Preparation method of high-activity calcium hydroxide

Abstract

The invention belongs to the technical field of preparation of calcium-based desulfurizers, and particularly relates to a preparation method of high-activity calcium hydroxide, which comprises the following steps: adding corresponding auxiliaries, and sequentially performing premixing, primary digestion, secondary digestion and tertiary digestion on the auxiliaries and quick lime to regulate the microstructure of the calcium-based desulfurizer calcium hydroxide, increase the specific surface area and increase the pore volume and pore diameter. And the desulfurizer has good fluidity and dispersibility, so that the diffusion resistance of gases such as SO2 and SO3 in pores of the desulfurizer in the sulfur fixation process is reduced, and the desulfurization efficiency and the utilization rate are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of calcium-based desulfurizing agent preparation, and particularly relates to a method for preparing highly active calcium hydroxide. Background Art

[0002] In recent years, flue gas dry desulfurization technology has been increasingly used in small and medium-sized flue gas desulfurization systems. The technology is mature and the operation is stable. Among them, the SDS desulfurization process route using sodium bicarbonate as the alkali source has rapidly expanded its market share due to its advantages such as high desulfurization efficiency, wide source of desulfurizers, and low difficulty in engineering implementation. With the increase in the number of equipment, the disadvantages of this technical route began to emerge, and how to deal with desulfurization ash has become a new environmental problem. Sodium-based desulfurization ash is a mixture of sodium sulfate, sodium sulfite, and sodium carbonate. It has good water solubility and is a general solid waste that is difficult to dispose of in compliance with regulations. At the same time, sodium-based desulfurizers perform poorly under low temperature conditions.

[0003] Calcium-based desulfurizers are mainly used in the process of flue gas desulfurization after coal combustion. Flue gas desulfurization can be generally divided into three categories: wet method, dry method and semi-dry method according to whether water is involved and the dry and wet state of the desulfurized product. In dry desulfurization, ordinary calcium hydroxide has poor reactivity and has the problem of large dosage. In CN117602852A (a method for preparing a calcium-based desulfurizer with high specific surface area), a method of secondary digestion and spraying digestion liquid during the digestion process is adopted to obtain calcium hydroxide with good reactivity. However, for the raw material quicklime with uneven quality in industrial waste residue, the process still has the problem of incomplete digestion and uneven calcium hydroxide produced, and it is still necessary to further separate large particles and incompletely digested calcium hydroxide, which leads to limited resource utilization rate of raw material quicklime.

[0004] The particle size, specific surface area, porosity and diffusion rate of reactants through the sulfide product layer of calcium-based desulfurizer determine the reaction process and the final result. Therefore, it is necessary to optimize the process, on the one hand, to improve the microstructure of calcium hydroxide to improve the utilization rate and desulfurization efficiency of calcium-based desulfurizer; on the other hand, to control costs and reduce resource consumption. Summary of the invention

[0005] In order to solve the problems raised by the background technology, the present invention provides a method for preparing highly active calcium hydroxide.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention provides a method for preparing highly active calcium hydroxide, comprising the following steps:

[0008] S1: the quicklime is crushed and mixed with the first auxiliary agent to obtain a first mixture;

[0009] S2: The first mixture enters the primary digester, and the sprayed second additive is stirred with the first mixture for 15-20 minutes to obtain a primary digestion product;

[0010] S3: The primary digestion product enters the secondary digester, and the sprayed third auxiliary agent is stirred with the primary digestion product for 15-20 minutes to obtain the secondary digestion product;

[0011] S4: The secondary digestion product enters the tertiary digester and is stirred to obtain the tertiary digestion product;

[0012] S5: The tertiary digestion products are dried and air-selected to obtain calcium hydroxide.

[0013] The second auxiliary agent in step S2 is prepared by mixing one or more of ethanol, propanol, diethanolamine, triethanolamine, isopropanol, ethylene glycol, and glycerol with water. The concentration of the sprayed second auxiliary agent is 3%-6%.

[0014] The third auxiliary agent in step S3 is prepared by mixing sucrose and / or polyethylene glycol with water, and the concentration of the sprayed third auxiliary agent is 3%-6%.

