JP7119898B2 - Boiler chemical cleaning method - Google Patents

Description

The present invention relates to a method of chemically cleaning a boiler, and more particularly to a method of chemically cleaning a steam separator and a furnace side thereof.

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

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

In the main steam pipe of such a thermal power boiler, a temporary pipe that circulates a chemical cleaning solution is installed at the cut part of the main steam pipe and the main steam shutoff valve, and a cleaning chemical solution containing polyaminocarboxylic acid etc. is circulated for chemical cleaning. A method for doing so is known (Patent Document 1).

When chemically cleaning only the steam separator and the furnace side of the boiler, the liquid temperature during cleaning is as high as 80 to 98 ° C, and vapor and splashes containing cleaning chemical components flow into the superheater side. In order to prevent this, as shown in FIG. 2, which will be described later, the superheater (non-washed part) and the main steam pipe are filled with pure water (ion-exchanged water) to which hydrazine and ammonia are added. The separator and the furnace side are chemically cleaned.

The method of filling the superheater (non-cleaned part) is to cut the main steam pipe drain pipe, etc., which is the end of the non-cleaned part, install a temporary pipe, and use a temporary pump, etc. to move the main steam pipe → final superheater → secondary Water is filled up to the steam separator, which is the boundary line with the washing section, through the superheater → the primary superheater.

When filling the superheater and main steam pipe with water, the temperature of the pipe material of the main steam pipe and the temperature of the main shutoff valve are lowered to 200°C or less, especially to 100°C or less before filling with water. If water is filled when the temperature exceeds 200°C, the steam oxide scale will peel off due to the difference in thermal contraction rate between the pipe material and the steam oxide scale. This is because the main shut-off valve may be rapidly cooled and the material may be adversely affected.

JP-A-64-23096

As described above, when the superheater and the main steam pipe are filled with water when the steam separator and the furnace side are chemically washed, the temperature of the main steam pipe and the main stop valve is 200°C or less, particularly 100°C. Since it is necessary to wait until the temperature cools down to ℃ or less, the cleaning period is lengthened.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for chemically cleaning a boiler that can shorten the construction period for chemically cleaning a steam separator of a boiler and the furnace side thereof.

The boiler chemical cleaning method of the present invention comprises an economizer to which feed water is introduced through a feedwater pipe, a furnace having wall pipes to which water from the economizer is introduced, and a steam separator to which the wall pipes are connected. and a superheater for superheating steam from the steam-water separator, a drain tank for receiving water from the steam-water separator, and a pipe for circulating the water in the drain tank to the water supply pipe. In the method of chemically cleaning the steam separator and the furnace side thereof, water is not enclosed in the superheating line and an expandable balloon is inserted into the connecting pipe at the outlet of the steam separator. It is characterized by separating the gas phase of the steam-water separator and the superheating line, and circulating the cleaning chemical to the steam-water separator and to the furnace side.

In one aspect of the present invention, an expandable balloon is inserted into the connecting pipe at the most upstream portion of the superheating line, inflated with air or an inert gas to seal the connecting pipe, and passed through the connecting pipe to the superheating line. Prevents entry of hot chemical vapors during chemical cleaning.

In one aspect of the present invention, the most upstream part of the superheating line is provided with a plurality of connecting pipes, and the balloon is inserted into each connecting pipe and sealed.

In the present invention, it is desirable that the temperature of the main steam pipe and the main stop valve provided in the main steam pipe is higher than 100° C. when the circulation of the cleaning chemical is started.

In the boiler chemical cleaning method of the present invention, the steam separator and the furnace side are chemically cleaned while supplying air or inert gas to the most upstream part of the superheating line. Chemical cleaning can be started without waiting until the temperature of the valve drops to 200° C. or less, particularly 100° C. or less, and the cleaning period can be shortened.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram explaining the chemical cleaning method of the boiler which concerns on embodiment. FIG. 3 is a block diagram illustrating a chemical cleaning method for a boiler according to a conventional example; It is a sectional view of a boiler. It is a system diagram of a boiler apparatus. FIG. 4 is a cross-sectional view showing a connecting tube and a balloon;

FIG. 3 shows an example of a boiler to which the cleaning method according to the embodiment of the invention can be applied. A water supply system diagram of the boiler is shown in FIG.

This boiler includes a furnace 9, a downstream exhaust gas flow path (rear flue), and an upstream exhaust gas flow path connecting the upper portion of the furnace 9 and the downstream exhaust gas flow path.

