Lakhasly

[١٠/‏٨ ٢:٥٦ م] MO AH: PEAK  SHAVING  PLANTS  AND  SATELLITE  FACILITIES :
Need  for  gas  storage  facilities . Because  natural  gas  fields  are  generally  located
Far  from  residential  and  industrial  consumers , storing  large  quantities  of  gas
near  the  point  of  consumption  to  supplement  the  normal  supply  of  pipeline
discussed  gas  storage  techniques , the  most  common  of  which  is  underground
storage  in  depleted  oil  or  gas  fields , salt  caverns , or  abandoned  mines  that  can
be  effectively  sealed . Where  underground  storage  is  unavailable , aboveground
storage  of  natural  gas  as  LNG  becomes  attractive , and  utilities  use  relatively
small  liquefaction , storage , and  regasification  plants  to  meet  the  demand . Plants
that  combine  all  three  of  these  tasks  are  referred  to  as  peak  shaving  plants .
“Stranded”  utilities , those  not  connected  to  the  national  pipeline  grid , rely
Upon  LNG  received  by  truck  to  support  their  customer s. Any  LNG  facilities
Like  these , which  contain  only  storage  and  regasification  units , are  called
“satellite  facilities.”
shaving  facility . Gas  treating  and  compression  are  discussed  in  earlier  chapters .
This  chapter  discusses  liquefaction , liquid  storage , and  regasification . Odorant
injection  may  or  may  not  be  required  at  the  peak  shaving  plant .
[١٠/‏٨ ٢:٥٨ م] MO AH: the   first   peak  shaving   plant   built   in   the   United   States   was   in   Cleveland  , Ohio , in  1941  (Miller  and  Clark , 1941) . Although  the  plant  performed  successfully  for  several  years , in  October  1943 , a ةmetallurgical  failure  in  a  storage  tank  resulted  in  a fire  and  explosion  ( GAO , 1978 )  that  destroyed  the  plant , with  a heavy  loss of  life . * Although  this  disaster  was  a  major  setback  to  the  industry ,  in  2004  the  United  States  had  59  peak  shaving  plants ,  39  satellite  facilities ,  four  LNG  marine - import  terminals , and  one  LNG  marine – export  terminal  ( Energy  Information  Administration , 2004 ) .
BASELOAD PLANTS AND STRANDED RESERVES:
Baseload  plants  exist  to  provide  the  industrial  world  with  gas  from  stranded  reserves  in  remote  places . Stranded  gas  reserves  are  located  where  no  economic use  for  thenatural  gas  exists  at  the  point  of  origin  and  where  transportation  of the  gas  by  pipeline  to  a  point  of  end  use  is  not feasible . Romanow  ( 2001 )  
[١٠/‏٨ ٢:٥٨ م] MO AH: estimates  that approximately  60%  of  the  world’s  gas  reserves  are  considered  stranded . When compressed  gas  pipelines  are  impractical  or  impossible , a  limited  number  of conventional  options  are  Open   (Taylor  et  al. , 2001 )  , such   as   compression   and  transport   of  the  gas  in  specially built  ships  (Wagner, 2002) , conversion  of  the natural  gas  into  a  liquid  through  gas – to - liquid  (GTL)  technology , and liquefaction  and  shipment  of the  gas  in  specially  built  LNG  vessels . Leibon  et al . (1986)  as  well  as  Taylor  et  al . (2001)  evaluate  the  status  of  several  of  the technologies . Hidayati  et  al . (1998)  compare  the  cost  of  a  compressed gas  pipeline  to  LNG  carriers  for  a  large  Indonesian  project . Some  unconventional  methods  that  have  been  considered  include  conversion  of  the  natural  gas  to hydrates  for  shipping  ( Gudmundsson  and  Mork , 2001 )  and  even  use  of  a  train of  airships  that   natural  gas . Presently ,  LNG  is  the  most  viable  option  in  almost all  situation  involving  stranded  reserves , if  the  gas  can  be  pipelined  to  a  seaport. However , to  economically  justify  a  traditional  baseload  LNG  plant  requires reserves  of  approxi - mately  3  Tcf  (80 Bm3) . Newer  designs  have  reduced  the reserve  volumes  down  to  around 1 Tcf (30 Bm3)  (Price et al.2000).
As  Figure  13.2  shows , bringing  the  gas  from  the  field  to  the  customer  involves
four  steps  (Energy Information Administration, 2003b):

1.  Gas  production , gathering , and  processing


2.  LNG  production , including  gas  treating , liquefaction , NGL  condensate
   Removal , and  LNG  storage  and  loading


