Method for removing SOx from gas using ethylene glycol composite solution

Abstract

An ethylene glycol composite solution is used for removing SO.sub.x from a gas. The ethylene glycol composite solution is made by mixing ethylene glycol and/or polyethylene glycol with an organic acid and/or organic acid salt containing no nitrogen atom in a molecule. The ethylene glycol composite solution is brought into contact with the gas containing SO.sub.x to absorb the SO.sub.x in the gas. The ethylene glycol composite solution loaded with absorbed SO.sub.x is regenerated by heating, vacuuming, gas stripping, ultrasonic treatment, microwave treatment, or radiation treatment to release by-products of sulfur dioxide and sulfur trioxide, and the regenerated ethylene glycol composite solution is recycled for use.

Claims

1. A method for removing SO.sub.x from a gas, comprising: mixing ethylene glycol, polyethylene glycol, or both ethylene glycol and polyethylene glycol with an organic acid, an organic acid salt, or both the organic acid and the organic acid salt to form a composite solution, wherein the organic acid and the organic acid salt are compounds that contain no nitrogen atoms; bringing the composite solution into contact with the gas containing SO.sub.x to absorb the SO.sub.x in the gas, wherein SO.sub.x is SO.sub.2, SO.sub.3, or a mixture thereof, and wherein the composite solution contains one or more additives selected from the group consisting of organic amines, amides, sulfones, sulfoxides, and metallorganic compounds.

2. The method for removing SO.sub.x from a gas according to claim 1, wherein the organic acid is an organic monoacid, an organic polyacid, or a mixture thereof; the organic acid salt is an organic monoacid salt, an organic polyacid salt, or a mixture thereof.

3. The method for removing SO.sub.x from a gas according to claim 2, wherein the organic acid is selected from the group consisting of formic acid, acetic acid, butyric acid, ethanedioic acid, propanedioic acid, butanedioic acid, tannin acid, polygallic acid, citric acid, and mixtures thereof, and the organic acid salt is a carboxylic acid salt formed by combining the organic acid with one or more selected from the group consisting of sodium ions, potassium ions, magnesium ions, calcium ions, and transition metal ions.

4. The method for removing SO.sub.x from a gas according to claim 1, wherein the composite solution contain less than 50% in mass of water, and less than 30% in mass of the organic acid, the organic salt, or both.

5. The method for removing SO.sub.x from a gas according to claim 1, wherein a mass content of the additives in the composite solution is less than 10%.

6. The method for removing SO.sub.x from a gas according to claim 1, wherein the composite solution absorbs the SO.sub.x in the gas under atmospheric pressure or an elevated pressure at a temperature of 20 to 80 C.

7. The method for removing SO.sub.x from a gas according to claim 1, further comprising regenerating the composite solution loaded with absorbed SO.sub.x by heating, vacuuming, gas stripping, ultrasonic treatment, microwave treatment, or radiation treatment at a temperature of 0 to 300 C. to release SO.sub.x from the composite solution; and recycling the regenerated composite solution.

8. The method for removing SO.sub.x from a gas according to claim 1, wherein the gas is a flue gas, a waste gas, an industrial raw material gas containing SO.sub.x, or mixtures thereof.

9. A method for removing SO.sub.x from a gas, comprising: mixing ethylene glycol, polyethylene glycol, or both ethylene glycol and polyethylene glycol with an organic acid, an organic acid salt, or both the organic acid and the organic acid salt to form a composite solution, wherein the organic acid and the organic acid salt are compounds that contain no nitrogen atoms; bringing the composite solution into contact with the gas containing SO.sub.x to absorb the SO.sub.x in the gas, wherein SO.sub.x is SO.sub.2, SO.sub.3, or a mixture thereof, the organic acid is selected from the group consisting of formic acid, acetic acid, butyric acid, ethanedioic acid, propanedioic acid, butanedioic acid, tannin acid, polygallic acid, citric acid, and mixtures thereof, and the organic acid salt is a carboxylic acid salt formed by combining the organic acid with one or more selected from the group consisting of sodium ions, potassium ions, magnesium ions, calcium ions, and transition metal ions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a desulfurization-absorption process.

