CONVERSION OF BIOMASS TO BIOFUELS WSU ChE 481/581 & UI BAE 504 LECTURER: MANUEL GARCIA-PEREZ, Ph.D....
-
Upload
dakota-kennett -
Category
Documents
-
view
218 -
download
0
Transcript of CONVERSION OF BIOMASS TO BIOFUELS WSU ChE 481/581 & UI BAE 504 LECTURER: MANUEL GARCIA-PEREZ, Ph.D....
CONVERSION OF BIOMASS TO BIOFUELS
WSU ChE 481/581 & UI BAE 504
LECTURER: MANUEL GARCIA-PEREZ , Ph.D.
Department of Biological Systems Engineering205 L.J. Smith Hall, Phone number: 509-335-7758
e-mail: [email protected]
MEEETING PLACE: EME B46, TUESDAY AND THURSDAY 1:25-2:40 AM
CREDIT HOURS: 3
THERMOCHEMICAL CONVERSION SECTION
OUTLINE OF OUR PREVIOUS LECTURE
A.- GASIFICATION
B.- COMBUSTION
C.- HYDROTHERMAL CONVERSION
LECTURE 1
INTRODUCTION TO BIOMASS THERMOCHEMICAL CONVERSION TECHNOLOGIES AND THERMO-CHEMICAL REACTIONS
LECTURE 2
TORREFACTION AND PYROLYSIS (SLOW AND FAST)
LECTURE 3
GASIFICATION, COMBUSTION AND HYDROTHERMAL CONVERSION
LECTURE 4
CHARACTERIZATION AND USES OF PRODUCTS OF THERMOCHEMICAL REACTIONS (THERMOCHEMICAL BIO-REFINERIES)
OVERVIEW OF THE THERMOCHEMICAL SECTION
FOURTH LECTURE OUTLINE
CHARACTERIZATION AND USES OF PRODUCTS OF THERMOCHEMICAL REACTIONS (THERMOCHEMICAL BIO-REFINERIES):
A.- BIO-OIL
C.- SYNTHESIS GAS
B.- BIO-CHAR
A.- BIO-OIL
PYROLYSIS OIL IS A DARK-BROWN, FREE FLOWING LIQUID FUEL DERIVED FROM PLANT MATERIAL VIA FAST PYROLYSIS. PYROLYSIS OIL CAN BE STORED, PUMPED AND TRANSPORTED LIKE PETROLEUM PRODUCTS AND CAN BE COMBUSTED DIRECTLY IN BOILERS, GAS TURBINES, AND SLOW TO MEDIUM SPEED DIESEL FOR HEAT AND POWER. IT HAS A DENSITY OF 1.2 kg/L, AND HEATING VALUE 16-19 GJ/t (APPROXIMATELY 55 % OF THE HEATING VALUE OF DIESEL ON A VOLUMETRIC BASIS AND 45 % ON A WEIGHT BASIS). PYROLYSIS OIL IS NOT DANGEROUS BUT IT IS ACIDIC. pH IS 2-3 COMPARED WITH DIESEL AT pH 5. IT IS NOT AN HOMOGENEOUS LIQUID. IF LEFT STANDING FOR LONG PERIODS, LIGNIN WILL EVENTUALLY PRECIPITATE.
THE ACIDIC AND CORROSIVE NATURE OF PYROLYSIS OIL MEANS THAT ENHANCEMENTS ARE REQUIERED FOR STORAGE AND TRANSPORTATION, BUT THESE ARE NOT ONEROUS. STORAGE VESSELS AND PIPING SHOULD BE STAINLESS 304, PVC, TEFLON OR LIKE SUBSTANCES.
Bradley D: European Market Study for Bio-oil (Pyrolysis Oil) Climate Change Solutions. National Team Leader – IEA Bioenergy Task 40-Biotrade.
BLADES BEFORE COMBUSTION BLADES AFTER COMBUSTION
ORENDA TURBINE
Brown R, Holmgren J: Fast Pyrolysis and Bio-Oil Upgrading . http://www.ars.usda.gov/sp2UserFiles/Program/307/biomasstoDiesel/RobertBrown& JenniferHolmgren presentationslides.pdf
DIRECT USE AS A FUEL
A.- BIO-OIL
THE CRUDE BIO-OIL CAN BE USED FOR THE GENERATION OF HEAT AND ELECTRICAL POWER. THE COMBUSTION OF PYROLYSIS OILS IN INTERMEDIATE SIZE BOILERS (100 kW to 1 MW) SEEMS TO BE ECONOMICALLY VIABLE. SEVERAL RESEARCH PROGRAMS HAVE BEEN UNDERTAKEN TO ADAPT MORE EFFICIENT SYSTEMS (TURBINES, STATIONARY DIESELS, BOILERS) TO BE ABLE TO OPERATE WITH BIO-OILS AS FUEL.
Meier D, Faix O: State of the art of applied fast pyrolysis of lignocellulosic materials- a review. Bioresource Technology 68 (1999) 71-77
THE HEATING VALUE OF BIO-OILS (ABOUT 17 MJ/kg WET WEIGHT BASIS OR 22 MJ/kg DRY WEIGHT BASIS) IS TYPICALLY ABOUT HALF OF THAT OF No 2 FUEL OIL. IT DOES NOT BURN EFFICIENTLY WITHOUT PRE-HEATING AND TEND TO GEL AFTER SITTING FOR PROLONGED PERIODS OF TIME. BECAUSE OF THESE PROPERTIES BIO-OIL DOES NOT CURRENTLY APPEAR TO BE A GOOD SUBSTITUTE FOR No 2 FUEL IN HOME HEATING APPLICATIONS.
BIO-OILS CAN BE USED IN INDUSTRIAL BOILERS BUT REQUIRES THE BOILER BE EQUIPPED WITH STAINLESS STEEL OR PLASTIC-LINED, FUEL INJECTION COMPONENTS AND STORAGE TANKS TO RESIST CORROSION, A SYSTEM THAT HEATS AND/OR STIRS THE BIO-OIL DURING STORAGE PREVENTING GELLING, AND A SYSTEM THAT PRE-HEATS THE INCOMING BIO-OIL TO A TEMPERATURE HIGH ENOUGH TO ENSURE A GOOD ATOMIZATION.
Laid DA, Brown RC, Amonette JE, Lehmann J: Review of the Pyrolysis Platform for coproducing bio-oil and bio-char. Bio-fuels, Bioproducts & Biorefining. 2009, 547-561
BIO-OIL COMPOSITION
CELLULOSE
WATER H2O
5-HYDROXYMETHYL FURFURAL
HEMICELLULOSE
LIGNIN
METHANOLCH3OH
GLYOXAL
H-C-C-H
O O
FORMALDEHYDE
H-C-H
O
FORMIC ACID
H-C-OH
O
HYDROXYACETALDEHYDE DIMER
HO
O
O
OH
ACETOL
CH3-C-CH2OH
O
ACETIC ACID
H3C-C-OH
O
CYCLOPENTANONEO
FURANS
2-FURALDEHYDE
OO O
OH
FURFURYL ALCOHOL
PHENOL
OH OH
CRESOL
CH3
VANILLIN
OHOCH3
O H METHANOLCH3OH
OHOCH3
O H
H3CO
VANILLIN
HO OCH3
CH3
EUGENOL
LEVOGLUCOSAN
OH
OHOH
OO
CELLOBIOSE
OH
OH
OOH
OH
OH
OH
OOH
OH
OH
OH
OHOH
OOH
SUGARS
XYLOSEARABINOSE
OH
HOO
OH
ETHYLENE GLYCOL
HOCH2CH2OH
H
OO
HHO
A.- BIO-OIL
PRODUCTS OF LIGNIN
A.- BIO-OIL
Bayerbach R, Meier D: Characterization of the water-insoluble fraction from fast Pyrolysis liquids (pyrolytic lignin) Part IV: Structure elucidation of oligomeric molecules. Journal of Analytical and Applied Pyrolysis, 85 (2009) 98-107.
