Tony Bridgwater Bioenergy Research Group European Bioenergy Research Institute Aston University Birmingham B4 7ET UK Biofuels2015 Valencia Spain 25 August 2015 2 What is pyrolysis ID: 437222
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Slide1
Fast pyrolysis for bioenergy and biofuels
Tony BridgwaterBioenergy Research GroupEuropean Bioenergy Research InstituteAston University, Birmingham B4 7ET, UK
Biofuels-2015, Valencia, Spain 25 August 2015Slide2
2
What is pyrolysis?Biomass is heated in the absence of air or oxygen to decompose or devolatilise the biomass into:
Solid char
Liquid as bio-oil, tar or pyroligneous liquor
Gas
Three
products are always produced
Product yields depend on biomass, vapour and solids residence time, and temperature
There are several modes of pyrolysis ...............Slide3
Pyrolysis modes
Mode
Conditions
Wt % products
Liquid
Char
Gas
Fast ~ 500ºC; very short hot vapour residence time (RT) ~1 s; short solids RT75%12%13% Inter-mediate ~ 400ºC; short HVRT ~10-30 s; moderate solids RT40% in 2 phases40%20%Slow~ 400ºC; long HVRT; very long solids RT35%35%30%Torre-faction~ 300ºC; long HVRT; long solids RTVapours85% solid15% vapoursGasif-ication~ 800-900ºC; short HVRT; short solids RT1-5%<1% (all burned)95-99%
3Slide4
Fast pyrolysis products
Fast pyrolysis aims to maximise organics as liquids. This comes from very high heating rates from small particle sizes of generally <3mm in
size
and < 10%
moisture
Clean wood
gives highest liquid yield up to 75 wt.% on dry biomass feed. This is single phase, low viscosity. Ash causes catalytic vapour cracking, hence lower organic yields, higher water and potential phase separationThe charcoal forms about 10-15 wt.% of the products. It retains virtually all the alkali metals. It is usually consumed in the process to provide process heat.4Slide5
5
Bio-oil yield from Aspen Poplar
Char
Gas
400 450 500 550 600 650
Reaction temperature, C
Yield, wt.% of dry feed
Organics
Reaction water
80%
70%
60%
50%
40%
30%
20%
10%
0%Slide6
6Fast pyrolysis requirements
Organics
provides the energy in the product and can be converted into chemicals and/or fuels. The organic yield is thus critical.
Fast pyrolysis requires:
High heating rates:
Small particle sizes needed as biomass has low thermal conductivity
Dry biomass
(<10wt.% water): Feed moisture goes into bio-oil product plus reaction waterCarefully controlled temperature: ~500C is optimum temperature for maximising liquid yieldRapid and effective char removal: Char and alkali metals are catalytic and reduce liquid yieldShort hot vapour residence time: Thermal cracking reduces liquid yieldSlide7
Catalysts
All biomass contains inorganic materials which act as a catalyst as well as contaminants.
C
atalysts can be added to the biomass prior to, during, or after fast pyrolysis.
Natural catalysts
Alkali metals (e.g. K, Ca, Na) as “ash”
Contaminants
Heavy metals (e.g. Fe) from soil and wastesNon-metals (e.g. S, Cl, P) may also be presentProductsChar (which contains the biomass ash)Synthetic catalysts for product enhancement In-situ Close coupled (ex-situ) RemoteSlide8
Effects of ash and contaminants
Catalysts as ash and char
crack
organic products from pyrolysis into water and carbon dioxide leading to:
a
lower organic content
vapour and liquid with less energy
And potentially a phase separated liquid product Potassium is the most active alkali metal in crackingChar is also catalytic from the alkali metal contentAsh contents of typically more than 3 wt.% ash can cause phase separation in the liquid. Phase separation is non-reversible and can only be remedied by addition of high proportions of ethanol or similar solvents.Slide9
Typical fast pyrolysis reaction system
BIOMASS
Gas
recycle
C
HAR
process heat
or exportQuenchGASBIO-OILESPGrindingDryingPyrolysis reactorChar removal9Slide10
Fast pyrolysis reactors
Fluid bed
Spouted fluid bed
Transported bed
Rotating cone
Ablative
Circulating fluid bed
VortexCentrifuge reactorAugur or ScrewRadiative-convectiveEntrained flowMicrowaveMoving bed and fixed bedCeramic ball downflowVacuumCommercial activities10Slide11
CFB or Transported bed reactor
BIO-OIL
BIOMASS
H
ot flue
gas
Gas recycle
Sand+CHARCombustorPyrolyserAirHot sandGASexportQuenchESPCyclones11Slide12
Fast pyrolysis: commercialisation
Ensyn (CA)
:
100 t/d
transported bed in
Canada +
8 or 9 in USA
BTG (NL) : 125 t/d Empyro 12Fortum (FI) & Metso (FI):Slide13
Fast pyrolysis liquid – bio-oil
13
Moisture content
25 %
pH
2.5
Specific gravity1.20Elemental analysis C H O N Ash56.4 %6.2 %37.3 %0.1 %0.1 %HHV as made17 MJ/kgViscosity (at 40°C)40-100 cpSolids (char)0.05 %Vacuum distillation residueMax. 50%Slide14
Decentralised fast pyrolysis
14
Bulk density
Biomass density can be as low as 100 kg/m
3
Bio-oil density is
1200 kg/m
3Bio-oil liquid storage, handling and transportTanks and pumps are used No windblown refuse, vermin, or mechanical handlingProvides optimum use of loading weight restrictionsCentral processor e.g. for biofuelSlide15
Direct use of whole bio-oil
Heat and power
15
Electricity
Heat
Boiler
Turbine
Fast pyrolysis to liquidsCHPEngineChemical substitution Phenolics in wood resinsPreservativesSlide16
Bio-oil for biofuels
Ind
irect
