Slaked lime and manufacturing method thereof

Abstract

To provide slaked lime with easy industrial handling and having excellent gas absorption performance equal to or more than slaked lime derived from a lime cake derivation and a manufacturing method thereof.SOLUTION: A manufacturing method of slaked lime includes a digestion step of heating a mixed liquor involving water, quick lime, and an alcohol and reacting water and quick lime to prepare a digestion reaction liquid; an aging step of storing the digestion reaction liquid to obtain an aged digestion reaction liquid; a dehydration step of solid-liquid separation from the aged digestion reaction liquid to obtain a composition; and a drying step of drying the composition to obtain slaked lime. The slaked lime has a pore volume of 0.14-0.20 ml / g for pores with a pore size of 20-100 nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to slaked lime and a method for producing the same, and more particularly to slaked lime which is also useful as an acid gas absorbent and a method for producing the same. [Background technology]

[0002] Slaked lime is used in various industries as an exhaust gas treatment agent for hydrogen chloride, sulfur oxides, etc. For example, in waste incineration plants, slaked lime is used as an alkaline flue gas treatment agent to remove hydrogen chloride and sulfur oxides, which are acidic components in the flue gas.

[0003] It is known that in terms of the relationship between exhaust gas adsorption performance and the physical properties of slaked lime, the larger the specific surface area, the better the adsorption performance for hydrogen chloride (HCl), and the larger the pore volume, the better the adsorption performance for sulfur oxides (SO2) (Non-Patent Document 1).

[0004] Taking advantage of these properties of slaked lime, various technologies have been proposed to utilize it as highly reactive slaked lime. For example, the use of slaked lime derived from calcium carbonate sludge (hereinafter referred to as "lime cake"), a by-product of the sugar manufacturing process, has been proposed (Non-Patent Document 2). This lime cake has a large pore volume (hereinafter referred to as "effective pore volume") with a pore diameter in the range of 20 to 100 nm (0.145 cm). 3 / g) and has high exhaust gas adsorption capacity, so it is expected to be a highly reactive hydrated lime. In addition, in the production of highly reactive hydrated lime, it has been proposed to add water containing dissolved chemicals such as alcohols as extinguishing water to quicklime in order to increase the specific surface area of ​​the resulting hydrated lime (Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Satoshi Iwashita, "Effect of slaked water ratio on pore structure and SO2 adsorption characteristics of hydrated lime", Journal of the Society of Inorganic Materials, 14, 300-305 (2007) [Non-patent document 2] Masahiro Sato, "Development of a high-performance flue gas treatment agent from sugar manufacturing waste," Report of the Industrial Research Institute of Hokkaido Research Organization, No. 314, 25-33 (2015) Summary of the Invention [Problem to be solved by the invention]

[0006] The lime cake-derived slaked lime described in the above-mentioned Non-Patent Document 1 was of low purity and did not meet the JIS standard for industrial slaked lime. Furthermore, the particle diameter of lime cake (CaCO3) was small, at approximately 10 μm, making it difficult to handle during the manufacturing process, as powder would fly around in the baking furnace during the lime cake baking process and would form clumps during the slaked lime baking process, adhering to the inner walls of the equipment. Therefore, there was a need for slaked lime that was easy to handle industrially and had flue gas adsorption performance equal to or better than that of lime cake-derived slaked lime. Furthermore, in conventional methods for producing highly reactive slaked lime, when chemicals such as alcohols are added to increase the specific surface area, the resulting slaked lime contains residual alcohol, which results in residual chemical oxygen demand (hereinafter also referred to as "COD"), making it difficult to reduce the environmental impact. For this reason, there has been a demand for a method for producing slaked lime that does not contain residual COD and reduces the environmental impact.

[0007] As described above, the present invention provides slaked lime that is easy to handle industrially and has excellent gas adsorption performance equal to or better than that of slaked lime derived from lime cake, and a method for producing the same. The present invention also provides a method for producing slaked lime in which no COD remains in the slaked lime produced by the above method. [Means for solving the problem]

[0008] The present invention relates to the following. (1) A method for producing slaked lime, comprising: a slaking step of heating a mixed liquid containing water, quicklime, and alcohol to react the water and quicklime to prepare a slaking reaction liquid; a maturing step of storing the slaking reaction liquid to obtain a matured slaking reaction liquid; a dehydrating step of performing solid-liquid separation from the matured slaking reaction liquid to obtain a composition; and a drying step of drying the composition to obtain slaking lime, wherein the slaking lime has a pore volume of 0.14 to 0.20 ml / g in a pore diameter range of 20 to 100 nm. (2) The method for producing slaked lime according to (1), wherein the alcohol is a monohydric or dihydric alcohol. (3) The method for producing slaked lime according to (1), wherein the alcohol is diethylene glycol. (4) The method for producing slaked lime according to (1), wherein the aging step is carried out at 70°C or higher for 4 hours or longer. (5) The method for producing slaked lime according to (1), wherein the slaking step is carried out at 30°C or higher for 3 hours or more, and the aging step is carried out at 70°C or higher for 15 hours or more. (6) A method for producing slaked lime according to any one of (1) to (5), comprising a further slaked step of adding quicklime to the aged slaked reaction liquid and reacting it. (7) The method for producing slaked lime according to (6), wherein the additional slaking step is carried out at 20°C or higher for 1 hour or more. (8) The method for producing slaked lime according to any one of (1) to (7), wherein the composition obtained in the dehydration step is washed with wash water before being subjected to the drying step. (9) Slaked lime having a pore volume of 0.14 to 0.20 ml / g with a pore diameter in the range of 20 to 100 nm. (10) The specific surface area of ​​slaked lime is 10 to 40 m 2 / g (9). (11) The slaked lime according to (9) or (10), wherein the pore volume of the slaked lime is 0.1 to 0.4 ml / g. (12) The slaked lime according to any one of (9) to (11), wherein the variability index CV value of the slaked lime is 0.1 to 0.3. [Effects of the Invention]

