JP2001072450A - Production of slag not containing chlorine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing chlorine-free slag by which the slag obtained by the treatments of municipal refuse incineration fly ash or industrial wastes can effectively be used by adjusting a waste mixture containing chlorine in a specific amount or more to a specified (Na+K) molar content/Cl molar content ratio and then melting the mixture. SOLUTION: A waste mixture contains chlorine in an amount of >=2%, and is adjusted to a (Na+K)/Cl of >=1.0. Na and K contained in incinerated fly ash or industrial wastes mostly exist in the form of Na2O and Nacl or K2O and KCl, and Cl exists in the form of Nacl, KCl or CaCl2. Especially, the CaCl2 has a lower vapor pressure by two figures than those of Nacl and KCl at a melting temperature of 1,400 deg.C, and can thereby not be removed by the melting treatment. But, when, for example, Na2O exits, the chlorine can be evaporated off as Nail by the reaction of the formula: CaCl2+Na2O → 2NaCl+CaO. Thereby, the Cl-free slag can be produced, when Na+K is sufficient for Cl contained in the melt mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a slag production method for effectively utilizing slag obtained by treating incinerated fly ash and industrial waste containing a large amount of chlorine as a raw material for ceramics and high-quality roadbed material. About the method.

[0002]

BACKGROUND OF THE INVENTION incineration fly ash and industrial waste of municipal solid waste in the incinerator ash, chlorine is NaCl, KCl, and there are many in the form of, such as CaCl _2. In melting these wastes, part of the chlorine is mixed into the molten slag and part of the chlorine is discharged as molten fly ash.

[0003] In order to produce a high-quality roadbed material from molten slag, a crystallization method has been known for some time. As a roadbed material, properties close to natural stone are required, and it is important that it is crystalline.Slag with a low crystallization rate is glassy, has a smooth surface, low frictional force, and poor water absorption,
Sufficient properties are not always obtained as a roadbed material, such as having a safety problem due to the sharp fracture surface. JP 57
Japanese Patent Publication No. 200259 discloses that a pyroxene-based crystal is precipitated by holding a molten slag at 900 to 1100 ° C. for about 15 minutes. In JP-A 4-132642 and JP-anneal crystallizing slag is disclosed a 900 ° C. from 1200 ° C. or less 10 ° C. / min, its chemical composition, SiO ₂ is 28-45
% Al ₂ O ₃ is 10 to 22% CaO is 24-44%, the Fe ₂ O ₃
It is 2 to 20%. These crystallization processes are characterized by depositing crystals from amorphous slag.

[0004] When a high-quality roadbed material is manufactured by the above-described crystallization process using slag in which chlorine is dissolved in slag, chlorine is not dissolved in precipitated crystals, so that chlorine is dissolved in glass. Chlorine precipitates as crystals of CaCl ₂ . When this slag is used as a roadbed material, there are problems such as collapse of the slag and an increase in the chlorine concentration of the eluate due to the deliquescence of CaCl ₂ , which is not practical. That is, the molten slag containing chlorine is required to be effectively used while the slag is in an amorphous state, and there is a great limitation in its application range such that it can be used only for low-grade materials such as backfill materials.

On the other hand, molten slag is disclosed in Japanese Patent Publication No. 8-29313.
As shown in the official gazette, it is also used as a ceramic raw material. The firing temperature differs depending on the porcelain plate and brick to be manufactured, but in applications where these slags are reheated, slag crystallization proceeds, the same reaction as described above proceeds, and chlorine is precipitated from the slag as CaCl ₂ crystals. . Precipitate
Since the vapor pressure of CaCl ₂ is low and cannot be removed during firing, it remains in a porcelain plate or brick, resulting in a defective product, which is unsuitable as a raw material.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of slag obtained by treating incinerated fly ash and industrial waste containing a large amount of chlorine, and is used as a high-quality roadbed material or a raw material for ceramics. The objective is to provide technology that can contribute to society through solving environmental problems by enabling effective use and recycling of incinerated fly ash and industrial waste containing a large amount of chlorine.

