The invention discloses a W
flame boiler adopting circulating
flue gas type slit-type direct-flow pulverized
coal burners, and relates to the technical field of boiler
combustion. The W
flame boiler solves the problems that an existing W
flame boiler is high in
NOx emission concentration, poor in
combustion stability, high in
fly ash combustible matter content, overtemperature of a
water cooling wall of a lower
hearth, large in wall temperature deviation and
slag bonding. According to the W flame boiler, the plurality of direct-flow pulverized
coal burners are symmetrically arranged on a front arch and a rear arch with the center line of a
hearth as the center, thin pulverized
coal airflow nozzles are arranged on the sides close to the
water cooling walls, main circulating
flue gas nozzles are arranged on the sides, close to the center lines of the direct-flow pulverized coal burners, of thick pulverized coal
airflow nozzles and the thin pulverized coal
airflow nozzles, secondary air nozzles are arranged on the sides, away from the center lines of the direct-flow pulverized coal burners, of the thick pulverized coal airflow nozzles and the thin pulverized coal airflow nozzles, and outer circulating
flue gas nozzles are arranged on the sides, close to the
water cooling walls in the width direction of the
hearth. The W flame boiler is used for reducing
NOx emission of a hearth outlet, enhancing stable
combustion and
burnout of pulverized coal, reducing overtemperature and thermal deviation of the water cooling walls of the front wall and the rear wall of the lower hearth, and preventing
slag bonding of the water cooling walls.