JP4838184B2 - Refractory for furnace inner wall, manufacturing method thereof, and waste treatment apparatus - Google Patents

Description

The present invention relates to a refractory material for a furnace inner wall of a furnace using ash generated by burning waste as a molten slag, a manufacturing method thereof, and a waste treatment apparatus.

  Conventionally, as a method of treating industrial waste such as municipal waste from households and offices, waste plastic, car shredder / dust, electronic equipment, cosmetics, etc., these wastes are converted into pyrolysis reactors. And pyrolyzing in a low oxygen atmosphere to produce pyrolysis gas and pyrolysis residue mainly composed of non-volatile components, and combustibles mainly composed of pyrolysis carbon separated from the pyrolysis residue and pyrolysis gas Is conducted to a combustion melting furnace for combustion treatment.

  Here, in a combustion melting furnace, combustion ash (ash) is heated by combustion heat to form molten slag, and this molten slag is caused to flow down the furnace inner wall covered with refractory and discharged from the bottom of the furnace. It is made to cool and solidify.

  By the way, refractories are widely used in industrial kilns, boilers, waste incinerators and the like that require high-temperature treatment such as steel, non-ferrous metals, cement, glass, and ceramics. In particular, when selecting a refractory material in an environment in contact with molten slag, it is necessary to consider severe high temperature corrosion due to the involvement of molten slag as well as the gas phase side environment such as oxygen partial pressure and alkali partial pressure.

  In general, oxide refractory materials are used in refractories used in an environment with a high oxygen partial pressure, and a chromium compound is included to improve corrosion resistance. However, when a refractory containing a chromium compound is used, there is a problem that the material cost is high.

On the other hand, in a waste melting furnace that melts waste with air, for example, a mixed refractory material of MgAl ₂ O ₄ (magnesia spinel) -alumina-magnesia is used in a magnesia-alumina composite system that does not contain chromium. It has been proposed (see Patent Document 1).

JP 2002-193681 A

However, molten slag obtained by melting ash derived from waste is a multi-component system based on silica (SiO ₂ ), alumina (Al ₂ O ₃ ), and calcia (CaO), and has a relatively low basicity. In the furnace, oxidizing gases such as chlorine and sulfur coexist in the gas phase. In such an environment, oxidizing components such as alumina and magnesia in the refractory are highly soluble, and the furnace is exposed to a high temperature in order to cause the molten slag to flow out in a molten state, so that the refractory component May elute into the slag, and wear of the refractory may progress.

  For this reason, in order to improve the corrosion resistance of the refractory to the molten slag, material design based on the reaction mechanism with the molten slag is indispensable. In other words, the viscosity of the molten slag plays an important role in the phenomenon of molten slag penetrating into the refractory and the phenomenon in which the refractory component moves into the molten slag, and this is the boundary phase between the refractory and molten slag. By controlling the reaction rate, wear due to spalling and melting of the refractory continues. From this point of view, it is important to develop a refractory in consideration of the viscosity of the molten slag that governs refractory wear.

  This invention makes it a subject to improve the corrosion resistance of the refractory material which contact | connects the molten slag derived from a waste, without containing chromium, based on the scientific knowledge regarding the viscosity of the molten slag until now.

  The present invention has been made based on the results of various investigations on the influence of molten slag produced in a furnace on the viscosity in the combustion treatment of waste. Hereinafter, the principle of the present invention will be described.

The molten slag derived from waste is mainly composed of SiO ₂ , Al ₂ O ₃ , and CaO, and R ₂ O (R is an alkali element), R′O (R ′ is an alkaline earth element), and iron oxide (FtO). ). The main component of the molten slag has a certain composition (CaO / SiO ₂ = 0.3 to 1.5, Al ₂ O ₃ = about 20% by weight). The main flow unit governing the viscosity in such a narrow composition range of molten slag is aluminosilicate ions, and the viscosity of the molten slag varies greatly depending on the degree of polymerization.

Research report on recent slag physical properties and structural analysis (Takataka Saito, 2 others, “Viscosity of CaO—SiO ₂ —Al ₂ O ₃ — (R ₂ O, RO) slag”, Steel Society, No. 148 According to the Fifth Autumn Lecture Meeting, Vol. 17 (2004) -542), Li ₂ O, Na ₂ O as alkali element oxides for the system mainly composed of SiO ₂ , Al ₂ O ₃ , and CaO. in K 2 _O each predetermined amount added was based, to exhibit an increase in specific viscosity system with the addition of K 2 _O is disclosed. In Li ₂ O and Na ₂ O, this phenomenon behaves like breaking up aluminosilicate ions, whereas K ₂ O is an amphoteric oxide in which slag Al ₂ O ₃ is aluminosilicate ions. By behaving to increase the degree of polymerization.