[0007]

The above object is achieved by the following invention. The first invention of the present invention relates to a method for producing a mixture of one or more wastes containing 2 wt% or more of chlorine with Na and K.
And adjusting the molar ratio (Na + K) / Cl 2 of Cl to 1.0 or more to melt the slag containing no chlorine.

In the second invention, the molar content of Na and K and Cl
The method for producing chlorine-free slag according to the first aspect of the present invention, characterized in that soda ash is added to adjust the molar content ratio (Na + K) / Cl 2 to 1.0 or more. . The third invention is characterized in that waste glass is added in order to adjust the ratio of the molar content of Na and K to the molar content of Cl (Na + K) / Cl to 1.0 or more. 1 is a method for producing slag containing no chlorine according to the invention. In the fourth invention,
The method for producing a chlorine-free slag according to any one of the first to third inventions, wherein the molten slag is cooled and then reheated for crystallization.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, in order to solve the conventional problems, the slag obtained by treating municipal incineration fly ash or industrial waste containing a large amount of chlorine and the slag obtained from the treatment of industrial wastes have been developed. Paying attention to the quantitative ratio, it has been found that this quantitative ratio is an important factor of chlorine emission, and the present invention has been achieved. Less than,
The present invention will be described in detail.

First, one or more kinds containing 2 wt% or more of chlorine.
Melt a mixture of two or more wastes at 1400 ° C or higher. The waste may be municipal waste incineration main ash, municipal waste fly ash, industrial waste or a mixture thereof. Of particular importance is the ratio of the sum of the Na and K mole contents (hereinafter R, Na + K = R) to the Cl mole content. The form of Na and K contained in incinerated fly ash and industrial waste is Na ₂ O
Or NaCl or K ₂ O or KCl
Is present in NaCl, KCl ₂ , CaCl ₂ . Among them, CaCl
₂ means that the vapor pressure at the melting temperature of 1400 ° C is 8.8563 × 10
^-3 atm, two orders of magnitude lower than that of NaCl or KCl,
Be melt processed municipal solid waste incineration fly ash and industrial waste, including CaCl _2, CaCl ₂ can not be excluded. However, for example, if Na ₂ O was present, then CaCl ₂ + Na ₂ O
→ It can be volatilized as NaCl by the reaction of 2NaCl + CaO.

[0011] Accordingly, Cl during melting is replaced with NaCl having a high vapor pressure or NaCl.
If there is a sufficient amount of R to volatilize as KCl, it is possible to produce a slag that does not contain Cl and is suitable for effective use. For this purpose, one having a sufficient R content in a mixture of one or more wastes may be used, or the proportion of the waste mixed may be adjusted so that the R content is sufficient. Theoretically, if R / Cl is 1 or more, all Cl will be volatilized, but in reality, because of the non-uniformity of the raw material,
It is desirable for R / Cl to be 1.15 or more in order to volatilize all Cl. There is no upper limit for R / Cl, but when adding a Na source from the outside, the problem of increased waste disposal, the problem of corrosion of refractory furnaces, and the use of slag as concrete aggregate In this case, there is a problem of an alkali-aggregate reaction, and excessive Na or K is not preferable. Remains in the slag
It is preferable that the total amount of Na and K is 5 wt% or less in terms of Na ₂ O and K ₂ O.

The reason why the chlorine contained in the waste is limited to 2% by weight or more is that R / Cl is always 1.0 or more in incinerated ash where a small amount of chlorine of 2% by weight or less exists. This is because there is no problem in the slag characteristics after melting.

[0013] Industrially, the above-mentioned reaction can be actively promoted by increasing the amount of gas introduced for the purpose of increasing the displacement of the slag melting furnace, and by increasing the melting time. By elongating the residence time, sufficient volatilization can be achieved.

[0014] R / Cl can be increased to 1.0 or more just by mixing waste.
If not, it is necessary to input R source as auxiliary material.
You. Industrially, the use of soda ash is inexpensive and slag
Effective in melting in an oxidizing atmosphere
Means. Soda ash is NaCO _ThreeIs the main component and oxygen
The equilibrium vapor pressure differs depending on the partial pressure. Oxygen is 0.2atm
, The vapor pressure of Na at 1400 ° C is about 1 × 10^-2Degree and low
So it can be used effectively without scattering
You.

