JP2000176308A - Dry electric dust collector and flue thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent accumulation of particles on a distribution plate of a dry electric dust collector. SOLUTION: Cold water is supplied to a pipe 24 from a pump 25 and the surface temperature of the pipe 24 is detected by a temperature sensor 26. A detected temperature 27 is input to a controller 28, which controls the pump 25 so as to keep the surface temperature of a distribution plate 10 at dew point of water or lower based on the detected temperature 27 and a previously stored dew point of steam contained in a waste gas. Consequently, the surface temperature of the distribution plate 10 is maintained at the dew point of the steam or lower. When the waste gas has passed through the distribution plate 10, condensation of steam occurs on the surface of the distribution plate 10, since the surface temperature of the distribution plate 10 is the dew point of water or lower, and particles of ammonium sulfate and ammonium nitrate having adhered to the surface of the distribution plate 10 are dissolved in the condensation water and removed. Consequently, accumulation of particles of ammonium sulfate and ammonium nitrate on the distribution plate 10 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry electric precipitator and a flue thereof, and more particularly to an ammonium precipitant produced by injecting ammonia into exhaust gas discharged from a boiler and containing sulfur oxides and nitrogen oxides. The present invention relates to a dry electric precipitator for collecting ammonium nitrate together with dust and a flue thereof.

[0002]

2. Description of the Related Art Exhaust gas discharged from a boiler using petroleum or heavy oil as fuel contains sulfur oxides and nitrogen oxides in addition to dust. Conventionally, when treating the exhaust gas of this boiler with an electron beam device, if sulfur oxides and nitrogen oxides are reacted with ammonia, they can be effectively used as fertilizers such as ammonium sulfate and ammonium nitrate. First, the exhaust gas from the boiler is sequentially led to an air heater and an electric dust collector, and dust in the exhaust gas that has passed through the air heater is removed by the electric dust collector.

[0003] Thereafter, the exhaust gas containing sulfur oxides and nitrogen oxides is cooled to about 60 ° C near the dew point of water by water spray cooling or the like, and then introduced into an electron beam device. Ammonia is injected into the exhaust gas at the entrance of the electron beam device, and sulfur oxides and nitrogen oxides in the exhaust gas react with ammonia in the electron beam device to generate ammonium sulfate and ammonium nitrate. Exhaust gas containing particles of ammonium sulfate and ammonium nitrate is led to a dry-type electrostatic precipitator through a flue, and ammonium sulfate and ammonium nitrate in the exhaust gas are collected by the dry-type electric precipitator.

[0004]

However, the particles of ammonium sulfate and ammonium nitrate generated by the electron beam apparatus have a strong adhesive property, and when introduced into a conventional dry-type electrostatic precipitator, the entrance of the dry-type electrostatic precipitator may be reduced. Attaches to distribution plate in enlarged flue. For this reason, there has been a problem that the amount of particles deposited on the distribution plate increases over a long period of operation, and the opening of the distribution plate is closed, and the pressure loss of the dry electric precipitator increases.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a dry-type electrostatic precipitator for preventing the accumulation of particles on a distribution plate of a dry-type electric precipitator and a flue thereof. And

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an ammonium sulfate or ammonium nitrate produced by injecting ammonia into exhaust gas containing sulfur oxides or nitrogen oxides and irradiating the exhaust gas with an electron beam. In a dry-type electrostatic precipitator that collects particles, a distribution plate that is provided on the inlet side of the dry-type electric precipitator and that diffuses the exhaust gas, and that the surface temperature of the distribution plate is higher than that of the water vapor contained in the exhaust gas. Cooling means for cooling the distribution plate so as to have a dew point or less.

According to the present invention, the cooling means cools the distribution plate so that the surface temperature of the distribution plate becomes equal to or lower than the dew point of the water vapor contained in the exhaust gas. When the exhaust gas supplied to the dry electrostatic precipitator is guided to the distribution plate, the surface temperature of the distribution plate is equal to or lower than the dew point of the water vapor contained in the exhaust gas. Ammonium sulfate and ammonium nitrate particles adhering to the surface are dissolved in the dew condensation water and removed. Therefore, it is possible to prevent the deposition of ammonium sulfate or ammonium nitrate particles on the distribution plate.

