JP2019158167A - Corrosion prevention metho on radiant heat transfer surface of boiler, and boiler - Google Patents

Abstract

To prevent a corrosion-proof layer on a radiant heat transfer surface from peeling off even when using a water injection device for removing dust.SOLUTION: In a boiler 20 including: a radiation chamber 28 connected to a waste incinerator 10 for recovering heat from exhaust gas, sectioned by a direction change part bending a passage of the exhaust gas, and including a radiant heat transfer surface 28A which receives radiation heat of the exhaust gas from an upstream side in an exhaust gas flow direction and generates steam; and a convective heat transfer chamber 30 which generates steam by heat exchange between the exhaust gas and a convective heat transfer surface of a heat transfer pipe and overheats the steam, a corrosion-proof layer 28B is formed on the radiant heat transfer surface 28A of the radiation chamber 28, onto which water may be injected from a water injection device 70 for removing dust attached on the radiant heat transfer surface 28A, by buildup welding of stainless steel or Ni-Cr-Mo alloy.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a corrosion prevention method and boiler for a radiant heat transfer surface of a boiler, and more particularly to a radiant heat transfer surface using a water jet device for dust removal, which is suitable for use in a garbage incineration facility having a power generation facility. The present invention relates to a corrosion prevention method for a radiant heat transfer surface of a boiler and a boiler that can prevent peeling of the corrosion protection layer.

  In the operation of a waste incineration facility with power generation facilities, maintaining and improving the amount of power generated and sold is one of the most important items after the stable treatment of waste.

  Power generation at a waste incineration facility is performed by recovering heat from a high-temperature exhaust gas obtained from the combustion of waste in an incinerator and generating steam at a predetermined temperature and pressure and introducing it into a turbine generator. ing.

  The boiler has a radiant chamber having a radiant heat transfer surface that generates steam by receiving radiant heat from the exhaust gas, a convection heat transfer chamber that generates steam by heat exchange between the exhaust gas and the convective heat transfer surface of the heat transfer tube, and further superheats. It has.

  In the radiant chamber, a radiant heat transfer tube is provided as a radiant heat transfer surface through which heated water is circulated on the outside of the steel side wall surrounding the exhaust gas flow path to generate steam by radiant heating.

  In the convection heat transfer chamber, a heat transfer tube (also referred to as a superheater) that contacts the exhaust gas in the exhaust gas flow path to generate steam by convective heat transfer and further superheats is disposed as a convection heat transfer surface. The convection heat transfer surface is configured by arranging a plurality of heat transfer tube groups in which a plurality of heat transfer tubes are arranged in the horizontal direction in the height direction.

  The convection heat transfer chamber may be provided with an economizer having a heat transfer tube that heats water in the exhaust gas flow path to produce heated water.

  The exhaust gas generated in refuse incineration contains dust of small particle size including chlorine, sulfur, heavy metals, etc., but if these adhere to the radiant and convective heat transfer surfaces of the boiler, the adhering dust will be Since it acts as a heat insulating material, heat transfer efficiency decreases. Thereby, the heat recovery efficiency also decreases. As a result, the amount of steam generated decreases, and the amount of power generated by the turbine generator decreases. In addition, the gap between the heat transfer tubes may be blocked by adhering dust, which may hinder the flow of exhaust gas.

  For this reason, equipment that periodically removes adhering dust is required. For example, as a technique for removing dust adhering to the radiation heat transfer surface of the radiation chamber, the applicant uses a water injection device in Patent Document 1. The technology that had been proposed.

JP 2017-181008 A

  However, when water or water vapor is injected to remove dust adhering to the radiant heat transfer surface during the operation of the incinerator, the temperature of the radiant heat transfer surface temporarily decreases and is again exposed to high-temperature furnace gas. Since the temperature returned, thermal expansion and contraction were repeated, and there was a problem that the anticorrosion layer applied for anticorrosion of the radiation heat transfer surface peeled off.

  This invention is made | formed in view of the said problem, and makes it a subject to prevent peeling of the anticorrosion layer of a radiation heat-transfer surface, even if it uses the water injection apparatus for dust removal.

  A thermal shock test was conducted to investigate the thermal shock resistance of the anticorrosion layer due to temperature alternation.

  In accordance with JIS H8304, 50mm x 50mm x 5mm SS400 plate is blasted using a steel grid, and the surface is cleaned to make the surface uneven, and then an anticorrosive layer is applied by overlay welding or thermal spraying. A test piece was obtained.

  Each test piece was heated to 300 ° C., which is the maximum temperature of the radiant heat transfer surface, in an electric furnace, and water-cooled immediately after removal from the furnace. The test piece was cleaned with alcohol, and after confirming damage (cracking and peeling), the presence or absence of cracking was confirmed with a 20-fold magnifier. The thermal shock was repeated up to 50 times, and those that were not damaged were accepted and those that were damaged were rejected. The test results are shown in Table 1.

