JPS5850925B2 - Method for producing hydroxylamine sulfate - Google Patents

Description

[Detailed Description of the Invention] This invention is applicable to nitrogen monoxide (hereinafter sometimes abbreviated as NO) and nitrogen dioxide (hereinafter sometimes abbreviated as NO2).
(hereinafter sometimes abbreviated as kNOx gas) containing nitrogen oxides (hereinafter sometimes abbreviated as ft-NOx) and ammonium sulfite aqueous solution (hereinafter sometimes abbreviated as normal ammonium sulfate aqueous solution). By contacting
This invention relates to an improvement in a method for producing hydroxylamine sulfate by absorbing NOx in NOx gas into an ammonium sulfite aqueous solution, and then further absorbing sulfur dioxide gas (hereinafter sometimes abbreviated as SO2 gas) into the obtained absorption liquid. It is something.

Hydroxylamine sulfate is an important compound as a raw material for a synthetic intermediate of epsilon caprolactam, which is a raw material for producing nylon 6.

Conventionally, as a method for producing hydroxylamine sulfate, NOx
By bringing gas into contact with ammonium sulfite aqueous solution, NOx
A method has been proposed in which NOx in the gas is absorbed into an ammonium sulfite aqueous solution, and then SO2 gas is further absorbed into the obtained absorption liquid [Special Publication No. 1972-2025 Seiya Ni-Otani, Akira Endo, Chemical Engineering, 26.1251 (1962)).

However, in the conventionally known method, the yield of hydroxylamine sulfate decreases unless the decomposition of ammonium nitrite, which is an intermediate produced, is prevented and the partial pressure of ammonia in the absorption liquid is reduced. It was necessary to keep the absorption temperature as low as possible when absorbing NOx.

In addition, the conventionally known method uses an ammonium sulfite aqueous solution in which the molar ratio of the ammonia component to the sulfur dioxide component (hereinafter sometimes abbreviated as NH3/SO2 molar ratio) is 2.05 to 2.25. Free ammonia in the absorption liquid obtained by absorbing NOx gas into this ammonium sulfite aqueous solution is likely to volatilize as a gas into the gas phase, so the yield of hydroxylamine sulfate is said to be only about 78% at most. There were drawbacks.

On the other hand, in order to further increase the yield of hydroxylamine sulfate, the NH3/SO2 molar ratio of the ammonium sulfite aqueous solution should be as small as possible, for example, about 2 or less, so that free ammonia in the absorption liquid does not volatilize as a gas into the gas phase. However, in this case, the pH of the absorption liquid tends to fluctuate greatly, and there is a risk that the pH of the absorption liquid will drop significantly and the reaction will proceed explosively.

That is, the conventionally known methods have a problem in that the yield of hydroxylamine sulfate must be sacrificed in order to proceed with the reaction safely.

Therefore, the inventors conducted intensive research to improve a method for solving the above-mentioned problems, allowing a series of reactions for producing hydroxylamine sulfate to proceed safely, and producing hydroxylamine sulfate at a high yield. As a result, (a) a bubble column and a packed tower were combined, (b) an aqueous solution containing ammonium sulfite and acidic ammonium sulfite was used instead of the ammonium sulfite aqueous solution in the conventionally known method, and (c) absorption in this aqueous solution was performed. When the NO/NO2 molar ratio in the NOx gas is adjusted within a specific range, and (e) the release rate of NOx gas is adjusted within a specific range, (e) NH3 in the aqueous solution containing ammonium sulfite and acidic ammonium sulfite is reduced. /
Surprisingly, even when the SO2 molar ratio was lowered to 1.85 or less, the reaction did not proceed explosively.

The inventors have discovered that hydroxylamine sulfate can be produced in a higher yield than conventionally known methods without particularly maintaining the absorption temperature at a low temperature, and have thus arrived at the present invention.

This invention produces hydroxylamine sulfate by (4) a step of absorbing a nitrogen oxide-containing gas into an ammonium sulfite aqueous solution, and (B) a step of subsequently absorbing sulfur dioxide gas into the obtained absorption liquid. In the method, the step (4) comprises: (1) ammonium sulfite and acidic nitrogen having a molar ratio of ammonia fraction to sulfur dioxide component (NH3/5O2) of 1.1 to 1.85 in a bubble column; An aqueous solution containing ammonium sulfate and nitric oxide (NO) and nitrogen dioxide (NO
2) and a nitrogen oxide-containing gas having a molar ratio (NO/N02) of 0.5 to 3, the gas is released into the bubble column at a rate of 15 m/unit cross-sectional area of the bubble discharge hole. SeC
A step of blowing the gas into contact with the aqueous solution in the bubble column in the above manner, and (U) In the packed column, the gas containing the residual nitrogen oxide that has passed through the bubble column and the ammonia component oxidation The molar ratio (NH3/5O2) with the sulfur component is 1.1 to 1.
The present invention relates to a method for producing hydroxylamine sulfate, which comprises the step of contacting ammonium sulfite (8) and an aqueous solution containing acidic ammonium sulfite.

According to the method of this invention, even if the NH3/SO2 molar ratio of the aqueous solution containing ammonium nitrite and acidic ammonium sulfite is lower than 2, the pH of the absorption liquid will drop significantly and the reaction will proceed explosively. (If) NOx absorption into an aqueous solution containing ammonium nitrite and acidic ammonium sulfite is carried out at 10-35°C.
Since it can be carried out with .

Next, the method of this invention will be explained in detail.

(1) Process The bubble column used in this process has a source side mass transfer coefficient (Hk
(sometimes abbreviated as L) is 2X10-2CrfL/S
eC or more is desirable, and examples of the bubble column include generally known bubble columns such as a bubble bell-type bubble column and a perforated plate-type bubble column.

Here, the source-side mass transfer coefficient kL is defined by the following formula (■) based on the description on page 161 of "Theory and Calculation of Chemical Machinery" [edited by Kamei Sanbe, Sangyo Tosho, published in 1972], and is defined by the following formula (■). NA s C obtained by measuring at 25°C in a physical absorption experiment of a pure carbon dioxide gas-water system where resistance can be ignored.
Calculated based on the value of A i.

[However, in the formula, NA is the moving speed of component A in the unit contact area between gas and liquid (unit: mole/d, sec)
, Ci represents the concentration of component A at the gas-liquid interface (unit: mole/cry), and CAL represents the concentration of AJff, min (unit: mole/cr) in the liquid.
y).

] If the kI is smaller than 2×10 ” crn/sec, the yield of the final product, hydroxylamine sulfate, will decrease due to an increase in the amount of ammonium nitrate, which is a by-product, which is undesirable.

When using a perforated plate type bubble column as a bubble column, the perforated plate's perforated holes (bubble release holes) should be made to have a diameter of 1 or more, and the flow rate of NOx gas passing through the perforated holes should be determined by the unit of perforated hole (bubble release holes). When the cross-sectional area is 15 m/SeC or more, the k
L can be made equal to or greater than 2×10 ”l/SeC.

It is not preferable to make the diameter of the drill hole smaller than 1 m because kL becomes small.

The concentration of ammonium sulfite in the aqueous solution containing ammonium sulfite and acidic ammonium sulfite is 0.05 to
0.5 mole/11 is preferable, and the concentration of acidic ammonium sulfite is 0.01 to 0.4 mole/11.
13 is preferable, and the total concentration of ammonium sulfite and acidic ammonium sulfite is 0.06 to 0.6.
mole/13 is preferred.

If the total concentration of ammonium sulfite and acidic ammonium sulfite in the aqueous solution is smaller than the above range, the reaction tends to proceed explosively, and if it is larger than the range, a large amount of ammonium nitrilotrisulfonate will be present. This is not preferred because it tends to be a by-product and the yield of hydroxylamine sulfate in step (B) decreases.

Further, the concentration of acidic ammonium sulfite in the aqueous solution is 0.
, 01 mole/l, it is not preferable because free ammonia tends to volatilize and the yield of hydroxylamine sulfate decreases.

The NH3/S02 molar ratio of the aqueous solution containing ammonium sulfite and acidic ammonium sulfite is 1.1 to 1, 85
and particularly preferably from 1.2 to 1.75.

