JPS61227841A - Preparation of filter assistant - Google Patents

Abstract

PURPOSE:To obtain a filter assistant consisting of a porous material wherein many holes are present by adding lime of the specified amount to the coal ashes, mixing the mixture and performing the hydrothermal reaction in an autoclave. CONSTITUTION:10-40pts.wt. is added to 100pts.wt. coal ashes and the mixture is mixed by adding water and the stirred slurry is heated in an autoclave to perform the hydrothermal reaction. Still more in this case, gypsum may be added to accelerate the reaction. A porous material wherein the many fine holes are present as shown in a figure is obtained by filtering, dehydrating and drying the obtained slurry of calcium silicate hydrate. The coal ashes to be used is preferably calcined at about 600 deg.C to remove the nonburned carbon as the pretreatment and furthermore it is more preferable that the degree of crystallization of coal ashes is increased by calcining them at about 1,000 deg.C. By such a method, the filter assistant exhibiting the same characteristics as diatom earth or above is obtained out of the coal ashes produced in great quantities.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing a filter aid using coal ash as a raw material □.

<Conventional Technology> Due to the energy situation in recent years, coal is once again being used extensively in thermal power plants, and a large amount of coal ash is being produced. However, as of now, no effective method for using this coal ash has been developed, and it is still considered as an unused resource or industrial waste.

On the other hand, as a filter aid used when the dispersed particles cause clogging of the filter medium due to their viscous nature, or when the dispersed particles are fine and have a low concentration, diatom-based filter aids have traditionally been used. Perlite has been mainly used, and fibrous filter agents made from wood pulp and carbonaceous filter aids have also been used to some extent.

<Problems to be solved by the invention> The present invention aims to produce an industrially useful filter aid from coal ash, which is abundantly produced but for which no effective use has been found. This is what I am trying to do.

<Means for Solving the Problems> In order to achieve the above-mentioned purpose, the present invention uses coal ash as a starting material by adding an appropriate amount of lime. , 10 to 40 parts by weight of lime are added and mixed, and then a hydrothermal reaction is carried out in an autoclave.

It is more preferable to use a raw material in which gypsum is added and mixed together with lime as a starting raw material because the reaction in the ol-crepe is accelerated.

In the method described in 1, the amount of lime added is set to 10 to 40 parts by weight because if it is less than 10 parts by weight, calcium silicate hydrate that provides a filtration effect on the surface of coal ash particles will not be sufficiently produced. Furthermore, if it exceeds 40% by weight, the reaction rate of the hydrothermal reaction in an autoclave will increase, but unreacted fine particles will remain, and during filtration, these unreacted fine particles will adhere to the filter medium and reduce the filtration effect. This is because it inhibits. Next, when gypsum is added to promote the reaction, if the amount added is less than the triple plate part, almost no effect will be seen; on the other hand, if it exceeds 15 parts by weight, it will remain as unreacted gypsum. Since it inhibits the filtration effect, the amount is set at 3 to 15 parts by weight.

The coal ash used may be used as is, but if it contains unburned carbon, it will take on a gray-black color.
Since the unburnt carbon (B) may have an adverse effect on the filtrate, it is preferable to calcinate it at 400 to 600°C as a pretreatment. Furthermore, by setting the pretreatment firing temperature to a high temperature of around 1000°C, various unstable substances contained in coal ash can be immobilized, preventing their elution into the filtrate, and reducing coal ash. The particles themselves are locally crystallized, and the subsequent 4
- Only the part of the glass phase that is not crystallized by the reaction in the tocrepe selectively reacts, and the crystalline phase remains in the form of 5. As a result, the coal ash becomes porous from the inside, resulting in the formation of porosity. The product takes on a more desirable form.

Next, in the reaction in 4-tocrepe, the higher the temperature, the higher the pressure and the faster the reaction rate, but in the case of the method of the present invention, a temperature of 220°C or lower is sufficient, and the reaction time is at most 48°C. It's enough time.

<Examples and effects> Examples of the present invention and filtration test results are shown below.

