KR101593555B1 - Method on Low Viscosity Control for Discharging of Non-combustible Waste Molten - Google Patents

Abstract

The present invention develops a glass / slag composition process necessary to vitrify highly viscous wastes to maintain PTM operating stability and melt viscosity of the final product, glass or slag, at a low 100 poise or less at the discharge site temperature (1300 ° C to 1500 ° C) And a method of adjusting a low viscosity for discharging a non-combustible waste melt.
In order to accomplish the above object, the present invention provides a method for adjusting a low viscosity for discharging a non-combustible waste melt, comprising the steps of: preparing a non-combustible waste containing 40 wt% or more of SiO ₂ in a plasma torch melting furnace _{1 to 5} wt% of CaO, 0.1 to ₃ wt% of FeO, _{1 to 8} wt% of CaF _2, 0.1 to ₅ wt% of Al ₂ O ₃ , 0.1 to ₅ wt% of MgO, 0.1 to ₅ wt% of Na ₂ O, And a low viscosity of the non-combustible waste is adjusted to 100 poise or less at a discharge site temperature of 1300 ° C to 1500 ° C.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting a low viscosity for discharging a non-combustible waste melt,

The present invention relates to a method of adjusting a low viscosity for discharging a non-combustible waste melt, and more particularly, to a method for adjusting the low viscosity of a non-combustible waste melt by using a plasma torch melter for metal, concrete, And a low viscosity adjusting method for discharging a non-combustible waste melt to maintain a low viscosity melting state of the melt for smooth discharge from the discharge port.

In general, vistification is being studied as a new method of meeting the disposal requirements of waste generated from nuclear power plants and reducing waste, while in the case of combustible wastes, a cold crucible induction melter (CCIM) In the case of non-combustible waste, a treatment using plasma torch melter (hereinafter referred to as "PTM") is being performed.

In particular, domestic commercialization vitrification facilities adopting CCIM for the vitrification of flammable wastes at Hanool nuclear power plants are in operation in Korea, and glassware and wastewater are being vitrified.

In addition, the United States and France have been conducting progressive vitrification studies for high-level and low-level radioactive waste using CCIM, but they are not accompanied by the construction and operation of vitrification commercial plants. In Japan and Russia, PTM-based radioisotope waste And the melting process for low-level radioactive waste is being carried out.

There is much interest in the treatment of CCIM or PTM in the treatment of sludge such as concen- trated boric acid and aluminum in heating ventilating and air conditioning systems to liberate nuclear waste generated globally have.

In particular, the viscosity, one of the main operating factors of vitrification, affects the integrity of the vitrification facility when the molten material is discharged. Therefore, the development of technology for the vitrification facility is also one of the main issues. There is also a lot of interest in research.

Korea Hydro & Nuclear Power Co., Ltd. is developing PTM application commercial technology for vitrification of highly viscous waste such as soil and concrete.

Plasma-based high-temperature melting technology is a technology for decomposing organic compounds and dissolving inorganic materials in non-conductive and non-combustible wastes such as concrete, metal, and soil generated in industrial sites to vitrify or ceramicize in a crystalline state. And is regarded as an environmentally friendly technology with little secondary waste generation.

High temperature plasma technology not only can rapidly and safely decompose organic compounds but also melts minerals to reduce volume and change the structure of molecules to produce slag or glass-ceramic solids.

The resulting final solids have excellent physical, chemical and mechanical properties.

Therefore, since the waste is melted or melted through the melting of the waste using the high temperature plasma, there is no problem of dissolving the harmful substance in the solidified material and the molten waste can be stably disposable.

The operating conditions of the melting furnace vary depending on the content of the waste during the melting process. There is a viscosity as a factor to maintain the melt fluidity and melt integrity in the melt pool.

As one example, when molten metal is melted, the melt viscosity affects the mass exchange rate between the metal layer and the slag. If the slag viscosity is low, the convection is good and the heat conduction due to the mixing of the slag and the metal is easy. .

However, if the viscosity is high, the diffusion movement of the ions forming the slag becomes dull and the electric conductivity is lowered.

This affects the operation of the plasma depending on the melting temperature and the chemical composition of the slag.

