KR101297988B1 - A method of high deusity calcium hydroxide with high specific surface area - Google Patents

Abstract

PURPOSE: A manufacturing method of high concentrated liquid-phased calcium hydroxide is provided to produce high concentrated liquid-phased calcium hydroxide with high specific surface area for maximizing the removal efficiency of the exhaust gas. CONSTITUTION: A manufacturing method of high concentrated liquid-phased calcium hydroxide with high specific surface area comprises the steps of: mixing 0.5-3 by weight of citric acid with 400-600 by weight of water based on 100 by weight of quick lime and dissolving; performing the hydration reaction by injecting 100 parts by weight of quick lime to the solution of the previous step and stirring the quick lime added solution for 30-60mins, and eliminating impurities through a screen with 40-70 mesh and dehydrating to produce calcium hydroxide cake with water content of 40-60% after finishing the hydration reaction. The calcium hydroxide cake has 40-60% by weight of soil content by injecting 1.0-3.0 by weight of acrylate dispersing agent based on 100 by weight of calcium hydroxide solid content. By adding the grinding process of attrition mill or disc mill, 500 parts by weight of zirconia with the vidro size of 0.4-1.2mm is used based on 100 parts by weight of quick lime to increase specific surface area. [Reference numerals] (AA) Wet hydration; (BB) Dry hydration

Description

A method of high deusity calcium hydroxide with high specific surface area

The present invention relates to a method for producing high-concentration liquid lime with a high specific surface area, and more particularly, by increasing the specific surface area during quicklime hydration, adding a dispersant, and wet grinding to fine grain size, thereby obtaining a slurry having a high solid content. The present invention relates to a method for producing slaked lime in liquid form, which increases the efficiency of removing exhaust gas.

The CO ₂ generated by the burning of fossil fuels causes many problems due to acid rain, deterioration of air quality, photochemical smog, etc., and strictly regulates the emission of pollutants. In order to remove such pollutants, flue gas desulfurization process is generally performed. This process is an essential process for efficiently removing sulfur oxides and other acid gas compounds generated during combustion and chemical processes, including thermal power plants. It is applied to various industrial discharge facilities. Currently widely used desulfurization systems include lime and gypsum using calcium carbonate (CaCO ₃ ), alkali absorption using caustic soda (NaOH) and magnesium hydroxide (Mg (OH) ₂ ), and lime (Ca (OH) ₂ ) It is divided into slurry wet desulfurization method, semi-dry desulfurization process of mixing and spraying slaked lime and water, and dry desulfurization method of adding alkaline powder. In particular, the wet desulfurization process of spraying the slurry of slaked lime has been evaluated as an economical flue gas desulfurization process using the advantages of low initial investment cost and relatively inexpensive slaked lime as raw materials because the reaction equipment is medium and small.

As mentioned above, slaked lime used for exhaust gas and water treatment is largely divided into dry and wet forms, but the conventional manufacturing method is a method of simply mixing water and additives during the hydration reaction, and there is no special particle size control. Porosity falls and only a certain specific surface area is improved. Accordingly, the collecting power of the harmful gas is somewhat higher than that of the conventional lime, but due to the large particle size distribution, the reaction area is lowered, the concentration of the harmful gas is high, or the removal efficiency in the continuous process is low, Responsiveness has not reached a satisfactory level.

In the case of conventional dry-type slaked lime, it is possible to manufacture slaked lime with an improved porous specific surface area by using additives, but simple grinding is possible through a mill such as a ball mill or a raymond mill. As a result, products having a large particle distribution of 325 mesh (43 μm) or more are being produced. In addition, the particle size control is difficult due to the coagulation phenomenon and the simultaneous reaction by the temperature rises to 200 ~ 300 ℃ during the hydration reaction. Therefore, the particle size of the slaked lime produced by the dry method is about 10 ~ 20㎛ coarse particles, there is a problem that the removal efficiency is significantly lowered when a large incineration facility and the concentration of the exhaust gas to be removed is high.

On the other hand, when hydrated lime is produced by liquid hydration method, it is possible to control the particle size smaller than the dry method because of low temperature hydration, but it is difficult to produce products with solid content of 20% or more due to the decrease in production yield and characteristics of hydrated lime. Constraints arise during transportation, storage, and use. In addition, although it has a small particle distribution of 7 ~ 10㎛ compared to the production of dry lime, it is difficult to control the concentration, due to the rather large particle distribution, the removal efficiency is limited, there is a large difference in hydration, reactivity according to activity However, due to the low solids content of less than 20% and high viscosity, it is difficult to transport and store. In addition, since it does not contain an additive dispersant, when dilution is used, sedimentation stability is lowered, and due to the limitation of solid content, there is a difficulty in application in the case of a large amount of exhaust gas exhaust facilities.

