CN217829524U - Preparation system for preparing nitric acid from conversion gas in nitrate production - Google Patents
Preparation system for preparing nitric acid from conversion gas in nitrate production Download PDFInfo
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- CN217829524U CN217829524U CN202221512699.6U CN202221512699U CN217829524U CN 217829524 U CN217829524 U CN 217829524U CN 202221512699 U CN202221512699 U CN 202221512699U CN 217829524 U CN217829524 U CN 217829524U
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Abstract
The utility model provides a preparation system for preparing nitric acid from conversion gas in nitrate production, which comprises a conversion unit, a gas-liquid separator and a gas-liquid separator, wherein the conversion unit is used for treating sodium sulfite mother liquor in conversion to obtain conversion gas for preparing nitric acid; an isothermal oxidation unit for obtaining NO through a gas supply unit X A gas; an acid absorption unit, the acid absorption unitUsing desalted water unit to make NO X Reacting the gas with water to form a nitric acid solution; a first circulating cooling unit which circulates the nitric acid solution at the bottom of the acid absorption unit to the acid absorption unit; the bottom of the acid absorption unit is connected with a nitric acid intermediate tank, the nitric acid intermediate tank and the conversion unit form a circulating pipeline through a second circulating cooling unit and a conversion circulating pump, so that part of nitric acid finished products in the nitric acid intermediate tank circulate to the conversion unit to form raw materials in the conversion unit. The utility model increases the concentration of nitrogen oxide, and improves the concentration of the finished nitric acid.
Description
Technical Field
The utility model relates to the technical field of the application of nitric acid solution in the nitrate production, in particular to a preparation system for preparing nitric acid from conversion gas in the nitrate production.
Background
Nitric acid is an important industrial raw material and is one of indispensable raw materials in the nitrate production industry. At present, in the production process of nitrate industry, raw material gas is generally produced by ammonia oxidation, and mainly contains NO and NO 2 Equal nitrogen oxides, N 2 、O 2 And water, wherein the raw material gas firstly enters a quick cooler for cooling, the cooled mixed raw material gas is introduced into an oxidation tower for oxidation, nitric oxide in the raw material gas is oxidized into nitrogen dioxide after oxidation, the oxidized gas is introduced into an absorption tower for absorption, and a nitric acid product is obtained at the bottom of the tower.
However, in the above-described conventional nitric acid production process, there are problems as follows:
(1) NO and O in raw material gas 2 The concentration is low (about 10 percent), the oxidation rate is slow, so that the concentration of the finally generated nitric acid is low, and the content of NO discharged by tail gas is high;
according to the literature: the main factors influencing the NO oxidation rate are temperature, pressure and NO concentration.
The NO oxidation reaction speed can be accelerated by pressurizing operation and reducing temperature, and the technology is generally adopted by the domestic existing nitric acid device. But increasing the pressure will substantially increase the investment costs.
The reaction speed of nitric oxide oxidation is in direct proportion to the product of the square of nitric oxide concentration and oxygen concentration, so that the NO concentration alpha in the gas is increased, the reaction speed can be greatly accelerated, and the reaction time is shortened. However, in actual production, the concentration of nitric oxide is limited by the ammonia oxidation process.
(2) N in gas 2 The concentration is high, the gas volume is large, the diameter of the dilute nitric acid tower is large, and the investment cost of a nitrate device is increased; the raw material gas is from the ammoxidation step, and the ammoxidation reaction is a reaction between oxygen in the air and gaseous ammonia, and thus N that does not participate in the reaction 2 Accounting for more than 65% of the total gas.
(3)NO 2 The concentration is low, which results in low concentration of nitric acid produced, and the concentration of nitric acid is only 35-40%. The conversion solution, namely nitrite mother liquor, needs to be further subjected to oxidation reaction with nitric acid to be changed into nitrate solution with higher water content, so that the steam consumption of the subsequent evaporation process is increased, and the energy consumption is increased.
According to the literature: the main factors influencing the concentration of the absorbed acid are the NO oxidation rate, temperature, pressure, NO 2 And (4) concentration.
The increase of NO oxidation rate, the decrease of temperature and the increase of pressure can both increase the absorption rate coefficient when the nitric acid aqueous solution absorbs the nitrogen oxide and increase the acid concentration.
It can be seen from the table of the absorption rate coefficients when nitrogen oxides are absorbed with an aqueous solution of nitric acid that NO is absorbed with NO 2 The concentration of (3) is increased and the acid concentration is increased.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide a preparation system of conversion gas system nitric acid in nitrate production, it replaces the dilute nitric acid production technology of current traditional nitrate production normal pressure method. Specifically, nitrogen oxides (high-purity NOx gas containing a small amount of water) from a conversion process are subjected to isothermal oxidation and absorption to obtain a nitric acid solution product with higher concentration, so that nitric acid with higher concentration is provided for a subsequent nitrate production section, the use amount of the nitric acid solution for conversion reaction is reduced, the use amount of steam is greatly reduced, and energy conservation and consumption reduction are realized. Mainly solves the problems of low nitric acid concentration, over-standard tail gas emission, high energy consumption and the like in the nitrate production industry. The method has the advantages that the recovery rate of the nitrogen oxide reaches more than 99.5 percent, the concentration of the nitric acid is more than 50 percent, the subsequent evaporation steam consumption is greatly saved, and the method has higher economic benefit and social environmental protection benefit.
