JP2002119830A - Method of treating waste gas from long term continuous operation equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of treating waste gas, in which the waste gas is treated continuously without stopping the operation even in an equipment operated continuously for a long term. SOLUTION: In the method of treating the waste gas in the equipment for treating the waste gas discharged from the long term continuous operation equipment, in which a waste gas treating line is divided into >=2 lines and each waste gas treating line is provided with a catalytic device, during the waste gas is treated using >=1 lines in >=2 waste gas treating lines, the catalytic performance of the catalytic device in other >=1 lines of the waste gas treating lines is recovered and at the point of time when the catalytic performance of the catalytic device in the waste gas treating lines under being used is lowered, the waste gas treating line is changed to the waste gas treating line having the catalytic device having recovered catalytic performance and the processes are successively repeated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating exhaust gas from a long-term continuous operation facility, and more particularly to an exhaust gas from a long-term continuous operation facility suitable for removing nitrogen oxides and dioxins in the exhaust gas. Regarding the processing method.

[0002]

2. Description of the Related Art In recent years, the harmfulness of organic chlorine compounds such as polychlorinated dibenzodioxins and polychlorinated dibenzofurans (hereinafter referred to as dioxins) contained in exhaust gas discharged from various facilities has become a problem. As methods for removing dioxins in exhaust gas, methods such as complete oxidative decomposition by high-temperature combustion, adsorption and removal by addition of an adsorbent, and solid-gas separation by low-temperature solidification are known, but recently, Patent No. 2633316 , Japanese Patent Publication No. 6-38863, Japanese Patent Application Laid-Open No. 63-290314, and the like.
A decomposition and removal method using a catalyst was proposed.

As a facility to which a method for decomposing and removing dioxins by a catalyst is applied, for example, a waste incineration facility can be mentioned. In such a waste incineration facility, it is common to install one catalyst device at the outlet of the dust remover for one incinerator. In addition, when nitrogen oxides are removed simultaneously with dioxins in exhaust gas, a reducing agent must be injected upstream of the catalyst device. Particularly, when ammonia or urea is used as a reducing agent, and SO ₃ and ammonia react acidic ammonium sulfate (NH ₄ HSO ₄₎ is generated, and this is the catalyst deterioration is a problem that promotes by adhering to the catalyst.

[0004] On the other hand, sintering equipment in the steel industry is also mentioned as equipment that may contain dioxins in exhaust gas.
When one catalyst unit is installed for one unit in the sintering facility, as in the waste incineration facility described above. A problem arises in that it is not possible to take measures to recover the data.

FIG. 3 is a system diagram showing an exhaust gas treatment apparatus in which one sintering facility (not shown) is provided with one catalyst device. In the figure, a dust removing device 32, a temperature raising device 33, and a catalyst device 34 are sequentially provided in an exhaust gas flue 36 through which an exhaust gas 31 flows, and a reducing agent injection means 35 is disposed at an inlet of the catalyst device 34.

In such an apparatus, the exhaust gas 31 discharged from a sintering facility (not shown) flows through an exhaust gas flue 36, is removed by a dust removing device 32, and is adjusted to a predetermined temperature by a temperature raising device 33. It flows into the catalyst device 34, where harmful components are decomposed and removed in the presence of the catalyst.

However, if the sintering equipment has a long period of time from start to stop, for example, 10 to 15 years and only one exhaust gas treatment system, the exhaust gas purification performance of the catalyst device may be reduced. However, the catalyst device could not be separated from the exhaust gas treatment system, and no means could be taken to restore the catalyst performance. For this reason, when installing a catalyst device, it was necessary to fill an enormous amount of catalyst suitable for long-term processing.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to improve the catalyst performance as needed when the catalyst performance is reduced even in equipment that is operated continuously for a long period of time. It is an object of the present invention to provide a method for treating exhaust gas from a long-term continuous operation facility, which can recover the exhaust gas and stably treat the exhaust gas for a long period of time.

[0009]

Means for Solving the Problems To solve the above problems, the invention claimed in the present application is as follows. (1) In an exhaust gas treatment method for introducing exhaust gas discharged from a facility that is continuously operated for a long period of time into an exhaust gas treatment system having a catalyst device, and decomposing and removing harmful components contained in the exhaust gas using a catalyst device, The treatment system is provided by branching into two or more systems, and the catalyst device is provided in each exhaust gas treatment system, and the exhaust gas treatment is performed by using one or more of the two or more exhaust gas treatment systems. Then, the catalyst activity of the catalyst device in one or more other exhaust gas treatment systems was restored, and at the time when the catalyst activity of the catalyst device in the exhaust gas treatment system in use decreased, the catalyst activity of the exhaust gas treatment system recovered. After switching to an exhaust gas treatment system with a catalyst device, the catalyst devices whose catalytic activity has been sequentially reduced are separated from the exhaust gas treatment system, and after the catalyst activity has been restored, the exhaust gas Incorporated into the processing system, characterized by treating the exhaust gas continuously for a long time, the processing method of the exhaust gas from the long-term continuous operation equipment.

