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    0 | P a g e 0 9 C H 3 0 0 6 A m a n S i n h a l

    DEPARTMENT OF CHEMICAL ENGINEERING,

    INDIAN INSTITUTE OF TECHNOLOGY KHARAGPUR

    (2012 2013)

    PYROLYSIS OF MICROALGAE FOR THE PRODUCTION OF

    RENEWABLE FUELS

    Submitted in fulfillment of the degree of

    Bachelor of Technology

    In

    Chemical Engineering

    By

    Aman SinhalRollNo.09CH3006

    UNDER THE SUPERVISION OF

    Dr . Saikat Chakraborty

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    Certificate

    This is to certify that the thesis entitled Pyrolysis of Microalgae for the production of Renewable

    Fuels submitted by Aman Sinhal to the Department of Chemical Engineering, in partial

    fulfilment for the award of the degree of Bachelor of Technology is an authentic record of the

    work carried out by him under my supervision and guidance. The thesis has fulfilled all the

    requirements as per the regulations of this institute and, in my opinion, has reached the standard

    needed for submission.

    Date: 01/05/2013

    ---------------------------------

    Dr. Saikat Chakraborty

    Department of Chemical Engineering

    Indian Institute of Technology, Kharagpur

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    Acknowledgement

    I would like to extend my heartfelt gratitude to Prof. Saikat Chakraborty for providing me with

    the opportunity to work on a project based on renewable energy source which is the need of thehour and is in the greater interest of the society. It is very difficult to describe her contribution to

    the thesis in words.

    I am thankful to Prof. N. C. Pradhan, Head of the Department of Chemical Engineering, IIT

    Kharagpur and the faculty members of the department for their invaluable support and

    encouragement. I am also thankful to Mr. Ankit Agarwal for providing important inputs for the

    preparation of the report as it is in the present form.

    Date: 1stMay, 2013 Aman Sinhal

    Place: Kharagpur 09CH3006

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    Abstract

    Pyrolysis involves the simultaneous change of chemical composition and physical phase, and is

    irreversible. It is a thermochemical decomposition of organic material at elevated temperatures without

    the participation of oxygen. The word is coined from the Greek-derived elements pyro "fire" and lysis

    "separating". In this work fast catalytic and non-catalytic pyrolysis of microalgae, Chlorella Vulgaris was

    studied to generate third generation biofuel.

    Fixed bed Pyrolysis reactor with the auger feed arrangement was designed to feed the biomass into the

    hot-zone. Heterogeneous catalyst such as Ni-ZSM5 was prepared from pentasil using ion exchange with

    Ni(NO3)2 to study the catalytic upgradation of biofuel from algae. To study the kinetics of pyrolysis of

    microalgae, it was pyrolysed in the thermogravimetric analyzer from room temperature to 800 0C in inert

    N2 atmosphere at different heating rates of 5,10,20,30,40 C/min.

    The results showed that three stages appeared during the pyrolysis process and with increase in heating

    rate, initial temperature, peak temperature and rate of conversion increases. The kinetic analysis of the

    stage 2, where the major decomposition take place during pyrolysis was done using iso-conversional and

    regression analysis methods. The activation energy of 51 KJ/mol and 49 KJ/mol was estimated using

    Flynn and Kissinger iso-conversional methods respectively. The combustion characteristics of biomass

    were also compared with pyrolysis in this study.

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    Contents

    ABSTRACT ........................................................ .............................................................. ........................... 2

    CHAPTER 1:INTRODUCTION............................................................ ........................................................... 6

    1.1OBJECTIVE OF WORK IN EACH OF THE PART........................................................ ........................... 9

    CHAPTER 2:LITERATURE REVIEW................................................. ......................................................... 10

    2.1REACTOR DESIGNS FOR PYROLYSIS............................................................................................ ... 11

    2.2BIO-OIL................................................................ .............................................................. .............. 13

    2.3FEEDSTOCK................................ ................................................................. .................................... 14

    2.4TYPES OF BIO OILS............................................................................................................ .............. 14

    2.5UPGRADING AND STABILITY OF BIO-OIL.................................................. .................................... 15

    CHAPTER 3:EXPERIMENTAL SETUP.................................................................... .................................... 16

    3.1EXPERIMENTAL PROCEDURE........................................................................................... .............. 19

    3.2SELECTION OF CATALYST............................................................................................................ ... 20

    3.3CATALYST PREPARATION PROTOCOL............................................................................. .............. 24

    FIGURE 6:PROTOCOL FOR PREPARATION OF CATALYST,NI-ZSM5 ............................................... 25

    3.4THERMOGRAVIMETRICANALYSIS................................................... .............................................. 26

    3.5MATERIALS REQUIRED FOR EXPERIMENT................ ................................................................. ... 27

    3.6METHOD OF EXPERIMENT......................................... ................................................................. ... 27

    CHAPTER 4:ALGAL PYROLYSIS REACTOR MODELING........................................................................... 28

    4.1DESCRIPTION OF EACH ZONE........................................................... .............................................. 29

    4.2MODELING EQUATIONS.................................................................................................... .............. 30

