JPS63287552A - Nitrogen oxide remover - Google Patents

Abstract

PURPOSE:To efficiently remove a nitrogen compound by formulating a material selected from alkali metals, transition metals including the group IB elements and the group IIB elements of the periodic table and tin with a carbon being a main component, and partially stabilizing with a sulfur compound. CONSTITUTION:After carbon such as an activated carbon, etc., is dipped in a solution of an alkali metal carbonate, nitrate, acetate, etc., is further dipped in a solution of an acetate, carbonate, etc., of one or more metals selected from the transition metals including group IB element and group IIB element of the periodic table, and tin, and is dried. Subsequently, the carbon is treated with the sulfur compound conforming with a service temperature and an oxidizing gas content in an exhaust gas to obtain the nitrogen oxide remover. The nitrogen oxide removing performance of the nitrogen oxide remover thus obtained is improved, and its effect for a mixture containing an oxidizing gas such as oxygen does not fall.

Description

[Detailed description of the invention] B. Industrial application fields The present invention relates to a nitrogen oxide remover.

Conventional technologyIn order to protect the environment, nitrogen monoxide (
Nitrogen oxides such as NO> and nitrogen dioxide (NO2) need to be reduced to nitrogen and rendered harmless before being released into the atmosphere.

As a dry method for removing nitrogen oxides from exhaust gas in factories, a methane reduction method using ammonia (NH3) is widely used. This method uses toxic ammonia, so great care must be taken to ensure safety.
Leakage of introduced ammonia becomes a major problem, increasing both the initial cost and running cost of the nitrogen oxide removal system. In particular, the use of toxic reducing gases such as ammonia is problematic from a safety point of view when removing nitrogen oxides from combustion exhaust gas near or within homes.

Examples of methods for removing nitrogen oxides that do not use reducing gas include a method in which nitrogen oxides are adsorbed on activated carbon, and a method in which nitrogen oxides are decomposed and removed using an alkali metal or a transition metal. However, the above adsorption method requires a large amount of activated carbon, and the above decomposition method requires 25% of the exhaust gas to increase the decomposition ability.
The temperature must be 0° C. or higher, and in the coexistence of oxidizing gases such as oxygen, the ability to decompose nitrogen oxides increases, but there is a problem that the nitrogen oxide remover ignites.

C.8 Purpose of the Invention The present invention solves the problems of the conventional nitrogen oxide remover as described above, and eliminates the need to remove reducing gas from the outside even in a temperature range from relatively low to high temperatures such as 200 to 400°C. It is an object of the present invention to provide a nitrogen oxide removing agent that stably and efficiently removes nitrogen oxides from combustion exhaust gas containing oxidizing gases such as oxygen without supplying nitrogen oxides.

21 Structure of the present invention The present invention is based on carbon, selected from the group consisting of one or more alkali metals, transition metals including elements of group IB and group nB of the periodic table, and tin. It relates to a nitrogen oxide remover (hereinafter simply referred to as a remover) containing one or more types of nitrogen oxides and partially stabilized by a sulfur compound.

The above-mentioned carbon includes graphite, coal, charcoal, fine carbon, or a substance containing carbon as a main component, and activated carbon, which belongs to fine carbon, is particularly preferable.

In addition, the above transition metals include nickel, iron, manganese,
Copper, zinc, cobalt, cerium, lanthanum, thorium, etc. can be preferably used.

E8 Effects of the Invention The removing agent based on the present invention is particularly effective in removing nitrogen oxides from gas at temperatures within the range of 200 to 400°C, even if it contains oxidizing gases such as oxygen. , there is no reduction in its effectiveness. It is thought that this unique effect is further enhanced by the synergistic effect of carbon, alkali metal, and transition metal.

Furthermore, the removal agent according to the invention has been stabilized with a sulfur compound. This treatment allows the sulfur compounds to form a stable remover surface. As a result, this remover
Although the activity is slightly reduced due to partial poisoning, the formation of this oxide suppresses rapid heat generation even under high temperature or high oxygen concentration, and exhibits a stable nitrogen oxide removal effect. Therefore, by controlling the sulfur compounds mentioned above, it is possible to produce a nitrogen oxide removing agent that meets the usage conditions.

To, Example The present invention will be explained in detail below.

First, a preferred method for producing a 14m compound removing agent will be described.

An alkali metal can be added to carbon by a method of immersing carbon in a solution of an alkali metal carbonate, nitrate, acetate, hydroxide, or the like.

To further add transition metals, etc., acetates of transition metals, etc.
Carbon supporting an alkali metal is immersed in a solution of carbonate, nitrate, hydroxide, etc. and then dried. Alternatively, carbon may be immersed in a solution such as an alkali ferrocyanide and then dried.

The remover produced as described above can be used to remove sulfur dioxide (SO2) depending on the operating temperature and the oxidizing gas content in the exhaust gas.
) and other sulfur compounds.

