JP5920586B2 - Diffuser for ejector-type thermal spraying equipment - Google Patents

Description

  The present invention relates to a diffuser of an ejector-type thermal spraying apparatus used for repairing an industrial kiln furnace, particularly a coke oven carbonization chamber using a silica brick.

  In industrial kilns, molten metal containers, and the like, damage is caused to the lining made of refractory material with the use thereof. For such damage, repairs are performed as appropriate. For example, many coke ovens in steelworks have been in operation for more than 20 years, and in particular, the walls of the carbonization chamber continue to be operated with repeated repairs.

  Here, as a technique for repairing while continuing the above-described operation, there is a thermal spray repair method in which a repair material is sprayed on a repair site while melting. Examples of the thermal spray repairing method include plasma spraying, laser spraying, and flame spraying. However, these thermal spray repair methods require a large-scale apparatus and have a costly problem.

  Therefore, in recent years, a thermal spraying method using a metal oxidation exothermic reaction has been used as a thermal spray repair method that can be realized with a relatively simple apparatus. In the thermal spraying method, first, a mixture (a thermal spray material) of a metal powder (combustion agent) and a refractory powder is transported with oxygen and sprayed onto a high-temperature repair surface. As a result, the metal powder undergoes an oxidative exothermic reaction and burns by receiving heat from the surface to be repaired. Then, the above-mentioned refractory powder is melted by the generated heat, and a sprayed body in which a refractory composition is formed and melted together with the metal oxide formed together is adhered to the repair surface. The material for the thermal spraying method is disclosed in, for example, Patent Documents 1 and 2, and the apparatus thereof is disclosed in Patent Document 3.

When performing thermal spraying using the oxidation exothermic reaction of the metal, an ejector-type thermal spraying apparatus is used as a powder fluid transporting means for spraying the thermal spray material onto the repair surface. The ejector-type thermal spraying apparatus utilizes a phenomenon in which a high-speed fluid is ejected from a nozzle and a suction force is generated by the wake, that is, an ejector effect.
In FIG. 1, the schematic diagram of an ejector type thermal spraying apparatus is shown. As shown in FIG. 1, the ejector-type thermal spraying apparatus 1 includes a hopper 40 that stores thermal spray material in powder form, and an ejector 10 that is provided below and sucks and discharges the thermal spray material using oxygen as a driving fluid. It consists of. A rubber hose is usually connected to the downstream side of the ejector 10, and a thermal spray lance is connected to the tip thereof.
The ejector 10 is composed of an ejector nozzle 11 for injecting oxygen, a suction chamber 20 whose discharge end is opened and the hopper 40 is opened, and a diffuser 30 provided downstream thereof. ing. The diffuser 30 includes a narrowed portion 31 whose inner diameter is suddenly narrowed once, a straight portion 32 obtained by extending the inner diameter of the narrowed portion 31 as it is, and an extended portion 33 whose inner diameter gradually increases from the downstream end of the straight portion 32. It is configured.

  In the above configuration, when oxygen gas is ejected from the ejector nozzle 11 toward the throttle portion 31 of the diffuser 30, the oxygen gas entrains the air in the suction chamber 20, and the flow involving the air is accelerated. The surroundings are decompressed by the wake. The thermal spray material stored in the hopper 40 is supplied to the suction chamber 20 by the suction force due to gravity and reduced pressure, and oxygen is mixed in the suction chamber 20. The mixture of the thermal spray material and oxygen passes through the diffuser 30 and is conveyed to the tip of the thermal spray lance. The thermal spray material discharged from the tip of the thermal spray lance receives heat from a high temperature coke oven, the metal oxidizes and burns, melts the refractory powder, and adheres to the furnace wall to form a thermal spray.

  In the case of the ejector-type thermal spraying apparatus 1, since the hard refractory powder collides with the inner wall of the diffuser 30, there is a problem that the inner wall 30 of the diffuser is worn and the inner diameter is enlarged. The wear of the diffuser 30 is likely to occur in the straight portion 32 from the downstream side of the throttle portion 31 of itself, and when the inner diameter in this portion increases, the flow rate of oxygen decreases, the suction force decreases, and the spraying material is discharged. The amount is reduced. For example, when the inner diameter is increased by about 10%, the transport amount of the thermal spray material with the same oxygen amount is reduced by about 10%.