In order to solve the above problems, in the name of the applicant, registered as a patent 10-0320244 for the manufacturing method of high active lime with a large specific surface area by adding an additive, but is manufactured in the form of powder, semi-dry, wet incinerator When used for the removal of exhaust gas, the sedimentation rate is fast and there is a problem of small reaction surface area. To compensate for this and to increase the effect, a dispersant is added to control the particle size and concentration, and the reaction area and the specific surface area are simultaneously used. In order to increase, by adding a dispersant of the acrylate (-[CH2 = CHCOOX] _n- , X: Na, K, Ca, etc.) system to secure sedimentation stability, finer particle size, enlarge the reaction area, There is a need to maximize the removal efficiency of the exhaust gas.

The present invention aims to solve the problems of the prior art as described above and to provide a method for producing liquid lime having a high specific surface area and high concentration so as to maximize the removal efficiency of the exhaust gas when used for exhaust gas discharge.

In order to accomplish the object of the present invention as described above,

Dissolving by adding 0.5 to 3 parts by weight of citric acid to 400 to 600 parts by weight of water based on 100 parts by weight of quicklime (S1);

Step (S2) after the step (S1) to add 100 parts by weight of quicklime to hydration reaction;

Removing the impurities after the completion of the hydration reaction and dehydrating to prepare a slaked lime cake having a water content of 40 to 60% (S3); And

A high concentration liquid phase having a high specific surface area, comprising the step (S4) of adding 1.0 to 3.0 parts by weight of an acrylate dispersant to 100 parts by weight of the slaked lime solids in the step (S3) to have 40 to 60% solids. Provided is a method for preparing slaked lime.

The present invention also relates to

100 parts by weight of quicklime, dissolving 0.5 to 3.0 parts by weight of citric acid in 40 to 120 parts by weight of water (SS1);

Preparing 100 parts by weight of quicklime after the step (SS1) simultaneously with the lysate and the hydration reactor to produce a hydrated lime powder having a specific surface area improved through a hydration reaction (SS2);

Step 1 to 3 parts by weight of 70 to 140 parts by weight of water and acrylate dispersant based on 100 parts by weight of solid content of 100 parts by weight of the slaked lime powder in step (SS2) to give a solid content of the slurry of 40 to 60 (SS3 Provided is a method for producing high concentration liquid calcined lime, which has a high specific surface area.

In the above, the specific surface area may be further improved by adding a grinding process after steps S4 and SS3, and in this case, it is preferable to use zirconia having a size of 0.4 to 1.2 mm.

In addition, the hydration reaction in the step (S2) is preferably carried out for 30 to 60 minutes, the impurity removal in the step (S3) is preferably carried out through a screen of 40 to 70 mesh.

According to the present invention, in the preparation of the liquid lime, the mixed liquid of the additives during the hydration reaction process, the dry and wet manufacturing method was possible to produce a liquid form of lime having a high specific surface area of 35 ~ 45㎡ / g. As a result of adding and grinding the dispersant and controlling the particle size to 2 to 3 µm, the reaction area was improved by 2 times or more, and the specific surface area was further increased by 10 to 15 m 2 / g through the grinding process. In addition, the viscosity, sedimentation stability and fluidity of the acrylate dispersant were maintained stably, and the solid content was increased to 40 to 60%, thus reducing the transportation cost and allowing flexible use regardless of the form of the incineration plant. It is expected to produce high density liquid lime with high specific surface area with excellent gas removal efficiency, and its effect as a harmful gas remover in environmental field.

