JP2011125766A - Exhaust gas treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas treatment apparatus allowing broadening of the degree of freedom of the design of a stack, suppressing heat insulation cost of the stack low, and achieving effective use of heat of exhaust gas flowing out of a denitration part and reduction of heat lord applied to the natural environment. <P>SOLUTION: The exhaust gas treatment apparatus includes a desulfurization part 6 for desulfurization treatment, a denitration part 7 for denitration treatment, a stack P discharging treated gas to the atmosphere, and an air blowing-in path 11 sending combustion air to a boiler B. The denitration part 7 is disposed downstream of the gas flow of the desulfurization part 6 in a flue 2 from the boiler B to the stack P. A temperature reducing heat exchanger 9 is provided for lowering the temperature of the treated gas to the atmosphere discharge level by heat-exchanging between the treated gas passed through the denitration part 7 and the combustion air passing through the air blowing-in path 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust gas treatment apparatus used for treating exhaust gas discharged when a fossil fuel such as coal is burned in a combustor such as a boiler.

  Conventionally, as an exhaust gas treatment apparatus as described above, for example, an exhaust gas treatment used in a so-called low dust denitration system in which a denitration unit is adjacent to an outlet of a coal fired boiler via an electric dust collector (high temperature EP). There is an exhaust gas treatment apparatus used for a so-called high dust denitration system, in which a denitration part is adjacent to an apparatus or an outlet of a coal fired boiler. The low dust denitration system in which an electrostatic precipitator is installed at the outlet of a coal-fired boiler has the disadvantage of having to enlarge the electrostatic precipitator to withstand high temperatures. Exhaust gas treatment devices used in the system are mainstream.

  By the way, in an environment where clean exhaust gas that has been dedusted and desulfurized flows, a highly active denitration catalyst can be used over a long period of time while suppressing both the planned catalyst amount and the catalyst pressure loss. In recent years, as described in Patent Document 1, an exhaust gas treatment apparatus of a type in which a denitration unit is disposed downstream of a desulfurization unit has been attempted.

JP-A-8-206446

However, in the exhaust gas treatment device of the type in which the denitration unit is arranged downstream of the desulfurization unit as described above, in addition to the merit in planning, such as the amount of planned denitration catalyst being reduced, a high dust denitration system and low dust denitration system Although there is an operational merit that the air heater located downstream of the denitration device as in the system is less likely to be clogged by the acidic ammonium sulfate generated from the reaction between the residual NH ₃ concentration that increases when the catalyst performance decreases and SO ₃ in the exhaust gas, It is necessary to raise the temperature of the exhaust gas flowing into the denitration section to the denitration catalyst operating temperature (about 200 ° C.).
In other words, since the exhaust gas at high temperature flows in the chimney located downstream of the denitration part, the determination of the diameter and material when designing the chimney is subject to severe restrictions.For example, the chimney is made of steel plate. In order to solve this problem, there is a problem that the heat insulation cost must be applied in an amount that can withstand the high-temperature exhaust gas flowing out from the denitration part. Has become a conventional problem.

  The present invention has been made paying attention to the above-described conventional problems, and can increase the degree of freedom in designing the chimney and can reduce the heat insulation cost of the chimney. An object of the present invention is to provide an exhaust gas treatment apparatus capable of realizing effective use of heat of a treated gas and reduction of a heat load applied to a natural environment.

  The invention according to claim 1 of the present invention is an exhaust gas treatment apparatus for treating exhaust gas discharged from a combustor when fossil fuel such as coal is burned in a combustor such as a boiler, and performs desulfurization treatment. A desulfurization section; a denitration section that performs denitration treatment with a denitration catalyst; a chimney that discharges treated gas that has undergone exhaust gas treatment to the atmosphere; and an air push-in path that feeds combustion air into the combustor, the denitration section Is disposed on the downstream side of the gas flow of the desulfurization section in the flue from the combustor to the chimney, between the treated gas that has passed through the denitration section and the combustion air that has passed through the air push-in path And a heat exchanger for reducing the temperature to reduce the temperature of the treated gas to an atmospheric emission level (a temperature corresponding to the environmental emission standard, for example, about 100 ° C.). As Ri, and the configuration of the exhaust gas treatment apparatus as a means for solving the conventional problems described above.

  Moreover, the exhaust gas treatment apparatus according to claim 2 of the present invention performs heat exchange between the exhaust gas that has passed through the desulfurization section and the exhaust gas at 450 to 500 ° C. in the combustor, and passes through the desulfurization section. The temperature of the exhaust gas is increased to the catalyst operating temperature (about 200 ° C.) of the denitration unit.

  In the exhaust gas treatment apparatus according to the present invention, an ordinary air heater and an electrostatic precipitator are sequentially disposed between the combustor and the desulfurization unit, and the air heater discharges combustion air passing through the air push-in path from the combustor. Preheated with exhaust gas, the electrostatic precipitator removes soot in the exhaust gas.

