1. 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:

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. from GPSA Handbooks

10. 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

11. from GPSA Handbooks

12. 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

13. from GPSA Handbooks

14. from GPSA Handbooks

15. 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