Nitrogen oxide absorption slurry and a preparation and use method thereof

Abstract

A nitrogen oxide absorption slurry and its preparation and use method for the removal of nitric oxide in gas streams, belonging to the technical field of air pollution control and related environmental protection, is characterized in that the absorption slurry contains one or more compounds of anhydrous ferric chloride, ferric chloride monohydrate, ferric chloride dihydrate and the complex of ferric chloride and chloride ions. The absorption slurry reacts with the nitric oxide in gas stream at a certain temperature, so that the nitric oxide in the gas stream is absorbed by the slurry, thereby achieving the purpose of gas purification. And the absorbent can be recycled after regeneration.

Claims

1. A nitrogen oxide absorption slurry for removing nitric oxide gas from gas streams, wherein said absorption slurry contains any one or two and more compounds of anhydrous ferric chloride, ferric chloride monohydrate, ferric chloride dihydrate, and a complex of ferric chloride and hydrochloric acid.

2. The preparation method of the absorption slurry according to claim 1, wherein the absorption slurry is prepared by mixing anhydrous ferric chloride and water, or anhydrous ferric chloride and hydrochloric acid, or anhydrous ferric chloride and ferric chloride monohydrate, or anhydrous ferric chloride and ferric chloride dihydrate, or anhydrous ferric chloride and ferric chloride hexahydrate, or anhydrous ferric chloride and ferric chloride monohydrate and hydrochloric acid, or anhydrous ferric chloride and ferric chloride dihydrate and hydrochloric acid, or anhydrous ferric chloride and ferric chloride hexahydrate and hydrochloric acid, respectively, according to said mass ratio under a certain temperature and atmosphere.

3. The preparation method of the absorption slurry according to claim 2, wherein said temperature for preparing the absorbent slurry is 35° C. and above, and said atmosphere is in the presence of air, nitrogen gas or hydrogen chloride gas.

4. The preparation method of the absorption slurry according to claim 1, wherein the absorption slurry is prepared by the dehydration of the ferric chloride solution, or by the dehydration of the mixture of ferric chloride and hydrochloric acid, under a certain temperature and atmosphere.

5. The preparation method of the absorption slurry according to claim 4, wherein said temperature for preparing the absorbent slurry is 65° C. and above, and said atmosphere is in the presence of air, nitrogen gas or hydrogen chloride gas.

6. The preparation method of the absorption slurry according to claim 2, wherein said water can be replaced by a salt solution or a mixture of salt and hydrochloric acid solution, and said salt can be a chloride or sulfate of alkali metal, alkaline earth metal or transition metal, which includes sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, manganese chloride, cobalt chloride, copper chloride, nickel chloride, aluminum chloride, and the corresponding sulfates.

7. The use method of the absorption slurry according to claim 1, wherein the absorption slurry is introduced into a nitrogen oxide absorption reactor and nitric oxide in gas stream is absorbed by chemical reaction with ferric chloride in the absorbent at a certain temperature.

8. The use method of the absorption slurry according to claim 7, wherein the nitrogen oxide absorption reactor can be a rotating, spraying, bubbling or moving bed type gas-liquid contact reactors, and the flow pattern in the reactor can be used arranged in co-current flow, counter flow and cross flow.

9. The use method of the absorption slurry according to claim 7, wherein the reaction temperature of the absorbent prepared by water and ferric chloride is from 35 to 110° C., and is from 35° C. to 130° C. prepared by hydrochloric acid and/or salt solution instead of water.

10. The regeneration method of the absorption slurry according to claim 1, wherein the regeneration of the absorbent can be implemented by heating or humidifying, or dissolving in water or hydrochloric acid solution to release the absorbed nitric oxide gas from the absorbent, and then followed by dehydration and chlorination process, where the desorption of nitric oxide gas from the absorbent, dehydration and chlorination can be performed simultaneously, and the temperature of said heating is 65° C. and above.

11. The regeneration method of the absorption slurry according to claim 10, wherein the dehydration and chlorination are carried out in the presence of hydrogen chloride gas.

12. The regeneration method of the absorption slurry according to claim 10, wherein the dehydration and chlorination can be carried out by adding sulfoxide chloride solution.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic structural view of a rotating absorption reactor according to Example 2 of the present disclosure.

(2) FIG. 2 is a schematic structural view of a scrubbing absorption reactor according to Examples 3, 5 and 8 of the present disclosure.

