Overview of Technologies for Converting Waste Agricultural Biomass into Energy Training on Technologies for Converting Waste Agricultural Biomass into Energy Organized by United Nations Environment Programme (UNEP DTIE IETC) 23-25 September, 2013 San Jose, Costa Rica Surya Prakash Chandak Senior Programme Officer International environmental Technology Centre Division of Technology, Industry and Economics Osaka, Japan
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Overview of Technologies for Converting Waste Agricultural Biomass into Energy
Overview of Technologies for Converting Waste Agricultural Biomass into Energy. Training on Technologies for Converting Waste Agricultural Biomass into Energy Organized by United Nations Environment Programme (UNEP DTIE IETC) 23-25 September, 2013 San Jose, Costa Rica. - PowerPoint PPT Presentation
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Overview of Technologies for Converting
Waste Agricultural Biomass into Energy
Training onTechnologies for Converting Waste Agricultural Biomass into Energy
Organized by
United Nations Environment Programme (UNEP DTIE IETC)
23-25 September, 2013San Jose, Costa Rica
Surya Prakash ChandakSenior Programme Officer
International environmental Technology CentreDivision of Technology, Industry and Economics
Osaka, Japan
CONTENT
Technology Classification
Direct Combustion
Densification
Thermo-chemical Conversion
Biological Conversion
Liquid Biofuels
Environmental Characteristics
Technology Selection
Technologies in Practice 2
TECHNOLOGY CLASSIFICATION Direct combustion of raw biomass is the simplest
method of extracting energy with lowest cost
– Therefore is the most common method of conversion.
– However, such a use faces the worst features of biomass - bulk and inconvenience.
Therefore, before bio-energy is used for end-use activities, it may have to be converted from its primary form into a form that is more convenient for transport and use.
– This may involve simple physical processing before combustion or upgrading to a variety of convenient secondary fuels (solid, liquid or gas) by means of certain conversion processes. 3
TECHNOLOGY CLASSIFICATION Methods of utilizing waste agricultural biomass
as a source of energy
WAB Resources
Conversion Processes
Intermediate Fuels
Biomass Fuels
Heat
Electricity
Mechanical Power
Direct Combustion / Gasification
HeatEngines
Generator
4RESOURCE TECHNOLOGY APPLICATION
TECHNOLOGY CLASSIFICATION Different processes and technologies are
available for converting biomass to energy.
Could be categorized as:– Direct combustion of the raw biomass– Combustion after simple physical processing,
DIRECT COMBUSTION Combustion of biomass has been widely used in
the past to generate heat– At present, it is making a comeback in many industrial
applications including generation of electricity,
Straightforward conversion of thermal energy into mechanical or electric power results in considerable losses– It is not possible to raise the ratio of thermal to
mechanical power above 60%. – However, if the low temperature waste heat can be
used productively, for instance for drying or heating purposes, much higher overall efficiencies can be obtained.
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DIRECT COMBUSTION Fuels and Combustion
Biomass combustion
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Combustion Unit
Air and Fuel Combustion
Products
Heat Energy
Light
Volatile Matter
Hot Flue Gas
Flame Front
Entrained Air
Burning CharAsh
Wood
Conduction to Wood
Radiation to Wood
Radiation to
Surrounding
Convective Heat to Surrounding
EnergyCombustion of ProductsOxidizerFuel
DIRECT COMBUSTION Biomass combustion
- Processes and temperatures in a burning piece of wood
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Gaseous-phase combustion Diffusion flame, mostly Turbulent – a ‘free’ fire T > 1000C (probably T < 1000C) Simultaneous heat and mass transfer with chemical reaction; Surface combustion – a slow process 500C < T < 800C Problem same as in zone A but with sources/sinks due to pyrolytic reactions 200C < T < 500C Heat conduction in a medium with a moving boundary; Mitigation of moisture & gases; Uncertain properties T < 200C
Figure 6.1: Processes and temperatures in a burning piece of wood
Flame
D
Char
C
Pyrolytic Zone
B
Virgin Wood
A
Hea
t Flo
w
Gas
Flo
w
Properties of Fuels– Solid.
DensityMoisture ContentVolatile Matter and Fixed CarbonSulfur ContentAsh Calorific Value
DIRECT COMBUSTION
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Fuel Volatile Matter Fixed Carbon Ash
Paddy Husk 63.3 14.0 22.7
Bagasse 74.0 19.3 6.7
Wood 77 - 87 13 - 21 0.1 - 2.0
Lignite 43.0 46.6 10.4
Anthracite Coal 5.0 80 15
DENSIFICATION Densification (briquetting or pelleting) is used to
improve characteristics of materials (especially low density biomass)– Productive transport,– Improved fuel characteristics.
Raw materials used include sawdust, loose crop residues, and charcoal fines.
The material is compacted under pressure– Depending on the material, the pressure, and the
speed of densification, additional binders may be needed to bind the material
13
DENSIFICATION There are two main briquetting technologies
– Piston press– Screw press.
In the piston press the material is punched into a die by a ram with a high pressure.
In the screw press, the material is compacted continuously by a screw.
With the screw press generally briquettes of higher quality can be produced.
