AN EXPLANATION AS TO WHY THERE’S A JET ENGINE IN A GAS PUMP
Once gas has been procured from rigs in the sea it is sent along to distribution centres. From these the gas is then transported to your house for you to then power your home. But how does it get there?
An Overview of Gas Compression
Gas has to be transported through pipelines, and for this to be possible compressors have to be used. There are 61 Gas Generator powered Compressor Trains across the National Transmission System (NTS).
A centrifugal compressor works by pressurising the gas in the NTS. This may be powered by a Power Turbine or an Electric Drive.
Power Turbines are driven by a Gas Generator which itself requires a starter motor to commence the action.
Explaining the Three Main Sections
There are three main sections of gas compression. They work together cyclically, constantly developing and delivering fuel to and from the turbine. It is a process referred to as a Brayton Cycle.
Below is an overview of each process:
| The Compressor | draws air into the engine,the air gets pressurised,the pressurised air is fed through to the combustion chamber,the speed at which the air is sent reaches hundreds of miles per hour. |
| The Combustion System | usually made up of a ring of fuel injectors these inject a constant stream of fuel into combustion chambers,in the combustion chambers, the fuel mixes with the pressurised air,this mixture is burned at more than 2000°F the combustion creates a stream of gas which is high pressure and high temperature,the stream enters and then expands through the turbine section |
| The Turbine | this is a complex array of both rotating and stationary aerofoil-section blades,as the hot, high pressure combustion gas travels through the turbine it makes the rotating blades spin,the rotating blades perform two functions:driving the compressor to draw more pressurised air into the combustion system,spinning a generator to produce electricity. |
The Gas Turbine
Jet engine designs are modified for non-aircraft purposes, such as powering industrial gas turbines. Many of these engines are modified, older, military turbojets such as the Pratt and Whitney J57 and J75 models.
Did you know Industrial Gas Turbines can generate up to 50,000 shaft horsepower?
– Siobhan
Gas turbines are rotary, combustion engines. They extract energy from a stream of combustion gas (see table above).
Propulsive thrust is obtained from a gas turbine engine. This can drive a generator, or a pump.
Gas turbines compress the gas, the pressure of the gas is increased, and if flows through the pipes.
Compression provides enough energy for the gas to then move through the pipeline, to your homes and businesses.
Compression in Scotland
There are 6 compressor sites in Scotland which support the delivery of north to south gas flow.
St Fergus is the key entry point for gas to the UK’s NTS; these sites all rely heavily on the functionality of St Fergus.
| Site | Utilisation: Run Hours per year* | Emissions: Kg of NOx per year* | Usage |
| St Fergus | 11,200 | 170,000 | Pressurises Gas from the NSMP sub terminal |
| Aberdeen | 4,800 | 19,300 | Required under medium to high St Fergus flows and to maintain Scotland offtake pressures |
| Avonbridge | 4,300 | 22,000 | Supports Scotland offtake pressures |
| Kirriemuir | 2,200 | 97,400 | Required under high St Fergus flows, to maintain Scotland offtake pressure and as back up to Aberdeen and Avonbridge |
| Wooler | 600 | 1,000 | Required under high St Fergus flows and to manage gas stock in Scotland |
| Moffat | <100 | 400 | Used for network resilience |
Compression in the North and West
There are 9 compressor sites in the North and West of the UK which support the delivery of north to south gas flow.
| Site | Utilisation: Run Hours per year* | Emissions: Kg of NOx per year* | Usage |
| Peterborough | 5,400 | 79,200 | Transmission of gas south, east and west and system flexibility |
| Hatton | 3,500 | 94,100 | Supports the Easington baseline and north to south flows on the East coast. Supports East to West flows including Teesside, Theddlethorpe and the I-UK interconnector. |
| Carnforth & Nether Kellet | 2,400 | 5,800 | Supports high flows north to south and high Easington flows |
| Bishop Auckland | 2,000 | 3,800 | Supports high Teesside and St Fergus flows |
| Wormington | 1,500 | 500 | Facilitates low and high Milford Haven flows and supports pressures in the South West and Wales. |
| Churchover | 1,000 | <100 | Facilitates low and high Milford Haven flows and supports pressures in Wales. |
| Alrewas | 100 | 600 | Facilitates high Milford Haven flows and supports North West storage and pressures in Wales. |
| Warrington | <100 | 200 | Specific activities e.g. maintenance and resilience |
| Felindre | <100 | <100 | Facilitates high Milford Haven flows |
Compression in the South and East
There are 8 compressor sites in the South and East of the UK. Variable supply and demand patterns in these areas require flexibility in the compression across the south and east.
| Site | Utilisation: Run Hours per year* | Emissions: Kg of NOx per year* | Usage |
| Huntingdon | 2,400 | 28,000 | Supports southern flows into the South East and South West during high demand |
| Lockerley | 500 | 0 | Supports pressures in the South West during high demand |
| Wisbech | 400 | 2,500 | Supports high flows to Peterborough |
| Diss | 400 | 900 | Supports high Bacton flows and high South East demand |
| Chelmsford | 300 | 500 | Supports high Bacton flows |
| Cambridge | 200 | 700 | Facilitates low and high Isle of Grain flows |
| Kings Lynn | 100 | 500 | Facilitates Bacton high and low flows |
| Aylesbury | <100 | <100 | Supports pressures in the South West. (Low run hours due to recent site works) |
The Journey from Turbine to Door
So, to clarify:
- GAS RETRIEVAL
Gas is located and then drilled for at sea. Much of the UK’s gas comes from the North Sea rigs.
- GAS TRANSPORTATION
The gas has to travel from the rigs, to the land, and then across the sea to UK coasts. When it arrives at the UK’s gas entry points, of which there are 7 major ones, it is committed into the NTS through feeders. These feeders transport the gas to distribution centres where it is kept in reservoirs.
- GAS COMPRESSION
Gas must be compressed in order to have the energy to travel through pipelines to homes and businesses. This process is where the power from the jet engines is used to drive the compressors. This forces the compressed gas through underground pipes.
- GAS USE
The gas finishes its journey at your premises, it can now be used to fulfil your fuel requirements.