A kind of preparation method of calcium hydroxide

Abstract

The present invention discloses a method for preparing calcium hydroxide. The method involves contacting quicklime with a digestion solution to conduct a digestion reaction. The digestion solution contains water and additives; the additives include an ionic surfactant, a nonionic surfactant, and a dispersant. The method for preparing highly active calcium hydroxide is simple, low-cost, and environmentally friendly. The resulting calcium hydroxide has a sulfur capacity of 80 mg / g or greater when reacting with sulfur dioxide, making it suitable for dry flue gas purification and other calcium hydroxide utilization applications.

Description

Technical Field

[0001] The invention relates to a preparation method of highly active calcium hydroxide, belonging to the technical field of gas pollution control. Background Art

[0002] Sulfur dioxide (SO2) emitted from industrial production processes is considered to be an important cause of environmental problems. There are many flue gas desulfurization (FGD) processes. The wet FGD process using limestone slurry as absorbent and the semi-dry FGD process using calcium hydroxide as absorbent are widely used due to their good operating stability and high desulfurization efficiency. However, for industrial equipment with low original SO2 emissions, such as coke oven flue gas, cement kiln, etc., the original SO2 emission concentration is less than 500mg / m 3 The investment and operating costs of these technologies are relatively high. Therefore, the advantages of the dry FGD process with direct flue injection are more prominent.

[0003] Currently, the desulfurization byproduct of the baking soda dry desulfurization process is a mixture of sodium sulfate, sodium sulfite, sodium carbonate, sodium chloride, and sodium fluoride. This is difficult to reuse and is easily soluble in water, which can easily pollute the environment. It is classified as general solid waste and difficult to dispose of in a compliant manner, and currently can only be piled up. Therefore, the development of a low-cost, high-efficiency dry desulfurization agent has become an urgent problem that needs to be solved.

[0004] Calcium-based desulfurizers are widely used due to their low price, wide resource availability, and alkaline properties. Calcium hydroxide has been proposed as a dry desulfurizer due to its more efficient deacidification performance, wide temperature adaptability, and relatively inert and easily handled by-products. Under dry flue gas desulfurization conditions, calcium hydroxide can directly react with SO2 in the flue gas to produce CaSO3 and CaSO4. However, the desulfurization products generated during the reaction can clog the pores on the surface of the calcium hydroxide particles, affecting Knudsen diffusion and resulting in very low calcium utilization.

[0005] In order to solve the above problems, the prior art generally enhances the reactivity and sulfur capacity of calcium-based desulfurizers by reducing the particle size of the absorbent and increasing its specific surface area and porosity. For example, Patent Document 1 discloses a method for preparing highly active nano calcium hydroxide, which uses a thermoreversible gel made of end-hydroxy polybutadiene and n-hexyl isocyanate as a crystallization medium for calcium hydroxide, and simultaneously adds stearate and urea to improve the crystal form of calcium hydroxide and provide surface properties of nano calcium hydroxide. Patent Document 2 discloses a process for preparing highly active anti-coagulation calcium hydroxide, which comprises crushing calcium oxide and subjecting it to multi-stage screening, and then subjecting it to multi-stage digestion, followed by filtering, dehydration, drying, and screening and filtering to obtain calcium hydroxide. Patent Document 3 discloses a method for preparing highly active calcium hydroxide, which comprises mixing quicklime with additives such as diethylene glycol, sucrose or n-butanol to digestion to prepare a calcium hydroxide slurry, which is then aged, filtered, dried, and powdered to obtain a specific surface area of ​​15-60 m 2 Patent Document 4 discloses an industrial preparation method for highly reactive nano calcium hydroxide powder, which includes limestone treatment and calcination, quicklime pressure digestion, and the final synthesis of nano calcium hydroxide. The obtained nano calcium hydroxide powder has a specific surface area of ​​not less than 50 m 2 / g. Patent Document 5 discloses a method for preparing nano-calcium hydroxide powder for accelerating flue gas desulfurization. Hexagonal boron nitride, calcium chloride, aluminum-magnesium hydrotalcite, sodium hydroxide, and an organic titanium catalyst are ultrasonically dissolved and mixed to produce saturated clear lime water. The nano-calcium hydroxide is then centrifugally washed and dried. Patent Document 6 discloses a method for preparing highly active calcium hydroxide. This method improves the desulfurization efficiency of calcium hydroxide by rationally using additives, controlling the water-cement ratio, and adjusting the additive dosage.

