A dry process for producing high specific surface area calcium hydroxide

Abstract

This invention discloses a dry-process production process for high specific surface area calcium hydroxide, belonging to the technical field of calcium hydroxide preparation. The dry-process production process for high specific surface area calcium hydroxide includes the following steps: preparing quicklime powder, preparing perlite composite material, preparing a mixture, digestion, drying, and grading to remove impurities. The preparation of the perlite composite material includes modification and compounding. The compounding method involves adding modified perlite, polycarboxylate superplasticizer, and stearic acid diethanolamide to water, controlling the temperature at 55-65℃, stirring for 15-25 minutes, then adding hydrochloric acid and trimethylolpropane, stirring for 8-12 minutes, filtering, washing, and drying to obtain the perlite composite material. The digestion includes primary digestion and secondary digestion. This invention improves the specific surface area, purity, and desulfurization efficiency of calcium hydroxide without introducing new impurities.

Description

Technical Field

[0001] This invention belongs to the field of calcium hydroxide preparation technology, specifically relating to a dry process for producing high specific surface area calcium hydroxide. Background Technology

[0002] Calcium hydroxide is a commonly used desulfurizing agent due to its superior desulfurization performance, wide temperature adaptability, and easy treatment of byproducts. As a desulfurizing agent, calcium hydroxide reacts with sulfur dioxide in flue gas to form calcium sulfite, which is then further oxidized to calcium sulfate by introducing air. In this process, the specific surface area, purity, porosity, and surface deposits of calcium hydroxide are important factors affecting the sulfur dioxide removal efficiency.

[0003] Industrially, calcium hydroxide is mostly prepared by directly hydrating quicklime. Quicklime is generally prepared by calcining and decomposing limestone, and its main component is calcium oxide, but it often contains various impurities such as quartz, iron oxide, aluminum, magnesium, potassium and their compounds.

[0004] The process of preparing calcium hydroxide from quicklime is divided into dry digestion and wet digestion. Dry digestion is the earliest powdering process in industrial application. It has a short digestion time, low water consumption, and high heat release, which can effectively solve the problems of high water consumption, high heat loss, high cost, and serious pollution in wet process. However, it is easy to have incomplete reaction, leaving some quicklime residue, and the resulting calcium hydroxide product has a small specific surface area and many impurities.

[0005] CN117510101A discloses a dry method for preparing calcium hydroxide with high specific surface area. This application improves the activity, specific surface area, and dispersibility of calcium hydroxide by preparing highly active lime and adding accelerators and dispersants. The accelerator is one or a combination of methanol, ethanol, propanol, isopropanol, n-butanol, etc., and the dispersant is one or a combination of sodium carboxylate, sodium sulfonate, sodium polyacrylate, and polyacrylamide.

[0006] CN117865514A discloses a method for preparing high specific surface area calcium hydroxide by a dry process with a low water-cement ratio. In the lime digestion process, by adding additives such as trithiocyanate and calcium lignosulfonate, the water-cement ratio required for the digestion process is reduced, thereby increasing the specific surface area of ​​calcium hydroxide.

[0007] As mentioned above, existing technologies have shown that in the process of preparing calcium hydroxide by dry slaking of quicklime, the specific surface area of ​​calcium hydroxide can be increased by adding additives such as accelerators and dispersants. However, the following problems also exist:

[0008] (1) The added organic additives are difficult to remove and remain in the product, adsorbed on the surface of calcium hydroxide particles;

[0009] (2) The calcium oxide digestion reaction is incomplete;

[0010] (3) The obtained calcium hydroxide has a high impurity content;

[0011] These issues all affect the desulfurization efficiency of calcium hydroxide as a desulfurizing agent in flue gas treatment. Therefore, providing a dry process for producing calcium hydroxide with high specific surface area, which increases the specific surface area and purity of calcium hydroxide without introducing new impurities, and thus enables calcium hydroxide to achieve higher desulfurization efficiency, is a problem that urgently needs to be solved in the existing technology. Summary of the Invention

[0012] To address the shortcomings of existing technologies, this invention provides a dry process for producing calcium hydroxide with high specific surface area, which increases the specific surface area of ​​calcium hydroxide, improves its purity, and enhances its desulfurization efficiency without introducing new impurities.