The melting furnace operating condition varies depending upon the waste molten matter content (or an inorganic ratio) In the composition of the wastes (concrete, soil material etc.) other than the metal is SiO _2, Al ₂ O _3, CaO and so on up the majority, In addition, Na ₂ O and MgO exist in small amounts.

Since the content of oxides that can lower the viscosity at a high temperature (1500 ° C or higher) is low in the melt, the discharge may not be smooth in an environment below 1500 ° C.

In general, it has been studied that the viscosity of pure SiO ₂ improves the flowability by adding a basic oxide such as CaO.

Generally, the metal slag has good flowability due to low viscosity at a melting furnace temperature of 1500 ° C or higher, and has high electric conductivity and plasma arc flame generation strength,

The melting temperature depends on the basicity (CaO / SiO ₂ ). When the components such as FeO, Na ₂ O and K ₂ O are high, the melting temperature is low and the melting temperature is high when MgOm and Fe ₂ O ₃ are high .

Registration No. 10-0524825 (Registered on October 21, 2005)

DISCLOSURE OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a glass / slag composition process for vitrifying highly viscous wastes, The present invention provides a low-viscosity adjusting method for discharging a non-combustible waste melt in which the temperature is kept as low as 100 poise or less at a temperature (1300 ° C to 1500 ° C).

In order to accomplish the above object, the present invention provides a method for adjusting a low viscosity for discharging a non-combustible waste melt, comprising the steps of: preparing a non-combustible waste containing 40 wt% or more of SiO ₂ in a plasma torch melting furnace _{1 to 5} wt% of CaO, 0.1 to ₃ wt% of FeO, _{1 to 8} wt% of CaF _2, 0.1 to ₅ wt% of Al ₂ O ₃ , 0.1 to ₅ wt% of MgO, 0.1 to ₅ wt% of Na ₂ O, And a low viscosity of the non-combustible waste is adjusted to 100 poise or less at a discharge site temperature of 1300 ° C to 1500 ° C.

As described above, the low-viscosity adjusting method for discharging incombustible waste melt according to the present invention has the following effects.

First, the present invention facilitates melting operation by using PTM to treat materials generated in an industrial field, and can easily provide the discharge.

Second, the present invention can establish non-flammable solid waste quality control management through development of glass or slag composition for PTM treatment.

Third, the present invention can develop a proper glass / slag composition according to the change of physical and chemical properties for maintaining the viscosity to maintain the PTM operating soundness, so that the solidification which is the final product of vitrification can be suitably applied without adversely affecting the PTM performance .

1 is a glass / slag composition vitrification process for maintaining a non-combustible waste having a high viscosity in a non-combustible waste at a low point according to the present invention.

Hereinafter, the present invention will be described in detail.

<Slag viscosity characteristics>

Melts generated when a metal-containing material is dissolved in a plasma melting furnace are residual materials separated from metals in a molten bath due to a difference in specific gravity, and are mostly composed of iron oxide and carbon, A slag, a metallurgical slag, and a base oxide.

The constituents of the glass or slag produced by the plasma melting are composed of basic oxides (Na ₂ O, CaO, MgO, MnO, FeO), neutral oxides (Fe ₂ O ₃ , Al ₂ O ₃ , TiO ₂ ) and acidic oxides (SiO ₂ , P ₂ O ₅ ). Most of the glass or slag is vitrified SiO ₂ .

P ₂ O ₅ to form glass or slag. Oxides such as SiO ₂ have a network and these oxides are called network formers.

Basic oxides such as Na ₂ O, CaO, and MnO are called network modifiers because they have the property of destroying the network structure.

Acidic glass or slag has a higher SiO ₂ content than the basic one and has a higher viscosity.

Non-combustible wastes, such as glass or slag from non-metallic materials such as concrete, are in the form of silicate oxides similar to rocks in their composition because they contain the majority of SiO ₂ .

In this case, since the flowability of the glass is not good, there is a possibility that the outlet clogging may occur according to the temperature change at the time of discharge.

Accordingly, when the waste is melted, the specific gravity is smaller than that of the metal forming the melt at the base of the plasma melting furnace, and the flowability is good, so that the pouring is good.

In general, glass or slag is a mixture of non-chargeable molecules, and the chemical behavior depends on the ratio of basic and acidic oxide components.

The ratio of such oxides is expressed as bacisity, which acts as a factor influencing the melt state such as electrical conductivity and viscosity during melting.

