In this case study, Detechtion Technologies optimized and consolidated booster/sales fleet setups for fuel savings and reduction of carbon dioxide emissions.
By loading up the Sales unit, it is possible to reduce the pressure differential on the Booster unit, which should result in an overall lower suction pressure on the Booster unit.
As a result of the popularity of rotary screw compressors, the tandem operation of screw and reciprocating compressors is frequent in the natural gas gathering industry. Normally, one or many screw compressors will serve as boosters and one or many reciprocating compressors will serve as sales units. The booster usually gathers the natural gas at a suction pressure ranging from 1 to 30 psig, then discharges it into the sales unit which then compresses the natural gas to higher pressures.
Whenever you have booster compressors pumping into sales compressors in series, you must have the downstream sales machines set up to pull hard, keeping discharge pressures on the boosters as low as possible, otherwise your system will not be optimized for maximum throughput. The phenomenon at work is changing volumetric efficiencies. As you reduce the compression ratio across the lead booster machine the volumetric efficiency will increase, see Figure 1, giving the opportunity to pull more gas into the compressor system and get it to sales.
Very simply stated: “The gas volume that does not get into and through the booster cannot be pumped to sales by the downstream compressor. This translates into lost revenue.”
The following case study illustrates the savings of optimizing a screw compressor boosting a reciprocating compressor.
A gas producer is operating a Waukesha F3521GSI linked to a Frick TDSH355L boosting 6 mmscfd into a Caterpillar G3516TALE coupled to a 3 stage Ariel JGT/4. The booster suction pressure was 9 psig and the slide valve was open to unload horsepower. The sales machine was backed off in speed, pockets were open to 2” on stage 1 and the bypass was open slightly.
By closing the pockets and speeding the driver up on the Sales unit, the Booster’s discharge pressure has been reduced by 30 psig. This resulted in a 5 psig inlet suction pressure drop, 17 mscf/d fuel gas savings and reduction of 391 Tons/Year in carbon dioxide emission.