DESULFURIZATION AND DENITRATION AGENT

Abstract

A desulfurization and denitration agent which is a mixture of polyalcohol and/or polyglycol substances, polycarboxylic acid substances and alkaline substances heated to above 90 C. and yielding, after condensation and/or polymerization, macromolecular or high-polymer ethers and/or esters for use in removing sulfur dioxides and/or nitrogen oxides from gases.

Claims

1. A desulfurization-denitration agent, which is a macromolecular or high molecular ether and/or ester obtained by mixing a polyol and/or a polymeric polyol, a polycarboxylic acid and an alkaline substance, then heating to above 90 C. and undergoing condensation and/or polymerization, wherein said polyol refers to an organic compound containing two or more hydroxyl groups in the molecule; said polymeric polyol is a high molecular or macromolecular substance linked by an ether bond formed by the condensation of a hydroxyl group in one polyol molecule with a hydroxyl group in another polyol molecule, where one water molecule is lost; said polycarboxylic acid is a compound at least containing two or more carboxyl groups in the same molecule; and said alkaline substance is an inorganic alkaline substance and/or an organic alkaline substance.

2. The desulfurization-denitration agent according to claim 1, wherein said polyol is selected from one or more of the following compounds: ethylene glycol, propylene glycol, 1,2,3-propanetriol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,4-butylene diol, pentanediol, neo-isopentyldiol, isopentyldiol, 1,5-pentanediol, 1,6-hexanediol, benzenediol, 1,2,4-butanetriol, isobutanetriol, pentanetriol, isopentanetriol, benzenetriol, pentaerythritol, pentanetetraol, isopentanetetraol, butanetetraol, gallic acid and tannin.

3. The desulfurization-denitration agent according to claim 1, wherein said polymeric polyol is selected from one or more of the following substances: polyethylene glycol, polypropylene glycol, polybutylene glycol, polypropanol, polybutanol, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polyethylene glycol monoethyl ether, polyethylene glycol diethyl ether.

4. The desulfurization-denitration agent according to claim 1, wherein said polycarboxylic acid is selected from one or more of the following compounds: ethanedioic acid, propanedioic acid, butanedioic acid, aminoethanedioic acid, nitrilotriacetic acid, EDTA, tartaric acid, tannin acid, polygallic acid and citric acid.

5. The desulfurization-denitration agent according to claim 1, wherein said inorganic alkaline substance includes ammonia as well as alkali metal, alkali earth metal or transition metal hydroxide, carbonate, carboxylate and complex.

6. The desulfurization-denitration agent according to claim 1, wherein said organic alkaline substance is an organic amine selected from aliphatic amines, aromatic amines and alkylol amines, said aliphatic amine is selected from: 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: 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: monomethanolamine, dimethanolamine, trimethanolamine, monoethanolamine, diethanolamine, triethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, N,N-diisopropylethanolamine, N-methyldiethanolamine, 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.

7. The desulfurization-denitration agent according to claim 1, wherein the molar ratio of the polyol and/or polymeric polyol:polycarboxylicacid:alkaline substance is 10:0.5-2:0.1-3, preferably 1:0.7-1:0.3-2, more preferably 1:0.9-1.3:0.5-1.5, very preferably 1:0.9-1.1:0.5-1.2, and most preferably 1:1:0.5-1.

8. A desulfurization-denitration solution, which is a solution formed by adding the desulfurization-denitration agent according to claim 1 to a solution composed of ethylene glycol and/or polyethylene glycol and/or water, wherein the content of said desulfurization-denitration agent is 0.1-50 wt %, preferably 2-30 wt %, more preferably 5-25 wt %, and most preferably 10-20 wt %.

9. A method for desulfurization and/or denitration of gases, comprising: contacting a gas with the desulfurization-denitration agent of claim 1, whereby removing sulfur dioxide, nitrogen oxides, or both from the gas.

10. The method according to claim 9, wherein said gas is selected from a group consisting of flue gases, incineration gases, coke-oven gases, synthetic waste gases from dyestuff plants, effluent gases from chemical fiber plants, and industrial feed gases or waste gases containing SOx, NOX, or both.

Description

DESCRIPTION OF DRAWING

[0049] FIG. 1 is a schematic diagram showing a process and apparatus for simulated flue gas desulfurization-denitration.

[0050] In FIG. 1: 1 represents a booster fan, 2 represents an absorption tower, 3 represents a desulfurization pump, 4 represents a rich liquid pump, 5 represents a lean liquid tank, 6 represents a lean liquid pump, 7 represents a cooler, 8 represents a heat exchanger, 9 represents a rich liquid heater, 10 represents a regeneration tower, 11 represents a concentration tower, 12 represents a flue gas before purification, 13 represents a flue gas after purification, 14 represents a lean liquid, 15 represents a rich liquid, 16 represents a regenerated desorbed gas, 17 represents a stripping steam, 18 represents a concentrated gas of sulfur dioxide and/or nitrogen oxides, 19 represents a condensed hot water, 20 represents a cooling water, and 21 represents a heating medium. For the meanings represented by circled symbols in the FIGURE: F.sub.1, F.sub.2, F.sub.3 and F.sub.4 respectively represent the flow rate of the flue gas 12 before purification, the flow rate of the desulfurized lean liquid 14, the flow rate of steam entering the regeneration tower 10 and the flow rate of steam entering the concentration tower 11; A.sub.1 represents the composition of the flue gas before purification 12, A.sub.2 represents the composition of the flue gas after purification 13, A.sub.3 represents the composition of the concentrated gas of sulfur dioxide and/or nitrogen oxides 18, A.sub.4 represents the content of SO.sub.2 and NO in the rich liquid 15 (including pH), A.sub.5 represents the content of SO.sub.2 and NO in the lean liquid 14 (including pH), and A.sub.6 represents the content of SO.sub.2 and NO in the condensed hot water 19; P.sub.1 represents the bottom pressure of the absorption tower 2, P.sub.2 represents the top pressure of the absorption tower 2, P.sub.3 represents the pressure in the regeneration tower 10, P.sub.4 represents the pressure of stripping steam 17, and P.sub.5 represents the pressure in the concentration tower 11; T.sub.1 represents the temperature at the bottom of the absorption tower 2, T.sub.2 represents the temperature at the top of the absorption tower 2, T.sub.3 represents the temperature in the regeneration tower 10, T.sub.4 represents the temperature of the stripping steam 17, T.sub.5 represents the temperature in the concentration tower 11, and T.sub.6 represents the temperature of the concentrated gas of sulfur dioxide and/or nitrogen oxides 18.

DETAILED DESCRIPTION

[0051] The actual purification effect of the desulfurization-denitration agent of 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.

[0052] The operation method is as follows:

[0053] A desulfurization-denitration solution (lean liquid 14) is firstly formed by dissolving a desulfurization-denitration agent of the present invention in ethylene glycol or polyethylene glycol, and the solution is injected into a lean liquid tank 5. All apparatus are activated for operation. The operation method is as follows:

