Design, Materials, Fabrication, Operation, and Inspection Guidelines for Corrosion Control in Hydroprocessing Reactor Effluent Air Cooler (REAC) Systems

API RECOMMENDED PRACTICE 932-B THIRD EDITION, JUNE 2019

Special Notes

API publications necessarily address problems of a general nature. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed.

Neither API nor any of API's employees, subcontractors, consultants, committees, or other assignees make any warranty or representation, either express or implied, with respect to the accuracy, completeness, or usefulness of the information contained herein, or assume any liability or responsibility for any use, or the results of such use, of any information or process disclosed in this publication. Neither API nor any of API's employees, subcontractors, consultants, or other assignees represent that use of this publication would not infringe upon privately owned rights.

API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to ensure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any authorities having jurisdiction with which this publication may conflict.

API publications are published to facilitate the broad availability of proven, sound engineering and operating practices. These publications are not intended to obviate the need for applying sound engineering judgment regarding when and where these publications should be used. The formulation and publication of API publications is not intended in any way to inhibit anyone from using any other practices.

Any manufacturer marking equipment or materials in conformance with the marking requirements of an API standard is solely responsible for complying with all the applicable requirements of that standard. API does not represent, warrant, or guarantee that such products do in fact conform to the applicable API standard.

Users of this Recommended Practice should not rely exclusively on the information contained in this document.

Sound business, scientific, engineering, and safety judgment should be used in employing the information contained

herein.

API is not undertaking to meet the duties of employers, manufacturers, or suppliers to warn and properly train and equip their employees, and others exposed, concerning health and safety risks and precautions, nor undertaking their obligations to comply with authorities having jurisdiction.

Information concerning safety and health risks and proper precautions with respect to particular materials and conditions should be obtained from the employer, the manufacturer or supplier of that material, or the material safety data sheet.

Where applicable, authorities having jurisdiction should be consulted.

Work sites and equipment operations may differ. Users are solely responsible for assessing their specific equipment and premises in determining the appropriateness of applying the Standard. At all times users should employ sound business, scientific, engineering, and judgment safety when using this Standard.

All rights reserved. No part of this work may be reproduced, translated, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher. Contact the Publisher, API Publishing Services, 200 Massachusetts Avenue, NW, Suite 1100, Washington, DC 20001-5571.

Copyright © 2019 American Petroleum Institute

ii

Foreword

Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything contained in the publication be construed as insuring anyone against liability for infringement of letters patent.

Shall: As used in a standard, “shall” denotes a minimum requirement to conform to the standard.

Should: As used in a standard, “should” denotes a recommendation or that which is advised but not required to conform to the standard.

May: As used in a standard, “may” denotes a course of action permissible within the limits of a standard. Can: As used in a standard, “can” denotes a statement of possibility or capability.

ThisdocumentwasproducedunderAPIstandardizationproceduresthatensureappropriatenotificationandparticipation in the developmental process and is designated as an API standard. Questions concerning the interpretation of the content of this publication or comments and questions concerning the procedures under which this publication was developed should be directed in writing to the Director of Standards, American Petroleum Institute, 200 Massachusetts Avenue NW, Washington, DC 20001. Requests for permission to reproduce or translate all or any part of the material published herein should also be addressed to the director.

Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years. A one-time extension of up to two years may be added to this review cycle. Status of the publication can be ascertained from the API Standards Department, telephone (202) 682-8000. A catalog of API publications and materials is published annually by API, 200 Massachusetts Avenue NW, Washington, DC 20001.

Suggested revisions are invited and should be submitted to the Standards Department, API, 200 Massachusetts Avenue NW, Washington, DC 20001, standards@api.org.

Contents

Page

1. Scope 1

2. Normative References 2

3. Terms, Definitions, and Acronyms 3

   1. Terms and Definitions 3

   2. Acronyms 5

4. Background of REAC Corrosion 5

   1. History of Reactor Effluent System Corrosion Surveys 5

   2. Typical Hydroprocessing Units 6

   3. Effluent Separation Designs 8

   4. REAC System Corrosion 8

5. Strategies to Promote System Reliability 11

   1. General 11

   2. Material Selection and Design 12

   3. Establishing an Integrity Operating Window 12

   4. Inspection Plans 13

6. Process Variables Affecting Corrosion 13

   1. Ammonium Bisulfide Concentration 13

   2. Process Conditions at the Water Dew Point 14

   3. Fluid Velocities 14

      2

   4. Hydrogen Sulfide (H S) Partial Pressure 17

   5. Flow Regime 18

   6. Chlorides 19

   7. Cyanides 20

   8. Other Process Variables 21

   9. Wash Water 21

   10. Corrosion Inhibitors 23

   11. Air Cooler Fan Operations 24

   12. Process Monitoring and Integrity Operating Windows (IOWs) 24

7. Materials of Construction 26

   1. General 26

   2. Material Selection Criteria 27

8. Equipment-specific Design Considerations 31

   1. Fin Fan Air Coolers 31

   2. Shell-and-tube Trim Coolers 33

   3. Hot High-pressure Separator (HHPS) 34

   4. Cold High-pressure Separator (CHPS) 34

   5. Heat Exchanger or Air Cooler Upstream of REAC 35

   6. Piping and Valves 36

9. Inspection of the REAC System 40

   1. General 40

   2. Reactor Effluent Air Coolers 41

   3. Shell and Tube Heat Exchangers 43

   4. Piping 43

      Contents

      
      

