Oxy-fuel combustion

Oxy-fuel combustion is recognized as an effective means for coal-fired power plants to continue operation in a carbon-constrained world. When air is replaced with oxygen as the combustion gas, an oxy-fuel power plant emits a flue gas stream that is highly enriched in CO 2 . Due to its high concentrations (80–90%, dry basis), CO 2 can be recovered relatively easily and economically with the flue gas compression train.

Obviously, when oxygen is used as the combustion gas, fuel combustion characteristics change so dramatically that current boiler technologies are not yet ready to cope on a large scale. Therefore, considerable modifications to the operation of a typical power plant will be needed. This chapter addresses the major challenges surrounding the oxy-fuel coal-fired power plants, including safety, plant control, corrosion and maintenance.

Coal-fired power plants can be considered as consisting of several major component blocks: coal preparation; combustion; steam generation; pollution control; and electricity generation. Coal is transported to the furnace with air, combusted in the furnace and the combustion products move in a largely one-directional flow to the stack. In oxy-fuel-fired power plants, additional components are required.

These notably include air separation units (ASUs) for oxygen production and flue gas compression trains for CO 2 purification and transport. Coal is now transported by recycled flue gas and the combustion products no longer move in a one-directional flow as a significant proportion is recycled back to the furnace. Apart from these obvious changes, we should also consider that the power plant’s control system must also be modified to accommodate these equipment changes and their interoperability. We also need to consider additional health and safety issues related to oxy-fuel firing.