In order to form a good thermal spray, it is necessary to keep the ratio of the sprayed material to be transported and the amount of oxygen to be supplied at a suitable value. In the initial stage, the ratio is maintained and spraying can be performed according to the design. it can. However, if the inner wall of the diffuser 30 is worn, the appropriate ratio cannot be maintained, and the diffuser 30 needs to be replaced.
In order to reduce the replacement frequency, it is necessary to use the diffuser 30 using a material with high wear resistance. Therefore, Patent Document 4 proposes a method of reducing the wear by improving the shape of the diffuser. Focusing on the shape of the inner wall of the diffuser, a structure in which the straight part is elongated by having a throttle part in which the cross-sectional area monotonously decreases, a straight part having a fixed length, and an extended part in which the cross-sectional area monotonously increases. It is.
By adopting this configuration, a thermal spraying apparatus capable of preventing or reducing wear that could not be sufficiently prevented even when tungsten carbide or boron carbide having high wear resistance was used was provided. Stainless steel (SUS304 ), The wear is very small and almost no wear occurs.
However, when the straight portion is lengthened, the pressure loss increases, and there is a problem that the sprayed material cannot be transported efficiently.

  Furthermore, as a recent trend, the number of kilns that need repair and the repair range have expanded, so the amount of repair has increased dramatically, and the amount of wear on the inner wall of the diffuser has increased proportionally. In response to the increase in the repair amount, the spraying amount of the thermal spray material per unit time has been increased from the conventional less than 50 kg / h to 100 kg / h or more. Due to this increase in the discharge amount per unit time, the wear of the inner wall of the diffuser also increases, and even if the configuration disclosed in Patent Document 4 is adopted, it cannot be said that it is sufficient. Specifically, when spraying was performed at 100 kg / h using a diffuser made of stainless steel (SUS304), it was necessary to replace the diffuser due to inner wall wear by discharging a sprayed material of about 200 kg.

  In order to improve the abrasion resistance, attempts have been made to improve the material of the diffuser. Patent Document 5 proposes a cold spray nozzle (diffuser) using an ejector, but an example using ceramics having high wear resistance such as silicon nitride, silicon carbide, zirconia, etc. as the material is shown. It is also commonly used.

  On the other hand, thermal spraying using the oxidation exothermic reaction of the metal transports the combustible material and the combustion-supporting material in the same pipe, so there is a backfire in which the combustion proceeds in the reverse direction or the friction when the flow inside the pipe is disturbed. Ignition may occur due to sparks and sparks generated in These are serious problems because they are accompanied by a loud explosion, and the operator may be injured by the damaged pipe, or the operator may be burned by the flame that is ejected from the damaged pipe.

JP 2009-120406 A JP 2012-188345 JP JP 2011-149078 A JP 2007-275816 A JP 2008-253889 A

As described above, in the ejector-type thermal spraying apparatus, on the other hand, it is necessary to increase the wear resistance of the diffuser and reduce the replacement frequency. However, materials with high wear resistance, such as ceramics, tend to have high volume resistivity.
On the other hand, as described above, the thermal spraying utilizing the oxidation exothermic reaction of the metal to which the present application is applied conveys the combustible material and the combustion-supporting material through the same pipe. There is a problem that ignition is caused by sparks or sparks. In particular, a material such as ceramic having high wear resistance as described above has a high volume resistivity, so that static electricity is likely to accumulate as will be described later, and therefore there is a problem that ignition by sparks or sparks is likely to occur.

  In the present invention, there has been proposed a diffuser for an ejector-type thermal spraying apparatus that has been proposed in view of the above-described prior art, has high wear resistance with respect to a demand for an increase in discharge amount, and can suppress the occurrence of flashback. The purpose is to propose.

  The inventors have found that there are mainly two causes of flashback as a result of searching for the cause of flashback while considering the wear resistance of the inner wall of the diffuser in the ejector-type thermal spraying apparatus.

  That is, one cause of backfire is ignition at the tip of the thermal spray lance, and the combustion expands to the thermal spray material in the rubber hose for material transportation and leads to backfire. Another cause is ignition in the diffuser.

  Furthermore, it has been found that there are the following two causes for the ignition in the diffuser.

  The first cause (1) is that when the inner wall of the diffuser is made of an easily oxidizable material such as a steel material, frictional heat is generated by the collision of the refractory particles to the inner wall of the diffuser and is oxidized by combining with the oxygen in the atmosphere. Either burn or ignite the side wall material that has peeled off due to wear. It causes fire in the diffuser. For example, among steel materials, when tool steel SKD having relatively high wear resistance was used for the diffuser, it ignited immediately after the start of thermal spraying. The tool steel SKD is inferior in wear resistance as a diffuser and cannot actually be used for the diffuser.