DETAILED DESCRIPTION

(3) Example 1: A preparation method of the absorbent: First weigh the anhydrous ferric chloride powder (industrial grade, net content 97%, the same below), water and ferric chloride hexahydrate (or other ferric chloride hydrates) respectively, according to predetermined mass ratio, and then the water or ferric chloride hexahydrate (or other ferric chloride hydrates) is added to the mixing reactor, and at the same time the temperature of the reactor is raised to a predetermined temperature in the presence of air or nitrogen or protective gas of hydrogen chloride (hydrogen chloride content: about 10-30% by volume, the same below), and then anhydrous ferric chloride powder is gradually added into the reactor, stirred and mixed. After all the materials are completely mixed, the preparation of the absorbent is completed. The mass ratio of materials, preparation temperature and other operating parameters are shown in table 1.

(4) TABLE-US-00001 TABLE 1 Operating parameters for the absorbent preparation Serial No. Mass ratio Temperature (° C.) Protective gas 1 FeCl.sub.3:H.sub.2O═25:1 100~110 HCl 2 FeCl.sub.3:H.sub.2O═9:1 35~45 Air 3 FeCl.sub.3:FeCl.sub.3•6H.sub.2O═12:1  90~100 N.sub.2 4 FeCl.sub.3:FeCl.sub.3•6H.sub.2O═8:1 70~80 N.sub.2 5 FeCl.sub.3:FeCl.sub.3•6H.sub.2O═3.5:1 45~55 N.sub.2 6 FeCl.sub.3:FeCl.sub.3•H.sub.2O═1.5:1 85~95 HCl 7 FeCl.sub.3:FeCl.sub.3•2H.sub.2O═1:1 60~70 N.sub.2

(5) Example 2: A rotating absorption reactor is adopted as the schematic structure shown in FIG. 1.

(6) The reactor includes of a horizontally placed rotating reactor column (2), a gas inlet (1) at one end of the reactor column and a gas outlet (4) at the other end, an absorbent inlet (3) at the upper part of the reactor column and a absorbent outlet (5) at the lower part, and the reactor is driven by a transmission system.

(7) An example Hastelloy made reactor column is 300 mm in diameter, and 1500 mm in length. Two ends of the reactor are conical shaped with a gas inlet and an outlet the inlet of both 150 mm in diameter. The rotation speed of the column is from about 45 to 60 rpm. The gas flow rate of to-be treated gas is about 120 m.sup.3/h (The residence time of the gas in the reactor is about 3 s), and the temperature of the gas stream in the reactor is adjusted from about 35 to 110° C. The gas stream before the inlet is composed of nitric oxide 500 ppm, sulfur dioxide about 300 ppm, carbon dioxide about 10%, oxygen about 8% (by volume, the same below), moisture about 10%, and the balance nitrogen gas. The amount of absorbent added into the reactor is about 30 kg.

(8) The treatment process is to add the absorbent to the reactor through the absorbent inlet (3), and to introduce the gas stream containing nitric oxide to the reactor from the gas inlet (1), and to drive the reactor column (2) rotating through a transmission system, so that the absorption slurry in the reactor flows along the inner wall of the column of the reactor and makes full contact with the gas. NO gas in gas stream is therefore absorbed by chemical reaction with the ferric chloride in the absorbent, and the purified gas stream is discharged from the gas outlet (4) at the other end of the reactor, and the saturated absorbent can be periodically discharged from the absorbent outlet (5). The average removal of nitric oxide for one hour is shown in table 2.

(9) TABLE-US-00002 TABLE 2 Effect of absorbent on nitric oxide removal Serial No. in Tab.1 Gas temperature (° C.) Average NO removal 1 105~110 45 1  95~100 60 1 85~90 70 2 40~45 20 3 100~105 55 3 90~95 65 3 80~85 70 4 65~70 65 5 35~40 20 6 70~75 50 7 50~55 15

(10) Example 3: A scrubbing absorption reactor is adopted as the schematic structure shown in FIG. 2. The reactor includes a column body (13), a gas inlet (1) at the lower part of the column, a gas outlet (4) at the upper part of the column. The upper part of the column is provided with an absorbent inlet (11) and a slurry sprayer (12), and the lower part is provided with an absorbent storage tank (8). The absorbent storage tank communicates with a slurry pump (6) though a connecting pipe (7), and the slurry pump communicates with the absorbent inlet (11) through an absorbent supplying pipe (10). The saturated absorbent can be sent to regeneration by a bypass pipe (9).

(11) The scrubbing column is an empty tower, using Hastelloy as the material. The dimension of the absorption column is 300 mm in diameter and 3500 mm in height with an effective spray height of about 2000 mm. The entire pipeline system is heat insulated.

