JP2001090904A - Rust preventing unit for heat exchanger of boiler plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rust preventing unit for a boiler plant preventing the increase in the corrosion and rusting of a thermal storage medium of a heat exchanger by preventing the intrusion of outside air into the inside of a plant when the plant is stopped and enabling to save the fuel consumption at the restart of the boiler. SOLUTION: A boiler plant stores heat from an exhaust gas in the heat storage medium of a heat exchanger 3 by introducing the exhaust gas from a boiler 1, exhausts the exhaust gas through a chimmey 5 into the air after dust collection processing by an electric precpitator 4, simultaneously introduces the outside air into the air side 3b of the heat exchanger 3, preheats the air by the heat stored in the heat storage medium and supplies the air to the boiler 1, wherein a damper 11 is arranged to a bypass duct 10 installing the bypass duct 10 in the lower part of the chimmey 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rust prevention device for a heat exchanger in a boiler plant used for a power plant or the like.

[0002]

2. Description of the Related Art A conventional boiler plant of this type, as shown in FIG. 2, performs a denitration treatment of an exhaust gas from a boiler 1 by a denitration device 2 as required, and then a gas in an air preheater, that is, a heat exchanger 3. The heat is introduced into the side 3a, and heat from the exhaust gas is stored in the heat transfer element (heat storage material) of the heat exchanger 3, and then the dust is collected by the electric dust collector 4 and discharged from the chimney 5 to the atmosphere. On the other hand, the combustion air of the boiler 1 is
Outside air is introduced from the air supply fan 6 to the air side 3 b of the heat exchanger 3, preheated by the heat stored in the heat transfer element, and supplied to the boiler 1. 7 is an auxiliary preheater.

[0003] By the way, the boiler plant of the above-mentioned type is usually stopped during regular inspections. However, in recent years, due to the balance between supply and demand of electric power and the like, the operation is performed on a daily, weekly, or several-weekly basis. It has been increasingly stopped.

[0004] When the boiler plant is stopped, the outside air enters the plant due to the ventilation force of the chimney 5 (normally about 10 mmAq), the whole plant is cooled, and a large amount of fuel is required at restart. For this reason, a method (banking) of closing the inlet damper 8 and the outlet damper 9 of the plant to prevent the intrusion of outside air, delaying the cooling of the plant, and reducing the fuel consumption at the time of restart is adopted. However, even if the inlet damper 8 and the outlet damper 9 are closed, there is a damper leak of several percent, and it is not possible to completely prevent the outside air from entering due to the ventilation power of the chimney 5.

[0005] If dust in exhaust gas containing sulfur such as sulfuric acid or ammonium sulfate adheres to the heat transfer element of the heat exchanger 3, moisture absorption / condensation starts when the relative humidity of the invading outside air is about 60%. Into a corrosive environment. Such moisture absorption / condensation selectively occurs particularly on the heat transfer element stopped on the air side 3b of the heat exchanger 3. If corrosion progresses and rusts due to condensation, not only will the life of the heat transfer element be shortened, but if corrosion further progresses, the rust will separate from the base material and cause rust, resulting in a narrow flow path. As a result, the pressure loss increases, and in some cases, it becomes difficult to start up the plant. Further, as a result of the floating rust being firmly held between the heat transfer elements, it becomes very difficult to remove the rust with a soot blower. Further, as described above, since the rust is concentrated on the heat transfer element located on the air side 3b, the pressure loss not only changes cyclically every half cycle of rotation, but also, in particular, the horizontal axis type. Rotational imbalance occurs in the heat exchanger.

[0006] Further, if there is a large amount of intruding outside air, a large amount of dehumidified dry air is required for dry storage, and if this dry air is insufficient, low humidity cannot be maintained. Since the amount of intruding outside air varies depending on the temperature difference between the ground and the sky, the wind speed, and the like, in addition to the height of the chimney, the existing entrance / exit dampers 8 and 9 cannot handle the situation.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to prevent outside air from entering the inside of a plant when the plant is stopped. Heat storage material for heat exchangers (heat transfer elements, etc.)
It is an object of the present invention to provide a rust prevention device for a heat exchanger in a boiler plant, which can prevent an increase in corrosion and rust of a fuel cell and reduce a fuel consumption required for restarting.