[0013] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0014] A dry process for producing high specific surface area calcium hydroxide includes the following steps: preparing quicklime powder, preparing perlite composite material, preparing a mixture, digesting, drying, and classifying and removing impurities.

[0015] The method for preparing quicklime powder is as follows: crush limestone, calcine it at 830-880℃ for 70-90 minutes, pulverize it, and pass it through a 1.5-2mm sieve to remove impurities to obtain quicklime powder.

[0016] The preparation of the perlite composite material includes modification and compositing;

[0017] The modification method is as follows: expandable perlite is added to water, and γ-glycidyl etheroxypropyltrimethoxysilane is added at the same time. The temperature is controlled at 75-85℃ at a speed of 380-420 rpm, and the mixture is stirred for 8-12 minutes. After stirring, the mixture is filtered, washed, and dried to obtain modified perlite.

[0018] The expanded perlite is 70-100 mesh expanded perlite, and the mass ratio of the expanded perlite, water, and γ-glycidyl etheroxypropyltrimethoxysilane is 20:450-550:0.8-1.2.

[0019] The composite method is as follows: add modified perlite, polycarboxylate superplasticizer and stearic acid diethanolamide to water, control the temperature at 55-65℃, stir for 15-25 minutes, then add hydrochloric acid and trimethylolpropane, stir for 8-12 minutes, filter, wash and dry to obtain perlite composite material.

[0020] The polycarboxylate superplasticizer is LCX-9 polycarboxylate superplasticizer;

[0021] The concentration of the hydrochloric acid is 36.5-37.0 wt%;

[0022] The mass ratio of the modified perlite, water, polycarboxylate superplasticizer, stearic acid diethanolamide, hydrochloric acid, and trimethylolpropane is 20:450-550:0.8-1.2:0.7-0.9:4.5-5.5:0.15-0.25.

[0023] The method for preparing the mixture is to mix quicklime powder and perlite composite material at a mass ratio of 100:7-9 to prepare the mixture.

[0024] The digestion includes primary digestion and secondary digestion;

[0025] The method of one digestion is as follows: under the stirring state of 600-800 rpm, water at 70-80℃ is atomized and sprayed onto the surface of the mixture. The digestion temperature is controlled at 85-95℃ and the digestion time is 8-10 minutes. After the one digestion is completed, one digested calcium hydroxide is obtained.

[0026] The mass ratio of the mixture to water is 10:2-3.

[0027] The secondary digestion method is as follows: saturated water-absorbing expanded perlite is added to the primary digested calcium hydroxide, stirred and mixed, and the temperature is raised to 103-106℃. The mixture is stirred and digested for 18-22 minutes at a speed of 350-450 rpm. After digestion, impurities are removed by passing the mixture through a 20-25 mesh sieve to obtain primary calcium hydroxide.

[0028] The expanded perlite is 100-120 mesh expanded perlite with a water absorption rate greater than 800%.

[0029] The mass ratio of the saturated expanded perlite after water absorption to the primary digested calcium hydroxide is 28-32:100.

[0030] The drying method involves drying primary calcium hydroxide at 108-112℃ for 1.8-2.2 hours to obtain calcium hydroxide powder.

[0031] The classification and impurity removal method involves classifying and removing calcium hydroxide powder by airflow at a rotation speed of 950-1050 rpm to obtain calcium hydroxide with high specific surface area.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] The dry process for producing high specific surface area calcium hydroxide of this invention can increase the specific surface area of ​​calcium hydroxide without introducing new impurities, thereby improving the purity and desulfurization efficiency of calcium hydroxide. The prepared calcium hydroxide has a specific surface area of ​​53.3-54.5 m².2 / g, purity is 96.8-97.7%, and sulfur penetration capacity is 119.6-124.3mg / g. Detailed Implementation

[0034] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described.

[0035] Example 1

[0036] A dry process for producing high specific surface area calcium hydroxide includes the following steps:

[0037] (1) Preparation of quicklime powder

[0038] The limestone was crushed, calcined at 830℃ for 90 minutes, pulverized, and passed through a 1.5mm sieve to remove impurities, thus obtaining quicklime powder.

