Limestone-gypsum wet flue gas desulfurization composite synergist and preparation method thereof

Abstract

The application discloses a limestone-gypsum wet flue gas desulfurization composite synergist and a preparation method thereof, and relates to the technical field of flue gas desulfurization. The limestone-gypsum wet flue gas desulfurization composite synergist comprises the following raw materials in parts by weight: 15-18 parts of organic acid, 5-8 parts of oxidation catalyst, 8-10 parts of sodium salt, 5-10 parts of magnesium salt, 12-15 parts of surfactant, 5-8 parts of organic acid alkali metal salt and 4-5 parts of dispersant. The dodecylalkene-1-yl butane diacid anhydride is reacted with N,N-dimethyl ethylenediamine to generate a monoamide compound, the monoamide compound is reacted with epichlorohydrin to generate a quaternary ammonium salt compound, and the quaternary ammonium salt compound is reacted with sodium p-aminobenzenesulfonate to generate a surfactant. The limestone-gypsum wet flue gas desulfurization composite synergist prepared by the application can promote the dissolution of calcium carbonate and has good desulfurization efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flue gas desulfurization, in particular to a limestone-gypsum wet flue gas desulfurization composite synergist and a preparation method thereof. BACKGROUND

[0002] At present, coal occupies a dominant position in the energy structure, and wet flue gas desulfurization technology is widely used in coal-fired power plants to control the content of SO2 and NOx pollutants in flue gas emissions. x However, this technology encounters multiple challenges in actual application. On the one hand, due to the widespread use of high-sulfur coal, the SO2 concentration in flue gas is significantly higher than the system design standard, and the traditional desulfurization device is difficult to achieve ultra-low emission targets. On the other hand, the limestone dissolution rate is slow, which not only easily causes equipment scaling and plugging, but also greatly increases maintenance costs. In view of these problems, under the premise of maintaining the original desulfurization equipment without modification, adding desulfurization composite synergist to the limestone slurry can improve the limestone dissolution rate and SO2 absorption efficiency.

[0003] Chinese invention patent with publication number CN103263843A discloses a wet flue gas desulfurization system, a flue gas desulfurization synergist, a preparation method and application thereof. The flue gas desulfurization synergist of the wet flue gas desulfurization system is composed of 12-50% magnesium salt, 19-57% sodium salt and 3-31% organic solvent by weight percentage. The preparation method is to mix and stir the magnesium salt, sodium salt and organic solvent uniformly to obtain the flue gas desulfurization synergist of the wet flue gas desulfurization system. The flue gas desulfurization synergist of the invention can promote SO2 absorption and limestone dissolution, but its desulfurization efficiency is general. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the present application is to provide a limestone-gypsum wet flue gas desulfurization composite synergist and a preparation method thereof.

[0005] To achieve the above-mentioned purpose, the present application realizes the following technical solutions:

[0006] A limestone-gypsum wet flue gas desulfurization composite synergist, comprising the following raw materials by weight fraction:

[0007] organic acid 15-18 parts, oxidation catalyst 5-8 parts, sodium salt 8-10 parts, magnesium salt 5-10 parts, surfactant 12-15 parts, organic acid alkali metal salt 5-8 parts, dispersant 4-5 parts;

[0008] The surfactant is prepared by the following method:

[0009] S1: 2-dodecylene-1-yl succinic anhydride reacts with N,N-dimethyl ethylenediamine to form a monoamide compound, and the reaction equation is as follows:

[0010]

[0011] S2: the monoamide compound is reacted with epichlorohydrin to generate a quaternary ammonium salt compound, and the reaction equation is as follows:

[0012]

[0013] S3: the quaternary ammonium salt compound is reacted with sodium p-aminobenzenesulfonate to generate a surfactant, and the reaction equation is as follows:

[0014]

[0015] In step S1, the molar ratio of the 2-dodecylene-1-yl succinic anhydride to N,N-dimethylethylenediamine is (1-1.1):1.

[0016] In step S2, the molar ratio of the monoamide compound to epichlorohydrin is 1:(1.1-1.3).