In order to achieve the above purpose, the present invention is implemented by the following technical solutions.
A preparation system for preparing nitric acid from conversion gas in nitrate production, which comprises,
the conversion unit is used for treating the sodium sulfite mother liquor in the conversion process to obtain conversion gas for preparing nitric acid;
an isothermal oxidation unit for oxidation of the converted gas to obtain NO by the gas supply unit X A gas;
an acid absorption unit connected with a desalted water unit, wherein the desalted water unit is connected with NO in the acid absorption unit X After the gas reacts, nitric acid solution and NO are obtained X Tail gas;
a first circulating cooling unit provided in the acid absorption unit for NO X Absorbing heat in the reaction of the gas and the acid solution, and circulating the nitric acid solution at the bottom of the acid absorption unit to the acid absorption unit;
the bottom of the acid absorption unit is connected with a nitric acid intermediate tank, the nitric acid intermediate tank and the conversion unit form a circulating pipeline through a second circulating cooling unit and a conversion circulating pump, so that part of nitric acid finished products in the nitric acid intermediate tank circulate to the conversion unit to form raw materials in the conversion unit.
In the technical scheme, the air supply unit is additionally arranged, so that the sodium sulfite mother liquor in the conversion unit in the existing preparation process can be further oxidized under the action of air to obtain more NOx gas, and at the moment, the temperature monitoring unit can be additionally arranged in the isothermal oxidation unit, so that the isothermal oxidation temperature is controlled to be 30-40 ℃, the concentration of nitrogen oxides is more than 25%, and the concentration of oxygen is more than 5% in the whole process; this process increases the concentration of nitrogen oxides and provides a basis for the production of high-concentration nitric acid.
In the technical scheme, the acid absorption unit is additionally arranged, in the process, the acid solution in the acid absorption unit is matched with desalted water, so that the bottom of the absorption unit can generate dilute nitric acid, the concentration is lower, and at the moment, the nitric oxide is absorbed to form nitric acid.
Among this technical scheme, the later stage is through the middle groove of nitric acid for the low concentration nitric acid that forms initially can be carried to the conversion unit in, carries out a series of oxidation and acid absorption once more, and then makes the nitric acid concentration that forms higher, compares in prior art's ordinary pressure method nitric acid preparation etc. and the nitric acid concentration that obtains is higher.
As a further improvement of the utility model, the conversion unit includes the conversion tower, the washing unit of conversion liquid washing in the conversion tower and be used for the gas-liquid separation's in the conversion tower separating element, separating element's gas vent with isothermal oxidation unit UNICOM.
In the technical scheme, the sodium sulfite mother liquor is complex and contains sodium carbonate, sodium nitrate, sodium nitrite, sodium chloride and the like, so that the nitric acid is washed by a series of washing separation and the like, and then is separated from other impurities to obtain primary nitric acid.
As a further improvement of the utility model, the nitric acid washing unit is connected with the nitric acid middle tank.
In the technical scheme, the nitric acid washing unit is connected with the nitric acid intermediate tank, on one hand, the nitric acid raw material is provided for the nitric acid intermediate tank, on the other hand, the washed nitric acid can be used as sodium sulfite mother liquor for conversion and the like, and the content of the nitric acid is further improved.
As a further improvement of the utility model, the device further comprises a heater positioned between the conversion unit and the sodium sulfite mother liquor transportation pipeline, and the heater is used for heating the sodium sulfite mother liquor to be not lower than 100 ℃.
In the technical scheme, the sodium sulfite mother liquor from the evaporation process is heated to 105 ℃ from low-pressure steam by a sodium sulfite mother liquor heater, and then impurities in the sodium sulfite mother liquor are removed by initial heating.
As a further improvement, the bottom of the conversion unit is communicated with a conversion liquid circulating pump, the conversion liquid circulating pump enables the bottom of the conversion unit to form a circulating system, the conversion liquid circulating pump is communicated with a PH value control unit, and the PH value control unit is used for controlling the PH value in the conversion unit.
In the technical scheme, circulation is formed in the conversion unit, circulation is formed at the bottom of the conversion tower, and the like, the conversion reaction is more sufficient, and the pH value is controlled because the conversion reaction can be completely converted in an acidic environment, namely, nitric acid in the conversion solution is excessive, the control index is 15g/L, and the conversion solution is used as an intermediate product, and sodium carbonate is added into a neutralizer to adjust the acidity of the solution to be 0.1g/L.
And the conversion solution treatment unit is communicated with the conversion solution circulating pump and enables the conversion solution to be discharged in an alkaline state through the neutralization device.