(2) FIG. 2 is a schematic diagram of desulfurization solution regeneration by a heating method.

(3) FIG. 3 is a schematic diagram of desulfurization solution regeneration by a vacuum method.

(4) FIG. 4 is a schematic diagram of desulfurization solution regeneration by a gas stripping method.

(5) FIG. 5 is a schematic diagram of desulfurization solution regeneration by an ultrasonication method, and/or a microwave method, and/or a radiation method.

(6) FIG. 6 is a schematic diagram of structure of a small-sized desulfurization-absorption device.

(7) FIG. 7 is a schematic diagram of structure of a small-sized heating and gas stripping-regeneration device.

DETAILED DESCRIPTION

(8) The desulfurization method by ethylene glycol composite solution according to the present invention will be described below with reference to some specific embodiments. The embodiments described hereinafter are only for better illustrating the present invention rather than limiting the claims of the present invention.

(9) The first process is a desulfurization-absorption process, and its embodiment is as shown in FIG. 1. The gas 2 containing SO.sub.x is fed from the bottom of the desulfurization tower 1 and contacted with the desulfurization lean liquor 4 counter-currently. The SO.sub.x in the gas 2 containing SO.sub.x is absorbed by the lean liquor 4. The gas 2 containing SO.sub.x is converted into purified gas 3 which is discharged out from the top of the desulfurization tower 1. The desulfurization lean liquor 4 with absorbed SO.sub.x is converted into desulfurization rich liquor 5 at the bottom of the desulfurization tower 1. The desulfurization rich liquor 5 is discharged out from the bottom of the desulfurization tower 1 and transferred to the desulfurization solution regeneration process to be regenerated by one or more of a heating method, a vacuum method, a gas stripping method, an ultrasonication method, a microwave method, and a radiation method.

(10) The second process is the regeneration process of desulfurization solution. The regeneration methods for it include a heating method, a vacuum method, a gas stripping method, an ultrasonication method, a microwave method, and a radiation method.

(11) The embodiment of regeneration method by heating is shown in FIG. 2. The desulfurization rich liquor 5 is transferred to the heating-regenerator 6 and is heated to release gaseous sulfur dioxide and/or sulfur trioxide 7. The gaseous sulfur dioxide and/or sulfur trioxide 7 may be transformed into by-products of liquid sulfur dioxide and/or sulfur trioxide of high purity by a certain processing means. Meanwhile, sulfur foams and/or dusts 8 may be produced or accumulated, and are separated from the main part of desulfurization solution. The separated sulfur foams and/or dusts 8 can be further processed into sulfur by-products, and there are also some ash residues discharged. The desulfurization rich liquor 5 is regenerated by heating-regenerator 6 and is then converted into the desulfurization lean liquor 4. The desulfurization lean liquor 4 can be transferred directly to the desulfurization-absorption process for recycle use. Alternatively, it can be transferred to the vacuum-regenerator and/or gas stripping-regenerator, and/or ultrasonication-regenerator, and/or microwave-regenerator, and/or radiation-regenerator to be further regenerated.

(12) The embodiment of regeneration method by vacuum is shown in FIG. 3. The desulfurization rich liquor 5 is transferred to the vacuum-regenerator 9, vacuum is created with the aid of vacuum machine 10 to release gaseous sulfur dioxide and/or sulfur trioxide 7. The gaseous sulfur dioxide and/or sulfur trioxide 7 may be transformed into by-products of liquid sulfur dioxide and/or sulfur trioxide of high purity by a certain processing means. Meanwhile, sulfur foams and/or dusts 8 may be produced or accumulated, and are separated from the main part of desulfurization solution. The separated sulfur foams and/or dusts 8 can be further processed into sulfur by-products, and there are also some ash residues discharged. The desulfurization rich liquor 5 is regenerated by vacuum-regenerator 9 and is then converted into the desulfurization lean liquor 4. The desulfurization lean liquor 4 can be transferred directly to the desulfurization-absorption process for recycle use. Alternatively, it can be transferred to the heating-regenerator and/or gas stripping-regenerator, and/or ultrasonication-regenerator, and/or microwave-regenerator, and/or radiation-regenerator to be further regenerated.

(13) The embodiment of regeneration method by gas stripping is shown in FIG. 4. The desulfurization rich liquor 5 is transferred to the gas stripping-regenerator 11, and contacted counter-currently with the inert gas 12 (including nitrogen, carbon dioxide, argon and water vapour, etc.) from the bottom of the gas stripping-regenerator 11. The sulfur dioxide and/or sulfur trioxide in the desulfurization rich liquor 5 are released into the inert gas and a mixed gas 13 of sulfur dioxide and/or sulfur trioxide with high concentration is formed and discharged from the top of the gas stripping-regenerator 11. The discharged sulfur dioxide and/or sulfur trioxide in the inert gas may be transformed into by-products of liquid sulfur dioxide and/or sulfur trioxide of high purity by a certain processing means. The desulfurization rich liquor 5 is regenerated by the gas striping-regenerator 11 and is then converted into the desulfurization lean liquor 4. The desulfurization lean liquor 4 can be transferred directly to the desulfurization-absorption process for recycle use. Alternatively, it can be transferred to the heating-regenerator and/or vacuum-regenerator, and/or ultrasonication-regenerator, and/or microwave-regenerator, and/or radiation-regenerator to be further regenerated.

(14) The embodiment of regeneration by ultrasonication method, and/or microwave method, and/or radiation method is shown in FIG. 5. The desulfurization rich liquor 5 is transferred to the ultrasonication-, and/or microwave-, and/or radiation-regenerator 14 and regenerated under the conditions of ultrasonication, and/or microwave, and/or radiation to release gaseous sulfur dioxide and/or sulfur trioxide 7. The gaseous sulfur dioxide and/or sulfur trioxide 7 may be transformed into by-products of liquid sulfur dioxide and/or sulfur trioxide of high purity by a certain processing means. Meanwhile, sulfur foams and/or dusts 8 may be produced or accumulated, and are separated from the main part of desulfurization solution. The separated sulfur foams and/or dusts 8 can be further processed into sulfur by-products, and there are also some ash residues discharged. The desulfurization rich liquor 5 is regenerated by ultrasonication-, and/or microwave-, and/or radiation-regenerator 14 and is then converted into the desulfurization lean liquor 4. The desulfurization lean liquor 4 can be transferred directly to the desulfurization-absorption process for recycle use. Alternatively, it can be transferred to the heating-regenerator, and/or vacuum-regenerator, and/or gas stripping-regenerator to be further regenerated.

(15) According to the specific concepts of the above embodiments, a small-sized absorption device shown in FIG. 6 and a small-sized heating and gas stripping-regeneration device shown in FIG. 7 were designed and mounted respectively.

(16) In the small-sized absorption device as shown in FIG. 6, 15 represented an absorption bottle (or a regeneration bottle when regenerating), 16 represented the ethylene glycol composite solution, 17 represented the gas containing sulfur dioxide, and 18 represented a vented gas.

(17) In the small-sized heating and gas stripping-regeneration device as shown in FIG. 7, 15 represented a regeneration bottle (or an absorption bottle when absorbing), 16 represented the ethylene glycol composite solution with absorbed sulfur dioxide, 19 represented a gas for gas stripping (N.sub.2 in this test), 20 represented the stripping gas containing sulfur dioxide, 21 represented a silicone oil for oil bath, and 22 represented a thermostatic heating pot.

