KR100600939B1 - Process for preparing artificial zeolite by a slurry reaction method - Google Patents

Abstract

FIELD OF THE INVENTION The present invention relates to a method for preparing artificial zeolites by slurry reaction method, wherein the method comprises alkalis having x kilograms and one normal concentration or higher normal concentration of incineration ash or other aluminosilicate-containing materials for preparing the slurry. Mixing y l of an aqueous solution of hydroxide at a ratio of y / x of 0.1 to 1.5 (l / kg); And

Heating the slurry to cause a zeolite forming reaction with water that is removed continuously or intermittently by steam to at least reduce the concentration of alkali that occurs essentially using the process of reaction to facilitate the reaction. It is characterized in that it is provided to prepare an artificial zeolite having a.

Zeolite, slurry, steam, normal concentration

Description

Production method of artificial zeolite by slurry reaction method {PROCESS FOR PREPARING ARTIFICIAL ZEOLITE BY A SLURRY REACTION METHOD}

1 is a graph showing the relationship between reaction time and conversion rate,

2 is a graph showing the relationship between alkali concentration and conversion rate,

3 is a graph showing the relationship between reaction temperature and reaction time,

4 is a flow chart of a continuous manufacturing system according to the present invention.

The present invention relates to a process for preparing zeolites from incineration ash such as flyash and other aluminosilicate-containing substances.

Since zeolites are crystalline aluminosilicates, naturally occurring zeolites are known as mordenite and clinoptilolite. Synthetic zeolites such as A and Y zeolites made from sodium silicate and sodium aluminate are used as catalysts, molecular sieves and the like.

On the other hand, it is also well known to prepare zeolites by heating a slurry of alkaline aqueous solution and fly ash at several tens to 100 캜 for several hours. This zeolite is generally called artificial zeolite. Artificial zeolites have similar ion exchangeability and absorbency as do natural and synthetic zeolites. However, its composition, crystal structure and purity are not precisely controlled compared to synthetic zeolites. Artificial zeolites, on the other hand, are cheaper and therefore suitable for high volume consumption applications such as, for example, soil improving materials and deodorants. However, because they must be cheaper for wider applications, improvements to the method of making them are required.

In the conventional method, it takes 5 hours for a mixture of 2.2 liters of aqueous alkali solution per kilogram of fly ash to be heated to 100 ° C (Japanese Patent Laid-Open No. 6-321525). We found that it took 20 hours to achieve 50% conversion.

In addition, the reaction mixture obtained after the reaction contains water glass, which is a by-product other than zeolite, and as a result, the reaction mixture is tacky and requires a high cost for solid (zeolite) -liquid separation. In addition, the separated zeolite is still sticky, requiring a large amount of water and time to wash with water.

The present invention preferably makes the solid-liquid separation easier or unnecessary by reducing the amount of by-product water glass (soluble silicate), thereby reducing wasteful consumption of sodium hydroxide, potassium hydroxide and the like, resulting in shorter reaction times. Provided is a process for producing high quality artificial zeolites, with a conversion rate of at least 50% to zeolites within.

Conventionally, the alkali concentration in the water phase of the reaction system decreases as the reaction proceeds. The inventors have found that byproducts of the water glass inhibit the reaction mixture from becoming non-tacky when the reduction in alkali concentration is at least suppressed or preferably avoided by evaporating and removing water from the reaction system during the reaction. It has been found that solid-liquid separation is easier or that most of the water in the reaction system can be evaporated at the end of the reaction. In some cases, there is no inherent difficulty with conventional methods of removing liquid from the reaction mixture. In addition, the supplied alkali is used more efficiently during the reaction.

Moreover, even if the reaction temperature rises above 100 ° C., a sufficient advantage, that is, an increase in crystallinity comparable to cost (Japanese Patent Application Laid-open No. 6-321525, paragraph 41) is not achieved, but the present inventors It has been found in the process that higher conversions can be achieved in a shorter time by applying a reaction temperature of 100 ° C. or more, and that the amount of alkali metal hydroxides, such as sodium hydroxide, is less, which is advantageous in thermal efficiency due to the smaller amount of water to be used. .

The present invention relates to a method for preparing artificial zeolite comprising the following steps:
mixing x kg of incineration ash or other aluminosilicate-containing material with an aqueous alkali metal hydroxide solution having a concentration of at least 1 N of y 1 to prepare a slurry, wherein the ratio y / x is 0.1 to 1.5 (ℓ / kg) being]; And

Heating the slurry to cause a zeolite-forming reaction (water is removed continuously or intermittently by evaporation, at least inhibiting the decrease in naturally occurring alkali concentrations as the reaction proceeds to promote the reaction).

Moreover, this invention includes the method in which heating is performed at the temperature of 100 degreeC or more and 350 degrees C or less.

