Group 9(Bio-Oil Pyrolysis) - Handout

FAST PYROLYSIS BIO-OIL

09/12/2010 GRUOP 9 BioRefinery Engineering

Jie Fu

Shimme Sharma

Hardik Savani

Oscar Abrica

FAST PYROLYSIS BIO-OIL

FAST PYROLYSIS BIO-OIL S U M M A R R Y

The depletion of conventional fuel has encouraged scientists to find out a substitute to replace it. Biomass like sawdust is a good renewable energy source in order to satisfy the demand up to some extent. Sawdust has been found to be most efficient when compared to other biomass that could be used in fast pyrolysis. Tons of sawdust is collected daily and turned into valuable bio-oil using the process of fast pyrolysis. A cyclone reactor is used to carry out the process because of its excellent heat transfer efficiency and a very short residence time. Optimum temperature used in this process is around 500o C to obtain maximum yield of bio-oil.

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Content Fast Pyrolysis Bio-Oil

Introduction 04 What is Bio-Oil What is Fast Pyrolysis Process Physical and Chemical Properties of Bio-Oil

Selecting the Raw Material 06 Typical Raw Material characteristics

Plant Location 06 Geography of our Plant Transportation and Costing

Fast Pyrolysis Process 07 Description of the Process Operating Conditions Mass Balances Energy Consumption

Fast Pyrolysis Plant Cost 11 Equipment Costs Capital Cost

Bio-Oil Applications 12 Bio-Oil Uses Advantages Challenges Up-Grading Bio-Oil

Results and Conclusion 13

References 14

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BIO-OIL (PYROLYSIS)

Introduction

At present, the renewable energy production is becoming more important aspect in order to satisfy the environmental concern over conventional fuels and its contribution to green house effects. The study data shows that biomass has contributed to the worlds 10-14% of the total energy supply.

Wood, agricultural wastes and other forms of biomass are some of the main renewable energy sources to produce required energy.

[a]

[2] Biomass is any biological matter that can be used to produce energy. Its composition basically includes celluloses, hemicelluloses, lignin and some minor amounts of other organics which makes it useful as a renewable energy source. Its conversion to energy takes up two approaches: biochemical (fermentation and anaerobic digestion) or thermochemical (combustion, gasification and fast pyrolysis). Pyrolysis has been widely used for its ability to produce liquid products.

[1,7]

Pyrolysis is a process where biomass is heated at very high temperature (usually between 400-700oC) in the absence of oxygen to produce a solid phase called charcoal (carbon and ash), non-condensable gases and a condensable vapour called pyrolysis oil (bio-oil).[2] It involves reactions like depolymerisation, hydrolysis, oxidation, dehydration and decarboxylation.[6]

Pyrolysis process takes up two approaches: one is slow or conventional pyrolysis and the other is fast or flash pyrolysis. Fast pyrolysis process is preferred over slow pyrolysis because of its ability to produce high liquid yield and low solid yield with a very short residence time. The most important advantage of fast pyrolysis is that the major product is in liquid form which can be easily stored and transported.

[4]

Reactors used to carry out pyrolysis are divided according to the size of the particles and their characteristic residence times.

[8]

Table 2: Comparison of different reactors

Types of reactor Particle size Residence time

Fixed bed Large 103 to 105 s

Vortex (Cyclone) Small 5 x10-3 to 10 s

Fluidized bed Medium 102 to 104 s

[8]Cyclone reactor has excellent heat transfer efficiency and a very short residence time (lower than a few seconds). In addition, solid by-products and unreacted particles

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can be automatically separated from gaseous products at the same time. The major advantage of using this reactor in fast pyrolysis is that it can carry out five essential reactions of pyrolysis process in the same vessel. These reactions include: (i) Fast heating of the raw materials; (ii) Chemical decomposition of the components; (iii) Efficient friction of the particles against the walls which eliminates the products; (iv) Further reactions of the primary products; (v) Cleaning of the evolved gas (simultaneous separation of char and ash at the bottom). Bio-Oil is a dark brownish viscous organic liquid made up of complex oxygenated compounds that bears some resemblance to fossil fuel. However, the heating value of bio-oil is lower than that of fossil fuel because of its high oxygen content.

[2]

The molecular composition of bio-oil varies significantly with the type of biomass and the pyrolysis conditions used. Its major components are water, water soluble compounds like acids, alcohols, ketones, aldehydes, substituted furans derived from cellulose and hemicelluloses, and water insoluble compounds like phenolic and cyclic oxygenates derived from lignin fraction of biomass.