MAIN MONOMERS OBTAINED FROM THE PYROLYSIS OF LIGNIN
DIMERIC STRUCTURE IN PYROLYTIC LIGNIN
BOILING POINT (100-200 oC) (Yield: 4-5 mass %)
WATER INSOLUBLE-CH2Cl2 SOLUBLE COMPOUNDS (Yield: 10-12 mass %)
A.- BIO-OIL
Bayerbach R, Meier D: Characterization of the water-insoluble fraction from fast Pyrolysis liquids (pyrolytic lignin) Part IV: Structure elucidation of oligomeric molecules. Journal of Analytical and Applied Pyrolysis, 85 (2009) 98-107.
STRUCTURAL PROPOSAL OF PYROLYSIS LIGNIN FOR (A) TETRAMETERS (B) PENTAMERS (C) HEXAMERS (D) HEPTAMERS (E) OCTAMERS
A B
B D
E
WATER -CH2Cl2 INSOLUBLE COMPOUNDS (YIELD AROUND 2 mass %)
A.- BIO-OIL
Meier D, Faix O: State of the art of applied fast pyrolysis of lignocellulosic materials- a review. Bioresource Technology 68 (1999) 71-77
Laid DA, Brown RC, Amonette JE, Lehmann J: Review of the Pyrolysis Platform for coproducing bio-oil and bio-char. Bio-fuels, Bioproducts & Biorefining. 2009, 547-561
BIO-OIL PRODUCED BY FAST PYROLYSIS OF CELLULOSIC BIOMASS IS AN EMULSION OF WATER (APPROXIMATELY 20 mass %) AND A WIDE RANGE OF ORGANIC COMPOUNDS INCLUDING ORGANIC ACIDS, ALDEHYDES, ALCOHOLS, PHENOLS, CARBOHYDRATES AND LIGNIN DERIVED OLIGOMERS.
Bayerbach R, Meier D: Characterization of the water-insoluble fraction from fast Pyrolysis liquids (pyrolytic lignin) Part IV: Structure elucidation of oligomeric molecules. Journal of Analytical and Applied Pyrolysis, 85 (2009) 98-107.
Brown R, Rover M, Li M, Kuzhiyi N, Johnston L, Jones S: What does it mean to characterize bio-oil? TC Biomass Conference, Chicago, IL, September 16-18, 2008
0
1
2
3
4
5
6
7
8
9
0 100 200 300 400 500
Temperature ( o C)
DT
G (
mas
s %
/min
)
A
B
C DE
F
A.- BIO-OIL
MONO-PHENOLS AND FURANS
WATER + ACETIC ACID + ACETOL
FORMIC ACID+ HAA
SUGARS
LIGNIN OLIGOMERS
OLIGOSUGARS
GC/MS
GC/FID
Crude Bio-oils
Family A,B Ethanol
Hydroxyacetaldehyde
Acetic acid
Formic acid
Acetaldehyde
Methyl glyoxal
Glyoxal
Acetol
Propionic acid
AcetoneMethyl formate
Methanol
Family C PhenolFurfuryl alcohol
CatecholHydroquinoneBernzenediol
Syringaldehyde
3-ethylphenol
LevoglucosanCellobiosan1,6-anhydroglucofuranoseFructose
Family D, F
Family E Oligomers
HYDROLYSIS AND FERMENTATION
(ETHANOL)
-C=O NH3
SLOW RELEASE FERTILIZER
-COOH
NOXOLENETM (NOx Reduction)
LimeBIOLIMETM
(NOx/SOx Reduction)
Phenolics
ADHESIVES, SUFACTANTS ADVANCED CARBONS
WOOD PRESERVATIVES
RESINS
SUFACTANTS
SteamAll functional
groups
SYNTHESIS GAS, HYDROGEN
Carbonyl groups
Carboxyl groups
Extractive derived comp.
APPLICATIONS USING THE WHOLE BIO-OILS APPLICATIONS USING FRACTIONS
SPECIAL CHEMICALS
DE- ICERS
RESINSANTI-OXIDANTSCO-POLYESTERS, CO-POLYAMIDESSUFACTANTS
SOLVENTSFUELS
HOW TO SEPARATE BIO-OIL FRACTIONS?
A.- BIO-OIL
USES
A.- BIO-OIL
THE ISOLATION OF CHEMICALS AND PRODUCING SPECIAL PRODUCTS BASED ON PYROLYSIS OILS IS AN ACTIVE AREA OF RESEARCH. SEVERAL PRODUCTS FROM BIO-OILS HAVE BEEN DEVELOPED: LIQUID SMOKE, PHENOL FORMALDEHYDE RESINS, PHENOLICS, LEVOGLUCOSAN, LEVOGLUCOSANONE, OCTANE ENHANCER, SLOW RELEASE FERTILIZER, NOX/SOX REDUCERS (BIOLIMETM). PYROLYTIC ACETIC ACID MEETS BETTER THE NEEDS OF ELECTRONIC CHIPS PRODUCTION. CREOSOTE, A FRACTION OF WOOD TAR, IS TRADITIONALLY USED IN THE PHARMACEUTICAL INDUSTRY, AND WATER FREE WOOD TARS IN VETERINARY MEDICINE.
Meier D, Faix O: State of the art of applied fast pyrolysis of lignocellulosic materials- a review. Bioresource Technology 68 (1999) 71-77
Laid DA, Brown RC, Amonette JE, Lehmann J: Review of the Pyrolysis Platform for coproducing bio-oil and bio-char. Bio-fuels, Bioproducts & Biorefining. 2009, 547-561
BIO-OIL CAN BE UP-GRADED INTO SYNTHETIC TRANSPORTATION FUELS. ONE APPROACH WOULD GASIFY BIO-OIL AND CONVERT SYNGAS TO SYNTHETIC GASOLINE AND DIESEL THROUGH FISCHER-TROPSCH (F-T) CATALYTIC SYNTHESIS. THE EUROPEAN UNION (EU) IS CONSIDERING THE DEVELOPMENT OF A DISTRIBUTED NETWORK OF BIOMASS PYROLYZERS THAT WOULD SUPPLY BIO-OIL TO A CENTRALIZED F-T REFINERY. THE HIGH INITIAL INVESTMENT REQUIRED TO BUILD A F-T REFINERY IS THE BIGGEST OBSTACLE TO THE ADOPTION OF THIS APPROACH IN THE US. FURTHERMORE F-T REFINERIES HAVE LOW CARBON-CONVERSION EFFICIENCIES (ABOUT 50 %).
