Waste Heat Recovery

boilers / superheaters

hot oil heaters

Indirect Fired (extractive)

An alternative to the direct-fired approach is the indirect (also known as "extractive") system. Extractive systems offer exceptional flexibility, especially when other sources of thermal oil heating sources are limited. The additional control provided by the induced draft fan allows for very precise regulation of the oil outlet temperature, even when faced with fluctuating waste flow rates.

Extractive systems are popular in gas plants utilizing membrane technology. Due to the relatively high hydrocarbon content in the permeate gas from the membrane system, the available heat duty from the flue gas is often much greater than that which is needed to be returned to the plant. A thermal oil heat exchanger placed directly in the flue gas path would generate more duty than could be effectively returned to the plant, since the oil circulation rate required to prevent degradation of the oil places constraints on the coil design.