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-   -   Coal combustion injection properties (http://www.cfd-online.com/Forums/fluent/97784-coal-combustion-injection-properties.html)

semo February 24, 2012 16:44

Coal combustion injection properties
 
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

shk12345 February 25, 2012 10:18

hi
 
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

semo February 28, 2012 12:33

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).

Vorch March 10, 2012 23:08

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,

bahramnourani June 13, 2013 04:54

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

NasharuddinMJ November 20, 2013 03:07

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.

bahramnourani November 20, 2013 15:03

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

maazulmosaid April 29, 2014 10:11

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?

bahramnourani April 30, 2014 12:20

Quote:

Originally Posted by maazulmosaid (Post 488917)
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

maazulmosaid April 30, 2014 13:22

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

khubaib_syed May 2, 2014 12:03

Similar problem
 
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 (Post 489161)
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



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