[0039] (2) Preparation of perlite composite materials

[0040] A. Modification

[0041] 70-mesh expanded perlite was added to water, along with γ-glycidyl etheroxypropyltrimethoxysilane. The temperature was controlled at 75°C, and the mixture was stirred at 380 rpm for 12 minutes. After stirring, the mixture was filtered, washed, and dried to obtain modified perlite.

[0042] The mass ratio of the expanded perlite, water, and γ-glycidyl etheroxypropyltrimethoxysilane is 20:450:0.8.

[0043] B. Composite

[0044] Modified perlite, polycarboxylate superplasticizer, and stearic acid diethanolamide were added to water, and the temperature was controlled at 55℃. The mixture was stirred at 280 rpm for 25 minutes. Then, hydrochloric acid and trimethylolpropane were added, and the mixture was stirred at 450 rpm for 12 minutes. The mixture was then filtered, washed, and dried to obtain the perlite composite material.

[0045] The polycarboxylate superplasticizer is LCX-9 polycarboxylate superplasticizer;

[0046] The concentration of the hydrochloric acid is 36.5 wt%.

[0047] The mass ratio of the modified perlite, water, polycarboxylate superplasticizer, stearic acid diethanolamide, hydrochloric acid, and trimethylolpropane is 20:450:0.8:0.7:4.5:0.15.

[0048] (3) Preparation of mixture

[0049] Quicklime powder and perlite composite material are mixed evenly at a mass ratio of 100:7 to prepare a mixture.

[0050] (4) Digestion

[0051] a. Primary digestion

[0052] Add the mixture into the digester, control the stirring speed of the digester to 600 rpm, spray 70°C water atomized on the surface of the mixture while stirring, control the digestion temperature to 85°C, and the digestion time to 10 min. After one digestion, one digested calcium hydroxide is obtained.

[0053] The mass ratio of the mixture to water is 10:2.

[0054] b. Secondary digestion

[0055] Saturated water-absorbing expanded perlite was added to primary digested calcium hydroxide. After stirring and mixing, the temperature was raised to 103℃ and digestion continued for 22 minutes. The stirring speed of the digester was controlled at 350 rpm. After digestion, impurities were removed by a 20-mesh sieve to obtain primary calcium hydroxide.

[0056] The expanded perlite is 100 mesh expanded perlite with a water absorption rate greater than 800%.

[0057] The mass ratio of the saturated expanded perlite after water absorption to the primary digested calcium hydroxide is 28:100.

[0058] (5) Drying

[0059] Calcium hydroxide powder was obtained by drying primary calcium hydroxide at 108℃ for 2.2 hours.

[0060] (6) Graded impurity removal

[0061] Calcium hydroxide powder was placed in an air classifier and the speed was adjusted to 950 rpm for classification and impurity removal to obtain calcium hydroxide with high specific surface area.

[0062] Example 2

[0063] A dry process for producing high specific surface area calcium hydroxide includes the following steps:

[0064] (1) Preparation of quicklime powder

[0065] The limestone is crushed, calcined at 850℃ for 80 minutes, pulverized, and passed through a 2mm sieve to remove impurities to obtain quicklime powder.

[0066] (2) Preparation of perlite composite materials

[0067] A. Modification

[0068] 80-mesh expanded perlite was added to water, along with γ-glycidyl oxypropyltrimethoxysilane. The temperature was controlled at 80°C, and the mixture was stirred at 400 rpm for 10 minutes. After stirring, the mixture was filtered, washed, and dried to obtain modified perlite.

[0069] The mass ratio of the expanded perlite, water, and γ-glycidyl etheroxypropyltrimethoxysilane is 20:500:1.

[0070] B. Composite

[0071] Modified perlite, polycarboxylate superplasticizer, and stearic acid diethanolamide were added to water, and the temperature was controlled at 60℃. The mixture was stirred at 300 rpm for 20 minutes. Then hydrochloric acid and trimethylolpropane were added, and the mixture was stirred at 500 rpm for 10 minutes. The mixture was then filtered, washed, and dried to obtain the perlite composite material.

[0072] The polycarboxylate superplasticizer is LCX-9 polycarboxylate superplasticizer;

[0073] The concentration of the hydrochloric acid was 36.7 wt%.

[0074] The mass ratio of the modified perlite, water, polycarboxylate superplasticizer, stearic acid diethanolamide, hydrochloric acid, and trimethylolpropane is 20:500:1:0.8:5:0.2.