[1]

Bio-oil is an acidic liquid with pH ranging between 2-4 making it highly unstable and corrosive. Hence, it is usually transported and stored in stainless steel containers. Specific gravity of bio-oil is about 1.10-1.25, which means it is heavier than water, fuel oil, and bulk density of biomass. It has a viscosity that ranges from 40 cP to 100 cP usually depending on the water content and the original feedstock. As bio-oil consists of large amount of oxygenated compounds, it tends to be polar and therefore does not readily mix with hydrocarbons. It has a tendency to phase separate when the water content in it reaches above 30 percent.

[3]

[20]

Table: 1 Properties of Pyrolysis Oil from sawdust

PHYSICAL PROPERTIES TYPICAL VALUE Moisture content 15%-30%

pH 2.5 Specific gravity 1.1-1.2

Elemental analysis C H O N

Ash

55%-58% 5%-8%

35%-40% 0.0%-0.2% 0.0%-0.2%

High heat value 6878-11175 Btu/lb (16-26 MJ/kg)

Char 1%-10%

Viscosity (104 0 F and 25% water)

40-100cP

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Raw Material: Why sawdust? Generally, there are so many kind of biomass can be used as raw material to produce

bio-oil, from high-valued crop seeds to relatively low-valued waste straws, from aquatic organisms to terrestrial plants. Here we choose sawdust as raw material to produce bio-oil not only depending on its relatively extensive and continuous sources but also considering these properties: bio-oil yields, calorific value, moisture and density. There is a general comparison among some raw materials.

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Table: 3 Different Raw Material Properties

Rice husk Corn stalk Cotton stalk

Sawdust

Bio-oil yields (wt%) 51.0 56.0 57.0 65.0 Calorific value (MJ/kg) 16.4 16.8 17.2 17.4 Moisture (wt%) 27.2 26.9 26.7 24.0 Density(kg/m3) 1120 1140 1155 1180

Compared with other similar biomass (high lignin cellulose content), sawdust has a relatively high density and low moisture content. But most important thing is that the bio-oil yield from sawdust is distinctively bigger than other types. It indicates that with the same raw material and energy input, we can get more bio-oil from using sawdust.

Plant Location: Our proposed plant is located about 6 kilometres from Nadiad and 13 kilometers

from Anand (Gujarat, INDIA). In addition, a nearby city called Vasad where many timber industries are situated could also provide around 35-40 tons/day saw dust. Approximately, around 105-110 tons/day of saw dust can be obtained from the timber industries situated within 15 kilometers radius of this area. Based on the quantity of saw dust available, we have proposed our plant at this location.

Transportation facilities and costing: Among several modes of transport available in INDIA, trucks have been the most

effective mode of transport in industrial sectors. Based on the geographical location of our proposed plant and the condition of roads available, the most suitable trucks are in the size of 17 tons capacity. The maximum weight carried out by this truck is around 8 tons of raw materials and the average travelling cost is $ 0.45 per kilometer.

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Producing Bio-Oil from sawdust using fast pyrolysis:

(d) Computer Software FlowSheet 100 tons of sawdust are gathered everyday as raw material to produce bio-oil

(pyrolysis oil), using the fast pyrolysis technique within a cyclone-reactor continuously.

The efficiency of sawdust converted into bio-oil is approximately 70%, with 15% syngas and 10% charcoal as by-product.

Given that an anaerobic atmosphere is required during the decomposition period, sand (SiO2) is heated in a different tank and therefore used as heat transfer medium (fluidized bed technique), to heat sawdust from ambient temperature to the temperature required, which is 500 within the cyclone-reactor.

After biomass is decomposed and turns into vapours form, there are some separations methods involved, to separate bio-oil and syngas. The proccess is optimized by using the syngas and charcoal as fuel for heating the sand, furthermore, there are some energy recovery stages within the whole procces.

Pre-treatment of sawdust:

Before undergoing the fast pyrolysis, sawdust is pretreated in a storage tank (volume 225m3; height: 2m; diameter: 12m). Pretreatment of raw material includes both

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reducing the diameter and drying moisture within the sawdust. Theoretically, the smaller the size and the less humidity sawdust have, the higher efficiency is from sawdust to bio-oil.

Hence, 45 tons of sawdust is being grinded to less than 5mm diameter and heated to 100 for 10 hours using hot flue gas generated from our process. The humidity of sawdust will be less than 8 wt% before it is processed. The process is repeated with 45tons sawdust.