Here, the NH3/SO2 molar ratio is defined as the molar concentration ratio of the ammonia component and the sulfur dioxide fraction defined by the following formulas (1) and (2) in an aqueous solution containing ammonium sulfite and acidic ammonium sulfite.

[Molar concentration of ammonia component]

[Molar concentration of free NH3] +2 r(NH+)2sO3
(Molar concentration of NH4H8Os) 10 (Molar concentration of NH4H8Os) ■
Molar concentration of sulfur dioxide component] [Molar concentration of (NH4)2SO3] 10 (NH4H8Oa
molar concentration] ■ (However,
Free NH3 is produced when the reaction between ammonium nitrite and acidic ammonium sulfite occurs.

) If the NH3/SO2 molar ratio is smaller than the above range, a large amount of ammonium nitrilotrisulfonate will be produced as a by-product, reducing the yield of hydroxylamine sulfate. Kiito,
Ammonia gas volatilizes easily in the gas phase, and ammonia gas and NOx gas react in the gas phase,
Large amounts of nitrogen, ammonium nitrite, ammonium nitrate, etc. are produced, reducing the yield of hydroxylamine sulfate.

Furthermore, ammonium nitrite and ammonium nitrate produced in the gas phase are discharged as a fume-like substance with a size of 10 μm or less, which is unfavorable from the viewpoint of pollution prevention.

An aqueous solution containing ammonium sulfite and acidic ammonium sulfite with a NH3/SO2 molar ratio of 1.1 to 85 can be prepared, for example, by blowing ammonia gas and sulfur dioxide gas into water and dissolving them; This can be easily carried out by dissolving ammonium sulfite and acidic ammonium sulfite in water.

When a perforated plate type bubble column is used as the bubble column, the depth from the top of the perforated plate in the bubble column to the liquid surface of the aqueous solution (liquid depth) may be 2 cIrL or more.

As the NOx gas used in the method of this invention, the molar ratio of NO and NO2 in the NOx gas (hereinafter, No/N02
It is preferable that the molar ratio (sometimes abbreviated as molar ratio) is 0.5 to 3.

If the No/N02 molar ratio in the NOx gas is smaller than the above range, ammonium nitrilotrisulfonate is likely to be produced as a by-product, and sulfite ions (80
3"-) and acidic sulfite ions (H8O3-) are oxidized to sulfate ions (SO2"-) and acidic sulfate ions (H8O,), the pH of the aqueous solution becomes strongly acidic and the reaction proceeds explosively. There is a risk of

Furthermore, if the No/N02 molar ratio in the NOx gas is larger than the above range, the amount of by-product ammonium nitrilotrisulfonate will decrease, but the amount of NOx gas absorbed will decrease, and the NOx concentration in the exhaust gas will increase. So I don't like it.

The NOx concentration in the NOx gas is preferably 1 to 15 volume ratios, and usually about 10 volume ratios is sufficient.

N having the above No/N02 molar ratio and NOx concentration
Ox gas may be produced by any industrial method; for example, it may be produced by catalytically oxidizing ammonia with oxygen in the presence of an oxidation catalyst such as a platinum catalyst or platinum-rhodium. can.

The rate of release of NOx gas into the bubble column is 15 m/SeC or more per unit cross-sectional area of the bubble discharge hole.

When the release rate is lower than l 5 l/SeC, the yield of hydroxylamine sulfate decreases, making it difficult to achieve the object of the present invention.

The temperature when absorbing NOx into an aqueous solution containing ammonium sulfite and acidic ammonium sulfite is 10-35
°C is appropriate.

Attempting to carry out the reaction while maintaining the absorption temperature at a temperature lower than 10'C is undesirable because the heat of reaction must be removed with a special refrigerant such as ammonia.
Furthermore, if the temperature is higher than 35°C, ammonium nitrilotrisulfonate is more likely to be produced, and ammonia gas is more likely to volatilize in the gas phase, which not only lowers the yield of hydroxylamine sulfate but also Moreover, ammonium nitrite and ammonium nitrate produced in the gas phase are discharged as a fume-like substance that is harmful to the environment, which is undesirable.

The aqueous solution containing ammonium sulfite and acidic ammonium sulfite is brought into contact with the NOx gas by releasing the NOx gas into the aqueous solution in the form of bubbles in a bubble column.

