Raw material preheating issue in ethylene plants
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I would like to ask: in the raw material preheating system of ethylene cracking furnaces, why is cyclic propane and LPG first heated and vaporized using quench water, and then superheated with low-pressure steam before being sent to the cracking furnace? Why isn’t it sent directly to the cracking furnace after passing through a low-pressure steam vaporizer, as is the case with other materials? I hope experienced colleagues can explain this to me!!
What are the consequences of C3/C4 gases not being superheated and liquid entrapping entering the furnace tube?
I think if liquid droplets enter the furnace tube, vaporization will occur, causing pressure fluctuations inside the furnace tube
There is also a convection section coil before the furnace tube
With liquid entrainment (two-phase flow), there will be problems with the flow meters and control valves, which are located upstream of the convection section. Therefore, after C3/C4 overheats, the pipeline must be insulated.
It is simply a matter of sequencing the heating processes when utilizing residual heat – first using cold water at a lower temperature for heating, and then using low-pressure steam at a higher temperature; this helps to save the heat from higher temperature sources and enables more efficient use of temperature.