[0006] References:

[0007] Patent Document 1: CN111439768A

[0008] Patent Document 2: CN108911535A

[0009] Patent Document 3: CN112358205A

[0010] Patent Document 4: CN112174179A

[0011] Patent Document 5: CN112960684A

[0012] Patent Document 6: CN113800787A Summary of the Invention

[0013] Problems to be solved by the invention

[0014] The methods disclosed in the prior art still cannot meet the needs. For example, Patent Documents 1 to 6 have problems such as long production processes, complex processes, large amounts of chemical reagents used, high costs, difficulty in controlling the production process, and disadvantages for mass production.

[0015] Therefore, there is still an urgent need to develop a preparation method for highly active calcium hydroxide, which has a simple process, low cost, is environmentally friendly, and the obtained calcium hydroxide has a high sulfur capacity and can be used for dry flue gas purification.

[0016] Solutions for solving problems

[0017] In response to the above technical problems, the inventors conducted in-depth research and found that when performing the digestion reaction of quicklime, the combined use of specific types of additives in the digestion water can improve the sulfur capacity of the obtained calcium hydroxide and reduce costs, thereby completing the present invention.

[0018] Specifically, the present invention solves the technical problem to be solved by the present invention through the following solutions.

[0019] [1] A method for preparing calcium hydroxide, comprising:

[0020] Sludge step: contacting quicklime with a sludge solution to carry out a sludge reaction, wherein the sludge solution comprises water and an additive;

[0021] The additives include:

[0022] (a) ionic surfactants;

[0023] (b) a nonionic surfactant, wherein the nonionic surfactant is one or more selected from the group consisting of alcoholamine compounds, compounds having an ether bond and multiple hydroxyl groups, and fatty alcohol polyoxyethylene ethers; and

[0024] (c) a dispersant, wherein the dispersant is one or more selected from the group consisting of lignin sulfonate, alkali metal phosphate, naphthalenesulfonic acid formaldehyde condensate, and polyvinyl alcohol.

[0025] [2] The method according to [1], wherein the additive comprises, relative to the mass of water, 0.05 to 0.2 mass% of the ionic surfactant, 0.05 to 0.2 mass% of the nonionic surfactant, and 0.01 to 0.1 mass% of the dispersant.

[0026] [3] The method according to [1] or [2], wherein the additive further comprises (d) an inorganic base; the amount of the (d) inorganic base is preferably 0.05 to 0.2% by mass relative to the mass of water.

[0027] [4] The method according to [1] or [2], characterized in that the additive further contains (e) a calcium salt relative to the mass of water; the amount of the (e) calcium salt relative to the mass of water is preferably 0.02 to 0.1 mass%.

[0028] [5] The method according to [1] or [2], wherein the ionic surfactant is one or more selected from anionic surfactants and cationic surfactants; the anionic surfactant is preferably selected from alkyl sulfonates and alkyl sulfates, more preferably selected from sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, sodium dodecylsulfate, and sodium hexadecylsulfonate; the cationic surfactant is preferably a quaternary ammonium salt, more preferably selected from dodecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide.

[0029] [6] The method according to [1] or [2], wherein the alcoholamine compound is selected from triethanolamine, diethanolamine, ethanolamine, diisopropylethanolamine, 2-dibutylaminoethanol, and 2-diethylaminoethanol;

[0030] The compound having an ether bond and multiple hydroxyl groups is selected from diethylene glycol, triethylene glycol, and tetraethylene glycol;

[0031] The fatty alcohol polyoxyethylene ether has the following chemical formula:

[0032] RO(CH2CH2O) n H

[0033] Wherein R is a saturated or unsaturated C12-C18 hydrocarbon group, which is a straight-chain hydrocarbon group or a branched hydrocarbon group; n is an integer of 1 to 20.

