Flare combustion technology has evolved over time and each evolution has been driven by the fundamental need to dispose of flare waste streams with efficient smokeless combustion. For purposes of understanding flare combustion evolution, each breakthrough in flare combustion represents a ‘generational’ change in technology. This article provides an overview and outlines three previous generations of flare combustion technology and introduces a new stage in steam flare technology. The patent-pending Callidus nViro-XSRTM 4G is a fourth-generation, low-pressure, elevated flare which further extends the art of combustion technology to minimise emissions.
The original first generation elevated low-pressure flare technology is a simple pipe flare. While still broadly used today, these 1G flares tend to smoke easily even with the lightest of hydrocarbons, methane.
The second generation of elevated flares added external steam such as an upper steam ring. The steam ring encircles the exit rim of the flare exit with nozzles that induct air from the surrounding atmosphere, driving combustion air and steam into the flare’s effluent stream. The injected air and steam serve to enhance combustion, thereby extending the smokeless capacity of the flare.
The smokeless capacity of a flare is defined as the maximum mass flow rate of the flare where the flame is not smoking (Ringlemann Scale 0 or R0). With these 2G flares it was found that saturated hydrocarbons such as methane, ethane and propane could be flared to some smokeless rates. However, at higher flare loads, larger flare tip diameters and with unsaturated hydrocarbons such as ethylene and propylene, these 2G flares have very low smokeless ratings.
The third generation of flares used steam to entrain and mix more air into the effluent stream. These 3G flares are characterised by steam jets around the periphery of the flare injecting steam and inducting air into a tube with a bell or venturi shaped tube that then subsequently injects the steam/air mixture into the effluent stream. These 3G flares may have up to three modes of steam injection with an ‘upper steam’ ring like a 2G flare, external air-injecting into a venturi steam ‘internal steam,’ and where some portion of the steam is injected into the effluent some distance upstream of the flare effluent exit nozzle ‘centre steam.’
A new generation
While both 2G and 3G flares rely on using the motive force of the steam to mix air into the flare effluent stream, 4G flare technology changes the paradigm of how steam energy and chemistry is used in the combustion process.
Written by Chris Ferguson and Kurt Kraus, Callidus Technologies, USA.
Read the article online at: https://www.hydrocarbonengineering.com/special-reports/30052019/a-generational-shift/