Kap3:PRODUCTION METHODS FROM FOSSIL FUELS

Lower Heating Value:

All energy when an amout of fuel is converted into energy by combustion from 25°C back to 150C (120 MJ/kg or 33,3 kWh/kg)

Higher Heatig Value:

All energy when an amout of fuel is converted into energy by combustion from 25°C back to 25°C (140 or 39,4)

• expensive

• Over time Ni-Particles form agglomerates (sintering)

• Corbon precipitation (coking) deactivation of catalyst

• sulfor poisoning

the diffrent green house gases have different ability to heat the atmosphere. In order to be able to compare them, they are converted to corresponding values for CO2

• the measurment is called GWP - global warming potential- and is given for a selected period of time (usually 100 years)

• GWP (Co2) = 1

• Steam reforming of natural gas

  • Sulphur removal

  • Conversion of methane and water vapour to hydrogen and CO – synthesis gas (syngas)

  • Conversion of CO and water to CO2 and hydrogen (water-gas shift reaction, WGS)

  • The WGS reaction reduces the amount of CO to ~0.2%

  • Removal of CO2 from hydrogen streamand separation of hydrogen from gas-stream (Pd membranes)

  • CO is a useful industrial gas. CO2 is not that much used

• Autothermal reforming

  • Combining steam reforming and partial oxidation

  • Sulphur removal

  • Conversion of hydrocarbon and oxygen to CO and hydrogen (partial oxidation)

  • Conversion of hydrocarbon and oxygen to CO2 and hydrogen (partial oxidation)

  • Conversion of methane and water vapour to hydrogen and CO (steam reforming)

  • Conversion of CO and water to CO2 and hydrogen (water-gas shift reaction)

  • Uses a mixture of air and water as an oxidizing agent

  • Must have catalyst. Often fixed-bed catalyst.

• Partial Oxidation

  • Sulphur removal

  • Conversion of hydrocarbon and oxygen to hydrogen and CO

  • Uses pure oxygen as an oxidizing agent,30-50% of the amount needed for complete combustion

  • Can also be used for heavier hydrocarbons, and coal.

  • Exothermic process (ΔH<0)

  • Must have catalyst. Often fixed-bedcatalyst.

  • Bigger problem with solid carbon precipitation. Removed with water,carbon slurry.

• Natural gas contains H2S and other sulfur compunds which hinders other reactions

• even small amounts destroy the catalyst over time

costs go up

( production costs are higher but if you sell the hydrogen you don’t have to pay CO2 taxes and the end costs differ not that much)