[0009] According to the present invention, there are provided slaked lime which is easy to handle industrially and has excellent gas adsorption performance equal to or better than that of slaked lime derived from lime cake, and a method for producing the same. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a pore distribution diagram of Example 1-1, Example 1-2, Comparative Example 1-4, and Comparative Example 1-5. [Figure 2] Fig. 2A is a particle size distribution diagram for Example 1-1 and Comparative Example 1-4, and Fig. 2B is a particle size distribution diagram for Example 1-2 and Comparative Example 1-5. [Figure 3] FIG. 3 is a schematic diagram of the equipment used in the gas adsorption test. [Figure 4] Figures 4A and 4B show breakthrough curves (elapsed time and C / C) calculated from the measurement results of the inlet gas concentration (C) of 102 ppm and the outlet concentration (C). Figure 4A shows the results of a gas adsorption test performed at a constant temperature blower dryer temperature of 150°C, and Figure 4B shows the results of a gas adsorption test performed at a constant temperature blower dryer temperature of 170°C. [Figure 5] FIG. 5 is a diagram showing the results of calculating the usage ratio of each slaked lime when the usage amount of the special slaked lime is set to 100 from the time until breakthrough of each slaked lime shown in FIG. [Figure 6] FIG. 6 is a graph showing the amount of SO2 adsorbed per kg of slaked lime. [Figure 7] FIG. 7 is a flow diagram showing the production process of slaked lime when a primary alcohol is used. [Figure 8] FIG. 8 is a flow diagram showing the production process of slaked lime when a dihydric alcohol is used. [Figure 9] FIG. 9 is a calibration curve showing the relationship between COD and DEG concentration. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described below with reference to embodiments, but the present invention is not limited to the following embodiments.

[0012] [Slaked lime] The present invention relates to hydrated lime having a pore volume of 0.14 to 0.20 ml / g when the pore diameter is in the range of 20 to 100 nm. According to the above-mentioned invention, the slaked lime is easy to handle industrially and has excellent gas adsorption performance equal to or better than that of slaked lime derived from lime cake. In addition, in a preferred embodiment, it has the property of not leaving any residual COD. In a preferred embodiment, it is preferable that any one of the following conditions is satisfied. - Specific surface area of ​​slaked lime is 10 to 40m 2 / g. The pore volume of slaked lime is 0.1~0.4ml / g. The CV value of slaked lime is 0.1 to 0.3.

[0013] [Method for producing slaked lime] The present invention relates to a method for producing slaked lime. (a) a slaking step in which a mixed liquid containing water, quicklime, and alcohol is heated to react with the water and quicklime to prepare a slaking reaction liquid; (b) a maturation step of storing the digestion reaction solution to obtain a matured digestion reaction solution; (c) a dehydration step of performing solid-liquid separation from the aging digestion reaction liquid to obtain a composition; (iv) a drying step of drying the composition to obtain slaked lime. The slaked lime obtained by this method preferably has a pore volume of 0.14 to 0.20 ml / g for pores with diameters in the range of 20 to 100 nm.

[0014] According to the above-mentioned production method, slaked lime that is easy to handle industrially and has excellent gas adsorption performance equal to or better than that of slaked lime derived from lime cake can be obtained. Furthermore, according to the above-mentioned production method, no COD remains in the obtained slaked lime, thereby reducing the environmental load.

[0015] The alcohol used in the slaking step may be a monohydric or dihydric alcohol. As a first embodiment, a method for producing slaked lime using a monohydric alcohol will be described below.

[0016] (First embodiment: Method for producing slaked lime when primary alcohol is used) FIG. 7 is a flow chart showing the production of slaked lime when a primary alcohol is used. (a) Digestion process First, prepare a wet mixing tank. Add quicklime, isopropyl alcohol (hereinafter referred to as "IPA") as a primary alcohol, and extinguishing water to the prepared wet mixing tank. The wet mixing tank is not particularly limited and various types can be used. The quicklime is not particularly limited, and examples include lump quicklime obtained by calcining limestone, granular quicklime obtained by dry-crushing quicklime, soft-burned quicklime, and hard-burned quicklime. Quicklime can also be obtained by calcining slaked lime, and this can also be used. However, using limestone is more economical and industrially viable.

[0017] The wet mixing tank is then operated to heat the mixture, causing the water and quicklime to react and obtain a slaking reaction liquid. The heating conditions for the slaking process are preferably 30°C or higher for 3 hours or longer. If the heating temperature and heating time are below the above-mentioned lower limits, the desired effective pore volume cannot be obtained. The resulting slaking reaction liquid is then appropriately screened to remove any residue.

[0018] (b) About the aging process The resulting digestion reaction solution is stored to obtain a matured digestion reaction solution. The heating conditions in the maturation step are preferably 70°C or higher for 4 hours or longer. This is because if the maturation temperature and heating time are below the above-mentioned lower limit values, the desired effective pore volume cannot be obtained. The maturation temperature is more preferably 70°C or higher for 15 hours or longer.

[0019] (c) Dehydration process The composition is obtained by performing solid-liquid separation from the aging-digestion reaction liquid. The method for separating the solid and liquid from the aging-digestion reaction liquid in the dehydration step is not particularly limited, and various methods can be used.

[0020] (d) Drying process The obtained composition is dried. There are no particular limitations on the drying method in the drying step, and various methods such as using a dryer can be used. The drying temperature in the drying step is 100 to 400°C. If the drying temperature is less than 100°C, it will take a long time to dry, and if it exceeds 400°C, it is not economical. The drying temperature is preferably 200 to 400°C, more preferably 250 to 350°C, and even more preferably 280 to 320°C. In this embodiment, the water and alcohol are simultaneously dried using a dryer, significantly reducing the COD remaining in the slaked lime. Furthermore, the exhaust gas discharged in the drying process is sent to a distiller, where alcohol is distilled and recovered. During the distillation process, water is also recovered along with the alcohol, and this alcohol-distilled water can be recycled and reused as slaked lime water. This makes it possible to provide a method for producing slaked lime without loss of alcohol additives.

[0021] As described above, slaked lime is produced which has excellent gas adsorption performance, does not leave COD, and reduces the environmental load. The method for producing slaked lime may further include an additional digestion step described below as an optional step.