(12) The treatment process is to supply the absorbent to the absorbent inlet of the scrubbing column through a slurry pump, and then the absorbent slurry is sprayed from the top in the column by a slurry sprayer, and the gas stream containing nitric oxide is introduced into the column from the gas inlet. The gas stream is in full contact with the absorbent droplets in the column, and the nitric oxide in the gas stream is absorbed. After reaction, the purified gas stream is discharged from the gas outlet of the reactor, and the absorbent circulates by the pump. The saturated absorbent can be sent to regeneration by a bypass pipe.

(13) The flow rate of gas stream is about 150 m.sup.3/h (the residence time of the gas in the reactor is about 2 s), and the gas composition is the same as in Example 2. The gas temperature of the gas stream in the column is about 80˜90° C., and the temperature of absorbent is roughly the same. The absorbent with the serial No. 3 in Tab. 1 is used in the test. The total amount of the absorbent added to the reactor is about 50 kg, and the circulation amount by the absorbent pump is about 350 kg/h. The maximum average removal of nitrogen oxides for one hour is about 75%.

(14) Example 4: A preparation method of the absorbent by mixing anhydrous ferric chloride powder with a hydrochloric acid solution with different concentrations: The preparation process is to add a hydrochloric acid solution to a mixing reactor, and then gradually add the ferric chloride powder, stirred and mixed. The reactor temperature is from room temperature to 120° C., and when the reactor temperature is higher than 60° C., the protective gas of hydrogen chloride (10-30% hydrogen chloride in nitrogen gas) is introduced into the reactor. After all the materials are completely mixed, the preparation of the absorbent is completed. The mass ratio of materials, preparation temperature and other operating parameters are shown in table 3.

(15) TABLE-US-00003 TABLE 3 Mass ratio and operating parameters for the absorbent preparation Mass ratio of Temperature Protection Serial No. HCl Con. (%) FeCl.sub.3:HCl (° C.) gas 8 0 15 70~75 N.sub.2 9 5 20 75~80 HCl 10 10 35 80~85 HCl 11 20 45 90~95 HCl 12 30 70 100~105 HCl 13 34 80 85~90 HCl 14 36 50 35~40 N.sub.2 15 36 100 115~120 HCl

(16) Example 5: The reactor shown in FIG. 2 was adopted. The temperature of the gas stream in the absorption column ranges from about 65 to 120° C., and other conditions are the same as in example 3. The maximum average removal of nitrogen oxide for one hour is shown in table 4.

(17) TABLE-US-00004 TABLE 4 Effect of absorbent on nitric oxide removal Serial No. Gas temperature (° C.) Average NO removal (%) 8 70~75 50 8 80~85 35 9 75~80 60 10 100~105 65 11 90~95 70 11 115~120 40 11 120~125 25 12 90~95 75 13  95~100 80 14 80~85 75 14 100~105 65 15 125~130 20

(18) Example 6: A preparation method of the absorbent: 30 parts of solid ferric chloride hexahydrate and 1 part of 36˜38% hydrochloric acid solution are weighed according to the mass ratio. The prepared hydrochloric acid solution is first added to a mixing reactor, and then ferric chloride hexahydrate is added gradually to the reactor, stirred and mixed (the temperature of the reactor may be raised to about 50˜60° C.). After all the added solid ferric chloride hexahydrate is completely dissolved, the temperature of the reactor is increased to about 150˜180° C. for dehydration in the presence of a mixed gas of nitrogen and hydrogen chloride (Hydrogen chloride gas about 30˜50% in volume). When the water content in the liquid phase decreased to about 4˜5% the weight of the material, the preparation of the absorbent is completed.

(19) Example 7: A preparation method of the absorbent: The absorbent is prepared by mixing anhydrous ferric chloride with different salt solutions. The preparation is to add a predetermined amount of water and solid salt to a mixing reactor. After the salt is completely dissolved, ferric chloride powder of a predetermined quality is then gradually added, And the other process is the same as that in above examples. After the ferric chloride and the salt solution are sufficiently mixed, the preparation of the absorbent is completed. The mass ratio of materials and operating parameters are shown in table 5.

