JPS60220129A - Treatment of exhaust gas - Google Patents

Abstract

PURPOSE:To perform the desulfurization and denitration of low temp. exhaust gas, in an exhaust gas treatment method, by removing NOx and SOx by a first reactor of a carbonaceous catalyst and mixing NH3 in exhaust gas to perform denitration and desulfurization in a second reactor while regenerating a catalyst before treating the same with NH3 for the purpose of reuse. CONSTITUTION:Exhaust gas having temp. of 100-200 deg.C is contacted with the carbonaceus catalyst bed falling in a reactor 2 through a line 1 to receive desulfurization and denitration treatment while the treated gas is subsequently introduced into a second moving bed type reactor 6. At this time, NH3 is added to the exhaust gas from a line 5. The exhaust gas is contacted with the carbonaceous catalyst bed in the reactor 6 to receive desulfurization and denitration treatment and the treated gas is treated by a dust collector 9 through a line 8 and discharged. The catalyst discharged from the reactor 6 is supplied to the upper part of the reactor 2 and supplied to a regenerator 11 while discharged from the reactor 2 to receive regeneration under heating and the regenerated catalyst is sent to an NH3 activation vessel 12 and treated with NH3 from a line 13 to be returned to the reactor 6 for the purpose of recirculation and use.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating exhaust gas in a low-temperature range containing an aA hydrochloride oxide and nitrogen oxide.

As a treatment method for exhaust gas containing high concentrations of sulfur oxides (Box) and nitrogen oxides (NO), such as coal and heavy oil-fired zeila exhaust gas and ironworks sintering furnace exhaust gas, ammonia is mixed into the exhaust gas. A known method is to process exhaust gas by passing it through a packed bed of carbonaceous catalysts.This method has the advantages of simultaneously removing SOx and NOx and allowing the catalyst to be reused. .

However, in order to efficiently remove NOx with this method, the temperature must be at least 200°C or higher, preferably 220-220°C.
A reaction temperature of about 50° C. is required, and NOx cannot be removed sufficiently at lower temperatures. However, at a reaction temperature of 200° C., there is a problem that a part of the carbonaceous catalyst is consumed by oxygen in the exhaust gas as C+02→CO2. Further, since the temperature of the exhaust gas from the blower is approximately 150°C at the outlet of the air heater, etc., it is disadvantageous that the exhaust gas must be preheated to a temperature of 200°C or higher.

In contrast, a method has been proposed that can remove not only SOx but also NOx at a high removal rate even at a temperature of about 150°C. In this method, ammonia is mixed into the exhaust gas, and this mixed gas is led to the first reactor to remove most of the SO
After removing X, ammonia is mixed into the treated gas again, and this mixed gas is led to the 20th reactor for reprocessing.

However, in this method, the amount of ammonia injected into the first reactor is limited to SOx1 in order to maintain the activity of the carbonaceous catalyst.
It is usually 0.2 to 0.8 moles per mole, which is uneconomical. In addition, when the catalyst is heated and regenerated, high concentration SO is recovered.
, high ammonia concentration in the gas (usually 0.3-2%)
This results in problems such as blockage and corrosion of subsequent equipment and reduced purity of recovered by-products. In addition, reducing the amount of ammonia injected at the inlet of the first reactor lowers the activity of the catalyst, so in order to obtain a high desulfurization and denitrification rate, the transfer speed of the catalyst in the reactor must be increased, and the catalyst powder There is also the problem that the number of people is increasing and it becomes uneconomical.

The purpose of the present invention is to provide high desulfurization and
It is an object of the present invention to provide a method for treating exhaust gas that provides a high denitrification rate and that does not cause equipment trouble due to the use of ammonia.

That is, in the exhaust gas treatment method of the present invention, exhaust gas containing sulfur oxides and nitrogen oxides at a temperature of about 100 to 200°C is introduced into a first reactor filled with a carbonaceous catalyst to perform desulfurization and denitrification treatment. Afterwards, this treated gas is mixed with ammonia and introduced into a second reactor filled with a carbonaceous catalyst for denitrification and desulfurization treatment, while the exhaust gas treatment involves heating and regenerating the carbonaceous catalyst used for exhaust gas treatment. The method is characterized in that the heated and regenerated carbonaceous catalyst is brought into contact with ammonia to be treated and then used for the treatment of exhaust gas.

The present invention will be explained with reference to a diagram showing an example of a process for treating exhaust gas containing SOx and NOx.

The exhaust gas whose temperature is controlled to about 100 to 200° C. is introduced into the first cross-flow moving bed reactor 2 via the line. The exhaust gas is discharged from the first reactor 2 after being desulfurized and denitrated by contacting the carbonaceous catalyst bed 3 descending within the first reactor 2 .

This discharged exhaust gas is introduced into a second cross-flow moving bed reactor 6 via line 4 . In this case, ammonia is injected via line 5, the exhaust gas cane flows down into the second reactor 6, and the carbonaceous catalyst bed flows down IIp! ! After being subjected to denitrification and desulfurization treatment, it is introduced into a dust collector 9 via a line 8. The gas treated by the dust collector 9 is released into the atmosphere through the dust collector 10, and the collected fly ash is
It is incinerated by A2- etc. In addition, it does not matter whether you use an electric dust collector, bag filter, or other multi-cyclone as a dust collector.