    4.3STEADY STATE MODELING TWO-PHASE CATALYTIC REACTOR (ZONE 3) ............................ ... 32

    CHAPTER 5:SIMULATIONS (STEADY STATE) ........................................... .............................................. 34

    CHAPTER 6:UNSTEADY STATE MODELING................................... ......................................................... 38

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    CHAPTER 7:SIMULATIONS (UNSTEADY STATE) ........................................................... ......................... 41

    CHAPTER 8:CONCLUSION...................................................................................... ................................... 49

    8.1SUMMARY......................................................... ................................................................. .............. 49

    8.2FUTURE WORK..................................... ................................................................. ......................... 50

    APPENDIX............................................................. .............................................................. ......................... 51

    REFERENCES........................................................................................................... .................................... 58

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    Chapter 1: Introduction

    In light of the degree of pollution that the environment has undergone in the last couple of

    decades, it is only natural that we look for renewable sources of energy. With the population

    explosion that the developing countries have resulted in, developing alternative sources of

    energy like bio-fuels are the need of the hour. The most common bio-fuels are biodiesel and bio-

    ethanol, which can replace diesel and gasoline, respectively, in today cars with little or none

    modifications of vehicle engines. In this report, we focus on the catalytic and non-catalytic

    pyrolysis, comparison and preparation of different catalyst used for thermal upgrading, kinetic

    study of the pyrolysis process through thermo gravimetric analysis and have a detailed

    model of the reactor system.

    Figure 1: Sample of Algae

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    The transportation and energy sector are the major sources of green house gas emissions. It is

    expected that with the development of new growing economies, such as India and China, the

    global consumption of energy will raise and lead to more environmental damage. One important

    goal is to take measures in transport emissions such as gradual replacement of fossil fuel by

    renewable energy sources, where bio-fuels are seen as real contributors to reach the goal in long

    term. The most common bio-fuels are biodiesel and bio-ethanol, which can replace diesel and

    gasoline. They are mainly produced from biomass or renewable energy sources and contribute to

    lower combustion emissions. Beside renewable, biodiesel is also non toxic and biodegradable.

    Several concerns have been raised about sustainability of this mode of production: to produce

    2,500 billion liters of biodiesel from oilseed rape (i.e. the current demand of petroleum diesel in

    the whole UK), 17.5 Mha would be required for plantation i.e. more than half the land area of

    UK itself. Moreover, the overall savings in energy and greenhouse gas emissions if the lifecycle of

    bio-fuel is considered as a whole are typically below what is normally anticipated; e.g. for

    biodiesel from oilseed rape or soya, a lifecycle assessment indicates that ca. 50% of the energy

    contained in the fuel will be spent in biodiesel processing itself. Biomass as a feedstock for bio-

    fuel production should have a low price, minimum by products and waste, not compete with food

    industry and grow fast with high solar yield.

    Algae, growing microorganisms found in water, are such an option. Algae are a very promising

    feedstock for the following reasons:

    1. High growth rate (up to 20 g dry algae per m2 per day),

    2. High yield per area (15 times higher than palm oil),

    3. High efficiency in CO2 capture and solar energy conversion (wt%),

    4. No competition with food agriculture.

    5. They can be grown in open water and in bio-photo reactors on non-arable land.

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    Algal biomass contains three main components - carbohydrates, proteins, and lipids. On an

    industrial scale only few algae species are produced, and the most widely cultivated is

    chlorella. From an economic point of view, fuel production from algae (or for that matter any

    biomass) requires utilization of the complete biomass as efficiently as possible. Generally, bio-

    fuel (bio-diesel) from algae is produced via extraction of lipids by organic solvents, e.g.

    hexane, or by pressing of dry algae, followed by transesterification in methanol using basic

    catalysts. The solid residue from the algae process contains minerals (up to 10%) which can

    be fed back to the growth cycle. However, the rest 60% is waste [1], which makes the process

    economically less attractive. For the high efficiency this process requires a special strain of

    algae to be cultivated, which increase the cost of the raw material thereby making whole

    process economy unviable at the industrial scale.

    Alternative to the transestrification, pyrolysis of algae utilizes the complete organic part of

    the biomass. Comparing the two processes the pyrolysis is simpler and produces the bio-oil

    under moderate condition (450-500 oC). Pyrolytic oils are usually mixtures of oxygenated

    components such as alcohols, ethers, aldehydes, ketones, phenols, esters, and acids. The

    quality of pyrolysis bio-oil from biomass (both algae and other plants) is up to now far too

    poor for direct use as transportation fuel or even for direct upgrading to fuel precursors at

    existing oil refineries. It is very viscous, acidic (pH

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    1.1 Objective of work in each of the part

    Algal Pyrolysis: Experiments

    I. Advance knowledge and understanding of an integrated pyrolysis-catalytic

    upgrading system, where we seek to produce a stable liquid fuel from algae.

    II. Preparation of different catalyst.

    III. Pyrolysis of biomass and model compound to better understand the pyrolysis of

    biomass.

    Algal Pyrolysis: Modeling and Simulation

    I. Modeling of the pyrolysis reactor system to study effect of different parameter of

    the Bio-fuel yield.

