JP2001182924A - Method of operating melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dissolve a problem that a work to determine a melting point and viscosity from a phase diagram, especially three component phase diagrams, needs knowledge to read a phase diagram and takes long for skill, and therefore, a mistake in reading often occurs, a trouble sometimes occurs to operation of a melting furnace and momentary countermeasure against the situation of the melting furnace is difficult to take. SOLUTION: A method of operating a melting furnace comprises a composition analyzing process for melting furnace discharge slag; a process to determine the melting point of discharge slag from a phase diagram regarding four components of SiO2, CaO, MgO, and Al2O3; a process wherein viscosity of discharge slag is obtained at the melting point determined at the process to determine the melting point; and a process from the melting point and viscosity determined at the processes, a proper melting furnace temperature and a component adjuster addition amount are determined, and control of the melting furnace temperature to a proper value and control of the component adjuster addition amount to a proper value are executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for operating a melting furnace such as a waste gasification melting furnace, an ash melting furnace, and an electric furnace.

[0002]

2. Description of the Related Art In recent years, the necessity of preventing environmental pollution due to dioxins generated by incineration of waste and recycling resources has been called out. Along with this, the development of technologies for gasifying and melting waste, or ash melting furnaces for the purpose of reducing the volume and use of ash has been promoted. Gasification and melting furnaces have the characteristics of generating high-temperature combustion gas by gasifying waste, melting waste to reduce volume, and decomposing dioxins to make them harmless. are doing. The ash melting furnace reduces the volume by melting incineration ash and fly ash, and the obtained slag can be used as roadbed material. Furthermore, since the molten fly ash discharged from the ash melting furnace contains heavy metals in a high concentration, reduction of yamamoto is expected.

[0003]

The operation of the above-mentioned melting furnace is described, for example, in Japanese Patent Application Laid-Open No. 5-64736, based on the amount and composition of the material to be melted (waste, limestone, coke, etc.) measured in advance. A method has been proposed in which the amount of a component regulator (limestone, quartz sand, etc.) is calculated and obtained from a phase diagram. Also, in Japanese Patent Application Laid-Open No. H11-0766993, the composition of slag discharged during operation is determined by fluorescent X
There has been proposed a quality control method for molten slag in which the amount of a component adjuster is adjusted based on the analysis result obtained by a line analyzer.

However, the operation of obtaining the melting point and viscosity from a phase diagram, particularly a three-component system phase diagram, requires knowledge of reading the phase diagram and also requires time. For this reason, there are many reading errors, which sometimes hinder the operation of the melting furnace, and there is a problem that it is difficult to instantaneously cope with the deterioration of the state of the melting furnace.

An object of the present invention is to solve the above problems and to provide a stable method of operating a melting furnace.

[0006]

The above object is achieved by the following invention. A composition analysis step of the slag discharged from the melting furnace,
Based on the composition analysis result of the discharged slag in the composition analysis step, the melting point of the discharged slag was obtained from the phase diagram of the four components of SiO ₂ , CaO, MgO, and Al ₂ O ₃ , and the melting point was obtained. The process of determining the viscosity of the discharged slag at the melting point, and the appropriate melting furnace temperature and the amount of the component regulator added from the melting point and the viscosity determined in these processes, and controlling the appropriate melting furnace temperature and the amount of the component regulator added. And a step of operating the melting furnace.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The components of slag discharged from a gasification melting furnace or an ash melting furnace are approximately 90% or more of four components of SiO ₂ , CaO, MgO and Al ₂ O ₃ . Therefore, it is sufficient to determine the melting point and viscosity of the slag based on the phase diagram of these four components. The phase diagram of the four components is 3 with one component fixed.
It is represented as a component system phase diagram. According to the method for operating a melting furnace according to the present invention, the melting point and the viscosity are automatically read from a ternary phase diagram based on the composition of the discharged slag, and the optimum slag component adjustment and temperature control in the melting furnace are performed. This makes it possible to respond quickly and accurately to changes in the furnace conditions.

The overall process of the present invention will be described with reference to the flowchart of FIG. First, in the composition analysis step of the slag discharged from the melting furnace, the composition analysis of the slag is performed using an analyzer such as a simple X-ray fluorescence analyzer. Next, in the process, the melting point is automatically obtained from the analysis result obtained in the previous process. Further, in the step, the viscosity of the slag at the obtained melting point (temperature) is automatically determined.

In the process, a three-component phase diagram is used. In the three-component phase diagram, those showing the melting point of the substance of the composition in units of 100 ° C. as shown in FIGS. 7 and 8 and those showing the viscosity at each temperature as shown in FIGS. is there. Based on these phase diagrams, a database in which melting points or viscosities are input is created on a sheet of spreadsheet software. First, the melting point database is obtained by dividing the inside of the equilateral triangle of the phase diagram into a lattice shape, digitizing the temperature indicating the melting point that can be read from the phase diagram into each cell, and inputting it. FIG. 5 shows the state of the database. Similarly, regarding the viscosity, the viscosity is quantified for each cell using the temperature as a parameter, and is input.

The melting point and viscosity of slag can be determined by combining the above database with software for automatically determining points on a phase diagram simply by inputting the composition of the three components to a personal computer.

The details of the three-component automatic plotting software will be described below. The phase diagram of SiO ₂ , CaO, MgO and Al ₂ O ₃ system (FIG. 6) is used as an example.