(20) TABLE-US-00005 TABLE 5 Mass ratio of materials and operating parameters Mass ratio of Serial FeCl.sub.3:salt Temperature Protection No. Salt solution solution (° C.) gas 16 5% NaCl 30 65~70 N.sub.2 17 25% NaCl 40 80~85 HCl 18 30% KCl 45 90~95 HCl 19 40% CaCl.sub.2 40 120~130 HCl 20 15% MgCl.sub.2 35  95~100 HCl 21 30% MgCl.sub.2 40 110~115 HCl 22 35% MnCl.sub.2 40 115~120 HCl 23 15% Na.sub.2SO.sub.4 35 60~65 N.sub.2 24 35% ZnSO.sub.4 40 100~105 HCl 25 35% CuSO.sub.4 40  95~100 HCl 26 15% NaCl + 10% HCl 40  95~100 HCl 27 15% Na.sub.2SO.sub.4 + 10% HCl 40  95~100 HCl 28 30% AlCl.sub.3 + 20% HCl 50 90~95 HCl 29 60% ZnCl.sub.2 + 20% HCl 45  95~100 HCl

(21) Example 8: The reactor shown in FIG. 2 was adopted. The temperature of the gas stream in the absorption column is from about 65 to 130° C. , and other conditions are the same as in example 3. The average removal of nitric oxide for one hour is shown in table 6.

(22) Table 6 Effect of Absorbent on Nitric Oxide Removal

(23) TABLE-US-00006 Serial No. in Tab. 5 Gas temperature (° C.) Average NO removal (%) 16 70~75 55 17 80~85 75 18 75~80 85 19 100~105 65 20 90~95 70 21 115~120 45 22 120~125 40 23 65~70 60 24 100~105 65 25 125~130 25 26 85~90 80 27 70~75 65 28 90~95 70 29 100~105 75

(24) Example 9: A method for regenerating the absorbent: The reacted absorbent of serial No. 4 used in example 2 is introduced to a regeneration reactor (the same as the mixing reactor for absorbent preparation, the same below), and then a 20% hydrochloric acid solution with an amount of about 0.1 to 0.3 of the volume of the absorbent is added to the reactor after evacuating the air in the reactor, stirred and mixed, and then the reactor is heated to the temperature of about 90 to 110° C. for a period of maintaining. The nitric oxide gas released from absorbent is recovered during the above process. After the release of nitric oxide is completed, a mixed gas of nitrogen and hydrogen chloride is introduced below the liquid surface in the reactor, and the same time, the temperature of the reactor is raised to about 120˜150° C. for dehydration. When the water content in liquid phase decreases to about 5˜7% (mass), the regeneration of the absorbent is completed.

(25) Example 10: A method for regenerating the absorbent: The reacted absorbent of serial No. 10 used in example 5 is added to a regeneration reactor. After the air in the reactor is evacuated, the reactor is heated to the temperature of about 150 to 160° C. for a period of maintaining, and at the same time, the nitric oxide gas released from absorbent is recovered. After the release of nitric oxide is completed, a mixed gas of nitrogen and hydrogen chloride is introduced below the liquid surface in the reactor for chlorination and dehydration. When the water content in the liquid phase decreases to 3˜5% (mass), the temperature of the reactor is adjusted to 100˜110° C., and lasts for a period of time, before completing the regeneration of the absorbent.

(26) Example 11: A method for regenerating the absorbent: The reacted absorbent of serial No. 17 used in example 8 is added to a regeneration reactor, and then 20% hydrochloric acid solution with an amount of about 0.1 to 0.3 of the volume of the absorbent is added to the reactor after evacuating the air in the reactor, stirred and mixed, and then the reactor is heated to the temperature of about 100˜110° C. for a period of maintaining. The nitric oxide gas released from absorbent is recovered during above process. After the release of nitric oxide is completed, a mixed gas of nitrogen and hydrogen chloride is introduced below the liquid surface in the reactor, and at the same time, the temperature of the reactor is raised to about 160˜180° C. for dehydration. When the water content in liquid phase decreases to about 3-5% (mass), the regeneration of the absorbent is completed.

(27) Example 12: A method for regenerating the absorbent: The absorbent after the reaction with the serial No. 11 used in example 5 was added to the regeneration reactor. After the air was evacuated, the temperature of the reactor was maintained the temperature of 95˜100° C., and then sulfoxide chloride liquid was slowly added by dropping to the reactor for dehydration and chlorination, stirring to make the absorbent slurry in the reactor fully contacted with the sulfoxide chloride liquid. The vaporized sulfoxide chloride in the reactor is returned to the reactor by a condensation reflux, and water vapor, nitric oxide, hydrogen chloride and sulfur dioxide generated during the reaction process are discharged through the non-condensable gas outlet of the condensation reflux for further treatment. The total dosage of sulfoxide chloride added to the reactor is about 6˜10 times the water removed from absorbent. When the water content in liquid phase decreases to about 2-3% (mass), the regeneration of the absorbent is completed.