[0022] (e) Additional digestion process Quicklime may be further added to the aged slaked reaction liquid produced as described above and reacted with the slaked lime, because the additional slaked lime increases the effective pore volume compared to that of the slaked lime obtained in the above steps (a) to (d). The amount of quicklime added in the additional slaking step is 1 to 20 mass %, preferably 3 to 10 mass %, and more preferably 4 to 5 mass %, based on the total amount of quicklime reacted in the slaking step (a). The heating conditions in the additional digestion step are preferably 20° C. or higher for 1 hour or longer.

[0023] Although the present invention has been described using the first embodiment, the present invention is not limited to this and includes various modifications. A second embodiment will be described, focusing on the differences from the first embodiment.

[0024] (Second embodiment: Method for producing slaked lime when dihydric alcohol is used) FIG. 8 is a flow diagram showing the production process of slaked lime when a dihydric alcohol is used. (a) Digestion process In the first embodiment described above, a monohydric alcohol is used as the alcohol, but the alcohol is not limited to this, and a dihydric alcohol may also be used. The secondary alcohol is not particularly limited and various types can be used, but it is preferable to use diethylene glycol (hereinafter also referred to as "DEG"). (c) Dehydration process In the first embodiment described above, the composition (dehydrated product) obtained by solid-liquid separation from the aging digestion reaction liquid was directly subjected to the drying process. However, the composition may be washed with wash water before being subjected to the drying process. By washing the composition with wash water, even if an alcohol additive remains in the composition, the amount of alcohol remaining in the composition can be reduced by washing away the alcohol additive. Thereafter, a filtrate containing the alcohol additive and the wash water is recovered. The recovered filtrate can be recycled and reused as slaked water for quicklime. This makes it possible to provide a method for producing slaked lime without loss of alcohol additive.

[0025] [Other embodiments] Slaked lime is used as a carbon dioxide absorbent. For example, as a measure to reduce emissions of "non-energy-origin carbon dioxide," a method has been proposed in which slaked lime is added to carbon dioxide generated by a chemical reaction process of calcium carbonate, thereby suppressing carbon dioxide emissions and producing calcium carbonate (Japanese Patent Application Laid-Open Publication No. 2016-034606). Therefore, since the slaked lime of the present invention has excellent gas adsorption performance for acidic gases such as hydrogen chloride and sulfur oxides, it is expected to also have high gas adsorption performance for carbon dioxide, an acidic gas. [Example]

[0026] The present invention will be described in more detail below using examples, comparative examples and preparation examples, but the present invention is not limited to these examples.

[0027] (raw materials) The following raw materials were used in the test examples and preparation examples. Diethylene glycol: Kanto Chemical Co., Ltd., product name: "Diethylene glycol" Quicklime: Hokkaido Lime Chemical Co., Ltd., product name: "Special Quicklime" (Device) Gas adsorption equipment In the gas adsorption test, a gas adsorption apparatus as shown in FIG. 3 was used. The gas adsorption apparatus 1 (1A, 1B) includes a two-neck flask 6 having a top opening 61 and a side opening 62; a silicone tube 4A connected to a two-neck flask 6 via a side port 62; a filter holder funnel 2 for vacuum filtration (inner diameter 37 mm, capacity 110 ml, hereinafter also referred to as "column 2") connected to a two-neck flask 6 via an upper opening 61; Glass beads 3 (Toshin Riko, No. 1, size 0.991-1.397 mm) placed inside column 2; and a silicon tube 4B connected to the upper end of the column 2. Silicone tube 4A is stainless steel heat exchange tube 5A (heat transfer area 0.15m 2 ) to an SO2 gas supply device 9. The silicon tube 4B is connected in this order to a stainless steel heat exchange tube 5B, a T-tube, a gas detection tube 11 that detects gas branched from the T-tube, and a beaker 23 that may contain barium chloride 13. The gas adsorption apparatus 1 can supply SO2 gas at a set temperature into the two-neck flask 6 by operating the SO2 gas supply device 9. Furthermore, the gas that has passed through the column 2 reacts with barium chloride 13 placed in the beaker 23 and turns yellow, making it possible to recognize that the SO2 gas has circulated through the gas adsorption apparatus 1. After that, the valve of the T-tube can be opened as appropriate, and the SO2 concentration in the gas can be measured using the gas detector tube 11.

[0028] ·Constant temperature blower dryer Constant temperature blower dryer (EYELA WFO-520W, operating range 40-210°C)

[0029] (Test Example 1) 1. Sample Preparation The samples of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-8 were prepared by the following method.

[0030] (Example 1-1, Example 1-2) (1) 800 g of water and 8.0 g of DEG were added to a container to prepare digested water containing DEG. (2) A beaker (1 L) was prepared as a digestion reaction vessel. 808 g of digested water containing DEG and 50 g of quicklime were added to the beaker. (3) The beaker containing the digested water was placed in a water bath, and the digested water was digested at the digestion temperature and for the digestion time shown in Table 1A by stirring at 300 rpm using a stirring blade to obtain a reaction solution. (4) Next, the beaker containing the reaction solution obtained in (3) was placed in a water bath and further aged by keeping it at the aging temperature and aging time shown in Table 1A. (5) After the digestion reaction, the solid and liquid were separated using a Nutsche filter, and the filter cake was dried at 300°C. (6) After drying, the hydrated lime was crushed in a mortar. (7) Then, the particles were passed through a sieve to make them 150 μm or less.

[0031] (Examples 1-3, Comparative Examples 1-6) The same procedure as in Example 1-1 was carried out, except that in step (1), the water was changed from 800 g to 960 g, the DEG was changed from 8.0 g to 9.7 g, the slaking water in step (2) was changed from 808 g to 969.7 g, the quicklime was changed from 50 g to 60 g, the slaking temperature and slaking time in step (3) and the aging temperature and aging time in step (4) were changed as shown in Table 1A.

[0032] (Examples 1-4, Comparative Examples 1-8) The same procedure as in Example 1-1 was carried out, except that in step (1), the water was changed from 800 g to 900 g, the DEG was changed from 8.0 g to 28.8 g, the slaking water in step (2) was changed from 808 g to 928.8 g, the quicklime was changed from 50 g to 75 g, the slaking temperature and slaking time in step (3) and the aging temperature and aging time in step (4) were changed as shown in Table 1A.

