Question

discuss about most suitable pressure changing devices to be used in the above pressure for pumping the lean oil to top of the absorption tower

Answer 1

A lean oil is used as absorbing medium for removing of a component of the gas.lean oil is hydrocarbon liquid and in a gas processing unit it is used absorber to remove heavier hydrocarbons from natural gas.Lean oil is usually a mixture of paraffins compounds havinf molecular weights between 100 to 200.The lean oil is used to absorb light hydrocarbon components from the gas.The light components are separated from the rich oil and the lean oil is recycled. The oldest kind of gas plants are absorption or lean oil plants,where a kerosene type oil is circulated through the plant.The lean oil is used to absorb light hydrocarbon components from the gas.The light components are separated from the rich oil and the lean oil is recycled.An industrial example is lean oil absorption that which is used to separate nitrogen and other impurities from natural gas.A lean oil is contacted with low quality natural gas, and the methane is selectively absorbed by the lean oil and leaving the impurities behind. The methane is subsequently regenerated from the rich oil as high quality natural gas.

A refrigrated system enhances the recovery of lighter hydrocarbon products such as ethane and propane.Refrigrated lean oil adsorption methods are used. Inlet gas enters a separator which helps to remove moisture from the gas stream. From the separator gas enters a heat exchanger which cools the inlet gas with the cold gas coming of the top of the absorber.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 heat exchanger and exits the system as fuel gas.The Demethanizer tower is a stripping tower where methane will be stripped from the rich oil.Methane will travel up the Demethanizer and exit the top traveling to an accumulator.The methane leaves the accumulator as residue gas.

A gas with hydrocarbon vapors enters the bottom of absorber column flows upward and comes in contact with the counter-flowing lean oil system.The lean oil preferentially absorbs the vapors from the gas, becoming enriched oil.rich oil is sent to a stripper where the absorbed vapors are removed by heating the rich oil and vaporizing the absorbed vapors.The rich oil is regenerated as lean oil and is recycled to the absorber to complete the process.The vaporized vapors are liquefied and transferred to storage.Each gaseous hydrocarbon goes into solution in the lean oil in inverse proportion to its vapor pressure and the lower the vapor pressure so greater the tendency to dissolve, each component being concentrated as an absorbate dissolved in the lean oil. Absorption can also be increased within an absorption column by an increased flow rate of lean oil, by decreased temperature because the vapor pressures of the absorbed compounds are lowered, and by increased pressure because more absorbate is dissolved by raising the partial pressures of the absorbates.Paraffinic lean oils are preferable for a natural gas.Lean oils are usually high-boiling gasoline fractions or distillate-fuel like kerosene which are chosen according to absorption capacity.Any hydrocarbon oil has a greater capacity to absorb chemically similar materials and most of the vapors to be absorbed from a natural gas are paraffinic so molecular weight of the lean oil must be balanced against the greater absorption capacity of a lower molecular weight oil.