By bringing an aqueous solution containing ammonium sulfite and acidic ammonium sulfite into contact with NOx gas in a bubble column, nitrogen dioxide, dinitrogen trioxide (N203), dinitrogen tetroxide (N204), etc. of NOx are added to the aqueous solution. It is absorbed to form ammonium nitrite and ammonium hydroxylamine disulfonate, the precursors of hydroxylamine sulfate.

The gas that has passed through the aqueous solution containing ammonium sulfite and acidic ammonium sulfite mainly contains nitrogen monoxide as NOx, so this gas containing residual nitrogen oxides is treated in the packed tower in the next step ([I). do.

(II) Step The packed tower used in this step preferably has a porosity of 60% or more.

If the porosity in the packed column is less than 60%, the pressure loss of gas containing residual nitrogen oxides will increase, and NO
This is not preferable because the residence time of the gas for oxidizing NO2 to NO2 cannot be maintained sufficiently.

Packed towers can be cylindrical, columnar, or honeycomb shaped.

Conventionally known fillers in the form of nets, rings, wedges, etc., such as pole rings, terrarets, virex,
Examples include countercurrent packed columns and cocurrent packed columns filled with net rings, Laschich rings, and the like.

The concentration of ammonium sulfite in the aqueous solution containing ammonium sulfite and acidic ammonium sulfite used in this step (II) is preferably 0.05 to 0.5 mole/l, and the concentration of acidic ammonium sulfite is 0.01 to 0.5 mole/l.
4 mole/13 is preferable, and the total concentration of ammonium sulfite and acidic ammonium sulfite is preferably 0.06 to 0.6 mole/A.

If the total concentration of ammonium sulfite and acidic ammonium sulfite in the aqueous solution is smaller than the above range, the reaction tends to proceed explosively, and if it is larger than the range, a large amount of ammonium nitrilotrisulfonate will be present. This is not preferred because it tends to produce by-products and the yield of hydroxylamine sulfate in step (B) decreases.

The NH3/SO2 molar ratio of the aqueous solution containing ammonium sulfite and acidic ammonium sulfite used in this step is:
1.1 to 1.8 are preferred, and 1.2 to 1.7 are particularly preferred.

If the NH3/SO2 molar ratio of the aqueous solution containing ammonium sulfite and acidic ammonium sulfite is smaller than the above range, ammonium nitrilotrisulfonate is likely to be produced as a by-product, and there is a risk that the reaction will proceed explosively. If it is larger than This is not preferable because it is discharged as a solid substance.

Note that the aqueous solution containing ammonium sulfite and acidic ammonium sulfite obtained by absorbing NOx in step (1) (
It is used as the aqueous solution containing ammonium sulfite and acidic ammonium sulfite in step (II), and the aqueous solution containing ammonium sulfite and acidic ammonium sulfite obtained by absorbing residual nitrogen oxide in step (II) as ammonium sulfite in step (1). and acidic ammonium sulfite, and the aqueous solution containing ammonium sulfite and acidic ammonium sulfite may be used in cycles between step (1) and step (II).

When an aqueous solution containing ammonium sulfite and acidic ammonium sulfite is recycled between step (I) and step (II), for example, fresh ammonium sulfite and It is preferable to add an aqueous solution containing acidic ammonium sulfite and adjust the NH3/SO2 molar ratio as appropriate.

In this step (II), the temperature at which the aqueous solution and the gas containing residual nitrogen oxide are brought into contact is 10 to 35°C.
is appropriate.

Attempting to maintain the temperature below 10°C is undesirable because the heat of reaction must be removed with a special refrigerant such as ammonia, and when the temperature rises above 35°C, ammonium nitrilotrisulfonate is produced. At the same time, the yield of hydroxylamine sulfate decreases because ammonia gas easily volatilizes in the gas phase, and ammonium nitrite and ammonium nitrate generated in the gas phase form a fume-like substance that is harmful to pollution. This is not desirable because it becomes waste and is discharged.

In the packed column, NO in the remaining nitrogen oxides is oxidized to NO
2, N2O3 and N2O4, and these converted nitrogen oxides are absorbed into the aqueous solution and become ammonium nitrite and ammonium hydroxylamine disulfonate.