1 is a manufacturing process chart of the method for producing liquid lime having a high specific surface area according to the present invention.
2 is a scanning electron microscope (SEM) photograph of quicklime according to firing conditions according to the present invention.
Figure 3 is a hydrated lime scanning electron microscope (SEM) photograph according to the present invention.
Figure 4 is a step-by-step limestone particle size distribution picture in accordance with the present invention.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

In the present invention, after adding and dissolving 0.5 to 3 parts by weight of citric acid in water corresponding to 400 to 600 parts by weight relative to 100 parts by weight of quicklime, 100 parts by weight of quicklime is added, and the active lime is added and stirred for 30 to 60 minutes. , Hydration reaction. If the reaction time is short, the unreacted quicklime is present and the hydration reaction is not completed. If the reaction time is over 60 minutes, the reaction is terminated, and the above becomes uneconomical. When the hydration reaction is completed, the impurities of the uncalcined substance are removed through the 40 ~ 70mesh, preferably 60mesh (279㎛) screen, which is the optimum condition for calcification, and the purity of hydrated lime is improved. After preparing 60% of the slaked lime cake, 1.0-3.0% of the acrylate dispersant was added to prepare a Sorcerous ash slurry having 40 to 60wt% solids. If the water is 400 parts by weight or less, the viscosity is high, the slurry is not slurried, and if it is 600 parts by weight or more, the reactivity (hydration reaction) is lowered, so as to add water, citric acid is 0.5 or less, the specific surface area does not increase More than 3, so it is uneconomical because of excessive reactivity and may be added in the above range.

In the present invention, after adding and dissolving 0.5 to 3.0 parts by weight of citric acid in water corresponding to 40 to 120 parts by weight relative to 100 parts by weight of quicklime, quick lime is added to a high activity and simultaneously hydrated in a hydrator. In order to improve the primary specific surface area through the production of slaked lime powder and the like, and to add water to the powdered slaked lime, 1.0 to 3.0 parts by weight of the acrylate dispersant compared to 100 parts by weight of the solid content in the slurry production The slaked lime slurry is prepared by the dry hydration method, which is maintained and the solid content of the final slurry is 40-60%. In order to further improve the particle size control of the primary slurry specific surface area improved lime slurry produced by the wet and dry method, it is ground using an Attrition Mill or a Disc Mill. If some of the aggregates formed between the slaked lime remains, it is necessary to solve these problems through the wet crushing is less reactive. At the time of the operation of the Attrition Mill, the bead uses zirconia, which is advantageous for producing fine particles, in a size of 0.4 to 1.2 mm, which is preferable for producing fine particles, and the filling ratio of the beads is 500 parts by weight based on 100 parts by weight of quicklime. desirable. 1.0-3.0 parts by weight of acrylate dispersant is added to 100 parts by weight of quicklime and ground for 15 to 30 minutes to strengthen the grinding performance, manufacture high solids, maintain viscosity, and settle stability. There is. In this way, by adjusting specific surface area, particle size and concentration of solids, it is possible to manufacture calcined lime suitable for the removal of harmful gas from incineration facilities, as well as transportation cost and tank storage efficiency, which are disadvantages of liquid form of slaked lime. Through this, it is possible to solve the problems of the prior art.

First, in the present invention, one of the important factors for increasing the specific surface area is the activity of quicklime. Quicklime is prepared by decarburizing limestone (CaCO ₃ ) by adding a heat source at 900 ~ 1,200 ℃. Firing method using fluid fuel (Bunker C oil, refined oil, diesel) receives only the amount of heat needed to remove CO _{2 because} it is fired through indirect heat, and does not receive heat directly on the limestone surface. to be. On the other hand, in the case of a kiln using solid fuel, the direct contact method is used, so in the case of the direct contact surface, heat is locally received, and the surface of quicklime melts or the activity becomes relatively low due to crystal growth. Occurs. Low activity quicklime decreases the reactivity with water or additives during the hydration reaction, and the complete surface is not easily hydrated, thus remaining as an unreacted quicklime, causing lower specific surface area. On the other hand, the surface structure of the hydrated lime prepared in the high activity quicklime shown in Figure 2 has a high specific surface area compared to the low-active quicklime as the pore and uniform small particles are aggregated to have a porosity and a high specific surface area, It can be easily predicted that the contact area with the emission gas is large, and the specific surface area according to the activity of quicklime is shown in Table 1 below.

