JP6208599B2 - Asbestos treatment method - Google Patents

Description

  The present invention relates to a method for treating asbestos.

Asbestos is composed of chrysotile (white asbestos: Mg ₃ Si ₈ O ₅ (OH) ₄ , melting point 1521 ° C.), crocidolite (Ao Asbestos: Na ₂ Fe ₅ Si ₈ O ₂₂ (OH) ₄ , melting point 1193 ° C.), and amosite ( Tea asbestos: (FeMg) ₆ Si ₈ O ₂₂ (OH) ₂ , melting point 1399 ° C.) Asbestos is a fine fibrous needle-like crystal that is known to cause damage to the respiratory tract, such as cancer, when sucked into the human body.

  However, asbestos has been used in large amounts as a building material in the past because of its high incombustibility, chemical resistance, and heat insulation. Currently, with the aging of buildings, a large amount of waste materials containing asbestos are born when the buildings are demolished. Until now, asbestos has been disposed of by landfill treatment after sufficient anti-scattering treatment. However, it is preferable to use a treatment method in which asbestos is rendered harmless by melting treatment because of an increase in the amount of asbestos waste and its strong harmfulness.

  The melting treatment is a method of melting and disposing asbestos in a general waste melting furnace. In the melting furnace, the melt is separated into two layers of a metal component and a slag component, the slag component is a harmless material, and the metal component is a smelting material. Since asbestos has silicon oxide as a constituent component as described above, it dissolves above the melting point and becomes harmless slag.

  The general waste melting furnace is operated at about 1000-1300 ° C, but it is possible to melt asbestos by partially heating the chrysotile by direct irradiation of the flame of the burner to create a state with a melting point of 1500 ° C or higher. It is. Once the asbestos unit composition collapses, the fine fiber structure cannot be reconstructed, its toxicity is significantly reduced, and it can be dissolved in the slag layer to form a harmless and stable form that can be discharged out of the system. It becomes.

  As a conventional asbestos treatment method, for example, the treatment method disclosed in Patent Document 1 is a melting method using an electric furnace. In the electric furnace, the temperature in the furnace can be partially adjusted to a high temperature, so that it is easy to raise the temperature to be higher than the melting point of asbestos. However, there are problems such as a large amount of expensive electric power required and electrode erosion. In order to improve this point, it is preferable that the heating device is a burner instead of an electrode.

In Patent Document 2, as a method for treating asbestos by a melting furnace using a burner, a method is described in which incinerated ash and asbestos are mixed and melted. On the other hand, in Patent Document 3, industrial waste is charged into a horizontal furnace, melted by a burner provided in the furnace, a slag bath is formed in a hot water reservoir, and asbestos is charged into the slag bath. Disclosed is a method for detoxifying asbestos that dissolves in a bath. Patent Document 4 discloses a method of adjusting the slag melting point of a composition composed of Al ₂ O ₃ —CaO—MgO—SiO ₂ when the fly ash is mixed with asbestos and melted.

Patent Publication No. Hei 7-171536 Japanese Patent Publication No. 2-303585 Patent Publication No. 2003-181212 Patent Publication No. 2007-275839

  In the method of Patent Document 2, it is shown that if the mixing ratio of molten ash and incinerated ash is 3: 7, asbestos can be efficiently detoxified, but the melting point of the generated slag is 1355 ° C. The melt flow temperature is 1375 ° C. When this ratio is 4: 6, the melting point must be 1407 ° C. and the melt temperature must be as high as 1445 ° C. It is difficult to achieve a high temperature of 1400 ° C. or higher by heating with a burner.

  In any of the methods of Patent Document 3 and Patent Document 4, it is difficult to maintain an environment above the melting point of asbestos by heating with a burner, but the generated slag layer acts as a solvent and melts asbestos. However, in the method of treating asbestos by melting in a slag bath, when an excessive amount of asbestos is added, it is difficult to obtain homogeneous slag because the specific gravity of the molten asbestos is small. Mixing and melting using a slag layer as a solvent detoxifies asbestos, but at the same time, slag is an important valuable material used for building materials and cement aggregates. Attenuate. Stirring is easily conceived for homogenizing the slag, but generally, natural agitation by heat convection is adopted in a melting furnace, and physical forced stirring is not preferable. This is because the metal layer and the slag layer are mixed to cause a problem in separation.

  From the above, heating and melting of asbestos by a burner includes technical problems to be solved. An object of this invention is to provide the processing method of asbestos which can be heated with a burner with a waste melting furnace, and can collect | recover high quality slag in view of said subject.

