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Pulverized Coal Burner Guide

1. Tangential pulverized coal burners are commonly used in power plant boilers and fire the coal in a swirling pattern around an imaginary circle for improved combustion. 2. Burners have primary air nozzles that inject coal and secondary air nozzles that provide combustion air stacked alternately. 3. Design considerations for bituminous coal burners include coal ignition around 0.4m from the nozzle due to the interaction of lower velocity primary air and higher velocity secondary air.

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390 views14 pages

Pulverized Coal Burner Guide

1. Tangential pulverized coal burners are commonly used in power plant boilers and fire the coal in a swirling pattern around an imaginary circle for improved combustion. 2. Burners have primary air nozzles that inject coal and secondary air nozzles that provide combustion air stacked alternately. 3. Design considerations for bituminous coal burners include coal ignition around 0.4m from the nozzle due to the interaction of lower velocity primary air and higher velocity secondary air.

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sen_subhasis_58
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© Attribution Non-Commercial (BY-NC)
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PULVERIZED COAL BURNER

Types of PF firing
1. 2. 3. 4. Front firing Opposed jet firing Tangential firing Down-shot firing (good for fuels with low VM)

Tangentially fired burner


Four sets of burners are located on all corners. Burners fire tangent to an imaginary circle Top burner is at least 17 m below the superheater

DB- Burner for coal


(Low NOx emission)

PF burner for Bituminous coal


Burner nozzles are rectangular in section Primary and secondary air nozzles are stacked alternately Primary air carries the coal. Secondary air provides the combustion air Oil burner stacked in between help ignition Burners can be tilted to shift position of the flame

Tangential flame Front view

Tangential burner- Top view

Firing circle
The axis of each burner is tangent to imaginary circle diameter, d0. d0= (0.05 to 0.13) (a+b)/2 The flame axis is shifted to tangent to an actual circle of diameter dy. Strong vortex formed helps stabilize the flame Jet velocity, w varies with radial distance w = k r-n 0<n<1 where r > dy/2 0>n>-1 when r < dy/2

Design of PF burner for bituminous coal


Coal in primary air ignites around 0.4m away from the nozzle Low velocity primary air, W1 (24-25 m/s) is entrained by high velocity secondary air, W2 (36-50 m/s) Oxygen required for combustion is received from the secondary air Over-fire or tertiary air can be added to control NOx.

Burner air velocities (m/s)


Capacity per burner MW 23.3 Anthracite etc. Bituminous etc

Primary W1 18-10

W2 28-30

W1 24-26

Secondary W2 36-42

34.9
52.3

18-20
20-22

29-32
34-37

26-28
28-30

42-48
48-50

Bituminous burner design norms


Capacity of each burner is generally in the range of 25-50 MWt Typical value of primary air, secondary and tertiary air are about 20%, 65% & 15% respectively of total air respectively. Typical grate & wall heat release rates are 4.9 & 0.23 MW/m2 respectively

Heat input per burner increases with furnace cross section and Ash fusion temperature

Burner capacity

Burner inclination
Air nozzle Tertiary Upper upward Secondary 0-12 Upper downward Secondary 5-15

Inclination angle 5 - 15

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