[0017] In step S3, the molar ratio of the quaternary ammonium salt compound to sodium p-aminobenzenesulfonate is (2.1-2.2):1.

[0018] The organic acid is one of citric acid and adipic acid.

[0019] The oxidation catalyst is one of manganese sulfate and ferrous sulfate.

[0020] The magnesium salt is one of magnesium chloride and magnesium sulfate; and the sodium salt is one of sodium sulfate and sodium chloride.

[0021] The alkali metal salt of the organic acid is one of sodium formate and sodium benzoate.

[0022] The dispersant is sodium polyacrylate.

[0023] A preparation method of a limestone-gypsum wet flue gas desulfurization composite synergist comprises the following steps:

[0024] (1) the following components are weighed by weight parts: 15-18 parts of organic acid, 5-8 parts of oxidation catalyst, 8-10 parts of sodium salt, 5-10 parts of magnesium salt, 12-15 parts of surfactant, 5-8 parts of alkali metal salt of organic acid, and 4-5 parts of dispersant;

[0025] (2) the above materials are mixed and stirred to be fully mixed and uniform, and are added into a planetary ball mill to be ground into powder, thereby obtaining the limestone-gypsum wet flue gas desulfurization composite synergist.

[0026] Due to the above technical scheme, the beneficial effects of the present application include:

[0027] The desulfurization composite synergist prepared by the method has good calcium carbonate dissolution rate and desulfurization efficiency. DETAILED DESCRIPTION

[0028] The application will be further described in connection with the following examples, but the application is not limited to these examples.

[0029] Example 1: Preparation of a surfactant

[0030] S1: 150ml of chloroform, 0.1mol of 2-dodecylene-1-yl succinic anhydride was added into a reaction kettle, stirred and mixed, 100ml of chloroform solution containing 0.1mol of N,N-dimethyl ethylenediamine was added dropwise at 25℃, and the dropping was completed after 30min, and the reaction was kept for 3h, and then cooled to 0℃, and the precipitate was separated after standing for 4h, and then filtered, and then recrystallized with 100ml of chloroform, and then filtered, and then dried at 40℃ under vacuum for 8h to obtain a monoamide compound; the nuclear magnetic hydrogen spectrum data is as follows: 1 H NMR (300 MHz, Chloroform- d ) δ 11.14(s, 1H), 6.90 (t, J = 4.3 Hz, 1H), 5.55 (dtq, J = 15.2, 6.9, 1.5 Hz, 1H),5.44 - 5.28 (m, 1H), 3.28 (td, J = 6.1, 4.3 Hz, 2H), 2.91 - 2.78 (m, 1H),2.73 - 2.12 (m, 12H), 2.00 (tdq, J = 7.8, 5.0, 1.2 Hz, 2H), 1.37 - 1.18 (m,14H), 0.97 - 0.82 (m, 3H);

[0031] S2: 300ml of isopropyl alcohol, 0.1mol of monoamide compound was added into a reaction kettle, stirred and mixed, 0.11mol of epichlorohydrin was added dropwise at room temperature, and the dropping was completed after 20min, and then the temperature was increased to reflux, and the reaction was kept for 10h, and then cooled to room temperature, and then distilled at 60℃ under reduced pressure for 3h to obtain a quaternary ammonium salt compound; the nuclear magnetic hydrogen spectrum data is as follows: 1 H NMR (300 MHz, Chloroform- d) δ 11.14 (s, 1H), 8.24 (t, J = 3.5 Hz, 1H), 5.55 (dtq, J = 15.2, 6.9, 1.5 Hz, 1H), 5.44 - 5.28 (m, 1H), 3.93 - 3.49 (m, 7H), 3.38 - 3.06 (m, 8H), 2.93 - 2.75 (m, 1H), 2.74 - 2.11 (m, 4H), 2.05 - 1.92 (m, 2H), 1.37 - 1.18 (m, 14H), 0.96 - 0.82 (m, 3H);

