The invention provides a compound
combustion boiler. By the boiler, fuel is fully combusted,
pollution emission is avoided, and energy is saved and consumption is reduced in the using process; and the boiler is provided with at least one three-dimensional
hearth and at least one directional
combustion-supporting air-cooled revolving grate
hearth, and is characterized in that: a
slag discharging outlet of the boiler is provided with a directional
combustion-supporting air-cooled revolving grate compound
hearth with an
assembly slag discharging plate or
slag discharging teeth; a revolving grate is arranged at the bottom of the compound hearth; the outer end of the revolving grate is assembled with the slag discharging plate or slag discharging teeth; a
flue gas return chamber is formed below the grate; a
flue gas return fan is arranged outside the
flue gas return chamber; a fan is arranged outside the compound hearth; and
flue gas discharged by the boiler circularly enters the
flue gas return chamber at the bottom of the directional combustion-supporting air-cooled revolving grate compound hearth through the
flue gas return fan, and is mixed with air, subjected to secondary combustion by the boiler at high temperature, and discharged into the
atmosphere through a flue gas discharging
pipe, a flue gas discharging fan and a flue gas discharging
chimney.