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NO x removal from flue gas by an integrated physicochemical absorption and biological denitrification process
Author(s) -
van der Maas Peter,
van den Bosch Pim,
Klapwijk Bram,
Lens Piet
Publication year - 2005
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.20420
Subject(s) - bioreactor , flue gas , chemistry , denitrification , denitrifying bacteria , scrubber , nox , absorption (acoustics) , wet scrubber , pulp and paper industry , nitrogen , combustion , materials science , organic chemistry , composite material , engineering
An integrated physicochemical and biological technique for NO x removal from flue gas, the so‐called BioDeNO x process, combines the principles of wet absorption of NO in an aqueous Fe(II)EDTA 2− solution with biological reduction of the sorbed NO in a bioreactor. The biological reduction of NO to di‐nitrogen gas (N 2 ) takes place under thermophilic conditions (55°C). This study demonstrates the technical feasibility of this BioDeNO x concept in a bench‐scale installation with a continuous flue gas flow of 650 l.h −1 (70–500 ppm NO; 0.8–3.3% O 2 ). Stable NO removal with an efficiency of at least 70% was obtained in case the artificial flue gas contained 300 ppm NO and 1% O 2 when the bioreactor was inoculated with a denitrifying sludge. An increase of the O 2 concentration of only 0.3% resulted in a rapid elevation of the redox potential (ORP) in the bioreactor, accompanied by a drastic decline of the NO removal efficiency. This was not due to a limitation or inhibition of the NO reduction, but to a limited biological iron reduction capacity. The latter leads to a depletion of the NO absorption capacity of the scrubber liquor, and thus to a poor NO removal efficiency. Bio‐augmentation of the reactor mixed liquor with an anaerobic granular sludge with a high Fe(III) reduction capacity successfully improved the bioreactor efficiency and enabled to treat a flue gas containing at least 3.3% O 2 and 500 ppm NO with an NO removal efficiency of over 80%. The ORP in the bioreactor was found to be a proper parameter for the control of the ethanol supply, needed as electron donor for the biological regeneration process. The NO removal efficiency as well as the Fe(III)EDTA − reduction rate were found to decline at ORP values higher than –140 mV (pH 7.0). For stable BioDeNO x operation, the supply of electron donor (ethanol) can be used to control the ORP below that critical value. © 2005 Wiley Periodicals, Inc.