JP6303836B2 - Chemical cleaning method for boiler - Google Patents

Description

  The present invention relates to a chemical cleaning method for a boiler, and more particularly to a method for chemically cleaning a brackish water separator and a furnace side thereof.

  An example of the steam system of the thermal power generation boiler is shown in FIG. Steam generated by burning fuel in the furnace 152 by the burner 151 is supplied to the high-pressure turbine 157 through the steam drum 153, the saturated steam pipe 154, the superheater 155, the main steam pipe 156, and the main steam stop valve 156a. . Then, the steam that has worked in the high-pressure turbine 157 is sent to the reheater 159 through the low-temperature reheat steam pipe 158 and heated, and then passed through the high-temperature reheat steam pipe 160 to the intermediate-pressure turbine 161 and the low-pressure turbine 162. Supplied to do work. The steam that has worked in the low-pressure turbine 162 is condensed in the condenser 163 and then returned to the furnace 152 again through the deaeration pipe 164 and the boiler feed water pump 165.

  The main steam pipe 156 is connected to a drain pipe 156b having a drain valve.

  In such a steam system of a thermal power generation boiler, a chemical cleaning method is known in which a cleaning chemical is circulated through an evaporation tube, a steam drum, a downpipe, a collecting header, and the like (Patent Document 1).

  When chemically cleaning only the boiler water separator and the furnace side than that, in order to prevent the cleaning chemical vapor or splash from flowing into the superheater, water is filled in the superheater and the main steam pipe, Chemical cleaning of the brackish water separator and the furnace side is performed.

  When water filling was performed on the superheater and the main steam pipe, it was necessary to lower the temperature until the temperature of the main steam stop valve became 100 ° C. or lower before performing water filling. This is because if water filling is performed when the main steam stop valve is higher than 100 ° C., the water will boil and there is a risk of affecting the equipment.

JP 55-46350 A

  As described above, when chemical cleaning is performed on the brackish water separator and the furnace side, it is necessary to wait until the main steam stop valve cools to 100 ° C. or lower when the superheater and the main steam pipe are filled with water. Therefore, the cleaning period was long.

  An object of this invention is to provide the chemical cleaning method of the boiler which can shorten the work period in the case of carrying out the chemical cleaning of the brackish water separator of a boiler and the furnace side rather than it than before.

  The boiler chemical cleaning method of the present invention includes a economizer in which feed water is introduced by a feed pipe, a furnace having a wall pipe into which water from the economizer is introduced, and a brackish water separator in which the wall pipe is connected. Chemically cleaning a boiler having a superheater that superheats steam from the brackish water separator, a drain tank that receives water from the brackish water separator, and a pump and piping that circulates the water in the drain tank to the water supply pipe In the method of chemically cleaning the brackish water separator and the furnace side thereof, after filling the uppermost stream part of the superheat line with water, the cleaning chemical solution is circulated to the brackish water separator and the furnace side of the steam separator. A circulation step that is performed, and then an extrusion step in which clean water for extrusion is supplied to the main steam pipe to extrude the cleaning chemical liquid.

  In the present invention, when water is filled in the uppermost stream portion of the superheat line, the temperature of the main steam stop valve provided in the main steam pipe is higher than 100 ° C., and when the extrusion process is performed, the main steam is It is preferable that the temperature of a stop valve is 100 degrees C or less.

  In the boiler chemical cleaning method of the present invention, water filling is performed only on the uppermost stream portion of the superheating line, and then the brackish water separator and the furnace side are chemically cleaned, so that the main steam stop valve is cooled to 100 ° C or lower. The chemical cleaning can be started without waiting until the cleaning is completed, and the cleaning period can be shortened.

It is a block diagram explaining the chemical cleaning method of the boiler which concerns on embodiment. It is a block diagram explaining the chemical cleaning method of the boiler which concerns on embodiment. It is sectional drawing of a boiler. It is a systematic diagram of a boiler apparatus.

  FIG. 3 shows a configuration diagram of a boiler to which the cleaning method according to the embodiment of the present invention is applied. The boiler includes a furnace 9, a downstream exhaust gas passage (rear flue), and an upstream exhaust gas passage connecting the upper portion of the furnace 9 and the downstream exhaust gas passage.

  High-temperature combustion gas generated from a plurality of burners 80 provided at the lower part of the furnace 9 rises in the furnace 9. The combustion gas passes through the upstream side exhaust gas passage and the downstream side exhaust gas passage and is discharged from the passage outlet 93 to the outside of the boiler as low temperature exhaust gas. In the furnace 9, a water cooling wall lower peripheral wall pipe 10, an upper water cooling wall pipe 12 and a nose wall pipe 105 are provided. The water-cooled wall lower peripheral wall tube 10 extends upward from the lower portion of the furnace 9 in a spiral manner in the furnace 9. Each of the upper water-cooled wall tubes 12 composed of a plurality of tubes extends vertically in the furnace 9 toward the upper portion of the furnace 9. The nose tube 105 is also composed of a plurality of tubes.