[0033] (Examples 1-5 and 1-6) (1) 900 g of water and 28.8 g of DEG were added to a container to prepare digested water containing DEG. (2) A beaker (1 L) was prepared as a digestion reaction vessel. 928.8 g of digested water containing DEG and 75 g of quicklime were added to the beaker. (3) The beaker containing the digested water was placed in a water bath, and the digested water was digested at the digestion temperature and for the digestion time shown in Table 1B by stirring at 300 rpm using a stirring blade to obtain a reaction solution. (4) Next, the beaker containing the reaction solution obtained in (3) was placed in a water bath and further aged by keeping it warm under the aging temperature and aging time conditions shown in Table 1B. (5) 3.4 g of quicklime was added to the reaction solution obtained in (4), and the reaction solution was further heated in a water bath and further digested under the conditions of the digestion temperature and the digestion time shown in Table 1B. (6) After the digestion reaction, the solid and liquid were separated using a Nutsche filter, and the filter cake was dried at 300°C. (7) After drying, the hydrated lime was crushed in a mortar. (8) Then, the particles were passed through a sieve to make them 150 μm or less.

[0034] (Comparative Examples 1-1 to 1-5, and 1-7) The same procedure as in Example 1-1 was carried out, except that the digestion temperature and digestion time in step (3) and the aging temperature and aging time in step (4) were changed as shown in Table 1A.

[0035] 2. Evaluation of the physical properties of slaked lime (Specific surface area (BET method), pore volume (BJH method)) The specific surface area and pore volume of the obtained hydrated lime were measured using a specific surface area / pore distribution measuring device (Microtrack-Bel, BELSORP MINI X). The specific surface area was measured using the BET multipoint method. The pore volume was determined by the BJH method, where the cumulative pore volume of pores with diameters of 2.0 nm to 200 nm was used. (effective pore volume) Of the pore volumes determined by the BJH method, the cumulative pore volume of pores with diameters of 20 to 100 nm was taken as the effective pore volume. (Measurement of particle size distribution) Measurements were made using a laser diffraction particle size distribution analyzer (HELOS&RODOS, range width 0.5-175 μm) manufactured by Sympatec. (SEM observation) The surfaces of the obtained hydrated lime were observed using a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, model number "S-4800") The samples were Example 1-1 and Comparative Example 1-4.

[0036] The results are shown in Tables 1A, 1B, 1, 2A, and 2B. Table 1A shows the specific surface area, pore volume, and effective pore volume for the slaked limes obtained in Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-8, and Table 1B shows the specific surface area, pore volume, and effective pore volume for the slaked limes obtained in Examples 1-5 and 1-6.

[0037] [Table 1]

[0038] In Table 1A, a comparison of Example 1-1 and Comparative Example 1-3 shows that Comparative Example 1-3 had a digestion temperature of 65°C, which was lower than that of Example 1-1, and therefore had a lower effective pore volume. Furthermore, a comparison of Example 1-1 and Comparative Example 1-7 shows that Comparative Example 1-7 had the same digestion temperature, digestion time, and aging temperature as Example 1-1, but the aging time was 2 hours, which was shorter than that of Example 1-1. Therefore, it was found that when the digestion reaction was carried out at 72°C for 2 hours and then the temperature was maintained at 72°C for 4 hours, the effective pore volume was 0.14 ml / g or more.

[0039] Furthermore, in Table 1A, a comparison of Example 1-3 and Example 1-2 shows that the effective pore volume was almost the same when the digestion reaction at 72°C for 2 hours was followed by incubation (aging) at 72°C for 16 hours and when the digestion reaction at 72°C for 4 hours was followed by incubation (aging) at 72°C for 4 hours or more. Therefore, it was found that the effective pore volume was 0.14 ml / g or more when the digestion reaction at 72°C for 2 hours was followed by incubation (aging) at 72°C for 4 hours or more.

[0040] In Table 1A, a comparison of Examples 1-4 and Comparative Examples 1-8 reveals that the effective pore volume is 0.14 ml / g or more when the digestion reaction is carried out at 33°C for 3.5 hours and then maintained at 72°C for 19 hours.

[0041] In Tables 1A and 1B, a comparison between Examples 1-4 and 1-5 reveals that the effective pore volume can be increased to 0.16 ml / g or more by further adding quicklime after the aging process of the digested reaction liquid.

[0042] In Table 1B, a comparison of Examples 1-5 and 1-6 reveals that when quicklime was added after the aging step of the slaked reaction liquid and the slaked reaction was carried out for an additional 3 hours at 23°C, the effective pore volume became even larger, reaching 0.19 or more. This effective pore volume value was significantly larger than the effective pore volume of slaked lime according to the prior art, and was a surprising result that even those skilled in the art would not have predicted.

[0043] SEM observation revealed that in Example 1-1 and Comparative Example 1-4, relatively large hexagonal plate-shaped primary particles of hydrated lime measuring 1 to 5 μm and fine primary particles of about 50 nm were observed, with the majority of the particles being about 50 nm. It was believed that these fine particles contributed to the high specific surface area.

[0044] 1, comparing Examples 1-1 and 1-2 with Comparative Examples 1-4 and 1-5, the volume distribution of slaked lime of 30 to 40 nm increased by digesting at 72° C. for 2 hours and then incubating at 72° C. for 4 hours. Furthermore, in Example 1-2, the volume distribution of pore diameters of 100 nm or more decreased, and the shape of the graph was sharp.

[0045] In Figure 2, comparing Example 1-1 with Comparative Example 1-4, and Example 1-2 with Comparative Example 1-5, it was found that the particles of slaked lime became larger when digested at 72°C for 2 hours and then kept at 72°C for 4 hours.

[0046] (Test Example 2: Aging test by storing digestion reaction solution at room temperature) 1. Sample Preparation Examples 2-1, 2-2, and Comparative Example 2-1 were prepared by the following method.

