JPH09255324A - Production of zeolite and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a zeolite capable of effectively producing the zeolite than heretofore by allowing coal ash to react with sodium hydroxide and to provide a production device. SOLUTION: The coal ash is mixed with a sodium hydroxide aq. soln. having <=16wt.% sodium hydroxide concn. to make slurry 3, and the coal ash is allowed to react preliminarily with the sodium hydroxide at a temp. < above 100 deg.C. The slurry 3 (3a) is supplied continuously to a pressure reactor 5 and heated to above 100 deg.C to allow the coal ash to react with the sodium hydroxide. Then the slurry 3 (3a) is raised the temp. and the preliminary reaction is executed efficiently and also a heat recovery from the high temp. slurry discharged continuously from the pressure reactor 5 is executed by subjecting the slurry 3 (3b) discharged continuously from the pressure reactor 5 to heat exchange with the slurry 3 (3a) to be subjected to the preliminary reaction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing zeolite from coal ash (fly ash) generated in power generation equipment using coal as an energy source.

[0002]

2. Description of the Related Art A large amount of coal ash generated in a power generation facility using coal as an energy source is used as a cement raw material or a roadbed material, but about half of the coal ash is landfilled. Therefore, as a method of using this coal ash for high value-added applications, a method of producing zeolite used as an ion exchanger, an adsorbent, a reaction catalyst, etc. by reacting with sodium hydroxide has come to the attention. There is.

By the way, as a method for producing zeolite by reacting coal ash with sodium hydroxide, for example,
As shown in FIG. 2, the coal ash 52 stored in the fly ash hopper 51 is put in a reaction tank 55 together with an aqueous sodium hydroxide solution 54 adjusted to a predetermined concentration and temperature in an aqueous sodium hydroxide solution tank 53, and in a slurry state. After heating and stirring the coal ash and sodium hydroxide for a predetermined period of time to make the coal ash into a zeolite, the slurry 61 is extracted to a buffer tank 56 and sent to a dewatering device 57 to separate an aqueous sodium hydroxide solution, A method is used in which the product is washed in the washing tank 58, dehydrated by the dehydrator 59, and dried by the dryer 60 to obtain a product.

[0004]

However, in the above conventional method, since the reaction rate of coal ash and sodium hydroxide is slow, it takes a long time to react the coal ash with sodium hydroxide to form zeolite. However, there is a problem that the equipment becomes large. That is, when the reaction temperature is low and the concentration of the sodium hydroxide aqueous solution is lower than the predetermined concentration, the reaction itself between coal ash and sodium hydroxide is slowed, and the reaction temperature is raised to increase the sodium hydroxide aqueous solution. When the concentration is increased to increase the excess amount of sodium hydroxide, in the early stage of the reaction, the zeolitic reaction occurs rapidly, but the particle surface of the coal ash is covered with the reaction product (crystalline film). Then, the subsequent reaction is hindered, and it becomes difficult to continue and efficiently carry out the reaction. Therefore, in the conventional zeolite manufacturing method, there is a problem that the manufacturing apparatus (reactor) becomes large and the manufacturing cost increases.

The present invention solves the above-mentioned problems, and a method and a method for producing a zeolite capable of producing a zeolite more efficiently than before by efficiently reacting coal ash with sodium hydroxide. The purpose is to provide a device.

[0006]

In order to achieve the above object, a method for producing zeolite of the present invention is to prepare a slurry by mixing coal ash with an aqueous sodium hydroxide solution having a sodium hydroxide concentration of 16% by weight or less. After preliminarily reacting coal ash with sodium hydroxide at a temperature not exceeding 100 ° C, the slurry is continuously supplied to a pressure reaction tank and heated to a temperature exceeding 100 ° C under pressure to produce coal. The ash and sodium hydroxide are reacted with each other, and the slurry after the reaction discharged from the pressure reaction tank is subjected to the preliminary reaction (preliminary reaction).
By exchanging heat with the slurry to be performed,
It is characterized in that heat is recovered from the slurry after the reaction discharged from the pressure reaction tank.

