Gas denitration process and apparatus

Abstract

A process and an apparatus for gas denitration, involving first the use of an oxidizing agent to oxidize NO in a gas to NO.sub.2, then using a denitration agent to absorb the NO.sub.2 in the gas, thus achieving the purpose of denitration.

Claims

1. A process for removing NO from a mixed gas, comprising: a. oxidizing NO in the mixed gas using an oxidizing agent to produce NO.sub.2; b. removing NO.sub.2 in the mixed gas by absorption using a denitration agent to obtain a NO.sub.2-enriched denitration agent and a NO.sub.2-removed mixed gas; and c. treating the NO.sub.2-enriched denitration agent to obtain a NO.sub.2-lean denitration agent and using the NO.sub.2-lean denitration agent as the dentritration agent in step b, and wherein said denitration agent is a hydroxide or carbonate solution containing Li, Na, K, Mg, Ca, or mixtures thereof.

2. The process according to claim 1, wherein the oxidizing agent in step a is one or more selected from the group consisting of free radical oxygen, O.sub.3, O.sub.2, organic acid anhydride, permanganic acid, permanganate, tungstic acid, pertungstic acid, tungstate, pertungstate, titanic acid, pertitanic acid, titanate, pertitanate, molybdic acid, permolybdic acid, molybdate, permolybdate, dichromic acid, dichromate, hydrogen peroxide, ferric acid, and ferrate.

3. The process according to claim 1, wherein the oxidizing agent in step a is a composite oxidizing agent, comprising one or more selected from the group consisting of free radical oxygen, O.sub.3, O.sub.2, organic acid anhydride, permanganic acid, permanganate, tungstic acid, pertungstic acid, tungstate, pertungstate, titanic acid, pertitanic acid, titanate, pertitanate, molybdic acid, permolybdic acid, molybdate, permolybdate, dichromic acid, dichromate, hydrogen peroxide, ferric acid, ferrate, gold, silver, and palladium.

4. The process according to claim 1, further comprising a step of preparing O.sub.3 and/or free radical oxygen.

5. The process according to claim 1, wherein the step b is carried out in a denitration tower, and said NO.sub.2-containing mixed gas contacts with the denitration agent countercurrently.

6. The process according to claim 1, wherein in the step c, a part of the NO.sub.2-enriched denitration agent is evaporative-concentrated, cooled and crystallized to obtain a product of M(NO.sub.3).sub.n, where n is a natural number; after crystallization, a mother liquid is supplemented with fresh denitration agent to form the NO.sub.2-lean denitration agent.

7. The process according to claim 1, wherein the denitration agent in the step b is a polyethylene glycol solution, an ethylene glycol solution, or a mixture thereof.

8. The process according to claim 7, wherein the polyethylene glycol solution and/or ethylene glycol and/or aqueous solution further contains a denitration additive, said denitration additive is in an amount of 0.5-40 wt %; wherein the denitration additive is an organic compound which is formed by mixing a polyol, a polyacid and an organic amine according to a certain proportion, then heating to above 120 C., and carrying out esterification and/or etherification, wherein the proportion is such that the molar ratio of the polyol: the polyacid: the organic amine is 1:0.5-2:0.1-3.

9. The process according to claim 7, wherein in the step c, the NO.sub.2-enriched denitration agent is regenerated in a regeneration tower using a regeneration method selected from one or more of gas stripping method, heating method, vacuumizing method, ultrasonic method, microwave method, and radiation method.

10. The process according to claim 9, further comprising: d. concentrating a NO.sub.2-containing regenerated gas released from the regeneration tower in a concentration tower to obtain NO.sub.2.

11. The process according to claim 10, wherein in the step d, the NO.sub.2-containing regenerated gas enters the concentration tower at a middle part of the concentration tower, and is cooled by a cooling device at an upper part of the concentration tower, whereby NO.sub.2 gas is discharged from a top of the concentration tower, and a cooled condensed water is discharged from a bottom of the concentration tower.

12. An apparatus for removing NO from a mixed gas, comprising: an O.sub.3 or free radical oxygen [O] generator, a gas mixer, a catalytic oxidizer, a denitration tower, a solvent tank and an evaporative crystallizer, wherein one end of the gas mixer is provided with a mixed gas inlet, pipelines connect between said O.sub.3 or free radical oxygen [O] generator and the gas mixer, between the gas mixer and the catalytic oxidizer, between the catalytic oxidizer and the denitration tower, between the denitration tower and the solvent tank, and between the solvent tank and the evaporative crystallizer, wherein the pipeline between said denitration tower and the solvent tank is equipped with a diverter valve which introduces part of the NO.sub.2-enriched denitration agent into the evaporative crystallizer.