production
G
asification
of bio-oil followed by hydrocarbon or alcohol
synthesis. There are many technical and economic advantages of gasification of liquid bio-oil rather than solid biomass Direct productionVia catalytic upgrading of liquid or vapourCatalyst can be added to biomass; incorporated into the fluid bed material; use of a close coupled reactor; use of a remote reactorEx-situ or secondary reaction offers independent control over process conditions; 16Slide17
Direct routes
Indirect routes
Pyrolysis
routes to biofuels
Hydrocarbons, BioSNG,
Syndiesel
, Syngasoline, BioLPGSyngasZeolitecrackingLiquid bio- oilAlcoholsGasificationHydro-treatingConversion e.g. Fischer TropschMethanol + MTG etc.Fast pyrolysisAdditives
Esters
Blends
BiomassSlide18
Vapour cracking
Zeolite cracking
rejects oxygen as CO
2
Vapour processing in a close coupled
process
No hydrogen requirement, no pressure
Projected yield of around 18wt.% aromatics This is now being developed by e.g. Kior and othersZSM-5 has attracted most attention due to shape selectivity to aromatics, with promoters such as Ga or Ni.The catalyst rapidly cokes which requires frequent regeneration as in an FCC unit. Oxygen is thus removed as CO and CO2 compared to H2O in hydroprocessing. Production of aromatics is also likely to be of significant interest to the chemicals sector.Slide19
Hydrodeoxygenation (HDO)
Hydro-deoxygenation
rejects oxygen as H
2
O
Liquid processing with
hydrogen and high pressureProjected yield of around 15wt.% for refiningOriginal research used sulphided CoMo or NiMo catalysts on aluminosilicate which tended to hydrolyse due to waterMore recently, precious metal catalysts on inert supports have been developed with a preference for Pd and RuExtent of deoxygenation depends on:Severity of upgrading conditions – pressure, temperature, catalyst and residence timeBio-oil production process and feedstockIt is likely that multiple upgrading steps will be neededSlide20
HDO
2
Coking
limits catalyst performance and life
Complete deoxygenation is very difficult especially with phenols
Recent research has moved to
partial
HDO, but all processes are high pressure (<200 bars) and moderate temperature (<400C) Provision of hydrogen remains a major challenge. Low hydrogen conversion requires costly recycling with hydrogen separation and compression. Completion of partial upgrading in conventional refineries is an attractive opportunityHydrodeoxygenation has been combined with other techniquesSlide21
Hydrogen
Since the hydrogen requirement is significant, it should be renewable and sustainable. Few refineries have a hydrogen surplus
Hydrogen can be generated by
gasification
of biomass, shifting CO to H
2
followed by scrubbing CO
2Bio-oil can be phase separated. The organic phase containing typically 20% water can be hydroprocessed and the aqueous phase can be steam reformed to hydrogen. The necessary purity of hydrogen is unknown, but some CO shifting may take place in the hydroprocessing reactor removing the need for dedicated shift reactors.Slide22
Other upgrading methods
A variety of methods and catalysts have been investigated in recent years as exemplified below:
Acid cracking in supercritical ethanol
Aqueous-phase reforming + dehydration + hydrogenation
Blending
Dicationic
ionic liquid C
6(mim)2−HSO4Esterification of pyrolysis vapoursEsterification of liquid bio-oilHydrogenation−esterification over bifunctional Pt catalystsReactive distillationSolid acid catalysts 40SiO2/TiO2−SO42- Solid base catalysts 30K2CO3/Al2O3−NaOHSteam reforming ZnO, MgO and Zn-Al and Mg-Al mixed oxidesSlide23
EsterificationSlide24
C
hemicals
Fractionated oil
Liquid
smoke (commercial)
Anhydrosugars
Asphalt
De-icersFuel additivesHydrogenPreservativeResin precursorsSlow release fertiliserSpecific chemicalsAcetic acid (commercial)FurfuralHydroxyacetaldehydeLevoglucosanLevoglucosenoneMaltolPhenol and phenolicsSlide25
Combinations
Biomass
Liquid
Vapour
Whole oil
Chemicals
Hydrocarbons
Improved bio-oilHydrogenCatalysisFast pyrolysisWaterExtractionAqueousOrganicRefiningCatalytic fast pyrolysisSeparationModific-ationCatalysisSlide26
Fast pyrolysis for primary conversion
Hydro-treating
Zeolite cracking
Hydrogen separation
Electricity
Heat
Fast pyrolysis
GasificationSynthesisTransport fuelsRefiningSlurryCharLiquidChemicals26Slide27
Slow pyrolysis and chemical recovery
Usine Lambiotte
carbonisers
and liquid
tar processing
Usine Lambiotte primary distillation columnSlide28
Opportunity from ~100,000 t/y wood
t/year
€/t
k€/
y
%
Charcoal
25,000*1002,50031.5Total pyroligneous liquid40,000Water30,000Organics10,000Acids and alcohols3,8304521,73221.8Oils3101,258390Fine chemicals5649,7322,78535.1Fuel5,80490522Total organics10,0005435,42968.5Total income7,92928Slide29
Conclusions
Pyrolysis is very
flexible
in the process and products.
Fast pyrolysis provides a
liquid
as an energy carrier
The liquid is alkali metal free Decentralised pyrolysis plants offer improvementsBio-oil can be used for fuel, chemicals and/or biofuelsFast pyrolysis technology needs to be improved to reduce costs and increase liquid yield and qualityFast pyrolysis liquid upgrading needs to be developed and demonstrated 29Slide30
Thank you