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
  • C01B21/40—Preparation by absorption of oxides of nitrogen

Definitions

• the present invention relates to a method for breaking the NO to NO 2 cycle in the production of nitric acid and the recovery of nitric oxide, and more particularly to apparatus and methods for the recycle of NO x gas, recovery and the production of nitric acid.
• Equations (2) and (3) describe the cycle eliminated by the present invention. As can be seen from equations (2) and (3), the reaction of every three moles of NO 2 with water to form two moles of nitric acid return one of the three moles of oxidized nitrogen as
• one-third of the oxidized nitrogen has to be reoxidized with oxygen every time that two-thirds are reacted with water to form nitric acid.
• these reactions require the return of one-third of the nitric dioxide to the gas phase as nitric oxide (NO), Eq. (3), which then re-requires the termolar reaction to nitric dioxide (NO 2 ), Eq. (2), and then an additional liquid phase reaction to convert two-thirds of this NO 2 to nitric acid (HNO 3 ), with one-third of the entering NO 2 again being returned to the gas phase as NO for an additional gas phase reaction, and so on.
• NO nitric oxide
• HNO 3 nitric acid
• Typical discharge rates from such plants are about 3.9 MT (metric ton) of gases being discharged per each MT of 100% HNO 3 produced
• the discharged gases contain a typical concentration of 0.02% to 0.20% NO x .
• the elevated pressures used to increase the reaction rate also causes greater losses of the expensive platinum catalyst and lower efficiencies in ammonia oxidation and conversion to nitric acid.
• the invention provides a method for rapidly removing nitric oxide (NO) from the gas phase by reaction with catalyzed nitric acid.
• the reaction forms nitric trioxide (N 2 O 3 ) in solution.
• the homogeneous catalyst required is dissolved nitrite (NO 2 -) ion.
• nitrite ion When nitrite ion is present, the reaction is both rapid and quantitative.
• the principal object of the invention is to provide an improved method of effectively and economically recycling NO x into nitric acid.
• Another object of the invention is to provide a process for forming a trivalent nitrogen in solution which can be rapidly reacted with gaseous oxygen.
• Still another object of the invention is a process for the economical production and manufacture of nitric acid at atmospheric pressure while reducing or eliminating harmful environmental emissions.
• Part of the invention is the discovery that one can rapidly remove nitric oxide (NO) from the gas phase by reaction with catalyzed nitric acid.
• the reaction forms trivalent nitrogen in solution.
• the homogeneous catalyst is dissolved trivalent nitrogen (NO 2 -) ion.
• trivalent nitrogen (NO 2 -) ion When sufficient trivalent ion is present, the reaction is both rapid and quantitative. Although most texts on nitric and nitric oxides state that N 2 O 3 is rare or difficult to form, the present invention produces it rapidly and at such high concentrations that, if desired, one can form a dark blue, ink-like solution of N 2 O 3 in nitric acid and water.
• the other part of the present invention which breaks the NO to NO 2 gas phase cycle is the discovery that in the above solution, one can achieve rapid, quantitative oxidation of the N 2 O 3 in the liquid phase with dissolved oxygen rather than the conventional gas phase.
• the invention is a process which consists of the following steps:
• HNO 3 15 to 55% HNO 3
• HNO 3 Range 5 to 65% HNO 3 2
• NO 2 is present either from the process which is evolving the NO x or by gas phase oxidation where oxygen is present in the gases being supplied to the present invention, it is converted to HNO 3 and NO by the water present in the scrubbing HNO 3 /NO 2 solution as in Eq. (3).
• the resulting NO is reacted with the nitric and is oxidized in the liquid phase by the oxygen supplied. If desired, oxygen can be withheld and the resulting N 2 O 3 /HNO 3 solution can be stored or transferred to another site for oxidation to nitric acid at any convenient time.
• this process for generating nitric acid can be described as comprising the steps of: one, reacting a +2 oxidation gaseous nitrogen (NO), as shown in Table 1, with a +5 oxidation nitrogen in solution (HNO 3 ) to obtain a +3 oxidation nitrogen in solution (N 2 O 3 ); and two, reacting the +3 oxidation nitrogen (N 2 O 3 ), in the solution, with oxygen (O 2 ) and water (H 2 O) to produce a +5 oxidation nitrogen (HNO 3 ) while maintaining a level of a +3 oxidation nitrogen (N 2 O 3 ) in excess of added oxygen (O 2 ).
• the oxidation state also can be referred to as the valence state.
• Apparatus is set up with a source of nitric oxides and two or three nitric absorption vessels consisting of one-liter reactors containing nitric acid containing trivalent nitrogen.
• the scrubbing or reactant nitric acid is continuously circulated through a laboratory inductor. This supplies the energy required to circulate the nitric oxides through the vessels.
• the vessels are connected in a continuous loop.
• Oxygen addition is adjusted so as to maintain an excess of trivalent nitrogen in solution. No oxygen escapes into the head space. As this cycle continues, the collected and oxidized nitric oxide increases the concentration of the scrubbing nitric.
• Recovered nitric is 2.268 Kg as 100% HNO 3 or 99.17% of the supplied NO has been converted to nitric acid by the invention.
• the addition of this 2.268 Kg to the initial scrubbing nitric raises its concentration to 47.8%.
• a gaseous mixture of NO x with stoichiometric oxygen was passed through two reactors as described above.
• the total amount of nitric oxides fed into the system was
• the amount of nitric oxide recovered as nitric acid was 65.63 g., which was a recovery of 102.78%, essentially full recovery.
• This method breaks the mathematically infinite cycle of gas phase oxidation of nitric oxide (NO) to nitric dioxide (NO 2 ) and back to nitric oxide when nitric dioxide (NO 2 ) is reacted with water to nitric acid. Further, this invention provides a process for the recovery and production of nitric acid without the evolution of the gaseous nitrogen oxides into the environment.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Treating Waste Gases (AREA)
• Saccharide Compounds (AREA)
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• Physical Or Chemical Processes And Apparatus (AREA)

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• 1996
  • 1996-11-27 DK DK96942097T patent/DK0863843T3/da active
  • 1996-11-27 ES ES96942097T patent/ES2179958T3/es not_active Expired - Lifetime
  • 1996-11-27 AT AT96942097T patent/ATE220644T1/de not_active IP Right Cessation
  • 1996-11-27 NZ NZ324165A patent/NZ324165A/en not_active IP Right Cessation
  • 1996-11-27 JP JP9520697A patent/JPH11500707A/ja active Pending
  • 1996-11-27 CN CNB961997893A patent/CN1176845C/zh not_active Expired - Fee Related
  • 1996-11-27 EP EP96942097A patent/EP0863843B1/en not_active Expired - Lifetime
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  • 1996-11-29 ZA ZA9610047A patent/ZA9610047B/xx unknown
  • 1996-11-29 IN IN2067CA1996 patent/IN192282B/en unknown

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