Development Of GTL Technology

1- Introduction: The  world  consumes  energy  from  different  sources.  Some  of  the energy  comes  from  the  fossil  fuels  like  coal, crude oil, and natural gas, which  are  called  sustainable  energy  sources.  Some  others  come  from industrial  sources  like  the  nuclear  energy.  Also,  energy  obtained  from natural   sources   like   solar   energy,   wind,   and   waterfalls,   is   called renewable  energy  sources.  Natural  gas  provided  about  22%  of  the  total world energy consumption in 2004, and it is believed that this percentage

will rise to 24% in 2020. 

The worlds proved and potential natural gas reserves are estimated to be more than 6040 trillion cubic feet (Tcf)    . These reserves are enough by their  own,  with  the  current  production  capacities,  to  cover  the  worlds need  for  more  than  60  years.  Most  of  the  known  big  gas  resources  are stranded or remote because they are too far from the consumers, like the fields of Alaska and Siberia. These gas reserves are also very difficult to transport  because  they  need  either  to  be  pumped  through  very  long pipelines,  or  must  be  liquefied  and  transported  by  tankers  as  Liquefied Natural Gas (LNG). The world consumption of natural gas equal to about 2.5 Tcm, most of Natural  gas  is  four  times  more  expensive  to  transport  than  oil.  On  the other hand, converting natural gas into liquid to ease its transportation is even   more   expensive.   For   a   small   remote   natural   gas   field,   the transportation by either pumping the gas through very long pipelines, or by liquefying the gas and transporting it by LNG tankers is uneconomic, because both ways are very expensive, leaving these fields undeveloped. GTL has the potential to convert a significant percentage of this gas into several hundred billion barrels of liquid petroleum - enough to supply the world's  energy  needs  for  the  next  25-30  years.  GTL  offers  tremendous economic  value  to  the  countries  and/or  companies  that  control  these reserves.  GTL  will  permit  the  economic  development  of  these  remote natural gas discoveries that currently are deemed too far from market to be of economic value. GTL also will help to eliminate the need for flaring natural  gas,  associated  with  oil  production,  which  will  permit  earlier development  and  production  of  oil  fields  shut  in  by  the  inability  to dispose   of   the   associated   natural   gas,   and   reducing   the   negative environmental   impact   of   flaring.   The   expenses   consumed   in   these industrial  operations  can  be  invested  toward  the  production  of  valuable liquids  from  the  flared  gases  by  the  GTL  process.

it is consumed by the big industrial countries.

(a)Monetizing   standard   natural   gas   reserves   and   providing   a solution to Alaska gas fields. (b)Eliminating   costly   and   /   or   environmentally disadvantageous practices. (c) Creating environmentally-superior clean liquid fuels. (d)Investing the waste gas. (e) It can be used as integrating projects with LNG industry. (f) The  possibility  of  constructing  GTL  units  for  the  offshore  gas fields. (g) The possibility to monetize small stranded gas fields by using the new small mobile GTL plants. GTL will yield synthetic hydrocarbons of the highest quality that can be used  directly  as  fuels  or  blended  with  lower  quality  crude  oil  derived fuels   to   bring   them   up   to   compliance   with   increasingly   stringent environmental  and  performance  specifications.  The  diesel  produced  by GTL  process  is  crystal  clear  in  color,  of  high  combustion  quality,  and virtually sulfur free and. The sulfur content of the GTL diesel is less than 1 ppm (wt.) compared with 50 ppm of the conventional diesel. The (EPA) organization considers the diesel to be clean if its sulfur content does not exceed 15 ppm (wt.). The aromatics in the synthesis diesel are less than 1%  (vol.)  compared  with  35%  (vol.)  in  the  conventional  diesel.  The cetane  number  of  the  GTL  diesel  is  more  than  70  while  that  of  the ordinary diesel is less than 45   . Finally, the GTL products can be used as good fuels directly, or can be blended with other bad conventional fuels to improve their properties to comply with the tight specifications put by most governments to protect the environment, and the public health. The  world  consumption  of  petroleum  products  is  increasing  steadily, while  the  production  of  crude  oil  and  the  refining  capacities  are  not increasing in the same rate. Therefore a shortage of petroleum products supply is likely to happen in the  future,  and  the  main  new  source  which  is  expected  to  cover  this shortage is by the gas to liquids technology (GTL)   . The GTL industry is expected  to  grow  rapidly  throughout  the  present  century  because  of  the sharp  ascending  of  oil  prices.  These  expensive  prices  will  make  the chance  suitable  to  invest  in  this  field.  Many  countries  are  paying  great attention  toward  their  natural  gas  resources,  and  instead  of  flaring  this valuable material it is intending to change it to valuable liquids through the GTL industry. Huge contracts are being signed by these countries and by the specialist companies and billions of dollars will be invested. The coming decade will be the true beginning of the GTL industry after about one century of its discovery. 2- Definition of the GTL Process: Gas to Liquids (GTL) is a loosely defined term that is generally used to describe the chemical conversion of natural gas to some type of liquid products.  As  such,  it  excludes  the  production  of  liquefied  natural  gas (LNG), but includes the conversion of gas to methanol, liquid fuels, and petrochemicals,  being  the  most  common  applications.  In  other  words, (3) GTL is a process for converting natural gas into synthetic fuel    , which can  be  further  processed  into  fuels  and  other  hydrocarbon  -  based products.  In  the  simplest  of  terms,  the  GTL  process  tears  natural  gas molecules  apart  and  reassembles  them  into  longer  chain  molecules  like those  that  comprise  crude  oil.  GTL,  like polymerization, is the building up of larger molecules from smaller ones. CH  4 + 1/2 O2 CO + H2 CO + 2H2 - CH -    +   H  2O However,  with  this  particular  conversion  process,  the  result  is  virtually free of contaminants such as sulfur, aromatics and metals. This synthetic crude can then be refined into products such as Diesel fuel, Naphtha, Wax and  other  liquid  petroleum  or  specialty  products.  The  GTL  technology provides  huge  income  to  the  countries  which  develop  their  natural  gas reserves through this industry, as well as to the companies which invest through these projects. Natural   gas   can   be   converted   into   synthesis   gas   (a   mixture   of predominantly  CO  and  H  2)  by  several  complicated  chemical  steps.  The Gas to Liquids process is based on the following primary steps: (a) The desulphurization of natural gas (natural gas treatment). (b)The conversion of dry natural gas into synthesis gas. (c) The conversion of synthesis gas into synthetic crude. (d)Products upgrading.