A.- BIO-OIL
BIO-OIL REFINERIES (BIO-OIL FERMENTATION)
Brown R, Holmgren J: Fast Pyrolysis and Bio-Oil Upgrading . http://www.ars.usda.gov/sp2UserFiles/Program/307/biomasstoDiesel/RobertBrown& JenniferHolmgren presentationslides.pdf
TO PRODUCE GASOLINE AND DIESEL
A.- BIO-OIL
ANOTHER APPROACH WOULD HYDROCRACK BIO-OIL TO TRANSPORTATION FUELS IN A MANNER SIMILAR TO THE REFINING OF PETROLEUM TO GASOLINE. BIO-OIL VAPORS WILL BE RECOVERED AS A CARBOHYDRATE-DERIVED AQUEOUS PHASE AND A LIGNIN RICH FRACTION. THE AQUEOUS PHASE WOULD BE STEAM REFORMED TO HYDROGEN. THE LIGNIN FRACTION WOULD BE HYDROCRACKED TO HYDROCARBONS. THE LARGE VOLUME OF HYDROGEN REQUIRED FOR THIS PROCESS WOULD COME FROM THE STEAM REFORMER. THIS PROCESS IS ATTRACTIVE AND COULD EMPLOY THE INFRASTRUCTURE AT EXISTING PETROLEUM REFINERIES. Laid DA, Brown RC, Amonette JE, Lehmann J: Review of the Pyrolysis Platform for coproducing bio-oil and bio-char. Bio-fuels, Bioproducts & Biorefining. 2009, 547-561
BIO-OIL REFINERIES (GREEN GASOLINE FROM THE LIGNIN DERIVATIVES AND HYDROGEN FROM THE WATER SOLUBLE PHASE )
FIBROUS BIOMASS
PYRO
LYZE
R
CYCLONE
BIO-OIL RECOVERY
STEAM REFORMINGChar
Bio-oil vapor
Hydrogen
HYD
ROCR
ACKE
R
Carbohydrate derived aqueous phase
Lignin
Green Diesel
A.- BIO-OIL
REACTIVITY SCALE OF OXYGENATED GROUPS UNDER HYDROTREATMENT CONDITIONS
Elliott DC: Historical developments in Hydroprocessing Bio-oils. Energy & Fuels 2007, 21, 1792-1815
A.- BIO-OIL
HYDROTREATMENT OF WHOLE PYROLYSIS OILS
HYDROTREATING IS ONE OF THE KEY PROCESSES TO MEET QUALITY SPECIFICATIONS FOR REFINERY FUEL PRODUCTS.
HIGH PRESSURE IS USED TO ADD HYDROGEN AND PRODUCE PREMIUM DISTILLATE PRODUCTS
Mass %
Pyrolysis Oil 100H2
Feed
Products
4-5
Lt ends 15
Gasoline 30
DieselWater, CO2
851-52
Brown R, Holmgren J: Fast Pyrolysis and Bio-Oil Upgrading . http://www.ars.usda.gov/sp2UserFiles/Program/307/biomasstoDiesel/RobertBrown&JenniferHolmgren presentationslides.pdf
“38”
Jones SB, Holladay JE, Valkenburg C, Stevens DJ, Walton C, Kinchin C, Elliott DC, Czernik S: Production of Gasoline and Diesel from Biomass via Fast Pyrolysis. Hydrotreating and Hydrocracking. A Design Case. Pacific Northwest National Laboratory. US DOE. Contact DE-ACO5-76 RL)1830. PNNL-18284.
BLOCK DIAGRAM (PYROLYSIS PLANT COUPLESD WITH A BIO-OIL REFINERY) (OVER 2000 TONS/DAY)
BLOCK DIAGRAM (PYROLYSIS PLANT NOT COUPLED WITH A BIO-OIL REFINERY)
STABLE OILSUNSTABLE OILS
REFINERIES
A.- BIO-OIL
FLOW DIAGRAM FOR PYROLYSIS OIL STABILIZATION (BIO-OIL REFINERIES)
Jones SB, Holladay JE, Valkenburg C, Stevens DJ, Walton C, Kinchin C, Elliott DC, Czernik S: Production of Gasoline and Diesel from Biomass via Fast Pyrolysis, Hydrotreating and Hydrocracking: A Design Case. US Department of Energy, February 2009, PNNL-18284 Rev. 1. DE-AC05-76RL01830
PYROLYSIS OIL
HYDROGEN
FUEL GAS TO REFORMER
UP-GRADED BIO-OIL TO
DEBUTANIZER
WASTE WATER 2000 T/DAY OF HYBRID POPLAR UNIT TO PRODUCE 76 MILLION GALLONS/YEAR OF GASOLINE AND DIESEL (115 gal/t)
Cost of production: 1.74 $/gal gasoline/diesel
A.- BIO-OIL
Jones SB, Holladay JE, Valkenburg C, Stevens DJ, Walton C, Kinchin C, Elliott DC, Czernik S: Production of Gasoline and Diesel from Biomass via Fast Pyrolysis. Hydrotreating and Hydrocracking. A Design Case. Pacific Northwest National Laboratory. US DOE. Contact DE-ACO5-76 RL)1830. PNNL-18284.
HYDROCRACKING AND PRODUCT SEPARATION
REFINERIES
A.- BIO-OIL
UP-GRADED BIO-OIL
FUEL GAS TO REFORMERS
NAPHTHA
DIESEL
USES
B.- BIO-CHAR
BIOCHAR IS A COMBUSTIBLE SOLID (18 MJ/kg) THAT CAN BE BURNED TO GENERATE ENERGY IN MOST SYSTEMS THAT ARE CURRENTLY BURNING COAL. THE SUFUR CONTENT OF BIO-CHAR IS LOW AND HENCE INDUSTRIAL COMBUSTION OF BIO-CHAR GENERALLY DOES NOT REQUIRE TECHNOLOGY FOR REMOVING SOx FROM EMISSIONS TO MEET EPA EMISSION LIMITS. EMISSIONS OF NOX FROM COMBUSTION OF BIOCHAR ARE COMPARABLE TO THAT COMING FROM COAL COMBUSTION AND REQUIRE ABATEMENT TECHNOLOGY. THE ASH CONTENT OF BIO-CHAR DEPENDS SUBSTANTIALLY ON THE FEESTOCK. SOME BIOMASSES SUCH AS CORN STOVER AND RICE HUSK CONTAIN HIGH LEVELS OF Si, AND AFTER PYROLYSIS IT IS CONCENTRATED IN THE ASH. COMBUSTION OF HIGH Si BIO-CHAR WILL CAUSE SCALING IN THE WALL OF THE COMBUSTION CHAMBER AND DECREASE THE USABLE LIFE OF THESE CHAMBERS.
LOW-ASH BIO-CHARS CAN BE USE IN METALLURGY AND AS A FEEDTOCK FOR PRODUCTION OF ACTIVATED CARBON, WHICH HAS MANY USES, SUCH AS AN ADSORBENT TO REMOVE ODORANTS FROM AIR STREAMS AND BOTH ORGANIC AND INORGANIC CONTAMINANTS FROM WASTE WATER STREAMS.
