CN108114596B - Composition for purifying nitrogen oxide and use method thereof - Google Patents

Composition for purifying nitrogen oxide and use method thereof Download PDF

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Publication number
CN108114596B
CN108114596B CN201711366974.1A CN201711366974A CN108114596B CN 108114596 B CN108114596 B CN 108114596B CN 201711366974 A CN201711366974 A CN 201711366974A CN 108114596 B CN108114596 B CN 108114596B
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ceramic balls
aqueous
sodium chlorite
catalytic
catalyst
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CN201711366974.1A
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Chinese (zh)
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CN108114596A (en
Inventor
金伟
杨小雪
左志军
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北京联飞翔科技股份有限公司
河北深思新材料技术有限公司
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/92Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404Removing only nitrogen compounds
    • B01D53/9409Nitrogen oxides
    • B01D53/9413Processes characterised by a specific catalyst
    • B01D53/9418Processes characterised by a specific catalyst for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/92Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404Removing only nitrogen compounds
    • B01D53/9409Nitrogen oxides
    • B01D53/9413Processes characterised by a specific catalyst
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2258/00Sources of waste gases
    • B01D2258/01Engine exhaust gases
    • B01D2258/012Diesel engines and lean burn gasoline engines

Abstract

The invention provides a method for purifying nitrogen oxideThe composition comprises an aqueous solution of sodium chlorite, catalytic ceramic balls and an aqueous solution of a reducing agent, wherein the catalytic ceramic balls are formed by attaching a catalyst to filler ceramic balls2Then introducing the oxidized nitrogen oxide gas into the aqueous solution of a reducing agent for reaction to generate N2Thereby realizing the purification of nitrogen oxides. The composition can be used for deeply purifying nitrogen oxide, the purification rate reaches over 88 percent, the required equipment is simple, the cost is low, and the composition is more suitable for purifying NO in tail gas discharged by a diesel engineX

Description

Composition for purifying nitrogen oxide and use method thereof

Technical Field

The invention relates to the technical field of pollution gas treatment, in particular to a composition for purifying nitrogen oxides and a using method thereof.

Background

With the rapid development of economy, the problem of environmental pollution caused by energy consumption is increasingly serious. Currently, the total worldwide NOx emissions are 5800 million tons per year. NOx, which is one of the main substances responsible for acid rain, is also an important substance responsible for photochemical smog formation in the atmosphere and consumes O, is extremely harmful to the environment3Is an important factor of.

The exhaust emission of diesel engine is mainly PM (particulate matter) and NOx, and NO in NOx discharged from diesel engine is about 90%. At present, the Selective Catalytic Reduction (SCR) method is mainly adopted to purify nitrogen oxides discharged by a diesel engine, and NH is used3As reducing agent, at V2O5Under the action of catalysts such as Fe molecular sieve or Cu molecular sieve, NOx in the oxygen-enriched tail gas is selectively reduced to N2. In practical application, the SCR system mostly takes urea aqueous solution with the mass fraction of 32.5% as NH3The source, aqueous urea solution, being sprayed in the form of tiny dropletsInjecting the mixture into an exhaust pipe in front of an SCR converter, and generating HNCO and NH by pyrolysis reaction when the temperature is over 200 DEG C3. The urea SCR system has the problems of easy corrosion of pipelines, short service life of nozzles, easy urea deposition, easy inactivation of catalysts and the like, and the method consumes a large amount of ammonia resources and has adverse effects on the production and use of agricultural fertilizers.

Therefore, people turn the sight to wet flue gas denitrification. Publication No. CN101385942A discloses a liquid phase oxidation-absorption two-stage wet flue gas denitration process, which adopts one or a mixture of more of potassium permanganate, sodium chlorite, sodium hypochlorite, calcium hypochlorite, hydrogen peroxide and chlorine dioxide as an oxidant, so that nitric oxide in flue gas is in contact reaction with the oxidant, after part of nitric oxide is oxidized into nitrogen dioxide, the nitric oxide in the oxidized flue gas is absorbed by alkali liquor, and corresponding nitrite is generated. However, in the prior art, nitrogen monoxide in the flue gas is partially oxidized into nitrogen dioxide, and parameters such as the concentration of a liquid-phase oxidant, a pH value, a liquid-gas ratio and the supply amount of the oxidant need to be determined according to the amount of the flue gas and the concentration of nitrogen oxides in the flue gas, so that the parameters are more, the oxidation degree is difficult to accurately control, and the final denitration efficiency is more than 80%, which needs to be improved.

