Rather than simply losing pressure energy across a valve or similar let-down device, an Ejector can be driven (delivering the same pressure let-down), but performing a gas compression duty, for free! In some cases, the technique can also be used for Flare Gas Recovery
Transvac has used this technique effectively in upstream oil & gas, where high pressure Wells are being choked. Rather than wasting the pressure energy across the choke valve, the Ejector nozzle becomes, in effect, a choke and uses the energy usefully. The available high-pressure energy is used to drive an Ejector to assist weak, low pressure wells – or even revive dead / shut-in wells!
In a recent project in Saudi Arabia, a pressure let-down opportunity was identified at a gas and oil separation plant (GOSP), which operated with high- and low-pressure gas compression trains.
Transvac was able to install an Ejector package which utilised the otherwise-wasted pressure energy, lost across a valve in the high-pressure (HPPT) stream, to entirely eliminate the low-pressure (LPPT) mechanical compressor.
Not only does this Ejector package operate using existing waste energy, it eliminated the running costs and significant maintenance of the low-pressure compressor.
Fuel Gas pressure was being let down to feed boiler burners. An Ejector can be used to perform the pressure let down. This reduces flaring and also fuel gas requirements for the burners.