The aqueous solution containing ammonium nitrite and ammonium hydroxylamine disulfonate obtained by absorbing NOx in the steps (1) and (Jl) is subjected to S
By absorbing O□ gas, ammonium nitrite in the absorption liquid is converted to ammonium hydroxylamine disulfonate, and ammonium hydroxylamine disulfonate is converted to hydroxylamine sulfate.

In addition, when this absorption liquid absorbs SO2 gas, the number of moles of ammonium nitrite in the absorption liquid, the total number of moles of unreacted ammonium sulfite, unreacted acidic ammonium sulfite, and molecular ammonia (number of moles equivalent to ammonia)
It is desirable to adjust the ratio (number of moles equivalent to NH3/number of moles of NH, No2) to about 1.

If the above ratio is greater than 1, acidic ammonium sulfite produced by the reaction between molecular ammonia in the absorption liquid and absorbed SO2 will react with ammonium hydroxylamine disulfonate, resulting in a decrease in the yield of hydroxylamine sulfate. In addition, when the above ratio is smaller than 1, in the process of converting ammonium hydroxylamine disulfonate to hydroxylamine sulfate, unreacted ammonium nitrite is converted to nitrogen and dinitrogen monoxide (N203). This is not preferable because it becomes easier to convert.

(Number of moles equivalent to NH3) in the absorption liquid / (NH4NO2
When the ratio is smaller than 1, the ratio of (number of moles) can be adjusted by blowing ammonia gas into the absorption liquid, adding an aqueous ammonia solution or an aqueous ammonium sulfite solution,
When the ratio is greater than 1, this can be achieved by adding ammonium nitrite to the absorption liquid.

Isolation of hydroxylamine sulfate from a product solution containing hydroxylamine sulfate obtained by further absorbing SO2 gas into the absorption solution can be performed by a known method, but without isolating hydroxylamine sulfate, The above-mentioned product liquid can also be used as it is for the synthesis reaction of cyclohexanone oxime, which is a synthetic intermediate of epsilon caprolactam.

Next, the process (1) and (
II) One example of the process will be explained using a flow sheet.

FIG. 1 is a schematic diagram of an apparatus in which a countercurrent packed column 2 is provided above a perforated plate type bubble column 1 for use in steps (1) and (II).

NOx gas is supplied into the perforated plate type bubble column 1 through the line 3, and the NOx gas is released from the perforated plate 4 into the aqueous solution 5 containing ammonium sulfite and acidic ammonium sulfite, and is brought into contact with the aqueous solution 5 to absorb NOx. .

The gas containing residual nitrogen oxides that has passed through the aqueous solution 5 is supplied from the bottom to the packed bed 6 of the countercurrent packed column 2 located at the top of the perforated plate type bubble column 1, and ammonium sulfite flows down from the nozzle 7. and an aqueous solution 8 containing acidic ammonium sulfite, and the remaining nitrogen oxides are removed from the packed bed 6.
The gas that is absorbed by the aqueous solution 8 flowing down and passed through the packed bed 6 is discharged from a line 9 as exhaust gas.

On the other hand, the aqueous solution 5 containing ammonium sulfite and acidic ammonium sulfite in the perforated plate bubble column 1 is circulated through circulation lines 10, 11. and 12 are supplied to the packed bed 6 from the nozzle 7 in the countercurrent packed column 2.

The NH3/SO2 molar ratio of the aqueous solution supplied to the packed bed 6 is controlled by the circulation lines 4, 9 and 10 through the line 13.
is prepared by mixing an aqueous solution containing fresh ammonium sulfite and acidic ammonium sulfite that is supplied to the solution.

Further, the temperature of the aqueous solutions 5 and 8 circulating through the perforated plate type bubble column 1 and the countercurrent packed column 2 is as follows:
and 8 are regulated by cooling them with a cooler 14 provided in the middle of the circulation lines io, ii, and 12.

The aqueous solution 8 supplied to the countercurrent packed column 2 through the line 12 flows down through the packed bed 6 from the nozzle 7, and is again supplied into the perforated plate type bubble column 1.

An aqueous solution containing ammonium nitrite and ammonium hydroxylamine disulfonate produced by contact between the circulating aqueous solutions 5 and 8 and NOx gas is continuously withdrawn from the perforated plate type bubble column 1 through a withdrawal line 15, and is used as an absorption liquid ( B) Subject to process.