The present invention will be described with reference to FIG. 1, but is not limited thereto.

1 shows the results of experiments made by using a pressurized agitation autoclave. Fly ash and 3.5N aqueous sodium hydroxide solution are fed at a rate of 2 kg / 1 L and heated to 150 ° C. The horizontal axis represents reaction time and the vertical axis represents conversion to zeolite. The conversion is measured by X-ray fluorescence spectroscopy.

As disclosed in curve A of FIG. 1 according to the invention, at 45 minutes after the start of heating, an aliquot of water corresponding to 10% by weight of the fly ash supplied is removed by evaporation from the valve at the top of the autoclave. do. The conversion rate before water is removed is about 15%, the increase of which is extremely small. However, the conversion rate after the water is removed sharply increases. The conversion rate exceeds 30% at 1.5 hours, but its increase tends to be small. The water is removed continuously from 1.5 hours to 2 hours after starting the heating. Then, the conversion rate increases sharply again to reach 57%.

If no water removal is carried out according to the invention, the conversion remains at about 20% even in 2 hours. In order to achieve higher conversions by conventional methods, the amount of sodium hydroxide to be fed may be made larger to reduce the decrease in the concentration of sodium hydroxide. In general, the use of an aqueous sodium hydroxide solution having a concentration of 4N or more is avoided in consideration of corrosion of the apparatus, and consequently the supply amount of the aqueous sodium hydroxide solution is inevitably increased. Curve B in FIG. 1 shows an extreme example of this case. In other words, when an amount of 20 times the amount used in Curve A, which is 10 L of 3.5 N aqueous sodium hydroxide solution per kilogram of fly ash, is used, a high conversion rate of 50% or more can be achieved in 1.5 hours. However, this is not practical because of the low production volume per volume of the reactor and the high cost of heating and post-treatment of large aqueous solutions. In Japanese Patent Application Laid-open No. 6-321525, 2.2 L of 2N aqueous sodium hydroxide solution is used per kg of fly ash, whereas in the present invention, the amount of aqueous sodium hydroxide solution is 1.5 L or less, which is extremely unachievable by conventional methods. High conversions are obtained.

The reaction mixture prepared using the process of the invention is preferably not in a slurry state but in a solid state. The reaction mixture obtained in the conventional process is tacky due to the by-product water glass (soluble silicate) and contains a large amount of water. Therefore, it is difficult to separate the liquid. The invention described in Japanese Patent Application Laid-open No. 6-321525 solves the above problem by lowering the temperature of the slurry to 70 ° C. or lower and then separating and purifying the product crystals and the excess aqueous alkali solution using a liquid separation device. In the present invention, the liquid separation method is preferably no longer used.

The reaction mixture obtained was preferably washed to remove residual alkali metal hydroxides. Unlike conventional methods, there are no difficulties in cleaning and liquid separation. For washing, an aqueous calcium chloride solution or diluted hydrochloric acid solution is preferable.

Incinerator ash as a raw material includes residues after incineration of coal, activated sludge, paper sludge, and waste, among which fly ash is preferable. Aluminosilicate-containing materials other than incineration ashes include naturally occurring minerals such as analcite, dolomite, feldspar and volcanic ash.

The concentration of the alkali hydroxide aqueous solution is 1N or more, preferably 2N to 4N. If the concentration is lower than the lower limit, the reaction rate is too small to achieve high conversion in a short time. The data supporting this is shown in FIG. 2. A large amount of 20 liters of aqueous sodium hydroxide solution having a selected concentration per kg of fly ash is fed to a pressurized stirred autoclave. Then, as the reaction proceeds, the decrease in the concentration of sodium hydroxide is small, and the relationship between the concentration and the conversion can be seen. The reaction is carried out at 150 ° C. for 2 hours. The vertical axis represents the selected concentration and the horizontal axis represents the achieved conversion. A concentration of 2N is required at a 30% conversion rate and a concentration of 3N at a 50% conversion rate. Therefore, when a smaller amount of aqueous sodium hydroxide solution is used in accordance with the present invention, the sodium hydroxide is consumed as the reaction proceeds, followed by removal of water in accordance with the present invention to maintain the concentration of sodium hydroxide at this level by removing water. It can be seen that a conversion rate can be achieved.

As the alkali metal hydroxide, sodium hydroxide or potassium hydroxide is preferably used.

0.1 L to 1.5 L, preferably 0.2 L to 0.7 L, of aqueous sodium hydroxide solution is mixed with 1 kg of each of the incineration ash or aluminosilicate-containing material (hereinafter represented by fly ash as a typical example). Usually, the amount of aqueous sodium hydroxide solution is smaller when the concentration of the solution is high and larger when the concentration is low.