On the other hand, when soda ash is used for melting the reducing atmosphere, the vapor pressure of metallic Na rapidly increases, which is not desirable. For example, the metal Na vapor pressure at an oxygen partial pressure of 1 × 10 ⁻¹⁰ is 3 atm, and the added Na sublimates before reacting with CaCl ₂ . Therefore, soda ash cannot be used for melting in a reducing atmosphere.

For melting the reducing atmosphere, the addition of waste glass is the most effective means. Waste glass contains about 15 wt% Na ₂
It contains O ₂ and is not dissolved in Na ₂ O alone, but dissolved in glass. This means that the activity of Na ₂ O can be reduced by about five orders of magnitude, the Na vapor pressure is reduced by about five orders, and R / Cl in a reducing atmosphere is increased.
It can sufficiently contribute to the function of discharging Cl.

The molten slag in which Cl is volatilized by the above method can be granulated with water to produce a glassy slag, or can be air-cooled into a massive slag. Also,
Crystallized slag can be produced by slow cooling or reheating in order to obtain a good roadbed material. When crystals are precipitated from the slag, chlorine cannot be dissolved in the crystals, so that the dissolved chlorine concentrates in the glass and precipitates when the temperature exceeds the solid solution limit. Depending on the slag composition, CaCl ₂ or
It precipitates in the form of KCl and NaCl. If the chlorine content is high,
The above-mentioned chloride easily precipitates on the slag. The chlorine concentration at which chloride cannot be confirmed even after crystallization is about 0.5 wt% or less.

[0018]

Next, the present invention will be described based on embodiments.

[Example 1] After mixing municipal solid waste incineration ash generated from city A with low chlorine content and municipal waste incinerated ash generated from city B with various ratios,
A reducing atmosphere in a resistance heating electric furnace using carbon electrodes,
(Steam partial pressure 15-35%, remaining gas, carbon monoxide 40-70
vol%, hydrogen 10 ~ 30vol%, remaining nitrogen gas), 1450 ℃ ~
Melted at 1500 ° C. Table 1 shows the composition of the municipal solid waste incineration ash of City A and the components of the incineration ash of City B used here. About 20 ° C / min
And cooled to produce an amorphous slag. Table 2 shows that A
City and B city incineration ash mixing amount, R / Cl (the ratio of the sum of Na mole content and K mole content and the mole content of Cl), Cl before melting
Shows the total amount and chemical composition of the molten slag. High chlorine content
When melted only with incineration ash from City B, 1
It can be seen that chlorine in slag can be reduced to 0.4 wt% or less by mixing and melting incinerator ash with less chlorine, while containing 0.8% chlorine. When chlorine in the slag was 0.4 wt% or less, R / Cl was 1.0 or more in molar ratio, and when chlorine content was 0.1 wt% or less, R / Cl was 1.2 or more.

[0020]

[Table 1]

[0021]

[Table 2]

[Example 2] In the same manner as in Example 1, municipal solid waste incineration ash generated from City A and low chlorine content incinerated ash generated from City B were mixed together. Reduced atmosphere (water vapor partial pressure 15-35%, remaining gas, carbon monoxide 40-70) in a resistance heating electric furnace using electrodes
vol%, hydrogen 10 ~ 30vol%, remaining nitrogen gas), 1450 ℃ ~
Melted at 1500 ° C. Cool down to 1200 ° C at about 2 ° C / min,
The slag was cooled to 700 ° C at a rate of about 1.2 ° C / min to produce slowly cooled slag. Table 3 shows the incinerated ash mixing amount and R / Cl of City A and City B.
(The ratio of the sum of Na mole content and K mole content to the mole content of Cl), the total amount of Cl before melting, the chemical composition of the slowly cooled molten slag, and the precipitated mineral layer phase showing the constituent phases of the slowly cooled slag ( X-ray diffraction method). In addition, 2 m slow cooling slag
m or less, and an eluate was prepared by a method according to the Environment Agency Notification No. 46, the eluate was analyzed, and the chlorine elution amount was measured. The results are also shown in Table 3. When the raw materials were blended with R / Cl of 1.0 or more, a slag which was crystalline and had a small chlorine elution amount was obtained.