  The second cause (2) is the occurrence of sparks due to static electricity. When the conductivity of the diffuser is low, static electricity due to friction is generated between the refractory particles flowing in the diffuser and the diffuser wall. When the conductivity of the diffuser is low, the static electricity accumulates and gradually becomes a high voltage. And if it becomes a high voltage, it will discharge in an atmosphere and a spark will generate | occur | produce. This becomes an ignition source, and the coexisting metal particles ignite and ignite. For example, when an alumina ceramic with high wear resistance was used for the diffuser, it ignited immediately after the start of thermal spraying. Therefore, when applying highly wear-resistant ceramics as a diffuser material for an ejector-type thermal spraying apparatus, it is considered necessary to take measures to prevent static electricity from escaping to a high voltage by suppressing the volume resistivity.

The present invention has been made based on the discovery as described above. That is, the present invention provides an ejector-type thermal spraying apparatus using ceramics having a volume resistivity of 10 ⁵ Ω · cm or less and a fracture toughness value of 5 MPa · m ^1/2 or more. It is a diffuser.

  ADVANTAGE OF THE INVENTION According to this invention, in the diffuser for ejector type thermal spraying apparatuses, it has high abrasion resistance with respect to the request | requirement of discharge amount increase, and it becomes possible to suppress generation | occurrence | production of a backfire.

The schematic diagram of an ejector type thermal spraying apparatus.

  In the following, an embodiment of the image forming apparatus of the present invention will be described for the understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.

The present invention is a diffuser for an ejector-type thermal spraying apparatus, characterized by using ceramics having a volume resistivity of 10 ⁵ Ω · cm or less and a fracture toughness value of 5 MPa · m ^1/2 or more. is there.

Here, when a configuration in which the volume resistivity is 10 ⁵ Ω · cm or less is adopted, static electricity generated on the inner wall of the diffuser flows to the metal holding member through the diffuser body and is diffused to the outside. Therefore, the diffuser body does not become a high voltage, and as a result, no spark is generated. In the present invention, there is no particular limitation as long as the volume resistivity is 10 ⁵ Ω · cm or less. For example, when the volume resistivity is 10 ³ Ω · cm or less, static electricity can be effectively dissipated. Can be promoted, which is preferable. The volume resistivity is the reciprocal of the conductivity (electrical conductivity), and is a small value when the conductivity is high and a high value when the conductivity is low.

On the other hand, in the present invention, when the volume resistivity is higher than 10 ⁵ Ω · cm, static electricity generated by friction between the diffuser wall and the refractory particles cannot be sufficiently dissipated to the outside. It accumulates in and becomes a high voltage. Therefore, a spark is generated in the oxygen flow in the diffuser, causing ignition in the diffuser, which is not preferable. Furthermore, if ignition occurs in the diffuser, it results in a backfire, which not only interrupts the work but also causes a safety problem for the worker, which is not preferable.

  Here, as described above, in a diffuser with low wear resistance, wear of the inner wall of the diffuser becomes significant due to continued use of thermal spraying, and the replacement frequency of the diffuser increases. Therefore, in the present invention, ceramics with high wear resistance are employed as the material of the diffuser.

That is, if a structure having a fracture toughness value of 5 MPa · m ^1/2 or more is adopted, wear of the inner diameter of the diffuser becomes difficult to occur, and the replacement frequency of the diffuser is lowered. Further, the cause of wear on the inner wall of the ceramic diffuser is considered to be micro-destruction due to collision of refractory particles. If the fracture toughness is high, the micro-destruction is less likely to occur, and wear is less likely to occur. In the present invention, the fracture toughness value is not particularly limited as long as it is 5 MPa · m ^1/2 or more. For example, if the fracture toughness value is 6 MPa · m ^1/2 or more, microfracture is effectively prevented. Since generation | occurrence | production can be prevented, it is preferable.

On the other hand, in the present invention, when the fracture toughness value is lower than 5 MPa · m ^1/2 , the microfracture frequently occurs and wear tends to progress, which is not preferable.

Therefore, in the present invention, as described above, the volume resistivity is 10 ⁵ Ω · cm or less to suppress the occurrence of sparks due to static electricity, and at the same time, the fracture toughness value is 5 MPa · m ^1/2 or more to prevent microfracture. This is a diffuser for an ejector-type thermal spraying device made of ceramics that prevents generation and has high wear resistance.

