Transcript Slide 1

Thermo and Bio-chemical
Conversion Technologies
OLADE
ALFREDO BARRIGA, PHD
ESPOL – ECUADOR
September 2011
Biomass Natural Cycle
Biomass in Ecuador
Rice Husks
Cane Bagasse
Oil palm husks
RESIDUAL BIOMASS FROM PLANTS
PATHS FOR UTILIZATION OF BIOMASS FOR ENERGY
BIOMASS
Animal or vegetal
Moist
Obtained with moisture
content above 60%
Physical Precesses
Drying-Compac
Chopping
Mechanical Press
Biological
Processes
Fermentation
(alcohol)
Bacterian
digestion
Dry
Obtained with moisture
content below 60%
Thermochemical
Processes
Combustion
Pyrolisis
Gasification
Liquefaction
Typical residual Biomass
 Crop residues, stalks and branches, etc.
Bagasse from the process of extracting sugar cane juice (sugar
production, alcohol, etc.).
 Rice hulls.
 Shell and oil palm bundle branches.
Remains of wood industrialization
planks, etc.
bark, side cutting damaged
 Sawdust and wood shavings in a production of wooden elements.
Biomass Characteristics
Bagasse
Chips from Olive
tree(db)
Cotton(db)
Pine bark(db)
Oak bark(db)
Redwood
bark (db)
Ultimate analysis
Carbon
Hydrogen
Nitrogen
Sulphur
Ashes
Oxygen
23,4
2,8
0,1
0,6
1,7
20,0
49,52
5,90
0,39
<0,05
1,74
42,45
47,03
5,42
1,04
0,13
5,37
41,01
53,40
5,60
0,10
0,10
2,90
37,90
49,70
5,40
0,10
0,20
5,30
39,30
51,90
5,10
0,10
0,10
0,40
42,40
Immediate analysis
Moisture
Volatile
Fixed Carbon
Ashes
52,00
40,20
6,10
1,70
-81,79
16,47
1,74
-73,78
20,85
5,37
-72,9
24,2
2,90
-76,00
18,70
5,30
-72,60
27,00
0,40
HHV (kcal/kg)
2 224
4 610
4 297
5 021
4 654
4 643
25,21
6,59
2,98
2,61
2,36
39,00
14,0
3,0
-0,30
11,10
0,10
3,30
-2,00
14,30
4,00
3,50
-7,40
Ash Analysis
SiO2
Al2O3
Fe2O3
P2O5
SO3
Biofuels Comparison Chart
Ultimate analysis
Carbon
Hydrogen
Nitrogen
Sulphur
Ashes
Oxygen
Proximate analysis
Moisture
Volatile
Fixed Carbon
Ashes
HHV (kcal/kg)
Gasoil
Fuel Oil
Natural Gas
Coal
Biomass
(typical)
86,0
11,1
1,0
0,8
0,1
1,0
84,6
9,7
1,0
1,5
0,5
2,7
72,8
22,6
4,6
0,0
0,0
0,0
75,8
5,1
1,5
1,6
5,0
8,2
50,0
5,5
1,0
<0,2
2,0-5,0
40,0
1,0
1,5
0,0
5,0
35,0
50,0
10,0
variable
65,0
20,0
2,0-5,0
10 300
10 100
12 450
7 500
4 500
THERMO-CHEMICAL PROCESSES
Thermochemical processes (pyrolysis, gasification and combustion)
consist on the organic components decomposition of biomass at
high temperatures.
Main thermo-chemical processes are:
Combustion
Pyrolysis
Gasification
Thermal Decomposition Processes for Biomass
LIGNOCELLULOSE IN AIR SCHEME COMBUSTION
AIR
FLAME
CHAR
ASH
VOLATILE
WOOD
-
CHARCOAL
DRYING
-
ROASTING
-
PYROLYSIS
COMBUSTION
Pyrolysis
Is the incomplete combustion of biomass at elevated temperatures in the
absence of oxygen, around 500 degrees celsius. Charcoal is obtained by heating
wood until its complete carbonization occurs, leaving only carbon and
inorganic ash. In many parts of the world, charcoal is still produced by burning
a pile of wood that has been mostly covered with mud or bricks during a lot of
time, even days to relatively low temperatures (350 °C)
BIOMASS + HEAT  Carbon + Liquid + gaseous
Gaseous fuel combustion (Methane)
Liquid fuel combustion (fuel oil)
Biomass fuel combustion (wood)
Pyrolysis Technologies
Technology
Residence
time
Maximum
Temperature
(°C)
Carbonization
Hours-days
300-500
Charcoal
30 MJ/ Kg
400-600
Bio-óil.
Coal.