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THERMOCHEMICAL CONVERSION In thermochemical conversion, biomass is
subjected to appropriate temperatures and pressures and normally a restricted supply of oxygen
Pyrolysis is the basic thermochemical process to convert biomass into more valuable or more convenient products– In fact, it is the oldest method of processing one fuel
in order produce better one
Conventional pyrolysis involves heating the original material in the near-absence of air, typically at 300 - 500C, until the volatile matters has been driven off. 15
THERMOCHEMICAL CONVERSION The residue is then the char (more commonly
known as charcoal)– Char has about twice the energy density of the
original fuel and burns at a much higher temperature
For many centuries, and in much of the world still today, charcoal is produced by pyrolysis of wood. – Depending on the moisture content and the efficiency
of process, 4 - 10 kg of wood are required to produce one kg of charcoal
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THERMOCHEMICAL CONVERSION With more sophisticated pyrolysis techniques,
the volatile matters can be collected– Careful choice of the temperature at which the
process takes place allows the control of the composition.
– The products formed are normally a gas, an oil-like liquid and charcoal
– The distribution of these products is dependent on the feedstock, temperature and pressure of reaction, the time spent in the reaction zone and the heating rate.
– High temperature pyrolysis (1000C) maximizes the production of gas (gasification) while lower temperature pyrolysis processes (<600C) have been used for the production of charcoal (carbonization).
– Another approach to produce liquid fuels and chemicals from biomass is direct catalytic liquefaction
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BIOLOGICAL CONVERSION Biological conversion consists of exposing
biomass to certain microorganisms.
The secondary fuels produced are the result of metabolic activity of the microorganisms.
Production of Ethanol and biogas are the two most common biological conversion processes.
Ethanol fermentation from carbohydrates is probably one of the oldest processes known to man. – Today, it is widely regarded as an important potential
alternative source of liquid fuels for the transport sector. 18
LIQUID BIOFUELS Definition
- The term biofuels generally refers to liquid fuels made from biological sources, which include pure plant oil (PPO), bioethanol and biodiesel.
- Global biofuel production from year 2000 to 2011
ENVIRONMENTAL PERFORMANCES Impacts of emissions from biomass combustion
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Component Biomass Sources Climate, environmental and health impactCarbon dioxide (CO2) Major combustion product
from all biomass fuelsClimate: Direct GHG. However, biomassis a CO2-neutral fuel
Carbon monoxide (CO)
Incomplete combustion of all biomass fuels
Climate: Indirect GHG through ozone formation. Health: Reduced oxygen uptake especially influences people with asthma, and embryos. Suffocation in extreme cases.
Methane (CH4) Incomplete combustion of all biomass fuels
Climate: Direct GHG. Indirect GHG through ozone formation.
Non Methane VolatileOrganic Components(NMVOC)
Incomplete combustion of all biomass fuels
Climate: Indirect GHG through ozone formation. Health: Negative effect on human respiratory system
Particles Soot, char and condensed heavy hydrocarbons (tar) from incomplete combustion of all biomass fuels. Fly ash and salts
Climate and environment: Reversed greenhouse effect through aerosol formation. Indirect effects of heavy-metal concentrations in deposited particles.Health: Negative effect on the human respiratory system. Carcinogenic effects
ENVIRONMENTAL PERFORMANCES Impacts of emissions from biomass combustion
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Component Biomass Sources Climate, environmental and health impactNitric oxides(NOX = NO and NO2)
Minor combustion product from all biomass fuels containing nitrogen. Additional NOx may beformed from nitrogen in the air under certain conditions
Climate and environment: Indirect greenhouse effect through ozone formation. Reversed greenhouse effect through aerosol formation. Acid precipitation. Vegetation damage. Smog formation. Corrosion and material damage. Health: Negative effect on the human respiratory system. NO2 is toxic
Nitrous oxide (N2O)
Minor combustion product from all biomass fuels containing nitrogen
Climate: Direct GHG. Health: Indirect effect through ozone depletion in the stratosphere
Ammonia (NH3)
Small amounts may be emitted as a result of incomplete conversion of NH3 from pyrolysis/ gasification
Environment: Acid precipitation. Vegetation damage. Corrosion and material damage. Health: Negative effect on the human respiratory system.
Sulphur oxides(SOX = SO2 and SO3)
Minor combustion product from all biomass fuels containing sulphur.
Climate and environment: Reversed greenhouse effect through aerosol formation. Acid precipitation. Vegetation damage. Smog formation. Corrosion and material damage. Health: Negative effect on the human respiratory system, asthmatic effect
ENVIRONMENTAL PERFORMANCES Impacts of emissions from biomass combustion
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Component Biomass sources Climate, environmental and health impactHeavy metals All biomass fuels contain
heavy metals to some degree, which will remain in the ash or evaporate
Health: Accumulate in the food chain. Some are toxic and some have carcinogenic effects
Ground levelozone (O3)
Secondary combustion product from atmospheric reactions, including CO, CH4, NMVOC and NOX
Climate and environment: Direct GHG.Vegetation damage. Smog formation.Material damage. Health: Indirect effect through ozone depletion in the stratosphere. Negative effect on the human respiratory system, asthmaticeffect
Hydrogen Chloride (HCl)
Minor combustion product from all biomass fuels containing chlorine
Environment: Acid precipitation. Vegetation damage. Corrosion and material damage. Health: Negative effect on the human respiratory system. Toxic
Dioxins and FuransPCDD/PCDF
Small amounts may be emitted as a result of reactions including carbon, chlorine, and oxygen in the presence of catalysts (Cu)
Health: Highly toxic. Liver damage. Central nervous system damage. Reduced immunity defense. Accumulate in the food chain