(2) The step of restoring the catalytic activity of the catalyst device is a step of adding a catalyst to the catalyst device separated from the exhaust gas treatment system, replacing the catalyst, or regenerating the catalyst. Described in (1) above,
A method for treating exhaust gas from long-term continuous operation equipment. (3) A method for treating exhaust gas which contains nitrogen oxides and decomposes and removes harmful components in the exhaust gas while injecting a reducing agent upstream of each catalyst device, wherein the performance of the catalyst device is improved. The method of treating exhaust gas from long-term continuous operation equipment according to (1) or (2), wherein the step of recovering is a step of stopping the injection of the reducing agent into the catalyst device. (4) The method for treating exhaust gas from a long-term continuous operation facility according to any one of the above (1) to (3), wherein the long-term continuous operation facility is a sintering facility.

In the present invention, the exhaust gas treatment system is branched into two or more exhaust gas treatment systems, and while one or more of the two or more exhaust gas treatment systems is being treated, the other one or more exhaust gas treatment systems are used. The catalytic performance of the catalytic device is restored, and when the catalytic activity of the catalytic device in the exhaust gas processing system in use decreases, the exhaust gas processing system is switched to the exhaust gas processing system having the catalytic device whose catalytic performance has been restored. To continuously treat the exhaust gas for a long period of time.

In the present invention, the long-term continuous operation equipment is
This refers to equipment such as sintering equipment, which has a long period of time from startup to shutdown, for example, 10 to 15 years. As harmful components contained in the exhaust gas, for example, dioxins such as polychlorinated dibenzodioxin, polychlorinated dibenzofuran,
And nitrogen oxides. Further, as a catalyst for decomposing and removing these harmful components, a catalyst containing, for example, titanium oxide as a main component and one or more oxides such as vanadium, molybdenum, and tungsten added thereto is used.

In the present invention, the recovery of the activity of the catalyst whose activity has been reduced can be achieved by disconnecting the catalyst device from the exhaust gas treatment system,
During this time, the separation is carried out by adding catalyst to the separated catalyst device, replacing the catalyst, or regenerating the catalyst. The disconnection of the catalyst device from the exhaust gas treatment system is performed, for example, by providing shield valves before and after each catalyst device in two or more exhaust gas treatment systems and closing the shield valves.

In the present invention, the exhaust gas contains nitrogen oxides.
If this occurs, it is necessary to inject a reducing agent upstream of the catalyst device.
It is necessary. Examples of the reducing agent include ammonia and urea.
Used, but SO in the exhaust gas_ThreeReacts with ammonia
Acid ammonium sulfate (NH_FourHSO_Four ) Is generated and this is
The adhesion may accelerate the reduction of catalytic activity.
In the case, acidic ammonium sulfate adhering to the catalyst stops the injection of the reducing agent
Decomposition and removal by flowing exhaust gas
Is done. Therefore, the reducing agent is injected upstream of the catalytic
In an exhaust gas treatment method for decomposing elemental oxides, a reducing agent
The exhaust gas is allowed to flow while the
Thus, the catalyst performance can be restored.

In the present invention, it is possible to use two exhaust gas treatment systems and alternately use one system at a time and a system for restoring the activity of the catalyst. The system may be used to treat exhaust gas, during which a plurality of systems may be disconnected from the exhaust gas treatment system to restore catalytic activity.

[0016]

Next, the present invention will be described in detail with reference to examples. FIG. 1 is an apparatus system diagram when the present invention is applied to a sintering facility. In the figure, this device is an exhaust gas flue 20 provided with a dust removing device 2 and a temperature increasing device 3 in order.
A branch exhaust gas flue 21 that branches off the exhaust gas flue 20;
22 and 23, and a catalyst device 4 provided in each of the branch exhaust gas flues 21, 22 and 23 and filled with a catalyst obtained by adding vanadium oxide to titanium oxide, for example.
5 and 6, a pair of exhaust gas shielding valves 7, 8 and 9 provided before and after the catalyst devices 4, 5 and 6, respectively;
It mainly comprises reducing agent injection means 10, 11 and 12 provided at the inlets of the respective catalyst devices 4, 5 and 6.