Laid DA, Brown RC, Amonette JE, Lehmann J: Review of the Pyrolysis Platform for coproducing bio-oil and bio-char. Bio-fuels, Bioproducts & Biorefining. 2009, 547-561
USES
B.- BIO-CHAR
AN EMERGIN NEW USE OF BIO-CHAR IS AS A SOIL AMENDMENT. THE HARVESTING OF CROP RESIDUES FOR THE PRODUCTION OF BIOENERGY COULD HAVE ADVERSE IMPACTS ON SOIL AND ENVRIONMENTAL QUALITY. THE HARVESTING OF RESIDUES REMOVES SUBSTANTIAL AMOUNT OF PLANT NUTRIENTS FROM SOIL AGRO-ECOSYSTEMS. UNLESS THESE NUTRIENTS ARE REPLACED BY ADDITION OF SYNTHETIC FERTILIZERS, MANURE OR OTHER SOIL AMENDMENTS, THE PRODUCTIVITY OF THE SOIL WILL DECLINE. EVEN IF SYNTHETIC FERTILIZERS ARE ADDED TO MAINTAIN SOIL FERTILITY, THE SUSTAINED REMOVAL OF CROP RESIDUES WITHOUT COMPENSATING ORGANIC AMENDMENTS WILL CAUSE A DECLINE IN LEVELS OF SOIL ORGANIC MATTER, A DECLINE IN THE CATION EXCHANGE CAPACITY, A DECLINE IN WATER HOLDING CAPACITY AND ACCELERATED ACIDIFICATION OF SOILS. THE RETURN OF THE BIO-CHAR CO-PRODUCT OF PYROLYSIS TO THE SOIL FROM WHICH THE BIOMASS WAS HARVESTED HAS ALSO BEEN PROPOSED AS A MEANS TO ENHANCE SOIL QUALITY AND THEREBY THE SUSTAINABILITY OF BIOENERGY PRODUCTION SYSTEMS. FURTHERMORE, MANY OF THE NUTRIENTS IN BIOMASS ARE RECOVERED WITH THE CHAR PRODUCT OFFERING OPPORTUNITIES FOR NUTRIENT RECYCLING.
Laid DA, Brown RC, Amonette JE, Lehmann J: Review of the Pyrolysis Platform for coproducing bio-oil and bio-char. Bio-fuels, Bioproducts & Biorefining. 2009, 547-561
THE HISTORY OF TERRA PRETA (DARK EARTH)
B.- BIO-CHAR
FRANCISCO DE ORELLANA WAS THE FIRST EUROPEAN TO EXPLORE THE CENTRAL AMAZON IN THE YEAR 1542. HE REPORTED BACK TO THE SPANISH COURT THAT A LARGE AGRICULTURAL CIVILIZATION EXISTED ALONG THE BANKS OF THE AMAZON. FOR CENTURIES, MOST PEOPLE ASSUMED THAT DE ORELLANA HAS INVENTED THE STORIES OF A CIVILIZATION IN AMAZONIA. BUT DURING THE TWENTIETH CENTURY, ANTHROPOLOGISTS FOUND EVIDENCE OF EXTENSIVE REGIONS OF TERRA PRETA SOILS WITH POT SHARDS AND OTHER ARTIFACTS ASSOCIATED WITH A LARGE CIVILIZATION. THESE SOILS HAVE HIGH CONTENTS OF BIO-CHAR EXHIBIT VERY HIGH FERTILITY COMPARED WITH THE INFERTILE OXISOLS OF THE REGION.
Laid DA, Brown RC, Amonette JE, Lehmann J: Review of the Pyrolysis Platform for coproducing bio-oil and bio-char. Bio-fuels, Bioproducts & Biorefining. 2009, 547-561
REPRESENTATIVE TERRA PRETA AND OXISOLS PROFILES.
TERRA PRETA SOILS TYPICALLY HAVE HIGHER LEVELS OF ORGANIC MATTER, HIGHER MOISTURE-HOLDING CAPACITY, AND HIGHER LEVELS OF BIOAVAILABLE N, P, Ca AND K THAN THE OXISOLS FROM WHICH THEY ARE DERIVED.
B.- BIO-CHAR
THE APPLICATION OF BIO-CHAR TO SOIL IS PROPOSED AS A NOVEL APPROACH TO ESTABLISH A SIGNIFICANT, LONG-TERM SINK FOR ATMOSPHERIC CARBON DIOXIDE IN TERRESTRIAL ECOSYSTEMS. APART FROM POSITIVE EFFECTS IN BOTH REDUCING EMISSIONS AND INCREASING THE SEQUESTRATION OF GREENHOUSE GASES. CONVERSION OF BIOMASS C TO BIO-CHAR C (SLOW PYROLYSIS) LEADS TO SEQUESTRATION OF ABOUT 50 % OF THE INITIAL C COMPARED TO THE LOW AMOUNTS RETAINED AFTER BURNING (3%) AND BIOLOGICAL DECOMPOSITION (<10 - 20 % AFTER 5 - 10 YEARS), THEREFORE YIELDING MORE STABLE SOIL C THAN BURNING OR DIRECT LAND APPLICATION OF BIOMASS. SOME ANALYSES REVELEAD THAT UP TO 12 % OF THE TOTAL ANTHROPOGENIC C EMISSIONS BY LAND USE CHANGE CAN BE OFF SET ANNUALLY IN SOIL, IF SLASH-AND CHAR IS REPLACED BY SLASH AND CHAR SYSTEMS.
Lehmann J, Gaunt J, Rondon M: Bio-char sequestration in terrestrial ecosystems – a review. Mitigation and Adaptation Strategies for Global Change (2006) 11: 403-427.
RANGE OF BIOMASS CARBON REMAINING AFTER DECOMPOSITION OF CROP RESIDUES.
BIOCHAR CAN RESULT IN A NET REMOVAL OF CARBON FROM THE ATMOSPHERE, ESPECIALLY WITH ENHANCED NET PRIMARY PRODUCTIVITY
B.- BIO-CHAR
PRODUCTION OF ACTIVATED CARBON
Ioannidou O, Zabaniotou A: Agricultural residues as precursors for activated carbon production – A review. Renewable and Sustainable Energy Reviews 11 (2007) 1966-2005
PHYSICAL ACTIVATION: IT IS A TWO CONSECUTIVE STEP PROCESS. IT INVOLVES CARBONIZATION OF A CARBONACEOUS MATERIAL FOLLOWED BY THE ACTIVATION OF THE RESULTING CHAR AT ELEVATED TEMPERATURES IN THE PRESENCE OF A SUITABLE OXIDIZING AGENT SUCH AS CARBON DIOXIDE, STEAM, AIR OR THEIR MIXTURES. THE ACTIVATION GAS IS USUALLY CO2, SINCE IT IS CLEAN, EASY TO HANDLE AND IT FACILITATES CONTROL OF THE ACTIVATION PROCESS DUE TO THE SLOW REACTION RATE AT TEMPERATURES AROUND 800 oC. CARBONIZATION TEMPERATURE RANGE BETWEEN 400 AND 850 oC, THE ACTIVATION TEMPERATURE RANGE BETWEEN 600 AND 900 oC.