[0047] Example 2-1 (1) 300 g of water and 3.5 g of DEG were added to a container to prepare digested water containing DEG. (2) A Dewar vessel (1 L) was prepared as a digestion reaction vessel. 303.5 g of digested water containing DEG and 50 g of quicklime were placed in the Dewar vessel. (3) Then, the mixture was digested for 2 hours while stirring at 300 rpm using a stirring blade. (4) After 2 hours of digestion, the digestion reaction solution was placed in a plastic bottle and stored at room temperature for 33 days. (5) The digestion reaction solution obtained in (4) was subjected to solid-liquid separation using a Nutsche separator and dried at 300°C. (6) After drying, the slaked lime was crushed in a mortar and passed through a sieve to make it 150 μm or less.

[0048] (Example 2-2) The same procedure as in Example 2-1 was carried out, except that in step (1), the water was changed from 300 g to 600 g, DEG was changed from 3.5 g to 5.0 g, the slaked water in step (2) was changed from 303.5 g to 605 g, quicklime was changed from 50 g to 100 g, and the 33 days in step (4) was changed to 6 days.

[0049] (Comparative Example 2-1) (1) 300 g of digested water and 3.5 g of DEG were added to a container to prepare digested water containing DEG. (2) A Dewar vessel (1 L) was used as a digestion reaction vessel. 303.5 g of digested water containing DEG and 50 g of quicklime were placed in the Dewar vessel. (3) Then, the mixture was digested for 2 hours while stirring at 300 rpm using a stirring blade. (4) After 2 hours of digestion, the resulting digestion reaction solution was subjected to solid-liquid separation using a Nutsche separator and dried at 100°C. (5) After drying, the slaked lime was crushed in a mortar and passed through a sieve to make it 150 μm or less.

[0050] 2. Evaluation of the physical properties of slaked lime (specific surface area, pore volume, effective pore volume) Measurement was carried out in the same manner as in Test Example 1.

[0051] The results are shown in Table 2.

[0052] [Table 2]

[0053] In Table 2, comparing Examples 2-1 and 2-2 with Comparative Example 2-1, it was found that when the digestion reaction liquid was stored at room temperature for 6 or 33 days, the effective pore volume of the obtained slaked lime increased compared to when the digestion reaction liquid was not stored. It was found that storing the digestion reaction liquid at room temperature for 6 days or more made it possible to obtain slaked lime with an effective pore volume of 0.14 ml / g or more.

[0054] (Test Example 3: Gas Adsorption Test) 1. Sample As samples, the slaked lime obtained in Example 1-1, Calbride (registered trademark) (Ube Material Industries, Ltd.), Tamakalk-ECO (registered trademark) (Okutama Kogyo Co., Ltd.), and Tokutokusen (Hokkaido Sekki Kako Co., Ltd., special number) were used. 2. Gas adsorption test (Gas adsorption test method) Figure 3 is a schematic diagram of the equipment used in the gas adsorption test. The following explanation will be made with reference to Figure 3 as needed. (1) A gas adsorption apparatus 1 (1A, 1B) shown in Fig. 3 was prepared. This gas adsorption apparatus 1 was placed in a constant temperature blower dryer 30 (EYELA WFO-520W, operating range 40 to 210°C). (2) 100 g of glass beads and approximately 1 g of sample (slaked lime) were added to a beaker and mixed thoroughly to prepare glass beads 3 with 0.67 to 0.68 g of slaked lime attached to the glass beads. (3) A stainless steel perforated plate 20 was placed at the bottom of the column, and untreated glass beads 22 were placed on top of it to a layer thickness of about 8 mm, and glass beads 3 with hydrated lime attached were then loaded into column 2. (4) The top of column 2 was then sealed with a silicone stopper, and silicone tube 4B was inserted into the top of column 2. A stainless steel heat exchange tube 5B, a T-tube, a gas detector tube 11 for detecting gas branched from the T-tube, and a beaker 23 equipped with barium chloride 13 for detecting SO2 gas (discoloration from blue to yellow) were connected in this order. A two-neck flask 6 was placed at the bottom of column 2. (5) By operating the SO2 gas supply device 9, SO2 gas (N2 base, 102 ppm) was introduced into the bottom of the column 2 at 1.0 L / min (linear velocity 16 mm / sec), and the time was measured with a stopwatch. The gas flowing into the column 2 was passed through a stainless steel heat exchange tube 5A (heat transfer area 0.15 m) in a constant temperature air blower dryer 30. 2 The exhaust gas was cooled by passing it through a stainless steel cooling pipe 5B outside the constant temperature blower dryer 30. (6) The time when the barium chloride 13 turned yellow was recorded. After that, the SO2 concentration in the exhaust gas was measured every few minutes using the gas detector tube 11.

[0055] (breakthrough curve) The inflow gas concentration (C0) was set to 102 ppm, and the concentration ratio (C / C0) was calculated from the measured exhaust SO2 concentration (C) and plotted against time.

[0056] (Calculation of the ratio of highly reactive slaked lime used) The amount of SO2 adsorption per 1 kg of each type of slaked lime was calculated as described below. The reciprocal of this is the amount of lime (kg) required to adsorb 1 mol of SO2 gas. The ratio of highly reactive slaked lime used was calculated as x in the following formula, assuming the amount of Tokutokusen used as 100. Amount of highly reactive slaked lime used: Amount of Tokujosen used = x:100

[0057] (length of adsorption band) The times at which C / C0 = 0.05 and 0.5 were read from the breakthrough curve in Figure 4 and calculated using (Equation 1). Adsorption zone length [mm] = 2 × packed bed length [mm] × (1 – breakthrough point [min] / C / C0 = 0.5 point [min]) (Equation 1)

[0058] (adsorption band ratio) For each slaked lime, the ratio to the length of the adsorption band in Example 1-1 was calculated.

[0059] (SO2 adsorption amount per 1 kg of slaked lime) If the time until the breakthrough point (C / C0 = 0.05) is defined as the breakthrough time, the amount of SO2 adsorbed per kg of slaked lime can be calculated using the following formula. Gas flow rate x breakthrough time x SO2 concentration ÷ 24 (L / mol, 20°C) ÷ hydrated lime beads (g) × 1,000 = adsorption amount (mol / kg)

[0060] The results are shown in Table 3 and Figures 4 to 6. Table 3 shows the adsorption band length and adsorption ratio of the sample obtained in the gas adsorption test.

