Energi BiomassSemester 1/2011

Pyrolysis

Harmen Burhanuddin, S.T., M.T.

Fuel preparation, fuel upgrading and other technologiesBio-oil production from fast pyrolysisCharcoal production RDF Briquetting technology

Pretreatment: mechanical

Conversion technologies

What is Pyrolysis?Pirolisis proses - konversi Thermal bahan padat dalam suasana inert dan tahap awal dari proses pembakaran dan gasifikasi - Pirolisis biomassa menghasilkan Char (padat), Bio-minyak (cair) dan gas bahan bakar (gas)

Types of pyrolysis

Slow pyrolysisFast pyrolysis Heating rate

Characteristic

Product

Applications Slow

Extensive tar interaction with solid and tar cracking

Solid

Carbonisation for charcoal production Fast (rapid/flash)

Minimised interaction of tar with solid and tar cracking by immediate quenching

Liquid

Rapid pyrolysis for bio-oil production Synthesis gas production

Typical product yields (dry wood basis)

ModeConditionsLiquidCharGasFast pyrolysis moderate temperature, high heating rate, short residence time particularly vapour75%12%13% Carbonisation low temperature, very long residence time30%35%35%Gasification high temperature, long residence times5%10%85%

Applications of pyrolysis

Fast pyrolysis for bio-oil productionFast heating rate process with immediate quenching of liquid product could result up to 70 % bio-oil yield

Bio-oil is brownish, vicious liquid (but still low compared to crude oil) and immiscible with any form of hydrocarbon liquid

Liquid products from fast pyrolysis have significantly different properties compared to those from slow pyrolysis

Bio-oil production technologiesHigh yield of fast pyrolysis liquid can be obtained from- Very high heating rates (i.e. >1000C/s)- Moderate vapour temperatures (i.e. below around 600 C)- Low vapour residence times - Rapid quenching of the resultant vapour

High temperatures required from pyrolysis can be obtained from- Heating the gas-solid mix through the reactor wall- Heating with a heat transfer medium (e.g. preheated recycle gas)- Heating through exothermic chemical reactions inside the reactor (e.g. partial oxidation)- Heating the particle directly through reactor wall

Since thermal conductivity of biomass is low, rapid heating to achieve fast pyrolysis conditions imposes an upper particle size of 3 to 5 mm, above which may cause slow rate of heat of penetration and severe degradation of primary products

Bubbling fluidised bed reactor (BFB)Reactors for bio-oil production Good temperature control Char removal is usually by ejection and entrainment; separation by cyclone Easy scaling Well understood technology since first experiments at University of Waterloo in 1980s Small particle sizes needed Heat transfer to bed at large scale has to be proven

Circulating fluidised bed reactor (CFB)- Good temperature control in reactor- Larger particle sizes possible- CFB suitable for very large throughputs- Well understood technology- Hydrodynamics more complex, larger gas flows in the system- Char is finer due to more attrition at higher velocities; separation is by cyclone- Closely integrated char combustion requires careful control- Heat transfer to bed at large scale has to be proven.

Rotating cone reactor Centrifugation drives hot sand and biomass up rotating heated cone Vapors are condensed- Char is burned and hot sand is recirculated

Overview of fast pyrolysis reactor[* Countries that join PYNE network; Ref: www.pyne.co.uk]

PropertyStatus #Bio-oilwt%ComplexityFeed sizeInert gas needSpecific sizeScaleupFluid bedDemo75MediumSmallHighMediumEasyCFBPilot75HighMediumHighLargeEasyEntrained None65HighSmallHighLargeEasyRotating conePilot65HighV smallLowSmallHardAblativeLab75HighLargeLowSmallHardVacuumDemo60HighLargeLowLargeHard# Demo = demonstration (200 2000 kg h-1)# Pilot = pilot plant (200 200 kg h-1)# Lab = laboratory (1 20 kg h-1)

Bio-oil characteristicsTypical properties of wood pyrolysis bio-oil

Physical property Typical value CharacteristicsMoisture content 20-30%pH 2.5Specific gravity 1.20Elemental analysis C 55-58% H 5.5-7.0% O 35-40% N 0-0.2% Ash 0-0.2%HHV as produced 16-19 MJ/kgViscosity (40 C and 25% water) 40-100 cpSolids (char) 0.1 0.5%Vacuum distillation residueup to 50%Liquid fuelReady substitution for conventional fuels in many stationary applications such as boilers, engines, turbinesHeating value of 17 MJ/kg at 25%wt. water, is about 40% that of fuel oil/dieselDoes not mix with hydrocarbon fuelsNot as stable as fossil fuelsQuality needs definition for each application

Advantages of fast pyrolysis for bio-oil productionBio-oil is cheaper to transport than biomassBio-oil has a volumetric energy density of 20 GJ/m3, but only 4 GJ/m3 for woodchips Bio-oil is cleaner and has low ash content than biomassMinerals like K, Cr, and Cu remain in the char (solid product), not in liquid productThe cost of bio-oil production is relatively low due to the mild conditions