Therefore, as a method for obtaining highly reactive liquid lime, 250-400 (4N-HCl 50g method) of quicklime having a high activity value is used as a raw material and 400 to 600 parts by weight of citric acid (Citric) acid) dissolve 0.5 to 3.0 parts by weight in 100 parts by weight of quicklime in advance, add quicklime, proceed with a hydration reaction at a speed of 250 rpm for 30 to 60 minutes, and when the hydration reaction is completed, 60mesh (279㎛) The screen is used to remove impurities, thereby improving the purity of slaked lime, and dehydrating to prepare a hydrated lime cake of 40 to 60%, and adding 1.0 to 3.0 parts by weight of an acrylate dispersant to 100 parts by weight of solids. , Wet hydration method for preparing a slurry of hydrated lime with 40 to 60% solids, and another method by adding 0.5 to 3.0 parts by weight of citric acid to 100 parts by weight of quicklime, dissolved in 100 to 100 parts by weight of quicklime , Activity By adding high quicklime to the hydrator simultaneously, improving the primary specific surface area through the production of hydrated lime powder and the like, and adding water to the prepared powdered lime, the acrylate dispersant in the preparation of slurry 100 1.0 to 3.0 parts by weight relative to parts by weight to maintain the viscosity to prepare a slaked lime slurry by dry hydration method having a solid content of the final slurry of 40 to 60%. In order to control the particle size of the slurry having improved primary specific surface area by using the wet or dry method, an Attrition Mill or a Disk Mill is used to grind the beads. Bead) was used in the zirconia 0.4 ~ 1.2mm advantageous for the production of hydrated lime, the filling ratio of the beads was filled 500 parts by weight compared to 100 parts by weight of quicklime. 1.0 to 3.0 parts by weight of acrylate dispersant is added to 100 parts by weight of quicklime, and ground for 15 to 30 minutes in order to strengthen the grinding performance, to prepare a solid, to maintain viscosity, and to settle stability.

In the above wet grinding, the particle size of calcium hydroxide is controlled by using an Attrition Mill or a Disk Mill. Another reason for the use of attrition mills or disc mills for wet grinding is that the method of preparing slaked lime slurry of this method is characterized by coarse particle size and large particle size distribution in areas where the flow velocity is significantly reduced in the slurry introduction tube and nozzle area in semi-dry desulfurization. This is because it not only minimizes clogging of the nozzle tip due to the slurry particles having, but also has a narrow particle size distribution and a small particle size, thereby providing excellent reaction efficiency.

In addition, although the particle size of the wet pulverized calcium hydroxide is preferably 2 ~ 3㎛, when grinding the calcium hydroxide to 2㎛ or less, there is a problem that the amount of dispersant added according to the yield decrease and viscosity increase. The viscosity is preferably 300 to 1000 cps. When the viscosity is 300 cps or less, the sedimentation property is increased, whereas when 1000 cps or more, the sedimentation stability is lowered, and the spraying process is difficult in the reactor due to difficulty in conveying and stirring and problems in the process.

In addition, the purity can be increased by removing SiO ₂ and unbaked limestone through the screen immediately after hydration, and the high concentration liquid type of 40 ~ 60% or more is technically prepared for the part that was only able to be manufactured to 20% or less solids through dehydration process. It is possible to manufacture slaked lime.

The following examples are intended to assist the understanding of those skilled in the art and are not intended to limit the present invention.

Comparative Example 1

500 g of quicklime having an activity value of 250 to 300 was added to 2.5 kg of water, using a stirrer, stirred at 250 rpm for 1 hour, and measuring the specific surface area of the filtrate from which impurities were removed using 60 mesh.

Comparative Example 2

500 g of quicklime having an activity value of 250 to 300 was added to 2.5 kg of water, using a stirrer, stirred at 250 rpm for 1 hour, and using 60mesh to remove impurities. The filtrate was prepared using a filter press to prepare a 40% solids cake, and then 40 g of acrylate was ground using an Attrition Mill for 30 minutes, followed by a screen of 325mesh (43㎛), followed by specific surface area measurement.

Example 1

After dissolving 5 g of citric acid in 2.5 kg of water, 500 g of quicklime having an activity of 250 to 300 was added thereto, and stirred at 250 rpm for 1 hour using a stirrer, and measuring the specific surface area of the filtrate from which impurities were removed using 60 mesh.

[Example 2]

After dissolving 5 g of citric acid in 2.5 kg of water, 500 g of quicklime having an activity of 250 to 300 was added thereto, stirred at 250 rpm for 1 hour using a stirrer, and removed impurities using 60 mesh. The filtrate was prepared using a filter press to prepare a 40% solids cake, and then 40 g of acrylate was ground using an Attrition Mill for 30 minutes, followed by a screen of 325mesh (43㎛), followed by specific surface area measurement.

[Example 3]

After dissolving 5 g of citric acid in 300 g of water, 500 g of quicklime having an activity of 250 to 300 was added, placed in a hydrator, hydrated for 1 hour, and impurities were removed using a 1 mm screen, and then the specific surface area of the lime powder was measured.

