Flare gas recovery with high pressure gas - should I use one or two ejector stages?

If the ratio of discharge gas pressure to flare gas pressure is high, you should consider using a two stage ejector if the compression ratio required is >4:1. For examples: Flare gas pressure 2.3 bara and flow rate 1000kg/hr; high pressure gas 84 bara; discharge pressure required 12 bara:

One stage => requires 8200 kg/hr of HP Gas

Two stages => requires only 3300 kg/hr of HP Gas

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