JP3248166B2 - Catalyst regeneration method for exhaust gas denitration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for regenerating a deteriorated denitration catalyst in an exhaust gas denitration system using a hydrocarbon-based reducing agent.

[0002]

2. Description of the Related Art A combustion gas discharged from a diesel engine or the like contains nitrogen oxides (NOx), and a process of denitrifying this exhaust gas using a reducing agent is generally performed. In this case, in order to effectively remove NOx in the exhaust gas, various denitration systems using a hydrocarbon-based reducing agent as a reducing agent have been developed. If such a denitration device is used for a long time, calcium sulfate or carbon will adhere to the catalyst.
Deposits gradually decrease the denitration performance.

[0003] As a method of regenerating a deteriorated catalyst,
A method of regenerating a denitration catalyst by air blowing, or as described in JP-B-62-26818, a packed bed filled with a denitration catalyst is heated to 450 to 400% by a heating burner or the like.
A method of supplying a heated gas heated to 550 ° C. is known.

[0004]

In a denitration apparatus using a hydrocarbon-based reducing agent, the rate of catalyst deterioration due to carbon adhesion is higher than in an apparatus using ammonia as a reducing agent. Also, regeneration by heating is more advantageous. In the case of an ammonia-based reducing agent, regeneration by spraying steam can be considered, but in the case of a hydrocarbon-based reducing agent, since the gas temperature is low and sulfate is generated, spraying of steam cannot be applied. In addition, a method of supplying a high-temperature gas using a burner or the like requires a special heating device, and the operation is complicated. Also, because of the high temperature gas,
The catalyst may be overheated locally, possibly leading to catalyst damage. For example, zeolite catalysts can withstand relatively high temperatures, but even above 700 ° C. the likelihood of damage increases.

[0005] The present invention has been made in view of the above points, and an object of the present invention is to regenerate a deteriorated catalyst in an exhaust gas denitration apparatus using a hydrocarbon-based reducing agent.
An object of the present invention is to provide a catalyst regeneration method in which the temperature of exhaust gas introduced into a catalyst filling section is temporarily increased, a special heating device is not required, the operation is simple, and the catalyst is not likely to be damaged.

[0006]

To achieve the above object, according to the Invention The catalyst regeneration method of an exhaust gas denitration apparatus of the present invention, a catalytic reactor in an exhaust gas denitration apparatus using charcoal hydrocarbon-based reducing agent, in the exhaust gas On the other hand, the catalyst is divided into a plurality of stages of catalyst loading sections in series, a cooler is provided upstream of the catalyst loading section of each stage, and a hydrocarbon-based reducing agent is added upstream of each catalyst loading section, so that the catalyst To regenerate the catalyst in the filling section,
Hydrocarbons return to the upstream stage of the divided catalyst packing section
By increasing the amount of Motozai, it is characterized by controlling the 300 to 400 ° C. temporarily raise the exhaust gas temperature to be introduced into the catalyst packed portion of each stage. In this case, 300-40
The state in which the exhaust gas at 0 ° C. is introduced into the catalyst filling section is set to 30-60
It is preferable to hold the catalyst for a period of minutes, but when the catalyst is frequently regenerated, the time may be less than 30 minutes.

[0007] In the method of the invention described above, the function of the cooler, which is provided on the upstream side of the catalyst-filled portion is stopped, it is also possible to control and hold the exhaust gas temperature. Also, in the method of the present invention, a bypass of the exhaust gas to the catalytic reactor
A pipe is provided and the exhaust gas inflow direction of the catalyst filling section is switched,
In some cases, the heated exhaust gas may flow through the catalyst charging section (see FIGS. 4 and 5). Further, in these methods of the present invention, a part of the exhaust gas at the outlet of the catalyst filling section is bypassed.
In some cases, the exhaust gas is returned to the upstream side of the catalyst charging section by a pipe so that the heated exhaust gas flows through the catalyst charging section (see FIG. 6).

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, in which combustion exhaust gas discharged from a diesel engine is denitrated. In addition, the present invention
The present invention is not limited to the embodiment described below, and may be applied to denitration of exhaust gas from another internal combustion engine. Further, in the present embodiment, the case where the catalyst reactor is divided into a plurality of stages of catalyst filling sections is described, but it is of course possible to adopt a configuration in which the catalyst filling section is not divided.

