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First Approximation Of Fuel Gas Consumption For Gas Turbine Driven Compressor Station




First Approximation Of Fuel Gas Consumption For Gas Turbine Driven Compressor Station Dear All,

A lot of us are required to do preliminary utility estimation calculations during the Feasibility / Concept stage of a project. Another terminology often used is the Pre-FEED stage of a project. In fact this is often where non-availability of data or insufficient data becomes a bottle-neck. In such cases some minimum data with certain empirical calculation methods help to arrive at figures which may be used to for high end (+/- 30%) cost estimation of a project and help establish its feasibility.

Today's blog entry as the subject line says, is with regards to compressor stations, for transport of natural gas through long-distance pipelines. An approximation for fuel consumption can be done using certain empirical formulas. The formula is presented herewith:

F = (14 / NHV)*(Pturbine + Pauxiliary)

where:
F = Fuel Gas consumption of the compressor and the auxiliary systems associated with the compressor, Sm3/h
NHV = "Net heating Value" of the Fuel Gas to be used, MJ/Sm3 (eg: Natural Gas ~ 41 MJ/Sm3 with a certain composition)
Pturbine = Turbine power requirement, kW
Pauxiliary = Power consumption in kW of auxiliaries associated with the compressor package, which includes electricity, lubricating oil system, cooling system etc.. This has a strong dependency on local climatic conditions and on the extent of gas sourced power used for such auxiliaries.

Note: Sm3 refers to standard cubic meter at standard conditions of temperature (15 deg C ) and pressure (101.325 kPa (abs))

That is all for today folks. Look forward to comments from your side.

Regards,
Ankur




Thank you

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ADITYA.DUBEY
Jun 04 2016 02:38 PM

Sir

Thanks for sharing this useful info.

 

I wanted to know if fuel-gas is pre-heated before it goes to turbine for combustion,will it reduce the fuel gas consumption of turbine??

 

If yes,Will it be same as the amount of fuel-gas/energy is used to pre-heat the fuel gas??

 

Regards

Aditya

Sir

Thanks for sharing this useful info.

 

I wanted to know if fuel-gas is pre-heated before it goes to turbine for combustion,will it reduce the fuel gas consumption of turbine??

 

If yes,Will it be same as the amount of fuel-gas/energy is used to pre-heat the fuel gas??

 

Regards

Aditya

Aditya,

 

Fuel Gas pre-heating in the Fuel Gas treatment unit is for maintaining the temperature well above its dew point. Generally keeping a fuel gas temperature of 50-55 deg C ensures that you are well above the dew point and there is no chance of any dangerous condensation and formation of liquid droplets which can damage the turbine.

 

GT manufacturers normally recommend optimum inlet temperature range. If the optimum fuel gas temperature cannot be obtained from the Fuel Gas Treatment Unit then additional heating would be required.

 

In such a case it is best to utilize any source of available and unutilized waste heat. In normal operations even the exhaust gases from the turbine can be utilized to pre-heat the fuel gas. For cold start-up, an alternative source of waste heat would be required. This will lead to operating expenditure (OPEX) savings. I will not call it exactly as energy savings

 

For large power generating turbines such as Frame 5 & Frame 6 I have seen the turbine exhaust gases connected to a WHRU unit for generating HP steam or providing hot oil (thermic fluid) for process plant heating. This is now a common practice in new chemical process plants which generate captive power using large gas turbines

 

Hope this helps.

 

Regards,

Ankur

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ADITYA.DUBEY
Jun 05 2016 02:33 PM

Thank you sir.It really helped.

 

Regards

Aditya

Thank you so much

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