JPH0544408B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing zeolite molded products, and more specifically, to a method for producing zeolite molded products with high strength and wear resistance that enable stable operation management of the granulation process and stable quality control. Regarding the method.

<Industrial Application Fields> Zeolite has been developed for many uses such as drying, purification, separation, ion exchange, catalysts and catalyst carriers due to its excellent adsorption properties, ion exchange properties, catalytic properties, etc. It is used in petroleum refining, chemical and petrochemical industry, gas refining industry, natural gas industry, electrical industry, paint industry, and other industries such as double glazing and analysis.

Here, zeolite includes naturally occurring natural zeolite and synthetic zeolite produced by synthesis, and has the general formula M _2/o O・Al ₂ O ₃・xSiO ₂・yH ₂ O (where M is an alkali metal or It is a crystalline aluminosilicate with a composition of alkaline earth metals, where n is their valence.

The zeolite in the present invention does not specify either natural zeolite or synthetic zeolite. Furthermore, although the cations contained in zeolite can be easily ion-exchanged into other cations, the zeolite used in the present invention does not specify this cation.

Among zeolites, synthetic zeolites themselves are fine crystals or aggregates of crystals in the range of 0.1 to 50 microns, and are non-binding powders. In order to use this product industrially, it is necessary to make it into some kind of molded product suitable for the purpose of use. As the shape of the molded product,
Generally, they are columnar (pellet), spherical (bead), granule, or fine granule, and for special purposes, there are also honeycomb, tube, plate, core, and other shapes.

<Prior art> In order to granulate zeolite, the binder is generally used in an amount of 10 to 30 parts per 100 parts of the dry weight of the zeolite.
part is added. As a binder, kaolin,
Clays such as attapulgite, montmorillonite, bentonite, allofen, and sepiolite are used alone or in combination of two or more. As binders other than clay, alumina, silica, etc. are also used alone or in combination with clay. In addition to the binder, various organic and inorganic additives are used as granulation aids for zeolite dry weight.
They are often used alone or in combination in a range of 0.01 to 5 parts per 100 parts. Examples of granulation aids include methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, crystalline cellulose, lignin, stearic acid, starch, gum arabic, sodium silicate, and sodium polyphosphate.

Zeolite granulation methods include, for example, rolling granulation, extrusion granulation, spray granulation, fluidized granulation, and compression granulation, and the present invention relates to extrusion granulation. When producing a zeolite molded product by extrusion granulation, zeolite powder and binder and granulation aid powder are dry-mixed in advance using a known mixer such as a ribbon blender or conical blender, and then kneaded using a known kneader or other kneader. It is common to add liquid using a machine, add water, knead, and then extrude and granulate. The granulation aid may be added in advance as an aqueous solution.

<Problems to be Solved by the Invention> Among the several characteristics that a zeolite molded product must have, mechanical strength, abrasion resistance, and shape uniformity are mentioned. When molding zeolite by extrusion granulation, there are a very large number of governing factors that affect these product properties, and since each of these governing factors has a synergistic effect, the granulation mechanism has not been systematically elucidated. The current situation is that there is no such thing. The governing factors that can be considered in granulating zeolite can be broadly divided into (1) raw materials, (2) pre-processes, and (3) granulation steps.

First, when considering raw materials, there are particle shape, physical properties, particle size distribution, moisture content, temperature, type of binder and its addition ratio, etc. The particle shape also differs depending on the type of zeolite and its synthesis method, and the clay used as a binder differs depending on the type. In terms of physical properties, zeolites generally have dilatancy, and clays exhibit thixotropy. Furthermore, the powder characteristics vary widely depending on the type of zeolite and the type of binder clay. The moisture content is
The amount of adhered water and the amount of crystallized water differ depending on the degree of dryness of the zeolite powder and the type of zeolite. Clay also has crystallized water, interlayer water, and attached water, which vary depending on the type of clay, degree of dryness, storage atmosphere, etc.