FIG. 1 shows an apparatus for carrying out a catalyst regeneration method for an exhaust gas denitration apparatus according to a first embodiment of the present invention. In FIG. 1, exhaust gas discharged from a diesel engine (not shown) is cooled by a cooler 10 to a temperature suitable for a denitration reaction, and then introduced into a catalytic reactor 14 through an exhaust gas duct 12. For example, a Pt-supported zeolite catalyst (for example, 0.5 wt% Pt
When using zeolite (for example, MFI type zeolite), exhaust gas from a diesel engine (about 430 ° C.)
Is cooled to 240 to 250 ° C. by the cooler 10 before being introduced into the catalytic reactor 14. The catalyst reactor 1
The cooler 10 at the four inlets may be an exhaust gas temperature control device. The catalyst reactor 14 is divided into a plurality of catalyst filling sections (catalyst tanks or catalyst layers) 16 (four stages in FIG. 1 as an example), and the exhaust gas upstream of the second and subsequent catalyst filling sections 16 is divided. A cooler 18 is provided in the duct 12, and a reducing agent addition pipe 20 is connected as a reducing agent adding means to the exhaust gas duct 12 between the cooler 18 and the catalyst filling section 16 of each stage.

The exhaust gas introduced into the catalytic reactor 14 is added with a hydrocarbon-based reducing agent from a reducing agent addition pipe 20 and
It is introduced into the catalyst filling section 16 of the stage, where the exhaust gas is denitrated. The temperature of the exhaust gas discharged from the first-stage catalyst filling section 16 has increased due to the reaction with the hydrocarbon-based reducing agent, and the temperature range suitable for the denitration reaction (240 to 250 in the case of the Pt-zeolite catalyst, ° C). FIG.
Is a comparison of the temperature of the catalyst-filled portion when the intercooling is performed by the cooler and when the cooler is stopped. The cooler 18 on the upstream side of the catalyst-filled portion 16 is operated to perform the intercooling of the exhaust gas. Is performed, as shown in FIG.
The inlet temperature of the fourth-stage catalyst filling section is kept at around 250 ° C., and almost no temperature rise is observed. In addition, the outlet temperature of the first to fourth stages of the catalyst charging section is also 3 times that of the first stage.
Almost no increase from about 00 ° C. Since the inlet temperature of each catalyst filling section is about 250 ° C., which is a temperature suitable for a denitration reaction for a Pt-zeolite catalyst, a high denitration rate of about 70% can be obtained.

On the other hand, the cooler 1 on the upstream side of the catalyst
2, the inlet temperature and the outlet temperature increase as going from the first stage to the fourth stage catalyst filling section, and as shown in FIG. At about 360 ° C., and the outlet temperature has risen to about 440 ° C. In this case, since the temperature of each catalyst filling section exceeds the temperature range suitable for the denitration reaction for the Pt-zeolite-based catalyst, the denitration rate is about 40%. Thus, 1
By stopping the intermediate cooling of the exhaust gas when the inlet temperature of the catalyst filling section 16 of the stage is about 250 ° C., the heat of reaction with the hydrocarbon-based reducing agent is increased toward the downstream catalyst filling section. 16 rises, and the final stage catalyst charging section 1
At exit 6, the temperature is about 440 ° C. However, the outlet temperature of the first-stage catalyst charging section 16 is set at 3
Since the temperature has not reached 00 ° C., it is difficult to regenerate the catalyst in the first stage catalyst filling section 16. However, even when the exhaust gas temperature at the inlet of the first-stage catalyst filling section 16 is low, the cooler 10 on the upstream side of the catalyst
The temperature of the catalyst filling section 16 of the stage can be set to a temperature at which the catalyst can be regenerated. However, in this case, on the contrary, the temperature of the downstream catalyst charging section 16 becomes too high, so that the reducing agent addition pipe 2
The reaction heat is controlled by adjusting the amount of the hydrocarbon-based reducing agent to be added from 0 or / and the cooler 1 in the catalytic reactor 14
8, it is necessary to control the catalyst filling section 16 on the downstream side so as not to be overheated.

FIG. 3 shows the measurement results of the change over time in the exhaust gas temperature and the denitration rate when the catalyst is actually regenerated by raising the temperature. The exhaust gas temperature at the catalyst reactor inlet is about 250 ° C.
The denitration rate, which was about 70% at the time, gradually decreased, and when the denitration rate reached about 30% (↓ in FIG. 3), the function of the cooler was stopped or the amount of the hydrocarbon-based reducing agent added. The transition of the denitration rate when the catalyst is regenerated by controlling the exhaust gas temperature to about 300 ° C. by increasing the exhaust gas temperature and maintaining the temperature for about 40 minutes is shown. The regeneration of the denitration catalyst temporarily increases the denitration rate to about 80% after regeneration.
The denitration rate has been at a high level of about 70%. From this, it is understood that the regeneration treatment of the catalyst by the above-mentioned temperature rise removes calcium sulfate and carbon adhered and deposited on the catalyst surface, and recovers the denitration performance of the catalyst.