  Table 2 shows the welding conditions for overlay welding, Table 3 shows the chemical composition (wt%) of the welding wire, and Table 4 shows the composition of the thermal spray material.

  Conventional flame spraying and atmospheric plasma spraying (APS) in which a high-melting-point material is sprayed in the atmosphere using a high-temperature, high-speed plasma jet as a heat source have poor adhesion and all have failed.

  In contrast, when stainless steel SUS309 and Ni-Cr-Mo alloy Inconel 625, Hastelloy C276, and Hastelloy C22 were overlay welded, acceptable results were obtained.

  The present invention has been made on the basis of the above knowledge, and is divided by a turning portion that bends the flow path of the exhaust gas to be connected to the waste incinerator and recovers heat from the exhaust gas, and is upstream of the exhaust gas flow direction. A radiant chamber with a radiant heat transfer surface that generates steam by receiving the radiant heat of the exhaust gas, and a convection heat transfer chamber that generates steam by heat exchange between the exhaust gas and the convective heat transfer surface of the heat transfer tube and further superheats In order to remove dust adhering to the radiant heat transfer surface, on the radiant heat transfer surface of the radiant chamber for injecting water from a water injection device, a build-up of stainless steel or Ni-Cr-Mo alloy is provided. The said subject is solved by forming an anticorrosion layer by welding.

  Here, the stainless steel can be SUS309.

  Further, the Ni—Cr—Mo alloy may be Inconel 625, Hastelloy C276, and Hastelloy C22.

  The present invention is also divided by a turning section that bends the exhaust gas flow path and is connected to the waste incinerator to recover heat from the exhaust gas, and receives the radiant heat of the exhaust gas from the upstream side in the exhaust gas flow direction. A radiation chamber having a radiation heat transfer surface for generating steam, and a boiler having a convection heat transfer chamber that generates steam by heat exchange between the exhaust gas and the convection heat transfer surface of the heat transfer tube and further superheats, the radiation chamber A water injection device for removing dust adhering to the radiant heat transfer surface by injecting water onto the radiant heat transfer surface, the anticorrosion layer by overlay welding of stainless steel or Ni-Cr-Mo alloy on the radiant heat transfer surface By providing a boiler characterized in that is formed, the above-mentioned problem is solved.

  According to the present invention, it is possible to prevent peeling of the anticorrosion layer on the radiant heat transfer surface even if a water jet device for dust removal is used.

Sectional drawing which shows the structure of embodiment of this invention

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by the content described in the following embodiment. In addition, constituent elements in the embodiments described below include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in the so-called equivalent range. Furthermore, the constituent elements disclosed in the embodiments described below may be appropriately combined, or may be appropriately selected and used.

  First, a boiler connected to a waste incinerator to which the present invention is applied will be described. As shown in FIG. 1, a boiler 20 connected to an incinerator 10 for recovering heat from exhaust gas is divided by two turning portions 21 and 22 that bend the exhaust gas flow path, and upstream of the exhaust gas flow direction. The first radiation chamber 26, the second radiation chamber 28, and the convection heat transfer chamber 30 are provided. A gas mixing chamber 24 is provided in the vicinity of the inlet of the first radiation chamber 26 that receives exhaust gas from the incinerator 10. The exhaust gas introduced from the incinerator 10 flows from the lower side of the first radiation chamber 26 to the upper side, from the upper side to the lower side of the second radiation chamber 28, and from the lower side to the upper side of the convection heat transfer chamber 30.

  The first radiation chamber 26 and the second radiation chamber 28 are each provided with a radiation heat transfer surface that generates radiant heat from the exhaust gas and generates steam.

  The convection heat transfer chamber 30 includes a screen tube 32, a horizontal evaporation tube 44, a secondary superheater 34, a primary superheater 38, and an economizer 42 from the upstream side in the exhaust gas flow direction. Each of the secondary superheater 34 and the primary superheater 38 includes a heat transfer tube group in which a plurality of heat transfer tubes arranged in a horizontal direction are provided in multiple stages in the height direction, and the heat transfer tube group constitutes a convection heat transfer surface. In addition, steam is generated by heat exchange with the exhaust gas to further overheat. The screen tube 32 is provided with a heat transfer tube in the shape of a flag to cool the exhaust gas introduced into the convection heat transfer chamber 30. The horizontal evaporation pipe 44 is a heat transfer pipe that heats the water heated by the economizer 42 and generates steam.

  In the present embodiment, the second radiation chamber 28 is provided with a water ejection device 70 that ejects and removes water from the dust adhering to the radiation heat transfer surface 28A of the second radiation chamber 28. . The water injection device 70 includes a plurality of injection ports, a water injection nozzle 71 that moves up and down in the second radiation chamber 28, a water supply pipe 72 that supplies water to the water injection nozzle 71, and the water injection nozzle 71. An elevating mechanism 73 that moves up and down is provided.

