1. Gas Processing
Lean Oil
Absorption

2. The design of Lean Oil Absorption Unit is dedicated to the separation of methane and ethane from the inlet gas. The composition of inlet gas contains both methane and ethane which will be separated from the gas stream with this process.
Lean Oil Absorption

3. Inlet gas enters a separator which helps to remove moisture from the gas stream. From the separator gas enters a gas/gas exchanger (heat exchanger) which cools the inlet gas with the cold gas coming of the top of the absorber/contactor.
Inlet Gas

4. Increasing the “Cool” Factor
Inlet gas exits the gas/gas exchanger and enters a chiller for further cooling. Refrigerant is needed to promote increased cooling of the gas before it enters the absorber. Remember contactors/absorbers operate most effectively at higher pressure and low temperatures.
Increasing the “Cool” Factor

5. Contactor/Absorber Cool gas enters the absorber/absorber
The function of this absorber is to capture as much of the ethane as possible.
So the desired product of this unit is ethane.
Lean oil enters the top of the absorber and travels down the column from tray to tray.
The lean oil attaches to the ethane from the inlet gas traveling upward. Becoming Rich Oil.
This process leaves mostly methane behind.
Methane is released out the top of the absorber and enters a gas scrubber.
Methane travels to the gas/gas heat exchanger and exits the system as fuel gas.
Contactor/Absorber

6. Absorbers are not 100% efficient so a Demethanizer column is needed. 
Rich oil will have some methane entrained with the ethane so it must be sent to a heater. 
The heater increases the temperature of the high pressure/rich oil. 
The rich oil enters a flash drum lowering the pressure of the liquid. 
Remember, that distillation/fractionation/stripping/regenerator towers run efficiently at high temps and low pressures. The Demethanizer tower is a stripping tower where methane will be stripped from the Rich Oil.
After decreasing the pressure of the Rich Oil it enters another heater raising the temperature even further before being routed to the Demethanizer tower.  A reboiler continues to heats up the rich oil promoting the only the release of methane from the Rich Oil (operating temps are critical so ethane is not released from rich oil.
Methane will travel up the Demethanizer and exit the top traveling to an accumulator.  The methane leaves the accumulator as residue gas. 
Demethanizer

7. Ethane Rich Oil leaves the bottom of the Demethanizer column.
Rich oil goes to the Lean/Rich heat exchanger further the rich oil before entering the Deethanizer.
Ethane from the rich oil will be removed by this column.
Ethane vapor travels up the column after being heated by the reboiler.
Ethane vapors go out the top of this column and enter a condenser.
The condenser will liquefy the ethane vapors into liquid which enter way an accumulator.
A portion of the liquid ethane is sent back to the column as reflux to increase ethane product purity and some and the rest leaves as ethane product.
Deethanizer

8. High temperature/Low Pressure/Lean oil leaves the bottom of the Deethanizer.
All Methane and Ethane hydrocarbons have been released.
To be able to reuse the lean oil again we must decrease its temperature and increase the pressure before re-entering the absorber.
Hot Lean Oil first goes enters the Lean/Rich heat exchanger giving up its heat to the rich oil.
Allowing the Lean Oil to cool before being pumped to the reboiler of the Demethanizer Tower.
The lean oil is used to heat the reboiler for the Demethanization tower.
The lean oil is then routed to a Lean Oil Cooler further dropping the temperature before entering an accumulator. 
Lean Oil

9. The accumulator is where the Lean Oil is presaturated before it is allowed to re- enter the absorber. (We will discuss presaturation later). Finally the Lean Oil enters a chiller taking the Lean Oil to its lowest temperature before entering the absorber to start the whole process over.
Final Steps