JPH0124559B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is capable of solidifying sludge or sludge containing organic substances such as sugars, petroleum decomposition products, oils and fats, heavy metal oxides, chlorides, hydroxides, phosphoric acid, inorganic phosphates, organic phosphorus compounds, etc. is large,
The present invention also relates to a method for solidifying sludge or sludge to obtain a solidified product having acid resistance and heat resistance. Conventionally, various hydraulic substances have been used as treatment materials for this type of sludge or sludge, but each has advantages and disadvantages. For example, ordinary Portland cement or quick-setting cement containing calcium aluminate can be solidified even if it contains organic matter, and its strength can be relatively increased, but its poor acid resistance and heat resistance make it difficult to use effectively. has restrictions. On the other hand, a mixture of granulated blast furnace slag and gypsum or cement has greater acid resistance, heat resistance, and heavy metal sequestering effect than ordinary Portland cement, but it is said that the strength of the solidified product is low and shrinkage is large. There are drawbacks. As a result of various studies in order to solve these drawbacks, the present invention has developed a method that uses a mixture of a specific granulated blast furnace slag as the main material and a small amount of alkali metal hydroxide as a treatment material. For example, the present inventors discovered that it is possible to sufficiently solidify sludge or sludge containing organic matter, heavy metal compounds, phosphates, etc., and not only sequester heavy metals but also impart acid resistance and heat resistance to the solidified material, and the present invention This is the completed version. That is, in the present invention, pulverized granulated blast furnace slag having a Blaine specific surface area of 5000 cm ² /g or more and 1 to 30 parts by weight of an alkali metal hydroxide are added and mixed to sludge or sludge. This is a method for solidifying sludge or sludge, which is characterized by solidifying it. Granulated blast furnace slag, which is the main material of the present invention, is a by-product of the steel industry, and is a material with extremely weak hydraulic properties or latent hydraulic properties. This shows that. An example of its chemical composition in weight percent is SiO ₂ 32-36%, Al ₂ O ₃ 12-20%, CaO 35-36%.
43%, MgO 0.5-10%, and _TiO2 0.1-3%.
This composition is compared to Portland cements.
It has low CaO content and does not produce Ca(OH) ₂ upon hydration, giving it excellent acid resistance and heat resistance. In the present invention, an alkali metal hydroxide is used as an alkali stimulant in liquid or powder form. Specific substances include sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.
Sodium hydroxide is most preferred. Hydration of Portland cements proceeds in areas with high pH values, so a drop in pH due to the contamination of acidic substances from sludge or sludge significantly impedes hydration. To prevent this, it is necessary to maintain a high PH value by adding an alkaline substance, but since the present invention adds an alkali metal hydroxide, the amount of addition can be adjusted to prevent condensation. can be controlled. In the present invention, there is a suitable range for the fineness of the granulated blast furnace slag and the proportion of alkali metal hydroxide used in terms of strength development. Its fineness is a Blaine specific surface area (hereinafter referred to as Blaine value) of 5000 cm ² /g or more,
The proportion of alkali metal hydroxide in granulated blast furnace slag is within the range that does not make the sludge or sludge acidic.
The amount is 1 to 30 parts by weight per 100 parts by weight. If the fineness of the granulated blast furnace slag is coarser than 5000 cm ² /g or if the alkali metal hydroxide is less than 1 part by weight, the strength of the solidified product will be low. There is little advantage in adding more than 30 parts by weight of alkali metal hydroxide, and it affects acid resistance and heat resistance. The Blaine value here is a value representing the fineness of cement, and is usually expressed in terms of surface area per gram of cement. The calculation method is to use a Blaine air permeation device specified in JIS R5201 to determine the speed of air passing through a cell filled with cement based on the change time of the solution head, and calculate it by comparison with the standard test. 3100-3400 for ordinary Portland cement
cm ² /g, and early-strength Portland cement shows a higher value. (From the Concrete Terminology Dictionary of the Japan Concrete Institute) The reactivity of hydraulic materials such as cement has a strong correlation with the surface area of particles that come into contact with water, and the above air permeation method (Blaine method) is a simple method for measuring this. has been adopted. The vitrification rate of the granulated blast furnace slag is preferably 75% or more, particularly 90% or more from the viewpoint of strength development.
Furthermore, the effects of the present invention can be further enhanced by using an alkali metal hydroxide in combination with an alkali metal carbonate or hydrogen carbonate. The amount used is 1 to 30 parts by weight, preferably 2 to 10 parts by weight, per 100 parts by weight of slag. As the alkali metal carbonate or hydrogen carbonate, sodium carbonate, potassium carbonate, lithium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, etc. can be used. As explained above, the present invention is a method for solidifying sludge or sludge using granulated blast furnace slag powder and alkali metal hydroxide as treatment materials, and the solidified material treated by this method has high strength and heat resistance. , acid resistance and heavy metal sequestering properties can all be significantly improved compared to those using conventional hydraulic materials,
It has the normative effect of expanding the scope of its effective use. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 20% by weight of the treated material shown in Table 2 was added to sludge collected from near the Amagasaki seabed and had the properties shown in Table 1, and a 4 x 4 x 16 cm specimen was formed.
Cured at ℃ and 80% RH. Table 3 shows the measurement results of compressive strength and heavy metal sequestration effect at each material age.
The treated material symbols A and B are those of the present invention. The effect of sequestering heavy metals is determined by crushing and classifying the hardened material that has been cured until the age of 28 days into particles with a particle size of 0.5 to 5 mm, adding 500 g of water to 50 g of this material, shaking for 6 hours, and then separating. Hg, Cd, Pd, and As were determined by atomic absorption spectrometry, and Cr ⁶⁺ and CN ^- were determined by ion electrode method.

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[Table] Next, the weight change when the cured material cured until the age of 28 days was immersed in a 2% aqueous solution of hydrochloric acid or sulfuric acid for 7 days and 28 days, and the
After firing for a time and cooling, the strength was measured. The results are shown in Table 4.

【table】

[Table] As is clear from Tables 3 and 4, the present invention has improved solidified product strength, heavy metal sequestering effect, acid resistance, and heat resistance compared to conventional treatment materials using hydraulic substances. It can be seen that both are large.

Claims (1)

[Claims] 1 Blaine specific surface area 5000 for sludge or sludge
Fine powder granulated blast furnace slag of cm ² /g or more and the slag
A method for solidifying sludge or sludge, which comprises adding and mixing 1 to 30 parts by weight of an alkali metal hydroxide to 100 parts by weight and solidifying the mixture.