An apparatus for preparing high specific surface area calcium hydroxide

Abstract

This invention discloses an apparatus for preparing high specific surface area calcium hydroxide, comprising a lime premixing tank and a digestion reactor. The lime premixing tank contains a ribbon agitator connected to a stirring motor at the top of the tank. Steam is conveyed to the premixing tank via a Venturi mixer I. A powder distributor and baffles within the reactor ensure uniform material distribution and gas-solid separation. A closed-loop tail gas treatment system is employed, with a sawtooth distributor and spiral nozzles in the scrubbing tower providing efficient dust removal. Purified wastewater is recycled to Venturi mixer II via a booster pump for reuse. Water is atomized and replenished in the reaction zone via spiral nozzle II to enhance the three-phase reaction. The product settles via baffles and is discharged under control by a rotary valve, then collected after cooling by a screw conveyor. This invention, through a closed-loop design of premixing-steam conveying-tail water reuse-separation, achieves continuous production and efficient resource utilization, significantly improving the specific surface area and production efficiency of calcium hydroxide.

Description

Technical Field

[0001] This utility model belongs to the field of calcium hydroxide production technology, specifically relating to an apparatus for preparing high specific surface area calcium hydroxide. Background Technology

[0002] Calcium hydroxide (also known as quicklime) is an important inorganic chemical product. Due to its strong alkalinity, excellent adsorption properties, and rapid reaction with acidic gases, it is widely used in flue gas desulfurization, wastewater treatment, building materials, pharmaceutical preparation, food processing, and petrochemicals. In recent years, with increasingly stringent environmental standards and rapid industrial technological development, the market's quality requirements for calcium hydroxide have been continuously rising. Traditional calcium hydroxide, due to its limited specific surface area, low reactivity, and underdeveloped pore structure, can no longer meet the demands of high-end applications. In contrast, high specific surface area calcium hydroxide (referred to as high specific surface area calcium hydroxide) has significant advantages in flue gas purification, fine chemicals, and environmental protection materials due to its larger specific surface area, higher reactivity, better dispersibility, and richer pore structure, and is gradually replacing ordinary calcium hydroxide products. With the maturity of related technologies, the market demand for high specific surface area calcium hydroxide is rapidly expanding, making research on its preparation process and specialized equipment increasingly important.

[0003] Currently, the industrial processes for preparing calcium hydroxide are mainly divided into two categories: dry processes and wet processes.

[0004] Dry processes typically employ airflow or mechanical stirring to react calcium oxide with water vapor or a small amount of liquid water to produce calcium hydroxide. This process offers advantages such as a short process flow, low energy consumption, relatively small equipment investment, and a high degree of automation, making it suitable for large-scale continuous production. However, the core issue with dry processes lies in their heterogeneous solid-gas or solid-liquid reaction mode, where the distribution and diffusion rate of moisture directly affect reaction efficiency. Due to the localized non-uniformity of moisture during the reaction, a calcium hydroxide coating can quickly form on the surface of calcium oxide particles, hindering further digestion of the internal calcium oxide. This results in a lower specific surface area of ​​the final product, and the residual incompletely reacted calcium oxide can affect product purity. Furthermore, traditional dry processes often require multi-stage reactions and long maturation periods to improve conversion rates, which not only increases energy consumption but also reduces production efficiency.

[0005] The wet process employs a higher liquid-to-solid ratio for the digestion reaction. The resulting slurry undergoes filtration, dehydration, drying, and pulverization to ultimately yield calcium hydroxide. The advantages of the wet process include a uniform reaction system, effectively avoiding calcium oxide encapsulation, resulting in high product purity and a more thorough reaction. However, the wet process also has significant disadvantages: a long process flow involving multiple post-processing steps, leading to substantial equipment investment; high energy consumption, especially in the drying stage which requires a large amount of heat energy; and a high equipment failure rate, as the corrosive and abrasive nature of the slurry makes pumps, valves, and filtration equipment prone to damage, resulting in high maintenance costs. Furthermore, while the calcium hydroxide produced by the wet process has high purity, its specific surface area improvement is limited, typically failing to meet the requirements for high specific surface area calcium hydroxide.

[0006] To address these issues, researchers have proposed several improvement schemes in recent years. For example, they have introduced efficient mixing equipment (such as Venturi mixers and fluidized bed reactors) into dry processes to optimize the distribution of water vapor or atomized water, or employed ultrafine grinding and surface modification techniques in wet processes to increase the specific surface area of ​​the product. However, these methods either still suffer from uneven reaction or lead to significantly increased costs due to process complexity.

