Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Nitrogen or nitrogenous component
Patent
1994-06-22
1996-07-30
Straub, Gary P.
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Nitrogen or nitrogenous component
42324407, C01B 2102
Patent
active
055409024
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the cleaning of gases to remove toxic impurities, and especially to the cleaning of fumes from power stations prior to being expelled into the atmosphere.
It relates more particularly to a process for cleaning a gas to remove oxides of nitrogen, especially nitrogen monoxide (NO), and to remove sulphur dioxide.
Fossil fuels (coal, coke, petrol, petroleum derivatives) usually contain sulphur or sulphur compounds, and also nitrogen compounds. Consequently, the fumes generated by their combustion in air or in the presence of oxygen are usually contaminated with sulphur dioxide and with oxides of nitrogen. 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 sulphur dioxide, nitrogen monoxide and nitrogen dioxide means that they have to be removed from the fumes before the latter are expelled into the atmosphere.
In U.S. Pat. No. 4,838,147 (Waagner Biro AG) a process is proposed for cleaning fumes to remove oxides of nitrogen, according to which 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 where the fumes simultaneously contain oxides of nitrogen and sulphur dioxide, the alkali metal sulphite is formed in situ in the fumes by introducing into the latter an alkali metal bicarbonate or carbonate.
The disadvantage of this known process is that it necessitates the use of a number of reagents, including a gaseous reagent (ammonia) whose toxic nature implies extensive safety measures.
International Patent Application WO 86/06711 describes a two-stage process for cleaning a gas containing sulphur dioxide, nitrogen monoxide and nitrogen dioxide. In a first step, a mixture of oxygen and a hydrocarbon is introduced into the gas to be cleaned, which is maintained at a high temperature (greater than 800.degree. F. or 700 K), so as to oxidize the nitrogen monoxide to nitrogen dioxide via the intermediacy of peroxyl ions; in a second step, the gas collected from the first step is treated with sodium bicarbonate in order to remove from it sulphur dioxide and nitrogen dioxide, with the formation of sodium sulphite, sodium sulphate, sodium nitrate and nitrogen.
This known process has the disadvantage of requiring a number of reagents (oxygen, hydrocarbon, sodium bicarbonate). It has the additional disadvantage of necessitating a complex set-up for the injection of a mixture of oxygen and hydrocarbon into a gas at high temperature (greater than 700 K).
SUMMARY OF THE INVENTION
The invention overcomes the disadvantages of the known processes described above by providing a new process which enables efficient cleaning of a gas to remove nitrogen monoxide and sulphur dioxide to be effected by means of an alkali metal bicarbonate, without requiring any costly or dangerous additional reagent, and which, moreover, can be employed at moderate temperature.
Consequently, the invention relates to a process for cleaning a gas containing nitrogen monoxide and sulphur dioxide by means of an alkali metal bicarbonate, according to which a quantity of oxygen is employed in the gas which is at least equal to the stoichiometric quantity required to oxidize the nitrogen monoxide to nitrogen dioxide.
The invention applies to all gases which simultaneously contain nitrogen monoxide (NO) and sulphur dioxide (SO.sub.2). It applies especially 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 is applied to fumes, the combustible material is not critical and may equally be a gas, a liquid or a solid. It may contain a fossil fuel (such as natural gas, petroleum and its derivatives, coal and coke), biomass, or flammable inorganic or organic substances originati
REFERENCES:
patent: 4839147 (1989-06-01), Lindbauer et al.
patent: 5002741 (1991-03-01), Hooper
patent: 5165902 (1992-11-01), Bortz et al.
Dunn Jr. Thomas G.
Solvay ( Societe Anonyme)
Straub Gary P.
LandOfFree
Process for cleaning a gas containing nitrogen monoxide and sulp 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 cleaning a gas containing nitrogen monoxide and sulp, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for cleaning a gas containing nitrogen monoxide and sulp will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1656349