Mercury emissions from German fluidized bed sludge incinerators -- A status report
In 1996 19% of the 2.7 million tons dry matter of sewage sludge produced in Germany were disposed by incineration. Incineration of the sludge is carried out mainly in fluidized bed combustors. German emission regulations set a limit to the mercury emission of 0.05 mg/m{sup 3} (under standard condition, dry basis) the observance of which requires special flue gas cleaning installations. In the present paper, an overview is given on the state of the art of flue gas cleaning with respect to mercury emissions from sewage sludge incineration in Germany. A total of 13 plants were examined. Because of the thermochemical instability of the mercury compounds only elemental mercury will exist inside the combustion chamber. During the cooling of the flue gas the elemental mercury reacts depending on the presence of other flue gas components to several mercurous and mercuric compounds. Measurements in the plants investigated indicate that the ratio of elemental to chemically bound mercury decreases with increasing chlorine content in the sludge feed. Different types of gas cleaning systems are used to remove the mercury from the flue gas which may be grouped into two categories, namely scrubbers and adsorbers, respectively. The mercury sink in the cleaning system will therefore be either the excess water of a wet scrubber or the laden adsorbent from an adsorber. If the amount of the practically water-insoluble elemental mercury is below the emission limit wet scrubbers will be sufficient to remove the mercuric and mercurous species. Otherwise elemental mercury has to be additionally removed by adding agents to oxidize the mercury for capture in a scrubber or by an adsorbent. Only 1--6% of the mercury supplied with the sludge is found in the fly ash separated with electrostatic precipitators. The different kinds of mercury capture systems used in German fluidized bed sludge incineration plants, the mercury concentrations in the cleaned flue gas and the removal efficiencies with respect to mercury are presented.
- Research Organization:
- Technical Univ. Hamburg-Harburg, Hamburg (DE)
- OSTI ID:
- 20006731
- Report Number(s):
- CONF-990534-; TRN: IM200008%%338
- Resource Relation:
- Conference: 15th International Conference on Fluidized Bed Combustion, Savannah, GA (US), 05/16/1999--05/19/1999; Other Information: 1 CD-ROM. Operating system required: Windows 3.x; Windows 95/98/NT; Macintosh, Power Macintosh; UNIX. All systems need 2X CD-ROM drive.; PBD: 1999; Related Information: In: Proceedings of the 15th national conference on fluidized bed combustion, by Reuther, R.B. [ed.], [1800] pages.
- Country of Publication:
- United States
- Language:
- English
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