CHEMICAL ACTIVATION: THE TWO STEPS ARE CARRIED OUT SIMULTANEOUSLY, WITH THE PRECURSOR BEING MIXED WITH CHEMICAL ACTIVATING AGENTS, AS DEHYDRATING AGENTS AND OXIDANTS. CHEMICAL ACTIVATION OFFERS SEVERAL ADVANTAGES SINCE IT IS CARRIED OUT IN A SINGLE STEP, COMBINING CARBONIZATION AND ACTIVATION, PERFORMED AT LOWER TEMPERATURES AND THEREFORE RESULTING IN THE DEVELOPMENT OF A BETTER POROUS STRUCTURE, ALTHOUGH THE ENVIRONMENTAL CONCERNS OF USING CHEMICAL AGENTS FOR ACTIVATION COULD BE DEVELOPED. BESIDE PART OF THE ADDITIVES USED (ZINC SALTS, PHOSPHORIC ACID) CAN BE EASILY RECOVERED. THE MOST COMMON CHEMICAL AGENTS USED ARE: ZnCl2, KOH, H3PO4 AND K2CO3. TEMPERATURES (BETWEEN 300 AND 850 oC)
STEAM-PYROLYSIS: THE RAW BIOMASS IS EITHER HEATED AT MODERATE TEMPERATURE (500-700 oC) UNDER A FLOW OF PURE STEAM, OR HEATED AT 700-800 oC UNDER A FLOW OF JUST STEAM.
B.- BIO-CHAR
Ioannidou O, Zabaniotou A: Agricultural residues as precursors for activated carbon production – A review. Renewable and Sustainable Energy Reviews 11 (2007) 1966-2005
PROPERTIES OF ACTIVATED CARBON
SURFACE AREA: THE BET SURFACE AREA OF CHAR IS IMPORTANT, BECAUSE, LIKE OTHER PHYSICO-CHEMICAL CHARACTERISTICS, IT MAY STRONGLY AFFECT THE REACTIVITY AND COMBUSTION BEHAVIOUR OF THE CHAR. THE INCREASE IN THE SURFACE AREA IS DUE TO THE OPENING OF THE RESTRICTED PORES.
SIZE OF PORES: BOTH SIZE AND DISTRIBUTION OF MICROPORES, MESOPORES AND MACROPORES DETERMINE THE ADSORPTIVE PROPERTIES OF ACTIVATED CARBONS. FOR EXAMPLE SMALL PORE SIZE WILL NOT TRAP LARGE ADSORBATE MOLECULES, AND LARGE PORES MAY NOT BE ABLE TO RETAIN SMALL ADSORBATES. MATERIALS WITH HIGH CONTENT OF LIGNIN DEVELOP ACTIVATED CARBONS WITH MACROPOROUS STRUCTURE, WHILE RAW MATERIALS WITH HIGHER CONTENT OF CELLULOSE YIELD ACTIVATED CARBON WITH A PREDOMINANTLY MICROPOROUS STRUCTURE.
ACIDIC SURFACES ARE IN GENERAL FAVOURABLE FOR BASIC GAS ADSORPTION SUCH AS AMMONIA WHILE ACTIVATED CARBONES WITH BASIC SURFACE CHEMICAL PROPERTIES ARE SUITABLE FOR ACID GAS ADSORPTION SUCH AS SULPHUR DIOXIDE.
ACTIVATED CARBON CAN ALSO BE USED TO REMOVE POLLUTANTS FROM LIQUID PHASE. MOST OF THE RELEVANT BEEN THE WASTE WATER TREATMENT, THE DRINKING WATER, THE INDUSTRIAL EFFLUENTS PURIFICATION AND GROUND WATER TREATMENT. ACTIVATED CARBONS ARE USED FOR THE REMOVAL OF PHENOLS, PHENOLIC COMPOUNDS, HEAVY METALS AND DYES, METAL IONS AND MERCURY (II). PHENOLIC COMPOUNDS EVEN IN LOW CONCENTRATIONS CAN BE AN OBSTACULE TO USE AND RE-USE WATER. PHENOLS CAUSE UNPLEASANT TASTE AND ODOUR OF DRINKING WATER AND EXERT NEGATICE EFFECTS ON DIFFERENT BIOLOGICAL SYSTEMS. THEY ALSO ADSORB ARSENIC OR CAN BE USED AS A SUPPORT CATALYST FOR LIQUID PHASE REACTIONS.
PRODUCTION AND COMPOSITION
C.- SYNTHESIS GAS: Introduction
IN PRINCIPLE SYNGAS (PRIMARILY CONSISTING OF CO AND H2) CAN BE PRODUCED FROM ANY HYDROCARBON FEEDSTOCK INCLUDING: NATURAL GAS, NAPHTHA, RESIDUAL OIL, PETROLEUM COKE, COAL AND BIOMASS. THE CONVERSION OF SYNGAS INTO LIQUID FUELS AMOUNT FOR MORE THAN HALF THE CAPITAL COST OF THESE PLANTS. THE CHOICE OF TECHNOLOGY FOR SYNGAS PRODUCTION ALSO DEPENDS ON THE SCALE OF THE SYNTHESIS GAS OPERATION. SYNGAS PRODUCTION FROM SOLID FUELS IS MORE EXPENSIVE THAN FROM NATURAL GAS BECAUSE IT REQUIRES HIGHER CAPITAL INVESTMENTS WITH THE ADDITION OF FEEDSTOCK HANDLING AND MORE COMPLEX SYNGAS PURIFIATION OPERATIONS.
Spath PL, Dayton DC: Preliminary Screening-Technical and Economic Assessment of Synthesis Gas to Fuels and Chemicals with Emphasis on the Potential for Biomass-Derived Syngas. NREL/tp-510-34929
IN ITS SIMPLEST FORM, SYNGAS IS COMPOSED OF TWO DIATIOMIC MOLECULES CO
AND H2 THAT PROVIDE THE BUILDING BLOCKS UPON WHICH AN ENTIRE FIELD OF FUEL SCIENCE AND TECHNOLOGY IS BASED. THIS MIXTURE HAD MANY NAMES DEPENDING ON HOW IT WAS FORMED AND USED: PRODUCER GAS, TOWN GAS, BLUE WATER GAS, SYNTHESIS GAS AND SYNGAS. THE BEGINNING OF THE 20th CENTURY SAW THE DAWN OF FUELS AND CHEMICALS SYNTHESIS FROM SYNGAS.
Steam ReformingOr
Partial Oxidation
Natural Gas Naphtha
Coal Biomass
CO2 + H2
CO + H2
(Syngas)
AmmoniaSynthesis
HydrotreatingHydrogenation
Fuel Cell Power
FT Synthesis of Liquid Fuels
Methanol Synthesis
Catalytic processes based on H2 or syngas are among the most basic and critically important processes in providing food, fuel, and chemical resources
C.- SYNTHESIS GAS: Introduction
Spath PL, Dayton DC: Preliminary Screening-Technical and Economic Assessment of Synthesis Gas to Fuels and Chemicals with Emphasis on the Potential for Biomass-Derived Syngas. NREL/tp-510-34929
SYNTHESIS GAS CONVERSION PROCESSES
C.- SYNTHESIS GAS: Introduction
The first ammonia synthesis plant was started-up in 1913 by BASF with a total production capacity of 30 tons per day. Synthetic ammonia production grew from 10,000 tons per year in 1913 to about 120 million tons per year in 2000. Large-scale ammonia synthesis has made it feasible for the world’s industrial-agriculture complex to feed a population of several billion people
Ammonia Synthesis
The first large-scale synthesis of methanol in 1923 from syngas marked the beginning of the modern chemical industry. Conversion to formaldehyde is currently one of the largest chemical applications of methanol and accounts for usage of about 60% of the methanol produce.
