Transvac has developed a range of Ejectors that use waste (free) energy usefully which help in the urgent drive to reduce energy costs and thereby carbon emissions. Once a suitable source of high-pressure gas or liquid has been found there are many potential applications where an Ejector can be used as a reliable and robust gas Compressor.
Typical examples include:
Waste or excess gas energy can be used to drive Ejectors. For example: High-pressure, gas energy from an existing mechanical Compressor that is normally wasted across an anti-surge valve when in recycle mode, can be used to drive a gas Ejector.
The Ejector becomes the 1st stage compressor and offers a lower inlet pressure than the original mechanical compressor. Because of this, the wells/upstream process now operates against a lower back-pressure, which will boost production in accordance with the productivity index (PI) of the well. The Ejector then compresses the suction stream up to meet the required inlet pressure of the mechanical compressor.
With globally 1000’s of existing mechanical Compressors in recycle with waste energy available, the opportunities to use waste energy usefully are vast.
Compressor recycle opportunity used to boost production by lowering separator pressure. Although the Ejector is handling gas, a lower separator pressure will boost gas, oil and condensate production.
Compressor recycle opportunity used for Flare Gas Recovery, by capturing and compressing waste gas.
Compressor recycle opportunity used to de-bottleneck or eliminate an LP compressor.
In many oil & gas facilities, produced water, injection water, seawater, amine, multiphase or other high-pressure liquids can be used to drive an Ejector. Where an existing liquid stream is available, but at a lower pressure than required by the Ejector, a booster pump can be added to boost the pressure to drive an Ejector. High pressure liquids are simply ‘borrowed’ and typically returned back to the process.
Transvac continues to improve the operating efficiency of liquid driven Ejectors, meaning that even less liquid flow is required, when compared to older, less efficient traditional Ejector designs. This continual improvement makes more projects viable, especially when only small ‘slipstream’ flows from existing high-pressure pumps are available. This is of particular importance for facilities in remote or desert climates, where for example water usage is at a premium.
High pressure water used to drive an Ejector for Flare Gas Recovery
High pressure injection water used to boost production from a multi-phase well.
High pressure injection water used to capture, compress and re-inject CO2.
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.