BIOMASS AND BIOENERGY 38 (2012)68-94 Available at www.sciencedirect.com BIOMASS BIOENERGY ScienceDirect ELSEVIER http://www.elsevier.com/locate/biombioe Review of fast pyrolysis of biomass and product upgrading A.V.Bridgwater* Aston University Bioenergy Research Group,Aston Triangle,Birmingham B4 7ET,UK ARTICLE INFO ABSTRACT Article history: This paper provides an updated review on fast pyrolysis of biomass for production of Received 27 August 2010 a liquid usually referred to as bio-oil.The technology of fast pyrolysis is described including Received in revised form the major reaction systems.The primary liquid product is characterised by reference to the 27 January 2011 many properties that impact on its use.These properties have caused increasingly Accepted 28 January 2011 extensive research to be undertaken to address properties that need modification and this Available online 3 March 2011 area is reviewed in terms of physical,catalytic and chemical upgrading.Of particular note is the increasing diversity of methods and catalysts and particularly the complexity and Keywords: sophistication of multi-functional catalyst systems.It is also important to see more Fast pyrolysis companies involved in this technology area and increased take-up of evolving upgrading Biomass processes. Bio-oil 2011 Elsevier Ltd.All rights reserved. Catalyst 1. Introduction technology with applications in most industrialised and developing countries and development is concentrated on Biomass fuels and residues can be converted to more valuable resolving environmental problems [2].Gasification has been energy forms via a number of processes including thermal, practiced for many years and while there are many examples biological,and mechanical or physical processes.While bio- of demonstration and pre-commercial activities [3,4]there are logical processing is usually very selective and produces a small still surprisingly few successful operational units.This review number of discrete products in high yield using biological focuses on the emerging advanced technology of fast pyrol- catalysts,thermal conversion often gives multiple and often ysis both as an integrated process for production of a liquid complex products,in very short reaction times with inorganic fuel that can be used directly and as an intermediate pre- catalysts often used to improve the product quality or spec- treatment step to convert solid biomass into a higher energy trum.Pyrolysis has been applied for thousands of years for content transportable liquid for subsequent processing for charcoal production but it is only on the last 30 years that fast heat,power,biofuels,and chemicals.This technology is pyrolysis at moderate temperatures of around 500C and very widely expected to offer a considerable contribution in the short reaction times of up to 2 s has become of considerable short term in terms of versatility,improved efficiency and interest.This is because the process directly gives high yields of environmental acceptability. liquids of up to 75 wt%which can be used directly in a variety of applications [1]or used as an efficient energy carrier. Fig.1 summarises the markets for the products from the Fast pyrolysis three main thermal processes available for converting bio- mass to a more useful energy form-pyrolysis,gasification and Pyrolysis is thermal decomposition occurring in the absence combustion.Combustion is a well-established commercial of oxygen.Lower process temperatures and longer vapour ·Tel.:+441212043381;fax:+441212043680 E-mail address:a.v.bridgwater@aston.ac.uk. 0961-9534/$-see front matter@2011 Elsevier Ltd.All rights reserved. doi10.1016/j.biombioe.2011.01.048