Method of treating asbestos in accordance with the present invention, the asbestos-containing waste was charged into the slag of 2 layers separated waste melting furnace and a small slug of large mat and the specific gravity of, provided in the waste melting furnace Using a burner having an oxygen ratio of 0.7 or more, maintaining the temperature of the slag at 1100 ° C. to 1400 ° C., exceeding 0% of the residence time of the slag in the waste melting furnace, and a period of 60% or less, The slag is agitated.

The oxygen ratio of the burner may be 0.7 or more and 1 or less. The slag may be agitated for a period exceeding 0% of the residence time of the slag in the waste melting furnace and not exceeding 40% . When the iron content of the slag is 10 wt% or less, iron oxide may be added to the slag. The burner flame may be directly applied to the asbestos fed from the waste melting furnace inlet. The burner may be provided in a range of 30 cm to 40 cm from the outer edge of the charging port. An oxygen lance may be inserted from a position different from the burner, and oxygen may be sprayed from the oxygen lance to the surface of the slag. During the stirring, the slag may be intermittently stirred. After the iron concentration of the slag becomes 10 wt% or more, the slag may be discharged from the waste melting furnace. A plurality of the burners may be provided in the waste melting furnace. In the waste melting furnace, a first charging port and a second charging port arranged closer to the slag discharge port than the first charging port are provided, and a melt processing object and slag are formed in the first charging port. Flux may be charged and the asbestos-containing waste may be charged into the second charging port.

  According to the present invention, high quality slag can be recovered by heating with a burner in a waste melting furnace.

It is a top view of a waste melting furnace. It is a front view of a waste melting furnace.

  Hereinafter, an embodiment for carrying out the present invention will be described.

(Embodiment)
Below, the processing method of asbestos which concerns on one Embodiment is demonstrated. 1 and 2 are schematic diagrams of a waste melting furnace 100 used in the asbestos treatment method. FIG. 1 is a schematic diagram of the upper surface of the waste melting furnace 100, and FIG. 2 is a schematic diagram of the front surface of the waste melting furnace 100.

  As illustrated in FIGS. 1 and 2, the ceiling of the waste melting furnace 100 includes a plurality of general waste inlets 10, an asbestos inlet 20, a plurality of ceiling burners 30 a for general waste, and an asbestos outlet. A plurality of ceiling burners 30b are provided. The ceiling burners 30a and 30b are burners that use heavy oil or the like as fuel. A plurality of side burners 40 are provided on the upstream side surface of the waste melting furnace 100. On the downstream side surface of the waste melting furnace 100, a slag discharge port 50 is provided. A metal discharge port 60 is provided in the lower front portion of the waste melting furnace 100.

  The ceiling burner 30a is disposed at a position where the raw material input from the general waste input port 10 can be heated. The ceiling burner 30b is arranged at a position where the asbestos thrown from the asbestos throwing opening 20 can be directly irradiated with a flame. In order to directly irradiate the asbestos with the flame, the ceiling burner 30b is preferably disposed at a position of 30 cm to 40 cm from the outer edge of the asbestos inlet 20.

From the general waste input port 10, a general object such as general waste and molten fly ash and a slag forming flux are input. The objects to be melted include sludge, slag, burning husk, printed circuit board, pad scrap, waste catalyst, metal scrap, waste shot, grinding scrap, dust, and the like. “Sludge” includes dewatered sludge, plating sludge, polishing sludge, sewage sludge, and the like. Dehydrated sludge is mainly composed of Ca and Fe. The plating sludge is mainly composed of Cu, Fe, S, and Ca. Burning husk is incineration residue. The printed board is made of Cu and plastic. The iron slag is Al ₂ O ₃ powder or the like, and the pad scrap is a brake pad or the like. Waste shots are waste materials such as shot blasting grains. Dust is soot. When the object to be processed contains valuable metals, iron sulfide can be added to produce a mat, and the valuable metals can be captured in the mat. In addition to sludge and the like, industrial waste that can be reused as slag can be treated. These charged raw materials are heated and melted by the flames of the side burner 40 and the ceiling burner 30a. Thereby, the raw material is separated into two layers into a metal layer (mat) having a large specific gravity and a slag layer having a small specific gravity.

Asbestos-containing waste is introduced into the slag from the asbestos inlet 20. The installation position of the asbestos inlet 20 is a place where the above-described raw material and flux are allowed to stand for separation after being melted (set ring portion), and closer to the slag outlet 50 than the general waste inlet 10. Position. When asbestos is charged, asbestos-containing waste can be promoted by directly irradiating the asbestos-containing waste with a flame by a plurality of burners 30b provided beside the asbestos charging port 20. In the waste melting furnace 100, the solution has already been separated into two layers, but the slag having a small specific gravity is on the surface layer and functions as a solvent, so that asbestos dissolves sequentially in the slag even below the melting point. The slag is preferably SiO ₂ —CaO—FeO slag or SiO ₂ —CaO—MgO slag which is common in non-ferrous refining. Furthermore, Al ₂ O ₃ may also be included as a component, but when this content is high, the melting point of the slag increases.

