CN115784179A - Process for co-producing nitric acid with various concentrations through super-azeotropic rectification - Google Patents
Process for co-producing nitric acid with various concentrations through super-azeotropic rectification Download PDFInfo
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- CN115784179A CN115784179A CN202211438336.7A CN202211438336A CN115784179A CN 115784179 A CN115784179 A CN 115784179A CN 202211438336 A CN202211438336 A CN 202211438336A CN 115784179 A CN115784179 A CN 115784179A
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- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 title claims abstract description 139
- 229910017604 nitric acid Inorganic materials 0.000 title claims abstract description 139
- 238000000034 method Methods 0.000 title claims abstract description 50
- 239000002253 acid Substances 0.000 claims abstract description 155
- 238000010521 absorption reaction Methods 0.000 claims abstract description 54
- 230000003647 oxidation Effects 0.000 claims abstract description 11
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 11
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 100
- 239000007789 gas Substances 0.000 claims description 80
- 238000004061 bleaching Methods 0.000 claims description 39
- 229910021529 ammonia Inorganic materials 0.000 claims description 34
- 238000006864 oxidative decomposition reaction Methods 0.000 claims description 27
- 238000003860 storage Methods 0.000 claims description 20
- 239000007788 liquid Substances 0.000 claims description 18
- 238000006243 chemical reaction Methods 0.000 claims description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 239000000203 mixture Substances 0.000 claims description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 6
- 239000000498 cooling water Substances 0.000 claims description 6
- 239000001301 oxygen Substances 0.000 claims description 6
- 229910052760 oxygen Inorganic materials 0.000 claims description 6
- 238000000354 decomposition reaction Methods 0.000 claims description 4
- 238000005086 pumping Methods 0.000 claims description 4
- 238000004064 recycling Methods 0.000 claims description 4
- 239000002918 waste heat Substances 0.000 claims description 4
- 239000003054 catalyst Substances 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims description 3
- 238000009826 distribution Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- PXXKQOPKNFECSZ-UHFFFAOYSA-N platinum rhodium Chemical compound [Rh].[Pt] PXXKQOPKNFECSZ-UHFFFAOYSA-N 0.000 claims description 3
- 239000002994 raw material Substances 0.000 claims description 3
- 230000008016 vaporization Effects 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 14
- 238000000605 extraction Methods 0.000 abstract description 5
- 238000005265 energy consumption Methods 0.000 abstract 1
- 230000001360 synchronised effect Effects 0.000 abstract 1
- YIXJRHPUWRPCBB-UHFFFAOYSA-N magnesium nitrate Chemical compound [Mg+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O YIXJRHPUWRPCBB-UHFFFAOYSA-N 0.000 description 22
- 229910002056 binary alloy Inorganic materials 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 238000012856 packing Methods 0.000 description 4
- 238000010533 azeotropic distillation Methods 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
- Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
Abstract
A process for co-producing nitric acid with various concentrations by super-azeotropic rectification comprises an oxidation process, an absorption process and a rectification process. The flow of the oxidation procedure is consistent with that of the existing dilute nitric acid production, the absorption procedure NO mainly adopts dilute nitric acid oxidation, and a super-azeotropic acid absorption process is adopted during absorption, so that compared with the traditional process, the process can enable the extraction concentration to reach about 80%. The process for co-producing nitric acid with various concentrations by super-azeotropic rectification provided by the invention can realize synchronous completion of production of dilute nitric acid and concentrated nitric acid in the same set of device, the yield of the dilute nitric acid and the yield of the concentrated nitric acid can be adjusted and controlled, and meanwhile, the process has the advantages of low device investment, low energy consumption per ton of nitric acid, low production cost and the like.
Description
Technical Field
The invention relates to a process for coproducing nitric acid with various concentrations by super-azeotropic distillation.
Background
The magnesium nitrate method for preparing dilute nitric acid is the existing mature technology, but only dilute nitric acid or concentrated nitric acid with single concentration can be prepared, for production enterprises, nitric acid products with various concentrations including concentrated nitric acid are often needed, if concentrated nitric acid or nitric acid with several different concentrations needs to be synchronously produced, several different production lines are needed, and the mode is too high in cost and is not suitable for large-scale implementation.
Disclosure of Invention
The invention aims to solve the technical problem of providing a process for co-producing nitric acid with various concentrations by super-azeotropic distillation, which can simultaneously produce nitric acid products with different concentrations on one production line and can adjust the yield of dilute nitric acid and concentrated nitric acid according to market demands.