Fast Pyrolysis: At the beginning of the process, sawdust is feed continuously by using a screw

feeder [4] to the cyclone-reactor [10]

with a feed rate of 1.16 kg/s. Meanwhile, a flow of heated sand (50050) is fed into the cyclone-reactor at 5 times the feed rate (5.8kg/s) of sawdust.

Particles enter tangentially into the reactor and then are rapidly thrown against the wall of cyclone-reactor. During this process, the contact of heated sand and sawdust leads to increase in temperature of sawdust within a pretty short period of time (around 1 to 2 seconds). Then sawdust is transformed into bio-oil vapor, syngas and charcoal.

Within the cyclone-reactors high-speed rotating conditions and the driving force of

N2 [4]

, solid components (charcoal, sand and unreacted sawdust are automatically separated from the gaseous products (bio-oil vapor and syngas). Then the gaseous components flow through the stainless steel pipe to a condenser, where vaporous bio-oil is condensed using a reflux of cooling bio-oil and cooling water. Whereas, syngas is recycled to the sand tank for heating the sand.

In addition, charcoal together with N2

and unreacted sawdust is also recycled back to the burner tank.

Heat Carrier: Sand is heated in the burner tank using syngas, charcoal (coming from the cyclone-

reactor), and natural gas as fuel. It is important to notice that the sand is always in movement, this ensures all the sand particles within the reactor are heated. After sand is heated, flue gases are directed to a second cyclone, where ashes are separated from the hot flue gas and collected at the bottom. The flue gas is then used as a driving force to generate power through gas turbine.

The flue gases coming out of gas turbine are of relatively high temperature, around 200-150. Therefore, instead of emitting them directly to the atmosphere, we recycle them to dry the sawdust.

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Cooling System: The bio-oil vapor formed, is relatively high in temperature, hence need to be cooled

down to temperature below 50 as soon as possible to prevent it from undergoing further reactions. Therefore, to gain bio-oil of high quality and quantity, immediate cooling is a key factor.

Previously, immiscible liquid was used a quenching agent to cool down the bio oil. According to recent research, [13]

it is mentioned that previously made and cooled bio-oil reflux can be used to cool down the bio-oil vapor because it saves both the energy and the effort to separate bio oil from immiscible liquid. In addition, water is also used as another cooling agent. As a consequence, energy is saved during the condensation process and the steam generated from water during heat exchange, is used to generate power through a steam turbine.

After the condensation process, bio-oil is transported to a storage tank. For the process, both pipes and tank are made up of stainless steel due to the low pH and corrosive properties of the bio-oil [15]. The volume of tank which is used to store bio-oil is 120m3

(height: 2m; diameter: 9m).

Mass Balance per Day:

Mass input Sawdust 100 tons N2 346.587 kg Air 895.104 kg

Mass output Bio-oil 70 tons Flue gas 16.242 tons (Which can be used to drive a gas turbine and then dry sawdust)

Mass consumed within system Syngas 15 tons Charcoal 10 tons Volume of cyclone reactor: V=67m Height3.5m; Diameter: 5m

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Energy accounting:

Total Q needed to heat sand CP Mass flow rate of sand R=5.8 kg/s

(SiO2)=830 J/kg

Initial temperature Ti=25

Targeting temperature Tt=100 QT=CP

R (Tt-Ti) =3610.5 kJ/s

Q provided by burning charcoal Mass flow rate of sawdust Rs=1.16 kg/s Proportion of charcoal produced from sawdust=10% Mass flow rate of charcoal Rchar=Rs=0.116 kg/s Average heating value of charcoal Ca=27.91 MJ/kg Temperature of charcoal coming from cyclone Ti=300

Targeting temperature of charcoal Tt=550 Q provided by charcoal Qchar=CaRs(Tt-Ti)=3237.56kJ/s

Natural gas needed to burn charcoal Q provided by burning natural gas to heat sand Qng=QTSpecific heating value of Natural gas Cng=54 MJ/kg

-Qchar=372.94 kJ/s

Mass flow rate of Natural gas Rng=QngCng=0.006906kg/s

Cooling water Initial temperature of bio-oil vapor Ti=300

Targeting temperature of bio-oil Tt=50 Cp(water)=4.2kJ/kg Cp(bio-oil)=23260kJ/kg Mass flow rate of bio-oilRoil=1.16kg/s70%=0.812kg/s Heat need to be removed from bio-oil vapor: Q=Cp(bio-oil)Roil(Ti-Tt)=4721780 kJ/s To simplify, assume that all bio-oil vapor is cooled by water Rwater=Q (Cp(water)(Tt-Ti))~5 m3

