# Flare P erformance Testing with PFTIR

John Zink

Final Report February 1 7 th , 2014

John Zink
Process Burner Test Facility
11920 East Apache
Tulsa, OK 74116

Prepared by
Clean Air Engineering, Inc.
Project No: 12325John Zink

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# 1.0 Introduction

John Zink conducted performance testing at the John Zink test facility in Tulsa,

Oklahoma from November 18

- 22, 2013. Two ground flare burner tips were tested. The

first burner tested was a steam

- assisted tip (SKEC). The second burner tested was a

pressure

- assisted tip (LRGO). The purpose of this test was to determine the combustion efficiency of the LRGO and the SKEC burners under conditions representative of the

burners’ expected normal operation when installed at a DOW Chemical facility in Texas. The perf ormance tests were conducted using a Passive Fourier Transform Infrared (PFTIR) instrument developed by Industrial Monitor and Control Corporation (IMACC). This report summarizes the test results and compares them to results from previous flare

tests.

The purpose and major benefit of an assisted flare is to significantly reduce the amount of smoke (visible emissions) that would otherwise be created by combustion. The burners tested in this program include steam

- assist and pressure

- assist. In a typical syst em, an assist medium such as steam or air is injected into the flare combustion zone to deliver educted air as well as mixing energy. Pressure assisted flares rely on increased exit velocity of the flare gas to educt more air into the gas. Over

- assist is a generic description of an undesirable operating condition possible in assisted flare systems. For example, in

an over

- steaming scenario, the amount of steam and educted air introduced into the combustion reaction zone diminishes, rather than promotes, the efficiency of the combustion process if introduced in large enough quantities relative to the flare gas flow

rate.

The operating envelope of a flare is bounded by excess smoke (too little assist) on one side and decreased combustion efficiency resulting in excess emissions of volatile organic compounds (VOCs) (too much assist) on the other. Smoke suppression is easily monitored by visually observing whether smoke is present. However, the ability to measure or even identify excess emissions caused by over

- assisting is a more difficult task. Standard emission estimation techniques have generally assumed a 98% destruction efficiency or higher when calculating VOC emissions from flares regardless of assist rate.

Regulatory requirements for flares are containe d in 40 CFR §60.18 and §63.11. These requirements were developed from a series of flare emissions tests led by the United States Environmental Protection Agency (US EPA) from 1983

– 1986. The requirements include maintaining a flare pilot, operating with a minimum net heating value of 300 BTU/scf in the vent gas, operating at exit velocities of less than 60 ft/s (or up to 400 ft/s depending upon the vent gas net heating value), and operating with a limited amount of visible emissions. However, a flare can b e operated in compliance with these requirements and still have low combustion efficiency due to over

- assisting.

Prior to the recent refinery tests of flare performance, including the US EPA tests in the

mid

- 1980s, flare tests were conducted on pilot

- scal e test flares at or flares operating at moderate to high vent gas loads. However, a flare typically operates at low vent gas loads (i.e. high turndown) under normal conditions until a process upset or other operatingJohn Zink

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condition requires the operator to flar e waste gas. Thus, the flare normally operates at high turndown for the majority of the operating year, a condition for which there was little to no available performance data.

In the past, measuring the combustion products from a flare was difficult and dangerous. However, recent technological advances have produced remote sensing instruments capable of measuring combustion products such as carbon dioxide, carbon monoxide, and select hydrocarbons without the safety hazards introduced by physically samplin g a flare plume. One such instrument is the PFTIR, which characterizes a plume’s chemical make

up (carbon dioxide, carbon monoxide, and total hydrocarbons) in units of concentration × pathlength. Using this technology, the absolute concentration cannot be determined from a flare plume, but the product of concentration × pathlength (e.g., ppmv × meters), can be used in combustion efficiency calculations. The PFTIR is a relatively new tool and was recently blind

- validated against extractive sampling results f or flare plume testing by TCEQ and the University of Texas in 2010. The PFTIR was first used for refinery flare testing at MPC Texas City in 2009. Several accuracy, precision, and bias checks were performed during the recent flare tests to better character ize the PFTIR measurement technique.



# 2.0 Test Conditions

Combustion efficiency was measured under several combinations of vent gas composition and flare operating parameters. Propylene , Tulsa natural gas (TNG), and nitrogen were used as vent gas components. E ach of these combinations is referred to as a “test condition” in this report. The following test conditions were used during this project.

