Abstract: An indirect Brayton cycle is employed for an energy recovery system useful for large mass flow applications, such as a cast-iron making cupola. Exhaust gases from the cupola (elevated in temperature due to conversion by burning to CO.sub.2 and due to elimination of cooling of the exhaust passages) are directed to a turbine (which extracts energy to drive a compressor and electrical generator), the exhaust gases are then expanded (reduced in pressure), passed through a heat exchanger to release additional heat units to an air supply feeding the cupola, and then through the compressor to be raised in pressure to ambient for dumping. The exhaust gases are roughly filtered prior to entry into the recovery system and fine filtered after leaving the system prior to dumping; the residual temperature of the fine filtered exhaust gases is about 390.degree. F.