Driver Selection Criteria 1

[MIANCH]

Hi,
what is logic behind for selection of electric motor or gas turbine for pumps, can anyone have selection criteria standard then please share or refer to me.
Thanks.

 

[1503-44]

Electric is often chosen simply to meet emission air quality targets, or noise restrictions, but becomes very costly when grid power is not available and onsite generators must be installed to power them.

Gas turbines can run off the fuel gas pipeline without need to connect anything to the electric grid, so no long power lines, or substations are required. If no grid is nearby, gen sets can be much smaller, since no driver power is needed.

Grid power is typically very reliable. You might need three gas turbines to achieve the same reliability.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[MJCronin]

There are also some minimum practical hp size requirements for a gas/combustion turbine in mechanical drive service

(Due to the soaring roller-coaster cost of natural gas, the fuel cost and fuel availability can eliminate this option!)

Although some would disgaree, I believe about 500 kilowats is the smallest practical size

Gas turbines. of course, become much more attractive if the heat of the exhaust can somehow be harvested in the process

GT waste heat is often used to generate supplementary steam, or pre-heat feedstock or feedwater

https://www.epa.gov/sites/default/f...gy_characterization_-_combustion_turbines.pdf

MJCronin
Sr. Process Engineer

 

[georgeverghese]

Part load operation with EM combined with VFD is much better than for GT. Single shaft GT turndown on fuel rate flattens out at 80% of rated speed. For 2 shaft GT, think it flattens out at about 60% of rated speed (which may be sufficient for your case??, but at much higher cost).

In actual operation, many machines run at part load, so variable speed capability and performance count towards total life cost.

 

[MIANCH]

Georg,
Please explain in simple terminology, for me difficult to understand your terminology.

 

[georgeverghese]

Dont know how else to put it.
It may be easier if you can tell us more what your current system configuration is for power generation. Even then, many other factors may affect selection, such as layout and some electrical details which may be bottlenecks.
Multiple Power gen turbines operating in parallel can be individually switched on and off to better match total power demand and so give you fuel savings also.

 

[LittleInch]

There is no "standard" or "code" as far as I know for this, only bespoke studies which look at a variety of issues.

For "pumps" it is pretty rare to see a Gas Turbine (GT) as the power is relatively low (<5MW) as is the speed of operation so a GT would need a gearbox.. They are most commonly electric drives or engine driven.

Compressors on the other hand can be much higher power (20-30MW) and run at much higher speeds. They also tend to be in the middle of no where so a large electric supply is not always available. Plus the gas is sometimes thought of as "free".

So items to consider include:
Power requirement
Power supply (electric or gas) available
CAPEX
OPEX
Size (GTs are much much bigger)
Maintenance costs
Emissions
Noise
Ability to use waste heat (GTs)
Turndown required (GT's are not so good at this)



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