[0034] [7] The method according to [1] or [2], wherein the lignin sulfonate is selected from sodium lignin sulfonate and potassium lignin sulfonate, and the metaphosphate is selected from sodium metaphosphate and potassium metaphosphate.

[0035] [8] The method according to [3], wherein the inorganic base is one or more selected from alkali metal hydroxides, preferably selected from sodium hydroxide and potassium hydroxide.

[0036] [9] The method according to [4] is characterized in that the calcium salt is one or more selected from water-soluble calcium salts, preferably one or more selected from calcium chloride, calcium gluconate, calcium dihydrogen phosphate, calcium nitrate, calcium bicarbonate, calcium bisulfate, calcium bisulfite, calcium hypochlorite, calcium bromide, calcium iodide, calcium chlorate, calcium perchlorate, and calcium permanganate.

[0037]

[10] The method according to [1] or [2], wherein the digestion reaction time is 0.5 to 2 hours; the digestion reaction temperature is above 70°C; the mass ratio of water to quicklime in the digestion solution is (0.8 to 8):1, preferably (1 to 7):1, more preferably (1.1 to 6):1, and further preferably (1.15 to 5.5):1.

[0038]

[11] The method according to [1] or [2], wherein the method further comprises a post-processing step, wherein the post-processing step comprises one or more of dehydration, drying, pulverization and screening.

[0039]

[12] Calcium hydroxide prepared by the method described in any one of [1] to

[11] , having a sulfur content of 80 mg / g or more.

[0040] Effects of the Invention

[0041] The preparation method of the highly active calcium hydroxide of the present invention is simple in process, low in cost, and environmentally friendly; the obtained calcium hydroxide has a high sulfur capacity and can be used in dry flue gas purification and other calcium hydroxide utilization fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the desulfurization system used in the sulfur capacity test in the Examples section. DETAILED DESCRIPTION

[0043] The following describes the technical features of the present invention in detail. The technical features described below are described based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples.

[0044] <Terms and Definitions>

[0045] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints A and B.

[0046] In this specification, the numerical range expressed using "above" or "below" means a numerical range including the number.

[0047] In this specification, the use of "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process.

[0048] In this specification, "optionally" or "optional" is used to indicate that certain substances, components, execution steps, application conditions and other factors are used or not used.

[0049] In this specification, the unit names used are all international standard unit names, and unless otherwise stated, the "%" used to describe solids or liquids means weight or mass percentage, and the "%" used to describe gases means volume or molar percentage.

[0050] In this specification, references to "preferred embodiments," "embodiments," and the like mean that the specific elements (e.g., features, structures, properties, and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein and may or may not be present in other embodiments. In addition, it should be understood that the elements may be combined in any suitable manner in the various embodiments.

[0051] An object of the present invention is to provide a method for preparing calcium hydroxide, comprising:

[0052] Sludge step: contacting quicklime with a sludge solution to carry out a sludge reaction, wherein the sludge solution comprises water and an additive;

[0053] The additives include:

[0054] (a) ionic surfactants;

[0055] (b) a nonionic surfactant, wherein the nonionic surfactant is one or more selected from the group consisting of alcoholamine compounds, compounds having an ether bond and multiple hydroxyl groups, and fatty alcohol polyoxyethylene ethers; and

[0056] (c) a dispersant, wherein the dispersant is one or more selected from the group consisting of lignin sulfonate, alkali metal phosphate, naphthalenesulfonic acid formaldehyde condensate, and polyvinyl alcohol.

[0057] In a preferred embodiment, the additive further comprises (d) an inorganic base.

[0058] In a preferred embodiment, the additive further comprises (e) a calcium salt.