Methanol Synthesis
Fischer-Tropsch Synthesis (FTS), the production of liquid hydrocarbons from syngas, was developed by Fischer and Tropsch in the mid-1920s. It played an important role in supplying the fuel needs of Germany during World War II when its petroleum supplies were cut off and has been the main source of fuels and chemical for South Africa since the 1950s. It is a developing option for environmentally-sound production of chemicals and liquid fuels from biomass, coal, and natural gas.
Fischer-Tropsch Synthesis
C.- SYNTHESIS GAS: Introduction
Steam Reforming (SR):CnHm + nH2O = nCO + (n + 1/2m)H2
CH4 + H2O = CO + 3H2
CO2 Reforming (Dry Reforming):CH4 + CO2 = 2CO + 2H2
Partial Oxidation (POX):CH4 + ½ O2 = CO + 2H2
Autothermal Reforming (ATR)CH4 + H2O = CO + 3H2
n* (CH4 + ½ O2 = CO + 2H2)
Ho=200 kJ/mol
Ho=247 kJ/mol
Ho=-40 kJ/mol
Thermally Neutral Process Is Possible
* Gasification is a process where one oxidizes the solid with either O2 or H2O (ex. Coal Gasification)
C.- SYNTHESIS GAS: Production
SR
POX
ATR
0.0 1.0 2.0 3.0 4.0 5.0
H2/CO RatioNatural GasNaphtha
THE SYNGAS COMPOSITION, MOST IMPORTANTLY THE H2/CO RATIO, VARIES AS A FUNCTION OF PRODUCTION AND FEEDSTOCK. STEAM METHANE REFORMING YIELDS H2/CO RATIOS OF 3/1 WHILE COAL GASIFICATION YIELDS RATIOS CLOSER TO UNITY OR LOWER.
C.- SYNTHESIS GAS: Production
THE DOMINANT TECHNOLOGY FOR HYDROGEN PRODUCTION IS STEAM METHANE REFORMING. IF THE FEEDSTOCK IS METHANE THEN 50 % OF THE HYDROGEN COME FROM THE STEAM. THE REFORMIG REACTION IS HIGHLY ENDOTHERMIC AND IS FAVORED BY HIGH TEMPERATURES AND LOW PRESSURES. THE SHIFT REACTION IS EXOTHERMIC AND IS FAVORED AT LOW TEMPERATURES. IN INDUSTRIAL REFORMERS, THE REFORMING AND SHIFT REACTUONS RESULT IN A PRODUCT COMPOSITION THAT CLOSELY APPROACHES EQUILIBRIUM. THE REFORMER STEAM TO CARBON RATIO IS USUALLY BETWEEN 2-6 DEPENDING ON THE PROCESS CONDITIONS. EXCESS STEAM IS USED TO PREVENT COKING IN THE REFORMER TUBES. CONVENTIONAL STEAM REFORMING CATALYSTS ARE 10-33 mass % NiO ON A SUPPORT (ALIMINA, CEMENT OR MAGNESIA).
Spath PL, Dayton DC: Preliminary Screening-Technical and Economic Assessment of Synthesis Gas to Fuels and Chemicals with Emphasis on the Potential for Biomass-Derived Syngas. NREL/tp-510-34929
C.- SYNTHESIS GAS: Production
H2S + ZnO ZnS + H2O CO + H2O CO2 + H2
THE DOMINANT TECHNOLOGY FOR HYDROGEN PRODUCTION IS STEAM METHANE REFORMING. IF THE FEEDSTOCK IS METHANE THEN 50 % OF THE HYDROGEN COME FROM THE STEAM. THE REFORMIG REACTION IS HIGHLY ENDOTHERMIC AND IS FAVORED BY HIGH TEMPERATURES AND LOW PRESSURES. THE SHIFT REACTION IS EXOTHERMIC AND IS FAVORED AT LOW TEMPERATURES. IN INDUSTRIAL REFORMERS, THE REFORMING AND SHIFT REACTUONS RESULT IN A PRODUCT COMPOSITION THAT CLOSELY APPROACHES EQUILIBRIUM. THE REFORMER STEAM TO CARBON RATIO IS USUALLY BETWEEN 2-6 DEPENDING ON THE PROCESS CONDITIONS. EXCESS STEAM IS USED TO PREVENT COKING IN THE REFORMER TUBES. CONVENTIONAL STEAM REFORMING CATALYSTS ARE 10-33 mass % NiO ON A SUPPORT (ALIMINA, CEMENT OR MAGNESIA).
Spath PL, Dayton DC: Preliminary Screening-Technical and Economic Assessment of Synthesis Gas to Fuels and Chemicals with Emphasis on the Potential for Biomass-Derived Syngas. NREL/tp-510-34929
C.- SYNTHESIS GAS: Production
LIGHT OXYGENATED COMPOUNDS
3C2H6 + 4H2O 2CH4 + 4CO + 9H2
C CH
H
H
HH
H
Ethane Steam Reforming
Reaction Mechanism
The first step involves a rapid dehydrogenation of ethane to C2H5
C.- SYNTHESIS GAS: Production
C2H5OH + 3H2O 2CO2 +6H2
C CH
H
OH
HH
H
C CH
HH
H
C CH H
OH
H
dehydrogenation-H2
dehydration-H2O
acetaldehyde
coke
CH4 + COdecomposition
steam reforming+3H2O
5H2 + 2CO2
Ethanol Steam Reforming (ESR)
??? Surface intermediates
C.- SYNTHESIS GAS: Production
ALTHOUGH STEAM REFORMING HAS BEEN AROUND FOR MANY YEARS, MORE STUDIES ON THE REFORMING OF OXIGENATED HYDROCARBONS IS NEEDED.
C.- SYNTHESIS GAS: Production
C.- SYNTHESIS GAS: Production of Ammonia
3H2 + N2 2NH3 H (500oC) = -109 kJ/mol N2
AMMONIA IS MANUFACTURED FROM NITROGEN FIXED FROM THE ATMOSPHERE AND HYDROGEN. THE PROCESS WAS DEVELOPED IN THE EARLY 1900s BY FRITZ HABER AND CARL BOSCH USING A PROMOTDED IRON CATALYST.