Next, regarding the pre-process, dry powder mixing time, liquid addition and
Typical controlling factors include water addition time and its addition method, presence or absence of plasticity, kneading machine type, kneading time, temperature, etc. Controlling factors in the granulation process include granulation shape, granulation hardness and softness, adhesion, aperture ratio of a die or screen and its thickness, extrusion speed, screw type, etc.

Among these many controlling factors, when the equipment used and the combination of zeolite, binder, and granulation aid are specified, the factor that most controls the granulation property is the amount of liquid and water added. In other words, comprehensive moisture management is the biggest problem. As mentioned above, zeolite contains water of crystallization, and depending on the drying conditions of the zeolite powder, the amount of crystallized water and the presence or absence of attached water may vary. On the other hand, the crystallization water, interlayer water, and adhesion water of the clay used for the binder also change. In addition, heat generation occurs in each process of dry powder mixing, kneading, and granulation, and the amount of evaporated water changes depending on the temperature and humidity of the process atmosphere. For these reasons, comprehensive moisture control during granulation is difficult, and conventionally the moisture content after kneading has been measured and readjusted to the optimum conditions.

Specifically speaking, the reason why moisture management is necessary is that if the moisture content after kneading is lower than the optimum moisture content, the load on the extrusion granulator will increase, causing heat generation in the die or screen section. increases, the granulation becomes unstable, and the shape of the molded product becomes uneven or cracked. On the other hand, if the water content after kneading is higher than the optimum water content, the molded products will adhere to each other after extrusion granulation, and a uniform shape will not be maintained, and the mechanical strength of the molded product will also decrease. The tolerance range for this optimum water content is extremely low, ±0.5%, and if a kneaded product with a water content outside this range is extruded and granulated, the aforementioned operational instability and product properties will deteriorate. Because of this,
In terms of process control during granulation, careful attention was paid to moisture control and a huge amount of effort was expended.

The present invention was developed as a result of intensive studies on how to constantly control the moisture content to the optimum value.
In the previous process, the coarsely granulated mass is kneaded (in the conventional method,
We discovered that by controlling the particle size of the agglomerates, granulation can always be carried out under optimal conditions, resulting in stable granulation and stable quality of molded products. In addition, we have now provided a method for manufacturing molded products with high mechanical strength.

<Means for Solving the Problems> The present invention involves dry powder mixing of some or all of the zeolite, binder, and granulation aid in a mixer, and the mixed powder being rotated in the same machine or in a separate machine. By adding water or adding a solution in which part or all of the granulation aid is dissolved or dispersed, the particle size of the kneaded coarse granulated mass consisting of zeolite, binder, granulation aid and water is preferably in the range of 1 to 50 mm. is adjusted to have a diameter in the range of 1 to 30 mm, and the kneaded coarsely granulated mass is extruded and granulated.

In the kneading process for producing zeolite molded products, the three phases of the solid zeolite, binder, and granulation aid, the liquid (mainly water and a part of the granulation aid solution), and the gas (mainly air) are filled in some way. Formed with style. In order to stably perform extrusion granulation, the ideal packing method for wet powder or kneaded mass is solid,
The solid phase is continuous, the liquid phase is continuous, and the gas phase is absent. In other words, the ideal state is that there is only enough liquid to fill the solid phase surface and the voids between the solids, and there are no voids where gas exists.If the kneaded mass is granulated in this state, the mechanical strength of the molded product will be is high and has high wear resistance. In order to create a kneaded mass in this ideal state, it is sufficient to apply a force to cause the powder to coagulate and adhere under swirling motion, and to add enough liquid to fill the voids. Here, as a guideline for the amount of liquid sufficient to fill the voids, the kneaded mass is spherical and coarsely granulated to have a particle size in the range of 1 to 50 mm, preferably in the range of 1 to 30 mm. For example, when extrusion granulation is performed on kneaded powder in the form of powder less than 1 mm after kneading, there are signs of moisture deficiency, i.e. heat generation increases in the screen or die part of the granulator, the granulation becomes unstable, and molding The shape of the product has noticeable cracks or cracks. On the other hand, if a kneaded coarse granulated mass larger than 50 mm is obtained after kneading, extrusion granulation will show signs of excessive water content, that is, the molded products will adhere to each other, and their mechanical strength will also decrease.