  On the other hand, as for the refractory base material, alumina-based oxidants are generally widely used as refractories in this field (for example, Patent Document 1). By being stable. However, free alumina is not necessarily a suitable base material because of its high solubility in slag.

Therefore, in order to solve the above-mentioned problem, the present invention is a refractory for a furnace inner wall of a furnace that melts and slags ash generated by burning waste, and the refractory is made of zirconia as a base material. In addition, potassium titanate (K ₂ Ti ₄ O ₉ ) is mixed and contained in an amount of 1 to 4% by weight .

In this way, in the refractory in contact with the molten slag of the waste, by including potassium titanate (K ₂ Ti ₄ O ₉ ) as a potassium compound, the refractory component is eluted from the surface in contact with the molten slag, and the molten slag The concentration of potassium oxide in it can be increased. And the polymerization degree of an aluminosilicate ion increases by the density | concentration of the potassium oxide in molten slag increasing, and the viscosity of molten slag can be made larger in connection with it. For this reason, the penetration of the molten slag into the open pores of the refractory is suppressed, and the thickness of the concentration boundary layer in which the refractory component diffuses increases. As a result, the wear of the refractory can be suppressed.

In addition, since the refractory base material does not contain structurally free alumina in any of zirconia, zircon, mullite and spinel, it suppresses the local increase in Al ₂ O ₃ concentration in the slag. The aluminosilicate ions can be easily polymerized. In particular, a zirconia refractory has a high melting point and low thermal conductivity, and therefore has high stability against molten slag. As the base material of the refractory, commercially available raw materials such as electrofused products and sintered products can be used.

Thus, in this invention, the corrosion resistance with respect to the molten slag of a refractory can be further improved by containing potassium titanate in a base material of zirconia . Here, if the addition rate of potassium titanate is in the range of 1 to 4% by weight, if it is less than 1% by weight, the effect of improving the corrosion resistance accompanying the increase in the polymerization rate of aluminosilicate ions cannot be obtained, On the other hand, if it exceeds 4% by weight, the aggregation of potassium titanate in the refractory increases, so that, for example, the bonding of zirconia particles in the base material becomes weak, and the durability of the refractory may be reduced. is there.

  Since the refractory of the present invention can exhibit high corrosion resistance without adding a chromium compound, it can have high durability for a furnace inner wall in a corrosive environment and can keep material costs low. .

  In addition, the waste treatment apparatus of the present invention burns combustibles contained in a pyrolysis reactor and pyrolysis gas discharged from the pyrolysis reactor, and a pyrolysis reactor. A combustion melting furnace for melting and converting incombustible substances contained in cracked gas and thermal decomposition residue into a molten slag is provided, and the furnace inner wall of the combustion melting furnace is formed of the above-described refractory for the inner wall of the furnace.

  ADVANTAGE OF THE INVENTION According to this invention, the corrosion resistance of the refractory material which contact | connects the molten slag derived from a waste can be improved, without containing chromium.

  Hereinafter, embodiments of the refractory for a furnace inner wall according to the present invention will be described.

  Table 1 shows examples of constituent components of the refractory for a furnace inner wall according to the present invention. The sintered body of the refractory of this example has three types of particle sizes (coarse particles, medium particles, fine particles) for commercially available electro-fused zirconia (for example, “Zirbon” manufactured by Fukushima Steel), which is a zirconia base material. ) Is used to adjust the particle size. Then, a mixture obtained by adding an additive and a sintering aid to this powder is pressure-molded by a uniaxial press, and heated in an air atmosphere at a temperature of 1600 to 1700 ° C. for 10 to 40 hours to obtain a predetermined shape. Thus obtained sintered body is obtained.

Here, in electrofused zirconia, coarse particles refer to particles having a particle size of 1 mm or more and less than 3 mm, intermediate particles refer to particles having a particle size of 150 μm or more and less than 1 mm, and fine particles refer to particles having a particle size of less than 150 μm. Further, titanium lactate (TiC ₆ H ₁₀ O ₇ ) is used as the sintering aid, and potassium titanate (K ₂ Ti ₄ O ₉ ) is used as the additive. In place of potassium titanate, potassium oxalate (IV) dihydrate that is thermally decomposed into potassium titanate may be used.

