JP2008101856A - Operation method of boiler superheater in waste treatment facility, and boiler superheater of waste treatment facility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To elongate a service life of a boiler superheater by equalizing reduction in thickness caused by high-temperature corrosion of the boiler superheater in a boiler of a waste treatment facility. <P>SOLUTION: In the boiler superheater 2 comprising a low-temperature portion side to which steam is supplied and a high-temperature portion side which heats the steam supplied to the low-temperature portion side and from which the superheated steam is taken out, a steam supply pipe 3 and a superheated steam taking-out pipe 5 switch the high-temperature portion side from which the superheated steam is taken out to the low-temperature portion side to which the steam is supplied, and switch the low-temperature side to which the steam is supplied to the high-temperature portion side from which the superheated steam is taken out, by two bypass pipes composed of a steam supplying switching pipe 8 for switching the high-temperature portion side from which the superheated steam is taken out to the low-temperature portion side to which the steam is supplied, and a superheated steam taking-out supplying pipe 9 for switching the low-temperature side to which the steam is supplied to the high-temperature portion side from which the superheated steam is taken out, at a time point when the boiler superheater 2 is used for a specific period, and the reduction of thickness at the high-temperature portion side reaches design limit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method of operating a boiler superheater of a waste treatment facility and a boiler superheater of a waste treatment facility capable of extending the life of the boiler superheater by uniformizing corrosion of the boiler superheater of the waste treatment facility. About.

  In a waste treatment facility equipped with a waste treatment furnace such as a waste incinerator or a waste melting furnace, the combustible gas generated in the waste treatment furnace is burned and heat is recovered in a boiler, and the generated steam is sent to a steam turbine. Supply and generate electricity.

  Boiler superheater tubes for waste boilers are exposed to severe high-temperature corrosive environments due to high-concentration hydrogen chloride in combustion exhaust gas, chlorides in fly ash, and sulfides. When a steel pipe (STB or the like) is used, the upper limit of the steam temperature is limited to about 300 ° C. in order to prevent high temperature corrosion. For example, in Patent Document 1, the tube wall temperature on the high temperature side of a boiler superheater in a waste incinerator is measured, and when the tube wall temperature becomes a predetermined temperature or higher, cooling water is mixed to make the boiler superheater lower than the predetermined temperature. It is disclosed to prevent high temperature corrosion.

  On the other hand, in order to increase the power generation efficiency, it is effective to increase the steam temperature and pressure, so the steam temperature generated by the boiler is increased. For example, Patent Document 2 describes that the material of a boiler superheater in a garbage incinerator is high Ni stainless steel or super metal having high temperature corrosion resistance.

FIG. 4 is a conceptual diagram showing an example of a conventional boiler superheater arranged in a waste treatment facility. In FIG. 4, the boiler further heats the steam at about 300 ° C. supplied from the evaporator 1 to the pipe 4 through the steam supply pipe 3 from the evaporator 1 by evaporating water to generate steam at about 350 ° C. The boiler superheater 2 which produces | generates this superheated steam is provided. The superheated steam taken out at about 350 ° C. is sent to a supply destination such as a steam turbine through the superheated steam extraction pipe 5. In the figure, 6 and 7 are gate valves.
Japanese Patent Laid-Open No. 5-280707 Japanese Patent No. 2769671

  However, the boiler superheater described in Patent Document 2 uses expensive high-Ni stainless steel or supermetal to prevent high-temperature corrosion, so that the equipment cost is higher than that of a boiler steel pipe (STB or the like). There is a drawback. On the other hand, in the case of boiler steel pipes, there is a problem of thinning due to high temperature corrosion.

  FIG. 3 is a graph showing the relationship between the steam temperature and the amount of thinning of the boiler superheater.

