Gene Beebe. September 20 th 2016

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1 BTU Measurement from Fuel Gas to Flare Gene Beebe Vector Controls and Automation Group September 20 th 2016

2 2/16/2017 Vector Controls and Automation Group 2

3 What is BTU? Amountof heat requiredto raise the temperatureof one pound of water (at or near 39.2degrees Fahrenheit) by one degree Fahrenheitin practical terms, the amount of heat generated by one lighted stick of match BTU can be measured in Net (dry) or Gross (wet) values depending on applications 2/16/2017 Vector Controls and Automation Group 3

4 WobbeIndex is used to compare the combustion energy of different composition fuel gases. If two fuels have identical WobbeIndices, the energy output will also be identical if combusted under the same conditions* Heating Value is the amount ofheat released during the combustion of a specified amount of gas* CARI (Combustion Air Requirement Index ) the required amount of dry air to burn 1Nm 3 of fuel gas compensated for the specific gravity of the gas. Air Demand the required amount of dry air to burn 1Nm 3 of fuel gas (Stoichiometric Air/Fuel ratio) Specific Gravity** (Relative Density) the ratio of gas density / air density 2/16/2017 Vector Controls and Automation Group 4

5 Difference between BTU and Wobbe Formula: Wobbe Index = HeatingValue Specific Gravity Same heating value but different quality. 2/16/2017 Vector Controls and Automation Group 5

calibration and maintenance Thermopile Vary gas and air mixture to produce a Wobbe value Indirect calculation of BTU Uses

6 How to Measure BTU? Gas Chromatography Gas Composition measured then calculate BTU Speciates stream Measurement cycles varies Require routine calibration and maintenance Thermopile Vary gas and air mixture to produce a Wobbe value Indirect calculation of BTU Uses open flame for combustion Residual Oxygen Measure Wobbe or BTU buy using the a zirconia cell during combustion in oven. Different configurations based on sample pressure and application 2/16/2017 Vector Controls and Automation Group 6

value of a fuel gas is defined as the amount of heat (energy)

7 Typical combustion process Restriction(= P) Thermal load = Heating value (MJ/Nm3) x Gas flow (m3/hr) Gas flow The heating value of a fuel gas is defined as the amount of heat (energy) released once it is combusted. 2/16/2017 Vector Controls and Automation Group 7

8 BTU in Fuel Gas Optimal control Use the CARI signal for feed forward air/fuel ratio control Use the Wobbe Index (or heating value) signal for feed forward control and/or monitoring of the thermal load 2/16/2017 Vector Controls and Automation Group 8

9 FLARE GAS MONITORING Flares are used to eliminate waste gas and are an important part of a plants safety system. Flaring gas is an undesired process (environmental and economical) 150 billion cubic meters of gas is flared annually. -> equivalent of 2.4 million barrels of oil per day (!!!) Why measure flare gas:? Monitor overall plant efficiency Comply to local legislation (to guarantee proper destruction efficiency) Like the 40 CFR / 671 (existing flares in Petroleum Refinery Industry) Optimize natural gas blending 2/16/2017 Vector Controls and Automation Group 9

10 Typical Flare installation Knock out drum (remove liquids, like oil and/or water) Seal drum. (to prevent for flashback) Steam injection. Optimize the mixing of gas and air increased combustion efficiency smokeless burning An ignition system Flare gas recovery system (optional) re-use flare gas as fuel gas in combustion applications Continuous BTU analyzers are often used to stabilize fuel gas quality (fuel gas application) 2/16/2017 Vector Controls and Automation Group 10

11 Probe Location

12 Probe Configuration

13 Plan Ahead Is there access points? Is there room for enclosure? Measure twice

14 Installation is as important as Specification

15 January 30th 2019! 2/16/2017 Vector Controls and Automation Group 15

16 Ruling Highlights Legislation around flaring is intensified US Refinery Sector Rule (RSR) 40 CFR Section and specifies continues measurement of the Net Heating value of flare gas in BTU/SCF: Maintaina minimum BTU value of 270 BTU/SCF Implementation date for US refineries BTU measurement based on composition analysis (calculated BTU) or Direct measurement using a continuous calorimeter Minimum one measurement per 15 minutes Accuracy: +/-2% of Span for calorimeter +/- 10% per analyte for GC (based on triplicate measurement) Availability: 95% based on a 12 months rolling time period 2/16/2017 Vector Controls and Automation Group 16

17 FLARE GAS MONITORING Allowed types of measurement per 40 CFR / 671 Component measurement Calorimeter Grab sampling system No measurement required Calculated Net HV based on recording of individual components Dedicated Net HV measurement Collecting a cannister for compositional analysis Pipeline quality gas (annual grab sample) Minimum one measurement per 15 minutes Optional H2 measurement Once every 8 hours while there is flow Gas streams with consistent composition (requires exemption) 17

18 @2015 Hobré Instruments BV 18

FLARE GAS MEASUREMENT AND RECOVERY OF FUEL FEED GAS WITH RESIDUAL OXYGEN CALORIMETRY

FLARE GAS MEASUREMENT AND RECOVERY OF FUEL FEED GAS WITH RESIDUAL OXYGEN CALORIMETRY David Hailey Ph.D. Product Manager Cosa Instrument 7125 North Loop East Houston, TX 77028 KEYWORDS Combustion Air Requirement