NAOIMC. National AirOil Group Bulletin 3521284 East Sedgley Avenue, Philadelphia, PA 19134Telephone (215) 743-5300 (800) 523-3495 Outside PA FAX (215) 743-3018 Telex 84-5403

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Automatic Control Systemfor Complete Combustion/

Smokeless Flaring

Designed for use on anyflare system - usingpower gas or steam -tosuppress smoking. Alsofor control of assist gasfor complete combus-tion. Combines econo-my with smokeless

n complete combustion/smokeless flaring with efficientexpenditure of steam and/or gas n built-in backup. eliminates need for continuous visual monitoring

Retractable probe monitors flaregas flow rate.

NAOs fully automatic flare-controlsystem insures optimum combustion offlare-stack effluents, regardless of theflow rate and the composition of thewaste gas.

Since flow-rate velocity andcomposition both affect completecombustion and smoke production,the NAO control system incorporatesseparate sensors and individualsignal-linearization equipment tocontinuously monitor velocities andradiation intensities.

Measuring flow rate alone will notincorporate any provision for changes

f- in gas composition. As the flare-gasJ composition varies, the ratio of steam

or power gas to hydrocarbon flow mustbe properly adjusted.

Many low-molecular-weight gases

do not smoke. Therefore, the use of BUILT.IN BACKUPsteam or power gas is not required. Since either sensing sub-systemImproper control of steam or power (velocity or radiation) will indicategas can create noisy flaring and approximate steam or gas require-wasted energy. ments for optimum flaring, the NAO

With a pair of sub-systems for system provides its own backup.continuous monitoring of velocity and Plug-in modular construction andradiation, the NAO automatic control state-of-the-art electronic componentssystem provides a fully automated insure reliable, trouble-free operation,method of flaring waste gases day in, day out, year after year. Main-smokelessly and efficiently, or with tenance is minimal.reduced noise levels. Details on opposite side.

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NAO Full~Automatic, Smokeless Flaring SystemDESCRIPTION OF OPEFIATION

Electronic signals, generated by separate flow andradiation-intensity sensors, are individuallylinearized - then combined electronically to dictateefficient steam-flow control.

A Each thermocouple monitors the flame radiation through a small slot in thesurrounding pipe. B Retractable probe, with three elements, utilizes heat-transfermeasurements to continuously monitor the flow rate.

NAOs automatic steam-control systemfor smokeless flaring incorporates twosub-systems to continuously monitorflare-gas flow rates and radiationintensities.

FLARE-GAS FLOW SIGNALSThis electronic flow sensor employsthree elements in a retractable probe.All are inserted in the waste-gas flowstream. The flow rate is determined bymeans of the convective heat transferbetween the sensing elements.

The mV output of the velocity sensoris linearized and converted to astandard 4-20 mA signal, proportionalto the required flow rate. However,since saturated and unsaturatedhydrocarbons require different steam

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ratios, an automatic weightingnetwork is incorporated to fine-tunethe output signal.

FLAME.AADIATION SIGNALSDirect measurement of flametemperatures with thermocouplesisnt practical for this application. Theshort life of a direct-measurementthermocouple prevents its use forcontinuous sensing.

Radiation from the flame, however,provides a strong, reliable indicationof the gas composition. This radiationis continuously monitored by NAOsradiant-heat sensing sub-system.

The radiant-heat sensor employstwo thermocouples, mounted instainless-steel pipes near the stack tip.Each thermocouple, mounted at a 45angle, monitors the flame through a

75 YEARS OF LEADERSHIPBY DESIGN

small slot in the surrounding pipe. Thepipe minimizes convective losses to the 7ambient arr. Thus, the temperatures -sensed by the couples are solelydependent upon the incident-radiation level.

Both thermocouples are mountedclose enough to see the flame - butnot so near that high temperatures areexperienced.

The mV output from the pair ofthermocouples is fed to a convertorand linearizer. This linearizer providesa 4-20 mA signal, proportional to flameradiation and gas composition. (Thehighest operating temperatures occurwhen the optimum amount of steam isintroduced for complete mixing andsmokeless combustion. Insufficientsteam will produce a lower flameradiation due to incomplete, smokycombustion. Excess steam willpartially quench the flame; and it willbe indicated by a lower flameradiation -with wasted steam.)

MAIN CONTROL PANELAll plug-in components, with theexception of the pipe-mountedthermocouples and the retractablevelocity sensor, are housed in a 19-inchstandard control-rack cabinet. On thefront of this cabinet are convenientcontrols, including a manual loadmgknob, and a set of switches for variousmodes of automatic control: velocityonly, radiation only, or combinedvelocity/radiation closed-loop control.

The velocity sensor responds rapidlyto changes in the flow rate. Hence, itwill track that variable quickly andprovide lag-free signals for thesteam-control valve.

Conversely, the radiation-sensingsub-system, which is relativelyinsensitive to changes in flow rate, willfine-tune the system for optimumsteam consumption, in relation to gascomposition.

(800) 523-3495 ,?Outside PA

1284 East Sedgley Ave., Philadelphia, PA 19134, U.S.A. Telephone (215) 7435300, FAX (215) 743-3018, Telex 845403Offices in major cities of the world. @NAO IOM-87 PRlNTED1NU.S.A

JFS III75 YEARS OF LEADERSHIPBY DESIGN

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