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Fischer-Tropsch Products
Separation Train Team #6 Sydney Almeida Ida Shinder Emilia Tanu Noah Wichrowski
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PROCESS OVERVIEW GASIFICATION FISCHER-TROPSCH REACTION
SEPARATION AND PRODUCT UPGRADING BIOMASS COAL NATURAL GAS SYNGAS (CO AND H2) SYNTHETIC CRUDE OIL DIESEL NAPHTHA JET FUEL 1 2 3 Step 2 results in long chain waxy molecules (to avoid unwanted small hydrocarbons/gas byproducts). From this step, a diesel fraction can be separated (not shown) by vacuum distillation (source: ) the remaining waxy products are then hydroprocessed ( hydro-isomerisation and hydrocracking) to produce the desired, lighter products. (Source: ) Adapted from (de Klerk, 2012).
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Fischer-Tropsch (FT) Reaction
Catalytic chemical reaction where carbon monoxide (CO) and hydrogen (H2) produced by the gasification of coal (syngas) are converted to hydrocarbons or liquid fuel. Main Reactions: (2n+1) H2 + n CO CnH(2n+2) + n H2O 2n H2 + n CO CnH2n + n H2O Side Reactions: CO + H2O H2 + CO2 2n H2 + n CO CnH(2n+2)O + (n-1) H2O 2 CO C + CO2 The process objective is to produce hydrocarbons of larger molecular weight and thus, products of higher economic value. The side reaction is generally undesired, this reaction occurs during the gasification of coal, producing carbon dioxide. In gas to liquid processes, methane can be used as an FT reactant. Time: 1 minute Besides the hydrocarbons that must be separated - need to also get rid of water and +CO2 (for all reactions listed) (van der Laan, 1999)
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FT PRODUCTS SEPARATION HEURISTICS: CORROSIVENESS MOLECULAR WEIGHT COMPONENT CONDENSING ABILITY COMPONENT SEPARABILITY DESIRED PRODUCT IN THE DISTILLATE COMPONENTS IN EXCESS HYDROCARBONS LIGHT (METHANE) LIQUID (FUEL) OLEFINS (ALKENES) PARAFFINS (ALKANES) LOW AMOUNTS OF OXYGENATES (ALCOHOL AND ORGANIC ACIDS) DIESEL GASOLINE JET FUEL NAPHTHA PETROLEUM FT products should be long/waxy hydrocarbons. Note 1/30 (8:23 PM): Add something about general desired undesired products, then specify for separation train specific. = Wax and condensate (recovered from overhead vapor) separated from the catalyst in the reactor. (Ghosh, Hickey, & Jaffe, 2006) (Towler & Sinnott, 2013)
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PROCESS FLOW DIAGRAM GASIFICATION FT REACTOR
SEPARATION AND PRODUCT UPGRADING Note: recycle gases (C1-C4) back to FT reactor (not shown in PFD - could redirect the light recovery stream - there are multiple). Although this PFD focus on Natural gas as the starting point of syn gas sequence - the choice of feed does not have a huge impact on product separation (?) (Shuster, 2013)
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SEPARATION SEQUENCE CO2 REMOVAL FUEL GAS/AQUEOUS OXYGENATES
FRACTIONAL DISTILLATION (Shuster, 2013)
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Fractional Distillation
Citation: (Bowen, Irwin, & Canchi, 2007)
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Fractional Distillation
Product fractionator divides hydrocarbons into vapor stream (light hydrocarbons) and three liquid streams. The vapor stream is combined with light hydrocarbon recovery from product upgrading into the fuel gas pool. NAPHTHA MIDDLE DISTILLATE WAX HYDROTREATING HYDROTREATING HYDROCRACKING Naphtha saturates up to 177 degrees C Middle Distillate saturates between degrees C Wax (heavy hydrocarbons) saturates after 343 degrees C (Griesbaum et al., 2005; Cherqaoui & Villemin, 1994)
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PRODUCT UPGRADING C4, C5/C6 ISOMERIZATION/ALKYLATION
NAPHTHA HYDROTREATING AND REFORMATION WAX HYDROCRACKING DISTILLATE HYDROTREATING (Shuster, 2013)
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Butane Isomerization and Alkylation
Converts nC4 to iC4 for better usage as a reactant for alkylation C5/C6 isomerization changes n-paraffins to branched isoparaffins for a higher octane rating Hydrogen is used to prevent dehydrogenation and coking (Ophardt, 2003) (Sie Neftehim, n.d.)