Examples of the hydrocarbon reducing agent include, for example, ethylene, propylene, LPG, butene, octane, octene, nonane, decane, tetradecane, hexadecane, kerosene, light oil, heavy oil and the like. Examples of the denitration catalyst include, in addition to the above-described platinum (Pt) -supported zeolite catalyst, platinum-supported alumina or zeolite or alumina or copper, cobalt, nickel, manganese, iron, silver, and indium. Among them, zeolite or alumina containing at least one kind is exemplified. Examples of the structure of the catalyst include a honeycomb formed article and a packed layer of a pellet catalyst.

FIGS. 4 and 5 show an apparatus for carrying out a catalyst regeneration method for an exhaust gas denitration apparatus according to a second embodiment of the present invention. In the present embodiment, a bypass pipe for exhaust gas is provided in a catalytic reactor so that the flow direction of exhaust gas is switched during regeneration of a catalyst. As shown in FIG. 4, in the normal case, the exhaust gas whose temperature has been adjusted by the cooler 22 flows from the upstream side to the downstream side of the catalyst charging unit 24 divided into a plurality of stages (four stages in FIG. 4 as an example). The valves (eg, dampers) 28, 30 provided in the exhaust gas duct 26 are opened, and the valves (eg, dampers) 3 provided in the exhaust gas bypass pipes 32, 34 so that the denitration is performed by flowing.
6, 38 are closed. In some cases, a cooler may be provided upstream of the second and subsequent stages of the catalyst filling section 24 to perform intermediate cooling of exhaust gas. On the other hand, as shown in FIG. 5, when performing regeneration of the catalyst, the function of the cooler 22 is stopped,
As the exhaust gas from a diesel engine or the like flows from the downstream side to the upstream side of the catalyst filling unit 24 to regenerate the catalyst,
Valves 36, 38 provided in exhaust gas bypass pipes 32, 34
Is switched to open, and the valves 28 and 30 provided in the exhaust gas duct 26 are switched to closed. As described above, by providing the exhaust gas bypass pipe and switching the flow direction of the exhaust gas, the catalyst can be regenerated without a heating device such as a burner even in a low temperature state. Other configurations and operations are the same as those in the first embodiment of the present invention.

FIG. 6 shows an apparatus for carrying out a catalyst regeneration method for an exhaust gas denitration apparatus according to a third embodiment of the present invention. In the present embodiment, a part of the exhaust gas at the outlet of the catalytic reactor is returned to the inlet side of the catalytic reactor by a bypass pipe. As shown in FIG. 6, a part of the exhaust gas flowing from the upstream side to the downstream side of the catalyst charging unit 24 divided into a plurality of stages (in FIG. It is returned to the upstream side of the catalyst filling section 24 of the stage. In this case, as shown in FIG.
The configuration may be such that the zero blower 42 is operated using the turbine 46 of the supercharger 44. 48 is a supercharger 4
A blower 4 and a check valve 50 are provided. In some cases, a cooler may be provided upstream of the second and subsequent stages of the catalyst filling section 24 to perform intermediate cooling of exhaust gas. As described above, by returning a part of the heated exhaust gas at the outlet of the catalyst reactor to the inlet side of the catalyst reactor, the regeneration of the catalyst filling portion in the upstream stage is facilitated, and the denitration rate is also improved. There are advantages. Other configurations and operations are the same as those in the first and second embodiments of the present invention.

[0016]