Gas
20 MJ/ Kg
30 MJ/ Kg
5-10 MJ/Nm3
450-600
Coal
Gas
30MJ/ Kg
10-20 MJ/Nm3
700-900
Coal
Gas
30 MJ/ Kg
15-20 MJ/Nm3
Slow
Fast
Fast
5-30 min.
≤1s
≤1s
Main
Product
Calorific
value(Dry
basis)
When biomass is subjected to pyrolysis, products obtained
are such as:
Solid (Charcoal)
Liquid (Bio-fuel oil) (Bio-oil)
Gases (Gaseous fuel with low or medium calorific value)
Basic products in pyrolysis depend on:
•Reactor temperature.
•Heating rate related to the particle size.
•Residence time of products inside reactor.
•Technology and its operational parameters.
COMBUSTION
Combustion is a process in which biomass is oxidized
to carbon dioxide (CO2), water. The overall equation
of combustion reaction is the reverse of
photosynthesis.
BIOMASS + O2  CO2 + H2O + HEAT + (Other species)*
* CO, HC, Soot, Oxidized minerals , tar, moisture and other
Types of Biomass Combustion
Chamber
Main combustion technologies for biomass
Biomass Combustion Technologies
Grate combustion.of the following types: fixed
bed, horizontal and inclined grate, mobile
grate and vibrating grate.
Fluidized bed: is based on the combustion
reaction in a fluidized bed in which the fuel
particles move similarly to those of a liquid.
Moving Grate
Fuente: Manual de Energía Térmica con biomasa
Inclined Grate Furnace
Fluidized bubbling bed furnace
Operating Temperature in Chamber
Operating temperature depends on several factors such as:
 Fuel Calorific Value.
 Biomass moisture.
Excess Air Percentage.
 Heat transfer to the chamber walls.
 Heat loss to the outside.
Combustion completion.
Humidity effects on biomass calorific
value
Fluid Dynamic Effects of Particles
Particles to fall freely in a fluid environment (air or combustion
gases for example) fall at a rate dependent upon fluid forces (drag).
These drag forces depend on the viscosity fluid, and the particle
shape. In the case of irregular shaped particles, as are most of the
biomass "chopped" as bagasse, husks, etc.. the drag coefficient
depends on the wake formed by the passage downstream of the
particle.
Influx of chipped biomass through inlet
Flame Shape in Biomass Combustion
Flame shape depends on:
Ratio of gas-phase combustion of pyrolysis products to rate of
burning of the carbonaceous residue.
Relative position of the biomass at the time of combustion.
Geometry and distribution of air supply: from below the grate, and
above it.
Presence of vortex effects which are induced by tangential entry of
air.
Efficiency of various thermal
processes with Biomass
Process
Intermediate Fuel
Energetic content on initial
biomass (%)
Heat
Combustion
Pyrolysis
(Carbonization)
70-75
Gasification
65-80
Electricity or
mechanic work
65-95
20-35
60-70
22-30
22-27
Industrial Combustion Problems of
Residual Biomass
The main problems of residual biomass operation are:
 Formation of agglomerates and slag on the grate (slagging).
 Fouling on interior surfaces.
 Metal surfaces corrosion.
Slag formed in Biomass Combustion
Fouling on boiler tubes
Control and Emissions
Combustion plants produce effluent gases, solids and liquids. Particles are
one of the most important emissions on biomass combustion.
GAS TREATMENT SYSTEMS
•CYCLONIC SYSTEMS
•BAG FILTERS
•WET SCRUBBER
•ELECTROSTATIC FILTERS
BIOGAS
Biogas is the gaseous product of anaerobic digestion of organic
waste under appropriate conditions of temperature, dilution,
residence time, and others. It comprises approximately 60% of CH4
and CO2 rest, with small amounts of other gases. Organic substrates
are used such as manure mixed with straw and agricultural residues
and agro-industrial production.
BIOGAS GENERATION PROCESS
The raw material for biogas generation can be processed in either batch or semi
continuous production. Reactors are built using metal, plastic or masonry
components.
Gas begins to appear a short time after initial loading of the reactor, first slowly,
and not always generating combustible gases., Methane starts to appear under
the right conditions, along with carbon dioxide in the form of biogas.
The biogas generated is stored within the digester or in a separate container
(GASHOLDER) which can be use outside the digester. The effluent contains some
of the organic compounds and nutrients, which can be used as fertilizer. It also
forms some bottom sludge, which need to be removed periodically.
STEPS IN THE PRODUCTION OF BIOGAS
Stage 1
Stage 2
Stage 3
Stage 4
• Hydrolysis or
liquefaction
• The hydrolytic
enzymes
produced by
bacteria.
Hydrolysis is
therefore the
conversion of
polymers into
their monomers.
• Acido-genesis
• The hydrolysis
products are
converted into
organic acids
such as acetic,
propionic and
butyric acids.
