CN115557476B - Nitrogen dioxide preparation device and preparation method - Google Patents
Nitrogen dioxide preparation device and preparation method Download PDFInfo
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- CN115557476B CN115557476B CN202211151536.4A CN202211151536A CN115557476B CN 115557476 B CN115557476 B CN 115557476B CN 202211151536 A CN202211151536 A CN 202211151536A CN 115557476 B CN115557476 B CN 115557476B
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- MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 title claims abstract description 59
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 title claims abstract description 59
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- 239000007788 liquid Substances 0.000 claims abstract description 163
- LPXPTNMVRIOKMN-UHFFFAOYSA-M sodium nitrite Chemical compound [Na+].[O-]N=O LPXPTNMVRIOKMN-UHFFFAOYSA-M 0.000 claims abstract description 140
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 88
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 87
- 235000010288 sodium nitrite Nutrition 0.000 claims abstract description 70
- 239000007789 gas Substances 0.000 claims abstract description 69
- 238000006243 chemical reaction Methods 0.000 claims abstract description 41
- 239000012295 chemical reaction liquid Substances 0.000 claims abstract description 17
- 230000003647 oxidation Effects 0.000 claims abstract description 14
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 14
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 17
- 229910052760 oxygen Inorganic materials 0.000 claims description 17
- 239000001301 oxygen Substances 0.000 claims description 17
- 238000004519 manufacturing process Methods 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 8
- 230000005484 gravity Effects 0.000 claims description 2
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 abstract description 40
- 235000010344 sodium nitrate Nutrition 0.000 abstract description 20
- 239000004317 sodium nitrate Substances 0.000 abstract description 20
- 239000000047 product Substances 0.000 abstract description 16
- 239000006227 byproduct Substances 0.000 abstract description 6
- 239000002253 acid Substances 0.000 abstract description 5
- 239000003595 mist Substances 0.000 abstract description 4
- 239000000126 substance Substances 0.000 abstract description 2
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 56
- 239000000243 solution Substances 0.000 description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 229910001868 water Inorganic materials 0.000 description 9
- WFPZPJSADLPSON-UHFFFAOYSA-N dinitrogen tetraoxide Chemical compound [O-][N+](=O)[N+]([O-])=O WFPZPJSADLPSON-UHFFFAOYSA-N 0.000 description 8
- 239000000463 material Substances 0.000 description 7
- 239000002994 raw material Substances 0.000 description 5
- 238000001704 evaporation Methods 0.000 description 4
- 230000008020 evaporation Effects 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 238000012856 packing Methods 0.000 description 3
- 238000005086 pumping Methods 0.000 description 3
- IOVCWXUNBOPUCH-UHFFFAOYSA-N Nitrous acid Chemical compound ON=O IOVCWXUNBOPUCH-UHFFFAOYSA-N 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 230000000711 cancerogenic effect Effects 0.000 description 1
- 231100000357 carcinogen Toxicity 0.000 description 1
- 239000003183 carcinogenic agent Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 235000013312 flour Nutrition 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- 230000000802 nitrating effect Effects 0.000 description 1
- 238000012946 outsourcing Methods 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 230000036284 oxygen consumption Effects 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
- 239000006200 vaporizer Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/20—Nitrogen oxides; Oxyacids of nitrogen; Salts thereof
- C01B21/36—Nitrogen dioxide (NO2, N2O4)
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/0006—Controlling or regulating processes
- B01J19/0013—Controlling the temperature of the process
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
Abstract
The invention relates to a nitrogen dioxide preparation device and a preparation method, which belong to the technical field of chemical industry and aim to improve the quality of nitrogen dioxide gas and reduce the content of sodium nitrite in byproducts. Comprises a sodium nitrite feeding tank and a heater I; a dilute nitric acid feed tank, a generator, a mixer, a separator and an oxidation system; the liquid outlet of the acid feed tank is communicated with the nitric acid liquid outlet main circuit, then is communicated with the liquid removing section of the generator through the nitric acid liquid outlet branch I, is converged with the sodium nitrite liquid outlet pipeline through the nitric acid liquid outlet branch II, and then is connected with the reaction section in the middle of the generator through the mixer; the top gas outlet of the generator is communicated with the gas inlet of the separator; the gas outlet of the separator is communicated with the oxidation system; the bottom liquid outlet of the generator is connected with the circulating liquid inlet of the generator through the liquid outlet branch of the reaction liquid. The device has the advantages that the utilization rate of sodium nitrite and dilute nitric acid is high, the yield of nitrogen dioxide is high, the acid mist content of nitrogen dioxide is low, and the quality is good; the sodium nitrite content in the sodium nitrate product as a byproduct is low.
Description
Technical Field
The invention belongs to the technical field of chemical industry, and particularly relates to a nitrogen dioxide preparation device and a preparation method.
Background
Nitrogen dioxide is an important compound and is used in a wide variety of applications, such as nitric acid, nitrating agents, oxidizing agents, catalysts, inhibitors, standard gases, rocket fuels, flour bleaches, and the like.
For most enterprises (except nitric acid plants) using nitrogen dioxide in China, the nitrogen dioxide source is generated by taking nitric acid and sodium nitrite as raw materials by self-generation through two ways of outsourcing and self-manufacturing, and for most enterprises, the hazard degree is classified into class II (high hazard) due to the toxicity hazard index THI=59. When sodium nitrite reacts with nitric acid, sodium nitrate, nitrogen dioxide, nitric oxide and water are generated, and the chemical reaction formula is as follows:
2NaNO 2 +2HNO 3 ＝2NaNO 3 +NO 2 +NO+H 2 O
when the method is used for preparing, firstly, desalted water is injected into a material dissolving tank, sodium nitrite solid is injected, material dissolving is stirred, sodium nitrite solution is prepared, and the sodium nitrite solution is transferred into a sodium nitrite feeding tank by a material transferring pump; pumping outsourced nitric acid into a nitric acid feeding tank by a pump; and then respectively pumping sodium nitrite and sodium nitrate out of the respective tanks/tanks by using a sodium nitrite and nitric acid feed pump, feeding the sodium nitrite and the sodium nitrate into the generator, and reacting under heating to generate sodium nitrate, nitrogen dioxide, nitric oxide and water, wherein an aqueous solution formed by the sodium nitrate and the water is pumped out from the bottom of the generator, sodium nitrate byproducts are generated through evaporation and crystallization, and the mixed gas of the nitrogen dioxide and the nitric oxide flows out from the top of the generator, is simply removed and is fed into a using unit as a product. The defects and disadvantages of the existing nitrogen dioxide preparation method and device are that (1) half of the prepared nitrogen dioxide gas is nitric oxide gas, and the nitric acid carried in the gas has high content, which causes great trouble for subsequent use; (2) The sodium nitrite content in the sodium nitrate solution generated after the reaction is higher, which directly leads to the exceeding of the sodium nitrite content in the sodium nitrate product obtained by evaporation and crystallization.
Disclosure of Invention
The invention aims to provide a nitrogen dioxide preparation device and a preparation method using sodium nitrite and nitric acid as raw materials, which can improve the quality of nitrogen dioxide gas and reduce the content of sodium nitrite in byproducts.
The technical scheme adopted by the invention is as follows: the nitrogen dioxide preparation device comprises a sodium nitrite feeding tank and a heater I; a dilute nitric acid feed tank, a generator, a mixer, a separator and an oxidation system; the generator vertically comprises a kettle liquid section at the bottom, a reaction section at the middle part and a liquid removal section at the upper part; the liquid outlet of the sodium nitrite feeding tank is communicated with the liquid inlet of the first heater, and the liquid outlet of the first heater is communicated with the liquid inlet of the mixer; the liquid outlet of the dilute nitric acid feeding tank is communicated with the main nitric acid liquid outlet passage, then communicated with a cold feed inlet positioned above the liquid removing section on the generator through the first nitric acid liquid outlet passage, and communicated with the liquid inlet of the mixer after being converged with the liquid outlet pipeline of sodium nitrite through the second nitric acid liquid outlet passage; the liquid outlet of the mixer is communicated with the mixed feed inlet of the reaction section in the middle of the generator; the top gas outlet of the generator is communicated with the gas inlet of the separator; the gas outlet of the separator is communicated with the oxidation system; the bottom liquid outlet of the generator is branched through the main liquid outlet path of the reaction liquid, is communicated with the circulating liquid inlet of the generator through the first liquid outlet path of the reaction liquid, outputs a product through the second liquid outlet path of the reaction liquid, and is provided with a second heater.
Further, the mixing feed inlet of the generator is located vertically above the circulating liquid inlet of the generator.
Further, the oxidation system includes a converter and a gasifier; an oxygen inlet pipeline is arranged on the converter, and a gas inlet of the converter is communicated with a gas outlet of the separator; the liquid inlet of the gasifier is communicated with the liquid outlet of the converter through a mixed liquid conveying pipeline.
Further, a buffer tank is communicated with a gas outlet of the gasifier.
Further, a condensate return channel is arranged, and the condensate return channel comprises a condensate branch pipe I, a condensate branch pipe II, a condensate branch pipe III, a condensate branch pipe IV and a condensate main pipe connected with a condensate inlet of a kettle liquid section of the generator; the first condensate branch pipe is connected with a bottom liquid outlet of the separator, and the other end of the first condensate branch pipe is connected with a condensate main pipe; the second condensate branch pipe is connected with one end of the oxygen inlet pipeline adjacent to the converter, and the other end of the second condensate branch pipe is connected with the condensate main pipe; the third condensate branch pipe is connected to one end of the mixed liquor conveying pipeline adjacent to the gasifier, and the other end of the mixed liquor conveying pipeline is connected to the condensate main pipe; and the condensate branch pipe IV is connected to a liquid outlet at the bottom of the buffer tank, and the other end of the condensate branch pipe IV is connected to a condensate main pipe.
Further, a nitric acid feeding pump is arranged on a nitric acid liquid outlet main path of the dilute nitric acid feeding tank; and a sodium nitrite feeding pump is arranged on a sodium nitrite liquid outlet pipeline of the sodium nitrite feeding tank.
The preparation method of nitrogen dioxide by adopting the preparation device of nitrogen dioxide comprises the steps of feeding sodium nitrite solution into a heater I to raise the temperature to 80-95 ℃;
dividing dilute nitric acid into two parts, wherein one part is sent to the upper part of a liquid removing section of the generator from a nitric acid liquid outlet branch I, and the other part is sent to a reaction section of the generator from a nitric acid liquid outlet branch II and a sodium nitrite solution sent from a heater I after being converged together and then sent to a mixer together for mixing;
extracting the solution part of the kettle liquid section of the generator, heating to 80-95 ℃ by a second heater, and sending the solution part back to the generator through a circulating liquid inlet of the generator;
the pressure in the generator is 0.3-0.6 Mpa, and the temperature in the kettle liquid section and the reaction section of the generator is 80-90 ℃.
The beneficial effects of the invention are as follows:
firstly, the dilute nitric acid is divided into two parts, one part directly reacts with sodium nitrite, and the other part adopts cold feeding to control the temperature of gas generated by the reaction and drops into a kettle liquid section of the generator to react with unreacted sodium nitrite, so that the utilization rate of the sodium nitrite and the dilute nitric acid is high, and the nitrogen dioxide yield is high;
and secondly, one part of the solution in the kettle liquid section of the generator is heated and then returned to the generator to heat the kettle liquid section and the reaction section of the generator, so that sodium nitrite and dilute nitric acid react more thoroughly, the sodium nitrite content in a byproduct sodium nitrate product is low, and the quality requirement of an industrial grade product is met.
And thirdly, one part of the solution in the kettle liquid section of the generator is heated and then returned to the generator to heat the kettle liquid section and the reaction section of the generator, so that nitric oxide and nitrogen dioxide dissolved in the kettle liquid are flashed off, and the yield of the nitrogen dioxide is improved.
Fourthly, oxidizing the nitric oxide and the nitrogen dioxide from the generator through an oxidation system, so that the nitric oxide content in the nitrogen dioxide product is low; the dilute nitric acid cold feed is used for removing liquid from the gas, and the gas is matched with a subsequent separator for removing liquid, so that the acid mist content in the gas is low, and the obtained nitrogen dioxide is low in acid mist content.
Drawings
FIG. 1 is a flow chart of the present invention;
fig. 2 is a partial enlarged view at a of fig. 1.
In the figure, a sodium nitrite feeding tank 1, a sodium nitrite liquid outlet pipeline 1A, a dilute nitric acid feeding tank 2, a nitric acid liquid outlet main pipeline 2A, a nitric acid liquid outlet branch pipeline 2C, a nitric acid liquid outlet branch pipeline 2B, a sodium nitrite feeding pump 3, a nitric acid feeding pump 4, a heater I5, a mixer 6, a generator 7, a kettle liquid section 7A, a reaction section 7B, a liquid removing section 7C, a liquid removing filler layer 7D, a reaction liquid outlet main pipeline 7E, a reaction liquid outlet branch pipeline 7F, a reaction liquid outlet branch pipeline 7G, a separator 8, a converter 9, a mixed liquid conveying pipeline 9A, a gasifier 10, a buffer tank 11, an oxygen gas inlet pipeline 12, a heater II 13, a condensate main pipeline 14A, a condensate branch pipeline 14B, a condensate branch pipeline 14C, a condensate branch pipeline III 14D and a condensate branch pipeline IV 14E.
Detailed Description
The invention is further illustrated in the following figures and examples, in which:
the nitrogen dioxide preparation device, as shown in figure 1, comprises a sodium nitrite feeding tank 1 and a heater I5; a dilute nitric acid feed tank 2, a generator 7, a mixer 6, a separator 8 and an oxidation system; the generator 7 vertically comprises a kettle liquid section 7A at the bottom, a reaction section 7B at the middle part and a liquid removal section 7C at the upper part; the generator 7 is provided with a mixing feed inlet, a gas outlet, a liquid outlet, a cold feed inlet, a circulating liquid inlet and a condensate inlet which are communicated with the inner cavity of the generator. And the reaction section 7B with a mixed feed inlet positioned in the middle part is used for introducing mixed liquid of dilute nitric acid and sodium nitrite into the generator 7. The gas outlet is positioned at the top end of the generator 7 and is used for outputting gas generated by the reaction of dilute nitric acid and sodium nitrite. The liquid outlet is positioned at the bottom end of the generator 7 and is used for outputting the solution which is remained in the kettle liquid section 7A after the reaction of the dilute nitric acid and the sodium nitrite. The cold feed inlet is located above the liquid removal section 7C of the generator 7 for introducing dilute nitric acid. The circulating liquid inlet is positioned at the lower part of the reaction section 7B and is used for introducing the heated circulating liquid. The condensate inlet is positioned on the side wall of the kettle liquid section 7A and is used for returning condensate to the kettle liquid section 7A.
The liquid outlet of the sodium nitrite feeding tank 1 is communicated with the liquid inlet of the heater I5, and the liquid outlet of the heater I5 is communicated with the liquid inlet of the mixer 6; the liquid outlet of the dilute nitric acid feeding tank 2 is communicated with the main nitric acid liquid outlet path 2A, then communicated with the generator 7 through the first nitric acid liquid outlet branch path 2C, and then converged with the sodium nitrite liquid outlet pipeline 1A through the second nitric acid liquid outlet branch path 2B, and then communicated with the liquid inlet of the mixer 6; the liquid outlet of the mixer 6 is communicated with a reaction section 7B in the middle of the generator 7; the gas outlet at the top of the generator 7 is communicated with the gas inlet of the separator 8; the gas outlet of the separator 8 is communicated with an oxidation system; the liquid outlet at the bottom end of the generator 7 is branched through the main liquid outlet path 7E of the reaction liquid, is communicated with the generator 7 through the first liquid outlet branch path 7F of the reaction liquid, outputs a product through the second liquid outlet branch path 7G of the reaction liquid, and is provided with the second heater 13 on the first liquid outlet branch path 7F of the reaction liquid.
The nitrogen dioxide preparation device disclosed by the invention is characterized in that sodium nitrite aqueous solution prepared according to set concentration is sent into a sodium nitrite feeding tank 1, pumped out by a sodium nitrite feeding pump 3, sent into a heater I5 through a sodium nitrite liquid outlet pipeline 1A and heated to 80-95 ℃; dilute nitric acid is sent into a dilute nitric acid feeding tank 2, pumped by a nitric acid feeding pump 4 and divided into two parts, wherein one part is mixed with heated sodium nitrate solution through a nitric acid liquid outlet branch II 2B and then sent into a reaction section 7B in the middle of a generator 7, nitric acid and nitrous acid react in the generator 7 to generate sodium nitrate, nitric oxide, nitrogen dioxide and water, the process is endothermic reaction, and the reaction needs heating.
According to the invention, the solution in the generator 7 is pumped out, and a part of the solution is heated to about 95 ℃ through the second heater 13 and then is returned to the middle lower part of the reaction section 7B of the generator 7 through the first reaction liquid outlet branch 7F, so that heat is provided for the generator 7, the temperature of the reaction section 7B of the generator 7 and below is maintained at 85-90 ℃, and enough heat is provided for endothermic reaction.
The higher the temperature of the materials below the mixed feed inlet of the generator 7 and inside the generator 7, the more beneficial the generated nitric oxide and nitrogen dioxide gas overflows from the solution and flows upwards, and finally flows out of the gas outlet at the top of the generator 7. However, when the temperature is high, the water and sodium nitrate liquid entrained in the nitric oxide and nitrogen dioxide gas are relatively large, so that the quality of the nitric oxide is affected, and in addition, the nitrogen oxide gas pipeline and equipment are easily blocked due to the introduction of nitrate in winter. According to the invention, one of two dilute nitric acids is fed into the generator 7 through the nitric acid liquid outlet branch 2C from a cold feed port, which is called cold feed, and is used for controlling the temperature at the top of the generator 7, the dilute nitric acid is used for flushing nitric oxide gas overflowed from the solution, sodium nitrate carried in the gas is flushed back into the generator 7, and meanwhile, the gas is cooled, the temperature of the gas is cooled to 50-70 ℃, and the brought amount of saturated water is reduced. The gas after liquid removal flows out from a gas outlet at the top of the generator 7 and then enters the separator 8 to further remove liquid in the gas, and the mixed gas after liquid removal is sent to an oxidation system. The dilute nitric acid for cooling falls to a kettle liquid section 7A of the generator 7 under the action of gravity, and the dilute nitric acid further reacts with sodium nitrite which is not thoroughly reacted in the kettle liquid section 7A to generate sodium nitrate, so that the content of sodium nitrite in the solution obtained in the kettle liquid section 7A is obviously reduced.
The sodium nitrate aqueous solution generated in the generator 7 flows downwards into a kettle liquid section 7A at the bottom of the generator 7, is pumped out from the bottom through a reaction circulating pump, and is used for controlling the temperature of the kettle liquid section 7A of the generator 7 except for one part of circulating, and the other part of circulating is used as byproduct solution prepared by nitrogen dioxide, and is sent out of a device after the liquid level of the generator 7 is regulated, and industrial sodium nitrate products are obtained through evaporation crystallization, centrifugal filtration, drying and packaging.
According to the invention, the solution pumped out of the generator 7 is heated by the heater II 13 and then returned to the generator 7 through the first reaction liquid outlet branch 7F from the circulating liquid inlet, firstly, heat is provided for materials in the generator 7, the reaction temperature in the generator 7 is controlled within the range of 85-95 ℃, and the smooth progress of the reaction is ensured; and secondly, through circulation, nitric oxide and nitrogen dioxide dissolved in the solution are flashed off, and unreacted dilute nitric acid and sodium nitrite react more thoroughly.
Because nitrous acid belongs to a carcinogen, the sodium nitrite content in sodium nitrate products is strictly controlled, and in order to ensure that the sodium nitrite content in the sent sodium nitrate solution does not exceed the standard, excessive nitric acid is added in production, so that the sodium nitrite is thoroughly reacted. In the traditional nitrogen oxide generation system, excessive nitric acid is added into the upper middle reaction section of the generator, or dilute nitric acid removed from nitrogen oxide gas is condensed and sent into the upper middle reaction section of the generator to directly participate in the reaction, but the effect is not ideal, and the sodium nitrite content of the product at the generated position is still higher. According to the invention, dilute nitric acid is introduced into the upper part of the generator 7 in a cold feeding mode, and flows into the bottom of the generator 7, and the temperature of the kettle liquid section 7A at the bottom of the generator 7 is increased to enable the dilute nitric acid to react with sodium nitrite which is not thoroughly reacted, so that the sodium nitrite content of a product at the generation position is obviously reduced.
In order to facilitate the reaction of the raw materials, it is preferable that the mixing feed inlet of the generator 7 is located above the circulating liquid inlet of the generator 7 in the vertical direction. Since the solution portion extracted from the generator 7 is returned to the generator 7 as a circulating liquid from the circulating liquid inlet of the generator 7, the circulating liquid inlet of the generator 7 is located below the mixing feed inlet, and the reaction raw materials are not diluted by the return of the circulating liquid, which is advantageous for the raw material reaction. Moreover, the cycle of mixing the circulating liquid into the existing solution in the generator 7 is short, which is more beneficial to flash evaporation and release of the nitric oxide and nitrogen dioxide dissolved in the solution.
The liquid removing section 7C of the generator 7 is provided with a liquid removing packing layer 7D, and the liquid removing packing layer 7D is positioned at a section below the cold feed inlet and above the hot feed, and the section of the packing material mainly intercepts and removes dilute nitric acid which is carried in the nitrogen oxide gas and comprises the cold feed and sodium nitrate and sodium nitrite solution which are not washed by the dilute nitric acid.
The nitrogen oxide obtained from the generator 7 is a mixed gas of nitric oxide and nitrogen dioxide, the volume of the two gases is half of that of the mixed gas, and the mixed gas is sent into the separator 8 to remove the carried trace nitric acid liquid and then flows out from a gas outlet at the top of the separator 8. The separator 8 is a coalesced liquid separator. The oxidation system is used for converting the mixed gas into nitrogen dioxide. In the present invention, the oxidation system comprises a reformer 9 and a gasifier 10. The lateral wall of converter 9 bottom is provided with the gas entry that is used for letting in nitrogen oxide gas, and the top is provided with the liquid outlet that is used for nitrogen dioxide and the mixed liquid outflow of dinitrogen tetroxide, and the bottom is provided with the oxygen entry that is used for letting in oxygen. The converter 9 is provided with an oxygen inlet pipe 12, and the oxygen inlet pipe 12 is connected to an oxygen inlet. The bottom end of the gasifier 10 is provided with a liquid inlet into which the mixed liquid of nitrogen dioxide and dinitrogen tetroxide flows, and the top end is provided with a gas outlet for flowing out nitrogen dioxide gas. The gas inlet of the converter 9 is communicated with the gas outlet of the separator 8; the liquid inlet of the gasifier 10 is communicated with the liquid outlet of the converter 9 through a mixed liquid conveying pipeline 9A.
The mixed gas of nitric oxide and nitrogen dioxide is discharged from a gas outlet at the top of the separator 8 after the carried trace nitric acid liquid is removed by the separator 8, and enters the converter 9 from a gas inlet at the bottom of the converter 9. The metered oxygen is introduced into the reformer 9 from an oxygen inlet at the bottom end of the reformer 9 via an oxygen introduction line 12. After the oxygen enters the converter 9, the nitric oxide therein reacts with the oxygen and is converted into nitrogen dioxide, the conversion reaction is exothermic, and the released heat is cooled by low-temperature water. After the conversion is finished, the materials in the converter 9 are mixed liquid of nitrogen dioxide and dinitrogen tetroxide. The mixed liquid flows out from the liquid outlet at the top of the converter 9, the mixed liquid of nitrogen dioxide and dinitrogen tetroxide can be pumped out from the liquid outlet at the top through a pump, and is conveyed to the gasifier 10 through a mixed liquid conveying pipeline 9A, and is heated and gasified into nitrogen dioxide gas through steam in the gasifier 10.
The gas outlet of the gasifier 10 is connected to a buffer tank 11. The vaporized nitrogen dioxide gas flows in from the gas outlet at the top of the vaporizer 10, is sent to the gas buffer tank 11, is buffered, and is sent out to the device after pressure adjustment, and is sent to the usage unit.
If the gas contains a small amount or a trace amount of water, nitric acid is generated with nitrogen dioxide to be condensed, and in order to discharge nitric acid condensate in the system, a condensate return channel is preferably arranged, wherein the condensate return channel comprises a condensate branch pipe I14B, a condensate branch pipe II 14C, a condensate branch pipe III 14D, a condensate branch pipe IV 14E and a condensate main pipe 14A connected with a condensate inlet of a kettle section 7A of the generator 7; the first condensate branch pipe 14B is connected to a bottom liquid outlet of the separator 8, and the other end of the first condensate branch pipe is connected to the condensate main pipe 14A; the second condensate branch pipe 14C is connected with one end of the oxygen inlet pipeline 12 adjacent to the converter 9, and the other end is connected with the condensate main pipe 14A; the third condensate branch pipe 14D is connected to one end of the mixed liquor conveying pipeline 9A adjacent to the gasifier 10, and the other end is connected to the condensate main pipe 14A; the fourth condensate branch pipe 14E is connected to a liquid outlet at the bottom of the buffer tank 11, and the other end is connected to the condensate main pipe 14A.
The nitric acid condensate is input into the kettle liquid section 7A of the generator 7 through the condensate main pipe 14A, and can further react with unreacted sodium nitrite, so that the content of sodium nitrite in the product is further improved and reduced.
Of course, the nitric acid condensate may be fed to the dilute nitric acid feed tank 2 for recovery in addition to the tank section 7A of the generator 7.
The above embodiment has been described as requiring pumping of dilute nitric acid and sodium nitrite, so the nitric acid feed pump 4 is provided on the nitric acid outlet main path 2A of the dilute nitric acid feed tank 2; the sodium nitrite liquid pipeline 1A of the sodium nitrite feeding tank 1 is provided with a sodium nitrite feeding pump 3.
In the concrete production, the reaction condition of sodium nitrite and nitric acid is that the pressure is 0.3-0.6 MPa, and the reaction temperature is 60-90 ℃; reaction conditions of nitric oxide and oxygen: the pressure is 0.3-0.5 MPa, and the reaction temperature is 0-20 ℃.
Example 1: the nitrogen dioxide preparation device disclosed by the invention is used for preparing nitrogen dioxide, the nitrogen dioxide productivity scale of the device is 2000 tons/year, the running time of the nitrogen dioxide preparation device is 7200 hours/year, and the industrial sodium nitrite consumption is about 3000 tons/year; industrial grade 50% nitric acid consumption is about 4600 tons/year; industrial oxygen consumption is about 262.5 tons/year. The mass percentage of oxygen in the produced nitrogen dioxide product gas is lower than 1.0 percent, and the mass percentage of nitric acid in the nitrogen dioxide product gas is lower than 0.01 percent. The nitrogen dioxide product has good quality, the content exceeds 99 percent, and the content of nitric oxide and acid mist is low.
Claims (6)
1. The nitrogen dioxide preparation device is characterized in that: comprises a sodium nitrite feeding tank (1) and a first heater (5); a dilute nitric acid feed tank (2), a generator (7), a mixer (6), a separator (8) and an oxidation system;
the generator (7) vertically comprises a kettle liquid section (7A) at the bottom, a reaction section (7B) at the middle part and a liquid removal section (7C) at the upper part;
the liquid outlet of the sodium nitrite feeding tank (1) is communicated with the liquid inlet of the first heater (5), and the liquid outlet of the first heater (5) is communicated with the liquid inlet of the mixer (6);
the liquid outlet of the dilute nitric acid feeding tank (2) is communicated with the nitric acid liquid outlet main circuit (2A), and then is communicated with a cold feed inlet positioned above the liquid removing section (7C) on the generator (7) through a nitric acid liquid outlet branch circuit I (2B), nitric acid is fed into the generator (7), and falls to a kettle liquid section (7A) of the generator (7) under the action of gravity, and is communicated to a liquid inlet of the mixer (6) after being converged with a sodium nitrite liquid outlet pipeline (1A) through a nitric acid liquid outlet branch circuit II (2C);
the liquid outlet of the mixer (6) is communicated with the mixed feed inlet of the reaction section (7B) in the middle of the generator (7);
the top gas outlet of the generator (7) is communicated with the gas inlet of the separator (8); the gas outlet of the separator (8) is communicated with an oxidation system;
the bottom liquid outlet of the generator (7) is branched through a reaction liquid outlet main path (7E), is communicated with the circulating liquid inlet of the generator (7) through a reaction liquid outlet branch path I (7F), outputs a product through a reaction liquid outlet branch path II (7G), and is provided with a heater II (13) on the reaction liquid outlet branch path I (7F);
feeding the sodium nitrite solution into a heater I (5) to heat to 80-95 ℃;
dividing dilute nitric acid into two parts, wherein one part is sent to the upper part of a liquid removing section (7C) of the generator (7) through a nitric acid liquid outlet branch I (2B), and the other part is sent to a reaction section (7B) of the generator (7) through a nitric acid liquid outlet branch II (2C) and a sodium nitrite solution sent by a heater I (5) after being converged and then sent to a mixer (6) together for mixing;
the solution part of the kettle liquid section (7A) of the generator (7) is pumped out, heated to 80-95 ℃ by a second heater (13) and then returned to the generator (7) through a circulating liquid inlet of the generator (7);
the pressure in the generator (7) is 0.3-0.6 Mpa, and the temperature in the kettle liquid section (7A) and the reaction section (7B) of the generator (7) is 80-90 ℃.
2. The nitrogen dioxide production apparatus of claim 1, wherein: the mixing feed inlet of the generator (7) is vertically above the circulating liquid inlet of the generator (7).
3. The nitrogen dioxide production apparatus according to claim 1 or 2, wherein: the oxidation system comprises a converter (9) and a gasifier (10); an oxygen inlet pipeline (12) is arranged on the converter (9), and a gas inlet of the converter (9) is communicated with a gas outlet of the separator (8); the liquid inlet of the gasifier (10) is communicated with the liquid outlet of the converter (9) through a mixed liquid conveying pipeline (9A).
4. A nitrogen dioxide production apparatus as claimed in claim 3, wherein: the gas outlet of the gasifier (10) is communicated with a buffer tank (11).
5. The nitrogen dioxide production apparatus as claimed in claim 4, wherein: the device is provided with a condensate return channel, and the condensate return channel comprises a condensate branch pipe I (14B), a condensate branch pipe II (14C), a condensate branch pipe III (14D), a condensate branch pipe IV (14E) and a condensate main pipe (14A) connected with a condensate inlet of a kettle liquid section (7A) of the generator (7);
the first condensate branch pipe (14B) is connected with a bottom liquid outlet of the separator (8), and the other end of the first condensate branch pipe is connected with a condensate main pipe (14A);
the second condensate branch pipe (14C) is connected to one end of the oxygen inlet pipeline (12) adjacent to the converter (9), and the other end of the second condensate branch pipe is connected to the condensate main pipe (14A);
the condensate branch pipe III (14D) is connected to one end of the mixed liquor conveying pipeline (9A) adjacent to the gasifier (10), and the other end is connected to the condensate main pipe (14A);
and the fourth condensate branch pipe (14E) is connected to a liquid outlet at the bottom of the buffer tank (11), and the other end of the fourth condensate branch pipe is connected to the condensate main pipe (14A).
6. The nitrogen dioxide production apparatus according to claim 1 or 2, wherein: a nitric acid feeding pump (4) is arranged on a nitric acid liquid outlet main path (2A) of the dilute nitric acid feeding tank (2);
the sodium nitrite liquid outlet pipeline (1A) of the sodium nitrite feeding tank (1) is provided with a sodium nitrite feeding pump (3).
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