[0075] (3) Preparation of mixture

[0076] Quicklime powder and perlite composite material are mixed evenly at a mass ratio of 100:8 to prepare a mixture.

[0077] (4) Digestion

[0078] a. Primary digestion

[0079] Add the mixture to the digester, control the stirring speed of the digester to 700 rpm, spray 75°C water atomized on the surface of the mixture while stirring, control the digestion temperature to 90°C, and the digestion time to 8 minutes. After one digestion, one digested calcium hydroxide is obtained.

[0080] The mass ratio of the mixture to water is 10:2.5.

[0081] b. Secondary digestion

[0082] Saturated water-absorbing expanded perlite was added to the primary digested calcium hydroxide. After stirring and mixing, the temperature was raised to 105℃ and digestion continued for 20 minutes. The stirring speed of the digester was controlled at 400 rpm. After digestion, impurities were removed with a 25-mesh sieve to obtain primary calcium hydroxide.

[0083] The expanded perlite is 120 mesh expanded perlite with a water absorption rate greater than 800%.

[0084] The mass ratio of the saturated expanded perlite after water absorption to the primary digested calcium hydroxide is 30:100.

[0085] (5) Drying

[0086] Calcium hydroxide powder was obtained by drying primary calcium hydroxide at 110℃ for 2 hours.

[0087] (6) Graded impurity removal

[0088] Calcium hydroxide powder was placed in an air classifier and the speed was adjusted to 1000 rpm for classification and impurity removal to obtain calcium hydroxide with high specific surface area.

[0089] Example 3

[0090] A dry process for producing high specific surface area calcium hydroxide includes the following steps:

[0091] (1) Preparation of quicklime powder

[0092] The limestone is crushed, calcined at 880℃ for 70 minutes, pulverized, and passed through a 2mm sieve to remove impurities to obtain quicklime powder.

[0093] (2) Preparation of perlite composite materials

[0094] A. Modification

[0095] 100-mesh expanded perlite was added to water, along with γ-glycidyl oxypropyltrimethoxysilane. The temperature was controlled at 85°C, and the mixture was stirred at 420 rpm for 8 minutes. After stirring, the mixture was filtered, washed, and dried to obtain modified perlite.

[0096] The mass ratio of the expanded perlite, water, and γ-glycidyl etheroxypropyltrimethoxysilane is 20:550:1.2.

[0097] B. Composite

[0098] Modified perlite, polycarboxylate superplasticizer, and stearic acid diethanolamide were added to water, and the temperature was controlled at 65℃. The mixture was stirred at 320 rpm for 15 minutes. Then hydrochloric acid and trimethylolpropane were added, and the mixture was stirred at 550 rpm for 8 minutes. The mixture was then filtered, washed, and dried to obtain the perlite composite material.

[0099] The polycarboxylate superplasticizer is LCX-9 polycarboxylate superplasticizer;

[0100] The concentration of the hydrochloric acid is 37.0 wt%;

[0101] The mass ratio of the modified perlite, water, polycarboxylate superplasticizer, stearic acid diethanolamide, hydrochloric acid, and trimethylolpropane is 20:550:1.2:0.9:5.5:0.25.

[0102] (3) Preparation of mixture

[0103] Quicklime powder and perlite composite material are mixed evenly at a mass ratio of 100:9 to prepare a mixture.

[0104] (4) Digestion

[0105] a. Primary digestion

[0106] Add the mixture into the digester, control the stirring speed of the digester to 800 rpm, and spray 80°C water atomized and sprayed on the surface of the mixture while stirring. Control the digestion temperature at 95°C and the digestion time at 8 minutes. After one digestion, one digested calcium hydroxide is obtained.

[0107] The mass ratio of the mixture to water is 10:3.

[0108] b. Secondary digestion

[0109] Saturated water-absorbing expanded perlite was added to primary digested calcium hydroxide. After stirring and mixing, the temperature was raised to 106℃ and digestion continued for 18 minutes. The stirring speed of the digester was controlled at 450 rpm. After digestion, impurities were removed by a 25-mesh sieve to obtain primary calcium hydroxide.

[0110] The expanded perlite is 120 mesh expanded perlite with a water absorption rate greater than 800%.

