KR102555516B1 - Process for preparation of porous ceramic filter - Google Patents

Abstract

The present invention comprises a raw material preparation step; A slurry preparation step of preparing a slurry by applying ball milling; A drying step of injecting the slurry into a spray dryer to which a rotary atomizer is applied to dry and produce granules; A blending step of mixing the granules by introducing them into a V-mixer; A molding step of generating a molded product in a filter shape from the granules that have undergone the blending step; and a firing step of treating the molding by applying heat to the molding. Provides a method for manufacturing a porous ceramic filter, wherein the raw materials include inorganic substances, dispersants, water, and organic substances, thereby reducing input energy and ensuring uniform distribution of granules, resulting in uneven distribution of granules. It is possible to improve the physical properties of the ceramic filter by preventing non-uniform composition of the fired body and difficulty in diffusion control.

Description

Porous ceramic filter manufacturing method {PROCESS FOR PREPARATION OF POROUS CERAMIC FILTER}

The present invention relates to a method for manufacturing a porous ceramic filter used for removing dust, soot, waste gas, fume, and VOC generated in industrial processes.

BACKGROUND OF THE INVENTION Due to the industrialization era, damages caused by harmful substances such as dust, soot, and waste gas occur, and filtering technology for filtering these harmful substances before they are discharged to the outside is also developing day by day.

Filters are typically classified into organic filters and inorganic filters according to materials, and polymer filters and ceramic filters are generally used as types of filters that are currently mainly used.

Compared to ceramic filters, polymer filters can easily control large-area pores and are inexpensive. Using these characteristics, stability can be brought about in the manufacturing process, and it has significant economic advantages. However, in the case of an organic filter, there are weak problems in heat resistance, chemical resistance, abrasion resistance and flame retardancy.

On the other hand, ceramic filters have much better heat resistance, chemical resistance, and abrasion resistance than polymer filters, and in particular, have excellent heat resistance. In general, alumina is applied to a ceramic filter base material, which has the advantage of being able to easily control the pores of the filter because the particle size is relatively subdivided and uniform quality can be obtained, and the physical strength of the base material is strong to ensure reliability of filtration. There is an advantage to being However, since a high temperature is used for a certain period of time during the drying process and the sintering process, a large amount of energy is required, and when a fine alumina ceramic substrate is used, if proper dispersion is not performed, a problem in that the ceramic properties are not good occurs. Accordingly, there is a demand for a method for manufacturing a ceramic filter that is easy to manufacture and can ensure proper dispersion of ceramic particles.

The present invention was derived to solve the above-mentioned problems, and its purpose is to provide a method for manufacturing a ceramic filter capable of securing ceramic properties by reducing energy input to the manufacturing process and securing proper dispersion of ceramic particles. there is.

The present invention comprises a raw material preparation step; A slurry preparation step of preparing a slurry by applying ball milling; A drying step of injecting the slurry into a spray dryer to which a rotary atomizer is applied to dry and produce granules; A blending step of mixing the granules by introducing them into a V-mixer; A molding step of generating a molded product in a filter shape from the granules that have undergone the blending step; and a sintering step of treating the molding by applying heat, wherein the raw material includes an inorganic material, a dispersant, water, and an organic material.

According to one embodiment of the present invention, by applying calcined alumina to the formulation of the raw material of the present invention, the sintering time is shortened and the sintering temperature is lowered, thereby reducing the energy input to the sintering process.

In addition, according to one embodiment of the present invention, it is possible to reduce the time and energy required for drying by applying a spray dryer.

In addition, according to one embodiment of the present invention, in the manufacture of a ceramic filter using granules, uniform distribution of the granules can be secured through a blending step using a V-mixer, resulting in a fired body according to non-uniform distribution of granules. It is possible to improve physical properties of the ceramic filter by preventing non-uniformity in composition and difficulty in diffusion control.

1 is a flowchart of a method for manufacturing a ceramic filter according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention are described in detail. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms, but only the present embodiments make the disclosure of the present invention complete and provide the content of the present invention to those skilled in the art. It is provided to inform you more completely.

Terms used in this specification are used to describe specific embodiments and are not intended to limit the present invention.

As used herein, the singular form may include the plural form unless the context clearly indicates otherwise. Also, when used herein, "comprises" and/or "comprising" specifies the presence of the recited shapes, numbers, steps, operations, members, elements, and/or groups thereof, and one or more other shapes. , does not exclude the presence or addition of numbers, operations, elements, elements and/or groups. As used herein, the term "and/or" includes any one and all combinations of one or more of the listed items.