Disclosure of Invention

The invention aims to provide a composition for purifying nitrogen oxide and a using method thereof, which overcome the problems, can deeply purify the nitrogen oxide by using the composition, has the purification rate of more than 88 percent, has simple required equipment and low cost, and is more suitable for purifying NO in tail gas discharged by a diesel engineX

The technical scheme adopted by the invention is as follows:

a composition for purifying nitrogen oxides, which comprises an aqueous solution of sodium chlorite, catalytic ceramic balls and an aqueous solution of a reducing agent, wherein the catalytic ceramic balls are formed by attaching a catalyst on filler ceramic balls.

The technical proposal adopts sodium chlorite aqueous solution to oxidize NO in nitrogen oxide into NO completely in the presence of catalytic ceramic balls2And then the aqueous solution of the reducing agent is used to react NO2Reduction to N2Wherein chlorous acidThe reaction process of sodium and NO is as follows:

NaClO2+2NO→2NO2+NaCl

in the prior art, a series of parameters are controlled to only partially oxidize NO, and the catalytic ceramic ball is used for completely oxidizing NO, so that the subsequent reaction is single and easy to control, and the reaction is more sufficient to ensure that the purification rate is higher.

Preferably, the mass fraction of sodium chlorite is 4-6%. The purification rate is higher by controlling the mass fraction of sodium chlorite within the range.

Preferably, the reducing agent is sodium sulfite with the mass fraction of 20%. The generated by-products have other purposes, and the probability of causing secondary pollution is reduced. The reaction formula is as follows:

2NO2+4Na2SO3→4Na2SO4+N2

the reaction condition is simple, the generated nitrogen is nontoxic and can be directly discharged into the air, and the generated sodium sulfate can be used for manufacturing water glass, porcelain glaze, paper pulp, drying agents and the like.

Preferably, the catalyst in the catalytic ceramic ball is one of copper nitrate, ferric nitrate and cerium nitrate.

Preferably, the filler ceramic balls are inert alumina ceramic balls, and grooves are formed in the surfaces of the balls. The inert alumina ceramic ball has high temperature and high pressure resistance, low water absorption and stable chemical performance, can resist the corrosion of acid, alkali and other organic solvents, and can resist the temperature change in the production process. The grooves are arranged on the surface of the sphere, so that the specific surface area of the sphere is increased, the dispersibility of materials is further increased, and meanwhile, gas or liquid distribution points are increased, and the catalyst is supported and protected. But the larger the specific surface area is, the better the specific surface area is, so that microporous or open-pore ceramic balls are not suitable for use, otherwise, the flux is too large, the system resistance is too small, and the reaction is too violent and unsafe.

Preferably, the inert alumina ceramic ball is made of corundum, and the diameter of the inert alumina ceramic ball is 8-13 mm. The corundum inert alumina ceramic ball has stronger high temperature resistance and corrosion resistance, and when the diameter is selected, the small inert alumina ceramic ball has insufficient compressive strength, is not beneficial to ball milling to enable a catalyst to be attached, and is too big to be beneficial to uniform dispersion of the catalyst, so the selected diameter is 8-13 mm.

In the technical scheme, the preparation method of the catalytic ceramic ball comprises the following steps: putting a catalyst and inert alumina ceramic balls in a mass ratio of 1: 3.5-5 into a ball milling tank, adding 1/4 parts by weight of water of the catalyst, carrying out ball milling for 5-10min, attaching the catalyst to the inert alumina ceramic balls, and then sintering at 400 ℃ to obtain the catalytic ceramic balls.

The preparation method is simple and easy to operate, the catalyst is uniformly distributed in the grooves of the spheres due to the proper proportion of the catalyst and the inert alumina ceramic spheres, and the catalyst and the spheres are connected into a whole after sintering, so that the dispersion area of the catalyst is increased.

Preferably, the mass ratio of the sodium chlorite aqueous solution to the catalytic ceramic ball to the aqueous solution of the reducing agent is 1:1-1.5:1, preferably 1:1.2: 1. Within the range of the mixture ratio, the catalytic effect is best, NO can be completely oxidized, and the potential safety hazard caused by over severe reaction can be avoided.