    II. Classifying the reactor into different zones and model equation for each of them.

    III. Using TGA and pyrolytic experiment data, simulate the model equation for

    concentration and temperature.

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    Chapter 2: Literature Review

    A detailed investigation of the mechanism of pyrolysis is a challenging task because numerous

    intermediate substances are involved. Moreover, the chemical mechanisms are often affected and

    influenced by physical phenomena like heat transfer, especially in the presence of particles of

    different size classes. Such effects can be minimized in thermogravimetric investigations, hence

    these are often used to derive global kinetic rate constants for pyrolytic processes.

    There are generally three types of pyrolysis:

    1. Conventional or slow pyrolysis

    I. In slow pyrolysis there is high vapor residence time, slow heating rate leading to

    the high yield of the gaseous and solid products.

    2. Fast pyrolysis

    I. Fast pyrolysis is a high temperature process in which biomass is rapidly heated

    in absence of oxygen.

    II. Fast pyrolysis has four essential features process:

    a.very high heating and heat transfer rates are used which usually requires

    a finely ground biomass,

    b. a controlled pyrolysis reaction temperature,

    c.short vapor residence times are used. Fourth, pyrolysis vapors and

    aerosols are rapidly cooled to give bio-oil and

    d. is controlled to give high liquid yields.

    III. There are several different type of reactor used in research for pyrolysis

    yielding largely varying product both in composition and yield.

    3. Flash Pyrolysis

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    2.1 Reactor designs for Pyrolysis

    There is a huge variation in yield with change in the design of the pyrolysis. There are

    generally three type of reactor employed in pyrolysis of microalgae.

    1) Fluidized bed reactor

    I. This reactor generally uses sand as heating medium for the feedstock.

    II. Fluidized bed reactor is generally attached to a cyclone to separate char

    from the solid product. Since the technology of this reactor is well

    established most of the industrial scale experiments were done using

    this type of reactor.

    2) Fixed bed type reactor

    I. It is simple in design but since the char is deposited at the bottom of the

    reactor.

    II. Since the char is heated, it may contribute to the secondary breaking of

    the pyrolysis vapour. This is one of the major drawback of this type of

    reaction.

    III. This type of reactor is majorly used at laboratory scale to study the effect

    of temperature, catalyst, feedstock and the other parameters affecting

    the yield of the product.

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    3) Microwave reactor.

    I. Some of the latest research shows that another type of reactor i.e.

    microwave reactor have a high efficiency in producing biofuel. In

    microwave reactor there is much more uniform heating compared to

    that of fixed or fluidized bed reactor.

    II. Microwave heating is fundamentally difference from all other pyrolysis

    techniques as the biomass particles are heated from within and not by

    external heat transfer from a high temperature heat source .

    III. In microwave reactor generally we require a receptor to absorb energy,

    but in our case it has been found that char from the pyrolysis is itself a

    very good microwave receptor which can be recycled for the use.

    IV. Microwave reactor doesnt require any sweep gas to remove the gaseous

    product from the reactor.

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    2.2 Bio-oil

    Pyrolysis oil sometimes also known as bio crude or bio-oil, is a synthetic fuel under investigation

    as substitute for petroleum. It is extracted by biomass to liquid technology of destructive

    distillation from dried biomass in a reactor at temperature of about 500C with subsequent

    cooling.

    Pyrolytic oil (or bio-oil) is a kind of tar and normally contains too high levels of oxygen to be a

    hydrocarbon. As such it is distinctly different from similar petroleum products. It is composed of

    a very complex mixture of oxygenated hydrocarbons with an appreciable proportion of water

    from both the original moisture and reaction product. Solid char may also be present. The liquid

    is formed by rapidly quenching and thus freezing the intermediate productsof flash degradation

    of biomass. The liquid thus contain many reactive species, which contribute to its unusual

    attributes. 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.

    There are several factors affecting the composition of bio-oil, mainly feedstock composition,

    reacting temperature, reactor design, and residence time. As a result, the critical issue is to bring

    the reacting biomass particles to the optimum process temperature and minimize their exposure

    to the lower temperatures that favour formation of charcoal, and high temperature which would

    lead to the secondary reaction. Aging is a well-known phenomenon caused by continued slow

    secondary reactions in the liquid which manifests as an increase in viscosity with time. Bio-fuel

    need to be upgraded to be able to be used at commercial scale.

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    2.3 Feedstock

    There has been developed fast pyrolysis technology for maximizing liquid yields. However, most

    of the research has concentrated on lignocellulosic materials such as pine wood, cotton straw and

    stalk. But fast pyrolysis of microalgae that usually have higher photosynthetic efficiency, larger

    biomass, faster growth compared to those of lignocellulosic is fastly getting attention.

    Heterotrophic growth of C. protothecoides results in high production of biomass and

    accumulation of high lipid content in cells. Applying this cell engineering to the fuel production

    of fast pyrolysis, Heterotrophic culture not only can be used for improving the efficiency and

    reducing the cost of biomass production but also can be used for efficient production of some

    metabolites favourable for bio-oil production.