As a further improvement of the utility model, the acid absorption unit comprises a first acid absorption tower and a second acid absorption tower, the first acid absorption tower and the second acid absorption tower form a circulation pipeline through a connecting pipeline and a nitric acid pump.
In this technical scheme, set up two solitary acid absorption towers, and two acid absorption towers are parallelly connected and are set up, and then make the supply volume and the supply route of acid more diversified, and two acid absorption towers form circulation pipeline, and then make nitrogen oxide can be carried out further NOx by acid absorption tower and absorb, form nitric acid.
As a further improvement of the present invention, the first acid absorption unit is connected to the gas supply unit, and the second acid absorption unit is connected to the desalted water unit.
In the technical scheme, different substances are introduced into the two acid absorption units, and then the oxidized converter is oxidized and mixed again through air, NOx gas is further absorbed and absorbed through the acid absorption tower, desalted water from the outside of a boundary area is sent to the upper part of the second acid absorption tower, a cooling coil is arranged between tower plates of the absorption towers, absorption heat and oxidation heat are removed through circulating water, and nitric oxide forms nitric acid through the desalted water.
As a further improvement of the utility model, the device also comprises a condensed acid pump positioned at the bottom of the isothermal oxidation unit, and the condensed acid pump is respectively communicated with the top of the first acid absorption unit and the bottom of the second acid absorption unit.
Among this technical scheme, through the condensation acid pump for nitrogen oxide can be through the condensation acid pump, with the condensation acid of different concentrations, squeezes into acid absorption tower well upper portion, makes its inside tray, and condensation acid concentration can be adjusted, corresponds and obtains corresponding concentration.
As a further improvement of the present invention, the bottom of the first acid absorption unit is provided with a circulating acid pump, the circulating acid pump passes through the first circulating cooling unit forms a circulating pipeline at the side of the first acid absorption unit, and communicates with the middle tank of the nitric acid.
In the technical scheme, dilute nitric acid at the bottom of the first acid absorption unit enters a 3 rd layer tower plate at the lower part of an acid tower through a circulating acid pump and a first circulating cooling unit, and returns to the bottom of the tower through the 3 layers of tower plates in the tower, the dilute nitric acid forms a circulation, and the concentration of the nitric acid reaches about 45 percent and then is pumped to a dilute nitric acid intermediate tank through the circulating acid pump.
As a further improvement of the utility model, the system also comprises a tail gas separator, the tail gas separator is communicated with the acid absorption unit, and NO is discharged through the alkali treatment unit X And (4) tail gas.
According to the technical scheme, after the steps of oxidation, acid absorption, desalted water acid absorption and the like are carried out, the nitrogen-oxidized tail gas obtained by the tail gas separator is less, the discharge is convenient, and the tail gas can be directly discharged through the acid tower separator.
Further, the device also comprises a conversion circulating acid pump positioned between the nitric acid intermediate tank and the conversion unit, and a pH value adjusting unit which is arranged close to the sodium sulfite mother liquor conversion unit and is used for adjusting the pH value output by the acid absorption unit.
Drawings
FIG. 1 is a schematic structural diagram of a system for preparing nitric acid from a conversion gas in nitrate production according to the present invention;
in the figure:
1. a conversion unit; 11. a conversion tower; 12. a sodium sulfite mother liquor washing unit; 13. a nitric acid scrubbing unit; 14. a separation unit; 15. a conversion solution circulating pump; 16. a pH value control unit; 17. a conversion solution treatment unit; 2. an isothermal oxidation unit; 21. a condensed acid pump; 3. an air supply unit; 4. an acid absorption unit; 41. a first circulating cooling unit; 42. a first acid absorption column; 43. a second acid absorption column; 44. connecting a pipeline; 45. a nitric acid pump; 46. a circulating acid pump; 5. a desalted water unit; 7. a nitric acid intermediate tank; 71. a second circulation cooling unit; 72. a conversion circulating pump; 8. a heater; 9. and a tail gas separator.
Detailed Description
The present invention is described in detail with reference to the embodiments shown in the drawings, but it should be understood that these embodiments are not intended to limit the present invention, and those skilled in the art should understand that the functions, methods, or structural equivalents or substitutions made by these embodiments are within the scope of the present invention.
Example 1
The core components are mainly described in this embodiment.
A preparation system for preparing nitric acid from conversion gas in nitrate production, which comprises,
the conversion unit 1 is used for treating sodium sulfite mother liquor in conversion to obtain conversion gas for preparing nitric acid;
an isothermal oxidation unit 2, said isothermal oxidation unit 2 being for oxidation of a conversion gas, by means of a gas supply unit 3, to obtain NO X A gas;
an acid absorption unit 4, wherein the acid absorption unit 4 is connected with a desalted water unit 5, and the desalted water unit 5 is connected with NO in the acid absorption unit 4 X After the gas reacts, nitric acid solution and NO are obtained X Tail gas;
a first circulation cooling unit 41, the acid absorption unit 4 is provided with the first circulation cooling unit 41, and the first circulation cooling unit 41 is used for NO X Absorbing heat in the reaction of the gas and the acid solution and adding nitric acid at the bottom of the acid absorption unitThe solution is circulated to the acid absorption unit 4;
the bottom of the acid absorption unit 6 is connected with the nitric acid intermediate tank 7, the nitric acid intermediate tank 7 forms a circulating pipeline with the conversion unit 1 through a second circulating cooling unit 71 and a conversion circulating pump 72, so that part of the nitric acid finished products in the nitric acid intermediate tank 7 are circulated to the conversion unit 1 to form the raw materials in the conversion unit.
