8/10/2019 Electrolyte Modeling Basics.ppt
1/39
Opening new do ors wi th Chemist ry
THINK SIMULATION!
Electrolyte Modeling BasicsProcess Simulation
OLI Systems, Inc.
8/10/2019 Electrolyte Modeling Basics.ppt
2/39
THINK
SIMULATION
2
Agenda
Introductions
Overview of Process Simulation
The basic OLI Process (Neutral 1)
Essentials Controllers
Recycles
Sour Gas SweeteningSimple Crude Distillation
OLI Pro (Neutral 1 again)
8/10/2019 Electrolyte Modeling Basics.ppt
3/39
THINK
SIMULATION
3
Introductions
OLI Staff Jim BertholdDirector of Customer Support
Robert YoungDirector of product support
Chris DepetrisDirector of product development
Hongang ZhaoOLI Engine Support
AQSim
Pat McKenzieDirector of OLI Business
DevelopmentAJ GerbinoSenior Partner
Attendees
8/10/2019 Electrolyte Modeling Basics.ppt
4/39
THINK
SIMULATION
4
Overview of Process Simulation
OLI Supports several Process SimulatorsAspen PLUS
Aspen Hysys
IDEAS
gProms
OLI
ESP
OLI Pro ProII
Unisim
8/10/2019 Electrolyte Modeling Basics.ppt
5/39
THINK
SIMULATION
5
Overview of Process Simulation
We will discuss only the OLI Simulators
Environmental Simulation Program (ESP)
OLI Pro
Analyzers
8/10/2019 Electrolyte Modeling Basics.ppt
6/39
THINK
SIMULATION
6
Overview of Process Simulation
ESP Development started in 1990
Funded by a consortium of companies
Aker Kvaerner (formerly Davy McKee)
Chevron
Dupont
ExxonMobil (formerly Exxon)
ICI
Shell
Development Continues
8/10/2019 Electrolyte Modeling Basics.ppt
7/39
THINK
SIMULATION
7
Overview of Process Simulation
OLI Pro
Created from Honeywells Unisim Design
Updated as Unisim is updated
Contains all of the OLI thermodynamics Does not contain all of OLIs specialized unit
operations
8/10/2019 Electrolyte Modeling Basics.ppt
8/39
THINK
SIMULATION
8
Overview of Process Simulation
OLI has a vast experience in simulation
Upstream flow assurance
Subsurface flow modeling
Acid gas scrubbing Organic pollutant stripping
Dynamic pH control
Biological treatment
Crude distillation
More
8/10/2019 Electrolyte Modeling Basics.ppt
9/39
THINK
SIMULATION
9
The basic OLI Process (Neutral1)
8/10/2019 Electrolyte Modeling Basics.ppt
10/39
THINK
SIMULATION
10
The basic OLI Process (Neutral1)
We will be using ESP
Defining the chemistry model
Create the process
Mix blockPhase separate block
pH neutralizer block
Run the process
Review the results
8/10/2019 Electrolyte Modeling Basics.ppt
11/39
THINK
SIMULATION
11
The basic OLI Process (Neutral1)
8/10/2019 Electrolyte Modeling Basics.ppt
12/39
THINK
SIMULATION
12
The basic OLI Process (Neutral1)
Controllers
Frequently the adjustment of pH requires theNeutralizer Block to perform a difficult
calculation. The calculation is difficult because the set point
of the Neutralizer may be on the steep part of thetitration curve.
There may be significant phenomenologicalchanges that occur while the unit is adjusting thepH.
8/10/2019 Electrolyte Modeling Basics.ppt
13/39
THINK
SIMULATION
13
The basic OLI Process (Neutral1)
Controllers Frequently the Neutralizer Block is not a suitable
block because:
To control the pH you must adjust anotherupstream or downstream block
You need to control something other than pH
The set point may be an impossible case.
8/10/2019 Electrolyte Modeling Basics.ppt
14/39
THINK
SIMULATION
14
The basic OLI Process (Neutral1)
Controllers Frequently the Neutralizer Block is not a suitable
block because:
To control the pH you must adjust anotherupstream or downstream block
You need to control something other than pH
The set point may be an impossible case.
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
15/39
THINK
SIMULATION
15
The basic OLI Process (Neutral1)
Controllers Some other parameters that can be controlled
are:
pH
Temperature
Pressure
Flow
ConcentrationOxidation/Reduction Potential
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
16/39
THINK
SIMULATION
16
The basic OLI Process (Neutral1)
Phase change limitations to pH control
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
17/39
THINK
SIMULATION
17
The basic OLI Process (Neutral1)
Feed contains
H2O
Cl2
CO2
Scrubbed with
NaOH
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
18/39
THINK
SIMULATION
18
The basic OLI Process (Neutral1)
Cl2(vap)= Cl2(aq)Cl2(aq)+ H2O = H
++ Cl-+ HClO(aq)
HClO(aq)=H++ClO-
As the pH increases with added NaOH, all these equilibria are shifted to theright. This scrubs the chlorine
CO2(vap)=CO2(aq)
CO2(aq)+H2O=H++HCO3
-
HCO3-
=H+
+CO3-2
HCO3
-+Na+=NaHCO3(s)But these equilibria are also shifted to the right.