[0061] [Table 3]

[0062] As shown in Figure 5, the usage ratio of slaked lime in Example 1-1 was reduced by 77% at 20°C, 82% at 150°C, and 84% at 170°C compared to Tokujosen. Furthermore, Example 1-1 had the lowest usage ratio of highly reactive slaked lime compared to other slaked limes at 20°C, 150°C, and 170°C. Therefore, the gas adsorption performance of the slaked lime obtained in Example 1-1 was superior to that of conventional highly reactive slaked limes such as Tokujosen, Calbride (registered trademark), and Tamacalc-ECO (registered trademark).

[0063] 6, Example 1-1 had better SO2 adsorption performance than other highly reactive hydrated limes at 20°C, 150°C, and 170°C. In particular, the SO2 adsorption performance at high temperature (170°C) was significantly better. From Table 1, the effective pore volume of Example 1-1 is 0.144 ml / g. Therefore, from the results of Table 3, it can be inferred that the hydrated limes obtained in Examples 1-2 to 1-6, 2-1, 2-2, and Preparation Example 3-2 described below, which have an effective pore volume of 0.14 ml / g or more, have excellent gas adsorption performance.

[0064] In Table 3, the shorter the adsorption band length, the thinner the slaked lime layer on the surface of the bag filter can be during industrial production. At all temperatures of 20°C, 150°C, and 170°C, the adsorption band length of Example 1-1 was the shortest compared to the other slaked limes. The temperature in the flue gas treatment equipment at an actual incineration facility is 150 to 170°C, and based on the results of the adsorption band length ratios at 150°C and 170°C in Table 3, it is estimated that Example 1-1 can reduce the pressure loss of the bag filter by approximately 20 to 50% compared to the other slaked limes.

[0065] (Test Example 4: Dehydrated cake washing) 1. Test Method (Example 4-1) (1) 600 g of water and 20 g of DEG were added to a container to prepare digested water containing DEG. (2) A Dewar vessel (1 L) was prepared as a digestion reaction vessel. 620 g of digested water containing DEG and 100 g of quicklime were placed in the Dewar vessel. (3) The mixture was then digested for 2 hours while stirring at 300 rpm using a stirring blade. (4) After 2 hours of digestion reaction, the resulting digestion reaction liquid was separated into solid and liquid using a Nutsche, and the cake was washed by spraying water onto it using a washing bottle while still in the suction state. (5) The filter cake obtained by solid-liquid separation was dried at 100°C. (6) After drying, the hydrated lime was crushed in a mortar. (7) Then, the particles were passed through a sieve to make them 150 μm or less.

[0066] (Example 4-2) The same procedure as in Example 4-1 was carried out, except that the amount of quicklime in step (2) was changed from 100 g to 50 g.

[0067] (Example 4-3) The same method as in Example 4-1 was used to prepare the product, except that the amount of DEG was changed from 20 g to 40 g.

[0068] (Comparative Example 4-1, Comparative Example 4-2) (1) 600 g of digested water and 20 g of DEG were added to a container to prepare digested water containing DEG. (2) A Dewar vessel (1 L) was prepared as a digestion reaction vessel. 620 g of digested water containing DEG and 100 g of quicklime were placed in the Dewar vessel. (3) The mixture was then digested for 2 hours while stirring at 300 rpm using a stirring blade. (4) After 2 hours of digestion, the resulting digestion reaction solution was subjected to solid-liquid separation using a Nutsche separator. (5) The filter cake obtained by solid-liquid separation was dried at 400°C. (6) After drying, the hydrated lime was crushed in a mortar. (7) Then, the particles were passed through a sieve to make them 150 μm or less.

[0069] 2. Evaluation Method (COD measurement) COD was determined by preparing leachates of the slaked lime obtained in Examples 4-1 to 4-3, Comparative Examples 4-1, and 4-2 in accordance with the method prescribed in Environment Agency Notification No. 13 of 1973, and by measuring the oxygen consumption by potassium permanganate (CODMn) at 17.100°C in accordance with JIS K 0102 "Testing Methods for Industrial Wastewater." (Creating a calibration curve) Six DEG aqueous solutions with different concentrations were prepared by mixing DEG with water, and the COD of each sample was measured. The COD versus DEG concentration was plotted to create a calibration curve (Figure 9). (Calculation of DEG concentration) DEG concentrations were calculated from the calibration curve in Figure 9 . (specific surface area, effective pore volume) Measurement was carried out in the same manner as in Test Example 1.

[0070] The results are shown in Table 4. Table 4 shows the amount of DEG recovered by washing the cake. The DEG loss in the table is the amount of DEG attached to the hydrated lime.

[0071] [Table 4]

[0072] From Table 4, it can be seen that the DEG loss in Examples 4-1, 4-2, and 4-3 was close to 0, and it is believed that DEG can be recovered by washing the cake. Comparing Examples 4-1 to 4-3 with Comparative Examples 4-1 and 4-2, there was no difference in the specific surface area depending on whether the cake was washed or not, and therefore it is believed that cake washing does not affect physical properties such as the specific surface area.

[0073] (Preparation example 1: quicklime particle size) 1. Sample Preparation (Preparation Example 1-1), (Preparation Example 1-2) The same operation as in Example 1-1 of Test Example 1 above was carried out, except that the raw material quicklime was passed through a sieve to adjust the particle size of the quicklime so as to obtain the particle size of the quicklime shown in Table 5.

[0074] 2. Evaluation of the physical properties of slaked lime (specific surface area, pore volume, effective pore volume) Measurement was carried out in the same manner as in Test Example 1.

[0075] The results are summarized in Table 5.

[0076] [Table 5]

[0077] The specific surface area, pore volume, and effective pore volume of hydrated lime when quicklime with a particle size of 0 to 2 mm was used were almost the same as when quicklime with a particle size of 2 to 5 mm was used.

