Oxygen is used instead of ambient air and is either extracted from air on the site, or more usually, bought in bulk.
The energy requirement to concentrate oxygen from the air is considerable, and this should be included in any energy calculations (see Section 184.108.40.206).
Within the glass industry, there is a large diversity in glass melt production capacities, glass types and applied glass furnace types. For several cases, a conversion to oxygen firing ( e.g. compared to recuperative furnaces, for relatively small furnaces and for special glass) very often improves the overall energy efficiency ( taking into account the primary energy equivalent required to produce the oxygen). However, for other cases the energy consumption for oxygen generation is as high or even higher than the saved energy. This is especially the case when comparing overall energy efficiency of oxygen-fired glass furnaces with end-port fired regenerative glass furnaces for large scale container glass production. However, it is expected that further developments in oxygen-fired glass furnaces will improve their energy efficiency in the near future. Energy savings do not always offset the costs of the oxygen to be purchased.
Not widely used in all sectors. In the glass sector, producers try to control temperatures in the glass furnace combustion space to levels acceptable for the applied refractory materials and necessary to melt glass of the required quality. A conversion to oxygen firing generally does not mean increased furnace temperatures (refractory or glass temperatures), but may improve heat transfer. In the case of oxygen firing, furnace temperatures need to be more tightly controlled, but are not higher than those in air-fired furnaces (only temperatures of the cores of the flames may be higher).
The price for bought-in oxygen is high or if self-produced has a high demand on electrical power. The investment in an air separation unit is substantial and will strongly determine the cost effectiveness of firing with oxygen.
Energy Efficiency (2009) 3.1.6