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
19/39
THINK
SIMULATION
19
The basic OLI Process (Neutral1)
Cl2(vap)= Cl2(aq)Cl2(aq)+ H2O = H
++ Cl-+ HClO(aq)
HClO(aq)=H++ClO-
CO2(vap)=CO2(aq)
CO2(aq)+H2O=H++HCO3
-
HCO3-=H++CO3
-2
HCO3-+Na+=NaHCO3(s)As a species concentration becomes fixed by the equilibrium, then the
pH remains constant.
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
20/39
THINK
SIMULATION
20
The basic OLI Process (Neutral1)
Controller Remove the pH neutralizer
Add a manipulate block to control NaOH addition
Add a new mixer block to mix the separatedliquid with the manipulated NaOH
Add a control block
Run the process
Review the results
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
21/39
THINK
SIMULATION
21
The basic OLI Process (Neutral1)
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
22/39
THINK
SIMULATION
22
The basic OLI Process (Neutral1)
Adding Recycle Loops Frequently a process recycles part or all of certain
streams back to up-stream units.
There are many reasons for using a recyclestream.
minimization of waste
increase of residence time
purification of product.
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
23/39
THINK
SIMULATION
23
The basic OLI Process (Neutral1)
Recycle Loops Modify chemistry model
Add mix block for halite addition
Add a split block
Connect recycle stream to original mix block
Run process
Review results
How much Caustic Reagent was used?More than in no-recycle case?
Less?
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
24/39
THINK
SIMULATION
24
Sour Gas Sweetening
DEA Absorber
Feed Gas Rich Amine
Flash Drum
Clean Gas
Flash Vapor
Flash Liquid
DEA Regenerator
Recycle
CO2-H2S
Water MixWater Make-UpWater
Water In
Recycle 1
DEA Mix
DEA Make-UpDEA
DEA InWater
Control
DEA
Control
Recycled DEA
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
25/39
THINK
SIMULATION
25
Sour Gas Sweetening
This application brief presents the case of sweetening(purifying) a sour gas from a natural gas well.
Several unit operations are employed to simulate atypical gas sweetening process configuration.
Once the sour gas components have been removed, thescrubbing liquor is regenerated to remove captured sourcomponents.
These components are corrosive and metal selection can
be an issue.
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
26/39
THINK
SIMULATION
26
Sour Gas Sweetening
For this example we will take a natural gas stream is approximatelytwo mole percent (mol%) sour. This means that for every 100 moles of gas there are 2 moles of
hydrogen sulfide (H2S). In addition to H2S, it is desirable to remove carbon dioxide
(CO2) since this constituent lowers the heating value of the gas
and increases the volume of gas that must be transported. Most all alkanolamine plants are designed to maximize the
removal of both of these acid gases. In a typical gas cleaning plant, natural gas is fed to an absorber
operating at high pressure. The gas is scrubbed using an approximately 58 weight percent
(wt%) diethanolamine (DEA) solution. The scrubbed sweet gas is sent on for further processing or
drying and transport via pipeline.
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
27/39
THINK
SIMULATION
27
Sour Gas Sweetening
The rich DEA solution exiting the absorber is sent to aflash drum operating at a much lower pressure. This step removes any light-end hydrocarbons that were
captured in the absorber. The light-end gases are sent on for further processing.
Next, the hydrocarbon-free DEA solution is fed to aregeneration column. Here heat is applied to strip the acid gas components out
of the DEA solution. Make-up water and DEA are added to maintain the lean 58
wt% DEA solution. This solution is then recycled to the absorber.
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
28/39
SIMULATION
28
Sour Gas Sweetening
Why does adding DEA remove CO2and H2S? The absorption of hydrogen sulfide gas follows these
equilibria:
H2S (vap) = H2S (aq) (1)
H2S (aq) = H+
+ HS-
(2) HS-(aq) = H+ + S-2 (3)
Adding a basic reagent such as DEA increases the pH ofthe solution. pH is defined as:
pH = - log aH+ (4)
where aH+is the activity of the hydrogen ion. The activityof the hydrogen ion is defined as:
aH+ = H+[H+] (5)
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
29/39
SIMULATION
29
Sour Gas Sweetening
Carbon dioxide follows a similar equation path: CO2(vap) = CO2(aq) (6)
CO2(aq) + H2O = H++ HCO3
- (7)
HCO3-
= H+
+ CO32-
(8)
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
30/39
SIMULATION
30
Sour Gas Sweetening
Where does the basic reagent come from? Adding DEA ((C2H5O)2NH) to a solution will make it more
basic:
(C2H5O)2NH + H2O = (C2H5O)2NH2+ + OH- (9)
H2O = H+ + OH- (10)
Adding DEA to the solution forces water to dissociate (Eq.10).