Here, if the material of the diffuser according to the present invention is a ceramic having a volume resistivity of 10 ⁵ Ω · cm or less and a fracture toughness value of 5 MPa · m ^1/2 or more, There is no particular limitation as long as the purpose is not impaired. Examples of the material of the diffuser include ceramics obtained by adding ceramic particles having high conductivity to high toughness ceramics. Specifically, TiC, ZrC, VC, TaC, Mo, and the like are applied to high toughness ceramics having a fracture toughness value of 5 MPa · m ^1/2 or more, such as Si ₃ N ₄ , ZrO ₂ , SiC, α-SiAlON, β-SiAlON. High conductivity of one or more selected from carbides such as ₂ C, nitrides such as TiN, ZrN, VN, TaN, NbN, and silicides such as TiSi ₂ , ZrSi, NbSi ₂ , MoSi ₂ , PtSi A ceramic obtained by adding ceramic particles. Here, the additive concentration of the high conductivity ceramic particles is preferably in the range of 5 to 40% by volume, for example.

  Further, in ceramic materials, it is said that a material having high hardness has relatively high wear resistance, and the hardness is evaluated by Vickers hardness measured by a Vickers hardness meter. In the diffuser according to the present invention, it is important that the high toughness described above and the volume resistivity are not more than a certain value, but further, the material of the diffuser according to the present invention has Vickers hardness. The Vickers hardness is preferably 1350 or more, more preferably 1200 or more.

By the way, as a material of the diffuser, it may be possible to use a WC—Co cemented carbide, but as described in Patent Document 4, the WC—Co hard alloy cannot provide sufficient wear resistance. It was. The cause is not necessarily clear, but is estimated as follows. That is, the WC-Co cemented carbide is obtained by sintering WC particles using Co as a sintering aid, and is known as an abrasion resistant material. Although the hardness of the WC particle itself is high, the hardness of Co as a binding aid is low. Therefore, the material of the WC-Co cemented carbide as a whole is lower in hardness than ceramics such as Si ₃ N ₄ , SiAlON, etc., and therefore is considered to be inferior in wear resistance. In addition, Co, which is a binder, is easily oxidized like a steel material, and heat is generated in a minute part by collision of refractory particles, and minute oxidation proceeds with the heat, resulting in an increase in wear as a whole. Estimated.

  Moreover, the ejector type thermal spraying apparatus using the diffuser according to the present invention is not particularly limited as long as the object of the present invention is not impaired, and a general ejector type thermal spraying apparatus is applied. Here, the spraying amount of the ejector-type spraying device varies depending on the capacity of the hopper, the size of the ejector and the ejector, the amount of oxygen gas ejected from the ejector, and the like. It is set within the range of kg / h. A rubber hose is usually connected to the downstream side of the diffuser, and a thermal spray lance is connected to the tip of the rubber hose. Although the length of the said rubber hose is not specifically limited, For example, it exists in the range of several m to several dozen m.

  The diffuser for ejector type thermal spraying apparatuses according to the present invention will be specifically described below by presenting examples and comparative examples.

First, based on α-SiAlON (Si ₃ N ₄ : Y ₂ O ₃ : AlN = 91: 5: 4, α-SiAlON and β-Si ₃ N ₄ complex), 20% by volume of TiN was externally added. A diffuser made of a material was designated as Example 1. In addition, a diffuser made of α-SiAlON as a base and added with 15% by volume of TiN is used as Example 2, and further, α-SiAlON is used as a base and TiN is added as a material of 10% by volume. This diffuser was designated as Example 3.

On the other hand, a diffuser made of SUS304 was used as Comparative Example 1 and the diffuser made using tool steel SKD was used as Comparative Example 2 with the diffuser made of metal. Moreover, the diffuser created using WC-Co cemented carbide was set as Comparative Example 3. Further, a diffuser made of a material based on α-SiAlON (with no addition of TiN in Example 1) as a material of the diffuser is set as Comparative Example 4, and β-SiAlON (z = 0.5) is used. A diffuser made of the base material was designated as Comparative Example 5. Further, as a highly wear-resistant ceramic, a diffuser made of a material based on ZrO ₂ is set as Comparative Example 6, a diffuser made of a material based on SiC is set as Comparative Example 7, and Al ₂ O ₃ is used as a base. The diffuser made of the material made was made Comparative Example 8, and the diffuser made of the material based on B ₄ C was made Comparative Example 9.