  The rear flue is defined by a rear heat transfer wall 33 formed of a plurality of tubes. The rear flue is divided into two gas flow paths by a dividing wall 120 extending along the flow of exhaust gas. The dividing wall 120 is also composed of a plurality of tubes.

  A reheater 71 is disposed in one divided gas flow path of the rear flue, and a primary superheater 40 and the economizer 2 are disposed in the other divided gas flow path. Moreover, you may provide an evaporator in a division | segmentation gas flow path as needed.

  The rear flue is defined by a ceiling wall 30 made of a plurality of tubes, a side wall, and the like. A secondary superheater 50 and a tertiary superheater 60 are disposed in the upstream exhaust gas flow path. Furthermore, a quaternary superheater may be installed.

  Next, the water supply system of this boiler will be described. Water supply to the boiler is first supplied to the economizer 2 from a water supply pipe 1 having a water supply valve 1a. In the economizer 2, the water supplied from the economizer inlet header 100 absorbs heat from the exhaust gas flow while passing through the economizer 2, and then from the economizer outlet header 101 to the water cooling wall downcomer. 3 is supplied. The water passing through the water cooling wall descending pipe 3 is distributed to the water cooling wall lower header 103 and rises while absorbing the heat in the furnace 9 through the water cooling wall lower peripheral wall pipe 10 surrounding the furnace 9 spirally. Water is heated to near saturation temperature.

  The high-temperature water rising up the water-cooling wall lower peripheral wall pipe 10 flows into the furnace 9 intermediate fluid mixing header 11, where the temperature is equalized and then the upper water-cooling wall provided at the upper part of the furnace 9 While ascending the tube 12 or the nose wall tube 105, the heat in the furnace 9 is absorbed and becomes a mixed fluid of liquid high-temperature water and gas-phase steam. This mixed fluid flows from the water-cooled wall upper header 104 or the nose wall header 106 into the furnace 9 upper fluid mixing header 13 to equalize the fluid temperature, and is further provided above the boiler front. It flows into the brackish water separator 20 and is separated into steam and water. The separated water is circulated again from the drain tank 21 to the water supply pipe 1 through a circulation pipe 22 having a boiler circulation pump 24 and valves 23 and 25. Further, the steam separated by the brackish water separator 20 is supplied to the ceiling wall inlet header 107.

  The steam supplied to the ceiling wall inlet header 107 passes through the ceiling wall tube constituting the ceiling wall 30 provided from the upper portion of the furnace 9 to the upper portion of the downstream exhaust gas flow path, and then the ceiling wall outlet header 108. In the meantime, it is heated by heat absorption and becomes superheated steam.

  The superheated steam collected in the ceiling wall outlet header 108 is distributed to the rear heat transfer wall inlet header 110 through the rear heat transfer wall descending pipe 31 and the rear heat transfer wall inlet connecting pipe 109, and further to the rear heat transfer wall 33. After being heated at the rear heat transfer wall outlet header 111 and the rear heat transfer wall outlet connecting tube 112, or from the rear heat transfer wall 33 to the rear heat transfer wall rear wall outlet header 34.

  The superheated steam gathered in the rear heat transfer wall rear wall outlet header 34 flows into the primary superheater 40 installed in the rear flue via the primary superheater communication pipe 35 and then provided in the upper part of the furnace 9. After being heated in turn through the secondary superheater 50 and the tertiary superheater 60, they are sent to the high pressure turbine via the main steam pipe 61 and the main steam stop valve 62.

  The exhaust steam that has worked in the high-pressure steam turbine is guided to a reheater 71 installed in the rear flue by a low-temperature reheat steam pipe (not shown) and heated to a reheat steam temperature of a predetermined temperature. , Sent to medium pressure turbine. A gas distribution damper 90 is provided at the outlet of the rear flue, and by adjusting the flow rate of gas passing therethrough, the total heat absorption amount in the reheater 71 is adjusted and can be controlled to a predetermined reheat steam temperature.

  When chemically cleaning the brackish water separator 20 and the upstream side of the boiler, after stopping the operation of the boiler, as shown in FIGS. A temporary pipe 26 is provided so as to bypass 25, and a temporary circulation pump 27 is provided in the temporary pipe 26. The temporary pipe 26 is connected to the downstream side of the water supply valve 1 a in the water supply pipe 1.

  In addition, a temporary water filling pipe 41 is connected to the communication pipe 35, and a temporary water level meter 42 for detecting the water level in the primary superheater 40 is provided in the communication pipe 35.

  A chemical solution can be supplied to the brackish water separator 20 from a chemical solution tank (not shown) via a temporary cleaning chemical solution supply pipe.

