10 replies to this topic

[Maryvonne]

Hello,

 

I am student currently trying to design a furnace and I am trying to do the mass and energy balance. My aim is to find overall efficiency of the furnace. So I have

 

mass of process fluid + mass of fuel oil + mass of air = mass of flue gas + mass of process fluid

 

I have the mass of the process fluid, I can obtain the mass of air and flue gas per kg of fuel oil but I am not sure how to obtain the mass of the fuel oil. I thought of using the energy balance

 

Qfuel = Qabsorbed +Qflue gas+Qloss

 

where Qfuel =mass of fuel oil x NCV

Qabsorbed  = mCp delta T

 

I am assuming Qloss is 5% of Qfuel but..

 

I dont know how to obtain Qflue gas.I know it is:mass of flue gases x Cp x delta T but I m not sure what the delta T is and how to obtain the temperature.

 

Please help.

 

 

[Maryvonne]

Also, is a vacuum furnace designed the same way as an atmospheric furnace?

[breizh]

Hi,

 

Consider reading this document , it should support your study .

Hope this helps

Breizh

[Maryvonne]

Hi breizh

 

Thank you for the document, It is great. My only problem is that it says it is specific to gaseous fuel but I am burning fuel oil

[breizh]

http://www.delavanin...of_fuel_oil.pdf

 

Hope this helps !

 

 

Breizh

Edited by breizh, 09 March 2014 - 06:17 AM.

[Maryvonne]

Thank breizh but it doesn't show how to calculate efficiency.

[PingPong]

You should try to understand what is in the articles and only then you can apply the info. You can not expect an article that is exactly applicable to your specific heater.

 

Heater efficiency mainly depends on the stack temperature, but also on percentage excess air used for the burners, composition of the flue gas, and heat loss through the heater walls.

 

Stack temperature depends on your heater design. It is always higher than the process inlet temperature to the convection bank, so as to have sufficient temperature difference for heat transfer. Only you can set the right stack temperature for your specific heater.

[Maryvonne]

Thank you. Also, is a vacuum furnace designed the same way as an atmospheric furnace? My research just shows furnace design, it doesn't specify.

[PingPong]

Calculating the efficiency is the same for a vacuum furnace as for any other furnace.

 

Actually designing the vacuum furnace to determine length, diameter and layout of the radiant coils is much more complicated, because in vacuum static pressure of liquid in the coils has a huge impact on the absolute pressure at each point in the coils.

[Maryvonne]

Can I use a pressure jet atomiser be used for gasoil ranging from C10 to C18. Sources say it is used for lighter fuel oil but this is not defined

Edited by Maryvonne, 13 March 2014 - 06:19 PM.

[PingPong]

I am not a burner specialist, but I expect that all what matters for the pressure jet atomiser burner is the viscosity of the fuel oil, not the number of C-atoms in the fuel oil molecules.

 

Check your sources for mention of viscosity.