Review of fast pyrolysis of biomass and product upgrading A.V. Bridgwater* Aston University Bioenergy Research Group, Aston Triangle, Birmingham B4 7ET, UK article info Article history: Received 27 August 2010 Received in revised form 27 January 2011 Accepted 28 January 2011 Available online 3 March 2011 Keywords: Fast pyrolysis Biomass Bio-oil Catalyst abstract This paper provides an updated review on fast pyrolysis of biomass for production of a liquid usually referred to as bio-oil. The technology of fast pyrolysis is described including the major reaction systems. The primary liquid product is characterised by reference to the many properties that impact on its use. These properties have caused increasingly extensive research to be undertaken to address properties that need modification and this area is reviewed in terms of physical, catalytic and chemical upgrading. Of particular note is the increasing diversity of methods and catalysts and particularly the complexity and sophistication of multi-functional catalyst systems. It is also important to see more companies involved in this technology area and increased take-up of evolving upgrading processes. ª 2011 Elsevier Ltd. All rights reserved. 1. Introduction Biomass fuels and residues can be converted to more valuable energy forms via a number of processes including thermal, biological, and mechanical or physical processes. While biological processing is usually very selective and produces a small number of discrete products in high yield using biological catalysts, thermal conversion often gives multiple and often complex products, in very short reaction times with inorganic catalysts often used to improve the product quality or spectrum. Pyrolysis has been applied for thousands of years for charcoal production but it is only on the last 30 years that fast pyrolysis at moderate temperatures of around 500 C and very short reaction times of up to 2 s has become of considerable interest. This is because the process directly gives high yields of liquids of up to 75 wt.% which can be used directly in a variety of applications [1] or used as an efficient energy carrier. Fig. 1 summarises the markets for the products from the three main thermal processes available for converting biomass to a more useful energy form - pyrolysis, gasification and combustion. Combustion is a well-established commercial technology with applications in most industrialised and developing countries and development is concentrated on resolving environmental problems [2]. Gasification has been practiced for many years and while there are many examples of demonstration and pre-commercial activities [3,4] there are still surprisingly few successful operational units. This review focuses on the emerging advanced technology of fast pyrolysis both as an integrated process for production of a liquid fuel that can be used directly and as an intermediate pretreatment step to convert solid biomass into a higher energy content transportable liquid for subsequent processing for heat, power, biofuels, and chemicals. This technology is widely expected to offer a considerable contribution in the short term in terms of versatility, improved efficiency and environmental acceptability. 2. Fast pyrolysis Pyrolysis is thermal decomposition occurring in the absence of oxygen. Lower process temperatures and longer vapour * Tel.: þ44 121 204 3381; fax: þ44 121 204 3680. E-mail address: a.v.bridgwater@aston.ac.uk. Available at www.sciencedirect.com http://www.elsevier.com/locate/biombioe biomass and bioenergy 38 (2012) 68 e9 4 0961-9534/$ e see front matter ª 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.biombioe.2011.01.048
BIOMASS AND BIOENERGY 38 (2012)68-94 69 Primary Conversion Conversion product Market Char Storage Charcoal Pyrolysis Bio-oil Storage Biofuels chemicals Fuel gas Turbine Gasification Engine Electricity CHP Combustion Heat Boiler Heat Fig.1-Products from thermal biomass conversion. residence times favour the production of charcoal.High Short hot vapour residence times of typically less than 2s to temperatures and longer residence times increase biomass minimise secondary reactions, conversion to gas,and moderate temperatures and short Rapid removal of product char to minimise cracking of vapour residence time are optimum for producing liquids. vapours, Three products are always produced,but the proportions can Rapid cooling of the pyrolysis vapours to give the bio-oil be varied over a wide range by adjustment of the process product parameters.Table 1 and Fig.2 indicate the product distribu- tion obtained from different modes of pyrolysis,showing the As fast pyrolysis for liquids occurs in a few seconds or less, considerable flexibility achievable by changing process heat and mass transfer processes and phase transition conditions.Fast