  When the steam temperature is increased from about 300 ° C. to about 350 ° C. using a boiler steel pipe as the boiler superheater tube, as shown in FIG. 3, there is almost no thinning at the steam temperature of about 300 ° C. In the region exceeding about 300 ° C., the high temperature corrosion becomes severe as the temperature rises to 325 ° C. and 350 ° C., and the amount of thinning of the pipe is predicted to be almost proportional to the temperature rise and the use time. Therefore, in the boiler superheater, the steam temperature is the lowest (about 300 ° C) on the boiler superheater inlet side and the highest temperature (about 350 ° C) on the boiler superheater outlet side. The thinning amount on the outlet side becomes the maximum, and the thinning amount on the boiler superheater inlet side is almost zero. The boiler superheater has a short life because the boiler superheater must be replaced periodically (2 to 3 years) when the set amount of thinning is high because the amount of thinning due to high-temperature corrosion is large on the boiler superheater outlet side. In addition, there is a problem that initial cost or running cost is increased.

  Then, this invention aims at equalizing the thinning by the high temperature corrosion of the boiler superheater of the boiler in a waste treatment facility, and extending the lifetime of a boiler superheater.

  The operation method of the boiler superheater of the waste treatment facility of the present invention comprises a low temperature part side to which steam is supplied, and a high temperature part side to extract the superheated steam by heating the steam supplied to the low temperature part side, In the operation method of the boiler superheater of the waste treatment facility, the boiler superheater has been used for a certain period of time, and when the amount of thinning on the high temperature part has reached or approached the design limit, the high temperature part from which superheated steam was taken out The side is switched to the low temperature part side to which steam is supplied, and the low temperature side to which the steam is supplied is switched to the high temperature part side from which superheated steam is taken out. In this configuration, the low temperature portion side has a steam temperature at which high temperature corrosion does not occur, and the high temperature portion side has a superheated steam temperature at which high temperature corrosion occurs.

  Moreover, the boiler superheater of the waste treatment facility of the present invention is connected to the steam input pipe at the low temperature part side which is the steam inlet side of the boiler superheater of the waste treatment facility, and becomes the superheated steam outlet side of the boiler superheater. A steam supply switching pipe that connects the superheated steam extraction pipe to the high temperature part side, and the steam supply pipe and superheated steam extraction pipe switch the high temperature part from which superheated steam was taken out to the low temperature part side to which steam is supplied. And two bypass pipes composed of a superheated steam extraction switching pipe for switching the low temperature side supplying the steam to the high temperature portion side from which the superheated steam is taken out. The boiler superheater is provided with a first gate valve for the steam supply pipe, and a second gate valve for the superheated steam take-out pipe. The steam supply pipe and the superheated steam take-out pipe are the steam supply switching pipe and the superheated steam. Connected by two bypass pipes consisting of extraction pipes, one end of the steam supply switching pipe is connected to the inlet side of the first gate valve of the steam supply pipe, and the other end is the second gate valve of the superheated steam extraction pipe One end of the superheated steam take-out switching pipe is connected to the outlet side of the first gate valve of the superheated steam take-out pipe, and the other end is connected to the outlet side of the second gate valve of the superheated steam take-out pipe The steam supply switching pipe may be provided with a third gate valve, and the superheated steam extraction switching pipe may be provided with a fourth gate valve. Further, it may be possible to change the external pipe by bypass modification without providing a valve at the time of switching.

  The present invention uses a boiler superheater for a certain period, reverses the flow of steam and superheated steam when the amount of thinning of the boiler superheater high temperature part approaches the design limit, and the high temperature greatly reduced by high temperature corrosion. The boiler superheater tube is switched by switching the low temperature part side to the low temperature part side where there is almost no thinning to reduce the high temperature corrosion to suppress the thinning and switching the low temperature part side where there was almost no thinning to the high temperature part side where high temperature corrosion occurs. The overall thickness reduction can be made uniform, and as a result, it is possible to extend the life of the boiler superheater about twice as much as before.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a conceptual diagram showing an embodiment of a boiler superheater according to the present invention.

