# Coal combustion injection properties

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 February 24, 2012, 15:44 Coal combustion injection properties #1 Member   Join Date: Jun 2010 Posts: 31 Rep Power: 16 Hello, I am trying to model Coal combustion in a furnace with Fluent. I am using nonpremixed model and coal calculator. Coal powder+air mixture is introduced to the furnace by the burner. My question is when I specify the injection for the coal, the mass flow is for the coal not for the air+coal mixture, right? I specify the air flow in the inlet BC. Lets say I have 10 lb/sec coal and 15 lb/sec air going into the furnace: Burner inlet BC mass inlet : 15 lb/sec Burner inlet BC mixture fraction :10/(10+15)=0.4 Coal injection mass flow :10 lb/sec Coal injection velocity : (calculated from coal density, inlet area and mass flow) Is this the correct approach? Thanks in advance for any comments... semo

 February 25, 2012, 09:18 hi #2 Senior Member   shoeb khan Join Date: Nov 2011 Posts: 179 Rep Power: 14 hi may be i may be wrong but what i think this should be solved in the follwoing way take velocity inlet for coal and air not mass flow inlets second the phase volume fraction should be on volume basis not on the mass basis. regards shk

 February 28, 2012, 11:33 #3 Member   Join Date: Jun 2010 Posts: 31 Rep Power: 16 Thank you for your reply. What about the coal+air mixture? Coal particles are transported with air. I would think since coal is defined by injection on inlet surface seperately the inlet BC should have the air flow only (non-premixed combustion).

 March 10, 2012, 22:08 #4 New Member   jorge Join Date: Oct 2010 Posts: 7 Rep Power: 15 hi, I think (and I may be wrong) that the coal velocity its only the velocity from the air that transport the coal (so you have to calculate it with de air density at the respective temperature, surface and air mass flow), and the coal mass flow its only for the coal. Im right now modellating a tangentially fired pulverized coal boiler, and for BC for the air in the same surface that the injection, I put velocity inlet and specify 0.23 for de mass fraction of O2. That will modelate de primary air. I hope that this helps you,

 June 13, 2013, 03:54 #5 New Member   Bahram Join Date: Apr 2013 Posts: 8 Rep Power: 13 Dear Semo I define the excess air of fuel by selecting a suitable mass flow of air at the boundary condition of the Fluent software,but I see that by increasing the excess air of fuel the maximum temperature is increased!?? I expect that the adiabatic flame temperature is dropped down by increasing the excess air of fuel. Please guide me that how can I define the excess air of fuel at the non premixed combustion model. Thanks Bahram

 November 20, 2013, 02:07 #6 New Member   Nasharuddin MJ Join Date: Feb 2013 Posts: 5 Rep Power: 13 hi bahram i'm not sure whether u have solve the problem with excess air. just want to share with u guys. u can start with stoichiometry. then increase as you need with reference to your stoichio. you can double check with gas species at outlet. Normally with excess air, both CO and OH will fully combust and small portion of O2 (depend on your %e.a). If u increase excess air and the temp goes up, check both CO and OH in your combustion chamber whether they have fully combust. if not, that just mean that u provide more O2 to complete the combustion.

 November 20, 2013, 14:03 #7 New Member   Bahram Join Date: Apr 2013 Posts: 8 Rep Power: 13 Hi NasharuddinMJ Thanks for your replying.My fuel was solid, and the combustion of solid fuels should be injecteded at Fluent.My mistake was that I didn't inject my solid fuel. Thanks

 April 29, 2014, 09:11 #8 Member   Maaz Ul Mosaid Join Date: Jan 2014 Location: Pakistan Posts: 32 Rep Power: 12 Are you using 3d or 2d? which meshing type you used? please help me . i am in real need please share your experience with me which model you used?

April 30, 2014, 11:20
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Bahram
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Quote:
 Originally Posted by maazulmosaid Are you using 3d or 2d? which meshing type you used? please help me . i am in real need please share your experience with me which model you used?
Hi maazulmosaid

My geometry was symmetry, then I used a 2d model. I think that starting with a simple geometry will reduce your computation time wonderfully, and let you correct the mistakes of your boundary conditions in a short time.
I could get rapid convergent with structured quadrilateral grids which was meshed by gambit automatically.
I think that the combustion model which u want to choose for your simulation depends on to the kind and phase of your fuel(solid,liquid,gas) and the state that it mixes with air.
I think that all of the combustion models can give u reasonable results.When i used species transport combustion model the maximum temperature was higher than the maximum temperature which was resulted by nonpremixed combustion model.
I think that nonpremixed combustion model is suitable when we want to consider equilibrium reactions.
Examples of Ansys Fluent will help u.

Bahram

 April 30, 2014, 12:22 #10 Member   Maaz Ul Mosaid Join Date: Jan 2014 Location: Pakistan Posts: 32 Rep Power: 12 Thansk Behram for replying Have you done 3d coal combustion. I am working on 3d coal combustion My chamber is 400 cm in height and 8 cm in diameter My problem is that volatile conv and char conv is very low and i am not getting converged solution Can you please help me in this matter my email is maazulmosaid@hotmail.com

May 2, 2014, 11:03
Similar problem
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I am attempting to do a tutorial that you posted on another post

http://wenku.baidu.com/view/49fa818ecc22bcd126ff0c14

I am getting the error of mass imbalance in reaction-1 stociometery

Quote:
 Originally Posted by maazulmosaid Thansk Behram for replying Have you done 3d coal combustion. I am working on 3d coal combustion My chamber is 400 cm in height and 8 cm in diameter My problem is that volatile conv and char conv is very low and i am not getting converged solution Can you please help me in this matter my email is maazulmosaid@hotmail.com

 April 25, 2016, 14:19 Validation Paper #12 New Member   shailin Join Date: Apr 2016 Posts: 4 Rep Power: 10 HI all , i need a basic cal combustion paper for validation purposes. i am a bsc graduation student. anyone a suggestion? i dont already know much about this subject thats why im asking for advice?

May 16, 2017, 19:40
coal combustion
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Quote:
 Originally Posted by bahramnourani Hi maazulmosaid My geometry was symmetry, then I used a 2d model. I think that starting with a simple geometry will reduce your computation time wonderfully, and let you correct the mistakes of your boundary conditions in a short time. I could get rapid convergent with structured quadrilateral grids which was meshed by gambit automatically. I think that the combustion model which u want to choose for your simulation depends on to the kind and phase of your fuel(solid,liquid,gas) and the state that it mixes with air. I think that all of the combustion models can give u reasonable results.When i used species transport combustion model the maximum temperature was higher than the maximum temperature which was resulted by nonpremixed combustion model. I think that nonpremixed combustion model is suitable when we want to consider equilibrium reactions. Examples of Ansys Fluent will help u. Bahram
hello,
i work with coal combustion,non premixed combustion and dpm but the poblem i have in species result just co2 and H2O i dont find ho,co,,, i dont know where is the poblem,help me please if u have any idea