pyrolysis for liquids production is currently of phenomena,as well as chemical reaction kinetics,play particular interest as the liquid can be stored and transported, important roles.The critical issue is to bring the reacting and used for energy,chemicals or as an energy carrier. biomass particles to the optimum process temperature and minimise their exposure to the lower temperatures that 2.1. Principles favour formation of charcoal.One way this objective can be achieved is by using small particles,for example in the flui- In fast pyrolysis,biomass decomposes very quickly to dised bed processes that are described later.Another possi- generate mostly vapours and aerosols and some charcoal and bility is to transfer heat very fast only to the particle surface gas.After cooling and condensation,a dark brown homoge- that contacts the heat source which is used in ablative nous mobile liquid is formed which has a heating value about processes that are described later. half that of conventional fuel oil.A high yield of liquid is The main product,bio-oil,is obtained in yields of up to obtained with most biomass feeds low in ash.The essential 75 wt.%on a dry-feed basis,together with by-product char and features of a fast pyrolysis process for producing liquids are: gas which can be used within the process to provide the process heat requirements so there are no waste streams Very high heating rates and very high heat transfer rates at other than flue gas and ash.Liquid yield depends on biomass the biomass particle reaction interface usually require type,temperature,hot vapour residence time,char separa- a finely ground biomass feed of typically less than 3 mm as tion,and biomass ash content,the last two having a catalytic biomass generally has a low thermal conductivity, effect on vapour cracking. Carefully controlled pyrolysis reaction temperature of A fast pyrolysis process includes drying the feed to typi- around 500C to maximise the liquid yield for most biomass, cally less than 10%water in order to minimise the water in the Table 1-Typical product weight yields(dry wood basis)obtained by different modes of pyrolysis of wood. Mode Conditions Liquid Solid Gas Fast ~500C,short hot vapour residence time ~1s 75% 12%char 13% Intermediate ~500C,hot vapour residence time 10-30s 50%in 2 phases 25%char 25% Carbonisation (slow) ~400C,long vapour residence hours-days 30% 35%char 35% Gasification -750-900°C 5% 10%char 85% Torrefaction(slow) ~290C,solids residence time 10-60 min 0%unless condensed,then up to 5% 80%solid 20%
residence times favour the production of charcoal. High temperatures and longer residence times increase biomass conversion to gas, and moderate temperatures and short vapour residence time are optimum for producing liquids. Three products are always produced, but the proportions can be varied over a wide range by adjustment of the process parameters. Table 1 and Fig. 2 indicate the product distribution obtained from different modes of pyrolysis, showing the considerable flexibility achievable by changing process conditions. Fast pyrolysis for liquids production is currently of particular interest as the liquid can be stored and transported, and used for energy, chemicals or as an energy carrier. 2.1. Principles In fast pyrolysis, biomass decomposes very quickly to generate mostly vapours and aerosols and some charcoal and gas. After cooling and condensation, a dark brown homogenous mobile liquid is formed which has a heating value about half that of conventional fuel oil. A high yield of liquid is obtained with most biomass feeds low in ash. The essential features of a fast pyrolysis process for producing liquids are: Very high heating rates and very high heat transfer rates at the biomass particle reaction interface usually require a finely ground biomass feed of typically less than 3 mm as biomass generally has a low thermal conductivity, Carefully controlled pyrolysis reaction temperature of around 500 C to maximise the liquid yield for most biomass, Short hot vapour residence times of typically less than 2 s to minimise secondary reactions, Rapid removal of product char to minimise cracking of vapours, Rapid cooling of the pyrolysis vapours to give the bio-oil product. As fast pyrolysis