GB1577869A - Creation of Inventions and Patents with Artificial Intelligence

GB1577869A – Process for obtaining nitric acid of a concentration higher than the azeotropic concentration by means of the absorption of nitrogen oxides in dilute nitric acid
– Google Patents

GB1577869A – Process for obtaining nitric acid of a concentration higher than the azeotropic concentration by means of the absorption of nitrogen oxides in dilute nitric acid
– Google Patents
Process for obtaining nitric acid of a concentration higher than the azeotropic concentration by means of the absorption of nitrogen oxides in dilute nitric acid

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Publication number
GB1577869A

GB1577869A
GB15607/77A
GB1560777A
GB1577869A
GB 1577869 A
GB1577869 A
GB 1577869A
GB 15607/77 A
GB15607/77 A
GB 15607/77A
GB 1560777 A
GB1560777 A
GB 1560777A
GB 1577869 A
GB1577869 A
GB 1577869A
Authority
GB
United Kingdom
Prior art keywords
nitric acid
gas mixture
superazeotropic
concentration
azeotropic
Prior art date
1976-06-08
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

Expired

Application number
GB15607/77A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

MARZO RODRIGO J

MARZO RODRIGO L

Original Assignee
MARZO RODRIGO J
MARZO RODRIGO L
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1976-06-08
Filing date
1977-04-14
Publication date
1980-10-29

1977-04-14
Application filed by MARZO RODRIGO J, MARZO RODRIGO L
filed
Critical
MARZO RODRIGO J

1980-10-29
Publication of GB1577869A
publication
Critical
patent/GB1577869A/en

Status
Expired
legal-status
Critical
Current

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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