[0032] S3: 400 ml of deionized water, 0.21 mol of quaternary ammonium salt compound and 0.1 mol of sodium p-aminobenzenesulfonate were added to the reaction kettle, stirred and mixed, 200 ml of isopropyl alcohol was added, heated to 70°C, reacted for 24h, cooled to room temperature, and the pH was adjusted to 8 using 10 wt% sodium hydroxide solution; 65°C, 3h, 150 ml of deionized water was added and stirred for 15 min, then slowly added to 350 ml of cold acetone (5°C, same below), stirred and precipitated, filtered, washed with cold acetone (3x50 ml), 50°C vacuum dried for 12h, to obtain the surfactant; its nuclear magnetic resonance hydrogen spectrum data are as follows: 1 H NMR (300 MHz, Chloroform- d ) δ 8.32 (t, J =3.5 Hz, 2H), 7.77 - 7.66 (m, 2H), 6.99 - 6.89 (m, 2H), 6.11 (d, J = 6.6 Hz,2H), 5.73 - 5.56 (m, 2H), 5.43 - 5.28 (m, 2H), 4.32 (tq, J = 8.0, 6.3 Hz,2H), 3.80 - 3.34 (m, 16H), 3.31 (s, 6H), 3.19 (s, 6H), 3.05 - 2.91 (m, 2H),2.73 - 2.09 (m, 8H), 2.05 - 1.93 (m, 4H), 1.39 - 1.18 (m, 28H), 0.98 - 0.82(m, 6H).

[0033] Example 2 Preparation of surfactant:

[0034] S1: 150ml of chloroform, 0.105mol of 2-dodecylene-1-yl succinic anhydride was added into the reaction kettle, stirred and mixed, 100ml of N,N-dimethyl ethylenediamine solution containing 0.1mol of chloroform was added dropwise at 30°C, 30min dropwise, 2.5h of reaction, cooled to 0°C, 4h of standing precipitate, filtration, recrystallization with 100ml of chloroform, filtration, 40°C vacuum drying for 8h, to obtain a monoamide compound;

[0035] S2: 300ml of isopropyl alcohol, 0.1mol of monoamide compound was added into the reaction kettle, stirred and mixed, 0.12mol of epichlorohydrin was added dropwise at room temperature, 20min dropwise, 12h of reaction at reflux, cooled to room temperature, 3h of distillation at 60°C under reduced pressure, to obtain a quaternary ammonium salt compound;

[0036] S3: 400ml of deionized water, 0.215mol of quaternary ammonium salt compound and 0.1mol of sodium p-aminobenzenesulfonate were added into the reaction kettle, stirred and mixed, 200ml of isopropyl alcohol was added, heated to 75°C, reacted for 20h, cooled to room temperature, the pH was adjusted to 8 using 10wt% sodium hydroxide solution; 3h of distillation at 65°C under reduced pressure, 150ml of deionized water was added and stirred for 15min, then slowly added into 350ml of cold acetone, stirred and precipitated, filtered, washed with cold acetone (3x50ml), 50°C vacuum drying for 12h, to obtain a surfactant.

[0037] Example 3 Preparation of surfactant:

[0038] S1: 150ml of chloroform, 0.105mol of 2-dodecylene-1-yl succinic anhydride was added into the reaction kettle, stirred and mixed, 100ml of N,N-dimethyl ethylenediamine solution containing 0.1mol of chloroform was added dropwise at 30°C, 30min dropwise, 2.5h of reaction, cooled to 0°C, 4h of standing precipitate, filtration, recrystallization with 100ml of chloroform, filtration, 40°C vacuum drying for 8h, to obtain a monoamide compound;

[0039] S2: 300ml of isopropyl alcohol, 0.1mol of monoamide compound was added into the reaction kettle, stirred and mixed, 0.12mol of epichlorohydrin was added dropwise at room temperature, 20min dropwise, 12h of reaction at reflux, cooled to room temperature, 3h of distillation at 60°C under reduced pressure, to obtain a quaternary ammonium salt compound;

[0040] S3: 400 ml of deionized water, 0.22 mol of quaternary ammonium salt compound and 0.1 mol of sodium p-aminobenzenesulfonate were added into a reaction kettle, stirred and mixed, 200 ml of isopropyl alcohol was added, heated to 80°C, reacted for 18 h, cooled to room temperature, and the pH was adjusted to 8 using 10 wt% sodium hydroxide solution; 65°C, 3h, 150 ml of deionized water was added and stirred for 15 min, then slowly added into 350 ml of cold acetone, stirred and precipitated, filtered, washed with cold acetone (3x50 ml), and vacuum dried at 50°C for 12 h to obtain the surfactant.

[0041] Example 4 Preparation of limestone-gypsum wet flue gas desulfurization composite synergist:

[0042] (1) Take: organic acid (citric acid) 15 g, oxidation catalyst (manganese sulfate) 5 g, sodium salt (sodium sulfate) 8 g, magnesium salt (magnesium chloride) 5 g, surfactant (prepared in example 1) 12 g, organic acid alkali metal salt (sodium formate) 5 g, dispersant (sodium polyacrylate) 4 g;

[0043] (2) Mix the above materials, stir at room temperature for 20 min at 300 r / min; add the mixed material into a planetary ball mill, grind at 500 r / min for 15 min, stop for 15 min, and grind again at 500 r / min for 15 min to obtain the limestone-gypsum wet flue gas desulfurization composite synergist.

[0044] Example 5 Preparation of limestone-gypsum wet flue gas desulfurization composite synergist:

[0045] (1) Take: organic acid (citric acid) 15 g, oxidation catalyst (manganese sulfate) 5 g, sodium salt (sodium sulfate) 8 g, magnesium salt (magnesium chloride) 5 g, surfactant (prepared in example 1) 12 g, organic acid alkali metal salt (sodium formate) 5 g, dispersant (sodium polyacrylate) 4 g;

[0046] (2) Mix the above materials, stir at room temperature for 20 min at 300 r / min; add the mixed material into a planetary ball mill, grind at 500 r / min for 15 min, stop for 15 min, and grind again at 500 r / min for 15 min to obtain the limestone-gypsum wet flue gas desulfurization composite synergist.

[0047] Example 6 Preparation of limestone-gypsum wet flue gas desulfurization composite synergist:

[0048] (1) Take: organic acid (citric acid) 15 g, oxidation catalyst (manganese sulfate) 5 g, sodium salt (sodium sulfate) 8 g, magnesium salt (magnesium chloride) 5 g, surfactant (prepared in example 1) 12 g, organic acid alkali metal salt (sodium formate) 5 g, dispersant (sodium polyacrylate) 4 g;

[0049] (2) The above materials are mixed, stirred at room temperature at 300 r / min for 20 min; the mixed material is added into a planetary ball mill, ground at 500 r / min for 15 min, stopped for 15 min, and then ground at 500 r / min for another 15 min, to obtain the limestone-gypsum wet flue gas desulfurization composite synergist.

[0050] Comparative Example 1

[0051] The raw material composition and preparation method of the limestone-gypsum wet flue gas desulfurization composite synergist are basically the same as those in Example 5, except that the surfactant is replaced with equal weight of a quaternary ammonium salt compound prepared by the method of step S2 in Example 2.

[0052] Comparative Example 2

[0053] The raw material composition and preparation method of the limestone-gypsum wet flue gas desulfurization composite synergist are basically the same as those in Example 5, except that the surfactant is replaced with equal weight of a surfactant prepared by the following method:

[0054] The preparation method of the surfactant is basically the same as that in Example 2, except that 2-dodecylene-1-yl succinic anhydride in step S1 is replaced with equal molar amount of butyl succinic anhydride.

[0055] Comparative Example 3

[0056] The raw material composition and preparation method of the limestone-gypsum wet flue gas desulfurization composite synergist are basically the same as those in Example 5, except that the surfactant is replaced with equal weight of a surfactant prepared by the following method:

[0057] The preparation method of the surfactant is basically the same as that in Example 2, except that sodium p-aminobenzenesulfonate in step S3 is replaced with equal molar amount of aminomethanesulfonic acid.

