JP2008074629A - Method for producing particulate slaked lime - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for simply producing particulate slaked lime with reduced cohesiveness regardless of the type of unslaked lime, although slaked lime having significantly different particle diameters has been produced even if it is slaked under the same conditions depending on composition and a burning method of unslaked lime used as a raw material. <P>SOLUTION: A method for producing slaked lime by slaking unslaked lime comprises adding 0.1-3.0 pts.wt. of a polymer having an anionic group based on 100 pts.wt. of unslaked lime, wherein the polymer having an anionic group is preferably a polymer obtained by polymerizing at least one monomer selected from the group consisting of a monomer having a carboxyl group such as acrylic acid and methacrylic acid, a monomer having a sulfonic acid group such as styrene sulfonic acid, a monomer having an amide group such as acrylamide, and a monomer obtained by partly modifying the above monomers or by substituting a terminal group thereof. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to slaked lime that is effective as a raw material for calcium carbonate, an adsorbent for harmful gases in incinerators, a soil conditioner, and the like. It relates to a method of manufacturing.

Slaked lime, which is fine and has low cohesiveness, is known to be effective for calcium carbonate raw materials, adsorbents for harmful gases in incinerators, soil improvers, and the like because of its large specific surface area and high reactivity. The slaked lime as the precipitated calcium carbonate raw material has finer particles and less agglomeration, has a larger contact area with the carbon dioxide gas, increases the reaction rate, and atomizes the generated calcium carbonate.

However, depending on the composition of the quicklime used as the raw material for the slaked lime and the firing method, the particle size varies greatly even if it is hydrated under the same conditions. Therefore, the present invention provides a method for easily obtaining fine slaked lime with little agglomeration regardless of the type of raw lime.

  As a method for obtaining fine slaked lime so far, a method of removing coarse particles from a slaked lime slurry by liquid cyclone treatment (Patent Document 1), a method of wet pulverization with a sand grinder (Patent Document 2), etc. have been proposed. In this way, mechanical treatment requires capital investment and increases the number of processes, and metal parts of the machine and fragments such as glass beads are mixed by grinding, etc., or contaminated and whiteness of slaked lime itself May decrease.

  Moreover, ethanol and methanol are mixed with digested water to perform a soothing reaction (Patent Document 3), and methanol and / or ethanol are mixed with water so that the alcohol concentration is 5 to 60% by volume, Furthermore, there are also known methods (Patent Document 4) in which a soothing reaction is performed with digested water to which a surfactant is added, but these methods require a large amount of alcohol such as methanol and ethanol, ketones, ethers, and aldehydes. In addition, special equipment such as a heating device, a degassing device, and an alcohol recovery tower is required. Similarly, there is a method (Patent Document 5) in which alcohols, amines, saccharides and the like are added to digested water and no special apparatus is used, but the same point is used in a large amount.

In addition, a method of removing coarse particles from slaked lime slurry (Patent Document 6) and a method of dispersing dispersed coarse particles again (Patent Document 7) are known, but the former has a slaked lime loss of 20 The yield is poor at ˜70%, and the latter requires a device for redispersion.
JP-A-6-56422 Japanese Patent Publication No.54-28399 Japanese Patent Publication No. 6-8194 Japanese Patent Laid-Open No. 5-193997 JP-A-10-101331 JP 59-21521 A JP 2004-345915 A

  An object of the present invention is to develop a technique for obtaining slaked lime having a small particle size and a low cohesiveness without causing the above problems.

  As a result of repeated investigations on means for reducing the particle size of slaked lime, the present inventors added a polymer having an anionic group when calcifying quick lime and agglomerated fine particles regardless of the type of quick lime. It has been found that slaked lime with low properties can be obtained.

The present invention includes the following inventions.
(1) A method for producing slaked lime by adding 0.1 to 3.0 parts by weight of a polymer having an anionic group in the step of producing slaked lime by dehydrating quick lime and having the anionic group The polymer is a monomer having a carboxyl group such as acrylic acid or methacrylic acid, a monomer having a sulfonic acid group such as styrene sulfonic acid, a monomer having an amide group such as acrylamide, a partial modification of these monomers, or a terminal group Among the substituted monomers, at least one kind is used as a monomer, and the polymerized polymer is a polymerized polymer (1) described in (1) The molecular weight of the polymer having the anionic group is in the range of 1,000 to 10,000,000. The method for producing slaked lime as described in (1) or (2) (4) The temperature when starting the decontamination of quicklime is 40 ° C or higher and 90 ° C or lower (1) to 3) hydrated lime manufacturing process (5) and stirring at a shear rate of 7 / s or more when slaking quicklime performed (1) to (4) slaked lime method according according.
(6) 5-10 μm calcium carbonate produced using slaked lime produced by the production method according to (1) to (5) as a raw material.

