Legislation to control NOx emissions, one cause of acid rain and ozone induced smog, has created an impetus to control NOx emissions. Selective Non Catalytic Reduction (SNCR) using urea chemistry is utilized to control NOx emissions from boilers, municipal waste incinerators, refinery furnaces, recovery boilers, utilities and other stationary combustion sources. Control requires injecting urea-based solutions into the flue gas at specified temperatures. Urea solutions accelerate CaCO3 precipitation in industrial waters used for dilution, and thereby interfere with proper application of the urea solution. The negative effect of urea solutions on hardness stability is discussed as well as how CaCO3 precipitation in urea solution can be controlled by suitable scale inhibitors.

Subject
Water, Precipitation (solids), Alkalinity, Precipitates, Nozzles, Scale inhibitors, Calcite, Inhibitor treatment, Scale, Risk reduction, Urea, Hardness, Chemical reactions
Keywords:
urea, CaCO3, scale control, CaCO3 inhibitor, SNCR, NOx emission, boiler, incinerator, refinery, recovery boiler
© 1997 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
1997
Association for Materials Protection and Performance (AMPP)
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