[0054] As shown in FIG. 1: a flue gas before purification 12 with a temperature below 80 C. (the optimal temperature is below 35 C.) is pressurized by a booster fan 1 and then enters an absorption tower 2 from the bottom, while a lean liquid 14 enters the absorption tower 2 from the top. In the absorption tower 2, the flue gas before purification 12 contacts directly with the lean liquid 14. By this time, sulfur dioxide and/or nitrogen oxides and a small amount of carbon dioxide in the flue gas before purification 12 are absorbed by the lean liquid 14, the flue gas before purification 12 with sulfur dioxide and/or nitrogen oxides and a small amount of carbon dioxide being absorbed is converted to a flue gas after purification 13, and flows out from the top of the absorption tower 2 and is discharged into atmosphere, while contents A.sub.1 and A.sub.2 of sulfur dioxide and/or nitrogen oxides, carbon dioxide and oxygen in the flue gas before purification 12 and the flue gas after purification 13 are analyzed online. The lean liquid 14 with absorbed sulfur dioxide and/or nitrogen oxides and a small amount of carbon dioxide is converted to a rich liquid 15, flows out from the bottom of the absorption tower 2, is pressurized by a rich liquid pump 4, and is subjected to heat exchange through the shell pass of a heat exchanger 8 with the hot lean liquid 14 from a regeneration tower 10 to raise the temperature, and is then heated by a hot medium 21 to above 90 C. through a rich liquid heater 9. The rich liquid 15 with a temperature higher than 90 C. enters the regeneration tower 10 from the upper end, while a stripping steam 17 enters the regeneration tower 10 from the bottom. In the regeneration tower 10, the rich liquid 15 with a temperature higher than 90 C. is brought into direct contact with the stripping steam 17. By this time, the sulfur dioxide and/or nitrogen oxides and a small amount of carbon dioxide in the rich liquid 15 are desorbed, and enter into the stripping steam 17 to be mixed into a regenerated desorbed gas 16, which flows out from the top of the regeneration tower 10. After releasing sulfur dioxide and/or nitrogen oxides and a small amount of carbon dioxide, the rich liquid 15 with a temperature higher than 90 C. is converted to the hot lean liquid 14 with a temperature higher than 90 C., which flows out from the bottom of the regeneration tower 10 and is subjected to heat exchange through the tube pass of the heat exchanger 8 with the rich liquid 15 in the shell pass sent from the rich liquid pump 4 to lower the temperature. The lean liquid 14 with lowered temperature moves along the tube pass of a cooler 7, is cooled to room temperature by a cooling water 20 in the shell pass, and is pressurized by a lean liquid pump 6 and sent to the lean liquid tank 5. Then, the lean liquid 14 in the lean liquid tank 5 is pressurized by a desulfurization pump 3 and sent to the absorption tower 2 for desulfurization and/or denitration. The desulfurization-denitration solution works in such a way: the lean liquid 14 is converted to the rich liquid 15 after it absorbs sulfur dioxide and/or nitrogen oxides and a small amount of carbon dioxide in the absorption tower 2, whereas in the regeneration tower 10, the rich liquid 15 is heated, gas stripped and/or vacuum regenerated and again converted to the lean liquid 14, and the lean liquid 14 is again recycled for use, and it cycles continuously like this. The regenerated desorbed gas 16 flowing out from the top of the regeneration tower 10 enters a concentration tower 11 from the middle, and contacts with the distilled water condensed from the upper end of the concentration tower 11. In the condensing section of the concentration tower 11, water vapor in the regenerated desorbed gas 16 is condensed by the cooling water 20. A concentrated gas 18 of sulfur dioxide and/or nitrogen oxides comprised of non-condensing mixed gas of sulfur dioxide and/or nitrogen oxides and a small amount of carbon dioxide and the like flows out from the concentration tower 11, and can be recovered as a raw material gas, while condensed distilled water contains sulfur dioxide and/or nitrogen oxides and the like and continues flowing to the bottom of the concentration tower 11, and contacts with the stripping steam 17 coming from the bottom. Sulfur dioxide and/or nitrogen oxides and other gases in the distilled water are stripped and desorbed by the stripping steam 17, such that the condensed water is essentially free of sulfur dioxide and/or nitrogen oxides and other gases, reaching the standard of condensed hot water 19 for recovery, and can be recycled for use.

[0055] With respect to the process and apparatus for simulated flue gas desulfurization-denitration shown in FIG. 1, the specifications for various apparatus are as follows:

[0056] Absorption tower 2: 2194, total height 7.2 m, 4-layer packing, each 1 m high, 316L stainless steel material;

[0057] Lean liquid tank 5: 4503, total height 2.0 m, 316L stainless steel material;

[0058] Cooler 7: 1593, tube 101, length 1.5 m, total heat exchange area 3.9 m.sup.2,316L stainless steel material;

[0059] Heat exchanger 8: 1593, 2 units, tube 101, length 1.5 m, heat exchange area 23.9 m.sup.2, 2193, 1 unit, tube 61, length 1.4 m, heat exchange area 9.63 m.sup.2, total heat exchange area 23.9+9.63=17.43 m.sup.2,316L stainless steel material;

[0060] Rich liquid heater 9: 1593, tube 321, length 0.9 m, total heat exchange area 1.63 m.sup.2, titanium material;

[0061] Regeneration tower 10: 2194, total height 5.57 m, upper section with one layer of packing with a height of 1.5 m, lower end is empty tower, 316L stainless steel material;

[0062] Concentration tower 11: 1594, total height 6.2 m, upper end is titanium tube condenser, middle section with one layer of packing with a height of 1.5 m, lower section with one layer of packing with a height of 2.0 m, 316L stainless steel material.