[0023]

[Table 3]

Example 3 Municipal waste incineration ash with a high chlorine content generated from City B was mixed with soda ash, and then melted at 1500 ° C. in an oxidizing atmosphere in an externally heated electric furnace. About 20
It was cooled at a rate of ° C./min to produce an amorphous slag. Table 4
In addition, the mixed amount of incinerated ash and soda ash in City B, R / Cl (the ratio of the sum of Na mole content and K mole content and the mole content of Cl), the total Cl content before melting, and the chemical composition of molten slag Indicated. R / Cl
In slag containing 1.0 or more, the chlorine content is 0.4 wt%
I was able to keep it below.

[0025]

[Table 4]

Example 4 Municipal refuse incineration ash with a high chlorine content generated from city B and waste glass generated from city C were mixed, and then reduced in a reducing atmosphere in a resistance heating type electric furnace using a carbon electrode. (15-35% of steam partial pressure, 40-70vol% of carbon monoxide, 10-30vol% of hydrogen, remaining nitrogen gas in the remaining gas)
Melted at 1450-1500 ° C. Table 5 shows the composition of the municipal solid waste incineration ash of City B and the chemical composition of the waste glass of City C used at this time. It was cooled at a rate of about 20 ° C./min to produce an amorphous slag. Table 6 shows the amount of incinerated ash and waste glass in City B, R / Cl
(The sum of the Na mole content and the K mole content and the ratio of the Cl mole content), the total Cl content before melting, and the chemical composition of the molten slag are shown. As R / Cl increases, the chlorine content in the slag decreases, and R / Cl is 1.0 or more and the chlorine content is 0.4 wt% or less, and if R / Cl is 1.2 or more, the chlorine content is 0.1 wt%.
It was as follows.

[0027]

[Table 5]

[0028]

[Table 6]

[Example 5] Amorphous slag having a chlorine content of 4.0% by weight by adding 20% by weight of waste glass from City C to 80% by weight of incineration ash from City B produced in Example 4 and City B 66wt% incinerated ash
34% by weight of waste glass from City C, and 0.3% by weight of amorphous slag containing chlorine was heated at a rate of 10 ° C./min to 1000 ° C. in the air atmosphere and kept at 1000 ° C. for 1 hour. . When these slags were measured by X-ray diffraction, two types of crystals, anorthite and gallenite, were observed.Approximately 70 vol% of the slag was added to the product with 20 wt% waste glass and approximately 65 vol% to the product with 34 wt% waste glass.
Was crystalline. The crystallized slag was pulverized to 2 mm or less and subjected to a dissolution test in accordance with the method prescribed by the Environment Agency Notification No. 46 to examine the chlorine content of the eluate. As a result, waste glass
In the 20 wt% additive, chlorine elutes at 75 mg / l, whereas 34
In the case of wt% additive, the value was below the detection limit of 1 mg / l.

[0030]

According to the slag production method of the present invention,
Slag obtained by treating incinerated fly ash and industrial waste containing a large amount of chlorine can be manufactured as slag that does not contain chlorine. This can contribute to society through solving environmental problems.

Continuing on the front page (72) Inventor Keisuke Nakahara 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. F-term (reference) 4D004 AA18 AA46 BA02 CA04 CA29 CA32 CA37 CA50 CB13 CB31 CC11 CC12 DA02 DA03 DA06 DA10 4G012 JL03 JM04

Claims (4)

[Claims] 1. A mixture of one or more wastes containing 2 wt% or more of chlorine, wherein the ratio of the molar content of Na and K to the molar content of Cl (Na + K) / Cl is 1.0 or more. A method for producing chlorine-free slag, characterized in that the slag is adjusted and melted. 2. The method according to claim 1, wherein soda ash is added to adjust the ratio of the molar content of Na and K to the molar content of Cl (Na + K) / Cl to 1.0 or more. The method for producing chlorine-free slag according to the above. 3. The waste glass is added to adjust the ratio of the molar content of Na and K to the molar content of Cl (Na + K) / Cl to 1.0 or more. The method for producing chlorine-free slag according to the above. 4. The method for producing a chlorine-free slag according to claim 1, wherein the molten slag is cooled and then reheated to be crystallized.