Hereinafter, it will be described in detail with reference to the drawings.

1 is a flowchart illustrating a method of manufacturing a ceramic filter according to an embodiment of the present invention.

Referring to FIG. 1 , the ceramic filter manufacturing method may include raw material preparation (101), slurry preparation (102), drying (103), blending (104), molding (105), and firing (106) steps.

In the raw material preparation step 101, raw materials required for manufacturing a ceramic filter may be prepared. The raw material may include an inorganic material, a dispersant, water, and an organic material. In this case, 60.6 to 62.9 parts by weight of the inorganic material, 0.8 to 1.0 parts by weight of the dispersant, 30.0 to 31.5 parts by weight of the water, and 6.3 to 6.9 parts by weight of the organic material may be prepared and then introduced into subsequent processes.

The inorganic material may be composed of a mixture of a main raw material and an inorganic additive, and may be formed in a ratio of main raw material: inorganic additive = 80:20 based on weight.

The main raw material may include alumina (Al ₂ O ₃ ). As for the alumina, calcined alumina may be applied. The calcined alumina can be calcined at a relatively low temperature compared to sintered alumina or fused alumina, so that processability can be improved when applied to the formulation of the present invention, for example, the sintering time can be shortened and the sintering temperature can be lowered. . A particle size of the calcined alumina may be 1 μm to 5 μm. When the particle size of the calcined alumina is within the above range, porosity and mechanical strength of the ceramic filter may be improved. By applying the calcined alumina to the formulation of the raw material of the present invention, the sintering time is shortened and the sintering temperature is lowered, thereby reducing the energy input to the sintering process.

The inorganic additive is used as a source of MgO, CaO, SiO ₂ . The inorganic additive may include talc, clay, and limestone, and may be composed of talc:clay:limestone = 5:13:2 ratio by weight. Adding an inorganic additive composed of the above ratio to the mixing of the raw materials of the present invention can help form a liquid phase during firing.

The dispersant may be an anionic aqueous dispersant. For example, polycarboxylic acid ammonium salts may be included. When the polycarboxylic acid ammonium salt dispersant is applied to the raw material formulation of the present invention, the inorganic material can be evenly dispersed in the slurry preparation step (102).

Distilled water or ID-Water may be used as the water.

The organic material may be composed of a mixture of a binder, a plasticizer, a release agent, and an antifoaming agent, and may be composed of a ratio of binder : plasticizer : release agent : antifoamer = 7 : 1.5 : 2.0 : 0.2 based on weight. When the organic component described later is included in the formulation of the raw material of the present invention in such a ratio, shape retention and strength are imparted to maintain the shape during molding, and warpage and cracking due to shrinkage or warping during drying are prevented. This can be prevented and productivity can be improved during molding.

For example, the binder may include one or more of PVA, PVB, MC, EC, and CMC, and may include, for example, PVA. The plasticizer may include glycerin or PEG, for example, PEG. The release agent may include stearic acid, a synthetic polymer, and a fluorinated compound, and may include stearic acid, for example. The antifoaming agent may include at least one of polyether-based, alcohol-based, metal soap-based, and amide-based antifoaming agents, and for example, may include polyether-based antifoaming agents.

In the case of applying the organic materials of the above components to the formulation of the raw material of the present invention, it does not contain alkalis such as Na, K, and Li and residual heavy metals such as Fe, Ni, Co, and Cr, and the decomposition gas is toxic and strong acid. · It is not strongly alkaline, the organic substance does not react with the inorganic substance, it is easy to dissolve in water, and it can be completely decomposed and volatilized at low temperature (300 ~ 400 ℃) in an oxidizing, non-oxidizing atmosphere.

The slurry preparation step 102 prepares a slurry from the raw material using a milling machine, and may include a first milling step and a second milling step. When milling is performed in the step of preparing a slurry by mixing the raw materials of the present invention, a uniform distribution of the formed granules can be secured, preventing uneven composition of the fired body due to non-uniform distribution of the granules and difficulty in controlling diffusion, resulting in ceramic The physical properties of the filter can be improved. A specific method is described below.

The milling machine may apply a ball milling machine. At this time, the balls used in the ball mill may be stainless steel balls having a size of 3 to 5 mm, and the rotational speed of the ball mill may be set to 400 to 700 RPM, but may be set differently according to equipment conditions.

The first milling step may be completed by checking the particle size while performing milling for about 1 hour to 1 hour 30 minutes after the inorganic material, dispersant and water are introduced into the ball mill.