The method for producing zeolite according to claim 1, characterized in that the preliminary reaction between the coal ash and sodium hydroxide is carried out at a temperature of 80 to 100 ° C.

Further, the reaction in the pressure reaction tank is carried out by 105
It is characterized in that it is performed at a temperature of ~ 130 ° C.

The sodium hydroxide concentration in the aqueous sodium hydroxide solution is set to 2 to 16% by weight.

Further, the content rate (slurry concentration) of coal ash in the slurry supplied to the pressure reaction tank is set to 10 to 30% by weight.

Further, the zeolite manufacturing apparatus of the present invention is an apparatus for carrying out the above-described zeolite manufacturing method of the present invention, and a mixing tank for mixing coal ash with an aqueous sodium hydroxide solution to form a slurry, A preliminary reaction tank for preliminarily reacting the coal ash in the slurry with sodium hydroxide at a temperature of ℃ or less, and the slurry at 100 ° C under pressure.
A pressure reaction tank for heating coal ash to react with sodium hydroxide by heating to a temperature above 100 ° C., a slurry supply means for continuously supplying the slurry from the mixing tank to the pressure reaction tank, and the pressurization. A heat exchanger for raising the temperature of the slurry in the mixing tank by exchanging heat with the slurry continuously discharged from the reaction tank and preliminarily reacting the coal ash and sodium hydroxide in the slurry. It is characterized by doing.

The mixing tank is also used as the preliminary reaction tank for preliminarily reacting the coal ash in the slurry with sodium hydroxide.

In the zeolite manufacturing method and manufacturing apparatus of the present invention, the phrase "continuously supplying the slurry to the pressure reaction tank" literally means continuously supplying the slurry without interruption. It is a broad concept including an intermittent continuous supply mode. Further, "continuously discharged from the pressurized reaction tank" is a broad concept including not only the mode of discharging the slurry continuously without being interrupted literally but also the mode of intermittent continuous discharge. .

[0014]

In the method for producing zeolite of the present invention,
Sodium hydroxide concentration in sodium hydroxide aqueous solution is 1
The crystalline film formed on the surface of the coal ash particles is efficiently dissolved by preliminarily reacting at 6% by weight or less and at a temperature of 100 ° C. or less, and then 10% in a pressure reaction tank.
Since the zeolite formation reaction is carried out at a temperature above 0 ° C, it is possible to prevent the surface of the coal ash from being covered by the reaction product (crystalline film) of sodium hydroxide and coal ash and hindering the reaction. Therefore, it becomes possible to efficiently proceed the zeolite formation reaction.

Further, since the slurry discharged from the pressure reaction tank is heat-exchanged with the slurry to be preliminarily reacted, heat can be efficiently recovered from the high temperature slurry discharged from the pressure reaction tank. In addition to being able to carry out the pre-reaction, it is possible to raise the temperature of the slurry to be pre-reacted and to efficiently pre-react the coal ash and sodium hydroxide in the slurry, improving the overall reaction efficiency. It is possible to let

Further, in the zeolite manufacturing method of the present invention, since the operation is a continuous type, the concept of the multi-stage tank type reactor makes it possible to reduce the volume of the reaction tank and efficiently recover heat. However, in the case of a conventional batch-type manufacturing apparatus, not only is the volume of the reaction tank increased, but it is also difficult to efficiently recover heat.

Further, by setting the preliminary reaction temperature to 80 to 100 ° C., it becomes possible to efficiently advance the preliminary reaction between the coal ash and sodium hydroxide. The temperature range of 80 to 100 ° C is a temperature that can be easily realized by heat exchange with the slurry (for example, 105 to 130 ° C) heated in the pressure reaction tank. However, if it is not possible to raise the temperature to the prescribed temperature only by the above heat exchange,
It is also possible to separately raise the temperature to a predetermined temperature by using a heat source such as steam.