Catalyst: K promoted Fe
P = 125 bar
C.- SYNTHESIS GAS: Production of Ammonia
3H2 + N2 2NH3 H (500oC) = -109 kJ/mol N2
Ammonia Synthesis Loop For a Large Capacity (1000 ton per day)
(H2:N2 = 2.2-3.1:1)
C.- SYNTHESIS GAS: Production of Ammonia
3H2 + N2 2NH3 H (500oC) = -109 kJ/mol N2
C.- SYNTHESIS GAS: Production of Ammonia
3H2 + N2 2NH3 H (500oC) = -109 kJ/mol N2
At 400oC At 400oC
METHANOL SYNTHESIS BEGAN IN THE 1800s WITH THE ISOLATION OF “WOOD” ALCOHOL FROM THE DRY DISTILLATION (PYROLYSIS) OF WOOD. RESEARCH AND DEVELOPMENT EFFORTS AT THE BIGINNING OF THE 20tH CENTURY INVOLVING THE CONVERSION OF SYNGAS TO LIQUID FUELS AND CHEMICALS LED TO THE DISCOVERY OF A METHANOL SYNTHESIS PROCESS CURRENTLY WITH DEVELOPMENT OF THE FISCHER-TROPSCH SYNTHESIS. IN FACT METHANOL IS A BYPRODUCT OF FISCHER-TROPSCH SYNTHESIS WHEN ALKALI METAL PROMOTED CATALYSTS ARE USED. METHANOL SYNTHSIS IS NOW WELL-DEVELOPED WITH HIGH ACTIVITY AND VERY HIGH SELECTIVITY. FOR ECONOMIX REASONS, METHANOL IS ALMOST EXCLUSIVELY PRODUCED VIA REFORMING OF NATURAL GAS (90 % OF THE WORLDWIDE METHANOL). HOWEVER A VARIETY OF FEEDSTOCKS OTHER THAN NATURAL GAS CAN BE USED TO PRODUCE ETHANOL.
CURRENT INTEREST IN METHANOL IS DUE TO ITS POTENTIAL AS FUEL AND ITS USED AS CHEMICAL. IN PARTICULAR, METHANOL CAN BE USED DIRECTLY OR BLENDED WITH OTHER PETROLEUM PRODUCTS AS A CLEAN BURNING TRANSPORTATION FUEL. METHANOL IS ALSO AN IMPORTANT CHEMICAL INTERMEDIATE USED TO PRODUCE: FORMALDEHYDE, DIMETHYL ETHER (DME), METHYL TER-BUTYL ETHER (MTBE), ACETIC ACID, OLEFINS, METHYL AMINES, AND METHYL HALIDES.
Spath PL, Dayton DC: Preliminary Screening-Technical and Economic Assessment of Synthesis Gas to Fuels and Chemicals with Emphasis on the Potential for Biomass-Derived Syngas. NREL/tp-510-34929
C.- SYNTHESIS GAS: Production of Methanol
C.- SYNTHESIS GAS
CATALYTIC METHANOL SYNTHESIS FROM SYNGAS IS A CLASSICAL HIGH-TEMPERATURE, HIGH-PRESSURE EXOTHERMIC EQUILIBRIUM LIMITED SYNTHESIS REACTION. THE CHEMISTRY OF THIS REACTION IS AS FOLLOWS:
CHEMISTRY
CATALYSTS
FOR METHANOL SYNTHESIS, A STOICHIOMETRIC RATIO, DEFINED AS (H2-CO2)/(CO+CO2) OF SLIGHTLY ABOUT 2 IS PREFERRED. THIS MEANS THAT THERE WILL BE JUST THE STOICHIOMETRIC AMOUNT OF HYDROGEN NEEDED FOR METHANOL SYNTHESIS. THE FEED GAS COMPOSITION FOR METANOL SYNTHESIS IS TYPICALLY ADJUSTED TO CONTAIN 4-8 % CO2 FOR MAXIMUM ACTIVITY AND SELECTIVITY.
THE FIRST HIGH-TEMPERATURE, HIGH PRESSURE METHANOL SYNTHESIS CATALYSTS WERE ZnO/Cr2O3 AND WERE OPERATED AT 350 oC and 250-350 bar. IN 1966 ICI INTRODUCED A NEW, MORE ACTIVE Cu/ZnO/Al2O3 CATALYST THAT BEGAN A NEW GENERATION OF METHANOL PRODUCTION BY USING LOW TEMPERATURES (220-275 oC), LOW PRESSURE (50-100 bar) .
Spath PL, Dayton DC: Preliminary Screening-Technical and Economic Assessment of Synthesis Gas to Fuels and Chemicals with Emphasis on the Potential for Biomass-Derived Syngas. NREL/tp-510-34929
PRODUCTION OF METHANOL
CO + H2O H2 + CO2 H (25oC) = -41.2 kJ/mol CO
CO2 + 3H2 CH3OH + H2O H (25oC) = -49.5 kJ/mol CO2
CO + 2H2 CH3OH H (25oC) = -90.6 kJ/mol COH (327OC) = -105.5 kJ/mol CO
C.- SYNTHESIS GAS: Production of Methanol
CO + H2O H2 + CO2 H (25oC) = -41.2 kJ/mol CO
CO2 + 3H2 CH3OH + H2O H (25oC) = -49.5 kJ/mol CO2
CO + 2H2 CH3OH H (25oC) = -90.6 kJ/mol CO H (327OC) = -105.5 kJ/mol CO
Operated with Cu/ZnO/Al2O3 at 220~327oC and 50~100atm
C.- SYNTHESIS GAS: Production of Methanol
CO + H2O H2 + CO2 H (25oC) = -41.2 kJ/mol CO
CO2 + 3H2 CH3OH + H2O H (25oC) = -49.5 kJ/mol CO2
CO + 2H2 CH3OH H (25oC) = -90.6 kJ/mol CO H (327OC) = -105.5 kJ/mol CO
Operated with Cu/ZnO/Al2O3 at 220~327oC and 50~100atm
Increasing in Equilibrium Conversion
C.- SYNTHESIS GAS: Production of Methanol
CO + H2O H2 + CO2 H (25oC) = -41.2 kJ/mol CO
CO2 + 3H2 CH3OH + H2O H (25oC) = -49.5 kJ/mol CO2
CO + 2H2 CH3OH H (25oC) = -90.6 kJ/mol CO H (327OC) = -105.5 kJ/mol CO
Operated with Cu/ZnO/Al2O3 at 220~327oC and 50~100atm
Increasing in Equilibrium Conversion
ONCE THE NATURAL GAS IS REFORMED THE RESULTING SYNTHESIS GAS IS FED TO A REACTOR VESSEL IN THE PRESENCE OF CATALYST TO PRODUCE METHANOL AND WATER VAPOR. THIS CRUDE METHANOL WHICH USUALLY CONTAINS UP TO 18 % WATER, PLUS ETHANOL, HIGHER ALCOHOLS, KETONES AND ETHERS IS FED TO A DISTILLATION PLANT THAT CONSISTS OF A UNIT THAT REMOVES THE VOLATILES AND A UNIT THAT REMOVES THE WATER AND HIGHER ALCOHOLS. THE UNREACTED SYNGAS IS RECIRCULATED BACK TO THE METHANOL CONVERTED RESULTING IN AN OVERALL CONVERSION EFFICIENCY OF 99 %.