/s (Which can be used to drive a steam turbine, and then directed to a cooling tower)

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PYROLYSIS Bio-Oil Plan Cost

EQUIMENT COST (1000 US DLS) Sawdust Storage Tank $082.78

Bio-Oil Storage Tank $108.22

Cyclone-Reactor $071.74

Screw Feeder (Conveyor-Solid 5m)

$010.82

Air Compressor $064.61

Cyclone $044.83

Centrifugal Pump $002.86

Condenser $039.13

Natural Gas Supply (Annual)

$454.18

Nitrogen Supply (Annual) $366.13

Water Supply (Annual) $462.03

Sawdust $950.95

Transportation (Annual)

$163.80

TOTAL COST $2822.08

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Applications: 1. Several types of valuable chemicals like, Acetic acid, Propionic acid, Formic

acid, Calcium chloride, etc. can be separated from the bio-oil based on their water solubility.

2. The whole product can be converted into useful chemical because of its most abundant functional groups like carbonyl, carboxyl and phenolic group. Hence we need not to separate the non-reacting part of the bio-oil.

3. It can be used as bio-fertilizer by reacting with urea and ammonia. 4. It can be used as insecticides and fungicides due to the presence of the chemical

compounds like phenolic and terpenoid. 5. It is also used as a wood preservative instead of creosote to protect wood from

fungal infection. 6. It can be used to improve the appearance of uneven skin like stretch marks, skin

burns, dried skin etc. 7. It can be used as a fuel when mixed with diesel with the aid of surfactants.

Since bio-oil cannot mix with hydrocarbon, surfactants can be used to emulsify it with diesel fuel.

Advantages:

1. Have high flash point and therefore less flammable than diesel oil. 2. Exhaust fumes are less toxic with less carbondioxide and sulphurdioxide. 3. Since, it is derived from organic sources, is biologically degradable and less

damaging. 4. Direct application in various types of energy power station like boilers.

Challenges of Bio-oil

1. Production of bio-oil is still under research and development, hence, its cost is

slightly higher than the fossil fuel. 2. Availability of large amount of raw material per day remains a problem. 3. Bio-oil produced may have inconsistent quality which could affect its marketing. 4. Bio-oil produced is unstable and may require upgrading techniques like

hyrotreatment to make it stable, thus adding to the net cost of production. 5. Engine modification required in order to make bio-oil compatible to

conventional fuel. 6. Since bio-oil is a recent technology, the consumers are still unfamiliar with its

use.

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7. Environmental health and safety issues need to be considered during its production, transportation, and use.

8. The heating value of bio oil if half of that of petroleum fuel.

Upgrading of Bio Oil One of the main disadvantage of using bio oil as a fuel is that it is highly oxygenated

with a low octane number which makes it difficult for transportation and storage. Hydrodeoxygenation (a process of hydro-treatment) could be used to upgrade the bio oil by adding hydrogen and eliminating oxygen. It produces a highly valuable hydrocarbon (like cyclohexane and benzene) composed bio oil which would satisfy the standards of transportation. The formation of saturated C-C bond and water in the reaction increases the stability of bio oil by decreasing the acidity, moisture content, viscosity and increasing the heating value. However, this process might be complicated and expensive.

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Marketing: The bio-oil produced from fast pyrolysis could be sold to chemical industries, power

generating industries, fuel industries, cosmetic industries, and pharmaceutical industries. Given our proposed location, many of these industries are situated within 50 km radius, mainly in Ahmadabad and Baroda (the two major cities having most pharmaceutical, petroleum and cosmetic industries).

Ash generated from the process could also be marketed to the fertilizer making industries.

Result and conclusion:

Due to the high efficiency of fast pyrolysis technique, 70 tons of bio-oil can be produced from 100tons of sawdust per day and the char and syngas produced are recycled reducing the power cost. If the process is strictly carried out within the limits of anaerobic atmosphere in cyclone reactor, high and fast heat to sawdust and rapid condensing of bio-oil vapor, we might be able to achieve a highly efficient process. Hence, with a certain upgrading, bio-oil will cherish a brighter future.

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References [1] E. Salehi, J.Abedi and T. Harding (2009) Bio-Oil from sawdust: Pyrolysis of

sawdustin a Fixed Bed system. Energy and fuels, 23; 3767-3772. [2] Samy Sadaka and A.A. Boateng. Pyrolysis And Bio-Oil. University of Arkansas,

United States Department of Agriculture FSA1052. [3] Hyeon Su Heo et al (2010). Bio-oil production from fast pyrolysis of waste

furniture sawdust in a fluidized bed. 101; S91-S96. [4] Suchithra Thangalazhy-Gopakumar, Sushil Adhikari (2010) Physiochemical

properties of bio-oil produced at various temperatures from pine wood using an auger reactor, Bioresource Technology 101; 83898395.