[0015] In step S2, the weight ratio of the total amount of the second auxiliary agent sprayed to the first mixture or the weight ratio of the total amount of the third auxiliary agent sprayed to the primary digestion product is 0.9-1:1.

[0016] In the step S1, the weight ratio of quicklime to the first auxiliary agent is 1:0.004-0.006.

[0017] In step S1, the first auxiliary agent is one or more of fly ash, aluminum chloride, aluminum oxide, and quartz powder.

[0018] In the step S5, drying is performed to achieve a moisture content of less than 2%;

[0019] Air separation: if the 325 mesh screening rate is less than 85%, it will be crushed and then air separated.

[0020] The calcium hydroxide has a specific surface area of ​​40-50m 2 / g, pore volume is 0.20-0.27cm 3 / g, and the average pore size is 20-24nm.

[0021] Beneficial Effects

[0022] The invention adjusts the microstructure of calcium hydroxide, a calcium-based desulfurizer, by adding an auxiliary agent during the digestion process of quicklime, thereby increasing the specific surface area, the pore volume and the pore diameter, and having good fluidity and dispersibility, thereby reducing the diffusion resistance of gases such as SO2 and SO3 in the pores of the desulfurizer during the desulfurization process, thereby improving the desulfurization efficiency and utilization rate. DETAILED DESCRIPTION

[0023] The following examples are intended to illustrate the present invention rather than to further limit the present invention.

[0024] In the process of preparing highly active calcium hydroxide, if the raw material quicklime itself is of excellent quality, the reaction is easy to control and the loss of the obtained product is small. However, in actual production, in order to reduce the cost of raw materials as much as possible, it is more inclined to seek the reuse of solid waste resources. For example, when using industrial waste slag as quicklime as raw material, there is no doubt that the quality of the raw material quicklime is uneven. It is only the quicklime that is screened after the activity is tested to distinguish the quality. This greatly complicates the production process and is not conducive to actual production needs. How to truly realize the full utilization of solid waste resources and control the process is the goal.

[0025] The present invention provides a method for preparing highly active calcium hydroxide, comprising the following steps:

[0026] S1: The quicklime is crushed and mixed with the first auxiliary agent to obtain a first mixture.

[0027] Quicklime is used as raw material and can be crushed by a vertical crusher. The crushed quicklime is mixed with a first auxiliary agent. Preferably, the first auxiliary agent in step S1 is one or more of fly ash, aluminum chloride, aluminum oxide, and quartz powder.

[0028] The first auxiliary agent is premixed with quicklime to affect the surface activity of the quicklime. Furthermore, the weight ratio of quicklime to the first auxiliary agent is 1:0.004-0.006, so as to improve the pore characteristics and increase the specific surface area.

[0029] S2: The first mixture enters the primary digester, and the sprayed second auxiliary agent is stirred with the first mixture for 15-20 minutes to obtain a primary digestion product.

[0030] Preferably, the second auxiliary agent is prepared by mixing one or more of ethanol, propanol, diethanolamine, triethanolamine, isopropanol, ethylene glycol, glycerol and water, and the concentration of the sprayed second auxiliary agent is 3%-6%.

[0031] S3: The primary digestion product enters the secondary digester, and the sprayed third auxiliary agent is stirred with the primary digestion product for 15-20 minutes to obtain the secondary digestion product.

[0032] Although in theory, the conversion of CaO to Ca(OH)2 can be achieved by simply adding water, maximizing the conversion rate and improving the microstructure of the sulfur-fixing agent calcium hydroxide to enhance the desulfurization effect are closely related to the specific process. For example, when too much water is added, CaO soaking in water is not conducive to digestion, and will cause CaO to calcify in the water and form hard small spheres. In addition, adding water directly will also produce a large amount of hot steam and dust, which will block the exhaust pipe of the digester.

[0033] Therefore, in order to ensure a mild reaction and to regulate the microstructure of the product, such as specific surface area, pore volume, and pore size, a second or third auxiliary agent is added during the digestion process. The second or third auxiliary agent is sprayed onto the surface of the reactant to react. The reaction equation is CaO+H2O=Ca(OH)2.

