JPH09290132A - Apparatus for removing nitrogen oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively use heat being consumed by repeating of heating and cooling of an adsorption column in an apparatus for removing NOx using a temp. swing type adsorption column. SOLUTION: In an apparatus for removing NOx provided with an NOx adsorption tower 2 filled with a catalyst for adsorption and desorption of NOx by temp. swing system, an apparatus 8 for NOx decomposition catalyst, a heating gas system 6 wherein heating gas is circulated in an NOx adsorption column through the apparatus 8 for NOx decomposition catalyst and a cooling gas system 4 for the NOx adsorption column, a heat accumulator 12 which performs heat exchange by passing selectively the cooling gas from the NOx adsorption tower 2 and the heating gas of the heating gas system 6 through it, is provided to make it possible to utilize excess heat when the NOx adsorption column is heated in the initial stage of cooling of the NOx adsorption column.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for removing nitrogen oxides, which enables effective utilization of heat.

[0002]

2. Description of the Related Art FIG. 2 is a temperature swing type nitrogen oxide (hereinafter referred to as NOx) removing device (low concentration denitration device).
FIG.

The to-be-processed gas G containing NOx such as tunnel exhaust gas is introduced into the NOx adsorption tower 2 after being dedusted by the electrostatic precipitator 1. NO in the adsorption tower 2 at low temperature and room temperature
It is filled with a catalyst that adsorbs x and desorbs when the temperature rises. The gas that has been cleaned by adsorbing and removing NOx with this catalyst is
It is released to the atmosphere through systems 15, 16.

After the adsorption operation for a certain time, the adsorption tower 2
The dampers 17 and 18 provided in the upstream and downstream parts of the adsorption tower 2 are switched to NOx desorption concentration (heating) operation.
The gas inside is introduced into the heating gas system 6 by the blower 3 and heated by the heater 7, and the upper NOx decomposition catalyst device 8 and NO
NOx is desorbed from the catalyst in the NOx adsorption tower 2 into the heated gas by circulating the loop composed of the x adsorption tower 2, and is decomposed and removed by the NOx decomposition catalyst device 8.

When NOx is decomposed and removed for a certain period of time, the adsorption operation is switched to again. However, since the adsorption is performed at room temperature, the system has a loop consisting of the cooler 5 and the NOx adsorption tower 2 before the adsorption operation. The NOx adsorption tower 2 is switched and the NOx adsorption tower 2 is cooled. This loop branches from the heating gas system 6 between the blower 3 and the heater 7, joins the heating gas system 6 between the NOx decomposition catalyst device 8 and the NOx adsorption tower 2, and the cooler 5 is provided. A cooling gas system 4 is provided. In this way, the NOx adsorption operation at room temperature and the NO
x Desorption / concentration / decomposition operation is performed alternately with a fixed time (about once a day).

The bypass system 9 uses the NOx decomposing catalyst device 10 for a part of the gas expanded by heating during the heating operation.
In order to cool the gas through the reactor to a temperature close to the atmospheric temperature with the cooler 11 and discharge it into the atmospheric air, as shown in FIG.
It is installed so as to connect between 5, 16 and the heating gas system 6.

Further, the valves 20a, 20b; 23a, 23
Reference numeral b; 24 is a valve provided in each of the cooling gas system 4, the heating gas system 6 and the bypass system 9 for switching the above operation, and the arrow in FIG. 2 indicates the gas flow.

[0008]

In the NOx removing device (low-concentration denitration device) shown in FIG. 2, the heater 7 is required as a heating source for desorption and concentration of adsorbed NOx. The heating process and the cooling process are alternately repeated, and a large amount of heat is consumed.

The present invention has been made to solve this problem.

[0010]

The present invention provides NO at low temperatures.
An adsorption tower filled with a catalyst that adsorbs x and desorbs NOx when the temperature rises, an NOx decomposition catalyst device, and heating gas heated by a heating means is supplied to the adsorption tower through the NOx decomposition catalyst device, and the catalyst in the adsorption tower A gas to be treated in an adsorption tower that is equipped with a heating gas system that circulates a heated gas containing desorbed NOx to a heating means and a cooling gas system that supplies a cooling gas to the adsorption tower In the NOx removing device, which adsorbs NOx in the catalyst to the catalyst and desorbs the NOx adsorbed in the catalyst in the heating gas in the adsorption tower heated by the heating gas of the heating gas system, cooling from the adsorption tower A heat storage body for selectively exchanging heat between the gas and the heating gas is provided.

According to the present invention, in the NOx removing apparatus provided with the heating gas system for circulating the heating gas to the adsorption tower and the cooling gas system for supplying the cooling gas to the adsorption tower, the NOx removal apparatus is used for the removal from the adsorption tower. Since the cooling gas and the heating gas are provided with a heat storage body for selectively exchanging heat by passing therethrough, at the initial stage of cooling when the heating operation of the adsorption tower is switched to the cooling operation,
The residual heat of the adsorption tower during the heating gas operation is stored in the heat storage body via the cooling gas. This heat heats the heating gas at the beginning of the next heating operation and is used as a heat source during the heating operation.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIG. The present invention has the following configuration in parallel with the heating gas system 6 and the cooling gas system 4 of the NOx removing device shown in FIG. 2 and is discharged from the heating gas of the heating gas system and the NOx adsorption tower of the cooling gas system. A heat storage system for selectively exchanging heat with gas is provided, and in FIG. 1, the same parts as those in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

That is, in the present embodiment, the system 13, which forms a heat storage system by branching from the portion between the blower 3 and the heater 7 on the upstream side of the branch point of the cooling gas system 4 of the heating gas system 6,
14 are provided. The system 13 joins the cooling gas system 4 on the downstream side of the cooler 5 through the upper valve 21b that has passed through the heat storage body 12 through the valve 21a. Also, system 1
Reference numeral 4 merges with the heating gas system 6 between the heater 7 and the NOx decomposition catalyst device 8 via the upper valve 22b that has passed through the heat storage body 12 via the valve 22a.