[0063] Booster fan 1: Model 2HB710-AH37, air volume 318 m.sup.3/hr, air pressure 290 to 390 mbar (29 kPa to 39 kPa), Shanghai Likai Mechanical & Electrical device Co., Ltd.;

[0064] Rich liquid pump 4, desulfurization pump 3 and lean liquid pump 6: Models IHG25-160, flow rate 4.0 m.sup.3/hr, pumping head 32 m, 1.5 KW, 1 unit for each, 316L stainless steelmaterial, Shanghai Changshen Pump Manufacturing Co., Ltd.;

[0065] Flue gas flowmeter: Model LZB-50 glass rotor flowmeter, measuring range: 50-250 m.sup.3/hr, Jiangyin Keda Instrument Factory;

[0066] Desulfurization-denitration solution flowmeter: rich liquid pump, lean liquid pump and desulfurization pumpoutlet liquid flowmeter, Model LZB-32S glass pipeline flowmeter, measuring range: 0.4-4 m.sup.3/hr, Jiangyin Keda Instrument Factory;

[0067] Steam flowmeter (for gas stripping regeneration tower): Model LUGB-2303-P.sub.2 vortex flowmeter, measuring range: 8-80 m.sup.3/hr, Beijing Bangyu Chengxin Industrial Control Technology Development Co., Ltd.;

[0068] Steam flowmeter (for concentration tower): Model GHLUGB-25 vortex flowmeter, measuring range: 10-60 m.sup.3/hr, Tianjin Guanghua Kaite Flow Meter Co., Ltd.;

[0069] For the inlet and outlet gases of the absorption tower 2 as well as the gases desorbed from the concentration tower 11, all components were on-line analyzed by continuous flue gas analyzer, wherein the contents of SO.sub.2, NO and O.sub.2 were analyzed by ultraviolet JNYQ-I-41 type gas analyzer, the content of CO.sub.2 was analyzed by JNYQ-I-41C type infrared gas analyzer, manufactured by Xi'an Juneng Instrument Co., Ltd.; At the same time, the contents of SO.sub.2, NO and CO.sub.2 in the gas were analyzed and calibrated by chemical analysis method, and compared with values of instrumental analysis. In the chemical analysis method, the content of SO.sub.2 in the gas was analyzed by iodometric method, the content of CO.sub.2 in the gas was analyzed by barium chloride method, and the content of NO in the gas was analyzed by naphthyl ethylenediamine hydrochloride colorimetric method.

[0070] The contents of SO.sub.2, NO and CO.sub.2 in the lean liquid 14, the rich liquid 15 and the condensed hot water 19 were analyzed by chemical methods, in which: the content of SO.sub.2 in the solution was analyzed byiodometric method, the content of CO.sub.2 in the solution was analyzed by barium chloride method, the content of NO in the solution was analyzed by naphthyl ethylenediamine hydrochloride colorimetric method, and the pH of the solution was measured by electric potential pH meter.

[0071] Gas mixing was performed with air, SO.sub.2, NO/NO.sub.2 and CO.sub.2, and the gas compositions are shown in the data records of each experimental step.

[0072] According to the desulfurization-denitration agent of the present invention, the following four desulfurization-denitration solutions were formulated for experiments, and the experimental results are as follows:

[0073] Solution 1: The desulfurization-denitration solution, composed of 15% (w/w) of desulfurization-denitration agent, 75% (w/w) of ethylene glycol and 10% (w/w) of water, said desulfurization-denitration agent was synthesized by mixing ethylene glycol, citric acid and potassium hydroxide (1:1:1 molar ratio).

[0074] The synthetic method of this desulfurization-denitration agent was as follows: 48 Kg citric acid was first dissolved in 50 Kg distilled water, and then 23.5 Kg potassium hydroxide was added slowly to the aqueous solution of citric acid while slowly cooling, such that the temperature did not exceed 50 C.; after thorough dissolution, a potassium citrate solution was formed, then 15.5 Kg ethylene glycol was added to the potassium citrate solution and uniform stirring was carried out; the mixture was heated to 90 C.-120 C. and reaction went for 3 hours to obtain 137 Kg reactant mixture, in which the desulfurization-denitration agent was 78 Kg, and water was 59 Kg. Then, 7 Kg water was evaporated under reduced pressure, leaving 130 Kg aqueous solution of desulfurization-denitration agent, in which the desulfurization-denitration agent was 78 Kg, and water was 52 Kg. Then, 390 Kg ethylene glycol was added to this 130 Kg aqueous solution of desulfurization-denitration agent, stirred and mixed, obtaining 520 Kg desulfurization-denitration solution composed of 15% (w/w) of desulfurization-denitration agent, 75% (w/w) of ethylene glycol and 10% (w/w) of water, and this desulfurization-denitration solution was used in the following test:

