JP4888888B2 - Grate - Google Patents

Description

  The present invention relates to a grate used in a stoker incinerator or the like.

  Incinerators such as stoker-type incinerators are required to burn at higher temperatures from the viewpoints of suppressing the generation of dioxins, improving heat recovery efficiency, and improving power generation efficiency, and the stoker grate used in incinerators. Etc. tend to be used in a more severe corrosive environment in which chloride corrosion or sulfide corrosion occurs simultaneously with high temperature oxidation. If a grate or the like is used in such a severe corrosive environment, material damage occurs. Therefore, it is necessary to periodically stop the furnace and replace the grate or the like in a relatively short period of time.

Periodic replacement of the above-described grate etc. is a necessary work in order to continue using the incinerator. However, since these operations are performed while the incinerator is stopped, the operating rate of the incinerator is reduced, and a period in which incineration, heat recovery, and power generation cannot be performed occurs. In addition, since parts must be replaced inside the incinerator, it is necessary to deal with dioxin exposure. As described above, the replacement work of the incinerator parts such as the grate leads to an increase in the running cost of the incinerator and an increase in the work labor load, and it is desired to reduce the frequency of performing them as much as possible.

  Here, it is known to use heat-resistant cast steel (for example, JIS SCH2 or SCH13), which is an Fe-Cr-Ni-C alloy, for the grate and the like, and an alloy with improved corrosion resistance has also been proposed. . (See Patent Document 1)

  In addition, it is proposed to coat the surface with ceramics with excellent corrosion resistance (see Patent Document 2 or 3), and to increase the corrosion resistance by forming a Ni-Cr alloy layer by electroplating and then performing Cr-Al vapor diffusion treatment. Has been. (See Patent Document 4)

  In addition to this, a method of suppressing corrosion and extending the life by cooling the grate and using it is widely used.

JP 2003-328090 A Japanese Patent Laid-Open No. 06-340958 JP 60-008615 A JP 59-157272 A

  Even when heat-resistant cast steel having corrosion resistance as described in Patent Document 1 is used for a grate, iron is inferior in chlorinated corrosion resistance, particularly in an environment containing chlorine, such as an incinerator, and thus further improves. There is room.

  Further, in the coating with ceramics as referred to in Patent Document 2 or 3, adhesion with the side to be coated becomes a problem, and particularly in a grate having a large thermal fluctuation, peeling of the film becomes a big problem.

  In addition, in electroplating as in Patent Document 4, the process for coating is complicated, and in addition to forming a coating layer on the entire surface, the film thickness becomes non-uniform due to current concentration at the corners, etc. Therefore, it may be necessary to perform additional machining at a site where dimensional accuracy is required, resulting in a significant cost increase. Furthermore, in order to obtain a sufficient life against corrosion by the coating layer, it is necessary to make the coating layer sufficiently thick, but there are technical difficulties in electroplating.

  On the other hand, as a method for forming a sufficiently thick coating layer on the grate surface, thermal spraying or overlay welding can be considered. However, if the entire surface of the grate is covered with a thick coating layer, the alloy layer may peel or break due to the difference in thermal expansion coefficient between the heat-resistant cast steel that is the base material and the corrosion-resistant alloy layer that covers the surface. It is feared that the grate is distorted by the above. Further, since the grate has a sliding portion, there is a concern that a sliding failure may be a problem from the viewpoint of dimensional accuracy. By reworking the coating layer, additional costs are incurred.

  In addition, even when cooling and using, air cooling often does not provide sufficient cooling in the main combustion zone, etc., causing significant grate corrosion damage, and water cooling makes the grate structure complicated and excessive. There is a case where the grate surface temperature is lowered by the cooling and the combustion efficiency is deteriorated.

  The present invention has been made in view of the above circumstances, and provides a grate that exhibits excellent corrosion resistance without excessive cooling in a high temperature corrosive environment and is low in cost.

  The grate of the present invention is a grate used in an incinerator, and a part of the surface of the grate is covered with a Ni-based alloy layer containing 10 to 30% Cr by mass%. It is a characteristic grate.