[0034] Preferably, the third auxiliary agent is prepared from sucrose and / or polyethylene glycol and water, and the concentration of the sprayed third auxiliary agent is 3%-6%.

[0035] The second or third additive can be adsorbed on the surface of the digestion product particles, which can not only prevent the particles from growing, but also form a strong hydrogen bond with calcium hydroxide as an anchoring functional group, forming an anchoring point on the surface of the calcium hydroxide particles, effectively reducing the surface energy of the particles and preventing the agglomeration of tiny calcium hydroxide particles.

[0036] Moreover, in order to avoid adding too much water, the amount of water added is further controlled, and the weight ratio of the total amount of the second auxiliary agent sprayed in step S2 to the first mixture or the weight ratio of the total amount of the third auxiliary agent sprayed to the primary digestion product is 0.9-1:1.

[0037] S4: The secondary digestion product enters the tertiary digester and is stirred to obtain the tertiary digestion product.

[0038] The secondary digestion product completes most (70-80%) of the digestion reaction, and then enters the tertiary digester and is fully stirred to complete the remaining digestion.

[0039] In order to achieve process controllability, the first-stage digester in step S2 or the second-stage digester in step S3 or the third-stage digester in step S4 are arranged in sequence from high to low, wherein a spray system is provided on the top of the first-stage digester and the second-stage digester. The spray system consists of a plurality of multi-point spray heads to facilitate multi-point spraying, and the spraying amount is quantitatively controlled by PLC.

[0040] In addition, considering the effect of temperature on the digestion rate, further, the first-stage digester of step S2 or the second-stage digester of step S3 or the third-stage digester of step S4 is provided with an insulation layer inside, and the insulation temperature is 90-140°C, so as to shorten the digestion time and improve the digestion rate.

[0041] S5: The tertiary digestion products are dried and air-selected to obtain calcium hydroxide.

[0042] Specifically, a dryer can be used for drying. The dryer uses natural gas to heat thermal oil. The thermal oil and air exchange heat indirectly, and the hot air is used to dry the tertiary digestion product.

[0043] To ensure the quality of calcium hydroxide, preferably, in step S5, drying is performed to achieve a moisture content of less than 2%.

[0044] For air separation, if the 325-mesh screening rate is above 85%, it is considered qualified; if the 325-mesh screening rate is lower than 85%, it is crushed and then air separated.

[0045] The calcium hydroxide obtained by the preparation method provided by the present invention has a small particle size and a specific surface area of ​​40-50m 2 / g, pore volume is 0.20-0.27cm 3 / g, and the average pore size is 20-24nm.

[0046] The invention adjusts the microstructure of calcium hydroxide, a calcium-based desulfurizer, by adding an auxiliary agent during the digestion process of quicklime, thereby increasing the specific surface area, the pore volume and the pore diameter, and having good fluidity and dispersibility, thereby reducing the diffusion resistance of gases such as SO2 and SO3 in the pores of the desulfurizer during the desulfurization process, thereby improving the desulfurization efficiency and utilization rate.

[0047] Example 1

[0048] S1: The quicklime is crushed and mixed with the first auxiliary agent fly ash at a weight ratio of 1:0.005 to obtain a first mixture.

[0049] S2: The first mixture enters the primary digester, and the sprayed second auxiliary agent is stirred with the first mixture for 15 minutes to obtain a primary digestion product; wherein, the second auxiliary agent is an aqueous solution of ethanol, and the concentration of the sprayed second auxiliary agent is 4%; the insulation temperature is 140°C; the weight ratio of the total amount of the second auxiliary agent sprayed to the first mixture is 0.95:1.

[0050] S3: The primary digestion product enters the secondary digester, and the sprayed third auxiliary agent is stirred with the primary digestion product for 20 minutes to obtain the secondary digestion product;

[0051] The third auxiliary agent is an aqueous solution of polyethylene glycol, and the concentration of the sprayed third auxiliary agent is 6%; the insulation temperature is 130° C.; the weight ratio of the total amount of the sprayed third auxiliary agent to the primary digestion product is 0.9:1.