[5] M. Asadullah et al. (2007). Production of bio-oil from fixed bed pyrolysis of bagasse, Fuel 86; 2514-2520.

[6] Sun-Hoon Lee et al. (2008). The yields and composition of bio-oil produced from Quercus Acutissima in a bubbling fluidized bed pyrolyzer. Pyrolysis 83; 110-114.

[7] Dinesh Mohan, Charles U. Pittman, Jr., and Philip H. Steele (2006). Pyrolysis of wood/biomass for bio-oil: A critical review. Energy and fuel 20; 848-889. [8] J. Lede, F. Verzaro, B. Antoine and J. Villermaux (1986). Flash pyrolysis of wood in a cyclone reactor. 309-317 [9] Murni M. Ahmad, M. Fitrir R. Nordin and M. Tazli Azizan (2010). Upgrading of Bio-Oil into High-Value Hydrocarbons via Hydrodeoxygenation. 7(6); 746-755. [10] Jacques Lede (2000).The Cyclone: A Multifunctional Reactor for the Fast Pyrolysis of Biomass. 39, 893-903. [11] S. Czernik and A.V. Bridgwater (2004). Overview of application of biomass fast pyrolysis oil. Energy and fuel 18; 590-598. [12] Sukiran, M.A., et al., (2009). Bio-Oil from Pyrolysis of Palm Empty Fruit Bunches. American Journal of Applied Sciences, 6(5), pp. 869-875. [13] Jacques Lede, Francois Broust , Fatou-Toutie Ndiaye (2007). Properties of bio-oils produced by biomass fast pyrolysis in a cyclone reactor, Fuel 86; 18001810. [14] Xifrng. ZHU (2008). Biomass fast pyrolysis for bio-oil. University of Science and technology of china. [15] Lu Qiang, Li Wen-Zhi, Zhu Xi-Feng (2009). Over view of fuel properties of biomass fast pyrolysis oils. Energy conversion and management 50; 1376-1383. [16] Jackson, S.W., et al., 2010. Wood 2 Energy a State of the Science and Technology Report. The University of Tennessee, Institute of Agriculture. [17] Bui, V.N., et al., 2008. Co-processing of Pyrolysis Bio-Oils and Gas-Oil for new generation of Bio-Fuels: Hydrodeoxygenation of guaiacol and SRGO mixed fed. [18] Smith, J.M., Van Ness, H.C., Abbott, M.M., 2007. Introduction to Chemical Engineering Thermodynamics. 7ed. McGraw-Hill. [19] Park, Y.P., et al., 2004. Bio-Oil from Rice Straw by Pyrolysis Using Fluidized Bed and Char Removal System. Prepr. Paper, Journal of the American Chemical Society, Div. Fuel Chem, 49(2); 800-801.

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Bridgewater , AV, S. Czernik, J.Piskorz (2002). The status of biomass fast pyrolysis. Vol: 2

Web-sources:

[a] http://www1.eere.energy.gov/maps_data/pdfs/eere_databook.pdf [b] http://software.cstb.fr/ThOp/Applets/combustion/appletEn/CalcCombEn.html [Accessed 07 Dec 2010] [c] www.btg-btl.com

[d] Computer Software FlowSheet

Cover PageFAST PYROLYSIS BIO1FAST PYROLYSIS BIO2

ContentContentFast Pyrolysis Bio-OilIntroduction 04Selecting the Raw Material 06Plant Location 06Fast Pyrolysis Process 07Fast Pyrolysis Plant Cost 11Bio-Oil Applications 12Results and Conclusion 13References 14

Body - PYROLYSIS Bio-OilIntroductionRaw Material: Why sawdust?Plant Location:Transportation facilities and costing:Producing Bio-Oil from sawdust using fast pyrolysis:(d) Computer Software FlowSheet

Pre-treatment of sawdust:Fast Pyrolysis:Heat Carrier:Cooling System:Mass Balance per Day:Energy accounting:PYROLYSIS Bio-Oil Plan CostApplications:Advantages:Challenges of Bio-oilUpgrading of Bio OilMarketing:Result and conclusion:ReferencesWeb-sources:[d] Computer Software FlowSheet

EQUIMENT COST (1000 US DLS)