Amine hydrochlorides in refinery overheads

33 Pages·2014·0.89 MB·English

by  Macaden, Santosh

Amine hydrochlorides in refinery overheads:
Solving corrosion problems through
electrolyte process simulation

Prodip Kundu

OLI Systems Inc.
2014 Software Global Customer Conference
September 30 - October 2, 2014
Refinery overhead corrosion
 Contain complex mixtures of hydrocarbons, water, inorganic and organic
acids, and various ionic species.
 Composition and phase behavior changes rapidly as it is being condensed.
 Acids or salts present in the overhead system can cause corrosion when the
right conditions exist.
 Organic neutralizing amines are commonly used to combat corrosion in

refinery crude column overhead systems.
 Corrosion due to neutralizing amines in refinery overhead systems and
subsequent corrosion-related failures are frequently reported.
 In order to avoid expensive material solutions (i.e., Ti), we need to
understand the overhead chemistry better.
Refinery overhead corrosion
Acidic chloride-based corrosion:
Residual salts hydrolysis:
Amine hydrochloride salts formation:
RNH v + HCl v ↔ RNH Cl s/l
2 3

+ −
RNH Cl s/l + H O ↔ RNH aq + Cl (aq)
3 2 3
Refinery overhead corrosion
Root Cause of Failures:
 Failures can be traced to the formation of amine hydrochlorides, either as
hygroscopic solids or concentrated solutions.
 Lack of understanding of physical properties, thermochemical behavior and
phase equilibria of amines and their hydrochloride salts.
OLI Systems’ Mixed-Solvent Electrolyte (MSE) model:
 Phase equilibria in mixtures containing various amines, ammonia, HCl, CO ,
2
H S, water and hydrocarbons.
2
 The model predicts the formation of solid salts or concentrated amine
hydrochloride solutions that may induce corrosion.
Mixed-solvent electrolyte model (MSE):
Thermophysical Framework
Gas-phase
Excess Gibbs Thermo-
equation of
energy model chemistry of
state
species
Standard-state
Adsorption
properties of Themodynamic
models
solution
framework
species
Phase and Transport
chemical properties and
equilibrium surface
tension
algorithm
Applications (process, corrosion, oilfield scaling, etc.)
Structure of the thermodynamic model
 Definition of species that may exist in the liquid,
vapor, and solid phases
 Excess Gibbs energy model for solution nonideality
 Calculation of standard-state properties
Helgeson-Kirkham-Flowers equation for ionic and neutral

aqueous species
Standard thermochemistry for solid and gas species

 Algorithm for solving phase and chemical equilibria
Standard-state properties:
Aqueous species
 Helgeson-Kirkham-Flowers-Tanger equation
 Temperature and pressure dependence of partial
molar volumes and heat capacities based on ion
solvation theory
 Computation of standard-state Gibbs energy and
enthalpy of formation and entropy by
thermodynamic integration
 Estimation methods for the HKF parameters
Outline of the model:
Solution nonideality
ex ex ex ex
G G G G

Excess Gibbs energy  LR  LC  II
RT RT RT RT

LR Debye-Hückel theory for long-range electrostatic
interactions
LC Local composition model (UNIQUAC) for neutral
molecule interactions
II Ionic interaction term for specific ion-ion and ion-
molecule interactions
Gex  
II  n  x x B I  ion interaction parameters
 i  i j ij x
RT
 
i i j

B ( I )  b  c exp(  I  a )
ij x ij ij x 1
Outline of the model:
Chemical equilibrium calculations

For a sample chemical reaction:
aA  bB  cC  dD Standard-state

chemical
potential of i
At equilibrium
G0  xc  xd c d 
  ln C D  C D 
0 0
  with G  v 
RT  xa  xb a b  i i
A B A B
i

 Solu bility and vapor-liquid equilibria are governed by
analogous equations

 Infinite-dilution properties
Thermochemical databases for aqueous systems

Helgeson-Kirkham-Flowers model for T and P dependence

MSE-AmineHCL Databank
Thermodynamic Framework
Mixed-solvent electrolyte model (MSE)

Subset of the chemistry of
interest (i.e., CO , H S, H O,
2 2 2
Parameters for
NH , HCL, NH CL, 56 Hydro-
3 4
amine hydrochlorides
carbons and selected mixtures)

MSE Databank AmineHCL Databank
Private databank, available
MSE Databank only to consortium members
until November 15, 2014

New MSE databank, available
from November 15, 2014