In the exhaust gas treatment apparatus according to claim 1 of the present invention, heat exchange is performed between the external air passing through the air push-in path and the treated gas that has passed through the denitration section by the heat exchanger for temperature reduction. In addition, since the temperature of the treated gas is lowered to about 100 ° C., which is an atmospheric emission level, it is possible to effectively use heat energy and to realize a reduction in heat load on the natural environment. Become.
In addition, since the treated gas at the atmospheric emission level is discharged from the chimney, the conditions for determining the diameter and material when designing the chimney will be relaxed, for example, the chimney is made of steel plate In this case, the heat insulation cost can be reduced by the amount that can reduce the coating amount of the heat insulating material.

  Further, in the exhaust gas treatment apparatus according to claim 2 of the present invention, heat is exchanged between the exhaust gas in the combustor and the exhaust gas that has passed through the desulfurization section by the heat exchanger for temperature increase. Energy can be utilized more effectively.

  Since the exhaust gas treatment apparatus according to claim 1 of the present invention has the above-described configuration, the degree of freedom in designing the chimney can be increased, and the heat insulation cost of the chimney can be kept low. It is possible to achieve an excellent effect that it is also possible to realize effective use of the battery and to reduce the heat load applied to the natural environment.

  In addition, since the exhaust gas treatment apparatus according to claim 2 of the present invention has the above-described configuration, it has a very excellent effect that it is possible to realize further effective utilization of heat.

BRIEF DESCRIPTION OF THE DRAWINGS It is schematic structure explanatory drawing which shows the waste gas processing apparatus by one Example of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an exhaust gas treatment apparatus according to an embodiment of the present invention.

As shown in FIG. 1, this exhaust gas treatment device 1 includes an air heater 3, an electric dust collector 4, an exhaust gas treatment flue 2 from a coal-saving boiler (combustor) B to a chimney P from a coal-saving section Ba. induction fan 5, serves to sequentially arrange the desulfurization unit 6 and the denitration unit 7, the inlet of the denitration unit 7, not shown, which converts by reducing nO _X by injecting ammonia into the exhaust gas to nitrogen and water vapor An ammonia injection nozzle is arranged.

  The air heater 3 heats the air introduced into the air pushing path 11 from the outside by the pushing fan 10 with the heat of the exhaust gas discharged from the coal burning boiler B, and sends it to the coal burning boiler B as combustion air.

In this case, a temperature raising heat exchanger 8 is connected to the exhaust gas flow upstream side of the denitration unit 7, while a temperature reduction heat exchanger 9 is connected to the exhaust gas flow downstream side of the denitration unit 7.
The temperature raising heat exchanger 8 on the upstream side of the exhaust gas flow of the denitration unit 7 is about 50 ° C. exhaust gas that has passed through the desulfurization unit 6 with heat of exhaust gas of 450 to 500 ° C. in the coal-saving boiler Ba of the coal burning boiler B. Is increased to about 200 ° C., which is the catalyst operating temperature of the denitration unit 7.

  On the other hand, the temperature reducing heat exchanger 9 on the downstream side of the exhaust gas flow of the denitration unit 7 is introduced by the pusher fan 10 and passed through the denitration unit 7 by the air from the outside passing through the air push-in path 11. Heat is recovered from the treated gas, and the temperature of the treated gas is reduced to about 100 ° C., which is an atmospheric emission level.

  In this exhaust gas treatment device 1, the denitration unit 7 is disposed on the downstream side of the gas flow of the electrostatic precipitator 4 and the desulfurization unit 6, that is, the denitration unit in an environment where clean exhaust gas that has been dedusted and desulfurized flows. 7 is arranged so that a highly active denitration catalyst can be used for a long period of time while suppressing both the planned catalyst amount and the catalyst pressure loss.

  Here, a comparison in terms of planning and operation of an exhaust gas treatment apparatus (high dust denitration system) in which a denitration unit is adjacent to an outlet of a conventional coal-fired boiler and an exhaust gas treatment apparatus 1 according to this embodiment is shown. It is shown in 1. In this case, comparison was made based on the design specifications of the denitration part that adopted the high-dust wear-resistant type denitration catalyst in the conventional exhaust gas treatment equipment, the blockage environment of the air heater, and the corrosive environment of other equipment such as an electrostatic precipitator. .

As described above, in the exhaust gas treatment apparatus 1 according to this embodiment in which the denitration part 7 is disposed on the downstream side of the desulfurization part 6, the highly active type denitration catalyst has a planned catalyst amount and a catalyst as compared with the conventional exhaust gas treatment apparatus. There is an advantage in terms of planning that the lifetime of the denitration catalyst can be extended while suppressing any pressure loss.
In addition, in the exhaust gas treatment apparatus 1 according to this embodiment, compared with the conventional exhaust gas treatment apparatus, NH ₃ is eliminated when the catalyst performance is reduced, and thus the operational advantage that the clogging environment of the air heater 3 due to acidic ammonium sulfate is reduced, There is an operational advantage that the corrosive environment caused by SO ₃ generated in the denitration unit 7 is reduced.

