The SP4 is a Combined Heat and Power (CHP) plant. As well as generating electricity, it produces steam for refinery processes.

Graphic of generation
Generating steam and electricity.

The SP4 is similar to a conventional power station. It:

  • burns a fuel to
  • produce steam which
  • turns a turbine that
  • drives the generator.

However, there are two important differences:

  • for fuel, it uses by-products of the refinery processes: refinery gas and fuel oil;
  • the steam is collected once it has turned the turbines and is channelled back into the refinery.

The SP4 has a dual boiler which can burn either refinery gas or fuel oil. These are both surplus products from the refining process. The boiler heats water at high pressure to produce superheated steam. The superheated steam flows through the blades of a turbine to drive the generator.

The steam is cooled in a heat exchanger. This makes the pressure lower on this side and ensures that the the steam keeps flowing. However, the heat exchanger only cools the steam down to 180°C (and 900 kPa). It can now be piped into the steam main as a useful resource.

The heat exchanger uses cold water from the river and this gets warmed up. However, instead of going back into the river, this preheated water can be fed into the steam generator - thus reducing the amount of waste.

A conventional power station produces steam by burning coal. Again, this steam drives a turbine and is cooled using river water or cooling towers. However, the warmed up cooling water is usually put back into the river, wasting the enrgy that was used to heat it up.

Photo of SP4
The SP4 steam and electricity generator.