Process and device for recycling nitrogen dioxide

Abstract

The invention discloses a process and a device for recycling nitrogen dioxide, which are characterized in that degassed crude dimethyl sulfoxide is used as a raw material, nitrogen dioxide is absorbed by two stages of crude dimethyl sulfoxide and enters a micro-channel reactor to be used as a catalyst for oxidizing dimethyl sulfide, and recycling is realized. The device comprises a tail gas absorption unit, a microreactor unit, a heat exchanger unit and a separator unit, the technology adopts a dimethyl sulfoxide low-temperature absorption technology, and has the advantages of cyclic utilization of nitrogen oxides, energy conservation and emission reduction, convenience in operation, greenness, high efficiency and the like.

Description

Technical Field

[0001] This invention belongs to the field of chemical distillation technology, specifically relating to a process and apparatus for the recycling of nitrogen dioxide, which realizes the recycling of nitrogen dioxide in a green and efficient manner. Background Art

[0002] Nitrogen dioxide (NO2) is an inorganic compound with the chemical formula NO2 and a molecular weight of 46. It is a yellowish-brown gas at room temperature and pressure and is soluble in water. Chemical properties: Nitrogen dioxide is a strong oxidizing agent, capable of spontaneous combustion with many fuels. It is one of the most important rocket propellants. It is relatively easy to maintain in a liquid state, therefore it is mainly used to form storable liquid propellants. It was widely used in early liquid-fueled intercontinental ballistic missiles, such as the US Titan ICBM, the Soviet Proton launch vehicle, and the Chinese Long March 2 launch vehicle. Nitrogen dioxide is highly toxic and corrosive. Inhalation is extremely toxic and can cause serious health problems such as pulmonary edema.

[0003] Nitrogen dioxide is used as a catalyst in the oxidation of dimethyl sulfide. During the reaction, it is stripped in gaseous form, absorbed by liquid alkali, and a small amount is released into the atmosphere. This process results in significant waste of nitrogen dioxide and environmental pollution. How to recycle nitrogen dioxide during the oxidation of dimethyl sulfide has become a technical challenge. Summary of the Invention

[0004] The purpose of this invention is to address existing technological bottlenecks by developing a process and apparatus for the recycling of nitrogen dioxide.

[0005] A device for recycling nitrogen dioxide, wherein the bottom outlet of the secondary absorption tower is connected to the middle inlet of the primary absorption tower via a secondary circulation pump; The bottom outlet of the primary absorption tower is connected to the shell side of the heat exchanger via a primary circulating pump. The shell side of the heat exchanger is connected to the top inlet of the crude dimethyl sulfoxide feed tank.

[0006] The bottom outlet of the crude dimethyl sulfoxide feed tank is connected to the bottom inlet of the microreactor via a crude dimethyl sulfoxide pump. The top outlet of the microreactor is connected to the bottom inlet of the tube side of the heat exchanger. The upper outlet of the tube side of the heat exchanger is connected to the middle inlet of the separator. The top outlet of the separator is connected to the primary absorption tower.

[0007] A dimethyl sulfide pipe is connected to the bottom inlet of the microreactor; oxygen and nitrogen dioxide pipes are connected to the side wall inlet at the bottom of the microreactor.

[0008] The top outlet of the primary absorption tower is connected to the middle inlet of the secondary absorption tower; the upper part of the secondary absorption tower is equipped with a degassed dimethyl sulfoxide inlet pipe.

[0009] The bottom outlet of the primary absorption tower is connected to the upper inlet of the primary absorption tower via a primary circulation pump to form a circulation system. The bottom outlet of the secondary absorption tower is connected to the upper inlet of the secondary absorption tower through a secondary circulation pump to form a circulation.

[0010] The process implemented in the above device includes an exhaust gas absorption unit, a microreactor unit, a heat exchanger unit, and a separator unit.

[0011] The tail gas absorption unit employs a two-stage absorption process. The first-stage absorption tower receives dimethyl sulfoxide from the second-stage absorption process via a second-stage circulation pump. Nitrogen dioxide from the separator is then separated and enters the first-stage absorption tower. The dimethyl sulfoxide is circulated and sprayed through the first-stage circulation pump. Unabsorbed nitrogen dioxide enters the second-stage absorption tower through the top of the first-stage absorption tower. Liquid nitrogen from the bottom of the first-stage absorption tower is pumped into the lower inlet of the heat exchanger shell via a first-stage circulation pump.

[0012] The secondary absorption tower introduces degassed dimethyl sulfoxide into the tower and absorbs the nitrogen dioxide that was not absorbed in the primary absorption tower again. After being circulated and washed by the secondary circulation pump, it is discharged from the outlet.

[0013] In the microreactor unit, the inlet of the crude dimethyl sulfoxide pump is connected to the bottom of the crude dimethyl sulfoxide feed tank, and the outlet is connected to the bottom of the microreactor. Dimethyl sulfide and crude dimethyl sulfoxide enter the microreactor from the bottom, while oxygen and nitrogen dioxide enter from the bottom of the microreactor.

[0014] In the heat exchanger unit, the top of the microreactor is connected to the bottom inlet of the heat exchanger tube layer, the upper outlet of the tube layer goes to the middle inlet of the separator, and the upper outlet of the shell layer is connected to the top of the crude dimethyl sulfoxide feeding tank, so as to realize the heat exchange between the reaction product in the tube side and the crude dimethyl sulfoxide material in the shell side, recover heat through the heat exchanger, and cool down the crude dimethyl sulfoxide after the reaction.

[0015] In the separator unit, the separated dimethyl sulfoxide is discharged from the bottom of the separator to the next process; nitrogen dioxide is discharged from the top of the separator to the primary absorption tower, thus achieving recycling.

[0016] The microreactor is made of C4 material, while the other equipment and pipelines are made of 321 material.

[0017] Another technical solution of the present invention is to provide a process for recycling nitrogen dioxide, comprising the following process steps: S1. The degassed dimethyl sulfoxide enters the secondary absorption tower, where it absorbs nitrogen dioxide gas from the primary absorption tower through circulation. The absorption is stabilized by low-temperature water control, and the absorbed dimethyl sulfoxide solution enters the primary absorption tower. S2. The nitrogen dioxide gas separated from the separator enters the primary absorption tower, where the acid value of crude dimethyl sulfoxide is increased through circulating absorption. The absorption temperature is controlled by low-temperature water, and a crude dimethyl sulfoxide solution with a higher acid value is obtained and enters the shell side of the heat exchanger. S3. The crude dimethyl sulfoxide with a higher acid value in the shell side of the heat exchanger exchanges heat with the dimethyl sulfoxide reacting in the tube side of the heat exchanger. The crude dimethyl sulfoxide with a higher acid value in the shell side enters the crude dimethyl sulfoxide feeding tank; the reacted dimethyl sulfoxide goes to the separator. S4. The crude dimethyl sulfoxide feed tank is fed into the microreactor via a crude dimethyl sulfoxide pump. It reacts with oxygen, nitrogen dioxide and dimethyl sulfide in the microreactor to produce dimethyl sulfoxide, i.e., the reacted dimethyl sulfoxide. S5. The dimethyl sulfoxide from the reaction enters the separator for separation to obtain refined dimethyl sulfoxide, and the separated nitrogen dioxide gas enters the primary absorption tower; S6. Repeat the loop from S1 to S5.

[0018] In S1, the degassed dimethyl sulfoxide has a value of 0.01-40 mg / g, including 90-99% dimethyl sulfoxide, 1-8% nitrogen dioxide, and a moisture content of less than 1000 PPM; After absorption, the acid value is 10-40 mg / g.

[0019] In the secondary absorption tower, dimethyl sulfoxide is used as the absorbent; a low-temperature water temperature control method is adopted for cooling to absorb nitrogen dioxide. The cooling water temperature is 5-12℃, and the temperature of the secondary absorption tower is controlled at 20-40℃.

[0020] In S2, the absorbed solution contains 90-99% dimethyl sulfoxide, which is a dimethyl sulfoxide with a high acid value of 20-60 mg / g, and has a water content of less than 1000 PPM.

[0021] The primary absorption tower uses dimethyl sulfoxide (DMSO) absorbed by the secondary absorption tower as the absorbent; a low-temperature water-based temperature control method is used to absorb nitrogen dioxide, with the cooling water temperature between 20-40℃ and the secondary absorption tower temperature controlled between 20-50℃.

[0022] In S4, the feed temperature of dimethyl sulfoxide with a high acid value entering the microreactor is controlled at 30-60℃; the reaction temperature of the microreactor is controlled at 40-120℃, and the acid value after the reaction is controlled at 20-70mg / g.

[0023] The oxygen feed flow rate is 2-5 kg / h, the nitrogen dioxide feed flow rate is 0.2-1 kg / h, the oxygen to nitrogen dioxide volume ratio is 5-10:1, the dimethyl sulfide feed flow rate is 6-20 kg / h, and the crude dimethyl sulfoxide feed flow rate is 150-300 kg / h.

[0024] In the technical solution of the present invention, crude dimethyl sulfoxide is used as the absorbent in the exhaust gas absorption unit. Under low temperature conditions, nitrogen dioxide is absorbed twice by a circulating pump using the principle of two-stage absorption, and nitrogen dioxide is recovered.

[0025] In the microreactor unit, the principle of nitrogen dioxide dissolving in dimethyl sulfoxide is utilized. The recovered nitrogen dioxide is dissolved in dimethyl sulfoxide, and the dimethyl sulfide oxidation is carried out using the SV type mixing equipment of Atlan Equipment Co., Ltd. at a specific temperature and flow rate.

[0026] In the heat exchanger unit, the absorbed dimethyl sulfoxide is exchanged with the reacted dimethyl sulfoxide, which reduces energy waste and is beneficial for micro-reaction control.

[0027] The separator unit employs a highly efficient gas-liquid separation device to perform gas-liquid separation on the crude dimethyl sulfoxide.

[0028] This invention utilizes the principle that nitrogen dioxide dissolves in dimethyl sulfoxide. Nitrogen dioxide is absorbed at different temperatures, and then its oxidizing properties are used to oxidize dimethyl sulfide. This reduces the emission of toxic and harmful gases, realizes the recycling of nitrogen dioxide, simplifies the operation process, reduces production costs, breaks the conventional dimethyl sulfide oxidation reaction, and reduces by-products. Attached Figure Description

[0029] Figure 1 This is a structural diagram of the apparatus used in the process described in this invention. In the diagram, 01 is the crude dimethyl sulfoxide feed tank, 02 is the crude dimethyl sulfoxide pump, 03 is the dimethyl sulfide pipeline, 04 is the oxygen and nitrogen dioxide pipeline, 05 is the microreactor, 06 is the heat exchanger, 07 is the separator, 08 is the dimethyl sulfoxide product discharge pipe, 09 is the primary absorption tower, 10 is the primary circulation pump, 11 is the secondary absorption tower, 12 is the degassed dimethyl sulfoxide inlet pipe, 13 is the discharge port, and 14 is the secondary circulation pump. Detailed Implementation

[0030] In this invention, different acid values ​​and temperatures were selected to test the absorption and recovery effect of nitrogen oxides, and the yield of dimethyl sulfide oxidation in the micro-reaction was also tested.

[0031] Example 1 A device for recycling nitrogen dioxide, wherein the bottom outlet of the secondary absorption tower 11 is connected to the middle inlet of the primary absorption tower 9 via a secondary circulation pump 14; The bottom outlet of the primary absorption tower 9 is connected to the shell side of the heat exchanger 06 via the primary circulation pump 10; The shell side of heat exchanger 06 is connected to the top inlet of crude dimethyl sulfoxide feed tank 01.

[0032] The bottom outlet of the crude dimethyl sulfoxide feed tank 01 is connected to the bottom inlet of the microreactor 05 via the crude dimethyl sulfoxide pump 02. The top outlet of the microreactor 05 is connected to the bottom inlet of the tube side of the heat exchanger 06. The upper outlet of the tube side of the heat exchanger 06 is connected to the middle inlet of the separator 07. The top outlet of the separator 07 is connected to the primary absorption tower 9.

[0033] The bottom inlet of the microreactor 05 is also connected to a dimethyl sulfide pipe 03; the side wall inlet of the lower part of the microreactor 05 is connected to an oxygen and nitrogen dioxide pipe 04.

[0034] The top outlet of the primary absorption tower 9 is connected to the middle inlet of the secondary absorption tower 11; the upper part of the secondary absorption tower 11 is provided with a degassed dimethyl sulfoxide inlet pipe 12.

[0035] The bottom outlet of the primary absorption tower 9 is connected to the upper inlet of the primary absorption tower 9 via the primary circulation pump 10 to form a circulation. The bottom outlet of the secondary absorption tower 11 is connected to the upper inlet of the secondary absorption tower 11 through the secondary circulation pump 14 to form a circulation.

[0036] Example 2 The apparatus of Example 1 is used to carry out the following process: a process for recycling nitrogen dioxide, which includes a tail gas absorption unit, a microreactor unit, a heat exchanger unit, and a separator unit; The exhaust gas absorption unit employs a two-stage absorption process, wherein: Step 1: Add degassed crude dimethyl sulfoxide 12 to the secondary absorption tower 11 at a liquid level of 800 mm. The acid value is 0.01 mg / g. Start the secondary circulation pump 14. Keep the cooling water temperature at 5-12℃ and control the absorption temperature at 20℃. Introduce nitrogen oxide gas from the primary absorption tower 09. Absorb for 4 hours. Detect the crude dimethyl sulfoxide acid value at 38 mg / g and the color at soybean oil color.

[0037] Step 2: The dimethyl sulfoxide absorbed to 38 mg / g is sent to the primary absorption tower 09 via the secondary circulation pump 14, with the liquid level controlled at 800 mm. The primary circulation pump 10 is started, the cooling water temperature is maintained at 20-25℃, and the absorption temperature is controlled at 20-30℃. Nitrogen oxide gas from the top of separator 07 is introduced, and absorption is carried out for 1 hour. The crude dimethyl sulfoxide acid value is measured to be 59 mg / g, and the color is dark green.

[0038] Step 3: Dimethyl sulfoxide at 30℃ and with an acid value of 40mg / g is sent to the heat exchanger through the primary circulation pump 10 for heat exchange and then enters the crude dimethyl sulfoxide feeding tank 01, controlling the liquid level in the tank to 800mm-1200mm.

[0039] Crude dimethyl sulfoxide (DMSO) is fed into microreactor 05 at a flow rate of 200 kg / h via pump 02, with the feed temperature controlled at 30-45°C. Oxygen and nitrogen dioxide are fed at a flow rate of 4 kg / h and 0.5 kg / h respectively, mixed at a volume ratio of 8:1 before entering microreactor 05. Dimethyl sulfide (DMSO) is fed into microreactor 05 at a flow rate of 15 kg / h and reacted at 90-100°C. The resulting crude DMSO passes through heat exchanger 06 and undergoes gas-liquid separation via separator 07. The nitrogen oxide gas is sent to the primary absorption tower 09. The liquid crude DMSO is discharged from the bottom of separator 07 (DMSO 08) and either enters the downstream or partial recycling process.

[0040] Step 4: After completing the cycle in Step 3, start continuous feeding and control the liquid levels in the primary absorption tower 09 and the secondary absorption tower 11 to 500mm-800mm. After 1 hour, once the system is stable, record and observe the temperature inside the microreactor, the acid value of dimethyl sulfoxide 08, and the acid values ​​of the absorbent liquid in the primary absorption tower 09 and the secondary absorption tower 11.

[0041]

[0042] Data shows that, under the condition of feeding dimethyl sulfoxide at 40°C, the higher the acid value of dimethyl sulfoxide, the higher the outlet temperature. At the same time, the acid values ​​of the primary and secondary absorption towers show a decreasing trend, proving that nitrogen oxides can be completely absorbed.

[0043] Example 3 The method and steps are the same as in Example 1. In step one only, the acid value of the degassed crude dimethyl sulfoxide 12 was 20 mg / g. The secondary circulation pump 14 was started, and the absorption was carried out for 1 hour. The acid value of the crude dimethyl sulfoxide was measured to be 33 mg / g, and the color was soybean oil color.

[0044] In step two, the crude dimethyl sulfoxide value of the absorption solution is controlled at 47 mg / g.

[0045] After the system has been running stably for one hour, data monitoring will begin, as detailed below:

[0046] Data shows that under the condition of 40℃ feed of dimethyl sulfoxide, the acid value of dimethyl sulfoxide decreases and the outlet temperature decreases. At the same time, the use of degassed crude dimethyl sulfoxide 12 with an acid value of 20 mg / g can meet the requirements of the absorbent. The acid values ​​of the primary and secondary absorption towers show a downward trend, proving that nitrogen oxides can be completely absorbed.

[0047] Example 4 The method and steps are the same as in Example 1. In step one only, the crude dimethyl sulfoxide (DMSO) 12 was degassed, with an acid value of 20 mg / g. The secondary circulation pump 14 was started, and the absorption lasted for 2 hours. The crude DMSO acid value was measured to be 30 mg / g, and the color was soybean oil color.

[0048] In step two only, the crude dimethyl sulfoxide value of the absorption solution is controlled at 39 mg / g.

[0049] In step three only, the feed temperature of the crude dimethyl sulfoxide is gradually adjusted to 35°C via the crude dimethyl sulfoxide pump. After the system has been running stably for one hour, data monitoring will begin, as detailed below:

[0050] Data shows that when dimethyl sulfoxide (DMSO) is fed at 35-38℃, the acid value of DMSO decreases and the outlet temperature decreases. At the same time, the acid value of DMSO shows a downward trend, proving that nitrogen oxides can be completely absorbed and that there is still room for the acid value of DMSO to decrease.

[0051] Example 5 The method and steps are the same as in Example 1. In step one only, the crude dimethyl sulfoxide 12 was degassed, with an acid value of 20 mg / g. The secondary circulation pump 14 was started, and the absorption lasted for 3 hours. The crude dimethyl sulfoxide acid value was measured to be 23.5 mg / g, and the color was soybean oil color.

[0052] In step two only, the crude dimethyl sulfoxide value of the absorption solution is controlled at 30 mg / g, and the absorption temperature is controlled at 25℃.

[0053] After the system has been running stably for one hour, data monitoring will begin, as detailed below:

[0054] Data shows that under the condition of feeding dimethyl sulfoxide at 35°C, the acid value of dimethyl sulfoxide and the reactor outlet temperature, as well as the acid value absorbed by dimethyl sulfoxide, tend to be stable in the micro-reaction.

[0055] Example 5 The method and steps are the same as in Example 1. In step one only, the crude dimethyl sulfoxide 12 was degassed, with an acid value of 20 mg / g. The secondary circulation pump 14 was started, and the absorption lasted for 3 hours. The crude dimethyl sulfoxide acid value was measured to be 22.6 mg / g, and the color was soybean oil color.

[0056] In step two only, the dimethyl sulfoxide value of the absorption solution is controlled at 30 mg / g, and the absorption temperature is controlled at 20℃.

[0057] After the system has been running stably for one hour, data monitoring will begin, as detailed below:

[0058] Data shows that, under the condition of feeding dimethyl sulfoxide at 30°C, the acid value of dimethyl sulfoxide and the reactor outlet temperature in the micro-reaction process are relatively stable, and the acid value absorbed by dimethyl sulfoxide is smaller than that in Case 4, which is more conducive to absorption.

[0059] Under these conditions, the absorption of nitrogen oxides is effective, and the optimal temperature control for the reaction is met.

[0060] Example 6 The method and steps are the same as in Example 1. In step one only, the crude dimethyl sulfoxide 12 was degassed, with an acid value of 20 mg / g. The temperature was controlled at 35℃. The secondary circulation pump 14 was started, and the absorption lasted for 2.5 hours. The crude dimethyl sulfoxide acid value was detected to be 22 mg / g, and the color was soybean oil. A pale yellow substance was found at the discharge port 13. The absorption effect was poor, and nitrogen oxides were overflowing. The secondary absorption temperature increased, which was not conducive to the absorption of tail gas.

[0061] in conclusion: When the acid value of the degassed crude dimethyl sulfoxide 12 is controlled at 20 mg / g and the color is soybean oil-colored, the acid value of the primary absorption tower 09 is controlled at 29-39 mg / g and the acid value of the secondary absorption tower 11 is controlled at 22-30 mg / g, and the temperature is controlled at 20-30℃, the absorption effect is the best and meets the relevant conditions for feeding into the microreactor. All the generated nitrogen dioxide tail gas is absorbed and recycled.

Claims

1. A device for recycling nitrogen dioxide, characterized in that: The bottom outlet of the secondary absorption tower (11) is connected to the middle inlet of the primary absorption tower (9) via a secondary circulation pump (14); The bottom outlet of the primary absorption tower (9) is connected to the shell side of the heat exchanger (06) via a primary circulation pump (10); The shell side of the heat exchanger (06) is connected to the top inlet of the crude dimethyl sulfoxide feeding tank (01).

2. The nitrogen dioxide recycling device according to claim 1, characterized in that: The bottom outlet of the crude dimethyl sulfoxide feeding tank (01) is connected to the bottom inlet of the microreactor (05) via the crude dimethyl sulfoxide pump (02), the top outlet of the microreactor (05) is connected to the bottom inlet of the tube side of the heat exchanger (06), the upper outlet of the tube side of the heat exchanger (06) is connected to the middle inlet of the separator (07), and the top outlet of the separator (07) is connected to the primary absorption tower (9).

3. The nitrogen dioxide recycling device according to claim 2, characterized in that: The bottom inlet of the microreactor (05) is also connected to a dimethyl sulfide pipeline (03); and the side wall inlet at the lower part of the microreactor (05) is connected to an oxygen and nitrogen dioxide pipeline (04).

4. The nitrogen dioxide recycling device according to claim 3 is characterized in that: The top outlet of the primary absorption tower (9) is connected to the middle inlet of the secondary absorption tower (11); a degassed dimethyl sulfoxide inlet pipe (12) is arranged at the upper part of the secondary absorption tower (11).

5. The nitrogen dioxide recycling device according to claim 1, characterized in that: The bottom outlet of the primary absorption tower (9) is connected to the upper inlet of the primary absorption tower (9) through a primary circulation pump (10) to form a circulation; The bottom outlet of the secondary absorption tower (11) is connected to the upper inlet of the secondary absorption tower (11) through a secondary circulation pump (14) to form a circulation.

6. A process for recycling nitrogen dioxide, characterized in that: The process includes the following: S1. Degassed dimethyl sulfoxide enters the secondary absorption tower, and the nitrogen dioxide gas from the primary absorption tower is absorbed by circulation, and the absorption is stabilized by low-temperature water. The absorbed dimethyl sulfoxide solution enters the primary absorption tower; S2. The nitrogen dioxide gas separated from the separator enters the primary absorption tower, and through cyclic absorption, the acid value of the crude dimethyl sulfoxide is increased by low temperature control, and the crude dimethyl sulfoxide solution with a high acid value is obtained and enters the shell side of the heat exchanger; S3. The saturated crude dimethyl sulfoxide in the shell side of the heat exchanger is heat exchanged with the reacted dimethyl sulfoxide in the tube side of the heat exchanger, and the crude dimethyl sulfoxide with a higher shell acid value enters the crude dimethyl sulfoxide feeding tank; the reacted dimethyl sulfoxide goes to the separator; S4. The crude dimethyl sulfoxide feed tank enters the microreactor through a crude dimethyl sulfoxide pump, and reacts with oxygen, nitrogen dioxide, and dimethyl sulfide in the microreactor to obtain dimethyl sulfoxide, that is, the reacted dimethyl sulfoxide; S5. The dimethyl sulfoxide reacted enters a separator for separation to obtain a separated dimethyl sulfoxide, and the separated nitrogen dioxide gas enters a primary absorption tower; S6. Implement the cycle of S1-S5 again.

7. The process for recycling nitrogen dioxide according to claim 6, characterized in that: In S1, the degassed dimethyl sulfoxide has an acid value of 0.01-40 mg / g, includes 90-99% dimethyl sulfoxide, 1-8% nitrogen dioxide, and a moisture content of less than 1000 PPM; The temperature of the secondary absorption tower is controlled at 20-40°C, and the acid value obtained after absorption is 10-40 mg / g.

8. The process for recycling nitrogen dioxide according to claim 6, characterized in that: In S2, the solution after absorption contains 90-99% dimethyl sulfoxide, is absorption saturated dimethyl sulfoxide, has an acid value of 20-60 mg / g, and has a water content of less than 1000 PPM; the temperature of the secondary absorption tower is controlled at 20-50°C.

9. The process for recycling nitrogen dioxide according to claim 6, characterized in that: In S4, the feed temperature of the dimethyl sulfoxide with a higher acid value entering the microreactor is controlled at 30-60° C.; the reaction temperature of the microreactor is controlled at 40-120° C., and the acid value after the reaction is controlled at 20-70 mg / g.

10. The process for recycling nitrogen dioxide according to claim 9, characterized in that: The oxygen feed flow rate is 2-5 kg / h, the nitrogen dioxide feed flow rate is 0.2-1 kg / h; the volume ratio of oxygen to nitrogen dioxide is 5-10:1; the dimethyl sulfide feed flow rate is 6-20 kg / h; the crude dimethyl sulfoxide feed flow rate is 150-300 kg / h.

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