      Page

   5. Pressure Vessels—Separators and Heat Exchanger Shells 45

      9.10 Use of Infrared Thermography for Monitoring REAC System Operations 45

10. Limitations and Recent Improvements in the Industry Knowledge Base 47

    1. Experience 47

    2. Recent Joint Industry Research 47

Annex A (normative) Process Calculations and Other Estimates 50

Annex B (informative) Bibliography 58

Figures

1. Example Hydrotreating Unit Process Flow Diagram 7

2. Example Hydrocracking Unit Process Flow Diagram 7

3. Example Process Scheme with a CHPS 9

4. Example Process Scheme with a CHPS and CLPS 9

5. Example Process Scheme with Two Separators, a HHPS and CHPS 10

6. Example Process Scheme with Four Separators 10

7. Curves Showing Effect of NH4HS Concentration on Corrosion of Carbon Steel through Small Orifice

   (0.15 in.) Coupons 14

8. Isocorrosion Curves for Carbon Steel at Various NH4HS Concentrations and Velocities through Small

   Orifice (0.15 in.) Coupons 15

9. Tie-in Plot for Carbon Steel at 1 wt % NH4HS Concentrations and Various Velocities through Small Orifice

   (0.15 in.) Coupons [130 °F (55 °C), 0 ppm Free Cyanide] 16

10. Tie-in Plot for Carbon Steel at 25 wt % NH4HS Concentrations and Various Velocities through Small Orifice

    (0.15 in.) Coupons [130 °F (55 °C), 0 ppm Free Cyanide]. 16

11. Curves Showing Effect of H2S Partial Pressure on Corrosion of Carbon Steel through Small Orifice

    (0.15 in.) Coupons 17

12. Tie-in Plot for 316L SS at 1 wt % NH4HS Concentrations and Various Velocities through Small Orifice

    (0.15 in.) Coupons [130 °F (55 °C)] 18

13. Alloy 2205 REAC Failures as a Function of Ammonium Bisulfide Concentration and Total Pressure 29

14. Relative Alloy Performance in Aqueous NH4HS Service 31

15. Illustration of a Balanced and Unbalanced Inlet Piping Configuration 38

16. Cross-section of Internal Surface of Failed REAC Outlet Nozzle 42

17. Erosion-Corrosion of Carbon Steel Piping Elbow 44

18. IR Image of Water Wash Injection Locations 46

19. IR Image of Water Wash Injection Location 46

20. IR Image of the Top of the Air Cooler Tubes Showing Poor Water Wash Distribution 47

A.1 Estimating Ammonium Salt Deposition Temperature from Process Stream Composition 53

Tables

1. Factors Affecting REAC System Corrosion and Fouling 2

2. Quality Parameters of Injected Wash Water 21

3. Suggested Process Variables to Consider for Monitoring or Inclusion in an Integrity Operating Window 25

   Contents

   Page

4. Referenced Material Compositions 27

5. Suggested Locations for IR Monitoring 46

A.1 Reactor Effluent Mix 50

Design, Materials, Fabrication, Operation, and Inspection Guidelines for Corrosion Control in Hydroprocessing Reactor Effluent Air Cooler (REAC) Systems

1. Scope

   
   

   4

   4

   1. This recommended practice provides guidance to engineering and plant personnel on equipment and piping design, material selection, fabrication, operation, and inspection practices to manage corrosion and fouling in the wet sections of hydroprocessing reactor effluent systems. The reactor effluent system includes the equipment and piping subject to ammonium salting, NH HS corrosion, and associated fouling. This system usually begins at the last feed/effluent exchanger or first water injection point and continues through the cold high- pressure separator (1, 2, and 3 separator designs) or cold high- and low-pressure separators (4 and 5 separator designs). The reactor effluent system specifically excludes the stripper, fractionator, and final separation sections. However, guidance in this document may be applicable to ammonium salt corrosion mitigation in those areas, as well. The majority of these systems have an air cooler; however, some systems utilize only shell and tube heat exchangers. Reactor effluent systems are prone to fouling and corrosion by ammonium bisulfide (NH HS) and

      4

      ammonium chloride (NH Cl) salts.

      
      

   2. An understanding of all variables impacting corrosion and fouling in these systems is necessary to improve the reliability, safety, and environmental impact associated with them. Past attempts to define generic optimum equipment design and acceptable operating variables to minimize fouling and corrosion have had limited success due to the interdependence of the variables. Corrosion can occur at high rates and be extremely localized, making it difficult to inspect for deterioration and to accurately predict remaining life of equipment and piping. Within the refining industry, continuing equipment replacements, unplanned outages, and catastrophic incidents illustrate the current need to better understand the corrosion characteristics and provide guidance on all factors that can impact fouling and corrosion.

      
      

   3. This recommended practice is applicable to process streams in which NH Cl and NH HS salts can form

      4 4

      and deposit in equipment and piping or dissolve in water to form aqueous solutions of these salts. Included in

      this practice are:

      
      

      • details of deterioration mechanisms;

        
        

      • methods to assess and monitor the corrosivity of systems;

        
        

      • details on materials selection, design, and fabrication of equipment for new and revamped processes;

        
        

      • considerations in equipment repairs; and

        
        

      • details of an inspection plan.

      
      

   4. Table 1 lists factors affecting reactor effluent air cooler (REAC) system performance and section reference

      for more detail.

      
      

   5. Materials and corrosion specialists should be consulted for additional unit-specific interpretation and application of this document. Each facility needs to establish its own safe operating envelope to ensure satisfactory service. This recommended practice helps to identify key variables necessary for monitoring and establishing the operating envelope.

      
      

      2

   6. Other equipment downstream of the REAC can also deteriorate from these ammonium salts. These include the recycle and sour gas systems and the H S stripper and product fractionator overhead systems. Although these are beyond the scope of this document, plant personnel should be alert to these other locations where ammonium salt fouling and corrosion can occur.