Carbon Content, Sampling, and Calculation

API TECHNICAL REPORT 2572 FIRST EDITION, MAY 2013

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Copyright © 2013 American Petroleum Institute

Foreword

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iii

Contents

Page

1. Scope 1

2. Terms, Definitions, and Symbols 1

   1. Terms and Definitions 1

   2. Symbols 3

3. Sample Collection and Handling 3

   1. General 3

   2. Gas Fuel Sample Collection and Handling 3

   3. Liquid Fuel Sample Collection and Handling 3

   4. Frequency of Sampling 3

4. Sample Analysis 3

   1. Introduction 3

   2. Chromatographic Analysis of Fuel Samples 4

   3. Test Methods for Determination of Carbon Content 4

5. Determination of Carbon Content and Calculation of Emissions 4

   1. Introduction 4

   2. Carbon Content of a Pure Component 4

   3. Carbon Content Calculated from Product Analysis 4

   4. Estimation of Carbon Content from Other Fuel Properties 6

   5. Calculation of Emissions 7

6. Reporting Period Carbon Content Uncertainty 7

   1. Objective 7

   2. Reporting Period Carbon Content Calculated from Multiple Gas Samples 7

Annex A (informative) Estimation of Carbon Content Correlation to Fuel Properties 10

Annex B (informative) Estimation of Carbon Content Uncertainty 16

Bibliography 23

Figures

1. Calculated Carbon Content to Relative Density Correlation 12

2. Nitrogen Upset Fuel Carbon Content Calculated from Monte Carlo Simulation Results 13

3. Nitrogen Upset Fuel Carbon Content vs Relative Density 13

4. Multiple Component Variations Carbon Content Calculated from Monte Carlo Simulation 14

5. Multiple Component Variations Fuel Carbon Content vs Relative Density 14

1. Spot Sample Adjusted Carbon Content to Relative Density Correlation 17

2. Quarterly Sampling and Relative Density Calculations Compared to Quarterly Sampling 19

3. Monthly Sampling and Relative Density Calculations Compared to Monthly Sampling 21

4. Composition Variability of the Four Fuel Streams 22

Tables

1. Example Carbon Content Calculation for a Fuel Mixture Reported in Mole Fraction 5

2. Example Carbon Content Calculation for a Fuel Mixture Reported in Mass Fraction 6

1. Average Process Composition 10

2. Average Process Composition Plus Nitrogen 11

1. Spot Sample Sets 18

2. Stream Compositions 18

3. Summary of Improvement in Annual Carbon Content Determination 19

4. Summary of Standard Deviation, Uncertainty, and Quarterly/Monthly Sampling Data 20

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Introduction

Carbon emission quantities can be calculated from either the volume/mass of fuel or feedstock fed to a process (as applicable) and carbon content of the process or fuel supply, or by directly measuring volume/mass emissions.

This Technical Report (TR) provides guidance on the sampling and calculation of carbon content of process or fuel supplies. The API companion technical report, API TR 2571, Fuel Gas Measurement, can be referenced for guidance on measuring the volume/mass of process fuel gas or feedstock, and the API Compendium of Greenhouse Gas Emissions Estimation Methodologies for the Oil and Natural Gas Industry can be reference for guidance on the calculation of emissions.

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Carbon Content, Sampling, and Calculation

1. Scope

   This Technical Report (TR) provides guidance and a methodology for determination of carbon content from hydrocarbon-based petroleum and petrochemical products, and the uncertainty of the average carbon content as calculated from multiple samples taken during a reporting period. This method is intended to make use of industry- accepted mixture property data and test methods with no new or modified test methods introduced in this document. The method is applicable to carbon-content-based reporting or trading for all gaseous and liquid hydrocarbons.

   
   

   This TR provides references and supplemental information on applicable industry practices based on the published resources, existing industry standards, industry-accepted physical constants or properties of hydrocarbons for measurement, sampling, sampling frequency, and analysis of hydrocarbon samples.

   
   

2. Terms, Definitions, and Symbols

2.1 Terms and Definitions

For the purposes of this document, the following definitions apply.

2.1.1

accuracy

The ability of a measurement instrument to indicate values closely approximating the true value of the quantity measured.

2.1.2

bias

Any influence on a result that produces an incorrect approximation of the true value of the variable being measured. Bias is the result of a predictable systematic error.

2.1.3

calibration

The process or procedure of adjusting an instrument so that its indication or registration is in satisfactorily close agreement with a reference standard.

2.1.4

carbon content

The fraction of carbon in the fluid expressed as percent by weight.

2.1.5

compensation

The adjustment of the measured value to reference conditions (e.g. pressure compensation).

2.1.6

continuous emission monitoring system CEMS

The equipment required to sample, analyze, measure, and provide, by means of monitoring at regular intervals, a record of gas concentrations, pollutant emission rates, or gas volumetric flow rates, individually or in combination, from stationary sources.

2.1.7

flowing compressibility

The compressibility of the fluid at actual flowing temperature and pressure.

1