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The design of the Puertollano power station is based on the concept of a plant with the maximum integration of the gasification island, combined cycle and air separation unit.
This integration is based on:
- Total air flow supply from the gas turbine compressor to the air separation unit, even during start-up.
- The waste nitrogen (2-4% oxygen) produced in the air separation unit is sent to the gas turbine as a dilution gas to limit formation of thermal nitrogen oxides (NOx) and increase the turbine power.
- The distillation column for air separation is pressurized and supplies 85% pure oxygen and pure nitrogen (over 96%).
- Heat recovery in the gasification process is used as an energy contribution to the combined cycle by steam production at various pressure levels. A large water/steam system also guarantees steam supply and condensate collection for optimum energy recovery.
This unit produces the oxygen to supply the gasifier and nitrogen for drying and pneumatic transportation of the fuel, pressurization, inertization and especially dilution of the syngas. The unit uses a high-pressure, cryogenic distillation process.
Gasification uses a pressurized entrained flow process which can process a wide variety of types and qualities of solid fuel which is turned into syngas. The gas goes through successive heat recovery and filtration stages and a sulphur removal system before being sent to the combined cycle.
The gas turbine can operate with either syngas or natural gas. The residual heat in the turbine exhaust gases is used in a heat recovery steam generator which produces steam with which additional electricity can be generated in a conventional steam turbine with condensation cycle.