[0007] Chinese patent literature discloses "A high specific surface area calcium hydroxide production line" (publication number: CN116903271A). The method includes a working silo group and a digestion unit. The digestion system is reasonably designed and can be used for the production of ordinary calcium hydroxide. However, its material mixing system adopts a traditional mechanical stirring method, which results in insufficient mixing uniformity and easy formation of dead zones, leading to insufficient contact between lime powder and digestion aid. The tail gas treatment only adopts a simple water film dust removal, which has limited dust removal efficiency and does not realize wastewater recycling, which wastes resources and increases environmental pressure. The reaction zone lacks an effective flow guiding structure, resulting in uneven reaction and serious product entrainment.

[0008] Chinese patent literature discloses "A continuous mixing device for the production of high specific surface area calcium hydroxide and its usage method" (Publication No.: CN116099429A). This equipment, with its reasonable layout design, can meet the needs of calcium hydroxide production and solve the problem of raw materials easily adhering to the inner wall of the device and the stirring rod, causing waste. However, its mixing system adopts a conventional stirring structure, which has limited mixing uniformity and is prone to material agglomeration, affecting the specific surface area of ​​the final product. The tail gas treatment system is relatively simple and lacks an efficient dust recovery and wastewater recycling mechanism, which not only causes raw material waste but may also cause environmental problems. The reactor does not have a dedicated flow guiding and separation structure, resulting in incomplete separation of products and waste gas, affecting reaction efficiency.

[0009] In summary, existing calcium hydroxide preparation processes still have significant shortcomings in terms of specific surface area improvement, reaction uniformity, and energy consumption control. Faced with the core problems of poor reaction uniformity, limited pore structure control methods, and significant energy consumption and environmental pressures in the preparation of high specific surface area calcium hydroxide using traditional processes, developing a novel preparation device capable of "precise control of the reaction process, directional regulation of pore structure, and efficient recycling of resources" has become a crucial issue that the industry urgently needs to address. Summary of the Invention

[0010] The purpose of this invention is to provide an apparatus for preparing high specific surface area calcium hydroxide, so as to solve the problems of existing equipment being difficult to scale up the production of high specific surface area calcium hydroxide and having relatively high costs.

[0011] To solve the above technical problems, the present invention adopts the following technical solution:

[0012] An apparatus for preparing high specific surface area calcium hydroxide includes a synergistic system consisting of a lime premixing tank and a digestion reactor.

[0013] Furthermore, the lime premixing tank is a tank with arc-shaped heads at the top and bottom.

[0014] Furthermore, the tank body with arc-shaped caps at the top and bottom is cylindrical.

[0015] Furthermore, the cylindrical tank with arc-shaped heads at the top and bottom has a volume of one-fifth to one-half that of the main reactor.

[0016] Furthermore, the lime premix tank is equipped with a lime powder inlet, a digestion aid inlet, and an ultrasonic level gauge at the top.

[0017] Furthermore, the lime premix tank is equipped with a lime powder discharge port and a Venturi mixer I at the bottom.

[0018] Furthermore, the Venturi mixer I is connected to the digestion reactor.

[0019] Furthermore, the lime premixing tank is equipped with a ribbon agitator.

[0020] Furthermore, the digestion reactor is equipped with a powder distributor.

[0021] Furthermore, the diameter of the powder distributor is 2 to 10 times the diameter of the feed inlet and pipe of the digester reactor.

[0022] The technical principle of this utility model:

[0023] This invention addresses the shortcomings of traditional quicklime hydration processes by optimizing the process and innovating equipment to achieve the preparation of high-specific-surface-area calcium hydroxide. First, a ribbon agitator in a lime premixing tank forces lime powder and slaking aids into a convective mixture, eliminating local concentration gradients and resolving the issue of uncontrolled reaction rates. The mixture then enters Venturi mixer I, where it undergoes a rapid gas-solid reaction with water vapor. Mass transfer efficiency is enhanced based on the Knudsen diffusion effect, and steam kinetic energy is used to disperse the powder, constructing a high-porosity reaction intermediate. A tail gas scrubber recovers waste heat from the reaction to heat tap water. After pressurization, the water and aid mixture form a turbulent jet in Venturi mixer II. This jet is atomized through a spiral nozzle and enters a novel slaking reactor, where it undergoes a secondary liquid-solid reaction with a gas-solid fluidized bed formed by a powder distributor. This reactor utilizes two-fluid atomization technology and laminar flow distribution principles to overcome the mass transfer limitations of traditional dry slaking, avoiding crystal rearrangement during the slaking process. In-situ carbonization suppression technology further enhances product purity. The final product is rapidly cooled by a screw conveyor with an integrated cooling system, which suppresses crystal transformation and yields calcium hydroxide products with the required specific surface area, achieving synergistic optimization of energy consumption and cost.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. This utility model designs a novel digestion reactor with a simple structure and convenient installation, which effectively solves the problem of industrial production of high specific surface area calcium hydroxide. It is particularly suitable for industrial automated control production, and has low production cost, resulting in good economic and social benefits.