3. LNG shipping


4.  LNG  receiving  facilities , which  include  unloading , storage , regasification , and distribution .
   Depending  on  the  specific  situation , not  all  plants  will  have  all  the  processes shown, and  some  plants  may  have  additional  processes.
   countries , Indonesia , Malaysia , Qatar , and  Algeria , accounted  for  64%  of  the
   world’s  exports , and  two  countries , Japan  and  South  Korea , accounted  for  63%
   [١٠/‏٨ ٢:٥٩ م] MO AH: of  the  world’s  imports  (Energy  Information  Administration , 2003b )
   [١٠/‏٨ ٢:٥٩ م] MO AH: LIQUEFACTION CYCLES:
   The  two  most  common  methods  that  have  been  used  in  engineering  practice  to
   produce  low  temperatures  are  Joule – Thomson  expansion  and  expansion  in  an
   engine  doing  externa l work . This  section  discusses  each  of  these  processes  in
   [١٠/‏٨ ٢:٥٩ م] MO AH: detail  and  analyzes  them  thermodynamically
   [١٠/‏٨ ٣:٠١ م] MO AH: EXPANDER CYCLES:
   The  point  was  made  during  the  discussion  of  the Joule - Thomson  expansion that  it  was  a  thermodynamically  irreversible   process . Expansion  of  high -pressure  gas  to  the  lower  pressure  in  a  reversible  or  nearly  reversible  manner providesc two  distinct  improvements  over  the  Joulev -Thomson  expansion . First , in  the  reversible  expansion , a  large  fraction  of  the  work  required  to  compress the  gas  can  be  recovered  and  used  elsewhere  in  the  cycle . This  property provides   an   increase   incycle  efficiency . Second , the  reversible  process  will result  in  a  much  larger  cooling  Reciprocating   machines  are  rarely  used  in  LNG  facilities .
   Similar  to  dynamic  compressors , dynamic  expanders  can  be  centripetal  flow
   or  axial  flow . In  centripetal  machines  (i.e., turboexpanders) , the  gas  enters
   through  nozzles  around  the  periphery  of  the  wheel , expands , and  transmits  work  to  the  wheel , which  causes  it  to  rotate , and  finally  exhausts  at  low pressure  at  the  axis  of  the  machine . Chapter  7  provides  more  details .  Axial - flow  expanders  have  as  their  counterparts  steam  turbines . Centripetal  machines have  isentropic  efficiencies  on  the  order  of  85  to  90% ,  whereas  axial - flow expanders  are  about  80%  efficient  (Swearingen, 1968) . Turboexpanders  are  high -speed  machines , generally  designed  to  operate  from  10,000  to  100,000  rpm , depending  on  the   throughput .
   For  design  purposes , several  techniques  may  be  used  to  compute  the  expected
   enthalpy  change , but  the  simplest  and  apparently  satisfactory  method  is  to  use
   the  ideal  value  from  a P - H  or  T -  S  diagram , and  correct  this  value  with  the
   anticipated  turboexpander  efficiency  (Swearingen, 1968; Williams, 1970) . The
   work  generated  in  the  expander  must  be  removed  from  the  system  if  the  full
   thermodynamic  efficiency  of  the  cycle  is  to  be  realized . The  general  practice  in  large - scale  operations  is  to  couple  the  turboexpander  to  a  gas  compressor . Recip – rocating  expanders  would  naturally  be  coupled  with  reciprocating compressors , and  turboexpanders  coupled  with  centrifugal  compressors . The available  expander  work  can  be  very  large . Swearingen  (1968)  states  that  a turboexpander  handling  500   MMcfd (14 Sm3/d)  at  pipeline  pressure  would develop  10,000 hp (7,500kW) . Surprisingly , the  turbineb rotor  would  only  be  18 inches  in  diameter . In  small-scale  operations , recovery  of  the  expander  work  is often  not  economically .
   STORAGE OF LNG :
   Discussions  of  LNG  storage  facilities  are  normally  divided  into  two  major
   Categories :  aboveground  and  in  ground . Each  has  three  natural  subcategories , and  each  is  discussed  below . Also , LNG  storage  involves  a feature  peculiar  to the  orage  of  cryogenic  liquid  mixtures ,  stratification . This  section  includes  a dis-cussion  of  this  important  phenomenon .
   CRYOGENIC ABOVEGROUND STORAGE:
   Three  basic  types  of  aboveground  storage  vessels  are  in  use:
   • Steel
   • Prestressed  concrete
   • Hybrid  (combinations  of  steel  and  concrete)
   Each  type  of  construction  will  be  discussed  briefly .
   Steel:
   Double -,  and  full-containment  steel  tanks . Storage  of  LNG  in  aboveground metal  tanks  is  a  widely  accepted  method  for  both  baseload  and  peak  shaving uses.  Nine  percent−nickel  steel  is  the  most  widely  used  metal  for  large  LNG tanks . Because  of  its  high  cost , stainless  steel  is  generally  used  only  for  small vessels ,  LNG  plant  piping , and  heat  exchangers . The  conventional configuration is  a  double-walled , flat-bottomed  tank , with  the  annular  space  between  the walls  filled  with  an  insulating   material .  Long  (1998)  discusses two  types  of   
   9%  nickel  steel  construction , the  single - containment  and  the  double-containment  tank . The  single-containment  tank  is  obviously  less  expensive  to build  but  has  the  obvious   disadvantage   of   only   one  containment  wall  that  is compatible  with  LNG . An  economic  study  by  Long  (1998)  indicated  a  12  to 17%  cost s differential  between  the  full – and  double-containment .