for liquids occurs in a few seconds or less, heat and mass transfer processes and phase transition phenomena, as well as chemical reaction kinetics, play important roles. The critical issue is to bring the reacting biomass particles to the optimum process temperature and minimise their exposure to the lower temperatures that favour formation of charcoal. One way this objective can be achieved is by using small particles, for example in the fluidised bed processes that are described later. Another possibility is to transfer heat very fast only to the particle surface that contacts the heat source which is used in ablative processes that are described later. The main product, bio-oil, is obtained in yields of up to 75 wt.% on a dry-feed basis, together with by-product char and gas which can be used within the process to provide the process heat requirements so there are no waste streams other than flue gas and ash. Liquid yield depends on biomass type, temperature, hot vapour residence time, char separation, and biomass ash content, the last two having a catalytic effect on vapour cracking. A fast pyrolysis process includes drying the feed to typically less than 10% water in order to minimise the water in the P mir yra tcudorp noisrevnoC noisrevnoC tekraM ilP sleufoiB rahC egarotS laocrahC enibruT Ga noitacifis P o y ls r y is sagleuF lio-oiB egarotS sleufoiB & acimehc sl Ga noitacifis oitsubmoC n eH at elE c yticirt C& HP relioB enignE oitsubmoC n eH at relioB taeH Fig. 1 e Products from thermal biomass conversion. Table 1 e Typical product weight yields (dry wood basis) obtained by different modes of pyrolysis of wood. Mode Conditions Liquid Solid Gas Fast w500 C, short hot vapour residence time w 1 s 75% 12% char 13% Intermediate w500 C, hot vapour residence time w 10e30 s 50% in 2 phases 25% char 25% Carbonisation (slow) w400 C, long vapour residence hours / days 30% 35% char 35% Gasification w750e900 C 5% 10% char 85% Torrefaction (slow) w290 C, solids residence time w 10e60 min 0% unless condensed, then up to 5% 80% solid 20% biomass and bioenergy 38 (2012) 68 e9 4 69
70 BIOMASS AND BIOENERGY 38 (2012)68-94 100% ▣Organics 90% 80% Water 70% ▣Char 60% ■Gas 50% 40% 30% 20% 10% 0% Fast Intermediate Carbonisation Gasification Slow Slow-Torrefaction Fig.2-Product spectrum from pyrolysis. product liquid oil,grinding the feed to give sufficiently small product collection,storage and,when relevant,upgrading. particles to ensure rapid reaction,fast pyrolysis,rapid and Several comprehensive reviews of fast pyrolysis processes for efficient separation of solids(char),and rapid quenching and liquids production are available such as [5-9). collection of the liquid product (often referred to as bio-oil). Table 2 lists most of the known recent and current activi- Virtually any form of biomass can be considered for fast ties in fast pyrolysis arranged by reactor type and maximum pyrolysis.While most work has been carried out on wood known throughput.There has been considerable growth and because of its consistency and comparability between tests, expansion of activities over the last few years with more over 100 different biomass types have been tested by many innovation in the types of reactor explored by academic laboratories,ranging from agricultural wastes such as straw, institutions.It is disappointing to see so much re-invention olive pits and nut shells to energy crops such as miscanthus and poor appreciation of the underlying fundamental and sorghum,forestry wastes such as bark and solid wastes requirements of fast pyrolysis as well as a reluctance to carry such as sewage sludge and leather wastes. out basic reviews of past research publications. In all cases,a commercial process comprises three main There are increasing activities on fixed bed and related stages from feed reception to delivery of one or more useful systems that are unlikely to give high liquid yields but are likely products: to give phase separated liquids.Phase separated liquid prod- ucts may be desirable in some applications where fraction- Feed reception,storage,handling,preparation and pre- ation is required,but it would seem preferable to control such treatment; separation rather than rely on poor design and process