2.0 Natural gas processing natural gas is gaseous form of petroleum mostly methane (C1), some ethane(C2), propane (C3), butanes (C4), pentanes (C5), hexanes (C6) and C7+ Reserves at Year End: Natural Gas: 1.6 trillion m3 (56.5 trillion ft3) Production: 484 million m3/d (17.1 billion ft3/d) Prices: Natural Gas – Nymex Henry Hub $8,300 US$/MJ (8.77 US$/mmbtu)   Exports: 289 million m3/d (10.2 billion ft3/d) Share of Primary Energy Consumption (2000): 30% Crude Oil: 38% Coal: 11% Electricity – Hydro: 10% Electricity – Nuclear: 3% Other:

Simplified PFD for Sour Gas Processing Plant C1 , C2, H2O Dehydration/Compression C1 , C2, H2S, CO2 etc.. Acid Gas Removal H2S, CO2 HC, SO2, CO2 Sulphur Recovery Inlet Separators S condensate (C2-C5+) Condensate Stabilization C3 , C4 Propane/Butane Processing e.g. deep cut, turboexpansion C5+ Simplified PFD for Sour Gas Processing Plant

Point of processing is to meet pipeline/storage/use specifications Pipeline Specification (Typical) Oxygen 10 ppm Nitrogen 3 % CO2 2-3% pipeline to 100 ppm for LPG plant feed H2S low as 4 ppm (0.25grains/100 scf) for pipeline higher for fuel gas CS2, COS, RSH 20 grains/100 scf Natural Gas Liquid (NGL) Specifications: H2S, Sulfurs Pass Copper Strip, ASTM D-2420 CO2 varies – 0.35 LVP of Ethane content 1000 ppm or less, depends on application

Simplified PFD for Sable Island Acid Gas Injection acid gas Dehydration Dewpoint Control and Compression Gas Sweetening gas from wells Inlet Separation light gases natural gas to market C2-C5+ Condensate Stabilization C5+ Simplified PFD for Sable Island

Condensate stabilization/ fractionation C1, C2 some C3-C4 C1, C2 some C3-C4 +H2O dehy comp Amine plant C1, C2 some C3-C4 +contaminants SO2, CO2, CO etc.. acid gas Claus Plant Inlet Sep S C5+,C3-C4 C3-C4 Condensate stabilization/ fractionation C5+ Sour Gas Plant in AB

2.1 Auxiliary Equipment a) fired equipment - heat exchangers throughout plant, furnaces used in utility and SRU 2 types (figure 8-2) i.         direct fired - combustion gases heat process stream which is contained in pipes ii.       fire tube - combustion gases are surrounded by a liquid that either is used as a heat transfer medium or is the process stream itself application characteristics direct fired regeneration gas heaters more equip/controls amine reboilers higher ηthermal lower space forced/natural combust firetube line heaters low heat duty C3+ vaporizers skid mount gly/am reboilers forced/natural combust low P steam gen less hot spot

b) HE - discussed in section 1.3   c) cooling towers detail in section 1.3 purpose cool process water by ambient air  achieved by maximize evaporation of H2O in droplets exposed to maximum air flow over longest time (picture) mech draft – fans move air and natural draft – use density d) pumps/turbines - mostly centrifugal type due to lower cost, smaller space, and low maintenance e) compressors/expanders compressors used inlet and sales gas to boost pressure + displacement dynamic thermal

f) refrigeration used in: NGL/LPG recovery HC dewpoint control reflux condensation for light HC fractions LNG plants - refrigerant type selected by T requirements, availability, economics, previous experience e.g. natural gas plant may use C2 and C3 while due availability and economics olefin plant may use ethylene and propylene  i.   mech refrigeration most common simple cycle of expansion, evaporation, compression, condensation Absorption Refrigeration if low cost of n.gas, low level heat source, and electricity rates

from GPSA Handbooks

2.2 Inlet Separators discussed fractionators in general, separator is like one stage of a fractionator where adjust P of incoming gas to separate v and l 4 major sections primary section – sep main portion of free l by abrupt change in momentum or direction (nozzle) secondary or gravity sectn – use gravity to enhance sep of entrained droplets gas moves at low velocity w/ little turbulence coalescing sectn – coalescer (wire, mesh, vane elements, cyclonic passage) or mist extractor removes droplets can’t be sep by gravity by impingement on surface limits l carryover into gas (<0.013 mL/m3) sump/l collection – recover l from ii and iii – provides surge V for degassing a slug catching b) orientation vertical – high v:l ratio or total gas V low horizontal – used large V total fluids and large amounts of dissolved gas in l spherical – occasionally used where high P and compact size needed, l volumes are small new are small valve types on platforms

from GPSA Handbooks

2.5 Fractionation separate gas mixtures into individual products in next section discuss bulk separation of NGLs from gas which differs from this discussion absorption -type units also used  use trays/packing types of fractionators at gas plants demethanizer – product bottom is C2+, OH is C1 deethanizer - product bottom is C3+, OH is C1/C2 commercial C3, C3/C4 (LPG), C4, C4/gasoline, natural gasoline e.g. at gas plant in AB deethan run depending price butane depropanizer debutanizer

from GPSA Handbooks

from GPSA Handbooks

b) Product specs material balance around column is 1st step in design calcs  need to assume product stream compositions defined in terms of % recovery of component in OH or bottom OR composition of component in either product OR specify physical properties (Pvap) in either product   c) design in fractionation there usually 2 components which are key in separation lightest component in bottom (LK) heaviest component in OH (HK) these components are adjacent to each other in volatility in hand calcs make the assumption all components heavier than than heaviest in OH are in bottoms