Discuss the issue of carbon recovery in ethylene plants
Thread Content
I would like to ask everyone about the processes for recovering C5 hydrocarbons. In ethylene cracking or other facilities, how are the C5 compounds produced as by-products recovered? C5 is highly volatile, and simple circulating water cooling is insufficient for recovery. I would appreciate your advice: should it be pressure liquefaction or cryogenic cooling? Or is it absorbed by the circulating fluid? The dry gas from our unit contains some light hydrocarbons, and recovering them is quite troublesome.
C5 can be cooled by circulating water at 0.3 MPa. Are light hydrocarbons referring to ethylene, propylene, propane, and ethane?
It mainly contains a lot of pentane, with some butane as well. Deep cryogenic recovery at atmospheric pressure was used, but the results were not satisfactory.
This is under consideration; the dry gas comes mainly from the hydrogenation section, and the pressure can be controlled at around 5 bar. Have you tried recovery at normal temperature under pressure?
For mainly C4 and higher reformed fractions, such distillation towers are used.
Oh, there’s no need to separate them specifically, as the amount is small. Basically, most of the dry gas produced through hydrogenation is sent to the flare, which is a waste as it gets burned uselessly. The inlet to the gas pipeline network is also unstable, which makes it not worth it; therefore, it is desired to collect the light hydrocarbons from this dry gas before it exits the hydrogenation unit.
Yes, these C4 and lower Reorganization components are relatively easy to recover
C5 can be easily condensed with just a slight increase in pressure; the top pressure in the C5 separation unit of 0.02 MPa is sufficient to cause condensation. I wonder if the size of the condenser in your unit is insufficient? Or is there non-condensable gas entrained in the material?
0.02 MPa seems too low; the saturated vapor pressure of C5 at 35°C is surely higher than that value, not to mention the partial pressure!
The previous set of oil and gas recovery units can use both cryogenic methods and membrane separation,,,,