  Combustion in the grate burns while the waste or the like put on the dry grate is transferred to the main combustion and the post-combustion grate. As the waste and the like move, the grate surface is an environment where the state covered with the waste and the exposed state are repeated. Although salt contained in waste accelerates corrosion, it is not an environment where salt continues to accumulate on the metal surface like a superheater tube, etc., and the grate surface comes into contact with waste due to the movement of waste etc. And a state in which the salt contained in the waste remains away from the waste as if it was applied to the surface.

表１の結果から明らかな通り、発明者らは、Ｎｉ基合金が極めて優れた耐食性を有する事を見出し、火格子にＮｉ基合金を用いることとした。また、Ｎｉ基合金は高価であるため、コスト的な面から、表面にＮｉ基合金層を被覆させることとした。 The inventor of this application simulated the environment of such a grate, repeatedly puts and removes the test piece with respect to the salt at a high temperature, and conducted a corrosion test of the test piece. The corrosion test results are shown in Table 1.

As apparent from the results in Table 1, the inventors found that the Ni-based alloy has extremely excellent corrosion resistance, and decided to use the Ni-based alloy for the grate. Further, since the Ni-based alloy is expensive, the Ni-based alloy layer is coated on the surface from the viewpoint of cost.

  In the grate of the present invention, the incinerator may be a stalker furnace, and the Ni-based alloy layer may cover the front side of the grate with the transfer direction of the incinerated material as the front.

The inventors further investigated the damage situation of the grate made of SCH2 used for about one year in the actual machine. Table 2 shows the results of measuring the amount of thinning for the grate. Here, the measurement positions A to E in Table 2 are shown in the schematic diagram of the grate shown in FIG.

  As shown in Table 2, it can be seen that the amount of thinning is small in the upper stage of the front surface, and that severe thinning occurs from the middle stage to the lower stage. It was expected that the top surface of the grate would come into contact with corrosive components such as chlorine in the garbage due to contact with the dust, and further wear due to sliding, resulting in high temperature corrosion wear and severe thinning. Rather, it was found that the amount of thinning was slight. Therefore, it has been found that if the thickness reduction of the front surface is suppressed, the life of the grate can be extended, and the front surface is covered. Coating only a portion of the grate with a Ni-based alloy layer reduces material and manufacturing costs. In addition, since it is not necessary to cover the entire surface, it is not necessary to consider the dimensional accuracy of the sliding part, etc., and since the coating layer is a part, overall thermal strain occurs, causing grate distortion and cracking of the coating layer. It is in a form that hardly peels off. Furthermore, there is a possibility that peeling may occur due to the difference in thermal expansion between Ni-base alloy and cast steel, but by covering the entire grate rather than the entire grate, peeling of the film due to the difference in thermal expansion is avoided. can do.

  In addition, the stove furnace hearth has an operating grate and fixed grate alternately arranged, a part of the upper surface of the grate becomes a sliding part, and the grate is arranged with a predetermined gap in the hearth. Dimensional accuracy is required for the sliding part and the side surface. Depending on the dimensional accuracy, it may be necessary to machine the top and side surfaces, which may result in machining costs and increase the cost of the grate. In this case, it is effective to cover only the front surface. It is.

  In the grate of the present invention, the Ni-based alloy layer may further cover an upper surface extending rearward from the upper end side of the front surface. The incinerator may be a sliding stoker furnace, and a sliding portion of the upper surface may not be covered with the Ni-based alloy layer.

  In the grate of the present invention, the Ni-based alloy layer may further cover a side surface extending rearward from the side edge of the front surface.

  When covering the upper surface or side surface with the Ni-based alloy layer, if only the front surface is covered, corrosion must proceed from the interface between the coating layer and the base material, which may lead to peeling of the coating layer. This is because such coating can be performed according to the corrosive environment.

  In the grate of the present invention, the Ni-based alloy layer may be metallurgically bonded by forming a reaction phase by metal bonding between the base material and the Ni-based alloy layer by heat treatment. Here, the grate generally cools the back surface, and in the case of an operating grate, it is used particularly in an environment in which rapid temperature fluctuation occurs due to movement back and forth. Depending on the waste quality, combustion temperature, operating conditions, etc., the normal physical coating alone may cause the coating layer to peel off due to thermal stress, in which case it physically adheres to the base material. The adhesion strength of the coating layer can be greatly improved by metallurgically bonding the state by heat treatment.