The secondary milling step may include preparing a slurry by adding the organic material to the ball mill in which the primary milling has been completed and additionally performing milling for about 10 to 15 minutes. At this time, air bubbles generated during the first milling step may be removed by the antifoaming agent.

After the milling is completed, the slurry is stored while continuously stirring so as not to precipitate.

Drying (103) is a step of drying the slurry to form granules, and a spray dryer capable of drying the dry particles in a form that is close to spherical and has excellent fluidity can be applied.

The spray dryer may use a spray dryer to which a rotary atomizer is applied. By using a spray dryer to which the rotary atomizer is applied, the slurry is formed in the form of granules having a particle size of 20 to 200 μm, and the spray dryer process conditions are adjusted so that the granules do not become doughnuts. Uniformity of the granules It is possible to improve the physical properties of the ceramic filter by securing a uniform distribution.

The blending step 104 is a step of mixing the granules having various particle sizes in a uniform distribution, and a mixer used in a mechanical mixing method may be applied. For example, any one of a V-mixer, a Y-mixer, a double cone mixer, a zero-gravity mixer, and a three-dimensional mixer may be selected and used, but the mixing of the raw materials of the present invention It is preferable to use a V-mixer.

The rotation speed of the V-mixer may be 10 to 20 times/min, and the operating time may be 20 to 30 minutes. Accordingly, uniform distribution of the granules to which the blending step 104 is applied can be ensured, and non-uniform composition of the plastic body due to non-uniform distribution of granules and difficulty in diffusion control can be prevented, thereby improving the physical properties of the ceramic filter. can

The molding step (105) is a step of forming a molded article by molding into a filter shape using the granules that have undergone the blending step (104), and is a step of forming a molded article of a certain shape by dry molding the granules. The dry molding is to manufacture a molded body by charging powder into a mold of a certain shape and applying a certain pressure, and for example, a dry press method can be applied.

During molding by the dry press method, the molding pressure is usually 0.7 to 1.0 kgf/cm 2 . In general molding, the molding pressure is increased so that the granules can be broken, but in filter molding, it is preferable to form with a relatively low pressure so that the granules are not broken.

In the firing (106) step, the molded article after molding is heat-treated at a high temperature to impart mechanical strength to the filter, and the first heat treatment is performed in the range of room temperature to 800 ° C. to remove the organic binder remaining after the molding process After the degreasing process and the degreasing process, a secondary heat treatment at a temperature of 1350 to 1400 ° C. for 1 hour or less, and then a multi-stage process of cooling may be applied. At this time, the maximum temperature may be set to a temperature at which the liquid phase starts to form in the temperature range of 1350 ° C to 1400 ° C. The liquid phase can impart bonding strength to the calcined alumina, which is the main raw material. If the maximum firing temperature exceeds the above numerical range, the liquid phase is excessively generated, which adversely affects the formation of pores, resulting in poor physical properties of the ceramic filter. If it is less than the above numerical range, it may be difficult to obtain sufficient mechanical strength.

Example

Raw materials having the composition ratios shown in Table 1 below were prepared.

division content
[Unit: parts by weight] mineral main raw material Alumina (LS130 _ Nippon Light Metal Co.) 49.3 weapon
additive Talc (SP3000 _ Dawon Chemical) 3.1 Clay (CL3000) 8.0 Limestone (TL-1000) 1.2 Dispersant (SN5468 _ SAN NOPCO LIMITED) 0.9 water (distilled water) 30.8 organic matter Binder (PVA 205MB _ KURARAY POVAL) 4.3 Plasticizer (PEG #400) 0.9 Release agent (LU6418 _ SAN NOPCO LIMITED) 1.2 Defoamer (SN485 _ SAN NOPCO LIMITED) 0.1 Sum 100.0

According to the composition ratio as shown in Table 1 (here, the unit is parts by weight), inorganic substances, dispersants and water were put into a ball mill (BAM-22_NANO IN TECH co.,ltd), and primary milling was performed at 400 RPM for 1 hour. carry out At this time, the ball used in the ball mill is a stainless steel ball having a size of 5 mm.

In the second milling step, a slurry is prepared by inputting an organic material according to the composition ratio as shown in Table 1 to the ball mill after the first milling and performing milling at 400 RPM for 10 minutes.

The slurry prepared as described above is put into a spray dryer (COC-12_Seo gang engineering co.,ltd) to which a rotary atomizer is applied to generate granules.

Experimental Example 1: Application of blending step

The granules were blended by applying a V-mixer (VM-50 _ Sungchang Machinery Co., Ltd.) at a rotation speed of 15 times per minute and an operating time of 30 minutes.