  A water jet nozzle 71 is disposed in the second radiation chamber 28, and water is sprayed onto the radiation heat transfer surface 28A of the second radiation chamber 28 to remove the adhering dust. Even in a large boiler having a boiler width of 5 m or more that is difficult to apply or a small boiler having a boiler width of 3 m or less, it is possible to efficiently remove dust adhering to the radiant heat transfer surface 28A.

  Here, in the first embodiment of the present invention, good results could be obtained by forming the anticorrosion layer 28B by overlay welding of SUS309 described in Table 1.

  In the second embodiment of the present invention, good results could be obtained by forming the anticorrosion layer 28B by overlay welding of Inconel 625.

  In the third embodiment of the present invention, good results could be obtained by forming the anticorrosion layer 28B by overlay welding of Hastelloy C276.

  Furthermore, in the fourth embodiment of the present invention, good results could be obtained by forming the anticorrosion layer 28B by overlay welding of Hastelloy C22.

  In this way, according to the present invention, it is possible to prevent the anticorrosion layer 28B from peeling off the radiation heat transfer surface 28A even if the water jet device 70 for dust removal is used, and to maintain the heat collection amount of the boiler 20. Thus, problems that occur when the water injection device 70 is used can be prevented. Therefore, it becomes possible to efficiently remove dust adhering to the boiler inner wall during operation, and the amount of heat collected by the boiler can be maintained. Further, by preventing the corrosion of the boiler inner wall surface and the waste heat recovery pipe surface due to heavy metals and salts contained in the attached dust, the maintenance cost can be reduced and the operation of the incineration facility with easy operation management becomes possible.

  In the said embodiment, although the anticorrosion layer 28B by this invention was formed in 28A of radiation | emission heat transfer surfaces of the 2nd radiation chamber 28, the formation object of an anticorrosion layer is not limited to this.

  Moreover, in the said embodiment, although this invention was applied to the boiler connected with the municipal waste incinerator, the application object of this invention is not limited to this.

DESCRIPTION OF SYMBOLS 10 ... Incinerator 20 ... Boiler 21, 22 ... Turning part 26 ... 1st radiation chamber 28 ... 2nd radiation chamber 28A ... Radiation heat transfer surface 28B ... Anticorrosion layer 30 ... Convection heat transfer chamber 32 ... Screen tube 34 ... Secondary Superheater 38 ... Primary superheater 42 ... Economizer 44 ... Horizontal evaporation pipe 70 ... Water injection device 71 ... Water injection nozzle 72 ... Water supply pipe 73 ... Elevating mechanism

Claims (6)

Radiation transmission that generates steam by receiving the radiant heat of the exhaust gas from the upstream side in the exhaust gas flow direction, separated by a turning section that bends the exhaust gas flow path and is connected to the waste incinerator to recover heat from the exhaust gas. In a boiler having a radiant chamber having a hot surface and a convective heat transfer chamber that generates steam by heat exchange between the exhaust gas and the convective heat transfer surface of the heat transfer tube and further overheats,
In order to remove dust adhering to the radiant heat transfer surface, an anticorrosion layer is formed on the radiant heat transfer surface of the radiant chamber through which water is injected from a water injection device by overlay welding of stainless steel or Ni-Cr-Mo alloy An anticorrosion method for a radiant heat transfer surface of a boiler, characterized by forming.   The said stainless steel is SUS309, The corrosion prevention method of the radiation heat-transfer surface of the boiler of Claim 1 characterized by the above-mentioned.   The said Ni-Cr-Mo alloy is Inconel 625, Hastelloy C276, and Hastelloy C22, The corrosion prevention method of the radiation heat-transfer surface of the boiler of Claim 1 characterized by the above-mentioned. Radiation transmission that generates steam by receiving the radiant heat of the exhaust gas from the upstream side in the exhaust gas flow direction, separated by a turning section that bends the exhaust gas flow path and is connected to the waste incinerator to recover heat from the exhaust gas. In a boiler having a radiant chamber having a hot surface and a convective heat transfer chamber that generates steam by heat exchange between the exhaust gas and the convective heat transfer surface of the heat transfer tube and further overheats,
A water injection device for removing dust adhering to the radiation heat transfer surface by injecting water into the radiation chamber;
A boiler having a corrosion prevention layer formed by overlay welding of stainless steel or Ni—Cr—Mo alloy on the radiation heat transfer surface.   The boiler according to claim 4, wherein the stainless steel is SUS309.   The boiler according to claim 4, wherein the Ni—Cr—Mo alloy is Inconel 625, Hastelloy C276, and Hastelloy C22.

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