JPS6049012B2 - How to regenerate denitrification catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is a method for treating sulfur oxides (SOx) and nitrogen oxides (NOx).
) and a method for treating exhaust gas and regenerating a catalyst.

When using the ammonia reduction method for denitrification treatment of exhaust gas containing SOx, it must be applied to exhaust gas of 335 to 320°C or lower. ・ 1 stop゛9← / KTUU
C Ha, Se ZF,, 斗μH force [(Ni(,).SO,
), which causes negative effects such as a decrease in catalyst activity and an increase in catalyst pressure loss, making long-term stable operation impossible, so it is currently not used. In this invention, a part of the catalyst of a denitrification reactor whose denitrification function has deteriorated due to the adhesion of acidic ammonium sulfate or ammonium sulfate produced by low-temperature denitrification is heated at 350 to 450°C.
Preferably, the temperature is raised to 350 to 400°C, the deposits are decomposed and gasified and removed, and the catalyst which has recovered its denitration function is intended to be reused for denitration.

FIG. 2 shows an example of how the denitrification performance efficiency changes over time in a low temperature range of 250°C.

That is, the denitrification rate gradually decreases with the passage of time, and when used as is, it becomes impossible to maintain the desired performance in a relatively short period of time. This indicates that when this is heated and maintained at a temperature above the decomposition temperature of acidic ammonium sulfate (for example, 400° C.) at point A, which is the allowable limit of the denitrification efficiency, the denitrification rate is recovered to the initial point.

In other words, the (hi) and (roni) sections J are for low-temperature denitrification, and the (euro) sections are for thermal decomposition. Based on these characteristics, after using a reactor containing a catalyst for a certain period of time, the catalyst whose performance has deteriorated is heated and heated to restore the catalyst performance and used repeatedly. There are things that make it possible to maintain denitrification performance. Another advantage of the invention is that it allows for miniaturization of conventional catalyst heating equipment.

In order to treat the entire amount of catalyst in the denitrification catalyst reactor simultaneously and intermittently, it is necessary to heat the entire amount of catalyst contained therein at the same time, which requires a large amount of material and equipment as a heat source, and This is not an economical method because the entire equipment must be designed to withstand high temperature conditions. When carrying out the method according to the present invention, the amount of catalyst to be heated and regenerated may be a part of the catalyst contained in the denitrification catalyst reactor, so that less than 4 to 5% of the exhaust gas to be treated from the exhaust gas generation source is recovered. It is sufficient to bypass the heating and raise the temperature, making it possible to significantly reduce equipment and operating costs.

Furthermore, it is possible to save energy by recovering heat by exchanging heat between the bypass gas and the exhaust gas after the catalyst heat treatment, and it is possible to reduce fuel costs for the heat source for catalyst regeneration.

Preferably, during heating regeneration of the catalyst, ammonium sulfate and acidic ammonium sulfate adhering to the catalyst are decomposed and vaporized to generate NH3 gas, and the NOx contained in the bypassed exhaust gas is decomposed and vaporized.
By reacting with H2O (5N2), it is possible to simultaneously remove NOx and NH3 in the exhaust gas produced during heating regeneration of the catalyst in the presence of a denitrification catalyst, which can kill two birds with one stone.

The present invention will be explained below with reference to the drawings. FIG. 1 shows an apparatus and piping according to the present invention.

Specify sources of gas containing SOx and NOx such as coke ovens, sintering machines, and boilers in plants. Indicated by No. 1. Further, this gas generation source shall include equipment for heating the exhaust gas from these gas generation sources to a temperature of 200 to 300'C, which is the low temperature denitrification reaction temperature. The waste gas to be treated from these gas generation sources passes through the waste gas to be treated pipe 2 and is led to the reactor 3; during this time, necessary NH3 gas is injected from the pipe 2a. There is a catalyst layer 4 in the reactor 3, which denitrates the exhaust gas by passing it therethrough. After denitration, the exhaust gas passes through an exhaust gas outlet duct 5, is sucked in by a fan 6, and is discharged into the atmosphere from a chimney 7. If the gas pressure on the upstream side is positive enough to pass through the catalyst layer, the fan 6 is not necessary. In the embodiment shown in FIG. 1, a catalyst extraction device 9 is provided at the bottom of the catalyst layer 4, and connected to this is another part of the catalyst of the denitrification reactor.

