Lesson 1, Topic 1
In Progress
Natural Gas
- Natural gas is versatile.
- It can make electricity, heat homes and fuel transportation.
- It produces fewer emissions, and much less carbon than coal or oil.
Gas Power (Open Cycle Gas)
Open Brayton Power Cycle (Gas Turbine)
- 1-2: isentropic compression
- 2 3: constant pressure combustion process (heat addition)
- 3 4: isentropic expansion combustion products at atmospheric pressure
- 4-1: constant pressure heat rejection until temperature returns to initial conditions
Combine Cycle Gas Power Station
- Natural gas is burnt in a mixture of compressed air after being drawn through filters and compressed
- Combustion produces high pressure, high temperature combustion gases that drive a turbine connected to a generator.
- Generator spins an electromagnet (~50 revolutions a second), inside copper wire conductors
- Exhaust gases are sent to the Heat Recovery Steam Generator to boil water producing superheated steam.
- remaining exhaust gas is released through a large chimney\
- Superheated steam directed to a steam turbine that drives another generator
- producing more electricity
- The steam powered generator increases the overall efficiency >
- Spent steam is condensed and cooled back to liquid water for reuse
- Another water stream is pumped through the condenser and cooled using cooling towers
Conventional natural gas
- Crude oil wells ( associated gas)
- traditionally flared as waste gas (Nigeria)
- gas cap above crude /dissolved in crude
- Natural gas from gas wells ( non associated gas)
- little or no crude oil
- typically produce only raw natural gas
- Condensate wells ( non associated gas)
- produce raw natural gas & some low MW HC
- liquid at ambient conditions
Leakage
Waste gas flaring unwanted associated gas
- ~140 150 billion cubic meters (bcm) of natural gas is flared into the atmosphere annually
- translates into 270 290 million tons of CO2