In such a configuration, the exhaust gas 1 containing, for example, dioxins discharged from the sintering equipment (not shown) flows through the exhaust gas flue 20, passes through the dust removing device 2 and the temperature raising device 3, and removes dust and temperature. After being adjusted, they respectively flow into the branch exhaust gas flues 21, 22 and 23 via the shut-off valves 7, 8 and 9 on the inlet side, and are injected as necessary from the reducing agent injection means 10, 11 and 12, for example. The ammonia flows into the catalyst devices 4, 5 and 6 together with the ammonia, and harmful components are decomposed and removed in the presence of the catalyst. However, if it is necessary to restore the catalytic activity of the catalyst device 4, the catalyst device of the branch exhaust gas flue 21 This is performed by closing the exhaust gas shielding valves 7 before and after 4 to disconnect the catalyst device 4 from the exhaust gas treatment system, increasing the amount of catalyst loaded in the catalyst device 4, and replacing or regenerating the catalyst. At this time, the exhaust gas shielding valves 8 and 9 of the branch exhaust gas flues 22 and 23 are open, and the exhaust gas 1 is continuously processed by the catalyst devices 5 and 6. And one of the catalyst devices 5 or 6, for example, the catalyst device 5
When the catalytic activity of the exhaust gas flue gas decreases, the exhaust gas shielding valve 8 of the branch exhaust gas flue 22 is closed to disconnect the catalytic device 5 from the processing system, and a recovery operation of the catalytic activity is performed in the same manner as described above. The shut-off valve 21 is opened, whereby the catalyst device 4 having recovered the activity is incorporated into the exhaust gas treatment system, and thereafter, the exhaust gas treatment using the catalyst devices 4 and 6 is performed. Hereinafter, the branch pipe having the catalyst device in use and the catalyst device being regenerated is sequentially cut off or incorporated into the exhaust gas treatment system, and the continuous treatment operation mainly using the two systems is repeated.

According to this embodiment, the exhaust gas flue is divided into a plurality of, for example, three systems, and the branch exhaust gas flue used for exhaust gas treatment and the branch exhaust gas flue for restoring the catalytic activity are sequentially switched. As a result, exhaust gas treatment using a catalyst device having a sufficient catalytic activity at all times becomes possible, and dioxins as harmful substances in exhaust gas can be continuously decomposed and removed for a long period of time.

In the present embodiment, the dust removing device 2 includes
For example, an electric dust collector or a bag filter is used. Further, as the temperature raising device 3, for example, a heat exchanger or a direct combustion type hot air generator is used. In the present embodiment, the exhaust gas flue is branched into three systems, but the number of branches is not particularly limited as long as it is two or more systems.

In this embodiment, when the exhaust gas 1 contains nitrogen oxides, ammonia is injected as a reducing agent from the reducing agent injection means 10 to 12 provided on the upstream side of each of the catalyst devices 4 to 6. However, in this case, for example, when the catalyst of the catalyst device 4 is regenerated, the injection of the reducing agent in the reducing agent injection means 10 is stopped, and the exhaust gas 1 is allowed to flow without the injection of the reducing agent. The catalyst activity can be restored. At this time, for example, ammonia is injected into the catalyst devices 5 and 6 from the reducing agent injection means 11 and 12, so that the denitration performance of the entire device is ensured,
The exhaust gas 1 is continuously processed. Hereinafter, the reducing agent injection means 1 provided in the branch exhaust gas flue 21, 22 and 23
By sequentially stopping the injection of the reducing agent at 0, 11, and 12, the exhaust gas treatment operation using, for example, a two-way branched exhaust gas flue is continued while the catalyst activity is restored.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific embodiments of the present invention (examples of actual machines) will be described. Example 1 For one sintering facility, the apparatus shown in FIG. 1 having three exhaust gas treatment systems each equipped with a catalyst device was used, and the conditions shown in Table 1, namely, the exhaust gas treatment amount: 1,400,000 N
m ³ / h, exhaust gas temperature: 200 ° C., continuous operation period: 10
NOx concentration emitted from sintering equipment in 2005: 200 ppm
The exhaust gas of the catalyst device is sequentially recovered using the two exhaust gas treatment systems while sequentially recovering the catalytic activity of the catalyst device.
When treated so that the Ox concentration becomes 100 ppm,
The ratio of the required amount of catalyst to the prior art (Comparative Example 1 described later) was 0.22. When the outlet NH ₃ concentration is 10
It was adjusted to be ppm.