13. An apparatus for removing NO from a mixed gas, comprising: a gas mixer, a catalytic oxidizer, a denitration tower, a regeneration tower and a concentration tower, wherein one end of the gas mixer is provided with an inlet for the mixed gas and an oxidizing agent, pipelines connect between said gas mixer and the catalytic oxidizer, between the catalytic oxidizer and the denitration tower, between the denitration tower and the regeneration tower, and between the regeneration tower and the concentration tower, wherein a NO.sub.2-lean denitration agent is recycled from a NO.sub.2-lean denitration agent outlet at the bottom of the regeneration tower back to a denitration agent inlet at the upper part of the denitration tower through the pipeline.

14. The apparatus for removing NO from a mixed gas according to claim 13, wherein a lean liquid tank is provided between said regeneration tower and the denitration tower, the NO.sub.2-lean denitration agent discharged from the bottom of the regeneration tower enters the lean liquid tank and flows out from the bottom of the lean liquid tank, and flows into the denitration agent inlet at the upper part of the denitration tower through the pipeline.

15. The apparatus for removing NO from a mixed gas according to claim 14, wherein indirect heat exchangers are provided between the denitration tower and the regeneration tower, between the regeneration tower and the lean liquid tank, wherein the heat medium is the NO.sub.2-lean denitration agent discharged from the regeneration tower, and the cold medium is the NO.sub.2-enriched denitration agent discharged from the denitration tower.

16. A denitration additive for removing NO.sub.2 from a mixed gas, wherein said denitration additive is an organic compound which is formed by mixing a polyol, a polyacid and an organic amine in a certain proportion, then heating to above 120 C., and carrying out esterification and/or etherification, wherein the proportion is such that the molar ratio of the polyol: the polyacid: the organic amine is 1:0.5-2:0.1-3.

17. The denitration additive according to claim 16, wherein said polyol is an organic compound containing two or more hydroxyl groups at the same time in the same organic molecule.

18. The denitration additive according to claim 17, wherein said polyacid is an organic compound containing two or more carboxylic acid groups in the same molecule.

19. The denitration additive according to claim 16, wherein said polyol is selected from one or more of ethylene glycol, propylene glycol, glycerol, butanediol, butanetriol, isobutanediol, isobutanetriol, pentanediol, pentanetriol, pentanetetraol, isopentanediol, isopentanetriol, isopentanetetraol, polyethylene glycol, polypropanol and polybutanol.

20. The denitration additive according to claim 16, wherein said polyacid is an organic compound containing two or more carboxylic acid groups in the same molecule.

21. The denitration additive according to claim 16, wherein said polyacid is selected from one or more of ethanedioic acid, propanedioic acid, butanedioic acid, aminoethanedioic acid, nitrilotriacetic acid, EDTA, tannin acid, polygallic acid and citric acid.

22. The denitration additive according to claim 16, wherein said organic amine is selected from aliphatic amines, aromatic amines and alkylol amines, said aliphatic amine is selected from one or more of methylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dipropylamine, tripropylamine, n-propylamine, isopropylamine, monobutylamine, dibutylamine, tributylamine, n-butylamine, sec-butylamine, isobutylamine, t-butylamine, ethylenediamine, propylenediamine, hexamethylenediamine, triethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethylenepolyamine, cyclopentylamine, cyclohexylamine and cycloheptylamine; said aromatic amine is selected from one or more of aniline, N-methylaniline, N-ethylaniline, N-propylaniline, N-butylaniline, N,N-dimethylaniline, N,N-diethylaniline, N,N-dipropylaniline, N,N-dibutylaniline, phenylenediamine, -naphthylamine, halogenated aniline, nitroaniline and sulfoaniline; said alkylol amine is selected from one or more of monomethanolamine, dimethanolamine, trimethanolamine, monoethanolamine, diethanolamine, triethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, N,N-diisopropylethanolamine, N-methyldiethanolamine (MDEA), monopropanolamine, dipropanolamine, tripropanolamine, isopropanolamine, diisopropanolamine, triisopropanolamine, monobutanolamine, dibutanolamine, tributanolamine, N-hydroxyethylethylenediamine, N,N-dihydroxyethylethylenediamine, N,N-dihydroxyethylaniline, N-ethyl-N-hydroxyethylaniline, N-methyl-N-hydroxyethylaniline, o-aminophenol, m-aminophenol, p-aminophenol, 2,4,6-tris(dimethylaminomethyl)phenol, 3-diethylaminophenol, 2-amino-5-nitrophenol, ammonia cefotaxime acid, N-methylpyrrolidinol, 2,4-diamino-6-hydroxypyrimidine, cyanuric acid, 2-(2-hydroxy-5-methylphenyl)benzotriazole, gamma acid, J acid, phenyl J acid, Chicago acid and its salts, H acid and its salts, di-J acid, scarlet acid and its salts.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram showing the simple oxidation gas denitration process and apparatus.