  The oxygen ratio in the combustion by the ceiling burner 30b is preferably 0.7 or more. This is because if the oxygen ratio is small, the ceiling burner 30b may cause incomplete combustion and a sufficient temperature cannot be obtained. On the other hand, if the oxygen ratio is too large, a large amount of nitrogen oxide is generated, which may increase the load on the denitration process of the exhaust gas treatment. Therefore, the oxygen ratio in the combustion by the ceiling burner 30b is preferably 0.7 or more and 1 or less.

Moreover, an oxygen lance may be inserted from a position different from the ceiling burners 30a and 30b and the side burner 40, and oxygen may be sprayed directly onto the slag. In this case, the heat of reaction in the waste melting furnace 100 can be increased by the supplied oxygen. Moreover, when oxygen is sprayed directly on the slag, the divalent iron component in the slag is effectively oxidized to Fe ₂ O ₃ , and the effect of improving the fluidity of the slag is also expected. It is preferable that the slag does not solidify and has low viscosity and fluidity when discharged. Therefore, the temperature of slag is maintained at 1100 ° C to 1400 ° C.

  Asbestos dissolved in the slag forms a phase having a smaller specific gravity in the slag as the input amount increases. Since this asbestos melt phase does not sufficiently diffuse only by thermal convection, it is desirable to physically (force) agitate the slag. However, when physical stirring is performed, the separated slag layer and the metal layer are mixed again, and the separation of the two layers is deteriorated. Therefore, it is not constantly stirred, but is stirred for a maximum of 60% or less of the total residence time with respect to the residence time of the slag in the waste melting furnace 100. In other words, the slag is agitated for a period that exceeds 0% of the residence time of the slag in the waste melting furnace 100 and is 60% or less. By intermittently stirring, deterioration of two-layer separation can be suppressed. The stirring method is not particularly specified, and any stirring method may be used as long as the slag becomes homogeneous. For example, a method of stirring slag with wood, oxygen lance or the like may be used. For the purpose of homogenizing the slag, it is preferable to stir the slag for a period exceeding 0% of the residence time of the slag in the waste melting furnace 100 and not more than 40%.

  Slag in which a large amount of melted asbestos has melted tends to reduce the specific gravity. If the specific gravity of the slag is small, there is an advantage that the separability from the metal is improved, but the value of the slag having too small specific gravity is reduced as a building material or cement aggregate. In recent years, the demand for slag as an aggregate of caisson and cement is high, and slag with a small specific gravity is not suitable for this. Therefore, although the specific gravity can be adjusted by the iron content, the iron content of the raw material supplied to the waste melting furnace 100 is not constant. Moreover, since a large amount of substances that act as reducing agents, such as carbon derived from incineration ash, is contained, the amount of iron reduced and distributed to the metal layer also increases.

Therefore, the iron content of the slag discharged from the slag discharge port 50 is preferably 10 wt% or more, and when this value is not reached, a method of increasing the specific gravity by adding iron oxide to the slag layer is preferable. However, excessive divalent iron oxide deteriorates the fluidity of the slag, so that the iron content is included in the slag as Fe ₂ O ₃ by supplying sufficient oxygen. Fe ₂ O ₃ improves slag fluidity.

The slag in which asbestos is melted is discharged from the slag discharge port 50 when a predetermined amount is reached. The metal is also discharged from the metal discharge port 60 and used for the valuable metal recovery process. A portion of the discharged slag is sampled, the iron content is measured immediately, and the iron oxide input amount is adjusted to enable stable operation. The measurement can be used even with simple quantitative determination using fluorescent X-rays. In general, the waste melting furnace 100 is operated in a continuous manner while appropriately discharging the solution. However, the waste melting furnace 100 can be applied not only to a continuous type but also to a batch type melting furnace. The present invention is particularly effective when the treatment amount of the asbestos-containing material is 20 t / day or more per one furnace (capacity 150 to 190 m ³ ).

  According to this embodiment, since slag is heated using a burner, cost can be suppressed compared with the case where an electric furnace is used. By setting the oxygen ratio in the burner to 0.7 or more, it is possible to increase the flame temperature and promote the dissolution of asbestos. It is also effective in maintaining the slag temperature. Since slag functions as a solvent, dissolution of asbestos can be promoted. Further, by stirring only for a period of 0 to 60% of the slag residence time, the slag composition can be made uniform, accumulation of refractory materials on the furnace bottom is suppressed, and the slag bath is widened. Can keep. Further, by blowing oxygen with an oxygen lance, Fe, S and the like in the melt can be oxidized, and a high melting point substance can be dissolved.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these.