In the embodiment, an air supply unit is added, so that the sodium sulfite mother liquor in the conversion unit in the existing preparation process can be further oxidized under the action of air to obtain more NOx gas, and at the moment, a temperature monitoring unit can be added in the isothermal oxidation unit, so that the isothermal oxidation temperature is controlled to be 30-40 ℃, the concentration of nitrogen oxide is more than 25%, and the concentration of oxygen is more than 5% in the whole process; this process increases the concentration of nitrogen oxides and provides a basis for the production of high-concentration nitric acid.
In the embodiment, the acid absorption unit is added, in the process, the acid solution in the acid absorption unit is matched with desalted water, so that dilute nitric acid can be generated at the bottom of the absorption unit, the concentration is low, and at the moment, nitric oxide is absorbed to form nitric acid.
In this embodiment, the later stage is through groove in the middle of the nitric acid for the low concentration nitric acid that initially forms can be carried to the conversion unit in, carries out a series of oxidation and acid absorption once more, and then makes the nitric acid concentration that forms higher, compares in the normal pressure method nitric acid preparation among the prior art etc. and the nitric acid concentration that obtains is higher.
Example 2
In this example, the description is given in conjunction with a conversion unit.
Referring to fig. 1, the reforming unit 1 includes a reforming tower 11, a washing unit for washing a reforming liquid in the reforming tower 11, and a separation unit 14 for gas-liquid separation in the reforming tower 11, and an exhaust port of the separation unit 14 is communicated with the isothermal oxidation unit 2.
Further, the conversion solution is mostly sodium sulfite mother liquor and nitric acid, so the washing unit includes a sodium sulfite mother liquor washing unit 12 and a nitric acid washing unit 13.
In this embodiment, since the sodium sulfite mother liquor is relatively complex and contains sodium carbonate, sodium nitrate, sodium nitrite, sodium chloride, and the like, it is necessary to wash nitric acid through a series of washing separation and the like, and then separate nitric acid from other impurities to obtain primary nitric acid.
Further, the nitric acid washing unit 13 is connected to the nitric acid intermediate tank 7.
In this embodiment, the nitric acid washing unit is connected with the nitric acid intermediate tank, on one hand, the nitric acid raw material is provided for the nitric acid intermediate tank, and on the other hand, the washed nitric acid can be used as a sodium sulfite mother liquor for conversion and the like, so that the content of the nitric acid is further increased.
For preliminary pretreatment, a heater 8 is further included between the conversion unit 1 and the sodium sulfite mother liquor transportation pipeline, and the heater 8 is used for heating the sodium sulfite mother liquor pretreatment to not less than 100 ℃.
In this example, the sodium sulfite mother liquor from the evaporation process is heated from low-pressure steam to 105 ℃ by a sodium sulfite mother liquor heater, and further, by initial heating, some impurities and the like in the sodium sulfite mother liquor are removed.
Referring to the attached drawing 1, a conversion solution circulating pump 15 is communicated with the bottom of the conversion unit 1, the conversion solution circulating pump 15 enables the bottom of the conversion unit 1 to form a circulating system, a PH control unit 16 is communicated with the conversion solution circulating pump 15, and the PH control unit 16 is used for controlling the PH value in the conversion unit.
In the embodiment, circulation is formed in the conversion unit, circulation is formed at the bottom of the conversion tower, and the like, so that the conversion reaction is more sufficient, the pH value is controlled, the conversion reaction needs to be completely converted under an acidic environment, namely, nitric acid in the conversion solution is excessive, the control index is 15g/L, and the conversion solution is used as an intermediate product, sodium carbonate is added into a neutralizer to adjust the acidity of the solution to alkalinity of 0.1g/L.
Further, the device also comprises a conversion solution treatment unit 17 communicated with the conversion solution circulating pump 15, wherein the conversion solution treatment unit 17 enables the conversion solution to be discharged in an alkaline state through a neutralization device.
Example 3
In this embodiment, the description will be mainly given in conjunction with an acid absorption unit.
Referring to fig. 1, the acid absorption unit 4 includes a first acid absorption tower 40, and a second acid absorption tower 43, and the first acid absorption tower 42 and the second acid absorption tower 43 form a circulation line through a connection line 44 and a nitric acid pump 45.
In this embodiment, set up two solitary acid absorption towers, and two acid absorption towers are parallelly connected to be set up, and then make the supply volume and the supply route of acid more diversified, and two acid absorption towers form circulation pipeline, and then make nitrogen oxide can be carried out further NOx by acid absorption tower and absorb, form nitric acid.
