PRELMINARY VERSION

Prediction of NH4HS Corrosion in Sour Water Systems

Predict-SW 3.0

Failure PreventionRisk Mitigation

Optimized Material Selection

By

Vishal Lagad

Sridhar Srinivasan

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Agenda

• Introduction to Sour Water Corrosion in Refinery Systems

• Overview of Predict-SW 3.0

• Published Case studies (New data Vs Old, inaccurate rules of thumb)

• Integration with Unisim-Design (R390)

• Conclusions and Discussions

3

Hydrotreating / Hydroprocessing Background

• Used to remove undesirable sulfur and/or nitrogen

- Use H2, catalyst and heat

Catalyst

S

H2

Hydrocarbon

4

Hydrotreating / Hydroprocessing

• Results in de-sulfurized product, H2S and NH3

Catalyst

H2SHydrocarbon

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Ammonium Bisulfide (NH4HS) Corrosion

• The H2S and NH3 byproducts can form salts upon cooling down

• These NH4HS salts lead to REAC plugging, and if wet, rapid underdeposit corrosion

• This salt is readily dissolved in water and hence water washed ahead of the salt formation point

• This produces the NH4HS solutions, also called sour water

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Problem Areas in Refinery Sour Water Handling

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Sour Water Corrosion JIP Inception

• Absence of quantified data made corrosion prediction / prevention of failure difficult

• In 2000, Shell Global Solutions and other large operating companies commissioned Honeywell to run a Joint Industry Project designed to generate data

• Purpose: To create a definitive, engineering basis for dealing with sour water corrosion

• Phase I (H2S Dominated Regime): was completed in June 2003

• Phase II (NH3 Dominated Regime): was completed in March 2007

• Phase III (Completing the picture - Cyanide corrosion): currently in progress

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Predict-SW: Industry recognition and acceptance

• Two papers presented at Corrosion/06 at San Diego - (one by Shell Global and the other by Flint Hills Resources) –

- Paper Nos. 06576 and 06577)

• Both papers attest to the value proposition the software brings through application of new technology and Honeywell IP

• Key takeaway from papers: - Every refinery will benefit from having this system because it can

prevent failures, and will offer substantial Cost Savings (material replacement, maintenance planning)

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Traditional NH4HS Corrosion Limits/Rules

• Question to refiners: Do you use any of the following limits for all or most applications (existing or new)?

-NH4HS concentration limit such as 2%, 8%

-Velocity limit such as 20 ft/s

-A pH limit or acceptable range of pH

-KP limit (Kp is the product of mole percent Ammonia and mole percent H2S in the vapor phase)

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Abandon old rules, Embrace new technology

Recommendation from Shell Paper: Abandon these “old” rules

• They may be too conservative- That costs you money

• They may be non-conservative- That increases your risk of failures

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New Key Parameters for NH4HS Corrosion

• Do you consider any of the following for all or most applications (existing or new)?

-Effect of H2S partial pressure

-Effect of NH3 partial pressure

-Effect of temperature

-Effect of hydrocarbon/sour water mixtures

-Effect of chemical treatments

-Effect of Cyanide levels

-Wall shear stress and flow regimes, especially for multiphase applications

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New Technology - Predict-SW 3.0

Adopt these “new” rules

• Results available from Predict-SW have characterized the effects of the four key variables and other relevant parameters needed to predict NH4HS corrosion

• Predict-SW 3.0 incorporates H2S data from Phase I and NH3 data from Phase II of the JIP

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NH4HS Corrosion Prediction using Predict-SW

• Four key variables- NH4HS concentration

- Wall shear stress (not velocity)

- H2S partial pressure

- NH3 partial pressure (from Phase II – Predict-SW 2.5 SE)

• Other relevant variables- Temperature

- Hydrocarbon content

- Chemical treatments (APS and Imidazoline)

- CN content

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NH4HS Corrosion Prediction

Predict-SW 3.0

• Incorporates- Large database of quantitative corrosion data developed

by Sour Water JIP

- Flow modeling calculations for wall shear stress

- Algorithms/rule sets to address effect of the three key variables and other relevant variables

• Predicts NH4HS corrosion rate of 14 materials in H2S dominated conditions and 6 materials in NH3dominated conditions.

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Predict-SW 3.0 Materials Included

Alloys in red are included in Phase II (NH3 dominated) conditions

• Carbon steel

• 410 SS

• 304 SS

• 316 SS

• Alloy 2205

• Alloy 2507

• Alloy 400

• Alloy 600

• Alloy 625

• Alloy 20Cb-3

• Alloy 800

• Alloy 825

• Alloy C-276

• AL6XN (6% Mo)

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Predict-SW Experience - FHR

• Flint Hills Hydrotreater A*

- Recycle gas piping from CHPS at 130 F (sat. vapor)

- 10” Schedule 120 carbon steel elbow (not insulated)

- > 99% vapor, balance sour water

- 10 wt% NH4HS

- 32 ft/s velocity

- 100 psia H2S

- Measured corrosion rate ���� 68 mpy

*Paper No. 06577, Corrosion/06, San Diego, 2006

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FHR Hydrotreater A – Predict-SW Experience

Reactor

HHPS

CHPS

Sour WaterFlash Drum

HLPS

Feed

Charge

Heater

REAC

CLPS

To Fractionator

Off Gas

AmineAbsorber

Rich Amine

LeanAmine

Sweet H2

Feed / Effluent

Exchangers

Slop Oil

To SWS

WaterWash

H2

H2

Quench

Off Gas

Separator

Reactor

HHPS

CHPS

Sour WaterFlash Drum

HLPS

Feed

Charge

Heater

REAC

CLPS

To Fractionator

Off Gas

AmineAbsorber

Rich Amine

LeanAmine

Sweet H2

Feed / Effluent

Exchangers

Slop Oil

To SWS

WaterWash

H2

H2

Quench

Off Gas

Separator

High corrosion rate location

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FHR Hydrotreater A – Predict-SW Experience

• Predict-SW was used to predict the corrosion rate for this case- Churn Flow – 10 Pa wall shear stress

- Measured CR of CS = 68 mpy

- Predicted corrosion rate for CS = 65 mpy

- Predicted corrosion rate for 825 = 2 mpy

• Line was replaced with carbon steel overlayed with alloy 825

• The new line was not insulated and has not experienced any problems since 2002

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FHR Hydrotreater B: Outlet REAC Piping*

6"

8"

10"

12"

14"

20"

1" - 12 BWGTubes

*Paper No. 06577, Corrosion/06, San Diego, 2006

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FHR Hydrotreater B - Predict-SW Experience

• Using old rules of thumb, there were serious concerns for corrosion in this REAC circuit

• Carbon steel inlet / outlet piping and associated carbon steel air-fin exchangers- 8 wt% NH4HS at 130 F

- 27 psia H2S

- Bulk velocities approaching 80 ft/s on the inlet and 30 ft/s on the outlet

- Kp = 0.25

• Traditional rules of thumb indicated moderate to severe corrosion based on Kp, severe corrosion based on NH4HS and velocity

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FHR Hydrotreater B - Predict-SW Experience

• No significant loss was detected by inspection

• Plans made to replace CS piping with CS overlayed with alloy 825, plus upgrade of the fin-fans to alloy 2205

• Cost approaching US$10 million

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FHR Hydrotreater B - Predict-SW Experience

• Predict-SW was used to predict the corrosion rate for the various inlet and outlet piping circuits

• Maximum of 25 Pa wall shear stress

• Predicted corrosion was a maximum of 4 mpy

• Plans to upgrade material were dropped, money saved!!

• Continued inspection has revealed an average of 5 to 7 mpy- The low corrosion rates were the result of low wall shear

stress combined with a low H2S partial pressure

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Case Study : BP Refinery

• Iso-cracker stage I air cooler tubes were seeing corrosion problems

- Up to 6% NH4HS and 300°F at inlet.

- Predicted corrosion rate of CS with Predict-SW = 12 mpy

- Measured average corrosion (metal loss) rate in the first four years of unit operation: 13 mpy

- Predict-SW recommended material for low (<1 mpy) corrosion: Alloy 825 (21Cr-3Mo-20Fe-Ni)

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BP Case Study Summary

• Multiphase streams across multiple tube rows resulted in non-uniform flow distribution

• This means that different rows may see different flow patterns and wall shear stress levels

• Predict-SW used to perform multipoint sensitivity analyses to characterize worst case locations and conditions

• Pro-active application of Predict-SW resulted in - The ability to make changes to avoid potential costly failures,

- Significantly reduced operational risk…. enhance productivity and increase plant safety.

- Now being applied to all refinery sour water handling systems.

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Predict-SW Interface : Inputs

•Access to actual

JIP Data

•Easy to use

Interface

•Simplified Inputs

•Extensive

Functionality

•Units Flexibility

•Context sensitive

Help system

•3-D Balanced

Piping Setup

•XP and Vista

compatible

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Predict-SW Interface : Results

• Corrosion rates

• Flow regime

• Wall shear stress

• Flow parameters

• Phase comparisons

• Customizable Charts

and Grids

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Predict-SW 3.0: How does it work?