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Naphtha Hydrotreating And Reformation
Uses hydrogen to convert olefins → paraffins Reformation Improves octane number by increasing aromatic content and decreasing olefin content Produces hydrogen used in hydrotreating Primary Reactions: Dehydrogenation: naphthenes → aromatics Isomerization: paraffins → branched paraffins (first paragraph is good) (Jechura, 2016)
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WAX HYDROCRACKING TWO MAIN REACTIONS:
CATALYTIC CRACKING OF LONG CARBON CHAINS (WAX AND OILS) INTO LIGHTER, MORE VALUABLE HYDROCARBONS SATURATING THE NEW HYDROCARBONS WITH HYDROGEN Hydrocracking -“Cracks” or fractionates gas oil, which has a higher boiling point, into the distillate molecules used in gasoline (with hydrogen and a catalyst) -Reaction 1: catalytic cracking of long carbon chains into unsaturated hydrocarbons -Reaction 2: saturation of these new hydrocarbons with hydrogen -Hydrogen is also used to control the temperature of the process, as high temperatures are needed into hydrocracking but within safe limits -Energy is consumed when the hydrocarbons are broken and released when the carbon hydrogen bonds are made (“Hydrocracking …”, U.S. Energy Information Administration)
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Distillate Hydrotreating
Improves quality of distillate products like: Kerosene Jet fuel diesel oil Product properties: Smoke Point Stability Color Odor Aromatic Composition (“Hydrotreating,” Shell Global)
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QUESTIONS? COMMENTS? Summary?
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References Ansorge, J. “Shell Middle Distillate Synthesis: Fischer-Tropsch Catalysis in Natural Gas Conversion to High Quality Products,” Shell International Oil Products B.V (n.d.) Bacha, J. et al. “Diesel Fuels Technical Review,” Chevron (2007). Bowen, B. H.; Irwin, H. W.; Canchi, D. “Coal-to-Liquids (CTL) & Fischer-Tropsch Processing (FT),” Purdue University (2007). Cherqaoui, D.; Villemin, D. “Use of a Neural Network to Determine the Boiling Point of Alkanes,” J. Chem. Soc. Faraday Trans., 1994, 90(1), de Klerk, A. “Gas-to-Liquids Conversion,” US Department of Energy (2012). "Distillate Hydrotreating." Honeywell UOP, Honeywell International Inc., 2017, Accessed 31 Jan Ghosh, P.; Hickey, K. J.; Jaffe, S. B. “Development of a Detailed Gasoline Composition-Based Octane Model,” Ind. Eng. Chem. Res. 2006, 45, Griesbaum, K et al. "Hydrocarbons" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. "Hydrocracking is an important Source of Diesel and Jet Fuel." U.S. Energy Information Administration, 18 Jan. 2013, Accessed 31 Jan "Hydrotreating." Shell Global, Accessed 31 Jan Jechura, J. "Gasoline Upgrading: Catalytic Reforming, Isomerization, and Alkylation." Colorado School of Mines (2016). Accessed 31 Jan Rockwell, J. “Gas-to-Liquids,” ConocoPhillips (2003). Shuster, E. “Analysis of Natural Gas-to-Liquid Transportation Fuels via Fischer-Tropsch,” US Department of Energy (2013). Sie Neftehim, LLC “Butane Isomerization Isomalk-3” (n.d.). Accessed 31 Jan Towler, G. T.; Sinnott, R. Chemical Engineering Design: Principles, Practice, and Economics of Plant and Process Design, Butterworth-Heinemann: Waltham, MA (2013). van der Laan, G. P. “Kinetics, Selectivity, and Scale-up of the Fischer-Tropsch Synthesis,” University of Groningen (1999). “What is Gasoline?” Elmhurst College (2003), Accessed 31 Jan
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