[0026] 2. This utility model innovatively mixes lime powder with a digestion aid first, solving the problem of uncontrollable reaction rate between lime and water. Then, steam is used to react rapidly with the lime powder, and gaseous water reacts with the lime, effectively increasing the contact area and reaction efficiency. At the same time, it can also disperse the powder, thereby increasing the specific surface area and porosity of calcium hydroxide.

[0027] 3. This utility model innovatively uses a powder distributor to evenly distribute high-pressure powder in the digestion reactor, and then uses a spiral nozzle to atomize the additive mixture and react it with the powder in a secondary reaction. This effectively solves the problem of incomplete reaction between steam and lime, and avoids the problem of reduced calcium hydroxide specific surface area caused by the aging process required by conventional dry digestion, thus producing high-purity calcium hydroxide.

[0028] 4. The lime powder premixing tank of this utility model uses a ribbon agitator, which can evenly mix the digestion aid with the lime powder.

[0029] 5. This utility model features environmental optimization and rational resource utilization. This is mainly reflected in the tail gas scrubber at the top of the digester, which serves as a treatment device for the digestion reaction tail gas. Simultaneously, due to the high temperature of the tail gas after the reaction, tap water can be heated and used as digestion water, reducing energy consumption. The screw conveyor at the bottom is equipped with a cooling system, which can lower the temperature of the calcium hydroxide, allowing the produced calcium hydroxide to be directly packaged and sold. Meanwhile, the heated tap water can be returned to the system for lime digestion or steam preparation. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the apparatus for preparing high specific surface area calcium hydroxide according to this invention.

[0031] In the attached diagram: 1-Lime powder premixing tank; 101-Lime powder inlet; 102-Premixing tank motor; 103-Digestion aid inlet; 104-Ultrasonic level gauge; 105-Screw ribbon agitator; 106-Lime powder discharge outlet; 107-Steam inlet; 108-Venturi mixer I; 109-Digestion reactor inlet and piping; 2-Digestion reactor; 201-Digestion reactor exhaust outlet; 202-Serrated gas distributor; 203-Tail gas scrubber; 204-Tail gas scrubber corrugated plate; 205-Spiral nozzle I; 206-Water inlet and piping; 207-Drain outlet; 208-Booster pump; 209-Booster pump inlet; 210-Booster pump outlet; 211-Venturi mixer II; 212-Venturi mixer discharge port; 213-Auxiliary agent mixture inlet; 214-Digester reactor inlet and piping; 215-Screw nozzle II; 216-Powder distributor; 217-Guide plate; 218-Discharge port; 219-Rotary feed valve; 220-Screw conveyor inlet; 221-Screw conveyor motor; 222-Screw conveyor cooling water inlet; 223-Screw conveyor; 224-Screw conveyor drain; 225-Screw conveyor discharge port; 226-Digester reactor support. Detailed Implementation

[0032] The present utility model patent will be further described in detail below with reference to the accompanying drawings and examples:

[0033] Example:

[0034] An apparatus for preparing high specific surface area calcium hydroxide comprises a lime premixing tank 1 and a digestion reactor 2. The lime premixing tank 1 is equipped with a ribbon agitator 105, which is connected to a stirring motor 102 at the top of the premixing tank 1. Lime powder enters from the lime powder inlet 101 at the top of the lime premixing tank 1, and digestion aid is added from the digestion aid inlet 103. The mixture is mixed under the monitoring of an ultrasonic level gauge 104. The initially mixed powder is discharged from the lime powder discharge outlet 106 at the bottom of the lime premixing tank 1 and enters the Venturi mixer I 108.

[0035] The Venturi mixer I 108 has an inlet connected to the lime powder discharge outlet 106. Steam enters from the steam inlet 107 of the Venturi mixer I 108 and reacts with the lime powder containing the digestion aid to prepare high specific surface area calcium hydroxide. Due to the short reaction time, some calcium oxide remains that has not fully reacted. Under the action of steam, the mixed powder is transported to the inlet and pipe 109 of the digestion reactor and enters the digestion reactor 2. The inlet and pipe 109 of the digestion reactor are equipped with a powder distributor 216. The high-velocity powder experiences a rapid pressure drop inside the digestion reactor 2. After impacting the powder distributor 216, the powder is evenly distributed inside the digestion reactor 2 and undergoes a secondary digestion reaction with the atomized aid mixture from the spiral nozzle II 215.