In order to solve the technical problem, the invention provides a process for coproducing nitric acid with various concentrations by using super-azeotropic rectification, which comprises the following steps:
(1) Storing raw material liquid ammonia from an ammonia storage in a liquid ammonia intermediate tank, passing through a liquid ammonia filter under the action of a liquid ammonia pump, sending the filtered liquid ammonia to a liquid ammonia evaporator to evaporate into gaseous ammonia, sending the obtained gaseous ammonia into an ammonia-air mixer through the gas ammonia filter, and using low-temperature cooling water generated by the liquid ammonia evaporator as a heat source for vaporizing the liquid ammonia after heat exchange is carried out on the middle part and the upper part of a sub-azeotropic acid absorption tower; air sequentially passes through an air filter and an air dehumidifier, then enters an air compressor to be pressurized to 0.45 MPa, passes through a first gas heat exchanger, enters an ammonia-air mixer to be mixed with gas ammonia, then passes through an ammonia-air filter, enters an ammonia oxidation furnace and a waste heat boiler, 96.5 percent of ammonia reacts with oxygen in the air to generate NO, and 3.5 percent of ammonia reacts with oxygen in the air to generate N under the action of a platinum-rhodium catalyst in the ammonia oxidation furnace 2 And H 2 O, the specific reaction formula is as follows:
4 NH 3 + 5 O 2 = 4 NO + 6 H 2 O ， △ = -906 kJ
4 NH 3 + 3 O 2 = 6 H 2 O + 2 N 2 ，△ = -1267.3 kJ
(2) The temperature of a product discharged from the ammoxidation furnace is 820 to 850 ℃, the product sequentially passes through a high-temperature gas-gas heat exchanger, an economizer and a quick cooler, the gas is cooled to 49 ℃, water generated by the reaction is condensed to form condensed acid, and then the condensed acid is separated by a first gas-liquid separator and then is led into a condensed acid bleaching tower; NO dissolved in condensed acid in a condensed acid bleaching tower 2 The secondary air sent to the tower bottom is stripped, the stripping gas is merged with the gas at the outlet of the oxidative decomposition tower and enters NO X A compressor section; condensed acid bleaching42-45% of condensed acid in the tower enters a dilute acid tank, wherein a part of the condensed acid enters a sub-azeotropic acid absorption tower through a dilute acid pump for recycling, and the rest of the condensed acid is sent out of the system;
(3) Heating the gas separated from the first gas-liquid separator by a gas heat exchanger, cooling by a first water cooler, controlling the temperature to be 160-220 ℃, allowing the gas to enter an oxidative decomposition tower, delivering dilute nitric acid with the mass fraction of 55-60% from a sub-azeotropic acid absorption tower to the top of the oxidative decomposition tower, contacting the gas and the liquid in the oxidative decomposition tower to generate an endothermic decomposition reaction of the nitric acid, wherein the reaction formula is as follows:
NO + 2 HNO 3 = 3 NO 2 + H 2 O ， △H = 73.65 kJ
(4) After the oxidative decomposition reaction, the nitric acid with the mass fraction reduced to 25% is discharged from the oxidative decomposition tower, enters a sub-azeotropic acid absorption tower through a liquid-liquid heat exchanger and a first acid pump, and the prepared nitric acid with the mass fraction of 55% -60% flows into an acid storage tank after passing through a sub-azeotropic acid bleaching tower, and is discharged out of the system through a fourth acid pump; the other part of the nitric acid exchanges heat with the outlet of the oxidative decomposition tower by mass fraction of 25% and then is recycled to the oxidative decomposition tower after the liquid-liquid heat exchanger, and the main reaction in the sub-azeotropic acid absorption tower is as follows:
2 NO + O 2 = 2 NO 2 ， △H = -122.58 kJ
3 NO 2 + H 2 O = 2 HNO 2 + NO ， △H =-136.2 kJ
the reaction is carried out under 1.10MPa, a 3-layer coil cooler is arranged in a sub-azeotropic acid absorption tower, the upper 2 layers are cooled by low-temperature cooling water in the step (1), the lower part is cooled by circulating water, the temperature at the top of the tower is controlled to be 18 ℃, the volume fraction of NO is reduced to the value that NO is reduced after the tail gas discharged from the tower is treated by a second gas heat exchanger, a high-temperature gas heat exchanger and an ammonia reduction tail gas treatment device<25×10- 6 Then the mixture enters a tail gas turbine to be recycled, and finally the mixture is discharged to the atmosphere through an exhaust funnel;
(5) Rich in NO coming out from the top of the oxidative decomposition column 2 The gas and NO-containing gas from condensed acid bleaching tower, sub-azeotropic acid bleaching tower and strong acid bleaching tower 2 Is mixed with the secondary air before entering NO X The compressor is compressed to 1.10MPa and then goes throughCooling the two gas heat exchangers and the second water cooler, and delivering the cooled gas to a super-azeotropic acid absorption tower, wherein NO in the gas is in the super-azeotropic acid absorption tower 2 The residual gas is sent to a sub-azeotropic acid absorption tower for absorption;
(6) 70% of nitric acid mass fraction coming out of the bottom of the vacuum rectification tower enters the top of a super-azeotropic acid absorption tower through a heat exchanger and a strong acid pump, NO in gas in the absorption tower is absorbed by the solution and the solution reacts with the NO to generate nitric acid:
4 NO 2 + O 2 + 2 H 2 O = 4 HNO 3 ， △H = -397.8 kJ
(7) The mass fraction of the nitric acid leaving the bottom of the super-azeotropic acid absorption tower is about 80 percent, the nitric acid enters a strong acid bleaching tower after being decompressed to 0.45 MPa, and NO is removed in the tower by secondary air x Then, decompressing the nitric acid with the mass fraction of 80%, and then entering a vacuum rectifying tower through a heat exchanger;
(8) When the concentrated nitric acid is not produced, the super-azeotropic acid absorption tower can produce the nitric acid with the mass fraction of 68 percent, the nitric acid enters an acid storage tank after being bleached by a strong acid bleaching tower, and finally the nitric acid is pumped out of the system by a second acid pump;
(9) Taking out the concentrated nitric acid vapor with the mass fraction of 99% from the top of the vacuum rectifying tower, allowing the concentrated nitric acid vapor to enter a second gas-liquid separator through a concentrated nitric acid bleaching tower and a concentrated nitric acid condenser, pumping away NO carried by non-condensable gas by a vacuum system, separating condensed concentrated nitric acid solution with the concentration of 99%, allowing one stream of the condensed concentrated nitric acid solution to enter a distribution acid seal, allowing the other stream of the condensed nitric acid solution to enter the vacuum rectifying tower, allowing the other stream of the condensed nitric acid solution to enter the concentrated nitric acid bleaching tower, bleaching, allowing the bleached concentrated nitric acid solution to enter a concentrated nitric acid storage tank of a product through a finished product acid cooler, and finally pumping the product out of the system through a third acid pump.
At HNO 3 -H 2 Only 1 azeotropic point appears in an O binary system, and the mass fraction of nitric acid at the azeotropic point is 68.4 percent when the pressure is 101.3 kPa; the azeotropic point rises and falls along with the increase and decrease of the pressure, but the content of the nitric acid at the azeotropic point is almost unchanged; the region after passing the azeotropic point shows no further 2 nd azeotropic point. So theoretically, dilute nitric acid with a content of over the azeotropic point (68.4%) can completely distill off concentrated nitric acid. The theory of rectifying super-azeotropic acid to prepare concentrated nitric acid is proved in industrial production, such as magnesium nitrate process to prepare concentrated nitric acid, the rectifying section isHNO 3 -H 2 The production process of the O binary system, in which the feed composition exceeds the azeotropic point (68.4%), produces qualified concentrated nitric acid, is just the verification of the theory, so that the rectification of the super-azeotropic acid to prepare the concentrated nitric acid is feasible from the theory to practice.
The invention has the advantages that:
the prior magnesium nitrate method for preparing the concentrated nitric acid is a two-step acid forming process, while the super-azeotropic acid rectification method for preparing the concentrated nitric acid is a one-step acid forming process, the process method enlarges the production of the concentrated nitric acid, and simultaneously can adjust the output of the dilute nitric acid and the concentrated nitric acid according to the market requirement: after the feeding amount of the middle-control rectifying tower is reduced, dilute nitric acid with corresponding mass can be respectively extracted from a condensed acid storage tank or a sub-azeotropic acid storage tank or a super-azeotropic acid storage tank, meanwhile, the extraction of products with mass fractions of 40% -45%, 55% -60% and 75% -80% is realized, 68% of super-azeotropic acid can be extracted after the feeding of the vacuum rectifying tower is stopped, and the combined production of the dilute nitric acid and the concentrated nitric acid is realized without stopping the whole system.
In the invention, the sub-azeotropic acid with the concentration of 55-60 percent is used for oxidizing NO, so that on one hand, the unoxidized NO is oxidized to generate NO 2 On the other hand, the sub-azeotropic acid is reduced to NO 2 Further increases NO to be absorbed in the super azeotropic absorption tower 2 Balancing partial pressure in favor of NO 2 Absorption, and 75-80% of formation.
Compared with the traditional double-pressurization dilute nitric acid synthesis re-extraction rectification process, the dilute nitric acid synthesized in the system absorption process is super-azeotropic acid, so that the rectification process can be directly rectified without an extractant. Thus compared with the traditional method: (1) the method directly saves the cyclic working procedure of evaporating and concentrating the extractant (magnesium nitrate), does not need an evaporator and an intercooler any more, and can save medium-pressure steam by about 15.5t/h. (2) The rectification operation does not need an extractant magnesium nitrate any more, so that the production capacity of a single rectifying tower is greatly improved, for example, 15 ten thousand tons, the super-azeotropic rectification method only needs 3 phi 1500 regular packing towers, the magnesium nitrate method only needs 9 phi 1000 regular packing towers, the medium-pressure steam consumption can be reduced to 6 to 7t/h from the traditional 14.5t/h, and 9t/h of the steam produced by the whole system can completely meet the rectification requirement. The process of the invention can save a large amount of equipment pipeline investment and machine material consumption.
Drawings
FIG. 1 is a schematic flow diagram of the present invention.
In the figure: 1. liquid ammonia intermediate tank 2, liquid ammonia pump 3, liquid ammonia filter 4.1# liquid ammonia evaporator 5.2# liquid ammonia evaporator 6, gas ammonia filter 7, ammonia air mixer 8, air filter 9, air dehumidifier 10, steam turbine, NO X The system comprises a compressor, an air compressor and a tail gas turbine, and comprises a four-in-one unit 11, a first gas heat exchanger, 12, an ammonia air filter 13, an oxidation furnace and a waste heat boiler 14, a furnace water circulating pump 15, a steam drum 16, a high-temperature gas-gas heat exchanger 17, an economizer 18, a quick cooler 19, a first gas-liquid separator 20, a first water cooler 21, a dilute acid tank 22, a dilute acid pump 23, a bleaching air heat exchanger 24, a second gas heat exchanger 25, an ammonia reduction 26, an oxidation and decomposition tower 27, a first acid pump 28, a sub-azeotropic acid absorption tower 29, a sub-azeotropic acid bleaching tower 30, a super azeotropic acid absorption tower 31, an acid storage tank 32, a fourth acid pump 33, a second water cooler 34, a strong acid bleaching tower 35, a strong acid pump 36, a heat exchanger 37, a vacuum rectification tower 38, a heater 39, a concentrated nitric acid bleaching tower 40, a concentrated nitric acid condenser 41, a second gas-liquid separator 42, a distributing acid seal 43, a finished acid cooler 44, an acid cooler 44, a condensed acid bleaching tower 46, a second acid pump 46, a concentrated nitric acid storage tank 48, a third acid pump 49, a third acid pump, a heat exchanger 49 and a third acid pump.
Detailed Description
A process for co-producing nitric acid with various concentrations by super-azeotropic rectification comprises the following steps:
(1) Storing raw material liquid ammonia from an ammonia storage in a liquid ammonia intermediate tank, passing through a liquid ammonia filter under the action of a liquid ammonia pump, sending the filtered liquid ammonia to a liquid ammonia evaporator to be evaporated into gas ammonia, sending the obtained gas ammonia into an ammonia-air mixer through the gas ammonia filter, and using low-temperature cooling water generated by the liquid ammonia evaporator as a heat source for vaporizing the liquid ammonia after heat exchange is carried out on the middle part and the upper part of a sub-azeotropic acid absorption tower; air sequentially passes through an air filter and an air dehumidifier, then enters an air compressor to be pressurized to 0.45 MPa, passes through a first gas heat exchanger, enters an ammonia-air mixer to be mixed with gas ammonia, then passes through an ammonia-air filter, enters an ammonia oxidation furnace and a waste heat boiler, and is subjected to 96 times of action of a platinum-rhodium catalyst in the ammonia oxidation furnace.5% of ammonia reacts with oxygen in the air to produce NO,3.5% of ammonia reacts with oxygen in the air to produce N 2 And H 2 O, the specific reaction formula is as follows:
4 NH 3 + 5 O 2 = 4 NO + 6 H 2 O ， △ = -906 kJ
4 NH 3 + 3 O 2 = 6 H 2 O + 2 N 2 ，△ = -1267.3 kJ
(2) The temperature of a product discharged from the ammoxidation furnace is 820 to 850 ℃, the product sequentially passes through a high-temperature gas-gas heat exchanger, an economizer and a quick cooler, the gas is cooled to 49 ℃, water generated by the reaction is condensed to form condensed acid, and then the condensed acid is separated by a first gas-liquid separator and then is led into a condensed acid bleaching tower; NO dissolved in condensed acid in a condensed acid bleaching tower 2 The secondary air sent to the tower bottom is stripped, and the stripping gas is merged with the gas at the outlet of the oxidative decomposition tower and enters NO X A compressor section; 42-45% of condensed acid in the condensed acid bleaching tower enters a dilute acid tank, wherein a part of the condensed acid enters a sub-azeotropic acid absorption tower through a dilute acid pump for recycling, and the rest is sent out of the system;
(3) Heating the gas separated from the first gas-liquid separator by a gas heat exchanger, cooling by a first water cooler, controlling the temperature to be 160-220 ℃, allowing the gas to enter an oxidative decomposition tower, delivering dilute nitric acid with the mass fraction of 55-60% from a sub-azeotropic acid absorption tower to the top of the oxidative decomposition tower, contacting the gas and the liquid in the oxidative decomposition tower to generate an endothermic decomposition reaction of the nitric acid, wherein the reaction formula is as follows:
NO + 2 HNO 3 = 3 NO 2 + H 2 O ， △H = 73.65 kJ
(4) After the oxidative decomposition reaction, the nitric acid with the mass fraction reduced to 25% is discharged from the oxidative decomposition tower, passes through a liquid-liquid heat exchanger and a first acid pump and then enters a sub-azeotropic acid absorption tower, and a part of the prepared nitric acid with the mass fraction of 55% -60% and the part of the prepared nitric acid with the mass fraction of 55% -60% passes through a sub-azeotropic acid bleaching tower and then flows into an acid storage tank, and is discharged out of the system through a fourth acid pump; the other part of the nitric acid exchanges heat with the outlet of the oxidative decomposition tower with the mass fraction of 25 percent, and then is recycled to the oxidative decomposition tower, and the main reaction in the sub-azeotropic acid absorption tower is as follows:
2 NO + O 2 = 2 NO 2 ， △H = -122.58 kJ
3 NO 2 + H 2 O = 2 HNO 2 + NO ， △H =-136.2 kJ
the reaction is carried out under 1.10MPa, 3 layers of coil coolers are arranged in a sub-azeotropic acid absorption tower, the upper 2 layers are cooled by low-temperature cooling water in the step (1), the lower part is cooled by circulating water, the temperature at the top of the tower is controlled at 18 ℃, the volume fraction of NO is reduced to be less than that of NO after the tail gas discharged from the tower is treated by a second gas heat exchanger, a high-temperature gas heat exchanger and an ammonia reduction tail gas treatment device<25×10- 6 Then the mixture enters a tail gas turbine for recycling, and is discharged into the atmosphere after being discharged by an exhaust funnel;
(5) Rich in NO coming out of the top of the oxidative decomposition column 2 The gas and NO-containing gas from condensed acid bleaching tower, sub-azeotropic acid bleaching tower and strong acid bleaching tower 2 Is mixed with the secondary air before entering NO X The compressor is compressed to 1.10MPa, and then the gas is cooled by a second gas heat exchanger and a second water cooler and sent to a super-azeotropic acid absorption tower, and NO in the gas is in the super-azeotropic acid absorption tower 2 The residual gas is sent to a sub-azeotropic acid absorption tower for absorption;
(6) 70% of nitric acid mass fraction coming out of the bottom of the vacuum rectification tower enters the top of a super-azeotropic acid absorption tower through a heat exchanger and a strong acid pump, NO in gas in the absorption tower is absorbed by the solution and the solution reacts with the NO to generate nitric acid:
4 NO 2 + O 2 + 2 H 2 O = 4 HNO 3 ， △H = -397.8 kJ
(7) The mass fraction of the nitric acid leaving the bottom of the super azeotropic acid absorption tower is about 80 percent, the nitric acid enters a strong acid bleaching tower after being decompressed to 0.45 MPa, and NO is removed in the tower by secondary air x Then, decompressing the nitric acid with the mass fraction of 80%, and then entering a vacuum rectifying tower through a heat exchanger;
(8) When the concentrated nitric acid is not produced, the super-azeotropic acid absorption tower can produce the nitric acid with the mass fraction of 68 percent, the nitric acid enters an acid storage tank after being bleached by a strong acid bleaching tower, and finally the nitric acid is pumped out of the system by a second acid pump;
(9) The concentrated nitric acid vapor with the mass fraction of 99% is taken out from the top of the vacuum rectification tower, enters a second gas-liquid separator through a concentrated nitric acid bleaching tower and a concentrated nitric acid condenser, NO carried by non-condensable gas is pumped away by a vacuum system, condensed concentrated nitric acid solution with the concentration of 99% enters a distribution acid seal after being separated, one flow of the condensed nitric acid solution flows back to the vacuum rectification tower, the other flow of the condensed nitric acid solution enters the concentrated nitric acid bleaching tower, is bleached and then enters a product concentrated nitric acid storage tank through a finished product acid cooler, and finally is sent out of the system through a third acid pump.
Referring to fig. 1, the liquid ammonia evaporator in this embodiment adopts a double parallel structure, which is a # 1 liquid ammonia evaporator and a # 2 liquid ammonia evaporator. Steam turbine, NO in this example X The compressor, the air compressor and the tail gas turbine are a four-in-one unit.
At HNO 3 -H 2 Only 1 azeotropic point appears in an O binary system, and the mass fraction of nitric acid at the azeotropic point is 68.4 percent when the pressure is 101.3 kPa; the azeotropic point rises and falls along with the increase and decrease of the pressure, but the content of the nitric acid at the azeotropic point is almost unchanged; the region after passing the azeotropic point shows no further 2 nd azeotropic point. So theoretically, dilute nitric acid with a content exceeding the azeotropic point (68.4%) can completely distill off concentrated nitric acid. The theory of rectifying super-azeotropic acid to prepare concentrated nitric acid is proved in industrial production, such as magnesium nitrate process to prepare concentrated nitric acid, the rectifying section is HNO 3 -H 2 The production process of the O binary system, the feed composition of which exceeds the azeotropic point (68.4 percent), produces qualified concentrated nitric acid, and is verified by the theory, so that the rectification of the super-azeotropic acid to prepare the concentrated nitric acid is feasible from the theory to practice.
The invention has the advantages that:
the prior magnesium nitrate method for preparing the concentrated nitric acid is a two-step acid forming process, while the super-azeotropic acid rectification method for preparing the concentrated nitric acid is a one-step acid forming process, the process method enlarges the production of the concentrated nitric acid, and simultaneously can adjust the output of the dilute nitric acid and the concentrated nitric acid according to the market requirement: after the feeding amount of the middle-control rectifying tower is reduced, dilute nitric acid with corresponding mass can be extracted from a condensed acid storage tank or a sub-azeotropic acid storage tank or a super-azeotropic acid storage tank respectively, and meanwhile, the extraction of products with the mass fractions of 40% -45%, 55% -60% and 75% -80% is realized, and after the feeding of the vacuum rectifying tower is stopped, 68% of super-azeotropic acid can be extracted, and the combined production of the dilute nitric acid and the concentrated nitric acid is realized without stopping the whole system.
In the invention, the subazeotropic acid with the concentration of 55-60 percent is used for oxidizing NO, so that the unoxidized NO is oxidized to generate NO 2 On the other hand, the sub-azeotropic acid is reduced to NO 2 Further increases NO to be absorbed in the super azeotropic absorption tower 2 Balancing partial pressure in favor of NO 2 Absorption, and 75-80% of formation.
Compared with the traditional double-pressurization dilute nitric acid synthesis re-extraction rectification process, the dilute nitric acid synthesized in the system absorption process is super-azeotropic acid, so that the rectification process can be directly rectified without an extractant. Thus compared to conventional methods: (1) the method directly saves the cyclic working procedure of evaporating and concentrating the extractant (magnesium nitrate), does not need an evaporator and an intercooler any more, and can save medium-pressure steam by about 15.5t/h. (2) The rectification operation does not need an extractant of magnesium nitrate any more, so that the production capacity of a single tower of a rectification tower is greatly improved, for example, 15 ten thousand tons, the super-azeotropic rectification method only needs 3 phi 1500 regular packing towers, while the magnesium nitrate method needs 9 phi 1000 regular packing towers, the medium-pressure steam consumption can be reduced to 6-7 t/h from the traditional 14.5t/h, and 9t/h of the total self-produced steam can completely meet the rectification requirement. The process of the invention can save a large amount of equipment pipeline investment and machine material consumption.
Claims (1)
1. A process for co-producing nitric acid with various concentrations by super-azeotropic rectification is characterized by comprising the following steps:
(1) Storing raw material liquid ammonia from an ammonia storage in a liquid ammonia intermediate tank, passing through a liquid ammonia filter under the action of a liquid ammonia pump, sending the filtered liquid ammonia to a liquid ammonia evaporator to evaporate into gaseous ammonia, sending the obtained gaseous ammonia into an ammonia-air mixer through the gas ammonia filter, and using low-temperature cooling water generated by the liquid ammonia evaporator as a heat source for vaporizing the liquid ammonia after heat exchange is carried out on the middle part and the upper part of a sub-azeotropic acid absorption tower; air sequentially passes through an air filter and an air dehumidifier, then enters an air compressor to be pressurized to 0.45 MPa, passes through a first gas heat exchanger, then enters an ammonia-air mixer to be mixed with gas ammonia, then passes through an ammonia-air filter, then enters an ammonia oxidation furnace and a waste heat boiler, and is subjected to the action of a platinum-rhodium catalyst in the ammonia oxidation furnace96.5% of ammonia reacts with oxygen in the air to form NO,3.5% of ammonia reacts with oxygen in the air to form N 2 And H 2 O, the specific reaction formula is as follows:
4 NH 3 + 5 O 2 = 4 NO + 6 H 2 O ， △ = -906 kJ
4 NH 3 + 3 O 2 = 6 H 2 O + 2 N 2 ，△ = -1267.3 kJ
(2) The temperature of a product discharged from the ammoxidation furnace is 820 to 850 ℃, the product sequentially passes through a high-temperature gas-gas heat exchanger, an economizer and a quick cooler, the gas is cooled to 49 ℃, water generated by the reaction is condensed to form condensed acid, and then the condensed acid is separated by a first gas-liquid separator and then is led into a condensed acid bleaching tower; NO dissolved in condensed acid in a condensed acid bleaching tower 2 The secondary air sent to the tower bottom is stripped, and the stripping gas is merged with the gas at the outlet of the oxidative decomposition tower and enters NO X A compressor section; 42-45% of condensed acid in the condensed acid bleaching tower enters a dilute acid tank, wherein one part of the condensed acid enters a sub-azeotropic acid absorption tower through a dilute acid pump for recycling, and the rest is sent out of the system;
(3) Heating the gas separated from the first gas-liquid separator by a gas heat exchanger, cooling by a first water cooler, controlling the temperature to be 160-220 ℃, allowing the gas to enter an oxidative decomposition tower, delivering dilute nitric acid with the mass fraction of 55-60% from a sub-azeotropic acid absorption tower to the top of the oxidative decomposition tower, contacting the gas and the liquid in the oxidative decomposition tower to generate an endothermic decomposition reaction of the nitric acid, wherein the reaction formula is as follows:
NO + 2 HNO 3 = 3 NO 2 + H 2 O ， △H = 73.65 kJ
(4) After the oxidative decomposition reaction, the nitric acid with the mass fraction reduced to 25% is discharged from the oxidative decomposition tower, passes through a liquid-liquid heat exchanger and a first acid pump and then enters a sub-azeotropic acid absorption tower, and a part of the prepared nitric acid with the mass fraction of 55% -60% and the part of the prepared nitric acid with the mass fraction of 55% -60% passes through a sub-azeotropic acid bleaching tower and then flows into an acid storage tank, and is discharged out of the system through a fourth acid pump; the other part of the nitric acid exchanges heat with the outlet of the oxidative decomposition tower with the mass fraction of 25 percent, and then is recycled to the oxidative decomposition tower, and the main reaction in the sub-azeotropic acid absorption tower is as follows:
2 NO + O 2 = 2 NO 2 ， △H = -122.58 kJ
3 NO 2 + H 2 O = 2 HNO 2 + NO ， △H =-136.2 kJ
the reaction is carried out under 1.10MPa, a 3-layer coil cooler is arranged in a sub-azeotropic acid absorption tower, the upper 2 layers are cooled by low-temperature cooling water in the step (1), the lower part is cooled by circulating water, the temperature at the top of the tower is controlled to be 18 ℃, the volume fraction of NO is reduced to the value that NO is reduced after the tail gas discharged from the tower is treated by a second gas heat exchanger, a high-temperature gas heat exchanger and an ammonia reduction tail gas treatment device<25×10- 6 Then the mixture enters a tail gas turbine to be recycled, and finally the mixture is discharged to the atmosphere through an exhaust funnel;
(5) Rich in NO coming out from the top of the oxidative decomposition column 2 The gas and NO-containing gas from condensed acid bleaching tower, sub-azeotropic acid bleaching tower and strong acid bleaching tower 2 Is mixed with the secondary air before entering NO X The compressor is compressed to 1.10MPa, and then the gas is cooled by a second gas heat exchanger and a second water cooler and sent to a super-azeotropic acid absorption tower, and NO in the gas is in the super-azeotropic acid absorption tower 2 The residual gas is sent to a sub-azeotropic acid absorption tower for absorption;
(6) 70% of nitric acid mass fraction coming out from the bottom of the vacuum rectifying tower enters the top of the super-azeotropic acid absorption tower through a heat exchanger and a strong acid pump, NO in gas in the absorption tower is absorbed by the solution and exothermic reaction is carried out to generate nitric acid:
4 NO 2 + O 2 + 2 H 2 O = 4 HNO 3 ， △H = -397.8 kJ
(7) The mass fraction of the nitric acid leaving the bottom of the super azeotropic acid absorption tower is about 80 percent, the nitric acid enters a strong acid bleaching tower after being decompressed to 0.45 MPa, and NO is removed in the tower by secondary air x Then, decompressing the nitric acid with the mass fraction of 80%, and then entering a vacuum rectifying tower through a heat exchanger;
(8) When the concentrated nitric acid is not produced, the super-azeotropic acid absorption tower can produce the nitric acid with the mass fraction of 68 percent, the nitric acid enters an acid storage tank after being bleached by a strong acid bleaching tower, and finally the nitric acid is pumped out of the system by a second acid pump;
(9) Taking out the concentrated nitric acid vapor with the mass fraction of 99% from the top of the vacuum rectifying tower, allowing the concentrated nitric acid vapor to enter a second gas-liquid separator through a concentrated nitric acid bleaching tower and a concentrated nitric acid condenser, pumping away NO carried by non-condensable gas by a vacuum system, separating condensed concentrated nitric acid solution with the concentration of 99%, allowing one stream of the condensed concentrated nitric acid solution to enter a distribution acid seal, allowing the other stream of the condensed nitric acid solution to enter the vacuum rectifying tower, allowing the other stream of the condensed nitric acid solution to enter the concentrated nitric acid bleaching tower, bleaching, allowing the bleached concentrated nitric acid solution to enter a concentrated nitric acid storage tank of a product through a finished product acid cooler, and finally pumping the product out of the system through a third acid pump.
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| US4031187A (en) * | 1974-12-20 | 1977-06-21 | Societa' Italiana Resine S.I.R. S.P.A. | Process for the production of nitric acid |
| CN1686790A (en) * | 2005-04-18 | 2005-10-26 | 天脊煤化工集团有限公司 | Method and equipment for producing nitric acid in optional intermediate density |
| CN102838096A (en) * | 2012-09-24 | 2012-12-26 | 杭州先进富春化工有限公司 | Joint production method and production device of dilute nitric acid and concentrated nitric acid |
| CN103112835A (en) * | 2012-11-11 | 2013-05-22 | 安徽金禾实业股份有限公司 | Indirect bleaching method in concentrated nitric acid production process |
| CN103496680A (en) * | 2013-10-10 | 2014-01-08 | 中国海洋石油总公司 | Preparation method of NOx gas with ultrahigh concentration and method for producing concentrated nitric acid by using NOx gas with ultrahigh concentration |
| CN105366653A (en) * | 2014-08-25 | 2016-03-02 | 蒋小华 | Nitric acid production technology with double-pressurized method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4031187A (en) * | 1974-12-20 | 1977-06-21 | Societa' Italiana Resine S.I.R. S.P.A. | Process for the production of nitric acid |
| CN1686790A (en) * | 2005-04-18 | 2005-10-26 | 天脊煤化工集团有限公司 | Method and equipment for producing nitric acid in optional intermediate density |
| CN102838096A (en) * | 2012-09-24 | 2012-12-26 | 杭州先进富春化工有限公司 | Joint production method and production device of dilute nitric acid and concentrated nitric acid |
| CN103112835A (en) * | 2012-11-11 | 2013-05-22 | 安徽金禾实业股份有限公司 | Indirect bleaching method in concentrated nitric acid production process |
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