• Aceto-genesis
• The products
concerned are
converted to
acetic acid,
hydrogen and
carbon dioxide.
• Methano-genesis
• At this stage
metabolic CH4 is
generated from
acetic acid or
mixtures of H2
and CO2, may
also be formed
from other
substrates such
as formic acid
and methanol.
CHARACTERICTICS OF BIOGAS
Flash Point 700 º C (350 º C Diesel, gasoline and propane close to 500 º C).
The flame temperature reaches 870 º C.
Biogas typically contains:
60% methane (CH4)
40% of carbon dioxide (CO2).
The longer the retention time, the higher the methane content, and that the
calorific value.
PARAMETERS AFFECTING THE OPERATION OF
BIODIGESTOR
•Daily amount of total solids.
•Retention time.
•Specific production of gas per day, depending on the raw material.
•Mass temperature of the digester agitation.
•Physical and chemical characteristics of the raw material.
•Level of pH.
•Presence of harmful elements.
PRODUCTIVITY OF BIOGAS SYSTEM WITHOUT AGITATION
Product
Temperature (oC)
Productivity
(m3/kg)
Content of
methane %
Retention Time
(days)
Cattle dung
(India)
11-31
0.23 – 0.50
--
--
Cattle manure
(Germany)
15.5 – 17.3
0.20 – 0.29
--
--
Chicken Manure 34.6
0.31*
60
30
pig manure
0.7
60
15
32.6
* Based on volatile solids
Reference: Methane generation from human, animal, and
agricultural waste. USA, Academy of Science, 1977
COMPARISON OF PRODUCTIVITY AND RETENTION TIME
WITH CATTLE MANURE MIXTURES AGRICULTURAL WASTE
Waste mixed
with manure
Production at 24 Production at
days
80 days
(m3/kg)
(m3/kg)
Content of
methane at 21
days %
None
0.063
0.21
60
Sugarcane 0.4%
0.07
0.21
58
Cellulose 1%
0.084
0.21
53
Sugarcane 1% +
Urea 1%
0.087
0.26
68
Leaves 20% no
pulses
0.081
0.22
68
Reference: Methane generation from human, animal, and
agricultural waste. USA, Academy of Science, 1977
BIOGAS PRODUCTION FROM COW MANURE: Temperature and retention time
Author’s own elaboration based on data from multiple
sources
NITROGEN CONTENT AND C/N
Raw Material
N (%)
C/N
Animal urine
15-18
0.8
Animal blood
10 14
3
Cow dung
1.7
18
Horse manure
2.3
25
Pig manure
3.8
--
Farm manure
2.15
14
Amaranth
3.6
11
Reference: Methane generation from human, animal, and
agricultural waste.
NITROGEN CONTENT AND C/N
All materials are composed of fermentation mostly of carbon (C) and contain
nitrogen (N). The C / N ratio influences the production of gas, this is optimal
when C / N ranges between 20:1 and 30: 1.
For example, chicken manure (high N) mixed with rice chaff, is a high gas
production.
If you suspect that digestion is being disturbed by toxic substances, add water or
fermenting material, thus decreasing the concentration.
PREPARATION OF THE MIXTURE
SOURCE: ENYA
AUXILIARY ELEMENTS FOR BIOGAS
SOURCE: ENYA
ANAEROBIC DIGESTION
Anaerobic digestion and biogas anaerobic microbiological process is linked to the
treatment of biodegradable waste and yielding as end product called "biogas", which is
formed from organic matter biomass. It is therefore an environmental echnology
energy component with an interesting
ANAEROBIC
DIGESTION OF
BIOMASS
NATURAL
SYNTHETIC
• DESCOMPOSITION OF TERRESTRIAL VEGETATION
• DESCOMPOSITION OF ORGANIC MATTER ON WATER BODIES
ANAEROBICS DIGESTER
• Agricultural waste
• Urban waste
BIOGAS
CH4 50-75%
CO2 25-50%
FUEL
• Home
• Transport
• Electricity Generation
Compost
WASTE
COMPOST
• Agricultural use
• High nutrient content
LANDFILLS
• Agricultural waste
• Urban waste
PRODUCTS
51
BIOMASS AS RENOVABLE SOURCE OF ENERGY
Dr. Roberto Best y Brown
BIODIGESTORS
• Hindu Type
www.energianatural.com.ar/biogas02.html
Biodigestor Hindú Model
www.energianatural.com.ar/biogas02.html
BIODIGESTORS
• Chinese type
Biodigestor Chinese Model
www.energianatural.com.ar/biogas02.html
Biodigestors
• MODERN TYPE
- Has 2 Flexible membrane
- Superior black membrane
Horizontal Digestor, Plastic Cover
http://www.ruralcostarica.com/biodigester.html