(18) In the experiment, as shown in FIG. 6, about 100 ml fresh ethylene glycol composite solution 16 was charged into the absorption bottle 15. A certain amount (L, liter) of gas 17 containing sulfur dioxide was blown into the absorption bottle 15 containing the ethylene glycol composite solution 16 at room temperature and passed through the ethylene glycol composite solution 16. The sulfur dioxide in the gas was absorbed by the ethylene glycol composite solution 16. The gas with sulfur dioxide removed was referred to as the vented gas 18. The vented gas 18 was discharged outside. At the same time, the content of sulfur dioxide (C*.sub.SO2, g/L) in the ethylene glycol composite solution 16 was measured using iodimetry. Then, the absorption bottle containing the ethylene glycol composite solution with absorbed sulfur dioxide was placed into the thermostatic heating pot in the oil bath. At this time, the absorption bottle 15 served as the regeneration bottle 15. The content of sulfur dioxide in the ethylene glycol composite solution 16 had already been measured and it could be used as the ethylene glycol composite solution 16 with absorbed sulfur dioxide to be regenerated. As shown in FIG. 7, the temperature in the thermostatic heating pot 22 was adjusted to a desired constant temperature to heat the silicone oil 21 for oil bath. When the temperature of the system was kept at the desired temperature (t, C.), the gas 19 for gas stripping (N.sub.2 in this test) was blown into the regeneration bottle 15. The gas 19 for gas stripping (N.sub.2 in this test) was sufficiently contacted with the ethylene glycol composite solution 16 containing sulfur dioxide. At this time, the sulfur dioxide contained in the ethylene glycol composite solution 16 was transferred into the gas 19 for gas stripping (N.sub.2 in this test). At this time, the gas 19 for gas stripping (N.sub.2 in this test) containing sulfur dioxide was transformed into the stripping gas 20 containing sulfur dioxide, vented and discharged outside. After being regenerated for a period of time (T, min) by heating and gas stripping, the regeneration bottle 15 was taken out and cooled to normal temperature with water. The content of sulfur dioxide (C.sub.SO2, g/L) in the regenerated ethylene glycol composite solution 16 was measured using iodimetry. The absorption and regeneration of the regenerated ethylene glycol composite solution 16 were repeated many times in accordance with the above steps. The changes appeared in the ethylene glycol composite solution were observed. According to the above test, the experiments for the absorption and desorption of SO.sub.2 contained in the gas were repeated many times with a system of 84% EG (ethylene glycol)+6% citric acid monopotassium salt+10% citric acid, a system of 93% EG (ethylene glycol)+7% citric acid monopotassium salt, a system of 60% PEG (polyethylene glycol 400)+3.3% citric acid+4% citric acid monopotassium salt+32.7% H.sub.2O, a system of 60% PEG+3% citric acid+5% citric acid monopotassium salt+32% H.sub.2O, a system of 60% PEG+8% citric acid+5% citric acid monopotassium salt+27% H.sub.2O, a system of 76% EG (ethylene glycol)+22% acetic acid+2% acetic acid potassium salt, and a system of 60% EG+30% water+7.8% oxalic acid monopotassium salt+2.2% oxalic acid. The experiment data were listed in Tables 1 to 7 respectively.

(19) TABLE-US-00001 TABLE 1 The absorption and desorption of SO.sub.2 with 84% EG (ethylene glycol) + 6% citric acid monopotassium salt + 10% citric acid(100 mL) Volume of Content of Content of gas to be sulfur dioxide sulfur dioxide absorbed in the polyol in the polyol Number of (the content composite composite Appearance times for of SO.sub.2 in the solution after solution after of the polyol absorption gas is about absorption regeneration Regeneration Regeneration composite and 1%) L C*.sub.SO2 C.sub.SO2 temperature t time solution after regeneration (litre) (g/L) (g/L) ( C.) T (min) regeneration 1.sup.st 30 3.6288 0.2097 150 45 no changes in 2.sup.nd 40 4.4029 0.2097 150 45 color 3.sup.rd 50 4.6610 0.4516 150 45 3.sup.rd 50 5.6448 0.2419 150 45 5.sup.th 50 5.5158 0.3226 150 45 6.sup.th 50 5.6125 0.2903 150 45

