JPS6051023B2 - Corrosion prevention equipment for power plants - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corrosion prevention device for condensate cooling pipes in a power plant where pH management (control) of condensate and feed water is performed using a volatile alkaline water treatment agent.

This type of power generation Plato, which has already been proposed, has a high-pressure turbine 1 and a low-pressure turbine 2, as shown in FIG.
The steam that has completed its work is returned to the condenser 3, where it exchanges heat with cooling water (seawater) to generate condensate, and at this time, approximately 45% of the ammonia contained in the steam is The air is transferred to an air extractor 4 attached to the condenser 3 through a connecting pipe 5.

Furthermore, about 10% of this 45% ammonia amount is gasified and released into the atmosphere from the atmosphere discharge pipe 6. Therefore, the remaining amount of ammonia, about 35%, is returned to the condenser 3 together with the drain through a drain pipe (recovery pipe) 8 equipped with a drain valve 7. In addition, the insufficient amount (10%) of ammonia that has been reduced by being gasified and released into the atmosphere is transferred from the ammonia storage tank 9 connected to the supply pipe 11 to the ammonia injection pump 10 in the condenser 3. It is designed to be replenished by injecting it into the outlet side 13a of the condensate pump 13 of the condensate pipe system 12.

In this way, the condensate containing ammonia is transferred to each of the low pressure feed water heaters (also referred to as low pressure heaters) 14a, 14b) disposed in the condensate pipe system 12), the deaerator 19, and the water supply pipe system 1.
The water is supplied to the boiler 18 while being heated through a water supply pump 16 provided at 5 and high pressure water heaters (also referred to as high pressure heaters) 17a and 17b.

Here, the condensate (feed water) is generated into steam, and the main steam pipe 2
0 to a high-pressure turbine 1 and a low-pressure turbine 2, which drive the high-pressure turbine 1 and low-pressure turbine 2 to rotate a generator (not shown). However, in the power plant described above, since the ammonia contained in the air extractor 4 is recovered into the condenser 3 again, the ammonia concentration in the condenser 3 becomes high.
Copper elution from the large number of copper pipes as condensate cooling pipes incorporated in the condenser 3 increases significantly, and as a result, the condensate cooling pipes are corroded and damaged over time. This not only impairs the function of the condenser 3 and lowers the operating efficiency of the power plant, but also has disadvantages such as wasteful release of ammonia from the air extractor 4 into the atmosphere. On the other hand, in general, power generation plants use ammonia solution to control pH ( P
H control), deoxygenation is performed by degassing and injection of hydrazine.

In particular, PH control using the ammonia solution is controlled at a PH concentration as high as possible in consideration of corrosion protection of steel piping and heat exchanger tubes.

As a result, the condensate cooling pipes that return the steam that has finished its work in the turbines 1 and 2 to the condenser 3 in power plants are mainly made of aluminum brass from the standpoint of heat transfer (thermal conductivity) and economy. A polished copper alloy is used.

On the other hand, in the air cooling pipe system where non-condensable gases gather, the ammonia concentration in the steam approaches approximately 100%, which causes an ammonia attack phenomenon in the condensate pipe system and water supply pipe system. , there is a risk of a condenser cooling pipe leakage accident.

That is, when this is expressed as a chemical reaction formula for a tube made of copper material (Cu), it is as follows.

This chemical reaction formula shows that dissolved oxygen as well as ammonia concentration plays a large role in the corrosion of copper pipes.

Therefore, as a means to prevent the ammonia attack phenomenon that has been implemented so far, the cooling pipe of the air cooling section is made of a material with excellent ammonia resistance, such as a cupronickel or titanium pipe.

In particular, titanium tubes are a material with extremely excellent corrosion resistance, and by using them, ammonia attack phenomenon in the air cooling section can be prevented. However, recently, an ammonia attack phenomenon has also occurred in the tubes near the air cooling section. Therefore, as a means to prevent this ammonia attack phenomenon, it may be possible to reduce the amount of ammonia injected, but this would conversely result in a decrease in pH due to ammonia in the condensate and water supply pipe system. This may cause inconveniences such as increasing the amount of iron eluted, which had been suppressed until now.

On the other hand, as a countermeasure to these problems, the use of titanium tubes may be considered, but this not only increases the cost but also reduces the heat transfer efficiency of the titanium tubes and reduces the condensing capacity of the condenser 3. There are other difficulties.

Therefore, as a result of chemical analysis of the ammonia attack phenomenon in condensate and water supply pipe systems, the present inventor found that
It was discovered that the drain of the air extractor 4 attached to the tank had a large effect on the ammonia attack phenomenon.

That is, as shown in Table 1, when the drain from the air extractor 4 is collected into the condenser 3. When the pH of the condensate is 9.2, the ammonia concentration is 0.86 ppm, and the amount of copper eluted is 3 to 5 ppb.

Further, when the pH of the drain of the air extractor 4 is 10.9, the ammonia concentration is 1000 ppm, and the copper is
It was found that the amount was 10 to 18 ppb. On the other hand, when the drain from the air extractor 4 is collected into the condensate pipe system, when the pH of the condensate is 8.9, the ammonia concentration is 0.6.
The amount of copper eluted is 4 ppm, and the amount of copper eluted is 1 to 2 ppb.
Further, when the pH of the drain of the air extractor 4 is 10.6, the ammonia concentration is 700 ppm, and the amount of copper eluted is 3 to 4 ppb.

