JP2730820B2 - Method for producing zeolite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing zeolite from sewage sludge or incinerated ash.

[0002]

BACKGROUND OF THE INVENTION Zeolites are minerals called _{zeolite, Me 2 / n O · Al} 2 O 3 · xSiO 2 · yH 2 O (Me: alkaline or alkaline-earth, x, y: coefficient) by the general formula It is a hydrous aluminosilicate mineral having a three-dimensional crystal structure represented. This zeolite is known to contain a large amount of water in the crystal, release this water when heated or depressurized, and has the ability to adsorb molecules into the vacated crystal.

[0003] Generally, the quality of zeolite is evaluated by base substitution capacity (CEC), and relatively inexpensive natural zeolite is CEC.
Is about 150 meq / 100g. Synthetic zeolites produced industrially from sodium aluminate, sodium silicate, and NaOH have excellent adsorption performance with a CEC of 400-600 meq / 100g, but cost per million tons of several million yen. It has the disadvantage of being very expensive.

Therefore, recently, Japanese Patent Application Laid-Open No. Hei.
As disclosed in Japanese Patent Application Laid-Open No. HEI 3-40914, a method of synthesizing zeolite by boiling fly ash generated from coal ash together with NaOH or the like has been studied. However, the zeolite synthesized by this method has a CEC of 200 to 350 meq / 100 g according to its catalog value, which is less expensive than the conventional synthetic zeolite, but has a problem that the CEC value is low. Moreover, a zeolite manufacturing apparatus that boil fly ash with NaOH requires a large amount of heat, and also has a problem that a large amount of NaOH waste liquid is generated from the zeolite manufacturing apparatus.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and produces a zeolite having a CEC almost equivalent to that of a synthetic zeolite at a very low cost and without causing problems such as NaOH waste liquid. It has been completed to provide a method for producing a zeolite.

[0006]

Means for Solving the Problems To solve the above problems, the present inventors have focused on wastes such as sewage sludge containing SiO ₂ and Al ₂ O ₃ as the main components in the inorganic component. They found that zeolite can be synthesized from waste that had been difficult to dispose of as a raw material. The low CEC of zeolite made from fly ash is also low due to the small amount of glassy components contributing to the formation of zeolite in fly ash and the difficulty in separating produced and unproduced substances. I found something. Furthermore, the amount of heat required for the zeolite generator can use the waste heat of the melting furnace for slag, which is widely used in the treatment of sewage sludge, and the NaOH waste liquid can be effectively used for SOx absorption in the exhaust gas of the melting furnace. I found what I could do.

The present invention has been completed on the basis of the above-mentioned findings. Melting sewage sludge or its incinerated ash in a melting furnace to form granulated slag, and adding NaOH to the slag to boil the zeolite. Along with the generation, the waste heat of the melting furnace is recovered and used as a heat source for a zeolite manufacturing device and a drying device for the generated zeolite, and NaOH waste liquid from the zeolite manufacturing device is used as SOx in the exhaust gas of the melting furnace.
It is characterized in that it is used for absorption. Hereinafter, the present invention will be described in more detail with reference to the illustrated embodiments.

[0008]

【Example】

Example 1 Example in which incinerated ash is used as a raw material FIG. 1 shows an example in which incinerated ash of a sewage sludge dewatered cake is used as a raw material. First, incinerated ash is melted in a melting furnace 1 at 1300 to 1500 ° C., and is poured into water to form granulated slag. As a result, granulated slag of several mm to several tens mm is obtained, but may be crushed and classified as needed. Granulated slag, unlike fly ash, has almost no crystal parts and almost 100% vitreous material suitable for zeolite synthesis.

The granulated slag is then mixed with high-concentration NaOH at 85 to 100 ° C. for several hours to several hours in the zeolite production apparatus 2.
Boil for 10 hours. As a result, zeolite is synthesized by hydrothermal synthesis.The synthesized zeolite is fine powder of several μm or less, while unreacted granulated slag is several mm to
Since it has a particle size of several tens of mm, it can be easily separated by a separation device 3 such as a sieve.

Next, the synthesized zeolite is dehydrated by a dehydrator 4 and further dried by a drying device 5 at a high temperature of 100 ° C. or more to obtain a product. The zeolite thus obtained has a high purity and is commercially available synthetic zeolite CE
Compared to C, it is almost the same, and it is made of fly ash but has much better quality than CEC.

On the other hand, the exhaust gas of about 1200 ° C. discharged from the melting furnace 1 is generally heat-exchanged by a heat exchanger 6, dust is removed by a dust remover 7, and SOx in the exhaust gas is removed by an absorption tower 8. And released into the atmosphere. The type of the heat exchanger 6 is not particularly limited. In the present invention, a part of the heat recovered in this way is returned to the melting furnace 1 as shown by a broken line in FIG. 1, and the remainder is effectively used as a heat source for the zeolite production apparatus 2 and the drying apparatus 5 for the generated zeolite. Used.

In the zeolite production apparatus 2, high concentration NaOH
Is used, but what is consumed here is Na ⁺
OH ^- it becomes a surplus. On the other hand, what is needed in the absorption tower 8 OH ^-
Therefore, if NaOH waste liquid from the zeolite manufacturing apparatus 2 is sent to the absorption tower 8, SOx in the exhaust gas of the melting furnace 1 can be absorbed, and at the same time, NaOH emission to the outside of the system is greatly reduced. be able to.

Embodiment 2—Example Using Sewage Sludge Dewatered Cake as Raw Material In the second embodiment shown in FIG. 2, a sewage sludge dewatered cake is used as a raw material. In this case, the sewage sludge dewatered cake containing 65 to 85% of water is first dried in a drier 9 until the water content becomes about 5%, and then put into the melting furnace 1 to be melted to form granulated slag. I do. The method for synthesizing zeolite from the granulated slag is the same as in Example 1. Exhaust gas from the melting furnace 1 is collected by a heat exchanger 6 including a waste heat boiler, and the steam generated thereby is sent to the above-described dryer 9, zeolite manufacturing apparatus 2, drying apparatus 5 and the like for effective use. Na
The point that the waste liquid of OH is effectively used in the absorption tower 8 is the same as in the first embodiment.

[0014]

The effects of the method for producing a zeolite of the present invention are summarized as follows. Zeolite with a high CEC value can be synthesized from sewage sludge and its incinerated ash, which had previously been difficult to dispose of. The waste heat of the melting furnace that has been conventionally installed for the treatment of sewage sludge can be recovered and used as a heat source for a zeolite manufacturing device and a drying device for the generated zeolite, thereby reducing running costs. it can. The NaOH waste liquid discharged from the zeolite manufacturing equipment can be used for SOx absorption in the exhaust gas of the melting furnace,
The amount of waste liquid discharged from OH can be reduced, and at the same time, the running cost of the absorption tower can be reduced.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing a first embodiment of the present invention.

FIG. 2 is a flow sheet showing a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Melting furnace 2 Zeolite manufacturing apparatus 5 Drying apparatus 6 Heat exchanger 8 Absorption tower

Claims (1)

(57) [Claims] 1. A sewage sludge or its incinerated ash is melted in a melting furnace to form granulated slag, and NaOH is added to the slag to boil to generate zeolite, and the waste heat of the melting furnace is recovered. It is used as a heat source for the zeolite production equipment and the drying equipment for the generated zeolite, and the NaOH waste liquid from the zeolite production equipment is used as SOx in the exhaust gas of the melting furnace.
A method for producing a zeolite, which is used for absorption.