Chromatographic Analysis of Natural Gas Liquids

Ben James

President, Petrochemical Services

Sherry Laboratories

Who is Sherry Laboratories

• Founded in 1947, an industry leader in independent, third-party testing

• 10 laboratories

• Accredited testing

• Technical expertise

• Mission critical

Sherry Environmental Testing

Sherry Petrochemical Testing & Standards

Manufacturing

Sherry Materials Testing

Sherry Engineering Group

Sherry Microbiological & Food Testing

Sherry Subsidiaries

Hydrocarbon Lab

• Serves industries such as:– Natural Gas Production– Gas Transmission Pipeline– Drilling and Exploration– Liquid Hydrocarbon

Fractionation

• Provides services such as:– Gas Analysis– Liquid Analysis– Condensate Analysis– Sulfur and Mercaptans– Extended Analysis– Flash and Shrink Test

Reference Standards

• Serves industries such as:– Natural Gas Production– Gas Transmission Pipeline– Drilling and Exploration– Liquid Hydrocarbon

Fractionation

• Provides products such as:– Natural Gas Blends– GPA and Custody Transfer

Chromatographic Standards– Petrochemical Mixtures– Refinery Gas Mixtures– On-line Chromatograph

Calibration Gas

Analytical Methods

• GPA 2177– “Method for the Analysis of Demethanized Hydrocarbon

Liquid Mixtures Containing Nitrogen and Carbon Dioxide by Gas Chromatography”

• GPA 2186– “Method for the Extended Analysis of Hydrocarbon Liquid

Mixtures Containing Nitrogen and Carbon Dioxide by Temperature Programmed Gas Chromatography”

Composite Sampler

• Sample Probe

– Center 1/3 of Pipe

– Not located in dead-end or recirculation area

• Tubing to Pump

– Small Enough to Ensure That a Fresh, Representative Sample is at the Pump Suction Prior to Each Stroke

– High Pressure, Low Temperature

Composite Sampler

• Sample Pump– Flow Proportional

– Repeatable Volume

• Sample Accumulator– Floating Piston Type

– Mixer

– Sufficient Back Pressure

– Choose Back Pressure Gas Carefully

– Never Fill More than 80%

Transport Cylinder

Transport Cylinder

Sampling

• Mix Well

• Adequate Purging

• Transfer under Pressure

• Check For Leaks

• 80% Maximum

• D.O.T Regulations

Typical AutomaticSampling System

From the PipelineTo the Chromatograph

• 500,000 barrels

• To 15,000 cc

• To 1/2 microliter

• Less than 1 part in 150,000,000,000,000

• Sample Must be Representative of the Product Pumped

Chromatograph Systems

• Sample injection system

• Pressure, Flow and Temperature Control

• Columns

• Detectors

• Integrator or Computer Systems

• Calibration

• Calculations

The Chromatograph

Sample Injection

• Pressurize Inert Gas Side of Sample Cylinder

• Mix Sample

• Connect Product Side to Sample System

• Shut Purge / Block Valve

• Admit Sample to System

• Purge Slowly and Sufficiently

• Block In

• Inject Sample

Sample Injection System

Inert Gas

Purge/Block

Valve(s)

Carrier Gas

To Chromatograph

Injector

Filter

Sample Injection System

Column

Packed Column

Capillary Column

Column

• Polar

• Non-Polar

• Temperature

• Flow

• Temperature Programming

• Combinations of Columns

Hexanes Plus

• Back Flush

• Pre Cut

• Temperature Programming

Back Flush

Pre Cut

Extended Analysis

• Hexanes Plus Fraction of Sample

– Over 100 components

• Physical Properties Depend on Mix of These Components

• Average Molecular Weight

• Average Density

Temperature Program

Temperature

Detectors

• Thermal Conductivity

• Flame Ionization

Thermal Conductivity Detector

• Universal

• Wire Filament or Bead

• Conductivity of Gas Determines Temperature of Detector Filament

• Linearity

• Sensitivity

Thermal Conductivity

Flame Ionization Detector

• More Sensitive Than TCD

• Higher Linear Range

• Not Sensitive to H2S or CO2

• Flame May Be Objectionable

Column

Effluent

Air

Hydrogen

Flame

Tip

Collector

Flame

Electrical

Signal

Detectors

TCD

FID

Integration or Computer

• Adequate separation

• Integration parameters

• Peak identification

• Calibration

Chromatogram

Calibration

• 80 Mole %

• 80,000 Counts from Integrator

• 80 / 80,000 = 0.001 Calibration Factor

• 79,000 Counts

• 79,000 x 0.001 = 79 Mole %

Evaluating Calibration Standard

• Run as an Unknown

• Outside Lab Verification

• Plot of Response Factors

• Control Charts

• GPA 2198

GPA 2177

• Chromatograph Repeatability and Reproducibility Criteria

• Revision 01/07/08

• Natural Gas Liquids

Plot

Calculations

• Industry Standards for Calculations

• Industry Standards for Physical Constants

– Latest Versions

Summary

• Good Sample to Chromatograph

• Sample Injection

• Peak Separation

• Detector Response

• Integration

• Calibration

• Calculations

Contact Us

Request Info Online at

www.sherrylabs.com/requestinformation

337.232.3568

2129 West Willow Street, Scott, LA 70583

105 Dalton Street, Suite E, Shreveport, LA 71106