In the exhaust gas treatment apparatus 1 having such a configuration, first, the heat of the high-temperature exhaust gas generated in the coal-fired boiler B is recovered to some extent by the air heater 3, and then the dust contained in the exhaust gas is removed by the electric dust collector 4. Then, the exhaust gas from which the dust is removed is guided to the desulfurization section 6 by the induction fan 5 to remove SO ₂ .

Next, the temperature of the exhaust gas having a temperature of about 50 ° C. that has passed through the desulfurization unit 6 is increased by the heat of the exhaust gas at 450 to 500 ° C. in the coal-saving boiler Ba of the coal-fired boiler B by the heat exchanger 8 for raising temperature. After raising the temperature to about 200 ° C., NH ₃ is injected from an ammonia injection nozzle (not shown) at the inlet of the denitration unit 7, and NO _X (nitrogen oxide) contained in the exhaust gas is converted into nitrogen and water vapor in the denitration unit 7. to remove the NO _X by decomposing.

Since the treated gas from which NO _X has been removed by passing through the denitration unit 7 in this way has risen to about 200 ° C., which is the catalyst operating temperature, the air push-in path by the heat exchanger 9 for temperature reduction. The heat exchange with the combustion air passing through 11 is performed, that is, the heat of the treated gas is recovered by the external air introduced by the pushing fan 10, and the temperature of the treated gas is set to about 100, which is an atmospheric release level. After being lowered to ° C., it is discharged from the chimney P into the atmosphere.

  As described above, in the exhaust gas treatment apparatus 1 according to this embodiment, heat is generated between the exhaust gas in the coal-saving section Ba of the coal-fired boiler B and the exhaust gas that has passed through the desulfurization section 6 by the heat exchanger 8 for heating. In addition to the exchange, the heat exchanger 9 for temperature reduction also exchanges heat between the external air that passes through the air push-in path 11 and the treated gas that has passed through the denitration unit 7. Therefore, heat energy can be used effectively.

  Further, in the exhaust gas treatment apparatus 1 according to this embodiment, the temperature of the treated gas that has passed through the denitration unit 7 is lowered to about 100 ° C., which is the atmospheric emission level, by the heat exchanger 9 for temperature reduction. Therefore, it is possible to reduce the thermal load on the natural environment, and the conditions for determining the diameter and material when designing the chimney will be eased. Therefore, the heat insulation cost can be reduced correspondingly.

  In the above-described embodiment, the temperature of the exhaust gas that has passed through the desulfurization unit 6 is set to be a coal-fired boiler by disposing the temperature raising heat exchanger 8 between the coal-saving unit Ba and the desulfurization unit 6 outlet of the coal-fired boiler B. Although the case where the heat of the exhaust gas from B is used to increase the catalyst operating temperature to about 200 ° C. has been shown, the present invention is not limited to this. For example, the temperature of the exhaust gas that has passed through the desulfurization section 6 is adjusted to the afterburner. You may make it raise by.

  The configuration of the exhaust gas treatment apparatus according to the present invention is not limited to the configuration of the above-described embodiment.

DESCRIPTION OF SYMBOLS 1 Exhaust gas processing apparatus 2 Flue 6 Desulfurization part 7 Denitration part 8 Heat exchanger for temperature rise 9 Heat exchanger for temperature reduction 11 Air pushing path B Coal-fired boiler (combustor)
P Chimney

Claims (2)

An exhaust gas treatment device for treating exhaust gas discharged from a combustor when fossil fuel is combusted in the combustor,
A desulfurization section for performing desulfurization treatment;
A denitration unit that performs denitration treatment with a denitration catalyst;
A chimney that discharges the treated gas that has been subjected to exhaust gas treatment to the atmosphere;
An air pushing path for sending combustion air to the combustor;
The denitration part is arranged on the gas flow downstream side of the desulfurization part in the flue from the combustor to the chimney,
A heat exchanger for temperature reduction that performs heat exchange between the treated gas that has passed through the denitration unit and the combustion air that has passed through the air push-in path to lower the temperature of the treated gas to an atmospheric discharge level; An exhaust gas treatment apparatus characterized by being provided.   A heat exchanger for raising temperature that performs heat exchange between the exhaust gas that has passed through the desulfurization part and the exhaust gas in the combustor and raises the temperature of the exhaust gas that has passed through the desulfurization part to the catalyst operating temperature of the denitration part. The exhaust gas treatment apparatus according to claim 1 provided.

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