Technical barriers for bio-oil utilisationPoor fuel quality (relative to conventional fuel oils)Chemical instabilityVariable moisture content and heating valueInconsistent physical propertiesCorrosion in equipmentContamination by particulatesNo quality standard for bio-oilHigh cost of production (compared to other alternative fuels, 10-100% more than fossil fuel)Immiscible with crude oil, therefore a need ofi) conversion or upgradingii) discrete pyrolysis liquid storage, distribution and utilisation systems

The most important issues that need to be addressed are:- Scale-up- Cost reduction- Improving product quality including setting norms and standards for producers and users- Environment health and safety issues in handling, transport and usage - Encouragement for developers to implement processes and users to implement applications- Information dissemination

Upgrading of bio-oilSince properties of bio-oil change with time: viscosity increases, volatility decreases, phase separation, deposits, gums, upgrading is necessary to increase stabilityThe most reactive compounds in bio-oils have unsaturated double bonds which could be used as a measure for instabilityPhysical upgrading- Filtration for char removal- Emulsification with hydrocarbons- Addition of low-viscosity solventChemical upgrading- Reaction with alcohols or phenolic derivatives- Catalytic deoxygenation: mild hydrotreating- Catalytic (zeolite) vapor cracking

Applications of pyrolysis liquid

Combustion application- Bio-oil can be used as a retrofit to the existing oil-fired burners with minor modifications, when raw biomass cannot be used without major reconstruction - Problems reported are suspended char causing problems in atomisation and incomplete combustion

Power generation- Peak power provision is possible with a small pyrolysis plant or transportation of liquid to the plant- Bio-oil has been successfully fired in a diesel test engine and behave similar to diesel in term of engine parameters and emissions

- Power generation using bio-oil has potential for short-term opportunity, esp. for small-scale

- Due to its high efficiency, the cost for power generation is reduced

- Growth in size of fast pyrolysis plants

Bio-oil production & utilisation referencesForestera, Finland- Liquefied woodchip pilot plant- Liquid fuel is produced by fast pyrolysis up to 500 C followed by condensation of vapours- Yield of liquid is 60-70 % - Installed solid separation process (solid content reduced to 0.1 % wt) is found to improve stability, reduce particulate emissions during combustion and eliminate sludge formation during storage

Rotating cone reactor, University of Twente - 75 wt% bio-oil and only 15 wt% char and gas are produced as primary products - 250 kg/h pilot plant - Rotational speed of the cone: 300 rpm - Require: Particle size < 6 mm Moisture content < 10 wt%

Bio-oil production using sugarcane biomass residues at Fast Pyrolysis Pilot Plant in Brazil - Bioware Technology, Fluidised bed design

Co-firing of bio-oil with coal at Manitowoc, Wisconsin - 25 tonnes of dry feed per day- Hardwood derived bio-oil is co-fired with coal for the commercial production of electricity - The effect of bio-oil combustion on emissions and boiler operation was observed during operation when the bio-oil co-firing was about 5% of the total fuel input to the boiler

ENERSLUDGE Technology, Australia- Bio-oil from sewage sludge- When produced oil is combusted in an engine to produce electricity, the process generates 925 kWh/ t of sludge processed- Average conversion product data _________________________________________________ Product Yield GCV % of Biosolids (%) (MJ / kg) Energy _________________________________________________ Oil 29 30 45 Char 43 18 40 NCG 14 15 11 RW 14 6 4___________________________________________________

Charcoal productionProduction of char, material of high carbon content, low ash, high heating valueSlow pyrolysis process: carbonisationCarbonisation for charcoal production, mainly from wood, but other sources may be coconut shells and crop residues

History of charcoal productionCharcoal is produced by burning wood under conditions that severely limit the amount of oxygen available for combustion The object is to reduce the wood to a form of carbon by removing the other constituents Produced gases and other volatiles in the smoke are allowed to escapemay be recaptured, condensed, and converted to useful byproducts. Example is wood vinegar. Because of their removal in large part, charcoal burns more "cleanly"--that is, with little or no smoke or flame

Production cycle

Typical properties:

Applications: Charcoal for the barbecue and cooking marketCharcoal for heating, energy production, mineral refining, and industrial useCharcoal as a precursor to the production of carbon for industrial use and activated carbon

PropertiesCharcoalRice huskMoisture (%) Volatile matter (%)Ash (%)Fixed carbon (%)Calorific value (kcal/kg)5.0-9.5 6.3-9.0 1.1-2.5 82-92 7200-85008.258.913.219.73380

Charcoal kilnsCharcoal manufacturing kilns generally can be classified as either batch or continuous multiple hearth kilns; continuous multiple hearth kilns