】εExample - A slurry made by adding 20 times the weight of water to a mixed powder made by adding and mixing 10011 parts of coal ash and 18 parts by weight of CaO was mixed and stirred at 180°C for 24 hours. A hydrothermal reaction was carried out while stirring in an autoclave to obtain a calcium silicate hydrate slurry.

The calcium silicate hydrate slurry thus obtained was filtered, dehydrated, and dried at 100° C. for 24 hours. The obtained powder was observed under an electron microscope and the results are shown in FIG. 1. As can be seen from this photograph, it was a porous material containing many fine pores.

Blood loss■Also, to remove unburned carbon mixed in coal ash, 60%
Calcium silicate hydrate was obtained in the same manner as in Example 1 using coal ash heat-treated at 0° C. for 4 hours.

20 parts by weight of CaO was added to 100 parts by weight of 111 parts of coal ash that was heated at 1000°C for 8 hours to remove unburned carbon mixed in and to increase the crystallinity of the coal ash. 5 parts by weight of Ca S 04.2 H20 were added and mixed to obtain a mixed powder. For this mixed powder, the weight ratio is 2
The slurry, which was mixed and stirred with 0 times the amount of water, was stirred in an autoclave at 180°C for 24 hours while undergoing a hydrothermal reaction. The powder obtained in the same manner as in Example 1 was then observed with an electron microscope, and the results are shown in Figure 2.As can be seen from this photograph, fine pores are connected not only to the outer layer but also to the core. It was a porous body.

This is confirmed by treating the powder with 2NHC1 to remove calcium silicate hydrate, and observing the coal ash itself using an electron microscope. The results are shown in Figure 3. It is also believed that coal ash itself is porous. For comparison, an electron micrograph of untreated coal ash is shown in FIG. 4, and although the surface was rough and uneven, it was not porous.

The results of a filtration experiment using the prototype filter aid obtained in the above examples and commercially available diatomaceous earth are shown below.

In this experiment, a pressure filter with a filtration area of 63.6 cd was used, and each filter aid was body-fed to the frog's eye clay slurry to reach Ruth's constant pressure filtration coefficient [cj/se
c] (value at slurry temperature of 20°C) was determined. At that time, the filtration pressure was I Kglcd, the slurry concentration was 01,
The volume ratio of the filter aid in the solid content was 05 and 067.

Table 1 below shows t: the physical property values of the samples used in the experiment, and Table 2 shows 2o for the constant pressure filtration rate coefficient.

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, l To1 □ (7)゛ , :11 (q) Mini',,,4 &'l l', :'-'+・,,
111゛・,,′, -8-3≧, <Effects of the invention> ”-As stated above, in the method of the present invention, A1 has many pores due to the hydrothermal reaction in the autoclave. It is possible to obtain a filter aid made of a porous material, and especially when coal ash is fired at a high temperature (1000°C) before the hydrothermal reaction in an autoclave, the porosity is as high as 0.09 compared to 0.08 for diatomaceous material. As shown in Table 2 above, the constant pressure filtration coefficient is equal to or higher than that of existing diatomaceous earth filter aids, demonstrating excellent filtration properties.

Therefore, it has great effects on industry as a means of utilizing unused resources.

[Brief explanation of the drawing]

Figure 1 shows 30% of the filter aid particles obtained in Example 1 of the present invention.
00x electron micrograph, Figure 2 is a 7000x electron micrograph of the filter aid particles obtained in Example 3, and Figure 3 is a 7000x electron micrograph of the coal ash particles treated in Example 3. Figure 4 is an electron micrograph of 3000 untreated coal ash particles.
Magnified electron micrograph 14° Fig. 1 Fig. 2 Fig. 3 Fig. 4

Claims (1)

[Claims] 1. A filter aid characterized in that 10 to 40 parts by weight of lime are added and mixed to 100 parts by weight of coal ash, and then a hydrothermal reaction is carried out in an autoclave. Production method. 2. A method for producing a filter aid, which comprises adding and mixing 10 to 40 parts by weight of lime and 3 to 15 parts by weight of gypsum to 100 parts by weight of coal ash, and then carrying out a hydrothermal reaction in an autoclave.