[0008]

The rust prevention device for a heat exchanger in a boiler plant according to the present invention introduces exhaust gas from a boiler to the gas side of the heat exchanger and transfers heat from the exhaust gas to the heat exchanger. Heat is stored in the heat storage material, and then the dust is collected by an electric dust collector and discharged into the atmosphere from the chimney.
As boiler combustion air, outside air is introduced into the air side of the heat exchanger, preheated by the heat stored in the heat storage material, and supplied to the boiler in a boiler plant. And a damper is provided in the bypass duct.
It is also characterized in that the opening of the damper is variable.

Further, the rust prevention device for a heat exchanger in a boiler plant according to the present invention introduces exhaust gas from a boiler to the gas side of a heat exchanger and stores heat from the exhaust gas in a heat storage material of the heat exchanger. Then, the dust is collected by an electric dust collector and discharged from the chimney into the atmosphere, and outside air is introduced into the air side of the heat exchanger as combustion air for the boiler, and heat is stored in the heat storage material. In a boiler plant that is preheated by the generated heat and supplied to the boiler, a bypass duct is installed in an exhaust gas duct downstream of the heat exchanger on the gas side, and a damper is provided in the bypass duct. It is also characterized in that the opening of the damper is variable.

Further, the rust prevention device for a heat exchanger in a boiler plant according to the present invention introduces exhaust gas from a boiler to the gas side of a heat exchanger and stores heat from the exhaust gas in a heat storage material of the heat exchanger. Then, the dust is collected by an electric dust collector and discharged from the chimney into the atmosphere, and outside air is introduced into the air side of the heat exchanger as combustion air for the boiler, and heat is stored in the heat storage material. Preheated by the heat
In the boiler plant for supplying the boiler, a damper is provided in an exhaust gas duct downstream of the heat exchanger on the gas side. It is also characterized in that the opening of the damper is variable.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, boiler 1, denitration device 2, heat exchanger 3, electric precipitator 4, chimney 5, air supply fan 6, auxiliary preheater 7, inlet damper 8
The structure and operation of the outlet damper 9 are the same as those of the conventional device shown in FIG.

A bypass duct 10 is installed below the chimney 5. A damper 11 is provided in the bypass duct 10. A bypass duct 12 is installed in the exhaust gas duct 13 connected from the electric precipitator 4 to the chimney 5 in a bypass manner.
The bypass duct 12 is also provided with a damper 14. These dampers 11 and 14 have a structure in which the degree of opening can be freely controlled. In addition, a plurality of combinations of these bypass ducts 10, 12 and dampers 11, 14 can be installed at various locations for each purpose, and the damper at the target position can be selected and operated arbitrarily to control the entry point of the outside air freely. It is.

When the plant is stopped, these dampers 1
When the ducts 1 and 14 are opened, the bypass ducts 10 and 12 having a small pressure loss and a large draft difference due to the ventilation force of the chimney 5.
Since the outside air is positively sucked from the outside, there is almost no possibility that the outside air enters the inside of the plant. When the size of the damper opening is 1.5 m, suction is performed at about 8 m / sec.
The restart is only required for a short time to close the dampers 11 and 14, and the startup can be performed as usual.

Although the dampers 11 and 14 become closing dampers at the time of plant operation, the draft difference is almost zero or slightly positive. Therefore, a damper having a particularly good leak performance is not required. In some situations, the use of a closure plate is desirable.

Reference numeral 15 denotes a damper, which is installed at an appropriate position in the exhaust gas duct 13. The damper 15
From the gas side 3a of the heat exchanger 3 to the electric precipitator 4
May be installed at an appropriate position of the exhaust gas duct 16 connected to the exhaust gas duct 16. In short, the installation area of the damper 15 is
As long as it is an exhaust gas duct in the downstream area of the heat exchanger 3, it may be provided at any place, or a plurality of exhaust ducts may be provided.

The damper 15 also has a structure in which the degree of opening can be freely controlled. The operation of closing the damper 15 causes the exhaust gas duct 13 downstream of the heat exchanger 3 to be closed.
Or 16 is shut off directly. By directly shutting off the duct 13 or 16, the inflow outside air is reduced by improving the leak performance as compared with the existing damper 9, and the inflow of outside air is further reduced at the time of banking by a synergistic effect with the existing damper 9. .

