Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Nitrogen or nitrogenous component
Patent
1994-06-22
1995-11-07
Langel, Wayne
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Nitrogen or nitrogenous component
C01B 2102
Patent
active
054645999
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the cleaning of gases to remove toxic impurities, in particular to the cleaning of fumes from power stations before they are expelled into the atmosphere.
It relates more particularly to a process for cleaning a gas to remove oxides of nitrogen and, especially, to remove nitrogen monoxide (NO)
2. Description of the Related Art
The fumes generated by the combustion of gaseous, liquid or solid combustible materials are usually contaminated by oxides of nitrogen originating from the nitrogen in atmospheric air and, in some cases, from nitrogen compounds present in the fuel. In these fumes, nitrogen monoxide (NO) constitutes the majority of the oxides of nitrogen, the remainder consisting principally of nitrogen dioxide (NO.sub.2).
The high toxicity of nitrogen monoxide and of nitrogen dioxide means that they have to be removed from the fumes before the latter are expelled into the atmosphere.
U.S. Pat. No. 4,839,147 (Waagner Biro AG) proposes a process for cleaning fumes to remove oxides of nitrogen, in which an alkali metal sulphite and ammonia gas are introduced into the fumes so as to reduce the oxides of nitrogen to dinitrogen monoxide (N.sub.2 O) which is subsequently reduced to nitrogen by the ammonia. In the case of fumes which simultaneously contain oxides of nitrogen and sulphur dioxide, the alkali metal sulphite is formed in situ in the fumes by introducing an alkali metal bicarbonate or carbonate into these fumes.
The disadvantage of this known process is that it requires the use of a number of reagents, including a gaseous reagent (ammonia) whose toxic nature implies considerable safety measures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 and 2 are diagrams indicating the composition of the gases referred to in the Examples.
SUMMARY OF THE INVENTION
The invention overcomes this disadvantage of the known process described above by providing a new process which makes it possible to carry out efficient cleaning of a gas to remove nitrogen monoxide, without requiring the use of a dangerous gaseous reagent, and which can be carried out at a moderate temperature while giving excellent results.
Consequently, the invention relates to a process for cleaning a gas containing nitrogen monoxide by means of an alkali metal compound, according to which a quantity of oxygen is employed in the gas which is at least equal to the stoichiometric quantity which is necessary in order to oxidize the nitrogen monoxide to nitrogen dioxide, and, for the alkali metal compound, an alkali metal pyrosulphite is selected and is employed in a quantity which is sufficient to convert the nitrogen monoxide in the gas to alkali metal nitrate and nitrite.
In the case where the gas to be treated contains nitrogen monoxide and nitrogen dioxide, a quantity of alkali metal pyrosulphite is preferably used which is at least sufficient to decompose the nitrogen monoxide and the nitrogen dioxide into alkali metal nitrite and alkali metal nitrate.
The invention applies to all gases containing nitrogen monoxide (NO). It applies in particular to the gases generated by the combustion of combustible materials in the presence of air or oxygen. Hereinafter, a gas originating from the combustion of a combustible material will be called "fumes". In the case where the invention applies to fumes, the combustible material is not critical and may be either a gas, a liquid or a solid. It may comprise a fossil fuel (such as petroleum and its derivatives, coal and coke), biomass, or flammable organic or inorganic substances originating, for example, from household or municipal waste. The origin of the fumes is likewise not critical, and they may for example originate from an electricity-producing power station, from a centralized plant for long-distance heating or from a plant for incineration of household or municipal refuse.
The gas treated in the process according to the invention necessarily contains nitrogen monoxide (NO). It may contain other oxides of nitrogen in ad
REFERENCES:
patent: 4141961 (1979-02-01), Miller
patent: 4588567 (1986-05-01), Miller
patent: 4839147 (1989-06-01), Lindbauer et al.
patent: 5002741 (1991-03-01), Hooper
Dunn Jr. Thomas G.
Langel Wayne
Solvay ( Societe Anonyme)
LandOfFree
Process for purifying a gas to remove nitrogen monoxide therefro does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for purifying a gas to remove nitrogen monoxide therefro, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for purifying a gas to remove nitrogen monoxide therefro will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-195620