(20) TABLE-US-00002 TABLE 2 The absorption and desorption of SO.sub.2 with 93% EG (ethylene glycol) + 7% citric acid monopotassium salt(100 mL) Volume of Content of Content of gas to be sulfur dioxide sulfur dioxide absorbed in the polyol in the polyol Number of (the content composite composite Appearance times for of SO.sub.2 in the solution after solution after of the polyol absorption gas is about absorption regeneration Regeneration Regeneration composite and 1%) L C*.sub.SO2 C.sub.SO2 temperature t time solution after regeneration (litre) (g/L) (g/L) ( C.) T (min) regeneration 1.sup.st 10.5 1.2096 0.5645 135 30 no changes in 2.sup.nd 20 2.1612 0.9838 135 30 color 3.sup.rd 10 1.7741 0.6451 135 30 3.sup.rd 10 1.6934 0.6129 140 45 5.sup.th 27 3.7901 1.9837 140 30 6.sup.th 13 3.3385 1.1773 140 30 7.sup.th 10 2.1492 0.4838 140 90 8.sup.th 38 4.5481 0.8064 145 60 9.sup.th 30 4.1610 0.7741 145 60 10.sup.th 30 4.2739 0.8548 145 60 11.sup.th 30 4.5158 0.4838 150 90

(21) TABLE-US-00003 TABLE 3 The absorption and desorption of SO.sub.2 with 60% PEG + 3.3% citric acid + 4% citric acid monopotassium salt + 32.7% H.sub.2O(150 mL) Volume of Content of Content of gas to be sulfur dioxide sulfur dioxide absorbed in the polyol in the polyol Number of (the content composite composite Appearance times for of SO.sub.2 in the solution after solution after of the polyol absorption gas is about absorption regeneration Regeneration Regeneration composite and 1%) L C*.sub.SO2 C.sub.SO2 temperature t time solution after regeneration (litre) (g/L) (g/L) ( C.) T (min) regeneration 1.sup.st 20 2.2579 0.2592 150 60 no changes in 2.sup.nd 20 2.5915 0.6479 150 15 color 3.sup.rd 15 2.9155 0.1296 150 30 3.sup.rd 15 2.2676 0.1296 150 30 5.sup.th 15 1.9436 0.1296 150 30 6.sup.th 15 2.1056 0.1296 150 30 7.sup.th 15 1.9436 0.1296 150 30 8.sup.th 15 2.0408 0.1296 150 30 9.sup.th 15 2.0732 0.1296 150 30 10.sup.th 15 2.0408 0.1296 150 30 11.sup.th 15 1.9436 0.1296 150 30 12.sup.th 15 2.1056 0.1296 150 30 13.sup.th 15 1.9436 0.1296 150 30 14.sup.th 15 2.0084 0.1296 150 30 15.sup.th 15 1.9436 0.1296 150 30 16.sup.th 10 1.4577 0.1296 120 30

(22) TABLE-US-00004 TABLE 4 The absorption and desorption of SO.sub.2 with 60% PEG + 3% citric acid + 5% citric acid monopotassium salt + 32% H.sub.2O(150 mL) Volume of Content of Content of gas to be sulfur dioxide sulfur dioxide absorbed in the polyol in the polyol Number of (the content composite composite Appearance times for of SO.sub.2 in the solution after solution after of the polyol absorption gas is about absorption regeneration Regeneration Regeneration composite and 1%) L C*.sub.SO2 C.sub.SO2 temperature t time solution after regeneration (litre) (g/L) (g/L) ( C.) T (min) regeneration 1.sup.st 16 2.2028 1.2310 120 30 no changes in 2.sup.nd 15 2.9802 0.4211 130 30 color 3.sup.rd 15 2.2676 0.5507 130 30 3.sup.rd 15 2.5915 0.3239 130 30 5.sup.th 30 4.0816 0.1296 130 30 6.sup.th 15 2.4295 0.1296 130 30 7.sup.th 15 2.4619 0.1296 130 30 8.sup.th 15 2.4295 0.1296 130 30 9.sup.th 19 3.1422 0.3239 130 30 10.sup.th 15 2.5915 0.2592 130 30 11.sup.th 15 2.7535 0.1296 130 30