[0111] The mass ratio of the saturated expanded perlite after water absorption to the primary digested calcium hydroxide is 32:100.

[0112] (5) Drying

[0113] Calcium hydroxide powder was obtained by drying primary calcium hydroxide at 112℃ for 1.8 hours.

[0114] (6) Graded impurity removal

[0115] Calcium hydroxide powder was placed in an air classifier and the speed was adjusted to 1050 rpm for classification and impurity removal to obtain calcium hydroxide with high specific surface area.

[0116] Comparative Example 1

[0117] Comparative Example 1 uses the dry process for producing high specific surface area calcium hydroxide as described in Example 2. The difference is that the step of preparing perlite composite material is omitted, and the step of preparing the mixture is changed to: mixing quicklime powder, ethylene glycol and sodium carboxylate of cellulose in a mass ratio of 100:0.4:0.35 to prepare a mixture.

[0118] Comparative Example 2

[0119] Comparative Example 2 adopts the dry process for producing high specific surface area calcium hydroxide described in Example 2. The difference is that the step of preparing perlite composite material is omitted, and the step of preparing the mixture is changed to: mixing quicklime powder, 80 mesh expanded perlite, polycarboxylate superplasticizer and stearic acid diethanolamide in a mass ratio of 100:7:0.4:0.35 to prepare a mixture.

[0120] Comparative Example 3

[0121] Comparative Example 3 adopts the dry process for producing high specific surface area calcium hydroxide described in Example 2. The difference is that the step of preparing perlite composite material is omitted, and the step of preparing the mixture is changed to: mixing quicklime powder, polycarboxylate superplasticizer and stearic acid diethanolamide in a mass ratio of 100:0.4:0.35 to prepare a mixture.

[0122] Comparative Example 4

[0123] Comparative Example 4 adopts the dry high specific surface area calcium hydroxide production process described in Example 2. The difference is that the digestion step is changed to: adding the mixture into the digester, controlling the stirring speed of the digester to 700 rpm, spraying 75°C water atomized on the surface of the mixture while stirring, controlling the digestion temperature at 90°C, digestion time at 28 min, and removing impurities with a 1 mm sieve after digestion to obtain primary calcium hydroxide.

[0124] The mass ratio of the mixture to water is 10:2.5.

[0125] Experimental Example 1

[0126] The high specific surface area calcium hydroxides prepared in Examples 1-3 and Comparative Examples 1-4 were tested using a surface area analyzer (BET). The test results are as follows:

[0127] Table 1. Specific surface area of ​​calcium hydroxide in the examples and comparative examples.

[0128]

[0129] As can be seen from Table 1, in Comparative Example 2, the preparation of the perlite composite material was omitted, and expanded perlite, polycarboxylate superplasticizer, stearic acid diethanolamide and quicklime powder were simply mixed. In Comparative Example 3, the preparation of the perlite composite material was omitted, and polycarboxylate superplasticizer, stearic acid diethanolamide and quicklime powder were simply mixed. The specific surface area of ​​calcium hydroxide obtained in Comparative Examples 2 and 3 was significantly lower than that in Example 2, indicating that the preparation of perlite composite material and the mixing of perlite composite material with quicklime powder can effectively increase the specific surface area of ​​calcium hydroxide.

[0130] The specific surface area of ​​calcium hydroxide in Comparative Example 4 was significantly lower than that in Example 2, indicating that the secondary digestion step can increase the specific surface area of ​​calcium hydroxide.

[0131] The surface of perlite composite materials has abundant polar groups with strong affinity for water, such as carboxyl, hydroxyl, and polyoxyalkyl groups. Carboxyl groups can react with calcium ions to form complexes, reducing the calcium ion concentration, slowing down the crystallization rate of calcium hydroxide and making its particle size smaller, thereby increasing its specific surface area. Hydroxyl and polyoxyalkyl groups have strong affinity for water, and through surface effects such as wetting and lubrication, they improve the dispersion and flowability of the digested calcium hydroxide, reduce frictional resistance, prevent its agglomeration, improve the dispersibility of calcium hydroxide particles, and increase its specific surface area.