[0059] The preparation method of calcium hydroxide of the present invention is described in detail below from aspects such as additives, digestion reaction conditions, and method steps.

[0060] additive

[0061] In this specification, unless otherwise specified, the term "additive" refers to the components in the digestion solution other than water, and the content of the additive or the components contained therein refers to the mass percentage relative to the water in the digestion solution.

[0062] The additives used in the preparation method of the present invention include (a) an ionic surfactant, (b) a nonionic surfactant, and (c) a dispersant, and optionally (d) an inorganic base and / or (e) a calcium salt. The individual components of the additives of the present invention are described in detail below.

[0063] (a) Ionic surfactants

[0064] In one embodiment, the ionic surfactant used in the present invention is one or more selected from anionic surfactants and cationic surfactants.

[0065] Preferably, the anionic surfactant is selected from alkyl sulfonates and alkyl sulfates; more preferably, the anionic surfactant is selected from sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, sodium lauryl sulfate, and sodium hexadecylsulfonate.

[0066] Preferably, the cationic surfactant is a quaternary ammonium salt; more preferably, it is selected from dodecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide.

[0067] In the present invention, the amount of the ionic surfactant used is 0.05 to 0.2 mass %, preferably 0.06 to 0.15 mass %, more preferably 0.07 to 0.12 mass %, and even more preferably 0.075 to 0.1 mass % relative to the mass of water.

[0068] (b) Nonionic surfactants

[0069] The nonionic surfactant used in the present invention is one or more selected from alcoholamine compounds, compounds having ether bonds and multiple hydroxyl groups, and fatty alcohol polyoxyethylene ethers.

[0070] Herein, "alcoholamine compound" refers to a compound having both a hydroxyl group and an amino group. Preferably, the alkanolamine compound can be selected from triethanolamine, diethanolamine, ethanolamine, diisopropylethanolamine, 2-dibutylaminoethanol, and 2-diethylaminoethanol.

[0071] Preferably, the compound having an ether bond and multiple hydroxyl groups can be selected from diethylene glycol, triethylene glycol, and tetraethylene glycol.

[0072] Fatty alcohol polyoxyethylene ether has the following chemical formula:

[0073] RO(CH2CH2O) n H

[0074] Wherein R is a saturated or unsaturated C12-C18 hydrocarbon group, which may be a straight-chain hydrocarbon group or a branched hydrocarbon group; n is an integer of 1-20.

[0075] Preferably, the fatty alcohol polyoxyethylene ether can be selected from AEO-3, AEO-7, AEO-9, and peregal.

[0076] In the present invention, the amount of the nonionic surfactant used is 0.05 to 0.2 mass %, preferably 0.06 to 0.15 mass %, more preferably 0.07 to 0.12 mass %, and even more preferably 0.075 to 0.1 mass %, relative to the mass of water.

[0077] (c) Dispersant

[0078] The dispersant used in the present invention is one or more selected from lignin sulfonate, alkali metal phosphate, naphthalenesulfonic acid formaldehyde condensate, and polyvinyl alcohol.

[0079] Preferably, the lignin sulfonate is selected from sodium lignin sulfonate and potassium lignin sulfonate.

[0080] Preferably, the metaphosphate is selected from sodium metaphosphate and potassium metaphosphate.

[0081] In the present invention, the amount of the dispersant used is 0.01-0.1 mass %, preferably 0.02-0.08 mass %, more preferably 0.03-0.07 mass %, and even more preferably 0.035-0.06 mass %, relative to the mass of water.

[0082] (d) Inorganic base

[0083] The inorganic base used in the present invention is one or more selected from alkali metal hydroxides, preferably selected from sodium hydroxide and potassium hydroxide.

[0084] In the present invention, the amount of the inorganic base used is 0.05 to 0.2 mass %, preferably 0.06 to 0.15 mass %, more preferably 0.07 to 0.12 mass %, and even more preferably 0.075 to 0.1 mass %, relative to the mass of water.

[0085] (e) Calcium salts

[0086] The calcium salt used in the present invention is one or more selected from water-soluble calcium salts.