[0052] S4: The secondary digestion product enters the tertiary digester, the insulation temperature is 100°C, and it is fully stirred to obtain the tertiary digestion product.

[0053] S5: The tertiary digestion products are dried and air-selected to obtain calcium hydroxide.

[0054] Example 2

[0055] S1: The crushed quicklime is mixed with a first auxiliary agent, a composition of aluminum chloride and aluminum oxide, at a weight ratio of 1:0.006 to obtain a first mixture, wherein the weight ratio of aluminum chloride to aluminum oxide in the composition is 0.2:1.

[0056] S2: The first mixture enters the primary digester, and the sprayed second auxiliary agent is stirred with the first mixture for 20 minutes to obtain a primary digestion product; wherein, the second auxiliary agent is an aqueous solution of diethanolamine, and the concentration of the sprayed second auxiliary agent is 6%; the insulation temperature is 130°C; the weight ratio of the total amount of the second auxiliary agent sprayed to the first mixture is 1:1.

[0057] S3: The primary digestion product enters the secondary digester, and the sprayed third auxiliary agent is stirred with the primary digestion product for 15 minutes to obtain the secondary digestion product;

[0058] The third auxiliary agent is a sucrose aqueous solution, and the concentration of the sprayed third auxiliary agent is 5%; the insulation temperature is 120° C.; the weight ratio of the total amount of the sprayed third auxiliary agent to the primary digestion product is 0.95:1.

[0059] S4: The secondary digestion product enters the tertiary digester, the insulation temperature is 90°C, and it is fully stirred to obtain the tertiary digestion product.

[0060] S5: The tertiary digestion products are dried and air-selected to obtain calcium hydroxide.

[0061] Example 3

[0062] S1: The crushed quicklime is mixed with the first auxiliary agent quartz powder at a weight ratio of 1:0.004 to obtain a first mixture.

[0063] S2: The first mixture enters the primary digester, and the sprayed second auxiliary agent is stirred with the first mixture for 20 minutes to obtain a primary digestion product; wherein the second auxiliary agent is an aqueous solution of isopropanol and ethylene glycol, and the concentration of the sprayed second auxiliary agent is 3%, wherein the concentration ratio of isopropanol to ethylene glycol is 1:0.4; the insulation temperature is 135°C; the weight ratio of the total amount of the second auxiliary agent sprayed to the first mixture is 0.9:1.

[0064] S3: The primary digestion product enters the secondary digester, and the sprayed third auxiliary agent is stirred with the primary digestion product for 15 minutes to obtain the secondary digestion product;

[0065] The third auxiliary agent is an aqueous solution of sucrose and polyethylene glycol, and the concentration of the sprayed third auxiliary agent is 3%, wherein the concentration ratio of sucrose to polyethylene glycol is 0.5:1; the insulation temperature is 100°C; and the weight ratio of the total amount of the sprayed third auxiliary agent to the primary digestion product is 1:1.

[0066] S4: The secondary digestion product enters the tertiary digester, the insulation temperature is 95°C, and it is fully stirred to obtain the tertiary digestion product.

[0067] S5: The tertiary digestion products are dried and air-selected to obtain calcium hydroxide.

[0068] Example 4

[0069] S1: The crushed quicklime is mixed with a first auxiliary agent, a composition of aluminum chloride, fly ash and aluminum oxide at a weight ratio of 1:0.006 to obtain a first mixture, wherein the weight ratio of aluminum chloride, fly ash and aluminum oxide in the composition is 0.2:0.4:1.

[0070] S2: The first mixture enters the primary digester, and the sprayed second auxiliary agent is stirred with the first mixture for 20 minutes to obtain a primary digestion product; wherein, the second auxiliary agent is an aqueous solution of diethanolamine, and the concentration of the sprayed second auxiliary agent is 6%; the insulation temperature is 130°C; the weight ratio of the total amount of the second auxiliary agent sprayed to the first mixture is 1:1.