[0078] (Preparation Example 2: Addition of diethylene glycol) 1. Sample Preparation (Preparation Example 2-1) In Comparative Example 1-5 of Test Example 1, the same procedure as in Comparative Example 1-5 was performed except that the amount of water in step (1) was changed from 800 g to 600 g, DEG was not added, and the digested water in step (2) was changed from 808 g to 600 g. (Preparation Example 2-2) The same procedure as in Comparative Example 1-5 of Test Example 1 was carried out. (Preparation Example 2-3) The same procedure as in Comparative Example 1-5 of Test Example 1 was carried out, except that the amount of DEG in step (1) was changed from 8.0 g to 40.0 g, and the amount of digested water in step (2) was changed from 808 g to 840 g.

[0079] 2. Evaluation of the physical properties of slaked lime (specific surface area, pore volume, effective pore volume) Measurement was carried out in the same manner as in Test Example 1.

[0080] The results are summarized in Table 6.

[0081] [Table 6]

[0082] The specific surface area of ​​slaked lime without DEG (0%) is 14.6m 2 / g, while the specific surface area of ​​slaked lime with a 1% DEG addition rate was 32.3 m 2 / g, the specific surface area of ​​5% slaked lime is 26.7m 2 / g. It was confirmed that the addition of DEG increases the specific surface area of ​​hydrated lime. There was no significant difference in the pore volume and effective pore volume between the presence and absence of DEG.

[0083] (Preparation example 3: drying temperature) 1. Sample Preparation (Preparation Example 3-1) (1) 600 g of water and 5.0 g of DEG were added to a container to prepare digested water containing DEG. (2) A Dewar vessel (1 L) was prepared as a digestion reaction vessel. 605 g of digested water containing DEG and 100 g of quicklime were placed in the Dewar vessel. (3) Then, the mixture was digested for 2 hours while stirring at 300 rpm using a stirring blade. (4) After 2 hours of digestion, the digestion reaction solution was placed in a plastic bottle and stored at room temperature for 6 days. (5) The digestion reaction solution obtained in (4) was subjected to solid-liquid separation using a Nutsche separator and dried at 200°C. (6) After drying, the slaked lime was crushed in a mortar and passed through a sieve to make it 150 μm or less.

[0084] (Preparation Example 3-2) The same procedure as in Preparation Example 3-1 was carried out, except that the drying temperature in step (5) was changed from 200°C to 300°C.

[0085] (Preparation Example 3-3) The same procedure as in Preparation Example 3-1 was carried out, except that the drying temperature in step (5) was changed from 200°C to 400°C.

[0086] 2. Evaluation of the physical properties of slaked lime (specific surface area, pore volume, effective pore volume) Measurement was carried out in the same manner as in Test Example 1.

[0087] The results are summarized in Table 7.

[0088] [Table 7]

[0089] Table 7 confirms that the pore volume increases as the drying temperature increases. The effective pore volume was highest when dried at 300°C.

[0090] (Preparation Example 4: Digestion reaction solution temperature and filterability) 1. Sample Preparation (Preparation Example 4-1) (1) 600 g of water and 4 g of DEG were added to a container to prepare digested water containing DEG. (2) A Dewar vessel (1 L) was prepared as a digestion reaction vessel. 604 g of digested water containing DEG and 100 g of quicklime (soft-burned quicklime with an activity of 180 mL / 10 min and a particle size of 0 to 2 mm) were placed in the Dewar vessel. (3) Then, the mixture was stirred and digested for 2 hours.

[0091] (Preparation Example 4-2) (1) 600 g of digested water and 7 g of DEG were added to a container to prepare digested water containing DEG. (2) A Dewar vessel (1 L) was prepared as a digestion reaction vessel. 607 g of digested water containing DEG and 100 g of quicklime (soft-burned quicklime with an activity of 174 mL / 10 min and a particle size of 0 to 2 mm) were placed in the Dewar vessel. (3) Then, the mixture was digested for 2 hours while stirring at 450 rpm using a stirring blade.

[0092] (Preparation Example 4-3) (1) 300 g of digested water and 3.5 g of DEG were added to a container to prepare digested water containing DEG. (2) A Dewar vessel (1 L) was prepared as a digestion reaction vessel. 303.5 g of digested water containing DEG and 50 g of quicklime (soft-burned quicklime with an activity of 174 mL / 10 min and a particle size of 0 to 2 mm) were placed in the Dewar vessel. (3) Then, the mixture was digested for 2 hours while stirring at 300 rpm using a stirring blade.

[0093] (Preparation Example 4-4) (1) 600 g of digested water and 5 g of DEG were added to a container to prepare digested water containing DEG. (2) A Dewar vessel (1 L) was prepared as a digestion reaction vessel. 605 g of digested water containing DEG and 100 g of quicklime (soft-burned quicklime with an activity of 180 mL / 10 min and a particle size of 2 to 5 mm) were placed in the Dewar vessel. (3) Then, the mixture was digested for 2 hours while stirring at 300 rpm using a stirring blade.

[0094] (Preparation Example 4-5) (1) 600 g of digested water and 20 g of DEG were added to a container to prepare digested water containing DEG. (2) A Dewar vessel (1 L) was prepared as a digestion reaction vessel. 620 g of digested water containing DEG and 100 g of quicklime (soft-burned quicklime with an activity of 110 mL / 10 min and a particle size of 0 to 2 mm) were placed in the Dewar vessel. (3) Then, the mixture was digested for 2 hours while stirring at 300 rpm using a stirring blade.

[0095] 2. Evaluation of filterability Filtration was performed using a porcelain Buchner funnel (hereinafter also referred to as "Nutsche") and 5A filter paper (110 mm), and suction was performed with a vacuum pump. Filterability was judged as "good" if approximately 300 ml of slurry poured into the funnel was filtered within 30 seconds, "poor" if it took more than 2 minutes, and "normal" otherwise.

[0096] The results obtained are summarized in Table 8.