control. Conversion of solid biomass by fast pyrolysis to a more usable form of energy in liquid form which is known as bio- 2.2.1.Bubbling fluid beds oil; Bubbling fluid beds have the advantages of a well understood Conversion of this primary liquid product by processing, technology that is simple in construction and operation,good refining or clean-up to a marketable end-product such as temperature control and very efficient heat transfer to electricity,heat,biofuels and/or chemicals. biomass particles arising from the high solids density.Fig.3 shows a typical configuration using electrostatic precipita- tors for coalescence and collection of what are referred to as 2.2. Fast pyrolysis reactors aerosols.These are incompletely depolymerised lignin frag- ments which seem to exist as a liquid with a substantial At the heart of a fast pyrolysis process is the reactor.Although molecular weight.Evidence of their liquid basis is found in the it probably represents only about 10-15%of the total capital accumulation of liquid in the ESP which runs down the plates cost of an integrated system,most research and development to accumulate in the bio-oil product.Demisters for agglom- has focused on developing and testing different reactor eration or coalescence of the aerosols have been used but configurations on a variety of feedstocks,although increasing published experience suggest that this is less effective. attention is now being paid to control and improvement of liquid quality and improvement of liquid collection systems 2.2.1.1.Heating.Heating can be achieved in a variety of ways The rest of the fast pyrolysis process consists of biomass and scaling is well understood.However,heat transfer to bed reception,storage and handling,biomass drying and grinding, at large scales of operation has to be considered carefully
product liquid oil, grinding the feed to give sufficiently small particles to ensure rapid reaction, fast pyrolysis, rapid and efficient separation of solids (char), and rapid quenching and collection of the liquid product (often referred to as bio-oil). Virtually any form of biomass can be considered for fast pyrolysis. While most work has been carried out on wood because of its consistency and comparability between tests, over 100 different biomass types have been tested by many laboratories, ranging from agricultural wastes such as straw, olive pits and nut shells to energy crops such as miscanthus and sorghum, forestry wastes such as bark and solid wastes such as sewage sludge and leather wastes. In all cases, a commercial process comprises three main stages from feed reception to delivery of one or more useful products: Feed reception, storage, handling, preparation and pretreatment; Conversion of solid biomass by fast pyrolysis to a more usable form of energy in liquid form which is known as biooil; Conversion of this primary liquid product by processing, refining or clean-up to a marketable end-product such as electricity, heat, biofuels and/or chemicals. 2.2. Fast pyrolysis reactors At the heart of a fast pyrolysis process is the reactor. Although it probably represents only about 10e15% of the total capital cost of an integrated system, most research and development has focused on developing and testing different reactor configurations on a variety of feedstocks, although increasing attention is now being paid to control and improvement of liquid quality and improvement of liquid collection systems. The rest of the fast pyrolysis process consists of biomass reception, storage and handling, biomass drying and grinding, product collection, storage and, when relevant, upgrading. Several comprehensive reviews of fast pyrolysis processes for liquids production are available such as [5e9]. Table 2 lists most of the known recent and current activities in fast pyrolysis arranged by reactor type and maximum known throughput. There has been considerable growth and expansion of activities over the last few years with more innovation in the types of reactor explored by academic institutions. It is disappointing to see so much re-invention and poor appreciation of the underlying fundamental requirements of fast pyrolysis as well as a reluctance to carry out basic reviews of past research publications. There are increasing activities on fixed bed and related systems that are unlikely to give high liquid yields but are likely to give phase separated liquids. Phase separated liquid products may be desirable in some applications where fractionation is required, but it would seem preferable to control such separation rather than rely on poor design and process control. 