Although the size of the kneaded coarse granulated mass depends on the swirling time and the swirling speed, it changes the most depending on the amount of water added or the amount of liquid added. The binder and granulation aid are selected in a combination that facilitates agglomeration of all components including zeolite, and the minimum agglomeration units during kneading adhere to each other in the presence of moisture and grow in a snowballing manner. Excess moisture in this state controls the size of the kneaded coarse granules, and the appropriate amount of moisture is enough to penetrate into the minimum unit of agglomeration. They stagnate, promote mutual adhesion, and rapidly increase the size of the kneaded coarse granules.

From the above, in order to bring the optimum moisture for granulation, it is necessary to add water or liquid so that the size of the coarse granulated mass in the previous step is in the range of 1 to 50 mm, preferably in the range of 1 to 30 mm. I know it's good.

In the extrusion granulation method according to the present invention, in the previous step of kneading the mixture with zeolite, binder, and granulation aid, the particle size of the kneaded coarse granulated mass is 1 to 50 mm,
More desirably, it is a method of adding water or liquid so that the thickness is in the range of 1 to 30 mm. If the kneaded coarse granulated mass in the above range is extruded and granulated, the operation of the granulation process will always be stable, and in addition, the shape of the molded product will be uniform, mechanical strength will be increased, and wear resistance will also be increased. Furthermore, there is no need to measure moisture during or after kneading, and process control can be greatly simplified.

Furthermore, as a kneader used in the pre-process, conventionally used kneaders and the like are unsuitable because they cannot produce granular materials, and a mixing agitator with a granulation function such as a Henschel mixer is suitable.

<Effects of the Invention> As is clear from the above description, according to the present invention (1) the shape of the zeolite molded product can always be made uniform.

(2) Mechanical strength and wear resistance of zeolite molded products can be increased.

(3) The granulation process of zeolite molded products is always stabilized, making operational management easier.

(4) Moisture adjustment in the pre-granulation process of zeolite molded products becomes easy, and process control such as moisture measurement can be omitted.

<Examples> The present invention will be specifically explained below using Examples.
Note that the present invention is not limited to the zeolite, binder, granulation aid, and equipment used in the Examples.

Example 1 5 kg of 4A type zeolite powder (as anhydrous)
4.14Kg) Weighed 1.22Kg of acidic clay powder and 40g of carboxyl methyl cellulose powder, put them into a vertical mixer Henschel mixer FM75C (manufactured by Mitsui Miike Seisakusho), and mixed them at a circumferential speed of 20.2 m/sec for 10 minutes.
Dry powder mixing was performed for minutes. After that, after adding 2.25 kg of pure water for 30 seconds under rotating conditions at a circumferential speed of 10.7 m/sec,
The rotation speed was increased to a circumferential speed of 20.2 m/sec, and kneading was continued for 5 minutes. As a result of measuring the particle size distribution of the kneaded coarse granulated mass taken out from the Henschel mixer, it was found that it was 1 to 10 mm5.
%, 10~20mm8%, 20~30mm85%, 30~40mm2%
It was hot. This kneaded coarse granulated mass is extruded into a granulator EXDF.
-100 type (manufactured by Fuji Paudal). The mounting die has a hole diameter of 3 mm and a die thickness of 10 mm. Granulation was very smooth and well-shaped pellets were obtained. This is dried in a fluidized bed dryer with a hot air temperature of 120℃ for 30 minutes.
After drying for a minute, it was fired at 550°C for 2 hours in a static electric firing furnace. The mechanical strength of the fired pellets was measured at 20 points using a Kiya type hardness tester, and the average value was 9.2 kg.

