Reverse-jet swirl pulverized coal burner with multi-stage recirculations

A reverse-jet swirl pulverized coal burner with multi-stage recirculations, comprising:

• a pre-combustion housing, the pre-combustion housing having a pre-combustion chamber and a housing outlet located on one side of the pre-combustion chamber;
• a primary coal-air structure passing through the pre-combustion housing and extending into the pre-combustion chamber, the primary coal-air structure being configured to separate a primary coal-air flow into a fuel-rich coal-air flow and a fuel-lean coal-air flow, and an outlet end of the primary coal-air structure extending toward the housing outlet;
• a rich-lean output structure disposed at the outlet end of the primary coal-air structure, the rich-lean output structure being configured to output the fuel-lean coal-air flow and block the fuel-rich coal-air flow to make the fuel-rich coal-air flow reversely flow to the pre-combustion chamber;
• an inner secondary air structure disposed on the pre-combustion housing and around the primary coal-air structure, the inner secondary air structure is configured to introduce an inner secondary air into the pre-combustion chamber, thereby forming a first-stage recirculation zone in the pre-combustion chamber and forming a second-stage recirculation zone at an end of the rich-lean output structure away from the primary coal-air structure;
• and
• an outer secondary air structure sleeved outside the pre-combustion housing, the outer secondary air structure being configured to transport an outer secondary air, thereby forming a third-stage recirculation zone at the housing outlet;
• wherein the pre-combustion housing comprises a cone section and an expansion section connected to the cone section, an end of the expansion section away from the cone section is the housing outlet of the pre-combustion housing;
• an inclination angle of the expansion section is greater than an inclination angle of the cone section;
• wherein the outer secondary air structure comprises an outer secondary air inlet channel, an outer secondary air outlet channel, and tangential vanes;
• the outer secondary air inlet channel and the outer secondary air outlet channel are connected and fluid communicated in a stepped manner;
• the tangential vanes are disposed in a connection area between the outer secondary air inlet channel and the outer secondary air outlet channel.