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Avantis • Foxboro • SimSci-Esscor • Triconex

Molecular Level Description of Crude Oils and Complex Hydrocarbon Streams

Lanny Carr – Invensys Process System

REFINING CHINA 2006

April 24 -26

Beijing, China

Invensys Confidential

…we could remove the uncertainty about using old assay data as the basis for how we process today’s feedstocks?

…we could reduce inherent assay errors by using measurements that we can take at the plant site?

…we could make those corrections on a daily basis?

…we could produce deeper information about true compositional nature of feedstocks and other process streams?

…we could use that detailed knowledge as more accurate input to planning and optimization tools for daily operational improvements?

…what if?

What if…


Laboratory measurements of distillation yield behavior.

A convenient way to lump crude oil into a manageable number of pseudocomponents.

Laboratory measurements of properties of these pseudocomponents.

Source of data for API correlations.

Source of data for Linear and Simulation Programs.

Assays - What they are…


High quality assays are costly and time-consuming to produce.

Library assays go out-of-date as fields mature.

Input data used to select assays are often just bulk properties that are insensitive to distributed properties.

Blending during gathering and transportation can create compositional characteristics difficult to mimic with available assays.

Even perfect assays can fail, for fundamental reasons, to fully account for compositional differences that govern the refining outcome.

Assays - the Problems...


Crude oil quality is difficult to measure.

Analytical measurements contain error.

Need to rely on data of unknown quality.

‘Typical’ assays are commonly used in place of ‘measured’ assays.

Bulk property correlations contain deviations and are insensitive to important compositional variations.

LP models and simulators don’t always agree with the refinery operation.

Issues when Evaluating Quality


The Z - Based Structural Index Correlation

All compounds in crude oil are classified according to the general empirical formula:

CnH2n+zNuSvOw…– z-vectors are the classifying numbers

– ‘n’ is the primary correlating variable

[Z-BaSICtm] Method


All crudes are made up of a few dozen classes of compounds.

Each class has a mass distribution with respect to molecular weight.

Each class and molecular weight set are comprised of multiple isomers.

In short, crude oil may be described by mass distributions with respect to 3 independent variables, ‘z’, ‘n’ and ‘i’.

Crude Oil Composition - Simplified


Refining operations are processes to:

– alter the classes (hydrogenation, reforming, HDS, HDN, etc.)

– alter the molecular weight (FCC, HC, alkylation, coking, etc.)

– alter the isomer structure (isomerization, cat. dewaxing, etc.)

In Short, refining alters the ‘z’, ‘n’, and ‘i’ character of crude oil.

Refinery Operations - Simplified


Correlation of Boiling Point with ‘n’ and ‘z’


Correlation of density with ‘n’ and ‘z’


Density

0.50.60.70.80.9

11.11.21.31.41.5

0 10 20 30 40 50Carbon number

g/c

cDensity vs Carbon Number


'n' 'z' Pv coefficients density Weight fraction

16.00 2.0 17.07 4926 -88.0 .773 .00334 13.14 -6.0 16.70 4328 -116.9 .957 .00018 15.00 -10.0 16.12 4385 -105.5 .927 .00526 14.00 -14.0 15.64 4132 -113.0 .962 .00117 14.00 -12.0 15.84 4223 -115.9 .938 .00461 16.00 -6.0 15.91 4159 -121.5 .840 .00250 14.29 -10.0 15.42 4162 -93.5 1.051 .00358 18.00 2.0 16.11 4241 -120.5 .775 .00120 15.29 -10.0 15.56 4354 -95.4 1.035 .00048 16.00 -8.0 15.84 4167 -124.0 .900 .00094 17.00 2.0 16.15 4300 -123.4 .777 .00319

C16-C17 excerpt


Jet A Property Variations


Jet A Heating Value at Constant Density


Jet A Aromatics vs. Paraffinsat Constant Density.