In particular, when used under conditions where ignition is likely to occur, it is effective to reduce the amount of alkali metal added or to compound it with a heat-resistant substance such as alumina or titania before performing the stabilization treatment as described above. For such removers, 25% by volume
It becomes possible to process the following exhaust gas containing oxygen up to 450°C.

Specific examples will be described below.

A remover was prepared by impregnating commercially available activated carbon with potassium, cerium, and manganese. This remover is K2CO
Activated carbon was dipped in the solution of 3 and dried, dipped in an acetic acid solution of cerium and manganese, and then dried again in the air. Hereinafter, such a remover will be referred to as C/K/Ce
/ M n.

The remover produced as described above was loaded into a quartz tube container and treated in a nitrogen stream containing about 100 ppm of sulfur dioxide gas (flow rate 21/min, temperature 200°C) for more than 1 hour. , and treated for 1 hour in a nitrogen stream at a temperature higher than the exhaust gas temperature used.

12ml of this remover! (apparent volume) was fixed in a quartz tube with an inner diameter of 251 layers using glass wool, and NO
300 volume ppm, CozlO volume %, H2O1
After passing a gas consisting of 0% by volume, 5% by volume of oxygen, and the remainder substantially nitrogen, the gas flow rate to the removal agent-filled layer was increased to 24%! /m
Adjusted to in. Thereafter, the temperature was raised to a predetermined reaction temperature, and changes in NO concentration in the gas were measured using a chemiluminescent NOx analyzer.

FIG. 1 shows the No removal rate when the reaction was carried out for 10 hours at reaction temperatures of 200°C, 300°C, and 400°C.

The No removal rate was maintained at a substantially constant value 1.5 to 2.5 hours after the start of the reaction.

As can be seen from Fig. 1, the removing agent used in this example did not require the supply of reducing gas, and was used under the conditions of 300°C and a space velocity (based on the reducing agent filling volume) of 10,000 hr-'' containing oxygen. The removal rate of No in the gas was maintained at approximately 30% for 10 hours.The removal effect of this remover increases as the reaction temperature is increased, and the No removal rate of approximately 80% was maintained at a reaction temperature of 400°C. showed that.

Side punishment skin l In the same manner as in Example 1 above, C/ni/Z n
/Sn remover was produced and subjected to similar stabilization treatment.

Using this remover, the same test as in Example 1 was conducted. Similarly to Example 1, this example also showed a substantially constant No removal rate after 1.5 to 2.5 hours.

The relationship between the reaction temperature and the No removal rate after 10 hours is also shown in FIG. In this example as well, the reaction temperature is 40
It shows a stable No removal effect even at 0°C. To further improve the properties, heat treatment is performed before use.

S] 1 series 1 C/ni/Cu/M in the same manner as in Example 1 above
An n-removal agent was prepared and subjected to the same treatment.

Using this C/K/Cu/Mn remover,
The reaction temperature was 350°C, and the oxygen concentration in the gas was 4 to 20.
The test was conducted in the same manner as in Example 1, except that the volume was varied between % and % by volume.

The test results are shown in Figure 2.

It can be seen that with the C/K/Cu/Mn removal agent, the higher the oxygen concentration of the gas, the higher the NO removal rate.

This tendency for the oxygen concentration in the gas is a common tendency for the removal agents based on the present invention.

C/Cs prepared in the same manner as in Example 1 above.
/Zn/Th was composited with r-AlzO3 (20% by weight) and water glass as a binder to prepare a removal agent. This removing agent was subjected to the same stabilization treatment as in Example 1, and the effect of removing No from exhaust gas at 250 to 450°C was investigated. The results are shown in FIG.

C/N prepared in the same manner as in Example 1 above
a/F e/Z n, r-AlzO3 (20
% by weight) and water glass as a binder to prepare a remover. This removing agent was subjected to the same stabilization treatment as in Example 1, and the effect of removing No from exhaust gas at 250 to 450°C was investigated. The results are also shown in Figure 3.

In both Examples 4 and 5, compounding with Al2O3 was performed to obtain S
In the O2-treated sample, no significant decrease in the No removal effect was observed, and the remover could be used even at 450°C. Also,
As a binder, hydraulic binders such as alumina cement also exhibit excellent removal effects.

In the present invention, the oxidizing gas contained in the gas from which nitrogen oxides are to be removed is not limited to the above-mentioned oxygen; for example, nitrogen oxides in gases containing 8202 etc. can also be used. It can be removed effectively as well.

[Brief explanation of the drawing]

The drawings all show examples of the present invention. Figure 1 is a graph showing the relationship between reaction temperature and No removal rate, and Figure 2 is a graph showing the relationship between oxygen concentration in gas and No removal rate. FIG. 3 is a graph showing the relationship between reaction temperature and No removal rate according to another example.

Claims (1)

[Claims] 1. The main component is carbon, and contains one or more alkali metals and one or more transition metals, including elements of group I B and group IIB of the periodic table, and tin. and partially stabilized by a sulfur compound.