Conventionally, reaction was performed at 100 degrees C or less. However, the time required to achieve the selected conversion is significantly shorter by setting the reaction temperature above 100 ° C. FIG. 3 shows that 10 L of 3.5 N aqueous sodium hydroxide solution per kilogram of fly ash is fed to a pressurized stirred autoclave and heated at a selected temperature to determine the required reaction time to obtain a selected conversion (50% -60%). Data from the experiment is shown. Although a large amount of aqueous sodium hydroxide solution is used, it takes 20 hours to achieve a high conversion of 50% at 100 ° C. according to conventional methods. However, 6 hours and 1.7 hours at 125 DEG C and 150 DEG C, respectively, are sufficient. In these experiments, in order to obtain easy-to-understand data, large amounts of aqueous sodium hydroxide solution are used and water is not removed. The same trend was observed when the amount of aqueous sodium hydroxide solution was reduced and water removal was carried out. In the conventional method in which a large amount of aqueous solution is used, if the reaction is carried out at a high temperature, a lot of heat is required, which is uneconomical. This is avoided in this method. However, disadvantages have been observed in materials of thermal efficiency and quality required for the device at temperatures above 350 ° C.

In the above, embodiments of the batch method for the present invention have been described. Next, an embodiment of the continuous method will be described.

In FIG. 4, the fly ash F is fed to the rotary screw type mixing extruder 1 at a rate of 100 kg (about 0.1 m 3) / hr. At the same time, 3.5N aqueous sodium hydroxide solution (A) is fed to the rotary screw-type mixing extruder 1 at a rate of 50 l / hr. The resulting slurry is fed to a pressurized screw-stirring mixing reactor 3 with a screw pump 2. The reactor 3 is equipped with a jacket of heating medium and heated to 150 ° C. The internal pressure of the reactor 3 is maintained at 5 atm (gauge) mainly by heating. The slurry is discharged after 40 minutes in the reactor 3 and passed to the flash evaporator 4 (the amount of water corresponding to about 10% by weight of the fly ash fed at 100 kg / hr is removed by evaporation). The remaining slurry is fed in a form similar to the pressurized screw agitating-mixing reactor 6 with a screw pump 5 and treated at 150 ° C., 5 atm (gauge) for 40 minutes, then about 10 kg of water. / hr is evaporated in the flash evaporator (7). The remaining slurry is then fed to a stir-mix reactor 9 with a pump 8. The reactor 9 is also heated up to 150 ° C., but the water is gradually recovered from the outlet and discharged in the middle without being closed differently from the reactor 3 and the reactor 6. The slurry fed to the pump 8 loses most of its water for 40 minutes of residence in the reactor 9. At the outlet of the reactor 9, it is not in the slurry state but is a zeolite product in solid and separated form. This is supplied to the washing tower 10 and washed with an aqueous calcium chloride solution. This washing removes a small amount of unreacted sodium ions remaining in the product, while at the same time replacing some of the sodium in the zeolite with calcium. Alternatively, sodium ions can be removed by washing with diluted aqueous hydrochloric acid solution. The resulting slurry is transferred to a belt-press dehydrator 12 with a screw pump 11 for compacting and dehydration, and then to the dryer 14 to be dried via the belt conveyor 13 to the final product 15. ). Artificial zeolites having a conversion of 57% are obtained in an amount of 1.25 times the weight of the fly ash as a raw material.

As described above, the reactors 3 and 6 operate at a pressure of 5 atm which occurs by setting the temperature to 150 ° C. in the presence of water, but pressurization is not critical to the invention. In fact, the intended reaction to form the zeolite proceeds by heating at 150 ° C. under vapor pressure without pressure.

Claims (5)

Process for preparing artificial zeolite comprising the following steps: mixing x kg of incineration ash or other aluminosilicate-containing material with an aqueous alkali metal hydroxide solution having a concentration of at least 1 N of y 1 to prepare a slurry, wherein the ratio of y / x is 0.1 to 1.5 (ℓ / kg) being]; And Heating the slurry to cause a zeolite-forming reaction (water is removed continuously or intermittently by evaporation, at least inhibiting the decrease in naturally occurring alkali concentrations as the reaction proceeds to promote the reaction). The method of claim 1, Heating is performed at the temperature of 100 degreeC or more and 350 degrees C or less. The method according to claim 1 or 2, The reaction mixture obtained after the reaction is washed to remove alkali without performing liquid separation treatment. The method according to claim 1 or 2, The reaction mixture obtained after the reaction is not a highly viscous slurry containing water glass produced by the side reaction, but a solid that is easy to wash. The method according to claim 1 or 2, The incineration ash is a flyash produced by the combustion of coal, activated sludge, paper sludge or garbage.

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