[0071] S3: The primary digestion product enters the secondary digester, and the sprayed third auxiliary agent is stirred with the primary digestion product for 15 minutes to obtain the secondary digestion product;

[0072] The third auxiliary agent is a sucrose aqueous solution, and the concentration of the sprayed third auxiliary agent is 5%; the insulation temperature is 120° C.; the weight ratio of the total amount of the sprayed third auxiliary agent to the primary digestion product is 0.95:1.

[0073] S4: The secondary digestion product enters the tertiary digester, the insulation temperature is 90°C, and it is fully stirred to obtain the tertiary digestion product.

[0074] S5: The tertiary digestion products are dried and air-selected to obtain calcium hydroxide.

[0075] Example 5

[0076] S1: The crushed quicklime is mixed with a first auxiliary agent, a composition of aluminum chloride, fly ash and aluminum oxide at a weight ratio of 1:0.006 to obtain a first mixture, wherein the weight ratio of aluminum chloride, fly ash and aluminum oxide in the composition is 0.2:0.4:1.

[0077] S2: The first mixture enters the primary digester, and the sprayed second auxiliary agent is stirred with the first mixture for 20 minutes to obtain a primary digestion product; wherein the second auxiliary agent is an aqueous solution of diethanolamine and glycerol, and the concentration of the sprayed second auxiliary agent is 6%, wherein the concentration ratio of diethanolamine to glycerol is 0.3:1; the insulation temperature is 130°C; the weight ratio of the total amount of the second auxiliary agent sprayed to the first mixture is 1:1.

[0078] S3: The primary digestion product enters the secondary digester, and the sprayed third auxiliary agent is stirred with the primary digestion product for 15 minutes to obtain the secondary digestion product;

[0079] The third auxiliary agent is a sucrose aqueous solution, and the concentration of the sprayed third auxiliary agent is 5%; the insulation temperature is 120° C.; the weight ratio of the total amount of the sprayed third auxiliary agent to the primary digestion product is 0.95:1.

[0080] S4: The secondary digestion product enters the tertiary digester, the insulation temperature is 90°C, and it is fully stirred to obtain the tertiary digestion product.

[0081] S5: The tertiary digestion products are dried and air-selected to obtain calcium hydroxide.

[0082] Comparative Example 1

[0083] S1: After the quicklime is crushed, it enters the primary digester, and the sprayed second auxiliary agent is stirred with the crushed quicklime for 20 minutes to obtain a primary digestion product; wherein the second auxiliary agent is an aqueous solution of diethanolamine and glycerol, and the concentration of the sprayed second auxiliary agent is 6%, wherein the concentration ratio of diethanolamine to glycerol is 0.3:1; the insulation temperature is 130°C; and the weight ratio of the total amount of the second auxiliary agent sprayed to the crushed quicklime is 1:1.

[0084] S2: The primary digestion product enters the secondary digester, and the sprayed third auxiliary agent is stirred with the primary digestion product for 15 minutes to obtain the secondary digestion product;

[0085] The third auxiliary agent is a sucrose aqueous solution, and the concentration of the sprayed third auxiliary agent is 5%; the insulation temperature is 120° C.; the weight ratio of the total amount of the sprayed third auxiliary agent to the primary digestion product is 0.95:1.

[0086] S3: The secondary digestion product enters the tertiary digester, the insulation temperature is 90°C, and it is fully stirred to obtain the tertiary digestion product.

[0087] S4: The tertiary digestion products are dried and air-selected to obtain calcium hydroxide.

[0088] Comparative Example 2

[0089] S1: The crushed quicklime is mixed with a first auxiliary agent, a composition of aluminum chloride, fly ash and aluminum oxide at a weight ratio of 1:0.006 to obtain a first mixture, wherein the weight ratio of aluminum chloride, fly ash and aluminum oxide in the composition is 0.2:0.4:1.