試験用試料は、上記のようにして得られた焼結体の相状態をＸ線解析により確認した後、φ１０ｍｍの丸棒状に切り出して作製し、回転侵食装置により実機から採取した溶融スラグに浸漬させて、回転侵食試験を実施した。

The test sample was prepared by checking the phase state of the sintered body obtained as described above by X-ray analysis, then cutting it into a φ10 mm round bar, and immersing it in molten slag collected from the actual machine by a rotary erosion device. And a rotary erosion test was performed.

  FIG. 1 shows a schematic diagram of a rotary erosion device. In the rotary erosion apparatus, an alumina crucible 3 that fills molten slag is contained in a container 1, and a test sample 7 supported by an alumina rotary shaft 5 is immersed in the molten slag 11 in the crucible 3. Are arranged to be. The test sample 7 is rotated by a motor 9 connected to the rotary shaft 5. A heater (not shown) for heating the molten slag 11 is disposed around the crucible 3. In the container, a mixed gas (nitrogen 95%, oxygen 5%) is supplied from the cylinder 13 and adjusted to substantially atmospheric pressure.

  Table 2 shows the composition of the molten slag 11. The test sample 7 was rotated at a rotational speed of 60 rpm, a mixed gas was flowed, and after a rotary erosion test at 1400 ° C. for 10 hours, the test sample 7 was taken out and cut, and the amount of corrosion wear ( mm). The results are shown in Table 1.

次に、カリウム化合物の溶出がスラグ粘度に及ぼす影響を確認するため、実機採取スラグ（スラグＫという。）と、このスラグＫに５重量％のカリウム化合物（ここでは、アルミン酸カリウムを用いた）を添加した系、及び、スラグＫに５重量％の酸化クロムを添加した系の３種類について試験用のスラグを作製し、粘度測定装置を用いて高温溶融状態のスラグ粘度について測定し比較した。

Next, in order to confirm the influence of the elution of the potassium compound on the slag viscosity, an actual machine-collected slag (referred to as slag K) and a 5 wt% potassium compound (here, potassium aluminate was used) in the slag K The slag for a test was produced about 3 types of the system which added 5 weight% chromium oxide to slag K, and measured and compared the slag viscosity of the high temperature molten state using the viscosity measuring apparatus.

  FIG. 2A shows a schematic diagram of a viscosity measuring apparatus. In the viscosity measuring apparatus, a crucible 23 made of Pt-20Rh that fills a test molten slag is accommodated in a container 21, and the crucible 23 is formed of the same material at one end of a rod 25 made of Pt-20Rh. The disk-shaped rotor 27 is disposed so as to be immersed in the molten slag 31. A rotating shaft 29 is connected to the bottom of the crucible 23 so that the crucible 23 rotates at a predetermined rotational speed. A heater 33 that heats the molten slag 31 is disposed around the crucible 23. The other end of the rod 25 is connected to a torque generator 35 obtained by improving the differential transformer shown in FIG.

  The transformer generator 35 includes a core 37 connected to the rod 25 and extending in the radial direction of the rod 25, and a coil 39 arranged so as to surround the rod 25. When the crucible 23 is rotated, the transformer generator 35 is configured. A torque is generated in the rod 25 by the viscous resistance of the molten slag 31, and a predetermined potential difference is generated by the rotation of the core 37.

  Using such a viscosity measuring apparatus, first, the crucible 23 was heated to raise the temperature of the molten slag 31 to 1600 ° C. and held for 90 minutes to stabilize the melt state. Then, the temperature was held at each measurement temperature for about 30 minutes at 50 ° C. while the temperature was lowered, and then the measurement was performed three times. Next, the same measurement was performed while raising the temperature again. Thus, the average of the values (potential difference) measured at the time of temperature rise and temperature fall was used as the measured value of the temperature. The apparent viscosity was obtained from the measured value using a calibration curve prepared in advance, and the effect of thermal expansion of the crucible 23 and the rod 25 at each temperature was corrected to obtain the viscosity. In addition, the error of repeated measurement and the variation of the measured value at the time of temperature increase and temperature decrease were about ± 3%.

  As a result of measuring the viscosity in this manner, the temperature dependence as shown in FIG. 3 was confirmed for all systems, and the system to which the potassium compound was added showed the same viscosity as the system to which chromium oxide was added. all right. The temperature dependence of the viscosity shows a linear tendency as shown in the figure up to a temperature about 100 ° C. higher than the slag melting point (for example, 1200 ° C.) due to the nature of the slag. By extrapolating to ° C., it can be seen that in the furnace environment, the system to which the potassium compound has been added exhibits a viscosity greater than the value of the slag K with no addition. Thus, the increase in viscosity due to the addition of the potassium compound is interpreted to be due to the fact that potassium increased the degree of polymerization of the aluminosilicate ion in the slag. That is, in a system to which a potassium compound is added, mass transfer is suppressed and corrosion resistance is improved by increasing the viscosity.