[0036] The digester reactor 2 is equipped with a tail gas scrubber 203 at the top. The dust-laden gas inside the digester is discharged from the exhaust port 201. Under the action of the sawtooth gas distributor 202 and the corrugated plate 204 of the tail gas scrubber, it is distributed at a low speed and evenly in the tail gas scrubber 203. Then, tap water is introduced from the water inlet and pipe 206. The dust-laden gas is sprayed by the spiral nozzle I 205. The purified tail gas is discharged. The washing wastewater is discharged from the drain port 207 to the booster pump inlet 209. After being pressurized by the booster pump 208, it is transported to the Venturi mixer II 211. It is mixed evenly with the additive mixture entering from the additive mixture inlet 213. Then, it is transported together to the digester inlet and pipe 214. Under the action of the spiral nozzle II 215, it is atomized and reacts with the powder to produce high-purity, high-specific-surface-area calcium hydroxide.

[0037] The prepared high specific surface area calcium hydroxide falls under gravity into the internal guide plate 217 of the digestion reactor 2, and then falls to the bottom of the digestion reactor 2. Because the lime reaction requires a certain period of time, most of the steam generated during the reaction rises from the other side of the guide plate 217 to the top of the digestion reactor 2, while the high specific surface area calcium hydroxide that has fallen to the bottom is discharged from the discharge port 218. Under the action of the rotary feed valve 219, it is evenly conveyed to the screw conveyor inlet 220 of the screw conveyor 223. Under the action of the screw conveyor motor 221, it is evenly stirred and undergoes heat exchange with the cold water entering through the screw conveyor cooling water inlet 222. The water is then discharged from the screw conveyor drain port 224, while the cooled high specific surface area calcium hydroxide is discharged from the screw conveyor discharge port 225. After packaging, the high specific surface area calcium hydroxide product is obtained.

[0038] The working principle of this utility model device is as follows:

[0039] Step 1: Add (100-800) mesh lime powder and slaking aid to the lime premixing tank, and simultaneously turn on the agitator of the lime premixing tank to mix the two evenly. Then send it to Venturi mixer I to react with steam at a temperature of (125-200)℃ and a pressure of (0.3-1)MPa to prepare a mixed powder of calcium hydroxide and calcium oxide with high porosity and high specific surface area.

[0040] Step 2: Introduce tap water into the exhaust gas scrubber, turn on the booster pump to pressurize the water discharged from the exhaust gas scrubber, and mix it evenly with the additive mixture entering from the additive mixture inlet in the Venturi mixer II; then, introduce it into the digestion reactor for atomization.

[0041] Step 3: The mixed powder prepared in Step 1 and the atomized mixed solution prepared in Step 2 are subjected to a secondary digestion reaction at a mass ratio of powder:mixed solution = 1:(0.6-1.5) to prepare calcium hydroxide with high purity and high specific surface area.

[0042] Step 4: The calcium hydroxide prepared in Step 3 is discharged from the discharge port of the digestion reactor and enters the screw conveyor for conveying and cooling before being discharged and packaged, thus obtaining a calcium hydroxide product with a high specific surface area.

[0043] The high specific surface area calcium hydroxide product was tested for specific surface area according to GB / T 19587-2017 "Determination of specific surface area of ​​solid materials by gas adsorption BET method" and for pore capacity according to GB / T 21650.2-2008 "Determination of pore size distribution and porosity of solid materials by mercury porosimetry and gas adsorption method - Part 2: Analysis of mesopores and macropores by gas adsorption method".

[0044] Those skilled in the art will recognize that the examples described herein are intended to help the reader understand the principles of this invention, and should be understood as not limiting the scope of protection of this invention to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on these technical teachings disclosed herein without departing from the scope of this invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. An apparatus for preparing high specific surface calcium hydroxide, characterized by, This includes a synergistic system consisting of a lime premixing tank and a digestion reactor; The lime premix tank is equipped with a lime powder inlet, a digestion aid inlet, and an ultrasonic level gauge at the top. The lime premix tank is equipped with a lime powder discharge port and a Venturi mixer I at the bottom; The Venturi mixer I is connected to the digestion reactor; The lime premixing tank is equipped with a ribbon agitator. The digestion reactor is equipped with a powder distributor.

2. A device for preparing high specific surface calcium hydroxide according to claim 1, characterized in that, The lime premixing tank is a tank with arc-shaped heads at the top and bottom.

3. The apparatus for preparing high specific surface area calcium hydroxide according to claim 2, characterized in that, The tank with arc-shaped caps at the top and bottom is cylindrical.

4. The apparatus for preparing high specific surface calcium hydroxide according to claim 3, characterized in that, The cylindrical tank with arc-shaped heads at the top and bottom has a volume of one-fifth to one-half that of the main reactor.

5. The apparatus for preparing high specific surface calcium hydroxide according to claim 1, wherein The diameter of the powder distributor is 2 to 10 times the diameter of the feed inlet and pipe of the digester reactor.

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