[0087] Preferably, the calcium salt is one or more selected from calcium chloride, calcium gluconate, calcium dihydrogen phosphate, calcium nitrate, calcium bicarbonate, calcium bisulfate, calcium bisulfite, calcium hypochlorite, calcium bromide, calcium iodide, calcium chlorate, calcium perchlorate, and calcium permanganate.

[0088] In the present invention, the amount of the inorganic base used is 0.02 to 0.1 mass %, preferably 0.02 to 0.08 mass %, more preferably 0.03 to 0.07 mass %, and even more preferably 0.035 to 0.06 mass % relative to the mass of water.

[0089] Digestion reaction conditions

[0090] In one embodiment, in the preparation method of the present invention, the digestion reaction time is 0.5 to 2 hours, preferably 40 to 90 minutes, and more preferably 45 to 80 minutes.

[0091] In one embodiment, in the preparation method of the present invention, the digestion reaction temperature is 70° C. or higher, preferably 80° C. or higher. In one embodiment, the digestion reaction temperature is 120° C. or lower, preferably 110° C. or lower, more preferably 100° C. or lower.

[0092] In one embodiment, in the digestion step, the mass ratio of water to quicklime in the digestion solution (also referred to herein as "water-lime ratio") is (0.8-8):1, preferably (1-7):1, more preferably (1.1-6):1, and further preferably (1.15-5.5):1.

[0093] step

[0094] The preparation method of the present invention comprises the digestion step described above, and optionally comprises a post-processing step, wherein the post-processing step comprises one or more of dehydration, drying, pulverization and screening.

[0095] The above-mentioned post-processing steps can be carried out in a conventional manner in the art. For example, the dehydration step can be carried out using a dehydrating device such as a filter press, a centrifuge or a suction filter to preliminarily dehydrate the calcium hydroxide slurry obtained in the digestion step to reduce the water content of the slurry to less than 30%. The drying step can be carried out using equipment such as a hot air drying oven, a rotary dryer, or a spray dryer to dry the preliminarily dehydrated calcium hydroxide slurry to a water content of less than 5% after drying. The dried calcium hydroxide can be fed into a pulverizing device such as a ball mill, a Raymond mill, a micro powder mill, or a jet mill for final pulverization. After pulverization, the calcium hydroxide particle size can be sieved. The sieving step can be carried out using a sieve with a mesh size of 100 to 500.

[0096] The sulfur content of the calcium hydroxide prepared by the method of the present invention is 80 mg / g or more, preferably 85 mg / g or more.

[0097] In this specification, "sulfur capacity" is an indicator used to evaluate the desulfurization performance of calcium hydroxide, which represents the total amount of sulfur dioxide that can be removed by calcium hydroxide before it becomes ineffective in a fixed bed reactor at 300°C.

[0098] The sulfur capacity can be obtained as follows:

[0099] In a fixed-bed reactor, a simulated flue gas composed of N2, O2, and SO2 is passed through a calcium hydroxide sample to obtain a SO2 breakthrough curve (i.e., a curve showing the relationship between outlet SO2 concentration and time). When the desulfurization efficiency (i.e., SO2 outlet concentration / SO2 inlet concentration*100%) is 30%, the calcium hydroxide is deemed to have failed, and the test is terminated. Based on the SO2 breakthrough curve, the sulfur capacity of the calcium hydroxide is calculated according to the following formula (1):

[0100]

[0101] In formula (1): C0 is the SO2 inlet concentration, mg / m 3 ; C ei is the SO2 outlet concentration, mg / m 3 ;γ is sulfur capacity, 10 -6 mg / g; Q is the total gas volume, mL / min; t f is the desulfurization time, min; m0 is the mass of calcium hydroxide, g.

[0102] Specifically, the sulfur capacity can be measured by the method described in the Examples section below.

[0103] The present invention also correspondingly relates to calcium hydroxide prepared by the method of the present invention, and the use of the calcium hydroxide in dry flue gas purification.