The basicity is an important parameter for controlling the melt in the plasma melting technique, and the flowability and melting temperature of the melt change depending on the basicity.

The average basicity is used as a ratio of CaO / SiO ₂ , (CaO + MgO) / SiO ₂ , (CaO + MgO) / (SiO ₂ + Al ₂ O ₃ ), and the slag having a basicity of 0.9 or less is acidic, 2.0 is mildly basic, 2.0 to 3.0 is mildly basic, and 3 or more is strongly basic.

However, as the basicity of the melt increases, the viscosity is lowered and it is not favorable to the vitrification operation characteristics. Therefore, the basicity of the melt is appropriately maintained in consideration of the melting conditions.

Usually, the electrical conductivity increases with the increase in the basicity of the glass or slag.

On the other hand, if the viscosity of the melt is low, convection of the melt becomes good, mixing of the glass or slag and heat conduction become easy, and melting refractory erosion becomes severe.

Since the viscosity and electric conductivity of the melt vary depending on the molten material, it is necessary to control the melt state with proper basicity for stable molten metal operation and smooth slag discharge.

In the present invention, the viscosity characteristics of the target wastes were studied using Urbain and Riboud models.

The Urbain model uses the Weymann-Frenkle equation η _L = ATexp (10 ³ B / T), which is a temperature function, as a glass or slag viscosity model for SiO ₂ -CaO-Al ₂ O ₃ systems and for viscosity (η _L ).

The parameter B is obtained from the glass or slag component at an absolute temperature Kelvin T which is composed of a glass former (SiO ₂ ), an intermediate (Al ₂ O ₃ etc.) and a modifier (CaO, FeO, MgO).

The Riboud model was derived empirically from the Weymann-Frenkle equation for the waste composed of network formers and modifiers using the melt composition components A and B of the Weymann-Frenkle equation.

In the present invention, the oxide composition of the waste is analyzed, and the viscosity of each waste is calculated by using a model equation.

In addition, the range of oxide distribution was derived from the deviation from the model equation by using the viscosity value measured in the laboratory.

<Viscosity model analysis>

The fluidity and viscosity of the glass or slag will affect the effluent, melt, etc. of molten slag during waste melting.

If the viscosity of the glass or slag is high, it may cause problems such as clogging of the outlet of the melting furnace. Therefore, it is necessary to increase the temperature of the melting furnace or lower the viscosity so that the basicity is mixed at a proper ratio.

When the basicity is high, the melting temperature of the glass or slag increases, so that the control of the basicity is important for proper melting furnace operation.

If the viscosity of the glass or slag is higher than 100 poise, it may cause problems such as clogging at the outlet of the melting furnace.

As a result of analyzing the viscosity distribution of the oxides with different composition, the basicity was about 0.3 when the SiO ₂ content was about 40 wt%, and the viscosity was high in this case.

In contrast, when the content of SiO ₂ was about 20 wt%, the basicity was about 1 and the viscosity was low.

For the stability of PTM operation and ease of operation of the molten metal, the viscosity distribution of the mixed waste was derived so that the waste oxides composition ratio can be considered when the waste such as concrete and soil is input.

These wastes were not easily discharged from the tapping trough due to their high viscosity (over 100 poise) when they were discharged after individual melting.

For mixed waste with an appropriate oxide composition, the melt was discharged smoothly at the outlet and the viscosity was low (less than 100 poise).

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

One of the technical problems of the vitrification process improvement aimed at in the present invention is to allow the melt to be maintained at a low viscosity (100 poise or less) through the development of a glass / slag composition so that the melt pool is smoothly formed.

1 is a glass / slag composition vitrification process chart for maintaining a non-combustible waste having a high viscosity in a non-combustible waste according to the present invention at a low point.

As shown in this figure, the method for adjusting the low viscosity for discharging incombustible waste melt according to the present invention comprises adding an oxide adjustment control agent at a melting temperature of 1500 캜 using an oxide composition in a non-combustible waste containing 40 wt% or more of SiO ₂ The composition change is maintained, and the low viscosity of the non-combustible waste is adjusted to 100 poise or less.