  The boiler includes an evaporator 1 that evaporates water and generates steam, and a boiler superheater 2 that further heats the steam supplied from the evaporator 1 to generate superheated steam. The steam outlet side of the evaporator 1 and the steam inlet side of the pipe 4 of the boiler superheater 2 are connected by the steam supply pipe 3, and the superheated steam outlet side of the pipe 4 of the boiler superheater 2 is connected to the superheated steam extraction pipe 5. Is done. The steam supply pipe 3 and the pipe 4 of the boiler superheater 2 use, for example, boiler steel pipe (STB) which is cheaper than expensive high Ni stainless steel or super metal.

  The steam supply pipe 3 is provided with a first gate valve 6, and the superheated steam extraction pipe 5 is provided with a second gate valve 7.

  The steam supply pipe 3 and the superheated steam take-out pipe 5 are connected by two bypass pipes including a steam supply change-over pipe 8 and a superheated steam take-out change-over pipe 9. One end of the steam supply switching pipe 8 is connected to the inlet side of the first gate valve 6 of the steam supply pipe 3, and the other end is connected to the inlet side of the second gate valve 7 of the superheated steam extraction pipe 7. One end of the superheated steam extraction switching pipe 9 is connected to the outlet side of the first gate valve 6 of the superheated steam outlet pipe 5, and the other end is connected to the outlet side of the second gate valve 7 of the superheated steam outlet pipe 5. Is done.

  The steam supply switching pipe 8 is provided with a third gate valve 10, and the superheated steam extraction switching pipe 9 is provided with a fourth gate valve 11.

  In the boiler heater of the present embodiment configured as described above, the switching operation of the flow of steam and superheated steam will be described.

  As shown in FIG. 1, before switching, the first gate valve 6 of the steam supply pipe 3 and the second gate valve 7 of the superheated steam extraction pipe 5 are opened, and the third gate valve of the steam supply switching pipe 8 is opened. 10 and the fourth gate valve 11 of the superheated steam extraction switching pipe 9 are closed. In this state, as shown by the arrow in FIG. 1, the steam of about 300 ° C. generated in the evaporator 1 is supplied to the pipe 4 of the boiler superheater 2 through the steam supply pipe 3 and the first gate valve 6. The The superheated steam superheated to about 350 ° C. by the boiler superheater 2 exits the boiler superheater 2 and is sent to the supply destination through the superheated steam extraction pipe 5 and the second gate valve 7.

  In the above state, the boiler superheater 2 is used for a certain period, and when it stops once or twice a year, the thickness of the steel pipe is measured from the manhole using an ultrasonic wall thickness gauge, and the piping on the high temperature side on the boiler superheater outlet side When the thinning amount of the metal nears the design limit, for example, when the design wall thickness is 2 mm and the adopted thickness is 8 mm, the superheated steam outlet portion is thinned most, but this is, for example, 3 to 4 mm (thickening amount 5 to 4 mm), the flow is switched so that the steam supply side and the superheated steam take-out side in the boiler superheater 2 are reversed.

  FIG. 2 is a diagram showing the flow of steam and superheated steam after switching.

  In FIG. 2, the first gate valve 6 and the second gate valve 7 are closed and the third gate valve 10 and the fourth gate valve 11 are opened to switch the flow of steam and superheated steam in reverse. In this state, as shown by the arrow in FIG. 2, steam at about 300 ° C. flows from the evaporator 1 through the steam supply pipe 3, the third gate valve 10, and the steam supply switching pipe 8 and enters the boiler superheater 2. . Before switching, the high temperature part on the take-out side of supersaturated steam at about 350 ° C. is switched to the inlet side, and steam at about 300 ° C. is supplied, so that the amount of thinning is near the design limit. When the high temperature part side becomes the low temperature part side, it is possible to stop the thinning due to high temperature corrosion.