Next, Examples and Comparative Examples will be shown.

Example 1 Steps (1) and (II) were carried out using an apparatus consisting of a perforated plate-type bubble column and a countercurrent packed column similar to that shown in FIG. 1 and having the sizes shown in Table 1. An absorption liquid containing ammonium nitrite and ammonium hydroxylamine disulfonate was obtained.

That is, the NO/No□ molar ratio is 1.04 and the NOx concentration is 9.
．． 01 volume width, oxygen concentration of 6.6 volume φ, and the remainder being nitrogen gas, NOx gas was supplied into the perforated plate bubble column 1 through the line 3 at a release rate of 25.6 m / sec,
NOx gas is supplied from the perforated plate 4 at a molar ratio of NH3/SO2 of 1.
80, ammonium sulfite concentration is 0.16 mole/
l, acidic ammonium sulfite concentration is 0.04 mole/
It was released into an aqueous solution 5 at 23°C containing ammonium sulfite and acidic ammonium sulfite (A), and the aqueous solution 5 was allowed to absorb NOx.

The gas containing the residual nitrogen oxides that has passed through the aqueous solution 5 is guided to the bottom of the packed bed 6 of the countercurrent packed tower 2 located at the top of the perforated plate type bubble column 1, and is led to the bottom of the packed bed 6 of the countercurrent packed tower 2 located at the top of the perforated plate type bubble column 1, where it is introduced into the ammonium sulfite and acidic gases flowing down from the nozzle 7. It was brought into countercurrent contact with an aqueous solution 8 containing ammonium sulfite, and the remaining nitrogen oxides were absorbed into the aqueous solution 8 flowing down through the packed bed 6.

The gas that rose and passed through the packed bed 6 was discharged from the line 9 as exhaust gas.

On the other hand, the aqueous solution 5 containing ammonium sulfite and acidic ammonium sulfite in the porous plate type bubble column 1 is 501/h
It was fed from nozzle 1 in countercurrent packed column 2 to packed bed 6 through circulation lines 10, 11 and 12 at a speed of r.

A new aqueous solution containing ammonium sulfite and acidic ammonium sulfite with a NH3/SO2 molar ratio of 1.65, an ammonium sulfite concentration of 1.58 mole/l, and an acidic ammonium sulfite concentration of 0.84 mole/l, Circulation lines 10, 11. and 12
By mixing at a rate of 1.281/hr through a line 13 provided in the middle of the aqueous solution 8, the NH3/SO2 molar ratio of the aqueous solution 8 supplied to the packed bed 6 is 1.73, and the ammonium sulfite concentration is 0.19 mole/hr. It 1 acidic ammonium sulfite concentration was adjusted to 0.07 mole/z.

Further, the aqueous solution 8 supplied to the countercurrent packed tower 2 is transferred to a cooler 14 provided in the middle of the circulation lines 10, 11, and 12.
The mixture was cooled to 20°C.

The aqueous solution 8 supplied to the countercurrent packed column 2 through the line 12 was allowed to flow down through the packed bed 6 from the nozzle 7, and was again supplied into the perforated plate type bubble column 1.

An aqueous solution containing ammonium nitrite and ammonium hydroxylamine disulfonate produced by contact between the circulating aqueous solutions 5 and 8 and NOx gas is continuously extracted from the perforated plate bubble column 1 through a line 15, and this is used as an absorption liquid for the following steps. (It was subjected to pressure step B.

(Step B) Number of moles equivalent to NH3 in the absorption liquid obtained in step (4)/NH4N
Since the ratio of O2 moles was 0.36, NH3/SO
2 molar ratio is 1.65, ammonium sulfite concentration is 1.5
By adding an aqueous solution containing ammonium sulfite and acidic ammonium sulfite with an acidic ammonium sulfite concentration of 0.8 mole/l and an acidic ammonium sulfite concentration of 0.84 mole/l to this absorption liquid, the number of NH3 equivalent moles/number of NH4NO2 moles of the absorption liquid The ratio was adjusted to 1.