[0058] Comparative Example 4

[0059] The raw material composition and preparation method of the limestone-gypsum wet flue gas desulfurization composite synergist are basically the same as those in Example 5, except that the surfactant is replaced with equal weight of a surfactant prepared by the following method:

[0060] S1: Add 150 ml of anhydrous chloroform and 0.105 mol of dodecacyanate to a reaction vessel, stir and mix well, add 0.15 mol of thionyl chloride dropwise, completing the addition in 30 min, stir at room temperature for 2 h, heat to reflux and react for 3 h, cool to room temperature, distill under reduced pressure at 50 °C for 3 h, dissolve the residue in 100 ml of dichloromethane to obtain an acyl chloride solution; add 200 ml of dichloromethane, 0.1 mol of N,N-dimethylethylenediamine and 0.1 mol of triethylamine to a reaction vessel, stir and mix well, cool to 0 °C, add the acyl chloride solution dropwise, completing the addition in 1 h, stir for 1 h, heat to reflux and react for 3 h, cool to room temperature, wash three times with saturated sodium bicarbonate (80 ml each time), distill under reduced pressure at 35 °C for 1 h, add 100 ml of diethyl ether and stir to precipitate, filter, dry under vacuum at 50 °C for 12 h to obtain a monoamide compound;

[0061] S2: Add 300 ml isopropanol and 0.1 mol monoamide compound to the reaction vessel, stir and mix well, add 0.12 mol epichlorohydrin dropwise at room temperature, and after 20 min, the mixture is heated to reflux and reacted for 12 h. After cooling to room temperature, remove the solvent and epichlorohydrin by vacuum distillation at 60 °C for 3 h to obtain the quaternary ammonium salt compound.

[0062] S3: Add 400 ml of deionized water, 0.215 mol of quaternary ammonium salt compound and 0.1 mol of sodium p-aminobenzenesulfonate to a reaction vessel, stir and mix well, add 200 ml of isopropanol, heat to 75 °C, react for 20 h, cool to room temperature, distill under reduced pressure at 65 °C for 3 h, add 150 ml of deionized water and stir for 15 min, then slowly add to 350 ml of cold acetone, stir to precipitate, filter, wash with cold acetone (3 × 50 ml), and dry under vacuum at 50 °C for 12 h to obtain the surfactant.

[0063] Comparative Example 5

[0064] The raw material composition and preparation method of the limestone-gypsum wet flue gas desulfurization composite synergist are basically the same as those in Example 5, except that the surfactant is replaced with an equal weight of a surfactant prepared by the following method:

[0065] S1: Add 150 ml of chloroform and 0.105 mol of 2-dodecen-1-ylsuccinic anhydride to a reaction vessel, stir and mix well. At 30°C, add 100 ml of chloroform solution containing 0.1 mol of N,N-dimethylethylenediamine dropwise over 30 min. Keep the reaction temperature constant for 2.5 h, cool to 0°C, let stand for 4 h to precipitate, filter, recrystallize using 100 ml of chloroform, filter, and dry under vacuum at 40°C for 8 h to obtain the monoamide compound.

[0066] S2: 200 ml of dichloromethane, 0.1 mol of monoamide compound were added into the reaction kettle, stirred and mixed, 0.15 mol of sulfoxide chloride was added dropwise, 10 min dropwise, heated to reflux, reacted for 5 h, cooled to room temperature to obtain an acyl chloride solution; 200 ml of dichloromethane, 0.11 mol of N,N-dimethylethylenediamine, 0.12 mol of triethylamine were added into the reaction kettle, stirred and mixed, the acyl chloride solution was added dropwise, 1 h dropwise, stirred for 1 h, heated to reflux, reacted for 3 h, cooled to room temperature, washed with saturated sodium bicarbonate three times (100 ml each time), 35°C reduced pressure distillation for 1 h, recrystallized with 180 ml of acetone, 50°C vacuum drying for 12 h to obtain a bisamide compound;