Spath PL, Dayton DC: Preliminary Screening-Technical and Economic Assessment of Synthesis Gas to Fuels and Chemicals with Emphasis on the Potential for Biomass-Derived Syngas. NREL/tp-510-34929
C.- SYNTHESIS GAS: Production of Methanol
ONE OF THE CHALLENGES ASSOCIATED WITH COMMERCIAL METHANOL IS REMOVING THE LARGE EXCESS HEAT OF REACTION. METHANOL SYNTHESIS CATALYST ACTIVITY INCREASES AT HIGH TEMPERATURES BUT SO DOES THE CHANGE FOR COMPETING SIDE REACTIONS. CATALYTIC LIFETIMES ARE ALSO REDUCED BY CONTINUOUS HIGH TEMPERATURE OPERATION AND TYPICALLY PROCESS TEMPERATURES ARE MAINTAINED BELOW 300 oC TO MINIMIZE CATALYST SINTERING.
OVERCOMING THE THERMODYNAMIC CONSTRAINS IS ANOTHER CHALLENGE IN COMMERCIAL METHANOL SYNTHESIS. THE MAXIMUM PER-PASS CONVERSION EFFICIENCY OF SYNGAS TO METHANOL IS LIMITED TO ABOUT 25 %. HIGHER EFFICIENCIES PER-PASS CAN BE REALIZED AT LOW TEMPERATURE WHERE THE METHANOL EQUILIBRIUM IS SHIFTED TOWARDS PRODUCTS, HOWEVER, CATALYST ACTIVITIES GENERALLY DECREASE AS THE TEMPERATURE IS LOWERED.
Spath PL, Dayton DC: Preliminary Screening-Technical and Economic Assessment of Synthesis Gas to Fuels and Chemicals with Emphasis on the Potential for Biomass-Derived Syngas. NREL/tp-510-34929
C.- SYNTHESIS GAS: Production of Methanol
C.- SYNTHESIS GAS: Production of Methanol
C.- SYNTHESIS GAS: Fischer-Tropsch Synthesis
History
Period 1: Discovery (1902-1928). FTS had its genesis in the early 1900s with the discovery by Sabatier and Senderens in 1902 that CO could be hydrogenated over Co, Fe, and Ni to methane. In 1925, Fischer and Tropsch first reported synthesis of hydrocarbon liquids and solid paraffins on Co-Fe catalysts under mild conditions of 250-300oC and 1 atm.
Period 2: Commercial Development of the Fischer Cobalt-Based Process (1928-1945). Fischer and Koch developed the precipitated Co/ThO2/kieselguhr catalyst between 1928 and 1934 which was to be the industrial standard for the next 12 years. They also found that the yields of different boiling point fractions were significantly affected by the operating temperature and pressure. In 1944, FTS provided 10-15% of Germany’s synthetic fuel production with a total capacity of 5.4 Mbbl/yr.
Period 3: The Age of Iron and Sasol (1946-1974). Following WWII, American and British Allies followed up their intense interest in the German synfuels industry by sending teams of scientists to Germany. The U.S. team was referred to as the Technical Oil Mission (TOM). Due to a perceived shortage of
C.- SYNTHESIS GAS: Fischer-Tropsch Synthesis
History (Continues)
petroleum, the U.S., Great Britain, and Germany continued to support the FTS R&D. This R&D led to the development of inexpensive Fe catalysts. The first commercial GTL-FT plant (7,000 bbl/day) was operated in Brownsville, Texas, in 1951 by a Texaco-led consortium using fluidized bed reactor with Fe catalysts. However, this plant was shut down in 1957 after high gas prices and low cost petroleum from the Middle East made operation uneconomical. This fluidized bed reactor concept with Fe catalysts were used to build the Sasol Plant in South Africa in 1955 for the large-scale commercial FTS. It continues to operate and to produce 140,000 bbl/yr of synthetic fuels.
Period 4: Rediscovery of FTS and Cobalt (1975-1990). The 1973 oil embargo stimulated considerable support in the U.S. and Europe for R&D of synfuels technologies. During its “heyday” (1980) of FT research, significant progress was realized in relating catalyst properties to activity and selectivity. These new insights and innovations led to the development at Sasol, Gulf, Shell, and Exxon of substantially more economical FTS of diesel processes.
Period 5: Birth/Growth of the GTL Industry Based on Biomass (1990-Present).
CHEMISTRY
FTS HAS LONG BEEN RECOGNIZED AS A POLYMERIZATION REACTION WITH THE BASIC STEPS OF:
1.- REACTANT (CO) ADSORPTION ON THE CATALYST SURFACE
2.- CHAIN INITIATION BY CO DISSOCIATION FOLLOWED BY HYDROGENATION
4.- CHAIN TERMINATION
5.- PRODUCT DESORPTION FROM THE CATALYST SURFACE
C.- SYNTHESIS GAS: Fischer-Tropsch Synthesis
3.- CHAIN GROWTH BY INSERTION OF ADDITIONAL CO MOLECULES FOLLOWED BY HYDROGENATION
H H
H
CH2
CH3
CH3 CH3 CH2 n (CH2)n
CH3
(CH2)n
H
H
+
-
CH3-(CH2)n-CH3
CH3-(CH2)(n-1)-HC=CH2
C.- SYNTHESIS GAS: Fischer-Tropsch Synthesis
FTS produces a broad spectrum of mainly alkanes and alkenes having carbon number from C1 to C50, the distribution of which is qualitatively governed by the Anderson-Schulz-Flory (ASF) kinetics:
Wn/n = (n-1) (1- )2 = rp / (rp +rt)
Wn is the weight of product containing n carbon atoms and is the chain growth propagation probability
The maximum obtainable weight percentage of light LPG hydrocarbons (C2-C4) is 56%, of gasoline (C5-C11) 47% and of diesel fuel (C12-C17) 40%
The value of increases with decreasing H2/CO ratio, decreasing reaction temperature, and increasing pressure
C.- SYNTHESIS GAS: Fischer-Tropsch Synthesis
TYPES OF FISCHER-TROPSCH SYNTHESIS REACTOR
Spath PL, Dayton DC: Preliminary Screening-Technical and Economic Assessment of Synthesis Gas to Fuels and Chemicals with Emphasis on the Potential for Biomass-Derived Syngas. NREL/tp-510-34929
REACTORSONE OF THE CHALLENGES WITH FTS, IS THE REMOVAL OF THE LARGE AMOUNT OF EXCESS HEAT GENERATED BY THE EXOTHERMIC SYNTHESIS REACTIONS. INSUFFICIENT HEAT REMOVAL LEADS TO LOCALIZED OVERHEATING WHICH RESULTS IN HIGH CARBON DEPOSITION LEADING TO CATALYST DEACTIVATION. METHANE FORMATION ALSO DOMINATES AT HIGHER TEMPERATURES AT THE EXPENSE OF DESIRED FTS PRODUCTS. FOR LARGE-SCALE COMMERCIAL FTS REACTORS HEAT REMOVAL AND TEMPERATURE CONTROL ARE THE MOST IMPORTANT DESIGN FEATURES TO OBTAIN OPTIMUM PRODUCT SELECTIVITY AND LONG CATALYST LIFETIMES. OVER THE YIELDS BASICALLY FOUR FTS REACTOR DESIGNS HAVE BEEN USED COMMERCIALLY.
C.- SYNTHESIS GAS: Fischer-Tropsch Synthesis