(23) TABLE-US-00005 TABLE 5 The absorption and desorption of SO.sub.2 with 60% PEG + 8% citric acid + 5% citric acid monopotassium salt + 27% H.sub.2O(150 mL) Volume of Content of Content of gas to be sulfur dioxide sulfur dioxide absorbed in the polyol in the polyol Number of (the content composite composite Appearance times for of SO.sub.2 in the solution after solution after of the polyol absorption gas is about absorption regeneration Regeneration Regeneration composite and 1%) L C*.sub.SO2 C.sub.SO2 temperature t time solution after regeneration (litre) (g/L) (g/L) ( C.) T (min) regeneration 1.sup.st 15 2.7859 0.1296 / 0 no changes in 2.sup.nd 15 2.4619 0.1296 130 30 color 3.sup.rd 15 2.5267 0.1296 130 30 3.sup.rd 15 2.4295 0.1296 130 30 5.sup.th 15 2.2676 0.1296 130 30 6.sup.th 15 2.1704 0.2592 130 30 7.sup.th 15 2.2676 0.2592 130 30 8.sup.th 15 2.3324 0.2592 130 30 9.sup.th 15 2.2676 0.2592 130 30 10.sup.th 15 2.2352 0.1296 130 30

(24) TABLE-US-00006 TABLE 6 The absorption and desorption of SO.sub.2 with 76% EG (ethylene glycol) + 22% acetic acid + 2% acetic acid potassium salt(130 mL) Volume of Content of Content of gas to be sulfur dioxide sulfur dioxide absorbed in the polyol in the polyol Number of (the content composite composite Appearance times for of SO.sub.2 in the solution after solution after of the polyol absorption gas is about absorption regeneration Regeneration Regeneration composite and 1%) L C*.sub.SO2 C.sub.SO2 temperature t time solution after regeneration (litre) (g/L) (g/L) ( C.) T (min) regeneration 1.sup.st 15 2.0408 0.1296 130 30 no changes in 2.sup.nd 15 2.4295 0.1296 130 30 color 3.sup.rd 15 2.2028 0.1296 130 30 3.sup.rd 15 2.3000 0.1296 130 30 5.sup.th 15 2.4295 0.1296 130 30 6.sup.th 15 2.5915 0.1296 130 30 7.sup.th 15 2.5267 0.1296 130 30 8.sup.th 15 2.7535 0.1296 130 30 9.sup.th 15 2.9155 0.2592 130 30 10.sup.th 15 2.8507 0.2592 130 30

(25) TABLE-US-00007 TABLE 7 The absorption and desorption of SO.sub.2 with 60% EG + 30% water + 7.8% oxalic acid monopotassium salt + 2.2% oxalic acid(150 mL) Volume of Content of Content of gas to be sulfur dioxide sulfur dioxide absorbed in the polyol in the polyol Number of (the content composite composite Appearance times for of SO.sub.2 in the solution after solution after of the polyol absorption gas is about absorption regeneration Regeneration Regeneration composite and 1%) L C*.sub.SO2 C.sub.SO2 temperature t time solution after regeneration (litre) (g/L) (g/L) ( C.) T (min) regeneration 1.sup.st 15 2.4295 0.1296 130 30 The solution 2.sup.nd 15 1.9436 0.1296 130 30 became milky 3.sup.rd 15 2.1056 0.1296 130 30 white and 3.sup.rd 15 2.1704 0.1296 130 30 slightly turbid 5.sup.th 15 2.1056 0.1296 130 30 during 6.sup.th 15 1.9436 0.1296 130 30 absorption, 7.sup.th 15 1.9436 0.1296 130 30 and the 8.sup.th 15 1.8788 0.1296 130 30 solution 9.sup.th 15 1.9436 0.1296 130 30 became 10.sup.th 15 1.8788 0.1296 130 30 colorless during regeneration

(26) From the above experimental data in Tables 1 to 7, it can be seen that these ethylene glycol composite solutions have good effects on absorption for SO.sub.2 and regeneration. This indicates that these systems are good desulfurization solvents for flue gases.