
Novel Method for Gas Separation By: Chris Wilson For: Senior Capstone 2008
Overview • Current process • New process • Economic comparison
Natural Gas Processing The Way it is Done • Current process • Remove excess water • Remove acid gas • Dehydrate • Remove mercury • Remove nitrogen • Separate NGL (ethane, and heavier hydrocarbons)
Water removal • Removes free liquid water and condensate gas • Sends the gas to a refinery • The water goes to waste
Natural Gas Processing Acid Gas Removal • Hydrogen sulfide • Mercaptans • Carbon dioxide • Acid gas removal processes • Amine treating • Benfield process • Sulfinol process • others
Natural Gas Processing Amine Treatment • Most common used amines • Monoethanolamine • Diethanolamine • Diisopropylyamine • Methylethanolamine • Hydrogen sulfide goes through a Claus process
Natural Gas ProcessingSulfinol Process • Used to reduce H2S, CO2, and mercaptans from gases • Great for treating large quantities of gas • Solvent absorbs the sour gas • Sulfolane is used
Natural Gas Processing Glycol Dehydration • Method for removing the water vapor from the gas • Usable glycols • Triethylene glycol – most commonly used • Diethylene glycol • Ethylene glycol • Tetraethylene glycol • Works by having the glycol adsorb the water
Pressure Swing Adsorption • Adsorbent material is used • Gas and material go under high pressure • Material adsorbs the gas ( H2S, mercaptans, CO2) • Disadvantages • Requires high pressures • Slow cycle times
Mercury removal • Current Processes • Activated carbon – through chemisorption. Activated has extremely high surface area • Mercury can damages aluminum heat exchangers • Those used in cryogenic processing plants • Those use in liquefaction plants
Nitrogen Rejection • Processes that can reject nitrogen • Cryogenic process • Absorption process (using lean oil or solvent) • Membrane separation • Adsorption process (activated carbon)
Natural Gas Processing Cryogenic Process • Common refrigerants used • Most common method for removal of impurities such as nitrogen • Disadvantages • Must reach extremely low temperatures • Only useful for large scale production
Natural Gas Processing Lean Oil Removal • Lean oil is fed countercurrent with the wet gas • Temperature and pressure are set to allow for the greatest absorption of unwanted gases
Natural Gas Processing Membranes • Driving force • Partial pressure • Type of material determine permeability D = diffusion coefficient (cm2/s) k = Henry’s law sorption coefficient (cm3/cm3cmHg) P1 = Permeability of component 1 P2 = Permeability of component 2
Demethanizer • The next step is to recover the NGL’s • Process • Cryogenics using a turbo-expander can be used • This is the most common • Lean oil adsorption can be used here
NGL recovery • Now the rest of the liquid is fed to three units • Deethanizer • Debutanizer • Depropanizer • Process • Each sent to a distillation column
Merox Processes • Mercaptan oxidation • Removes mercaptans from • Propane • Butane • Larger hydrocarbons
Novel Method • Technical information momentarily not available due to IP issues • However economics will be compared
Novel Method • Advantage • More cost effective than any previous methods • Less environmental impacts than previous methods • Separates all contaminants • Separates each component • Everything is done using one process