Petrochemicals and Biofuel

Use of Fischer-Tropsch to Convert Gas Coal or Biomass to Crudes

Section 1

FISCHER-TROPSCH SYNTHESIS

History Fischer-Tropsch Synthesis • In 1923, Two German scientists Franz Fischer and Hans Tropsch discovered synthesis gas could be converted into heavier hydrocarbons suitable as synthetic fuels • The Germans used Fischer-Tropsch (F-T) technology during World War II to produce 4.5 Million Barrels of Synthetic oil from coal to fuel the German Army • In 1955 Sasol-I was built by the South African Govt. to product synthetic oil from coal

• Expanded by building Sasol-II and Sasol-III in the 1980s • Current capacity is approximately 160 KB/D of synthetic oil

• Coal based Fischer-Tropsch is proven Technology operated successfully in South Africa for over 50 years

History of Gas-to- Liquids • The South African Govt. built a 12.5 Kb/D plant based on natural gas feed (GTL) at Mossel Bay SA in 1991 • Shell built a 12.5 KB/D GTL plant using natural gas at Bintulu Malaysia in 1993 • Qatar Petroleum and Sasol built a 35 KB/D GTL plant at Ras Laffan Qatar that started up in 2007. • To date GTL and CTL been technical successes with questionable economic viability. • Enormous investment cost is difficult to justify even with very low feed costs

History Fischer-Tropsch Synthesis (cont.) • More recently there has been interest in using operate a large plantBiomass, vegetation or wood chips as feed to F-T gasifier feed. • Small demonstration plants ( CH2 + H2O • Polymerization CH2 + CnH2n => Cn+1 H2n+2 • Termination CnH2n + H2 => CnH2n+2 • The distribution of N-Paraffin products is determined by the relative probability of polymerization instead of termination dfined as a

Fischer-Tropsch Product Distribution • Mechanism is similar to many other Polymer reactions: • Monomer formation: CO + 2H2 => CH2 + H2O • Polymerization CH2 + CnH2n => Cn+1 H2n+2 • Termination CnH2n + H2 => CnH2n+2 • The distribution of N-Paraffin products is determined by the probability that the chain continues to polymerize instead of terminating this probability is defined as a

Fischer-Tropsch Product Distribution • Mechanism is similar to many other Polymer reactions: • Monomer formation: CO + 2H2 => CH2- + H2O • Polymerization CH2-+ CnH2n- => Cn+1 H2n+2• Termination CnH2n- + H2 => CnH2n+2 • The distribution of N-Paraffin products is determined by the probability that the chain continues to polymerize instead of terminating this probability is defined as a • For commercial catalyst a varies between 0.5 and 0.95

Fischer-Tropsch Product Distribution • Described mathematically by the AndersonSchulz-Flory Distribution • PredictsWeight fraction by carbon no: – Wn = (1- a )2 a n-1

Fischer-Tropsch Product Qualities • Product quality depends on catalyst • Cobalt based catatyst primarily produces N-paraffins • Iron based catalyst produces more Oxygenates (primarily alcohols) and Olefins as byproducts.

• Lower temperature and higher activity catalyst tend to produce heavier products (higher a ) • Exceptionally high quality Diesel (80+CN) and Jet product • Naphtha Octane is low but may have high value as petrochemical feedstock • Heavy Wax is excellent FCCU or Lubes plant feed • Often mildly hydrocracked to form diesel • Plants that produce large amounts of light olefins will oligomerize C3/C4 olefins to produce addition diesel.

Fischer Tropsch Process Summary • Fischer –Tropsch (F-T) is a mature technology that has been successfully operated commercially for over 50 years. • The F-T process using synthesis gas ( a combination of Co and H2 ) as a building block to produce high quality synthetic crudes. • F-T feedstock is extremely flexible because any Hydrocarbon can be converting into synthesis gas via partial oxidation or steam reforming reactions • F-T products are a broad range of Hydrocarbons that required additional processing to maximize value.

Section 2

XTL PROCESS CONFIGURATIONS

Fischer-Tropsch Process Configurations • Three Step Process • Syngas Generation • F-T Synthesis • Product Upgrading

• Overall configuration is very similar for gas,coal or biomass feeds. • Syngas generation section must have a gasifier for solid feeds and solids handling facilities for feed and ash. • Conventional Steam Reforming followed by Secondary Reforming is typical for Natural gas feeds • F-T reaction and upgrading is the same independent of feed source – Mild Hydrocracking to maximize diesel is the most common upgrading method.