2.2.1. Bubbling fluid beds Bubbling fluid beds have the advantages of a well understood technology that is simple in construction and operation, good temperature control and very efficient heat transfer to biomass particles arising from the high solids density. Fig. 3 shows a typical configuration using electrostatic precipitators for coalescence and collection of what are referred to as aerosols. These are incompletely depolymerised lignin fragments which seem to exist as a liquid with a substantial molecular weight. Evidence of their liquid basis is found in the accumulation of liquid in the ESP which runs down the plates to accumulate in the bio-oil product. Demisters for agglomeration or coalescence of the aerosols have been used but published experience suggest that this is less effective. 2.2.1.1. Heating. Heating can be achieved in a variety of ways and scaling is well understood. However, heat transfer to bed at large scales of operation has to be considered carefully %08 %09 1 %00 scinagrO retaW 06 % %07 %08 rahC saG %03 %04 50% 0% 10% %02 0% Fig. 2 e Product spectrum from pyrolysis. 70 biomass and bioenergy 38 (2012) 68 e9 4
BIOMASS AND BIOENERGY 38 (2012)68-94 71 Table 2-Summary of fast pyrolysis reaction systems for liquids,recently and currently operational. Fast pyrolysis Industrial Units Max Research Max built size kg/h size kg/h Fluid bed Agritherm,Canada 200 Adelaide U,Australia Biomass Engineering Ltd,UK 200 Aston U.,UK Dynamotive,Canada 8000 Cirad,France RTI,Canada 20 Curtin U,Australia 2 ECN,NL East China U.Science and nk Technology,Shanghai,China Gent U.,Belgium 03 Guangzou Inst,China 10 Harbin Institute of Technology nk lowa State U.,USA 6 Monash U.Australia NREL,USA 10 PNNL,USA 1 Shandong U.Technology nk Shanghai JiaoTong U, Shenyang U.,China South East U.,China Texas A&M U.,USA 积 TNO,Netherlands 10 U.Basque Country,Spain nk U.Campinas,Brazil 100 U.Maine,USA 0.1 U.Melbourne,Australia 01 U.Naples,Italy 1 U.Science and Technology 650 of China U.Seoul,Korea nk U.Twente,Netherlands U.Western Ontario,Canada U.Zaragoza,Spain k USDA,ARS,ERRC,USA Virginia Tech.U.,USA 0.1 VTT,Finland VTI,Germany 6 Zhejiang U.,China Zhengzhou U.,China 2 Spouted fluid bed Ikerlan,Spain 10 Anhui U.of Science Technology,China U.Basque Country,Spain nk Transported Ensyn,Canada bed CFB Metso/UPM,Finland 81 4000 CPERI,Greece 400 Guangzhou Inst.Energy nk Conversion,China U.Birmingham,UK nk U.Nottingham,UK nk VTT,Finland 20 Rotating cone BTG,Netherlands 4 2000 BTG,Netherlands 10 Integral catalytic BioEcon,Netherlands nk nk Battelle Columbus,USA 1 pyrolysis Kior USA PNNL,USA 1 Technical U.of Munich nk U.Massachusetts-Amhurst,USA nk Virginia Tech.U.,USA 3? Vortex TNO,Netherlands 30 Centrifuge reactor Technical U.Denmark nk Ablative PyTec,Germany 250 Aston U.,UK 20 Institute of Engineering 15 Thermophysics,Ukraine Latvian State Institute,Latvia 0.15 Technical U.Denmark 1.5 Augur or Screw Abritech,Canada 2083 Auburn U.USA 1.0 Lurgi LR,Germany 500 KIT(FZK),Germany 500 Renewable Oil Intl,USA 200 Mississippi State U.,USA 2 Michigan State U.USA 0.5 Texas A&M U.,USA 30 (continued on next page)
Table 2 e Summary of fast pyrolysis reaction systems for liquids, recently and currently operational. Fast pyrolysis Industrial Units built Max size kg/h Research Max size kg/h Fluid bed Agritherm, Canada 2 200 Adelaide U, Australia 1 Biomass Engineering Ltd, UK 1 200 Aston U., UK 5 Dynamotive, Canada 4 8000 Cirad, France 2 RTI, Canada 5 20 Curtin U, Australia 2 ECN, NL 1 East China U. Science and Technology, Shanghai, China nk Gent U., Belgium 0.3 Guangzou Inst, China 10 Harbin Institute of Technology nk Iowa State U., USA 6 Monash U. Australia 1 NREL, USA 10 PNNL, USA 1 Shandong U. Technology nk Shanghai JiaoTong U, 1 Shenyang U., China 1 South East U., China 1 Texas A&M U., USA 42 TNO, Netherlands 10 U. Basque Country, Spain nk U. Campinas, Brazil 100 