Steam Assist Gas Flare Report
Steam Assisted Gas Flaring provides a safe and efficient gas release for hydrocarbon process equipment including refineries, olefins plants, and other chemical production facilities. Clean efficient operation of these devices relies on a detailed understanding of the fuel being flared to properly set the steam flow rate to avoid smoke formation and avoid over steaming the flare.
A recent analysis based on combustion fundamentals to investigate the relationship between fuel type, steam flow, and flammability has been completed. This analysis includes a review of the extensive previous flare testing sponsored by the US EPA and conducted at the John Zink test facility in Tulsa, OK as well as testing sponsored by the Chemical Manufactures Association. Based on this review of previous testing and fundamental combustion analysis, this work has been documented in an extensive technical monograph which provides the basis for two performance metrics including the Lower Heating Value (LHV) and Steam to Hydrocarbon mass ratio.
Steam Assisted Gas Flaring Technical Monograph
ABSTRACT
Combustion Efficiency Control in Single-stage, Industrial, Steam-assisted Open Flares
Dr. L. Douglas Smoot, Dr. Joseph D. Smith, and Robert E. Jackson
Combustion Resources, Inc., Provo, Utah and Systems Solutions Analysis, LLC, Owasso, Oklahoma
Report Number CR – SAS IF – 09A
This technical report has been prepared to identify and justify operating criteria and procedures to control and increase the combustion efficiency of open, single-stage, steam-assisted industrial flares. The report summarizes and illustrates typical characteristics of steam-assisted industrial flares. Typical flare operating criteria are noted and evaluated. Several potential technical methods for flare performance evaluation and control are briefly discussed, including heats of combustion, steam quantities, flammability limits, regimes of flare flow and use of adiabatic flame temperature. Uses of heats of combustion, flammability limits, steam limitations and adiabatic flame temperature are illustrated.
Computations were performed for a large number of flare cases with varying fuel molecular weight, purge flow rate, flare and vent gas lower heating value and steam/vent gas ratio. A correlation of adiabatic flame temperature with flare gas lower heating value (LHV) was developed which indicates that flare gas LHV value is an appropriate criterion for regulating flare operation. Results also indicate that vent gas LHV is not a reliable criterion for regulating flare performance. Computations for lean flammability limit show cases where flare gas combustion would not have occurred or would have been highly inefficient.
Additional computations were analyzed for specified values of flare gas lower heating value and steam/vent gas ratio for four different waste gas fuels of varying molecular weight and three levels each of purge flow rate and steam/vent gas ratio. Adiabatic flame temperature varied by only about +3%, further indicating that flare gas lower heating value is an appropriate control criterion to maintain high combustion efficiency. All of these cases yielded flammability ratios well above the lean flammability limit in the combustible zone with the lower values for low molecular weight fuels.
$3000.00