Removal of nitrogen oxides from industrial gases by use of oxidizing solutions in which nitrates are the oxidants
OwnerDonald W. Bolmeinventor
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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.
Claims19
A method of removing the sparingly soluble compound nitric oxide from industrial waste gases comprising an admixture of said nitric oxide and at least one other gas which includes the steps of:
- oxidizing the nitric oxide to the soluble trivalent state by so contacting it with an aqueous, nitrate ion containing solution as to effect the reaction
- 2NO + NO.sub.3.sup.- + H.sub.2 O .fwdarw. 3NO.sub.2.sup.- + 2H.sup.+;
- and dissolving the trivalent material in the water present in said solution to thereby separate the trivalent material from said gases;
- the concentration of nitrate ion in said solution being maintained in the range of 1-11.5 normal during the aforesaid steps to inhibit the decomposition of the dissolved trivalent material and the oxidation of the nitric oxide past the trivalent state, thereby maximizing the separation of the nitric oxide from the admixture.
A method of removing nitric oxide from industrial waste gases comprising an admixture of said oxide and at least one other gas which includes the step of so contacting the gases in said admixture with an aqueous, nitrate ion containing solution having a nitrate ion concentration in the range of 1-11.5 normal as to effect the reaction
- 2NO + NO.sub.3.sup.- H.sub.2 O .fwdarw. 3NO.sub.2.sup.- + 2H.sup.+
- at a rate ##EQU2## where [HNO.sub.2 ] is the trivalent nitrogen acid concentration in gram moles per liter,
- [H.sup.+] is the hydrogen ion activity in gram moles per liter,
- [NO.sub.3.sup.-] is the nitrate ion activity in gram moles per liter,
- (P.sub.NO) is the partial pressure of nitric oxide gas in atmospheres,
- k' is a temperature-correlated constant equal to about 1.6 at 25.degree. C., and
- k is a temperature-correlated constant equal to about 46 at 25.degree. C,
- thereby oxidizing said nitric oxide to the soluble trivalent state;
- and dissolving it in said solution to thereby separate said oxide from the admixture.
Dependencies are inferred from the claim text.