[0075] Operation was performed in accordance with the embodiment described above in the apparatus shown in FIG. 1 with this desulfurization-denitration solution, and the operating conditions were as follows:

[0076] T.sub.1=36-40.4 C., T.sub.2=30.3-31.9 C., T.sub.3=120.7-121.9 C., T.sub.4=not measured, T.sub.5=not measured, and T.sub.6=not measured;

[0077] P.sub.1=6.65 kPa, P.sub.2=not measured, P.sub.3=0 kPa, and P.sub.5=0 kPa;

[0078] F.sub.1=40 m.sup.3/hr, F.sub.2=0.232 m.sup.3/hr, F.sub.3=not measured, and F.sub.4=not measured.

[0079] Experiments were operated according to the procedures, below are the operating data taken from the dayshift on Apr. 12, 2014:

[0080] Gas composition before treatment A.sub.1: SO.sub.2: 690-838 ppm, NO.sub.X: not measured, [0081] CO.sub.2: not measured, O.sub.2: not measured.

[0082] Gas composition after treatment A.sub.2: SO.sub.2: 12.3-37 ppm, NO.sub.X: not measured, [0083] CO.sub.2: not measured, O.sub.2: not measured.

[0084] Desulfurization efficiency: 95.6%-98.24%.

[0085] Composition of gas released by regeneration A.sub.3:

[0086] SO.sub.2: not measured, NO.sub.X: not measured, [0087] CO.sub.2: not measured, O.sub.2: not measured.

[0088] Rich liquid composition A.sub.4: SO.sub.2: 0.81-1.06 g/L, NO.sub.X: not measured, pH: 2.56-2.75.

[0089] Lean liquid composition A.sub.5: SO.sub.2: 0.51-0.89 g/L, NO.sub.X: not measured, pH: 2.9-3.45.

[0090] Condensed hot water composition A.sub.6: SO.sub.2: not measured.

[0091] Solution 2: The desulfurization-denitration solution, composed of 15% (w/w) of desulfurization-denitration agent, 75% (w/w) of ethylene glycol and 10% (w/w) of water, said desulfurization-denitration agent was synthesized by mixing polyethylene glycol 400, citric acid and potassium hydroxide (1:1:1 molar ratio).

[0092] The synthetic method of this desulfurization-denitration agent was as follows: 24 Kg citric acid was first dissolved in 50 Kg distilled water, and then 11.75 Kg potassium hydroxide was added slowly to the aqueous solution of citric acid while slowly cooling, such that the temperature did not exceed 50 C.; after thorough dissolution, a potassium citrate solution was formed, then 50 Kg polyethylene glycol 400 was added to the potassium citrate solution and uniform stirring was carried out; the mixture was heated to 90 C.-120 C. and reaction went for 3 hours to obtain 135.75 Kg reactant mixture, in which the desulfurization-denitration agent was 81.25 Kg, and water was 54.5 Kg. Then, 404.25 Kg polyethylene glycol 400 was added to this 135.75 Kg aqueous solution of desulfurization-denitration agent, stirred and mixed, obtaining 540 Kg desulfurization-denitration solution composed of 15% (w/w) of desulfurization-denitration agent, 75% (w/w) of polyethylene glycol 400 and 10% (w/w) of water, and this desulfurization-denitration solution was used in the following test: Operation was performed in accordance with the embodiment described above in the apparatus shown in FIG. 1 with this desulfurization-denitration solution, and the operating conditions were as follows:

[0093] T.sub.1=31.4-35.8 C., T.sub.2=33.6-38.7 C., T.sub.3=92.6-107.9 C., T.sub.4=89.7-115.5 C., T.sub.5=89.8-100.2 C., and T.sub.6=29.6-46.1 C.;

[0094] P.sub.1=not measured, P.sub.2=not measured, P.sub.3=not measured, and P.sub.5=not measured;

[0095] F.sub.1=95 m.sup.3/hr, F.sub.2=0.238 m.sup.3/hr, F.sub.3=3.5-24.9 m.sup.3/hr, and F.sub.4=3.8-11.4 m.sup.3/hr.

[0096] Experiments were operated according to the procedures, below are the operating data taken from the nightshift on May 13, 2014.

[0097] Gas composition before treatment A.sub.1: SO.sub.2: 683.2-1083.7 ppm, NO.sub.X: not measured, [0098] CO.sub.2: 3.14-3.78% (v/v), O.sub.2: not measured.

