Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Nitrogen or nitrogenous component
Patent
1985-09-24
1987-06-02
Heller, Gregory A.
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Nitrogen or nitrogenous component
423242, 423243, C01B 2100, C01B 1700
Patent
active
046702342
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national phase applicator corresponding to the international application PCT/EP85/00018 filed Jan. 23, 1985 and based under the International Convention, in turn, on the following national applications:
The present invention relates to a process for the removal of oxides of nitrogen and oxides of sulfur, as well as other injurious substances from the smoke and gases discharged from combustion plants, mainly from generating plant boilers that are charged with fossil fuels, the oxides of nitrogen being reduced to simple nitrogen and the oxides of sulfur and any other injurious substances being removed by means of a scrubbing process.
BACKGROUND OF THE INVENTION
When fossil fuels are burned oxides of nitrogen (NO and NO.sub.2) result from thermal reaction of atmospheric nitrogen and atmospheric oxygen (thermal NO.sub.x), from reaction of nitrogen from the fuel with atmospheric oxygen (fuel NO.sub.x) and by conversion of compounds (radicals) that contain nitrogen with combustion air (prompt NO.sub.x).
The contents of oxides of nitrogen vary according to the fuel that is involved and according to combustion conditions. Once liberated to the atmosphere, the nitrogen oxides are subject to further chemical conversion, particularly photochemical conversion, which can subsequently lead to the formation of organic peroxide compounds with the hydrocarbons that are also present, and which in turn are responsible for extensive plant damage.
Together with the oxides of sulfur (SO.sub.2 and So.sub.3) that result from the sulfur compound in the fuels, as well as the acids that result from these, the oxides of nitrogen and their secondary products that are formed in the atmosphere are regarded as the principal cause of air pollution and the damage that results from such pollution.
At present there is a paucity of knowledge about the precise causal mechanisms of many of the types of such damage.
Legal regulations as well as guidlines and instructions have been enacted in various industrial nations with the aim of reducing emissions of the oxides of sulfur and nitrogen.
Catalytic process for the removal of oxides of nitrogen are known; in these processes NO and NO.sub.2 are reduced to simple nitrogen by reducing agents. In the combustion plants of power generating stations, for example, ammonia is used predominantly as the deoxidizing agent for oxides of nitrogen that are then converted to elementary nitrogen and water over various catalysts such as transition metal oxides, zeolites, activated charcoal, or activated coke.
Removal of sulfur oxides from the smoke gases is in many instances effected by contact with washing solutions that contain calcium ions that remove the oxides of sulfur, oxidized to sulfates, in the form of gypsum.
OBJECT OF THE INVENTION
It is the object of the present invention to improve the process of the type described in the introduction hereto with regard to its simplicity and the results that can be achieved.
SUMMARY OF THE INVENTION
According to the present invention this object is achieved in that ethylenediaminetetraacetic acid (EDTA) C.sub.10 H.sub.16 O.sub.8 N.sub.2 and a mono- and/or multi-base carboxylic acid, preferably formic acid, together with limestone, fine chalk or derivatives thereof, are added to the scrubbing liquid of a desulfuration plant. It has been found that because of the reduction of the SO.sub.2 and NO.sub.x components by the EDTA, the combined effect of both additives is more favorable, i.e. operates with a higher efficiency, and is more economical.
It is known that NO.sub.x can be removed from the smoke gas downstream of to a combustion plant by the addition of EDTA and iron-II sulfate and passing the gas to a desulfurization wash circulation system, it being necessary in such a case to maintain a special ratio of the SO.sub.2 and the NO.sub.x (a minimum of 2:1) and a certain oxygen content of the smoke gas.
It has been found that the simultaneous separation of NO.sub.x can be greatly increased and the
REFERENCES:
patent: 3923954 (1975-12-01), Petrey et al.
patent: 3932585 (1976-01-01), Moriguchi et al.
patent: 3971734 (1976-07-01), Bush
patent: 4222993 (1980-09-01), Holter et al.
Dewert Heribert
Gresch Heinrich
Holter Heinz
Igelbuscher Heinrich
Dubno Herbert
Heller Gregory A.
Holter Heinz
Ross Karl F.
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