rotary dryer burner sizing...

[kilnfab]

Trying to calculate the burner size required to dry 7 MTPH of 18% humidity sand in a rotary dryer. The dryer has been sized for retention time = 1hr or 2.2m ID inside refractory x 15m LG on 1degree incline. Plan on 6" castable refractory lining. Anyone know how to determine the heat input required relatively accurately ?? Assume efficient seals MO

 

[kilnfab]

Ok seems i need to do some heat balance work..anyone know of a good reference for this type of thing - specific to rotary equipment ?? Thanks. The rookie.

 

[Cormoran]

Kilnfab
Do you know final humidity content in sand? Do you know maximun RH in air for this humidity content?.
Alfredo

 

[kilnfab]

Cormoran,
They want the product humidity to be reduced from 18% to 0.5%. Not sure the RH - but client is in Costa Rica so i am gonna guess relatively high (~65%) ?
Thanks,
MO

 

[kilnfab]

Yes sir - visited the BBC weather page and the RH for the week is 65-81% so quite high indeed - i imagine this will make it more difficult to dry the sand ?
MO

 

[Cormoran]

You need one mass energy balance. Very important information is RH of air at dryer outlet. Then your dryer inputs are;
Fuel flow (Btu/hr)
Sand flow+sand water flow (he, Ce, Te)
Air flow , he funcion of (T & RH)
Your dryer outputs are.
Sand flow+sand water flow (he, Ce, Te)
Air flow , he funcion of (T & RH).

Air flow: You need RH and temp at dryer outlet to calculate this flow, with amount of water evaporated.

 

[kilnfab]

Thank you very much Comoran. This is a very interesting subject... i am studying like crazy and the logic you provide is very helpful. The way i see it if i want to determine the heat input required from what we have to date - i have to calculate the energy to replace the heat lost through the flue with the air movement as well as the energy required to heat the product enough to release all of the remaining water or 17.5% of the mass entering - does this sounds logical ? Well ok that doesn't include inefficiencies in the system - but roughly am i on the right track ??

 

[kilnfab]

Como
Do you feel 95% humidity leaving the dryer is a reasonable assumption at sea level ?
Mark