High-temperature combustion gas generated from a plurality of burners 80 provided in the lower portion of the furnace 9 rises inside the furnace 9 . The combustion gas passes through the upstream exhaust gas flow path and the downstream exhaust gas flow path and is discharged from the flow path outlet 93 as exhaust gas to the outside of the boiler. A water-cooled lower peripheral wall tube 10 , an upper water-cooled wall tube 12 and a nose wall tube 105 are provided in the furnace 9 . In this embodiment, the water-cooled lower peripheral wall pipe 10 extends upward from the lower portion of the furnace 9 in a spiral manner inside the furnace 9 . The upper water wall pipes 12 consisting of a plurality of pipes each extend vertically in the furnace 9 toward the upper part of the furnace 9 . The nose tube 105 also consists of multiple tubes.

The rear flue is defined by a rear heat transfer wall 33 or the like which consists of a plurality of tubes. The rear flue is divided into two gas channels by a dividing wall 120 which extends along the exhaust gas flow. The dividing wall 120 also consists of a plurality of tubes.

A reheater 71 is arranged in one of the gas divisions of the rear flue, and a primary superheater 40 and an economizer 2 are arranged in the other gas division. Also, an evaporator may be provided in the divided gas flow path as required.

The rear flue is defined by a ceiling wall 30 made up of a plurality of tubes, side walls and the like. A secondary superheater 50 and a tertiary superheater 60 are arranged in the upstream exhaust gas passage. A quaternary superheater may also be installed.

Next, the water supply system of this boiler will be described. Feedwater to the boiler is first supplied to the economizer 2 from the feedwater pipe 1 having the high-pressure feedwater heater 1h (FIG. 1) and the feedwater 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 flows from the economizer outlet header 101 to the water wall downcomer. 3. The water that has passed through the water-cooled wall descending pipe 3 is distributed to the water-cooled wall lower header 103 and rises through the water-cooled wall lower peripheral wall pipe 10 spirally surrounding the furnace 9 while absorbing the heat inside the furnace 9 . 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 its temperature is homogenized, and then the upper water-cooling wall provided in the upper part of the furnace 9. It absorbs heat in the furnace 9 while ascending the tube 12 or the nose wall tube 105 and becomes a mixed fluid of high temperature water in the liquid phase and steam in the gas phase. This mixed fluid flows from the water wall upper header 104 or the nose wall header 106 into the furnace 9 upper fluid mixing header 13 to equalize the fluid temperature. It flows into the steam separator 20 and is separated into steam and water. The separated water is recirculated from the drain tank 21 to the water supply pipe 1 via the boiler circulation pump 24 and the circulation pipe 22 having the valves 23 and 25 . Also, the steam separated by the steam 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 pipes constituting the ceiling wall 30 provided from the upper part of the furnace 9 to the upper part of the downstream exhaust gas flow path, and passes through the ceiling wall outlet header 108. , it is heated by heat absorption and becomes saturated steam.

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

The saturated steam gathered at the rear heat transfer wall rear wall outlet header 34 flows through the primary superheater connecting pipe 35 into the primary superheater 40 installed in the rear flue, and then installed at the upper part of the furnace 9. After being superheated in sequence through a secondary superheater 50 and a tertiary superheater (final superheater in this embodiment) 60, it is sent to the high-pressure turbine via a main steam pipe 61 and a main block valve 62.

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

In one aspect of chemically cleaning the steam separator 20 of the boiler and the upstream side thereof, after stopping the operation of the boiler, as shown in FIG. A temporary pipe 26 is provided so as to bypass 23 and 25, and a temporary circulation pump 27 is provided in the temporary pipe 26. - 特許庁The temporary pipe 26 is connected to the economizer 2 side of the water supply pipe 1 rather than the water supply valve 1a. If the recirculation pump 24 can be activated during chemical cleaning, the chemical cleaning can be performed only with the recirculation pump 24 without providing the temporary recirculation pump 27 .

Also, a stretchable balloon 45 is inserted into the connecting pipe 44 using an inspection hole or the like, and is inflated with air or inert gas. The material of the balloon is exemplified by rubber containing fiber reinforcing material.

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

A temporary supply pipe 64 for cleaning water (clean water such as pure water) having a valve 63 is connected to the drain pipe of the main steam pipe 61 on the upstream side of the main block valve 62 . Further, a temporary drain pipe 1c having a valve 1b is connected to the temporary pipe 26 or the water supply pipe 1 on the downstream side of the water supply valve 1a.