1. Calculate effective shear stress from process flow conditions

2. Convert the field shear stress into an equivalent lab flow loop velocity

3. Using lab velocity and NH4HS concentration, predict corrosion rates for all materials using the respective isocorrosion diagrams developed using REAL DATA

4. Correct corrosion rates for the effect of H2S partial pressure, temperature, hydrocarbon content and chemical treatment based on REAL DATA

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Iso-Corrosion plots in Predict-SW 3.0

• Ability to predict corrosion rates for all relevant data ranges

• Facilitates easy quantification of sour water corrosion

CONFIDENTIA

L DATA

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Additional Key Functionalities

• Automated Multi-point Analysis- Using MS Excel run multiple cases with one click!

• Automated Sensitivity Analysis- Evaluate parametric sensitivity to examine trends and check for

inflection points!

• Secure access to all program data, including reports, meeting presentations, corrosion rates and iso-corrosion curves

• Automatic Unit Conversions (SI / American)

• Access to the industry experts for insightful analyses

• Network and Corporate licensing for ease of deployment

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Multi-point Analysis using Excel

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Sensitivity Analysis in Predict-SW 3.0

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3-D Piping Model for Balanced Piping

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Secure, Electronic Data Access

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Predict-SW & UniSim : Process Intelligence

• UniSim Design facilitates process modeling

• Predict-SW performs corrosion modeling (quantification / prediction)

• Integration provides the ability to design, control and optimizeprocesses to limit or eliminate corrosion

• Implemented as part of USD release R370

• Vision:

- As part of the move to providing process control in real time, an integrated USD / Predict-SW provides the ability to: � “see” what process stream variables contribute to corrosion,

� how they impact operational boundaries, and

� how they can be controlled

- Logical path forward for integration with DCS for real-time closed loop analysis and control

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Reliability HS&E Compliance

Productivity

Operational Excellence

Risk Management

Knowledge Capture

Capital R

eturn

Improve PROCESS Performance Process Intelligence

Improve ASSET Effectiveness

Advanced ProcessControl (APC)

Process BoundaryManagement

PerformanceMonitoring

Laboratory InformationManagement (LIMS)

Real-TimeOptimization (RTO)

Process UnitMonitoring

Data Historization

Early EventDetection

Remote Perform.Management

Equipment HealthManagement

Process SimulationAnd Design

Unisim Design

Process ModelingProcess Optimization

Data Visualization

Refinery Planning And Scheduling

Process Management

Predict®-SW

Corrosion Quantification

Damage PreventionMultiphase Flow Modeling

Material Selection Design Planning

Unisim Predict-SW Integration Schematic

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Accessing Predict-SW within UniSim Design

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Predict-SW 3.0 Licensing Options

• License duration flexibility (1 year to 6 years)

• License user flexibility (single user to multiple network users)

• Comprehensive consulting support and customization services offered to all users through the Honeywell

• Various options available for licensing:- Single user workstation licenses

- Single / Multi user network based licenses

- Corporate (worldwide) Licenses

• Additional support available in the form of Enhanced Benefits Program

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Predict-SW: Functional Roles

• As a tool for corrosion quantification

• To support inspection planning, and allocation of resources towards situations that have potential for high corrosion

• To determine the right alloy or treatment choice (a more expensive material is not always better)

• To mitigate and minimize risk of failure (as a component in any RBI program)

• Applicable in various scenarios

- Material selection for new equipments

- Locating critical locations in existing plants

- Determining inspection intervals

- Evaluating materials or chemical treatment options

- Optimizing Asset Integrity and Reliability programs

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Conclusions

• Predict-SW 3.0 can be used by all refinery operators:

- Integrates with process data for better process optimization and asset protection

- Identifies key monitoring locations for risk reduction

- Supports better inspection and maintenance planning, and allocation of monitoring/equipment resources towards situations that have potential for high corrosion

- Determine the right alloy or treatment choice: A more expensive material is not always better

- Mitigate and minimize risk of failure (as a component in any RBIprogram).

- Potential cost of failure in REAC system has been reported to beup to $60 million per incident!

Demonstrated value proposition for operators from $1 million to $10 million per application of Predict-SW

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Conclusions

• Sour water corrosion prediction/ quantification is a complex task

• New data and technology is now available to address corrosion prediction and optimize material selection

• Adopt “new” and industry tested insight and move away from “old” rules of thumb

• Predict-SW 3.0 provides the ability to accurately quantify corrosion, and gives refinery operators the ability to effectively mitigate failure risk and minimize cost.