Radiation recuperators are high temperature heat exchangers that utilize radiation heat transfer to preheat combustion air or gas for the purpose of saving fuel. By recovering heat from the hot waste gas exiting a furnace and transferring it to the combustion air feeding the burners, fuel usage can be reduced by an average of thirty-five percent (35%), and in many cases, greater savings are realized. Waste gas temperatures entering radiation recuperators are usually in the 2000°F to 2500°F range, and combustion air preheat temperatures are usually in the 800°F to 1400°F range.
For very high temperature industrial furnaces, such as glass melting furnaces, recuperators are valuable tools for increasing furnace efficiency. Up to seventy-five percent (75%) of the available energy in the fuel may be carried out of the furnace in the waste gas, therefore, heat recovery is essential for fuel conservation and economical operation. With fuel costs rising, recuperation is certain to play a vital role in the future.
Thermal Transfer Corporation manufactures two (2) types of radiation recuperators - the TURA (TUbular RAdiation) type and the stack or double shell type. The TURA recuperator is most widely used on larger direct fired glass melters with firing rates typically between 15 MM.BTU/Hr. and 60 MM.BTU/Hr. The TURA design incorporates a cylindrical alloy steel tube bundle suspended within a refractory-lined outer shell, operating with waste gas temperatures up to 2600°F and generating air preheat temperatures as high as 1500°F. TURA recuperators have proven reliable under the adverse corrosion and fouling conditions often present in these larger melting furnaces.
The stack type recuperator is commonly used on smaller direct fired glass melters, with firing rates typically between 0.5 MM.BTU/Hr. and 20 MM.BTU/Hr. This design is comprised of concentric, cylindrical metallic inner and outer shells traditionally operating with waste gas temperatures up to 2300°F and combustion air temperatures up to 1000°F. However, recent advances in design and materials technology now permit higher temperature operation with the stack recuperator design. For the most demanding applications, both TURA and stack recuperators are used in combination to achieve very high combustion air preheat temperatures.