U. Maine, USA 0.1 U. Melbourne, Australia 0.1 U. Naples, Italy 1 U. Science and Technology of China 650 U. Seoul, Korea nk U. Twente, Netherlands 1 U. Western Ontario, Canada nk U. Zaragoza, Spain nk USDA, ARS, ERRC, USA 1 Virginia Tech. U., USA 0.1 VTT, Finland 1 vTI, Germany 6 Zhejiang U., China 3 Zhengzhou U., China 2 Spouted fluid bed Ikerlan, Spain 1 10 Anhui U. of Science & Technology, China 5 U. Basque Country, Spain nk Transported bed & CFB Ensyn, Canada 8 4000 CPERI, Greece 1 Metso/UPM, Finland 1 400 Guangzhou Inst. Energy Conversion, China nk U. Birmingham, UK nk U. Nottingham, UK nk VTT, Finland 20 Rotating cone BTG, Netherlands 4 2000 BTG, Netherlands 10 Integral catalytic pyrolysis BioEcon, Netherlands þ Kior USA nk nk Battelle Columbus, USA 1 PNNL, USA 1 Technical U. of Munich nk U. MassachusettseAmhurst, USA nk Virginia Tech. U., USA 3? Vortex TNO, Netherlands 30 Centrifuge reactor Technical U. Denmark nk Ablative PyTec, Germany 2 250 Aston U., UK 20 Institute of Engineering Thermophysics, Ukraine 15 Latvian State Institute, Latvia 0.15 Technical U. Denmark 1.5 Augur or Screw Abritech, Canada 4 2083 Auburn U. USA 1.0 Lurgi LR, Germany 1 500 KIT (FZK), Germany 500 Renewable Oil Intl, USA 4 200 Mississippi State U., USA 2 Michigan State U. USA 0.5 Texas A&M U., USA 30 (continued on next page) biomass and bioenergy 38 (2012) 68 e9 4 71
72 BIOMASS AND BIOENERGY 38 (2012)68-94 Table 2 (continued) Fast pyrolysis Industrial Units Max Research Max built size kg/h size kg/h Radiative-Convective CNRS-Nancy U.,France nk Entrained flow, Dalian U.of Technology,China nk Institute for Wood Chemistry,Latvia nk Shandong University of Technology 0.05 Microwave Carbonscape nk nk Chinese Academy of Sciences, nk New Zealand UK Dalian 116023,P.R.China Bioenergy 2020 gmbh, 1 nk National Inst.Advanced Industrial <0.1 Austria Sci.Technol.,Japan Shandong U.China <0.1 Technical U.Vienna,Austria nk U.Malaysia Sarawak <0.1 U.Minnesota,USA 10 U.Mississippi nk U.Nottingham,UK and China nk U.York,UK nk Washington State U.-Tricities,USA <1 Moving bed and Anhui Yineng Bio-energy 3 600 Anadolu University,Turkey nk fixed bed Ltd.,China U.Autonoma de Barcelona,Spain nk U.Science Technology of China -0.5 Ceramic ball Shandong University of 110 downflow Technology,China Unspecified U.Kentucky,USA nk U.Texas,USA nk Technical U.Compiegne,France nk Vacuum Pyrovac,Canada 3500 None known because of the scale-up limitations of different methods of at fast pyrolysis reaction temperatures,rapid and effective heat transfer.Fluid-bed pyrolysers give good and consistent char separation is important.This is usually achieved by performance with high liquid yields of typically 70-75 wt.% ejection and entrainment followed by separation in one or from wood on a dry-feed basis.Small biomass particle sizes of more cyclones so careful design of sand and biomass/char less than 2-3 mm are needed to achieve high biomass heating hydrodynamics is important.The high level of inert gases rates,and the rate of particle heating is usually the rate- arising from the high permanent gas flows required for fluid- limiting step. isation result in very low partial pressures for the condensable vapours and thus care is needed to design and operate efficient 2.2.1.2.Char.Vapour and solid residence time is controlledby heat exchange and liquid collection systems.In addition the the fluidising gas flow rate and is higher for char than for large inert gas flowrates result in relatively large equipment vapours.As char acts as an effective vapour cracking catalyst thus increasing cost. The byproduct char is typically about 15 wt.%of the Prepared Quench GAS products but about 25%of the energy of the biomass feed.It BIOMASS Cyclones cooler export can be used within the process to provide the process heat Dried and sized Gas requirements by combustion or it can be separated and recycle exported,in which case an alternative fuel is required. Depending on the reactor configuration and gas velocities, a large part of the char will be of a comparable size and shape Fluid as the biomass fed.The fresh char is pyrophoric i.e.it spon- bed taneously combusts when exposed to air so careful handling reactor and storage is required.This property deteriorates with time CHAR due to oxidation of active sites on the char surface process heat Electrostatic or export precipitator 2.2.1.3.Background.All the early work on fluid beds was ↓ carried out at the University of Waterloo in Canada,which CHAR BIO-OIL pioneering the science of fast pyrolysis and established a clear lead in this area for many years (e.g.