[0132] In the secondary digestion step, the saturated water-absorbing expanded perlite evaporates water vapor at high temperature. The water vapor reacts with some unreacted quicklime again, making the digestion of quicklime more thorough. Furthermore, the water vapor evaporated from the water-absorbing perlite can increase the porosity of the calcium hydroxide produced by digestion, thereby increasing the specific surface area of ​​calcium hydroxide.

[0133] Experimental Example 2

[0134] The high specific surface area calcium hydroxide prepared in Examples 1-3 and Comparative Examples 1-4 was tested for purity according to HG / T 4120-2009, and the test results are as follows:

[0135] Table 2 Purity of calcium hydroxide in the examples and comparative examples

[0136]

[0137] As can be seen from the test results in Table 2, the purity of calcium hydroxide in Comparative Examples 1-4 is lower than that in Example 2, indicating that the perlite composite material and the secondary digestion step can improve the purity of calcium hydroxide.

[0138] In the classification and impurity removal step of this invention, the specific gravity of the dried perlite composite material, expanded perlite, and calcium hydroxide differs greatly. The perlite composite material and expanded perlite can be easily removed by airflow classification without introducing new impurities into the prepared high specific surface area calcium hydroxide.

[0139] In the preparation of the perlite composite material, this invention uses γ-glycidyl etheroxypropyltrimethoxysilane to link the polycarboxylate superplasticizer, stearic acid diethanolamide, and expanded perlite. Trimethylolpropane allows the polycarboxylate superplasticizer and stearic acid diethanolamide on the perlite surface to crosslink, improving the bonding strength between the polycarboxylate superplasticizer, stearic acid diethanolamide, and perlite, preventing the polycarboxylate superplasticizer and stearic acid diethanolamide from detaching during the digestion reaction. The hydrophilicity of the perlite composite material itself slows down the rate of calcium oxide digestion into calcium hydroxide crystals, making it easier for the calcium hydroxide formed on the surface of quicklime to peel off, thus improving the digestion conversion rate. After digestion, impurities carried in the quicklime disperse, which can be removed in the classification and impurity removal step, improving the purity of calcium hydroxide.

[0140] After the first digestion, the reaction system contains small particles of quicklime coated with calcium hydroxide. In the second digestion step, the temperature of the reaction system is increased, and the water absorbed by the expanded perlite evaporates into water vapor at high temperature. The water vapor can cause the calcium hydroxide produced on the surface of the small particles of quicklime to peel off and react with the quicklime in the core, making the reaction more thorough. After digestion, the impurities carried in the quicklime are dispersed and can be removed in the classification and impurity removal step to improve the purity of calcium hydroxide.

[0141] Experimental Example 3

[0142] The high specific surface area calcium hydroxides prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to sulfur capacity testing, and the testing methods are as follows:

[0143] A U-shaped glass tube with branches, 300 mm long, 9 mm inner diameter, and 12 mm outer diameter, was used as the fixed bed of the adsorbent. 1 g of calcium hydroxide was weighed and filled into the U-shaped glass tube. The upper and lower ends of the calcium hydroxide were fixed with quartz wool and glass beads. After the adsorbent was loaded into the tube, the gas flow rate was set and the experiment was started after the flow rate remained constant. The outlet concentration was measured using a sulfur dioxide gas detector.

[0144] When the sulfur dioxide outlet concentration is set to a certain level, the sulfur capacity per unit mass of the desulfurizing agent from the start of desulfurization until the sulfur dioxide outlet concentration reaches that value is called the breakthrough sulfur capacity. The time required to reach this specific concentration is called the breakthrough time. When the outlet concentration reaches 200 ppm, it is considered breakthrough. The formula for calculating the breakthrough sulfur capacity is as follows:

[0145]

[0146] q -- Sulfur breakthrough capacity, mg / g; c -- Volume fraction of sulfur dioxide in feed gas, %; Q -- Flow rate in feed gas, mL / min; M -- Molar amount of sulfur dioxide, 64 g / mol; t -- Breakthrough time, min; V m--Standard state molar volume, 22.4 L / mol; M A --Amount of desulfurizing agent, in grams.

[0147] The feed gas consists of nitrogen, oxygen, and sulfur dioxide, with a sulfur dioxide concentration of 600 ppm, an oxygen concentration of 10%, and nitrogen as a balance gas.