(2) In FIG. 1: 1 represents a NO-containing gas, 2 represents a denitrated gas, 3 represents an O.sub.2 gas, 4 represents an O.sub.3 or free radical oxygen[O] generator, 5 represents an O.sub.2 or O.sub.3 or free radical oxygen[O] or a mixture thereof, 6 represents a mixer, 7 represents a catalytic oxidizer, 8 represents a denitration tower, 9 represents a lean liquid, 10 represents a rich liquid, 11 represents a solution tank, 12 represents a denitration pump, 13 represents a rich liquid to be concentrated, 14 represents an evaporative-concentrating crystallizer, 15 represents a concentrated mother liquid, 16 represents a M(NO.sub.3).sub.n product precipitated by crystallization, and 17 represents an inorganic or organic alkaline substance.

(3) FIG. 2 is a schematic diagram showing the oxidation gas denitration and regeneration process and apparatus.

(4) In FIG. 2: 1 represents a NO-containing gas, 2 represents a denitrated gas, 3 represents an O.sub.2 gas, 4 represents an O.sub.3 or free radical oxygen[O] generator, 5 represents an O.sub.2 or O.sub.3 or free radical oxygen[O] or a mixture thereof, 6 represents a mixer, 7 represents a catalytic oxidizer, 8 represents a denitration tower, 9 represents a lean liquid, 10 represents a rich liquid, 12 represents a denitration pump, 18 represents a rich liquid pump, 19 represents a lean liquid tank, 20 represents a cooler, 21 represents a heat exchanger, 22 represents a regeneration tower, 23 represents a heater, 24 represents a NO.sub.2 concentration tower, 25 represents a condenser, 26 represents a mixed gas of NO.sub.2 and steam, 27 represents a steam, 28 represents a condensed distilled water, 29 represents a cooling water, 30 represents a cooling water that is heated, and 31 represents a NO.sub.2 gas of high concentration.

DETAILED DESCRIPTION

(5) The gas denitration process and apparatus according to the present invention will be described below in conjunction with specific embodiments. The embodiments are intended to better illustrate the present invention, and should not be construed as limiting the claims of the present invention.

(6) The process of using the denitration agent of the first type and the operation method of the apparatus are shown in FIG. 1: O.sub.2 gas 3 enters a O.sub.3 or free radical oxygen [O] generator 4, and in the O.sub.3 or free radical oxygen [O] generator 4, O.sub.2 or O.sub.3 or free radical oxygen [O] or a mixture thereof 5 is produced; the O.sub.2 or O.sub.3 or free radical oxygen [O] or the mixture thereof 5 enters a mixer 6 to mix thoroughly with the mainstream of a NO-containing gas 1 in the mixer 6, and then enters a catalytic oxidizer 7. In the catalytic oxidizer 7, NO in the NO-containing gas 1 is catalytically oxidized to NO.sub.2 gas, and the NO-containing gas 1 is converted to a NO.sub.2-containing gas; the NO.sub.2-containing gas enters a denitration tower 8 from the bottom, and meanwhile, a solution containing denitration agent (lean liquid) 9 enters the denitration tower 8 from the top. In the denitration tower 8, the NO.sub.2-containing gas is in direct contact with the lean liquid 9; at this point, NO.sub.2 in the NO.sub.2-containing gas is absorbed by the lean liquid 9, the NO.sub.2-containing gas is converted to a denitrated gas 2, which flows out from the top of the denitration tower 8, and is discharged into atmosphere or subjected to further purification treatment. At the same time, the lean liquid 9 with absorbed NO.sub.2 is converted to a rich liquid 10, flows out from the bottom of the denitration tower 8 and enters a solution tank 11. Part of the rich liquid 13 in the solution tank 11 enters an evaporative-concentrating crystallizer 14, and a M(NO.sub.3).sub.n product 16 precipitated by crystallization is obtained; the remaining concentrated mother liquid 15 is returned to the solution tank 11, and the solution tank 11 is replenished with a fresh inorganic alkaline substance or organic alkaline substance 17. Then the rich liquid 10 is converted to the lean liquid 9, and is sent by a denitration pump 12 to the denitration tower 8 to absorb the NO.sub.2 component in the NO.sub.2-containing gas.