    2.4 Types of Bio oils

    Thermogravimetry is one of technique that has been employed study bio-oil fuel properties since

    the mass losses measured by this method depend on the volatility (or molar mass) of the

    fractions is investigated.

    These materials are generally represented as:

    1) 20 mass % of water

    2) 40 mass % of GC-detectable compounds

    3) 15 mass % of non-volatile HPLC detectable compounds

    4) 15 mass % of high molar mass non-detectable compounds.

    The grouping of bio-oil compounds in chemical families is very useful and necessary because

    these materials can be treated as a mixture of few groups instead of hundreds of compounds.

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    2.5 Upgrading and Stability of Bio-oil

    Upgrading bio-oil to a conventional transport fuel such as diesel, gasoline, kerosene, methane and

    LPG requires full deoxygenating and conventional refining by ways like:

    1) Hydrotreating

    2) Catalytic cracking

    Hydro-processing rejects oxygen as water by catalytic reaction with hydrogen. The process is

    typically high pressure (up to 20 MPa) and moderate temperature (up to 400 oC) and requires a

    hydrogen supply or source. The catalysts originally tested in were based on sulfided CoMo or

    NiMo supported on alumina or aluminosilicate and the process conditions are similar to those

    used in the desulfuriszation of petroleum fractions. Full hydrotreating gives a naphtha-like

    product that requires orthodox refining to derive conventional transport fuel. But there is a

    substantial hydrogen requirement in all hydrotreating, processes to hydrogenate the organic

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    Chapter 3: Experimental Setup

    1) A Moving bed reactor is used to perform pyrolysis of algal feedstock.

    2) An auger screw feeder was used to continuously feed microalgae particles, which fall

    by gravity into the hot reaction zone set at a prescribed temperature.

    3) The reactor system consisted of a 316 stainless steel tube (height=85 cm, diameter

    =2.54 cm), gas pre-heater, condenser system and auger feeder. The microalgae

    biomass particles were fed to a high temperature zone of the reactor.

    4) Quartz wool and product char is supported by porous quartz fritz (25 micron) located

    in the middle of the reactor.

    5) Reactor temperature was measured using a Ni-Cr thermocouple which is used to

    measure temperature as high as 1000 degree C.

    6) The flow rate of the gas was controlled by a bubble flow meter.

    Fig. 2(a) Feed Arrangement Fig. 2(b) Reactor inside the Furnace

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    Fig. 2(c) View of Pyrolysis Reactor

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    Fig. 3: Experimental Setup for Pyrolysis

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    3.1 Experimental Procedure

    1) Sweep gas (N2) is fed into the reactor into two parts. First part i.e. 50% of total feed gas is

    preheated at reactor temperature and second enters reactor at room temperature form

    the top with the feed. A furnace was used to supply initial heat needed for the pyrolysis.

    2) The auger screw feeder was used to continuously feed the microalgae into the bed at

    prescribed flow rate once the reactor reaches a required temperature.

    3) All the connection between reactor and condensing system is maintained at 400 oC so as

    to avoid any condensation in the pipe line. Product vapours were condensed and collected

    for analysis in a condensing system that contained three condensers located in an ice bath

    (0 oC), followed by a condenser operated with liquid N2 (-196 oC).

    4) The pyrolytic oil from the condenser will be analyzed using a gas chromatograph

    equipped with a mass selective. The GCMS conditions were as follow: ionization mode

    electron impact (70 eV); MS operated in the total ion current mode, scanning from 40 to

    550 m/z; interface temperature of 240 oC.

    5) The GC oven temperature program for the bio-oil samples was carried out at an initial

    temperature of 40 oC, which was held for 1 min, followed by a ramp at 20 oC / min to 320

    oC where it was held for 20 min.

    6) The injector temperature was 270 oC and the helium carrier gas was kept constant (1

    ml/min. The bio-oil samples (0.1 g) were diluted in dichloromethane (1 ml); and 1 l was

    injected to the GC.

    7) A mass spectral library data from the National Institute of Standards and Technology

    (NIST) was used for the identification of the compounds found in sample.

    8) The uncondensed vapor would be collected in the gas bags and would be analyzed for

    different hydrocarbon, H2, and other gases using gas spectrophotometer.

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    3.2 Selection of Catalyst

    CATALYST BIO OIL YIELD

    H-ZSM5 19.7

    K2Cr2O7 35.5

    KAc 37.5

    Al2O3 39

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    Fig. 4(a) Fig. 4(b)

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    Fig. 4(c) Fig. 4(d)

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    Fig 5: Pyrolysis Reactor

    CHAR

    PYROLYTIC FLUID

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    3.3 Catalyst Preparation Protocol

    1) The catalyst was prepared through ion-exchange.

    2) The protonated and sodium -ZSM-5 were prepared following the procedure employed by

    Metkar et al. H-ZSM5 was prepared by calcinating NH4ZSM-5 at 500 C for 5hrs.

    3) The Ni-ZSM-5 was prepared by a series of ion exchange and washing steps starting with

    the ammonium form and ending with the Nickel form; i.e., NH4+ H+ Na+ Ni+2.

