JPS6158238B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a method for making chromium sludge non-polluting, that is, a method that prevents chromium ions from being eluted. In addition to Cr, Kurometsuki Suratsuji contains Cu, Pb.
Industrial waste contains Zn, etc. and is rarely reused, making it difficult to dispose of. In other words, concrete hardens, reducing substances (such as coke) are mixed and fired, and Cr ₂ O ₃ is
There is a method of changing it to Cr ₃ C ₂ , or a method of mixing white clay or clay and firing it. However, if concrete is solidified, even if the elution test according to the Environment Agency notification is below the regulated value,
It is very difficult to completely stop the elution of chromium ions, and if you conduct an elution test on solidified concrete for a long period of time, such as one or three months, in a high pH solution (PH≒11), Cr ³⁺ ions will be released. teeth
It is reoxidized to Cr ⁶⁺ ions and the amount of elution increases. When combined with reducing substances such as coke and fired,
Cr ₂ O ₃ +C → Cr ₃ C ₂ should theoretically become stable, but it is very difficult to sinter and cool it in a completely reducing atmosphere, and since Cr ₂ O ₃ is mixed, the Environment Agency notification is required as mentioned above. Even if the elution is below the regulation value, if a long-term elution test is performed with a high pH solution,
Cr ³⁺ is reoxidized to Cr ⁶⁺ ions and exceeds the regulation value. Furthermore, when clay or clay is blended and dissolved, depending on the blended amount, it becomes vitrified during the cooling process, and chromium ions enter the glass composition and are no longer eluted. However, since white clay and clay are highly molten substances, they are not very desirable from a thermal energy standpoint. Also, even if a single sludge is dissolved in an oxidizing atmosphere,
Mainly composed of MgCrO ₄ and Cr ₂ O ₃ , the degree of vitrification is low, and a considerable amount of Cr ions are eluted, and even if dissolved in a reducing atmosphere, some Cr ₃ C ₂ is generated.
Since it contains MgCrO ₄ and Cr ₂ O ₃ and has a low degree of vitrification, it elutes a considerable amount of Cr ions, which increase when eluted for a long time in a solution with a high pH, and it is thought that there is a reoxidation phenomenon. Note that if fired or melted in a reducing atmosphere,
If it were completely changed to Cr ₃ C ₂ , it would be relatively stable and difficult to elute.
Cooling is very difficult to achieve. Even if slate or masa soil and sludge are melted in an oxidizing or reducing atmosphere, they will vitrify, but
Contains Cr ₂ O ₃ in addition to MgCrO ₄ , so dry Cr
Elute ions. Furthermore, cement (blast furnace cement, ordinary Portland cement), blast furnace water slag, calcium chloride, and lime were added to the sludge to accelerate solidification, and when an elution test was performed after solidification, some Cr ions were eluted.
When elution is carried out in a solution with a high pH for a long period of time, re-oxidation of Cr ions is observed, and the result is not complete. In order to solve the above problems, the present invention relates to a method for eluting chromium ions using soda-containing slag rich in Na ₂ O and containing a suitable amount of Fe and a silicate material. Here, soda-containing slag refers to slag treated with soda ash for desulfurization in steel smelting, for example, and is a low melting material (approximately 970°C), but the metals contained are crushed and recovered by magnetic separation. The tailings are disposed of in landfill. One of the objects of the present invention is to effectively utilize this soda-containing slag. In other words, when Metsukisuratsuji is simply melted, the temperature is quite high (approximately ₁₃₈₀ ℃ or higher), and the elution of chromium ions cannot be prevented. When melted, it melts at approximately 1250°C, and when cooled, vitrification progresses and elution of Cr ions can be almost prevented. However, when soda ash treated slag is mixed with silicic acid materials such as masa earth and metsuki sludge and dissolved, the soda ash treated slag is rich in Na ₂ O and contains an appropriate amount of Fe content, so it has a low Temperature (approx.
It melts at a temperature of 1,100 to 1,150℃), further progresses to vitrification, and no longer elutes chromium ions, making it possible to effectively utilize unused resources and industrial waste, leading to energy savings. The actual process of dissolution treatment to make it pollution-free is as follows. Metsukisuratsuji and reducing substances are mixed and melted in a furnace such as an electric furnace, and valuable metals are reduced and converted into metals, such as Fe-Cr. Mixing and agitation can be performed well by adding the above-mentioned mixture and making effective use of sensible heat to cause a dissolution reaction and extracting the sludge.
(Hereinafter referred to as pre-tapping) In addition, if a mixture of soda-containing slag and silicate salt rocks and minerals such as masa earth are put in contact with the slag flow during slag tapping, sensible heat will be effectively used to melt the mixture. , diffusion reaction can be carried out well. (Hereinafter, it will be referred to as "input at the same time.") Inject silicate rocks, minerals, and soda-containing slag such as Metsukisura Tsuji and Masa soil into the furnace.
Melted valuable metals are transferred to slag without being recovered. When recovering Fe-Ni by blending and dissolving a reducing substance in Nikkel Metsuki Suratsuji, in order to effectively utilize the sensible heat of the slag in the molten state to carry out the dissolution reaction, silicate materials such as Metsuki Suratsuji and Masa earth are used. If rocks, minerals, and soda-containing slag are blended and added to the slag, a good mixing-diffusion reaction can be carried out at the time of slag removal. The experiments that led to the completion of the present invention and their results are shown below. Metsukisuratsuji, Masa soil, used in this experiment.
Table 1 shows the chemical analysis values of slate and soda-containing slag.