On the other hand, the catalyst discharged from the second reactor 6 is
The catalyst supplied to the upper part of the first reactor 2 and discharged from the lower part of the first reactor 20 is led to the regenerator 11. The catalyst is heated in the regenerator 11 under a high temperature inert gas atmosphere.
It is heated to 0°C and regenerated. The regenerated catalyst is sent to the ammonia activator 12, treated by contacting with ammonia supplied through the line 13, and then returned to the upper part of the second reactor 6 for circulation.

Or as a catalyst flow, No.! The catalyst discharged from the reactor 2 and the second reactor 6) is supplied to the regenerator 11, and after regeneration, it is treated in the ammonia activator 12, and then the catalyst is discharged from the first reactor 2.
It may also be supplied to the second reactor 6 and used for circulation.

The high concentration SO and gas recovered by the regenerator 11 are transferred to the line 1.
4 and is supplied to the manufacturing process of sulfuric acid, sulfur, gypsum, etc.

A high temperature is preferable when treating the catalyst with ammonia, but
In terms of temperature increase, it is sufficient to raise the temperature from room temperature to SO'C. Also,
As ammonia, ammonia gas can be used directly, but it is preferable to use ammonia diluted with water vapor, nitrogen, exhaust gas, air, etc. to a concentration of about 0.1 to 15%. Note that when ammonia treatment is carried out at low temperatures (temperature to about 150°C), the amount of ammonia adsorbed on the catalyst is relatively large, and when the catalyst is supplied to the second reactor 6, the adsorbed ammonia is purged with exhaust gas. Since most of the adsorbed ammonia is purged by bringing the catalyst into contact with exhaust gas or air, it is preferable to supply the catalyst to the reactor.

Used ammonia gas can be recycled or used in line 15.
Since it can be directly supplied to the first reactor inlet or the second reactor inlet via the reactor, no treatment equipment is required.

The gas-solid contact between ammonia and the catalyst may be carried out using either a moving bed or a fluidized bed. In the case of a moving bed, the gas supply method may be parallel flow, countercurrent flow, or cross flow. Further, without providing an activator for bringing ammonia into contact with the catalyst, ammonia may be brought into contact within a conveyor for transporting the catalyst or the like.

In the 1g1 and second reactors of the present invention, carbonaceous catalysts such as activated carbon and activated coke grains obtained by activating coal with carbonized water vapor are generally used. Metal oxides such as copper can also be supported.

According to the present invention, the carbonaceous catalyst used in contact with the exhaust gas is heated and regenerated and then treated with ammonia to generate active basic compounds on the catalyst surface to increase the catalytic activity. Of course, high denitrification performance can be obtained even at a reaction temperature of around 150°C. In addition, in the present invention, the first
Since the amount of ammonia injected into the reactor is unnecessary or small, the amount of ammonia generated when heating and regenerating the catalyst is significantly reduced, which solves problems such as troubles with subsequent equipment and reduced purity of recovered products.

Hereinafter, the effects of the present invention will be specifically illustrated by examples.

Example Countercurrent type ammonia activator (activation conditions: N, +5% NH
, gas, temperature 180°C, activation time 30 minutes), and then supplied to a second cross-flow type moving bed reactor, and further filled with a granular carbonaceous catalyst discharged from this reactor. 1 cross-flow moving bed reactor with Sox 970p
pm 5NOx200pPmSOt 5%, H3O7%
The exhaust gas at 145°C containing
It passed at a speed of '. In this case, the residence time of the catalyst in the reactor was set to 33 hours. The desulfurization rate in this reactor was 90%, and the denitrification rate was 13%.

220 ppm of ammonia was added to the first reactor outlet gas.
was injected into the second cross-flow moving bed reactor at a space velocity of 800.
It passed at a speed of hr"". The residence time of the catalyst in the reactor in this case is set to 25 hours.

The desulfurization rate and the denitrification rate in the second reactor were 100% and 79%, respectively, relative to the gas introduced into the second reactor. That is, the overall desulfurization rate and denitrification rate are each Zo.

The rate was 81.7%. Also, NH, leakage amount is 7p
It was pm.

As a comparative example, the desulfurization rate in the first reactor was 83% as a result of processing under the same conditions as in Example 1 except that ammonia activation was not performed and the NH injection amount at the inlet of the second reactor was 290 ppm. , the denitrification rate was 8%. Further, the desulfurization rate and the denitrification rate in the second reactor were 100% and 68%, respectively.

That is, the overall desulfurization rate and denitrification rate are 100% and 70.6, respectively.
It was written in %. Further, the amount of NH leakage was 10 ppm.

[Brief explanation of drawings]

The figure shows an example of the exhaust gas treatment process of the present invention. 2... First cross-flow type moving bed reactor 6... Second cross-flow type moving bed reactor 9... Dust collection M 11... Regenerator 12... Ammonia activator

Claims (1)

[Claims] 1. Approximately 100 ~ containing sulfur oxides and nitrogen oxides
Exhaust gas at 200°C is introduced into a first reactor filled with a carbonaceous catalyst to undergo desulfurization and denitrification treatment, and then ammonia is mixed into this treated gas, and the mixture is introduced into a second reactor filled with a carbonaceous catalyst. In an exhaust gas treatment method that heats and regenerates the carbonaceous catalyst used for exhaust gas treatment, the carbonaceous catalyst that has been heated and regenerated is brought into contact with ammonia and treated, and then used for exhaust gas treatment. A method for treating exhaust gas characterized by: