Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Sulfur or sulfur containing component
Patent
1983-07-11
1985-05-28
Heller, Gregory A.
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Sulfur or sulfur containing component
110343, 110345, 423242, B01J 800, C01B 1700
Patent
active
045199957
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of desulfurizing flue gases generated in a coal firing operating according to the dry additive process and being provided with dust filters. Furthermore the invention concerns a device for practising this method.
In operating large-scale combustion plants, such as for example steam-generating plants for steam turbines, pollution control must be observed to an increasing extent. In particular the rate of emission of pollutants of the combustion plants has to be kept as low as possible. On the other hand, economy as well as low operational costs make it necessary to fire coal of lower quality, in particular lignite of this country, which in combustion produces a relatively high percentage of pollutants. Especially the concentration of sulfur in the form of sulfur dioxide and sulfur trioxide in the flue gases is of concern. In desulfurizing powerplant flue gases, it is in the first place the cost considerations which determine the applicability of a particular desulfurizing method as the equipment for desulfurizing exhausted flue gases requires a considerable apparatus expense and consequently high investment.
In order to reduce emission of sulfur during the firing, a method has already been devised according to which the so-called dry additives have been charged in the combustion space of the plant so as to chemically bind the sulfur constituents of the flue gases as far as possible. This known method uses particularly fine-grain calcium oxide or calcium carbonate blown into the firing space. In coal dust firing plants provided with a grinding and drying recycle system, the calcium oxide is admixed to the coal already before the coal is pulverized in the grinding mill. Both constituents are then fed together through the coal dust burner into the firing space or combustion chamber. This known dry additive process, however, does not yield satisfactory results under all circumstances, and among other factors the kind of coal employed plays its part. It has been found that the desulfurization is insufficient for some kinds of lignite, since apparently due to high temperatures in the firing space the admixed calcium oxide is burned out.
Furthermore, it has already been proposed to convey cold flue gas into the combustion chamber in order to optimize the temperature conditions for the reaction of the additives with the sulfur resp. with the respective sulfur compounds contained in the flue gas. A device operating according to this method will be described below.
The method according to this invention is characterized in the first place that the relative moisture of the flue gas is increased before its entry into the dust filters. According to another feature of this invention, the increase of the relative moisture of the flue gas can be achieved by cooling of the same to a lower temperature which, however, is above the condensation point of water in the flue gas. In particular, the increase of the relative moisture of the flue gas is accomplished by cooling the latter by means of a heat exchanger and/or by injection or spraying of water in the flue gas. The device for carrying out the method of this invention comprising a combustion chamber and filtering equipment for the flue gas is characterized by the provision of a heat exchanger and/or of a spray cooler arranged in the path of the discharged flue gas before its entry into the filtering equipment, so as to increase the relative moisture of the flue gas.
In the following the invention is described in more detail by way of example with reference to the drawings.
FIG. 1 is a schematic diagram of a combustion plant with coal dust firing having been omitted all parts not being of significance in this connection.
FIGS. 2 to 4 illustrate schematically different embodiments for carrying out the method of this invention.
The burner installation shown in FIG. 1 is provided with combustion space for firing coal dust and for desulfurizing by means of dry additives as known per se. As it has been proposed already by the applicant cold flue
REFERENCES:
patent: 3505008 (1970-04-01), Frevel
patent: 3976747 (1976-08-01), Shale et al.
patent: 4105744 (1978-08-01), Erdoess et al.
patent: 4185080 (1980-01-01), Rechmeier
patent: 4197278 (1980-04-01), Gehri et al.
Schrofelbauer Herbert
Staudinger Gernot
Heller Gregory A.
Osterreichische Draukraftwerke Aktiengesellschaft
Striker Michael J.
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