Example 4

5 g of citric acid was dissolved in 300 g of water, and 500 g of quicklime having an activity of 250 to 300 was added thereto, placed in a hydrator, hydrated for 1 hour, and impurities were removed using a 1 mm screen, followed by 400 g of water and 40 g of an acrylate dispersant. After the slaked lime slurry was prepared, using an Attrition Mill, grinding for 30 minutes, after 325mesh (43㎛) Screen, measuring the specific surface area.

[Example 5]

After dissolving 10 g of citric acid in 2.5 kg of water, 500 g of quicklime having an activity of 250 to 300 was added thereto, and stirred at 250 rpm for 1 hour using a stirrer, and measuring the specific surface area of the filtrate from which impurities were removed using 60 mesh.

[Example 6]

After dissolving 10 g of citric acid in 2.5 kg of water, 500 g of quicklime having an activity of 250 to 300 was added thereto, and stirred at 250 rpm for 1 hour using a stirrer, using 60 mesh to remove impurities. The filtrate was prepared using a filter press to prepare a 40% solids cake, and then 40 g of acrylate was ground using an Attrition Mill for 30 minutes, followed by a screen of 325mesh (43㎛), followed by specific surface area measurement.

The results of the above example are summarized in Table 2 below.

As in Comparative Example 1, the specific surface area when the additive was not treated was 14 m 2 / g, but when the wet grinding was performed by adding 2% mixed hydrate and mixed with 2% acrylate, the specific surface area was 54 m 2 / g. It was found to be relatively high, and similar results were obtained for the specific surface area of dry and wet hydration. In order to confirm the exhaust gas removal efficiency of the incinerator using the sample obtained in this example, the flow rate was supplied 20NL / min, the SOx concentration was measured using a 340ppm, GASTEC SOx tester, the exhaust concentration removal efficiency is shown in the table below Same as 3.

As a result of conducting the harmful gas removal test using the sample prepared through the above experiment, it was confirmed numerically that the smaller the particle size, the higher the specific surface area, the higher the removal efficiency, which contributes to the improvement of the removal efficiency. I mean.

In addition, the specific surface area was primarily increased through the additive treatment during the hydration reaction, and the specific surface area could be further increased by adding acrylate during the second wet grinding process. In addition, by refining the particle size, the reaction area is improved, and the solid content and the viscosity change are elastically adjusted according to the harmful gas content, so that it is possible to manufacture high-concentration liquid lime with a high specific surface area with excellent removal efficiency of harmful gases. Its effect and use are expected.

Claims (4)

Dissolving by adding 0.5 to 3 parts by weight of citric acid to 400 to 600 parts by weight of water based on 100 parts by weight of quicklime (S1);
After the step (S1) by adding 100 parts by weight of quicklime, the step of hydration reaction while stirring for 30 to 60 minutes (S2);
Removing the impurities through a screen of 40 to 70 mesh after the completion of the hydration reaction, and dehydrating to prepare a slaked lime cake having a water content of 40 to 60% (S3); And
Consisting 1.0 to 3.0 parts by weight of the acrylate dispersant to 100 parts by weight of the slaked lime solids in the step (S3) to have a solid content of 40 to 60% by weight (at S4), attrition mill or disc A method for producing high density liquid slaked lime with a high specific surface area by further adding a mill grinding process to increase the specific surface area by using 500 parts by weight of zirconia having a size of 0.4 to 1.2 mm with respect to 100 parts by weight of quicklime. 100 parts by weight of quicklime, dissolving 0.5 to 3.0 parts by weight of citric acid in 40 to 120 parts by weight of water (SS1);
Preparing 100 parts by weight of quicklime after the step (SS1) simultaneously with the lysate and the hydration reactor to produce a hydrated lime powder having a specific surface area improved through a hydration reaction (SS2);
Step 1 to 3 parts by weight of 70 to 140 parts by weight of water and acrylate dispersant based on 100 parts by weight of solid content of 100 parts by weight of the hydrated lime powder in step (SS2) to give 40 to 60% of the solids of the slurry ( SS3), which adds the grinding process of the Attrition Mill or Disc Mill, by using 500 to about 500 parts by weight of zirconia of 0.4 ~ 1.2mm size as 100 parts by weight of quicklime to improve the specific surface area. Liquid slaked lime manufacturing method delete delete

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