In order to achieve the above object, the present invention includes ammonium sulfate and ammonium nitrate particles generated by injecting ammonia into an exhaust gas containing a sulfur oxide or a nitrogen oxide and irradiating the exhaust gas with an electron beam. In the flue of the dry electric precipitator that guides the exhaust gas to the dry electric precipitator, a cooling means is provided for cooling the flue so that the surface temperature of the flue is equal to or lower than the dew point of water vapor contained in the exhaust gas. It is characterized by having.

According to the present invention, the cooling means cools the flue so that the surface temperature of the flue is lower than the dew point of water vapor contained in the exhaust gas. When flue gas containing ammonium sulfate or ammonium nitrate particles is introduced into the flue, the flue surface temperature is lower than the dew point of the water vapor contained in the flue gas. The attached ammonium sulfate and ammonium nitrate particles are dissolved in the dew condensation water and removed. Therefore, it is possible to prevent the accumulation of ammonium sulfate and ammonium nitrate particles in the flue.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a dry electric precipitator and a flue thereof according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows an example in which a dry electric precipitator according to the present invention is applied to a dust removal flow of dust in combustion gas generated from a boiler.

As shown in FIG. 1, the exhaust gas containing dust generated from the boiler 11 is first guided to an air heater 12, and the heat of the exhaust gas is recovered by the air heater 12. The exhaust gas from which the heat has been recovered is supplied to the electrostatic precipitator 13, where the dust in the exhaust gas is removed. The exhaust gas from which dust has been removed is guided to the cooling tower 14, where water is sprayed and the temperature is reduced to about 60 ° C. The cooled exhaust gas is led to the electron beam device 15.

Ammonia is injected into the exhaust gas at the entrance of the electron beam device 15, and in the electron beam device 15, sulfur oxides and nitrogen oxides in the exhaust gas react with ammonia to generate ammonium sulfate and ammonium nitrate particles. The particles generated in the electron beam device 15 are supplied to the dry electric precipitator 17 via the inlet flue 16 along the exhaust gas flow, and are supplied to the dry electric precipitator 1.
Collected at 7. The clean gas from which the particles have been removed is
8 to the atmosphere.

FIG. 2 is a cross-sectional view showing the structure of the dry electric precipitator 17. As shown in FIG. One end side of the dry electric precipitator 17 communicates with the inlet flue 16 and the other end side communicates with the outlet flue 19. The exhaust gas is supplied from the inlet flue 16 into the dry electric precipitator 17 in the direction of the arrow in the figure. On the inlet flue 16 side of the dry electric precipitator 17, there is formed an enlarged flue 21 which is widened along the exhaust gas flow, and in this enlarged flue 21, the distribution plate 10 is provided in a hollow structure. The exhaust gas supplied into the dry electric precipitator 17 is diffused by passing between the distribution plates 10.

The exhaust gas passing between the distribution plates 10 passes between the dust collecting electrode 23 and a discharge electrode (not shown). Dust collection pole 2
A DC voltage is applied between 3 and the discharge electrode, and corona discharge occurs. The particles in the gas are charged by the corona discharge, and are attached to and collected by the dust collecting electrode 23. The clean gas from which the particles have been removed is discharged from the dry electric precipitator 17 at an outlet flue 19.

FIG. 3 is a perspective view showing the assembly of the distribution plate 10. As shown in FIG. As shown in the figure, the distribution plate 10 includes a plurality of vertical plates 20, 20,... (Only two are shown in the figure) and a plurality of horizontal plates 22, 22,. It is constructed and assembled in a lattice. A pipe 24 is attached to the back side of the vertical plate 20 along the vertical plate 20, and one end of the pipe 24 is connected to a pump 25 (see FIG. 4).
Cold water is supplied from the pump 25 into the pipe 24, and the vertical plate 20 is cooled.