Batch units

A small, manually-loaded and -unloaded kilns producing typically 17.6 tons of charcoal during a 3-week cycle

Continuous units

Herreshoff patent

Refused Derived Fuel - RDFRDF covers a wide range of waste materials which have been processed to fulfil guideline, regulatory or industry specifications mainly to achieve a high calorific valueWaste derived fuels include residues from MSW recycling, industrial/trade waste, sewage sludge, industrial hazardous waste, biomass waste, etcRDF is uniformed, stable, high heating value, low in pollutants, easy for storage and transportation and combustible stability

Terms for MSW derived fuels

12 Refuse derived fuel (RDF)

Mixed waste The segregated high calorific fraction of municipal solid waste (MSW), commercial or industrial process wastes It has a poorer quality than 2. Recovered Fuel (REF), Packaging Derived Fuels (PDF), Paper and Plastic Fraction (PPF) and Process Engineered Fuel (PEF). Source-separated waste Processed, dry combustible MSW fraction (e.g. plastics and/or paper) which are too contaminated to be recycled. It has a higher calorific value, lower moisture content and lower ash content (on combustion) than RDF derived from mixed waste fractions.

The quantity of RDF produced per tonne of MSW varies depending on the type of collectiontreatment process quality requirement for recovered solid fuels

The rate of RDF production from MSW can vary between 23 and 85% by weight of waste processed depending on the treatment process used and country

Schematic Representation of MBT Process (Mechanical biological treatment)

RDF Process (Taiwan): involves putting solid waste into fuel pellets through

1. Crashing2. Selection - Taking out materials large and not good for combustion, e.g. metals, ceramics, glass 3. Drying4. Mixing - Adding limes and using catalyser de-odorizing system5. Pelletising

Quality of RDF from household and industrial sources (EU references)

Utilisation of RDF from MSWThe following options for the utilisation and conversion of RDF from MSW to energy have been used or could be used in the future:on-site in an integrated thermal conversion device, which could include grate or fluidised bed combustion, gasification or pyrolysisoff-site at a remote facility employing grate or fluidised bed combustion, gasification or pyrolysisco-combustion in coal fired boilersco-incineration in cement kilnsco-gasification with coal or biomass

Number of industrial plants co-incinerating RDF from industrial wastes in Europe

BriquettingBriquetting or densification is used to improve characteristics of materials for transport and use as energy source Raw materials include sawdust, loose crop residues, and charcoal finesUse mechanical means, but additional binders may be needed to bind the materialMain briquetting technologies are:Piston press - using a high pressure to punch the material into a dieScrew press - using a screw to continuously compact the material, also producing briquettes of higher quality

Block chart of a briquetting system

Products

RollRoll bearingHydraulic compressive force controllerScrewAuto feederRaw MaterialRough Structure of High Pressure Roll Press

Bio-briquette Features of bio-briquetteA wide variety of coal grades can be used as a raw materialBiomass materials of low utility value can be usedIt is excellent both in ignitability and burning property, and generates little smoke It produces little clinker, and ashes become sandy first from the surface70 to 80% of sulfur content in coal can be fixed in the ash

Outline of ProcessCoal Pre-Treatment SectionRaw coalDryingGrindingBiomass Pre-Treatment SectionBiomassDryingGrindingDesulfurisation Agent Supply SectionDesulfurisation AgentMixingMixing and BriquettingSectionBriquettingBio-BriquetteSlaked lime react to Sulfur Ca(OH)2 CaO H2OCaO SO2 O2 CaSO4

Mixing ratio:Coal 80%, Bagasse 20%, Slaked Lime 5%Shape:Almond typeSize:approx. 38mm26mm16mmCompressive strength 40kgf or moreProperties of Bio-Briquette

Relation between Time Lapsed and Smoke No.Smoke No. Valuation Basis

0Smoke doesnt occur.

1Smoke occurs a little, and it cant be confirmed with the eyes. 23 Smoke occurs a little, and it can be confirmed with the eyes.

45 Smoke occurs, and feels an unpleasantness. 69 Smoke occurs in quantity, and it cant be used. Coal

Bio-Briquette

Bagasse blending ratio [%]Ignition time [sec]Mark Coal Fuel Ratio A 4.4 B 4.4 C 2.4 D 1.1 E 0.9Bagasse blending ratio vs. Ignition time

Unburnt Matters in AshCoal properties: Ash content11.3%Volatile matters 40.8%Fixed carbon 46.3%

Mix RatioCoal: BiomassUnburnt matters In ash [%] 100 : 0 17.68 90 : 10 3.45 80 : 20 2.63 70 : 30 3.66

Ca/S Ratio vs. Percentage of Fixed SulfurPercentage of Fixed Sulfur [ % ]Ca/S Ratio [ - ]01234020406080100

Other briquette shapes, raw materialsBanknotes

1.22 15t/24t/23t/

1/51/10200400

1520%Ca/S1.226080%