The hydrogen ion is complexed with the DEA molecule tocreate a protonated species and leaving free hydroxideions.
This increases the pH and all of the vapor-liquid equilibriadescribed above (by Equations 1, 2, 3, 5, 6 and 7) willshift to the right.
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
31/39
SIMULATION
31
Sour Gas Sweetening
There is a secondary equilibrium involving DEAcarbamate ((C2H5O)2NCO2-):
(C2H5O)2NH + HCO3-= (C2H5O)2NCO2
-+ H2O (11)
This species is stable at low temperatures andhelps to remove carbon dioxide from the naturalgas.
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
32/39
SIMULATION
32
Sour Gas Sweetening
Steps to create the process New Process
New Chemistry
Build the process Run the process
Select Tear(s)
Evaulate results
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
33/39
SIMULATION
33
Simple Crude Distillation
Overview In this demonstration we will distill a typical crude using a
simple distillation scheme with a single side stripper.
The OLI approach to modeling distillation is to rigorouslyaccount for the effects of water in the oil and also considerthe effects of salts in both the water and oil phases.
Most other simulators only consider the water phase as apure phase.
Our approach will allow us to model such species as
chlorides and amine salts entrained and dissolved in theprocess streams.
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
34/39
SIMULATION
34
Simple Crude Distillation
Back Story Our example considers a crude oil after it has left
the production field.
In our case we have a relatively young well that
has produced 100,000 barrels of oil per day.10,000 barrels of this oil are produce water. In aReal sample, this produced water will consist ofmany different cations and anions as well asdissolved gases.
These dissolved species can cause a host ofproblems such as fouling, scaling and corrosion.
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
35/39
SIMULATION
35
Simple Crude Distillation
Back Story Continued In our example, the formation from which the oil was produced is
essentially just a salt dome (NaCl). Our oil and our produced waterwill be saturated with halite. The chloride ion can be a problemdownstream.
In normal processing this oil will be sent to an electrostatic desalterwhere the oil is washed and most of the salt is dissolved into thewater phase.
The problem with the wash water is that it also may containsignificant amounts of salt which are the introduced to the refinery.
The crude is usually maintained at moderate temperatures (150 oFto 250 oF) and at pressures sufficient to prevent boil-off (usually 75PSI above saturation pressure).
The pH of the desalted crude is maintained at pHs near neutral toprevent emulsion formation.
The desired salt content of the crude is usually near 3.5 mg/L (1pound per thousand barrels, PTB)
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
36/39
SIMULATION
36
Simple Crude Distillation
Desalter simulationor a funny thing happened on the way to the CDU
FLOW ADJUSTERNACL FORMATION A-NACL FRMSALT
SATFORMATION
BRINE
FORMATION
SOLID
C-BRINE
FLOW
OIL
WATER
MIX
OIL
FORMATION
CRUDE
SIMPLE
DESALTER
WASH
WATER
A-CAUSTIC
SALT WATER
DESALTED
CRUDE
M-CAUSTIC
CAUSTIC
C-
CRUDE
PH
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
37/39
SIMULATION
37
Simple Crude Distillation
Salt Composition
Stream: NACL FORMATION
Temperature 75 oF
Pressure 75 PSIA
Flow 128200 Lb/hr[1]
H2O 0.83 Mole fraction
NACL 0.17 Mole fraction
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
38/39
SIMULATION
38
Simple Crude Distillation
Crude Feed
Stream: OIL
Temperature 75 oF
Pressure 75 PSIA
Flow 1.1538E+06 Lb/hr[1]
CRUDE 0.9658 Mole fraction
CH4 0.0003 Mole fraction
C2H6 0.0006 Mole fraction
C3H8 0.0086 Mole fraction
n-C4H10 0.0193 Mole fraction
i-C4H10 0.0054 Mole fraction
[1]This is approximately 90,000 bbd
THINK
8/10/2019 Electrolyte Modeling Basics.ppt
39/39
SIMULATION
39
Simple Crude Distillation
Wash water is added to theseparator SIMPLE DESALTER at arate that is 6 % of the volume ofthe mixed oil and water streamFORMATION CRUDE. This isapproximately 6,000 bbd. Caustic
is added to keep the pH in the 7.0range.
The stream DESALTED CRUDE isthe stream that we will use in thedistillation simulation. Thecomposition of the stream isshown in the table to the right.
Stream: DESALTED CRUDE (a/k/a RAW CRUDE)
Temperature 250 oF
Pressure 110 PSIA
Flow 1.16773E+06 Lb/h (100,000 bbd)
H2O 0.0087 Mole fraction
CRUDE 0.9097 Mole fraction
CH4 0.0028 Mole fraction
C2H6 0.0056 Mole fraction
C3H8 0.0081 Mole fraction
n-C4H10 0.0181 Mole fraction
i-C4H10 0.0051 Mole fraction
NA2O 0.0165 Mole fraction
HCL 0.0330 Mole fraction
Density 1914.6 Lb/m3
Enthalpy -4.25003E+06 Cal/lmol
Top Related