Gas turbine driven compressors

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GAS TURBINE Driven COMPRESSORS

By: Satyendra Nath Dwivedi

Triune Energy Services, New Delhi

Nuovo Pignone MS 1002 R regenerative cycle gas turbines, (34% efficiency, rated 4,620 kw ISO) drives 4HG Reciprocating Compressor to compress natural gas from the pipeline (55 Bar)into artificial caverns (150 Bar) for storage. A two-stage epicyclic gearbox with gear ratio of 31:1 steps down turbine shaft speed to the compressor speed of 333 rpm.

A Gas turbine is an Internal Combustion Engine that converts heat energy of the fuel into mechanical energy via three main elements – a compressor, combustor and turbine.

As gas turbines operate in a continuous thermodynamic cycle, they have a higher power density than other types of internal combustion engines.

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Work output of a gas turbine increases with: Higher pressure ratio generated in the

compressor Higher combustor exit temperature,

normally restricted by the high temperature capability of combustor and turbine components

More efficient secondary systems (cooling, sealing)

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Functionally Gas turbines may be classified in two broad categories:

Gas Turbines for Power Generation Gas Turbines for Mechanical Drive Power Generation Gas Turbines are huge

and are normally operated in the Combined Cycle, using a Steam Turbine along with a Waste Heat Recovery Boiler.

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Combined cycle power plants feature gas and steam turbines.

The gas turbine generates electricity using natural gas fuel, while the steam turbine generates electricity using waste heat from the gas turbine.

The process is extremely efficient since exhaust heat is re-used that would otherwise be lost through the exhaust stack.

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A gas turbine compresses air and mixes it with fuel. The fuel is burned and the resultant hot air-fuel mixture is expanded through turbine blades, making them spin about a shaft. The spinning turbine drives a generator that converts the spinning energy into electricity.

Exhaust heat from the gas turbine is sent to a heat recovery steam generator (HRSG)

The HRSG creates steam using the gas turbine exhaust heat and delivers it to the steam turbine

The steam turbine delivers additional energy to the generator drive shaft

The generator converts the energy into electricity

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GE H Series Gas Turbine for Power Generation

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Gas turbines for mechanical drive applications may be classified in two broad categories:

Aero-derivative Gas Turbines Industrial Gas Turbines Industrial Gas Turbines are having frames,

bearings and fans of a heavier construction.

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GE Industrial Gas Turbines Mechanical Drive

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Rolls Royce Industrial Trent

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SOLAR Titan 250 (22MW)

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SOLAR Titan 250 (22MW)

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Gas turbines manufacturers for mechanical drive applications are:

GE Alstom Rolls Royce Siemens MAN Turbo Solar Dresser-Rand Mitsubishi Niigata

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Power Generation Applications and Customers mostly require:

Cost of Electricity Ruggedness Cost of Operation & Maintenance (O&M)

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Oil and Gas Applications and Customers mostly require:

High Availability/ Reliability Ruggedness High Power/ Weight Ratio

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Because of these inherent market differences,

Oil and Gas Customers often insist on Compliance to API Codes and are

willing to Accept the resultant high Turbomachinery Costs

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Gas turbines for the Petroleum, Chemical and Gas Industry services are covered under API Standard 616

(Fourth Edition, August 1998)

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‘Unit Responsibility’ (in accordance with Clause 3.5.1 of API 661) can be given either to Gas Turbine Vendor or to Compressor vendor.

For more complex projects ‘Unit Responsibility’ as Prime contractor is given to Compressor manufacturer (Gas turbine being off-the shelf and compressor being customized).

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As Turbocompressors are complex mechanical devices, they require electronic and mechanical controls as well as instrumentation.

The Control system of a Gas turbine driven compressor must, as a minimum, provide following functions through a Human Machine Interface (HMI):

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Machinery Monitoring and protection Equipment Starting, Shutdown, and

Protective sequencing Stable Equipment Operation Alarm, Shutdown Logic Backup (relay) Shutdown

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Driven Load Regulation Fuel/ Speed Control Process Control Surge Control

Communication – Supervisory Control and Data Acquisition (SCADA) - Interface

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Thank You

Satyendra Nath Dwivedi

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Gas turbine driven compressors

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