    Zeolite powder in the ammonium form (NH4-ZSM-5 MFI type) was provided by Sud-

    Chemie (Delhi,India) having a Si/Al ratio of 25.

    4) The NH4-ZSM-5 was then converted into the protonated form by calcining the powder at

    500oC for 5 hours.

    5) Exchange of H+ with Na+ involved contacting the H-ZSM-5 with a 0.1 M NaNO3 solution.

    The solution contained a concentration of Na+ that was about two times the number of

    Al3+ ions. This exchange was carried out for 3 hours in a continuously stirred solution at

    ambient temperature and a pH of 7-7.1.

    6) NH4OH or acetic acid was used to adjust the pH of the solution. After the ion exchange was

    completed the particles were filtered and dried at 110oC for about 2 hours.

    7) After ion- exchange, the salt is washed with de ionized water twice to remove any

    unwanted particle in the salt.

    8) In the final step Na-ZSM-5 was converted to Ni-ZSM-5 by performing ion-exchange in a

    solution containing nickel (II) nitrate Ni(NO3)2 of .

    9) Different conditions (e.g. concentration of Ni(NO3)2 , temperature, pH, and contact time)

    were employed to determine the procedure for content of nickel in the zeolite.

    10)Approximately Thirty grams of Na-ZSM5 were ion-exchanged with a Ni(NO3)2.

    11)After the ion exchange the sample is dried and washed.

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    Figure 6: Protocol for preparation of Catalyst, Ni-ZSM5

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    3.4 Thermogravimetric Analysis

    The study of the behaviour of biomass and its component plays a crucial role in modelling the

    kinetics and reactor of a biomass pyrolysis. The kinetics of biomass pyrolysis is important in

    context of thermo-chemical conversion process aimed at production of fuel gases, bio-oil or char.

    In our work we would be studying the pyrolysis kinetics of one of the most abundant and widely

    grown algae chlorella vulagaris. Algae are a complex material composed of lipids, carbohydrates

    and proteins. Lipid is the component of algae which decides the overall yield and property of the

    bio-oil from algae. While the other constituent like carbohydrate and protein plays an important

    role in stability of the bio-oil formed as they are the main source of oxygenates and nitrogenates

    formed during pyrolysis. Therefore, the study of the decomposition behaviour of each of the

    component along with the biomass will play crucial role in optimizing the pyrolysis setup.

    Another most prominent mechanism which is industrially employed to convert biomass into fuel

    is through Combustion. So here we have done a comparative study between pyrolysis and

    combustion by performing our thermogravimetry analysis in two different atmospheres, N2 and

    Air. Kinetic study for both the process were performed and compared in the study. The specific

    aim of the thermogravimetric analysis in our study is as follows:

    1) To study the decomposition behaviour under different heating rates and atmospheres.

    2) To compare pyrolytic and oxidizing behaviour of algae biomass.

    3) To model the kinetics of pyrolysis and combustion of bio-mass and its components.

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    3.5 Materials required for experiment

    Sample of chlorella vulgaris from Altret Bio-fuel. The sample was dried at 100 C for 24 hr.

    This table shows the theoretical composition of chlorella vulgaris from the literature.

    COMPONENT PERCENTAGE

    Protein 51-58

    Carbohydrate 12-17

    Lipids 14-20

    3.6 Method of Experiment

    Thermogravimetric Analysis was carried out on Perkin Elmer Pyris Diamond TG-DTA.

    Baselines were corrected by subtraction of predetermined baselines determined under indentical

    condition except for absence of a sample. Small sample were loaded into an alumina crucible for

    each run under non-isothermal conditions. Before the analysis sample was kept at 100 C for 24

    hrs to remove all the free moisture present in the sample. Then the sample was heated ate the

    heating rate of 5,10,20,30,40 C/min from 50 C up to 800 C in the atmosphere of Air or N2 to study

    the pyrolytic and combustion behavior. All the experiments were repeated thrice to validate the

    results.

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    Chapter 4: Algal Pyrolysis Reactor Modeling

    Besides experimental research, numerical simulation is another important tool for reactor design

    and experimental data interpretation. To have a complete understanding of the system, a model

    was developed in our work to simulate biomass pyrolysis behavior in Moving Bed Reactor. For

    the modeling of the moving bed reactor, reactor was divided into 4 different zone based upon the

    reaction taking place in each zone.

    Fig 7: Zones for modeling of reactor

    Heterogeneous Reactor

    Two Phase Catalytic Reactor

    Homogeneous Reactor

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    4.1 Description of each Zone

    Heterogeneous Reactor (Zone 1): In this zone primary reaction which is taking place is the

    decomposition of algal bio-mass into vapour and char. The composition of vapour phase in very

    complex and majorly consist of aromatic, non aromatic, oxygenates, nitrogenates, aromatic

    oxygenates and aromatic nitrogenates. The reaction kinetics in this zone would be modelled by

    the rate of degradation equation which was obtained from TGA. Due to the continuous generation

    of vapour there is an increase in vapour velocity. In this zone, little amount of secondary

    decomposition of vapour will also take place which is neglected in our case.