total sulfur distribution

0

1

2

3

4

5

500 600 700 800 900 1000 1100endpoint in F

% s

ulfu

rSpeciation with Molecular Modeling


Percent Distilled0 20.0 40.0 60.0 80.0 100.0

Te

mp

era

ture

(C

)

-100.0

100.0

300.0

500.0

700.0

900.0

Assay Processing for Stream QTL-CRUDE

Input TBP data

Fitted TBP Curve

Component Cuts

ROMeoNon Linear Planner

Old System

Cut-Point Base

(Pseudo Component)

51 Pure-components

39 High Fidelity Pseudo-

Components

0 10 20 30 40 50 60 70 80 90 100

0200400600800

1,0001,2001,4001,6001,800

Liquid Volume Percent, LV%

TB

P T

emp

erat

ure

, d

eg.

F

Lig

ht

Na

ph

tha

He

avy

Na

ph

tha

LGO RCHGOKERO

LPG

LN

HN

KERO

LGO

HGO

RC

LPG

LN

HN

KERO

LGO

HGO

RC

NL Planner System (Assay）


ZKQ density vs SimDis

0.5

0.6

0.7

0.8

0.9

1

1.1

-100 400 900 1400

Grouping of Hi Fidelity Pseudocomponents


composition of HN, dens =.7306, bp 80-150

0

10

20

30

40

50

60

13.8% 14.0% 14.2% 14.4% 14.6% 14.8% 15.0% 15.2% 15.4%

H content

n-paraffins

i-paraffins

mononaphthenes

dinaphthenes

monoaromatics

Heavy Naphtha Cut at Constant Density


ComponentEstimation

C4 C12

Assay

Blend Crudes & generate pure components & high fidelity

pseudo-components

Crude Assay

Library

ROMeo Online Model

Z-Basic

Update individualcrude ASSAYS from

online measurements & lab

data

Data ReconciliationPerformance Monitoring

Crude Assay Data Compensation Method


Z-BaSIC™ Information Logic

Preparation of original 'cp' files

'cp' file adjuster Z-BaSIC Applications

Physical Crude Oils and Intermediate

Process Streams

Laboratory and on-line monitored property data Composition and

Property Reports

Z-Assays(reconciled)

Model, Simulator and Optimizer Input files

First-Principal Simulators

Library Assays

LP Input files

HTSD, light gas analysis

Density

Elemental analysis -C, H, S, N, O & metals

GC-MSanalysis

Optional - NMR, viscosity, RVP, MW, etc.

NMR provides additional information for the Z-BaSIC convergence

• Total Hydrogen

• A, O, S Hydrogen

• Sulfur

Data Inputs & Outputs


Conventional

Assays

Pseudocomponents

________________

LP Sim Opt

Crude Oil or Monitors

Reference file

Pure components

+ Hi Fidelity Pseudocomponents

___________________

Props, Comp, Sim, Opt

Interface with Conventional Systems


Weight % Species+

Properties

Pseudo ComponentsPlus Distinct Species

Weight % HC minus Species+

Properties

Each Pseudo-Component

NL Planner/ROMeo

Reconciled Assay

Speciated Stream Preparation and Analysis


SimulatedUnit

Yield2 & Properties+

Components


Components


Components


Components


Components

…What can we do with Speciation?


Role Activity Technology

Process UnitTargets with

Refinery Wide Representation

Operator Set Operating Limits

APC Targets

Set Process Unit Detailed Targets

RefineryScheduler

Schedule Refinery

Approved Targets

Process UnitDetailed Targets

Set points

Schedule

RefineryPlanner

Refinery NLP or LPUpdate qualities

Develop Operating

Plan

Daily Targets with Refinery Wide

Representation

Daily Crude Mix

Daily Liftings Prices

ConstraintsOperationsManager

LostOpportunity

Price & Constraint Visibility


Overcomes limitations of existing crude oil assay technology

Enables crude oil analysis on a fundamental molecular level

Potential benefits in excess of $0.30/bbl

Moves technology to a more scientific basis for component speciation

Molecular Modeling - Advantages

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