  Further, a temporary supply pipe 64 for cleaning water (pure water such as pure water) having a valve 63 is connected to the main steam pipe 61 on the upstream side of the main steam stop valve 62. Further, a temporary drain pipe 1c having a valve 1b is connected to the water supply pipe 1 downstream of the water supply valve 1a.

  After the boiler operation is stopped, the temperature of the primary superheater 40 in the rear flue is lowered to about 100 ° C. or less, and then the primary superheater 40 is filled with water as shown in FIG. At this time, the main steam stop valve 62 is at a temperature higher than 100 ° C.

  Next, the valves 1a, 23, 25 and the valve 1b of the drain pipe 1c are closed, and after adding the cleaning chemical to the brackish water separator 20, the temporary circulation pump 27 is operated. Then, as shown in FIG. 1, the cleaning liquid in the brackish water separator 20 is drained tank 21, temporary pipe 26, water supply pipe 1, economizer 2, peripheral wall pipe 10 of furnace 9 and upper water-cooled pipe wall 12 or nose wall pipe 105. , The header 104 or 106 and the header 13 are circulated to the brackish water separator 20. During this time, the brackish water separator 20, the drain tank 21, the economizer 2, the wall pipes 10, 12, 105 and each header are chemically Washed.

  While this chemical cleaning is continued for a predetermined time, the temperature of the main steam stop valve 62 becomes 100 ° C. or lower. Therefore, after stopping the temporary circulation pump 27, the main steam stop valve 62 is closed, and as shown in FIG. 2, cleaning water (fresh water) is supplied from the supply pipe 64 to the main steam pipe 61, and the superheat pipes 60, 50, 40 are supplied. Then, the washing water is caused to flow backward to the brackish water separator 20 through the wall pipe 33 and the ceiling wall 30. A part of the washing water flowing back to the brackish water separator 20 flows out from the brackish water separator 20 through the drain tank 21 to the drain pipe 1c. The remaining portion of the washing water that has flowed back to the brackish water separator 20 is drained through the wall pipes 12 and 10 of the furnace 9, the nose wall pipe 105, the header 103, the descending pipe 3, the economizer 2, and the water supply pipe 1. It flows out from 1c.

  After the extrusion of the cleaning chemical remaining in the system is completed, after rust prevention and blowing, the temporary piping is removed, normal water washing and startup operations are performed, and the boiler operation is resumed.

  According to this cleaning method, chemical cleaning of the brackish water separator 20, the drain tank 21, the wall tube of the furnace 9, the economizer 2, etc. can be started before the main steam stop valve 62 becomes 100 ° C. or less. The construction period can be shortened accordingly. When the inventor actually performed the work, it took 11 days until the main steam stop valve cooled to 100 ° C., and the chemical cleaning work was started after the 12th day after the boiler stopped. According to the method of the present invention, chemical cleaning can be started on the 11th day, the work period can be shortened by one day, the boiler can be reactivated one day earlier, and the operating efficiency of the boiler is improved.

  In the above embodiment, the primary superheater 40 is filled with water, but a rear flue pipe other than the primary superheater 40 may be used.

DESCRIPTION OF SYMBOLS 1 Water supply pipe 2 Eco-saving device 9 Furnace 20 Steam separator 21 Drain tank 24 Recirculation pump 27 Temporary recirculation pump 40, 50, 60 Superheater 42 Temporary water level gauge 61 Main steam pipe 62 Main steam stop valve

Claims (4)

Superheats the economizer with which the water supply is introduced by the water supply pipe, the furnace having the wall pipe into which the water from the economizer is introduced, the brackish water separator connected with the wall pipe, and the steam from the brackish water separator A method of chemically cleaning a boiler having a superheater, a drain tank for receiving water from a brackish water separator, and a pump and piping for circulating water in the drain tank to the water supply pipe,
In the method of chemically cleaning the brackish water separator and the furnace side of the separator,
After performing water filling in the uppermost stream part of the superheat line, a circulation step of circulating a cleaning chemical to the brackish water separator and the furnace side, and
Thereafter, a boiler chemical cleaning method comprising: an extrusion step of supplying clean water for extrusion to a main steam pipe and extruding a cleaning chemical solution. In claim 1, when performing water filling to the most upstream part of the superheat line, the temperature of the main steam stop valve provided in the main steam pipe is higher than 100 ° C,
A chemical cleaning method for a boiler, wherein the temperature of the main steam stop valve is 100 ° C or lower when performing the extrusion step. In Claim 1 or 2, in order to perform the said circulation process, the temporary recirculation pump which bypasses the recirculation pump of a boiler is provided,
In order to perform the water filling, a temporary water filling pipe and a temporary water level meter for water filling water level detection are provided.   4. The chemical cleaning of a boiler according to claim 1, wherein the superheat line includes a plurality of superheaters arranged in series, and the water filling is performed on the superheater on the most upstream side. 5. Method.

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