Coal nozzle assembly for a steam generation apparatus
A steam generating system includes a furnace, a nozzle tip assembly for pulverized coal and primary air as well as means for conveying secondary air in the furnace. The nozzle according to the invention comprises a nozzle body ( 3 ) and several channels ( 5 ) being connected with the nozzle body, the channels are diverging from each other. At the exit faces ( 17 ) of the channels obstructions ( 13 ) are disposed to induce huge turbulences of the primary air when entering the furnace. Due to these turbulences the primary air and the entrained coal are mixed very well before being combusted in the furnace. This results in a better more effective combustion with reduced NOx-emissions.
1. A coal nozzle tip assembly for a steam generation apparatus, comprising: a nozzle body and several channels connected to the nozzle body, the channels arranged to diverge from each other, wherein at an end distal from the connection between the nozzle body and the channels each channel comprises an exit face, wherein a single obstruction is disposed in each exit face, the obstructions arranged to form a square interrupted by hollow spaces between the channels.
2. The coal nozzle tip assembly according to claim 1 , wherein at the connection between nozzle body and the channels, the nozzle body has a polygonal cross section area, the channels have a polygonal cross section area, and the cross section areas of the channels equals the cross section area of the nozzle body.
3. The coal nozzle tip assembly according to claim 2 , wherein at the connection between nozzle body and channels, the nozzle body has a square or rectangular cross section area and the channels have a square or rectangular cross section area.
4. The coal nozzle tip assembly according to claim 1 , wherein the cross section area of each channel increases starting from the connection between nozzle body and the group of channels towards the exit faces at the distal ends of the channels.
5. The coal nozzle tip assembly according to claim 1 , wherein the cross section area of each channel at the distal ends of the channels is greater than their cross section areas at the connection between nozzle body and the channels by a factor between 1.4 and 1.8.
6. The coal nozzle tip assembly according to claim 5 , wherein the factor is 1.6.
7. The coal nozzle tip assembly according to claim 1 , wherein the obstructions are in the form of a bar extending between two opposite corners of the channels.
8. The coal nozzle tip assembly according to claim 1 , wherein the obstructions cover approximately 50% of the cross section area of its exit face.
9. The coal nozzle tip assembly according to claim 1 , wherein the nozzle body, the channels and the obstructions are made of plain sheet metal.
10. The coal nozzle tip assembly according to claim 1 , wherein the nozzle tip is surrounded by an outer shroud that conveys secondary air.
11. The coal nozzle tip assembly according to claim 1 , wherein the nozzle tip is pivotally mounted to the nozzle body by pivot members.
12. The coal nozzle tip assembly according to claim 11 , further comprising sealing plates between the nozzle tip and the nozzle body.
13. The coal nozzle tip assembly according to claim 1 , wherein a catalyst is applied to the obstructions.
14. The coal nozzle tip assembly according to claim 13 , wherein the catalyst is Lanthanum Strontium Titanate doped with metals.
15. The coal nozzle tip assembly according to claim 13 , wherein the catalyst is of the perovskite-type having catalytic activity in a temperature range from 500° C. to 900° C.
16. A steam generating system, comprising:
a furnace;
at least one coal nozzle tip assembly to direct a flow of solid particles entrained in primary air into the furnace, wherein the at least one coal nozzle tip assembly includes a nozzle body and several channels connected to the nozzle body, the channels arranged to diverge from each other, wherein at an end distal from the connection between the nozzle body and the channels, each channel comprises an exit face, wherein a single obstruction is disposed in each exit face, the obstructions arranged to form a square interrupted by hollow spaces between the channels.
17. The steam generating system according to claim 16 , further comprising at least one duct to convey secondary air into the furnace, wherein the at least one duct is distant from the at least one coal nozzle tip assembly.