[0067] S3: 300 ml of isopropyl alcohol, 0.1 mol of bisamide compound were added into the reaction kettle, stirred and mixed, 0.22 mol of epichlorohydrin was added dropwise at room temperature, 20 min dropwise, heated to reflux, reacted for 12 h, cooled to room temperature, 60°C reduced pressure distillation for 3 h to obtain a quaternary ammonium salt compound;

[0068] S4: 400 ml of deionized water, 0.215 mol of quaternary ammonium salt compound and 0.1 mol of sodium p-aminobenzenesulfonate were added into the reaction kettle, stirred and mixed, 200 ml of isopropyl alcohol was added, heated to 75°C, reacted for 20 h, cooled to room temperature, 65°C reduced pressure distillation for 3 h, 150 ml of deionized water was added, stirred and pulped for 15 min, then slowly added into 350 ml of cold acetone, stirred and precipitated, filtered, washed with cold acetone (3 x 50 ml), 50°C vacuum drying for 12 h to obtain a surfactant.

[0069] Comparative Example 6

[0070] The raw material composition and preparation method of the limestone-gypsum wet flue gas desulfurization composite synergist are basically the same as those of Example 5, except that the surfactant is replaced with the same weight of a surfactant prepared by the following method:

[0071] S1: 150 ml of anhydrous chloroform, 0.105 mol of erucic acid were added into the reaction kettle, stirred and mixed, 0.15 mol of sulfoxide chloride was added dropwise, 30 min dropwise, stirred at room temperature for 2 h, heated to reflux, reacted for 3 h, cooled to room temperature, 50°C reduced pressure distillation for 3 h, the residue was dissolved in 100 ml of dichloromethane to obtain an acyl chloride solution; 200 ml of dichloromethane, 0.1 mol of N,N-dimethylethylenediamine, 0.1 mol of triethylamine were added into the reaction kettle, stirred and mixed, cooled to 0°C, the acyl chloride solution was added dropwise, 1 h dropwise, stirred for 1 h, heated to reflux, reacted for 3 h, cooled to room temperature, washed with saturated sodium bicarbonate three times (80 ml each time), 35°C reduced pressure distillation for 1 h, 100 ml of ether was added, stirred to precipitate the sediment, filtered, 50°C vacuum drying for 12 h to obtain a monoamide compound;

[0072] S2: 300 ml of isopropyl alcohol, 0.1 mol of monoamide compound were added into a reaction kettle, stirred and mixed, 0.12 mol of epichlorohydrin was added dropwise at room temperature, 20 min after dropping, the temperature was raised to reflux, and the reaction was carried out for 12 h, then the temperature was cooled to room temperature, and the reaction was carried out at 60°C for 3 h under reduced pressure to obtain a quaternary ammonium salt compound;

[0073] S3: 400 ml of deionized water, 0.215 mol of quaternary ammonium salt compound and 0.1 mol of sodium p-aminobenzenesulfonate were added into a reaction kettle, stirred and mixed, 200 ml of isopropyl alcohol was added, the temperature was raised to 75°C, and the reaction was carried out for 20 h, then the temperature was cooled to room temperature, and the reaction was carried out at 65°C for 3 h under reduced pressure, 150 ml of deionized water was added, stirred and pulped for 15 min, then slowly added into 350 ml of cold acetone, stirred and precipitated, filtered, washed with cold acetone (3 x 50 ml), and vacuum dried at 50°C for 12 h to obtain a surfactant.

[0074] Comparative Example 7

[0075] The raw material composition and preparation method of the limestone-gypsum wet flue gas desulfurization composite synergist were basically the same as those of Example 5, except that the surfactant was replaced by an equal weight of a surfactant prepared by the following method:

[0076] The preparation method of the surfactant was basically the same as that of Example 2, except that in step S3, sodium hydroxide solution was not used to adjust the pH after the reaction was completed, and the remaining operation steps were unchanged.