Using the blended granules, apply a pressure of 0.8kgf/cm2 with a dry press to create a molded product, and then perform the first heat treatment at 800 ° C, and the second heat treatment at 1350 ~ 1400 ° C for 1 hour. After cooling to prepare a sample.

For strength measurement, three-point flexural strength was measured using a strength tester (DTU-900 MHA, Daekyung tech, Korea), and porosity was measured using Archimedes' principle, and the results are shown in Table 2 below.

Comparative Example 1: No blending step applied

Using the granules not subjected to the blending step, apply a pressure of 0.8 kgf / cm 2 with a dry press to create a molded product, and then perform a first heat treatment at 800 ° C, and a second heat treatment at a temperature of 1350 ° C to 1400 ° C for 1 hour After cooling, samples were prepared.

For strength measurement, three-point flexural strength was measured using a strength tester (DTU-900 MHA, Daekyung tech, Korea), and porosity was measured using Archimedes' principle, and the results are shown in Table 2 below.

division robbery Porosity (%) Experiment result Experimental Example 1. Application of blending step 58.9 34.4 Comparative Example 1. No blending step applied 49.7 40.1

As can be seen from the values shown in Table 2, it can be seen that the strength increases and the porosity decreases in the sample to which the blending step is applied. This is interpreted as the fact that the strength is increased and the porosity is reduced because the granules are evenly mixed by size and sintered at a high stacking density through the blending step using the V-mixer of the present invention.

As described above, the detailed description of the present invention has been made by the embodiments with reference to the accompanying drawings, but since the above-described embodiments have only been described as preferred examples of the present invention, it is believed that the present invention is limited only to the above embodiments. Should not be understood, the scope of the present invention should be understood as the following claims and equivalent concepts.

Claims (4)

raw material preparation stage;
A slurry preparation step of preparing a slurry by applying ball milling;
A drying step of injecting the slurry into a spray dryer to which a rotary atomizer is applied to dry and produce granules;
A blending step of mixing the granules by introducing them into a V-mixer;
A molding step of generating a molded product in a filter shape from the granules that have undergone the blending step; and
A firing step of treating the molding by applying heat to it;
including,
The raw material includes 60.6 to 62.9 parts by weight of inorganic material, 0.8 to 1.0 parts by weight of dispersant, 30.0 to 31.5 parts by weight of water and 6.3 to 6.9 parts by weight of organic material based on 100 parts by weight of the raw material,
The inorganic material is composed of a mixture of main raw materials: inorganic additives in a ratio of 80: 20 by weight,
The main raw material is composed of calcined alumina having a particle size of 1 to 5 μm, which improves workability, shortens the sintering time, and reduces the energy input to the sintering process by lowering the sintering temperature.
The inorganic additive is used as a source of MgO, CaO, and SiO ₂ , and is composed of a mixture of Talc: Clay: Lime in a ratio of 5: 13: 2 based on weight to facilitate liquid phase formation, ,
The dispersant includes an ammonium polycarboxylic acid salt so that the inorganic material is evenly dispersed in the slurry preparation step,
The organic material is composed of a mixture of binder: plasticizer: release agent: antifoaming agent in a ratio of 7: 1.5: 2.0: 0.2 by weight to impart shape retention and strength so as to maintain the shape during molding, and to reduce shrinkage or distortion during drying. The occurrence of warping and cracking can be prevented, and productivity can be improved during molding.
In the slurry manufacturing step, the ball used for the ball milling is a stainless steel ball having a size of 3 to 5 mm, and the rotation speed of the ball mill is set to 400 to 700 rpm,
The slurry preparation step includes a first milling step and a second milling step,
The first milling step is to perform milling while checking the particle size for 1 hour to 1 hour 30 minutes after the inorganic material, the dispersant, and the water are introduced into the ball mill, and the Air bubbles are removed by the antifoaming agent,
The second milling step is to prepare a slurry by adding the organic material to the ball mill on which the first milling is completed and additionally performing milling for 10 to 15 minutes,
The blending step is performed under conditions of a rotation speed of 10 to 20 times/min of the V-mixer and an operating time of 20 to 30 minutes,
In the molding step, dry molding is applied, and a dry press method is applied,
The dry press method is performed at a molding pressure of 0.7 ~ 1.0 kgf / cm 2,
The firing step includes a multi-step process including a first heat treatment and a second heat treatment,
The first heat treatment is a degreasing process for removing the organic binder remaining in the molding step at room temperature to 800 ° C.
The secondary heat treatment is performed at 1350 ~ 1400 ℃ within 1 hour, porous ceramic filter manufacturing method.
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