  In the grate of the present invention, the Ni-based alloy layer may be a Ni-based self-fluxing alloy. Here, the Ni-based self-fluxing alloy is an alloy containing 10% or more of Cr based on Ni and further containing B, Si or the like as a melting point depressant, and melts around 1000 ° C. It is possible to easily perform a scientific combination.

  Further, the grate of the present invention can be manufactured by casting, and the manufacturing by casting is performed by the plate material of the Ni-based alloy layer or the plate material obtained by metallurgically bonding the Ni-based alloy layer, and the mother. It can be performed by the molten metal used as a material.

  The cast-in here refers to the Ni-based alloy layer formed in advance in a sand mold or the like into which molten metal is poured, and the Ni-based alloy layer is formed on the surface by casting the cast alloy therein. This is a method of forming a grate. The use of the cast-in method eliminates the need for reworking even when dimensional accuracy is required, thus simplifying the manufacturing process and reducing reworking costs, resulting in high-quality, low-cost products Can supply.

  In the grate of the present invention, the Ni-based alloy layer can be formed by thermal spraying. This method using thermal spraying is an effective means for countermeasures for extending the life of a grate in use, which covers already produced grate.

  As described above, according to the grate of the present invention, it is possible to provide a low-cost grate while exhibiting excellent corrosion resistance without excessive cooling in a high temperature corrosive environment.

  Hereinafter, the grate which is the first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a view showing a stoker-type combustion apparatus using the grate according to the first embodiment of the present invention as a hearth. As shown in FIG. 2, the fixed grate 101 and the movable grate 102 are alternately arranged in a staircase pattern along the garbage flow direction. The fixed grate 101 is fixed to a fixed frame 104, and the movable grate 102 is fixed to a movable frame 105 that reciprocates in accordance with the operation of a hydraulic cylinder 106 that is a driving machine. Further, the fixed grate 101 and the movable grate 102 are attached with a fixed grate 101 positioned below or a scraper 103 that slides on the upper surface of the movable grate 102. (In some cases, the scraper 103 is not attached and the movable grate 102 or the fixed grate 101 slides on the upper surface of the lower grate.) As a result, the garbage hopper (see FIG. The waste introduced from (not shown) is combusted while being sequentially sent downward while stirring. At this time, the movable grate 102 contacts and slides on the upper surface of the fixed grate 101 via the scraper 103.

  FIG. 3 shows only the movable grate 102 and the fixed grate 101, and the movable grate 102 slides on the fixed grate 101 within a range R that leaves a certain distance from the tip of the fixed grate 101.

  FIG. 4 shows a grate 10 commonly used for the movable grate 102 and the fixed grate 101. As shown in FIG. 4, a front cover layer 11, a top cover layer 12, and a side cover layer 13, which are Ni-based alloy layers, are provided on the front, top, and side surfaces of the grate. However, the sliding part on the upper surface and the part exceeding the side length corresponding to the front thick part are not covered. This Ni-based alloy layer is a Ni-based self-fluxing alloy (for example, Ni- (15-20) Cr- (3-4.5) B- (2-4.5) Si- (0.5-1) C). Combined.

  From the results of the corrosion test shown in Table 1, it can be seen that the amount of corrosion of the Ni-based alloy is about 1/60 compared to the current SCH2. Moreover, from the grate thinning measurement result in the actual machine shown in Table 2, the thinning of about 30 mm occurs annually. From these results, it can be estimated that the annual thickness reduction of the Ni-based alloy in the grate environment is 0.5 mm or less. From this result, it is considered that it is possible to double the life of the grate currently replaced in one year by coating the surface of the grate with a Ni-based alloy layer of about 0.5 mm. However, if the Ni-based alloy layer is extremely thick, manufacturing and material costs are more likely to cause stress, and peeling is promoted. Therefore, a desirable thickness is 0.5 to 5 mm. More preferably, it is 1-3 mm, and in this embodiment, it is 1 mm.