  On the other hand, as shown in Table 3, as a comparative material, only a base material containing no potassium compound (Comparative Example 1), a material containing 5% by weight of potassium titanate (Comparative Example 2), and 7.5% of potassium titanate As in the test sample of Table 1, three types including those containing% (Comparative Example 3) were cut into a round bar shape of φ10 mm and subjected to a rotary erosion test. As a result, as shown in Table 3, all samples showed a corrosion wear amount of 5 mm or more.

  From the above results, when 2.5% by weight of potassium titanate is added to a refractory whose base material is zirconia, the corrosion resistance is superior to the system in which no additive is added and 5% by weight or 7.5% by weight is added. Admitted. That is, when potassium titanate is added in excess of a predetermined amount, the aggregation of potassium titanate in the base material becomes large, so that the binding of zirconia particles becomes weak and the durability of the refractory decreases. Therefore, the upper limit of the addition rate of potassium titanate is 4% by weight. On the other hand, if the addition rate is less than 1% by weight, the effect of improving the corrosion resistance accompanying the increase in the polymerization rate of aluminosilicate ions cannot be obtained, so 1% by weight is the lower limit.

  Next, an embodiment of the refractory for the inner wall of the combustion melting furnace according to the present invention will be described. FIG. 4 is a longitudinal sectional view showing an embodiment of a combustion melting furnace to which the present invention is applied.

  The combustion melting furnace 41 of the present embodiment is formed in a vertical cylindrical shape, and a burner 43, a pyrolytic carbon blowing portion 45, and a pyrolytic gas blowing portion 47 are arranged at the top thereof. A furnace bottom 49 extending in a substantially horizontal direction is connected to the bottom of the combustion melting furnace 41, and a slag recovery port 51 is provided in the furnace bottom 49.

  Connected to the furnace bottom 49 is a flue 53 formed vertically up to a height near the top of the combustion melting furnace 41. An air heater 55 is disposed inside the flue 53. The air heater 55 is made of, for example, a ceramic heat transfer tube made of a single tube through which air flows. For example, a plurality of heat transfer tubes are arranged orthogonal to the flow direction of the combustion exhaust gas. The heat transfer tubes communicate with each other outside the furnace wall, and the air introduced from the outside of the furnace wall flows through each heat transfer tube, exchanges heat into heated air, and is discharged outside the furnace. The flue 53 is connected to a waste heat boiler (not shown) or the like with its top bent in the horizontal direction.

  When a fuel such as pyrolytic carbon is introduced together with the pyrolysis gas into the combustion melting furnace 1 configured as described above, the furnace bottom portion 49 is heated to a high temperature of about 1300 ° C., for example. Fly ash generated by the combustion is melted at the furnace bottom 49 while swirling in the furnace, and molten slag 57 is generated. The molten slag 57 generated here flows down along the furnace wall, falls from the slag recovery port 51 into a water tank outside the furnace, and is cooled and solidified.

  On the other hand, the high-temperature combustion exhaust gas (for example, 1100 ° C.) is cooled by heat exchange via the furnace bottom portion 49 and the flue 53 through the heat transfer tube surface of the air heater 55, and then into a waste heat boiler or the like. Supplied.

  In the combustion melting furnace 41, at least the inner wall 42 in the region where the molten slag 57 contacts is formed of the furnace wall refractory according to the present invention. In this example, a refractory material containing zirconia as a base material and containing 1 to 4% by weight of potassium titanate is used. That is, the inner wall 42 is formed of a refractory that has excellent corrosion resistance against the molten slag 57.

  Next, an embodiment of a waste treatment apparatus provided with such a combustion melting furnace 41 will be described. FIG. 5 is a system diagram showing an embodiment of a waste treatment apparatus to which the present invention is applied.

  The waste is crushed to a predetermined size, introduced into a rotating drum type pyrolysis reactor 63 by a screw feeder 61, heated to, for example, about 450 ° C., and pyrolyzed in a low oxygen atmosphere.

  The pyrolysis gas and pyrolysis residue generated from the pyrolysis reactor 63 are guided to the discharge device 65, and the pyrolysis gas is supplied to the combustion melting furnace 41 through the pipe 67 together with combustion air, while the pyrolysis residue is Then, after being guided to the cooling device 69 and cooled to about 80 ° C., for example, it is introduced into the sorting device 71.

