JPS5876129A - Removal of nitrogen oxide from gas stream - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for converting common nitrogen oxides such as nitrogen monoxide, nitrogen dioxide and nitrous oxide into nitrogen gas.
These nitrogen oxides are found in flue gases, exhaust from internal combustion engines,
Current methods for the conversion of nitrogen oxides from a variety of sources, such as the decomposition of nitric acid, require the use of anisotropic, noble metals, and high temperatures; however, the method of the present invention Use carbon particle reactants and temperatures that need not exceed about 550C.

U.S. Patent No. 1.352 describes highly chemically reactive carbon M structure.
．． It is described in No. +62. This process involves the conversion of carbon monoxide to carbon dioxide over a finely divided metal catalyst such as iron, manganese, niratol, or cobalt in the virtual absence of air at normal pressure and temperatures below 700'C. providing. - During the conversion, carbon is deposited on the catalyst and can be collected separately by mechanical or magnetic means.

The carbon thus formed is said to be ashless, highly pure, reactive, and suitable for nitrogen fixation methods.

U.S. Pat. No. 7,838,577 relates to a method for removing harmful reactive hydrocarbons as well as traces of nitrogen oxides by passing coke oven gas through a filter containing an adsorption medium. The adsorption medium is activated carbon, the catalytic activity of which is said to be increased by impregnation with metals or metal salts. The patentee discloses that other materials such as silica gel can be used in place of activated carbon.

Recently, U.S. Patent No. 4,060,589
1. NOx and Box are removed from the flue gas by passing it over picumen coke at a temperature between 2 and 7 °C.
A method to simultaneously reduce the components has been clarified. Water vapor in the flue gas reacts with coke to produce carbon monoxide and hydrogen, -carbon oxide reacts with NOx to produce hydrogen ij 802
It is said to react with The patentee states that the conversion is not believed to be carried out in a catalytic manner, but that the coke contains special metals, such as iron, which facilitate the reduction - this process , appears to be operational with SOx and some NOx present, both of which were present in trace amounts in the synthetic flue gas used in the examples.

Although the method of the present invention uses carbon, the carbon does not act as an adsorbent, but rather reacts chemically with the nitrogen oxides present to produce nitrogen gas. To be useful, such a process must be capable of transferring large amounts, but not traces, of nitrogen oxides at temperatures that are not significantly elevated.

Therefore, the purpose of the present invention is to solve the problem of No., NO2, NzO &
.

It is an object of the present invention to provide a process for converting large quantities of various nitrogen oxides, such as N20, with carbon substances that are chemically reactive therewith. Another object of the invention is to provide a method for converting large quantities of various nitrogen oxides, such as N20, which can be carried out at temperatures up to about 800°C. Another object of the present invention is to provide a method for converting the nitrogen oxides.

Another object of the present invention is to provide a method for converting the nitrogen oxides by using a carbon material that can be consumed during temporary use or regenerated in the reaction system during long-term use.

Yet another object of the present invention is to provide a process for the conversion of the above-mentioned nitrogen oxides by a relatively inexpensive compound that does not require a separate supply of anthonia and can be easily used with a variety of gas molecules. These and other objects, together with their advantages over the prior art, will become apparent from the following description. In general, the process of the present invention involves adding IWll or more of nitrogen oxide to the reactants in the vertical direction. Pressure during the reaction can range from normal pressure to about 20 to 30 atmospheres, including passing over the cord fiber material or host-to-host carbon particles at about 450 to about 750°C. It is also possible to carry out the process of the invention by cofeeding a carbon-containing gas with the nitrogen oxides, in which case the reactant materials can be regenerated continuously and simultaneously. If the carbon-containing gas is not a hydrocarbon, hydrogen gas can also be supplied. The components or reactants utilized in the practice of this invention include carbon fibers made of carbon and metals such as iron, nickel, or cobalt. It is a structure. Carbon fiber reactants are formed by depositing charcoal 51c onto a catalyst or host material, while using interhost carbon particles grown inside the host material rather than on the host material.

For illustrative purposes, even if the reactant material is carbon fiber or host-to-host carbon particles, it will be referred to hereafter as carbon fiber reactant or reactant; It means inside the host.

The host material consists of metals such as iron, nickel, or cobalt that can be preferentially loaded onto the support material. Suitable carrier materials include silica, alkyl, aluminum, silicon carbide,
Includes carborundum, zirconia, alundum, and mixtures thereof.