In the present embodiment, only the closing operation of the damper 15 is required in a short time, and the normal startup can be easily performed. The bypass damper 1 of the above embodiment
Contrary to 1 and 14, the leakage performance at the time of stopping (closing) is important, so for example, a guillotine damper or the like is preferably used.

In any of the embodiments, since almost no outside air enters the inside of the plant, the cooling of the apparatus after the stop of the plant is delayed, the banking effect can be maintained for a long time, and there is almost no outside air after the cooling. , Moisture absorption
No condensation occurs. Also, in the dry storage method by sending dehumidified dry air, there is almost no invasion outside air, so the amount of dry air can be reduced, and the allowable range of the outside air fluctuation becomes small. Can be.

The opening degree of the dampers 11, 14, 15 is adjusted, or the dampers 11, 14, 1, at the target position are adjusted.
By selecting 5, besides preventing the above-mentioned outside air from entering, when working inside the ducts 13 and 16, when taking in some outside air or when the relative humidity of the outside air is sufficiently low and dry. In such a case, when it is determined that it is better to introduce the outside air, ventilation in the duct can be allowed at an appropriate opening degree, that is, a flow rate and an inflow point depending on the situation.

Further, a combination with a control system, for example,
The system detects the relative humidity inside and outside the duct and the temperature inside the duct, automatically controls the target position damper and its opening, and controls the appropriate ventilation area and ventilation force.

[0021]

Advantages of the Invention 1) When the plant is stopped, by preventing the outside air from entering the inside of the plant due to the ventilation power of the chimney, it is possible to prevent moisture from adhering to the elements of the heat exchanger, especially to the element when the outside air has high humidity. The generated dew can be prevented, and increase and rust of corrosion of the element can be effectively prevented. 2) By reducing the cooling rate of the entire plant due to the reduction of intrusion outside air, the state of the elements of the heat exchanger above the atmospheric temperature can be maintained for a long time, and if the plant is shut down for a short time, the whole plant needs to be restarted. The fuel consumption can be reduced. 3) When the element is stored in a dry state using the dehumidified dry air, the amount of air to be blown can be greatly reduced by reducing the invasion outside air, and the quality of the storage is improved because the air flow is not affected by the fluctuation of the ventilation force. 4) In development, the opening degree of the damper can be automatically controlled in combination with the control system, so that the ventilation location and the ventilation force can be appropriately controlled.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a conventional plant device.

[Explanation of symbols]

 DESCRIPTION OF REFERENCE NUMERALS 1 boiler 2 denitration device 3 heat exchanger 3a gas side 3b air side 4 electric dust collector 5 chimney 6 air supply fan 7 auxiliary preheater 8 inlet damper 9 outlet damper 10 bypass duct 11 damper 12 bypass duct 13 exhaust gas duct 14 damper 15 Damper 16 duct

Claims (4)

[Claims] 1. An exhaust gas from a boiler is introduced into a gas side of a heat exchanger, and heat from the exhaust gas is stored in a heat storage material of the heat exchanger. In the boiler plant that discharges into the atmosphere and introduces outside air to the air side of the heat exchanger as combustion air for the boiler, preheats the heat stored in the heat storage material, and supplies the heat to the boiler, A rust prevention device for a heat exchanger, wherein a bypass duct is provided below the chimney and a damper is provided in the bypass duct. 2. The exhaust gas from the boiler is introduced into the gas side of the heat exchanger, and the heat from the exhaust gas is stored in the heat storage material of the heat exchanger. In the boiler plant that discharges into the atmosphere and introduces outside air to the air side of the heat exchanger as combustion air for the boiler, preheats the heat stored in the heat storage material, and supplies the heat to the boiler, A rust prevention device for a heat exchanger, wherein a bypass duct is provided in an exhaust gas duct downstream of a gas side of the heat exchanger, and a damper is provided in the bypass duct. 3. Exhaust gas from the boiler is introduced into the gas side of the heat exchanger, and heat from the exhaust gas is stored in the heat storage material of the heat exchanger. In the boiler plant that discharges into the atmosphere and introduces outside air to the air side of the heat exchanger as combustion air for the boiler, preheats the heat stored in the heat storage material, and supplies the heat to the boiler, A rust prevention device for a heat exchanger, wherein a damper is installed in an exhaust gas duct downstream of a gas side of the heat exchanger. 4. The rust prevention device for a heat exchanger in a boiler plant according to claim 1, wherein the degree of opening of the damper is variable.