7 Natural Gas Processing Acid Gas Removal Hydrogen sulfideMercaptansCarbon dioxideAcid gas removal processesAmine treatingBenfield processSulfinol processothers
8 Natural Gas Processing Amine Treatment Most common used aminesMonoethanolamineDiethanolamineDiisopropylyamineMethylethanolamineHydrogen sulfide goes through a Claus process64,000,000 metric tons of sulfur are produced from this process
10 Natural Gas Processing Sulfinol Process Used to reduce H2S, CO2, and mercaptans from gasesGreat for treating large quantities of gasSolvent absorbs the sour gasSulfolane is usedSulfolane, a clear colerless liquid, developed by shell in the 1960’s
13 Natural Gas Processing Glycol Dehydration Method for removing the water vapor from the gasUsable glycolsTriethylene glycol –most commonly usedDiethylene glycolEthylene glycolTetraethylene glycolWorks by having the glycol adsorb the water
14 Natural Gas Processing Glycol Dehydration Wet gas enters a contacting tower at the bottom. Dry glycol flows down the tower from the top, from tray to tray, or through packing material. A bubble cap configuration maximizes gas/glycol contact, removing water to levels below 5 lbs/MMscf. Systems can be designed to achieve levels down to 1lb/MMscf. The dehydrated gas leaves the tower at the top and returns to the pipeline or goes to other processing units. The water rich glycol leaves the tower at the bottom, and goes to the reconcentration system. In the reconcentration system, the wet glycol is filtered of impurities and heated to 400°F. Water escapes as steam, and the purified glycol returns to the tower where it contacts wet gas again.
15 Pressure Swing Adsorption Adsorbent material is usedGas and material go under high pressureMaterial adsorbs the gas ( H2S, mercaptans, CO2)DisadvantagesRequires high pressuresSlow cycle times
17 Mercury removal Current Processes Activated carbon – through chemisorption. Activated has extremely high surface areaMercury can damages aluminum heat exchangersThose used in cryogenic processing plantsThose use in liquefaction plants
19 Nitrogen Rejection Processes that can reject nitrogen Cryogenic processAbsorption process (using lean oil or solvent)Membrane separationAdsorption process (activated carbon)
20 Natural Gas Processing Cryogenic Process Common refrigerants usedMost common method for removal of impurities such as nitrogenDisadvantagesMust reach extremely low temperaturesOnly useful for large scale production
21 Natural Gas Processing Lean Oil Removal Lean oil is fed countercurrent with the wet gasTemperature and pressure are set to allow for the greatest absorption of unwanted gasesIn the ambient lean oil absorption process the natural gas is contacted with the lean oil (molecular weight of about 150) in an absorber column at the ambient temperature of about 100°F. The rich oil exiting the bottom of the absorber flows into a rich oil depropanizer (ROD) which separates the propane and lighter components and returns them to the gas stream. The rich oil is then fractionated in a still, where the NGL's (C4+) are recovered as an overhead product and the lean oil is recycled to the absorber column. Typically, 75 percent of butanes and percent of pentanes and heavier components are recovered. In the refrigerated lean oil absorption process, the lean oil is chilled against propane refrigerant to improve the recovery of propane to the 90 percent level, and depending upon the gas composition, up to 40 percent of ethane may be recovered (Elliot, 1997). Since reducing the molecular weight of lean oil enhances the lighter component absorption and an external refrigerant is used to chill the lean oil, 100 to 110 molecular weight lean oils are generally used in this process.
22 Natural Gas Processing Membranes Driving forcePartial pressureType of material determine permeabilityD = diffusion coefficient (cm2/s)k = Henry’s law sorption coefficient (cm3/cm3cmHg)P1 = Permeability of component 1P2 = Permeability of component 2
32 Novel MethodTechnical information momentarily not available due to IP issuesHowever economics will be comparedIf you want the access to this, then talk to OTD
33 Novel Method Advantage More cost effective than any previous methods Less environmental impacts than previous methodsSeparates all contaminantsSeparates each componentEverything is done using one processIf you want the access to this, then talk to OTD