High Temperature O₂ Generation for Power Cycles

Currently the oxygen required for the oxy-fuel combustion and precombustion decarbonisation technologies for a large scale power plant, can be produced by using the well established process of cryogenic distillation which has been practiced for over 100 years. However, the cost of oxygen contributes to a significant part of the cost of power both as a percentage of capital cost and as a percentage of energy consumed in the power cycle. For example, the oxygen unit contributes to as much as 33% of the capital cost of an oxy-fuel-boiler-based power generation system (with CO₂ capture) and also accounts for 67% of the power consumed internally in the power cycle.

Within ENCAP SP5 substantial research effort has been directed towards the development of low cost high temperature (600 -1000°C) oxygen generation technologies in order to achieve the cost reduction target set for carbon dioxide capture. The main priority is the research on oxygen carriers and oxygen transport dense ceramic membranes, using either oxygen transport ceramic membranes (OTM) or ceramic autothermal recovery (CAR).

Furthemore, SP5 evaluates possible integrations schemes of these novel oxygen generation options in the oxy-fuel and IRCC power plant concepts. Two promising options have been identified fulfilling the targets set by ENCAP:

• The combination of an oxygen transport ceramic membrane reactor with the IRCC cycle and
• The combination of a ceramic autothermal recovery reactor with the Oxy-fuel concept

In terms of energetic efficiency, OTM + IRCC results competitive with the corresponding scenario with cryogenic oxygen generation on the other hand CAR+Oxy-fuel boiler appears less competitive at the time being than the corresponding scenario with cryogenic oxygen generation but has reached a good technical maturity.