Flare Burning Combustion Calculation

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1) Input Fuel characteristics
2) Input kiln production data
3) Determine (goal seek) transport air flow rate : 5 kg/m3 for blower, 7 kg/m3 for pump
 - vary the transport flowrate - Nm3/h
 - note that blowers cannot take the higher material density rate
4) Obtain optimum or target flow rates values (swirl & axial)
For a first calculation, start with static pressures of 40.000 Pa  for axial, and 25.000 Pa for swirl - 10% primary air; 7% axial + transport (in case that no swirl is used). Use solver, changing the groove width, the axial holes diameters, the axial and the swirl static pressures. Add constraints on the axial pressure (35.000-60.000 Pa), and to the swirl pressure (>18.000 Pa if fan, 20.000-30.000 Pa if blower).
Note the optimum flow rates as well as cross section areas (mm2)
Ultimate target is Is = 1.8 and Sw = 0.15.
5) Dimension the barrel:
What is the free diameter required in the centre? Depends on how many fuels the plant wants to burn simultaneously: waste, oil, etc…
In theory, min. of 200 mm (8 in.) is needed for the bluff body effect although 6 in. has been used. Use standard pipes (see table). The outer diameter of this first pipe is the inside diameter for the swirl air channel. Continue to build, using the criteria below:
a) Swirl: Velocity in barrel: 15 to 25 m/s
Swirler angle = 30 - 40°; common to use 35°
18 to 22 vanes (or slots), 8 mm depth minimum
No straight stream through the swirler = long enough
b) Transport: Velocity in tip and barrel: 25 to 35 m/s
radial gap of annulus > or = to 10 mm (concentricity, plugging)
A slight reduction of the cross section area is being done at the tip, for 
a better fuel distribution around the annulus (automatic)
c) Axial:    Velocity in barrel = 15 to 25 m/s (trade-off weight of burner pipe versus
pressure drop). Target 20 holes, generally 16 to 24
Diameter of holes >or = to 12 mm
6) Once the barrel is complete, adjust the tip cross sectional areas Ultimate target is Is = 1.8 and Sw = 0.15, by adjusting the tip dimensions.
Change the tip cross sectional areas by adjusting the axial holes diameter and the width of groove for the swirl.

7) Optimise static pressures at tip, tip cross sectional area and all other constraints. Obtain the best balance for:
Target of Is = 1.8 and Sw = 0.15,.
Optimum flow rates

8) Confirm choice of fan or blower for swirl air based on static pressure in the tip - choice effects bias coefficient

9) Determine range for blowers: maximum for (Is,Sw)=(1.8,0.15), and minimum for (0.9,0.05). Check that , doing this, we stay in the range 
of 7 to 12% primary air.

Transport design: drawing instructions
Maximum angle of inlet = 12.5 degree with the burner axis
Enter from the top (better distribution)
Inlet rectangle: Internal width should be equal to internal 
diameter of outer pipe of the fuel annulus. The velocity 
should never decrease from the fuel intoduction into the line 
to the burner tip. (Settlement)

Calculation Reference
Flare Burning Combustion
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Gas Flaring
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Submitted On:
28 Jan 2016
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File Date:
28 Jan 2016
File Author:
Steve Haise
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#1 JohnDoyle[Admin] 2016-01-28 08:29
A great début calculation. I have awarded a free 6 month XLC Pro subscription by way of thanks. There was a #NAME error due to a reference to another file on your computer. It was being used to pick out Atm. Pressure which I set this to 760mmHg which resolved the problem.

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