Green Energy Koyal Group Inc. offers Waste Heat Recovery Boilers in three basic designs to provide the greatest flexibility of any manufacturer in selecting a unit that is designed to meet the specific requirements of each application. Boiler designs are customized for specific job conditions to provide optimum performance and maximum energy savings. Features: • Customized design engineered for your specific solution. • Available with dual chamber design or supplemental firing. • Roller-bearing supported single-hinged rear door for total fireside access (except wetback).