Deep grading combustion method and system for pulverized coal

The invention discloses a deep grading combustion method and a system for pulverized coal. The system comprises a pre-combustion device, a medium-temperature combustion device, and a separator, whichare sequentially connected. The pulverized coal is partially vaporized in the pre-combustion device to produce syngas, and the syngas enters the medium-temperature combustion device together with unburned fuel at a medium-temperature suspension combustion under the condition of graded ventilation. Combustion products are gas-solid separated by a separator, and separated solid particles are returned to the medium-temperature combustion device to participate in material circulation to circulate and burn. The pre-combustion device partially vaporizes the pulverized coal to obtain gasification syngas, which is burned in the medium-temperature combustion device, gasifies three types of fine, medium and coarse particles, and improves the residence time of pulverized coal particles in the whole system, is beneficial to t