    Heterogeneous Reactor (zone 2):In this zone the reaction taking place is same as that of zone

    1. But the major difference in the two zone is that there is a continue deposition of solid in zone 2

    and the solid phase is static in this case. The continuous decomposition of solid in this zone is

    taken care by assuming that due to the deposition of solid there is change in solid fraction within

    a given length of the reactor.

    Two Phase catalytic reactor (zone 3): In this zone the catalytic upgradation of the vapour

    would be taking place. The reaction which would take place in this zone are mainly conversion of

    oxygenates into hydrocarbon and water and nitrogenates into hydrocarbon and ammonia.

    Homogenous Reactor (zone 4):In this zone the secondary decomposition of vapour would take

    place. Higher molecular weight hydrocarbon would break down into the lower molecular weight

    hydrocarbon.

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    4.2 Modeling Equations

    The detailed 2-dimensional model describes that the concentration C(r,z, t) and temperature T(r,

    z ,t) as a function of the radial, axial coordinates and time is given by the following equations.

    MASS BALANCE

    where:

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    HEAT BALANCE

    where:

    But taking reasonable approximation depending upon our system could simplify the above

    equation to a great extent. We would model each zone separately with different set of

    assumptions in each case. As explained above both in Zone 1 and 2, basic reaction taking place is

    same. In both the zone pyrolysis of solid particle is taking place to give us char and gas as our

    product. So if we model a individual particle of a biomass separately, its model would remain

    same in both the zone. The difference would come in the manner how we integrate the

    simultaneous reaction taking place on different particle in space and time. Let us start with

    modeling single solid particle and would later in the chapter deal with the specifics of Zone 1 & 2.

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    4.3 Steady State Modeling Two-phase Catalytic reactor (Zone 3)

    Governing Equations assuming 1stOrder Kinetics

    (

    )

    (

    )

    where:

    Cmis the Dimensionless mixing Cup concentration

    Csis the Dimensionless surface concentration

    is the Dimensionless mixing cup temperatureis the Dimensionless surface temperature

    Z is the Dimensionless axial time

    Da1= Local mass Damkohler Number

    Da2= Local heat Damkohler Number

    B = Adiabatic temperature rise

    = Dimensionless activation energy

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    Boundary Conditions

    Cm =1 @ Z=0.6(a) & k3 = Da1.6(b)

    Constants Defined

    k1 = Da / Da1 & k3 = Da1

    k2 = Da / Da2 & k4 = B*Da2

    Assumingtending to infinity the equations reduce to

    ( )

    (

    )

    Differentiating Equation (9) w.r.t. Z

    (

    )

    Equating equations (12) & (7) we get:

    Similarly by Differentiating Equation (10) w.r.t. Z and following same procedure we get:

    (

    )

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    Chapter 5: Simulations (Steady State)

    Fig. 8(a) CmVs Z

    In this plot we find that the mixing cup concentration at steady state for Zone 3 of a reactor

    decreases exponentially with Z (as we move outwards towards the surface) .

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    Fig. 8(b) CsVs Z

    In this plot we find that the suraface concentration at steady state for Zone 3 of a reactor

    increases exponentially with Z (as we move outwards towards the surface) .

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    36 | P a g e 0 9 C H 3 0 0 6 A m a n S i n h a l

    Fig. 8(c) m Vs ZIn this plot we find that the mixing cup temperature at steady state for Zone 3 of a reactor

    decreases exponentially with Z (as we move outwards towards the surface) .

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    37 | P a g e 0 9 C H 3 0 0 6 A m a n S i n h a l

    Fig. 8(d) s Vs ZIn this plot we find that the surface temperature at steady state for Zone 3 of a reactor decreases

    exponentially with Z (as we move outwards towards the surface) .

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    38 | P a g e 0 9 C H 3 0 0 6 A m a n S i n h a l

    Chapter 6: Unsteady State Modeling

    Unlike the first two zones where the reaction term is coming in the conservation equation, in this zone

    the reaction term would appear in the boundary condition. Equations given below in dimensionless

    form is given below generally describe such system.

    (

    ) (

    )

    (

    ) (

    )

    Where:

    C = CL2 at y = yL2 at

    Boundary Conditions

    at at

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    39 | P a g e 0 9 C H 3 0 0 6 A m a n S i n h a l

    (

    )

    ( )

    where:

    In the two phase model we eliminates the transverse co-ordinate by using the concept of an e!ective

    transfer coeffcient between the bulk and the surface. Specifically, the local mass transfer coefficient or

    Sherwood number which is defined by:

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    and the heat transfer coeffcient expressed using Nusselt number as:

    When constant values are used for the Sherwood and Nusselt numbers, the one-dimensional two-

    phase model is described by the differential-algebraic system and where cm(ym) is the mixing cup

    concentration(temperature). When constant values are used for the Sherwood and Nusselt numbers,

    the one-dimensional two-phase model is described by the differential-algebraic system.

