US4138470A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of preventing escape of nitrogen oxides from an aqueous nitrate solution
Assignee: Individual
•
Filing: 1977-08-22
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Granted: 1979-02-06
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Expires: 1997-08-22
Abstract
Abstract Nitric oxide may be removed from gases which it is admixed by contacting the gases with aqueous solutions containing nitrate ions in sufficient concentration to oxidize the nitric oxide to nitrous acid and to retain it in the solution under stable conditions. Other oxides of nitrogen can also be absorbed producing nitrous acid which is retained in the aqueous solution in a similar manner. Thereafter, the scrubbing solution is regenerated under controlled conditions, producing a gas stream which contains the recovered nitrogen oxides in relatively high concentration and a scrubbing solution which can be recycled. The recovered nitrogen oxides may be used in the manufacture of nitric acid or other compounds or decomposed into harmless gases.
Inventors
- 👤 Donald W. Bolme
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 01:25
CPC Classifications
B; B01; B01D; B01D53/00; B01D53/34; B01D53/46; B01D53/54; B01D53/56; C; C01; C01B; C01B21/00; C01B21/20; C01B21/36
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
128 words
A method for preventing the escape of nitrogen oxide from an acid bath and for preventing the boilover of such bath, said method comprising the steps of so controlling the nitric acid and total nitrate concentrations of said bath as to maintain the oxidizing potential of the bath at a level which is effective to convert the nitrogen oxides to the trivalent state by promoting the reaction: 2NO + NO.sub.3.sup.- + H.sub.2 O→3NO.sub.2.sup.- + 2H.sup.+ ; dissolving the trivalent material in the water present in said bath; removing a portion of the solution from the body thereof; removing trivalent materials in the separation portion of the aqueous solution therefrom; and returning that portion of the solution from which the trivalent materials were removed to said body of solution.
Claim 2
Independent Claim
128 words
A method for preventing the escape of nitrogen oxide from an acid bath and for preventing the boilover of such bath, said method comprising the steps of so controlling the nitric acid and total nitrate concentrations of said bath as to maintain the oxidizing potential of the bath at a level which is effective to convert the nitrogen oxides to the trivalent state by promoting the reaction: 2NO + NO.sub.3.sup.- + H.sub.2 O→3NO.sub.2.sup.- + 2H.sup.+ ; dissolving the trivalent material in the water present in said bath; removing a portion of the solution from the body thereof; removing trivalent materials in the separation portion of the aqueous solution therefrom; and returning that portion of the solution from which the trivalent materials were removed to said body of solution.
Claim 3
Dependent Claim
26 words
A method as defined in claim 1 in which the trivalent materials are removed by subjecting the separated portion of the aqueous solution of a vacuum.
Claim 4
Dependent Claim
23 words
A method as defined in claim 1 in which the trivalent materials are removed by heating the separated portion of the aqueous solution.
Claim 5
Dependent Claim
32 words
A method as defined in claim 1 in which the trivalent materials are removed by stripping the separated portion of the aqueous solutions with a gaseous material such as steam or air.
Claim 6
Dependent Claim
23 words
A method as defined in claim 1 in which said aqueous nitrate containing solution is a bath used to pickle or dissolve metals.
Claim 7
Dependent Claim
22 words
A method as defined in claim 1 in which said aqueous, nitrate containing solution contains copper nitrate as one of its constituents.
Claim 8
Dependent Claim
47 words
A method as defined in claim 1 in which the concentration of nitrate ion in said body of solution is maintained in the range of 1-11.5 normal to inhibit the decomposition of the dissolved trivalent material and the oxidation of the nitric oxide past the trivalent state.
Claim 9
Dependent Claim
26 words
A method as defined in claim 1 in which the nitrate ion concentration is said solution is maintained in the range of 2 to 8 normal.
Claim 10
Dependent Claim
49 words
A method as defined in claim 1 which includes the step of maintaining in said solution nitrate compounds which are capable of reacting with trivalent nitrogen compounds present in the solution to form unionized nitrite complexes and thereby prevent the escape of said trivalent nitrogen compounds from the solution.
Claim 11
Independent Claim
262 words
A method of converting nitrogen oxides released in a body of aqueous nitrate containing solution to the soluble trivalent form, dissolving the trivalent material in the said solution, and maintaining the amount of trivalent material contained in the said body of aqueous solution at or below a selected level to keep nitrogen oxide from escaping into the atmosphere and/or to prevent boilover, said method comprising the steps of so controlling the nitric acid and total nitrate concentrations in said body of solution as to keep the product of the hydrogen ion activity and the nitrate ion activity at a level which will effect the reaction 2NO + NO.sub.3.sup.- + H.sub.2 O → 3NO.sub.2.sup.- + 2H.sup.+ at a rate k'[HNO.sub.2 ] [H.sup.+ ] [NO.sub.3.sup.- ]- k [HNO.sub.2 ].sub.2.sup.4 /(P.sub.NO).sup.2 ≧ 0, where [HNO 2 ] is the trivalent nitrogen acid concentration in gram moles per liter, [H + ] is the hydrogen ion activity in gram moles per liter, [NO 3 - ] is the nitrate ion activity in gram moles per liter, [P NO ] is the partial pressure of nitric oxide gas in atmospheres, k' is a temperature-correlated constant equal to about 1.6 at 25° C., and k is a temperature-correlated constant equal to about 46 at 25° C.; dissolving the trivalent material in the water present in said solution; removing a portion of the solution from the body thereof; removing trivalent materials in the separated portion of the aqueous solution therefrom; and returning that portion of the solution from which the trivalent materials were removed to said body of solution.
Claim 12
Independent Claim
262 words
A method of converting nitrogen oxides released in a body of aqueous nitrate containing solution to the soluble trivalent form, dissolving the trivalent material in the said solution, and maintaining the amount of trivalent material contained in the said body of aqueous solution at or below a selected level to keep nitrogen oxide from escaping into the atmosphere and/or to prevent boilover, said method comprising the steps of so controlling the nitric acid and total nitrate concentrations in said body of solution as to keep the product of the hydrogen ion activity and the nitrate ion activity at a level which will effect the reaction 2NO + NO.sub.3.sup.- + H.sub.2 O → 3NO.sub.2.sup.- + 2H.sup.+ at a rate k'[HNO.sub.2 ] [H.sup.+ ] [NO.sub.3.sup.- ]- k [HNO.sub.2 ].sub.2.sup.4 /(P.sub.NO).sup.2 ≧ 0, where [HNO 2 ] is the trivalent nitrogen acid concentration in gram moles per liter, [H + ] is the hydrogen ion activity in gram moles per liter, [NO 3 - ] is the nitrate ion activity in gram moles per liter, [P NO ] is the partial pressure of nitric oxide gas in atmospheres, k' is a temperature-correlated constant equal to about 1.6 at 25° C., and k is a temperature-correlated constant equal to about 46 at 25° C.; dissolving the trivalent material in the water present in said solution; removing a portion of the solution from the body thereof; removing trivalent materials in the separated portion of the aqueous solution therefrom; and returning that portion of the solution from which the trivalent materials were removed to said body of solution.
Claim 13
Dependent Claim
26 words
A method as defined in claim 10 in which the trivalent materials are removed by subjecting the separated portion of the aqueous solution to a vacuum.
Claim 14
Dependent Claim
32 words
A method as defined in claim 10 in which the trivalent materials are removed by stripping the separated portion of the aqueous solutions with a gaseous material such as steam or air.
Claim 15
Dependent Claim
23 words
A method as defined in claim 10 in which said aqueous nitrate containing solution is a bath used to pickle or dissolve metals.
Claim 16
Dependent Claim
22 words
A method as defined in claim 10 in which said aqueous, nitrate containing solution contains copper nitrate as one of its constituents.
Claim 17
Dependent Claim
47 words
A method as defined in claim 10 in which the concentration of nitrate ion in said body of solution is maintained in the range of 1-11.5 normal to inhibit the decomposition of the dissolved trivalent material and the oxidation of the nitric oxide past the trivalent state.
Claim 18
Dependent Claim
26 words
A method as defined in claim 10 in which the nitrate ion concentration in said solution is maintained in the range of 2 to 8 normal.
Claim 19
Dependent Claim
49 words
A method as defined in claim 10 which includes the step of maintaining in said solution nitrate compounds which are capable of reacting with trivalent nitrogen compounds present in the solution to form unionized nitrite complexes and thereby prevent the escape of said trivalent nitrogen compounds from the solution.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-02-05 | 1982-08-07 | 1983-02-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-02-05 | 1986-08-07 | 1987-02-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-02-05 | 1990-08-07 | 1991-02-06 | $7700.00 | Window Closed / Lapsed |