In the present embodiment configured as described above, when the heating operation for desorbing NOx from the catalyst of the NOx adsorption tower 2 with the dampers 17 and 18 closed is completed, the damper 1
7 and 18 are kept closed and valves 21a and 2
1b is opened and valves 20a, 20b; 22a, 22
b; 23a and 23b are closed. As a result, NOx
The high temperature gas in the adsorption tower 2 is fed into the system 13 by the blower 3.
Will be circulated through the heat storage body 12. Therefore, N
The Ox adsorption tower 2 is cooled by this circulating gas, and part of the residual heat remaining in the NOx adsorption tower 2 after the heating operation is part of the heat storage body 1.
The heat is stored in 2.

Then, with the dampers 17 and 18 closed, the valves 20a and 20b are opened and the valves 21a and 21a are opened.
21b; 22a, 22b; 23a, 23b are closed.
As a result, the gas in the NOx adsorption tower 2 circulates and flows through the cooling gas system 4, and by cooling the gas by the cooler 5, the NOx adsorption tower 2 is cooled to room temperature.

When the NOx adsorption tower 2 is cooled to room temperature in this way, the dampers 17 and 18 are opened and the valve 2 is opened.
0a, 20b; 21a, 21b; 22a, 22b; 23
a and 23b are closed, and the gas to be processed G containing NOx is N
It is introduced into the Ox adsorption tower 2. As a result, the gas to be processed G
The NOx therein is adsorbed by the catalyst packed in the NOx adsorption tower 2, and the gas from which NOx has been removed is supplied from the NOx adsorption tower 2 to the system 1
It is released to the atmosphere through 5,16.

After the NOx adsorption operation at room temperature for a certain period of time, the dampers 17 and 18 are closed and the valve 22 is closed.
a, 22b are opened, valves 20a, 20b; 21a,
21b; 23a and 23b are closed. By this, N
The gas in the Ox adsorption tower 2 is circulated to the NOx adsorption tower 2 through the system 14 by the blower 3, the gas is heated by the heat storage body 12 as described above, and the NOx adsorption is performed by the heated gas. The tower 2 is heated. Through this step, the NOx adsorption tower 2 is initially heated.

Next, with the dampers 17 and 18 closed, the valves 23a and 23b are opened and the valves 20a and 2b are opened.
0b; 21a, 21b; 22a, 22b are closed. As a result, the gas in the adsorption tower 2 is circulated to the NOx adsorption tower 2 through the heating gas system 6 by the blower 3, and the gas is heated by the heater 7 of the heating gas system 6 so that the heating gas is NOx. The NOx adsorption tower 2 is circulated through the adsorption tower 2, the NOx adsorption tower 2 is heated by this heating gas, and the NOx adsorbed by the catalyst packed in the adsorption tower 2 is desorbed in the heating gas. The desorbed NOx is decomposed and removed by the NOx decomposition catalyst device 8 provided in the heating gas system 6.

As described above, in the present embodiment, NOx
The initial cooling residual heat of the cooling tower 2 is stored in the heat storage body 12, and NOx
The NOx adsorption tower 2 is used by using this heat storage in the initial heating of the adsorption tower 2.
The NOx adsorption tower 2 can be heated by heating the heating gas of No. 2, and the energy can be effectively used.

In the embodiment of the present invention described above,
In the initial heating of the NOx adsorption tower 2, the cooling gas emitted from the NOx adsorption tower 2 is passed through the heat storage body 12 and returned to the NOx adsorption tower 2 to be circulated. In the present invention, this cooling gas is circulated. It is also possible to allow the cooling gas emitted from the NOx adsorption tower without passing through the heat storage body to pass through the heat storage body to be cooled and then discharged.

[0021]

According to the NOx removal apparatus of the present invention, a large amount of heat consumed by repeated heating and cooling of the adsorption tower can be utilized by the heat storage of the heat storage body, and a great energy saving can be achieved. You can

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention.

FIG. 2 is a system diagram of a conventional NOx removal device.

[Explanation of symbols]

2 NOx adsorption tower 3 blower 4 cooling gas system 5 cooler 6 heating gas system 7 heater 8 NOx decomposition catalyst device 9 bypass system 10 NOx decomposition catalyst device 11 cooler 12 heat storage body 13, 14, 15, 16 system 17, 18 damper 20a, 20b, 21a, 22b, 23a, 24b, 24 valve G Gas to be treated

Claims (1)

[Claims] 1. An adsorption tower filled with a catalyst that adsorbs nitrogen oxides at a low temperature and desorbs nitrogen oxides at a high temperature, a nitrogen oxide decomposition catalyst device, and a heating gas heated by a heating means as a nitrogen oxide catalyst. A heating gas system that circulates a heating gas containing nitrogen oxides desorbed from the catalyst in the adsorption tower to the heating means, and a cooling gas system that supplies a cooling gas to the adsorption tower. , Adsorbing nitrogen oxides in the gas to be treated to the catalyst in the adsorption tower cooled by the cooling gas in the cooling gas system, and removing the nitrogen oxides adsorbed in the catalyst in the adsorption tower heated by the heating gas in the heating gas system In a nitrogen oxide removing device adapted to be desorbed in a heating gas, a cooling gas discharged from an adsorption tower and a heat storage body for selectively exchanging the heating gas for heat exchange are provided. Oxide removal device.