[0022]

[Table 1]

Example 2 A similar process was performed as in Example 1 except that the injection of the reducing agent was stopped as an operation for restoring the activity of the catalyst. ) Was 0.18.

Comparative Example 1 For one sintering facility, one system of exhaust gas treatment equipment provided with one catalyst device was used.
A year later, the catalyst charge was determined to replace the catalyst, and the same exhaust gas as in Example 1 was treated so that the NOx concentration at the catalyst device outlet became 100 ppm. It was 5 times.

The required catalyst amounts in Examples 1 and 2 and Comparative Example 1 are shown in comparison with FIG. In FIG. 2, according to Examples 1 and 2 in which the exhaust gas treatment system was divided into three systems and the treatment was performed while sequentially recovering the catalytic activity, the required amount of catalyst was smaller than that in Comparative Example 1 in which the exhaust gas treatment system was one system. It can be seen that it was significantly reduced.

[0026]

According to the invention described in claim 1 of the present application,
Without stopping long-term continuous operation equipment, it is possible to recover the catalytic activity of the catalytic device whose activity has decreased,
The exhaust gas can be treated continuously for a long period of time, and the total amount of required catalyst can be reduced. According to the invention described in claim 2 of the present application, in addition to the effects of the above invention, the catalyst activity can be effectively recovered.

According to the invention described in claim 3 of the present application, in addition to the effects of the above invention, the catalyst performance can be more effectively recovered. Therefore, the total amount of required catalyst over a long period can be further reduced. According to the invention described in claim 4 of the present application, exhaust gas discharged from a sintering facility and containing harmful components such as dioxin can be stably treated for a long period of time.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system of an exhaust gas treatment apparatus to which the present invention is applied.

FIG. 2 is a diagram showing a comparison between the effects of the present invention and the prior art.

FIG. 3 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exhaust gas, 2 ... Dust removal device, 3 ... Heating device, 4, 5, 6
... Catalyst device, 7, 8, 9 ... Exhaust gas cutoff valve, 10, 11,
12 ... reducing agent injection means, 20 ... exhaust gas flue, 21, 2
2, 23: branch exhaust gas flue, 31: exhaust gas, 32: dust removing device, 33: heating device, 34: catalyst device, 35: reducing agent injection means, 36: exhaust gas flue.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yoshimichi Mori 6-9 Takaracho, Kure-shi, Hiroshima Pref. Inside the Kure Factory (72) Inventor Yoshinori Nagai 6-9 Takaracho, Kure-shi, Hiroshima Babcock-Hitachi Co., Ltd. 4D048 AA06 AA11 AC03 AC04 BA07X BA13X BA23X BA26X BA27X BA42X BD07 BD10 CC25 CC33 CC38 CC52 CD03 CD05 DA01 DA06 DA10 4K001 AA10 CA44 GA10 GB09

Claims (4)

[Claims] An exhaust gas discharged from a facility that is operated continuously for a long time is introduced into an exhaust gas treatment system having a catalyst device, and harmful components contained in the exhaust gas are decomposed using the catalyst device.
In the exhaust gas treatment method to be removed, the exhaust gas treatment system is provided by branching into two or more systems, and the catalyst device is provided in each exhaust gas treatment system. During the exhaust gas treatment using one or more exhaust gas treatment systems, the catalytic performance of the catalyst device in one or more other exhaust gas treatment systems is restored, and when the catalytic activity of the catalyst device in the exhaust gas treatment system in use decreases, the exhaust gas The processing system is switched to an exhaust gas processing system having a catalyst device whose catalyst performance has been restored, and thereafter, the catalyst device whose catalytic performance has been reduced is sequentially separated from the exhaust gas processing system, and the catalyst performance is restored, and then incorporated into the exhaust gas processing system. Characterized by continuously treating the exhaust gas for a long time,
A method for treating exhaust gas from long-term continuous operation equipment. 2. The method according to claim 1, wherein the step of restoring the catalytic performance of the catalytic device is a step of adding, exchanging, or regenerating the catalyst in the catalytic device separated from the exhaust gas treatment system. The method for treating exhaust gas from a long-term continuous operation facility according to claim 1. 3. A method for treating exhaust gas, wherein the exhaust gas contains nitrogen oxides and decomposes and removes harmful components in the exhaust gas while injecting a reducing agent upstream of each catalyst device. The method for treating exhaust gas from long-term continuous operation equipment according to claim 1 or 2, wherein the step of restoring the performance is a step of stopping the injection of the reducing agent into the catalyst device. 4. The method for treating exhaust gas from a long-term continuous operation facility according to claim 1, wherein the long-term continuous operation facility is a sintering facility.