Oxyfuel furnaces are usually designed as cross fired melting furnaces where the fuel used (mostly natural gas) is combusted together with oxygen. The greatest advantage is in the low energy consumption, since little nitrogen is used for combustion. Compared with a cross fired or end fired furnace the energy consumption of an oxyfuel furnace is reduced by approx. 5 – 10 %, compared with a recuperative furnace the reduction in energy consumption is even 25 – 40 %.
HORN® oxyfuel furnaces are specially designed for the particular characteristics of firing a furnace with fuel and oxygen. Especially the reduced flue gas volume requires a modification of the superstructure design. If flat flame burners are used, the arch has to be kept relatively low, otherwise it will become too cold and this will lead to rat holes.
For longer life, the exhaust can be placed rather in direction of the middle of the furnace or even near the throat thus ensuring an adequate heating in batch charging area due to burners in this area and reducing carry-over (dust). Too high flue gas velocities in exhaust and subsequent piping can lead to difficulties in furnace pressure control and can even lead to high furnace pressure due to insufficient flue gas flow rate.
Cold spots would lead to damages due to the infiltration of alkalis which cause burnouts in the arch, thus leading to reduced furnace life. To avoid such problems the HORN® oxyfuel furnaces are therefore adequately insulated and sealed. In general oxyfuel furnaces are used for a melting output of 50 – 400 t/d, in some special cases as small as 2 t/d specialty glass. The maximum furnace size is approximately the same as for regenerative cross-fired furnaces, i.e. 750 t/d.