Comparative Example 1 The same amounts of zeolite, acid clay, and carboxymethyl cellulose as in Example 1 were weighed, and the same amounts were weighed in a kneader.
Pour into FM-NW-20 type (manufactured by Fuji Kaki) and
Dry powder mixing was performed for minutes. Then add 2.25Kg of pure water to 1
After addition, the mixture was kneaded for 30 minutes. The kneaded material taken out from the kneader was in the form of powder with a particle size of 1 mm or less, and no coarsely kneaded granules were observed. This kneaded material was granulated, dried, and fired in the same manner as in Example 1, and the mechanical strength of the pellets was measured, and the average value was 5.5 kg.
It was hot. During granulation, the pellets were not extruded from the entire surface of the die, resulting in clogged holes and cracked pellet surfaces.

Example 2 Synthetic mordenite powder 11.2Kg (as anhydrous)
10Kg) Weigh 2.94Kg of acidic clay powder and 100g of carboxymethyl cellulose, and mix the dry powders with a Henschel mixer at a circumferential speed of 20.2m/sec for 10 minutes, then add 6.25Kg of pure water at a circumferential speed of 10.7m/sec. The rotation speed was immediately increased to 27.3 m/sec, and although signs of coarse granulation agglomeration were observed after 10 minutes, swirling was continued for an additional 10 minutes. As a result of measuring the particle size distribution of the kneaded coarse granulated mass taken out from the Henschel mixer, 1-10 mm 12%, 10-20 mm 75%, 20-20 mm
It was 10% for 30mm and 3% for 30-50mm. This kneaded coarse granulated mass was granulated using an extrusion granulator equipped with a die having a die hole diameter of 1.5 mm and a die thickness of 4 mm, as described in Example 1 below.
The average mechanical strength of the pellets after the same post-treatment was 2.5 kg. The granulation state is smooth,
The shape of the pellets was also good.

Comparative example 2 After carrying out the same procedure as in Example 2 up to dry powder mixing, pure water was added.
6.59 kg was added at the same circumferential speed and addition time and kneaded, but after 10 minutes, the coarse granulated lumps had grown large, so they were taken out from the Henschel mixer and the particle size distribution was measured. As a result, all of the particles were in the form of dumplings with a size ranging from 50 to 100 mm. This was extruded and granulated under the same conditions as in Example 2, but because the coarse granulated mass had a large particle size, it was difficult to get caught in the extruder screw, and the pellets after extrusion adhered to each other severely. The shape was non-uniform. The mechanical strength of the molded products was 1.5 kg on average.

Example 3 Synthetic mordenite powder 12.5 kg (as anhydrous)
10Kg), 3.0Kg of Kibushi clay powder and 200g of carboxymethyl cellulose were each weighed, and after performing dry powder mixing for 5 minutes at a circumferential speed of 20.2m/sec using a Henschel mixer, 4Kg of a 5% solution of crystalline cellulose was added. , kneaded for 5 minutes. Since no coarse granulated lumps were observed during kneading, an additional 530 g of pure water was added and kneading was continued for 5 minutes. The particle size distribution of the kneaded coarse granulated mass taken out from the Henschel mixer is 10-20mm65%, 20-30mm
It was 35%. The pellets were granulated using a die with a hole diameter of 3 mm and subjected to the same post-treatment as in Example 1. The average mechanical strength of the pellets was 6.9 kg. Note that the granulation was smooth and had a good shape.

Comparative Example 3 After adding up to a 5% crystalline cellulose solution in the same manner as in Example 3, 800 g of pure water was added and kneaded for 5 minutes. The particle size of the kneaded coarse granulated mass taken out from the Henschel mixer was 40-50 mm (15%), 50-70 mm (85%), and the pellets after granulation adhered to each other and had an average mechanical strength of 4 kg. .

Claims (1)

[Claims] 1. When granulating a zeolite molded product formed from a mixture of zeolite and a binder, the particle size of the kneaded coarse granulated mass of the mixture of zeolite, binder, and granulation aid is adjusted to 1 to 50 mm; A method for forming zeolite characterized by extrusion granulation.