Venturi scrubbers are frequently used to remove particulates from steel mill blast furnace recycle systems1. Acidic and basic gases can also be absorbed in the scrubber. Components of the gases produce venturi effluents with high scaling potential, the most critical section for scale build-up being the venturi throat. Iron, in various forms, and particulates exacerbate the fouling tendency.

Seeded crystal growth and capillary blocking experiments were used to evaluate the effectiveness of four scale inhibitors. These were hydroxyethylidene diphosphonic acid (HEDP), aminotri(methylenephosphonic acid) (AMP), and two proprietary amine phosphonates (CP1, CP2). The latter two compounds were selected for their varying affinities for particulate iron surfaces.

There is some disagreement between seeded crystal growth and capillary blocking results. The generally higher dosages required in the seeded crystal work can be ascribed only in part to the additional crystal surface introduced in the procedure and to the longer duration at elevated temperatures.

All of the inhibitors show a linear loss of performance due to soluble iron in the capillary blocking test, the concentration of which, along with cost, controls inhibitor selection. Iron oxide (Fe2O3) is also shown to cause inhibitor loss in the pH stat test.

The presented approach has been successfully used to develop treatment programs for blast furnace gas scrubber recycle systems.

Subject
Water, Inhibitor performance, Iron oxide, Calcium carbonate, Phosphonates, Adsorption, Scrubbers, Iron, Solubility, Adsorption isotherms, Phosphorus, Acidity, Corrosion inhibitors
Keywords:
Scale, inhibition, calcium carbonate, steel mill, blast furnace, gas scrubber recycle, iron oxide, adsorption isotherms, pH stat, capillary tube blocking
© 1990 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).
1990
Association for Materials Protection and Performance (AMPP)
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