The method for producing slaked lime according to the present invention can provide a slaked lime slurry that is fine and low in viscosity and excellent in handling properties as compared with the conventional method. Moreover, in this invention, a special installation is not required and it can implement easily with the conventional digestion installation. Thereafter, the carbonation reaction was performed using the fine slaked lime obtained in the present invention, and it was confirmed that finer calcium carbonate was obtained than the slaked lime obtained by the conventional method.

The raw quicklime used in the present invention can be used regardless of the production area, size, and firing method. However, other than CaO is removed as a soaking residue. For this reason, in order to produce | generate slaked lime efficiently, the particle diameter of quick lime is so preferable that the CaO ratio in quick lime is high and the contact area with digestion water increases.

  The soaking tank used in the present invention may be of any capacity and shape, but the soaking reaction is an exothermic reaction, and slaked lime is a strong alkali, so it is preferably a heat-resistant and alkali-resistant material. Moreover, since the slaked lime particle | grains will become fine if it stirs at the time of soaking, it is preferable that it is a structure with a stirring function. Although this reason is not certain, it is thought that a particle diameter becomes small with the physical force by which the produced | generated slaked lime collides.

  The reaction of the present invention is performed in a form in which digested water and quicklime are reacted in a septic tank. At this time, if the water temperature is less than 40 ° C., the soaking reaction does not proceed easily, and the reaction takes time. If the water temperature exceeds 90 ° C., the reaction is exothermic and there is a risk of bumping. Therefore, the temperature of the hot water at the start of the reaction is preferably 40 ° C. or higher and 90 ° C. or lower. In addition, when the liquid temperature decreases due to heat dissipation during the soothing reaction, it is preferable to adjust the temperature so that it is 40 ° C. or higher and 90 ° C. or lower. The amount of digested water during the reaction is not particularly limited, but considering the concentration and viscosity of the slaked lime slurry to be produced, the amount of digested water is preferably 500 to 2500 parts by weight with respect to 100 parts by weight of input quicklime.

In the present invention, a polymer having an anionic group is added to digested water for reducing quick lime, or a polymer having an anionic group is added to and mixed with quick lime and / or coated. This is because the polymer is coordinated around the generated slaked lime and has an effect of suppressing the growth and secondary aggregation of the slaked lime. If the amount of the polymer added is less than 0.1 part, it cannot be sufficiently coordinated around the slaked lime, and if added over 3 parts, the effect will not only reach its peak but also cost will increase. It is preferable to add 1 to 3.0 parts.

Polymers having an anionic group to be added in the present invention include monomers having a carboxyl group such as acrylic acid and methacrylic acid, monomers having a sulfonic acid group such as styrenesulfonic acid, monomers having an amide group such as acrylamide, and the like. A polymer obtained by polymerization using at least one monomer that is partially modified or substituted with a terminal group as a monomer is preferred. This is slaked lime in water ^{_{Ca (OH) 2 ⇔Ca 2+ +}} 2OH - are ionized as, by electrical interaction between the anionic group, is because the polymer capable of coordinating efficiently Calcium . Among them, sodium polyacrylate is easy to ionize sodium, so the anion site of polyacrylic acid is easy to interact with Ca ²⁺ and has no odor and does not affect the environment compared to ammonium polyacrylate. Therefore, it is preferable.

  If the molecular weight of the polymer having an anionic group added in the present invention is less than 1000, the effect of suppressing aggregation of slaked lime is small, and if it is more than 10 million, the viscosity of the slaked lime slurry is excessively increased and the handling property is inferior. Within the range of ~ 10 million is preferred.

  In this invention, as above-mentioned, the particle diameter of slaked lime becomes small also by stirring at the time of soaking. The shear rate is preferably 7 / s or more because the effect is small when it is less than 7 / s. Further, it is more preferable to perform stirring using a vibro mixer or the like capable of stirring with up and down vibrations.

The soothing time in the present invention is not particularly defined. This is because the reaction rate of the soaking reaction and the amount of unreacted residue vary depending on the type of limestone used when producing quicklime, the firing conditions, and the like. After completion of the soaking reaction, the slaked lime slurry is passed through a 100 mesh screen to remove unreacted residues.

The fine slaked lime slurry synthesized as described above is preferable because the particle diameter is 1 μm or less and the cohesiveness is small. When used as a raw material for calcium carbonate, it is a slurry, and when used as an adsorbent for harmful gases in an incinerator and as a soil conditioner, it can be dried and used as a powder.

The slaked lime of the present invention is most suitable as a raw material for calcium carbonate, and the calcium carbonate produced by the carbonation reaction becomes a fine particle of 5 to 10 μm.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the examples and comparative examples, “parts” and “%” represent “parts by mass” and “% by mass”, respectively, unless otherwise specified.