[0097] [Table 8]

[0098] Comparing Preparation Example 4-4 with Preparation Examples 4-2 and 4-3, it was found that normal filtration was possible when the maximum temperature of the digestion reaction liquid was 73°C, but poor filterability was observed when the maximum temperature was 80°C and 92°C. In Preparation Example 4-2, the viscosity of the digestion reaction solution increased further at a maximum temperature of 92°C, and no movement was observed on the surface of the digestion reaction solution in the container, resulting in the stirring blades spinning freely, so the rotation speed was set to 450 rpm.In Preparation Example 4-1, the digestion reaction solution reached a maximum temperature of 93°C, and stirring was not possible even when the rotation speed was increased. From the above, it is presumed that in order to suppress the viscosity of the slaked lime slurry and ensure normal filtration, it is preferable to carry out slaking at a slaking reaction liquid temperature of 80°C or less. Preparation Example 4-5, which used hard-burned quicklime, had better filterability than Preparation Example 4-4, even though the maximum temperature of the slaked reaction liquid was 86°C. It is presumed that hard-burned quicklime has low activity and the particles of slaked lime produced are large, which is why the viscosity of the slaked lime slurry is low.

[0099] (Preparation Example 5: Water Ratio) 1. Sample Preparation (Preparation Example 5-1) (1) 600 g of digested water and 4 g of DEG were added to a container to prepare digested water containing DEG. (2) A Dewar vessel (1 L) was prepared as a digestion reaction vessel. 604 g of digested water containing DEG and 100 g of quicklime (activity 180 mL / 10 min, quicklime with a particle size of 0 to 2 mm) were added to the Dewar vessel. (3) Then, the mixture was digested for 2 hours while stirring at 300 rpm using a stirring blade.

[0100] (Preparation Example 5-2) (1) A Dewar vessel (1 L) was prepared as a digestion reaction vessel. 600 g of water and 50 g of quicklime (activity 180 mL / 10 min, quicklime with a particle size of 0 to 2 mm) were added to the Dewar vessel. (2) Then, the mixture was digested for 2 hours while stirring at 300 rpm using a stirring blade.

[0101] (Preparation Example 5-3) (1) 800 g of water and 8 g of DEG were added to a container to prepare digested water containing DEG. (2) A Dewar vessel (1 L) was prepared as a digestion reaction vessel. 808 g of digested water containing DEG and 50 g of quicklime (activity 180 mL / 10 min, quicklime with a particle size of 0 to 2 mm) were added to the Dewar vessel. (3) Then, the mixture was digested for 2 hours while stirring at 300 rpm using a stirring blade.

[0102] 2. Temperature measurement of digestion water The temperature of the digested water was measured using a thermometer (red liquid rod thermometer, 0–100°C). The water temperature immediately after the start of digestion was taken as the initial water temperature. The maximum temperature was the value at which the temperature of the digestion water was highest during the 2-hour digestion period.

[0103] The results are summarized in Table 9.

[0104] [Table 9]

[0105] The maximum temperature of the digestion reaction liquid was 93°C when the water ratio was 6, 73°C when the water ratio was 12, and 68°C when the water ratio was 16. This shows that the maximum temperature can be kept at 80°C or less when the water ratio is 12 or more. The results of Preparation Example 4 show that filterability is improved when the temperature of the digestion reaction liquid is 80°C or less, and therefore it is thought that filterability will be improved when the water ratio is 12 or more. [Industrial Applicability]

[0106] According to the present invention, there are provided slaked lime that is easy to handle industrially and has excellent gas adsorption performance equal to or better than that of slaked lime derived from lime cake, and a method for producing the same. The slaked lime with excellent gas adsorption performance according to the present invention can be used in smaller amounts than conventional slaked lime, which is expected to reduce industrial waste and carbon dioxide emissions during the production process and transportation.

[0107] 1(1A, 1B): Gas adsorption apparatus 2: Filter holder funnel for vacuum filtration (column) 3: Glass beads 4A, 4B: Silicone tube 5A, 5B: Stainless steel heat exchange tube 6: Two-neck flask 9: SO2 gas supply device 11: Gas detector tube 13: Barium chloride 20: Stainless steel strainer 22: Untreated glass beads 23: Beaker 30: Constant temperature air dryer 61: Upper entrance 61 62: Side entrance

Claims

1. a slaking step of heating a mixed liquid containing water, quicklime, and alcohol to react the water with the quicklime to prepare a slaking reaction liquid; a maturation step of storing the digestion reaction solution to obtain a matured digestion reaction solution; a dehydration step of performing solid-liquid separation from the aging digestion reaction liquid to obtain a composition; A method for producing slaked lime, comprising: a drying step of drying the composition to obtain slaked lime; The method for producing slaked lime, wherein the slaked lime has a pore volume of 0.14 to 0.20 ml / g in a pore diameter range of 20 to 100 nm.

2. 2. The method for producing slaked lime according to claim 1, wherein the alcohol is a monohydric or dihydric alcohol.

3. 2. The method for producing slaked lime according to claim 1, wherein the alcohol is diethylene glycol.

4. The method for producing slaked lime according to claim 1, wherein the aging step is carried out at 70°C or higher for 4 hours or longer.

5. The digestion step is carried out at 30° C. or higher for 3 hours or longer; The method for producing slaked lime according to claim 1, wherein the aging step is carried out at 70°C or higher for 15 hours or longer.

6. The method for producing slaked lime according to claim 1, further comprising a further slaking step of adding quicklime to the aging-slaking reaction liquid and reacting the quicklime.

7. The method for producing slaked lime according to claim 6, wherein the additional slaking step is carried out at 20°C or higher for 1 hour or longer.

8. The method for producing slaked lime according to claim 1, wherein the composition obtained in the dehydration step is washed with wash water before being subjected to the drying step.

9. Hydrated lime with a pore volume of 0.14 to 0.20 ml / g in the pore diameter range of 20 to 100 nm.

10. The specific surface area of ​​the slaked lime is 10 to 40 m 2 / g of slaked lime according to claim 9.

11. The slaked lime according to claim 9 or 10, wherein the pore volume of the slaked lime is 0.1 to 0.4 ml / g.

12. The slaked lime according to claim 9 or 10, wherein the variation index CV value of the slaked lime is 0.1 to 0.3.

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