Example 1
A general waste and a flux were charged as raw materials into a melting furnace (capacity 176 m ³ ) having a general waste disposal capacity of 153 t / day. The raw material was heated to 1100 ° C. with a burner, and asbestos-containing waste was added after the flux component formed a slag layer. At the time of charging, the burner 30b installed at the charging port was burned and adjusted so that the flame directly irradiated the asbestos-containing waste. The ceiling burners 30a and 30b were burned so that the temperature of the slag layer was maintained at 1100 to 1400 ° C. Oxygen was supplied into the furnace with an oxygen lance, and the oxygen outlet was adjusted so that oxygen was in direct contact with the slag surface. The oxygen ratio of the ceiling burners 30a and 30b was maintained at 0.7 or more.

  After charging asbestos, a wooden stir bar was inserted from the top of the furnace and the whole was stirred. The stirring time was 90 minutes every 90 minutes. This corresponds to 60% of the slag residence time. The fully melted slag layer was discharged as a solution from the slag discharge port 50. A portion of the discharged slag was collected, and the iron content was determined on-time by a calibration curve method using a fluorescent X-ray analyzer (model ZSX Primus II manufactured by Rigaku Corporation). When the iron content was less than 10 wt%, iron oxide was supplied to the slag layer. Since it was a continuous melting process, the metal layer increased as the process continued, but an appropriate amount was discharged appropriately.

This treatment was continued for 3 days. Table 1 shows changes in average slag temperature and iron quality. There was no problem with slag fluidity. Iron grade, asbestos throughput, temperature maintenance and fluidity of slag were not problems, and good asbestos treatment was achieved.

(Comparative Example 1)
Asbestos was treated under the same conditions as in Example 1 with an oxygen ratio of 0.5 and no supply from the oxygen lance. The operation was carried out under these conditions for two days. On the second day, deterioration of the fluidity of the slag was confirmed visually. Table 2 shows changes in average slag temperature and iron quality.

  The treatment amount of asbestos was insufficient in the first treatment, and when the treatment amount was increased under these conditions, the fluidity of the slag was deteriorated. Therefore, it can be seen that the oxygen ratio and the oxygen supply position are highly effective as measures for increasing the processing amount.

(Comparative Example 2)
Asbestos treatment was continuously performed without stirring under the same conditions as in Example 1. On the third and fourth days, deterioration of the slag fluidity was confirmed visually. Table 3 shows the results of changes in average slag temperature and iron quality.

  Although there is no problem on the first day and the second day, the slag gradually becomes non-uniform over time due to the continuous treatment under the condition without stirring, which causes a decrease in temperature and a deterioration in fluidity. Under these conditions, continuous treatment of asbestos of 22 t / day or more cannot be stably performed.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

Claims (11)

Asbestos-containing waste was charged into the slag of 2 layers separated waste melting furnace and a small slug of large mat and the specific gravity of,
Using a burner provided in the waste melting furnace and having an oxygen ratio of 0.7 or more, the temperature of the slag is maintained at 1100 ° C to 1400 ° C,
A method for treating asbestos, wherein the slag is agitated for a period exceeding 0% and not more than 60% of the residence time of the slag in the waste melting furnace.   The method for treating asbestos according to claim 1, wherein an oxygen ratio of the burner is set to 0.7 or more and 1 or less.   The method for treating asbestos according to claim 1 or 2, wherein the slag is stirred for a period exceeding 0% of the residence time of the slag in the waste melting furnace and not exceeding 40%.   The asbestos treatment method according to any one of claims 1 to 3, wherein iron oxide is added to the slag when the iron content of the slag is 10 wt% or less.   The asbestos treatment method according to any one of claims 1 to 4, wherein the flame of the burner is directly irradiated to the asbestos charged from an inlet of the waste melting furnace.   6. The asbestos treatment method according to claim 5, wherein the burner is provided in a range of 30 cm to 40 cm from an outer edge of the charging port.   The method for treating asbestos according to any one of claims 1 to 6, wherein an oxygen lance is inserted from a position different from the burner, and oxygen is blown from the oxygen lance to the surface of the slag.   The method for treating asbestos according to any one of claims 1 to 7, wherein the slag is intermittently stirred during the stirring.   The method for treating asbestos according to any one of claims 1 to 8, wherein the slag is discharged from the waste melting furnace after the iron concentration of the slag reaches 10 wt% or more.   The said burner is provided with two or more in the said waste melting furnace, The processing method of asbestos as described in any one of Claims 1-9 characterized by the above-mentioned. In the waste melting furnace, a first charging port and a second charging port arranged closer to the slag discharge port than the first charging port are provided,
The melt processing object and slag forming flux are charged into the first charging port,
The method for treating asbestos according to any one of claims 1 to 10, wherein the asbestos-containing waste is charged into the second charging port.

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