  The Ni-based alloy used here needs to contain Cr in order to form a protective film. When Cr is added in an amount of 10% or more, the corrosion resistance is remarkably improved, and when it is added in an amount of 30% or more, an α-Cr phase that adversely affects the corrosion resistance may be precipitated, so 10 to 30% is desirable. Preferably, it is 15 to 25%. In addition, depending on the method of forming the coating layer and the usage environment, there may be a case where an alloy containing Si, B, or the like is used when coating with Mo or W for improving the molten salt corrosion resistance or thermal spraying.

  Therefore, in the grate of the first embodiment, the Ni-based alloy is coated on the upper surface and the front surface that are directly exposed to the atmosphere of the incinerator, except for the sliding portion, and also on the side surface where the atmosphere gas may be circulated. Therefore, it can cover widely about the grate part which corrosion is a concern.

  Next, the grate 20 which is the 2nd Embodiment of this invention is demonstrated. FIG. 9 schematically shows a grate 20. Like the grate of the first embodiment, the grate 20 is used in the stoker-type combustion apparatus 100 shown in FIGS. 2 and 3 and is commonly used for the movable grate 102 and the fixed grate 101. This grate has a front coating layer 11 and a top coating layer 12 which are Ni-based alloy layers on the front and top surfaces. However, the sliding portion on the upper surface is not covered. Similar to the first embodiment, this Ni-based alloy layer is a Ni-based self-fluxing alloy and is metallurgically bonded. Although the side surface is not covered with the Ni-based alloy layer, the grate is arranged with a predetermined gap on the hearth, so the side surface is required to have dimensional accuracy, and machining is required after construction.

  Therefore, the construction cost can be reduced by not covering the side surfaces. This embodiment is effective in the case where the corrosive material does not wrap around the side surface and the corrosion of the Ni-based alloy / base metal interface does not become a problem.

  Next, the grate 30 which is the 3rd Embodiment of this invention is demonstrated. FIG. 10 schematically shows a grate 30. The grate 30 is used in the stoker-type combustion apparatus 100 shown in FIGS. 2 and 3 similarly to the grate of the first and second embodiments, and is commonly used for the movable grate 102 and the fixed grate 101. It is done. This grate has a front surface coating layer 11 that is a Ni-based alloy layer only on the front surface. Similar to the first and second embodiments, this Ni-based alloy layer is a Ni-based self-fluxing alloy and is metallurgically bonded. As shown in Table 2, since the thinning is preferential on the front surface, it is also effective to coat the Ni-based alloy only on the front surface.

  Therefore, in this case, it is possible to greatly reduce the construction cost, which is particularly effective when the progress of corrosion from the Ni-base alloy / base material interface on the side surface and the upper surface is not a problem.

  Therefore, according to the grate of the first to third embodiments of the present invention, since it has a Ni-based alloy coating layer having corrosion resistance, it does not lower the combustion temperature due to excessive cooling and can be used for a long time. Can continue to use. As a result, the frequency of replacing the grate is reduced, enabling long-term continuous operation of the incinerator, and reducing the running cost and labor required for replacement.

In addition, according to the first to third embodiments of the present invention, since the Ni-based alloy layer is used only in the portion where the corrosion amount of the grate is predicted to be large, the amount of Ni-based alloy to be used is reduced. Cost.
Moreover, although the grate of the 1st-3rd embodiment of this invention is manufactured by performing a fusion | melting process after spraying using a Ni-based self-fluxing alloy, even if it manufactures with a cast-in. Good. Here, a method for manufacturing the grate by casting using a cast-in technique will be described. FIG. 5 shows a sand mold 200 used for casting and a molten metal inlet 201. In this manufacturing method, first, as shown in FIG. 6, a Ni-based alloy layer plate 202 is installed in a sand mold 200. Next, molten metal is poured into the sand mold from the inlet 201, and the Ni-based alloy layer and the poured metal are metallurgically bonded.