3- The Synthesis Gas: In  the  latter  half  of  the  nineteenth  century,  complete  gasification  of coke  was  achieved  commercially  by  means  of  cyclic  gas  generator  in which the coke was alternately blasted with air to provide heat and steam to generate "Blue Water Gas", a name given to the gas because it formed from steam and burned with blue flame     . The discovery of blue gas is attributed to Fontana in 1780, who proposed making it by passing steam over incandescent carbon. The blue gas was composed of about 50% H2

and  40%  CO,  with  remainder  about  equal  parts  CO  2  and  N  2.  It  had  a calorific   value   of   about   11   MJ/m .   In   the   nineteenth   century,   gas distribution  networks  were  rapidly  built  up  in  most  large-  and  medium- size  cities,  particularly  in  the  industrialized  European  countries,  along with  gasworks  for  the  manufacture  of  the  blue  gas.  The  production  is carried  out  by  the  reaction  of  steam  on  incandescent  coke  (or  coal)  at temperatures around 1000 C and higher, where the rate and equilibrium are favorable, according to the principle equation:

C (amorphous) + H  2O (g)

CO (g)

+ H 2 (g)

H =

+ 53,850 Btu

Another reaction also occurs, apparently at several hundred degrees lower temperature:

C (amorphous) + 2H  2O (g)

CO2 (g)

+ 2H 2 (g)

H =

+ 39,350 Btu

These  hydrolysis  reactions  (reaction  with  water)  are  endothermic  and therefore   tend   to   cool   the   coke   (or   coal)   bed   rather   rapidly,   thus necessitating alternate "run" and "blow" periods. During the run period, the  foregoing  blue-gas  reactions  take  place,  and  salable,  or  make,  gas results; during the blow period, air is introduced and ordinary combustion ensues, thus reheating the coke to incandescence and supplying the Btu's required by the endothermic useful gas-making reactions plus the various heat  losses  of  the  system.  The  oxygenolysis  reactions  (reaction  with oxygen) are:

C (amorphous) C (amorphous)

+ O 2 (g) + CO 2 (g)

CO 2(g) 2CO (g)

H = - 173,930 Btu H = + 68,400 Btu

The name "Blue Water Gas" of the mixture CO and H 2 was changed to "Synthesis  Gas"  or  "Syngas",  a  name  which  is  given  to  mixtures  of gases  in  suitable  properties  for  the  production  of  synthesis  products without adding further reactants. Synthesis gas is composed primarily of carbon monoxide and hydrogen, and it is an odorless, colorless and toxic gas.  Its  specific  gravity  depends  to  percent  of  hydrogen  and  carbon monoxide  content,  and  will  burn  flameless  when  introduced  to  air  and o temperature  of  574 C.  Synthesis  gas  can  be  used  as  a  fuel  to  generate electricity or steam or used as a basic chemical building block for a large number  of  uses  in  the  petrochemical  and  refining  industries.  It  is  also utilized  as  a  source  of  hydrogen  for  production  of  methanol,  ammonia

and hydrogen delivery in gas treating operations and even as fuel.