sodium hydroxide solution storage tank. Then, they were atomized and reacted with each other, and the product was naturally filtered and washed. The product was washed with tap water for 4 times, and the obtained product was dispersed in 2000 mL of water. Finally, the purity and specific surface area of ​​the product (denoted as P20) were measured.

[0060] Experimental example: Comparative analysis of solid content and specific surface area of ​​calcium hydroxide desulfurizer produced by different methods

[0061] The specific surface area of ​​the product is the primary technical indicator that needs to be broken through in various calcium hydroxide preparation methods. There is no doubt that the method of adding samples in the preparation reaction has a significant impact on the specific surface area of ​​the product calcium hydroxide, whether a stabilizer is added or not. The BET specific surface area of ​​the dried and crushed calcium hydroxide (P1) is 4.78 M 2 / g. The BET specific surface area of ​​the dried and crushed calcium hydroxide (P2) was 3.87 M 2 / g. The BET specific surface area of ​​calcium hydroxide (P3) prepared by low-speed stirring drop reaction and spray drying is 8.20M 2 / g. Obviously, the specific surface area of ​​calcium hydroxide products obtained by these commonly used preparation methods is not large, and it is difficult to meet the requirements of the target product. Among them, the specific surface area of ​​P3 is more than twice that of P2, indicating that the spray drying method is easier to obtain calcium hydroxide products with large specific surface area. Spraying sodium hydroxide solution into calcium chloride solution for reaction is essentially a traditional liquid addition reaction method. The BET specific surface area of ​​the obtained product (P4) is 7.53M 2 / g.

[0062] The product dispersion was prepared by the micro-bead method (double spray) and the product was dried by spray drying. When the molar ratio of calcium chloride to sodium hydroxide was about 1:2, the BET specific surface area of ​​the product calcium hydroxide (P5) was 12.13 M 2 When the mass ratio of calcium chloride to sodium hydroxide is about 1:1 (amount ratio 1:2.75), the BET specific surface area of ​​the product calcium hydroxide (P6) is 16.04 M 2 / g. The experimental results show that compared with the products prepared by the conventional preparation method (P1, P2, P3, and P4), the specific surface area of ​​the products prepared by the micro-liquid bead method is significantly increased, but it still does not meet the requirements of the specific surface area of ​​the target product. Comparing the specific surface areas of P6 and P5, it can be seen that when the raw material sodium hydroxide is excessive, a product with a larger specific surface area can be obtained.

[0063] Equal weights of different types of stabilizers were added to the calcium chloride solution. When the molar ratio of calcium chloride to sodium hydroxide was 1:2.12, calcium hydroxide was prepared by the microbead preparation method. The BET specific surface area of ​​the spray-dried product was measured and shown in Table 1.

[0064] As can be seen from Table 1, compared with polyethylene glycol and polyethylene diamine stabilizers, the new stabilizers glucose and sucrose of the same mass can obtain calcium hydroxide products with larger specific surface areas. This type of new stabilizer has better price advantages, will not cause new environmental safety issues, and is easy to remove from the reaction product, making it easy to prepare high-content calcium hydroxide products.

[0065] Table 1 Effect of adding different stabilizers on the BET specific surface area of ​​calcium hydroxide product

[0066]

[0067] The amount of stabilizer added has a significant effect on the specific surface area of ​​the calcium hydroxide product. Except for the amount of stabilizer, other preparation parameters are kept the same. When 20g of sucrose stabilizer is added, the specific surface area of ​​the calcium hydroxide product (P11) is measured to be 23.99M 2 / g, when 30 g of sucrose stabilizer was added, the specific surface area of ​​the calcium hydroxide product (P12) was measured to be 27.36 M 2 / g, and when 40 g of sucrose stabilizer was added, the specific surface area of ​​the calcium hydroxide product (P13) was measured to be 26.16 M 2 / The above results show that the more sucrose is added as a stabilizer, the better. This shows that in order to obtain an ideal calcium hydroxide product with a large specific surface area, the amount of stabilizer added needs to be optimized. In addition, using 20g of glucose as a stabilizer, the specific surface area of ​​the calcium hydroxide product (P14) was measured to be 27.90M 2 / g; 30g of glucose was used as a stabilizer, and the specific surface area of ​​the calcium hydroxide product (P15) was measured to be 36.45M 2 / g; 40g of glucose was used as a stabilizer, and the specific surface area of ​​the calcium hydroxide product (P16) was measured to be 46.79M 2 / g. The above results show that within the measurement range, the effect of increasing the amount of glucose stabilizer on the specific surface area of ​​the calcium hydroxide product does not reach a maximum value. This shows that the effect of glucose stabilizer on the specific surface area of ​​the calcium hydroxide product is better than that of sucrose stabilizer.