Next, SO2 gas diluted with nitrogen was blown into this absorption liquid, and then water decomposition was performed at 100°C to obtain a product liquid containing hydroxylamine sulfate.

The production of hydroxylamine sulfate in this product solution was confirmed by adding acetone to the product solution to convert hydroxylamine sulfate into acetoxime.

In addition, sulfuric acid liberated by adding acetone to the produced liquid was titrated with a carbon powder to determine the yield of hydroxylamine sulfate relative to the amount of NOx supplied.

In addition, by titrating an aqueous solution in which a predetermined amount of exhaust gas is absorbed into a hydrogen peroxide solution with an alkali, NOx in the exhaust gas can be reduced.
The concentration was determined.

The results are shown in Table 2.

Examples 2 and 3 The reaction was carried out in the same manner as in Example 1 according to the reaction conditions shown in Table 2.

The results are shown in Table 2.

Comparative Example 1 The same procedure as in Example 1 was carried out according to the reaction conditions shown in Table 2, except that the aqueous solution containing ammonium sulfite and acidic ammonium sulfite was replaced with an aqueous ammonium sulfite solution.

The results are shown in Table 2.

Comparative Example 2 The same procedure as in Example 1 was carried out according to the reaction conditions shown in Table 2, except that the apparatus consisting of a combination of a perforated plate bubble column and a countercurrent packed column was replaced with a countercurrent packed column with a packed bed height of 55 crIL. operated.

The results are shown in Table 2.

Reference example 1 By changing the perforated hole in the perforated plate type bubble column from 1 mφ to 2Mφ, the release rate of NOx gas was increased to 25.6 m/SeC
The reaction was carried out in the same manner as in Example 1, except that the reaction conditions were changed to 6.4 m 2 /Sec.

The results are shown in Table 2.

Reference example 2 NO/NO2 molar ratio in the supplied NOx gas is 1.04
The same procedure as in Example 1 was carried out except for the reaction conditions shown in Table 2, except for the reaction conditions shown in Table 2.

The results are shown in Table 2.

Reference example 3 NO/NO2 molar ratio in the supplied NOx gas is 1.04
0.33 and operated in the same manner as in Example 1, crystals of ammonium nitrilotrisulfonate began to precipitate in the circulating aqueous solution, and as the reaction continued, gas generation became more intense and the reaction became stable. can no longer be maintained.

[Brief explanation of drawings]

Figure 1 shows the (1) process and (
II) Schematic diagram of the process. 1; Perforated plate type bubble column, 2: Countercurrent packed column, 3; NOx gas supply line, 4: Perforated plate, 5; Aqueous solution containing ammonium sulfite and acidic ammonium sulfite, 6: Packed bed,
7; nozzle, 8; aqueous solution containing ammonium sulfite and acidic ammonium sulfite, 9; gas discharge line, 10
; circulation line, 11; circulation line, 12; circulation line,
13; supply line for an aqueous solution containing ammonium sulfite and acidic ammonium sulfite; 14; cooler; 15; withdrawal line.

Claims (1)

[Scope of Claims] Hydroxyl sulfate is produced by 1 (A) a step of absorbing a nitrogen oxide-containing gas into an ammonium sulfite aqueous solution, and (B) a step of subsequently absorbing sulfur dioxide gas into the obtained absorption liquid. In the method for producing an amine, the step (4) includes (I) a molar ratio (NH3/5O2) of the ammonia fraction and the sulfur dioxide component in the bubble column of 1.1 to 1.85;
An aqueous solution containing ammonium sulfite and acidic ammonium sulfite, and a gas containing a nitrogen oxide having a molar ratio of nitrogen monoxide (NO) to nitrogen dioxide (NO/N02) of 0.5 to 3, are A step of blowing the gas into contact with the aqueous solution in the bubble column at a rate of release of the gas into the column of 15 m/SeC or more per unit cross-sectional area of the bubble discharge hole, and (II) in the packed column, The molar ratio (NH3/5O2) of the gas containing residual nitrogen oxides passed through the bubble column, the ammonia fraction, and the sulfur dioxide component is 1.1 to 1.
．． 8. A method for producing hydroxylamine sulfate, comprising the step of contacting ammonium sulfite and an aqueous solution containing acidic ammonium sulfite.