Coal combustion injection properties
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...
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.
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).
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,
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.
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.
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.
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