[0068] The amount of raw material sodium hydroxide also has a great influence on the specific surface area of ​​the product. When the mass ratio of calcium chloride and sodium hydroxide is increased from 444:350 (the molar ratio is about 1:2.12, P15) to 444:444 (the molar ratio is about 1:2.75, P17) under other conditions unchanged, the specific surface area of ​​the product increases from 36.45M 2 / g(P15) increased to 41.29M 2 / g (P17). The above results are consistent with the experimental results without adding stabilizer (P5 and P6). It shows that excessive use of sodium hydroxide can increase the specific surface area of ​​the product to a certain extent, but excessive use of alkali will lead to waste of raw materials, increase cost, and increase the post-processing steps.

[0069] The solid contents of the products washed with hot water (P19) and cold water (P18) were 198.3 g and 195.1 g respectively, and the difference in yield was not too large. However, hot water can effectively remove the carbon dioxide dissolved in the water and improve the purity of the product.

[0070] Calcium hydroxide was prepared by the microbead method using one of the combinations, and the specific surface area of ​​the product (P20) was measured to be 36.13 M 2 / g, the calcium content of the product measured by ICP method is 50.2%, which is equivalent to 92.8% calcium hydroxide content, which can meet the requirements of the set standards.

[0071] In summary, there are many factors that affect the specific surface area, purity and recovery rate of calcium hydroxide products. The micro-liquid bead method of the present invention can greatly increase the specific surface area of ​​the product, and can prepare calcium hydroxide products with different specific surface areas to meet different usage requirements. Among them, the specific surface area is greater than 35M 2 / g, products with a content greater than 90% can be used as high-quality calcium hydroxide desulfurizer.

[0072] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A method for producing a high-content and large-specific-surface-area calcium hydroxide desulfurizer using micro-liquid bead reaction, characterized in that: The following steps are involved: S1, dissolving calcium chloride and a low-cost natural polyhydroxy stabilizer in a certain amount of water to prepare a calcium chloride-stabilizer aqueous solution; S2, dissolving sodium hydroxide in a certain amount of water to obtain a sodium hydroxide aqueous solution; S3, spraying the calcium hydroxide-stabilizer aqueous solution and the sodium hydroxide aqueous solution into the reaction container at a certain speed in a spraying manner to perform a micro-bead reaction; S4. Filter the aqueous dispersion of the product after the reaction is completed, and wash it with hot water for no less than 3 times to remove the possible unreacted raw materials and the by-products of the reaction, sodium chloride and stabilizer, so as to obtain a high-content calcium hydroxide-bound water product; S5. After the cleaning is completed, the obtained calcium hydroxide product is dispersed again in a certain amount of water to obtain a calcium hydroxide aqueous dispersion, and then the calcium hydroxide aqueous dispersion is spray-dried according to the viscous liquid spray drying conditions to obtain a calcium hydroxide desulfurizer product with a high content and a large specific surface area that can meet the requirements of efficient desulfurization.

2. The method for producing a high-content and large-specific-surface-area calcium hydroxide desulfurizer using micro-liquid bead reaction according to claim 1, characterized in that: The low-cost natural polyhydroxy stabilizer includes monosaccharide or disaccharide, wherein the monosaccharide includes glucose, arabinose, fructose, xylose, and xylitol, and the disaccharide includes sucrose, lactose, and maltose.

3. A method for producing a high-content and large-specific-surface-area calcium hydroxide desulfurizer using micro-liquid bead reaction according to claim 2, characterized in that: The low-cost natural polyhydroxy stabilizer is sucrose, and the mass ratio of calcium chloride to sucrose is 111g:10g-15g.

4. The method for producing a high-content and large-specific-surface-area calcium hydroxide desulfurizer using micro-liquid bead reaction according to claim 2, characterized in that: The low-cost natural polyhydroxy stabilizer is glucose, and the mass ratio of calcium chloride to glucose is 111g:10g-20g.

5. The method for producing a high-content and large-specific-surface-area calcium hydroxide desulfurizer using micro-bead reaction according to claim 1, characterized in that: The molar ratio of the calcium chloride to the sodium hydroxide is 1:2.12-2.

75.

6. The method for producing a high-content and high-specific-surface-area calcium hydroxide desulfurizer using micro-bead reaction according to claim 1, characterized in that: In S1, the concentration of calcium chloride in the calcium chloride-stabilizer aqueous solution is 111-222 gg / 2000-4000 mL.

7. The method for producing a high-content and high-specific-surface-area calcium hydroxide desulfurizer using micro-bead reaction according to claim 1, characterized in that: In S2, the concentration of the sodium hydroxide in the sodium hydroxide aqueous solution is 165-444 g / 4000-8000 mL.

8. The method for producing a high-content and large-specific-surface-area calcium hydroxide desulfurizer using micro-bead reaction according to claim 1, characterized in that: In S5, the spray parameters are: fan, 60-80; temperature setting, 200-220℃, pump speed, 7-15; needle passing, 8-12S.

9. The method for producing a high-content and large-specific-surface-area calcium hydroxide desulfurizer using micro-liquid bead reaction according to claim 1, characterized in that: The solid-liquid ratio between the mass of the calcium hydroxide product and the volume of water in S5 is 1:15-25.

10. A high-content and large-specific-surface-area calcium hydroxide desulfurizing agent prepared by the method described in any one of claims 1 to 9.

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