User:Klonq/Oxy-Fuel

Oxy-Fuel refers to technology where the air supply is separated into oxygen and nitrogen components and pulverised coal is combusted in a pure oxygen environment. The advantage of this technology is that flue gases are almost pure CO2 and so transport and storeage costs are minimized.

Air consists primarily of nitrogen (80%) and oxygen (20%), following combustion the exhaust gas is still primarily nitrogen.

=Oxygen Production= Separation of air into its constituent gases at present requires 250-450 kWh/t O2. Present methods of large scale oxygen production use cryogenic freezers, it is predicted that in 2015 the scale of a cryogenic unit will still only be 50% the scale required for a world class pulverized fuel plant. Alternative methods for oxygen production are 20-100 smaller scale at present, with the exception of Ion Transport Membrane (ITM) and Catalytic Autothermal Reforming (CAR) there is not much hope for many of the alternative methods. CAR is still in the pilot stage and ITM is commercial however there are challenges in scaling up to more than 10 t O2/day.

=Recycled Flue Gases= Combusting coal in pure oxygen will burn at significantly higher temperatures, temperature of combustion can however be controlled by the air/fuel ratio (AFR) using recycled flue gases. This is effect means the coal is burnt in an oxygen and CO2 atmosphere. A secondary benefit to recycling flue gases is that there is oppertunity for more oxygen to react with coal, after a few passes the exhaust should be close to 100% CO2.