  The Ni-based alloy layer plate used at this time is a commercially available Ni-based alloy plate (for example, Ni-16Cr-8Fe-0.08C or Ni-22Cr-2Mo-14W-0.1C-0.02La), or casting or overlaying. Or what was manufactured by thermal spraying etc. and processed into the predetermined magnitude | size etc. can be used. In addition, as shown in FIG. 7, when the Ni-base alloy layer that has been set due to too much heat input is melted and diluted with the cast alloy that has been cast, the Ni-base alloy layer is formed on the high melting point plate 213. It is possible to prevent dilution of the Ni-based alloy by forming 211 and placing the high melting point plate in contact with the cast alloy. Conversely, if the heat input is small and a sufficient metallurgical binder phase is not formed between the Ni-base alloy and the base casting alloy, the plate 213 is made of a material having a low melting point or a material having a high reactivity with the casting alloy. By forming the Ni-based alloy layer 211 on the plate, it is possible to promote the generation of the binder phase and improve the interface strength. Here, a metallurgical reaction layer 212 is formed between the Ni-based alloy layer 211 and the plate 213. Further, as shown in FIG. 8, a release agent layer 222 may be provided between the plate 221 and the Ni-based alloy layer 223, and the plate 221 and the release agent layer 222 may be removed after casting. Here, when the plate 221 is easily detached, the release agent layer 222 may not be provided.

  Thus, by manufacturing by casting, even if a dimensional accuracy is required, the manufacturing process is simplified and it is possible to manufacture at low cost.

  In the first to third embodiments of the present invention, the Ni-based self-fluxing alloy is metallurgically bonded. However, the Ni-based self-fluxing alloy may not be used, and metallurgical It may not be a bond. For example, when spraying or overlaying is used, it is an effective means for prolonging the life of a grate that has already been constructed or a grate that is in use, and is particularly effective when repairing at an incineration facility. After removing surface deposits and corrosion products with sand blasting, etc., the Ni-based alloy layer is coated by thermal spraying or overlaying.

  As described above, the grate of the present invention can be applied to a grate used in a stoker-type incinerator or the like.

It is a figure which shows typically the measuring point of the thinning amount of the grate of SCH2. It is a figure of the stoker type combustion apparatus which uses the grate of the 1st-3rd embodiment of the present invention as a hearth. It is a figure which shows the mode of the movable grate and fixed grate of the stoker type combustion apparatus of FIG. It is a figure which shows the grate of the 1st Embodiment of this invention. It is a figure which shows the sand type | mold for manufacturing the grate of FIG. It is a figure which shows a mode when the board | plate of a Ni-based alloy layer is installed in the sand type | mold of FIG. It is a figure which shows the modification of the board installed in the sand mold of FIG. It is a figure which shows the modification of the board installed in the sand mold of FIG. It is a figure which shows the grate of the 2nd Embodiment of this invention. It is a figure which shows the grate of the 3rd Embodiment of this invention.

Explanation of symbols

10, 20, 30 Grate, 11 Front coating layer, 12 Top coating layer, 13 Side coating layer, 100 Stoker-type combustion device, 101 Fixed grate, 102 Movable grate, 103 Scraper, 104 Fixed frame, 105 Movable frame, 106 hydraulic cylinder, 200 sand mold, 201 inlet, 202 Ni-based alloy layer plate, 212 metallurgical reaction layer, 213, 221 metal plate, 222 release agent layer

Claims (7)

A grate used in an incinerator, wherein the grate is formed by casting a base material obtained by overlaying or spraying a Ni-based self-soluble Ni-based alloy with a molten metal as a base material. grate, wherein a portion of the surface of the is to so that is covered with Ni-based alloy layer of Ni-based self-fluxing containing 10-30% of Cr by weight%. The grate according to claim 1, wherein the Ni-based alloy layer has a thickness of 0.5 to 5 mm. The incinerator is stoker, the Ni-based alloy layer, the transport direction of the material to be incinerated as a front, grate according to claim 1 or 2, characterized in that covers the front of the grate. The grate according to claim 3 , wherein the Ni-based alloy layer further covers an upper surface extending rearward from an upper end side of the front surface. The grate according to claim 4 , wherein the incinerator is a sliding stoker furnace, and a sliding portion of the upper surface is not covered with the Ni-based alloy layer. The grate according to any one of claims 1 to 5 , wherein the Ni-based alloy layer further covers a side surface extending rearward from a side edge of the front surface. The grate according to any one of claims 1 to 6 , wherein the Ni-based alloy layer is metallurgically bonded by heat treatment.

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