(7) The process of using the denitration agent of the second type and the operation method of the apparatus are shown in FIG. 2: O.sub.2 gas 3 enters a O.sub.3 or free radical oxygen [O] generator 4, and in the O.sub.3 or free radical oxygen [O] generator 4, O.sub.2 or O.sub.3 or free radical oxygen [O] or a mixture thereof 5 is produced; the O.sub.2 or O.sub.3 or free radical oxygen [O] or the mixture thereof 5 enters a mixer 6 to mix thoroughly with the mainstream of a NO-containing gas 1 in the mixer 6, and then enters a catalytic oxidizer 7. In the catalytic oxidizer 7, NO in the NO-containing gas 1 is catalytically oxidized to NO.sub.2 gas, the NO.sub.2-containing gas enters a denitration tower 8 from the bottom, and meanwhile, a lean liquid 9 enters the denitration tower 8 from the top. In the denitration tower 8, the NO.sub.2-containing gas is in direct contact with the lean liquid 9; at this point, NO.sub.2 is absorbed by the lean liquid 9, the NO.sub.2-containing gas is converted to a denitrated gas 2, which flows out from the top of the denitration tower 8, and is discharged into atmosphere or subjected to further purification treatment. At the same time, the lean liquid 9 with absorbed NO.sub.2 is converted to a rich liquid 10, and the rich liquid 10 is pressurized by a rich liquid pump 18, then is heat-exchanged with the hot lean liquid 9 from a regeneration tower 22 through the shell pass of a heat exchanger 21, thus the temperature rises; then it passes through a rich liquid heater 23 and is heated by a steam 27 (the heated steam may be replaced by a liquid having a temperature higher than 100 C. or a flue gas of 130 to 170 C.) to above 70 C.; the rich liquid 10 having a temperature higher than 70 C. enters the regeneration tower 22 from the upper end, while the stripping steam 27 enters the regeneration tower 22 from the bottom; in the regeneration tower 22, the rich liquid 10 having a temperature higher than 70 C. is in direct contact with the stripping steam 27; at this point, NO.sub.2 in the rich liquid 10 is desorbed, and is mixed into the stripping steam 27 to form a mixed gas 26 of NO.sub.2 and stream, which flows out from the top of the regeneration tower 22; at this point, the rich liquid 10 is converted to the hot lean liquid 9 having a temperature higher than 70 C., and flows out from the bottom of the regeneration tower 22; it passes through the tube pass of the heat exchanger 21 and is heat-exchanged with the rich liquid 10 in the shell pass that is sent from the rich liquid pump 18, thus the temperature decreases; the lean liquid 9 having decreased temperature travels along the tube pass of a cooler 20 and is cooled to room temperature by a cooling water 29 of the shell pass, and automatically flows into a lean liquid tank 19, then the lean liquid 9 in the lean liquid tank 19 is pressurized by a denitration agent pump 12 and again sent to the denitration tower 8 for denitration. The denitration solution works in such a way that, in the denitration tower 8, the lean liquid 9 absorbs NO.sub.2 and is converted to the rich liquid 10, and in the regeneration tower 22, the rich liquid 10 is heated, stripped and/or vacuum-regenerated, thus is again converted to the lean liquid 9, and the lean liquid 9 is again recycled for use, and it cycles continuously like this. The mixed gas 26 of NO.sub.2 and steam flowing out from the top of the regeneration tower 22 enters a NO.sub.2 concentration tower 24 from the middle part, and contacts with the distilled water condensed from the upper end of the NO.sub.2 concentration tower 24; in a condenser 25, the water vapor in the mixed gas 26 is condensed by the cooling water 29, and a NO.sub.2 gas 31 of high concentration that is not condensed and that contains a small amount of impurities flows out from the top of the condenser 25, and can be recycled as a feed gas; while the condensed distilled water containing substances such as NO.sub.2 and the like continues to flow to the bottom of the NO.sub.2 concentration tower 24, and contacts with the stripping steam 27 from the bottom; the gases such as NO.sub.2 and the like in the distilled water are stripped by the stripping steam 27 and desorbed, so that the condensed water is substantially free of such gases as NO.sub.2 and the like, and the condensed distilled water 28 meeting the standards of distilled water is sent for recycle use. In the whole process, the cooling water 29 is heated and converted to a heated cooling water 30, which can be recycled for use as a boiler replenishing hot water, and the condensed distilled water 28 can be recycled for use.