[Table] This raw material was pulverized to 0.3 mm or less, blended, made into a Zegel cone, heated in a siliconite electric furnace at a heating rate of 15°C per minute, and measured the melting temperature. Table 2 shows the results. show.

【table】

[Table] In addition, the same sample crushed to 3 mm or less was placed in a graphite crucible (reducing atmosphere) and an electrofused magnesia crucible (oxidizing atmosphere), held in a siliconite electric furnace maintained at 1350°C for 15 minutes, and then released outside the furnace. After cooling, perform a long-term elution test using a solution with a pH of approximately 11 according to the method notified by the Environment Agency, and an autoclave test (200℃, 20Kg/cm ² , held for 3 hours) for slag particle sizes of 5 to 10 mm. The disintegration rate was determined as a disintegrating product, and the produced minerals were subjected to X-ray diffraction to examine the main produced minerals, some examples of which are shown in Table 3.

【table】

[Table] JIS A 1101 and the above prototype slag
According to JIS A 1121, surface dry specific gravity, water absorption rate, and Los Angeles pickpocket weight loss test were conducted, and the results are shown in Table 4.

[Table] In addition, even if chromium tsuki suraji is cement solidified, there is a risk of re-oxidation of chromium ions (Cr ³⁺ → Cr ⁶⁺ ) due to the high pH (approximately 12), so it cannot be used in blast furnaces. Cement, ordinary portland cement,
Using blast furnace water slag (pulverized to the same particle size as cement), etc., pellets with a diameter of approximately 10 to 15 mm were cured in a moist air (14 days), and a solution of PH = 11 was prepared according to the method prescribed by the Environment Agency.
Soak the pellets in a proportion of 10g in 100c.c.
After 30 and 90 days, the Cr ion concentration in the eluate solution was measured and shown in Table 5.

[Table] From the results of the above experiment, the following is revealed. In other words, from Table 3, it is possible to considerably suppress the elution of chromium ions by adding masa soil or slate to Kurometsuki Slatsutsuji, but if chromium ions are immersed in a solution with a high pH for a long period of time, a considerable amount still remains. This is not sufficient as there is elution of chromium ions. However, if soda-containing slag is added together with silicate materials such as masa soil and slate, the elution of chromium ions can be greatly suppressed. In either case, the chromium ion elution will be ND or 0.01ppm. This is thought to be because adding soda-containing slag lowers the melting temperature of the mixture and improves its fluidity, making it easier to gasify the mixture evenly. For example, if the T/Cr is increased to 15% by weight, it becomes N/D, but if it is increased too much to 21% or 70% by weight, the melting temperature will be lower, but the soda content will be too excessive and no reaction will occur. There is a soda content that is eluted in the free state, and chromium ions are also eluted along with this free soda content, and the amount of chromium ions eluted increases again as shown in Table 3 above, so the amount of soda-containing slag is 15% by weight. % or less. The main purpose of the method of the present invention is to suppress the elution of chromium ions as much as possible;
Since the method of the present invention is applicable to cases where the following conditions are met, the method notified by the Environment Agency in Table 3 above and PH11
An example in which the eluted ion concentration (T·Cr) is 0.01 ppm or less in any case of immersion in a solution of is considered an example of the present invention, and other examples are considered as a comparative example. That is, in the case of electrofused magnesia crucible melting shown on page 10 above in Table 3, the examples shown in the 6th, 7th, 10th, and 112th rows from the top are examples of the present invention, and the others are comparative examples. In the case of graphite crucible melting on page 11, the examples shown in the 6th, 7th, 10th, and 12th columns from the top are examples of the present invention, and the others are comparative examples. In this way, the amount of soda-containing slag in the total formulation can be reduced from 10 to
The remaining amount is 15% by weight, and the rest is masa soil and other materials as long as the conditions of treating as much of the target material, Kurometsuki Slatsuji as possible, and not raising the melting temperature (Table 2) too high during treatment are met. The amount of slate added was 35-40% by weight. When the formulation of the present invention in this range is calculated based on the chemical composition shown in Table 1 above, SiO ₂ 34.87-39.35% by weight, Al ₂ O ₃ 7.78
~8.~94 wt%, _{Fe2O3 3.81} ~5.11 wt%,
CaO5.74-7.41% by weight, MgO1.28-1.51% by weight,
_Cr2O3 18.59~18.97% by weight, _{Na2O + K2O2.53} ~
It becomes 4.17% by weight. Furthermore, from Table 4, it can be seen that the treated material treated by the method of the present invention can be effectively used as various aggregates. As described above, according to the method of the present invention, an appropriate amount of unused SiO ₂ -based resources and soda-containing slag, which is a low-melting industrial waste, is mixed with chromium sludge and dissolved, thereby producing chromium ions. It does not elute and can be effectively used as aggregate, etc.

Claims (1)

[Claims] 1 Silicate materials consisting of masa earth and/or slate
35-40% by weight, 10-15% by weight of soda-containing slag,
These 3 are so that the rest is Kurometsuki Suratsuji.
A pollution-free method for chrommetsuki suratsuji, which is characterized by mixing chromium methane and carrying out a dissolution reaction.