Since the late 1970s, the pulp and paper industry has invested large amounts of time and money to promote the development of effective ways of combatting accelerated corrosion in critical recovery boiler components. Various solutions to this costly problem have been proposed and subsequently tested in both the laboratory and the field. Included among these solutions have been composite tubing (a high alloy outer sheath protecting a low alloy core tube) and both field-applied and shop-applied coatings for the protection of exposed surfaces. At the October, 1988, BLRBAC meeting in Atlanta, Combustion Engineering, Inc. (C-E) and Consolidated Papers, Inc. presented a paper1  describing C-E’s patented chromizing process (U. S. Patent No. 4,963,395 and No. 4,993,359) and outlining its superior performance to date in chemical recovery boilers. A progress report2  on the service record of chromized recovery boiler tubing was presented at the September, 1989, TAPPI Engineering Conference. As additional service time has been logged on operating units with chromized components installed, there has been a confirmation of the superior resistance of chromized surfaces to the rigors of a recovery boiler furnace environment.

The topics discussed in this paper include:

  • A review of the principal mechanisms of attack in a recovery boiler and the areas in the boiler most vulnerable to the attack; the review includes a brief discussion of commonly used surface protection methods.

  • A brief review of the chromizing process as it is applied to the protection of major chemical recovery boiler components.

  • The results of a continuing test program to evaluate the performance of chromized smelt spouts in recovery boilers experiencing forced replacements of unprotected spouts at intervals of less than one year.

Subject
Steel surfaces, Coatings, Recovery boilers, Metal surfaces, Tubes, Chromium, Walls, Furnaces, Tubing, Composites, Waterwalls, Corrosion protection, Corrosion resistance
Keywords:
chromizing, chemical recovery, high-temperature diffusion, smelt spout
© 1993 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).
1993
Association for Materials Protection and Performance (AMPP)
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