Example 1

(8) According to the denitration process and apparatus shown in FIG. 1, a set of small size simulated industrial gas denitration device was made and installed. The forms of various devices in the apparatus are as follows:

(9) NO-containing gas 1 was a prepared cylinder gas, with a NO content of 1000-5000 ppm;

(10) NO.sub.X content in the denitrated gas 2 was analyzed by the ultraviolet JNYQ-I-41 type gas analyzer manufactured by Xi'an Juneng Instrument Co., Ltd;

(11) O.sub.2 gas 3 was a cylinder gas of pure oxygen;

(12) O.sub.3 or free radical oxygen [O] generator 4 was self designed and manufactured, with an ionization area of 180 mm240 mm, a plate gap adjustment range of 0.1-2 mm, a frequency of high frequency power supply of 5.4 MHz, an output voltage of 0-3000V and an output power of 1 KW;

(13) O.sub.2 or O.sub.3 or free radical oxygen [O] or a mixture thereof 5 was a mixed gas of free radical oxygen [O], O.sub.3 and O.sub.2.

(14) Mixer 6 was a glass tube filled with wire packings;

(15) Catalytic oxidizer 7 was a glass absorption bottle filled with a catalyst such as potassium permanganate or the like;

(16) Denitration tower 8 was a glass absorption bottle, and lean liquid 9 denitration agent was a 15% NaOH aqueous solution;

(17) M(NO.sub.3).sub.n product precipitated by crystallization 16 was NaNO.sub.3.

(18) The operation method of the above apparatus was as follows: the flow rate of the NO-containing gas 1 was adjusted to 1 L/hr and stabilized; NO concentration as shown by the ultraviolet JNYQ-I-41 type gas analyzer was read as 1013 ppm; the flow rate of O.sub.2 gas 3 through the O.sub.3 or free radical oxygen [O] generator 4 was adjusted, and after mixing in the mixer 6, the total flow rate was stabilized to be 1.2 L/hr (that is, the flow rate of O.sub.2 was 0.2 L/hr); NO concentration read from that shown by the ultraviolet JNYQ-I-41 type gas analyzer was stabilized substantially between 780-830 ppm, and then the following tests were carried out:

(19) 1. When the O.sub.3 or free radical oxygen [O] generator 4 was not powered, and O.sub.3 or free radical oxygen [O] was not available, the mixed gas was first passed through the glass absorption bottle working as the catalytic oxidizer 7 (filled with potassium permanganate), and then passed through the glass absorption bottle working as the denitration tower 8 (filled with a 15% NaOH aqueous solution); NO concentration read from that shown by the ultraviolet JNYQ-I-41 type gas analyzer was stabilized substantially between 50-60 ppm, and the denitration efficiency was 92% to 95%.

(20) 2. When the O.sub.3 or free radical oxygen [O] generator 4 was not powered, and the gas component supplied by the O.sub.3 or free radical oxygen [O] generator 4 was O.sub.2 with a concentration of 100%, the mixed gas was first passed through the glass absorption bottle working as the catalytic oxidizer 7 (but the glass absorption bottle was not filled with any catalyst), and then passed through the glass absorption bottle working as the denitration tower 8 (filled with a 15% NaOH aqueous solution); NO concentration read from that shown by the ultraviolet JNYQ-I-41 type gas analyzer was stabilized substantially between 850-950 ppm, and the denitration efficiency was 6% to 16%.

(21) 3. When the O.sub.3 or free radical oxygen [O] generator 4 was powered, and when the gas components supplied by the O.sub.3 or free radical oxygen [O] generator 4 were O.sub.3 with a concentration of 10% and O.sub.2 with a concentration of 90%, the mixed gas was first passed through the glass absorption bottle working as the catalytic oxidizer 7 (but the glass absorption bottle was not filled with any catalyst), and then passed through the glass absorption bottle working as the denitration tower 8 (filled with a 15% NaOH aqueous solution); NO concentration read from that as shown by the ultraviolet JNYQ-I-41 type gas analyzer wasstabilized substantially between 500-600 ppm, and the denitration efficiency was 40.8% to 51%.