[0077] Comparative Example 8

[0078] The raw material composition and preparation method of the limestone-gypsum wet flue gas desulfurization composite synergist were basically the same as those of Example 5, except that the surfactant was replaced by an equal weight of cocamide propyl betaine.

[0079] The sodium polyacrylate used in the present application has a model number of ARONVIS SX and is manufactured by Beijing Aisir Science and Technology Co., Ltd.

[0080] The desulfurization composite synergists prepared in Examples 4-6 and Comparative Examples 1-8 of the present application were subjected to limestone dissolution, calcium sulfite oxidation and flue gas desulfurization tests, and the results are shown in Table 1.

[0081] Limestone dissolution test: the desulfurization composite synergist prepared in the examples and comparative examples is mixed with 100 ml of 3 wt% limestone slurry (the content of the desulfurization composite synergist is 500 mg / L), and the temperature is raised to 50°C. The solution is titrated with 0.1M HCl at a rotation speed of 300 r / min. The automatic titrator is set to a pH value of 5.5, and the solution is continuously recorded for 1 h. The limestone dissolution rate is calculated as follows: X(t)=(c×v) / (2×m / Mn)×100%; wherein c is the molar concentration of HCl; v is the volume of HCl consumed in 1 h; m is the total mass of calcium carbonate; and Mn is the relative molecular mass of calcium carbonate.

[0082] Calcium sulfite oxidation rate test: the desulfurization composite synergist prepared in the examples and comparative examples is mixed with 100 ml of 1 wt% CaSO3 (the content of the desulfurization composite synergist is 500 mg / L), and 1 ml of 36 wt% concentrated hydrochloric acid is added and mixed. The temperature is set to 50°C, the rotation speed is 300 r / min, and a mixed gas of nitrogen, oxygen and carbon dioxide (the ratio is 4:1:5) is introduced at a total flow rate of 0.2 L / min. After the mixed gas is introduced for 5 min, the concentration CO of SO4 2- in the solution is measured using an automatic potentiometric titrator equipped with a lead nitrate electrode. The concentration C1 of SO4 2- is measured again after 60 min. The oxidation rate of CaSO3 is calculated as follows: R=(C1-C0) / t, wherein C1 is the concentration of sulfate in 60 min, in units of μmol / L; C0 is the initial concentration of sulfate, in units of μmol / L; and t is the time, in units of s.

[0083] Flue gas desulfurization test: the desulfurization composite synergist prepared in the examples and comparative examples is mixed with 100 ml of 3 wt% limestone slurry (the content of the desulfurization composite synergist is 500 mg / L), and the temperature is controlled at 50°C and the rotation speed is 500 r / min. The limestone slurry with the desulfurization synergist is stirred for 4 h. The limestone slurry with the desulfurization synergist is added to an absorption tower, and the performance is tested as follows: the SO2 concentration of the inlet flue gas is designed to be 3000 mg / Nm 3 (equilibrium gas is nitrogen), the liquid-gas ratio is 10.5, the SO2 concentration of the outlet flue gas is monitored, and then the desulfurization efficiency is calculated as follows: desulfurization efficiency=(inlet SO2 concentration-outlet SO2 concentration) / inlet SO2 concentration. The results are shown in Table 1.

[0084] Table 1 Performance test data table

[0085]

[0086] As can be seen from Table 1, the limestone-gypsum flue gas desulfurization composite synergist prepared in Examples 4-6 can promote the dissolution of calcium carbonate, increase the oxidation rate of calcium sulfite, and exhibit good desulfurization efficiency.