Test P1H LRGO Pressure

- assist burners. 100% Propylene

. Objective: To determine the combustion efficiency of the LRGO burner using pure propylene at the maximum operating pressure

. Three replicates were conducted.

Test P1L LRGO Pressure

- assist burners. 100% Propylene. Objective: To determine the combustio n efficiency of the LRGO burner using pure propylene at the minimum operating pressure. Three replicates were conducted.

Test P2H LRGO Pressure

- assist burners. Propylene / nitrogen mix

. Objective: To determine the combustion efficiency of the LRGO burner using a propylene / nitrogen mix diluted to the minim um NHV required for stability when the LRGO burner
is operating at the maximum operating pressure. Three replicates were conducted.

Test P2 L LRGO Pressure

- assist burners. Propylene / nitrogen mix. Objective: To determine the combustio n efficiency of the L RGO burner using the same propylene / nitrogen mix as Test P2H at the minimum operating pressure. Three replicates were conducted.John Zink

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Test P 3H LRGO Pressure

- assist burners. Propylene / TNG / nitrogen mix. Objective: To determine the combustio n efficiency of the LRGO burner using a mixture of 50% / 50% TNG / Propylene mixture diluted to the minimum NHV required for stability when the LRGO burner is operating at the maximum operating pressure. Three replicates

were conducted.

Test P3L LRGO Pressure

- assist b urners. Propylene / TNG / nitrogen mix. Objective: To determine the combustion efficiency of the LRGO burner using the same propylene / TNG / nitrogen mix as Test P3H at the minimum operating pressure. Three replicates were conducted.

Test P4 LRGO Pressure

- assist burners. 90% Hydrogen / 10% TNG mix. Objective: To observe the stability of the LRGO burner flame when the fuel is predominantly hydrogen and when the LRGO burner is operating at the maximum
operating pressure. Emissions measurements were n ot taken during this test.

Test S1 SKEC Steam

- assist burners. Propylene / nitrogen mix. Objective: To determine the combustion efficiency of the SKEC burner using a propylene

/ n itrogen mixture diluted to the minimum NHV required for stability when the LR GO

burner is operating at sonic velocity and while steam flow is set at design flow rate.

Test S2 SKEC Steam

- assist burners. Propylene / nitrogen mix. Objective: To determine the combustion efficiency of the LRGO burner using the same propylene / nitrogen mix and flow rate as Test S2 while steam flow is off.

Test S3 SKEC Steam

- assist burners. Propylene / nitrogen mix. Objective: To determine the combustion efficiency of the SKEC burner using a propylene / nitrogen mixture with the steam flow at the minimu m design rate. The nitrogen flow is the minimum available from the nitrogen delivery system while the propylene flow is adjusted to achieve a stable flame.

Test S4 SKEC Steam

- assist burners. Propylene / nitrogen mix. Objective: To determine the combustion efficiency of the SKEC burner using a p ropylene / nitrogen mixture of 7 00 BTU/scf and steam flow at the minimum design rate. Fuel flow was the maximum flow rate where the SKEC flame was stable.

Test S5 SKEC Steam

- assist burners. Propylene / nitrogen mix. Objective: To determine the combustion efficiency of the SKEC burner using a propylene / nitrogen mixture with the steam flow at a pressure of 10 psig. The nitrogen flow is the minimum available from the nitrogen delivery system while the propylene flow i s adjusted to achieve a stable flame.

Test S6 SKEC Steam

- assist burners. Propylene / nitrogen mix. Objective: To determine the combustion efficiency of the SKEC burner using propylene fuel

. The steam rate is set to the maximum design flow while the fuel is adjusted to achieve the incipient smoke point.John Zink

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# 3.0 Results

A summary of results from the LR GO tests are shown in Figure 3

- 1 and 3

- 2 below. Table 1 contains summary data from the LRGO test runs. Test run P1L (3) was conducted under poor wind conditions that prevented accurate measurements. The P1L (3) data is excluded from the P1L results presented in Figures 3

- 1 and 3

- 2.

Figure 3

- 1: NHVcz vs. CE for LRGO Burners

Figure 3

- 2: Tip Velocity vs. NHV cz for LRGO BurnersJohn Zink

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A summary of results from the SKEC tests are shown in Figure 3

- 3 and 3

- 4 below. Table 1 contains summary data from the SKEC test runs.

Figure 3

- 3 : NHVcz vs. CE for SKEC Burners

Figure 3

- 4 : Tip Velocity vs. NHV cz for SKEC BurnerJohn Zink

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Table 1: Data Summary