Further, the first acid absorption unit 42 is connected to the gas supply unit 3, and the second acid absorption unit 43 is communicated with the desalted water unit 5.
In this embodiment, different substances are introduced into the two acid absorption units, and then the oxidized converter is oxidized and mixed again through air, and further absorbs and absorbs NOx gas through the acid absorption tower, and desalted water from outside the battery compartment is sent to the upper part of the second acid absorption tower, a cooling coil is arranged between tower plates of the absorption towers to remove absorption heat and oxidation heat through circulating water, and nitric oxide passes through the desalted water to form nitric acid.
Further, a condensed acid pump 21 is also included at the bottom of the isothermal oxidation unit 2, and the condensed acid pump 21 is respectively communicated with the top of the first acid absorption unit 42 and the bottom of the second acid absorption unit 43.
In this embodiment, through the condensation acid pump for nitrogen oxide can be through the condensation acid pump, with the condensation acid of different concentrations, squeezes into upper-middle part of acid absorption tower, makes its inside tray, and condensation acid concentration can adjust, corresponds and obtains corresponding concentration.
Furthermore, a circulating acid pump 46 is arranged at the bottom of the first acid absorption unit 42, and the circulating acid pump 46 forms a circulating pipeline at the side of the first acid absorption unit 42 through the first circulating cooling unit 41 and is communicated with the nitric acid intermediate tank 7.
In the embodiment, dilute nitric acid at the bottom of the first acid absorption unit enters the 3 rd-layer tower plate at the lower part of the acid tower through the first circulating cooling unit by the circulating acid pump, returns to the bottom of the tower through the 3-layer tower plate in the tower, and is circulated, and the nitric acid is pumped to the dilute nitric acid intermediate tank by the circulating acid pump after the concentration of the nitric acid reaches about 45%.
Further, the device also comprises a tail gas separator 9, wherein the tail gas separator 9 is communicated with the acid absorption unit 4, and NO is discharged through an alkali treatment unit X And (4) tail gas.
In the embodiment, after the steps of oxidation, acid absorption of desalted water and the like, the tail gas separator obtains fewer nitrogen oxide tail gases, and the nitrogen oxide tail gases are conveniently discharged.
Example 4
In this embodiment, the description is given in conjunction with different application cases.
Adopt the device system in the utility model, carry out the conversion reaction with sodium sulfite mother liquor and rare nitric acid and generate the feed gas, get into the nitric acid process and produce nitric acid.
Firstly, selecting a sodium sulfite mother liquor containing 78.6 percent of water, 0.4 percent of sodium carbonate, 5.2 percent of sodium nitrate, 15.4 percent of sodium nitrite and 0.4 percent of sodium chloride with the temperature of 76.5 ℃, heating to 105 ℃ by steam through a heater 8 at the flow rate of 8241.1kg/hr, and entering the middle part of a conversion tower 1; secondly, neutralizing water with the molar content of 77.4 percent and nitric acid with the molar content of 22.6 percent, entering the middle part of the conversion tower 1 through a conversion circulating pump 72 at the flow rate of 5362kg/hr, carrying out conversion reaction at the pressure of 221.3KPa and the temperature of 95 ℃, discharging converted gas generated by the conversion reaction from the top of the tower after washing and cooling by dilute nitric acid, and entering an acid absorption process to be used as raw material gas for producing the nitric acid.
The converted gas contains 2.4 mol percent of water, 71.6 mol percent of NO and 23.2 mol percent of NO 2 2.8% of CO 2 Working gas amount 665Nm 3 H is used as the reference value. Enters the bottom of the reforming gas isothermal oxidation tower at the pressure of 190KPa and the temperature of 38.2 ℃ to be mixed with secondary air, and the mixed gas in the gas supply unit 3 contains 14.0 percent of mole contentO of (a) 2 52.8% of N 2 2.0% of water, 22.8% of NO, 7.4% of NO 2 0.9% of CO 2 Working gas amount 1969.3Nm 3 H is used as the reference value. The NOx gas was further oxidized at a pressure of 189KPa and a temperature of 40 ℃. The gas composition at the outlet of the top of the oxidation tower contains 4.6 mol% of O 2 58.6% of N 2 2.2% of water, 3.4% of NO, 30.2% of NO 2 1% of CO 2 The degree of oxidation of NO is 89.9%, and the working gas quantity is 1944Nm 3 /h。
The gas at the outlet of the converted gas isothermal oxidation tower and the bleaching air introduced at the bottom of the first acid absorption tower 42 contain 20.6 mol% of O 2 77.6% of N 2 And the mixed working condition gas amount of 1.8 percent of water at the bottom of the tower is 2453.2Nm 3 H, after the NOx gas further absorbs the NOx gas through the first acid absorption tower 42 and the second acid absorption tower 43 in sequence, the liquid is separated through an acid tower tail gas separator (namely, a tail gas separator), and the outlet gas forms O with the mol content of 4.2 percent 2 89.4% of N 2 2.8% of water, 2.5% of NO, 1.1% of CO 2 Operating gas quantity 1644Nm 3 And h, entering an alkali absorption process.
Desalted water (namely, desalted water unit 5) from outside the battery limits is sent to the upper part of a second acid absorption tower 43, cooling coils are arranged between tower plates of the absorption towers to remove absorption heat and oxidation heat through circulating water, the pressure is 180KPa, and the temperature is 35.7 ℃. Dilute nitric acid with 31 percent of bottom acid concentration enters the upper part of a first acid absorption tower 42 through a circulating acid pump 46, cooling coils are arranged between tower plates of the absorption towers to remove absorption heat and oxidation heat through low-temperature closed-loop circulating water, the bottom dilute nitric acid passes through the circulating acid pump 46, is cooled through a circulating acid cooler (namely a first circulating cooling unit 41) and then enters a tower plate at the lower part of the acid tower on the 3 rd layer, the dilute nitric acid returns to the tower bottom through the tower plates at the 3 layers in the tower to form circulation, the dilute nitric acid contains water with 77.4 percent of molar content, 22.6 percent of acid, the concentration is 50.5 percent, the 4950.9kg/hr flow rate, and the finished product acid is sent to a dilute nitric acid intermediate tank 7 through the circulating acid pump 46 and enters the middle part of a conversion tower through a conversion circulating pump 72.
The converted gas isothermal oxidation tower bottom condensed acid is pumped into a tray with corresponding concentration at the upper part of the middle part of the first acid absorption tower 42 through a condensed acid pump 21 according to the concentration of the condensed acid.
The traditional process is adopted, the process in the utility model is combined, and the raw material gas from ammonia oxidation enters the nitric acid procedure to produce nitric acid.
Firstly, the catalyst is prepared by mixing N with the molar content of 66.8 percent 2 5.3% of O 2 Gas, 9.9% NO, 18.1% H 2 O is used as a raw material gas, enters into a NOx fast cooler E-707301 at the temperature of 209.3 ℃ and the pressure of 190kPa at the flow rate of 12581.7kg/hr, and is further cooled to 40 ℃ in the NOx fast cooler, in the process, part of NO is oxidized into NO2, in addition, part of NO2 is absorbed by water condensed in the raw material gas to form condensed dilute nitric acid, the flow rate of the condensed dilute nitric acid is 1564.523kg/hr, and the concentration of the nitric acid is 19.73%.
Secondly, according to the existing device, after the raw material gas is cooled by a NOx quick cooler, the composition of the raw material gas is changed into N with the molar content of 81.9 percent due to the formation of dilute nitric acid 2 3.9% of O 2 Gas, 7.6% NO, 3.3% NO 2 3.4% of H 2 And O. Working condition gas amount 5346.5Nm of nitrogen oxide quick cooler outlet raw material gas 3 H, entering an oxidation tower T101 and mixing secondary air at the bottom of the tower for further oxidation to oxidize most of NO in the feed gas into NO 2 The temperature at the top of the isothermal oxidation column (i.e., isothermal oxidation unit 2) was 40 ℃ and the pressure was 189kPa. Containing 4.2 mol% of O 2 82.6% of N 2 3.3% of water, 4.0% of NO, 5.9% of NO 2 NO oxidation rate of 59.8%, working gas amount of 6906.9Nm 3 /h。
The gas at the outlet of the isothermal oxidation tower and the bleaching air introduced at the bottom of the first acid absorption tower 42 contained 20.6 mol% of O 2 77.6% N 2 1.8 percent of water is mixed at the bottom of the tower, the mixed water sequentially passes through a first acid absorption tower 42 and a second acid absorption tower 43 to further absorb NOx gas, liquid is separated by an acid tower tail gas separator 9, and outlet gas forms O with the molar content of 4.1 percent 2 90.7% of N 2 3.6 percent of water, 1.6 percent of NO, and working condition gas amount 6339.7Nm 3 And/h enters an alkali absorption process.
Desalted water (namely, desalted water unit 5) from outside the battery limits is sent to the upper part of a second acid absorption tower 43, and cooling coils are arranged between tower plates of the absorption towers to remove absorption heat and oxidation heat through circulating water, wherein the pressure is 180KPa, and the temperature is 35.7 ℃. The bottom dilute nitric acid is pressurized by a nitric acid pump 45 and enters the upper part of a first acid absorption tower 42, cooling coils are arranged between tower plates of the absorption towers to remove absorption heat and oxidation heat through low-temperature closed-loop circulating water, the dilute nitric acid with the bottom acid concentration of 20 percent passes through a circulating acid pump 46, is cooled by a circulating acid cooler (namely a first circulating cooling unit 41) and then enters a tower plate at the 3 rd layer at the lower part of the acid tower, the dilute nitric acid returns to the tower bottom through the tower plates at the 3 layers in the tower to form circulation, the dilute nitric acid comprises water with the molar content of 84.4 percent, 15.6 percent nitric acid and the acid concentration of 39.2 percent, the finished acid is sent to a nitric acid intermediate tank 7 through the circulating acid pump 46 and enters the middle part of a conversion tower through a conversion circulating pump 71.
The condensed acid of the fast cooler enters the bottom of the isothermal oxidation tower, and is pumped into a tower tray with corresponding concentration at the upper part of the middle part of the first acid absorption tower 42 through a condensed acid pump 21 according to the concentration of the condensed acid.
The traditional process and the new process are combined, and the system in the utility model is combined, and the raw material gas from ammonia oxidation and conversion enters the nitric acid process to produce nitric acid.
The feed gas from ammonia oxidation contains 66.8 mol% N 2 5.3% of O 2 Gas, 9.9% NO, 18.1% H 2 O, at a temperature of 209.3 ℃ and a pressure of 190kPa, at a flow rate of 6286.6kg/hr and a feed gas from the conversion process comprising 71.6% NO, 23.2% NO on a molar basis 2 2.4% of H 2 O, 2.8% CO 2 The raw material gas is further cooled to 40 ℃ in the NOx fast cooler at the temperature of 38.2 ℃ and the pressure of 190kPa, part of NO is oxidized into NO2 in the process, in addition, part of NO2 is absorbed by water condensed in the raw material gas to form condensed dilute nitric acid, the flow rate of the condensed dilute nitric acid is 867kg/hr, and the concentration of the nitric acid is 29.36%.
After the raw material gas is cooled by NOx quick cooler, the raw material gas can be formed into dilute nitric acidThe composition was changed to contain 74.2 mol% of N 2 2.3% of O 2 Gas, 12.9% NO, 6.9% NO 2 3.4% of H 2 O, 0.3% CO 2 . Working condition gas amount 2989.5Nm of nitrogen oxide quick cooler outlet raw material gas 3 H, mixing the raw material gas with secondary air at the bottom of the tower for further oxidation to oxidize most of NO in the raw material gas into NO 2 The temperature at the top of the isothermal oxidation tower is 40 ℃ and the pressure is 189kPa. Containing 4.2 mol% of O 2 77.1% of N 2 3.1% of water, 4.4% of NO, 10.9% of NO 2 NO oxidation rate of 71.2%, working gas amount of 3943.7Nm 3 /h。
The gas at the outlet of the isothermal oxidation tower and the bleaching air introduced at the bottom of the first acid absorption tower 42 contained 20.6 mol% of O 2 77.6% N 2 1.8 percent of water is mixed at the bottom of the tower, the mixed water sequentially passes through a first acid absorption tower 42 and a second acid absorption tower 43 to further absorb NOx gas, liquid is separated by an acid tower tail gas separator 9, and outlet gas forms O with the molar content of 4.2 percent 2 90.5% of N 2 2.8 percent of water, 2.3 percent of NO, and working condition gas amount 4057.7Nm 3 And/h enters an alkali absorption process.
Desalted water from outside the battery limits is sent to the upper part of a second acid absorption tower 43, cooling coils are arranged between tower plates of the absorption towers to remove absorption heat and oxidation heat through circulating water, the pressure is 180KPa, and the temperature is 35.7 ℃. The dilute nitric acid at the bottom enters the upper part of a first acid absorption tower 42 through a nitric acid pump 45, cooling coils are arranged between tower plates of the absorption towers to remove absorption heat and oxidation heat through low-temperature closed-loop circulating water, the dilute nitric acid with the acid concentration of 26% at the bottom enters a 3 rd-layer tower plate at the lower part of the acid tower after being cooled by a circulating acid cooler (namely a first circulating cooling unit) through a circulating acid pump 46, the dilute nitric acid returns to the bottom of the tower through the 3-layer tower plate in the tower to form circulation, the dilute nitric acid comprises water with the molar content of 81.5%, nitric acid with the acid concentration of 18.5% and 44.3%, the finished acid is sent to a dilute nitric acid intermediate tank 7 through the circulating acid pump 46 and enters the middle part of a conversion tower through a conversion circulating pump 72.
The condensed acid of the fast cooler enters the bottom of the isothermal oxidation tower, and is pumped into a tower tray with corresponding concentration at the upper part of the middle part of the first acid absorption tower 42 through a condensed acid pump 21 according to the concentration of the condensed acid.
Case key process data comparison table:
as can be seen from the above 3 cases: the concentration of NOx in the oxidation tower is higher, and the oxidation of NO into NO can be effectively promoted 2 And (6) processing. Acid absorption tower NO 2 The concentration is higher, and the increase of the concentration of the nitric acid can be effectively promoted. Because the conversion gas is adopted as the raw material gas to produce the nitric acid, N in the nitric oxide gas in each device in the nitric acid procedure 2 The concentration of the nitrogen is greatly reduced, the gas flow in the equipment is greatly reduced, the volume of the equipment is reduced, and the investment is greatly reduced.
The utility model aims to improve various problems existing in the middle of the current actual operation of the dilute nitric acid process by the normal pressure method, provide a preparation system for preparing nitric acid by converting gas in nitrate production, and replace the prior dilute nitric acid production process by the normal pressure method in the traditional nitrate production. Specifically, nitrogen oxides (high-purity NOx gas containing a small amount of water) from a conversion process are subjected to isothermal oxidation and absorption to obtain a nitric acid solution product with higher concentration, so that nitric acid with higher concentration is provided for a subsequent nitrate production section, the use amount of the nitric acid solution for conversion reaction is reduced, the use amount of steam is greatly reduced, and energy conservation and consumption reduction are realized. Mainly solves the problems of low nitric acid concentration, over-standard tail gas emission, high energy consumption and the like in the nitrate production industry. The method has the advantages that the recovery rate of the nitrogen oxide reaches more than 99.5 percent, the concentration of the nitric acid is more than 50 percent, the subsequent evaporation steam consumption is greatly saved, and the method has higher economic benefit and social environmental protection benefit.
The above list of details is only for the practical implementation of the present invention, and they are not intended to limit the scope of the present invention, and all equivalent implementations or modifications that do not depart from the technical spirit of the present invention should be included in the scope of the present invention.
It is obvious to a person skilled in the art that the invention is not restricted to details of the above-described exemplary embodiments, but that it can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (10)
1. A preparation system for preparing nitric acid from conversion gas in nitrate production is characterized by comprising,
the conversion unit is used for treating the sodium sulfite mother liquor in the conversion process to obtain conversion gas for preparing nitric acid;
an isothermal oxidation unit for oxidation of the converted gas to obtain NO by the gas supply unit X A gas;
an acid absorption unit connected with a desalted water unit, wherein the desalted water unit is connected with NO in the acid absorption unit X After the gas reacts, nitric acid solution and NO are obtained X Tail gas;
a first circulating cooling unit arranged in the acid absorption unit and used for NO X In the reaction of gases with acid solutionsAbsorbing heat, and circulating the nitric acid solution at the bottom of the acid absorption unit to the acid absorption unit;
the bottom of the acid absorption unit is connected with a nitric acid intermediate tank, the nitric acid intermediate tank and the conversion unit form a circulating pipeline through a second circulating cooling unit and a conversion circulating pump, so that part of nitric acid finished products in the nitric acid intermediate tank circulate to the conversion unit to form raw materials in the conversion unit.
2. The system for preparing nitric acid from conversion gas in nitrate production as claimed in claim 1, wherein the conversion unit comprises a conversion tower, a washing unit for washing conversion liquid in the conversion tower and a separation unit for gas-liquid separation in the conversion tower, and a gas outlet of the separation unit is communicated with the isothermal oxidation unit.
3. The system for preparing nitric acid from conversion gas in nitrate salt production according to claim 2, wherein the washing unit comprises a sodium sulfite mother liquor washing unit and a nitric acid washing unit, and the nitric acid washing unit is connected with the nitric acid intermediate tank.
4. The system for preparing nitric acid from conversion gas in nitrate production according to claim 1, further comprising a heater between the conversion unit and the sodium sulfite mother liquor transportation pipeline, wherein the heater is used for pre-treating and heating the sodium sulfite mother liquor to not less than 100 ℃.
5. The system for preparing nitric acid from reformed gas in nitrate production according to claim 1, wherein a reformed liquid circulating pump is connected to the bottom of the reforming unit, the bottom of the reforming unit forms a circulating system through the reformed liquid circulating pump, and a pH value control unit is connected to the reformed liquid circulating pump and used for controlling the pH value in the reforming unit.
6. The system for preparing nitric acid from conversion gas in nitrate salt production according to claim 1, wherein the acid absorption unit comprises a first acid absorption tower and a second acid absorption tower, and the first acid absorption tower and the second acid absorption tower form a circulation pipeline through a connecting pipeline and a nitric acid pump.
7. The system for preparing nitric acid from conversion gas in nitrate salt production according to claim 6, wherein the first acid absorption unit is connected with the gas supply unit, and the second acid absorption unit is communicated with the desalted water unit.
8. The system for preparing nitric acid from conversion gas in nitrate salt production according to claim 6, further comprising a condensed acid pump located at the bottom of the isothermal oxidation unit, wherein the condensed acid pump is respectively communicated with the top of the first acid absorption unit and the bottom of the second acid absorption unit.
9. The system for preparing nitric acid from conversion gas in nitrate production according to claim 6, wherein a circulating acid pump is arranged at the bottom of the first acid absorption unit, and the circulating acid pump forms a circulating pipeline on the side of the first acid absorption unit through the first circulating cooling unit and is communicated with the nitric acid intermediate tank.
10. The system for preparing nitric acid from conversion gas in nitrate production according to claim 6, further comprising a tail gas separator, wherein the tail gas separator is communicated with the acid absorption unit, and NO is discharged through an alkali treatment unit X And (4) tail gas.
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| CN117101380A (en) * | 2023-05-25 | 2023-11-24 | 西安明时工程技术有限责任公司 | Process for improving oxidation degree of NO in industrial production |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117101380A (en) * | 2023-05-25 | 2023-11-24 | 西安明时工程技术有限责任公司 | Process for improving oxidation degree of NO in industrial production |
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