6 replies to this topic

[gautam_n]

If the temperature of solids and gas at inlet is higher than that of the outlet in a concurrent direct rotary dryer, will it effect thermal efficiency calculations in any way?

I have been trying to calculate the thermal efficiency for a dryer used in DAP plant, but I am ending up with answer >1 !!! Please find the spread sheet attached with the values. Kindly point out where I may have gone wrong if possible.

Attached Files

•  dryer thrml eff.xlsx   10.53KB   94 downloads

[breizh]

Hi ,
How did you take account the solid in your energy balance ?
you need to perform a heat balance taking account all components (solid , gas) . Hin =Hout !

A simple drawing should help you (us) to vizualize all the streams involved .
Hope this helps


Breizh

Edited by breizh, 05 September 2012 - 06:58 PM.

[gautam_n]

I am attaching a simple diagram for the dryer , with the inlet and out let conditions specified.

Attached Files

•  dryer info.JPG   21.4KB   52 downloads

[gautam_n]

Hi ,
How did you take account the solid in your energy balance ?
you need to perform a heat balance taking account all components (solid , gas) . Hin =Hout !

A simple drawing should help you (us) to vizualize all the streams involved .
Hope this helps


Breizh

Thank you Mr.Breizh,

I have performed heat balance to get Q= 774951.6 kcal/hr , and found the heat supplied by using the formula
Q_heater = (T_g1-T_ga)/(T_g1-T_g2)[S(X₁-X₂)λ_s + SC_ps(T_s2-T_s1) + Q] = 2085779 kcal/hr .

Vaporization load [S(X₁-X₂)λ_s] for the process is around 2101090. Then Vaporization load/Heat Supplied = >1.0

Do I have to account for any losses here,even after accounting for 10% losses, the efficiency will be above 90%. Wondering whether its feasible. Kindly provide me with some explanation and point out any mistakes on my part.

[breizh]

Just to clarify with you :

enthalpy balance :
in : Solid + water imbibition (liquid phase) ; hot gas for drying with its water content (gas phase)
out : Solid +water imbibition residual (liquid phase) ; hot gas with water (gas phase ) +losses if any

Note : Prepare a table Xcel for us to review your calculation with all the material involved per stream where we can see
mass in = mass out .
Hin = Hout +losses . >>>> Hout/Hin = Efficiency



Breizh

Edited by breizh, 08 September 2012 - 06:07 AM.

[Abel1956]

Dear Breizh,

I would like to submit a case study concerning the performances of a DAP rotary dryer. The plant have been revamped to increase its capacity, the engineering company stated that the dryer have enough capacity. Unfortunately, the dryed product is not in specification of moisture, we get more thant 2 % instead of less than 1.5%. Could you please help me to set up the method for verifying the performance of the dryer considering this new capacity.
thank you very much for your reply.

Abel

[breizh]

Abel ,
You need to review the calculation note provided by the engineering company and check the discrepency with what you are observing on the field .


Breizh