In one method for preparing the host material, a solution of a metal salt, such as a nitrate, in water is used to impregnate an already prepared support; on the other hand, the metal reagent and the colloidal support can be spray-dried together; Unsupported forms such as , steel wire, metal rods, etc. can be used.

If carrier impregnation is used, then this t is approximately 350 to 70
Calcination for 1 to 6 hours at 0't gives the metal oxide.The catalyst is then reduced by adding water or a typical reducing agent such as hydrazine2.The catalyst thus formed or the host material is The composition consists of about 3 to 95 g of the metal and about 97 to 59 g of the carrier, preferably a composition of 10 to 401 of the metal and 9 to 601 of the carrier, respectively.

For example, after reducing the host material with hydrogen, carbon fibers are deposited thereon. Preferably, carbon monoxide along with some hydrogen, or only hydrocarbons, are applied to the host at about 450%
The above precipitation can be easily carried out by heating at ~650'C for about 0.5~ε hours.

2. Based on volume. The ratio of gas, hydrogen to carbon oxide is approximately 0 to! ~about 1 to 2, preferably 1 to 5, by repeating the flow of hydrogen and carbon monoxide or of sulfurized hydrogen, and adding another flow of hydrogen here and there to remove some of the precipitated longitudinal cords. Hydrogen is not necessarily necessary, but its presence accelerates the reaction - as in the case of carbon oxide. As a result of the above transport of hydrogen and carbon monoxide, carbon Deposited on or within the host material - The composition of this fiber is partly carbon and partly metal from the host;
! The carbon content of the boat is about 5 to about 96 wt., and about 70 to about 96 wt.
Carbon is the reactant utilized for the conversion of nitrogen oxides to nitrogen in the process of the invention. If the carbon is in the IIJII form, depending on the system used for the conversion reaction, the fiber can be separated from the host substance! A friend can be used as it is formed. Because the reactant fibers are consumed during the conversion process, the reactant fibers are not referred to as catalysts.O Reactant carbon fibers can be used in known reactors for nitrogen oxide conversion; , fluidized beds (particularly when the host material is produced by spray drying), radial flow. The conversion process involves directing the nitrogen oxides directly onto the reactant carbon fibers at about 450 to about 750'C in a reactor.

The residence time of nitrogen oxides on carbon fibers varies depending on factors such as the reactor type and its dimensions, bed type, etc.
On a molar basis, carbon fibers are thought to be capable of converting from about 1 mole to more than 2% of nitrogen oxide per mole of reactant.In the above method, the reactant is eventually consumed and the conversion stops; When a continuous conversion process is rapid, it is also possible to carry out continuous and simultaneous regeneration of the reactant carbon fibers.

To do so, hydrogen to carbon oxide ratios of about 0:1 to 1:2, carbon to nitrogen oxide ratios of 1 to 1 or more, - more carbon-containing gas in the oxidized longitudinal and preferably some hydrogen. Instead of carbon dioxide, which is supplied with a stream of nitrogen oxides, methane, ethane, or other hydrocarbons such as kerosene or naphtha can be used, in which case less or no hydrogen is required.

Another variation is that the waste host can be removed from the reactor and regenerated separately, or the nitrogen oxide stream can be stopped while regeneration takes place. In the examples below, a given volume of nitrogen oxide is converted to nitrogen gas.・The reactant carbon fiber used in this method is Fe
Catalyst or host material consisting of 20 and 5i0280 3.79 ft - length g+, 28 tM, outer diameter 281,
This tube was made by placing it in a quartz tube with an internal diameter of 25 cm. This tube was placed in a high-power split tube furnace with a length of 63.51 m and an internal diameter of 3.175 mm, and each end was plugged for gas inlet and outlet.

The quartz tube and its contents were heated to 720°C.

Hydrogen was then passed through the tube at a rate of 49 α/min for 1 hour to reduce the metal. At this point the catalyst or host material turned gray. The water bulk flow rate was then reduced and the temperature was increased to 550'C.
A mixture of g water (32 cr,/min) and -carbon oxide (16 gac/min) was then passed through the tube from left to right for 30 minutes and then reversed for an additional 30 minutes. O, which ensured better coverage of the host and satisfactory deposition of carbon fibers, then the mixed gas flow was stopped and hydrogen only (10
9 cc/min) from left to right for 30 minutes to remove some of the precipitated carbon. After this treatment, the initially used flow of hydrogen and carbon monoxide was passed again from left to right for 30 minutes. did. As shown in the Examples below, the reactant carbon fibers were prepared for nitrogen oxide conversion in the same quartz tube containing the Example reactant carbon fibers and host material.
Nitrogen oxides to be converted 230C/min flow n to 550°C
After 30 minutes, a gas sample was taken from the effluent.