[0104] Example

[0105] The present invention will be further described by enumerating specific examples of implementation below. It should be understood that these embodiments are only intended to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content described in the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope of the present invention.

[0106] Sulfur capacity test

[0107] The desulfurization performance of calcium hydroxide was tested in a quartz fixed bed reactor. Figure 1 As shown. The desulfurization temperature is 300℃, and the concentrations of SO2 and O2 at the outlet are measured using an infrared gas analyzer (flue gas analyzer). The amount of calcium hydroxide used is 0.3g, and the simulated flue gas consists of N2, O2, and SO2. The gas concentration is adjusted using a mass flow meter. The concentration of SO2 is 500ppm (1428.57mg / m 3 ), O2 concentration is 12%, N2 is the balance gas, and the total gas flow rate is 500mL / min. When the desulfurization efficiency (i.e., SO2 outlet concentration / SO2 inlet concentration*100%) reaches 30%, the calcium hydroxide is considered to have failed and the test is terminated. The sulfur capacity of calcium hydroxide is calculated according to the above formula (1) based on the SO2 breakthrough curve.

[0108] Specific surface area test

[0109] The specific surface area of ​​calcium hydroxide samples was tested using the BET method (static volumetric method). Calcium hydroxide was placed in a nitrogen environment, allowing physical adsorption to occur on the surface of the calcium hydroxide at liquid nitrogen temperature. The specific surface area of ​​the sample was calculated based on the BET equation by measuring the adsorption pressure and adsorbed gas flow rate at adsorption equilibrium.

[0110] The content of each additive shown in the following Tables 1 to 6 is a mass percentage relative to water.

[0111] Reference Examples R1 to R11

[0112] The corresponding additives were added to a 250 mL Erlenmeyer flask in the amounts shown in Table 1. 100 mL of deionized water was added to the flask, followed by 20 g of quicklime. The flask was then placed in a 90°C water bath and stirred for 60 minutes. The mixture was then filtered, dried for 12 hours, ground, and sieved (75 microns) to obtain finished calcium hydroxide. The sulfur capacity of each sample was determined according to the sulfur capacity test method described above, as shown in Table 1.

[0113] Table 1

[0114]

[0115] As can be seen from Table 1, when various additives are used alone, except for the case where triethanolamine is used in a very large amount (reference example R8), the sulfur capacity meets the requirements of actual industrial production, while the other additives cannot obtain satisfactory results.

[0116] Reference examples R12~R19

[0117] According to the amount shown in Table 2, calcium hydroxide was prepared in the same manner as in Reference Example R1 and the sulfur capacity was tested. The results are shown in Table 2.

[0118] Table 2

[0119]

[0120] As shown in Table 2, when (a) an ionic surfactant and (b) a nonionic surfactant are used in combination, a large amount of (b) the nonionic surfactant (reference examples R14, R18 and R19) must be used to obtain calcium hydroxide having a sulfur capacity that meets the requirements of actual industrial production.

[0121] However, nonionic surfactants such as triethanolamine and diethylene glycol are very expensive, so the formulations using large amounts of these nonionic surfactants are cost-unacceptable.

[0122] Examples E1 to E3 and Comparative Examples C1 to C5

[0123] According to the types and amounts of additives shown in Table 3, calcium hydroxide was prepared and tested for sulfur capacity in the same manner as in Reference Example R1. The results are shown in Table 3.

[0124] Table 3

[0125]

[0126] As shown in Table 3, when (a) an ionic surfactant, (b) a nonionic surfactant, and (c) a dispersant are used in combination, even when a very small amount of the nonionic surfactant (b) is used, the sulfur capacity can still meet practical requirements (Example E1). Furthermore, since the amount of the nonionic surfactant (b) used is small, the cost is also very advantageous.

[0127] When (a) an ionic surfactant, (b) a nonionic surfactant, (c) a dispersant, and (d) an inorganic base are used in combination, the sulfur capacity is significantly improved compared to the case of using (a) to (c) (Example E2). Furthermore, since only a small amount of inorganic base is required, it is also cost-effective.