The invention also provides a using method of the composition for purifying the nitrogen oxide, which comprises the steps of firstly atomizing the aqueous solution of sodium chlorite into fine liquid drops to cover the liquid drops, enabling the liquid drops to pass through the catalytic ceramic balls to form counter flow with the gas containing the nitrogen oxide, and oxidizing NO in the gas containing the nitrogen oxide by the sodium chlorite to generate NO2Then introducing the oxidized nitrogen oxide gas into the aqueous solution of a reducing agent for reaction to generate N2Thereby realizing the purification of nitrogen oxides.

In the technical scheme, the sodium chlorite aqueous solution is atomized into fine liquid drops to cover the liquid drops, and the liquid drops form countercurrent through the catalytic ceramic balls and the gas containing the nitrogen oxide so as to increase the contact reaction area and facilitate full reaction.

In a particular embodiment, the nitrogen oxide-containing gas of the present invention is an exhaust gas emitted from a diesel engine.

Compared with the prior art, the invention has the beneficial effects that:

the composition of the invention has reasonable collocation, and the NO in the nitrogen oxide is completely oxidized into NO by using a liquid-phase oxidant sodium chlorite solution in the presence of a catalyst2And then NO is converted by using an aqueous solution containing a reducing agent2Reduction to N2The reaction is completely easy to control, the purification rate is up to more than 88 percent, the required equipment is simple and low in cost, and the urea solution can replace the urea solution on a diesel vehicle and is suitable for deeply purifying NO in the tail gas discharged by a diesel engineX

Detailed Description

The following describes the embodiments of the present invention in further detail with reference to specific examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Example 1

The embodiment provides a composition for purifying nitrogen oxides, which comprises 4 mass percent of aqueous sodium chlorite solution, copper nitrate catalytic ceramic balls and 20 mass percent of aqueous sodium sulfite solution. The preparation method of the copper nitrate catalytic ceramic ball comprises the following steps: putting 20 parts by weight of copper nitrate and 100 parts by weight of inert alumina ceramic balls into a ball milling tank, adding 5 parts by weight of water, carrying out ball milling for 5min, attaching the copper nitrate to the inert alumina ceramic balls, and then sintering at 400 ℃ to prepare the copper nitrate catalytic ceramic balls, wherein the inert alumina ceramic balls are corundum, grooves are formed in the surfaces of the balls, and the diameter of the inert alumina ceramic balls is 8 mm.

The present embodiment also provides a method for using the above composition, comprising: injecting 100 parts by weight of sodium chlorite solution into a catalytic oxidation device; placing 120 parts by weight of copper nitrate catalytic ceramic balls above a sodium chlorite solution in a catalytic oxidation device; injecting 100 parts by weight of sodium sulfite aqueous solution into an absorption device;

then the tail gas discharged by the diesel engine is introduced into the bottom of the catalytic oxidation device, the sodium chlorite solution is atomized into fine liquid drops through a spraying system to cover the cross section layer of the whole catalytic oxidation device, the fine liquid drops pass through the copper nitrate catalytic ceramic balls and form counter flow with the tail gas to be fully contacted, and the NO in the tail gas is catalytically oxidized into NO by the sodium chlorite solution2Then the mixture is introduced into an absorption device to react with sodium sulfite solution to react NO2Reduction to N2. After being treated by the method, the nitrogen oxide in the tail gas discharged by the diesel engineThe purification rate of the product reaches 91 percent.

Based on example 1, a parallel experiment was performed with respect to "mass fraction of sodium chlorite", and the results are shown in table 1.

TABLE 1 influence of the mass fraction of sodium chlorite on the purification rate

Mass fraction of sodium chlorite 0.1% 1% 2% 4% 6% 8% 10% Purification rate 81% 86% 88% 91% 90% 87% 83%

Example 2

The embodiment provides a composition for purifying nitrogen oxides, which comprises 6 mass percent of aqueous sodium chlorite solution, cerium nitrate catalytic ceramic balls and 20 mass percent of aqueous calcium sulfite solution. Wherein the cerium nitrate catalytic ceramic ball is formed by attaching cerium nitrate on an inert alumina ceramic ball, and the preparation method comprises the following steps: putting 20 parts by weight of cerium nitrate and 75 parts by weight of inert alumina ceramic balls into a ball milling tank, adding 5 parts by weight of water, carrying out ball milling for 10min, attaching the cerium nitrate to the inert alumina ceramic balls, and then sintering at 400 ℃ to prepare the cerium nitrate catalytic ceramic balls, wherein the inert alumina ceramic balls are corundum, grooves are formed in the surfaces of the balls, and the diameter of the inert alumina ceramic balls is 13 mm.