Analyzed by gas chromatography, it was found to contain a significantly high molten nitrogen content but no nitrogen oxides.Table tlA1 shows 3 examples, Example 1 - Nitric oxide, Example 2 - Nitrogen oxide. Nitrogen Oxide, Example 3 - Analysis of nitrogen dioxide effluent gas is reported.

Each was converted as shown above. A comparative experiment was carried out by using 5.872f of the above carbon-free Fe-8102 catalyst. The amount of nitrogen produced was much lower, at 97%. Nitric oxide was found in the effluent. The amount of nitrogen or other gas in the effluent was determined by gas chromatography and, as can be seen from the data in Table 1, very high conversions of various nitrogen oxides to nitrogen gas were obtained. .

In Examples 2 and 3, respectively, N20
Although the residual amount of NO2 and NO2 could not be measured (based on the large amount of nitrogen gas produced and present in the effluent gas, the amount of N20 and NO2 is zero or close to zero - considering the conversion of NO, one mole of carbon Approximately 0.5 moles play.N02
Assuming a 100S conversion of No at a flow rate of 30 C/min, the carbon reactant is not completely removed until more than 2 hours of use. Based on these results, the method of the present invention is useful for converting nitrogen oxides to nitrogen. Carbon fiber reactants can be used to treat a variety of gas streams where nitrogen oxides are undesirable. For example, one can be nitric acid and/or the nitrogen oxide decomposition products of the nitric acid process. By using a device containing a specific amount of reactant carbon fiber, when filling a tank of nitric acid, the fc can readily deplete the oxides normally encountered when emptying into nitrogen. In this system, regeneration is Other non-critical uses include flue gas, flue gas treatment, feed pretreatment, effluent treatment, impurity removal, etc. Depending on the costs involved and the practical possibilities, the process can be adapted for one-time use or continuous conversion. As mentioned above, the reactant carbon fibers that can be used in the implementation of the process are disclosed here in various quantities. of iron, nickel, or cobalt. It is to be understood that variations of those shown above fall within the scope of the claims of the invention, and that the invention is not limited by the examples shown. It should be understood that the examples are for illustrative purposes only and that the selection of metals, reducing agents, carbon-containing gases, host materials, etc. can be determined without departing from the spirit of the invention. Yes, in short, the technical scope of the present invention! l includes all variations that fall within the scope of the claims Continued from page 1 @ Inventor Louis Joseph Veerenyi 1266 Roland Road, 4 Lindburst, Ohio 4412, USA

Claims (1)

Claims: (1) A process for converting nitrogen oxides to nitrogen gas, comprising the step of conveying the nitrogen oxides onto a reactant carbon fiber material at a temperature of about 450 to about 750°C. (2) Nitrogen oxides together with carbon-containing gas about 450 to about 7
A process for the continuous conversion of nitrogen oxides to nitrogen gas, characterized by the step of feeding the reactant carbon fiber material onto the reactant carbon fiber material at a temperature of 11 or 21, wherein carbon constitutes about 5 to about 98% by weight of the reactant material (4) Reducing metals and silica, silicon carbide, aluminum,
The reactant carbon fiber material is supported by a host material consisting of a carrier material selected from the group consisting of alundum, dinuconia, carborundum, and mixtures thereof, and the reactant material has 5 to 98% carbon by weight. A method for converting nitrogen oxides into nitrogen gas according to claim (3), the remainder of which is a metal. -1 The carbon-containing gas is carbon monoxide, methane, ethane,
A method for converting nitrogen oxides to nitrogen gas according to claim 1, wherein the ratio of hydrogen to carbon-containing gas is from about 0:1 to about 1:2, selected from the group consisting of kerosene and naphtha. (6) The ratio of carbon to nitrogen oxide is 1:1!
A method for converting nitrogen oxides into nitrogen gas according to claim (6), wherein the conversion of nitrogen oxides is carried out at a pressure in the range of about 1 to 30 atmospheres ( The method for converting nitrogen oxides into nitrogen gas according to 1) or (2).