[0128] When (a) an ionic surfactant, (b) a nonionic surfactant, (c) a dispersant, (d) an inorganic base, and (e) a calcium salt are used in combination, the sulfur capacity is further significantly improved compared to the case of using (a) to (d) (Example E3). Furthermore, since only a small amount of calcium salt is required, it is also cost-effective.

[0129] In contrast, in Comparative Examples C1 to C5 in which (a) to (c) were not used simultaneously, no satisfactory results were obtained regardless of whether (d) and (e) were used or not.

[0130] The experimental results in Table 3 show that the use of (a) to (c) as additives is essential for obtaining calcium hydroxide with a sulfur capacity that meets practical requirements and is cost-effective. Furthermore, the use of (d) or (e) in addition to (a) to (c) can further increase the sulfur capacity without significantly increasing the cost.

[0131] Examples E4 to E8

[0132] According to the types and amounts of additives shown in Table 4, calcium hydroxide was prepared and tested for sulfur capacity in the same manner as in Reference Example R1. The results are shown in Table 4.

[0133] Table 4

[0134]

[0135] As shown in Table 4, satisfactory results can be obtained when different (a) ionic surfactants, (b) nonionic surfactants and (c) dispersants are used.

[0136] Examples E9-E10

[0137] According to the types and amounts of additives shown in Table 5, except for changing the amount of quicklime so that the water-cement ratio is as shown in Table 5, calcium hydroxide was prepared and tested for sulfur capacity in the same manner as Reference Example R1. The results are shown in Table 5.

[0138] Table 5

[0139]

[0140] As can be seen from Table 5, when the additive formulation of the present invention is used, calcium hydroxide having a sulfur capacity that meets the requirements of actual industrial production can be obtained within a relatively wide range of water-cement ratios.

[0141] Reference Example R20~R21

[0142] According to the types and amounts of additives shown in Table 6, calcium hydroxide was prepared and tested for sulfur capacity in the same manner as Reference Example R1. The results are shown in Table 6. In addition, the specific surface area of ​​the calcium hydroxide obtained in Example E3 and Reference Examples R20 and R21 was tested using the method described above. The results are shown in Table 6.

[0143] Table 6

[0144]

[0145] It can be seen from Table 6 that calcium hydroxide with high sulfur capacity also has a high specific surface area, but a high specific surface area is not the decisive factor for high sulfur capacity.

[0146] Reference Example R22

[0147] Calcium hydroxide was prepared in the same manner as in Reference Example R20 using 0.017% hydrogen peroxide, 0.017% calcium stearate, and 0.017% ethanol relative to the mass of water as additives, and the sulfur capacity and specific surface area were tested. In addition, the specific surface area of ​​the calcium hydroxide obtained in Reference Example R2 was tested, and the results are shown in Table 7.

[0148] Table 7

[0149]

[0150] As can be seen from Table 7, the sulfur capacities of the calcium hydroxides obtained from Reference Example R2 and Reference Example R22 are not much different, but the specific surface areas are quite different, which also indicates that the specific surface area is not the decisive factor for sulfur capacity.

[0151] The additives used in Reference Example R22 are similar to those in Patent Document 6, and the sulfur capacity of the calcium hydroxide obtained therefrom is significantly lower than that of the present invention.

[0152] Industrial applicability

[0153] The preparation method of the present invention can be widely used in industry for the preparation of highly active calcium hydroxide, in particular for desulfurization.

Claims

1. A method for preparing calcium hydroxide, characterized in that, The method comprises: Sludge step: contacting quicklime with a sludge solution to carry out a sludge reaction, wherein the sludge solution comprises water and an additive; The additives include: (a) ionic surfactants; (b) a nonionic surfactant, wherein the nonionic surfactant is one or more selected from the group consisting of alcoholamine compounds, compounds having an ether bond and multiple hydroxyl groups, and fatty alcohol polyoxyethylene ethers; and (c) a dispersant, wherein the dispersant is one or more selected from the group consisting of lignin sulfonate, alkali metal phosphate, naphthalenesulfonic acid formaldehyde condensate, and polyvinyl alcohol; Wherein, relative to the mass of water, the additive comprises: 0.05-0.2 mass % of the ionic surfactant, 0.05-0.2 mass % of the nonionic surfactant, and 0.01-0.1 mass % of the dispersant.