Further, by setting the heating temperature of the slurry in the pressure reaction tank to 105 to 130 ° C., it becomes possible to efficiently proceed the reaction within a practical operating pressure range. The reaction rate of coal ash and sodium hydroxide is
It tends to increase as the heating temperature of the slurry in the pressure reaction tank increases, but if it is attempted to heat it to a temperature exceeding 130 ° C., the pressure becomes high, which leads to an increase in equipment costs and operating costs. Absent.

Further, in the method for producing zeolite of the present invention, it is preferable that the sodium hydroxide concentration of the aqueous sodium hydroxide solution is in the range of 2 to 16% by weight. When the amount is less than 10% by weight, the reaction rate decreases, and when the amount exceeds 16% by weight, a crystalline film is formed on the surface of the coal ash and the reaction rate decreases, which is not preferable.

Further, in the method for producing zeolite of the present invention, it is preferable that the content (slurry concentration) of coal ash in the slurry supplied to the pressure reactor is 10 to 30% by weight. If the slurry concentration exceeds 30% by weight, it becomes difficult to handle the slurry.
If it is less than wt%, the handling amount of the sodium hydroxide aqueous solution per unit treatment amount of coal ash increases, which leads to enlargement of equipment, which is not desirable.

Further, in the zeolite manufacturing apparatus of the present invention, the slurry in which the coal ash and the sodium hydroxide aqueous solution are mixed in the mixing tank is mixed in the preliminary reaction tank at 10
After preliminarily reacting at a temperature of 0 ° C. or lower, it is continuously sent to a pressure reaction tank and heated to a temperature of more than 100 ° C. under pressure so that the reaction between coal ash and sodium hydroxide As the high temperature slurry discharged from the pressurized reaction tank efficiently exchanges heat with the slurry to be preliminarily reacted, heat is recovered from the slurry after reaction and the slurry to be preliminarily reacted. Can be efficiently heated.

Therefore, by using the zeolite manufacturing apparatus of the present invention, the above zeolite manufacturing method can be reliably carried out and the zeolite can be manufactured efficiently.

When the mixing tank is also used as a preliminary reaction tank for preliminarily reacting the coal ash in the slurry with sodium hydroxide, the construction of the apparatus is simplified to reduce the equipment cost and save the equipment. It becomes possible to make space.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be shown and the features thereof will be described in more detail. FIG. 1 is a diagram showing a zeolite manufacturing apparatus according to an embodiment of the present invention.

As shown in FIG. 1, the zeolite manufacturing apparatus is a mixing tank for mixing coal ash 1 with an aqueous sodium hydroxide solution 2 to form a slurry 3 (3a) (also serves as a preliminary reaction tank in this embodiment). 4) and slurry 3 (3
a) is heated under pressure to a temperature over 100 ° C. to react the coal ash with sodium hydroxide, and the slurry 3 (3a) is continuously mixed from the mixing tank 4 to the pressure reaction tank 5. Slurry supply means 6 for supplying, and pressure reaction tank 5
The heat exchanger 7a for causing the slurry 3 (3b) continuously discharged from the tank to exchange heat with the slurry 3 (3a) in the mixing tank 4 to raise the temperature of the slurry 3 (3a) in the mixing tank 4.
A slurry tank 8 for storing the slurry 3 (3c) after being discharged from the pressure reaction tank 5 and subjected to heat exchange; a dehydrator 9 for dehydrating the slurry 3 (3c) sent from the slurry tank 8; It is configured by including a dryer 10 for drying the solid matter (zeolite). Furthermore, this zeolite manufacturing apparatus is provided with a hopper 1 for storing coal ash 1.
1, a stock solution tank 13 for storing a stock solution 12 of sodium hydroxide,
A sodium hydroxide tank 14 for storing an aqueous sodium hydroxide solution adjusted to a predetermined concentration is provided.

