A Heatec 3-pass thermal fluid heater heats a wood-drying kiln at Skeena Cellulose in Terrace, British Columbia, Canada. it has an output of 25 million Btu/hour and heats heating coils in the kiln. It also heats a steam generator that injects steam into the kiln to avoid drying the lumber too fast.
The heater is fired with natural gas. It has two helical coils arranged so burner gases make 3 passes over their surfaces before entering the exhaust stack. The 3-pass heater design is very efficient (estimated 86% LHV) because it ensures that more heat from the burner is transferred to the helical coils.
The heater extends through the roof of the building next to the kiln. its vertical configuration allows it to fit in very limited floor space.