Biomass high-temperature pre-pyrolysis efficient coupling combustion and ultralow NOx emission system

The biomass high-temperature pre-pyrolysis efficient coupling combustion and ultralow NOx emission system comprises a high-temperature pre-pyrolysis system and a modified circulating fluidized bed boiler body, and the modified circulating fluidized bed boiler body comprises a modified pyrolysis gas coupling technology, a flue gas recirculation technology and an over fire air technology. According to the pyrolysis gas coupling technology, biomass materials in a high-temperature pyrolysis device are pyrolyzed under the oxygen-deficient condition to obtain reducing gas, the reducing gas is input into a boiler body through a pyrolysis gas pipeline, and according to smoke recycling, a smoke circulating pipeline is led to an inlet of an air blower through an outlet of an induced draft fan to conduct smoke recycling. According to the over-fire air technology, after-fire air of a primary air fan is combined with air to be sent to the top of the boiler, the air volume of primary air and the air volume of secondary air