Typical GTL Process Flow Removed CO2 Air

Air Separation

Naphtha

Light Product HDS

O2

Kero

CO2 removal

F-T Liquid F-T Reaction

Feed Gas

Secondary Reformer

Steam

Primary Reformer

F-T Gas loop

Syn Gas

PSA: H2 removal for Hydroprocessing

Diesel

Vacuum Flash distillation

Liquid Product Separation

Wax hydrocracking

Wax Recycle Main Process Flows Recycles Air and O2

PROPRIETARY INFORMATION

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Steam Hydrogen

Typical CTL/BTL Process Flow Removed CO2 Air

Air Separation

Naphtha

Light Product HDS

O2

Kero

CO2 removal


Feed Coal/Biomass Gasifier Steam

Autothermal Reformer

F-T Gas loop

Syn Gas


Diesel



Wax hydrocracking



15

Steam Hydrogen

Syngas Generation Targets • Cobalt Catalyst – Only CO and H2 react

– All CO2 separated (component splitter) – CO2 recycle to Secondary controlled with “Adjust” to maintain desired H2 / CO ratio (approx 2.1)

• Iron Catalyst- CO2 also reacts

– Water has shift also occurs CO2 + H2  C0 + H2O – Amount removed controlled using Adjust to give Syngas with desired Riblett Ratio (1.0-1.05) • Riblett Ratio = H2 / (2*CO + 3*CO2)

– Some CO2 is removed for Riblett ratio control PROPRIETARY INFORMATION

16

F-T “Gas Loop” Considerations • Syngas conversion at F-T reactors is typically 6080% per pass – Product is flashed and flash gas is recyled – Unconverted Synthesis gas is recycled along with C4produced in the in the F-T reactor. – Small purge to syngas generation to prevent C1-C4 build up in recycle ”gas loop”.


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F-T “Gas Loop” Considerations • Syngas conversion at F-T reactors is typically 6080% per pass – Product is flashed and flash gas is recyled – Unconverted Synthesis gas is recycled along with C4produced in the in the F-T reactor. – Small purge to syngas generation to prevent C1-C4 build up in recycle ”gas loop”.


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Integrating F-T Into an existing Refinery • Petroleum coke is gasified to produce Syn Gas – A portion could be used for H2 production or power generation – Remaining Syngas goes to a F-T reactor to produce additional high quality refinery products. – Heavy F-T wax is excellent quality FCCU or HCU feed


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Integration of CTL into an existing Refinery Low Btu Gas to Refinery

Pet Coke Sweet Syngas

Sour Syngas

Scrubber

Gasifier

F-T Slurry Reactor

Sep Drum

Char and Slag

Purge gas

Naphtha

H2

HCU + Separator Drum

Diesel

Fractionator

Wax

Hydrocracked Wax + Lighter

F-T Liquid to FCC Feed HT Fractionator

Section 3

SYNGAS GENERATION AND PRODUCT UPGRADING

Syngas Generation Process Options • Catalytic Reforming of Natural gas in a Steam Methane Reformer. • Partial Oxidation of Coal/Biomass or Natural Gas • Catyaytic Secondary Reforming or “Autothermal Reforming” of Natural gas and/or Primary Reforming effluent over a fixed bed at 950-1000C • Gasification of Coal or Biomass typically at 1000-1300 C. • Gasification is considerably less reliable than reforming (8085% vs 99%) • Requires spare

• CO2 Removal and operating conditions adjusted to achieve H2/CO ratio or Riblett ratio target


Air Separation

Naphtha

Light Product HDS

O2

Kero

CO2 removal




F-T Gas loop

Syn Gas


Diesel



Wax hydrocracking



23

Steam Hydrogen

Steam Methane Reforming Furnace

Gasification Reactor

Syngas Generation Chemistry • Partial Oxidation Reactions (O2 limited): • CxHy + ½ x O2 => x CO + ½ y H2 • CO + ½ O2 => CO2 • H2 + ½ O2 => H2O • Reforming: CH4+ H2O  3H2+ CO • Equilibrium limited:

Kref = P2(CO)(H2)3 /((CH4)(H20)) • Water gas Shift: CO + H2O  H2 + CO2

Kshift = (CO2)(H2)/((CO)(H20)


Air Separation

Naphtha

Light Product HDS

O2

Kero

CO2 removal




F-T Gas loop

Syn Gas


Diesel



Wax hydrocracking



27

Steam Hydrogen

Product Upgrading Options • Fractionation to recover Naphtha, Jet and Diesel Products: • Diesel and Jet is extremely high quality • Gasoline Octane is low • Naphtha Specialty chemical value may be higher with expensive recovery options like Molex. • F-T wax (heavier than diesel cut) can be converted to high quality diesel in low severity HydroIsom/Hydrocracking reactor • May be more valuable as specialty wax or lubricants but market Is limited

Summary • Fischer-Tropsh is a commercially proven technology that can be used to convert any Hydrocarbon into a high value synthetic crude. • It is a three step process: • Syngas generation • F-T Synthesis • Product Upgrading

• The Diesel and Jet product is extremely high quality • Investment cost is extremely high. • Economics are more attractive than they have been in the past because of low natural gas prices and high crude oil values.

Backup Material



Oxygen Coal Water