That is, as described above, by changing the collection of drain from the air extractor 4 from the condenser 3 to the condensate pipe system 12, the ammonia concentration in the condensate can be reduced.

As a result, the amount of copper eluted is also reduced, and the ammonia attack phenomenon can be suppressed as much as possible. moreover,
When the drain from the upper air extractor 4 is collected into the condensate pipe system 12, the amount of ammonia transferred to the air extractor 4 is reduced. The amount of ammonia gas released into the atmosphere through the atmosphere discharge pipe 6 can also be eliminated. In order to reduce the ammonia attack phenomenon in the condenser cooling pipe in this way, it is optimal to change the collection location of the drain from the air extractor 4 from the condenser 3 to the condenser pipe system 12. It has been found.
The present invention has been made in view of the above-mentioned circumstances, and includes providing a recovery pipe in an air extractor attached to a condenser, and connecting one end of the recovery pipe to the condensate pipe system of the condenser. This is a power generation plant whose purpose is to reduce the ammonia attack phenomenon, prevent corrosion of condensate cooling pipes, and at the same time reduce the use of ammonia and save ammonia labor. There are some that provide corrosion protection equipment.
Hereinafter, the present invention will be described with reference to an illustrated embodiment. It should be noted that the present invention will be described with the same reference numerals attached to the same constituent members as in the above-described specific example. In Fig. 2, reference numeral 3 is a condenser in the power generation Plato, which uses an alkaline water treatment agent to manage the pH of condensate and feed water. A container 4 is attached via a connecting pipe 5, and an atmospheric discharge pipe 6 for discharging gasified ammonia is installed in this air extractor 4.

Further, one end of a recovery pipe 22 equipped with an injection pump 21 for injecting condensate is connected to the air extractor 4, and each branch pipe 22a, 2 divided into two from the middle is connected to this recovery pipe 22.
2b is provided. And this one branch pipe 22a
is the condensate pump 1 of the condensate pipe system 12 via the on-off valve 23
3, and the other branch pipe 22b
is connected to the outlet side 14b1 of the low-pressure feedwater heater 14b of the condensate pipe system 12 via the on-off valve 24. Therefore, when the steam that has completed its work in the high pressure turbine 1 and the low pressure turbine 2 flows into the condenser 3, about 33% of the ammonia contained in the steam flowing into the condenser 3 is transferred to the air extractor 4. to move to.

In this step, approximately 8% of the ammonia gas is discharged into the atmosphere through the atmosphere discharge pipe 6. Approximately 25% of the ammonia contained in the drain of the air extractor 4 is transferred as drain from the recovery pipe 22 to the condensate pipe system 1 by the injection pump 21.
2 will be collected. In particular, in the case of a heat exchanger tube made of a copper alloy, the condensate pipe system 12 is preferably the outlet side 14b1 of the low pressure feed water heater 14b, and in the case of a heat exchanger tube made of a steel pipe, the drain recovery port is preferably a condensate pipe system 12 connected to the outlet side 14b1 of the low pressure feed water heater 14b. The inlet side of the vessel 14a, that is, the outlet side 13a of the condensate pump 13 is desirable.

In this way, by collecting the condensate of the air extractor 4 through the recovery pipe 22 into the condensate pipe system 12, the condenser 3
The ammonia concentration inside is approximately 2
It is possible to reduce the amount of copper to about 5%, reduce the amount of copper eluted to 112% or less, and improve the ammonia attack resistance effect.

Incidentally, although the present invention has been described with reference to a specific example of a thermal power plant, since steam is injected into the combustion chamber of a gas turbine for NOx countermeasures, the amount of make-up is larger than in conventional power plants. Moreover, the design can be freely changed so that it can be used for a combined cycle power generation plant that combines a gas turbine and a steam turbine equipped with a condenser into which a large amount of dissolved oxygen flows.

As described above, according to the present invention, in a power generation plant where the pH of condensate and feed water is managed using an alkaline water treatment agent, an air extractor is attached to the condenser, and Since the recovery pipe equipped with an injection pump is connected to the condensate pipe system of the condenser, it is possible to significantly reduce the ammonia attack phenomenon and prevent corrosion of the condensate cooling pipe. It is possible to reduce the amount of ammonia used and save labor, and the configuration is simple.
It can be easily integrated into existing power plants.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a power plant that has already been proposed, and FIG. 2 is a system diagram of a corrosion prevention device for a power plant according to the present invention. 1... High pressure turbine, 2... Low pressure turbine, 3... Condenser, 4... Air extractor,
12... Condensate pipe system, 13... Condensate pump, 14a, 14b... Low pressure feed water heater, 17
a, 17b...High pressure feed water heater, 18...Boiler, 19...Deaerator, 22...Recovery pipe, 22a, 22b...Branch tube.

Claims (1)

[Claims] 1. In a power generation plant in which the pH of condensate and feed water is controlled using a water treatment agent, an air extractor is attached to the condenser, and an injection pump installed in the air extractor is provided. A corrosion prevention device for a power generation plant, characterized in that one end of a recovery pipe is connected to a condensate pipe system of the condenser. 2 The recovery pipe is divided into two branch pipes equipped with on-off valves, and one branch pipe is connected to the outlet side of the condensate pump of the condensate pipe system, and the other branch pipe is connected to the outlet side of the condensate pump of the condensate pipe system. The corrosion prevention device for a power generation plant according to claim 1, wherein the corrosion prevention device is connected to the outlet side of the low pressure feed water heater.