  The separation device 71 uses, for example, a known method such as a fluid type, a sieve, a magnetic separation type, an eddy current type, a centrifugal type, and a combustible granular material such as pyrolytic carbon, a metal component of a non-combustible component, Sorted into non-metallic components. Here, in addition to the pyrolytic carbon particles, the combustible particles include relatively large combustibles, and these are stored in the hopper 73 after the pulverization process. Other separated components are appropriately discharged into a container or a hopper, and the granular material in the hopper 73 is introduced into the combustion melting furnace 41 through a pipe line 75.

  The pyrolytic carbon and the pulverized product introduced into the combustion melting furnace 41 form a swirl flow in a high-temperature atmosphere to form a molten slag 57 and fall from the slag recovery port 51 to the water tank 77 through the inner wall 42. Here, as described above, the combustion exhaust gas is heat recovered by the air heater 55 installed in the downstream side flue of the combustion melting furnace 41, and the heated air is used as a heat source for heating of the pyrolysis reactor 63. Used. The heated air is not limited to the heat source of the pyrolysis reactor 63, and may be used as another heat source.

  The combustion exhaust gas heat-recovered by the air heater 55 is cooled to, for example, 600 ° C., and is efficiently recovered in the waste heat boiler 79 on the downstream side. Here, the waste heat boiler 79 generates steam using heat recovered from the combustion exhaust gas, and rotates the steam turbine generator 81 to recover electric power.

  The combustion exhaust gas discharged from the waste heat boiler 79 is guided to a dust collector 83 to be removed, and then purified by a gas purification device such as a desalination device 85, and then from a chimney 89 to the atmosphere via an induction fan 87. Released.

  In the waste treatment apparatus of the present embodiment, the inner wall 42 of the combustion melting furnace 41 is formed of a composite refractory material in which potassium titanate is added to zirconia as a base material. In the molten slag 57, the viscosity increases due to the action of the potassium compound eluted from the refractory and the mass transfer is suppressed. Thereby, the furnace inner wall can suppress erosion of the refractory material by molten slag, and can maintain high corrosion resistance. Moreover, since the furnace inner wall of this Embodiment is provided with high durability and does not contain a chromium compound, the manufacturing cost can be kept low.

  In addition, the refractory for the furnace inner wall of the present invention is optimally used for the furnace inner wall of the combustion melting furnace of the waste treatment apparatus as described above, but is not limited to this, a treatment furnace other than waste, Needless to say, it can also be applied to incinerators.

The schematic diagram of the rotary erosion apparatus for evaluating the abrasion resistance of the refractory for furnace inner walls formed by applying the present invention is shown. The viscosity measuring apparatus for evaluating the temperature dependence of the viscosity of the refractory for furnace inner walls to which this invention is applied is shown, (a) is an external view of the apparatus, and (b) is an enlarged view of A. It is a figure which shows the result evaluated about the viscosity of the refractory for furnace inner walls formed by applying this invention. 1 is a longitudinal sectional view showing an embodiment of a combustion melting furnace to which the present invention is applied. It is a systematic diagram showing one embodiment of a waste disposal apparatus to which the present invention is applied.

Explanation of symbols

41 Combustion melting furnace 42 Inner wall 49 Furnace bottom 51 Slag recovery port 55 Air heater 57 Melting slag

Claims (3)

It is a refractory for the inner wall of a furnace that melts and slags ash generated by burning waste, and 1 to 4% by weight of potassium titanate (K ₂ Ti ₄ O ₉ ) is mixed with the zirconia base material. Refractories for furnace inner walls that are included . To the zirconia powder used as the base material, potassium titanate (K ₂ Ti ₄ O ₉ ) Or Titanium (IV) Potassium Oxalate dihydrate and the mixture with the addition of sintering aids is pressed and then heated to sinter in air It is a manufacturing method of the refractory material for furnace inner walls, Comprising: The said additive is a manufacturing method of the refractory for furnace inner walls added so that it may contain 1-4 weight% after sintering.   A pyrolysis reactor for pyrolyzing waste, and a non-combustible substance contained in the pyrolysis gas and the pyrolysis residue by burning combustible substances contained in the pyrolysis gas and the pyrolysis residue discharged from the pyrolysis reactor The waste processing apparatus provided with the combustion melting furnace which melts and slags a thing, The furnace inner wall of the said combustion melting furnace is formed with the refractory material for furnace inner walls of Claim 1.

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