In the three-component phase diagram, a composition of 100% of each component is placed at the apex of an equilateral triangle, and the perpendicular drawn from the apex is divided into 10 equal parts, and 10% is divided from below. The scale is usually marked on the side as shown. That is, SiO ₂ : 30%, CaO: 50
% And Al ₂ O ₃ : 20%, they are located at points in the figure. As described above, the following method was used as a method for writing points in the figure having three axes on the X and Y coordinates. The composition ratio of SiO ₂ is Y = a point on the "composition ratio of SiO _2". The composition ratio of CaO is Y = −31 ^/ 2X + 2 (100− “Ca
The composition ratio of Al ₂ O ₃ is the upper point. The composition ratio of Al ₂ O ₃ is Y = 3 ^1/2 X−2 × “the composition ratio of Al ₂ O ₃ ”. These are the intersections of the straight lines indicated by.

In this way, the composition of the three components can be described on the X and Y coordinates. It should be noted that the sum of the three components of the slag component is not always 100%. Also, MgO
It does not mean that the sum of the four components obtained by adding is 100%. In such a case, the total amount is corrected to 100%. However, when the corrected composition ratio is written on a state diagram, three straight lines may not intersect. For example, the case shown in FIGS. In this case, the center of gravity of a triangle formed by three straight lines is used as the composition of the slag.

If the melting point of the slag obtained in the step deviates from the actual furnace temperature, or if the viscosity of the slag at the furnace temperature deviates from an appropriate value, the process proceeds to the final step. That is, operations such as immediately increasing the oxygen concentration of the blown air are performed to adjust the temperature in the furnace, and to adjust the addition amount of the component adjusting agent. Conventionally, the steps up to were manually performed, but by automatically taking in the slag composition obtained from the simple X-ray fluorescence analyzer, simply setting the slag in the analyzer,
The above automatic control becomes possible.

Also, by displaying the three-component system phase diagram on the screen during operation, it is possible to visually confirm the basicity calculation compared with the method of performing the basicity calculation using a personal computer disclosed in Japanese Patent Laid-Open No. 5-64736. There are fewer mistakes and reliability is improved.

[0016]

EXAMPLES (Example 1) Table 1 shows the composition of slag discharged during operation of the gasification and melting furnace.

[0017]

[Table 1]

FIG. 7 shows 20% -Al ₂ O of the SiO ₂ —CaO—MgO—Al ₂ O ₃ system.
Correlation system at liquidus temperature on _three sides (Osborn, Devries, Gee and
Figure 9 shows an automatic plot of the composition of the discharged slag. The melting point was 1350 ° C. as shown in FIG. Further, the viscosity at 1450 ° C. is calculated as shown in FIG. 2 to be 13 poise, and as shown in FIG.
The viscosity at 9 was found to be 9 poise. Furnace temperature is 1
Although the temperature was 470 ° C., the oxygen concentration was increased by 1% and the furnace temperature was raised by 30 ° C. in order to reduce the viscosity to the target viscosity of 10 poise or less. This treatment made the slag discharge smooth.

[0019]

Example 2 Table 2 shows the ash composition of waste and coke to be melted during operation of the gasification and melting furnace.

[0020]

[Table 2]

This is illustrated on a phase diagram as shown in the ash composition of FIG. However, since the melting point and the viscosity were 1490 ° C. and 70 poise (FIG. 4), respectively, CaCO ₃ was used so that the target melting point was 1450 ° C. or less and the viscosity was 10 poise or less (the range enclosed by a circle in FIG. 8). Operation was performed after adding 30 kg. With this formulation, the expected melting point of the slag is 1310 ° C and the viscosity is 9.
Dropped to 5.

[0022]

As described above, according to the method for operating a melting furnace according to the present invention, it is possible to quickly and accurately respond to a change in the furnace condition of the melting furnace, and to stabilize the operation of the melting furnace. effective.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the entire process of the present invention.

FIG. 2 is an isoviscosity curve diagram of a CaO—MgO—Al ₂ O ₃ —SiO ₂ system at 1450 ° C. on a 40% -SiO ₂ surface.

FIG. 3 is an isoviscosity curve diagram of a CaO—MgO—Al ₂ O ₃ —SiO ₂ system at 1500 ° C. on a 40% -SiO ₂ surface.

FIG. 4 is a diagram of an isoviscosity curve of a CaO—MgO—Al ₂ O ₃ —SiO ₂ system at 1450 ° C. on a 50% -SiO ₂ surface.

FIG. 5 is an example of a liquidus diagram database.

FIG. 6 is an explanatory diagram of a three-component system automatic plot.

FIG. 7 is a liquidus diagram in Example 1.

FIG. 8 is a liquidus diagram in Example 2.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuichi Yamakawa 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Tsuneo Matsudaira 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun F-term (reference) in Honko Co., Ltd. 3K061 AA24 AB02 AB03 AC03 BA10 CA11 DA12 3K062 AA24 AB03 AC03 BA01 CB03 DA01 DA40 DB30

Claims (1)

[Claims] 1. A process for analyzing the composition of slag discharged from a melting furnace and a result of analyzing the composition of the discharged slag in the composition analysis process, the slag discharged from a phase diagram for four components of SiO ₂ , CaO, MgO, and Al ₂ O ₃ . The step of determining the melting point of the, and the step of determining the viscosity of the discharged slag at the melting point determined in the step of determining the melting point, the appropriate melting furnace temperature and the amount of component modifier added from the melting point and the viscosity determined in these steps, A method for operating a melting furnace, comprising a step of controlling a proper melting furnace temperature and a control amount of a component adjusting agent.