Further, the above-mentioned zeolite production apparatus is
Dewatering machine (dewatering machine) 9 for dehydrating the slurry containing the produced zeolite, and water washing tank 2 for washing dehydrated solid matter with water
2. A dehydrator 23 for re-dehydrating the solid matter after washing with water, a dryer 10 for drying the re-dehydrated solid matter, and the like are provided. There are no particular restrictions on the types of dehydrator and dryer, and various dehydrators and dryers having prescribed dehydration performance and drying performance can be used.

In the mixing tank 4 which also serves as a preliminary reaction tank,
A stirrer 4a is provided for surely mixing the coal ash and sodium hydroxide to form a slurry, and for efficiently performing a preliminary reaction of the coal ash and sodium hydroxide. Also, a stirrer 5a for stirring the slurry 3 to efficiently react the coal ash and the sodium hydroxide in the slurry is provided.

Further, in the above zeolite manufacturing apparatus, the slurry supplying means 6 for continuously supplying the slurry 3 (3a) from the mixing tank 4 to the pressure reaction tank 5 includes the mixing tank 4 and the pressure reaction tank. 5, a slurry supply line 16a, a part of a circulation line 17 for withdrawing the slurry 3 (3b) in the pressurized reaction tank 5 from the bottom and an inflow from the top, a pump 21 and the like. . However, the configuration of the slurry supply means 6 is not limited to this, and may have another configuration. Further, a heater 19 for heating the slurry 3 (3b) is arranged in a portion of the circulation line 17 that constitutes a part of the slurry supply means 6.

Next, a method for producing zeolite using the zeolite producing apparatus configured as described above and the operation of the zeolite producing apparatus will be described. First, the coal ash 1 is supplied from the hopper 11 and the sodium hydroxide aqueous solution 2 of about 3.5 N (about 12.3% by weight) is supplied from the sodium hydroxide tank 14 to the mixing tank 4 and mixed to form the slurry 3 (3a). ). The slurry concentration is about 30% by weight here. Then, the slurry 3 (3a) in the mixing tank 4 is continuously supplied to the pressure reaction tank 5 and heated to about 120 ° C. under a pressure of 0.8 kg / cm ² G to heat the coal ash and water in the slurry. Sodium oxide is reacted and the coal ash is made into zeolite. At this time, the slurry 3 (3
b) is taken out from the bottom and allowed to react while being circulated through the circulation line 17. Further, the slurry 3 (3b) circulating in the circulation line 17
A part of is introduced to the heat exchanger 7a via the liquid sending line 20,
Slurry supply line 16a, slurry circulation line 16b
After heat exchange with the slurry 3 (3a) in the mixing tank 4 which circulates via the heat exchanger 7b and after heat exchange with the sodium hydroxide aqueous solution 2 supplied from the sodium hydroxide tank 14 to the mixing tank 4 in the heat exchanger 7b. , Liquid is sent to the slurry tank 8. In this embodiment, by performing the heat exchange, the temperature of the slurry 3 (3b) after the reaction is lowered to about 30 ° C., while the slurry 3 in the mixing tank 4 is
The temperature of (3a) was raised to about 90 ° C. In this way, the temperature of the slurry 3 (3a) in the mixing tank 4 is raised to about 90 ° C., so that the coal ash and the hydroxide in the slurry 3 (3a) are also mixed in the mixing tank (preliminary reaction tank) 4. The preliminary reaction of sodium proceeds efficiently. Next, the slurry 3 (3c) in the slurry tank 8 is sent to the dehydrator 9 to be dehydrated, and the separated solid matter (zeolite cake) is washed in the water washing tank 22 and then again dehydrated in the dehydrator 23, The product, zeolite, is obtained by sending it to the dryer 10 and drying it. A part of the separated liquid separated by the dehydrator is circulated to the sodium hydroxide tank 14 and used as a diluting liquid of the sodium hydroxide stock solution.

