W-staged flame boiler for multi-stage combustion with multi-ejection and its method thereof

A W-shaped flame boiler for multi-stage combustion with multi-ejection, comprising a lower chamber 1, an upper chamber 2 positioned below said lower chamber 1, a combustion chamber formed by two boiler arches which are front boiler arch 3 and rear boiler arch 15 respectively, a plurality of fuel-rich pulverized coal flow nozzles 10, a plurality of fuel-lean pulverized coal flow nozzles 12, a plurality of lower secondary air nozzles 14, a plurality of inner secondary air nozzles 11, and a plurality of outer secondary air nozzles 13, wherein said inner and outer secondary air nozzles 11, 13 generate two sequent air flows, wherein said fuel-rich pulverized coal flow nozzles 10, said inner secondary air nozzles 11, said fuel-lean pulverized coal flow nozzles 12, and said outer secondary air nozzles 13 are alignedly and orderly located between a center line 2-1 of said combustion chamber and a front water cooled wall 2-2 of said combustion chamber at said front boiler arch 3 and between said center line 2-1 of said combustion chamber to a rear water cooled wall 2-3 of said combustion chamber at said rear boiler arch 15, wherein a plurality of lower secondary air nozzles 14 are provided at said front and rear water cooled wall 2-2, 2-3 of said lower chamber 1 respectively at a position that said lower secondary air nozzles 14 are inclinedly extended from said front and rear water cooled wall 2-2, 2-3, wherein an inclination angle α of each of said lower secondary air nozzles 14 is about 25°-45°, wherein said fuel-rich pulverized coal flow nozzles 10 are grouped to form a plurality of fuel-rich pulverized coal flow nozzle arrangements 16, each said fuel-rich pulverized coal flow nozzle arrangement 16 has two fuel-rich pulverized coal flow nozzles 10 positioned close to each other, wherein said fuel-rich pulverized coal flow nozzle arrangements 16 are aligned at an in-line formation along a transverse direction of said combustion chamber and evenly spaced apart with each other, wherein said fuel-lean pulverized coal flow nozzles 12 are grouped to form a plurality of fuel-lean pulverized coal flow nozzle arrangements 17, each said fuel-lean pulverized coal flow nozzle arrangement 17 has two fuel-lean pulverized coal flow nozzles 12 positioned close to each other, wherein said fuel-lean pulverized coal flow nozzle arrangements 17 are aligned at an in-line formation along said transverse direction of said combustion chamber and evenly spaced apart with each other, wherein said inner secondary air nozzles 11 are aligned at an in-line formation along said transverse direction of said combustion chamber and evenly spaced apart with each other, wherein said outer secondary air nozzles 13 are aligned at an in-line formation along said transverse direction of said combustion chamber and evenly spaced apart with each other, wherein said fuel-rich pulverized coal flow nozzles 10, said fuel-lean pulverized coal flow nozzles 12, said lower secondary air nozzles 14, said inner secondary air nozzles 11 and said outer secondary air nozzles 13 are all communicating with said lower chamber 1, wherein said fuel-rich pulverized coal flow nozzles 10, said fuel-lean pulverized coal flow nozzles 12, said lower secondary air nozzles 14, said inner secondary air nozzles 11 and said outer secondary air nozzles 13 all have a cross section selected from the group consisting of rectangular cross section and round cross section, wherein said fuel-rich pulverized coal flow nozzle 10 with rectangular cross section has a length-width ratio of 4˜5:1.