[0087] The surface active agent added in the composite synergist of the present application contains quaternary ammonium salt cation, sodium carboxylate / sodium benzene sulfonate double anion and dodecyl hydrophobic chain, wherein the quaternary ammonium salt is strongly electrostatically adsorbed on the surface of the negative limestone and calcium sulfite to form an oriented interface layer; the carboxylate specifically chelates Ca 2+ The sulfonic acid group prevents particle agglomeration through high hydration; the long-chain alkyl group is adsorbed on the surface of CaCO3 through hydrophobic association, and the polar hydrophilic group (carboxylate, sulfonic acid group, quaternary ammonium salt) is directed outward, making the surface of CaCO3 hydrophilic, avoiding particle agglomeration, and expanding the effective reaction area, thereby improving the SO2 absorption efficiency. The synergistic effect of the three together builds a high-efficiency reaction microenvironment, promotes the dissolution of calcium carbonate and improves the oxidation rate of calcium sulfite, thereby showing good desulfurization efficiency. In Comparative Example 7, the carboxylic acid on the surface active agent is not ionized, the oxygen atom contains a lone pair of electrons, but the proton occupies the bonding site, and the molecule is electrically neutral, so it cannot form a coordination bond with the positively charged calcium ion, and therefore the dissolution rate of calcium carbonate is reduced. In Comparative Examples 4-6, the surface active agent does not contain carboxylate, and cannot promote the dissolution of calcium carbonate through chelation with calcium ions.

[0088] The above is only a preferred embodiment of the present application and is not intended to limit the present application; however, for ordinary skilled persons in the art, some minor changes, modifications and equivalent changes made to the above disclosed technical content without departing from the scope of the technical solutions of the present application are equivalent embodiments of the present application; at the same time, any equivalent changes, modifications and evolution of the above embodiments made according to the essential technology of the present application are still within the protection scope of the technical solutions of the present application.

Claims

1. A limestone-gypsum wet flue gas desulfurization composite synergist, characterized in that, The ingredients include the following parts by weight: 15-18 parts organic acid, 5-8 parts oxidation catalyst, 8-10 parts sodium salt, 5-10 parts magnesium salt, 12-15 parts surfactant, 5-8 parts organic acid alkali metal salt, and 4-5 parts dispersant; The oxidation catalyst is one of manganese sulfate and ferrous sulfate; The magnesium salt is one of magnesium chloride and magnesium sulfate; The sodium salt is one of sodium sulfate and sodium chloride; The surfactant is prepared by the following method: S1: 2-Dodecen-1-ylsuccinic anhydride reacts with N,N-dimethylethylenediamine to form a monoamide compound. S2: Monoamide compounds react with epichlorohydrin to form quaternary ammonium salt compounds. S3: Quaternary ammonium salt compounds react with sodium p-aminobenzenesulfonate to generate surfactants.

2. The limestone-gypsum wet flue gas desulfurization composite synergist according to claim 1, characterized in that, In step S1, the molar ratio of 2-dodecen-1-ylsuccinic anhydride to N,N-dimethylethylenediamine is (1-1.1):

1.

3. The limestone-gypsum wet flue gas desulfurization composite synergist according to claim 1, characterized in that, In step S2, the molar ratio of the monoamide compound to epichlorohydrin is 1:(1.1-1.3).

4. The limestone-gypsum wet flue gas desulfurization composite synergist according to claim 1, characterized in that, In step S3, the molar ratio of the quaternary ammonium salt compound to sodium p-aminobenzenesulfonate is (2.1-2.2):

1.

5. The limestone-gypsum wet flue gas desulfurization composite synergist according to claim 1, characterized in that, The organic acid is either citric acid or adipic acid.

6. The limestone-gypsum wet flue gas desulfurization composite synergist according to claim 1, characterized in that, The organic acid alkali metal salt is one of sodium formate and sodium benzoate.

7. The limestone-gypsum wet flue gas desulfurization composite synergist according to claim 1, characterized in that, The dispersant is sodium polyacrylate.

8. A method for preparing the limestone-gypsum wet flue gas desulfurization composite synergist according to any one of claims 1-7, characterized in that, Includes the following steps: (1) Weigh out the following by weight: 15-18 parts organic acid, 5-8 parts oxidation catalyst, 8-10 parts sodium salt, 5-10 parts magnesium salt, 12-15 parts surfactant, 5-8 parts organic acid alkali metal salt, and 4-5 parts dispersant; (2) Mix and stir the above materials until they are fully mixed and uniform. Add them to a planetary ball mill and grind them into powder to obtain limestone-gypsum wet flue gas desulfurization composite enhancer.

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