At this time, cold water may be supplied from the upper end of each pipe 24, and the cold water reaching the lower end may be circulated again to the upper end of each pipe 24, or cold water may be supplied from the upper end of one pipe 24. Alternatively, the cold water reaching the lower end may be circulated to the upper end of the second pipe 24, and this may be repeated. As shown in FIG. 2, a temperature sensor 26 is provided at the other end of the pipe 24, and detects a surface temperature of the pipe 24. This temperature sensor 26 is connected to a control device 28 by a signal cable 27.
And the detected temperature is controlled by the control device 28.
Is input to The dew point of the water vapor contained in the exhaust gas is stored in the control device 28 in advance. The control device 28 is connected to the pump 25 via a cable 29, and controls the pump 25 based on the previously stored dew point and the detected temperature.

Next, the operation of the dry electric precipitator structured as described above will be described. Pump 25 is connected to pipe 24
, And the surface temperature of the pipe 24 is detected by a temperature sensor 26. The detected temperature 27 is input to a control device 28, which controls the pump 2 based on the detected temperature 27 and a previously stored dew point.
5 is controlled. That is, the control device 28 controls the pump 25 so that the water flow rate in the pipe 24 increases when the detected temperature is higher than the dew point, and decreases the water flow rate in the pipe 24 when the detected temperature is lower than the dew point. The pump 25 is controlled so that As a result, the surface temperature of the distribution plate 10 is maintained below the dew point of water vapor. When the exhaust gas passes between the distribution plates 10, since the surface temperature of the distribution plates 10 is lower than the dew point of water, water vapor condenses on the surfaces of the distribution plates 10, and particles of ammonium sulfate and ammonium nitrate adhered to the surfaces of the distribution plates 10. Is dissolved in dew water and removed. Therefore, accumulation of ammonium sulfate or ammonium nitrate particles on the distribution plate 10 can be prevented.

Although FIG. 3 shows an example in which the pipe 24 is attached only to the vertical plate 20, as shown in FIG.
2 may be provided with pipes 30, 30,. In this case, the pipe 30 is curved at the intersection of the vertical plate 20 and the horizontal plate 22 so as not to cross the pipe 24. Also,
As shown in FIG. 5, the square pipes 50 and 54 may be provided in a lattice shape, and may also be used as a distribution plate.

FIG. 6 is a perspective view showing the structure of the inlet flue 16. As shown in the figure, the outer circumference of the inlet flue 16 is surrounded by a ventilation path 32, and the space between the inlet flue 16 and the ventilation path 32 communicates with a fan 34 and an air supply duct 36. Air is supplied between the flue 16 and the ventilation passage 32. The entrance flue 16 is provided with a temperature sensor 41 for detecting the surface temperature of the entrance flue 16. Temperature sensor 4
1 is connected to the control device 42 via a signal cable 43, and the detected temperature is input to the control device 42.
The dew point of the water vapor contained in the exhaust gas is stored in the control device 42 in advance. The control device 42 is connected to the fan 34 by a cable 44, and controls the rotation speed of the fan 34 based on the dew point stored in advance and the detected temperature.

The bottom surface of the inner wall 33 is inclined, and a drain outlet 35 is formed at the lowermost end of the bottom surface. Next, the operation of the inlet flue 16 configured as described above will be described. A fan 34 is provided between the inlet flue 16 and the ventilation passage 32.
, And the surface temperature of the inlet flue 16 is detected by the temperature sensor 41 and input to the control device 42. The control device 42 controls the rotation speed of the fan 34 based on the detected temperature and the previously stored dew point. That is, the control device 42 controls to increase the rotation speed of the fan 34 when the detected temperature is higher than the dew point, and decreases or reduces the rotation speed of the fan 34 when the detected temperature is lower than the dew point. Control to stop. As a result, the surface temperature of the inlet flue 16 is maintained below the dew point of water vapor. When the exhaust gas flows through the inlet flue 16, since the surface temperature of the inlet flue 16 is lower than the dew point of water vapor, the water vapor condenses on the surface of the inlet flue 16, and ammonium sulfate or nitric acid adhered to the surface of the inlet flue 16. Particles are melted in the dew condensation water and flow down to be drained from the drain outlet 35. Therefore, it is possible to prevent the particles of ammonium sulfate and ammonium nitrate from being deposited on the inlet flue 16.