[0099] Gas composition after treatment A.sub.2: SO.sub.2: 5.8-10.9 ppm, NO.sub.X: not measured, [0100] CO.sub.2: 3.27-3.92% (v/v), O.sub.2: not measured.

[0101] Desulfurization efficiency: 98.49%-99.46%.

[0102] Composition of gas released by regeneration A.sub.3: [0103] SO.sub.2: 79.98% (v/v), NO.sub.X: not measured, [0104] CO.sub.2: not measured, O.sub.2: not measured.

[0105] Rich liquid composition A.sub.4: SO.sub.2: 1.2233-1.9282 g/L, NO.sub.X: not measured, pH: 3.65-3.92.

[0106] Lean liquid composition A.sub.5: SO.sub.2: 0.0622-0.2281 g/L, NO.sub.X: not measured, pH: 3.94-4.02.

[0107] Condensed hot water composition A.sub.6: SO.sub.2: 0.0019-0.0031 g/L.

[0108] Solution 3: The desulfurization-denitration solution, composed of 15% (w/w) of desulfurization-denitration agent, 75% (w/w) of polyethylene glycol 200 and 10% (w/w) of water, said desulfurization-denitration agent was synthesized by mixing ethylene glycol, citric acid and N-methyldiethanolamine (MDEA) (1:1:1 molar ratio).

[0109] The synthetic method of this desulfurization-denitration agent was as follows: 48 Kg citric acid was first dissolved in 50 Kg distilled water, and then 29.75 Kg N-methyldiethanolamine (MDEA) was added slowly to the aqueous solution of citric acid while slowly cooling, such that the temperature did not exceed 50 C.; after thorough dissolution, a citric acid MDEA solution was formed, then 15.5 Kg ethylene glycol was added to the citric acid MDEA solution and uniform stirring was carried out; the mixture was heated to 90 C.-120 C. and reaction went for 3 hours to obtain 143.25 Kg reactant mixture, in which the desulfurization-denitration agent was 88.75 Kg, and water was 54.5 Kg. Then, 442.5 Kg ethylene glycol and 4.25 Kg distilled water was added to this 143.25 Kg aqueous solution of desulfurization-denitration agent, stirred and mixed, obtaining 590 Kg desulfurization-denitration solution composed of 15% (w/w) of desulfurization-denitration agent, 75% (w/w) of ethylene glycol and 10% (w/w) of water, and this desulfurization-denitration solution was used in the following test:

[0110] Operation was performed in accordance with the embodiment described above in the apparatus shown in FIG. 1 with this desulfurization-denitration solution, and the operating conditions were as follows:

[0111] T.sub.1=30.6-36.5 C., T.sub.2=21.6-28.2 C., T.sub.3=125-127.1 C., T.sub.4=123.8-127.1 C., T.sub.5=103-118 C., and T.sub.6=27.8-29.9 C.;

[0112] P.sub.1=6.4-7 kPa, P.sub.2=2.6-2.85 kPa, P.sub.3=3.5-4.45 kPa, and P.sub.5=0.95-1.55 kPa;

[0113] F.sub.1=164 m.sup.3/hr, F.sub.2=0.125 m.sup.3/hr, F.sub.3=19.7-20.2 m.sup.3/hr, and F.sub.4=0-4.2 m.sup.3/hr.

[0114] Experiments were operated according to the procedures, below are the operating data taken from the nightshift on Jan. 7, 2015.

[0115] Gas composition before treatment A.sub.1: SO.sub.2: 1366.5-1977 ppm, NO.sub.X: not measured, [0116] CO.sub.2: 3.3-8% (v/v), O.sub.2: 23.7-24.9% (v/v).

[0117] Gas composition after treatment A.sub.2: SO.sub.2: 6-8.5 ppm, NO.sub.X: not measured, [0118] CO.sub.2: 3.0-7.7% (v/v), O.sub.2: 20.7-21.6% (v/v).

[0119] Desulfurization efficiency: 99.39%-99.58%.

[0120] Composition of gas released by regeneration A.sub.3:

[0121] SO.sub.2: 89.9%-90.1% (v/v), NO.sub.X: 0.1% (v/v), [0122] CO.sub.2: 1.5-2.9% (v/v), O.sub.2: not measured.