That is, the method for adjusting the low viscosity for discharging incombustible waste according to the present invention is a method for adjusting the melting point of a non-combustible waste such as metal, concrete, and soil generated in a nuclear power plant by using the oxide composition of non-combustible waste in a plasma torch melting furnace, Glass or slag composition viscosity to prevent abnormal behavior such as boiling and swelling of molten pool formed at high viscosity at 1500 ° C and maintain low viscosity (below 100 poise) at melting point integrity and discharge site temperature (1300 ℃ ~ 1500 ℃) Adjustment.

[Example] Non-combustible waste vitrification process

In general, when the waste is melted, the metal having a high specific gravity constitutes the base portion of the melt and the other inorganic substance having a low specific gravity forms the upper layer, so that the metal layer is discharged through the lower outlet of the melting furnace and the upper slag layer is discharged to the bottom or side of the melting furnace.

Since the composition, basicity, and specific gravity of the melt are determined from the inorganic composition of the waste at first, the most important thing concerning the discharge of the melt is the structure of the melt discharge system of the melting furnace, the temperature and the viscosity of the melt.

Here, the temperature of the melt can be controlled by controlling the power balance, and the viscosity of the melt can be controlled within a certain range by adding flux.

<Viscosity>

The viscosity according to the basicity of the waste was compared.

As shown in Fig. 1, the higher the basicity of glass or slag, the lower the viscosity. However, at 1,500 ℃ or lower, the basicity and viscosity distribution show a rapid variation.

[Figure 1]

<Solid matter composition distribution>

After the PTM is operated and the plasma is used for melting, the metal and glass or slag in the melting furnace are melted to form a molten pool, and the current and voltage supplied to the torch remain stable.

Changes in torch operating conditions and melting conditions may also be seen depending on the nature of some of the wastes input prior to melt discharge (eg, high water content and high organic matter content).

Concrete slump or tex waste, compared to waste such as concrete and soil, partial pressure increase in the melting furnace, and swelling phenomenon due to the change of the molten pool condition occurred temporarily.

Therefore, it is necessary to control the mixing ratio of the input amount and the waste type in order to stabilize the operation of the molten metal when the waste is charged.

As a result of analyzing the concrete and soil used in the present invention, it is mainly composed of SiO2 and CaO as shown in Table 1. As a result of the analysis of the molten solid composition using the mixture, the oxide composition of each sample was found to be the distribution of the oxide composition according to the mixing ratio by the theoretical simulation Respectively.

Oxide Composition Distribution of Waste and Slag (Unit: wt%)

oxide

concrete

soil
waste
Glass-ceramics
waste
Glass-ceramics

SiO ₂

50 to 60
55 to 65
60 to 70
65-75
CaO
6-10
8-12
1-4
1-5

Fe ₂ O ₃
2 to 5
0.1 to 2
1 to 8
0.1-3

FeO
0.1 to 2
10-15
0.1-5
1 to 8

CaF ₂
0.1 to 2
0.1 to 2
0.1-5
0.1-5

Al ₂ O ₃
2 to 6
8-15
8-18
15-25

MgO
0.1 to 1
1-4
0.1-5
0.1-5

Na ₂ O
0.1 to 2
1-4
1-5
0.1-5

100: Low viscosity adjustment method for non-combustible waste melt discharge

Claims (1)

To prevent the boiling and swelling behavior of molten pools formed at the melting temperature (> 1500 ℃) in plasma torch melting furnace using the oxide composition of non-combustible wastes from metal, concrete and soil non-combustible wastes generated from facilities in nuclear power plants As a viscosity adjustment method for maintaining a low viscosity (100 poise or less) at the melting furnace integrity and discharge site temperature (1300 ° C to 1500 ° C)
SiO ₂ from the SiO ₂ 65~75wt% melting temperature 1500 ℃ in a plasma torch melter, using the oxide composition in the ratio of the soft waste non-combustible waste contains at least 40wt%, CaO 1~5wt%, FeO 0.1~3wt%, CaF _{2 to} 8 wt% of Al ₂ O ₃ , 0.1 to ₅ wt% of Al ₂ O ₃ , 0.1 to ₅ wt% of MgO and 0.1 to 5 wt% of Na ₂ O was added to maintain the compositional change, Wherein a low viscosity of said non-combustible waste is adjusted to be less than 100 poise at ~ 1500 ° C.

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