[0021]

As described above, according to the dry type electrostatic precipitator of the present invention, the cooling means cools the distribution plate so that the surface temperature of the distribution plate becomes lower than the dew point of water vapor contained in the exhaust gas. As a result, water vapor is condensed on the surface of the distribution plate, and particles of ammonium sulfate and ammonium nitrate attached to the surface of the distribution plate are melted and removed by the dew water. Therefore, it is possible to prevent the deposition of ammonium sulfate or ammonium nitrate particles on the distribution plate.

Further, according to the flue of the dry type electrostatic precipitator of the present invention, the cooling means cools the flue so that the surface temperature of the flue is lower than the dew point of water vapor contained in the exhaust gas. Water vapor condenses on the surface of the flue, and particles of ammonium sulfate and ammonium nitrate adhering to the surface of the flue are dissolved in the condensed water and removed. Therefore, it is possible to prevent the accumulation of ammonium sulfate and ammonium nitrate particles in the flue.

[Brief description of the drawings]

FIG. 1 Dust removal flow of dust in combustion gas generated from a boiler

FIG. 2 is a cross-sectional view showing a configuration of the dry electric precipitator shown in FIG.

FIG. 3 is a diagram showing a configuration of a distribution plate shown in FIG. 2;

FIG. 4 is a diagram showing a case where a pipe is also attached to a horizontal plate.

FIG. 5 is a diagram showing a case where a square pipe is applied to a pipe;

FIG. 6 is a perspective view showing a configuration of an inlet flue shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Distribution board 15 ... Electron beam device 16 ... Inlet flue 17 ... Dry electric precipitator 20 ... Vertical plate 22 ... Horizontal plate 24, 30, 50, 54 ... Pipe 25 ... Pump 26, 41 ... Temperature sensor 28, 42 ... Control device 32 ... Ventilation path 34 ... Fan

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D002 AA02 AA12 AB01 AC01 BA03 BA09 DA07 FA10 GA03 GB03 HA05 4D054 AA02 BA01 CA14 CA20 EA02 EA16 EA21 EA24

Claims (4)

[Claims] 1. A dry electrostatic precipitator for collecting particles of ammonium sulfate or ammonium nitrate generated by injecting ammonia into an exhaust gas containing sulfur oxides and nitrogen oxides and irradiating an electron beam, wherein the dry electric A distribution plate that is provided on the inlet side of the dust collector and diffuses the exhaust gas, and a cooling unit that cools the distribution plate so that a surface temperature of the distribution plate is equal to or lower than a dew point of water vapor included in the exhaust gas. A dry-type electrostatic precipitator comprising: 2. The cooling means comprises: a pipe attached to the distribution plate or a pipe serving also as the distribution plate; a pump for supplying a refrigerant to the pipe; and a temperature detection unit for detecting a surface temperature of the distribution plate. When the detected temperature is higher than the dew point, the flow rate of the refrigerant in the pipe is increased, and when the detected temperature is lower than the dew point, the pump is controlled to reduce the flow rate of the refrigerant in the pipe. The dry electric precipitator according to claim 1, further comprising: a control unit configured to perform the control. 3. A dry electric precipitator for introducing an exhaust gas containing ammonium sulfate or ammonium nitrate particles generated by injecting ammonia into an exhaust gas containing sulfur oxides and nitrogen oxides and irradiating an electron beam to a dry electric precipitator. In a flue of a dust collector, a dry electric dust collector characterized by comprising cooling means for cooling the flue so that the surface temperature of the flue is equal to or lower than the dew point of water vapor contained in the exhaust gas. Flue. 4. A cooling system comprising: a ventilation path surrounding an outer periphery of the flue; a fan for supplying air between the flue and the ventilation path; and a temperature detecting means for detecting a surface temperature of the flue. When the detected temperature is higher than the dew point, the flow rate of air between the flue and the ventilation path is increased, and when the detected temperature is lower than the dew point, the flow rate between the flue and the ventilation path is increased. The flue of the dry type dust collector according to claim 3, further comprising: a controller that controls the fan so as to reduce the flow rate of the air.