[10-121).Bubbling fluid Recycle gas beds have been selected for further development by several heaterand/or oxidiser companies,including Union Fenosa [13],who built and oper- ated a 200 kg/h pilot unit in Spain based on the University of Fig.3-Bubbling fluid bed reactor with electrostatic Waterloo process which was dismantled some years ago; precipitator. Dynamotive,who operated a 75 kg/h and 400 kg/h pilot unit
because of the scale-up limitations of different methods of heat transfer. Fluid-bed pyrolysers give good and consistent performance with high liquid yields of typically 70e75 wt.% from wood on a dry-feed basis. Small biomass particle sizes of less than 2e3 mm are needed to achieve high biomass heating rates, and the rate of particle heating is usually the ratelimiting step. 2.2.1.2. Char. Vapour and solid residence time is controlled by the fluidising gas flow rate and is higher for char than for vapours. As char acts as an effective vapour cracking catalyst at fast pyrolysis reaction temperatures, rapid and effective char separation is important. This is usually achieved by ejection and entrainment followed by separation in one or more cyclones so careful design of sand and biomass/char hydrodynamics is important. The high level of inert gases arising from the high permanent gas flows required for fluidisation result in very low partial pressures for the condensable vapours and thus care is needed to design and operate efficient heat exchange and liquid collection systems. In addition the large inert gas flowrates result in relatively large equipment thus increasing cost. The byproduct char is typically about 15 wt.% of the products but about 25% of the energy of the biomass feed. It can be used within the process to provide the process heat requirements by combustion or it can be separated and exported, in which case an alternative fuel is required. Depending on the reactor configuration and gas velocities, a large part of the char will be of a comparable size and shape as the biomass fed. The fresh char is pyrophoric i.e. it spontaneously combusts when exposed to air so careful handling and storage is required. This property deteriorates with time due to oxidation of active sites on the char surface. 2.2.1.3. Background. All the early work on fluid beds was carried out at the University of Waterloo in Canada, which pioneering the science of fast pyrolysis and established a clear lead in this area for many years (e.g. [10e12]). Bubbling fluid beds have been selected for further development by several companies, including Union Fenosa [13], who built and operated a 200 kg/h pilot unit in Spain based on the University of Waterloo process which was dismantled some years ago; Dynamotive, who operated a 75 kg/h and 400 kg/h pilot unit Table 2 (continued) Fast pyrolysis Industrial Units built Max size kg/h Research Max size kg/h Radiative-Convective CNRS e Nancy U., France nk Entrained flow, Dalian U. of Technology, China nk Institute for Wood Chemistry, Latvia nk Shandong University of Technology 0.05 Microwave Carbonscape New Zealand & UK nk nk Chinese Academy of Sciences, Dalian 116023, P. R. China nk Bioenergy 2020 þ gmbh, Austria 1 nk National Inst. Advanced Industrial Sci. & Technol., Japan <0.1 Shandong U. China <0.1 Technical U. Vienna, Austria nk U. Malaysia Sarawak <0.1 U. Minnesota, USA 10 U. Mississippi nk U. Nottingham, UK and China nk U. York, UK nk Washington State U.-Tricities, USA <1 Moving bed and fixed bed Anhui Yineng Bio-energy Ltd., China 3 600 Anadolu University, Turkey nk U. Auto`noma de Barcelona, Spain nk U. Science & Technology of China w0.5 Ceramic ball downflow Shandong University of Technology, China 110 Unspecified U. Kentucky, USA nk U. Texas, USA nk Technical U. Compiegne, France nk Vacuum Pyrovac, Canada 1 3500 None known Fig. 3 e Bubbling fluid bed reactor with electrostatic precipitator. 72 biomass and bioenergy 38 (2012) 68 e9 4