1. Crude Unit Overhead Modeling The technology that makes it possible
Chemistry in Refining Overheads A Focus Group of the OLI MSE Consortium – 2008
Pat McKenzie, AQSim
Jim Berthold, OLI CTW, September, 2006

2. Chemistry in Refining Overheads
Motivation
This project will address a major cause of overhead corrosion, the formation of amine chloride salt deposits
Overview
Project background
Project approach
Status
Amine list
Questions
CTW, September 2006
Chemistry in Refining Overheads

3. Chemistry in Refining Overheads
Business Case
Corrosion source Amine-HCl salt deposits on hot metal surfaces
Prevention Prevent salt formation
Method Operate refinery unit above “salt point” T
Challenge What is a safe temperature?
Solution Predict sublimation point and dew point Ts in mixtures
Opportunity This Focus Group
CTW, September 2006
Chemistry in Refining Overheads

4. Chemistry in Refining Overheads
Goal
The goal of this project is to simulate the behavior of overhead refining streams
This will enable the simulation software users to determine optimal operating conditions, in order to minimize - or to prevent - the deposition of amine chloride salts in the overheads
For “typical” overhead chemistry
H2O
Sulfides, sulfates
Chlorides
NH3 and the amines
Light hydrocarbons
CTW, September 2006
Chemistry in Refining Overheads

5. Chemistry in Refining Overheads
Available technology
Electrolyte simulation is the core competency (a.k.a. ionic modeling)
Simulation techniques
Behavior of electrolytes – acid/base chemistry
Existing thermodynamic frameworks for ionic modeling can predict
Dew points
Sublimation points (“salt point”)
General phase equilibrium behavior for systems containing electrolytes and non-electrolytes
CTW, September 2006
Chemistry in Refining Overheads

6. Chemistry in Refining Overheads
What is needed
-> The amine system parameters for the model
To obtain the parameters
Experimental work measure amine-HCl salt data where no published / literature data exists
Data development work develop a thermo-physical property database for the amine-HCl salts
Once obtained
Application development set up cases to calculate sublimation point and dew point
…For user-defined refining overhead streams, of varying compositions
CTW, September 2006
Chemistry in Refining Overheads

7. Mixed Solvent Electrolyte Model: a new thermodynamic model
This work requires OLI’s newer mixed solvent electrolyte (MSE) framework
Amine-rich dew points are beyond the concentration limit of OLI’s aqueous model: 30 molal ionic strength
Sublimation as a phenomenon is only available in the MSE model, not the aqueous model
CTW, September 2006
Chemistry in Refining Overheads

8. Mixed Solvent Electrolyte Model Key points to remember
Predicts water chemistry speciation
vapor, solid, aqueous, 2nd liquid phase
Predicts behavior of many electrolyte solutions
Dilute solutions, solid saturation, pure salts, pure solutes
Electrolytes in organic solvents
Water-organic-salt systems in the full range of concentrations
At temperatures up to 90% Tcrit of the mixture
Predicts based (primarily) on binary interactions
Predictions, not interpolations
CTW, September 2006
Chemistry in Refining Overheads

9. Advantages of the MSE framework
No local modeling is needed
Adding components to a system is handled without further data refitting (provided they are in the database already)
No local optimization is needed
Modification of k-values or vapor pressure coefficients (e.g., Antoine) is a common practice in some models, not required in the MSE model
Some systems benefit from ternary interaction parameters
Example: I2, HI, H2SO4 – needed the ternary
This is not expected in for the amine systems
CTW, September 2006
Chemistry in Refining Overheads

10. Chemistry in Refining Overheads
Past work
Shell Global Solutions, Inc.
Made some of these measurements
Used OLI’s previous, aqueous model to regress parms
Univ of Alberta - gas sweetening operations
Amines, water, CO2, H2S, and some HCs
Left out the critical (to us) HCl component
Learning from past work
Work will be done in high-concentration model
Past experience in measurements will be used
Literature – public - data used wherever possible
CTW, September 2006
Chemistry in Refining Overheads

11. Approach: Experimental work
Vapor-Liquid Equilibrium (VLE)
Solid-Liquid Equilibrium (SLE)
Titration measurements (for ionization of amines)
Calorimetric measurements (melting points, heat cap)
Avoid direct sublimation point measurements
Sublimation equipment is expensive, more risk
VLE, SLE measurement equipment “off the shelf”
Potential corrosovity creates special needs
SwRI factored this into the design of equipment
CTW, September 2006
Chemistry in Refining Overheads

12. Chemistry in Refining Overheads
Data development work
Work will include
Literature searches for any available data
Specification of data to measure experimentally
Data regressions of compiled data into the model
For a particular amine, constituent subsystems would be:
Amine
Amine + water
Dissociation behavior between the amine and the ionized form of the amine
Amine + water + CO2 + H2S
Amine hydrochloride + water
CTW, September 2006
Chemistry in Refining Overheads

13. Example systems, NH4Cl & NH4HS
Solid-gas equilibrium computations for pure NH4Cl and NH4HS
NH4Cl
NH4HS
CTW, September 2006
Chemistry in Refining Overheads

14. Chemistry in Refining Overheads
VLE for NH3 – H2S – H2O
Accurate representation of solid-gas equilibria for NH4HS and nonideality of the NH3 – H2S – H2O ternary should ensure correct predictions of solid-gas-liquid equilibria in the ternary system
CTW, September 2006
Chemistry in Refining Overheads

15. Chemistry in Refining Overheads
Status
JIP underway
SwRI is the experimental partner
Amine list has being compiled
Equipment has been designed
Literature search is nearly complete
CTW, September 2006
Chemistry in Refining Overheads

16. Amines to be studied – 1st 10
Trimethylamine TMA
Cyclohexylamine
3-methoxypropylamine MOPA
2-dimethylaminoethanol DMEA
Diethanolamine DEA
Dimethylisopropanolamine DMIPA
Dimethylamine DMA
Ethylenediamine EDA
Monoethanolamine MEA
Morpholine
CTW, September 2006
Chemistry in Refining Overheads

17. Amines to be studied – next 8
Methylamine
Methyldiethanolamine MDEA
Ethylamine
N-methylmorpholine
Diglycolamine DGA
Diethylamine
N-butylamine
Sec-butylamine
CTW, September 2006
Chemistry in Refining Overheads

18. Chemistry in Refining Overheads
Questions?
Thanks for your attention!
CTW, September 2006
Chemistry in Refining Overheads