According to the method according to the above embodiment,
A sodium hydroxide aqueous solution of about 3.5 N (about 12.3% by weight) was used, and the sodium hydroxide aqueous solution and coal ash were mixed to form a slurry, which was preliminary prepared at a temperature of about 90 ° C. in the mixing tank 4. The crystalline film formed on the surface of the coal ash particles by the reaction is efficiently dissolved, and then the slurry 3
Since (3a) is continuously supplied from the mixing tank 4 to the pressure reaction tank 5 and heated to about 120 ° C. under pressure to cause reaction, the surface of the coal ash reacts with sodium hydroxide and coal ash. It is possible to prevent the reaction from being covered with the reaction product of 1 and hindering the reaction, and to efficiently proceed the zeolitic reaction.

The slurry 3 (3b) continuously discharged from the pressure reaction tank 5 is mixed with the slurry 3 (3b) in the mixing tank 4.
The temperature of the slurry 3 (3a) in the mixing tank 4 is raised to about 90 ° C. by heat exchange with a), so that the coal ash and the sodium hydroxide can be efficiently preliminarily reacted in the mixing tank 4. It becomes possible and the pressurized reaction tank 5
It is possible to efficiently recover heat from the high temperature slurry 3 (3b) discharged from, and it is possible to improve the efficiency as a whole.

In the above embodiment, the case where the pressure reaction tank has one stage has been described, but it is also possible to have a multi-stage configuration of two or more stages. This also applies to the mixing tank.

In the above embodiment, the case where the heat exchange between the slurry discharged from the pressure reaction tank and the slurry in the mixing tank is performed in one stage has been described.
It is also possible to have a multi-stage configuration of more than one stage. Further, in the above embodiment, the case where the mixing tank is also used as the preliminary reaction tank has been described, but a preliminary reaction tank may be provided separately from the mixing tank.

The present invention is not limited to the above embodiment in other respects as well, and the specific structure of the mixing tank and the pressure reaction tank, operating conditions such as pressure and temperature, pressure reaction With respect to the method of supplying the slurry to the tank, various applications and modifications can be made within the scope of the invention.

[0035]

As described above, according to the method for producing zeolite of the present invention, the sodium hydroxide concentration in the aqueous sodium hydroxide solution is set to 16% by weight or less, and the coal ash and the hydroxide in the slurry are heated at a temperature of 100 ° C. or less. After preliminarily reacting sodium, the pressure reaction tank is designed to carry out the zeolitic reaction at a temperature exceeding 100 ° C.
It is possible to prevent the surface of the coal ash from being covered with the reaction product (crystalline film) of sodium hydroxide and the coal ash and hindering the reaction, so that the zeolite-forming reaction can proceed efficiently.

Further, since the slurry discharged from the pressure reaction tank is heat-exchanged with the slurry to be preliminarily reacted, heat can be efficiently recovered from the high temperature slurry discharged from the pressure reaction tank. In addition to being able to carry out the pre-reaction, it is possible to raise the temperature of the slurry to be pre-reacted and to efficiently pre-react the coal ash and sodium hydroxide in the slurry, improving the overall reaction efficiency. It will be possible. Therefore, according to the method for producing zeolite of the present invention, it is possible to cause the coal ash and sodium hydroxide to react with each other efficiently, and to greatly improve the productivity of zeolite.

Further, by setting the preliminary reaction temperature to 80 to 100 ° C., the preliminary reaction of coal ash and sodium hydroxide can be efficiently progressed, and the present invention can be further carried out.

Further, by setting the heating temperature of the slurry in the pressure reaction tank within the range of 105 to 130 ° C., it becomes possible to efficiently proceed the reaction within a practical operating pressure range.

Further, by setting the concentration of sodium hydroxide in the aqueous sodium hydroxide solution in the range of 2 to 16% by weight, the reaction between coal ash and sodium hydroxide that prevents the amorphous solubilization on the surface of the coal ash. It becomes possible to suppress the formation of a film of the product and to efficiently proceed the zeolitic reaction, and the present invention can be more practically performed.