After the operation of the boiler is stopped, the temperature of the connecting pipe 44 at the outlet of the steam separator is lowered to 200° C. or less, particularly 100° C. or less, and then an elastic balloon 45 is inserted into the connecting pipe 44 and inflated as shown in FIG. be. At this time, the temperature of the main steam pipe 61 or the main stop valve 62 is higher than 200°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 steam separator 20, the temporary circulation pump 27 is activated. Then, as shown in FIG. 1, the cleaning liquid in the steam separator 20 is the drain tank 21, the temporary pipe 26, the water supply pipe 1, the economizer 2, the peripheral wall pipe 10 of the furnace 9, and the upper water cooling pipe wall 12 or nose wall pipe 105, the header 104 or 106, and the header 13 to the steam-water separator 20, the steam-water separator 20, the drain tank 21, the economizer 2, the wall pipes 10, 12, 105 and each pipe The feed is chemically cleaned.

While continuing this chemical cleaning for a predetermined time, the temperature of the main steam pipe 61 and the main stop valve 62 becomes 200° C. or less, particularly 100° C. or less. Therefore, the temporary circulation pump 27 is stopped, the main block valve 62 is closed, and the balloon 45 in the steam separator outlet connecting pipe 44 is removed. may be supplied, and washing water may flow back to the steam separator 20 through the superheater pipes 60, 50, 40, the wall pipe 33, and the ceiling wall 30 to wash the steam system. Part of the wash water that has flowed back to the steam separator 20 flows out from the steam separator 20 through the drain tank 21 and into the drain pipe 1c. The rest of the wash water flowing back into the steam separator 20 is discharged through the wall pipes 12 and 10 of the furnace 9, the nose wall pipe 105, the header 103, the downcomer pipe 3, the economizer 2, and the water supply pipe 1. out of tube 1c.

After the cleaning chemicals remaining in the system are pushed out, rust prevention and blowing are performed, the temporary piping is removed, normal water washing and starting operation are performed, and the operation of the boiler is resumed.

According to this cleaning method, the steam separator 20, the drain tank 21, the wall pipe of the furnace 9, the economizer 2, etc. are chemically cleaned before the temperature of the main steam pipe 61 and the main shutoff valve 62 becomes 100° C. or less. can be started, and the construction period can be shortened accordingly.

The method for chemically cleaning a boiler according to the present invention has been described above based on the embodiment shown in FIG. Not even. For example, the nose wall tube 105 may be omitted, and the water-cooled lower peripheral wall tube 10 may extend upward from the lower portion of the furnace 9 substantially vertically.

[Comparative example]
FIG. 2 shows a case where a conventional cleaning method is applied to the boiler of FIG. In this conventional method, after the temperature of the main steam pipe 61 and the main block valve 62 is lowered to 100° C. or less, the superheaters 40, 50, 60 (non-cleaning portions) and the main steam pipe 61 are filled with pure water containing hydrazine and ammonia. (Ion-exchanged water) is filled, and then the steam separator 20, the evaporator tube of the furnace 9, the economizer 2, etc. are chemically washed.

The method of filling the superheaters 40, 50, 60 (non-washed parts) with water is through the main steam pipe 61 → final superheater 60 → secondary superheater 50 → primary superheater 40 using a temporary pump 64a and a temporary supply pipe 64. , water is filled up to the steam separator 20, which is the boundary line with the washing section.

In this case, the main steam pipe 61 and the main block valve 62 cannot be filled with water until the temperature drops to 200° C. or less, especially 100° C. or less, and chemical cleaning cannot be performed until after that.

1 water supply pipe 2 economizer 9 furnace 20 steam separator 20a steam separator air vent 21 drain tank 24 recirculation pump 27 temporary recirculation pump 40, 50, 60 superheater 42 temporary water level gauge 44 connecting pipe 45 balloon 61 main Steam pipe 62 Main block valve

Claims (2)

An economizer into which feed water is introduced through a water supply pipe, a furnace having a wall pipe into which water from the economizer is introduced, a steam separator connected to the wall pipe, and steam from the steam separator A method for chemically cleaning a boiler having a superheater that overheats, a drain tank that receives water from a steam-water separator, and a pipe that circulates the water in the drain tank to the water supply pipe, the steam-water separation In the method of chemically cleaning the vessel and the furnace side thereof,
Without encapsulating water in the superheating line, an expandable balloon is inserted into the connecting pipe at the outlet of the steam separator and inflated to separate the gas phase of the steam separator and the superheating line, and A chemical cleaning method for a boiler, characterized by circulating a cleaning chemical to the furnace side. 2. The method of chemically cleaning a boiler according to claim 1, wherein the temperature of the main steam pipe and the main stop valve provided in the main steam pipe is higher than 100[deg.] C. when the circulation of the cleaning chemical is started.

Images