  The superheated steam heated to about 350 ° C. by the boiler superheater 2 exits the boiler superheater 2 and is connected to the steam supply pipe 3, the fourth gate valve 11, the superheated steam take-out switching pipe 9, and the superheated steam take-out pipe 5. And sent to the supplier.

  Before switching, the low-temperature part where there was almost no thinning, which was on the steam inlet side of about 300 ° C, was switched to the high-temperature part side of superheated steam, about 350 ° C. It can be used until the high-temperature corrosion of the piping advances and the amount of thinning approaches the design limit on the high-temperature part side. Then, when the amount of thinning approaches the design limit, the entire boiler superheater is replaced.

  In this way, by switching between the inlet side and the outlet side of the steam and superheated steam of the boiler superheater during use, the thinning is made uniform, and conventionally, the boiler superheater was replaced in 2 to 3 years. By switching the present invention, it can be extended to 4 to 6 years, and the life can be extended about twice.

It is a conceptual diagram which shows one Example of the boiler superheater of this invention. It is a figure which shows the flow after the switching of the boiler superheater of this invention, and the flow of superheated steam. It is a graph which shows the relationship between steam temperature and the amount of thinning of a boiler superheater. It is a conceptual diagram which shows an example of the conventional boiler superheater arrange | positioned at a waste treatment facility.

Explanation of symbols

1: Evaporator 2: Boiler superheater 3: Steam supply pipe 4: Boiler superheater pipe
5: Pipe for superheated steam extraction 6: First gate valve 7: Second gate valve 8: Pipe for switching steam supply 9: Pipe for switching superheated steam extraction 10: Third gate valve 11: Fourth gate valve

Claims (4)

In a method for operating a boiler superheater of a waste treatment facility, comprising a low-temperature part side to which steam is supplied and a high-temperature part side for heating the steam supplied to the low-temperature part side and taking out superheated steam,
When the boiler superheater is used for a certain period of time, and the amount of thinning on the high-temperature part side reaches or approaches the design limit, the high-temperature part side where the superheated steam was taken out is switched to the low-temperature part side where steam is supplied A method for operating a boiler superheater of a waste treatment facility, characterized in that the low temperature part side supplying steam is switched to a high temperature part side from which superheated steam is taken out.   2. The method of operating a boiler superheater of a waste treatment facility according to claim 1, wherein the low temperature portion side has a steam temperature at which high temperature corrosion does not occur, and the high temperature portion side has a superheated steam temperature at which high temperature corrosion occurs. The low temperature part which is the steam inlet side of the boiler superheater of the waste treatment facility is connected by a steam supply pipe, and the superheated steam extraction pipe is connected to the high temperature part which is the superheated steam outlet side of the boiler superheater,
Steam supply piping and superheated steam extraction piping are used to switch the steam supply switching piping that switches the high-temperature part from which superheated steam has been taken out to the low-temperature part to which steam is supplied, and the low-temperature side that has supplied steam is superheated steam A boiler superheater of a waste treatment facility, characterized in that it is connected by two bypass pipes composed of a superheated steam take-out switching pipe for switching to a high-temperature part side from which water is taken out.   The steam supply pipe is provided with a first gate valve, and the superheated steam take-out pipe is provided with a second gate valve. The steam supply pipe and the superheated steam take-out pipe are composed of a steam supply switching pipe and a superheated steam take-out pipe. Connected by two bypass pipes, one end of the steam supply switching pipe is connected to the inlet side of the first gate valve of the steam supply pipe, and the other end is connected to the inlet side of the second gate valve of the superheated steam outlet pipe One end of the superheated steam take-out switching pipe is connected to the outlet side of the first gate valve of the superheated steam take-out pipe, and the other end is connected to the outlet side of the second gate valve of the superheated steam take-out pipe to switch the steam supply The boiler superheater of the waste treatment facility according to claim 1, wherein a third gate valve is provided in the pipe for use and a fourth gate valve is provided in the pipe for switching over the superheated steam extraction.

Images