The content (slurry concentration) of coal ash in the slurry supplied to the pressure reactor is 10 to 30% by weight.
By setting it in the range of 1, it becomes possible to prevent the handling thereof from becoming particularly difficult and prevent the slurry amount to be treated from becoming excessively large, and to efficiently react the coal ash and sodium hydroxide. .

Further, by using the zeolite production apparatus of the present invention, the zeolite production method of the present invention can be reliably carried out, and the zeolite can be produced efficiently.

Further, by using the mixing tank as a preliminary reaction tank for preliminarily reacting the coal ash and the sodium hydroxide in the slurry, the structure of the apparatus is simplified and the equipment cost is reduced and the equipment space is saved. It becomes possible to plan.

[Brief description of drawings]

FIG. 1 is a view showing a zeolite manufacturing apparatus used for carrying out a zeolite manufacturing method of the present invention.

FIG. 2 is a diagram showing a conventional zeolite manufacturing apparatus.

[Explanation of symbols]

 1 Coal ash 2 Sodium hydroxide aqueous solution 3 (3a, 3b, 3c) Slurry 4 Mixing tank 4a Stirrer 5 Pressurized reaction tank 5a Stirrer 6 Slurry supply means 7a, 7b Heat exchanger 8 Slurry tank 9 Dehydrator 10 Dryer 11 Hopper 12 Sodium hydroxide stock solution 13 Stock solution tank 14 Sodium hydroxide tank 15 Neutralization tank 16a Slurry supply line 16b Slurry circulation line 17 Circulation line 19 Heater 20 Liquid transfer line 21 Pump 22 Wash tank 23 Dehydrator

Claims (7)

[Claims] 1. Coal ash is mixed with an aqueous sodium hydroxide solution having a sodium hydroxide concentration of 16% by weight or less to form a slurry, and the coal ash and sodium hydroxide are preliminarily reacted at a temperature not exceeding 100 ° C. After that, the slurry is continuously supplied to a pressure reaction tank and heated to a temperature of more than 100 ° C. under pressure to react the coal ash with sodium hydroxide. The slurry is heat-exchanged with the slurry to be subjected to the preliminary reaction (preliminary reaction), whereby heat is recovered from the reacted slurry discharged from the pressurized reaction tank. Method for producing zeolite. 2. The method for producing zeolite according to claim 1, wherein the preliminary reaction between the coal ash and sodium hydroxide is carried out at a temperature of 80 to 100 ° C. 3. The reaction in the pressure reactor is 105 to 1
The method for producing zeolite according to claim 1 or 2, wherein the method is performed at a temperature of 30 ° C. 4. The method for producing zeolite according to claim 1, wherein the sodium hydroxide concentration in the aqueous sodium hydroxide solution is 2 to 16% by weight. 5. The content (slurry concentration) of coal ash in the slurry supplied to the pressure reactor is 10 to 30% by weight.
The method for producing zeolite according to any one of claims 1 to 4, wherein 6. A mixing tank for mixing coal ash with an aqueous solution of sodium hydroxide to form a slurry, a preliminary reaction tank for preliminarily reacting the coal ash in the slurry with sodium hydroxide at a temperature of 100 ° C. or lower, A pressure reaction tank for heating the slurry to a temperature of more than 100 ° C. under pressure to react the coal ash with sodium hydroxide; and a slurry for continuously supplying the slurry from the preliminary reaction tank to the pressure reaction tank. The slurry supplying means, the slurry continuously discharged from the pressure reaction tank and the slurry to be subjected to the preliminary reaction are heat-exchanged to generate heat from the slurry after the reaction discharged from the pressure reaction tank. A zeo for carrying out the method according to any one of claims 1 to 5, further comprising a heat exchanger for collecting and raising the temperature of the slurry in the preliminary reaction tank. Ito of manufacturing equipment. 7. The apparatus for producing zeolite according to claim 6, wherein the mixing tank is also used as the preliminary reaction tank for preliminarily reacting the coal ash in the slurry with sodium hydroxide.