[0123] Rich liquid composition A.sub.4: SO.sub.2: 3.959-6.331 g/L, NO.sub.X: not measured, pH: 3.14-3.64.

[0124] Lean liquid composition A.sub.5: SO.sub.2: 0.446-0.522 g/L, NO.sub.X: not measured, pH: 4.16-4.19.

[0125] Condensed hot water composition A.sub.6: SO.sub.2: 0.0011-0.0017 g/L.

[0126] Solution 4: The desulfurization-denitration solution, composed of 15% (w/w) of desulfurization-denitration agent, 75% (w/w) of polyethylene glycol 200 and 10% (w/w) of water, said desulfurization-denitration agent was synthesized by mixing polyethylene glycol 200, citric acid and N-methyldiethanolamine (MDEA) (1:1:1 molar ratio).

[0127] The synthetic method of this desulfurization-denitration agent was as follows: 48 Kg citric acid was first dissolved in 50 Kg distilled water, and then 29.75 Kg N-methyldiethanolamine (MDEA) was added slowly to the aqueous solution of citric acid while slowly cooling, such that the temperature did not exceed 50 C.; after thorough dissolution, a citric acid MDEA solution was formed, then 50 Kg polyethylene glycol 200 was added to the citric acid MDEA solution and uniform stirring was carried out; the mixture was heated to 90 C.-120 C. and reaction went for 3 hours to obtain 177.75 Kg reactant mixture, in which the desulfurization-denitration agent was 173.25 Kg, and water was 54.5 Kg. Then, 812.25 Kg polyethylene glycol 200 and 55.5 Kg distilled water were added to this 177.75 Kg aqueous solution of desulfurization-denitration agent, stirred and mixed, obtaining 1100 Kg desulfurization-denitration solution composed of 15% (w/w) of desulfurization-denitration agent, 75% (w/w) of polyethylene glycol 200 and 10% (w/w) of water, and this desulfurization-denitration solution was used in the following test: Operation was performed in accordance with the embodiment described above in the apparatus shown in FIG. 1 with this desulfurization-denitration solution, and the operating conditions were as follows:

[0128] T.sub.1=28.6-31.8 C., T.sub.2=25.7-27 C., T.sub.3=120.5-121.7 C., T.sub.4=112.9-113.7 C., T.sub.5=105-105.5 C., and T.sub.6=67.3-73.4 C.;

[0129] P.sub.1=8.89-9 kPa, P.sub.2=1.95-2.15 kPa, P.sub.3=2.15-3.1 kPa, and P.sub.5=1.75-2.35 kPa;

[0130] F.sub.1=140 m.sup.3/hr, F.sub.2=0.202 m.sup.3/hr, F.sub.3=19.7-20.2 m.sup.3/hr, and F.sub.4=0-4.2 m.sup.3/hr.

[0131] Experiments were operated according to the procedures, below are the operating data taken from the nightshift on Feb. 11, 2015.

[0132] Gas composition before treatment A.sub.1: SO.sub.2: 1302-2815.5 ppm, NO.sub.X: 49.8-459 ppm, [0133] CO.sub.2: 4.7-5.6% (v/v), O.sub.2: 20.6-20.7% (v/v).

[0134] Gas composition after treatment A.sub.2: SO.sub.2: 4-14.5 ppm, NO.sub.X: 0-0.1 ppm, CO.sub.2: 4.0-4.2% (v/v), O.sub.2: 18.5-18.7% (v/v).

[0135] Desulfurization efficiency: 99.44%-99.65%; denitration efficiency: 100%.

[0136] Composition of gas released by regeneration A.sub.3:

[0137] SO.sub.2: 89.9%-90.1% (v/v), NO.sub.X: 0-0.1% (v/v), [0138] CO.sub.2: 4.1-9.6% (v/v), O.sub.2: not measured.

[0139] Rich liquid composition A.sub.4: SO.sub.2: 3.51-5.76 g/L, NO.sub.X: not measured, pH: 4.6-4.85.

[0140] Lean liquid composition A.sub.5: SO.sub.2: 0.19-0.22 g/L, NO.sub.X: not measured, pH: 5.34-5.58.

[0141] Condensed hot water composition A.sub.6: SO.sub.2: 0.004-0.423 g/L.

[0142] From the above experimental results, it can be seen that the desulfurization-denitration agent of the present invention has a better effect, and can be used for actual industrialization to remove sulfur dioxide and nitrogen oxides from gases.