[0148] Table 3. Breakthrough sulfur capacity of calcium hydroxide in the examples and comparative examples

[0149]

[0150] As shown in Table 3, the sulfur penetration capacity of calcium hydroxide in Comparative Examples 1 and 2 is significantly lower than that in Example 2. The sulfur penetration capacity of calcium hydroxide in Comparative Examples 1 and 2 decreases by 33.5% and 24.0% respectively compared to Example 2. Combined with Table 1, it can be seen that the specific surface area of ​​calcium hydroxide in Comparative Examples 1 and 2 decreases by 25.7% and 15.2% respectively compared to Example 2. The rate of decrease in sulfur penetration capacity is significantly higher than the rate of decrease in specific surface area. The calcium hydroxide prepared in Comparative Examples 1 and 2 has residual additives. The additives adhere to the surface of calcium hydroxide, affecting the reaction between sulfur dioxide and calcium hydroxide, reducing the sulfur penetration capacity of calcium hydroxide, and affecting the desulfurization efficiency of calcium hydroxide.

[0151] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dry process for producing high specific surface area calcium hydroxide, characterized in that, The dry process for producing high specific surface area calcium hydroxide includes the following steps: preparing quicklime powder, preparing perlite composite material, preparing a mixture, digesting, drying, and classifying and removing impurities; The preparation of the perlite composite material includes modification and compositing; The modification method is as follows: expandable perlite is added to water, and γ-glycidyl etheroxypropyltrimethoxysilane is added at the same time. The temperature is controlled at 75-85℃, and the mixture is stirred for 8-12 minutes. After stirring, the mixture is filtered, washed, and dried to obtain modified perlite. The composite method is as follows: add modified perlite, polycarboxylate superplasticizer and stearic acid diethanolamide to water, control the temperature at 55-65℃, stir for 15-25 minutes, then add hydrochloric acid and trimethylolpropane, stir for 8-12 minutes, filter, wash and dry to obtain perlite composite material. The digestion includes primary digestion and secondary digestion; The method of one-time digestion is as follows: under stirring, water at 70-80℃ is atomized and sprayed onto the surface of the mixture. The digestion temperature is controlled at 85-95℃ and the digestion time is 8-10 minutes. After one-time digestion, one-time digested calcium hydroxide is obtained. The secondary digestion method is as follows: saturated expanded perlite that has absorbed water is added to the primary digested calcium hydroxide, stirred and mixed, and the temperature is raised to 103-106℃. Stirring and digestion are continued for 18-22 minutes. After digestion, the mixture is sieved to remove impurities and primary calcium hydroxide is obtained.

2. The dry process for producing high specific surface area calcium hydroxide according to claim 1, characterized in that, The method for preparing the mixture is to mix quicklime powder and perlite composite material evenly to prepare the mixture.

3. The dry process for producing high specific surface area calcium hydroxide according to claim 2, characterized in that, The mass ratio of the quicklime powder and perlite composite material is 100:7-9.

4. The dry process for producing high specific surface area calcium hydroxide according to claim 1, characterized in that, In the modification step, the mass ratio of expanded perlite, water, and γ-glycidyl etheroxypropyltrimethoxysilane is 20:450-550:0.8-1.

2.

5. The dry process for producing high specific surface area calcium hydroxide according to claim 1, characterized in that, In the composite step, the mass ratio of modified perlite, water, polycarboxylate superplasticizer, stearic acid diethanolamide, hydrochloric acid, and trimethylolpropane is 20:450-550:0.8-1.2:0.7-0.9:4.5-5.5:0.15-0.

25.

6. The dry process for producing high specific surface area calcium hydroxide according to claim 1, characterized in that, The polycarboxylate superplasticizer is LCX-9 polycarboxylate superplasticizer, and the hydrochloric acid concentration is 36.5-37.0 wt%.

7. The dry process for producing high specific surface area calcium hydroxide according to claim 1, characterized in that, In the first digestion step, the mass ratio of the mixture to water is 10:2-3.

8. The dry process for producing high specific surface area calcium hydroxide according to claim 1, characterized in that, In the secondary digestion step, the expanded perlite is 100-120 mesh expanded perlite with a water absorption rate greater than 800%; the mass ratio of the expanded perlite after saturation with water to the calcium hydroxide from the primary digestion is 28-32:100.

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