    ( )

    ( )

    Where,

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    Chapter 7: Simulations (Unsteady State)

    Fig. 9(a) Cmvs Time

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    Fig. 9(b)Cmvs Z

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    Fig. 9(c)Cmvs Time

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    Fig. 9(d) Csvs Z

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    Fig. 9(e)

    mvs Time

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    46 | P a g e 0 9 C H 3 0 0 6 A m a n S i n h a l

    Fig. 9(f)

    mvs Z

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    47 | P a g e 0 9 C H 3 0 0 6 A m a n S i n h a l

    Fig. 9(g) svs Time

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    Fig. 9(h)

    svs Z

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    Chapter 8: Conclusion

    8.1 Summary

    1) From thermogravimetric analysis we were able to study the pyrolysis behavior of

    the biomass at different heating rates.

    2) A pyrolytic reactor has been designed to extract the bio-oil from biomass via

    pyrolysis.

    3) For the modeling of pyrolysis reactor, it was divided into 4 sub zones depending

    upon type of reaction taking place.

    4) Modeling equations were formulated for zone 3.

    5) The Variation of Surface concentration, Mixing Cup concentration, Surface

    Temperature & Mixing cup Temperature are given as follows:

    I. Mixing Cup concentration increases with time

    II. Mixing Cup concentration decreases as we move outwards towards the surface

    III. Surface concentration increases with time

    IV. Surface concentration decreases as we move outwards

    V. Mixing cup Temperature increases with time

    VI. Mixing cup Temperature decreases initially as we move outwards towards the

    surface but then gradually starts to increase after attaining minima.

    VII. Surface Temperature initially increases exponentially with time but later starts

    decreasing in a parabolic fashion after attaining maxima.

    VIII. Surface Temperature remains almost constant.

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    50 | P a g e 0 9 C H 3 0 0 6 A m a n S i n h a l

    8.2 Future Work

    1) Thermogravimetric analysis and kinetic modeling of each of the component of bio-

    mass i.e. lipid, protein and carbohydrate

    2) Performing the pyrolysis experiment for different catalysis and compare the

    upgradation of oil in each case.

    3) Preparation of different catalyst which could lead to a better quality of oil.

    4) Study of pyrolysis of model compounds of carbohydrate, protein and lipids to better

    understand the chemistry behind the pyrolysis of bio-mass.

    5) In the future catalyzed and non-catalyzed pyrolysis of the biomass will be

    performed to have a understanding of the biomass and its pyrolysis characteristics.

    6) Study of individual component will also allow us to decide the criterion for the

    selection of catalyst for the upgradation purposes

    7) The final aim of this study is to have a detailed understanding of the pyrolysis

    system of the microalgae Chlorella vulgaris through modeling and experimentation.

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    Appendix

    clc;

    clear all;

    close all;

    %Parameters Defining (They need to be assigned values)---------------------

    Da = 1 ;

    Dapm = 0.1 ;

    Daph = 0.3 ;

    gam = 1 ;

    R = 1 ;

    clea = 31

    k1= Dapm*R ;

    k2= Daph*R ;

    k4= Da/Dapm ;

    k5= Da/Daph ;

    L = 1;

    T = 1;

    p = 21;

    n = 101;

    xp1 = L/(p-1)

    xt1 = T/(n-1)

    delx= 1 ;

    delt= 1 ;

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    C0 = 1;

    T0 = 0.5;

    %-------------------------------------------------------------------------- %Need to assign c0 and t0 ; these are initial values

    %-------------------------------------------------------------------------

    fori = 1:delx:p

    cm(i,1) = C0 - ((0.1)*(C0)*((i-1)/(p-1)));

    tam(i,1) = T0 - ((0.1)*(T0)*((i-1)/(p-1)));

    end

    %-----------------------------------------------------------------------

    %calculating tas,cs initially at t = 0

    %calculated using succesive iteration

    %--------------------------------------------------------------------------

    forp1 = 1:delx:p

    start=1;

    i=-1;

    diff1=0;

    diff2=0;

    while(start)

    i = i + 0.01;

    i1 = i;

    i2 = i1 + 0.01;

    diff1 = (i1-tam(p1,1)) + k2*(cm(p1,1))*exp(i1/(1+(i1/gam)))/(1 +

    (k1*exp(i1/(1+(i1/gam)))));

    diff2 = (i2-tam(p1,1)) + k2*(cm(p1,1))*exp(i2/(1+(i2/gam)))/(1 +

    (k1*exp(i2/(1+(i2/gam)))));

    if((diff1*diff2)

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    tas(p1,1)=i2;

    cs(p1,1)= cm(p1,1)/(1 + (k1*exp(i2/(1+(i2/gam)))));

    endtas

    clea

    %--------------------------------------------------------------------------

    %Discretization of the diiferential equation...

    %The scheme used is forward space and forward time.....................