The thermal spray test was carried out by mounting the diffuser prepared above on a normal ejector-type thermal spraying apparatus and spraying a thermal spray material composed of 15% by mass of metal Si powder and 85% by mass of silica as refractory particles. Here, the carrier gas was oxygen having a purity of 100%, the flow rate was 32 Nm ³ / h, and the material supply rate was 100 kg / h.

  Here, the evaluation of the presence or absence of ignition in the created diffuser was performed by visually confirming whether or not the thermal spray material was ignited while spraying 2 kg. When it ignites, it is set as “Yes”, and when it does not ignite, it is set as “None”.

  The amount of wear of the inner wall of the diffuser in the created diffuser was evaluated using a diffuser with an inner diameter of 10.0 mm of the throttle portion and the amount of change in the inner diameter of the diffuser after spraying the sprayed material with a predetermined amount of 50 kg (diameter of the diameter). This was done by measuring the amount of enlargement. The amount of change in the inner diameter of the diffuser corresponds to the amount of wear of the diffuser. In the above evaluation, with respect to a material having no ignition and relatively good wear resistance, the passage amount was increased to 200 kg thermal spray (actual use) and 10,000 kg thermal spray (actual use), and the amount of change in inner diameter at that time was examined. . In addition, this evaluation (wear test) was not performed about the diffuser which ignited in the above-mentioned evaluation of the presence or absence of ignition. In addition, when the amount of change in the inner diameter of the diffuser was significant at a predetermined spraying amount in this evaluation, this evaluation was not performed with a larger amount of spraying. When this evaluation was not performed, “−” was given.

  Table 1 shows the evaluation results of the presence or absence of ignition and the amount of wear when the material of the diffuser of the ejector-type thermal spraying device is changed.

  As shown in Table 1, in Examples 1-3, there is no ignition, and further, no abrasion is observed even at a thermal spraying amount corresponding to 10000 kg on-site use, and good wear resistance is exhibited. Understood.

  On the other hand, in Comparative Example 1, since the volume resistivity was sufficiently low, no ignition was observed, but the wear resistance was poor, and the inner diameter was increased by 2.0 mm with a spraying amount of 200 kg. Here, the following SKD ignites despite the low volume resistivity, whereas the SUS used in Comparative Example 1 did not ignite because the SUS material is difficult to oxidize. Therefore, it is estimated that it did not become a source of ignition. In Comparative Example 2, the volume resistivity was sufficiently low, but as described above, it ignited immediately after the start of thermal spraying. Further, in Comparative Example 3, the volume resistivity was sufficiently low and there was no ignition, but slight wear was observed in the thermal spraying of 200 kg. However, in the thermal spraying with an amount of 10,000 kg (actual thermal spraying), the inner diameter was increased 1.0 mm from the initial 10.0 mm to 11.0 mm. As a result, as described above, the sprayed material discharge amount was reduced by about 10%, so that it was necessary to replace the diffuser. Therefore, in Comparative Example 3, the wear resistance was insufficient as compared with Example 1-3.

Moreover, in Comparative Example 4-8, in any case, it ignited immediately after spraying. This is presumed that any material of Comparative Example 4-8 had a volume resistivity higher than 10 ⁵ Ω · cm and was ignited by static sparks.

Further, in Comparative Example 9, since the specific volume resistivity was as small as 6.7 Ω · cm and no ignition occurred, the fracture toughness value was as low as 3 MPa · m ^1/2 , so that wear was observed. Compared with -3, the wear resistance was insufficient.

Thus, the diffuser for an ejector-type thermal spraying apparatus according to the present invention uses ceramics having a volume resistivity of 10 ⁵ Ω · cm or less and a fracture toughness value of 5 MPa · m ^1/2 or more. It is characterized by that. As a result, the wear resistance is high with respect to the demand for increasing the discharge amount, and the occurrence of flashback can be suppressed.

  The present invention is a diffuser for an ejector-type thermal spraying device used for repairing an industrial kiln furnace, particularly a coke oven carbonization chamber using a silica brick, and particularly has high wear resistance for the demand for increased discharge amount. It is useful as a diffuser for an ejector-type thermal spraying device that can suppress the occurrence of flashback.

Claims (1)

A diffuser for an ejector-type thermal spraying apparatus using ceramics having a volume resistivity of 10 ⁵ Ω · cm or less and a fracture toughness value of 5 MPa · m ^1/2 or more.

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