As described above, the present invention has the following effects. (1) In an exhaust gas denitration apparatus using a hydrocarbon-based reducing agent, the temperature of the exhaust gas introduced into the catalyst filling section is set to 300 to 40
Since the temperature is temporarily raised to 0 ° C. and held, it is possible to efficiently regenerate the denitration catalyst deteriorated due to the adhesion and deposition of carbon and calcium sulfate. Further, by using the regenerated catalyst, it is possible to obtain high denitration performance. (2) The function of the cooler provided on the upstream side of the catalyst charging section is stopped, or the amount of the hydrocarbon-based reducing agent added to the upstream side of the catalyst charging section is increased to be introduced into the catalyst charging section. Since the temperature of the exhaust gas to be heated may be raised, a special heating device is not required, and the operation is simple. In addition, the catalyst is not overheated locally, and there is no risk of damage to the catalyst. (3) by increasing the amount of toward the upstream stage of the catalyst packed portion hydrocarbon reductant, without exhaust gas temperature is too high the catalyst filled portion of the downstream side, in the catalyst-packed portion of each stage The exhaust gas temperature can be controlled to a temperature at which the catalyst can be efficiently regenerated. (4) When the exhaust gas inflow direction of the catalyst filling section is switched so that the heated exhaust gas flows through the catalyst filling section, the catalyst can be regenerated without a heating device such as a burner even in a low temperature state. (5) When a part of the exhaust gas at the outlet of the catalyst charging section is returned to the upstream side of the catalyst charging section so that the heated exhaust gas flows through the catalyst charging section, regeneration of the catalyst without a heating device such as a burner is performed. In addition to this, there is an advantage that regeneration of the upstream catalyst-filled portion is facilitated, and that the denitration rate is also improved.

[Brief description of the drawings]

FIG. 1 is a systematic schematic configuration diagram showing an apparatus for performing a catalyst regeneration method for an exhaust gas denitration apparatus according to a first embodiment of the present invention.

FIG. 2 is a graph comparing the inlet temperature and the outlet temperature of each catalyst-filled part when the exhaust gas is denitrated using the apparatus shown in FIG. 1 when the cooler is functioning and when the cooler is stopped. .

FIG. 3 is a graph showing the change over time in the exhaust gas temperature and the denitration rate when the catalyst is regenerated by increasing the temperature.

FIG. 4 is a system diagram illustrating a schematic configuration during normal operation according to a second embodiment of the present invention.

FIG. 5 is a system diagram illustrating a schematic configuration during a regeneration operation according to a second embodiment of the present invention.

FIG. 6 is a system diagram showing a schematic configuration of a third embodiment of the present invention.

[Explanation of symbols]

 10, 18, 22 Cooler 12, 26 Exhaust gas duct 14 Catalytic reactor 16, 24 Catalyst filling section 20 Reducing agent addition pipe 28, 30, 36, 38 Valve 32, 34, 40 Exhaust gas bypass pipe 42, 48 Blower 44 Supercharging Machine 46 turbine 50 check valve

Continuing from the front page (72) Inventor Masahiro Sugata 1-1, Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries, Ltd. Inside the Akashi Plant (72) Eiichi Shirai 3-1-1, Higashi-Kawasaki-cho, Chuo-ku, Kobe Kawasaki Heavy Industries Kobe Factory, Ltd. (56) References JP-A-57-207547 (JP, A) JP-A-7-132212 (JP, A) JP-A-7-100335 (JP, A) JP-A-7-243322 ( JP, A) JP-A-9-57062 (JP, A) JP-A-8-105318 (JP, A) JP-A-7-119444 (JP, A) JP-A-62-225231 (JP, A) JP Hei 8-49533 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 53/86 B01D 53/94 F01N 3/04-3/38

Claims (4)

(57) [Claims] 1. A catalyst reactor in an exhaust gas denitration apparatus using a hydrocarbon-based reducing agent is divided into a plurality of stages of catalyst loading sections in series with respect to an exhaust gas flow, and cooled upstream of each stage of the catalyst loading section. vessel provided with a, so as to add the upstream hydrocarbon reducing agent in each catalyst packed portion, to regenerate the catalyst of the catalyst packed portion, are in the upstream stage of the divided catalyst packed section
As the amount of the hydrocarbon-based reducing agent increases, the temperature of the exhaust gas introduced into the catalyst-filled section of each stage is temporarily increased, and
A method for regenerating a catalyst for an exhaust gas denitration apparatus, wherein the catalyst is controlled at a temperature of from 00 to 400 ° C. Wherein the function of the cooler disposed upstream of the catalyst packed section is stopped, the catalyst regeneration method of an exhaust gas denitration apparatus of claim 1 wherein the control and hold the exhaust gas temperature. 3. An exhaust gas bypass pipe is provided in the catalytic reactor.
Only, by switching the exhaust gas inflow direction of the catalyst-filled portion, and claim 1 heated by the exhaust gas to flow catalyst packed portion
Is a method for regenerating a catalyst in an exhaust gas denitration apparatus according to item 2 . 4. A part of the exhaust gas at the outlet of the catalyst filling section is bypassed.
3. The method for regenerating a catalyst in an exhaust gas denitration apparatus according to claim 1, wherein the exhaust gas whose temperature has been raised is returned to an upstream side of the catalyst charging section by a heat pipe so that the heated exhaust gas flows through the catalyst charging section.