(22) 4. When the O.sub.3 or free radical oxygen [O] generator 4 was powered, and the gas components supplied by the O.sub.3 or free radical oxygen [O] generator 4 were [O] with a concentration of 3% and O.sub.2 with a concentration of 97%, the mixed gas was first passed through the glass absorption bottle working as the catalytic oxidizer 7 (but the glass absorption bottle was not filled with any catalyst), and then passed through the glass absorption bottle working as the denitration tower 8 (filled with a 15% NaOH aqueous solution); NO concentration read from that as shown by the ultraviolet JNYQ-I-41 type gas analyzer was stabilized substantially between 20-40 ppm, and the denitration efficiency was 96% to 98%.

(23) 5. When the O.sub.3 or free radical oxygen [O] generator 4 was powered, and the gas components supplied by the O.sub.3 or free radical oxygen [O] generator 4 were [O] with a concentration of 3% and O.sub.2 with a concentration of 97%, the mixed gas was first passed through the glass absorption bottle working as the catalytic oxidizer 7 (the glass absorption bottle was filled with potassium permanganate), and then passed through the glass absorption bottle working as the denitration tower 8 (filled with a 15% NaOH aqueous solution); NO concentration read from that shown by the ultraviolet JNYQ-I-41 type gas analyzer was stabilized substantially between 0-5 ppm, and the denitration efficiency was 99.5% to 100%.

(24) From the above tests, it can be seen that when free radical oxygen [O] and potassium permanganate are used for co-catalytic oxidation, the denitration effect is the best, and the denitration rate is 99.5%-100%; slightly inferior is the use of free radical oxygen [O] alone for oxidation, the denitration effect is slightly inferior, and the denitration rate is 96%-98%; more inferior is the use of potassium permanganate alone for co-catalytic oxidation, the denitration effect is more inferior, and the denitration rate is 92% to 95%; even more inferior is the use of O.sub.3 alone for oxidation, the denitration effect is even more inferior, and the denitration rate is 40.8%-51%; and when O.sub.2 is used alone for oxidation, the effect is the most inferior, and the denitration rate is only 6%-16%.

Example 2

(25) According to the process and apparatus shown in FIG. 2, a very simple denitration device was designed. With the device, the gas was allowed to pass directly through a glass absorption bottle filled with 100 mL denitration agent for absorption, and then the ultraviolet JNYQ-I-41 type gas analyzer was used to directly measure the concentration of NO in the outlet gas of the glass absorption bottle. To make the test more intuitive and simpler, a cylinder gas prepared from N.sub.2 and NO.sub.2 was used directly for the absorption test. The content of NO.sub.2 in the test cylinder gas was 5000 ppm; In the test method, a depressuring valve of the cylinder gas was directly connected to the inlet of the glass absorption bottle, then the outlet of the glass absorption bottle was directly connected to the ultraviolet JNYQ-I-41 type gas analyzer, and the gas flow rate was adjusted to 1.5 L/hr. The gas was injected into the glass absorption bottle, and recording of the absorption time was started. When the NO.sub.2 concentration displayed on the ultraviolet JNYQ-I-41 type gas analyzer was slowly increased from 0 to 1000 ppm, gas charging was stopped and gas charging time T.sub.1 (min) was recorded. Then, the glass absorption bottle with absorbed NO.sub.2 (filled with 100 mL denitration agent) was transferred to an oil bath heater for being heated (the temperature was 80 C.), regenerated by N.sub.2 stripping for 30 min and cooled. And then absorption at the same flow rate was carried out and time T.sub.2 was recorded. With the same method and under the same conditions, regeneration for 30 min, cooling and again absorption were carried out. In such a way, repeated absorption and repeated regeneration were carried out, and the recorded times T.sub.n were as follows: T.sub.1 was 45 min, T.sub.2 was 40 min, T.sub.3 was 39 min, T.sub.4 was 38 min, T.sub.5 was 39 min, T.sub.6 was 40 min, T.sub.7 was 38 min, and T.sub.8 was 38 min. After more than 30 times of absorption and regeneration, the absorption time was substantially stabilized around 26 min, indicating that the denitration agent (R-M) was stable and could be recycled for use. At the same time, that is, with such simple absorption-regeneration-absorption-regeneration . . . , which can proceed continuously, and with little change in the absorption capacity of the denitration agent, the oxidation gas denitration regeneration process and apparatus shown in FIG. 2 are sufficient to achieve the industrialization process of gas denitration and by-production of NO.sub.2 products as well as the function of really turning wastes into valuables.