3 replies to this topic

[Beautifulmind]

HI . i would like to know about the draft related to petroleum refinery furnaces .. what is draft and on what factors does it depend ? how can i improve the effinciency of furnace ?

[benoyjohn]

Draft is the other name signifying the driving force for air inflow into the furnace. It can be measured in mmWC of vacuum. Assuming a natural draft furnace, it depends on a lot of factors like the ambient conditions, the dampner opening, the burner air register opening etc.

About efficiency, to improve it use less fuel to transfer the same amount of heat to the fluid heated.

The ways may be
Optimise the excess air in to furnace
Reduce flue gas stack outlet temperatures
Improve burner efficiencies.

etc..

[Bharat Abhyankar]

HI . i would like to know about the draft related to petroleum refinery furnaces .. what is draft and on what factors does it depend ? how can i improve the effinciency of furnace ?

Refinery furnaces are mostly Balanced draft (i.e. with FD and ID fan).
Attached diagram will help engineers to understand typical signature of furnace draft.
1. Radiant arch pressure is the maximum pressure point in furnace.
2. Maintaining it negative will ensure smooth operation.
3. Furnace efficiency can be improved in following areas:
>> Stack Temperature
>> Air preheater temperature
>> Excess air or Air to Fuel ratio.

Attached Files

•  Fired Heater.JPG   57.89KB   43 downloads

[JMW]

Assuming the fuel is notionally heavy fuel oil (I say notionally because though the fuel is usually quoted to a particular specification it is often self produced from residuum with some low cost low viscosity cutter stock - and a handy way to get rid of "mistakes" so that fuel quality can be very variable.)
Poor fuel quality or consistency can result in a strategy of flame inspection, frequent lab analysis to try and determine the EVT (Equiviscous temperature - the temperature at which the viscosity will be optimum - and then the fuel heaters are controlled to this temperature and excess oxygen to try and offset poor viscosity control which results in poor atomisation.

If you use this means to control heating the cost savings of using a viscometer to control the fuel heater will be substantial, will result in less fuel used, lower emissions because of more complete combustion and less frequent soot blowing, fewer tube burn throughs and less maintenance.
One petrochemical plant is said to have saved £100,000 a year switching to viscosity control from temperature control.
See www.viscoanalyser.com
http://www.engineeri...slm/slm106.html