C01B21/38—Nitric acid

C01B21/44—Concentration

Description

PATENT SPECIFICATION
( 21) Application No 15607/77 ( 31) Convention Application No 448675 ( 33) Spain (ES) ( 22) Filed 14 Apr 1977 ( 19) ( 32) Filed 8 Jun 1976 in // ( 44) Complete Specification Published 29 Oct 1980 ( 51) INT CL 3 ( 52) Index at A( C Oi B 21/40 cceptance CIA 2 B ( 54) A PROCESS FOR OBTAINING NITRIC ACID OF A CONCENTRATION HIGHER THAN THE AZEOTROPIC CONCENTRATION BY MEANS OF THE ABSORPTION OF NITROGEN OXIDES IN DILUTE NITRIC ACID ( 71) We, Luis MARZO RODRIGO and Jesus MARZO RODRIGO, Spanish citizens, of Avda Bruselas No 69 Madrid -28 and Cebreros No 76, Madrid -11, Spain, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement:This invention is concerned with a process for producing commercially pure nitric acid.
Practically all the nitric acid produced irndustrially is obtained starting with ammonia by catalytic oxidation of the ammonia in accordance with the reaction:
4 NH 3 + 5 O 4 NO + 6 H 2 o + Heat (I) The quantity of water formed is important and when it is desired to produce acid with a high concentration it is necessary to eliminate the water almost entirely since, as is shown in the literature, if the water referred to is not eliminated, the maximum concentration of nitric acid possible is of the order of 77 %.
The NO (nitric oxide) is considered to be a nitrogenous oxide having a low degree of oxidation, which in the presence of oxygen and at low temperature oxidizes to NO 2 (nitrogen dioxide) of a high degree of oxidation in accordance with the reaction:
2 NO + 02 2 NO 2 + Heat (II) It is precisely this nitrogen dioxide (or its dimer) that is absorbed in water to form nitric acid in accordance with the reaction:
3 NO 2 + H 20 -> 2 HNO 3 + NO + Heat (III) At a greater pressure of the nitrogen oxides that enter into contact with the water, a greater concentration of nitric acid may be obtained.
For reasons of safety, the maximum concentration of ammonia in the mixture with air for effecting reaction (I) does not usually exceed 12 % if the reaction is carried out at low pressure, or 10 % it it is carried out at high pressure.
The conventional processes for the production of nitric acid usually involve compression of the gases or after effecting reaction (I) up to pressures of 4 or 5 atmosphere (medium pressure processes), 7 or 8 atmos 50 phere (high pressure processes) and 10 to 12 atmosphere (very high pressure) Depending on the pressures at which reactions (I) and (II) are carried out, different processes are obtained, but all of them have in common the 55 factor that the partial pressure of the highly oxidized nitrogen oxides at the beginning of the absorption stage is not usually sufficiently high to produce large percentages of acid of a concentration higher than the azeotropic 60 concentration ( 68 % by weight).
Therefore, there are known processes for increasing the above-mentioned partial pressure in which, in addition to operating at high pressures, cycles of nitrogen dioxide are 65 established by means of the absorption stage in such a way that NO 2 is added to the gases thet enter into absorption and the part that is not absorbed is washed with nitric acid of to 75 % by weight, the washing acid is 70 again expelled and returns to the beginning of the absorption zone In these processes the gases are usually compressed immediately after they are cooled sufficiently to allow the water produced in accordance with reaction 75 (I) to separate from the reagent gases Consequently, the oxidation of NO to NO 2 is easily achieved, since reaction (II) is favoured by high pressures and low temperatures.
According to the present invention, there 80 is provided a process for producing commercially pure nitric acid comprising the steps of ( 1) reacting a gas mixture containing NO with subazeotropic nitric acid to form NO 2; ( 2) compressing the resultant gas mixture 85 containing NO 2; ( 3) passing azeotropic nitric acid from step ( 4) below and the compressed gas mixture through an absorption chamber to form superazeotropic nitric acid; ( 4) distilling the superazeotropic nitric acid 90 to separate it into commercially pure nitric acid and azeotropic nitric acid; ( 5) passing Lv_ ( 11) 1 577 869 (a) the gases which have passed through the from the reaction of ammonia with oxygen to absorption chamber and (b) the spent nitric to form NO and water.
acid from the reaction step ( 1) into another The accompanying drawing is a simplified absorption chamber to form subaieotropic flow diagram of a plant in which an embodiacid; and ( 6) passing the subazeotropic nitric ment of a process of the present invention is 70 acid to step ( 1) conducted The plant oxidation of ammonia In the reaction step ( 1) above, the following is effected at low pressure (which has the reaction takes place: advantage that on condensation of the water 2 HNO 3 + NO + Heat 3 NO 2 + H 2 O (IV) formed in accordance with reaction (I), the The advantages of this step are: quantity of nitric acid in the water is minimal 75 ( 1) The oxidation of No to NO, is achieved, and, of course vev much less than that obalmost completely, maintaining very low quantities of non-oxidized NO, which is required in order to produce, by chemical absorption, the superazeotropic nitric acid.
( 2) As 3 mols of NO 2 are produced for every mol of NO, a very large increase is obtained in the NO 2 content of the reagent gases.
It is also important to indicate that both in the process of the invention and in those already known, only part of the gases that are sent to the chamber utilised in step ( 3) above will give rise to superazeotropic nitric acid since, for the reasons of chemical equilibrium, there is a partial pressure of nitrogen oxides in equilibrium with azeotropic nitric acid and below the partial pressure referred to, it is not possible to obtain superazeotropic nitric acid.
In the known processes, once the said partial pressure is attained, the off gases are usually subjected to a washing (that it to say physical absorption) with nitric acid of average concentration ( 60 to 75 %) at very low temperatures so that the recovery is achieved of almost all nitrogen oxides so that the emission of oxides into the atmosphere is low Furthermore, the washing acid charged with oxides is subsequently subjected to a desorption operation (generally by means of secondary air and operation at low pressure), and the NO 2 is recovered which is reincorporated into the cycle by means of the same secondary air.
In the process according to the invention, when the gases reach the partial pressure of equilibrium, they are absorbed in the spent nitric acid and react, in accordance with reaction (III) giving rise to subazeotropic nitric acid which is precisely that which is utilized in order to oxidize the NO to NO 2 in accordance with reaction (IV) Furthermore, if this absorption step is effected at very high pressure, low emissions of oxides into the atmosphere are also achieved.
An additional advantage of the process of the invention over previously proposed processes is that the process does not require gaseous NO 2 as a feedstock.
The process of the present invention preferably includes the step of removing water from the gas mixture containing NO before effecting step ( 1) This is particularly important in the case where the gas mixture containing NO is one which has been obtained tained in condensation processes with higher pressures).
In the diagram referred to, a tower (system 7) in which the oxidation of NO to NO 2 is 80 produced also functions at low pressure which presents the advantage compared with operation at higher pressures that the larger part of the nitrogen oxides before conversion of NO to NO 2 are in the form of NO and there 85 fore, taking into account that 3 mols of NO 2 are obtained for each mol of NO in accordance with reaction IV, the quantity of NO 2 is greater than can be achieved by the processes that operate at higher pressure in which 90 the nitrogen oxides are usually displaced towards NO 2.
In accordance with the flow diagram, ammonia and air are mixed and reacted in a reactor 1, in accordance with reaction (I) 95 The resultant gases are cooled in various heat exchangers 2, 3 and 4, whose operation is irrelevant for the purpose of the patent.
In a cooler 5, the dew point of the gas mixture is achieved, and the water formed in 100 the previous reaction condenses and is separated in a cooler 6.
As this water generally contains a small amount of nitric acid, part of it may be passed as shown, to an absorption tower ( 10) while 105 the dry gas mixture is passed to an oxidation system 7, where reaction IV takes place between NO in the gas mixture and dilute nitric acid from the absorption tower 10.
From the oxidation system 7 two streams 110 are obtained, namely a gas stream and a liquid stream The liquid stream is spent nitric acid which is passed to the tower 10 for concentration to produce subazeotropic nitric acid, and the gas stream, which is very rich in NO 2, 115 is sent to a compressor 8.
In the compressor, the gases are compressed to 6-15 atmospheres (preferably 10-13 atmospheres) at which stage the partial pressure of the nitrogen oxides is very high (between 1 and 120 4 atmospheres) The compressed gases are passed on to a superazeotropic absorption system 9 In the system 9, the gases enter into contact with nitric acid of azeotropic concentration froma distillation tower 11, 125 whereby the concentration of the acid is increased and the partial pressure of the nitrogen oxides is reduced to a value close to the equilibrium with azeotropic nitric acid.
Acid of a concentration higher than azeo 130 1 577 869 1 577 869 tropic concentration is distilled in the tower 11, to give two streams, one of practically pure nitric acid and the other of azeotropic nitric acid which is passed to the system 9 as described above.
With regard to gases poor in NO 2 ‘ they pass from the system 9 to the subazeotropic absorption tower 10, where in countercurrent with aqueous solutions of nitric acid they are absorbed, giving rise to an acid of a concentration lower than the azeotropic concentration, which is returned to the oxidation system 7.
The process is sufficiently versatile that the respective proportions of dilute nitric acid and pure nitric acid can be varied at will between 0 and 100 %.
The gases from which the nitrogen oxides have been eliminated is heated in conventional heat exchangers and recovers its energy generally by means of an expansion turbine coupled to a compressor group with which the energy consumption of the compressor is considerably reduced.

Claims (4)

WHAT WE CLAIM IS:-

1 A process for producing commercially pure nitric acid comprising the steps of ( 1) reacting a gas mixture containing NO with subazeotropic nitric acid to form NO 2, ( 2) compressing the resultant gas mixture containing NO 21 ( 3) passing azeotropic nitric acid from step ( 4) below and the compressed gas mixture through an absorption chamber to form superazeotropic nitric acid, 35 ( 4) distilling the superazeotropic nitric acid to separate it into commercially pure nitric acid and azeotropic nitric acid, ( 5) passing (a) the gases which have passed through the absorption chamber and (b) the 40 spent nitric acid from the reaction step ( 1) into another absorption chamber to form superazeotropic acid, and ( 6) passing the superazeotropic nitric acid to step ( 1) 45

2 A process as claimed in claim 1, wherein the gas mixture containing NO is one which has been obtained from the reaction of ammonia with oxygen to form NO and water, and the process further includes the step of re so moving water from the gas mixture containing NO before effecting step ( 1).

3 A process for producing commercially pure nitric acid substantially as hereinbefore described with reference to the accompanying 55 drawing.

4 Nitric acid when produced by the process as claimed in any preceding claim.
MARKS & CLERK Alpha Tower, ATV Centre, Birmingham Bl ITT AGENTS FOR THE APPLICANTS Printed for Her Majesty’s Stationery Office by MULTIPLEX techniques ltd, St Mary Cray, Kent 1980 Published at the Patent Office, 25 Southampton Buildings, London WC 2 l AY, from which copies may be obtained.

GB15607/77A
1976-06-08
1977-04-14
Process for obtaining nitric acid of a concentration higher than the azeotropic concentration by means of the absorption of nitrogen oxides in dilute nitric acid

Expired

GB1577869A
(en)

Applications Claiming Priority (1)

Application Number
Priority Date
Filing Date
Title

ES448675A

ES448675A1
(en)

1976-06-08
1976-06-08
Process for obtaining nitric acid of a concentration higher than the azeotropic concentration by means of the absorption of nitrogen oxides in water or diluted nitric acid

Publications (1)

Publication Number
Publication Date

GB1577869A
true

GB1577869A
(en)

1980-10-29

Family
ID=8471725
Family Applications (1)

Application Number
Title
Priority Date
Filing Date

GB15607/77A
Expired

GB1577869A
(en)

1976-06-08
1977-04-14
Process for obtaining nitric acid of a concentration higher than the azeotropic concentration by means of the absorption of nitrogen oxides in dilute nitric acid

Country Status (4)

Country
Link

US
(1)

US4064221A
(en)

AR
(1)

AR208440A1
(en)

ES
(1)

ES448675A1
(en)

GB
(1)

GB1577869A
(en)

Families Citing this family (6)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

DE2850054A1
(en)

1978-11-14
1980-05-29
Uhde Gmbh

METHOD FOR PRODUCING Nitric Acid

DE3138814C2
(en)

1981-09-30
1985-03-07
Davy McKee AG, 6000 Frankfurt

Process for the simultaneous production of highly concentrated and dilute nitric acid

DE3869490D1
(en)

1987-06-29
1992-04-30
Atomic Energy Authority Uk

METHOD FOR THE ELECTROCHEMICAL TREATMENT OF SUBSTANCES.

US6284212B1
(en)

1998-11-10
2001-09-04
O’brien Robert N.
Method of nitric acid formation using a catalytic solution

US6737034B2
(en)

2001-08-02
2004-05-18
The United States Of America As Represented By The Secretary Of The Army
Nitric acid production

WO2005078787A1
(en)

2004-02-16
2005-08-25
Sharp Kabushiki Kaisha
Thin film transistor and manufacturing method thereof, display apparatus, method for modifying oxide film, method for forming oxide film, semiconductor device, method for manufacturing semiconductor device and equipment for manufacturing semiconductor device

Family Cites Families (5)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

US2088057A
(en)

1932-03-03
1937-07-27
Du Pont
Production of nitric acid from oxides of nitrogen

US2098953A
(en)

1934-05-26
1937-11-16
Chemical Construction Corp
Nitric acid manufacture

DE657192C
(en)

1934-08-14
1938-02-26
Hydro Nitro S A

Production of highly concentrated nitric acid from diluted nitric acid

US3399965A
(en)

1963-09-11
1968-09-03
Pullman Inc
Production of 68 to 70% nitric acid

GB1306581A
(en)

1969-02-28
1973-02-14
Pintsch Bamag Ag
Process for the production of nitric acid with a concentration of over 70percent by weight

1976

1976-01-01
AR
AR264336A
patent/AR208440A1/en
active

1976-06-08
ES
ES448675A
patent/ES448675A1/en
not_active
Expired

1976-09-07
US
US05/720,559
patent/US4064221A/en
not_active
Expired – Lifetime

1977

1977-04-14
GB
GB15607/77A
patent/GB1577869A/en
not_active
Expired

Also Published As

Publication number
Publication date

ES448675A1
(en)

1977-01-01

US4064221A
(en)

1977-12-20

AR208440A1
(en)

1976-12-27

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