2. The method according to claim 1, characterized in that The additive further comprises (d) an inorganic base.

3. The method according to claim 2, characterized in that The amount of the (d) inorganic base is 0.05 to 0.2% by mass relative to the mass of water.

4. The method according to claim 1 or 2, characterized in that The additive further comprises (e) a calcium salt relative to the mass of water.

5. The method according to claim 4, characterized in that The amount of the (e) calcium salt is 0.02 to 0.1% by mass relative to the mass of water.

6. The method according to claim 1 or 2, characterized in that The ionic surfactant is one or more selected from anionic surfactants and cationic surfactants.

7. The method according to claim 6, characterized in that The anionic surfactant is selected from alkyl sulfonates and alkyl sulfates.

8. The method according to claim 6, characterized in that The anionic surfactant is selected from sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, sodium lauryl sulfate, and sodium hexadecylsulfonate.

9. The method according to claim 6, characterized in that The cationic surfactant is a quaternary ammonium salt.

10. The method according to claim 6, characterized in that The cationic surfactant is selected from lauryltrimethylammonium bromide and hexadecyltrimethylammonium bromide.

11. The method according to claim 1 or 2, characterized in that The alcoholamine compound is selected from triethanolamine, diethanolamine, ethanolamine, diisopropylethanolamine, 2-dibutylaminoethanol, and 2-diethylaminoethanol; The compound having an ether bond and multiple hydroxyl groups is selected from diethylene glycol, triethylene glycol, and tetraethylene glycol; The fatty alcohol polyoxyethylene ether has the following chemical formula: RO(CH2CH2O) n H Wherein R is a saturated or unsaturated C12-C18 hydrocarbon group, which is a straight-chain hydrocarbon group or a branched hydrocarbon group; n is an integer of 1 to 20.

12. The method according to claim 1 or 2, characterized in that The lignin sulfonate is selected from sodium lignin sulfonate and potassium lignin sulfonate, and the alkali metal phosphate is selected from sodium metaphosphate and potassium metaphosphate.

13. The method according to claim 2, characterized in that The inorganic base is one or more selected from alkali metal hydroxides.

14. The method according to claim 2, characterized in that The inorganic base is selected from sodium hydroxide and potassium hydroxide.

15. The method according to claim 4, characterized in that The calcium salt is one or more selected from water-soluble calcium salts.

16. The method according to claim 4, characterized in that The calcium salt is one or more selected from calcium chloride, calcium gluconate, calcium dihydrogen phosphate, calcium nitrate, calcium bicarbonate, calcium bisulfate, calcium bisulfite, calcium hypochlorite, calcium bromide, calcium iodide, calcium chlorate, calcium perchlorate, and calcium permanganate.

17. The method according to claim 1 or 2, characterized in that The digestion reaction time is 0.5 to 2 hours; the digestion reaction temperature is above 70° C.; and the mass ratio of water to quicklime in the digestion solution is (0.8 to 8):

1.

18. The method according to claim 17, characterized in that The mass ratio of water to quicklime in the digestion solution is (1-7):

1.

19. The method according to claim 18, characterized in that The mass ratio of water to quicklime in the digestion solution is (1.1~6):

1.

20. The method according to claim 19, characterized in that The mass ratio of water to quicklime in the digestion solution is (1.15~5.5):

1.

21. The method according to claim 1 or 2, characterized in that The method further comprises a post-processing step comprising one or more of dehydration, drying, pulverization and screening.

22. The calcium hydroxide prepared by the method according to any one of claims 1 to 21, wherein the sulfur content is more than 80 mg / g.

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