The particle diameter of slaked lime prepared in Examples and Comparative Examples was measured with a laser diffraction particle size distribution meter (Microtrack 9320HRA manufactured by Nikkiso Co., Ltd.) using isopropyl alcohol as a dispersion solvent, and the median diameter of the volume distribution (Median diameter) ) Was defined as the average particle size. The viscosity of the slaked lime slurry was measured using a B-type viscometer (B-type viscometer manufactured by Toki Sangyo Co., Ltd.). The results are shown in Table 1.

  Using slaked lime prepared in Examples and Comparative Examples as a raw material, carbonization was performed in a reaction tank described in JP-A No. 05-163018 to obtain a calcium carbonate slurry. The reaction conditions are described below, and the reaction time and physical properties of the generated calcium carbonate slurry are shown in Table 2. The particle diameter of the calcium carbonate slurry was measured with a laser diffraction particle size distribution meter (Microtrack 9320HRA manufactured by Nikkiso Co., Ltd.) using ion-exchanged water as a dispersion solvent, and the center diameter (Median diameter) of the volume distribution was determined as the average particle diameter. did. Moreover, the viscosity was measured using a B-type viscometer (B-type viscometer manufactured by Toki Sangyo Co., Ltd.).

<Reaction conditions>
Slaked lime slurry concentration 11%
Slaked lime slurry volume 15L
Blowing carbon dioxide concentration 25%
Amount of carbon dioxide injected 36 L / min Stirring shear rate during reaction 15 / s

Example 1
780 parts of digestion water prepared by adding 1 part of polyacrylic acid soda (trade name: Aron T-50, molecular weight 6000, manufactured by Toa Gosei Co., Ltd.) to massive quicklime (manufactured by Yabashi Kogyo Co., Ltd.) is prepared in advance. While the digestion water was heated to 50 ° C. in the reaction vessel and stirred at a shear rate of 20 / s, quick lime was added and mixed to obtain a slaked lime slurry.

Example 2
To powdery quicklime (manufactured by Yabashi Kogyo Co., Ltd.), 1 part of polyacrylic acid soda (trade name: Aron T-50, molecular weight 6000 manufactured by Toa Gosei Co., Ltd.) is added and mixed well. While 780 parts of digested water was heated to 50 ° C. and stirred at a shear rate of 20 / s in the reaction tank, quick lime was added and mixed to obtain a slaked lime slurry.

Example 3
A slaked lime slurry was obtained in the same manner as in Example 1 except that the slaked water was heated to 80 ° C. in the reaction vessel.

Example 4
A slaked lime slurry was obtained in the same manner as in Example 1 except that the slaked water was set to 20 ° C. in the reaction vessel.

Example 5
A slaked lime slurry was obtained in the same manner as in Example 1 except that the stirring speed in the reaction vessel was 40 / s.

Example 6
A slaked lime slurry was obtained in the same manner as in Example 1 except that the stirring speed in the reaction vessel was 2 / s.

Comparative Example 1
780 parts of digestion water is prepared in advance for massive quicklime (manufactured by Yabashi Kogyo Co., Ltd.). While the digestion water was heated to 50 ° C. in the reaction vessel and stirred at a shear rate of 20 / s, quick lime was added and mixed to obtain a slaked lime slurry.

Comparative Example 2
A slaked lime slurry was obtained in the same manner as in Example 1 except that polyvinyl pyrrolidone (trade name: polyvinyl pyrrolidone K-15, molecular weight 10,000 manufactured by Kishida Chemical Co., Ltd.) was used instead of sodium polyacrylate.

Comparative Example 3
A slaked lime slurry was prepared in the same manner as in Example 1 except that a polymer mainly composed of acrylic amide and acrylic acid (trade name: Diafloc AP335C, molecular weight 16 million, manufactured by Daianitrix) was used instead of polyacrylic acid soda. Obtained.

Comparative Example 4
A slaked lime slurry was obtained in the same manner as in Example 1 except that the amount of sodium polyacrylate added was 0.01 parts.

Claims (5)

  A method for producing slaked lime, comprising adding 0.1 to 3.0 parts by mass of anti-lime lime in the step of producing slaked lime by dehydrating quick lime   The polymer having an anionic group is a monomer having at least one of a monomer having a carboxyl group, a monomer having a sulfonic acid group, and a monomer in which these monomers are partially modified or substituted with terminal groups. 2. The method for producing slaked lime according to claim 1, wherein the slaked lime is a polymer.   3. The method for producing slaked lime according to claim 1, wherein the polymer having an anionic group has a molecular weight in a range of 1,000 to 10,000,000.   The method for producing slaked lime according to any one of claims 1 to 3, wherein the temperature at the start of calcification of quicklime is 40 ° C or higher and 90 ° C or lower.   The method for producing slaked lime according to any one of claims 1 to 4, wherein stirring is performed at a shear rate of 7 / s or more when the quick lime is hydrated.