Given the wide choice of burner models and different burner sizes, it is important to select a burner that delivers product quality as well as system efficiency. Product quality is always the over-riding factor as there is no point in saving energy at the cost of quality. Scrap product wastes 100% of the energy used to produce it.
Anything that goes into a furnace is heated up to the furnace temperature before exiting it. Energy saving is achieved by:
- Minimising whatever enters the furnace
- Improving the way energy is transferred from the burner to the product
- Limiting the temperature at which the furnace operates
- Recovering energy from the exhaust products leaving the furnace
One can either reduce the weight of carriers and other furnace furniture or decrease the amount of excess air being supplied through the burners. Reducing excess air levels, for instance from 25% to 10% on a furnace operating at 1000°C will save almost 20% of the energy required to do the same job in a furnace.
Improving energy transfer method
Improving the way energy is transferred may involve fitting better high velocity burners to enhance convective heat transfer, or selecting a specialised burner such as the Lanemark small-bore immersion tube burner to increase the heat transfer surface area when tank heating.
Limiting the temperature at which a furnace operates
This can be achieved by maximising convective heat transfer to reduce radiant transfer. For example, using medium velocity burners on an aluminium melting furnace could allow the roof temperature to be lowered by 150°C, reducing the energy requirement by more than 10%.
Recovering energy from exhaust products
Recovering energy that would otherwise be lost to the atmosphere through stack losses can reduce furnace energy requirements dramatically. The energy in the stack gasses can be used to preheat the incoming load or the combustion air being used by the burners. Heating the combustion air through a recuperator will be limited to a preheat of 450°C, resulting in an energy saving of 26% on a furnace operating at 1200°C, when compared to cold air operation.
Regenerative burners can be fitted to achieve greater energy savings. The combustion air preheat achieved through regenerative recovery on a furnace operating at 1200°C would exceed 1000°C, producing an energy saving of 50% when compared to cold air operation. These reductions in the fuel usage and the temperature of the exhaust gasses will reduce the amount of atmospheric emissions, which can be further lowered using the low NOx features provided in the regenerative burners.
Hurll Nu-Way offers burners to suit a broad range of applications:
- Lanemark FD range offering high excess air operation and suitable for firing ovens up to 400°C enhancing the convective heat transfer
- Flat flame burners and infrared panels for radiant energy transfer in the Nu-Way family of package burners for lower temperature ranges
- Five NA burners including the Twin-Bed range of regenerative burners available for higher temperature applications