Furnaces – Process – Treating fuel constituent or combustion product
Patent
1995-12-06
1998-10-27
Kamen, Noah P.
Furnaces
Process
Treating fuel constituent or combustion product
110205, 110229, 110346, F23J 1100
Patent
active
058265210
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method for reducing emissions during the incineration of waste in an incinerator installation, wherein a portion of the flue gas being produced in the course of incineration is returned to the inlet of the incineration installation in a continuous cycle, wherein the oxygen required for combustion is admixed as pure oxygen to the returned flue gas for generating synthetic air composed of flue gas and pure oxygen, wherein the ratio of flue gas and oxygen is 4:1 to 1:1, preferably 2:1 to 1.5:1, and wherein the combination takes place while excluding the ambient air and wherein further flue gas purification is performed in a flue gas purification installation.
Such a method is known from U.S. Pat. No. 5,179,903. In the process disclosed there is an increase in the concentration of chlorine, heavy metals and sulfur dioxide inside the flue gas cycle, which includes a first combustion zone (1), a second combustion zone (2), a cooling zone (3), a solids separation zone (4), a blower (30), a zone for generating synthetic air (5) and a heat exchanger (33).
In view of the large proportion of flue gas circulating in the cycle with respect to the total amount of flue gas being generated, namely one-fifth to one-half, this increase in the concentration after the start-up phase is considerable and also leads to a considerable increase in the concentration of chlorine, heavy metals and sulfur dioxide in the portion of the flue gas which is exhausted to the ambient air via a purification installation (wet gas scrubbing zone (6)) and a further purification zone (7). It is necessary to embody the purification installation (6) correspondingly large to prevent the emission of the increased concentrations.
Furthermore, the upgrade of these components in the flue gas cycle leads to damage to the metal parts thereof. In addition, there is the danger of an escape of these components through not completely sealed places in the cycle.
Such a method is also known from DE 40 26 245 A1. This method is based in principle on employing "pure oxygen without dilution" (see col. 1, line 58; col. 3, lines 47/48, and claim 1) in order to achieve a considerable reduction of the volume for which the installation must be designed, but it mentions that "for preventing overheating" and when needed, cooled waste gas is returned again into the combustion chamber and the oxygen is diluted with it (col. 2, lines 43/44 and 50/51). It is also mentioned that the use of pure oxygen, with or without dilution, prevents the generation of nitrogen oxide and other emissions (col. 1, lines 51/52 and col. 2, line 9/10). Because of the statement in this publication, that the waste gas return is to take place only "as needed" and to prevent overheating of the installation, but that on the other hand a scaling down of the installation is sought by using pure oxygen "without inerts", it is to be assumed that the admixture of returned flue gas takes place only in small amounts and not continuously. This can also be inferred from the fact that the temperatures of 1600.degree. C. (col. 4, line 57) cited in this publication are relatively high.
It is disadvantageous with respect to this known method that, if ever a cycle and/or a return of a not inconsiderable portion of the waste gas is to take place, an enrichment with noxious materials being created during combustion in a revolving cylinder will take place in the cycle, which can result in corrosion of the installation and also requires a larger layout of the downstream flue gas purification installation. Finally, as already indicated above, the use of pure oxygen, even with the admixture of cooled flue gas "if required", leads to increased temperatures in the revolving cylinder and therefore is not suitable for retrofitting existing combustion installations which actually operate with ambient air.
In general, it is of great importance when incinerating waste (household waste and special waste) to reduce the portions of noxious material in the flue gas. I
REFERENCES:
patent: 4900401 (1990-02-01), Horton
patent: 4961391 (1990-10-01), Mok et al.
patent: 5179903 (1993-01-01), Abboud et al.
patent: 5309850 (1994-05-01), Downs et al.
Patent Abstracts of Japan, Combustion of Powdered Coal, JP 59 024 115, Tanaka Riyouichi, vol. 8, No. 116 (M-299) 30 May 1984.
Marz Herbert
Schumann Bernd
Teller Matthias
Kamen Noah P.
SBW Sonderabfallentsorgung Badenwurttemberg GmbH
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