[0090] S2: The first mixture enters the primary digester, and the sprayed third auxiliary agent is stirred with the first mixture for 20 minutes to obtain a primary digestion product; wherein the third auxiliary agent is an aqueous solution of sucrose, and the concentration of the sprayed third auxiliary agent is 5%; the insulation temperature is 130°C; the weight ratio of the total amount of the sprayed third auxiliary agent to the first mixture is 1:1.

[0091] S3: The primary digestion product enters the secondary digester, and the sprayed second additive is stirred with the primary digestion product for 15 minutes to obtain the secondary digestion product;

[0092] The second auxiliary agent is an aqueous solution of diethanolamine and glycerol, and the concentration of the sprayed second auxiliary agent is 6%, wherein the concentration ratio of diethanolamine to glycerol is 0.3:1; the insulation temperature is 120°C; and the weight ratio of the total amount of the second auxiliary agent sprayed to the primary digestion product is 0.95:1.

[0093] S4: The secondary digestion product enters the tertiary digester, the insulation temperature is 90°C, and it is fully stirred to obtain the tertiary digestion product.

[0094] S5: The tertiary digestion products are dried and air-selected to obtain calcium hydroxide.

[0095] Experimental Results

[0096] The specific surface area, pore volume and pore size of the calcium hydroxide of Examples 1-3 and Comparative Examples 1 and 2 were tested. The results are shown in Table 1.

[0097] Table 1 Specific surface area, pore volume and pore size of calcium hydroxide

[0098]

[0099] It can be seen from Table 1 that, compared with Comparative Example 1 and Comparative Example 2, the calcium hydroxide of Examples 1-5 has a high specific surface area, a large pore volume and a pore diameter, indicating that the preparation method of the present application can regulate the microstructure of calcium hydroxide, increase the specific surface area of ​​calcium hydroxide, and increase the pore volume and pore diameter.

Claims

1. A method for preparing highly active calcium hydroxide, characterized in that: The following steps are involved: S1: the quicklime is crushed and mixed with the first auxiliary agent to obtain a first mixture; S2: The first mixture enters the primary digester, and the sprayed second additive is stirred with the first mixture for 15-20 minutes to obtain a primary digestion product; S3: The primary digestion product enters the secondary digester, and the sprayed third auxiliary agent is stirred with the primary digestion product for 15-20 minutes to obtain the secondary digestion product; S4: The secondary digestion product enters the tertiary digester and is stirred to obtain the tertiary digestion product; S5: The tertiary digestion products are dried and air-selected to obtain calcium hydroxide.

2. The preparation method of highly active calcium hydroxide according to claim 1, characterized in that The second auxiliary agent in step S2 is prepared by mixing one or more of ethanol, propanol, diethanolamine, triethanolamine, isopropanol, ethylene glycol, and glycerol with water. The concentration of the sprayed second auxiliary agent is 3%-6%.

3. The preparation method of highly active calcium hydroxide according to claim 1, characterized in that, The third auxiliary agent in step S3 is prepared by mixing sucrose and / or polyethylene glycol with water, and the concentration of the sprayed third auxiliary agent is 3%-6%.

4. The preparation method of highly active calcium hydroxide according to claim 1, characterized in that, In step S2, the weight ratio of the total amount of the second auxiliary agent sprayed to the first mixture or the weight ratio of the total amount of the third auxiliary agent sprayed to the primary digestion product is 0.9-1:

1.

5. The preparation method of highly active calcium hydroxide according to claim 1, characterized in that, In the step S1, the weight ratio of quicklime to the first auxiliary agent is 1:0.004-0.

006.

6. The method for preparing highly active calcium hydroxide according to claim 1, wherein In step S1, the first auxiliary agent is one or more of fly ash, aluminum chloride, aluminum oxide, and quartz powder.

7. The preparation method of highly active calcium hydroxide according to claim 1, characterized in that, In the step S5, drying is performed to achieve a moisture content of less than 2%; Air separation: if the 325 mesh screening rate is less than 85%, it will be crushed and then air separated.

8. The method for preparing highly active calcium hydroxide according to claim 1, wherein The calcium hydroxide has a specific surface area of ​​40-50m 2 / g, pore volume is 0.20-0.27cm 3 / g, and the average pore size is 20-24nm.

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