The present embodiment also provides a method for using the above composition, comprising: injecting 100 parts by weight of sodium chlorite solution into a catalytic oxidation device; placing 110 parts by weight of cerium nitrate catalytic ceramic balls above a sodium chlorite solution in a catalytic oxidation device; injecting 100 parts by weight of sodium sulfite aqueous solution into an absorption device;

then the tail gas discharged by the diesel engine is introduced into the bottom of the catalytic oxidation device, the sodium chlorite solution is atomized into fine liquid drops through a spraying system to cover the cross section of the whole catalytic oxidation device, the fine liquid drops pass through the cerium nitrate catalytic ceramic balls and form counter flow with the tail gas to be fully contacted, and the NO in the tail gas is catalytically oxidized into NO by the sodium chlorite solution2Then the mixture is introduced into an absorption device to react with the calcium sulfite solution to generate NO2Reduction to N2. After the treatment by the method, the purification rate of nitrogen oxides in the tail gas discharged by the diesel engine reaches 88 percent.

Comparative example 1

The rest is the same as example 1 except that the composition of this comparative example does not comprise catalytic ceramic balls. And finally, the purification rate of the nitrogen oxides in the tail gas discharged by the diesel engine is 78%.

Comparative example 2

The rest is the same as example 1 except that copper nitrate in this comparative example is not made into catalytic ceramic balls but is directly placed on the cross-sectional layer of the catalytic oxidation apparatus. And finally, the purification rate of the nitrogen oxides in the tail gas discharged by the diesel engine is 80%.

Comparative example 3

The procedure was as in example 1 except that the weight ratio of the aqueous sodium chlorite solution to the aqueous copper nitrate catalytic ceramic balls to the aqueous sodium sulfite solution was 1:0.8: 1. And finally, the purification rate of the nitrogen oxides in the tail gas discharged by the diesel engine is 82%.

Finally, the method of the present invention is only a preferred embodiment and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (8)

1. The use method of the composition for purifying the nitrogen oxide is characterized in that the composition comprises an aqueous solution of sodium chlorite, an aqueous solution of a catalytic ceramic ball and a reducing agent, wherein the catalytic ceramic ball is formed by attaching a catalyst on a filler ceramic ball, and the catalyst is one of copper nitrate, ferric nitrate and cerium nitrate;
the preparation method of the catalytic ceramic ball comprises the following steps: putting a catalyst and inert alumina ceramic balls in a mass ratio of 1: 3.5-5 into a ball milling tank, adding 1/4 parts by weight of water of the catalyst, carrying out ball milling, attaching the catalyst to the inert alumina ceramic balls, and sintering at 400 ℃ to obtain catalytic ceramic balls;
the using method comprises the steps of firstly atomizing the sodium chlorite aqueous solution into small liquid drops to cover the liquid drops, enabling the liquid drops to pass through the catalytic ceramic balls to form counter flow with the gas containing the nitrogen oxide, and oxidizing NO in the gas containing the nitrogen oxide by the sodium chlorite to generate NO2Then introducing the oxidized nitrogen oxide gas into the aqueous solution of a reducing agent for reaction to generate N2Thereby realizing the purification of nitrogen oxides.
2. The use according to claim 1, wherein the mass fraction of sodium chlorite is 4 to 6 percent.
3. The use method according to claim 1, characterized in that the reducing agent is sodium sulfite with a mass fraction of 20%.
4. The use method of claim 1, wherein the filler ceramic balls are inert alumina ceramic balls, and grooves are formed on the surfaces of the balls.
5. The use method of claim 4, wherein the inert alumina ceramic balls are made of corundum and have a diameter of 8-13 mm.
6. The use method of claim 1, wherein the mass ratio of the aqueous sodium chlorite solution to the aqueous catalytic ceramic ball to the aqueous reducing agent solution is 1:1-1.5: 1.
7. The use method of claim 6, wherein the mass ratio of the aqueous sodium chlorite solution to the aqueous catalytic ceramic ball to the aqueous reducing agent solution is 1:1.2: 1.
8. The use according to claim 1, wherein the gas containing nitrogen oxides is the exhaust gas emitted from a diesel engine.
CN201711366974.1A 2017-12-18 2017-12-18 Composition for purifying nitrogen oxide and use method thereof CN108114596B (en)

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CN101279185B (en) * 2007-12-29 2010-12-08 浙江工业大学 Gas phase oxidation-liquid phase reduction method for absorbing and removing nitrous oxides in exhaust air
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