A catalyst heating device 10 is provided as a catalyst container requiring regeneration. The catalyst in the catalyst heating device 10 is supplied with gas heated to a temperature necessary to gasify and remove the attached ammonium sulfate and acidic ammonium sulfate, and the catalyst whose performance has been recovered is returned to the upper part of the reactor by the catalyst transport device 11. It is returned into the catalyst bed by the filling device 8.

The heating gas passes through a bypass gas duct 12 branching from the exhaust gas pipe 2, is sucked in by a gas booster fan 13, and is sent to a combustion furnace 14 having a burner 19. Note that the bypass gas extraction point may be from the high-temperature zone of the gas generation source 1 of the plant;
7 and the fuel system will be unnecessary. In the combustion furnace 14, in order to raise the temperature of the bypassed exhaust gas to a required temperature of 350 to 450'C, the exhaust gas produced by burning fuel (the type of fuel is not regulated) is mixed with the bypassed exhaust gas and a catalyst is heated. The exhaust gas is further passed through an exhaust gas duct 16 to the reactor outlet exhaust gas 5 and discharged from a chimney 7 via a fan 6. Note that if a heat exchanger 18 is provided in the exhaust gas duct 16 to exchange heat with the exhaust gas of the bypass gas duct 12, it is possible to further reduce operating costs.

This invention has the following features.

That is, in a method of removing NOx from a combustion exhaust gas containing sulfur oxides and nitrogen oxides using a denitrification catalyst reactor having a catalyst, part of the combustion exhaust gas is The sample is taken out and heated as exhaust gas at a temperature suitable for catalyst regeneration in a catalyst heating device that accommodates a part of the catalyst in the denitrification catalyst reactor, gasifying the attached ammonium sulfate and acidic ammonium sulfate and regenerating the catalyst. At the same time, NH3 generated by decomposition and N in the heating gas are
This method is characterized by removing Ox by suitably reacting in the presence of a catalyst, reducing the size of the device, and achieving high efficiency operation by regenerating the energy-saving catalyst.

By carrying out this invention, the exhaust gas containing SOx and NOx from the exhaust gas generation source is left as it is when the temperature is below 450'C, and when the temperature has dropped to below 350°C, it is heated and the amount is reduced. A part of the catalyst in the denitrification reactor can be sequentially regenerated using the heating gas, and the NH3 gas generated during the regeneration can be converted into NOx in the heating gas.
In the presence of a denitrification catalyst, the reaction can be carried out effectively to prevent harmful leaks of NH3 and NOx, and to achieve an energy-saving effect.

Moreover, the catalyst can be regenerated even when the denitrification reactor is operating, improving plant thermal efficiency by effectively utilizing the heat retained in the plant exhaust gas, and processing exhaust gas containing SOx and NOx, reducing NOx in the exhaust gas from the chimney. It has various effects such as being able to reduce the amount of space required.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the arrangement of the apparatus and the pipe system according to the present invention, and FIG. 2 is a diagram showing changes in the denitrification rate over time when the present invention is implemented. 1... SOx, NOX containing gas generation source, 2...
...Exhaust gas pipe line requiring treatment, 3...Reactor containing catalyst, 4...Catalyst layer, 5...Exhaust gas outlet duct, 6... Fan, 7... Chimney, 8... Catalyst filling device, 9... Catalyst extraction device, 10... Catalyst heating device, 11...
・Catalyst transport device, 12... Bypass gas duct, 13... Gas booster fan, 14...
... Combustion furnace, 15... Gas duct, 16...
...Exhaust gas duct, 17...Air fan,
18...Heat exchanger, 191001 Banina.

Claims (1)

[Claims] 1. A method for reducing nitrogen oxides in the exhaust gas by adding ammonia to the combustion exhaust gas containing sulfur oxides and nitrogen oxides, and then bringing the mixture into contact with a circulating catalyst in a denitrification reactor. For the catalyst in the reactor located in the exhaust gas passage, ammonia added to the combustion exhaust gas is supplied to carry out the denitrification reaction, and the denitrification reaction is performed outside the exhaust gas passage of the denitrification reactor. The catalyst located at the bottom is introduced into a catalyst heating device, and a part of the combustion exhaust gas is branched from upstream of the denitrification reactor, and only the exhaust gas after being heated to 350 to 450°C is sent to the catalyst heating device. By supplying the catalyst, a catalyst regeneration reaction is performed, and the exhaust gas after the regeneration reaction is guided to the downstream exhaust gas duct of the denitrification reactor, and the regenerated catalyst is re-charged from the upper part of the catalyst reactor for circulation use. A method for regenerating a denitrification catalyst, characterized by: