CN110540178A - Medium-pressure nitric acid production process and equipment - Google Patents
Medium-pressure nitric acid production process and equipment Download PDFInfo
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- CN110540178A CN110540178A CN201910849952.3A CN201910849952A CN110540178A CN 110540178 A CN110540178 A CN 110540178A CN 201910849952 A CN201910849952 A CN 201910849952A CN 110540178 A CN110540178 A CN 110540178A
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- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 title claims abstract description 47
- 229910017604 nitric acid Inorganic materials 0.000 title claims abstract description 47
- 238000004519 manufacturing process Methods 0.000 title claims description 22
- 239000007789 gas Substances 0.000 claims abstract description 123
- 238000001179 sorption measurement Methods 0.000 claims abstract description 67
- 239000002808 molecular sieve Substances 0.000 claims abstract description 66
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims abstract description 66
- 238000000034 method Methods 0.000 claims abstract description 62
- 238000010521 absorption reaction Methods 0.000 claims abstract description 55
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 47
- 230000003647 oxidation Effects 0.000 claims abstract description 44
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 43
- 230000008569 process Effects 0.000 claims abstract description 32
- 238000003795 desorption Methods 0.000 claims abstract description 26
- 238000004061 bleaching Methods 0.000 claims abstract description 24
- 239000003054 catalyst Substances 0.000 claims abstract description 20
- 230000008929 regeneration Effects 0.000 claims abstract description 17
- 238000011069 regeneration method Methods 0.000 claims abstract description 17
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 11
- 238000006243 chemical reaction Methods 0.000 claims abstract description 10
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 21
- 229910052697 platinum Inorganic materials 0.000 claims description 11
- 238000009834 vaporization Methods 0.000 claims description 11
- 230000008016 vaporization Effects 0.000 claims description 11
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- 238000011084 recovery Methods 0.000 claims description 7
- 239000007788 liquid Substances 0.000 claims description 5
- 239000002253 acid Substances 0.000 claims description 4
- 230000003197 catalytic effect Effects 0.000 claims description 4
- 238000007599 discharging Methods 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 238000000926 separation method Methods 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 2
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 abstract description 48
- 229910021529 ammonia Inorganic materials 0.000 abstract description 20
- GQPLMRYTRLFLPF-UHFFFAOYSA-N Nitrous Oxide Chemical compound [O-][N+]#N GQPLMRYTRLFLPF-UHFFFAOYSA-N 0.000 abstract description 17
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 15
- 229910052799 carbon Inorganic materials 0.000 abstract description 15
- 230000007547 defect Effects 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000010531 catalytic reduction reaction Methods 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000004035 construction material Substances 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 239000003337 fertilizer Substances 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000011112 process operation Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 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
- C01B21/24—Nitric oxide (NO)
- C01B21/26—Preparation by catalytic or non-catalytic oxidation of ammonia
-
- 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
- C01B21/24—Nitric oxide (NO)
- C01B21/26—Preparation by catalytic or non-catalytic oxidation of ammonia
- C01B21/28—Apparatus
-
- 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
- C01B21/38—Nitric acid
-
- 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
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Separation Of Gases By Adsorption (AREA)
Abstract
the invention discloses a process for producing nitric acid by a medium pressure method, which is characterized by comprising the following steps: the ammonia oxidation and absorption pressure is 0.5-0.6 MPa; enabling tail gas of the absorption tower to pass through a carbon molecular sieve Temperature Swing Adsorption (TSA) treatment device to reduce the content of nitrogen oxides in the tail gas to be less than 100mg/Nm 3; the process air of the air compressor is used as the regeneration desorption gas of the carbon molecular sieve temperature swing adsorption treatment device, and the regeneration desorption gas containing the nitrogen oxide can be returned to the oxidation reactor for reuse; adding a layer of N2O decomposition catalyst in the oxidation reactor to reduce the content of N2O to 50-100 PPM through reaction; the nitric acid bleaching tower is arranged at the bottom of the absorption tower, and the two towers are integrated, so that the process flow is shortened, and the equipment investment is reduced.
Description
Technical Field
The invention belongs to the technical field of chemical industry, relates to a medium-pressure nitric acid production process and production equipment, and particularly relates to a medium-pressure nitric acid production process and production equipment for recycling nitrogen oxides in tail gas by adopting carbon molecular sieve Temperature Swing Adsorption (TSA).
Background
Nitric acid is an important basic chemical raw material, and is widely applied to the preparation of dyes, explosives, medicines, plastics, nitrogen fertilizers and chemical reagents, and is used for metallurgy and organic synthesis. At present, the domestic and external processes for producing nitric acid by using ammonia and air include a normal pressure method, a medium pressure method, a high pressure method and a double pressure method.
the atmospheric process, i.e. the oxidation of ammonia and the absorption of nitrogen oxides, is carried out at atmospheric pressure. The method has the characteristics of simple production process and equipment, low system pressure, stable process operation, high ammonia oxidation rate, low consumption of raw materials and auxiliary materials, and no need of large-scale rotating equipment; the defects are low production strength, large equipment volume, more oxidation furnaces and absorption towers, low heat energy utilization rate, low absorption rate, low product concentration, high NOx content in tail gas and easy generation of serious pollution. The tail gas is required to be absorbed by alkali or treated by other methods, the arrangement is not compact, the occupied area is large, and more capital construction materials and investment are needed.
The medium-pressure method is characterized in that the oxidation of ammonia and the absorption of nitrogen oxides are carried out under the pressure of 0.35-0.6 MPa. The method has the characteristics that the equipment is compact, the production strength is improved, the capital investment and the special steel consumption are less, so the absorption pressure is high, the NO2 absorption rate is high, the concentration of the finished acid is high, the volume of the absorption tower is small, and the energy recovery rate is high; the defects are that the production strength is still low, ammonia is oxidized under pressurization, the oxidation rate is slightly low, the platinum loss is large, the content of NOx in tail gas is higher, and the tail gas still needs to be treated to reach the standard and be discharged.
The high pressure method, ammonia oxidation and NOx absorption are carried out under the pressure of 0.71-1.2 MPa, and the basic flow is similar to the full medium pressure method. The method has the characteristics that the pressure in the whole process is provided by an air compressor, the flow is simple, the equipment arrangement is compact, the capital investment is low, the consumption of steel is low, the production strength is high, the absorption rate is high, the product concentration is high, and the energy recovery rate is high; the disadvantages are low ammonia oxidation rate, high ammonia consumption, large platinum catalytic loading, short service cycle, large consumption and high NOx content in the tail gas, thus leading to high tail gas treatment cost and higher production cost.
the double-pressurization method is characterized in that ammonia oxidation and nitrogen oxide absorption are respectively carried out under two different pressures, the ammonia oxidation of the method adopts medium pressure (0.35-0.6 MPa), and the NOx absorption adopts high pressure (1.0-1.5 MPa). The method has the advantages of low ammonia consumption and platinum consumption, high absorption rate, high absorption system pressure, small volume, high acid concentration, high production strength, low production cost, low emission of NOx in tail gas, and reasonable comprehensive energy recovery. Therefore, the nitric acid production process is widely applied at home and abroad. But the defects of the nitric acid production process by the double-pressurization method are as follows:
1. More nitrogen oxide gas compressors and high-pressure nitrogen oxide systems are needed;
2. the emission of NOx in the tail gas is still as high as 400mg/Nm3, in order to reach the national emission index of 100mg/Nm3, an ammonia selective catalytic reduction reaction device is generally added in a tail gas system, partial ammonia is consumed, and the ammonia reacts with nitrogen oxide under the action of a catalyst to generate nitrogen, so that the emission of NOx in the tail gas reaches the standard;
3. The nitrogen oxide gas after the oxidation reactor reaction contains 1000-1500 PPM N2O, N2O is high equivalent greenhouse gas, the greenhouse effect of unit mass is 310 times of that of CO2, and the nitrogen oxide gas is a main trade item of CDM internationally.
disclosure of Invention
Aiming at the problems, the invention provides a process for producing nitric acid by a medium-pressure method, wherein the ammonia oxidation and absorption pressure is 0.5-0.6 MPa; enabling tail gas of the absorption tower to pass through a carbon molecular sieve Temperature Swing Adsorption (TSA) treatment device to reduce the content of nitrogen oxides in the tail gas to be less than 100mg/Nm 3; the process air of an air compressor is used as the regeneration desorption gas of the carbon molecular sieve temperature swing adsorption treatment device, and the regeneration desorption gas containing the nitrogen oxide can be returned to the oxidation reactor for reuse; adding a layer of N2O decomposition catalyst in the oxidation reactor to reduce the content of N2O to 50-100 PPM through reaction; the nitric acid bleaching tower is arranged at the bottom of the absorption tower, so that the two towers are integrated, the process flow is shortened, and the equipment investment is reduced.
The technical scheme adopted by the invention is as follows:
A process for producing nitric acid by a medium pressure method comprises the following process steps:
S1: mixing ammonia gas with air according to a certain ammonia-to-air ratio, and introducing the mixed gas into an oxidation reactor;
s2: carrying out catalytic oxidation reaction on the mixed gas in an oxidation reactor at the reaction temperature of 800-950 ℃ and the ammoxidation pressure of 0.5-0.6 MPa to generate primary gas containing NOx;
S3: after the primary gas is subjected to heat recovery and rapid cooling separation treatment, introducing the obtained NOx-containing secondary gas and the primary dilute nitric acid into an integrated tower, wherein the upper part of the integrated tower is an absorption tower, and the lower part of the integrated tower is a bleaching tower;
s4: introducing secondary gas into the bottom of the absorption tower, taking desalted water at the top as absorption liquid to perform two-phase countercurrent reaction with the secondary gas to generate nitric acid, introducing primary dilute nitric acid into a corresponding acid concentration tray of the absorption tower, wherein the absorption pressure is 0.5-0.6 MPa, the nitric acid falls into a bleaching tower to perform NOx removal treatment, and tail gas containing NOx is discharged from the top of the absorption tower;
S5: carrying out temperature swing adsorption treatment on the tail gas containing NOx in the step 4 by adopting a molecular sieve, absorbing heat of the purified tail gas by the heat exchanger in the step S3, recovering energy by an expansion machine, and then emptying; the regeneration gas obtained after the desorption on the molecular sieve is mixed with the mixed gas in the step S1.
Further, at least one group of molecular sieve adsorption tanks is arranged in step S5, each group including two molecular sieve adsorption tanks arranged in parallel; the two molecular sieve adsorption tanks in the group are dynamically changed between an adsorption state and a desorption state, and when one molecular sieve adsorption tank is in the adsorption state, the other molecular sieve adsorption tank is in the desorption state.
further, in step S3, a heater is connected to an inlet or an outlet of the heat exchanger at the hot side, boiler feed water is heated by the heater and then enters the steam drum, and then is heated, vaporized and superheated in the oxidation reactor through the coil pipe, and the generated superheated steam is used for recovering energy through the turbine.
Further, the mixed gas is reacted through the platinum catalyst layer to generate NOx in step S2, and N2O is decomposed through the N2O decomposition catalyst layer to generate nitrogen gas.
further, the air in step S1 comes from the air compressor, and all or part of the mechanical power of the air compressor comes from the expander in step S5.
further, the desorption gas of the molecular sieve adsorption tank in the step S5 and the desorption gas of the bleaching tower in the step S4 are both from the air compressor, and the air pressure at the outlet of the compressor is 0.35-0.6 MPa, and more preferably 0.5-0.6 MPa.
further, the molecular sieve adsorption tank adopts a carbon molecular sieve for temperature swing adsorption.
Based on the same inventive concept, the invention also provides a medium-pressure nitric acid production device, which comprises an ammonia-air mixer, an oxidation reactor, a heat exchanger, a quick cooler, an integrated tower and a molecular sieve adsorption tank which are sequentially connected; a heater for heating boiler feed water is connected to an inlet or an outlet at the hot side of the heat exchanger, a boiler feed water pipe is connected to a steam drum, a vaporization coil is connected between a water phase outlet and a gas phase inlet of the steam drum, the vaporization coil is arranged in the oxidation reactor, a gas phase outlet of the steam drum is connected with a superheating coil, the superheating coil is arranged below the vaporization coil in the oxidation reactor, and an outlet of the superheating coil is connected with a turbine; the tail gas outlet of the molecular sieve adsorption tank is connected with the cold side inlet of the heat exchanger, the cold side outlet of the heat exchanger is connected with the expander, and the regenerated gas outlet of the molecular sieve adsorption tank is connected with the ammonia-air mixer.
furthermore, the integrated tower is divided into two parts by a wire mesh, the upper part is an absorption tower, and the lower part is a bleaching tower.
And further, the device also comprises at least one air compressor, wherein a process air pipe of the air compressor is connected to the ammonia-air mixer, the bleaching tower and the molecular sieve adsorption tank, and all or part of mechanical power of the air compressor is from the turbine and the expander.
Furthermore, the tail gas outlet of the absorption tower is connected with at least one group of molecular sieve adsorption tanks, each group comprises two molecular sieve adsorption tanks which are arranged in parallel, and the states of the molecular sieve adsorption tanks are dynamically adjusted through a reversing valve.
further, a platinum catalyst layer and an N2O decomposition catalyst layer are sequentially provided in the oxidation reactor.
further, the molecular sieve adsorption tank adopts a carbon molecular sieve for temperature swing adsorption.
in summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
1. The emission content of NOx in the exhausted tail gas is less than 100mg/Nm3, the content of N2O is less than 100PPM, and the method is an environment-friendly and low-consumption nitric acid production process;
2. NOx in tail gas of the absorption tower and/or the bleaching tower returns to the oxidation reactor for reuse, an ammonia selective catalytic reduction reaction device is not needed, and the ammonia consumption ratio is low;
3. two pressure levels are not needed for oxidation and absorption, a high-pressure nitrogen oxide system is not needed, and the flow is compact;
4. The nitric acid bleaching tower and the absorption tower are combined into one, which is beneficial to saving equipment investment;
5. the carbon molecular sieve temperature swing adsorption device does not need to be provided with an inlet and outlet heat exchanger and a pressurizing fan, the flow is shortened, the equipment is reduced, and the investment cost is saved.
Drawings
the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
fig. 1 is a schematic diagram of the structural principle of the present invention.
Description of reference numerals:
1-an air compressor, 2-an expander, 3-an oxidation reactor, 4-a platinum catalyst layer, 5-N2O decomposition catalyst layer, 6-an ammonia-air mixer, 7-a heat exchanger, 8-a heater, 9-a quick cooler, 10-a pump, 11-a bleaching tower, 12-an absorption tower, 13-a molecular sieve adsorption tank, 14-an exhaust cylinder, 15-a steam drum and 16-a turbine;
in the figure, an excess line and a deficiency line represent the respective directions of the two pipelines at the intersection of the pipelines so as to prevent ambiguity.
Detailed Description
all of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.
Any feature disclosed in this specification may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.
The invention relates to a process for producing nitric acid by a medium-pressure method, wherein the ammonia oxidation and absorption pressure is 0.5-0.6 MpaG; enabling tail gas of the absorption tower to pass through a carbon molecular sieve Temperature Swing Adsorption (TSA) treatment device to reduce the content of nitrogen oxides in the tail gas to be less than 100mg/Nm 3; the process air of an air compressor is used as the regeneration desorption gas of the carbon molecular sieve temperature swing adsorption treatment device, and the regeneration desorption gas containing the nitrogen oxide can be returned to the oxidation reactor for reuse; adding a layer of N2O decomposition catalyst in the oxidation reactor to reduce the content of N2O to 50-100 PPM through reaction; the nitric acid bleaching tower is arranged at the bottom of the absorption tower, so that the two towers are integrated, the flow is shortened, and the equipment investment is reduced.
Example 1:
The embodiment specifically relates to a process for producing nitric acid by a medium-pressure method, which takes the production of 20 ten thousand tons of nitric acid annually as an example, and comprises the following process steps:
S1: compressing air to 0.5-0.6 Mpa by adopting an air compressor at the speed of 102100Nm3/h, wherein 75600Nm3/h of process air and 93300Nm3/h of ammonia gas are mixed in an ammonia-air mixer, and then introducing the mixed gas into an oxidation reactor;
s2: the mixed gas sequentially passes through a platinum catalyst layer and an N2O decomposition catalyst layer arranged in an oxidation reactor from top to bottom to carry out catalytic oxidation reaction of ammonia at the reaction temperature of 860-900 ℃ to generate primary gas containing NOx;
Wherein the mixed gas reacts to generate NOx when passing through the platinum catalyst layer, and then N2O is decomposed to generate nitrogen gas through the N2O decomposition catalyst layer, so that the content of N2O is reduced to about 100 PPM;
S3: the primary gas is cooled to about 50 ℃ through a heat exchanger and a heater and a quick cooler, gas-liquid two phases are separated in the quick cooler to obtain secondary gas containing NOx and primary dilute nitric acid, the secondary gas is introduced to the bottom of an absorption tower, the primary dilute nitric acid is introduced into the absorption tower, a bleaching tower is arranged below the absorption tower, and the absorption tower and the bleaching tower are integrated, namely the whole tower is an integrated tower;
The boiler feed water is heated by the heater, namely, the primary gas heats the boiler feed water when flowing through the heater, the heated boiler feed water enters a steam drum and is heated to be vaporized through a vaporization coil arranged in the oxidation reactor, steam flows back to the steam drum and is heated to be superheated through a superheating coil arranged below the vaporization coil in the oxidation reactor, the temperature of the superheated steam is about 420 ℃, and the superheated steam is recycled by a turbine;
S4: introducing secondary gas into the bottom of the absorption tower, pumping primary dilute nitric acid into the absorption tower, carrying out two-phase countercurrent reaction on the secondary gas and desalted water to generate nitric acid, allowing the nitric acid to fall into a bleaching tower, carrying out NOx removal treatment by process air introduced from the bottom of the bleaching tower, and discharging tail gas containing NOx from the top of the absorption tower;
wherein, the process air for bleaching the nitric acid comes from the air compressor, the air quantity is 18000Nm3/h, the process air carries out NOx in the nitric acid, and enters the absorption tower from the top of the bleaching tower to be mixed with the secondary gas;
S5: carrying out temperature swing adsorption treatment on the tail gas containing NOx in the step S4 by using a carbon molecular sieve, absorbing heat of the purified tail gas by using the heat exchanger in the step S3, recovering energy by using an expansion machine, and then emptying the tail gas through an exhaust funnel; 8500Nm3/h of process air is used as desorption gas to desorb NOx on the molecular sieve, and the regeneration gas obtained after desorption is mixed with the mixed gas in the step S1;
The temperature swing adsorption treatment process is carried out in two molecular sieve adsorption tanks which are arranged in parallel, the molecular sieve adsorption tanks are dynamically changed between an adsorption state and a desorption state through reversing valves, namely, when one molecular sieve adsorption tank is in the adsorption state, the other molecular sieve adsorption tank is in the desorption state, and the specific working state is described as follows:
Entering tail gas containing NOx from an end A of a first molecular sieve adsorption tank, adsorbing and purifying the tail gas by a carbon molecular sieve, discharging the tail gas from the end A', enabling the purified gas to pass through a heat exchanger and absorb heat, then recovering energy by an expander, and then emptying; the process air as desorption gas enters from the end B' of the second molecular sieve adsorption tank, the regeneration gas obtained after desorption is discharged from the end B, and the regeneration gas returns to the ammonia-air mixer to be mixed with the mixed gas;
The tail gas containing NOx enters from the end B of the second molecular sieve adsorption tank, is discharged from the end B' after being adsorbed and purified by the carbon molecular sieve, and the purified gas passes through a heat exchanger to absorb heat, then is subjected to energy recovery by an expander and then is emptied; and the process air as desorption gas enters from the end A' of the first molecular sieve adsorption tank, the regeneration gas obtained after desorption is discharged from the end A, and the regeneration gas returns to the ammonia-air mixer to be mixed with the mixed gas.
In this embodiment, the air compressor, the turbine and the expansion mechanism form an air compressor unit, and the mechanical power of the air compressor comes from the turbine and the expansion mechanism.
Referring to fig. 1, the production equipment adopting the production process of the nitric acid by the medium-pressure method comprises an ammonia-air mixer 6, an oxidation reactor 3, a heat exchanger 7, a quick cooler 9, an integrated tower and a molecular sieve adsorption tank 13 which are connected in sequence; a platinum catalyst layer 4 and an N2O decomposition catalyst layer 5 are sequentially arranged in the oxidation reactor 3; a hot gas inlet or outlet of the heat exchanger 7 is connected with a heater 8 for heating boiler feed water, a boiler feed water pipe is connected to a steam drum 15, a vaporization coil is connected between a water phase outlet and a gas phase inlet of the steam drum 15, the vaporization coil is arranged in the oxidation reactor, a gas phase outlet of the steam drum 15 is connected with a superheating coil, the superheating coil is arranged below the vaporization coil in the oxidation reactor 3, and an outlet of the superheating coil is connected with a turbine 16; a gas-liquid separation device is arranged in the quick cooler 9, and a gas outlet and a liquid outlet are both connected with the integrated tower; the tail gas outlet of the molecular sieve adsorption tank 13 is connected with the cold gas inlet of the heat exchanger 7, the cold gas outlet of the heat exchanger 7 is connected with the expander 16, and the regenerated gas outlet of the molecular sieve adsorption tank 13 is connected with the ammonia-air mixer 6.
the integrated tower is divided into an upper part and a lower part by a wire mesh, the upper part is an absorption tower 12, the lower part is a bleaching tower 11, the wire mesh has good defoaming effect, and a wire mesh is also arranged at a tail gas outlet at the top of the absorption tower 12. The upper part of the absorption tower 12 is provided with a spray water pipe for spraying desalted water and a circulating water pipe for cooling, and the bottom of the bleaching tower 11 is provided with a nitric acid outlet.
the tail gas outlet of the absorption tower 12 is connected with two molecular sieve adsorption tanks 13 which are arranged in parallel, and the state of the molecular sieve adsorption tanks 13 is dynamically adjusted through a reversing valve. The specific operating conditions are described below:
Entering tail gas containing NOx from an end A of a first molecular sieve adsorption tank, discharging the tail gas from the end A' after adsorption and purification by a carbon molecular sieve, passing the purified gas through a heat exchanger 7 and absorbing heat, recovering energy through an expander 2, and then exhausting the tail gas through an exhaust funnel 14; the process air as desorption gas enters from the end B' of the second molecular sieve adsorption tank, the regeneration gas obtained after desorption is discharged from the end B, and the regeneration gas returns to the ammonia-air mixer 6 to be mixed with the mixed gas;
the tail gas containing NOx enters from the end B of the second molecular sieve adsorption tank, is exhausted from the end B' after being adsorbed and purified by the carbon molecular sieve, and the purified gas passes through the heat exchanger 7 and absorbs heat, then is subjected to energy recovery by the expander 2 and then is exhausted by the exhaust funnel 14; the process air as desorption gas enters from the end A' of the first molecular sieve adsorption tank, the regeneration gas obtained after desorption is discharged from the end A, and the regeneration gas returns to the ammonia-air mixer 6 to be mixed with the mixed gas.
And the device also comprises an air compressor 1, wherein a process air pipe of the air compressor 1 is connected to the ammonia-air mixer 6, the bleaching tower 11 and the molecular sieve adsorption tank 13, and the mechanical power of the air compressor 1 is converted from the chemical energy of the turbine 16 and the expander 2.
The invention is not limited to the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification and any novel method or process steps or any novel combination of features disclosed.
Claims (10)
1. a process for producing nitric acid by a medium pressure method is characterized by comprising the following process steps:
S1: mixing ammonia gas with air according to a certain ammonia-to-air ratio, and introducing the mixed gas into an oxidation reactor;
S2: carrying out catalytic oxidation reaction on the mixed gas in an oxidation reactor at the reaction temperature of 800-950 ℃ and the ammoxidation pressure of 0.5-0.6 MPa to generate primary gas containing NOx;
s3: after the primary gas is subjected to heat recovery and rapid cooling separation treatment, introducing the obtained NOx-containing secondary gas and the primary dilute nitric acid into an integrated tower, wherein the upper part of the integrated tower is an absorption tower, and the lower part of the integrated tower is a bleaching tower;
s4: introducing secondary gas into the bottom of the absorption tower, performing two-phase countercurrent reaction on desalted water serving as absorption liquid at the top of the absorption tower and the secondary gas to generate nitric acid, introducing primary dilute nitric acid into a tower tray with corresponding acid concentration of the absorption tower, wherein the absorption pressure is 0.5-0.6 MPa, allowing the nitric acid to fall into a bleaching tower for NOx removal treatment, and discharging tail gas containing NOx from the top of the absorption tower;
s5: carrying out temperature swing adsorption treatment on the tail gas containing NOx in the step 4 by adopting a molecular sieve, absorbing heat of the purified tail gas by the heat exchanger in the step S3, recovering energy by an expansion machine, and then emptying; the regeneration gas obtained after the desorption on the molecular sieve is mixed with the mixed gas in the step S1.
2. The process for producing nitric acid according to claim 1, wherein at least one set of molecular sieve adsorption tanks is provided in step S5, each set comprising two molecular sieve adsorption tanks disposed in parallel; the two molecular sieve adsorption tanks in the group are dynamically changed between an adsorption state and a desorption state, and when one molecular sieve adsorption tank is in the adsorption state, the other molecular sieve adsorption tank is in the desorption state.
3. The process of producing nitric acid according to claim 1 or 2, wherein the inlet or outlet of the heat exchanger at the hot side of step S3 is connected to a heater, the boiler feed water is heated by the heater and then enters the steam drum, and the boiler feed water is heated, vaporized and superheated in the oxidation reactor through the coil pipe, and the generated superheated steam is passed through a turbine to recover energy.
4. the process for producing nitric acid according to claim 1 or 2, wherein the mixed gas is reacted with a platinum catalyst layer to produce NOx in step S2, and N2O is decomposed with a N2O decomposition catalyst layer to produce nitrogen.
5. The process for the production of nitric acid according to claim 1 or 2, wherein the air in step S1 is from an air compressor and all or part of the mechanical power of the air compressor is from the expander in step S5.
6. The equipment for producing the nitric acid by the medium-pressure method is characterized by comprising an ammonia-air mixer, an oxidation reactor, a heat exchanger, a quick cooler, an integrated tower and a molecular sieve adsorption tank which are sequentially connected; a heater for heating boiler feed water is connected to an inlet or an outlet at the hot side of the heat exchanger, a boiler feed water pipe is connected to a steam drum, a vaporization coil is connected between a water phase outlet and a gas phase inlet of the steam drum, the vaporization coil is arranged in the oxidation reactor, a gas phase outlet of the steam drum is connected with a superheating coil, the superheating coil is arranged below the vaporization coil in the oxidation reactor, and an outlet of the superheating coil is connected with a turbine; the tail gas outlet of the molecular sieve adsorption tank is connected with the cold side inlet of the heat exchanger, the cold side outlet of the heat exchanger is connected with the expander, and the regenerated gas outlet of the molecular sieve adsorption tank is connected with the ammonia-air mixer.
7. the apparatus for producing nitric acid according to claim 6, wherein the integrated tower is divided into an upper part and a lower part by a screen, the upper part is an absorption tower, and the lower part is a bleaching tower.
8. The plant for producing nitric acid according to claim 6 or 7, further comprising at least one air compressor, wherein the process gas pipe of the air compressor is connected to the ammonia-air mixer, the bleaching tower and the molecular sieve adsorption tank, and all or part of the mechanical power of the air compressor comes from the turbine and the expander.
9. The apparatus for producing nitric acid according to claim 6 or 7, wherein the tail gas outlet of the absorption tower is connected with at least one group of molecular sieve adsorption tanks, each group comprises two molecular sieve adsorption tanks arranged in parallel, and the states of the molecular sieve adsorption tanks are dynamically adjusted through a reversing valve.
10. the apparatus for producing nitric acid according to claim 6 or 7, wherein a platinum catalyst layer and a N2O decomposition catalyst layer are provided in this order in the oxidation reactor.
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| CN113184816A (en) * | 2021-05-21 | 2021-07-30 | 江西金利达钾业有限责任公司 | Process for producing dilute nitric acid |
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| EP4209454A1 (en) | 2022-01-11 | 2023-07-12 | Yara International ASA | Mono pressure system for producing nitric acid and method of operating thereof |
| EP4238932A1 (en) | 2022-03-03 | 2023-09-06 | Yara International ASA | Dual pressure system for producing nitric acid and method of operating thereof |
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