    %--------------------------------------------------------------------------

    fort1 = 1:delt:(n-delt)

    t2 = t1+delt;

    cm(1,t2) = cm(1,t1) + (cm(1,t1)-cm(2,t1))*(delt*xt1)/(delx*xp1) +

    k4*(delt*xt1)*(cm(1,t1)-cs(1,t1))

    tam(1,t2) = tam(1,t1) + (tam(1,t1)-tam(2,t1))*(delt*xt1)/(delx*xp1) +

    k5*(delt*xt1)*(tam(1,1)-tas(1,t1));

    forp1 = 2:delx:p-1

    cm(p1,t2) = cm(p1,t1) + (cm(p1-1,t1)- cm(p1+1,t1))*(0.5*delt*xt1)/(delx*xp1) +

    k4*(delt*xt1)*(cm(p1,t1)-cs(p1,t1));

    tam(p1,t2) = tam(p1,t1) + (tam(p1-1,t1)- tam(p1+1,t1))*(0.5*delt*xt1)/(delx*xp1)

    + k5*(delt*xt1)*(tam(p1,1)-tas(p1,t1));

    end

    cm(p,t2)= cm(p,t1) + (cm(p-1,t1)-cm(p,t1))*(delt*xt1)/(delx*xp1) + k4*(delt*xt1)*(cm(p,t1)-

    cs(p,t1));

    tam(p,t2) = tam(p,t1) + (tam(p-1,t1)-tam(p,t1))*(delt*xt1)/(delx*xp1) +

    k5*(delt*xt1)*(tam(p,t1)-tas(p,t1));

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    start=1;

    i=-1;

    diff1=0;

    diff2=0;

    forp1 = 1:delx:p

    while(start)

    i = i + 0.01;

    i1 = i;

    i2 = i1 + 0.01;

    diff1 = (i1-tam(p1,t2)) + k2*(cm(p1,t2))*exp(i1/(1+(i1/gam)))/(1 +

    (k1*exp(i1/(1+(i1/gam)))));

    diff2 = (i2-tam(p1,t2)) + k2*(cm(p1,t2))*exp(i2/(1+(i2/gam)))/(1 +

    (k1*exp(i2/(1+(i2/gam)))));

    if((diff1*diff2)

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    fort1 = 1:delt:n

    ha = t1;

    x1 = 0:delx:p-1 ;

    plot(x1,cm(x1+1,ha))hold on

    end

    end%check

    if(0)

    forx1 = 1:delx:p

    ha = x1;

    t1 = 0:delt:n-1 ;

    plot(t1,cm(ha,t1+1))

    hold on

    end

    end%check

    %-----------------------------Tam---------------------------------------

    if(0)

    fort1 = 1:delt:n

    ha = t1;

    x1 = 0:delx:p-1 ;

    plot(x1,tam(x1+1,ha))

    hold on

    end

    end%check

    if(0)

    forx1 = 1:delx:p

    ha = x1;

    t1 = 0:delt:n-1 ;

    plot(t1,tam(ha,t1+1))

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    hold on

    end

    end%check

    %------------------------------Cs-----------------------------------

    if(0)

    fort1 = 1:delt:n

    ha = t1;

    x1 = 0:delx:p-1 ;

    plot(x1,cs(x1+1,ha))

    hold on

    end

    end%check

    if(0)

    forx1 = 1:delx:p

    ha = x1;

    t1 = 0:delt:n-1 ;

    plot(t1,cs(ha,t1+1))

    hold on

    end

    end%check

    %--------------------Tas-----------------------------------------------

    if(0)

    fort1 = 1:delt:n

    ha = t1;

    x1 = 0:delx:p-1 ;

    plot(x1,tas(x1+1,ha))

    hold on

    end

    end%check

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    %if(0)

    forx1 = 1:delx:p

    ha = x1;t1 = 0:delt:n-1 ;

    plot(t1,tas(ha,t1+1))

    hold on

    end

    %end

    %---------------------------------------------------------------------

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    References

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    from pyrolysis of Chlorella protothecoides. J Appl Phycol 2000;12:147 52.

    [2] AV Bridgwater . Principles and practice of biomass fast pyrolysis processes for liquids. J Anal

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    [3] SRA Kersten, WP van Swaaij ,L Lefferts ,K Seshan. Options for Catalysis in the thermochemical

    conversion of biomass into fuels. Willey-VCH; 2007. p. 119e62.

    [4] PL Desbene ,M Essageph ,B Desmazieres ,F Applied Catalysis B: Environmental, Villeneuve

    .Analysis of biomass pyrolysis oils by combination of various liquid chromatography techniques

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    [5] Ye N, Li D, Chen L, Zhang X, Xu D (2010) Comparative Studies of the Pyrolytic and Kinetic

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    [6]Meir D.New Methods for chemical and physical characterization and round robin testing.In:

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    p.92101. [35]Scholze B, Hanser C, Meier D.

    [7] Q Lu , X F Zhu, W Z Li, et al. On-line catalytic upgrading of biomass fast pyrolysis products.

    Chinese Sci Bull, 2009, 54: 1941-1948.

    [8] Beatriz Valle, Ana G. Gayubo, Andr_es T. Aguayo, Martin Olazar, and Javier Bilbao Selective

    Production of Aromatics by Crude Bio-oil Valorization with a Nickel-Modified HZSM-5 Zeolite

    Catalyst Energy Fuels 2010, 24, 20602070.

    [9]A kinetic study of pyrolysis and combustion of microalgae Chlorella vulgaris using thermo-

    gravimetric analysis by Ankit Agrawal, Saikat Chakraborty, Department of Chemical Engineering,

    Indian Institute of Technology, Kharagpur.